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Sample records for ternary carbide fueled

  1. ENTIRELY AQUEOUS SOLUTION-GEL ROUTE FOR THE PREPARATION OF ZIRCONIUM CARBIDE, HAFNIUM CARBIDE AND THEIR TERNARY CARBIDE POWDERS

    Directory of Open Access Journals (Sweden)

    Zhang Changrui

    2016-07-01

    Full Text Available An entirely aqueous solution-gel route has been developed for the synthesis of zirconium carbide, hafnium carbide and their ternary carbide powders. Zirconium oxychloride (ZrOCl₂.8H₂O, malic acid (MA and ethylene glycol (EG were dissolved in water to form the aqueous zirconium carbide precursor. Afterwards, this aqueous precursor was gelled and transformed into zirconium carbide at a relatively low temperature (1200 °C for achieving an intimate mixing of the intermediate products. Hafnium and the ternary carbide powders were also synthesized via the same aqueous route. All the zirconium, hafnium and ternary carbide powders exhibited a particle size of ∼100 nm.

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

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    Dr. Ronald Baney

    2008-12-15

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

  3. Mechanically activated synthesis of nanocrystalline ternary carbide Fe{sub 3}Mo{sub 3}C

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    Zakeri, M. [Materials Science Department, Islamic Azad University (Saveh branch), Saveh (Iran, Islamic Republic of)], E-mail: M_zakeri@iau-saveh.ac.ir; Rahimipour, M.R. [Ceramic Department, Materials and Energy Research Center, Tehran (Iran, Islamic Republic of); Khanmohammadian, A. [Materials Science Department, Islamic Azad University (Saveh branch), Saveh (Iran, Islamic Republic of)

    2008-09-25

    In this investigation, Fe{sub 3}Mo{sub 3}C ternary carbide was synthesized from the elemental powders of 3Mo/3Fe/C by mechanical milling and subsequent heat treatment. Structural and morphological evolutions of powders were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed that no phase transformation occurs during milling. A nanostructure Mo (Fe) solid solution obtained after 30 h of milling. With increasing milling time to 70 h no change takes place except grain size reduction to 9 nm and strain enhancement to 0.86%. Milled powders have spheroid shape and very narrow size distribution about 2 {mu}m at the end of milling. Fe{sub 3}Mo{sub 3}C was synthesized during annealing of 70 h milled sample at 700 deg. C. Undesired phases of MoOC and Fe{sub 2}C form at 1100 deg. C. No transformation takes place during annealing of 10 h milled sample at 700 deg. C. Mean grain size and strain get to 69 nm and 0.23% respectively with annealing of 70 h milled sample at 1100 deg. C.

  4. Theoretical study of physical properties and oxygen incorporation effect in nanolaminated ternary carbides 211-MAX phases

    KAUST Repository

    Kanoun, Mohammed

    2012-01-01

    In this chapter, we employ ab initio approaches to review some important physical properties of nanolaminated ternary carbides MAX phases. We fi rstly use an all electron full-potential linearized augmented plane-wave method within the generalized gradient approximation and the density functional theory approaches, to explore the existence of a steric effect on the M site in these compounds. The elastic properties are also reported in order to assess the mechanical stability. The substitution of oxygen for carbon in Ti 2 SnC M n +1 AX n, forming Ti 2 SnC 1- x O x, is examined next, where we simulated the effect of oxygen incorporation on mechanical and electronic properties using projector augmented wave method. We show that oxygen has interesting effects on both of elastic and electronic properties, that the bulk modulus decreases when oxygen concentration increases. The bonding in Ti 2 SnC 1- x O x has a tendency to a covalent-ionic nature with the presence of metallic character. © 2012 Woodhead Publishing Limited.

  5. Development and Evaluation of Mixed Uranium-Refractory Carbide/Refractory Carbide Cer-Cer Fuels Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this proposal a new carbide-based fuel is introduced with outstanding potential to eliminate the loss of uranium, minimizes the loss of uranium, and retains...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-08-11

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

  7. Elastic and electronic properties of antiperovskite-type Pd- and Pt-based ternary carbides from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bannikov, V.V.; Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru

    2013-11-15

    Highlights: • 23 Pd- and Pt-based antiperovskite-type ternary carbides are probed from first principles. • Structural, elastic, electronic properties and inter-atomic bonding are evaluated. • A rich variety of mechanical and electronic properties was predicted. -- Abstract: By means of first-principles calculations, the structural, elastic, and electronic properties of a broad series of proposed Pd- and Pt-based antiperovskite-type ternary carbides AC(Pd,Pt){sub 3}, where A are Zn, Ca, Al, Ga, In, Ge, Hg, Sn, Cd, Pb, Ag, Sc, Ti, Y, Nb, Mo, and Ta, have been studied, and their stability, elastic constants, bulk, shear, and Young’s moduli, compressibility, Pugh’s indicator, Poisson’s ratio, indexes of elastic anisotropy, as well as electronic properties have been evaluated. We found that these materials should demonstrate a rich variety of mechanical and electronic properties depending on the type of A sublattices, which can include (unlike the majority of known 3d-metal-based antiperovskites) both sp elements and d atoms. We believe that the presented results will be useful for future synthesis of these phases, as well as for expanding our knowledge of this interesting group of antiperovskite-type materials.

  8. Carbide-based fuel system for undersea vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Burke, A. Alan; Carreiro, Louis G.; Greene, Eric S. [Naval Undersea Warfare Center, Division Newport (NUWCDIVNPT), 1176 Howell Street, Building 1302/2, Newport, RI 02841 (United States)

    2008-01-21

    In underwater applications such as unmanned undersea vehicle (UUV) propulsion, mass and volume constraints often dictate system energy density and specific energy, which are targeted to exceed 300 Wh L{sup -1} and 300 Wh kg{sup -1}, respectively, in order to compete with state-of-the-art battery technologies. To address this need, a novel carbide-based fuel system (CFS) intended for use with a solid oxide fuel cell (SOFC) is under development that is capable of achieving these energy metrics as well as sequestering carbon dioxide. The proposed CFS uses calcium carbide and calcium hydride that react with water to generate acetylene and hydrogen as the fuel and calcium hydroxide as a carbon dioxide scrubber. The acetylene is hydrogenated to ethane and then reformed to syngas (carbon monoxide and hydrogen) before being utilized by the SOFC. Carbon dioxide effluent from the SOFC is reacted with the calcium hydroxide to produce a storable solid, calcium carbonate, thus eliminating gas evolution from the UUV. A system configuration is proposed and discussion follows concerning energy storage metrics, operational parameters and preliminary safety analysis. (author)

  9. The analysis of fuel constituent redistribution for ternary metallic fuel slug

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byoung Oon; Lee, Dong Uk; Kim, Young Kyun; Chang, Jin Wook; Lee, Ki Bok; Kim, Young Il

    2004-02-01

    U-TRU-Zr metallic alloy is being considered as the fuel slug for the proliferation resistance core of KALIMER. The radial fuel constituent migration is a general phenomenon in the metallic alloys. This phenomenon may affect the in-reactor performance of metallic fuel rods, influencing such factors as melting temperature, thermal conductivity, power generation rate, phase boundaries and eutectic melting of the fuel slug. Thus, constituent redistribution modeling is essential when developing a metallic fuel performance code. The constituent migration model adopted in this report was based on the Ishida's model and Hofman's theory. A subroutine program has been made and installed into the MACSIS code to simulate constituent redistribution. The radial profile of Zr redistribution was calculated for the ternary metallic fuel, and compared with the measured data.

  10. Coating parameters of zirconium carbide on advanced TRISO fuels

    Science.gov (United States)

    Dulude, Michael C.

    The feasibility of using very high temperature reactors (VHTR) as part of the next generation of nuclear reactors greatly depends on the tri-structural isotropic (TRISO) fuel particles reliability to retain both gaseous and metallic fission products created in irradiated UO2. Most research devoted to TRISO fuel particles has focused on the characteristics and retention ability of silicon carbide as the main barrier against metallic fission products. This work investigates the deposition parameters necessary to create advanced TRISO particles consisting of the standard SiC TRISO coatings with an additional layer of ZrC applied directly to the UO2 fuel kernel. The additional ZrC layer will act as an oxygen getter to prevent failure mechanisms experienced in TRISO particles. Two failure mechanisms that are of the most concern are the over pressurization of the particles and kernel migration within the TRISO particles. In this study successful ZrC coatings were created and the deposition characteristics were analyzed via optical and SEM microscopy techniques. The ZrC layer was confirmed through XRD analysis. This investigation also reduced U3O8 microspheres to UO2 in an argon atmosphere. The oxygen to metal ratio from the reduced U3O8 was back calculated from oxidation analysis performed with a TGA machine. Once consistent repeatability is shown with coating surrogate zirconia kernels, advanced TRISO coatings will be deposited on the UO2 fuel kernels.

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

    Science.gov (United States)

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

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

  12. Emissions from Petrol Engine Fueled Gasoline–Ethanol–Methanol (GEM Ternary mixture as Alternative Fuel

    Directory of Open Access Journals (Sweden)

    Thangavelu Saravana Kannan

    2015-01-01

    Full Text Available The increasing demands of petroleum fuels due to the rapid development automotive society coupled with the environmental pollution issues have inspired the efforts on exploring alternative fuels for internal combustion engines. Bioethanol obtained from biomass and bioenergy crops has been proclaimed as one of the feasible alternative to gasoline. In this study, the effect of gasoline–ethanol–methanol (GEM ternary blend on the emission characteristics of petrol engine was studied. Three different fuel blends, namely, E0 (gasoline, G75E21M4 (75% gasoline, 21% hydrous ethanol and 4% methanol and E25 (25% anhydrous ethanol and 75% gasoline were tested in a 1.3-l K3-VE spark-ignition engine. The results indicate that, when G75E21M4 fuel blend was used, a significant drop in CO, CO2, NOx and HC emissions by about 42%, 15%, 7% and 5.2% compared to E0, respectively. Moreover, the emission results for G75E21M4 are marginally lower than E25 whereas; HC emission was slightly higher than E25.

  13. Molybdenum Carbide Synthesis Using Plasmas for Fuel Cells

    Science.gov (United States)

    2013-06-01

    Acid Fuel Cells, Proton Exchange Membrane Fuel Cells, Molten Carbonate Fuel Cells, Solid Oxide Fuel Cell, and Direct and Indirect Methanol Fuel Cell...Mathias, D. P. Miller, C. K. Mittelsteadt, T. Xie, and S. G. Yan, P. T. Yu, “Two Fuel Cell Cars in Every Garage?” The Electrochemical Society Interface...G. Colsman, B. Emonts, B. Hohlein, R. Menzer, and E. Riedel, “Hydrogen from methanol for fuel cells in mobile systems: development of compact

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

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Larry Lorin

    2001-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    H. radulescu

    2001-09-28

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

  16. GEN IV: Carbide Fuel Elaboration for the 'Futurix Concepts' experiment

    Energy Technology Data Exchange (ETDEWEB)

    Vaudez, Stephane; Riglet-Martial, Chantal; Paret, Laurent; Abonneau, Eric [Commissariat a l' Energie Atomique (C.E.A.), Direction de l' Energie Nucleaire, Centre d' Etudes de Cadarache, 13108 Saint Paul lez Durance Cedex (France)

    2008-07-01

    In order to collect information on the behaviour of the future GFR (Gas Fast Reactor) fuel under fast neutron irradiation, an experimental irradiation program, called 'Futurix-concepts' has been launched at the CEA. The considered concept is a composite material made of a fissile fuel embedded in an inert ceramic matrix. Fissile fuel pellets are made of UPuN or UPuC while ceramics are SiC for the carbide fuel and TiN for the nitride fuel. This paper focuses on the description of the carbide composite fabrication. The UPuC pellets are manufactured using a metallurgical powder process. Fabrication and handling of the fuels are carried out in glove boxes under a nitrogen atmosphere. Carbide fuel is synthesized by carbo-thermic reduction under vacuum of a mixture of actinide oxide and graphitic carbon up to 1550 deg. C. After ball milling, the UPuC powder is pressed to create hexagonal or spherical compacts. They are then sintered up to 1750 deg. C in order to obtain a density of 85 % of the theoretical one. The sintered pellets are inserted into an inert and tight capsule of SiC. In order to control the gap between the fuel and the matrix precisely, the pellets are abraded. The inert matrix is then filled with the pellets and the whole system is sealed by a BRASiC{sup R} process at high temperature under a helium atmosphere. Fabrication of the sample to be irradiated was done in 2006 and the irradiation began in May 2007 in the Phenix reactor. This presentation will detail and discuss the results obtained during this fabrication phase. (authors)

  17. Novel niobium carbide/carbon porous nanotube electrocatalyst supports for proton exchange membrane fuel cell cathodes

    Science.gov (United States)

    Nabil, Y.; Cavaliere, S.; Harkness, I. A.; Sharman, J. D. B.; Jones, D. J.; Rozière, J.

    2017-09-01

    Niobium carbide/carbon nanotubular porous structures have been prepared using electrospinning and used as electrocatalyst supports for proton exchange membrane fuel cells. They were functionalised with 3.1 nm Pt particles synthesised by a microwave-assisted polyol method and characterised for their electrochemical properties. The novel NbC-based electrocatalyst demonstrated electroactivity towards the oxygen reduction reaction as well as greater stability over high potential cycling than a commercial carbon-based electrocatalyst. Pt/NbC/C was integrated at the cathode of a membrane electrode assembly and characterised in a single fuel cell showing promising activity and power density.

  18. Reactor Physics Assessment of Thick Silicon Carbide Clad PWR Fuels

    Science.gov (United States)

    2013-06-01

    Be was modeled in SERPENT ; the depletion of Be at 60 MWd/kg in 5.5% 235 U enriched fuel was negligible as the difference between the SERPENT predicted...SIMULATE in the evaluation of core physics performance. 77 Comparison of ENDF-VI based CASMO results with ENDF-VII based SERPENT results for PuO2

  19. Acid resistance of palm oil fuel ash and metakaolin ternary blend cement mortar

    Directory of Open Access Journals (Sweden)

    Jamilu Usman

    2017-07-01

    Full Text Available This paper examines the effects of blend of Palm Oil fuel ash (POFA and Metakaolin (MK on the resistance of cement mortar to sulphuric acid (H2SO4 attack. Tests were conducted on POFA and MK ternary blended cement mortar immersed in a 3% H2SO4 solution for up 180 d. Binaries of POFA/cement and MK/cement as well as plain ordinary Portland cement (OPC mortar was also tested for comparison. The parameters measured include residual compressive strength and residual mass. Additionally, the microstructures of the specimens were analysed using the X-ray diffraction and Fourier transformed infrared techniques. The residual compressive strengths of the mortar specimens for plain OPC, binary blend of POFA and cement, binary blend of MK and cement, and ternary blend of POFA, MK and cement after 180 d of immersion in the acid solution were 25, 30, 33, and 32%, respectively. Moreover, the corresponding residual masses of the specimens were 39, 52, 58, and 54%. Accordingly, the ternary blended mortar performed better in resisting H2SO4 attack than the plain OPC and binary blend of POFA/cement mortars.

  20. Structure of the ternary carbide Ti{sub 3}SnC{sub 2} from ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Kanoun, M B; Jaouen, M [Laboratoire de Metallurgie Physique, UMR 6630 du CNRS, Universite de Poitiers SP2MI, Boulevard Marie et Pierre Curie, Teleport 2, Boite Postale 30179-86962 Futuroscope Chasseneuil Cedex (France)], E-mail: Michel.Jaouen@univ-poitiers.fr

    2008-02-27

    We have investigated the structural properties and electronic structure of the recently discovered layered ternary Ti{sub 3}SnC{sub 2} using the first-principles all-electron full-potential augmented plane wave method within the generalized-gradient approximation and the local density approximation. The lattice constants obtained after geometry optimization are in good agreement with experiment data and the bulk modulus is predicted. The band structure shows that the electrical conductivity is metallic and anisotropic with a high density of states at Fermi level. The analysis of the projected local density of states shows that the major hybrids come from Ti d and C p states.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-09-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lumin [Univ. of Michigan, Ann Arbor, MI (United States). Department of Nuclear Engineering and Radiological Science; Wierschke, Jonathan Brett [Univ. of Michigan, Ann Arbor, MI (United States). Department of Nuclear Engineering and Radiological Science

    2015-04-08

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

  3. Evaluation of the mechanical performance of silicon carbide in TRISO fuel at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rohbeck, Nadia, E-mail: nadia.rohbeck@manchester.ac.uk; Xiao, Ping, E-mail: p.xiao@manchester.ac.uk

    2016-09-15

    The HTR design envisions fuel operating temperatures of up to 1000 °C and in case of an accident even 1600 °C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore, simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600 °C up to 2200 °C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100 °C onwards, but initial signs of porosity formation were visible already at 1800 °C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600 °C to 2000 °C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in situ up to 500 °C using a high temperature nanoindentation facility. This approach allows conducting tests while the specimen and indenter tip are heated to a specific measurement temperature, thus obtaining reliable values for the temperature dependent mechanical properties of the material. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500 °C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value.

  4. Silver diffusion through silicon carbide in microencapsulated nuclear fuels TRISO; Difusion de plata a traves de carburo de silicio en combustibles nucleares microencapsulados TRISO

    Energy Technology Data Exchange (ETDEWEB)

    Cancino T, F.; Lopez H, E., E-mail: Felix.cancino@cinvestav.edu.mx [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Saltillo, Av. Industria Metalurgica No. 1062, Col. Ramos Arizpe, 25900 Saltillo, Coahuila (Mexico)

    2013-10-15

    The silver diffusion through silicon carbide is a challenge that has persisted in the development of microencapsulated fuels TRISO (Tri structural Isotropic) for more than four decades. The silver is known as a strong emitter of gamma radiation, for what is able to diffuse through the ceramic coatings of pyrolytic coal and silicon carbide and to be deposited in the heat exchangers. In this work we carry out a recount about the art state in the topic of the diffusion of Ag through silicon carbide in microencapsulated fuels and we propose the role that the complexities in the grain limit can have this problem. (Author)

  5. Development and Evaluation of Mixed Uranium-Refractory Carbide/Refractory Carbide Cer-Cer Fuels Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A new carbon-based fuel is introduced with outstanding potential to eliminate the loss of uranium, minimize the loss of carbon, and retain fission products for many...

  6. Molecular dynamics simulations of ternary PtxPdyAuz fuel cell nanocatalyst growth

    DEFF Research Database (Denmark)

    Brault, P.; Coutanceau, C.; C. Jennings, Paul

    2016-01-01

    Molecular dynamics simulation of PEMFC cathodes based on ternary Pt70Pd15Au15 and Pt50Pd25Au25 nanocatalysts dispersed on carbon indicate systematic Au segregation from the particle bulk to the surface, leading to an Au layer coating the cluster surface and to the spontaneous formation of a Pt@Pd...

  7. Highly efficient transition metal and nitrogen co-doped carbide-derived carbon electrocatalysts for anion exchange membrane fuel cells

    Science.gov (United States)

    Ratso, Sander; Kruusenberg, Ivar; Käärik, Maike; Kook, Mati; Puust, Laurits; Saar, Rando; Leis, Jaan; Tammeveski, Kaido

    2018-01-01

    The search for an efficient electrocatalyst for oxygen reduction reaction (ORR) to replace platinum in fuel cell cathode materials is one of the hottest topics in electrocatalysis. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites made by pyrolysis of cheap materials are the most promising with control over the porosity and final structure of the catalyst a crucial point. In this work we show a method of producing a highly active ORR catalyst in alkaline media with a controllable porous structure using titanium carbide derived carbon as a base structure and dicyandiamide along with FeCl3 or CoCl2 as the dopants. The resulting transition metal-nitrogen co-doped carbide derived carbon (M/N/CDC) catalyst is highly efficient for ORR electrocatalysis with the activity in 0.1 M KOH approaching that of commercial 46.1 wt.% Pt/C. The catalyst materials are also investigated by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to characterise the changes in morphology and composition causing the raise in electrochemical activity. MEA performance of M/N/CDC cathode materials in H2/O2 alkaline membrane fuel cell is tested with the highest power density reached being 80 mW cm-2 compared to 90 mW cm-2 for Pt/C.

  8. Surface science and electrochemical studies of metal-modified carbides for fuel cells and hydrogen production

    Science.gov (United States)

    Kelly, Thomas Glenn

    Carbides of the early transition metals have emerged as low-cost catalysts that are active for a wide range of reactions. The surface chemistry of carbides can be altered by modifying the surface with small amounts of admetals. These metal-modified carbides can be effective replacements for Pt-based bimetallic systems, which suffer from the drawbacks of high cost and low thermal stability. In this dissertation, metal-modified carbides were studied for reactions with applications to renewable energy technologies. It is demonstrated that metal-modified carbides possess high activity for alcohol reforming and electrochemical hydrogen production. First, the surface chemistry of carbides towards alcohol decomposition is studied using density functional theory (DFT) and surface science experiments. The Vienna Ab initio Simulation Package (VASP) was used to calculate the binding energies of alcohols and decomposition intermediates on metal-modified carbides. The calculated binding energies were then correlated to reforming activity determined experimentally using temperature programmed desorption (TPD). In the case of methanol decomposition, it was found that tungsten monocarbide (WC) selectively cleaved the C-O bond to produce methane. Upon modifying the surface with a single layer of metal such as Ni, Pt, or Rh, the selectivity shifted towards scission of the C-H bonds while leaving the C-O bond intact, producing carbon monoxide (CO) and H2. High resolution energy loss spectroscopy (HREELS) was used to examine the bond breaking sequence as a function of temperature. From HREELS, it was shown that the surfaces followed an activity trend of Rh > Ni > Pt. The Au-modified WC surface possessed too low of a methanol binding energy, and molecular desorption of methanol was the most favorable pathway on this surface. Next, the ability of Rh-modified WC to break the C-C bond of C2 and C3 alcohols was demonstrated. HREELS showed that ethanol decomposed through an acetaldehyde

  9. Molecular dynamics simulations of ternary PtxPdyAuz fuel cell nanocatalyst growth

    DEFF Research Database (Denmark)

    Brault, P.; Coutanceau, C.; C. Jennings, Paul

    2016-01-01

    Molecular dynamics simulation of PEMFC cathodes based on ternary Pt70Pd15Au15 and Pt50Pd25Au25 nanocatalysts dispersed on carbon indicate systematic Au segregation from the particle bulk to the surface, leading to an Au layer coating the cluster surface and to the spontaneous formation of a Pt......@Pd@Au core-shell structure. For Au content below 25 at%, surface PtxPdy active sites are available for efficient oxygen reduction reaction, in agreement with DFT calculations and experimental data. Simulations of direct core@shell system prepared in conditions mimicking those of plasma sputtering deposition...

  10. Magnesium carbide synthesis from methane and magnesium oxide - a potential methodology for natural gas conversion to premium fuels and chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, A.F.; Modestino, A.J.; Howard, J.B. [Massachusetts Institute of Technology, Cambridge, MA (United States)] [and others

    1995-12-31

    Diversification of the raw materials base for manufacturing premium fuels and chemicals offers U.S. and international consumers economic and strategic benefits. Extensive reserves of natural gas in the world provide a valuable source of clean gaseous fuel and chemical feedstock. Assuming the availability of suitable conversion processes, natural gas offers the prospect of improving flexibility in liquid fuels and chemicals manufacture, and thus, the opportunity to complement, supplement, or displace petroleum-based production as economic and strategic considerations require. The composition of natural gas varies from reservoir to reservoir but the principal hydrocarbon constituent is always methane (CH{sub 4}). With its high hydrogen-to-carbon ratio, methane has the potential to produce hydrogen or hydrogen-rich products. However, methane is a very chemically stable molecule and, thus, is not readily transformed to other molecules or easily reformed to its elements (H{sub 2} and carbon). In many cases, further research is needed to augment selectivity to desired product(s), increase single-pass conversions, or improve economics (e.g. there have been estimates of $50/bbl or more for liquid products) before the full potential of these methodologies can be realized on a commercial scale. With the trade-off between gas conversion and product selectivity, a major challenge common to many of these technologies is to simultaneously achieve high methane single-pass conversions and high selectivity to desired products. Based on the results of the scoping runs, there appears to be strong indications that a breakthrough has finally been achieved in that synthesis of magnesium carbides from MgO and methane in the arc discharge reactor has been demonstrated.

  11. Highly dispersed molybdenum carbide as non-noble electrocatalyst for PEM fuel cells: Performance for CO electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Guil-Lopez, R.; Martinez-Huerta, M.V.; Pena, M.A.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica (CSIC), Marie Curie 2, Cantoblanco, E-28049 Madrid (Spain); Guillen-Villafuerte, O.; Pastor, E. [Departamento de Quimica Fisica, Universidad de La Laguna, Astrofisico Francisco Sanchez s/n, E-38071 La Laguna, Tenerife (Spain)

    2010-08-15

    CO electrooxidation on nanocrystalline molybdenum carbide has been studied through CO stripping measurements using cyclic voltammetry. The active molybdenum carbide was obtained from the carbothermic reduction of really very small molybdenum oxide particles supported on Vulcan XC-72 carbon black (CB). In order to obtain highly dispersed molybdenum carbide particles, low molybdenum loading and control of the carbothermic reduction conditions of CB-supported molybdenum oxide were employed to avoid Mo sintering during the carburization process. This work provides experimental evidence on the CO electrooxidation capability of the Mo carbide phase, which to the best of our knowledge is reported for the first time. The small particle size of carbide electrocatalyst exhibited better performance for CO electrooxidation than the commercial bulk molybdenum carbide sample. (author)

  12. Modification of Nafion membranes with ternary composite materials for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Fang Yong; Wang Tongtao; Miao Ruiying; Tang Ling [Department of Physical chemistry, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); Wang Xindong, E-mail: echem@ustb.edu.c [Department of Physical chemistry, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China)

    2010-02-28

    Composite membranes for direct methanol fuel cells (DMFCs) were prepared by using Nafion115 membrane modification with polyvinyl alcohol (PVA), polyimide (PI) and 8-trimethoxysilylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS). The performance of the composite membranes was evaluated in terms of water sorption, dimensional stability, thermal stability, proton conductivity, methanol permeability and cell performance. The proton conductivity was slightly decreased by 1-3% compared with Nafion115, which still kept the high proton conduction of Nafion115. The methanol permeability of Nafion/PI-PVA-TSPS composite membranes was remarkably reduced by 35-55% compared with Nafion115. The power density of DMFCs with Nafion/PI-PVA-TSPS composite membranes reached to 100 mW/cm{sup 2}, exceeding that with Nafion115 (68m W/cm{sup 2}).

  13. Methanol electro-oxidation on platinum modified tungsten carbides in direct methanol fuel cells: a DFT study.

    Science.gov (United States)

    Sheng, Tian; Lin, Xiao; Chen, Zhao-Yang; Hu, P; Sun, Shi-Gang; Chu, You-Qun; Ma, Chun-An; Lin, Wen-Feng

    2015-10-14

    In exploration of low-cost electrocatalysts for direct methanol fuel cells (DMFCs), Pt modified tungsten carbide (WC) materials are found to be great potential candidates for decreasing Pt usage whilst exhibiting satisfactory reactivity. In this work, the mechanisms, onset potentials and activity for electrooxidation of methanol were studied on a series of Pt-modified WC catalysts where the bare W-terminated WC(0001) substrate was employed. In the surface energy calculations of a series of Pt-modified WC models, we found that the feasible structures are mono- and bi-layer Pt-modified WCs. The tri-layer Pt-modified WC model is not thermodynamically stable where the top layer Pt atoms tend to accumulate and form particles or clusters rather than being dispersed as a layer. We further calculated the mechanisms of methanol oxidation on the feasible models via methanol dehydrogenation to CO involving C-H and O-H bonds dissociating subsequently, and further CO oxidation with the C-O bond association. The onset potentials for the oxidation reactions over the Pt-modified WC catalysts were determined thermodynamically by water dissociation to surface OH* species. The activities of these Pt-modified WC catalysts were estimated from the calculated kinetic data. It has been found that the bi-layer Pt-modified WC catalysts may provide a good reactivity and an onset oxidation potential comparable to pure Pt and serve as promising electrocatalysts for DMFCs with a significant decrease in Pt usage.

  14. Uranium Carbide Powder Ignition Studies

    Energy Technology Data Exchange (ETDEWEB)

    Berthinier, C.; Coullomb, S.; Rado, C.; Le Guyadec, F. [CEA, DEN, DTEC, SDTC, LEME, F-30207 Bagnols-sur-Ceze (France); Chatillon, C.; Blanquet, E.; Boichot, R. [SIMAP, Sciences et Ingenierie des Materiaux et Procedes, INPG-CNRS-UJF ENSEEG, BP 75, 38402 St Martin-d' Heres (France)

    2009-06-15

    Mixed (U, Pu) carbide, constituted by means of 80% of uranium monocarbide (UC), is considered as a possible fuel material for future gas fast reactors or sodium fast reactor. However, UC undergoes a strong exothermic reaction with air and fine powders of UC are pyrophoric. Thus, it is necessary to understand this high reactivity in order to determine safe handling conditions for the production and reprocessing of carbide fuels. UC powder was obtained by arc melting and milling. The reactivity of uranium carbide was studied in oxidizing atmosphere and different experimental devices were used to determine ignition temperatures. The phases formed at the various observed stages of the oxidation process were determined by post-mortem X ray diffraction analysis. Studies were first performed using small quantities of UC powder (around 50 mg) in Differential Thermal Analysis / Thermogravimetric Analysis (DTA/TGA) and Differential Scanning Calorimetry (DSC). Experiments were realized using different parameters, such as heating rate and gas flow rate and composition, to determine their influence on pyro-phoricity. Results obtained with small quantities (tens of milligrams) revealed that UC powder is highly reactive in air in the range 200- 250 deg. C. Studies were also performed in the 'Pyro' test facility multi-function furnace allowing CCD camera recording, during heating and ignition, through view-ports. Lower ignition temperatures, around 100 deg. C, were obtained using around 1 g UC powder samples. Results are discussed and analysed with theory of burning curve ignition and numerical simulations. Simulations aim to understand the influence of the different parameters on pyro-phoricity. Small scale simulations (on a spherical grain) confirm the influence of UC grains size, heat rate and gas composition on powder ignition temperature with small quantities. The issue is now to understand the influence of grain pile form factor and volume on the pyro-phoricity of

  15. Ternary fission

    Indian Academy of Sciences (India)

    2015-08-05

    Aug 5, 2015 ... We present the ternary fission of 252Cf and 236U within a three-cluster model as well as in a level density approach. The competition between collinear and equatorial geometry is studied by calculating the ternary fragmentation potential as a function of the angle between the lines joining the stationary ...

  16. Ternary fission

    Indian Academy of Sciences (India)

    Recently, we have studied the various aspects associated with the ternary fission process. A model, called the three-cluster model (TCM) [1–6] has been put forth. This accounts for the energy minimization of all possible ternary breakups of a heavy radioactive nucleus. Further, within the TCM we have analysed the ...

  17. Page 1 Structure and superconductivity in ternary systems of ...

    Indian Academy of Sciences (India)

    Structure and superconductivity in ternary systems of compounds 299. Erra B2 structure do not have T. above 1:2 K (Ku and Meisner 1981); (iii) for. Ao.67Pt3B the T. are 1-6, 28 and 56K for A = Ca,Sr and Ba (Shelton 1978) and. (iv) AOs B, A = Th, T = 3 K; A = Y, T = 6K (Ku 1980). 3. Ternary carbides. Of the known ternary ...

  18. First-principles study of structural stability, elastic and electronic properties of ternary rare earth-transition metal—Borides and carbides (RT{sub x}Z, R=Sc, Y, and La, T=Pt and Pd, Z=B and C, and x=2, 3, and 4)

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Tiankai; Wang, Yachun; Li, Hui [Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Lian, Jie [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Zhang, Jingwu, E-mail: zjw@ysu.edu.cn [Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Gou, Huiyang, E-mail: huiyang.gou@gmail.com [Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2013-12-15

    Using first-principles total energy calculations (CASTEP code), the structural stability, elastic, and electronic properties of ternary rare earth-transition metal borides and carbides (RT{sub x}Z, R=Sc, Y, and La, T=Pt and Pd, Z=B and C, and x=2, 3, and 4) compounds were studied. Results show that RT{sub 3}Z compounds with tetragonal P4mm structure are energetically more favorable than usually cubic perovskite-type structure. Furthermore, RT{sub 3}Z with perovskite structure is found to be mechanically unstable with the negative C{sub 44}. Formation enthalpy calculations indicate that Pt-based borides are easier to be synthesized compared with Pd-based ones and counterpart carbides, respectively. Elastic constants, bulk moduli, shear moduli, Young's moduli, and Poisson's ratio of studied compounds have been calculated. Also, all the studied compounds show ductile behavior. Moreover, total and partial density of states (DOSs) and bonding charge density were employed to elucidate the bonding features of these compounds. The results reveal that the covalency between Pt-5d and Z-2p as well as T-nd (n=4 for Pd and 5 for Pt) and B-2p states, are the cause of the relatively higher elastic moduli of Pt-based compounds and R–T-borides, respectively.

  19. Innovative coating of nanostructured vanadium carbide on the F/M cladding tube inner surface for mitigating the fuel cladding chemical interactions

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yong [Univ. of Florida, Gainesville, FL (United States); Phillpot, Simon [Univ. of Florida, Gainesville, FL (United States)

    2017-11-29

    Fuel cladding chemical interactions (FCCI) have been acknowledged as a critical issue in a metallic fuel/steel cladding system due to the formation of low melting intermetallic eutectic compounds between the fuel and cladding steel, resulting in reduction in cladding wall thickness as well as a formation of eutectic compounds that can initiate melting in the fuel at lower temperature. In order to mitigate FCCI, diffusion barrier coatings on the cladding inner surface have been considered. In order to generate the required coating techniques, pack cementation, electroplating, and electrophoretic deposition have been investigated. However, these methods require a high processing temperature of above 700 oC, resulting in decarburization and decomposition of the martensites in a ferritic/martensitic (F/M) cladding steel. Alternatively, organometallic chemical vapor deposition (OMCVD) can be a promising process due to its low processing temperature of below 600 oC. The aim of the project is to conduct applied and fundamental research towards the development of diffusion barrier coatings on the inner surface of F/M fuel cladding tubes. Advanced cladding steels such as T91, HT9 and NF616 have been developed and extensively studied as advanced cladding materials due to their excellent irradiation and corrosion resistance. However, the FCCI accelerated by the elevated temperature and high neutron exposure anticipated in fast reactors, can have severe detrimental effects on the cladding steels through the diffusion of Fe into fuel and lanthanides towards into the claddings. To test the functionality of developed coating layer, the diffusion couple experiments were focused on using T91 as cladding and Ce as a surrogate lanthanum fission product. By using the customized OMCVD coating equipment, thin and compact layers with a few micron between 1.5 µm and 8 µm thick and average grain size of 200 nm and 5 µm were successfully obtained at the specimen coated between 300oC and

  20. SILICON CARBIDE GRAIN BOUNDARY DISTRIBUTIONS, IRRADIATION CONDITIONS, AND SILVER RETENTION IN IRRADIATED AGR-1 TRISO FUEL PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Lillo, T. M.; Rooyen, I. J.; Aguiar, J. A.

    2016-11-01

    Precession electron diffraction in the transmission electron microscope was used to map grain orientation and ultimately determine grain boundary misorientation angle distributions, relative fractions of grain boundary types (random high angle, low angle or coincident site lattice (CSL)-related boundaries) and the distributions of CSL-related grain boundaries in the SiC layer of irradiated TRISO-coated fuel particles. Two particles from the AGR-1 experiment exhibiting high Ag-110m retention (>80%) were compared to a particle exhibiting low Ag-110m retention (<19%). Irradiated particles with high Ag-110m retention exhibited a lower fraction of random, high angle grain boundaries compared to the low Ag-110m retention particle. An inverse relationship between the random, high angle grain boundary fraction and Ag-110m retention is found and is consistent with grain boundary percolation theory. Also, comparison of the grain boundary distributions with previously reported unirradiated grain boundary distributions, based on SEM-based EBSD for similarly fabricated particles, showed only small differences, i.e. a greater low angle grain boundary fraction in unirradiated SiC. It was, thus, concluded that SiC layers with grain boundary distributions susceptible to Ag-110m release were present prior to irradiation. Finally, irradiation parameters were found to have little effect on the association of fission product precipitates with specific grain boundary types.

  1. Neutron Damage and MAX Phase Ternary Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Barsoum, Michael [Drexel Univ., Philadelphia, PA (United States); Hoffman, Elizabeth [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Sindelar, Robert [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Garcua-Duaz, Brenda [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Kohse, Gordon [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2014-06-17

    The Demands of Gen IV nuclear power plants for long service life under neutron radiation at high temperature are severe. Advanced materials that would withstand high temperatures (up to 1000+ C) to high doses in a neutron field would be ideal for reactor internal structures and would add to the long service life and reliability of the reactors. The objective of this work is to investigate the response of a new class of machinable, conductive, layered, ternary transition metal carbides and nitrides - the so-called MAX phases - to low and moderate neutron dose levels.

  2. Impact of ternary blends of biodiesel on diesel engine performance

    Directory of Open Access Journals (Sweden)

    Prem Kumar

    2016-06-01

    Full Text Available The Pongamia and waste cooking oils are the main non edible oils for biodiesel production in India. The aim of the present work is to evaluate the fuel properties and investigate the impact on engine performance using Pongamia and waste cooking biodiesel and their ternary blend with diesel. The investigation of the fuel properties shows that Pongamia biodiesel and waste cooking biodiesel have poor cold flow property. This will lead to starting problem in the engine operation. To overcome this problem the ternary blends of diesel, waste cooking biodiesel and Pongamia biodiesel are prepared. The cloud and pour point for ternary blend, (WCB20:PB20:D60 were found to be 7 °C and 6.5 °C which are comparable to cloud and pour point of diesel 6 °C and 5 °C, respectively. The result of the test showed that brake specific fuel consumption for Pongamia biodiesel and waste cooking biodiesel is higher than ternary blend, (WCB20:PB20:D60 due to their lower energy content. The brake thermal efficiency of ternary blend and diesel is comparable while the Pongamia and waste cooking biodiesel have low efficiency. The result of investigation showed that ternary blend can be developed as alternate fuel.

  3. Ternary chalcopyrite semiconductors

    CERN Document Server

    Shay, J L; Pamplin, B R

    2013-01-01

    Ternary Chalcopyrite Semiconductors: Growth, Electronic Properties, and Applications covers the developments of work in the I-III-VI2 and II-IV-V2 ternary chalcopyrite compounds. This book is composed of eight chapters that focus on the crystal growth, characterization, and applications of these compounds to optical communications systems. After briefly dealing with the status of ternary chalcopyrite compounds, this book goes on describing the crystal growth of II-IV-V2 and I-III-VI2 single crystals. Chapters 3 and 4 examine the energy band structure of these semiconductor compounds, illustrat

  4. Optical characterization of one-step synthesis of ternary nanoalloy by laser ablation of stainless steel target in Hexane

    Science.gov (United States)

    Soliman, Wafaa; El-Ansary, Sara; Badr, Yehia

    2017-12-01

    In this work, we ablated stainless steel target in Hexane by 355 nm by tuning laser power to synthesize ternary nanoalloys from its constituents. XRD patterns didn't match with any machine code of carbides, carbonyls and oxides of target elements. Also, they didn't match with any of binary alloys, suggesting the formation of carbides or carbonyls of ternary nanoalloys. In addition, the optical properties of nanoalloys confirms the resonance fluorescence and multistep excitation. By tuning laser power, the shape of nanoalloys is controlled.

  5. 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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-02-01

    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.

  6. ɛ-Iron carbide as a low-temperature Fischer-Tropsch synthesis catalyst

    Science.gov (United States)

    Xu, Ke; Sun, Bo; Lin, Jun; Wen, Wen; Pei, Yan; Yan, Shirun; Qiao, Minghua; Zhang, Xiaoxin; Zong, Baoning

    2014-12-01

    ɛ-Iron carbide has been predicted to be promising for low-temperature Fischer-Tropsch synthesis (LTFTS) targeting liquid fuel production. However, directional carbidation of metallic iron to ɛ-iron carbide is challenging due to kinetic hindrance. Here we show how rapidly quenched skeletal iron featuring nanocrystalline dimensions, low coordination number and an expanded lattice may solve this problem. We find that the carbidation of rapidly quenched skeletal iron occurs readily in situ during LTFTS at 423-473 K, giving an ɛ-iron carbide-dominant catalyst that exhibits superior activity to literature iron and cobalt catalysts, and comparable to more expensive noble ruthenium catalyst, coupled with high selectivity to liquid fuels and robustness without the aid of electronic or structural promoters. This finding may permit the development of an advanced energy-efficient and clean fuel-oriented FTS process on the basis of a cost-effective iron catalyst.

  7. ε-Iron carbide as a low-temperature Fischer-Tropsch synthesis catalyst.

    Science.gov (United States)

    Xu, Ke; Sun, Bo; Lin, Jun; Wen, Wen; Pei, Yan; Yan, Shirun; Qiao, Minghua; Zhang, Xiaoxin; Zong, Baoning

    2014-12-12

    ε-Iron carbide has been predicted to be promising for low-temperature Fischer-Tropsch synthesis (LTFTS) targeting liquid fuel production. However, directional carbidation of metallic iron to ε-iron carbide is challenging due to kinetic hindrance. Here we show how rapidly quenched skeletal iron featuring nanocrystalline dimensions, low coordination number and an expanded lattice may solve this problem. We find that the carbidation of rapidly quenched skeletal iron occurs readily in situ during LTFTS at 423-473 K, giving an ε-iron carbide-dominant catalyst that exhibits superior activity to literature iron and cobalt catalysts, and comparable to more expensive noble ruthenium catalyst, coupled with high selectivity to liquid fuels and robustness without the aid of electronic or structural promoters. This finding may permit the development of an advanced energy-efficient and clean fuel-oriented FTS process on the basis of a cost-effective iron catalyst.

  8. Thermal-hydraulics analysis of a PWR reactor using zircaloy and carbide silicon reinforced with type S fibers as fuel claddings: Simulation of a channel blockage transient

    Energy Technology Data Exchange (ETDEWEB)

    Matuck, Vinicius; Ramos, Mario C.; Faria, Rochkhudson B.; Reis, Patricia A.L.; Costa, Antonella L.; Pereira, Claubia, E-mail: rochkdefaria@yahoo.com.br, E-mail: matuck747@gmail.com, E-mail: patricialire@yahoo.com.br, E-mail: marc5663@gmail.com, E-mail: antonella@nuclear.ufmg.br, E-mail: claubia@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (Brazil). Departamento de Engenharia Nuclear

    2017-11-01

    A detailed thermal-hydraulic reactor model using as reference data from the Angra 2 Final Safety Analysis Report (FSAR) has been developed and SiC reinforced with Hi-Nicalon type S fibers (SiC HNS) was used as fuel cladding. The goal is to compare its behavior from the thermal viewpoint with the Zircaloy, at the steady- state and transient conditions. The RELAP-3D was used to perform the thermal-hydraulic analysis and a blockage transient has been investigated at full power operation. The transient considered is related to total obstruction of a core cooling channel of one fuel assembly. The calculations were performed using a point kinetic model. The reactor behavior after this transient was analyzed and the time evolution of cladding and coolant temperatures mass flow and void fraction are presented. (author)

  9. Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

    Science.gov (United States)

    Gaballa, Osama Gaballa Bahig

    Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering

  10. Thermodynamics of fuels with a bio-synthetic component (IV): (Vapor + liquid) equilibrium data for the ternary mixture (ethyl 1,1-dimethylethyl ether + 1-hexene + toluene) at T = 313.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Villamanan, Rosa M. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, Paseo del Cauce s/n, 47011 Valladolid (Spain)], E-mail: rvillama@dce.uva.es; Segovia, Jose J. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, Paseo del Cauce s/n, 47011 Valladolid (Spain)], E-mail: josseg@eis.uva.es; Carmen Martin, M. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, Paseo del Cauce s/n, 47011 Valladolid (Spain)], E-mail: mcmg@eis.uva.es; Vega-Maza, David [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, Paseo del Cauce s/n, 47011 Valladolid (Spain)], E-mail: davveg@eis.uva.es; Chamorro, Cesar R. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, Paseo del Cauce s/n, 47011 Valladolid (Spain)], E-mail: cescha@eis.uva.es; Villamanan, Miguel A. [Research Group TERMOCAL-Thermodynamics and Calibration University of Valladolid, Paseo del Cauce s/n, 47011 Valladolid (Spain)], E-mail: miguel.villamanan@eis.uva.es

    2009-02-15

    The paper reports experimental p-x data for the ternary system (ethyl 1,1-dimethylethyl ether + 1-hexene + toluene) at T = 313.15 K. The ether, synthesized from ethanol of biological origin, increases the interest of this compound as an additive for gasolines. An isothermal total pressure cell was used for the measurements. Data reduction by Barker's method provides correlations for G{sup E}, using Wilson, NRTL, UNIQUAC models and the Wohl expansion for the ternary system and the calculation of the vapor phase composition. Good results are obtained for the correlation by all the models.

  11. Approximately Ternary Homomorphisms on C*-Ternary Algebras

    Directory of Open Access Journals (Sweden)

    Eon Wha Shim

    2013-01-01

    functional equation: fx2-x1/3+fx1-3x3/3+f3x1+3x3-x2/3=fx1, by the direct method. Under the conditions in the main theorems, we can show that the related mappings must be zero. In this paper, we correct the conditions and prove the corrected theorems. Furthermore, we prove the Hyers-Ulam stability and the superstability of C*-ternary homomorphisms and C*-ternary derivations on C*-ternary algebras by using a fixed point approach.

  12. Microstructural Study of Titanium Carbide Coating on Cemented Carbide

    DEFF Research Database (Denmark)

    Vuorinen, S.; Horsewell, Andy

    1982-01-01

    Titanium carbide coating layers on cemented carbide substrates have been investigated by transmission electron microscopy. Microstructural variations within the typically 5µm thick chemical vapour deposited TiC coatings were found to vary with deposit thickness such that a layer structure could...

  13. Composition optimization of self-lubricating chromium carbide-based composite coatings for use to 760 deg C

    Science.gov (United States)

    Dellacorte, C.; Sliney, H. E.

    1986-01-01

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

  14. Composition optimization of self-lubricating chromium-carbide-based composite coatings for use to 760 C

    Science.gov (United States)

    Dellacorte, Chris; Sliney, Harold E.

    1987-01-01

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

  15. Partially fluorinated aarylene polyethers and their ternary blends with PBI and H3PO4

    DEFF Research Database (Denmark)

    Li, Qingfeng; Jensen, Jens Oluf; Pan, Chao

    2008-01-01

    Ternary blend membranes based on sulphonated partially fluorinated arylene polyether, polybenzimidazole (PBI) and phosphoric acid were prepared and characterised as electrolyte for high temperature proton exchange membrane fuel cells. Partially fluorinated arylene polyether was first prepared from......% and modulus of 50 MPa at 150 degrees C. Based on these ternary membranes large MEAs with an active area of 256 cm(2) have been prepared for a 2 kW(el) stack showing good performance and reproducibility....

  16. Experimental Investigation of Ternary Alloys for Fusion Breeding Blankets

    Energy Technology Data Exchange (ETDEWEB)

    Choi, B. William [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chiu, Ing L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-26

    Future fusion power plants based on the deuterium-tritium (DT) fuel cycle will be required to breed the T fuel via neutron reactions with lithium, which will be incorporated in a breeding blanket that surrounds the fusion source. Recent work by LLNL proposed the used of liquid Li as the breeder in an inertial fusion energy (IFE) power plant. Subsequently, an LDRD was initiated to develop alternatives ternary alloy liquid metal breeders that have reduced chemical reactivity with water and air compared to pure Li. Part of the work plan was to experimentally investigate the phase diagrams of ternary alloys. Of particular interest was measurement of the melt temperature, which must be low enough to be compatible with the temperature limits of the steel used in the construction of the chamber and heat transfer system.

  17. Data transmission is faster with ternary coding

    CERN Document Server

    Bruins, T

    1974-01-01

    Discusses a ternary data transmission system for an effective rate of up to 6 megabits per second over a 1-mile line of ordinary twisted- pair cable. The methods are discussed of implementing a ternary data transmission system. (0 refs).

  18. Silicon Carbide Electronic Devices

    Science.gov (United States)

    Neudeck, P. G.

    2001-01-01

    The status of emerging silicon carbide (SiC) widebandgap semiconductor electronics technology is briefly surveyed. SiC-based electronic devices and circuits are being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot function. Projected performance benefits of SiC electronics are briefly illustrated for several applications. However, most of these operational benefits of SiC have yet to be realized in actual systems, primarily owing to the fact that the growth techniques of SiC crystals are relatively immature and device fabrication technologies are not yet sufficiently developed to the degree required for widespread, reliable commercial use. Key crystal growth and device fabrication issues that limit the performance and capability of high-temperature and/or high-power SiC electronics are identified. The electrical and material quality differences between emerging SiC and mature silicon electronics technology are highlighted.

  19. Graphene Nanoplatelet Reinforced Tantalum Carbide

    Science.gov (United States)

    2015-08-27

    et. al. Ultrahigh-pressure consolidation and deformation of tantalum carbide at ambient and high temperatures. Acta Materialia 61-11 (2013) 4001-4009...matrix to reinfor- cement . Al–5BNNT exhibits high deformability as it undergoes 75% thickness reduction in a single pass of cold rolling without...4009Ultrahigh-pressure consolidation and deformation of tantalum carbide at ambient and high temperatures Debrupa Lahiri a, Virendra Singh b, Giovani

  20. Tungsten carbide encapsulated in nitrogen-doped carbon with iron/cobalt carbides electrocatalyst for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jie; Chen, Jinwei, E-mail: jwchen@scu.edu.cn; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin, E-mail: rl.wang@scu.edu.cn

    2016-12-15

    Graphical abstract: A hybrid catalyst was prepared via a quite green and simple method to achieve an one-pot synthesis of the N-doping carbon, tungsten carbides, and iron/cobalt carbides. It exhibited comparable electrocatalytic activity, higher durability and ability to methanol tolerance compared with commercial Pt/C to ORR. - Highlights: • A novel type of hybrid Fe/Co/WC@NC catalysts have been successfully synthesized. • The hybrid catalyst also exhibited better durability and methanol tolerance. • Multiple effective active sites of Fe{sub 3}C, Co{sub 3}C, WC, and NC help to improve catalytic performance. - Abstract: This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe{sub 3}C and Co{sub 3}C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe{sub 3}C, and Co{sub 3}C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

  1. Electrocatalyst for alcohol oxidation at fuel cell anodes

    Science.gov (United States)

    Adzic, Radoslav [East Setauket, NY; Kowal, Andrzej [Cracow, PL

    2011-11-02

    In some embodiments a ternary electrocatalyst is provided. The electrocatalyst can be used in an anode for oxidizing alcohol in a fuel cell. In some embodiments, the ternary electrocatalyst may include a noble metal particle having a surface decorated with clusters of SnO.sub.2 and Rh. The noble metal particles may include platinum, palladium, ruthenium, iridium, gold, and combinations thereof. In some embodiments, the ternary electrocatalyst includes SnO.sub.2 particles having a surface decorated with clusters of a noble metal and Rh. Some ternary electrocatalysts include noble metal particles with clusters of SnO.sub.2 and Rh at their surfaces. In some embodiments the electrocatalyst particle cores are nanoparticles. Some embodiments of the invention provide a fuel cell including an anode incorporating the ternary electrocatalyst. In some aspects a method of using ternary electrocatalysts of Pt, Rh, and SnO.sub.2 to oxidize an alcohol in a fuel cell is described.

  2. Silicon Carbide Growth

    Science.gov (United States)

    2005-01-01

    Andrew Trunek has focused on supporting the Sic team through the growth of Sic crystals, making observations and conducting research that meets the collective needs and requirements of the team while fulfilling program commitments. Cancellation of the Ultra Efficient Engine Technology (UEET) program has had a significant negative impact on resources and research goals. This report highlights advancements and achievements made with this cooperative agreement over the past year. NASA Glenn Research Center (GRC) continues to make advances in silicon carbide (SiC) research during the past year. Step free surfaces were used as substrates for the deposition of GaN epilayers that yielded very low dislocation densities. Defect free 3C- SiC was successfully nucleated on step free mesas and test diodes were fabricated. Web growth techniques were used to increase the usable surface area of dislocation free SiC by approximately equal to 40%. The greatest advancement has been attained on stepped surfaces of SiC. A metrology standard was developed using high temperature etching techniques titled "Nanometer Step Height Standard". This development culminated in being recognized for a 2004 R&D100 award and the process to produce the steps received a NASA Space Act award.

  3. Magnetic composites based on metallic nickel and molybdenum carbide: A potential material for pollutants removal

    Energy Technology Data Exchange (ETDEWEB)

    Mambrini, Raquel V.; Fonseca, Thales L. [Departamento de Quimica, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Dias, Anderson [Departamento de Quimica, Universidade Federal de Ouro Preto, Ouro Preto, MG 35400-000 (Brazil); Oliveira, Luiz C.A.; Araujo, Maria Helena [Departamento de Quimica, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Moura, Flavia C.C., E-mail: flaviamoura@ufmg.br [Departamento de Quimica, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil)

    2012-11-30

    Highlights: Black-Right-Pointing-Pointer New magnetic molybdenum carbide composites can be prepared by CVD from ethanol. Black-Right-Pointing-Pointer Magnetic molybdenum carbide shows promising results for pollutants removal. Black-Right-Pointing-Pointer The carbide composites can be easily recovered magnetically and reused. - Abstract: New magnetic composites based on metallic nickel and molybdenum carbide, Ni/Mo{sub 2}C, have been produced via catalytic chemical vapor deposition from ethanol. Scanning electron microscopy, thermal analysis, Raman spectroscopy and X-ray diffraction studies suggest that the CVD process occurs in a single step. This process involves the reduction of NiMo oxides at different temperatures (700, 800 and 900 Degree-Sign C) with catalytic deposition of carbon from ethanol producing molybdenum carbide on Ni surface. In the absence of molybdenum the formation of Ni/C was observed. The magnetic molybdenum carbide was successfully used as pollutants removal by adsorption of sulfur and nitrogen compounds from liquid fuels and model dyes such as methylene blue and indigo carmine. The dibenzothiofene adsorption process over Ni/Mo{sub 2}C reached approximately 20 mg g{sup -1}, notably higher than other materials described in the literature and also removed almost all methylene blue dye. The great advantage of these carbide composites is that they may be easily recovered magnetically and reused.

  4. Novel fabrication of silicon carbide based ceramics for nuclear applications

    Science.gov (United States)

    Singh, Abhishek Kumar

    Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These materials include refractory alloys based on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as SiC--SiCf; carbon--carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor components is necessary for improved efficiency. Improving thermal conductivity of the fuel can lower the center-line temperature and, thereby, enhance power production capabilities and reduce the risk of premature fuel pellet failure. Crystalline silicon carbide has superior characteristics as a structural material from the viewpoint of its thermal and mechanical properties, thermal shock resistance, chemical stability, and low radioactivation. Therefore, there have been many efforts to develop SiC based composites in various forms for use in advanced energy systems. In recent years, with the development of high yield preceramic precursors, the polymer infiltration and pyrolysis (PIP) method has aroused interest for the fabrication of ceramic based materials, for various applications ranging from disc brakes to nuclear reactor fuels. The pyrolysis of preceramic polymers allow new types of ceramic materials to be processed at relatively low temperatures. The raw materials are element-organic polymers whose composition and architecture can be tailored and varied. The primary focus of this study is to use a pyrolysis based process to fabricate a host of novel silicon carbide-metal carbide or oxide composites, and to synthesize new materials based on mixed-metal silicocarbides that cannot be processed using conventional techniques. Allylhydridopolycarbosilane (AHPCS), which is an organometal polymer, was used as the precursor for silicon carbide. Inert gas pyrolysis of AHPCS produces near-stoichiometric amorphous

  5. Silicon carbide as platform for energy applications

    DEFF Research Database (Denmark)

    Syväjärvi, Mikael; Jokubavicius, Valdas; Sun, Jianwu

    Silicon carbide is emerging as a novel material for a range of energy and environmental technologies. Previously, silicon carbide was considered as a material mainly for transistor applications. We have initiated the use of silicon carbide material towards optoelectronics in general lighting and ...

  6. Some new ternary linear codes

    Directory of Open Access Journals (Sweden)

    Rumen Daskalov

    2017-07-01

    Full Text Available Let an $[n,k,d]_q$ code be a linear code of length $n$, dimension $k$ and minimum Hamming distance $d$ over $GF(q$. One of the most important problems in coding theory is to construct codes with optimal minimum distances. In this paper 22 new ternary linear codes are presented. Two of them are optimal. All new codes improve the respective lower bounds in [11].

  7. Nearly Ternary Quadratic Higher Derivations on Non-Archimedean Ternary Banach Algebras: A Fixed Point Approach

    Directory of Open Access Journals (Sweden)

    M. Eshaghi Gordji

    2011-01-01

    Full Text Available We investigate the stability and superstability of ternary quadratic higher derivations in non-Archimedean ternary algebras by using a version of fixed point theorem via quadratic functional equation.

  8. Robust tribo-mechanical and hot corrosion resistance of ultra-refractory Ta-Hf-C ternary alloy films.

    Science.gov (United States)

    Yate, Luis; Coy, L Emerson; Aperador, Willian

    2017-06-08

    In this work we report the hot corrosion properties of binary and ternary films of the Ta-Hf-C system in V 2 O 5 -Na 2 SO 4 (50%wt.-50%wt.) molten salts at 700 °C deposited on AISI D3 steel substrates. Additionally, the mechanical and nanowear properties of the films were studied. The results show that the ternary alloys consist of solid solutions of the TaC and HfC binary carbides. The ternary alloy films have higher hardness and elastic recoveries, reaching 26.2 GPa and 87%, respectively, and lower nanowear when compared to the binary films. The corrosion rates of the ternary alloys have a superior behavior compared to the binary films, with corrosion rates as low as 0.058 μm/year. The combination and tunability of high hardness, elastic recovery, low nanowear and an excellent resistance to high temperature corrosion demonstrates the potential of the ternary Ta-Hf-C alloy films for applications in extreme conditions.

  9. Determination of thorium in plutonium-thorium oxides and carbides

    Energy Technology Data Exchange (ETDEWEB)

    Walker, L.F.; Temer, D.J.

    1979-10-01

    Thorium is determined in (PuTh)C and (PuTh)O/sub 2/ by complexometric titration with ethylenediaminetetraacetic acid (EDTA) following separation on anion-exchange resin. Carbides are first oxidized by ignition in air at about 800/sup 0/C. Oxide or oxidized carbide samples are dissolved in acids by the sealed-reflux technique or by heating in beakers. The plutonium is selectively sorbed from the 12M hydrochloric acid solution of the fuel on a Bio-Rad AG1-X2 anion-exchange resin column, and the eluted thorium is titrated with EDTA using xylenol orange as the indicator. The average recovery of thorium in 20 samples is 99.98% with a relative standard deviation of 0.07%.

  10. Understanding the Irradiation Behavior of Zirconium Carbide

    Energy Technology Data Exchange (ETDEWEB)

    Motta, Arthur [Pennsylvania State Univ., University Park, PA (United States); Sridharan, Kumar [Univ. of Wisconsin, Madison, WI (United States); Morgan, Dane [Univ. of Wisconsin, Madison, WI (United States); Szlufarska, Izabela [Univ. of Wisconsin, Madison, WI (United States)

    2013-10-11

    Zirconium carbide (ZrC) is being considered for utilization in high-temperature gas-cooled reactor fuels in deep-burn TRISO fuel. Zirconium carbide possesses a cubic B1-type crystal structure with a high melting point, exceptional hardness, and good thermal and electrical conductivities. The use of ZrC as part of the TRISO fuel requires a thorough understanding of its irradiation response. However, the radiation effects on ZrC are still poorly understood. The majority of the existing research is focused on the radiation damage phenomena at higher temperatures (>450{degree}C) where many fundamental aspects of defect production and kinetics cannot be easily distinguished. Little is known about basic defect formation, clustering, and evolution of ZrC under irradiation, although some atomistic simulation and phenomenological studies have been performed. Such detailed information is needed to construct a model describing the microstructural evolution in fast-neutron irradiated materials that will be of great technological importance for the development of ZrC-based fuel. The goal of the proposed project is to gain fundamental understanding of the radiation-induced defect formation in zirconium carbide and irradiation response 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

  11. Fabrication and characterization of fully ceramic microencapsulated fuels

    Energy Technology Data Exchange (ETDEWEB)

    Terrani, K.A., E-mail: kurt.terrani@gmail.com [Fuel Cycle and Isotopes Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kiggans, J.O.; Katoh, Y. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Shimoda, K. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Montgomery, F.C.; Armstrong, B.L.; Parish, C.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Hinoki, T. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Hunn, J.D. [Fuel Cycle and Isotopes Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Snead, L.L. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2012-07-15

    The current generation of fully ceramic microencapsulated fuels, consisting of Tristructural Isotropic fuel particles embedded in a silicon carbide matrix, is fabricated by hot pressing. Matrix powder feedstock is comprised of alumina-yttria additives thoroughly mixed with silicon carbide nanopowder using polyethyleneimine as a dispersing agent. Fuel compacts are fabricated by hot pressing the powder-fuel particle mixture at a temperature of 1800-1900 Degree-Sign C using compaction pressures of 10-20 MPa. Detailed microstructural characterization of the final fuel compacts shows that oxide additives are limited in extent and are distributed uniformly at silicon carbide grain boundaries, at triple joints between silicon carbide grains, and at the fuel particle-matrix interface.

  12. Fabrication and characterization of fully ceramic microencapsulated fuels

    Science.gov (United States)

    Terrani, K. A.; Kiggans, J. O.; Katoh, Y.; Shimoda, K.; Montgomery, F. C.; Armstrong, B. L.; Parish, C. M.; Hinoki, T.; Hunn, J. D.; Snead, L. L.

    2012-07-01

    The current generation of fully ceramic microencapsulated fuels, consisting of Tristructural Isotropic fuel particles embedded in a silicon carbide matrix, is fabricated by hot pressing. Matrix powder feedstock is comprised of alumina-yttria additives thoroughly mixed with silicon carbide nanopowder using polyethyleneimine as a dispersing agent. Fuel compacts are fabricated by hot pressing the powder-fuel particle mixture at a temperature of 1800-1900 °C using compaction pressures of 10-20 MPa. Detailed microstructural characterization of the final fuel compacts shows that oxide additives are limited in extent and are distributed uniformly at silicon carbide grain boundaries, at triple joints between silicon carbide grains, and at the fuel particle-matrix interface.

  13. On Some Ternary LCD Codes

    OpenAIRE

    Darkunde, Nitin S.; Patil, Arunkumar R.

    2018-01-01

    The main aim of this paper is to study $LCD$ codes. Linear code with complementary dual($LCD$) are those codes which have their intersection with their dual code as $\\{0\\}$. In this paper we will give rather alternative proof of Massey's theorem\\cite{8}, which is one of the most important characterization of $LCD$ codes. Let $LCD[n,k]_3$ denote the maximum of possible values of $d$ among $[n,k,d]$ ternary $LCD$ codes. In \\cite{4}, authors have given upper bound on $LCD[n,k]_2$ and extended th...

  14. Superconducting state parameters of ternary metallic glasses

    Indian Academy of Sciences (India)

    Administrator

    pseudopotential to ternary metallic glasses involves the assumption of pseudoions with average properties, which are assumed to replace three types of ions in the ternary systems, and a gas of free electrons is assumed to perme- ate through them. The electron–pseudoion is accounted by the pseudopotential, and the ...

  15. Ternary rhythm and the lapse constraint

    NARCIS (Netherlands)

    Elenbaas, N.; Kager, R.W.J.

    2004-01-01

    Ternary rhythmic systems differ from binary systems in stressing every third syllable in a word, rather than every second. Ternary rhythm is well-established for only a small group of languages, including Chugach Alutiiq, Cayuvava, and Estonian, and possibly Winnebago. Nevertheless the stress

  16. NOVEL SUPPORTED BIMETALLIC CARBIDE CATALYSTS FOR COPROCESSING OF COAL WITH WASTE METERIALS

    Energy Technology Data Exchange (ETDEWEB)

    S. Ted Oyama; David F. Cox; Chunshan Song; Fred Allen; Weilin Wang; Viviane Schwartz; Xinqin Wang; Jianli Yang

    2001-01-01

    The overall objectives of this project are to explore the potential of novel monometallic and bimetallic Mo-based carbide catalysts for heavy hydrocarbon coprocessing, and to understand the fundamental chemistry related to the reaction pathways of coprocessing and the role of the catalysts in the conversion of heavy hydrocarbon resources into liquid fuels based on the model compound reactions.

  17. High-Efficient Circuits for Ternary Addition

    Directory of Open Access Journals (Sweden)

    Reza Faghih Mirzaee

    2014-01-01

    Full Text Available New ternary adders, which are fundamental components of ternary addition, are presented in this paper. They are on the basis of a logic style which mostly generates binary signals. Therefore, static power dissipation reaches its minimum extent. Extensive different analyses are carried out to examine how efficient the new designs are. For instance, the ternary ripple adder constructed by the proposed ternary half and full adders consumes 2.33 μW less power than the one implemented by the previous adder cells. It is almost twice faster as well. Due to their unique superior characteristics for ternary circuitry, carbon nanotube field-effect transistors are used to form the novel circuits, which are entirely suitable for practical applications.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-09-01

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

  19. Microstructure and mechanical properties of proton irradiated zirconium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Yang Yong [Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706 (United States)], E-mail: yyang@cae.wisc.edu; Dickerson, Clayton A.; Swoboda, Hannah [Material Science Program, University of Wisconsin-Madison, Madison, WI 53706 (United States); Miller, Brandon; Allen, Todd R. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706 (United States)

    2008-09-01

    Zirconium carbide is a candidate ceramic being considered for metal-carbide-base composite-type fuels, as well as for an alternative coating material for TRISO particle fuels. Ensuring adequate mechanical properties and dimensional stability in response to radiation is a key part in developing a practical ZrC-base fuel. The existing available radiation response data for ZrC is limited and insufficient. In the present study, ZrC was irradiated with a 2.6 MeV proton beam at 800 deg. C to doses of 0.7 and 1.5 dpa. Following radiation, the radiation induced damage microstructure is comprised of a high density of nanometer-sized Frank loops, but no irradiation induced amorphization, voids, or precipitates were observed. A slight lattice expansion was found in the irradiated ZrC, in good agreement with the reported results from neutron irradiation. The changes in microhardness and fracture toughness properties induced in the irradiated samples were measured using indentation techniques. The hardness and the fracture toughness both increase with increasing radiation dose.

  20. Pathology of silicon carbide pneumoconiosis.

    Science.gov (United States)

    Massé, S; Bégin, R; Cantin, A

    1988-03-01

    Silicon carbide is a widely used synthetic abrasive manufactured by heating silica and coke in electric furnaces at 2400 degrees C. Until recently it had been considered a relatively inert dust in humans and animals. However, several roentgenologic surveys had revealed lesions similar to low-grade silicosis. A recent epidemiological study has revealed a 35% incidence of pulmonary problems. Tissues from three such workers were available for light microscopy. A mixed pneumoconiosis was found, and lesions can be summarized as follows: (a) abundance of intraalveolar macrophages associated with a mixture of inhaled particles including carbon, silicon, pleomorphic crystals, silicon carbide, and ferruginous bodies showing a thin black central core; (b) nodular fibrosis, generally profuse, containing silica and ferruginous bodies and associated with large amount of carbon pigment; (c) interstitial fibrosis, less prominent than the nodular form; (d) carcinoma in two cases. We believe this pneumoconiosis is sufficiently characteristic to be recognized as a distinct entity. The Stanton hypothesis on fiber properties and carcinogenesis could be applied to silicon carbide dust. At present, it appears that the occupational hazard is limited to the manufacturing process and powdered product used in some industries.

  1. Silicon carbide fibers and articles including same

    Science.gov (United States)

    Garnier, John E; Griffith, George W

    2015-01-27

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

  2. Methods for producing silicon carbide fibers

    Science.gov (United States)

    Garnier, John E.; Griffith, George W.

    2016-03-01

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

  3. Theoretical investigation on electronic and mechanical properties of ternary actinide (U, Np, Pu) nitrides

    Science.gov (United States)

    Zhang, Yu-Juan; Zhou, Zhang-Jian; Lan, Jian-Hui; Bo, Tao; Ge, Chang-Chun; Chai, Zhi-Fang; Shi, Wei-Qun

    2017-09-01

    Actinide mononitrides as a promising advanced nuclear fuel have recently earned much attention. We herein studied the electronic and mechanical properties of the ternary actinide mixed mononitrides A0.5B0.5 N (A, B = U, Np, and Pu) using the density functional theory +U method. It is found that in the studied ternary mixed mononitrides, the 5f electronic states of all actinide atoms maintain the local electronic character and do not overlap with each other. Compared with their corresponding binary mononitrides, the U-N bond becomes more ionic, where the Np-N and Pu-N bonds become more covalent in ternary actinide mixed mononitrides. The mechanical properties (such as bulk and shear moduli, Young's modulus, and Poisson's ratio) of three ternary actinide (U-Pu) mononitrides are found to be similar to that of their corresponding binary actinide mononitrides and thus are expected not to misbehave with actinide mononitrides in respect of mechanics. In addition, all the three ternary actinide mononitrides have no imaginary frequencies in their vibration curves and correspondingly satisfy the stability criteria for elastic constants of tetragonal structures.

  4. Neutronics Evaluation of Lithium-Based Ternary Alloys in IFE Blankets

    Energy Technology Data Exchange (ETDEWEB)

    Jolodosky, A. [Univ. of California, Berkeley, CA (United States); Fratoni, M. [Univ. of California, Berkeley, CA (United States)

    2015-09-22

    , low electrical conductivity and therefore low MHD pressure drop, low chemical reactivity, and extremely low tritium inventory; the addition of sodium (FLiNaBe) has been considered because it retains the properties of FliBe but also lowers the melting point. Although many of these blanket concepts are promising, challenges still remain. The limited amount of beryllium available poses a problem for ceramic breeders such as the HCPB. FLiBe and FLiNaBe are highly viscous and have a low thermal conductivity. Lithium lead possesses a poor thermal conductivity which can cause problems in both DCLL and LiPb blankets. Additionally, the tritium permeation from these two blankets into plant components can be a problem and must be reduced. Consequently, Lawrence Livermore National Laboratory (LLNL) is attempting to develop a lithium-based alloy—most likely a ternary alloy—which maintains the beneficial properties of lithium (e.g. high tritium breeding and solubility) while reducing overall flammability concerns for use in the blanket of an inertial fusion energy (IFE) power plant. The LLNL concept employs inertial confinement fusion (ICF) through the use of lasers aimed at an indirect-driven target composed of deuterium-tritium fuel. The fusion driver/target design implements the same physics currently experimented at the National Ignition Facility (NIF). The plant uses lithium in both the primary coolant and blanket; therefore, lithium-related hazards are of primary concern. Although reducing chemical reactivity is the primary motivation for the development of new lithium alloys, the successful candidates will have to guarantee acceptable performance in all their functions. The scope of this study is to evaluate the neutronics performance of a large number of lithium-based alloys in the blanket of the IFE engine and assess their properties upon activation. This manuscript is organized as follows: Section 12 presents the models and methodologies used for the analysis; Section

  5. Aerolization During Boron Nanoparticle Multi-Component Fuel Group Burning Studies

    Science.gov (United States)

    2014-02-03

    mixed results. Boron has excellent potential as a liquid fuel additive due to its high volumetric and gravimetric heating value. Boron carbide (B4C...due to its high volumetric and gravimetric heating value. Boron Carbide (B4C) is widely available due to its commercial application as an abrasive...alternate fuels and new technologies being considered include biofuels , synthetic fuel designs, and hydrogen fuel cells. Although these new energy

  6. Performance Estimation for Lowpass Ternary Filters

    Directory of Open Access Journals (Sweden)

    Brenton Steele

    2003-11-01

    Full Text Available Ternary filters have tap values limited to −1, 0, or +1. This restriction in tap values greatly simplifies the multipliers required by the filter, making ternary filters very well suited to hardware implementations. Because they incorporate coarse quantisation, their performance is typically limited by tap quantisation error. This paper derives formulae for estimating the achievable performance of lowpass ternary filters, thereby allowing the number of computationally intensive design iterations to be reduced. Motivated by practical communications systems requirements, the performance measure which is used is the worst-case stopband attenuation.

  7. Low temperature chemical processing of graphite-clad nuclear fuels

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Robert A.

    2017-10-17

    A reduced-temperature method for treatment of a fuel element is described. The method includes molten salt treatment of a fuel element with a nitrate salt. The nitrate salt can oxidize the outer graphite matrix of a fuel element. The method can also include reduced temperature degradation of the carbide layer of a fuel element and low temperature solubilization of the fuel in a kernel of a fuel element.

  8. Thermal radiative and thermodynamic properties of solid and liquid uranium and plutonium carbides in the visible-near infrared range

    CERN Document Server

    Fisenko, Anatoliy I

    2016-01-01

    The knowledge of thermal radiative and thermodynamic properties of uranium and plutonium carbides under extreme conditions is essential for designing a new metallic fuel materials for next generation of a nuclear reactor. The present work is devoted to the study of the thermal radiative and thermodynamic properties of liquid and solid uranium and plutonium carbides at their melting/freezing temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and normal total emissivity are calculated using experimental data for the frequency dependence of the normal spectral emissivity of liquid and solid uranium and plutonium carbides in the visible-near infrared range. It is shown that the thermal radiative and thermodynamic functions of uranium carbide have a slight difference during liquid-to-solid transition. Unlike UC, such a difference between these ...

  9. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

    Veggel, A.A. van; Ende, D.A. van den; Bogenstahl, J.; Rowan, S.; Cunningham, W.; Gubbels, G.H.M.; Nijmeijer, H.

    2008-01-01

    For bonding silicon carbide optics, which require extreme stability, hydroxide catalysis bonding is considered [Rowan, S., Hough, J. and Elliffe, E., Silicon carbide bonding. UK Patent 040 7953.9, 2004. Please contact Mr. D. Whiteford for further information: D.Whiteford@admin.gla.ac.uk]. This

  10. Ternary networks reliability and Monte Carlo

    CERN Document Server

    Gertsbakh, Ilya; Vaisman, Radislav

    2014-01-01

    Ternary means “based on three”. This book deals with reliability investigations of  networks whose components subject to failures can be in three states –up, down and middle (mid), contrary to traditionally considered networks  having only binary (up/down) components. Extending binary case to ternary allows to consider more realistic and flexible models for communication, flow and supply networks.

  11. Synthesis of ternary nitrides by mechanochemical alloying

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Zhu, J.J.; Lindelov, H.

    2002-01-01

    Ternary metal nitrides ( of general formula MxM'N-y(z)) attract considerable interest because of their special mechanical, electrical, magnetic, and catalytic properties. Usually they are prepared by ammonolysis of ternary oxides (MxM'O-y(m)) at elevated temperatures. We show that ternary...... nitrides by mechanochemical alloying of a binary transition metal nitride (MxN) with an elemental transition metal. In this way, we have been able to prepare Fe3Mo3N and Co3Mo3N by ball-milling of Mo2N with Fe and Co, respectively. The transformation sequence from the starting materials ( the binary...... nitride and the transition metal) to the ternary nitride was followed by Mossbauer spectroscopy (for Fe3Mo3N) and by X-ray powder diffraction ( for both Fe3Mo3N and Co3Mo3N). Usually, the preparation of a given ternary nitride by ammonolysis of a ternary oxide is dependent on the availability of an oxide...

  12. Bergman Clusters, Multiple Bonds, and Defect Planes: Synthetic Outcomes of Chemical Frustration in Ternary Intermetallic Systems

    Science.gov (United States)

    Hadler, Amelia Beth

    Intermetallics crystallize in a variety of complex structures, many of which show unusual bonding or intriguing properties. Understanding what factors drive this structural chemistry would be a valuable step towards designing new intermetallics with specific structures or properties. One pathway towards understanding and predicting the structures of complex intermetallics is chemical frustration, a design tool which harnesses competition between incompatible bonding or packing modes to induce complexity in ternary intermetallic systems. The research outlined in this thesis focuses on developing chemical frustration through exploratory synthesis in ternary systems designed to induce frustration between the tetrahedral close packing of many intermetallics and the simple cubic packing seen for ionic salts or elemental metals. Syntheses in three systems yielded six new ternary intermetallics, four of which crystallize in novel structure types. Three were discovered in the Ca-Cu-Cd system: Ca5Cu2Cd and Ca2Cu 2Cd9, which adopt ternary variants of binary structures, and Ca10Cu2Cd27, which crystallizes in a new structure built from Bergman clusters. All three structures can be traced to electronic packing frustration induced by the similar electronegativities but different metallic radii of Cu and Cd. The Gd-Fe-C system yielded the new carbometalate Gd13Fe 10C13 and an oxycarbide derivative. These phases crystallize in structures built from Gd tricapped trigonal prisms interpenetrated by an Fe-C network. Theoretical analyses reveal that Fe-Fe and Fe-C multiple bonding is found throughout this network. A theoretical investigation of similar carbides uncovers additional metal-metal, metal-carbon, and carbon-carbon multiple bonding. This unusual bonding stabilizes the carbides by satisfying preferred electron counts for their transition metal sites. One new phase, Mg4.5Pd5Ge1.5, was found in the Mg-Pd-Ge system. Its structure is closely related to the CsCl-type structure of

  13. Fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, Hirofumi.

    1989-05-22

    This invention aims to maintain a long-term operation with stable cell output characteristics by uniformly supplying an electrolyte from the reserver to the matrix layer over the entire matrix layer, and further to prevent the excessive wetting of the catalyst layer by smoothly absorbing the volume change of the electrolyte, caused by the repeated stop/start-up of the fuel cell, within the reserver system. For this purpose, in this invention, an electrolyte transport layer, which connects with an electrolyte reservor formed at the electrode end, is partly formed between the electrode material and the catalyst layer; a catalyst layer, which faces the electrolyte transport layer, has through-holes, which connect to the matrix, dispersely distributed. The electrolyte-transport layer is a thin sheet of a hydrophilic fibers which are non-wovens of such fibers as carbon, silicon carbide, silicon nitride or inorganic oxides. 11 figs.

  14. Thermal Expansion of Hafnium Carbide

    Science.gov (United States)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  15. Ternary interaction parameters in calphad solution models

    Energy Technology Data Exchange (ETDEWEB)

    Eleno, Luiz T.F., E-mail: luizeleno@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Fisica; Schön, Claudio G., E-mail: schoen@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Computational Materials Science Laboratory. Department of Metallurgical and Materials Engineering

    2014-07-01

    For random, diluted, multicomponent solutions, the excess chemical potentials can be expanded in power series of the composition, with coefficients that are pressure- and temperature-dependent. For a binary system, this approach is equivalent to using polynomial truncated expansions, such as the Redlich-Kister series for describing integral thermodynamic quantities. For ternary systems, an equivalent expansion of the excess chemical potentials clearly justifies the inclusion of ternary interaction parameters, which arise naturally in the form of correction terms in higher-order power expansions. To demonstrate this, we carry out truncated polynomial expansions of the excess chemical potential up to the sixth power of the composition variables. (author)

  16. Ternary carbon composite films for supercapacitor applications

    Science.gov (United States)

    Tran, Minh-Hai; Jeong, Hae Kyung

    2017-09-01

    A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1933 m2 g-1 and low equivalent series resistance of 2 Ω, demonstrating that it improve the electrochemical performance for supercapacitor applications.

  17. A study of phase separation in ternary alloys

    Indian Academy of Sciences (India)

    Keywords. Ternary systems; Cahn–Hilliard equations; spinodal decomposition. Abstract. We have studied the evolution of microstructure when a disordered ternary alloy is quenched into a ternary miscibility gap. We have used computer simulations based on multicomponent Cahn–Hilliard (CH) equations for A and B, ...

  18. Wear and corrosion behaviour of tungsten carbide based coatings with different metallic binder

    Science.gov (United States)

    Kamdi, Z.; Apandi, M. N. M.; Ibrahim, M. D.

    2017-12-01

    Tungsten carbide based coating has been well known as wear and corrosion resistance materials. However, less study is done on comparing the coating with different binder. Thus, in this work the wear and corrosion behaviour of high velocity oxy-fuel (HVOF) coatings, namely (i) tungsten carbide cobalt and (ii) tungsten carbide nickel will be evaluated. Both coatings were characterised using X-ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). The wear behaviour has been examined using the modified grinder machine by weight loss measurement. Two types of abrasive have been used that include 3 g by weight alumina and silica. While for the corrosion behaviour, it is monitored by three electrodes of electrochemical test and immersion test for 30 days in an acidic environment. The electrolyte used was 0.5 M sulphuric acids (H2SO4). It was found that the cobalt binder shows higher wear resistance compares to the nickel binder for both slurry types. The harder alumina compared to silica results in higher wear rate with removal of carbide and binder is about the same rate. For silica abrasive, due to slightly lower hardness compared to the carbide, the wear is dominated by binder removal followed by carbide detachment. For corrosion, the nickel binder shows four times higher wear resistance compared to the cobalt binder as expected due to its natural behaviour. These finding demonstrate that the selection of coating to be used in different application in this case, wear and corrosion shall be chosen carefully to maximize the usage of the coating.

  19. Ternary-fragmentation-driving potential energies of 252Cf

    Science.gov (United States)

    Karthikraj, C.; Ren, Zhongzhou

    2017-12-01

    Within the framework of a simple macroscopic model, the ternary-fragmentation-driving potential energies of 252Cf are studied. In this work, all possible ternary-fragment combinations of 252Cf are generated by the use of atomic mass evaluation-2016 (AME2016) data and these combinations are minimized by using a two-dimensional minimization approach. This minimization process can be done in two ways: (i) with respect to proton numbers (Z1, Z2, Z3) and (ii) with respect to neutron numbers (N1, N2, N3) of the ternary fragments. In this paper, the driving potential energies for the ternary breakup of 252Cf are presented for both the spherical and deformed as well as the proton-minimized and neutron-minimized ternary fragments. From the proton-minimized spherical ternary fragments, we have obtained different possible ternary configurations with a minimum driving potential, in particular, the experimental expectation of Sn + Ni + Ca ternary fragmentation. However, the neutron-minimized ternary fragments exhibit a driving potential minimum in the true-ternary-fission (TTF) region as well. Further, the Q -value energy systematics of the neutron-minimized ternary fragments show larger values for the TTF fragments. From this, we have concluded that the TTF region fragments with the least driving potential and high Q values have a strong possibility in the ternary fragmentation of 252Cf. Further, the role of ground-state deformations (β2, β3, β4, and β6) in the ternary breakup of 252Cf is also studied. The deformed ternary fragmentation, which involves Z3=12 -19 fragments, possesses the driving potential minimum due to the larger oblate deformations. We also found that the ground-state deformations, particularly β2, strongly influence the driving potential energies and play a major role in determining the most probable fragment combinations in the ternary breakup of 252Cf.

  20. Porous nuclear fuel element for high-temperature gas-cooled nuclear reactors

    Science.gov (United States)

    Youchison, Dennis L [Albuquerque, NM; Williams, Brian E [Pacoima, CA; Benander, Robert E [Pacoima, CA

    2011-03-01

    Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

  1. Porous nuclear fuel element with internal skeleton for high-temperature gas-cooled nuclear reactors

    Science.gov (United States)

    Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

    2013-09-03

    Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

  2. Self-triggered coordination with ternary controllers

    NARCIS (Netherlands)

    De Persis, Claudio; Frasca, Paolo

    2012-01-01

    This paper regards coordination of networked systems with ternary controllers. We develop a hybrid coordination system which implements a self-triggered communication policy, based on polling the neighbors upon need. We prove that the proposed scheme ensures finite-time convergence to a neighborhood

  3. Ternary Dynamic Images In Robotic Smooth Pursuit

    Science.gov (United States)

    Morasso, Pietro; Tagliasco, Vincenzo

    1984-02-01

    Early stages of visuo-motor interaction are considered with regard to dynamic scene analysis. Target fixation and tracking is distinguished from target visual analysis. The notion of target specification is elaborated upon. The use of ternary dynamic images is shown as an example of target tracking.

  4. Ternary alloy nanocatalysts for hydrogen evolution reaction

    Indian Academy of Sciences (India)

    Ternary alloy nanocatalysts for hydrogen evolution reaction. SOUMEN SAHA1, SONALIKA VAIDYA2, KANDALAM V RAMANUJACHARY3,. SAMUEL E LOFLAND4 and ASHOK K GANGULI1,2,∗. 1Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India. 2Institute of Nano Science and ...

  5. First-principles study of point defects in thorium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Pérez Daroca, D., E-mail: pdaroca@tandar.cnea.gov.ar [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, (1033) Buenos Aires (Argentina); Jaroszewicz, S. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Llois, A.M. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, (1033) Buenos Aires (Argentina); Mosca, H.O. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA, Av. General Paz 1499, (1650) San Martin, Buenos Aires (Argentina)

    2014-11-15

    Thorium-based materials are currently being investigated in relation with their potential utilization in Generation-IV reactors as nuclear fuels. One of the most important issues to be studied is their behavior under irradiation. A first approach to this goal is the study of point defects. By means of first-principles calculations within the framework of density functional theory, we study the stability and formation energies of vacancies, interstitials and Frenkel pairs in thorium carbide. We find that C isolated vacancies are the most likely defects, while C interstitials are energetically favored as compared to Th ones. These kind of results for ThC, to the best authors’ knowledge, have not been obtained previously, neither experimentally, nor theoretically. For this reason, we compare with results on other compounds with the same NaCl-type structure.

  6. Magnetic composites based on metallic nickel and molybdenum carbide: a potential material for pollutants removal.

    Science.gov (United States)

    Mambrini, Raquel V; Fonseca, Thales L; Dias, Anderson; Oliveira, Luiz C A; Araujo, Maria Helena; Moura, Flávia C C

    2012-11-30

    New magnetic composites based on metallic nickel and molybdenum carbide, Ni/Mo(2)C, have been produced via catalytic chemical vapor deposition from ethanol. Scanning electron microscopy, thermal analysis, Raman spectroscopy and X-ray diffraction studies suggest that the CVD process occurs in a single step. This process involves the reduction of NiMo oxides at different temperatures (700, 800 and 900°C) with catalytic deposition of carbon from ethanol producing molybdenum carbide on Ni surface. In the absence of molybdenum the formation of Ni/C was observed. The magnetic molybdenum carbide was successfully used as pollutants removal by adsorption of sulfur and nitrogen compounds from liquid fuels and model dyes such as methylene blue and indigo carmine. The dibenzothiofene adsorption process over Ni/Mo(2)C reached approximately 20 mg g(-1), notably higher than other materials described in the literature and also removed almost all methylene blue dye. The great advantage of these carbide composites is that they may be easily recovered magnetically and reused. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Carbides composite surface layers produced by (PTA)

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-12-16

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

  8. Silicon Carbide Etching Using Chlorine Trifluoride Gas

    Science.gov (United States)

    Habuka, Hitoshi; Oda, Satoko; Fukai, Yasushi; Fukae, Katsuya; Takeuchi, Takashi; Aihara, Masahiko

    2005-03-01

    The etch rate, chemical reactions and etched surface of β-silicon carbide are studied in detail using chlorine trifluoride gas. The etch rate is greater than 10 μm min-1 at 723 K with a flow rate of 0.1 \\ell min-1 at atmospheric pressure in a horizontal reactor. The maximum etch rate at a substrate temperature of 773 K is 40 μm min-1 with a flow rate of 0.25 \\ell min-1. The step-like pattern that initially exists on the β-silicon carbide surface tends to be smoothed; the root-mean-square surface roughness decreases from its initial value of 5 μm to 1 μm within 15 min; this minimum value is maintained for more than 15 min. Therefore, chlorine trifluoride gas is considered to have a large etch rate for β-silicon carbide associated with making a rough surface smooth.

  9. Silicon carbide microsystems for harsh environments

    CERN Document Server

    Wijesundara, Muthu B J

    2011-01-01

    Silicon Carbide Microsystems for Harsh Environments reviews state-of-the-art Silicon Carbide (SiC) technologies that, when combined, create microsystems capable of surviving in harsh environments, technological readiness of the system components, key issues when integrating these components into systems, and other hurdles in harsh environment operation. The authors use the SiC technology platform suite the model platform for developing harsh environment microsystems and then detail the current status of the specific individual technologies (electronics, MEMS, packaging). Additionally, methods

  10. Low alloy steels that minimize the hydrogen-carbide reaction. Final technical report, October 1, 1978-September 30, 1979. Part I

    Energy Technology Data Exchange (ETDEWEB)

    Kar, R. J.; Parker, E. R.; Zackay, V. F.

    1979-01-01

    This report presents results obtained during the first year of a research program to investigate important metallurgical parameters that control the reactions of hydrogen with carbides in steels. Preliminary work included a detailed literature review of th phenomenon of decarburization and methane bubble formation in steels and a suitable experimental technique for investigating hydrogen attack in laboratory conditions was established. Detailed microstructural-mechanical property evaluations were carried out on two series of alloys; the first was based on a plain carbon steel to which binary and ternary alloy additions were made to vary the carbide structure and morphology and assess these effects on the observed hydrogen attack resistance. The second group of steels consisted of commercial Mn-Mo-Ni (A 533 B) and Cr-Mo (A 542 type) steels and their alloy modifications, with a view towards developing steels with improved hydrogen attack resistance.

  11. Ternary rare earth-lanthanide sulfides

    Science.gov (United States)

    Takeshita, Takuo; Gschneidner, Jr., Karl A.; Beaudry, Bernard J.

    1987-01-06

    A new ternary rare earth sulfur compound having the formula: La.sub.3-x M.sub.x S.sub.4 where M is a rare earth element selected from the group europium, samarium and ytterbium and x=0.15 to 0.8. The compound has good high-temperature thermoelectric properties and exhibits long-term structural stability up to 1000.degree. C.

  12. Panchromatic Sequentially Cast Ternary Polymer Solar Cells.

    Science.gov (United States)

    Ghasemi, Masoud; Ye, Long; Zhang, Qianqian; Yan, Liang; Kim, Joo-Hyun; Awartani, Omar; You, Wei; Gadisa, Abay; Ade, Harald

    2017-01-01

    A sequential-casting ternary method is developed to create stratified bulk heterojunction (BHJ) solar cells, in which the two BHJ layers are spin cast sequentially without the need of adopting a middle electrode and orthogonal solvents. This method is found to be particularly useful for polymers that form a mechanically alloyed morphology due to the high degree of miscibility in the blend. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Ternary alloy nanocatalysts for hydrogen evolution reaction

    Indian Academy of Sciences (India)

    Cu–Fe–Ni ternary alloys (size ∼55–80 nm) with varying compositions viz. CuFeNi (A1), CuFe2Ni (A2) and CuFeNi2 (A3) were successfully synthesized using microemulsion. It is to be noted that synthesis of nanocrystallineternary alloys with precise composition is a big challenge which can be overcome by choosing an ...

  14. Fuel flexible fuel injector

    Science.gov (United States)

    Tuthill, Richard S; Davis, Dustin W; Dai, Zhongtao

    2015-02-03

    A disclosed fuel injector provides mixing of fuel with airflow by surrounding a swirled fuel flow with first and second swirled airflows that ensures mixing prior to or upon entering the combustion chamber. Fuel tubes produce a central fuel flow along with a central airflow through a plurality of openings to generate the high velocity fuel/air mixture along the axis of the fuel injector in addition to the swirled fuel/air mixture.

  15. Equilibrium study for ternary mixtures of biodiesel

    Science.gov (United States)

    Doungsri, S.; Sookkumnerd, T.; Wongkoblap, A.; Nuchitprasittichai, A.

    2017-11-01

    The liquid-liquid equilibrium (LLE) data for the ternary mixtures of methanol + fatty acid methyl ester (FAME) + palm oil and FAME + palm oil + glycerol at various temperatures from 35 to 55°C, the tie lines and binodial curves were also investigated and plotted in the equilibrium curve. The experimental results showed that the binodial curves of methanol + FAME + palm oil depended significantly with temperature while the binodial curves of FAME + palm oil + glycerol illustrated insignificant change with temperatures. The interaction parameters between liquid pair obtained for NRTL (Nonrandom Two-Liquid) and UNIQUAC (Universal Quasi-Chemical Theory) models from the experimental data were also investigated. It was found that the correlated parameters of UNIQUAC model for system of FAME + palm oil + glycerol, denoted as a13 and a31, were 580.42K and -123.69K, respectively, while those for system of methanol + FAME + palm oil, denoted as a42 and a24, were 71.48 K and 965.57K, respectively. The ternary LLE data reported here would be beneficial for engineers and scientists to use for prediction of yield and purity of biodiesel for the production. The UNIQUAC model agreed well with the experimental data of ternary mixtures of biodiesel.

  16. The Ternary Alpha Energy Distribution Revisited

    Science.gov (United States)

    Wagemans, Cyriel; Janssens, Peter; Heyse, Jan; Serot, Olivier; Geltenbort, Peter; Soldner, Torsten

    2004-02-01

    The shape of the energy distribution of the particles emitted in ternary fission has been studied since the discovery of the phenomenon for a large variety of fissioning systems. The general tendency of the observations is that most particles have a Gaussian-shaped energy distribution, except the α-particles, for which mostly an important non-Gaussian tailing on the low-energy side is reported. The origin of this tailing is generally ascribed to the decay of ternary 5He particles in an α-particle and a neutron. Since the experiments reported in the literature are rarely optimised for measuring the low-energy part of the α-spectrum, we realised good experimental conditions for studying the 235U(nth,f) ternary α energy distribution at the High Flux Reactor of the ILL in Grenoble. Thanks to a very intense and clean neutron beam, a small, very thin sample of highly enriched U could be used, with an activity of only 1.6 Bq. So the measurements could be done without absorber in between the sample and the ΔE-E detector. With the resulting low detection limit of 6 MeV, a clearly asymmetric energy distribution was obtained, in agreement with most data in the literature.

  17. More statistics on intermetallic compounds - ternary phases.

    Science.gov (United States)

    Dshemuchadse, Julia; Steurer, Walter

    2015-05-01

    How many different intermetallic compounds are known so far, and in how many different structure types do they crystallize? What are their chemical compositions, the most abundant ones and the rarest ones? These are some of the questions we are trying to find answers for in our statistical analysis of the structures of the 20,829 intermetallic phases included in the database Pearson's Crystal Data, with the goal of gaining insight into some of their ordering principles. In the present paper, we focus on the subset of 13,026 ternary intermetallics, which crystallize in 1391 different structure types; remarkably, 667 of them have just one representative. What makes these 667 structures so unique that they are not adopted by any other of the known intermetallic compounds? Notably, ternary compounds are known in only 5109 of the 85,320 theoretically possible ternary intermetallic systems so far. In order to get an overview of their chemical compositions we use structure maps with Mendeleev numbers as ordering parameters.

  18. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Carbon incorporation into the silicate network results in the formation of rigid carbidic glasses with improved physical, mechanical and thermal properties. This generated great interest in the development of these heteroatom structured materials through different processing routes. In the present studies, sol–gel.

  19. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    Carbon incorporation into the silicate network results in the formation of rigid carbidic glasses with improved physical, mechanical and thermal properties. This generated great interest in the development of these heteroatom structured materials through different processing routes. In the present studies, sol–gel processing ...

  20. Producing Silicon Carbide/Silicon Nitride Fibers

    Science.gov (United States)

    1986-01-01

    Manufacturing process makes CxSiyNz fibers. Precursor fibers spun from extruding machine charged with polycarbosilazane resin. When pyrolyzed, resin converted to cross-linked mixture of silicon carbide and silicon nitride, still in fiber form. CxSiyNz fibers promising substitutes for carbon fibers in high-strength, low-weight composites where high electrical conductivity unwanted.

  1. Casimir forces from conductive silicon carbide surfaces

    NARCIS (Netherlands)

    Sedighi Ghozotkhar, Mehdi; Svetovoy, V. B.; Broer, W. H.; Palasantzas, G.

    2014-01-01

    Samples of conductive silicon carbide (SiC), which is a promising material due to its excellent properties for devices operating in severe environments, were characterized with the atomic force microscope for roughness, and the optical properties were measured with ellipsometry in a wide range of

  2. Silicon Carbide Power Devices and Integrated Circuits

    Science.gov (United States)

    Lauenstein, Jean-Marie; Casey, Megan; Samsel, Isaak; LaBel, Ken; Chen, Yuan; Ikpe, Stanley; Wilcox, Ted; Phan, Anthony; Kim, Hak; Topper, Alyson

    2017-01-01

    An overview of the NASA NEPP Program Silicon Carbide Power Device subtask is given, including the current task roadmap, partnerships, and future plans. Included are the Agency-wide efforts to promote development of single-event effect hardened SiC power devices for space applications.

  3. Visible light emission from porous silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang

    2017-01-01

    Light-emitting silicon carbide is emerging as an environment-friendly wavelength converter in the application of light-emitting diode based white light source for two main reasons. Firstly, SiC has very good thermal conductivity and therefore a good substrate for GaN growth in addition to the small...

  4. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    In firing of products by conventionally sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered silicon carbide by such a method is a useful material for a varieties of applications ranging from kiln furniture to membrane material.

  5. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first...... demonstrates that details of the coordination geometry affect the carbide chemical shift equally as much as variations in the nature of the auxiliary ligands. Furthermore, the kinetics of formation of the sqaure pyramidal dicyano complex, trans-[RuC(CN)2(PCy3)2], from RuC has been examined and the reaction...... found to be quite sluggish and of first order in both RuC and cyanide with a rate constant of k = 0.0104(6) M–1 s–1. Further reaction with cyanide leads to loss of the carbide ligand and formation of trans-[Ru(CN)4(PCy3)2]2–, which was isolated and structurally characterized as its PPh4+ salt....

  6. Pyrotechnic Smoke Compositions Containing Boron Carbide

    Science.gov (United States)

    2012-06-10

    approach the performance of the AN-M8 HC composition (Al/ZnO/C2Cl6). 15. SUBJECT TERMS smoke, pyrotechnic, boron carbide 16. SECURITY CLASSIFICATION ...reduction of phosphate. This hypothesis was confirmed in an unexpected and alarming way, when the strong fishy- garlic odor of phosphorus and phosphines

  7. Ternary q-Virasoro-Witt Hom-Nambu-Lie algebras

    Energy Technology Data Exchange (ETDEWEB)

    Ammar, F [Faculte des Sciences, Universite de Sfax, BP 1171, 3000 Sfax (Tunisia); Makhlouf, A [Laboratoire de Mathematiques, Informatique et Applications, Universite de Haute Alsace, 4, rue des Freres Lumiere F-68093 Mulhouse (France); Silvestrov, S, E-mail: Faouzi.Ammar@rnn.fss.t, E-mail: Abdenacer.Makhlouf@uha.f, E-mail: sergei.silvestrov@math.lth.s [Centre for Mathematical Sciences, Lund University, Box 118, SE-221 00 Lund (Sweden)

    2010-07-02

    In this paper we construct ternary q-Virasoro-Witt algebras which q-deform the ternary Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos using su(1, 1) enveloping algebra techniques. The ternary Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos depend on a parameter and are not Nambu-Lie algebras for all but finitely many values of this parameter. For the parameter values for which the ternary Virasoro-Witt algebras are Nambu-Lie, the corresponding ternary q-Virasoro-Witt algebras constructed in this paper are also Hom-Nambu-Lie because they are obtained from the ternary Nambu-Lie algebras using the composition method. For other parameter values this composition method does not yield a Hom-Nambu-Lie algebra structure for q-Virasoro-Witt algebras. We show however, using a different construction, that the ternary Virasoro-Witt algebras of Curtright, Fairlie and Zachos, as well as the general ternary q-Virasoro-Witt algebras we construct, carry a structure of the ternary Hom-Nambu-Lie algebra for all values of the involved parameters.

  8. Design and Thermal Analysis for Irradiation of Pyrolytic Carbon/Silicon Carbide Diffusion Couples in the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Gerczak, Tyler J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Smith, Kurt R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    Tristructural-isotropic (TRISO)–coated particle fuel is a promising advanced fuel concept consisting of a spherical fuel kernel made of uranium oxide and uranium carbide, surrounded by a porous carbonaceous buffer layer and successive layers of dense inner pyrolytic carbon (IPyC), silicon carbide (SiC) deposited by chemical vapor , and dense outer pyrolytic carbon (OPyC). This fuel concept is being considered for advanced reactor applications such as high temperature gas-cooled reactors (HTGRs) and molten salt reactors (MSRs), as well as for accident-tolerant fuel for light water reactors (LWRs). Development and implementation of TRISO fuel for these reactor concepts support the US Department of Energy (DOE) Office of Nuclear Energy mission to promote safe, reliable nuclear energy that is sustainable and environmentally friendly. During operation, the SiC layer serves as the primary barrier to metallic fission products and actinides not retained in the kernel. It has been observed that certain fission products are released from TRISO fuel during operation, notably, Ag, Eu, and Sr [1]. Release of these radioisotopes causes safety and maintenance concerns.

  9. Characterization on carbide of a novel steel for cold work roll during solidification process

    Energy Technology Data Exchange (ETDEWEB)

    Guo, J.; Liu, L.G.; Li, Q.; Sun, Y.L. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Gao, Y.K. [Institute of Aeronautical Materials, Beijing 100095 (China); Ren, X.J. [School of Engineering, Liverpool John Moores University, Liverpool L3 3AF (United Kingdom); Yang, Q.X., E-mail: qxyang@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2013-05-15

    A novel steel for cold work roll was developed in this work. Its phase structures were determined by X-ray diffraction, and phase transformation temperatures during the cooling process were measured by Differential Scanning Calorimeter. The Fe–C isopleths of the steel were calculated by Thermo-Calc to preliminarily determine the characteristic temperatures of the different phases. Then the specimens were quenched at these characteristic temperatures. The typical microstructures were observed by Optical Microscopy and Field Emission Scanning Electron Microscopy with Energy Disperse Spectroscopy. The results show that α-Fe, MC, M{sub 2}C and M{sub 7}C{sub 3} precipitate when the specimen is cooled slowly to room temperature. According to the DSC curve and the Fe–C isopleths, the characteristic temperatures of the phase transformation and carbide precipitation are chosen as 1380 °C, 1240 °C, 1200 °C and 1150 °C respectively. Primary austenite precipitates at 1380 °C, then eutectic reaction occurs in residual liquid after quenching and the eutectic microstructures distribute along the crystal grain boundary. The eutectic MC is leaf-like and eutectic M{sub 2}C is fibrous-like. Both of them precipitate in ternary eutectic reaction simultaneously at 1240 °C, grow together in the form of dendrite along the crystal grain boundary. Secondary MC precipitates from the austenitic matrix at 1200 °C and nucleates at the position where eutectic MC located accompanied by the dissolving of eutectic carbides. The mixed secondary M{sub 2}C and M{sub 7}C{sub 3} precipitate at 1150 °C. The secondary M{sub 2}C is strip-like and honeycomb-like, while the M{sub 7}C{sub 3} is chrysanthemum-like and maze-like. - Highlights: • The solidification process was analyzed by Thermo-Calc, DSC, XRD and SEM observation. • Primary and secondary carbides precipitated during solidification were determined. • The three dimensional morphologies of all carbides was observed. • The

  10. Rover fuel element development activities: July-September 1971

    Energy Technology Data Exchange (ETDEWEB)

    Napier, J.M.; Marrow, G.B.

    1971-11-30

    Experimental studies designed to fabricate NERVA graphite fuel elements capable of cyclic operations at exit gas temperatures of approximately 4400/degree/R were continued during this report period. Carbon precursor materials, manufacturing parameters, and deposition of carbide films are included in these studies. Accomplishments include the following: three commercial powders were extruded into elements having a desirable coefficient of thermal expansion; molded graphites using low-fired filler carbons and uncured short organic fibers produced graphites having an improved strain-to-failure value; thick-walled tubes of vapor-deposited zirconium carbide were produced, and the chemical composition was determined; vapor-deposited zirconium carbide coatings were applied to fuel-element bores; experimental graphite fuel elements were hot-gas tested; uranium-loaded ion exchange beads survived a heat treatment cycle of 2800/degree/C for three hours. Organic precursor carbon studies were oriented toward modification of the CAI polymers. 2 refs., 66 figs., 23 tabs.

  11. Balanced ternary addition using a gated silicon nanowire

    NARCIS (Netherlands)

    Mol, J.A.; Van der Heijden, J.; Verduijn, J.; Klein, M.; Remacle, F.; Rogge, S.

    2011-01-01

    Ternary logic has the lowest cost of complexity, here, we demonstrate a CMOS hardware implementation of a ternary adder using a silicon metal-on-insulator single electron transistor. Gate dependent rectifying behavior of a single electron transistor (SET) results in a robust three-valued output as a

  12. Density-Driven segregation in Binary and Ternary Granular Systems

    NARCIS (Netherlands)

    Windows-Yule, Kit; Parker, David

    2015-01-01

    We present a first experimental study of density-induced segregation within a three-dimensional, vibrofluidised, ternary granular system. Using Positron Emission Particle Tracking (PEPT), we study the steady-state particle distributions achieved by binary and ternary granular beds under a variety of

  13. A high-speed interconnect network using ternary logic

    DEFF Research Database (Denmark)

    Madsen, Jens Kargaard; Long, S. I.

    1995-01-01

    This paper describes the design and implementation of a high-speed interconnect network (ICN) for a multiprocessor system using ternary logic. By using ternary logic and a fast point-to-point communication technique called STARI (Self-Timed At Receiver's Input), the communication between...

  14. Densities and Excess Molar Volume for the Ternary Systems (1 ...

    African Journals Online (AJOL)

    methylimidazolium methyl sulphate ([BMIM]+[MeSO4]-) were determined. The ternary systems studied were ([BMIM]+[MeSO4]-+ nitromethane + methanol or ethanol or 1-propanol) at the temperatures (303.15 and 313.15) K. The ternary excess molar ...

  15. Single polymer-based ternary electronic memory material and device.

    Science.gov (United States)

    Liu, Shu-Juan; Wang, Peng; Zhao, Qiang; Yang, Hui-Ying; Wong, Jenlt; Sun, Hui-Bin; Dong, Xiao-Chen; Lin, Wen-Peng; Huang, Wei

    2012-06-05

    A ternary polymer memory device based on a single polymer with on-chain Ir(III) complexes is fabricated by combining multiple memory mechanisms into one system. Excellent ternary memory performances-low reading, writing, and erasing voltages and good stability for all three states-are achieved. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Formation of ternary Mg–Cu–Dy bulk metallic glasses

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The glass-forming ability (GFA) of ternary Mg–Cu–Dy alloys was systematically investigated by using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) techniques. The results showed that a series of ternary Mg–Cu–Dy bulk metallic glasses (BGMs) with a diameter of 4–8 mm were suc-.

  17. Tribological Characteristics of Tungsten Carbide Reinforced Arc Sprayed Coatings using Different Carbide Grain Size Fractions

    Directory of Open Access Journals (Sweden)

    W. Tillmann

    2017-06-01

    Full Text Available Tungsten carbide reinforced coatings play an important role in the field of surface engineering to protect stressed surfaces against wear. For thermally sprayed coatings, it is already shown that the tribological properties get mainly determined by the carbide grain size fraction. Within the scope of this study, the tribological characteristics of iron based WC-W2C reinforced arc sprayed coatings deposited using cored wires consisting of different carbide grain size fractions were examined. Microstructural characteristics of the produced coatings were scrutinized using electron microscopy and x-ray diffraction analyses. Ball-on-disk test as well as Taber Abraser and dry sand rubber wheel test were employed to analyze both the dry sliding and the abrasive wear behavior. It was shown that a reduced carbide grain size fraction as filling leads to an enhanced wear resistance against sliding. In terms of the Taber Abraser test, it is also demonstrated that a fine carbide grain size fraction results in an improved wear resistant against abrasion. As opposed to that, a poorer wear resistance was found within the dry sand rubber wheel tests. The findings show that the operating mechanisms for both abrasion tests affect the stressed surface in a different way, leading either to microcutting or microploughing.

  18. Polycation-Based Ternary Gene Delivery System.

    Science.gov (United States)

    Liu, Shuai; Guo, Tianying

    2015-01-01

    Recent progress in gene therapy has opened the door for various human diseases. The greatest challenge that gene vectors still face is the ability to sufficiently deliver nucleic acid into target cells. To overcome various barriers, plenty of researches have been undertaken utilizing diverse strategies, among which a wide variety of polycation/pDNA vectors have been developed and explored frequently. For enhanced transfection efficiency, polycations are constantly utilized with covalent modifications, which however lead to reduced positive charge density and changed properties of polycation/pDNA complexes. Accordingly, non-covalent or ternary strategy is proposed. The cationic properties of polycations can be retained and the transfection efficiency can be enhanced by introducing additional polymers with functional groups via non-covalent assembly. This review will discuss the construction and advantages of ternary complexes gene delivery system, including low toxicity and enhanced gene expression both in vitro and in vivo. Recent progress and expectations with promising results that may have some reference for clinical application are also discussed.

  19. Plasmonic spectral tunability of conductive ternary nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Kassavetis, S.; Patsalas, P., E-mail: ppats@physics.auth.gr [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Bellas, D. V.; Lidorikis, E. [Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina (Greece); Abadias, G. [Institut Pprime, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, 86962 Chasseneuil-Futuroscope (France)

    2016-06-27

    Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as Ti{sub x}Ta{sub 1−x}N, Ti{sub x}Zr{sub 1−x}N, Ti{sub x}Al{sub 1−x}N, and Zr{sub x}Ta{sub 1−x}N share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400–700 nm) and UVA (315–400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

  20. Irregular Homogeneity Domains in Ternary Intermetallic Systems

    Directory of Open Access Journals (Sweden)

    Jean-Marc Joubert

    2015-12-01

    Full Text Available Ternary intermetallic A–B–C systems sometimes have unexpected behaviors. The present paper examines situations in which there is a tendency to simultaneously form the compounds ABx, ACx and BCx with the same crystal structure. This causes irregular shapes of the phase homogeneity domains and, from a structural point of view, a complete reversal of site occupancies for the B atom when crossing the homogeneity domain. This work reviews previous studies done in the systems Fe–Nb–Zr, Hf–Mo–Re, Hf–Re–W, Mo–Re–Zr, Re–W–Zr, Cr–Mn–Si, Cr–Mo–Re, and Mo–Ni–Re, and involving the topologically close-packed Laves, χ and σ phases. These systems have been studied using ternary isothermal section determination, DFT calculations, site occupancy measurement using joint X-ray, and neutron diffraction Rietveld refinement. Conclusions are drawn concerning this phenomenon. The paper also reports new experimental or calculated data on Co–Cr–Re and Fe–Nb–Zr systems.

  1. Carbide and boride laser modification of steels

    Science.gov (United States)

    Major, Boguslaw; Ebner, Reinhold

    1997-10-01

    Microstructure modification by laser remelting or laser alloying was studied on carbon Ck45 and high speed steels. Laser remelting of Ck45 by overlapping laser tracks led to a great refinement of martensitic structure, especially in the heat affected zone of subsequent laser track. High speed steel (HSS) M2 after laser remelting showed, beside the tetragonal martensite, the diffraction lines of cubic carbides of the M6C and M12C types. Laser alloying of M2 HSS using vanadium carbide (VC) additions caused increasing of eutectic in the interdendritic space, which was accompanied with reduction of the M6C and rising of the MC. M2 HSS laser alloyed with molybdenum carbide (Mo2C) showed formation of the M6C for the hipereutectic compositions while at the highest concentrations of molybdenum, primary dendrites of the M2C and stabilized ferrite were stated. High additions of borides: CrB or VB2; developed formation of the primary borides of blocky type containing a high amount of W, Cr or W, V, respectively. Laser alloying of Ck45 by means of: CrB, VB2 and B4C showed: in the case of CrB an eutectic (alpha) '/M3(C,B)/M2B as well as primary precipitates of the M2B phase for hipereutectic compositions; by adding VB2, the M3B2 and M2B phases were identified experimentally for hipereutectic concentrations; for alloying using B4C, the cellular dendritic structure together with primary borides of the (tau) -M23(C,B)6 phase were stated for hipereutectic compositions. The phase diagrams of M2 HSS + (VC or Mo2C) as well as Ck45 + B4C systems were calculated to predict changes of the constitutions due to laser alloying. Comparison of the solidification structures established experimentally with the calculated phase diagrams revealed a good correlation for the carbides, especially.

  2. Manufacturing technology for contacts to silicon carbide

    Directory of Open Access Journals (Sweden)

    Kudryk Ya.Ya.

    2013-02-01

    Full Text Available The authors classified the results of investigations of resistivity of ohmic contacts to silicon carbide made without any semiconductor surface modification. A set of contacts with better parameters were analysed. From the results of this analysis, some recommendations were made concerning optimal contact-forming layers for p- and n-SiC types of 4H, 6H, 3C, 15R, 21R polytypes.

  3. Low blow Charpy impact of silicon carbides

    Science.gov (United States)

    Abe, H.; Chandan, H. C.; Bradt, R. C.

    1978-01-01

    The room-temperature impact resistance of several commercial silicon carbides was examined using an instrumented pendulum-type machine and Charpy-type specimens. Energy balance compliance methods and fracture toughness approaches, both applicable to other ceramics, were used for analysis. The results illustrate the importance of separating the machine and the specimen energy contributions and confirm the equivalence of KIc and KId. The material's impact energy was simply the specimen's stored elastic strain energy at fracture.

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

    Energy Technology Data Exchange (ETDEWEB)

    Reiche, Helmut Matthias [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-25

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

  5. Stereology of carbide phase in modified hypereutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

    Full Text Available In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and rare-earth (RE. The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  6. Thermal conductivity of rare earth-uranium ternary oxides of the type RE 6UO 12

    Science.gov (United States)

    Krishnaiah, M. V.; Seenivasan, G.; Srirama Murti, P.; Mathews, C. K.

    2002-11-01

    The knowledge of thermophysical properties of the rare earth uranium ternary oxides of the type RE 6UO 12 (RE=La, Gd and Dy) is essential to understand the fuel performance during reactor operation and for modeling fuel behavior. Literature on the high temperature properties of this compound is not available and there is no report at all on the thermal conductivity of these compounds. Hence a study of thermal conductivity of this compound has been taken up. The compounds were synthesized by a solution combustion method using metal nitrates and urea. Thermal diffusivity of these compounds was measured by the laser flash method in the temperature range 673-1373 K. The specific heat data was computed using Neumann-Kopp's law. Thermal conductivity was calculated using the measured thermal diffusivity value, density and specific heat data for different temperatures. The temperature dependence of thermal conductivity and the implication of structural aspects of these compounds on the data are discussed here.

  7. Silicon Carbide Corrugated Mirrors for Space Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Trex Enterprises Corporation (Trex) proposes technology development to manufacture monolithic, lightweight silicon carbide corrugated mirrors (SCCM) suitable for...

  8. Carbides in Nodular Cast Iron with Cr and Mo

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2007-07-01

    Full Text Available In these paper results of elements microsegregation in carbidic nodular cast iron have been presented. A cooling rate in the centre of the cross-section and on the surface of casting and change of moulding sand temperature during casting crystallization and its self-cooling have been investigated. TDA curves have been registered. The linear distribution of elements concentration in an eutectic grain, primary and secondary carbides have been made. It was found, that there are two kinds of carbides: Cr and Mo enriched. A probable composition of primary and secondary carbides have been presented.

  9. Characterization of silicon-silicon carbide ceramic derived from carbon-carbon silicon carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Vijay K. [Indian Institute of Technology, Varanasi (India). Dept. of Mechanical Engineering; Krenkel, Walter [Univ. of Bayreuth (Germany). Dept. of Ceramic Materials Engineering

    2013-04-15

    The main objective of the present work is to process porous silicon - silicon carbide (Si - SiC) ceramic by the oxidation of carboncarbon silicon carbide (C/C - SiC) composites. Phase studies are performed on the oxidized porous composite to examine the changes due to the high temperature oxidation. Further, various characterization techniques are performed on Si- SiC ceramics in order to study the material's microstructure. The effects of various parameters such as fiber alignment (twill weave and short/chopped fiber) and phenolic resin type (resol and novolak) are characterized.

  10. FLiNaK compatibility studies with Inconel 600 and silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Yoder, Graydon L., E-mail: yodergljr@ornl.gov [Oak Ridge National Laboratory, Bldg. 5700, MS 6167 Bethel Valley Rd., Oak Ridge, TN 37831 (United States); Heatherly, Dennis; Wilson, Dane [Oak Ridge National Laboratory, Bldg. 5700, MS 6167 Bethel Valley Rd., Oak Ridge, TN 37831 (United States); Caja, Mario [Electrochemical Systems, Inc. (ESI), 9320 Collingwood Rd., Knoxville, TN 37922 (United States)

    2016-10-15

    Highlights: • A versatile experimental design has been developed to examine liquid fluoride salt materials compatibility behavior. • Samples of silicon carbide and a grafoil/nickel spiral wound gasket were exposed to FLiNaK salt at 700 °C for 90 days and showed no degradation. • Alloy 600 showed material effects penetrating up to 300 μm below the salt interface after exposure to the salt for 90 days at 700 °C. • Comparison of the Alloy 600 corrosion results with existing data indicated that results were comparable to the few corrosion results available for Alloy 600. • Sapphire viewing windows incorporated in the experiment showed fogging by condensed salt components at the highest test temperatures. - Abstract: A small liquid fluoride salt test apparatus has been constructed and testing has been conducted to examine the compatibility of silicon carbide (SiC), Inconel 600 and a spiral wound gasket material in FLiNaK, the ternary eutectic alkaline metal fluoride salt mixture. These tests were conducted to evaluate materials and sealing systems that could be used in fluoride salt systems. Three months of testing at 700 °C was conducted to assure that these materials and seals would be acceptable when operating under prototypic operating conditions. The SiC specimens showed little or no change over the test period, while the spiral wound gasket material did not show any degradation except that salt might have been seeping into the outermost spirals of the gasket. The Inconel 600 specimens showed regions of voiding which penetrated the specimen surface to about 250 μm in depth. Analysis indicated that the salt had leached chrome from the Inconel surface, as was expected for this material.

  11. Processes and applications of silicon carbide nanocomposite fibers

    Science.gov (United States)

    Shin, D. G.; Cho, K. Y.; Jin, E. J.; Riu, D. H.

    2011-10-01

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and γ-Al2O3. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200°C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  12. Facile Synthesis of Ternary Boron Carbonitride Nanotubes

    Directory of Open Access Journals (Sweden)

    Luo Lijie

    2009-01-01

    Full Text Available Abstract In this study, a novel and facile approach for the synthesis of ternary boron carbonitride (B–C–N nanotubes was reported. Growth occurred by heating simple starting materials of boron powder, zinc oxide powder, and ethanol absolute at 1150 °C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B–C–N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor–liquid–solid (VLS mechanism was proposed for the growth of the nanotubes.

  13. The ternary system: Silicon-tantalum-uranium

    Energy Technology Data Exchange (ETDEWEB)

    Rogl, Peter, E-mail: peter.franz.rogl@univie.ac.a [Institute of Physical Chemistry, University of Vienna, A-1090 Wien, Waehringerstrasse 42 (Austria); Noel, Henri [Laboratoire de Chimie du Solide et Materiaux, UMR-CNRS 6226, Universite de Rennes I, Avenue du General Leclerc, F-35042 Rennes, Cedex (France)

    2010-09-01

    Phase equilibria in the ternary system Si-Ta-U have been established in an isothermal section at 1000 {sup o}C by optical microscopy, electron probe microanalysis and X-ray diffraction. Two novel ternary compounds were observed and were characterised by X-ray powder Rietveld refinement: stoichiometric {tau}{sub 1}-U{sub 2}Ta{sub 3}Si{sub 4} (U{sub 2}Mo{sub 3}Si{sub 4}-type, P2{sub 1}/c; a = 0.70011(1), b = 0.70046(1), c = 0.68584(1) nm, ss = 109.38(1); R{sub F} = 0.073, X-ray powder Rietveld refinement) and {tau}{sub 2}-U{sub 2-x}Ta{sub 3+x}Si{sub 4} at x {approx} 0.30 (Sc{sub 2}Re{sub 3}Si{sub 4}-type = partially ordered Zr{sub 5}Si{sub 4}-type, P4{sub 1}2{sub 1}2; a = b = 0.69717(3)(1), c = 1.28709(4) nm; R{sub F} = 0.056; X-ray single crystal data). Mutual solubility of U-silicides and Ta-silicides are found to be very small i.e. below about 1 at.%. Due to the equilibrium tie-line Ta{sub 2}Si-U(Ta), no compatibility exists between the U-rich silicides U{sub 3}Si or U{sub 3}Si{sub 2} and tantalum metal. Single crystals obtained from alloys slowly cooled from liquid (2000 {sup o}C), yielded a fully ordered compound U{sub 2}Ta{sub 2}Si{sub 3}C (unique structure type; Pmna, a = 0.68860(1); b = 2.17837(4); c = 0.69707(1) nm; R{sub F2} = 0.048).

  14. Characterisation of TRISO fuel particles

    Energy Technology Data Exchange (ETDEWEB)

    Lopez H, E. [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Saltillo, Carretera Saltillo-Monterrey Km 13.5, 25900 Ramos Arizpe, Coahuila (Mexico); Yang, D., E-mail: eddie.lopez@cinvestav.edu.mx [The Academy of Armoured Forces Engineering, Science and Technology on Remanufacturing Laboratory, 100072 Beijing (China)

    2012-10-15

    The TRISO (tri structural isotropic) coated fuel particle is a key component contributing to the inherent safety of the High Temperature Reactor. A uranium kernel is coated with three layers of pyrolytic carbon and one of silicon carbide. The purpose of these coatings is to work as a miniature fission product containment vessel capable of enclosing all important radio nuclei under normal and off-normal reactor operating conditions. Due to the importance of these coatings, is of great interest to establish characterisation techniques capable of providing a detailed description of their microstructure and physical properties. Here we describe the use of Raman spectroscopy and two modulator generalised ellipsometry to study the anisotropy and thermal conductivity of pyrolytic carbon coatings, as well as the stoichiometry of the silicon carbide coatings and fibres. (Author)

  15. Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

    Science.gov (United States)

    Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

    2017-02-01

    A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V ( vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

  16. Characterization of Nanometric-Sized Carbides Formed During Tempering of Carbide-Steel Cermets

    Directory of Open Access Journals (Sweden)

    Matus K.

    2016-06-01

    Full Text Available The aim of this article of this paper is to present issues related to characterization of nanometric-sized carbides, nitrides and/or carbonitrides formed during tempering of carbide-steel cermets. Closer examination of those materials is important because of hardness growth of carbide-steel cermet after tempering. The results obtained during research show that the upswing of hardness is significantly higher than for high-speed steels. Another interesting fact is the displacement of secondary hardness effect observed for this material to a higher tempering temperature range. Determined influence of the atmosphere in the sintering process on precipitations formed during tempering of carbide-steel cermets. So far examination of carbidesteel cermet produced by powder injection moulding was carried out mainly in the scanning electron microscope. A proper description of nanosized particles is both important and difficult as achievements of nanoscience and nanotechnology confirm the significant influence of nanocrystalline particles on material properties even if its mass fraction is undetectable by standard methods. The following research studies have been carried out using transmission electron microscopy, mainly selected area electron diffraction and energy dispersive spectroscopy. The obtained results and computer simulations comparison were made.

  17. Constituent Redistribution in U-Zr Metallic Fuel Using the Advanced Fuel Performance Code BISON

    Energy Technology Data Exchange (ETDEWEB)

    Galloway, Jack D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Unal, Cetin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Matthews, Christopher [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-30

    Previous work done by Galloway, et. al. on EBR-II ternary (U-Pu-Zr) fuel constituent redistribution yielded accurate simulation data for the limited data sets of Zr redistribution. The data sets included EPMA scans of two different irradiated rods. First, T179, which was irradiated to 1.9 at% burnup, was analyzed. Second, DP16, which was irradiated to 11 at% burnup, was analyzed. One set of parameters that most accurately represented the zirconium profiles for both experiments was determined. Since the binary fuel (U-Zr) has previously been used as the driver fuel for sodium fast reactors (SFR) as well as being the likely driver fuel if a new SFR is constructed, this same process has been initiated on the binary fuel form. From limited binary EPMA scans as well as other fuel characterization techniques, it has been observed that zirconium redistribution also occurs in the binary fuel, albeit at a reduced rate compared to observation in the ternary fuel, as noted by Kim et. al. While the rate of redistribution has been observed to be slower, numerous metallographs of U-Zr fuel show distinct zone formations.

  18. Development of tungsten carbide-cobalt coatings

    Science.gov (United States)

    Fitzsimmons, Mark

    1999-09-01

    The discovery of WC, and the development of cemented carbides (WC-Co and WC-TiC-Co) have spawned advancements in higher speed machining of steel. The development of chemically vapor deposited (CVD) coatings has allowed even greater speeds to be realized. The production of titanium components, well known for their high specific strength, low density, corrosion resistance, and elevated temperature properties, would greatly benefit from a similar development allowing high speed machining processes. Currently, no known tool material exists that can effectively machine titanium at high speeds due to insufficient high temperature strength and/or chemical resistance. To address this problem an investigation into the development of a composite tool material combining toughness, high temperature strength and chemical resistance was pursued. Cemented carbide (WC-Co) is currently the most chemically resistant and commercially used tool material for machining Ti. The concept of applying a WC-Co coating on a high temperature deformation resistant substrate material was investigated. Two approaches, namely (i) laminated and (ii) co-deposited coatings, were chosen to chemically vapor deposit WC-Co. Thermodynamic and kinetic calculations were performed to aid in the development of CVD processes for deposition of WC and Co. The systems investigated were WF6-CH4-H2 and WCl6-CH4-H 2 for WC deposition and CoCl2-H2 for Co deposition. In the case of laminated structures the goal was to deposit nanometer scale alternating layers of WC and Co. However, development of a laminated structure led to the discovery that porosity always occurred in the Co layers at the WC/Co interface. Mass balance calculations, SEM, EDS, XRD, and metallographic analyses aided in determining that the porosity was due to the Kirkendall effect. It was observed that the diffusion of Co was enhanced by higher concentrations of soluble C in the Co layers. Effective diffusion barriers, such as TiC, were found to help

  19. Review of Reactivity Experiments for Lithium Ternary Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jolodosky, A. [Univ. of California, Berkeley, CA (United States); Bolind, A. [Univ. of California, Berkeley, CA (United States); Fratoni, M. [Univ. of California, Berkeley, CA (United States)

    2015-09-28

    Lithium is often the preferred choice as breeder and coolant in fusion blankets as it offers high tritium breeding, excellent heat transfer and corrosion properties, and most importantly, it has very high tritium solubility and results in very low levels of tritium permeation throughout the facility infrastructure. However, lithium metal vigorously reacts with air and water and exacerbates plant safety concerns. Consequently, Lawrence Livermore National Laboratory (LLNL) is attempting to develop a lithium-based alloy—most likely a ternary alloy—which maintains the beneficial properties of lithium (e.g. high tritium breeding and solubility) while reducing overall flammability concerns for use in the blanket of an inertial fusion energy (IFE) power plant. The LLNL concept employs inertial confinement fusion (ICF) through the use of lasers aimed at an indirect-driven target composed of deuterium-tritium fuel. The fusion driver/target design implements the same physics currently experimented at the National Ignition Facility (NIF). The plant uses lithium in both the primary coolant and blanket; therefore, lithium related hazards are of primary concern. Reducing chemical reactivity is the primary motivation for the development of new lithium alloys, and it is therefore important to come up with proper ways to conduct experiments that can physically study this phenomenon. This paper will start to explore this area by outlining relevant past experiments conducted with lithium/air reactions and lithium/water reactions. Looking at what was done in the past will then give us a general idea of how we can setup our own experiments to test a variety of lithium alloys.

  20. Stress in tungsten carbide-diamond like carbon multilayer coatings

    NARCIS (Netherlands)

    Pujada, B.R.; Tichelaar, F.D.; Janssen, G.C.A.M.

    2007-01-01

    Tungsten carbide-diamond like carbon (WC-DLC) multilayer coatings have been prepared by sputter deposition from a tungsten-carbide target and periodic switching on and off of the reactive acetylene gas flow. The stress in the resulting WC-DLC multilayers has been studied by substrate curvature.

  1. Production of boron carbide powder by carbothermal synthesis of ...

    Indian Academy of Sciences (India)

    TECS

    structure with 12-atom icosahedral clusters which are linked by direct covalent bonds and through three-atom interico- sahedral chains. Boron carbide has single phase ... in nuclear industry due to its high neutron absorption co- efficient (Sinha et al 2002). Boron carbide can be prepared by reaction of elemental boron and ...

  2. Production of nano structured silicon carbide by high energy ball ...

    African Journals Online (AJOL)

    The size, shape and texture of the fresh as well as nano structured Silicon carbide powder were studied using Scanning Electron Microscopy (SEM). The fresh Silicon carbide powder particles were mostly angular in shape. The shape of the 50h milled particles is irregular and the surface morphology is rough.

  3. SEM investigation of minor constituents of carbide materials ...

    Indian Academy of Sciences (India)

    Shungite is a black, precambrian poorly crystalline minera- loid composed mainly of a natural mixture of amorphous carbon and silicate minerals, mainly quartz, .... Microchemical analysis of carbide composite material prepared from a mixture of carbidized shungite and alumina. Pointa. Elemental composition (EDS data)b ...

  4. Stochastic Distribution of Wear of Carbide Tools during Machining ...

    African Journals Online (AJOL)

    The increasing awareness of wear of carbide tools during machining operation has created doubts about the ability of this tool material to withstand stress and strain induced by the machining process. Manufacturers are beginning to question their dependence on carbide tools, seeing that they no longer meet their expected ...

  5. Size dependence of nanoscale wear of silicon carbide

    Science.gov (United States)

    Chaiyapat Tangpatjaroen; David Grierson; Steve Shannon; Joseph E. Jakes; Izabela Szlufarska

    2017-01-01

    Nanoscale, single-asperity wear of single-crystal silicon carbide (sc- SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native...

  6. Magnetoconductivity and electrical transport of polyaniline coated ternary carbide Ti0.9Al0.1C

    Science.gov (United States)

    Mukherjee, P. S.; Gupta, K.; Rana, D.; Meikap, A. K.

    2017-11-01

    In this paper, we report the mechanism of electrical transport properties of polyaniline coated Ti0.9Al0.1C prepared by chemical route. Samples are characterized by X-ray diffraction technique and morphology has been observed by field emission scanning electron microscope. Semiconducting behavior is obtained for the samples and this behavior has been analyzed by different existing models. Out of different models the Mott's variable range hopping is the most suitable for analyzing the dc conductivity at lower temperatures. Correlated barrier hopping type of charge transfer process is followed in alternating current conductivity. We observe a transformation from negative to positive dc and ac magnetoconductivity by incorporating Ti0.9Al0.1C in polyaniline. Dielectric properties and impedance analysis are described by Maxwell-Wagner capacitor model. We determine different parameters like localization length, hopping distance, density of states from the analysis of the experimental data. The theory regarding magnetic field dependent ac conductivity is insufficient. This result will be a significant hint for a new theoretical challenge.

  7. White light emission from engineered silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan

    Silicon carbide (SiC) is a wide indirect bandgap semiconductor. The light emission efficiency is low in nature. But this material has very unique physical properties like good thermal conductivity, high break down field etc in addition to its abundance. Therefore it is interesting to engineer its...... is demonstrated. After optimizing the passivation conditions, strong blue-green emission from porous SiC is demonstrated as well. When combining the yellow emission from co-doped SiC and blue-green from porous SiC, a high color rendering index white light source is achieved....

  8. Silicon carbide nanowires: synthesis and cathodoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Huczko, Andrzej; Dabrowska, Agnieszka [Department of Chemistry, Warsaw University (Poland); Savchyn, Volodymyr; Karbovnyk, Ivan [Department of Electronics, Ivan Franko National University of Lviv (Ukraine); Popov, Anatoli I. [Institut Laue-Langevin, Grenoble (France); Institute of Solid State Physics, University of Latvia, Riga (Latvia)

    2009-12-15

    Silicon carbide nanowires have been synthesized via a combustion synthesis route. Structural studies showed that obtained SiC nanowires belong dominantly to 3C polytype with zincblend structure. Cathodoluminescence spectra from these nanostructures within the temperature range of 77..300 K, show obvious differences with respect to the bulk materials. The exciton band of the bulk 3C-SiC is significantly damped and the prevailing line is found to be at 1.99 eV (77 K), proving the key role of defect centers in optical properties of the investigated nanomaterial. Purified SiC nanowires. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  9. Supported molybdenum carbide for higher alcohol synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Christensen, Jakob Munkholt; Chiarello, Gian Luca

    2013-01-01

    carbide, while the selectivity to methanol follows the opposite trend. The effect of Mo2C loading on the alcohol selectivity at a fixed K/Mo molar ratio of 0.14 could be related to the amount of K2CO3 actually on the active Mo2C phase and the size, structure and composition of the supported carbide......Molybdenum carbide supported on active carbon, carbon nanotubes, and titanium dioxide, and promoted by K2CO3, has been prepared and tested for methanol and higher alcohol synthesis from syngas. At optimal conditions, the activity and selectivity to alcohols (methanol and higher alcohols) over...... supported molybdenum carbide are significantly higher compared to the bulk carbide. The CO conversion reaches a maximum, when about 20wt% Mo2C is loaded on active carbon. The selectivity to higher alcohols increases with increasing Mo2C loading on active carbon and reaches a maximum over bulk molybdenum...

  10. Positron annihilation lifetime study of interfaces in ternary polymer blends

    Science.gov (United States)

    Meghala, D.; Ramya, P.; Pasang, T.; Raj, J. M.; Ranganathaiah, C.; Williams, J. F.

    2013-06-01

    A new method based on positron lifetime spectroscopy is developed to characterize individual interfaces in ternary polymer blends and hence determine the composition dependent miscibility level. The method owes its origin to the Kirkwood-Risemann-Zimm (KRZ) model for the evaluation of the hydrodynamic interaction parameters (αij) which was used successfully for a binary blend with a single interface. The model was revised for the present work for ternary polymer blends to account for three interfaces. The efficacy of this method is shown for two ternary blends namely poly(styrene-co-acrylonitrile)/poly (ethylene-co-vinylacetate)/poly(vinyl chloride) (SAN/EVA/PVC) and polycaprolactone /poly(styrene-co-acrylonitrile)/poly(vinyl chloride) (PCL/SAN/PVC) at different compositions. An effective hydrodynamic interaction parameter, αeff, was introduced to predict the overall miscibility of ternary blends.

  11. HVOF and HVAF Coatings of Agglomerated Tungsten Carbide-Cobalt Powders for Water Droplet Erosion Application

    Science.gov (United States)

    Tarasi, F.; Mahdipoor, M. S.; Dolatabadi, A.; Medraj, M.; Moreau, C.

    2016-12-01

    Water droplet erosion (WDE) is a phenomenon caused by impingement of water droplets of several hundred microns to a few millimeters diameter at velocities of hundreds of meters per second on the edges and surfaces of the parts used in such services. The solution to this problem is sought especially for the moving compressor blades in gas turbines and those operating at the low-pressure end of steam turbines. Thermal-sprayed tungsten carbide-based coatings have been the focus of many studies and are industrially accepted for a multitude of wear and erosion resistance applications. In the present work, the microstructure, phase analysis and mechanical properties (micro-hardness and fracture toughness) of WC-Co coatings are studied in relation with their influence on the WDE resistance of such coatings. The coatings are deposited by high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes. The agglomerated tungsten carbide-cobalt powders were in either sintered or non-sintered conditions. The WDE tests were performed using 0.4 mm water droplets at 300 m/s impact velocity. The study shows promising results for this cermet as WDE-resistant coating when the coating can reach its optimum quality using the right thermal spray process and parameters.

  12. PLUTONIUM METALLIC FUELS FOR FAST REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    STAN, MARIUS [Los Alamos National Laboratory; HECKER, SIEGFRIED S. [Los Alamos National Laboratory

    2007-02-07

    Early interest in metallic plutonium fuels for fast reactors led to much research on plutonium alloy systems including binary solid solutions with the addition of aluminum, gallium, or zirconium and low-melting eutectic alloys with iron and nickel or cobalt. There was also interest in ternaries of these elements with plutonium and cerium. The solid solution and eutectic alloys have most unusual properties, including negative thermal expansion in some solid-solution alloys and the highest viscosity known for liquid metals in the Pu-Fe system. Although metallic fuels have many potential advantages over ceramic fuels, the early attempts were unsuccessful because these fuels suffered from high swelling rates during burn up and high smearing densities. The liquid metal fuels experienced excessive corrosion. Subsequent work on higher-melting U-PuZr metallic fuels was much more promising. In light of the recent rebirth of interest in fast reactors, we review some of the key properties of the early fuels and discuss the challenges presented by the ternary alloys.

  13. Phase field crystal modeling of ternary solidification microstructures

    OpenAIRE

    Berghoff, Marco; Nestler, Britta

    2015-01-01

    In the present work, we present a free energy derivation of the multi-component phase-field crystal model [1] and illustrate the capability to simulate dendritic and eutectic solidification in ternary alloys. Fast free energy minimization by a simulated annealing algorithm of an approximated crystal is compared with the free energy of a fully simulated phase field crystal structure. The calculation of ternary phase diagrams from these free energies is described. Based on the free energies rel...

  14. Subarrayed Antenna Array Synthesis Using Ternary Adjusting Method

    Directory of Open Access Journals (Sweden)

    Guolong He

    2014-01-01

    Full Text Available Ternary adjusting method is proposed and combined with particle swarm optimization (PSO algorithm for subarrayed antenna array synthesis. Ternary variables are introduced to represent element adjustments between adjacent subarrays. Compared to previous methods, rounding-off operations are not required any longer, and the equation constraint of the fixed total element number is also removed, which effectively reduces the complexity of implementation while obtaining improved topology exploration capability simultaneously.

  15. Fuel Exhaling Fuel Cell.

    Science.gov (United States)

    Manzoor Bhat, Zahid; Thimmappa, Ravikumar; Devendrachari, Mruthyunjayachari Chattanahalli; Kottaichamy, Alagar Raja; Shafi, Shahid Pottachola; Varhade, Swapnil; Gautam, Manu; Thotiyl, Musthafa Ottakam

    2018-01-18

    State-of-the-art proton exchange membrane fuel cells (PEMFCs) anodically inhale H 2 fuel and cathodically expel water molecules. We show an unprecedented fuel cell concept exhibiting cathodic fuel exhalation capability of anodically inhaled fuel, driven by the neutralization energy on decoupling the direct acid-base chemistry. The fuel exhaling fuel cell delivered a peak power density of 70 mW/cm 2 at a peak current density of 160 mA/cm 2 with a cathodic H 2 output of ∼80 mL in 1 h. We illustrate that the energy benefits from the same fuel stream can at least be doubled by directing it through proposed neutralization electrochemical cell prior to PEMFC in a tandem configuration.

  16. Effect of Carbide Dissolution on Chlorine Induced High Temperature Corrosion of HVOF and HVAF Sprayed Cr3C2-NiCrMoNb Coatings

    Science.gov (United States)

    Fantozzi, D.; Matikainen, V.; Uusitalo, M.; Koivuluoto, H.; Vuoristo, P.

    2018-01-01

    Highly corrosion- and wear-resistant thermally sprayed chromium carbide (Cr3C2)-based cermet coatings are nowadays a potential highly durable solution to allow traditional fluidized bed combustors (FBC) to be operated with ecological waste and biomass fuels. However, the heat input of thermal spray causes carbide dissolution in the metal binder. This results in the formation of carbon saturated metastable phases, which can affect the behavior of the materials during exposure. This study analyses the effect of carbide dissolution in the metal matrix of Cr3C2-50NiCrMoNb coatings and its effect on chlorine-induced high-temperature corrosion. Four coatings were thermally sprayed with HVAF and HVOF techniques in order to obtain microstructures with increasing amount of carbide dissolution in the metal matrix. The coatings were heat-treated in an inert argon atmosphere to induce secondary carbide precipitation. As-sprayed and heat-treated self-standing coatings were covered with KCl, and their corrosion resistance was investigated with thermogravimetric analysis (TGA) and ordinary high-temperature corrosion test at 550 °C for 4 and 72 h, respectively. High carbon dissolution in the metal matrix appeared to be detrimental against chlorine-induced high-temperature corrosion. The microstructural changes induced by the heat treatment hindered the corrosion onset in the coatings.

  17. Charge distribution in the ternary fragmentation of {sup 252}Cf

    Energy Technology Data Exchange (ETDEWEB)

    Senthil Kannan, M.T.; Balasubramaniam, M. [Bharathiar University, Department of Physics, Coimbatore (India)

    2017-08-15

    We present here, for the first time, a study on ternary fragmentation charge distribution of {sup 252}Cf using the convolution integral method and the statistical theory. The charge distribution for all possible charge combinations of a ternary breakup are grouped as a bin containing different mass partitions. Different bins corresponding to various third fragments with mass numbers from A{sub 3} = 16 to 84 are identified with the available experimental masses. The corresponding potential energy surfaces are calculated using the three cluster model for the two arrangements A{sub 1} + A{sub 2} + A{sub 3} and A{sub 1} + A{sub 3} + A{sub 2}. The ternary fragmentation yield values are calculated for the ternary combination from each bin possessing minimum potential energy. The yields of the resulting ternary combinations as a function of the charge numbers of the three fragments are analyzed for both the arrangements. The calculations are carried out at different excitation energies of the parent nucleus. For each excitation energy the temperature of the three fragments are iteratively computed conserving the total energy. The distribution of fragment temperatures corresponding to different excitation energies for some fixed third fragments are discussed. The presence of the closed shell nucleus Sn in the favourable ternary fragmentation is highlighted. (orig.)

  18. Improved silicon carbide for advanced heat engines

    Science.gov (United States)

    Whalen, Thomas J.

    1987-01-01

    This is the second annual technical report entitled, Improved Silicon Carbide for Advanced Heat Engines, and includes work performed during the period February 16, 1986 to February 15, 1987. The program is conducted for NASA under contract NAS3-24384. The objective is the development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines. The fabrication methods used are to be adaptable for mass production of such parts on an economically sound basis. Injection molding is the forming method selected. This objective is to be accomplished in a two-phase program: (1) to achieve a 20 percent improvement in strength and a 100 percent increase in Weibull modulus of the baseline material; and (2) to produce a complex shaped part, a gas turbine rotor, for example, with the improved mechanical properties attained in the first phase. Eight tasks are included in the first phase covering the characterization of the properties of a baseline material, the improvement of those properties and the fabrication of complex shaped parts. Activities during the first contract year concentrated on two of these areas: fabrication and characterization of the baseline material (Task 1) and improvement of material and processes (Task 7). Activities during the second contract year included an MOR bar matrix study to improve mechanical properties (Task 2), materials and process improvements (Task 7), and a Ford-funded task to mold a turbocharger rotor with an improved material (Task 8).

  19. Ultrasmall Carbide Nanospheres - Formation and Electronic Properties

    Science.gov (United States)

    Reinke, Petra; Monazami, Ehsan; McClimon, John

    2015-03-01

    Metallic nanoparticles are highly coveted but are subject to rapid Ostwald ripening even at moderate temperatures limiting study of their properties. Ultrasmall transition metal carbide ``nanospheres'' are synthesized by a solid-state reaction between fullerene as carbon scaffold, and a W surface. This produces nanospheres with a narrow size distribution below 2.5 nm diameter. The nanosphere shape is defined by the scaffold and densely packed arrays can be achieved. The metal-fullerene reaction is temperature driven and progresses through an intermediate semiconducting phase until the fully metallic nanospheres are created at about 350 C. The reaction sequence is observed with STM, and STS maps yield the local density of states. The reaction presumably progresses by stepwise introduction of W-atoms in the carbon scaffold. The results of high resolution STM/STS in combination with DFT calculations are used to unravel the reaction mechanism. We will discuss the transfer of this specific reaction mechanism to other transition metal carbides. The nanospheres are an excellent testbed for the physics and chemistry of highly curved surfaces.

  20. Maxwell-Stefan diffusion coefficient estimation for ternary systems: an ideal ternary alcohol system.

    Science.gov (United States)

    Allie-Ebrahim, Tariq; Zhu, Qingyu; Bräuer, Pierre; Moggridge, Geoff D; D'Agostino, Carmine

    2017-06-21

    The Maxwell-Stefan model is a popular diffusion model originally developed to model diffusion of gases, which can be considered thermodynamically ideal mixtures, although its application has been extended to model diffusion in non-ideal liquid mixtures as well. A drawback of the model is that it requires the Maxwell-Stefan diffusion coefficients, which are not based on measurable quantities but they have to be estimated. As a result, numerous estimation methods, such as the Darken model, have been proposed to estimate these diffusion coefficients. However, the Darken model was derived, and is only well defined, for binary systems. This model has been extended to ternary systems according to two proposed forms, one by R. Krishna and J. M. van Baten, Ind. Eng. Chem. Res., 2005, 44, 6939-6947 and the other by X. Liu, T. J. H. Vlugt and A. Bardow, Ind. Eng. Chem. Res., 2011, 50, 10350-10358. In this paper, the two forms have been analysed against the ideal ternary system of methanol/butan-1-ol/propan-1-ol and using experimental values of self-diffusion coefficients. In particular, using pulsed gradient stimulated echo nuclear magnetic resonance (PGSTE-NMR) we have measured the self-diffusion coefficients in various methanol/butan-1-ol/propan-1-ol mixtures. The experimental values of self-diffusion coefficients were then used as the input data required for the Darken model. The predictions of the two proposed multicomponent forms of this model were then compared to experimental values of mutual diffusion coefficients for the ideal alcohol ternary system. This experimental-based approach showed that the Liu's model gives better predictions compared to that of Krishna and van Baten, although it was only accurate to within 26%. Nonetheless, the multicomponent Darken model in conjunction with self-diffusion measurements from PGSTE-NMR represents an attractive method for a rapid estimation of mutual diffusion in multicomponent systems, especially when compared to exhaustive

  1. Development of a new family of cemented carbides for geothermal drilling. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rowcliff, D.J.

    1983-10-01

    The contractor fabricated samples of cemented carbides based on tantalum carbide and niobium carbide with cobalt and nickel binders. These materials were evaluated for use as rock-bit inserts in geothermal drilling. Carbon content in the niobium carbide (NbC/sub x/) and the tantalum carbide (TaC/sub x/) was varied (x is 0.83 to 1.0) and the effect of these changes on the carbides' mechanical properties was examined. Hardness, toughness, and abrasive wear resistance of the new materials were measured and compared to properties of tungsten carbide grades used in rock-bit inserts.

  2. Mesoscale inhomogeneities in an aqueous ternary system

    Science.gov (United States)

    Subramanian, Deepa; Hayward, Stephen; Altabet, Elia; Collings, Peter; Anisimov, Mikhail

    2012-02-01

    Aqueous solutions of certain low-molecular-weight organic compounds, such as alcohols, amines, or ethers, which are considered macroscopically homogeneous, show the presence of mysterious mesoscale inhomogeneities, order of a hundred nm in size. We have performed static and dynamic light scattering experiments in an aqueous ternary system consisting of tertiary butyl alcohol and propylene oxide. Tertiary butyl alcohol is completely soluble in water and in propylene oxide, and forms strong hydrogen bonds with water molecules. Based on results of the study, we hypothesize that the mesoscale inhomogeneities are akin to a micro phase separation, resulting from a competition between water molecules and propylene oxide molecules, wanting to be adjacent to amphiphilic tertiary butyl alcohol molecules. Coupling between two competing order parameters, super-lattice binary-alloy-like (``antiferromagnetic'' type) and demixing (``ferromagnetic'' type) may explain the formation of these inhomogeneities. Long-term stability investigation of this supramolecular structure has revealed that these inhomogeneities are exceptionally long-lived non-equilibrium structures that persist for weeks or even months.

  3. Determination of moisture and low temperature volatiles in solid fuels

    Energy Technology Data Exchange (ETDEWEB)

    Jenke, D.R.; Hannifan, M.R.

    1983-09-01

    The reaction of calcium carbide with moisture in a closed reactor to form acetylene, when combined with gas chromatographic analysis of the products and measurement of pressure change during reaction, provides an accurate and rapid determination method for moisture and volatile content of solid fuels.

  4. Computational Studies of Physical Properties of Boron Carbide

    Energy Technology Data Exchange (ETDEWEB)

    Lizhi Ouyang

    2011-09-30

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

  5. Precipitation behavior of carbides in high-carbon martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao; Shi, Chang-min [University of Science and Technology, Beijing (China). State Key Laboratory of Advanced Metallurgy; Li, Ji-hui [Yang Jiang Shi Ba Zi Group Co., Ltd, Guangdong (China)

    2017-01-15

    A fundamental study on the precipitation behavior of carbides was carried out. Thermo-calc software, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, X-ray diffractometry and high-temperature confocal laser scanning microscopy were used to study the precipitation and transformation behaviors of carbides. Carbide precipitation was of a specific order. Primary carbides (M7C3) tended to be generated from liquid steel when the solid fraction reached 84 mol.%. Secondary carbides (M7C3) precipitated from austenite and can hardly transformed into M23C6 carbides with decreasing temperature in air. Primary carbides hardly changed once they were generated, whereas secondary carbides were sensitive to heat treatment and thermal deformation. Carbide precipitation had a certain effect on steel-matrix phase transitions. The segregation ability of carbon in liquid steel was 4.6 times greater that of chromium. A new method for controlling primary carbides is proposed.

  6. A silicon carbide array for electrocorticography and peripheral nerve recording

    Science.gov (United States)

    Diaz-Botia, C. A.; Luna, L. E.; Neely, R. M.; Chamanzar, M.; Carraro, C.; Carmena, J. M.; Sabes, P. N.; Maboudian, R.; Maharbiz, M. M.

    2017-10-01

    Objective. Current neural probes have a limited device lifetime of a few years. Their common failure mode is the degradation of insulating films and/or the delamination of the conductor-insulator interfaces. We sought to develop a technology that does not suffer from such limitations and would be suitable for chronic applications with very long device lifetimes. Approach. We developed a fabrication method that integrates polycrystalline conductive silicon carbide with insulating silicon carbide. The technology employs amorphous silicon carbide as the insulator and conductive silicon carbide at the recording sites, resulting in a seamless transition between doped and amorphous regions of the same material, eliminating heterogeneous interfaces prone to delamination. Silicon carbide has outstanding chemical stability, is biocompatible, is an excellent molecular barrier and is compatible with standard microfabrication processes. Main results. We have fabricated silicon carbide electrode arrays using our novel fabrication method. We conducted in vivo experiments in which electrocorticography recordings from the primary visual cortex of a rat were obtained and were of similar quality to those of polymer based electrocorticography arrays. The silicon carbide electrode arrays were also used as a cuff electrode wrapped around the sciatic nerve of a rat to record the nerve response to electrical stimulation. Finally, we demonstrated the outstanding long term stability of our insulating silicon carbide films through accelerated aging tests. Significance. Clinical translation in neural engineering has been slowed in part due to the poor long term performance of current probes. Silicon carbide devices are a promising technology that may accelerate this transition by enabling truly chronic applications.

  7. Carbide inclusions in delta-phase plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Baros, T. (Thomas); Davis, C. C. (Charles C.); Hawkins, H. T. (Heather T.); Ruggiero, M. J. (Matthew J.); Valentine, S. J. (Scott J.); Storey, B. G. (Bradford G.); Roybal, L. (Lawrence)

    2004-01-01

    Inclusions in plutonium alloys are common and depend on the processing parameters and age of the material. Plutonium-bearing compounds frequently observed as inclusions include: hydrides, nitrides, oxides, and carbides. Optical metallography and electron probe microanalysis (EPMA) were used to characterize plutonium carbide (PuC) inclusions in delta-phase plutonium. The structural complexities of plutonium combined with its radioactivity, pyrophoric nature, and toxicity create a unique challenge to revealing and interpreting its microstructures. Samples of delta-phase Pu-239 were used in this study. Note that the delta phase is stabilized to room temperature by the addition of {approx}1 wt% gallium. After samples are cut, mounted in epoxy, ground, and polished, they are then electropolished at 40 V in an etchant of 10 vol.% nitric acid and 90 vol.% dimethylformamide and electroetched at 6 V in the same etchant. Optical micrographs were collected using an inverted metallograph equipped with a digital camera. Back-scattered electron images and elemental maps of the plutonium, carbon, and gallium content were collected using an EPMA equipped with wavelength dispersive spectrometers. After reviewing our data and consulting work done by Cramer and Bergin it was determined that the inclusions were acicular plutonium carbides and were formed during the casting process at the time the material was manufactured. It is believed that these inclusions would affect the high strain-rate properties. The response of plutonium alloys during implosion is critical to the performance and reliability of a nuclear weapon. We plan to further investigate these inclusions to gather information about orientation, composition, structure, and concentration. An x-ray diffractometer with a 10 {micro}m beam diameter will be used to gather information on the orientation and structure of individual inclusions. A field-emission scanning electron microscope (SEM) with a WDS will be used at low

  8. Two-layer synchronized ternary quantum-dot cellular automata wire crossings

    Science.gov (United States)

    2012-01-01

    Quantum-dot cellular automata are an interesting nanoscale computing paradigm. The introduction of the ternary quantum-dot cell enabled ternary computing, and with the recent development of a ternary functionally complete set of elementary logic primitives and the ternary memorizing cell design of complex processing structures is becoming feasible. The specific nature of the ternary quantum-dot cell makes wire crossings one of the most problematic areas of ternary quantum-dot cellular automata circuit design. We hereby present a two-layer wire crossing that uses a specific clocking scheme, which ensures the crossed wires have the same effective delay. PMID:22507371

  9. Hugoniot equation of state and dynamic strength of boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Grady, Dennis E. [Applied Research Associates, Southwest Division, 4300 San Mateo Blvd NE, A-220, Albuquerque, New Mexico 87110-129 (United States)

    2015-04-28

    Boron carbide ceramics have been particularly problematic in attempts to develop adequate constitutive model descriptions for purposes of analysis of dynamic response in the shock and impact environment. Dynamic strength properties of boron carbide ceramic differ uniquely from comparable ceramics. Furthermore, boron carbide is suspected, but not definitely shown, to undergoing polymorphic phase transformation under shock compression. In the present paper, shock-wave compression measurements conducted over the past 40 years are assessed for the purpose of achieving improved understanding of the dynamic equation of state and strength of boron carbide. In particular, attention is focused on the often ignored Los Alamos National Laboratory (LANL) Hugoniot measurements performed on porous sintered boron carbide ceramic. The LANL data are shown to exhibit two compression anomalies on the shock Hugoniot within the range of 20–60 GPa that may relate to crystallographic structure transitions. More recent molecular dynamics simulations on the compressibility of the boron carbide crystal lattice reveal compression transitions that bear similarities to the LANL Hugoniot results. The same Hugoniot data are complemented with dynamic isentropic compression data for boron carbide extracted from Hugoniot measurements on boron carbide and copper granular mixtures. Other Hugoniot measurements, however, performed on near-full-density boron carbide ceramic differ markedly from the LANL Hugoniot data. These later data exhibit markedly less compressibility and tend not to show comparable anomalies in compressibility. Alternative Hugoniot anomalies, however, are exhibited by the near-full-density data. Experimental uncertainty, Hugoniot strength, and phase transformation physics are all possible explanations for the observed discrepancies. It is reasoned that experimental uncertainty and Hugoniot strength are not likely explanations for the observed differences. The notable

  10. The all boron carbide diode neutron detector: Comparison with theory

    Energy Technology Data Exchange (ETDEWEB)

    Caruso, A.N. [Department of Physics and Astronomy, Behlen Laboratory of Physics, University of Nebraska, P.O. Box 880111, Lincoln, NE 68588-0111 (United States); Nebraska Center for Materials and Nanoscience, 116 Brace Laboratory, University of Nebraska, P.O. Box 880111, Lincoln, NE 68588-0111 (United States); College of Engineering, N245 Walter Scott Engineering Center, 17th Vine Street, University of Nebraska-Lincoln, Lincoln, NE 68588-0511 (United States); Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, ND 58102 (United States); Dowben, P.A. [Department of Physics and Astronomy, Behlen Laboratory of Physics, University of Nebraska, P.O. Box 880111, Lincoln, NE 68588-0111 (United States) and Nebraska Center for Materials and Nanoscience, 116 Brace Laboratory, University of Nebraska, P.O. Box 880111, Lincoln, NE 68588-0111 (United States)]. E-mail: pdowben@unl.edu; Balkir, S. [Nebraska Center for Materials and Nanoscience, 116 Brace Laboratory, University of Nebraska, P.O. Box 880111, Lincoln, NE 68588-0111 (United States); Department of Electrical Engineering, College of Engineering, 237N Walter Scott Engineering Center, 17th Vine Street, University of Nebraska-Lincoln, Lincoln, NE 68588-0511 (United States); Schemm, Nathan [Nebraska Center for Materials and Nanoscience, 116 Brace Laboratory, University of Nebraska, P.O. Box 880111, Lincoln, NE 68588-0111 (United States); Department of Electrical Engineering, College of Engineering, 237N Walter Scott Engineering Center, 17th Vine Street, University of Nebraska-Lincoln, Lincoln, NE 68588-0511 (United States)] (and others)

    2006-11-25

    A boron carbide diode detector, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theory. Small deviations from the model calculations occur due to the detection efficiencies of the {sup 10}B capture products Li plus {alpha} sum signal differing somewhat from expectation in the thin diodes. The performance of the all boron carbide neutron detector does depart from the behavior of devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector), as is expected.

  11. Acetylene bubble-powered autonomous capsules: towards in situ fuel.

    Science.gov (United States)

    Moo, James Guo Sheng; Wang, Hong; Pumera, Martin

    2014-12-28

    A fuel-free autonomous self-propelled motor is illustrated. The motor is powered by the chemistry of calcium carbide and utilising water as a co-reactant, through a polymer encapsulation strategy. Expulsion of acetylene bubbles powers the capsule motor. This is an important step, going beyond the toxic hydrogen peroxide fuel used normally, to find alternative propellants for self-propelled machines.

  12. Stable field emission from nanoporous silicon carbide

    Science.gov (United States)

    Kang, Myung-Gyu; Lezec, Henri J.; Sharifi, Fred

    2013-02-01

    We report on a new type of stable field emitter capable of electron emission at levels comparable to thermal sources. Such an emitter potentially enables significant advances in several important technologies which currently use thermal electron sources. These include communications through microwave electronics, and more notably imaging for medicine and security where new modalities of detection may arise due to variable-geometry x-ray sources. Stable emission of 6 A cm-2 is demonstrated in a macroscopic array, and lifetime measurements indicate these new emitters are sufficiently robust to be considered for realistic implementation. The emitter is a monolithic structure, and is made in a room-temperature process. It is fabricated from a silicon carbide wafer, which is formed into a highly porous structure resembling an aerogel, and further patterned into an array. The emission properties may be tuned both through control of the nanoscale morphology and the macroscopic shape of the emitter array.

  13. Silicon carbide devices for radiation hard applications

    Energy Technology Data Exchange (ETDEWEB)

    McMullin, P.G.; Barrett, D.L.; Hopkins, R.H.; Spitznagel, J.A. (Westinghouse Sciences and Technology Center, 1310 Beulah Road, Pittsburgh, Pennsylvania 15235 (United States)); Powell, J.A. (NASA Lewis Research Center, 21000 Brookpark Road, Cleveland Ohio 44135 (United States)); Thome, F.V. (Sandia National Laboratory, Albuquerque, New Mexico 87123 (United States))

    1993-01-15

    Silicon carbide has long been recognized as a favorable material for applications at high temperatures and in radiation environments, but device development has been hindered by lack of adequate substrates. This paper reviews the current Westinghouse material development effort aimed at the growth of high quality 6H boules and describes 6H SiC devices fabricated on Westinghouse substrates. MESFET and MOSFET transistors were made in a microwave power design layout. The MESFET and MOSFET transistors were subjected to a total gamma irradiation of 1 megaGray (100 megarad) and exhibited threshold voltage shifts of about 0.4 and 1.2 Volts respectively with little change in bulk material parameters.

  14. Silicon carbide devices for radiation hard applications

    Science.gov (United States)

    McMullin, Paul G.; Barrett, Donovan L.; Hopkins, Richard H.; Spitznagel, John A.; Powell, J. Anthony; Thome, Frank V.

    1993-01-01

    Silicon carbide has long been recognized as a favorable material for applications at high temperatures and in radiation environments, but device development has been hindered by lack of adequate substrates. This paper reviews the current Westinghouse material development effort aimed at the growth of high quality 6H boules and describes 6H SiC devices fabricated on Westinghouse substrates. MESFET and MOSFET transistors were made in a microwave power design layout. The MESFET and MOSFET transistors were subjected to a total gamma irradiation of 1 megaGray (100 megarad) and exhibited threshold voltage shifts of about 0.4 and 1.2 Volts respectively with little change in bulk material parameters.

  15. Neutron irradiation induced amorphization of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Snead, L.L.; Hay, J.C. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  16. Arsenic carbide monolayer: First principles prediction

    Science.gov (United States)

    Naseri, Mosayeb

    2017-11-01

    Using the first principles calculation, a new pentagonal indirect band gap semiconductor namely arsenic carbide monolayer (As2C) is predicted. The calculated cohesive energy of -5.69 eV/atom the thermodynamic stability of the predicted monolayer. Furthermore, the kinetic stability of the monolayer is examined by phonon dispersion calculation, where the absence of imaginary modes and high value of maximum phonon frequency confirms the high dynamic stability of the proposed monolayer. Investigating in the electronic properties of the As2C monolayer indicates that it is a semiconductor with an indirect band gap of 1.62 eV. Analyzing the optical properties of the As2C monolayer imply that the monolayer has high UV light absorption, however, it has an almost zero absorption in visible region of electromagnetic spectra. The specific electronic and optical properties imply that As2C monolayer may be used in new generation of nano-optoelectronic technology design.

  17. Silicon Carbide Nanotube Oxidation at High Temperatures

    Science.gov (United States)

    Ahlborg, Nadia; Zhu, Dongming

    2012-01-01

    Silicon Carbide Nanotubes (SiCNTs) have high mechanical strength and also have many potential functional applications. In this study, SiCNTs were investigated for use in strengthening high temperature silicate and oxide materials for high performance ceramic nanocomposites and environmental barrier coating bond coats. The high · temperature oxidation behavior of the nanotubes was of particular interest. The SiCNTs were synthesized by a direct reactive conversion process of multiwall carbon nanotubes and silicon at high temperature. Thermogravimetric analysis (TGA) was used to study the oxidation kinetics of SiCNTs at temperatures ranging from 800degC to1300degC. The specific oxidation mechanisms were also investigated.

  18. Helium behaviour in implanted boron carbide

    Directory of Open Access Journals (Sweden)

    Motte Vianney

    2015-01-01

    Full Text Available When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He(d,p4He nuclear reaction (NRA method. From the evolution of the width of implanted 3He helium profiles (fluence 1 × 1015/cm2, 3 MeV corresponding to a maximum helium concentration of about 1020/cm3 as a function of annealing temperatures, an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced (Ea = 0.52 ± 0.11 eV/atom. The dynamic of helium clusters was observed by transmission electron microscopy (TEM of samples implanted with 1.5 × 1016/cm2, 2.8 to 3 MeV 4He ions, leading to an implanted slab about 1 μm wide with a maximum helium concentration of about 1021/cm3. After annealing at 900 °C and 1100 °C, small (5–20 nm flat oriented bubbles appeared in the grain, then at the grain boundaries. At 1500 °C, due to long-range diffusion, intra-granular bubbles were no longer observed; helium segregates at the grain boundaries, either as bubbles or inducing grain boundaries opening.

  19. Oxidation behaviour of boron carbide powder

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.Q. [College of Materials Science and Engineering, Nanjing University of Technology, New Model Road 5, Nanjing, Jiangsu 210009 (China)]. E-mail: Li.Yuanqiang@nims.go.jp; Qiu, T. [College of Materials Science and Engineering, Nanjing University of Technology, New Model Road 5, Nanjing, Jiangsu 210009 (China)

    2007-01-25

    Isothermal oxidation behaviour of powdered boron carbide (B{sub 4}C) with the fine (1.52 {mu}m), medium (22.5 {mu}m) and coarse (59.6 {mu}m) particle size has been studied in air ranging from 500 to 800 deg. C. The oxidation rate strongly depends on the particle size of boron carbide and temperature. The smaller particle size the higher oxidation rate of B{sub 4}C powder due to its larger surface area. When B{sub 4}C powder is oxidized in air, a B{sub 2}O{sub 3} glass film is formed on the surface of B{sub 4}C grain which retards the further oxidation reaction. The oxidation kinetics is approximately fitted to the diffusion-controlled rate law which can be described by the Jander's equation. The apparent activation energy for the fine-, medium- and coarse-B{sub 4}C powders is 209.4 {+-} 11.4, 212.7 {+-} 35.8 and 219.2 {+-} 45.3 kJ mol{sup -1}, respectively, slightly varying with the impurity content of B{sub 4}C powders. The type of rate law suggests that the diffusion of oxygen through the oxide layer is the rate-limiting step in the oxidation reactions. In addition, the change in the oxidation process at higher oxidation fraction might associate with the B{sub 2}O{sub 3} volatilization at higher temperatures.

  20. Fuel System Compatibility Issues for Prometheus-1

    Energy Technology Data Exchange (ETDEWEB)

    DC Noe; KB Gibbard; MH Krohn

    2006-01-20

    Compatibility issues for the Prometheus-1 fuel system have been reviewed based upon the selection of UO{sub 2} as the reference fuel material. In particular, the potential for limiting effects due to fuel- or fission product-component (cladding, liner, spring, etc) chemical interactions and clad-liner interactions have been evaluated. For UO{sub 2}-based fuels, fuel-component interactions are not expected to significantly limit performance. However, based upon the selection of component materials, there is a potential for degradation due to fission products. In particular, a chemical liner may be necessary for niobium, tantalum, zirconium, or silicon carbide-based systems. Multiple choices exist for the configuration of a chemical liner within the cladding; there is no clear solution that eliminates all concerns over the mechanical performance of a clad/liner system. A series of tests to evaluate the performance of candidate materials in contact with real and simulated fission products is outlined.

  1. Identification and tackling of a parasitic surface compound in SiC and Si-rich carbide films

    Energy Technology Data Exchange (ETDEWEB)

    Canino, M., E-mail: canino@bo.imm.cnr.it [CNR-IMM, via Gobetti 101, 40129 Bologna (Italy); Summonte, C.; Allegrezza, M. [CNR-IMM, via Gobetti 101, 40129 Bologna (Italy); Shukla, Rimpy [CNR-IMM, via Gobetti 101, 40129 Bologna (Italy); Centre of Non-Conventional Energy Resources, University of Rajasthan, Jaipur (India); Jain, I.P. [Centre of Non-Conventional Energy Resources, University of Rajasthan, Jaipur (India); Bellettato, M.; Desalvo, A.; Mancarella, F.; Sanmartin, M. [CNR-IMM, via Gobetti 101, 40129 Bologna (Italy); Terrasi, A. [CNR-IMM, via Santa Sofia 64, 95123 Catania (Italy); Löper, P.; Schnabel, M.; Janz, S. [Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, 79110 Freiburg (Germany)

    2013-05-15

    Highlights: ► Silicon carbide and silicon rich carbide films are prepared by PECVD. ► Annealing at 1100 °C promotes Si nanocrystal formation in SiC. ► A parasitic SiO{sub x}C{sub y} compound is formed on the surface during annealing. ► The surface affects optical and electrical properties of the nanocrystal layer. ► We analyze a fabrication sequence that minimizes oxidation. ► The resulting surface is SiC-rich. -- Abstract: Silicon carbide and silicon rich carbide (SiC and SRC) thin films were prepared by PECVD and annealed at 1100 °C. Such a treatment, when applied to SiC/SRC multilayers, aimed at the formation of silicon nanocrystals, that have attracted considerable attention as tunable band-gap materials for photovoltaic applications. Optical and structural techniques (X-ray photoelectron spectroscopy, Reflectance and Transmittance, Fourier Transformed Infrared Spectroscopy) were used to evidence the formation, during the annealing treatment in nominally inert atmosphere, of a parasitic ternary SiO{sub x}C{sub y} surface compound, that consumed part of the originally deposited material and behaved as a preferential conductive path with respect to the nanocrystal layer in horizontal electrical conductivity measurements. The SiO{sub x}C{sub y} compound was HF-resistant, with composition dependent on the underlying matrix. It gave rise to a Si-O related vibration in FTIR analysis, that may be misinterpreted as due to silicon oxide. The compound, if neglected, can affect the structural and electrical characterization of the material. To overcome this problem, a procedure is analyzed, based on the deposition of a sacrificial capping a-Si:H layer that partially oxidizes, and is removed by tetra methyl ammonium hydroxide (TMAH) after annealing. XPS analysis revealed that the resulting surface is mainly made up of SiC regardless of the composition of the underlying SRC layer. Subsequent SF{sub 6}:O{sub 2} dry etching results in a porous SiC-rich surface

  2. Liquid-liquid equilibria for ternary polymer mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Suk Yung [Division of Chemical Engineering and Molecular Thermodynamics Laboratory, Hanyang University, Seoul 133-791 (Korea, Republic of); Bae, Young Chan, E-mail: ycbae@hanyang.ac.kr [Division of Chemical Engineering and Molecular Thermodynamics Laboratory, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2011-01-24

    Graphical abstract: We developed a molecular thermodynamic model for multicomponent systems and discribed the phase equilibrium for ternary polymer mixtures by using the model parameters obtained from the binary systems. Research highlights: {yields} Model parameters were obtained from the binary systems. {yields} The obtained parameters were directly used to predict the ternary data. {yields} The undetermined parameters were used to correlate the ternary data. {yields} The proposed model agreed well with the experimental data. - Abstract: A molecular thermodynamic model for multicomponent systems based on a closed-packed lattice model is presented based on two contributions; entropy and energy contribution. The calculated liquid-liquid equilibria of ternary chainlike mixtures agreed with Monte Carlo simulation results. The proposed model can satisfactorily predict Types 0, 1, 2 and 3 phase separations of the Treybal classification. The model parameters obtained from the binary systems were used to directly predict real ternary systems and the calculated results correlated well with experimental data using few adjustable parameters. Specific interactions in associated binary systems were considered using a secondary lattice.

  3. Fossil fuels -- future fuels

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Fossil fuels -- coal, oil, and natural gas -- built America`s historic economic strength. Today, coal supplies more than 55% of the electricity, oil more than 97% of the transportation needs, and natural gas 24% of the primary energy used in the US. Even taking into account increased use of renewable fuels and vastly improved powerplant efficiencies, 90% of national energy needs will still be met by fossil fuels in 2020. If advanced technologies that boost efficiency and environmental performance can be successfully developed and deployed, the US can continue to depend upon its rich resources of fossil fuels.

  4. Novel Manufacturing Process for Unique Mixed Carbide Refractory Composites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This STTR Phase I project will establish the feasibility of an innovative manufacturing process to fabricate a range of unique hafnium/silicon based carbide...

  5. Stereological Analysis of Carbides in Hypoeutectic Chromium Cast Iron

    Directory of Open Access Journals (Sweden)

    Gromczyk M.

    2015-06-01

    Full Text Available The results of research on stereological parameters of carbides in modified hypoeutectic chromium cast iron were shown in the paper. The effect of distance the casting heat centre of casting to the carbide phase morphology was examined. The samples for metallographic examination were taken from various locations of the model casting prepared in a special tester. This model casting was designed to simulate the solidification of heavy castings. Using the proposed methodology the relation of the distance from the model mould and the size, perimeter, length, width and the shape factor of carbides was examined. During the analysis, the values of stereological parameters of carbides changed on various sections of the model casting.

  6. Exploring a novel approach to fabricate vanadium carbide ...

    Indian Academy of Sciences (India)

    -shell structure; composite materials; mesoporous material; solid-state reaction. ... A novel approach to the fabrication of vanadium carbide encapsulated into carbon nanotube (VC@C) core-shell structured composite by thermal treatment with ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Bragg-Sitton, Shannon M. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2013-09-01

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

  8. Ternary Pt/Rh/SnO2 electrocatalysts for oxidizing ethanol to CO2

    Science.gov (United States)

    Kowal, A.; Li, M.; Shao, M.; Sasaki, K.; Vukmirovic, M. B.; Zhang, J.; Marinkovic, N. S.; Liu, P.; Frenkel, A. I.; Adzic, R. R.

    2009-04-01

    Ethanol, with its high energy density, likely production from renewable sources and ease of storage and transportation, is almost the ideal combustible for fuel cells wherein its chemical energy can be converted directly into electrical energy. However, commercialization of direct ethanol fuel cells has been impeded by ethanol's slow, inefficient oxidation even at the best electrocatalysts. We synthesized a ternary PtRhSnO2/C electrocatalyst by depositing platinum and rhodium atoms on carbon-supported tin dioxide nanoparticles that is capable of oxidizing ethanol with high efficiency and holds great promise for resolving the impediments to developing practical direct ethanol fuel cells. This electrocatalyst effectively splits the C-C bond in ethanol at room temperature in acid solutions, facilitating its oxidation at low potentials to CO2, which has not been achieved with existing catalysts. Our experiments and density functional theory calculations indicate that the electrocatalyst's activity is due to the specific property of each of its constituents, induced by their interactions. These findings help explain the high activity of Pt-Ru for methanol oxidation and the lack of it for ethanol oxidation, and point to the way to accomplishing the C-C bond splitting in other catalytic processes.

  9. Process for preparing fine-grain metal carbide powder

    Science.gov (United States)

    Kennedy, C.R.; Jeffers, F.P.

    Fine-grain metal carbide powder suitable for use in the fabrication of heat resistant products is prepared by coating bituminous pitch on SiO/sub 2/ or Ta/sub 2/O/sub 5/ particles, heating the coated particles to convert the bituminous pitch to coke, and then heating the particles to a higher temperature to convert the particles to a carbide by reaction of said coke therewith.

  10. Stability of MC Carbide Particles Size in Creep Resisting Steels

    Directory of Open Access Journals (Sweden)

    Vodopivec, F.

    2006-01-01

    Full Text Available Theoretical analysis of the dependence microstructure creep rate. Discussion on the effects of carbide particles size and their distribution on the base of accelerated creep tests on a steel X20CrMoV121 tempered at 800 °C. Analysis of the stability of carbide particles size in terms of free energy of formation of the compound. Explanation of the different effect of VC and NbC particles on accelerated creep rate.

  11. Bainite obtaining in cast iron with carbides castings

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2010-01-01

    Full Text Available In these paper the possibility of upper and lower bainite obtaining in cast iron with carbides castings are presented. Conditions, when in cast iron with carbides castings during continuous free air cooling austenite transformation to upper bainite or its mixture with lower bainte proceeds, have been given. A mechanism of this transformation has been given, Si, Ni, Mn and Mo distribution in the eutectic cell has been tested and hardness of tested castings has been determined.

  12. Microwave Sintering and Its Application on Cemented Carbides

    OpenAIRE

    Rumman Md Raihanuzzaman; Lee Chang Chuan; Zonghan Xie; Reza Ghomashchi

    2015-01-01

    Cemented carbides, owing to their excellent mechanical properties, have been of immense interest in the field of hard materials for the past few decades. A number of processing techniques have been developed to obtain high quality carbide tools, with a wide range of grain size depending on the application and requirements. Microwave sintering is one of the heating processes, which has been used to prepare a wide range of materials including ceramics. A deep understanding ...

  13. Completed Local Ternary Pattern for Rotation Invariant Texture Classification

    Directory of Open Access Journals (Sweden)

    Taha H. Rassem

    2014-01-01

    Full Text Available Despite the fact that the two texture descriptors, the completed modeling of Local Binary Pattern (CLBP and the Completed Local Binary Count (CLBC, have achieved a remarkable accuracy for invariant rotation texture classification, they inherit some Local Binary Pattern (LBP drawbacks. The LBP is sensitive to noise, and different patterns of LBP may be classified into the same class that reduces its discriminating property. Although, the Local Ternary Pattern (LTP is proposed to be more robust to noise than LBP, however, the latter’s weakness may appear with the LTP as well as with LBP. In this paper, a novel completed modeling of the Local Ternary Pattern (LTP operator is proposed to overcome both LBP drawbacks, and an associated completed Local Ternary Pattern (CLTP scheme is developed for rotation invariant texture classification. The experimental results using four different texture databases show that the proposed CLTP achieved an impressive classification accuracy as compared to the CLBP and CLBC descriptors.

  14. On the interpretation, verification and calibration of ternary probabilistic forecasts

    CERN Document Server

    Jupp, Tim E; Coelho, Caio A S; Stephenson, David B

    2011-01-01

    We develop a geometrical interpretation of ternary probabilistic forecasts in which forecasts and observations are regarded as points inside a triangle. Within the triangle, we define a continuous colour palette in which hue and colour saturation are defined with reference to the observed climatology. In contrast to current methods, forecast maps created with this colour scheme convey all of the information present in each ternary forecast. The geometrical interpretation is then extended to verification under quadratic scoring rules (of which the Brier Score and the Ranked Probability Score are well--known examples). Each scoring rule defines an associated triangle in which the square roots of the \\emph{score}, the \\emph{reliability}, the \\emph{uncertainty} and the \\emph{resolution} all have natural interpretations as root--mean--square distances. This leads to our proposal for a \\emph{Ternary Reliability Diagram} in which data relating to verification and calibration can be summarised. We illustrate these id...

  15. [Synthesis and luminescence properties of reactive ternary europium complexes].

    Science.gov (United States)

    Guo, Dong-cai; Shu, Wan-gen; Zhang, Wei; Liu, You-nian; Zhou, Yue

    2004-09-01

    In this paper, five new reactive ternary europium complexes were synthesized with the first ligand of 1,10-phenanthroline and the reactive second ligands of maleic anhydride, acrylonitrile, undecenoic acid, oleic acid and linoleic acid, and also characterized by means of elemental analysis, EDTA titrimetric method, FTIR spectra and UV spectra. The fluorescence spectra show that the five new ternary complexes have much higher luminescence intensity than their corresponding binary complexes, and the synergy ability sequence of the five reactive ligands is as follows: linoleic acid > oleic acid > acrylonitrile > maleic anhydride > undecenoic acid. At the same time, the reactive ternary europium complexes coordinated with the reactive ligands, which can be copolymerized with other monomers, will provide a new way for the synthesis of bonding-type rare earth polymer functional materials with excellent luminescence properties.

  16. Computational Design of Advanced Nuclear Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Savrasov, Sergey [Univ. of California, Davis, CA (United States); Kotliar, Gabriel [Rutgers Univ., Piscataway, NJ (United States); Haule, Kristjan [Rutgers Univ., Piscataway, NJ (United States)

    2014-06-03

    The objective of the project was to develop a method for theoretical understanding of nuclear fuel materials whose physical and thermophysical properties can be predicted from first principles using a novel dynamical mean field method for electronic structure calculations. We concentrated our study on uranium, plutonium, their oxides, nitrides, carbides, as well as some rare earth materials whose 4f eletrons provide a simplified framework for understanding complex behavior of the f electrons. We addressed the issues connected to the electronic structure, lattice instabilities, phonon and magnon dynamics as well as thermal conductivity. This allowed us to evaluate characteristics of advanced nuclear fuel systems using computer based simulations and avoid costly experiments.

  17. Carbides and possible hydrogen irreversible trapping sites in ultrahigh strength round steel.

    Science.gov (United States)

    Cheng, X Y; Li, H; Cheng, X B

    2017-12-01

    The carbides in ultrahigh strength round steel have been investigated by using laser-assisted atom probe tomography (APT) and high resolution transmission electron microscopy (HRTEM) in this paper. Two kinds of carbides are found and one is iron carbide M6C, where carbide formation elements Cr, Mn and Mo replace partial Fe, while the other is niobium carbide MC, where M includes V and Mo besides Nb. These two carbides, due to their different evaporation field, have various densities in reconstructed image of APT. After correction, the hydrogen content within these two carbides illustrates that M6C cannot trap hydrogen, while MC can. The different behaviors in trapping hydrogen between these two carbides may result from elements Fe or Cr in M6C carbide having weaker affinity for hydrogen than Nb and V have in MC. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Investigations of the ternary system beryllium-carbon-tungsten and analyses of beryllium on carbon surfaces; Untersuchung des ternaeren Systems Beryllium-Kohlenstoff-Wolfram und Betrachtungen von Beryllium auf Kohlenstoffoberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Kost, Florian

    2009-05-25

    Beryllium, carbon and tungsten are planned to be used as first wall materials in the future fusion reactor ITER. The aim of this work is a characterization of mixed material formation induced by thermal load. To this end, model systems (layers) were prepared and investigated, which give insight into the basic physical and chemical concepts. Before investigating ternary systems, the first step was to analyze the binary systems Be/C and Be/W (bottom-up approach), where the differences between the substrates PG (pyrolytic graphite) and HOPG (highly oriented pyrolytic graphite) were of special interest. Particularly X-ray photoelectron spectroscopy (XPS), low energy ion scattering (ISS) and Rutherford backscattering spectroscopy (RBS) were used as analysis methods. Beryllium evaporated on carbon shows an island growth mode, whereas a closed layer can be assumed for layer thicknesses above 0.7 nm. Annealing of the Be/C system induces Be{sub 2}C island formation for T{>=}770 K. At high temperatures (T{>=}1170 K), beryllium carbide dissociates, resulting in (metallic) beryllium desorption. For HOPG, carbide formation starts at higher temperatures compared to PG. Activation energies for the diffusion processes were determined by analyzing the decreasing beryllium amount versus annealing time. Surface morphologies were characterized using angle-resolved XPS (ARXPS) and atomic force microscopy (AFM). Experiments were performed to study processes in the Be/W system in the temperature range from 570 to 1270 K. Be{sub 2}W formation starts at 670 K, a complete loss of Be{sub 2}W is observed at 1170 K due to dissociation (and subsequent beryllium desorption). Regarding ternary systems, particularly Be/C/W and C/Be/W were investigated, attaching importance to layer thickness (reservoir) variations. At room temperature, Be{sub 2}C, W{sub 2}C, WC and Be{sub 2}W formation at the respective interfaces was observed. Further Be{sub 2}C is forming with increasing annealing temperatures

  19. Annual Report: Fuels (30 September 2012)

    Energy Technology Data Exchange (ETDEWEB)

    Link, Dirk [NETL; Morreale, Bryan [NETL

    2012-09-30

    The thermochemical conversion of fossil fuels through gasification will likely be the cornerstone of future energy and chemical processes due to its flexibility to accommodate numerous feeds (coal, biomass, natural gas, municipal waste, etc.) and to produce a variety of products (heat, specialty chemicals, power, etc.), as well as the inherent nature of the process to facilitate near zero emissions. Currently, the National Energy Technology Laboratory (NETL) Fuels Program has two pathways for syngas utilization: The production of transportation fuels, chemicals, or chemical intermediates. The hydrogen production as an intermediate for power production via advanced combustion turbines or fuel cells. Work under this activity focuses on the production, separation, and utilization of hydrogen from syngas using novel separation materials and processes. Advanced integrated gasification combined cycle (IGCC) schemes require the production of clean hydrogen to fuel innovative combustion turbines and fuel cells. This research focuses on the development and assessment of membranes tailored for application in the severe environments associated with syngas conversion. The specific goals of this research include: Provide data needed to fully understand the impact of syngas environments and hydrogen removal on relevant hydrogen separation materials. Utilize the understanding of material stability to engineer a membrane tailored for operations in the severe environments associated with syngas conversion. Provide unbiased evaluation of hydrogen separation membranes being developed within the Fuels Program. Precious metals and alloys of historic interest (Pd, Cu, Ag, Au, Pt), as well as novel materials (carbides and phosphides) are candidates for evaluation of function as hydrogen separation membranes. The first step in the transport of hydrogen through dense metals is the adsorption and dissociation of hydrogen on the membrane surface. Observation shows that coal-based syngas

  20. Thermodynamic Study of Sn-Bi-Nd, Tb Ternary Systems

    Science.gov (United States)

    Xu, F.; Chen, Y. T.; Ye, R.; Chen, Y. Y.; Su, X. H.; Wang, S. L.; Fu, C. Y.

    2017-09-01

    The aim of this study was to investigate the effect of the addition of rare earth elements on Sn-Bi-based alloy, and to study the phase equilibrium of Sn-Bi-Nd, Tb ternary systems by means of establishing the thermodynamic database. Combined with the thermodynamic parameters of relevant binary systems, the thermodynamic database of the Sn-Bi-Nd, Tb ternary systems has been developed to present the significant information for the design of low-temperature lead-free solder alloys.

  1. Ternary jitter-based true random number generator

    Science.gov (United States)

    Latypov, Rustam; Stolov, Evgeni

    2017-01-01

    In this paper a novel family of generators producing true uniform random numbers in ternary logic is presented. The generator consists of a number of identical ternary logic combinational units connected into a ring. All the units are provided to have a random delay time, and this time is supposed to be distributed in accordance with an exponential distribution. All delays are supposed to be independent events. The theory of the generator is based on Erlang equations. The generator can be used for test production in various systems. Features of multidimensional random vectors, produced by the generator, are discussed.

  2. Liquid-liquid equilibria for ternary polymer mixtures

    Science.gov (United States)

    Oh, Suk Yung; Bae, Young Chan

    2011-01-01

    A molecular thermodynamic model for multicomponent systems based on a closed-packed lattice model is presented based on two contributions; entropy and energy contribution. The calculated liquid-liquid equilibria of ternary chainlike mixtures agreed with Monte Carlo simulation results. The proposed model can satisfactorily predict Types 0, 1, 2 and 3 phase separations of the Treybal classification. The model parameters obtained from the binary systems were used to directly predict real ternary systems and the calculated results correlated well with experimental data using few adjustable parameters. Specific interactions in associated binary systems were considered using a secondary lattice.

  3. PM1 steganographic algorithm using ternary Hamming Code

    Directory of Open Access Journals (Sweden)

    Kamil Kaczyński

    2015-12-01

    Full Text Available PM1 algorithm is a modification of well-known LSB steganographic algorithm. It has increased resistance to selected steganalytic attacks and increased embedding efficiency. Due to its uniqueness, PM1 algorithm allows us to use of larger alphabet of symbols, making it possible to further increase steganographic capacity. In this paper, we present the modified PM1 algorithm which utilizies so-called syndrome coding and ternary Hamming code. The modified algorithm has increased embedding efficiency, which means fewer changes introduced to carrier and increased capacity.[b]Keywords[/b]: steganography, linear codes, PM1, LSB, ternary Hamming code

  4. The ternary system: silicon-uranium-vanadium

    Energy Technology Data Exchange (ETDEWEB)

    Noel, Henri [Laboratoire de Chimie du Solide et Materiaux, UMR-CNRS 6226, Universite de Rennes I, Avenue du General Leclerc, F-35042 Rennes, Cedex (France); Rogl, Peter Franz, E-mail: peter.franz.rogl@univie.ac.a [Institute of Physical Chemistry, University of Vienna, A-1090 Wien, Waehringerstrasse 42 (Austria)

    2010-09-01

    Phase equilibria in the system Si-U-V were established at 1100 {sup o}C by optical microscopy, EMPA and X-ray diffraction. Two ternary compounds were observed, U{sub 2}V{sub 3}Si{sub 4} and (U{sub 1-x}V{sub x}){sub 5}Si{sub 3}, for which the crystal structures were elucidated by X-ray powder data refinement and found to be isotypic with the monoclinic U{sub 2}Mo{sub 3}Si{sub 4}-type (space group P2{sub 1}/c; a = 0.6821(3), b = 0.6820(4), c = 0.6735(3) nm, {beta} = 109.77(1){sup o}) and the tetragonal W{sub 5}Si{sub 3}-type (space group I4/mcm, a = 1.06825(2), c = 0.52764(2) nm), respectively. (U{sub 1-x}V{sub x}){sub 5}Si{sub 3} appears at 1100 {sup o}C without any significant homogeneity region at x {approx} 0.2 resulting in a formula U{sub 4}VSi{sub 3} which corresponds to a fully ordered atom arrangement. DTA experiments clearly show decomposition of this phase above 1206 {sup o}C revealing a two-phase region U{sub 3}Si{sub 2} + V{sub 3}Si. At 1100 {sup o}C U{sub 4}VSi{sub 3} is in equilibrium with V{sub 3}Si, V{sub 5}Si{sub 3}, U{sub 3}Si{sub 2} and U(V). At 800 {sup o}C U{sub 4}VSi{sub 3} forms one vertex of the tie-triangle to U{sub 3}Si and V{sub 3}Si. Due to the rather high thermodynamic stability of V{sub 3}Si and the corresponding tie-lines V{sub 3}Si + liquid at 1100 {sup o}C and V{sub 3}Si + U(V) below 925 {sup o}C, no compatibility exists between U{sub 3}Si or U{sub 3}Si{sub 2} and vanadium metal.

  5. The coloring problem in the solid-state metal boride carbide ScB{sub 2}C{sub 2}. A theoretical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lassoued, Souheila [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Boucher, Benoit [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Boutarfaia, Ahmed [Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Gautier, Regis; Halet, Jean-Francois [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques

    2016-08-01

    The electronic properties of the layered ternary metal boride carbide ScB{sub 2}C{sub 2}, the structure of which consists of B/C layers made of fused five- and seven-membered rings alternating with scandium sheets, are analyzed. In particular, the respective positions of the B and C atoms (the so-called coloring problem) are tackled using density functional theory, quantum theory of atoms in molecules, and electron localizability indicator calculations. Results reveal that (i) the most stable coloring minimizes the number of B-B and C-C contacts and maximizes the number of boron atoms in the heptagons, (ii) the compound is metallic in character, and (iii) rather important covalent bonding occurs between the metallic sheets and the boron-carbon network.

  6. Effect of ultra high temperature ceramics as fuel cladding materials on the nuclear reactor performance by SERPENT Monte Carlo code

    Energy Technology Data Exchange (ETDEWEB)

    Korkut, Turgay; Kara, Ayhan; Korkut, Hatun [Sinop Univ. (Turkey). Dept. of Nuclear Energy Engineering

    2016-12-15

    Ultra High Temperature Ceramics (UHTCs) have low density and high melting point. So they are useful materials in the nuclear industry especially reactor core design. Three UHTCs (silicon carbide, vanadium carbide, and zirconium carbide) were evaluated as the nuclear fuel cladding materials. The SERPENT Monte Carlo code was used to model CANDU, PWR, and VVER type reactor core and to calculate burnup parameters. Some changes were observed at the same burnup and neutronic parameters (keff, neutron flux, absorption rate, and fission rate, depletion of U-238, U-238, Xe-135, Sm-149) with the use of these UHTCs. Results were compared to conventional cladding material zircalloy.

  7. Recent progress in gasoline surrogate fuels

    KAUST Repository

    Sarathy, Mani

    2017-12-06

    Petroleum-derived gasoline is currently the most widely used fuel for transportation propulsion. The design and operation of gasoline fuels is governed by specific physical and chemical kinetic fuel properties. These must be thoroughly understood in order to improve sustainable gasoline fuel technologies in the face of economical, technological, and societal challenges. For this reason, surrogate mixtures are formulated to emulate the thermophysical, thermochemical, and chemical kinetic properties of the real fuel, so that fundamental experiments and predictive simulations can be conducted. Early studies on gasoline combustion typically adopted single component or binary mixtures (n-heptane/isooctane) as surrogates. However, the last decade has seen rapid progress in the formulation and utilization of ternary mixtures (n-heptane/isooctane/toluene), as well as multicomponent mixtures that span the entire carbon number range of gasoline fuels (C4–C10). The increased use of oxygenated fuels (ethanol, butanol, MTBE, etc.) as blending components/additives has also motivated studies on their addition to gasoline fuels. This comprehensive review presents the available experimental and chemical kinetic studies which have been performed to better understand the combustion properties of gasoline fuels and their surrogates. Focus is on the development and use of surrogate fuels that emulate real fuel properties governing the design and operation of engines. A detailed analysis is presented for the various classes of compounds used in formulating gasoline surrogate fuels, including n-paraffins, isoparaffins, olefins, naphthenes, and aromatics. Chemical kinetic models for individual molecules and mixtures of molecules to emulate gasoline surrogate fuels are presented. Despite the recent progress in gasoline surrogate fuel combustion research, there are still major gaps remaining; these are critically discussed, as well as their implications on fuel formulation and engine

  8. Synergistic increase of oxygen reduction favourable Fe-N coordination structures in a ternary hybrid of carbon nanospheres/carbon nanotubes/graphene sheets.

    Science.gov (United States)

    Zhang, Shiming; Liu, Bin; Chen, Shengli

    2013-11-14

    A Fe/N co-doped ternary nanocarbon hybrid, with uniform bamboo-like carbon nanotubes (CNTs) in situ grown on/between the single/few-layer graphene sheets interspaced by carbon nanosphere aggregates, was prepared through a one-pot heat treatment of a precursor mixture containing graphene oxide, Vulcan XC-72 carbon nanospheres, nitrogen rich melamine and small amounts of Fe ions. Physical characterization including electron microscopic images, N2 adsorption-desorption isotherms, pore size distribution, XPS, XRD, Mössbauer spectra, and EDX revealed that the 0-D/1-D/2-D ternary hybrid architecture not only offered an optimized morphology for high dispersion of each nanocarbon moiety, while the carbon nanosphere interspaced graphene sheets have provided a platform for efficient reaction between Fe ions and melamine molecules, resulting in uniform nucleation and growth of CNTs and formation of high density Fe-N coordination assemblies that have been believed to be the active centers for the oxygen reduction reaction (ORR) in carbon-based nonprecious metal electrocatalysts. In the absence of graphene oxides or carbon nanospheres, a similar heat treatment was found to result in large amounts of elemental Fe and Fe carbides and entangled CNTs with wide diameter distributions. As a result, the ternary Fe/N-doped nanocarbon hybrid exhibits ORR activity much higher than the Fe-N doped single or binary nanocarbon materials prepared under similar heat treatment conditions, and approaching that of the state-of-the-art carbon-supported platinum catalyst (Pt/C) in acidic media, as well as superior stability and methanol tolerance to Pt/C.

  9. Nerva Fuel Element Development Program Summary Report - July 1966 through June 1972 Extrusion Studies

    Energy Technology Data Exchange (ETDEWEB)

    Napier, J. M.

    1973-09-21

    This part of the completion report pertaining to the NERVA graphite fuel element program covers data collected during the extrusion studies. The physical properties of the fuel element reached the following values: coefficient of thermal expansion (CTE) - 7.0 x 10-6/o C (25 - l,OOOo C); modulus of elasticity - 1.5 x lo6 psi; flexural strength - - 8,000 psi; ultimate strain to failure - 5,500 pidin; good thermal stress resistance. Matrices were produced which could be vapor coated with crack-free films of zirconium carbide. The CTE of the matrix was almost equal to the CTE of the zirconium carbide coating.

  10. Neutron irradiation induced amorphization of silicon carbide

    Science.gov (United States)

    Snead, L. L.; Hay, J. C.

    1999-07-01

    This paper provides the properties of bulk stoichiometric silicon carbide which has been amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60°C to a total fast neutron fluence of 2.6 × 10 25 n/m 2. Amorphization was seen in both materials as evidenced by TEM, electron diffraction and X-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density (-10.8%), elastic modulus as measured using a nanoindentation technique (-45%), hardness as measured by nanoindentation (-45%), and standard Vickers hardness (-24%). Similar property changes are observed for the amorphized CVD SiC. Using measured thermal conductivity data for the CVD SiC sample, the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than ˜125°C.

  11. Feasibility study of fluxless brazing cemented carbides to steel

    Science.gov (United States)

    Tillmann, W.; Sievers, N.

    2017-03-01

    One of the most important brazing processes is the joints between cemented carbides and steel for the tool industry such as in rotary drill hammers or saw blades. Even though this technique has already been used for several decades, defects in the joint can still occur and lead to quality loss. Mostly, the joining process is facilitated by induction heating and the use of a flux to enhance the wetting of the filler alloy on the surface of the steel and cemented carbide in an ambient atmosphere. However, although the use of flux enables successful joining, it also generates voids within the joint, which reduces the strength of the connection while the chemicals within the flux are toxic and polluting. In this feasibility study, a fluxless brazing process is used to examine the joint between cemented carbides and steel for the first time. For this, ultrasound is applied during induction heating to enable the wetting between the liquid filler metal and the surfaces of the cemented carbide and steel. The ultrasound generates cavitations within the liquid filler metal, which remove the oxides from the surface. Several filler metals such as a silver based alloy Ag449, pure Zn, and an AlSi-alloy were used to reduce the brazing temperature and to lower the thermal residual stresses within the joint. As a result, every filler metal successfully wetted both materials and led to a dense connection. The ultrasound has to be applied carefully to prevent a damage of the cemented carbide. In this regard, it was observed that single grains of the cemented carbide broke out and remained in the joint. This positive result of brazing cemented carbides to steel without a flux but using ultrasound, allows future studies to focus on the shear strength of these joints as well as the behavior of the thermally induced residual stresses.

  12. Studies on Molecular Interaction in Ternary Liquid Mixtures

    Directory of Open Access Journals (Sweden)

    R. Uvarani

    2010-01-01

    Full Text Available Ultrasonic velocity, density and viscosity for the ternary liquid mixtures of cyclohexanone with 1-propanol and 1-butanol in carbon tetrachloride were measured at 303 K. The acoustical parameters and their excess values were calculated. The trends in the variation of these excess parameters were used to discuss the nature and strength of the interactions present between the component molecules.

  13. Hierarchic structure formation in binary and ternary polymer blends

    NARCIS (Netherlands)

    Sprenger, M; Walheim, S; Budkowski, A; Steiner, U

    The phase morphology of multi-component polymer blends is governed by the interfacial interactions of its components. We discuss here the domain morphology in thin films of model binary and ternary polymer blends containing polystyrene, poly(methyl metacrylate), and poly(2-vinylpyridine) (PS, PMMA,

  14. Mechanical, microstructure and electrical properties of ternary ZnO ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 38; Issue 3. Mechanical, microstructure and electrical properties of ternary ZnO–V2O5–Mn3O4 varistor with sintering temperature. S El-Rabai A H Khafagy M T Dawoud M T Attia. Volume 38 Issue 3 June 2015 pp 773-781 ...

  15. Intermolecular Interactions in Ternary Glycerol–Sample–H2O

    DEFF Research Database (Denmark)

    Westh, Peter; Rasmussen, Erik Lumby; Koga, Yoshikata

    2011-01-01

    We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H2O systems at 25 °C. By measuring the excess partial molar enthalpy of Gly, HGlyEHEGly, we evaluated the Gly–Gly enthalpic interaction, HGly-GlyEHEGly--Gly, in the presence of various samples (S). For S, tert...

  16. Excess isentropic compressibility and speed of sound of the ternary ...

    Indian Academy of Sciences (India)

    These excess properties of the binary mixtures were fitted to Redlich-Kister equation, while the Cibulka's equation was used to fit the values related to the values to the ternary system. These excess properties have been used to discuss the presence of significant interactions between the component molecules in the binary ...

  17. Robust self-triggered coordination with ternary controllers

    NARCIS (Netherlands)

    De Persis, Claudio; Frasca, Paolo

    2013-01-01

    This paper regards the coordination of networked systems, studied in the framework of hybrid dynamical systems. We design a coordination scheme which combines the use of ternary controllers with a self-triggered communication policy. The communication policy requires the agents to measure, at each

  18. Univolatility curves in ternary mixtures: geometry and numerical computation

    DEFF Research Database (Denmark)

    Shcherbakova, Nataliya; Rodriguez-Donis, Ivonne; Abildskov, Jens

    2017-01-01

    We propose a new non-iterative numerical algorithm allowing computation of all univolatility curves in homogeneous ternary mixtures independently of the presence of the azeotropes. The key point is the concept of generalized univolatility curves in the 3D state space, which allows the main...... computational part to be reduced to a simple integration of a system of ordinary differential equations....

  19. Evaluation of griseofulvin binary and ternary solid dispersions with HPMCAS.

    Science.gov (United States)

    Al-Obaidi, Hisham; Buckton, Graham

    2009-01-01

    The stability and dissolution properties of griseofulvin binary and ternary solid dispersions were evaluated. Solid dispersions of griseofulvin and hydroxypropyl methylcellulose acetate succinate (HPMCAS) were prepared using the spray drying method. A third polymer, poly[N-(2-hydroxypropyl)methacrylate] (PHPMA), was incorporated to investigate its effect on the interaction of griseofulvin with HPMCAS. In this case, HPMCAS can form H bonds with griseofulvin directly; the addition of PHPMA to the solid dispersion may enhance the stability of the amorphous griseofulvin due to greater interaction with griseofulvin. The X-ray powder diffraction results showed that griseofulvin (binary and ternary solid dispersions) remained amorphous for more than 19 months stored at 85% RH compared with the spray-dried griseofulvin which crystallized totally within 24 h at ambient conditions. The Fourier transform infrared scan showed that griseofulvin carbonyl group formed hydrogen bonds with the hydroxyl group in the HPMCAS, which could explain the extended stability of the drug. Further broadening in the peak could be seen when PHPMA was added to the solid dispersion, which indicates stronger interaction. The glass transition temperatures increased in the ternary solid dispersions regardless of HPMCAS grade. The dissolution rate of the drug in the solid dispersion (both binary and ternary) has significantly increased when compared with the dissolution profile of the spray-dried griseofulvin. These results reveal significant stability of the amorphous form due to the hydrogen bond formation with the polymer. The addition of the third polymer improved the stability but had a minor impact on dissolution.

  20. Excess isentropic compressibility and speed of sound of the ternary ...

    Indian Academy of Sciences (India)

    relation (NR), Van Deal's ideal mixing relation (IMR) and Junjie's relation (JR). The results are used to ... The compounds used were 2-propanol (>99 mass%), diethyl ether (>99.5 mass%) and n-hexane (>99 .... The excess speed of sound, uE, is estimated in binary and ternary mixtures using the following expression:.

  1. Viscometric and thermodynamic studies of interactions in ternary ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 117; Issue 3. Viscometric and thermodynamic studies of interactions in ternary solutions containing sucrose and aqueous alkali metal halides at 293.15, 303.15 and 313.15 K. Reena Gupta Mukhtar Singh. Volume 117 Issue 3 May 2005 pp 275-282 ...

  2. Modeling adsorption of binary and ternary mixtures on microporous media

    DEFF Research Database (Denmark)

    Monsalvo, Matias Alfonso; Shapiro, Alexander

    2007-01-01

    The goal of this work is to analyze the adsorption of binary and ternary mixtures on the basis of the multicomponent potential theory of adsorption (MPTA). In the MPTA, the adsorbate is considered as a segregated mixture in the external potential field emitted by the solid adsorbent. This makes i...

  3. A Simple Refraction Experiment for Probing Diffusion in Ternary Mixtures

    Science.gov (United States)

    Coutinho, Cecil A.; Mankidy, Bijith D.; Gupta, Vinay K.

    2010-01-01

    Diffusion is a fundamental phenomenon that is vital in many chemical processes such as mass transport in living cells, corrosion, and separations. We describe a simple undergraduate-level experiment based on Weiner's Method to probe diffusion in a ternary aqueous mixture of small molecular-weight molecules. As an illustration, the experiment…

  4. Electron paramagnetic resonance study of ternary Cu compounds ...

    Indian Academy of Sciences (India)

    Abstract. We report here electron paramagnetic resonance (EPR) measurements at 9 and 34 GHz, and room temperature (T ), in powder and single crystal samples of the ternary compounds of copper nitrate or copper chloride with glycine and 1,10-phenanthroline [Cu(Gly)(phen)(H2O)]·NO3·1.5H2O (1) and.

  5. IMPROVING THE PROPERTIES OF MILD STEEL BY TERNARY ...

    African Journals Online (AJOL)

    Protective coatings are perhaps the most extensively used system for chemical and mechanical degradation in application. ... mechanical and electrochemical resistance bond needful during application. .... binary phase of SiC and ZrO2 results to a reduction in the hardness value compare to the ternary phase which is in ...

  6. Experimental examination of ternary fission in nuclear track emulsion

    Science.gov (United States)

    Mamatkulov, K. Z.; Ambrožová, I.; Artemenkov, D. A.; Bradnova, V.; Firu, E.; Haiduc, M.; Kakona, M.; Kattabekov, R. R.; Marey, A.; Neagu, A.; Ploc, O.; Rusakova, V. V.; Stanoeva, R.; Turek, K.; Zaitsev, A. A.; Zarubin, P. I.; Zarubina, I. G.

    2017-11-01

    Activities performed in preparation for the search for ternary fission of heavy nuclei and the analysis of fragment angular correlations with nuclear track emulsion and an automated microscope are detailed. Surface irradiation of nuclear emulsion by a Cf source was initiated. Planar events containing nothing but fragment triples were found and studied.

  7. Reactions of water and C1 molecules on carbide and metal-modified carbide surfaces.

    Science.gov (United States)

    Wan, Weiming; Tackett, Brian M; Chen, Jingguang G

    2017-04-03

    The formation of carbides can significantly modify the physical and chemical properties of the parent metals. In the current review, we summarize the general trends in the reactions of water and C1 molecules over transition metal carbide (TMC) and metal-modified TMC surfaces and thin films. Although the primary focus of the current review is on the theoretical and experimental studies of reactions of C1 molecules (CO, CO2, CH3OH, etc.), the reactions of water will also be reviewed because water plays an important role in many of the C1 transformation reactions. This review is organized by discussing separately thermal reactions and electrochemical reactions, which provides insights into the application of TMCs in heterogeneous catalysis and electrocatalysis, respectively. In thermal reactions, we discuss the thermal decomposition of water and methanol, as well as the reactions of CO and CO2 over TMC surfaces. In electrochemical reactions, we summarize recent studies in the hydrogen evolution reaction, electrooxidation of methanol and CO, and electroreduction of CO2. Finally, future research opportunities and challenges associated with using TMCs as catalysts and electrocatalysts are also discussed.

  8. Kinetics of niobium carbide precipitation in ferrite; Cinetiques de precipitation du carbure de niobium dans la ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Gendt, D

    2001-07-01

    The aim of this study is to develop a NbC precipitation modelling in ferrite. This theoretical study is motivated by the fact it considers a ternary system and focus on the concurrence of two different diffusion mechanisms. An experimental study with TEP, SANS and Vickers micro-hardening measurements allows a description of the NbC precipitation kinetics. The mean radius of the precipitates is characterized by TEM observations. To focus on the nucleation stage, we use the Tomographic Atom Probe that analyses, at an atomistic scale, the position of the solute atoms in the matrix. A first model based on the classical nucleation theory and the diffusion-limited growth describes the precipitation of spherical precipitates. To solve the set of equations, we use a numerical algorithm that furnishes an evaluation of the precipitated fraction, the mean radius and the whole size distribution of the particles. The parameters that are the interface energy, the solubility product and the diffusion coefficients are fitted with the data available in the literature and our experimental results. It allows a satisfactory agreement as regards to the simplicity of the model. Monte Carlo simulations are used to describe the evolution of a ternary alloy Fe-Nb-C on a cubic centred rigid lattice with vacancy and interstitial mechanisms. This is realized with an atomistic description of the atoms jumps and their related frequencies. The model parameters are fitted with phase diagrams and diffusion coefficients. For the sake of simplicity, we consider that the precipitation of NbC is totally coherent and we neglect any elastic strain effect. We can observe different kinetic paths: for low supersaturations, we find an expected precipitation of NbC but for higher supersaturations, the very fast diffusivity of carbon atoms conducts to the nucleation of iron carbide particles. We establish that the occurrence of this second phenomenon depends on the vacancy arrival kinetics and can be related

  9. Neutronics Study on LEU Nuclear Thermal Rocket Fuel Options

    Energy Technology Data Exchange (ETDEWEB)

    Venneri, Paolo; Kim, Yong Hee [KAIST, Daejeon (Korea, Republic of); Howe, Steven [CSNR, Idaho (United States)

    2014-10-15

    This has resulted in a non-trivial simplification of the tasks needed to develop such an engine and the quick initial development of the concept. There are, however, a series of key core-design choices that are currently under scrutiny in the field that have to be resolved in order for the LEU-NTR to be fully developed. The most important of these is the choice of fuel: carbide composite or tungsten cermet. This study presents a first comparison of the two fuel types specifically in the neutronic application to the LEU-NTR, keeping in mind the unique neutronic environment and the system requirements of the system. The scope of the study itself is limited to a neutronics study of the two fuels and only a cursory overview of the material properties of the fuels themselves... The results of this study have led to two major conclusions. First of all is that the carbide composite fuel is, from a neutronics standpoint, a much better fuel. It has a low absorption cross-section, is inherently a strong moderator, is able to achieve a higher reactivity using smaller amounts of fissile material, and can potentially enable a smaller reactor. Second is that despite its neutronic difficulties (high absorption, inferior moderating abilities, and lower k-infinity values) the tungsten cermet fuel is still able to perform satisfactorily in an LEU-NTR, largely due to its ability to have an extremely high fuel loading.

  10. Technology development for phosphoric acid fuel cell powerplant (phase 2)

    Science.gov (United States)

    Christner, L.

    1979-01-01

    The status of technology for the manufacturing and testing of 1200 sq. cm cell materials, components, and stacks for on-site integrated energy systems is assessed. Topics covered include: (1) preparation of thin layers of silicon carbide; (2) definition and control schemes for volume changes in phosphoric acid fuel cells; (3) preparation of low resin content graphite phenolic resin composites; (4) chemical corrosion of graphite-phenolic resin composites in hot phosphoric acid; (5) analysis of electrical resistance of composite materials for fuel cells; and (6) fuel cell performance and testing.

  11. Heat-Resistance of the Powder Cobalt Alloys Reinforced by Niobium or Titanium Carbide

    OpenAIRE

    Cherepova, T.S.; Dmitrieva, G.P.; V.K. Nosenko

    2016-01-01

    The characteristics of heat-resistance of powder cobalt alloys at 1100 °C were investigated. These alloys were developed for the protection of workers banding shelves GTE blades from wear. The alloys were prepared by hot pressing powders of cobalt, chromium, aluminum, iron and niobium or titanium carbides. The values of heat resistance alloys containing carbides between 30 and 70% (vol.) depend on the type made of carbide alloys: alloys with titanium carbide superior in heat-resistant alloy o...

  12. Dilatometry Analysis of Dissolution of Cr-Rich Carbides in Martensitic Stainless Steels

    Science.gov (United States)

    Huang, Qiuliang; Volkova, Olena; Biermann, Horst; Mola, Javad

    2017-12-01

    The dissolution of Cr-rich carbides formed in the martensitic constituent of a 13 pct Cr stainless steel was studied by dilatometry and correlative electron channeling contrast examinations. The dissolution of carbides subsequent to the martensite reversion to austenite was associated with a net volume expansion which in turn increased the dilatometry-based apparent coefficient of thermal expansion (CTEa) during continuous heating. The effects of carbides fraction and size on the CTEa variations during carbides dissolution are discussed.

  13. Combined Photoemission Spectroscopy and Electrochemical Study of a Mixture of (Oxy)carbides as Potential Innovative Supports and Electrocatalysts.

    Science.gov (United States)

    Calvillo, Laura; Valero-Vidal, Carlos; Agnoli, Stefano; Sezen, Hikmet; Rüdiger, Celine; Kunze-Liebhäuser, Julia; Granozzi, Gaetano

    2016-08-03

    Active and stable non-noble metal materials, able to substitute Pt as catalyst or to reduce the Pt amount, are vitally important for the extended commercialization of energy conversion technologies, such as fuel cells and electrolyzers. Here, we report a fundamental study of nonstoichiometric tungsten carbide (WxC) and its interaction with titanium oxycarbide (TiOxCy) under electrochemical working conditions. In particular, the electrochemical activity and stability of the WxC/TiOxCy system toward the ethanol electrooxidation reaction (EOR) and hydrogen evolution reaction (HER) are investigated. The chemical changes caused by the applied potential are established by combining photoemission spectroscopy and electrochemistry. WxC is not active toward the ethanol electrooxidation reaction at room temperature but it is highly stable under these conditions thanks to the formation of a passive thin film on the surface, consisting mainly of WO2 and W2O5, which prevents the full oxidation of WxC. In addition, WxC is able to adsorb ethanol, forming ethoxy groups on the surface, which constitutes the first step for the ethanol oxidation. The interaction between WxC and TiOxCy plays an important role in the electrochemical stability of WxC since specific orientations of the substrate are able to stabilize WxC and prevent its corrosion. The beneficial interaction with the substrate and the specific surface chemistry makes tungsten carbide a good electrocatalyst support or cocatalyst for direct ethanol fuel cells. However, WxC is active toward the HER and chemically stable under hydrogen reduction conditions, since no changes in the chemical composition or dissolution of the film are observed. This makes tungsten carbide a good candidate as electrocatalyst support or cocatalyst for the electrochemical production of hydrogen.

  14. Elastic and piezoresistive properties of nickel carbides from first principles

    Science.gov (United States)

    Kelling, Jeffrey; Zahn, Peter; Schuster, Jörg; Gemming, Sibylle

    2017-01-01

    The nickel-carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube and graphene growth, where nickel carbide intermediates may be involved or carbide interface layers form in the end. Nickel-carbon composite thin films comprising Ni3C are especially interesting in mechanical sensing applications. Due to the metastability of nickel carbides, formation conditions and the coupling between mechanical and electrical properties are not yet well understood. Using first-principles electronic structure methods, we calculated the elastic properties of Ni3C ,Ni2C , and NiC , as well as changes in electronic properties under mechanical strain. We observe that the electronic density of states around the Fermi level does not change under the considered strains of up to 1%, which correspond to stresses up to 3 GPa . Relative changes in conductivity of Ni3C range up to maximum values of about 10%.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jingguan [University of Delaware

    2014-03-04

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

  16. Analysis of carbides and inclusions in high speed tool steels

    DEFF Research Database (Denmark)

    Therkildsen, K.T.; Dahl, K.V.

    2002-01-01

    The fracture surfaces of fatigued specimens were investigated using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The aim was to quantify the distribution of cracked carbides and non-metallic inclusions on the fracturesurfaces as well as on polished cross...... sections. The specimens were made of Böhler P/M steel grade 390s and 690s in both micro-clean and conventional grades. The results show that the content of non-metallic inclusions are higher in the conventionalgrades than in the microclean grades, but there were found to be no link between non-metallic...... inclusions and the crack initiation. Surprisingly, no differences were found between the carbide size distributions of the micro-clean and conventional grades.Also, the distribution of the fractured carbides was found to be the same regardless of steel type, manufacturing method or location on the specimen....

  17. Ordering of carbon atoms in boron carbide structure

    Energy Technology Data Exchange (ETDEWEB)

    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)

    2013-05-15

    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.

  18. Sintering of nano crystalline α silicon carbide by doping with boron ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Sinterable nano silicon carbide powders of mean particle size (37 nm) were prepared by attrition milling and chemical processing of an acheson type alpha silicon carbide having mean particle size of 0⋅39 µm. (390 nm). Pressureless sintering of these powders was achieved by addition of boron carbide of 0⋅5 wt ...

  19. Sintering of nano crystalline α silicon carbide by doping with boron ...

    Indian Academy of Sciences (India)

    Sinterable nano silicon carbide powders of mean particle size (37 nm) were prepared by attrition milling and chemical processing of an acheson type alpha silicon carbide having mean particle size of 0.39 m (390 nm). Pressureless sintering of these powders was achieved by addition of boron carbide of 0.5 wt% together ...

  20. Formation of Silicon Carbide in the Silicomanganese Process

    OpenAIRE

    Davidsen, Jens Erik

    2011-01-01

    As the silicon content in a silicomanganese alloy increase, silicon carbide becomes the stable carbon phase. Little work is published on the formation of silicon carbide in the SiMn process. This thesis examines the formation of SiC through the reaction between slag, metal and coke. The goal of the thesis has been to determine where and how SiC is formed in the silicomanganese process. Focus has been given to formation through liquid-solid reactions.The investigation was carried out by heatin...

  1. Fluorescent silicon carbide materials for white LEDs and photovoltaics

    DEFF Research Database (Denmark)

    Syväjärvi, Mikael; Ou, Haiyan; Wellmann, Peter

    the luminescence appears in the visible region which is used to produce a white LED with pure white light without need of phosphors [2]. The cubic silicon carbide polytype is challenging to master, and we have explored the growth of this crystal structure. It has a lower bandgap, and by a similar doping concept...... in cubic silicon carbide. The impurity photovoltaic effect could lead to devices with efficiencies comparable to those of tandem systems, and could open a new road for very-high-efficiency solar cells. Such high performance can be reached only if the host material has a large energy gap, like cubic silicon...

  2. Nanofibre growth from cobalt carbide produced by mechanosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Barriga-Arceo, L [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, Colonia San Bartolo Atepehuacan, Mexico DF, 07730 (Mexico); Orozco, E [Instituto de Fisica UNAM, Apartado Postal 20-364 CP 01000, DF (Mexico); Garibay-Febles, V [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, Colonia San Bartolo Atepehuacan, Mexico DF, 07730 (Mexico); Bucio-Galindo, L [Instituto de Fisica UNAM, Apartado Postal 20-364 CP 01000, DF (Mexico); Mendoza Leon, H [FM-UPALM, IPN, Apartado Postal 75-395 CP 07300, DF (Mexico); Castillo-Ocampo, P [UAM-Iztapalapa, Apartado Postal 55-334 CP 09340, DF (Mexico); Montoya, A [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, Colonia San Bartolo Atepehuacan, Mexico DF, 07730 (Mexico)

    2004-06-09

    Mechanical alloying was used to prepare cobalt carbide. Microstructural characterization of samples was performed by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy methods. In order to produce carbon nanotubes, the cobalt carbide was precipitated after heating at 800 and 1000 deg. C for 10 min. Nanofibres of about 10-50 nm in diameter, 0.04-0.1 {mu}m in length and 20-200 nm in diameter and 0.6-1.2 {mu}m in length were obtained after heating at 800 and 1000 deg. C, respectively, by means of this process.

  3. Ultrathin fiber poly-3-hydroxybutyrate, modified by silicon carbide nanoparticles

    Science.gov (United States)

    Olkhov, A. A.; Krutikova, A. A.; Goldshtrakh, M. A.; Staroverova, O. V.; Iordanskii, A. L.; Ischenko, A. A.

    2016-11-01

    The article presents the results of studies the composite fibrous material based on poly-3-hydroxybutyrate (PHB) and nano-size silicon carbide obtained by the electrospinning method. Size distribution of the silicon carbide nanoparticles in the fiber was estimated by X-ray diffraction technique. It is shown that immobilization of the SiC nanoparticles to the PHB fibers contributes to obtaining essentially smaller diameter of fibers, high physical-mechanical characteristics and increasing resistance to degradation in comparison with the fibers of PHB.

  4. Core-Shell Structured Magnetic Ternary Nanocubes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lingyan; Wang, Xin; Luo, Jin; Wanjala, Bridgid N.; Wang, Chong M.; Chernova, Natalya; Engelhard, Mark H.; Liu, Yao; Bae, In-Tae; Zhong, Chuan-Jian

    2010-12-01

    While transition metal-doped ferrite nanoparticles constitute an important class of soft magnetic nanomaterials with spinel structures, the ability to control the shape and composition would enable a wide range of applications in homogeneous or heterogeneous reactions such as catalysis and magnetic separation of biomolecules. This report describes novel findings of an investigation of core-shell structured MnZn ferrite nanocubes synthesized in organic solvents by manipulating the reaction temperature and capping agent composition in the absence of the conventionally-used reducing agents. The core-shell structure of the highly-monodispersed nanocubes (~20 nm) are shown to consist of an Fe3O4 core and an (Mn0.5Zn0.5)(Fe0.9, Mn1.1)O4 shell. In comparison with Fe3O4 and other binary ferrite nanoparticles, the core-shell structured nanocubes were shown to display magnetic properties regulated by a combination of the core-shell composition, leading to a higher coercivity (~350 Oe) and field-cool/zero-field-cool characteristics drastically different from many regular MnZn ferrite nanoparticles. The findings are discussed in terms of the unique core-shell composition, the understanding of which has important implication to the exploration of this class of soft magnetic nanomaterials in many potential applications such as magnetic resonance imaging, fuel cells, and batteries.

  5. Thermodynamic calculations in ternary titanium–aluminium–manganese system

    Directory of Open Access Journals (Sweden)

    ANA I. KOSTOV

    2008-04-01

    Full Text Available Thermodynamic calculations in the ternary Ti–Al–Mn system are shown in this paper. The thermodynamic calculations were performed using the FactSage thermochemical software and database, with the aim of determining thermodynamic properties, such as activities, coefficient of activities, partial and integral values of the enthalpies and Gibbs energies of mixing and excess energies at two different temperatures: 2000 and 2100 K. Bearing in mind that no experimental data for the Ti–Al–Mn ternary system have been obtained or reported. The obtained results represent a good base for further thermodynamic analysis and may be useful as a comparison with some future critical experimental results and thermodynamic optimization of this system.

  6. A New Multifunctional Sensor for Measuring Concentrations of Ternary Solution

    Science.gov (United States)

    Wei, Guo; Shida, