Powered by Deep Web Technologies
Note: This page contains sample records for the topic "hafnium carbide four-foot" 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.


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

It's Elemental - The Element Hafnium  

NLE Websites -- All DOE Office Websites (Extended Search)

Lutetium Lutetium Previous Element (Lutetium) The Periodic Table of Elements Next Element (Tantalum) Tantalum The Element Hafnium [Click for Isotope Data] 72 Hf Hafnium 178.49 Atomic Number: 72 Atomic Weight: 178.49 Melting Point: 2506 K (2233°C or 4051°F) Boiling Point: 4876 K (4603°C or 8317°F) Density: 13.3 grams per cubic centimeter Phase at Room Temperature: Solid Element Classification: Metal Period Number: 6 Group Number: 4 Group Name: none What's in a name? From the Latin word for the city of Copenhagen, Hafnia. Say what? Hafnium is pronounced as HAF-neeem. History and Uses: Hafnium was discovered by Dirk Coster, a Danish chemist, and Charles de Hevesy, a Hungarian chemist, in 1923. They used a method known as X-ray spectroscopy to study the arrangement of the outer electrons of atoms in

4

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

5

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

NLE Websites -- All DOE Office Websites (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...

6

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

7

Hafnium nitride for hot carrier solar cells  

Science Journals Connector (OSTI)

Abstract Hot carrier solar cells is an attractive technology with the potential of reaching high energy conversion efficiencies approaching the thermodynamic limit of infinitely stacked multi-junction solar cells: 65% under one sun and 86% under maximally concentrated. The hot carrier solar cell is conceptually simple consisting of two key components: absorber and energy selective contacts. High efficiencies are achieved by minimising the energy lost to thermalisaton of hot photo-generated carriers while absorbing majority of the solar spectrum. For this to be achieved, energy selective contacts are required to allow the extraction of carriers fast enough at an energy level above the electronic band edge. It is critical for the absorber to be able to maintain a hot carrier population for a sufficiently long time period for the extraction of carriers while they are hot. Bulk materials with a large gap between acoustic and optical branches in the phonon dispersion are predicted to exhibit slow hot carrier thermalisation rates. Hafnium nitride is such a material with a large gap in its phonon dispersion and is identified as a potential material to be used as a hot carrier absorber. Hafnium nitride has been deposited using reactive sputtering and characterised to investigate material properties and carrier cooling rates.

Simon Chung; Santosh Shrestha; Xiaoming Wen; Yu Feng; Neeti Gupta; Hongze Xia; Pyng Yu; Jau Tang; Gavin Conibeer

2014-01-01T23:59:59.000Z

8

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

9

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

SciTech Connect

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

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

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

18

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

19

Amorphous hafnium-indium-zinc oxide semiconductor thin film transistors  

Science Journals Connector (OSTI)

We reported on the performance and electrical properties of co-sputtering-processed amorphous hafnium-indium-zinc oxide (?-HfIZO) thin film transistors (TFTs). Co-sputtering-processed ?-HfIZO thin films have shown an amorphous phase in nature. ...

Sheng-Po Chang; San-Syong Shih

2012-01-01T23:59:59.000Z

20

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

NLE Websites -- All DOE Office Websites (Extended Search)

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

22

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

NLE Websites -- All DOE Office Websites (Extended Search)

Union Carbide in Nuclear Energy Note: Union Carbide Nuclear Division, which started out as Carbide and Carbon Chemicals Company, operated the Atomic Energy CommissionEnergy...

23

Oxygen and nitrogen diffusion in ?-hafnium from first principles  

SciTech Connect

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

24

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

25

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

26

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

27

Nanoscale Engineering Of Radiation Tolerant Silicon Carbide....  

NLE Websites -- All DOE Office Websites (Extended Search)

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

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

1993-01-01T23:59:59.000Z

29

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

30

Microwave processing for carbide ceramics  

SciTech Connect

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

31

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

32

Silicon Carbide, SiC  

Science Journals Connector (OSTI)

Silicon carbide occurring naturally as hexagonal crystals and associated with diamond, graphite, and amorphous carbon was first reported in 1904/05 by Moissan as a component of the hydrochloric acid insoluble ...

Vera Haase; Gerhard Kirschstein; Hildegard List; Sigrid Ruprecht

1985-01-01T23:59:59.000Z

33

Hafnium metallocene compounds used as cathode interfacial layers for enhanced electron transfer in organic solar cells  

Science Journals Connector (OSTI)

We have used hafnium metallocene compounds as cathode interfacial layers for organic solar cells [OSCs]. A metallocene compound consists of...6, 6]-phenyl C61 butyric acid methyl ester, bis-(ethylcyclopentadienyl...

Keunhee Park; Seungsik Oh; Donggeun Jung; Heeyeop Chae

2012-01-01T23:59:59.000Z

34

Growth mode evolution of hafnium oxide by atomic layer deposition  

SciTech Connect

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

35

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

36

Combustion Synthesis of Silicon Carbide 389 Combustion Synthesis of Silicon Carbide  

E-Print Network (OSTI)

Combustion Synthesis of Silicon Carbide 389 X Combustion Synthesis of Silicon Carbide Alexander S velocity and 17 #12;Properties and Applications of Silicon Carbide390 reaction rate throughout the mixture by graphite during SHS of carbides. Local reaction initiation is typically accomplished by hot tungsten wire

Mukasyan, Alexander

37

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

38

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

39

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

SciTech Connect

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

40

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

42

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

43

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

44

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

45

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

46

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

47

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

NLE Websites -- All DOE Office Websites (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...

48

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

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

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

49

Amorphization of Silicon Carbide by Carbon Displacement. | EMSL  

NLE Websites -- All DOE Office Websites (Extended Search)

of Silicon Carbide by Carbon Displacement. Amorphization of Silicon Carbide by Carbon Displacement. Abstract: We have used molecular dynamics simulations to examine the possibility...

50

Titanium Carbide Bipolar Plate for Electrochemical Devices  

SciTech Connect

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

51

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

52

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

53

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

SciTech Connect

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

54

Union Carbides 20 years in nuclear energy, part 2  

NLE Websites -- All DOE Office Websites (Extended Search)

magnetic separators were discontinued December 23, 1946, as production units. "1947 - Carbide Carbon Chemical Company replaced Tennessee Eastman Corporation as the operating...

55

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

SciTech Connect

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

56

On the phase formation of sputtered hafnium oxide and oxynitride films  

SciTech Connect

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

57

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

58

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

59

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

60

Electroextraction of boron from boron carbide scrap  

SciTech Connect

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Silicon Carbide Power Semiconductor Devices in the Cleanroom...  

NLE Websites -- All DOE Office Websites (Extended Search)

Silicon Carbide Power Semiconductor Devices in the Cleanroom Silicon Carbide Power Semiconductor Devices in the Cleanroom Ron Olson 2012.10.04 I would like to introduce Zach Stum,...

62

Making Silicon Carbide Devices in the Cleanroom | GE Global Research  

NLE Websites -- All DOE Office Websites (Extended Search)

Silicon Carbide Devices in the Cleanroom Making Silicon Carbide Devices in the Cleanroom Ron Olson 2012.08.23 As the Wide Bandgap Process and Fab manager for the GE Global Research...

63

Silicon Carbides in the Cleanroom | GE Global Research  

NLE Websites -- All DOE Office Websites (Extended Search)

Clean Room: Silicon Carbides GE Global Research is working on nanoscale silicon carbide devices. Find out what we're doing. You Might Also Like 2-1-10-v-working-at-ge-resear...

64

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.

65

Lithium carbide is prospective material for breeder of fusion reactor  

Science Journals Connector (OSTI)

It is shown that lithium carbide is a prospective material for breeder of fusion reactor. The lithium carbide equivalent dose rate reaches...?5...Sv/h) one minute after the irradiation with fusion reactor neutron...

M. V. Alenina; V. P. Kolotov; Yu. M. Platov

2014-03-01T23:59:59.000Z

66

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

67

Carbides composite surface layers produced by (PTA)  

SciTech Connect

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

68

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

69

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

70

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

71

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

72

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

73

High Q silicon carbide microdisk resonator  

SciTech Connect

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

74

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

75

PWR cores with silicon carbide cladding  

SciTech Connect

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

76

16 - Applications of Refractory Carbides and Nitrides  

Science Journals Connector (OSTI)

Publisher Summary This chapter reviews the applications of refractory carbides and nitrides in each of the following industrial categories: (1) automotive and aerospace, (2) industrial machinery and equipment, (3) cutting and grinding tools, (4) armor, (5) nuclear, (6) semiconductor, and (6) optical. Many of the automotive and aerospace applications of refractory carbides and nitrides are of a structural and chemical nature, especially in applications involving high temperature and/or corrosive environments where most metals are no longer suitable. These applications are usually in the bulk form and are made possible by recent advances in processing technology. Relatively large parts can now be produced to near-net shape with little machining required. Applications of refractory carbides and nitrides are found extensively in machinery and equipment for protection against wear, erosion, and chemical attack. Both bulk materials and coatings are used. The most important bulk material is tungsten carbide sintered with a metallic binder that is usually cobalt. Cutting and grinding tools are a special case of wear and corrosion applications. Cutting tools have a sharp edge for the purpose of shaving and generating a material chip. This edge must remain sharp for the tool to perform properly. Grinding tools are different in that they have an abrasive-coated surface that generates a powder as opposed to the chip of a cutting tool.

Hugh O. Pierson

1996-01-01T23:59:59.000Z

77

Process for coating tungsten carbide with cobalt metal  

SciTech Connect

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

78

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

SciTech Connect

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

79

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

80

Tailoring the index of refraction of nanocrystalline hafnium oxide thin films  

SciTech Connect

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

SciTech Connect

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

82

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

SciTech Connect

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

83

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

84

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

85

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

86

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

NLE Websites -- All DOE Office Websites (Extended Search)

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

87

E-Print Network 3.0 - americium carbides Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

The internal... have revealed numerous internal grains, mainly refractory carbides (TiC) but also a number of rare... phases such as kamacite, taenite, iron carbide...

88

E-Print Network 3.0 - advanced silicon carbide Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Carnegie Mellon University Collection: Materials Science 26 3 Carbide Precipitation Carbides are largely responsible for the commercial failure of many of the early Summary:...

89

Preparation and electrocatalytic activity of tungsten carbide and titania nanocomposite  

SciTech Connect

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

90

Potential of Silicon Carbide-Derived Carbon for Carbon Capture  

Science Journals Connector (OSTI)

Potential of Silicon Carbide-Derived Carbon for Carbon Capture ... In contrast to conventional carbons made from natural precursors, carbide derived carbons (CDCs),(8, 10-13) being synthesized from an inorganic source, have no polar functional groups and are composed of purely covalently bonded carbon. ...

S. K. Bhatia; T. X. Nguyen

2011-08-08T23:59:59.000Z

91

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

92

The chemical vapor deposition of zirconium carbide onto ceramic substrates  

SciTech Connect

Zirconium carbide is an attractive ceramic material due to its unique properties such as high melting point, good thermal conductivity, and chemical resistance. The controlled preparation of zirconium carbide films of superstoichiometric, stoichiometric, and substoichiometric compositions has been achieved utilizing zirconium tetrachloride and methane precursor gases in an atmospheric pressure high temperature chemical vapor deposition system.

Glass, John A, Jr.; Palmisiano, Nick, Jr.; Welsh, R. Edward

1999-07-01T23:59:59.000Z

93

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.

94

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

95

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

SciTech Connect

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

96

High temperature intermetallic binders for HVOF carbides  

SciTech Connect

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

97

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.

98

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.

99

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.

100

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Route to transition metal carbide nanoparticles through cyanamide and metal oxides  

SciTech Connect

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

102

Computational Studies of Physical Properties of Boron Carbide  

SciTech Connect

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

103

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

SciTech Connect

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

104

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

105

Separation of Nuclear Fuel Surrogates from Silicon Carbide Inert Matrix  

SciTech Connect

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

106

Vacancy Hardening and Softening in Transition Metal Carbides and Nitrides  

SciTech Connect

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

107

Comparison Measurements of Silicon Carbide Temperature Monitors  

SciTech Connect

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

108

Asymmetric twins in rhombohedral boron carbide  

SciTech Connect

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

109

UNION CARBIDE MZALS DIVISION tiiAGARA FALLS, NEW YDRK  

Office of Legacy Management (LM)

PRELIF",INARY SURVEY 0' PRELIF",INARY SURVEY 0' ELECTRDMET iORPDF.&TiCIN UNION CARBIDE MZALS DIVISION tiiAGARA FALLS, NEW YDRK Work performed by the Health and Safety Research Division Dak Ridge National Laboratory Oak Ridge, Tennessee 37830 OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for the DEPARTMENT OF ENERGY as part of the Fornierly Utilized Sites-- Remedial Action Program ,ELECTRD?'ISi 60RPOR:TION UNiON CARBIDE METALS DIVlSIOti NiASARA FALLS, NEA YORK At the requests o f the Department of Energy (DOE, then ERDA), a preliminary survey was performed at the former Electromet Plant (cur- rently Union Carbide Corporation - Metals Division plant) in Niagara Falls, Neh' York (see Fig. l), on August 24, 1976, to assess the radio- logical status 0 f those facilities utilized under~Manhattan Engineer

110

Surface roughening in ion implanted 4H-silicon carbide  

Science Journals Connector (OSTI)

Silicon carbide (SiC) devices have the potential to yield new components with functional capabilities that far exceed components based on silicon devices. Selective doping of SiC by ion implantation is an importa...

M. A. Capano; S. Ryu; J. A. Cooper Jr.; M. R. Melloch

1999-01-01T23:59:59.000Z

111

Union Carbide's 20 years in nuclear energy, part 1  

NLE Websites -- All DOE Office Websites (Extended Search)

along with a note that he thought I might be interested in this "old "glossy" on Union Carbide." He was right and I certainly appreciated him thinking of me. I found some really...

112

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

113

Cryogenic optical testing of sandwich-type silicon carbide mirrors  

Science Journals Connector (OSTI)

The experimental cryogenic performance of 160-mm-diameter silicon carbide (SiC) mirrors, one of which, a 700-mm-diameter mirror, is to be used as a primary mirror of the Japanese...

Kaneda, Hidehiro; Onaka, Takashi; Kawada, Mitsunobu; Murakami, Hiroshi

2003-01-01T23:59:59.000Z

114

Carbon monoxide-silicon carbide interaction in HTGR fuel particles  

Science Journals Connector (OSTI)

The corrosion of the coating-layers of silicon carbide (SiC) by carbon monoxide (CO) was observed in irradiated Triso-coated uranium dioxide particles, used in high-temperature gas-cooled reactors, by optical ...

Kazuo Minato; Toru Ogawa; Satoru Kashimura; Kousaku Fukuda

1991-05-01T23:59:59.000Z

115

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

NLE Websites -- All DOE Office Websites (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...

116

Understanding the Irradiation Behavior of Zirconium Carbide  

SciTech Connect

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

117

Nanostructured carbide catalysts for the hydrogen economy  

SciTech Connect

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

118

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.

119

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.

120

Phase Behavior of Pseudobinary Precious Metal?Carbide Systems  

SciTech Connect

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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.

122

Ordering of carbon atoms in boron carbide structure  

SciTech Connect

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

123

Union Carbide pursuing direct conversion of methane to ethylene  

SciTech Connect

Union Carbide has begun developing an alternative source for ethylene. If a new program is successful, Carbide will be able to supplement present sources of ethylene by direct catalytic conversion of methane. The program also will provide an alternative means for possible future production of distillate motor fuels. Most ethylene consumed today is derived from dehydrogenation of ethane or propane. These sources are becoming increasingly tight, and alternatives are being sought by most polyethylene producers. Alternative sources have been on Carbide's research agenda at least since 1969, when the possibilities of converting methane were first examined. Following the Arab oil embargo of 1974 and the subsequent crude oil and natural gas price rises, most attention turned to coal conversion, at least in the U.S. However, inherent difficulties diminished the immediate prospects for utilizing coal as a source of fuels and petrochemical feedstocks.

Haggin, J.

1988-07-04T23:59:59.000Z

124

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

125

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

126

Structure-Property Relationship in Metal Carbides and Bimetallic Alloys  

SciTech Connect

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

127

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

128

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

129

-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

130

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

131

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

132

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

133

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

134

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

135

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

136

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

137

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

138

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

139

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.

140

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

142

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.

143

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

144

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.

145

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

146

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

147

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

148

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

149

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.

150

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.

151

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

152

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

153

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.

154

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.

155

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.

156

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.

157

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

158

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

159

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

160

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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.

162

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.

163

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

E-Print Network (OSTI)

) that are otherwise difficult to produce (e.g., transition metal/borides, carbides, and nitrides).1,2 Many earlierCatalytically Assisted Self-Propagating High-Temperature Synthesis of Tantalum Carbide Powders Troy/carbon/tantalum carbide combustion synthesis system has been examined to determine the effects of transport agents

Wooldridge, Margaret S.

164

The growth mechanism of grain boundary carbide in Alloy 690  

SciTech Connect

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

165

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

166

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

167

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

168

Electronic states in epitaxial graphene fabricated on silicon carbide  

SciTech Connect

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

169

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

170

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. 5 figs.

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

1999-01-19T23:59:59.000Z

171

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

172

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

173

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

174

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

SciTech Connect

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

175

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

176

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.

177

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.

178

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

179

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

180

Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons  

SciTech Connect

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 "hafnium carbide four-foot" 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

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

182

Surface Coating of Tungsten Carbide by Electric Exploding of Contact  

SciTech Connect

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

183

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

SciTech Connect

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

184

SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS  

SciTech Connect

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

185

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

186

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

187

Preparation of silicon carbide film by a plasma focus device  

Science Journals Connector (OSTI)

Silicon carbide (SiC) films were grown on the silicon (100) substrate by a 20 kJ Mather-type dense plasma focus device. The preparation method and characterization data are presented. X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (SEM) and nano-indentor were employed for the characterization of the samples obtained at different axial position of 50 mm, 90 mm, 130 mm and 170 mm, respectively. Polycrystalline 3CSiC were obtained at the position of 90 mm and 130 mm from XRD and FTIR spectra. SEM image showed that the silicon carbide films obtained at the position of 90 mm are porous on surface layer. Nano-indentor indicates that the film obtained at the position of 130 mm has the highest mechanical hardness.

Z.P. Wang; H.R. Yousefi; Y. Nishino; H. Ito; K. Masugata

2008-01-01T23:59:59.000Z

188

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

189

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

190

Carbide precipitation in gamma-TiAl alloys  

SciTech Connect

Carbide precipitation in gamma-TiAl is observed and found to involve the formation of coherent, rod-shaped perovskite precipitates as a metastable transition phase. At temperatures above 750 deg C, the formation of plate-shaped H-phase particles on dislocations and grain boundaries is accompanied by dissolution of the perovskite precipitate dispersions. This temperature regime includes possible service temperatures for gamma-TiAl-based alloys. 10 refs.

Chen, S.; Beaven, P.A.; Wagner, R. (GKSS-Forschungszentrum Geesthacht GmbH, (Germany))

1992-04-01T23:59:59.000Z

191

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

192

15 - Processing of Refractory Carbides and Nitrides (Coatings)  

Science Journals Connector (OSTI)

Publisher Summary This chapter reviews the coating processes of refractory carbides and nitrides. Coatings of refractory carbides and nitrides have great industrial importance with a wide range of applications in semiconductors and other electronic components, in cutting tools, gas-turbine vanes and blades, precision bearings, punch sets, extruders, prostheses, and many other products. The surface of a material may be exposed to wear, corrosion, radiation, electrical or magnetic fields, and other phenomena and hence, it must have the ability to withstand these environments. This can be accomplished by coating the base material to obtain a composite in which the surface properties may be considerably different from those of the substrate. Chemical vapor deposition (CVD) and physical vapor deposition (PVD) belong to the class of vapor-transfer processes, which are atomistic in naturethat is, the deposition species are atoms or molecules or a combination of these. The coatings are also commonly known as thin-films when their thickness is less than 10 ?m. CVD is a versatile process that is well adapted to the production of all the refractory carbides and nitrides, not only as coatings but also as powders, bulk/monolithic components, and fibers. It may be defined as the deposition of a solid on a heated surface from a chemical reaction in the vapor phase.

Hugh O. Pierson

1996-01-01T23:59:59.000Z

193

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

SciTech Connect

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

194

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

195

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

196

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

197

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

198

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

199

Tunable carbon nanotube-tungsten carbide nanoparticles heterostructures by vapor deposition  

SciTech Connect

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

200

E-Print Network 3.0 - amorphous silicon carbide Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

50, mai 1989 Summary: revetementdans le substrat. Abstract - Cuttingtools made of A1203+TiC, silicon nitride,carbide, and stabi- lized... with Tic, silicon nitride,...

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Synthesis of uranium nitride and uranium carbide powder by carbothermic reduction  

SciTech Connect

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

Dunwoody, J.T.; Stanek, C.R.; McClellan, K.J.; Voit, S.L.; Volz, H.M. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Hickman, R.R. [NASA Marshall Space Flight Center, Huntsville, Alabama (United States)

2007-07-01T23:59:59.000Z

202

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

NLE Websites -- All DOE Office Websites (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...

203

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.

204

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

205

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.

206

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

SciTech Connect

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

207

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.

208

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

209

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

210

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

211

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

212

Irradiation and annealing of p-type silicon carbide  

SciTech Connect

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

213

PROPERTIES OF DEFECTS AND IMPLANTS IN Mg+ IMPLANTED SILICON CARBIDE  

SciTech Connect

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

214

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

215

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

216

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

217

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

218

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

219

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.

220

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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.

222

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

223

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

224

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

225

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.

