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Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
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We encourage you to perform a real-time search of NLEBeta
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1

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

2

Hafnium radioisotope recovery from irradiated tantalum  

DOE Patents (OSTI)

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

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

2001-01-01T23:59:59.000Z

3

Zirconium and hafnium separation at Y-12  

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

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

4

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

5

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

6

Hot Wire Chemical Vapor Deposition with Carbide Filaments ...  

Many of the current industry cells in production have come through NREL, ... One deposition technology utilized at NREL deals with hot wire chemical ...

7

Controlled Synthesis of Highly Ordered Hafnium Oxide Nanotube ...  

Science Conference Proceedings (OSTI)

Hafnium oxide is of interest because it has high thermal, chemical and mechanical ... energy storage, solar energy conversion and sensors, through better control over ... Agricultural-Waste Biomass for Hydrogen Adsorption via Nano-Particle...

8

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...

9

Carbide and carbonitride surface treatment method for refractory metals  

DOE Patents (OSTI)

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

10

Aerogel-supported filament  

DOE Patents (OSTI)

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

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

1995-01-01T23:59:59.000Z

11

Aerogel-supported filament  

DOE Patents (OSTI)

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

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

1995-05-16T23:59:59.000Z

12

Amorphous hafnium-indium-zinc oxide semiconductor thin film transistors  

Science Conference Proceedings (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

13

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

14

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

15

Cemented Carbides for Machining Applications  

Science Conference Proceedings (OSTI)

Table 9   Recommended speed and feed ranges for uncoated and coated carbide grades...for general-purpose

16

Implementation Challenges for Sintered Silicon Carbide Fiber ...  

Science Conference Proceedings (OSTI)

The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system...

17

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

18

The Nitriding of Hafnium and Zirconium Using a Laser-sustained Plasma.  

E-Print Network (OSTI)

??A parametric study of laser and laser-sustained plasma interactions in nitrogen atmosphere with zirconium (Zr) and hafnium (Hf) metal was conducted to investigate the formation (more)

Strait, Timmy

2013-01-01T23:59:59.000Z

19

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

SciTech Connect

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

Singh, M.; Levine, S.R.

1995-07-01T23:59:59.000Z

20

Filament wound structure and method  

DOE Patents (OSTI)

The present invention relates to a filament wound spherical structure comprising a plurality of filament band sets disposed about the surface of a mandrel with each band of each set formed of a continuous filament circumferentially wound about the mandrel a selected number of circuits and with each circuit of filament being wound parallel to and contiguous with an immediate previously wound circuit. Each filament band in each band set is wound at the same helix angle from the axis of revolution of the mandrel and all of the bands of each set are uniformly distributed about the mandrel circumference. The pole-to-equator wall thickness taper associated with each band set, as several contiguous band sets are wound about the mandrel starting at the poles, is accumulative as the band sets are nested to provide a complete filament wound sphere of essentially uniform thickness.

Dritt, William S. (Oak Ridge, TN); Gerth, Howard L. (Knoxville, TN); Knight, Jr., Charles E. (Knoxville, TN); Pardue, Robert M. (Knoxville, TN)

1977-01-01T23:59:59.000Z

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


21

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

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

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

22

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

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

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

23

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

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

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

24

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

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

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

25

Method of Preparing Hydrous Hafnium, Cerium, or Aluminum Oxide Gels and Spherules  

An internal gelatin process for preparing hydrous hafnium, cerium, or aluminum oxidemicrospheres was invented at ORNL. The invention is a type of sol-gel process thatsolidifies droplets of solution as they enter into a warm environment. The resulting ...

26

Studies on the dynamics of limited filaments  

E-Print Network (OSTI)

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

Bonde, Jeffrey David

2010-01-01T23:59:59.000Z

27

METHOD OF MAKING TUNGSTEN FILAMENTS  

DOE Patents (OSTI)

A method of making tungsten filaments is described in which the tungsten is completely free of isotope impurities in the range of masses 234 to 245 for use in mass spectrometers. The filament comprises a tantalum core generally less than 1 mil in diameter having a coating of potassium-free tantalum-diffused tungsten molecularly bonded thereto. In the preferred process of manufacture a short, thin tantalum filament is first mounted between terminal posts mounted in insulated relation through a backing plate. The tungsten is most conveniently vapor plated onto the tantalum by a tungsten carbonyl vapor decomposition method having a critical step because of the tendency of the tantalum to volatilize at the temperature of operntion of the filament. The preferred recipe comprises volatilizing tantalum by resistance henting until the current drops by about 40%, cutting the voltage back to build up the tungsten, and then gradually building the temperature back up to balance the rate of tungsten deposition with the rate of tantalum volatilization. (AEC)

Frazer, J.W.

1962-12-18T23:59:59.000Z

28

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

29

High P-T phase transitions and P-V-T equation of state of hafnium  

Science Conference Proceedings (OSTI)

We measured the volume of hafnium at several pressures up to 67 GPa and at temperatures between 300 to 780 K using a resistively heated diamond anvil cell with synchrotron x-ray diffraction at the Advanced Photon Source. The measured data allows us to determine the P-V-T equation of state of hafnium. The previously described [Xia et al., Phys. Rev. B 42, 6736-6738 (1990)] phase transition from hcp ({alpha}) to simple hexagonal ({omega}) phase at 38 GPa at room temperature was not observed even up to 51 GPa. The {omega} phase was only observed at elevated temperatures. Our measurements have also improved the experimental constraint on the high P-T phase boundary between the {omega} phase and high pressure bcc ({beta}) phase of hafnium. Isothermal room temperature bulk modulus and its pressure derivative for the {alpha}-phase of hafnium were measured to be B{sub 0} = 112.9{+-}0.5 GPa and B{sub 0}'=3.29{+-}0.05, respectively. P-V-T data for the {alpha}-phase of hafnium was used to obtain a fit to a thermodynamic P-V-T equation of state based on model by Brosh et al. [CALPHAD 31, 173-185 (2007)].

Hrubiak, Rostislav; Drozd, Vadym; Karbasi, Ali; Saxena, Surendra K. (FIU)

2012-07-18T23:59:59.000Z

30

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...

31

Titanium Carbide Bipolar Plate for Electrochemical Devices  

DOE Patents (OSTI)

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

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

1998-05-08T23:59:59.000Z

32

Titanium carbide bipolar plate for electrochemical devices  

Science Conference Proceedings (OSTI)

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

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

2000-07-04T23:59:59.000Z

33

Preparation of silicon carbide fibers  

DOE Patents (OSTI)

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

Wei, G.C.

1983-10-12T23:59:59.000Z

34

Manufacture of silicon carbide using solar energy  

SciTech Connect

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

35

LIQUID PHASE SINTERING OF METALLIC CARBIDES  

DOE Patents (OSTI)

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

Hammond, J.; Sease, J.D.

1964-01-21T23:59:59.000Z

36

Manufacture of silicon carbide using solar energy  

DOE Patents (OSTI)

This invention is comprised of 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, G.C.

1991-04-08T23:59:59.000Z

37

Carbothermal synthesis of silicon carbide  

DOE Green Energy (OSTI)

Silicon carbide powders were synthesized from various silica and carbon sources by a carbothermal reduction process at temperatures between 1500 and 1600/sup 0/C. The silica sources were fumed silica, methyltrimethoxysilane, and microcrystalline quartz. The carbon sources were petroleum pitch, phenolic resin, sucrose, and carbon black. Submicron SiC powders were synthesized. Their morphologies included equiaxed loosely-bound agglomerates, equiaxed hard-shell agglomerates, and whiskers. Morphology changed with the furnace atmosphere (argon, nitrogen, or nitrogen-4% hydrogen). The best sintering was observed in SiC derived from the fumed-silica-pitch and fumed-silica-sucrose precursors. The poorest sintering was observed in SiC derived from microcrystalline quartz and carbon black. 11 refs., 16 figs., 10 tabs.

Janney, M.A.; Wei, G.C.; Kennedy, C.R.; Harris, L.A.

1985-05-01T23:59:59.000Z

38

Densification of nano-sized boron carbide .  

E-Print Network (OSTI)

??Boron carbide nano-powders, singly-doped over a range of compositions, were pressurelessly-sintered at identical temperature and atmospheric conditions in a dif- ferential dilatometer to investigate sintering (more)

Shupe, John

2009-01-01T23:59:59.000Z

39

Method for preparing boron-carbide articles  

DOE Patents (OSTI)

The invention is directed to the preparation of boron carbide articles of various configurations. A stoichiometric mixture of particulate boron and carbon is confined in a suitable mold, heated to a temperature in the range of about 1250 to 1500$sup 0$C for effecting a solid state diffusion reaction between the boron and carbon for forming the boron carbide (B$sub 4$C), and thereafter the resulting boron-carbide particles are hot-pressed at a temperature in the range of about 1800 to 2200$sup 0$C and a pressure in the range of about 1000 to 4000 psi for densifying and sintering the boron carbide into the desired article.

Benton, S.T.; Masters, D.R.

1975-10-21T23:59:59.000Z

40

Process for making silver metal filaments  

DOE Patents (OSTI)

This invention relates to a process for making filaments of metal compounds and more particularly to a process for making silver metal filaments. The United States Government has rights to this invention pursuant to Contract No. DE-AC05-8421400 with Lockheed Martin Energy Systems, Inc. awarded by the US Department of Energy.

Bamberger, C.E.

1998-04-01T23:59:59.000Z

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


41

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

Mukasyan, Alexander

42

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

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

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

43

Double Cemented Carbide-Dual Composite - Programmaster.org  

Science Conference Proceedings (OSTI)

Symposium, Professor K. K. Chawla Honorary Symposium on Fibers, Foams and ... Implementation Challenges for Sintered Silicon Carbide Fiber Bonded...

44

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

45

Fabrication of thorium bearing carbide fuels  

DOE Patents (OSTI)

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

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

1981-01-01T23:59:59.000Z

46

Filamentation laser femtoseconde IR : Interaction de deux filaments et Source de rayonnement secondaire longue distance.  

E-Print Network (OSTI)

??Les lasers femtoseconde amplifis permettent grce leur trs grande puissance d'tudier de nouveaux phnomnes physiques tels que la filamentation laser, le faisceau laser se (more)

Durand, Magali

2011-01-01T23:59:59.000Z

47

Experimental study of filamentation in laser-plasma interactions  

SciTech Connect

The filamentation instability can lead to regions of increased laser intensity when a spatially nonuniform laser beam interacts with a plasma. An experimental technique will be described which identifies the density perturbation produced by filaments. The growth of filaments has been investigated and, when the laser intensity is large enough, the transverse density profile of the filament can be measured. Evidence of filament growth influenced by plasma flow and density gradients is presented. 19 refs., 4 figs.

Young, P.E.

1991-01-07T23:59:59.000Z

48

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

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

20 Years in Nuclear Energy The Nuclear Age This series of articles is taken from a publication produced by Union Carbide Nuclear Division in the early 1960s which provides some...

49

Union Carbides 20 years in nuclear energy, part 2  

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

the second part of the Y-12 portion of the 1962 publication, Union Carbide's 20 years in nuclear energy, which was provided to me by Tim Gawne of the Oak Ridge National Labora-...

50

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

51

Titanium-Silicon Carbide Composite Lattice Structures  

E-Print Network (OSTI)

Titanium-Silicon Carbide Composite Lattice Structures A Dissertation Presented to the faculty utilize carbon fiber reinforced polymer (CFRP) honeycombs and lattice structures. Few options exist be applied to SiC monofilaments to create very high specific modulus and strength fibers

Wadley, Haydn

52

PWR cores with silicon carbide cladding  

Science Conference Proceedings (OSTI)

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

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

2012-07-01T23:59:59.000Z

53

METHODS FOR THE ANALYSIS OF BERYLLIUM CARBIDE  

SciTech Connect

Analytical methods are given for determining the composition and impurities of beryllium carbide. A summary of the experimental work leading to these procedures and supporting data are also presented. Analytical procedures for the determination of free and combined carbon, moisture, nitrogen, beryllium oxide, silica, iron, total beryllium, and beryllium metal are outlined. Diagrams of special apparatus used are included. (auth)

Bridges, W.L.; Funston, E.S.; Reed, S.A.

1949-03-21T23:59:59.000Z

54

SOLAR MAGNETIZED 'TORNADOES': RELATION TO FILAMENTS  

Science Conference Proceedings (OSTI)

Solar magnetized 'tornadoes', a phenomenon discovered in the solar atmosphere, appear as tornado-like structures in the corona but are rooted in the photosphere. Like other solar phenomena, solar tornadoes are a feature of magnetized plasma and therefore differ distinctly from terrestrial tornadoes. Here we report the first analysis of solar 'tornadoes' (two papers which focused on different aspects of solar tornadoes were published in the Astrophysical Journal Letters and Nature, respectively, during the revision of this Letter). A detailed case study of two events indicates that they are rotating vertical magnetic structures probably driven by underlying vortex flows in the photosphere. They usually exist as a group and are related to filaments/prominences, another important solar phenomenon whose formation and eruption are still mysteries. Solar tornadoes may play a distinct role in the supply of mass and twists to filaments. These findings could lead to a new explanation of filament formation and eruption.

Su Yang; Veronig, Astrid; Temmer, Manuela [IGAM-Kanzelhoehe Observatory, Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Wang Tongjiang [Department of Physics, Catholic University of America, Washington, DC 20064 (United States); Gan Weiqun, E-mail: yang.su@uni-graz.at [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2012-09-10T23:59:59.000Z

55

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

SciTech Connect

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

Collins, Jack Lee [ORNL; Hunt, Rodney Dale [ORNL; Simmerman, S. G. [University of Tennessee, Knoxville (UTK)

2009-02-01T23:59:59.000Z

56

Infrared Radiation Filament And Metnod Of Manufacture  

SciTech Connect

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

Johnson, Edward A. (Bedford, MA)

1998-11-17T23:59:59.000Z

57

METHOD FOR PRODUCING CEMENTED CARBIDE ARTICLES  

DOE Patents (OSTI)

A method is described for making molded materials of intricate shape where the materials consist of mixtures of one or more hard metal carbides or oxides and matrix metals or binder metals thereof. In one embodiment of the invention 90% of finely comminuted tungsten carbide powder together with finely comminuted cobalt bonding agent is incorporated at 60 deg C into a slurry with methyl alcohol containing 1.5% paraffin, 3% camphor, 3.5% naphthalene, and 1.8% toluene. The compact is formed by the steps of placing the slurry in a mold at least one surface of which is porous to the fluid organic system, compacting the slurry, removing a portion of the mold from contact with the formed object and heating the formed object to remove the remaining organic matter and to sinter the compact.

Onstott, E.I.; Cremer, G.D.

1959-07-14T23:59:59.000Z

58

Method of thermochemically treating silicon carbide fibers derived from polymers  

SciTech Connect

A method is described of thermochemically treating polymeric-derived silicon carbide fiber comprising the step of: annealing a silicon carbide fiber derived from organosilicon polymeric precursors said fiber further including at least: (1) excess carbon and oxygen, (2) excess silicon and oxygen, or (3) nitrogen, at a temperature between 800 C and 1,800 C, thus outgassing from said silicon carbide fiber at least one member selected from the group consisting of nitrogen, silicon monoxide and carbon monoxide, in intimate contact with carbon particles and in the presence of a gas capable of reacting in the presence of said carbon particles and said silicon carbide fiber, with products and byproducts formed as a result of said outgassing to form silicon carbide, so that said annealing step provides an annealed fiber wherein at least said silicon of the silicon carbide at said modified surface of said annealed fiber was originally present in said fiber prior to said annealing step.

Wallace, J.S.; Bender, B.A.; Schrodt, D.

1993-07-27T23:59:59.000Z

59

PWR Cores with Silicon Carbide Cladding  

Science Conference Proceedings (OSTI)

The feasibility of using present-generation pressurized water reactor (PWR) fuel design, with silicon carbide rather than zirconium-based alloy cladding, to reach higher operational power levels and discharge burnups has been evaluated. A preliminary fuel design using fuel rods with the same dimensions as Westinghouse robust fuel assemblies (RFA), but with fuel pellets that have 10 volume percent central holes, has been adopted. The central holes mitigate the higher fuel temperatures that occur due to th...

2011-07-15T23:59:59.000Z

60

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

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


61

Light sources based on semiconductor current filaments  

DOE Patents (OSTI)

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

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

2003-01-01T23:59:59.000Z

62

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

SciTech Connect

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

63

RECENT ADVANCES IN THE POWDER METALLURGY OF URANIUM CARBIDE  

SciTech Connect

uranium carbide, uranium metal is converted to uranium hydride powder and then carburized using propane gas. The carbide particles are irregular, of a relatively uniform size, and highly pyrophoric. Paraffin, camphor, cetyl alcohol, beeswax, and carbowax are used as lubricants and binders for compacting uranium carbide powder. Sintering studies were conducted for various times and temperatures, primarily in vacuum. An investigation is in progress to evaluate the effect of carbon content on the properties and irradiation stability of uranium carbide. It is shown that the powder metallurgy technique achieves a product wfth reasonably good density and apparentiy adequate properties for reactor utilization. (M.C.G.)

Kalish, H.S.

1962-10-31T23:59:59.000Z

64

Creep Behavior of a Zirconium Diboride-silicon Carbide Composite ...  

Science Conference Proceedings (OSTI)

Presentation Title, Creep Behavior of a Zirconium Diboride-silicon Carbide ... High Temperature Degradation of Carbon-fiber-reinforced Phenolic-resin Matrix

65

The Aqueous Corrosion Response of Titanium Carbide-Stainless ...  

Science Conference Proceedings (OSTI)

Aero-Thermal Performance Testing of Silicon Carbide Flexible TPS in a 30kW ICP ... Fiber-Optic Sensors Based on Microstructured Fibers for Measurement of...

66

Current Status and Issues of Silicon Carbide Composites for Nuclear ...  

Science Conference Proceedings (OSTI)

High-purity silicon carbide composites consisting of the high purity and highly crystalline fibers and matrices have proven the excellent mechanical performance...

67

HIGH SURFACE AREA SILICON CARBIDE-COATED CARBON AEROGEL ...  

Carbon aerogels can be coated with sol-gel silica and the silica can be converted to silicon carbide, improving the thermal stability of the carbon ae ...

68

Nanostructure Formation and Carbides Dissolution in Rail Steel ...  

Science Conference Proceedings (OSTI)

Feb 1, 2002 ... Nanostructure Formation and Carbides Dissolution in Rail Steel Deformed by High Pressure Torsion by Yu.V. Ivanisenko, R.Z. Valiev,...

69

Spark Plasma Sintering of Annular Zirconium Carbide Powder ...  

Science Conference Proceedings (OSTI)

Presentation Title, Spark Plasma Sintering of Annular Zirconium Carbide Powder Pellets:Processing and Simulation. Author(s), Xialu Wei, Wei Li, Eugene A.

70

Preparation and properties of electrically conducting ceramics based on indium oxide-rare earth oxides-hafnium oxides  

DOE Green Energy (OSTI)

Electrically conducting refractory oxides based on adding indium oxide to rare earth-stabilized hafnium oxide are being studied for use in magnetohydrodynamic (MHD) generators, fuel cells, and thermoelectric generators. The use of indium oxide generally increases the electrical conductivity. The results of measurements of the electrical conductivity and data on corrosion resistance in molten salts are presented.

Marchant, D.D.; Bates, J.L.

1983-09-01T23:59:59.000Z

71

Intergalactic Filaments as Isothermal Gas Cylinders  

E-Print Network (OSTI)

Using a cosmological simulation at redshift 5, we find that the baryon-rich cores of intergalactic filaments radiating from galaxies commonly form isothermal gas cylinders. The central gas density is typically about 500 times the cosmic mean total density, and the temperature is typically 1-2 times 10^4 K, just above the Lyman alpha cooling floor. These findings argue that the hydrodynamic properties of the gas are more important than the dark matter in determining the structure. Filaments form a major pipeline for the transport of gas into the centers of galaxies. Since the temperature and ionization state of the gas completely determine the mass per unit length of an isothermal gas cylinder, our findings suggest a constraint upon gas transport into galaxies by this mechanism.

Harford, A Gayler

2010-01-01T23:59:59.000Z

72

Molybdenum disilicide composites reinforced with zirconia and silicon carbide  

DOE Patents (OSTI)

This patent pertains to 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. Fabrication, fracture toughness, and bend strength are covered.

Petrovic, J.J.

1992-12-31T23:59:59.000Z

73

Dynamic compaction of tungsten carbide powder.  

Science Conference Proceedings (OSTI)

The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.

Gluth, Jeffrey Weston; Hall, Clint Allen; Vogler, Tracy John; Grady, Dennis Edward

2005-04-01T23:59:59.000Z

74

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

SciTech Connect

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

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

2009-03-23T23:59:59.000Z

75

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

76

Plasma planar filament instability and Alfven waves  

E-Print Network (OSTI)

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

Garcia de Andrade

2007-03-05T23:59:59.000Z

77

Method of producing silicon carbide articles  

DOE Patents (OSTI)

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

Milewski, John V. (Los Alamos, NM)

1985-01-01T23:59:59.000Z

78

Light Ions Response of Silicon Carbide Detectors  

E-Print Network (OSTI)

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

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

2006-12-14T23:59:59.000Z

79

Texaco, carbide form hydrogen plant venture  

Science Conference Proceedings (OSTI)

This paper reports that Texaco Inc. and Union Carbide Industrial Gases Inc. (UCIG) have formed a joint venture to develop and operate hydrogen plants. The venture, named HydroGEN Supply Co., is owned by Texaco Hydrogen Inc., a wholly owned subsidiary of Texaco, and UCIG Hydrogen Services Inc., a wholly owned subsidiary of UCIG. Plants built by HydroGEN will combine Texaco's HyTEX technology for hydrogen production with UCIG's position in cryogenic and advanced air separation technology. Texaco the U.S. demand for hydrogen is expected to increase sharply during the next decade, while refinery hydrogen supply is expected to drop. The Clean Air Act amendments of 1990 require U.S. refiners to lower aromatics in gasoline, resulting in less hydrogen recovered by refiners from catalytic reforming units. Meanwhile, requirements to reduce sulfur in diesel fuel will require more hydrogen capacity.

Not Available

1992-03-30T23:59:59.000Z

80

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

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

of publication here in full. The title of the document is Union Carbide's 20 years in nuclear energy. "The Y-12 Plant was built on a "crash" basis during World War II to...

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


81

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

82

Progress in studies on carbon and silicon carbide nanocomposite materials  

Science Conference Proceedings (OSTI)

Silicon carbide nanofiber and carbon nanotubes are introduced. The structure and application of nanotubers (nanofibers) in carbon/carbon composites are emphatically presented. Due to the unique structure of nanotubers (nanofibers), they can modify the ...

Peng Xiao; Jie Chen; Xian-feng Xu

2010-01-01T23:59:59.000Z

83

Research on Using Carbide Slag to Mineralize the Carbon Dioxide ...  

Science Conference Proceedings (OSTI)

... we come up with the crafts of using waste calcium carbide to mineralize CO2 in electrolytic aluminum waste gas, design and make out Venturi gas-liquid-solid...

84

Reactor physics assessment of thick silicon carbide clad PWR fuels  

E-Print Network (OSTI)

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

Bloore, David A. (David Allan)

2013-01-01T23:59:59.000Z

85

Tungsten carbide-cobalt by Three Dimensional Printing  

E-Print Network (OSTI)

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

Kelley, Andrew, III

1998-01-01T23:59:59.000Z

86

Biophysics of filament length regulation by molecular motors  

E-Print Network (OSTI)

Regulating physical size is an essential problem that biological organisms must solve from the subcellular to the organismal scales, but it is not well understood what physical principles and mechanisms organisms use to sense and regulate their size. Any biophysical size-regulation scheme operates in a noisy environment and must be robust to other cellular dynamics and fluctuations. This work develops theory of filament length regulation inspired by recent experiments on kinesin-8 motor proteins, which move with directional bias on microtubule filaments and alter microtubule dynamics. Purified kinesin-8 motors can depolymerize chemically-stabilized microtubules. In the length-dependent depolymerization model, the rate of depolymerization tends to increase with filament length, because long filaments accumulate more motors at their tips and therefore shorten more quickly. When balanced with a constant filament growth rate, this mechanism can lead to a fixed polymer length. However, the mechanism by which kinesin-8 motors affect the length of dynamic microtubules in cells is less clear. We study the more biologically realistic problem of microtubule dynamic instability modulated by a motor-dependent increase in the filament catastrophe frequency. This leads to a significant decrease in the mean filament length and a narrowing of the filament length distribution. The results improve our understanding of the biophysics of length regulation in cells.

Hui-Shun Kuan; M. D. Betterton

2013-02-13T23:59:59.000Z

87

Effect of filament power removal on a fluorescent lamp system  

SciTech Connect

Two techniques are used to measure the effects of removing the filament power from a two-lamp, F-40, rapid-start fluorescent lamp system. The changes are measured for a standard CBM core-coil ballast and for a solid-state ballast operating the lamp at high frequency. There is a 4 tp 6% increase in system efficacy when the filament power is removed. Removal of filament power also decreases filament temperature from 1000/sup 0/C to below 700/sup 0/C in lamps operated at 60 Hz, and from above 600/sup 0/C to 300/sup 0/C in lamps operated at high frequency. The study shows that the arc current and anode fall also determine filament temperature.

Verderber, R.R.; Morse, O.; Rubinstein, F.M.

1985-07-01T23:59:59.000Z

88

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

89

Nanostructured carbide catalysts for the hydrogen economy  

Science Conference Proceedings (OSTI)

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

Ram Seshadri, Susannah Scott, Juergen Eckert

2008-07-21T23:59:59.000Z

90

Mechanical properties of silicon carbide. (Latest citations from Engineered Materials abstracts). Published Search  

SciTech Connect

The bibliography contains citations concerning the mechanical characteristics and properties of silicon carbides. Citations discuss bend strength, crack propagation, creep rupture strength, ductile brittle fracture, fatigue strength, elastic modulus, shear strength, and tensile strength. Structure and chemistry of fiber/matrix interfaces for silicon carbide fiber reinforced materials are included. Sintering of silicon carbide and silicon carbide whisker reinforced composites are covered in separate bibliographies. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1996-02-01T23:59:59.000Z

91

Ordering of carbon atoms in boron carbide structure  

Science Conference Proceedings (OSTI)

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

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

2013-05-15T23:59:59.000Z

92

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

93

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

94

Investigation of thermal filamentation instability over Gakona, Alaska  

E-Print Network (OSTI)

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

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

2007-01-01T23:59:59.000Z

95

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

96

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

97

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

98

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

99

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.

Janney, M.A.

1985-03-12T23:59:59.000Z

100

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

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


101

Sodium compatibility studies of low friction carbide coatings for reactor application  

SciTech Connect

Design requirements for low friction materials in FFTF have led to an experimental sodium compatibility program, the objective of which is to select and qualify a low friction coating for the fuel assembly duct load pad. Results are given for chromium carbide and titanium carbide-based coatings on stainless steel exposed to 1160 deg F sodium for several thousand hours. A chromium carbide coating (with a nichrome binder) having an average corrosion rate of approximately 0.25 mpy exhibits optimum sodium compatibility behavior of the materials examined. Both plasma-sprayed chromium carbide and titanium carbide based coatings were found to be unstable when exposed to sodium. (auth)

Whitlow, G.A.; Miller, R.L.; Schrock, S.L.; Wu, P.C.S.

1973-09-01T23:59:59.000Z

102

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

103

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

E-Print Network (OSTI)

; Silicon carbide fibers; Densification 1. Introduction Silicon carbide (SiC) fiber reinforced titanium 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

Wadley, Haydn

104

Evolution of Genes and Gene Networks in Filamentous Fungi  

E-Print Network (OSTI)

The Pezizomycotina, commonly known as the filamentous fungi, are a diverse group of organisms that have a major impact on human life. The filamentous fungi diverged from a common ancestor approximately 200 700 million years ago. Because of the diversity and the wealth of biological and genomic tools for the filamentous fungi it is possible to track the evolutionary history of genes and gene networks in these organisms. In this dissertation I focus on the evolution of two genes (lolC and lolD) in the LOL secondary metabolite gene cluster in Epichlo and Neotyphodium genera, the evolution of the MAP kinase-signaling cascade in the filamentous fungi, the regulation of the gene networks involved in asexual development in Neurospora crassa, and the identification of two genes in the N. crassa asexual development gene network, acon-2 and acon-3. I find that lolC and lolD originated as an ancient duplication in the ancestor of the filamentous fungi, which were later recruited in the LOL gene cluster in the fungal endophyte lineage. In the MAP kinase-signaling cascade, I find that the MAPK component is the most central gene in the gene network. I also find that the MAPK signaling cascade originated as three copies in the ancestor to eukaryotes, an arrangement that is maintained in filamentous fungi. My observations of gene expression profiling during N. crassa asexual development show tissue specific expression of genes. Both the vegetative mycelium and the aerial hyphae contribute to the formation of macroconidiophores. Also, with the help of genomic tools recently developed by researchers in the filamentous fungal community, I identified NCU00478 and NCU07617 as the genes with mutations responsible for two aconidial strains of N. crassa, acon-2 and acon-3 respectively.

Greenwald, Charles Joaquin

2010-08-01T23:59:59.000Z

105

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

106

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

E-Print Network (OSTI)

A novel high-k gate dielectric material, i.e., hafnium-doped tantalum oxide (Hf-doped TaOx), has been studied for the application of the future generation metal-oxidesemiconductor field effect transistor (MOSFET). The film's electrical, chemical, and structural properties were investigated experimentally. The incorporation of Hf into TaOx impacted the electrical properties. The doping process improved the effective dielectric constant, reduced the fixed charge density, and increased the dielectric strength. The leakage current density also decreased with the Hf doping concentration. MOS capacitors with sub-2.0 nm equivalent oxide thickness (EOT) have been achieved with the lightly Hf-doped TaOx. The low leakage currents and high dielectric constants 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 TaOx films and the Si substrate to engineer the high-k/Si interface layer formation and properties. The electrical characterization result shows that the insertion of a 5 ?? TaNx between the doped TaOx films and the Si substrate decreased the film's leakage current density and improved the effective dielectric constant (keffective) value. The improvement of these dielectric properties can be attributed to the formation of the TaOxNy interfacial layer after high temperature O2 annealing. The main drawback of the TaNx interface layer is the high interface density of states and hysteresis, which needs to be decreased. Advanced metal nitride gate electrodes, e.g., tantalum nitride, molybdenum nitride, and tungsten nitride, were investigated as the gate electrodes for atomic layer deposition (ALD) HfO2 high-k dielectric material. Their physical and electrical properties were affected by the post metallization annealing (PMA) treatment conditions. Work functions of these three gate electrodes are suitable for NMOS applications after 800?°C PMA. Metal nitrides can be used as the gate electrode materials for the HfO2 high-k film. The novel high-k gate stack structures studied in this study are promising candidates to replace the traditional poly-Si-SiO2 gate stack structure for the future CMOS technology node.

