Sample records for filament hafnium carbide

  1. Hafnium

    SciTech Connect (OSTI)

    NONE

    1994-02-01T23:59:59.000Z

    Having been predicted from atomic number sequence, it was the first element to be discovered by X-ray methods in 1923, following spectroscopic examination of zirconium minerals by D. Coster and G. C. de Hevesey. Hafnium derives its name from {open_quotes}Hafnia{close_quotes}, the Latin name for Copenhagen. The crustal abundance of hafnium is estimated at 2.8-4.5 ppm. The element hafnium is commonly found only in solid solution with zirconium in various zirconium ores, and is a by-product of zirconium metal production. The major commercial mineral source of hafnium is zircon; a minor source is baddeleyite. Zircon, typically 67% zirconium plus hafnium oxides, is found in alluvial or beach deposits together with other heavy minerals such as rutile and ilmenite. The ratio of zirconium to hafnium in zircon averages about 50:1. Recovery is accomplished by mining, dredging on scraping, followed by wet concentration by gravity processing and then dry separation, usually by magnetic or electrostatic processes. The zirconium/hafnium concentrate is separated by liquid-liquid extraction using methyl isobutyl ketone, or extractive distillation to produce hafnium oxide. Hafnium sponge is produced by reacting the oxide with chlorine in a fluid bed chlorinator, followed by a {open_quotes}Kroll-type{close_quotes} reaction. Additional refining of the metal is possible by electrofining, electron beam melting, or the iodide process. Refined hafnium metal is regularly referred to as {open_quotes}crystal bar hafnium-iodide metal{close_quotes}, or ductile hafnium.

  2. Definition of prominent thermal mechanisms associated with the buoyancy-induced transport of hafnium-carbide within a solidifying uranium-hafnium alloy

    SciTech Connect (OSTI)

    Taylor, M.J. (Oak Ridge K-25 Site, TN (United States)); Mackiewicz-Ludtka, G. (Oak Ridge Y-12 Plant, TN (United States))

    1992-12-01T23:59:59.000Z

    Environmental concerns over uranium wastes generated interest in using existing uranium stockpiles as feed materials. One obstacle to recycling is accumulation of carbon that can degrade as-cast mechanical properties. A program was begun to develop a casting procedure capable of reducing the C content in components made from recycled uranium to levels comparable with virgin feed stock. Trace amounts of Hf are added to form low-density Hf C, which floats to the top of the casting, and can be removed at a later time. Developing this procedure requires modeling carbide transport within solidifying uranium, and this necessitates solving a coupled, nonlinear fluid dynamics, heat transfer, and solution thermodynamics problem. The heat transfer facet was addressed first. Steady-state and transient thermal performance of a laboratory-scale casting assembly was characterized to identify those mechanisms that have a prominent influence on modeling uranium melt solidification. The analysis showed that (1) at least first-order accurate definitions for all thermal mechanisms were required to obtain meaningful agreement with experimental data; (2) prominent mechanisms were thermal contact resistances, liquid uranium natural convection, and internal heat generation; and (3) accurately modeling assembly geometry and enclosure radiation heat transfer would also improve agreement. It was recommended that a second-generation thermal model should be constructed which would include each of these elements.

  3. ZIRCONIUM AND HAFNIUM--1998 86.1 ZIRCONIUM AND HAFNIUM

    E-Print Network [OSTI]

    and tables were prepared by Imogene P. Bynum, statistical officer, and the world production table Berzelius produced the first impure zirconium metal in 1824. Commercial metal production is by reduction by passing hafnium tetrachloride over a tungsten filament in 1925 (van Arkel and de Boer, 1925). Commercial

  4. Development of single crystal filaments. Final report

    SciTech Connect (OSTI)

    Milewski, J.V.; Shoultz, R.A.; Bourque-McConnell, M.M.

    1995-04-01T23:59:59.000Z

    The program just completed addresses a route to a more efficient longer-lasting electric light bulb filament. All current filaments for light bulbs are metallic in nature. They are subject to embrittlement with age (large grain growth) and relatively high vapor pressures which limits their operating temperature. There is evidence which suggests advantages to using high temperature refractory single crystal fibers as a filament for a light bulb. These refractory materials may include materials such as hafnium or tantalum carbide which have melting points about 500{degrees}C higher than tungsten. Another advantage is that single crystal fibers have a very high degree of crystalline perfection with very few voids and dislocations. Without these imperfections, the atomic mobility at high temperatures is highly restricted. Thus single crystal fibers are very stable at high temperature and will last longer. The efficiencies result from running these single crystal ceramic fiber filaments at higher temperatures and the higher emissivity of the carbide filaments compared to tungsten. The amount of visible light is proportional to the 4the power of the temperature thus a 500{degrees}C higher operating give about a 3-fold increase in radiation in the visible range. The program accomplishments can be summarized as follows: (1) Single crystal fibers of JfC sufficient crystal quality for light bulb filament applications were made. (2) The HfC fiber furnace growth chamber, power control and data collection system was developed for the laboratory scale plant. (3) method for mounting and apparatuses for testing the single crystal fiber filaments were developed and built.

  5. Silver-hafnium braze alloy

    DOE Patents [OSTI]

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

    2003-12-16T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    2013-08-06T23:59:59.000Z

    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.

  7. Zirconium and hafnium separation at Y-12

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

    and hafnium separation at Y-12 When then Captain Hyman G. Rickover completed his nuclear reactor training at the Clinton Laboratories in 1947, he quickly saw the advantage of using...

  8. Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

    E-Print Network [OSTI]

    Danon, Yaron

    the time-of-flight technique. Lithium-6 glass scintillation detectors were used for transmission for natural hafnium, it did affect the way the hafnium interactions would change with exposure to a neutron

  9. Helical filaments

    SciTech Connect (OSTI)

    Barbieri, Nicholas; Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin [Townes Laser Institute, CREOL—The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Hosseinimakarem, Zahra; Johnson, Eric [Micro-Photonics Laboratory – Center for Optical Material Science, Clemson, Anderson, South Carolina 29634 (United States)

    2014-06-30T23:59:59.000Z

    The shaping of laser-induced filamenting plasma channels into helical structures by guiding the process with a non-diffracting beam is demonstrated. This was achieved using a Bessel beam superposition to control the phase of an ultrafast laser beam possessing intensities sufficient to induce Kerr effect driven non-linear self-focusing. Several experimental methods were used to characterize the resulting beams and confirm the observed structures are laser air filaments.

  10. 2006 Minerals Yearbook ZIRCONIUM AND HAFNIUM

    E-Print Network [OSTI]

    .S. Geological Survey from a voluntary survey of domestic operations. Of the 44 operations surveyed, 31 did concentrates are developed by a second voluntary survey of domestic mining operations. Of the two domestic2006 Minerals Yearbook ZIRCONIUM AND HAFNIUM U.S. Department of the Interior U.S. Geological Survey

  11. Carbide and carbonitride surface treatment method for refractory metals

    DOE Patents [OSTI]

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

    1996-12-03T23:59:59.000Z

    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.

  12. ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)

    E-Print Network [OSTI]

    concentrates: Australia, 48%; South Africa, 47%; and other, 5%. Zirconium, unwrought, including powder: France, 51%; Germany, 10%; United Kingdom, 10%; South Africa, 9%; and other, 20%. Hafnium, unwrought: France. The leading consumers of zirconium metal and hafnium metal are the nuclear energy and chemical process

  13. ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)

    E-Print Network [OSTI]

    consumers of zirconium and hafnium metal are the nuclear energy and chemical process industries. Salient during metal production and fabrication and was recycled by companies in Oregon and Utah. Scrap zirconium. Zirconium and hafnium metal were produced from zircon by two domestic producers, one in Oregon and the other

  14. ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)

    E-Print Network [OSTI]

    @usgs.gov, fax: (703) 648-7757] #12;187 ZIRCONIUM AND HAFNIUM Events, Trends, and Issues: Domestic consumption coatings, and sandblasting. The leading consumers of zirconium and hafnium metal are the nuclear energy,080 2,300 Zirconium oxide1 2,260 3,340 2,400 2,970 1,700 Consumption, zirconium ores and concentrates

  15. Microwave sintering of boron carbide

    DOE Patents [OSTI]

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

    1988-06-10T23:59:59.000Z

    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.

  16. Endocytosis in filamentous fungi 

    E-Print Network [OSTI]

    Kalkman, Edward R I C

    2007-01-01T23:59:59.000Z

    Endocytosis is little understood in filamentous fungi. For some time it has been controversial as to whether endocytosis occurs in filamentous fungi. A comparative genomics analysis between Saccharomyces cerevisiae and ...

  17. Carbide and carbonitride surface treatment method for refractory metals

    DOE Patents [OSTI]

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

    1996-01-01T23:59:59.000Z

    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.

  18. 2005 Minerals Yearbook ZirconiuM and HafniuM

    E-Print Network [OSTI]

    2005 Minerals Yearbook ZirconiuM and HafniuM U.S. Department of the Interior U.S. Geological Survey of the mining and processing of heavy-mineral sands containing the titanium minerals ilmenite and rutile.). duPont produced zircon from its heavy-mineral sands operation near Starke, fL. iluka produced zircon

  19. ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)

    E-Print Network [OSTI]

    ). Government Stockpile: None. Events, Trends, and Issues: Domestic consumption of zirconium mineral coatings, and sandblasting. The leading consumers of zirconium and hafnium metal are the nuclear energy,610 1,720 Zirconium oxide1 1,520 1,600 2,260 3,340 2,270 Consumption, zirconium ores and concentrates

  20. ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)

    E-Print Network [OSTI]

    Stockpile: None. Events, Trends, and Issues: Domestic consumption of zirconium mineral concentrates coatings, and sandblasting. The leading consumers of zirconium and hafnium metal are the nuclear energy,830 1,910 Zirconium oxide1 1,600 2,260 3,340 2,400 3,310 Consumption, zirconium ores and concentrates

  1. Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

    SciTech Connect (OSTI)

    MJ Trbovich; DP Barry; RE Slovacck; Y Danon; RC Block; JA Burke; NJ Drindak; G Leinweber; RV Ballad

    2004-10-13T23:59:59.000Z

    The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions. Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically-enriched liquid samples. The liquid samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY [1] and INTER [2] codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little.

  2. Development of hafnium and comparison with other pressurized water reactor control rod materials

    SciTech Connect (OSTI)

    Keller, H.W.; Hollein, D.A.; Hott, A.C.; Shallenberger, J.M.

    1982-12-01T23:59:59.000Z

    Development of a special application of hafnium for pressurized water reactor control rods is discussed. A unique feature of the design is the sealing of the hafnium material inside protective stainless steel tubing, whereas in prior applications the hafnium material was exposed directly to the reactor primary coolant. A comparison is made of the new hafnium design with silver-indium-cadmium and B/sub 4/C hybrid control rod material design applications. The advantages and disadvantages of the alternative designs are summarized, including performance and fabrication considerations.

  3. Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

    SciTech Connect (OSTI)

    Trbovich, M J; Barry, D P; Slovacek, R E; Danon, Y; Block, R C; Francis, N C; Lubert, M; Burke, J A; Drindak, N J; Lienweber, G; Ballad, R

    2007-02-06T23:59:59.000Z

    The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005 - 200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. Accurate hafnium cross sections and resonance parameters are needed in order to quantify the effects of hafnium found in zirconium, a metal commonly used in reactors. The accuracy of the cross sections and the corresponding resonance parameters used in current nuclear analysis tools are rapidly becoming the limiting factor in reducing the overall uncertainty on reactor physics calculations. Experiments measuring neutron capture and transmission are routinely performed at the Rensselaer Polytechnic Institute (RPI) LINAC using the time-of flight technique. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m, respectively. Capture experiments were performed using a sixteen section NaI multiplicity detector at a flight path length of 25 m. These experiments utilized several thicknesses of metallic and isotope-enriched liquid Hf samples. The liquid Hf samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analyses were performed using the R-matrix Bayesian code SAMMY. A combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005 - 200 eV. Additionally, resonance integrals were calculated, along with errors for each hafnium isotope, using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previous values. The {sup 176}Hf resonance integral, based on this work, is approximately 73% higher than the ENDF/B-VI value. This is due primarily to the changes to resonance parameters in the 8 eV resonance, the neutron width presented in this work is more than twice that of the previous value. The calculated elemental hafnium resonance integral however, changed very little.

  4. Union Carbides Last 20 Years in Oak Ridge

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

    Energy Research and Development AdministrationDepartment of Energy's Oak Ridge, Paducah and Portsmouth facilities, how about the last 20 years of Union Carbide's tenure here...

  5. Modified silicon carbide whiskers

    DOE Patents [OSTI]

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

    1991-01-01T23:59:59.000Z

    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.

  6. Modified silicon carbide whiskers

    DOE Patents [OSTI]

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

    1991-05-21T23:59:59.000Z

    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.

  7. Phase transformations in some hafnium-tantalum-titanium-zirconium alloys

    SciTech Connect (OSTI)

    Ohriner, E.K. [Oak Ridge National Lab., TN (United States); Kapoor, D. [Army ARDEC, Picatinny Arsenal, NJ (United States)

    1997-11-01T23:59:59.000Z

    Phase transformations in hafnium alloys are of interest as a means of achieving a material which exhibits flow softening and high localized strains during deformation at high strain rates. Hafnium transforms from a body-centered-cubic beta phase to a hexagonal alpha phase upon cooling below 1749{degrees}C. Hafnium-based alloys containing up to 17.5% Ti, up to 17.5% Ta, and up to 7.3% Zr by weight were button-arc melted and, in some cases, hot extruded to obtain a refined grain size. A number of alloys were shown to have beta solvus temperatures in the range of 1100 to 1300{degrees}C and showed evidence of a shear transformation upon water quenching. The Vickers microhardness of the quenched materials are typically above 350 HV as compared to 300 HV or less for materials with an alpha plus beta structure. Quenching dilatometry indicates a martensite start temperature of about 750{degrees}C for the Hf-7.5 Ta-10 Ti-1 Zr alloy and 800{degrees}C or more for the Hf-7.5 Ta-7.5 Ti-1 Zr alloy. Tensile tests at 1 s{sup {minus}1} strain rate show a constant ultimate tensile strength for temperatures up to 600{degrees}C for the above two alloys and a rapid decrease in strength with a further increase in temperature.

  8. 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)

    1993-01-01T23:59:59.000Z

    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.

  9. Nanoscale Engineering Of Radiation Tolerant Silicon Carbide....

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

    Engineering Of Radiation Tolerant Silicon Carbide. Nanoscale Engineering Of Radiation Tolerant Silicon Carbide. Abstract: Radiation tolerance is determined by how effectively the...

  10. Aerogel-supported filament

    DOE Patents [OSTI]

    Wuest, Craig R. (Danville, CA); Tillotson, Thomas M. (Tracy, CA); Johnson, III, Coleman V. (Dallas, TX)

    1995-01-01T23:59:59.000Z

    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.

  11. Aerogel-supported filament

    DOE Patents [OSTI]

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

    1995-05-16T23:59:59.000Z

    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.

  12. Low cost fabrication of silicon carbide based ceramics and fiber reinforced composites

    SciTech Connect (OSTI)

    Singh, M.; Levine, S.R.

    1995-07-01T23:59:59.000Z

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC`s) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  13. Breakup of Liquid Filaments

    E-Print Network [OSTI]

    Castrejon-Pita, Alfonso A.; Castrejon-Pita, J.R.; Hutchings, I.M.

    2012-01-01T23:59:59.000Z

    , including the dispersion of liquid drugs into res- pirable droplets, microfluidics, crop- and paint-spraying, and ink-jet printing [2–4]. There are also biological sys- tems in which either long filaments remain intact, or many droplets are formed [5, 6...

  14. A look back at Union Carbides FIRST 20 Years in Nuclear Energy...

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

    A look back at Union Carbide's FIRST 20 Years in Nuclear Energy The Y-12 Plant Milestones Note: Union Carbide Nuclear Division, which started out as Carbide and Carbon Chemicals...

  15. A look back at Union Carbides FIRST 20 Years in Nuclear Energy...

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

    The Y-12 Plant Note: Union Carbide Nuclear Division, which started out as Carbide and Carbon Chemicals Company, operated the Atomic Energy CommissionEnergy Research and...

  16. Solid friction between soft filaments

    E-Print Network [OSTI]

    Ward, Andrew; Schwenger, Walter; Welch, David; Lau, A W C; Vitelli, Vincenzo; Mahadevan, L; Dogic, Zvonimir

    2015-01-01T23:59:59.000Z

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes' drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the prop...

  17. Solid friction between soft filaments

    E-Print Network [OSTI]

    Andrew Ward; Feodor Hilitski; Walter Schwenger; David Welch; A. W. C. Lau; Vincenzo Vitelli; L. Mahadevan; Zvonimir Dogic

    2015-03-04T23:59:59.000Z

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes' drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

  18. Hafnium-doped tantalum oxide high-k gate dielectric films for future CMOS technology 

    E-Print Network [OSTI]

    Lu, Jiang

    2007-04-25T23:59:59.000Z

    A novel high-k gate dielectric material, i.e., hafnium-doped tantalum oxide (Hf-doped TaOx), has been studied for the application of the future generation metal-oxidesemiconductor field effect transistor (MOSFET). The ...

  19. Environmental behavior of hafnium : the impact on the disposition of weapons-grade plutonium

    E-Print Network [OSTI]

    Cerefice, Gary Steven

    1999-01-01T23:59:59.000Z

    Experimental and analytical studies were performed to examine the environmental behavior of hafnium and its utility as a neutron poison for the disposition of weapons-grade plutonium in Yucca Mountain. The hydrolysis of ...

  20. Electrical characteristics and interface structure of magnetic tunnel junctions with hafnium oxyfluoride barrier

    SciTech Connect (OSTI)

    Yu, Y.Y.; Kim, D.S.; Char, K. [Center for Strongly Correlated Materials Research and School of Physics, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2004-12-01T23:59:59.000Z

    We have studied the effects of fluorine inclusion on the electrical transport characteristics and interface structure of the hafnium oxide barrier in a magnetic tunnel junction. The tunneling magnetoresistance (TMR) and resistance-area (RA) as a function of oxidation time show that the TMR ratio of the hafnium oxyfluoride barrier is higher (8.3%) than that of the hafnium oxide barrier (5.7%) at their optimum conditions, and the oxyfluoride barrier junctions maintain a high TMR ratio even when the RA product increases by three orders of magnitude. X-ray photoelectron spectroscopy analysis shows that the fluorine atoms in the oxyfluoride barrier play an important role in the formation of a barrier with uniform composition. We believe that the initial fluoride layer is causing the subsequent oxygen diffusion to slow down, resulting in the formation of a defect-free hafnium oxide layer. These results are consistent with what we have found for aluminum oxyfluoride barriers.

  1. Growth mode evolution of hafnium oxide by atomic layer deposition

    SciTech Connect (OSTI)

    Nie, Xianglong; Ma, Fei; Ma, Dayan, E-mail: madayan@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, Shaanxi (China); Xu, Kewei [State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, People's Republic of China and Department of Physics and Opt-electronic Engineering, Xi'an University of Arts and Science, Xi'an 710065, Shaanxi (China)

    2014-01-15T23:59:59.000Z

    HfO{sub 2} thin films were deposited using tetrakis-ethylmethylamido hafnium and H{sub 2}O as precursors on silicon by atomic layer deposition (ALD). The morphology and microstructures at different ALD cycles were characterized by atomic force microscopy and high-resolution transmission electron microscopy. Based on the height–height correlation function and power spectral density function, quantitative analysis of surface morphologies was performed. Three characteristic dimensions (?{sub 1}, ?{sub 2}, and ?{sub 3}) corresponding to three surface structures, islands, local and global fluctuations, were identified. The evolution of ALD growth mode at range of the three critical scales was investigated, respectively. It suggests the transformation of growth mode from quasi two-dimensional layer-by-layer to three-dimensional island for global fluctuations.

  2. Chaperonin filaments: The archael cytoskeleton

    SciTech Connect (OSTI)

    Trent, J.D.; Kagawa, H.K.; Yaoi, Takuro; Olle, E.; Zaluzec, N.J.

    1997-08-01T23:59:59.000Z

    Chaperonins are multi-subunit double-ring complexed composed of 60-kDa proteins that are believed to mediate protein folding in vivo. The chaperonins in the hyperthermophilic archaeon Sulfolobus shibatae are composed of the organism`s two most abundant proteins, which represent 4% of its total protein and have an intracellular concentration of {ge} 3.0 mg/ml. At concentrations of 1.0 mg/ml, purified chaperonin proteins aggregate to form ordered filaments. Filament formation, which requires Mg{sup ++} and nucleotide binding (not hydrolysis), occurs at physiological temperatures under conditions suggesting filaments may exist in vivo. If the estimated 4,600 chaperonins per cell, formed filaments in vivo, they could create a matrix of filaments that would span the diameter of an average S. shibatae cell 100 times. Direct observations of unfixed, minimally treated cells by intermediate voltage electron microscopy (300 kV) revealed an intracellular network of filaments that resembles chaperonin filaments produced in vitro. The hypothesis that the intracellular network contains chaperonins is supported by immunogold analyses. The authors propose that chaperonin activity may be regulated in vivo by filament formation and that chaperonin filaments may serve a cytoskeleton-like function in archaea and perhaps in other prokaryotes.

  3. Filament-Filament Switching Can Be Regulated by Separation Between Filaments Together with Cargo Motor Number

    E-Print Network [OSTI]

    Erickson, Robert P; Gross, Steven P; Yu, Clare C; Kabla, Alexandre J

    2013-01-01T23:59:59.000Z

    that a single engaged motor cannot switch between filaments.EL, Goldman YE (2010) Motor number controls cargo switchingtransport: molecular motors navigate a complex cytoskeleton.

  4. The sedimentation of flexible filaments

    E-Print Network [OSTI]

    Lei Li; Harishankar Manikantan; David Saintillan; Saverio E. Spagnolie

    2013-06-19T23:59:59.000Z

    The dynamics of a flexible filament sedimenting in a viscous fluid are explored analytically and numerically. Compared to the well-studied case of sedimenting rigid rods, the introduction of filament compliance is shown to cause a significant alteration in the long-time sedimentation orientation and filament geometry. A model is developed by balancing viscous, elastic, and gravitational forces in a slender-body theory for zero-Reynolds-number flows, and the filament dynamics are characterized by a dimensionless elasto-gravitation number. Filaments of both non-uniform and uniform cross-sectional thickness are considered. In the weakly flexible regime, a multiple-scale asymptotic expansion is used to obtain expressions for filament translations, rotations, and shapes. These are shown to match excellently with full numerical simulations. Furthermore, we show that trajectories of sedimenting flexible filaments, unlike their rigid counterparts, are restricted to a cloud whose envelope is determined by the elasto-gravitation number. In the highly flexible regime we show that a filament sedimenting along its long axis is susceptible to a buckling instability. A linear stability analysis provides a dispersion relation, illustrating clearly the competing effects of the compressive stress and the restoring elastic force in the buckling process. The instability travels as a wave along the filament opposite the direction of gravity as it grows and the predicted growth rates are shown to compare favorably with numerical simulations. The linear eigenmodes of the governing equation are also studied, which agree well with the finite-amplitude buckled shapes arising in simulations.

  5. Reinvestigation of high pressure polymorphism in hafnium metal

    SciTech Connect (OSTI)

    Pandey, K. K., E-mail: kkpandey@barc.gov.in; Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India); Gyanchandani, Jyoti; Dey, G. K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India); Somayazulu, M. [Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015 (United States); Sikka, S. K. [Indian National Science Academy, New Delhi-110 002 (India)

    2014-06-21T23:59:59.000Z

    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.

  6. Diamond-silicon carbide composite

    DOE Patents [OSTI]

    Qian, Jiang; Zhao, Yusheng

    2006-06-13T23:59:59.000Z

    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. Abrasive slurry composition for machining boron carbide

    DOE Patents [OSTI]

    Duran, E.L.

    1984-11-29T23:59:59.000Z

    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.

  8. Abrasive slurry composition for machining boron carbide

    DOE Patents [OSTI]

    Duran, Edward L. (Santa Fe, NM)

    1985-01-01T23:59:59.000Z

    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. Method for making boron carbide cermets

    DOE Patents [OSTI]

    Cline, C.F.; Fulton, F.J.

    1987-11-03T23:59:59.000Z

    A method for synthesizing low density cermets of boron carbide and a metal binder, using decomposition of a metallic compound at controlled temperature and pressure is disclosed.

  10. U.S. GEOLOGICAL SURVEY--MINERALS INFORMATION 1 ZIRCONIUM AND HAFNIUM

    E-Print Network [OSTI]

    U.S. GEOLOGICAL SURVEY--MINERALS INFORMATION 1 ZIRCONIUM AND HAFNIUM By Joseph Gambogi Zirconium at crust; however, zircon is the primary naturally occurring mineral the Old Hickory deposit south of the mining and processing zircon (Mineral Sands Report, 1997b). of heavy-mineral sands for the titanium

  11. Synthesis and characterization of hafnium and molybdenum bifunctional initiators for the preparation of triblock copolymers

    E-Print Network [OSTI]

    Gabert, Andrea Jennifer

    2007-01-01T23:59:59.000Z

    Chapter 1. Three monofunctional mixed alkyl hafnium complexes containing the (MesNpy)2 ligand ([(MesitylNCH2)2CMe(2-CsH4N)]2) were synthesized. (MesNpy)Hf(Neo)R ((2b), R = Me; Neo = CH2CMe2Ph) and (MesNpy)Hf(CH2TMS)(R), ...

  12. Ancient recycled mantle lithosphere in the Hawaiian plume: OsmiumHafnium isotopic evidence from

    E-Print Network [OSTI]

    Reiners, Peter W.

    Ancient recycled mantle lithosphere in the Hawaiian plume: Osmium­Hafnium isotopic evidence from that recycled (i.e. previously subducted) basaltic oceanic crust (with or without sediments) is part of an ancient (N2 Ga) depleted and recycled mantle lithosphere that is part of the upwelling Hawaiian plume

  13. Galaxy pairs align with galactic filaments

    E-Print Network [OSTI]

    Tempel, Elmo

    2015-01-01T23:59:59.000Z

    Context. Gravitational collapse theory and numerical simulations suggest that the velocity field within large-scale galaxy filaments is dominated by motions along the filaments. Aims. Our aim is to check whether observational data reveal any preferred orientation of galaxy pairs with respect to the underlying filaments as a result of the expectedly anisotropic velocity field. Methods. We use galaxy pairs and galaxy filaments identified from the Sloan Digital Sky Survey data. For filament extraction, we use the Bisous model that is based the marked point process technique. During the filament detection, we use the centre point of each pair instead of the positions of galaxies to avoid a built-in influence of pair orientation on the filament construction. For pairs lying within filaments (3012 cases), we calculate the angle between the line connecting galaxies of each pair and their host filament. To avoid redshift-space distortions, the angle is measured in the plain of the sky. Results. The alignment analysis...

  14. Nitride-bonded silicon carbide composite filter

    SciTech Connect (OSTI)

    Thomson, B.N.; DiPietro, S.G.

    1995-12-01T23:59:59.000Z

    The objective of this program is to develop and demonstrate an advanced hot gas filter, using ceramic component technology, with enhanced durability to provide increased resistance to thermal fatigue and crack propagation. The material is silicon carbide fiber reinforced nitride bonded silicon carbide.

  15. 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)

    2000-07-04T23:59:59.000Z

    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.

  16. The production of iron carbide

    SciTech Connect (OSTI)

    Anderson, K.M.; Scheel, J. [Nucor Iron Carbide, Inc., Point Lisas (Trinidad and Tobago)

    1997-12-31T23:59:59.000Z

    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.

  17. Nonequilibrium transport in superconducting filaments

    SciTech Connect (OSTI)

    Arutyunov, K.YU.; Danilova, N.P.; Nikolaeva, A.A. [Academy of Sciences of the Moldavian SSR, Kishinev (Russian Federation)

    1995-04-01T23:59:59.000Z

    The step-like current-voltage characteristics of highly homogeneous single-crystalline tin and indium thin filaments has been measured. The length of the samples L approximately 1 cm was much greater than the nonequilibrium quasiparticle relaxation length Lambda. It was found that the activation of a successive i-th voltage step occurs at current significantly greater than the one derived with the assumption that the phase slip centers are weakly interacting on a scale L much greater than Lambda. The observation of `subharmonic` fine structure on the voltage-current characteristics of tin filaments confirms the hypothesis of the long-range phase slip centers interaction.

  18. Manufacture of silicon carbide using solar energy

    DOE Patents [OSTI]

    Glatzmaier, Gregory C. (Boulder, CO)

    1992-01-01T23:59:59.000Z

    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.

  19. Infrared spectroscopic study of atomic layer deposition mechanism for hafnium silicate thin films using HfCl2N,,SiMe3...22 and H2O

    E-Print Network [OSTI]

    George, Steven M.

    Infrared spectroscopic study of atomic layer deposition mechanism for hafnium silicate thin films was used to study the atomic layer deposition mechanism of hafnium silicate films with dichlorobis EOT.2 Among many other high-k materials, hafnium silicate is considered to be the most promising

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

    DOE Patents [OSTI]

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16T23:59:59.000Z

    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.

  1. Silver transport in CVD silicon carbide

    E-Print Network [OSTI]

    MacLean, Heather J. (Heather Jean), 1974-

    2004-01-01T23:59:59.000Z

    Ion implantation and diffusion couple experiments were used to study silver transport through and release from CVD silicon carbide. Results of these experiments show that silver does not migrate via classical diffusion in ...

  2. Electroextraction of boron from boron carbide scrap

    SciTech Connect (OSTI)

    Jain, Ashish [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Anthonysamy, S., E-mail: sas@igcar.gov.in [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ghosh, C. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ravindran, T.R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Divakar, R.; Mohandas, E. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India)

    2013-10-15T23:59:59.000Z

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ? 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  3. Unusual Filaments Inside the Umbra

    E-Print Network [OSTI]

    Kleint, Lucia

    2013-01-01T23:59:59.000Z

    We analyze several unusual filamentary structures, which appeared in the umbra of one of the sunspots in AR 11302. They do not resemble typical light bridges, neither in morphology, nor in evolution. We analyze data from SDO/HMI to investigate their temporal evolution, Hinode/SP for photospheric inversions, IBIS for chromospheric imaging, and SDO/AIA for the overlying corona. Photospheric inversions reveal a horizontal, inverse Evershed flow along these structures, which we call umbral filaments. Chromospheric images show brightenings and energy dissipation, while coronal images indicate that bright coronal loops seem to end in these umbral filaments. These rapidly evolving features do not seem to be common, and are possibly related to the high flare-productivity of the active region. Their analysis could help to understand the complex evolution of active regions.

  4. UNUSUAL FILAMENTS INSIDE THE UMBRA

    SciTech Connect (OSTI)

    Kleint, L. [High Altitude Observatory/NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); Sainz Dalda, A., E-mail: kleintl@ucar.edu [Stanford-Lockheed Institute for Space Research, Stanford University, HEPL, 466 Via Ortega, Stanford, CA 94305 (United States)

    2013-06-10T23:59:59.000Z

    We analyze several unusual filamentary structures which appeared in the umbra of one of the sunspots in AR 11302. They do not resemble typical light bridges in morphology or in evolution. We analyze data from SDO/HMI to investigate their temporal evolution, Hinode/SP for photospheric inversions, IBIS for chromospheric imaging, and SDO/AIA for the overlying corona. Photospheric inversions reveal a horizontal, inverse Evershed flow along these structures, which we call umbral filaments. Chromospheric images show brightenings and energy dissipation, while coronal images indicate that bright coronal loops seem to end in these umbral filaments. These rapidly evolving features do not seem to be common, and are possibly related to the high flare-productivity of the active region. Their analysis could help to understand the complex evolution of active regions.

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

    SciTech Connect (OSTI)

    Alshershby, Mostafa; Ren, Yu; Qin, Jiang; Hao, Zuoqiang; Lin, Jingquan [School of Science, Changchun University of Science and Technology, Changchun 130022 (China)] [School of Science, Changchun University of Science and Technology, Changchun 130022 (China)

    2013-05-20T23:59:59.000Z

    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.

  6. Combustion Synthesis of Silicon Carbide 389 Combustion Synthesis of Silicon Carbide

    E-Print Network [OSTI]

    Mukasyan, Alexander

    Combustion Synthesis of Silicon Carbide 389 X Combustion Synthesis of Silicon Carbide Alexander S. Mukasyan University of Notre Dame USA 1. Introduction Combustion synthesis (CS) is an effective technique by which combustion synthesis can occur: self - propagating high-temperature synthesis (SHS) and volume

  7. Carbide-derived carbons - From porous networks to nanotubes and...

    Office of Scientific and Technical Information (OSTI)

    Carbide-derived carbons - From porous networks to nanotubes and graphene Re-direct Destination: Carbide-derived carbons (CDCs) are a large family of carbon materials derived from...

  8. The diffusion bonding of silicon carbide and boron carbide using refractory metals

    SciTech Connect (OSTI)

    Cockeram, B.V.

    1999-10-01T23:59:59.000Z

    Joining is an enabling technology for the application of structural ceramics at high temperatures. Metal foil diffusion bonding is a simple process for joining silicon carbide or boron carbide by solid-state, diffusive conversion of the metal foil into carbide and silicide compounds that produce bonding. Metal diffusion bonding trials were performed using thin foils (5 {micro}m to 100 {micro}m) of refractory metals (niobium, titanium, tungsten, and molybdenum) with plates of silicon carbide (both {alpha}-SiC and {beta}-SiC) or boron carbide that were lapped flat prior to bonding. The influence of bonding temperature, bonding pressure, and foil thickness on bond quality was determined from metallographic inspection of the bonds. The microstructure and phases in the joint region of the diffusion bonds were evaluated using SEM, microprobe, and AES analysis. The use of molybdenum foil appeared to result in the highest quality bond of the metal foils evaluated for the diffusion bonding of silicon carbide and boron carbide. Bonding pressure appeared to have little influence on bond quality. The use of a thinner metal foil improved the bond quality. The microstructure of the bond region produced with either the {alpha}-SiC and {beta}-SiC polytypes were similar.

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

    DOE Patents [OSTI]

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

    1987-01-01T23:59:59.000Z

    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.

  10. 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)

    1981-01-01T23:59:59.000Z

    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.

  11. Carbides composite surface layers produced by (PTA)

    SciTech Connect (OSTI)

    Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

    2013-12-16T23:59:59.000Z

    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.

  12. The WSRT virgo filament survey

    E-Print Network [OSTI]

    Attila Popping; Robert Braun

    2007-03-27T23:59:59.000Z

    In the last few years the realization has emerged that the universal baryons are almost equally distributed by mass in three components: (1) galactic concentrations, (2) a warm-hot intergalactic medium (WHIM) and (3) a diffuse intergalactic medium. These three components are predicted by hydrodynamical simulations and are probed by QSO absorption lines. To observe the WHIM in neutral hydrogen, observations are needed which are deeper than log(N$_{HI}$)=18. The WHIM should appear as a Cosmic Web, underlying the galaxies with higher column densities. We have used the WSRT, to simulate a filled aperture by observing at very high hour angles, to reach very high column density sensitivity. To achieve even higher image fidelity, an accurate model of the WSRT primary beam was developed. This will be used in the joint deconvolution of the observations. To get a good overview of the distribution and kinematics of the Cosmic Web, a deep survey of 1500 square degrees of sky was undertaken, containing the galaxy filament extending between the Local Group and the Virgo Cluster. The auto-correlation data has been reduced and has an RMS of $\\Delta N_{HI} = 4.2\\times10^{16}$ cm$^{-2}$ over 20 kms$^{-1}$. Several sources have been tentatively detected, which were previously unknown, as well as an indication for diffuse intergalactic filaments.

  13. Radiation damage in neutron irradiated boron carbide

    SciTech Connect (OSTI)

    Shcherbak, V.I.; Bykov, V.N.; Rudenko, V.A.; Tarasikov, V.P.

    1986-09-01T23:59:59.000Z

    In view of the fact that there is no information on the microstructure of specimens of boron carbide containing up to 60% B 10 isotope and irradiated at a temperature of 350-370 C, the authors undertook a detailed study of the radiation-induced defects in such material. The microstructure of unexposed boron carbide is characterized by the presence of pores originating during the technological process, dislocations, and twins. Irradiation of B/sub 4/C leads to the formation of defects measuring 3-20 nm and exhibiting a contrast that is characteristic of dislocation loops or two-dimensional second-phase precipitates and spherical pores measuring 1-4 nm in diameter. A specific microstructural feature of irradiated boron carbide is the formation of 30 nm wide zones that are free from pores and other radiation-induced defects near the gain boundaries. The obtained results indicate that irradiation of boron carbide in the 350-370 C range leads to the formation of several types of defects that can be detected by their image contrast under different conditions of photographing.

  14. High Q silicon carbide microdisk resonator

    SciTech Connect (OSTI)

    Lu, Xiyuan [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Lee, Jonathan Y. [Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627 (United States); Feng, Philip X.-L. [Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio 44106 (United States); Lin, Qiang, E-mail: qiang.lin@rochester.edu [Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627 (United States); Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

    2014-05-05T23:59:59.000Z

    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.

  15. PHYSICAL REVIEW B 83, 115329 (2011) Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001)

    E-Print Network [OSTI]

    Garfunkel, Eric

    PHYSICAL REVIEW B 83, 115329 (2011) Diffusion and interface growth in hafnium oxide and silicate­oxide­semiconductor (CMOS) technology necessary.1,2 Transition metal (Hf, Zr, La) oxides, silicates, and ternary Hf to be desirable to have at least one monolayer of SiO2 at the dielectric/Si interface. The Hf oxide (silicate

  16. TUNGSTEN AND HAFNIUM DISTRIBUTION IN CALCIUM-ALUMINUM INCLUSIONS (CAIs) FROM ALLENDE AND EFREMOVKA. M. Humayun1

    E-Print Network [OSTI]

    Grossman, Lawrence

    TUNGSTEN AND HAFNIUM DISTRIBUTION IN CALCIUM-ALUMINUM INCLUSIONS (CAIs) FROM ALLENDE AND EFREMOVKA with, or even earlier than, metal from CAIs and chondrules [3]. Tungsten isotope compositions represent veins [5]. Tungsten mobility is cause for concern, but is not sufficient evidence against the Kleine et

  17. RSISTIVIT LECTRIQUE A BASSE TEMPRATURE DU NIOBIUM ET D'ALLIAGES NIOBIUM-HAFNIUM EN PHASE CUBIQUE

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    879 RÉSISTIVITÉ ÉLECTRIQUE A BASSE TEMPÉRATURE DU NIOBIUM ET D'ALLIAGES NIOBIUM-HAFNIUM EN PHASE électrique de deux échantillons de niobium et d'échantillons d'alliages Nb-Hf en phase cubique, de expression mathématique de la résistivité des échan- tillons. Pour le niobium, cette expression est analogue

  18. ZIRCONIUM AND HAFNIUM--2003 85.1 References that include a section mark () are found in the Internet

    E-Print Network [OSTI]

    a voluntary survey of domestic operations. Of the 45 operations surveyed, 28 responded. Data by a second voluntary survey of domestic mining operations. Of the two domestic zircon producers, which have in the Internet References Cited section. ZIRCONIUM AND HAFNIUM By James B. Hedrick Domestic survey data

  19. EVIDENCE FOR MIXED HELICITY IN ERUPTING FILAMENTS

    SciTech Connect (OSTI)

    Muglach, K. [ARTEP, Inc., Ellicott City, MD (United States); Wang, Y.-M. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Kliem, B., E-mail: muglach@nrl.navy.mi, E-mail: yi.wang@nrl.navy.mi, E-mail: bkliem@uni-potsdam.d [MSSL, University College London, Holmbury St. Mary, Dorking, Surrey (United Kingdom)

    2009-09-20T23:59:59.000Z

    Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise. This rotation of the filament axis is generally interpreted as a conversion of twist into writhe in a kink-unstable magnetic flux rope. Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Here, we describe two non-active-region filament events recorded with the Extreme-Ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory in which the sense of rotation appears to be opposite to that expected from the helicity of the post-event arcade. Based on these observations, we suggest that the rotation of the filament axis is, in general, determined by the net helicity of the erupting system, and that the axially aligned core of the filament can have the opposite helicity sign to the surrounding field. In most cases, the surrounding field provides the main contribution to the net helicity. In the events reported here, however, the helicity associated with the filament 'barbs' is opposite in sign to and dominates that of the overlying arcade.

  20. Diamond-silicon carbide composite and method

    DOE Patents [OSTI]

    Zhao, Yusheng (Los Alamos, NM)

    2011-06-14T23:59:59.000Z

    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.

  1. CarbideDerived Carbons From Porous Networks to Nanotubes and...

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

    low-temper- ature carbon formation for nanopowders. Also, a better understanding of graphene formation during high-temperature vacuum decomposition of silicon carbide has been...

  2. Atomistic modeling of amorphous silicon carbide using a bond...

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

    there is partial recovery of shortrange order. Citation: Devanathan R, F Gao, and WJ Weber.2007."Atomistic modeling of amorphous silicon carbide using a bond-order...

  3. Amorphization of Silicon Carbide by Carbon Displacement. | EMSL

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

    plays a significant role in the amorphization. Citation: Devanathan R, F Gao, and WJ Weber.2004."Amorphization of Silicon Carbide by Carbon Displacement."Applied Physics Letters...

  4. Filament Activation in Response to Magnetic Flux Emergence and Cancellation in Filament Channels

    E-Print Network [OSTI]

    Li, Ting; Ji, Haisheng

    2015-01-01T23:59:59.000Z

    We make a comparative analysis for two filaments that showed quite different activation in response to the flux emergence within the filament channels. The observations from the Solar Dynamics Observatory (SDO) and Global Oscillation Network Group (GONG) are carried out to analyze the two filaments on 2013 August 17-20 and September 29. The first event showed that the main body of the filament was separated into two parts when an active region (AR) emerged with a maximum magnetic flux of about 6.4*10^21 Mx underlying the filament. The close neighborhood and common direction of the bright threads in the filament and the open AR fan loops suggest similar magnetic connectivity of these two flux systems. The equilibrium of the filament was not destroyed within 3 days after the start of the emergence of the AR. To our knowledge, similar observations have never been reported before. In the second event, the emerging flux occurred nearby a barb of the filament with a maximum magnetic flux of 4.2*10^20 Mx, about one ...

  5. Preparation and electrocatalytic activity of tungsten carbide and titania nanocomposite

    SciTech Connect (OSTI)

    Hu, Sujuan; Shi, Binbin; Yao, Guoxing [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)] [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China); Li, Guohua, E-mail: nanozjut@zjut.edu.cn [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)] [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China); Ma, Chunan [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)] [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, School of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310032 (China)

    2011-10-15T23:59:59.000Z

    Graphical abstract: The electrocatalytic activity of tungsten carbide and titania nanocomposite is related to the structure, crystal phase and chemical components of the nanocomposite, and is also affected by the property of electrolyte. A synergistic effect exists between tungsten carbide and titania of the composite. Highlights: {yields} Electrocatalytic activity of tungsten carbide and titania nanocomposite with core-shell structure. {yields} Activity is related to the structure, crystal phase and chemical component of the nanocomposite. {yields} The property of electrolyte affects the electrocatalytic activity. {yields} A synergistic effect exists between tungsten carbide and titania of the composite. -- Abstract: Tungsten carbide and titania nanocomposite was prepared by combining a reduced-carbonized approach with a mechanochemical approach. The samples were characterized by X-ray diffraction, transmission electron microscope under scanning mode and X-ray energy dispersion spectrum. The results show that the crystal phases of the samples are composed of anatase, rutile, nonstoichiometry titanium oxide, monotungsten carbide, bitungsten carbide and nonstoichiometry tungsten carbide, and they can be controlled by adjusting the parameters of the reduced-carbonized approach; tungsten carbide particles decorate on the surface of titania support, the diameter of tungsten carbide particle is smaller than 20 nm and that of titania is around 100 nm; the chemical components of the samples are Ti, O, W and C. The electrocatalytic activity of the samples was measured by a cyclic voltammetry with three electrodes. The results indicate that the electrocatalytic activities of the samples are related to their crystal phases and the property of electrolyte in aqueous solution. A synergistic effect between titania and tungsten carbide is reported for the first time.

  6. Filament velocity scaling laws for warm ions

    SciTech Connect (OSTI)

    Manz, P. [Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany) [Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany); Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Carralero, D.; Birkenmeier, G.; Müller, H. W.; Scott, B. D. [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany)] [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Müller, S. H. [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego 92093 (United States)] [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego 92093 (United States); Fuchert, G. [Insitut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, 70569 Stuttgart (Germany)] [Insitut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, 70569 Stuttgart (Germany); Stroth, U. [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany) [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany)

    2013-10-15T23:59:59.000Z

    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-Alfvén 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.

  7. Filamentary structures in dense plasma focus: Current filaments or vortex filaments?

    SciTech Connect (OSTI)

    Soto, Leopoldo, E-mail: lsoto@cchen.cl; Pavez, Cristian; Moreno, José [Comisión Chilena de Energía Nuclear, CCHEN, Casilla 188-D, Santiago (Chile); Center for Research and Applications in Plasma Physics and Pulsed Power, P4, Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, República 220, Santiago (Chile); Castillo, Fermin [Universidad Nacional Autónoma de México, Cuernavaca, México (Mexico); Veloso, Felipe [Instituto de Física, Pontificia Universidad Católica de Chile, 7820436 Santiago (Chile); Auluck, S. K. H. [Bhabha Atomic Research Center, Mumbai 400 085 (India)

    2014-07-15T23:59:59.000Z

    Recent observations of an azimuthally distributed array of sub-millimeter size sources of fusion protons and correlation between extreme ultraviolet (XUV) images of filaments with neutron yield in PF-1000 plasma focus have re-kindled interest in their significance. These filaments have been described variously in literature as current filaments and vortex filaments, with very little experimental evidence in support of either nomenclature. This paper provides, for the first time, experimental observations of filaments on a table-top plasma focus device using three techniques: framing photography of visible self-luminosity from the plasma, schlieren photography, and interferometry. Quantitative evaluation of density profile of filaments from interferometry reveals that their radius closely agrees with the collision-less ion skin depth. This is a signature of relaxed state of a Hall fluid, which has significant mass flow with equipartition between kinetic and magnetic energy, supporting the “vortex filament” description. This interpretation is consistent with empirical evidence of an efficient energy concentration mechanism inferred from nuclear reaction yields.

  8. Nanostructured Molybdenum Carbide: Sonochemical Synthesis and Catalytic Properties

    E-Print Network [OSTI]

    Suslick, Kenneth S.

    of metal salts.5,6 Sonochemical decomposition of transition metal carbonyl compounds has also been proven to be a useful technique to generate nanophase transition metals.7,8 Recently, molybdenum and tungsten carbides; the preparation of interstitial carbides of molybdenum and tungsten with high surface areas, however, is very

  9. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOE Patents [OSTI]

    Petrovic, J.J.

    1995-01-17T23:59:59.000Z

    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.

  10. Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity,

    E-Print Network [OSTI]

    Cambridge, University of

    Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity, and coarsening N. Fujita and H. K. D. H. Bhadeshia The growth of niobium carbide in austenite involves the diffusion of both niobium and carbon. These elements diffuse at very different rates. A model is presented

  11. Generation of stable overlaps between antiparallel filaments

    E-Print Network [OSTI]

    D. Johann; D. Goswami; K. Kruse

    2015-03-26T23:59:59.000Z

    During cell division, sister chromatids are segregated by the mitotic spindle, a bipolar assembly of interdigitating antiparallel polar filaments called microtubules. Establishing a stable overlap region is essential for maintenance of bipolarity, but the underlying mechanisms are poorly understood. Using a particle-based stochastic model, we find that the interplay of motors and passive cross linkers can robustly generate partial overlaps between antiparallel filaments. Our analysis shows that motors reduce the overlap in a length-dependent manner, whereas passive cross linkers increase it independently of the length. In addition to maintaining structural integrity, passive cross linkers can thus also have a dynamic role for size regulation.

  12. Generation of stable overlaps between antiparallel filaments

    E-Print Network [OSTI]

    Johann, D; Kruse, K

    2015-01-01T23:59:59.000Z

    During cell division, sister chromatids are segregated by the mitotic spindle, a bipolar assembly of interdigitating antiparallel polar filaments called microtubules. Establishing a stable overlap region is essential for maintenance of bipolarity, but the underlying mechanisms are poorly understood. Using a particle-based stochastic model, we find that the interplay of motors and passive cross linkers can robustly generate partial overlaps between antiparallel filaments. Our analysis shows that motors reduce the overlap in a length-dependent manner, whereas passive cross linkers increase it independently of the length. In addition to maintaining structural integrity, passive cross linkers can thus also have a dynamic role for size regulation.

  13. Current Filamentation Instability in Laser Wakefield Accelerators

    SciTech Connect (OSTI)

    Huntington, C. M.; Drake, R. P. [Atmospheric, Oceanic and Space Science, University of Michigan, Ann Arbor, Michigan, 48103 (United States); Thomas, A. G. R.; McGuffey, C.; Matsuoka, T.; Chvykov, V.; Kalintchenko, G.; Yanovsky, V.; Maksimchuk, A.; Krushelnick, K. [Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Kneip, S.; Najmudin, Z.; Palmer, C. [Blackett Laboratory, Imperial College London, London, SW7 2BZ (United Kingdom); Katsouleas, T. [Platt School of Engineering, Duke University, Durham, North Carolina, 27708 (United States)

    2011-03-11T23:59:59.000Z

    Experiments using an electron beam produced by laser-wakefield acceleration have shown that varying the overall beam-plasma interaction length results in current filamentation at lengths that exceed the laser depletion length in the plasma. Three-dimensional simulations show this to be a combination of hosing, beam erosion, and filamentation of the decelerated beam. This work suggests the ability to perform scaled experiments of astrophysical instabilities. Additionally, understanding the processes involved with electron beam propagation is essential to the development of wakefield accelerator applications.

  14. Terahertz radiation from a laser plasma filament

    SciTech Connect (OSTI)

    Wu, H.-C.; Meyer-ter-Vehn, J. [Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany); Ruhl, H. [Department fuer Physik der Ludwig-Maximillians-Universitaet, Theresienstrasse 37A, D-80333 Muenchen (Germany); Sheng, Z.-M. [Institute of Plasma Studies, Department of Physics, Shanghai Jiaotong University, Shanghai 200240 (China); Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China)

    2011-03-15T23:59:59.000Z

    By the use of two-dimensional particle-in-cell simulations, we clarify the terahertz (THz) radiation mechanism from a plasma filament formed by an intense femtosecond laser pulse. The nonuniform plasma density of the filament leads to a net radiating current for THz radiation. This current is mainly located within the pulse and the first cycle of the wakefield. As the laser pulse propagates, a single-cycle and radially polarized THz pulse is constructively built up forward. The single-cycle shape is mainly due to radiation damping effect.

  15. Corrosion and wear resistance of tungsten carbide-cobalt and tungsten carbide-cobalt-chromium thermal spray coatings

    SciTech Connect (OSTI)

    Quets, J.; Alford, J.R.

    1999-07-01T23:59:59.000Z

    Tungsten carbide thermal spray coatings provide wear surfaces to new and overhauled components for various industries. Their wear resistance is obtained by incorporating small tungsten carbide particles into a metal matrix. This presentation will show what parameters influence their corrosion resistance in the ASTM B-117 Salt Spray Corrosion Test,

  16. Dispersion aspects of silicon carbide gelcasting

    SciTech Connect (OSTI)

    Bleier, A.

    1991-09-01T23:59:59.000Z

    The principal objective of this research was to increase the solid loading of silicon carbide (SiC) powder, in an appropriate liquid medium, to a level that is useful for gelcasting technology. A number of factors that determine the maximum concentration of silicon carbide that can be incorporated into a pourable ceramic suspension have been identified. The pH of the system is the most critical processing parameter. Its proper adjustment (pH 11 to 13) allows SiC concentrations exceeding 50%, based on volume, to be routinely achieved without the use of additional dispersing agents. The particle size of SiC was also found to affect the maximum, attainable concentration. The surface area of the powder and the presence of free carbon in the powder, though not significantly influencing the suspension properties, determine the concentration of initiator required to induce polymerization and gelation. SiC specimens have been gelcast for powders in the size range of 0.8 to 8.5 {mu}m; the powders employed contain either {approximately} 0 or 19% carbon by weight. Finally, the generation of bubbles, typically encountered by the use of ammonia to adjust pH has been circumvented by the use of tetramethylammonium hydroxide.

  17. High temperature intermetallic binders for HVOF carbides

    SciTech Connect (OSTI)

    Shaw, K.G. [Xform, Inc., Cohoes, NY (United States); Gruninger, M.F.; Jarosinski, W.J. [Praxair Specialty Powders, Indianapolis, IN (United States)

    1994-12-31T23:59:59.000Z

    Gas turbines technology has a long history of employing the desirable high temperature physical attributes of ceramic-metallic (cermet) materials. The most commonly used coatings incorporate combinations of WC-Co and Cr{sub 3}C{sub 2}-NiCr, which have also been successfully utilized in other non-turbine coating applications. Increased turbine operating temperatures and other high temperature service conditions have made apparent the attractive notion of increasing the temperature capability and corrosion resistance of these coatings. In this study the intermetallic binder NiAl has been used to replace the cobalt and NiCr constituents of conventional WC and Cr{sub 3}C{sub 2} cermet powders. The composite carbide thermal spray powders were fabricated for use in the HVOF coating process. The structure of HVOF deposited NiAl-carbide coatings are compared directly to the more familiar WC-Co and Cr{sub 3}C{sub 2}-NiCr coatings using X-ray diffraction, back-scattered electron imaging (BEI) and electron dispersive spectroscopy (EDS). Hardness variations with temperature are reported and compared between the NiAl and Co/NiCr binders.

  18. Light sources based on semiconductor current filaments

    DOE Patents [OSTI]

    Zutavern, Fred J. (Albuquerque, NM); Loubriel, Guillermo M. (Albuquerque, NM); Buttram, Malcolm T. (Sandia Park, NM); Mar, Alan (Albuquerque, NM); Helgeson, Wesley D. (Albuquerque, NM); O'Malley, Martin W. (Edgewood, NM); Hjalmarson, Harold P. (Albuquerque, NM); Baca, Albert G. (Albuquerque, NM); Chow, Weng W. (Cedar Crest, NM); Vawter, G. Allen (Albuquerque, NM)

    2003-01-01T23:59:59.000Z

    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.

  19. Phase-locked controlled filament laser

    SciTech Connect (OSTI)

    Salzman, J.; Larsson, A.; Yariv, A.

    1986-09-15T23:59:59.000Z

    A broad area semiconductor laser with induced self-focusing in the form of a phase-locked array of filaments is demonstrated. The multifilamentary laser has a single lobed and nearly diffraction limited far-field pattern, for injection currents up to I-italicapprox. =1.85I-italic/sub th/.

  20. Computational Studies of Physical Properties of Boron Carbide

    SciTech Connect (OSTI)

    Lizhi Ouyang

    2011-09-30T23:59:59.000Z

    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.

  1. Separation of Nuclear Fuel Surrogates from Silicon Carbide Inert Matrix

    SciTech Connect (OSTI)

    Dr. Ronald Baney

    2008-12-15T23:59:59.000Z

    The objective of this project has been to identify a process for separating transuranic species from silicon carbide (SiC). Silicon carbide has become one of the prime candidates for the matrix in inert matrix fuels, (IMF) being designed to reduce plutonium inventories and the long half-lives actinides through transmutation since complete reaction is not practical it become necessary to separate the non-transmuted materials from the silicon carbide matrix for ultimate reprocessing. This work reports a method for that required process.l

  2. 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)

    1994-01-01T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    McGilvery, Catriona M. [Imperial College, London; De Gendt, S [Imperial College, London; Payzant, E Andrew [ORNL; Craven, A J [Imperial College, London; MacKenzie, M [Imperial College, London; McComb, D W [Imperial College, London

    2012-01-01T23:59:59.000Z

    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.

  4. Silicon carbide mirrors for high power applications

    SciTech Connect (OSTI)

    Takacs, P.Z.

    1981-11-01T23:59:59.000Z

    The advent of synchrotron radiation (SR) sources and high energy lasers (HEL) in recent years has brought about the need for optical materials that can withstand the harsh operating conditions in such devices. SR mirrors must be ultra-high vacuum compatible, must withstand intense x-ray irradiation without surface damage, must maintain surface figure under thermal loading and must be capable of being polished to an extremely smooth surface finish. Chemical vapor deposited (CVD) silicon carbide in combination with sintered substrate material meets these requirements and offers additional benefits as well. It is an extremely hard material and offers the possibility of being cleaned and recoated many times without degradation of the surface finish, thereby prolonging the lifetime of expensive optical components. It is an extremely strong material and offers the possibility of weight reduction over conventional mirror materials.

  5. Light Ions Response of Silicon Carbide Detectors

    E-Print Network [OSTI]

    M. De Napoli; G. Raciti; E. Rapisarda; C. Sfienti

    2006-12-14T23:59:59.000Z

    Silicon carbide (SiC) Schottky diodes 21 mum thick with small surfaces and high N-dopant concentration have been used to detect alpha particles and low energy light ions. In particular 12C and 16O beams at incident energies between 5 and 18 MeV were used. The diode active-region depletion-thickness, the linearity of the response, energy resolution and signal rise-time were measured for different values of the applied reverse bias. Moreover the radiation damage on SiC diodes irradiated with 53 MeV 16O beam has been explored. The data show that SiC material is radiation harder than silicon but at least one order of magnitude less hard than epitaxial silicon diodes. An inversion in the signal was found at a fluence of 10^15 ions/cm^2.

  6. In-Pile Experiment of a New Hafnium Aluminide Composite Material to Enable Fast Neutron Testing in the Advanced Test Reactor

    SciTech Connect (OSTI)

    Donna Post Guillen; Douglas L. Porter; James R. Parry; Heng Ban

    2010-06-01T23:59:59.000Z

    A new hafnium aluminide composite material is being developed as a key component in a Boosted Fast Flux Loop (BFFL) system designed to provide fast neutron flux test capability in the Advanced Test Reactor. An absorber block comprised of hafnium aluminide (Al3Hf) particles (~23% by volume) dispersed in an aluminum matrix can absorb thermal neutrons and transfer heat from the experiment to pressurized water cooling channels. However, the thermophysical properties, such as thermal conductivity, of this material and the effect of irradiation are not known. This paper describes the design of an in-pile experiment to obtain such data to enable design and optimization of the BFFL neutron filter.

  7. Structure and dynamics of penumbral filaments

    E-Print Network [OSTI]

    Cobo, B Ruiz

    2008-01-01T23:59:59.000Z

    High-resolution observations of sunspots have revealed the existence of dark cores inside the bright filaments of the penumbra. Here we present the stationary solution of the heat transfer equation in a stratified penumbra consisting of nearly horizontal magnetic flux tubes embedded in a stronger and more vertical field. The tubes and the external medium are in horizontal mechanical equilibrium. This model produces bright filaments with dark cores as a consequence of the higher density of the plasma inside the flux tube, which shifts the surface of optical depth unity toward higher (cooler) layers. Our results suggest that the surplus brightness of the penumbra is a natural consequence of the Evershed flow, and that magnetic flux tubes about 250 km in diameter can explain the morphology of sunspot penumbra.

  8. Structure and dynamics of penumbral filaments

    E-Print Network [OSTI]

    B. Ruiz Cobo; L. R. Bellot Rubio

    2008-10-14T23:59:59.000Z

    High-resolution observations of sunspots have revealed the existence of dark cores inside the bright filaments of the penumbra. Here we present the stationary solution of the heat transfer equation in a stratified penumbra consisting of nearly horizontal magnetic flux tubes embedded in a stronger and more vertical field. The tubes and the external medium are in horizontal mechanical equilibrium. This model produces bright filaments with dark cores as a consequence of the higher density of the plasma inside the flux tube, which shifts the surface of optical depth unity toward higher (cooler) layers. Our results suggest that the surplus brightness of the penumbra is a natural consequence of the Evershed flow, and that magnetic flux tubes about 250 km in diameter can explain the morphology of sunspot penumbra.

  9. Collective dynamics of active filament complexes

    E-Print Network [OSTI]

    Nogucci, Hironobu

    2015-01-01T23:59:59.000Z

    Networks of biofilaments are essential for the formation of cellular structures and they support various biological functions. Previous studies have largely investigated the collective dynamics of rod-like biofilaments; however, the shapes of actual subcelluar componensts are often more elaborate. In this study, we investigated an active object composed of two active filaments, which represents a progression from rod-like biofilaments to complex-shaped biofilaments. Specifically, we numerically assessed the collective behaviors of these active objects and observed several types of dynamics depending on the density and the angle of the two filaments as shape parameters of the object. Among the observed collective dynamics, moving density bands that we named 'moving smectic' are reported here for the first time. By using statistical analyses of the orbits of individual objects and the interactions among them, the mechanisms underlying the rise of these dynamics patterns in the system were determined. This study...

  10. Safety of light water reactor fuel with silicon carbide cladding

    E-Print Network [OSTI]

    Lee, Youho

    2013-01-01T23:59:59.000Z

    Structural aspects of the performance of light water reactor (LWR) fuel rod with triplex silicon carbide (SiC) cladding - an emerging option to replace the zirconium alloy cladding - are assessed. Its behavior under accident ...

  11. Rapid Wolff–Kishner reductions in a silicon carbide microreactor

    E-Print Network [OSTI]

    Newman, Stephen G.

    2014-01-01T23:59:59.000Z

    Wolff–Kishner reductions are performed in a novel silicon carbide microreactor. Greatly reduced reaction times and safer operation are achieved, giving high yields without requiring a large excess of hydrazine. The corrosion ...

  12. Reactor physics assessment of thick silicon carbide clad PWR fuels

    E-Print Network [OSTI]

    Bloore, David A. (David Allan)

    2013-01-01T23:59:59.000Z

    High temperature tolerance, chemical stability and low neutron affinity make silicon carbide (SiC) a potential fuel cladding material that may improve the economics and safety of light water reactors (LWRs). "Thick" SiC ...

  13. Tungsten carbide-cobalt by Three Dimensional Printing

    E-Print Network [OSTI]

    Kelley, Andrew, III

    1998-01-01T23:59:59.000Z

    Three Dimensional Printing is an additive manufacturing process for rapid prototyping ceramic and metallic parts [Sachs, et al, 1990]. Green (not sintered) tungsten carbide-cobalt parts must have a density greater than 50% ...

  14. Hot filament CVD of boron nitride films

    DOE Patents [OSTI]

    Rye, Robert R. (Albuquerque, NM)

    1992-01-01T23:59:59.000Z

    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.

  15. Reconnection of vortex filaments and Kolmogorov spectrum

    E-Print Network [OSTI]

    Sergey K. Nemirovskii

    2014-04-19T23:59:59.000Z

    The energy spectrum of the 3D velocity field, induced by collapsing vortex filaments is studied. One of the aims of this work is to clarify the appearance of the Kolmogorov type energy spectrum $E(k)\\varpropto k^{-5/3}$, observed in many numerical works on discrete vortex tubes (quantized vortex filaments in quantum fluids). Usually, explaining classical turbulent properties of quantum turbulence, the model of vortex bundles, is used. This model is necessary to mimic the vortex stretching, which is responsible for the energy transfer in classical turbulence. In our consideration we do not appeal to the possible "bundle arrangement" but explore alternative idea that the turbulent spectra appear from singular solution, which describe the collapsing line at moments of reconnection. One more aim is related to an important and intensively discussed topic - a role of hydrodynamic collapse in the formation of turbulent spectra. We demonstrated that the specific vortex filament configuration generated the spectrum $E(k)$ close to the Kolmogorov dependence and discussed the reason for this as well as the reason for deviation. We also discuss the obtained results from point of view of the both classical and quantum turbulence.

  16. 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)

    1996-09-01T23:59:59.000Z

    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.}

  17. Microwave processing of ceramic oxide filaments. Annual report, FY1997

    SciTech Connect (OSTI)

    Vogt, G.J.

    1998-12-31T23:59:59.000Z

    The objective of the microwave filament processing project is to develop microwave techniques to manufacture continuous ceramic oxide filaments. Microwave processing uses the volumetric absorption of microwave power in oxide filament tows to drive off process solvents, to burn out organic binders, and to sinter the dried fibers to produce flexible, high-strength ceramic filaments. The technical goal is to advance filament processing technology by microwave heating more rapidly with less energy and at a lower cost than conventional processing, but with the same quality as conventional processing. The manufacturing goal is to collaborate with the 3M Company, a US manufacturer of ceramic oxide filaments, to evaluate the technology using a prototype filament system and to transfer the microwave technology to the 3M Company. Continuous ceramic filaments are a principal component in many advanced high temperature materials like continuous fiber ceramic composites (CFCC) and woven ceramic textiles. The use of continuous ceramic filaments in CFCC radiant burners, gas turbines, waste incineration, and hot gas filters in U.S. industry and power generation is estimated to save at least 2.16 quad/yr by year 2010 with energy cost savings of at least $8.1 billion. By year 2010, continuous ceramic filaments and CFCC`s have the potential to abate pollution emissions by 917,000 tons annually of nitrous oxide and 118 million tons annually of carbon dioxide (DOE Report OR-2002, February, 1994).

  18. Understanding the Irradiation Behavior of Zirconium Carbide

    SciTech Connect (OSTI)

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

    2013-10-11T23:59:59.000Z

    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.

  19. Microwave guiding in air along single femtosecond laser filament

    SciTech Connect (OSTI)

    Ren Yu; Alshershby, Mostafa; Qin Jiang; Hao Zuoqiang; Lin Jingquan [School of Science, Changchun University of Science and Technology, Changchun 130022 (China)

    2013-03-07T23:59:59.000Z

    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.

  20. Product: Tetrakis(dimethylamino)hafnium P-6280-B Date: February 2005 Copyright 2002, 2004-2005, Praxair Technology, Inc. Page 1 of 8

    E-Print Network [OSTI]

    Rubloff, Gary W.

    -2005, Praxair Technology, Inc. Page 1 of 8 All rights reserved. Revised Praxair Material Safety Data Sheet (See-6280-B) Trade Name: Praxair® TDMAH Chemical Name: Tetrakis(dimethylamino)hafnium Synonyms: Tetrakis Telephone: Emergencies: 1-800-645-4633* Company Name: Praxair, Inc. CHEMTREC: 1-800-424-9300* 39 Old

  1. Tailoring femtosecond laser pulse filamentation using plasma photonic lattices

    SciTech Connect (OSTI)

    Suntsov, Sergiy; Abdollahpour, Daryoush; Panagiotopoulos, Paris [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, 71110 Heraklion (Greece); Papazoglou, Dimitrios G.; Tzortzakis, Stelios [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, 71110 Heraklion (Greece); Materials Science and Technology Department, University of Crete, P.O. Box 2208, 71003 Heraklion (Greece); Couairon, Arnaud [Centre de Physique Theorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-07-08T23:59:59.000Z

    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.

  2. actin filament nucleation: Topics by E-print Network

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

    Abstract. From recent studies of locomoting fish keratocytes it was proposed that the dynamic turnover of actin filaments takes place by a nucleation-release mechanism, which...

  3. Microwave diagnostics of femtosecond laser-generated plasma filaments

    SciTech Connect (OSTI)

    Papeer, J.; Ehrlich, Y.; Zigler, A. [Racah Institute of Physics, Hebrew University, Jerusalem, 91904 (Israel); Mitchell, C.; Penano, J.; Sprangle, P. [Plasma Division, Naval Research Lab, Washington, DC, 20375 (United States)

    2011-10-03T23:59:59.000Z

    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.

  4. Plasma planar filament instability and Alfven waves

    E-Print Network [OSTI]

    Garcia de Andrade

    2007-03-05T23:59:59.000Z

    Inhomogeneous plasmas filaments instabilities are investigated by using the techniques of classical differential geometry of curves where Frenet torsion and curvature describe completely the motion of curves. In our case the Frenet frame changes in time and also depends upon the other coordinates taking into account the inhomogeneity of the plasma. The exponential perturbation method so commonly used to describe cosmological perturbatons is applied to magnetohydrodynamic (MHD) plasma equations to find longitudinal modes describing Alfven waves propagation modes describing plasma waves in the medium. Stability is investigated in the imaginary axis of the spectra of complex frequencies ${\\omega}$ or $Im(\\omega)\

  5. area carbide-derived carbon: Topics by E-print Network

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

    21 22 23 24 25 Next Page Last Page Topic Index 1 Carbide and Carbide-Derived Carbon Materials with Hierarchical Pore Architecture. Open Access Theses and Dissertations Summary:...

  6. Carbide process picked for Chinese polyethylene plant

    SciTech Connect (OSTI)

    Alperowicz, N.

    1993-02-10T23:59:59.000Z

    Union Carbide (Danbury, CT) is set to sign up its eighth polyethylene (PE) license in China. The company has been selected to supply its Unipol technology to Jilin Chemical Industrial Corp. (JCIC) for a 100,000-m.t./year linear low-density PE (LLDPE) plant at Jilin. The plant will form part of a $2-billion petrochemical complex, based on a 300,000-m.t./year ethylene unit awarded to a consortium made up of Samsung Engineering (Seoul) and Linde. A 10,000-m.t./year butene-1 unit will also be built. Toyo Engineering, Snamprogetti, Mitsubishi Heavy Industries, and Linde are competing for the contract to supply the LLDPE plant. The signing is expected this spring. Two contenders are vying to supply an 80,000-m.t./year phenol plant for JCIC. They are Mitsui Engineering, offering the Mitsui Petrochemical process, and Chisso, with UOP technology. Four Unipol process PE plants are under construction in China and three are in operation. At Guangzhou, Toyo Engineering is building a 100,000-m.t./year plant, due onstream in 1995, while Snamprogetti is to finish construction of two plants in the same year at Zhonguyan (120,000 m.t./year) and at Maoming (140,000 m.t./year). The Daquing Design Institute is responsible for the engineering of a 60,000-m.t./year Unipol process PE plant, expected onstream early in 1995. Existing Unipol process PE plants are located in Qilu (60,000 m.t./year LLDPE and 120,000 m.t./year HDPE) and at Taching (60,000 m.t./year HDPE).

  7. Pulsed energy synthesis and doping of silicon carbide

    DOE Patents [OSTI]

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

    1995-06-20T23:59:59.000Z

    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)

    1995-01-01T23:59:59.000Z

    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. Structure-Property Relationship in Metal Carbides and Bimetallic Alloys

    SciTech Connect (OSTI)

    Chen, Jingguan [University of Delaware] [University of Delaware

    2014-03-04T23:59:59.000Z

    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.

  10. Bifurcations of flame filaments in chaotically mixed combustion reactions

    E-Print Network [OSTI]

    Gottwald, Georg A.

    Bifurcations of flame filaments in chaotically mixed combustion reactions Shakti N. Menon and Georg ranging fields. Be- sides in the case of combustion, where mixing-induced bifurcations may lead mixing has a significant effect on combustion processes and in particular on flame filamental structures

  11. Radiofrequency conical emission from femtosecond filaments in air

    SciTech Connect (OSTI)

    Forestier, B.; Houard, A.; Durand, M.; Andre, Y. B.; Prade, B.; Mysyrowicz, A. [Laboratoire d'Optique Appliquee, ENSTA ParisTech, CNRS UMR 7639, Ecole Polytechnique, 91761 Palaiseau (France); Dauvignac, J.-Y.; Perret, F.; Pichot, Ch. [Laboratoire d'Electronique, Antennes et Telecommunications, CNRS UMR 6071, Universite Nice-Sophia Antipolis, 250 rue Albert Einstein, 06560 Valbonne (France); Pellet, M. [Ministere de la Defense, F-00457 Armees (France)

    2010-04-05T23:59:59.000Z

    We show that the broadband conical emission associated with filaments in air extends down to the radiofrequency region. This rf emission which originates from the longitudinal oscillation of charged ions formed during filamentation is strongly enhanced by the presence of a longitudinal static electric field.

  12. 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)

    1995-01-01T23:59:59.000Z

    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.

  13. 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)

    2002-01-01T23:59:59.000Z

    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.

  14. The extreme nonlinear optics of gases and femtosecond optical filamentation

    SciTech Connect (OSTI)

    Milchberg, H. M.; Chen, Y.-H.; Cheng, Y.-H.; Jhajj, N.; Palastro, J. P.; Rosenthal, E. W.; Varma, S.; Wahlstrand, J. K.; Zahedpour, S. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

    2014-10-15T23:59:59.000Z

    Under certain conditions, powerful ultrashort laser pulses can form greatly extended, propagating filaments of concentrated high intensity in gases, leaving behind a very long trail of plasma. Such filaments can be much longer than the longitudinal scale over which a laser beam typically diverges by diffraction, with possible applications ranging from laser-guided electrical discharges to high power laser propagation in the atmosphere. Understanding in detail the microscopic processes leading to filamentation requires ultrafast measurements of the strong field nonlinear response of gas phase atoms and molecules, including absolute measurements of nonlinear laser-induced polarization and high field ionization. Such measurements enable the assessment of filamentation models and make possible the design of experiments pursuing applications. In this paper, we review filamentation in gases and some applications, and discuss results from diagnostics developed at Maryland for ultrafast measurements of laser-gas interactions.

  15. Process for forming silicon carbide films and microcomponents

    DOE Patents [OSTI]

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

    1999-01-01T23:59:59.000Z

    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.

  16. Process for forming silicon carbide films and microcomponents

    DOE Patents [OSTI]

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

    1999-01-19T23:59:59.000Z

    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.

  17. Method for forming fibrous silicon carbide insulating material

    DOE Patents [OSTI]

    Wei, G.C.

    1983-10-12T23:59:59.000Z

    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.

  18. Method for forming fibrous silicon carbide insulating material

    DOE Patents [OSTI]

    Wei, George C. (Oak Ridge, TN)

    1984-01-01T23:59:59.000Z

    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. Computational Approach to Photonic Drilling of Silicon Carbide

    SciTech Connect (OSTI)

    Samant, Anoop N [University of Tennessee, Knoxville (UTK); Daniel, Claus [ORNL; Chand, Ronald H [ORNL; Blue, Craig A [ORNL; Dahotre, Narendra B [University of Tennessee, Knoxville (UTK)

    2009-01-01T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    1995-01-01T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

    Koc, R.; Glatzmaier, G.C.

    1995-05-23T23:59:59.000Z

    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.

  2. Process for preparing fine grain titanium carbide powder

    DOE Patents [OSTI]

    Janney, M.A.

    1985-03-12T23:59:59.000Z

    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.

  3. Differential sthA gene expression between filamentous and isolated forms of Sphaerotilus natans

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    : The activated sludge is the most commonly used technology for biological wastewater treatment. Filamentous to find more efficient treatments against bulking the molecular mechanisms of filamentation have

  4. 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.

    1985-05-06T23:59:59.000Z

    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.

  5. Geometry and Optimal Packing of Twisted Columns and Filaments

    E-Print Network [OSTI]

    Gregory M. Grason

    2015-01-30T23:59:59.000Z

    This review presents recent progress in understanding constraints and consequences of close-packing geometry of filamentous or columnar materials possessing non-trivial textures, focusing in particular on the common motifs of twisted and toroidal structures. The mathematical framework is presented that relates spacing between line-like, filamentous elements to their backbone orientations, highlighting the explicit connection between the inter-filament {\\it metric} properties and the geometry of non-Euclidean surfaces. The consequences of the hidden connection between packing in twisted filament bundles and packing on positively curved surfaces, like the Thomson problem, are demonstrated for the defect-riddled ground states of physical models of twisted filament bundles. The connection between the "ideal" geometry of {\\it fibrations} of curved three-dimensional space, including the Hopf fibration, and the non-Euclidean constraints of filament packing in twisted and toroidal bundles is presented, with a focus on the broader dependence of metric geometry on the simultaneous twisting and folded of multi-filament bundles.

  6. Nuclear breeder reactor fuel element with silicon carbide getter

    DOE Patents [OSTI]

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

    1987-01-01T23:59:59.000Z

    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.

  7. Standard specification for nuclear-Grade boron carbide pellets

    E-Print Network [OSTI]

    American Society for Testing and Materials. Philadelphia

    2007-01-01T23:59:59.000Z

    1.1 This specification applies to boron carbide pellets for use as a control material in nuclear reactors. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

  8. Surface Coating of Tungsten Carbide by Electric Exploding of Contact

    SciTech Connect (OSTI)

    Grigoryev, Evgeny G. [General Physics Department, Moscow Engineering Physics Institute, Kashirskoe sh. 31, Moscow, 115409 (Russian Federation)

    2011-01-17T23:59:59.000Z

    Electric exploding of a tungsten carbide--cobalt material near-by high-speed steel surface forms on it a hardening coating. The essential structure properties of the formed coatings are determined by parameters of contact exploding electrode at the pulse current amplitude from above 106 A/cm2 and duration less than 10-4 s. The metallographic investigations of coating structures were done by microscope 'Neophot-24'. They have shown that the contact electric exploding caused the transfer of tungsten carbide and cobalt on the surface of high-speed steel. The breakdown of tungsten carbide--cobalt material took place during electrical exploding. The hardening layers of tungsten carbide and pure nanocrystalline tungsten have been formed upon the surface of high-speed steel as a result of electric exploding. Crystalline grains of tungsten have an almost spherical form and their characteristic size less than 400 nanometers. Micro hardness of the coating layers and high-speed steel structures was measured.

  9. Tungsten-yttria carbide coating for conveying copper

    DOE Patents [OSTI]

    Rothman, Albert J. (Livermore, CA)

    1993-01-01T23:59:59.000Z

    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.

  10. Epitaxial graphene on silicon carbide: Introduction to structured graphene

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Epitaxial graphene on silicon carbide: Introduction to structured graphene Ming Ruan 1 , Yike Hu 1, France Abstract We present an introduction to the rapidly growing field of epitaxial graphene on silicon present, highly evolved state. The potential of epitaxial graphene as a new electronic material is now

  11. Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons

    SciTech Connect (OSTI)

    Z. Zak Fang, H. Y. Sohn

    2009-03-10T23:59:59.000Z

    This report contains detailed information of the research program entitled "Development of Bulk Nanocrystalline Cemented Tungsten Carbide Materials for Industrial Applications". The report include the processes that were developed for producing nanosized WC/Co composite powders, and an ultrahigh pressure rapid hot consolidation process for sintering of nanosized powders. The mechanical properties of consolidated materials using the nanosized powders are also reported.

