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Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
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We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


1

Synthesis and Characterization of Single Crystalline Hafnium Carbide Nanowires  

E-Print Network [OSTI]

transition metal carbide (TMC) nanowires has been reported, no HfC nanowires have been successfully syntheSynthesis and Characterization of Single Crystalline Hafnium Carbide Nanowires Jinshi Yuan,,§ Han carbide (HfC) is the most refractory compound known to mankind. A catalyst-assisted chemical vapor deposi

Qin, Lu-Chang

2

SIGNATURES OF THE s-PROCESS IN PRESOLAR SILICON CARBIDE GRAINS: BARIUM THROUGH HAFNIUM  

E-Print Network [OSTI]

SIGNATURES OF THE s-PROCESS IN PRESOLAR SILICON CARBIDE GRAINS: BARIUM THROUGH HAFNIUM Qing-Zhu Yin have been determined in a silicon carbide­rich sample of the Murchison carbonaceous chondrite, using carbide, silicon nitride, and various refractory oxides (e.g., Zinner 1998). Grains of silicon carbide (Si

Lee, Cin-Ty Aeolus

3

Hafnium  

SciTech Connect (OSTI)

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.

NONE

1994-02-01T23:59:59.000Z

4

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

5

Silver-hafnium braze alloy  

DOE Patents [OSTI]

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.

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

2003-12-16T23:59:59.000Z

6

Formulation and method for preparing gels comprising hydrous hafnium oxide  

DOE Patents [OSTI]

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.

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

2013-08-06T23:59:59.000Z

7

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments  

E-Print Network [OSTI]

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

Danon, Yaron

8

E-Print Network 3.0 - alpha -particle-irradiated hafnium Sample...  

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

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

9

Carbide and carbonitride surface treatment method for refractory metals  

DOE Patents [OSTI]

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.

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

1996-12-03T23:59:59.000Z

10

Microwave sintering of boron carbide  

DOE Patents [OSTI]

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.

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

1988-06-10T23:59:59.000Z

11

Endocytosis in filamentous fungi  

E-Print Network [OSTI]

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 ...

Kalkman, Edward R I C

2007-01-01T23:59:59.000Z

12

As-Received, Ozone Cleaned and Ar+ Sputtered Surfaces of Hafnium Oxide Grown by Atomic Layer Deposition and Studied by XPS  

SciTech Connect (OSTI)

In this study, X-ray photoelectron spectroscopy (XPS) characterization was performed on 47 nm thick hafnium oxide (HfO{sub 2}) films grown by atomic layer deposition using TEMA-Hf/H{sub 2}O at 250 C substrate temperature. HfO{sub 2} is currently being studied as a possible replacement for Silicon Oxide (SiO{sub 2}) as a gate dielectric in electronics transistors. XPS spectra were collected on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe using a monochromatic Al K{sub a} X-ray (1486.7 eV) excitation source. The sample was analyzed under the following conditions: as received, after UV irradiation for five minutes, and after sputter cleaning with 2 kV Ar{sup +} ions for 180 seconds. Survey scans showed carbon, oxygen, and hafnium as the major species in the film, while the only minor species of argon and carbide was detected after sputtering. Adventitious carbon initially composed approximately 18.6 AT% of the surface, but after UV cleaning it was reduced to 2.4 AT%. This demonstrated that that the majority of carbon was due to adventitious carbon. However, after 2 kV Ar{sup +} sputtering there was still only trace amounts of carbon at {approx}1 AT%, Some of this trace carbon is now in the form of a carbide due to the interaction with Ar{sup +} used for sputter cleaning. Furthermore, the stoiciometric ratio of oxygen and hafnium is consistent with a high quality HfO{sub 2} film.

Engelhard, Mark H.; Herman, Jacob A.; Wallace, Robert; Baer, Donald R.

2012-06-27T23:59:59.000Z

13

Carbide and carbonitride surface treatment method for refractory metals  

DOE Patents [OSTI]

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.

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

1996-01-01T23:59:59.000Z

14

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

E-Print Network [OSTI]

%; South Africa, 37%; China, 3%; Canada, 1%; and other, 2%. Zirconium, unwrought, including powder: France coatings, and sandblasting. The leading consumers of zirconium and hafnium metal are the nuclear energy Kingdom, 5%; and other, 9%. Tariff: Item Number Normal Trade Relations 12-31-08 Zirconium ores

15

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

E-Print Network [OSTI]

of hafnium metal was insignificant. Import Sources (1997-2000): Zirconium ores and concentrates: South Africa%; Germany, 7%; United Kingdom, 2%; and other, 9%. Tariff: Item Number Normal Trade Relations 12 Stockpile, the U.S. Department of Energy (DOE) held over 500 tons of zirconium in various forms. DOE also

16

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

E-Print Network [OSTI]

Sources (2002-05): Zirconium ores and concentrates: Australia, 57%; South Africa, 35%; China, 4%; Canada consumers of zirconium and hafnium metal are the nuclear energy and chemical process industries. Salient%; Japan, 4%; and other, 2%. Tariff: Item Number Normal Trade Relations 12-31-06 Zirconium ores

17

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

E-Print Network [OSTI]

of hafnium metal was insignificant. Import Sources (1998-2001): Zirconium ores and concentrates: South Africa%; Germany, 8%; United Kingdom, 3%; and other, 9%. Tariff: Item Number Normal Trade Relations 12,838 short tons) of zirconium ore (baddeleyite) during fiscal year 2002. The U.S. Department of Energy (DOE

18

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

E-Print Network [OSTI]

concentrates: South Africa, 52%; Australia, 43%; and other, 5%. Zirconium, unwrought, including powder: Japan. The leading consumers of zirconium metal and hafnium metal are the nuclear energy and chemical process, 58%; Australia, 24%; Germany, 11%; other, 7%. Tariff: Item Number Normal Trade Relations 12

19

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

E-Print Network [OSTI]

%; South Africa, 46%; China, 3%; Russia, 1%; and other, 1%. Zirconium, unwrought, including powder: France coatings, and sandblasting. The leading consumers of zirconium and hafnium metal are the nuclear energy, 21%; Canada, 8%; United Kingdom, 6%; and other, 5%. Tariff: Item Number Normal Trade Relations 12

20

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

E-Print Network [OSTI]

was insignificant. Import Sources (2008­11): Zirconium mineral concentrates: Australia, 52%; South Africa, 42. The leading consumers of zirconium metal and hafnium metal are the nuclear energy and chemical process: Item Number Normal Trade Relations 12­31­12 Zirconium ores and concentrates 2615.10.0000 Free

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

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

E-Print Network [OSTI]

concentrates: Australia, 49%; South Africa, 44%; and other, 7%. Zirconium, unwrought, including powder: Germany. The leading consumers of zirconium metal and hafnium metal are the nuclear energy and chemical process, 17%; United Kingdom, 5%; and other, 9%. Tariff: Item Number Normal Trade Relations 12-31-11 Zirconium

22

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

E-Print Network [OSTI]

%; South Africa, 32%; China, 4%; Canada, 2%; and other, 1%. Zirconium, unwrought, including powder: France coatings, and sandblasting. The leading consumers of zirconium and hafnium metal are the nuclear energy, 2%; Austria, 1%; and other, 1%. Tariff: Item Number Normal Trade Relations 12-31-07 Zirconium ores

23

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments  

SciTech Connect (OSTI)

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.

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

2004-10-13T23:59:59.000Z

24

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

SciTech Connect (OSTI)

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.

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

1982-12-01T23:59:59.000Z

25

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments  

SciTech Connect (OSTI)

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.

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

26

Modified silicon carbide whiskers  

DOE Patents [OSTI]

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.

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

1991-05-21T23:59:59.000Z

27

Modified silicon carbide whiskers  

DOE Patents [OSTI]

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.

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

1991-01-01T23:59:59.000Z

28

Process for microwave sintering boron carbide  

DOE Patents [OSTI]

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.

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

1993-10-12T23:59:59.000Z

29

Process for microwave sintering boron carbide  

DOE Patents [OSTI]

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.

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

30

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...

31

Oxygen and nitrogen diffusion in ?-hafnium from first principles  

SciTech Connect (OSTI)

We use a combination of density functional theory and multistate diffusion formalism to analyze the diffusion of oxygen and nitrogen in technologically important hafnium metal. Comparing the local density approximation and the Perdew-Burke-Ernzerhof version of the generalized gradient approximation, we find that a better description of the hafnium lattice in the latter results in the correct sequence of stable and transition states for oxygen interstitials leading to essentially quantitative agreement with experiment. For oxygen diffusion, we find an isotropic temperature-dependent diffusion coefficient of D=0.082e{sup ?2.04/k{sub B}T}cm{sup 2}s{sup ?1} utilizing interstitial sites with hexahedral and octahedral coordination. For the diffusivity of nitrogen, we find that an additional stable interstitial site, the crowdion site, exists and that the diffusion coefficient is D=0.15e{sup ?2.68/k{sub B}T}cm{sup 2}s{sup ?1}. Our results also reproduce the experimental observation that nitrogen diffusivity is lower than that of oxygen in hafnium.

O'Hara, Andrew; Demkov, Alexander A., E-mail: demkov@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)

2014-05-26T23:59:59.000Z

32

Carbide Precipitation in Steel Weld Metals  

E-Print Network [OSTI]

Carbide Precipitation in Steel Weld Metals www.msm.cam.ac.uk/phase-trans #12 diffusion into austenite Carbon diffusion into austenite and carbide precipitation in ferrite Carbide precipitation from austenite CASE 2: elimination of carbides #12;#12;#12;0.110.090.070.050.03 0.2 0.4 0.6 0.8 1

Cambridge, University of

33

Microwave processing for carbide ceramics  

SciTech Connect (OSTI)

The US Bureau of Mines (USBM) has developed a process for synthesizing carbide ceramics in a microwave-induced plasma (MIP). For example, the process forms tungsten carbide with only 0.04% free carbon impurity at an average particle size of 0.05 {mu}m. Starting materials are tungsten oxide, carbon, and carbon monoxide. Commercial methods to produce tungsten carbide require heating to 1,500 C for up to 7 hours. Using the USBM method, tungsten carbide can be produced in approximately 10 minutes using a 30 kW, 915 mHz microwave unit. The reaction is carried out in a short-circuited waveguide to create a standing wave. Reactants rest on a carbon pedestal inside a closed zirconia crucible filled with carbon monoxide. The crucible is place at a field maximum within the waveguide. The waveguide was filled with helium to protect the waveguide. A procedure for producing carbide on a larger scale is described. Other ceramic compounds have been produced using this method, including silicon carbide and titanium carbide.

Tolley, W.K.; Church, R.H. [Bureau of Mines, Salt Lake City, UT (United States). Salt Lake City Research Center

1995-08-01T23:59:59.000Z

34

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

SciTech Connect (OSTI)

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.

Singh, M.; Levine, S.R.

1995-07-01T23:59:59.000Z

35

Aerogel-supported filament  

DOE Patents [OSTI]

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.

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

1995-01-01T23:59:59.000Z

36

Aerogel-supported filament  

DOE Patents [OSTI]

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.

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

1995-05-16T23:59:59.000Z

37

Rheology of silicon carbide/vinyl ester nanocomposites  

E-Print Network [OSTI]

New York, 1999. SILICON CARBIDE/VINYL ESTER NANOCOMPOSITESRheology of Silicon Carbide/Vinyl Ester NanocompositesABSTRACT: Silicon carbide (SiC) nanoparticles with no

Yong, Virginia; Hahn, H. Thomas

2006-01-01T23:59:59.000Z

38

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

SciTech Connect (OSTI)

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.

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

39

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

E-Print Network [OSTI]

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 ...

Cerefice, Gary Steven

1999-01-01T23:59:59.000Z

40

Classification of Carbide Distributions using ScaleSpace Methods Classification of Carbide Distributions using Scale  

E-Print Network [OSTI]

Classification of Carbide Distributions using Scale­Space Methods #12; Classification of Carbide­structure of the steel, which in turn influences the mechanical properties. Specifi­ cally, the distribution of carbide is essential, since cracks propagate within the carbide agglomerations. In current quality control

Lindeberg, Tony

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

3 Carbide Precipitation Carbides are largely responsible for the commercial failure of many of the early  

E-Print Network [OSTI]

.1. Transition carbides, such as and the various orthorhombic forms listed in Table 3.1, only form because Precipitation 64 Table 3.1 Carbides in bainite or in tempered bainite. Fe, M/C is the ratio of metal to car- bon3 Carbide Precipitation Carbides are largely responsible for the commercial failure of many

Cambridge, University of

42

Growth mode evolution of hafnium oxide by atomic layer deposition  

SciTech Connect (OSTI)

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 heightheight 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.

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

43

Atomic Layer Deposition of Insulating Hafnium and Zirconium Nitrides  

E-Print Network [OSTI]

author. E-mail: gordon@chemistry.harvard.edu. (1) Toth, L. E. Transition Metal Carbides and Nitrides homoleptic tetrakis(dialkylamido)- metal(IV) complexes and ammonia at low substrate temperatures (150-250 °C). The precursor vapors were alternately pulsed into a heated reactor, yielding 1.15-1.20 ? of metal nitride film

44

Diamond-silicon carbide composite  

DOE Patents [OSTI]

Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=58 GPa, T=1400K2300K) 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.

Qian, Jiang; Zhao, Yusheng

2006-06-13T23:59:59.000Z

45

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

SciTech Connect (OSTI)

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

Utkin, A.V., E-mail: utkinalex@hotmail.com; Prokip, V.E.; Baklanova, N.I.

2014-01-15T23:59:59.000Z

46

Abrasive slurry composition for machining boron carbide  

DOE Patents [OSTI]

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.

Duran, Edward L. (Santa Fe, NM)

1985-01-01T23:59:59.000Z

47

Microstructure and properties of IN SITU toughened silicon carbide  

E-Print Network [OSTI]

IN SITU TOUGHENED SILICON CARBIDE LUTGARD C. DE JONGHE 1,2 ,In Situ Toughened Silicon Carbide Lutgard C. De Jonghe 1,2 ,USA ABSTRACT A silicon carbide with a fracture toughness as

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

2003-01-01T23:59:59.000Z

48

Method for making boron carbide cermets  

DOE Patents [OSTI]

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.

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

1987-11-03T23:59:59.000Z

49

Method for making boron carbide cermets  

DOE Patents [OSTI]

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.

Cline, Carl F. (Danville, CA); Fulton, Fred J. (Livermore, CA)

1987-01-01T23:59:59.000Z

50

Crystal Structure and Formation Energy of -carbide Using First  

E-Print Network [OSTI]

Crystal Structure and Formation Energy of -carbide Using First Principles CalculationsIntroduction · Martensite (') -carbide -carbide -carbide Cementite () · Silicon promotes the formation of -carbide below-456(2008) 900, 100s 200, 20s 250, 30 s Ms = 302(1.0 wt%Si), 293 (1.7 wt%Si) 1.0wt% Si : No -carbide 1.7wt% Si

Cambridge, University of

51

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

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

modeling of amorphous silicon carbide using a bond-order potential. Atomistic modeling of amorphous silicon carbide using a bond-order potential. Abstract: Molecular dynamics...

52

Mechanisms of tungsten carbide-cobalt nanoparticle-induced angiogenesis.  

E-Print Network [OSTI]

??Hard metal or cemented carbide consists of a powder mixture of 80 to 90% oftungsten carbide (WC) and 5 to 10% of metallic cobalt (Co). (more)

Zhu, Yingxue.

2010-01-01T23:59:59.000Z

53

Titanium carbide bipolar plate for electrochemical devices  

DOE Patents [OSTI]

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.

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

54

Silicon nitride/silicon carbide composite powders  

DOE Patents [OSTI]

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.

Dunmead, Stephen D. (Midland, MI); Weimer, Alan W. (Midland, MI); Carroll, Daniel F. (Midland, MI); Eisman, Glenn A. (Midland, MI); Cochran, Gene A. (Midland, MI); Susnitzky, David W. (Midland, MI); Beaman, Donald R. (Midland, MI); Nilsen, Kevin J. (Midland, MI)

1996-06-11T23:59:59.000Z

55

Titanium Carbide Bipolar Plate for Electrochemical Devices  

SciTech Connect (OSTI)

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

LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

1998-05-08T23:59:59.000Z

56

Nitride-bonded silicon carbide composite filter  

SciTech Connect (OSTI)

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.

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

1995-12-01T23:59:59.000Z

57

The production of iron carbide  

SciTech Connect (OSTI)

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.

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

1997-12-31T23:59:59.000Z

58

Galaxy pairs align with galactic filaments  

E-Print Network [OSTI]

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...

Tempel, Elmo

2015-01-01T23:59:59.000Z

59

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

E-Print Network [OSTI]

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), ...

Gabert, Andrea Jennifer

2007-01-01T23:59:59.000Z

60

Nonequilibrium transport in superconducting filaments  

SciTech Connect (OSTI)

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.

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

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Studies on the dynamics of limited filaments  

E-Print Network [OSTI]

A study on the dynamics of filaments in the presence of a diagnostic, conductive limiter is presented. Plasma filaments are coherent structures present in many fusion devices and transport a significant amount of particles ...

Bonde, Jeffrey David

2010-01-01T23:59:59.000Z

62

Classi cation of Carbide Distributions using Scale-Space Methods Classi cation of Carbide Distributions using Scale  

E-Print Network [OSTI]

Classi cation of Carbide Distributions using Scale-Space Methods #12;Classi cation of Carbide-structure of the steel, which in turn in uences the mechanical properties. Speci - cally, the distribution of carbide is essential, since cracks propagate within the carbide agglomerations. In current quality control

Lindeberg, Tony

63

Manufacture of silicon carbide using solar energy  

DOE Patents [OSTI]

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.

Glatzmaier, Gregory C. (Boulder, CO)

1992-01-01T23:59:59.000Z

64

Modelling Precipitation of Carbides in Martensitic Steels  

E-Print Network [OSTI]

embrittlement is one of the major factors responsible for failure. It is believed that carbide particles can act as hydrogen trapping sites, thus reducing the risk of embrittlement. The thesis begins with a review of the physical metallurgy of secondary...

Yamasaki, Shingo

65

Silver transport in CVD silicon carbide  

E-Print Network [OSTI]

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 ...

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

2004-01-01T23:59:59.000Z

66

Electroextraction of boron from boron carbide scrap  

SciTech Connect (OSTI)

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.

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

67

Transient analysis of silicon carbide power MOSFET.  

E-Print Network [OSTI]

??This thesis illustrates the transient performance of Silicon carbide (4H-SiC) Power MOSFET. Transient analysis enables the designer to understand the thermal stress the semiconductor device (more)

Pushpakaran, Bejoy

2012-01-01T23:59:59.000Z

68

Chemical solution deposition of ferroelectric yttrium-doped hafnium oxide films on platinum electrodes  

SciTech Connect (OSTI)

Ferroelectric hafnium oxide films were fabricated by chemical solution deposition with a remnant polarization of >13 ?C/cm{sup 2}. The samples were prepared with 5.2?mol.?% yttrium-doping and the thickness varied from 18?nm to 70?nm. The hafnium oxide layer was integrated into a metal-insulator-metal capacitor using platinum electrodes. Due to the processing procedure, no thickness dependence of the ferroelectric properties was observed. To confirm the ferroelectric nature of the deposited samples, polarization, capacitance, and piezoelectric displacement measurements were performed. However, no evidence of the orthorhombic phase was found which has been proposed to be the non-centrosymmetric, ferroelectric phase in HfO{sub 2}.

Starschich, S.; Griesche, D.; Schneller, T.; Bttger, U. [Institut fr Werkstoffe der Elektrotechnik 2, RWTH Aachen University, Sommerfeldstrae 24, D-52074 Aachen (Germany); Waser, R. [Institut fr Werkstoffe der Elektrotechnik 2, RWTH Aachen University, Sommerfeldstrae 24, D-52074 Aachen (Germany); Peter Grnberg Institut 7, Forschungszentrum Jlich GmbH, D-52425 Jlich (Germany)

2014-05-19T23:59:59.000Z

69

Unusual Filaments Inside the Umbra  

E-Print Network [OSTI]

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.

Kleint, Lucia

2013-01-01T23:59:59.000Z

70

UNUSUAL FILAMENTS INSIDE THE UMBRA  

SciTech Connect (OSTI)

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.

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

71

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

E-Print Network [OSTI]

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

George, Steven M.

72

Combustion Synthesis of Silicon Carbide 389 Combustion Synthesis of Silicon Carbide  

E-Print Network [OSTI]

by which combustion synthesis can occur: self - propagating high-temperature synthesis (SHS) and volume of the SHS mode (Fig.1a) is that locally initiated, the self-sustained reaction rapidly propagatesCombustion Synthesis of Silicon Carbide 389 X Combustion Synthesis of Silicon Carbide Alexander S

Mukasyan, Alexander

73

On the phase formation of sputtered hafnium oxide and oxynitride films  

SciTech Connect (OSTI)

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

Sarakinos, K.; Music, D.; Mraz, S.; Baben, M. to; Jiang, K.; Nahif, F.; Braun, A.; Zilkens, C.; Schneider, J. M. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 16, D-52056 Aachen (Germany); Konstantinidis, S. [Laboratoire de Chimie Inorganique et Analytique, Universite de Mons, Avenue Copernic 1, 7000 Mons (Belgium); Renaux, F.; Cossement, D. [Materia Nova Research Center, Avenue Copernic 1, 7000 Mons (Belgium); Munnik, F. [Forschungszentrum Dresden Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany)

2010-07-15T23:59:59.000Z

74

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

SciTech Connect (OSTI)

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

Petrosky, J. C. (Air Force Institute of Technology, Wright-Patterson Air Force Base, OH); McClory, J. W. (Air Force Institute of Technology, Wright-Patterson Air Force Base, OH); Bielejec, Edward Salvador; Foster, J. C. (Air Force Institute of Technology, Wright-Patterson Air Force Base, OH)

2010-10-01T23:59:59.000Z

75

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...

76

Temperature Dependent Pspice Model of Silicon Carbide Power MOSFET  

E-Print Network [OSTI]

Temperature Dependent Pspice Model of Silicon Carbide Power MOSFET Yutian Cui1 Madhu Chinthavali2-- This paper provides a behavioral model in Pspice for a silicon carbide (SiC) power MOSFET rated at 1200 V

Tolbert, Leon M.

77

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

SciTech Connect (OSTI)

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.

Cockeram, B.V.

1999-10-01T23:59:59.000Z

78

Deposition method for producing silicon carbide high-temperature semiconductors  

DOE Patents [OSTI]

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.

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

1987-01-01T23:59:59.000Z

79

Inter-filament Attractions Narrow the Length Distribution of Actin Filaments  

E-Print Network [OSTI]

We show that the exponential length distribution that is typical of actin filaments under physiological conditions dramatically narrows in the presence of (i) crosslinker proteins (ii) polyvalent counterions or (iii) depletion mediated attractions. A simple theoretical model shows that in equilibrium, short-range attractions enhance the tendency of filaments to align parallel to each other, eventually leading to an increase in the average filament length and a decrease in the relative width of the distribution of filament lengths.

David Biron; Elisha Moses; Itamar Borukhov; S. A. Safran

2004-06-13T23:59:59.000Z

80

Carbides composite surface layers produced by (PTA)  

SciTech Connect (OSTI)

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.

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

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Joining of porous silicon carbide bodies  

DOE Patents [OSTI]

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

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

1990-05-01T23:59:59.000Z

82

Fabrication of thorium bearing carbide fuels  

DOE Patents [OSTI]

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.

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

83

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

E-Print Network [OSTI]

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 for the overall transformation kinetics of niobium carbide precipitation in austenite that takes into account

Cambridge, University of

84

Master Thesis: Simulation of plastic deformation in cemented carbide inserts  

E-Print Network [OSTI]

Master Thesis: Simulation of plastic deformation in cemented carbide inserts Background Sandvik in cemented carbide, high-speed steel and other hard materials such as diamond, cubic boron nitride in cemented carbide inserts will be performed using the FEM software Ansys and AdvantEdge. The work

Haviland, David

85

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires  

E-Print Network [OSTI]

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires Wensheng Shi Kong, SAR, China Silicon carbide (SiC) nanowires were synthesized at 900°C by the laser ablation and composite nanostructures,4 have been fabricated by this technique. Silicon carbide (SiC) is a wide

Zheng, Yufeng

86

PECVD Silicon Carbide Waveguides for Multichannel G. Pandraud  

E-Print Network [OSTI]

PECVD Silicon Carbide Waveguides for Multichannel Sensors G. Pandraud Kavli Institute of Nano Deposition (PECVD) Silicon Carbide (SiC) waveguides. Thin SiC films have been deposited onto Si substrates with a SiO2 film acting as a cladding layer around the carbide core. In the sensor, the evanescent tale

Technische Universiteit Delft

87

Liquid phase sintering of silicon carbide  

DOE Patents [OSTI]

Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.