Lu, Jiang

2005-12-01T23:59:59.000Z

107

Intensity clamping in the filament of femtosecond laser radiation  

SciTech Connect

We have studied numerically the evolution of the light field intensity and induced refractive index of a medium upon filamentation of femtosecond laser radiation in air. It is shown that the intensity clamping results from the dynamic balance of optical powers of nonlinear lenses, induced by radiation due to the Kerr nonlinearity of air, and laser plasma produced during photoionisation. We have found the relation between the peak values of the light field intensity and the electron density in laser-produced plasma, as well as the transverse sizes of the filament and the plasma channel. (effects of laser radiation on matter)

Kandidov, V P; Fedorov, V Yu; Tverskoi, O V; Kosareva, O G; Chin, S L

2011-04-30T23:59:59.000Z

108

Zipping mechanism for force-generation by growing filament bundles  

E-Print Network (OSTI)

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

Torsten Kuehne; Reinhard Lipowsky; Jan Kierfeld

2011-03-02T23:59:59.000Z

109

Zipping mechanism for force-generation by growing filament bundles  

E-Print Network (OSTI)

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

Kuehne, Torsten; Kierfeld, Jan

2011-01-01T23:59:59.000Z

110

Time-dependent simulations of filament propagation in photoconducting switches  

SciTech Connect

The authors present a model for investigating filamentary structures observed in laser-triggered photoswitches. The model simulates electrons and holes in two-dimensional cylindrical (r-z) geometry, with realistic electron and hole mobilities and field dependent impact ionization. Because of the large range of spatial and temporal scales to be resolved, they are using an explicit approach with fast, direct solution of the field equation. A flux limiting scheme is employed to avoid the time-step constraint due to the short time for resistive relaxation in the high density filament. Self-consistent filament propagation with speeds greater than the carrier drift velocity are observed in agreement with experiments.

Rambo, P.W.; Lawson, W.S. [Lawrence Livermore National Lab., CA (United States); Capps, C.D.; Falk, R.A. [Boeing Defense & Space Group, Seattle, WA (United States)

1994-05-01T23:59:59.000Z

111

SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS  

Science Conference Proceedings (OSTI)

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

DR. DENNIS NAGLE; DR. DAJIE ZHANG

2009-03-26T23:59:59.000Z

112

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

113

Process for growing silicon carbide whiskers by undercooling  

SciTech Connect

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

114

Structural and mechanical properties of intermediate filaments under extreme conditions and disease  

E-Print Network (OSTI)

Intermediate filaments are one of the three major components of the cytoskeleton in eukaryotic cells. It was discovered during the recent decades that intermediate filament proteins play key roles to reinforce cells subjected ...

Qin, Zhao, Ph. D. Massachusetts Institute of Technology

2013-01-01T23:59:59.000Z

115

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

E-Print Network (OSTI)

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

Yeh, Roger, 1980-

2005-01-01T23:59:59.000Z

116

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

E-Print Network (OSTI)

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

Goldman, Robert D.

117

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

118

Influence of carbon content on physicomechanical characteristics of boron carbide  

Science Conference Proceedings (OSTI)

Temperature and amplitude dependences of dynamic shear modulus (SM) and of internal friction (IF) have been measured on boron carbide samples with different carbon content. The samples were investigated at frequencies of torsion oscillations from 0.5 to 5 Hz and at amplitudes of oscillatory deformation from 5x10{sup -6} to 1x10{sup -2} at temperatures from 80 to 1000 K. It was shown that absolute values of SM, of critical amplitudes of oscillatory deformation and of shear elastic limit decreased with the decrease of carbon content in the samples. Simultaneously, activation energy of the intensive relaxation-type IF in the vicinity of 450-470 K was also decreased. Cyclic deformation at 1000 K provided additional decrease to physicomechanical characteristics while at annealing in vacuum at the temperatures of 1273 and 1773 K these structure-sensitive properties significantly increased. The observed changes of physicomechanical characteristics were attributed to possible changes of inter-atomic forces in the structure of boron carbide samples. - Graphical abstract: Amplitude dependence of the IF of the compacted samples of boron carbide: B{sub 4,3}C initial-(1) and after annealing at the 1773 K, 5 h-(2); B{sub 6,5}C initial-(3) and after annealing at the 1773 K, 5 h-(4)

Lezhava, D. [F. Tavadze Institute of Metallurgy and Materials Science, Georgian Academy of Sciences, 15, Alexander Kazbegi Avenue, Tbilisi 0160 (Georgia)]. E-mail: t_otari@hotmail.com; Darsavelidze, G. [F. Tavadze Institute of Metallurgy and Materials Science, Georgian Academy of Sciences, 15, Alexander Kazbegi Avenue, Tbilisi 0160 (Georgia); Gabunia, D. [F. Tavadze Institute of Metallurgy and Materials Science, Georgian Academy of Sciences, 15, Alexander Kazbegi Avenue, Tbilisi 0160 (Georgia); Tsagareishvili, O. [F. Tavadze Institute of Metallurgy and Materials Science, Georgian Academy of Sciences, 15, Alexander Kazbegi Avenue, Tbilisi 0160 (Georgia); Antadze, M. [F. Tavadze Institute of Metallurgy and Materials Science, Georgian Academy of Sciences, 15, Alexander Kazbegi Avenue, Tbilisi 0160 (Georgia); Gabunia, V. [F. Tavadze Institute of Metallurgy and Materials Science, Georgian Academy of Sciences, 15, Alexander Kazbegi Avenue, Tbilisi 0160 (Georgia)

2006-09-15T23:59:59.000Z

119

Method for removing oxide contamination from silicon carbide powders  

DOE Patents (OSTI)

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

Brynestad, J.; Bamberger, C.E.

1984-08-01T23:59:59.000Z

120

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

Science Conference Proceedings (OSTI)

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

Vojvodic, Aleksandra

2012-05-11T23:59:59.000Z

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


121

Low Wind Speed Technology Phase II: Breakthrough in Power Electronics from Silicon Carbide; Peregrine Power LLC  

DOE Green Energy (OSTI)

This fact sheet describes a subcontract with Peregrine Power LLC to perform baseline characterization of Silicon carbide (SiC) chips to determine their operating characteristics.

Not Available

2006-03-01T23:59:59.000Z

122

Characterization of the carbides and the martensite phase in powder-metallurgy high-speed steel  

SciTech Connect

A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M{sub 6}C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V{sub 6}C{sub 5}, while the tungsten-rich carbides were M{sub 6}C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.

Godec, Matjaz, E-mail: matjaz.godec@imt.si [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Batic, Barbara Setina; Mandrino, Djordje; Nagode, Ales; Leskovsek, Vojteh [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Skapin, Sreco D. [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Jenko, Monika [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia)

2010-04-15T23:59:59.000Z

123

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

E-Print Network (OSTI)

Nanocrystals embedded zirconium-doped hafnium oxide (ZrHfO) high-k gate dielectric films have been studied for the applications of the future metal oxide semiconductor field effect transistor (MOSFET) and nonvolatile memory. ZrHfO has excellent gate dielectric properties and can be prepared into MOS structure with a low equivalent oxide thickness (EOT). Ruthenium (Ru) modification effects on the ZrHfO high-k MOS capacitor have been investigated. The bulk and interfacial properties changed with the inclusion of Ru nanoparticles. The permittivity of the ZrHfO film was increased while the energy depth of traps involved in the current transport was lowered. However, the barrier height of titanium nitride (TiN)/ZrHfO was not affected by the Ru 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 can be replaced by the novel floating gate structure composed of discrete nanodots embedded in the high-k film. By replacing the SiO2 layer with the ZrHfO film, promising memory functions, e.g., low programming voltage and long charge retention time, can be expected. In this study, the ZrHfO high-k MOS capacitors that separately contain nanocrystalline ruthenium oxide (nc-RuO), indium tin oxide (nc-ITO), and zinc oxide (nc-ZnO) have been successfully fabricated by the sputtering deposition method followed with the rapid thermal annealing process. Material and electrical properties of these kinds of memory devices have been investigated using analysis tools such as XPS, XRD, and HRTEM; electrical characterizations such as C-V, J-V, CVS, and frequency-dependent measurements. All capacitors showed an obvious memory window contributed by the charge trapping effect. The formation of the interface at the nc-RuO/ZrHfO and nc-ITO/ZrHfO contact regions was confirmed by the XPS spectra. Charges were deeply trapped to the bulk nanocrystal sites. However, a portion of holes were loosely trapped at the nanocrystal/ZrHfO interface. Charges trapped to the different sites lead to different detrapping characteristics. For further improving the memory functions, the dual-layer nc-ITO and -ZnO embedded ZrHfO gate dielectric stacks have been fabricated. The dual-layer embedded structure contains two vertically-separated nanocrystal layers with a higher density than the single-layer embedded structure. The critical memory functions, e.g., memory window, programming efficiency, and charge retention can be improved by using the dual-layer nanocrystals embedded floating gate structure. This kind of gate dielectric stack is vital for the next-generation nonvolatile memory applications.

Lin, Chen-Han

2011-08-01T23:59:59.000Z

124

X-ray and Optical Filaments in M87  

E-Print Network (OSTI)

We compare a very deep X-ray image of M87, at the center of the Virgo Cluster, to high-quality optical images of the low excitation emission-line gas in the same region. There are striking coincidences of detail between the two. We explore the possiblity that this represents a thermal interaction between hot gas at 10^7 K and warm gas at 10^4 K. We find two temperatures are present in the X-ray gas, with the lower more prevelant in the vicinity of the optical filaments. Electron conduction from the hot phase to the cooler one provides a quantitatively acceptable energy source for the optical filaments, and we show additionally that it can do so for the brightest X-ray cluster, Perseus. If operative, conduction in the presence of gas-rich galaxy mergers, may explain the presence of "cool cores" in clusters of galaxies.

William B. Sparks; Megan Donahue; Andres Jordan; Laura Ferrarese; Patrick Cote

2004-02-09T23:59:59.000Z

125

Mechanical properties of silicon carbide. (Latest citations from Engineered Materials abstracts). NewSearch  

SciTech Connect

The bibliography contains citations concerning the mechanical characteristics and properties of silicon carbides. Citations discuss bend strength, crack propagation, creep rupture strength, ductile brittle fracture, fatigue strength, elastic modulus, shear strength, and tensile strength. Structure and chemistry of fiber/matrix interfaces for silicon carbide fiber reinforced materials are included. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1994-11-01T23:59:59.000Z

126

Development of a Commercial Processfor the Production of Silicon Carbide Fibrils  

E-Print Network (OSTI)

into the annulus of the boat. The MTS is dissociated to allow the carbon and silicon components to be dissolved. Department of Energy desires to use Silicon Carbide Fibrils as reinforcement for fiber reinforced silicon fiber paper as a substitute for the silicon carbide fibrils for chemical vapor infiltration development

127

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

SciTech Connect

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

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

2012-10-15T23:59:59.000Z

128

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

129

Plate-shape voids in neutron irradiated boron carbide  

SciTech Connect

From symposium on pore structures and properties of materials; Prague, Czechoslovakia (18 Sep 1973). Several processes are known to produce lattice vacancies in sufficient excess of the thermal equilibrium concentration that they precipitate out as voids. In the case of certain nuclear transmutations, a solid solution of gas is simultaneously produced at a concentration corresponding to a high equilibrium pressure and, if this gas diffuses into the voids, the equilibrium shape for the void is a thin flat cavity. Transmission electron microscopy was used to examine both the nucleation of such voids in neutron- irradiated boron carbide and their transformation to more compact shapes during fission gas release. (auth)

Ashbee, K.H.G.; DuBose, C.K.H.

1974-04-30T23:59:59.000Z

130

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

131

Optical and electronic properties of two dimensional graphitic silicon carbide  

E-Print Network (OSTI)

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

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

2012-01-01T23:59:59.000Z

132

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)

133

Displacement Damage in Silicon Carbide Irradiated in Fission Reactors  

SciTech Connect

Calculations are performed for displacement damage in SiC due to irradiation in the neutron environments of various types of nuclear reactors using the best available models and nuclear data. The displacement damage calculations use recently developed damage functions for SiC that are based on extensive molecular dynamics simulations of displacement events1. Displacements per atom (DPA) cross sections for SiC have been calculated as a function of neutron energy, and they are presented here in tabular form to facilitate their use as the standard measure of displacement damage for irradiated SiC. DPA cross sections averaged over the neutron energy spectrum are calculated for neutron spectra in the cores of typical commercial reactors and in the test sample irradiation regions of several materials test reactors used in both past and present irradiation testing. Particular attention is focused on a next-generation high-temperature gas-cooled pebble bed reactor, for which the high-temperature properties of silicon carbide fiber-reinforced silicon carbide composites are well suited. Calculated transmutations and activation levels in a pebble bed reactor are compared to those in other reactors.

Heinisch, Howard L.; Greenwood, Lawrence R.; Weber, William J.; Williford, Rick E.

2004-04-05T23:59:59.000Z

134

Rotating-filaments-pairs in a hexagonal superlattice state in dielectric barrier discharge  

SciTech Connect

Rotating-filaments-pairs in a hexagonal superlattice state (HSS) are studied in a dielectric barrier discharge system. The evolution and phase diagrams of HSS are given. The wavelength of HSS and the mean diameter of the two rotating filaments all decrease with the increase of applied voltage. The instantaneous orientations of rotating-filaments-pairs are equal probability approximately. There is a larger peak and a smaller one in both the probability density functions of the rotation speed ({omega}) of rotating filaments and that of the distance (D) between two rotating filaments. According to the fitting curves of ln{omega}{sup 2} vs. lnD, {omega}{sup 2} is inversely proportional to D{sup 7}. The rotation of filaments is discussed theoretically by the force among surface charges.

Dong Lifang; Yang Yujie; Li Ben; Fan Weili; Song Qian [College of Physics Science and Technology, Hebei University, Baoding 071002 (China) and Hebei Key Laboratory of Optic-electronic Information Materials, Baoding 071002 (China)

2011-12-15T23:59:59.000Z

135

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

Science Conference Proceedings (OSTI)

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

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

2012-08-15T23:59:59.000Z

136

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

Science Conference Proceedings (OSTI)

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

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

2011-11-15T23:59:59.000Z

137

Structure and mechanical properties of liquid crystalline filaments  

SciTech Connect

The formation of stable freely suspended filaments is an interesting peculiarity of some liquid crystal phases. So far, little is known about their structure and stability. Similarly to free-standing smectic films, an internal molecular structure of the mesophase stabilizes these macroscopically well-ordered objects with length to diameter ratios of 10{sup 3} and above. In this paper, we report observations of smectic liquid crystal fibers formed by bent-shaped molecules in different mesophases. Our study, employing several experimental techniques, focuses on mechanical and structural aspects of fiber formation such as internal structure, stability, and mechanical and optical properties.

Eremin, Alexey; Nemes, Alexandru; Stannarius, Ralf; Schulz, Mario; Nadasi, Hajnalka; Weissflog, Wolfgang [Otto-von-Guericke-Universitaet Magdeburg, FNW/ IEP/ ANP, Postfach 4120, D-39016 Magdeburg (Germany); LKA Sachsen-Anhalt, Postfach 180165, D-39028 Magdeburg (Germany); Institut fuer Physikalische Chemie, Martin-Luther-Universitaet Halle-Wittenberg, Muehlpforte 1, D-06108 Halle (Germany)

2005-03-01T23:59:59.000Z

138

Topological Defects, Surface Geometry and Cohesive Energy of Twisted Filament Bundles  

E-Print Network (OSTI)

Cohesive assemblies of filaments are a common structural motif found in diverse contexts, ranging from biological materials such as fibrous proteins, to artificial materials such as carbon nanotube ropes and micropatterned filament arrays. In this paper, we analyze the complex dependence of cohesive energy on twist, a key structural parameter of both self-assembled and fabricated filament bundles. Based on the analysis of simulated ground states of cohesive bundles, we show that the non-linear influence of twist derives from two distinct geometric features of twisted bundles: (i) the geometrical frustration of inter-filament packing in the bundle cross-section; and (ii) the evolution of the surface geometry of bundles with twist, which dictates the cohesive cost of non-contacting filaments at the surface. Packing frustration in the bundle core gives rise to the appearance of a universal sequence of topological defects, excess 5-fold disclinations, with increasing twist, while the evolution of filament contact at the surface of the bundle generically favors twisted geometries for sufficiently long filaments. Our analysis of both continuum and discrete models of filament bundles shows that, even in the absence of external torque or intrinsic chirality, cohesive energy universally favors twisted ground states above a critical (length/radius) aspect ratio and below a critical filament stiffness threshold.

Isaac R. Bruss; Gregory M. Grason

2013-03-06T23:59:59.000Z

139

Dust-acoustic filamentation of a current-driven dusty plasma  

Science Conference Proceedings (OSTI)

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

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

2011-06-15T23:59:59.000Z

140

Tailoring the filamentation of intense femtosecond laser pulses with periodic lattices  

Science Conference Proceedings (OSTI)

We show numerically that by using periodic lattices the filamentation of intense femtosecond laser pulses, otherwise a result of competing nonlinear effects, can be well controlled with respect to its properties. The diffraction induced by the lattice provides a regularizing mechanism to the nonlinear self-action effects involved in filamentation. We demonstrate a new propagation regime of intense lattice solitons bridging the field of spatial solitons with that of femtosecond laser filamentation. The effective filamentation control is expected to have an important impact on numerous applications.

Panagiotopoulos, P.; Tzortzakis, S. [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, GR-71110 Heraklion (Greece); Efremidis, N. K. [Department of Applied Mathematics, University of Crete, P.O. Box 2208, GR-71003 Heraklion (Greece); Papazoglou, D. G. [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, P.O. Box 1527, GR-71110 Heraklion (Greece); Department of Materials Science and Technology, University of Crete, P.O. Box 2208, GR-71003 Heraklion (Greece); Couairon, A. [Centre de Physique Theorique, Centre National de la Recherche Scientifique, Ecole Polytechnique, F-91128 Palaiseau (France)

2010-12-15T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
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141

Preparation and uses of amorphous boron carbide coated substrates  

DOE Patents (OSTI)

Cloth is coated at a temperature below about 1000/sup 0/C with amorphous boron-carbon deposits in a process which provides a substantially uniform coating on all the filaments making up each yarn fiber bundle of the cloth. The coated cloths can be used in the as-deposited condition for example as wear surfaces where high hardness values are needed; or multiple layers of coated cloths can be hot-pressed to form billets useful for example in fusion reactor wall armor. Also provided is a method of controlling the atom ratio of B:C of boron-carbon deposits onto any of a variety of substrates, including cloths.

Riley, R.E.; Newkirk, L.R.; Valencia, F.A.; Wallace, T.C.

1979-12-05T23:59:59.000Z

142

Preparation and uses of amorphous boron carbide coated substrates  

DOE Patents (OSTI)

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

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

1981-09-01T23:59:59.000Z

143

In situ electrochemical dilatometry of carbide-derived carbons  

SciTech Connect

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

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

2011-01-01T23:59:59.000Z

144

Method of producing novel silicon carbide articles. [Patent application  

DOE Patents (OSTI)

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

Milewski, J.V.

1982-06-18T23:59:59.000Z

145

Epitaxial Growth and Characterization of Silicon Carbide Films  

DOE Green Energy (OSTI)

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

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

2006-01-01T23:59:59.000Z

146

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

147

In-situ Electrochemical Dilatometry of Carbide-derived Carbons  

DOE Green Energy (OSTI)

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

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

2011-01-01T23:59:59.000Z

148

Advanced Measurements of Silicon Carbide Ceramic Matrix Composites  

Science Conference Proceedings (OSTI)

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

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

2012-08-01T23:59:59.000Z

149

CAN OVERTURNING MOTIONS IN PENUMBRAL FILAMENTS BE DETECTED?  

Science Conference Proceedings (OSTI)

Numerical simulations indicate that the filamentation of sunspot penumbrae and the associated systematic outflow (the Evershed effect) are due to convectively driven fluid motions constrained by the inclined magnetic field. We investigate whether these motions, in particular the upflows in the bright filaments and the downflows at their edges, can be reliably observed with existing instrumentation. We use a snapshot from a sunspot simulation to calculate two-dimensional maps of synthetic line profiles for the spectral lines Fe I 7090.4 A and C I 5380.34 A. The maps are spatially and spectrally degraded according to typical instrument properties. Line-of-sight velocities are determined from line bisector shifts. We find that the detectability of the convective flows is strongly affected by spatial smearing, particularly so for the downflows. Furthermore, the line-of-sight velocities are dominated by the Evershed flow unless the observation is made very near the disk center. These problems may have compromised recent attempts to detect overturning penumbral convection. Lines with a low formation height are best suited for detecting the convective flows.

Bharti, Lokesh; Schuessler, Manfred [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau (Germany); Rempel, Matthias, E-mail: bharti@mps.mpg.de [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States)

2011-09-20T23:59:59.000Z

150

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

151

Laser microfabrication and testing of silicon carbide diaphragms for MEMS applications.  

E-Print Network (OSTI)

??Laser microfabrication of silicon carbide for MEMS applications was explored. 3C-SiC and 6H-SiC were laser micromachined using various lasers. 3C-SiC thin films were patterned using (more)

Pecholt, Benjamin

2009-01-01T23:59:59.000Z

152

Laser microfabrication and testing of silicon carbide diaphragms for MEMS applications.  

E-Print Network (OSTI)

?? Laser microfabrication of silicon carbide for MEMS applications was explored. 3C-SiC and 6H-SiC were laser micromachined using various lasers. 3C-SiC thin films were patterned (more)

Pecholt, Benjamin Francis

2009-01-01T23:59:59.000Z

153

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

E-Print Network (OSTI)

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

Carpenter, David Michael

2011-01-01T23:59:59.000Z

154

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

E-Print Network (OSTI)

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

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

2011-01-01T23:59:59.000Z

155

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

E-Print Network (OSTI)

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

Stempien, John D. (John Dennis)

2011-01-01T23:59:59.000Z

156

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

157

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

Science Conference Proceedings (OSTI)

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

None

2010-09-01T23:59:59.000Z

158

A comparison of carbide fracture during fixed depth and fixed load scratch tests  

SciTech Connect

In order to simulate abrasion of dual-phase materials containing large carbides under fixed depth conditions an apparatus has been designed and used to perform scratch tests at a fixed depth of cut on such materials. The scratch test consists of two support arms tipped with small steel balls held in contact with surface by /sup 700/ g, while the scratch tool is mounted on the tip of a central arm whose adjustable length allow control of the depth of cut. The scratch tool does not deflect significant when it encounters a large carbide. Scratch tests with the new apparatus have been performed on Co-base Stellite alloys containing large Cr-rich carbides, using individual particles of alumina as scratch tools to generate fixed depth scratches. A in situ SEM scratch test apparatus has also been used to genrate fixed load scratches. Comparison of the scratches shows that for comparable average scratch depths, under fixed load conditions the scratch tool deflects over the carbides without causing fracture, but that since it cannot deflect under fixed depth conditions it induces gross carbide fracture. Results suggest that the fixed depth scratch test can be successfully employed to simulate fixed depth abrasion, which has been previously shown to generate gross carbide fracture in these alloys. The in situ SEM scratch test simulates fixed load abrasion conditions such as those which occur in rubber wheel abrasion tests. 12 refs., 9 figs

Prasad, S.V.; Kosel, T.H.

1985-01-01T23:59:59.000Z

159

Actin filament segmentation using spatiotemporal active- surface and active-contour models  

Science Conference Proceedings (OSTI)

We introduce a novel algorithm for actin filament segmentation in a 2D TIRFM image sequence. We treat the 2D time-lapse sequence as a 3D image volume and propose an over-grown active surface model to segment the body of a filament on all slices simultaneously. ...

Hongsheng Li; Tian Shen; Dimitrios Vavylonis; Xiaolei Huang

2010-09-01T23:59:59.000Z

160

Three-halves harmonic emission from a laser filament in a plasma channel  

SciTech Connect

A self-trapped laser filament is susceptible to decay-producing radially localized Langmuir waves. A nonlinear interaction of the pump wave with the density oscillation at the Langmuir frequency gives rise to three-halves harmonic emissions. Using a basis-function expansion technique, the emitted power in the backward direction is obtained. It decreases with the increasing size of the filament.

Mishra, G.; Talukdar, I.; Tripathi, V.; Tripathi, V.K. (Indian Inst. of Tech., New Delhi (India). Dept. of Physics)

1989-12-01T23:59:59.000Z

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


161

Formation and evolution of interstellar filaments; Hints from velocity dispersion measurements  

E-Print Network (OSTI)

We investigate the gas velocity dispersions of a sample of filaments recently detected as part of the Herschel Gould Belt Survey in the IC5146, Aquila, and Polaris interstellar clouds. To measure these velocity dispersions, we use 13CO, C18O, and N2H+ line observations obtained with the IRAM 30m telescope. Correlating our velocity dispersion measurements with the filament column densities derived from Herschel data, we show that interstellar filaments can be divided into two regimes: thermally subcritical filaments, which have transonic velocity dispersions (c_s ~dispersions scaling roughly as the square root of column density (\\sigma_tot ~ \\Sigma^0.5), and are self-gravitating. The higher velocity dispersions of supercritical filaments may not directly arise from supersonic interstellar turbulence but may be driven by gravitational contraction/accretion...

Arzoumanian, Doris; Peretto, Nicolas; Konyves, Vera

2013-01-01T23:59:59.000Z

162

Powering The Intra-cluster Filaments in Cool-Core Clusters of Galaxies  

E-Print Network (OSTI)

The first radio surveys of the sky discovered that some large clusters of galaxies contained powerful sources of synchrotron emission. Optical images showed that long linear filaments with bizarre emission-line spectra permeated the intra-cluster medium. Recent observations in the infrared and radio show that these filaments have very strong emission lines of molecular hydrogen and carbon monoxide. The mass of molecular material is quite large, the gas is quite warm, and the filaments have not formed stars despite their ~Gyr age. I will discuss the general astrophysical context of large clusters of galaxies and how large masses of molecular gas can be heated to produce what we observe. The unique properties of the filaments are a result of the unique environment. Magnetically confined molecular filaments are surrounded by the hot intra-cluster medium. Thermal particles with keV energies enter atomic and molecular regions and produce a shower of secondary nonthermal electrons. These secondaries collisionally h...

Ferland, Gary J

2011-01-01T23:59:59.000Z

163

Filament and Flare Detection in H{\\alpha} image sequences  

E-Print Network (OSTI)

Solar storms can have a major impact on the infrastructure of the earth. Some of the causing events are observable from ground in the H{\\alpha} spectral line. In this paper we propose a new method for the simultaneous detection of flares and filaments in H{\\alpha} image sequences. Therefore we perform several preprocessing steps to enhance and normalize the images. Based on the intensity values we segment the image by a variational approach. In a final postprecessing step we derive essential properties to classify the events and further demonstrate the performance by comparing our obtained results to the data annotated by an expert. The information produced by our method can be used for near real-time alerts and the statistical analysis of existing data by solar physicists.

Riegler, Gernot; Ptzi, Werner; Veronig, Astrid

2013-01-01T23:59:59.000Z

164

Structural Modeling and Molecular Dynamics Simulation of the Actin Filament  

DOE Green Energy (OSTI)

Actin is a major structural protein of the eukaryotic cytoskeleton and enables cell motility. Here, we present a model of the actin filament (F-actin) that not only incorporates the global structure of the recently published model by Oda et al. but also conserves internal stereochemistry. A comparison is made using molecular dynamics simulation of the model with other recent F-actin models. A number of structural determents such as the protomer propeller angle, the number of hydrogen bonds, and the structural variation among the protomers are analyzed. The MD comparison is found to reflect the evolution in quality of actin models over the last 6 years. In addition, simulations of the model are carried out in states with both ADP or ATP bound and local hydrogen-bonding differences characterized.

Splettstoesser, Thomas [University of Heidelberg; Holmes, Kenneth [Max Planck Institute, Heidelberg, Germany; Noe, Frank [DFG Research Center Matheon, FU Berlin, Germany; Smith, Jeremy C [ORNL

2011-01-01T23:59:59.000Z

165

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

SciTech Connect

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

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

2012-05-15T23:59:59.000Z

166

USE OF SILICON CARBIDE MONITORS IN ATR IRRADIATION TESTING  

Science Conference Proceedings (OSTI)

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

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

2012-07-01T23:59:59.000Z

167

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

SciTech Connect

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

Cao, Wenda; Goode, Philip R. [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Blvd., Newark, NJ 07102 (United States); Ning, Zongjun; Yurchyshyn, Vasyl [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92316 (United States); Ji Haisheng, E-mail: wcao@bbso.njit.ed [Purple Mountain Observatory, Nanjing 210008 (China)

2010-08-10T23:59:59.000Z

168

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

Science Conference Proceedings (OSTI)

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

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

2011-01-01T23:59:59.000Z

169

Measurements of the Motion of Plasma Filaments in a Plasma Ball  

Science Conference Proceedings (OSTI)

Measurements were made of the motion of the filamentary structures in a plasma ball using high speed cameras and other optical detectors. These filaments traverse the ball radially at ~106 cm/sec at the driving frequency of ~26 kHz, and drift upward through the ball at ~1 cm/sec. Varying the applied high voltage and frequency caused the number, length, and diameter of the filaments to change. A custom plasma ball was constructed to observe the effects of varying gas pressure and species on the filament structures.

M. Campanell, J. Laird, T. Provost, S. Vasquez, S.J. Zweben

2010-01-26T23:59:59.000Z

170

Boundary-induced orientation of dynamic filament networks and vesicle agglomerations  

E-Print Network (OSTI)

We find a statistical mechanism that can adjust orientations of intracellular filaments to cell geometry in absence of organizing centers. The effect is based on random and isotropic filament (de-)polymerization dynamics and is independent of filament interactions and explicit regulation. It can be understood by an analogy to electrostatics and appears to be induced by the confining boundaries; for periodic boundary conditions no orientational bias emerges. Including active transport of particles, the model reproduces experimental observations of vesicle accumulations in transected axons.

Philip Greulich; Ludger Santen

2011-06-28T23:59:59.000Z

171

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

172

Formation of Solar Filaments by Steady and Nonsteady Chromospheric Heating  

E-Print Network (OSTI)

It has been established that cold plasma condensations can form in a magnetic loop subject to localized heating of the footpoints. In this paper, we use grid-adaptive numerical simulations of the radiative hydrodynamic equations to parametrically investigate the filament formation process in a pre-shaped loop with both steady and finite-time chromospheric heating. Compared to previous works, we consider low-lying loops with shallow dips, and use a more realistic description for the radiative losses. We demonstrate for the first time that the onset of thermal instability satisfies the linear instability criterion. The onset time of the condensation is roughly \\sim 2 hr or more after the localized heating at the footpoint is effective, and the growth rate of the thread length varies from 800 km hr-1 to 4000 km hr-1, depending on the amplitude and the decay length scale characterizing this localized chromospheric heating. We show how single or multiple condensation segments may form in the coronal portion. In th...

Xia, C; Keppens, R; van Marle, A J

2011-01-01T23:59:59.000Z

173

Diluted magnetic semiconductor effects in Mn-implanted silicon carbide  

Science Conference Proceedings (OSTI)

Light transmission and Faraday rotation spectra measured at the temperature of 2 K were compared for silicon carbide single crystals of 4H polytype (4H-SiC), implanted with 3.8 x 10{sup 16} cm{sup -2} of Mn ions at the beam energy of 190 keV, and a control 4H-SiC single crystal sample, which was not implanted. Mn ion implantation led to the creation of a Mn-doped surface layer with the average Mn concentration of 10{sup 21} cm{sup -3} and a thickness of approximately 0.2 {mu}m. Transmission of light through the implanted crystal changed only slightly in comparison with the control sample, which however, corresponded to a relatively strong attenuation in the implanted layer. This was interpreted as a result of scattering, which emerges in the surface layer due to optical nonuniformities, created by the high energy ion irradiation. The presence of a thin Mn-ion-containing surface layer led, despite its small thickness, to noticeable changes in the sample Faraday rotation spectra. The estimated values of the Verdet constant for this layer were about three orders of magnitude larger and of opposite sign compared to the Verdet constant values of the undoped sample. Magnetic field dependencies of the Faraday rotation contribution from the implanted layer were found to be saturating functions, which points to a proportionality of the Faraday rotation to the magnetization of the paramagnetic Mn ion subsystem. Based on these findings we conclude that the Mn-implanted SiC layer exhibits magneto-optical properties typical of a diluted magnetic semiconductor. At the same time, no ferromagnetic ordering was observed in the studied (Si, Mn)C sample.

Komarov, A. V.; Ryabchenko, S. M. [Institute of Physics of the National Academy of Sciences of Ukraine, 46 Nauki Ave., Kiev 03028 (Ukraine); Los, A. V. [ISS Ltd., Semiconductors and Circuits Lab, 15 Bozhenko Street, Kiev 03680 (Ukraine); Freescale Semiconductor Ukraine LLC., 15 Bozhenko Street, Kiev 03680 (Ukraine); Romanenko, S. M. [ISS Ltd., Semiconductors and Circuits Lab, 15 Bozhenko Street, Kiev 03680 (Ukraine)

2011-04-15T23:59:59.000Z

174

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

175

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

176

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

177

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

178

Cavitation erosion of cobalt based STELLITE alloys, cemented carbides and surface treated low alloy steels  

SciTech Connect

Results are given for erosion-resistance tests involving several STELLITE alloys, cemented carbides and surface-treated alloy steels. It is shown that the cobalt-rich, solid-solution phase of the STELLITE alloys is the basis of their erosion resistance, while the erosion of cemented carbides is predominantly controlled by the binder phase. It is also found that nickel-based tungsten carbides are more erosion-resistant than those based on cobalt. It is demonstrated for the case of the low-alloy steels that surface treatment can improve their erosion rates, and that application of a proprietary nitrocarburizing method to the same steels results in a similar performance improvement only after the initial loss of the compound layer.

Heathcock, C.J. (Cape Town, Univ., Rondebosch, Republic of South Africa); Ball, A.

1981-03-30T23:59:59.000Z

179

Patterns and intrinsic fluctuations in semi-dilute motor-filament systems.  

SciTech Connect

We perform Brownian dynamics simulations of molecular motor-induced ordering and structure formations in semi-dilute cytoskeletal filament solutions. In contrast to the previously studied dilute case where binary filament interactions prevail, the semi-dilute regime is characterized by multiple motor-mediated interactions. Moreover, the forces and torques exerted by motors on filaments are intrinsically fluctuating quantities. We incorporate the influences of thermal and motor fluctuations into our model as additive and multiplicative noises, respectively. Numerical simulations reveal that filament bundles and vortices emerge from a disordered initial state. Subsequent analysis of motor noise effects reveals: (i) Pattern formation is very robust against fluctuations in motor force; (ii) bundle formation is associated with a significant reduction of the motor fluctuation contributions; (iii) the time scale of vortex formation and coalescence decreases with increases in motor noise amplitude.

Swaminathan, S.; Ziebert, F.; Aranson, I. S.; Karpeev, D.; Northwestern Univ.; UMR CNRS Gulliver

2010-04-01T23:59:59.000Z

180

Nonlinear competition between asters and stripes in filament-motor-systems  

E-Print Network (OSTI)

A model for polar filaments interacting via molecular motor complexes is investigated which exhibits bifurcations to spatial patterns. It is shown that the homogeneous distribution of filaments, such as actin or microtubules, may become either unstable with respect to an orientational instability of a finite wave number or with respect to modulations of the filament density, where long wavelength modes are amplified as well. Above threshold nonlinear interactions select either stripe patterns or periodic asters. The existence and stability ranges of each pattern close to threshold are predicted in terms of a weakly nonlinear perturbation analysis, which is confirmed by numerical simulations of the basic model equations. The two relevant parameters determining the bifurcation scenario of the model can be related to the concentrations of the active molecular motors and of the filaments respectively, which both could be easily regulated by the cell.

Falko Ziebert; Walter Zimmermann

2005-02-09T23:59:59.000Z

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


181

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

Science Conference Proceedings (OSTI)

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

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

2011-10-15T23:59:59.000Z

182

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

SciTech Connect

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

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

2010-07-20T23:59:59.000Z

183

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

DOE Green Energy (OSTI)

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

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

1994-10-01T23:59:59.000Z

184

Time-Dependent Failure Mechanisms in Silicon Carbide Composites for Fusion Energy Applications  

SciTech Connect

Silicon carbide has many properties that are attractive for applications in fusion energy systems. The reliability of monolithic silicon carbide is insufficient for its use in large components, due to its brittle failure behavior and flaw sensitivity. Ceramic matrix composites, on the other hand, offer greater flaw tolerance and reliability, but their failure mechanisms are less well understood. This work has focussed on studying potential failure mechanisms in silicon carbide fiber-reinforced, silicon carbide matrix (SiCf/SiCm) composites. In the event of cracks caused by accidental overloads, excessive creep, thermal shock from plasma disruptions, handling during installation, or resulting from processing, subcritical crack growth will occur due to creep of fibers that bridge the crack faces. It is presumed that irradiation will enhance the creep rate of the fibers and, subsequently, the subcritical crack growth rate. At certain temperatures the presence of even small amounts of oxygen leads to oxidation of the interphase material to gaseous products. In this case, subcritical crack growth occurs by a separate mechanism. In addition, fiber shrinkage or weakening due to exposure to radiation can promote additional failure mechanisms, including embrittlement. These mechanisms, the conditions, under which they occur, and the current state of models of the crack growth mechanisms will be discussed.

Lewinsohn, Charles A.; Youngblood, Gerald E.; Henager, Charles H.; Simonen, Edward P.; Jones, Russell H.

2000-11-01T23:59:59.000Z

185

Method of deposition of silicon carbide layers on substrates and product  

SciTech Connect

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

Angelini, Peter (Oak Ridge, TN); DeVore, Charles E. (Knoxville, TN); Lackey, Walter J. (Oak Ridge, TN); Blanco, Raymond E. (Oak Ridge, TN); Stinton, David P. (Knoxville, TN)

1984-01-01T23:59:59.000Z

186

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

Science Conference Proceedings (OSTI)

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

Li Ting; Zhang Jun, E-mail: liting@nao.cas.cn, E-mail: zjun@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2012-11-20T23:59:59.000Z

187

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

DOE Patents (OSTI)

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

Bettger, Kenneth J; Stark, David H

2013-08-20T23:59:59.000Z

188

DISPERSIONS OF URANIUM CARBIDES IN ALUMINUM PLATE-TYPE RESEARCH REACTOR FUEL ELEMENTS  

DOE Green Energy (OSTI)

The technical feasibility of employing uranium carbide aluminun dispersions in aluminum-base research reactor fuel elements was investigated This study was motivated by the need to obtain higher uranium loadings in these fuel elements. Although toe MTR-type unit, containing a 13 18 wt% U-Al alloy is a proven reactor component, fabrication problems of considerable magnitude arise when attempts are made to increase the uranium investment in the alloy to more than 25 wt.%. Au approach to these fabrication difficulties is to select a compound with significantly higher density tban UAl/sub 4/ or UAl/sub 3/ compounds of the alloy system which when dispersed in aluminum powder, will reduce the volume occupied by the brittle, fissile phase. The uranium carbides, with densities ranging from 11.68 to 13.63 g/cm/sup 3/), appear to be suited for this application and were selected for development as a fuel material for aluminum-base dispersions. Studies were conducted at 580 to 620 deg C to determine the chemical compatibility of carbides with aluminum in sub-size cold- pressed comparts as well as in full-size fabricated fuel plates. Procedures were also developed to prepare uranium carbides, homogernously disperse the compounds in aluminum, roll clad the dispersions to form composite plates, and braze the plates into fuel assemblies. Corrosion tests of the fuel material were conducted in 20 and 60 deg C water to determine the integrity of the fuel material in the event of sin inadventent cladding failure. In addition, specimens were prepared to evaluate penformance under extensive irradiation Prior to studying the uranium carbide-aluminum system, methods for preparing the carbides were investigated. Are melting uranium and carnon was satisfactory for obtaining small quantities of various carbides. Later, reaction of graphite with UO/sub 2/ was successfully employed in the preparation of large quantities of UC/sub 2/, Studies of the chemical compatibility of cold-pressed compacts containing 50 wt% uranium carbide dispersed in aluminum revealed a marked trend toward stebifity as the carbon content of the uranium carbide increased from 446 to 9.20% C. Severe volume increases occurred in monocarbide dispersions with attendant formation of large quantities of the uranium-allumnim inter-metallic compounds. Dicarbide dispersions, on the other band, exhibited negligible reaction with aluminum after extended periods at 580 and 620 deg C. However, it was demonstrated that hydrogen can promote a reaction in UC/sub 2/-Al compacts. The hydrogen appears to reduce the UC/sub 2/ to UC which can subsequently react with aluminum producing the previously noted deleterious effects. A growth study at 605 deg C of composite fuel plates containing 59 wt.% UC/sub 2/ revealed insignificant changes within processing periods envisioned for fuel element processing. However, plate elongations as high as 2.5% were observed after 100 hr at this temperature. Severe blistering which occurred on fuel plates fabricated in the initial stages of the investigation was attributed to gaseous hydrocarbons, and the condition was ellminated by vacuum degasification of cold-pressed compacts. With the exception of the degasification requirement, procedures for manufacturing UC- bearing fuel elements were identical to those specified for the Geneva Conference Reactor fuel elements. Dispersions of uranium dicarbide corroded catastrophically in 20 and 60 deg C water, thus limiting the application of this material However, spocimens were prepared and insented in the MTR to evaluate the irradiation behavior of this fuel because of its potential application in onganic- cooled reactors. (auth)

Thurber, W.C.; Beaver, R.J.

1959-11-19T23:59:59.000Z

189

Self-compression by femtosecond pulse filamentation: Experiments versus numerical simulations  

SciTech Connect

We analyze pulse self-compression in femtosecond filaments, both experimentally and numerically. We experimentally demonstrate the compression of 45 fs pulses down to a duration of 7.4 fs at millijoule pulse energies. This sixfold compression in a self-generated filament does not require any means for dispersion compensation and is highly efficient. We compare our results to numerical simulations, providing a complete propagation model that accounts for full dispersion, pressure variations, Kerr nonlinearity and plasma generation in multiphoton and tunnel regimes. The equations are numerically integrated and allow for a quantitative comparison with the experiment. Our experiments and numerical simulations reveal a characteristic spectrotemporal structure of the self-compressed pulses, consisting of a compressible blue wing and an incompressible red pedestal. We explain the underlying mechanism that leads to this structure and examine the scalability of filament self-compression with respect to pulse energy and gas pressure.

Skupin, Stefan; Berge, Luc [Departement de Physique Theorique et Appliquee, CEA-DAM/Ile de France, B.P. 12, 91680 Bruyeres-le-Chatel (France); Stibenz, Gero; Sokollik, Thomas; Schnuerer, Matthias; Zhavoronkov, Nickolai; Steinmeyer, Guenter [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2a, 12489 Berlin (Germany); Lederer, Falk [Institute for Condensed Matter Theory and Solid State Optics, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany)

2006-11-15T23:59:59.000Z

190

Genetic Regulation of Differentiated Microbial Filaments | U.S. DOE Office  

Office of Science (SC) Website

Genetic Regulation of Differentiated Microbial Filaments Genetic Regulation of Differentiated Microbial Filaments Biological and Environmental Research (BER) BER Home About Research Facilities Science Highlights Searchable Archive of BER Highlights External link Benefits of BER Funding Opportunities Biological & Environmental Research Advisory Committee (BERAC) News & Resources Contact Information Biological and Environmental Research U.S. Department of Energy SC-23/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-3251 F: (301) 903-5051 E: sc.ber@science.doe.gov More Information » September 2012 Genetic Regulation of Differentiated Microbial Filaments Discovering how a microbe makes complex structures to perform complex functions. Print Text Size: A A A Subscribe FeedbackShare Page

191

Mesoscopic model for filament orientation in growing actin networks: the role of obstacle geometry  

E-Print Network (OSTI)

Propulsion by growing actin networks is a universal mechanism used in many different biological systems. Although the core molecular machinery for actin network growth is well preserved in most cases, the geometry of the propelled obstacle can vary considerably. In recent years, filament orientation distribution has emerged as an important observable characterizing the structure and dynamical state of the growing network. Here we derive several continuum equations for the orientation distribution of filaments growing behind stiff obstacles of various shapes and validate the predicted steady state orientation patterns by stochastic computer simulations based on discrete filaments. We use an ordinary differential equation approach to demonstrate that for flat obstacles of finite size, two fundamentally different orientation patterns peaked at either +35/-35 or +70/0/-70 degrees exhibit mutually exclusive stability, in agreement with earlier results for flat obstacles of very large lateral extension. We calculat...

Weichsel, Julian; 10.1088/1367-2630/15/3/035006

2013-01-01T23:59:59.000Z

192

NONLINEAR FORCE-FREE MODELING OF MAGNETIC FIELDS IN A SOLAR FILAMENT  

SciTech Connect

We present a striking filament pattern in the nonlinear force-free (NLFF) chromospheric magnetic field of the active region NOAA 10956. The NLFF chromospheric field is extrapolated from the Hinode high-resolution photospheric vector magnetogram using the weighted optimization method. The modeled structure is characterized by a highly sheared field with strong horizontal magnetic components and has a virtually identical shape and location as the filament seen in H{alpha}. The modeled field strength agrees with the recent He I 10830 A observations by Kuckein et al.. The unequivocal resemblance between the NLFF extrapolation and the H{alpha} observation not only demonstrates the ability of the NLFF field to reproduce chromospheric features, but also provides a valuable diagnostic tool for the filament magnetic fields.

Jing Ju; Yuan Yuan; Xu Yan; Liu Rui; Wang Haimin [Space Weather Research Laboratory, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Wiegelmann, Thomas, E-mail: ju.jing@njit.ed, E-mail: yy46@njit.ed, E-mail: yx2@njit.ed, E-mail: rui.liu@njit.ed, E-mail: haimin@flare.njit.ed, E-mail: wiegelmann@linmpi.mpg.d [Max Planck Institut fuer Sonnensystemforschung (MPS), Max-Planck-Strasse 2, 37191 Katlenburg-Lindau (Germany)

2010-08-10T23:59:59.000Z

193

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

DOE Patents (OSTI)

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

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

1994-01-01T23:59:59.000Z

194

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

DOE Patents (OSTI)

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

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

1994-10-18T23:59:59.000Z

195

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

SciTech Connect

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

Wang, Y.-M.; Sheeley, N. R. Jr. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Stenborg, G., E-mail: yi.wang@nrl.navy.mil, E-mail: neil.sheeley@nrl.navy.mil, E-mail: guillermo.stenborg.ctr.ar@nrl.navy.mil [George Mason University, Fairfax, VA 22030 (United States)

2013-06-10T23:59:59.000Z

196

Tensile mechanical properties and strengthening mechanism of hybrid carbon nanotube and silicon carbide nanoparticle-reinforced magnesium alloy composites  

Science Conference Proceedings (OSTI)

AZ91 magnesium alloy hybrid composites reinforced with different hybrid ratios of carbon nanotubes (CNTs) and silicon carbide (SiC) nanoparticulates were fabricated by semisolid stirring assisted ultrasonic cavitation. The results showed that grains ...

Xia Zhou; Depeng Su; Chengwei Wu; Liming Liu

2012-01-01T23:59:59.000Z

197

Nonlinear theory of kinetic Alfven waves propagation and multiple filament formation  

Science Conference Proceedings (OSTI)

In this paper, the filamentation of kinetic Alfven waves (KAWs) has been studied by assuming that the incident Gaussian beam of KAWs may not remain Gaussian during the filament formation. The solution of the nonlinear dynamical equation of KAWs has been obtained by developing the semi-analytical approach in solar wind plasma. Magnetic field structures of the KAW have been presented in x-z plane. The analytical theory using eikonal approximation has been used beyond the paraxial domain. The effect on spectral index of the turbulence has also been studied.

Sharma, R. P.; Malik, M.; Singh, H. D. [Centre for Energy Studies, Indian Institute of Technology Delhi, 110016 (India)

2008-06-15T23:59:59.000Z

198

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

SciTech Connect

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

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

2012-10-31T23:59:59.000Z

199

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

Science Conference Proceedings (OSTI)

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

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

2012-07-15T23:59:59.000Z

200

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

Science Conference Proceedings (OSTI)

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

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

2011-11-15T23:59:59.000Z

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


201

Evidence for long range movement of Bi-2212 within the filament bundle on melting and its significant effect on J  

E-Print Network (OSTI)

. The measurement of the Ag area (the white fraction of the images) for each sample was made by image analysisEvidence for long range movement of Bi-2212 within the filament bundle on melting and its.1088/0953-2048/24/7/075016 Evidence for long range movement of Bi-2212 within the filament bundle on melting and its significant

McQuade, D. Tyler

202

Analysis of copper ion filaments and retention of dual-layered devices for resistance random access memory applications  

Science Conference Proceedings (OSTI)

For improvement of switching uniformity, we propose a dual-layer structure with different resistance values in each layer. During the forming process, a current path is created in a high-resistance region which localizes filament formation in ultra-thin ... Keywords: Copper filament, Dual-layer, Resistance random access memory (ReRAM)

Jaesik Yoon; Joonmyoung Lee; Hyejung Choi; Ju-Bong Park; Dong-jun Seong; Wootae Lee; Chunhum Cho; Seonghyun Kim; Hyunsang Hwang

2009-07-01T23:59:59.000Z

203

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

SciTech Connect

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

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

2013-01-01T23:59:59.000Z

204

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

Science Conference Proceedings (OSTI)

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

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

2011-08-15T23:59:59.000Z

205

Iron carbide on titania surface modified with group VA oxides as Fisher-Tropsch catalysts  

SciTech Connect

Catalysts comprising iron carbide on a surface modified titania support wherein said support comprises a surface modifying oxide of tantalum, niobium, vanadium and mixtures thereof supported on said titania wherein at least a portion of said surface modifying oxide is in a non-crystalline form. These catalysts are useful for Fischer-Tropsch hydrocarbon synthesis reactions. Preferably, at least about 25 wt. % of said surface modifying oxide will be in a non-crystalline form.

Wachs, I. E.; Cherisch, C. C.; Fiato, R. A.

1985-12-17T23:59:59.000Z

206

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

207

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

208

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

E-Print Network (OSTI)

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

209

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

E-Print Network (OSTI)

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

B. Ruiz Cobo; L. R. Bellot Rubio

2008-06-04T23:59:59.000Z

210

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

Science Conference Proceedings (OSTI)

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

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

2012-12-10T23:59:59.000Z

211

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

Science Conference Proceedings (OSTI)

Hafnium oxide (HfO?) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO? ceramic target has been employed for sputtering while varying the Ts from room temperature to 500?C during deposition. The effect of Ts on the growth and microstructure of deposited HfO? films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO? films. Structural characterization indicates that the HfO? films grown at Ts200 ?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

212

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

Science Conference Proceedings (OSTI)

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

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

2010-12-15T23:59:59.000Z

213

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

214

Spindles and active vortices in a model of confined filament-motor mixtures  

E-Print Network (OSTI)

Robust self-organization of subcellular structures is a key principle governing the dynamics and evolution of cellular life. In fission yeast cells undergoing division, the mitotic spindle spontaneously emerges from the interaction of microtubules, motor proteins and the confining cell walls, and asters and vortices have been observed to self-assemble in quasi-two dimensional microtubule-kinesin assays. Their is no clear microscopic picture of the role of the active motors driving this pattern formation, and the relevance of continuum modeling to filament-scale structures remains uncertain. Here we present results of numerical simulations of a discrete filament-motor protein model confined to a pressurised cylindrical box. Stable spindles, nematic configurations, asters and high-density semi-asters spontaneously emerge, the latter pair having also been observed in cytosol confined within emulsion droplets. State diagrams are presented delineating each stationary state as the pressure, motor speed and motor density are varied. We further highlight a parameter regime where vortices form exhibiting collective rotation of all filaments, but have a finite life-time before contracting to a semi-aster. Quantifying the distribution of life-times suggests this contraction is a Poisson process. Equivalent systems with fixed volume exhibit persistent vortices with stochastic switching in the direction of rotation, with switching times obeying similar statistics to contraction times in pressurised systems. Furthermore, we show that increasing the detachment rate of motors from filament plus-ends can both destroy vortices and turn some asters into vortices. Based on our findings we argue the need for a deeper understanding of the microscopic activities underpinning macroscopic self-organization in active gels and urge further experiments to help bridge these lengths.

David A. Head; W. J. Briels; Gerhard Gompper

2011-07-22T23:59:59.000Z

215

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

Science Conference Proceedings (OSTI)

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

Sun Zhanliang; Chen Jinhai; Rudolph, Wolfgang [University of New Mexico, Department of Physics and Astronomy, Albuquerque, New Mexico 87131 (United States)

2011-04-15T23:59:59.000Z

216

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

DOE Patents (OSTI)

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

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

1998-07-07T23:59:59.000Z

217

CRITICAL STUDIES OF DILUTE CARBIDE FAST REACTOR CORE. ZPR-III Assembly 34  

SciTech Connect

Critical studies were made with a simulated, large, dilute power reactor having uranium carbide as fuel. The uranium in the core was 30.7% enriched, and the atomic ratio of uranium to carbon was 0.946. The critical mass was 503.01 kg U/sup 235/ and the critical volume 574.47 liters. Central reactivity coefficients, effective fission crosssection ratios, heterogeneity effects, reactivity worth of distributed materials, foil irradiations, and the average prompt neutron lifetime were measured. Multigroup calculations using the Yiftah, Okrent, and Moldauer crosssection set overestimated k for the critical configuration by 4.7%. (auth)

Hubert, R.J.; Long, J.K.; McVean, R.L.; Gasidlo, J.M.

1961-05-01T23:59:59.000Z

218

Effect of high temperature hydrogenation on the fracture strength of a sintered alpha silicon carbide  

DOE Green Energy (OSTI)

The effect of high temperature hydrogenation on the strength of a pressureless sintered alpha silicon carbide was studied as a function of time. Samples were soaked in argon or a hydrogen-argon mixture (40:60, mole %) at 1400/sup 0/C for times of up to 50 hours. The samples were then broken in four point flexure at room temperature. It was found that the hydrogen attacked the material at grain boundaries, leaving loose SiC grains on the surface. Fifty hours in a hydrogenous atmosphere at 1400/sup 0/C caused an average 26% strength decrease. Surface degradation was evaluated using optical and scanning electron microscopy.

Jero, P.D.

1985-01-01T23:59:59.000Z

219

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

DOE Green Energy (OSTI)

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

Buss, R.J.

1997-02-01T23:59:59.000Z

220

Carbide Composition Changes in Power Plant Steels as a Method of Remanent Creep Life Prediction  

E-Print Network (OSTI)

the enrichment kinetics are much faster than in a low alloy steel. However, it has been found that the equilibrium alloy carbide precipitates during the commercial stress-relief heat treatment and does not change in composition during further tempering... . OptllTUSe demqn of condenser lanes Relocate suction pennts ftt !>quId CII>Q pumps A1r extracuon Rotors Thl'rmal51ft 1.lCal stress r,lL "rs E."mate thermal fatigue endurance Measure creep stram7 Temporary repa.rr Replacement HP and IP steam chests Th...

Thomson, Rachel Clare

1992-12-08T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
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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

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

Science Conference Proceedings (OSTI)

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

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

2011-12-15T23:59:59.000Z

222

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

Science Conference Proceedings (OSTI)

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

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

2012-09-06T23:59:59.000Z

223

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

DOE Patents (OSTI)

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

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

1982-01-01T23:59:59.000Z

224

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

SciTech Connect

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

Taylor, Larry Lorin

2001-01-01T23:59:59.000Z

225

J. Am. Ceram. Soc., 80 [1] 14248 (1997) Elastic Properties of Laminated Calcium Aluminosilicate/Silicon Carbide  

E-Print Network (OSTI)

J. Am. Ceram. Soc., 80 [1] 142­48 (1997) Elastic Properties of Laminated Calcium Aluminosilicate/Silicon Carbide Composites Determined by Resonant Ultrasound Spectroscopy Yongmei Liu, Yi He, Fuming Chu of unidirectional and 0 /90 crossply Carbon Co., Tokyo, Japan) SiC fibers have been the subject of particularly

Wadley, Haydn

226

COLD MOLECULAR GAS ALONG THE COOLING X-RAY FILAMENT IN A1795  

SciTech Connect

We present the results of interferometric observations of the cool core of A1795 at CO(1-0) using the Combined Array for Research in Millimeter-wave Astronomy. In agreement with previous work, we detect a significant amount of cold molecular gas (3.9 {+-} 0.4 Multiplication-Sign 10{sup 9} M{sub Sun }) in the central {approx}10 kpc. We report the discovery of a substantial clump of cold molecular gas at clustercentric radius of 30 kpc (2.9 {+-} 0.4 Multiplication-Sign 10{sup 9} M{sub Sun }), coincident in both position and velocity with the warm, ionized filaments. We also place an upper limit on the H{sub 2} mass at the outer edge of the star-forming filament, corresponding to a distance of 60 kpc (<0.9 Multiplication-Sign 10{sup 9} M{sub Sun }). We measure a strong gradient in the H{alpha}/H{sub 2} ratio as a function of radius, suggesting different ionization mechanisms in the nucleus and filaments of A1795. The total mass of cold molecular gas ({approx}7 Multiplication-Sign 10{sup 9} M{sub Sun }) is roughly 30% of the classical cooling estimate at the same position, assuming a cooling time of 10{sup 9} yr. Combining the cold molecular gas mass with the UV-derived star formation rate and the warm, ionized gas mass, the spectroscopically derived X-ray cooling rate is fully accounted for and in good agreement with the cooling byproducts over timescales of {approx}10{sup 9} yr. The overall agreement between the cooling rate of the hot intracluster medium and the mass of the cool gas reservoir suggests that, at least in this system, the cooling flow problem stems from a lack of observable cooling in the more diffuse regions at large radii.

McDonald, Michael [Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139 (United States); Wei, Lisa H. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Veilleux, Sylvain, E-mail: mcdonald@space.mit.edu, E-mail: lisa.wei@cfa.harvard.edu, E-mail: veilleux@astro.umd.edu [Astroparticle Physics Laboratory, NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771 (United States)

2012-08-20T23:59:59.000Z

227

Mesoscopic model for filament orientation in growing actin networks: the role of obstacle geometry  

E-Print Network (OSTI)

Propulsion by growing actin networks is a universal mechanism used in many different biological systems. Although the core molecular machinery for actin network growth is well preserved in most cases, the geometry of the propelled obstacle can vary considerably. In recent years, filament orientation distribution has emerged as an important observable characterizing the structure and dynamical state of the growing network. Here we derive several continuum equations for the orientation distribution of filaments growing behind stiff obstacles of various shapes and validate the predicted steady state orientation patterns by stochastic computer simulations based on discrete filaments. We use an ordinary differential equation approach to demonstrate that for flat obstacles of finite size, two fundamentally different orientation patterns peaked at either +35/-35 or +70/0/-70 degrees exhibit mutually exclusive stability, in agreement with earlier results for flat obstacles of very large lateral extension. We calculate and validate phase diagrams as a function of model parameters and show how this approach can be extended to obstacles with piecewise straight contours. For curved obstacles, we arrive at a partial differential equation in the continuum limit, which again is in good agreement with the computer simulations. In all cases, we can identify the same two fundamentally different orientation patterns, but only within an appropriate reference frame, which is adjusted to the local orientation of the obstacle contour. Our results suggest that two fundamentally different network architectures compete with each other in growing actin networks, irrespective of obstacle geometry, and clarify how simulated and electron tomography data have to be analyzed for non-flat obstacle geometries.

Julian Weichsel; Ulrich S. Schwarz

2013-04-13T23:59:59.000Z

228

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

SciTech Connect

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

Liu Rui [CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei 230026 (China); Kliem, Bernhard [Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam (Germany); Toeroek, Tibor; Titov, Viacheslav S.; Lionello, Roberto; Linker, Jon A. [Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States); Liu Chang; Wang Haimin, E-mail: rui.liu@njit.edu [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, NJIT, Newark, NJ 07102 (United States)

2012-09-01T23:59:59.000Z

229

Complete Genome Sequence of the Filamentous Anoxygenic Phototrophic Bacterium Chloroflexus aurantiacus  

Science Conference Proceedings (OSTI)

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

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

2011-01-01T23:59:59.000Z

230

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

DOE Green Energy (OSTI)

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

231

Early Stage R&D Technologies - Energy Innovation Portal  

Hot Wire Chemical Vapor Deposition with Carbide Filaments. ... Stem cell therapies are a viable treatment options for some human diseases.

