National Library of Energy BETA

Sample records for filament hafnium carbide

  1. Silver-hafnium braze alloy

    DOE Patents [OSTI]

    Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

    2003-12-16

    A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.

  2. Hafnium radioisotope recovery from irradiated tantalum

    DOE Patents [OSTI]

    Taylor, Wayne A. (Los Alamos, NM); Jamriska, David J. (Los Alamos, NM)

    2001-01-01

    Hafnium is recovered from irradiated tantalum by: (a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum; (b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution; (c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate; (d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution; (e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange; (f) separating fluoride ion complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride to obtain a second precipitate containing the hafnium and iron; (g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron; (h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange; (i) drying the ion exchanged hafnium solution to obtain hafnium isotopes. Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by cation exchange, then anion exchange, is performed.

  3. Ferroelectricity in undoped hafnium oxide

    SciTech Connect (OSTI)

    Polakowski, Patrick; Mller, Johannes

    2015-06-08

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 420?nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization P{sub r} of up to 10??C?cm{sup ?2} as well as a read/write endurance of 1.6??10{sup 5} cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  4. Formulation and method for preparing gels comprising hydrous hafnium oxide

    DOE Patents [OSTI]

    Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C

    2013-08-06

    Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

  5. Carbide and carbonitride surface treatment method for refractory metals

    DOE Patents [OSTI]

    Meyer, G.A.; Schildbach, M.A.

    1996-12-03

    A carbide and carbonitride surface treatment method for refractory metals is provided, in steps including, heating a part formed of boron, chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten or zirconium, or alloys thereof, in an evacuated chamber and then introducing reaction gases including nitrogen and hydrogen, either in elemental or water vapor form, which react with a source of elemental carbon to form carbon-containing gaseous reactants which then react with the metal part to form the desired surface layer. Apparatus for practicing the method is also provided, in the form of a carbide and carbonitride surface treatment system including a reaction chamber, a source of elemental carbon, a heating subassembly and a source of reaction gases. Alternative methods of providing the elemental carbon and the reaction gases are provided, as well as methods of supporting the metal part, evacuating the chamber with a vacuum subassembly and heating all of the components to the desired temperature. 5 figs.

  6. Microwave sintering of boron carbide

    DOE Patents [OSTI]

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  7. Electron-beam-evaporated thin films of hafnium dioxide for fabricating

    Office of Scientific and Technical Information (OSTI)

    electronic devices (Journal Article) | SciTech Connect Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices Citation Details In-Document Search This content will become publicly available on June 17, 2016 Title: Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices Thin films of hafnium dioxide (HfO2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this

  8. Carbide and carbonitride surface treatment method for refractory metals

    DOE Patents [OSTI]

    Meyer, Glenn A. (Danville, CA); Schildbach, Marcus A. (Livermore, CA)

    1996-01-01

    A carbide and carbonitride surface treatment method for refractory metals is provided, in steps including, heating a part formed of boron, chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten or zirconium, or alloys thereof, in an evacuated chamber and then introducing reaction gases including nitrogen and hydrogen, either in elemental or water vapor form, which react with a source of elemental carbon to form carbon-containing gaseous reactants which then react with the metal part to form the desired surface layer. Apparatus for practicing the method is also provided, in the form of a carbide and carbonitride surface treatment system (10) including a reaction chamber (14), a source of elemental carbon (17), a heating subassembly (20) and a source of reaction gases (23). Alternative methods of providing the elemental carbon (17) and the reaction gases (23) are provided, as well as methods of supporting the metal part (12), evacuating the chamber (14) with a vacuum subassembly (18) and heating all of the components to the desired temperature.

  9. Synthesis and Characterization of a Hafnium Derivative of the MOF

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    UiO-66-NH2 and its use in Biomass Related Catalysis | The Ames Laboratory Synthesis and Characterization of a Hafnium Derivative of the MOF UiO-66-NH2 and its use in Biomass Related Catalysis Catalysis plays an important role in the synthesis of chemicals. One such process in which they are indispensable is in the conversion of biomass into fuel and commodity products. This area of research is an active research area due to the finite fossil fuel reserves. Development of catalysts that are

  10. Modified silicon carbide whiskers

    DOE Patents [OSTI]

    Tiegs, T.N.; Lindemer, T.B.

    1991-05-21

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  11. Modified silicon carbide whiskers

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN); Lindemer, Terrence B. (Oak Ridge, TN)

    1991-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  12. PROCESS OF RECOVERING ZIRCONIUM VALUES FROM HAFNIUM VALUES BY SOLVENT EXTRACTION WITH AN ALKYL PHOSPHATE

    DOE Patents [OSTI]

    Peppard, D.F.

    1960-02-01

    A process of separating hafnium nitrate from zirconium nitrate contained in a nitric acid solution by selectively. extracting the zirconium nitrate with a water-immiscible alkyl phosphate is reported.

  13. Aerogel-supported filament

    DOE Patents [OSTI]

    Wuest, Craig R.; Tillotson, Thomas M.; Johnson, III, Coleman V.

    1995-01-01

    The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces.

  14. Aerogel-supported filament

    DOE Patents [OSTI]

    Wuest, C.R.; Tillotson, T.M.; Johnson, C.V. III

    1995-05-16

    The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces. 6 Figs.

  15. Process for microwave sintering boron carbide

    DOE Patents [OSTI]

    Holcombe, Cressie E. (440 Sugarwood Dr., Knoxville, TN 37922); Morrow, Marvin S. (Rte. #3, Box 113, Kingston, TN 37763)

    1993-01-01

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  16. Process for microwave sintering boron carbide

    DOE Patents [OSTI]

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  17. Steelmaking with iron carbide

    SciTech Connect (OSTI)

    Geiger, G.H.; Stephens, F.A. )

    1993-01-01

    The concept of using iron carbide in steelmaking is not new. Tests were run several decades ago, using carbide made from ore, in steelmaking furnaces. The problem was that at that time, the need for the product was not clear and the economics of production were not favorable. In the early 1970's Frank M. Stephens, Jr., conceived the basis for the present process, and considerable development work has been done during the past decade to bring the carbide production process to its present state, with the first commercial unit now under construction. The process utilizes the following overall reaction to produce Fe[sub 3]C from ore: 3Fe[sub 2]O[sub 3] + 5H[sub 2] + 2 CH[sub 4][equals]2 Fe[sub 3]C + 9 H[sub 2]O. Hydrogen gas from a natural gas reformer is blended with natural gas to form the process gas that is recirculated through the fluid bed reactor, the cooling tower, to remove reaction product water, and back through the reactor again, after reheating. The closed loop nature of the process means that virtually 100% of the process reagents are utilized by the process. The only exception is that a small stream of the process gas is burned as fuel in the reheating step, in order to maintain the level of inerts in the process gas at an acceptable level. The quantity of the bleed stream is entirely dependent on the concentration of inert gases in the fuel supply.

  18. Methods of producing continuous boron carbide fibers

    DOE Patents [OSTI]

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  19. A look back at Union Carbides [first] 20 Years in Nuclear Energy...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    first 20 Years in Nuclear Energy The Gaseous Diffusion Plants Note: Union Carbide Nuclear Division, which started out as Carbide and Carbon Chemicals Company, operated the...

  20. Reinvestigation of high pressure polymorphism in hafnium metal

    SciTech Connect (OSTI)

    Pandey, K. K. Sharma, Surinder M.; Gyanchandani, Jyoti; Dey, G. K.; Somayazulu, M.; Sikka, S. K.

    2014-06-21

    There has been a recent controversy about the high pressure polymorphism of Hafnium (Hf). Unlike, the earlier known ??? structural transition at 38??8?GPa, at ambient temperature, Hrubiak et al. [J. Appl. Phys. 111, 112612 (2012)] did not observe it till 51?GPa. They observed this transition only at elevated temperatures. We have reinvestigated the room temperature phase diagram of Hf, employing x-ray diffraction (XRD) and DFT based first principles calculations. Experimental investigations have been carried out on several pure and impure Hf samples and also with different pressure transmitting media. Besides demonstrating the significant role of impurity levels on the high pressure phase diagram of Hf, our studies re-establish room temperature ??? transition at high pressures, even in quasi-hydrostatic environment. We observed this transition in pure Hf with equilibrium transition pressure P{sub o}?=?44.5?GPa; however, with large hysteresis. The structural sequence, transition pressures, the lattice parameters, the c/a ratio and its variation with compression for the ? and ? phases as predicted by our ab-initio scalar relativistic (SR) calculations are found to be in good agreement with our experimental results of pure Hf.

  1. Composition and microstructure of zirconium and hafnium germanates obtained by different chemical routes

    SciTech Connect (OSTI)

    Utkin, A.V. Prokip, V.E.; Baklanova, N.I.

    2014-01-15

    The phase composition and morphology of zirconium and hafnium germanates synthesized by ceramic and co-precipitation routes were studied. The products were characterized using high-temperature X-ray diffraction analysis (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and thermal (TG/DTA) analysis. To investigate the phase composition and stoichiometry of compounds the unit cell parameters were refined by full-profile Rietveld XRD analysis. The morphology of products and its evolution during high-temperature treatment was examined by SEM analysis. It was stated that there is the strong dependence of the phase composition and morphology of products on the preparation route. The ceramic route requires a multi-stage high-temperature treatment to obtain zirconium and hafnium germanates of 95% purity or more. Also, there are strong diffusion limitations to obtain hafnium germanate Hf{sub 3}GeO{sub 8} by ceramic route. On the contrary, the co-precipitation route leads to the formation of nanocrystalline single phase germanates of stoichiometric composition at a relatively low temperatures (less than 1000 C). The results of quantitative XRD analysis showed the hafnium germanates are stoichiometric compounds in contrast to zirconium germanates that form a set of solid solutions. This distinction may be related to the difference in the ion radii of Zr and Hf. - Graphical abstract: The phase composition and morphology of zirconium and hafnium germanates synthesized by ceramic and co-precipitation routes were studied. It was stated that there is the strong dependence of the phase composition and morphology of products on the preparation route. Display Omitted - Highlights: Zr and Hf germanates were synthesized by ceramic and co-precipitation routes. The morphology of products depends on the synthesis parameters. Zirconium germanates forms a set of solid solutions. Hafnium germanates are stoichiometric compounds.

  2. Vanadium Carbide Coating Process | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Vanadium Carbide Coating Process Vanadium Carbide Coating Process Innovative Process Enhances Wear Resistance of Metals, Saving Energy, Waste, and Costs Traditional methods of coating steel surfaces with a layer of hard metal carbide require large capital investment, produce toxic and hazardous gases, are costly to operate, and require multiple heat-treatment steps during processing. Vanadium carbide (VC) coating technology provides a superior protective coating for steel surfaces and eliminates

  3. Optically Directed Assembly of Continuous Mesoscale Filaments...

    Office of Scientific and Technical Information (OSTI)

    Optically Directed Assembly of Continuous Mesoscale Filaments Title: Optically Directed Assembly of Continuous Mesoscale Filaments Authors: Bahns, J. T. ; Sankaranarayanan, S. K. ...

  4. Electron emitting filaments for electron discharge devices

    DOE Patents [OSTI]

    Leung, K.N.; Pincosy, P.A.; Ehlers, K.W.

    1983-06-10

    Electrons are copiously emitted by a device comprising a loop-shaped filament made of lanthanum hexaboride. The filament is directly heated by an electrical current produced along the filament by a power supply connected to the terminal legs of the filament. To produce a filament, a diamond saw or the like is used to cut a slice from a bar made of lanthanum hexaboride. The diamond saw is then used to cut the slice into the shape of a loop which may be generally rectangular, U-shaped, hairpin-shaped, zigzag-shaped, or generally circular. The filaments provide high electron emission at a relatively low operating temperature, such as 1600/sup 0/C. To achieve uniform heating, the filament is formed with a cross section which is tapered between the opposite ends of the filament to compensate for nonuniform current distribution along the filament due to the emission of electrons from the filament.

  5. Electron emitting filaments for electron discharge devices

    DOE Patents [OSTI]

    Leung, Ka-Ngo (Hercules, CA); Pincosy, Philip A. (Oakland, CA); Ehlers, Kenneth W. (Alamo, CA)

    1988-01-01

    Electrons are copiously emitted by a device comprising a loop-shaped filament made of lanthanum hexaboride. The filament is directly heated by an electrical current produced along the filament by a power supply connected to the terminal legs of the filament. To produce a filament, a diamond saw or the like is used to cut a slice from a bar made of lanthanum hexaboride. The diamond saw is then used to cut the slice into the shape of a loop which may be generally rectangular, U-shaped, hairpin-shaped, zigzag-shaped, or generally circular. The filaments provide high electron emission at a relatively low operating temperature, such as 1600.degree. C. To achieve uniform heating, the filament is formed with a cross section which is tapered between the opposite ends of the filament to compensate for non-uniform current distribution along the filament due to the emission of electrons from the filament.

  6. Diamond-silicon carbide composite

    DOE Patents [OSTI]

    Qian, Jiang; Zhao, Yusheng

    2006-06-13

    Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=5–8 GPa, T=1400K–2300K) to form composites having high fracture toughness. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPa.dot.m1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness. X-ray diffraction patterns and Raman spectra indicate that amorphous silicon is partially transformed into nanocrystalline silicon at 5 GPa/873K, and nanocrystalline silicon carbide forms at higher temperatures.

  7. Conductivities and Seebeck Coefficients of Boron Carbides:

    Office of Scientific and Technical Information (OSTI)

    ''Softening-Bipolaron'' Hopping (Journal Article) | SciTech Connect Conductivities and Seebeck Coefficients of Boron Carbides: ''Softening-Bipolaron'' Hopping Citation Details In-Document Search Title: Conductivities and Seebeck Coefficients of Boron Carbides: ''Softening-Bipolaron'' Hopping The most conspicuous feature of boron carbides' electronic transport properties is their having both high carrier densities and large Seebeck coefficients. The magnitudes and temperature dependencies of

  8. Abrasive slurry composition for machining boron carbide

    DOE Patents [OSTI]

    Duran, Edward L. (Santa Fe, NM)

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  9. Abrasive slurry composition for machining boron carbide

    DOE Patents [OSTI]

    Duran, E.L.

    1984-11-29

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  10. Hafnium nitride buffer layers for growth of GaN on silicon

    DOE Patents [OSTI]

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16

    Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 {character pullout}m. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.

  11. Shock-wave strength properties of boron carbide and silicon carbide

    SciTech Connect (OSTI)

    Grady, D.E.

    1994-02-01

    Time-resolved velocity interferometry measurements have been made on boron carbide and silicon carbide ceramics to assess dynamic equation-of-state and strength properties of these materials. Hugoniot pecursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides.

  12. Conductivities and Seebeck Coefficients of Boron Carbides:'...

    Office of Scientific and Technical Information (OSTI)

    Conductivities and Seebeck Coefficients of Boron Carbides: ''Softening-Bipolaron'' Hopping Citation Details In-Document Search Title: Conductivities and Seebeck Coefficients of...

  13. Silicon carbide fibers and articles including same

    DOE Patents [OSTI]

    Garnier, John E; Griffith, George W

    2015-01-27

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  14. Radiation effects on the electrical properties of hafnium oxide based MOS capacitors.

    SciTech Connect (OSTI)

    Petrosky, J. C.; McClory, J. W.; Bielejec, Edward Salvador; Foster, J. C.

    2010-10-01

    Hafnium oxide-based MOS capacitors were investigated to determine electrical property response to radiation environments. In situ capacitance versus voltage measurements were analyzed to identify voltage shifting as a result of changes to trapped charge with increasing dose of gamma, neutron, and ion radiation. In situ measurements required investigation and optimization of capacitor fabrication to include dicing, cleaning, metalization, packaging, and wire bonding. A top metal contact of 200 angstroms of titanium followed by 2800 angstroms of gold allowed for repeatable wire bonding and proper electrical response. Gamma and ion irradiations of atomic layer deposited hafnium oxide on silicon devices both resulted in a midgap voltage shift of no more than 0.2 V toward less positive voltages. This shift indicates recombination of radiation induced positive charge with negative trapped charge in the bulk oxide. Silicon ion irradiation caused interface effects in addition to oxide trap effects that resulted in a flatband voltage shift of approximately 0.6 V also toward less positive voltages. Additionally, no bias dependent voltage shifts with gamma irradiation and strong oxide capacitance room temperature annealing after ion irradiation was observed. These characteristics, in addition to the small voltage shifts observed, demonstrate the radiation hardness of hafnium oxide and its applicability for use in space systems.

  15. On the phase formation of sputtered hafnium oxide and oxynitride films

    SciTech Connect (OSTI)

    Sarakinos, K.; Music, D.; Mraz, S.; Baben, M. to; Jiang, K.; Nahif, F.; Braun, A.; Zilkens, C.; Schneider, J. M.; Konstantinidis, S.; Renaux, F.; Cossement, D.; Munnik, F.

    2010-07-15

    Hafnium oxynitride films are deposited from a Hf target employing direct current magnetron sputtering in an Ar-O{sub 2}-N{sub 2} atmosphere. It is shown that the presence of N{sub 2} allows for the stabilization of the transition zone between the metallic and the compound sputtering mode enabling deposition of films at well defined conditions of target coverage by varying the O{sub 2} partial pressure. Plasma analysis reveals that this experimental strategy facilitates control over the flux of the O{sup -} ions which are generated on the oxidized target surface and accelerated by the negative target potential toward the growing film. An arrangement that enables film growth without O{sup -} ion bombardment is also implemented. Moreover, stabilization of the transition sputtering zone and control of the O{sup -} ion flux without N{sub 2} addition is achieved employing high power pulsed magnetron sputtering. Structural characterization of the deposited films unambiguously proves that the phase formation of hafnium oxide and hafnium oxynitride films with the crystal structure of HfO{sub 2} is independent from the O{sup -} bombardment conditions. Experimental and theoretical data indicate that the presence of vacancies and/or the substitution of O by N atoms in the nonmetal sublattice favor the formation of the cubic and/or the tetragonal HfO{sub 2} crystal structure at the expense of the monoclinic HfO{sub 2} one.

  16. Fact Sheet: Award-Winning Silicon Carbide Power Electronics ...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Award-Winning Silicon Carbide Power Electronics (October 2012) Fact Sheet: Award-Winning Silicon Carbide Power Electronics (October 2012) Operating at high temperatures and with ...

  17. Preparation of silicon carbide fibers

    DOE Patents [OSTI]

    Wei, G.C.

    1983-10-12

    Silicon carbide fibers suitable for use in the fabrication of dense, high-strength, high-toughness SiC composites or as thermal insulating materials in oxidizing environments are fabricated by a new, simplified method wherein a mixture of short-length rayon fibers and colloidal silica is homogenized in a water slurry. Water is removed from the mixture by drying in air at 120/sup 0/C and the fibers are carbonized by (pyrolysis) heating the mixture to 800 to 1000/sup 0/C in argon. The mixture is subsequently reacted at 1550 to 1900/sup 0/C in argon to yield pure ..beta..-SiC fibers.

  18. The production of iron carbide

    SciTech Connect (OSTI)

    Anderson, K.M.; Scheel, J.

    1997-12-31

    From start-up in 1994 to present, Nucor`s Iron Carbide plant has overcome many obstacles in achieving design production. Many of these impediments were due to flaws in equipment design. With the integration existing within the plant, limitations in any one system reduced the operating capacity of others. For this reason, as modifications were made and system capacities were increased, the need for additional modifications became apparent. Subsequently, operating practices, maintenance scheduling, employee incentives, and production objectives were continually adapted. This paper discusses equipment and design corrections and the quality issues that contributed to achieving the plant`s production capacity.

  19. Titanium carbide bipolar plate for electrochemical devices

    DOE Patents [OSTI]

    LaConti, Anthony B. (Lynnfield, MA); Griffith, Arthur E. (Lynn, MA); Cropley, Cecelia C. (Acton, MA); Kosek, John A. (Danvers, MA)

    2000-07-04

    A corrosion resistant, electrically conductive, non-porous bipolar plate is made from titanium carbide for use in an eletrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  20. PARTIAL SLINGSHOT RECONNECTION BETWEEN TWO FILAMENTS

    SciTech Connect (OSTI)

    Jiang, Yunchun; Hong, Junchao; Yang, Jiayan; Bi, Yi; Zheng, Ruisheng; Yang, Bo; Li, Haidong; Yang, Dan

    2013-02-10

    We present a rare observation of an interaction between two filaments around AR 11358 and AR 11361 on 2011 December 3 that is strongly suggestive of the occurrence of slingshot reconnection. A small elbow-shaped active-region filament (F12) underwent a failed eruption that brought it into contact with a nearby larger, thicker filament (F34). Accompanied by the appearance of complicated internal structures below the erupting F12, its two legs separated away from each other and then connected into F34. This process led the filaments to change their connectivity to form two newly linked filaments, and one of them showed a clear inverse {gamma}-shape. However, the alteration in the filament connectivity was imperfect since F34 is discernible after the eruption. These observations can be interpreted as a partial slingshot reconnection between two filaments that had unequal axial magnetic flux.

  1. Determination of Ideal Broth Formulations Needed to Prepare Hydrous Hafnium Oxide Microspheres via the Internal Gelation Process

    SciTech Connect (OSTI)

    Collins, Jack Lee; Hunt, Rodney Dale; Simmerman, S. G.

    2009-02-01

    A simple test-tube methodology was used to determine optimum process parameters for preparing hydrous hafnium oxide microspheres by the internal gelation process. Broth formulations of hafnyl chloride [HfOCl{sub 2}], hexamethylenetetramine, and urea were found that can be used to prepare hydrous hafnium oxide gel spheres in the temperature range of 70-90 C. A few gel-forming runs were made in which microspheres were prepared with some of these formulations in order to equate the test-tube gelation times with actual gelation times. These preparations confirmed that the test-tube methodology is reliable for determining the ideal broths.

  2. LIQUID PHASE SINTERING OF METALLIC CARBIDES

    DOE Patents [OSTI]

    Hammond, J.; Sease, J.D.

    1964-01-21

    An improved method is given for fabricating uranium carbide composites, The method comprises forming a homogeneous mixture of powdered uranium carbide, a uranium intermetallic compound which wets and forms a eutectic with said carbide and has a non-uranium component which has a relatively high vapor pressure at a temperature in the range 1200 to 1500 deg C, and an organic binder, pressing said mixture to a composite of desired green strength, and then vacuum sintering said composite at the eutectic forming temperature for a period sufficient to remove at least a portion of the non-uranium containing component of said eutectic. (AEC)

  3. Manufacture of silicon carbide using solar energy

    DOE Patents [OSTI]

    Glatzmaier, Gregory C. (Boulder, CO)

    1992-01-01

    A method is described for producing silicon carbide particles using solar energy. The method is efficient and avoids the need for use of electrical energy to heat the reactants. Finely divided silica and carbon are admixed and placed in a solar-heated reaction chamber for a time sufficient to cause a reaction between the ingredients to form silicon carbide of very small particle size. No grinding of silicon carbide is required to obtain small particles. The method may be carried out as a batch process or as a continuous process.

  4. Union Carbides Last 20 Years in Oak Ridge ? part 3

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    national news event that captured Carbide's top management attention was the Three Mile Island, Pennsylvania nuclear accident. ORNL responded quickly, sending experts to help....

  5. A look back at Union Carbides first 20 Years in Nuclear Energy...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    from Manhattan District. "March, 1948 - Carbide accepted operating contract, and name was changed to Oak Ridge National Laboratory. "1948 - Construction started on...

  6. Diagnosis of femtosecond plasma filament by channeling microwaves along the filament

    SciTech Connect (OSTI)

    Alshershby, Mostafa; Ren, Yu; Qin, Jiang; Hao, Zuoqiang; Lin, Jingquan

    2013-05-20

    We introduce a simple, fast, and non-intrusive experimental method to obtain the basic parameters of femtosecond laser-generated plasma filament. The method is based on the channeling of microwaves along both a plasma filament and a well-defined conducting wire. By comparing the detected microwaves that propagate along the plasma filament and a copper wire with known conductivity and spatial dimension, the basic parameters of the plasma filament can be easily obtained. As a result of the possibility of channeling microwave radiation along the plasma filament, we were then able to obtain the plasma density distribution along the filament length.

  7. Fabrication of thorium bearing carbide fuels

    DOE Patents [OSTI]

    Gutierrez, R.L.; Herbst, R.J.; Johnson, K.W.R.

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750/sup 0/C and 2000/sup 0/C were used during the reduction cycle. Sintering temperatures of 1800/sup 0/C and 2000/sup 0/C were used to prepare fuel pellet densities of 87% and > 94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproductibility of chemical and phase composition.

  8. Conductivities and Seebeck Coefficients of Boron Carbides:

    Office of Scientific and Technical Information (OSTI)

    ''Softening-Bipolaron'' Hopping (Journal Article) | SciTech Connect Conductivities and Seebeck Coefficients of Boron Carbides: ''Softening-Bipolaron'' Hopping Citation Details In-Document Search Title: Conductivities and Seebeck Coefficients of Boron Carbides: ''Softening-Bipolaron'' Hopping × You are accessing a document from the Department of Energy's (DOE) SciTech Connect. This site is a product of DOE's Office of Scientific and Technical Information (OSTI) and is provided as a public

  9. Selective etching of silicon carbide films

    DOE Patents [OSTI]

    Gao, Di; Howe, Roger T.; Maboudian, Roya

    2006-12-19

    A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

  10. Optically Directed Assembly of Continuous Mesoscale Filaments...

    Office of Scientific and Technical Information (OSTI)

    Optically Directed Assembly of Continuous Mesoscale Filaments Bahns, J. T.; Sankaranarayanan, S. K. R. S.; Gray, S. K.; Chen, L. Not Available American Physical Society None USDOE...

  11. Measurement of birefringence inside a filament

    SciTech Connect (OSTI)

    Yuan Shuai; Wang, Tie-Jun; Chin, See Leang; Kosareva, Olga; Panov, Nikolay; Makarov, Vladimir; Zeng Heping

    2011-07-15

    We quantified the ultrafast birefringence induced in the filament in an atomic gas by measuring the filament-induced polarization rotation of a probe pulse. Based on the dephasing of the probe's orthogonal polarization components in argon, the experiment was done at 1 atm by copropagating a linearly polarized 400-nm probe pulse with an 800-nm pump pulse which generated the filament. The probe's elliptical polarization states were shown under various initial pump-probe polarization schemes. These states were verified by comparing the filament-induced probe polarization rotation angle and the ellipticity of the probe polarization.

  12. Growth of filaments and saturation of the filamentation instability

    SciTech Connect (OSTI)

    Gedalin, M.; Medvedev, M.; Spitkovsky, A.; Krasnoselskikh, V.; Vaivads, A.; Perri, S.

    2010-03-15

    The filamentation instability of counterstreaming beams is a nonresonant hydrodynamic-type instability whose growth rate is a smooth function of the wavelength (scale). As a result, perturbations with all unstable wavelengths develop, and the growth saturates due to the saturation of available current. For a given scale, the magnetic field at saturation is proportional to the scale. As a result, the instability develops in a nearly linear regime, where the unstable modes stop growing as soon as the saturation of the corresponding wavelength is reached. At each moment there exists a dominant scale of the magnetic field which is the scale that reached saturation at this particular time. The smaller scales do not disappear and can be easily distinguished in the current structure. The overall growth of the instability stops when the loss of the streaming ion energy because of deceleration is comparable to the initial ion energy.

  13. Joining of porous silicon carbide bodies

    DOE Patents [OSTI]

    Bates, Carl H. (Worcester, MA); Couhig, John T. (Worcester, MA); Pelletier, Paul J. (Thompson, CT)

    1990-05-01

    A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.

  14. Fabrication of thorium bearing carbide fuels

    DOE Patents [OSTI]

    Gutierrez, Rueben L. (Los Alamos, NM); Herbst, Richard J. (Los Alamos, NM); Johnson, Karl W. R. (Los Alamos, NM)

    1981-01-01

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750.degree. C. and 2000.degree. C. were used during the reduction cycle. Sintering temperatures of 1800.degree. C. and 2000.degree. C. were used to prepare fuel pellet densities of 87% and >94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproducibility of chemicals and phase composition. Methods employing liquid techniques that form carbide microspheres or alloying-techniques which form alloys of thorium-uranium or thorium-plutonium suffer from limitation on the quantities processed of because of criticality concerns and lack of precise control of process conditions, respectively.

  15. Carbides composite surface layers produced by (PTA)

    SciTech Connect (OSTI)

    Tajoure, Meloud; Tajouri, Ali E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar E-mail: dr.mokhtarphd@yahoo.com; Akreem, Mosbah

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  16. Laser-Induced Ionization Efficiency Enhancement On A Filament For Thermal Ionization Mass Spectrometry

    SciTech Connect (OSTI)

    Siegfried, M.

    2015-10-14

    The evaluation of trace Uranium and Plutonium isotope ratios for nanogram to femtogram material quantities is a vital tool for nuclear counter-proliferation and safeguard activities. Thermal Ionization Mass Spectrometry (TIMS) is generally accepted as the state of the art technology for highly accurate and ultra-trace measurements of these actinide ratios. However, the very low TIMS ionization yield (typically less than 1%) leaves much room for improvement. Enhanced ionization of Nd and Sm from a TIMS filament was demonstrated using wavelength resonance with a nanosecond (pulse width) laser operating at 10 Hz when light was directed toward the filament.1 For this study, femtosecond and picosecond laser capabilities were to be employed to study the dissociation and ionization mechanisms of actinides/lanthanides and measure the enhanced ionization of the metal of interest. Since the underlying chemistry of the actinide/lanthanide carbides produced and dissociated on a TIMS filament is not well understood, the experimental parameters affecting the photodissociation and photoionization with one and two laser beams were to be investigated.

  17. Deposition method for producing silicon carbide high-temperature semiconductors

    DOE Patents [OSTI]

    Hsu, George C. (La Crescenta, CA); Rohatgi, Naresh K. (W. Corine, CA)

    1987-01-01

    An improved deposition method for producing silicon carbide high-temperature semiconductor material comprising placing a semiconductor substrate composed of silicon carbide in a fluidized bed silicon carbide deposition reactor, fluidizing the bed particles by hydrogen gas in a mildly bubbling mode through a gas distributor and heating the substrate at temperatures around 1200.degree.-1500.degree. C. thereby depositing a layer of silicon carbide on the semiconductor substrate.

  18. Wake-up effects in Si-doped hafnium oxide ferroelectric thin films

    SciTech Connect (OSTI)

    Zhou, Dayu, E-mail: zhoudayu@dlut.edu.cn [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China) [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024 (China); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Xu, Jin [Department of Electronic Engineering, Dalian Neusoft University of Information, Dalian 116023 (China)] [Department of Electronic Engineering, Dalian Neusoft University of Information, Dalian 116023 (China); Li, Qing; Guan, Yan [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)] [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Cao, Fei; Dong, Xianlin [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)] [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Mller, Johannes [Fraunhofer IPMS-CNT, Koengisbruecker Strasse 180, 01109 Dresden (Germany)] [Fraunhofer IPMS-CNT, Koengisbruecker Strasse 180, 01109 Dresden (Germany); Schenk, Tony; Schrder, Uwe [Namlab gGmbH/TU Dresden, Noethnitzer Strasse 64, 01187 Dresden (Germany)] [Namlab gGmbH/TU Dresden, Noethnitzer Strasse 64, 01187 Dresden (Germany)

    2013-11-04

    Hafnium oxide based ferroelectric thin films have shown potential as a promising alternative material for non-volatile memory applications. This work reports the switching stability of a Si-doped HfO{sub 2} film under bipolar pulsed-field operation. High field cycling causes a wake-up in virgin pinched polarization hysteresis loops, demonstrated by an enhancement in remanent polarization and a shift of negative coercive voltage. The rate of wake-up is accelerated by either reducing the frequency or increasing the amplitude of the cycling field. We suggest de-pinning of domains due to reduction of the defect concentration at bottom electrode interface as origin of the wake-up.

  19. Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

    SciTech Connect (OSTI)

    Vargas, Mirella [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)] [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States); Murphy, N. R. [Materials and Manufacturing Directorate (RX), 3005 Hobson Way, Wright-Patterson Air Force Base (WPAFB), Dayton, Ohio 45433 (United States)] [Materials and Manufacturing Directorate (RX), 3005 Hobson Way, Wright-Patterson Air Force Base (WPAFB), Dayton, Ohio 45433 (United States); Ramana, C. V., E-mail: rvchintalapalle@utep.edu [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

    2014-03-10

    Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s}?=?25700?C). HfO{sub 2} films grown at T{sub s}?

  20. Plasma Blobs and Filaments: Fusion Scientists Discover Secrets...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Plasma Blobs and Filaments: Fusion Scientists Discover Secrets of Turbulent Edge Transport American Fusion News Category: U.S. Universities Link: Plasma Blobs and Filaments: Fusion...

  1. Detection and characterization of multi-filament evolution during...

    Office of Scientific and Technical Information (OSTI)

    of multi-filament evolution during resistive switching. Citation Details In-Document Search Title: Detection and characterization of multi-filament evolution during resistive ...

  2. Unwinding motion of a twisted active region filament

    SciTech Connect (OSTI)

    Yan, X. L.; Xue, Z. K.; Kong, D. F.; Liu, J. H.; Xu, C. L.

    2014-12-10

    To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5? obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.

  3. Liquid phase sintering of silicon carbide

    DOE Patents [OSTI]

    Cutler, R.A.; Virkar, A.V.; Hurford, A.C.

    1989-05-09

    Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1,600 C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase. 4 figs.

  4. Making Silicon Carbide Devices | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Making Silicon Carbide Devices in the Cleanroom Click to email this to a friend (Opens in new window) Share on Facebook (Opens in new window) Click to share (Opens in new window) Click to share on LinkedIn (Opens in new window) Click to share on Tumblr (Opens in new window) Making Silicon Carbide Devices in the Cleanroom Ron Olson 2012.08.23 As the Wide Bandgap Process and Fab manager for the GE Global Research cleanroom, I wanted to take some time to give you the dirt on our clean room over the

  5. THERMAL AND CHEMICAL EVOLUTION OF COLLAPSING FILAMENTS

    SciTech Connect (OSTI)

    Gray, William J.; Scannapieco, Evan

    2013-05-10

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, Z Almost-Equal-To 0.1 Z{sub Sun} filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form a dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10{sup -3} Z{sub Sun} filaments, the collapse proceeds much more slowly. This is mostly due to the lower initial temperatures, which lead to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbursting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occurs. We find that we achieve similar accretion rates as NGC 5253 but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

  6. Filaments in simulations of molecular cloud formation

    SciTech Connect (OSTI)

    Gmez, Gilberto C.; Vzquez-Semadeni, Enrique

    2014-08-20

    We report on the filaments that develop self-consistently in a new numerical simulation of cloud formation by colliding flows. As in previous studies, the forming cloud begins to undergo gravitational collapse because it rapidly acquires a mass much larger than the average Jeans mass. Thus, the collapse soon becomes nearly pressureless, proceeding along its shortest dimension first. This naturally produces filaments in the cloud and clumps within the filaments. The filaments are not in equilibrium at any time, but instead are long-lived flow features through which the gas flows from the cloud to the clumps. The filaments are long-lived because they accrete from their environment while simultaneously accreting onto the clumps within them; they are essentially the locus where the flow changes from accreting in two dimensions to accreting in one dimension. Moreover, the clumps also exhibit a hierarchical nature: the gas in a filament flows onto a main, central clump but other, smaller-scale clumps form along the infalling gas. Correspondingly, the velocity along the filament exhibits a hierarchy of jumps at the locations of the clumps. Two prominent filaments in the simulation have lengths ?15 pc and masses ?600 M {sub ?} above density n ? 10{sup 3} cm{sup 3} (?2 10{sup 3} M {sub ?} at n > 50 cm{sup 3}). The density profile exhibits a central flattened core of size ?0.3 pc and an envelope that decays as r {sup 2.5} in reasonable agreement with observations. Accretion onto the filament reaches a maximum linear density rate of ?30 M {sub ?} Myr{sup 1} pc{sup 1}.

  7. Prealloyed catalyst for growing silicon carbide whiskers

    DOE Patents [OSTI]

    Shalek, Peter D. (Los Alamos, NM); Katz, Joel D. (Niagara Falls, NY); Hurley, George F. (Los Alamos, NM)

    1988-01-01

    A prealloyed metal catalyst is used to grow silicon carbide whiskers, especially in the .beta. form. Pretreating the metal particles to increase the weight percentages of carbon or silicon or both carbon and silicon allows whisker growth to begin immediately upon reaching growth temperature.

  8. High Q silicon carbide microdisk resonator

    SciTech Connect (OSTI)

    Lu, Xiyuan; Lee, Jonathan Y.; Feng, Philip X.-L.; Lin, Qiang

    2014-05-05

    We demonstrate a silicon carbide (SiC) microdisk resonator with optical Q up to 5.12??10{sup 4}. The high optical quality, together with the diversity of whispering-gallery modes and the tunability of external coupling, renders SiC microdisk a promising platform for integrated quantum photonics applications.

  9. Method for fabricating boron carbide articles

    DOE Patents [OSTI]

    Ardary, Zane L. (Oak Ridge, TN); Reynolds, Carl D. (Clinton, TN)

    1980-01-01

    The present invention is directed to the fabrication of boron carbide articles having length-to-diameter or width ratios greater than 2 to 1. The process of the present invention is practiced by the steps comprising hot pressing boron carbide powder into article segments or portions in which the segments have a length-to-diameter or width ratio less than 1.5, aligning a plurality of the initially hot-pressed segments in a hot-pressing die with the end surfaces of the segments placed in intimate contact with one another, and then hot pressing the aligned segments into an article of the desired configuration. The resulting article exhibits essentially uniform density throughout the structure with the bonds between the segments being equivalent in hardness, strength, and density to the remainder of the article.

  10. Diamond-silicon carbide composite and method

    DOE Patents [OSTI]

    Zhao, Yusheng (Los Alamos, NM)

    2011-06-14

    Uniformly dense, diamond-silicon carbide composites having high hardness, high fracture toughness, and high thermal stability are prepared by consolidating a powder mixture of diamond and amorphous silicon. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPam.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness.

  11. Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Xiao, Zhigang; Kisslinger, Kim

    2015-06-17

    Thin films of hafnium dioxide (HfO2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ring oscillator to test themore » quality of the HfO2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO2 thin film functioned very well as the gate oxide.« less

  12. Investigation of crystallization processes from hafnium silicate powders prepared from an oxychloride sol-gel

    SciTech Connect (OSTI)

    McGilvery, Catriona M.; De Gendt, S; Payzant, E Andrew; Craven, A J; MacKenzie, M; McComb, D W

    2012-01-01

    Hafnium oxide and silicate materials are now incorporated into working CMOS devices, however the crystallisation mechanism is still poorly understood. In particular, addition of SiO2 to HfO2 has been shown to increase the crystallisation temperature of HfO2 hence allowing it to remain amorphous under current processing conditions. Building on earlier work we here investigate bulk HfxSi1-xO2 samples to determine the effect of SiO2 on the crystallisation pathway. Techniques such as XRD, HTXRD, thermal analysis techniques and TEM are used. It is found that the addition of SiO2 has very little affect on the crystallisation path at temperatures below 900 C but at higher temperatures a second t-HfO2 phase nucleates and is stabilised due to the strain of the surrounding amorphous SiO2 material. With an increase in SiO2 content the temperature at which this nucleation and stabilisation occurs is increased. The effect of strain has implications for inhibiting the crystallisation of the high-k layer, reduction of grain boundaries and hence diffusion, reduction of formation of interface layers and the possibility of stabilising t-HfO2 rather than m-HfO2 hence increasing the dielectric of the layer.

  13. Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

    SciTech Connect (OSTI)

    Xiao, Zhigang; Kisslinger, Kim

    2015-06-17

    Thin films of hafnium dioxide (HfO2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ring oscillator to test the quality of the HfO2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO2 thin film functioned very well as the gate oxide.

  14. Interaction and merging of two sinistral filaments

    SciTech Connect (OSTI)

    Jiang, Yunchun; Yang, Jiayan; Liu, Yu; Li, Haidong; Wang, Haimin; Ji, Haisheng; Li, Jianping

    2014-09-20

    In this paper, we report the interaction and subsequent merging of two sinistral filaments (F1 and F2) occurring at the boundary of AR 9720 on 2001 December 6. The two filaments were close and nearly perpendicular to each other. The interaction occurred after F1 was erupted and the eruption was impeded by a more extended filament channel (FC) standing in the way, in which F2 was embedded. The erupted material ran into FC along its axis, causing F1 and F2 to merge into a single structure that subsequently underwent a large-amplitude to-and-fro motion. A significant plasma heating process was observed in the merging process, making the mixed material largely disappear from the H? passband, but appear in Extreme Ultraviolet Telescope 195 images for a while. These observations can serve as strong evidence of merging reconnection between the two colliding magnetic structures. A new sinistral filament was formed along FC after the cooling of the merged and heated material. No coronal mass ejection was observed to be associated with the event; though, the eruption was accompanied by a two-ribbon flare with a separation motion, indicating that the eruption had failed. This event shows that, in addition to overlying magnetic fields, such an interaction is an effective restraint to make a filament eruption fail in this way.

  15. Boron-carbide-aluminum and boron-carbide-reactive metal cermets

    DOE Patents [OSTI]

    Halverson, Danny C. (Manteca, CA); Pyzik, Aleksander J. (Seattle, WA); Aksay, Ilhan A. (Seattle, WA)

    1986-01-01

    Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.

  16. Filament velocity scaling laws for warm ions

    SciTech Connect (OSTI)

    Manz, P.; Max-Planck-Institut fr Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching ; Carralero, D.; Birkenmeier, G.; Mller, H. W.; Scott, B. D.; Mller, S. H.; Fuchert, G.; Stroth, U.; Physik-Department E28, Technische Universitt Mnchen, James-Franck-Str. 1, 85748 Garching

    2013-10-15

    The dynamics of filaments or blobs in the scrape-off layer of magnetic fusion devices are studied by magnitude estimates of a comprehensive drift-interchange-Alfvn fluid model. The standard blob models are reproduced in the cold ion case. Even though usually neglected, in the scrape-off layer, the ion temperature can exceed the electron temperature by an order of magnitude. The ion pressure affects the dynamics of filaments amongst others by adding up to the interchange drive and the polarisation current. It is shown how both effects modify the scaling laws for filament velocity in dependence of its size. Simplifications for experimentally relevant limit regimes are given. These are the sheath dissipation, collisional, and electromagnetic regime.

  17. Bipolaron Hopping Conduction in Boron Carbides (Journal Article...

    Office of Scientific and Technical Information (OSTI)

    Language: English Subject: 36 MATERIALS SCIENCE; BORON CARBIDES; ELECTRIC CONDUCTIVITY; TEMPERATURE RANGE 0400-1000 K; POLARONS; ACTIVATION ENERGY; SEEBECK EFFECT; CARRIER DENSITY

  18. Infrared Radiation Filament And Metnod Of Manufacture

    DOE Patents [OSTI]

    Johnson, Edward A.

    1998-11-17

    An improved IR radiation source is provided by the invention. A radiation filament has a textured surface produced by seeded ion bombardment of a metal foil which is cut to a serpentine shape and mounted in a windowed housing. Specific ion bombardment texturing techniques tune the surface to maximize emissions in the desired wavelength range and to limit emissions outside that narrow range, particularly at longer wavelengths. A combination of filament surface texture, thickness, material, shape and power circuit feedback control produce wavelength controlled and efficient radiation at much lower power requirements than devices of the prior art.

  19. Silicon dioxide and hafnium dioxide evaporation characteristics from a high-frequency sweep e-beam system

    SciTech Connect (OSTI)

    Chow, R. [Lawrence Livermore National Laboratory, Livermore, California 94551-0808 (United States); Tsujimoto, N. [MDC Vacuum Products Corporation, Hayward, California 94545 (United States)

    1996-09-01

    Reactive oxygen evaporation characteristics were determined as a function of the front-panel control parameters provided by a programmable, high-frequency sweep e-beam system. An experimental design strategy used deposition rate, beam speed, pattern, azimuthal rotation speed, and dwell time as the variables. The optimal settings for obtaining a broad thickness distribution, efficient silicon dioxide boule consumption, and minimal hafnium dioxide defect density were generated. The experimental design analysis showed the compromises involved with evaporating these oxides. {copyright} {ital 1996 Optical Society of America.}

  20. GRAVITATIONAL INFALL ONTO MOLECULAR FILAMENTS. II. EXTERNALLY PRESSURIZED CYLINDERS

    SciTech Connect (OSTI)

    Heitsch, Fabian

    2013-10-10

    Two aspects of the evolution of externally pressurized, hydrostatic filaments are discussed. (1) The free-fall accretion of gas onto such a filament will lead to filament parameters (specifically, FWHM-column-density relations) inconsistent with the observations of Arzoumanian et al., except for two cases: for low-mass, isothermal filaments, agreement is found as in the analysis by Fischera and Martin. Magnetized cases, for which the field scales weakly with the density as B?n {sup 1/2}, also reproduce observed parameters. (2) Realistically, the filaments will be embedded not only in gas of non-zero pressure, but also of non-zero density. Thus, the appearance of sheet-embedded filaments is explored. Generating a grid of filament models and comparing the resulting column density ratios and profile shapes with observations suggests that the three-dimensional filament profiles are intrinsically flatter than isothermal, beyond projection and evolution effects.

  1. Light sources based on semiconductor current filaments

    DOE Patents [OSTI]

    Zutavern, Fred J.; Loubriel, Guillermo M.; Buttram, Malcolm T.; Mar, Alan; Helgeson, Wesley D.; O'Malley, Martin W.; Hjalmarson, Harold P.; Baca, Albert G.; Chow, Weng W.; Vawter, G. Allen

    2003-01-01

    The present invention provides a new type of semiconductor light source that can produce a high peak power output and is not injection, e-beam, or optically pumped. The present invention is capable of producing high quality coherent or incoherent optical emission. The present invention is based on current filaments, unlike conventional semiconductor lasers that are based on p-n junctions. The present invention provides a light source formed by an electron-hole plasma inside a current filament. The electron-hole plasma can be several hundred microns in diameter and several centimeters long. A current filament can be initiated optically or with an e-beam, but can be pumped electrically across a large insulating region. A current filament can be produced in high gain photoconductive semiconductor switches. The light source provided by the present invention has a potentially large volume and therefore a potentially large energy per pulse or peak power available from a single (coherent) semiconductor laser. Like other semiconductor lasers, these light sources will emit radiation at the wavelength near the bandgap energy (for GaAs 875 nm or near infra red). Immediate potential applications of the present invention include high energy, short pulse, compact, low cost lasers and other incoherent light sources.

  2. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOE Patents [OSTI]

    Petrovic, J.J.

    1995-01-17

    Compositions are disclosed consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  3. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOE Patents [OSTI]

    Petrovic, John J. (Los Alamos, NM)

    1995-01-01

    Compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  4. Ultratough, Thermally Stable Polycrystalline Diamond/Silicon Carbide

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Nanocomposites for Drill Bits | Department of Energy Ultratough, Thermally Stable Polycrystalline Diamond/Silicon Carbide Nanocomposites for Drill Bits Ultratough, Thermally Stable Polycrystalline Diamond/Silicon Carbide Nanocomposites for Drill Bits PDF icon nanocomposites_drill_bits.pdf More Documents & Publications ITP Nanomanufacturing: Nanomanufacturing Portfolio: Manufacturing Processes and Applications to Accelerate Commercial Use of Nanomaterials, January 2011 A History or

  5. Solar filament material oscillations and drainage before eruption

    SciTech Connect (OSTI)

    Bi, Yi; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Li, Haidong; Yang, Dan; Yang, Bo

    2014-08-01

    Both large-amplitude longitudinal (LAL) oscillations and material drainage in a solar filament are associated with the flow of material along the filament axis, often followed by an eruption. However, the relationship between these two motions and a subsequent eruption event is poorly understood. We analyze a filament eruption using EUV imaging data captured by the Atmospheric Imaging Array on board the Solar Dynamics Observatory and the H? images from the Global Oscillation Network Group. Hours before the eruption, the filament was activated, with one of its legs undergoing a slow rising motion. The asymmetric activation inclined the filament relative to the solar surface. After the active phase, LAL oscillations were observed in the inclined filament. The oscillation period increased slightly over time, which may suggest that the magnetic fields supporting the filament evolve to be flatter during the slow rising phase. After the oscillations, a significant amount of filament material was drained toward one filament endpoint, followed immediately by the violent eruption of the filament. The material drainage may further support the change in magnetic topology prior to the eruption. Moreover, we suggest that the filament material drainage could play a role in the transition from a slow to a fast rise of the erupting filament.

  6. Computational Studies of Physical Properties of Boron Carbide

    SciTech Connect (OSTI)

    Lizhi Ouyang

    2011-09-30

    The overall goal is to provide valuable insight in to the mechanisms and processes that could lead to better engineering the widely used boron carbide which could play an important role in current plight towards greener energy. Carbon distribution in boron carbide, which has been difficult to retrieve from experimental methods, is critical to our understanding of its structure-properties relation. For modeling disorders in boron carbide, we implemented a first principles method based on supercell approach within our G(P,T) package. The supercell approach was applied to boron carbide to determine its carbon distribution. Our results reveal that carbon prefers to occupy the end sites of the 3-atom chain in boron carbide and further carbon atoms will distribute mainly on the equatorial sites with a small percentage on the 3-atom chains and the apex sites. Supercell approach was also applied to study mechanical properties of boron carbide under uniaxial load. We found that uniaxial load can lead to amorphization. Other physical properties of boron carbide were calculated using the G(P,T) package.

  7. Hot filament CVD of boron nitride films

    DOE Patents [OSTI]

    Rye, Robert R.

    1992-01-01

    Using a hot filament (.apprxeq.1400.degree. C.) to activate borazine (B.sub.3 N.sub.3 H.sub.6) molecules for subsequent reaction with a direct line-of-sight substrate, transparent boron ntiride films as thick as 25,000 angstroms are grown for a substrate temperature as low as 100.degree. C. The minimum temperature is determined by radiative heating from the adjacent hot filament. The low temperature BN films show no indication of crystallinity with X-ray diffraction (XRD). X-ray photoelectron spectra (XPS) show the films to have a B:N ratio of 0.97:1 with no other XPS detectable impurities above the 0.5% level. Both Raman and infrared (IR) spectroscopy are characteristic of h-BN with small amounts of hydrogen detected as N-H and B-H bands in the IR spectrum. An important feature of this method is the separation and localization of the thermal activation step at the hot filament from the surface reaction and film growth steps at the substrate surface. This allows both higher temperature thermal activation and lower temperature film growth.

  8. Silicon Carbide in the Cleanroom | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Inside the GE Global Research Clean Room: Silicon Carbide Click to email this to a friend (Opens in new window) Share on Facebook (Opens in new window) Click to share (Opens in new window) Click to share on LinkedIn (Opens in new window) Click to share on Tumblr (Opens in new window) Inside the GE Global Research Clean Room: Silicon Carbide GE Global Research is working on nanoscale silicon carbide devices. Find out what we're doing. You Might Also Like 2-1-10-v-working-at-ge-research The Dirt

  9. UNION CARBIDE MZALS DIVISION tiiAGARA FALLS, NEW YDRK

    Office of Legacy Management (LM)

    PRELIF",INARY SURVEY 0' ELECTRDMET iORPDF.&TiCIN UNION CARBIDE MZALS DIVISION tiiAGARA FALLS, NEW YDRK Work performed by the Health and Safety Research Division Dak Ridge National Laboratory Oak Ridge, Tennessee 37830 OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for the DEPARTMENT OF ENERGY as part of the Fornierly Utilized Sites-- Remedial Action Program ,ELECTRD?'ISi 60RPOR:TION UNiON CARBIDE METALS DIVlSIOti NiASARA FALLS, NEA YORK At the requests o f the

  10. Method of producing silicon carbide articles

    DOE Patents [OSTI]

    Milewski, John V. (Los Alamos, NM)

    1985-01-01

    A method of producing articles comprising reaction-bonded silicon carbide (SiC) and graphite (and/or carbon) is given. The process converts the graphite (and/or carbon) in situ to SiC, thus providing the capability of economically obtaining articles made up wholly or partially of SiC having any size and shape in which graphite (and/or carbon) can be found or made. When the produced articles are made of an inner graphite (and/or carbon) substrate to which SiC is reaction bonded, these articles distinguish SiC-coated graphite articles found in the prior art by the feature of a strong bond having a gradual (as opposed to a sharply defined) interface which extends over a distance of mils. A method for forming SiC whisker-reinforced ceramic matrices is also given. The whisker-reinforced articles comprise SiC whiskers which substantially retain their structural integrity.

  11. Method of preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals

    DOE Patents [OSTI]

    Peng, Yu-Min (Hsinchu, TW); Wang, Jih-Wen (Hsinchu, TW); Liue, Chun-Ying (Tau-Yung, TW); Yeh, Shinn-Horng (Kaohsiung, TW)

    1994-01-01

    A method for preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals includes the steps of washing the silicon carbide particles with an organic solvent; washing the silicon carbide particles with an inorganic acid; grinding the silicon carbide particles; and heating the silicon carbide particles in a nickel-containing solution at a boiling temperature for a predetermined period of time.

  12. Raman and FTIR Studies on Nanostructure Formation on Silicon Carbide

    Office of Scientific and Technical Information (OSTI)

    (Conference) | SciTech Connect Raman and FTIR Studies on Nanostructure Formation on Silicon Carbide Citation Details In-Document Search Title: Raman and FTIR Studies on Nanostructure Formation on Silicon Carbide No abstract prepared. Authors: Muntele, Iulia C. [1] ; Muntele, C. I. [1] ; Ila, Dr. Daryush [1] ; Poker, David B [2] ; Hensley, Dale K [2] + Show Author Affiliations Alabama A&M University, Normal ORNL Publication Date: 2003-01-01 OSTI Identifier: 978142 DOE Contract Number:

  13. Microwave guiding in air along single femtosecond laser filament

    SciTech Connect (OSTI)

    Ren Yu; Alshershby, Mostafa; Qin Jiang; Hao Zuoqiang; Lin Jingquan

    2013-03-07

    Microwave guiding along single plasma filament generated through the propagation of femtosecond (fs) laser pulses in air has been demonstrated over a distance of about 6.5 cm, corresponding to a microwave signal intensity enhancement of more than 3-fold over free space propagation. The current propagation distance along the fs laser filament is in agreement with the calculations and limited by the relatively high resistance of the single plasma filament. Using a single fs laser filament to channel microwave radiation considerably alleviate requirements to the power of fs laser pulses compared to the case of the circular filaments waveguide. In addition, it can be used as a simple and non-intrusive method to obtain the basic parameters of laser-generated plasma filament.