226

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

227

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

228

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

229

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

230

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

231

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

232

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

233

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

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Award-Winning Silicon Carbide Power Electronics Award-Winning Silicon Carbide Power Electronics (October 2012) Fact Sheet: Award-Winning Silicon Carbide Power Electronics (October 2012) Operating at high temperatures and with reduced energy losses, two silicon carbide power electronics (PE) projects were awarded the prestigious R&D 100 Award. This technology was funded as a Small Business Innovation Research project as part of DOE's Energy Storage Program effort to develop and commercialize a new generation of PE systems. PE systems are a critical part of all energy storage systems, interfacing the energy storage device and the load (the end user) and often accounting for greater than 25% of the overall storage system cost. Fact Sheet: Award-Winning Silicon Carbide Power Electronics (October 2012)

234

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

SciTech Connect

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

235

Coal fly ashcarbide lime bricks: An environment friendly building product  

Science Journals Connector (OSTI)

Abstract Coal fly ash and carbide lime are industrial by-products of coal combustion in thermal power plants and of manufacture of acetylene gas, respectively, available in profusion in southern Brazil. Research has been carried out to search for possible use of such materials to produce environmental friendly bricks that have high compressive strength. This study aims to evaluate strength controlling parameters of coal fly ashcarbide lime mixtures, as well as to show that porosity/carbide lime (?/Lv) ratio (corresponding to porosity divided by the volumetric carbide lime content) can be used to predict compressive strength (qu). The controlling parameters evaluated here are carbide lime content, porosity, curing temperature, curing time and porosity/carbide lime ratio. A number of unconfined compression tests were carried out. The results show that a power function adapts better the relation qu versus ?/Lv, in which Lv is adjusted by an exponent (in this case 0.11) for all coal fly ashcarbide lime mixtures studied. Equations that control the compressive strength for each curing period and curing temperature examined can be formulated using this unique ratio. Preferred strategies for varying ranges of qu are also proposed based on the energy required for heating, considering distinct curing periods and temperatures.

Nilo Cesar Consoli; Ceclia Gravina da Rocha; Rodrigo Beck Saldanha

2014-01-01T23:59:59.000Z

236

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

237

SANS and TEM studies of carbide precipitation and creep damage in type 304 stainless steel  

SciTech Connect

Small-angle neutron scattering (SANS) and transmission electron microscopy (TEM) studies were performed to characterize the carbide (M/sub 23/C/sub 6/) precipitation and creep damage induced in type 304 stainless steel in the primary creep stage. The size distribution of matrix carbides evaluated from SANS analyses was consistent with TEM data, and the expected accelerated kinetics of precipitation under applied stress was confirmed. Additional SANS measurements after the postcreep solution annealing were made in order to differentiate cavities from the carbides. Potential advantages and difficulties associated with characterization of creep-induced cavitation by the SANS techniques are discussed.

Yoo, M.H.; Ogle, J.C.; Schneibel, J.H.; Swindeman, R.W.

1984-01-01T23:59:59.000Z

238

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

SciTech Connect

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

239

Silicon carbide tritium permeation barrier for steel structural components.  

SciTech Connect

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

240

High surface area silicon carbide-coated carbon aerogel  

SciTech Connect

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

DECODING THE MESSAGE FROM METEORITIC STARDUST SILICON CARBIDE GRAINS  

SciTech Connect

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

242

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

243

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

244

Advanced Measurements of Silicon Carbide Ceramic Matrix Composites  

SciTech Connect

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

245

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

Office of Legacy Management (LM)

e e - .' N"lr 7% PRELIMINARY SURVEY OF THE UNION CARBIDE CORPORATION METALS DIVISION PLANT, NIAGARA FALLS, NEW YORK Work performed by the Health and Safety Research Division Oak Ridge Natjonal Laboratory Oak Ridge, Tennessee 37830 December 1980 OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for the DEPARTMENT OF ENERGY as part of the Formerly Utilized Sites-- Remedial Action Program PRELIMINARY SURVEY OF THE UNION CARBIDE CORPORATION METALS DIVISION PLANT, NIAGARA FALLS, NEW YORK B. A. Berven and R. W. Doane Introduction On September 2;, 1980, two representatives from Oak Ridge National Laboratory visited Union Carbide Corporation's Metal Division Plant (UCC-MD) in Niagara Falls, New York. The purpose of the visit was to

246

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

247

Preliminary study of neutron absorption by concrete with boron carbide addition  

SciTech Connect

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

248

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

249

High-Temperature Oxidation Resistance of Refractory Silicon NitrideSilicon Carbide Materials  

Science Journals Connector (OSTI)

Silicon nitride and carbide are promising materials for use as refractories; they are highly resistant to mineral acids and alkalis, have a high melting point, and are thermally very stable [1].

I. N. Godovannaya; O. I. Popova

1972-01-01T23:59:59.000Z

250

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

251

E-Print Network 3.0 - aluminide-bonded carbide ceramics Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

R. Begleyw Summary: include TBCs on superalloys, EBCs on sili- con-based ceramics, or TiCNbN coatings on cemented carbide... with Diffusion Aluminide Bond Coatings,'' Mater....

252

E-Print Network 3.0 - aluminium carbides Sample Search Results  

NLE Websites -- All DOE Office Websites (Extended Search)

temperatures. In the industrialproduction of A1203on cemented carbide cutting tools... TiCA1,03 interfaces have shown that aluminium oxide samples with good adhesionare Article...

253

Characteristics of 6H-silicon carbide PIN diodes prototyping by laser doping  

Science Journals Connector (OSTI)

Silicon carbide PIN diodes have been fabricated using a direct-write laser-doping technique that reduces defect generation compared to the conventional ion-implantation technique. Nitrogen and aluminum were su...

Z. Tian; N. R. Quick; A. Kar

2005-01-01T23:59:59.000Z

254

Effect of WC/TiC grain size ratio on microstructure and mechanical properties of WCTiCCo cemented carbides  

E-Print Network (OSTI)

of TiC powder as 1 lm. The microstructures of sintered WC­TiC­10 wt%Co cemented carbides were than that expected by modified Hall­Petch type equation. Transverse rupture strength of WC­20TiC­10 wt for decades [1]. Generally, cemented carbides are based on the WC­Co and some cubic carbide such as TiC, Ta

Hong, Soon Hyung

255

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

256

Developing a High Thermal Conductivity Fuel with Silicon Carbide Additives  

SciTech Connect

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

257

USE OF SILICON CARBIDE MONITORS IN ATR IRRADIATION TESTING  

SciTech Connect

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

258

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

259

Nano-precipitation in hot-pressed silicon carbide  

SciTech Connect

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

260

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Magnetism in hafnium dioxide  

Science Journals Connector (OSTI)

Thin films of HfO2 produced by pulsed-laser deposition on sapphire, yttria-stabilized zirconia, or silicon substrates show ferromagnetic magnetization curves with little hysteresis and extrapolated Curie temperatures far in excess of 400K. The moment does not scale with film thickness, but in terms of substrate area it is typically in the range 150400?Bnm?2. The magnetization exhibits a remarkable anisotropy, which depends on texture and substrate orientation. Pure HfO2 powder develops a weak magnetic moment on heating in vacuum, which is eliminated on annealing in oxygen. Lattice defects are the likely source of the magnetism.

J. M. D. Coey; M. Venkatesan; P. Stamenov; C. B. Fitzgerald; L. S. Dorneles

2005-07-22T23:59:59.000Z

262

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

SciTech Connect

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

263

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.

264

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

265

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

266

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

267

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

268

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

Office of Legacy Management (LM)

Carbide and Carbon Co - TN 10 Carbide and Carbon Co - TN 10 FUSRAP Considered Sites Site: Union Carbide and Carbon Co (TN.10) Designated Name: Alternate Name: Location: Evaluation Year: Site Operations: Site Disposition: Radioactive Materials Handled: Primary Radioactive Materials Handled: Radiological Survey(s): Site Status: This site is one of a group of 5 FUSRAP considered sites for which records are available that provide a reasonably complete historical account of their operations and relationship, if any, with MED/AEC operations. However, additional analyses of these historical records, and more recent documentation of decisions concerning the authority and other considerations related to the elimination of these sites from further consideration under FUSRAP is warranted. These analyses will provide the

269

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

270

Glycerol electrooxidation on highly active Pd supported carbide/C aerogel composites catalysts  

Science Journals Connector (OSTI)

The nanosized carbide supported on carbon aerogel composites have been synthesized by polycondensation of resorcinol and formaldehyde (RF) method in the presence of sodium tungstate and sodium molybdate. The materials are characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy (EDS), and cyclic voltammetry. The Pd nanoparticles supported on binary-carbide and carbon aerogel composites (Pd@WC-Mo2C/C) for glycerol oxidation are investigated for the first time. The Pd@WC-Mo2C/C as electrocatalyst shows a superior activity toward the glycerol oxidation in terms of the peak current density, which is almost two times higher than that of Pd/C and show better poison-resistant ability. The binary transition-metal carbide will be the potential catalyst support for the direct alcohol fuel cells.

Xiaofei Zhang; Pei Kang Shen

2013-01-01T23:59:59.000Z

271

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

272

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

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Silicon Carbide Technology Breakthrough Silicon Carbide Technology Breakthrough Silicon carbide (SiC) is a semiconductor material under rapid development for use in power electronic (PE) systems due to its unique material and electronic properties. SiC potentially offers several advantages over conventional silicon (Si) for use in PE devices. Comparatively, individual SiC devices (in theory) can endure temperatures up to 600°C (standard Si PE devices are typically limited to 150°C), withstand more voltage, tolerate a larger current density, and operate at a higher frequency. This augmented performance of SiC devices in turn leads to PE devices that are significantly more energy efficient in their operation. Research and development is ongoing to produce SiC PE products with higher currents

273

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

274

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.

275

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

276

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

277

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

278

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

279

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.

280

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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.

282

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

283

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

284

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.

285

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

286

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

287

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.

288

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.

289

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

SciTech Connect

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

290

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

SciTech Connect

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

291

Diffusion and impurity segregation in hydrogen-implanted silicon carbide  

SciTech Connect

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

292

2.04 - Processing of Silicon Carbide-Based Ceramics  

Science Journals Connector (OSTI)

Abstract The history of the success of the covalently bonded compound silicon carbide (SiC) started more than a century ago (1893) with the synthesis of raw SiC by Edward Goodrich Acheson. Though even today Acheson's process is still current, other synthesis methods have also been developed for the production of SiC powders, whiskers, platelets, and fibers. Due to its low chemical reactivity, it turned out to be difficult to develop methods and processes for the production of SiC-based ceramics. In the past, many approaches for processing SiC have been attempted with specific benefits and limitations in each case. Today a large spectrum of SiC-based ceramics manufactured by a wide variety of processing techniques exists. In order to get a systematic overview over the complex set of SiC-based ceramics, they can be divided into three groups. The first group includes porous ceramics with relatively coarse SiC particles bonded in a matrix of amorphous aluminum silicate. These SiC-based ceramics may be compared with the well-known traditional silicate ceramics in terms of processing technique via sintering in air and corresponding microstructure evolution. Some grinding tools, refractory bricks and foam filters belong to this silicate bonded SiC-based ceramics. The second group is sintered as well, but the focus of attention is more sharply directed toward keeping the intrinsic characteristics of SiC as a polycrystalline ceramic material. Typically they are sintered in protective atmospheres utilizing solid-state, liquid-phase or vapor-phase (evaporation-condensation) mechanisms. However, some of the desired properties can sometimes only be achieved by using pressure-assisted sintering techniques such as axial hot pressing, hot isostatic pressing or field-assisted sintering. This group of sintered SiC-based ceramics also contains some advanced modifications such as in situ toughened or nanostructured ceramics. The third group uses three reaction bonding processes for consolidation, namely liquid-solid, gas phase, and polymer-derived reaction bonding, in order to reduce the maximum consolidation temperature and to increase densification with the aim to achieve low-to-zero shrinkage. All reaction bonding approaches result in untoughened SiC ceramics like nitride bonded, chemical vapor infiltrated silicon, carbon bonded, and ex situ toughened ceramic matrix composites (i.e. carbon and SiC fiber-reinforced ceramics). Through reaction bonding, paper and even natural products like wood can be converted into SiC-based ceramics.

Jochen Kriegesmann

2014-01-01T23:59:59.000Z

293

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

SciTech Connect

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

294

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

SciTech Connect

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

295

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.

296

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

297

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

SciTech Connect

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

298

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

SciTech Connect

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

299

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

E-Print Network (OSTI)

June 2014 Keywords: Low-temperature combustion syn- thesis Tungsten carbide Electrocatalyst Gas burning on the environment, and reduce dependence on fossil fuels, development of pure electric and fuel of highly efficient low-cost electrode catalysts for the oxygen reduction cathode, metaleair batteries have

Volinsky, Alex A.

300

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.

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

302

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

SciTech Connect

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

303

Structure and chemistry of a metal cluster with a four-coordinate carbide carbon atom  

SciTech Connect

Molecular metal clusters with carbide carbon atoms of low coordination number have been prepared; they are the anionic (HFe/sub 4/C(CO)/sub 12//sup -/) and (Fe/sub 4/C(CO)/sub 12//sup 2 -/) clusters. An x-ray crystallographic analysis of a tetraaminozinc salt of the latter has established a butterfly array of iron atoms with the carbide carbon atom centered above the wings of the Fe/sub 4/ core. Each iron atom was bonded to three peripheral carbonyl ligands. The distances from the carbide carbon to iron were relatively short, particularly those to the apical iron atoms (1.80 A average). Protonation of the anionic carbide clusters reversibly yielded HFe/sub 4/(CH)(CO)/sub 12/, and methylation of the dianion gave (Fe/sub 4/(CC(O)CH/sub 3/)(CO)/sub 12//sup -/). Oxidation of (Fe/sub 4/C(CO)/sub 12//sup 2 -/) yielded the coordinately unsaturated Fe/sub 4/C(CO)/sub 12/ cluster, which was extremely reactive. Hydrogen addition to this iron cluster was rapid below 0/sup 0/C, and a C-H bond was formed in this transformation.

Davis, J.H. (Argonne National Lab., IL); Beno, M.A.; Williams, J.M.; Zimmie, J.A.; Tachikawa, M.; Muetterties, E.L.

1981-02-01T23:59:59.000Z

304

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

SciTech Connect

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

305

Ternary rare earth and actinoid transition metal carbides viewed as carbometalates  

SciTech Connect

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

306

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

SciTech Connect

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

307

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

SciTech Connect

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

308

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

309

Nonlinear-optical and structural properties of nanocrystalline silicon carbide films  

SciTech Connect

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

310

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

SciTech Connect

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

311

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

SciTech Connect

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

312

Corrosion of silicon carbide hot gas filter candles in gasification environment  

Science Journals Connector (OSTI)

Abstract Reliable cleaning of the fuel gas is required to meet the environmental regulations and to prevent corrosion and erosion of downstream components. The aggressive process environment in biomass-gasification power generation systems or in biofuels production systems can cause corrosion in ceramic hot gas filter candles used to clean the fuel gas. Therefore, to improve the reliability and durability of filters, the influence of steam, ash, and alkaline (earth) metals on the corrosion processes was studied for silicon carbide filter candles fabricated by Pall Schumacher. Exposures with biomass and lignite ashes caused a macroscopically expansion as well as microstructural effects that were analysed by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy. All effects are discussed and it is shown that the employment of silicon carbide filter candles in water vapour containing, alkali-rich gasification environment at high temperature is problematic.

Sarah Schaafhausen; Elena Yazhenskikh; Steffen Heidenreich; Michael Mller

2014-01-01T23:59:59.000Z

313

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

314

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

SciTech Connect

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

315

Laser-enhanced diffusion of nitrogen and aluminum dopants in silicon carbide  

Science Journals Connector (OSTI)

The diffusivities of different types of dopant atoms in silicon carbide wafers are generally very low. Nd:YAG and excimer lasers have been used to dope silicon carbide with nitrogen and aluminum, respectively. Mathematical models have been presented for the temperature distributions in the wafers to understand the diffusion mechanisms in the laser doping process. Since the silicon carbide substrate reaches its peritectic temperature (3100K) at irradiances of 80.6 and 61MW/cm2 for Nd:YAG and excimer lasers, respectively, lower irradiances were used to achieve solid-state diffusion. The Nd:YAG laser doping process doped nitrogen to a depth of 800nm; the KrF excimer laser doping process produced aluminum dopant depths of 200 and 450nm for different numbers of laser pulses. Two distinct diffusion regions, near-surface and far-surface regions, were identified in the dopant concentration profiles, indicating different diffusion mechanisms in these two regions. The effective diffusion coefficients of nitrogen and aluminum were determined for both regions and found to be 2.4נ10?5 and 9.2נ10?6cm2/s in the near- and far-surface regions for nitrogen, respectively, and 1.2נ10?5 and 1.3נ10?6cm2/s in the near- and far-surface regions for aluminum, respectively. The calculated diffusivities are at least six orders of magnitude higher than the typical values for nitrogen and aluminum, which indicate that the laser doping process enhances significantly the diffusion of dopants in silicon carbide.

Z. Tian; N.R. Quick; A. Kar

2006-01-01T23:59:59.000Z

316

The microstructure and hardness of silicon carbide synthesized by plasma pressure compaction  

Science Journals Connector (OSTI)

Using fine powders of silicon and carbon, silicon carbide was synthesized and compacted using the technique of plasma pressure compaction (P2C). The test samples were obtained by consolidating the powder particles at temperatures of 1400 and 1800C. Microhardness measurements revealed an increase with an increase in temperature of compaction and increased hold time. The conjoint influence of temperature and time of hold at temperature on microstructural development and hardness is presented and discussed.

B.G. Ravi; O.A. Omotoye; T.S. Srivatsan; M. Petrorali; T.S. Sudarshan

2000-01-01T23:59:59.000Z

317

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

318

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

319

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.

320

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

SciTech Connect

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

322

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

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

323

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

324

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

SciTech Connect

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

325

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

SciTech Connect

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

326

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

SciTech Connect

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

327

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

E-Print Network (OSTI)

Ni S Al Zr V Mn Co Mg, Cu, Mo Quantity (Weight 4) by Chemical Analysis 98 ' 5 0. 6 0. 2 0. 03 0. 60 Quantity (ppm) by Spectrographic Analysis 400 170 130 35 15 150 300 70 250 25 10 10 is smaller than for the silicon carbide... was machined to contain the bottom portion of the evacuation tube, removing the weld surface for these two parts from the disk region of the cap and decreasing the rigidity of the cap. This was recommended by previous research for the purpose of making...

Oakeson, David Oscar

1992-01-01T23:59:59.000Z

328

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

329

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

330

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

SciTech Connect

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

331

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

SciTech Connect

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

332

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

SciTech Connect

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

333

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

SciTech Connect

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

334

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

SciTech Connect

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

335

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

336

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

SciTech Connect

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

337

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

SciTech Connect

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

338

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

SciTech Connect

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

339

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

SciTech Connect

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

340

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

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Sulfur-Emission-Free Process of Molybdenum Carbide Synthesis by Lime-Enhanced Molybdenum Disulfide Reduction with Methane  

Science Journals Connector (OSTI)

Sulfur-Emission-Free Process of Molybdenum Carbide Synthesis by Lime-Enhanced Molybdenum Disulfide Reduction with Methane ... Molybdenite (MoS2) concentrate is the major mineral for molybdenum extraction. ... This understanding is critical for practical application of this reaction to produce Mo2C in an economic and green process. ...

Samad Ghasemi; Mohammad Hasan Abbasi; Ali Saidi; Jae Yul Kim; Jae Sung Lee

2011-10-28T23:59:59.000Z

342

Deposition of high-density silicon carbide coatings by fluidized-bed pyrolysis of chlorinated silane derivatives  

Science Journals Connector (OSTI)

Comparative analysis of the processes for preparation of high-density silicon carbide coatings by the fluidized-bed pyrolysis of the SiCl4 + CH4 + H2 + Ar and CH3SiCl3 + H2 + Ar mixtures on pyrocarboncoated zirco...

S. D. Kurbakov; T. A. Mireev

2009-04-01T23:59:59.000Z

343

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

E-Print Network (OSTI)

jet will disrupt the pool, unless mitigated by a splash suppressor. A SOLENOID CAPTURE SYSTEM Collider (MC) Comments Beam Power 4 MW No existing target system will survive at this power Ep 8 GeV yieldAbove: Power deposition in the superconducting magnets and the tungsten-carbide + water shield

McDonald, Kirk

344

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

SciTech Connect

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

345

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

SciTech Connect

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

Nixdorf, R.D.

1999-04-01T23:59:59.000Z

346

OAK RIDGE NATIONAL LABORATORY OPER*TEO BY UNION CARBIDE CORPORATION  

Office of Legacy Management (LM)

~$ ., . .Y.' ~$ ., . .Y.' ~. : ' : ,,, OAK RIDGE NATIONAL LABORATORY OPER*TEO BY UNION CARBIDE CORPORATION NUCLEAR DIVISION ' . ' : .m POST OFFICE BOX X OAK RIDGE, TENNESSEE ,X,0 ,. June 20, 1980 .~ ,, M r. Arthur J. 'Whitman Environmental and Safety 'Engineering Division U.S. Department of Energy ,) Washington, Oit. 20545 ., Dear Art: Soil Sample Analysis, City of Woburn Landfill, Woburn, Massachusetts ,,During a.radiological survey of the old.and new city of Woburn landfills (i-e: trip report.to Woburn, Massachusetts, A. J. Whitman to W . E. Mott, Gecember 7, 1979), six,soil. samples were collected and analyzed by gamma spectrometry and neutron absorption methods. The results of,these analyses'are given. below. ,.~ ,. 226Ra "'Th 238u - pci/g pciJcJ pci/g Sampl .y

347

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

Office of Legacy Management (LM)

/ / I' I OAK RIDGE NATIONAL LABORATORY OPERATED B Y UNION CARBIDE CORPORATION NUCLEAR DIVISION POST OFFICE BOK X OAK RIDGE, TENNESSEE 37830 August 21, 1979 Department of Energy, Oak Ridge Operations Attention: E. L. Keller, Director for Technical Services Division Post Office Box E Oak Ridge, Tennessee 37830 Gentlemen: Formerly Utilized Site-Remedial Action Program - Post Decontamination Radiological Survey of a portion of the Former Kellex Laboratory Site, Jersey City, New Jersey Decontamination of three (3) small land areas on the Levco portion of the former Kellex Laboratory site was completed by the Tobar Construction Company during the week ending August 11, 1979. Health physics and environmental monitoring services during clean-up operations were provided

348

ESS 2012 Peer Review - Experimental Investigation of Silicon Carbide Power Device Reliability - Robert Kaplar, SNL  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Experimental Investigation Experimental Investigation of Silicon Carbide Power Device Reliability September 27, 2012 Robert Kaplar, David Hughart, Sandeepan DasGupta, Matthew Marinella, Mark Smith, and Stanley Atcitty The authors gratefully acknowledge the support of Dr. Imre Gyuk of the United States Department of Energy, Office of Electricity Delivery and Energy Reliability, Energy Storage Program * Wide-bandgap semiconductors have material properties that make them theoretically superior to Silicon for power device applications * Lower power loss and reduced cooling requirements would increase the efficiency and reduce the size and complexity of power conversion systems linking energy storage to the grid, thus reducing overall system cost * However, wide-bandgap materials and devices are far less mature

349

SILICON CARBIDE MICRO-DEVICES FOR COMBUSTION GAS SENSING UNDER HARSH CONDITIONS  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen containing species in chemically reactive, high temperature environments. Robust metallization and electrical contacting techniques have been developed for device operation at elevated temperatures. To characterize the time response of the sensor responses in the millisecond range, a conceptually new apparatus has been built. Software has been developed to cope with the requirements of fast sensor control and data recording. In addition user friendly software has been developed to facilitate use of the SiC sensors for industrial process control applications.