232

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

233

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

234

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

235

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

SciTech Connect

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

236

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

237

Optimization of a hybrid exchange-correlation functional for silicon carbides  

SciTech Connect

A hybrid exchange-correlation functional is optimized in order to accurately describe the nature of silicon carbides (SiC) in the framework of ab-initio calculations based on density functional theory (DFT), especially with an aim toward future applications in defect studies. It is shown that the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional with the screening parameter of 0.15 -1 outperforms conventional exchange-correlation functionals and other popular hybrid functionals regarding description of band structures in SiC. High transferability is proven through assessment over various SiC polytypes, silicon and diamond. Excellent performance is also confirmed for other fundamental material properties including elastic constants and phonon frequency.

Oda, Takuji [University of Tennessee, Knoxville (UTK); Zhang, Yanwen [ORNL; Weber, William J [ORNL

2013-01-01T23:59:59.000Z

238

[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

239

Interaction of silver and palladium with silicon carbide in HTGR fuel particles. Preliminary report  

Science Conference Proceedings (OSTI)

Fuel particles for the High-Temperature Gas-Cooled Reactor contained a layer of pyrolytic silicon carbide, which acts as a pressure vessel and provides containment for metallic fission products. The SiC layer is deposited by the thermal decomposition of methyltrichlorosilane (CH/sub 3/SiCl/sub 3/ or MTS) in an excess of hydrogen. Certain fission products, notably silver and palladium, can cause degradation of the SiC during irradiation. The purpose of this study is to develop a quantitative data base to better understand noble-metal attack as well as to evaluate the relationship between SiC deposition conditions and noble-metal release. The interaction between SiC and noble-metal fission product elements was investigated in the temperature range 1200 to 1500/sup 0/C.

Lauf, R.J.

1980-07-01T23:59:59.000Z

240

Synthesis and Analysis of Alpha Silicon Carbide Components for Encapsulation of Fuel Rods and Pellets  

Science Conference Proceedings (OSTI)

The chemical, mechanical and thermal properties of silicon carbide (SiC) along with its low neutron activation and stability in a radiation field make it an attractive material for encapsulating fuel rods and fuel pellets. The alpha phase (6H) is particularly stable. Unfortunately, it requires very high temperature processing and is not readily available in fibers or near-net shapes. This paper describes an investigation to fabricate a-SiC as thin films, fibers and near-net-shape products by direct conversion of carbon using silicon monoxide vapor at temperatures less than 1700 C. In addition, experiments to nucleate the alpha phase during pyrolysis of polysilazane, are also described. Structure and composition were characterized using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Preliminary tensile property analysis of fibers was also performed.

Kevin M. McHugh; John E. Garnier; George W. Griffith

2011-09-01T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
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to obtain the most current and comprehensive results.


241

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

242

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

DOE Green Energy (OSTI)

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

243

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

DOE Patents (OSTI)

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

Barton, Thomas J. (Ames, IA); Ijadi-Maghsoodi, Sina (Ames, IA); Pang, Yi (Ames, IA)

1994-05-17T23:59:59.000Z

244

Suppression of stimulated Raman scattering due to localization of electron plasma wave in laser beam filaments  

Science Conference Proceedings (OSTI)

The filamentation of the high power laser beam by taking off-axial contribution is investigated when ponderomotive nonlinearity is taken into account. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. It is observed that the weak electron plasma wave (EPW) propagating in the z direction is nonlinearly coupled in the modified filamentary regions of the laser beam. The semianalytical solution of the nonlinear coupled EPW equation in the presence of laser beam filaments has been found and it is observed that the nonlinear coupling between these two waves leads to localization of the EPW. Stimulated Raman scattering (SRS) of this EPW is studied and backreflectivity has been calculated. Further, the localization of EPW affects the eigenfrequency and damping of plasma wave. As a result of this, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the backreflectivity. For the typical laser beam and plasma parameters with wavelength ({lambda}=1064 nm), power flux ({approx_equal}10{sup 16} W cm{sup -2}), and plasma density (n/n{sub cr})=0.2; the backreflectivity was found to be suppressed by a factor of around 20%.

Sharma, Prerana; Sharma, R. P. [Centre for Energy Studies, Indian Institute of Technology, New Delhi 110016 (India)

2009-03-15T23:59:59.000Z

245

Oil filaments produced by an impeller in a water stirred thank  

E-Print Network (OSTI)

In this video, the mechanism followed to disperse an oil phase in water using a Scaba impeller in a cylindrical tank is presented. Castor oil (viscosity = 500 mPas) is used and the Reynolds number was fixed to 24,000. The process was recorded with a high-speed camera. Initially, the oil is at the air water interface. At the beginning of the stirring, the oil is dragged into the liquid bulk and rotates around the impeller shaft, then is pushed radially into the flow ejected by the impeller. In this region, the flow is turbulent and exhibits velocity gradients that contribute to elongate the oil phase. Viscous thin filaments are generated and expelled from the impeller. Thereafter, the filaments are elongated and break to form drops. This process is repeated in all the oil phase and drops are incorporated into the dispersion. Two main zones can be identified in the tank: the impeller discharge characterized by high turbulence and the rest of the flow where low velocity gradients appear. In this region surface f...

Sanjuan-Galindo, Rene; Ascanio, Gabriel; Zenit, Roberto

2010-01-01T23:59:59.000Z

246

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

Science Conference Proceedings (OSTI)

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

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

2008-08-01T23:59:59.000Z

247

Signatures in a Giant Radio Galaxy of a Cosmological Shock Wave at Intersecting Filaments of Galaxies  

E-Print Network (OSTI)

Sensitive images of low-level, Mpc-sized radio cocoons offer new opportunities to probe large scale intergalactic gas flows outside clusters of galaxies. New radio images of high surface brightness sensitivity at strategically chosen wavelengths of the giant radio galaxy NGC 315 (Mack et al. 1997,1998) reveal significant asymmetries and particularities in the morphology, radio spectrum and polarization of the ejected radio plasma. We argue that the combination of these signatures provides a sensitive probe of an environmental shock wave. Analysis of optical redshifts in NGC 315 vicinity confirms its location to be near, or at a site of large-scale flow collisions in the 100 Mpc sized Pisces-Perseus Supercluster region. NGC 315 resides at the intersection of several galaxy filaments, and its radio plasma serves there as a `weather station' (Burns 1998) probing the flow of the elusive and previously invisible IGM gas. If our interpretation is correct, this is the first indication for a shock wave in flows caused by the cosmological large scale structure formation, which is located in a filament of galaxies. The possibility that the putative shock wave is a source of gamma-rays and ultra high energy cosmic rays is briefly discussed.

Torsten A. Ensslin; Patrick Simon; Peter L. Biermann; Ulrich Klein; Sven Kohle; Philipp P. Kronberg; Karl-Heinz Mack

2000-12-19T23:59:59.000Z

248

Hf-Ir (Hafnium - Iridium)  

Science Conference Proceedings (OSTI)

Hf-Ir crystallographic data...Hf-Ir crystallographic data Phase Composition, wt% Ir Pearson symbol Space group (βHf) 0 to ~10.5 cI 2 Im m (αHf) 0 to ~1.5 hP 2 P 6 3 / mmc Hf 2 Ir ~28 to 35.0 cF 96 Fd m Hf 5 Ir 3 39.3 hP 16 P 6 3 / mcm HfIr 51.9 to 59 o ** ? HfIr 3 76 to 82 cP 4 Pm m (Ir) ~91 to 100 cF 4 Fm m...

249

Effect of energetic electrons on dust charging in hot cathode filament discharge  

Science Conference Proceedings (OSTI)

The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.

Kakati, B.; Kausik, S. S.; Saikia, B. K. [Centre of Plasma Physics, Institute for Plasma Research, Nazirakhat, Sonapur 782 402, Kamrup, Assam (India); Bandyopadhyay, M. [ITER-India, Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India)

2011-03-15T23:59:59.000Z

250

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

E-Print Network (OSTI)

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

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

2004-07-22T23:59:59.000Z

251

Effects of the background plasma temperature on the current filamentation instability  

SciTech Connect

The effects of thermal anisotropy of background plasma on the current-filamentation instability (CFI) in an asymmetric counterstreaming system are investigated with a fully relativistic kinetic model. It is found that both the temperature and the thermal anisotropy of the background plasma play important roles in the development of the CFI. It is also pointed out that the thermal anisotropy of the background plasma dominates over the space charge effect in suppressing the CFI. A parametric study of the CFI is presented in the context of fast ignition. A new way to suppress CFI and its detrimental effects on the fast electron beam divergence has been proposed. The results of the analytical estimations are verified by 2D3V particle-in-cell simulations.

Jia Qing [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Cai, Hong-bo; He, X. T. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Wang Weiwu [Graduate School, China Academy of Engineering Physics, P.O. Box 2101, Beijing 100088 (China); Zhu Shaoping [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Sheng, Z. M. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China)

2013-03-15T23:59:59.000Z

252

Thick-to-Thin Filament Surface Distance Modulates Cross-Bridge Kinetics in Drosophila Flight Muscle  

Science Conference Proceedings (OSTI)

The demembranated (skinned) muscle fiber preparation is widely used to investigate muscle contraction because the intracellular ionic conditions can be precisely controlled. However, plasma membrane removal results in a loss of osmotic regulation, causing abnormal hydration of the myofilament lattice and its proteins. We investigated the structural and functional consequences of varied myofilament lattice spacing and protein hydration on cross-bridge rates of force development and detachment in Drosophila melanogaster indirect flight muscle, using x-ray diffraction to compare the lattice spacing of dissected, osmotically compressed skinned fibers to native muscle fibers in living flies. Osmolytes of different sizes and exclusion properties (Dextran T-500 and T-10) were used to differentially alter lattice spacing and protein hydration. At in vivo lattice spacing, cross-bridge attachment time (t{sub on}) increased with higher osmotic pressures, consistent with a reduced cross-bridge detachment rate as myofilament protein hydration decreased. In contrast, in the swollen lattice, t{sub on} decreased with higher osmotic pressures. These divergent responses were reconciled using a structural model that predicts t{sub on} varies inversely with thick-to-thin filament surface distance, suggesting that cross-bridge rates of force development and detachment are modulated more by myofilament lattice geometry than protein hydration. Generalizing these findings, our results suggest that cross-bridge cycling rates slow as thick-to-thin filament surface distance decreases with sarcomere lengthening, and likewise, cross-bridge cycling rates increase during sarcomere shortening. Together, these structural changes may provide a mechanism for altering cross-bridge performance throughout a contraction-relaxation cycle.

Tanner, Bertrand C.W.; Farman, Gerrie P.; Irving, Thomas C.; Maughan, David W.; Palmer, Bradley M.; Miller, Mark S. (IIT); (Vermont); (BU)

2012-09-19T23:59:59.000Z

253

Structural properties of Zn-ZnO core-shell microspheres grown by hot-filament CVD technique  

Science Conference Proceedings (OSTI)

We report the hot-filament chemical vapor deposition (HFCVD) growth of Zn-ZnO core-shell microspheres in the temperature range of 350-650C only using ZnO pellets as raw material. The samples were characterized by scanning electron microscope (SEM), ...

R. Lpez; T. Daz; G. Garca; R. Galeazzi; E. Rosendo; A. Coyopol; M. Pacio; H. Jurez; A. I. Oliva

2012-01-01T23:59:59.000Z

254

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

E-Print Network (OSTI)

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

Kioussis, Nicholas

255

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

DOE Green Energy (OSTI)

The current work continues a project completed in 1999 by ReMaxCo Technologies in which a novel, microwave based, VLS Silicon Carbide Fibrils concept was verified. This project continues the process development of a pilot scale commercial reactor. Success will lead to sufficient quantities of fibrils to expand work by ORNL and others on heat exchanger tube development. A semicontinuous, microwave heated, vacuum reactor was designed, fabricated and tested in these experiments. Cylindrical aluminum oxide reaction boats are coated, on the inner surface, with a catalyst and placed into the reactor under a light vacuum. A series of reaction boats are then moved, one at a time, through the reactor. Each boat is first preheated with resistance heaters to 850 C to 900 C. Each reaction boat is then moved, in turn, to the microwave heated section. The catalyst is heated to the required temperature of 1200 C to 1300 C while a mixture of MTS (methyl trichlorosilane) and hydrogen are introduced into the annulus of the boat. The MTS is dissociated to allow the carbon and silicon components to be dissolved into the catalyst. The catalyst saturates and precipitates silicon carbide onto the surface of the reaction boat to grow the Fibrils. The reaction continues as long as the MTS is introduced into the reactor. The major obstacle that had to be overcome during this project was the performance of the reactor. The original design of the reactor focused the microwaves in such a manner that they missed the catalyst/Fibrils growth zone. The microwaves did react with the insulation and the reactor was heated by heating the insulation. Modifications were made to the reactor to focus the microwaves on the catalyst. SiC Fibrils were produced using both MTS and Starfire SP4000 as feed-gas precursors. Both precursors produced fibrils at temperatures of less than 1000 C. The new Starfire SP4000 produced fibrils as low as 800 C, without the use of hydrogen and without producing the hazardous hydrochloric acid. Experimental results and scanning electron microscopy of the Fibril products are presented. Future work to improve on these results is discussed.

Nixdorf, R.D.

2003-04-22T23:59:59.000Z

256

Size-Scaling of Tensile Failure Stress in a Hot-Pressed Silicon Carbide  

Science Conference Proceedings (OSTI)

Quasi-static Weibull strength-size scaling of hot-pressed silicon carbide is described. Two surface conditions (uniaxial ground and uniaxial ground followed by grit blasting) were explored. Strength test coupons sampled effective areas from the very small (4 x 10{sup -3} mm{sup 2}) to the very large (4 x 10{sup 4} mm{sup 2}). Equibiaxial flexure and Hertzian ring crack initiation were used for the strength tests, and characteristic strengths for several different specimen geometries were analyzed as a function of effective area. Characteristic strength was found to substantially increase with decreased effective area for both surface conditions. Weibull moduli of 9.4- and 11.7 well-represented strength-size scaling for the two ground conditions between an effective area range of 10{sup -1} and 4 x 10{sup 4} mm{sup 2}. Machining damage was observed to be the dominant flaw type over this range. However, for effective areas <10{sup -1} mm{sup 2}, the characteristic strength increased rapidly for both ground surface conditions as the effective area decreased, and one or more of the inherent assumptions behind the classical Weibull strength-size scaling were in violation in this range. The selections of a ceramic strength to account for ballistically induced tile deflection and expanding cavity modeling are considered in context with the measured strength-size scaling. The observed size-scaling is briefly discussed with reference to dynamic strength.

Wereszczak, Andrew A [ORNL; Kirkland, Timothy Philip [ORNL; Strong, Kevin T [ORNL; Campbell, James [U.S. Army research Laboratory, Adelphi, MD; LaSalvia, Jerry [U.S. Army research Laboratory, Adelphi, MD; Miller, Herbert [U.S. Army research Laboratory, Adelphi, MD

2010-01-01T23:59:59.000Z

257

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

E-Print Network (OSTI)

Recent technological advances have allowed silicon (Si) semiconductor technology to approach the theoretical limits of the Si material; however, power device requirements for many applications are at a stage that the present Si-based power devices 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 offer one such alternative. SiC based power devices exhibit superior properties such as very low switching losses, fast switching behavior, improved reliability and high temperature operation capabilities. Power factor correction stage of power supplies is identified as an area where application of these devices would prove advantageous. In this thesis a high performance, high efficiency, SiC based power factor correction stage is discussed. The proposed topology takes advantage of the superior properties of SiC semiconductor based devices and the reduced number of devices that the dual boost power factor correction topology requires to achieve high efficiency, small size and better performance at high temperature. In addition to this analysis of SiC based power devices is carried out to study their characteristics and performance.

Durrani, Yamin Qaisar

2005-08-01T23:59:59.000Z

258

OTEC performance tests of the Union Carbide enhanced-tube condenser  

DOE Green Energy (OSTI)

Results of performance tests conducted on a Union Carbide enhanced-tube condenser with wire wrapping on the ammonia side and internal axial fins on the water side are reported. This unit performed satisfactorily and was free of operational difficulties. At design operating conditions (a heat duty of 3.2 million Btu/h, an inlet water temperature of 40/sup 0/F, and a water flow rate of 3200 gpm) the steady-state value of the overall heat transfer coefficient was found to be 818 Btu/h.ft/sup 2/./sup 0/F, and the ammonia-side and water-side heat transfer coefficients were 5180 and 1130 Btu/h.ft/sup 2/./sup 0/F, respectively. The water-side pressure drop was 1.8 psi. Varying the heat duty from 2.4 million to 4.0 million Btu/h had a negligible effect on thermal performance. The value obtained for the ammonia-side heat transfer coefficient at nominal conditions is about two times that predicted by the Nusselt expression for condensation on a smooth tube. The water-side coefficient is within 3% of the value predicted by the Noranda correlation for finned tubes.

Yung, D T; Hillis, D L; Lorenz, J J; Sather, N F

1979-05-01T23:59:59.000Z

259

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

260

Boron carbide-based coatings on graphite for plasma facing components  

SciTech Connect

In the effort to evaluate boron-rich coatings as plasma facing surfaces in fusion devices, a new process for applying boron carbide (B{sub 4}C) coatings to graphite was developed. The process entails eutectic melting of the carbon (C) substrate surface with a precursor layer of B{sub 4}C particles. Adherent coatings were achieved which consisted of two layers: a surface layer and a graded penetration zone in the outer portion of the substrate. The surface-layer microstructure was multiphase and ranged from reaction-sintered structures of sintered B{sub 4}C particles in an eutectic-formed matrix to that of hypereutectic carbon particles in a B{sub 4}C-C eutectic matrix. Because of high surface energy, the coating generally developed a nonuniform thickness. Quantitative evaluations of the coating were performed with limiters in the TEXTOR fusion device and with coupons in electron beam tests. Test results revealed the following: good adherence of the coating even after remelting; and, during remelting, diagnostics detected a corresponding interaction of boron with the plasma.

Valentine, P.G.; Trester, P.W. [General Atomics, San Diego, CA (United States); Winter, J.; Linke, J.; Duwe, R.; Wallura, E.; Philipps, V. [Kernforschungsanlage Juelich GmbH (Germany)

1994-01-01T23:59:59.000Z

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


261

Equilibrium predictions of the role of organosilicon compounds in the chemical vapor deposition of silicon carbide  

DOE Green Energy (OSTI)

Equilibrium calculations are reported for a range of conditions used to deposit silicon carbide (SiC) from Si-C-H mixtures such as those using SiH{sub 4}, C{sub 2}H{sub 4}, and H{sub 2} as reactants. Included are 37 molecules containing both silicon and carbon, allowing as assessment to be made of the importance of organosilicon species to the deposition process. The results indicate that Si{sub 2}C and SiCH{sub 2} may contribute to epitaxial SiC deposition and that formation of these and other organosilicon species is favored by low H{sub 2} concentrations. In addition, simulations of gas-phase equilibria expected under low-pressure, low-temperature conditions show that some organosilicon radicals that are kinetically favored are also thermodynamically favored. These include SiC{sub 2}, SiCCH, and HSiCCH, which could results from the reactor of SiH{sub 2} with unsaturated reactants such as C{sub 2}H{sub 2}. The results suggest that combining an inert carrier gas with an excess of a surface-reactive hydrocarbon such as C{sub 2}H{sub 2} could increase deposition rates without forming silicon-rich deposits. 25 refs.

Allendorf, M.D.

1992-06-01T23:59:59.000Z

262

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

SciTech Connect

Radiation-resistant advanced silicon carbide (SiC/SiC) composites have been developed as a promising candidate of the high-temperature operating advanced fusion reactor. With the completion of the 'proof-of-principle' phase in development of 'nuclear-grade' SiC/SiC composites, the R&D on SiC/SiC composites 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 are specifically reviewed. Importantly high-temperature neutron irradiation effects on microstructural evolution, thermal and electrical conductivities and mechanical properties including the fiber/matrix interfacial strength are specified under various irradiation conditions, indicating seemingly very minor influence on the composite performance in the design temperature range.

Nozawa, Takashi [Japan Atomic Energy Agency (JAEA); Hinoki, Tatsuya [Kyoto University, Japan; Hasegawa, Akira [Tohoku University, Japan; Kohyama, Akira [Kyoto University, Japan; Katoh, Yutai [ORNL; Snead, Lance Lewis [ORNL; HenagerJr., Charles H. [Pacific Northwest National Laboratory (PNNL); Hegeman, Hans [NRG Petten

2009-01-01T23:59:59.000Z

263

Influence of substrate temperature on growth of nanocrystalline silicon carbide by reactive magnetron sputtering  

SciTech Connect

Hydrogenated nanocrystalline silicon carbide were grown at various deposition temperatures T{sub d} from 200 to 600 deg. C by means of reactive magnetron sputtering in a plasma of 80% H{sub 2} and 20% Ar mixture. A detailed investigation of the structural, compositional, phase nature, and morphology was carried out by complementary sophisticated techniques, such as Fourier transform infrared spectroscopy, x-ray diffraction (XRD), Rutherford backscattering, nuclear reaction, and elastic recoil detection analysis techniques, in addition to conventional and high-resolution transmission electron microscopy (HRTEM) observations. A crystallization onset with a fraction of 35% was observed for T{sub d}=300 deg. C, which improved to 80% for T{sub d}=600 deg. C, reflected by an increasing density of the SiC nanocrystals which kept an average size of about 5 nm. The observed fiber textures present <102> and <11l> texture components, with l larger than 2, while SiC nanocrystals elongated along the [111] direction are also evidenced. These latter are supported by the careful analyses of the HRTEM images which show evidence of faulted growing cubic SiC, as the origin of the very close hexagonal 6H-SiC structure taken into account in the XRD refinement. These various features were found quite consistent with the optical properties of the layers, and, in particular, the evolutions of both optical gap and static refractive index.

Colder, H.; Rizk, R.; Morales, M.; Marie, P.; Vicens, J.; Vickridge, I. [Structure des Interfaces et Fonctionnalite des Couches Minces (SIFCOM), Unite Mixte de Recherche (UMR) 6176, Ecole Nationale Superieure d'Ingenieurs de Caen, ENSICAEN, 6 Boulevard Marechal Juin, 14050 Caen (France); Systeme d'Analyse par Faisceau d'Ions Rapides (SAFIR), GPS, Unite Mixte de Recherche (UMR) 7588, Campus Boucicaut, 140, Rue de Lourmel, 75015 Paris (France)

2005-07-15T23:59:59.000Z

264

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

265

DC Electrical Conductivity of Silicon Carbide Ceramics and Composites for Flow Channel Insert Applications  

SciTech Connect

High purity chemically vapor-deposited silicon carbide (SiC) and 2D continuous SiC fiber, chemically vapor-infiltrated SiC matrix composites with pyrocarbon interphases were examined for temperature dependent (RT to 800 C) electrical conductivity and the influence of neutron irradiation on it. In the 2D composites, trans-thickness electrical conductivity was dominated by bypass conduction via interphase network at relatively low temperatures, whereas conduction through SiC constituents dominated at higher temperatures. The Influence of neutron irradiation on electrical properties appeared very strong for SiC, resulting typically in by orders lower ambient conductivity and steeper temperature dependency. Through-thickness electrical conductivity of neutron-irradiated 2D SiC composites with thin PyC interphase will likely in the order of 10 S/m in the typical operating temperature range for flow channel inserts. Mechanisms of electrical conduction in the composites and irradiation-induced modification of electrical conductivity of the composites and their constituents are discussed.

Katoh, Yutai [ORNL; Kondo, Sosuke [ORNL; Snead, Lance Lewis [ORNL

2009-01-01T23:59:59.000Z

266

Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage  

Science Conference Proceedings (OSTI)

On-board hydrogen storage is a key requirement for fuel cell-powered cars and trucks. Porous carbon-based materials can in principle adsorb more hydrogen per unit weight at room temperature than liquid hydrogen at -176 oC. Achieving this goal requires interconnected pores with very high internal surface area, and binding energies between hydrogen and carbon significantly enhanced relative to H2 on graphite. In this project a systematic study of carbide-derived carbons, a novel form of porous carbon, was carried out to discover a high-performance hydrogen sorption material to meet the goal. In the event we were unable to improve on the state of the art in terms of stored hydrogen per unit weight, having encountered the same fundamental limit of all porous carbons: the very weak interaction between H2 and the carbon surface. On the other hand we did discover several strategies to improve storage capacity on a volume basis, which should be applicable to other forms of porous carbon. Further discoveries with potentially broader impacts include Proof that storage performance is not directly related to pore surface area, as had been previously claimed. Small pores (supercapacitors with record high specific capacitance, and perm-selective membranes which bind cytokines for control of infections and possibly hemodialysis filters.

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

2010-01-07T23:59:59.000Z

267

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

DOE Green Energy (OSTI)

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

268

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

Science Conference Proceedings (OSTI)

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

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

2010-03-11T23:59:59.000Z

269

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

DOE Patents (OSTI)

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

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

1996-01-23T23:59:59.000Z

270

Activity of tungsten and rhenium filaments in CH sub 4 /H sub 2 and C sub 2 H sub 2 /H sub 2 mixtures: Importance for diamond CVD  

DOE Green Energy (OSTI)

The resistance R, spectral emissivity {epsilon}, and power consumption of W and Re filaments heated to 2500 {degree}C in mixtures of CH{sub 4} or C{sub 2}H{sub 2} in H{sub 2} have been measured in a series of experiments focusing on the state of the filament activity, i.e., its ability to dissociate the reactant gases. It has been found that these properties of the filaments, as well as the partial pressures of CH{sub 4} and C{sub 2}H{sub 2} in the reaction chamber, depend critically on both the filament temperature and the reactant ratio, e.g., C{sub 2}H{sub 2}/H{sub 2}. Specifically, both W and Re filaments show sharp jumps in power consumption at essentially the same temperature, signaling strong increases in filament activity and, hence, production of atomic hydrogen. These results are proposed to be due to the removal of non-reactive carbon from the surface of the filament via etching by atomic hydrogen and are consistent with the predictions of our thermodynamic model for the C-H system. Evidence for gas phase reactions is presented and the role of thermal diffusion is discussed. The emissivities of the W and Re filaments are observed to have significantly different temperature dependences which are attributed to differences in the phase diagrams for the W-C and Re-C systems. The implications of these results for hot-filament diamond CVD are discussed.

Sommer, M.; Smith, F.W. (Department of Physics, The City College of the City University of New York, New York, NY (USA))

1990-11-01T23:59:59.000Z

271

Evaluations of University of Wisconsin Silicon Carbide Temperature Monitors 300 LO and 400 LO B  

SciTech Connect

Silicon carbide (SiC) temperature monitors 05R4-02-A KG1403 (300 LO) and 05R4-01-A KG1415 (400 LO B) were evaluated at the High Temperature Test Lab (HTTL) to determine their peak irradiation temperatures. HTTL measurements indicate that the peak irradiation temperature for the 300 LO monitor was 295 {+-} 20 C and the peak irradiation temperature for the 400 LO B monitor was 294 {+-} 25 C. Two silicon carbide (SiC) temperature monitors irradiated in the Advanced Test Reactor (ATR) were evaluated at the High Temperature Test Lab (HTTL) to determine their peak temperature during irradiation. These monitors were irradiated as part of the University of Wisconsin Pilot Project with a target dose of 3 dpa. Temperature monitors were fabricated from high density (3.203 g/cm3) SiC manufactured by Rohm Haas with a nominal size of 12.5 mm x 1.0 mm x 0.75 mm (see Attachment A). Table 1 provides identification for each monitor with an expected peak irradiation temperature range based on preliminary thermal analysis (see Attachment B). Post irradiation calculations are planned to reduce uncertainties in these calculated temperatures. Since the early 1960s, SiC has been used as a post-irradiation temperature monitor. As noted in Reference 2, several researchers have observed that neutron irradiation induced lattice expansion of SiC annealed out when the post-irradiation annealing temperature exceeds the peak irradiation temperature. As noted in Reference 3, INL uses resistivity measurements to infer peak irradiation temperature from SiC monitors. Figure 1 depicts the equipment at the HTTL used to evaluate the SiC monitors. The SiC monitors are heated in the annealing furnace using isochronal temperature steps that, depending on customer needs, can range from 50 to 800 C. This furnace is located under a ventilation hood within the stainless steel enclosure. The ventilation system is activated during heating so that any released vapors are vented through this system. Annealing temperatures are recorded using a National Institute of Standards and Technology (NIST) traceable thermocouple inserted into an alumina tube in the furnace. After each isochronal annealing, the specimens are placed in a specialized fixture located in the constant temperature chamber (maintained at 30 C) for a minimum of 30 minutes. After the 30 minute wait time, each specimen's resistance is measured using the specialized fixture and a calibrated DC power analyzer. This report discusses the evaluation of the SiC monitors and presents the results. Testing was conducted in accordance with Reference 3. Sections 2 and 3 present the data collected for each monitor and provide interpretation of the data. Section 4 presents the evaluated temperature results.

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

2011-12-01T23:59:59.000Z

272

Surface impurity removal from DIII-D graphite tiles by boron carbide grit blasting  

SciTech Connect

During the latter half of 1992, the DIII-D tokamak at General Atomics (GA) underwent several modifications of its interior. One of the major tasks involved the removal of accumulated metallic impurities from the surface of the graphite tiles used to line the plasma facing surfaces inside of the tokamak. Approximately 1500 graphite tiles and 100 boron nitride tiles from the tokamak were cleaned to remove the metallic impurities. The cleaning process consisted of several steps: the removed graphite tiles were permanently marked, surface blasted using boron carbide (B{sub 4}C) grit media (approximately 37 {mu}m. diam.), ultrasonically cleaned in ethanol to remove loose dust, and outgassed at 1000{degrees}C. Tests were done using, graphite samples and different grit blaster settings to determine the optimum propellant and abrasive media pressures to remove a graphite layer approximately 40-50 {mu}m deep and yet produce a reasonably smooth finish. EDX measurements revealed that the blasting technique reduced the surface Ni, Cr, and Fe impurity levels to those of virgin graphite. In addition to the surface impurity removal, tritium monitoring was performed throughout the cleaning process. A bubbler system was set up to monitor the tritium level in the exhaust gas from the grit blaster unit. Surface wipes were also performed on over 10% of the tiles. Typical surface tritium concentrations of the tiles were reduced from about 500 dpm/100 cm{sup 2} to less than 80 dpm/100 cm{sup 2} following the cleaning. This tile conditioning, and the installation of additional graphite tiles to cover a high fraction of the metallic plasma facing surfaces, has substantially reduced metallic impurities in the plasma discharges which has allowed rapid recovery from a seven-month machine opening and regimes of enhanced plasma energy confinement to be more readily obtained. Safety issues concerning blaster operator exposure to carcinogenic metals and radioactive tritium will also be addressed.

Lee, R.L.; Hollerbach, M.A.; Holtrop, K.L.; Kellman, A.G.; Taylor, P.L.; West, W.P.

1993-11-01T23:59:59.000Z

273

Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage  

SciTech Connect

On-board hydrogen storage is a key requirement for fuel cell-powered cars and trucks. Porous carbon-based materials can in principle adsorb more hydrogen per unit weight at room temperature than liquid hydrogen at -176 oC. Achieving this goal requires interconnected pores with very high internal surface area, and binding energies between hydrogen and carbon significantly enhanced relative to H2 on graphite. In this project a systematic study of carbide-derived carbons, a novel form of porous carbon, was carried out to discover a high-performance hydrogen sorption material to meet the goal. In the event we were unable to improve on the state of the art in terms of stored hydrogen per unit weight, having encountered the same fundamental limit of all porous carbons: the very weak interaction between H2 and the carbon surface. On the other hand we did discover several strategies to improve storage capacity on a volume basis, which should be applicable to other forms of porous carbon. Further discoveries with potentially broader impacts include Proof that storage performance is not directly related to pore surface area, as had been previously claimed. Small pores (< 1.5 nm) are much more effective in storing hydrogen than larger ones, such that many materials with large total surface areas are sub-par performers. Established that the distribution of pore sizes can be controlled during CDC synthesis, which opens the possibility of developing high performance materials within a common family while targeting widely disparate applications. Examples being actively pursued with other funding sources include methane storage, electrode materials for batteries and supercapacitors with record high specific capacitance, and perm-selective membranes which bind cytokines for control of infections and possibly hemodialysis filters.

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

2010-01-07T23:59:59.000Z

274

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 intern attached to the Maintenance Department, with access to virtually every staff and line component of the organization. The intent of this report is to demonstrate that this experience fulfills the requirements of the Doctor of Engineering internship. The author's internship activities can be divided into three major categories which correspond to the three principal internship objectives. The first objective required a study of the organization and how the individual parts function together to produce results. This study was conducted by taking part in various diverse orientations and small projects throughout the organization. The second objective called for development of interpersonal and management skills. This was accomplished by participating in all forms of daily business activities, talking with the observing managers, receiving formal management training and taking advantage of every opportunity to practice these important skills. The third objective required an identifiable contribution be made to one or more particular projects. The three principal projects to which the author contributed involved inventory control, industrial hygiene, and maintenance workforce utilization. The result of the internship experience was an appreciation for both the technical and non-technical aspects of operating a large chemical plant. The conclusion of the report is that the objectives were met and the internship requirement for the degree of Doctor of Engineering has been satisfied.

Tippett, Donald Dwight, 1947-

1981-12-01T23:59:59.000Z

275

OTEC performance tests of the Union Carbide sprayed-bundle evaporator  

DOE Green Energy (OSTI)

Results of performance tests on a Union Carbide sprayed-bundle evaporator with High Flux titanium tubes are reported. This unit performed satisfactorily and was free of operational problems. Under nominal operating conditions (3200 gpm water flow rate, 3.2 million Btu/hr heat duty, and 40 gpm ammonia feed rate), the overall heat transfer coefficient (U/sub 0/) was found to be 760 Btu/hr ft/sup 2/ /sup 0/F and the ammonia-side and water-side coefficients were 4600 and 1300 Btu/hr ft/sup 2/ /sup 0/F, respectively. The overall water-side pressure drop in the heat exchanger was 4.0 psi, and the vapor quality measured at various heat duties and ammonia feed rates was 99.2 +- 0.25%. Variations in heat duty (from 2.4 million to 4.0 million Btu/hr) and ammonia inlet temperature (from 52 to 72/sup 0/F) did not affect the value of U/sub 0/, nor did changes in ammonia feed rate in the range of 40 to 100 gpm. However, a minimum ammonia feed rate below which U/sub 0/ decreased sharply was observed; this corresponded to a local tube loading of 20 lb/hr ft and was essentially independent of heat duty. Finally contact between the liquid ammonia and the High Flux surface under nonboiling conditions appeared to deactivate nucleation sites, reducing U/sub 0/ to < 700 Btu/hr ft/sup 2/ /sup 0/F. The deactivated surface could be reactivated by drying out the tubes while maintaining warm water flow.

Hillis, D L; Lorenz, J J; Yung, D T; Sather, N F

1979-05-01T23:59:59.000Z

276

OTEC performance tests of the Union Carbide flooded-bundle evaporator  

DOE Green Energy (OSTI)

Results of performance tests conducted on a Union Carbide flooded-bundle evaporator with High Flux titanium tubes are reported. At design operating conditions (a heat duty of 3.2 million Btu/hr, an inlet water temperature of 80/sup 0/F, and a water flow rate of 3200 gpm) the steady-state value of the overall heat transfer coefficient (U/sub 0/) was found to be 785 Btu/hr ft/sup 2/ /sup 0/F, and the ammonia-side and water-side heat transfer coefficients were 4800 and 1400 Btu/hr ft/sup 2/ /sup 0/F, respectively. The water-side pressure drop was 2.7 psi. Variations in heat duty (+-25%) and liquid ammonia feed temperature (over the range of 48 to 64/sup 0/F) did not affect thermal performance significantly. On the other hand, U/sub 0/ was reduced appreciably by operational shutdowns during which nonboiling ammonia remained in contact with the High Flux surface for periods of 30 minutes or more. During a one-hour shutdown the value of U/sub 0/ decreased to 690 Btu/hr ft/sup 2/ /sup 0/F, and values as low as 600 Btu/hr ft/sup 2/ /sup 0/F were reached for longer shutdowns. Such contact appears to deactivate some of the nucleate boiling sites, thus reducing the heat transfer coefficient. Although operation of the evaporator under boiling conditions reverses this effect, reactivation takes place much more slowly than deactivation. Procedures for avoiding this problem in the operation of the High Flux flooded-bundle evaporator are given.

Lewis, L G; Sather, N F

1978-12-01T23:59:59.000Z

277

Simulation of current-filament dynamics and relaxation in the Pegasus Spherical Tokamak  

Science Conference Proceedings (OSTI)

Nonlinear numerical computation is used to investigate the relaxation of non-axisymmetric current-channels from washer-gun plasma sources into 'tokamak-like' plasmas in the Pegasus toroidal experiment [Eidietis et al. J. Fusion Energy 26, 43 (2007)]. Resistive MHD simulations with the NIMROD code [Sovinec et al. Phys. Plasmas 10(5), 1727-1732 (2003)] utilize ohmic heating, temperature-dependent resistivity, and anisotropic, temperature-dependent thermal conduction corrected for regions of low magnetization to reproduce critical transport effects. Adjacent passes of the simulated current-channel attract and generate strong reversed current sheets that suggest magnetic reconnection. With sufficient injected current, adjacent passes merge periodically, releasing axisymmetric current rings from the driven channel. The current rings have not been previously observed in helicity injection for spherical tokamaks, and as such, provide a new phenomenological understanding for filament relaxation in Pegasus. After large-scale poloidal-field reversal, a hollow current profile and significant poloidal flux amplification accumulate over many reconnection cycles.

O'Bryan, J. B.; Sovinec, C. R.; Bird, T. M. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)

2012-08-15T23:59:59.000Z

278

EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE BARNARD 5 STAR-FORMING CORE: EMBEDDED FILAMENTS REVEALED  

SciTech Connect

We present {approx}6.'5 x 8' Expanded Very Large Array (EVLA) mosaic observations of the NH{sub 3} (1,1) emission in the Barnard 5 region in Perseus, with an angular resolution of 6''. This map covers the coherent region, where the dense gas presents subsonic non-thermal motions (as seen from single dish observations with the Green Bank Telescope, GBT). The combined EVLA and GBT observations reveal, for the first time, a striking filamentary structure (20'' wide or 5000 AU at the distance of Perseus) in this low-mass star-forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. The observed separation between the B5-IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The observed region displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions.

Pineda, Jaime E.; Longmore, Steven [ESO, Karl Schwarzschild Street 2, 85748 Garching bei Munchen (Germany); Goodman, Alyssa A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Arce, Hector G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Caselli, Paola [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Corder, Stuartt, E-mail: jaime.pineda@manchester.ac.uk [North American ALMA Science Center, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

2011-09-20T23:59:59.000Z

279

Grain size dependent mechanical properties of nanocrystalline diamond films grown by hot-filament CVD  

DOE Green Energy (OSTI)

Nanocrystalline diamond (NCD) films with a thickness of {approx}6 {micro}m and with average grain sizes ranging from 60 to 9 nm were deposited on silicon wafers using a hot-filament chemical vapor deposition (HFCVD) process. These samples were then characterized with the goal to identify correlations between grain size, chemical composition and mechanical properties. The characterization reveals that our films are phase pure and exhibit a relatively smooth surface morphology. The levels of sp{sup 2}-bonded carbon and hydrogen impurities are low, and showed a systematic variation with the grain size. The hydrogen content increases with decreasing grain size, whereas the sp{sup 2} carbon content decreases with decreasing grain size. The material is weaker than single crystalline diamond, and both stiffness and hardness decrease with decreasing grain size. These trends suggest gradual changes of the nature of the grain boundaries, from graphitic in the case of the 60 nm grain size material to hydrogen terminated sp{sup 3} carbon for the 9 nm grain size material. The films exhibit low levels of internal stress and freestanding structures with a length of several centimeters could be fabricated without noticeable bending.

Wiora, M; Bruehne, K; Floeter, A; Gluche, P; Willey, T M; Kucheyev, S O; Van Buuren, A W; Hamza, A V; Biener, J; Fecht, H

2008-08-01T23:59:59.000Z

280

THE IMPACT OF THERMODYNAMICS ON GRAVITATIONAL COLLAPSE: FILAMENT FORMATION AND MAGNETIC FIELD AMPLIFICATION  

Science Conference Proceedings (OSTI)

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

Peters, Thomas; Klessen, Ralf S.; Federrath, Christoph; Smith, Rowan J. [Zentrum fuer Astronomie, Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Schleicher, Dominik R. G. [Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Banerjee, Robi [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Sur, Sharanya, E-mail: tpeters@physik.uzh.ch [Raman Research Institute, C. V. Raman Avenue, Sadashivnagar, Bangalore 560080 (India)

2012-12-01T23:59:59.000Z

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


281

Clusters, Groups, and Filaments in the Chandra Deep Field-South up to Redshift 1  

E-Print Network (OSTI)

We present a comprehensive structure detection analysis of the 0.3 square degree area of the MUSYC-ACES field which covers the Chandra Deep Field-South (CDFS). Using a density-based clustering algorithm on the MUSYC and ACES photometric and spectroscopic catalogues we find 62 over-dense regions up to redshifts of 1, including, clusters, groups and filaments. All structures are confirmed using the DBSCAN method, including the detection of nine structures previously reported in the literature. We present a catalogue of all structures present including their central position, mean redshift, velocity dispersions, and classification based on their morphological and spectroscopic distributions. In particular we find 13 galaxy clusters and 6 large groups/small clusters. Comparison of these massive structures with published XMM-Newton imaging (where available) shows that $80\\%$ of these structures are associated with diffuse, soft-band (0.4 - 1 keV) X-ray emission including $90\\%$ of all objects classified as cluster...

Dehghan, Siamak

2013-01-01T23:59:59.000Z

282

Standard Test Methods for Properties of Continuous Filament Carbon and Graphite Fiber Tows  

E-Print Network (OSTI)

1.1 These test methods cover the preparation and tensile testing of resin-impregnated and consolidated test specimens made from continuous filament carbon and graphite yarns, rovings, and tows to determine their tensile properties. 1.2 These test methods also cover the determination of the density and mass per unit length of the yarn, roving, or tow to provide supplementary data for tensile property calculation. 1.3 These test methods include a procedure for sizing removal to provide the preferred desized fiber samples for density measurement. This procedure may also be used to determine the weight percent sizing. 1.4 These test methods include a procedure for determining the weight percent moisture adsorption of carbon or graphite fiber. 1.5 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. 1.6 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 t...

American Society for Testing and Materials. Philadelphia

1999-01-01T23:59:59.000Z

283

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

DOE Green Energy (OSTI)

The main objective of this program was to develop an efficient and economically viable microwave processing technique to process cobalt cemented tungsten carbide with improved properties for drill-bits for advanced drilling operations for oil, gas, geothermal and excavation industries. The program was completed in three years and successfully accomplished all the states goals in the original proposal. In three years of the program, we designed and built several laboratory scale microwave sintering systems for conducting experiments on Tungsten carbide (WC) based composites in controlled atmosphere. The processing conditions were optimized and various properties were measured. The design of the system was then modified to enable it to process large commercial parts of WC/Co and in large quantities. Two high power (3-6 kW) microwave systems of 2.45 GHz were built for multi samples runs in a batch process. Once the process was optimized for best results, the technology was successfully transferred to our industrial partner, Dennis Tool Co. We helped them to built couple of prototype microwave sintering systems for carbide tool manufacturing. It was found that the microwave processed WC/Co tools are not only cost effective but also exhibited much better overall performance than the standard tools. The results of the field tests performed by Dennis Tool Co. showed remarkable advantage and improvement in their overall performance. For example: wear test shows an increase of 20-30%, corrosion test showed much higher resistance to the acid attack, erosion test exhibited about 15% better resistance than standard sinter-HIP parts. This proves the success of microwave technology for WC/Co based drilling tools. While we have successfully transferred the technology to our industrial partner Dennis Tool Co., they have signed an agreement with Valenite, a world leading WC producer of cutting and drilling tools and wear parts, to push aggressively the new microwave technology in to the marketplace.

Dinesh Agrawal; Rustum Roy

2000-11-01T23:59:59.000Z

284

Vaporization behavior of non-stoichiometric refractory carbide materials and direct observations of the vapor phase using laser diagnostics  

DOE Green Energy (OSTI)

Transition metal and actinide carbides, such as ZrC or NbC and UC or ThC, exhibit a wide range of stoichiometry, and therefore vaporize incongruently. At long times, steady state vaporization can be achieved where relative concentrations of atomic species on solid surface equals that in the gas phase. The surface composition under these steady state conditions is termed the congruently vaporizing composition, (CVC). Modeling the vaporization or corrosion behavior of this dynamic process is complex and requires an understanding of how the surface composition changes with time and a knowledge of CVC, which is both temperature and atmosphere dependent. This paper describes vaporization and corrosion behavior of non-stoichiometric refractory carbide materials and, as an example, describes a thermokinetic model that characterizes the vaporization behavior of the complex carbide U{sub x}Zr{sub 1-x}C{sub y} in hydrogen at 2500 to 3200 K. This model demonstrates that steady state corrosion of U{sub x}Zr{sub l-x}C{sub y} is rate limited by gaseous transport of Zr where partial pressure of Zr is determined by CVC. This paper also briefly describes efforts to image and characterize the vapor phase above the surface of ZrC in static and flowing gas environments using planar laser induced fluorescence. We have developed the method for monitoring and controlling the corrosion behavior of nuclear fuels in nuclear thermal rockets. However, the techniques described can be used, to image boundary layers, and could be used verifying corrosion models.

Butt, D.P.; Wantuck, P.J.; Rehse, S.J.; Wallace, T.C. Sr.

1993-09-01T23:59:59.000Z

285

Filamentation-induced third-harmonic generation in air via plasma-enhanced third-order susceptibility  

Science Conference Proceedings (OSTI)

We study, both experimentally and theoretically, the underlying physics of third-harmonic generation in air by a filamented infrared femtosecond laser pulse propagating through a thin plasma channel. It is shown that the recently observed more than two-order-of-magnitude increase of the efficiency of third-harmonic generation occurs due to the plasma-enhanced third-order susceptibility. An estimate of the effective value of this susceptibility is given.

Suntsov, S.; Abdollahpour, D.; Tzortzakis, S. [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, 71110, Heraklion (Greece); Papazoglou, D. G. [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, 71110, Heraklion (Greece); Materials Science and Technology Department, University of Crete, 71003, Heraklion (Greece)

2010-03-15T23:59:59.000Z

286

Summary of the radiological assessment of the fuel cycle for a thorium-uranium carbide-fueled fast breeder reactor  

Science Conference Proceedings (OSTI)

A large fraction of the potential fuel for nuclear power reactors employing fissionable materials exists as ores of thorium. In addition, certain characteristics of a fuel system based on breeding of the fissionable isotope {sup 233}U from thorium offer the possibility of a greater resistance to the diversion of fissionable material for the fabrication of nuclear weapons. This report consolidates into a single source the principal content of two previous reports which assess the radiological environmental impact of mining and milling of thorium ore and of the reprocessing and refabrication of spent FBR thorium-uranium carbide fuel.

Tennery, V.J.; Bomar, E.S.; Bond, W.D.; Meyer, H.R.; Morse, L.E.; Till, J.E.; Yalcintas, M.G.

1980-01-01T23:59:59.000Z

287

IMPULSIVE ACCELERATION OF CORONAL MASS EJECTIONS. II. RELATION TO SOFT X-RAY FLARES AND FILAMENT ERUPTIONS  

SciTech Connect

Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic field is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In {approx}60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than {+-}5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.

Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.; Temmer, M. [Kanzelhoehe Observatory-IGAM, Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Vrsnak, B. [Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, HR-10000 Zagreb (Croatia)

2012-08-10T23:59:59.000Z

288

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

Science Conference Proceedings (OSTI)

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

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

2006-06-01T23:59:59.000Z

289

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. I. Unusual History of an Eruptive Filament  

E-Print Network (OSTI)

This is the first of four companion papers, which analyze a complex eruptive event of 18 November 2003 in AR 10501 and the causes of the largest Solar Cycle 23 geomagnetic storm on 20 November 2003. Analysis of a complete data set, not considered before, reveals a chain of eruptions to which hard X-ray and microwave bursts responded. A filament in AR 10501 was not a passive part of a larger flux rope, as usually considered. The filament erupted and gave origin to a CME. The chain of events was as follows: i) an eruption at 07:29 accompanied by a not reported M1.2 class flare associated with the onset of a first southeastern CME1, which is not responsible for the superstorm; ii) a confined eruption at 07:41 (M3.2 flare) that destabilized the filament; iii) the filament acceleration (07:56); iv) the bifurcation of the eruptive filament that transformed into a large cloud; v) an M3.9 flare in AR 10501 associated to this transformation. The transformation of the filament could be due to its interaction with the m...

Grechnev, V V; Slemzin, V A; Chertok, I M; Filippov, B P; Rudenko, G V; Temmer, M

2013-01-01T23:59:59.000Z

290

On the control of filamentation of intense laser beams propagating in underdense plasma  

SciTech Connect

In indirect drive ICF ignition designs, the laser energy is delivered into the hohlraum through the laser entrance holes (LEH), which are sized as small as practicable to minimize X-ray radiation losses. On the other hand, deleterious laser plasma processes, such as filamentation and stimulated back-scatter, typically increase with laser intensity. Ideally, therefore, the laser spot shape should be a close fit to the LEH, with uniform (envelope) intensity in the spot and minimal energy at larger radii spilling onto the LEH material. This keeps the laser intensity as low as possible consistent with the area of the LEH aperture and the power requirements of the design. This can be achieved (at least for apertures significantly larger than the laser's aberrated focal spot) by the use of custom-designed phase plates. However, outfitting the 192 beam (National Ignition facility) NIF laser with multiple sets of phase plates optimized for a variety of different LEH aperture sizes is an expensive proposition. It is thus important to assess the impact on laser-plasma interaction processes of using phase plates with a smaller than optimum focal spot (or even no phase plates at all!) and then de-focusing the beam to expand it to fill the LEH and lower its intensity. We find significant effects from the lack of uniformity of the laser envelope out of the focal plane, from changes in the characteristic sizes of the laser speckle, and on the efficacy of additional polarization and/or SSD beam smoothing. We quantify these effects with analytic estimates and simulations using our laser plasma interaction code pF3D.

Williams, E A

2005-10-21T23:59:59.000Z

291

Analytical and experimental evaluation of joining silicon nitride to metal and silicon carbide to metal for advanced heat engine applications  

DOE Green Energy (OSTI)

This report summarizes the results of Phase I of Analytical and Experimental Evaluation of Joining Silicon Nitride to Metal and Silicon Carbide to Metal and Silicon Carbide to Metal for Advanced Heat Engine Applications. A general methodology was developed to optimize the joint geometry and material systems for 650 and 950{degree}C applications. Failure criteria were derived to predict the fracture of the braze and ceramic. Extensive finite element analyses (FEA), using ABAQUS code, were performed to examine various joint geometries and to evaluate the affect of different interlayers on the residual stress state. Also, material systems composed of coating materials, interlayers, and braze alloys were developed for the program based on the chemical stability and strength of the joints during processing and service. Finally, the FEA results were compared with experiments using an idealized strength relationship. The results showed that the measured strength of the joint reached 30--90% of the strength by predicted by FEA. Overall results demonstrated that FEA is an effective tool for designing the geometries of ceramic-metal joints and that joining by brazing is a relevant method for advanced heat engine applications. 33 refs., 54 figs., 36 tabs.

Kang, S.; Selverian, J.H.; Kim, H.; O'Niel, D.; Kim, K. (GTE Labs., Inc., Waltham, MA (USA))

1990-04-01T23:59:59.000Z

292

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

DOE Green Energy (OSTI)

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

293

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

DOE Green Energy (OSTI)

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, this is significantly higher than the device response to room temperature gas or that predicted from vacuum chamber studies. The enhanced catalytic activity of the platinum sensing film under energy plant operating conditions was investigated via AFM, x-ray diffraction, TEM and x-ray photoelectron spectroscopy. Our characterization indicated that exposure to high temperature gases significantly modifies the morphology of the Pt catalytic film and the Pt/SiO{sub 2} interfacial region, which we tentatively attribute to the enhanced hydrogen sensitivity of the sensing film. A model for the hydrogen/oxygen response of the SiC device under atmospheric conditions was developed. It is based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO{sub 2}-SiC interface. The optimum operating set point for the SiC sensor with respect to response time and long term reliability was determined to be close to mid-gap. Ultrahigh vacuum (UHV) techniques were used to investigate the effects of sulfur contamination on the Pt gate. Exposure to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20-600 times greater than the H2S level, rapidly coated the gate with a monolayer of sulfur. Although hydrogen exposure could not remove the adsorbed sulfur, oxygen was effective at removing sulfur with no evidence of irreversible changes in device behavior. The role of oxygen in the functioning of the SiC sensors was also investigated. All of the results are consistent with oxygen acting through its surface reactions with hydrogen, including the need for oxygen to reset the device to a fully hydrogen-depleted state and competition between hydrogen oxidation and hydrogen diffusion to metal/oxide interface sites. A strong sensor response to the unsaturated linear hydrocarbon propene (C{sub 3}H{sub 6}) was observed.

Ruby Ghosh; Reza Loloee; Roger Tobin

2008-09-30T23:59:59.000Z

294

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

295

KINEMATICS AND EXCITATION OF THE RAM PRESSURE STRIPPED IONIZED GAS FILAMENTS IN THE COMA CLUSTER OF GALAXIES  

SciTech Connect

We present the results of deep imaging and spectroscopic observations of very extended ionized gas (EIG) around four member galaxies of the Coma Cluster of galaxies: RB 199, IC 4040, GMP 2923, and GMP 3071. The EIGs were serendipitously found in an H{alpha} narrowband imaging survey of the central region of the Coma Cluster. The relative radial velocities of the EIGs with respect to the systemic velocities of the parent galaxies from which they emanate increase almost monotonically with the distance from the nucleus of the respective galaxies, reaching {approx} - 400 to - 800 km s{sup -1} at around 40-80 kpc from the galaxies. The one-sided morphologies and the velocity fields of the EIGs are consistent with the predictions of numerical simulations of ram pressure stripping. We found a very low velocity filament (v{sub rel} {approx} -1300 km s{sup -1}) at the southeastern edge of the disk of IC 4040. Some bright compact knots in the EIGs of RB 199 and IC 4040 exhibit blue continuum and strong H{alpha} emission. The equivalent widths of the H{alpha} emission exceed 200 A and are greater than 1000 Angstrom-Sign for some knots. The emission-line intensity ratios of the knots are basically consistent with those of sub-solar abundance H II regions. These facts indicate that intensive star formation occurs in the knots. Some filaments, including the low-velocity filament of the IC 4040 EIG, exhibit shock-like emission-line spectra, suggesting that shock heating plays an important role in ionization and excitation of the EIGs.

Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Yagi, Masafumi; Komiyama, Yutaka; Kashikawa, Nobunari [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Furusawa, Hisanori [Astronomical Data Center, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Hattori, Takashi [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'Ohoku Place, Hilo, HI 96720 (United States); Okamura, Sadanori, E-mail: yoshidam@hiroshima-u.ac.jp [Department of Astronomy, University of Tokyo, Tokyo 113-0033 (Japan)

2012-04-10T23:59:59.000Z

296

Insights into the mechanism of Rad51 recombinase from the structure and properties of a filament interface mutant  

Science Conference Proceedings (OSTI)

Rad51 protein promotes homologous recombination in eukaryotes. Recombination activities are activated by Rad51 filament assembly on ssDNA. Previous studies of yeast Rad51 showed that His352 occupies an important position at the filament interface, where it could relay signals between subunits and active sites. To investigate, we characterized yeast Rad51 H352A and H352Y mutants, and solved the structure of H352Y. H352A forms catalytically competent but salt-labile complexes on ssDNA. In contrast, H352Y forms salt-resistant complexes on ssDNA, but is defective in nucleotide exchange, RPA displacement and strand exchange with full-length DNA substrates. The 2.5 {angstrom} crystal structure of H352Y reveals a right-handed helical filament in a high-pitch (130 {angstrom}) conformation with P61 symmetry. The catalytic core and dimer interface regions of H352Y closely resemble those of DNA-bound Escherichia coli RecA protein. The H352Y mutation stabilizes Phe187 from the adjacent subunit in a position that interferes with the {gamma}-phosphate-binding site of the Walker A motif/P-loop, potentially explaining the limited catalysis observed. Comparison of Rad51 H352Y, RecA-DNA and related structures reveals that the presence of bound DNA correlates with the isomerization of a conserved cis peptide near Walker B to the trans configuration, which appears to prime the catalytic glutamate residue for ATP hydrolysis.

Chen, Jianhong; Villanueva, Nicolas; Rould, Mark A.; Morrical, Scott W. (Vermont)

2010-09-03T23:59:59.000Z

297

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

Science Conference Proceedings (OSTI)

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

298

Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique  

DOE Patents (OSTI)

A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

Molenbroek, Edith C. (Utrecht, NL); Mahan, Archie Harvin (Golden, CO); Gallagher, Alan C. (Louisville, CO)

2000-09-26T23:59:59.000Z

299

Structural Properties Studies of Zinc Oxide Thin Film Grown on Silicon Carbide by Means of X-ray Diffraction Technique  

Science Conference Proceedings (OSTI)

In this work, the structural properties of the zinc oxide (ZnO) thin film on silicon carbide (6H-SiC) grown by radio frequency sputtering technique are investigated thoroughly by means of X-ray diffraction (XRD) technique. Both conventional XRD phase analysis and rocking curve measurements are carried out in order to determine the crystalline structure and the crystalline quality of the ZnO sample. From the phase analysis, intense peaks correspond to ZnO(002), iC(006) and their multiple reflections, i.e. ZnO(004) and SiC(0012) are observed. This result suggests that the ZnO thin film is in wurzite structure. Through the simulation of XRD rocking curve of the ZnO(002) peak, the lattice mismatch of 5.49% is obtained.

Ching, C. G.; Ng, S. S.; Hassan, Z.; Hassan, H. Abu; Al-Hardan, N. H.; Abdullah, M. J. [Nano-optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Penang (Malaysia)

2011-03-30T23:59:59.000Z

300

Composition and method for brazing graphite to graphite  

DOE Patents (OSTI)

The present invention is directed to a brazing material for joining graphite structures that can be used at temperatures up to about 2800.degree. C. The brazing material formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600.degree. C. with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800.degree. C. so as to provide a brazed joint consisting essentially of hafnium carbide. This brazing temperature for hafnium carbide is considerably less than the eutectic temperature of hafnium carbide of about 3150.degree. C. The brazing composition also incorporates the thermosetting resin so that during the brazing operation the graphite structures may be temporarily bonded together by thermosetting the resin so that machining of the structures to final dimensions may be completed prior to the completion of the brazing operation. The resulting brazed joint is chemically and thermally compatible with the graphite structures joined thereby and also provides a joint of sufficient integrity so as to at least correspond with the strength and other properties of the graphite.

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

1984-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "filament hafnium carbide" from the National Library of EnergyBeta (NLEBeta).
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to obtain the most current and comprehensive results.


301

Cyclic fatigue and resistance-curve behavior of an in situ toughened silicon carbide with Al-B-C additions  

Science Conference Proceedings (OSTI)

The room-temperature crack-growth properties of an in situ toughened, monolithic silicon carbide are reported. Hot pressing was performed at 1900 C with 3 wt.% Al, 2 wt.% C and 0.6 wt.% B additions. Compared to a commercial SiC (Hexoloy SA), significant improvements in both the fracture toughness and cyclic fatigue-crack propagation resistance have been achieved through control of the {beta} to {alpha} transformation. Using fatigue-precracked, disk-shaped compact-tension specimens, marked rising resistance-curve behavior was measured over the first {approximately}600 {micro}m of crack extension, leading to a plateau fracture toughness of K{sub c} {approximately} 9.1 MPa{radical}m; this represents more than a threefold increase over the toughness of Hexoloy, where a K{sub c} value of 2.5 MPa{radical}m was measured with no evidence of a resistance curve. Cyclic fatigue-crack growth rates in the toughened SiC were found to be faster than those under sustained loads (static fatigue) at the same stress-intensity level. The cyclic fatigue-crack growth resistance was found to be far superior to that of Hexoloy. Whereas cracking in the commercial SiC became unstable when the maximum stress intensity K{sub max} exceeded {approximately}2 MPa{radical}m, thresholds for fatigue-crack growth in the in situ toughened material exceeded a K{sub max} of 7 MPa{radical}m. Such dramatic improvements in the crack-growth resistance of SiC are attributed to a microstructure consisting of a network of interlocking, plate-like predominantly {alpha}-phase grains, which combine to both bridge and deflect the crack. These results represent the first reported evidence of cyclic fatigue behavior in a monolithic silicon carbide and the first direct measurement of the resistance curve properties in this ceramic.

Gilbert, C.J.; Cao, J.J.; Moberlychan, W.J.; DeJonghe, L.C.; Ritchie, R.O. [Lawrence Berkeley Lab., CA (United States). Materials Science Div.]|[Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

1996-08-01T23:59:59.000Z

302

The Ecological Genomics of Fungi: Repeated Elements in Filamentous Fungi with a Focus on Wood-Decay Fungi  

Science Conference Proceedings (OSTI)

In the last decade, the genome of several dozen filamentous fungi have been sequenced. Interestingly, vast diversity in genome size was observed (Fig. 2.1) with 14-fold differences between the 9 Mb of the human pathogenic dandruff fungus (Malassezia globosa; Xu, Saunders, et al., 2007) and the 125 Mb of the ectomycorrhizal black truffle of P rigord (Tuber melanosporum; Martin, Kohler, et al., 2010). Recently, Raffaele and Kamoun (2012) highlighted that the genomes of several lineages of filamentous plant pathogens have been shaped by repeat-driven expansion. Indeed, repeated elements are ubiquitous in all prokaryote and eukaryote genomes; however, their frequencies can vary from just a minor percentage of the genome to more that 60 percent of the genome. Repeated elements can be classified in two major types: satellites DNA and transposable elements. In this chapter, the different types of repeated elements and how these elements can impact genome and gene repertoire will be described. Also, an intriguing link between the transposable elements richness and diversity and the ecological niche will be highlighted.

Murat, Claude [INRA, Nancy, France; Payen, Thibaut [INRA, Nancy, France; Petitpierre, Denis [INRA, Nancy, France; Labbe, Jessy L [ORNL

2013-01-01T23:59:59.000Z

303

A review of the efficacy of silicon carbide hot-gas filters in coal gasification and pressurized fluidized bed combustion environments  

SciTech Connect

Reviews of relevant literature and interviews with individuals cognizant of the state of the art in ceramic filters for hot-gas cleaning were conducted. Thermodynamic calculations of the stability of various ceramic phases were also made. Based on these calculations, reviews, and interviews, conclusions were reached regarding the use of silicon carbide-based ceramics at hot-gas filter media. Arguments are presented that provide the basis for the conclusion that high-purity silicon carbide is a viable material in the integrated coal gasification combined cycle (IGCC) and pressurized fluidized-bed combustion (PFBC) environments which were examined. Clay-bonded materials are, the authors concluded, suspect for these applications, their extensive use notwithstanding. Operations data reviewed focused primarily on clay-bonded filters, for which a great deal of experience exists. The authors used the clay-bonded filter experience as a point of reference for their review and analysis.

Judkins, R.R.; Stinton, D.P.; DeVan, J.H. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1996-07-01T23:59:59.000Z

304

In Situ Expression of Acidic and Thermophilic Carbohydrate Active Enzymes by Filamentous Fungi (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)  

Science Conference Proceedings (OSTI)

Annika Mosier, graduate student from Stanford University presents a talk titled "In Situ Expression of Acidic and Thermophilic Carbohydrate Active Enzymes by Filamentous Fungi" at the JGI User 7th Annual Genomics of Energy & Environment Meeting on March 22, 2012 in Walnut Creek, Calif

Mosier, Annika [Stanford University

2012-03-22T23:59:59.000Z

305

Development of a Commercial Process for the Production of Silicon Carbide Fibrils - Draft Phase II Final Report  

DOE Green Energy (OSTI)

The current work continues a project completed in 1999 by ReMaxCo Technologies in which a novel, microwave based, VLS Silicon Carbide Fibrils concept was verified. This project continues the process development of a pilot scale commercial reactor. Success will lead to sufficient quantities of fibrils to expand work by ORNL and others on heat exchanger tube development. A semi-continuous, microwave heated, vacuum reactor was designed, fabricated and tested in these experiments. Cylindrical aluminum oxide reaction boats are coated, on the inner surface, with a catalyst and placed into the reactor under a light vacuum. A series of reaction boats are then moved, one at a time, through the reactor. Each boat is first preheated with resistance heaters to 850 C to 900 C. Each reaction boat is then moved, in turn, to the microwave heated section. The catalyst is heated to the required temperature of 1200 C to 1300 C while a mixture of MTS (methyl trichlorosilane) and hydrogen are introduced into the annulus of the boat. The MTS is dissociated to allow the carbon and silicon components to be dissolved into the catalyst. The catalyst saturates and precipitates silicon carbide onto the surface of the reaction boat to grow the Fibrils. The reaction continues as long as the MTS is introduced into the reactor. The major obstacle that had to be overcome during this project was the performance of the reactor. The original design of the reactor focused the microwaves in such a manner that they missed the catalyst/Fibrils growth zone. The microwaves did react with the insulation and the reactor was heated by heating the insulation. Modifications were made to the reactor to focus the microwaves on the catalyst. SiC Fibrils were produced using both MTS and Starfire SP4000 as feed-gas precursors. Both precursors produced fibrils at temperatures of less than 1000 C. The new Starfire SP4000 produced fibrils as low as 800 C, without the use of hydrogen and without producing the hazardous hydrochloric acid. Experimental results and scanning electron microscopy of the Fibril products are presented. Future work to improve on these results is discussed.

Nixdorf, RD

2002-10-24T23:59:59.000Z

306

Composition and method for brazing graphite to graphite  

DOE Patents (OSTI)

A brazing material is described for joining graphite structures that can be used up to 2800/sup 0/C. The brazing material is formed of a paste-like composition of hafnium carbide and uranium oxide with a thermosetting resin. The uranium oxide is converted to uranium dicarbide during the brazing operation and then the hafnium carbide and uranium dicarbide form a liquid phase at a temperature about 2600/sup 0/C with the uranium diffusing and vaporizing from the joint area as the temperature is increased to about 2800/sup 0/C so as to provide a brazed joint consisting essentially of hafnium carbide. The resulting brazed joint is chemically and thermally compatible with the graphite structures.

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

1982-08-10T23:59:59.000Z

307

Short-lived fission product measurements from >0.1 MeV neutron-induced fission using boron carbide.  

Science Conference Proceedings (OSTI)

A boron carbide shield was designed, custom fabricated, and used to create a fast fission energy neutron spectrum. The fissionable isotopes 233, 235, 238U, 237Np, and 239Pu were separately placed inside of this shield and irradiated under pulsed conditions at the Washington State University 1 MW TRIGA reactor. A unique set of fission product gamma spectra were collected at short times (4 minutes to 1 week) post-fission. Gamma spectra were collected on single-crystal high purity germanium detectors and on Pacific Northwest National Laboratory's (PNNL's) Direct Simultaneous Measurement (DSM) system composed of HPGe detectors connected in coincidence. This work defines the experimental methods used to produce and collect the gamma data, and demonstrates the validity of the measurements. It is important to fully document this information so the data can be used with high confidence for the advancement of nuclear science and non-proliferation applications. The gamma spectra collected in these and other experiments will be made publicly available at https://spcollab.pnl.gov/sites/gammadata or via the link at http://rdnsgroup.pnl.gov. A revised version of this publication will be posted with the data to make the experimental details available to those using the data.

Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce D.; Friese, Judah I.; Kephart, Rosara F.; Kephart, Jeremy D.

2012-02-01T23:59:59.000Z

308

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

309

Mechanical behavior at 20 and 1200 C of Nicalon-silicon-carbide-fiber-reinforced alumina-matrix composites  

SciTech Connect

Tensile and fracture tests were conducted at 20 and 1,200 C on a ceramic-matrix composite that was composed of an alumina (Al{sub 2}O{sub 3}) matrix that was bidirectionally reinforced with 37 vol% silicon carbide (SiC) Nicalon fibers. The composite presented nonlinear behavior at both temperatures; however, the strength and toughness were significantly reduced at 1,200 C. In accordance with this behavior, matrix cracks were usually stopped or deflected at the fiber/matrix interface, and fiber pullout was observed on the fracture surfaces at 20 and 1,200 C. The interfacial sliding resistance at ambient and elevated temperatures was estimated from quantitative microscopy analyses of the saturation crack spacing in the matrix. The in situ fiber strength was determined both from the defect morphology on the fibers and from the size of the mirror region on the fiber fracture surfaces. It was shown that composite degradation at elevated temperature was due to the growth of defects on the fiber surface during high-temperature exposure.

Celemin, J.A.; Pastor, J.Y.; Llorca, J.; Elices, M. [Polytechnic Univ. of Madrid (Spain). Dept. of Materials Science

1997-10-01T23:59:59.000Z

310

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

DOE Green Energy (OSTI)

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

311

Product technology and market assessment for silicon carbide whisker reinforced alumina heat-exchanger tubes. Final report  

Science Conference Proceedings (OSTI)

This report describes a study designed to develop an assessment of key performance features, desirable technical specifications and market potential for silicon carbide whisker-reinforced alumina (henceforth SCWRA) tubes for heat exchanger applications in a number of industries. The results of the first stage of a Delphi study conducted in the US market are presented. The second phase of the study is in progress. The first stage results suggest that there is a small market for SCWRA tubes in heat exchanger applications. The market is expected to grow steadily during the 1990`s. With appropriate performance specifications and competitive pricing, growth should come from (a) new applications that permit recovery in cases that were previously infeasible and (b) selective, partial substitution and replacement of current ceramics and metal/ceramic composites in existing applications. We identify key performance factors and detailed specifications needed in six designated industries (primary metals, fabricated metals, chemicals, glass, utility and incinerators). Reliability, durability and low maintenance costs emerge as critical performance factors across these industries. The data show that although ceramics are recognized as having better properties, enhancing reliability and durability and thus improving maintenance cost performance is a key priority. Such improvements, reflected in the objectives for SCWRA tubes, should facilitate adoption in both new and existing applications. At this time, we are unable to assess market size directly. However, expert judgment provided indices tracking the projected market for heat exchanger tubes from 1990 to 2005.

Loutfy, R.O.; Withers, J.C. [Materials and Electrochemical Research Corp., Tucson, AZ (United States); Chakravarti, D. [Arizona Univ., Tucson, AZ (United States)

1993-10-01T23:59:59.000Z

312

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

E-Print Network (OSTI)

Pure gases such as methane, carbon dioxide and steam were used to make comparisons between Leiden and Berlin virial expansions for the calculation of the compressibility factor, fugacity coefficient and enthalpy residual. Results show that the Leiden expansion is better than the Berlin expansion with truncation after the second virial coefficient for both expansions, and also with truncation after the third virial coefficient for both expansions. Also, joining techniques to join silicon carbide to steel were studied. Brazing is the technique more used, and several active filler metals such as Ag-Cu-In-Ti, Ag-Cu-Ti, plus carbon fibers Ag-Cu-Hf and Niobium were used. This review shows that the strength of the joint is affected by the amount of active filler metal in the alloy, heating element and atmosphere, composition and surface of SiC, thickness of the joint, and time. In general, brazing temperature is limited by the melting point of the filler metals, which is generally below 1000 ?C. An alternative to overcome this problem in brazing is using a functionally graded material (FGM) that is formed with the native elements. This FGM has one end of almost 100% stainless steel, which is joined using very well known processes of joining metals. The other end of the FGM, which is almost 100% SiC, is joined using a reaction-forming method that produces an interlayer of SiC plus Si and supports temperatures as high as 1350 ?C.

Santana Rodriguez, Gabriel Enrique

2003-01-01T23:59:59.000Z

313

Materials characterization of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites. Part 1: Tensile and fatigue behavior  

Science Conference Proceedings (OSTI)

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. Fatigue life was found to be sensitive to fiber layup sequence. Increasing the test temperature from 24 C to 427 C decreased fatigue life. Interface debonding and matrix and fiber fracture were characteristic of tensile behavior regardless of test temperature. In the tensile fracture process, interface debonding between SiC and the graphite coating and between the graphite coating and the carbon core could occur. A greater amount of coating degradation at 427 C than at 24 C reduced the Ti/SiC interface bonding integrity, which resulted in lower tensile properties at 427 C. During tensile testing, a crack could initiate from the debonded Ti/SiC interface and extend to the debonded interface of the neighboring fiber. The crack tended to propagate through the matrix and the interface. Dimpled fracture was the prime mode of matrix fracture. Interface debonding, matrix cracking, and fiber bridging were identified as the prime modes of fatigue mechanisms. To a lesser extent, fiber fracture was observed during fatigue. However, fiber fracture was believed to occur near the final stage of fatigue failure. In fatigued specimens, facet-type fracture appearance was characteristic of matrix fracture morphology. Theoretical modeling of the fatigue behavior of Ti/SCS-6 composites is presented in Part 2 of this series of articles.

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); Chiang, K.T.; Loh, D.H. [Rockwell International Corp., Canoga Park, CA (United States). Rocketdyne Div.

1995-12-01T23:59:59.000Z

314

Fluoride-Salt-Cooled High-Temperature Reactor (FHR) with Silicon-Carbide-Matrix Coated-Particle Fuel  

Science Conference Proceedings (OSTI)

The FHR is a new reactor concept that uses coated-particle fuel and a low-pressure liquid-salt coolant. Its neutronics are similar to a high-temperature gas-cooled reactor (HTGR). The power density is 5 to 10 times higher because of the superior cooling properties of liquids versus gases. The leading candidate coolant salt is a mixture of {sup 7}LiF and BeF{sub 2} (FLiBe) possessing a boiling point above 1300 C and the figure of merit {rho}C{sub p} (volumetric heat capacity) for the salt slightly superior to water. Studies are underway to define a near-term base-line concept while understanding longer-term options. Near-term options use graphite-matrix coated-particle fuel where the graphite is both a structural component and the primary neutron moderator. It is the same basic fuel used in HTGRs. The fuel can take several geometric forms with a pebble bed being the leading contender. Recent work on silicon-carbide-matrix (SiCm) coated-particle fuel may create a second longer-term fuel option. SiCm coated-particle fuels are currently being investigated for use in light-water reactors. The replacement of the graphite matrix with a SiCm creates a new family of fuels. The first motivation behind the effort is to take advantage of the superior radiation resistance of SiC compared to graphite in order to provide a stable matrix for hosting coated fuel particles. The second motivation is a much more rugged fuel under accident, repository, and other conditions.

Forsberg, C. W. [Massachusetts Institute of Technology (MIT); Terrani, Kurt A [ORNL; Snead, Lance Lewis [ORNL; Katoh, Yutai [ORNL

2012-01-01T23:59:59.000Z

315

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

DOE Green Energy (OSTI)

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

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

1999-04-05T23:59:59.000Z

316

Complete genome sequence of the filamentous gliding predatory bacterium Herpetosiphon aurantiacus type strain (114-95T)  

Science Conference Proceedings (OSTI)

Herpetosiphon aurantiacus Holt and Lewin 1968 is the type species of the genus Herpetosiphon, which in turn is the type genus of the family Herpetosiphonaceae, type family of the order Herpe- tosiphonales in the phylum Chloroflexi. H. aurantiacus cells are organized in filaments which can rapidly glide. The species is of interest not only because of its rather isolated position in the tree of life, but also because Herpetosiphon ssp. were identified as predators capable of facultative pre- dation by a wolf pack strategy and of degrading the prey organisms by excreted hydrolytic en- zymes. The genome of H. aurantiacus strain 114-95T is the first completely sequenced genome of a member of the family Herpetosiphonaceae. The 6,346,587 bp long chromosome and the two 339,639 bp and 99,204 bp long plasmids with a total of 5,577 protein-coding and 77 RNA genes was sequenced as part of the DOE Joint Genome Institute Program DOEM 2005.

Kiss, Hajnalka [Los Alamos National Laboratory (LANL); Nett, Markus [Hans Knll Institute, Jena, Germany; Domin, Nicole [Hans Knll Institute, Jena, Germany; Martin, Karin [Hans Knll Institute, Jena, Germany; Maresca, Julia A. [Pennsylvania State University, University Park, PA; Copeland, A [U.S. Department of Energy, Joint Genome Institute; Lapidus, Alla L. [U.S. Department of Energy, Joint Genome Institute; Lucas, Susan [U.S. Department of Energy, Joint Genome Institute; Berry, Kerrie W. [United States Department of Energy Joint Genome Institute; Glavina Del Rio, Tijana [U.S. Department of Energy, Joint Genome Institute; Dalin, Eileen [U.S. Department of Energy, Joint Genome Institute; Tice, Hope [U.S. Department of Energy, Joint Genome Institute; Pitluck, Sam [U.S. Department of Energy, Joint Genome Institute; Richardson, P M [U.S. Department of Energy, Joint Genome Institute; Bruce, David [Los Alamos National Laboratory (LANL); Goodwin, Lynne A. [Los Alamos National Laboratory (LANL); Han, Cliff [Los Alamos National Laboratory (LANL); Detter, J. Chris [U.S. Department of Energy, Joint Genome Institute; Schmutz, Jeremy [Stanford University; Brettin, Thomas S [ORNL; Land, Miriam L [ORNL; Hauser, Loren John [ORNL; Kyrpides, Nikos C [U.S. Department of Energy, Joint Genome Institute; Ivanova, N [U.S. Department of Energy, Joint Genome Institute; Goker, Markus [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Woyke, Tanja [U.S. Department of Energy, Joint Genome Institute; Klenk, Hans-Peter [DSMZ - German Collection of Microorganisms and Cell Cultures GmbH, Braunschweig, Germany; Bryant, Donald A. [Pennsylvania State University, University Park, PA

2011-01-01T23:59:59.000Z

317

Electron Beam Melting and Recycling of Hafnium  

Science Conference Proceedings (OSTI)

... Boosted Suction (DDBS) System Doubles Pot Suction, Reduces Roof Emission ... Phase Change Materials in Thermal Energy Storage for Concentrating Solar...

318

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

SciTech Connect

ADEPT Project: Currently, charging the battery of an electric vehicle (EV) is a time-consuming process because chargers can only draw about as much power from the grid as a hair dryer. APEI is developing an EV charger that can draw as much power as a clothes dryer, which would drastically speed up charging time. APEI's charger uses silicon carbide (SiC)-based power transistors. These transistors control the electrical energy flowing through the charger's circuits more effectively and efficiently than traditional transistors made of straight silicon. The SiC-based transistors also require less cooling, enabling APEI to create EV chargers that are 10 times smaller than existing chargers.

None

2010-09-14T23:59:59.000Z

319

Conversion of light hydrocarbon gases to metal carbides for production of liquid fuels and chemicals. Quarterly technical progress report, January 1--March 31, 1995  

DOE Green Energy (OSTI)

The methane plasma stabilization problem was resolved with the reconfiguration of the DC power supply to give a higher open circuit voltage to enable operation of the arc at higher voltage levels and with the installation of a solenoid around the plasma reactor to magnetically rotate the are. Cathode tip erosion problems were encountered with the 1/4-inch graphite and tungsten tips which necessitated a redesign of the plasma reactor. The new plasma reactor consists of an enlarged 3/4-inch O.D. graphite tip to reduce current density and a 1-inch I.D. graphite anode. Products from MgO/CH{sub 4} scoping runs in the redesigned reactor under conditions of excess MgO gave strong indications that a breakthrough has finally been achieved i.e. that synthesis of magnesium carbides from MgO and methane in the arc discharge reactor has been demonstrated. Significant quantities of hydrocarbons, primarily C{sub 3}H{sub 4} and C{sub 2}H{sub 2}, were detected in the headspace above hydrolyzed solid samples by GC analysis. In one run, solids glowed upon exposure to the atmosphere, strongly suggesting carbide reaction with moisture in the air, exothermically forming acetylenes which ignited instantaneously in the presence of oxygen and elevated temperatures arising from localized heat-up of the specimens.

Diaz, A.F.; Modestino, A.J.; Pride, J.D.; Howard, J.B.; Tester, J.W.; Peters, W.A.

1995-05-01T23:59:59.000Z

320

Fine uniform filament superconductors  

DOE Patents (OSTI)

A multifilamentary superconductor composite having a high fill factor is formed from a plurality of stacked monofilament precursor elements, each of which includes a low density superconductor precursor monofilament. The precursor elements all have substantially the same dimensions and characteristics, and are stacked in a rectilinear configuration and consolidated to provide a multifilamentary precursor composite. The composite is thereafter thermomechanically processed to provide a superconductor composite in which each monofilament is less than about 50 microns thick.

Riley, Jr., Gilbert N. (Marlborough, MA); Li, Qi (Marlborough, MA); Roberts, Peter R. (Groton, MA); Antaya, Peter D. (Sutton, MA); Seuntjens, Jeffrey M. (Singapore, SG); Hancock, Steven (Worcester, MA); DeMoranville, Kenneth L. (Jefferson, MA); Christopherson, Craig J. (Worcester, MA); Garrant, Jennifer H. (Natick, MA); Craven, Christopher A. (Bedford, MA)

2002-01-01T23:59:59.000Z

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


321

Breakup of Liquid Filaments  

E-Print Network (OSTI)

fields of view: a Nikkor 18-55 mm for 1515 cm2, and a macro Tamron SP AF90 for 55 cm2. In drop-on-demand ink-jet printing, the speed of the jet is mainly controlled by the amplitude of the first volt- age peak, and its diameter by the duration...

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

2012-01-01T23:59:59.000Z

322

Journal of Undergraduate A Refereed Journal for Undergraduate Research in the Pure & Applied Sciences,  

E-Print Network (OSTI)

, page 65); 2) Scanning electron micro- scope image of hafnia coated poly-caprolactone (PCL) fibers under. C. Skaalure, S. C. Oppegard and D. T. Eddington Plasma Assisted Synthesis of a Molybdenum Carbide-emulsions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 P. A. Chando, S. S. Ray and A. L. Yarin Atomic Layer Deposition of Hafnium Oxide on Silicon

Illinois at Chicago, University of

323

Conversion of light hydrocarbon gases to metal carbides for production of liquid fuels and chemicals. Quarterly technical status report, October 1, 1994--December 31, 1994  

DOE Green Energy (OSTI)

Scoping runs with up to 0.125 cfm methane in 1 cfm (ambient temperature) of argon and 12g/min of MgO were performed in October using a graphite anode and tungsten cathode in the new plasma reactor. A GC analysis of the gas sample from the cooling chamber and of the head space gas above the hydrolyzed solid sample revealed the presence of C{sub 3}H{sub 4} and C{sub 2}H{sub 2}, which suggests the formation of magnesium carbide. However, a similar run performed with MgO feeding into a pure argon plasma gave similar results, indicating possible reaction of the graphite electrode with the MgO to form carbides and/or direct formation of C{sub 3}H{sub 4} and C{sub 2}H{sub 2} in the arc. A GC analysis of the gas sample taken from the cooling chamber from a run in an argon plasma without MgO feeding did no yield any C{sub 3}H{sub 4} and C{sub 2}H{sub 2}, suggesting that the MgO powder is hydrated and is a probable hydrogen source. Thus far, the main obstacle to performing a 100% methane/MgO scoping run is the instability of the methane plasma. Two approaches are being taken to address this issue: increasing the open circuit voltage of the power supply to permit operation of an arc at higher voltage levels and magnetically rotating the arc with a solenoid around the plasma reactor. The latter approach is currently being pursued.

Diaz, A.F.; Modestino, A.J.; Pride, J.D.; Howard, J.B.; Tester, J.W.; Peters, W.A.

1995-02-01T23:59:59.000Z

324

Conversion of light hydrocarbon gases to metal carbides for production of liquid fuels and chemicals. Quarterly technical status report, April 1--June 30, 1993  

SciTech Connect

Previous work at MIT indicates that essentially stoichiometric, rather than catalytic, reactions with alkaline earth metal oxides offer technical and economic promise as an innovative approach to upgrading natural gas to premium products such as liquid hydrocarbon fuels and chemicals. In this approach, methane would be reacted with relatively low cost and recyclable alkaline earth metal oxides, such as CaO and MgO, at high temperatures (>1500{degrees}C) to achieve very high (i.e. approaching 100%) gas conversions to H{sub 2}, CO and the corresponding alkaline earth metal carbides. These carbides exist stably in solid form at dry ambient conditions and show promise for energy storage and long distance transport. The overall objective of the proposed research is to develop new scientific and engineering knowledge bases for further assessment of the approach by performing laboratory-scale experiments and thermodynamic and thermochemical kinetics calculations. Work on this project will be performed according to two tasks. Under Task 1 (Industrial Chemistry), a laboratory-scale electric arc discharge plasma reactor is being constructed and will be used to assess the technical feasibility of producing Mg{sub 2}C{sub 3} from MgO and methane, and to identify the operating conditions of interest for the commercial production of Mg{sub 2}C{sub 3} and/or CaC{sub 2} from MgO and/or CaO and methane. Under Task 2 (Mechanistic Foundations), preliminary thermodynamic calculations were performed for the Ca-C-H-O and Mg-C-H-O systems using the Chemkin program. A scoping run with CaO in an electrical screen heater reactor under reduced methane pressure was also conducted. No appreciable quantity of acetylene was detected upon hydrolysis of the solid residue. This can be attributed to the very small quantity of methane at the very low pressure coupled with inadequate contacting of whatever methane was present with the CaO powder.

Diaz, A.F.; Modestino, A.J.; Howard, J.B.; Peters, W.A.

1993-08-01T23:59:59.000Z

325

Conversion of light hydrocarbon gases to metal carbides for production of liquid fuels and chemicals. Quarterly technical status report, January 1--March 31, 1993  

SciTech Connect

Work on this project will be performed according to two tasks: Task 1, Industrial Chemistry and Applied Kinetics of Light Hydrocarbon Gas Conversion to Metal Carbides H{sub 2} and CO. We are building a laboratory-scale electric are discharge reactor, in which to assess the technical feasibility of producing Mg{sub 2}C{sub 3}, H{sub 2}, and CO from methane and MgO. We will also do experimental runs with CaO as well as mixtures of CaO and MgO and measure conversions of methane, CaO and/or MgO, and yields of Mg{sub 2}C{sub 3}, and/or CaC{sub 2}, H{sub 2}, and CO to identify the operating conditions of interest for implementing these reactions on a commercial scale. Reaction conditions and parameters will be chosen based on the previous work at MIT with CaO and CH, and on results of thermodynamic and thermochemical kinetics calculations. Task 2: Mechanistic Foundations-For Convertings Light Hydrocarbon Gases to Metal Carbides-H{sub 2} and CO. We will evaluate the technical feasibility of carrying out methane reactions with CaO and MgO by thermal (e.g. 1500--2000{degrees}C) rather than under plasma conditions by performing experiments with the use of electrical screen heaters, heated tubular reactors, or other suitable apparatus. Extents and global rates of methane conversion, and yields as well as global production rates of CaC{sub 2}, Mg{sub 2}C{sub 3}, H{sub 2} and CO will be measured upon subjecting mixtures of methane and CaO and/or MgO to high temperatures and controlled residence times. We will conduct hypothesis-testing of possible mechanistic pathways with selected experiments and perform reaction modeling to better understand the underlying chemical and physical processes that could influence process scale-up possibilities.

Diaz, A.F.; Modestino, A.J.; Howard, J.B.; Peters, W.A.

1993-04-01T23:59:59.000Z

326

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

Science Conference Proceedings (OSTI)

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

327

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

DOE Green Energy (OSTI)

This report summarizes the results of Phase 2 of Analytical and Experimental Evaluation of Joining Silicon Nitride to Metal and Silicon Carbide to Metal for Advanced Heat Engine Applications. A general methodology was developed to optimize the joint geometry and material systems for 650{degrees}C applications. Failure criteria were derived to predict the fracture of the braze and ceramic. Extensive finite element analyses (FEA) were performed to examine various joint geometries and to evaluate the affect of different interlayers on the residual stress state. Also, material systems composed of coating materials, interlayers, and braze alloys were developed for the program based on the chemical stability and strength of the joints during processing, and service. The FEA results were compared with experiments using two methods: (1) an idealized strength relationship of the ceramic, and (2) a probabilistic analysis of the ceramic strength (NASA CARES). The results showed that the measured strength of the joint reached 30--80% of the strength predicted by FEA. Also, potential high-temperature braze alloys were developed and evaluated for the high-temperature application of ceramic-metal joints. 38 tabs, 29 figs, 20 refs.

Kang, S.; Selverian, J.H.; O`Neil, D.; Kim, H. [GTE Labs., Inc., Waltham, MA (US)] [GTE Labs., Inc., Waltham, MA (US); Kim, K. [Brown Univ., Providence, RI (US). Div. of Engineering] [Brown Univ., Providence, RI (US). Div. of Engineering

1993-05-01T23:59:59.000Z

328

Utility-Scale Silicon Carbide Power Transistors: 15 kV SiC IGBT Power Modules for Grid Scale Power Conversion  

SciTech Connect

ADEPT Project: Cree is developing silicon carbide (SiC) power transistors that are 50% more energy efficient than traditional transistors. Transistors act like a switch, controlling the electrical energy that flows through an electrical circuit. Most power transistors today use silicon semiconductors to conduct electricity. However, transistors with SiC semiconductors operate at much higher temperatures, as well as higher voltage and power levels than their silicon counterparts. SiC-based transistors are also smaller and require less cooling than those made with traditional silicon power technology. Cree's SiC transistors will enable electrical circuits to handle higher power levels more efficiently, and they will result in much smaller and lighter electrical devices and power converters. Cree, an established leader in SiC technology, has already released a commercially available SiC transistor that can operate at up to 1,200 volts. The company has also demonstrated a utility-scale SiC transistor that operates at up to 15,000 volts.