  14. A FILAMENT ERUPTION ON 2010 OCTOBER 21 FROM THREE VIEWPOINTS

    SciTech Connect (OSTI)

    Filippov, Boris

    2013-08-10

    A filament eruption on 2010 October 21 observed from three different viewpoints by the Solar Terrestrial Relations Observatory and the Solar Dynamic Observatory is analyzed by also invoking data from the Solar and Heliospheric Observatory and the Kanzelhoehe Solar Observatory. The position of the filament just before the eruption at the central meridian not far from the center of the solar disk was favorable for photospheric magnetic field measurements in the area below the filament. Because of this, we were able to calculate with high precision the distribution of the coronal potential magnetic field near the filament. We found that the filament began to erupt when it approached the height in the corona where the magnetic field decay index was greater than 1. We also determined that during the initial stage of the eruption the filament moved along the magnetic neutral surface.

  15. Tailoring femtosecond laser pulse filamentation using plasma photonic lattices

    SciTech Connect (OSTI)

    Suntsov, Sergiy; Abdollahpour, Daryoush; Panagiotopoulos, Paris; Papazoglou, Dimitrios G.; Tzortzakis, Stelios; Couairon, Arnaud

    2013-07-08

    We demonstrate experimentally that by using transient plasma photonic lattices, the attributes of intense femtosecond laser filaments, such as peak intensity and length, can be dynamically controlled. The extended plasma lattice structure is generated using two co-propagating non-diffracting intense Bessel beams in water. The use of such transient lattice structures to control the competition between linear and nonlinear effects involved in filamentation opens the way for extensive control of the filamentation process.

  16. Understanding the Irradiation Behavior of Zirconium Carbide

    SciTech Connect (OSTI)

    Motta, Arthur; Sridharan, Kumar; Morgan, Dane; Szlufarska, Izabela

    2013-10-11

    Zirconium carbide (ZrC) is being considered for utilization in high-temperature gas-cooled reactor fuels in deep-burn TRISO fuel. Zirconium carbide possesses a cubic B1-type crystal structure with a high melting point, exceptional hardness, and good thermal and electrical conductivities. The use of ZrC as part of the TRISO fuel requires a thorough understanding of its irradiation response. However, the radiation effects on ZrC are still poorly understood. The majority of the existing research is focused on the radiation damage phenomena at higher temperatures (>450{degree}C) where many fundamental aspects of defect production and kinetics cannot be easily distinguished. Little is known about basic defect formation, clustering, and evolution of ZrC under irradiation, although some atomistic simulation and phenomenological studies have been performed. Such detailed information is needed to construct a model describing the microstructural evolution in fast-neutron irradiated materials that will be of great technological importance for the development of ZrC- based fuel. The goal of the proposed project is to gain fundamental understanding of the radiation-induced defect formation in zirconium carbide and irradiation response (ZrC) by using a combination of state-of-the-art experimental methods and atomistic modeling. This project will combine (1) in situ ion irradiation at a specialized facility at a national laboratory, (2) controlled temperature proton irradiation on bulk samples, and (3) atomistic modeling to gain a fundamental understanding of defect formation in ZrC. The proposed project will cover the irradiation temperatures from cryogenic temperature to as high as 800{degree}C, and dose ranges from 0.1 to 100 dpa. The examination of this wide range of temperatures and doses allows us to obtain an experimental data set that can be effectively used to exercise and benchmark the computer calculations of defect properties. Combining the examination of radiation-induced microstructures mapped spatially and temporally, microstructural evolution during post-irradiation annealing, and atomistic modeling of defect formation and transport energetics will provide new, critical understanding about property changes in ZrC. The behavior of materials under irradiation is determined by the balance between damage production, defect clustering, and lattice response. In order to predict those effects at high temperatures so targeted testing can be expanded and extrapolated beyond the known database, it is necessary to determine the defect energetics and mobilities as these control damage accumulation and annealing. In particular, low-temperature irradiations are invaluable for determining the regions of defect mobility. Computer simulation techniques are particularly useful for identifying basic defect properties, especially if closely coupled with a well-constructed and complete experimental database. The close coupling of calculation and experiment in this project will provide mutual benchmarking and allow us to glean a deeper understanding of the irradiation response of ZrC, which can then be applied to the prediction of its behavior in reactor conditions.

  17. Microwave diagnostics of femtosecond laser-generated plasma filaments

    SciTech Connect (OSTI)

    Papeer, J.; Ehrlich, Y.; Zigler, A.; Mitchell, C.; Penano, J.; Sprangle, P.

    2011-10-03

    We present a simple non-intrusive experimental method allowing a complete single shot temporal measurement of laser produced plasma filament conductivity. The method is based on filament interaction with low intensity microwave radiation in a rectangular waveguide. The suggested diagnostics allow a complete single shot temporal analysis of filament plasma decay with resolution better than 0.3 ns and high spatial resolution along the filament. The experimental results are compared to numerical simulations, and an initial electron density of 7 x 10{sup 16 }cm{sup -3} and decay time of 3 ns are obtained.

  18. Hollow cylindrical plasma filament waveguide with discontinuous finite thickness cladding

    SciTech Connect (OSTI)

    Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan

    2013-01-15

    We have explored here a hollow cylindrical laser plasma multifilament waveguide with discontinuous finite thickness cladding, in which the separation between individual filaments is in the range of several millimeters and the waveguide cladding thickness is in the order of the microwave penetration depth. Such parameters give a closer representation of a realistic laser filament waveguide sustained by a long stable propagation of femtosecond (fs) laser pulses. We report how the waveguide losses depend on structural parameters like normalized plasma filament spacing, filament to filament distance or pitch, normal spatial frequency, and radius of the plasma filament. We found that for typical plasma parameters, the proposed waveguide can support guided modes of microwaves in extremely high frequency even with a cladding consisting of only one ring of plasma filaments. The loss of the microwave radiation is mainly caused by tunneling through the discontinuous finite cladding, i.e., confinement loss, and is weakly dependent on the plasma absorption. In addition, the analysis indicates that the propagation loss is fairly large compared with the loss of a plasma waveguide with a continuous infinite thickness cladding, while they are comparable when using a cladding contains more than one ring. Compared to free space propagation, this waveguide still presents a superior microwave transmission to some distance in the order of the filamentation length; thus, the laser plasma filaments waveguide may be a potential channel for transporting pulsed-modulated microwaves if ensuring a long and stable propagation of fs laser pulses.

  19. Methods for tape fabrication of continuous filament composite...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    to Search Methods for tape fabrication of continuous filament composite parts and articles of manufacture thereof United States Patent Patent Number: 8,545,657 Issued: October...

  20. Nanostructured carbide catalysts for the hydrogen economy

    SciTech Connect (OSTI)

    Ram Seshadri, Susannah Scott, Juergen Eckert

    2008-07-21

    The above quote, taken from the executive summary of the Report from the US DOE Basic Energy Sciences Workshop held August 6–8, 2007,[1] places in context the research carried out at the University of California, Santa Barbara, which is reported in this document. The enormous impact of heterogeneous catalysis is exemplified by the Haber process for the synthesis of ammonia, which consumes a few % of the world’s energy supply and natural gas, and feeds as many as a third of the world’s population. While there have been numerous advances in understanding the process,[2] culminating in the awarding of the Nobel Prize to Gerhard Ertl in 2007, it is interesting to note that the catalysts themselves have changed very little since they were discovered heuristically in the the early part of the 20th century. The thesis of this report is that modern materials chemistry, with all the empirical knowledge of solid state chemistry, combined with cutting edge structural tools, can help develop and better heterogeneous catalysis. The first part of this report describes research in the area of early transition metal carbides (notably of Mo and W), potentially useful catalysts for water gas shift (WGS) and related reactions of use to the hydrogen economy. Although these carbides have been known to be catalytically useful since the 1970s,[3] further use of these relatively inexpensive materials have been plagued by issues of low surface areas and ill-defined, and often unreactive surfaces, in conjunction with deactivation. We have employed for the first time, a combination of constant-wavelength and time-of-flight neutron scattering, including a total scattering analysis of the latter data, to better understand what happens in these materials, in a manner that for the first time, reveals surface graphitic carbon in these materials in a quantitative manner. Problems of preparation, surface stability, and irreversible reactivity have become manifest in this class of materials that discourage us from pursuing these materials further.

  1. Method for simultaneously coating a plurality of filaments

    DOE Patents [OSTI]

    Miller, Paul A. (1004 Matia Ct. NE., Albuquerque, NM 87123); Pochan, Paul D. (3308 Morris St. NE., #11, Albuquerque, NM 87111); Siegal, Michael P. (9900 Spain NE., Apt. W-2123, Albuquerque, NM 87111); Dominguez, Frank (11341 Academy Ridge Rd. NE., Albuquerque, NM 87111)

    1995-01-01

    Methods and apparatuses for coating materials, and the products and compositions produced thereby. Substances, such as diamond or diamond-like carbon, are deposited onto materials, such as a filament or a plurality of filaments simultaneously, using one or more cylindrical, inductively coupled, resonator plasma reactors.

  2. GALAXY SPIN ALIGNMENT IN FILAMENTS AND SHEETS: OBSERVATIONAL EVIDENCE

    SciTech Connect (OSTI)

    Tempel, Elmo; Libeskind, Noam I. E-mail: nlibeskind@aip.de

    2013-10-01

    The properties of galaxies are known to be affected by their environment. One important question is how their angular momentum reflects the surrounding cosmic web. We use the Sloan Digital Sky Survey to investigate the spin axes of spiral and elliptical galaxies relative to their surrounding filament/sheet orientations. To detect filaments, a marked point process with interactions (the {sup B}isous model{sup )} is used. Sheets are found by detecting 'flattened' filaments. The minor axes of ellipticals are found to be preferentially perpendicular to hosting filaments. A weak correlation is found with sheets. These findings are consistent with the notion that elliptical galaxies formed via mergers, which predominantly occurred along the filaments. The spin axis of spiral galaxies is found to align with the host filament, with no correlation between spiral spin and sheet normal. When examined as a function of distance from the filament axis, a much stronger correlation is found in the outer parts, suggesting that the alignment is driven by the laminar infall of gas from sheets to filaments. When compared with numerical simulations, our results suggest that the connection between dark matter halo and galaxy spin is not straightforward. Our results provide an important input to the understanding of how galaxies acquire their angular momentum.

  3. Process for the production of superconductor containing filaments

    DOE Patents [OSTI]

    Tuominen, Olli P. (Candler, NC); Hoyt, Matthew B. (Arden, NC); Mitchell, David F. (Asheville, NC); Morgan, Carol W. (Asheville, NC); Roberts, Clyde Gordon (Asheville, NC); Tyler, Robert A. (Canton, NC)

    2002-01-01

    Superconductor containing filaments having embedments of superconducting material surrounded by a rayon matrix are formed by preparing a liquid suspension which contains at least 10 weight percent superconducting material; forming a multicomponent filament having a core of the suspension and a viscose sheath which contains cellulose xanthate; and thereafter, regenerating cellulose from the cellulose xanthate to form a rayon matrix.

  4. Method for simultaneously coating a plurality of filaments

    DOE Patents [OSTI]

    Miller, P.A.; Pochan, P.D.; Siegal, M.P.; Dominguez, F.

    1995-07-11

    Methods and apparatuses are disclosed for coating materials, and the products and compositions produced thereby. Substances, such as diamond or diamond-like carbon, are deposited onto materials, such as a filament or a plurality of filaments simultaneously, using one or more cylindrical, inductively coupled, resonator plasma reactors. 3 figs.

  5. Conduction in alumina with atomic scale copper filaments

    SciTech Connect (OSTI)

    Xu, Xu; Liu, Jie; Anantram, M. P.

    2014-10-28

    The conductance of atomic scale filaments with three and seven Cu atoms in ?-alumina are calculated using ab initio density functional theory. We find that the filament with 3 Cu atoms is sufficient to increase the conductance of 1.3?nm thick alumina film by more than 10{sup 3} times in linear response. As the applied voltage increases, the current quickly saturates and differential resistance becomes negative. Compared to the filament with three Cu atoms, while the conductance of the filament with seven Cu atoms is comparable in linear response, they carry as much as twenty times larger current at large biases. The electron transport is analyzed based on local density of states, and the negative differential resistance in the seven Cu filaments occurs due to their narrow bandwidth.

  6. Structure-Property Relationship in Metal Carbides and Bimetallic Alloys

    SciTech Connect (OSTI)

    Chen, Jingguan

    2014-03-04

    The primary objective of our DOE/BES sponsored research is to use carbide and bimetallic catalysts as model systems to demonstrate the feasibility of tuning the catalytic activity, selectivity and stability. Our efforts involve three parallel approaches, with the aim at studying single crystal model surfaces and bridging the materials gap and pressure gap between fundamental surface science studies and real world catalysis. The utilization of the three parallel approaches has led to the discovery of many intriguing catalytic properties of carbide and bimetallic surfaces and catalysts. During the past funding period we have utilized these combined research approaches to explore the possibility of predicting and verifying bimetallic and carbide combinations with enhanced catalytic activity, selectivity and stability.

  7. Pulsed energy synthesis and doping of silicon carbide

    DOE Patents [OSTI]

    Truher, J.B.; Kaschmitter, J.L.; Thompson, J.B.; Sigmon, T.W.

    1995-06-20

    A method for producing beta silicon carbide thin films by co-depositing thin films of amorphous silicon and carbon onto a substrate is disclosed, whereafter the films are irradiated by exposure to a pulsed energy source (e.g. excimer laser) to cause formation of the beta-SiC compound. Doped beta-SiC may be produced by introducing dopant gases during irradiation. Single layers up to a thickness of 0.5-1 micron have been produced, with thicker layers being produced by multiple processing steps. Since the electron transport properties of beta silicon carbide over a wide temperature range of 27--730 C is better than these properties of alpha silicon carbide, they have wide application, such as in high temperature semiconductors, including HETEROJUNCTION-junction bipolar transistors and power devices, as well as in high bandgap solar arrays, ultra-hard coatings, light emitting diodes, sensors, etc.

  8. Pulsed energy synthesis and doping of silicon carbide

    DOE Patents [OSTI]

    Truher, Joel B. (San Rafael, CA); Kaschmitter, James L. (Pleasanton, CA); Thompson, Jesse B. (Brentwood, CA); Sigmon, Thomas W. (Beaverton, OR)

    1995-01-01

    A method for producing beta silicon carbide thin films by co-depositing thin films of amorphous silicon and carbon onto a substrate, whereafter the films are irradiated by exposure to a pulsed energy source (e.g. excimer laser) to cause formation of the beta-SiC compound. Doped beta-SiC may be produced by introducing dopant gases during irradiation. Single layers up to a thickness of 0.5-1 micron have been produced, with thicker layers being produced by multiple processing steps. Since the electron transport properties of beta silicon carbide over a wide temperature range of 27.degree.-730.degree. C. is better than these properties of alpha silicon carbide, they have wide application, such as in high temperature semiconductors, including hetero-junction bipolar transistors and power devices, as well as in high bandgap solar arrays, ultra-hard coatings, light emitting diodes, sensors, etc.

  9. The growth mechanism of grain boundary carbide in Alloy 690

    SciTech Connect (OSTI)

    Li, Hui; Xia, Shuang; Zhou, Bangxin; Peng, Jianchao

    2013-07-15

    The growth mechanism of grain boundary M{sub 23}C{sub 6} carbides in nickel base Alloy 690 after aging at 715 C was investigated by high resolution transmission electron microscopy. The grain boundary carbides have coherent orientation relationship with only one side of the matrix. The incoherent phase interface between M{sub 23}C{sub 6} and matrix was curved, and did not lie on any specific crystal plane. The M{sub 23}C{sub 6} carbide transforms from the matrix phase directly at the incoherent interface. The flat coherent phase interface generally lies on low index crystal planes, such as (011) and (111) planes. The M{sub 23}C{sub 6} carbide transforms from a transition phase found at curved coherent phase interface. The transition phase has a complex hexagonal crystal structure, and has coherent orientation relationship with matrix and M{sub 23}C{sub 6}: (111){sub matrix}//(0001){sub transition}//(111){sub carbide}, <112{sup }>{sub matrix}//<21{sup }10>{sub transition}//<112{sup }>{sub carbide}. The crystal lattice constants of transition phase are c{sub transition}=?(3)a{sub matrix} and a{sub transition}=?(6)/2a{sub matrix}. Based on the experimental results, the growth mechanism of M{sub 23}C{sub 6} and the formation mechanism of transition phase are discussed. - Highlights: A transition phase was observed at the coherent interfaces of M{sub 23}C{sub 6} and matrix. The transition phase has hexagonal structure, and is coherent with matrix and M{sub 23}C{sub 6}. The M{sub 23}C{sub 6} transforms from the matrix directly at the incoherent phase interface.

  10. Method for forming fibrous silicon carbide insulating material

    DOE Patents [OSTI]

    Wei, George C. (Oak Ridge, TN)

    1984-01-01

    A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.

  11. Process for synthesizing titanium carbide, titanium nitride and titanium carbonitride

    DOE Patents [OSTI]

    Koc, Rasit (Lakewood, CO); Glatzmaier, Gregory C. (Boulder, CO)

    1995-01-01

    A process for synthesizing titanium carbide, titanium nitride or titanium carbonitride. The process comprises placing particles of titanium, a titanium salt or titanium dioxide within a vessel and providing a carbon-containing atmosphere within the vessel. The vessel is heated to a pyrolysis temperature sufficient to pyrolyze the carbon to thereby coat the particles with a carbon coating. Thereafter, the carbon-coated particles are heated in an inert atmosphere to produce titanium carbide, or in a nitrogen atmosphere to produce titanium nitride or titanium carbonitride, with the heating being of a temperature and time sufficient to produce a substantially complete solid solution.

  12. Process for synthesizing titanium carbide, titanium nitride and titanium carbonitride

    DOE Patents [OSTI]

    Koc, R.; Glatzmaier, G.C.

    1995-05-23

    A process is disclosed for synthesizing titanium carbide, titanium nitride or titanium carbonitride. The process comprises placing particles of titanium, a titanium salt or titanium dioxide within a vessel and providing a carbon-containing atmosphere within the vessel. The vessel is heated to a pyrolysis temperature sufficient to pyrolyze the carbon to thereby coat the particles with a carbon coating. Thereafter, the carbon-coated particles are heated in an inert atmosphere to produce titanium carbide, or in a nitrogen atmosphere to produce titanium nitride or titanium carbonitride, with the heating being of a temperature and time sufficient to produce a substantially complete solid solution.

  13. Computational Approach to Photonic Drilling of Silicon Carbide

    SciTech Connect (OSTI)

    Samant, Anoop N; Daniel, Claus; Chand, Ronald H; Blue, Craig A; Dahotre, Narendra B

    2009-01-01

    The ability of lasers to carry out drilling processes in silicon carbide ceramic was investigated in this study. A JK 701 pulsed Nd:YAG laser was used for drilling through the entire depth of silicon carbide plates of different thicknesses. The laser parameters were varied in different combinations for a well controlled drilling through the entire thickness of the SiC plates. A drilling model incorporating effects of various physical phenomena such as decomposition, evaporation induced recoil pressure, and surface tension was developed. Such comprehensive model was capable of advance prediction of the energy and time required for drilling a hole through any desired depth of material.

  14. Process for forming silicon carbide films and microcomponents

    DOE Patents [OSTI]

    Hamza, A.V.; Balooch, M.; Moalem, M.

    1999-01-19

    Silicon carbide films and microcomponents are grown on silicon substrates at surface temperatures between 900 K and 1700 K via C{sub 60} precursors in a hydrogen-free environment. Selective crystalline silicon carbide growth can be achieved on patterned silicon-silicon oxide samples. Patterned SiC films are produced by making use of the high reaction probability of C{sub 60} with silicon at surface temperatures greater than 900 K and the negligible reaction probability for C{sub 60} on silicon dioxide at surface temperatures less than 1250 K. 5 figs.

  15. Process for preparing fine grain titanium carbide powder

    DOE Patents [OSTI]

    Janney, M.A.

    1985-03-12

    A method for preparing finely divided titanium carbide powder in which an organotitanate is reacted with a carbon precursor polymer to provide an admixture of the titanium and the polymer at a molecular level due to a crosslinking reaction between the organotitanate and the polymer. The resulting gel is dried, pyrolyzed to drive off volatile components and provide carbon. The resulting solids are then heated at an elevated temperature to convert the titanium and carbon to high-purity titanium carbide powder in a submicron size range.

  16. Process for forming silicon carbide films and microcomponents

    DOE Patents [OSTI]

    Hamza, Alex V. (Livermore, CA); Balooch, Mehdi (Berkeley, CA); Moalem, Mehran (Berkeley, CA)

    1999-01-01

    Silicon carbide films and microcomponents are grown on silicon substrates at surface temperatures between 900 K and 1700 K via C.sub.60 precursors in a hydrogen-free environment. Selective crystalline silicon carbide growth can be achieved on patterned silicon-silicon oxide samples. Patterned SiC films are produced by making use of the high reaction probability of C.sub.60 with silicon at surface temperatures greater than 900 K and the negligible reaction probability for C.sub.60 on silicon dioxide at surface temperatures less than 1250 K.

  17. Process for preparing fine grain titanium carbide powder

    DOE Patents [OSTI]

    Janey, Mark A. (Concord, TN)

    1986-01-01

    A method for preparing finely divided titanium carbide powder in which an organotitanate is reacted with a carbon precursor polymer to provide an admixture of the titanium and the polymer at a molecular-level due to a crosslinking reaction between the organotitanate and the polymer. The resulting gel is dried, pyrolyzed to drive off volatile components and provide carbon. The resulting solids are then heated at an elevated temperature to convert the titanium and carbon to high-purity titanium carbide powder in a submicron size range.

  18. Method for forming fibrous silicon carbide insulating material

    DOE Patents [OSTI]

    Wei, G.C.

    1983-10-12

    A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.

  19. ERUPTION OF A SOLAR FILAMENT CONSISTING OF TWO THREADS

    SciTech Connect (OSTI)

    Bi Yi; Jiang Yunchun; Li Haidong; Hong Junchao; Zheng Ruisheng E-mail: jyc@ynao.ac.cn

    2012-10-10

    The trigger and driving mechanism for the eruption of a filament consisting of two dark threads was studied with unprecedented high cadence and resolution of He II 304 A observations made by the Atmospheric Imagining Assembly (AIA) on board the Solar Dynamics Observatory (SDO) and the observations made by the Solar Magnetic Activity Research Telescope and the Extreme Ultraviolet Imager (EUVI) telescope on board the Solar Terrestrial Relations Observatory Ahead (STEREO-A). The filament was located at the periphery of the active region NOAA 11228 and erupted on 2011 June 6. At the onset of the eruption, a turbulent filament thread was found to be heated and to elongate in stride over a second one. After it rose slowly, most interestingly, the elongating thread was driven to contact and interact with the second one, and it then erupted with its southern leg being wrapped by a newly formed thread produced by the magnetic reconnection between fields carried by the two threads. Combining the observations from STEREO-A/EUVI and SDO/AIA 304 A images, the three-dimensional shape of the axis of the filament was obtained and it was found that only the southern leg of the eruptive filament underwent rotation. We suggest that the eruption was triggered by the reconnection of the turbulent filament thread and the surrounding magnetic field, and that it was mainly driven by the kink instability of the southern leg of the eruptive filament that possessed a more twisted field introduced by the reconnection-produced thread.

  20. ORIGIN OF THE DENSE CORE MASS FUNCTION IN CONTRACTING FILAMENTS

    SciTech Connect (OSTI)

    Myers, Philip C.

    2013-02-20

    Mass functions of starless dense cores (CMFs) may arise from contraction and dispersal of core-forming filaments. In an illustrative model, a filament contracts radially by self-gravity, increasing the mass of its cores. During this contraction, FUV photoevaporation and ablation by shocks and winds disperse filament gas and limit core growth. The stopping times of core growth are described by a waiting-time distribution. The initial filament column density profile and the resulting CMF each match recent Herschel observations in detail. Then low-mass cores have short growth ages and arise from the innermost filament gas, while massive cores have long growth ages and draw from more extended filament gas. The model fits the initial density profile and CMF best for mean core density 2 Multiplication-Sign 10{sup 4} cm{sup -3} and filament dispersal timescale 0.5 Myr. Then the typical core mass, radius, mean column density, and contraction speed are respectively 0.8 solar masses, 0.06 pc, 6 Multiplication-Sign 10{sup 21} cm{sup -2}, and 0.07 km s{sup -1}, also in accord with observed values.

  1. Boron-carbide-aluminum and boron-carbide-reactive metal cermets. [B/sub 4/C-Al

    DOE Patents [OSTI]

    Halverson, D.C.; Pyzik, A.J.; Aksay, I.A.

    1985-05-06

    Hard, tough, lighweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidated step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modules of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi..sqrt..in. These composites and methods can be used to form a variety of structural elements.

  2. Method for homogenizing alloys susceptible to the formation of carbide stringers and alloys prepared thereby

    DOE Patents [OSTI]

    Braski, David N. (Oak Ridge, TN); Leitnaker, James M. (Kingston, TN)

    1980-01-01

    A novel fabrication procedure prevents or eliminates the reprecipitation of segregated metal carbides such as stringers in Ti-modified Hastelloy N and stainless steels to provide a novel alloy having carbides uniformly dispersed throughout the matrix. The fabrication procedure is applicable to other alloys prone to the formation of carbide stringers. The process comprises first annealing the alloy at a temperature above the single phase temperature for sufficient time to completely dissolve carbides and then annealing the single phase alloy for an additional time to prevent the formation of carbide stringers upon subsequent aging or thermomechanical treatment.

  3. Nuclear breeder reactor fuel element with silicon carbide getter

    DOE Patents [OSTI]

    Christiansen, David W. (Kennewick, WA); Karnesky, Richard A. (Richland, WA)

    1987-01-01

    An improved cesium getter 28 is provided in a breeder reactor fuel element or pin in the form of an extended surface area, low density element formed in one embodiment as a helically wound foil 30 located with silicon carbide, and located at the upper end of the fertile material upper blanket 20.

  4. Method of deposition of silicon carbide layers on substrates

    DOE Patents [OSTI]

    Angelini, P.; DeVore, C.E.; Lackey, W.J.; Blanco, R.E.; Stinton, D.P.

    1982-03-19

    A method for direct chemical vapor deposition of silicon carbide to substrates, especially nuclear waste particles, is provided by the thermal decomposition of methylsilane at 800 to 1050/sup 0/C when the substrates have been confined within a suitable coating environment.

  5. Tungsten-yttria carbide coating for conveying copper

    DOE Patents [OSTI]

    Rothman, Albert J. (Livermore, CA)

    1993-01-01

    A method is provided for providing a carbided-tungsten-yttria coating on the interior surface of a copper vapor laser. The surface serves as a wick for the condensation of liquid copper to return the condensate to the interior of the laser for revolatilization.

  6. Collective alignment of polar filaments by molecular motors.

    SciTech Connect (OSTI)

    Ziebert, F.; Aranson, I. S.; Vershinin, M.; Gross, S. P.; Materials Science Division; Univ. of California at Irvine

    2009-04-01

    We study the alignment of polar biofilaments, such as microtubules and actin, subject to the action of multiple molecular motors attached simultaneously to more than one filament. Focusing on a paradigm model of only two filaments interacting with multiple motors, we were able to investigate in detail the alignment dynamics. While almost no alignment occurs in the case of a single motor, the filaments become rapidly aligned due to the collective action of the motors. Our analysis shows that the alignment time is governed by the number of bound motors and the magnitude of the motors stepping fluctuations. We predict that the time scale of alignment is in the order of seconds, much faster than that reported for passive crosslink-induced bundling. In vitro experiments on the alignment of microtubules by multiple-motor covered beads are in qualitative agreement. We also discuss another mode of fast alignment of filaments, namely the cooperation between motors and passive crosslinks.

  7. Apparatus for coating and impregnating filament with resin

    DOE Patents [OSTI]

    Robinson, S.C.; Pollard, R.E.

    1986-12-17

    The present invention is directed to an apparatus for evenly coating and impregnating a filament with binder material. Dimension control and repeatability of the coating and impregnating characteristics are obtained with the apparatus.

  8. THREE-DIMENSIONAL SHAPE AND EVOLUTION OF TWO ERUPTIVE FILAMENTS

    SciTech Connect (OSTI)

    Li Ting; Zhang Jun; Yang Shuhong; Zhao Hui E-mail: zjun@nao.cas.c E-mail: v00975@phys.nthu.edu.t

    2010-09-01

    On 2009 September 26, a dramatic and large filament (LF) eruption and a small filament (SF) eruption were observed in the He II 304 A line by the two EUVI telescopes aboard the STEREO A and B spacecraft. The LF heads out into space and becomes the bright core of a gradual coronal mass ejection (CME), while the eruption of the SF is characterized by motions of the filament materials. Using stereoscopic analysis of EUVI data, we reconstruct the three-dimensional shape and evolution of two eruptive filaments. For the first time, we investigate the true velocities and accelerations of 12 points along the axis of the LF, and find that the velocity and acceleration vary with the measured location. The highest points among the 12 points are the fastest in the first half hour, and then the points at the low-latitude leg of the LF become the fastest. For the SF, it is an asymmetric whip-like filament eruption, and the downward motions of the material lead to the disappearance of the former high-latitude endpoint and the formation of a new low-latitude endpoint. Based on the temporal evolution of the two filaments, we infer that the two filaments lie in the same filament channel. By combining the EUVI, COR1, and COR2 data of STEREO A together, we find that there is no impulsive or fast acceleration in this event. It displays a weak and persistent acceleration for more than 17 hr. The average velocity and acceleration of the LF are 101.8 km s{sup -1} and 2.9 m s{sup -2}, respectively. The filament eruptions are associated with a slow CME with an average velocity of 177.4 km s{sup -1}. The velocity of the CME is nearly 1.6 times as large as that of the filament material. This event is one example of a gradual filament eruption associated with a gradual CME. In addition, the moving direction of the LF changes from a non-radial to a nearly radial direction with a variation of inclination angle of nearly 38.{sup 0}2.

  9. Optically Directed Assembly of Continuous Mesoscale Filaments (Journal

    Office of Scientific and Technical Information (OSTI)

    Article) | SciTech Connect Optically Directed Assembly of Continuous Mesoscale Filaments Citation Details In-Document Search Title: Optically Directed Assembly of Continuous Mesoscale Filaments Authors: Bahns, J. T. ; Sankaranarayanan, S. K. R. S. ; Gray, S. K. ; Chen, L. Publication Date: 2011-02-28 OSTI Identifier: 1099937 Type: Publisher's Accepted Manuscript Journal Name: Physical Review Letters Additional Journal Information: Journal Volume: 106; Journal Issue: 9; Journal ID: ISSN

  10. Detection and characterization of multi-filament evolution during resistive

    Office of Scientific and Technical Information (OSTI)

    switching. (Journal Article) | SciTech Connect Detection and characterization of multi-filament evolution during resistive switching. Citation Details In-Document Search Title: Detection and characterization of multi-filament evolution during resistive switching. Abstract not provided. Authors: Mickel, Patrick R. ; Lohn, Andrew ; Marinella, Matthew Publication Date: 2014-05-01 OSTI Identifier: 1145719 Report Number(s): SAND2014-4055J 518013 DOE Contract Number: DE-AC04-94AL85000 Resource

  11. Filamentous Carbon Particles for Cleaning Oil Spills - Energy Innovation

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Portal Industrial Technologies Industrial Technologies Hydrogen and Fuel Cell Hydrogen and Fuel Cell Find More Like This Return to Search Filamentous Carbon Particles for Cleaning Oil Spills DOE Grant Recipients Contact GRANT About This Technology Technology Marketing Summary The invention provides methods and apparatus for the creation of carbon filaments used for cleaning oil spills. Crude oil and other petroleum products can cause severe damage to the environment and wildlife when spilled

  12. 7-forming, superconducting filaments through bicomponent dry spinning

    DOE Patents [OSTI]

    Tuominen, Olli P. (Ogden, UT); Morgan, Carol W. (Asheville, NC); Burlone, Dominick A. (Asheville, NC); Blankenship, Keith V. (Asheville, NC)

    2001-01-01

    Fibers which contain potentially superconducting material are dry spun by the steps of preparing a suspension of potentially superconducting powder in a thickened solvent; preparing a solution of fiber-forming polymer; supplying the suspension and the solution to a spinning apparatus; in the spinning apparatus, arranging the solution and the suspension in a bicomponent arrangement; extruding the arranged solution and suspension from a spinneret as a bicomponent filament; and removing the solvent from the filament.

  13. STATUS OF HIGH FLUX ISOTOPE REACTOR IRRADIATION OF SILICON CARBIDE/SILICON CARBIDE JOINTS

    SciTech Connect (OSTI)

    Katoh, Yutai; Koyanagi, Takaaki; Kiggans, Jim; Cetiner, Nesrin; McDuffee, Joel

    2014-09-01

    Development of silicon carbide (SiC) joints that retain adequate structural and functional properties in the anticipated service conditions is a critical milestone toward establishment of advanced SiC composite technology for the accident-tolerant light water reactor (LWR) fuels and core structures. Neutron irradiation is among the most critical factors that define the harsh service condition of LWR fuel during the normal operation. The overarching goal of the present joining and irradiation studies is to establish technologies for joining SiC-based materials for use as the LWR fuel cladding. The purpose of this work is to fabricate SiC joint specimens, characterize those joints in an unirradiated condition, and prepare rabbit capsules for neutron irradiation study on the fabricated specimens in the High Flux Isotope Reactor (HFIR). Torsional shear test specimens of chemically vapor-deposited SiC were prepared by seven different joining methods either at Oak Ridge National Laboratory or by industrial partners. The joint test specimens were characterized for shear strength and microstructures in an unirradiated condition. Rabbit irradiation capsules were designed and fabricated for neutron irradiation of these joint specimens at an LWR-relevant temperature. These rabbit capsules, already started irradiation in HFIR, are scheduled to complete irradiation to an LWR-relevant dose level in early 2015.

  14. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    SciTech Connect (OSTI)

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm{sup -3} (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial SiC materials are much lower due to phonon scattering by impurities (e.g., sintering aids located at the grain boundaries of these materials). The thermal conductivity of our SiC was determined using the laser flash method and it is 214 W/mK at 373 K and 64 W/mK at 1273 K. These values are very close to those of pure SiC and are much higher than those of SiC materials made by industrial processes. This SiC made by our LSI process meets the thermal properties required for use in high temperature heat exchanger. Cellulose and phenolic resin carbons lack the well-defined atomic structures associated with common carbon allotropes. Atomic-scale structure was studied using high resolution transmission electron microscopy (HRTEM), nitrogen gas adsorption and helium gas pycnometry. These studies revealed that cellulose carbon exhibits a very high degree of atomic disorder and angstrom-scale porosity. It has a density of only 93% of that of pure graphite, with primarily sp2 bonding character and a low concentration of graphene clusters. Phenolic resin carbon shows more structural order and substantially less angstrom-scale porosity. Its density is 98% of that of pure graphite, and Fourier transform analysis of its TEM micrographs has revealed high concentrations of sp3 diamond and sp2 graphene nano-clusters. This is the first time that diamond nano-clusters have been observed in carbons produced from phenolic resin. AC and DC electrical measurements were made to follow the thermal conversion of microcrystalline cellulose to carbon. This study identifies five regions of electrical conductivity that can be directly correlated to the chemical decomposition and microstructural evolution during carbonization. In Region I, a decrease in overall AC conductivity occurs due to the initial loss of the polar groups from cellulose molecules. In Region II, the AC conductivity starts to increase with heat treatment temperature due to the formation and growth of conducting carbon clusters. In Region III, a further increase of AC conductivity with increasing heat treatment temperature is obs

  15. Filamentation of Beam-Shaped Femtosecond Laser Pulses

    SciTech Connect (OSTI)

    Polynkin, Pavel; Kolesik, Miroslav; Moloney, Jerome

    2010-10-08

    When ultra-intense and ultra-short optical pulses propagate in transparent dielectrics, the dynamic balance between multiple linear and nonlinear effects results in the generation of laser filaments. These peculiar objects have numerous interesting properties and can be potentially used in a variety of applications from remote sensing to the optical pulse compression down to few optical cycles to guiding lightning discharges away from sensitive sites. Materializing this practical potential is not straightforward owing to the complexity of the physical picture of filamentation. In this paper, we discuss recent experiments on using beam shaping as a means of control over the filament formation and dynamics. Two particular beam shapes that we have investigated so far are Bessel and Airy beams. The diffraction-free propagation of femtosecond Bessel beams allows for the creation of extended plasma channels in air. These extended filaments can be used for the generation of energetic optical pulses with the duration in the few-cycle range. In the case of filamentation of femtosecond Airy beams, the self-bending property of these beams allows for the creation of curved filaments. This is a new regime of the intense laser-pulse propagation in which the linear self-bending property of the beam competes against the nonlinear self-channeling. The bent filaments generated by ultra-intense Airy beams emit forward-propagating broadband radiation. Analysis of the spatial and spectral distribution of this emission provides for a valuable tool for analyzing the evolution of the ultra-intense optical pulse along the optical path.

  16. Dynamic Star Formation in the Massive DR21 Filament

    SciTech Connect (OSTI)

    Schneider, N.; Csengeri, T.; Bontemps, S.; Motte, F.; Simon, R.; Hennebelle, P.; Federrath, C.; Klessen, R.; /ZAH, Heidelberg /KIPAC, Menlo Park

    2010-08-25

    The formation of massive stars is a highly complex process in which it is unclear whether the star-forming gas is in global gravitational collapse or an equilibrium state supported by turbulence and/or magnetic fields. By studying one of the most massive and dense star-forming regions in the Galaxy at a distance of less than 3 kpc, i.e. the filament containing the well-known sources DR21 and DR21(OH), we attempt to obtain observational evidence to help us to discriminate between these two views. We use molecular line data from our {sup 13}CO 1 {yields} 0, CS 2 {yields} 1, and N{sub 2}H{sup +} 1 {yields} 0 survey of the Cygnus X region obtained with the FCRAO and CO, CS, HCO{sup +}, N{sub 2}H{sup +}, and H{sub 2}CO data obtained with the IRAM 30m telescope. We observe a complex velocity field and velocity dispersion in the DR21 filament in which regions of the highest column-density, i.e., dense cores, have a lower velocity dispersion than the surrounding gas and velocity gradients that are not (only) due to rotation. Infall signatures in optically thick line profiles of HCO{sup +} and {sup 12}CO are observed along and across the whole DR21 filament. By modelling the observed spectra, we obtain a typical infall speed of {approx}0.6 km s{sup -1} and mass accretion rates of the order of a few 10{sup -3} M{sub {circle_dot}} yr{sup -1} for the two main clumps constituting the filament. These massive clumps (4900 and 3300 M{sub {circle_dot}} at densities of around 10{sup 5} cm{sup -3} within 1 pc diameter) are both gravitationally contracting. The more massive of the clumps, DR21(OH), is connected to a sub-filament, apparently 'falling' onto the clump. This filament runs parallel to the magnetic field. Conclusions. All observed kinematic features in the DR21 filament (velocity field, velocity dispersion, and infall), its filamentary morphology, and the existence of (a) sub-filament(s) can be explained if the DR21 filament was formed by the convergence of flows on large scales and is now in a state of global gravitational collapse. Whether this convergence of flows originated from self-gravity on larger scales or from other processes cannot be determined by the present study. The observed velocity field and velocity dispersion are consistent with results from (magneto)-hydrodynamic simulations where the cores lie at the stagnation points of convergent turbulent flows.

  17. Decay of helical Kelvin waves on a quantum vortex filament

    SciTech Connect (OSTI)

    Van Gorder, Robert A.

    2014-07-15

    We study the dynamics of helical Kelvin waves moving along a quantum vortex filament driven by a normal fluid flow. We employ the vector form of the quantum local induction approximation (LIA) due to Schwarz. For an isolated filament, this is an adequate approximation to the full Hall-Vinen-Bekarevich-Khalatnikov dynamics. The motion of such Kelvin waves is both translational (along the quantum vortex filament) and rotational (in the plane orthogonal to the reference axis). We first present an exact closed form solution for the motion of these Kelvin waves in the case of a constant amplitude helix. Such solutions exist for a critical wave number and correspond exactly to the Donnelly-Glaberson instability, so perturbations of such solutions either decay to line filaments or blow-up. This leads us to consider helical Kelvin waves which decay to line filaments. Unlike in the case of constant amplitude helical solutions, the dynamics are much more complicated for the decaying helical waves, owing to the fact that the rate of decay of the helical perturbations along the vortex filament is not constant in time. We give an analytical and numerical description of the motion of decaying helical Kelvin waves, from which we are able to ascertain the influence of the physical parameters on the decay, translational motion along the filament, and rotational motion, of these waves (all of which depend nonlinearly on time). One interesting finding is that the helical Kelvin waves do not decay uniformly. Rather, such waves decay slowly for small time scales, and more rapidly for large time scales. The rotational and translational velocity of the Kelvin waves depend strongly on this rate of decay, and we find that the speed of propagation of a helical Kelvin wave along a quantum filament is large for small time while the wave asymptotically slows as it decays. The rotational velocity of such Kelvin waves along the filament will increase over time, asymptotically reaching a finite value. These decaying Kelvin waves correspond to wave number below the critical value for the Donnelly-Glaberson instability, and hence our results on the Schwarz quantum LIA correspond exactly to what one would expect from prior work on the Donnelly-Glaberson instability.

  18. Diamond-Silicon Carbide Composite And Method For Preparation Thereof

    DOE Patents [OSTI]

    Qian, Jiang (Los Alamos, NM); Zhao, Yusheng (Los Alamos, NM)

    2005-09-06

    Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=5-8 GPa, T=1400K-2300K) to form composites having high fracture toughness. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPa.multidot.m.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness. X-ray diffraction patterns and Raman spectra indicate that amorphous silicon is partially transformed into nanocrystalline silicon at 5 GPa/873K, and nanocrystalline silicon carbide forms at higher temperatures.

  19. Protective coating for alumina-silicon carbide whisker composites

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN)

    1989-01-01

    Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.

  20. TRANSIENT BRIGHTENINGS ASSOCIATED WITH FLUX CANCELLATION ALONG A FILAMENT CHANNEL

    SciTech Connect (OSTI)

    Wang, Y.-M.; Muglach, K. E-mail: karin.muglach@nasa.gov

    2013-02-15

    Filament channels coincide with large-scale polarity inversion lines of the photospheric magnetic field, where flux cancellation continually takes place. High-cadence Solar Dynamics Observatory (SDO) images recorded in He II 30.4 nm and Fe IX 17.1 nm during 2010 August 22 reveal numerous transient brightenings occurring along the edge of a filament channel within a decaying active region, where SDO line-of-sight magnetograms show strong opposite-polarity flux in close contact. The brightenings are elongated along the direction of the filament channel, with linear extents of several arcseconds, and typically last a few minutes; they sometimes have the form of multiple two-sided ejections with speeds on the order of 100 km s{sup -1}. Remarkably, some of the brightenings rapidly develop into larger scale events, forming sheetlike structures that are eventually torn apart by the diverging flows in the filament channel and ejected in opposite directions. We interpret the brightenings as resulting from reconnections among filament-channel field lines having one footpoint located in the region of canceling flux. In some cases, the flow patterns that develop in the channel may bring successive horizontal loops together and cause a cascade to larger scales.

  1. Process for growing silicon carbide whiskers by undercooling

    DOE Patents [OSTI]

    Shalek, P.D.

    1987-10-27

    A method of growing silicon carbide whiskers, especially in the [beta] form, is disclosed using a heating schedule wherein the temperature of the atmosphere in the growth zone of a furnace is first heated to or beyond the growth temperature and then is cooled to or below the growth temperature to induce nucleation of whiskers at catalyst sites at a desired point in time which results in the selection. 3 figs.

  2. Process for growing silicon carbide whiskers by undercooling

    DOE Patents [OSTI]

    Shalek, Peter D. (Los Alamos, NM)

    1987-01-01

    A method of growing silicon carbide whiskers, especially in the .beta. form, using a heating schedule wherein the temperature of the atmosphere in the growth zone of a furnace is first heated to or beyond the growth temperature and then is cooled to or below the growth temperature to induce nucleation of whiskers at catalyst sites at a desired point in time which results in the selection.

  3. Ceramic composites reinforced with modified silicon carbide whiskers

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN); Lindemer, Terrence B. (Oak Ridge, TN)

    1990-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  4. Method for removing oxide contamination from silicon carbide powders

    DOE Patents [OSTI]

    Brynestad, J.; Bamberger, C.E.

    1984-08-01

    The described invention is directed to a method for removing oxide contamination in the form of oxygen-containing compounds such as SiO/sub 2/ and B/sub 2/O/sub 3/ from a charge of finely divided silicon carbide. The silicon carbide charge is contacted with a stream of hydrogen fluoride mixed with an inert gas carrier such as argon at a temperature in the range of about 200/sup 0/ to 650/sup 0/C. The oxides in the charge react with the heated hydrogen fluoride to form volatile gaseous fluorides such as SiF/sub 4/ and BF/sub 3/ which pass through the charge along with unreacted hydrogen fluoride and the carrier gas. Any residual gaseous reaction products and hydrogen fluoride remaining in the charge are removed by contacting the charge with the stream of inert gas which also cools the powder to room temperature. The removal of the oxygen contamination by practicing the present method provides silicon carbide powders with desirable pressing and sintering characteristics. 1 tab.

  5. Effect of filament supports on emissive probe measurements

    SciTech Connect (OSTI)

    Wang, X.; Howes, C. T.; Horanyi, M.; Robertson, S.

    2013-01-15

    We have constructed an emissive probe with a thin tungsten filament spot-welded across two nickel wires insulated with ceramic paint. We show that the ceramic supports covering the nickel wires have a large effect on the potential measurements in low-density plasmas. It is found that the potential measured by the emissive probe is more negative than the potential derived from a Langmuir probe current-voltage (I-V) characteristic curve when the plasma density is so low that the emitting filament remains immersed in the sheaths of the ceramic supports. The length of the filament L needs to be larger than about 2 Debye lengths (L > 2{lambda}{sub De}) in order to avoid the influence of the ceramic supports and to achieve reliable plasma potential measurements using emissive probes.

  6. Investigation on collisions of filament pairs in dielectric barrier discharge

    SciTech Connect (OSTI)

    Dong, Lifang; Zhang, Chao; Li, Ben; Zhang, Xinpu; He, Yafeng; Li, Xuechen; Hebei Key Laboratory of Optic-electronic Information Materials, Baoding 071002

    2013-12-15

    Collisions of filament pairs in a hexagonal superlattice pattern in dielectric barrier discharge are investigated on different timescales. In the evolution of the pattern, the space scale of each hexagon cell decreases with the increasing voltage. The duration of one collision is seven half voltage cycles at least. Two stable orientations of a pair are approximately perpendicular to each other and the orientational changes occurring during the entire colliding process should be a multiple of 30. The time interval between two consecutive collisions decreases with the increasing voltage. The distance between the paired spots decreases nonmonotonically. Based on the discharge order of the pattern, it is inferred that the collision should be the interaction between a discharging filament and the surface charges deposited by another discharged filament, and the nonmonotonic decrease of distance D is explained.

  7. Fact Sheet: Award-Winning Silicon Carbide Power Electronics (October 2012)

    Energy Savers [EERE]

    | Department of Energy Award-Winning Silicon Carbide Power Electronics (October 2012) Fact Sheet: Award-Winning Silicon Carbide Power Electronics (October 2012) Operating at high temperatures and with reduced energy losses, two silicon carbide power electronics (PE) projects were awarded the prestigious R&D 100 Award. This technology was funded as a Small Business Innovation Research project as part of DOE's Energy Storage Program effort to develop and commercialize a new generation of

  8. PRELIMINARY SURVEY OF THE UNION CARBIDE CORPORATION METALS DIVISION PLANT, NIAGARA FALLS, NEW YORK

    Office of Legacy Management (LM)

    e - .' N"lr 7% PRELIMINARY SURVEY OF THE UNION CARBIDE CORPORATION METALS DIVISION PLANT, NIAGARA FALLS, NEW YORK Work performed by the Health and Safety Research Division Oak Ridge Natjonal Laboratory Oak Ridge, Tennessee 37830 December 1980 OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for the DEPARTMENT OF ENERGY as part of the Formerly Utilized Sites-- Remedial Action Program PRELIMINARY SURVEY OF THE UNION CARBIDE CORPORATION METALS DIVISION PLANT, NIAGARA FALLS,

  9. Dual-frequency terahertz emission from splitting filaments induced by lens tilting in air

    SciTech Connect (OSTI)

    Zhang, Zhelin; Chen, Yanping Yang, Liu; Yuan, Xiaohui; Liu, Feng; Chen, Min; Xu, Jianqiu; Zhang, Jie; Sheng, Zhengming

    2014-09-08

    Dual-frequency terahertz radiation from air-plasma filaments produced with two-color lasers in air has been demonstrated experimentally. When a focusing lens is tilted for a few degrees, it is shown that the laser filament evolves from a single one to two sub-filaments. Two independent terahertz sources emitted from the sub-filaments with different frequencies and polarizations are identified, where the frequency of terahertz waves from the trailing sub-filament is higher than that from the leading sub-filament.

  10. INSIGHTS INTO FILAMENT ERUPTION ONSET FROM SOLAR DYNAMICS OBSERVATORY OBSERVATIONS

    SciTech Connect (OSTI)

    Sterling, Alphonse C.; Moore, Ronald L.; Freeland, Samuel L. E-mail: ron.moore@nasa.gov

    2011-04-10

    We examine the buildup to and onset of an active region filament confined eruption of 2010 May 12, using EUV imaging data from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Array and line-of-sight magnetic data from the SDO Helioseismic and Magnetic Imager. Over the hour preceding eruption the filament undergoes a slow rise averaging {approx}3 km s{sup -1}, with a step-like trajectory. Accompanying a final rise step {approx}20 minutes prior to eruption is a transient preflare brightening, occurring on loops rooted near the site where magnetic field had canceled over the previous 20 hr. Flow-type motions of the filament are relatively smooth with speeds {approx}50 km s{sup -1} prior to the preflare brightening and appear more helical, with speeds {approx}50-100 km s{sup -1}, after that brightening. After a final plateau in the filament's rise, its rapid eruption begins, and concurrently an outer shell 'cocoon' of the filament material increases in emission in hot EUV lines, consistent with heating in a newly formed magnetic flux rope. The main flare brightenings start {approx}5 minutes after eruption onset. The main flare arcade begins between the legs of an envelope-arcade loop that is nearly orthogonal to the filament, suggesting that the flare results from reconnection among the legs of that loop. This progress of events is broadly consistent with flux cancellation leading to formation of a helical flux rope that subsequently erupts due to onset of a magnetic instability and/or runaway tether cutting.

  11. Synthesis of uranium nitride and uranium carbide powder by carbothermic reduction

    SciTech Connect (OSTI)

    Dunwoody, J.T.; Stanek, C.R.; McClellan, K.J.; Voit, S.L.; Volz, H.M.; Hickman, R.R.

    2007-07-01

    Uranium nitride and uranium carbide are being considered as high burnup fuels in next generation nuclear reactors and accelerated driven systems for the transmutation of nuclear waste. The same characteristics that make nitrides and carbides candidates for these applications (i.e. favorable thermal properties, mutual solubility of nitrides, etc.), also make these compositions candidate fuels for space nuclear reactors. In this paper, we discuss the synthesis and characterization of depleted uranium nitride and carbide for a space nuclear reactor program. Importantly, this project emphasized that to synthesize high quality uranium nitride and carbide, it is necessary to understand the exact stoichiometry of the oxide feedstock. (authors)

  12. Tunable carbon nanotube-tungsten carbide nanoparticles heterostructures by vapor deposition

    SciTech Connect (OSTI)

    Xia, Min; Guo, Hongyan; Ge, Changchun; Yan, Qingzhi Lang, Shaoting

    2014-05-14

    A simple, versatile route for the synthesis of carbon nanotube (CNT)-tungsten carbide nanoparticles heterostructures was set up via vapor deposition process. For the first time, amorphous CNTs (?-CNTs) were used to immobilized tungsten carbide nanoparticles. By adjusting the synthesis and annealing temperature, ?-CNTs/amorphous tungsten carbide, ?-CNTs/W{sub 2}C, and CNTs/W{sub 2}C/WC heterostructures were prepared. This approach provides an efficient method to attach other metal carbides and other nanoparticles to carbon nanotubes with tunable properties.

  13. Alignments of galaxies within cosmic filaments from SDSS DR7

    SciTech Connect (OSTI)

    Zhang, Youcai; Yang, Xiaohu; Wang, Huiyuan; Wang, Lei; Mo, H. J.; Van den Bosch, Frank C. E-mail: xyang@sjtu.edu.cn

    2013-12-20

    Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7, we examine the alignment between the orientation of galaxies and their surrounding large-scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments and strongly suggest that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

  14. Filamentation in air at 1550 nm : initial experimentation with new laser

    Office of Scientific and Technical Information (OSTI)

    source. (Conference) | SciTech Connect SciTech Connect Search Results Conference: Filamentation in air at 1550 nm : initial experimentation with new laser source. Citation Details In-Document Search Title: Filamentation in air at 1550 nm : initial experimentation with new laser source. We report air filamentation by a 1550 nm subpicosecond pulse. During filamentation, the continuum generated was less than expected. A large amount of third harmonic was also generated. Authors: Gruetzner,

  15. Irradiation and annealing of p-type silicon carbide

    SciTech Connect (OSTI)

    Lebedev, Alexander A.; Bogdanova, Elena V.; Grigor'eva, Maria V.; Lebedev, Sergey P. [A.F. Ioffe Physical-Technical Institute, St. Petersburg, 194021 (Russian Federation); Kozlovski, Vitaly V. [St. Petersburg State Polytechnic University, St. Petersburg, 195251 (Russian Federation)

    2014-02-21

    The development of the technology of semiconductor devices based on silicon carbide and the beginning of their industrial manufacture have made increasingly topical studies of the radiation hardness of this material on the one hand and of the proton irradiation to form high-receptivity regions on the other hand. This paper reports on a study of the carrier removal rate (V{sub d}) in p-6H-SiC under irradiation with 8 MeV protons and of the conductivity restoration in radiation- compensated epitaxial layers of various p-type silicon carbide polytypes. V{sub d} was determined by analysis of capacitance-voltage characteristics and from results of Hall effect measurements. It was found that the complete compensation of samples with the initial value of Na - Nd ? 1.5 10{sup 18} cm{sup ?3} occurs at an irradiation dose of ?1.1 10{sup 16} cm{sup ?2}. It is shown that specific features of the sublimation layer SiC (compared to CVD layers) are clearly manifested upon the gamma and electron irradiation and are hardly noticeable under the proton and neutron irradiation. It was also found that the radiation-induced compensation of SiC is retained after its annealing at ?1000C. The conductivity is almost completely restored at T ? 1200C. This character of annealing of the radiation compensation is independent of a silicon carbide polytype and the starting doping level of the epitaxial layer. The complete annealing temperatures considerably exceed the working temperatures of SiC-based devices. It is shown that the radiation compensation is a promising method in the technology of high-temperature devices based on SiC.