Ruby N. Ghosh; Peter Tobias; Roger G. Tobin

2004-04-01T23:59:59.000Z

350

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

DOE Patents (OSTI)

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

Quinby, Thomas C. (Kingston, TN)

1985-01-01T23:59:59.000Z

351

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

DOE Patents (OSTI)

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

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

1994-01-01T23:59:59.000Z

352

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

DOE Patents (OSTI)

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

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

1994-11-01T23:59:59.000Z

353

Near-Field Radiative Heat Transfer between Metamaterials coated with Silicon Carbide Film  

E-Print Network (OSTI)

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

Basu, Soumyadipta; Wang, Liping

2014-01-01T23:59:59.000Z

354

Quantum-confined single photon emission at room temperature from Silicon carbide tetrapods  

E-Print Network (OSTI)

Controlled engineering of isolated solid state quantum systems is one of the most prominent goals in modern nanotechnology. In this letter we demonstrate a previously unknown quantum system namely silicon carbide tetrapods. The tetrapods have a cubic polytype core (3C) and hexagonal polytype legs (4H) a geometry that creates a spontaneous polarization within a single tetrapod. Modeling of the tetrapod structures predict that a bound exciton should exist at the 3C 4H interface. The simulations are confirmed by the observation of fully polarized and narrowband single photon emission from the tetrapods at room temperature. The single photon emission provides important insights towards understanding the quantum confinement effects in non-spherical nanostructures. Our results pave the way to a new class of crystal phase nanomaterials that exhibit single photon emission at room temperature and therefore are suitable for sensing, quantum information and nanophotonics.

Castelletto, Stefania; Magyar, Andrew P; Gentle, Angus; Gali, Adam; Aharonovich, Igor

2014-01-01T23:59:59.000Z

355

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

E-Print Network (OSTI)

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

Radulaski, Marina; Mller, Kai; Lagoudakis, Konstantinos G; Zhang, Jingyuan Linda; Buckley, Sonia; Kelaita, Yousif A; Alassaad, Kassem; Ferro, Gabriel; Vu?kovi?, Jelena

2014-01-01T23:59:59.000Z

356

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

E-Print Network (OSTI)

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

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

2014-12-08T23:59:59.000Z

357

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

SciTech Connect

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

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

2013-11-14T23:59:59.000Z

358

Use of Silicon Carbide as Beam Intercepting Device Material: Tests, Issues and Numerical Simulations  

E-Print Network (OSTI)

Silicon Carbide (SiC) stands as one of the most promising ceramic material with respect to its thermal shock resistance and mechanical strengths. It has hence been considered as candidate material for the development of higher performance beam intercepting devices at CERN. Its brazing with a metal counterpart has been tested and characterized by means of microstructural and ultrasound techniques. Despite the positive results, its use has to be evaluated with care, due to the strong evidence in literature of large and permanent volumetric expansion, called swelling, under the effect of neutron and ion irradiation. This may cause premature and sudden failure, and can be mitigated to some extent by operating at high temperature. For this reason limited information is available for irradiation below 100C, which is the typical temperature of interest for beam intercepting devices like dumps or collimators. This paper describes the brazing campaign carried out at CERN, the results, and the theoretical and numeric...

Delonca, M; Gil Costa, M; Vacca, A

2014-01-01T23:59:59.000Z

359

Evaluation of microstructural damage and alteration of polytypes to determine the aging of silicon carbide  

SciTech Connect

Irradiated silicon carbide (SiC) exhibits higher carrier content but a decrease in conductivity with increased irradiation. It was theorized that this conflicting data was due to structural damage due to irradiation. This theory was supported by the fact that non-irradiated 50{mu}m thick SiC is transparent for visible light and the higher the irradiation dose, the material of the same thickness became less transparent. However, changes in microscopy and polyforms observed by transmission electron microscopy in SiC due to irradiation were minor. Although existence of different polymorphs of SiC was documented, direct proof of the proposed theory has not yet been achieved.

Koenig, T. W.; Mishra, B.; Olson, D. L. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401 (United States); Meshi, L.; Foxman, Z.; Landau, A. [Ben-Gurion University of the Negev at Beer-Sheva, P.O.B. 653 Beer Sheva, 84105 (Israel); Riesterer, J. L.; Kennedy, J. R. [Advanced Test Reactor, Idaho National Laboratory, Idaho Falls, ID 83415 (United States)

2013-01-25T23:59:59.000Z

360

Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide  

E-Print Network (OSTI)

1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide powder and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Total Carbon by Combustion and Gravimetry 7-17 Total Boron by Titrimetry 18-28 Isotopic Composition by Mass Spectrometry 29-38 Chloride and Fluoride Separation by Pyrohydrolysis 39-45 Chloride by Constant-Current Coulometry 46-54 Fluoride by Ion-Selective Electrode 55-63 Water by Constant-Voltage Coulometry 64-72 Impurities by Spectrochemical Analysis 73-81 Soluble Boron by Titrimetry 82-95 Soluble Carbon by a Manometric Measurement 96-105 Metallic Impurities by a Direct Reader Spectrometric Method 106-114

American Society for Testing and Materials. Philadelphia

2004-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

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

SciTech Connect

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

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

1994-12-31T23:59:59.000Z

362

Effect of nanosilicon carbide on the carbonisation process of coal tar pitch  

Science Journals Connector (OSTI)

Abstract The study describes the effect of silicon carbide (SiC) nanopowder on the process of coal tar pitch thermal decomposition during heat treatment to a temperature of 2000C. The influence of nanosized SiC powder on the pyrolysis mechanism of carbonisation product yield, as well as structural and microstructural parameters of carbon obtained via carbonisation and further heating up to 2000C was studied. The results show that the incorporation of a suitable amount of ceramic nanopowder into the liquid coal tar pitch results in a decrease in the crystallite sizes of carbon residue, while further heating up to 2000C gives rise to two carbon phases, differing in crystallinity and interplanar distance between graphene layers. The SiC addition enhances the formation of well-ordered graphite domains in comparison with those present within a pure carbon matrix.

Danuta Mikociak; Anna Magiera; Grzegorz Labojko; Stanislaw Blazewicz

2014-01-01T23:59:59.000Z

363

Interaction of noble-metal fission products with pyrolytic silicon carbide  

SciTech Connect

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain layers of pyrolytic carbon and silicon carbide, which act as a miniature pressure vessel and form the primary fission product barrier. Of the many fission products formed during irradiation, the noble metals are of particular interest because they interact significantly with the SiC layer and their concentrations are somewhat higher in the low-enriched uranium fuels currently under consideration. To study fission product-SiC interactions, particles of UO/sub 2/ or UC/sub 2/ are doped with fission product elements before coating and are then held in a thermal gradient up to several thousand hours. Examination of the SiC coatings by TEM-AEM after annealing shows that silver behaves differently from the palladium group.

Lauf, R.J.; Braski, D.N.

1982-01-01T23:59:59.000Z

364

Stress testing on silicon carbide electronic devices for prognostics and health management.  

SciTech Connect

Power conversion systems for energy storage and other distributed energy resource applications are among the drivers of the important role that power electronics plays in providing reliable electricity. Wide band gap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) will help increase the performance and efficiency of power electronic equipment while condition monitoring (CM) and prognostics and health management (PHM) will increase the operational availability of the equipment and thereby make it more cost effective. Voltage and/or temperature stress testing were performed on a number of SiC devices in order to accelerate failure modes and to identify measureable shifts in electrical characteristics which may provide early indication of those failures. Those shifts can be interpreted and modeled to provide prognostic signatures for use in CM and/or PHM. Such experiments will also lead to a deeper understanding of basic device physics and the degradation mechanisms behind failure.

Kaplar, Robert James; Brock, Reinhard C.; Marinella, Matthew; King, Michael Patrick; Smith, Mark A.; Atcitty, Stanley

2011-01-01T23:59:59.000Z

365

Surface hardening of Fe-based alloy powders by Nd:YAG laser cladding followed by electrospark deposition with WC-Co cemented carbide  

Science Journals Connector (OSTI)

This paper presents the results of a study concerned with the surface hardening of Fe-based alloys and WC-8Co cemented carbide by integrating laser cladding and the electrospark deposition processes. Specimens of...

Jiansheng Wang; Huimin Meng; Hongying Yu; Zishuan Fan; Dongbai Sun

2010-08-01T23:59:59.000Z

366

Design and testing of a boron carbide capsule for spectral-tailoring in mixed-spectrum reactors  

SciTech Connect

A boron carbide capsule has been designed and used for spectral-tailoring experiments at the TRIGA reactor at Washington State Univ.. Irradiations were conducted in pulsed mode and in continuous operation for up to 4 h. A cadmium cover was used to reduce thermal heating. The neutron spectrum calculated with the Monte Carlo N-particle transport code 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. The design of a capsule using boron carbide fully enriched in {sup 10}B shows that it is possible to produce a neutron spectrum similar to that of {sup 235}U fission. (authors)

Greenwood, L.R.; Wittman, R. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Pierson, B.P. [Univ. of Michigan, Ann Arbor, MI 48109 (United States); Metz, L.A.; Payne, R.; Finn, E.C.; Friese, J.I. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States)

2011-07-01T23:59:59.000Z

367

Electric Discharge Sintering and Joining of Tungsten Carbide--Cobalt Composite with High-Speed Steel Substrate  

SciTech Connect

Simultaneous electro discharge sintering of high strength structure of tungsten carbide-cobalt composite and connection it with high-speed steel substrate is investigated and suitable operating parameters are defined. Tungsten carbide-cobalt and high-speed steel joining was produced by the method of high voltage electrical discharge together with application of mechanical pressure to powder compact. It was found that the density and hardness of composite material reach its maximum values at certain magnitudes of applied pressure and high voltage electrical discharge parameters. We show that there is an upper level for the discharge voltage beyond which the powder of composite material disintegrates like an exploding wire. Due to our results it is possible to determine optimal parameters for simultaneous electro discharge sintering of WC-Co and bonding it with high-speed steel substrate.

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

2011-01-17T23:59:59.000Z

368

SILICON CARBIDE MICRO-DEVICES FOR COMBUSTION GAS SENSING UNDER HARSH CONDITIONS  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen containing species in chemically reactive, high temperature environments. For these capacitive sensors we have determined that the optimum sensor operating point in terms of sensor lifetime and response time is at midgap. Detailed measurements of the oxide leakage current as a function of temperature were performed to investigate the high temperature reliability of the devices. In addition, robust metallization and electrical contacting techniques have been developed for device operation at elevated temperatures. To characterize the time response of the sensor responses in the millisecond range, a conceptually new apparatus has been built. Using laser induced fluorescence imaging techniques we have shown that the gas underneath the sensor can be completely exchanged with a time constant under 1 millisecond. Ultrahigh vacuum studies of the surface chemistry of the platinum gate have shown that sensor deactivation by adsorbed sulfur is a possible problem. Investigations on the chemical removal of sulfur by catalytic oxidation or reduction are continuing.

Ruby N. Ghosh; Peter Tobias; Roger G. Tobin

2004-10-01T23:59:59.000Z

369

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

E-Print Network (OSTI)

Primitive meteorites contain small amounts of presolar minerals that formed in the winds of evolved stars or in the ejecta of stellar explosions. Silicon carbide is the best studied presolar mineral. Based on its isotopic compositions it was divided into distinct populations that have different origins: Most abundant are the mainstream grains which are believed to come from 1.5-3 Msun AGB stars of roughly solar metallicitiy. The rare Y and Z grains are likely to come from 1.5-3 Msun AGB stars as well, but with subsolar metallicities (0.3-0.5x solar). Here we report on C and Si isotope and trace element (Zr, Ba) studies of individual, submicrometer-sized SiC grains. The most striking results are: (1) Zr and Ba concentrations are higher in Y and Z grains than in mainstream grains, with enrichments relative to Si and solar of up to 70x (Zr) and 170x (Ba), respectively. (2) For the Y and Z grains there is a positive correlation between Ba concentrations and amount of s-process Si. This correlation is well explain...

Hoppe, P; Vollmer, C; Groener, E; Heck, P R; Gallino, R; Amari, S; 10.1071/AS08033

2009-01-01T23:59:59.000Z

370

Recent advances and issues in development of silicon carbide composites for fusion applications  

SciTech Connect

Radiation-resistant advanced silicon carbide composites (SiC/SiC) have been developed as a promising candidate of the high-temperature operating advanced fusion DEMO reactor. With the completion of the proof-of-principle phase in development of nuclear-grade SiC/SiC, the R&D on SiC/SiC is shifting toward the more pragmatic phase, i.e., industrialization of component manufactures and data-basing. In this paper, recent advances and issues in 1) development of component fabrication technology including joining and functional coating, e.g., a tungsten overcoat as a plasma facing barrier, 2) recent updates in characterization of non-irradiated properties, e.g., strength anisotropy and chemical compatibility with solid lithium-based ceramics and lead-lithium liquid metal breeders, and 3) irradiation effects were specifically reviewed. Importantly high-temperature neutron irradiation effects on microstructural evolution, thermal and electrical conductivities and mechanical properties including the fiber/matrix interfacial strength were specified under various irradiation conditions, indicating seemingly very minor influence on the composite performance in the design temperature range.

Nozawa, T.; Hinoki, Tetsuya; Hasegawa, Akira; Kohyama, Akira; Katoh, Yutai; Snead, Lance L.; Henager, Charles H.; Hegeman, Hans

2009-04-30T23:59:59.000Z

371

Fatigue behavior of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites  

SciTech Connect

Flexure fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-poly, continuous silicon carbide (SiC) fibers. The Ti/SCS-6 composites had an 8-ply, (0{degree}, 90{degree}, +45{degree}, {minus}45{degree}), symmetric lay-up. During fatigue testing, four stages of flexure deflection behavior were observed. The deflection at stage 1 increased slightly with fatigue cycling, while that at stage 2 increased significantly with cycling. Interestingly, the deflection at stage 3 again increased negligibly with fatigue cycling. Stage 4 was associated with final failure, and the deflection increased abruptly. In the stage 1 region of the deflection behavior, no cracks were observed, the Ti/SiC interface debonding could be present, and the deflection changed slightly with cycling. When the stage 2 region commenced, cracks began to initiate. As stage 2 progressed, both crack density and crack length increased. The increased crack density and crack length contributed to the great increase in the deflection during stage 2. In stage 3, significant crack deflection and branching, and fiber bridging occurred, and crack density remained relatively constant. Crack deflection and branching, and fiber bridging slowed down crack driving force, and little crack extension was observed, which resulted in an insignificant amount of increase in the stage 3 deflection. The breakage of fibers in stage 4 significantly increased deflection.

Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering] [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Diaz, E.S. [Westinghouse Science and Technology Center, Pittsburgh, PA (United States)] [Westinghouse Science and Technology Center, Pittsburgh, PA (United States); Chiang, K.T.; Loh, D.H. [Rockwell International Corp., Canoga Park, CA (United States). Rocketdyne Div.] [Rockwell International Corp., Canoga Park, CA (United States). Rocketdyne Div.

1995-05-15T23:59:59.000Z

372

Radiation-tolerant joining technologies for silicon carbide ceramics and composites  

SciTech Connect

Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, TiSiC MAX-phase joining, calciaalumina glassceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 ?C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to 3 dpa at 500 ?C, thus indicating the first results obtained on irradiation-stable SiC joints. Under the more aggressive irradiation conditions (800 ?C, 5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

Katoh, Yutai; Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel; Koyanagi, Takaaki; Hinoki, Tetsuya; Henager, Charles H.; Ferraris, Monica

2014-05-01T23:59:59.000Z

373

Anisotropy of the solid-state epitaxy of silicon carbide in silicon  

SciTech Connect

A new method for the solid-state synthesis of epitaxial layers is developed, in which a substrate participates in the chemical reaction and the reaction product grows not on the substrate surface, as in traditional epitaxial methods, but inside the substrate. This method offers new opportunities for elastic-energy relaxation due to a mechanism operating only in anisotropic media, specifically, the attraction of point defects formed during the chemical reaction. The attracting point centers of dilatation form relatively stable objects, dilatation dipoles, which significantly reduce the total elastic energy. It is shown that, in crystals with cubic symmetry, the most favorable arrangement of dipoles is the ?111? direction. The theory is tested by growing silicon carbide (SiC) films on Si (111) substrates by chemical reaction with carbon monoxide CO. High-quality single-crystal SiC-4H films with thicknesses of up to 100 nm are grown on Si (111). Ellipsometric analysis showed that the optical constants of the SiC-4H films are significantly anisotropic. This is caused not only by the lattice hexagonality but also by a small amount (about 26%) of carbon atoms remaining in the film due to dilatation dipoles. It is shown that the optical constants of the carbon impurity correspond to strongly anisotropic highly oriented pyrolytic graphite.

Kukushkin, S. A., E-mail: kukushkin_s@yahoo.com; Osipov, A. V. [Russian Academy of Sciences, Institute of Problems of Machine Science (Russian Federation)

2013-12-15T23:59:59.000Z

374

Optical Spectroscopy of Tungsten Carbide for Uncertainty Analysis in Electron Electric Dipole Moment Search  

E-Print Network (OSTI)

We perform laser induced fluorescence(LIF) spectroscopy on a pulsed supersonic beam of tungsten carbide(WC) molecules, which has been proposed as a candidate molecular system for a permanent Electric Dipole Moment(EDM) search of the electron in its rovibrational ground state of the X3Delta1 state. In particular, [20.6]Omega=2, v'=4 <- X3Delta1,v"=0 transition at 485nm was used for the detection. The hyperfine structure and the Omega-doublet of the transition are measured, which are essential for estimating the size of the potential systematic uncertainties for electron EDM measurement. For further suppression of the systematic uncertainty, an alternative electron EDM measurement scheme utilizing the g factor crossing point of the Omega-doublet levels is discussed. On the other hand, flux and internal temperature of the molecular beam are characterized, which sets the limit on the statistical uncertainty of the electron EDM experiment. With the given results, the prospect of electron EDM experiment with the...

Lee, J; Skripnikov, L V; Petrov, A N; Titov, A V; Mosyagin, N S; Leanhardt, A E

2012-01-01T23:59:59.000Z

375

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

SciTech Connect

As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state suggests that there are preferred Si <100> interstitial splits. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C-SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C-SiC single crystal at 1573 K has been determined to be 3.80.410e-19 m2/sec.

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

2015-01-01T23:59:59.000Z

376

Evidence for Radiogenic Sulfur-32 in Type AB Presolar Silicon Carbide Grains?  

E-Print Network (OSTI)

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

Fujiya, Wataru; Zinner, Ernst; Pignatari, Marco; Herwig, Falk

2013-01-01T23:59:59.000Z

377

Silicon carbide absorption features: dust formation in the outflows of extreme carbon stars  

E-Print Network (OSTI)

Infrared carbon stars without visible counterparts are generally known as extreme carbon stars. We have selected a subset of these stars with absorption features in the 10-13 $\\mu$m range, which has been tentatively attributed to silicon carbide (SiC). We add three new objects meeting these criterion to the seven previously known, bringing our total sample to ten sources. We also present the result of radiative transfer modeling for these stars, comparing these results to those of previous studies. In order to constrain model parameters, we use published mass-loss rates, expansion velocities and theoretical dust condensation models to determine the dust condensation temperature. These show that the inner dust temperatures of the dust shells for these sources are significantly higher than previously assumed. This also implies that the dominant dust species should be graphite instead of amorphous carbon. In combination with the higher condensation temperature we show that this results in a much higher acceleration of the dust grains than would be expected from previous work. Our model results suggest that the very optically thick stage of evolution does not coincide with the timescales for the superwind, but rather, that this is a very short-lived phase. Additionally, we compare model and observational parameters in an attempt to find any correlations. Finally, we show that the spectrum of one source, IRAS 17534$-$3030, strongly implies that the 10-13 $\\mu$m feature is due to a solid state rather than a molecular species.

Angela K. Speck; Adrian B. Corman; Kristina Wakeman; Caleb H. Wheeler; Grant Thompson

2008-10-15T23:59:59.000Z

378

Crystallization characteristics and chemical bonding properties of nickel carbide thin film nanocomposites  

E-Print Network (OSTI)

The crystal structure and chemical bonding of magnetron-sputtering deposited nickel carbide Ni$_{1-x}$C$_{x}$ (0.05$\\leq$x$\\leq$0.62) thin films have been investigated by high-resolution X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and soft X-ray absorption spectroscopy. By using X-ray as well as electron diffraction, we found carbon-containing hcp-Ni (hcp-NiC$_{y}$ phase), instead of the expected rhombohedral-Ni$_{3}$C. At low carbon content (4.9 at\\%) the thin film consists of hcp-NiC$_{y}$ nanocrystallites mixed with a smaller amount of fcc-NiC$_{x}$. The average grain size is about 10-20 nm. With the increase of carbon content to 16.3 at\\%, the film contains single-phase hcp-NiC$_{y}$ nanocrystallites with expanded lattice parameters. With further increase of carbon content to 38 at\\%, and 62 at\\%, the films transform to X-ray amorphous materials with hcp-NiC$_{y}$ and fcc-NiC$_{x }$ nanodomain structures in an amorphous carbon-rich matrix. Ram...