None

2010-09-01T23:59:59.000Z

329

A CHANDRA STUDY OF THE LARGE-SCALE SHOCK AND COOL FILAMENTS IN HYDRA A: EVIDENCE FOR SUBSTANTIAL GAS DREDGE-UP BY THE CENTRAL OUTBURST  

Science Conference Proceedings (OSTI)

We present the results of a Chandra study of the Hydra A galaxy cluster, where a powerful active galactic nucleus (AGN) outburst created a large-scale cocoon shock. We investigated possible azimuthal variations in shock strength and shape, finding indications for a weak shock with a Mach number in the range {approx}1.2-1.3. We measured the temperature change across the shock front. However, the detection of a temperature rise in the regions immediately inside of the front is complicated by the underlying temperature profile of the cluster atmosphere. We measured the global temperature profile of the cluster up to 700 kpc, which represents the farthest measurement obtained with Chandra for this cluster. A 'plateau' in the temperature profile in the range {approx}70-150 kpc indicates the presence of cool gas, which is likely the result of uplift of material by the AGN outburst. After masking the cool filaments visible in the hardness ratio map, the plateau disappears and the temperature profile recovers a typical shape with a peak around 190 kpc, just inside the shock front. However, it is unlikely that such a temperature feature is produced by the shock as it is consistent with the general shape of the temperature profiles observed for relaxed galaxy clusters. We studied the spectral properties of the cool filaments finding evidence that {approx}10{sup 11} M{sub sun} of low-entropy material has been dredged up by the rising lobes from the central 30 kpc to the observed current position of 75-150 kpc. The energy required to lift the cool gas is {approx}> 2.2 x 10{sup 60} erg, which is comparable to the work required to inflate the cavities and is {approx}25% of the total energy of the large-scale shock. Our results show that the AGN feedback in Hydra A is acting not only by directly heating the gas, but also by removing a substantial amount of potential fuel for the supermassive black hole.

Gitti, Myriam; Nulsen, Paul E. J.; David, Laurence P.; McNamara, Brian R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wise, Michael W. [ASTRON Netherlands Institute for Radio Astronomy, P.O. Box 2, 7990 AA Dwingeloo (Netherlands)

2011-05-01T23:59:59.000Z

330

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

DOE Green Energy (OSTI)

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

331

Evaluation of Neutron Irradiated Silicon Carbide and Silicon Carbide Composites  

SciTech Connect

The effects of fast neutron irradiation on SiC and SiC composites have been studied. The materials used were chemical vapor deposition (CVD) SiC and SiC/SiC composites reinforced with either Hi-Nicalon{trademark} Type-S, Hi-Nicalon{trademark} or Sylramic{trademark} fibers fabricated by chemical vapor infiltration. Statistically significant numbers of flexural samples were irradiated up to 4.6 x 10{sup 25} n/m{sup 2} (E>0.1 MeV) at 300, 500 and 800 C in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Dimensions and weights of the flexural bars were measured before and after the neutron irradiation. Mechanical properties were evaluated by four point flexural testing. Volume increase was seen for all bend bars following neutron irradiation. Magnitude of swelling depended on irradiation temperature and material, while it was nearly independent of irradiation fluence over the fluence range studied. Flexural strength of CVD SiC increased following irradiation depending on irradiation temperature. Over the temperature range studied, no significant degradation in mechanical properties was seen for composites fabricated with Hi-Nicalon{trademark} Type-S, while composites reinforced with Hi-Nicalon{trademark} or Sylramic fibers showed significant degradation. The effects of irradiation on the Weibull failure statistics are also presented suggesting a reduction in the Weibull modulus upon irradiation. The cause of this potential reduction is not known.

Newsome G, Snead L, Hinoki T, Katoh Y, Peters D

2007-03-26T23:59:59.000Z

332

The Breakup of Dense Filaments  

Science Conference Proceedings (OSTI)

The breakup of a long strip of dense fluid flowing over a sloping bottom is examined with the aid of a nonlinear two-layer analytical model. The inviscid strip is bounded by the sloping bottom from below and an interface (that intersects the ...

Doron Nof

1990-06-01T23:59:59.000Z

333

Silicon carbide/SRBSN composites  

Science Conference Proceedings (OSTI)

Ceramic matrix composites have been produced using unidirectionally aligned Textron SCS-6 fibers in a sintered reaction bonded silicon nitride (SRBSN) matrix. A tape casting technique was used to produce a prepreg sheet that could be cut and stacked to form a layup. Sintering aids were MgO, Al2O3, and Y2O3 either singly or in combination, final sintering being carried out under pressure at temperatures up to 1750 C. The three-point bend strength of the material varied between 448 and 513 MPa and showed no variation with oxidation time at 1000 C up to 25 hours. Interfacial shear strength measured by indentation was 4 MPa; some samples had a reaction layer at the interface and a shear strength of greater than MPa. Within sections 6 mm from exposed fiber ends, the interfacial carbon layers were partially removed, and the interfacial shear strength was reduced with increasing oxidation time. 4 refs.

Razzell, A.G.; Lewis, M.H.

1991-08-01T23:59:59.000Z

334

Nanostructured Carbide Derived Carbon (CDC)  

... can be grown at rates up to 100 micrometers per hour and is composed of graphite, diamond, amorphous carbon and carbon "nano-onions" ...

335

Fatigue Failure in Tungsten Carbide  

Science Conference Proceedings (OSTI)

Mercury porosimetry can be applied to determine the percent interconnected porosity. ... Failure Analysis of Duplex Stainless Steel Wet Flue Gas Desulfurization ... The Role of Corrosion and Oxidation in High Temperature Failures: Valuable...

336

PROCESS OF PREPARING URANIUM CARBIDE  

DOE Patents (OSTI)

A process of preparing uranium monocarbide is de scribed. Uranium metal is dissolved in cadmium, zinc, cadmium-- zinc, or magnesium-- zinc alloy and a small quantity of alkali metal is added. Addition of stoichiometric amounts of carbon at 500 to 820 deg C then precipitates uranium monocarbide. (AEC)

Miller, W.E.; Stethers, H.L.; Johnson, T.R.

1964-03-24T23:59:59.000Z

337

Molybdenum sulfide/carbide catalysts  

DOE Patents (OSTI)

The present invention provides methods of synthesizing molybdenum disulfide (MoS.sub.2) and carbon-containing molybdenum disulfide (MoS.sub.2-xC.sub.x) catalysts that exhibit improved catalytic activity for hydrotreating reactions involving hydrodesulfurization, hydrodenitrogenation, and hydrogenation. The present invention also concerns the resulting catalysts. Furthermore, the invention concerns the promotion of these catalysts with Co, Ni, Fe, and/or Ru sulfides to create catalysts with greater activity, for hydrotreating reactions, than conventional catalysts such as cobalt molybdate on alumina support.

Alonso, Gabriel (Chihuahua, MX); Chianelli, Russell R. (El Paso, TX); Fuentes, Sergio (Ensenada, MX); Torres, Brenda (El Paso, TX)

2007-05-29T23:59:59.000Z

338

The matching of a one-dimensional numerical simulation and experiment results for low viscosity Newtonian and non-Newtonian fluids during fast filament stretching and subsequent break-up  

E-Print Network (OSTI)

D modeling when com- pared with 2D modeling is a decrease in computing time of at least 2 orders of magnitude and this enables the lubrication model to effectively explore effects such as operating conditions and fluids properties [Hoeve et al. (2010... of the paper is as follows: in Sec. II, the mathematical formulation is detailed and the 1D constitutive equations derived. In addition, the fluids and the experi- mental apparatus are presented. The comparison of the model for fluid filament stretching...

Tembely, M.; Vadillo, D.; Mackley, M.R.; Soucemarianadin, A.

2012-01-23T23:59:59.000Z

339

Hafnium isotopes in Arctic Ocean water Bettina Zimmermann a  

E-Print Network (OSTI)

-GEOMAR, 24148 Kiel, Germany d Laboratory for Isotope Geology, Swedish Museum of Natural History, Box 50007, SEHafnium isotopes in Arctic Ocean water Bettina Zimmermann a , Don Porcelli b,*, Martin Frank c-104 05 Stockholm, Sweden e Department of Geology, Wayne State University, Detroit, MI 48202, USA f

Baskaran, Mark

340

Matrix Studies on Solvent Extraction of Zirconium and Hafnium from ...  

Science Conference Proceedings (OSTI)

Sorption of Se(IV) and Se(VI) Ions onto Biomass Ash ... Tellurium Supply Sensitivity to Growth of Non-Traditional Copper Extraction Techniques - Implications for...

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


341

Material characterization of the clay bonded silicon carbide candle filters and ash formations in the W-APF system after 500 hours of hot gas filtration at AEP. Appendix to Advanced Particle Filter: Technical progress report No. 11, January--March 1993  

SciTech Connect

(1) After 500 hours of operation in the pressurized fluidized-bed combustion gas environment, the fibrous outer membrane along the clay bonded silicon carbide Schumacher Dia Schumalith candles remained intact. The fibrous outer membrane did not permit penetration of fines through the filter wall. (2) An approximate 10-15% loss of material strength occurred within the intact candle clay bonded silicon carbide matrix after 500 hours of exposure to the PFBC gas environment. A relatively uniform strength change resulted within the intact candles throughout the vessel (i.e., top to bottom plenums), as well as within the various cluster ring positions (i.e., outer versus inner ring candle filters). A somewhat higher loss of material strength, i.e., 25% was detected in fractured candle segments removed from the W-APF ash hopper. (3) Sulfur which is present in the pressurized fluidized-bed combustion gas system induced phase changes along the surface of the binder which coats the silicon carbide grains in the Schumacher Dia Schumalith candle filter matrix.

Alvin, M.A.

1993-04-05T23:59:59.000Z

342

Filamentous Carbon Particles for Cleaning Oil Spills  

cleaning oil spills. Crude oil and other petroleum products can cause severe damage to the environment and wildlife when spilled into the water. Oil is not only transferred by supertanker, but also by underwater pipelines an kept in coastal ...

343

Rapid Filamentation Zones in Intense Tropical Cyclones  

Science Conference Proceedings (OSTI)

Intense tropical cyclones often possess relatively little convection around their cores. In radar composites, this surrounding region is usually echo-free or contains light stratiform precipitation. While subsidence is typically quite pronounced ...

Christopher M. Rozoff; Wayne H. Schubert; Brian D. McNoldy; James P. Kossin

2006-01-01T23:59:59.000Z

344

Material properties of actin filament bundles  

E-Print Network (OSTI)

Actin is an ubiquitous structural protein fundamental to such biological processes as cell motility and muscle contraction. Our model system is the acrosomal process of the Limulus sperm which extends a 60 tm long actin ...

Robertson, Alec, 1974-

2009-01-01T23:59:59.000Z

345

In-fiber semiconductor filament arrays  

E-Print Network (OSTI)

One-dimensional nanostructures with high aspect-ratios and nanometer cross-sectional dimensions have been the focus of recent studies in the persistent drive to miniaturize devices. Conventional bottom-up methods such as ...

Deng, Daosheng

2010-01-01T23:59:59.000Z

346

Process for making silver metal filaments  

DOE Patents (OSTI)

A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

Bamberger, Carlos E. (Oak Ridge, TN)

1997-01-01T23:59:59.000Z

347

Recent Developments in Cemented Carbides A Commercially ...  

Science Conference Proceedings (OSTI)

Lignocellulosic-Based Carbon Fibers from Biofuel Production Wastes Magnesium Sheets Produced by Extrusion Magnetite Formation Observed with TEM on...

348

Chemical Compatibility between Carbide Fuels and Cladding ...  

Science Conference Proceedings (OSTI)

Abstract Scope, The Gas-cooled Fast Reactor is a high temperature helium cooled reactor. ... A leak-tight metallic intermediate barrier (W-Re, Nb-Zr, Ta) is also...

349

Radiation Resistance of Nanocrystalline Silicon Carbide  

Science Conference Proceedings (OSTI)

Advances in Materials Research in the Yucca Mountain Project An Investigation of Annealing Treatments For Optimizing the As-Fabricated Microstructure of...

350

Kinetics of Nano Ti Carbides Precipitation  

Science Conference Proceedings (OSTI)

About this Abstract. Meeting, Materials Science & Technology 2011. Symposium, Steel Product Metallurgy and Applications. Presentation Title, Kinetics of Nano...

351

Nanoscale Engineering Of Radiation Tolerant Silicon Carbide  

Science Conference Proceedings (OSTI)

Radiation tolerance is determined by how effectively the microstructure can remove point defects produced by irradiation. Engineered nanocrystalline SiC with a high-density of stacking faults (SFs) has significantly enhanced recombination of interstitials and vacancies, leading to selfhealing of irradiation-induced defects. While single crystal SiC readily undergoes an irradiationinduced crystalline to amorphous transformation at room temperature, the nano-engineered SiC with a high-density of SFs exhibits more than an order of magnitude increase in radiation resistance. Molecular dynamics simulations of collision cascades show that the nano-layered SFs lead to enhanced mobility of interstitial Si atoms. The remarkable radiation resistance in the nano-engineered SiC is attributed to the high-density of SFs within nano-sized grain structures that significantly enhance point defect annihilation.

Zhang, Yanwen; Ishimaru, Manabu; Varga, Tamas; Oda, Takuji; Hardiman, Christopher M.; Xue, Haizhou; Katoh, Yutai; Shannon, Steven; Weber, William J.

2012-08-14T23:59:59.000Z

352

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

353

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

354

Spark Plasma Sintering of Silicon Carbide Ceramics  

Science Conference Proceedings (OSTI)

Advances in Current Activated Tip-Based Sintering (CATS) Advances in Synthesis and Densification of Heterogeneous Materials Application of Metal Injection...

355

Silicon Carbide Derived Carbons: Experiments and Modeling  

SciTech Connect

The main results of the computational modeling was: 1. Development of a new genealogical algorithm to generate vacancy clusters in diamond starting from monovacancies combined with energy criteria based on TBDFT energetics. The method revealed that for smaller vacancy clusters the energetically optimal shapes are compact but for larger sizes they tend to show graphitized regions. In fact smaller clusters of the size as small as 12 already show signatures of this ?¢????graphitization?¢????. The modeling gives firm basis for the ?¢????slit-pore?¢???? modeling of porous carbon materials and explains some of their properties. 2. We discovered small vacancy clusters and their physical characteristics that can be used to spectroscopically identify them. 3. We found low barrier pathways for vacancy migration in diamond-like materials by obtaining for the first time optimized reaction pathways.

Kertesz, Miklos [Georgetown University, Washington DC 20057

2011-02-28T23:59:59.000Z

356

Modelling Precipitation of Carbides in Martensitic Steels  

E-Print Network (OSTI)

-composition IG Intergranular fracture MVC Microvoid coalescence rupture MTDATA Metallurgical and Thermochemical Databank PC Pre-stressed concrete QC Quasi-cleavage fracture SSCC Sulfide stress corrosion cracking TEM Transmission electron microscope TMCP... in high tensile strength steel. 11 1.4 Hydrogen embrittlement 1.4.3 Fracture modes The fracture modes of hydrogen embrittlement include microvoid coalescence (MVC), quasi-cleavage fracture (QC) and intergranular fracture (IG) [48]. The QC mode...

Yamasaki, Shingo

357

Eight Two-Dimensional Transition Metal Carbides  

Science Conference Proceedings (OSTI)

... Films for TCO Applications Hybrid Aerogel/Nanorod Functional Materials for Energy and Sensing Applications Isotopically Engineered Silicon Nanowires.

358

ELECTROCHEMICAL MACHINING OF CARBIDES AND BORIDES  

E-Print Network (OSTI)

psig) Flow '1' 1 Ure /),V (volts) II ~ rate I I I hole }Iflarge capacitor (300,000 mFd at 50 Volts) across the outputof delivering 500 amps at 30 Volts maximum; the cutting

Dissaux, Bernard Antoine

2011-01-01T23:59:59.000Z

359

Electrochemical Hydrogen Insertion in Titanium Carbide  

Science Conference Proceedings (OSTI)

Author(s), Julien Nguyen, Nicolas Glandut, Cdric Jaoul, Pierre Lefort. On-Site Speaker (Planned), Julien Nguyen. Abstract Scope, It has been shown that...

360

Silicon carbide oxidation in high temperature steam  

E-Print Network (OSTI)

The commercial nuclear power industry is continually looking for ways to improve reactor productivity and efficiency and to increase reactor safety. A concern that is closely regulated by the Nuclear Regulatory Commission ...

Arnold, Ramsey Paul

2011-01-01T23:59:59.000Z

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


361

Alternative Catalyst Supports Based on Metal Carbides  

Science Conference Proceedings (OSTI)

Addressing Materials Processing Issues for USC Steam Turbines: Cast Versions of ... Co-Production of Pure Hydrogen and Electricity from Coal Syngas via the...

362

Boron Carbide Nanowires: Low Temperature Synthesis, Structural ...  

Science Conference Proceedings (OSTI)

... nanowires are synthesized by co-pyrolysis of diborane and methane in a low ... Energy Generation and Storage Applications of TiO2 Nanotubular Arrays by...

363

Harsh Environment Silicon Carbide Sensor Technology Geothermal...  

Open Energy Info (EERE)

and mechanical robustness of SiC sensors at temperatures as high as 600oC and in dry steam. State California Objectives In the proposed work, two types of physical sensors...

364

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

365

METHOD OF MAKING SPHERICAL ACTINIDE CARBIDE  

DOE Patents (OSTI)

This patent describes a method of making uniform, spherical, nonpyrophoric UC. UO/sub 2/ and carbon are mixed in stoichiometric proportions and passed through a plasma flame of inert gas at 10,000 to 13,000 deg C. (AEC)

White, G.D.; O' Rourke, D.C.

1962-12-25T23:59:59.000Z

366

Boron Carbide Nanowires: Synthesis and Characterization  

Science Conference Proceedings (OSTI)

The mechanical and thermal transport properties of as-synthesized nanowires were studied by a home-built manipulator within a scanning electron microscope,

367

© 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

368

Hybrid nuclear reactor grey rod to obtain required reactivity worth  

DOE Patents (OSTI)

Hybrid nuclear reactor grey rods are described, wherein geometric combinations of relatively weak neutron absorber materials such as stainless steel, zirconium or INCONEL, and relatively strong neutron absorber materials, such as hafnium, silver-indium cadmium and boron carbide, are used to obtain the reactivity worths required to reach zero boron change load follow. One embodiment includes a grey rod which has combinations of weak and strong neutron absorber pellets in a stainless steel cladding. The respective pellets can be of differing heights. A second embodiment includes a grey rod with a relatively thick stainless steel cladding receiving relatively strong neutron absorber pellets only. A third embodiment includes annular relatively weak netron absorber pellets with a smaller diameter pellet of relatively strong absorber material contained within the aperture of each relatively weak absorber pellet. The fourth embodiment includes pellets made of a homogeneous alloy of hafnium and a relatively weak absorber material, with the percentage of hafnium chosen to obtain the desired reactivity worth.

Miller, John V. (Munhall, PA); Carlson, William R. (Scott Township, Allegheny County, PA); Yarbrough, Michael B. (Hempfield Township, Westmoreland County, PA)

1991-01-01T23:59:59.000Z

369

Union Carbides Last 20 Years in Oak Ridge ? part 2  

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

Technical Division had a steadily growing team of technical specialists to work on a uranium enrichment idea that if successful could make the gaseous diffusion process...

370

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

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

cannot be handled directly because of radiation hazards. Complex equipment to accomplish remote handling was designed to dejacket fuel elements prior to chemical processing for...

371

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

372

A Silicon and Hafnium Modified Plasma Sprayed MCrAlY Coating ...  

Science Conference Proceedings (OSTI)

Advanced gas turbine engines operate with very high combustor exit temperatures to achieve maximum engine performance and efficiency. These increasingly.

373

Advanced materials for solid oxide fuel cells: Hafnium-Praseodymium-Indium Oxide System  

DOE Green Energy (OSTI)

The HfO/sub 2/-PrO/sub 1.83/-In/sub 2/O/sub 3/ system has been studied at the Pacific Northwest Laboratory to develop alternative, highly electrically conducting oxides as electrode and interconnection materials for solid oxide fuel cells. A coprecipitation process was developed for synthesizing single-phase, mixed oxide powders necessary to fabricate powders and dense oxides. A ternary phase diagram was developed, and the phases and structures were related to electrical transport properties. Two new phases, an orthorhombic PrInO/sub 3/ and a rhombohedral Hf/sub 2/In/sub 2/O/sub 7/ phase, were identified. The highest electronic conductivity is related to the presence of a bcc, In/sub 2/O/sub 3/ solid solution (ss) containing HfO/sub 2/ and PrO/sub 1.83/. Compositions containing more than 35 mol % of the In/sub 2/O/sub 3/ ss have electrical conductivities greater than 10/sup /minus/1/ (ohm-cm)/sup /minus/1/, and the two or three phase structures that contain this phase appear to exhibit mixed electronic-ionic conduction. The high electrical conductivities and structures similar to the Y/sub 2/O/sub 3/-stabilized ZrO/sub 2/(HfO/sub 2/) electrolyte give these oxides potential for use as cathodes in solid oxide fuel cells. 21 refs.

Bates, J.L.; Griffin, C.W.; Weber, W.J.

1988-06-01T23:59:59.000Z

374

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

Science Conference Proceedings (OSTI)

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

375

Supporting Information History-dependent depolymerization of actin filaments  

E-Print Network (OSTI)

a similar role as the parameters introduced by Jegou et al. in Ref [1], which are called vADP-Pi depol and vADP depol . As expected, the values obtained for these parameters (WT 1.5 and WD 7) are rather closeADP-Pi depol is an "effective depolymerization velocity". Since our model is also a two-state model, similar

Lacoste, David

376

Methane Decomposition: Production of Hydrogen and Carbon Filaments  

E-Print Network (OSTI)

) is an obvious source for hydrogen. Steam reforming of methane represents the current trend for hydrogen. The process required to eliminate CO from the hydrogen produced in the steam reformer is briefly described below. The steam reformer products containing B10% CO (depending on the feedstock and conditions

Goodman, Wayne

377

Dendritic Actin Filament Nucleation Causes Traveling Waves and Patches  

E-Print Network (OSTI)

The polymerization of actin via branching at a cell membrane containing nucleation-promoting factors is simulated using a stochastic-growth methodology. The polymerized-actin distribution displays three types of behavior: a) traveling waves, b) moving patches, and c) random fluctuations. Increasing actin concentration causes a transition from patches to waves. The waves and patches move by a treadmilling mechanism which does not require myosin II. The effects of downregulation of key proteins on actin wave behavior are evaluated.

Anders E. Carlsson

2010-05-28T23:59:59.000Z

378

Process for producing fine and ultrafine filament superconductor wire  

DOE Patents (OSTI)

A process for producing a superconductor wire made up of a large number of round monofilament rods is provided for, comprising assembling a multiplicity of round monofilaments inside each of a multiplicity of thin wall hexagonal tubes and then assembling a number of said thin wall hexagonal tubes within an extrusion can and subsequently consolidating, extruding and drawing the entire assembly down to the desired wire size.

Kanithi, Hem C. (15 Briar Ct., Chesire, CT 06410)

1992-01-01T23:59:59.000Z

379

Smoke sheets for graph-structured vortex filaments  

Science Conference Proceedings (OSTI)

Smoke is one of the core phenomena which fluid simulation techniques in computer graphics have attempted to capture. It is both well understood mathematically and important in lending realism to computer generated effects. In an attempt to overcome the ...

Alfred Barnat; Nancy S. Pollard

2012-07-01T23:59:59.000Z

380

Enzymatic Degradation of Cellulose by the Filamentous Fungus Neurospora crassa  

E-Print Network (OSTI)

Industry: The Technical Feasibility of a Billion-Ton Annual Supply, Department of Energy,Supply for a Bioenergy and Bioproducts Industry, Department of Energy,

Phillips, Christopher Michael

2011-01-01T23:59:59.000Z

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


381

Filamentation instability of lower hybrid waves in a plasma  

SciTech Connect

It is shown that a strong lower hybrid wave is modulationally unstable to perturbations propagating along its own wave vector. The instability relies critically on the finite thermal corrections to the lower hybrid dispersion relation. (auth)

Kaw, P. K.

1976-02-01T23:59:59.000Z

382

Fibrous ceramic monoliths made from multi-phase ceramic filaments  

DOE Patents (OSTI)

A method for producing composite ceramic material is provided wherein a core ceramic structure is produced and simultaneously enveloped with a sleeve of similar material.

Goretta, Kenneth C. (Downers Grove, IL); Singh, Dileep (Naperville, IL); Polzin, Bryant J. (Mundelein, IL); Cruse, Terry (Lisle, IL); Picciolo, John J. (Lockport, IL)

2008-11-18T23:59:59.000Z

383

Enzymatic Degradation of Cellulose by the Filamentous Fungus Neurospora crassa  

E-Print Network (OSTI)

U.S. Billion-Ton Update: Biomass Supply for a Bioenergy andBiomass as feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply,supply. One alternative lies in the use of non-edible plant biomass

Phillips, Christopher Michael

2011-01-01T23:59:59.000Z

384

Process for producing fine and ultrafine filament superconductor wire  

DOE Patents (OSTI)

A process for producing a superconductor wire made up of a large number of round monofilament rods is provided for, comprising assembling a multiplicity of round monofilaments inside each of a multiplicity of thin wall hexagonal tubes and then assembling a number of said thin wall hexagonal tubes within an extrusion can and subsequently consolidating, extruding and drawing the entire assembly down to the desired wire size. 8 figs.

Kanithi, H.C.

1992-02-18T23:59:59.000Z

385

Challenges in Applying Diamond Coatings to Carbide Twist Drills  

Science Conference Proceedings (OSTI)

Despite of the attractive advantage of applying diamond coating to drills, ... Investigation of a Hybrid Cutting Tool Design for Shearing Operations of Sheet Metals.

386

024- Reactive Sintering and Mechanical Property of Boron Carbide ...  

Science Conference Proceedings (OSTI)

125- Influence of Gas Flow Rate Ratio on the Structural Properties of a-SiC:H Prepared by ... 145- The Synergy of XRD and XRF in a Shale and Slate Analysis.

387

104- Carbide Change and Recrystallization Behavior of Inconel 617 ...  

Science Conference Proceedings (OSTI)

... structural materials for nuclear reactors and high-temperature gas-cooled reactors. .... 145- The Synergy of XRD and XRF in a Shale and Slate Analysis.

388

The Precipitation of Primary Carbides in Alloy 718  

Science Conference Proceedings (OSTI)

F.H.Froes and T. Khan, publ.Trans Tech Publications, USA, 1991, .... Q. 8. 5 100 e. PE. 2. 50. 0. -. Plaln i+erdendrttic. -. Total interdendrltlc. -. Ploln lntradedMlc.

389

Microstructure Development of Nickel Matrix/Carbide Composites  

Science Conference Proceedings (OSTI)

Characterization of Concentrate, Pellet and DRI Samples for Trace Elements Characterization of Dust Generated in the BOF Converter Characterization of...

390

Future High Voltage Silicon Carbide Power Devices Future ...  

Science Conference Proceedings (OSTI)

... PFC) in Switch Mode Power Supplies (SMPS) Anti-Parallel rectifier in Motor Control Boost Converter and Inverter Section for solar conversion ...

2013-04-20T23:59:59.000Z

391

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

392

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

393

Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics  

DOE Patents (OSTI)

The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

Becher, Paul F. (Oak Ridge, TN); Tiegs, Terry N. (Lenoir City, TN)

1987-01-01T23:59:59.000Z

394

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

395

Extreme Environment Silicon Carbide Hybrid Temperature & Pressure Optical Sensors  

SciTech Connect

This final report contains the main results from a 3-year program to further investigate the merits of SiC-based hybrid sensor designs for extreme environment measurements in gas turbines. The study is divided in three parts. Part 1 studies the material properties of SiC such as temporal response, refractive index change with temperature, and material thermal response reversibility. Sensor data from a combustion rig-test using this SiC sensor technology is analyzed and a robust distributed sensor network design is proposed. Part 2 of the study focuses on introducing redundancy in the sensor signal processing to provide improved temperature measurement robustness. In this regard, two distinct measurement methods emerge. A first method uses laser wavelength sensitivity of the SiC refractive index behavior and a second method that engages the Black-Body (BB) radiation of the SiC package. Part 3 of the program investigates a new way to measure pressure via a distance measurement technique that applies to hot objects including corrosive fluids.

Nabeel Riza

2010-09-01T23:59:59.000Z

396

Evaluation of the Thermophysical Properties of Silicon Carbide ...  

Science Conference Proceedings (OSTI)

Quality and Process Performance of Rotary Kilns and Shaft Calciners Real Time Temperature Distribution during Sealing Process and Room Temperature Air...

397

Nano-Scale Carbide Characterization in a Tempered Martensitic ...  

Science Conference Proceedings (OSTI)

... in a Tempered Martensitic 9Cr Steel Used for Ultrasupercritical Steam Power Plants ... Nanoparticle Catalysts for Hydrogen Production from Methanol and Methane ... Term Aging on Creep Properties of HP Alloy Hydrogen Reformer Tubes.

398

B15: Microwave Sintering of Carbide and Oxide Nanomaterials  

Science Conference Proceedings (OSTI)

B7: Synthesis and Electrical Properties of K2NiF4-Type (Ca2-xLnx)MnO4 (Ln=Nd and Sm) B8: Monitoring Oxygen Diffusion in Gd-Doped Ceria by Null...

399

Development of Alternate Materials to Cemented Carbides without ...  

Science Conference Proceedings (OSTI)

Advances in Current Activated Tip-Based Sintering (CATS) Advances in Synthesis and Densification of Heterogeneous Materials Application of Metal Injection...

400

Silicon Carbide Nanostructures for Micro-Supercapacitor Applications  

Science Conference Proceedings (OSTI)

3D Nanostructured Bicontinuous Electrodes: Path to Ultra-High Power and Energy ... High Energy Density Lithium Capacitors Using Carbon-Carbon Electrodes.

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


401

Grain Boundary delta-phase Morphologies, Carbides and Notch ...  

Science Conference Proceedings (OSTI)

penetrates through the grains while, due to the coarser grains, this does not occur in the problem material as ..... 9 of eight edition of Metals Handbook). ... Development, were necessary for the rapidly growing understanding of the fundamental.

402

Effects of Proton Irradiation on Zirconium Carbide with Different ...  

Science Conference Proceedings (OSTI)

About this Abstract. Meeting, Materials Science & Technology 2012. Symposium, Materials Development for Nuclear Applications and Extreme Environments.

403

Carbides and Their Influence on Notched Low Cycle Fatigue ...  

Science Conference Proceedings (OSTI)

Gas turbine disks are typically produced by 'hot-die' forging of billet ... The disk represented a forging shape for a large gas turbine engine with outer and inner...

404

High Voltage Silicon Carbide NIST Workshop May 2012  

Science Conference Proceedings (OSTI)

... Page 3. Solid-State Power Substation (SSPS) ... Duration of test: 2 hours Load: 3000 A Inlet water 25C ... radar, - TRL6 testing in Q4 2012 ...

2012-07-02T23:59:59.000Z

405

021- Polyimide-Tantalum Bromide Synthesis of Tantalum Carbide  

Science Conference Proceedings (OSTI)

125- Influence of Gas Flow Rate Ratio on the Structural Properties of a-SiC:H Prepared by ... 145- The Synergy of XRD and XRF in a Shale and Slate Analysis.

406

Plasma Erosion Resistance of High Purity Silicon Carbide under ...  

Science Conference Proceedings (OSTI)

About this Abstract. Meeting, Materials Science & Technology 2013. Symposium, Advanced Materials for Harsh Environments. Presentation Title, Plasma...

407

METHOD FOR ELECTRO-NICKEL PLATING WOLFRAM CARBIDE  

DOE Patents (OSTI)

A WC body can be electroplated with Ni after anodic etching in Na/sub 4/ P/sub 2/O/sub 7/ solution (200 g/l) with a Pb cathode. A current density of 2 amp/in./sup 2/ for 10 min is sufficient. This allows Ni to be electrodeposited in an adherent coating which is weldable. (T.R.H.)

Slatin, H.L.

1959-05-01T23:59:59.000Z

408

Low-temperature Synthesis of Silicon Carbide Porous Ceramics ...  

Science Conference Proceedings (OSTI)

Synthesis and Characterization of Plasma Polymerized Thin Films Deposited from Benzene and Hexamethyldisiloxane Using (PECVD) Method Synthesis and...

409

Evaluation of vanadium carbide for mitigating fuel cladding chemical ...  

Science Conference Proceedings (OSTI)

... Materials and Fuels for the Current and Advanced Nuclear Reactors III ... L38: A Theoretical Model of Corrosion Rate Distribution in Liquid LBE Flow Loop at...

410

Evaluation of Silicon Carbide Joining for Nuclear and Fusion ...  

Science Conference Proceedings (OSTI)

In the recent collaborative project among the U.S. Fusion Materials Program, ... Cold Spray Technology: A Potential Approach to Address Materials Aging Issues ...

411

Strength and Corrosion Resistance of Silicon Carbide to Silicon ...  

Science Conference Proceedings (OSTI)

Abstract Scope, Ceramic heat exchange systems and other ceramic arrays depend on the ... Ceramic heat exchangers are increasingly important for use as high...

412

High temperature Hexoloy{trademark} SX silicon carbide. Final report  

SciTech Connect

HEXOLOY{reg_sign} SX-SiC, fabricated with Y and Al containing compounds as sintering aids, has been shown to possess significantly improved strength and toughness over HEXOLOY{reg_sign}SA-SiC. This study was undertaken to establish and benchmark the complete mechanical property database of a first generation material, followed by a process optimization task to further improve the properties. Mechanical characterization on the first generation material indicated that silicon-rich pools, presumably formed as a reaction product during sintering, controlled the strength from room temperature to 1,232 C. At 1,370 C in air, the material was failing due to a glass-phase formation at the surface. This glass-phase formation was attributed to the reaction of yttrium aluminates, which exist as a second phase in the material, with the ambient. This process was determined to be a time-dependent one that leads to slow crack growth. Fatigue experiments clearly indicated that the slow crack growth driven by the reaction occurred only at temperatures >1,300 C, above the melting point of the glass phase. Process optimization tasks conducted included the selection of the best SiC powder source, studies on mixing/milling conditions for SiC powder with the sintering aids, and a designed experiment involving a range of sintering and post-treatment conditions. The optimization study conducted on the densification variables indicated that lower sintering temperatures and higher post-treatment pressures reduce the Si-rich pool formation, thereby improving the room-temperature strength. In addition, it was also determined that furnacing configuration and atmosphere were critical in controlling the Si-rich formation.

Srinivasan, G.V.; Lau, S.K.; Storm, R.S. [Carborundum Co., Niagara Falls, NY (United States)

1994-09-01T23:59:59.000Z

413

The Effect of Carbide Morphologies on Elevated Temperature ...  

Science Conference Proceedings (OSTI)

temperature control. Fatigue conditions were as follows: Load control. T = 850oC. ?? = 690 MPa ..... Instrumentation Center (MAIC) at the University of Florida for.

414

Grain Size Dependence of Radiation Response in Silicon Carbide  

Science Conference Proceedings (OSTI)

CASL: The Consortium for Advanced Simulation of Light Water Reactors: A U.S. ... Strategies for Studying High Dose Irradiation Effects in Reactor Components.

415

Aero-Thermal Performance Testing of Silicon Carbide Flexible TPS ...  

Science Conference Proceedings (OSTI)

... and gas-phase measurements including infrared pyrometry, cold-wall heat flux, total pressure, and ... A Review of Metallic Systems Used in Offshore, Sour Environments: The Effect of ... High-temperature Foam-reinforced Thermal Insulation.

416

Processing of Tungsten Carbide Reinforced Ceramic and Metal ...  

Science Conference Proceedings (OSTI)

Symposium, J. Materials and Processes for Enhanced Performance ... Separation and Recovery Process of Rare Metals from Oil Desulfurization Spent Catalyst.

417

B38: Reactive Sintering of Tungsten Carbide with Stainless Steel ...  

Science Conference Proceedings (OSTI)

A18: Effect of Local Alendronate Delivery on In Vivo Osteogenesis From PCL ... A7: On-the-fly System Design for High Precision/Ultra Fast/Wide Area Fabrication .... C19: Dissolution Behavior of Cu Under Bump Metallization in Ball Grid Array ... High Volume and Fast Turnaround Automated Inline TEM Sample Preparation.

418

NUCLEOSYNTHETIC TUNGSTEN ISOTOPE ANOMALIES IN ACID LEACHATES OF THE MURCHISON CHONDRITE: IMPLICATIONS FOR HAFNIUM-TUNGSTEN CHRONOMETRY  

Science Conference Proceedings (OSTI)

Progressive dissolution of the Murchison carbonaceous chondrite with acids of increasing strengths reveals large internal W isotope variations that reflect a heterogeneous distribution of s- and r-process W isotopes among the components of primitive chondrites. At least two distinct carriers of nucleosynthetic W isotope anomalies must be present, which were produced in different nucleosynthetic environments. The co-variation of {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W in the leachates follows a linear trend that is consistent with a mixing line between terrestrial W and a presumed s-process-enriched component. The composition of the s-enriched component agrees reasonably well with that predicted by the stellar model of s-process nucleosynthesis. The co-variation of {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W in the leachates provides a means for correcting the measured {sup 182}W/{sup 184}W and {sup 182}W/{sup 183}W of Ca-Al-rich inclusions (CAI) for nucleosynthetic anomalies using the isotopic variations in {sup 183}W/{sup 184}W. This new correction procedure is different from that used previously, and results in a downward shift of the initial {epsilon}{sup 182}W of CAI to -3.51 {+-} 0.10 (where {epsilon}{sup 182}W is the variation in 0.01% of the {sup 182}W/{sup 183}W ratio relative to Earth's mantle). This revision leads to Hf-W model ages of core formation in iron meteorite parent bodies that are {approx}2 Myr younger than previously calculated. The revised Hf-W model ages are consistent with CAI being the oldest solids formed in the solar system, and indicate that core formation in some planetesimals occurred within {approx}2 Myr of the beginning of the solar system.

Burkhardt, Christoph; Wieler, Rainer [Institute of Geochemistry and Petrology, Clausiusstrasse 25, ETH Zurich, CH-8092 Zurich (Switzerland); Kleine, Thorsten [Institut fuer Planetologie, Westfaelische Wilhelms-Universitaet Muenster, Wilhelm-Klemm-Strasse 10, D-48149 Muenster (Germany); Dauphas, Nicolas, E-mail: burkhardt@erdw.ethz.ch [Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States)

2012-07-01T23:59:59.000Z

419

Method for locating metallic nitride inclusions in metallic alloy ingots  

DOE Patents (OSTI)

A method of determining the location and history of metallic nitride and/or oxynitride inclusions in metallic melts. The method includes the steps of labeling metallic nitride and/or oxynitride inclusions by making a coreduced metallic-hafnium sponge from a mixture of hafnium chloride and the chloride of a metal, reducing the mixed chlorides with magnesium, nitriding the hafnium-labeled metallic-hafnium sponge, and seeding the sponge to be melted with hafnium-labeled nitride inclusions. The ingots are neutron activated and the hafnium is located by radiometric means. Hafnium possesses exactly the proper metallurgical and radiochemical properties for this use.

White, Jack C. (Albany, OR); Traut, Davis E. (Corvallis, OR); Oden, Laurance L. (Albany, OR); Schmitt, Roman A. (Corvallis, OR)

1992-01-01T23:59:59.000Z

420

Report on the Fracture Analysis of HfB{sub 2}-SiC and ZrB{sub 2}-SiC Composites  

DOE Green Energy (OSTI)

Hafnium diboride-silicon carbide (HS) and zirconium diboride-silicon carbide (ZS) composites are potential materials for high temperature, thermal shock applications such as for components on re-entry vehicles. In order to establish material constants necessary for evaluation of in situ fracture, bars fractured in four-point flexure were examined using fractographic principles. The fracture toughness was determined from measurements of the critical crack sizes and the strength values and the crack branching constants were established to use in forensic fractography for future in-flight tests. The fracture toughnesses range from about 13 MPam{sup 1/2} at room temperature to about 6 MPam{sup 1/2} at 1400 C for ZrB{sub 2}-Sic composites and from about 13 MPam{sup 1/2} at room temperature to about 4 MPam{sup 1/2} at 1400 C for HfB{sub 2}-SiC composites. Thus, the toughnesses of either the HS or ZS composites have the potential for use in thermal shock applications. Processing and manufacturing defects limited the strength of the test bars. However, examination of the microstructure on the fracture surfaces shows that the processing of these composites can be improved. There is potential for high toughness composites with high strength to be used in thermal shock conditions if the processing and handling are controlled.

MECHOLSKY, JR. JOHN J.

2001-09-01T23:59:59.000Z

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


421

It's Elemental - The Element Lutetium  

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

(Hafnium) Hafnium The Element Lutetium Click for Isotope Data 71 Lu Lutetium 174.9668 Atomic Number: 71 Atomic Weight: 174.9668 Melting Point: 1936 K (1663C or 3025F)...

422

Alloy Grades  

Science Conference Proceedings (OSTI)

...properties similar to those of zirconium, its nuclear properties are markedly different. Hafnium is a neutron absorber, but zirconium is

423

Formulation and method for preparing gels comprising hydrous ...  

Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient ... Building Energy ... Solar Thermal;

424

Molecular Dynamics Simulation of the alpha-Helix to beta-Sheet Transition in Coiled Protein Filaments: Evidence for a Critical Filament Length Scale  

E-Print Network (OSTI)

The alpha-helix to beta-sheet transition (?-? transition) is a universal deformation mechanism in alpha-helix rich protein materials such as wool, hair, hoof, and cellular proteins. Through a combination of molecular and ...

Buehler, Markus J.

425

Analytical and experimental evaluation of joining silicon carbide to silicon carbide and silicon nitride to silicon nitride for heat engine applications  

DOE Green Energy (OSTI)

Techniques were developed to produce reliable ceramic-ceramic joins and analytical models were developed to predict the mechanical performance of the joins at room and elevated temperatures. Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} (Norton NCX-5100) and {beta}-Sic (Norton NCX-4500) were joined to themselves in the green state prior to final densification. The joins and controls were chemically and mechanically characterized at room and elevated temperatures to prepare the data banks for analytical modeling. Analytical models combining finite element and probabilistic software were developed that are capable of predicting the reliability of the joined components under fast fracture and creep.

Foley, M.R.; Rossi, G.A.; Sundberg, G.J.; Wade, J.A.; Wu, F.J. (Norton Co., Northboro, MA (United States). Advanced Ceramics Div.)

1992-04-01T23:59:59.000Z

426

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

DOE Green Energy (OSTI)

Techniques were developed to produce reliable ceramic-ceramic joins and analytical models were developed to predict the mechanical performance of the joins at room and elevated temperatures. Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} (Norton NCX-5100) and {beta}-Sic (Norton NCX-4500) were joined to themselves in the green state prior to final densification. The joins and controls were chemically and mechanically characterized at room and elevated temperatures to prepare the data banks for analytical modeling. Analytical models combining finite element and probabilistic software were developed that are capable of predicting the reliability of the joined components under fast fracture and creep.

Foley, M.R.; Rossi, G.A.; Sundberg, G.J.; Wade, J.A.; Wu, F.J. [Norton Co., Northboro, MA (United States). Advanced Ceramics Div.

1992-04-01T23:59:59.000Z

427

Estimate of dielectric density using spectroscopic ellipsometry  

Science Conference Proceedings (OSTI)

The optical dielectric functions for hafnium oxide and hafnium silicate films were extracted from spectroscopic ellipsometry measurements and the density then calculated using a previously proposed method. The values obtained were then compared to those ... Keywords: Density, Gadolinium oxide, Hafnium silicate, Medium energy ion scattering, Spectroscopic ellipsometry, X-ray reflectometry

W. Davey; O. Buiu; M. Werner; I. Z. Mitrovic; S. Hall; P. Chalker

2009-07-01T23:59:59.000Z

428

doi:10.1016/j.gca.2004.03.009 New constraints on the sources and behavior of neodymium and hafnium in seawater from  

E-Print Network (OSTI)

University, 61 Route 9W, Palisades, NY 10964, USA 2 Institute for Isotope Geology and Mineral Resources, ETH Sec. 2, Nankang, Taipei 115, Taiwan, ROC 4 U.S. Geological Survey, 345 Middlefield Road, MS-999, Menlo seawater measurements of Hf isotopes and the limited number of Hf isotope time-series obtained from

429

Lifetime embrittlement of reactor core materials  

DOE Green Energy (OSTI)

Over a core lifetime, the reactor materials Zircaloy-2, Zircaloy-4, and hafnium may become embrittled due to the absorption of corrosion- generated hydrogen and to neutron irradiation damage. Results are presented on the effects of fast fluence on the fracture toughness of wrought Zircaloy-2, Zircaloy-4, and hafnium; Zircaloy-4 to hafnium butt welds; and hydrogen precharged beta treated and weld metal Zircaloy-4 for fluences up to a maximum of approximately 150 x 10{sup 24} n/M{sup 2} (> 1 Mev). While Zircaloy-4 did not exhibit a decrement in K{sub IC} due to irradiation, hafnium and butt welds between hafnium and Zircaloy-4 are susceptible to embrittlement with irradiation. The embrittlement can be attributed to irradiation strengthening, which promotes cleavage fracture in hafnium and hafnium-Zircaloy welds, and, in part, to the lower chemical potential of hydrogen in Zircaloy-4 compared to hafnium, which causes hydrogen, over time, to drift from the hafnium end toward the Zircaloy-4 end and to precipitate at the interface between the weld and base-metal interface. Neutron radiation apparently affects the fracture toughness of Zircaloy-2, Zircaloy-4, and hafnium in different ways. Possible explanations for these differences are suggested. It was found that Zircaloy-4 is preferred over Zircaloy-2 in hafnium-to- Zircaloy butt-weld applications due to its absence of a radiation- induced reduction in K{sub IC} plus its lower hydrogen absorption characteristics compared with Zircaloy-2.

Kreyns, P.H..; Bourgeois, W.F.; Charpentier, P.L.; Kammenzind, B.F.; Franklin, D.G. [Bettis Atomic Power Lab., West Mifflin, PA (United States); White, C.J. [Knolls Atomic Power Lab., Schenectady, NY (United States)

1994-08-01T23:59:59.000Z

430

Filamentation Instability of Interacting Current Sheets in Striped Relativistic Winds: The Origin of Low Sigma?  

E-Print Network (OSTI)

I outline a mechanism, akin to Weibel instabilities of interpenetrating beams, in which the neighboring current sheets in a striped wind from an oblique rotator interact through a two stream-like mechanism (a Weibel instability in flatland), to create an anomalous resistivity that heats the sheets and causes the magnetic field to diffusively annihilate in the wind upstream of the termination shock. The heating has consequences for observable unpulsed emission from pulsars.

Jonathan Arons

2007-10-28T23:59:59.000Z

431

THE INFLUENCE OF THE MASS RATIO ON THE ACCELERATION OF PARTICLES BY FILAMENTATION INSTABILITIES  

SciTech Connect

Almost all sources of high-energy particles and photons are associated with jet phenomena. Prominent sources of such highly relativistic outflows are pulsar winds, active galactic nuclei (AGNs), and gamma-ray bursts. The current understanding of these jets assumes diluted plasmas which are best described as kinetic phenomena. In this kinetic description, particle acceleration to ultrarelativistic speeds can occur in completely unmagnetized and neutral plasmas through insetting effects of instabilities. Even though the morphology and nature of particle spectra are understood to a certain extent, the composition of the jets is not known yet. While Poynting-flux-dominated jets (e.g., occurring in pulsar winds) are certainly composed of electron-positron plasmas, the understanding of the governing physics in AGN jets is mostly unclear. In this paper, we investigate how the constituting elements of an electron-positron-proton plasma behave differently under the variation of the fundamental mass ratio m{sub p} /m{sub e}. We initially studied unmagnetized counterstreaming plasmas using fully relativistic three-dimensional particle-in-cell simulations to investigate the influence of the mass ratio on particle acceleration and magnetic field generation in electron-positron-proton plasmas. We covered a range of mass ratios m{sub p}/m{sub e} between 1 and 100 with a particle number composition of n{sub p}{sup +}/ n{sub e}{sup +} of 1 in one stream, therefore called the pair-proton stream. Protons are injected in the other one, therefore from now on called the proton stream, whereas electrons are present in both to guarantee charge neutrality in the simulation box. We find that with increasing proton mass the instability takes longer to develop and for mass ratios >20 the particles seem to be accelerated in two phases which can be accounted for by the individual instabilities of the different species. This means that for high mass ratios the coupling between electrons/positrons and the heavier protons, which occurs in low mass ratios, disappears.

Burkart, Thomas; Elbracht, Oliver; Ganse, Urs; Spanier, Felix, E-mail: fspanier@astro.uni-wuerzburg.d [Lehrstuhl fuer Astronomie, Universitaet Wuerzburg, Am Hubland, D-97074 Wuerzburg (Germany)

2010-09-10T23:59:59.000Z

432

The ecology of chemical defence in a filamentous marine red alga.  

E-Print Network (OSTI)

??I investigated the ecological functions of halogenated secondary metabolites from the red alga Asparagopsis armata, their localisation in specialised cells and also their cost of (more)

Paul, Nicholas Andrew

2006-01-01T23:59:59.000Z

433

Incorporating stochastic influences in assembly models: application to intermediate filament polymerisation.  

E-Print Network (OSTI)

??The focus of this thesis is the inclusion of stochasticity into mathematical models of assembly with particular interest to the in vitro polymerisation of intermediate (more)

Craig, Morgan

2011-01-01T23:59:59.000Z

434

Method and apparatus for deregistering multi-filament tow and product thereof  

DOE Patents (OSTI)

A method and apparatus for deregistering drawn crimped nylon multifilament tow includes the steps of stretching the tow under constant controlled tension at a temperature below the glass transition temperature of the nylon. The apparatus includes means for sensing the tension of the tow between the feed and draw sections of a stretching device and producing a signal representative of the tension sensed and a controller for changing the speed of the draw section actuated by said signal.

Lukhard, Craig R. (Newark, DE); Potter, Jerry F. (Seaford, DE); Todd, Maurice C. (Chadds Ford, PA)

1995-01-01T23:59:59.000Z

435

Type B plutonium transport package development that uses metallic filaments and composite materials  

Science Conference Proceedings (OSTI)

A new package was developed for transporting Pu and U quantities that are currently carried in DOT-6M packages. It uses double containment with threaded closures and elastomeric seals. A composite overpack of metallic wire mesh and ceramic or quartz cloth insulation is provided for protection in accidents. Two prototypes were subjected to dynamic crush tests. A thermal computer model was developed and benchmarked by test results to predict package behavior in fires. The material performed isotropically in a global fashion. A Type B Pu transport package can be developed for DOE Pu shipments for less than $5000 if manufactured in quantity. 5 figs, 6 refs. (DLC)

Pierce, J.D.; Moya, J.L.; McClure, J.D.; Hohnstreiter, G.F. (Sandia National Labs., Albuquerque, NM (United States)); Golliher, K.G. (USDOE Albuquerque Operations Office, NM (United States))

1991-01-01T23:59:59.000Z

436

Stability of spiral wave vortex filaments with phase twists Keeyeol Nam,* Edward Ott,  

E-Print Network (OSTI)

. Guzdar, and Michael Gabbay Institute for Plasma Research, University of Maryland, College Park, Maryland

Rubloff, Gary W.

437

Effects of p-Cresol on photosynthetic and respiration rates of a filamentous green alga (spirogyra)  

Science Conference Proceedings (OSTI)

The effects of spilled phenols and cresols from coal gasification plants on the green alga SPIROYRA was investigated in experimental streams built by the US EPA near Monticello, Minnesota. P-Cresol at low concentrations inhibited photosynthesis and increased algal respiration rates. (JMT)

Stout, J. (Michigan State Univ., East Lansing); Kilham, S.S.

1983-01-01T23:59:59.000Z

438

Using a model filamentous fungus to unravel mechanisms of lignocellulose deconstruction  

E-Print Network (OSTI)

and Glass Biotechnology for Biofuels 2013, 6:6 http://Somerville C: Cellulosic biofuels. Annu Rev Plant Biol 2009,plants and enzymes for biofuels production. Science 2007,

Znameroski, Elizabeth A; Glass, N Louise

2013-01-01T23:59:59.000Z

439

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

E-Print Network (OSTI)

these problems typically requires coupling fluid dynam- ics and structural mechanics and solving the two of a stationary bluff body may harness the kinetic energy from the vortices generated by the body [47 in which the stress exerted by the structure on the fluid is spread onto the collocated grid points near

Liao, James C.

440

Dynamics of bead formation, filament thinning and breakup in weakly viscoelastic jets  

E-Print Network (OSTI)

The spatiotemporal evolution of a viscoelastic jet depends on the relative magnitude of capillary, viscous, inertial and elastic stresses. The interplay of capillary and elastic stresses leads to the formation of very thin ...

Ardekani, Arezoo

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


441

DEVELOPMENT of CEMENT BASED CROSS-PLY LAMINATES by FILAMENT WINDING TECHNIQUE  

E-Print Network (OSTI)

of the device to be embedded...........................................53 3.2.2 Preparation and layup.1.1 Actuation, sensing, and dynamic measurements.......................106 4.1.2 Mathematical model of the plant multiplication of a nx2n matrix by a 2nx1 state vector, resulting in NC operations: 22 #12;Control Plant

Mobasher, Barzin

442

R-curve response of silicon carbide whisker-reinforced alumina: Microstructural influence  

SciTech Connect

Rising fracture resistance with crack extension (R-curve response) can lead to improvements in the mechanical reliability of ceramics. To understand how microstructures influence the R-curve behavior, direct observations of crack interactions with microstructural features were conducted on SiC whisker-reinforced alumina. The contribution of the dominant toughening mechanisms to the R-curve behavior of these composites is discussed using experimental and theoretical studies.

Sun, E.Y.; Hsueh, C.H.; Becher, P.F.

1995-12-31T23:59:59.000Z

443

163- Quantitative Analysis of Carbide Evolution Behaviours for 2.25 ...  

Science Conference Proceedings (OSTI)

125- Influence of Gas Flow Rate Ratio on the Structural Properties of a-SiC:H Prepared by ... 145- The Synergy of XRD and XRF in a Shale and Slate Analysis.

444

J. A. Lane OAK RIDGE NATIONAL LABORATORY OPERATED BY UNION CARBIDE...  

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

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Oil and Natural Gas 2 4 Consensus Forecast of U.S. Energy Supply. and Demand to the Year...

445

Ion Distribution And Electronic Stopping Power For Au ions In Silicon Carbide  

SciTech Connect

Accurate knowledge of ion distribution and electronic stopping power for heavy ions in light targets is highly desired due to the large errors in prediction by the widely used Stopping and Range of Ions in Matter (SRIM) code. In this study, Rutherford backscattering spectrometry (RBS)and secondary ion mass spectrometry (SIMS) are used as complementary techniques to determine the distribution of Au ions in SiC with energie sfrom 700 keV to 15 MeV. In addition, asingle ion technique with an improved data analysis procedure is applied to measure the electronic stopping power for Au ions in SiC with energies up to ~70 keV/nucleon. Large overestimation of the electronic stopping power is found by SRIM prediction in the low energy regime up to ~50 keV/nucleon. The stopping power data and the ion ranges are crosschecked with each other and a good agreement is achieved.

Jin, Ke; Zhang, Yanwen; Xue, Haizhou; Zhu, Zihua; Weber, William J.

2013-07-15T23:59:59.000Z

446

Load partitioning in honycomb-like silicon carbide aluminum alloy composites.  

DOE Green Energy (OSTI)

A 50/50 vol.% Al/SiC composite was made via melt infiltration of an aluminum alloy into a porous beech wood-derived SiC preform. The honeycomb-like composite microstructure consisted of an interconnected SiC phase surrounding discrete Al 'fibers' aligned in the growth direction of the beech wood. High energy synchrotron X-ray diffraction was used to measure the volume averaged lattice strains in both the SiC and Al phases during in situ compressive loading up to an applied stress of -530MPa. Load transfer from the Al to the SiC was observed, and the Al yielded at an applied stress of above -213MPa. The elastic behavior of the composite was modeled with both an isostrain rule of mixtures calculation and variational bounds for the effective elastic modulus. Furthermore, calculations of the von Mises effective stress of the SiC and Al phases showed that the wood-derived SiC was a more effective reinforcement than either SiC particle- or whisker-reinforced composites.

Wikes, T. E.; Harder, B. J.; Almer, J. D.; Faber, K. T.; Northwestern Univ.

2009-01-01T23:59:59.000Z

447

Silicon carbide whisker reinforced ceramic 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 1,600 to 1,950 C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness which represents as much as a two-fold increase over that of the matrix material.

Wei, G.C.

1989-01-24T23:59:59.000Z

448

Chemical Vapor Deposition of Silicon Carbide Epitaxial Films and their Characterization  

DOE Green Energy (OSTI)

A chemical vapor deposition (CVD) system was designed and fabricated in our laboratory and SiC homo-epitaxial layers were grown in the CVD process using silicon tetrachloride and propane precursors with hydrogen as a carrier gas. The temperature field was generated using numerical modeling. Gas flow rates, temperature field, and the gradients are found to influence the growth rates of the epitaxial layers. Growth rates were found to increase as the temperature increased at high carrier gas flow rate, while at lower carrier gas flow rate, growth rates were observed to decrease as the temperature increased. Based on the equilibrium model, 'thermodynamically controlled growth' accounts for the growth rate reduction. The grown epitaxial layers were characterized using various techniques. Reduction in the threading screw dislocation (SD) density in the epilayers was observed. Suitable models were developed for explaining the reduction in the SD density as well as the conversion of basal plane dislocations (BPDs) into threading edge dislocations (TEDs).

Dhanaraj,G.; Chen, Y.; Dudley, M.; Cai, D.; Zhang, H.

2007-01-01T23:59:59.000Z

449

Silicon carbide whisker reinforced ceramic 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 disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

Wei, George C. (Oak Ridge, TN)

1993-01-01T23:59:59.000Z

450

Optically-initiated silicon carbide high voltage switch with contoured-profile electrode interfaces  

DOE Patents (OSTI)

An improved photoconductive switch having a SiC or other wide band gap substrate material with opposing contoured profile cavities which have a contoured profile selected from one of Rogowski, Bruce, Chang, Harrison, and Ernst profiles, and two electrodes with matching contoured-profile convex interface surfaces.

Sullivan, James S.; Hawkins, Steven A.

2012-09-04T23:59:59.000Z

451

Silicon carbide whisker reinforced ceramic 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.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

Wei, George C. (Oak Ridge, TN)

1985-01-01T23:59:59.000Z

452

Silicon carbide whisker reinforced ceramic 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 disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MP.am.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

Wei, George C. (Oak Ridge, TN)

1989-01-01T23:59:59.000Z

453

Silicon Carbide Composite Fabrication and Mechanical and Thermal Performance for Nuclear Reactor Applications  

Science Conference Proceedings (OSTI)

Materials / Proceedings of the Fifteenth International Conference on Emerging Nuclear Energy Systems

H. E. Khalifa; C. P. Deck; K. C. Chen; C. A. Back

454

Quantitative X-ray microanalysis of submicron carbide formation in chromium (III) oxide rich scale  

SciTech Connect

This paper discusses the chemical microanalysis techniques adapted to identify the precipitates that form on the surface of, or within, the oxide scale of a Fe-22Cr ferritic steel during exposure to a carbon-monoxide rich environment at 750C for 800 hours. Examination of oxidized test coupons revealed the presence of a fiber like structure at the surface, shown in figure 1. Other studies have reported that these structures are carbon precipitates.

Collins, W.K.; Ziomek-Moroz, M.; Holcomb, G.R.; Danielson, P.; Hunt, A.H

2007-08-01T23:59:59.000Z

455

Effect of Neutron Irradiation on Tensile Properties of Unidirectional Silicon Carbide Composites  

SciTech Connect

Tensile properties of uni-directionally reinforced Hi-Nicalon EType S SiC fiber, chemically vapor-infiltrated (CVI) SiC-matrix composites, with either pyrolytic carbon (PyC) or multilayered PyC/SiC interphase, were characterized following neutron irradiations to the maximum fluence of 7.7x1025 n/m2 at 380 and 800 C. The stress - strain behavior of the multilayered interphase composites remained unmodified after irradiation. The PyC interphase composite increased in ultimate tensile stress and strain to failure following neutron irradiation, whereas the proportional limit stress exhibited a slight decrease. Potential mechanisms for these changes include accommodation of misfit stress through irradiation creep, reduced interfacial friction, and differential swelling among individual composite constituents.

Katoh, Yutai [ORNL; Nozawa, Takashi [ORNL; Snead, Lance Lewis [ORNL; Hinoki, Tatsuya [ORNL

2007-01-01T23:59:59.000Z

456

Prism-coupled surface wave accelerator based on silicon carbide Burton Neuner III,1  

E-Print Network (OSTI)

University Station C1500, Austin, Texas 78712, USA 2 LMI, UMR-CNRS 5615, Universite´ Claude Bernard Lyon 1.-Q. Lee, R. Noble, V. Rawat, and J. Spencer, Phys. Rev. ST Accel. Beams 13, 121301 (2010). [10] A. Mizrahi (1999). [20] C. E. Weitzel, J. W. Palmour, C. H. Carter Jr., K. Moore, K. K. Nordquist, S. Allen, C

Shvets, Gennady

457