  12. Nonquasineutral relativistic current filaments and their X-ray emission

    SciTech Connect (OSTI)

    Gordeev, A. V. [Russian Research Centre Kurchatov Institute (Russian Federation); Losseva, T. V. [Russian Academy of Sciences, Institute of Geosphere Dynamics (Russian Federation)

    2009-02-15T23:59:59.000Z

    Nonquasineutral electron current filaments with the azimuthal magnetic field are considered that arise due to the generation of electron vorticity in the initial (dissipative) stage of evolution of a current-carrying plasma, when the Hall number is small ({sigma}B/en{sub e}c << 1) because of the low values of the plasma conductivity and magnetic field strength. Equilibrium filamentary structures with both zero and nonzero net currents are considered. Structures with a zero net current type form on time scales of t < t{sub sk} = (r{sub 0{omega}pe}/c){sup 2}t{sub st}, where t{sub sk} is the skin time, t{sub st} is the typical time of electron-ion collisions, and r{sub 0} is the radius of the filament. It is shown that, in nonquasineutral filaments in which the current is carried by electrons drifting in the crossed electric (E{sub r}) and magnetic (B{sub {theta}}) fields, ultrarelativistic electron beams on the typical charge-separation scale r{sub B} = B/(4{pi}en{sub e}) (the so-called magnetic Debye radius) can be generated. It is found that, for comparable electron currents, the characteristic electron energy in filaments with a nonzero net current is significantly lower than that in zero-net-current filaments that form on typical time scales of t < t{sub sk}. This is because, in the latter type of filaments, the oppositely directed electron currents repel one another; as a result, both the density and velocity of electrons increase near the filament axis, where the velocities of relativistic electrons are maximum. Filaments with a zero net current can emit X rays with photon energies h {omega} up to 10 MeV. The electron velocity distributions in filaments, the X-ray emission spectra, and the total X-ray yield per unit filament length are calculated as functions of the current and the electron number density in the filament. Analytical estimates of the characteristic lifetime of a radiating filament and the typical size of the radiating region as functions of the plasma density are obtained. The results of calculations are compared with the available experimental data.

  13. Vector spectropolarimetry of dark-cored penumbral filaments with Hinode

    E-Print Network [OSTI]

    L. R. Bellot Rubio; S. Tsuneta; K. Ichimoto; Y. Katsukawa; B. W. Lites; S. Nagata; T. Shimizu; R. A. Shine; Y. Suematsu; T. D. Tarbell; A. M. Title; J. C. del Toro Iniesta

    2007-08-21T23:59:59.000Z

    We present spectropolarimetric measurements of dark-cored penumbral filaments taken with Hinode at a resolution of 0.3". Our observations demonstrate that dark-cored filaments are more prominent in polarized light than in continuum intensity. Far from disk center, the Stokes profiles emerging from these structures are very asymmetric and show evidence for magnetic fields of different inclinations along the line of sight, together with strong Evershed flows of at least 6-7 km/s. In sunspots closer to disk center, dark-cored penumbral filaments exhibit regular Stokes profiles with little asymmetries due to the vanishing line-of-sight component of the horizontal Evershed flow. An inversion of the observed spectra indicates that the magnetic field is weaker and more inclined in the dark cores as compared with the surrounding bright structures. This is compatible with the idea that dark-cored filaments are the manifestation of flux tubes carrying hot Evershed flows.

  14. Investigation of thermal filamentation instability over Gakona, Alaska

    E-Print Network [OSTI]

    Cohen, Joel (Joel A.), S.B. Massachusetts Institute of Technology

    2007-01-01T23:59:59.000Z

    The thermal filamentation instability has been invoked to explain the formation of parallel plate waveguides in mid-latitude ionospheric plasmas during Arecibo, Puerto Rico heating experiments in 1997. The geometry of the ...

  15. Apparatus for coating and impregnating filament with resin

    DOE Patents [OSTI]

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

    1986-12-17T23:59:59.000Z

    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.

  16. Chile, 2009 HYDRAULIC MANAGEMENT OF FILAMENTOUS ALGAE IN

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    7 th ISE & 8 th HIC Chile, 2009 HYDRAULIC MANAGEMENT OF FILAMENTOUS ALGAE IN OPEN-CHANNEL NETWORKS mechanical interventions to avoid overflows. Moreover, drifting algae cells increase water turbidity

  17. Persistence of strain in motor-filament assemblies

    E-Print Network [OSTI]

    Arvind Gopinath; Raghunath Chelakkot; L. Mahadevan

    2015-01-12T23:59:59.000Z

    Crosslinked semi-flexible and flexible filaments that are actively deformed by molecular motors occur in various natural settings, such as the ordered eukaryotic flagellum, and the disordered cytoskeleton. The deformation of these composite systems is driven by active motor forces and resisted by passive filament elasticity, and structural constraints due to permanent cross-links. Using a mean field theory for a one-dimensional ordered system, we show that the combination of motor activity and finite filament extensibility yields a characteristic persistence length scale over which active strain decays. This decay length is set by the ability of motors to respond to combination of the weak extensional elasticity, passive shear resistance and the viscoelastic properties of the motor assembly, and generalizes the notion of persistence in purely thermal filaments to active systems.

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

    SciTech Connect (OSTI)

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

    2014-09-01T23:59:59.000Z

    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.

  19. 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)

    2001-01-01T23:59:59.000Z

    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.

  20. The Discovery of Balmer-filaments Encircling SNR RCW 86

    E-Print Network [OSTI]

    R. Chris Smith

    1997-10-17T23:59:59.000Z

    We report the discovery of Balmer-dominated filaments along almost the complete periphery of the supernova remnant RCW 86 (also known as G 315.2-2.3 or MSH 14-63). Using the UM/CTIO Curtis Schmidt telescope, we obtained deep CCD images in the emission of Halpha and [S II], together with continuum images to remove stellar confusion. After continuum subtraction, we discovered a network of Halpha filaments reaching almost completely around the remnant. Most of the newly identified filaments show no corresponding [S II] emission, indicating that they belong to the peculiar ''Balmer-dominated'' class of filaments. Comparison of these Balmer filaments with existing radio and X-ray images of RCW 86 shows an overall similarity, although interesting differences are apparent upon detailed inspection. While further observations of these newly identified optical filaments may eventually provide more detailed information on the kinematics and distance to RCW 86, the distance currently remains uncertain. We argue that the shorter distance estimates of ~1 kpc are still favored.

  1. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    SciTech Connect (OSTI)

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26T23:59:59.000Z

    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

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

    DOE Patents [OSTI]

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

    2005-09-06T23:59:59.000Z

    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.

  3. Carbon-rich icosahedral boron carbide designed from first principles

    SciTech Connect (OSTI)

    Jay, Antoine; Vast, Nathalie; Sjakste, Jelena; Duparc, Olivier Hardouin [Ecole Polytechnique, Laboratoire des Solides Irradiés, CEA-DSM-IRAMIS, CNRS UMR 7642, F-91120 Palaiseau (France)

    2014-07-21T23:59:59.000Z

    The carbon-rich boron-carbide (B{sub 11}C)C-C has been designed from first principles within the density functional theory. With respect to the most common boron carbide at 20% carbon concentration B{sub 4}C, the structural modification consists in removing boron atoms from the chains linking (B{sub 11}C) icosahedra. With C-C instead of C-B-C chains, the formation of vacancies is shown to be hindered, leading to enhanced mechanical strength with respect to B{sub 4}C. The phonon frequencies and elastic constants turn out to prove the stability of the carbon-rich phase, and important fingerprints for its characterization have been identified.

  4. Protective coating for alumina-silicon carbide whisker composites

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN)

    1989-01-01T23:59:59.000Z

    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.

  5. Microstructure and properties of IN SITU toughened silicon carbide

    SciTech Connect (OSTI)

    De Jonghe, Lutgard C.; Ritchie, Robert O.; Zhang, Xiao Feng

    2003-05-01T23:59:59.000Z

    A silicon carbide with a fracture toughness as high as 9.1 MPa.m1/2 has been developed by hot pressing b-SiC powder with aluminum, boron, and carbon additions (ABC-SiC). Central in this material development has been systematic transmission electron microscopy (TEM) and mechanical characterizations. In particular, atomic-resolution electron microscopy and nanoprobe composition quantification were combined in analyzing grain boundary structure and nanoscale structural features.

  6. Ceramic composites reinforced with modified silicon carbide whiskers

    DOE Patents [OSTI]

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

    1990-01-01T23:59:59.000Z

    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.

  7. Method for removing oxide contamination from silicon carbide powders

    DOE Patents [OSTI]

    Brynestad, J.; Bamberger, C.E.

    1984-08-01T23:59:59.000Z

    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.

  8. Steam Reforming on Transition-metal Carbides from Density-functional Theory

    SciTech Connect (OSTI)

    Vojvodic, Aleksandra

    2012-05-11T23:59:59.000Z

    A screening study of the steam reforming reaction on clean and oxygen covered early transition-metal carbides surfaces is performed by means of density-functional theory calculations. It is found that carbides provide a wide spectrum of reactivities, from too reactive via suitable to too inert. Several molybdenum-based systems are identified as possible steam reforming catalysts. The findings suggest that carbides provide a playground for reactivity tuning, comparable to the one for pure metals.

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

    SciTech Connect (OSTI)

    Xia, Min; Guo, Hongyan; Ge, Changchun [Institute of Special Ceramics and Powder Metallurgy, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing (China); Institute of Powder Metallurgy and Advanced Ceramics, Southwest Jiaotong University, 111, 1st Section, Northern 2nd Ring Road, Chengdu (China); Yan, Qingzhi, E-mail: qzyan@ustb.edu.cn; Lang, Shaoting [Institute of Special Ceramics and Powder Metallurgy, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing (China)

    2014-05-14T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Van Gorder, Robert A., E-mail: rav@knights.ucf.edu [Department of Mathematics, University of Central Florida, Orlando, Florida 32816-1364 (United States)

    2014-07-15T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Zhang, Zhelin; Chen, Yanping, E-mail: yanping.chen@sjtu.edu.cn; Yang, Liu; Yuan, Xiaohui; Liu, Feng; Chen, Min; Xu, Jianqiu; Zhang, Jie [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Sheng, Zhengming [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2014-09-08T23:59:59.000Z

    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.

  12. How Filaments are Woven into the Cosmic Web

    E-Print Network [OSTI]

    J. Richard Bond; Lev Kofman; Dmitri Pogosyan

    1995-12-21T23:59:59.000Z

    Observations indicate galaxies are distributed in a filament-dominated web-like structure. Numerical experiments at high and low redshift of viable structure formation theories also show filament-dominance. We present a simple quantitative explanation of why this is so, showing that the final-state web is actually present in embryonic form in the overdensity pattern of the initial fluctuations, with nonlinear dynamics just sharpening the image. The web is largely defined by the position and primordial tidal fields of rare events in the medium, with the strongest filaments between nearby clusters whose tidal tensors are nearly aligned. Applications of the cosmic web theory to observations include probing cluster-cluster bridges by weak gravitational lensing, X-rays, and the Sunyaev-Zeldovich effect and probing high redshift galaxy-galaxy bridges by low column density Lyman alpha absorption lines.

  13. Zipping mechanism for force-generation by growing filament bundles

    E-Print Network [OSTI]

    Torsten Kuehne; Reinhard Lipowsky; Jan Kierfeld

    2011-03-02T23:59:59.000Z

    We investigate the force generation by polymerizing bundles of filaments, which form because of short-range attractive filament interactions. We show that bundles can generate forces by a zipping mechanism, which is not limited by buckling and operates in the fully buckled state. The critical zipping force, i.e. the maximal force that a bundle can generate, is given by the adhesive energy gained during bundle formation. For opposing forces larger than the critical zipping force, bundles undergo a force-induced unbinding transition. For larger bundles, the critical zipping force depends on the initial configuration of the bundles. Our results are corroborated by Monte Carlo simulations.

  14. Preparation of molybdenum carbides with multiple morphologies using surfactants as carbon sources

    SciTech Connect (OSTI)

    Wang, Hongfen, E-mail: wanghongfen11@163.com [Institute of Material Science and Engineering, Ocean University of China, Qingdao 266100 (China)] [Institute of Material Science and Engineering, Ocean University of China, Qingdao 266100 (China); Wang, Zhiqi [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101 (China)] [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101 (China); Chen, Shougang [Institute of Material Science and Engineering, Ocean University of China, Qingdao 266100 (China)] [Institute of Material Science and Engineering, Ocean University of China, Qingdao 266100 (China)

    2012-10-15T23:59:59.000Z

    Molybdenum carbides with surfactants as carbon sources were prepared using the carbothermal reduction of the appropriate precursors (molybdenum oxides deposited on surfactant micelles) at 1023 K under hydrogen gas. The carburized products were characterized using scanning electron microscopy (SEM), X-ray diffraction and BET surface area measurements. From the SEM images, hollow microspherical and rod-like molybdenum carbides were observed. X-ray diffraction patterns showed that the annealing time of carburization had a large effect on the conversion of molybdenum oxides to molybdenum carbides. And BET surface area measurements indicated that the difference of carbon sources brought a big difference in specific surface areas of molybdenum carbides. - Graphical abstract: Molybdenum carbides having hollow microspherical and hollow rod-like morphologies that are different from the conventional monodipersed platelet-like morphologies. Highlights: Black-Right-Pointing-Pointer Molybdenum carbides were prepared using surfactants as carbon sources. Black-Right-Pointing-Pointer The kinds of surfactants affected the morphologies of molybdenum carbides. Black-Right-Pointing-Pointer The time of heat preservation at 1023 K affected the carburization process. Black-Right-Pointing-Pointer Molybdenum carbides with hollow structures had larger specific surface areas.

  15. ORDER AND DISORDER IN CARBIDES AND NITRIDES Ch. H. DE NOVION and V. MAURICE

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    transition metals, rare earths and actinides react with carbon and nitrogen to form metallic carbides or nitrogen 2p atomic electron states : they may be described by a stacking of units consisting of a central and nitrides is their large composition range, for example Tico.,, to Tic,.,, for titanium mono- carbide

  16. 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.

    1997-07-01T23:59:59.000Z

    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.

  17. Nanostructured tungsten carbide catalysts for polymer electrolyte fuel cells X. G. Yanga

    E-Print Network [OSTI]

    Nanostructured tungsten carbide catalysts for polymer electrolyte fuel cells X. G. Yanga and C. Y/air polymer electrolyte fuel cell using nanoscale tungsten carbide as the anode catalyst and carbon supported, thereby creating a fundamental technology to reduce the cost of future fuel cell engines. The tungsten

  18. 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

    2014-05-27T23:59:59.000Z

    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.

  19. Development of a Robust Tri-Carbide Fueled Reactor for Multimegawatt Space Power and Propulsion Applications

    SciTech Connect (OSTI)

    Samim Anghaie; Travis W. Knight; Johann Plancher; Reza Gouw

    2004-08-11T23:59:59.000Z

    An innovative reactor core design based on advanced, mixed carbide fuels was analyzed for nuclear space power applications. Solid solution, mixed carbide fuels such as (U,Zr,Nb)c and (U,Zr, Ta)C offer great promise as an advanced high temperature fuel for space power reactors.

  20. Novel fabrication and enhanced photosensitivity of selenium filament arrays by optical-fiber thermal drawing

    E-Print Network [OSTI]

    Deng, D. S.

    We report break-up of cylindrical shell into well-ordered filament arrays by optical-fiber thermal drawing. Enhanced photosensitivity of centimeter-long crystalline-Se nano-filaments is observed and the mechanism is ...

  1. Direct Measurement of the Electron Density of Extended Femtosecond Laser Pulse-Induced Filaments

    SciTech Connect (OSTI)

    Chen, Y.-H.; Varma, S.; Antonsen, T. M.; Milchberg, H. M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

    2010-11-19T23:59:59.000Z

    We present direct time- and space-resolved measurements of the electron density of femtosecond laser pulse-induced plasma filaments. The dominant nonlinearity responsible for extended atmospheric filaments is shown to be field-induced rotation of air molecules.

  2. Closed-loop controlled filament stretching and break-up of polymer solutions

    E-Print Network [OSTI]

    Yeh, Roger, 1980-

    2005-01-01T23:59:59.000Z

    A constant true (radial) strain rate filament stretching experiment has been the Holy Grail of extensional rheological studies. These experiments are performed on a Filament Stretching Extensional Rheometer (FiSER). A ...

  3. Heat transfer to a silicon carbide/water nanofluid.

    SciTech Connect (OSTI)

    Yu, W.; France , D. M.; Smith, D. S.; Singh, D.; Timofeeva, E. V.; Routbort, J. L.; Univ. of Illinois at Chicago

    2009-07-01T23:59:59.000Z

    Heat transfer experiments were performed with a water-based nanofluid containing 170-nm silicon carbide particles at a 3.7% volume concentration and having potential commercial viability. Heat transfer coefficients for the nanofluid are presented for Reynolds numbers ranging from 3300 to 13,000 and are compared to the base fluid water on the bases of constant Reynolds number, constant velocity, and constant pumping power. Results were also compared to predictions from standard liquid correlations and a recently altered nanofluid correlation. The slip mechanisms of Brownian diffusion and thermophoresis postulated in the altered correlation were investigated in a series of heating and cooling experiments.

  4. PROPERTIES OF DEFECTS AND IMPLANTS IN Mg+ IMPLANTED SILICON CARBIDE

    SciTech Connect (OSTI)

    Jiang, Weilin; Zhu, Zihua; Varga, Tamas; Bowden, Mark E.; Manandhar, Sandeep; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2013-09-25T23:59:59.000Z

    As a candidate material for fusion reactor designs, silicon carbide (SiC) under high-energy neutron irradiation undergoes atomic displacement damage and transmutation reactions that create magnesium as one of the major metallic products. The presence of Mg and lattice disorder in SiC is expected to affect structural stability and degrade thermo-mechanical properties that could limit SiC lifetime for service. We have initiated a combined experimental and computational study that uses Mg+ ion implantation and multiscale modeling to investigate the structural and chemical effects in Mg implanted SiC and explore possible property degradation mechanisms.

  5. 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)

    1994-01-01T23:59:59.000Z

    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.

  6. Optical and electronic properties of two dimensional graphitic silicon carbide

    E-Print Network [OSTI]

    Lin, Xiao; Lin, Shisheng; Hakro, Ayaz Ali; Cao, Te; Chen, Hongsheng; Zhang, Baile

    2012-01-01T23:59:59.000Z

    Optical and electronic properties of two dimensional few layers graphitic silicon carbide (GSiC), in particular monolayer and bilayer, are investigated by density functional theory and found different from that of graphene and silicene. Monolayer GSiC has direct bandgap while few layers exhibit indirect bandgap. The bandgap of monolayer GSiC can be tuned by an in-plane strain. Properties of bilayer GSiC are extremely sensitive to the interlayer distance. These predictions promise that monolayer GSiC could be a remarkable candidate for novel type of light-emitting diodes utilizing its unique optical properties distinct from graphene, silicene and few layers GSiC.

  7. Method of fabricating silicon carbide coatings on graphite surfaces

    DOE Patents [OSTI]

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

    1994-07-26T23:59:59.000Z

    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.

  8. Z .Surface and Coatings Technology 130 2000 164 172 Production of high-density Ni-bonded tungsten carbide

    E-Print Network [OSTI]

    Ghoniem, Nasr M.

    Z .Surface and Coatings Technology 130 2000 164 172 Production of high-density Ni-bonded tungsten spraying; Nickel; Tungsten carbide 1. Introduction 1.1. General Since the mid-1990s, the market share of cemented Z .carbides has surpassed that of high-speed steels HSS , Z .with tungsten carbide WC having 50

  9. Characterization of terahertz emission from a dc-biased filament in air

    SciTech Connect (OSTI)

    Chen Yanping; Wang Tiejun; Marceau, Claude; Chin, See Leang [Centre d'Optique, Photonique et Laser (COPL), and Departement de Physique, de genie physique et d'optique, Universite Laval, Quebec, Quebec G1V 0A6 (Canada); Theberge, Francis; Chateauneuf, Marc; Dubois, Jacques [Defence Research and Development Canada-Valcartier, 2459 Pie-XI Blvd. North, Quebec, Quebec G3J 1X5 (Canada); Kosareva, Olga [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation)

    2009-09-07T23:59:59.000Z

    We demonstrate that the terahertz emission from a dc-biased filament can be regarded as a sum of an elliptically polarized terahertz source (generated by a filament without external electric field) and a linearly polarized terahertz source induced by the external electric field applied to the filament. The peak frequency and linewidth of the linearly polarized terahertz source are related to the average plasma density of the filament.

  10. Bright X-ray galaxies in SDSS filaments

    E-Print Network [OSTI]

    Tugay, A V

    2013-01-01T23:59:59.000Z

    Eighteen bright X-ray emitting galaxies were found in nearby filaments within SDSS region. Basic X-ray spectral parameters were estimated for these galaxies using power law model with photoelectric absorption. A close pair of X-ray galaxies was found.

  11. Micromechanical Modeling of Filament Wound Cement-Based Composites

    E-Print Network [OSTI]

    Mobasher, Barzin

    Micromechanical Modeling of Filament Wound Cement-Based Composites B. Mobasher, M.ASCE1 Abstract: A theoretical model to predict the response of laminated cement-based composites is developed. The micromechanical model simulates the mechanical response of a multilayer cement-based composite laminate under

  12. actin filament dynamics: Topics by E-print Network

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

    actin filament dynamics First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Role of ATP-Hydrolysis in the...

  13. Cell Host & Microbe Actin and Intermediate Filaments Stabilize

    E-Print Network [OSTI]

    Valdivia, Raphael

    Cell Host & Microbe Article Actin and Intermediate Filaments Stabilize the Chlamydia trachomatis inclusions within a cell leading to the highest yield of EBs (Wilson et al., 2006). The expansion of inclu- sions is likely fueled by the acquisition of membrane lipids from Golgi-derived vesicles (Carabeo et al

  14. The role of filament activation in a solar eruption

    E-Print Network [OSTI]

    da Costa, Fatima Rubio; Fletcher, Lyndsay; Romano, Paolo; Labrosse, Nicolas

    2014-01-01T23:59:59.000Z

    Observations show that the mutual relationship between filament eruptions and solar flares cannot be described in terms of an unique scenario. In some cases, the eruption of a filament appears to trigger a flare, while in others the observations are more consistent with magnetic reconnection that produces both the flare observational signatures (e.g., ribbons, plasma jets, post-flare loops, etc.) and later the destabilization and eruption of a filament. We study an event which occurred in NOAA 8471, where a flare and the activation of (at least) two filaments were observed on 28 February 1999. By using imaging data acquired in the 1216, 1600, 171 and 195 \\AA\\ TRACE channels and by BBSO in the continnum and in H$\\alpha$, a morphological study of the event is carried out. Using TRACE 1216 and 1600 \\AA\\ data, an estimate of the "pure" Ly$\\alpha$ power is obtained. The extrapolation of the magnetic field lines is done using the SOHO/MDI magnetograms and assuming a potential field. The potential magnetic field ext...

  15. The genome sequence of the filamentous fungus Neurospora crassa

    E-Print Network [OSTI]

    Kellis, Manolis

    The genome sequence of the filamentous fungus Neurospora crassa James E. Galagan1 , Sarah E. Calvo1 , Edward L. Braun10 , Alex Zelter4,11 , Ulrich Schulte12 , Gregory O. Kothe3 , Gregory Jedd13 , Werner Mewes14,15 , Chuck Staben16 , Edward Marcotte17 , David Greenberg18 , Alice Roy1 , Karen Foley1 , Jerome

  16. Polymerization and Structure of Nucleotide-free Actin Filaments

    E-Print Network [OSTI]

    Polymerization and Structure of Nucleotide-free Actin Filaments Enrique M. De La Cruz1,2 , Anna of nucleotide-free actin (NFA). First, actin lacking bound nucleotide denatures rapidly without stabilizing of the bound nucleotide. We used apyrase, EDTA and Dowex-1 to prepare actin that is stable in sucrose and $99

  17. The solar photospheric abundance of hafnium and thorium. Results from CO5BOLD 3D hydrodynamic model atmospheres

    E-Print Network [OSTI]

    Elisabetta Caffau; L. Sbordone; H. -G. Ludwig; P. Bonifacio; M. Steffen; N. T. Behara

    2008-03-25T23:59:59.000Z

    Context: The stable element hafnium (Hf) and the radioactive element thorium (Th) were recently suggested as a suitable pair for radioactive dating of stars. The applicability of this elemental pair needs to be established for stellar spectroscopy. Aims: We aim at a spectroscopic determination of the abundance of Hf and Th in the solar photosphere based on a \\cobold 3D hydrodynamical model atmosphere. We put this into a wider context by investigating 3D abundance corrections for a set of G- and F-type dwarfs. Method: High-resolution, high signal-to-noise solar spectra were compared to line synthesis calculations performed on a solar CO5BOLD model. For the other atmospheres, we compared synthetic spectra of CO5BOLD 3D and associated 1D models. Results: For Hf we find a photospheric abundance A(Hf)=0.87+-0.04, in good agreement with a previous analysis, based on 1D model atmospheres. The weak Th ii 401.9 nm line constitutes the only Th abundance indicator available in the solar spectrum. It lies in the red wing of an Ni-Fe blend exhibiting a non-negligible convective asymmetry. Accounting for the asymmetry-related additional absorption, we obtain A(Th)=0.09+-0.03, consistent with the meteoritic abundance, and about 0.1 dex lower than obtained in previous photospheric abundance determinations. Conclusions: Only for the second time, to our knowledge, has am non-negligible effect of convective line asymmetries on an abundance derivation been highlighted. Three-dimensional hydrodynamical simulations should be employed to measure Th abundances in dwarfs if similar blending is present, as in the solar case. In contrast, 3D effects on Hf abundances are small in G- to mid F-type dwarfs and sub-giants, and 1D model atmospheres can be conveniently used.

  18. Replacing precious metals with carbide catalysts for hydrogenation reactions

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

    Ruijun, Hou [Tsinghua Univ., Beijing (China). Beijing Key Lab. of Green Chemical Reaction Engineering and Technology; Columbia Univ., New York, NY (United States); Chen, Jingguang G. [Columbia Univ., New York, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States); Chang, Kuan [Tsinghua Univ., Beijing (China). Beijing Key Lab. of Green Chemical Reaction Engineering and Technology; Wang, Tiefeng [Tsinghua Univ., Beijing (China). Beijing Key Lab. of Green Chemical Reaction Engineering and Technology

    2015-04-01T23:59:59.000Z

    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.

  19. 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

    2015-04-01T23:59:59.000Z

    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 Nimore »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.« less

  20. Effect of laser beam filamentation on coexisting stimulated Raman and Brillouin scattering

    SciTech Connect (OSTI)

    Sharma, R. P.; Vyas, Ashish; Kishor Singh, Ram [Centre for Energy Studies, IIT, Delhi 110016 (India)] [Centre for Energy Studies, IIT, Delhi 110016 (India)

    2013-10-15T23:59:59.000Z

    This paper presents the study of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) when both of these processes are coexisting and pump laser beam initial power is more than filamentation threshold. On account of the ponderomotive nonlinearity, the pump laser beam gets filamented, and both the scattering processes (SRS and SBS) get affected. Simultaneous presence of SRS and SBS (five wave interaction case) also affect the pump filamentation process due to pump depletion. Both the scattering processes (SRS and SBS) are enhanced due to filamentation of laser beam. Results are also compared with the three wave interaction case (either SRS or SBS) with and without filamentation.

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

    DOE Patents [OSTI]

    Milewski, J.V.

    1982-06-18T23:59:59.000Z

    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.

  2. DECODING THE MESSAGE FROM METEORITIC STARDUST SILICON CARBIDE GRAINS

    SciTech Connect (OSTI)

    Lewis, Karen M.; Lugaro, Maria; Gibson, Brad K.; Pilkington, Kate, E-mail: maria.lugaro@monash.edu, E-mail: karen.michelle.lewis@gmail.com, E-mail: bkgibson@uclan.ac.uk, E-mail: kpilkington@uclan.ac.uk [Monash Centre for Astrophysics (MoCA), Monash University, Clayton VIC 3800 (Australia)

    2013-05-01T23:59:59.000Z

    Micron-sized stardust grains that originated in ancient stars are recovered from meteorites and analyzed using high-resolution mass spectrometry. The most widely studied type of stardust is silicon carbide (SiC). Thousands of these grains have been analyzed with high precision for their Si isotopic composition. Here we show that the distribution of the Si isotopic composition of the vast majority of stardust SiC grains carries the imprints of a spread in the age-metallicity distribution of their parent stars and of a power-law increase of the relative formation efficiency of SiC dust with the metallicity. 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 modeling of dust condensation in stellar winds as a function of the metallicity.

  3. Epitaxial Growth and Characterization of Silicon Carbide Films

    SciTech Connect (OSTI)

    Dhanaraj,G.; Dudley, M.; Chen, Y.; Ragothamachar, B.; Wu, B.; Zhang, H.

    2006-01-01T23:59:59.000Z

    Silicon carbide (SiC) epitaxial layers have been grown in a chemical vapor deposition (CVD) system designed and fabricated in our laboratory. Silicon tetrachloride-propane as well as silane-propane were used as precursor gases. The hot zone was designed based on simulation by using numerical modeling. Growth rates up to 200 {mu}m could be achieved. A new growth-assisted hydrogen etching was developed to show the distribution of the micropipes present in the substrate. Higher growth rate was observed on off-axis (0 0 0 1) 4 H SiC compared to the on-axis (0 0 0 1) wafer and growth mechanism was explained.

  4. The world`s first commercial iron carbide plant

    SciTech Connect (OSTI)

    Prichard, L.C.; Schad, D.

    1995-12-01T23:59:59.000Z

    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.

  5. In situ electrochemical dilatometry of carbide-derived carbons

    SciTech Connect (OSTI)

    Hantel, M M [Paul Scherrer Institut, Villigen, Switzerland; Presser, Volker [ORNL; Gogotsi, Yury [ORNL

    2011-01-01T23:59:59.000Z

    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.

  6. In-situ Electrochemical Dilatometry of Carbide-derived Carbons

    SciTech Connect (OSTI)

    Hantel, M. M.; Presser, V.; Kotz, R.; Gogotsi, Y.

    2011-01-01T23:59:59.000Z

    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 Å. 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 Å, which could be described with pore swelling.

  7. High surface area silicon carbide-coated carbon aerogel

    DOE Patents [OSTI]

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

    2014-01-14T23:59:59.000Z

    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.

  8. The outer filament of Centaurus A as seen by MUSE

    E-Print Network [OSTI]

    Santoro, F; Morganti, R; Oosterloo, T A; Tremblay, G

    2015-01-01T23:59:59.000Z

    We investigate signatures of a jet-interstellar medium (ISM) interaction using optical integral-field observations of the so-called outer filament near Centaurus A, expanding on previous results obtained on a more limited area. Using the Multi Unit Spectroscopic Explorer (MUSE) on the VLT during science verification, we observed a significant fraction of the brighter emitting gas across the outer filament. The ionized gas shows complex morphology with compact blobs, arc-like structures and diffuse emission. Based on the kinematics, we identified three main components. The more collimated component is oriented along the direction of the radio jet. The other two components exhibit diffuse morphology together with arc-like structures also oriented along the radio jet direction. Furthermore, the ionization level of the gas is found to decrease from the more collimated component to the more diffuse components. The morphology and velocities of the more collimated component confirm our earlier results that the outer...

  9. Synthesis of high purity sinterable silicon carbide powder

    SciTech Connect (OSTI)

    Boecker, W.D.; Mehosky, B.L.; Rogers, R.S.C.; Storm, R.S.; Venkateswaran, V. (Carborundum Co., Niagara Falls, NY (USA). Structural Ceramics Div.)

    1989-11-01T23:59:59.000Z

    High purity, submicron silicon carbide powders were produced via gas phase synthesis using a hydrogen/argon plasma. Two test facilities were constructed, a bench-scale unit and a larger pilot scale reactor. Three candidate silicon sources were evaluated:silicon tetrachloride (SiCl{sub 4}). dimethyldichlorosilane (CH{sub 3}){sub 2}(SiCl{sub 2}) and methyltrichlorosilane (CH{sub 3}SiCl{sub 3}). Product powders were evaluated on the basis of pressureless sinterability, surface area, agglomeration, particle size distribution, phase distribution and chemistry. Three commercial powders, Starck A10, Starck B10, and Carborundum submicron alpha silicon carbide, were also evaluated for comparison to the product powders. Powders were reproducibly synthesized at a rate of one pound per hour for standard run times of five hours. Product powders exhibited chemical and physical properties equal to or exceeding the commercial powders evaluated. In limited attempts to pressureless sinter the product powders, densities of 91% of theoretical were obtained with as-produced powder. Post-processing permitted densities in excess of 97% of theoretical. X-ray diffraction of the product indicates that the product powders are primarily beta poly-types, with traces of alpha present. Increased production rates to a target level of seven pounds per hour were not possible due to current transients produced by the pilot scale power supply. Extensive unsuccessful efforts to reduce or eliminate the transients are described. Low recovered product yields resulted from a failure of a product collection filter that was not discovered until the completion of the project.

  10. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    SciTech Connect (OSTI)

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

    2012-08-01T23:59:59.000Z

    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.

  11. Radiofrequency plasma antenna generated by femtosecond laser filaments in air

    SciTech Connect (OSTI)

    Brelet, Y.; Houard, A.; Point, G.; Prade, B.; Carbonnel, J.; Andre, Y.-B.; Mysyrowicz, A. [Laboratoire d'Optique Appliquee, ENSTA ParisTech, Ecole Polytechnique, CNRS, 91761 Palaiseau (France); Arantchouk, L. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, Palaiseau (France); Pellet, M. [Etat-major de la Marine Nationale, Paris (France)

    2012-12-24T23:59:59.000Z

    We demonstrate tunable radiofrequency emission from a meter-long linear plasma column produced in air at atmospheric pressure. A short-lived plasma column is initially produced by femtosecond filamentation and subsequently converted into a long-lived discharge column by application of an external high voltage field. Radiofrequency excitation is fed to the plasma by induction and detected remotely as electromagnetic radiation by a classical antenna.

  12. Evolution of Genes and Gene Networks in Filamentous Fungi

    E-Print Network [OSTI]

    Greenwald, Charles Joaquin

    2011-10-21T23:59:59.000Z

    ........................................................................... 62 1 CHAPTER I INTRODUCTION The Pezizomycotina, a subphylum within the phylum Ascomycota, commonly known as the filamentous fungi, are a diverse group of important organisms. There are over 60,000 species representing between 210... in a secondary metabolite gene cluster responsible for roles in the loline biosynthetic pathway of Epichlo? and Neotyphodium species. Two genes lolC and lolD were of interest because: 1) lolines are unique to these closely related species; and 8 2...

  13. Persistence of activity in noisy motor-filament assemblies

    E-Print Network [OSTI]

    Raghunath Chelakkot; Arvind Gopinath; L. Mahadevan

    2015-01-12T23:59:59.000Z

    Long, elastic filaments cross-linked and deformed by active molecular motors occur in various natural settings. The overall macroscopic mechanical response of such a composite network depends on the coupling between the active and the passive properties of the underlying constituents and nonlocal interactions between different parts of the composite. In a simple one dimensional system, using a mean field model, it has been shown that the combination of motor activity and finite filament extensibility yields a persistence length scale over which strain decays. Here we study a similar system, in the complementary limit of strong noise and moderate extensibility, using Brownian multi-particle collision dynamics-based numerical simulations that includes the coupling between motor kinetics and local filament extensibility. While the numerical model shows deviations from the mean field predictions due to the presence of strong active noise caused by the variations in individual motor activity, several qualitative features are still retained. Specifically, for fixed motor attachment and detachment rates, the decay is length is set by the ratio of the passive elasticity to the active shear resistance generated by attached motors. Our study generalizes the notion of persistence in passive thermal systems to actively driven systems with testable predictions.

  14. 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. [Department of Physics, University of Michigan, Ann Arbor, MI (United States); Sheldon, Erin S. [Brookhaven National Laboratory, Upton, NY (United States)

    2013-08-20T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    2004-07-20T23:59:59.000Z

    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.

  16. Behavior of triplex silicon carbide fuel cladding designs tested under simulated PWR conditions

    E-Print Network [OSTI]

    Stempien, John D. (John Dennis)

    2011-01-01T23:59:59.000Z

    A silicon carbide (SiC) fuel cladding for LWRs may allow a number of advances, including: increased safety margins under transients and accident scenarios, such as loss of coolant accidents; improved resource utilization ...

  17. Response of Nanocrystalline 3C Silicon Carbide to Heavy-Ion Irradiatio...

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

    Citation: Jiang W, H Wang, I Kim, IT Bae, G Li, P Nachimuthu, Z Zhu, Y Zhang, and WJ Weber.2009."Response of Nanocrystalline 3C Silicon Carbide to Heavy-Ion...

  18. Reactor physics considerations for implementing silicon carbide cladding into a PWR environment

    E-Print Network [OSTI]

    Dobisesky, Jacob P. (Jacob Paul), 1987-

    2011-01-01T23:59:59.000Z

    Silicon carbide (SiC) offers several advantages over zirconium (Zr)-based alloys as a potential cladding material for Pressurized Water Reactors: very slow corrosion rate, ability to withstand much higher temperature with ...

  19. Microstructural changes induced by low energy heavy ion irradiation in titanium silicon carbide

    E-Print Network [OSTI]

    Boyer, Edmond

    Microstructural changes induced by low energy heavy ion irradiation in titanium silicon carbide CNRS 6622, Parc Valrose, 06108 Nice cedex 2, France ABSTRACT Low energy ion irradiation was used

  20. An assessment of silicon carbide as a cladding material for light water reactors

    E-Print Network [OSTI]

    Carpenter, David Michael

    2011-01-01T23:59:59.000Z

    An investigation into the properties and performance of a novel silicon carbide-based fuel rod cladding under PWR conditions was conducted. The novel design is a triplex, with the inner and outermost layers consisting of ...

  1. Utility-Scale Silicon Carbide Semiconductor: Monolithic Silicon Carbide Anode Switched Thyristor for Medium Voltage Power Conversion

    SciTech Connect (OSTI)

    None

    2010-09-01T23:59:59.000Z

    ADEPT Project: GeneSiC is developing an advanced silicon-carbide (SiC)-based semiconductor called an anode-switched thyristor. This low-cost, compact SiC semiconductor conducts higher levels of electrical energy with better precision than traditional silicon semiconductors. This efficiency will enable a dramatic reduction in the size, weight, and volume of the power converters and electronic devices it's used in.GeneSiC is developing its SiC-based semiconductor for utility-scale power converters. Traditional silicon semiconductors can't process the high voltages that utility-scale power distribution requires, and they must be stacked in complicated circuits that require bulky insulation and cooling hardware. GeneSiC's semiconductors are well suited for high-power applications like large-scale renewable wind and solar energy installations.

  2. 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)

    2015-01-01T23:59:59.000Z

    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 Hf–OH plays a role as an adsorption site for TEMAH. The reaction mechanism of room temperature HfO{sub 2} ALD is discussed in this paper.

  3. Characterization and refinement of carbide coating formation rates and dissolution kinetics in the Ta-C system

    SciTech Connect (OSTI)

    Rodriguez, P.J.

    1996-10-01T23:59:59.000Z

    The interaction between carbide coating formation rates and dissolution kinetics in the tantalum-carbon system was investigated. The research was driven by the need to characterize carbide coating formation rates. The characterization of the carbide coating formation rates was required to engineer an optimum processing scheme for the fabrication of the ultracorrosion-resistant composite, carbon-saturated tantalum. A packed-bed carburization process was successfully engineered and employed. The packed-bed carburization process produced consistent, predictable, and repeatable carbide coatings. A digital imaging analysis measurement process for accurate and consistent measurement of carbide coating thicknesses was developed. A process for removing the chemically stable and extremely hard tantalum-carbide coatings was also developed in this work.

  4. 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)

    2011-11-15T23:59:59.000Z

    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.

  5. 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)

    2012-08-15T23:59:59.000Z

    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.

  6. Dust-acoustic filamentation of a current-driven dusty plasma

    SciTech Connect (OSTI)

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

    2011-06-15T23:59:59.000Z

    The thermal motion effect of charged particles in the filamentation of a current-driven dusty plasma in the dust-acoustic frequency region is investigated by using the Lorentz transformed conductivity of the dusty plasma components and the total dielectric permittivity tensor of the dusty plasma in the laboratory frame. Obtaining the dispersion relation for dust-acoustic waves and considering the filamentation instability, the establishment time of the filamentation structure and the instability development threshold are derived. Moreover, it is shown that the current layer divides into separate current filaments.