Furlan, Andrej; Hultman, Lars; Jansson, Ulf; Magnuson, Martin

2014-01-01T23:59:59.000Z

379

Tritium trapping in silicon carbide in contact with solid breeder under high flux isotope reactor irradiation  

SciTech Connect

The trapping of tritium in silicon carbide (SiC) injected from ceramic breeding materials was examined via tritium measurements using imaging plate (IP) techniques. Monolithic SiC in contact with ternary lithium oxide (lithium titanate and lithium aluminate) as a ceramic breeder was irradiated in the High Flux Isotope Reactor (HFIR) in Oak Ridge, Tennessee, USA. The distribution of photo-stimulated luminescence (PSL) of tritium in SiC was successfully obtained, which separated the contribution of 14C -rays to the PSL. The tritium incident from ceramic breeders was retained in the vicinity of the SiC surface even after irradiation at 1073 K over the duration of ~3000 h, while trapping of tritium was not observed in the bulk region. The PSL intensity near the SiC surface in contact with lithium titanate was higher than that obtained with lithium aluminate. The amount of the incident tritium and/or the formation of a Li2SiO3 phase on SiC due to the reaction with lithium aluminate under irradiation likely were responsible for this observation.

H. Katsui; Y. Katoh; A. Hasegawa; M. Shimada; Y. Hatano; T. Hinoki; S. Nogami; T. Tanaka; S. Nagata; T. Shikama

2013-11-01T23:59:59.000Z

380

Silicon Carbide Temperature Monitor Measurements at the High Temperature Test Laboratory  

SciTech Connect

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

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

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

An ab initio study on compressibility of Al-containing MAX-phase carbides  

SciTech Connect

The compressibility of Al-containing MAX carbides was investigated in details using first-principle calculations based on density functional theory. The bond stiffness and bond angle as a function of pressure were examined. The M-Al bond stiffness is about 1/31/2 of M-C bond stiffness. The M-C bond close to Al atoms has the highest bond stiffness in M{sub 3}AlC{sub 2} and M{sub 4}AlC{sub 3} phases, with the similar bond stiffness of the other two bonds in the latter. Generally, the bond stiffness of the strongest M-C bond increases with increasing VEC (Valence Electron Concentration), which also affects the bond stiffness of other bonds. Of most importance, the bulk moduli are 0.256 of the mean bond stiffness for three series. With increasing pressure, M-Al bond angle increases, but M-C bond angles decreases, which indicates that M-Al and M-C bonds shift towards basal plane and along c-axis, respectively. As a result, the compressibility becomes more difficult along c-axis than a-axis. Some abnormal phenomena in the compressibility of Al-containing M{sub n+1}AlX{sub n} phases with VEC?=?6 are attributed to the thermodynamical instability of these compounds.

Bai, Yuelei, E-mail: baiyl@hit.edu.cn, E-mail: baiyl.hit@gmail.com; He, Xiaodong, E-mail: baiyl@hit.edu.cn, E-mail: baiyl.hit@gmail.com; Wang, Rongguo [National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080 (China); Zhu, Chuncheng [College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025 (China)

2013-11-07T23:59:59.000Z

382

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

DOE Patents (OSTI)

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

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

1996-01-23T23:59:59.000Z

383

Effects of Grain Morphology and Impurities on the Infrared Spectra of Silicon Carbide Particles  

E-Print Network (OSTI)

In this paper we demonstrate that distinguishing between the polytypes of silicon carbide by means of infrared features in small-grain spectra is impossible. Therefore, the infrared spectra of carbon stars, unfortunately, do not provide a means for drawing comparisons between the crystal structures of grains condensed in these environments and found in meteorites. This is proven first by comparing theoretical band profiles calculated for ellipsoidal particles, which show clearly a strong dependence on the axis ratio of the ellipsoids but negligible differences for the two most common polytypes. Second, spectra measured on submicron particle samples in the laboratory do not show any obvious correlation of band position or shape to the polytype. However, we demonstrate by measurements on SiC whiskers that grain shape is able to determine the spectrum completely. A further strong systematic influence on the band profile can be exerted by plasmon-phonon coupling due to conductivity of the SiC material. The latter fact probably is responsible for the confusion in the astronomical literature about spectral properties of SiC grains. We show that, although the conductivity seems to be a common property of many SiC laboratory samples, it is, however, independent of the polytype.

H. Mutschke; Th. Henning; D. Clment; A. C. Andersen

2001-11-15T23:59:59.000Z

384

Corrosion resistant coatings for silicon carbide heat exchanger tubes -- Volume 3. Final report  

SciTech Connect

The development of a silicon carbide (SiC) heat exchanger is a critical step in the development of the Externally-Fired Combined Cycle (EFCC) power system. SiC is the only material that provides the necessary combination of resistance to creep, thermal shock, and oxidation. While the SiC structure materials provide the thermomechanical and thermophysical properties needed for an efficient system, the mechanical properties of the SiC tubes are severely degraded through corrosion by the coal combustion products. To obtain the necessary service life of thousands of hours at temperature, a protective coating is needed that is stable with both the SiC tube and the coal combustion products, resists erosion from the particle laden gas stream, is thermal shock resistant, adheres to SiC during repeated thermal shocks (start-up, process upsets, shut-down), and allows the EFCC system to be cost competitive. This demanding set of technical performance and cost drivers was used in reviewing and selecting candidate protective materials. After a review of open literature, discussion with leading researchers in materials for coal combustion environments, and preliminary thermodynamic studies, a total of ten materials were identified for future study that were grouped into three categories: alumina-based materials, materials stable with SiO{sub 2}, and low expansion materials.

Boss, D.E.

1996-06-07T23:59:59.000Z

385

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

SciTech Connect

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

Shannon M. Bragg-Sitton

2013-09-01T23:59:59.000Z

386

Fe-24 wt.%Cr-4.1 wt.%C hardfacing alloy: Microstructure and carbide refinement mechanisms with ceria additive  

SciTech Connect

The microstructure and carbide refinement mechanisms of Fe-24 wt.%Cr-4.1 wt.%C hardfacing alloys with 0 wt.%, 0.5 wt.%, 1.0 wt.%, 2 wt.%, and 4 wt.% ceria additives have been systematically investigated in this work. Optical microscopy, field emission scanning electron microscopy with energy dispersive spectrometer, and X-ray diffraction were collectively used to study the microstructure, the phase components, and the chemical formation of inclusion formed in the welding process. Wear-resistance of the alloys was comparatively studied using an abrasive wear testing machine. The structure analysis results show that the Fe-Cr-C hardfacing alloy mainly consists of martensite, retained austenite, MC carbide and M{sub 7}C{sub 3} carbide. With increasing ceria additive contents, the average size of the primary M{sub 7}C{sub 3} carbide decreases and reaches a most refined state in the alloy with 2 wt.% ceria additives. Comparative wear tests data shows that the wear resistance of the hardfacing alloys with ceria additives is better than that without ceria additive. In a good agreement with the carbide refinement results, the wear resistance of the alloy reaches an optimum level in the sample with 2 wt.% ceria additive. The main RE inclusion type identified with in-situ XRD analysis is RE inclusion Ce{sub 2}O{sub 2}S. Thermodynamics calculation confirms that this type of RE inclusion could precipitate prior to M{sub 7}C{sub 3} carbides, and act as a heterogeneous nucleus for M{sub 7}C{sub 3} in the welding process, which effectively provides a mechanism for significant refinement of the M{sub 7}C{sub 3} carbide and improves its wear resistance. - Graphical Abstract: Rare Earth inclusion (Ce{sub 2}O{sub 2}S) distributes in the primary M{sub 7}C{sub 3} carbide. Moreover, Ce{sub 2}O{sub 2}S, which acts as heterogeneous nuclei of the primary M{sub 7}C{sub 3} carbide, is medium effective. Therefore, the primary M{sub 7}C{sub 3} carbide has been refined. Highlights: Black-Right-Pointing-Pointer Micro-hardness of primary M{sub 7}C{sub 3} carbide in Fe-Cr-C hardfacing alloy is 1594 HV. Black-Right-Pointing-Pointer RE inclusion Ce{sub 2}O{sub 2}S can be observed in the primary M{sub 7}C{sub 3} carbide. Black-Right-Pointing-Pointer Ce{sub 2}O{sub 2}S as heterogeneous nuclei of the Cr{sub 7}C{sub 3} is medium effective. Black-Right-Pointing-Pointer Primary carbide is most refined with 2 wt.% ceria additive.

Zhou, Y.F.; Yang, Y.L.; Jiang, Y.W.; Yang, J. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)] [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ren, X.J. [School of Engineering, Liverpool John Moores University, Liverpool L3 3AF (United Kingdom)] [School of Engineering, Liverpool John Moores University, Liverpool L3 3AF (United Kingdom); Yang, Q.X., E-mail: qxyang@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2012-10-15T23:59:59.000Z

387

Effect of the Support on the Electronic Structure of Au Nanoparticles Supported on Transition Metal Carbides: Choice of the Best Substrate for Au Activation  

SciTech Connect

Periodic density functional theory calculations on large supercells have been carried out to investigate the atomic and electronic structure of small gold particles (Au{sub 2}, Au{sub 4}, Au{sub 9}, Au{sub 13}, and Au{sub 14}) supported on the (001) surface of various transition metal carbides (TiC, ZrC, VC, and {delta}-MoC). All the supported Au particles exhibited strong interactions with the C sites of the metal-carbide surfaces. Nevertheless, the interactions between adsorbed Au atoms were attractive, thus ultimately facilitating nucleation of two- or three-dimensional metal particles. The presence of the underlying carbide strongly modified the electronic structure and charge density of the supported metal particles resulting in the experimentally proven improved catalytic performance of the resulting systems as compared with cases where the support is an oxide. The electronic perturbations were quite strong for two-dimensional gold particles directly in contact with the carbide substrates and gradually decreased for two-layer and three-layer thick supported particles. While all the metal carbides examined induced a qualitatively similar perturbation on the supported Au particles, the effect is significantly larger for ZrC thus suggesting that the resulting model catalyst would perform even better than the already tried Au/TiC system.

Rodriguez, J.A.; Florez, E.; Feria, L.; Vies, F.; Illas, F.

2009-10-16T23:59:59.000Z

388

Effect of the Support on the Electronic Structure of Au Nanoparticles Supported on Transition Metal Carbides: Choice of the Best Substrate for Au Activation  

SciTech Connect

Periodic density functional theory calculations on large supercells have been carried out to investigate the atomic and electronic structure of small gold particles (Au{sub 2}, Au{sub 4}, Au{sub 9}, Au{sub 13}, and Au{sub 14}) supported on the (001) surface of various transition metal carbides (TiC, ZrC, VC, and {delta}-MoC). All the supported Au particles exhibited strong interactions with the C sites of the metal-carbide surfaces. Nevertheless, the interactions between adsorbed Au atoms were attractive, thus ultimately facilitating nucleation of two- or three-dimensional metal particles. The presence of the underlying carbide strongly modified the electronic structure and charge density of the supported metal particles resulting in the experimentally proven improved catalytic performance of the resulting systems as compared with cases where the support is an oxide. The electronic perturbations were quite strong for two-dimensional gold particles directly in contact with the carbide substrates and gradually decreased for two-layer and three-layer thick supported particles. While all the metal carbides examined induced a qualitatively similar perturbation on the supported Au particles, the effect is significantly larger for ZrC thus suggesting that the resulting model catalyst would perform even better than the already tried Au/TiC system.

Florez, E.; Feria, L; Vines, F; Rodriguez, J; Illas, F

2009-01-01T23:59:59.000Z

389

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

SciTech Connect

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

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

2014-10-15T23:59:59.000Z

390

HINTS FOR NEUTRINO-PROCESS BORON IN PRESOLAR SILICON CARBIDE GRAINS FROM SUPERNOVAE  

SciTech Connect

We have studied more than 1000 presolar silicon carbide (SiC) grains from the Murchison CM2 chondrite for C- and Si-isotopic compositions. Twelve SiC X grains, characterized by strong enrichments in {sup 28}Si and believed to originate from Type II Supernovae (SNeII), were also measured for Li- and B-isotopic compositions. None of these grains show resolvable isotope anomalies in Li or B. For the seven X grains without Li and B contributions from nearby or attached SiC grains of distinct origins we find on average {sup 7}Li/{sup 6}Li = 11.83 {+-} 0.29 (solar system: 12.06) and {sup 11}B/{sup 10}B = 4.68 {+-} 0.31 (solar system: 4.03). The average {sup 7}Li/{sup 6}Li is compatible with the solar system ratio and the lithium in the X grains is likely largely dominated by contaminating Li of laboratory or meteoritic origin. Also, most of the boron in X grains appears to be contamination but the small {sup 11}B excess of {approx}16%, significant at the 2{sigma} level, can be considered a hint for the presence of boron produced by the neutrino process in the parent SNeII. Despite this finding, a quantitative comparison of the B isotope and abundance data of X grains with model predictions reveals deficiencies in our current understanding of the details of B production in SNeII as well as on B chemistry and condensation in SNII ejecta.

Fujiya, Wataru [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hoppe, Peter; Ott, Ulrich, E-mail: fujiya@eps.s.u-tokyo.ac.jp [Max Planck Institute for Chemistry, J.-J.-Becher-Weg 27, 55128 Mainz (Germany)

2011-03-20T23:59:59.000Z

391

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

SciTech Connect

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

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

2013-10-15T23:59:59.000Z

392

Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors  

SciTech Connect

The Advanced High-Temperature Reactor (AHTR) is a new reactor concept that uses a liquid fluoride salt coolant and a solid high-temperature fuel. Several alternative fuel types are being considered for this reactor. One set of fuel options is the use of pin-type fuel assemblies with silicon carbide (SiC) cladding. This report provides (1) an initial viability assessment of using SiC as fuel cladding and other in-core components of the AHTR, (2) the current status of SiC technology, and (3) recommendations on the path forward. Based on the analysis of requirements, continuous SiC fiber-reinforced, chemically vapor-infiltrated SiC matrix (CVI SiC/SiC) composites are recommended as the primary option for further study on AHTR fuel cladding among various industrially available forms of SiC. Critical feasibility issues for the SiC-based AHTR fuel cladding are identified to be (1) corrosion of SiC in the candidate liquid salts, (2) high dose neutron radiation effects, (3) static fatigue failure of SiC/SiC, (4) long-term radiation effects including irradiation creep and radiation-enhanced static fatigue, and (5) fabrication technology of hermetic wall and sealing end caps. Considering the results of the issues analysis and the prospects of ongoing SiC research and development in other nuclear programs, recommendations on the path forward is provided in the order or priority as: (1) thermodynamic analysis and experimental examination of SiC corrosion in the candidate liquid salts, (2) assessment of long-term mechanical integrity issues using prototypical component sections, and (3) assessment of high dose radiation effects relevant to the anticipated operating condition.

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

2007-09-01T23:59:59.000Z

393

Rovibronically selected and resolved two-color laser photoionization and photoelectron study of nickel carbide cation  

SciTech Connect

We have performed a two-color laser photoionization and photoelectron study of nickel carbide (NiC) and its cation (NiC{sup +}). By preparing NiC in a single rovibronic level of an intermediate vibronic state via visible laser excitation prior to ultraviolet laser photoionization, we have measured the photoionization efficiency spectrum of NiC near its ionization threshold, covering the formation of NiC{sup +}(X {sup 2}{Sigma}{sup +};v{sup +}=0-3). We have also obtained well-resolved rotational transitions for the v{sup +}=0 and 1 vibrational bands of the NiC{sup +}(X {sup 2}{Sigma}{sup +}) ground state. The assignment of rotational transitions observed between the neutral NiC intermediate state and the NiC{sup +} ion ground state has allowed the direct determination of a highly precise value for the ionization energy of NiC, IE(NiC)=67 525.1{+-}0.5 cm{sup -1} (8.372 05{+-}0.000 06 eV). This experiment also provides reliable values for the vibrational spacing [{Delta}G(1/2)=859.5{+-}0.5 cm{sup -1}], rotational constants (B{sub e}{sup +}=0.6395{+-}0.0018 cm{sup -1} and {alpha}{sub e}{sup +}=0.0097{+-}0.0009 cm{sup -1}), and equilibrium bond distance (r{sub e}{sup +}=1.628 A) for the NiC{sup +}(X {sup 2}{Sigma}{sup +}) ground state. The experimental results presented here are valuable for benchmarking the development of more reliable ab initio quantum computation procedures for energetic and spectroscopic calculations of transition metal-containing molecules.

Chang, Yih Chung [Department of Chemistry, University of California, Davis, Davis, California 95616 (United States); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106, Taiwan (China); Shi Xiaoyu; Ng, C. Y. [Department of Chemistry, University of California, Davis, Davis, California 95616 (United States); Lau, Kai-Chung [Department of Biology and Chemistry, City University of Hong Kong, Kowloon (Hong Kong); Yin Qingzhu [Department of Geology, University of California, Davis, Davis, California 95616 (United States); Liou, H. T. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106, Taiwan (China)

2010-08-07T23:59:59.000Z

394

Optical constants of magnetron sputtered boron carbide thin films from photoabsorption data in the range 30 to 770 eV  

SciTech Connect

This work discusses the experimental determination of the optical constants (refractive index) of DC-magnetron-sputtered boron carbide films in the 30-770 eV photon energy range. Transmittance measurements of three boron carbide films with thicknesses of 54.2, 79.0 and 112.5 nm were performed for this purpose. These are the first published experimental data for the refractive index of boron carbide films in the photon energy range above 160 eV, and for the near-edge x-ray absorption fine structure (NEXAFS) regions around the boron K (188 eV), carbon K (284.2 eV) and oxygen K (543.1 eV) absorption edges. The density, composition, surface chemistry and morphology of the films in this manuscript were also investigated using Rutherford Backscattering (RBS), X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and extreme ultraviolet (EUV) reflectance measurements.

Soufli, R; Aquila, A L; Salmassi, F; Fernandez-Perea, M; Gullikson, E M

2008-05-21T23:59:59.000Z

395

Metal-like self-organization of periodic nanostructures on silicon and silicon carbide under femtosecond laser pulses  

SciTech Connect

Periodic structures were generated on Si and SiC surfaces by irradiation with femtosecond laser pulses. Self-organized structures with spatial periodicity of approximately 600?nm appear on silicon and silicon carbide in the laser fluence range just above the ablation threshold and upon irradiation with a large number of pulses. As in the case of metals, the dependence of the spatial periodicity on laser fluence can be explained by the parametric decay of laser light into surface plasma waves. The results show that the proposed model might be universally applicable to any solid state material.

Gemini, Laura [Advanced Research Center for beam Science, Institute for Chemical Research, Kyoto University, 611-0011 Kyoto (Japan); Department of Physics, Graduate School of Science, Kyoto University, 606-85802 Kyoto (Japan); FNSPE, Czech Technical University in Prague, 11519 Prague (Czech Republic); HiLASE Project, Institute of Physics, ASCR, 18221 Prague (Czech Republic); Hashida, Masaki; Shimizu, Masahiro; Miyasaka, Yasuhiro; Inoue, Shunsuke; Tokita, Shigeki; Sakabe, Shuji [Advanced Research Center for beam Science, Institute for Chemical Research, Kyoto University, 611-0011 Kyoto (Japan); Department of Physics, Graduate School of Science, Kyoto University, 606-85802 Kyoto (Japan); Limpouch, Jiri [FNSPE, Czech Technical University in Prague, 11519 Prague (Czech Republic); Mocek, Tomas [HiLASE Project, Institute of Physics, ASCR, 18221 Prague (Czech Republic)

2013-11-21T23:59:59.000Z

396

From electronic structure to catalytic activity: A single descriptor for adsorption and reactivity on transition-metal carbides  

E-Print Network (OSTI)

Adsorption and catalytic properties of the polar (111) surface of transition-metal carbides (TMC's) are investigated by density-functional theory. Atomic and molecular adsorption are rationalized with the concerted-coupling model, in which two types of TMC surface resonances (SR's) play key roles. The transition-metal derived SR is found to be a single measurable descriptor for the adsorption processes, implying that the Br{\\o}nsted-Evans-Polanyi relation and scaling relations apply. This gives a picture with implications for ligand and vacancy effects and which has a potential for a broad screening procedure for heterogeneous catalysts.

Vojvodic, Aleksandra; Ruberto, Carlo; Lundqvist, Bengt I

2009-01-01T23:59:59.000Z

397

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

SciTech Connect

We used the DV-X alpha method to analyze the high-resolution soft X-ray emission and absorption spectra in the CK region of titanium carbide (TiC). The spectral profiles of the X-ray emission and absorption can be ssuscfucelly reproduced by the occupied and unoccupied density of states (DOS ), respectively, in the C2p orbitals of the center carbon atoms in a Ti62C63 cluster model, suggesting that the center carbon atom in a large cluster model expanded to the cubic-structured 53 (= 125) atoms provides sufficient DOS for the X-ray spectral analysis of rock-salt structured metal carbides.

Shimomura, Kenta; Muramatsu, Yasuji; Denlinger, Jonathan D.; Gullikson, Eric M.

2008-10-31T23:59:59.000Z

398

ROLE OF C AND P SITES ON THE CHEMICAL ACTIVITY OF METAL CARBIDE AND PHOSPHIDES: FROM CLUSTERS TO SINGLE-CRYSTAL SURFACES  

SciTech Connect

Transition metal carbides and phosphides have shown tremendous potential as highly active catalysts. At a microscopic level, it is not well understood how these new catalysts work. Their high activity is usually attributed to ligand or/and ensemble effects. Here, we review recent studies that examine the chemical activity of metal carbide and phosphides as a function of size, from clusters to extended surfaces, and metal/carbon or metal/phosphorous ratio. These studies reveal that the C and P sites in these compounds cannot be considered as simple spectators. They moderate the reactivity of the metal centers and provide bonding sites for adsorbates.

RODRIGUEZ,J.A.; VINES, F.; LIU, P.; ILLAS, F.

2007-07-01T23:59:59.000Z

399

Structural and chemical phase transitions in tungsten carbide films evidenced by the analysis of their stiffness tensors  

SciTech Connect

Brillouin light scattering (BLS) is used to provide a comprehensive study of thin tungsten carbide films deposited on single crystal silicon substrates whose distinctive nature depends critically on the deposition parameters. The use of stepped films in these slow-on-fast systems provides enhanced data sets and allows the velocity dispersion of the observed surface excitations, including the discrete Rayleigh and Sezawa modes to be studied in detail. Comprehensive and powerful methods of data analysis and interpretation including the recently developed Monte Carlo (MC) method, the surface Green's function, and classical approaches are applied to extract the effective elastic constants and density of each of the films. The MC and Green's function methods are used to remove ambiguities in Sezawa mode assignments and to identify a mode-crossing event. Auger electron spectroscopy and x-ray diffraction investigations confirm conclusions about chemical composition and microstructure obtained by BLS including a structural phase transition, thus leading to a consistent description of elastic, structural, and chemical properties of tungsten carbide films as a function of their deposition conditions. The anisotropic elastic tensors of the various films are employed for an analysis of the angular dependent Young's modulus and the shear modulus, suggesting implications for the film performance in wear protection. Finally, an estimate of the elastic anisotropy of the {alpha}-W{sub 2}C single crystal is provided on the basis of the effective elastic constants of a nanocrystalline W{sub 2}C film.

Wittkowski, T.; Jung, K.; Hillebrands, B.; Comins, J. D. [Fachbereich Physik und Forschungsschwerpunkt MINAS, Technische Universitaet Kaiserslautern, Erwin Schroedinger-Strasse 56, D-67663 Kaiserlautern (Germany); DST/NRF Centre of Excellence in Strong Materials, School of Physics, University of the Witwatersrand, Johannesburg, Wits 2050 (South Africa) and Materials Physics Research Institute, School of Physics, University of the Witwatersrand, Johannesburg, Wits 2050 (South Africa)

2006-10-01T23:59:59.000Z

400

Silicon carbide grains of type C provide evidence for the production of the unstable isotope $^{32}$Si in supernovae  

E-Print Network (OSTI)

Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae, within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotpic signatures of explosive supernova nucleosynthesis have been found in primitive meteorites. Much rarer silicon carbide grains of type C are a special sub-group of SiC grains from supernovae. They show peculiar abundance signatures for Si and S, isotopically heavy Si and isotopically light S, which appear to to be in disagreement with model predictions. We propose that C grains are formed mostly from C-rich stellar material exposed to lower SN shock temperatures than the more common type X grains. In this scenario, extreme $^{32}$S enrichments observed in C grains may be explained by the presence of short-lived $^{32}$Si ($\\tau$$_{1/2}$ = 153 years) in the ejecta, produced by neutron capture processes starting from the stable Si isotopes. No mixing from deeper Si-rich material and/or fractionation of Si from S due to mole...

Pignatari, M; Bertolli, M G; Trappitsch, R; Hoppe, P; Rauscher, T; Fryer, C; Herwig, F; Hirschi, R; Timmes, F X; Thielemann, F -K

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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.


401

Mechanochemical synthesis of tungsten carbide nano particles by using WO{sub 3}/Zn/C powder mixture  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Nano particles of WC are synthesized by mechanochemical process. ? Zn was used to reduce WO{sub 3}. ? By removing ZnO from the milling products with an acid leaching, WC will be the final products. ? XRD results showed that the reduction reactions were completed after 36 h. ? TEM and SEM images showed that the morphology of produced powder is nearly spherical like. -- Abstract: In this research we introduce a new, facile, and economical system for fabrication of tungsten carbide (WC) nano particle powder. In this system WO{sub 3}, Zn, and C have been ball-milled for several hours, which led to the synthesis of tungsten carbide nano particles. The synthesized WC can successfully be separated from the ball-milled product by subjecting the product powder to diluted HCl for removing ZnO and obtaining WC. X-ray diffraction (XRD) analysis indicates that the reduction of WO{sub 3} will be completed gradually by increasing milling time up to 36 h. Scanning electron microscope (SEM), and transmission electron microscope (TEM) images show that after 36 h of milling the particle size of the fabricated powder is nano metric (about 20 nm). Results have shown that this system can surmount some main problems occurred in previous similar WC synthesizing systems. For example carbothermic reduction reactions, which lead to the synthesis of W{sub 2}C instead of WC, would not be activated because in this system reactions take place gradually.

Hoseinpur, Arman, E-mail: arman.hoseinpur@stu-mail.um.ac.ir [Department of Materials and Metallurgical Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111, Islamic Republic of Iran (Iran, Islamic Republic of)] [Department of Materials and Metallurgical Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111, Islamic Republic of Iran (Iran, Islamic Republic of); Vahdati Khaki, Jalil; Marashi, Maryam Sadat [Department of Materials and Metallurgical Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111, Islamic Republic of Iran (Iran, Islamic Republic of)] [Department of Materials and Metallurgical Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111, Islamic Republic of Iran (Iran, Islamic Republic of)

2013-02-15T23:59:59.000Z

402

Reaction rate uncertainties and 26Al in AGB silicon carbide stardust  

E-Print Network (OSTI)

Stardust is a class of presolar grains each of which presents an ideally uncontaminated stellar sample. Mainstream silicon carbide (SiC) stardust formed in the extended envelopes of carbon-rich asymptotic giant branch (AGB) stars and incorporated the radioactive nucleus 26Al as a trace element. The aim of this paper is to analyse in detail the effect of nuclear uncertainties, in particular the large uncertainties of up to four orders of magnitude related to the 26Al_g+(p,gamma)27Si reaction rate, on the production of 26Al in AGB stars and compare model predictions to data obtained from laboratory analysis of SiC stardust grains. Stellar uncertainties are also briefly discussed. We use a detailed nucleosynthesis postprocessing code to calculate the 26Al/27Al ratios at the surface of AGB stars of different masses (M = 1.75, 3, and 5 M_sun) and metallicities (Z = 0.02, 0.012, and 0.008). For the lower limit and recommended value of the 26Al_g(p,gamma)27Si reaction rate, the predicted 26Al/27Al ratios replicate the upper values of the range of the 26Al/27Al ratios measured in SiC grains. For the upper limit of the 26Al_g(p,gamma)27Si reaction rate, instead, the predicted 26Al/27Al ratios are approximately 100 times lower and lie below the range observed in SiC grains. When considering models of different masses and metallicities, the spread of more than an order of magnitude in the 26Al/27Al ratios measured in stellar SiC grains is not reproduced. We propose two scenarios to explain the spread of the 26Al/27Al ratios observed in mainstream SiC, depending on the choice of the 26Al_g+p reaction rate. One involves different times of stardust formation, the other involves extra-mixing processes. Stronger conclusions will be possible after more information is available from future nuclear experiments on the 26Al_g+p reaction.

M. A. van Raai; M. Lugaro; A. I. Karakas; C. Iliadis

2007-12-21T23:59:59.000Z

403

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

SciTech Connect

Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo{sub 2}C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Mo{sub 2}C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft{sup 2} at a feed pressure of only 20 psig. The highest H{sub 2}/N{sub 2} selectivity obtained with this approach was 4.9. A transport model using dusty gas theory was derived to describe the hydrogen transport in the Mo{sub 2}C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo{sub 2}C catalyst layers. We have fabricated a Mo{sub 2}C/V composite membrane that in pure gas testing delivered a H{sub 2} flux of 238 SCFH/ft{sup 2} at 600 C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ?99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft{sup 2}.psi. However, during testing of a Mo{sub 2}C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft{sup 2}.psi was obtained which was stable during the entire test, meeting the permeance associated with the 2010 DOE target flux. Lastly, the Mo{sub 2}C/V composite membranes were shown to be stable for at least 168 hours = one week, including cycling at high temperature and alternating He/H{sub 2} exposure.

Way, J.; Wolden, Colin

2013-09-30T23:59:59.000Z

404

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen-containing species in chemically reactive, high temperature environments. For fast and stable sensor response measurements, a gate activation process is required. Activation of all sensors took place by switching back and forth between oxidizing (1.0% oxygen in nitrogen) and reducing (10% hydrogen in nitrogen) gases for several hours at a sensor temperature {ge}620 C. All 52 devices on the sensor chip were activated simultaneously by flooding the entire chip with gas. The effects of activation on surface morphology and structure of Pt gates before and after activation were investigated. The optical images obtained from Pt gates demonstrated a clear transition from a smooth and shiny surface to a grainy and cloudy surface morphology. XRD scans collected from Pt gates suggest the presence of an amorphous layer and species other than Pt (111) after activation. The reliability of the gate insulator of our metal-oxide-SiC sensors for long-term device operation at 630 C was studied. We find that the dielectric is stable against breakdown due to electron injection from the substrate with gate leakage current densities as low at 5nA/cm{sup 2} at 630 C. We also designed and constructed a new nano-reactor capable of high gas flow rates at elevated pressure. Our reactor, which is a miniature version of an industrial reactor, is designed to heat the flowing gas up to 700 C. Measurements in ultrahigh vacuum demonstrated that hydrogen sulfide readily deposits sulfur on the gate surface, even at the very high hydrogen/hydrogen sulfide ratios (10{sup 3}-10{sup 5}) expected in applications. Once deposited, the sulfur adversely affects sensor response, and could not be removed by exposure to hydrogen at the temperatures and pressures accessible in the ultrahigh vacuum experiments. Oxygen exposures, however, were very effective at removing sulfur, and the device performance after sulfur removal was indistinguishable from performance before exposure to H{sub 2}S.

Ruby N. Ghosh; Reza Loloee; Roger G. Tobin; Yung Ho Kahng

2006-04-01T23:59:59.000Z

405

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

SciTech Connect

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.

Gomez, T.; Florez, E; Rodriguez, J; Illas, F

2010-01-01T23:59:59.000Z

406

Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method  

SciTech Connect

We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of FischerTropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

2012-06-01T23:59:59.000Z

407

Activation of Noble Metals on Metal-Carbide Surfaces: Novel Catalysts for CO Oxidation, Desulfurization and Hydrogenation Reactions  

SciTech Connect

This perspective article focuses on the physical and chemical properties of highly active catalysts for CO oxidation, desulfurization and hydrogenation reactions generated by depositing noble metals on metal-carbide surfaces. To rationalize structure-reactivity relationships for these novel catalysts, well-defined systems are required. High-resolution photoemission, scanning tunneling microscopy (STM) and first-principles periodic density-functional (DF) calculations have been used to study the interaction of metals of Groups 9, 10 and 11 with MC(001) (M = Ti, Zr, V, Mo) surfaces. DF calculations give adsorption energies that range from 2 eV (Cu, Ag, Au) to 6 eV (Co, Rh, Ir). STM images show that Au, Cu, Ni and Pt grow on the carbide substrates forming two-dimensional islands at very low coverage, and three-dimensional islands at medium and large coverages. In many systems, the results of DF calculations point to the preferential formation of admetal-C bonds with significant electronic perturbations in the admetal. TiC(001) and ZrC(001) transfer some electron density to the admetals facilitating bonding of the adatom with electron-acceptor molecules (CO, O{sub 2}, C{sub 2}H{sub 4}, SO{sub 2}, thiophene, etc.). For example, the Cu/TiC(001) and Au/TiC(001) systems are able to cleave both S-O bonds of SO{sub 2} at a temperature as low as 150 K, displaying a reactivity much larger than that of TiC(001) or extended surfaces of bulk copper and gold. At temperatures below 200 K, Au/TiC is able to dissociate O{sub 2} and perform the 2CO + O{sub 2} {yields} 2CO{sub 2} reaction. Furthermore, in spite of the very poor hydrodesulfurization performance of TiC(001) or Au(111), a Au/TiC(001) surface displays an activity for the hydrodesulfurization of thiophene higher than that of conventional Ni/MoS{sub x} catalysts. In general, the Au/TiC system is more chemically active than systems generated by depositing Au nanoparticles on oxide surfaces. Thus, metal carbides are excellent supports for enhancing the chemical reactivity of noble metals.

Rodriguez J. A.; Illas, F.

2012-01-01T23:59:59.000Z

408

Influence of different illumination profiles on the on-state resistances of silicon carbide photoconductive semiconductor switches  

SciTech Connect

Characteristics of a silicon-carbide (SiC) photoconductive switch under different illumination profiles are presented. We triggered a V-doped semi-insulated 6H-SiC switch with lateral geometry using a laser beam of 532-nm wavelength. Photoconductivity tests for different spot profiles and locations show that such switches achieve a minimum on-state resistance when the switching gap is illuminated. The differences between on-state resistances are small for various partial illuminations of the switching gap. Semiconductor modeling is used to simulate the electric field and current profiles for different partial illuminations. The simulation results show poor on-state switch performance when partially illuminated. Based on these results, a more revealing circuit model for the switch matches well with experimental results for partial illuminations.

Wang, Langning, E-mail: wanglangning@126.com; Xun, Tao; Yang, Hanwu; Liu, Jinliang; Zhang, Yu [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)] [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2014-04-15T23:59:59.000Z

409

On Titanium Carbide Nanoparticles as the Origin of the 21 Micron Emission Feature in Post-Asymptotic Giant Branch Stars  

E-Print Network (OSTI)

Titanium carbide (TiC) nanocrystals were recently proposed as the carrier of the mysterious 21$\\mum$ emission feature observed in post-asymptotic giant branch stars, based on their close spectral match and the presolar nature of meteoritic TiC nanograins (which reveals their stellar ejecta origin). But we show in this {\\it Letter} that the Kramers-Kronig dispersion relations, which relate the wavelength-integrated extinction cross section to the total dust mass, would impose a lower bound on the TiC mass. This Kramers-Kronig lower limit exceeds the maximum available TiC mass by a factor of at least $\\simali$50, independent of the absolute value of the ultraviolet/visible absorptivity of nano TiC. The TiC model is therefore readily ruled out by the Kramers-Kronig physical principle.

Aigen Li

2003-11-04T23:59:59.000Z

410

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

SciTech Connect

In this work, we investigate the processes leading to the room-temperature growth of silicon carbide thin films by supersonic molecular beam epitaxy technique. We present experimental data showing that the collision of fullerene on a silicon surface induces strong chemical-physical perturbations and, for sufficient velocity, disruption of molecular bonds, and cage breaking with formation of nanostructures with different stoichiometric character. We show that in these out-of-equilibrium conditions, it is necessary to go beyond the standard implementations of density functional theory, as ab initio methods based on the Born-Oppenheimer approximation fail to capture the excited-state dynamics. In particular, we analyse the Si-C{sub 60} collision within the non-adiabatic nuclear dynamics framework, where stochastic hops occur between adiabatic surfaces calculated with time-dependent density functional theory. This theoretical description of the C{sub 60} impact on the Si surface is in good agreement with our experimental findings.

Taioli, Simone [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Department of Physics, University of Trento, Trento (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (Italy); Department of Chemistry, University of Bologna, Bologna (Italy); Garberoglio, Giovanni [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Simonucci, Stefano [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (Italy); Department of Physics, University of Camerino, Camerino (Italy); Beccara, Silvio a [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Department of Physics, University of Trento, Trento (Italy); Aversa, Lucrezia [Institute of Materials for Electronics and Magnetism, IMEM-CNR, Trento (Italy); Nardi, Marco [Institute of Materials for Electronics and Magnetism, IMEM-CNR, Trento (Italy); Institut fuer Physik, Humboldt-Universitaet zu Berlin, Berlin (Germany); Verucchi, Roberto [Institute of Materials for Electronics and Magnetism, FBK-CNR, Trento (Italy); Iannotta, Salvatore [Institute of Materials for Electronics and Magnetism, IMEM-CNR, Parma (Italy); Dapor, Maurizio [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Department of Materials Engineering and Industrial Technologies, University of Trento, Trento (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Padova (Italy); and others

2013-01-28T23:59:59.000Z

411

Mechanism and kinetics of carbide dissolution in near alpha Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-0.7Nd titanium alloy  

SciTech Connect

The present work evaluates the influence of bulk carbon content and aging temperature on the stability of carbide in near alpha Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-0.7Nd titanium alloy. The carbide particles were formed during heat treatment in the {beta} phase field and preserved by water quenching. Subsequent aging treatments at 750-850 Degree-Sign C caused partial dissolution of these precipitates, as a result of the peritectoid reaction between the {beta} phase and carbide. The models based on interface reaction controlled dissolution, via uniform atomic detachment, dislocation mechanism or vacancy flow, yielded experimental predictions comparable to the observed dissolution kinetics. Furnace cooling after heat treatment in the {beta} phase field dissolved carbide particles completely, and the microstructure changed from acicular-like or block {alpha} to equiaxed {alpha} with increase of carbon content. - Highlights: Black-Right-Pointing-Pointer Carbide dissolution occurs at precipitate/matrix interfaces, forming {beta}-depleted zone. Black-Right-Pointing-Pointer Peritectoid reaction is responsible for drastic reduction of carbide volume fraction. Black-Right-Pointing-Pointer Slower dissolution rate is accounted by dislocation, vacancy flow, and curvature. Black-Right-Pointing-Pointer Lamellar changed to equiaxed {alpha} with increasing carbon from {beta} furnace cooling.

Zhang, S.Z., E-mail: szzhangyt@163.com [School of Environmental and Materials Engineering, Yantai University, 32 Qingquan Road, Yantai 264005 (China); Li, M.M. [School of Environmental and Materials Engineering, Yantai University, 32 Qingquan Road, Yantai 264005 (China); Yang, R. [Titanium Alloy Laboratory, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

2011-12-15T23:59:59.000Z

412

Composites comprising silicon carbide fibers dispersed in magnesia-aluminate matrix and fabrication thereof and of other composites by sinter forging  

DOE Patents (OSTI)

A novel ceramic-ceramic composite of a uniform dispersion of silicon carbide fibers in a matrix of MgO.multidot.nAl.sub.2 O.sub.3 wherein n ranges from about 1 to about 4.5, said composite comprising by volume from 1 to 50% silicon carbide fibers and from 99 to 50% MgO.multidot.nAl.sub.2 O.sub.3. The composite is readily fabricated by forming a powder comprising a uniform dispersion of silicon carbide fibers in poorly crystalline phase comprising MgO and Al.sub.2 O.sub.3 in a mole ratio of n and either (a) hot pressing or preferably (b) cold pressing to form a preform and then forging utilizing a temperature in the range of 1100.degree. C. to 1900.degree. C. and a strain rate ranging from about 10.sup.-5 seconds .sup.-1 to about 1 seconds .sup.-1 so that surfaces cracks do not appear to obtain a shear deformation greater than 30%.

Panda, Prakash C. (Ithaca, NY); Seydel, Edgar R. (Ithaca, NY); Raj, Rishi (Ithaca, NY)

1989-10-03T23:59:59.000Z

413

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

SciTech Connect

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

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

2010-03-11T23:59:59.000Z

414

Zirconium and hafnium separation at Y-12  

NLE Websites -- All DOE Office Websites (Extended Search)

Walt Disney in 1954 named 20,000 leagues under the sea that used the same Nautilus sub- marine name. Nautilus was authorized by congress in July, 1951. Construction took 18...

415

A wide bandgap silicon carbide (SiC) gate driver for high-temperature and high-voltage applications  

SciTech Connect

Limitations of silicon (Si) based power electronic devices can be overcome with Silicon Carbide (SiC) because of its remarkable material properties. SiC is a wide bandgap semiconductor material with larger bandgap, lower leakage currents, higher breakdown electric field, and higher thermal conductivity, which promotes higher switching frequencies for high power applications, higher temperature operation, and results in higher power density devices relative to Si [1]. The proposed work is focused on design of a SiC gate driver to drive a SiC power MOSFET, on a Cree SiC process, with rise/fall times (less than 100 ns) suitable for 500 kHz to 1 MHz switching frequency applications. A process optimized gate driver topology design which is significantly different from generic Si circuit design is proposed. The ultimate goal of the project is to integrate this gate driver into a Toyota Prius plug-in hybrid electric vehicle (PHEV) charger module. The application of this high frequency charger will result in lighter, smaller, cheaper, and a more efficient power electronics system.

Lamichhane, Ranjan [University of Arkansas; Ericson, Milton Nance [ORNL; Frank, Steven Shane [ORNL; BRITTONJr., CHARLES L. [Oak Ridge National Laboratory (ORNL); Marlino, Laura D [ORNL; Mantooth, Alan [University of Arkansas; Francis, Matt [APEI, Inc.; Shepherd, Dr. Paul [University of Arkansas; Glover, Dr. Michael [University of Arkansas; Podar, Mircea [ORNL; Perez, M [University of Arkansas; Mcnutt, Tyler [APEI, Inc.; Whitaker, Mr. Bret [APEI, Inc.; Cole, Mr. Zach [APEI, Inc.

2014-01-01T23:59:59.000Z

416

On Silicon Carbide Grains as the Carrier of the 21 Micron Emission Feature in Post-Asymptotic Giant Branch Stars  

E-Print Network (OSTI)

The mysterious 21mu emission feature seen in 12 proto-planetary nebulae (PPNe) remains unidentified since its first detection in 1989. Over a dozen of candidate materials have been proposed within the past decade, but none of them has received general acceptance. Very recently, silicon carbide (SiC) grains with impurities were suggested to be the carrier of this enigmatic feature, based on recent laboratory data that doped SiC grains exhibit a resonance at \\~21mu. This proposal gains strength from the fact that SiC is a common dust species in carbon-rich circumstellar envelopes. However, SiC dust has a strong vibrational band at ~11.3mu. We show in this Letter that in order to be consistent with the observed flux ratios of the 11.3mu feature to the 21mu feature, the band strength of the 21mu resonance has to be very strong, too strong to be consistent with current laboratory measurements. But this does not yet readily rule out the SiC hypothesis since recent experimental results have demonstrated that the 21mu resonance of doped SiC becomes stronger as the C impurity increases. Further laboratory measurements of SiC dust with high fractions of C impurity are urgently needed to test the hypothesis of SiC as the carrier of the 21mu feature.

B. W. Jiang; Ke Zhang; Aigen Li

2005-07-27T23:59:59.000Z

417

The Effect of High Temperature Annealing on the Grain Characteristics of a Thin Chemical Vapor Deposition Silicon Carbide Layer.  

SciTech Connect

The unique combination of thermo-mechanical and physiochemical properties of silicon carbide (SiC) provides interest and opportunity for its use in nuclear applications. One of the applications of SiC is as a very thin layer in the TRi-ISOtropic (TRISO) coated fuel particles for high temperature gas reactors (HTGRs). This SiC layer, produced by chemical vapor deposition (CVD), is designed to withstand the pressures of fission and transmutation product gases in a high temperature, radiation environment. Various researchers have demonstrated that macroscopic properties can be affected by changes in the distribution of grain boundary plane orientations and misorientations [1 - 3]. Additionally, various researchers have attributed the release behavior of Ag through the SiC layer as a grain boundary diffusion phenomenon [4 - 6]; further highlighting the importance of understanding the actual grain characteristics of the SiC layer. Both historic HTGR fission product release studies and recent experiments at Idaho National Laboratory (INL) [7] have shown that the release of Ag-110m is strongly temperature dependent. Although the maximum normal operating fuel temperature of a HTGR design is in the range of 1000-1250C, the temperature may reach 1600C under postulated accident conditions. The aim of this specific study is therefore to determine the magnitude of temperature dependence on SiC grain characteristics, expanding upon initial studies by Van Rooyen et al, [8; 9].

Isabella J van Rooyen; Philippus M van Rooyen; Mary Lou Dunzik-Gougar

2013-08-01T23:59:59.000Z

418

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

E-Print Network (OSTI)

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

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

2008-03-10T23:59:59.000Z

419

A study on processing, characterization and erosion wear behavior of silicon carbide particle filled ZA-27 metal matrix composites  

Science Journals Connector (OSTI)

Abstract Metal matrix composites are mostly used as such structural engineering components where solid particle erosion is a common mode of failure. In this article, the study is concentrate on the processing and characterization of ZA-27 metal matrix composite (MMC) reinforced with silicon carbide (SiC) particle in different weight percentage ranging from 09wt% in a step of 3% each and also reported on their solid particle erosion wear response. A widely used and simple liquid metallurgy technique called stir casting technique is used for the fabrication of these composite materials. Erosion trials are made as per the experimental design based on Taguchis L16 orthogonal array. Predominantly influential parameters affecting the wear rate are identified. The results indicate that erosion wear rate of this composite is influence more by impact velocity and filler content respectively compare to others factors. It also shows the good filler characteristics of SiC particles as wear rate decreases with the increase in filler content in the matrix material.

Srimant Kumar Mishra; Sandhyarani Biswas; Alok Satapathy

2014-01-01T23:59:59.000Z

420

On the Dissociation of Molecular Hydrogen by Au Supported on Transition Metal Carbides: Choice of the Most Active Support  

SciTech Connect

A systematic density functional study of the adsorption and dissociation of H{sub 2} on the clean (001) surface of various transition metal carbides (TMCs; TM = Ti, Zr, V, Mo) and on Au{sub 4} nanoclusters supported on these TMCs is presented. It is found that the H{sub 2} dissociation on the bare clean TMCs strongly depends on the chemical nature of the support. Thus, the H{sub 2} molecule interacts rather strongly with TiC(001) and ZrC(001) but very weakly with VC(001) and {delta}-MoC(001). For the supported Au{sub 4} cluster, two different types of molecular mechanisms are found. For Au{sub 4}/TiC(001) and Au{sub 4}/ZrC(001), H{sub 2} dissociation leads to a H atom directly interacting with the Au{sub 4} cluster while the second H atom is transferred to the support. In contrast, for Au{sub 4}/VC(001) and Au{sub 4}/{delta}-MoC(001), both H atoms interact with the Au{sub 4} cluster. Overall, the present study suggests that, among the systems studied, Au/ZrC is the best substrate for H{sub 2} dissociation.

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

2011-03-15T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Atomic and vacancy ordering in carbide {zeta}-Ta{sub 4}C{sub 3-x} (0.28{<=}x{<=}0.40) and phase equilibria in the Ta-C system  

SciTech Connect

The structure of nonstoichiometric carbide phase {zeta}-Ta{sub 4}C{sub 3-x} formed in the tantalum-carbon (Ta-C) system is studied by X-ray and neutron powder diffraction and metallography. Investigated carbide {zeta}-TaC{sub 0.67} crystallizes in a trigonal (rhombohedral) space group R3-barm with cell parameters a{sub tr}=1.0180(1) nm, {alpha}{sub tr}=17.64 deg. (or a{sub h}=0.31216(2) nm, c{sub h}=3.0058(1) nm in hexagonal axes). The closely packed metal sublattice in carbide {zeta}-Ta{sub 4}C{sub 3-x} consists of alternating blocks where metal atoms are located in the same manner as on the FCC sublattice of the cubic carbide TaC{sub y} and the HCP sublattice of the hexagonal carbide Ta{sub 2}C{sub y}. This metal sublattice represents a transition sublattice between these FCC and HCP sublattices. An ordered distribution of atoms C and structural vacancies in carbide {zeta}-Ta{sub 4}C{sub 3-x} is revealed and the distribution function of atoms C is calculated for nonmetal sublattice sites, on which ordering takes place. It is shown that one long-range order parameter {eta} describes the ordering of {zeta}-carbide and the {eta} value in the investigated {zeta}-Ta{sub 4}C{sub 3-x} phase does not exceed 0.7. Carbide {zeta}-Ta{sub 4}C{sub 3-x} is stable in bulk and powdered states over a wide temperature interval of 300 to {approx}2400 K and has a narrow homogeneity interval from TaC{sub 0.65} to TaC{sub 0.68}. Microhardness of disordered and ordered tantalum carbide TaC{sub y} with the basic B1 structure and trigonal carbide {zeta}-Ta{sub 4}C{sub 3-x} is measured. The phase diagram of the Ta-C system is refined considering data obtained for the {zeta}-Ta{sub 4}C{sub 3-x} phase. - Graphical abstract: Ordered distribution of carbon atoms C and structural vacancies in a unit cell of the trigonal (space group R3-barm) {zeta}-Ta{sub 4}C{sub 3-x} phase. The closely packed metal sublattice in carbide {zeta}-Ta{sub 4}C{sub 3-x} consists of alternating blocks where Ta atoms are located in the same manner as on the FCC sublattice of the cubic carbide TaC{sub y} and the HCP sublattice of the hexagonal carbide Ta{sub 2}C{sub y}.

Gusev, A.I. [Institute of Solid State Chemistry, Ural Division of the Russian Academy of Sciences, 620041 Yekaterinburg (Russian Federation)], E-mail: gusev@ihim.uran.ru; Kurlov, A.S.; Lipatnikov, V.N. [Institute of Solid State Chemistry, Ural Division of the Russian Academy of Sciences, 620041 Yekaterinburg (Russian Federation)

2007-11-15T23:59:59.000Z

422

Superconducting and structural properties of {delta}-MoC{sub 0.681} cubic molybdenum carbide phase  

SciTech Connect

The superconducting and lattice properties of {delta}-MoC{sub 0.681} were studied by electromagnetic measurements, synchrotron X-ray diffraction, neutron diffraction, and electron diffraction. The superconducting properties (T{sub c}=12 K) of {delta}-MoC{sub 0.681} were well characterized by a weak coupling model. The carbon vacancies present in the host cubic structure were found to be robust, although the material was synthesized from stoichiometric carbon and Mo powder under a high-pressure of 6 GPa. A thermodynamically-stable structure with ordered vacancies did not account for the robust features of {delta}-MoC{sub 0.681} since the vacancies are unlikely to be ordered in long range in the host structure. A model based on inherent phonon instability theoretically predicted for a stoichiometric MoC phase might be responsible for the robust features of {delta}-MoC{sub 0.681}. - Graphical Abstract: The cubic molybdenum carbide shows an excellent superconductivity with robust carbon vacancies. Inherent phonon instability theoretically predicted for a stoichiometric MoC phase might be responsible for the vacancies rather than a thermodynamically-stable structure with vacancies ordering. Highlights: Black-Right-Pointing-Pointer The 12 K superconductivity is well characterized by a weakly coupling model. Black-Right-Pointing-Pointer Carbon vacancies are robust and disordered in the cubic host structure. Black-Right-Pointing-Pointer Inherent phonon instability might be responsible for the robust carbon vacancies in {delta}-MoC{sub 0.681}.

Sathish, C.I. [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Guo, Yanfeng, E-mail: GUO.Yanfeng@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Wang, Xia [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, Yoshihiro [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Li, Jun [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Zhang, Shoubao [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Matsushita, Yoshitaka [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan)] [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Shi, Youguo; Tian, Huanfang; Yang, Huaixin; Li, Jianqi [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)] [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yamaura, Kazunari, E-mail: YAMAURA.Kazunari@nims.go.jp [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan) [Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2012-12-15T23:59:59.000Z

423

VOLUME 89, NUMBER 1 P H Y S I C A L R E V I E W L E T T E R S 1 JULY 2002 Self-Organization of a Carbide Superlattice during Deposition of Carbon on Mo  

E-Print Network (OSTI)

of carbides in transition metals has long been a subject of interest since the Industrial Revolution. Re- cently, many of the same transition metals have been used as catalysts for the production of single-Organization of a Carbide Superlattice during Deposition of Carbon on Mo F. Tsui* and P. A. Ryan Department of Physics

424

Uniform nano-ripples on the sidewall of silicon carbide micro-hole fabricated by femtosecond laser irradiation and acid etching  

SciTech Connect

Uniform nano-ripples were observed on the sidewall of micro-holes in silicon carbide fabricated by 800-nm femtosecond laser and chemical selective etching. The morphology of the ripple was analyzed using scanning electronic microscopy. The formation mechanism of the micro-holes was attributed to the chemical reaction of the laser affected zone with mixed solution of hydrofluoric acid and nitric acid. The formation of nano-ripples on the sidewall of the holes could be attributed to the standing wave generated in z direction due to the interference between the incident wave and the reflected wave.

Khuat, Vanthanh [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Electronics and Information Engineering, Xi'an Jiaotong University, No. 28, Xianning West Road, Xi'an 710049 (China); Le Quy Don Technical University, No. 100, Hoang Quoc Viet Street, Hanoi 7EN-248 (Viet Nam); Chen, Tao; Gao, Bo; Si, Jinhai, E-mail: jinhaisi@mail.xjtu.edu.cn; Ma, Yuncan; Hou, Xun [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Electronics and Information Engineering, Xi'an Jiaotong University, No. 28, Xianning West Road, Xi'an 710049 (China)

2014-06-16T23:59:59.000Z

425

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)

of substoichiometric titanium carbide TiC1-x V. Moisy-Maurice and C. H. de Novion C.E.A./IRDI/DMECN/DTech, Laboratoire des échantillons de TiC1-x, (0,5 ~ 1 - x ~ 0,97). Quand la teneur x en lacunes de carbone augmente, (i 4p du titane (situé à 10-15 eV au-dessus du niveau de Fermi EF dans TiC0,97) se déplace

Paris-Sud XI, Université de

426

Ab initio calculations of the physical properties of transition metal carbides and nitrides and possible routes to high-T{sub c} superconductivity  

SciTech Connect

We report ab initio linear-response calculations of the phonon spectra and the electron-phonon interaction for several transition metal carbides and nitrides in a NaCl-type structure. For NbC, the kinetic, optical, and superconducting properties are calculated in detail at various pressures and the normal-pressure results are found to agree well with the experiment. Factors accounting for the relatively low critical temperatures T{sub c} in transition metal compounds with light elements are considered and the possible ways of increasing T{sub c} are discussed.

Maksimov, E. G., E-mail: maksimov@lpi.ru; Ebert, S. V. [Lebedev Physics Institute (Russian Federation); Magnitskaya, M. V.; Karakozov, A. E. [Vereshchagin Institute for High Pressure Physics (Russian Federation)

2007-10-15T23:59:59.000Z

427

Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films  

SciTech Connect

Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (?-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0?nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4?nm and P5 from 570.2 to 587.8?nm with temperature increasing from 600 to 900?C. But then are both blue-shifted, P4 to 500.2?nm and P5 to 573.8?nm from 900 to 1200?C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich ?-SiC: H materials.

Wen, Guozhi [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); School of Electronic and Electrical Engineering, Wuhan Polytechnic University, Wuhan, Hubei 430023 (China); Zeng, Xiangbin, E-mail: eexbzeng@mail.hust.edu.cn; Wen, Xixin; Liao, Wugang [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

2014-04-28T23:59:59.000Z

428

Effect of radio-frequency bias voltage on the optical and structural properties of hydrogenated amorphous silicon carbide  

SciTech Connect

Hydrogenated amorphous silicon carbide (a-Si{sub 1{minus}x}C{sub x}:H) films have been deposited using the electron cyclotron resonance chemical vapor deposition process under varying negative rf-bias voltage at the substrate. The optical and structural properties of these films are characterized using Rutherford backscattering spectroscopy, transmittance/reflectance spectrophotometry, photothermal deflection spectroscopy, Fourier transform infrared absorption, Raman scattering, and room temperature photoluminescence (PL). These films deposited using a gas mixture of silane, methane, and hydrogen at a constant gas flow ratio showed a slight increase in the carbon fraction x, but very obvious structural transformation, at increasing rf induced bias voltage from {minus}20 to {minus}120 V. Near stoichiometric a-Si{sub 1{minus}x}C{sub x}:H films with a carbon fraction x of almost 0.5 are achieved at low bias voltage range from {minus}20 to {minus}60 V. Visible PL with relatively low efficiency can be observed from such films at room temperature. For larger bias voltages from {minus}80 to {minus}120 V, slightly C-rich a-Si{sub 1{minus}x}C{sub x}:H films (x{gt}0.5) with larger optical gaps are obtained. These films have relatively higher PL efficiency, and the relative quantum efficiency was also found to depend strongly on the optical gap. Structurally, it was found that there is an increase in the hydrogen content and carbon sp{sup 2} bonding in the films at larger bias voltages. The latter leads to an increase in the disorder in the films. The linear relationship observed between the Urbach energy E{sub 0} and B factor in the Tauc equation suggests that the local defects related to microstructural disorder resulting from alloying with carbon dominate the overall defect structure of the films. Substrate biasing is noted to be crucial for the formation of Si{endash}C bonds, as deduced from the Raman scattering results. {copyright} 2001 American Institute of Physics.

Cui, J.; Rusli; Yoon, S. F.; Teo, E. J.; Yu, M. B.; Chew, K.; Ahn, J.; Zhang, Q.; Osipowicz, T.; Watt, F.

2001-06-01T23:59:59.000Z

429

Peculiar Structures of Small Magnesium Carbide Clusters: MgC2, (MgC2)2, and (MgC2)4 Alexander I. Boldyrev and Jack Simons*  

E-Print Network (OSTI)

larger clusters, which is reminiscent of what is seen in transition metal met-car compounds. Recently weLETTERS Peculiar Structures of Small Magnesium Carbide Clusters: MgC2, (MgC2)2, and (MgC2

Simons, Jack

430

Performance of high-velocity oxy-fuel-sprayed chromium carbide-nickel chromium coating in an actual boiler environment of a thermal power plant  

SciTech Connect

The present study aims to evaluate the performance of a high-velocity oxy-fuel (HVOF)-sprayed Cr{sub 3}C{sub 2}-NiCr (chromium carbide-nickel chromium) coating on a nickel-based super-alloy in an actual industrial environment of a coal-fired boiler, with the objective to protect the boiler super-heater and reheater tubes from hot corrosion. The tests were performed in the platen super heater zone of a coal-fired boiler for 1,000 h at 900 degrees C under cyclic conditions. The Cr{sub 3}C{sub 2}-NiCr coating imparted the necessary protection to the nickel-based super alloy in the given environment. The dense and flat splat structure of the coating, and the formation of oxides of chromium and nickel and their spinels, might have protected the substrate super alloy from the inward permeation of corrosive species.

Sidhu, T.S.; Prakash, S.; Agrawal, R.D. [Industrial Technology Institute, Roorkee (India)

2007-09-15T23:59:59.000Z

431

Wide band-gap, fairly conductive p-type hydrogenated amorphous silicon carbide films prepared by direct photolysis; solar cell application  

SciTech Connect

Wide optical band-gap (2.0--2.3 eV) undoped and boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) films have been prepared by both direct photo and rf glow discharge (GD plasma) decomposition of pure methylsilanes or acetylene and disilane gas mixtures. The photochemically prepared p-type films showed higher dark conductivities and lower activation energies. For an optical band gap of 2.0 eV a high conductivity of 7.0 x 10/sup -5/ (S cm/sup -1/) and a low activation energy of 0.33 eV have been measured. The first trial of these wide band-gap, fairly conductive films as a window layer in a p-i-n solar cell showed the high conversion efficiency of 9.46% under AM1 insolation.

Yamada, A.; Kenne, J.; Konagai, M.; Takahashi, K.

1985-02-01T23:59:59.000Z

432

Neutron diffraction study of the formation of ordered antiphase domains in cubic titanium carbide TiC{sub 0.60}  

SciTech Connect

A series of superstructural reflections (described within the sp. gr. Fd3m) are found to be split into three symmetric parts in the neutron powder diffraction pattern of titanium carbide TiC{sub 0.60} annealed at a temperature of 600 Degree-Sign C. No splitting of superstructural reflections is observed in the neutron diffraction pattern of TiC{sub 0.60} annealed at relatively high temperatures (780 Degree-Sign C). This phenomenon can be explained by that fact that the ordering of carbon atoms at relatively high temperatures (780 Degree-Sign C) is accompanied by the formation of randomly oriented rather large antiphase domains (APDs) (450 A). At relatively low temperatures (600 Degree-Sign C), stacking faults arise in the arrangement of partially ordered carbon atoms. In this case, relatively small ordered APDs (290 A) are formed, along with disordered ones.

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

2013-05-15T23:59:59.000Z

433

Effect of mechanical processing and heat treatment of powders on their sinterability characteristics linked with their method of manufacture. IV. The v/v vs tau function in a temperature jump in the sintering of porous bodies from molybdenum and tungsten carbide powders  

SciTech Connect

Use was made of molybdenum and tungsten carbide powders, which exhibit fairly high densification rates. The main object of the sintering of specimens from a molybdenum powder was to find out to what extent the behavior in a temperature jump of a metal differing markedly in physical properties (and electronic shell structure) from the metals investigated earlier resembled or differed from that of those metals. A molybdenum powder produced by the reduction of molybdenum trioxide with hydrogen at 800 C was chosen for investigation and experiments with tungsten carbide were carried out on two batches of powders produced at low and high carbidization temperatures. The study showed that the behavior of a porous specimen from the molybdenum powder did not differ from that of other metal powders. The behavior of tungsten carbide specimens in a temperature jump was similar to that of the metal powders studied in a previous investigation.

Ivensen, V.A.

1986-04-01T23:59:59.000Z

434

Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets  

E-Print Network (OSTI)

1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Boron by Titrimetry 7 to 13 Separation of Boron for Mass Spectrometry 14 to 19 Isotopic Composition by Mass Spectrometry 20 to 23 Separation of Halides by Pyrohydrolysis 24 to 27 Fluoride by Ion-Selective Electrode 28 to 30 Chloride, Bromide, and Iodide by Amperometric Microtitrimetry 31 to 33 Trace Elements by Emission Spectroscopy 34 to 46 1.3 The values stated in SI units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (F...

American Society for Testing and Materials. Philadelphia

1994-01-01T23:59:59.000Z

435

Materials characterization of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites. Part 2: Theoretical modeling of fatigue behavior  

SciTech Connect

Flexural fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-ply, continuous silicon carbide (SiC) fibers. The titanium composites had an eight-ply (0, 90, +45, {minus}45 deg) symmetric layup. Mechanistic investigation of the fatigue behavior is presented in Part 1 of this series. In Part 2, theoretical modeling of the fatigue behavior was performed using finite element techniques to predict the four stages of fatigue deflection behavior. On the basis of the mechanistic understanding, the fiber and matrix fracture sequence was simulated from ply to ply in finite element modeling. The predicted fatigue deflection behavior was found to be in good agreement with the experimental results. Furthermore, it has been shown that the matrix crack initiation starts in the 90 deg ply first, which is in agreement with the experimental observation. Under the same loading condition, the stress in the 90 deg ply of the transverse specimen is greater than that of the longitudinal specimen. This trend explains whey the longitudinal specimen has a longer fatigue life than the transverse specimen, as observed in Part 1.

Chiang, K.T.; Loh, D.H. [Rockwell International Corp., Canoga Park, CA (United States). Rocketdyne Div.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Diaz, E.S. [Westinghouse Science and Technology Center, Pittsburgh, PA (United States)

1995-12-01T23:59:59.000Z

436

Effect of temperature and particle velocity on the erosion of a silicon carbide continuous fibre reinforced calcium aluminosilicate glassceramic matrix composite  

Science Journals Connector (OSTI)

A unidirectional silicon carbide continuous fibre reinforced calcium aluminosilicate (CAS/SiC) glassceramic matrix composite has been subjected to silica sand solid particle erosion over the temperature range 20726C. Initial tests were conducted with a constant mass flow rate of gas of 40 l min?1. This gave a wear rate of 0.16 mg g?1 at room temperature which increased to 0.260.02 mg g?1 at 400C and above. When the increase in gas velocity, and hence particle velocity, was taken into account the wear rate was predicted to decrease with increasing temperature for a constant particle velocity. A wear rate of 0.06 mg g?1 was measured at 300C, which showed excellent agreement with the prediction of 0.07 mg g?1. As the main mechanism of material removal is via lateral cracking, this decrease in wear rate is broadly consistent with the release of residual axial tensile stresses in the matrix resulting from mismatches in the coefficients of thermal expansion of the two phases on cooling down from the processing temperature.