Cutler, Raymond A. (Bountiful, UT); Virkar, Anil V. (Salt Lake City, UT); Hurford, Andrew C. (Salt Lake City, UT)

1989-01-01T23:59:59.000Z

88

The WSRT virgo filament survey  

E-Print Network [OSTI]

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.

Attila Popping; Robert Braun

2007-03-27T23:59:59.000Z

89

High Q silicon carbide microdisk resonator  

SciTech Connect (OSTI)

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.

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

90

Prealloyed catalyst for growing silicon carbide whiskers  

DOE Patents [OSTI]

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

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

1988-01-01T23:59:59.000Z

91

PWR cores with silicon carbide cladding  

SciTech Connect (OSTI)

The feasibility of using silicon carbide rather than Zircaloy cladding, to reach higher power levels and higher discharge burnups in PWRs has been evaluated. A preliminary fuel design using fuel rods with the same dimensions as in the Westinghouse Robust Fuel Assembly but with fuel pellets having 10 vol% central void has been adopted to mitigate the higher fuel temperatures that occur due to the lower thermal conductivity of the silicon carbide and to the persistence of the open clad-pellet gap over most of the fuel life. With this modified fuel design, it is possible to achieve 18 month cycles that meet present-day operating constraints on peaking factor, boron concentration, reactivity coefficients and shutdown margin, while allowing batch average discharge burnups up to 80 MWD/kgU and peak rod burnups up to 100 MWD/kgU. Power uprates of 10% and possibly 20% also appear feasible. For non-uprated cores, the silicon carbide-clad fuel has a clear advantage that increases with increasing discharge burnup. Even for comparable discharge burnups, there is a savings in enriched uranium. Control rod configuration modifications may be required to meet the shutdown margin criterion for the 20% up-rate. Silicon carbide's ability to sustain higher burnups than Zircaloy also allows the design of a licensable two year cycle with only 96 fresh assemblies, avoiding the enriched uranium penalty incurred with use of larger batch sizes due to their excessive leakage. (authors)

Dobisesky, J. P.; Carpenter, D.; Pilat, E.; Kazimi, M. S. [Center for Advanced Nuclear Energy Systems, Dept. of Nuclear Science and Engineering, Massachusetts Inst. of Technology, 77 Massachusetts Avenue 24-215, Cambridge, MA 02139-4307 (United States)

2012-07-01T23:59:59.000Z

92

Process for coating tungsten carbide with cobalt metal  

SciTech Connect (OSTI)

A process is described for coating tungsten carbide with cobalt metal, the process comprising: (a) forming an aqueous slurry of tungsten carbide having a particle size of no greater than - 100 mesh, and zinc metal powder; (b) adding ammonia to the slurry with the amount of the ammonia being sufficient so that the slurry is basic after the subsequent addition of cobalt chloride in step c; (c) adding to the resulting ammoniated slurry, a solution of cobalt chloride with agitation, to form a coating of partially reduced cobalt on the tungsten carbide; (d) removing the resulting cobalt coated tungsten carbide from the resulting liquor; and (e) heating the cobalt coated tungsten carbide in a reducing atmosphere to effect the essentially complete reduction of the cobalt and to produce a cobalt metal coating on the tungsten carbide, the coating making up no greater than about 15% of weight of the tungsten carbide.

Ritsko, J.E.; Lee, J.S.

1989-01-31T23:59:59.000Z

93

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

E-Print Network [OSTI]

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

Grossman, Lawrence

94

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

E-Print Network [OSTI]

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

Garfunkel, Eric

95

Processing and properties of extruded tungsten-hafnium and tungsten-steel composites  

SciTech Connect (OSTI)

The purpose of this study was to evaluate the processing behavior and properties of tungsten-hafnium (W-Hf) and W-steel composites produced by hot extrusion of canned powders. The W-Hf composite was consolidated by extrusion of blended powders with preheat temperatures over the temperature range of 1100 to 1400{degrees}C. All extrusions produced fully dense material which exhibits elongation of the tungsten phase within the hafnium matrix. The flow stress, as characterized by the extrusion constant, decreases with increasing temperature up to 1300{degrees}C and increases substantially at 1400{degrees}C as significant quantities of intermetallic phase are formed during preheating. The room-temperature (RT) hardness and compressive yield stress increase modestly with increased extrusion ratio and are not affected by extrusion temperature in the range 1100 to 1300{degrees}C. The microstructures are essentially fully recrystallized at the 1300{degrees}C preheat temperature and partially recrystallized at lower temperatures. Additionally, a mixture of tungsten and steel powder was consolidated to full density by hot extrusion at a 1000{degrees}C preheat temperature and a reduction ratio of 4.2. Increased reduction of the W-steel composite results in increased RT hardness.

Ohriner, E.K.; Sikka, V.K. [Oak Ridge National Lab., TN (United States); Kapoor, D. [Army Armament Research and Development Engineering Center, Dover, NJ (United States)

1995-02-01T23:59:59.000Z

96

Diamond-silicon carbide composite and method  

DOE Patents [OSTI]

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.

Zhao, Yusheng (Los Alamos, NM)

2011-06-14T23:59:59.000Z

97

Sandia National Laboratories: silicon carbide thyristors  

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:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administration the1developmentturbineredox-active perovskiteremovingsensors andsilicon carbide

98

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

DOE Patents [OSTI]

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

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

1986-01-01T23:59:59.000Z

99

Design of duplex low-carbon steels with carbide forming elements  

E-Print Network [OSTI]

Molybdenum X3 a strong carbide forming element MoC). (in the form of alloy carbides. Molybdenum improves grain1) Niobium is a strong carbide forming element (NbC). The

Costello, Peter K.

2012-01-01T23:59:59.000Z

100

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

Broader source: Energy.gov (indexed) [DOE]

Operating at high temperatures and with reduced energy losses, two silicon carbide power electronics (PE) projects were awarded the prestigious R&D 100 Award. This technology was...

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Laser Processing of Refractory Metal - Refractory Carbide Alloys.  

E-Print Network [OSTI]

??The objective of the present study was to laser process a refractory metal refractory carbide alloy based on W-Ti-C ternary system for severe service (more)

Rajput, Deepak

2008-01-01T23:59:59.000Z

102

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...

103

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

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

Nanocrystalline 3C Silicon Carbide to Heavy-Ion Irradiation. Response of Nanocrystalline 3C Silicon Carbide to Heavy-Ion Irradiation. Abstract: Nanostructured materials are...

104

Periodic alignment of Si quantum dots on hafnium oxide coated single wall carbon nanotubes  

SciTech Connect (OSTI)

We demonstrate a bottom up approach for the aligned epitaxial growth of Si quantum dots (QDs) on one-dimensional (1D) hafnium oxide (HfO{sub 2}) ridges created by the growth of HfO{sub 2} thin film on single wall carbon nanotubes. This growth process creates a high strain 1D ridge on the HfO{sub 2} film, which favors the formation of Si seeds over the surrounding flat HfO{sub 2} area. Periodic alignment of Si QDs on the 1D HfO{sub 2} ridge was observed, which can be controlled by varying different growth conditions, such as growth temperature, growth time, and disilane flow rate.

Olmedo, Mario; Martinez-Morales, Alfredo A.; Ozkan, Mihrimah; Liu Jianlin [Department of Electrical Engineering, University of California, Riverside, California 92521 (United States); Liu Gang; Lau, C.N. [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Yengel, Emre; Ozkan, Cengiz S. [Department of Mechanical Engineering, University of California, Riverside, California 92521 (United States)

2009-03-23T23:59:59.000Z

105

Tailoring the index of refraction of nanocrystalline hafnium oxide thin films  

SciTech Connect (OSTI)

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

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

2014-03-10T23:59:59.000Z

106

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

SciTech Connect (OSTI)

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

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

2013-11-04T23:59:59.000Z

107

High-k (k=30) amorphous hafnium oxide films from high rate room temperature deposition  

SciTech Connect (OSTI)

Amorphous hafnium oxide (HfO{sub x}) is deposited by sputtering while achieving a very high k{approx}30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfO{sub x} (cubic k{approx}30). The films also possess a high electrical resistivity of 10{sup 14} {Omega} cm, a breakdown strength of 3 MV cm{sup -1}, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate ({approx}25 nm min{sup -1}) makes these high-k amorphous HfO{sub x} films highly advantageous for plastic electronics and high throughput manufacturing.

Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Milne, William I.; Flewitt, Andrew J. [Department of Engineering, Electrical Engineering Division, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J. [Plasma Quest Ltd., Unit 1B, Rose Estate, Osborn Way, Hook, Hampshire RG27 9UT (United Kingdom)

2011-06-20T23:59:59.000Z

108

Preparation and electrocatalytic activity of tungsten carbide and titania nanocomposite  

SciTech Connect (OSTI)

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.

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

109

Molybdenum disilicide composites reinforced with zirconia and silicon carbide  

DOE Patents [OSTI]

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.

Petrovic, J.J.

1995-01-17T23:59:59.000Z

110

Molybdenum disilicide composites reinforced with zirconia and silicon carbide  

DOE Patents [OSTI]

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

Petrovic, John J. (Los Alamos, NM)

1995-01-01T23:59:59.000Z

111

Method for producing silicon nitride/silicon carbide composite  

DOE Patents [OSTI]

Silicon carbide/silicon nitride composites are prepared by carbothermal reduction of crystalline silica powder, carbon powder and optionally crsytalline silicon nitride powder. The crystalline silicon carbide portion of the composite has a mean number diameter less than about 700 nanometers and contains nitrogen.

Dunmead, Stephen D. (Midland, MI); Weimer, Alan W. (Midland, MI); Carroll, Daniel F. (Midland, MI); Eisman, Glenn A. (Midland, MI); Cochran, Gene A. (Midland, MI); Susnitzky, David W. (Midland, MI); Beaman, Donald R. (Midland, MI); Nilsen, Kevin J. (Midland, MI)

1996-07-23T23:59:59.000Z

112

Nanostructured Molybdenum Carbide: Sonochemical Synthesis and Catalytic Properties  

E-Print Network [OSTI]

to be a useful technique to generate nanophase transition metals.7,8 Recently, molybdenum and tungsten carbides of metal salts.5,6 Sonochemical decomposition of transition metal carbonyl compounds has also been provenNanostructured Molybdenum Carbide: Sonochemical Synthesis and Catalytic Properties Taeghwan Hyeon

Suslick, Kenneth S.

113

Filament velocity scaling laws for warm ions  

SciTech Connect (OSTI)

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

Manz, P. [Physik-Department E28, Technische Universitt Mnchen, James-Franck-Str. 1, 85748 Garching (Germany) [Physik-Department E28, Technische Universitt Mnchen, James-Franck-Str. 1, 85748 Garching (Germany); Max-Planck-Institut fr Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Carralero, D.; Birkenmeier, G.; Mller, H. W.; Scott, B. D. [Max-Planck-Institut fr Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany)] [Max-Planck-Institut fr Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Mller, 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 fr Grenzflchenverfahrenstechnik und Plasmatechnologie, Universitt Stuttgart, 70569 Stuttgart (Germany)] [Insitut fr Grenzflchenverfahrenstechnik und Plasmatechnologie, Universitt Stuttgart, 70569 Stuttgart (Germany); Stroth, U. [Max-Planck-Institut fr Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany) [Max-Planck-Institut fr Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Physik-Department E28, Technische Universitt Mnchen, James-Franck-Str. 1, 85748 Garching (Germany)

2013-10-15T23:59:59.000Z

114

Reconnection of vortex filaments and Kolmogorov spectrum  

E-Print Network [OSTI]

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...

Nemirovskii, Sergey K

2014-01-01T23:59:59.000Z

115

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

SciTech Connect (OSTI)

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,

Quets, J.; Alford, J.R.

1999-07-01T23:59:59.000Z

116

Infrared Radiation Filament And Metnod Of Manufacture  

DOE Patents [OSTI]

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

Johnson, Edward A. (Bedford, MA)

1998-11-17T23:59:59.000Z

117

Terahertz radiation from a laser plasma filament  

SciTech Connect (OSTI)

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.

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

118

High temperature intermetallic binders for HVOF carbides  

SciTech Connect (OSTI)

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.

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

119

Dispersion aspects of silicon carbide gelcasting  

SciTech Connect (OSTI)

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.

Bleier, A.

1991-09-01T23:59:59.000Z

120

High-rate chemical vapor deposition of nanocrystalline silicon carbide films by radio frequency thermal plasma  

E-Print Network [OSTI]

High-rate chemical vapor deposition of nanocrystalline silicon carbide films by radio frequency Semiconductor, Eden Prairie, MN, USA Received 10 July 2002; accepted 14 July 2002 Abstract Silicon carbide films; Nanomaterials; Silicon carbide; Thermal plasmas; Thin films; Si tetrachlorine precursor Silicon carbide has

Zachariah, Michael R.

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

J. Am. Cerum. SOC., 72 [5] 775-80 (1989) Processingof Boron Carbide-Aluminum Composites  

E-Print Network [OSTI]

J. Am. Cerum. SOC., 72 [5] 775-80 (1989) journal Processingof Boron Carbide-Aluminum Composites, Universityof California, Livermore, California 94550 The processing problems associated with boron carbide carbide, aluminum, processing, cermets.] I. Introduction ORON CARBIDE (B4C)+is a very hard (9.5+ in Mohs

Aksay, Ilhan A.

122

Rectification of evanescent heat transfer between dielectric-coated and uncoated silicon carbide plates  

E-Print Network [OSTI]

Rectification of evanescent heat transfer between dielectric-coated and uncoated silicon carbide://jap.aip.org/authors #12;Rectification of evanescent heat transfer between dielectric-coated and uncoated silicon carbide-infinite bodies of the dielectric-coated silicon carbide and uncoated silicon carbide. The permittivity

Fan, Shanhui

123

Gas phase spectroscopy of alkali carbides: The pure rotational spectrum of KC ,,X 4  

E-Print Network [OSTI]

observation of potassium carbide, and of any alkali metal carbide species. The molecule was produced under d, and possible ways to better activate C­C and C­H bonds.1 Investigating metal carbide species also can lead- faces. Finally, it has recently been suggested that adding metal carbides to H2 may provide high energy

Ziurys, Lucy M.

124

Computational Studies of Physical Properties of Boron Carbide  

SciTech Connect (OSTI)

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.

Lizhi Ouyang

2011-09-30T23:59:59.000Z

125

Light sources based on semiconductor current filaments  

DOE Patents [OSTI]

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.

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

126

Route to transition metal carbide nanoparticles through cyanamide and metal oxides  

SciTech Connect (OSTI)

We have designed an efficient route to the synthesis of transition metal carbide nanoparticles starting from an organic reagent cyanamide and transition metal oxides. Four technologically important metal carbide nanoparticles such as tungsten carbide, niobium carbide, tantalum carbide and vanadium carbide were synthesized successfully at moderate temperatures. It is found that cyanamide is an efficient carburization reagent and that the metal oxides are completely transmitted into the corresponding carbide nanoparticles. A possible mechanism is proposed to explain the results of the reaction between cyanamide and the metal oxides.

Li, P.G. [Department of Physics, Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Xiasha College Park, Hangzhou 310018 (China)], E-mail: peigangiphy@yahoo.com.cn; Lei, M.; Tang, W.H. [Department of Physics, Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Xiasha College Park, Hangzhou 310018 (China)

2008-12-01T23:59:59.000Z

127

Separation of Nuclear Fuel Surrogates from Silicon Carbide Inert Matrix  

SciTech Connect (OSTI)

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

Dr. Ronald Baney

2008-12-15T23:59:59.000Z

128

Vacancy Hardening and Softening in Transition Metal Carbides and Nitrides  

SciTech Connect (OSTI)

The effects of vacancies on mechanical properties of the transition metal carbides and nitrides are studied using the ab initio pseudopotential approach. Calculated shear elastic stiffness and electronic structures show that the vacancy produces entirely different effects on the mechanical strength of groups IVb nitrides and Vb carbides. It is found that the occupation of shear-unstable metallic dd bonding states changes essentially in an opposite way for the carbides and nitrides in the presence of vacancies, resulting in different responses to shear stress. Our study provides an atomistic understanding of the anomaly in hardness for these substoichiometric materials.

Jhi, Seung-Hoon; Louie, Steven G.; Cohen, Marvin L.; Ihm, Jisoon

2001-04-09T23:59:59.000Z

129

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

DOE Patents [OSTI]

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.

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

130

Comparison Measurements of Silicon Carbide Temperature Monitors  

SciTech Connect (OSTI)

As part of the efforts initiated through the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) program to make Silicon Carbide (SiC) temperature monitors available, a capability was developed at the Idaho National Laboratory (INL) to complete post-irradiation evaluations of these monitors. INL selected the resistance measurement approach for detecting peak irradiation temperature from SiC temperature monitors. To demonstrate this new capability, comparison measurements were completed by INL and Oak Ridge National Laboratory (ORNL) on identical samples subjected to identical irradiation conditions. Results reported in this paper indicate that the resistance measurement approach can yield similar peak irradiation temperatures if appropriate equipment is used and appropriate procedures are followed.

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

2010-06-01T23:59:59.000Z

131

Asymmetric twins in rhombohedral boron carbide  

SciTech Connect (OSTI)

Superhard materials consisting of light elements have recently received considerable attention because of their ultrahigh specific strength for a wide range of applications as structural and functional materials. However, the failure mechanisms of these materials subjected to high stresses and dynamic loading remain to be poorly known. We report asymmetric twins in a complex compound, boron carbide (B{sub 4}C), characterized by spherical-aberration-corrected transmission electron microscopy. The atomic structure of boron-rich icosahedra at rhombohedral vertices and cross-linked carbon-rich atomic chains can be clearly visualized, which reveals unusual asymmetric twins with detectable strains along the twin interfaces. This study offers atomic insights into the structure of twins in a complex material and has important implications in understanding the planar defect-related failure of superhard materials under high stresses and shock loading.

Fujita, Takeshi, E-mail: tfujita@wpi-aimr.tohoku.ac.jp; Guan, Pengfei; Madhav Reddy, K.; Hirata, Akihiko; Guo, Junjie [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Chen, Mingwei, E-mail: mwchen@wpi-aimr.tohoku.ac.jp [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

2014-01-13T23:59:59.000Z

132

Light Ions Response of Silicon Carbide Detectors  

E-Print Network [OSTI]

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.

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

2006-12-14T23:59:59.000Z

133

Silicon carbide mirrors for high power applications  

SciTech Connect (OSTI)

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.

Takacs, P.Z.

1981-11-01T23:59:59.000Z

134

Reactor physics assessment of thick silicon carbide clad PWR fuels  

E-Print Network [OSTI]

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 ...

Bloore, David A. (David Allan)

2013-01-01T23:59:59.000Z

135

Safety of light water reactor fuel with silicon carbide cladding  

E-Print Network [OSTI]

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 ...

Lee, Youho

2013-01-01T23:59:59.000Z

136

Tungsten carbide-cobalt by Three Dimensional Printing  

E-Print Network [OSTI]

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% ...

Kelley, Andrew, III

1998-01-01T23:59:59.000Z

137

In situ electrochemical dilatometry of carbide-derived carbons  

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

electrochemical dilatometry of carbide-derived carbons M.M. Hantel a , V. Presser b , R. Ktz a, , Y. Gogotsi b a Electrochemistry Laboratory, Paul Scherrer Institut, CH-5232...

138

Rapid WolffKishner reductions in a silicon carbide microreactor  

E-Print Network [OSTI]

WolffKishner 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 ...

Newman, Stephen G.

2014-01-01T23:59:59.000Z

139

Conductive two-dimensional titanium carbide clay with high...  

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

MAX phases, which comprise a .70-member family of layered, hexagonal early-transition-metal carbides and nitrides 13 . To date, all MXenes have been produced by etching MAX...

140

Novel synthesis of hafnium oxide nanoparticles by precipitation method and its characterization  

SciTech Connect (OSTI)

Highlights: ? HfO{sub 2} NPs were prepared by precipitation method. ? XRD and Raman analysis revealed the presence of monoclinic phase. ? The average particle size of HfO{sub 2} NPs is 20 nm. ? The method is a simple, low cost and eco-friendly approach. -- Abstract: Hafnium oxide nanoparticles (HfO{sub 2} NPs) have been successfully synthesized by means of a novel precipitation method and were characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), UVvisible, Fourier transform infrared (FTIR) and laser Raman spectroscopy. The XRD and Raman analysis revealed the presence of pure monoclinic HfO{sub 2} NPs. FESEM image showed that the HfO{sub 2} NPs were of spherical shape with an average particle size of about 20 nm. The optical band gap of the HfO{sub 2} NPs was found to be 6.12 eV. Advantages of this method were simple and low cost of synthesis of HfO{sub 2} NPs includes the small and narrow particle size distribution.

Ramadoss, Ananthakumar; Krishnamoorthy, Karthikeyan [Nanomaterials and System Lab, Department of Mechanical System Engineering, Jeju National University, Jeju 690-756 (Korea, Republic of)] [Nanomaterials and System Lab, Department of Mechanical System Engineering, Jeju National University, Jeju 690-756 (Korea, Republic of); Kim, Sang Jae, E-mail: kimsangj@jejunu.ac.kr [Nanomaterials and System Lab, Department of Mechanical System Engineering, Jeju National University, Jeju 690-756 (Korea, Republic of); Department of Mechatronics Engineering, Jeju National University, Jeju 690-756 (Korea, Republic of)

2012-09-15T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

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

SciTech Connect (OSTI)

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.

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

142

Hard Magnets I: 2-17, Nitrides, Carbides Frederick Pinkerton, Chairman Structure and magnetic properties of rare-earth iron nitrides, carbides  

E-Print Network [OSTI]

Hard Magnets I: 2-17, Nitrides, Carbides Frederick Pinkerton, Chairman Structure and magnetic properties of rare-earth iron nitrides, carbides and carbonitrides (invited) Z. Altounian, X. Chen, L. X develops for R=Sm upon nitriding/carbiding with an anisotropy field that is almost double the value for Nd

Ryan, Dominic

143

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

SciTech Connect (OSTI)

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.

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

2010-06-01T23:59:59.000Z

144

Collective dynamics of active filament complexes  

E-Print Network [OSTI]

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...

Nogucci, Hironobu

2015-01-01T23:59:59.000Z

145

Acceleration and vortex filaments in turbulence  

E-Print Network [OSTI]

We report recent results from a high resolution numerical study of fluid particles transported by a fully developed turbulent flow. Single particle trajectories were followed for a time range spanning more than three decades, from less than a tenth of the Kolmogorov time-scale up to one large-eddy turnover time. We present some results concerning acceleration statistics and the statistics of trapping by vortex filaments.

F. Toschi; L. Biferale; G. Boffetta; A. Celani; B. J. Devenish; A. Lanotte

2005-01-23T23:59:59.000Z

146

Reconnection of vortex filaments and Kolmogorov spectrum  

E-Print Network [OSTI]

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.

Sergey K. Nemirovskii

2014-04-19T23:59:59.000Z

147

Hot filament CVD of boron nitride films  

DOE Patents [OSTI]

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.

Rye, Robert R. (Albuquerque, NM)

1992-01-01T23:59:59.000Z

148

Understanding the Irradiation Behavior of Zirconium Carbide  

SciTech Connect (OSTI)

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.