  7. Sufficient conditions for the additivity of stall forces generated by multiple filaments or motors

    E-Print Network [OSTI]

    Tripti Bameta; Dipjyoti Das; Dibyendu Das; Ranjith Padinhateeri; Mandar M. Inamdar

    2015-03-23T23:59:59.000Z

    Molecular motors and cytoskeletal filaments mostly work collectively under opposing forces. This opposing force may be due to cargo carried by motors, or resistance coming from cell membrane pressing against the cytoskeletal filaments. Certain recent studies have shown that the collective maximum force (stall force) generated by multiple cytoskeletal filaments or molecular motors may not always be just a simple sum of stall force for individual filaments or motors. To understand this phenomena of excess or deficit collective force generation, we study a broad class of models of both cytoskeletal filaments and molecular motors. We argue that the stall force generated by a group of filaments or motors is additive, i.e., the stall force of N filaments(motors) is N times the stall force of one filament (motor), when the system is in equilibrium at stall. Consequently, we show that this additivity typically does not hold when the system departs from equilibrium at stall. We thus present a novel and unified understanding of existing models exhibiting such non- addivity, and generalize our arguments by developing new models that demonstrate this phenomena. We also propose a quantity similar to thermodynamic efficiency to provide a simple understanding of deviation from stall-force additivity for filament and motor collectives.

  8. Frontispiece: origin of extraordinary stability of square-planar carbon atoms in surface carbides of cobalt and nickel.

    E-Print Network [OSTI]

    Nandula, A; Trinh, QT; Saeys, M; Alexandrova, AN

    2015-01-01T23:59:59.000Z

    Carbides of Cobalt and Nickel** Anjan Nandula, Quang Thangcarbides of cobalt and nickel are exception- ally stable,C binds to cobalt and nickel with a remarkable affinity,

  9. Origin of Extraordinary Stability of Square-Planar Carbon Atoms in Surface Carbides of Cobalt and Nickel.

    E-Print Network [OSTI]

    Nandula, A; Trinh, QT; Saeys, M; Alexandrova, AN

    2015-01-01T23:59:59.000Z

    Carbides of Cobalt and Nickel** Anjan Nandula, Quang Thangcarbides of cobalt and nickel are exception- ally stable,C binds to cobalt and nickel with a remarkable affinity,

  10. Spectroscopic constants and potential energy curves of tungsten carbide

    SciTech Connect (OSTI)

    Balasubramanian, K. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)

    2000-05-01T23:59:59.000Z

    Spectroscopic constants (R{sub e},{omega}{sub e},T{sub e},{mu}{sub e}) and potential energy curves for 40 low-lying electronic states of the diatomic tungsten carbide (WC) were obtained using the complete active space multiconfiguration self-consistent field followed by the multireference singles+doubles configuration interaction and full first- and second-order configuration interaction calculations that included up to 6.4 mil configurations. Spin-orbit effects were included through the enhanced relativistic configuration interaction method described here for 28 electronic states of WC lying below {approx}20 000 cm-1. The spin-orbit splitting of the ground state of WC was found to be very large (4394 cm-1). The ground and excited electronic states of the W atom were also computed and were found to be in good agreement with the experimental data. The nature of bonding was analyzed through the composition of orbitals, leading configurations, Mulliken populations, and dipole moments. The dissociation energy of WC was computed including spin-orbit and electron correlation effects. The recent photoelectron spectra of WC{sup -} were assigned on the basis of our computed results. (c) 2000 American Institute of Physics.

  11. Evaluation of CVD silicon carbide for synchrotron radiation mirrors

    SciTech Connect (OSTI)

    Takacs, P.Z.

    1981-07-01T23:59:59.000Z

    Chemical vapor deposited silicon carbide (CVD SiC) is a recent addition to the list of materials suitable for use in the harsh environment of synchrotron radiation (SR) beam lines. SR mirrors for use at normal incidence must be ultrahigh vacuum compatible, must withstand intense x-ray irradiation without surface damage, must be capable of being polished to an extremely smooth surface finish, and must maintain surface figure under thermal loading. CVD SiC exceeds the performance of conventional optical materials in all these areas. It is, however, a relatively new optical material. Few manufacturers have experience in producing optical quality material, and few opticians have experience in figuring and polishing the material. The CVD material occurs in a variety of forms, sensitively dependent upon reaction chamber production conditions. We are evaluating samples of CVD SiC obtained commercially from various manufacturers, representing a range of deposition conditions, to determine which types of CVD material are most suitable for superpolishing. At the time of this writing, samples are being polished by several commercial vendors and surface finish characteristics are being evaluated by various analytical methods.

  12. USE OF SILICON CARBIDE MONITORS IN ATR IRRADIATION TESTING

    SciTech Connect (OSTI)

    K. L. Davis; B. Chase; T. Unruh; D. Knudson; J. L. Rempe

    2012-07-01T23:59:59.000Z

    In April 2007, the Department of Energy (DOE) designated the Advanced Test Reactor (ATR) a National Scientific User Facility (NSUF) to advance US leadership in nuclear science and technology. By attracting new users from universities, laboratories, and industry, the ATR will support basic and applied nuclear research and development and help address the nation's energy security needs. In support of this new program, the Idaho National Laboratory (INL) has developed in-house capabilities to fabricate, test, and qualify new and enhanced temperature sensors for irradiation testing. Although most efforts emphasize sensors capable of providing real-time data, selected tasks have been completed to enhance sensors provided in irradiation locations where instrumentation leads cannot be included, such as drop-in capsule and Hydraulic Shuttle Irradiation System (HSIS) or 'rabbit' locations. For example, silicon carbide (SiC) monitors are now available to detect peak irradiation temperatures between 200°C and 800°C. Using a resistance measurement approach, specialized equipment installed at INL's High Temperature Test Laboratory (HTTL) and specialized procedures were developed to ensure that accurate peak irradiation temperature measurements are inferred from SiC monitors irradiated at the ATR. Comparison examinations were completed by INL to demonstrate this capability, and several programs currently rely on SiC monitors for peak temperature detection. This paper discusses the use of SiC monitors at the ATR, the process used to evaluate them at the HTTL, and presents representative measurements taken using SiC monitors.

  13. Synthesis, thermal stability, and photocatalytic activity of nanocrystalline titanium carbide

    SciTech Connect (OSTI)

    Chen, Youjian; Zhang, Hong [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China)] [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, DeKun [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China) [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Nanomaterials and Chemistry Key Laboratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, Jianhua, E-mail: mjh820@ustc.edu [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China) [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Nanomaterials and Chemistry Key Laboratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ye, Hongnan; Qian, Gaojin; Ye, Yi [Oujiang College, Wenzhou University, Wenzhou, Zhejiang 325027 (China)] [Oujiang College, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2011-11-15T23:59:59.000Z

    Highlights: {yields} The synthesized temperature is lower than some conventional methods. {yields} These raw materials are safe; all manipulations are rather safe and convenient. {yields} The product exhibits photocatalytic activity in degradation of Rhodamine-B. -- Abstract: Titanium carbide (TiC) was prepared via one simple route by the reaction of metallic magnesium powders with titanium dioxide (TiO{sub 2}) and potassium acetate (CH{sub 3}COOK) in an autoclave at 600 {sup o}C and 8 h. Phase structure and morphology were characterized by X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). The results indicated that the product was cubic TiC, which consisted of particles with an average size of about 100 nm in diameter. The product was also studied by the thermogravimetric analysis (TGA) and its photocatalysis. It had good thermal stability and oxidation resistance below 350 {sup o}C in air. In addition, we discovered that the cubic TiC powders exhibited photocatalytic activity in degradation of Rhodamine-B (RhB) under 500 W mercury lamp light irradiation.

  14. Developing a High Thermal Conductivity Fuel with Silicon Carbide Additives

    SciTech Connect (OSTI)

    baney, Ronald; Tulenko, James

    2012-11-20T23:59:59.000Z

    The objective of this research is to increase the thermal conductivity of uranium oxide (UO{sub 2}) without significantly impacting its neutronic properties. The concept is to incorporate another high thermal conductivity material, silicon carbide (SiC), in the form of whiskers or from nanoparticles of SiC and a SiC polymeric precursor into UO{sub 2}. This is expected to form a percolation pathway lattice for conductive heat transfer out of the fuel pellet. The thermal conductivity of SiC would control the overall fuel pellet thermal conductivity. The challenge is to show the effectiveness of a low temperature sintering process, because of a UO{sub 2}-SiC reaction at 1,377°C, a temperature far below the normal sintering temperature. Researchers will study three strategies to overcome the processing difficulties associated with pore clogging and the chemical reaction of SiC and UO{sub 2} at temperatures above 1,300°C:

  15. Thermal evolution behavior of carbides and {gamma} Prime precipitates in FGH96 superalloy powder

    SciTech Connect (OSTI)

    Zhang Lin, E-mail: zhanglincsu@163.com [State Key Laboratory for Advanced Metals and Materials, Beijing Key Laboratory for Powder Metallurgy and Particulate Materials, University of Science and Technology Beijing, Beijing, 100083 (China); Liu Hengsan, E-mail: lhsj63@sohu.com [State Key Laboratory for Advanced Metals and Materials, Beijing Key Laboratory for Powder Metallurgy and Particulate Materials, University of Science and Technology Beijing, Beijing, 100083 (China); He Xinbo, E-mail: xb_he@163.com [State Key Laboratory for Advanced Metals and Materials, Beijing Key Laboratory for Powder Metallurgy and Particulate Materials, University of Science and Technology Beijing, Beijing, 100083 (China); Rafi-ud-din, E-mail: rafiuddi@gmail.com [State Key Laboratory for Advanced Metals and Materials, Beijing Key Laboratory for Powder Metallurgy and Particulate Materials, University of Science and Technology Beijing, Beijing, 100083 (China); Qu Xuanhui, E-mail: quxh@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, Beijing Key Laboratory for Powder Metallurgy and Particulate Materials, University of Science and Technology Beijing, Beijing, 100083 (China); Qin Mingli, E-mail: mlqin75@hotmail.com [State Key Laboratory for Advanced Metals and Materials, Beijing Key Laboratory for Powder Metallurgy and Particulate Materials, University of Science and Technology Beijing, Beijing, 100083 (China); Li Zhou, E-mail: zhouli621@126.com [National Key Lab of High Temperature Structural Materials, Beijing Institute of Aeronautical Materials, Beijing, 100095 (China); Zhang Guoqing, E-mail: g.zhang@126.com [National Key Lab of High Temperature Structural Materials, Beijing Institute of Aeronautical Materials, Beijing, 100095 (China)

    2012-05-15T23:59:59.000Z

    The characteristics of rapidly solidified FGH96 superalloy powder and the thermal evolution behavior of carbides and {gamma} Prime precipitates within powder particles were investigated. It was observed that the reduction of powder size and the increase of cooling rate had transformed the solidification morphologies of atomized powder from dendrite in major to cellular structure. The secondary dendritic spacing was measured to be 1.02-2.55 {mu}m and the corresponding cooling rates were estimated to be in the range of 1.4 Multiplication-Sign 10{sup 4}-4.7 Multiplication-Sign 10{sup 5} K{center_dot}s{sup -1}. An increase in the annealing temperature had rendered the phase transformation of carbides evolving from non-equilibrium MC Prime carbides to intermediate transition stage of M{sub 23}C{sub 6} carbides, and finally to thermodynamically stable MC carbides. The superfine {gamma} Prime precipitates were formed at the dendritic boundaries of rapidly solidified superalloy powder. The coalescence, growth, and homogenization of {gamma}' precipitates occurred with increasing annealing temperature. With decreasing cooling rate from 650 Degree-Sign C{center_dot}K{sup -1} to 5 Degree-Sign C{center_dot}K{sup -1}, the morphological development of {gamma} Prime precipitates had been shown to proceed from spheroidal to cuboidal and finally to solid state dendrites. Meanwhile, a shift had been observed from dendritic morphology to recrystallized structure between 900 Degree-Sign C and 1050 Degree-Sign C. Moreover, accelerated evolution of carbides and {gamma}' precipitates had been facilitated by the formation of new grain boundaries which provide fast diffusion path for atomic elements. - Highlights: Black-Right-Pointing-Pointer Microstructural characteristic of FGH96 superalloy powder was investigated. Black-Right-Pointing-Pointer The relation between microstructure, particle size, and cooling rate was studied. Black-Right-Pointing-Pointer Thermal evolution behavior of {gamma} Prime and carbides in loose FGH96 powder was studied.

  16. Inherent safety advantages of carbide fuel systems and technical issues regarding natural convection in LMRs

    SciTech Connect (OSTI)

    Barthold, W.P. [Barthold and Associates, Inc., Albuquerque, NM (United States)

    1984-08-01T23:59:59.000Z

    The scope of work is to summarize inherent safety advantages that are unique to the use of a carbide based fuel system and to summarize the technical issues regarding natural convection flow in LMFBR cores. As discussed in this report, carbide fuel provides the designer with far greater flexibility than oxide fuel. Carbide fuel systems can be designed to eliminate major accident initiators. They turn quantitative advantages into a qualitative advantage. The author proposed to LANL a series of core design and component concepts that would greatly enhance the safety of carbide over oxide systems. This report cites a series of safety advantages which potentially exist for a carbide fuel system. Natural convection issues have not been given much attention in the past. Only during the last few years has this issue been addressed in some detail. Despite claims to the contrary by some of the LMR contractors, the author does not think that the natural convection phenomena is fully understood. Some of the approximations made in natural convection transient analyses have probably a greater impact on calculated transient temperatures than the effects under investigation. Only integral in-pile experimental data and single assembly out-of-pile detailed data are available for comparisons with analytical models and correlations. Especially for derated cores, the natural convection capability of a LMR should be far superior to that of a LWR. The author ranks the natural convection capability of the LMR as the most important inherent safety feature.

  17. Formation of beads-on-a-string structures during breakup of viscoelastic filaments

    E-Print Network [OSTI]

    of Technology, Cambridge, MA 02139, USA e-mail: obasaran@purdue.edu Breakup of viscoelastic filaments is pervasive in both nature and technology. If a filament is formed by placing a drop of saliva between a thumb the growth of the bead and delays pinch-off, which leads to a relatively long-lived beaded structure. We also

  18. Averaged implicit hydrodynamic model of semiflexible filaments Preethi L. Chandran and Mohammad R. K. Mofrad*

    E-Print Network [OSTI]

    Mofrad, Mohammad R. K.

    , in order to better resolve the drag profiles along the filament. A large part of the hydrodynamic dragAveraged implicit hydrodynamic model of semiflexible filaments Preethi L. Chandran and Mohammad R 2009; published 26 March 2010 We introduce a method to incorporate hydrodynamic interaction in a model

  19. Sufficient conditions for the additivity of stall forces generated by multiple filaments or motors

    E-Print Network [OSTI]

    Bameta, Tripti; Das, Dibyendu; Padinhateeri, Ranjith; Inamdar, Mandar M

    2015-01-01T23:59:59.000Z

    Molecular motors and cytoskeletal filaments mostly work collectively under opposing forces. This opposing force may be due to cargo carried by motors, or resistance coming from cell membrane pressing against the cytoskeletal filaments. Certain recent studies have shown that the collective maximum force (stall force) generated by multiple cytoskeletal filaments or molecular motors may not always be just a simple sum of stall force for individual filaments or motors. To understand this phenomena of excess or deficit collective force generation, we study a broad class of models of both cytoskeletal filaments and molecular motors. We argue that the stall force generated by a group of filaments or motors is additive, i.e., the stall force of N filaments(motors) is N times the stall force of one filament (motor), when the system is in equilibrium at stall. Consequently, we show that this additivity typically does not hold when the system departs from equilibrium at stall. We thus present a novel and unified underst...

  20. Fitting of random tessellation models to keratin filament Michael Beil1

    E-Print Network [OSTI]

    Schmidt, Volker

    - physical properties of epithelial cells is poorly understood. This is at least partially due to a lack to Keratin Filament Networks 1 Introduction Keratins belong to the group of intermediate filament proteins proteins (Coulombe and Omary, 2002; Strnad et al., 2002). However, the knowledge about the processes

  1. Strong Enhancement of Terahertz Radiation from Laser Filaments in Air by a Static Electric Field

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Strong Enhancement of Terahertz Radiation from Laser Filaments in Air by a Static Electric Field radiation from the laser filament is highly sensitive to the presence of a transverse electric field. We observe a three order of magnitude enhancement of the terahertz (THz) energy radiated by a femtosecond

  2. Self-compression of ultra-short laser pulses down to one optical cycle by filamentation

    E-Print Network [OSTI]

    Keller, Ursula

    Self-compression of ultra-short laser pulses down to one optical cycle by filamentation A. COUAIRON 27 February 2005; in final form 2 June 2005) Theoretical studies of filamentation of ultra-short near. This suggests a very simple design for the generation of ultra-short, sub-femtosecond XUV optical pulses. 1

  3. Functional role of tropomyosin on thin filament activation and cross bridge kinetics in transgenic cardiac muscle: a model study

    E-Print Network [OSTI]

    Krishnamoorthy, Gayathri

    1999-01-01T23:59:59.000Z

    Regulation of contractile activity in cardiac muscle is a cooperative interaction between thick and thin filament sarcomeric proteins. Tropomyosin (Tm), an essential thin filament protein, interacts with troponin (Tn) and regulates muscle...

  4. Threshold irradiation dose for amorphization of silicon carbide

    SciTech Connect (OSTI)

    Snead, L.L.; Zinkle, S.J.

    1997-03-01T23:59:59.000Z

    The amorphization of silicon carbide due to ion and electron irradiation is reviewed with emphasis on the temperature-dependent critical dose for amorphization. The effect of ion mass and energy on the threshold dose for amorphization is summarized, showing only a weak dependence near room temperature. Results are presented for 0.56 MeV silicon ions implanted into single crystal 6H-SiC as a function of temperature and ion dose. From this, the critical dose for amorphization is found as a function of temperature at depths well separated from the implanted ion region. Results are compared with published data generated using electrons and xenon ions as the irradiating species. High resolution TEM analysis is presented for the Si ion series showing the evolution of elongated amorphous islands oriented such that their major axis is parallel to the free surface. This suggests that surface or strain effects may be influencing the apparent amorphization threshold. Finally, a model for the temperature threshold for amorphization is described using the Si ion irradiation flux and the fitted interstitial migration energy which was found to be {approximately}0.56eV. This model successfully explains the difference in the temperature dependent amorphization behavior of SiC irradiated with 0.56 MeV Si{sup +} at 1 x 10{sup -3} dpa/s and with fission neutrons irradiated at 1 x 10{sup -6} dpa/s irradiated to 15 dpa in the temperature range of {approximately}340{+-}10K.

  5. Above: Power deposition in the superconducting magnets and the tungsten-carbide + water shield inside them, according to a

    E-Print Network [OSTI]

    McDonald, Kirk

    Above: Power deposition in the superconducting magnets and the tungsten-carbide + water shield FOR A MUON COLLIDER (TUP265, PAC11) The concept for a muon-production system for a muon collider (or neutrino Magnet shield WC beads + water Shield must dissipate 2.4 MW Superconducting magnets tungsten-carbide (WC

  6. Effect of Heat Treatment on Silicon Carbide Based Joining Materials for Fusion Energy

    SciTech Connect (OSTI)

    Lewinsohn, Charles A.; Jones, Russell H.; Nozawa, T.; Kotani, M.; Kishimoto, H.; Katoh, Y.; Kohyama, A.

    2001-10-01T23:59:59.000Z

    Two general approaches to obtaining silicon carbide-based joint materials were used. The first method relies on reactions between silicon and carbon to form silicon carbide, or to bond silicon carbide powders together. The second method consists of pyrolysing a polycarbosilane polymer to yield an amorphous, covalently bonded material. In order to assess the long-term durability of the joint materials, various heat treatments were performed and the effects on the mechanical properties of the joints were measured. Although the joints derived from the polycarbosilane polymer were not the strongest, the value of strength measured was not affected by heat treatment. On the other hand, the value of the strength of the reaction-based joints was affected by heat treatment, indicating the presence of residual stresses or unreacted material subsequent to processing. Further investigation of reaction-based joining should consist of detailed microscopic studies; however, continued study of joints derived from polymers is also warranted.

  7. 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

    2013-01-22T23:59:59.000Z

    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.

  8. Steam reforming on transition-metal carbides from density-functional theory

    E-Print Network [OSTI]

    Vojvodic, Aleksandra

    2009-01-01T23:59:59.000Z

    A screening study of the steam reforming reaction (CH_4 + H_2O -> CO + 3H_2) on early transition-metal carbides (TMC's) is performed by means of density-functional theory calculations. The set of considered surfaces includes the alpha-Mo_2C(100) surfaces, the low-index (111) and (100) surfaces of TiC, VC, and delta-MoC, and the oxygenated alpha-Mo_2C(100) and TMC(111) surfaces. It is found that carbides provide a wide spectrum of reactivities towards the steam reforming reaction, from too reactive via suitable to too inert. The reactivity is discussed in terms of the electronic structure of the clean surfaces. Two surfaces, the delta-MoC(100) and the oxygen passivated alpha-Mo_2C(100) surfaces, are identified as promising steam reforming catalysts. These findings suggest that carbides provide a playground for reactivity tuning, comparable to the one for pure metals.

  9. Diamond growth on WC-Co substrates by hot filament chemical vapor deposition: Effect of filamentsubstrate separation

    E-Print Network [OSTI]

    Bristol, University of

    Polycrystalline diamond films have been grown by hot filament (HF) chemical vapor deposition on WC-Co bar is an established technique for growing hard, wear- resistant polycrystalline diamond films on a range of substratesDiamond growth on WC-Co substrates by hot filament chemical vapor deposition: Effect of filament

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

    SciTech Connect (OSTI)

    Garraway, R. [Nucor Iron Carbide Inc., Point Lisas (Trinidad and Tobago)

    1996-12-31T23:59:59.000Z

    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.

  11. 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)

    1995-01-01T23:59:59.000Z

    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.

  12. Inertial blob-hole symmetry breaking in magnetised plasma filaments

    E-Print Network [OSTI]

    Kendl, Alexander

    2015-01-01T23:59:59.000Z

    Symmetry breaking between the propagation velocities of magnetised plasma filaments with large positive (blob) and negative (hole) amplitudes, as implied by a dimensional analysis scaling, is studied with global ("full-n") non-Boussinesq gyrofluid computations, which include finite inertia effects through nonlinear polarisation. Interchange blobs on a flat density background have higher inertia and propagate more slowly than holes. In the presence of a large enough density gradient, the effect is reversed: blobs accelerate down the gradient and holes are slowed in their propagation up the gradient. Drift wave blobs spread their initial vorticity rapidly into a fully developed turbulent state, whereas primary holes can remain coherent for many eddy turnover times. The results bear implications for plasma edge zonal flow evolution and tokamak scrape-off-layer transport.

  13. Dry soldering with hot filament produced atomic hydrogen

    DOE Patents [OSTI]

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

    1995-04-25T23:59:59.000Z

    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.

  14. Force generation by Myosin II Filaments in Compliant Networks

    E-Print Network [OSTI]

    Samantha Stam; Jon Alberts; Margaret L. Gardel; Edwin Munro

    2014-07-08T23:59:59.000Z

    Myosin II isoforms with varying mechanochemistry and filament size interact with filamentous actin (F-actin) networks to generate contractile forces in cells. How their properties control force production in environments with varying stiffness is poorly understood. Here, we incorporated literature values for properties of myosin II isoforms into a cross-bridge model. Similar actin gliding speeds and force-velocity curves expected from previous experiments were observed. Motor force output on an elastic load was regulated by two timescales--that of their attachment to F-actin, which varied sharply with the ensemble size, motor duty ratio, and external load, and that of force build up, which scaled with ensemble stall force, gliding speed, and load stiffness. While such regulation did not require force-dependent kinetics, the myosin catch bond produced positive feedback between attachment time and force to trigger switch-like transitions from short attachments and small forces to high force-generating runs at threshold parameter values. Parameters representing skeletal muscle myosin, non-muscle myosin IIB, and non-muscle myosin IIA revealed distinct regimes of behavior respectively: (1) large assemblies of fast, low-duty ratio motors rapidly build stable forces over a large range of environmental stiffness, (2) ensembles of slow, high-duty ratio motors serve as high-affinity cross-links with force build-up times that exceed physiological timescales, and (3) small assemblies of low-duty ratio motors operating at intermediate speeds may respond sharply to changes in mechanical context--at low forces or stiffness, they serve as low affinity cross-links but they can transition to effective force production via the positive feedback mechanism described above. These results reveal how myosin isoform properties may be tuned to produce force and respond to mechanical cues in their environment.

  15. High Metallicity, Photoionised Gas in Intergalactic Large-Scale Filaments

    E-Print Network [OSTI]

    Bastien Aracil; Todd M. Tripp; David V. Bowen; Jason X. Proschaska; Hsiao-Wen Chen; Brenda L. Frye

    2006-08-21T23:59:59.000Z

    We present high-resolution UV spectra of absorption-line systems toward the low-z QSO HS0624+6907 (z=0.3700). Coupled with spectroscopic galaxy redshifts, we find that many of these absorbers are integalactic gas clouds distributed within large-scale structures. The gas is cool (T0.9). STIS data reveal a cluster of 13 HI Lyman alpha lines within a 1000 km/s interval at z=0.0635. We find 10 galaxies at this redshift with impact parameters ranging from 135 h^-1 kpc to 1.37 h^-1 Mpc. We attribute the HI Lya absorptions to intragroup medium gas, possibly from a large-scale filament viewed along its long axis. Remarkably, the metallicity is near-solar, [M/H] = -0.05 +/- 0.4 (2 sigma uncertainty), yet the nearest galaxy which might pollute the IGM is at least 135 h_70^-1 kpc away. Tidal stripping from nearby galaxies appears to be the most likely origin of this highly enriched, cool gas. More than six Abell galaxy clusters are found within 4 degree of the sight line suggesting that the QSO line of sight passes near a node in the cosmic web. At z~0.077, we find absorption systems as well as galaxies at the redshift of the nearby clusters Abell 564 and Abell 559. We conclude that the sight line pierces a filament of gas and galaxies feeding into these clusters. The absorber at z_abs = 0.07573 associated with Abell 564/559 also has a high metallicity with [C/H] > -0.6, but again the closest galaxy is relatively far from the sight line (293 h^-1 kpc).

  16. AC Loss Reduction in Filamentized YBCO Coated Conductors with Virtual Transverse Cross-cuts

    SciTech Connect (OSTI)

    Zhang, Yifei [ORNL; Duckworth, Robert C [ORNL; Ha, Tam T [ORNL; List III, Frederick Alyious [ORNL; Gouge, Michael J [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; X, Xiong, [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2011-01-01T23:59:59.000Z

    While the performance of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO)-based coated conductors under dc currents has improved significantly in recent years, filamentization is being investigated as a technique to reduce ac loss so that the 2nd generation (2G) high temperature superconducting (HTS) wires can also be utilized in various ac power applications such as cables, transformers and fault current limiters. Experimental studies have shown that simply filamentizing the superconducting layer is not effective enough to reduce ac loss because of incomplete flux penetration in between the filaments as the length of the tape increases. To introduce flux penetration in between the filaments more uniformly and further reduce the ac loss, virtual transverse cross-cuts were made in superconducting filaments of the coated conductors fabricated using the metal organic chemical vapor deposition (MOCVD) method. The virtual transverse cross-cuts were formed by making cross-cuts (17 - 120 {micro}m wide) on the IBAD (ion beam assisted deposition)-MgO templates using laser scribing followed by depositing the superconducting layer ({approx} 0.6 {micro}m thick). AC losses were measured and compared for filamentized conductors with and without the cross-cuts under applied peak ac fields up to 100 mT. The results were analyzed to evaluate the efficacy of filament decoupling and the feasibility of using this method to achieve ac loss reduction.

  17. Analytical and experimental evaluation of joining silicon carbide to silicon carbide and silicon nitride to silicon nitride for advanced heat engine applications Phase 2. Final report

    SciTech Connect (OSTI)

    Sundberg, G.J.; Vartabedian, A.M.; Wade, J.A.; White, C.S. [Norton Co., Northboro, MA (United States). Advanced Ceramics Div.

    1994-10-01T23:59:59.000Z

    The purpose of joining, Phase 2 was to develop joining technologies for HIP`ed Si{sub 3}N{sub 4} with 4wt% Y{sub 2}O{sub 3} (NCX-5101) and for a siliconized SiC (NT230) for various geometries including: butt joins, curved joins and shaft to disk joins. In addition, more extensive mechanical characterization of silicon nitride joins to enhance the predictive capabilities of the analytical/numerical models for structural components in advanced heat engines was provided. Mechanical evaluation were performed by: flexure strength at 22 C and 1,370 C, stress rupture at 1,370 C, high temperature creep, 22 C tensile testing and spin tests. While the silicon nitride joins were produced with sufficient integrity for many applications, the lower join strength would limit its use in the more severe structural applications. Thus, the silicon carbide join quality was deemed unsatisfactory to advance to more complex, curved geometries. The silicon carbide joining methods covered within this contract, although not entirely successful, have emphasized the need to focus future efforts upon ways to obtain a homogeneous, well sintered parent/join interface prior to siliconization. In conclusion, the improved definition of the silicon carbide joining problem obtained by efforts during this contract have provided avenues for future work that could successfully obtain heat engine quality joins.

  18. The origin of 2.7 eV luminescence and 5.2 eV excitation band in hafnium oxide

    SciTech Connect (OSTI)

    Perevalov, T. V., E-mail: timson@isp.nsc.ru [A. V. Rzhanov Institute of Semiconductor Physics of SB RAS, 13 Lavrentieva Ave, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk (Russian Federation); Aliev, V. Sh.; Gritsenko, V. A. [A. V. Rzhanov Institute of Semiconductor Physics of SB RAS, 13 Lavrentieva Ave, 630090 Novosibirsk (Russian Federation); Saraev, A. A. [Boreskov Institute of Catalysis of SB RAS, 5 Lavrentieva Ave, 630090 Novosibirsk (Russian Federation); Kaichev, V. V. [Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk (Russian Federation); Boreskov Institute of Catalysis of SB RAS, 5 Lavrentieva Ave, 630090 Novosibirsk (Russian Federation); Ivanova, E. V.; Zamoryanskaya, M. V. [Ioffe Physicotechnical Institute of RAS, 26 Politechnicheskaya St., 194021 St. Petersburg (Russian Federation)

    2014-02-17T23:59:59.000Z

    The origin of a blue luminescence band at 2.7 eV and a luminescence excitation band at 5.2 eV of hafnia has been studied in stoichiometric and non-stoichiometric hafnium oxide films. Experimental and calculated results from the first principles valence band spectra showed that the stoichiometry violation leads to the formation of the peak density of states in the band gap caused by oxygen vacancies. Cathodoluminescence in the non-stoichiometric film exhibits a band at 2.65 eV that is excited at the energy of 5.2 eV. The optical absorption spectrum calculated for the cubic phase of HfO{sub 2} with oxygen vacancies shows a peak at 5.3?eV. Thus, it could be concluded that the blue luminescence band at 2.7?eV and HfO{sub x} excitation peak at 5.2?eV are due to oxygen vacancies. The thermal trap energy in hafnia was estimated.

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

    SciTech Connect (OSTI)

    Miyamoto, N., E-mail: nmiyamot@mail.doshisha.ac.jp; Okajima, Y.; Wada, M. [Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)] [Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)

    2014-02-15T23:59:59.000Z

    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.

  20. Benefits of Silicon Carbide Schottky Diodes in Boost APFC Operating in CCM

    E-Print Network [OSTI]

    Benefits of Silicon Carbide Schottky Diodes in Boost APFC Operating in CCM Sam Ben solution to Boost APFC stage operating under CCM conditions. I. Introduction Boost derived Active Power true when the APFC stage operates in the Continuous Current Mode (CCM) in which the diode current does

  1. Standard specification for nuclear-grade aluminum oxide-boron carbide composite pellets

    E-Print Network [OSTI]

    American Society for Testing and Materials. Philadelphia

    2005-01-01T23:59:59.000Z

    1.1 This specification applies to pellets composed of mixtures of aluminum oxide and boron carbide that may be ultimately used in a reactor core, for example, in neutron absorber rods. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

  2. Towards new binary compounds: Synthesis of amorphous phosphorus carbide by pulsed laser deposition

    SciTech Connect (OSTI)

    Hart, Judy N., E-mail: Judy.Hart@bristol.ac.uk [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); May, Paul W.; Allan, Neil L. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom)] [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Hallam, Keith R. [Interface Analysis Centre, University of Bristol, 121 St. Michaels Hill, Bristol BS2 8BS (United Kingdom)] [Interface Analysis Centre, University of Bristol, 121 St. Michaels Hill, Bristol BS2 8BS (United Kingdom); Claeyssens, Frederik [Kroto Research Institute, Department of Materials Science and Engineering, University of Sheffield, Broad Lane, Sheffield S3 7HQ (United Kingdom)] [Kroto Research Institute, Department of Materials Science and Engineering, University of Sheffield, Broad Lane, Sheffield S3 7HQ (United Kingdom); Fuge, Gareth M.; Ruda, Michelle [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom)] [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Heard, Peter J. [Interface Analysis Centre, University of Bristol, 121 St. Michaels Hill, Bristol BS2 8BS (United Kingdom)] [Interface Analysis Centre, University of Bristol, 121 St. Michaels Hill, Bristol BS2 8BS (United Kingdom)

    2013-02-15T23:59:59.000Z

    We have recently undertaken comprehensive computational studies predicting possible crystal structures of the as yet unknown phosphorus carbide as a function of composition. In this work, we report the synthesis of amorphous phosphorus-carbon films by pulsed laser deposition. The local bonding environments of carbon and phosphorus in the synthesised materials have been analysed by x-ray photoelectron spectroscopy; we have found strong evidence for the formation of direct P-C bonding and hence phosphorus carbide. There is a good agreement between the bonding environments found in this phosphorus carbide material and those predicted in the computational work. In particular, the local bonding environments are consistent with those found in the {beta}-InS-like structures that we predict to be low in energy for phosphorus:carbon ratios between 0.25 and 1. Highlights: Black-Right-Pointing-Pointer We have synthesised amorphous phosphorus-carbon films by pulsed laser deposition. Black-Right-Pointing-Pointer X-ray photoelectron spectroscopy results indicate formation of direct P-C bonds and hence phosphorus carbide. Black-Right-Pointing-Pointer Local bonding environments are consistent with those in predicted structures.

  3. Catalytically Assisted Self-Propagating High-Temperature Synthesis of Tantalum Carbide Powders

    E-Print Network [OSTI]

    Wooldridge, Margaret S.

    Catalytically Assisted Self-Propagating High-Temperature Synthesis of Tantalum Carbide Powders Troy high-temperature combustion synthesis (SHS) of materials has gained recognition for its energy in the context of gas-phase and solid-phase transport models. I. Introduction IN RECENT years, self-propagating

  4. Synthesis, structure, and superconducting properties of tantalum carbide nanorods and nanoparticles

    E-Print Network [OSTI]

    McHenry, Michael E.

    Synthesis, structure, and superconducting properties of tantalum carbide nanorods and nanoparticles, and HRSEM. Superconducting properties were characterized using a SQUID magnetometer. For reactions at lower in the rock salt structure and has a superconducting transition temperature of 9.7 K. In TaC nanorods

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

    SciTech Connect (OSTI)

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

    2011-01-01T23:59:59.000Z

    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 processing–structure–properties relationships facilitates tuning of the carbon material to the requirements of a certain application.

  6. Additive-assisted synthesis of boride, carbide, and nitride micro/nanocrystals

    SciTech Connect (OSTI)

    Chen, Bo [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China)] [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China); Yang, Lishan [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Shandong University), Ministry of Education, and School of Materials Science and Engineering, Shandong University, Jinan 250061 (China)] [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Shandong University), Ministry of Education, and School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Heng, Hua; Chen, Jingzhong; Zhang, Linfei; Xu, Liqiang [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China)] [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China); Qian, Yitai, E-mail: ytqian@sdu.edu.cn [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China)] [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China); Yang, Jian, E-mail: yangjian@sdu.edu.cn [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China)] [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, and Department of Chemistry, Shandong University, Jinan 250100 (China)

    2012-10-15T23:59:59.000Z

    General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB{sub 2}, ZrB{sub 2}, NbB{sub 2}, CeB{sub 6}, PrB{sub 6}, SmB{sub 6}, EuB{sub 6}, LaB{sub 6}), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN{sub 2}, VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN{sub 3} with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to {approx}850 Degree-Sign C, once the autoclave was heated to 100 Degree-Sign C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds. - Graphical abstract: An additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S. Highlights: Black-Right-Pointing-Pointer An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. Black-Right-Pointing-Pointer The reaction mechanism is demonstrated by the case of SiC nanowires. Black-Right-Pointing-Pointer The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.

  7. Physica D xxx (2003) xxxxxx Dynamic supercoiling bifurcations of growing elastic filaments

    E-Print Network [OSTI]

    Wolgemuth, Charles

    2003-01-01T23:59:59.000Z

    Physica D xxx (2003) xxx­xxx Dynamic supercoiling bifurcations of growing elastic filaments Charles xxx (2003) xxx­xxx essentially unchanging as the three-dimensional form develops, and the properties

  8. MHD Seismology of a loop-like filament tube by observed kink waves

    E-Print Network [OSTI]

    Pant, V; Banerjee, D; Goossens, M; Chen, P F; Joshi, N C; Zhou, Y H

    2015-01-01T23:59:59.000Z

    We report and analyze the observational evidence of global kink oscillations in a solar filament as observed in H alpha by National Solar Observatory (NSO)/Global Oscillation Network Group (GONG) instrument. An M1.1-class flare in active region 11692 on 2013 March 15 induced a global kink mode in the filament lying in the south-west of AR11692.We find periods of about 61 - 67 minutes and damping times of 92 - 117 minutes at three vertical slice positions chosen in and around the filament apex. We find that the waves are damped. From the observed global kink mode period and damping time scale using the theory of resonant absorption we perform prominence seismology. We estimate a lower cut-off value for the inhomogeneity length-scale to be around 0.34 - 0.44 times the radius of the filament cross-section.

  9. Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments

    E-Print Network [OSTI]

    Codis, Sandrine; Pogosyan, Dmitry

    2015-01-01T23:59:59.000Z

    The geometry of the cosmic web drives in part the spin acquisition of galaxies. This can be explained in a Lagrangian framework, by identifying the specific long-wavelength correlations within the primordial Gaussian random field which are relevant to spin acquisition. Tidal Torque Theory is revisited in the context of such anisotropic environments, biased by the presence of a filament within a wall. The point process of filament-type saddles represents it most efficiently. The constrained misalignment between the tidal and the inertia tensors in the vicinity of filament-type saddles simply explains the distribution of spin directions. This misalignment implies in particular an azimuthal orientation for the spins of more massive galaxies and a spin alignment with the filament for less massive galaxies. This prediction is found to be in qualitative agreement with measurements in Gaussian random fields and N-body simulations. It relates the transition mass to the geometry of the saddle, and accordingly predicts...

  10. Near-Infrared Spectroscopy of Molecular Filaments in the Reflection Nebula NGC 7023

    E-Print Network [OSTI]

    Paul Martini; K. Sellgren; Joseph L. Hora

    1997-02-11T23:59:59.000Z

    We present near-infrared spectroscopy of fluorescent molecular hydrogen (H_2) emission from molecular filaments in the reflection nebula NGC 7023. We derive the relative column densities of H_2 rotational-vibrational states from the measured line emission and compare these results with several model photodissociation regions covering a range of densities, incident UV-fields, and excitation mechanisms. Our best-fit models for one filament suggest, but do not require, either a combination of different densities, suggesting clumps of 10^6 cm^{-3} in a 10^4 - 10^5 cm^{-3} filament, or a combination of fluorescent excitation and thermally-excited gas, perhaps due to a shock from a bipolar outflow. We derive densities and UV fields for these molecular filaments that are in agreement with previous determinations.

  11. Topological instability along filamented invariant surfaces B. A. Carreras and V. E. Lynch

    E-Print Network [OSTI]

    Martín-Solís, José Ramón

    of quasicoherent structures. In this situation, the isosurfaces of the velocity stream function have a web. These filaments form a complex web in the plasma. The filamentary surfaces can result in the ap- pearance

  12. Effective elasticity of a flexible filament bound to a deformable cylindrical surface

    E-Print Network [OSTI]

    Andela Šari?; Josep C. Pàmies; Angelo Cacciuto

    2010-05-13T23:59:59.000Z

    We use numerical simulations to show how a fully flexible filament binding to a deformable cylindrical surface may acquire a macroscopic persistence length and a helical conformation. This is a result of the nontrivial elastic response to deformations of elastic sheets. We find that the filament's helical pitch is completely determined by the mechanical properties of the surface, and can be tuned by varying the filament binding energy. We propose simple scaling arguments to understand the physical mechanism behind this phenomenon and present a phase diagram indicating under what conditions one should expect a fully flexible chain to behave as a helical semi-flexible filament. Finally, we discuss the implications of our results.

  13. Pulse shortening, spatial mode cleaning, and intense terahertz generation by filamentation in xenon

    SciTech Connect (OSTI)

    Akturk, Selcuk; D'Amico, Ciro; Franco, Michel; Couairon, Arnaud; Mysyrowicz, Andre [Laboratoire d'Optique Appliquee, Ecole Nationale Superieure des Techniques Avancees-Ecole Polytechnique, CNRS UMR 7639 F-91761 Palaiseau Cedex, France and Centre de Physique Theorique, CNRS UMR 7644, Ecole Polytechnique, F-91128 Palaiseau Cedex (France)

    2007-12-15T23:59:59.000Z

    We performed a comprehensive study of filamentation in xenon. Due to its high nonlinear refraction index, but relatively low ionization potential, xenon can support filamentation at peak powers lower than in air. In our experiments, we studied pulse shortening, spatial mode cleaning, and generation of terahertz radiation. We observed that in xenon, self-compression is easily obtainable and terahertz radiation generation efficiency is significantly stronger as compared to air.

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

    DOE Patents [OSTI]

    Deng, Xunming; Povolny, Henry S.

    2004-06-29T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Lites, B. W.; Kubo, M. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A. [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover Street, Organization ADBS, Building 252, Palo Alto, CA 94304 (United States); Okamoto, T. J. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Otsuji, K., E-mail: lites@ucar.ed [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)

    2010-07-20T23:59:59.000Z

    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.

  16. Fields and Filaments in the Core of the Centaurus Cluster

    E-Print Network [OSTI]

    G. B. Taylor; A. C. Fabian; G. Gentile; S. W. Allen; C. Crawford; J. S. Sanders

    2007-08-24T23:59:59.000Z

    We present high resolution images of the Faraday Rotation Measure (RM) structure of the radio galaxy PKS 1246-410, at the center of the Centaurus cluster. Comparison with Halpha-line and soft X-ray emission reveals a correspondence between the line-emitting gas, the soft X-ray emitting gas, regions with an excess in the RM images, and signs of depolarization. Magnetic field strengths of 25 microG, organized on scales of ~1 kpc, and intermixed with gas at a temperature of 5 x 10^6 K with a density of ~0.1 cm^-3 can reproduce the observed RM excess, the depolarization, and the observed X-ray surface brightness. This hot gas may be in pressure equilibrium with the optical line-emitting gas, but the magnetic field strength of 25 microG associated with the hot gas provides only 10% of the thermal pressure and is therefore insufficient to account for the stability of the line-emitting filaments.

  17. Filaments, Collapse and Outflows in Massive Star Formation

    E-Print Network [OSTI]

    Robi Banerjee; Ralph E. Pudritz

    2008-07-04T23:59:59.000Z

    We present results from our numerical simulations of collapsing massive molecular cloud cores. These numerical calculations show that massive stars assemble quickly with mass accretion rates exceeding 10^-3 Msol/yr and confirm that the mass accretion during the collapsing phase is much more efficient than predicted by selfsimilar collapse solutions, dM/dt ~ c^3/G. We find that during protostellar assembly out of a non-turbulent core, the mass accretion reaches 20 - 100 c^3/G. Furthermore, we explore the self-consistent structure of bipolar outflows that are produced in our three dimensional magnetized collapse simulations. These outflows produce cavities out of which radiation pressure can be released, thereby reducing the limitations on the final mass of massive stars formed by gravitational collapse. Additional enhancement of the mass accretion rate comes from accretion along filaments that are built up by supersonic turbulent motions. Our numerical calculations of collapsing turbulent cores result in mass accretion rates as high as 10^-2 Msol/yr.

  18. Stability of filaments in star-forming clouds and the formation of prestellar cores in them

    E-Print Network [OSTI]

    Anathpindika, S

    2015-01-01T23:59:59.000Z

    It is now widely accepted that dense filaments of molecular gas are integral to the process of stellar birth. While numerical simulations have succeeded in reproducing filamentary structure in turbulent gas and analytic calculations have predicted the formation of dense gas filaments via radial collapse, the exact process(es) that generate/s such filaments which then form prestellar cores within them, is unclear. In this work we therefore study numerically the formation of a dense filament using a relatively simple set-up of a uniform-density cylinder in pressure equilibrium with its confining medium. In particular, we examine if its propensity to form a dense filament and further, to the formation of prestellar cores within this filament bears on the gravitational state of the initial volume of gas. We report a radial collapse leading to the formation of a dense filamentary cloud is likely when the initial volume of gas is at least critically stable (characterised by the approximate equality between the mass...

  19. Composition optimization of self-lubricating chromium carbide-based composite coatings for use to 760/sup 0/C

    SciTech Connect (OSTI)

    DellaCorte, C.; Sliney, H.E.

    1986-01-01T23:59:59.000Z

    This paper describes new compositions of self-lubricating coatings that contain chromium carbide. A bonded chromium carbide was used as the ''base stock'' because of the known excellent wear resistance and the chemical stability of chromium carbide. ''Additives'' were silver and barium fluoride/calcium fluoride eutectic. The coating constituents were treated as a termary system consisting of: (1) the bonded carbide base material, (2) silver, and (3) the eutectic. A study to determine the optimum amounts of each constituent was performed. The various compositions were prepared by powder blending. The blended powders were then plasma sprayed onto a superalloy substrates and diamond ground to the desired coating thickness. Friction and wear studies were performed at temperatures from 25 to 760/sup 0/C in helium and hydrogen. A variety of counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications such as piston ring/cylinder liner couples for Stirling engines.

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

    SciTech Connect (OSTI)

    Salas, E.; Jiménez Riobóo, R. J.; Jiménez-Villacorta, F.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain)] [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Sánchez-Marcos, J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain) [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Dept. Química-Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Muñoz-Martín, A.; Prieto, J. E.; Joco, V. [Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)] [Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2013-12-07T23:59:59.000Z

    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.

  1. Constraints on (Omega_m,Omega_Lambda) using distributions of inclination angles for high redshift filaments

    E-Print Network [OSTI]

    M. Weidinger; P. Moller; J. P. U. Fynbo; B. Thomsen; M. P. Egholm

    2002-05-24T23:59:59.000Z

    In this paper we present a scale free method to determine the cosmological parameters (Omega_m, Omega_Lambda). The method is based on the requirement of isotropy of the distribution of orientations of cosmological filaments. The current structure formation paradigm predicts that the first structures to form are voids and filaments, causing a web-like structure of the matter distribution at high redshifts. Recent observational evidence suggests that the threads, or filaments, of the cosmic web most easily are mapped in Ly-alpha emission. We describe how such a 3D map can be used to constrain the cosmological parameters in a way which, contrary to most other cosmological tests, does not require the use of a standard rod or a standard candle. We perform detailed simulations in order to define the optimal survey parameters for the definition of an observing programme aimed to address this test, and to investigate how statistical and observational errors will influence the results. We conclude that observations should target filaments of comoving size 15-50 Mpc in the redshift range 2-4, and that each filament must be defined by at least four Ly-alpha emitters. Detection of 20 filaments will be sufficient to obtain a result, while 50 filaments will make it possible to place significant new constraints on the values of Omega_m and Omega_Lambda permitted by the current supernova observations. In a future paper we study how robust these conclusions are to systematic velocities in the survey box.

  2. Tribological evaluation of high-speed steels with a regulated carbide phase

    SciTech Connect (OSTI)

    Richter, Janusz

    2003-06-15T23:59:59.000Z

    Wear resistance of a commercial steel and titanium-niobium high-speed steels with a regulated carbide phase was evaluated by employing a micro-scale abrasive wear test with alumina particles. The worn volumes and corresponding wear coefficients were the lowest for the new non-ledeburitic grades containing titanium, then the two niobium grades, the conventional (both wrought and by powder metallurgy) steels exhibited the worse wear resistance. Fractography SEM observations together with energy-dispersive X-ray (EDX) chemical analysis revealed the decisive role of the steels' MC particles in the wear process. These carbides influenced the abrasion by stoppage of the wear scars and/or changing their trajectories. Directional and nondirectional abrasion modes in the steels tested using alumina and carborundum abrasives were found and are discussed.

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

    SciTech Connect (OSTI)

    Brodyn, M. S.; Volkov, V. I., E-mail: volkov@iop.kiev.ua; Lyakhovetskii, V. R.; Rudenko, V. I. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine); Puzilkov, V. M.; Semenov, A. V. [National Academy of Sciences of Ukraine, Institute of Monocrystals (Ukraine)

    2012-02-15T23:59:59.000Z

    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.

  4. Modeling the formation of boron carbide particles in an aerosol flow reactor

    SciTech Connect (OSTI)

    Xiong, Y.; Pratsinis, S.E. (Dept. of Chemical Engineering, Center for Aerosol Processes, Univ. of Cincinnati, Cincinnati, OH (United States)); Weimer, A.W. (Ceramics and Advanced Materials Research, Dow Chemical U.S.A., Midland, MI (United States))

    1992-11-01T23:59:59.000Z

    In this paper the formation of submicron crystals of boron carbide (B[sub 4]C) by coagulation and sintering by the rapid carbothermal reduction of intimately mixed carbon-boron oxide powders in an aerosol flow reactor at temperatures above the boiling point of boron oxide is investigated. High heating rates (10[sup 5] K/s) force rapid evaporation of boron oxide and suboxides from the precursor powder, resulting in its rupture and formation of boron carbide molecular clusters that grow to macroscopic particles by coagulation. Consequently, the formation and growth of B[sub 4]C particles are described by simultaneous interparticle collision and coalescence using a two-dimensional particle-size distribution model that traces the evolution of both size and shape characteristics of the particles through their volume and surface area. In addition to the coagulation term, the governing population balance equation includes a coalescence contribution based on B[sub 4]C sintering law.

  5. Photonic Crystal Cavities in Cubic (3C) Polytype Silicon Carbide Films

    E-Print Network [OSTI]

    Marina Radulaski; Thomas M. Babinec; Sonia Buckley; Armand Rundquist; J Provine; Kassem Alassaad; Gabriel Ferro; Jelena Vu?kovi?

    2013-11-30T23:59:59.000Z

    We present the design, fabrication, and characterization of high quality factor and small mode volume planar photonic crystal cavities from cubic (3C) thin films (thickness ~ 200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1,250 - 1,600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

  6. Cyanophycin Mediates the Accumulation and Storage of Fixed Carbon in Non-Heterocystous Filamentous Cyanobacteria from Coniform Mats

    E-Print Network [OSTI]

    Liang, Biqing

    Thin, filamentous, non-heterocystous, benthic cyanobacteria (Subsection III) from some marine, lacustrine and thermal environments aggregate into macroscopic cones and conical stromatolites. We investigate the uptake and ...

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

    SciTech Connect (OSTI)

    Huang, T. W. [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China)] [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Zhou, C. T. [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China) [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Science College, National University of Defense Technology, Changsha 410073 (China); Zhang, H. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)] [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); He, X. T. [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China) [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)

    2013-07-15T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Van Gorder, Robert A., E-mail: rav@knights.ucf.edu [Department of Mathematics, University of Central Florida, Orlando, Florida 32816-1364 (United States)

    2014-06-15T23:59:59.000Z

    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.

  9. 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)

    1991-01-01T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    1991-02-19T23:59:59.000Z

    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. An excursion set model of the cosmic web: The abundance of sheets, filaments and halos

    E-Print Network [OSTI]

    Jiajian Shen; Tom Abel; H. J. Mo; Ravi Sheth

    2006-03-27T23:59:59.000Z

    We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of this approach, which we develop here, large scale structure shows a clear hierarchy of morphologies: the mass in large-scale sheets is partitioned up among lower mass filaments, which themselves are made-up of still lower mass halos. Our approach provides analytic estimates of the mass fraction in sheets, filaments and halos, and its evolution, for any background cosmological model and any initial fluctuation spectrum. In the currently popular $\\Lambda$CDM model, our analysis suggests that more than 99% of the cosmic mass is in sheets, and 72% in filaments, with mass larger than $10^{10} M_{\\odot}$ at the present time. For halos, this number is only 46%. Our approach also provides analytic estimates of how halo abundances at any given time correlate with the morphology of the surrounding large-scale structure, and how halo evolution correlates with the morphology of large scale structure.

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

    DOE Patents [OSTI]

    Bettger, Kenneth J; Stark, David H

    2013-08-20T23:59:59.000Z

    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.

  13. 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)

    1994-01-01T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    1994-10-18T23:59:59.000Z

    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.

  15. 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 (IBS) [IBS; (BBRI); (UPENN-MED)

    2013-11-20T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)] [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)

    2013-09-15T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Abdollahpour, Daryoush [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, GR-71110 Heraklion (Greece); Physics Department, University of Crete, GR-71003 Heraklion (Greece); Papazoglou, Dimitrios G.; Tzortzakis, Stelios [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, GR-71110 Heraklion (Greece); Materials Science and Technology Department, University of Crete, GR-71003 Heraklion (Greece)

    2011-11-15T23:59:59.000Z

    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.

  18. Robustness of the filamentation instability for asymmetric plasma shells collision in arbitrarily oriented magnetic field

    SciTech Connect (OSTI)

    Bret, A. [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)] [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)

    2013-10-15T23:59:59.000Z

    The filamentation instability triggered when two counter streaming plasma shells overlap appears to be the main mechanism by which collisionless shocks are generated. It has been known for long that a flow aligned magnetic field can completely suppress this instability. In a recent paper [Phys. Plasmas 18, 080706 (2011)], it was demonstrated in two dimensions that for the case of two cold, symmetric, relativistically colliding shells, such cancellation cannot occur if the field is not perfectly aligned. Here, this result is extended to the case of two asymmetric shells. The filamentation instability appears therefore as an increasingly robust mechanism to generate shocks.

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

    SciTech Connect (OSTI)

    Feng Liubin [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190 (China); Institute of Atomic and Molecular Physics and Department of Physics, Sichuan University, Chengdu 610065 (China); Lu Xin; Liu Xiaolong; Li Yutong; Chen Liming; Ma Jinglong; Dong Quanli; Wang Weimin [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190 (China); Xi Tingting [College of Physical Sciences, Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Sheng Zhengming; Zhang Jie [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190 (China); Key Laboratory for Laser Plasmas of the Ministry of Education of China and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); He Duanwei [Institute of Atomic and Molecular Physics and Department of Physics, Sichuan University, Chengdu 610065 (China)

    2012-07-15T23:59:59.000Z

    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.

  20. The effect of geometry on the design of filament-wound fiberglass tension lugs

    E-Print Network [OSTI]

    Braswell, James Lee

    1981-01-01T23:59:59.000Z

    stress cr1terion of failure and published material property data. From these analyt1cal results it 1s concluded that increased structural efficiency can be obtained by tak1ng advantage of the shape latitude available through filament wind1ng...

  1. Tesla coil discharges guided by femtosecond laser filaments in air Yohann Brelet1

    E-Print Network [OSTI]

    Boyer, Edmond

    1 Tesla coil discharges guided by femtosecond laser filaments in air Yohann Brelet1 , Aurélien, Palaiseau, France A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 k experiments of laser guided discharges obtained in air by high voltage bursts delivered by a compact Tesla

  2. An efficient immersed boundary-lattice Boltzmann method for the hydrodynamic interaction of elastic filaments

    E-Print Network [OSTI]

    Luo, Haoxiang

    An efficient immersed boundary-lattice Boltzmann method for the hydrodynamic interaction of elastic flapping in the Kármán gait and the entrainment regions near a cylinder is studied to model fish swimming in these regions. Significant drag reduction is found for the filament, and the result is consistent

  3. Plasma density inside a femtosecond laser filament in air: Strong dependence on external focusing

    E-Print Network [OSTI]

    Becker, Andreas

    Plasma density inside a femtosecond laser filament in air: Strong dependence on external focusing­16 . The plasma generation balances the self-focusing effect and leads to a limited peak intensity 17­19 along, Germany Received 10 March 2006; published 27 September 2006 Our experiment shows that external focusing

  4. Raman and Photoluminescence Spectroscopy of Nanocrystalline Diamond Films grown by Hot Filament CVD

    E-Print Network [OSTI]

    Bristol, University of

    H4 flow-rate ratio of standard polycrystalline diamond deposition parameters on formationRaman and Photoluminescence Spectroscopy of Nanocrystalline Diamond Films grown by Hot Filament CVD of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia b,c Diamond Research Laboratory, School

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

    SciTech Connect (OSTI)

    Burin, Michael [CSUSM

    2014-11-18T23:59:59.000Z

    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.

  6. Intermittent Divertor Filaments in the National Spherical Torus Experiment and Their Relation to Midplane Blobs

    SciTech Connect (OSTI)

    R.J. Maqueda, D.P. Stotler and the NSTX Team.

    2010-05-19T23:59:59.000Z

    While intermittent filamentary structures, also known as blobs, are routinely seen in the low-field-side scrape-off layer of the National Spherical Torus Experiment (NSTX) (Ono et al 2000 Nucl. Fusion 40 557), fine structured filaments are also seen on the lower divertor target plates of NSTX. These filaments, not associated with edge localized modes, correspond to the interaction of the turbulent blobs seen near the midplane with the divertor plasma facing components. The fluctuation level of the neutral lithium light observed at the divertor, and the skewness and kurtosis of its probability distribution function, is similar to that of midplane blobs seen in D?; e.g. increasing with increasing radii outside the outer strike point (OSP) (separatrix). In addition, their toroidal and radial movement agrees with the typical movement of midplane blobs. Furthermore, with the appropriate magnetic topology, i.e. mapping between the portion of the target plates being observed into the field of view of the midplane gas puff imaging diagnostic, very good correlation is observed between the blobs and the divertor filaments. The correlation between divertor plate filaments and midplane blobs is lost close to the OSP. This latter observation is consistent with the existence of ‘magnetic shear disconnection’ due to the lower X-point, as proposed by Cohen and Ryutov (1997 Nucl. Fusion 37 621).

  7. Wave-pinned filaments of scroll waves Tams Bnsgi, Jr., Kevin J. Meyer, and Oliver Steinbocka

    E-Print Network [OSTI]

    Steinbock, Oliver

    Wave-pinned filaments of scroll waves Tamás Bánsági, Jr., Kevin J. Meyer, and Oliver Steinbocka Received 5 November 2007; accepted 26 December 2007; published online 6 March 2008 Scroll waves are three can be pinned to the wake of traveling wave pulses. This pinning is studied in experiments with the 1

  8. of a brownian ratchet. Thermal fluctuations of the flexible actin filaments expose the tip

    E-Print Network [OSTI]

    Ahissar, Ehud

    of a brownian ratchet. Thermal fluctuations of the flexible actin filaments expose the tip long enough for a new monomer to attach. Once the tip springs back, it ratchets the membrane forward by the length of one monomer. Brownian ratchets have found a life of their own in the physics literature

  9. Measuring molecular rupture forces between single actin filaments and actin-binding proteins

    E-Print Network [OSTI]

    Kamm, Roger D.

    Measuring molecular rupture forces between single actin filaments and actin-binding proteins Jorge, and accepted by the Editorial Board April 24, 2008 (received for review June 29, 2007) Actin-binding proteins to model the mechanical properties of actin networks grown in vitro; however, there is a lack

  10. Direct imaging of the acoustic waves generated by femtosecond filaments in air

    E-Print Network [OSTI]

    Milchberg, Howard

    Direct imaging of the acoustic waves generated by femtosecond filaments in air J. K. Wahlstrand, N of spatial single- and higher-mode 50 fs, 800 nm pulses in air at 10 Hz and 1 kHz repetition rates. Results in air [9]. They claimed a positive gas density perturba- tion on axis with a microsecond lifetime

  11. Atomistic Simulation Approach to a Continuum Description of Self-Assembled b-Sheet Filaments

    E-Print Network [OSTI]

    Kamm, Roger D.

    be applicable to developing continuum elastic ribbon models of other b-sheet filaments and amyloid fibrils promise as a three-dimensional cell culture matrix or as a tissue engi- neering scaffold. Due to the short). Another important aspect of b-sheet peptide self-assembly is its similarity to amyloid fibrils found

  12. Experimental observation of a traveling plasma grating formed by two crossing filaments in gases

    SciTech Connect (OSTI)

    Durand, Magali [Laboratoire d'Optique Appliquee, ENSTA ParisTech-Ecole Polytechnique-CNRS, 91761 Palaiseau (France); ONERA, Chemin de la Huniere, 91761 Palaiseau (France); Liu Yi; Forestier, Benjamin; Houard, Aurelien; Mysyrowicz, Andre [Laboratoire d'Optique Appliquee, ENSTA ParisTech-Ecole Polytechnique-CNRS, 91761 Palaiseau (France)

    2011-03-21T23:59:59.000Z

    The spatial motion and effective duration of a traveling plasma grating formed by two interfering femtosecond laser filaments in gases is characterized by its Doppler effect imparted on a probe pulse. The shift velocity determined experimentally agrees with the theoretical calculations.

  13. Modulational and filamentational instabilities of two electromagnetic pulses in a radiation background

    E-Print Network [OSTI]

    M. Marklund; P. K. Shukla; G. Brodin; L. Stenflo

    2004-10-21T23:59:59.000Z

    The nonlinear interaction, due to quantum electrodynamical (QED) effects, between two electromagnetic pulses and a radiation gas is investigated. It is found that the governing equations admit both modulational and filamentational instabilities. The instability growth rates are derived, and the results are discussed.

  14. Heat transfer in sunspot penumbrae. Origin of dark-cored penumbral filaments

    E-Print Network [OSTI]

    B. Ruiz Cobo; L. R. Bellot Rubio

    2008-10-07T23:59:59.000Z

    Context: Observations at 0.1" have revealed the existence of dark cores in the bright filaments of sunspot penumbrae. Expectations are high that such dark-cored filaments are the basic building blocks of the penumbra, but their nature remains unknown. Aims: We investigate the origin of dark cores in penumbral filaments and the surplus brightness of the penumbra. To that end we use an uncombed penumbral model. Methods: The 2D stationary heat transfer equation is solved in a stratified atmosphere consisting of nearly horizontal magnetic flux tubes embedded in a stronger and more vertical field. The tubes carry an Evershed flow of hot plasma. Results: This model produces bright filaments with dark cores as a consequence of the higher density of the plasma inside the tubes, which shifts the surface of optical depth unity toward higher (cooler) layers. Our calculations suggest that the surplus brightness of the penumbra is a natural consequence of the Evershed flow, and that magnetic flux tubes about 250 km in diameter can explain the morphology of sunspot penumbrae.

  15. Rf-plasma synthesis of nanosize silicon carbide and nitride. Final report

    SciTech Connect (OSTI)

    Buss, R.J.

    1997-02-01T23:59:59.000Z

    A pulsed rf plasma technique is capable of generating ceramic particles of 10 manometer dimension. Experiments using silane/ammonia and trimethylchlorosilane/hydrogen gas mixtures show that both silicon nitride and silicon carbide powders can be synthesized with control of the average particle diameter from 7 to 200 nm. Large size dispersion and much agglomeration appear characteristic of the method, in contrast to results reported by another research group. The as produced powders have a high hydrogen content and are air and moisture sensitive. Post-plasma treatment in a controlled atmosphere at elevated temperature (800{degrees}C) eliminates the hydrogen and stabilizes the powder with respect to oxidation or hydrolysis.

  16. High temperature erosion and fatigue resistance of a detonation gun chromium carbide coating for steam turbines

    SciTech Connect (OSTI)

    Quets, J.M.; Walsh, P.N. [Praxair Surface Technologies, Inc., Indianapolis, IN (United States); Srinivasan, V. [Westinghouse Electric Corp., Orlando, FL (United States); Tucker, R.C. Jr. [Praxair Surface Technologies, Inc., Indianapolis, IN (United States)

    1994-12-31T23:59:59.000Z

    Chromium carbide based detonation gun coatings have been shown to be capable of protecting steam turbine components from particle erosion. To be usable, however, erosion resistant coatings must not degrade the fatigue characteristics of the coated components. Recent studies of the fatigue properties of a detonation gun coated martensitic substrate at 538 C (1,000 F) will be presented with an emphasis on its long term performance. This study will show the retention of acceptable fatigue performance of coated substrates into the high cycle regime, and will include a discussion on the mechanism of fatigue.

  17. Excitation and recombination dynamics of vacancy-related spin centers in silicon carbide

    SciTech Connect (OSTI)

    Hain, T. C.; Hertel, T. [Institute of Physical and Theoretical Chemistry, Julius-Maximilian University of Würzburg, 97074 Würzburg (Germany); Fuchs, F.; Astakhov, G. V., E-mail: astakhov@physik.uni-wuerzburg.de [Experimental Physics VI, Julius-Maximilian University of Würzburg, 97074 Würzburg (Germany); Soltamov, V. A. [Ioffe Physical-Technical Institute, 194021 St. Petersburg (Russian Federation); Baranov, P. G. [Ioffe Physical-Technical Institute, 194021 St. Petersburg (Russian Federation); St. Petersburg State Polytechnical University, 195251 St. Petersburg (Russian Federation); Dyakonov, V., E-mail: dyakonov@physik.uni-wuerzburg.de [Experimental Physics VI, Julius-Maximilian University of Würzburg, 97074 Würzburg (Germany); Bavarian Center for Applied Energy Research (ZAE Bayern), 97074 Würzburg (Germany)

    2014-04-07T23:59:59.000Z

    We generate silicon vacancy related defects in high-quality epitaxial silicon carbide layers by means of electron irradiation. By controlling the irradiation fluence, the defect concentration is varied over several orders of magnitude. We establish the excitation profile for optical pumping of these defects and evaluate the optimum excitation wavelength of 770?nm. We also measure the photoluminescence dynamics at room temperature and find a monoexponential decay with a characteristic lifetime of 6.1?ns. The integrated photoluminescence intensity depends linear on the excitation power density up to 20?kW/cm{sup 2}, indicating a relatively small absorption cross section of these defects.

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

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your Density Isn't YourTransport in RepresentativeDepartment ofDepartmentLast TenPrice of|SNL OnSilicon Carbide|

  19. 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 [Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital-263 002 (India); Filippov, Boris [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow (Russian Federation); Chandra, Ramesh, E-mail: navin@aries.res.in, E-mail: njoshi98@gmail.com, E-mail: aks@aries.res.in [Department of Physics, D.S.B. Campus, Kumaun University, Nainital-263 002, Uttarakhand (India)

    2013-07-01T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Alexander, Caroline E.; Walsh, Robert W.; Régnier, Stéphane [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom)] [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Cirtain, Jonathan; Winebarger, Amy R. [NASA Marshall Space Flight Center, VP 62, Huntsville, AL 35812 (United States)] [NASA Marshall Space Flight Center, VP 62, Huntsville, AL 35812 (United States); Golub, Leon; Korreck, Kelly; Weber, Mark [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kobayashi, Ken [Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States)] [Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Platt, Simon; Mitchell, Nick [School of Computing, Engineering and Physical Sciences, University of Central Lancashire, Preston PR1 2HE (United Kingdom)] [School of Computing, Engineering and Physical Sciences, University of Central Lancashire, Preston PR1 2HE (United Kingdom); DePontieu, Bart; Title, Alan [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover Street, Org. ADBS, Bldg. 252, Palo Alto, CA (United States)] [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover Street, Org. ADBS, Bldg. 252, Palo Alto, CA (United States); DeForest, Craig [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States)] [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Kuzin, Sergey [P.N. Lebedev Physical institute of the Russian Academy of Sciences, Leninskii prospekt, 53, 119991 Moscow (Russian Federation)] [P.N. Lebedev Physical institute of the Russian Academy of Sciences, Leninskii prospekt, 53, 119991 Moscow (Russian Federation)

    2013-09-20T23:59:59.000Z

    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 Å) 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 Å). 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.

  1. TWO MASS DISTRIBUTIONS IN THE L 1641 MOLECULAR CLOUDS: THE HERSCHEL CONNECTION OF DENSE CORES AND FILAMENTS IN ORION A

    SciTech Connect (OSTI)

    Polychroni, D. [Department of Astrophysics, University of Athens, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis, 15784 Zografos, Athens (Greece)] [Department of Astrophysics, University of Athens, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis, 15784 Zografos, Athens (Greece); Schisano, E.; Elia, D.; Molinari, S.; Turrini, D.; Rygl, K. L. J.; Benedettini, M.; Busquet, G.; Di Giorgio, A. M.; Pestalozzi, M.; Pezzuto, S. [Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), via del Fosso del Cavaliere 100, I-00133 Roma (Italy)] [Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Roy, A.; André, Ph.; Hennemann, M.; Hill, T.; Könyves, V. [Laboratoire AIM, CEA/IRFU CNRS/INSU Université Paris Diderot, Paris-Saclay, F-91191 Gif-sur-Yvette (France)] [Laboratoire AIM, CEA/IRFU CNRS/INSU Université Paris Diderot, Paris-Saclay, F-91191 Gif-sur-Yvette (France); Martin, P. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)] [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Di Francesco, J. [National Research Council Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)] [National Research Council Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Arzoumanian, D. [IAS, CNRS (UMR 8617), Université Paris-Sud, Bâtiment 121, F-91400 Orsay (France)] [IAS, CNRS (UMR 8617), Université Paris-Sud, Bâtiment 121, F-91400 Orsay (France); Bontemps, S., E-mail: dpolychroni@phys.uoa.gr [Université de Bordeaux, Laboratoire d' Astrophysique de Bordeaux, CNRS/INSU, UMR 5804, BP 89, F-33271, Floirac Cedex (France); and others

    2013-11-10T23:59:59.000Z

    We present Herschel survey maps of the L 1641 molecular clouds in Orion A. We extracted both the filaments and dense cores in the region. We identified which of the dense sources are proto- or pre-stellar, and studied their association with the identified filaments. We find that although most (71%) of the pre-stellar sources are located on filaments there, is still a significant fraction of sources not associated with such structures. We find that these two populations (on and off the identified filaments) have distinctly different mass distributions. The mass distribution of the sources on the filaments is found to peak at 4 M {sub ?} and drives the shape of the core mass function (CMF) at higher masses, which we fit with a power law of the form dN/dlogM?M {sup –1.4±0.4}. The mass distribution of the sources off the filaments, on the other hand, peaks at 0.8 M {sub ?} and leads to a flattening of the CMF at masses lower than ?4 M {sub ?}. We postulate that this difference between the mass distributions is due to the higher proportion of gas that is available in the filaments, rather than in the diffuse cloud.

  2. Phase evolution in carbide dispersion strengthened nanostructured copper composite by high energy ball milling

    SciTech Connect (OSTI)

    Hussain, Zuhailawati; Nur Hawadah, M. S. [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2012-09-06T23:59:59.000Z

    In this study, high-energy ball milling was applied to synthesis in situ nanostructured copper based composite reinforced with metal carbides. Cu, M (M=W or Ti) and graphite powder mixture were mechanically alloyed for various milling time in a planetary ball mill with composition of Cu-20vol%WC and Cu-20vol%TiC. Then the as-milled powder were compacted at 200 to 400 MPa and sintered in a vacuum furnace at 900 Degree-Sign C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W{sub 2}C and WC phases) was observed after sintering of Cu-W-C mixture while TiC precipitated in as-milled powder of Cu-Ti-C composite after 5 h and become amorphous with longer milling. Mechanism of MA explained the cold welding and fracturing event during milling. Cu-W-C system shows fracturing event is more dominant at early stage of milling and W particle still existed after milling up to 60 h. While in Cu-Ti-C system, cold welding is more dominant and all Ti particles dissolved into Cu matrix.

  3. 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)

    1982-01-01T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Taylor, Larry Lorin

    2001-01-01T23:59:59.000Z

    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.

  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. [Space Science Office, ZP13, NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States); Hara, Hirohisa, E-mail: alphonse.sterling@nasa.gov, E-mail: ron.moore@nasa.gov, E-mail: hirohisa.hara@nao.ac.jp [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2012-12-10T23:59:59.000Z

    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. Effects of stochastic growth and inter-filament correlation in an actin-inspired many-body Brownian ratchet

    E-Print Network [OSTI]

    Hohlfeld, Evan

    2012-01-01T23:59:59.000Z

    We present a computational and theoretical study of a many-body Brownian ratchet, in which a "gel" of multiple, stiff polymerizing filaments pushes a diffusing obstacle. Our results show that steady-state dynamics of this system are strongly influenced by a layer of depleted filament density at the obstacle-gel interface. Inter-filament correlations within this molecule-thick layer have dramatic consequences for the velocity and structure of the growing gel. These emergent behaviors can be captured by mean field theories that emphasize the non-additivity of polymerization forces and indicate a key role for the fluctuating gap between gel and obstacle.

  7. Effects of filament-matrix interfaces on the mechanical properties of SiC-reinforced Si sub 3 N sub 4: A Review

    SciTech Connect (OSTI)

    Schilling, C.H.

    1989-09-01T23:59:59.000Z

    This report summarizes the results of a literature review of the effects of filament-matrix interfaces on the mechanical properties of ceramic composites composed of SiC-filament-reinforced Si{sub 3}N{sub 4}. A general review of the processing and mechanical properties of SiC-filament-reinforced Si{sub 3}N{sub 4} is presented with special emphasis on research pertaining to processing-related effects on filament-matrix interfaces and the resulting effects of these interfaces on fracture behavior. A review of coating techniques for ceramic filaments is also presented, and recommendations are made for future directions in processing SiC-filament-reinforced Si{sub 3}N{sub 4} with mechanical properties that are enhanced by the microstructure of the filament-matrix interface. 148 refs., 1 tab.

  8. IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 58, NO. 1, JANUARY 2011 21 Efficiency Impact of Silicon Carbide Power

    E-Print Network [OSTI]

    Tolbert, Leon M.

    ), silicon carbide (SiC), wind generation. I. INTRODUCTION VARIABLE speed capability allows a wind turbine to operate at speeds which produce the greatest amount of power and minimizes torque perturbations the voltage and frequency of the generated power vary with the turbine speed, a converter is required

  9. Accuracy of truncated Leiden and Berlin virial expansions for pure gases and sealing joints between silicon carbide and stainless steel

    E-Print Network [OSTI]

    Santana Rodriguez, Gabriel Enrique

    2003-01-01T23:59:59.000Z

    carbide to steel were studied. Brazing is the technique more used, and several active filler metals such as Ag-Cu-In-Ti, Ag-Cu-Ti, plus carbon fibers Ag-Cu-Hf and Niobium were used. This review shows that the strength of the joint is affected by the amount...

  10. Structural and electronic properties of cobalt carbide Co2C and its surface stability: Density functional theory study

    E-Print Network [OSTI]

    Li, Weixue

    in Fischer­Tropsch syn- thesis, which agrees well with experimental findings. The density of states (DOSs­14], dehydrogenation [15], hydrogenolysis [16, 17] and Fischer­Tropsch synthesis (FTS) [18­22] etc., approaching activity of cobalt, iron and iron carbide in Fischer­Tropsch synthesis (FTS)[24­43], relative little

  11. Deposition of silicon carbide films using a high vacuum metalorganic chemical vapor deposition method with a single source precursor

    E-Print Network [OSTI]

    Boo, Jin-Hyo

    , high temperature, and high radiation environments. Conventional silicon carbide chemical vapor deposition CVD processes generally utilized multiple precursors such as silane and hydrocarbons, and required temperature alternatives to the conventional SiC CVD methods must be considered. To do this, a relatively

  12. 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.

    1998-07-07T23:59:59.000Z

    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.

  13. Chapter 30: Quantum Physics 9. The tungsten filament in a standard light bulb can be considered a blackbody radiator.

    E-Print Network [OSTI]

    Kioussis, Nicholas

    . 1 Chapter 30: Quantum Physics 9. The tungsten filament in a standard light bulb can be considered frequency is that of infrared electromagnetic radiation, the light bulb radiates more energy in the infrared

  14. Particle acceleration and radiation friction effects in the filamentation instability of pair plasmas

    E-Print Network [OSTI]

    D'Angelo, M; Sgattoni, A; Pegoraro, F; Macchi, A

    2015-01-01T23:59:59.000Z

    The evolution of the filamentation instability produced by two counter-streaming pair plasmas is studied with particle-in-cell (PIC) simulations in both one (1D) and two (2D) spatial dimensions. Radiation friction effects on particles are taken into account. After an exponential growth of both the magnetic field and the current density, a nonlinear quasi-stationary phase sets up characterized by filaments of opposite currents. During the nonlinear stage, a strong broadening of the particle energy spectrum occurs accompanied by the formation of a peak at twice their initial energy. A simple theory of the peak formation is presented. The presence of radiative losses does not change the dynamics of the instability but affects the structure of the particle spectra.

  15. 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)

    2010-12-15T23:59:59.000Z

    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.

  16. The Origin of the Galactic Center Nonthermal Radio Filaments: Young Stellar Clusters

    E-Print Network [OSTI]

    F. Yusef-Zadeh

    2003-08-01T23:59:59.000Z

    The unusual class of magnetized nonthermal radio filaments (NTF), threads and streaks with their unique physical characteristics are found only within the inner couple of degrees of the Galactic center. Also, a number of young, mass-losing and rare stellar clusters are recognized to lie in the Galactic center region. The latter characteristic of the Galactic center region is used to explain the origin of the nonthermal radio filaments. We consider a mechanism in which the collective winds of massive WR and OB stars within a dense stellar environment produce shock waves that can accelerate particles to relativistic energies. This mechanism is an extension of a model originally proposed by Rosner and Bodo (1996), who suggested that energetic nonthermal particles are produced in a terminal shock of mass-losing stars. The large-scale distribution of the magnetic field in the context of this model is argued to have neither poloidal geometry nor pervasive throughout the Galactic center region.

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

    DOE Patents [OSTI]

    Muradov, Nazim

    2010-04-06T23:59:59.000Z

    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.

  18. Development of a Commercial Process for the Production of Silicon Carbide Fibrils

    SciTech Connect (OSTI)

    Nixdorf, R.D.