  16. Method of fabricating silicon carbide coatings on graphite surfaces

    DOE Patents [OSTI]

    Varacalle, D.J. Jr.; Herman, H.; Burchell, T.D.

    1994-07-26

    The vacuum plasma spray process produces well-bonded, dense, stress-free coatings for a variety of materials on a wide range of substrates. The process is used in many industries to provide for the excellent wear, corrosion resistance, and high temperature behavior of the fabricated coatings. In this application, silicon metal is deposited on graphite. This invention discloses the optimum processing parameters for as-sprayed coating qualities. The method also discloses the effect of thermal cycling on silicon samples in an inert helium atmosphere at about 1,600 C which transforms the coating to silicon carbide. 3 figs.

  17. Method of fabricating silicon carbide coatings on graphite surfaces

    DOE Patents [OSTI]

    Varacalle, Jr., Dominic J. (Idaho Falls, ID); Herman, Herbert (Port Jefferson, NY); Burchell, Timothy D. (Oak Ridge, TN)

    1994-01-01

    The vacuum plasma spray process produces well-bonded, dense, stress-free coatings for a variety of materials on a wide range of substrates. The process is used in many industries to provide for the excellent wear, corrosion resistance, and high temperature behavior of the fabricated coatings. In this application, silicon metal is deposited on graphite. This invention discloses the optimum processing parameters for as-sprayed coating qualities. The method also discloses the effect of thermal cycling on silicon samples in an inert helium atmosphere at about 1600.degree.C. which transforms the coating to silicon carbide.

  18. Silicon nitride/silicon carbide composite densified materials prepared using composite powders

    DOE Patents [OSTI]

    Dunmead, S.D.; Weimer, A.W.; Carroll, D.F.; Eisman, G.A.; Cochran, G.A.; Susnitzky, D.W.; Beaman, D.R.; Nilsen, K.J.

    1997-07-01

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  19. Method of enhanced lithiation of doped silicon carbide via high temperature annealing in an inert atmosphere

    SciTech Connect (OSTI)

    Hersam, Mark C.; Lipson, Albert L.; Bandyopadhyay, Sudeshna; Karmel, Hunter J; Bedzyk, Michael J

    2014-05-27

    A method for enhancing the lithium-ion capacity of a doped silicon carbide is disclosed. The method utilizes heat treating the silicon carbide in an inert atmosphere. Also disclosed are anodes for lithium-ion batteries prepared by the method.

  20. Infrared study on room-temperature atomic layer deposition of HfO{sub 2} using tetrakis(ethylmethylamino)hafnium and remote plasma-excited oxidizing agents

    SciTech Connect (OSTI)

    Kanomata, Kensaku [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Japan and Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Ohba, Hisashi; Pungboon Pansila, P.; Ahmmad, Bashir; Kubota, Shigeru; Hirahara, Kazuhiro; Hirose, Fumihiko, E-mail: fhirose@yz.yamagata-u.ac.jp [Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510 (Japan)

    2015-01-01

    Room-temperature atomic layer deposition (ALD) of HfO{sub 2} was examined using tetrakis (ethylmethylamino)hafnium (TEMAH) and remote plasma-excited water and oxygen. A growth rate of 0.26?nm/cycle at room temperature was achieved, and the TEMAH adsorption and its oxidization on HfO{sub 2} were investigated by multiple internal reflection infrared absorption spectroscopy. It was observed that saturated adsorption of TEMAH occurs at exposures of ?1??10{sup 5}?L (1 L?=?1??10{sup ?6} Torr s) at room temperature, and the use of remote plasma-excited water and oxygen vapor is effective in oxidizing the TEMAH molecules on the HfO{sub 2} surface, to produce OH sites. The infrared study suggested that HfOH plays a role as an adsorption site for TEMAH. The reaction mechanism of room temperature HfO{sub 2} ALD is discussed in this paper.

  1. Replacing precious metals with carbide catalysts for hydrogenation reactions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; Wang, Tiefeng

    2015-03-03

    Molybdenum carbide (Mo₂C and Ni/Mo₂C) catalysts were compared with Pd/SiO₂ for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO₂, Mo₂C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo₂C could be completely regenerated by H₂ treatment at 723 K for the three molecules. The Ni modified Mo₂C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Nimore » modified Mo₂C catalysts, 8.6%Ni/Mo₂C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO₂. Compared to Pd/SiO₂, both Mo₂C and Ni/Mo₂C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.« less

  2. Replacing precious metals with carbide catalysts for hydrogenation reactions

    SciTech Connect (OSTI)

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; Wang, Tiefeng

    2015-03-03

    Molybdenum carbide (Mo?C and Ni/Mo?C) catalysts were compared with Pd/SiO? for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO?, Mo?C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo?C could be completely regenerated by H? treatment at 723 K for the three molecules. The Ni modified Mo?C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Ni modified Mo?C catalysts, 8.6%Ni/Mo?C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO?. Compared to Pd/SiO?, both Mo?C and Ni/Mo?C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.

  3. In situ transmission electron microscopy analysis of conductive filament during solid electrolyte resistance switching

    SciTech Connect (OSTI)

    Fujii, Takashi; Arita, Masashi; Takahashi, Yasuo; Fujiwara, Ichiro

    2011-05-23

    An in situ transmission electron microscopy (TEM) analysis of a solid electrolyte, Cu-GeS, during resistance switching is reported. Real-time observations of the filament formation and disappearance process were performed in the TEM instrument and the conductive-filament-formation model was confirmed experimentally. Narrow conductive filaments were formed corresponding to resistance switching from high- to low-resistance states. When the resistance changed to high-resistance state, the filament disappeared. It was also confirmed by use of selected area diffractometry and energy-dispersive x-ray spectroscopy that the conductive filament was made of nanocrystals composed mainly of Cu.

  4. Preparation and uses of amorphous boron carbide coated substrates

    DOE Patents [OSTI]

    Riley, Robert E. (Los Alamos, NM); Newkirk, Lawrence R. (Los Alamos, NM); Valencia, Flavio A. (Santa Fe, NM)

    1981-09-01

    Cloth is coated at a temperature below about 1000.degree. C. with amorphous boron-carbon deposits in a process which provides a substantially uniform coating on all the filaments making up each yarn fiber bundle of the cloth. The coated cloths can be used in the as-deposited condition for example as wear surfaces where high hardness values are needed; or multiple layers of coated cloths can be hot-pressed to form billets useful for example in fusion reactor wall armor. Also provided is a method of controlling the atom ratio of B:C of boron-carbon deposits onto any of a variety of substrates, including cloths.

  5. Simultaneous transverse oscillations of a prominence and a filament and longitudinal oscillation of another filament induced by a single shock wave

    SciTech Connect (OSTI)

    Shen, Yuandeng; Liu, Ying D.; Chen, P. F.; Ichimoto, Kiyoshi

    2014-11-10

    We present the first stereoscopic and Doppler observations of simultaneous transverse oscillations of a prominence and a filament and longitudinal oscillation of another filament launched by a single shock wave. Using H? Doppler observations, we derive the three-dimensional oscillation velocities at different heights along the prominence axis. The results indicate that the prominence has a larger oscillation amplitude and damping time at higher altitude, but the periods at different heights are the same (i.e., 13.5 minutes). This suggests that the prominence oscillates like a linear vertical rigid body with one end anchored on the Sun. One of the filaments shows weak transverse oscillation after the passing of the shock, which is possibly due to the low altitude of the filament and the weakening (due to reflection) of the shock wave before the interaction. Large-amplitude longitudinal oscillation is observed in the other filament after the passing of the shock wave. The velocity amplitude and period are about 26.8 km s{sup 1} and 80.3 minutes, respectively. We propose that the orientation of a filament or prominence relative to the normal vector of the incoming shock should be an important factor for launching transverse or longitudinal filament oscillations. In addition, the restoring forces of the transverse prominence are most likely due to the coupling of gravity and magnetic tension of the supporting magnetic field, while that for the longitudinal filament oscillation is probably the resultant force of gravity and magnetic pressure.

  6. Method for silicon carbide production by reacting silica with hydrocarbon gas

    DOE Patents [OSTI]

    Glatzmaier, G.C.

    1994-06-28

    A method is described for producing silicon carbide particles using a silicon source material and a hydrocarbon. The method is efficient and is characterized by high yield. Finely divided silicon source material is contacted with hydrocarbon at a temperature of 400 C to 1000 C where the hydrocarbon pyrolyzes and coats the particles with carbon. The particles are then heated to 1100 C to 1600 C to cause a reaction between the ingredients to form silicon carbide of very small particle size. No grinding of silicon carbide is required to obtain small particles. The method may be carried out as a batch process or as a continuous process. 5 figures.

  7. Optical limiting effects in nanostructured silicon carbide thin films

    SciTech Connect (OSTI)

    Borshch, A A; Starkov, V N; Volkov, V I; Rudenko, V I; Boyarchuk, A Yu; Semenov, A V

    2013-12-31

    We present the results of experiments on the interaction of nanosecond laser radiation at 532 and 1064 nm with nanostructured silicon carbide thin films of different polytypes. We have found the effect of optical intensity limiting at both wavelengths. The intensity of optical limiting at ? = 532 nm (I{sub cl} ? 10{sup 6} W cm{sup -2}) is shown to be an order of magnitude less than that at ? = 1064 nm (I{sub cl} ? 10{sup 7} W cm{sup -2}). We discuss the nature of the nonlinearity, leading to the optical limiting effect. We have proposed a method for determining the amount of linear and two-photon absorption in material media. (nonlinear optical phenomena)

  8. The world`s first commercial iron carbide plant

    SciTech Connect (OSTI)

    Prichard, L.C.; Schad, D.

    1995-12-01

    The paper traces the development of Nucor`s investigation of clean iron unit processes, namely, direct reduction, and the decision to build and operate the world`s first commercial iron carbide plant. They first investigated coal based processes since the US has abundant coal reserves, but found a variety of reasons for dropping the coal-based processes from further consideration. A natural gas based process was selected, but the failure to find economically priced gas supplies stopped the development of a US based venture. It was later found that Trinidad had economically priced and abundant supplies of natural gas, and the system of government, the use of English language, and geographic location were also ideal. The cost estimates required modification of the design, but the plant was begun in April, 1993. Start-up problems with the plant are also discussed. Production should commence shortly.

  9. High surface area silicon carbide-coated carbon aerogel

    DOE Patents [OSTI]

    Worsley, Marcus A; Kuntz, Joshua D; Baumann, Theodore F; Satcher, Jr, Joe H

    2014-01-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust. Carbon aerogels can be coated with sol-gel silica and the silica can be converted to silicone carbide, improved the thermal stability of the carbon aerogel.

  10. Method of producing novel silicon carbide articles. [Patent application

    DOE Patents [OSTI]

    Milewski, J.V.

    1982-06-18

    A method of producing articles comprising reaction-bonded silicon carbide (SiC) and graphite (and/or carbon) is given. The process converts the graphite (and/or carbon) in situ to SiC, thus providing the capability of economically obtaining articles made up wholly or partially of SiC having any size and shape in which graphite (and/or carbon) can be found or made. When the produced articles are made of an inner graphite (and/or carbon) substrate to which SiC is reaction bonded, these articles distinguish SiC-coated graphite articles found in the prior art by the feature of a strong bond having a gradual (as opposed to a sharply defined) interface which extends over a distance of mils. A method for forming SiC whisker-reinforced ceramic matrices is also given. The whisker-reinforced articles comprise SiC whiskers which substantially retain their structural integrity.

  11. In situ electrochemical dilatometry of carbide-derived carbons

    SciTech Connect (OSTI)

    Hantel, M M; Presser, Volker; Gogotsi, Yury

    2011-01-01

    The long life durability and extraordinary stability of supercapacitors are ascribed to the common concept that the charge storage is purely based on double-layer charging. Therefore the ideal supercapacitor electrode should be free of charge induced microscopic structural changes. However, recent in-situ investigations on different carbon materials for supercapacitor electrodes have shown that the charge and discharge is accompanied by dimensional changes of the electrode up to several percent. This work studies the influence of the pore size on the expansion behavior of carbon electrodes derived from titanium carbide-derived carbons with an average pore size between 5 and 8 Using tetraethylammonium tetrafluoroborate in acetonitrile, the swelling of the electrodes was measured by in situ dilatometry. The experiments revealed an increased expansion on the negatively charged electrode for pores below 6 , which could be described with pore swelling.

  12. STUDYING INTERCLUSTER GALAXY FILAMENTS THROUGH STACKING gmBCG GALAXY CLUSTER PAIRS

    SciTech Connect (OSTI)

    Zhang Yuanyuan; Dietrich, Joerg P.; McKay, Timothy A.; Nguyen, Alex T. Q.; Sheldon, Erin S.

    2013-08-20

    We present a method to study the photometric properties of galaxies in filaments by stacking the galaxy populations between pairs of galaxy clusters. Using Sloan Digital Sky Survey data, this method can detect the intercluster filament galaxy overdensity with a significance of {approx}5{sigma} out to z = 0.40. Using this approach, we study the g - r color and luminosity distribution of filament galaxies as a function of redshift. Consistent with expectation, filament galaxies are bimodal in their color distribution and contain a larger blue galaxy population than clusters. Filament galaxies are also generally fainter than cluster galaxies. More interestingly, the observed filament population seems to show redshift evolution at 0.12 < z < 0.40: the blue galaxy fraction has a trend to increase at higher redshift; such evolution is parallel to the ''Butcher-Oemler effect'' of galaxy clusters. We test the dependence of the observed filament density on the richness of the cluster pair: richer clusters are connected by higher density filaments. We also test the spatial dependence of filament galaxy overdensity: this quantity decreases when moving away from the intercluster axis between a cluster pair. This method provides an economical way to probe the photometric properties of filament galaxies and should prove useful for upcoming projects like the Dark Energy Survey.

  13. CARMA LARGE AREA STAR FORMATION SURVEY: OBSERVATIONAL ANALYSIS OF FILAMENTS IN THE SERPENS SOUTH MOLECULAR CLOUD

    SciTech Connect (OSTI)

    Fernndez-Lpez, M.; Looney, L.; Lee, K.; Segura-Cox, D.; Arce, H. G.; Plunkett, A.; Mundy, L. G.; Storm, S.; Teuben, P. J.; Pound, M.; Isella, A.; Kauffmann, J.; Tobin, J. J.; Rosolowsky, E.; Kwon, W.; Ostriker, E.; Tassis, K.; Shirley, Y. L.

    2014-08-01

    We present the N{sub 2}H{sup +} (J = 1 ? 0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey. The observations cover 250 arcmin{sup 2} and fully sample structures from 3000 AU to 3pc with a velocity resolution of 0.16kms{sup 1}, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N{sub 2}H{sup +} emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N{sub 2}H{sup +} filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence.

  14. Observations and implications of large-amplitude longitudinal oscillations in a solar filament

    SciTech Connect (OSTI)

    Luna, M.; Knizhnik, K.; Muglach, K.; Karpen, J.; Gilbert, H.; Kucera, T. A.; Uritsky, V.

    2014-04-10

    On 2010 August 20, an energetic disturbance triggered large-amplitude longitudinal oscillations in a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. In the present work, we analyze this periodic motion in a large fraction of the filament to characterize the underlying physics of the oscillation as well as the filament properties. The results support our previous theoretical conclusions that the restoring force of large-amplitude longitudinal oscillations is solar gravity, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Based on our previous work, we used the fitted parameters to determine the magnitude and radius of curvature of the dipped magnetic field along the filament, as well as the mass accretion rate onto the filament threads. These derived properties are nearly uniform along the filament, indicating a remarkable degree of cohesiveness throughout the filament channel. Moreover, the estimated mass accretion rate implies that the footpoint heating responsible for the thread formation, according to the thermal nonequilibrium model, agrees with previous coronal heating estimates. We estimate the magnitude of the energy released in the nearby event by studying the dynamic response of the filament threads, and discuss the implications of our study for filament structure and heating.

  15. Confined partial filament eruption and its reformation within a stable magnetic flux rope

    SciTech Connect (OSTI)

    Joshi, Navin Chandra; Kayshap, Pradeep; Uddin, Wahab; Srivastava, Abhishek K.; Dwivedi, B. N.; Filippov, Boris; Chandra, Ramesh; Choudhary, Debi Prasad E-mail: njoshi98@gmail.com

    2014-05-20

    We present observations of a confined partial eruption of a filament on 2012 August 4, which restores its initial shape within ?2 hr after eruption. From the Global Oscillation Network Group H? observations, we find that the filament plasma turns into dynamic motion at around 11:20 UT from the middle part of the filament toward the northwest direction with an average speed of ?105 km s{sup 1}. A little brightening underneath the filament possibly shows the signature of low-altitude reconnection below the filament eruptive part. In Solar Dynamics Observatory/Atmospheric Imaging Assembly 171 images, we observe an activation of right-handed helically twisted magnetic flux rope that contains the filament material and confines it during its dynamical motion. The motion of cool filament plasma stops after traveling a distance of ?215 Mm toward the northwest from the point of eruption. The plasma moves partly toward the right foot point of the flux rope, while most of the plasma returns after 12:20 UT toward the left foot point with an average speed of ?60 km s{sup 1} to reform the filament within the same stable magnetic structure. On the basis of the filament internal fine structure and its position relative to the photospheric magnetic fields, we find filament chirality to be sinistral, while the activated enveloping flux rope shows a clear right-handed twist. Thus, this dynamic event is an apparent example of one-to-one correspondence between the filament chirality (sinistral) and the enveloping flux rope helicity (positive). From the coronal magnetic field decay index, n, calculation near the flux rope axis, it is evident that the whole filament axis lies within the domain of stability (i.e., n < 1), which provides the filament stability despite strong disturbances at its eastern foot point.

  16. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    SciTech Connect (OSTI)

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The Advanced Measurements work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of in-service degradation. Examples include composite density, distribution of porosity, fiber-matrix bond character, uniformity of weave, physical damage, and joint quality at interface bonds.

  17. Filamentation of femtosecond laser radiation with a non-Gaussian transverse spatial profile

    SciTech Connect (OSTI)

    Biryukov, A A; Panov, N A; Volkov, M V; Uryupina, D S; Volkov, Roman V; Kosareva, O G; Savel'ev-Trofimov, Andrei B

    2011-11-30

    The filamentation of a femtosecond laser pulse with a non-Gaussian transverse intensity profile has been studied experimentally and by numerical simulation. The results demonstrate that the distance to the filamentation region can be evaluated using the Marburger formula in which the critical power of self-focusing at a beam quality factor M{sup 2} exceeds that for a Gaussian beam by a factor of (M{sup 2}){sup 2}. The characteristics of the filament resulting from self-focusing depend little on the beam quality factor: both the filament energy and diameter coincide. If the beam is passed through an aperture, a filament forms on a diffraction ring, and its parameters coincide with those of a filament formed with no slit (provided the initial pulse parameters coincide).

  18. Velocity scaling for filament motion in scrape-off layer plasmas

    SciTech Connect (OSTI)

    Kube, R.; Garcia, O. E.

    2011-10-15

    The velocity scaling for isolated plasma filaments in non-uniformly magnetized plasmas with respect to filament amplitude and cross-field size has been investigated by means of numerical simulations. The model includes electric currents due to magnetic gradient and curvature drifts, polarization drifts, and parallel currents through sheaths, where the magnetic field lines intersect material walls. In the ideal limit, the radial velocity of the filament increases with the square root of its size. When sheath currents dominate over polarization currents, the filament velocity is inversely proportional to the square of its size. In the presence of sheath currents, the velocity is maximum for an intermediate filament size determined by the balance between diamagnetic, polarization, and sheath currents. The parameter dependence of this filament size and velocity is elucidated. The results are discussed in the context of blob-like structures in basic laboratory plasma experiments and in the scrape-off layer of magnetically confined plasmas.

  19. Reaction-Forming Method for Producing Near Net-Shape Refractory Metal Carbides

    DOE Patents [OSTI]

    Palmisiano, Marc N.; Jakubenas, Kevin J.; Baranwal, Rita

    2004-07-20

    A method for reaction forming refractory metal carbides. The method involves the fabrication of a glassy carbon preform by casting an organic, resin-based liquid mixture into a mold and subsequently heat treating it in two steps, which cures and pyrolizes the resin resulting in a porous carbon preform. By varying the amounts of the constituents in the organic, resin-based liquid mixture, control over the density of the carbon preform is obtained. Control of the density and microstructure of the carbon preform allows for determination of the microstructure and properties of the refractory metal carbide material produced. The glassy carbon preform is placed on a bed of refractory metal or refractory metal--silicon alloy. The pieces are heated above the melting point of the metal or alloy. The molten metal wicks inside the porous carbon preform and reacts, forming the refractory metal carbide or refractory metal carbide plus a minor secondary phase.

  20. CLUSTER FORMATION TRIGGERED BY FILAMENT COLLISIONS IN SERPENS SOUTH

    SciTech Connect (OSTI)

    Nakamura, Fumitaka; Kawabe, Ryohei; Shinnaga, Hiroko; Sugitani, Koji; Tanaka, Tomohiro; Kimura, Kimihiko; Tokuda, Kazuki; Kozu, Minato; Okada, Nozomi; Hasegawa, Yutaka; Ogawa, Hideo; Nishitani, Hiroyuki; Mizuno, Izumi; Dobashi, Kazuhito; Shimoikura, Tomomi; Shimajiri, Yoshito; Kameno, Seiji; Momose, Munetake; Nakajima, Taku; and others

    2014-08-20

    The Serpens South infrared dark cloud consists of several filamentary ridges, some of which fragment into dense clumps. On the basis of CCS (J{sub N} = 4{sub 3}-3{sub 2}), HC{sub 3}N (J = 5-4), N{sub 2}H{sup +} (J = 1-0), and SiO (J = 2-1, v = 0) observations, we investigated the kinematics and chemical evolution of these filamentary ridges. We find that CCS is extremely abundant along the main filament in the protocluster clump. We emphasize that Serpens South is the first cluster-forming region where extremely strong CCS emission is detected. The CCS-to-N{sub 2}H{sup +} abundance ratio is estimated to be about 0.5 toward the protocluster clump, whereas it is about 3 in the other parts of the main filament. We identify six dense ridges with different V {sub LSR}. These ridges appear to converge toward the protocluster clump, suggesting that the collisions of these ridges may have triggered cluster formation. The collisions presumably happened within a few 10{sup 5}yr because CCS is abundant only for a short time. The short lifetime agrees with the fact that the number fraction of Class I objects, whose typical lifetime is 0.4 10{sup 5}yr, is extremely high, about 70% in the protocluster clump. In the northern part, two ridges appear to have partially collided, forming a V-shape clump. In addition, we detected strong bipolar SiO emission that is due to the molecular outflow blowing out of the protostellar clump, as well as extended weak SiO emission that may originate from the filament collisions.

  1. Bipolaron Hopping Conduction in Boron Carbides (Journal Article) | SciTech

    Office of Scientific and Technical Information (OSTI)

    Connect Bipolaron Hopping Conduction in Boron Carbides Citation Details In-Document Search Title: Bipolaron Hopping Conduction in Boron Carbides × You are accessing a document from the Department of Energy's (DOE) SciTech Connect. This site is a product of DOE's Office of Scientific and Technical Information (OSTI) and is provided as a public service. Visit OSTI to utilize additional information resources in energy science and technology. A paper copy of this document is also available for

  2. Ultratough, Thermally Stable Polycrystalline Diamond/Silicon Carbide Nanocomposites for Drill Bits

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Ultratough, Thermally Stable Polycrystalline Diamond/Silicon Carbide Nanocomposites for Drill Bits Synthesis, Characterization, and Application of Nanostructured Diamond/ Silicon Carbide Composites for Improved Drill Bit Performance Industrial drilling, mining, cutting, and grinding make heavy use of superhard materials with superior wear resistance. In the oil and gas drilling industry, the use of polycrystalline diamond compact (PDC) drill bits has become increasingly common, with PDC drill

  3. Fact Sheet: Award-Winning Silicon Carbide Power Electronics (October 2012)

    Office of Environmental Management (EM)

    Silicon Carbide Technology Breakthrough Silicon carbide (SiC) is a semiconductor material under rapid development for use in power electronic (PE) systems due to its unique material and electronic properties. SiC potentially offers several advantages over conventional silicon (Si) for use in PE devices. Comparatively, individual SiC devices (in theory) can endure temperatures up to 600°C (standard Si PE devices are typically limited to 150°C), withstand more voltage, tolerate a larger current

  4. DOE - Office of Legacy Management -- Union Carbide and Carbon Co - TN 10

    Office of Legacy Management (LM)

    Carbide and Carbon Co - TN 10 FUSRAP Considered Sites Site: Union Carbide and Carbon Co (TN.10) Designated Name: Alternate Name: Location: Evaluation Year: Site Operations: Site Disposition: Radioactive Materials Handled: Primary Radioactive Materials Handled: Radiological Survey(s): Site Status: This site is one of a group of 5 FUSRAP considered sites for which records are available that provide a reasonably complete historical account of their operations and relationship, if any, with MED/AEC

  5. Filamentation instability of current-driven dust ion-acoustic waves in a collisional dusty plasma

    SciTech Connect (OSTI)

    Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 19839-63113 (Iran, Islamic Republic of); Haghtalab, T.; Khorashadizadeh, S. M. [Physics Department, Birjand University, Birjand 97179-63384 (Iran, Islamic Republic of)

    2011-11-15

    A theoretical investigation has been made of the dust ion-acoustic filamentation instability in an unmagnetized current-driven dusty plasma by using the Lorentz transformation formulas. The effect of collision between the charged particles with neutrals and their thermal motion on this instability is considered. Developing the filamentation instability of the current-driven dust ion-acoustic wave allows us to determine the period and the establishment time of the filamentation structure and threshold for instability development.

  6. Simulation of filamentation instability of a current-carrying plasma by particle in cell method

    SciTech Connect (OSTI)

    Niknam, A. R.; Mostafavi, P. S.; Komaizi, D.; Salahshoor, M. [Laser-Plasma Research Institute, Shahid Beheshti University, G. C., Tehran 19839-63113 (Iran, Islamic Republic of)

    2012-08-15

    The nonlinear dynamics of filamentation instability in a weakly ionized current-carrying plasma in the diffusion frequency region is studied using particle in cell simulation. The effects of electron thermal motion and ion-neutral collision on the evolution of this instability in the nonlinear stage of the filaments coalescence are discussed. It is found that the coalescence of the current filaments is enhanced by increasing the temperature and is delayed by increasing the collision frequency.

  7. Kink instability evidenced by analyzing the leg rotation of a filament

    SciTech Connect (OSTI)

    Yan, X. L.; Xue, Z. K.; Ma, L.; Kong, D. F.; Qu, Z. Q.; Liu, J. H.; Li, Z.

    2014-02-20

    Kink instability is a possible mechanism for solar filament eruption. However, it is very difficult to directly measure the twist of the solar filament from observation. In this paper, we measured the twist of a solar filament by analyzing its leg rotation. An inverse S-shaped filament in the active region NOAA 11485 was observed by the Atmospheric Imaging Assembly of the Solar Dynamics Observatory on 2012 May 22. During its eruption, the leg of the filament exhibited a significant rotation motion. The 304 images were used to uncurl the circles, the centers of which are the axis of the filament's leg. The result shows that the leg of the filament rotated up to about 510 (about 2.83?) around the axis of the filament within 23 minutes. The maximal rotation speed reached 100 degrees/minute (about 379.9 km s{sup 1} at radius 18''), which is the fastest rotation speed reported. We also calculated the decay index along the polarity inversion line in this active region and found that the decline of the overlying field with height is not fast enough to trigger the torus instability. According to the kink instability condition, this indicates that the kink instability is the trigger mechanism for the solar filament eruption.

  8. THE DISAPPEARING SOLAR FILAMENT OF 2003 JUNE 11: A THREE-BODY PROBLEM

    SciTech Connect (OSTI)

    Balasubramaniam, K. S.; Pevtsov, A. A.; Cliver, E. W.; Martin, S. F.; Panasenco, O.

    2011-12-20

    The eruption of a large quiescent filament on 2003 June 11 was preceded by the birth of a nearby active region-a common scenario. In this case, however, the filament lay near a pre-existing active region and the new active region did not destabilize the filament by direct magnetic connection. Instead it appears to have done so indirectly via magnetic coupling with the established region. Restructuring between the perturbed fields of the old region and the filament then weakened the arcade overlying the midpoint of filament, where the eruption originated. The inferred rate ({approx}11 Degree-Sign day{sup -1}) at which the magnetic disturbance propagates from the mature region to destabilize the filament is larger than the mean speed ({approx}5 Masculine-Ordinal-Indicator -6 Degree-Sign day{sup -1}) but still within the scatter obtained for Bruzek's empirical relationship between the distance from a newly formed active region to a quiescent filament and the time from active region appearance to filament disappearance. The higher propagation speed in the 2003 June 11 case may be due to the 'broadside' (versus 'end-on') angle of attack of the (effective) new flux to the coronal magnetic fields overlying a central section of the axis of the filament.

  9. Filamentation of IR and UV femtosecond pulses upon focusing in air

    SciTech Connect (OSTI)

    Dergachev, A A; Ionin, Andrei A; Kandidov, V P; Seleznev, L V; Sinitsyn, D V; Sunchugasheva, E S; Shlenov, Svyatoslav A

    2013-01-31

    The filamentation of IR and UV laser pulses has been studied numerically and experimentally for different initial beam focusing geometries, and linear electron density profiles along the plasma channel of filaments have been obtained. The results demonstrate that changes in laser beam focusing have a stronger effect on filament and plasma channel parameters for UV radiation than for IR radiation. Focusing causes individual high fluence regions produced by refocusing to merge to form a continuous extended filament with a continuous plasma channel. (nonlinear optical phenomena)

  10. THE CONTRACTION OF OVERLYING CORONAL LOOP AND THE ROTATING MOTION OF A SIGMOID FILAMENT DURING ITS ERUPTION

    SciTech Connect (OSTI)

    Yan, X. L.; Qu, Z. Q.; Xue, Z. K.; Deng, L. H.; Ma, L.; Kong, D. F.; Liu, J. H.

    2013-06-15

    We present an observation of overlying coronal loop contraction and rotating motion of the sigmoid filament during its eruption on 2012 May 22 observed by the Solar Dynamics Observatory (SDO). Our results show that the twist can be transported into the filament from the lower atmosphere to the higher atmosphere. The successive contraction of the coronal loops was due to a suddenly reduced magnetic pressure underneath the filament, which was caused by the rising of the filament. Before the sigmoid filament eruption, there was a counterclockwise flow in the photosphere at the right feet of the filament and the contraction loops and a convergence flow at the left foot of the filament. The hot and cool materials have inverse motion along the filament before the filament eruption. Moreover, two coronal loops overlying the filament first experienced brightening, expansion, and contraction successively. At the beginning of the rising and rotation of the left part of the filament, the second coronal loop exhibited rapid contraction. The top of the second coronal loop also showed counterclockwise rotation during the contraction process. After the contraction of the second loop, the left part of the filament rotated counterclockwise and expanded toward the right of NOAA AR 11485. During the filament expansion, the right part of the filament also exhibited counterclockwise rotation like a tornado.

  11. Dark Matter and Synchrotron Emission from Galactic Center Radio Filaments

    SciTech Connect (OSTI)

    Linden, Tim; Hooper, Dan; Yusef-Zadeh, Farhad

    2011-11-10

    The inner degrees of the Galactic center contain a large population of filamentary structures observed at radio frequencies. These so-called non-thermal radio filaments (NRFs) trace magnetic field lines and have attracted significant interest due to their hard (S_v ~ -0.1 +/- 0.4) synchrotron emission spectra. The origin of these filaments remains poorly understood. We show that the electrons and positrons created through the annihilations of a relatively light (~5-10 GeV) dark matter particle with the cross section predicted for a simple thermal relic can provide a compelling match to the intensity, spectral shape, and flux variation of the NRFs. Furthermore, the characteristics of the dark matter particle necessary to explain the synchrotron emission from the NRFs is consistent with those required to explain the excess gamma-ray emission observed from the Galactic center by the Fermi-LAT, as well as the direct detection signals observed by CoGeNT and DAMA/LIBRA.

  12. Current sheet oscillations in the magnetic filament approach

    SciTech Connect (OSTI)

    Erkaev, N. V.; Semenov, V. S.; Biernat, H. K.

    2012-06-15

    Magnetic filament approach is applied for modeling of nonlinear 'kink'-like flapping oscillations of thin magnetic flux tubes in the Earth's magnetotail current sheet. A discrete approximation for the magnetic flux tube was derived on a basis of the Hamiltonian formulation of the problem. The obtained system of ordinary differential equations was integrated by method of Rosenbrock, which is suitable for stiff equations. The two-dimensional exact Kan's solution of the Vlasov equations was used to set the background equilibrium conditions for magnetic field and plasma. Boundary conditions for the magnetic filament were found to be dependent on the ratio of the ionospheric conductivity and the Alfven conductivity of the magnetic tube. It was shown that an enhancement of this ratio leads to the corresponding increase of the frequency of the flapping oscillations. For some special case of boundary conditions, when the magnetic perturbations vanish at the boundaries, the calculated frequency of the 'kink'-like flapping oscillations is rather close to that predicted by the 'double gradient' analytical model. For others cases, the obtained frequency of the flapping oscillations is somewhat larger than that from the 'double gradient' theory. The frequency of the nonlinear flapping oscillations was found to be a decreasing function of the amplitude.

  13. AN INTERACTING GALAXY SYSTEM ALONG A FILAMENT IN A VOID

    SciTech Connect (OSTI)

    Beygu, B.; Van de Weygaert, R.; Van der Hulst, J. M.; Kreckel, K.; Van Gorkom, J. H.

    2013-05-15

    Cosmological voids provide a unique environment for the study of galaxy formation and evolution. The galaxy population in their interiors has properties significantly different from average field galaxies. As part of our Void Galaxy Survey (VGS), we have found a system of three interacting galaxies (VGS{sub 3}1) inside a large void. VGS{sub 3}1 is a small elongated group whose members are embedded in a common H I envelope. The H I picture suggests a filamentary structure with accretion of intergalactic cold gas from the filament onto the galaxies. We present deep optical and narrowband H{alpha} data, optical spectroscopy, near-UV, and far-UV Galaxy Evolution Explorer and CO(1-0) data. We find that one of the galaxies, a Markarian object, has a ring-like structure and a tail evident both in optical and H I. While all three galaxies form stars in their central parts, the tail and the ring of the Markarian object are devoid of star formation. We discuss these findings in terms of a gravitational interaction and ongoing growth of galaxies out of a filament. VGS{sub 3}1 is one of the first observed examples of a filamentary structure in a void. It is an important prototype for understanding the formation of substructure in a void. This system also shows that the galaxy evolution in voids can be as dynamic as in high-density environments.

  14. LARGE-AMPLITUDE LONGITUDINAL OSCILLATIONS IN A SOLAR FILAMENT

    SciTech Connect (OSTI)

    Luna, M.

    2012-05-01

    We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.

  15. Filamentation instability of nonextensive current-driven plasma in the ion acoustic frequency range

    SciTech Connect (OSTI)

    Khorashadizadeh, S. M. Rastbood, E.; Niknam, A. R.

    2014-12-15

    The filamentation and ion acoustic instabilities of nonextensive current-driven plasma in the ion acoustic frequency range have been studied using the Lorentz transformation formulas. Based on the kinetic theory, the possibility of filamentation instability and its growth rate as well as the ion acoustic instability have been investigated. The results of the research show that the possibility and growth rate of these instabilities are significantly dependent on the electron nonextensive parameter and drift velocity. Besides, the increase of electrons nonextensive parameter and drift velocity lead to the increase of the growth rates of both instabilities. In addition, the wavelength region in which the filamentation instability occurs is more stretched in the presence of higher values of drift velocity and nonextensive parameter. Finally, the results of filamentation and ion acoustic instabilities have been compared and the conditions for filamentation instability to be dominant mode of instability have been presented.

  16. Dry soldering with hot filament produced atomic hydrogen

    DOE Patents [OSTI]

    Panitz, Janda K. G. (Edgewood, NM); Jellison, James L. (Albuquerque, NM); Staley, David J. (Los Lunas, NM)

    1995-01-01

    A system for chemically transforming metal surface oxides to metal that is especially, but not exclusively, suitable for preparing metal surfaces for dry soldering and solder reflow processes. The system employs one or more hot, refractory metal filaments, grids or surfaces to thermally dissociate molecular species in a low pressure of working gas such as a hydrogen-containing gas to produce reactive species in a reactive plasma that can chemically reduce metal oxides and form volatile compounds that are removed in the working gas flow. Dry soldering and solder reflow processes are especially applicable to the manufacture of printed circuit boards, semiconductor chip lead attachment and packaging multichip modules. The system can be retrofitted onto existing metal treatment ovens, furnaces, welding systems and wave soldering system designs.

  17. Dry soldering with hot filament produced atomic hydrogen

    DOE Patents [OSTI]

    Panitz, J.K.G.; Jellison, J.L.; Staley, D.J.

    1995-04-25

    A system is disclosed for chemically transforming metal surface oxides to metal that is especially, but not exclusively, suitable for preparing metal surfaces for dry soldering and solder reflow processes. The system employs one or more hot, refractory metal filaments, grids or surfaces to thermally dissociate molecular species in a low pressure of working gas such as a hydrogen-containing gas to produce reactive species in a reactive plasma that can chemically reduce metal oxides and form volatile compounds that are removed in the working gas flow. Dry soldering and solder reflow processes are especially applicable to the manufacture of printed circuit boards, semiconductor chip lead attachment and packaging multichip modules. The system can be retrofitted onto existing metal treatment ovens, furnaces, welding systems and wave soldering system designs. 1 fig.

  18. A MULTI-SPACECRAFT VIEW OF A GIANT FILAMENT ERUPTION DURING 2009 SEPTEMBER 26/27

    SciTech Connect (OSTI)

    Gosain, Sanjay; Schmieder, Brigitte; Artzner, Guy; Bogachev, Sergei; Toeroek, Tibor

    2012-12-10

    We analyze multi-spacecraft observations of a giant filament eruption that occurred during 2009 September 26 and 27. The filament eruption was associated with a relatively slow coronal mass ejection. The filament consisted of a large and a small part, and both parts erupted nearly simultaneously. Here we focus on the eruption associated with the larger part of the filament. The STEREO satellites were separated by about 117 Degree-Sign during this event, so we additionally used SoHO/EIT and CORONAS/TESIS observations as a third eye (Earth view) to aid our measurements. We measure the plane-of-sky trajectory of the filament as seen from STEREO-A and TESIS viewpoints. Using a simple trigonometric relation, we then use these measurements to estimate the true direction of propagation of the filament which allows us to derive the true R/R{sub Sun }-time profile of the filament apex. Furthermore, we develop a new tomographic method that can potentially provide a more robust three-dimensional (3D) reconstruction by exploiting multiple simultaneous views. We apply this method also to investigate the 3D evolution of the top part of filament. We expect this method to be useful when SDO and STEREO observations are combined. We then analyze the kinematics of the eruptive filament during its rapid acceleration phase by fitting different functional forms to the height-time data derived from the two methods. We find that for both methods an exponential function fits the rise profile of the filament slightly better than parabolic or cubic functions. Finally, we confront these results with the predictions of theoretical eruption models.

  19. SUNSPOT ROTATION, SIGMOIDAL FILAMENT, FLARE, AND CORONAL MASS EJECTION: THE EVENT ON 2000 FEBRUARY 10

    SciTech Connect (OSTI)

    Yan, X. L.; Qu, Z. Q.; Kong, D. F.

    2012-07-20

    We find that a sunspot with positive polarity had an obvious counterclockwise rotation and resulted in the formation and eruption of an inverse S-shaped filament in NOAA Active Region 08858 from 2000 February 9 to 10. The sunspot had two umbrae which rotated around each other by 195 Degree-Sign within about 24 hr. The average rotation rate was nearly 8 Degree-Sign hr{sup -1}. The fastest rotation in the photosphere took place during 14:00 UT to 22:01 UT on February 9, with a rotation rate of nearly 16 Degree-Sign hr{sup -1}. The fastest rotation in the chromosphere and the corona took place during 15:28 UT to 19:00 UT on February 9, with a rotation rate of nearly 20 Degree-Sign hr{sup -1}. Interestingly, the rapid increase of the positive magnetic flux occurred only during the fastest rotation of the rotating sunspot, the bright loop-shaped structure, and the filament. During the sunspot rotation, the inverse S-shaped filament gradually formed in the EUV filament channel. The filament experienced two eruptions. In the first eruption, the filament rose quickly and then the filament loops carrying the cool and the hot material were seen to spiral counterclockwise into the sunspot. About 10 minutes later, the filament became active and finally erupted. The filament eruption was accompanied with a C-class flare and a halo coronal mass ejection. These results provide evidence that sunspot rotation plays an important role in the formation and eruption of the sigmoidal active-region filament.

  20. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    With this study, amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphousmore » silicon carbide being shown to surpass amorphous silicon for temperatures above 300°C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.« less

  1. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    SciTech Connect (OSTI)

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    With this study, amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  2. Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

    DOE Patents [OSTI]

    Lillo, Thomas M.; Chu, Henry S.; Harrison, William M.; Bailey, Derek

    2013-01-22

    Methods of forming composite materials include coating particles of titanium dioxide with a substance including boron (e.g., boron carbide) and a substance including carbon, and reacting the titanium dioxide with the substance including boron and the substance including carbon to form titanium diboride. The methods may be used to form ceramic composite bodies and materials, such as, for example, a ceramic composite body or material including silicon carbide and titanium diboride. Such bodies and materials may be used as armor bodies and armor materials. Such methods may include forming a green body and sintering the green body to a desirable final density. Green bodies formed in accordance with such methods may include particles comprising titanium dioxide and a coating at least partially covering exterior surfaces thereof, the coating comprising a substance including boron (e.g., boron carbide) and a substance including carbon.

  3. NEW OBSERVATION OF FAILED FILAMENT ERUPTIONS: THE INFLUENCE OF ASYMMETRIC CORONAL BACKGROUND FIELDS ON SOLAR ERUPTIONS

    SciTech Connect (OSTI)

    Liu, Y.; Xu, Z.; Su, J.; Lin, H.; Shibata, K.; Kurokawa, H.

    2009-05-01

    Failed filament eruptions not associated with a coronal mass ejection (CME) have been observed and reported as evidence for solar coronal field confinement on erupting flux ropes. In those events, each filament eventually returns to its origin on the solar surface. In this Letter, a new observation of two failed filament eruptions is reported which indicates that the mass of a confined filament can be ejected to places far from the original filament channel. The jetlike mass motions in the two failed filament eruptions are thought to be due to the asymmetry of the background coronal magnetic fields with respect to the locations of the filament channels. The asymmetry of the coronal fields is confirmed by an extrapolation based on a potential field model. The obvious imbalance between the positive and negative magnetic flux (with a ratio of 1:3) in the bipolar active region is thought to be the direct cause of the formation of the asymmetric coronal fields. We think that the asymmetry of the background fields can not only influence the trajectories of ejecta, but also provide a relatively stronger confinement for flux rope eruptions than the symmetric background fields do.

  4. THREE-DIMENSIONAL RECONSTRUCTION OF AN ERUPTING FILAMENT WITH SOLAR DYNAMICS OBSERVATORY AND STEREO OBSERVATIONS

    SciTech Connect (OSTI)

    Li Ting; Zhang Jun; Zhang Yuzong; Yang Shuhong E-mail: zjun@nao.cas.cn

    2011-09-20

    On 2010 August 1, a global solar event was launched involving almost the entire Earth-facing side of the Sun. This event mainly consisted of a C3.2 flare, a polar crown filament eruption, and two Earth-directed coronal mass ejections. The observations from the Solar Dynamics Observatory (SDO) and STEREO showed that all the activities were coupled together, suggesting a global character of the magnetic eruption. We reconstruct the three-dimensional geometry of the polar crown filament using observations from three different viewpoints (STEREO A, STEREO B, and SDO) for the first time. The filament undergoes two eruption processes. First, the main body of the filament rises up, while it also moves toward the low-latitude region with a change in inclination by {approx}48{sup 0} and expands only in the altitudinal and latitudinal direction in the field of view of the Atmospheric Imaging Assembly. We investigate the true velocities and accelerations of different locations along the filament and find that the highest location always has the largest acceleration during this eruption process. During the late phase of the first eruption, part of the filament material separates from the eastern leg. This material displays a projectile motion and moves toward the west at a constant velocity of 141.8 km s{sup -1}. This may imply that the polar crown filament consists of at least two groups of magnetic systems.

  5. EVIDENCE OF FILAMENT UPFLOWS ORIGINATING FROM INTENSITY OSCILLATIONS ON THE SOLAR SURFACE

    SciTech Connect (OSTI)

    Cao, Wenda; Goode, Philip R.; Ning, Zongjun; Yurchyshyn, Vasyl; Ji Haisheng

    2010-08-10

    A filament footpoint rooted in an active region (NOAA 11032) was well observed for about 78 minutes with the 1.6 m New Solar Telescope at the Big Bear Solar Observatory on 2009 November 18 in H{alpha} {+-}0.75 A. This data set had high cadence ({approx}15 s) and high spatial resolution ({approx}0.''1) and offered a unique opportunity to study filament dynamics. As in previous findings from space observations, several dark intermittent upflows were identified, and they behave in groups at isolated locations along the filament. However, we have two new findings. First, we find that the dark upflows propagating along the filament channel are strongly associated with the intensity oscillations on the solar surface around the filament footpoints. The upflows start at the same time as the peak in the oscillations, illustrating that the upflow velocities are well correlated with the oscillations. Second, the intensity of one of the seven upflows detected in our data set exhibits a clear periodicity when the upflow propagates along the filament. The periods gradually vary from {approx}10 to {approx}5 minutes. Our results give observational clues on the driving mechanism of the upflows in the filament.

  6. Core and filament formation in magnetized, self-gravitating isothermal layers

    SciTech Connect (OSTI)

    Van Loo, Sven; Keto, Eric; Zhang, Qizhou

    2014-07-01

    We examine the role of the gravitational instability in an isothermal, self-gravitating layer threaded by magnetic fields on the formation of filaments and dense cores. Using a numerical simulation, we follow the non-linear evolution of a perturbed equilibrium layer. The linear evolution of such a layer is described in the analytic work of Nagai et al. We find that filaments and dense cores form simultaneously. Depending on the initial magnetic field, the resulting filaments form either a spiderweb-like network (for weak magnetic fields) or a network of parallel filaments aligned perpendicular to the magnetic field lines (for strong magnetic fields). Although the filaments are radially collapsing, the density profile of their central region (up to the thermal scale height) can be approximated by a hydrodynamical equilibrium density structure. Thus, the magnetic field does not play a significant role in setting the density distribution of the filaments. The density distribution outside of the central region deviates from the equilibrium. The radial column density distribution is then flatter than the expected power law of r {sup 4} and similar to filament profiles observed with Herschel. Our results do not explain the near constant filament width of ?0.1pc. However, our model does not include turbulent motions. It is expected that the accretion-driven amplification of these turbulent motions provides additional support within the filaments against gravitational collapse. Finally, we interpret the filamentary network of the massive star forming complex G14.225-0.506 in terms of the gravitational instability model and find that the properties of the complex are consistent with being formed out of an unstable layer threaded by a strong, parallel magnetic field.

  7. Overlying extreme-ultraviolet arcades preventing eruption of a filament observed by AIA/SDO

    SciTech Connect (OSTI)

    Chen, Huadong; Ma, Suli; Zhang, Jun

    2013-11-20

    Using the multi-wavelength data from the Atmospheric Imaging Assembly/Solar Dynamic Observatory (AIA/SDO) and the Sun Earth Connection Coronal and Heliospheric Investigation/Solar Terrestrial Relations Observatory (SECCHI/STEREO), we report a failed filament eruption in NOAA AR 11339 on 2011 November 3. The eruption was associated with an X1.9 flare, but without any coronal mass ejection (CME), coronal dimming, or extreme ultraviolet (EUV) waves. Some magnetic arcades above the filament were observed distinctly in EUV channels, especially in the AIA 94 and 131 wavebands, before and during the filament eruption process. Our results show that the overlying arcades expanded along with the ascent of the filament at first until they reached a projected height of about 49 Mm above the Sun's surface, where they stopped. The following filament material was observed to be confined by the stopped EUV arcades and not to escape from the Sun. After the flare, a new filament formed at the low corona where part of the former filament remained before its eruption. These results support that the overlying arcades play an important role in preventing the filament from successfully erupting outward. We also discuss in this paper the EUV emission of the overlying arcades during the flare. It is rare for a failed filament eruption to be associated with an X1.9 class flare, but not with a CME or EUV waves. Therefore, this study also provides valuable insight into the triggering mechanism of the initiation of CMEs and EUV waves.

  8. Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

    DOE Patents [OSTI]

    Halverson, Danny C. (Manteca, CA); Landingham, Richard L. (Livermore, CA)

    1988-01-01

    A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.

  9. Nucor`s start up of the world`s first commercial iron carbide plant

    SciTech Connect (OSTI)

    Garraway, R.

    1996-12-31

    Nucor began startup of its 900 Tonnes/day Fe{sub 3}C plant in July 1994 and the process has produced a high quality iron carbide. The major process variables and their importance to achieving design capacity are discussed, along with results of tests using the carbide to supplement scrap metal at Nucor Steel Mills. With the potential to burn the Carbon in the Fe{sub 3}C to CO and CO{sub 2}, the conversion of pure Fe{sub 3}C to 1 Tonne of steel will require: 55% of what is required using 100% scrap and 40% of what is required using 100% DRI.

  10. Plasma channels in a filament of a femtosecond laser pulse focused by an axicon

    SciTech Connect (OSTI)

    Chekalin, S V; Kompanets, V O; Dokukina, A E; Smetanina, E O; Kandidov, V P

    2014-06-30

    We report the results of experimental and numerical investigation of the influence of the wavefront curvature of femtosecond light focused by an axicon on the length and position of plasma channels in the filament under conditions of normal and anomalous group velocity dispersion in fused silica. It is shown that a change in the wavefront curvature by a value much greater than the longitudinal dimensions of the filament noticeably changes the geometry of the plasma channel position. The role of axicon focusing for ordering multiple filamentation is studied experimentally. (extreme light fields and their applications)

  11. Fluctuation of an ion beam extracted from an AC filament driven Bernas-type ion source

    SciTech Connect (OSTI)

    Miyamoto, N. Okajima, Y.; Wada, M.

    2014-02-15

    Argon ion beam fluctuation from an AC filament driven Bernas-type ion source is observed. The ion beam was measured by an 8 measurement elements beam profile monitor. The amplitude of the beam current fluctuation stayed in the same level from 100 Hz to 1 kHz of the filament heating frequency. The beam current fluctuation frequency measured by the beam profile monitor was equal to the frequency of the AC filament operation. The fluctuation amplitudes of the beam current by AC operation were less than 7% and were in the same level of the DC operation.

  12. Temporal evolution of femtosecond laser induced plasma filament in air and N{sub 2}

    SciTech Connect (OSTI)

    Papeer, J.; Botton, M.; Zigler, A.; Gordon, D.; Sprangle, P.

    2013-12-09

    We present single shot, high resolution, time-resolved measurements of the relaxation of laser induced plasma filaments in air and in N{sub 2} gas. Based on the measurements of the time dependent electromagnetic signal in a waveguide, an accurate and simple derivation of the electron density in the filament is demonstrated. This experimental method does not require prior knowledge of filament dimensions or control over its exact spatial location. The experimental results are compared to numerical simulations of air plasma chemistry. Results reveal the role of various decay mechanisms including the importance of O{sub 4}{sup +} molecular levels.

  13. The splitted laser beam filamentation in interaction of laser and an exponential decay inhomogeneous underdense plasma

    SciTech Connect (OSTI)

    Xia Xiongping; Yi Lin; Xu Bin; Lu Jianduo

    2011-10-15

    The splitted beam filamentation in interaction of laser and an exponential decay inhomogeneous underdense plasma is investigated. Based on Wentzel-Kramers-Brillouin (WKB) approximation and paraxial/nonparaxial ray theory, simulation results show that the steady beam width and single beam filamentation along the propagation distance in paraxial case is due to the influence of ponderomotive nonlinearity. In nonparaxial case, the influence of the off-axial of {alpha}{sub 00} and {alpha}{sub 02} (the departure of the beam from the Gaussian nature) and S{sub 02} (the departure from the spherical nature) results in more complicated ponderomotive nonlinearity and changing of the channel density and refractive index, which led to the formation of two/three splitted beam filamentation and the self-distortion of beam width. In addition, influence of several parameters on two/three splitted beam filamentation is discussed.

  14. Filament formation and erasure in molybdenum oxide during resistive switching cycles

    SciTech Connect (OSTI)

    Kudo, Masaki; Arita, Masashi Ohno, Yuuki; Takahashi, Yasuo

    2014-10-27

    In-situ filament observations were carried out on the Cu/MoO{sub x}/TiN resistive random access memory (ReRAM) by using transmission electron microscopy. Multiple positive and negative I-V cycles were investigated. Clear set-reset bipolar switch corresponding to the characteristics of conventional ReRAM devices was recognized. Filament grew from TiN to Cu in the set cycle and shrank from TiN to Cu in the reset cycle. However, there was no clear contrast change in the image at the switching moment, and thus, switching is thought to occur in a local region of the filament. When the current was large at reset, the filament shrank much, and its position tended to change.