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

2013-10-11T23:59:59.000Z

149

Nanostructured carbide catalysts for the hydrogen economy  

SciTech Connect (OSTI)

The above quote, taken from the executive summary of the Report from the US DOE Basic Energy Sciences Workshop held August 68, 2007,[1] places in context the research carried out at the University of California, Santa Barbara, which is reported in this document. The enormous impact of heterogeneous catalysis is exemplified by the Haber process for the synthesis of ammonia, which consumes a few % of the worlds energy supply and natural gas, and feeds as many as a third of the worlds population. While there have been numerous advances in understanding the process,[2] culminating in the awarding of the Nobel Prize to Gerhard Ertl in 2007, it is interesting to note that the catalysts themselves have changed very little since they were discovered heuristically in the the early part of the 20th century. The thesis of this report is that modern materials chemistry, with all the empirical knowledge of solid state chemistry, combined with cutting edge structural tools, can help develop and better heterogeneous catalysis. The first part of this report describes research in the area of early transition metal carbides (notably of Mo and W), potentially useful catalysts for water gas shift (WGS) and related reactions of use to the hydrogen economy. Although these carbides have been known to be catalytically useful since the 1970s,[3] further use of these relatively inexpensive materials have been plagued by issues of low surface areas and ill-defined, and often unreactive surfaces, in conjunction with deactivation. We have employed for the first time, a combination of constant-wavelength and time-of-flight neutron scattering, including a total scattering analysis of the latter data, to better understand what happens in these materials, in a manner that for the first time, reveals surface graphitic carbon in these materials in a quantitative manner. Problems of preparation, surface stability, and irreversible reactivity have become manifest in this class of materials that discourage us from pursuing these materials further.

Ram Seshadri, Susannah Scott, Juergen Eckert

2008-07-21T23:59:59.000Z

150

Microwave processing of ceramic oxide filaments. Annual report, FY1997  

SciTech Connect (OSTI)

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).

Vogt, G.J.

1998-12-31T23:59:59.000Z

151

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

SciTech Connect (OSTI)

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.}

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

152

Elasticity, strength, and toughness of single crystal silicon carbide, ultrananocrystalline diamond, and hydrogen-free tetrahedral amorphous  

E-Print Network [OSTI]

Elasticity, strength, and toughness of single crystal silicon carbide, ultrananocrystalline diamond carbide 3C-SiC , ultrananocrystalline diamond, and hydrogen-free tetrahedral amorphous carbon

Espinosa, Horacio D.

153

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]

-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

Rubloff, Gary W.

154

Phase Behavior of Pseudobinary Precious Metal?Carbide Systems  

SciTech Connect (OSTI)

Transition metal carbides exhibit a variety of interesting material properties, including electrochemical stability. When combined with precious metals, Ta and W carbides have shown promise as fuel cell electrode materials; yet, the phase behavior of these precious metal?carbide systems is largely unexplored. We investigated P-M-C phase behavior with P = Pt, Pd, and Ru and M = Ta and W using composition spread thin films. We attained limited control of the deposited carbide phase through variation of the sputter atmosphere and demonstrated decreased corrosion of W?C materials with increasing C content. A high-throughput X-ray diffraction and X-ray fluorescence experiment was employed for thin film characterization, which revealed solubility of Pt, Pd, and Ru in cubic WC. Density functional calculations of the lattice parameter dependence on carbon concentration enabled the determination of carbon concentration from the X-ray data as a function of transition metal stoichiometry. Our measurement of variations in the C stoichiometry and evolution of thin film texture with transition metal composition yielded surprising results. We detail how the combination of the composition spread technique, the high-throughput thin film characterization, and the density functional modeling of ternary carbide alloys provided a deep understanding of the chemical systems.

Gregoire, John M.; Tague, Michele E.; Smith, Eva H.; Dale, Darren; DiSalvo, Francis J.; Abrua, Hctor D.; Hennig, Richard G.; van Dover, R. Bruce

2010-01-01T23:59:59.000Z

155

Plasma planar filament instability and Alfven waves  

E-Print Network [OSTI]

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)\

Garcia de Andrade

2007-03-05T23:59:59.000Z

156

Abundances of presolar silicon carbide grains in primitive meteorites determined by NanoSIMS  

E-Print Network [OSTI]

Abundances of presolar silicon carbide grains in primitive meteorites determined by NanoSIMS Jemma carbide (SiC) grains estimated from their noble gas components show significant variations in even

Nittler, Larry R.

157

Ordering of carbon atoms in boron carbide structure  

SciTech Connect (OSTI)

Boron carbide crystals have been obtained in the entire compositional range according to the phase diagram by self-propagating high-temperature synthesis (SHS). Based on the results of X-ray diffraction investigations, the samples were characterized by the unit-cell metric and reflection half-width in the entire range of carbon concentrations. A significant spread in the boron carbide unit-cell parameters for the same carbon content is found in the data in the literature; this spread contradicts the structural concepts for covalent compounds. The SHS samples have not revealed any significant spread in the unit-cell parameters. Structural analysis suggests that the spread of parameters in the literary data is related to the unique process of ordering of carbon atoms in the boron carbide structure.

Ponomarev, V. I., E-mail: i2212@yandex.ru; Kovalev, I. D.; Konovalikhin, S. V.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

2013-05-15T23:59:59.000Z

158

Pulsed energy synthesis and doping of silicon carbide  

DOE Patents [OSTI]

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.

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

1995-06-20T23:59:59.000Z

159

Pulsed energy synthesis and doping of silicon carbide  

DOE Patents [OSTI]

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.

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

160

Structure-Property Relationship in Metal Carbides and Bimetallic Alloys  

SciTech Connect (OSTI)

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.

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

2014-03-04T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

The growth mechanism of grain boundary carbide in Alloy 690  

SciTech Connect (OSTI)

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

Li, Hui, E-mail: huili@shu.edu.cn [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Institute of Materials, Shanghai University, Shanghai 200072 (China); Xia, Shuang; Zhou, Bangxin [Institute of Materials, Shanghai University, Shanghai 200072 (China); Peng, Jianchao [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China)

2013-07-15T23:59:59.000Z

162

Tungsten carbide synthesized by low-temperature combustion as gas diffusion electrode catalyst  

E-Print Network [OSTI]

Tungsten carbide synthesized by low-temperature combustion as gas diffusion electrode catalyst Ping June 2014 Keywords: Low-temperature combustion syn- thesis Tungsten carbide Electrocatalyst Gas diffusion electrode a b s t r a c t Tungsten carbide powder, which is used as the catalyst for a gas

Volinsky, Alex A.

163

A kinetic model of diamond nucleation and silicon carbide interlayer formation during chemical vapor deposition  

E-Print Network [OSTI]

A kinetic model of diamond nucleation and silicon carbide interlayer formation during chemical February 2005 Available online 7 April 2005 Abstract The presence of thin silicon carbide intermediate of carbon atoms into the silicon carbide layer and the morphology and orientation of the diamond film

Dandy, David

164

Journal of Statistical Physics A Free Energy Model of Boron Carbide  

E-Print Network [OSTI]

Journal of Statistical Physics A Free Energy Model of Boron Carbide --Manuscript Draft-- Manuscript Number: Full Title: A Free Energy Model of Boron Carbide Article Type: SI: Dedicated to M.E. Fisher, J.K. Percus and B. Widom Keywords: boron carbide; third law; first principles; thermodynamics Corresponding

Widom, Michael

165

-carbide in Alloy Steels: First-principles Jae Hoon Jang a  

E-Print Network [OSTI]

-carbide in Alloy Steels: First-principles Assessment Jae Hoon Jang a In Gee Kim a H. K. D. H that the silicon can enhance the formation of ­carbide; the mechanism of this effect is not understood words: Steels, -carbide, cementite, silicon, tempering There are two long­established reasons for adding

Cambridge, University of

166

New Silicon Carbide Schottky-gate Bipolar Mode Field Effect Transistor (SiC SBMFET)  

E-Print Network [OSTI]

New Silicon Carbide Schottky-gate Bipolar Mode Field Effect Transistor (SiC SBMFET) without PN. In this paper, we propose a novel Schottky-gate BMFET (SBMFET) using P- type 4H Silicon-Carbide 13,41, a wide, Silicon Carbide, Field effect transistor, Simulation. I. INTRODUCTION TH E BMFET operates in bipolar mode

Kumar, M. Jagadesh

167

Carbide-Derived Carbons for Adsorptive Removal of VOCs from Air Streams  

E-Print Network [OSTI]

Carbide-Derived Carbons for Adsorptive Removal of VOCs from Air Streams References 1. USEPA Literature Results Carbide-Derived Carbons Motivation Future Research · The effect of pore size and pore size decreasing removal cost is an advancement for the industry and the environment. Carbide-derived carbons (CDCs

Das, Suman

168

Shear-band structure in ballistically tested carbide-free bainitic steels  

E-Print Network [OSTI]

Shear-band structure in ballistically tested carbide-free bainitic steels L. C. D. Fieldinga , H. K recently been commercialised, with the steel structure consisting of carbide-free, nanostructured bainitic of the carbide-free mixtures of bainitic ferrite and retained austenite. It is with this in mind that bainitic

Cambridge, University of

169

In vitro cellular responses to silicon carbide nanoparticles: impact of physico-chemical  

E-Print Network [OSTI]

1 In vitro cellular responses to silicon carbide nanoparticles: impact of physico-chemical features of Nanoparticle Research 14, 10 (2012) 1143" DOI : 10.1007/s11051-012-1143-7 #12;2 Abstract Silicon carbide, and of the oxidation state of the surface on cellular H2O2 production. Keywords silicon carbide nanoparticles, laser

Paris-Sud XI, Université de

170

Structural changes induced by heavy ion irradiation in titanium silicon carbide J.C. Nappa,  

E-Print Network [OSTI]

Structural changes induced by heavy ion irradiation in titanium silicon carbide Authors J.C. Nappéa, UMR 8609, Bât. 108, 91405 Orsay, France ABSTRACT Carbide-type ceramics, which have remarkable at high temperature. The MAX phases, and more particularly titanium silicon carbide, are distinguished

Paris-Sud XI, Université de

171

Highpressure behavior of iron carbide (Fe7C3) at inner core conditions  

E-Print Network [OSTI]

Highpressure behavior of iron carbide (Fe7C3) at inner core conditions Mainak Mookherjee,1 Yoichi at high pressures have demonstrated that Fe7C3 iron carbide is a likely candidate for the Earth's inner behavior of iron carbide (Fe7C3) at inner core conditions, J. Geophys. Res., 116, B04201, doi:10

Steinle-Neumann, Gerd

172

Nano Res. 2012, 5(12): 896902896 Fabrication of Patterned Boron Carbide Nanowires and Their  

E-Print Network [OSTI]

Nano Res. 2012, 5(12): 896­902896 Fabrication of Patterned Boron Carbide Nanowires Large-area patterned boron carbide nanowires (B4C NWs) have been synthesized using chemical vapor for flexible cold cathode materials. KEYWORDS Boron carbide nanowires, patterned, field emission properties

Gao, Hongjun

173

Catalyst-Free Synthesis and Characterization of Metastable Boron Carbide Nanowires  

E-Print Network [OSTI]

Catalyst-Free Synthesis and Characterization of Metastable Boron Carbide Nanowires By Aruna Velamakanni, K. J. Ganesh, Yanwu Zhu, Paulo J. Ferreira, and Rodney S. Ruoff* 1. Introduction Boron carbide] Boroncarbidealsofindsapplicationintheaerospace industry as a rocket propellant.[4,5] Bulk boron carbide has a low fracture toughness which makes

174

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

E-Print Network [OSTI]

Towards new binary compounds: Synthesis of amorphous phosphorus carbide by pulsed laser deposition Available online 28 November 2012 Keywords: Phosphorus carbide Pulsed laser deposition X-ray photoelectron possible crystal structures of the as yet unknown phosphorus carbide as a function of composition

Bristol, University of

175

Modeling the interface area aspect ratio of carbide grains in WCCo composites  

E-Print Network [OSTI]

Modeling the interface area aspect ratio of carbide grains in WC­Co composites Xiaokun Yuan a Keywords: Cemented carbide Electron backscattered diffraction Interface area aspect ratio Five parameter analysis The average interface area aspect ratios of carbide grains in WC­Co composites are measured from

Rohrer, Gregory S.

176

Heavy Element Abundances in Presolar Silicon Carbide Grains from Low-Metallicity AGB Stars  

E-Print Network [OSTI]

Heavy Element Abundances in Presolar Silicon Carbide Grains from Low-Metallicity AGB Stars Peter explosions. Silicon carbide is the best studied presolar mineral. Based on its isotopic compositions the identified presolar minerals are diamond, silicon carbide (SiC), graphite, silicon nitride (Si3N4), corundum

177

Comments on "Effect of carbide distribution on the fracture toughness in the transition  

E-Print Network [OSTI]

Comments on "Effect of carbide distribution on the fracture toughness in the transition temperature´eriaux, UMR CNRS 7633 BP 87, 91003 Evry Cedex, France Abstract Critical cleavage stress values and carbide for the behavior of SA 508 steel. A new model based on the weakest link concept with the determined carbide size

Paris-Sud XI, Université de

178

DESIGN, MODELING, TESTING, AND SPICE PARAMETER EXTRACTION OF DIMOS TRANSISTOR IN 4H-SILICON CARBIDE  

E-Print Network [OSTI]

DESIGN, MODELING, TESTING, AND SPICE PARAMETER EXTRACTION OF DIMOS TRANSISTOR IN 4H-SILICON CARBIDE (DIMOS) transistor structure in 4H-Silicon Carbide (SiC) is presented. Simulation for transport Silicon carbide (SiC), a wide bandgap material, shows a tremendous potential for high temperature

Tolbert, Leon M.

179

Boron Carbide and Silicon Oxide Hetero-nanonecklaces via Temperature Modulation  

E-Print Network [OSTI]

Boron Carbide and Silicon Oxide Hetero-nanonecklaces via Temperature Modulation Jifa Tian, Xingjun ReceiVed April 23, 2008 ABSTRACT: Boron carbide and silicon oxide (BCSiO) hetero-nanonecklaces have been-500 nm silicon oxide nanoballs onto 20-30 nm boron carbide nanowires. Synthetic analysis shows that a two

Gao, Hongjun

180

Silicon Carbide Power Device Characterization for HEVs Burak Ozpineci1,3  

E-Print Network [OSTI]

Silicon Carbide Power Device Characterization for HEVs Burak Ozpineci1,3 burak@ieee.org Leon M: The emergence of silicon carbide- (SiC-) based power semiconductor switches, with their superior features material. Another material, silicon carbide (SiC), with superior properties compared with Si, is a good

Tolbert, Leon M.

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

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

E-Print Network [OSTI]

Microstructural changes induced by low energy heavy ion irradiation in titanium silicon carbide, and it was validated on irradiated silicon carbide. The swelling of Ti3SiC2 was estimated to 2.2 ±0 to these working conditions, non-oxide refractory ceramics are required as fuel cladding. Thus, carbides turn out

Boyer, Edmond

182

Epitaxy of Nanocrystalline Silicon Carbide on Si(111) at Room Temperature  

E-Print Network [OSTI]

Epitaxy of Nanocrystalline Silicon Carbide on Si(111) at Room Temperature Roberto Verucchi carbide (SiC) has unique chemical, physical, and mechanical properties. A factor strongly limiting Si or plastics that cannot withstand high temperatures. Silicon carbide (SiC) has unique properties that make

Alfè, Dario

183

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 lossless snubber to a design with a Silicon Carbide (SiC) diode without snubber. The theoretical of the Silicon Carbide (SiC) Schottky diodes (Infineon) changes the pictures completely. As will be detailed

184

7 Physical Model of Carbide Precipitation 2 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  

E-Print Network [OSTI]

Contents 7 Physical Model of Carbide Precipitation 2 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1 #12;Chapter 7 Physical Model of Carbide Precipitation 7.1 Introduction If the austempering process is held for prolonged periods of time precipitation of carbides from retained austenite occurs

Cambridge, University of

185

Characterization and Modeling of Silicon Carbide Power Devices and Paralleling Operation  

E-Print Network [OSTI]

Characterization and Modeling of Silicon Carbide Power Devices and Paralleling Operation Yutian Cui silicon carbide (SiC) power devices. The devices have been tested for both static and dynamic like silicon carbide (SiC) and gallium nitride (GaN) are becoming more attractive. SiC power devices

Tolbert, Leon M.

186

Effects of Silicon Carbide (SiC) Power Devices on HEV PWM Inverter Losses*  

E-Print Network [OSTI]

Effects of Silicon Carbide (SiC) Power Devices on HEV PWM Inverter Losses* Burak Ozpineci1,3 burak and Education Oak Ridge, TN 37831-0117 Abstract-The emergence of silicon carbide- (SiC-) based power, silicon carbide (SiC) with its superior properties compared with Si, is a good candidate to be used

Tolbert, Leon M.

187

DOI: 10.1002/chem.200901982 Template-Synthesized Porous Silicon Carbide as an Effective Host  

E-Print Network [OSTI]

DOI: 10.1002/chem.200901982 Template-Synthesized Porous Silicon Carbide as an Effective Host, especially those that can work more du- rably under harsh conditions. Silicon carbide (SiC) is a promising has been de- veloped for the fabrication of porous silicon carbide (SiC) by means of sin- tering

Bao, Xinhe

188

Integrated packaging allows for improvement in switching characteristics of silicon carbide devices  

E-Print Network [OSTI]

Integrated packaging allows for improvement in switching characteristics of silicon carbide devices will be available after the conference. Abstract Silicon Carbide devices can achieve very high switching speed-mode filtering). The consequences on the switching speed are discussed. 1. Introduction Silicon carbide (Si

Paris-Sud XI, Université de

189

SYSTEM IMPACT OF SILICON CARBIDE POWER DEVICES BURAK OZPINECI1,3  

E-Print Network [OSTI]

SYSTEM IMPACT OF SILICON CARBIDE POWER DEVICES BURAK OZPINECI1,3 , LEON M. TOLBERT1,2 , SYED K carbide- (SiC-) based power semiconductor switches, with their superior features compared with silicon, silicon carbide (SiC), with superior properties compared with Si, is a good candidate to be used

Tolbert, Leon M.

190

Accepted Manuscript Abundances of presolar silicon carbide grains in primitive meteorites deter-  

E-Print Network [OSTI]

Accepted Manuscript Abundances of presolar silicon carbide grains in primitive meteorites deter.R., Alexander, C.M., Orthous-Daunay, o-R., Franchi, I.A., Hoppe, P., Abundances of presolar silicon carbide of presolar silicon carbide grains in primitive meteorites determined by NanoSIMS Jemma Davidsona,1,* , Henner

Nittler, Larry R.

191

Thermodynamic stability of oxide, nitride, and carbide coating materials in liquid Sn25Li  

E-Print Network [OSTI]

Thermodynamic stability of oxide, nitride, and carbide coating materials in liquid Sn­25Li S of various oxides, carbides, and nitrides in Sn­Li is estimated as a function of lithium composition K most of the studied nitrides, carbides, and some oxides were found to be stable (DrG > 0). However

Ghoniem, Nasr M.

192

Carbon 41 (2003) 10961099 Effect of boron carbide particle addition on the  

E-Print Network [OSTI]

Carbon 41 (2003) 1096­1099 Effect of boron carbide particle addition on the thermomechanical behavior of carbon matrix silicon carbide particle composites a ,1 a , b b * ´Jorge Sanchez-Coronado , D, silicon carbide is used in combination with held at the maximum temperature for 1 h in a nitrogen carbon

Chung, Deborah D.L.

193

Short-and intermediate-range structural correlations in amorphous silicon carbide: A molecular dynamics study  

E-Print Network [OSTI]

Short- and intermediate-range structural correlations in amorphous silicon carbide: A molecular-range structural correlations in amorphous silicon carbide a-SiC are studied in terms of partial pair distributions.43.Dq, 61.43.Bn, 61.66.Dk, 81.05.Gc I. INTRODUCTION Silicon carbide SiC has been receiving increasing

Southern California, University of

194

Materials Science Forum, Vols. 426432, 2003, pp. 3542. Advances in the Kinetic Theory of Carbide Precipitation  

E-Print Network [OSTI]

Materials Science Forum, Vols. 426­432, 2003, pp. 35­42. Advances in the Kinetic Theory of Carbide Pembroke Street, Cambridge CB2 3QZ, U.K., www.msm.cam.ac.uk/phase­trans Keywords : Carbides, kinetics and reversion of carbides can determine the quality of steels. This paper is a review of efforts towards better

Cambridge, University of

195

Adhesion, stability, and bonding at metal/metal-carbide interfaces: Al/WC Donald J. Siegel  

E-Print Network [OSTI]

of adhesion between metals and transition metal carbides/nitrides based on Density Functional Theory(DFT)[14Adhesion, stability, and bonding at metal/metal-carbide interfaces: Al/WC Donald J. Siegel the nature of metal/carbide bonding. Based on the surface and interfacial free energies, we find that both

Adams, James B

196

Trends in elasticity and electronic structure of transition-metal nitrides and carbides from first principles  

E-Print Network [OSTI]

Trends in elasticity and electronic structure of transition-metal nitrides and carbides from first 2005 The elastic properties of selected transition-metal TM nitrides and carbides in B1 structure the transition-metal nitrides and carbides remain unclear and a challenge for engineering hard materials

Wu, Zhigang

197

Optical spectroscopy of tungsten carbide ,,WC... Shane M. Sickafoose, Adam W. Smith, and Michael D. Morse  

E-Print Network [OSTI]

transition-metal carbide, WC. A low-resolution scan revealed a five-member vibrational progression beginning to the isovalent molecule MoC and other transition-metal carbides. © 2002 American Institute of Physics. DOI: 10 this end, we have embarked on a study of the diatomic transition-metal carbides, and have al- ready

Morse, Michael D.

198

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

E-Print Network [OSTI]

with transition metals and yield inter- esting transition metal carbides.8­11 In a recent study12 it was reportedSynthesis, structure, and superconducting properties of tantalum carbide nanorods and nanoparticles 1997) Tantalum carbide nanorods and nanoparticles have been synthesized using a vapor-solid reaction

McHenry, Michael E.

199

Method for forming fibrous silicon carbide insulating material  

DOE Patents [OSTI]

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.

Wei, G.C.

1983-10-12T23:59:59.000Z

200

Method for forming fibrous silicon carbide insulating material  

DOE Patents [OSTI]

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.

Wei, George C. (Oak Ridge, TN)

1984-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Process for synthesizing titanium carbide, titanium nitride and titanium carbonitride  

DOE Patents [OSTI]

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.

Koc, R.; Glatzmaier, G.C.

1995-05-23T23:59:59.000Z

202

Process for synthesizing titanium carbide, titanium nitride and titanium carbonitride  

DOE Patents [OSTI]

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.

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

1995-01-01T23:59:59.000Z

203

Process for preparing fine grain titanium carbide powder  

DOE Patents [OSTI]

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.

Janey, Mark A. (Concord, TN)

1986-01-01T23:59:59.000Z

204

Process for forming silicon carbide films and microcomponents  

DOE Patents [OSTI]

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.

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

1999-01-01T23:59:59.000Z

205

Electronic states in epitaxial graphene fabricated on silicon carbide  

SciTech Connect (OSTI)

An analytical expression for the density of states of a graphene monolayer interacting with a silicon carbide surface (epitaxial graphene) is derived. The density of states of silicon carbide is described within the Haldane-Anderson model. It is shown that the graphene-substrate interaction results in a narrow gap of {approx}0.01-0.06 eV in the density of states of graphene. The graphene atom charge is estimated; it is shown that the charge transfer from the substrate is {approx}10{sup -3}-10{sup -2}e per graphene atom.

Davydov, S. Yu., E-mail: Sergei_Davydov@mail.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-08-15T23:59:59.000Z

206

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

DOE Patents [OSTI]

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.

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

1985-05-06T23:59:59.000Z

207

Method for simultaneously coating a plurality of filaments  

DOE Patents [OSTI]

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.

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

208

ATP Hydrolysis Stimulates Large Length Fluctuations in Single Actin Filaments  

E-Print Network [OSTI]

ATP Hydrolysis Stimulates Large Length Fluctuations in Single Actin Filaments Evgeny B. Stukalin is investigated theoretically using a stochastic model that takes into account the hydrolysis of ATP filaments. It is found that the ATP hydrolysis has a strong effect on dynamic properties of single actin

209

Process for the production of superconductor containing filaments  

DOE Patents [OSTI]

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.

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

210

Bifurcations of flame filaments in chaotically mixed combustion reactions  

E-Print Network [OSTI]

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

Gottwald, Georg A.