    1999-04-01T23:59:59.000Z

    A patent was issued on ''VLS'' silicon carbide fibrils to North American Phillips Corporation in 1975. Various laboratories and companies have been attempting to improve this process and scale it to larger quantities since that time. All of these efforts met with minimal success because they were using the original technology while attempting to improve the equipment. The principal impediments have been: (1) Slow crystal growth during fibril production; (2) Sensitive stoichiometry factors in the crystal growth chamber; and (3) Precise control of a high temperature process. The principal investigator has scaled silicon carbide whisker production at American Matrix and the SiC fiber process at Advanced Composite Materials Corporation from grams in the laboratory to tons per year production. This project is a proof-of-concept effort to apply some of the recent technology to the problems listed above in the fibril growth process. Two different technology approaches were investigated. A major problem with fibril growth has been generating a consistent supply of the required SiO gas reactant, which is a product of reducing SiO{sub 2}. The first approach, in this project addresses the SiO gas production, involved mixing silica and carbon fibrous raw materials in the immediate proximity of the graphite fibril growth plates to generate SiO nearer to individual sites of fibril growth. Iron bearing catalyst was painted on the graphite plates and the SiO generator mix was placed above the plate. This system was then heated to 1600/1650 C in a graphite resistance furnace. Some fibrils were started but the growth rate and fibril quality were unacceptably low. A second approach, which uses MTS + H{sub 2} gases to address stoichiometry control, was investigated to improve fibril growth rates while reducing the previous high temperature requirements for the process. A partial vacuum chamber was construct inside a commercial microwave furnace. The fibril growth container was coated with an iron catalyst and brought to 1200 C by the microwave field. A mixture of hydrogen and methyl trichlorosilane gases were fed to the fibril reaction container. Excellent silicon carbide fibrils were produced at a growth rate that was over four times greater than previously reported processes. The next phase of the development will be an optimization of operating parameters to improve fibril yield in the microwave growth process. The development activities will then move to the construction and testing of a pilot unit.

  19. The Influence of Filaments in the Private Flux Region on Divertor Particle and Power Deposition

    E-Print Network [OSTI]

    Harrison, J R; Thornton, A J; Walkden, N R

    2015-01-01T23:59:59.000Z

    The transport of particles via intermittent filamentary structures in the private flux region of plasmas in the MAST tokamak has been investigated using a fast framing camera recording visible light emission from the volume of the lower divertor, as well as Langmuir probes and IR thermography monitoring particle and power fluxes to plasma-facing surfaces in the divertor. The visible camera data suggests that, in the divertor volume, fluctuations in light emission above the X-point are strongest in the scrape-off layer (SOL). Conversely, in the region below the X-point, it is found that these fluctuations are strongest in the private flux region (PFR) of the inner divertor leg. Detailed analysis of the appearance of these filaments in the camera data suggests that they are approximately circular, around 1-2cm in diameter. The most probable toroidal mode number is between 2 and 3. These filaments eject plasma deeper into the private flux region, sometimes by the production of secondary filaments, moving at a sp...

  20. 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 Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

    2014-02-15T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Nguyen, Ba Nghiep; Simmons, Kevin L.

    2013-07-22T23:59:59.000Z

    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].

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

    SciTech Connect (OSTI)

    Jamie Marie Rintelman

    2004-12-19T23:59:59.000Z

    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.

  3. Joining of silicon carbide using interlayer with matching coefficient of thermal expansion

    SciTech Connect (OSTI)

    Perham, T. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering; [Lawrence Berkeley National Lab., CA (United States)

    1996-11-01T23:59:59.000Z

    The primary objective of this study is to develop a technique for joining a commercially available Silicon Carbide that gives good room temperature strength and the potential for good high temperature strength. One secondary objective is that the joining technique be adaptable to SiC{sub f}/SiC composites and/or Nickel based superalloys, and another secondary objective is that the materials provide good neutron irradiation resistance and low activation for potential application inside nuclear fusion reactors. The joining techniques studied here are: (1) reaction bonding with Al-Si/Si/SiC/C; (2) reaction/infiltration with calcium aluminum silicate; (3) ion exchange mechanism to form calcium hexaluminate (a refractory cement); and (4) oxide frit brazing with cordierite.

  4. Visible Photoluminescence from Cubic (3C) Silicon Carbide Microdisks Coupled to High Quality Whispering Gallery Modes

    E-Print Network [OSTI]

    Marina Radulaski; Thomas M. Babinec; Kai Müller; Konstantinos G. Lagoudakis; Jingyuan Linda Zhang; Sonia Buckley; Yousif A. Kelaita; Kassem Alassaad; Gabriel Ferro; Jelena Vu?kovi?

    2014-12-08T23:59:59.000Z

    We present the design, fabrication and characterization of cubic (3C) silicon carbide microdisk resonators with high quality factor modes at visible and near infrared wavelengths (600 - 950 nm). Whispering gallery modes with quality factors as high as 2,300 and corresponding mode volumes V ~ 2 ({\\lambda}/n)^3 are measured using laser scanning confocal microscopy at room temperature. We obtain excellent correspondence between transverse-magnetic (TM) and transverse-electric (TE) polarized resonances simulated using Finite Difference Time Domain (FDTD) method and those observed in experiment. These structures based on ensembles of optically active impurities in 3C-SiC resonators could play an important role in diverse applications of nonlinear and quantum photonics, including low power optical switching and quantum memories.

  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)

    1994-01-01T23:59:59.000Z

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

    DOE Patents [OSTI]

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

    1994-11-01T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

    Quinby, T.C.

    1984-08-30T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    1994-05-17T23:59:59.000Z

    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.

  9. A comprehensive study of thermoelectric and transport properties of ?-silicon carbide nanowires

    SciTech Connect (OSTI)

    Valentín, L. A.; Betancourt, J.; Fonseca, L. F., E-mail: luis.fonseca@upr.edu [Department of Physics University of Puerto Rico, Rio Piedras (Puerto Rico); Pettes, M. T.; Shi, L. [Department of Mechanical Engineering, The University of Texas at Austin, Texas 78712 (United States); Soszy?ski, M.; Huczko, A. [Department of Chemistry, Warsaw University, Pasteur 1 Str., 02-093 Warsaw (Poland)

    2013-11-14T23:59:59.000Z

    The temperature dependence of the Seebeck coefficient, the electrical and thermal conductivities of individual ?-silicon carbide nanowires produced by combustion in a calorimetric bomb were studied using a suspended micro-resistance thermometry device that allows four-point probe measurements to be conducted on each nanowire. Additionally, crystal structure and growth direction for each measured nanowire was directly obtained by transmission electron microscopy analysis. The Fermi level, the carrier concentration, and mobility of each nanostructure were determined using a combination of Seebeck coefficient and electrical conductivity measurements, energy band structure and transport theory calculations. The temperature dependence of the thermal and electrical conductivities of the nanowires was explained in terms of contributions from boundary, impurity, and defect scattering.

  10. The effects of erodent particle size and composition on the erosion of chromium carbide based coatings

    SciTech Connect (OSTI)

    Walsh, P.N.; Quets, J.M.; Tucker, R.C. Jr. [Praxair Surface Technologies, Inc., Indianapolis, IN (United States)

    1994-12-31T23:59:59.000Z

    A number of studies and field experience have demonstrated the efficacy of use of chromium carbide based coatings on steam turbine components to reduce the effects of solid particle erosion. To optimize the performance of these coatings, a cost effective laboratory test is needed to facilitate the choice of coating composition, morphology, and deposition method. A variety of test types and test parameters have been reported with varying relative rankings of the various coatings evaluated. A critical review of past work has been made, with new data added for clarification. The particle size of the erodent used as well as its composition has been shown to be of particular importance. A correlation between field experience and selected laboratory test parameters then facilitates the optimum choice of coatings.

  11. Cryochemical and CVD processing of shperical carbide fuels for propulsion reactors

    SciTech Connect (OSTI)

    Blair, H.T.; Carroll, D.W.; Matthews, R.B. (Los Alamos National Laboratory, MS E505, Los Alamos, New Mexico (USA))

    1991-01-10T23:59:59.000Z

    Many of the nuclear propulsion reactor concepts proposed for a manned mission to Mars use a coated spherical particle fuel form similar to that used in the Rover and NERVA propulsion reactors. The formation of uranium dicarbide microspheres using a cryochemical process and the coating of the UC{sub 2} spheres with zirconium carbide using chemical vapor deposition are being developed at Los Alamos National Laboratory. The cryochemical process is described with a discussion of the variables affecting the sphere formation and carbothermic reduction to produce UC{sub 2} spheres from UO{sub 2}. Emphasis is placed on minimizing the wastes produced by the process. The ability to coat particles with ZrC was recaptured, and improvements in the process and equipment were developed. Volatile organometallic precursors were investigated as alternatives to the original ZrCl{sub 4} precursor.

  12. A review of carbide fuel corrosion for nuclear thermal propulsion applications

    SciTech Connect (OSTI)

    Pelaccio, D.G.; El-Genk, M.S. [Univ. of New Mexico, Albuquerque, NM (United States). Inst. for Space Nuclear Power Studies; Butt, D.P. [Los Alamos National Lab., NM (United States)

    1993-12-01T23:59:59.000Z

    At the operation conditions of interest in nuclear thermal propulsion reactors, carbide materials have been known to exhibit a number of life limiting phenomena. These include the formation of liquid, loss by vaporization, creep and corresponding gas flow restrictions, and local corrosion and fuel structure degradation due to excessive mechanical and/or thermal loading. In addition, the radiation environment in the reactor core can produce a substantial change in its local physical properties, which can produce high thermal stresses and corresponding stress fractures (cracking). Time-temperature history and cyclic operation of the nuclear reactor can also accelerate some of these processes. The University of New Mexico`s Institute for Space Nuclear Power Studies, under NASA sponsorship has recently initiated a study to model the complicated hydrogen corrosion process. In support of this effort, an extensive review of the open literature was performed, and a technical expert workshop was conducted. This paper summarizes the results of this review.

  13. Monocrystalline silicon carbide nanoelectromechanical systems Y. T. Yang, K. L. Ekinci, X. M. H. Huang, L. M. Schiavone, and M. L. Roukesa)

    E-Print Network [OSTI]

    Roukes, Michael L.

    C devices have primarily been fabricated from polycrystalline 3C-SiC poly-SiC thin films deposited diMonocrystalline silicon carbide nanoelectromechanical systems Y. T. Yang, K. L. Ekinci, X. M. H

  14. Separate determination of the amplitude of thermal vibrations and static atomic displacements in titanium carbide by neutron diffraction

    SciTech Connect (OSTI)

    Khidirov, I., E-mail: khidirov@inp.uz; Parpiev, A. S. [Uzbekistan Academy of Sciences, Institute of Nuclear Physics (Uzbekistan)

    2011-05-15T23:59:59.000Z

    The amplitude of thermal (dynamic) atomic vibrations and meansquare static atomic displacements in titanium carbide TiC{sub x} (x = 0.97, 0.88, 0.70) have been separately determined by measuring neutron diffraction patterns at two temperatures (T{sub 1} = 300 K and T{sub 2} = 80 K). The static lattice distortions in stoichiometric titanium carbide are experimentally found to be negligible. In the TiC{sub x} homogeneity range, the amplitude {radical}u{sup 2}{sub dyn} of thermal atomic vibrations significantly increases with a decrease in the carbon concentration. The Debye temperature has been determined for the first time in the TiC{sub x} homogeneity range at both room and liquid-nitrogen temperatures.

  15. Technical Review Report for the Justification for Shipment of Sodium-Bonded Carbide Fuel Pins in the T-3 Cask

    SciTech Connect (OSTI)

    West, M; DiSabatino, A

    2008-01-04T23:59:59.000Z

    This report documents the review of the Fluor Submittal (hereafter, the Submittal), prepared by Savannah River Packaging Technology (SRPT) of Savannah River National Laboratory (SRNL), at the request of the Department of Energy's (DOE) Richland Operations Office, for the shipment of unirradiated and irradiated sodium-bonded carbide fuel pins. The sodium-bonded carbide fuel pins are currently stored at the Fast Flux Test Facility (FFTF) awaiting shipment to Idaho National Laboratory (INL). Normally, modified contents are included into the next revision of the SARP. However, the contents, identified to be shipped from FFTF to Idaho National Laboratory, are a one-way shipment of 18 irradiated fuel pins and 7 unirradiated fuel pins, where the irradiated and unirradiated fuel pins are shipped separately, and can be authorized with a letter amendment to the existing Certificate of Compliance (CoC).

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

    SciTech Connect (OSTI)

    Marceau, Claude, E-mail: claude.marceau.2@ulaval.ca; Thomas, Steven; Kassimi, Yacine; Gingras, Guillaume; Witzel, Bernd [Centre d'Optique, Photonique et Laser, Pavillon d'optique-photonique Québec (Québec), Université Laval, Québec G1V 0A6 (Canada)

    2014-02-03T23:59:59.000Z

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

    SciTech Connect (OSTI)

    Linnanto, Juha Matti [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Freiberg, Arvi [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu (Estonia)

    2014-10-06T23:59:59.000Z

    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 B808–866 antenna complexes to the reaction center complex, in general agreement with the present understanding of this complex system.

  18. Complete Genome Sequence of the Filamentous Anoxygenic Phototrophic Bacterium Chloroflexus aurantiacus

    SciTech Connect (OSTI)

    Tang, Kuo-Hsiang [Washington University, St. Louis; Barry, Kerrie [U.S. Department of Energy, Joint Genome Institute; Chertkov, Olga [Los Alamos National Laboratory (LANL); Dalin, Eileen [U.S. Department of Energy, Joint Genome Institute; Han, Cliff [Los Alamos National Laboratory (LANL); Hauser, Loren John [ORNL; Honchak, Barbara M [Washington University, St. Louis; Karbach, Lauren E [Washington University, St. Louis; Land, Miriam L [ORNL; Lapidus, Alla L. [Joint Genome Institute, Walnut Creek, California; Larimer, Frank W [ORNL; Mikhailova, Natalia [U.S. Department of Energy, Joint Genome Institute; Pitluck, Sam [Joint Genome Institute, Walnut Creek, California; Pierson, Beverly K [University of Puget Sound, Tacoma, WA

    2011-01-01T23:59:59.000Z

    Chloroflexus aurantiacus is a thermophilic filamentous anoxygenic phototrophic (FAP) bacterium, and can grow phototrophically under anaerobic conditions or chemotrophically under aerobic and dark conditions. According to 16S rRNA analysis, Chloroflexi species are the earliest branching bacteria capable of photosynthesis, and Cfl. aurantiacus has been long regarded as a key organism to resolve the obscurity of the origin and early evolution of photosynthesis. Cfl. aurantiacus contains a chimeric photosystem that comprises some characters of green sulfur bacteria and purple photosynthetic bacteria, and also has some unique electron transport proteins compared to other photosynthetic bacteria.

  19. 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. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Jacob, W. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)

    2011-11-15T23:59:59.000Z

    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.

  20. 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

    2014-05-01T23:59:59.000Z

    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, Ti–Si–C MAX-phase joining, calcia–alumina glass–ceramic 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.

  1. 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)

    1996-01-23T23:59:59.000Z

    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.

  2. An investigation of silicon carbide-water nanofluid for heat transfer applications.

    SciTech Connect (OSTI)

    Singh, D.; Timofeeva, E.; Yu, W.; Routbort, J.; France, D.; Smith, D.; Lopez-Cepero, J. M. (Energy Systems); ( NE)

    2009-03-15T23:59:59.000Z

    Thermal conductivity and mechanical effects of silicon carbide nanoparticles uniformly dispersed in water were investigated. Mean size of SiC particles was 170 nm with a polydispersity of {approx}30% as determined from small-angle x-ray scattering and dynamic light scattering techniques. Room temperature viscosity of the nanofluids ranged from 2 to 3 cP for nominal nanoparticle loadings 4-7 vol %. On a normalized basis with water, viscosity of the nanofluids did not significantly change with the test temperature up to 85 C. Optical microscopy of diluted nanofluid showed no agglomeration of the nanoparticles. Thermal conductivity of the fluid was measured as a function of the nominal nanoparticle loading ranging from 1 to 7 vol %. Enhancement in thermal conductivity was approximately 28% over that of water at 7 vol % particle loadings under ambient conditions. Enhancements in thermal conductivities for the nanofluids with varying nanoparticle loadings were maintained at test temperatures up to 70 C. Results of thermal conductivity have been rationalized based on the existing theories of heat transfer in fluids. Implications of using this nanofluid for engineering cooling applications are discussed.

  3. Magnesium behavior and structural defects in Mg+ ion implanted silicon carbide

    SciTech Connect (OSTI)

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-01-01T23:59:59.000Z

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state suggests that there are preferred Si <100> interstitial splits. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C-SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C-SiC single crystal at 1573 K has been determined to be 3.8±0.4×10e-19 m2/sec.

  4. Fission Yield Measurements from Highly Enriched Uranium Irradiated Inside a Boron Carbide Capsule

    SciTech Connect (OSTI)

    Metz, Lori A.; Friese, Judah I.; Finn, Erin C.; Greenwood, Lawrence R.; Kephart, Rosara F.; Hines, Corey C.; King, Matthew D.; Henry, Kelley; Wall, Donald E.

    2013-05-01T23:59:59.000Z

    A boron carbide capsule was previously designed and tested by Pacific Northwest National Laboratory (PNNL) and Washington State University (WSU) for spectral-tailoring in mixed spectrum reactors. The presented work used this B4C capsule to create a fission product sample from the irradiation of highly enriched uranium (HEU) with a fast fission neutron spectrum. An HEU foil was irradiated inside of the capsule in WSU’s 1 MW TRIGA reactor at full power for 200 min to produce 5.8 × 1013 fissions. After three days of cooling, the sample was shipped to PNNL for radiochemical separations and analysis by gamma and beta spectroscopy. Fission yields for products were calculated from the radiometric measurements and compared to measurements from thermal neutron induced fission (analyzed in parallel with the non-thermal sample at PNNL) and published evaluated fast-pooled and thermal nuclear data. Reactor dosimetry measurements were also completed to fully characterize the neutron spectrum and total fluence of the irradiation.

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

    DOE Patents [OSTI]

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

    1996-01-23T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Shannon M. Bragg-Sitton

    2013-09-01T23:59:59.000Z

    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.

  7. 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

    2013-11-01T23:59:59.000Z

    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 ß-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.

  8. Effect of Decreasing of Cobalt Content in Properties for Diamond/Cemented Carbide Tools

    SciTech Connect (OSTI)

    Waratta, A.; Hamdi, M. [Department of Design and Manufacture, Faculty of Engineering, University of Malaya (Malaysia); Ariga, T. [Department of Materials Science, School of Engineering, Tokai University (Japan)

    2010-03-11T23:59:59.000Z

    Powder metallurgy plays a role in manufacturing such as automotive and cutting tool applications. Diamond/cemented carbide tools are also made from this technique. Diamond particle and other matrix materials were employed in this study. The purpose is to investigate the physical and mechanical properties of different Cobalt (Co) content samples by using Taguchi's method. The materials used in the experiments were mixed by using a ball-mill machine. The mixed powders were pressed by conventional method. Then the green samples were sintered in a vacuum furnace. After reaching 500 deg. C, the samples were sintered with Argon (Ar) gas. The sintered samples were investigated density by immersion method, porosity by water saturation method, and hardness by Vicker hardness tester. It was found that with 59.5% Co content, plain diamond type, sintering temperature of 950 deg. C, sintering time of 40 minutes, and pressure of 625 MPa, density, porosity, and hardness got the best result in this study. From the Taguchi's analysis, the significant factors effected the performance were composition, sintering temperature, and sintering time.

  9. Analysis of microwave leaky modes propagating through laser plasma filaments column waveguide

    SciTech Connect (OSTI)

    Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan [School of Science, Changchun University of Science and Technology, Changchun 130022 (China)

    2012-12-15T23:59:59.000Z

    A plasma column waveguide formed by a bundle of closely spaced plasma filaments induced by the propagation of ultrafast laser pulses in air and revived by a longer infrared laser pulse is shown to support microwave radiation. We consider values of both the plasma electron density and microwave frequency for which the refractive index of plasma is lower than the refractive index of air; therefore, a leaky plasma waveguide can be realized in extremely high frequency band. The guiding mechanism does not require high conductance of the plasma and can be easily excited by using commercial femtosecond laser sources. A theoretical study of leaky mode characteristics of isotropic and homogeneous plasma column waveguides is investigated with several values of plasma and waveguide structure parameters. The microwave transmission loss was found to be mainly caused by the microwave leakage through the air-plasma interface and is weakly dependent on the plasma absorption. In spite of losses of microwaves caused by leakage and plasma absorption, it is shown to be much lower than both that accompanying to surface waves attaching to single conducting plasma wire and the free space propagation over distances in the order of the filament length, which opens exciting perspectives for short distance point to point wireless transmission of pulsed-modulated microwaves.

  10. DIRECT OBSERVATIONAL EVIDENCE OF FILAMENT MATERIAL WITHIN INTERPLANETARY CORONAL MASS EJECTIONS

    SciTech Connect (OSTI)

    Lepri, S. T.; Zurbuchen, T. H., E-mail: slepri@umich.ed, E-mail: thomasz@umich.ed [Department of Atmospheric, Oceanic, and Space Sciences University of Michigan, Ann Arbor, MI 48109-2143 (United States)

    2010-11-01T23:59:59.000Z

    Coronal mass ejections (CMEs) are explosive events that escape the Sun's corona carrying solar material and energy into the heliosphere. The classic picture of a CME observed in the corona presents a 'three-part structure', including a bright front at the leading edge indicating dense plasma, a low-density cavity, the possible signature of an embedded magnetic flux rope, and the so-called core, a high-density region observed to be associated with an erupting filament. Although there are experimental analogs to the first two parts of the CME when observed in situ, there are only a handful of in situ observations of cold, filament-type plasma. This has been a source of major uncertainty and qualitative disagreement between remote and in situ observations of these ejecta. We present the first comprehensive and long-term survey of such low charge states observed by the Advanced Composition Explorer Solar Wind Ion Composition Spectrometer, using a novel data analysis process developed to identify ions with low ionic charge states. Using a very stringent set of observational signatures, we find that more than 4% of detected interplanetary CMEs have significant contributions of ions with low charge states. These time periods of low-charge ions often occur concurrent with some of the hottest ions, previously interpreted to be affected by flare heating during the CME initiation.

  11. Finite element analyses of continuous filament ties for masonry applications : final report for the Arquin Corporation.

    SciTech Connect (OSTI)

    Quinones, Armando, Sr. (Arquin Corporation, La Luz, NM); Bibeau, Tiffany A.; Ho, Clifford Kuofei

    2008-08-01T23:59:59.000Z

    Finite-element analyses were performed to simulate the response of a hypothetical vertical masonry wall subject to different lateral loads with and without continuous horizontal filament ties laid between rows of concrete blocks. A static loading analysis and cost comparison were also performed to evaluate optimal materials and designs for the spacers affixed to the filaments. Results showed that polypropylene, ABS, and polyethylene (high density) were suitable materials for the spacers based on performance and cost, and the short T-spacer design was optimal based on its performance and functionality. Simulations of vertical walls subject to static loads representing 100 mph winds (0.2 psi) and a seismic event (0.66 psi) showed that the simulated walls performed similarly and adequately when subject to these loads with and without the ties. Additional simulations and tests are required to assess the performance of actual walls with and without the ties under greater loads and more realistic conditions (e.g., cracks, non-linear response).

  12. Conference Proceedings (Refereed Invited Reviews). 1. "Role of Large-Scale Magnetic Fields and Material Flows in the Formation of Solar Filaments

    E-Print Network [OSTI]

    Mackay, Duncan

    Conference Proceedings (Refereed Invited Reviews). 1. "Role of Large-Scale Magnetic Fields Scale Structures and their Role in Solar Activity, ASP Conference Proceedings Series, 346, 177. 2. "The-297. Conference Proceedings (Others). 1. "Basic Magnetic Field Configurations for Filament Channels and Filaments

  13. 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., E-mail: rav@knights.ucf.edu [Department of Mathematics, University of Central Florida, Orlando, Florida 32816-1364 (United States)

    2014-11-15T23:59:59.000Z

    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.

  14. Effect of quantum well non-uniformities on lasing threshold, linewidth, and lateral near field filamentation in violet (Al,In)GaN laser diodes

    SciTech Connect (OSTI)

    Jeschke, J.; Zeimer, U.; Redaelli, L.; Einfeldt, S.; Weyers, M. [Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin (Germany); Kneissl, M. [Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin (Germany); Institute of Solid State Physics, Technical University of Berlin, 10623 Belin (Germany)

    2014-10-27T23:59:59.000Z

    The lateral near field patterns and filamentation effects of gain guided broad area (Al,In)GaN-based laser diodes emitting around 415?nm have been investigated. Diodes from the same laser bar, which are close to each other, show nearly the same number and widths of filaments. Comparison of different bars, which are from the same wafer but further apart from each other, reveals that a higher number of filaments correlates with a higher laser threshold and broader spectral linewidth. Cathodoluminescence mappings at 80?K show strong variations of the quantum well band gap and hence of the emission wavelength for the bars with strong filamentation. These observations confirm previous theoretical predictions stating that large band gap fluctuations increase the threshold current and spectral linewidth. Furthermore, filamentation is enhanced as well because of a reduction of the carrier diffusion length.

  15. The Role of tantalum in TiC-WC-TaC-Co sintered carbides. II. influence of tantalum content on the structure and properties of TiC-WC-TaC-Co three-phase sintered carbides

    SciTech Connect (OSTI)

    Cheburaeva, R.F.; Chaporova, I.N.

    1986-10-01T23:59:59.000Z

    This work is devoted to a study of the influence of tantalum on the structure and properties of three-phase alloys. The investigations were made with a constant weight ratio of Ti:WC = 35:65% and an unchanged carbon content. The alloys were prepared by mixing of the (T, W, Ta)C carbides with cobalt and tungsten carbide. The pressed specimens were given a preliminary sinter in hydrogen at 923-973 K and a final one in a vacuum furnace at 1773 K. The microstructure, density, and bend and compressive strengths at room and increased temperatures, coeffiecients of cutting life and strength (in comparison with a standard taken as unity), and adhesion interaction were determined. The coefficient of cutting life was determined by transverse machining of steel. The coefficient of strength was determined by the method of breaking feed in milling of 50 steel with a single-tooth cutter. The adhesion interaction of TiC-WC-TaC-Co alloys with the material being machined (50 steel) was determined in vacuum (which eliminated the additional influence of oxidation of the alloy) at 873 K with a load of 1000N. Tantalum carbide additions have a favorable influence on the physicomechanical and service properties of TiC-WC-Co alloys. Their bend strength at room and increased temperatures increases and there is an increase in the total deformation and the work for deformation at increased temperatures, a reduction in oxidation and adhesion interaction with the material being machined, and a significant increase in wear resistance in cutting. Graphs and tables are included.

  16. Characterization of boron carbide particulate reinforced in situ copper surface composites synthesized using friction stir processing

    SciTech Connect (OSTI)

    Sathiskumar, R., E-mail: sathiscit2011@gmail.com [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Murugan, N., E-mail: murugan@cit.edu.in [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Dinaharan, I., E-mail: dinaweld2009@gmail.com [Department of Mechanical Engineering, V V College of Engineering, Tisaiyanvilai, 627 657 Tamil Nadu (India); Vijay, S.J., E-mail: vijayjoseph@karunya.edu [Centre for Research in Metallurgy (CRM), School of Mechanical Sciences, Karunya University, Coimbatore, 641 114 Tamil Nadu (India)

    2013-10-15T23:59:59.000Z

    Friction stir processing has evolved as a novel solid state technique to fabricate surface composites. The objective of this work is to apply the friction stir processing technique to fabricate boron carbide particulate reinforced copper surface composites and investigate the effect of B{sub 4}C particles and its volume fraction on microstructure and sliding wear behavior of the same. A groove was prepared on 6 mm thick copper plates and packed with B{sub 4}C particles. The dimensions of the groove was varied to result in five different volume fractions of B{sub 4}C particles (0, 6, 12, 18 and 24 vol.%). A single pass friction stir processing was done using a tool rotational speed of 1000 rpm, travel speed of 40 mm/min and an axial force of 10 kN. Metallurgical characterization of the Cu/B{sub 4}C surface composites was carried out using optical microscope and scanning electron microscope. The sliding wear behavior was evaluated using a pin-on-disk apparatus. Results indicated that the B{sub 4}C particles significantly influenced the area, dispersion, grain size, microhardness and sliding wear behavior of the Cu/B{sub 4}C surface composites. When the volume fraction of B{sub 4}C was increased, the wear mode changed from microcutting to abrasive wear and wear debris was found to be finer. Highlights: • Fabrication of Cu/B{sub 4}C surface composite by friction stir processing • Analyzing the effect of B{sub 4}C particles on the properties of Cu/B4C surface composite • Increased volume fraction of B{sub 4}C particles reduced the area of surface composite. • Increased volume fraction of B{sub 4}C particles enhanced the microhardness and wear rate. • B{sub 4}C particles altered the wear mode from microcutting to abrasive.

  17. Growth of silicon quantum dots by oxidation of the silicon nanocrystals embedded within silicon carbide matrix

    SciTech Connect (OSTI)

    Kole, Arindam; Chaudhuri, Partha, E-mail: erpc@iacs.res.in [Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata-700032 (India)

    2014-10-15T23:59:59.000Z

    A moderately low temperature (?800 °C) thermal processing technique has been described for the growth of the silicon quantum dots (Si-QD) within microcrystalline silicon carbide (?c-SiC:H) dielectric thin films deposited by plasma enhanced chemical vapour deposition (PECVD) process. The nanocrystalline silicon grains (nc-Si) present in the as deposited films were initially enhanced by aluminium induced crystallization (AIC) method in vacuum at a temperature of T{sub v} = 525 °C. The samples were then stepwise annealed at different temperatures T{sub a} in air ambient. Analysis of the films by FTIR and XPS reveal a rearrangement of the ?c-SiC:H network has taken place with a significant surface oxidation of the nc-Si domains upon annealing in air. The nc-Si grain size (D{sub XRD}) as calculated from the XRD peak widths using Scherrer formula was found to decrease from 7 nm to 4 nm with increase in T{sub a} from 250 °C to 800 °C. A core shell like structure with the nc-Si as the core and the surface oxide layer as the shell can clearly describe the situation. The results indicate that with the increase of the annealing temperature in air the oxide shell layer becomes thicker and the nc-Si cores become smaller until their size reduced to the order of the Si-QDs. Quantum confinement effect due to the SiO covered nc-Si grains of size about 4 nm resulted in a photoluminescence peak due to the Si QDs with peak energy at 1.8 eV.

  18. IMPACT EVALUATION OF AN ENERGY SAVINGS PLAN PROJECT AT THE LINDE DIVISION OF UNION CARBIDE CORPORATION

    SciTech Connect (OSTI)

    Spanner, G. E.; Sullivan, G. P.

    1992-04-01T23:59:59.000Z

    This impact evaluation of an energy conservation measure (ECM) that was recently installed at the Linde Division of Union Carbide Corporation (Linde) was conducted far the Bonneville Power Administration (Bonneville) as part of an evaluation of its Energy Savings Plan (ESP) Program. The Program makes acquisition payments to firms that install energy conservation measures in their industrial processes. The objective of this impact evaluation was to assess how much electrical energy is being saved at Linde as a result of the ESP and to determine how much the savings cost Bonneville and the region. The impact of the ECM was evaluated with a combination of engineering analysis, financial analysis, site visit and interviews, and submittal reviews (Linde's Completion Report and Abstract). The ECM itself consists of replacing the plant's nitrogen feed compressor with a larger unit, which allows the plant to meet its argon demand using less compressed air and which results in net energy savings. Energy savings resulting from this ECM were 4,376,500 kWh/yr for the first two years after installation, but, because of a change in Linde's market position, long-term savings are expected to be lower at 2,549,200 kWh/yr. Linde considers energy consumption and savings on a per ton basis to be proprietary, so they are not reported here. The ECM cost $361,4.96 to install, and Linde received payment of $161,426 from Bonneville for the acquisition of energy savings. This ECM would not have been implemented without the acquisition payment from Bonneville. The levelized cost of these energy savings to Bonneville will be 4.5 mills/kWh over the ECM's expected 15-year life, and the levelized cost to th.e region will be 5.9 mills/kWh.

  19. EVIDENCE FOR RADIOGENIC SULFUR-32 IN TYPE AB PRESOLAR SILICON CARBIDE GRAINS?

    SciTech Connect (OSTI)

    Fujiya, Wataru; Hoppe, Peter [Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz (Germany)] [Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz (Germany); Zinner, Ernst [Laboratory for Space Sciences and Physics Department, Campus Box 1105, Washington University, St. Louis, MO 63130 (United States)] [Laboratory for Space Sciences and Physics Department, Campus Box 1105, Washington University, St. Louis, MO 63130 (United States); Pignatari, Marco [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)] [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Herwig, Falk, E-mail: wataru.fujiya@mpic.de, E-mail: peter.hoppe@mpic.de, E-mail: ekz@wustl.edu, E-mail: mpignatari@gmail.com, E-mail: fherwig@uvic.ca [Department of Physics and Astronomy, University of Victoria, Canada, P.O. Box 3055, Victoria, BC V8W 3P6 (Canada)] [Department of Physics and Astronomy, University of Victoria, Canada, P.O. Box 3055, Victoria, BC V8W 3P6 (Canada)

    2013-10-20T23:59:59.000Z

    We report C, Si, and S isotope measurements on 34 presolar silicon carbide grains of Type AB, characterized by {sup 12}C/{sup 13}C < 10. Nitrogen, Mg-Al-, and Ca-Ti-isotopic compositions were measured on a subset of these grains. Three grains show large {sup 32}S excesses, a signature that has been previously observed for grains from supernovae (SNe). Enrichments in {sup 32}S may be due to contributions from the Si/S zone and the result of S molecule chemistry in still unmixed SN ejecta or due to incorporation of radioactive {sup 32}Si from C-rich explosive He shell ejecta. However, a SN origin remains unlikely for the three AB grains considered here, because of missing evidence for {sup 44}Ti, relatively low {sup 26}Al/{sup 27}Al ratios (a few times 10{sup –3}), and radiogenic {sup 32}S along with low {sup 12}C/{sup 13}C ratios. Instead, we show that born-again asymptotic giant branch (AGB) stars that have undergone a very-late thermal pulse (VLTP), known to have low {sup 12}C/{sup 13}C ratios and enhanced abundances of the light s-process elements, can produce {sup 32}Si, which makes such stars attractive sources for AB grains with {sup 32}S excesses. This lends support to the proposal that at least some AB grains originate from born-again AGB stars, although uncertainties in the born-again AGB star models and possible variations of initial S-isotopic compositions in the parent stars of AB grains make it difficult to draw a definitive conclusion.

  20. Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage

    SciTech Connect (OSTI)

    Fisher, John E.; Gogotsi, Yury; Yildirim, Taner

    2010-01-07T23:59:59.000Z

    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.

  1. Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors

    SciTech Connect (OSTI)

    Katoh, Yutai [ORNL; Wilson, Dane F [ORNL; Forsberg, Charles W [ORNL

    2007-09-01T23:59:59.000Z

    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.

  2. A STUDY OF THE ORIENTATION OF INTERPLANETARY MAGNETIC CLOUDS AND SOLAR FILAMENTS Yuming Wang,1,2

    E-Print Network [OSTI]

    Wang, Jingxiu

    environment around Earth. Large nonre- current geomagnetic storms are mainly caused by coronal mass ejections are not perpendicular to the Earth-Sun line, indicating that the measured part of the MC is not its leading front. INTRODUCTION In the current paradigm, filament-associated magnetic clouds (MCs) are thought to be the result

  3. Supercontinuum emission and enhanced self-guiding of infrared femtosecond filaments sustained by third-harmonic generation in air

    E-Print Network [OSTI]

    Skupin, Stefan

    and Solid State Optics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany 3-wave mixing and cross-phase modulation. Third, the filamentation is accompanied by a conical emission plasma generation comes into play. Self-induced ionization then depletes the back of the pulse and keeps

  4. High-mass star formation triggered by collision between CO filaments in N159 West in the Large Magellanic Cloud

    E-Print Network [OSTI]

    Fukui, Yasuo; Tokuda, Kazuki; Morioka, Yuuki; Onishi, Toshikazu; Torii, Kazufumi; Ohama, Akio; Nayak, Omnarayani; Meixner, Margaret; Sewilo, Marta; Indebetouw, Remy; Kawamura, Akiko; Saigo, Kazuya; Yamamoto, Hiroaki; Tachihara, Kengo; Minamidani, Tetsuhiro; Inoue, Tsuyoshi; Madden, Suzanna; Galametz, Maud; Lebouteiller, Vianney; Mizuno, Norikazu; Chen, Rosie

    2015-01-01T23:59:59.000Z

    We have carried out 13CO (J=2-1) observations of the active star-forming region N159 West in the LMC with ALMA. We have found that the CO distribution at a sub-pc scale is highly elongated with a small width. These elongated clouds called "filaments" show straight or curved distributions with a typical width of 0.5-1.0 pc and a length of 5-10 pc. All the known infrared YSOs are located toward the filaments. We have found broad CO wings of two molecular outflows toward young high-mass stars in N159W-N and N159W-S, whose dynamical timescale is ~10^4 yrs. This is the first discovery of protostellar outflow in external galaxies. For N159W-S which is located toward an intersection of two filaments we set up a hypothesis that the two filaments collided with each other ~10^5 yrs ago and triggered formation of the high-mass star having ~37Mo. The colliding clouds show significant enhancement in linewidth in the intersection, suggesting excitation of turbulence in the shocked interface layer between them as is consist...

  5. Non-filamentated ultra-intense and ultra-short pulse fronts in three-dimensional Raman seed amplification

    SciTech Connect (OSTI)

    Lehmann, G.; Spatschek, K. H. [Institut für Theoretische Physik, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf (Germany)] [Institut für Theoretische Physik, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf (Germany)

    2014-05-15T23:59:59.000Z

    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.

  6. Trapping and Destruction of Long-Range High-Intensity Optical Filaments by Molecular Quantum Wakes in Air

    E-Print Network [OSTI]

    Milchberg, Howard

    in Air S. Varma, Y.-H. Chen, and H. M. Milchberg Institute for Research in Electronics and Applied in atmospheric air on the long-range filamentary propagation of intense femtosecond laser pulses. In a pump following a pump pulse filamenting in air has a dramatic effect on the propagation of an intense probe pulse

  7. Interaction between a flexible filament and a downstream rigid body Fang-Bao Tian,1,2

    E-Print Network [OSTI]

    Luo, Haoxiang

    Interaction between a flexible filament and a downstream rigid body Fang-Bao Tian,1,2 Haoxiang Luo- action between rigid objects. In the situation that one rigid object is located in the downstream wake bodies in tandem arrangement, the downstream one suffers a drag increase and flaps with a larger

  8. 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)

    2011-03-15T23:59:59.000Z

    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.

  9. Overdensity of X-Ray sources near 3C 295: a candidate filament

    E-Print Network [OSTI]

    V. D'Elia; F. Fiore; F. Cocchia

    2004-07-22T23:59:59.000Z

    We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster (z=0.46) aimed at the search for clustering of X-ray sources. Three different methods of analysis, namely a chip by chip logN-logS, a two dimensional Kolmogorov-Smirnov test, and the angular correlation function (ACF) show a strong overdensity of sources in the North-East of the field. In particular, the ACF shows a clear signal on scales of 0.5 - 5 arcmin. This correlation angle is > 2 times higher than that of a sample of 8 ACIS-I field at the 2.5 sigma confidence level. If this overdensity is spatially associated to the cluster, we are observing a 'filament' of the large scale structure of the Universe. We discuss some first results that seem to indicate such an association.

  10. Self-similar condensation of rotating magnetized self-gravitating isothermal filaments

    E-Print Network [OSTI]

    P. Hennebelle

    2002-10-18T23:59:59.000Z

    Ordinary differential equations describing the self-similar collapse of a rotating, magnetized, self-gravitating and isothermal filament are derived. Explicit homologous solutions are studied with special emphasis on the bifurcation that occurs at the magnetosonic critical point. It is shown that there is a critical value for the toroidal magnetic field slope at the origin above which no bifurcation occurs, the solution remains homologous, and below which the density and the poloidal magnetic field tend to zero at large radius (envelope) whereas the toroidal magnetic field and azimuthal velocity relax towards a constant value. A series of spatial profiles of density, velocity and magnetic field, potentially useful for comparison with numerical or observational studies, is obtained numerically and discussed.