  15. Filamentous carbon catalytic deposition of coal-tar pitch fraction on corundum

    SciTech Connect (OSTI)

    Martynkova, G.S.; Supova, M.

    2007-01-15

    Our work was focused on deposition of volatile hydrocarbons of carbonaceous precursor on corundum wafer, taking advantage of a metallic catalyst incorporated in precursor. Coal tar-pitch, namely a fraction soluble in toluene, served as precursor material for deposition of filamentous material. The toluene-soluble fraction of tar-pitch originally contained metallic particles of iron and nickel. During heat treatment up to 1000{sup o}C, metallic particles accompanied the volatile hydrocarbons conducive to forming a filamentous deposit. The deposit obtained demonstrates a semicrystalline material that has an irregular filamentous structure with an average filament diameter of 30 {mu}m. The presence of catalysts after the deposition process was proved in the deposit but catalysts were not found in the residuum.

  16. Observation of laser multiple filamentation process and multiple electron beams acceleration in a laser wakefield accelerator

    SciTech Connect (OSTI)

    Li, Wentao; Liu, Jiansheng; Wang, Wentao; Chen, Qiang; Zhang, Hui; Tian, Ye; Zhang, Zhijun; Qi, Rong; Wang, Cheng; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2013-11-15

    The multiple filaments formation process in the laser wakefield accelerator (LWFA) was observed by imaging the transmitted laser beam after propagating in the plasma of different density. During propagation, the laser first self-focused into a single filament. After that, it began to defocus with energy spreading in the transverse direction. Two filaments then formed from it and began to propagate independently, moving away from each other. We have also demonstrated that the laser multiple filamentation would lead to the multiple electron beams acceleration in the LWFA via ionization-induced injection scheme. Besides, its influences on the accelerated electron beams were also analyzed both in the single-stage LWFA and cascaded LWFA.

  17. Method of deposition of silicon carbide layers on substrates and product

    DOE Patents [OSTI]

    Angelini, Peter; DeVore, Charles E.; Lackey, Walter J.; Blanco, Raymond E.; Stinton, David P.

    1984-01-01

    A method for direct chemical vapor deposition of silicon carbide to substrates, especially nuclear waste particles, is provided by the thermal decomposition of methylsilane at about 800.degree. C. to 1050.degree. C. when the substrates have been confined within a suitable coating environment.

  18. Carbide-derived carbons - From porous networks to nanotubes and graphene

    SciTech Connect (OSTI)

    Presser, V.; Heon, M.; Gogotsi, Y.

    2011-02-09

    Carbide-derived carbons (CDCs) are a large family of carbon materials derived from carbide precursors that are transformed into pure carbon via physical (e.g., thermal decomposition) or chemical (e.g., halogenation) processes. Structurally, CDC ranges from amorphous carbon to graphite, carbon nanotubes or graphene. For halogenated carbides, a high level of control over the resulting amorphous porous carbon structure is possible by changing the synthesis conditions and carbide precursor. The large number of resulting carbon structures and their tunability enables a wide range of applications, from tribological coatings for ceramics, or selective sorbents, to gas and electrical energy storage. In particular, the application of CDC in supercapacitors has recently attracted much attention. This review paper summarizes key aspects of CDC synthesis, properties, and applications. It is shown that the CDC structure and properties are sensitive to changes of the synthesis parameters. Understanding of processingstructureproperties relationships facilitates tuning of the carbon material to the requirements of a certain application.

  19. Mechanisms of leiomodin 2-mediated regulation of actin filament in muscle

    Office of Scientific and Technical Information (OSTI)

    cells (Journal Article) | SciTech Connect Mechanisms of leiomodin 2-mediated regulation of actin filament in muscle cells Citation Details In-Document Search Title: Mechanisms of leiomodin 2-mediated regulation of actin filament in muscle cells Authors: Chen, Xiaorui ; Ni, Fengyun ; Kondrashkina, Elena ; Ma, Jianpeng ; Wang, Qinghua [1] ; NWU) [2] ; Rice) [2] + Show Author Affiliations Baylor ( Publication Date: 2015-12-04 OSTI Identifier: 1228088 Resource Type: Journal Article Resource

  20. Plasma channels during filamentation of a femtosecond laser pulse with wavefront astigmatism in air

    SciTech Connect (OSTI)

    Dergachev, A A; Kandidov, V P; Shlenov, S A; Ionin, A A; Mokrousova, D V; Seleznev, L V; Sinitsyn, D V; Sunchugasheva, E S; Shustikova, A P

    2014-12-31

    We have demonstrated experimentally and numerically the possibility of controlling parameters of plasma channels formed during filamentation of a femtosecond laser pulse by introducing astigmatism in the laser beam wavefront. It is found that weak astigmatism increases the length of the plasma channel in comparison with the case of aberration-free focusing and that strong astigmatism can cause splitting of the plasma channel into two channels located one after another on the filament axis. (interaction of laser radiation with matter. laser plasma)

  1. SYMPATHETIC PARTIAL AND FULL FILAMENT ERUPTIONS OBSERVED IN ONE SOLAR BREAKOUT EVENT

    SciTech Connect (OSTI)

    Shen Yuandeng; Liu Yu; Su Jiangtao

    2012-05-01

    We report two sympathetic solar eruptions including a partial and a full flux rope eruption in a quadrupolar magnetic region where a large and a small filament resided above the middle and the east neutral lines, respectively. The large filament first rose slowly at a speed of 8 km s{sup -1} for 23 minutes; it then accelerated to 102 km s{sup -1}. Finally, this filament erupted successfully and caused a coronal mass ejection. During the slow rising phase, various evidence for breakout-like external reconnection has been identified at high and low temperature lines. The eruption of the small filament started around the end of the large filament's slow rising. This filament erupted partially, and no associated coronal mass ejection could be detected. Based on a potential field extrapolation, we find that the topology of the three-dimensional coronal field above the source region is composed of three low-lying lobes and a large overlying flux system, and a null point located between the middle lobe and the overlying antiparallel flux system. We propose a possible mechanism within the framework of the magnetic breakout model to interpret the sympathetic filament eruptions, in which the magnetic implosion mechanism is thought to be a possible link between the sympathetic eruptions, and the external reconnection at the null point transfers field lines from the middle lobe to the lateral lobes and thereby leads to the full (partial) eruption of the observed large (small) filament. Other possible mechanisms are also discussed briefly. We conclude that the structural properties of coronal fields are important for producing sympathetic eruptions.

  2. A chain of winking (oscillating) filaments triggered by an invisible extreme-ultraviolet wave

    SciTech Connect (OSTI)

    Shen, Yuandeng; Tian, Zhanjun; Zhao, Ruijuan; Ichimoto, Kiyoshi; Ishii, Takako T.; Shibata, Kazunari

    2014-05-10

    Winking (oscillating) filaments have been observed for many years. However, observations of successive winking filaments in one event have not yet been reported. In this paper, we present the observations of a chain of winking filaments and a subsequent jet that are observed right after the X2.1 flare in AR11283. The event also produced an extreme-ultraviolet (EUV) wave that has two components: an upward dome-like wave (850 km s{sup 1}) and a lateral surface wave (554 km s{sup 1}) that was very weak (or invisible) in imaging observations. By analyzing the temporal and spatial relationships between the oscillating filaments and the EUV waves, we propose that all the winking filaments and the jet were triggered by the weak (or invisible) lateral surface EUV wave. The oscillation of the filaments last for two or three cycles, and their periods, Doppler velocity amplitudes, and damping times are 11-22 minutes, 6-14 km s{sup 1}, and 25-60 minutes, respectively. We further estimate the radial component magnetic field and the maximum kinetic energy of the filaments, and they are 5-10 G and ?10{sup 19} J, respectively. The estimated maximum kinetic energy is comparable to the minimum energy of ordinary EUV waves, suggesting that EUV waves can efficiently launch filament oscillations on their path. Based on our analysis results, we conclude that the EUV wave is a good agent for triggering and connecting successive but separated solar activities in the solar atmosphere, and it is also important for producing solar sympathetic eruptions.

  3. Hot-filament chemical vapor deposition chamber and process with multiple gas inlets

    DOE Patents [OSTI]

    Deng, Xunming; Povolny, Henry S.

    2004-06-29

    A thin film deposition method uses a vacuum confinement cup that employs a dense hot filament and multiple gas inlets. At least one reactant gas is introduced into the confinement cup both near and spaced apart from the heated filament. An electrode inside the confinement cup is used to generate plasma for film deposition. The method is used to deposit advanced thin films (such as silicon based thin films) at a high quality and at a high deposition rate.

  4. Structural basis for the prion-like MAVS filaments in antiviral innate

    Office of Scientific and Technical Information (OSTI)

    immunity (Journal Article) | SciTech Connect Structural basis for the prion-like MAVS filaments in antiviral innate immunity Citation Details In-Document Search Title: Structural basis for the prion-like MAVS filaments in antiviral innate immunity Authors: Xu, Hui ; He, Xiaojing ; Zheng, Hui ; Huang, Lily J ; Hou, Fajian ; Yu, Zhiheng ; de la Cruz, Michael Jason ; Borkowski, Brian ; Zhang, Xuewu ; Chen, Zhijian J ; Jiang, Qiu-Xing [1] ; HHMI) [2] + Show Author Affiliations (UTSMC) (

  5. EMERGENCE OF HELICAL FLUX AND THE FORMATION OF AN ACTIVE REGION FILAMENT CHANNEL

    SciTech Connect (OSTI)

    Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K.

    2010-07-20

    We present comprehensive observations of the formation and evolution of a filament channel within NOAA Active Region (AR) 10978 from Hinode/Solar Optical Telescope and TRACE. We employ sequences of Hinode spectro-polarimeter maps of the AR, accompanying Hinode Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode Broadband Filter Instrument filtergrams in the Ca II H line and G-band, Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 A image sequences. The development of the channel resembles qualitatively that presented by Okamoto et al. in that many indicators point to the emergence of a pre-existing sub-surface magnetic flux rope. The consolidation of the filament channel into a coherent structure takes place rapidly during the course of a few hours, and the filament form then gradually shrinks in width over the following two days. Particular to this filament channel is the observation of a segment along its length of horizontal, weak (500 G) flux that, unlike the rest of the filament channel, is not immediately flanked by strong vertical plage fields of opposite polarity on each side of the filament. Because this isolated horizontal field is observed in photospheric lines, we infer that it is unlikely that the channel formed as a result of reconnection in the corona, but the low values of inferred magnetic fill fraction along the entire length of the filament channel suggest that the bulk of the field resides somewhat above the low photosphere. Correlation tracking of granulation in the G band presents no evidence for either systematic flows toward the channel or systematic shear flows along it. The absence of these flows, along with other indications of these data from multiple sources, reinforces (but does not conclusively demonstrate) the picture of an emerging flux rope as the origin of this AR filament channel.

  6. Role of filament annealing in the kinetics and thermodynamics of nucleated polymerization

    SciTech Connect (OSTI)

    Michaels, Thomas C. T.; Knowles, Tuomas P. J.

    2014-06-07

    The formation of nanoscale protein filaments from soluble precursor molecules through nucleated polymerization is a common form of supra-molecular assembly phenomenon. This process underlies the generation of a range of both functional and pathological structures in nature. Filament breakage has emerged as a key process controlling the kinetics of the growth reaction since it increases the number of filament ends in the system that can act as growth sites. In order to ensure microscopic reversibility, however, the inverse process of fragmentation, end-to-end annealing of filaments, is a necessary component of a consistent description of such systems. Here, we combine Smoluchowski kinetics with nucleated polymerization models to generate a master equation description of protein fibrillization, where filamentous structures can undergo end-to-end association, in addition to elongation, fragmentation, and nucleation processes. We obtain self-consistent closed-form expressions for the growth kinetics and discuss the key physics that emerges from considering filament fusion relative to current fragmentation only models. Furthermore, we study the key time scales that describe relaxation to equilibrium.

  7. RESONANTLY DAMPED KINK MAGNETOHYDRODYNAMIC WAVES IN A PARTIALLY IONIZED FILAMENT THREAD

    SciTech Connect (OSTI)

    Soler, R.; Oliver, R.; Ballester, J. L. E-mail: ramon.oliver@uib.e

    2009-12-10

    Transverse oscillations of solar filament and prominence threads have been frequently reported. These oscillations have the common features of being of short period (2-10 minutes) and being damped after a few periods. The observations are interpreted as kink magnetohydrodynamic (MHD) wave modes, whereas resonant absorption in the Alfven continuum and ion-neutral collisions are candidates to be the damping mechanisms. Here, we study both analytically and numerically the time damping of kink MHD waves in a cylindrical, partially ionized filament thread embedded in a coronal environment. The thread model is composed of a straight and thin, homogeneous filament plasma, with a transverse inhomogeneous transitional layer where the plasma physical properties vary continuously from filament to coronal conditions. The magnetic field is homogeneous and parallel to the thread axis. We find that the kink mode is efficiently damped by resonant absorption for typical wavelengths of filament oscillations, the damping times being compatible with the observations. Partial ionization does not affect the process of resonant absorption, and the filament plasma ionization degree is only important for the damping for wavelengths much shorter than those observed. To our knowledge, this is the first time that the phenomenon of resonant absorption is studied in a partially ionized plasma.

  8. STAR FORMATION IN THE TAURUS FILAMENT L 1495: FROM DENSE CORES TO STARS

    SciTech Connect (OSTI)

    Schmalzl, Markus; Kainulainen, Jouni; Henning, Thomas; Launhardt, Ralf; Quanz, Sascha P.; Alves, Joao; Goodman, Alyssa A.; Pineda, Jaime E.; Roman-Zuniga, Carlos G.

    2010-12-10

    We present a study of dense structures in the L 1495 filament in the Taurus Molecular Cloud and examine its star-forming properties. In particular, we construct a dust extinction map of the filament using deep near-infrared observations, exposing its small-scale structure in unprecedented detail. The filament shows highly fragmented substructures and a high mass-per-length value of M{sub line} = 17 M{sub sun} pc{sup -1}, reflecting star-forming potential in all parts of it. However, a part of the filament, namely B 211, is remarkably devoid of young stellar objects. We argue that in this region the initial filament collapse and fragmentation is still taking place and star formation is yet to occur. In the star-forming part of the filament, we identify 39 cores with masses from 0.4 to 10 M{sub sun} and preferred separations in agreement with the local Jeans length. Most of these cores exceed the Bonnor-Ebert critical mass, and are therefore likely to collapse and form stars. The dense core mass function follows a power law with exponent {Gamma} = 1.2 {+-} 0.2, a form commonly observed in star-forming regions.

  9. NEW VACUUM SOLAR TELESCOPE OBSERVATIONS OF A FLUX ROPE TRACKED BY A FILAMENT ACTIVATION

    SciTech Connect (OSTI)

    Yang, Shuhong; Zhang, Jun; Liu, Zhong; Xiang, Yongyuan E-mail: zjun@nao.cas.cn

    2014-04-01

    One main goal of the New Vacuum Solar Telescope (NVST) which is located at the Fuxian Solar Observatory is to image the Sun at high resolution. Based on the high spatial and temporal resolution NVST H? data and combined with the simultaneous observations from the Solar Dynamics Observatory for the first time, we investigate a flux rope tracked by filament activation. The filament material is initially located at one end of the flux rope and fills in a section of the rope; the filament is then activated by magnetic field cancellation. The activated filament rises and flows along helical threads, tracking the twisted flux rope structure. The length of the flux rope is about 75Mm, the average width of its individual threads is 1.11Mm, and the estimated twist is 1?. The flux rope appears as a dark structure in H? images, a partial dark and partial bright structure in 304 , and as a bright structure in 171 and 131 images. During this process, the overlying coronal loops are quite steady since the filament is confined within the flux rope and does not erupt successfully. It seems that, for the event in this study, the filament is located and confined within the flux rope threads, instead of being suspended in the dips of twisted magnetic flux.

  10. Steady State Sputtering Yields and Surface Compositions of Depleted Uranium and Uranium Carbide bombarded by 30 keV Gallium or 16 keV Cesium Ions.

    SciTech Connect (OSTI)

    Siekhaus, W. J.; Teslich, N. E.; Weber, P. K.

    2014-10-23

    Depleted uranium that included carbide inclusions was sputtered with 30-keV gallium ions or 16-kev cesium ions to depths much greater than the ions range, i.e. using steady-state sputtering. The recession of both the uraniums and uranium carbides surfaces and the ion corresponding fluences were used to determine the steady-state target sputtering yields of both uranium and uranium carbide, i.e. 6.3 atoms of uranium and 2.4 units of uranium carbide eroded per gallium ion, and 9.9 uranium atoms and 3.65 units of uranium carbide eroded by cesium ions. The steady state surface composition resulting from the simultaneous gallium or cesium implantation and sputter-erosion of uranium and uranium carbide were calculated to be U??Ga??, (UC)??Ga?? and U??Cs?, (UC)??Cs??, respectively.

  11. Characterization of transition carbides in quench and partitioned steel microstructures by Mössbauer spectroscopy and complementary techniques

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Pierce, D. T.; Coughlin, D. R.; Williamson, D. L.; Clarke, K. D.; Clarke, A. J.; Speer, J. G.; De Moor, E.

    2015-05-01

    Quenching and partitioning (Q&P) produces steel microstructures with martensite and austenite that exhibit promising property combinations for third generation advanced high strength steels. Understanding the kinetics of reactions that compete for available carbon, such as carbide formation, is critical for alloying and processing design and achieving austenite enrichment and retention during Q&P. Mössbauer effect spectroscopy (MES) was used to characterize Q&P microstructures in a 0.38C-1.54Mn-1.48Si wt.% steel after quenching to 225 °C and partitioning at 400 °C for 10 or 300 s, with an emphasis on transition carbides. The recoilless fraction for η-carbide was calculated and a correction for saturationmore » of the MES absorption spectrum was applied, making quantitative measurements of small amounts of η-carbide, including non-stoichiometric η-carbide, possible in Q&P microstructures. Complementary transmission electron microscopy confirmed the presence of η-carbides, and MES and X-ray diffraction were used to characterize the austenite. The amount of η-carbide formed during Q&P ranged from 1.4 to 2.4 at.%, accounting for a substantial portion (~24% to 41%) of the bulk carbon content of the steel. The amount (5.0 at.%) of η-carbide that formed after quenching and tempering (Q&T) at 400 °C for 300 s was significantly greater than after partitioning at 400 °C for 300 s (2.4 at.%), suggesting that carbon partitioning from martensite to austenite occurs in conjunction with η-carbide formation during Q&P in these specimens.« less

  12. Characterization of transition carbides in quench and partitioned steel microstructures by Mössbauer spectroscopy and complementary techniques

    SciTech Connect (OSTI)

    Pierce, D. T.; Coughlin, D. R.; Williamson, D. L.; Clarke, K. D.; Clarke, A. J.; Speer, J. G.; De Moor, E.

    2015-05-01

    Quenching and partitioning (Q&P) produces steel microstructures with martensite and austenite that exhibit promising property combinations for third generation advanced high strength steels. Understanding the kinetics of reactions that compete for available carbon, such as carbide formation, is critical for alloying and processing design and achieving austenite enrichment and retention during Q&P. Mössbauer effect spectroscopy (MES) was used to characterize Q&P microstructures in a 0.38C-1.54Mn-1.48Si wt.% steel after quenching to 225 °C and partitioning at 400 °C for 10 or 300 s, with an emphasis on transition carbides. The recoilless fraction for η-carbide was calculated and a correction for saturation of the MES absorption spectrum was applied, making quantitative measurements of small amounts of η-carbide, including non-stoichiometric η-carbide, possible in Q&P microstructures. Complementary transmission electron microscopy confirmed the presence of η-carbides, and MES and X-ray diffraction were used to characterize the austenite. The amount of η-carbide formed during Q&P ranged from 1.4 to 2.4 at.%, accounting for a substantial portion (~24% to 41%) of the bulk carbon content of the steel. The amount (5.0 at.%) of η-carbide that formed after quenching and tempering (Q&T) at 400 °C for 300 s was significantly greater than after partitioning at 400 °C for 300 s (2.4 at.%), suggesting that carbon partitioning from martensite to austenite occurs in conjunction with η-carbide formation during Q&P in these specimens.

  13. The interaction of polarized microwaves with planar arrays of femtosecond laser-produced plasma filaments in air

    SciTech Connect (OSTI)

    Marian, Anca; El Morsli, Mbark; Vidal, Francois; Payeur, Stephane; Kieffer, Jean-Claude; Chateauneuf, Marc; Theberge, Francis; Dubois, Jacques

    2013-02-15

    The interaction of polarized microwaves with subwavelength arrays of parallel plasma filaments, such as those produced by the propagation of high-power femtosecond laser pulses in ambient air, was investigated by calculating the reflection and transmission coefficients as a function of the incidence angles using the finite-difference time-domain (FDTD) method. The time evolution of these coefficients was calculated and compared with experiments. It is found that the plasma filaments array becomes transparent when the polarization of the microwave radiation is perpendicular to the filaments axis, regardless the incidence angle of the microwave with respect to the filaments, except near grazing incidence. Increasing the filaments electron density or diameter, or decreasing the electron collision frequency or filaments spacing, decreases the transmission and increases the reflection. Transmission decreases when increasing the number of filament layers while reflection remains unchanged as the number of filament layers exceeds a given number ({approx}3 in our case). Transmission slightly increases when disorder is introduced in the filament arrays. The detailed calculation results are compared with those obtained from the simple birefringent slab model, which provides a convenient framework to calculate approximately the properties of filament arrays.

  14. Carbide Coatings for Nickel Alloys, Graphite and Carbon/Carbon Composites to be used in Fluoride Salt Valves

    SciTech Connect (OSTI)

    Nagle, Denis; Zhang, Dajie

    2015-10-22

    The focus of this research was concerned with developing materials technology that supports the evolution of Generation IV Advanced High Temperature Reactor (AHTR) concepts. Specifically, we investigate refractory carbide coatings for 1) nickel alloys, and 2) commercial carbon-carbon composites (CCCs). Numerous compelling reasons have driven us to focus on carbon and carbide materials. First, unlike metals, the strength and modulus of CCCs increase with rising temperature. Secondly, graphite and carbon composites have been proven effective for resisting highly corrosive fluoride melts such as molten cryolite [Na?AlF?] at ~1000C in aluminum reduction cells. Thirdly, graphite and carbide materials exhibit extraordinary radiation damage tolerance and stability up to 2000C. Finally, carbides are thermodynamically more stable in liquid fluoride salt than the corresponding metals (i.e. Cr and Zr) found in nickel based alloys.

  15. Elastic properties of B-C-N films grown by N{sub 2}-reactive sputtering from boron carbide targets

    SciTech Connect (OSTI)

    Salas, E.; Jimnez Riobo, R. J.; Jimnez-Villacorta, F.; Prieto, C.; Snchez-Marcos, J.; Dept. Qumica-Fsica Aplicada, Universidad Autnoma de Madrid, Cantoblanco, 28049 Madrid ; Muoz-Martn, A.; Prieto, J. E.; Joco, V.

    2013-12-07

    Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B{sub 4}C target and N{sub 2} as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions.

  16. THE SPIN AND ORIENTATION OF DARK MATTER HALOS WITHIN COSMIC FILAMENTS

    SciTech Connect (OSTI)

    Zhang Youcai; Yang Xiaohu; Lin Weipeng; Faltenbacher, Andreas; Springel, Volker; Wang Huiyuan

    2009-11-20

    Clusters, filaments, sheets, and voids are the building blocks of the cosmic web. Forming dark matter halos respond to these different large-scale environments, and this in turn affects the properties of galaxies hosted by the halos. It is therefore important to understand the systematic correlations of halo properties with the morphology of the cosmic web, as this informs both about galaxy formation physics and possible systematics of weak lensing studies. In this study, we present and compare two distinct algorithms for finding cosmic filaments and sheets, a task which is far less well established than the identification of dark matter halos or voids. One method is based on the smoothed dark matter density field and the other uses the halo distributions directly. We apply both techniques to one high-resolution N-body simulation and reconstruct the filamentary/sheet like network of the dark matter density field. We focus on investigating the properties of the dark matter halos inside these structures, in particular, on the directions of their spins and the orientation of their shapes with respect to the directions of the filaments and sheets. We find that both the spin and the major axes of filament halos with masses approx<10{sup 13} h {sup -1} M{sub sun} are preferentially aligned with the direction of the filaments. The spins and major axes of halos in sheets tend to lie parallel to the sheets. There is an opposite mass dependence of the alignment strength for the spin (negative) and major (positive) axes, i.e. with increasing halo mass the major axis tends to be more strongly aligned with the direction of the filament, whereas the alignment between halo spin and filament becomes weaker with increasing halo mass. The alignment strength as a function of the distance to the most massive node halo indicates that there is a transit large-scale environment impact: from the two-dimensional collapse phase of the filament to the three-dimensional collapse phase of the cluster/node halo at small separation. Overall, the two algorithms for filament/sheet identification investigated here agree well with each other. The method based on halos alone can be easily adapted for use with observational data sets.

  17. Deposition of device quality, low hydrogen content, amorphous silicon films by hot filament technique using "safe" silicon source gas

    DOE Patents [OSTI]

    Mahan, Archie Harvin (Golden, CO); Molenbroek, Edith C. (Boulder, CO); Nelson, Brent P. (Golden, CO)

    1998-01-01

    A method of producing hydrogenated amorphous silicon on a substrate by flowing a stream of safe (diluted to less than 1%) silane gas past a heated filament.

  18. Effects of higher-order Kerr nonlinearity and plasma diffraction on multiple filamentation of ultrashort laser pulses in air

    SciTech Connect (OSTI)

    Huang, T. W.; Zhou, C. T.; Institute of Applied Physics and Computational Mathematics, Beijing 100094; Science College, National University of Defense Technology, Changsha 410073 ; Zhang, H.; He, X. T.; Institute of Applied Physics and Computational Mathematics, Beijing 100094

    2013-07-15

    The effect of higher-order Kerr nonlinearity on channel formation by, and filamentation of, ultrashort laser pulses propagating in air is considered. Filament patterns originating from multiphoton ionization of the air molecules with and without the higher-order Kerr and molecular-rotation effects are investigated. It is found that diverging multiple filaments are formed if only the plasma-induced defocusing effect is included. In the presence of the higher-order Kerr effects, the light channel can exist for a long distance. The effect of noise on the filament patterns is also discussed.

  19. General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation

    SciTech Connect (OSTI)

    Van Gorder, Robert A.

    2014-06-15

    In his study of superfluid turbulence in the low-temperature limit, Svistunov [Superfluid turbulence in the low-temperature limit, Phys. Rev. B 52, 3647 (1995)] derived a Hamiltonian equation for the self-induced motion of a vortex filament. Under the local induction approximation (LIA), the Svistunov formulation is equivalent to a nonlinear dispersive partial differential equation. In this paper, we consider a family of rotating vortex filament solutions for the LIA reduction of the Svistunov formulation, which we refer to as the 2D LIA (since it permits a potential formulation in terms of two of the three Cartesian coordinates). This class of solutions holds the well-known Hasimoto-type planar vortex filament [H. Hasimoto, Motion of a vortex filament and its relation to elastica, J. Phys. Soc. Jpn. 31, 293 (1971)] as one reduction and helical solutions as another. More generally, we obtain solutions which are periodic in the space variable. A systematic analytical study of the behavior of such solutions is carried out. In the case where vortex filaments have small deviations from the axis of rotation, closed analytical forms of the filament solutions are given. A variety of numerical simulations are provided to demonstrate the wide range of rotating filament behaviors possible. Doing so, we are able to determine a number of vortex filament structures not previously studied. We find that the solution structure progresses from planar to helical, and then to more intricate and complex filament structures, possibly indicating the onset of superfluid turbulence.

  20. Methods for transforming and expression screening of filamentous fungal cells with a DNA library

    DOE Patents [OSTI]

    Teter, Sarah; Lamsa, Michael; Cherry, Joel; Ward, Connie

    2015-06-02

    The present invention relates to methods for expression screening of filamentous fungal transformants, comprising: (a) isolating single colony transformants of a DNA library introduced into E. coli; (b) preparing DNA from each of the single colony E. coli transformants; (c) introducing a sample of each of the DNA preparations of step (b) into separate suspensions of protoplasts of a filamentous fungus to obtain transformants thereof, wherein each transformant contains one or more copies of an individual polynucleotide from the DNA library; (d) growing the individual filamentous fungal transformants of step (c) on selective growth medium, thereby permitting growth of the filamentous fungal transformants, while suppressing growth of untransformed filamentous fungi; and (e) measuring activity or a property of each polypeptide encoded by the individual polynucleotides. The present invention also relates to isolated polynucleotides encoding polypeptides of interest obtained by such methods, to nucleic acid constructs, expression vectors, and recombinant host cells comprising the isolated polynucleotides, and to methods of producing the polypeptides encoded by the isolated polynucleotides.

  1. Formation of conical emission of supercontinuum during filamentation of femtosecond laser radiation in fused silica

    SciTech Connect (OSTI)

    Kandidov, V. P. Smetanina, E. O.; Dormidonov, A. E.; Kompanets, V. O.; Chekalin, S. V.

    2011-09-15

    The formation of conical emission of supercontinuum during filamentation of femtosecond laser pulses with central wavelengths in a wide range is studied experimentally, numerically, and analytically. The frequency-angular intensity distribution of the spectral components of conical emission is determined by the interference of supercontinuum emission in a filament of a femtosecond laser pulse. The interference of supercontinuum emission has a general character, exists at different regimes of group velocity dispersion, gives rise to the fine spectral structure after the pulse splitting into subpulses and the formation of a distributed supercontinuum source in an extended filament, and causes the decomposition of the continuous spectrum of conical emission into many high-contrast maxima after pulse refocusing in the filament. In spectroscopic studies with a tunable femtosecond radiation source based on a TOPAS parametric amplifier, we used an original scheme with a wedge fused silica sample. Numerical simulations have been performed using a system of equations of nonlinear-optical interaction of laser radiation under conditions of diffraction, wave nonstationarity, and material dispersion in fused silica. The analytic study is based on the interference model of formation of conical emission by supercontinuum sources moving in a filament.

  2. Motor-mediated microtubule self-organization in dilute and semi-dilute filament solutions.

    SciTech Connect (OSTI)

    Swaminathan, S.; Ziebert, F.; Aranson, I. S.; Karpeev, D.

    2011-01-01

    We study molecular motor-induced microtubule self-organization in dilute and semi-dilute filament solutions. In the dilute case, we use a probabilistic model of microtubule interaction via molecular motors to investigate microtubule bundle dynamics. Microtubules are modeled as polar rods interacting through fully inelastic, binary collisions. Our model indicates that initially disordered systems of interacting rods exhibit an orientational instability resulting in spontaneous ordering. We study the existence and dynamic interaction of microtubule bundles analytically and numerically. Our results reveal a long term attraction and coalescing of bundles indicating a clear coarsening in the system; microtubule bundles concentrate into fewer orientations on a slow logarithmic time scale. In semi-dilute filament solutions, multiple motors can bind a filament to several others and, for a critical motor density, induce a transition to an ordered phase with a nonzero mean orientation. Motors attach to a pair of filaments and walk along the pair bringing them into closer alignment. We develop a spatially homogenous, mean-field theory that explicitly accounts for a force-dependent detachment rate of motors, which in turn affects the mean and the fluctuations of the net force acting on a filament. We show that the transition to the oriented state can be both continuous and discontinuous when the force-dependent detachment of motors is important.

  3. ANALYSIS OF THE SIMULTANEOUS ROTATION AND NON-RADIAL PROPAGATION OF AN ERUPTIVE FILAMENT

    SciTech Connect (OSTI)

    Bi Yi; Jiang Yunchun; Yang Jiayan; Zheng Ruisheng; Hong Junchao; Li Haidong; Yang Dan; Yang Bo

    2013-08-20

    The rotation of eruptive filaments is not only related to the kink instability occurring in the solar corona but also may result from the interaction between the large-scale magnetic field and the eruptions themselves. This interaction could likewise make the filament deflect in the radial direction. By means of data obtained by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and observations from the Solar Terrestrial Relations Observatory, we study an eruptive filament showing both rotation and non-radial motion. The consequence of the three-dimensional reconstruction of the filament axis indicates that a significant rotation was simultaneous with the severe deflection in the latitude during the eruption. In combination with the results of a derived coronal magnetic configuration, our observations suggested that the non-radial motion resulted from the interaction between the eruption and an overlying pseudostreamer. Moreover, we find that the deflection of the eruption is asymmetric, with its eastern segment being dragged more significantly than its western one. Therefore, we suggested that the action of the asymmetric deflection is possibly an alternative mechanism for the rotation of the eruptive filament.

  4. SDO/AIA OBSERVATIONS OF LARGE-AMPLITUDE LONGITUDINAL OSCILLATIONS IN A SOLAR FILAMENT

    SciTech Connect (OSTI)

    Li Ting; Zhang Jun E-mail: zjun@nao.cas.cn

    2012-11-20

    We present the first Solar Dynamics Observatory/Atmospheric Imaging Assembly observations of the large-amplitude longitudinal (LAL) oscillations in the south and north parts (SP and NP) of a solar filament on 2012 April 7. Both oscillations are triggered by flare activities close to the filament. The period varies with filamentary threads, ranging from 44 to 67 minutes. The oscillations of different threads are out of phase, and their velocity amplitudes vary from 30 to 60 km s{sup -1}, with a maximum displacement of about 25 Mm. The oscillations of the SP repeat for about four cycles without any significant damping and then a nearby C2.4 flare causes the transition from the LAL oscillations of the filament to its later eruption. The filament eruption is also associated with a coronal mass ejection and a B6.8 flare. However, the oscillations of the NP damp with time and die out at last. Our observations show that the activated part of the SP repeatedly shows a helical motion. This indicates that the magnetic structure of the filament is possibly modified during this process. We suggest that the restoring force is the coupling of the magnetic tension and gravity.

  5. Filament-strung stand-off elements for maintaining pane separation in vacuum insulating glazing units

    DOE Patents [OSTI]

    Bettger, Kenneth J; Stark, David H

    2013-08-20

    A vacuum insulating glazing unit (VIGU) comprises first and second panes of transparent material, first and second anchors, a plurality of filaments, a plurality of stand-off elements, and seals. The first and second panes of transparent material have edges and inner and outer faces, are disposed with their inner faces substantially opposing one another, and are separated by a gap having a predetermined height. The first and second anchors are disposed at opposite edges of one pane of the VIGU. Each filament is attached at one end to the first anchor and at the other end to the second anchor, and the filaments are collectively disposed between the panes substantially parallel to one another. The stand-off elements are affixed to each filament at predetermined positions along the filament, and have a height substantially equal to the predetermined height of the gap such that the each stand-off element touches the inner surfaces of both panes. The seals are disposed about the edges of the panes, enclosing the stand-off elements within a volume between the panes from which the atmosphere may be evacuated to form a partial vacuum.

  6. Nonlinear-optical and structural properties of nanocrystalline silicon carbide films

    SciTech Connect (OSTI)

    Brodyn, M. S.; Volkov, V. I. Lyakhovetskii, V. R.; Rudenko, V. I.; Puzilkov, V. M.; Semenov, A. V.

    2012-02-15

    The aim of this study is to investigate the nonlinearity of refraction in nanostructured silicon carbide films depending on their structural features (synthesis conditions for such films, substrate temperature during their deposition, concentration of the crystalline phase in the film, Si/C ratio of atomic concentrations in the film, and size of SiC nanocrystals formed in the film). The corresponding dependences are obtained, as well as the values of nonlinear-optical third-order susceptibility {chi}{sup (3)}({omega}; {omega}, -{omega}, {omega}) for various silicon polytypes (3C, 21R, and 27R) which exceed the value of {chi}{sup (3)} in bulk silicon carbide single crystals by four orders of magnitude.

  7. Status of steady-state irradiation testing of mixed-carbide fuel designs. [LMFBR

    SciTech Connect (OSTI)

    Harry, G.R.

    1983-01-01

    The steady-state irradiation program of mixed-carbide fuels has demonstrated clearly the ability of carbide fuel pins to attain peak burnup greater than 12 at.% and peak fluences of 1.4 x 10/sup 23/ n/cm/sup 2/ (E > 0.1 MeV). Helium-bonded fuel pins in 316SS cladding have achieved peak burnups of 20.7 at.% (192 MWd/kg), and no breaches have occurred in pins of this design. Sodium-bonded fuel pins in 316SS cladding have achieved peak burnups of 15.8 at.% (146 MWd/kg). Breaches have occurred in helium-bonded fuel pins in PE-16 cladding (approx. 5 at.% burnup) and in D21 cladding (approx. 4 at.% burnup). Sodium-bonded fuel pins achieved burnups over 11 at.% in PE-16 cladding and over 6 at.% in D9 and D21 cladding.

  8. Method of synthesizing bulk transition metal carbide, nitride and phosphide catalysts

    DOE Patents [OSTI]

    Choi, Jae Soon; Armstrong, Beth L; Schwartz, Viviane

    2015-04-21

    A method for synthesizing catalyst beads of bulk transmission metal carbides, nitrides and phosphides is provided. The method includes providing an aqueous suspension of transition metal oxide particles in a gel forming base, dropping the suspension into an aqueous solution to form a gel bead matrix, heating the bead to remove the binder, and carburizing, nitriding or phosphiding the bead to form a transition metal carbide, nitride, or phosphide catalyst bead. The method can be tuned for control of porosity, mechanical strength, and dopant content of the beads. The produced catalyst beads are catalytically active, mechanically robust, and suitable for packed-bed reactor applications. The produced catalyst beads are suitable for biomass conversion, petrochemistry, petroleum refining, electrocatalysis, and other applications.

  9. Process of making titanium carbide (TiC) nano-fibrous felts

    DOE Patents [OSTI]

    Fong, Hao; Zhang, Lifeng; Zhao, Yong; Zhu, Zhengtao

    2015-01-13

    A method of synthesizing mechanically resilient titanium carbide (TiC) nanofibrous felts comprising continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix, comprising: (a) electrospinning a spin dope for making precursor nanofibers with diameters less than 0.5 J.Lm; (b) overlaying the nanofibers to produce a nanofibrous mat (felt); and then (c) heating the nano-felts first at a low temperature, and then at a high temperature for making electrospun continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix; and (d) chlorinating the above electrospun nano-felts at an elevated temperature to remove titanium for producing carbide derived carbon (CDC) nano-fibrous felt with high specific surface areas.

  10. Irradiation creep of nano-powder sintered silicon carbide at low neutron fluences

    SciTech Connect (OSTI)

    Koyanagi, Takaaki; Shimoda, Kazuya; Kondo, Sosuke; Hinoki, Tatsuya; Ozawa, Kazumi; Katoh, Yutai

    2014-12-01

    The irradiation creep behavior of nano-powder sintered silicon carbide was investigated using the bend stress relaxation method under neutron irradiation up to 1.9 dpa. The creep deformation was observed at all temperatures ranging from 380 to 1180 C mainly from the irradiation creep but with the increasing contributions from the thermal creep at higher temperatures. Microstructural observation and data analysis were performed.

  11. Solubility of niobium carbide and niobium carbonitride in alloyed austenite and ferrite

    SciTech Connect (OSTI)

    Sharma, R.C.; Kirkaldy, J.S.; Lakshmanan, V.K.

    1984-03-01

    The available data on the solubility of niobium carbide and niobium carbonitride in plain carbon and alloyed austenite has been analyzed via dilute solution thermodynamics with a view to establishing a consistent set of interaction parameters for predicting austenite + niobium carbonitride equilibria. The computation algorithm includes the prediction of phase mass fractions as a function of alloy composition and temperature between 900/sup 0/ and 1300/sup 0/C (tie lines). Analogous ferrite equilibri are included.

  12. I' I OAK RIDGE NATIONAL LABORATORY OPERATED B Y UNION CARBIDE CORPORATION

    Office of Legacy Management (LM)

    / I' I OAK RIDGE NATIONAL LABORATORY OPERATED B Y UNION CARBIDE CORPORATION NUCLEAR DIVISION POST OFFICE BOK X OAK RIDGE, TENNESSEE 37830 August 21, 1979 Department of Energy, Oak Ridge Operations Attention: E. L. Keller, Director for Technical Services Division Post Office Box E Oak Ridge, Tennessee 37830 Gentlemen: Formerly Utilized Site-Remedial Action Program - Post Decontamination Radiological Survey of a portion of the Former Kellex Laboratory Site, Jersey City, New Jersey Decontamination

  13. OAK RIDGE NATIONAL LABORATORY OPER*TEO BY UNION CARBIDE CORPORATION

    Office of Legacy Management (LM)

    ~$ ., . .Y.' ~. : ' : ,,, OAK RIDGE NATIONAL LABORATORY OPER*TEO BY UNION CARBIDE CORPORATION NUCLEAR DIVISION ' . ' : .m POST OFFICE BOX X OAK RIDGE, TENNESSEE ,X,0 ,. June 20, 1980 .~ ,, M r. Arthur J. 'Whitman Environmental and Safety 'Engineering Division U.S. Department of Energy ,) Washington, Oit. 20545 ., Dear Art: Soil Sample Analysis, City of Woburn Landfill, Woburn, Massachusetts ,,During a.radiological survey of the old.and new city of Woburn landfills (i-e: trip report.to Woburn,

  14. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

    DOE Patents [OSTI]

    Tiegs, T.N.; Lindemer, T.B.

    1991-02-19

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  15. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN); Lindemer, Terrence B. (Oak Ridge, TN)

    1991-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  16. The All Boron Carbide Diode Neutron Detector: Experiment and Modeling Approach

    SciTech Connect (OSTI)

    Sabirianov, Ildar F.; Brand, Jennifer I. |; Fairchild, Robert W.

    2008-07-01

    Boron carbide diode detectors, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theoretical expectations. The performance of the all boron carbide neutron detector differs, as expected, from devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector). Diodes were fabricated from natural abundance boron (20% {sup 10}B and 80% {sup 11}B.) directly on the metal substrates and metal contacts applied to the films as grown. The total boron depth was on the order of 2 microns. This is clearly not a conversion-layer configuration. The diodes were exposed to thermal neutrons generated from a paraffin moderated plutonium-beryllium source in moderated and un-moderated, as well as shielded and unshielded experimental configurations, where the expected energy peaks at at 2.31 MeV and 2.8 MeV were clearly observed, albeit with some incomplete charge collection typical of thinner diode structures. The results are compared with other boron based thin film detectors and literature models. (authors)

  17. Heat transfer mechanism with thin filaments including ceramic high temperature heat exchanger

    DOE Patents [OSTI]

    Im, K.H.; Ahluwalia, R.K.

    1994-10-18

    A radiative heat transfer mechanism in a furnace is described having burners through which pulverized coal and air are burned producing combustion gases and contaminants. A plurality of elongated conduits are positioned inside the furnace proximate to the burners generally parallel to the flow of combustion gases in the furnace. A plurality of thin filaments are inside each of the elongated hollow conduits, the filaments having diameters in the range of from about 1 micrometer to about 1,000 micrometers and having an infrared radiation cross-section sufficient to cause the filaments to heat upon exposure to infrared radiation. Blower mechanism is associated with the elongated conduits for limiting the amount of soot and ash which deposit on the conduits to preserve the radiative and convective transfer of heat energy from the combustion gases to the conduits. 7 figs.

  18. Heat transfer mechanism with thin filaments including ceramic high temperature heat exchanger

    DOE Patents [OSTI]

    Im, Kwan H. (Naperville, IL); Ahluwalia, Rajesh K. (Burr Ridge, IL)

    1994-01-01

    A radiative heat transfer mechanism in a furnace having burners through which pulverized coal and air are burned producing combustion gases and contaminants. A plurality of elongated conduits are positioned inside the furnace proximate to the burners generally parallel to the flow of combustion gases in the furnace. A plurality of thin filaments are inside each of the elongated hollow conduits, the filaments having diameters in the range of from about 1 micrometer to about 1,000 micrometers and having an infrared radiation cross-section sufficient to cause the filaments to heat upon exposure to infrared radiation. Blower mechanism is associated with the elongated conduits for limiting the amount of soot and ash which deposit on the conduits to preserve the radiative and convective transfer of heat energy from the combustion gases to the conduits.

  19. USING CORONAL CELLS TO INFER THE MAGNETIC FIELD STRUCTURE AND CHIRALITY OF FILAMENT CHANNELS

    SciTech Connect (OSTI)

    Sheeley, N. R. Jr.; Warren, H. P.; Martin, S. F.; Panasenco, O.

    2013-08-01

    Coronal cells are visible at temperatures of {approx}1.2 MK in Fe XII coronal images obtained from the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory spacecraft. We show that near a filament channel, the plumelike tails of these cells bend horizontally in opposite directions on the two sides of the channel like fibrils in the chromosphere. Because the cells are rooted in magnetic flux concentrations of majority polarity, these observations can be used with photospheric magnetograms to infer the direction of the horizontal field in filament channels and the chirality of the associated magnetic field. This method is similar to the procedure for inferring the direction of the magnetic field and the chirality of the fibril pattern in filament channels from H{alpha} observations. However, the coronal cell observations are easier to use and provide clear inferences of the horizontal field direction for heights up to {approx}50 Mm into the corona.

  20. FROM DUSTY FILAMENTS TO MASSIVE STARS: THE CASE OF NGC 7538 S

    SciTech Connect (OSTI)

    Naranjo-Romero, Raul; Zapata, Luis A.; Vazquez-Semadeni, Enrique; Takahashi, Satoko; Palau, Aina; Schilke, Peter

    2012-09-20

    We report on high-sensitivity and high angular resolution archival Submillimeter Array observations of the large ({approx}15,000 AU) putative circumstellar disk associated with the O-type protostar NGC 7538 S. Observations of the continuum resolve this putative circumstellar disk into five compact sources, with sizes {approx}3000 AU and masses {approx}10 M{sub Sun }. This confirms the results of recent millimeter observations made with CARMA/BIMA toward this object. However, we find that most of these compact sources eject collimated bipolar outflows, revealed by our silicon monoxide (SiO J = 5-4) observations, and confirm that these sources have a (proto)stellar nature. All outflows are perpendicular to the large and rotating dusty structure. We propose therefore that, rather than being a single massive circumstellar disk, NGC 7538 S could instead be a large and massive contracting or rotating filament that is fragmenting at scales of 0.1-0.01 pc to form several B-type stars, via the standard process involving outflows and disks. As in recent high spatial resolution studies of dusty filaments, our observations also suggest that thermal pressure does not seem to be sufficient to support the filament, so that either additional support needs to be invoked or else the filament must be in the process of collapsing. A smoothed particle hydrodynamics numerical simulation of the formation of a molecular cloud by converging warm neutral medium flows produces contracting filaments whose dimensions and spacings between the stars forming within them, as well as their column densities, strongly resemble those observed in the filament reported here.

  1. RHESSI AND TRACE OBSERVATIONS OF MULTIPLE FLARE ACTIVITY IN AR 10656 AND ASSOCIATED FILAMENT ERUPTION

    SciTech Connect (OSTI)

    Joshi, Bhuwan; Kushwaha, Upendra; Cho, K.-S.; Veronig, Astrid M.

    2013-07-01

    We present Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Transition Region and Coronal Explorer (TRACE) observations of multiple flare activity that occurred in the NOAA active region 10656 over a period of 2 hr on 2004 August 18. Out of four successive flares, three were class C events, and the final event was a major X1.8 solar eruptive flare. The activities during the pre-eruption phase, i.e., before the X1.8 flare, are characterized by three localized episodes of energy release occurring in the vicinity of a filament that produces intense heating along with non-thermal emission. A few minutes before the eruption, the filament undergoes an activation phase during which it slowly rises with a speed of {approx}12 km s{sup -1}. The filament eruption is accompanied by an X1.8 flare, during which multiple hard X-ray (HXR) bursts are observed up to 100-300 keV energies. We observe a bright and elongated coronal structure simultaneously in E(UV) and 50-100 keV HXR images underneath the expanding filament during the period of HXR bursts, which provides strong evidence for ongoing magnetic reconnection. This phase is accompanied by very high plasma temperatures of {approx}31 MK, followed by the detachment of the prominence from the solar source region. From the location, timing, strength, and spectrum of HXR emission, we conclude that the prominence eruption is driven by the distinct events of magnetic reconnection occurring in the current sheet below the erupting prominence. These multi-wavelength observations also suggest that the localized magnetic reconnections associated with different evolutionary stages of the filament in the pre-eruption phase play an important role in destabilizing the active-region filament through the tether-cutting process, leading to large-scale eruption and X-class flare.

  2. Fe XII STALKS AND THE ORIGIN OF THE AXIAL FIELD IN FILAMENT CHANNELS

    SciTech Connect (OSTI)

    Wang, Y.-M.; Sheeley, N. R. Jr.; Stenborg, G. E-mail: neil.sheeley@nrl.navy.mil

    2013-06-10

    Employing Fe XII images and line-of-sight magnetograms, we deduce the direction of the axial field in high-latitude filament channels from the orientation of the adjacent stalklike structures. Throughout the rising phase of the current solar cycle 24, filament channels poleward of latitude 30 Degree-Sign overwhelmingly obeyed the hemispheric chirality rule, being dextral (sinistral) in the northern (southern) hemisphere, corresponding to negative (positive) helicity. During the deep minimum of 2007-2009, the orientation of the Fe XII stalks was often difficult to determine, but no obvious violations of the rule were found. Although the hemispheric trend was still present during the maximum and early declining phase of cycle 23 (2000-2003), several high-latitude exceptions were identified at that time. From the observation that dextral (sinistral) filament channels form through the decay of active regions whose Fe XII features show a counterclockwise (clockwise) whorl, we conclude that the axial field direction is determined by the intrinsic helicity of the active regions. In contrast, generation of the axial field component by the photospheric differential rotation is difficult to reconcile with the observed chirality of polar crown and circular filament channels, and with the presence of filament channels along the equator. The main role of differential rotation in filament channel formation is to expedite the cancellation of flux and thus the removal of the transverse field component. We propose further that, rather than being ejected into the heliosphere, the axial field is eventually resubmerged by flux cancellation as the adjacent unipolar regions become increasingly mixed.

  3. Structure of a Longitudinal Actin Dimer Assembled by Tandem W Domains: Implications for Actin Filament Nucleation

    SciTech Connect (OSTI)

    Rebowski, Grzegorz; Namgoong, Suk; Boczkowska, Malgorzata; Leavis, Paul C.; Navaza, Jorge; Dominguez, Roberto

    2013-11-20

    Actin filament nucleators initiate polymerization in cells in a regulated manner. A common architecture among these molecules consists of tandem WASP homology 2 domains (W domains) that recruit three to four actin subunits to form a polymerization nucleus. We describe a low-resolution crystal structure of an actin dimer assembled by tandem W domains, where the first W domain is cross-linked to Cys374 of the actin subunit bound to it, whereas the last W domain is followed by the C-terminal pointed end-capping helix of thymosin {beta}4. While the arrangement of actin subunits in the dimer resembles that of a long-pitch helix of the actin filament, important differences are observed. These differences result from steric hindrance of the W domain with intersubunit contacts in the actin filament. We also determined the structure of the first W domain of Vibrio parahaemolyticus VopL cross-linked to actin Cys374 and show it to be nearly identical with non-cross-linked W-Actin structures. This result validates the use of cross-linking as a tool for the study of actin nucleation complexes, whose natural tendency to polymerize interferes with most structural methods. Combined with a biochemical analysis of nucleation, the structures may explain why nucleators based on tandem W domains with short inter-W linkers have relatively weak activity, cannot stay bound to filaments after nucleation, and are unlikely to influence filament elongation. The findings may also explain why nucleation-promoting factors of the Arp2/3 complex, which are related to tandem-W-domain nucleators, are ejected from branch junctions after nucleation. We finally show that the simple addition of the C-terminal pointed end-capping helix of thymosin {beta}4 to tandem W domains can change their activity from actin filament nucleation to monomer sequestration.

  4. Terahertz emission from a two-color plasma filament in a slot waveguide

    SciTech Connect (OSTI)

    Dietze, D.; Unterrainer, K.; Darmo, J.

    2012-02-27

    Terahertz emission in forward direction from a long two-color filament placed in the center of a slot waveguide is reported. The waveguide improves the collection and imaging of the generated THz radiation. By tuning the plate separation and position of the waveguide along the filament axis, the emitted mode can be matched to the collection optics. We achieved an increase of the detected electric field by 40% and of the THz pulse energy by four times compared to the case without waveguide.

  5. Numerical studies of third-harmonic generation in laser filament in air perturbed by plasma spot

    SciTech Connect (OSTI)

    Feng Liubin; Lu Xin; Liu Xiaolong; Li Yutong; Chen Liming; Ma Jinglong; Dong Quanli; Wang Weimin; Xi Tingting; Sheng Zhengming; Zhang Jie; He Duanwei

    2012-07-15

    Third-harmonic emission from laser filament intercepted by plasma spot is studied by numerical simulations. Significant enhancement of the third-harmonic generation is obtained due to the disturbance of the additional plasma. The contribution of the pure plasma effect and the possible plasma-enhanced third-order susceptibility on the third-harmonic generation enhancement are compared. It is shown that the plasma induced cancellation of destructive interference [Y. Liu et al., Opt. Commun. 284, 4706 (2011)] of two-colored filament is the dominant mechanism of the enhancement of third-harmonic generation.

  6. Femtosecond laser pulse filamentation under anomalous dispersion in fused silica. Part 1. Numerical investigation

    SciTech Connect (OSTI)

    Smetanina, E O; Kompanets, V O; Chekalin, Sergei V; Kandidov, V P

    2012-10-31

    We report the results of investigation of femtosecond laser pulse filamentation in fused silica by varying the wavelength in the range from 800 to 2300 nm. It is shown that in the case of the anomalous group-velocity dispersion, a sequence of 'light bullets' with a high spatial and temporal localisation of the light field is formed along the filament. The relation of the formation and propagation of light bullets with the formation of an isolated anti-Stokes wing of the supercontinuum spectrum is established. (nonlinear optical phenomena)

  7. Four-dimensional visualization of single and multiple laser filaments using in-line holographic microscopy

    SciTech Connect (OSTI)

    Abdollahpour, Daryoush; Papazoglou, Dimitrios G.; Tzortzakis, Stelios

    2011-11-15

    It is shown, both through simulations and experiments, that the in-line holographic microscopy technique can be used to retrieve very small refractive-index perturbations caused during the filamentation of ultrashort laser pulses. This technique provides the possibility of having spatially and temporally (four dimensions) resolved measurements of refractive-index changes, down to 10{sup -4}, from objects with diameters as small as 10 {mu}m. Moreover, we demonstrate the power of the technique in discriminating multiple filaments in a precise quantitative way.

  8. Formation of current filaments and magnetic field generation in a quantum current-carrying plasma

    SciTech Connect (OSTI)

    Niknam, A. R.; Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M.

    2013-09-15

    The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.

  9. Imaging and spectroscopic observations of a filament channel and the implications for the nature of counter-streamings

    SciTech Connect (OSTI)

    Chen, P. F.; Fang, C.; Harra, L. K.

    2014-03-20

    The dynamics of a filament channel are observed with imaging and spectroscopic telescopes before and during the filament eruption on 2011 January 29. The extreme ultraviolet (EUV) spectral observations reveal that there are no EUV counterparts of the H? counter-streamings in the filament channel, implying that the ubiquitous H? counter-streamings found by previous research are mainly due to longitudinal oscillations of filament threads, which are not in phase between each other. However, there exist larger-scale patchy counter-streamings in EUV along the filament channel from one polarity to the other, implying that there is another component of unidirectional flow (in the range of 10 km s{sup 1}) inside each filament thread in addition to the implied longitudinal oscillation. Our results suggest that the flow direction of the larger-scale patchy counter-streaming plasma in the EUV is related to the intensity of the plage or active network, with the upflows being located at brighter areas of the plage and downflows at the weaker areas. We propose a new method to determine the chirality of an erupting filament on the basis of the skewness of the conjugate filament drainage sites. This method suggests that the right-skewed drainage corresponds to sinistral chirality, whereas the left-skewed drainage corresponds to dextral chirality.

  10. Evaluation of Codisposal Viability for TH/U Carbide (Fort Saint Vrain HTGR) DOE-Owned Fuel

    SciTech Connect (OSTI)

    H. radulescu

    2001-09-28

    There are more than 250 forms of US Department of Energy (DOE)-owned spent nuclear fuel (SNF). Due to the variety of the spent nuclear fuel, the National Spent Nuclear Fuel Program has designated nine representative fuel groups for disposal criticality analyses based on fuel matrix, primary fissile isotope, and enrichment. The Fort Saint Vrain reactor (FSVR) SNF has been designated as the representative fuel for the Th/U carbide fuel group. The FSVR SNF consists of small particles (spheres of the order of 0.5-mm diameter) of thorium carbide or thorium and high-enriched uranium carbide mixture, coated with multiple, thin layers of pyrolytic carbon and silicon carbide, which serve as miniature pressure vessels to contain fission products and the U/Th carbide matrix. The coated particles are bound in a carbonized matrix, which forms fuel rods or ''compacts'' that are loaded into large hexagonal graphite prisms. The graphite prisms (or blocks) are the physical forms that are handled in reactor loading and unloading operations, and which will be loaded into the DOE standardized SNF canisters. The results of the analyses performed will be used to develop waste acceptance criteria. The items that are important to criticality control are identified based on the analysis needs and result sensitivities. Prior to acceptance to fuel from the Th/U carbide fuel group for disposal, the important items for the fuel types that are being considered for disposal under the Th/U carbide fuel group must be demonstrated to satisfy the conditions determined in this report.

  11. Compact 180-kV Marx generator triggered in atmospheric air by femtosecond laser filaments

    SciTech Connect (OSTI)

    Arantchouk, L. Larour, J.; Point, G.; Brelet, Y.; Carbonnel, J.; Andr, Y.-B.; Mysyrowicz, A.; Houard, A.

    2014-03-10

    We developed a compact Marx generator triggered in atmospheric air by a single femtosecond laser beam undergoing filamentation. Voltage pulses of 180?kV could be generated with a subnanosecond jitter. The same laser beam was also used to initiate simultaneously guided discharges up to 21?cm long at the output of the generator.

  12. RUI: Structure and Behavior of RF-Driven Plasma Filaments in High-Pressure Gases

    SciTech Connect (OSTI)

    Burin, Michael

    2014-11-18

    The filamentary discharge seen within commercial plasma globes is commonly enjoyed, yet not well understood. We investigate filament properties in a plasma globe using a variable high voltage amplifier. Results from the 3-year grant period and their physics are discussed.

  13. SYMPATHETIC FILAMENT ERUPTIONS FROM A BIPOLAR HELMET STREAMER IN THE SUN

    SciTech Connect (OSTI)

    Yang Jiayan; Jiang Yunchun; Zheng Ruisheng; Bi Yi; Hong Junchao; Yang Bo

    2012-01-20

    On 2005 August 5, two solar filaments erupted successively from different confined arcades underlying a common overarching multiple-arcade bipolar helmet streamer. We present detailed observations of these two events and identify them as sympathetic filament eruptions. The first (F1) is a small active-region filament located near the outskirts of the streamer arcade. It underwent a nonradial eruption, initially moving in the interior of the streamer arcade and resulting in an over-and-out coronal mass ejection. The second filament (F2), a larger quiescent one far away from F1, was clearly disturbed during the F1 eruption. It then underwent a very slow eruption and finally disappeared completely and permanently. Because two belt-shaped diffuse dimmings formed along the footprints of the streamer arcade in the first eruption and persisted throughout the complete disappearance of F2, the eruption series are interpreted as sympathetic: the simple expansion of the common streamer arcade forced by the F1 eruption weakened magnetic flux overlying F2 and thus led to its slow eruption, with the dimming formation indicating their physical connection. Our observations suggest that multiple-arcade bipolar helmet-streamer configurations are appropriate to producing sympathetic eruptions. Combined with the recent observations of unipolar-streamer sympathetic events, it appears that a multiple-arcade unipolar or bipolar helmet streamer can serve as a common magnetic configuration for sympathetic eruptions.

  14. Charge division using carbon filaments for obtaining coordinate information from detection of single electrons

    SciTech Connect (OSTI)

    Bird, F.; Shapiro, S.; Ashford, V.; McShurley, D.; Reif, R.; Lirth, D.W.G.S.; Williams, S.

    1985-09-01

    Seven micron diameter Carbon filaments forming the anode of a multiwire proportional chamber have been used to detect single electrons. Charge division techniques applied to the 5 cm long wire resulted in a position resolution of sigma/L < 2% for a collected signal charge of 30 fC.

  15. Inviscid evolution of large amplitude filaments in a uniform gravity field

    SciTech Connect (OSTI)

    Angus, J. R.; Krasheninnikov, S. I.

    2014-11-15

    The inviscid evolution of localized density stratifications under the influence of a uniform gravity field in a homogeneous, ambient background is studied. The fluid is assumed to be incompressible, and the stratification, or filament, is assumed to be initially isotropic and at rest. It is shown that the center of mass energy can be related to the center of mass position in a form analogous to that of a solid object in a gravity field g by introducing an effective gravity field g{sub eff}, which is less than g due to energy that goes into the background and into non-center of mass motion of the filament. During the early stages of the evolution, g{sub eff} is constant in time and can be determined from the solution of a 1D differential equation that depends on the initial, radially varying density profile of the filament. For small amplitude filaments such that ?{sub 0} ? 1, where ?{sub 0} is the relative amplitude of the filament to the background, the early stage g{sub eff} scales linearly with ?{sub 0}, but as ?{sub 0}??,?g{sub eff}?g and is thus independent of ?{sub 0}. Fully nonlinear simulations are performed for the evolution of Gaussian filaments, and it is found that the time t{sub max}, which is defined as the time for the center of mass velocity to reach its maximum value U{sub max}, occurs very soon after the constant acceleration phase and so U{sub max}?g{sub eff}(t=0)t{sub max}. The simulation results show that U{sub max}?1/t{sub max}??(?{sub 0}) for ?{sub 0} ? 1, in agreement with theory and results from previous authors, but that U{sub max} and t{sub max} both scale approximately with ?(?{sub 0}) for ?{sub 0} ? 1. The fact that U{sub max} and t{sub max} have the same scaling with ?{sub 0} for large amplitude filaments is in agreement with the theory presented in this paper.

  16. A STUDY OF A FAILED CORONAL MASS EJECTION CORE ASSOCIATED WITH AN ASYMMETRIC FILAMENT ERUPTION

    SciTech Connect (OSTI)

    Joshi, Navin Chandra; Srivastava, Abhishek K.; Uddin, Wahab; Kayshap, Pradeep; Filippov, Boris; Chandra, Ramesh E-mail: njoshi98@gmail.com

    2013-07-01

    We present multi-wavelength observations of an asymmetric filament eruption and associated coronal mass ejection (CME) and coronal downflows on 2012 June 17 and 18 from 20:00-05:00 UT. We use SDO/AIA and STEREO-B/SECCHI observations to understand the filament eruption scenario and its kinematics, while LASCO C2 observations are analyzed to study the kinematics of the CME and associated downflows. SDO/AIA limb observations show that the filament exhibits a whipping-like asymmetric eruption. STEREO/EUVI disk observations reveal a two-ribbon flare underneath the southeastern part of the filament that most probably occurred due to reconnection processes in the coronal magnetic field in the wake of the filament eruption. The whipping-like filament eruption later produces a slow CME in which the leading edge and the core propagate, with an average speed of Almost-Equal-To 540 km s{sup -1} and Almost-Equal-To 126 km s{sup -1}, respectively, as observed by the LASCO C2 coronagraph. The CME core formed by the eruptive flux rope shows outer coronal downflows with an average speed of Almost-Equal-To 56 km s{sup -1} after reaching Almost-Equal-To 4.33 R{sub Sun }. Initially, the core decelerates at Almost-Equal-To 48 m s{sup -2}. The plasma first decelerates gradually up to a height of Almost-Equal-To 4.33 R{sub Sun} and then starts accelerating downward. We suggest a self-consistent model of a magnetic flux rope representing the magnetic structure of the CME core formed by an eruptive filament. This rope loses its previous stable equilibrium when it reaches a critical height. With some reasonable parameters, and inherent physical conditions, the model describes the non-radial ascending motion of the flux rope in the corona, its stopping at some height, and thereafter its downward motion. These results are in good agreement with observations.

  17. Analytical and Experimental Evaluation of Joining Silicon Carbide to Silicon Carbide and Silicon Nitride to Silicon Nitride for Advanced Heat Engine Applications Phase II

    SciTech Connect (OSTI)

    Sundberg, G.J.

    1994-01-01

    Techniques were developed to produce reliable silicon nitride to silicon nitride (NCX-5101) curved joins which were used to manufacture spin test specimens as a proof of concept to simulate parts such as a simple rotor. Specimens were machined from the curved joins to measure the following properties of the join interlayer: tensile strength, shear strength, 22 C flexure strength and 1370 C flexure strength. In parallel, extensive silicon nitride tensile creep evaluation of planar butt joins provided a sufficient data base to develop models with accurate predictive capability for different geometries. Analytical models applied satisfactorily to the silicon nitride joins were Norton's Law for creep strain, a modified Norton's Law internal variable model and the Monkman-Grant relationship for failure modeling. The Theta Projection method was less successful. Attempts were also made to develop planar butt joins of siliconized silicon carbide (NT230).

  18. ANTI-PARALLEL EUV FLOWS OBSERVED ALONG ACTIVE REGION FILAMENT THREADS WITH HI-C

    SciTech Connect (OSTI)

    Alexander, Caroline E.; Walsh, Robert W.; Rgnier, Stphane; Cirtain, Jonathan; Winebarger, Amy R.; Golub, Leon; Korreck, Kelly; Weber, Mark; Kobayashi, Ken; Platt, Simon; Mitchell, Nick; DePontieu, Bart; Title, Alan; DeForest, Craig; Kuzin, Sergey

    2013-09-20

    Plasma flows within prominences/filaments have been observed for many years and hold valuable clues concerning the mass and energy balance within these structures. Previous observations of these flows primarily come from H? and cool extreme-ultraviolet (EUV) lines (e.g., 304 ) where estimates of the size of the prominence threads has been limited by the resolution of the available instrumentation. Evidence of 'counter-steaming' flows has previously been inferred from these cool plasma observations, but now, for the first time, these flows have been directly imaged along fundamental filament threads within the million degree corona (at 193 ). In this work, we present observations of an AR filament observed with the High-resolution Coronal Imager (Hi-C) that exhibits anti-parallel flows along adjacent filament threads. Complementary data from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager are presented. The ultra-high spatial and temporal resolution of Hi-C allow the anti-parallel flow velocities to be measured (70-80 km s{sup 1}) and gives an indication of the resolvable thickness of the individual strands (0.''8 0.''1). The temperature of the plasma flows was estimated to be log T (K) = 5.45 0.10 using Emission Measure loci analysis. We find that SDO/AIA cannot clearly observe these anti-parallel flows or measure their velocity or thread width due to its larger pixel size. We suggest that anti-parallel/counter-streaming flows are likely commonplace within all filaments and are currently not observed in EUV due to current instrument spatial resolution.

  19. Evaluation of Aluminum-Boron Carbide Neutron Absorbing Materials for Interim Storage of Used Nuclear Fuel

    SciTech Connect (OSTI)

    Wang, Lumin; Wierschke, Jonathan Brett

    2015-04-08

    The objective of this work was to understand the corrosion behavior of Boral® and Bortec® neutron absorbers over long-term deployment in a used nuclear fuel dry cask storage environment. Corrosion effects were accelerated by flowing humidified argon through an autoclave at temperatures up to 570°C. Test results show little corrosion of the aluminum matrix but that boron is leaching out of the samples. Initial tests performed at 400 and 570°C were hampered by reduced flow caused by the rapid build-up of solid deposits in the outlet lines. Analysis of the deposits by XRD shows that the deposits are comprised of boron trioxide and sassolite (H3BO3). The collection of boron- containing compounds in the outlet lines indicated that boron was being released from the samples. Observation of the exposed samples using SEM and optical microscopy show the growth of new phases in the samples. These phases were most prominent in Bortec® samples exposed at 570°C. Samples of Boral® exposed at 570°C showed minimal new phase formation but showed nearly the complete loss of boron carbide particles. Boron carbide loss was also significant in Boral samples at 400°C. However, at 400°C phases similar to those found in Bortec® were observed. The rapid loss of the boron carbide particles in the Boral® is suspected to inhibit the formation of the new secondary phases. However, Material samples in an actual dry cask environment would be exposed to temperatures closer to 300°C and less water than the lowest test. The results from this study conclude that at the temperature and humidity levels present in a dry cask environment, corrosion and boron leaching will have no effect on the performance of Boral® and Bortec® to maintain criticality control.

  20. In Situ Synthesis of Uranium Carbide and its High Temperature Cubic Phase

    SciTech Connect (OSTI)

    Reiche, Helmut Matthias; Vogel, Sven C.

    2015-03-25

    New in situ data for the U-C system are presented, with the goal of improving knowledge of the phase diagram to enable production of new ceramic fuels. The none quenchable, cubic, ?-phase, which in turn is fundamental to computational methods, was identified. Rich datasets of the formation synthesis of uranium carbide yield kinetics data which allow the benchmarking of modeling, thermodynamic parameters etc. The order-disorder transition (carbon sublattice melting) was observed due to equal sensitivity of neutrons to both elements. This dynamic has not been accurately described in some recent simulation-based publications.

  1. A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

    SciTech Connect (OSTI)

    Kim, Young-ho; Irie, Hiroshi; Hashimoto, Kazuhito

    2008-05-05

    A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO{sub 3}) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400-530 nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO{sub 3}.

  2. Adhesion of diamond coatings synthesized by oxygen-acetylene flame CVD on tungsten carbide

    SciTech Connect (OSTI)

    Marinkovic, S.; Stankovic, S.; Dekanski, A.

    1995-12-31

    The results of a study concerned with chemical vapor deposition of diamond on tungsten carbide cutting tools using an oxygen-acetylene flame in a normal ambient environment are presented. Effects of preparation conditions on the adhesion of the coating have been investigated, including different surface treatment, different position of the flame with respect to the coated surface, effect of an intermediate poorly crystalline diamond layer, etc. In particular, effect of polishing and ultrasonic lapping with diamond powder was compared with that of a corresponding treatment with SiC powder.

  3. Process for the production of hydrogen and carbonyl sulfide from hydrogen sulfide and carbon monoxide using a metal boride, nitride, carbide and/or silicide catalyst

    SciTech Connect (OSTI)

    McGuiggan, M.F.; Kuch, P.L.

    1984-05-08

    Hydrogen and carbonyl sulfide are produced by a process comprising contacting gaseous hydrogen sulfide with gaseous carbon monoxide in the presence of a metal boride, carbide, nitride and/or silicide catalyst, such as titanium carbide, vanadium boride, manganese nitride or molybdenum silicide.

  4. A dynamically collapsing core and a precursor of a core in a filament supported by turbulent and magnetic pressures

    SciTech Connect (OSTI)

    Furuya, Ray S.; Kitamura, Yoshimi; Shinnaga, Hiroko E-mail: kitamura@isas.jaxa.jp

    2014-10-01

    To study physical properties of the natal filament gas around the cloud core harboring an exceptionally young low-mass protostar GF 9-2, we carried out J = 1-0 line observations of {sup 12}CO, {sup 13}CO, and C{sup 18}O molecules using the Nobeyama 45 m telescope. The mapping area covers ? one-fifth of the whole filament. Our {sup 13}CO and C{sup 18}O maps clearly demonstrate that the core formed at the local density maxima of the filament, and the internal motions of the filament gas are totally governed by turbulence with Mach number of ?2. We estimated the scale height of the filament to be H = 0.3-0.7 pc, yielding the central density of n {sub c} = 800-4200 cm{sup 3}. Our analysis adopting an isothermal cylinder model shows that the filament is supported by the turbulent and magnetic pressures against the radial and axial collapse due to self-gravity. Since both the dissipation timescales of the turbulence and the transverse magnetic fields can be comparable to the free-fall time of the filament gas of 10{sup 6} yr, we conclude that the local decay of the supersonic turbulence and magnetic fields made the filament gas locally unstable, hence making the core collapse. Furthermore, we newly detected a gas condensation with velocity width enhancement to ?0.3 pc southwest of the GF 9-2 core. The condensation has a radius of ?0.15 pc and an LTE mass of ?5 M {sub ?}. Its internal motion is turbulent with Mach number of ?3, suggesting a gravitationally unbound state. Considering the uncertainties in our estimates, however, we propose that the condensation is a precursor of a cloud core, which would have been produced by the collision of the two gas components identified in the filament.

  5. OBSERVATIONS FROM SDO, HINODE, AND STEREO OF A TWISTING AND WRITHING START TO A SOLAR-FILAMENT-ERUPTION CASCADE

    SciTech Connect (OSTI)

    Sterling, Alphonse C.; Moore, Ronald L.; Hara, Hirohisa E-mail: ron.moore@nasa.gov

    2012-12-10

    We analyze data from SDO (AIA, HMI), Hinode (SOT, XRT, EIS), and STEREO (EUVI) of a solar eruption sequence of 2011 June 1 near 16:00 UT, with an emphasis on the early evolution toward eruption. Ultimately, the sequence consisted of three emission bursts and two filament ejections. SDO/AIA 304 A images show absorbing-material strands initially in close proximity which over {approx}20 minutes form a twisted structure, presumably a flux rope with {approx}10{sup 29} erg of free energy that triggers the resulting evolution. A jump in the filament/flux rope's displacement (average velocity {approx}20 km s{sup -1}) and the first burst of emission accompanies the flux-rope formation. After {approx}20 more minutes, the flux rope/filament kinks and writhes, followed by a semi-steady state where the flux rope/filament rises at ({approx}5 km s{sup -1}) for {approx}10 minutes. Then the writhed flux rope/filament again becomes MHD unstable and violently erupts, along with rapid (50 km s{sup -1}) ejection of the filament and the second burst of emission. That ejection removed a field that had been restraining a second filament, which subsequently erupts as the second filament ejection accompanied by the third (final) burst of emission. Magnetograms from SDO/HMI and Hinode/SOT, and other data, reveal several possible causes for initiating the flux-rope-building reconnection, but we are not able to say which is dominant. Our observations are consistent with magnetic reconnection initiating the first burst and the flux-rope formation, with MHD processes initiating the further dynamics. Both filament ejections are consistent with the standard model for solar eruptions.

  6. UNVEILING A NETWORK OF PARALLEL FILAMENTS IN THE INFRARED DARK CLOUD G14.225-0.506

    SciTech Connect (OSTI)

    Busquet, Gemma; Zhang, Qizhou; Ho, Paul T. P.; Palau, Aina; Girart, Josep M.; Liu, Hauyu Baobab; Sanchez-Monge, Alvaro; Estalella, Robert; De Gregorio-Monsalvo, Itziar; Pillai, Thushara; Wyrowski, Friedrich; Santos, Fabio P.; Franco, Gabriel A. P.

    2013-02-20

    We present the results of combined NH{sub 3} (1,1) and (2,2) line emission observed with the Very Large Array and the Effelsberg 100 m telescope of the infrared dark cloud G14.225-0.506. The NH{sub 3} emission reveals a network of filaments constituting two hub-filament systems. Hubs are associated with gas of rotational temperature T{sub rot} {approx} 15 K, non-thermal velocity dispersion {sigma}{sub NT} {approx} 1 km s{sup -1}, and exhibit signs of star formation, while filaments appear to be more quiescent (T{sub rot} {approx} 11 K and {sigma}{sub NT} {approx} 0.6 km s{sup -1}). Filaments are parallel in projection and distributed mainly along two directions, at P.A. {approx} 10 Degree-Sign and 60 Degree-Sign , and appear to be coherent in velocity. The averaged projected separation between adjacent filaments is between 0.5 pc and 1 pc, and the mean width of filaments is 0.12 pc. Cores within filaments are separated by {approx}0.33 {+-} 0.09 pc, which is consistent with the predicted fragmentation of an isothermal gas cylinder due to the {sup s}ausage{sup -}type instability. The network of parallel filaments observed in G14.225-0.506 is consistent with the gravitational instability of a thin gas layer threaded by magnetic fields. Overall, our data suggest that magnetic fields might play an important role in the alignment of filaments, and polarization measurements in the entire cloud would lend further support to this scenario.

  7. Kinetics of laser-pulse vaporization of uranium carbide by mass spectrometry. [LMFBR

    SciTech Connect (OSTI)

    Tehranian, F.

    1983-06-01

    The kinetics of uranium carbide vaporization in the temperature range 3000 K to 5200 K was studied using a Nd-glass laser with peak power densities from 1.6 x 10/sup 5/ to 4.0 x 10/sup 5/ watts/cm/sup 2/. The vapor species U, UC/sub 2/, C/sub 1/ and C/sub 3/ were detected and analyzed by a quadrupole mass spectrometer. From the mass spectrometer signals number densities of the various species in the ionizer were obtained as functions of time. The surface of the irradiated uranium carbide was examined by scanning electron microscope and the depth profile of the crater was obtained. In order to aid analysis of the data, the heat conduction and species diffusion equations for the solid (or liquid) were solved numerically by a computer code to obtain the temperature and composition transients during laser heating. A sensitivity analysis was used to study the effect of uncertainties in the input parameters on the computed surface temperatures.

  8. Method for preparing configured silicon carbide whisker-reinforced alumina ceramic articles

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN)

    1987-01-01

    A ceramic article of alumina reinforced with silicon carbide whiskers suitable for the fabrication into articles of complex geometry are provided by pressureless sintering and hot isostatic pressing steps. In accordance with the method of the invention a mixture of 5 to 10 vol. % silicon carbide whiskers 0.5 to 5 wt. % of a sintering aid such as yttria and the balance alumina powders is ball-milled and pressureless sintered in the desired configuration in the desired configuration an inert atmosphere at a temperature of about 1800.degree. C. to provide a self-supporting configured composite of a density of at least about 94% theoretical density. The composite is then hot isostatically pressed at a temperature and pressure adequate to provide configured articles of at least about 98% of theoretical density which is sufficient to provide the article with sufficient strength and fracture toughness for use in most structural applications such as gas turbine blades, cylinders, and other components of advanced heat engines.

  9. Irradiation-induced effects of proton irradiation on zirconium carbides with different stoichiometries

    SciTech Connect (OSTI)

    Y. Huang; B.R. Maier; T.R. Allen

    2014-10-01

    Zirconium carbide (ZrC) is being considered for utilization in deep burn TRISO fuel particles for hightemperature, gas-cooled reactors. Zirconium carbide has a cubic B1 type crystal structure along with a very high melting point (3420 ?C), exceptional hardness and good thermal and electrical conductivities. Understanding the ZrC irradiation response is crucial for establishing ZrC as an alternative component in TRISO fuel. Until now, very few studies on irradiation effects on ZrC have been released and fundamental aspects of defect evolution and kinetics are not well understood although some atomistic simulations and phenomenological studies have been performed. This work was carried out to understand the damage evolution in float-zone refined ZrC with different stoichiometries. Proton irradiations at 800 ?C up to doses of 3 dpa were performed on ZrCx (where x ranges from 0.9 to 1.2) to investigate the damage evolution. The irradiation-induced defects, such as density of dislocation loops, at different stoichiometries and doses which were characterized by transmission electron microscopy (TEM) is presented and discussed.

  10. Method for fracturing silicon-carbide coatings on nuclear-fuel particles

    DOE Patents [OSTI]

    Turner, Lloyd J. (Oak Ridge, TN); Willey, Melvin G. (Knoxville, TN); Tiegs, Sue M. (Lenoir City, TN); Van Cleve, Jr., John E. (Kingston, TN)

    1982-01-01

    This invention is a device for fracturing particles. It is designed especially for use in "hot cells" designed for the handling of radioactive materials. In a typical application, the device is used to fracture a hard silicon-carbide coating present on carbon-matrix microspheres containing nuclear-fuel material, such as uranium or thorium compounds. To promote remote control and facilitate maintenance, the particle breaker is pneumatically operated and contains no moving parts. It includes means for serially entraining the entrained particles on an anvil housed in a leak-tight chamber. The flow rate of the gas is at a value effecting fracture of the particles; preferably, it is at a value fracturing them into product particulates of fluidizable size. The chamber is provided with an outlet passage whose cross-sectional area decreases in the direction away from the chamber. The outlet is connected tangentially to a vertically oriented vortex-flow separator for recovering the product particulates entrained in the gas outflow from the chamber. The invention can be used on a batch or continuous basis to fracture the silicon-carbide coatings on virtually all of the particles fed thereto.

  11. Very low Schottky barrier height at carbon nanotube and silicon carbide interface

    SciTech Connect (OSTI)

    Inaba, Masafumi Suzuki, Kazuma; Shibuya, Megumi; Lee, Chih-Yu; Masuda, Yoshiho; Tomatsu, Naoya; Norimatsu, Wataru; Kusunoki, Michiko; Hiraiwa, Atsushi; Kawarada, Hiroshi

    2015-03-23

    Electrical contacts to silicon carbide with low contact resistivity and high current durability are crucial for future SiC power devices, especially miniaturized vertical-type devices. A carbon nanotube (CNT) forest formed by silicon carbide (SiC) decomposition is a densely packed forest, and is ideal for use as a heat-dissipative ohmic contact in SiC power transistors. The contact resistivity and Schottky barrier height in a Ti/CNT/SiC system with various SiC dopant concentrations were evaluated in this study. Contact resistivity was evaluated in relation to contact area. The Schottky barrier height was calculated from the contact resistivity. As a result, the Ti/CNT/SiC contact resistivity at a dopant concentration of 3??10{sup 18?}cm{sup ?3} was estimated to be ?1.3??10{sup ?4} ??cm{sup 2} and the Schottky barrier height of the CNT/SiC contact was in the range of 0.400.45?eV. The resistivity is relatively low for SiC contacts, showing that CNTs have the potential to be a good ohmic contact material for SiC power electronic devices.

  12. Fort Saint Vrain HTGR (Th/U carbide) Fuel Characteristics for Disposal Criticality Analysis

    SciTech Connect (OSTI)

    Taylor, Larry Lorin

    2001-01-01

    DOE-owned spent nuclear fuels encompass many fuel types. In an effort to facilitate criticality analysis for these various fuel types, they were categorized into eight characteristic fuel groups with emphasis on fuel matrix composition. Out of each fuel group, a representative fuel type was chosen for analysis as a bounding case within that fuel group. Generally, burnup data, fissile enrichments and total fuel mass govern the selection of the representative or candidate fuel within that group. For the HTGR group, the Fort Saint Vrain (FSV) reactor fuel has been chosen for the evaluation of viability for waste co-disposal. The FSV reactor was operated by Public Service of Colorado as a licensed power reactor. The FSV fuel employs a U/Th carbide matrix in individually pyrolytic carbon-coated particles. These individual particles are in turn coated with silicon carbide (SiC) and contained within fuel compacts, that are in turn embedded in graphite blocks that comprised the structural core of the reactor.

  13. Filamentous carbon particles for cleaning oil spills and method of production

    DOE Patents [OSTI]

    Muradov, Nazim

    2010-04-06

    A compact hydrogen generator is coupled to or integrated with a fuel cell for portable power applications. Hydrogen is produced via thermocatalytic decomposition (cracking, pyrolysis) of hydrocarbon fuels in oxidant-free environment. The apparatus can utilize a variety of hydrocarbon fuels, including natural gas, propane, gasoline, kerosene, diesel fuel, crude oil (including sulfurous fuels). The hydrogen-rich gas produced is free of carbon oxides or other reactive impurities, so it could be directly fed to any type of a fuel cell. The catalysts for hydrogen production in the apparatus are carbon-based or metal-based materials and doped, if necessary, with a sulfur-capturing agent. Additionally disclosed are two novel processes for the production of two types of carbon filaments, and a novel filamentous carbon product. The hydrogen generator can be conveniently integrated with high temperature fuel cells to produce an efficient and self-contained source of electrical power.

  14. Spatial and temporal evolution of filamentation instability in a current-carrying plasma

    SciTech Connect (OSTI)

    Mohammadhosseini, B. [Laser-Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Department of Physics, Imam Khomeini International University, Qazvin 34149-16818 (Iran, Islamic Republic of); Niknam, A. R. [Laser-Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Shokri, B. [Laser-Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Department of Physics, Shahid Beheshti University, G. C., Evin, Tehran 19839-63113 (Iran, Islamic Republic of)

    2010-12-15

    The spatial and temporal evolution of the electric and magnetic fields in a current-carrying plasma is investigated in the nonlinear regime. Using the magnetohydrodynamic equations, a nonlinear diffusion equation for the magnetic field in the plasma is obtained. This nonlinear equation is numerically solved and the spatiotemporal evolution of the electric and magnetic fields and the electron density distribution are plotted. It is shown that as the time passes, the profile of the electric and magnetic fields changes from a sinusoidal shape to a saw-tooth one and the electron density distribution becomes very steepened. Also, the mechanism of the filament formation is then discussed. Furthermore, the effects of the thermal motion, collisions, and ion mass on growth rate of filaments as well as the saturation time are argued. Finally, it is found that the energy dissipation is associated with the aforementioned effects and strong plasma density gradient.

  15. Determination of the transient electron temperature in a femtosecond-laser-induced air plasma filament

    SciTech Connect (OSTI)

    Sun Zhanliang; Chen Jinhai; Rudolph, Wolfgang

    2011-04-15

    The transient electron temperature in a weakly ionized femtosecond-laser-produced air plasma filament was determined from optical absorption and diffraction experiments. The electron temperature and plasma density decay on similar time scales of a few hundred picoseconds. Comparison with plasma theory reveals the importance of inelastic collisions that lead to energy transfer to vibrational degrees of freedom of air molecules during the plasma cooling.

  16. Deposition of device quality, low hydrogen content, amorphous silicon films by hot filament technique using ``safe`` silicon source gas

    DOE Patents [OSTI]

    Mahan, A.H.; Molenbroek, E.C.; Nelson, B.P.

    1998-07-07

    A method is described for producing hydrogenated amorphous silicon on a substrate by flowing a stream of safe (diluted to less than 1%) silane gas past a heated filament. 7 figs.

  17. Experimental study of filamentation of high-power ultrashort laser pulses with initial angular divergence in air

    SciTech Connect (OSTI)

    Geints, Yu E; Zemlyanov, A A; Kabanov, Andrey M; Matvienko, Gennady G; Stepanov, A N

    2013-04-30

    Experimental study of the nonlinear propagation of near-IR gigawatt femtosecond laser pulses in air in the self-focusing and filamentation regimes have been performed in open air and in laboratory. The influence of the initial geometric divergence (both positive and negative) of the laser beam with an irregular intensity profile on the transverse light energy distribution at the end of the path is studied. It is shown experimentally that the displacement of the filamentation region due to geometric focusing or defocusing, makes it possible to control the number and spatial location of light energy density peaks in the receiving plane. The conditions under which a light filament can be reconstructed after the beam transmission through a linear focal waist are determined. A semi-empirical threshold relation is obtained for the beam focusing force and the beam power, when light beam undergoes filamentation behind the geometric focus of the optical system. (extreme light fields and their applications)

  18. Robustness of the filamentation instability in arbitrarily oriented magnetic field: Full three dimensional calculation

    SciTech Connect (OSTI)

    Bret, A., E-mail: antoineclaude.bret@uclm.es [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain and Instituto de Investigaciones Energticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

    2014-02-15

    The filamentation (Weibel) instability plays a key role in the formation of collisionless shocks which are thought to produce Gamma-Ray-Bursts and High-Energy-Cosmic-Rays in astrophysical environments. While it has been known for long that a flow-aligned magnetic field can completely quench the instability, it was recently proved in 2D that in the cold regime, such cancelation is possible if and only if the field is perfectly aligned. Here, this result is finally extended to a 3D geometry. Calculations are conducted for symmetric and asymmetric counter-streaming relativistic plasma shells. 2D results are retrieved in 3D: the instability can never be completely canceled for an oblique magnetic field. In addition, the maximum growth-rate is always larger for wave vectors lying in the plan defined by the flow and the oblique field. On the one hand, this bears consequences on the orientation of the generated filaments. On the other hand, it certifies 2D simulations of the problem can be performed without missing the most unstable filamentation modes.

  19. Mechanism of actin filament nucleation by the bacterial effector VopL

    SciTech Connect (OSTI)

    Yu, Bingke; Cheng, Hui-Chun; Brautigam, Chad A.; Tomchick, Diana R.; Rosen, Michael K.

    2012-05-02

    Vibrio parahaemolyticus protein L (VopL) is an actin nucleation factor that induces stress fibers when injected into eukaryotic host cells. VopL contains three N-terminal Wiskott-Aldrich homology 2 (WH2) motifs and a unique VopL C-terminal domain (VCD). We describe crystallographic and biochemical analyses of filament nucleation by VopL. The WH2 element of VopL does not nucleate on its own and requires the VCD for activity. The VCD forms a U-shaped dimer in the crystal, stabilized by a terminal coiled coil. Dimerization of the WH2 motifs contributes strongly to nucleation activity, as do contacts of the VCD to actin. Our data lead to a model in which VopL stabilizes primarily lateral (short-pitch) contacts between actin monomers to create the base of a two-stranded filament. Stabilization of lateral contacts may be a common feature of actin filament nucleation by WH2-based factors.

  20. A Multiscale Modeling Approach to Analyze Filament-Wound Composite Pressure Vessels

    SciTech Connect (OSTI)

    Nguyen, Ba Nghiep; Simmons, Kevin L.

    2013-07-22

    A multiscale modeling approach to analyze filament-wound composite pressure vessels is developed in this article. The approach, which extends the Nguyen et al. model [J. Comp. Mater. 43 (2009) 217] developed for discontinuous fiber composites to continuous fiber ones, spans three modeling scales. The microscale considers the unidirectional elastic fibers embedded in an elastic-plastic matrix obeying the Ramberg-Osgood relation and J2 deformation theory of plasticity. The mesoscale behavior representing the composite lamina is obtained through an incremental Mori-Tanaka type model and the Eshelby equivalent inclusion method [Proc. Roy. Soc. Lond. A241 (1957) 376]. The implementation of the micro-meso constitutive relations in the ABAQUS finite element package (via user subroutines) allows the analysis of a filament-wound composite pressure vessel (macroscale) to be performed. Failure of the composite lamina is predicted by a criterion that accounts for the strengths of the fibers and of the matrix as well as of their interface. The developed approach is demonstrated in the analysis of a filament-wound pressure vessel to study the effect of the lamina thickness on the burst pressure. The predictions are favorably compared to the numerical and experimental results by Lifshitz and Dayan [Comp. Struct. 32 (1995) 313].

  1. The impact of a filament eruption on nearby high-lying cool loops

    SciTech Connect (OSTI)

    Harra, L. K.; Matthews, S. A.; Long, D. M.; Doschek, G. A.; De Pontieu, B.

    2014-09-10

    The first spectroscopic observations of cool Mg II loops above the solar limb observed by NASA's Interface Region Imaging Spectrograph (IRIS) are presented. During the observation period, IRIS is pointed off-limb, allowing the observation of high-lying loops, which reach over 70 Mm in height. Low-lying cool loops were observed by the IRIS slit-jaw camera for the entire four-hour observing window. There is no evidence of a central reversal in the line profiles, and the Mg II h/k ratio is approximately two. The Mg II spectral lines show evidence of complex dynamics in the loops with Doppler velocities reaching 40 km s{sup 1}. The complex motions seen indicate the presence of multiple threads in the loops and separate blobs. Toward the end of the observing period, a filament eruption occurs that forms the core of a coronal mass ejection. As the filament erupts, it impacts these high-lying loops, temporarily impeding these complex flows, most likely due to compression. This causes the plasma motions in the loops to become blueshifted and then redshifted. The plasma motions are seen before the loops themselves start to oscillate as they reach equilibrium following the impact. The ratio of the Mg h/k lines also increases following the impact of the filament.

  2. Solid-state graphene formation via a nickel carbide intermediate phase [Nickel carbide (Ni3C) as an intermediate phase for graphene formation

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Xiong, W; Zhou, Yunshen; Hou, Wenjia; Guillemet, Thomas; Silvain, Jean-François; Lahaye, Michel; Lebraud, Eric; Xu, Shen; Wang, Xinwei; Cullen, David A; et al

    2015-11-10

    Direct formation of graphene with controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications. Despite significant progress achieved in understanding the formation of graphene on metallic surfaces through chemical vapor deposition (CVD) of hydrocarbons, very limited research is available elucidating the graphene formation process via rapid thermal processing (RTP) of solid-state amorphous carbon, through which graphene is formed directly on dielectric surfaces accompanied by autonomous nickel evaporation. It is suggested that a metastable hexagonal nickel carbide (Ni3C) intermediate phase plays a critical role in transforming amorphous carbon to 2D crystalline graphene and contributing to themore » autonomous Ni evaporation. Temperature resolved carbon and nickel evolution in the RTP process is investigated using Auger electron spectroscopic (AES) depth profiling and glancing-angle X-ray diffraction (GAXRD). Formation, migration and decomposition of the hexagonal Ni3C are confirmed to be responsible for the formation of graphene and the evaporation of Ni at 1100 °C. The Ni3C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation, and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.« less

  3. Discovery of a pre-existing molecular filament associated with supernova remnant G127.1+0.5

    SciTech Connect (OSTI)

    Zhou, Xin; Yang, Ji; Fang, Min; Su, Yang

    2014-08-20

    We performed millimeter observations in CO lines toward the supernova remnant (SNR) G127.1+0.5. We found a molecular filament at 4-13 km s{sup 1} consisting of two distinct parts: a straight part coming out of the remnant region and a curved part in the remnant region. The curved part is coincides well with the bright SNR shell detected in 1420 MHz radio continuum and mid-infrared observations in the northeastern region. In addition, redshifted line wing broadening is found only in the curved part of the molecular filament, which indicates a physical interaction. These provide strong evidences, for the first time, to confirm the association between an SNR and a pre-existing long molecular filament. Multi-band observations in the northeastern remnant shell could be explained by the interaction between the remnant shock and the dense molecular filament. RADEX radiative transfer modeling of the quiet and shocked components yield physical conditions consistent with the passage of a non-dissociative J-type shock. We argue that the curved part of the filament is fully engulfed by the remnant's forward shock. A spatial correlation between aggregated young stellar objects (YSOs) and the adjacent molecular filament close to the SNR is also found, which could be related to the progenitor's activity.

  4. USING TWISTED FILAMENTS TO MODEL THE INNER JET IN M 87

    SciTech Connect (OSTI)

    Hardee, P. E.; Eilek, J. A.

    2011-07-01

    Radio and optical images of the M 87 jet show bright filaments, twisted into an apparent double helix, extending from HST-1 to knot A. Proper motions within the jet suggest a decelerating jet flow passing through a slower, accelerating wave pattern. We use these observations to develop a mass and energy flux-conserving model describing the jet flow and conditions along the jet. Our model requires the jet to be an internally hot, but subrelativistic plasma, from HST-1 to knot A. Subsequently, we assume that the jet is in pressure balance with an external cocoon and we determine the cocoon conditions required if the twisted filaments are the result of the Kelvin-Helmholtz (KH) unstable elliptical mode. We find that the cocoon must be cooler than the jet at HST-1 but must be about as hot as the jet at knot A. Under these conditions, we find that the observed filament wavelength is near the elliptical mode maximum growth rate and growth is rapid enough for the filaments to develop and saturate well before HST-1. We generate a pseudo-synchrotron image of a model jet carrying a combination of normal modes of the KH instability. The pseudo-synchrotron image of the jet reveals that (1) a slow decline in the model jet's surface brightness is still about five times faster than the real jet, (2) KH-produced dual helically twisted filaments can appear qualitatively similar to those on the real jet if any helical perturbation to the jet is very small or nonexistent inside knot A, and (3) the knots in the real jet cannot be associated with the twisted filamentary features and are unlikely to be the result of a KH instability. The existence of the knots in the real jet, the limb brightening of the real jet in the radio, and the slower decline of the surface brightness of the real jet indicate that additional processes-such as unsteady jet flow and internal particle acceleration-are occurring within the jet. Disruption of the real jet beyond knot A by KH instability is consistent with the jet and cocoon conditions we find at knot A.

  5. .beta.-silicon carbide protective coating and method for fabricating same

    DOE Patents [OSTI]

    Carey, Paul G. (Mountain View, CA); Thompson, Jesse B. (Brentwood, CA)

    1994-01-01

    A polycrystalline beta-silicon carbide film or coating and method for forming same on components, such as the top of solar cells, to act as an extremely hard protective surface, and as an anti-reflective coating. This is achieved by DC magnetron co-sputtering of amorphous silicon and carbon to form a SiC thin film onto a surface, such as a solar cell. The thin film is then irradiated by a pulsed energy source, such as an excimer laser, to synthesize the poly- or .mu.c-SiC film on the surface and produce .beta.--SiC. While the method of this invention has primary application in solar cell manufacturing, it has application wherever there is a requirement for an extremely hard surface.

  6. Diorganosilacetylene-alt-diorganosilvinylene polymers and a process densifying porous silicon-carbide bodies

    DOE Patents [OSTI]

    Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

    1994-05-17

    The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R.sup.1)(R.sup.2)Si--C.tbd.C--(R.sup.3)(R.sup.4)Si--CH=CH--].sub.n-- , wherein n.gtoreq.2; and each R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

  7. Diorganosilacetylene-alt-diorganosilvinylene polymers and a process densifying porous silicon-carbide bodies

    DOE Patents [OSTI]

    Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

    1994-05-17

    The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R[sup 1])(R[sup 2])Si--C[triple bond]C-(R[sup 3])(R[sup 4])Si--CH[double bond]CH--][sub n]--, wherein n[>=]2; and each R[sup 1], R[sup 2], R[sup 3], and R[sup 4] is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

  8. Method for production of ceramic oxide and carbide bodies by polymer inclusion and decomposition

    DOE Patents [OSTI]

    Quinby, Thomas C. (Kingston, TN)

    1985-01-01

    A method for the preparation of thin, free-standing metal oxide films which are useful as nuclear accelerator target materials. Cations of any metal except those of Group IA and precious metals, such as, U, Zr, Nd, Ce, Th, pr or Cr, are absorbed on a thin film of polymeric material, such as, carboxymethylcellulose, viscose rayon or cellophane. The cation impregnated polymeric material is dried. Then the impregnated film is heated in an inert atmosphere to form a carbonized membrane. The carbonized membrane is oxidized to yield a thin, self-supporting, metal oxide membrane. Or, the membrane can be heated in an inert atmosphere to yield a thin, self-supporting, metal carbide-containing membrane.

  9. Method for production of ceramic oxide and carbide bodies by polymer inclusion and decomposition

    DOE Patents [OSTI]

    Quinby, T.C.

    1984-08-30

    A method for the preparation of thin, free-standing metal oxide films which are useful as nuclear accelerator target materials is described. Cations of any metal except those of Group IA and precious metals, such as, U, Zr, Nd, Ce, Th, Pr or Cr, are absorbed on a thin film of polymeric material, such as carboxymethylcellulose, viscose rayon or cellophane. The cation impregnated polymeric material is dried. Then the impregnated film is heated in an inert atmosphere to form a carbonized membrane. The carbonized membrane is oxidized to yield a thin, self-supporting, metal oxide membrane. Or, the membrane can be heated in an inert atmosphere to yield a thin, self-supporting, metal carbide-containing membrane.

  10. [beta]-silicon carbide protective coating and method for fabricating same

    DOE Patents [OSTI]

    Carey, P.G.; Thompson, J.B.

    1994-11-01

    A polycrystalline beta-silicon carbide film or coating and method for forming same on components, such as the top of solar cells, to act as an extremely hard protective surface, and as an anti-reflective coating are disclosed. This is achieved by DC magnetron co-sputtering of amorphous silicon and carbon to form a SiC thin film onto a surface, such as a solar cell. The thin film is then irradiated by a pulsed energy source, such as an excimer laser, to synthesize the poly- or [mu]c-SiC film on the surface and produce [beta]-SiC. While the method of this invention has primary application in solar cell manufacturing, it has application wherever there is a requirement for an extremely hard surface. 3 figs.

  11. Ionization-induced annealing of pre-existing defects in silicon carbide

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhang, Yanwen; Sachan, Ritesh; Pakarinen, Olli H; Chisholm, Matthew F; Liu, Peng; Xue, Haizhou; Weber, William J

    2015-01-01

    A long-standing objective in materials research is to find innovative ways to remove preexisting damage and heal fabrication defects or environmentally induced defects in materials. Silicon carbide (SiC) is a fascinating wide-band gap semiconductor for high-temperature, high-power, high-frequency applications. Its high corrosion and radiation resistance makes it a key refractory/structural material with great potential for extremely harsh radiation environments. Here we show that the energy transferred to the electron system of SiC by energetic ions via inelastic ionization processes results in a highly localized thermal spike that can effectively heal preexisting defects and restore the structural order. This work revealsmorean innovative self-healing process using highly ionizing ions, and it describes a critical aspect to be considered in modeling SiC performance as either a functional or a structural material for device applications or high-radiation environments.less

  12. Near-field radiative heat transfer between metamaterials coated with silicon carbide thin films

    SciTech Connect (OSTI)

    Basu, Soumyadipta Yang, Yue; Wang, Liping

    2015-01-19

    In this letter, we study the near-field radiative heat transfer between two metamaterial substrates coated with silicon carbide (SiC) thin films. It is known that metamaterials can enhance the near-field heat transfer over ordinary materials due to excitation of magnetic plasmons associated with s polarization, while strong surface phonon polariton exists for SiC. By careful tuning of the optical properties of metamaterial, it is possible to excite electrical and magnetic resonances for the metamaterial and surface phonon polaritons for SiC at different spectral regions, resulting in the enhanced heat transfer. The effect of the SiC film thickness at different vacuum gaps is investigated. Results obtained from this study will be beneficial for application of thin film coatings for energy harvesting.

  13. Room-temperature near-infrared silicon carbide nanocrystalline emitters based on optically aligned spin defects

    SciTech Connect (OSTI)

    Muzha, A.; Fuchs, F.; Simin, D.; Astakhov, G. V.; Tarakina, N. V.; Trupke, M.; Soltamov, V. A.; Mokhov, E. N.; Baranov, P. G.; Dyakonov, V.; and others

    2014-12-15

    Bulk silicon carbide (SiC) is a very promising material system for bio-applications and quantum sensing. However, its optical activity lies beyond the near infrared spectral window for in-vivo imaging and fiber communications due to a large forbidden energy gap. Here, we report the fabrication of SiC nanocrystals and isolation of different nanocrystal fractions ranged from 600?nm down to 60?nm in size. The structural analysis reveals further fragmentation of the smallest nanocrystals into ca. 10-nm-size clusters of high crystalline quality, separated by amorphization areas. We use neutron irradiation to create silicon vacancies, demonstrating near infrared photoluminescence. Finally, we detect room-temperature spin resonances of these silicon vacancies hosted in SiC nanocrystals. This opens intriguing perspectives to use them not only as in-vivo luminescent markers but also as magnetic field and temperature sensors, allowing for monitoring various physical, chemical, and biological processes.

  14. Quantum Chemistry, and Eclectic Mix: From Silicon Carbide to Size Consistency

    SciTech Connect (OSTI)

    Jamie Marie Rintelman

    2004-12-19

    Chemistry is a field of great breadth and variety. It is this diversity that makes for both an interesting and challenging field. My interests have spanned three major areas of theoretical chemistry: applications, method development, and method evaluation. The topics presented in this thesis are as follows: (1) a multi-reference study of the geometries and relative energies of four atom silicon carbide clusters in the gas phase; (2) the reaction of acetylene on the Si(100)-(2x1) surface; (3) an improvement to the Effective Fragment Potential (EFP) solvent model to enable the study of reactions in both aqueous and nonaqueous solution; and (4) an evaluation of the size consistency of Multireference Perturbation Theory (MRPT). In the following section, the author briefly discusses two topics central to, and present throughout, this thesis: Multi-reference methods and Quantum Mechanics/Molecular Mechanics (QM/MM) methods.

  15. Computation studies into architecture and energy transfer properties of photosynthetic units from filamentous anoxygenic phototrophs

    SciTech Connect (OSTI)

    Linnanto, Juha Matti; Freiberg, Arvi

    2014-10-06

    We have used different computational methods to study structural architecture, and light-harvesting and energy transfer properties of the photosynthetic unit of filamentous anoxygenic phototrophs. Due to the huge number of atoms in the photosynthetic unit, a combination of atomistic and coarse methods was used for electronic structure calculations. The calculations reveal that the light energy absorbed by the peripheral chlorosome antenna complex transfers efficiently via the baseplate and the core B808866 antenna complexes to the reaction center complex, in general agreement with the present understanding of this complex system.

  16. Infrared pulse characterization using four-wave mixing inside a few cycle pulse filament in air

    SciTech Connect (OSTI)

    Marceau, Claude Thomas, Steven; Kassimi, Yacine; Gingras, Guillaume; Witzel, Bernd

    2014-02-03

    We demonstrate a four-wave mixing (FWM) technique to measure near- and mid-infrared (IR) laser pulse shapes in time domain. Few cycle 800?nm laser pulses were synchronized with the IR pulse and focused colinearly to generate a plasma filament in air. Second harmonic radiation around 400?nm was generated through FWM, with a yield proportional to the IR pulse intensity. Excellent signal to noise ratio was observed from 2.1??m to 18??m. With proper phase stabilization of the IR beam, this technique is a promising step toward direct electric field sensing of near-IR pulses in air.

  17. SLOW RISE AND PARTIAL ERUPTION OF A DOUBLE-DECKER FILAMENT. I. OBSERVATIONS AND INTERPRETATION

    SciTech Connect (OSTI)

    Liu Rui; Kliem, Bernhard; Toeroek, Tibor; Titov, Viacheslav S.; Lionello, Roberto; Linker, Jon A.; Liu Chang; Wang Haimin

    2012-09-01

    We study an active-region dextral filament that was composed of two branches separated in height by about 13 Mm, as inferred from three-dimensional reconstruction by combining SDO and STEREO-B observations. This 'double-decker' configuration sustained for days before the upper branch erupted with a GOES-class M1.0 flare on 2010 August 7. Analyzing this evolution, we obtain the following main results. (1) During the hours before the eruption, filament threads within the lower branch were observed to intermittently brighten up, lift upward, and then merge with the upper branch. The merging process contributed magnetic flux and current to the upper branch, resulting in its quasi-static ascent. (2) This transfer might serve as the key mechanism for the upper branch to lose equilibrium by reaching the limiting flux that can be stably held down by the overlying field or by reaching the threshold of the torus instability. (3) The erupting branch first straightened from a reverse S shape that followed the polarity inversion line and then writhed into a forward S shape. This shows a transfer of left-handed helicity in a sequence of writhe-twist-writhe. The fact that the initial writhe is converted into the twist of the flux rope excludes the helical kink instability as the trigger process of the eruption, but supports the occurrence of the instability in the main phase, which is indeed indicated by the very strong writhing motion. (4) A hard X-ray sigmoid, likely of coronal origin, formed in the gap between the two original filament branches in the impulsive phase of the associated flare. This supports a model of transient sigmoids forming in the vertical flare current sheet. (5) Left-handed magnetic helicity is inferred for both branches of the dextral filament. (6) Two types of force-free magnetic configurations are compatible with the data, a double flux rope equilibrium and a single flux rope situated above a loop arcade.

  18. Growth of highly oriented carbon nanotubes by plasma-enhanced hot filament chemical vapor deposition

    SciTech Connect (OSTI)

    Huang, Z.P.; Xu, J.W.; Ren, Z.F.; Wang, J.H.; Siegal, M.P.; Provencio, P.N.

    1998-12-01

    Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666 {degree}C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 {mu}m in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio, and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. {copyright} {ital 1998 American Institute of Physics.}

  19. Effect of the pre-existing carbides on the grain boundary network during grain boundary engineering in a nickel based alloy

    SciTech Connect (OSTI)

    Liu, Tingguang; Xia, Shuang; Li, Hui; Zhou, Bangxin; Bai, Qin

    2014-05-01

    Grain boundary engineering was carried out on an aging-treated nickel based Alloy 690, which has precipitated carbides at grain boundaries. Electron backscatter diffraction technique was used to investigate the grain boundary networks. Results show that, compared with the solution-annealed samples, the aging-treated samples with pre-existing carbides at grain boundaries need longer duration or higher temperature during annealing after low-strain tensile deformation for forming high proportion of low-? coincidence site lattice grain boundaries (more than 75%). The reason is that the primary recrystallization is inhibited or retarded owing to that the pre-existing carbides are barriers to grain boundaries migration. - Highlights: Study of GBE as function of pre-existing GB carbides, tensile strain and annealing Recrystallization of GBE is inhibited or retarded by the pre-existing carbides. Retained carbides after annealing show the original GB positions. More than 80% of special GBs were formed after the modification of GBE processing. Multiple twinning during recrystallization is the key process of GBE.