211

GALAXY SPIN ALIGNMENT IN FILAMENTS AND SHEETS: OBSERVATIONAL EVIDENCE  

SciTech Connect (OSTI)

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

Tempel, Elmo [Tartu Observatory, Observatooriumi 1, 61602 Travere (Estonia)] [Tartu Observatory, Observatooriumi 1, 61602 Travere (Estonia); Libeskind, Noam I., E-mail: elmo@to.ee, E-mail: nlibeskind@aip.de [Leibniz-Institut fr Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany)

2013-10-01T23:59:59.000Z

212

Solid-State Formation of Titanium Carbide and Molybdenum Carbide as Contcts for Carbon-Containing Semiconductors  

SciTech Connect (OSTI)

Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin Ti or Mo films and C substrates. Titanium carbide (TiC) was previously reported as a contact material to diamond and carbon nanotubes. However, the present study shows two disadvantages for the solid-state reaction of Ti and C. First, because Ti reacts readily with oxygen, a capping layer should be included to enable carbide formation. Second, the TiC phase can exist over a wide range of composition (about 10%, i.e., from Ti{sub 0.5}C{sub 0.5} to Ti{sub 0.6}C{sub 0.4}), leading to significant variations in the properties of the material formed. The study of the Mo-C system suggests that molybdenum carbide (Mo{sub 2}C) is a promising alternative, since the phase shows a lower resistivity (about 45% lower than for TiC), the carbide forms below 900 {sup o}C, and its formation is less sensitive to oxidation as compared with the Ti-C system. The measured resistivity for Mo{sub 2}C is p=59 {mu}{Omega} cm, and from kinetic studies an activation energy for Mo{sub 2}C formation of E{sub a}=3.15+/-0.15 eV was obtained.

Leroy,W.; Detavernier, C.; van Meirhaeghe, R.; Kellock, A.; Lavoie, C.

2006-01-01T23:59:59.000Z

213

Condensation of actin filaments pushing against a barrier  

E-Print Network [OSTI]

We develop a model to describe the force generated by the polymerization of an array of parallel biofilaments. The filaments are assumed to be coupled only through mechanical contact with a movable barrier. We calculate the filament density distribution and the force-velocity relation with a mean-field approach combined with simulations. We identify two regimes: a non-condensed regime at low force in which filaments are spread out spatially, and a condensed regime at high force in which filaments accumulate near the barrier. We confirm a result previously known from other related studies, namely that the stall force is equal to N times the stall force of a single filament. In the model studied here, the approach to stalling is very slow, and the velocity is practically zero at forces significantly lower than the stall force.

K. Tsekouras; D. Lacoste; K. Mallick; J. -F. Joanny

2011-10-06T23:59:59.000Z

214

The extreme nonlinear optics of gases and femtosecond optical filamentation  

SciTech Connect (OSTI)

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.

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

215

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

E-Print Network [OSTI]

: 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

Paris-Sud XI, Universit de

216

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

DOE Patents [OSTI]

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

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

1980-01-01T23:59:59.000Z

217

Temperature dependency of MOSFET device characteristics in 4H-and 6H-silicon carbide (SiC)  

E-Print Network [OSTI]

Temperature dependency of MOSFET device characteristics in 4H- and 6H-silicon carbide (SiC) Md was arranged by Prof. A. Iliadis Abstract The advantages of silicon carbide (SiC) over silicon are significant; Silicon carbide; Temperature variation effect 1. Introduction Silicon carbide, a wide bandgap material

Tolbert, Leon M.

218

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

E-Print Network [OSTI]

carbide coatings using an axially fed DC-plasmatron S. Sharafata,U , A. Kobayashib , S. Chena , N 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

Ghoniem, Nasr M.

219

Tungsten-yttria carbide coating for conveying copper  

DOE Patents [OSTI]

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.

Rothman, Albert J. (Livermore, CA)

1993-01-01T23:59:59.000Z

220

Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons  

SciTech Connect (OSTI)

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.

Z. Zak Fang, H. Y. Sohn

2009-03-10T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Nuclear breeder reactor fuel element with silicon carbide getter  

DOE Patents [OSTI]

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.

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

1987-01-01T23:59:59.000Z

222

Standard specification for nuclear-Grade boron carbide pellets  

E-Print Network [OSTI]

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.

American Society for Testing and Materials. Philadelphia

2007-01-01T23:59:59.000Z

223

Surface Coating of Tungsten Carbide by Electric Exploding of Contact  

SciTech Connect (OSTI)

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.

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

2011-01-17T23:59:59.000Z

224

Epitaxial graphene on silicon carbide: Introduction to structured graphene  

E-Print Network [OSTI]

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

Paris-Sud XI, Université de

225

Production of ozone and nitrogen oxides by laser filamentation  

SciTech Connect (OSTI)

We have experimentally measured that laser filaments in air generate up to 10{sup 14}, 3x10{sup 12}, and 3x10{sup 13} molecules of O{sub 3}, NO, and NO{sub 2}, respectively. The corresponding local concentrations in the filament active volume are 10{sup 16}, 3x10{sup 14}, and 3x10{sup 15} cm{sup -3}, and allows efficient oxidative chemistry of nitrogen, resulting in concentrations of HNO{sub 3} in the parts per million range. The latter forming binary clusters with water, our results provide a plausible pathway for the efficient nucleation recently observed in laser filaments.

Petit, Yannick; Henin, Stefano; Kasparian, Jerome; Wolf, Jean-Pierre [GAP Biophotonics, Universite de Geneve, 20 rue de l'Ecole de Medecine, CH1211 Geneve 4 (Switzerland)

2010-07-12T23:59:59.000Z

226

Stall force of polymerizing microtubules and filament bundles  

E-Print Network [OSTI]

We investigate stall force and polymerization kinetics of rigid protofilaments in a microtubule or interacting filaments in bundles under an external load force in the framework of a discrete growth model. We introduce the concecpt of polymerization cycles to describe the stochastic growth kinetics, which allows us to derive an exact expression for the stall force. We find that the stall force is independent of ensemble geometry and load distribution. Furthermore, the stall force is proportional to the number of filaments and increases linearly with the strength of lateral filament interactions. These results are corroborated by simulations, which also show a strong influence of ensemble geometry on growth kinetics below the stall force.

Jaroslaw Krawczyk; Jan Kierfeld

2011-02-10T23:59:59.000Z

227

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

SciTech Connect (OSTI)

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.

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

2014-09-01T23:59:59.000Z

228

Formation of beads-on-a-string structures during break-up of viscoelastic filaments  

E-Print Network [OSTI]

Break-up of viscoelastic filaments is pervasive in both nature and technology. If a filament is formed by placing a drop of saliva between a thumb and forefinger and is stretched, the filaments morphology close to break-up ...

Bhat, Pardeep P.

229

SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS  

SciTech Connect (OSTI)

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

DR. DENNIS NAGLE; DR. DAJIE ZHANG

2009-03-26T23:59:59.000Z

230

Apparatus for coating and impregnating filament with resin  

DOE Patents [OSTI]

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.

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

1986-12-17T23:59:59.000Z

231

Chile, 2009 HYDRAULIC MANAGEMENT OF FILAMENTOUS ALGAE IN  

E-Print Network [OSTI]

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

Paris-Sud XI, Université de

232

HFCVD of diamond at low substrate and low filament temperatures  

SciTech Connect (OSTI)

It has been discovered that the addition of a small amount of oxygen to the CH{sub 4} and H{sub 2} feed gas permits HFCVD of diamond at significantly lower filament and substrate temperatures. The effective O/C ratio here is much lower than that used in most studies of the oxygen effect. Careful control of the O/C and C/H ratios were found to be crucial to success. The effects of substrate and filament temperatures on growth rate and film quality were studied. Optimum conditions were found that gave reasonable growth rates ( {approximately}0.5 {mu}m/h ) with high film quality at filament temperatures below 1750{degrees}C and substrate temperatures below 600C. As a result, low temperature deposition has been realized. Power consumption can be reduced 50%, and the filament lifetime is extended indefinitely.

Tolt, Z.L.; Heatherly, L.; Clausing, R.E.; Shaw, R.W. [Oak Ridge National Lab., TN (United States); Feigerle, C.S. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry

1995-12-31T23:59:59.000Z

233

Spin alignment of dark matter haloes in filaments and walls  

E-Print Network [OSTI]

The MMF technique is used to segment the cosmic web as seen in a cosmological N-body simulation into wall-like and filament-like structures. We find that the spins and shapes of dark matter haloes are significantly correlated with each other and with the orientation of their host structures. The shape orientation is such that the halo minor axes tend to lie perpendicular to the host structure, be it a wall or filament. The orientation of the halo spin vector is mass dependent. Low mass haloes in walls and filaments have a tendency to have their spins oriented within the parent structure, while higher mass haloes in filaments have spins that tend to lie perpendicular to the parent structure.

Miguel A. Aragn-Calvo; Rien van de Weygaert; Bernard J. T. Jones; J. M. Thijs van der Hulst

2006-10-09T23:59:59.000Z

234

7-forming, superconducting filaments through bicomponent dry spinning  

DOE Patents [OSTI]

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.

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

235

The Discovery of Balmer-filaments Encircling SNR RCW 86  

E-Print Network [OSTI]

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.

R. Chris Smith

1997-10-17T23:59:59.000Z

236

Top-Down Fragmentation of a Warm Dark Matter Filament  

E-Print Network [OSTI]

We present the first high-resolution n-body simulations of the fragmentation of dark matter filaments. Such fragmentation occurs in top-down scenarios of structure formation, when the dark matter is warm instead of cold. In a previous paper (Knebe et al. 2002, hereafter Paper I), we showed that WDM differs from the standard Cold Dark Matter (CDM) mainly in the formation history and large-scale distribution of low-mass haloes, which form later and tend to be more clustered in WDM than in CDM universes, tracing more closely the filamentary structures of the cosmic web. Therefore, we focus our computational effort in this paper on one particular filament extracted from a WDM cosmological simulation and compare in detail its evolution to that of the same CDM filament. We find that the mass distribution of the halos forming via fragmentation within the filament is broadly peaked around a Jeans mass of a few 10^9 Msun, corresponding to a gravitational instability of smooth regions with an overdensity contrast around 10 at these redshifts. Our results confirm that WDM filaments fragment and form gravitationally bound haloes in a top-down fashion, whereas CDM filaments are built bottom-up, thus demonstrating the impact of the nature of the dark matter on dwarf galaxy properties.

Alexander Knebe; Julien Devriendt; Brad Gibson; Joseph Silk

2003-07-28T23:59:59.000Z

237

Diamond-Silicon Carbide Composite And Method For Preparation Thereof  

DOE Patents [OSTI]

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.

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

2005-09-06T23:59:59.000Z

238

Protective coating for alumina-silicon carbide whisker composites  

DOE Patents [OSTI]

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.

Tiegs, Terry N. (Lenoir City, TN)

1989-01-01T23:59:59.000Z

239

Carbon-rich icosahedral boron carbide designed from first principles  

SciTech Connect (OSTI)

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.

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

2014-07-21T23:59:59.000Z

240

Photonic Crystal Cavities in Cubic Polytype Silicon Carbide Films  

E-Print Network [OSTI]

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 1250 - 1600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

Radulaski, Marina; Buckley, Sonia; Rundquist, Armand; Provine, J; Alassaad, Kassem; Ferro, Gabriel; Vu?kovi?, Jelena

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Process for growing silicon carbide whiskers by undercooling  

DOE Patents [OSTI]

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

Shalek, Peter D. (Los Alamos, NM)

1987-01-01T23:59:59.000Z

242

Microstructure and properties of IN SITU toughened silicon carbide  

SciTech Connect (OSTI)

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.

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

2003-05-01T23:59:59.000Z

243

Ceramic composites reinforced with modified silicon carbide whiskers  

DOE Patents [OSTI]

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.

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

1990-01-01T23:59:59.000Z

244

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

SciTech Connect (OSTI)

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.

Vojvodic, Aleksandra

2012-05-11T23:59:59.000Z

245

High-Resolution Soft X-Ray Spectral Analysis in the CK Region of Titanium Carbide (TiC) using the DV-X alpha Molecular Orbital Method  

E-Print Network [OSTI]

in the CK Region of Titanium Carbide (TiC) using the DV-X?USA Keyword titanium carbide, soft X-ray spectroscopy,C K region of titanium carbide (TiC). The spectral profiles

Shimomura, Kenta

2010-01-01T23:59:59.000Z

246

High-Resolution Soft X-Ray Spectral Analysis in the CK Region of Titanium Carbide (TiC) using the DV-X alpha Molecular Orbital Method  

E-Print Network [OSTI]

of rock-salt structured metal carbides. K. Shimomura et al.in metals, such as metal carbides and carbon/metal alloys,the CK region of metal carbides, and analyzed the spectral

Shimomura, Kenta

2010-01-01T23:59:59.000Z

247

Tunable carbon nanotube-tungsten carbide nanoparticles heterostructures by vapor deposition  

SciTech Connect (OSTI)

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.

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

248

ARC DISCHARGE SYNTHESIS AND MORPHOLOGY CONTROL OF EARLY TRANSITION METAL CARBIDE NANOPATICLES.  

E-Print Network [OSTI]

??This work is directed to the understanding of the synthesis and morphology control of early transition metal carbides. Chapter 1 gives an introduction to fcc (more)

Grove , David

2010-01-01T23:59:59.000Z

249

Electronic properties and reliability of the silicon dioxide / silicon carbide interface.  

E-Print Network [OSTI]

??Silicon carbide has been preferred over other wide band-gap semiconductors for high power applications because of its unique ability to grow a thermal oxide, challenges (more)

Rozen, John

2008-01-01T23:59:59.000Z

250

LASER METALLIZATION AND DOPING FOR SILICON CARBIDE DIODE FABRICATION AND ENDOTAXY.  

E-Print Network [OSTI]

??Silicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field (more)

Tian, Zhaoxu

2006-01-01T23:59:59.000Z

251

E-Print Network 3.0 - alternative lmfbr carbide Sample Search...  

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

illustrating the rich behavior of carbo-nitride materials. The early transition metal carbides and nitrides... the calculations re- ported here were performed with the...

252

ATP hydrolysis stimulates large length fluctuations in single actin filaments  

E-Print Network [OSTI]

Polymerization dynamics of single actin filaments is investigated theoretically using a stochastic model that takes into account the hydrolysis of ATP-actin subunits, the geometry of actin filament tips, the lateral interactions between the monomers as well as the processes at both ends of the polymer. Exact analytical expressions are obtained for a mean growth velocity and for dispersion in length fluctuations. It is found that the ATP hydrolysis has a strong effect on dynamic properties of single actin filaments. At high concentrations of free actin monomers the mean size of unhydrolyzed ATP-cap is very large, and the dynamics is governed by association/dissociation of ATP-actin subunits. However, at low concentrations the size of the cap becomes finite, and the dissociation of ADP-actin subunits makes a significant contribution to overall dynamics. Actin filament length fluctuations reach the maximum at the boundary between two dynamic regimes, and this boundary is always larger than the critical concentration. Random and vectorial mechanisms of hydrolysis are compared, and it is found that they predict qualitatively similar dynamic properties. The possibility of attachment and detachment of oligomers is also discussed. Our theoretical approach is successfully applied to analyze the latest experiments on the growth and length fluctuations of individual actin filaments.

Evgeny B. Stukalin; Anatoly B. Kolomeisky

2005-07-27T23:59:59.000Z

253

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

SciTech Connect (OSTI)

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.

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

254

Submitted to ApJ Letters, June 29, 2005 Are Presolar Silicon Carbide Grains from Novae Actually from Supernovae?  

E-Print Network [OSTI]

Submitted to ApJ Letters, June 29, 2005 Are Presolar Silicon Carbide Grains from Novae Actually stellar nucleosynthesis and mixing. The best-studied presolar phase, silicon carbide (SiC), exhibits

Nittler, Larry R.

255

PII S0016-7037(01)00802-X Volatilization kinetics of silicon carbide in reducing gases: An experimental study with  

E-Print Network [OSTI]

PII S0016-7037(01)00802-X Volatilization kinetics of silicon carbide in reducing gases occurring hexagonal sili- con carbide ( -SiC), and -SiC, the cubic form, are occasion- ally reported

Grossman, Lawrence

256

How Filaments are Woven into the Cosmic Web  

E-Print Network [OSTI]

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.

J. Richard Bond; Lev Kofman; Dmitri Pogosyan

1995-12-21T23:59:59.000Z

257

Effect of filament supports on emissive probe measurements  

SciTech Connect (OSTI)

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

Wang, X.; Howes, C. T. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80309 (United States); NASA Lunar Science Institute: Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80309 (United States); Horanyi, M. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80309 (United States); NASA Lunar Science Institute: Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80309 (United States); Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Robertson, S. [NASA Lunar Science Institute: Colorado Center for Lunar Dust and Atmospheric Studies, Boulder, Colorado 80309 (United States); Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)

2013-01-15T23:59:59.000Z

258

Irradiation and annealing of p-type silicon carbide  

SciTech Connect (OSTI)

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

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

2014-02-21T23:59:59.000Z

259

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

DOE Patents [OSTI]

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.

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

260

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

SciTech Connect (OSTI)

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.

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

2014-05-27T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Four-point probe characterization of 4H silicon carbide N. Chandra a,  

E-Print Network [OSTI]

Four-point probe characterization of 4H silicon carbide N. Chandra a, , V. Sharma a , G.Y. Chung b carbide Four-point probe Thermionic-field emission Contact resistance a b s t r a c t We report on four

Schroder, Dieter K.

262

General Multiobjective Force Field Optimization Framework, with Application to Reactive Force Fields for Silicon Carbide  

E-Print Network [OSTI]

Fields for Silicon Carbide Andres Jaramillo-Botero,* Saber Naserifar, and William A. Goddard, III: (1) the ReaxFF reactive force field for modeling the adiabatic reactive dynamics of silicon carbide specific force field parameters for tripod metal templates, tripodMO(CO)3, using the root mean square

Goddard III, William A.

263

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

SciTech Connect (OSTI)

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.

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

264

Electronic structure and pairwise interactions in substoichiometric transition metal carbides and nitrides  

E-Print Network [OSTI]

1001 Electronic structure and pairwise interactions in substoichiometric transition metal carbides observations expéri- mentales. Abstract 2014 In substoichiometric transition metal carbides and nitrides This paper is devoted to the study of the ordering processes in substoichiometric transition metal carbi- des

Paris-Sud XI, Université de

265

carbides. The multiphase/polytypic region can be expected to occur also in the nitrides because  

E-Print Network [OSTI]

in valence electron concentration where sev- eral phases of the 3d, 4d, and 5d transition metal carbides have, Transition Metal Carbides and Nitrides (Academic Press, New York, 1971). 6. C. Maerky, M.-O. Guillou, J. L is predicted to be substantially enhanced over that of traditional transition metal car- bide/nitride coatings

Shen, Guoyin

266

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

E-Print Network [OSTI]

a possibility of replacing precious metal anode catalysts with transition metal compounds for hydrogen oxidation density of states of tungsten carbides resembles that of noble metal platinum.4,5 FundamentalNanostructured tungsten carbide catalysts for polymer electrolyte fuel cells X. G. Yanga and C. Y

267

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

E-Print Network [OSTI]

transition metals, rare earths and actinides react with carbon and nitrogen to form metallic carbides experimental evidence for short and long-range ordering of point defects in metallic transition metal, rareCOMPOUNDS. ORDER AND DISORDER IN CARBIDES AND NITRIDES Ch. H. DE NOVION and V. MAURICE SESI, C

Paris-Sud XI, Université de

268

PROPERTIES OF DEFECTS AND IMPLANTS IN Mg+ IMPLANTED SILICON CARBIDE  

SciTech Connect (OSTI)

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.

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

269

Optical and electronic properties of two dimensional graphitic silicon carbide  

E-Print Network [OSTI]

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.

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

2012-01-01T23:59:59.000Z

270

Method of fabricating silicon carbide coatings on graphite surfaces  

DOE Patents [OSTI]

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.

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

1994-01-01T23:59:59.000Z

271

Method of fabricating silicon carbide coatings on graphite surfaces  

DOE Patents [OSTI]

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.

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

1994-07-26T23:59:59.000Z

272

Making Silicon Carbide Devices in the Cleanroom | GE Global Research  

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:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: VegetationEquipment Surfaces and InterfacesAdministration -Lowellfor 2013 |SphericalSilicon Carbide

273

Nanoscale Engineering Of Radiation Tolerant Silicon Carbide. | EMSL  

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:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administration the Contributions andData andFleetEngineering Of Radiation Tolerant Silicon Carbide.

274

Zipping mechanism for force-generation by growing filament bundles  

E-Print Network [OSTI]

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.

Torsten Kuehne; Reinhard Lipowsky; Jan Kierfeld

2011-03-02T23:59:59.000Z

275

Non-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room temperature  

E-Print Network [OSTI]

Non-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room temperature Simone film crystal growth of silicon carbide (SiC), a semiconductor syn- thesized to replace silicon in harsh

Alfè, Dario

276

Brittle dynamic fracture of crystalline cubic silicon carbide ,,3C-SiC... via molecular dynamics simulation  

E-Print Network [OSTI]

Brittle dynamic fracture of crystalline cubic silicon carbide ,,3C-SiC... via molecular dynamics for three low-index crack surfaces, i.e., 110 , 111 , and 100 , in crystalline cubic silicon carbide 3C Institute of Physics. DOI: 10.1063/1.2135896 I. INTRODUCTION Potential applications of silicon carbide Si

Southern California, University of

277

CHIN.PHYS.LETT. Vol. 25, No. 9 (2008) 3463 Probing Field Emission from Boron Carbide Nanowires  

E-Print Network [OSTI]

CHIN.PHYS.LETT. Vol. 25, No. 9 (2008) 3463 Probing Field Emission from Boron Carbide Nanowires, Sun Yat-sen University, Guangzhou 510275 (Received 10 March 2008) High density boron carbide nanowires together suggest that boron carbide nanowires are promising candidates for electron emission nanodevices

Gao, Hongjun

278

A Comparison of Mechanical Properties of Three MEMS Materials -Silicon Carbide, Ultrananocrystalline Diamond, and Hydrogen-Free Tetrahedral  

E-Print Network [OSTI]

A Comparison of Mechanical Properties of Three MEMS Materials - Silicon Carbide investigated the mechanical properties of three new materials for MEMS/NEMS devices: silicon carbide (SiC) from mechanical, electrical, and tribological properties such as silicon carbide (SiC), ultrananocrystalline

Espinosa, Horacio D.

279

Interaction potential for silicon carbide: A molecular dynamics study of elastic constants and vibrational density of states for crystalline  

E-Print Network [OSTI]

Interaction potential for silicon carbide: A molecular dynamics study of elastic constants and vibrational density of states for crystalline and amorphous silicon carbide Priya Vashishta,a Rajiv K. Kalia Silicon carbide SiC has been proposed for a wide range of technological applications

Southern California, University of

280

Chem.Mater. 1996,7, 1419-1421 1419 Encapsulation of Iron Carbide in Carbon Nanocapsules  

E-Print Network [OSTI]

Chem.Mater. 1996,7, 1419-1421 1419 Encapsulation of Iron Carbide in Carbon Nanocapsules Nikolai S Manuscript Received April 24, 1995@ Whiskers of iron carbide encased in carbon shells have been prepared from microscopy. The iron carbide whiskers range in length from 300 to 500 nm, and their widths are approximately

Wang, Zhong L.

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Accepted to Diamond and Related Materials A kinetic model of diamond nucleation and silicon carbide interlayer formation during  

E-Print Network [OSTI]

Accepted to Diamond and Related Materials A kinetic model of diamond nucleation and silicon carbide Engineering, Colorado State University, Fort Collins, CO, USA Abstract The presence of thin silicon carbide diffusion of carbon atoms into the silicon carbide layer, and the morphology and orientation of the diamond

Dandy, David

282

Materials Science and Engineering A245 (1998) 293299 The wettability of silicon carbide by AuSi alloys  

E-Print Network [OSTI]

Materials Science and Engineering A245 (1998) 293­299 The wettability of silicon carbide by Au. Keywords: Wettability; Contact angle; Liquid metals; Silicon carbide 1. Introduction The interface properties of silicon carbide­liquid metals (wetting, adhesion, contact interaction) are im- portant

Grigoriev, Alexei

283

By Earle B. Amey Tungsten's unique high-temperature in Metal Bulletin (London). ferrotungsten, carbide powder blends, and  

E-Print Network [OSTI]

). ferrotungsten, carbide powder blends, and properties can be utilized advantageously in the As a result properties of its carbide continue to scrap, and sodium tungstate and away from the provide important items increased in all imported tungsten materials. the cemented carbide end-use sectors that A summary

284

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

E-Print Network [OSTI]

of Silicon Carbide Power Electronics for Modern Wind Turbine Full Scale Frequency Converter Hui Zhang, Member and fast switching speeds, silicon carbide (SiC) power electronics are considered for use in power), silicon carbide (SiC), wind generation. I. INTRODUCTION VARIABLE speed capability allows a wind turbine

Tolbert, Leon M.