  11. Filamentation of magnetosonic wave and generation of magnetic turbulence in laser plasma interaction

    SciTech Connect (OSTI)

    Modi, K. V., E-mail: kvmodi.iitd@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Mechanical Engineering Department, Government Engineering College Valsad, Gujarat 396001 (India); Tiwary, Prem Pyari, E-mail: prempyari@gmail.com [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Department of Physics and Computer Science, Dayal Bagh Educational Institute (Deemed University), Dayal Bagh, Agra 282005 (India); Singh, Ram Kishor, E-mail: ram007kishor@gmail.com; Sharma, R. P., E-mail: rpsharma@ces.iitd.ac.in [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Satsangi, V. R. [Department of Physics and Computer Science, Dayal Bagh Educational Institute (Deemed University), Dayal Bagh, Agra 282005 (India)

    2014-10-15T23:59:59.000Z

    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.

  12. Towards Real-Time Detection and Tracking of Blob-Filaments in Fusion Plasma Big Data

    E-Print Network [OSTI]

    Wu, Lingfei; Sim, Alex; Churchill, Michael; Choi, Jong Y; Stathopoulos, Andreas; Chang, Cs; Klasky, Scott

    2015-01-01T23:59:59.000Z

    Magnetic fusion could provide an inexhaustible, clean, and safe solution to the global energy needs. The success of magnetically-confined fusion reactors demands steady-state plasma confinement which is challenged by the blob-filaments driven by the edge turbulence. Real-time analysis can be used to monitor the progress of fusion experiments and prevent catastrophic events. However, terabytes of data are generated over short time periods in fusion experiments. Timely access to and analyzing this amount of data demands properly responding to extreme scale computing and big data challenges. In this paper, we apply outlier detection techniques to effectively tackle the fusion blob detection problem on extremely large parallel machines. We present a real-time region outlier detection algorithm to efficiently find blobs in fusion experiments and simulations. In addition, we propose an efficient scheme to track the movement of region outliers over time. We have implemented our algorithms with hybrid MPI/OpenMP and ...

  13. 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.

    1980-01-01T23:59:59.000Z

    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.

  14. Effects of atmosphere on the tribological properties of a chromium carbide based coating for use to 760 C

    SciTech Connect (OSTI)

    Dellacorte, C.; Sliney, H.E.

    1988-04-01T23:59:59.000Z

    The effect of atmosphere on the tribological properties of a plasma-sprayed chromium carbide based self-lubricating coating is reported. The coating contains bonded chromium carbide as the wear resistant base stock to which the lubricants silver and barium fluoride/calcium fluoride eutectic are added. It has been denoted as NASA PS200. Potential applications for the PS200 coating are cylinder wall/piston ring couples Stirling engines and foil bearing journal lubrication. Friction and wear studies were performed in helium, hydrogen, and moist air at temperatures from 25 to 760 C. In general, the atmosphere had a significant effect on both the friction and the wear of the coating and counterface material. Specimens tested in hydrogen, a reducing environment, exhibited the best tribological properties. Friction and wear increased in helium and air but are still within acceptable limits for intended applications. A variety of X-ray analyses was performed on the test specimens in an effort to explain the results. The following conclusions are made: (1) As the test atmosphere becomes less reducing, the coating experiences a higher concentration level of chromic oxide at the sliding interface which increases both the friction and wear. (2) Beneficial silver transfer from the parent coating to the counter-face material is less effective in air than in helium or hydrogen. (3) There may be a direct relationship between chromic oxide level present at the sliding interface and the friction coefficient. 7 references.

  15. SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE {sup 32}Si IN SUPERNOVAE

    SciTech Connect (OSTI)

    Pignatari, M.; Rauscher, T.; Thielemann, F.-K. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Zinner, E. [Laboratory for Space Sciences and the Physics Department, Washington University, St. Louis, MO 63130 (United States); Bertolli, M. G. [Theoretical Division (T-2), LANL, Los Alamos, NM 87545 (United States); Trappitsch, R. [Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States); Hoppe, P. [Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz (Germany); Fryer, C. [Computational Physics and Methods (CCS-2), LANL, Los Alamos, NM 87545 (United States); Herwig, F. [Department of Physics and Astronomy, University of Victoria, Victoria, BC (Canada); Hirschi, R. [Keele University, Keele, Staffordshire ST5 5BG (United Kingdom); Timmes, F. X. [Joint Institute for Nuclear Astrophysics, Notre Dame, IN 46556 (United States)

    2013-07-01T23:59:59.000Z

    Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae (SNe) within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotopic signatures of explosive SN nucleosynthesis have been found in primitive meteorites. Much rarer silicon carbide grains of type C are a special sub-group of SiC grains from SNe. They show peculiar abundance signatures for Si and S, isotopically heavy Si, and isotopically light S, which appear to be in disagreement with model predictions. We propose that C grains are formed mostly from C-rich stellar material exposed to lower SN shock temperatures than the more common type X grains. In this scenario, extreme {sup 32}S enrichments observed in C grains may be explained by the presence of short-lived {sup 32}Si ({tau}{sub 1/2} = 153 yr) in the ejecta, produced by neutron capture processes starting from the stable Si isotopes. No mixing from deeper Si-rich material and/or fractionation of Si from S due to molecular chemistry is needed to explain the {sup 32}S enrichments. The abundance of {sup 32}Si in the grains can provide constraints on the neutron density reached during the SN explosion in the C-rich He shell material. The impact of the large uncertainty of the neutron capture cross sections in the {sup 32}Si region is discussed.

  16. Aligned Carbon Nanotube Reinforced Silicon Carbide Composites by Chemical Vapor Infiltration

    SciTech Connect (OSTI)

    Gu, Zhan Jun [University of Georgia, Athens, GA; Yang, Ying Chao [University of South Carolina, Columbia; Li, Kai Yuan [University of Georgia, Athens, GA; Tao, Xin Yong [University of South Carolina, Columbia; Eres, Gyula [ORNL; Howe, Jane Y [ORNL; Zhang, Li Tong [Northwestern Polytechnical University, Xi'an, China; Li, Xiao Dong [University of South Carolina, Columbia; Pan, Zhengwei [ORNL

    2011-01-01T23:59:59.000Z

    Owing to their exceptional stiffness and strength1 4, carbon nanotubes (CNTs) have long been considered to be an ideal reinforcement for light-weight, high-strength, and high-temperature-resistant ceramic matrix composites (CMCs)5 10. However, the research and development in CNT-reinforced CMCs have been greatly hindered due to the challenges related to manufacturing including poor dispersion, damages during dispersion, surface modification, densification and sintering, weak tube/matrix interfaces, and agglomeration of tubes at the matrix grain boundaries5,11. Here we report the fabrication of high-quality aligned CNT/SiC composites by chemical vapor infiltration (CVI), a technique that is being widely used to fabricate commercial continuous-filament CMCs12 15. Using the CVI technique most of the challenges previously encountered in the fabrication of CNT composites were readily overcome. Nanotube pullouts, an important toughening mechanism for CMCs, were consistently observed on all fractured CNT/SiC samples. Indeed, three-point bending tests conducted on individual CNT/SiC nanowires (diameters: 50 200 nm) using an atomic force microscope show that the CNT-reinforced SiC nanowires are about an order of magnitude tougher than the bulk SiC. The tube/matrix interface is so intimate and the SiC matrix is so dense that a ~50-nm-thick SiC coating can effectively protect the inside nanotubes from being oxidized at 1600 C in air. The CVI method may be extended to produce nanotube composites from a variety of matrix

  17. Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations

    SciTech Connect (OSTI)

    Way, J.; Wolden, Colin

    2013-09-30T23:59:59.000Z

    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.

  18. Clusters, groups, and filaments in the Chandra deep field-south up to redshift 1

    SciTech Connect (OSTI)

    Dehghan, S.; Johnston-Hollitt, M., E-mail: siamak.dehghan@vuw.ac.nz [School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140 (New Zealand)

    2014-03-01T23:59:59.000Z

    We present a comprehensive structure detection analysis of the 0.3 deg{sup 2} area of the MUSYC-ACES field, which covers the Chandra Deep Field-South (CDFS). Using a density-based clustering algorithm on the MUSYC and ACES photometric and spectroscopic catalogs, we find 62 overdense regions up to redshifts of 1, including clusters, groups, and filaments. We also present the detection of a relatively small void of ?10 Mpc{sup 2} at z ? 0.53. All structures are confirmed using the DBSCAN method, including the detection of nine structures previously reported in the literature. We present a catalog of all structures present, including their central position, mean redshift, velocity dispersions, and classification based on their morphological and spectroscopic distributions. In particular, we find 13 galaxy clusters and 6 large groups/small clusters. Comparison of these massive structures with published XMM-Newton imaging (where available) shows that 80% of these structures are associated with diffuse, soft-band (0.4-1 keV) X-ray emission, including 90% of all objects classified as clusters. The presence of soft-band X-ray emission in these massive structures (M {sub 200} ? 4.9 × 10{sup 13} M {sub ?}) provides a strong independent confirmation of our methodology and classification scheme. In the closest two clusters identified (z < 0.13) high-quality optical imaging from the Deep2c field of the Garching-Bonn Deep Survey reveals the cD galaxies and demonstrates that they sit at the center of the detected X-ray emission. Nearly 60% of the clusters, groups, and filaments are detected in the known enhanced density regions of the CDFS at z ? 0.13, 0.52, 0.68, and 0.73. Additionally, all of the clusters, bar the most distant, are found in these overdense redshift regions. Many of the clusters and groups exhibit signs of ongoing formation seen in their velocity distributions, position within the detected cosmic web, and in one case through the presence of tidally disrupted central galaxies exhibiting trails of stars. These results all provide strong support for hierarchical structure formation up to redshifts of 1.

  19. Growth of Dome-Shaped Carbon Nanoislands on Ir(111): The Intermediate between Carbidic Clusters and Quasi-Free-Standing Graphene

    E-Print Network [OSTI]

    Alfè, Dario

    and Quasi-Free-Standing Graphene Paolo Lacovig,1 Monica Pozzo,2 Dario Alfe`,2 Paolo Vilmercati,3 of a long-range ordered graphene layer on Ir(111) assume a peculiar domelike shape. The understanding coupled carbidic carbon and a quasi-free-standing graphene layer, can provide information for a rational

  20. 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.

    2012-06-01T23:59:59.000Z

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer–Tropsch (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.

  1. Sierra Designs 20 degrees F Wild Bill Climashield Sleeping Bag ClimashieldTM HL, a high-loft continuous filament insulation, offers excellent thermal

    E-Print Network [OSTI]

    Walker, Lawrence R.

    -loft continuous filament insulation, offers excellent thermal efficiency, durability and water resistance Chest to create a pillow; no need for a pillow to take up valuable space in your backpack Insulated draft tube

  2. Composition and method for brazing graphite to graphite

    DOE Patents [OSTI]

    Taylor, Albert J. (Ten Mile, TN); Dykes, Norman L. (Oak Ridge, TN)

    1984-01-01T23:59:59.000Z

    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.

  3. Bubble formation within filaments of melt-processed Bi2212 wires and its strongly negative effect on the critical current density

    E-Print Network [OSTI]

    the Jc of Bi2212 round wires. 1. Introduction The high-temperature superconductor (HTS) Bi2Sr2CaCu2Ox (BiBubble formation within filaments of melt-processed Bi2212 wires and its strongly negative effect.1088/0953-2048/24/7/075009 Bubble formation within filaments of melt-processed Bi2212 wires and its strongly negative effect

  4. 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. [Kanzelhoehe Observatory-IGAM, Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Vrsnak, B. [Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, HR-10000 Zagreb (Croatia)

    2012-08-10T23:59:59.000Z

    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.

  5. Finite element analyses of continuous filament ties for masonry applications:final report for the Arquin Corporation.

    SciTech Connect (OSTI)

    Quinones, Armando (Arquin Corporation, La Luz, NM); Bibeau, Tiffany A.; Ho, Clifford Kuofei

    2006-06-01T23:59:59.000Z

    Finite-element analyses were performed to simulate the response of a hypothetical masonry shear wall with and without continuous filament ties to various lateral loads. The loads represented three different scenarios: (1) 100 mph wind, (2) explosive attack, and (3) an earthquake. In addition, a static loading analysis and cost comparison were performed to evaluate optimal materials and designs for the spacers affixed to the filaments. Results showed that polypropylene, ABS, and polyethylene (high density) were suitable materials for the spacers based on performance and cost, and the short T-spacer design was optimal based on its performance and functionality. Results of the shear-wall loading simulations revealed that simulated walls with the continuous filament ties yielded factors of safety that were at least ten times greater than those without the ties. In the explosive attack simulation (100 psi), the simulated wall without the ties failed (minimum factor of safety was less than one), but the simulated wall with the ties yielded a minimum factor of safety greater than one. Simulations of the walls subject to lateral loads caused by 100 mph winds (0.2 psi) and seismic events with a peak ground acceleration of 1 ''g'' (0.66 psi) yielded no failures with or without the ties. Simulations of wall displacement during the seismic scenarios showed that the wall with the ties resulted in a maximum displacement that was 20% less than the wall without the ties.

  6. The impact of thermodynamics on gravitational collapse: filament formation and magnetic field amplification

    E-Print Network [OSTI]

    Thomas Peters; Dominik R. G. Schleicher; Ralf S. Klessen; Robi Banerjee; Christoph Federrath; Rowan J. Smith; Sharanya Sur

    2012-09-26T23:59:59.000Z

    Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k rho^Gamma, with both sub-isothermal exponents Gamma 1. We find significant differences between these two cases. For Gamma > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For Gamma < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.

  7. Large Solar Energetic Particle Events Associated with Filament Eruptions Outside of Active Regions

    E-Print Network [OSTI]

    Gopalswamy, N; Akiyama, S; Yashiro, S; Xie, H; Thakur, N; Kahler, S W

    2015-01-01T23:59:59.000Z

    We report on four large filament eruptions (FEs) from solar cycles 23 and 24 that were associated with large solar energetic particle (SEP) events and interplanetary type II radio bursts. The post-eruption arcades corresponded to mostly C-class soft X-ray enhancements, but an M1.0 flare was associated with one event. However, the associated coronal mass ejections (CMEs) were fast (speeds about 1000 km/s) and appeared as halo CMEs in the coronagraph field of view. The interplanetary type II radio bursts occurred over a wide wavelength range indicating the existence of strong shocks throughout the inner heliosphere. No metric type II bursts were present in three events, indicating that the shocks formed beyond 2 to 3 Rs. In one case, there was a metric type II burst with low starting frequency indicating a shock formation height of about 2 Rs. The FE-associated SEP events did have softer spectra (spectral index greater than 4) in the 10 to 100 MeV range, but there were other low-intensity SEP events with spectr...

  8. Self-fabricated single mode waveguide in fluoride glass excited by self-channeled plasma filaments

    SciTech Connect (OSTI)

    Cho, Sung-Hak; Chang, Won-Seok; Kim, Jae-Goo; Whang, Kyoung-Hyun [Nano Machining Laboratory, Korea Institute of Machinery and Material (KIMM), 171 Jang-dong, Yuseong-Gu, Daejeon 305-343 (Korea, Republic of)

    2007-09-17T23:59:59.000Z

    Self-fabricated permanent structure of single mode waveguide in optical fluoride glasses was demonstrated using the self-channeled plasma filament excited by a femtosecond (130 fs) Ti:sapphire laser ({lambda}{sub p}=790 nm). The photoinduced refractive index modification in ZrF{sub 4}-BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF glasses reached a length of approximately 10-15 mm from the input surface of the optical glass with the diameters ranging from 5 to 8 {mu}m at the input intensities of more than 1.0x10{sup 12} W/cm{sup 2}. The graded refractive index profiles were fabricated to be a symmetric form from the center of optical fluoride glass, and a maximum value of refractive index change ({delta}n) was measured to be 1.3x10{sup -2}. The beam profile of the output beam transmitted through the modified region showed that the photoinduced refractive index modification produced a permanent structure of single mode waveguide.

  9. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    SciTech Connect (OSTI)

    NONE

    1997-10-01T23:59:59.000Z

    The main objective of this research project is the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Mullite will be employed as the inner (base) layer and the composition of the film will be continuously changed to a layer of pure alumina, which will function as the actual protective coating of the component. Chemical vapor deposition reactions of silica, alumina, and aluminosilicates (mullite) through hydrolysis of aluminum and silicon chlorides in the presence of CO{sub 2} and H{sub 2} will be employed to deposit compositionally graded films of mullite and alumina. Our studies will include the kinetic investigation of the silica, alumina, and aluminosilicate deposition processes, characterization of the composition, microstructure, surface morphology, and mechanical behavior of the prepared films, and modeling of the various deposition processes. During this six-month reporting period, we continued the work on the development and construction of the thermogravimetric chemical vapor deposition system that we intend to employ for studying the deposition of alumina, silica, and aluminosilicates (such as mullite) from mixtures of metal chlorides in H{sub 2} and CO{sub 2}. Specifically, we worked on the development of the tubular flow reactor that will be used for producing aluminum chloride for delivery to the chemical vapor deposition system and of the vapor and gas supply system. Various problems arising from condensation of aluminum chlorides in some sections of the supply line were resolved, and we expect to perform experiments using mixtures containing AlCl{sub 3} in the next reporting period. Preliminary experiments on the deposition of SiO{sub 2} from mixtures of methyltrichlorosilane (MTS) or tetrachlorosilane in H{sub 2} and CO{sub 2} were carried out, and the results showed that the deposition rates from MTS were much higher than those from SiCl{sub 4} and comparable to those reported in the literature for alumina deposition from AlC{sub 3}-H{sub 2}-CO{sub 2} mixtures of similar composition. It was thus decided to employ MTS as silicon source in our codeposition experiments, and a comprehensive investigation of thermodynamic equilibrium in the Al/Si/Cl/C/O/H system for compositions corresponding to MTS-AlCl{sub 3}-H{sub 2}-CO{sub 2} mixtures was conducted so as to identify the boundaries of the region of the space of operating parameters and conditions where preparation of functionally graded mullite/alumina coatings through CVD from metal chloride, CO{sub 2}, and H{sub 2} is feasible. The results showed that deposition of silica, alumina, mullite, and other aluminosilicates is feasible in a broad range of operating conditions from the equilibrated gas phase, but temperatures above 1148 K have to employed to obtain deposits of alumina and mullite if the solid phases are also at equilibrium with each other.

  10. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    SciTech Connect (OSTI)

    NONE

    1998-03-01T23:59:59.000Z

    The main objective of this research project is the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Mullite will be employed as the inner (base) layer and the composition of the film will be continuously changed to a layer of pure alumina, which will function as the actual protective coating of the component. Chemical vapor deposition reactions of silica, alumina, and aluminosilicates (mullite) through hydrolysis of aluminum and silicon chlorides in the presence of CO{sub 2} and H{sub 2} will be employed to deposit compositionally graded films of mullite and alumina. Our studies will include the kinetic investigation of the silica, alumina, and aluminosilicate deposition processes, characterization of the composition, microstructure, surface morphology, and mechanical behavior of the prepared films, and modeling of the various deposition processes. During this reporting period, the construction and development of the chemical vapor deposition system was completed, and experiments were conducted on the deposition of alumina, silica, and aluminosilicates (such as mullite) from mixtures of AlCl{sub 3} and CH{sub 3}SiCl{sub 3} in CO{sub 2} and H{sub 2}. Work was mainly done on the investigation of the effects of the reaction temperature on the deposition kinetics. It was found that the temperature had a positive effect on the single oxides deposition rates and the codeposition rate. The apparent activation energy values extracted from the deposition rate vs. temperature curves in the high temperature region were similar for the three deposition processes, having a value around 20 kcal/mol. The codeposition rates were higher, by a more than a factor of 2 in some cases, than the sum of the deposition rates of the two oxides in the independent experiments at the same operating conditions, and this result led to the conclusion that there should exist additional surface reaction steps in the codeposition process, that lead to solid formation and involve both silicon-containing and aluminum-containing species. The elemental analysis (EDXA) of films deposited from MTS-AlCl{sub 3}-CO{sub 2}- H2 mixtures showed that silicon oxide was the main component, and comparison of the deposition rates of SiO{sub 2} and Al{sub 2}O{sub 3} during codeposition with those seen in single species deposition experiments at the same conditions revealed that the codeposition process was characterized by a dramatic enhancement of the deposition of SiO{sub 2} and an equally dramatic reduction in the rate of Al{sub 2}O{sub 3} deposition. Since the enhanced codeposition rate was caused by increased silicon oxide deposition, it was concluded that the main deposition product of the additional surface reaction steps in codeposition must be silicon oxide. A comprehensive investigation of the effects of the other operating parameters on the kinetics of the codeposition process will be carried out in the next reporting period.

  11. Gas source molecular beam epitaxy of scandium nitride on silicon carbide and gallium nitride surfaces

    SciTech Connect (OSTI)

    King, Sean W., E-mail: sean.king@intel.com; Davis, Robert F. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nemanich, Robert J. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-11-01T23:59:59.000Z

    Scandium nitride (ScN) is a group IIIB transition metal nitride semiconductor with numerous potential applications in electronic and optoelectronic devices due to close lattice matching with gallium nitride (GaN). However, prior investigations of ScN have focused primarily on heteroepitaxial growth on substrates with a high lattice mismatch of 7%–20%. In this study, the authors have investigated ammonia (NH{sub 3}) gas source molecular beam epitaxy (NH{sub 3}-GSMBE) of ScN on more closely lattice matched silicon carbide (SiC) and GaN surfaces (<3% mismatch). Based on a thermodynamic analysis of the ScN phase stability window, NH{sub 3}-GSMBE conditions of 10{sup ?5}–10{sup ?4} Torr NH{sub 3} and 800–1050?°C where selected for initial investigation. In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Rutherford backscattering measurements showed all ScN films grown using these conditions were stoichiometric. For ScN growth on 3C-SiC (111)-(?3?×??3)R30° carbon rich surfaces, the observed attenuation of the XPS Si 2p and C 1s substrate core levels with increasing ScN thickness indicated growth initiated in a layer-by-layer fashion. This was consistent with scanning electron microscopy (SEM) images of 100–200?nm thick films that revealed featureless surfaces. In contrast, ScN films grown on 3C-SiC (111)-(3?×?3) and 3C-SiC (100)-(3?×?2) silicon rich surfaces were found to exhibit extremely rough surfaces in SEM. ScN films grown on both 3C-SiC (111)-(?3?×??3)R30° and 2H-GaN (0001)-(1?×?1) epilayer surfaces exhibited hexagonal (1?×?1) low energy electron diffraction patterns indicative of (111) oriented ScN. X-ray diffraction ?-2? rocking curve scans for these same films showed a large full width half maximum of 0.29° (1047?arc sec) consistent with transmission electron microscopy images that revealed the films to be poly-crystalline with columnar grains oriented at ?15° to the [0001] direction of the 6H-SiC (0001) substrate. In-situ reflection electron energy loss spectroscopy measurements determined the band-gap for the NH{sub 3}-GSMBE ScN films to be 1.5?±?0.3 eV, and thermal probe measurements indicated all ScN films to be n-type. The four point probe sheet resistance of the ScN films was observed to increase with decreasing growth temperature and decreased with unintentional oxygen incorporation. Hg probe capacitance–voltage measurements indicated N{sub D}-N{sub A} decreased with decreasing growth temperature from 10{sup 19} to 10{sup 20}/cm{sup 3} for the lowest resistivity films to ?5?×?10{sup 16}/cm{sup 3} for the highest resistivity films. In-situ ultraviolet photoelectron spectroscopy measurements additionally showed the valence band maximum moving from 1.4 to 0.8 eV below the Fermi level with decreasing growth temperature consistent with the increased resistivity and reduction in carrier concentration. These results suggest that additional reductions in ScN carrier concentrations can be achieved via continued optimization of ScN growth conditions and selection of substrate orientation and surface termination.

  12. Optical properties of silicon carbide for astrophysical applications I. New laboratory infrared reflectance spectra and optical constants

    E-Print Network [OSTI]

    Pitman, K M; Corman, A B; Speck, A K

    2008-01-01T23:59:59.000Z

    Silicon Carbide (SiC) optical constants are fundamental inputs for radiative transfer models of astrophysical dust environments. However, previously published values contain errors and do not adequately represent the bulk physical properties of the cubic (beta) SiC polytype usually found around carbon stars. We provide new, uncompromised optical constants for beta- and alpha-SiC derived from single-crystal reflectance spectra and investigate quantitatively whether there is any difference between alpha- and beta-SiC that can be seen in infrared spectra and optical functions. Previous optical constants for SiC do not reflect the true bulk properties, and they are only valid for a narrow grain size range. The new optical constants presented here will allow narrow constraints to be placed on the grain size and shape distribution that dominate in astrophysical environments. In addition, our calculated absorption coefficients are much higher than laboratory measurements, which has an impact on the use of previous d...

  13. Effects of a modular two-step ozone-water and annealing process on silicon carbide graphene

    SciTech Connect (OSTI)

    Webb, Matthew J., E-mail: matthew.webb@cantab.net; Lundstedt, Anna; Grennberg, Helena [Department of Chemistry—BMC, Uppsala University, Box 576, SE-751 23 Uppsala (Sweden); Polley, Craig; Niu, Yuran; Zakharov, Alexei A.; Balasubramanian, Thiagarajan [MAX IV Laboratory, Lund University, 22100 Lund (Sweden); Dirscherl, Kai [DFM—Danish Fundamental Metrology, Matematiktorvet 307, DK-2800 Lyngby (Denmark); Burwell, Gregory; Guy, Owen J. [College of Engineering, Faraday Tower, Singleton Park, Swansea University, Swansea SA2 8PP (United Kingdom); Palmgren, Pål [VG Scienta Scientific AB, Box 15120, Vallongatan 1, SE-750 15 Uppsala (Sweden); Yakimova, Rositsa [Department of Physics, Chemistry, and Biology, Linköping University, SE-581 83 Linköping (Sweden)

    2014-08-25T23:59:59.000Z

    By combining ozone and water, the effect of exposing epitaxial graphene on silicon carbide to an aggressive wet-chemical process has been evaluated after high temperature annealing in ultra high vacuum. The decomposition of ozone in water produces a number of oxidizing species, however, despite long exposure times to the aqueous-ozone environment, no graphene oxide was observed after the two-step process. The systems were comprehensively characterized before and after processing using Raman spectroscopy, core level photoemission spectroscopy, and angle resolved photoemission spectroscopy together with low energy electron diffraction, low energy electron microscopy, and atomic force microscopy. In spite of the chemical potential of the aqueous-ozone reaction environment, the graphene domains were largely unaffected raising the prospect of employing such simple chemical and annealing protocols to clean or prepare epitaxial graphene surfaces.

  14. Testing erosion-resistant chromium carbide plasma coatings on the TVA Paradise Unit-2 intermediate pressure turbine

    SciTech Connect (OSTI)

    Karr, O.F.; Frank, R.L.; Gaston, D.E. Jr.; Bradford, T.L.

    1986-05-01T23:59:59.000Z

    Solid particle erosion (SPE) is caused by oxide particles in steam. Hard oxide particles exfoliate from the inside surfaces of boiler tubes and steam lines and are carried by the steam to the turbine where they impact and erode stationary and moving turbine parts (nozzles, moving blades, stationary blades, seal strips, and shrouds around the blades). The first stages of the high pressure (HP) and intermediate pressure (IP) turbines experience the greatest amount of SPE. Though many owners experience erosion in the first stages of both HP (main steam) and IP (reheat steam) turbines, TVA's principal erosion experience is in the IP or reheat steam turbines. This report is limited to the first few stages of IP turbines, referred to as ''first reheat stages.'' Hard chromium carbide plasma coatings have been developed. The coating was installed in Paradise Unit-2 IP turbine, 9th and 10th stages. Pretest inspection report is given.

  15. Behavior of microwave-heated silicon carbide particles at frequencies of 2.0–13.5?GHz

    SciTech Connect (OSTI)

    Sugawara, H.; Hayashi, M.; Ishihara, S. [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro, Tokyo 152-8552 (Japan); Kashimura, K., E-mail: kashimura@isc.chubu.ac.jp [Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501 (Japan); Mitani, T.; Shinohara, N. [Kyoto University, Gokasyo, Uji, Kyoto 611-0011 (Japan)

    2014-07-21T23:59:59.000Z

    Silicon carbide is a key material in microwave (MW) processing and is used widely as a thermal insulator and catalytic agent. In this study, we experimentally investigated the temperature dependence of the MW-absorption properties of SiC particles at frequencies of 2.0–13.5?GHz. We heated SiC particles of different sizes using MW radiation. The heating behaviors of the particles were then compared with their MW-absorption properties. The heating behavior of the particles was dependent on their radii; this result was in keeping with theoretical predictions. Furthermore, the ?-SiC particles exhibited anomalous behaviors when subjected to microwave heating at temperatures of 1100?°C and higher. These behaviors were attributable to the transformation of ?-SiC into the ?-phase. The underlying mechanism for this transformation is discussed on the basis of the results of X-ray diffraction analysis.

  16. Composition and method for brazing graphite to graphite

    DOE Patents [OSTI]

    Taylor, A.J.; Dykes, N.L.

    1982-08-10T23:59:59.000Z

    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. Young Stellar Clusters, WR-type Phenomenon and the Origin of the Galactic Center Nonthermal Radio Filaments

    E-Print Network [OSTI]

    F. Yusef-Zadeh

    2004-11-27T23:59:59.000Z

    Recent observations of the Arches cluster located within a projected distance of 30 pc from the dynamical center of the Galaxy have shown the presence of diffuse and discrete X-ray continuum emission, diffuse 6.4keV line emission as well as thermal and nonthermal radio continuum emission. This young and dense stellar cluster is also recognized to be within the 95% error circle of an identified steady source of $\\gamma$-ray emission associated with the EGRET source 3EG J1746--2851. Much of the thermal and nonthermal emission can be explained by shocked gas resulting from colliding winds originating from massive binaries within the cluster. In particular, we argue that nonthermal particles could upscatter the radiation field of the cluster by ICS and account for the $\\gamma$-ray emission. We also consider that the fluorescent 6.4 keV line emission may be the result of the impact of low-energy relativistic particles on neutral gas distributed in the vicinity of the cluster. Lastly, we sketch an interpretation in which young stellar clusters and massive young binary systems are responsible for the origin of nonthermal radio filaments found throughout the inner 300pc of the Galaxy. The collimation of the nonthermal filaments may be done in the colliding wind region by the ionized surface of individual mass-losing stars of massive binary systems. In this picture, a WR-type phenomenon is expected to power a central star burst in the Galactic center in order to account for all the observed filaments.

  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)

    2000-09-26T23:59:59.000Z

    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. 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 [Blue Wave Semiconductors; Ermer, Henry K [Blue Wave Semiconductors; Sinsky, Phillip [Blue Wave Semiconductors; Seiser, Andrew [Blue Wave Semiconductors; Shaw, Robert W [ORNL; Wilson, Leslie L [ORNL

    2014-01-01T23:59:59.000Z

    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.

  20. Photoelectron Emission from Metal Surfaces Induced by VUV-emission of Filament Driven Hydrogen Arc Discharge Plasma

    E-Print Network [OSTI]

    Laulainen, J; Koivisto, H; Komppula, J; Tarvainen, O

    2015-01-01T23:59:59.000Z

    Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H^- 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.

  1. Journal of Physics and Chemistry of Solids 67 (2006) 25122516 Crystal chemistry of layered carbide, Ti3(Si0.43Ge0.57)C2

    E-Print Network [OSTI]

    Downs, Robert T.

    2006-01-01T23:59:59.000Z

    , Ti3(Si0.43Ge0.57)C2 Hexiong Yanga,Ã, B. Manouna , R.T. Downsb , A. Gangulyc , M.W. Barsoumc a Center structure of a layered ternary carbide, Ti3(Si0.43Ge0.57)C2, was studied with single-crystal X.0823(1) A° , c ¼ 17.7702(6) A° , and V ¼ 146.21(1) A° 3 . The Si and Ge atoms in the structure occupy

  2. An application of Ti-K X-ray absorption edges and fine structures to the study of substoichiometric titanium carbide TiC1-x

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    of substoichiometric titanium carbide TiC1-x V. Moisy-Maurice and C. H. de Novion C.E.A./IRDI/DMECN/DTech, Laboratoire-ray absorption coefficient were made around and up to 1000 eV above the titanium K-edge of TiC1-x samples (0 of titanium deduced from the edge-shift decreases, (ii) the bottom of the titanium 4p bands (situated at 10

  3. Review of corrosion behavior of ceramic heat exchanger materals: Corrosion characteristics of silicon carbide and silicon nitride. Final report, September 11, 1992--March 11, 1993

    SciTech Connect (OSTI)

    Munro, R.G.; Dapkunas, S.J.

    1993-09-01T23:59:59.000Z

    The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags.

  4. Synthesis of Nanostructured Carbides of Titanium and Vanadium from Metal Oxides and Ferroalloys Through High-energy Mechanical Milling and Heat Treatment

    SciTech Connect (OSTI)

    Basu, P.; Jian, P. F.; Seong, K. Y.; Seng, G. S.; Hussain, Z.; Aziz, A. [School of Materials and Minerals Resources Engineering, Universiti Sains Malaysia (USM), Engineering Campus, 14300 Nibong Tebal, Pulau Pinang (Malaysia); Masrom, A. K. [Advanced Materials Research Centre (AMREC), SIRIM Bhd, Kulim Hi-Tech Park, Kulim 09000 (Malaysia)

    2010-03-11T23:59:59.000Z

    Carbides of Ti and V have been synthesized directly from their oxides and ferroalloys through mechanical milling and heat treatment. The powder mixtures are milled in a planetary ball mill from 15-80 hours and subsequently heat treated at 1000-1300 deg. C for TiO{sub 2}-C mixtures, at 500-550 deg. C for V{sub 2}O{sub 5}-C mixtures and at 600-1000 deg. C for (Fe-V)-C mixtures. The milled and heat treated powders are characterized by SEM, EDAX, XRD, and BET techniques. Nanostructured TiC has been successfully synthesized under suitable processing conditions. However, carbides of vanadium is unidentified even though possibilities of V{sub 2}O{sub 5}-C reaction are indicated with an extent of induced amorphism in the powder mixture. Density, specific surface area and particle size of the milled and heat treated mixtures are correlated with heat treatment temperatures. Similar attempts are also made to synthesize vanadium carbides from industrial grade Fe-V.

  5. 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)

    1989-10-03T23:59:59.000Z

    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%.

  6. 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. [Helsinki Univ. of Technology, Espoo (Finland)

    1996-09-01T23:59:59.000Z

    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.

  7. Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

    SciTech Connect (OSTI)

    Jiang, Liming [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Fu, Honggang, E-mail: fuhg@vip.sina.com [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Functional Inorganic Material Chemistry, Heilongjiang University, Harbin 150080 (China); Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong [Key Laboratory of Functional Inorganic Material Chemistry, Heilongjiang University, Harbin 150080 (China)

    2014-01-01T23:59:59.000Z

    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.

  8. Optical properties of silicon carbide for astrophysical applications I. New laboratory infrared reflectance spectra and optical constants

    E-Print Network [OSTI]

    K. M. Pitman; A. M. Hofmeister; A. B. Corman; A. K. Speck

    2008-03-10T23:59:59.000Z

    Silicon Carbide (SiC) optical constants are fundamental inputs for radiative transfer models of astrophysical dust environments. However, previously published values contain errors and do not adequately represent the bulk physical properties of the cubic (beta) SiC polytype usually found around carbon stars. We provide new, uncompromised optical constants for beta- and alpha-SiC derived from single-crystal reflectance spectra and investigate quantitatively whether there is any difference between alpha- and beta-SiC that can be seen in infrared spectra and optical functions. Previous optical constants for SiC do not reflect the true bulk properties, and they are only valid for a narrow grain size range. The new optical constants presented here will allow narrow constraints to be placed on the grain size and shape distribution that dominate in astrophysical environments. In addition, our calculated absorption coefficients are much higher than laboratory measurements, which has an impact on the use of previous data to constrain abundances of these dust grains.

  9. 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

    2003-09-23T23:59:59.000Z

    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.

  10. 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

    2013-01-22T23:59:59.000Z

    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

  11. From Ultrananocrystalline Diamond to Single Crystal Diamond Growth in Hot Filament and Microwave Plasma-Enhanced CVD Reactors: a Unified Model for Growth Rates and

    E-Print Network [OSTI]

    Bristol, University of

    From Ultrananocrystalline Diamond to Single Crystal Diamond Growth in Hot Filament and Microwave, Moscow State UniVersity, 119991 Moscow, Russia ReceiVed: April 29, 2008 CVD Diamond can now be deposited either in the form of single crystal homoepitaxial layers, or as polycrystalline films with crystal sizes

  12. 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

    2012-03-22T23:59:59.000Z

    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

  13. 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, E-mail: jenschen@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Jeng, Jiann-Shing [Department of Materials Science, National University of Tainan, Tainan 700, Taiwan (China)

    2014-10-28T23:59:59.000Z

    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.

  14. A ROBUST MEASURE OF COSMIC STRUCTURE BEYOND THE POWER SPECTRUM: COSMIC FILAMENTS AND THE TEMPERATURE OF DARK MATTER

    SciTech Connect (OSTI)

    Obreschkow, D.; Power, C. [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia)] [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Bruderer, M. [Institut fuer Theoretische Physik, Albert-Einstein Allee 11, Universitaet Ulm, D-89069 Ulm (Germany)] [Institut fuer Theoretische Physik, Albert-Einstein Allee 11, Universitaet Ulm, D-89069 Ulm (Germany); Bonvin, C. [Kavli Institute for Cosmology Cambridge and Institute of Astronomy, Madingley Road, Cambridge CB3 OHA (United Kingdom)] [Kavli Institute for Cosmology Cambridge and Institute of Astronomy, Madingley Road, Cambridge CB3 OHA (United Kingdom)

    2013-01-10T23:59:59.000Z

    We discover that the mass of dark matter particles m {sub DM} is imprinted in phase correlations of the cosmic density field more significantly than in the two-point correlation. In particular, phase correlations trace m {sub DM} out to scales about five times larger than the two-point correlation. This result relies on a new estimator l(r) of pure phase information in Fourier space, which can be interpreted as a parameter-free and scale-invariant tracer of filament-like structure. Based on simulated density fields, we show how m {sub DM} can, in principle, be measured using l(r), given a suitably reconstructed density field.

  15. 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)

    2012-12-15T23:59:59.000Z

    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}.

  16. The Effects of Damage on Hydrogen-Implant-Induced Thin-Film Separation from Bulk Silicon Carbide

    SciTech Connect (OSTI)

    Gregory, R.B.; Holland, O.W.; Thomas, D.K.; Wetteroth, T.A.; Wilson, S.R.