  20. Nanostructured Metal Carbides for Aprotic Li-O2 Batteries. New Insights into Interfacial Reactions and Cathode Stability

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kundu, Dipan; Black, Robert; Adams, Brian; Harrison, Katharine; Zavadil, Kevin R.; Nazar, Linda F.

    2015-05-01

    The development of nonaqueous Li–oxygen batteries, which relies on the reversible reaction of Li + O2 to give lithium peroxide (Li2O2), is challenged by several factors, not the least being the high charging voltage that results when carbon is typically employed as the cathode host. We report here on the remarkably low 3.2 V potential for Li2O2 oxidation on a passivated nanostructured metallic carbide (Mo2C), carbon-free cathode host. Furthermore, online mass spectrometry coupled with X-ray photoelectron spectroscopy unequivocally demonstrates that lithium peroxide is simultaneously oxidized together with the LixMoO3-passivated conductive interface formed on the carbide, owing to their close redoxmore » potentials. We found that the process rejuvenates the surface on each cycle upon electrochemical charge by releasing LixMoO3 into the electrolyte, explaining the low charging potential.« less

  1. Metallic filament formation by aligned oxygen vacancies in ZnO-based resistive switches

    SciTech Connect (OSTI)

    Gu, Tingkun

    2014-05-28

    The electronic structure of ZnO with defects of oxygen vacancies were investigated by using first-principles methods. Some structure models were constructed in order to investigate the effects of the distribution of oxygen vacancies on the electronic properties of ZnO. By analyzing the calculated results, we found that only the aligned oxygen vacancies can form the conducting channel in ZnO, and the transformation of the oxygen vacancy from charged state to neutral state is consistent with the energetics rule of the forming aligned oxygen vacancies. As for the heterojunction of Pt/ZnO/Pt, the oxygen vacancies near the interface of Pt/ZnO depress the local Schottky barrier effectively, and the aligned oxygen vacancies in ZnO form a conducting filament connecting two Pt electrodes. The metallic filament formation in Pt/ZnO/Pt resistive switching cells should be closely related to the carrier injection from Pt electrode into ZnO and the arrangement of oxygen vacancies in ZnO slab.

  2. Growth of Highly-Oriented Carbon Nanotubes by Plasma-Enhanced Hot Filament Chemical Vapor Deposition

    SciTech Connect (OSTI)

    Huang, Z.P.; Provencio, P.N.; Ren, Z.F.; Siegal, M.P.; Wang, J.H.; Xu, J.W.

    1998-10-11

    Highly-oriented, multi-walled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666"C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 pm in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. In summary, we synthesized large-area highly-oriented carbon nanotubes at temperatures below 666C by plasma-enhanced hot filament chemical vapor deposition. Acetylene gas is used to provide carbon for nanotube growth and ammonia gas is used for dilution and catalysis. Plasma intensity is critical in determining the nanotube aspect ratios (diameter and length), and range of both site and height distributions within a given film.

  3. Processing aersols and filaments in a TM sub 010 microwave cavity at 2. 45 GHz

    SciTech Connect (OSTI)

    Vogt, G.J.; Unruh, W.P.

    1992-01-01

    As part of the development of generic microwave processes for spray-drying of homogeneous complex metal oxide powders and for inorganic fiber processing, we have investigated the use of 2.45 GHz microwaves in a high-Q single-mode TM{sub 010} cavity coupled directly to aerosols and fibers. Aqueous and ethanol aerosols of ferric nitrate solutions have been successfully dried at 1.8 kW of cavity power for a loaded Q greater than 6000 in flowing nitrogen gas. Similarly, we have observed extremely rapid heating rates in the TM{sub 010} cavity for small-diameter confined cylinders of water and lossy inorganic fibers. These observations suggest using 2.45 GHz microwave power for drying, calcining, and sintering extruded ceramic filaments. Droplet modeling indicates that the large dielectric shielding for spherical droplets can significantly limit the coupling of 2.45 GHz microwave with spherical aerosols, but not with fibers. Experimental observations on the microwave interactions with ferric nitrate aerosols and with ceramic filaments in the TM{sub 010} cavity are described.

  4. Levitation and collection of diamond fine particles in the rf plasma chamber equipped with a hot filament

    SciTech Connect (OSTI)

    Shimizu, S.; Shimizu, T.; Thomas, H. M.; Morfill, G. E.; Jacob, W.

    2011-11-15

    We demonstrate the levitation of diamond fine particles in a H{sub 2} rf plasma chamber equipped with a hot filament and heated electrodes. The levitation conditions should be carefully chosen to compensate the strong thermophoretic forces caused by the filament and the electrodes. This levitation technique with the existence of a hot filament can be applied, e.g., for the efficient growth of diamond layers on seed particles injected and levitated in an rf plasma with reactive gases, e.g., CH{sub 4}/H{sub 2}. Additionally, the method for direct capture of levitated particles on a planar substrate was established, which is useful if it is necessary to analyze the particles after the levitation.

  5. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.; Nash, Connor; Steirer, K. Xerxes; Clark, Jared; Robichaud, David J.; Ruddy, Daniel A.

    2016-01-21

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo2C) for the deoxygenation of acetic acid, anmore » abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.« less

  6. Monitoring the formation of carbide crystal phases during the thermal decomposition of 3d transition metal dicarboxylate complexes

    SciTech Connect (OSTI)

    Huba, ZJ; Carpenter, EE

    2014-06-06

    Single molecule precursors can help to simplify the synthesis of complex alloys by minimizing the amount of necessary starting reagents. However, single molecule precursors are time consuming to prepare with very few being commercially available. In this study, a simple precipitation method is used to prepare Fe, Co, and Ni fumarate and succinate complexes. These complexes were then thermally decomposed in an inert atmosphere to test their efficiency as single molecule precursors for the formation of metal carbide phases. Elevated temperature X-ray diffraction was used to identify the crystal phases produced upon decomposition of the metal dicarboxylate complexes. Thermogravimetric analysis coupled with an infrared detector was used to identify the developed gaseous decomposition products. All complexes tested showed a reduction from the starting M2+ oxidation state to the M oxidation state, upon decomposition. Also, each complex tested showed CO2 and H2O as gaseous decomposition products. Nickel succinate, iron succinate, and iron fumarate complexes were found to form carbide phases upon decomposition. This proves that transition metal dicarboxylate salts can be employed as efficient single molecule precursors for the formation of metal carbide crystal phases.

  7. DEVELOPMENT OF ADVANCED DRILL COMPONENTS FOR BHA USING MICROWAVE TECHNOLOGY INCORPORATING CARBIDE, DIAMOND COMPOSITES AND FUNCTIONALLY GRADED MATERIALS

    SciTech Connect (OSTI)

    Dinesh Agrawal; Rustum Roy

    2003-01-01

    The microwave processing of materials is a new emerging technology with many attractive advantages over the conventional methods. The advantages of microwave technology for various ceramic systems has already been demonstrated and proven. The recent developments at Penn State have succeeded in applying the microwave technology for the commercialization of WC/Co and diamond based cutting and drilling tools, effectively sintering of metallic materials, and fabrication of transparent ceramics for advanced applications. In recent years, the Microwave Processing and Engineering Center at Penn State University in collaboration with our industrial partner, Dennis Tool Co. has succeeded in commercializing the developed microwave technology partially funded by DOE for WC/Co and diamond based cutting and drilling tools for gas and oil exploration operations. In this program we have further developed this technology to make diamond-carbide composites and metal-carbide-diamond functionally graded materials. Several actual product of diamond-carbide composites have been processed in microwave with better performance than the conventional product. The functionally graded composites with diamond as one of the components has been for the first time successfully developed. These are the highlights of the project.

  8. Hydrogen desorption from hydrogen fluoride and remote hydrogen plasma cleaned silicon carbide (0001) surfaces

    SciTech Connect (OSTI)

    King, Sean W. Tanaka, Satoru; Davis, Robert F.; Nemanich, Robert J.

    2015-09-15

    Due to the extreme chemical inertness of silicon carbide (SiC), in-situ thermal desorption is commonly utilized as a means to remove surface contamination prior to initiating critical semiconductor processing steps such as epitaxy, gate dielectric formation, and contact metallization. In-situ thermal desorption and silicon sublimation has also recently become a popular method for epitaxial growth of mono and few layer graphene. Accordingly, numerous thermal desorption experiments of various processed silicon carbide surfaces have been performed, but have ignored the presence of hydrogen, which is ubiquitous throughout semiconductor processing. In this regard, the authors have performed a combined temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) investigation of the desorption of molecular hydrogen (H{sub 2}) and various other oxygen, carbon, and fluorine related species from ex-situ aqueous hydrogen fluoride (HF) and in-situ remote hydrogen plasma cleaned 6H-SiC (0001) surfaces. Using XPS, the authors observed that temperatures on the order of 7001000?C are needed to fully desorb C-H, C-O and Si-O species from these surfaces. However, using TPD, the authors observed H{sub 2} desorption at both lower temperatures (200550?C) as well as higher temperatures (>700?C). The low temperature H{sub 2} desorption was deconvoluted into multiple desorption states that, based on similarities to H{sub 2} desorption from Si (111), were attributed to silicon mono, di, and trihydride surface species as well as hydrogen trapped by subsurface defects, steps, or dopants. The higher temperature H{sub 2} desorption was similarly attributed to H{sub 2} evolved from surface O-H groups at ?750?C as well as the liberation of H{sub 2} during Si-O desorption at temperatures >800?C. These results indicate that while ex-situ aqueous HF processed 6H-SiC (0001) surfaces annealed at <700?C remain terminated by some surface CO and SiO bonding, they may still exhibit significant chemical reactivity due to the creation of surface dangling bonds resulting from H{sub 2} desorption from previously undetected silicon hydride and surface hydroxide species.

  9. Formation of a compound flux rope by the merging of two filament channels, the associated dynamics, and its stability

    SciTech Connect (OSTI)

    Joshi, Navin Chandra; Inoue, Satoshi; Magara, Tetsuya E-mail: njoshi98@gmail.com

    2014-11-01

    We present observations of compound flux rope formation, which occurred on 2014 January 1, via merging of two nearby filament channels, the associated dynamics, and its stability using multiwavelength data. We also discuss the dynamics of cool and hot plasma moving along the newly formed compound flux rope. The merging started after the interaction between the southern leg of the northward filament and the northern leg of the southward filament at ?01:21 UT and continued until a compound flux rope formed at ?01:33 UT. During the merging, the cool filament plasma heated up and started to move along both sides of the compound flux rope, i.e., toward the north (?265 km s{sup 1}) and south (?118 km s{sup 1}) from the point of merging. After traveling a distance of ?150 Mm toward the north, the plasma cooled down and started to return back to the south (?14 km s{sup 1}) after ?02:00 UT. The observations provide a clear example of compound flux rope formation via merging of two different flux ropes and the occurrence of a flare through tether cutting reconnection. However, the compound flux rope remained stable in the corona and had a confined eruption. The coronal magnetic field decay index measurements revealed that both the filaments and the compound flux rope axis lie within the stability domain (decay index <1.5), which may be the possible cause for their stability. The present study also deals with the relationship between the filament's chirality (sinistral) and the helicity (positive) of the surrounding flux rope.

  10. Channeling of microwave radiation in a double line containing a plasma filament produced by intense femtosecond laser pulses in air

    SciTech Connect (OSTI)

    Bogatov, N A; Kuznetsov, A I; Smirnov, A I; Stepanov, A N

    2009-10-31

    The channeling of microwave radiation is demonstrated experimentally in a double line in which a plasma filament produced in air by intense femtosecond laser pulses serves as one of the conductors. It is shown that during the propagation of microwave radiation in this line, ultrashort pulses are formed, their duration monotonically decreasing with increasing the propagation length (down to the value comparable with the microwave field period). These effects can be used for diagnostics of plasma in a filament. (laser applications and other topics in quantum electronics)

  11. Silicon Carbide Temperature Monitor Measurements at the High Temperature Test Laboratory

    SciTech Connect (OSTI)

    J. L. Rempe; K. G. Condie; D. L. Knudson; L. L. Snead

    2010-01-01

    Silicon carbide (SiC) temperature monitors are now available for use as temperature sensors in Advanced Test Reactor (ATR) irradiation test capsules. Melt wires or paint spots, which are typically used as temperature sensors in ATR static capsules, are limited in that they can only detect whether a single temperature is or is not exceeded. SiC monitors are advantageous because a single monitor can be used to detect for a range of temperatures that may have occurred during irradiation. As part of the efforts initiated by the ATR National Scientific User Facility (NSUF) to make SiC temperature monitors available, a capability was developed to complete post-irradiation evaluations of these monitors. As discussed in this report, the Idaho National Laboratory (INL) selected the resistance measurement approach for detecting peak irradiation temperature from SiC temperature monitors. This document describes the INL efforts to develop the capability to complete these resistance measurements. In addition, the procedure is reported that was developed to assure that high quality measurements are made in a consistent fashion.

  12. Strong visible electroluminescence from silicon nanocrystals embedded in a silicon carbide film

    SciTech Connect (OSTI)

    Huh, Chul Kim, Tae-Youb; Ahn, Chang-Geun; Kim, Bong Kyu

    2015-05-25

    We report the strong visible light emission from silicon (Si) nanocrystals (NCs) embedded in a Si carbide (SiC) film. Compared to Si NC light-emitting diode (LED) by employing the Si nitride (SiN{sub x}) film as a surrounding matrix, the turn-on voltage of the Si NC LED with the SiC film was significantly decreased by 4 V. This was attributed to a smaller barrier height for injecting the electrons into the Si NCs due to a smaller band gap of SiC film than a SiN{sub x} film. The electroluminescence spectra increases with increasing forward voltage, indicating that the electrons are efficiently injected into the Si NCs in the SiC film. The light output power shows a linear increase with increasing forward voltage. The light emission originated from the Si NCs in a SiC film was quite uniform. The power efficiency of the Si NC LED with the SiC film was 1.56 times larger than that of the Si NC LED with the SiN{sub x} film. The Si NCs in a SiC film show unique advantages and are a promising candidate for application in optical devices.

  13. Light Water Reactor Sustainability Program Status of Silicon Carbide Joining Technology Development

    SciTech Connect (OSTI)

    Shannon M. Bragg-Sitton

    2013-09-01

    Advanced, accident tolerant nuclear fuel systems are currently being investigated for potential application in currently operating light water reactors (LWR) or in reactors that have attained design certification. Evaluation of potential options for accident tolerant nuclear fuel systems point to the potential benefits of silicon carbide (SiC) relative to Zr-based alloys, including increased corrosion resistance, reduced oxidation and heat of oxidation, and reduced hydrogen generation under steam attack (off-normal conditions). If demonstrated to be applicable in the intended LWR environment, SiC could be used in nuclear fuel cladding or other in-core structural components. Achieving a SiC-SiC joint that resists corrosion with hot, flowing water, is stable under irradiation and retains hermeticity is a significant challenge. This report summarizes the current status of SiC-SiC joint development work supported by the Department of Energy Light Water Reactor Sustainability Program. Significant progress has been made toward SiC-SiC joint development for nuclear service, but additional development and testing work (including irradiation testing) is still required to present a candidate joint for use in nuclear fuel cladding.

  14. Carbide/nitride grain refined rare earth-iron-boron permanent magnet and method of making

    DOE Patents [OSTI]

    McCallum, R.W.; Branagan, D.J.

    1996-01-23

    A method of making a permanent magnet is disclosed wherein (1) a melt is formed having a base alloy composition comprising RE, Fe and/or Co, and B (where RE is one or more rare earth elements) and (2) TR (where TR is a transition metal selected from at least one of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Al) and at least one of C and N are provided in the base alloy composition melt in substantially stoichiometric amounts to form a thermodynamically stable compound (e.g. TR carbide, nitride or carbonitride). The melt is rapidly solidified in a manner to form particulates having a substantially amorphous (metallic glass) structure and a dispersion of primary TRC, TRN and/or TRC/N precipitates. The amorphous particulates are heated above the crystallization temperature of the base alloy composition to nucleate and grow a hard magnetic phase to an optimum grain size and to form secondary TRC, TRN and/or TRC/N precipitates dispersed at grain boundaries. The crystallized particulates are consolidated at an elevated temperature to form a shape. During elevated temperature consolidation, the primary and secondary precipitates act to pin the grain boundaries and minimize deleterious grain growth that is harmful to magnetic properties. 33 figs.

  15. Carbide/nitride grain refined rare earth-iron-boron permanent magnet and method of making

    DOE Patents [OSTI]

    McCallum, R. William (Ames, IA); Branagan, Daniel J. (Ames, IA)

    1996-01-23

    A method of making a permanent magnet wherein 1) a melt is formed having a base alloy composition comprising RE, Fe and/or Co, and B (where RE is one or more rare earth elements) and 2) TR (where TR is a transition metal selected from at least one of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Al) and at least one of C and N are provided in the base alloy composition melt in substantially stoichiometric amounts to form a thermodynamically stable compound (e.g. TR carbide, nitride or carbonitride). The melt is rapidly solidified in a manner to form particulates having a substantially amorphous (metallic glass) structure and a dispersion of primary TRC, TRN and/or TRC/N precipitates. The amorphous particulates are heated above the crystallization temperature of the base alloy composition to nucleate and grow a hard magnetic phase to an optimum grain size and to form secondary TRC, TRN and/or TRC/N precipitates dispersed at grain boundaries. The crystallized particulates are consolidated at an elevated temperature to form a shape. During elevated temperature consolidation, the primary and secondary precipitates act to pin the grain boundaries and minimize deleterious grain growth that is harmful to magnetic properties.

  16. SILICON CARBIDE MICRO-DEVICES FOR COMBUSTION GAS SENSING UNDER HARSH CONDITIONS

    SciTech Connect (OSTI)

    Ruby N. Ghosh; Peter Tobias; Roger G. Tobin

    2004-10-01

    A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen containing species in chemically reactive, high temperature environments. For these capacitive sensors we have determined that the optimum sensor operating point in terms of sensor lifetime and response time is at midgap. Detailed measurements of the oxide leakage current as a function of temperature were performed to investigate the high temperature reliability of the devices. In addition, robust metallization and electrical contacting techniques have been developed for device operation at elevated temperatures. To characterize the time response of the sensor responses in the millisecond range, a conceptually new apparatus has been built. Using laser induced fluorescence imaging techniques we have shown that the gas underneath the sensor can be completely exchanged with a time constant under 1 millisecond. Ultrahigh vacuum studies of the surface chemistry of the platinum gate have shown that sensor deactivation by adsorbed sulfur is a possible problem. Investigations on the chemical removal of sulfur by catalytic oxidation or reduction are continuing.

  17. Radiation-tolerant joining technologies for silicon carbide ceramics and composites

    SciTech Connect (OSTI)

    Katoh, Yutai; Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel; Koyanagi, Takaaki; Hinoki, Tetsuya; Henager, Charles H.; Ferraris, Monica

    2014-05-01

    Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, TiSiC MAX-phase joining, calciaalumina glassceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 ?C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to 3 dpa at 500 ?C, thus indicating the first results obtained on irradiation-stable SiC joints. Under the more aggressive irradiation conditions (800 ?C, 5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

  18. Tritium trapping in silicon carbide in contact with solid breeder under high flux isotope reactor irradiation

    SciTech Connect (OSTI)

    H. Katsui; Y. Katoh; A. Hasegawa; M. Shimada; Y. Hatano; T. Hinoki; S. Nogami; T. Tanaka; S. Nagata; T. Shikama

    2013-11-01

    The trapping of tritium in silicon carbide (SiC) injected from ceramic breeding materials was examined via tritium measurements using imaging plate (IP) techniques. Monolithic SiC in contact with ternary lithium oxide (lithium titanate and lithium aluminate) as a ceramic breeder was irradiated in the High Flux Isotope Reactor (HFIR) in Oak Ridge, Tennessee, USA. The distribution of photo-stimulated luminescence (PSL) of tritium in SiC was successfully obtained, which separated the contribution of 14C -rays to the PSL. The tritium incident from ceramic breeders was retained in the vicinity of the SiC surface even after irradiation at 1073 K over the duration of ~3000 h, while trapping of tritium was not observed in the bulk region. The PSL intensity near the SiC surface in contact with lithium titanate was higher than that obtained with lithium aluminate. The amount of the incident tritium and/or the formation of a Li2SiO3 phase on SiC due to the reaction with lithium aluminate under irradiation likely were responsible for this observation.

  19. Method for analyzing passive silicon carbide thermometry with a continuous dilatometer to determine irradiation temperature

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Campbell, Anne A.; Porter, Wallace D.; Katoh, Yutai; Snead, Lance Lewis

    2016-01-14

    Silicon carbide is used as a passive post-irradiation temperature monitor because the irradiation defects will anneal out above the irradiation temperature. The irradiation temperature is determined by measuring a property change after isochronal annealing, i.e., lattice spacing, dimensions, electrical resistivity, thermal diffusivity, or bulk density. However, such methods are time-consuming since the steps involved must be performed in a serial manner. This work presents the use of thermal expansion from continuous dilatometry to calculate the SiC irradiation temperature, which is an automated process requiring minimal setup time. Analysis software was written that performs the calculations to obtain the irradiation temperaturemore » and removes possible user-introduced error while standardizing the analysis. In addition, this method has been compared to an electrical resistivity and isochronal annealing investigation, and the results revealed agreement of the calculated temperatures. These results show that dilatometry is a reliable and less time-intensive process for determining irradiation temperature from passive SiC thermometry.« less

  20. Response to Comment on General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation [Phys. Fluids 26, 119101 (2014)

    SciTech Connect (OSTI)

    Van Gorder, Robert A.

    2014-11-15

    In R. A. Van Gorder, General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation, Phys. Fluids 26, 065105 (2014) I discussed properties of generalized vortex filaments exhibiting purely rotational motion under the low-temperature Svistunov model of the local induction approximation. Such solutions are stationary in terms of translational motion. In the Comment [N. Hietala, Comment on General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation [Phys. Fluids 26, 065105 (2014)], Phys. Fluids 26, 119101 (2014)], the author criticizes my paper for not including translational motion (although it was clearly stated that the filament motion was assumed rotational). As it turns out, if one is interested in studying the geometric structure of solutions (which was the point of my paper), one obtains the needed qualitative results on the structure of such solutions by studying the purely rotational case. Nevertheless, in this Response I shall discuss the vortex filaments that have both rotational and translational motions. I then briefly discuss why one might want to study such generalized rotating filament solutions, in contrast to simple the standard helical or planar examples (which are really special cases). I also discuss how one can study the time evolution of filaments which exhibit more complicated dynamics than pure translation and rotation. Doing this, one can study non-stationary solutions which initially appear purely rotational and gradually display other dynamics as the filaments evolve.

  1. Influence of the laser beam size on the length of a filament formed by high-power femtosecond laser radiation in air

    SciTech Connect (OSTI)

    Geints, Yu E; Zemlyanov, A A; Kabanov, A M; Matvienko, G G; Golik, S S

    2014-05-30

    The single-filamentation regime of GW femtosecond laser beams of millimetre diameter, propagating in atmospheric air under collimated and tight focusing, has been theoretically and experimentally (at wavelengths of 800 and 400 nm) investigated. The influence of the initial size of the light beam on the spatial characteristics of the filamentation region is systematically analysed. The filamentation length for collimated beams with the same initial power is found to nonmonotonically depend on the initial beam radius. In this case, the filament start point is displaced, and the longitudinal continuity of the related plasma channel is lost. For tightly focused beams, the observed filament length barely depends of the initial beam radius, provided that the peak intensity remains constant. (interaction of radiation with matter)

  2. Computational studies for plasma filamentation by magnetic field in atmospheric microwave discharge

    SciTech Connect (OSTI)

    Takahashi, Masayuki; Ohnishi, Naofumi

    2014-12-01

    Plasma filamentation is induced by an external magnetic field in an atmospheric discharge using intense microwaves. A discrete structure is obtained at low ambient pressure if a strong magnetic field of more than 1 T is applied, due to the suppression of electron diffusion, whereas a diffusive pattern is generated with no external field. Applying a magnetic field can slow the discharge front propagation due to magnetic confinement of the electron transport. If the resonance conditions are satisfied for electron cyclotron resonance and its higher harmonics, the propagation speed increases because the heated electrons easily ionize neutral particles. The streamer velocity and the pattern of the microwave plasma are positively controlled by adjusting two parameters—the electron diffusion coefficient and the ionization frequency—through the resonance process and magnetic confinement, and hot, dense filamentary plasma can be concentrated in a compact volume to reduce energy loss in a plasma device like a microwave rocket.

  3. Simulation of Current Filamentation Instability for an Accelerator Beam in a Capillary Plasma

    SciTech Connect (OSTI)

    Allen, Brian; Seyedi, Ashkan; Muggli, Patric; Martins, Joana; Silva, Luis O.; Huang Chengkun; Mori, Warren

    2010-11-04

    Current Filamentation Instability (CFI) is of central importance for the propagation of relativistic electron beams in plasmas. It could play an important role in the generation of magnetic fields and of radiation in the after-glow of gamma ray bursts as well as in hot electrons energy transport in the fast-igniter inertial confinement fusion concept. Using the particle-in-cell code QuickPIC, simulations of the electron beam at the Brookhaven National Laboratory--Accelerator Test Facility, BNL-ATF, propagating in a cm-long plasma were conducted. Simulation results show that with beam and plasma parameters achievable at the BNL-ATF, the CFI should be observed within 2 cm of plasma. Simulation results are presented for an experiment currently underway at BNL-ATF and possible diagnostics for characterizing the instability are discussed.

  4. Effect of energetic electrons on dust charging in hot cathode filament discharge

    SciTech Connect (OSTI)

    Kakati, B.; Kausik, S. S.; Saikia, B. K. [Centre of Plasma Physics, Institute for Plasma Research, Nazirakhat, Sonapur 782 402, Kamrup, Assam (India); Bandyopadhyay, M. [ITER-India, Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India)

    2011-03-15

    The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.

  5. Filamentation of magnetosonic wave and generation of magnetic turbulence in laser plasma interaction

    SciTech Connect (OSTI)

    Modi, K. V.; Tiwary, Prem Pyari; Singh, Ram Kishor Sharma, R. P.; Satsangi, V. R.

    2014-10-15

    This paper presents a theoretical model for the magnetic turbulence in laser plasma interaction due to the nonlinear coupling of magnetosonic wave with ion acoustic wave in overdense plasma. For this study, dynamical equations of magnetosonic waves and the ion acoustic waves have been developed in the presence of ponderomotive force due to the pump magnetosonic wave. Slowly converging and diverging behavior has been studied semi-analytically, this results in the formation of filaments of the magnetosonic wave. Numerical simulation has also been carried out to study nonlinear stage. From the results, it has been found that the localized structures become quite complex in nature. Further, power spectrum has been studied. Results show that the spectral index follows (?k{sup ?2.0}) scaling at smaller scale. Relevance of the present investigation has been shown with the experimental observation.

  6. Peculiarities of filamentation of sharply focused ultrashort laser pulses in air

    SciTech Connect (OSTI)

    Geints, Yu. E.; Zemlyanov, A. A.; Ionin, A. A.; Kudryashov, S. I.; Seleznev, L. V. Sinitsyn, D. V.; Sunchugasheva, E. S.

    2010-11-15

    Peculiarities of the self-focusing and filamentation of high-power femtosecond laser pulses in air have been experimentally and theoretically studied under conditions of broad variation of the beam focusing parameter. The influence of the numerical aperture (NA) of the initial radiation focusing on the main characteristics of laser-induced plasma columns (characteristic transverse size, length, and concentration of free electrons) is considered. It is established that, for a rigid (NA > 0.05) initial laser beam focusing, the transverse size of the plasma channel ceases to decrease at a level of R{sub pl} {approx} 2-4 {mu}m as a result of strong refraction of radiation on the plasma formed at the focal waist, which prevents further contraction of the laser beam due to its focusing and self-focusing.

  7. Non-filamentated ultra-intense and ultra-short pulse fronts in three-dimensional Raman seed amplification

    SciTech Connect (OSTI)

    Lehmann, G.; Spatschek, K. H.

    2014-05-15

    Ultra-intense and ultra-short laser pulses may be generated up to the exawatt-zetawatt regime due to parametric processes in plasmas. The minimization of unwanted plasma processes leads to operational limits which are discussed here with respect to filamentation. Transverse filamentation, which originally was derived for plane waves, is being investigated for seed pulse propagation in the so called ?-pulse limit. A three-dimensional (3D) three-wave-interaction model is the basis of the present investigation. To demonstrate the applicability of the three-wave-interaction model, the 1D pulse forms are compared with those obtained from 1D particle in cell and Vlasov simulations. Although wave-breaking may occur, the kinetic simulations show that the leading pumped pulse develops a form similar to that obtained from the three-wave-interaction model. In the main part, 2D and 3D filamentation processes of (localized) pulses are investigated with the three-wave-interaction model. It is shown that the leading pulse front can stay filamentation-free, whereas the rear parts show transverse modulations.

  8. Three dimensional simulations of plasma filaments in the scrape off layer: A comparison with models of reduced dimensionality

    SciTech Connect (OSTI)

    Easy, L.; Militello, F.; Omotani, J.; Havl?kov, E.; Dudson, B.; Tamain, P.; Naulin, V.; Nielsen, A. H.

    2014-12-15

    This paper presents simulations of isolated 3D filaments in a slab geometry obtained using a newly developed 3D reduced fluid code, written using the BOUT++ framework. First, systematic scans were performed to investigate how the dynamics of a filament are affected by its amplitude, perpendicular size, and parallel extent. The perpendicular size of the filament was found to have a strong influence on its motions, as it determined the relative importance of parallel currents to polarization and viscous currents, whilst drift-wave instabilities were observed if the initial amplitude of the blob was increased sufficiently. Next, the 3D simulations were compared to 2D simulations using different parallel closures; namely, the sheath dissipation closure, which neglects parallel gradients, and the vorticity advection closure, which neglects the influence of parallel currents. The vorticity advection closure was found to not replicate the 3D perpendicular dynamics and overestimated the initial radial acceleration of all the filaments studied. In contrast, a more satisfactory comparison with the sheath dissipation closure was obtained, even in the presence of significant parallel gradients, where the closure is no longer valid. Specifically, it captured the contrasting dynamics of filaments with different perpendicular sizes that were observed in the 3D simulations which the vorticity advection closure failed to replicate. However, neither closure successfully replicated the Boltzmann spinning effects nor the associated poloidal drift of the blob that was observed in the 3D simulations. Although the sheath dissipation closure was concluded to be more successful in replicating the 3D dynamics, it is emphasized that the vorticity advection closure may still be relevant for situations where the parallel current is inhibited from closing through the sheath due to effects such as strong magnetic shear around X points or increased resistivity near the targets.

  9. AN OVER-AND-OUT HALO CORONAL MASS EJECTION DRIVEN BY THE FULL ERUPTION OF A KINKED FILAMENT

    SciTech Connect (OSTI)

    Yang Jiayan; Jiang Yunchun; Bi Yi; Li Haidong; Hong Junchao; Yang Dan; Zheng Ruisheng; Yang Bo

    2012-04-10

    Over-and-out coronal mass ejections (CMEs) represent a broad class of CMEs that come from flare-producing magnetic explosions of various sizes but are laterally far offset from the flare, and their productions can be depicted by the magnetic-arch-blowout scenario. In this paper, we present observations of an over-and-out halo CME from the full eruption of a small kinking filament in an emerging active region (AR). In combination with the results of a derived coronal magnetic configuration, our observations showed that the CME was associated with a coronal helmet streamer, and the filament was located in the northern outskirts of the streamer base. Formed along a neutral line where flux cancellation was forced by the emerging AR with the surrounding opposite-polarity magnetic field, the filament underwent a full, non-radial eruption along the northern leg of the streamer arcade, accompanied by a clockwise deflection of the eruption direction. As a characteristic property of kink instability, the eruption displayed a clear inverse {gamma} shape, indicative of a writhing motion of the filament apex. Coronal dimmings, including a remote one, formed in opposite-polarity footprint regions of the streamer arcade during the eruption, and the consequent CME was laterally offset from the AR. These observations suggest that the kink instability is likely to be the driver in the eruption. The event can be well explained by putting this driver into the magnetic-arch-blowout model, in which the eruption-direction deflection and the full-eruption nature of the kinking filament are caused by the guiding action of the streamer arcade and the external reconnection between them.

  10. Evaluations of University of Wisconsin Silicon Carbide Temperature Monitors 300 LO and 400 LO B

    SciTech Connect (OSTI)

    K. L. Davis; J. L. Rempe; D. L. Knudson; B. M. Chase; T. C. Unruh

    2011-12-01

    Silicon carbide (SiC) temperature monitors 05R4-02-A KG1403 (300 LO) and 05R4-01-A KG1415 (400 LO B) were evaluated at the High Temperature Test Lab (HTTL) to determine their peak irradiation temperatures. HTTL measurements indicate that the peak irradiation temperature for the 300 LO monitor was 295 {+-} 20 C and the peak irradiation temperature for the 400 LO B monitor was 294 {+-} 25 C. Two silicon carbide (SiC) temperature monitors irradiated in the Advanced Test Reactor (ATR) were evaluated at the High Temperature Test Lab (HTTL) to determine their peak temperature during irradiation. These monitors were irradiated as part of the University of Wisconsin Pilot Project with a target dose of 3 dpa. Temperature monitors were fabricated from high density (3.203 g/cm3) SiC manufactured by Rohm Haas with a nominal size of 12.5 mm x 1.0 mm x 0.75 mm (see Attachment A). Table 1 provides identification for each monitor with an expected peak irradiation temperature range based on preliminary thermal analysis (see Attachment B). Post irradiation calculations are planned to reduce uncertainties in these calculated temperatures. Since the early 1960s, SiC has been used as a post-irradiation temperature monitor. As noted in Reference 2, several researchers have observed that neutron irradiation induced lattice expansion of SiC annealed out when the post-irradiation annealing temperature exceeds the peak irradiation temperature. As noted in Reference 3, INL uses resistivity measurements to infer peak irradiation temperature from SiC monitors. Figure 1 depicts the equipment at the HTTL used to evaluate the SiC monitors. The SiC monitors are heated in the annealing furnace using isochronal temperature steps that, depending on customer needs, can range from 50 to 800 C. This furnace is located under a ventilation hood within the stainless steel enclosure. The ventilation system is activated during heating so that any released vapors are vented through this system. Annealing temperatures are recorded using a National Institute of Standards and Technology (NIST) traceable thermocouple inserted into an alumina tube in the furnace. After each isochronal annealing, the specimens are placed in a specialized fixture located in the constant temperature chamber (maintained at 30 C) for a minimum of 30 minutes. After the 30 minute wait time, each specimen's resistance is measured using the specialized fixture and a calibrated DC power analyzer. This report discusses the evaluation of the SiC monitors and presents the results. Testing was conducted in accordance with Reference 3. Sections 2 and 3 present the data collected for each monitor and provide interpretation of the data. Section 4 presents the evaluated temperature results.

  11. New insights into the enigma of boron carbide inverse molecular behavior

    SciTech Connect (OSTI)

    Dera, Przemyslaw; Manghnani, Murli H.; Hushur, Anwar; Hu, Yi; Tkachev, Sergey

    2014-07-01

    Equation of state and compression mechanism of nearly stoichiometric boron carbide B{sub 4}C were investigated using diamond anvil cell single crystal synchrotron X-ray diffraction technique up to a maximum quasi-hydrostatic pressure of 74.0(1) GPa in neon pressure transmitting medium at ambient temperature. No signatures of structural phase transitions were observed on compression. Crystal structure refinements indicate that the icosahedral units are less compressible (13% volume reduction at 60 GPa) than the unit cell volume (18% volume reduction at 60 GPa), contrary to expectations based on the inverse molecular behavior hypothesis, but consistent with spectroscopic evidence and first principles calculations. The high-pressure crystallographic refinements reveal that the nature of the chemical bonds (two, versus three centered character) has marginal effect on the bond compressibility and the compression of the crystal is mainly governed by the force transfer between the rigid icosahedral structural units. - Graphical abstract: Single crystal measurements of equation of state and compression mechanism of B{sub 4}C show that the icosahedral units are less compressibe than the unit cell volume, despite the threei-ceneterd nature of some icosahedral bonds. - Highlights: Equation of state and compression mechanism of B{sub 4}C were measured to 75 GPa. No signatures of structural phase transitions were observed on compression. Icosahedral units are less compressibe than the unit cell volume. The nature of the chemical bonds has mariginal effect on the bond compressibility. The compression is governed by force transfer between the rigid icosahedra.

  12. Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage

    SciTech Connect (OSTI)

    Fisher, John E.; Gogotsi, Yury; Yildirim, Taner

    2010-01-07

    On-board hydrogen storage is a key requirement for fuel cell-powered cars and trucks. Porous carbon-based materials can in principle adsorb more hydrogen per unit weight at room temperature than liquid hydrogen at -176 oC. Achieving this goal requires interconnected pores with very high internal surface area, and binding energies between hydrogen and carbon significantly enhanced relative to H2 on graphite. In this project a systematic study of carbide-derived carbons, a novel form of porous carbon, was carried out to discover a high-performance hydrogen sorption material to meet the goal. In the event we were unable to improve on the state of the art in terms of stored hydrogen per unit weight, having encountered the same fundamental limit of all porous carbons: the very weak interaction between H2 and the carbon surface. On the other hand we did discover several strategies to improve storage capacity on a volume basis, which should be applicable to other forms of porous carbon. Further discoveries with potentially broader impacts include Proof that storage performance is not directly related to pore surface area, as had been previously claimed. Small pores (< 1.5 nm) are much more effective in storing hydrogen than larger ones, such that many materials with large total surface areas are sub-par performers. Established that the distribution of pore sizes can be controlled during CDC synthesis, which opens the possibility of developing high performance materials within a common family while targeting widely disparate applications. Examples being actively pursued with other funding sources include methane storage, electrode materials for batteries and supercapacitors with record high specific capacitance, and perm-selective membranes which bind cytokines for control of infections and possibly hemodialysis filters.

  13. Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors

    SciTech Connect (OSTI)

    Katoh, Yutai; Wilson, Dane F; Forsberg, Charles W

    2007-09-01

    The Advanced High-Temperature Reactor (AHTR) is a new reactor concept that uses a liquid fluoride salt coolant and a solid high-temperature fuel. Several alternative fuel types are being considered for this reactor. One set of fuel options is the use of pin-type fuel assemblies with silicon carbide (SiC) cladding. This report provides (1) an initial viability assessment of using SiC as fuel cladding and other in-core components of the AHTR, (2) the current status of SiC technology, and (3) recommendations on the path forward. Based on the analysis of requirements, continuous SiC fiber-reinforced, chemically vapor-infiltrated SiC matrix (CVI SiC/SiC) composites are recommended as the primary option for further study on AHTR fuel cladding among various industrially available forms of SiC. Critical feasibility issues for the SiC-based AHTR fuel cladding are identified to be (1) corrosion of SiC in the candidate liquid salts, (2) high dose neutron radiation effects, (3) static fatigue failure of SiC/SiC, (4) long-term radiation effects including irradiation creep and radiation-enhanced static fatigue, and (5) fabrication technology of hermetic wall and sealing end caps. Considering the results of the issues analysis and the prospects of ongoing SiC research and development in other nuclear programs, recommendations on the path forward is provided in the order or priority as: (1) thermodynamic analysis and experimental examination of SiC corrosion in the candidate liquid salts, (2) assessment of long-term mechanical integrity issues using prototypical component sections, and (3) assessment of high dose radiation effects relevant to the anticipated operating condition.

  14. NONLINEAR FORCE-FREE FIELD EXTRAPOLATION OF A CORONAL MAGNETIC FLUX ROPE SUPPORTING A LARGE-SCALE SOLAR FILAMENT FROM A PHOTOSPHERIC VECTOR MAGNETOGRAM

    SciTech Connect (OSTI)

    Jiang, Chaowei; Wu, S. T.; Hu, Qiang; Feng, Xueshang E-mail: wus@uah.edu E-mail: fengx@spaceweather.ac.cn

    2014-05-10

    Solar filaments are commonly thought to be supported in magnetic dips, in particular, in those of magnetic flux ropes (FRs). In this Letter, based on the observed photospheric vector magnetogram, we implement a nonlinear force-free field (NLFFF) extrapolation of a coronal magnetic FR that supports a large-scale intermediate filament between an active region and a weak polarity region. This result is a first, in the sense that current NLFFF extrapolations including the presence of FRs are limited to relatively small-scale filaments that are close to sunspots and along main polarity inversion lines (PILs) with strong transverse field and magnetic shear, and the existence of an FR is usually predictable. In contrast, the present filament lies along the weak-field region (photospheric field strength ? 100G), where the PIL is very fragmented due to small parasitic polarities on both sides of the PIL and the transverse field has a low signal-to-noise ratio. Thus, extrapolating a large-scale FR in such a case represents a far more difficult challenge. We demonstrate that our CESE-MHD-NLFFF code is sufficient for the challenge. The numerically reproduced magnetic dips of the extrapolated FR match observations of the filament and its barbs very well, which strongly supports the FR-dip model for filaments. The filament is stably sustained because the FR is weakly twisted and strongly confined by the overlying closed arcades.

  15. Summary of the radiological assessment of the fuel cycle for a thorium-uranium carbide-fueled fast breeder reactor

    SciTech Connect (OSTI)

    Tennery, V.J.; Bomar, E.S.; Bond, W.D.; Meyer, H.R.; Morse, L.E.; Till, J.E.; Yalcintas, M.G.

    1980-01-01

    A large fraction of the potential fuel for nuclear power reactors employing fissionable materials exists as ores of thorium. In addition, certain characteristics of a fuel system based on breeding of the fissionable isotope {sup 233}U from thorium offer the possibility of a greater resistance to the diversion of fissionable material for the fabrication of nuclear weapons. This report consolidates into a single source the principal content of two previous reports which assess the radiological environmental impact of mining and milling of thorium ore and of the reprocessing and refabrication of spent FBR thorium-uranium carbide fuel.

  16. Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations

    SciTech Connect (OSTI)

    Way, J.; Wolden, Colin

    2013-09-30

    Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo{sub 2}C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Mo{sub 2}C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft{sup 2} at a feed pressure of only 20 psig. The highest H{sub 2}/N{sub 2} selectivity obtained with this approach was 4.9. A transport model using dusty gas theory was derived to describe the hydrogen transport in the Mo{sub 2}C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo{sub 2}C catalyst layers. We have fabricated a Mo{sub 2}C/V composite membrane that in pure gas testing delivered a H{sub 2} flux of 238 SCFH/ft{sup 2} at 600 C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ?99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft{sup 2}.psi. However, during testing of a Mo{sub 2}C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft{sup 2}.psi was obtained which was stable during the entire test, meeting the permeance associated with the 2010 DOE target flux. Lastly, the Mo{sub 2}C/V composite membranes were shown to be stable for at least 168 hours = one week, including cycling at high temperature and alternating He/H{sub 2} exposure.

  17. Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions

    SciTech Connect (OSTI)

    Ruby Ghosh; Reza Loloee; Roger Tobin

    2008-09-30

    A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, this is significantly higher than the device response to room temperature gas or that predicted from vacuum chamber studies. The enhanced catalytic activity of the platinum sensing film under energy plant operating conditions was investigated via AFM, x-ray diffraction, TEM and x-ray photoelectron spectroscopy. Our characterization indicated that exposure to high temperature gases significantly modifies the morphology of the Pt catalytic film and the Pt/SiO{sub 2} interfacial region, which we tentatively attribute to the enhanced hydrogen sensitivity of the sensing film. A model for the hydrogen/oxygen response of the SiC device under atmospheric conditions was developed. It is based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO{sub 2}-SiC interface. The optimum operating set point for the SiC sensor with respect to response time and long term reliability was determined to be close to mid-gap. Ultrahigh vacuum (UHV) techniques were used to investigate the effects of sulfur contamination on the Pt gate. Exposure to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20-600 times greater than the H2S level, rapidly coated the gate with a monolayer of sulfur. Although hydrogen exposure could not remove the adsorbed sulfur, oxygen was effective at removing sulfur with no evidence of irreversible changes in device behavior. The role of oxygen in the functioning of the SiC sensors was also investigated. All of the results are consistent with oxygen acting through its surface reactions with hydrogen, including the need for oxygen to reset the device to a fully hydrogen-depleted state and competition between hydrogen oxidation and hydrogen diffusion to metal/oxide interface sites. A strong sensor response to the unsaturated linear hydrocarbon propene (C{sub 3}H{sub 6}) was observed.

  18. Elastic properties, sp fraction, and Raman scattering in low and high pressure synthesized diamond-like boron rich carbides

    SciTech Connect (OSTI)

    Zinin, Pavel V.; Burgess, Katherine; Jia, Ruth; Sharma, Shiv; Ming, Li-Chung; Liu, Yongsheng; Ciston, Jim; Hong, Shiming

    2014-10-07

    Dense BC{sub x} phases with high boron concentration are predicted to be metastable, superhard, and conductors or superconductors depending on boron concentration. However, up to this point, diamond-like boron rich carbides BC{sub x} (dl-BC{sub x}) phases have been thought obtainable only through high pressure and high temperature treatment, necessitating small specimen volume. Here, we use electron energy loss spectroscopy combined with transmission electron microscopy, Raman spectroscopy, surface Brillouin scattering, laser ultrasonics (LU) technique, and analysis of elastic properties to demonstrate that low pressure synthesis (chemical vapor deposition) of BC{sub x} phases may also lead to the creation of diamond-like boron rich carbides. The elastic properties of the dl-BC{sub x} phases depend on the carbon spversus sp content, which decreases with increasing boron concentration, while the boron bonds determine the shape of the Raman spectra of the dl-BC{sub x} after high pressure-high temperature treatment. Using the estimation of the density value based on the sp fraction, the shear modulus ? of dl-BC?, containing 10% carbon atoms with sp bonds, and dl-B?C?, containing 38% carbon atoms with sp bonds, were found to be ? = 19.3 GPa and ? = 170 GPa, respectively. The presented experimental data also imply that boron atoms lead to a creation of sp bonds during the deposition processes.

  19. Nanostructured Metal Carbides for Aprotic Li-O2 Batteries. New Insights into Interfacial Reactions and Cathode Stability

    SciTech Connect (OSTI)

    Kundu, Dipan; Black, Robert; Adams, Brian; Harrison, Katharine; Zavadil, Kevin R.; Nazar, Linda F.

    2015-05-01

    The development of nonaqueous Lioxygen batteries, which relies on the reversible reaction of Li + O2 to give lithium peroxide (Li2O2), is challenged by several factors, not the least being the high charging voltage that results when carbon is typically employed as the cathode host. We report here on the remarkably low 3.2 V potential for Li2O2 oxidation on a passivated nanostructured metallic carbide (Mo2C), carbon-free cathode host. Furthermore, online mass spectrometry coupled with X-ray photoelectron spectroscopy unequivocally demonstrates that lithium peroxide is simultaneously oxidized together with the LixMoO3-passivated conductive interface formed on the carbide, owing to their close redox potentials. We found that the process rejuvenates the surface on each cycle upon electrochemical charge by releasing LixMoO3 into the electrolyte, explaining the low charging potential.

  20. Mechanochemical synthesis of tungsten carbide nano particles by using WO{sub 3}/Zn/C powder mixture

    SciTech Connect (OSTI)

    Hoseinpur, Arman; Vahdati Khaki, Jalil; Marashi, Maryam Sadat

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ? Nano particles of WC are synthesized by mechanochemical process. ? Zn was used to reduce WO{sub 3}. ? By removing ZnO from the milling products with an acid leaching, WC will be the final products. ? XRD results showed that the reduction reactions were completed after 36 h. ? TEM and SEM images showed that the morphology of produced powder is nearly spherical like. -- Abstract: In this research we introduce a new, facile, and economical system for fabrication of tungsten carbide (WC) nano particle powder. In this system WO{sub 3}, Zn, and C have been ball-milled for several hours, which led to the synthesis of tungsten carbide nano particles. The synthesized WC can successfully be separated from the ball-milled product by subjecting the product powder to diluted HCl for removing ZnO and obtaining WC. X-ray diffraction (XRD) analysis indicates that the reduction of WO{sub 3} will be completed gradually by increasing milling time up to 36 h. Scanning electron microscope (SEM), and transmission electron microscope (TEM) images show that after 36 h of milling the particle size of the fabricated powder is nano metric (about 20 nm). Results have shown that this system can surmount some main problems occurred in previous similar WC synthesizing systems. For example carbothermic reduction reactions, which lead to the synthesis of W{sub 2}C instead of WC, would not be activated because in this system reactions take place gradually.

  1. Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments

    SciTech Connect (OSTI)

    Paxton, Walter F.; Bachand, George D.; Gomez, Andrew; Henderson, Ian M.; Bouxsein, Nathan F.

    2015-04-24

    In this study, we describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 45 h for corresponding lipid networks). The transport of materials in and on the polymer membranes differs substantially from the transport on analogous lipid networks. Specifically, our data suggest that polymer mobility in nanotubular structures is considerably different from planar or 3D structures, and is stunted by 1D confinement of the polymer subunits. Moreover, quantum dots adsorbed onto polymer nanotubes are completely immobile, which is related to this 1D confinement effect and is in stark contrast to the highly fluid transport observed on lipid tubules.

  2. Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Paxton, Walter F.; Bachand, George D.; Gomez, Andrew; Henderson, Ian M.; Bouxsein, Nathan F.

    2015-04-24

    In this study, we describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 4–5 h for corresponding lipid networks).more » The transport of materials in and on the polymer membranes differs substantially from the transport on analogous lipid networks. Specifically, our data suggest that polymer mobility in nanotubular structures is considerably different from planar or 3D structures, and is stunted by 1D confinement of the polymer subunits. Moreover, quantum dots adsorbed onto polymer nanotubes are completely immobile, which is related to this 1D confinement effect and is in stark contrast to the highly fluid transport observed on lipid tubules.« less

  3. Grain size dependent mechanical properties of nanocrystalline diamond films grown by hot-filament CVD

    SciTech Connect (OSTI)

    Wiora, M; Bruehne, K; Floeter, A; Gluche, P; Willey, T M; Kucheyev, S O; Van Buuren, A W; Hamza, A V; Biener, J; Fecht, H

    2008-08-01

    Nanocrystalline diamond (NCD) films with a thickness of {approx}6 {micro}m and with average grain sizes ranging from 60 to 9 nm were deposited on silicon wafers using a hot-filament chemical vapor deposition (HFCVD) process. These samples were then characterized with the goal to identify correlations between grain size, chemical composition and mechanical properties. The characterization reveals that our films are phase pure and exhibit a relatively smooth surface morphology. The levels of sp{sup 2}-bonded carbon and hydrogen impurities are low, and showed a systematic variation with the grain size. The hydrogen content increases with decreasing grain size, whereas the sp{sup 2} carbon content decreases with decreasing grain size. The material is weaker than single crystalline diamond, and both stiffness and hardness decrease with decreasing grain size. These trends suggest gradual changes of the nature of the grain boundaries, from graphitic in the case of the 60 nm grain size material to hydrogen terminated sp{sup 3} carbon for the 9 nm grain size material. The films exhibit low levels of internal stress and freestanding structures with a length of several centimeters could be fabricated without noticeable bending.

  4. THE THREE-DIMENSIONAL STRUCTURE OF AN ACTIVE REGION FILAMENT AS EXTRAPOLATED FROM PHOTOSPHERIC AND CHROMOSPHERIC OBSERVATIONS

    SciTech Connect (OSTI)

    Yelles Chaouche, L.; Kuckein, C.; Martinez Pillet, V.; Moreno-Insertis, F.

    2012-03-20

    The three-dimensional structure of an active region filament is studied using nonlinear force-free field extrapolations based on simultaneous observations at a photospheric and a chromospheric height. To that end, we used the Si I 10827 A line and the He I 10830 A triplet obtained with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope (Tenerife). The two extrapolations have been carried out independently from each other and their respective spatial domains overlap in a considerable height range. This opens up new possibilities for diagnostics in addition to the usual ones obtained through a single extrapolation from, typically, a photospheric layer. Among those possibilities, this method allows the determination of an average formation height of the He I 10830 A signal of Almost-Equal-To 2 Mm above the surface of the Sun. It allows, as well, a cross-check of the obtained three-dimensional magnetic structures to verify a possible deviation from the force-free condition, especially at the photosphere. The extrapolations yield a filament formed by a twisted flux rope whose axis is located at about 1.4 Mm above the solar surface. The twisted field lines make slightly more than one turn along the filament within our field of view, which results in 0.055 turns Mm{sup -1}. The convex part of the field lines (as seen from the solar surface) constitutes dips where the plasma can naturally be supported. The obtained three-dimensional magnetic structure of the filament depends on the choice of the observed horizontal magnetic field as determined from the 180 Degree-Sign solution of the azimuth. We derive a method to check for the correctness of the selected 180 Degree-Sign ambiguity solution.

  5. Observational evidence of torus instability as trigger mechanism for coronal mass ejections: The 2011 August 4 filament eruption

    SciTech Connect (OSTI)

    Zuccarello, F. P.; Poedts, S.; Seaton, D. B.; Mierla, M.; Rachmeler, L. A.; Romano, P.; Zuccarello, F. E-mail: Stefaan.Poedts@wis.kuleuven.be E-mail: marilena@oma.be E-mail: Paolo.Romano@oact.inaf.it

    2014-04-20

    Solar filaments are magnetic structures often observed in the solar atmosphere and consist of plasma that is cooler and denser than their surroundings. They are visible for dayseven weekswhich suggests that they are often in equilibrium with their environment before disappearing or erupting. Several eruption models have been proposed that aim to reveal what mechanism causes (or triggers) these solar eruptions. Validating these models through observations represents a fundamental step in our understanding of solar eruptions. We present an analysis of the observation of a filament eruption that agrees with the torus instability model. This model predicts that a magnetic flux rope embedded in an ambient field undergoes an eruption when the axis of the flux rope reaches a critical height that depends on the topology of the ambient field. We use the two vantage points of the Solar Dynamics Observatory (SDO) and the Solar TErrestrial RElations Observatory to reconstruct the three-dimensional shape of the filament, to follow its morphological evolution, and to determine its height just before eruption. The magnetograms acquired by SDO/Helioseismic and Magnetic Imager are used to infer the topology of the ambient field and to derive the critical height for the onset of the torus instability. Our analysis shows that the torus instability is the trigger of the eruption. We also find that some pre-eruptive processes, such as magnetic reconnection during the observed flares and flux cancellation at the neutral line, facilitated the eruption by bringing the filament to a region where the magnetic field was more vulnerable to the torus instability.