285

Improvement of pin-type amorphous silicon solar cell performance by employing double silicon-carbide p-layer structure  

E-Print Network [OSTI]

Improvement of pin-type amorphous silicon solar cell performance by employing double silicon-carbide Received 30 October 2003; accepted 18 November 2003 We investigated a double silicon-carbide p-layer structure consisting of a undiluted p-type amorphous silicon-carbide (p-a-SiC:H) window layer and a hydrogen

Kim, Yong Jung

286

Midinfrared Index Sensing of pL-Scale Analytes Based on Surface Phonon Polaritons in Silicon Carbide  

E-Print Network [OSTI]

Carbide Burton Neuner III, Dmitriy Korobkin, Chris Fietz, Davy Carole,§ Gabriel Ferro,§ and Gennady Shvets at the silicon carbide/analyte interface in the Otto configuration. Attenuated total reflectance measurements carbide gratings.3 Resonant techniques are often needed for sensing because, e.g., weak vibrational modes

Texas at Austin, University of

287

Bond-order potential for transition metal carbide cluster for the growth simulation of a single-walled carbon nanotube  

E-Print Network [OSTI]

Bond-order potential for transition metal carbide cluster for the growth simulation of a single for transition metal carbide cluster is developed in the form of the bond-order type potential function-order potential; Carbon nanotube; transition metal carbide cluster *Corresponding Author. Fax: +81-3-5841-8653 E

Maruyama, Shigeo

288

Characterization of new Co and Ru on -WC catalysts for Fischer-Tropsch reaction. Influence of the carbide surface state.  

E-Print Network [OSTI]

[8]. Among the group VI transition metal carbides, the hexagonal tungsten carbide WC is a remarkable proceeds on supported transition metal catalysts, Co or Fe on oxide supports generally Al2O3 or SiO2 [1 of the carbide surface state. A. Griboval-Constant(1) *, J.-M. Giraudon(1) , I. Twagishema(1) , G. Leclercq(1

Paris-Sud XI, Université de

289

First-Principles Study of MetalCarbide/Nitride Adhesion: Al/VC vs. Al/VN Donald J. Siegel  

E-Print Network [OSTI]

-oxide ce- ramics. Within this class, the transition metal carbides and ni- trides are a particularly knowledge, there have been only three studies of adhesion between metals and transition metal carbidesFirst-Principles Study of Metal­Carbide/Nitride Adhesion: Al/VC vs. Al/VN Donald J. Siegel

Adams, James B

290

Characterization of new Co and Ru on -WC catalysts for Fischer-Tropsch reaction. Influence of the carbide surface state.  

E-Print Network [OSTI]

of the metallic particles [8]. Among the group VI transition metal carbides, the hexagonal tungsten carbide WC monoxide and hydrogen. FT synthesis proceeds on supported transition metal catalysts, Co or Fe on oxide of the carbide surface state. A. Griboval-Constant(1) *, J.-M. Giraudon(1) , I. Twagishema(1) , G. Leclercq(1

Paris-Sud XI, Université de

291

Field effect in epitaxial graphene on a silicon carbide substrate Sarnoff Corporation, CN5300, Princeton, New Jersey 08543  

E-Print Network [OSTI]

deposition on the surfaces of transition metal or transition metal carbide single crystals, and the physical on a graphitized SiC surface, as opposed to highly conductive metal and metal carbide substrates that require1 Field effect in epitaxial graphene on a silicon carbide substrate Gong Gua) Sarnoff Corporation

Feenstra, Randall

292

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

E-Print Network [OSTI]

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 ...

Yeh, Roger, 1980-

2005-01-01T23:59:59.000Z

293

The role of filament activation in a solar eruption  

E-Print Network [OSTI]

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...

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

2014-01-01T23:59:59.000Z

294

The genome sequence of the filamentous fungus Neurospora crassa  

E-Print Network [OSTI]

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

Kellis, Manolis

295

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

296

INTRODUCTION Neural intermediate filaments (NIF) containing one or more of  

E-Print Network [OSTI]

INTRODUCTION Neural intermediate filaments (NIF) containing one or more of five different types, NIF possess common structural features, including a conserved alpha-helical central rod domain of NIF in the presence of NF-L (Zackroff et al., 1982; Hisanaga and Hirokawa, 1988; Balin and Lee, 1991

Goldman, Robert D.

297

Evolution of Genes and Gene Networks in Filamentous Fungi  

E-Print Network [OSTI]

......................................................................................................................... 137 ix LIST OF FIGURES FIGURE Page 1 Phylogenetic tree assembled from fungi with sequenced genomes ........... 5 2... (subsistence on detritus) lifestyle, may explain such rapid amino acid divergence. Figs. 1 and 2 are phylogenetic trees for the filamentous fungi. Fig. 2 shows the 10 major classes of the 5 Fig. 1: Phylogenetic tree assembled from fungi with sequenced...

Greenwald, Charles Joaquin

2011-10-21T23:59:59.000Z

298

Detection of an optical filament in the Monogem Ring  

E-Print Network [OSTI]

The Monogem Ring is a huge bright soft X-ray enhancement with a diameter of ~ 25$\\degr$. This 0.3 kpc distant structure is a peculiar Galactic supernova remnant in that it is obviously visible only in X-rays, due to its expansion into a region of extremely low ambient density: hence, practically no optical emission or a neutral HI shell was expected to be detectable. - Here we report on the discovery of a very faint arc-like nebula on a POSS II R film copy, at the south-eastern borders of the MR. Spectroscopy revealed this filament to have a very large [SII]$\\lambda$ 6716+6731/Halpha ratio of up to ~ 1.8, indicating shock excitation, and a low density of N_e thin (~ 1 arcmin), structured filament, stretching N-S. We believe that this filament belongs to the MR and became visible due to the interaction of the expanding remnant with a mild density increase in the interstellar medium. Only one other possible optical filament of the MR has been reported in the literature, but no spectrum was provided.

R. Weinberger; S. Temporin; B. Stecklum

2005-11-18T23:59:59.000Z

299

Influence of interlayer trapping and detrapping mechanisms on the electrical characterization of hafnium oxide/silicon nitride stacks on silicon  

SciTech Connect (OSTI)

Al/HfO{sub 2}/SiN{sub x}:H/n-Si metal-insulator-semiconductor capacitors have been studied by electrical characterization. Films of silicon nitride were directly grown on n-type silicon substrates by electron cyclotron resonance assisted chemical vapor deposition. Silicon nitride thickness was varied from 3 to 6.6 nm. Afterwards, 12 nm thick hafnium oxide films were deposited by the high-pressure sputtering approach. Interface quality was determined by using current-voltage, capacitance-voltage, deep-level transient spectroscopy (DLTS), conductance transients, and flatband voltage transient techniques. Leakage currents followed the Poole-Frenkel emission model in all cases. According to the simultaneous measurement of the high and low frequency capacitance voltage curves, the interface trap density obtained for all the samples is in the 10{sup 11} cm{sup -2} eV{sup -1} range. However, a significant increase in this density of about two orders of magnitude was obtained by DLTS for the thinnest silicon nitride interfacial layers. In this work we probe that this increase is an artifact that must be attributed to traps existing at the HfO{sub 2}/SiN{sub x}:H intralayer interface. These traps are more easily charged or discharged as this interface comes near to the substrate, that is, as thinner the SiN{sub x}:H interface layer is. The trapping/detrapping mechanism increases the capacitance transient and, in consequence, the DLTS measurements have contributions not only from the insulator/substrate interface but also from the HfO{sub 2}/SiN{sub x}:H intralayer interface.

Garcia, H.; Duenas, S.; Castan, H.; Gomez, A.; Bailon, L. [Departamento de Electricidad y Electronica, E.T.S.I. Telecomunicacion, Universidad de Valladolid, Campus 'Miguel Delibes', 47011 Valladolid (Spain); Toledano-Luque, M.; Prado, A. del; Martil, I.; Gonzalez-Diaz, G. [Departamento de Fisica Aplicada III (Electricidad y Electronica), Facultad de Ciencias Fisicas, Universidad Complutense, 28040 Madrid (Spain)

2008-11-01T23:59:59.000Z

300

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

E-Print Network [OSTI]

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.

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

2008-03-25T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Method for silicon carbide production by reacting silica with hydrocarbon gas  

DOE Patents [OSTI]

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

Glatzmaier, Gregory C. (Boulder, CO)

1994-01-01T23:59:59.000Z

302

The world`s first commercial iron carbide plant  

SciTech Connect (OSTI)

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.

Prichard, L.C.; Schad, D.

1995-12-01T23:59:59.000Z

303

In situ electrochemical dilatometry of carbide-derived carbons  

SciTech Connect (OSTI)

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.

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

2011-01-01T23:59:59.000Z

304

In-situ Electrochemical Dilatometry of Carbide-derived Carbons  

SciTech Connect (OSTI)

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.

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

2011-01-01T23:59:59.000Z

305

DECODING THE MESSAGE FROM METEORITIC STARDUST SILICON CARBIDE GRAINS  

SciTech Connect (OSTI)

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.

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

306

Decoding the message from meteoritic stardust silicon carbide grains  

E-Print Network [OSTI]

Micron-sized stardust grains that originated in ancient stars are recovered from meteorites and analysed using high-resolution mass spectrometry. The most widely studied type of stardust is silicon carbide (SiC). Thousands of these grains have been analysed 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 carry 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 modelling of dust condensation in stellar winds as function of the metallicity.

Lewis, Karen M; Gibson, Brad K; Pilkington, Kate

2013-01-01T23:59:59.000Z

307

Electron Spin Decoherence in Silicon Carbide Nuclear Spin Bath  

E-Print Network [OSTI]

In this paper, we study the electron spin decoherence of single defects in silicon carbide (SiC) nuclear spin bath. We find that, although the natural abundance of $^{29}\\rm{Si}$ ($p_{\\rm{Si}}=4.7\\%$) is about 4 times larger than that of $^{13}{\\rm C}$ ($p_{\\rm{C}}=1.1\\%$), the electron spin coherence time of defect centers in SiC nuclear spin bath in strong magnetic field ($B>300~\\rm{Gauss}$) is longer than that of nitrogen-vacancy (NV) centers in $^{13}{\\rm C}$ nuclear spin bath in diamond. The reason for this counter-intuitive result is the suppression of heteronuclear-spin flip-flop process in finite magnetic field. Our results show that electron spin of defect centers in SiC are excellent candidates for solid state spin qubit in quantum information processing.

Li-Ping Yang; Christian Burk; Mattias Widmann; Sang-Yun Lee; Jrg Wrachtrup; Nan Zhao

2014-09-16T23:59:59.000Z

308

Silicon carbide tritium permeation barrier for steel structural components.  

SciTech Connect (OSTI)

Chemical vapor deposited (CVD) silicon carbide (SiC) has superior resistance to tritium permeation even after irradiation. Prior work has shown Ultrametfoam to be forgiving when bonded to substrates with large CTE differences. The technical objectives are: (1) Evaluate foams of vanadium, niobium and molybdenum metals and SiC for CTE mitigation between a dense SiC barrier and steel structure; (2) Thermostructural modeling of SiC TPB/Ultramet foam/ferritic steel architecture; (3) Evaluate deuterium permeation of chemical vapor deposited (CVD) SiC; (4) D testing involved construction of a new higher temperature (> 1000 C) permeation testing system and development of improved sealing techniques; (5) Fabricate prototype tube similar to that shown with dimensions of 7cm {theta} and 35cm long; and (6) Tritium and hermeticity testing of prototype tube.

Causey, Rion A. (Sandia National Laboratories, Livermore, CA); Garde, Joseph Maurico; Buchenauer, Dean A. (Sandia National Laboratories, Livermore, CA); Calderoni, Pattrick (Idaho National Laboratory); Holschuh, Thomas, Jr.; Youchison, Dennis Lee; Wright, Matt; Kolasinski, Robert D. (Sandia National Laboratories, Livermore, CA)

2010-09-01T23:59:59.000Z

309

High surface area silicon carbide-coated carbon aerogel  

SciTech Connect (OSTI)

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.

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

2014-01-14T23:59:59.000Z

310

Advanced Measurements of Silicon Carbide Ceramic Matrix Composites  

SciTech Connect (OSTI)

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.

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

2012-08-01T23:59:59.000Z

311

Synthesis of high purity sinterable silicon carbide powder  

SciTech Connect (OSTI)

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.

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

312

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

SciTech Connect (OSTI)

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.

None

2010-09-01T23:59:59.000Z

313

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

E-Print Network [OSTI]

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 ...

Carpenter, David Michael

2011-01-01T23:59:59.000Z

314

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

DOE Patents [OSTI]

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.

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

2004-07-20T23:59:59.000Z

315

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

E-Print Network [OSTI]

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 ...

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

2011-01-01T23:59:59.000Z

316

Analysis of silicon carbide based semiconductor power devices and their application in power factor correction  

E-Print Network [OSTI]

cannot handle. The requirements include higher blocking voltages, switching frequencies, efficiency, and reliability. Material technologies superior to Si are needed for future power device developments. Silicon Carbide (SiC) based semiconductor devices...

Durrani, Yamin Qaisar

2005-11-01T23:59:59.000Z

317

Preliminary study of neutron absorption by concrete with boron carbide addition  

SciTech Connect (OSTI)

Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates the most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.

Abdullah, Yusof, E-mail: yusofabd@nuclearmalaysia.gov.my; Yusof, Mohd Reusmaazran; Zali, Nurazila Mat; Ahmad, Megat Harun Al Rashid Megat; Yazid, Hafizal [Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Ariffin, Fatin Nabilah Tajul; Ahmad, Sahrim [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia); Hamid, Roszilah [Department of Civil and Structural Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia); Mohamed, Abdul Aziz [College of Engineering, Universiti Tenaga National, Jalan Ikram-Uniten, 43000 Kajang, Selangor (Malaysia)

2014-02-12T23:59:59.000Z

318

Intern experience at the Union Carbide Corporation, Texas City plant: an internship report  

E-Print Network [OSTI]

This report presents a survey of the author's internship experience with Union Carbide Corporation's Texas City plant during the period July 1, 1980 through May 15, 1981. The ten and one-half month internship was spent as an engineering...

Tippett, Donald Dwight, 1947-

2013-03-13T23:59:59.000Z

319

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

E-Print Network [OSTI]

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 ...

Stempien, John D. (John Dennis)

2011-01-01T23:59:59.000Z

320

Radiofrequency plasma antenna generated by femtosecond laser filaments in air  

SciTech Connect (OSTI)

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.

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

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Initiation of a passivated interface between hafnium oxide and In(Ga)As(0 0 1)-(4x2)  

SciTech Connect (OSTI)

Hafnium oxide interfaces were studied on two related group III rich semiconductor surfaces, InAs(0 0 1)-(4x2) and In{sub 0.53}Ga{sub 0.47}As(0 0 1)-(4x2), via two different methods: reactive oxidation of deposited Hf metal and electron beam deposition of HfO{sub 2}. The interfaces were investigated with scanning tunneling microscopy and spectroscopy (STS). Single Hf atom chemisorption sites were identified that are resistant to oxidation by O{sub 2}, but Hf islands are reactive to O{sub 2}. After e{sup -} beam deposition of <<1 ML of HfO{sub 2}, single chemisorption sites were identified. At low coverage (<1 ML), the n-type and p-type HfO{sub 2}/InGaAs(0 0 1)-(4x2) interfaces show p-type character in STS, which is typical of clean InGaAs(0 0 1)-(4x2). After annealing below 200 deg. C, full coverage HfO{sub 2}/InGaAs(0 0 1)-(4x2) (1-3 ML) has the surface Fermi level shifted toward the conduction band minimum for n-type InGaAs, but near the valence band maximum for p-type InGaAs. This is consistent with the HfO{sub 2}/InGaAs(0 0 1)-(4x2) interface being at least partially unpinned, i.e., a low density of states in the band gap. The partially unpinned interface results from the modest strength of the bonding between HfO{sub 2} and InGaAs(0 0 1)-(4x2) that prevents substrate atom disruption. The fortuitous structure of HfO{sub 2} on InAs(0 0 1)-(4x2) and InGaAs(0 0 1)-(4x2) allows for the elimination of the partially filled dangling bonds on the surface, which are usually responsible for Fermi level pinning.

Clemens, Jonathon B.; Bishop, Sarah R.; Kummel, Andrew C. [Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Dr., 0358, La Jolla, California 92093-0358 (United States); Lee, Joon Sung [Department of Chemistry and Biochemistry/Materials Science and Engineering Program, University of California, San Diego, 9500 Gilman Dr., 0358, La Jolla, California 92093-0358 (United States); Droopad, Ravi [Department of Physics, Texas State University-San Marcos, San Marcos, Texas 78666 (United States)

2010-06-28T23:59:59.000Z

322

Development of a hot isostatic pressing process for manufacturing silicon carbide particulate reinforced iron  

E-Print Network [OSTI]

DEVELOPMENT OP A BOT ISOSTATIC PRBSSIHG PROCESS POR HAHUPACTURIHG SILICON CARBIDE PARTICULATE RBINPORCBD IRON A Thesis by DAVID OSCAR OAKESON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1992 Major Subject: Aerospace Engineering DEVELOPMENT OF A EOT ISOSTATIC PRESBING PROCESB FOR MANUFACTURING BILICON CARBIDE PARTICULATE REINFORCED IRON A Thesis by DAVID OSCAR OAKESON Approved...

Oakeson, David Oscar

1992-01-01T23:59:59.000Z

323

STUDYING INTERCLUSTER GALAXY FILAMENTS THROUGH STACKING gmBCG GALAXY CLUSTER PAIRS  

SciTech Connect (OSTI)

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.

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

324

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)

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

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

325

Biofuels production from hydrotreating of vegetable oil using supported noble metals, and transition metal carbide and nitride.  

E-Print Network [OSTI]

?? The focus of this research is to prepare non-sulfided hydrotreating catalysts, supported noble metal and transition metal carbide/ nitride, and evaluate their hydrocracking activities (more)

Wang, Huali

2012-01-01T23:59:59.000Z

326

Submicron carbon filament cement-matrix composites for electromagnetic interference shielding  

SciTech Connect (OSTI)

Carbon filaments of diameter 0.1 mm were found to be a much more effective additive than conventional carbon fibers of diameter 10 mm in providing cement pastes capable of electromagnetic interference shielding. With 0.54 vol. % filaments and a shield thickness of 4 mm, a shielding effectiveness of 30 dB was attained at 1--2 GHz. However, the filaments were less effective than the fibers for reinforcing and for providing strain sensing cement-matrix composites.

Fu, X.; Chung, D.D.L. [State Univ. of New York, Buffalo, NY (United States). Composite Materials Research Lab.] [State Univ. of New York, Buffalo, NY (United States). Composite Materials Research Lab.

1996-10-01T23:59:59.000Z

327

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

SciTech Connect (OSTI)

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.

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

328

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

SciTech Connect (OSTI)

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.

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

329

Nano-precipitation in hot-pressed silicon carbide  

SciTech Connect (OSTI)

Heat treatments at 1300 degrees C, 1400 degrees C, 1500 degrees C, and 1600 degrees C in Ar were found to produce nanoscale precipitates in hot-pressed silicon carbide containing aluminum, boron, and carbon sintering additives (ABC-SiC). The precipitates were studied by transmission electron microscopy (TEM) and nano-probe energy-dispersive X-ray spectroscopy (nEDS). The precipitates were plate-like in shape, with a thickness, length and separation of only a few nanometers, and their size coarsened with increasing annealing temperature, accompanied by reduced number density. The distribution of the precipitates was uniform inside the SiC grains, but depleted zones were observed in the vicinity of the SiC grain boundaries. A coherent orientation relationship between the precipitates and the SiC matrix was found. Combined high-resolution electron microscopy, computer simulation, and nEDS identified an Al4C3-based structure and composition for the nano-precipitates. Most Al ions in SiC lattice exsolved as precipitates during the annealing at 1400 to 1500 degrees C. Formation mechanism and possible influences of the nanoscale precipitates on mechanical properties are discussed.

Zhang, Xiao Feng; Sixta, Mark E.; Chen, Da; De Jonghe, Lutgard C.

2000-05-16T23:59:59.000Z

330

Silicon Carbide Photonic Crystal Cavities with Integrated Color Centers  

E-Print Network [OSTI]

The recent discovery of color centers with optically addressable spin states in 3C silicon carbide (SiC) similar to the negatively charged nitrogen vacancy center in diamond has the potential to enable the integration of defect qubits into established wafer scale device architectures for quantum information and sensing applications. Here we demonstrate the design, fabrication, and characterization of photonic crystal cavities in 3C SiC films with incorporated ensembles of color centers and quality factor (Q) to mode volume ratios similar to those achieved in diamond. Simulations show that optimized H1 and L3 structures exhibit Q as high as 45,000 and mode volumes of approximately $(\\lambda/n)^{3}$. We utilize the internal color centers as a source of broadband excitation to characterize fabricated structures with resonances tuned to the color center zero phonon line and observe Q in the range of 900-1,500 with narrowband photoluminescence collection enhanced by up to a factor of 10. By comparing the Q factors observed for different geometries with finite-difference time-domain simulations, we find evidence that nonvertical sidewalls are likely the dominant source of discrepancies between our simulated and measured Q factors. These results indicate that defect qubits in 3C SiC thin films show clear promise as a simple, scalable platform for interfacing defect qubits with photonic, optoelectronic, and optomechanical devices.

Greg Calusine; Alberto Politi; David D. Awschalom

2014-05-20T23:59:59.000Z

331

Developing a High Thermal Conductivity Fuel with Silicon Carbide Additives  

SciTech Connect (OSTI)

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 1,377C, 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 1,300C:

Ronald baney; James Tulenko

2012-11-20T23:59:59.000Z

332

USE OF SILICON CARBIDE MONITORS IN ATR IRRADIATION TESTING  

SciTech Connect (OSTI)

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 200C and 800C. 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.

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

2012-07-01T23:59:59.000Z

333

Silicon Carbide Photonic Crystal Cavities with Integrated Color Centers  

E-Print Network [OSTI]

The recent discovery of color centers with optically addressable spin states in 3C silicon carbide (SiC) similar to the negatively charged nitrogen vacancy center in diamond has the potential to enable the integration of defect qubits into established wafer scale device architectures for quantum information and sensing applications. Here we demonstrate the design, fabrication, and characterization of photonic crystal cavities in 3C SiC films with incorporated ensembles of color centers and quality factor (Q) to mode volume ratios similar to those achieved in diamond. Simulations show that optimized H1 and L3 structures exhibit Q as high as 45,000 and mode volumes of approximately (\\lambda/n). We utilize the internal color centers as a source of broadband excitation to characterize fabricated structures with resonances tuned to the color center zero phonon line and observe Q in the range of 900-1,500 with narrowband photoluminescence collection enhanced by up to a factor of 10. By comparing the Q factors obser...

Calusine, Greg; Awschalom, David D

2014-01-01T23:59:59.000Z

334

Evaluation of CVD silicon carbide for synchrotron radiation mirrors  

SciTech Connect (OSTI)

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.

Takacs, P.Z.

1981-07-01T23:59:59.000Z

335

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

SciTech Connect (OSTI)

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.

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

336

E-Print Network 3.0 - anaerobic filamentous fungus Sample Search...  

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

filamentous fungus Page: << < 1 2 3 4 5 > >> 1 ANAEROBIC RUMEN FUNGI: POTENTIAL AND APPLICATIONS Summary: . Yarlett et al. (1986) reported cryopreservation of the anaerobic fungus...

337

Dust-acoustic filamentation of a current-driven dusty plasma  

SciTech Connect (OSTI)

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.

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

338

Influence Of Ultrasonic Waves On The Formation Of High Pores Silicon Carbide  

SciTech Connect (OSTI)

The Challenge to produce a quality Silicon Carbide that combination high surface area is promising and this material can be used in many application such as Hydrogen storage materials. Synthesis of high surface area carbon materials by selective etching of Silicon Carbide with choric acid while exposing ultrasonic wave have been made.Powder Of Sic (surface area 17.8 m{sup 2}/g) was treated in the chloric acetic as well as their mixture of various compositions and various time exposure of ultrasonic waves. Surface area and pore size can be controlled by temperature and concentration composition of Chloric and time exposure of ultrasonic wave.The resultant carbon and carbon-silicon carbide composite powders were characterized X-ray diffraction and Electron microscope. To determine a conversion degree of silicon carbide due to influence of the ultrasonic wave, the samples were annealed in open air at 1000 deg. C. There by carbon component of the carbon/silicon carbide composite was completely oxidized. The analysis of the samples shows the strong influence of time exposure of ultrasonic waves on the formation of pores.

Toana, Musfirah C. F. [Physics Dept. University of Tadulako (Indonesia); Soegijono, B.; Hikam, M. [Physics Dept. University of Indonesia (Indonesia)

2009-09-14T23:59:59.000Z

339

Lateral downflows in sunspot penumbral filaments and their temporal evolution  

E-Print Network [OSTI]

We study the temporal evolution of downflows observed at the lateral edges of penumbral filaments in a sunspot located very close to the disk center. Our analysis is based on a sequence of nearly diffraction-limited spectropolarimetric scans of the Fe I 6173 A line taken with the CRISP instrument at the Swedish 1-m Solar Telescope. We compute Dopplergrams from the observed intensity profiles using line bisectors and filter the resulting velocity maps for subsonic oscillations. Lateral downflows appear everywhere in the center-side penumbra as small, weak patches of redshifts next to or along the edges of blueshifted flow channels. These patches have an intermittent life and undergo mergings and fragmentations quite frequently. The lateral downflows move together with the hosting filaments and react to their shape variations, very much resembling the evolution of granular convection in the quiet Sun. There is a good relation between brightness and velocity of the flow structures in the center-side penumbra, wi...

Pozuelo, S Esteban; Rodriguez, J de la Cruz

2015-01-01T23:59:59.000Z

340

Threshold irradiation dose for amorphization of silicon carbide  

SciTech Connect (OSTI)

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.

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

1997-03-01T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

The role of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh vacuum study  

E-Print Network [OSTI]

The role of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh conditions that elucidate the role of oxygen in the functioning of silicon carbide field-effect gas sensors hydrogen-depleted state; competition between hydrogen oxidation and hydrogen diffusion to metal/ oxide

Tobin, Roger G.

342

Materials Science and Engineering A244 (1998) 138144 The vacuum hot pressing behavior of silicon carbide fibers coated  

E-Print Network [OSTI]

carbide fibers coated with nanocrystalline Ti­6Al­4V Joseph M. Kunze *, Haydn N.G. Wadley Intelligent (VHP) of silicon carbide monofilaments coated with nanocrystalline Ti­6Al­4V has been studied. During micromechanical contact analysis for a metal coated fiber. Final stage densification was analyzed by modifying

Wadley, Haydn

343

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

E-Print Network [OSTI]

.V. All rights reserved. 1. Introduction Transition metal carbides (TMCs), typically including all 3 d ele- ments and 4 d/5 d elements of groups 3­6 early transition metals, possess unique physical and chemicalStructural and electronic properties of cobalt carbide Co2C and its surface stability: Density

Li, Weixue

344

Damages induced by heavy ions in titanium silicon carbide: effects of nuclear and electronic interactions at room temperature  

E-Print Network [OSTI]

, of general formula Mn+1AXn where n = {1,2,3}, M is an early transition metal, A is an A-group (mostly IIIADamages induced by heavy ions in titanium silicon carbide: effects of nuclear and electronic Thanks to their refractoriness, carbides are sensed as fuel coating for the IVth generation of reactors

Paris-Sud XI, Université de

345

13C and 15N N.M.R. in thorium carbides and carbonitrides J. L. Boutard (*),  

E-Print Network [OSTI]

) of 8.4 (i.e. ThCo.6No.4). In transition metal carbides and nitrides, a similar but more pronounced in the corresponding transition metal systems since y(ThC) = 2.12 m845 13C and 15N N.M.R. in thorium carbides and carbonitrides J. L. Boutard (*), SFMA, DECPu, Centre

Paris-Sud XI, Université de

346

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

E-Print Network [OSTI]

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

McDonald, Kirk

347

Loss-of-flow transient characterization in carbide-fueled LMFBRs  

SciTech Connect (OSTI)

One of the benefits derived from the use of carbide fuel in advanced Liquid Metal Fast Breeder Reactors (LMFBRs) is a decreased vulnerability to certain accidents. This can be achieved through the combination of advanced fuel performance with the enhanced reactivity feedback effects and passive shutdown cooling systems characteristic of the current 'inherently safe' plant concepts. The calculated core response to an unprotected loss of flow (ULOF) accident has frequently been used as a benchmark test of these designs, and the advantages of a high-conductivity fuel in relation to this type of transient have been noted in previous analyses. To evaluate this benefit in carbide-fueled LMFBRs incorporating representative current plant design features, limited calculations have been made of a ULOF transient in a small ('modular') carbide-fueled LMFBR.

Rothrock, R.B.; Morgan, M.M.; Baars, R.E.; Elson, J.S.; Wray, M.L.

1985-01-01T23:59:59.000Z

348

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

DOE Patents [OSTI]

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.

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

2013-01-22T23:59:59.000Z

349

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

E-Print Network [OSTI]

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.

Vojvodic, Aleksandra

2009-01-01T23:59:59.000Z

350

Fitting of random tessellation models to keratin filament Michael Beil1  

E-Print Network [OSTI]

- 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

Schmidt, Volker

351

RecA-mediated SOS induction requires an extended filament conformation but no ATP hydrolysis  

E-Print Network [OSTI]

RecA-mediated SOS induction requires an extended filament conformation but no ATP hydrolysis filament on single-stranded DNA and hydrolyzes ATP. The RecA K72R (recA2201) muta- tion eliminates in the presence of ATP. Strains with this mutation do not undergo SOS induction in vivo. We have combined the K72R

Cox, Michael M.

352

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

E-Print Network [OSTI]

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...

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

2015-01-01T23:59:59.000Z

353

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

E-Print Network [OSTI]

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

Paris-Sud XI, Universit de

354

Polymerization and Bundling Kinetics of FtsZ Filaments Ganhui Lan,* Alex Dajkovic,y  

E-Print Network [OSTI]

Polymerization and Bundling Kinetics of FtsZ Filaments Ganhui Lan,* Alex Dajkovic,y Denis Wirtz a kinetic model that describes the polymerization and bundling mechanism of FtsZ filaments. The model polymerization kinetics data of another researcher, and explains the cooperativity observed in FtsZ kinetics

Sun, Sean

355

Metallic photonic-band-gap filament architectures for optimized incandescent lighting Sajeev John and Rongzhou Wang  

E-Print Network [OSTI]

Metallic photonic-band-gap filament architectures for optimized incandescent lighting Sajeev John occur 3,4 . Tra- ditionally incandescent lighting filaments, despite being driven from equilibrium the blackbody spectrum. This suggests the pos- sibility of higher efficiency incandescent lighting, through

John, Sajeev

356

Published in 'Silicon Carbide, III-Nitrides and Related Materials', Year: 1998, pp: 829-832 Periodical: Materials Science Forum Vols. 264-268  

E-Print Network [OSTI]

Published in 'Silicon Carbide, III-Nitrides and Related Materials', Year: 1998, pp: 829@scientific.net © 1998 by Trans Tech Publications Ltd., Switzerland, http://www.ttp.net #12;Published in 'Silicon Carbide Publications Ltd., Switzerland, http://www.ttp.net #12;Published in 'Silicon Carbide, III-Nitrides and Related

Steckl, Andrew J.

357

Nuclear Instruments and Methods in Physics Research A 562 (2006) 380388 Modeling solid-state boron carbide low energy neutron detectors  

E-Print Network [OSTI]

carbide low energy neutron detectors C. Lundstedta,b , A. Harkena,c , E. Daya,c , B.W. Robertsona,c , S types of solid-state boron carbide detector. These results provide the basis for distinguishing between-section. At the University of Nebraska, Lincoln (UNL), a semiconducting form of boron carbide has been developed over

358

The formation of PdCx over Pd-based catalysts in vapor-phase vinyl acetate synthesis: does a PdAu alloy catalyst resist carbide formation?  

E-Print Network [OSTI]

­Au alloy catalyst resist carbide formation? Y.-F. Han, D. Kumar, C. Sivadinarayana, A. Clearfield, and D October 2003; accepted 24 February 2004 The formation of Pd carbide (PdCx) during the synthesis of vinyl­Au/SiO2; XRD. 1. Introduction The formation of carbides over supported Pd catalysts was first reported

Goodman, Wayne

359

Formation energy of -carbide using ab initio calculations Seung-Woo Seo, You Young Song, In Gee Kim, H. K. D. H. Bhadeshia  

E-Print Network [OSTI]

Formation energy of -carbide using ab initio calculations Seung-Woo Seo, You Young Song, In Gee Kim(Fe,Mn)3C with an anti-perovskite structure, known as -carbide, is easily found in strong, low is enhanced by the precipitation of -carbide, which is coherent with austenite, causes a shear band induced

Cambridge, University of

360

In vitro cellular responses to silicon carbide particles manufactured through the Acheson process: impact of physico-chemical features on pro-inflammatory and pro-  

E-Print Network [OSTI]

1 In vitro cellular responses to silicon carbide particles manufactured through the Acheson process ROS: Reactive Oxygen Species SiC: Silicon carbide SSA: Specific Surface Area TNF: Tumor Necrosis carbide (SiC) an industrial-scale product manufactured through the Acheson process, is largely employed

Paris-Sud XI, Université de

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Published in 'Silicon Carbide and Related Materials -1999', Year: 2000, pp: 273-276 Periodical: Materials Science Forum Vols. 338-342  

E-Print Network [OSTI]

Published in 'Silicon Carbide and Related Materials - 1999', Year: 2000, pp: 273-276 Periodical@scientific.net © 2000 by Trans Tech Publications Ltd., Switzerland, http://www.ttp.net #12;Published in 'Silicon Carbide., Switzerland, http://www.ttp.net #12;Published in 'Silicon Carbide and Related Materials - 1999', Year: 2000

Steckl, Andrew J.

362

Molecular dynamics simulations of hydrogen bombardment of tungsten carbide surfaces P. Trskelin,1 N. Juslin,1 P. Erhart,2 and K. Nordlund1  

E-Print Network [OSTI]

Molecular dynamics simulations of hydrogen bombardment of tungsten carbide surfaces P. Träskelin,1 and tungsten carbide WC is of interest both due to the use of hydrogen-containing plasmas in thin. INTRODUCTION Tungsten carbide WC exhibits extraordinary hardness and temperature resistance. It has long been

Nordlund, Kai

363

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

E-Print Network [OSTI]

Journal of Physics and Chemistry of Solids 67 (2006) 2512­2516 Crystal chemistry of layered carbide structure of a layered ternary carbide, Ti3(Si0.43Ge0.57)C2, was studied with single-crystal X structure 1. Introduction Layered carbides and nitrides, or the so-called Mn+1AXn (MAX) phases, where n is 1

Downs, Robert T.

364

Electronic and dynamic studies of boron carbide nanowires D. N. McIlroy, Daqing Zhang, Robert M. Cohen, and J. Wharton  

E-Print Network [OSTI]

Electronic and dynamic studies of boron carbide nanowires D. N. McIlroy, Daqing Zhang, Robert M and vibrational properties of boron carbide nanowires grown by plasma-enhanced chemical vapor deposition have been. The NEXAFS spectra are equivalent to corresponding spectra of single-crystal (B4C) boron carbide, consistent

Gilbert, Pupa Gelsomina De Stasio

365

Phosphorus carbides: theory and experiment F. Claeyssens, G. M. Fuge, N. L. Allan, P. W. May and M. N. R. Ashfold  

E-Print Network [OSTI]

Phosphorus carbides: theory and experiment F. Claeyssens, G. M. Fuge, N. L. Allan, P. W. May and M ratios 3 has served to trigger further research into new `phosphorus carbide' materials. Theoretical) The electronic structure and stability of different crystalline phosphorus carbide PxCy phases have been studied

Bristol, University of

366

Published in 'Silicon Carbide, III-Nitrides and Related Materials', Year: 1998, pp: 1149-1152 Periodical: Materials Science Forum Vols. 264-268  

E-Print Network [OSTI]

Published in 'Silicon Carbide, III-Nitrides and Related Materials', Year: 1998, pp: 1149@scientific.net © 1998 by Trans Tech Publications Ltd., Switzerland, http://www.ttp.net #12;Published in 'Silicon Carbide Publications Ltd., Switzerland, http://www.ttp.net #12;Published in 'Silicon Carbide, III-Nitrides and Related

Steckl, Andrew J.

367

ELSEVIER Joumal of Organometallic Chemistry 520 (1996) 227-230 The Union Carbide catalyst(Cp Cr + SiO2),  

E-Print Network [OSTI]

ELSEVIER Joumal of Organometallic Chemistry 520 (1996) 227- 230 o oumal Chemistry The Union Carbide-chemisches lnstitutder TUMfinchen,85747Garching,Germany Received 27 February 1996 Abstract The Union Carbide catalyst characteristics. Keywords: Solid-state NMR spectroscopy; Union Carbide catalyst; Chromium; Chromocenes

Bluemel, Janet

368

Solid phosphorus carbide? Frederik Claeyssens,a Neil L. Allan,*a Paul W. May,a Pablo Ordejnb and Josep M. Olivab  

E-Print Network [OSTI]

Solid phosphorus carbide? Frederik Claeyssens,a Neil L. Allan,*a Paul W. May,a Pablo Ordejónb The electronic structure of different phosphorus carbide solid phases with stoichiometry P4C3 is studied using these films `doped DLC'--instead, they have been termed `amorphous phosphorus carbide'. For many semiconductor

Bristol, University of

369

Carbide-Derived Nanoporous Carbon and Novel Core-Shell Xinqi Chen, Donald R. Cantrell, Kevin Kohlhaas, Sasha Stankovich, James A. Ibers,  

E-Print Network [OSTI]

of metal carbides by halogens. In this process, metal is extracted preferentially by the halogenCarbide-Derived Nanoporous Carbon and Novel Core-Shell Nanowires Xinqi Chen, Donald R. Cantrell, 2005. ReVised Manuscript ReceiVed NoVember 29, 2005 Carbide-derived carbon (CDC) nanowires (NWs) have

370

The near-edge structure in energy-loss spectroscopy: many-electron and magnetic effects in transition metal nitrides and carbides  

E-Print Network [OSTI]

in transition metal nitrides and carbides This article has been downloaded from IOPscience. Please scroll down-loss spectroscopy: many-electron and magnetic effects in transition metal nitrides and carbides A T Paxton, M van energies are systematically overestimated by 4.22 ± 0.44 eV in twelve transition metal carbides

Paxton, Anthony T.

371

Electronic structure of the 4d transition metal carbides: Dispersed fluorescence spectroscopy of MoC, RuC, and PdC  

E-Print Network [OSTI]

Electronic structure of the 4d transition metal carbides: Dispersed fluorescence spectroscopy of Mo transition metal carbides is also provided. © 2001 American Institute of Physics. DOI: 10.1063/1.1316042 I, and astrochemistry. Within the 4d se- ries, the diatomic transition metal carbides have aroused considerable interest

Morse, Michael D.

372

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]

remarkable physical proper- ties, cubic rocksalt transition metal carbides present a large domain of substoichiometric titanium carbide TiC1-x V. Moisy-Maurice and C. H. de Novion C.E.A./IRDI/DMECN/DTech, Laboratoire concentration on the bulk physical properties of the carbides has been extensively studied [2] ; but a detailed

Paris-Sud XI, Université de

373

Role of ATP-hydrolysis in the dynamics of a single actin filament  

E-Print Network [OSTI]

We study the stochastic dynamics of growth and shrinkage of single actin filaments taking into account insertion, removal, and ATP hydrolysis of subunits either according to the vectorial mechanism or to the random mechanism. In a previous work, we developed a model for a single actin or microtubule filament where hydrolysis occurred according to the vectorial mechanism: the filament could grow only from one end, and was in contact with a reservoir of monomers. Here we extend this approach in several ways, by including the dynamics of both ends and by comparing two possible mechanisms of ATP hydrolysis. Our emphasis is mainly on two possible limiting models for the mechanism of hydrolysis within a single filament, namely the vectorial or the random model. We propose a set of experiments to test the nature of the precise mechanism of hydrolysis within actin filaments.

Padinhateeri Ranjith; Kirone Mallick; Jean-Francois Joanny; David Lacoste

2010-01-07T23:59:59.000Z

374

Autonomous Motility of Active Filaments due to Spontaneous Flow-Symmetry Breaking  

E-Print Network [OSTI]

We simulate the nonlocal Stokesian hydrodynamics of an elastic filament which is active due a permanent distribution of stresslets along its contour. A bending instability of an initially straight filament spontaneously breaks flow symmetry and leads to autonomous filament motion which, depending on conformational symmetry, can be translational or rotational. At high ratios of activity to elasticity, the linear instability develops into nonlinear fluctuating states with large amplitude deformations. The dynamics of these states can be qualitatively understood as a superposition of translational and rotational motion associated with filament conformational modes of opposite symmetry. Our results can be tested in molecular-motor filament mixtures, synthetic chains of autocatalytic particles, or other linearly connected systems where chemical energy is converted to mechanical energy in a fluid environment.

Gayathri Jayaraman; Sanoop Ramachandran; Somdeb Ghose; Abhrajit Laskar; M. Saad Bhamla; P. B. Sunil Kumar; R. Adhikari

2012-10-10T23:59:59.000Z

375

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

SciTech Connect (OSTI)

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.

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

1996-12-31T23:59:59.000Z

376

Design and Testing of a Boron Carbide Capsule for Spectral Tailoring in Mixed-Spectrum Reactors  

SciTech Connect (OSTI)

A boron carbide capsule has been designed and used for spectral-tailoring experiments at the TRIGA reactor at Washington State University. Irradiations were conducted in pulsed mode and in continuous operation for up to 4 hours. A cadmium cover was used to reduce thermal heating. The neutron spectrum calculated with MCNP was found to be in good agreement with reactor dosimetry measurements using the STAY'SL computer code. The neutron spectrum resembles that of a fast reactor. Design of a capsule using boron carbide enriched in {sup 10}B shows that it is possible to produce a neutron spectrum similar to {sup 235}U fission.

Greenwood, Lawrence R.; Wittman, Richard S.; Pierson, Bruce D.; Metz, Lori A.; Payne, Rosara F.; Finn, Erin C.; Friese, Judah I.

2012-03-01T23:59:59.000Z

377

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

DOE Patents [OSTI]

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

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

1988-01-01T23:59:59.000Z

378

Influence of interface compounds on interface bonding characteristics of aluminium and silicon carbide  

SciTech Connect (OSTI)

The interface plays an important role in improving the mechanical properties of metal matrix composites. Hence, it is essential to evaluate interface bonding of Aluminium/Silicon carbide. The interface bonding of Aluminum/Silicon carbide samples were prepared by various processing temperatures at constant holding time. The interface compounds at the interface were evaluated by an energy dispersive spectroscope and diffusion length of compounds was calculated by Arrhenius equation. The interface structure was analyzed by a scanning electron microscope. The interface characteristics were evaluated by tensile test and microhardness test.

Sozhamannan, G.G., E-mail: sozhan30@yahoo.co.in [Department of Mechanical Engineering, College of Engineering, Anna University Chennai, Chennai-600025 (India); Prabu, S. Balasivanandha [Department of Mechanical Engineering, College of Engineering, Anna University Chennai, Chennai-600025 (India)

2009-09-15T23:59:59.000Z

379

Diffusion and impurity segregation in hydrogen-implanted silicon carbide  

SciTech Connect (OSTI)

Diffusion and segregation behavior of hydrogen and oxygen in silicon carbide subjected to H implantation and subsequent annealing were studied with a number of analytical techniques including Secondary Ion Mass Spectrometry (SIMS), Rutherford backscattering spectrometry in channeling geometry, field emission scanning electron microscopy, optical microscopy, cross-sectional transmission electron microscopy, and atomic force microscopy. H{sup +} implantation was carried out with energies of 200?keV, 500?keV, or 1?MeV to doses of 1??10{sup 16}, 1??10{sup 17}, or 2??10{sup 17} ion/cm{sup 2}, and thermal treatment was conducted in flowing argon for 1 to 2 h at temperatures of 740, 780, 1000, or 1100?C. The process of migration and eventual loss of hydrogen in a point defect regime is postulated to proceed to a large extent through ionized vacancies. This conclusion was derived from the observed substantial difference in H mobilities in n- vs. p-type SiC as the population of ionized vacancies is governed by the Fermi-Dirac statistics, i.e., the position of the Fermi level. For higher doses, a well defined buried planar zone forms in SiC at the maximum of deposited energy, comprising numerous microvoids and platelets that are trapping sites for hydrogen atoms. At a certain temperature, a more or less complete exfoliation of the implanted layer is observed. For a 1?MeV implant heated to 1100?C in nominally pure argon, SIMS profiling reveals a considerable oxygen peak of 10{sup 16} O atoms/cm{sup 2} situated at a depth close to that of the peak of the implanted H{sup +}. Similarly, 1100?C annealing of a 200?keV implant induces the formation of a thin oxide (4?nm), located at the interface between the implanted layer and the substrate as evidenced by both SIMS and HRTEM. The measurements were taken on the part of the sample that remained un-exfoliated. In view of a lack of convincing evidence that a hexagonal SiC might contain substantial amounts of oxygen, further investigation is under way to elucidate its presence in the irradiation-damaged films.

Barcz, A., E-mail: barcz@ite.waw.pl [Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Kozubal, M.; Ratajczak, J.; Go?aszewska, K. [Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Jakie?a, R.; Dyczewski, J.; Wojciechowski, T. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Celler, G. K. [Institute for Advanced Materials, Devices, and Nanotechnology (IAMDN)/Department of Materials Science and Engineering, Rutgers University, New Brunswick, New Jersey 08901 (United States)

2014-06-14T23:59:59.000Z

380

Dry soldering with hot filament produced atomic hydrogen  

DOE Patents [OSTI]

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.

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

1995-04-25T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Inertial blob-hole symmetry breaking in magnetised plasma filaments  

E-Print Network [OSTI]

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.

Kendl, Alexander

2015-01-01T23:59:59.000Z

382

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

E-Print Network [OSTI]

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

Bristol, University of

383

High Metallicity, Photoionised Gas in Intergalactic Large-Scale Filaments  

E-Print Network [OSTI]

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).

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

2006-08-21T23:59:59.000Z

384

Force generation by Myosin II Filaments in Compliant Networks  

E-Print Network [OSTI]

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.

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

2014-07-08T23:59:59.000Z

385

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)

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.

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

386

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

SciTech Connect (OSTI)

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.

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

387

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

SciTech Connect (OSTI)

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

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

2011-01-01T23:59:59.000Z

388

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

E-Print Network [OSTI]

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.

American Society for Testing and Materials. Philadelphia

2005-01-01T23:59:59.000Z

389

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

E-Print Network [OSTI]

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

Wooldridge, Margaret S.

390

Mechanical properties of WC10Co cemented carbides sintered from nanocrystalline spray conversion processed powders  

E-Print Network [OSTI]

Mechanical properties of WC±10Co cemented carbides sintered from nanocrystalline spray conversion as the spray conversion process [2]. The WC particle sizes in powders fabricated by the spray conversion: microstructural parameters such as WC grain size, Co mean free path and WC/WC contiguity; chemical factors

Hong, Soon Hyung

391

Characterizations of WC-10Co nanocomposite powders and subsequently sinterhip sintered cemented carbide  

SciTech Connect (OSTI)

Ultrafine WC-Co cemented carbides, combining high hardness and high toughness, are expected to find broad applications. In this study, WC-10Co-0.4VC-0.4Cr{sub 3}C{sub 2} (wt.%) nanocomposite powders, whose average grain size was about 30 nm, were fabricated by spray pyrolysis-continuous reduction and carbonization technology. The as-prepared nanocomposite powders were characterized and analyzed by chemical methods, scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET analysis and atomic force microscopy (AFM). Furthermore, 'sinterhip' was used in the sintering process, by which ultrafine WC-10Co cemented carbides with an average grain size of 240 nm were prepared. The material exhibited high Rockwell A hardness of HRA 92.8, Vickers hardness HV{sub 1} 1918, and transverse rapture strength (TRS) of 3780 MPa. The homogeneously dispersed grain growth inhibitors such as VC, Cr{sub 3}C{sub 2} in nanocomposite powder and the special nonmetal-metal nanocomposite structure of WC-10Co nanocomposite powder played very important roles in obtaining ultrafine WC-10Co cemented carbide with the desired properties and microstructure. There was an abundance of triple junctions in the ultrafine WC-10Co cemented carbide; these triple junctions endowed the sintered specimen with high mechanical properties.

Shi, X.L. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 122Luoshi Road, Wuhan 430070 (China)]. E-mail: sxl071932@126.com; Shao, G.Q. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 122Luoshi Road, Wuhan 430070 (China); Duan, X.L. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 122Luoshi Road, Wuhan 430070 (China); Xiong, Z. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 122Luoshi Road, Wuhan 430070 (China); Yang, H. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 122Luoshi Road, Wuhan 430070 (China)

2006-12-15T23:59:59.000Z

392

A Model of Gas-Phase Transport During the Initial Stages of Sintering of Silicon Carbide  

E-Print Network [OSTI]

A Model of Gas-Phase Transport During the Initial Stages of Sintering of Silicon Carbide Anil Kaza investigate this process using a computational model based on codiffusion of multiple gas species, which This paper describes a computational model that tracks diffu- sion of multiple gas species and so predicts

Matthewson, M. John

393

Thin Film Solid-State Reactions Forming Carbides as Contact Materials for Carbon-Containing Semiconductors  

SciTech Connect (OSTI)

Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin films. The solid-state reaction was examined between 11 transition metals (W, Mo, Fe, Cr, V, Nb, Mn, Ti, Ta, Zr, and Hf) and an amorphous carbon layer. Capping layers (C or TiN) of different thicknesses were applied to prevent oxidation. Carbide formation is evidenced for nine metals and the phases formed have been identified (for a temperature ranging from 100 to 1100 C). W first forms W{sub 2}C and then WC; Mo forms Mo{sub 2}C; Fe forms Fe{sub 3}C; Cr first forms metastable phases Cr{sub 2}C and Cr{sub 3}C{sub 2-x}, and finally forms Cr{sub 3}C{sub 2}; V forms VC{sub x}; Nb transforms into Nb{sub 2}C followed by NbC; Ti forms TiC; Ta first forms Ta{sub 2}C and then TaC; and Hf transforms into HfC. The activation energy for the formation of the various carbide phases has been obtained by in situ x-ray diffraction.

Leroy,W.; Detavernier, C.; Van Meirhaeghe, R.; Lavoie, C.

2007-01-01T23:59:59.000Z

394

Ternary rare earth and actinoid transition metal carbides viewed as carbometalates  

SciTech Connect (OSTI)

Ternary carbides A{sub x}T{sub y}C{sub z} (A=rare earth metals and actinoids; T=transition metals) with monoatomic species C{sup 4-} as structural entities are classified according to the criteria (i) metal to carbon ratio, (ii) coordination number of the transition metal by carbon atoms, and (iii) the dimensionality of the anionic network [T{sub y}C{sub z}]{sup n-}. Two groups are clearly distinguishable, depending on the metal to carbon ratio. Those where this ratio is equal to or smaller than 2 may be viewed as carbometalates, thus extending the sequence of complex anions from fluoro-, oxo-, and nitridometalates to carbometalates. The second group, metal-rich carbides with metal to carbon ratios equal to or larger than 4 is better viewed as typical intermetallics (''interstitial carbides''). The chemical bonding properties have been investigated by analyzing the Crystal Orbital Hamilton Population (COHP). The chemical bonding situation with respect to individual T-C bonds is similar in both classes. The main difference is the larger number of metal-metal bonds in the crystal structures of the metal-rich carbides.

Dashjav, Enkhtsetseg [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, D-01187 Dresden (Germany); Kreiner, Guido [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, D-01187 Dresden (Germany); Schnelle, Walter [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, D-01187 Dresden (Germany); Wagner, Frank R. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, D-01187 Dresden (Germany); Kniep, Ruediger [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Strasse 40, D-01187 Dresden (Germany)], E-mail: Kniep@cpfs.mpg.de; Jeitschko, Wolfgang [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Wilhelm-Klemm-Strasse 8, D-48149 Muenster (Germany)], E-mail: jeitsch@uni-muenster.de

2007-02-15T23:59:59.000Z

395

Catalytic hydrodenitrogenation of indole over molybdenum nitride and carbides with different structures  

E-Print Network [OSTI]

-derived feedstocks, is one of the hydropuri®- cation processes in the oil re®nery industry. These hydrotreating as commercial hydrotreating catalysts for more than 40 years. In recent years, however, these catalysts and carbides are superior to or compar- able to commercial hydrotreating catalysts. Recently Suslick et al. [11

Suslick, Kenneth S.

396

On the development of ice-templated silicon carbide scaffolds for nature-inspired structural materials  

E-Print Network [OSTI]

received most interest as a means to produce porous scaffolds by using ice as a template for complexOn the development of ice-templated silicon carbide scaffolds for nature-inspired structural of ceramic scaffolds using the ice-templating, or freeze casting, technique provides a relatively simple

Ritchie, Robert

397

Sulfur surface chemistry on the platinum gate of a silicon carbide based hydrogen sensor  

E-Print Network [OSTI]

monitoring, solid-oxide fuel cells, and coal gasification, require operation at much higher temperatures thanSulfur surface chemistry on the platinum gate of a silicon carbide based hydrogen sensor Yung Ho to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20­600 times greater

Tobin, Roger G.

398

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

SciTech Connect (OSTI)

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.

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

399

Transport study of hafnium(IV) and zirconium(IV) ions mutual separation by using Tri-n-butyl phosphate-xylene-based supported liquid membranes  

SciTech Connect (OSTI)

A Hf transport study through supported liquid membranes has been carried out to determine flux and permeability data for this metal ion. Tri-n-butyl phosphate (TBP)-xylene-based liquid membranes supported in polypropylene hydrophobic microporous film have been used. These data for hafnium and the previous data for zirconium have furnished the Zr to Hf flux ratio (S) as a function of nitric acid and TBP concentrations of the order of 12 in a single stage at room temperature. Optimum conditions for the separation of these two metal ions appear to 5-6 TBP mol/dm{sup 3} HNO{sub 3}, concentrations {le} 2.93 mol/dm{sup 3}, and 10C. The value of S from an aqueous solution containing 2.4% Hf with respect to Zr has been found to be >125 at 10C and 1.78 mol/dm{sup 3} TBP concentration in the membrane. The technique appears to be feasible for purification of Zr respect to Hf or vice versa.

Chaudry, M.A.; Ahmed, B. (Pakistan Inst. of Nuclear Science and Technology, Islamabad (Pakistan))

1992-02-01T23:59:59.000Z

400

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

SciTech Connect (OSTI)

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.

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

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

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

SciTech Connect (OSTI)

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

Xia Xiongping; Yi Lin [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Xu Bin [Department of Mathematics and Information Sciences, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou 450011 (China); Lu Jianduo [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Hubei Province Key Laboratory of Systems Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan 430081 (China)

2011-10-15T23:59:59.000Z

402

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

E-Print Network [OSTI]

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.

Paul Martini; K. Sellgren; Joseph L. Hora

1997-02-11T23:59:59.000Z

403

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

SciTech Connect (OSTI)

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

Li, Wentao; Liu, Jiansheng; Wang, Wentao; Chen, Qiang; Zhang, Hui; Tian, Ye; Zhang, Zhijun; Qi, Rong; Wang, Cheng; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)] [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2013-11-15T23:59:59.000Z

404

E-Print Network 3.0 - actin filaments evidence Sample Search...  

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

search results for: actin filaments evidence Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

405

E-Print Network 3.0 - actin filament dynamics Sample Search Results  

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

Sample search results for: actin filament dynamics Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

406

E-Print Network 3.0 - actin based filaments Sample Search Results  

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

Sample search results for: actin based filaments Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

407

E-Print Network 3.0 - actin filament elongation Sample Search...  

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search results for: actin filament elongation Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

408

E-Print Network 3.0 - actin filament assembly Sample Search Results  

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

search results for: actin filament assembly Page: << < 1 2 3 4 5 > >> 1 R728 Current Biology Vol 10 No 20 Cellular regulation of Summary: assembly and disassembly of a network of...

409

E-Print Network 3.0 - actin filament modeling Sample Search Results  

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

Sample search results for: actin filament modeling Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

410

E-Print Network 3.0 - actin filament formation Sample Search...  

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

search results for: actin filament formation Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

411

E-Print Network 3.0 - actin filament labels Sample Search Results  

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

Sample search results for: actin filament labels Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

412

E-Print Network 3.0 - actin filament organization Sample Search...  

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

search results for: actin filament organization Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

413

E-Print Network 3.0 - actin filament nucleation Sample Search...  

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

search results for: actin filament nucleation Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

414

E-Print Network 3.0 - actin filament networks Sample Search Results  

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

Sample search results for: actin filament networks Page: << < 1 2 3 4 5 > >> 1 Current Biology 16, 19241930, October 10, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016...

415

Real-Time Measurements of Actin Filament Polymerization by Total Internal Reflection Fluorescence Microscopy  

E-Print Network [OSTI]

Real-Time Measurements of Actin Filament Polymerization by Total Internal Reflection Fluorescence polymerization and its regulation by associated proteins requires an assay to monitor polymerization dynamics nucleotide. INTRODUCTION Actin polymerization contributes to many cellular processes under the control

416

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

E-Print Network [OSTI]

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

Martn-Sols, Jos Ramn

417

Filaments, Collapse and Outflows in Massive Star Formation  

E-Print Network [OSTI]

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.

Robi Banerjee; Ralph E. Pudritz

2008-07-04T23:59:59.000Z

418

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

SciTech Connect (OSTI)

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.

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

419

HUBBLE SPACE TELESCOPE OBSERVATIONS OF DUSTY FILAMENTS IN HERCULES A: EVIDENCE FOR ENTRAINMENT  

SciTech Connect (OSTI)

We present U-, V-, and I-band images of the host galaxy of Hercules A (3C 348) obtained with HST/WFC3/UVIS. We find a network of dusty filaments which are more complex and extended than seen in earlier Hubble Space Telescope (HST) observations. The filaments are associated with a faint blue continuum light (possibly from young stars) and faint H{alpha} emission. It seems likely that the cold gas and dust has been stripped from a companion galaxy now seen as a secondary nucleus. There are dusty filaments aligned with the base of the jets on both eastern and western sides of the galaxy. The morphology of the filaments is different on the two sides-the western filaments are fairly straight, while the eastern filaments are mainly in two loop-like structures. We suggest that despite the difference in morphologies, both sets of filaments have been entrained in a slow-moving boundary layer outside the relativistic flow. As suggested by Fabian et al., magnetic fields in the filaments may stabilize them against disruption. We consider a speculative scenario to explain the relation between the radio source and the shock and cavities in the hot intracluster medium seen in the Chandra data. We suggest that the radio source originally ({approx}60 Myr ago) propagated along a position angle of {approx}35 Degree-Sign where it created the shock and cavities. The radio source axis changed to its current orientation ({approx}100 Degree-Sign ) possibly due to a supermassive black hole merger and began its current epoch of activity about 20 Myr ago.

O'Dea, C. P.; Kharb, P. [School of Physics and Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 84 Lomb Memorial Dr., Rochester, NY 14623 (United States); Baum, S. A. [Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, 84 Lomb Memorial Dr., Rochester, NY 14623 (United States); Tremblay, G. R. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Muenchen (Germany); Cotton, W. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Perley, R. [National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States)

2013-07-01T23:59:59.000Z

420

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

SciTech Connect (OSTI)

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.

DellaCorte, C.; Sliney, H.E.

1986-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Fine-scale structures and material flows of quiescent filaments observed by New Vacuum Solar Telescope  

E-Print Network [OSTI]

Study on the small-scale structures and material flows of solar quiescent filaments is very important for understanding the formation and equilibrium of solar filaments. Using the high resolution H{\\alpha} data observed by the New Vacuum Solar Telescope (NVST), we present the structures of the barbs and the material flows along the threads across the spine in two quiescent filaments on 2013 September 29 and on 2012 November 2, respectively. During the evolution of the filament barb, several parallel tube-shaped structures formed and the width of the structures ranges from about 2.3 Mm to 3.3 Mm. The parallel tube-shaped structures merged together accompanied with the material flows from the spine to the barb. Moreover, the boundary between the barb and surrounding atmosphere is very neat. The counter-streaming flows were not found to appear alternately in the adjacent threads of the filament. However, the large-scale patchy counter-streaming flows are detected in the filament. The flows in one patch of the fi...

Yan, X L; Xiang, Y Y; Yang, L H

2015-01-01T23:59:59.000Z

422

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

E-Print Network [OSTI]

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...

Anathpindika, S

2015-01-01T23:59:59.000Z

423

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

SciTech Connect (OSTI)

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.

Salas, E.; Jimnez Riobo, R. J.; Jimnez-Villacorta, F.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientficas, Cantoblanco, 28049 Madrid (Spain)] [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientficas, Cantoblanco, 28049 Madrid (Spain); Snchez-Marcos, J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientficas, Cantoblanco, 28049 Madrid (Spain) [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientficas, Cantoblanco, 28049 Madrid (Spain); Dept. Qumica-Fsica Aplicada, Universidad Autnoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Muoz-Martn, A.; Prieto, J. E.; Joco, V. [Centro de Microanlisis de Materiales, Universidad Autnoma de Madrid, Cantoblanco, 28049 Madrid (Spain)] [Centro de Microanlisis de Materiales, Universidad Autnoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

2013-12-07T23:59:59.000Z

424

Effect of liquid phase composition on the microstructure and properties of (W,Ti)C cemented carbide cutting tools  

E-Print Network [OSTI]

comprises metal carbides (2­10 vol%), such as VC, ZrC, NbC, TaC, TiC, SiC, Cr3C2, and ThC2; this constituent, which controls the grain size and en- hance the metal carbides formations, is used to decrease the rate of refractory transition metals such as titanium. However, when alloying is attempted, the solid solubili- ties

Hong, Soon Hyung

425

Gelcasting of CRYSTAR{reg_sign} silicon carbide ceramics. CRADA final report  

SciTech Connect (OSTI)

This Cooperative Research and Development Agreement (CRADA) was undertaken to assess the applicability the gelcasting process for forming ceramic green bodies using Saint-Gobain/Norton Industrial Ceramics Corporation`s proprietary CRYSTAR{reg_sign} silicon carbide powder. A gelcasting process, specifically tailored to Saint-Gobain/Norton`s powder composition, was developed and used successfully to form green bodies for property evaluation. This preliminary evaluation showed that the gelcast material had characteristics and properties comparable to Norton`s baseline material. Wafer carrier molds were received from Norton for gelcasting a complex-shaped configuration with CRYSTAR{reg_sign} silicon carbide. Gelcasting experiments showed that Norton`s standard plaster of paris molds were incompatible with the gelcasting process. Mold surface treatments and the use of alternative castable mold materials were investigated, however, a successful process was not identified. The highest quality parts were cast in either glass or aluminum molds.

Nunn, S.D.; Willkens, C.A.

1998-12-31T23:59:59.000Z

426

Nonlinear-optical and structural properties of nanocrystalline silicon carbide films  

SciTech Connect (OSTI)

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.

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

427

Neutron-Rich Isotope Production Using a Uranium Carbide Carbon Nanotubes SPES Target Prototype  

SciTech Connect (OSTI)

The SPES (Selective Production of Exotic Species) project, under development at the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro (INFN-LNL), is a new-generation Isotope Separation On-Line (ISOL) facility for the production of radioactive ion beams by means of the proton-induced fission of uranium. In the framework of the research on the SPES target, seven uranium carbide discs, obtained by reacting uranium oxide with graphite and carbon nanotubes, were irradiated with protons at the Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory (ORNL). In the following, the yields of several fission products obtained during the experiment are presented and discussed. The experimental results are then compared to those obtained using a standard uranium carbide target. The reported data highlights the capability of the new type of SPES target to produce and release isotopes of interest for the nuclear physics community.

Corradetti, Stefano [ORNL; Biasetto, Lisa [INFN, Laboratori Nazionali di Legnaro, Italy; Manzolaro, Mattia [INFN, Laboratori Nazionali di Legnaro, Italy; Scarpa, Daniele [ORNL; Carturan, S. [INFN, Laboratori Nazionali di Legnaro, Italy; Andrighetto, Alberto [INFN, Laboratori Nazionali di Legnaro, Italy; Prete, Gianfranco [ORNL; Vasquez, Jose L [ORNL; Zanonato, P. [Dipartimento di Scienze Chimiche, Padova, Italy; Colombo, P. [Dipartimento di Ingegneria Meccanica, Padova, Italy; Jost, Carola [University of Tennessee, Knoxville (UTK); Stracener, Daniel W [ORNL

2013-01-01T23:59:59.000Z

428

Fischer-Tropsch Synthesis: Characterization and Reaction Testing of Cobalt Carbide  

SciTech Connect (OSTI)

Hydrogenation of carbon monoxide was investigated for cobalt carbide synthesized from Co{sub 3}O{sub 4} by CO carburization in a fixed-bed reactor. The cobalt carbide synthesized was characterized by BET surface area, X-ray diffraction, scanning electron microscopy, X-ray absorption near edge spectroscopy, and extended X-ray absorption fine structure spectroscopy. The catalysts were tested in the slurry phase using a continuously stirred tank reactor at P = 2.0 MPa, H{sub 2}/CO = 2:1 in the temperature range of 493-523 K, and with space velocities varying from 1 to 3 Nl h{sup -1} g{sub cat}{sup -1}. The results strongly suggest that a fraction of cobalt converts to a form with greater metallic character under the conditions employed. This was more pronounced on a Fischer-Tropsch synthesis run conducted at a higher temperature (523 versus 493 K).

Khalid S.; Mohandas J.C.; Gnanamani M.K.; Jacobs G.; Ma W.; Ji Y.; Davis B.H.

2011-08-15T23:59:59.000Z

429

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

SciTech Connect (OSTI)

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.

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

430

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

SciTech Connect (OSTI)

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.

Richter, Janusz

2003-06-15T23:59:59.000Z

431

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

E-Print Network [OSTI]

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.

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

2013-11-30T23:59:59.000Z

432

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

SciTech Connect (OSTI)

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

Koyanagi, Takaaki [ORNL; Shimoda, Kazuya [Kyoto University, Japan; Kondo, Sosuke [Kyoto University, Japan; Hinoki, Tatsuya [Kyoto University, Japan; Ozawa, Kazumi [ORNL; Katoh, Yutai [ORNL

2014-01-01T23:59:59.000Z

433

Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target  

SciTech Connect (OSTI)

Hafnium oxide (HfO?) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO? ceramic target has been employed for sputtering while varying the Ts from room temperature to 500?C during deposition. The effect of Ts on the growth and microstructure of deposited HfO? films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO? films. Structural characterization indicates that the HfO? films grown at Ts<200 ?C are amorphous while films grown at Ts>200 ?C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ?C. Nanocrystalline HfO? films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO? films. An interface layer (IL) formation occurs due to reaction at the HfO?-Si interface for HfO? films deposited at Ts>200 ?C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO?-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.

Aguirre, B.; Vemuri, R. S.; Zubia, David; Engelhard, Mark H.; Shutthanandan, V.; Kamala Bharathi, K.; Ramana, Chintalapalle V.

2011-01-01T23:59:59.000Z

434

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

DOE Patents [OSTI]

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.

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

1991-02-19T23:59:59.000Z

435

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

DOE Patents [OSTI]

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.

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

1991-01-01T23:59:59.000Z

436

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

E-Print Network [OSTI]

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.

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

2002-05-24T23:59:59.000Z

437

Effect of phosphorus on cleavage fracture in -carbide N. I. Medvedeva,1,2 R. A. Howell,2 D. C. Van Aken,2 and J. E. Medvedeva2  

E-Print Network [OSTI]

Effect of phosphorus on cleavage fracture in -carbide N. I. Medvedeva,1,2 R. A. Howell,2 D. C. Van of the phosphorus effect on ideal cleavage energy and critical stress in -carbide, Fe3AlC, a precipitate the cleavage characteristics of -carbide. We show that strong anisotropy of the Fe-P bonds in Fe3 Al,P C under

Medvedeva, Julia E.

438

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

SciTech Connect (OSTI)

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.

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

439

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

E-Print Network [OSTI]

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 ...

Liang, Biqing

440

THE SPIN AND ORIENTATION OF DARK MATTER HALOS WITHIN COSMIC FILAMENTS  

SciTech Connect (OSTI)

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

Zhang Youcai; Yang Xiaohu; Lin Weipeng [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Partner Group of MPA, Nandan Road 80, Shanghai 200030 (China); Faltenbacher, Andreas; Springel, Volker [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Strasse 1, 85748 Garching (Germany); Wang Huiyuan, E-mail: yczhang@shao.ac.c [Key Laboratory for Research in Galaxies and Cosmology, Center for Astrophysics, University of Science and Technology of China, 230026 (China)

2009-11-20T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

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

SciTech Connect (OSTI)

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

H. radulescu

2001-09-28T23:59:59.000Z

442

An Excursion Set Model of the Cosmic Web: the Abundance of Sheets, Filaments And Halos  

SciTech Connect (OSTI)

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 mass in sheets, and 72% of the mass in filaments, is stored in objects more massive than 10{sup 10}M{sub {circle_dot}} 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.

Shen, Jiajian; /Penn State U., Astron. Astrophys.; Abel, Tom; /KIPAC, Menlo Park; Mo, Houjun; /Massachusetts U., Amherst; Sheth, Ravi; /Pennsylvania U.

2006-01-11T23:59:59.000Z

443

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

E-Print Network [OSTI]

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.

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

2006-03-27T23:59:59.000Z

444

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

DOE Patents [OSTI]

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.

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

1994-01-01T23:59:59.000Z

445

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

DOE Patents [OSTI]

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.

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

1994-10-18T23:59:59.000Z

446

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

SciTech Connect (OSTI)

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

Naranjo-Romero, Raul; Zapata, Luis A.; Vazquez-Semadeni, Enrique [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Morelia 58090 (Mexico); Takahashi, Satoko [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Palau, Aina [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB-Facultat de Ciencies, Torre C5-parell 2, E-08193 Bellaterra (Spain); Schilke, Peter [I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Strasse 77, D-50937 Koeln (Germany)

2012-09-20T23:59:59.000Z

447

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

SciTech Connect (OSTI)

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.

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

448

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

SciTech Connect (OSTI)

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.

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

449

Stabilization of the filamentation instability and the anisotropy of the background plasma  

SciTech Connect (OSTI)

The interaction of a relativistic electron beam with an anisotropic Maxwellian plasma is investigated, with a focus on the stabilization condition for the filamentation instability. It is found that this condition is very sensitive to the anisotropy degree of the background plasma so that the investigation of the beam instability may not be easily decoupled from the state of the background plasma in typical fusion conditions. Furthermore, regardless of the plasma isotropy, filamentation can no longer be suppressed when the beam density exceeds a threshold value that is determined.

Bret, A.; Deutsch, C. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Laboratoire de Physique des Gaz et des Plasmas (CNRS-UMR 8578), Universite Paris XI, Batiment 210, 91405 Orsay cedex (France)

2006-02-15T23:59:59.000Z

450

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

SciTech Connect (OSTI)

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.

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

451

Observations of the filamentation of high-intensity laser-produced electron beams  

SciTech Connect (OSTI)

Filamented electron beams have been observed to be emitted from the rear of thin solid targets irradiated by a high-intensity short-pulse laser when there is low-density plasma present at the back of the target. These observations are consistent with a laser-generated beam of relativistic electrons propagating through the target, which is subsequently fragmented by a Weibel-like instability in the low-density plasma at the rear. These measurements are in agreement with particle-in-cell simulations and theory, since the filamentation instability is predicted to be dramatically enhanced when the electron beam density approaches that of the background plasma.