    1999-04-05T23:59:59.000Z

    Exfoliation of Sic by hydrogen implantation and subsequent annealing forms the basis for a thin-film separation process which, when combined with hydrophilic wafer bonding, can be exploited to produce silicon-carbide-on-insulator, SiCOI. Sic thin films produced by this process exhibit unacceptably high resistivity because defects generated by the implant neutralize electrical carriers. Separation occurs because of chemical interaction of hydrogen with dangling bonds within microvoids created by the implant, and physical stresses due to gas-pressure effects during post-implant anneal. Experimental results show that exfoliation of Sic is dependent upon the concentration of implanted hydrogen, but the damage generated by the implant approaches a point when exfoliation is, in fact, retarded. This is attributed to excessive damage at the projected range of the implant which inhibits physical processes of implant-induced cleaving. Damage is controlled independently of hydrogen dosage by elevating the temperature of the SiC during implant in order to promote dynamic annealing. The resulting decrease in damage is thought to promote growth of micro-cracks which form a continuous cleave. Channeled H{sup +} implantation enhances the cleaving process while simultaneously minimizing residual damage within the separated film. It is shown that high-temperature irradiation and channeling each reduces the hydrogen fluence required to affect separation of a thin film and results in a lower concentration of defects. This increases the potential for producing SiC01 which is sufficiently free of defects and, thus, more easily electrically activated.

  17. Powerful, Efficient Electric Vehicle Chargers: Low-Cost, Highly-Integrated Silicon Carbide (SiC) Multichip Power Modules (MCPMs) for Plug-In Hybrid Electric

    SciTech Connect (OSTI)

    None

    2010-09-14T23:59:59.000Z

    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.

  18. 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. [Mechanical and Material Engineering Department, Universiti Kebangsaan Malaysia, Bangi 43600 (Malaysia)

    2011-01-17T23:59:59.000Z

    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.

  19. Thickness independent reduced forming voltage in oxygen engineered HfO{sub 2} based resistive switching memories

    SciTech Connect (OSTI)

    Sharath, S. U., E-mail: sharath@oxide.tu-darmstadt.de; Kurian, J.; Komissinskiy, P.; Hildebrandt, E.; Alff, L. [Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Bertaud, T.; Walczyk, C.; Calka, P. [IHP, Im Technologiepark 25, 15236 Frankfurt Oder (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt Oder (Germany); Brandenburgische Technische Universität, Konrad-Zuse-Strasse 1, 03046 Cottbus (Germany)

    2014-08-18T23:59:59.000Z

    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.

  20. The Herschel view of massive star formation in G035.39--00.33: a dense and cold filament of W48 undergoing a mini-starburst

    E-Print Network [OSTI]

    Luong, Q Nguyen; Hennemann, M; Hill, T; Rygl, K L J; Schneider, N; Bontemps, S; Men'shchikov, A; André, Ph; Peretto, N; Anderson, L D; Arzoumanian, D; Deharveng, L; Didelon, P; Di Francesco, J; Griffin, M J; Kirk, J M; Konyves, V; Martin, P G; Maury, A; Minier, V; Molinari, S; Pestalozzi, M; Pezzuto, S; Reid, M; Roussel, H; Schuller, F; Testi, L; Ward-Thompson, D; White, G J; Zavagno, A

    2011-01-01T23:59:59.000Z

    The filament IRDC G035.39-00.33 in the W48 molecular complex is one of the darkest infrared clouds observed by Spitzer. It has been observed by the PACS (70 and 160 micron) and SPIRE (250, 350 and 500) cameras of the \\textit{Herschel} Space Observatory as part of the W48 molecular cloud complex in the framework of the HOBYS key programme. The observations reveal a sample of 28 compact sources (deconvolved FWHM sizes 20 solar mass. The cloud characteristics we derive from the analysis of their spectral energy distributions (20-50 solar mass with sizes of 0.1-0.2 pc and average densities of 2-20 x 10^5 cm^3) make these massive dense cores excellent candidates to form intermediate- to high-mass stars. Most of the massive dense cores are located inside the G035.39-00.33 filament and host IR-quiet high-mass protostars. The large number of protostars found in this filament suggests that we are witnessing a mini-burst of star formation with an efficiency of ~20% and a rate density of ~40 solar mass per year per kpc^...

  1. Long-lived filaments in fusion plasmas: review of observations and status of hypothesis of microdust-assembled skeletons

    E-Print Network [OSTI]

    A. B. Kukushkin; V. A. Rantsev-Kartinov

    2001-12-26T23:59:59.000Z

    A brief review is given of the progress in studying the long-lived filaments (LLFs) in fusion plasmas (tokamaks, Z-pinch, plasma focus). The paper reports on (i) resolving the fine structure of LLFs, and (ii) verification of our hypothesis (1998) which suggested the LLFs to possess a microsolid skeleton. The recent proof-of-concept studies showed the presence of tubular and cartwheel-like structures in (i) various dust deposits in tokamak T-10, in the range 10 nm - 10 mcm, and (ii) visible light images of plasma, in the range 100 mcm - 10 cm, at initial stage of discharge (e.g., before appearance of discharge electric current) in tokamak, plasma focus and vacuum spark. The topological similarity of the above structures (especially, "cartwheels") and the observed trend of assembling bigger tubules from smaller ones (i.e. the self-similarity) allow to draw a bridge between the microdust skeletons in the dust deposits and the centimeter scale LLFs in fusion plasmas.

  2. Complete genome sequence of the filamentous gliding predatory bacterium Herpetosiphon aurantiacus type strain (114-95T)

    SciTech Connect (OSTI)

    Kiss, Hajnalka [Los Alamos National Laboratory (LANL); Nett, Markus [Hans Knöll Institute, Jena, Germany; Domin, Nicole [Hans Knöll Institute, Jena, Germany; Martin, Karin [Hans Knöll Institute, Jena, Germany; Maresca, Julia A. [Pennsylvania State University, University Park, PA; Copeland, A [U.S. Department of Energy, Joint Genome Institute; Lapidus, Alla L. [U.S. Department of Energy, Joint Genome Institute; Lucas, Susan [U.S. Department of Energy, Joint Genome Institute; Berry, Kerrie W. [United States Department of Energy Joint Genome Institute; Glavina Del Rio, Tijana [U.S. Department of Energy, Joint Genome Institute; Dalin, Eileen [U.S. Department of Energy, Joint Genome Institute; Tice, Hope [U.S. Department of Energy, Joint Genome Institute; Pitluck, Sam [U.S. Department of Energy, Joint Genome Institute; Richardson, P M [U.S. Department of Energy, Joint Genome Institute; Bruce, David [Los Alamos National Laboratory (LANL); Goodwin, Lynne A. [Los Alamos National Laboratory (LANL); Han, Cliff [Los Alamos National Laboratory (LANL); Detter, J. Chris [U.S. Department of Energy, Joint Genome Institute; Schmutz, Jeremy [Stanford University; Brettin, Thomas S [ORNL; Land, Miriam L [ORNL; Hauser, Loren John [ORNL; Kyrpides, Nikos C [U.S. Department of Energy, Joint Genome Institute; Ivanova, N [U.S. Department of Energy, Joint Genome Institute; Goker, Markus [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Woyke, Tanja [U.S. Department of Energy, Joint Genome Institute; Klenk, Hans-Peter [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Bryant, Donald A. [Pennsylvania State University, University Park, PA

    2011-01-01T23:59:59.000Z

    Herpetosiphon aurantiacus Holt and Lewin 1968 is the type species of the genus Herpetosiphon, which in turn is the type genus of the family Herpetosiphonaceae, type family of the order Herpe- tosiphonales in the phylum Chloroflexi. H. aurantiacus cells are organized in filaments which can rapidly glide. The species is of interest not only because of its rather isolated position in the tree of life, but also because Herpetosiphon ssp. were identified as predators capable of facultative pre- dation by a wolf pack strategy and of degrading the prey organisms by excreted hydrolytic en- zymes. The genome of H. aurantiacus strain 114-95T is the first completely sequenced genome of a member of the family Herpetosiphonaceae. The 6,346,587 bp long chromosome and the two 339,639 bp and 99,204 bp long plasmids with a total of 5,577 protein-coding and 77 RNA genes was sequenced as part of the DOE Joint Genome Institute Program DOEM 2005.

  3. Neutron diffraction study of the formation of ordered antiphase domains in cubic titanium carbide TiC{sub 0.60}

    SciTech Connect (OSTI)

    Khidirov, I., E-mail: khidirov@inp.uz; Parpiev, A. S. [Academy of Sciences of Uzbekistan, Institute of Nuclear Physics (Uzbekistan)

    2013-05-15T23:59:59.000Z

    A series of superstructural reflections (described within the sp. gr. Fd3m) are found to be split into three symmetric parts in the neutron powder diffraction pattern of titanium carbide TiC{sub 0.60} annealed at a temperature of 600 Degree-Sign C. No splitting of superstructural reflections is observed in the neutron diffraction pattern of TiC{sub 0.60} annealed at relatively high temperatures (780 Degree-Sign C). This phenomenon can be explained by that fact that the ordering of carbon atoms at relatively high temperatures (780 Degree-Sign C) is accompanied by the formation of randomly oriented rather large antiphase domains (APDs) (450 A). At relatively low temperatures (600 Degree-Sign C), stacking faults arise in the arrangement of partially ordered carbon atoms. In this case, relatively small ordered APDs (290 A) are formed, along with disordered ones.

  4. Elastic properties, sp{sup 3} 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 [Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, Hawaii 96822 (United States); Liu, Yongsheng [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi'an Shanxi (China); Ciston, Jim [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hong, Shiming [Laboratory of High Pressure Physics, Southwest Jiaotong University, Chengdu, Sichuan (China)

    2014-10-07T23:59:59.000Z

    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 sp{sup 2} versus sp{sup 3} 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{sup 3} fraction, the shear modulus ? of dl-BC{sub 4}, containing 10% carbon atoms with sp{sup 3} bonds, and dl-B{sub 3}C{sub 2}, containing 38% carbon atoms with sp{sup 3} 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{sup 3} bonds during the deposition processes.

  5. A Corona Australis cloud filament seen in NIR scattered light I. Comparison with extinction of background stars

    E-Print Network [OSTI]

    M. Juvela; V. -M. Pelkonen; P. Padoan; K. Mattila

    2008-01-09T23:59:59.000Z

    With current near-infrared (NIR) instruments the near-infrared light scattered from interstellar clouds can be mapped over large areas. The surface brightness carries information on the line-of-sight dust column density. Therefore, scattered light could provide an important tool to study mass distribution in quiescent interstellar clouds at a high, even sub-arcsecond resolution. We wish to confirm the assumption that light scattering dominates the surface brightness in all NIR bands. Furthermore, we want to show that scattered light can be used for an accurate estimation of dust column densities in clouds with Av in the range 1-15mag. We have obtained NIR images of a quiescent filament in the Corona Australis molecular cloud. The observations provide maps of diffuse surface brightness in J, H, and Ks bands. Using the assumption that signal is caused by scattered light we convert surface brightness data into a map of dust column density. The same observations provide colour excesses for a large number of background stars. These data are used to derive an extinction map of the cloud. The two, largely independent tracers of the cloud structure are compared. Results. In regions below Av=15m both diffuse surface brightness and background stars lead to similar column density estimates. The existing differences can be explained as a result of normal observational errors and bias in the sampling of extinctions provided by the background stars. There is no indication that thermal dust emission would have a significant contribution even in the Ks band. The results show that, below Av=15mag, scattered light does provide a reliable way to map cloud structure. Compared with the use of background stars it can also in practice provide a significantly higher spatial resolution.

  6. The matching of polymer solution fast filament stretching, relaxation and break up experimental results with 1D and 2D numerical viscoelastic simulation

    E-Print Network [OSTI]

    Vadillo, D.C.; Tembely, M.; Morrison, N.F.; Harlen, O.G.; Mackley, M.R.; Soucemarianadin, A.

    D. C. Vadillo*1, M. Tembely**2, N.F. Morrison3, O. G. Harlen3, M. R. Mackley1 10 and A. Soucemarianadin***2 11 12 1Department of Chemical Engineering and Biotechnology, University of Cambridge, 13 CB2 3RA, UK 14 2Laboratory for Geophysical... . Rasmussen, P-Y. Longin, and O. Hassager, “Growth of non-635 axisymmetric disturbances of the free surface in the filament stretching rheometer: 636 Experiments and simulation,” J. Non-Newtonian Fluid Mech. 180, 163–186 (2002). 637 Bazilevsky A. V., V. M...

  7. 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 [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)] [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Bian, Jiming, E-mail: jmbian@dlut.edu.cn [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China) [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Dong [New Energy Source Research Center of Shenyang Institute of Engineering, Shengyang 110136 (China)] [New Energy Source Research Center of Shenyang Institute of Engineering, Shengyang 110136 (China); Miao, Lihua [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China) [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Department of Computer and Mathematical Basic Teaching, Shenyang Medical College, Shenyan 110034 (China)

    2013-11-18T23:59:59.000Z

    ?-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.

  8. 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)

    2002-01-01T23:59:59.000Z

    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.

  9. Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH{sub 4}/Ar plasma

    SciTech Connect (OSTI)

    Sankaran, K. J.; Tai, N. H., E-mail: inanlin@mail.tku.edu.tw, E-mail: nhtai@mse.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Huang, B. R.; Saravanan, A. [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Lin, I. N., E-mail: inanlin@mail.tku.edu.tw, E-mail: nhtai@mse.nthu.edu.tw [Department of Physics, Tamkang University, Tamsui 251, Taiwan (China)

    2014-10-28T23:59:59.000Z

    Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH{sub 4} and Ar under different negative bias voltages ranging from ?50 to ?200?V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under ?200?V, the electron field emission (EFE) process can be turned on at a field as small as 4.08?V/?m, attaining a EFE current density as large as 3.19?mA/cm{sup 2} at an applied field of 8.64?V/?m. But the films grown without bias (0?V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH{sub 4}/Ar plasma due to large applied bias voltage of ?200?V is the prime factor, which possibly forms interconnected paths for facilitating the transport of electrons that markedly enhance the EFE properties.

  10. 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. [GTE Labs., Inc., Waltham, MA (US); Kim, K. [Brown Univ., Providence, RI (US). Div. of Engineering

    1993-05-01T23:59:59.000Z

    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.

  11. Deposition of mullite and mullite-like coatings on silicon carbide by dual-source metal plasma immersion. Topical report, October 1995--September 1996

    SciTech Connect (OSTI)

    Brown, I.G.; Monteiro, O.R. [Lawrence Berkeley National Lab., CA (United States)

    1997-04-01T23:59:59.000Z

    Mullite and mullite-like coatings on silicon carbide have been produced by a Metal Plasma Immersion Ion Implantation and Deposition (Mepiiid) technique based on two cathodic vacuum arc sources and concurrent pulse biasing of the substrate in an oxygen atmosphere. The deposition was carried out at oxygen partial pressures of between 0.66 and 3.33 Pa. The Al:Si ratio in the films varied from 1:1 to 8:1 and was controlled by varying the pulse duration of the separate plasma guns. High bias voltage was used early in the deposition process in order to produce atomic mixing at the film-substrate interface, while lower bias voltage was used later in the deposition; low ion energy allows control of the physical properties of the film as well as faster deposition rates. The as-deposited films were amorphous, and crystalline mullite was formed by subsequent annealing at 1,100 C for 2 hours in air. Strong adhesion between the mullite and the SiC was achieved, in some cases exceeding the 70 MPa instrumental limit of the pull-tester.

  12. Optical constants of silicon carbide for astrophysical applications. II. Extending optical functions from IR to UV using single-crystal absorption spectra

    E-Print Network [OSTI]

    Hofmeister, A M; Goncharov, A F; Speck, A K

    2009-01-01T23:59:59.000Z

    Laboratory measurements of unpolarized and polarized absorption spectra of various samples and crystal stuctures of silicon carbide (SiC) are presented from 1200--35,000 cm$^{-1}$ ($\\lambda \\sim$ 8--0.28 $\\mu$m) and used to improve the accuracy of optical functions ($n$ and $k$) from the infrared (IR) to the ultraviolet (UV). Comparison with previous $\\lambda \\sim$ 6--20 $\\mu$m thin-film spectra constrains the thickness of the films and verifies that recent IR reflectivity data provide correct values for $k$ in the IR region. We extract $n$ and $k$ needed for radiative transfer models using a new ``difference method'', which utilizes transmission spectra measured from two SiC single-crystals with different thicknesses. This method is ideal for near-IR to visible regions where absorbance and reflectance are low and can be applied to any material. Comparing our results with previous UV measurements of SiC, we distinguish between chemical and structural effects at high frequency. We find that for all spectral re...

  13. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets

    E-Print Network [OSTI]

    American Society for Testing and Materials. Philadelphia

    1994-01-01T23:59:59.000Z

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Boron by Titrimetry 7 to 13 Separation of Boron for Mass Spectrometry 14 to 19 Isotopic Composition by Mass Spectrometry 20 to 23 Separation of Halides by Pyrohydrolysis 24 to 27 Fluoride by Ion-Selective Electrode 28 to 30 Chloride, Bromide, and Iodide by Amperometric Microtitrimetry 31 to 33 Trace Elements by Emission Spectroscopy 34 to 46 1.3 The values stated in SI units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (F...

  14. OPTICAL CONSTANTS OF SILICON CARBIDE FOR ASTROPHYSICAL APPLICATIONS. II. EXTENDING OPTICAL FUNCTIONS FROM INFRARED TO ULTRAVIOLET USING SINGLE-CRYSTAL ABSORPTION SPECTRA

    SciTech Connect (OSTI)

    Hofmeister, A. M.; Pitman, K. M. [Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130 (United States); Goncharov, A. F. [Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States); Speck, A. K. [Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, MO 65211 (United States)], E-mail: hofmeist@levee.wustl.edu

    2009-05-10T23:59:59.000Z

    Laboratory measurements of unpolarized and polarized absorption spectra of various samples and crystal structures of silicon carbide (SiC) are presented from 1200-35000 cm{sup -1} ({lambda} {approx} 8-0.28 {mu}m) and used to improve the accuracy of optical functions (n and k) from the infrared (IR) to the ultraviolet (UV). Comparison with previous {lambda} {approx} 6-20 {mu}m thin-film spectra constrains the thickness of the films and verifies that recent IR reflectivity data provide correct values for k in the IR region. We extract n and k needed for radiative transfer models using a new 'difference method', which utilizes transmission spectra measured from two SiC single-crystals with different thicknesses. This method is ideal for near-IR to visible regions where absorbance and reflectance are low and can be applied to any material. Comparing our results with previous UV measurements of SiC, we distinguish between chemical and structural effects at high frequency. We find that for all spectral regions, 3C ({beta}-SiC) and the E-vector perpendicular c-vector polarization of 6H (a type of {alpha}-SiC) have almost identical optical functions that can be substituted for each other in modeling astronomical environments. Optical functions for E-vector || c-vector of 6H SiC have peaks shifted to lower frequency, permitting identification of this structure below {lambda} {approx} 4 {mu}m. The onset of strong UV absorption for pure SiC occurs near 0.2 {mu}m, but the presence of impurities redshifts the rise to 0.33 {mu}m. Optical functions are similarly impacted. Such large differences in spectral characteristics due to structural and chemical effects should be observable and provide a means to distinguish chemical variation of SiC dust in space.

  15. A methodology to identify and quantify mobility-reducing defects in 4H-silicon carbide power metal-oxide-semiconductor field-effect transistors

    SciTech Connect (OSTI)

    Ettisserry, D. P., E-mail: deva@umd.edu; Goldsman, N. [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742 (United States); Lelis, A. [U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2014-03-14T23:59:59.000Z

    In this paper, we present a methodology for the identification and quantification of defects responsible for low channel mobility in 4H-Silicon Carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs). To achieve this, we use an algorithm based on 2D-device simulations of a power MOSFET, density functional simulations, and measurement data. Using physical modeling of carrier mobility and interface traps, we reproduce the experimental I-V characteristics of a 4H-SiC doubly implanted MOSFET through drift-diffusion simulation. We extract the position of Fermi level and the occupied trap density as a function of applied bias and temperature. Using these inputs, our algorithm estimates the number of possible trap types, their energy levels, and concentrations at 4H-SiC/SiO{sub 2} interface. Subsequently, we use density functional theory (DFT)-based ab initio simulations to identify the atomic make-up of defects causing these trap levels. We study silicon vacancy and carbon di-interstitial defects in the SiC side of the interface. Our algorithm indicates that the D{sub it} spectrum near the conduction band edge (3.25?eV) is composed of three trap types located at 2.8–2.85?eV, 3.05?eV, and 3.1–3.2?eV, and also calculates their densities. Based on DFT simulations, this work attributes the trap levels very close to the conduction band edge to the C di-interstitial defect.

  16. Status of cross-section data for gas production from vanadium and {sup 26}AL from silicon carbide in a D-T fusion reactor.

    SciTech Connect (OSTI)

    Gomes, I. C.

    1998-08-11T23:59:59.000Z

    Current designs of fusion-reactor systems seek to use radiation-resistant, low-activation materials that support long service lifetimes and minimize radioactive-waste problems after decommissioning. Reliable assessment of fusion materials performance requires accurate neutron-reaction cross sections and radioactive-decay constants. The problem areas usually involve cross sections since decay parameters tend to be better known. The present study was motivated by two specific questions: (i) Why are the {sup 51}V(n,np){sup 50}Ti cross section values in the ENDF/B-VI library so large (a gas production issue)? (ii) How well known are the cross sections associated with producing 7.4 x 10{sup 5} y {sup 26}Al in silicon carbide by the process {sup 28}Si(n,np+d){sup 27} Al(n,2n){sup 26}Al (a long-lived radioactivity issue)? The energy range 14-15 MeV of the D-T fusion neutrons is emphasized. Cross-section error bars are needed so that uncertainties in the gas and radioactivity generated over the lifetime of a reactor can be estimated. We address this issue by comparing values obtained from prominent evaluated cross-section libraries. Small differences between independent evaluations indicate that a physical quantity is well known while the opposite signals a problem. Hydrogen from {sup 51}V(n,p){sup 51}Ti and helium from {sup 51}V(n,{alpha}){sup 48}Sc are also important sources of gas in vanadium, so they too were examined. We conclude that {sup 51}V(n,p){sup 51}Ti is adequately known but {sup 51}V(n,np+d){sup 50}Ti is not. The status for helium generation data is quite good. Due to recent experimental work, {sup 27}Al(n,2n){sup 26}Al seems to be fairly well known. However, the situation for {sup 28}Si(n,np+d){sup 27}Al remains unsatisfactory.

  17. The matching of a “one-dimensional” numerical simulation and experiment results for low viscosity Newtonian and non-Newtonian fluids during fast filament stretching and subsequent break-up

    E-Print Network [OSTI]

    Tembely, M.; Vadillo, D.; Mackley, M.R.; Soucemarianadin, A.

    2012-01-23T23:59:59.000Z

    Research (LEGI), UMR 5519, University Joseph Fourier, Grenoble, BP 53, 38041 Grenoble Cedex, France D. Vadillo and M. R. Mackley Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA, United Kingdom A... al. (2002); Crassous et al. (2005); Kirschen- mann (2003)] to obtain linear viscoelastic data of the fluids under test, and a specially designed filament stretching apparatus (Cambridge Trimaster MkII) was used to achieve controlled stretching...

  18. Evaluation of Neutron Irradiated Silicon Carbide and Silicon Carbide Composites

    SciTech Connect (OSTI)

    Newsome G, Snead L, Hinoki T, Katoh Y, Peters D

    2007-03-26T23:59:59.000Z

    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.

  19. Silicon Carbide and Silicon Carbide Composites for Fusion Reactor Applications

    SciTech Connect (OSTI)

    Hinoki, Tatsuya [Kyoto University, Japan] [Kyoto University, Japan; Hasegawa, Akira [Tohoku University, Japan] [Tohoku University, Japan; Katoh, Yutai [ORNL] [ORNL; Snead, Lance Lewis [ORNL] [ORNL; Jung, H.C. [Kyoto University, Japan] [Kyoto University, Japan; Katsui, Hirokazu [Tohoku University, Japan] [Tohoku University, Japan; Kondo, Sosuke [ORNL] [ORNL; Zhong, Z. H. [Kyoto University, Japan] [Kyoto University, Japan; Park, Y. H. [Kyoto University, Japan] [Kyoto University, Japan; Shih, Chunghao [ORNL] [ORNL; Ozawa, Kazumi [ORNL] [ORNL; Parish, Chad M [ORNL] [ORNL; Meisner, Roberta Ann [ORNL] [ORNL

    2013-01-01T23:59:59.000Z

    This paper reviews recent achievements as to "nuclear-grade" SiC composites in particular for materials-system integration. SiC composite component development are reviewed including VHTR control rod scale model and compact intermediate heat exchanger scale mode by current joining and assembly techniques. Joining methods for SiC to metal and results of characterization of joint shear strength by the torsion tests using small specimens were also reviewed. The recent results of neutron irradiation experiments were also reviewed including detailed analysis of mechanical properties, irradiation creep and preliminary results on tritium behavior in SiC.

  20. The Molecular Architecture for the Intermediate Filaments of Hard [alpha]-Keratin Based on the Superlattice Data Obtained from a Study ofMammals Using Synchrotron Fibre Diffraction

    SciTech Connect (OSTI)

    James, Veronica (ANU)

    2014-09-24T23:59:59.000Z

    High- and low-angle X-ray diffraction studies of hard {alpha}-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 {alpha}-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, including 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 {alpha}-keratin. The results verify that the structure proposed by Feughelman and James meets the criteria for a valid {alpha}-keratin structure.

  1. Molybdenum sulfide/carbide catalysts

    SciTech Connect (OSTI)

    Alonso, Gabriel (Chihuahua, MX); Chianelli, Russell R. (El Paso, TX); Fuentes, Sergio (Ensenada, MX); Torres, Brenda (El Paso, TX)

    2007-05-29T23:59:59.000Z

    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.

  2. 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.

    2013-08-15T23:59:59.000Z

    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.

  3. Material characterization of the clay bonded silicon carbide candle filters and ash formations in the W-APF system after 500 hours of hot gas filtration at AEP. Appendix to Advanced Particle Filter: Technical progress report No. 11, January--March 1993

    SciTech Connect (OSTI)

    Alvin, M.A.

    1993-04-05T23:59:59.000Z

    (1) After 500 hours of operation in the pressurized fluidized-bed combustion gas environment, the fibrous outer membrane along the clay bonded silicon carbide Schumacher Dia Schumalith candles remained intact. The fibrous outer membrane did not permit penetration of fines through the filter wall. (2) An approximate 10-15% loss of material strength occurred within the intact candle clay bonded silicon carbide matrix after 500 hours of exposure to the PFBC gas environment. A relatively uniform strength change resulted within the intact candles throughout the vessel (i.e., top to bottom plenums), as well as within the various cluster ring positions (i.e., outer versus inner ring candle filters). A somewhat higher loss of material strength, i.e., 25% was detected in fractured candle segments removed from the W-APF ash hopper. (3) Sulfur which is present in the pressurized fluidized-bed combustion gas system induced phase changes along the surface of the binder which coats the silicon carbide grains in the Schumacher Dia Schumalith candle filter matrix.

  4. 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., E-mail: rav@knights.ucf.edu [Department of Mathematics, University of Central Florida, Orlando, Florida 32816-1364 (United States)

    2014-01-15T23:59:59.000Z

    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 Hänninen. 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 Hänninen 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 Hänninen claim, the dispersion relation obtained in my paper is consistent with LIA, where applicable. Finally, while Hietala and Hänninen 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)

  5. A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. III. Catastrophe of the Eruptive Filament in a Magnetic Null Point and Formation of an Opposite-Handedness CME

    E-Print Network [OSTI]

    Uralov, A M; Rudenko, G V; Myshyakov, I I; Chertok, I M; Filippov, B P; Slemzin, V A

    2014-01-01T23:59:59.000Z

    Our analysis in Papers I and II (Grechnev et al., 2014, Solar Phys. 289, 289 and 1279) of the 18 November 2003 solar event responsible for the 20 November geomagnetic superstorm has revealed a complex chain of eruptions. In particular, the eruptive filament encountered a topological discontinuity located near the solar disk center at a height of about 100 Mm, bifurcated, and transformed into a large cloud, which did not leave the Sun. Concurrently, an additional CME presumably erupted close to the bifurcation region. The conjectures about the responsibility of this compact CME for the superstorm and its disconnection from the Sun are confirmed in Paper IV (Grechnev et al., Solar Phys., submitted), which concludes about its probable spheromak-like structure. The present paper confirms the presence of a magnetic null point near the bifurcation region and addresses the origin of the magnetic helicity of the interplanetary magnetic clouds and their connection to the Sun. We find that the orientation of a magnetic...

  6. 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)

    2011-02-22T23:59:59.000Z

    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.

  7. ELECTROCHEMICAL MACHINING OF CARBIDES AND BORIDES

    E-Print Network [OSTI]

    Dissaux, Bernard Antoine

    2011-01-01T23:59:59.000Z

    behavior. The voltage oscillations were explained byextensively these voltage oscillations and, in contrast tovoltages and tool feed rates indicated that: • the oscillations

  8. Off-axis silicon carbide substrates

    DOE Patents [OSTI]

    Edgar, James; Dudley, Michael; Kuball, Martin; Zhang, Yi; Wang, Guan; Chen, Hui; Zhang, Yu

    2014-09-02T23:59:59.000Z

    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.

  9. Silicon carbide oxidation in high temperature steam

    E-Print Network [OSTI]

    Arnold, Ramsey Paul

    2011-01-01T23:59:59.000Z

    The commercial nuclear power industry is continually looking for ways to improve reactor productivity and efficiency and to increase reactor safety. A concern that is closely regulated by the Nuclear Regulatory Commission ...

  10. Process for preparing silicon carbide foam

    DOE Patents [OSTI]

    Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

    1997-09-16T23:59:59.000Z

    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.

  11. 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)

    1997-01-01T23:59:59.000Z

    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.

  12. Modelling Precipitation of Carbides in Martensitic Steels

    E-Print Network [OSTI]

    Cambridge, University of

    of Materials Science and Metallurgy, University of Cambridge, between October 2000 and November 2003. Except facilities in the Department of Materials Science and Metallurgy at the University of Cambridge. I would like of the physical metallurgy of secondary hardening steels and the phenomena of hydrogen embrittlement and hydrogen

  13. Silicon Carbide Derived Carbons: Experiments and Modeling

    SciTech Connect (OSTI)

    Kertesz, Miklos [Georgetown University, Washington DC 20057

    2011-02-28T23:59:59.000Z

    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.

  14. Modelling Precipitation of Carbides in Martensitic Steels

    E-Print Network [OSTI]

    Yamasaki, Shingo

    is greater than the yield stress of many commercial steels. II Sulfide stress corrosion cracking (SSCC) There were cases in which joints of pipes used in oil wells ruptured only a few days after the commencement of operation [45, 46]. These accidents were... -composition IG Intergranular fracture MVC Microvoid coalescence rupture MTDATA Metallurgical and Thermochemical Databank PC Pre-stressed concrete QC Quasi-cleavage fracture SSCC Sulfide stress corrosion cracking TEM Transmission electron microscope TMCP...

  15. Vanadium Carbide Coating Process | Department of Energy

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your DensityEnergy U.S.-China Electric Vehicle and03/02 TUEValidation of Innovative ExplorationanValue

  16. 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)

    1991-01-01T23:59:59.000Z

    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.

  17. Organic Acid Production by Filamentous Fungi

    E-Print Network [OSTI]

    -being. Indeed, organic acid fermentations are often not even identified as fungal bioprocesses, having been Aspergillus niger in aerated stirred-tank-reactors can convert glucose to citric acid with greater than 80 lipolytica, and related yeast species, may be in use commercially to produce citric acid (Lopez-Garcia, 2002

  18. Material properties of actin filament bundles

    E-Print Network [OSTI]

    Robertson, Alec, 1974-

    2009-01-01T23:59:59.000Z

    Actin is an ubiquitous structural protein fundamental to such biological processes as cell motility and muscle contraction. Our model system is the acrosomal process of the Limulus sperm which extends a 60 ýtm long actin ...

  19. Moment of Fluid Interface Reconstruction with Filaments

    SciTech Connect (OSTI)

    Jemison, Matthew B. [Los Alamos National Laboratory

    2012-08-15T23:59:59.000Z

    A moving system made up of multiple fluids (e.g. air and water) may be defined by an evolving interface with a changing topology. MOF uses a piecewise linear interface reconstruction to numerically model deforming boundaries. Given a volume fraction V and reference centroid x for a material in cell {Omega}, we seek to find an interface {Gamma} that exactly captures V and minimizes error in x. This differs from Volume of Fluid methods.

  20. In-fiber semiconductor filament arrays

    E-Print Network [OSTI]

    Deng, Daosheng

    2010-01-01T23:59:59.000Z

    One-dimensional nanostructures with high aspect-ratios and nanometer cross-sectional dimensions have been the focus of recent studies in the persistent drive to miniaturize devices. Conventional bottom-up methods such as ...

  1. Zirconium and Hafnium--2004 85. references that include a section mark () are found in the internet

    E-Print Network [OSTI]

    -mineral sand operations at Green cove Springs, fL; Stony creek, Va; and from its new mine in Lulaton, Ga. iluka of domestic mining operations. of the two domestic zircon producers, which have four mining and processing's florida operations included a dry mining mobile concentrator and a heavy-mineral sands processing plant

  2. Hafnium isotope evidence from Archean granitic rocks for deep-mantle origin of continental crust

    E-Print Network [OSTI]

    Mojzsis, Stephen J.

    of zircon crystallization. The advent of laser-ablation Lu­Hf isotope analysis of igneous and detrital

  3. Hafnium-doped tantalum oxide high-k gate dielectric films for future CMOS technology

    E-Print Network [OSTI]

    Lu, Jiang

    2007-04-25T23:59:59.000Z

    of the doped films were explained by their compositions and bond structures. The Hf-doped TaOx film is a potential high-k gate dielectric for future MOS transistors. A 5 Ã?Â? tantalum nitride (TaNx) interface layer has been inserted between the Hf-doped Ta...

  4. Nanocrystals Embedded Zirconium-doped Hafnium Oxide High-k Gate Dielectric Films

    E-Print Network [OSTI]

    Lin, Chen-Han

    2012-10-19T23:59:59.000Z

    , can be expected. In this study, the ZrHfO high-k MOS capacitors that separately contain nanocrystalline ruthenium oxide (nc-RuO), indium tin oxide (nc-ITO), and zinc oxide (nc-ZnO) have been successfully fabricated by the sputtering deposition method...

  5. Chemical Bonding, Interfaces and Defects in Hafnium Oxide/Germanium Oxynitride Gate Stacks on Ge (100)

    SciTech Connect (OSTI)

    Oshima, Yasuhiro; /Stanford U., Materials Sci. Dept.; Sun, Yun; /SLAC, SSRL; Kuzum, Duygu; /Stanford U.; Sugawara, Takuya; Saraswat, Krishna C.; Pianetta, Piero; /SLAC, SSRL; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.

    2008-10-31T23:59:59.000Z

    Correlations among interface properties and chemical bonding characteristics in HfO{sub 2}/GeO{sub x}N{sub y}/Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO{sub 2} atomic layer deposition (ALD). Ultra thin ({approx}1.1 nm), thermally stable and aqueous etch-resistant GeO{sub x}N{sub y} interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge{sub 3}N{sub 4} were synthesized. To evaluate GeO{sub x}N{sub y}/Ge interface defects, the density of interface states (D{sub it}) was extracted by the conductance method across the band gap. Forming gas annealed (FGA) samples exhibited substantially lower D{sub it} ({approx} 1 x 10{sup 12} cm{sup -2} eV{sup -1}) than did high vacuum annealed (HVA) and inert gas anneal (IGA) samples ({approx} 1x 10{sup 13} cm{sup -2} eV{sup -1}). Germanium core level photoelectron spectra from similar FGA-treated samples detected out-diffusion of germanium oxide to the HfO{sub 2} film surface and apparent modification of chemical bonding at the GeO{sub x}N{sub y}/Ge interface, which is related to the reduced D{sub it}.

  6. Method of Preparing Hydrous Hafnium, Cerium, or Aluminum Oxide Gels and

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville PowerCherries 82981-1cnHighand Retrievals from aRodMIT-HarvardEnergyMethod

  7. A look back at Union Carbides first 20 Years in Nuclear Energy...

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

    and 5,000 grams of enriched stable isotopes throughout the world for use in industry, agriculture, training and medicine. "RADIOISOTOPES FOR PEACEFUL USES" "The first...

  8. A look back at Union Carbides first 20 Years in Nuclear Energy...

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

    months, and exhibited at the Atoms for Peace Conference in Geneva, Switzerland. "1956 - Thermonuclear fusion research expanded to develop a promising new approach to achieving a...

  9. Union Carbides Last 20 Years in Oak Ridge ? part 2

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

    until finally shut down in 1987. (Rosenthal). 1962. A chemical explosion at the Paducah Gaseous Diffusion Plant resulted in a fire with damages estimated at 2 million. 1963. The...

  10. A look back at Union Carbides 20 Years in Nuclear Energy [The...

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

    Chemicals Company was called in. On January 18, 1943, a contract to operate a gaseous diffusion plant and to provide engineering and research help was signed by James A....

  11. A look back at Union Carbides [first] 20 Years in Nuclear Energy...

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

    Construction started in October 1959. December 1961 - The new Development Laboratory for Chemistry and Physics departments of Technical Division was completed. Construction...

  12. Union Carbides Last 20 Years in Oak Ridge ? part 4

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

    1950s was to produce some highly enriched lithium-6 for use in building the first thermonuclear, also called the hydrogen or super-bomb. The project from the beginning was highly...

  13. A look back at Union Carbides FIRST 20 Years in Nuclear Energy...

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

    "Radioisotopes are used as tracers in checking reactions in making chemicals and plastics. They permit accurate determinations that were impossible previously. "Agricultural...

  14. Union Carbides Last 20 Years in Oak Ridge ? part 3

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

    ion research facility at ORNL was named for Mr. Holifield instead. 1977. President Jimmy Carter announced that the next U. S. enrichment plant will be built at Portsmouth,...

  15. Union Carbides 20 years in nuclear energy, part 2

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

    (Note: while not listed at the time because of the need for secrecy, Lithium separation production using the COLEX (column exchange) process began in Buildings 9201-4 and 9201-5...

  16. 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.

    2005-03-15T23:59:59.000Z

    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.

  17. Occupational Medicine Implications of Engineered Nanoscale Particulate Matter

    E-Print Network [OSTI]

    Kelly, Richard J.

    2008-01-01T23:59:59.000Z

    Titanium Ytterbium Zirconium Animony Boron Carbon Cobalt Erbium Gallium Hafnium Iridium Lead Magnesium Neodymium Nitrogen

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

    Energy Savers [EERE]

    flywheels, electrochemical capacitors, superconducting magnetic energy storage (SMES), power electronics, and control systems, visit the Energy Storage page. Fact Sheet:...

  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)

    2012-02-28T23:59:59.000Z

    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. DIFFUSION OF MAGNESIUM AND MICROSTRUCTURES IN Mg+ IMPLANTED SILICON CARBIDE

    SciTech Connect (OSTI)

    Jiang, Weilin; Edwards, Danny J.; Jung, Hee Joon; Wang, Zheming; Zhu, Zihua; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2014-08-28T23:59:59.000Z

    Following our previous reports [ 1- 3], further isochronal annealing (2 hrs.) of the monocrystalline 6H-SiC and polycrystalline CVD 3C-SiC was performed at 1573 and 1673 K in Ar environment. SIMS data indicate that observable Mg diffusion in 6H-SiC starts and a more rapid diffusion in CVD 3C-SiC occurs at 1573 K. The implanted Mg atoms tend to diffuse deeper into the undamaged CVD 3C-SiC. The microstructure with Mg inclusions in the as-implanted SiC has been initially examined using high-resolution STEM. The presence of Mg in the TEM specimen has been confirmed based on EDS mapping. Additional monocrystalline 3C-SiC samples have been implanted at 673 K to ion fluence 3 times higher than the previous one. RBS/C analysis has been performed before and after thermal annealing at 1573 K for 12 hrs. Isothermal annealing at 1573 K is being carried out and Mg depth profiles being measured. Microstructures in both the as-implanted and annealed samples are also being examined using STEM.