  6. Design, Construction, and Implementation of Novel Biofuel Production Capabilities in Filamentous Fungi Presentation for BETO 2015 Project Peer Review

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Design, Construction, and Implementation of Novel Biofuel Production Capabilities in Filamentous Fungi March 26, 2015 Technology Area Review Kenneth S. Bruno Pacific Northwest National Laboratory This presentation does not contain any proprietary, confidential, or otherwise restricted information *On many slides, the slide notes section has important additional information* Goal Statement 2 Problem: Lack of robust platforms for biochemical conversion of lignocellulosic feedstocks Must have high

  7. Slow rise and partial eruption of a double-decker filament. II. A double flux rope model

    SciTech Connect (OSTI)

    Kliem, Bernhard; Trk, Tibor; Titov, Viacheslav S.; Lionello, Roberto; Linker, Jon A.; Liu, Rui; Liu, Chang; Wang, Haimin

    2014-09-10

    Force-free equilibria containing two vertically arranged magnetic flux ropes of like chirality and current direction are considered as a model for split filaments/prominences and filament-sigmoid systems. Such equilibria are constructed analytically through an extension of the methods developed in Titov and Dmoulin and numerically through an evolutionary sequence including shear flows, flux emergence, and flux cancellation in the photospheric boundary. It is demonstrated that the analytical equilibria are stable if an external toroidal (shear) field component exceeding a threshold value is included. If this component decreases sufficiently, then both flux ropes turn unstable for conditions typical of solar active regions, with the lower rope typically becoming unstable first. Either both flux ropes erupt upward, or only the upper rope erupts while the lower rope reconnects with the ambient flux low in the corona and is destroyed. However, for shear field strengths staying somewhat above the threshold value, the configuration also admits evolutions which lead to partial eruptions with only the upper flux rope becoming unstable and the lower one remaining in place. This can be triggered by a transfer of flux and current from the lower to the upper rope, as suggested by the observations of a split filament in Paper I. It can also result from tether-cutting reconnection with the ambient flux at the X-type structure between the flux ropes, which similarly influences their stability properties in opposite ways. This is demonstrated for the numerically constructed equilibrium.

  8. IMPULSIVE ACCELERATION OF CORONAL MASS EJECTIONS. II. RELATION TO SOFT X-RAY FLARES AND FILAMENT ERUPTIONS

    SciTech Connect (OSTI)

    Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M.; Vrsnak, B.

    2012-08-10

    Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic field is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In {approx}60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than {+-}5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.

  9. Direct evidence of an eruptive, filament-hosting magnetic flux rope leading to a fast solar coronal mass ejection

    SciTech Connect (OSTI)

    Chen, Bin; Gary, D. E.; Bastian, T. S.

    2014-10-20

    Magnetic flux ropes (MFRs) are believed to be at the heart of solar coronal mass ejections (CMEs). A well-known example is the prominence cavity in the low corona that sometimes makes up a three-part white-light (WL) CME upon its eruption. Such a system, which is usually observed in quiet-Sun regions, has long been suggested to be the manifestation of an MFR with relatively cool filament material collecting near its bottom. However, observational evidence of eruptive, filament-hosting MFR systems has been elusive for those originating in active regions. By utilizing multi-passband extreme-ultraviolet (EUV) observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly, we present direct evidence of an eruptive MFR in the low corona that exhibits a hot envelope and a cooler core; the latter is likely the upper part of a filament that undergoes a partial eruption, which is later observed in the upper corona as the coiled kernel of a fast, WL CME. This MFR-like structure exists more than 1 hr prior to its eruption, and displays successive stages of dynamical evolution, in which both ideal and non-ideal physical processes may be involved. The timing of the MFR kinematics is found to be well correlated with the energy release of the associated long-duration C1.9 flare. We suggest that the long-duration flare is the result of prolonged energy release associated with the vertical current sheet induced by the erupting MFR.

  10. Zirconium and hafnium separation at Y-12

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the sea by French author Jules Verne. Of course there was then a movie made by Walt Disney in 1954 named 20,000 leagues under the sea that used the same Nautilus sub- marine...

  11. Composition and method for brazing graphite to graphite

    DOE Patents [OSTI]

    Taylor, Albert J. (Ten Mile, TN); Dykes, Norman L. (Oak Ridge, TN)

    1984-01-01

    The present invention is directed to a brazing material for joining graphite structures that can be used at temperatures up to about 2800.degree. C. The brazing material formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600.degree. C. with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800.degree. C. so as to provide a brazed joint consisting essentially of hafnium carbide. This brazing temperature for hafnium carbide is considerably less than the eutectic temperature of hafnium carbide of about 3150.degree. C. The brazing composition also incorporates the thermosetting resin so that during the brazing operation the graphite structures may be temporarily bonded together by thermosetting the resin so that machining of the structures to final dimensions may be completed prior to the completion of the brazing operation. The resulting brazed joint is chemically and thermally compatible with the graphite structures joined thereby and also provides a joint of sufficient integrity so as to at least correspond with the strength and other properties of the graphite.

  12. Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

    SciTech Connect (OSTI)

    Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

    2012-06-01

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of FischerTropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

  13. Surface Quality of Ti-6%Al-4%V ELI When Machined Using CVD-Carbide Tools at High Cutting Speed

    SciTech Connect (OSTI)

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.; Yasir, A.; Zaid, Y.; Yanuar, B.

    2011-01-17

    Machining of Ti-6Al-4V ELI becomes more interested topic due to extremely weight-to-strength ratio and resistance to corrosion at elevated temperature. Quality of machined surface is presented by surface roughness, surface texture and damages of microstructure of titanium alloys. The turning parameters evaluated are cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev, depth of cut of 0.10-0.20 mm and tool grade of CVD carbide tools. The results show the trend lines of surface roughness value are higher at the initial machining and the surface texture profile has a strong correlation with the feed rate. At the machining condition of cutting speed of 95 m/min, feed rate of 0.35 mm/rev and depth of cut of 0.10 mm produced the with layer with thickness of 2.0 {mu}m.

  14. Photoimaging of the multiple filamentation of femtosecond laser pulses in poly(methyl methacrylate) doped with 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2-dioxaborine

    SciTech Connect (OSTI)

    Kulchin, Yu N; Vitrik, O B; Chekhlenok, A A; Zhizhchenko, A Yu; Proschenko, D Yu; Mirochnik, A G; Lyu Guohui

    2013-12-31

    We have studied the filamentation of femtosecond laser pulses (? = 800 nm, ?42 fs pulse duration) in poly(methyl methacrylate) doped with 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2- dioxaborine and the associated photomodification of the material. The results demonstrate that multiple filamentation occurs at pulse energies above 5 ?J. At a pulse energy of 1.5 mJ, it is accompanied by supercontinuum generation. The average filament length in PMMA is 9 mm and the filament diameter is ?10 ?m. An incident power density of ?10{sup 12} W cm{sup -2} ensures inscription of the filament pattern owing to two-photon photochemical processes. Preliminary exposure to continuous light at ? = 400 nm enables an ordered filament pattern to be written. (interaction of laser radiation with matter)

  15. Development of nanodiamond foils for H- stripping to Support the Spallation Neutron Source (SNS) using hot filament chemical vapor deposition

    SciTech Connect (OSTI)

    Vispute, R D; Ermer, Henry K; Sinsky, Phillip; Seiser, Andrew; Shaw, Robert W; Wilson, Leslie L

    2014-01-01

    Thin diamond foils are needed in many particle accelerator experiments regarding nuclear and atomic physics, as well as in some interdisciplinary research. Particularly, nanodiamond texture is attractive for this purpose as it possesses a unique combination of diamond properties such as high thermal conductivity, mechanical strength and high radiation hardness; therefore, it is a potential material for energetic ion beam stripper foils. At the ORNL Spallation Neutron Source (SNS), the installed set of foils must be able to survive a nominal five-month operation period, without the need for unscheduled costly shutdowns and repairs. Thus, a small foil about the size of a postage stamp is critical to the operation of SNS and similar sources in U.S. laboratories and around the world. We are investigating nanocrystalline, polycrystalline and their admixture films fabricated using a hot filament chemical vapor deposition (HFCVD) system for H- stripping to support the SNS at Oak Ridge National Laboratory. Here we discuss optimization of process variables such as substrate temperature, process gas ratio of H2/Ar/CH4, substrate to filament distance, filament temperature, carburization conditions, and filament geometry to achieve high purity diamond foils on patterned silicon substrates with manageable intrinsic and thermal stresses so that they can be released as free standing foils without curling. An in situ laser reflectance interferometry tool (LRI) is used for monitoring the growth characteristics of the diamond thin film materials. The optimization process has yielded free standing foils with no pinholes. The sp3/sp2 bonds are controlled to optimize electrical resistivity to reduce the possibility of surface charging of the foils. The integrated LRI and HFCVD process provides real time information on the growth of films and can quickly illustrate growth features and control film thickness. The results are discussed in the light of development of nanodiamond foils that will be able to withstand a few MW proton beam and hopefully will be able to be used after possible future upgrades to the SNS to greater than a 3MW beam.

  16. Composition and method for brazing graphite to graphite

    DOE Patents [OSTI]

    Taylor, A.J.; Dykes, N.L.

    1982-08-10

    A brazing material is described for joining graphite structures that can be used up to 2800/sup 0/C. The brazing material is formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600/sup 0/C with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800/sup 0/C so as to provide a brazed joint consisting essentially of hafnium carbide. The resulting brazed joint is chemically and thermally compatible with the graphite structures.

  17. THE HERSCHEL FILAMENT: A SIGNATURE OF THE ENVIRONMENTAL DRIVERS OF GALAXY EVOLUTION DURING THE ASSEMBLY OF MASSIVE CLUSTERS AT z = 0.9

    SciTech Connect (OSTI)

    Coppin, K. E. K.; Geach, J. E.; Webb, T. M. A.; Faloon, A.; O'Donnell, D.; Yan, R.; Ouellette, N.; Egami, E.; Ellingson, E.; Gilbank, D.; Hicks, A.; Barrientos, L. F.; Yee, H. K. C.; Gladders, M.

    2012-04-20

    We have discovered a 2.5 Mpc (projected) long filament of infrared-bright galaxies connecting two of the three {approx}5 Multiplication-Sign 10{sup 14} M{sub Sun} clusters making up the RCS 2319+00 supercluster at z = 0.9. The filament is revealed in a deep Herschel Spectral and Photometric Imaging REceiver (SPIRE) map that shows 250-500 {mu}m emission associated with a spectroscopically identified filament of galaxies spanning two X-ray bright cluster cores. We estimate that the total (8-1000 {mu}m) infrared luminosity of the filament is L{sub IR} {approx_equal} 5 Multiplication-Sign 10{sup 12} L{sub Sun }, which, if due to star formation alone, corresponds to a total SFR {approx_equal} 900 M{sub Sun} yr{sup -1}. We are witnessing the scene of the buildup of a >10{sup 15} M{sub Sun} cluster of galaxies, seen prior to the merging of three massive components, each of which already contains a population of red, passive galaxies that formed at z > 2. The infrared filament demonstrates that significant stellar mass assembly is taking place in the moderate density, dynamically active circumcluster environments of the most massive clusters at high redshift, and this activity is concomitant with the hierarchical buildup of large-scale structure.

  18. Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique

    DOE Patents [OSTI]

    Molenbroek, Edith C. (Utrecht, NL); Mahan, Archie Harvin (Golden, CO); Gallagher, Alan C. (Louisville, CO)

    2000-09-26

    A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

  19. Processing aersols and filaments in a TM{sub 010} microwave cavity at 2.45 GHz

    SciTech Connect (OSTI)

    Vogt, G.J.; Unruh, W.P.

    1992-05-01

    As part of the development of generic microwave processes for spray-drying of homogeneous complex metal oxide powders and for inorganic fiber processing, we have investigated the use of 2.45 GHz microwaves in a high-Q single-mode TM{sub 010} cavity coupled directly to aerosols and fibers. Aqueous and ethanol aerosols of ferric nitrate solutions have been successfully dried at 1.8 kW of cavity power for a loaded Q greater than 6000 in flowing nitrogen gas. Similarly, we have observed extremely rapid heating rates in the TM{sub 010} cavity for small-diameter confined cylinders of water and lossy inorganic fibers. These observations suggest using 2.45 GHz microwave power for drying, calcining, and sintering extruded ceramic filaments. Droplet modeling indicates that the large dielectric shielding for spherical droplets can significantly limit the coupling of 2.45 GHz microwave with spherical aerosols, but not with fibers. Experimental observations on the microwave interactions with ferric nitrate aerosols and with ceramic filaments in the TM{sub 010} cavity are described.

  20. Use of a TM sub 010 microwave cavity at 2. 45 GHz for aerosol and filament drying

    SciTech Connect (OSTI)

    Christiansen, D.E.; Unruh, W.P.

    1991-01-01

    As part of the development of a generic spray-drying process for aerosol preparation of homogeneous powders of complex metal oxide systems, we have investigated the use of 2.45 GHz power in a high-Q single-mode TM{sub 010} cavity coupled directly to aerosols of aqueous solutions. Partial success was attained with a concentrated solution of ferric nitrate. Although all particulates showed drying, only a few percent of the particles were fully dried prior to collection. The cavity operated at a power level just below that sufficient to cause electric field breakdown in the carrier gas (dry nitrogen). The large inherent dielectric shielding of the spherical droplets makes it difficult to couple enough power into an aerosol at 2.45 GHz to overcome the heat loss from individual droplets to the surrounding gas and achieve full particulate drying. The calculated and measured dielectric shielding of a thin cylinder of water aligned with the cavity electric field is very much smaller. We have produced heating rates in water {approximately}600 times more rapid than could be achieved with aerosols. This suggests using 2.45 GHz microwave power for drying extruded filaments and then calcining those dried filaments to ceramic fiber. 3 refs., 4 figs.

  1. THE FIRST BENT DOUBLE LOBE RADIO SOURCE IN A KNOWN CLUSTER FILAMENT: CONSTRAINTS ON THE INTRAFILAMENT MEDIUM

    SciTech Connect (OSTI)

    Edwards, Louise O. V.; Fadda, Dario; Frayer, David T.

    2010-12-01

    We announce the first discovery of a bent double lobe radio source (DLRS) in a known cluster filament. The bent DLRS is found at a distance of 3.4 Mpc from the center of the rich galaxy cluster, A1763. We derive a bend angle {alpha} = 25{sup 0}, and infer that the source is most likely seen at a viewing angle of {Phi} = 10{sup 0}. From measuring the flux in the jet between the core and further lobe and assuming a spectral index of 1, we calculate the minimum pressure in the jet, (8.0 {+-} 3.2) x 10{sup -13} dyn cm{sup -2}, and derive constraints on the intrafilament medium (IFM) assuming the bend of the jet is due to ram pressure. We constrain the IFM to be between (1-20) x 10{sup -29} gm cm{sup -3}. This is consistent with recent direct probes of the IFM and theoretical models. These observations justify future searches for bent double lobe radio sources located several megaparsecs from cluster cores, as they may be good markers of super cluster filaments.

  2. Composites comprising silicon carbide fibers dispersed in magnesia-aluminate matrix and fabrication thereof and of other composites by sinter forging

    DOE Patents [OSTI]

    Panda, Prakash C. (Ithaca, NY); Seydel, Edgar R. (Ithaca, NY); Raj, Rishi (Ithaca, NY)

    1989-10-03

    A novel ceramic-ceramic composite of a uniform dispersion of silicon carbide fibers in a matrix of MgO.multidot.nAl.sub.2 O.sub.3 wherein n ranges from about 1 to about 4.5, said composite comprising by volume from 1 to 50% silicon carbide fibers and from 99 to 50% MgO.multidot.nAl.sub.2 O.sub.3. The composite is readily fabricated by forming a powder comprising a uniform dispersion of silicon carbide fibers in poorly crystalline phase comprising MgO and Al.sub.2 O.sub.3 in a mole ratio of n and either (a) hot pressing or preferably (b) cold pressing to form a preform and then forging utilizing a temperature in the range of 1100.degree. C. to 1900.degree. C. and a strain rate ranging from about 10.sup.-5 seconds .sup.-1 to about 1 seconds .sup.-1 so that surfaces cracks do not appear to obtain a shear deformation greater than 30%.

  3. Active wear and failure mechanisms of TiN-coated high speed steel and TiN-coated cemented carbide tools when machining powder metallurgically made stainless steels

    SciTech Connect (OSTI)

    Jiang, L.; Haenninen, H.; Paro, J.; Kauppinen, V.

    1996-09-01

    In this study, active wear and failure mechanisms of both TiN-coated high speed steel and TiN-coated cemented carbide tools when machining stainless steels made by powder metallurgy in low and high cutting speed ranges, respectively, have been investigated. Abrasive wear mechanisms, fatigue-induced failure, and adhesive and diffusion wear mechanisms mainly affected the tool life of TiN-coated high speed steel tools at cutting speeds below 35 m/min, between 35 and 45 m/min, and over 45 m/min, respectively. Additionally, fatigue-induced failure was active at cutting speeds over 45 m/min in the low cutting speed range when machining powder metallurgically made duplex stainless steel 2205 and austenitic stainless steel 316L. In the high cutting speed range, from 100 to 250 m/min, fatigue-induced failure together with diffusion wear mechanism, affected the tool life of TiN-coated cemented carbide tools when machining both 316L and 2205 stainless steels. It was noticed that the tool life of TiN-coated high speed steel tools used in the low cutting speed range when machining 2205 steel was longer than that when machining 316L steel, whereas the tool life of TiN-coated cemented carbide tools used in the high cutting speed range when machining 316L steel was longer than that when machining 2205 steel.

  4. Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

    SciTech Connect (OSTI)

    Jiang, Liming; Fu, Honggang; Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong

    2014-01-01

    Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: The WC/PC composite with high specific surface area was prepared by a simple way. The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. The current density for methanol electro-oxidation is as high as 595.93 A g{sup ?1} Pt. The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. The performance of Pt/WC/PC is superior to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 C, exhibited a specific surface area (S{sub BET}) of 457.92 m{sup 2} g{sup ?1}. After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g{sup ?1} Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance.

  5. The W40 region in the gould belt: An embedded cluster and H II region at the junction of filaments

    SciTech Connect (OSTI)

    Mallick, K. K.; Ojha, D. K.; Kumar, M. S. N.; Samal, M. R.; Pirogov, L.

    2013-12-20

    We present a multiwavelength study of the W40 star-forming region using infrared (IR) observations in the UKIRT JHK bands, Spitzer Infrared Array Camera bands, and Herschel PACS bands, 2.12 ?m H{sub 2} narrowband imaging, and radio continuum observations from GMRT (610 and 1280 MHz), in a field of view (FoV) of ?34' 40'. Archival Spitzer observations in conjunction with near-IR observations are used to identify 1162 Class II/III and 40 Class I sources in the FoV. The nearest-neighbor stellar surface density analysis shows that the majority of these young stellar objects (YSOs) constitute the embedded cluster centered on the high-mass source IRS 1A South. Some YSOs, predominantly the younger population, are distributed along and trace the filamentary structures at lower stellar surface density. The cluster radius is measured to be 0.44 pcmatching well with the extent of radio emissionwith a peak density of 650 pc{sup 2}. The JHK data are used to map the extinction in the region, which is subsequently used to compute the cloud mass126 M {sub ?} and 71 M {sub ?} for the central cluster and the northern IRS 5 region, respectively. H{sub 2} narrowband imaging shows significant emission, which prominently resembles fluorescent emission arising at the borders of dense regions. Radio continuum analysis shows that this region has a blister morphology, with the radio peak coinciding with a protostellar source. Free-free emission spectral energy distribution analysis is used to obtain physical parameters of the overall photoionized region and the IRS 5 sub-region. This multiwavelength scenario is suggestive of star formation having resulted from the merging of multiple filaments to form a hub. Star formation seems to have taken place in two successive epochs, with the first epoch traced by the central cluster and the high-mass star(s)followed by a second epoch that is spreading into the filaments as uncovered by the Class I sources and even younger protostellar sources along the filaments. The IRS 5 H II region displays indications of swept-up material that has possibly led to the formation of protostars.

  6. Enhancement of oxidation resistance of graphite foams by polymer derived-silicon carbide coating for concentrated solar power applications

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kim, T.; Singh, D.; Singh, M.

    2015-05-01

    Graphite foam with extremely high thermal conductivity has been investigated to enhance heat transfer of latent heat thermal energy storage (LHTES) systems. However, the use of graphite foam for elevated temperature applications (>600 °C) is limited due to poor oxidation resistance of graphite. In the present study, oxidation resistance of graphite foam coated with silicon carbide (SiC) was investigated. A pre-ceramic polymer derived coating (PDC) method was used to form a SiC coating on the graphite foams. Post coating deposition, the samples were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The oxidation resistance of PDC-SiC coating was quantifiedmore » by measuring the weight of the samples at several measuring points. The experiments were conducted under static argon atmosphere in a furnace. After the experiments, oxidation rates (%/hour) were calculated to predict the lifetime of the graphite foams. The experimental results showed that the PDC-SiC coating could prevent the oxidation of graphite foam under static argon atmosphere up to 900 °C.« less

  7. High Dose Neutron Irradiation of Hi-Nicalon Type S Silicon Carbide Composites, Part 2. Mechanical and Physical Properties

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Katoh, Yutai; Nozawa, Takashi; Shih, Chunghao Phillip; Ozawa, Kazumi; Koyanagi, Takaaki; Porter, Wallace D; Snead, Lance Lewis

    2015-01-07

    Nuclear-grade silicon carbide (SiC) composite material was examined for mechanical and thermophysical properties following high-dose neutron irradiation in the High Flux Isotope Reactor at a temperature range of 573–1073 K. Likewise, the material was chemical vapor-infiltrated SiC-matrix composite with a two-dimensional satin weave Hi-Nicalon Type S SiC fiber reinforcement and a multilayered pyrocarbon/SiC interphase. Moderate (1073 K) to very severe (573 K) degradation in mechanical properties was found after irradiation to >70 dpa, whereas no evidence was found for progressive evolution in swelling and thermal conductivity. The swelling was found to recover upon annealing beyond the irradiation temperature, indicating themore » irradiation temperature, but only to a limited extent. Moreover, the observed strength degradation is attributed primarily to fiber damage for all irradiation temperatures, particularly a combination of severe fiber degradation and likely interphase damage at relatively low irradiation temperatures.« less

  8. The Effect of High Temperature Annealing on the Grain Characteristics of a Thin Chemical Vapor Deposition Silicon Carbide Layer.

    SciTech Connect (OSTI)

    Isabella J van Rooyen; Philippus M van Rooyen; Mary Lou Dunzik-Gougar

    2013-08-01

    The unique combination of thermo-mechanical and physiochemical properties of silicon carbide (SiC) provides interest and opportunity for its use in nuclear applications. One of the applications of SiC is as a very thin layer in the TRi-ISOtropic (TRISO) coated fuel particles for high temperature gas reactors (HTGRs). This SiC layer, produced by chemical vapor deposition (CVD), is designed to withstand the pressures of fission and transmutation product gases in a high temperature, radiation environment. Various researchers have demonstrated that macroscopic properties can be affected by changes in the distribution of grain boundary plane orientations and misorientations [1 - 3]. Additionally, various researchers have attributed the release behavior of Ag through the SiC layer as a grain boundary diffusion phenomenon [4 - 6]; further highlighting the importance of understanding the actual grain characteristics of the SiC layer. Both historic HTGR fission product release studies and recent experiments at Idaho National Laboratory (INL) [7] have shown that the release of Ag-110m is strongly temperature dependent. Although the maximum normal operating fuel temperature of a HTGR design is in the range of 1000-1250C, the temperature may reach 1600C under postulated accident conditions. The aim of this specific study is therefore to determine the magnitude of temperature dependence on SiC grain characteristics, expanding upon initial studies by Van Rooyen et al, [8; 9].

  9. Enhancement of oxidation resistance of graphite foams by polymer derived-silicon carbide coating for concentrated solar power applications

    SciTech Connect (OSTI)

    Kim, T.; Singh, D.; Singh, M.

    2015-05-01

    Graphite foam with extremely high thermal conductivity has been investigated to enhance heat transfer of latent heat thermal energy storage (LHTES) systems. However, the use of graphite foam for elevated temperature applications (>600 C) is limited due to poor oxidation resistance of graphite. In the present study, oxidation resistance of graphite foam coated with silicon carbide (SiC) was investigated. A pre-ceramic polymer derived coating (PDC) method was used to form a SiC coating on the graphite foams. Post coating deposition, the samples were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The oxidation resistance of PDC-SiC coating was quantified by measuring the weight of the samples at several measuring points. The experiments were conducted under static argon atmosphere in a furnace. After the experiments, oxidation rates (%/hour) were calculated to predict the lifetime of the graphite foams. The experimental results showed that the PDC-SiC coating could prevent the oxidation of graphite foam under static argon atmosphere up to 900 C.

  10. High dose neutron irradiation of Hi-Nicalon Type S silicon carbide composites, Part 1: Microstructural evaluations

    SciTech Connect (OSTI)

    Perez-Bergquist, Alex G; Nozawa, Takashi; Shih, Chunghao Phillip; Leonard, Keith J; Snead, Lance Lewis; Katoh, Yutai

    2015-01-01

    Over the past decade, significant progress has been made in the development of silicon carbide (SiC) composites, composed of near-stoichiometric SiC fibers embedded in a crystalline SiC matrix, to the point that such materials can now be considered nuclear grade. Recent neutron irradiation studies of Hi-Nicalon Type S SiC composites showed excellent radiation response at damage levels of 30 40 dpa at temperatures of 300 800 C. However, more recent studies of these same fiber composites irradiated to damage levels of >70 dpa at similar temperatures showed a marked decrease in ultimate flexural strength, particularly at 300 C. Here, electron microscopy is used to analyze the microstructural evolution of these irradiated composites in order to investigate the cause of the degradation. While minimal changes were observed in Hi-Nicalon Type S SiC composites irradiated at 800 C, substantial microstructural evolution is observed in those irradiated at 300 C. Specifically, carbonaceous particles in the fibers grew by 25% compared to the virgin case, and severe cracking occurred at interphase layers.

  11. The effect of carbon on surface quality of solid-state-sintered silicon carbide as optical materials

    SciTech Connect (OSTI)

    Chen, Jian Huang, Zhengren; Chen, Zhongming; Yuan, Ming; Liu, Yan; Zhu, Yunzhou

    2014-03-01

    The microstructure and the distribution of carbon (C) in silicon carbide (SiC) ceramics were investigated by scanning electron microscopy and transmission electron microscopy. The results show that C can restrain the growth of SiC grains and densify SiC ceramics with the increase of the C content, but residual C introduces a new phase-C to SiC ceramics. The hardness of C is less than that of SiC, so it's difficult to be polished as optical materials. The existence of C phase doesn't lead to the increase of surface roughness on SiC optical materials, but it leads to the decrease of the reflectance of SiC as the optical materials because the optical absorption of C in visible light is stronger than that of SiC. It indicates that C content is very important to the surface properties of SiC, which will affect the coating of chemical vapor deposition SiC or Si on the surface of SiC ceramics because of the different physical and chemical properties between C and SiC. - Highlights: The microstructure and the distribution of carbon were investigated. A new phase in the optical materials is introduced. It is difficult to be polished as the optical materials because of different phases. Carbon leads to the decrease of reflectance because of its absorption to light wave. The different properties may affect the coating of chemical vapor deposition on SiC.

  12. Transition metal carbides, nitrides and borides, and their oxygen containing analogs useful as water gas shift catalysts

    DOE Patents [OSTI]

    Thompson, Levi T.; Patt, Jeremy; Moon, Dong Ju; Phillips, Cory

    2003-09-23

    Mono- and bimetallic transition metal carbides, nitrides and borides, and their oxygen containing analogs (e.g. oxycarbides) for use as water gas shift catalysts are described. In a preferred embodiment, the catalysts have the general formula of M1.sub.A M2.sub.B Z.sub.C O.sub.D, wherein M1 is selected from the group consisting of Mo, W, and combinations thereof; M2 is selected from the group consisting of Fe, Ni, Cu, Co, and combinations thereof; Z is selected from the group consisting of carbon, nitrogen, boron, and combinations thereof; A is an integer; B is 0 or an integer greater than 0; C is an integer; O is oxygen; and D is 0 or an integer greater than 0. The catalysts exhibit good reactivity, stability, and sulfur tolerance, as compared to conventional water shift gas catalysts. These catalysts hold promise for use in conjunction with proton exchange membrane fuel cell powered systems.

  13. Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

    SciTech Connect (OSTI)

    Laulainen, J.; Kalvas, T.; Koivisto, H.; Komppula, J.; Tarvainen, O.

    2015-04-08

    Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H{sup ?} ion source (LIISA). It has been found that photoelectron currents obtained with Al, Cu, Mo, Ta and stainless steel (SAE 304) are on the same order of magnitude. The photoelectron currents depend linearly on the discharge power. It is shown experimentally that photoelectron emission is significant only in the short wavelength range of hydrogen spectrum due to the energy dependence of the quantum efficiency. It is estimated from the measured data that the maximum photoelectron flux from plasma chamber walls is on the order of 1 A per kW of discharge power.

  14. Hydrogen atom temperature measured with wavelength-modulated laser absorption spectroscopy in large scale filament arc negative hydrogen ion source

    SciTech Connect (OSTI)

    Nakano, H. Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Nishiyama, S.; Sasaki, K.

    2015-04-08

    The velocity distribution function of hydrogen atoms is one of the useful parameters to understand particle dynamics from negative hydrogen production to extraction in a negative hydrogen ion source. Hydrogen atom temperature is one of the indicators of the velocity distribution function. To find a feasibility of hydrogen atom temperature measurement in large scale filament arc negative hydrogen ion source for fusion, a model calculation of wavelength-modulated laser absorption spectroscopy of the hydrogen Balmer alpha line was performed. By utilizing a wide range tunable diode laser, we successfully obtained the hydrogen atom temperature of ?3000?K in the vicinity of the plasma grid electrode. The hydrogen atom temperature increases as well as the arc power, and becomes constant after decreasing with the filling of hydrogen gas pressure.

  15. In Situ Expression of Acidic and Thermophilic Carbohydrate Active Enzymes by Filamentous Fungi (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    ScienceCinema (OSTI)

    Mosier, Annika [Stanford University

    2013-01-22

    Annika Mosier, graduate student from Stanford University presents a talk titled "In Situ Expression of Acidic and Thermophilic Carbohydrate Active Enzymes by Filamentous Fungi" at the JGI User 7th Annual Genomics of Energy & Environment Meeting on March 22, 2012 in Walnut Creek, Calif

  16. In Situ Expression of Acidic and Thermophilic Carbohydrate Active Enzymes by Filamentous Fungi (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    SciTech Connect (OSTI)

    Mosier, Annika [Stanford University] [Stanford University

    2012-03-22

    Annika Mosier, graduate student from Stanford University presents a talk titled "In Situ Expression of Acidic and Thermophilic Carbohydrate Active Enzymes by Filamentous Fungi" at the JGI User 7th Annual Genomics of Energy & Environment Meeting on March 22, 2012 in Walnut Creek, Calif

  17. Joint contributions of Ag ions and oxygen vacancies to conducting filament evolution of Ag/TaO{sub x}/Pt memory device

    SciTech Connect (OSTI)

    Chung, Yu-Lung; Cheng, Wen-Hui; Chen, Wei-Chih; Jhan, Sheng-An; Chen, Jen-Sue; Jeng, Jiann-Shing

    2014-10-28

    The electroforming and resistive switching behaviors in the Ag/TaO{sub x}/Pt trilayer structure are investigated under a continual change of temperatures between 300?K and 100?K to distinguish the contributions of Ag ions and oxygen vacancies in developing of conducting filaments. For either electroforming or resistive switching, a significantly higher forming/set voltages is needed as the device is operated at 100?K, as compared to that observed when operating at 300?K. The disparity in forming/set voltages of Ag/TaO{sub x}/Pt operating at 300?K and 100?K is attributed to the contribution of oxygen vacancies, in addition to Ag atoms, in formation of conducting filament at 100?K since the mobilities of oxygen vacancies and Ag ions become comparable at low temperature. The presence of oxygen vacancy segment in the conducting filament also modifies the reset current from a gradually descending behavior (at 300?K) to a sharp drop (at 100?K). Furthermore, the characteristic set voltage and reset current are irreversible as the operation temperature is brought from 100?K back to 300?K, indicating the critical role of filament constituents on the switching behaviors of Ag/oxide/Pt system.

  18. MAGNETIC FIELDS OF AN ACTIVE REGION FILAMENT FROM FULL STOKES ANALYSIS OF Si I 1082.7 nm AND He I 1083.0 nm

    SciTech Connect (OSTI)

    Xu, Z.; Liu, Y.

    2012-04-20

    Vector magnetic fields of an active region filament in the photosphere and upper chromosphere are obtained from spectro-polarimetric observations recorded with the Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope. We apply Milne-Eddington inversions on full Stokes vectors of the photospheric Si I 1082.7 nm and the upper chromospheric He I triplet at 1083.0 nm to obtain the magnetic field vector and velocity maps in two atmosphere layers. We find that (1) a complete filament was already present in H{alpha} at the beginning of the TIP II data acquisition. Only a partially formed one, composed of multiple small threads, was present in He I. (2) The AR filament comprises two sections. One shows strong magnetic field intensities, about 600-800 G in the upper chromosphere and 800-1000 G in the photosphere. The other exhibits only comparatively weak magnetic field strengths in both layers. (3) The Stokes V signal is indicative of a dip in the magnetic field strength close to the chromospheric PIL. (4) In the chromosphere, consistent upflows are found along the PIL flanked by downflows. (5) The transversal magnetic field is nearly parallel to the PIL in the photosphere and inclined by 20 Degree-Sign -30 Degree-Sign in the chromosphere. (6) The chromospheric magnetic field around the filament is found to be in normal configuration, while the photospheric field presents a concave magnetic topology. The observations are consistent with the emergence of a flux rope with a subsequent formation of a filament.

  19. Fluoride-Salt-Cooled High-Temperature Reactor (FHR) with Silicon-Carbide-Matrix Coated-Particle Fuel

    SciTech Connect (OSTI)

    Forsberg, C. W.; Terrani, Kurt A; Snead, Lance Lewis; Katoh, Yutai

    2012-01-01

    The FHR is a new reactor concept that uses coated-particle fuel and a low-pressure liquid-salt coolant. Its neutronics are similar to a high-temperature gas-cooled reactor (HTGR). The power density is 5 to 10 times higher because of the superior cooling properties of liquids versus gases. The leading candidate coolant salt is a mixture of {sup 7}LiF and BeF{sub 2} (FLiBe) possessing a boiling point above 1300 C and the figure of merit {rho}C{sub p} (volumetric heat capacity) for the salt slightly superior to water. Studies are underway to define a near-term base-line concept while understanding longer-term options. Near-term options use graphite-matrix coated-particle fuel where the graphite is both a structural component and the primary neutron moderator. It is the same basic fuel used in HTGRs. The fuel can take several geometric forms with a pebble bed being the leading contender. Recent work on silicon-carbide-matrix (SiCm) coated-particle fuel may create a second longer-term fuel option. SiCm coated-particle fuels are currently being investigated for use in light-water reactors. The replacement of the graphite matrix with a SiCm creates a new family of fuels. The first motivation behind the effort is to take advantage of the superior radiation resistance of SiC compared to graphite in order to provide a stable matrix for hosting coated fuel particles. The second motivation is a much more rugged fuel under accident, repository, and other conditions.

  20. Cumulative fission yields of short-lived isotopes under natural-abundance-boron-carbide-moderated neutron spectrum

    SciTech Connect (OSTI)

    Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce; Wittman, Richard S.; Friese, Judah I.; Kephart, Rosara F.

    2015-04-09

    The availability of gamma spectroscopy data on samples containing mixed fission products at short times after irradiation is limited. Due to this limitation, data interpretation methods for gamma spectra of mixed fission product samples, where the individual fission products have not been chemically isolated from interferences, are not well-developed. The limitation is particularly pronounced for fast pooled neutron spectra because of the lack of available fast reactors in the United States. Samples containing the actinide isotopes 233, 235, 238U, 237Np, and 239Pu individually were subjected to a 2$ pulse in the Washington State University 1 MW TRIGA reactor. To achieve a fission-energy neutron spectrum, the spectrum was tailored using a natural abundance boron carbide capsule to absorb neutrons in the thermal and epithermal region of the spectrum. Our tailored neutron spectrum is unique to the WSU reactor facility, consisting of a soft fission spectrum that contains some measurable flux in the resonance region. This results in a neutron spectrum at greater than 0.1 keV with an average energy of 70 keV, similar to fast reactor spectra and approaching that of 235U fission. Unique fission product gamma spectra were collected from 4 minutes to 1 week after fission using single-crystal high purity germanium detectors. Cumulative fission product yields measured in the current work generally agree with published fast pooled fission product yield values from ENDF/B-VII, though a bias was noted for 239Pu. The present work contributes to the compilation of energy-resolved fission product yield nuclear data for nuclear forensic purposes.

  1. Neutron Scattering Studies of Liquid on or Confined in Nano- and Mesoporous Carbons, Including Carbide-Derived Carbons

    SciTech Connect (OSTI)

    Wesolowski, David J

    2014-07-01

    This project involved the synthesis of microporous graphitic-carbon powders with subnanometer average pore size, and very narrow pore size distributions, and the use of these materials in experimental studies of pore-fluid structure and dynamics. Samples of carbide-derived carbon powder, synthesized by extraction of the metal cations from TiC by a high temperature chlorination process, followed by high temperature vacuum annealing, were prepared by Ranjan Dash and his associates at CRADA partner Y-Carbon, Inc. The resulting material had average pore sizes ranging from 5 to 8 . These powders were used in two experiments conducted by researchers involved in the Energy Frontier Research Center Directed by David J. Wesolowski at ORNL, the Fluid Interface Reactions, Structures and Transport (FIRST) Center. FIRST-funded researchers at Drexel University collaborated with scientists at the Paul Scherrer Institute, Switzerland, to measure the expansion and contraction of the microporous carbon particles during charging and discharging of supercapactor electrodes composed of these particles (Hantell et al., 2011, Electrochemistry Communications, v. 13, pp. 1221-1224.) in an electrolyte composed of tetraethylammonium tetrafluoroborate dissolved in acetonitrile. In the second experiment, researchers at Oak Ridge National Laboratory and Drexel University conducted quasielastic neutron scattering studies of the diffusional dynamics of water imbibed into the micropores of the same material (Chathoth et al., 2011, EuroPhysics Journal, v. 95, pp. 56001/1-6). These studies helped to establish the role of pores approaching the size of the solvent and dissolved ions in altering diffusional dynamics, ion transport and physical response of conducting substrates to ion desolvation and entry into subnamometer pores.

  2. Superconducting and structural properties of {delta}-MoC{sub 0.681} cubic molybdenum carbide phase

    SciTech Connect (OSTI)

    Sathish, C.I. [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Guo, Yanfeng, E-mail: GUO.Yanfeng@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Wang, Xia [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, Yoshihiro [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Li, Jun [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Zhang, Shoubao [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Matsushita, Yoshitaka [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan)] [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Shi, Youguo; Tian, Huanfang; Yang, Huaixin; Li, Jianqi [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)] [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yamaura, Kazunari, E-mail: YAMAURA.Kazunari@nims.go.jp [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2012-12-15

    The superconducting and lattice properties of {delta}-MoC{sub 0.681} were studied by electromagnetic measurements, synchrotron X-ray diffraction, neutron diffraction, and electron diffraction. The superconducting properties (T{sub c}=12 K) of {delta}-MoC{sub 0.681} were well characterized by a weak coupling model. The carbon vacancies present in the host cubic structure were found to be robust, although the material was synthesized from stoichiometric carbon and Mo powder under a high-pressure of 6 GPa. A thermodynamically-stable structure with ordered vacancies did not account for the robust features of {delta}-MoC{sub 0.681} since the vacancies are unlikely to be ordered in long range in the host structure. A model based on inherent phonon instability theoretically predicted for a stoichiometric MoC phase might be responsible for the robust features of {delta}-MoC{sub 0.681}. - Graphical Abstract: The cubic molybdenum carbide shows an excellent superconductivity with robust carbon vacancies. Inherent phonon instability theoretically predicted for a stoichiometric MoC phase might be responsible for the vacancies rather than a thermodynamically-stable structure with vacancies ordering. Highlights: Black-Right-Pointing-Pointer The 12 K superconductivity is well characterized by a weakly coupling model. Black-Right-Pointing-Pointer Carbon vacancies are robust and disordered in the cubic host structure. Black-Right-Pointing-Pointer Inherent phonon instability might be responsible for the robust carbon vacancies in {delta}-MoC{sub 0.681}.

  3. Powerful, Efficient Electric Vehicle Chargers: Low-Cost, Highly-Integrated Silicon Carbide (SiC) Multichip Power Modules (MCPMs) for Plug-In Hybrid Electric

    SciTech Connect (OSTI)

    2010-09-14

    ADEPT Project: Currently, charging the battery of an electric vehicle (EV) is a time-consuming process because chargers can only draw about as much power from the grid as a hair dryer. APEI is developing an EV charger that can draw as much power as a clothes dryer, which would drastically speed up charging time. APEI's charger uses silicon carbide (SiC)-based power transistors. These transistors control the electrical energy flowing through the charger's circuits more effectively and efficiently than traditional transistors made of straight silicon. The SiC-based transistors also require less cooling, enabling APEI to create EV chargers that are 10 times smaller than existing chargers.

  4. Constriction model of actomyosin ring for cytokinesis by fission yeast using a two-state sliding filament mechanism

    SciTech Connect (OSTI)

    Jung, Yong-Woon; Mascagni, Michael

    2014-09-28

    We developed a model describing the structure and contractile mechanism of the actomyosin ring in fission yeast, Schizosaccharomyces pombe. The proposed ring includes actin, myosin, and ?-actinin, and is organized into a structure similar to that of muscle sarcomeres. This structure justifies the use of the sliding-filament mechanism developed by Huxley and Hill, but it is probably less organized relative to that of muscle sarcomeres. Ring contraction tension was generated via the same fundamental mechanism used to generate muscle tension, but some physicochemical parameters were adjusted to be consistent with the proposed ring structure. Simulations allowed an estimate of ring constriction tension that reproduced the observed ring constriction velocity using a physiologically possible, self-consistent set of parameters. Proposed molecular-level properties responsible for the thousand-fold slower constriction velocity of the ring relative to that of muscle sarcomeres include fewer myosin molecules involved, a less organized contractile configuration, a low ?-actinin concentration, and a high resistance membrane tension. Ring constriction velocity is demonstrated as an exponential function of time despite a near linear appearance. We proposed a hypothesis to explain why excess myosin heads inhibit constriction velocity rather than enhance it. The model revealed how myosin concentration and elastic resistance tension are balanced during cytokinesis in S. pombe.

  5. Hydrogenation of CO2 to methanol: Importance of metal–oxide and metal–carbide interfaces in the activation of CO2

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Rodriguez, José A.; Liu, Ping; Stacchiola, Dario J.; Senanayake, Sanjaya D.; White, Michael G.; Chen, Jingguang G.

    2015-09-30

    In this study, the high thermochemical stability of CO2 makes it very difficult to achieve the catalytic conversion of the molecule into alcohols or other hydrocarbon compounds, which can be used as fuels or the starting point for the generation of fine chemicals. Pure metals and bimetallic systems used for the CO2 → CH3OH conversion usually bind CO2 too weakly and, thus, show low catalytic activity. Here, we discuss a series of recent studies that illustrate the advantages of metal–oxide and metal–carbide interfaces when aiming at the conversion of CO2 into methanol. CeOx/Cu(111), Cu/CeOx/TiO2(110), and Au/CeOx/TiO2(110) exhibit an activity formore » the CO2 → CH3OH conversion that is 2–3 orders of magnitude higher than that of a benchmark Cu(111) catalyst. In the Cu–ceria and Au–ceria interfaces, the multifunctional combination of metal and oxide centers leads to complementary chemical properties that open active reaction pathways for methanol synthesis. Efficient catalysts are also generated after depositing Cu and Au on TiC(001). In these cases, strong metal–support interactions modify the electronic properties of the admetals and make them active for the binding of CO2 and its subsequent transformation into CH3OH at the metal–carbide interfaces.« less

  6. Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

    SciTech Connect (OSTI)

    Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

    2011-01-17

    The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

  7. Comment on General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation [Phys. Fluids 26, 065105 (2014)

    SciTech Connect (OSTI)

    Hietala, Niklas Hnninen, Risto

    2014-11-15

    Van Gorder considers a formulation of the local induction approximation, which allows the vortex to move in the direction of the reference axis [General rotating quantum vortex filaments in the low-temperature Svistunov model of the local induction approximation, Phys. Fluids 26, 065105 (2014)]. However, in his analytical and numerical study he does not use it. A mistake in the torsion of a helical vortex is also corrected.

  8. Thickness independent reduced forming voltage in oxygen engineered HfO{sub 2} based resistive switching memories

    SciTech Connect (OSTI)

    Sharath, S. U. Kurian, J.; Komissinskiy, P.; Hildebrandt, E.; Alff, L.; Bertaud, T.; Walczyk, C.; Calka, P.; Schroeder, T.

    2014-08-18

    The conducting filament forming voltage of stoichiometric hafnium oxide based resistive switching layers increases linearly with layer thickness. Using strongly reduced oxygen deficient hafnium oxide thin films grown on polycrystalline TiN/Si(001) substrates, the thickness dependence of the forming voltage is strongly suppressed. Instead, an almost constant forming voltage of about 3?V is observed up to 200?nm layer thickness. This effect suggests that filament formation and switching occurs for all samples in an oxidized HfO{sub 2} surface layer of a few nanometer thickness while the highly oxygen deficient thin film itself merely serves as a oxygen vacancy reservoir.

  9. Hydrogenation of CO2 to methanol: Importance of metal–oxide and metal–carbide interfaces in the activation of CO2

    SciTech Connect (OSTI)

    Rodriguez, José A.; Liu, Ping; Stacchiola, Dario J.; Senanayake, Sanjaya D.; White, Michael G.; Chen, Jingguang G.

    2015-09-30

    In this study, the high thermochemical stability of CO2 makes it very difficult to achieve the catalytic conversion of the molecule into alcohols or other hydrocarbon compounds, which can be used as fuels or the starting point for the generation of fine chemicals. Pure metals and bimetallic systems used for the CO2 → CH3OH conversion usually bind CO2 too weakly and, thus, show low catalytic activity. Here, we discuss a series of recent studies that illustrate the advantages of metal–oxide and metal–carbide interfaces when aiming at the conversion of CO2 into methanol. CeOx/Cu(111), Cu/CeOx/TiO2(110), and Au/CeOx/TiO2(110) exhibit an activity for the CO2 → CH3OH conversion that is 2–3 orders of magnitude higher than that of a benchmark Cu(111) catalyst. In the Cu–ceria and Au–ceria interfaces, the multifunctional combination of metal and oxide centers leads to complementary chemical properties that open active reaction pathways for methanol synthesis. Efficient catalysts are also generated after depositing Cu and Au on TiC(001). In these cases, strong metal–support interactions modify the electronic properties of the admetals and make them active for the binding of CO2 and its subsequent transformation into CH3OH at the metal–carbide interfaces.

  10. Fine uniform filament superconductors

    DOE Patents [OSTI]

    Riley, Jr., Gilbert N. (Marlborough, MA); Li, Qi (Marlborough, MA); Roberts, Peter R. (Groton, MA); Antaya, Peter D. (Sutton, MA); Seuntjens, Jeffrey M. (Singapore, SG); Hancock, Steven (Worcester, MA); DeMoranville, Kenneth L. (Jefferson, MA); Christopherson, Craig J. (Worcester, MA); Garrant, Jennifer H. (Natick, MA); Craven, Christopher A. (Bedford, MA)

    2002-01-01

    A multifilamentary superconductor composite having a high fill factor is formed from a plurality of stacked monofilament precursor elements, each of which includes a low density superconductor precursor monofilament. The precursor elements all have substantially the same dimensions and characteristics, and are stacked in a rectilinear configuration and consolidated to provide a multifilamentary precursor composite. The composite is thereafter thermomechanically processed to provide a superconductor composite in which each monofilament is less than about 50 microns thick.

  11. Scrape-off Layer Current Model for Filament Structure Observed during Edge Localized Modes (ELMs) in the DIII-D Tokamak

    SciTech Connect (OSTI)

    Takahashi, Hironori; Fredrickson, E. D.; Schaffer, M. J.

    2008-04-15

    The plasma in tokamaks often exhibits a relaxation oscillation called the edge localized mode (ELM), which is generally attributed to MHD instability driven by strong gradients at the plasma boundary. It is shown here that field-aligned currents flowing just outside the boundary may also play a role in the ELM process. The poloidal perturbation magnetic field during ELMs in the DIIID tokamak calculated from measured currents can reproduce prominent observed features, including a narrow magnetic structure at the outboard midplane similar to filaments observed earlier in DIIID and NSTX.

  12. Comment on Motion of a helical vortex filament in superfluid {sup 4}He under the extrinsic form of the local induction approximation [Phys. Fluids 25, 085101 (2013)

    SciTech Connect (OSTI)

    Hietala, Niklas Hnninen, Risto

    2014-01-15

    We comment on the paper by Van Gorder [Motion of a helical vortex filament in superfluid {sup 4}He under the extrinsic form of the local induction approximation, Phys. Fluids 25, 085101 (2013)]. We point out that the flow of the normal fluid component parallel to the vortex will often lead into the DonnellyGlaberson instability, which will cause the amplification of the Kelvin wave. We explain why the comparison to local nonlinear equation is unreasonable, and remark that neglecting the motion in the x-direction is not reasonable for a Kelvin wave with an arbitrary wavelength and amplitude. The correct equations in the general case are also derived.

  13. Synthesis of SiO{sub 2}/?-SiC/graphite hybrid composite by low temperature hot filament chemical vapor deposition

    SciTech Connect (OSTI)

    Zhang, Zhikun; Bi, Kaifeng; Liu, Yanhong; Qin, Fuwen; Liu, Hongzhu; Bian, Jiming; Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050 ; Zhang, Dong; Miao, Lihua; Department of Computer and Mathematical Basic Teaching, Shenyang Medical College, Shenyan 110034

    2013-11-18

    ?-SiC thin films were synthesized directly on graphite by hot filament chemical vapor deposition at low temperature. SiH{sub 4} diluted in hydrogen was employed as the silicon source, while graphite was functioned as both substrate and carbon source for the as-grown ?-SiC films. X-ray diffraction and Fourier transform infrared analysis indicate that SiO{sub 2}/?-SiC/graphite hybrid composite was formed after post annealing treatment, and its crystalline quality can be remarkably improved under optimized annealing conditions. The possible growth mechanism was proposed based on in situ etching of graphite by reactive hydrogen radicals at the atomic level.

  14. Total ionizing dose effect of ?-ray radiation on the switching characteristics and filament stability of HfOx resistive random access memory

    SciTech Connect (OSTI)

    Fang, Runchen; Yu, Shimeng; Gonzalez Velo, Yago; Chen, Wenhao; Holbert, Keith E.; Kozicki, Michael N.; Barnaby, Hugh

    2014-05-05

    The total ionizing dose (TID) effect of gamma-ray (?-ray) irradiation on HfOx based resistive random access memory was investigated by electrical and material characterizations. The memory states can sustain TID level ?5.2 Mrad (HfO{sub 2}) without significant change in the functionality or the switching characteristics under pulse cycling. However, the stability of the filament is weakened after irradiation as memory states are more vulnerable to flipping under the electrical stress. X-ray photoelectron spectroscopy was performed to ascertain the physical mechanism of the stability degradation, which is attributed to the Hf-O bond breaking by the high-energy ?-ray exposure.

  15. Zirconium and hafnium-catalyzed polymerization of methylenecyclopropane

    DOE Patents [OSTI]

    Marks, Tobin J. (Evanston, IL); Yang, Xinmin (Somerset, NJ); Jia, Li (Evanston, IL)

    1996-01-01

    A polymer having a repeating unit of ##STR1## and a method for preparing it through Zr-catalyzed polymerization of methylenecyclopropane is disclosed.

  16. Zirconium and hafnium-catalyzed polymerization of methylenecyclopropane

    DOE Patents [OSTI]

    Marks, Tobin J. (Evanston, IL); Yang, Xinmin (Somerset, NJ); Jia, Li (Evanston, IL)

    1997-01-01

    A polymer having a repeating unit of ##STR1## and a method for preparing it through Zr-catalyzed polymerization of methylenecyclopropane is disclosed.

  17. Method of Preparing Hydrous Hafnium, Cerium, or Aluminum Oxide...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    cerium, or aluminum oxide microspheres was invented at ORNL. The invention is a type of sol-gel process that solidifies droplets of solution as they enter into a warm environment....

  18. Analytical and experimental evaluation of joining silicon nitride to metal and silicon carbide to metal for advanced heat engine applications. Final report

    SciTech Connect (OSTI)

    Kang, S.; Selverian, J.H.; O`Neil, D.; Kim, H.; Kim, K.

    1993-05-01

    This report summarizes the results of Phase 2 of Analytical and Experimental Evaluation of Joining Silicon Nitride to Metal and Silicon Carbide to Metal for Advanced Heat Engine Applications. A general methodology was developed to optimize the joint geometry and material systems for 650{degrees}C applications. Failure criteria were derived to predict the fracture of the braze and ceramic. Extensive finite element analyses (FEA) were performed to examine various joint geometries and to evaluate the affect of different interlayers on the residual stress state. Also, material systems composed of coating materials, interlayers, and braze alloys were developed for the program based on the chemical stability and strength of the joints during processing, and service. The FEA results were compared with experiments using two methods: (1) an idealized strength relationship of the ceramic, and (2) a probabilistic analysis of the ceramic strength (NASA CARES). The results showed that the measured strength of the joint reached 30--80% of the strength predicted by FEA. Also, potential high-temperature braze alloys were developed and evaluated for the high-temperature application of ceramic-metal joints. 38 tabs, 29 figs, 20 refs.

  19. Nonlinear dynamics of the ion Weibel-filamentation instability: An analytical model for the evolution of the plasma and spectral properties

    SciTech Connect (OSTI)

    Ruyer, C. Gremillet, L. Debayle, A.; Bonnaud, G.

    2015-03-15

    We present a predictive model of the nonlinear phase of the Weibel instability induced by two symmetric, counter-streaming ion beams in the non-relativistic regime. This self-consistent model combines the quasilinear kinetic theory of Davidson et al. [Phys. Fluids 15, 317 (1972)] with a simple description of current filament coalescence. It allows us to follow the evolution of the ion parameters up to a stage close to complete isotropization, and is thus of prime interest to understand the dynamics of collisionless shock formation. Its predictions are supported by 2-D and 3-D particle-in-cell simulations of the ion Weibel instability. The derived approximate analytical solutions reveal the various dependencies of the ion relaxation to isotropy. In particular, it is found that the influence of the electron screening can affect the results of simulations using an unphysical electron mass.

  20. Heat Flux Calculation and Problem of Flaking of Boron Carbide Coatings on the Faraday Screen of the ICRH Antennas During Tore Supra High Power, Long Pulse Operation

    SciTech Connect (OSTI)

    Corre, Y.; Lipa, M.; Agarici, G.; Basiuk, V.; Colas, L.; Courtois, X.; Dumont, R. J.; Ekedahl, A.; Gardarein, J. L.; Klepper, C Christopher; Martin, V.; Moncada, V.; Portafaix, C.; Rigollet, F.; Tawizgant, R.; Travere, J. M.; Valliez, K.

    2011-01-01

    Reliable and repetitive high power and long pulse tokamak operation is strongly dependant of the ability to secure the Plasma Facing Components (PFCs). In Tore Supra, a network of 7 infrared (IR) video cameras is routinely used to prevent PFCs overheating and damage in selected regions. Real time feedback control and offline analysis are essential for basic protection and understanding of abnormal thermal events. One important limitation detected by the IR real time feed-back loop during high power RF operation (injected power of 9.5 MW over 26 s and 12 MW over 10 s have been achieved respectively in 2006 and 2008) is due to the interaction between fast ions which increase the power flux density and flaking of the boron carbide coatings on the Faraday screen box of the ICRH antennas. An IR-based experimental procedure is proposed in order to detect new flakes during plasma operation. The thermal response of the B4C coating is studied with and without flaking during plasma operation. The experimental heat flux deposited by fast ion losses on the Faraday screen is calculated for high (3.8 T) and low magnetic field (2 T) during high RF power operation (with fundamental hydrogen minority and second harmonic ICRH heating schemes respectively). The paper addresses both thermal science issues applied to machine protection and limitation due to fast ions issues during high RF power, long pulse operation. Safety margin to critical heat flux and number of fatigue cycles under heat load are presented in the paper.

  1. Non-contiguous finished genome sequence and contextual data of the filamentous soil bacterium Ktedonobacter racemifer type strain (SOSP1-21T)

    SciTech Connect (OSTI)

    Chang, Yun-Juan [ORNL; Land, Miriam L [ORNL; Hauser, Loren John [ORNL; Chertkov, Olga [Los Alamos National Laboratory (LANL); Glavina Del Rio, Tijana [U.S. Department of Energy, Joint Genome Institute; Nolan, Matt [U.S. Department of Energy, Joint Genome Institute; Copeland, A [U.S. Department of Energy, Joint Genome Institute; Tice, Hope [U.S. Department of Energy, Joint Genome Institute; Cheng, Jan-Fang [U.S. Department of Energy, Joint Genome Institute; Lucas, Susan [U.S. Department of Energy, Joint Genome Institute; Han, Cliff [Los Alamos National Laboratory (LANL); Goodwin, Lynne A. [Los Alamos National Laboratory (LANL); Pitluck, Sam [U.S. Department of Energy, Joint Genome Institute; Ivanova, N [U.S. Department of Energy, Joint Genome Institute; Ovchinnikova, Galina [U.S. Department of Energy, Joint Genome Institute; Pati, Amrita [U.S. Department of Energy, Joint Genome Institute; Chen, Amy [U.S. Department of Energy, Joint Genome Institute; Palaniappan, Krishna [U.S. Department of Energy, Joint Genome Institute; Mavromatis, K [U.S. Department of Energy, Joint Genome Institute; Liolios, Konstantinos [U.S. Department of Energy, Joint Genome Institute; Brettin, Thomas S [ORNL; Fiebig, Anne [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Rohde, Manfred [HZI - Helmholtz Centre for Infection Research, Braunschweig, Germany; Abt, Birte [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Goker, Markus [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Detter, J. Chris [U.S. Department of Energy, Joint Genome Institute; Woyke, Tanja [U.S. Department of Energy, Joint Genome Institute; Bristow, James [U.S. Department of Energy, Joint Genome Institute; Eisen, Jonathan [U.S. Department of Energy, Joint Genome Institute; Markowitz, Victor [U.S. Department of Energy, Joint Genome Institute; Hugenholtz, Philip [U.S. Department of Energy, Joint Genome Institute; Kyrpides, Nikos C [U.S. Department of Energy, Joint Genome Institute; Klenk, Hans-Peter [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Lapidus, Alla L. [U.S. Department of Energy, Joint Genome Institute

    2011-01-01

    Ktedonobacter racemifer corrig. Cavaletti et al. 2007 is the type species of the genus Ktedo- nobacter, which in turn is the type genus of the family Ktedonobacteraceae, the type family of the order Ktedonobacterales within the class Ktedonobacteria in the phylum Chloroflexi . Although K. racemifer shares some morphological features with the actinobacteria, it is of special interest because it was the first cultivated representative of a deep branching unclassi- fied lineage of otherwise uncultivated environmental phylotypes tentatively located within the phylum Chloroflexi . The aerobic, filamentous, non-motile, spore-forming Gram-positive heterotroph was isolated from soil in Italy. The 13,661,586 bp long non-contiguous finished genome consists of ten contigs and is the first reported genome sequence from a member of the class Ktedonobacteria. With its 11,453 protein-coding and 87 RNA genes, it is the largest prokaryotic genome reported so far. It comprises a large number of over-represented COGs, particularly genes associated with transposons, causing the genetic redundancy within the genome being considerably larger than expected by chance. This work is a part of the Ge- nomic Encyclopedia of Bacteria and Archaea project.

  2. The Molecular Architecture for the Intermediate Filaments of Hard α -Keratin Based on the Superlattice Data Obtained from a Study of Mammals Using Synchrotron Fibre Diffraction

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    James, Veronica

    2011-01-01

    High- and low-angle X-ray diffraction studies of hard α -keratin have been studied, and various models have been proposed over the last 70 years. Most of these studies have been confined to one or two forms of alpha keratin. This high- and low-angle synchrotron fibre diffraction study extends the study to cover all available data for all known forms of hard α -keratin including hairs, fingernails, hooves, horn, and quills from mammals, marsupials, and a monotreme, and it confirms that the model proposed is universally acceptable for all mammals. A complete Bragg analysis of the meridional diffraction patterns, includingmore » multiple-time exposures to verify any weak reflections, verified the existence of a superlattice consisting of two infinite lattices and three finite lattices. An analysis of the equatorial patterns establishes the radii of the oligomeric levels of dimers, tetramers, and intermediate filaments (IFs) together with the centre to centre distance for the IFs, thus confirming the proposed helices within helices molecular architecture for hard α -keratin. The results verify that the structure proposed by Feughelman and James meets the criteria for a valid α -keratin structure.« less

  3. Evaluation of Neutron Irradiated Silicon Carbide and Silicon Carbide Composites

    SciTech Connect (OSTI)

    Newsome G, Snead L, Hinoki T, Katoh Y, Peters D

    2007-03-26

    The effects of fast neutron irradiation on SiC and SiC composites have been studied. The materials used were chemical vapor deposition (CVD) SiC and SiC/SiC composites reinforced with either Hi-Nicalon{trademark} Type-S, Hi-Nicalon{trademark} or Sylramic{trademark} fibers fabricated by chemical vapor infiltration. Statistically significant numbers of flexural samples were irradiated up to 4.6 x 10{sup 25} n/m{sup 2} (E>0.1 MeV) at 300, 500 and 800 C in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Dimensions and weights of the flexural bars were measured before and after the neutron irradiation. Mechanical properties were evaluated by four point flexural testing. Volume increase was seen for all bend bars following neutron irradiation. Magnitude of swelling depended on irradiation temperature and material, while it was nearly independent of irradiation fluence over the fluence range studied. Flexural strength of CVD SiC increased following irradiation depending on irradiation temperature. Over the temperature range studied, no significant degradation in mechanical properties was seen for composites fabricated with Hi-Nicalon{trademark} Type-S, while composites reinforced with Hi-Nicalon{trademark} or Sylramic fibers showed significant degradation. The effects of irradiation on the Weibull failure statistics are also presented suggesting a reduction in the Weibull modulus upon irradiation. The cause of this potential reduction is not known.

  4. Union Carbides Last 20 Years in Oak Ridge

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    1965 (at the start of the last 20 year period we are describing) was Dr. Clarence E. Larson. He had come to Y-12 in 1943 from California (U. of C., Davis) where he was E. O....

  5. © 2012 ATI. All Rights Reserved

    Broader source: Energy.gov (indexed) [DOE]

    2 ATI. All Rights Reserved.  11,200 employees - worldwide  $5 billion in Sales in 2012  Global presence - Operations in 18 countries  Provides customer focused specialty metals solutions * Titanium and titanium alloys * Nickel-based alloys and superalloys * Stainless steels, grain oriented electrical steel & duplex alloys * Zirconium, Hafnium and Niobium alloys * Tungsten metals & carbide cutting tools * Powdered metals * High performance forgings, castings and machining

  6. Molybdenum sulfide/carbide catalysts

    DOE Patents [OSTI]

    Alonso, Gabriel (Chihuahua, MX); Chianelli, Russell R. (El Paso, TX); Fuentes, Sergio (Ensenada, MX); Torres, Brenda (El Paso, TX)

    2007-05-29

    The present invention provides methods of synthesizing molybdenum disulfide (MoS.sub.2) and carbon-containing molybdenum disulfide (MoS.sub.2-xC.sub.x) catalysts that exhibit improved catalytic activity for hydrotreating reactions involving hydrodesulfurization, hydrodenitrogenation, and hydrogenation. The present invention also concerns the resulting catalysts. Furthermore, the invention concerns the promotion of these catalysts with Co, Ni, Fe, and/or Ru sulfides to create catalysts with greater activity, for hydrotreating reactions, than conventional catalysts such as cobalt molybdate on alumina support.

  7. PROCESS OF PREPARING URANIUM CARBIDE

    DOE Patents [OSTI]

    Miller, W.E.; Stethers, H.L.; Johnson, T.R.

    1964-03-24

    A process of preparing uranium monocarbide is de scribed. Uranium metal is dissolved in cadmium, zinc, cadmium-- zinc, or magnesium-- zinc alloy and a small quantity of alkali metal is added. Addition of stoichiometric amounts of carbon at 500 to 820 deg C then precipitates uranium monocarbide. (AEC)

  8. Kallotenue papyrolyticum gen. nov., sp. nov., a cellulolytic and filamentous thermophile that represents a novel lineage (Kallotenuales ord. nov., Kallotenuaceae fam. nov.) within the class Chloroflexia

    SciTech Connect (OSTI)

    Cole, Jesse; Gieler, Brandon; Heisler, Devon; Palisoc, Maryknoll; Williams, Amanda; Dohnalkova, Alice; Ming, Hong; Yu, Tian T.; Dodsworth, Jeremy A.; Li, Wen J.; Hedlund, Brian P.

    2013-08-15

    Several closely-related, thermophilic, and cellulolytic bacterial strains, designated JKG1T, JKG2, JKG3, JKG4, and JKG5, were isolated from a cellulolytic enrichment (corn stover) incubated in the water column of Great Boiling Spring, NV. Strain JKG1T had cells of a diameter of 0.7 - 0.9 ?m and length of ~2.0 ?m that formed non-branched multicellular filaments reaching >300 ?m. Spores were not formed and dense liquid cultures were red. The temperature range for growth was 45-65 C, with an optimum of 55 C. The pH range for growth was 5.6-9.0, with an optimum of 7.5. JKG1T grew as an aerobic heterotroph, utilizing glucose, sucrose, xylose, arabinose, cellobiose, carboxymethylcellulose, filter paper, microcrystalline cellulose, xylan, starch, casamino acids, tryptone, peptone, yeast extract, acetate, citrate, lactate, pyruvate, and glycerol as sole carbon sources, and was not observed to photosynthesize. The cells stained Gram-negative. Phylogenetic analysis using 16S rRNA gene sequences placed the new isolates in the class Chloroflexia, but distant from other cultivated members, with the highest sequence identity of 82.5% to Roseiflexus castenholzii. The major quinone was menaquinone-9; no ubiquinones were detected. The major cellular fatty acids (>5%) were C18:0, anteiso-C17:0, iso-C18:0, and iso-C17:0. C16:0, iso-C16:0, and C17:0. The peptidoglycan amino acids were alanine, ornithine, glutamic acid, serine, and asparagine. Whole-cell sugars included mannose, rhamnose, glucose, galactose, ribose, arabinose, and xylose. Morphological, phylogenetic, and chemotaxonomic results suggest that JKG1T is representative of a new lineage within the class Chloroflexia, which we propose to designate Kallotenue papyrolyticum gen. nov., sp. nov., Kallotenuaceae fam. nov., Kallotenuales ord. nov.

  9. Thermoflexus hugenholtzii gen. nov., sp. nov., a thermophilic, microaerophilic, filamentous bacterium representing a novel class in the Chloroflexi, Thermoflexia classis nov., and description of Thermoflexaceae fam. nov. and Thermoflexales ord. nov.

    SciTech Connect (OSTI)

    Dodsworth, Jeremy A.; Gevorkian, Jonathan; Despujos, Fairuz; Cole, Jesse; Murugapiran, Senthil K.; Ming, Hong; Li, Wen J.; Zhang, Gengxin; Dohnalkova, Alice; Hedlund, Brian P.

    2014-06-06

    A thermophilic, filamentous, heterotrophic bacterium designated strain JAD2T was isolated from sediment of Great Boiling Spring in Nevada, USA. Cells had an average diameter of 0.3 m and length of 4.0 m, and formed filaments typically ranging in length from 20 m to 200 m. Filaments were negative for the Gram stain reaction, spores were not formed, and motility was not observed. The optimum temperature for growth was 75 C with a range from 67.5-75 C, and the optimum pH for growth was 6.75 with a range from 6.5-7.75. Peptone, tryptone or yeast extract were able to support growth when supplemented with a vitamin solution, but no growth was observed using a variety of defined organic substrates. Strain JAD2T was a facultative microaerophile, with optimal growth at 1% v/v O2 and an upper limit of 8% O2, and anaerobic growth was stimulated by fumarate but inhibited by sulfite and elemental sulfur. The major cellular fatty acids (>5%) were C16:0, C19:0, C18:0, C20:0, and C19:1. The genomic DNA G+C content was 69.3%. Phylogenetic and phylogenomic analyses using 16S rRNA gene sequences and other conserved genes placed JAD2T and other members of the yet-uncultivated GAL35 group within the phylum Chloroflexi, but not within any existing class in this phylum. These results indicate that strain JAD2T is the first cultivated representative of a new lineage within the phylum Chloroflexi, for which we propose the name Thermoflexus hugenholtzii gen. nov., sp. nov., type strain JAD2T, within Thermoflexia classis nov., Thermoflexales ord. nov., and Thermoflexaceae fam. nov.

  10. Response to Comment on Motion of a helical vortex filament in superfluid {sup 4}He under the extrinsic form of the local induction approximation [Phys. Fluids 26, 019101 (2014)

    SciTech Connect (OSTI)

    Van Gorder, Robert A.

    2014-01-15

    I agree with the authors regarding their comments on the Donnelly-Glaberson instability for such helical filaments as those obtained in my paper. I also find merit in their derivation of the quantum LIA (local induction approximation) in the manner of the LIA of Boffetta et al. However, I disagree with the primary criticisms of Hietala and Hnninen. In particular, though they suggest LIA and local nonlinear equation modes are not comparable since the former class of models contains superfluid friction parameters, note that since these parameters are small one may take them to zero and consider a qualitative comparison of the models (which is what was done in my paper). Second, while Hietala and Hnninen criticize certain assumptions made in my paper (and the paper of Shivamoggi where the model comes from) since the results break-down when Ak ? ?, note that in my paper I state that any deviations from the central axis along which the filament is aligned must be sufficiently bounded in variation. Therefore, it was already acknowledged that Ak(=|?{sub x}|) should be sufficiently bounded, precluding the Ak ? ? case. I also show that, despite what Hietala and Hnninen claim, the dispersion relation obtained in my paper is consistent with LIA, where applicable. Finally, while Hietala and Hnninen claim that the dispersion parameter should be complex valued, I show that their dispersion relation is wrong, since it was derived incorrectly (they assume the complex modulus of the potential function is constant, yet then use this to obtain a potential function with non-constant modulus)

  11. An innovative high-power constant-current pulsed-arc power-supply for a high-density pulsed-arc-plasma ion-source using a LaB{sub 6}-filament

    SciTech Connect (OSTI)

    Ueno, A.; Oguri, H.; Ikegami, K.; Namekawa, Y.; Ohkoshi, K.; Tokuchi, A.

    2010-02-15

    An innovative high-power constant-current (CC) pulsed-arc (PA) power-supply (PS) indispensable for a high-density PA plasma ion-source using a lanthanum hexaboride (LaB{sub 6}) filament was devised by combining a constant-voltage (CV) PA-PS, which is composed of an insulated gate bipolar transistor (IGBT) switch, a CV direct-current (dc) PS and a 270 mF capacitor with a CC-PA-PS, which is composed of an IGBT-switch, a CC-dc-PS and a 400 {mu}H inductor, through the inductor. The hybrid-CC-PA-PS succeeded in producing a flat arc-pulse with a peak power of 56 kW (400 Ax140 V) and a duty factor of more than 1.5%(600 {mu}sx25 Hz) for Japan Proton Accelerator Research Complex (J-PARC) H{sup -} ion-source stably. It also succeeded in shortening the 99% rising-time of the arc-pulse-current to about 20 {mu}s and tilting up or down the arc-pulse-current arbitrarily and almost linearly by changing the setting voltage of its CV-dc-PS.

  12. Influences of directionally solidified techniques and hafnium content on a nickel base high temperature alloy

    SciTech Connect (OSTI)

    Luobao, W.; Rongzhang, C.; Yuping, W.

    1984-03-01

    Two directionally solidified techniques, the power decrease (P.D.) and high rate solidification (H.R.S.) methods, are used to study the influences of the different Hf contents on the structures and properties of a nickel base high temperature alloy. When entering the alloy the Hf is mainly segregated in the interdentritic regions and gamma/gamma prime eutectic phases. After the alloy is added, there are noticeable changes in the microstructure. The amount of gamma/gamma prime eutectic phase noticeably increases. Its morphology also undergoes noticeable changes. The conditions of grain boundaries and interdentritic regions are improved. Several new types of Hf-rich microfacies also appeared. At 760 C, the endurance properties (especially the transverse properties) of the alloy noticeably rise with the increase of the Hf content. However, at 1040 C, the endurance life decreases with the increase of the Hf content. When the H.R.S. technique is used, the medium and high temperature performances of the alloy are both noticeably superior to the P.D. technique.

  13. Advanced materials for solid oxide fuel cells: Hafnium-Praseodymium-Indium Oxide System

    SciTech Connect (OSTI)

    Bates, J.L.; Griffin, C.W.; Weber, W.J.

    1988-06-01

    The HfO/sub 2/-PrO/sub 1.83/-In/sub 2/O/sub 3/ system has been studied at the Pacific Northwest Laboratory to develop alternative, highly electrically conducting oxides as electrode and interconnection materials for solid oxide fuel cells. A coprecipitation process was developed for synthesizing single-phase, mixed oxide powders necessary to fabricate powders and dense oxides. A ternary phase diagram was developed, and the phases and structures were related to electrical transport properties. Two new phases, an orthorhombic PrInO/sub 3/ and a rhombohedral Hf/sub 2/In/sub 2/O/sub 7/ phase, were identified. The highest electronic conductivity is related to the presence of a bcc, In/sub 2/O/sub 3/ solid solution (ss) containing HfO/sub 2/ and PrO/sub 1.83/. Compositions containing more than 35 mol % of the In/sub 2/O/sub 3/ ss have electrical conductivities greater than 10/sup /minus/1/ (ohm-cm)/sup /minus/1/, and the two or three phase structures that contain this phase appear to exhibit mixed electronic-ionic conduction. The high electrical conductivities and structures similar to the Y/sub 2/O/sub 3/-stabilized ZrO/sub 2/(HfO/sub 2/) electrolyte give these oxides potential for use as cathodes in solid oxide fuel cells. 21 refs.

  14. The Effect of the Presence of 2 wt% Hafnium in T-111

    SciTech Connect (OSTI)

    Barklay, Chadwick D.; Kramer, Daniel P.; Miller, Roger G.

    2006-01-20

    Tantalum alloys have been used by the U.S. Department of Energy as structural alloys for space nuclear power systems such as Radioisotopic Thermoelectric Generators (RTG) since the 1960s. Tantalum alloys are attractive for high temperature structural applications due to their high melting point, excellent formability, good thermal conductivity, good ductility (even at low temperatures), corrosion resistance, and weldability. A number of tantalum alloys have been developed over the years to increase high-temperature strength (Ta-10%W), and reduce creep strain (T-111). These tantalum alloys have demonstrated sufficient high-temperature toughness to survive prolonged exposure to the RTG's working environment. Due to the commercial unavailability of the tantalum alloy T-111, Ta-10%W is a possible candidate replacement material because of its high melting point (3037 deg. C), high elastic modulus (207 GPa), high yield, ultimate tensile strengths at both ambient and elevated temperatures, excellent ductility, and exceptional creep properties. Ta-10%W is also attractive due its commercial availability and low cost when compared to T-111. The objective of this paper is to compare and contrast Ta-10%W and T-111 for high-temperature nuclear based power conversion applications and to document research that must be conducted to fully characterize both materials.

  15. Electron-beam-evaporated thin films of hafnium dioxide for fabricating...

    Office of Scientific and Technical Information (OSTI)

    This content will become publicly available on June 17, 2016 Title: Electron-beam-evaporat... will become publicly available on June 17, 2016 Publisher's Version of Record 10.1116...

  16. Making Silicon Carbide Devices | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Devices in the Cleanroom Click to email this to a friend (Opens in new window) Share on Facebook (Opens in new window) Click to share (Opens in new window) Click to share on...

  17. Silicon Carbide Derived Carbons: Experiments and Modeling

    SciTech Connect (OSTI)

    Kertesz, Miklos

    2011-02-28

    The main results of the computational modeling was: 1. Development of a new genealogical algorithm to generate vacancy clusters in diamond starting from monovacancies combined with energy criteria based on TBDFT energetics. The method revealed that for smaller vacancy clusters the energetically optimal shapes are compact but for larger sizes they tend to show graphitized regions. In fact smaller clusters of the size as small as 12 already show signatures of this ?¢????graphitization?¢????. The modeling gives firm basis for the ?¢????slit-pore?¢???? modeling of porous carbon materials and explains some of their properties. 2. We discovered small vacancy clusters and their physical characteristics that can be used to spectroscopically identify them. 3. We found low barrier pathways for vacancy migration in diamond-like materials by obtaining for the first time optimized reaction pathways.

  18. Silicon Carbide Semiconductors | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Stum, the Wide Band Gap device engineer who is leading the "Next Generation SiC MOSFET" development program here at GRC. Zach and his team are working on improving key device...

  19. Optically initiated silicon carbide high voltage switch

    DOE Patents [OSTI]

    Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Sullivan, James S. (Livermore, CA); Sanders; David M. (Livermore, CA)

    2011-02-22

    An improved photoconductive switch having a SiC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

  20. Process for preparing silicon carbide foam

    DOE Patents [OSTI]

    Whinnery, LeRoy Louis (Livermore, CA); Nichols, Monte Carl (Livermore, CA); Wheeler, David Roger (Albuquerque, NM); Loy, Douglas Anson (Albuquerque, NM)

    1997-01-01

    A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolized in an inert atmosphere to form a SiC foam.

  1. Process for preparing silicon carbide foam

    DOE Patents [OSTI]

    Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

    1997-09-16

    A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolyzed in an inert atmosphere to form a SiC foam. 9 figs.

  2. Silicon Carbide Emitter Turn-Off Thyristor

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wang, Jun; Wang, Gangyao; Li, Jun; Huang, Alex Q.; Melcher, Jerry; Atcitty, Stan

    2008-01-01

    A novel MOS-conmore » trolled SiC thyristor device, the SiC emitter turn-off thyristor (ETO) is a promising technology for future high-voltage switching applications because it integrates the excellent current conduction capability of a SiC thyristor with a simple MOS-control interface. Through unity-gain turn-off, the SiC ETO also achieves excellent Safe Operation Area (SOA) and faster switching speeds than silicon ETOs. The world's first 4.5-kV SiC ETO prototype shows a forward voltage drop of 4.26 V at 26.5  A / cm 2 current density at room and elevated temperatures. Tested in an inductive circuit with a 2.5 kV DC link voltage and a 9.56-A load current, the SiC ETO shows a fast turn-off time of 1.63 microseconds and a low 9.88 mJ turn-off energy. The low switching loss indicates that the SiC ETO could operate at about 4 kHz if 100  W / cm 2 conduction and the 100  W / cm 2 turn-off losses can be removed by the thermal management system. This frequency capability is about 4 times higher than 4.5-kV-class silicon power devices. The preliminary demonstration shows that the SiC ETO is a promising candidate for high-frequency, high-voltage power conversion applications, and additional developments to optimize the device for higher voltage (>5 kV) and higher frequency (10 kHz) are needed.« less

  3. Harsh Environment Silicon Carbide Sensor Technology Geothermal...

    Open Energy Info (EERE)

    Cost Share 456,071.00 Total Project Cost 2,280,352.00 Principal Investigator(s) Albert P. Pisano, Professor and Department Chair, Department of Mechanical Engineering,...

  4. Off-axis silicon carbide substrates

    DOE Patents [OSTI]

    Edgar, James; Dudley, Michael; Kuball, Martin; Zhang, Yi; Wang, Guan; Chen, Hui; Zhang, Yu

    2014-09-02

    A method of epitaxial growth of a material on a crystalline substrate includes selecting a substrate having a crystal plane that includes a plurality of terraces with step risers that join adjacent terraces. Each terrace of the plurality or terraces presents a lattice constant that substantially matches a lattice constant of the material, and each step riser presents a step height and offset that is consistent with portions of the material nucleating on adjacent terraces being in substantial crystalline match at the step riser. The method also includes preparing a substrate by exposing the crystal plane; and epitaxially growing the material on the substrate such that the portions of the material nucleating on adjacent terraces merge into a single crystal lattice without defects at the step risers.

  5. Carbon p electron ferromagnetism in silicon carbide

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wang, Yutian; Liu, Yu; Wang, Gang; Anwand, Wolfgang; Jenkins, Catherine A.; Arenholz, Elke; Munnik, Frans; Gordan, Ovidiu D.; Salvan, Georgeta; Zahn, Dietrich R. T.; et al

    2015-03-11

    Ferromagnetism can occur in wide-band gap semiconductors as well as in carbon-based materials when specific defects are introduced. It is thus desirable to establish a direct relation between the defects and the resulting ferromagnetism. Here, we contribute to revealing the origin of defect-induced ferromagnetism using SiC as a prototypical example. We show that the long-range ferromagnetic coupling can be attributed to the p electrons of the nearest-neighbor carbon atoms around the VSiVC divacancies. Thus, the ferromagnetism is traced down to its microscopic electronic origin.

  6. Hybrid nuclear reactor grey rod to obtain required reactivity worth

    DOE Patents [OSTI]

    Miller, John V. (Munhall, PA); Carlson, William R. (Scott Township, Allegheny County, PA); Yarbrough, Michael B. (Hempfield Township, Westmoreland County, PA)

    1991-01-01

    Hybrid nuclear reactor grey rods are described, wherein geometric combinations of relatively weak neutron absorber materials such as stainless steel, zirconium or INCONEL, and relatively strong neutron absorber materials, such as hafnium, silver-indium cadmium and boron carbide, are used to obtain the reactivity worths required to reach zero boron change load follow. One embodiment includes a grey rod which has combinations of weak and strong neutron absorber pellets in a stainless steel cladding. The respective pellets can be of differing heights. A second embodiment includes a grey rod with a relatively thick stainless steel cladding receiving relatively strong neutron absorber pellets only. A third embodiment includes annular relatively weak netron absorber pellets with a smaller diameter pellet of relatively strong absorber material contained within the aperture of each relatively weak absorber pellet. The fourth embodiment includes pellets made of a homogeneous alloy of hafnium and a relatively weak absorber material, with the percentage of hafnium chosen to obtain the desired reactivity worth.

  7. Process for making silver metal filaments

    DOE Patents [OSTI]

    Bamberger, Carlos E. (Oak Ridge, TN)

    1997-01-01

    A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

  8. Optically Directed Assembly of Continuous Mesoscale Filaments...

    Office of Scientific and Technical Information (OSTI)

    None USDOE United States 2011-02-01 English Journal Article Journal Name: Physical Review Letters; Journal Volume: 106; Journal Issue: 9 Medium: X OSTI ID: 1099937, Legacy ID:...

  9. DEPOSITION OF METAL ON NONMETAL FILAMENT

    DOE Patents [OSTI]

    Magel, T.T.

    1959-02-10

    A method is described for purifying metallic uranium by passing a halogen vapor continuously over the impure uranium to form uranium halide vapor and immediately passing the halide vapor into contact with a nonmetallic refractory surface which is at a temperature above the melting point of uranium metal. The halide is decomposed at the heated surface depositing molten metal, which collects and falls into a receiver below.

  10. A look back at Union Carbides FIRST 20 Years in Nuclear Energy...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    in developing metal rolling techniques. "Because of Y-12's vast reservoir of industrial skills, many problems in areas such as metallurgy, special fabrications, chemistry,...

  11. A look back at Union Carbides 20 Years in Nuclear Energy [The...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of the intervening years. The publication covers all sites in Oak Ridge and to give a fuller picture of the total scope of accomplishments, I will include the Milestones from each...

  12. Union Carbides 20 years in nuclear energy, part 2

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    large-scale precision machining of beryllium began. "1953 - Additional uranium casting facilities and another uranium machining shop were installed and completed by fall. A...

  13. A look back at Union Carbides FIRST 20 Years in Nuclear Energy...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    large-scale precision machining of beryllium began. "1953 - Additional uranium casting facilities and another uranium machining shop were installed and completed by fall. A...

  14. A look back at Union Carbides FIRST 20 Years in Nuclear Energy...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    are the main research building, a power and utilities building, and an ores and minerals development laboratory. "FROM PRODUCTION TO RESEARCH - Uranium salts find their way into...

  15. Union Carbides Last 20 Years in Oak Ridge ? part 2

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    or the earth with each other's atmospheres. 1969. AEC Headquarters in Washington and ORO announced the start of the "Toll Enrichment" program using its K-25, Portsmouth, and...

  16. A look back at Union Carbides first 20 Years in Nuclear Energy...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    propulsion reactors, the 'package' reactors for power at remote locations, and swimming pool research reactors. Advanced power-producing reactors now being developed at ORNL...

  17. Union Carbides Last 20 Years in Oak Ridge ? part 4

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    whether and to what degree the program impacted employee health, and the program's impacts on the environment. The Mercury Task Force physically rounded up all the Y-12...

  18. Method of coating the interior surface of hollow objects with a diffusion coating

    DOE Patents [OSTI]

    Knowles, Shawn D.; Senor, David J.; Forbes, Steven V.; Johnson, Roger N.; Hollenberg, Glenn W.

    2005-03-15

    A method for forming a diffusion coating on the interior of surface of a hollow object wherein a filament, extending through a hollow object and adjacent to the interior surface of the object, is provided, with a coating material, in a vacuum. An electrical current is then applied to the filament to resistively heat the filament to a temperature sufficient to transfer the coating material from the filament to the interior surface of the object. The filament is electrically isolated from the object while the filament is being resistively heated. Preferably, the filament is provided as a tungsten filament or molybdenum filament. Preferably, the coating materials are selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Ge, Hg, In, K, Li, Mg, Mn, Na, Ni P, Pb, Pd, Pr, S, Sb, Sc, Se, Si, Sn, Sr, Te, Tl, Y, Yb, Zn, and combinations thereof. The invention additionally allows for the formation of nitrides, hydrides, or carbides of all the possible coating materials, where such compounds exist, by providing a partial pressure of nitrogen, hydrogen, hydrocarbons, or combination thereof, within the vacuum.

  19. NUCLEOSYNTHETIC TUNGSTEN ISOTOPE ANOMALIES IN ACID LEACHATES OF THE MURCHISON CHONDRITE: IMPLICATIONS FOR HAFNIUM-TUNGSTEN CHRONOMETRY

    SciTech Connect (OSTI)

    Burkhardt, Christoph; Wieler, Rainer; Kleine, Thorsten; Dauphas, Nicolas

    2012-07-01

    Progressive dissolution of the Murchison carbonaceous chondrite with acids of increasing strengths reveals large internal W isotope variations that reflect a heterogeneous distribution of s- and r-process W isotopes among the components of primitive chondrites. At least two distinct carriers of nucleosynthetic W isotope anomalies must be present, which were produced in different nucleosynthetic environments. The co-variation of {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W in the leachates follows a linear trend that is consistent with a mixing line between terrestrial W and a presumed s-process-enriched component. The composition of the s-enriched component agrees reasonably well with that predicted by the stellar model of s-process nucleosynthesis. The co-variation of {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W in the leachates provides a means for correcting the measured {sup 182}W/{sup 184}W and {sup 182}W/{sup 183}W of Ca-Al-rich inclusions (CAI) for nucleosynthetic anomalies using the isotopic variations in {sup 183}W/{sup 184}W. This new correction procedure is different from that used previously, and results in a downward shift of the initial {epsilon}{sup 182}W of CAI to -3.51 {+-} 0.10 (where {epsilon}{sup 182}W is the variation in 0.01% of the {sup 182}W/{sup 183}W ratio relative to Earth's mantle). This revision leads to Hf-W model ages of core formation in iron meteorite parent bodies that are {approx}2 Myr younger than previously calculated. The revised Hf-W model ages are consistent with CAI being the oldest solids formed in the solar system, and indicate that core formation in some planetesimals occurred within {approx}2 Myr of the beginning of the solar system.

  20. ZIRCONIUMHAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

    SciTech Connect (OSTI)

    Akram, W.; Schnbchler, M.; Sprung, P.; Vogel, N.

    2013-11-10

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (?1? in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (?2?). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ? 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ?}) SNII.

  1. Method for locating metallic nitride inclusions in metallic alloy ingots

    DOE Patents [OSTI]

    White, Jack C. (Albany, OR); Traut, Davis E. (Corvallis, OR); Oden, Laurance L. (Albany, OR); Schmitt, Roman A. (Corvallis, OR)

    1992-01-01

    A method of determining the location and history of metallic nitride and/or oxynitride inclusions in metallic melts. The method includes the steps of labeling metallic nitride and/or oxynitride inclusions by making a coreduced metallic-hafnium sponge from a mixture of hafnium chloride and the chloride of a metal, reducing the mixed chlorides with magnesium, nitriding the hafnium-labeled metallic-hafnium sponge, and seeding the sponge to be melted with hafnium-labeled nitride inclusions. The ingots are neutron activated and the hafnium is located by radiometric means. Hafnium possesses exactly the proper metallurgical and radiochemical properties for this use.

  2. Harsh Environment Silicon Carbide Sensor Technology for Geothermal Instrumentation

    Broader source: Energy.gov [DOE]

    Project objectives: Develop advanced sensor technology for the direct monitoring of geothermal reservoirs. Engineer sensors to survive and operate in H2O pressures up to 220 bar and temperatures as high as 374o C.

  3. Silicon Carbide (SiC) Technologies | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    for managing the flow of current for virtually everything ... For power generation sources like wind and solar energy, ... To get there, production costs need to go down while ...

  4. Irradiation creep of nano-powder sintered silicon carbide at...

    Office of Scientific and Technical Information (OSTI)

    Resource Type: Journal Article Resource Relation: Journal Name: Journal of Nuclear Materials; Journal Volume: 455; Journal Issue: 1-3; Conference: 16. International...

  5. Advanced Triso fuels with zirconium carbide for high temperature reactors

    SciTech Connect (OSTI)

    Lobach, Sergiy Y.; Knight, Travis W.; Jacob, Norman P.; Athon, Clifton E.

    2007-07-01

    There are several options for the advanced TRISO fuel: one is primarily replacement SiC with ZrC and the other is a concept involving a thin ZrC layer coating on the kernel, which is then enclosed in usual TRISO coatings. An effort at modeling, fabrication and testing of an advanced TRISO coated UO{sub 2} fuel particle design incorporating an added layer of ZrC over the fuel kernel is under investigation. The objectives of the coated particle development program are to define the essentials of a production route for the manufacture of kernels and coated particles and to identify the important process parameters that determine the particle properties. Still, the integrity of the ZrC coating is important, but not the main goal. The primary purpose of a ZrC coating examination in this study is to determine hot it serves as an oxygen getter to limit CO production and hence pressure buildup that would stress coatings leading to failure. This additional ZrC coating also aids in retaining fission products within the kernel, and carbon diffusion in the particle is limited hence kernel migration rates are slowed. The combined result being that failure rates of coated particles should decrease. (authors)

  6. Union Carbide's 20 years in nuclear energy, part 1

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    nuclear weapon components." The text of the document continues to highlight Y-12"s history and missions through 1962. I have reproduced the Y-12 portion of publication here...

  7. Silicon Carbide Applications in Power Electronics | GE Global...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    transition from Si-based chips to SiC-based chips." The announcement of a state-funded packaging facility in Utica, NY will also help to bring SiC to market faster. "We are...

  8. Optically-initiated silicon carbide high voltage switch

    DOE Patents [OSTI]

    Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Sullivan, James S. (Livermore, CA); Sanders, David M. (Livermore, CA)

    2012-02-28

    An improved photoconductive switch having a SIC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

  9. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    DOE Patents [OSTI]

    Becher, Paul F. (Oak Ridge, TN); Tiegs, Terry N. (Lenoir City, TN)

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  10. Silicon carbide whisker reinforced composites and method for making same

    DOE Patents [OSTI]

    Wei, G.C.

    1984-02-09

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties, especially increased fracture toughness. In the formation of these ceramic composites, the single-crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al/sub 2/O/sub 3/, mullite, or B/sub 4/C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600 to 1950/sup 0/C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m/sup 1/2/ which represents as much as a two-fold increase over that of the matrix material.

  11. Nanostructured tungsten carbide/cobalt alloys: Processing and properties

    SciTech Connect (OSTI)

    Wu, Li

    1993-12-31

    This research represents an extension of previous work on the synthesis and processing of nanostructured WC/Co alloys. The earlier work resulted in a novel thermochemical process for making nanostructured WC/Co powders (3-30 wt% Co), which involved the reductive decomposition and gas phase carburization of homogeneous precursor powders, prepared by spray drying aqueous solution mixtures of W and Co salts. A shortcoming of the process was the formation of a relatively large amount of uncombined carbon during gas phase carburization using pre CO. AnOtherr unsolved problem was the rapid coarsening of WC particles during liquid phase sintering, making it difficult to achieve the desired nanostructures in the fully consolidated materials. In the present work, both problems have been addressed and successfully overcome. Carburization in CO/H{sub 2} gas mixtures has been shown to be superior to carburization in pure CO, in that it avoids the formation of excess carbon without sacrificing the desirable high carburization rate. Another advantage is the finer WC grain size achieved, because of the shorter reaction time at relatively low temperatures, 650-750{degrees}C. Othe carbon source gases, such as CH{sub 4}/H{sub 2} and C{sub 2}H{sub 4}/H{sub 2} gas mixtures, cannot produce tungsten monocarbide at such low temperatures. Thus, carburization in CO/H{sub 2} gas mixtures appears to be optimal for synthesizing nanostructured WC/Co powders. As to liquid phase sintering of powder compacts, it has been demonstrated that mechanical mixing of a small amount of VC powder with the nanograined WC/Co powder inhibits grain growth. A striking result was the linear increase in hardness of WC/7 wt% Co with the amount of VC added, at least up to the solubility limit (about 10 wt%) of VC in liquid cobalt at the sintering temperature. Preliminary work has also demonstrated the feasibility of plasma spraying low-density nanostructured powders to produce dense, wear resistant coatings.

  12. High temperature Hexoloy{trademark} SX silicon carbide. Final report

    SciTech Connect (OSTI)

    Srinivasan, G.V.; Lau, S.K.; Storm, R.S.

    1994-09-01

    HEXOLOY{reg_sign} SX-SiC, fabricated with Y and Al containing compounds as sintering aids, has been shown to possess significantly improved strength and toughness over HEXOLOY{reg_sign}SA-SiC. This study was undertaken to establish and benchmark the complete mechanical property database of a first generation material, followed by a process optimization task to further improve the properties. Mechanical characterization on the first generation material indicated that silicon-rich pools, presumably formed as a reaction product during sintering, controlled the strength from room temperature to 1,232 C. At 1,370 C in air, the material was failing due to a glass-phase formation at the surface. This glass-phase formation was attributed to the reaction of yttrium aluminates, which exist as a second phase in the material, with the ambient. This process was determined to be a time-dependent one that leads to slow crack growth. Fatigue experiments clearly indicated that the slow crack growth driven by the reaction occurred only at temperatures >1,300 C, above the melting point of the glass phase. Process optimization tasks conducted included the selection of the best SiC powder source, studies on mixing/milling conditions for SiC powder with the sintering aids, and a designed experiment involving a range of sintering and post-treatment conditions. The optimization study conducted on the densification variables indicated that lower sintering temperatures and higher post-treatment pressures reduce the Si-rich pool formation, thereby improving the room-temperature strength. In addition, it was also determined that furnacing configuration and atmosphere were critical in controlling the Si-rich formation.

  13. Decoding the message from meteoritic stardust silicon carbide grains

    SciTech Connect (OSTI)

    Lewis, Karen M.; Lugaro, Maria; Gibson, Brad K.; Pilkington, Kate

    2014-05-02

    SiC mainstream grains are presolar grains believed to form in the envelopes of carbon rich asymptotic giant branch (AGB) stars with masses between 1.5 and 3 solar masses. These grains represent a conundrum as the {sup 29}Si and {sup 30}Si abundances indicate that they formed in stars of super-solar metallicity, before the solar system formed. To shed light on this problem, we use silicon isotopic abundances to derive an age-metallicity relation for the stars believed to have produced the SiC mainstream grains. For 2732 mainstream SiC grains listed in the Presolar Grain Database, we use the {sup 29}Si abundances with the latest galactic chemical evolution (GCE) models to derive [Fe/H], and {sup 30}Si abundances along with the models of Zinner et al. (2006) to determine an approximate birth age for the parent AGB star. Comparing our age-metallicity relation with observational relationships derived for nearby stars, we find that the spread of [Fe/H] is in agreement, but the mean [Fe/H] in our relation is higher by 0.2 dex. We propose that this difference is because stars with higher [Fe/H] produce more dust and thus are over-represented in our age metallicity diagram, a finding consistent with previous published works. This result offers a solution for the long-standing problem of silicon in Stardust SiC grains, confirms the necessity of coupling chemistry and dynamics in simulations of the chemical evolution of our Galaxy, and constrains the modelling of dust condensation in stellar winds as a function of the metallicity.

  14. Silicon Carbide (SiC) MOSFET | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    months to fabricate a SiC power device, so cracking the MOSFET code was far from straightforward. They had to break the process down step by step and ingredient by ingredient to...

  15. Process for producing fine and ultrafine filament superconductor wire

    DOE Patents [OSTI]

    Kanithi, Hem C. (15 Briar Ct., Chesire, CT 06410)

    1992-01-01

    A process for producing a superconductor wire made up of a large number of round monofilament rods is provided for, comprising assembling a multiplicity of round monofilaments inside each of a multiplicity of thin wall hexagonal tubes and then assembling a number of said thin wall hexagonal tubes within an extrusion can and subsequently consolidating, extruding and drawing the entire assembly down to the desired wire size.

  16. Rheological and structural properties of active filament solutions.

    SciTech Connect (OSTI)

    Ziebert, F.; Aranson, I. S.; Materials Science Division

    2008-01-01

    The rheology and the structure of a dilute semiflexible biofilament solution, like F-actin, interacting via molecular motors is probed by molecular dynamics simulations. Oscillatory external shear is used to measure the storage and loss moduli as a function of motor activity in a range of frequencies and for low shear rates. The overall effect of the motor activity on the rheological properties is interpreted as an increase of the temperature, with the effective temperature proportional to the density of motors. However, the effect of motors on the structural properties of the solution, such as the orientation correlation function, is opposite: the motors drastically increase the orientation correlation length whereas thermal fluctuations decrease it.

  17. Fibrous ceramic monoliths made from multi-phase ceramic filaments

    DOE Patents [OSTI]

    Goretta, Kenneth C.; Singh, Dileep; Polzin, Bryant J.; Cruse, Terry; Picciolo, John J.

    2008-11-18

    A method for producing composite ceramic material is provided wherein a core ceramic structure is produced and simultaneously enveloped with a sleeve of similar material.

  18. Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

    SciTech Connect (OSTI)

    Chuang Ren

    2013-02-13

    This grant has supported a study of some fundamental problems in current- and flow-driven instabilities in plasmas and their applications in inertial confinement fusion (ICF) and astrophysics. It addressed current-driven instabilities and their roles in fast ignition, and flow-driven instabilities and their applications in astrophysics.

  19. Filamentation in air at 1550 nm : initial experimentation with...

    Office of Scientific and Technical Information (OSTI)

    Authors: Gruetzner, James Kent ; Nelson, Thomas Robert ; Kohl, Ian Thomas 1 ; Bruner, Nichelle Lee 1 ; Law, Ryan J. + Show Author Affiliations (Voss Scientific, Albuquerque, ...

  20. Process for producing fine and ultrafine filament superconductor wire

    DOE Patents [OSTI]

    Kanithi, H.C.

    1992-02-18

    A process for producing a superconductor wire made up of a large number of round monofilament rods is provided for, comprising assembling a multiplicity of round monofilaments inside each of a multiplicity of thin wall hexagonal tubes and then assembling a number of said thin wall hexagonal tubes within an extrusion can and subsequently consolidating, extruding and drawing the entire assembly down to the desired wire size. 8 figs.

  1. Mechanisms of leiomodin 2-mediated regulation of actin filament...

    Office of Scientific and Technical Information (OSTI)

    Argonne, IL (US) Sponsoring Org: NIHOTHER Country of Publication: United States Language: ENGLISH Word Cloud More Like This Full Text Journal Articles DOI: 10.1073pnas.1512464

  2. Hot-Wire Chemical Vapor Deposition (HWCVD) technologies - Energy Innovation

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Portal Photovoltaic Solar Photovoltaic Find More Like This Return to Search Hot-Wire Chemical Vapor Deposition (HWCVD) technologies Rapid, controllable growth of epitaxial silicon films National Renewable Energy Laboratory Contact NREL About This Technology Publications: PDF Document Publication Landry, et al., WO 2011-106624, "Hot Wire Chemical Vaport Deposition (HWCVD) with Carbide Filaments" (1,533 KB) Technology Marketing Summary NREL scientists have discovered a unique way to

  3. A brief history of the Biology Complex, part 2

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    in Buildings 9733-1 and 9733-2 and was asked to join the nation-wide effort to find a method for freeing zirconium from its hafnium impurity. Removing the hafnium was necessary to...

  4. Microsoft Word - FR Notice - DOE CMS RFI 02-03-2016 FINAL

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    ... hafnium, helium, indium, lithium, magnesium, manganese, molybdenum, nickel, rhenium, selenium, silicon, tantalum, tellurium, tungsten, vanadium, and zirconium Technologies and ...

  5. High rate buffer layer for IBAD MgO coated conductors

    DOE Patents [OSTI]

    Foltyn, Stephen R. (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM); Arendt, Paul N. (Los Alamos, NM)

    2007-08-21

    Articles are provided including a base substrate having a layer of an oriented material thereon, and, a layer of hafnium oxide upon the layer of an oriented material. The layer of hafnium oxide can further include a secondary oxide such as cerium oxide, yttrium oxide, lanthanum oxide, scandium oxide, calcium oxide and magnesium oxide. Such articles can further include thin films of high temperature superconductive oxides such as YBCO upon the layer of hafnium oxide or layer of hafnium oxide and secondary oxide.

  6. Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

    2015-03-27

    Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to producemore » carbon monoxide and methane. In addition, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.« less

  7. Growth of bi- and tri-layered graphene on silicon carbide substrate via molecular dynamics simulation

    SciTech Connect (OSTI)

    Min, Tjun Kit; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    Molecular dynamics (MD) simulation with simulated annealing method is used to study the growth process of bi- and tri-layered graphene on a 6H-SiC (0001) substrate via molecular dynamics simulation. Tersoff-Albe-Erhart (TEA) potential is used to describe the inter-atomic interactions among the atoms in the system. The formation temperature, averaged carbon-carbon bond length, pair correlation function, binding energy and the distance between the graphene formed and the SiC substrate are quantified. The growth mechanism, graphitization of graphene on the SiC substrate and characteristics of the surface morphology of the graphene sheet obtained in our MD simulation compare well to that observed in epitaxially grown graphene experiments and other simulation works.

  8. Method for improving the toughness of silicon carbide-based ceramics

    DOE Patents [OSTI]

    Tein, T.Y.; Hilmas, G.E.

    1996-12-03

    Method of improving the toughness of SiC-based ceramics is disclosed. SiC, , AlN, Al{sub 2}O{sub 3} and optionally {alpha}-Si{sub 3}N{sub 4} are hot pressed to form a material which includes AlN polytypoids within its structure. 1 fig.

  9. Decomposition pathways of C2 oxygenates on Rh-modified tungsten carbide surfaces

    SciTech Connect (OSTI)

    Kelly, Thomas G.; Ren, Hui; Chen, Jingguang G.

    2015-03-27

    Ethanol decomposition on tungsten monocarbide (WC) and Rh-modified WC was investigated using ultrahigh vacuum (UHV) surface science experiments and density functional theory (DFT) calculations. DFT calculations indicated that the binding energies of ethanol and its decomposition intermediates on WC(0001) were modified by Rh, with Rh/WC(0001) showing similar values to those on Rh(111). Through temperature-programmed desorption (TPD) experiments on polycrystalline WC and Rh-modified WC, it was shown that the selectivity for ethanol decomposition was different on these surfaces. On WC, the C-O bond of ethanol was preferentially broken to produce ethylene; on Rh-modified WC, the C-C bond was broken to produce carbon monoxide and methane. In addition, high-resolution electron energy loss spectroscopy (HREELS) was used to determine likely surface intermediates. On Rh-modified WC, ethanol first formed ethoxy through O-H scission, then reacted through an aldehyde intermediate to form the C1 products.

  10. Method of forming single crystals of beta silicon carbide using liquid lithium as a solvent

    DOE Patents [OSTI]

    Lundberg, Lynn B. (Los Alamos, NM)

    1982-01-01

    A method of growing single crystals of beta SiC from solution using molten lithium as a solvent for polycrystalline SiC feed material. Reasonable growth rates are accomplished at temperatures in the range of about 1330.degree. C. to about 1500.degree. C.

  11. Method for improving the toughness of silicon carbide-based ceramics

    DOE Patents [OSTI]

    Tein, Tseng-Ying; Hilmas, Gregory E.

    1996-01-01

    Method of improving the toughness of SiC-based ceramics. SiC, , AlN, Al.sub.2 O.sub.3 and optionally .alpha.-Si.sub.3 N.sub.4 are hot pressed to form a material which includes AlN polytypoids within its structure.

  12. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOE Patents [OSTI]

    Wei, G.C.

    1989-01-24

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al{sub 2}O{sub 3}, mullite, or B{sub 4}C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1,600 to 1,950 C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness which represents as much as a two-fold increase over that of the matrix material.

  13. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOE Patents [OSTI]

    Wei, George C. [Oak Ridge, TN

    1989-01-24

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MP.am.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  14. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOE Patents [OSTI]

    Wei, George C. (Oak Ridge, TN)

    1993-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  15. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOE Patents [OSTI]

    Wei, George C.

    1993-11-16

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  16. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOE Patents [OSTI]

    Wei, George C. (Oak Ridge, TN)

    1985-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  17. Ultratough, Thermally Stable Polycrystalline Diamond/Silicon Carbide Nanocomposites for Drill Bits

    SciTech Connect (OSTI)

    2009-03-01

    This factsheet describes a research project whose goal is to develop and produce in quantity novel superhard and ultratough thermally stable polycrystalline (TSP) diamond/SiC nanocomposites reinforced with SiC/C nanofibers for drill-bit applications and multiple industrial functions.

  18. Optically-initiated silicon carbide high voltage switch with contoured-profile electrode interfaces

    DOE Patents [OSTI]

    Sullivan, James S.; Hawkins, Steven A.

    2012-09-04

    An improved photoconductive switch having a SiC or other wide band gap substrate material with opposing contoured profile cavities which have a contoured profile selected from one of Rogowski, Bruce, Chang, Harrison, and Ernst profiles, and two electrodes with matching contoured-profile convex interface surfaces.

  19. Coprocessed nuclear fuels containing (U, Pu) values as oxides, carbides or carbonitrides

    DOE Patents [OSTI]

    Lloyd, M.H.

    1981-01-09

    Method for direct coprocessing of nuclear fuels derived from a product stream of fuels reprocessing facility containing uranium, plutonium, and fission product values comprising nitrate stabilization of said stream vacuum concentration to remove water and nitrates, neutralization to form an acid deficient feed solution for the internal gelation mode of sol-gel technology, green spherule formation, recovery and treatment for loading into a fuel element by vibra packed or pellet formation technologies.

  20. Coprocessed nuclear fuels containing (U, Pu) values as oxides, carbides or carbonitrides

    DOE Patents [OSTI]

    Lloyd, Milton H. (Oak Ridge, TN)

    1983-01-01

    Method for direct coprocessing of nuclear fuels derived from a product stream of a fuels reprocessing facility containing uranium, plutonium, and fission product values comprising nitrate stabilization of said stream vacuum concentration to remove water and nitrates, neutralization to form an acid deficient feed solution for the internal gelation mode of sol-gel technology, green spherule formation, recovery and treatment for loading into a fuel element by vibra packed or pellet formation technologies.