Wei, M.S.; Beg, F.N.; Dangor, A.E.; Gopal, A.; Tatarakis, M.; Krushelnick, K. [Blackett Laboratory, Imperial College London SW7 2BZ (United Kingdom); Clark, E.L.; Evans, R.G. [Blackett Laboratory, Imperial College London SW7 2BZ (United Kingdom); Plasma Physics Department, AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom); Ledingham, K.W.D. [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Plasma Physics Department, AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom); McKenna, P. [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Norreys, P.A. [Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 OQX (United Kingdom); Zepf, M. [Department of Physics, The Queen's University, University Road, Belfast BT7 1NN (United Kingdom)

2004-11-01T23:59:59.000Z

452

genBRDF: Synthesizing Novel Analytic BRDFs with Genetic Programming Figure 1: Comparison of BRDFs modeling the tungsten carbide material from the MERL BRDF database. Each scene consists of a sphere  

E-Print Network [OSTI]

of BRDFs modeling the tungsten carbide material from the MERL BRDF database. Each scene consists that remains between state-of-the-art analytic BRDFs and measured data in the case of tungsten carbide

Weimer, Westley

453

Unveiling a network of parallel filaments in the Infrared Dark Cloud G14.225-0.506  

E-Print Network [OSTI]

We present the results of combined NH3(1,1) and (2,2) line emission observed with the Very Large Array and the Effelsberg 100m telescope of the Infrared Dark Cloud G14.225-0.506. The NH3 emission reveals a network of filaments constituting two hub-filament systems. Hubs are associated with gas of rotational temperature Trot \\sim 25 K, non-thermal velocity dispersion ~1.1 km/s, and exhibit signs of star formation, while filaments appear to be more quiescent (Trot \\sim 11 K, non-thermal velocity dispersion ~0.6 km/s). Filaments are parallel in projection and distributed mainly along two directions, at PA \\sim 10 deg and 60 deg, and appear to be coherent in velocity. The averaged projected separation between adjacent filaments is between 0.5 pc and 1pc, and the mean width of filaments is 0.12 pc. Cores within filaments are separated by ~0.33 pc, which is consistent with the predicted fragmentation of an isothermal gas cylinder due to the 'sausage'-type instability. The network of parallel filaments observed in G...

Busquet, Gemma; Palau, Aina; Liu, Hauyu Baobab; Snchez-Monge, lvaro; Estalella, Robert; Ho, Paul T P; de Gregorio-Monsalvo, Itziar; Pillai, Thushara; Wyrowski, Friedrich; Girart, Josep M; Santos, Fbio P; Franco, Gabriel A P

2012-01-01T23:59:59.000Z

454

Polymeric filament thinning and breakup in microchannels P. E. Arratia,1,* J. P. Gollub,1,2  

E-Print Network [OSTI]

Polymeric filament thinning and breakup in microchannels P. E. Arratia,1,* J. P. Gollub,1,2 and D the breakup process, compared to the Newtonian case. Qualitatively, polymeric filaments show much slower two main temporal regimes: flow- and capillary-driven. At early times both polymeric and Newtonian

Gollub, Jerry P.

455

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

SciTech Connect (OSTI)

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

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

1984-05-08T23:59:59.000Z

456

Effects of anneals in ammonia on the interface trap density near the band edges in 4Hsilicon carbide metal-oxide-semiconductor capacitors  

E-Print Network [OSTI]

­silicon carbide metal-oxide-semiconductor capacitors Gilyong Chung, Chin Che Tin, and John R. Williamsa) Physics. Silicon carbide is the only wide band gap semiconductor that has a native oxide, and metal temperature capacitance­voltage measurements are reported for SiO2/4H­SiC n and p type metal

Pantelides, Sokrates T.

457

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

E-Print Network [OSTI]

of hydrocarbon dissociation on transition metal (TM) sur- faces represents a challenging way to its synthesisGrowth of Dome-Shaped Carbon Nanoislands on Ir(111): The Intermediate between Carbidic Clusters coupled carbidic carbon and a quasi-free-standing graphene layer, can provide information for a rational

Alfè, Dario

458

The Effect of Excess Carbon on the Crystallographic, Microstructural, and Mechanical Properties of CVD Silicon Carbide Fibers  

SciTech Connect (OSTI)

Silicon carbide (SiC) fibers made by chemical vapor deposition (CVD) are of interest for organic, ceramic, and metal matrix composite materials due their high strength, high elastic modulus, and retention of mechanical properties at elevated processing and operating temperatures. The properties of SCS-6{trademark} silicon carbide fibers, which are made by a commercial process and consist largely of stoichiometric SiC, were compared with an experimental carbon-rich CVD SiC fiber, to which excess carbon was added during the CVD process. The concentration, homogeneity, and distribution of carbon were measured using energy dispersive x-ray spectroscopy (SEM/EDS). The effect of excess carbon on the tensile strength, elastic modulus, and the crystallographic and microstructural properties of CVD silicon carbide fibers was investigated using tensile testing, x-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Marzik, J V; Croft, W J; Staples, R J; MoberlyChan, W J

2006-12-05T23:59:59.000Z

459

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

SciTech Connect (OSTI)

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.

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

460

All-optical coherent population trapping with defect spin ensembles in silicon carbide  

E-Print Network [OSTI]

Divacancy defects in silicon carbide have long-lived electronic spin states and sharp optical transitions, with properties that are similar to the nitrogen-vacancy defect in diamond. We report experiments on 4H-SiC that investigate all-optical addressing of spin states with the zero-phonon-line transitions. Our magneto-spectroscopy results identify the spin $S=1$ structure of the ground and excited state, and a role for decay via intersystem crossing. We use these results for demonstrating coherent population trapping of spin states with divacancy ensembles that have particular orientations in the SiC crystal.

Olger V. Zwier; Danny O'Shea; Alexander R. Onur; Caspar H. van der Wal

2014-11-06T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Electronic Structure and Chemical Bonding of Amorphous Chromium Carbide Thin Films  

E-Print Network [OSTI]

The microstructure, electronic structure, and chemical bonding of chromium carbide thin films with different carbon contents have been investigated with high-resolution transmission electron microscopy, electron energy loss spectroscopy and soft x-ray absorption-emission spectroscopies. Most of the films can be described as amorphous nanocomposites with non-crystalline CrCx in an amorphous carbon matrix. At high carbon contents, graphene-like structures are formed in the amorphous carbon matrix. At 47 at% carbon content, randomly oriented nanocrystallites are formed creating a complex microstructure of three components. The soft x-ray absorption-emission study shows additional peak structures exhibiting non-octahedral coordination and bonding.

Magnuson, Martin; Lu, Jun; Hultman, Lars; Jansson, Ulf; 10.1088/0953-8984/24/22/225004

2012-01-01T23:59:59.000Z

462

Formation of graphene layers by vacuum sublimation of silicon carbide using a scanning heat source  

SciTech Connect (OSTI)

The kinetics of surface graphitization during dissociative vacuum evaporation of silicon carbide, under the effect of a scanning heat source, is studied. A model of the process is developed. The model provides a means for theoretically treating the dynamics of formation and the number of residual carbon atomic layers. The vapor stoichiometric coefficient which ensures the minimization of the number of structural defects in graphene, is optimized at the sublimation temperature: {theta} = 1/{eta}(T{sub max}). The proposed method can be used as a basis for graphene production technology.

Dmitriev, A. N.; Cherednichenko, D. I., E-mail: cheredni@fep.tti.sfedu.ru [Southern Federal University, Taganrog Technological Institute (Russian Federation)

2011-12-15T23:59:59.000Z

463

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

SciTech Connect (OSTI)

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.

Hain, T. C.; Hertel, T. [Institute of Physical and Theoretical Chemistry, Julius-Maximilian University of Wrzburg, 97074 Wrzburg (Germany); Fuchs, F.; Astakhov, G. V., E-mail: astakhov@physik.uni-wuerzburg.de [Experimental Physics VI, Julius-Maximilian University of Wrzburg, 97074 Wrzburg (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 Wrzburg, 97074 Wrzburg (Germany); Bavarian Center for Applied Energy Research (ZAE Bayern), 97074 Wrzburg (Germany)

2014-04-07T23:59:59.000Z

464

On the genesis of molybdenum carbide phases during reduction-carburization reactions  

SciTech Connect (OSTI)

Molybdenum carbide has been prepared according to the carbothermal reduction method. Carbon black substrate was used as C-source whereas a H{sub 2}-flow was the reducing agent. Two different H{sub 2} consumption steps were identified during the carburization treatment. The low temperature step is related to the reduction of Mo{sup 6+}-to-Mo{sup 4+}, the higher temperature process accounts for the deep reduction of Mo{sup 4+}-to-metal Mo{sup 0} and its subsequent reaction with C to form the Mo-carbide. The influences of the maximum carburization temperature, carburization time, gas hourly space velocity regarding Mo-loading, heating rate and temperature of Ar pre-treatment were analyzed. All these conditions are interrelated to each other. Thus, the carburization process ends at 700 Degree-Sign C when Mo-loading is 10 wt%, however Mo-loading higher than 10 wt% requires higher temperatures. Carburization temperatures up to 800 Degree-Sign C are needed to fulfill Mo-carbide formation with samples containing 50 wt% Mo. Nevertheless, Ar pre-treatment at 550 Degree-Sign C and slow heating rates favor the carburization, thus requiring lower carburization temperatures to reach the same carburization level. - Graphical Abstract: H{sub 2}-consumption profile (TPR) during the molybdenum carburization process, XRD patterns of the reduced Mo-samples after carburization and TEM-micrographs with two different enlargement of the samples with 5, 20 and 50 wt% Mo. Highlights: Black-Right-Pointing-Pointer Control of carburization variables: tailor the reduced/carbide Mo-phases (single/mixture). Black-Right-Pointing-Pointer Mo carburization in two stages: (1) Mo{sup 6+}-Mo{sup 4+}; (2) Mo{sup 4+}-Mo{sup 0} and, at once, MoC. Black-Right-Pointing-Pointer The carburization process is faster than Mo{sup 4+} reduction. Black-Right-Pointing-Pointer XPS probed: reduced Mo particles show core-shell structure. Black-Right-Pointing-Pointer Core: reduced Mo (Mo{sub 2}C, MoO{sub 2} and/or Mo{sup 0}); Shell: 2-3 nm of MoO{sub 3}.

Guil-Lopez, R., E-mail: rut.guil@icp.csic.es [Grupo de Energia y Quimica Sostenibles, ICP-CSIC, Marie Curie 2, Cantoblanco, 28049-Madrid (Spain); Nieto, E. [Grupo de Energia y Quimica Sostenibles, ICP-CSIC, Marie Curie 2, Cantoblanco, 28049-Madrid (Spain); Departamento de Tecnologia Quimica y Energetica, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, 28933-Mostoles (Spain); Botas, J.A. [Departamento de Tecnologia Quimica y Energetica, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, 28933-Mostoles (Spain); Fierro, J.L.G., E-mail: jlgfierro@icp.csic.es [Grupo de Energia y Quimica Sostenibles, ICP-CSIC, Marie Curie 2, Cantoblanco, 28049-Madrid (Spain)

2012-06-15T23:59:59.000Z

465

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

SciTech Connect (OSTI)

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

Kim, Young-ho [Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Irie, Hiroshi [Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Hashimoto, Kazuhito [Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2008-05-05T23:59:59.000Z

466

Mechanical Instability and Ideal Shear Strength of Transition Metal Carbides and Nitrides  

SciTech Connect (OSTI)

The ideal shear strength of transition metal carbides and nitrides is calculated with the use of the ab initio pseudopotential density functional method. The microscopic mechanism that limits the ideal strength is studied using full atomic and structural relaxation and the results of electronic structure calculations. It is shown that plasticity in perfect crystals can be triggered by electronic instabilities at finite strains. Our study explicitly demonstrates that the ideal strength in these materials is limited by the elastic instability which is in turn initiated by electronic instabilities. The potential application of alloy hardening due to the onset of instabilities at different strains is also discussed.

Jhi, Seung-Hoon; Louie, Steven G.; Cohen, Marvin L.; Morris, J. W.

2001-08-13T23:59:59.000Z

467

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

SciTech Connect (OSTI)

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.

Buss, R.J.

1997-02-01T23:59:59.000Z

468

JOURNAL DE PHYSIQUE Colloque C2,supplkment au n o 3, Tome 40, mars 1979,page C2-627 DETERMINATION OF RETAINED AUSTENITE IN STEELS ALLOYED WITH CARBIDE FORMERS  

E-Print Network [OSTI]

OF RETAINED AUSTENITE IN STEELS ALLOYED WITH CARBIDE FORMERS E. Kuzmann, L. Domonkos. M. Kocsis, S for the quantitative determination of the retained austenite in steels alloyed with carbide forming elements. By means of this method, the disturbing effect of the paramagnetic carbides containing iron can be eliminated

Paris-Sud XI, Université de

469

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

SciTech Connect (OSTI)

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.

Burin, Michael [CSUSM

2014-11-18T23:59:59.000Z

470

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

E-Print Network [OSTI]

Wave-pinned filaments of scroll waves Tams Bnsgi, 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

Steinbock, Oliver

471

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

E-Print Network [OSTI]

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

Ahissar, Ehud

472

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

E-Print Network [OSTI]

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

Kamm, Roger D.

473

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

E-Print Network [OSTI]

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

Milchberg, Howard

474

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

E-Print Network [OSTI]

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

Kamm, Roger D.

475

Condensation of FtsZ filaments can drive bacterial cell division  

E-Print Network [OSTI]

Condensation of FtsZ filaments can drive bacterial cell division Ganhui Lana , Brian R. Danielsb-ring undergoes a condensation transition from a low- density state to a high-density state and generates the condensation transition, but does not directly generate forces. In vivo fluorescence measurements show that Fts

Sun, Sean

476

Role of ATP-Hydrolysis in the Dynamics of a Single Actin Filament Padinhateeri Ranjith,  

E-Print Network [OSTI]

Role of ATP-Hydrolysis in the Dynamics of a Single Actin Filament Padinhateeri Ranjith, * Kirone, and ATP hydrolysis of subunits either according to the vectorial mechanism or to the random mechanism and by comparing two possible mechanisms of ATP hydro- lysis. Our emphasis is mainly on two possible limiting

Lacoste, David

477

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

E-Print Network [OSTI]

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

Bristol, University of

478

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

E-Print Network [OSTI]

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.

B. Ruiz Cobo; L. R. Bellot Rubio

2008-10-07T23:59:59.000Z

479

Annealing Accounts for the Length of Actin Filaments Formed by Spontaneous Polymerization  

E-Print Network [OSTI]

Annealing Accounts for the Length of Actin Filaments Formed by Spontaneous Polymerization David by spontaneous polymerization of highly purified actin monomers by fluorescence microscopy after labelingZ concentrations. INTRODUCTION Actin polymerization is important not only for cellular structure and function

480

Abstract The polymerization of filamentous proteins generates mechanical forces which drive many cellular  

E-Print Network [OSTI]

Abstract The polymerization of filamentous proteins generates mechanical forces which drive many microtubule. They found that the force is generally in the range predicted by the "polymerization ratchet generalize the polymerization ratchet model to take into account the "subsidy effect" that arises because

Oster, George

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481

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

SciTech Connect (OSTI)

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).

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

2010-05-19T23:59:59.000Z

482

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

E-Print Network [OSTI]

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

Becker, Andreas

483

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

E-Print Network [OSTI]

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

Boyer, Edmond

484

DOI: 10.1002/cphc.200900615 From Branched Networks of Actin Filaments to Bundles  

E-Print Network [OSTI]

DOI: 10.1002/cphc.200900615 From Branched Networks of Actin Filaments to Bundles Yifat Brill- ses. Cell movement is driven by the dynamic growth of polar actin networks of various structures,[1 containing the lamellipodium, but lacking the nucleus, micro- tubules and other organels can perform movement

Ben-Shaul, Avinoam

485

Portraits of some representatives of metal boride carbide and boride silicide compounds  

SciTech Connect (OSTI)

Different ternary alkaline-earth and rare-earth metal boron carbide and silicide compounds are examined using the solid-state language of Zintl-Klemm concept, band structures, and density of states, in order to show that the topology of the non-metal sub-lattice is highly dependent on the electron count. It is also shown that the chemistry of rare-earth metal-boron-silicon does not parallel that of rare-earth metal-boron-carbon. B-C bonds are easily formed in the latter, leading to a large variety of different structural arrangements, whereas Si-B bonds are hardly observed in the former, except in insertion compounds. - Graphical abstract: Some ternary alkaline-earth and rare-earth metal boron carbide and silicide compounds are examined using the solid-state language of Zintl-Klemm concept, band structures, and density of states, in order to show that the topology of the non-metal sub-lattice is highly dependent on the electron count.

Ben Yahia, Mouna [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Roger, Jerome [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Rocquefelte, Xavier [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Gautier, Regis [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Bauer, Joseph [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Guerin, Roland [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Saillard, Jean-Yves [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France); Halet, Jean-Francois [Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR 6511 CNRS-Universite de Rennes 1-ENSC Rennes, Institut de Chimie de Rennes, F-35042 Rennes (France)]. E-mail: halet@univ-rennes1.fr

2006-09-15T23:59:59.000Z

486

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

SciTech Connect (OSTI)

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.

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

487

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

SciTech Connect (OSTI)

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

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

2014-10-01T23:59:59.000Z

488

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

SciTech Connect (OSTI)

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.

Taylor, Larry Lorin

2001-01-01T23:59:59.000Z

489

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

DOE Patents [OSTI]

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.

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

490

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

DOE Patents [OSTI]

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

Tiegs, Terry N. (Lenoir City, TN)

1987-01-01T23:59:59.000Z

491

Solar-to-Hydrogen Photovoltaic/Photoelectrochemical Devices Using Amorphous Silicon Carbide as the Photoelectrode  

SciTech Connect (OSTI)

We report the use of hydrogenated amorphous silicon carbide (a-SiC:H) prepared by plasma enhanced chemical vapor deposition (PECVD) as the photoelectrode in an integrated 'hybrid' photoelectrochemical (PEC) cell to produce hydrogen directly from water using sunlight. Results on the durability of hydrogenated amorphous silicon carbide (a-SiC:H) photoelectrodes in an electrolyte are presented. In a pH2 electrolyte, the a-SiC:H photoelectrode exhibits excellent stability for 100 hour test so far performed. A photocurrent onset shift (anodically) after a 24- or 100-hour durability test in electrolyte is observed, likely due to changes in the surface chemical structure of the a-SiC:H photoelectrode. It is also observed that a thin SiOx layer native to the air exposed surface of the a-SiC:H affects the photocurrent and the its onset shift. Finally, approaches for eliminating the external bias voltage and enhancing the solar-to-hydrogen efficiency in a PV/PEC hybrid structure to achieve {>=} 10% are presented.

Hu, J.; Zhu, F.; Matulionis, I.; Kunrath, A.; Deutsch, T.; Kuritzky, L.; Miller, E.; Madan, A.

2008-01-01T23:59:59.000Z

492

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

SciTech Connect (OSTI)

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

Alexander, Caroline E.; Walsh, Robert W.; Rgnier, Stphane [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

493

[TiII] and [NiII] emission from the strontium filament of eta Carinae  

E-Print Network [OSTI]

We study the nature of the [TiII] and [NiII] emission from the so-called strontium filament found in the ejecta of eta Carinae. To this purpose we employ multilevel models of the TiII and NiII systems which are used to investigate the physical condition of the filament and the excitation mechanisms of the observed lines. For the TiII ion, for which no atomic data was previously available, we carry out ab initio calculations of radiative transition rates and electron impact excitation rate coefficients. It is found that the observed spectrum is consistent with the lines being excited in a mostly neutral region with an electron density of the order of $10^7$ cm$^{-3}$ and a temperature around 6000 K. In analyzing three observations with different slit orientations recorded between March~2000 and November~2001 we find line ratios that change among various observations, in a way consistent with changes of up to an order of magnitude in the strength of the continuum radiation field. These changes result from different samplings of the extended filament, due to the different slit orientations used for each observation, and yield clues on the spatial extent and optical depth of the filament. The observed emission indicates a large Ti/Ni abundance ratio relative to solar abundances. It is suggested that the observed high Ti/Ni ratio in gas is caused by dust-gas fractionation processes and does not reflect the absolute Ti/Ni ratio in the ejecta of \\etacar. We study the condensation chemistry of Ti, Ni and Fe within the filament and suggest that the observed gas phase overabundance of Ti

M. A. Bautista; H. Hartman; T. R. Gull; N. Smith; K. Lodders

2006-06-12T23:59:59.000Z

494

Explicit mean-field radius for nearly parallel vortex filaments in statistical equilibrium  

E-Print Network [OSTI]

Geophysical research has focused on flows, such as ocean currents, as two dimensional. Two dimensional point or blob vortex models have the advantage of having a Hamiltonian, whereas 3D vortex filament or tube systems do not necessarily have one, although they do have action functionals. On the other hand, certain classes of 3D vortex models called nearly parallel vortex filament models do have a Hamiltonian and are more accurate descriptions of geophysical and atmospheric flows than purely 2D models, especially at smaller scales. In these ``quasi-2D'' models we replace 2D point vortices with vortex filaments that are very straight and nearly parallel but have Brownian variations along their lengths due to local self-induction. When very straight, quasi-2D filaments are expected to have virtually the same planar density distributions as 2D models. An open problem is when quasi-2D model statistics behave differently than those of the related 2D system and how this difference is manifested. In this paper we study the nearly parallel vortex filament model of Klein, Majda, Damodaran in statistical equilibrium. We are able to obtain a free-energy functional for the system in a non-extensive thermodynamic limit that is a function of the mean square vortex position $R^2$ and solve \\emph{explicitly} for $R^2$. Such an explicit formula has never been obtained for a non-2D model. We compare the results of our formula to a 2-D formula of \\cite{Lim:2005} and show qualitatively different behavior even when we disallow vortex braiding. We further confirm our results using Path Integral Monte Carlo (Ceperley (1995)) \\emph{without} permutations and that the Klein, Majda, Damodaran model's asymptotic assumptions \\emph{are valid} for parameters where these deviations occur.

Timothy D. Andersen; Chjan C. Lim

2006-11-19T23:59:59.000Z

495

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

SciTech Connect (OSTI)

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

Busquet, Gemma [INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, I-00133 Roma (Italy); Zhang, Qizhou; Ho, Paul T. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Palau, Aina; Girart, Josep M. [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C-5 parell, E-08193 Bellaterra, Catalunya (Spain); Liu, Hauyu Baobab [Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan (China); Sanchez-Monge, Alvaro [INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-05125 Firenze (Italy); Estalella, Robert [Departament d'Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E-08028 Barcelona, Catalunya (Spain); De Gregorio-Monsalvo, Itziar [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Pillai, Thushara [Caltech Astronomy Department, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Wyrowski, Friedrich [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Santos, Fabio P.; Franco, Gabriel A. P., E-mail: gemma.busquet@iaps.inaf.it [Departamento de Fisica-ICEx-UFMG, Caixa Postal 702, 30.123-970 Belo Horizonte-MG (Brazil)

2013-02-20T23:59:59.000Z

496

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

SciTech Connect (OSTI)

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.

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

497

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

E-Print Network [OSTI]

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...

Santana Rodriguez, Gabriel Enrique

2003-01-01T23:59:59.000Z

498

Theoretical Analysis of the Adsorption of Late Transition Metal Atoms on the (001) Surface of Early Transition Metal Carbides  

SciTech Connect (OSTI)

The interaction of atoms of Groups 9, 10, and 11 with the (001) surface of TiC, ZrC, VC, and {delta}-MoC has been studied by means of periodic density functional calculations using slab models. The calculated values of the adsorption energy are rather large, especially for Groups 9 and 10 elements (E{sub ads} = 3-6 eV), but without clear trends along the series. Nevertheless, the analysis of the interaction at different sites indicates that the adsorbed atoms will be relatively mobile. Many of the admetals are electronically perturbed upon interaction with the carbide surfaces. Co, Ni, Cu, and Rh adatoms get positively or negatively charged, depending on the nature of the carbide substrate. Ir, Pd, Pt, and Au adatoms are always negatively charged. An analysis of the Bader charges for the most stable sites provides strong evidence that the most negative charge on the adatoms corresponds to the interaction with ZrC, followed by TiC. In the case of VC and {delta}-MoC, the charge on the adsorbed atoms may be slightly positive and of the same order for both carbides. The effect of the underlying carbide is large, with ZrC and TiC being predicted as the supports with the largest effect on the electronic structure of the adsorbed atoms with direct implications for the use of these systems in catalysis.

Rodriguez, J.A.; Gmez, T.; Florez, E.; Illas, F.

2010-01-28T23:59:59.000Z