A.L Ham; J.A Yeomans; J.F Watts

1999-01-01T23:59:59.000Z

437

Laser doping of chromium as a double acceptor in silicon carbide with reduced crystalline damage and nearly all dopants in activated state  

Science Journals Connector (OSTI)

Chromium, a p-type dopant, has been incorporated into silicon carbide by laser doping. Secondary ion mass spectrometric data revealed enhanced solid solubility (2.29נ1019cm?3 in 6HSiC and 1.42נ1919cm?3 in 4HSiC), exceeding the equilibrium limit (3נ1017cm?3 in 6HSiC above 2500C). The roughness, surface chemistry and crystalline integrity of the doped sample were examined by optical interferometry, energy dispersive X-ray spectrometry and transmission electron microscopy, respectively, and showed no crystalline disorder due to laser heating. Deep-level transient spectroscopy confirmed Cr as a deep-level acceptor with activation energies Ev+0.80eV in 4HSiC and Ev+0.45eV in 6HSiC. The Hall effect measurements showed that the hole concentration (1.942נ1019cm?3) is almost twice the average Cr concentration (1נ1019cm?3), confirming that almost all of the Cr atoms were completely activated to the double acceptor state by the laser-doping process without requiring any additional annealing step.

Sachin Bet; Nathaniel Quick; Aravinda Kar

2008-01-01T23:59:59.000Z

438

Mechanism of WO{sub 3} reduction and carburization in CH{sub 4}/H{sub 2} mixtures leading to bulk tungsten carbide powder catalysts  

SciTech Connect

The mechanism of bulk tungsten carbide catalysts synthesis from WO{sub 3} in CH{sub 4}/H{sub 2} mixtures has been studied using temperature programmed reactions associated with CH{sub 4}/D{sub 2} exchange reaction and in situ X-ray diffraction. Various experimental parameters have been studied such as partial pressures of reactants, heating rate, mass of precursor, or flow rate in order to determine the most important steps occurring during the transformation of WO{sub 3} to WC. It is shown that at temperatures below 900--923 K the diffusion within the solid particles is slow with respect to the rate of reduction of the surface, allowing the carburization of the surface in the presence of a core still partially oxidized. At higher temperatures, the diffusion is rapid, leading to a uniform reduction within the solid. In this case, the surface is continuously replenished in oxygen thus inhibiting the activation of methane and allowing the carburization to proceed only when the solid is deeply reduced. An inhibiting effect of hydrogen pressure on the interaction of methane with the surface has also been evidenced, an effect which excludes the possibility of an independent control of the reduction process from that of carburization. Finally the role of space velocity has also been elucidated.

Loefberg, A.; Frennet, A.; Leclercq, G.; Leclercq, L.; Giraudon, J.M.

2000-01-01T23:59:59.000Z

439

Silicon-on-insulator-based high-voltage, high-temperature integrated circuit gate driver for silicon carbide-based power field effect transistors  

SciTech Connect

Silicon carbide (SiC)-based field effect transistors (FETs) are gaining popularity as switching elements in power electronic circuits designed for high-temperature environments like hybrid electric vehicle, aircraft, well logging, geothermal power generation etc. Like any other power switches, SiC-based power devices also need gate driver circuits to interface them with the logic units. The placement of the gate driver circuit next to the power switch is optimal for minimising system complexity. Successful operation of the gate driver circuit in a harsh environment, especially with minimal or no heat sink and without liquid cooling, can increase the power-to-volume ratio as well as the power-to-weight ratio for power conversion modules such as a DC-DC converter, inverter etc. A silicon-on-insulator (SOI)-based high-voltage, high-temperature integrated circuit (IC) gate driver for SiC power FETs has been designed and fabricated using a commercially available 0.8--m, 2-poly and 3-metal bipolar-complementary metal oxide semiconductor (CMOS)-double diffused metal oxide semiconductor (DMOS) process. The prototype circuit-s maximum gate drive supply can be 40-V with peak 2.3-A sourcing/sinking current driving capability. Owing to the wide driving range, this gate driver IC can be used to drive a wide variety of SiC FET switches (both normally OFF metal oxide semiconductor field effect transistor (MOSFET) and normally ON junction field effect transistor (JFET)). The switching frequency is 20-kHz and the duty cycle can be varied from 0 to 100-. The circuit has been successfully tested with SiC power MOSFETs and JFETs without any heat sink and cooling mechanism. During these tests, SiC switches were kept at room temperature and ambient temperature of the driver circuit was increased to 200-C. The circuit underwent numerous temperature cycles with negligible performance degradation.

Tolbert, Leon M [ORNL; Huque, Mohammad A [ORNL; Blalock, Benjamin J [ORNL; Islam, Syed K [ORNL

2010-01-01T23:59:59.000Z

440

A methodology to identify and quantify mobility-reducing defects in 4H-silicon carbide power metal-oxide-semiconductor field-effect transistors  

SciTech Connect

In this paper, we present a methodology for the identification and quantification of defects responsible for low channel mobility in 4H-Silicon Carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs). To achieve this, we use an algorithm based on 2D-device simulations of a power MOSFET, density functional simulations, and measurement data. Using physical modeling of carrier mobility and interface traps, we reproduce the experimental I-V characteristics of a 4H-SiC doubly implanted MOSFET through drift-diffusion simulation. We extract the position of Fermi level and the occupied trap density as a function of applied bias and temperature. Using these inputs, our algorithm estimates the number of possible trap types, their energy levels, and concentrations at 4H-SiC/SiO{sub 2} interface. Subsequently, we use density functional theory (DFT)-based ab initio simulations to identify the atomic make-up of defects causing these trap levels. We study silicon vacancy and carbon di-interstitial defects in the SiC side of the interface. Our algorithm indicates that the D{sub it} spectrum near the conduction band edge (3.25?eV) is composed of three trap types located at 2.82.85?eV, 3.05?eV, and 3.13.2?eV, and also calculates their densities. Based on DFT simulations, this work attributes the trap levels very close to the conduction band edge to the C di-interstitial defect.

Ettisserry, D. P., E-mail: deva@umd.edu; Goldsman, N. [Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742 (United States); Lelis, A. [U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

2014-03-14T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Heat Flux Calculation and Problem of Flaking of Boron Carbide Coatings on the Faraday Screen of the ICRH Antennas During Tore Supra High Power, Long Pulse Operation  

SciTech Connect

Reliable and repetitive high power and long pulse tokamak operation is strongly dependant of the ability to secure the Plasma Facing Components (PFCs). In Tore Supra, a network of 7 infrared (IR) video cameras is routinely used to prevent PFCs overheating and damage in selected regions. Real time feedback control and offline analysis are essential for basic protection and understanding of abnormal thermal events. One important limitation detected by the IR real time feed-back loop during high power RF operation (injected power of 9.5 MW over 26 s and 12 MW over 10 s have been achieved respectively in 2006 and 2008) is due to the interaction between fast ions which increase the power flux density and flaking of the boron carbide coatings on the Faraday screen box of the ICRH antennas. An IR-based experimental procedure is proposed in order to detect new flakes during plasma operation. The thermal response of the B4C coating is studied with and without flaking during plasma operation. The experimental heat flux deposited by fast ion losses on the Faraday screen is calculated for high (3.8 T) and low magnetic field (2 T) during high RF power operation (with fundamental hydrogen minority and second harmonic ICRH heating schemes respectively). The paper addresses both thermal science issues applied to machine protection and limitation due to fast ions issues during high RF power, long pulse operation. Safety margin to critical heat flux and number of fatigue cycles under heat load are presented in the paper.

Corre, Y. [French Atomic Energy Commission (CEA), Cadarache, St. Paul lez Durance] [French Atomic Energy Commission (CEA), Cadarache, St. Paul lez Durance; Lipa, M. [CEA IRFM, St. Paul-lez-Durance, France] [CEA IRFM, St. Paul-lez-Durance, France; Agarici, G. [Fusion for Energy (F4E), Barcelona, Spain] [Fusion for Energy (F4E), Barcelona, Spain; Basiuk, V. [CEA IRFM, St. Paul-lez-Durance, France] [CEA IRFM, St. Paul-lez-Durance, France; Colas, L. [French Atomic Energy Commission (CEA)] [French Atomic Energy Commission (CEA); Courtois, X. [CEA, St. Paul Les Durance, France] [CEA, St. Paul Les Durance, France; Dumont, R. J. [French Atomic Energy Commission (CEA), Cadarache, St. Paul lez Durance] [French Atomic Energy Commission (CEA), Cadarache, St. Paul lez Durance; Ekedahl, A. [French Atomic Energy Commission (CEA), Institute for Magnetic Fusion Research (IRFM)] [French Atomic Energy Commission (CEA), Institute for Magnetic Fusion Research (IRFM); Gardarein, J. L. [University of Aix, Marseille, France] [University of Aix, Marseille, France; Klepper, C Christopher [ORNL] [ORNL; Martin, V. [French Atomic Energy Commission (CEA), Institute for Magnetic Fusion Research (IRFM)] [French Atomic Energy Commission (CEA), Institute for Magnetic Fusion Research (IRFM); Moncada, V. [CEA, St. Paul Les Durance, France] [CEA, St. Paul Les Durance, France; Portafaix, C. [CEA, St. Paul Les Durance, France] [CEA, St. Paul Les Durance, France; Rigollet, F. [University of Aix, Marseille, France] [University of Aix, Marseille, France; Tawizgant, R. [CEA, St. Paul Les Durance, France] [CEA, St. Paul Les Durance, France; Travere, J. M. [CEA, St. Paul Les Durance, France] [CEA, St. Paul Les Durance, France; Valliez, K. [CEA, St. Paul Les Durance, France] [CEA, St. Paul Les Durance, France

2011-01-01T23:59:59.000Z

442

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

E-Print Network (OSTI)

. Import Sources (1995-98): Zirconium ores and concentrates: South Africa, 53%; Australia, 45%; and other Kingdom, 4%. Tariff: Item Number Normal Trade Relations 12/31/99 Zirconium ores and concentrates 2615.S. Department of Energy (DOE) held over 500 tons of zirconium in various forms. DOE also maintained a supply

443

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

E-Print Network (OSTI)

was insignificant. Import Sources (1996-99): Zirconium ores and concentrates: South Africa, 56%; Australia, 41, 4%; and other, 9%. Tariff: Item Number Normal Trade Relations 12/31/00 Zirconium ores.S. Department of Energy (DOE) held over 500 tons of zirconium in various forms. DOE also maintained a stockpile

444

Hafnium silicide formation on Si(100) upon annealing  

SciTech Connect

High dielectric constant materials, such as HfO{sub 2}, have been extensively studied as alternatives to SiO{sub 2} in new generations of Si based devices. Hf silicate/silicide formation has been reported in almost all literature studies of Hf based oxides on Si, using different methods of preparation. A silicate interface resembles close to the traditional Si/SiO{sub 2}. The silicate very likely forms a very sharp interface between the Si substrate and the metal oxide, and would be suitable for device applications. However, the thermal instability of the interfacial silicate/oxide film leads to silicidation, causing a dramatic loss of the gate oxide integrity. Despite the importance of the Hf silicide surface and interface with Si, only a few studies of this surface are present in the literature, and a structural determination of the surface has not been reported. This paper reports a study of the Hf silicide formation upon annealing by using a combination of XPS, LEED, and x-ray photoelectron diffraction (XPD) analyses. Our results clearly indicate the formation of a unique ordered Hf silicide phase (HfSi{sub 2}), which starts to crystallize when the annealing temperature is higher than 550 deg. C.

Siervo, A. de [Experimentelle Physik 1, Universitaet Dortmund, Otto-Hahn-Str. 4, D 44221 Dortmund (Germany); Laboratorio Nacional de Luz Sincrotron, Caixa Postal 6192, 13084-971, Campinas, Sao Paulo (Brazil); Fluechter, C. R.; Weier, D.; Schuermann, M.; Dreiner, S.; Westphal, C. [Experimentelle Physik 1, Universitaet Dortmund, Otto-Hahn-Str. 4, D 44221 Dortmund (Germany); Carazzolle, M. F.; Pancotti, A.; Landers, R.; Kleiman, G. G. [Instituto de Fisica 'Gleb Wataghin', Universidade Estadual de Campinas, Caixa Postal 6165, 13083-970, Campinas, Sao Paulo (Brazil)

2006-08-15T23:59:59.000Z

445

Status of cross-section data for gas production from vanadium and {sup 26}AL from silicon carbide in a D-T fusion reactor.  

SciTech Connect

Current designs of fusion-reactor systems seek to use radiation-resistant, low-activation materials that support long service lifetimes and minimize radioactive-waste problems after decommissioning. Reliable assessment of fusion materials performance requires accurate neutron-reaction cross sections and radioactive-decay constants. The problem areas usually involve cross sections since decay parameters tend to be better known. The present study was motivated by two specific questions: (i) Why are the {sup 51}V(n,np){sup 50}Ti cross section values in the ENDF/B-VI library so large (a gas production issue)? (ii) How well known are the cross sections associated with producing 7.4 x 10{sup 5} y {sup 26}Al in silicon carbide by the process {sup 28}Si(n,np+d){sup 27} Al(n,2n){sup 26}Al (a long-lived radioactivity issue)? The energy range 14-15 MeV of the D-T fusion neutrons is emphasized. Cross-section error bars are needed so that uncertainties in the gas and radioactivity generated over the lifetime of a reactor can be estimated. We address this issue by comparing values obtained from prominent evaluated cross-section libraries. Small differences between independent evaluations indicate that a physical quantity is well known while the opposite signals a problem. Hydrogen from {sup 51}V(n,p){sup 51}Ti and helium from {sup 51}V(n,{alpha}){sup 48}Sc are also important sources of gas in vanadium, so they too were examined. We conclude that {sup 51}V(n,p){sup 51}Ti is adequately known but {sup 51}V(n,np+d){sup 50}Ti is not. The status for helium generation data is quite good. Due to recent experimental work, {sup 27}Al(n,2n){sup 26}Al seems to be fairly well known. However, the situation for {sup 28}Si(n,np+d){sup 27}Al remains unsatisfactory.

Gomes, I. C.

1998-08-11T23:59:59.000Z

446

Union Carbides Last 20 Years in Oak Ridge  

NLE Websites -- All DOE Office Websites (Extended Search)

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

447

Silicon Carbide and Silicon Carbide Composites for Fusion Reactor Applications  

SciTech Connect

This paper reviews recent achievements as to "nuclear-grade" SiC composites in particular for materials-system integration. SiC composite component development are reviewed including VHTR control rod scale model and compact intermediate heat exchanger scale mode by current joining and assembly techniques. Joining methods for SiC to metal and results of characterization of joint shear strength by the torsion tests using small specimens were also reviewed. The recent results of neutron irradiation experiments were also reviewed including detailed analysis of mechanical properties, irradiation creep and preliminary results on tritium behavior in SiC.

Hinoki, Tatsuya [Kyoto University, Japan] [Kyoto University, Japan; Hasegawa, Akira [Tohoku University, Japan] [Tohoku University, Japan; Katoh, Yutai [ORNL] [ORNL; Snead, Lance Lewis [ORNL] [ORNL; Jung, H.C. [Kyoto University, Japan] [Kyoto University, Japan; Katsui, Hirokazu [Tohoku University, Japan] [Tohoku University, Japan; Kondo, Sosuke [ORNL] [ORNL; Zhong, Z. H. [Kyoto University, Japan] [Kyoto University, Japan; Park, Y. H. [Kyoto University, Japan] [Kyoto University, Japan; Shih, Chunghao [ORNL] [ORNL; Ozawa, Kazumi [ORNL] [ORNL; Parish, Chad M [ORNL] [ORNL; Meisner, Roberta Ann [ORNL] [ORNL

2013-01-01T23:59:59.000Z

448

New ternary rare-earth metal boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) containing BC{sub 2} units: Crystal and electronic structures, magnetic properties  

SciTech Connect

The ternary rare-earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. The crystal structures of Tb{sub 15}B{sub 4}C{sub 14} and Er{sub 15}B{sub 4}C{sub 14} were determined from single crystal X-ray diffraction data. They crystallize in a new structure type in space group P4/mnc (Tb{sub 15}B{sub 4}C{sub 14}: a=8.1251(5) A, c=15.861(1) A, Z=2, R{sub 1}=0.041 (wR{sub 2}=0.088) for 1023 reflections with I{sub o}>2{sigma}(I{sub o}); Er{sub 15}B{sub 4}C{sub 14}: a=7.932(1) A, c=15.685(2) A, Z=2, R{sub 1}=0.037 (wR{sub 2}=0.094) for 1022 reflections with I{sub o}>2{sigma}(I{sub o})). The crystal structure contains discrete carbon atoms and bent CBC units in octahedra and distorted bicapped square antiprisms, respectively. In both structures the same type of disorder exists. One R atom position needs to be refined as split atom position with a ratio 9:1 indicative of a 10% substitution of the neighboring C{sup 4-} by C{sub 2}{sup 4-}. The actual composition has then to be described as R{sub 15}B{sub 4}C{sub 14.2}. The isoelectronic substitution does not change the electron partition of R{sub 15}B{sub 4}C{sub 14} which can be written as (R{sup 3+}){sub 15}(C{sup 4-}){sub 6}(CBC{sup 5-}){sub 4{center_dot}}e{sup -}. The electronic structure was studied with the extended Hueckel method. The investigated compounds Tb{sub 15}B{sub 4}C{sub 14}, Dy{sub 15}B{sub 4}C{sub 14} and Er{sub 15}B{sub 4}C{sub 14} are hard ferromagnets with Curie temperatures T{sub C}=145, 120 and 50 K, respectively. The coercive field B{sub C}=3.15 T for Dy{sub 15}B{sub 4}C{sub 14} is quite remarkable. - Graphical abstract: The ternary rare earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. Tb{sub 15}B{sub 4}C{sub 14} is a new member of the rare-earth metal boride carbide series in which the finite quasi-molecular CBC entities as well as isolated C atoms are embedded in the voids of the metal atom matrix. The structure of Tb{sub 15}B{sub 4}C{sub 14} contains two types of slabs: one slab contains finite bent CBC units and isolated carbon atoms whereas another is formed only from octahedral coordinated single carbon atoms. The electronic structure for the idealized composition corresponds to an electron partitioning according to (Tb{sup 3+}){sub 15}(C{sup 4-}){sub 6}(CBC{sup 5-}){sub 4{center_dot}}e{sup -} giving rise to a single electron per formula for Tb-Tb framework bonding. The magnetism of the ternary rare earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Tb, Dy, Er) is characterized by the onset of ferromagnetic order below T<150 K.

Babizhetskyy, Volodymyr, E-mail: v.babizhetskyy@fkf.mpg.d [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, Postfach 800665, D-70569 Stuttgart (Germany); Simon, Arndt; Mattausch, Hansjuergen [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, Postfach 800665, D-70569 Stuttgart (Germany); Hiebl, Kurt [Arbeitsgruppe Neue Materialien, Universitaet Wien, Waehringerstrasse 42, A-1090 Wien (Austria); Zheng Chong [Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115 (United States)

2010-10-15T23:59:59.000Z

449

© 2012 ATI. All Rights Reserved  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

ATI. All Rights Reserved. ATI. All Rights Reserved.  11,200 employees - worldwide  $5 billion in Sales in 2012  Global presence - Operations in 18 countries  Provides customer focused specialty metals solutions * Titanium and titanium alloys * Nickel-based alloys and superalloys * Stainless steels, grain oriented electrical steel & duplex alloys * Zirconium, Hafnium and Niobium alloys * Tungsten metals & carbide cutting tools * Powdered metals * High performance forgings, castings and machining capabilities Allegheny Technologies (ATI) Overview ATI is one of the largest and most diversified specialty metals producers in the world. We use innovative technologies to offer global markets a wide range of specialty metals solutions. ATI US Operating Facilities

450

Optically initiated silicon carbide high voltage switch  

DOE Patents (OSTI)

An improved photoconductive switch having a SiC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Sullivan, James S. (Livermore, CA); Sanders; David M. (Livermore, CA)

2011-02-22T23:59:59.000Z

451

Off-axis silicon carbide substrates  

DOE Patents (OSTI)

A method of epitaxial growth of a material on a crystalline substrate includes selecting a substrate having a crystal plane that includes a plurality of terraces with step risers that join adjacent terraces. Each terrace of the plurality or terraces presents a lattice constant that substantially matches a lattice constant of the material, and each step riser presents a step height and offset that is consistent with portions of the material nucleating on adjacent terraces being in substantial crystalline match at the step riser. The method also includes preparing a substrate by exposing the crystal plane; and epitaxially growing the material on the substrate such that the portions of the material nucleating on adjacent terraces merge into a single crystal lattice without defects at the step risers.

Edgar, James; Dudley, Michael; Kuball, Martin; Zhang, Yi; Wang, Guan; Chen, Hui; Zhang, Yu

2014-09-02T23:59:59.000Z

452

Process for preparing silicon carbide foam  

DOE Patents (OSTI)

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolyzed in an inert atmosphere to form a SiC foam. 9 figs.

Whinnery, L.L.; Nichols, M.C.; Wheeler, D.R.; Loy, D.A.

1997-09-16T23:59:59.000Z

453

Process for preparing silicon carbide foam  

DOE Patents (OSTI)

A method of preparing near net shape, monolithic, porous SiC foams is disclosed. Organosilicon precursors are used to produce polymeric gels by thermally induced phase separation, wherein, a sufficiently concentrated solution of an organosilicon polymer is cooled below its solidification temperature to form a gel. Following solvent removal from the gel, the polymer foam is pretreated in an oxygen plasma in order to raise its glass transition temperature. The pretreated foam is then pyrolized in an inert atmosphere to form a SiC foam.

Whinnery, LeRoy Louis (Livermore, CA); Nichols, Monte Carl (Livermore, CA); Wheeler, David Roger (Albuquerque, NM); Loy, Douglas Anson (Albuquerque, NM)

1997-01-01T23:59:59.000Z

454

ELECTROCHEMICAL MACHINING OF CARBIDES AND BORIDES  

E-Print Network (OSTI)

data for ZrC in 3N NaCl and TiC in 2N KN0 HUN Press. (after anodic dissolution of TiC and TiB . used. The otherILFord. >h'TiC in NaCI 3N (runs 21 to26) T

Dissaux, Bernard Antoine

2011-01-01T23:59:59.000Z

455

Laser doping of silicon carbide substrates  

Science Journals Connector (OSTI)

A direct-write laser conversion technique was used to produce n-type and p-type doped tracks on SiC substrates. Polycrystalline and single-crystal SiC substrates were investigated. The tracks irradiated in an ...

I. A. Salama; N. R. Quick; A. Kar

2002-01-01T23:59:59.000Z

456

Modelling Precipitation of Carbides in Martensitic Steels  

E-Print Network (OSTI)

grateful my son, Hiroki for his encouragement. ii #12;ABSTRACT The purpose of this work was to model where acknowledgement and reference are made to previous work, this work is, to the best of my knowledge, original. This dissertation is the result of my own work and includes nothing which is the outcome of work

Cambridge, University of

457

A study of some molecular addition compounds of zirconium and hafnium tetrahalides.  

E-Print Network (OSTI)

??addition complexes MX4-2L, where M is Zr or Hf, x is C1 or Br, and L is tetrahydrofuran or tetrahydrothiophene have been prepared. Thermochemical data (more)

Chung, F. M.

2009-01-01T23:59:59.000Z

458

Improving dispersibility of hafnium diboride in aqueous media using polyacrylic acid and ammonium citrate  

Science Journals Connector (OSTI)

Abstract It has been well accepted that polyacrylic acid (PAA) is an effective dispersant for metal diborides (such as ZrB2) in aqueous media. However, when dispersing HfB2 powder, the dispersing effect is reduced significantly. In this work, a second dispersant, ammonium citrate, was used to resolve this problem. It was found that a PAAammonium citrate binary dispersant system could effectively enhance the zeta potential, increase the PAA adsorption content, and improve the stability of HfB2. The apparent viscosities of the suspensions were also investigated. Results showed that the PAAammonium citrate binary dispersant system was effective for improving the dispersion of HfB2 particles in aqueous media.

Gang Wang; Rujie He; Feng He

2014-01-01T23:59:59.000Z

459

Chemical Bonding, Interfaces and Defects in Hafnium Oxide/Germanium Oxynitride Gate Stacks on Ge (100)  

SciTech Connect

Correlations among interface properties and chemical bonding characteristics in HfO{sub 2}/GeO{sub x}N{sub y}/Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO{sub 2} atomic layer deposition (ALD). Ultra thin ({approx}1.1 nm), thermally stable and aqueous etch-resistant GeO{sub x}N{sub y} interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge{sub 3}N{sub 4} were synthesized. To evaluate GeO{sub x}N{sub y}/Ge interface defects, the density of interface states (D{sub it}) was extracted by the conductance method across the band gap. Forming gas annealed (FGA) samples exhibited substantially lower D{sub it} ({approx} 1 x 10{sup 12} cm{sup -2} eV{sup -1}) than did high vacuum annealed (HVA) and inert gas anneal (IGA) samples ({approx} 1x 10{sup 13} cm{sup -2} eV{sup -1}). Germanium core level photoelectron spectra from similar FGA-treated samples detected out-diffusion of germanium oxide to the HfO{sub 2} film surface and apparent modification of chemical bonding at the GeO{sub x}N{sub y}/Ge interface, which is related to the reduced D{sub it}.

Oshima, Yasuhiro; /Stanford U., Materials Sci. Dept.; Sun, Yun; /SLAC, SSRL; Kuzum, Duygu; /Stanford U.; Sugawara, Takuya; Saraswat, Krishna C.; Pianetta, Piero; /SLAC, SSRL; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.

2008-10-31T23:59:59.000Z

460

Designations of ds2p energy levels in neutral zirconium, hafnium, and rutherfordium (Z=104)  

Science Journals Connector (OSTI)

We have examined available data for the odd-parity energy-level structures in Zr and Hf, stimulated by the designations of four predicted 6d7s27p levels in the homologous atom rutherfordium (Rf, Z=104) by Eliav et al. [Phys. Rev. Lett. 74, 1079 (1995)]. We point out some errors and deficiencies in the Zr data and give the results of Hartree-Fock calculations for Hf 5d6s26p and Rf 6d7s27p levels. Configuration interactions within the (d+s)3p complexes were included. The resulting eigenvectors allow meaningful LS-coupling designations for most of the levels belonging mainly to Hf 5d6s26p and for most of the predicted Rf levels belonging mainly to 6d7s27p. Some changes in the designations assigned to these levels in the literature are suggested: in particular, the lowest level of both Hf 5d6s26p and Rf 6d7s27p is most appropriately designated F2o3. We point out the need for systematic whole-row studies of the low odd-parity configurations in 4d- and 5d-shell spectra. 1996 The American Physical Society.

W. C. Martin and Jack Sugar

1996-03-01T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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

Process-dependent electronic states at Mo/hafnium oxide/Si interfaces  

SciTech Connect

The authors have used low energy electron-excited nanoscale depth-resolved cathodoluminescence spectroscopy (DRCLS) to probe the bulk and interface defect states of ultrathin Mo/HfO{sub 2}/Si with eight different process sequences. After atomic layer deposition of 4 nm HfO{sub 2} on Si and an O{sub 2} post-treatment, they deposited 10 nm Mo using either plasma vapor or electron beam deposition, with or without a subsequent 1000 deg. C N{sub 2} anneal and with or without a forming gas anneal. DRCLS revealed pronounced gap state emissions within the ultrathin films and their interfaces with Mo and Si. There are multiple deep level emissions below the {approx}5.9 eV near band edge, including peak emissions at 3.4, 3.5, and 3.9-4.3 eV that can be associated with HfO{sub 2} oxygen vacancies in different charge states predicted theoretically. In addition, states at 2-2.6 eV that resemble known SiO{sub 2}-related nonbonding oxygen hole centers and E{sup '} (positively charged O vacancy) native defects increase with depth within the 4 nm HfO{sub 2} film, suggesting the formation of a Hf silicate at the HfO{sub 2}/Si interface. No metal-specific interface states at the HfO{sub 2}/Mo interface are evident. Furthermore, different process steps produce large changes in these states and for at least one sequence, a dramatic decrease in both types of defects. The differences between process sequences can be understood in terms of known reactions at HfO{sub 2}-Si interfaces.

Walsh, S.; Fang, L.; Schaeffer, J. K.; Brillson, L. J. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Technology Solutions Organization, Freescale Semiconductor, Inc., Austin, Texas 78721 (United States); Department of Electrical and Computer Engineering, Department of Physics and Center for Materials Research, Ohio State University, Columbus, Ohio 43210 (United States)

2007-07-15T23:59:59.000Z

462

Energy loss of proton, alpha particle, and electron beams in hafnium dioxide films  

SciTech Connect

The electronic stopping power, S, of HfO{sub 2} films for proton and alpha particle beams has been measured and calculated. The experimental data have been obtained by the Rutherford backscattering technique and cover the range of 120-900 and 120-3000 keV for proton and alpha particle beams, respectively. Theoretical calculations of the energy loss for the same projectiles have been done by means of the dielectric formalism using the Mermin energy loss function--generalized oscillator strength (MELF-GOS) model for a proper description of the HfO{sub 2} target on the whole momentum-energy excitation spectrum. At low projectile energies, a nonlinear theory based on the extended Friedel sum rule has been employed. The calculations and experimental measurements show good agreement for protons and a quite good one for alpha particles. In particular, the experimental maximums of both stopping curves (around 120 and 800 keV, respectively) are well reproduced. On the basis of this good agreement, we have also calculated the inelastic mean-free path (IMFP) and the stopping power for electrons in HfO{sub 2} films. Our results predict a minimum value of the IMFP and a maximum value of the S for electrons with energies around 120 and 190 eV, respectively.

Behar, Moni; Fadanelli, Raul C.; Nagamine, Luiz C. C. M. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970 Porto Alegre, RS (Brazil); Abril, Isabel; Denton, Cristian D. [Departament de Fisica Aplicada, Universitat dAlacant, Apartat 99, E-03080 Alacant (Spain); Garcia-Molina, Rafael [Departamento de Fisica-CIOyN, Universidad de Murcia, Apartado 4021, E-30080 Murcia (Spain); Arista, Nestor R. [Division Colisiones Atomicas, Centro Atomico Bariloche, RA-8400 San Carlos de Bariloche (Argentina)

2009-12-15T23:59:59.000Z

463

Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties  

SciTech Connect

Thin film capacitors were fabricated by sputtering TiN-Y doped HfO{sub 2}-TiN stacks on silicon substrates. Yttrium was incorporated into the HfO{sub 2} layers by simultaneously sputtering from Y{sub 2}O{sub 3} and HfO{sub 2} sources. Electric polarization and relative permittivity measurements yield distinct ferroelectric properties as a result of low yttrium dopant concentrations in the range of 0.9-1.9 mol. %. Grazing incidence x-ray diffraction measurements show the formation of an orthorhombic phase in this range. Compared to atomic layer deposition films, the highest remanent polarization and the highest relative permittivity were obtained at significantly lower doping concentrations in these sputtered films.

Olsen, T. [NaMLab gGmbH, 01187 Dresden (Germany); Department of Electrical and Computer Engineering, University of Alberta, Edmonton T6G 2V4 (Canada); Schroeder, U.; Mueller, S.; Krause, A.; Martin, D.; Singh, A. [NaMLab gGmbH, 01187 Dresden (Germany); Mueller, J. [Fraunhofer CNT, 01099 Dresden (Germany); Geidel, M. [Institute of Semiconductors and Microsystems, Technische Universitaet Dresden, 01062 Dresden (Germany); Mikolajick, T. [NaMLab gGmbH, 01187 Dresden (Germany); Institute of Semiconductors and Microsystems, Technische Universitaet Dresden, 01062 Dresden (Germany)

2012-08-20T23:59:59.000Z

464

Nanocrystals Embedded Zirconium-doped Hafnium Oxide High-k Gate Dielectric Films  

E-Print Network (OSTI)

nanoparticles. These results can be important to the novel metal gate/high-k/Si MOS structure. The Ru-modified ZrHfO gate dielectric film showed a large breakdown voltage and a long lifetime. The conventional polycrystalline Si (poly-Si) charge trapping layer...

Lin, Chen-Han

2012-10-19T23:59:59.000Z

465

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

E-Print Network (OSTI)

of the doped films were explained by their compositions and bond structures. The Hf-doped TaOx film is a potential high-k gate dielectric for future MOS transistors. A 5 ?? tantalum nitride (TaNx) interface layer has been inserted between the Hf-doped Ta...

Lu, Jiang

2007-04-25T23:59:59.000Z

466

The Effect of the Presence of 2 wt% Hafnium in T-111  

SciTech Connect

Tantalum alloys have been used by the U.S. Department of Energy as structural alloys for space nuclear power systems such as Radioisotopic Thermoelectric Generators (RTG) since the 1960s. Tantalum alloys are attractive for high temperature structural applications due to their high melting point, excellent formability, good thermal conductivity, good ductility (even at low temperatures), corrosion resistance, and weldability. A number of tantalum alloys have been developed over the years to increase high-temperature strength (Ta-10%W), and reduce creep strain (T-111). These tantalum alloys have demonstrated sufficient high-temperature toughness to survive prolonged exposure to the RTG's working environment. Due to the commercial unavailability of the tantalum alloy T-111, Ta-10%W is a possible candidate replacement material because of its high melting point (3037 deg. C), high elastic modulus (207 GPa), high yield, ultimate tensile strengths at both ambient and elevated temperatures, excellent ductility, and exceptional creep properties. Ta-10%W is also attractive due its commercial availability and low cost when compared to T-111. The objective of this paper is to compare and contrast Ta-10%W and T-111 for high-temperature nuclear based power conversion applications and to document research that must be conducted to fully characterize both materials.

Barklay, Chadwick D. [University of Dayton, 300 College Park Dayton OH 45469-0240 (United States); Kramer, Daniel P. [University of Dayton Research Institute, 300 College Park Dayton OH 45469-0102 (United States); Miller, Roger G. [Argonne National Laboratory, P.O. Box 2528, Idaho Falls, ID 83403-2528 (United States)

2006-01-20T23:59:59.000Z

467

Union Carbides Last 20 Years in Oak Ridge ? part 4  

NLE Websites -- All DOE Office Websites (Extended Search)

1950s was to produce some highly enriched lithium-6 for use in building the first thermonuclear, also called the hydrogen or super-bomb. The project from the beginning was highly...

468

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

NLE Websites -- All DOE Office Websites (Extended Search)

March, 1948. "WORLD'S OLDEST - The Graphite Reactor is the second reactor built and the first with a sizeable power output. It has been in continuous operation at Oak Ridge...

469

ZIRCONIUM AND HAFNIUM (Data in metric tons of zirconium oxide (ZrO ) equivalent, unless otherwise noted)2  

E-Print Network (OSTI)

and concentrates: Australia, 51%; South Africa, 48%; and other, 1%. Zirconium, wrought, unwrought, waste and scrap: France, 69%; Australia, 21%; Germany, 8%; and United Kingdom, 2%. Tariff: Item Number Normal Trade, the U.S. Department of Energy (DOE) held over 500 tons of zirconium in various forms. DOE also

470

Unexpected carbon-carbon coupling between organic cyanides and isopropyl {beta}-carbon in a hafnium ene diamide complex  

SciTech Connect

Reaction of the ene diamide complex Cp*Hf({sigma}{sup 2},{pi}-iPr-DAB)Cl (1; Cp* = {eta}{sup 5}-C{sub 5}Me{sub 5}, iPr-DAB = 1,4-diisopropyl-1,4-diaza-1,3-butadiene) with organic cyanides was investigated. The crystal structure of the product, Cp*Hf[iPrNCH{double_bond}CHNC(Me){double_bond}CHC(tBu){double_bond}NH]Cl, is reported. The reaction is thought to proceed by two hydrogen transfers and a C-C coupling on the {beta}-carbon of an isopropyl group. NMR was used to identify reaction intermediates in the hydrogen transfer scheme.

Bol, J.E.; Hessen, B.; Teuben, J.H. [Univ. of Groningen (Netherlands); Smeets, W.J.J.; Spek, A.L. [Univ. of Utrecht (Netherlands)

1992-06-01T23:59:59.000Z

471

ZIRCONIUMHAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI  

SciTech Connect

Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (?1? in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (?2?). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ? 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ?}) SNII.

Akram, W.; Schnbchler, M. [School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Sprung, P. [Institut fr Planetologie, Universitt Mnster, Wilhelm-Klemm-Strasse 10, D-48149 Mnster (Germany); Vogel, N. [Institute for Geochemistry and Petrology, ETH, Clausiusstrasse 25, 8092 Zrich (Switzerland)

2013-11-10T23:59:59.000Z

472

O K-energy loss near-edge structure change induced by tantalum impurity in monoclinic hafnium oxide  

SciTech Connect

The present paper reports the energy loss near-edge structure (ELNES) study of monoclinic HfO{sub 2} (m-HfO{sub 2}) and tantalum doped m-HfO{sub 2} (Ta{sub 0.1}Hf{sub 0.9}O{sub 2}) thin films prepared by radio frequency magnetron co-sputtering method. A change in the O K-ELNES spectra was observed as the amount of dopant increases. In order to precise the common features and the differences as a function of Ta defect nature (substitutional or interstitial) in HfO{sub 2}, the O K-ELNES were commented with respect to density functional theory calculations implemented in Vienna ab initio simulation package code. The calculated Ta doped HfO{sub 2} band structure showed that substitutional tantalum is the dominant defect and the spectral differences between doped and non-doped HfO{sub 2} are mainly originated from the change in the local cation distribution around the oxygen atoms.

Yang, Mino [Analytical Engineering Group, Samsung Advanced Institute of Technology (SAIT), Samsung Electronics, Youngin-Si, Gyeonggi-Do, 446-712, Korea and School of Advanced Materials Science and Engineering SungKyunKwan University, Suwon 440-746 (Korea, Republic of); Baik, Hionsuck [Korea Basic Science Institute (KBSI), Seoul 136-713 (Korea, Republic of); Ivanovskaya, Viktoria; Colliex, Christian [Laboratoire de Physique des Solides, University Paris-Sud, UMR-CNRS 8502 91405, Orsay (France); Benayad, Anass [Analytical Engineering Group, Samsung Advanced Institute of Technology (SAIT), Samsung Electronics, Youngin-Si, Gyeonggi-Do 446-712 (Korea, Republic of)

2011-03-01T23:59:59.000Z

473

Silicon carbide and the origin of interstellar carbon grains  

Science Journals Connector (OSTI)

... nucleate homogeneously and grow rapidly above 1,400K from a gaseous mixture of methane and silane highly diluted in argon15. The objective of the present experiments was to determine whether ... The SiC/Si ratio was found to increase with temperature. In the present study, pyrolysis of a hydrogen-added mixture, 3% SiH4/3% CH4/60% H2/34% ...

M. Frenklach; C. S. Carmer; E. D. Feigelson

1989-05-18T23:59:59.000Z

474

The birefringence and dichroism of silicon carbide polytypes  

Science Journals Connector (OSTI)

...The dichroic schemesare typical of only n-type (nitrogen-doped) sic. The colours arise by promotion of free-ele.iions at the bottom of the conduction band up to higher levels in the conduction bands' (Biedermann, 1965) The value of d is insensitive...

J. P. Golightly

475

One pot synthesis of metal, carbides and polymeric aerogels .  

E-Print Network (OSTI)

??"Ultra-low density, tlnee-dimensional assemblies of nanoparticles are referred to as aerogels, and typically are derived from supercritical fluid (SCF) drying of wet-gels. Aerogels are generally (more)

Chandrasekaran, Naveen, 1983-

2011-01-01T23:59:59.000Z

476

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

NLE Websites -- All DOE Office Websites (Extended Search)

This capacitance is almost twice that of our previous report 8 , and our synthetic method also offers a much faster route to film production as well as the avoid- ance of...

477

Polytype control of spin qubits in silicon carbide  

E-Print Network (OSTI)

Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen vacancy centers in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials driven approach that could ultimately lead to "designer" spins with tailored properties. Here, we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including spins in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron-electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent spins, these interactions provide ...

Falk, Abram L; Calusine, Greg; Koehl, William F; Dobrovitski, Viatcheslav V; Politi, Alberto; Zorman, Christian A; Feng, Philip X -L; Awschalom, David D; 10.1038/ncomms2854

2013-01-01T23:59:59.000Z

478

Optically-initiated silicon carbide high voltage switch  

DOE Patents (OSTI)

An improved photoconductive switch having a SIC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Sullivan, James S. (Livermore, CA); Sanders, David M. (Livermore, CA)

2012-02-28T23:59:59.000Z

479

Quantitative analysis of inclusion distributions in hot pressed silicon carbide  

SciTech Connect

ABSTRACT Depth of penetration measurements in hot pressed SiC have exhibited significant variability that may be influenced by microstructural defects. To obtain a better understanding regarding the role of microstructural defects under highly dynamic conditions; fragments of hot pressed SiC plates subjected to impact tests were examined. Two types of inclusion defects were identified, carbonaceous and an aluminum-iron-oxide phase. A disproportionate number of large inclusions were found on the rubble, indicating that the inclusion defects were a part of the fragmentation process. Distribution functions were plotted to compare the inclusion populations. Fragments from the superior performing sample had an inclusion population consisting of more numerous but smaller inclusions. One possible explanation for this result is that the superior sample withstood a greater stress before failure, causing a greater number of smaller inclusions to participate in fragmentation than in the weaker sample.

Michael Paul Bakas

2012-12-01T23:59:59.000Z

480

Electrically driven spin resonance in silicon carbide color centers  

E-Print Network (OSTI)

We demonstrate that the spin of optically addressable point defects can be coherently driven with AC electric fields. Based on magnetic-dipole forbidden spin transitions, this scheme enables spatially confined spin control, the imaging of high-frequency electric fields, and the characterization of defect spin multiplicity. While we control defects in SiC, these methods apply to spin systems in many semiconductors, including the nitrogen-vacancy center in diamond. Electrically driven spin resonance offers a viable route towards scalable quantum control of electron spins in a dense array.

P. V. Klimov; A. L. Falk; B. B. Buckley; D. D. Awschalom

2013-10-17T23:59:59.000Z

Note: This page contains sample records for the topic "hafnium carbide four-foot" 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.


481

DIFFUSION OF MAGNESIUM AND MICROSTRUCTURES IN Mg+ IMPLANTED SILICON CARBIDE  

SciTech Connect

Following our previous reports [ 1- 3], further isochronal annealing (2 hrs.) of the monocrystalline 6H-SiC and polycrystalline CVD 3C-SiC was performed at 1573 and 1673 K in Ar environment. SIMS data indicate that observable Mg diffusion in 6H-SiC starts and a more rapid diffusion in CVD 3C-SiC occurs at 1573 K. The implanted Mg atoms tend to diffuse deeper into the undamaged CVD 3C-SiC. The microstructure with Mg inclusions in the as-implanted SiC has been initially examined using high-resolution STEM. The presence of Mg in the TEM specimen has been confirmed based on EDS mapping. Additional monocrystalline 3C-SiC samples have been implanted at 673 K to ion fluence 3 times higher than the previous one. RBS/C analysis has been performed before and after thermal annealing at 1573 K for 12 hrs. Isothermal annealing at 1573 K is being carried out and Mg depth profiles being measured. Microstructures in both the as-implanted and annealed samples are also being examined using STEM.

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

2014-08-28T23:59:59.000Z

482

Silicon carbide whisker reinforced composites and method for making same  

DOE Patents (OSTI)

The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties, especially increased fracture toughness. In the formation of these ceramic composites, the single-crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al/sub 2/O/sub 3/, mullite, or B/sub 4/C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600 to 1950/sup 0/C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m/sup 1/2/ which represents as much as a two-fold increase over that of the matrix material.

Wei, G.C.

1984-02-09T23:59:59.000Z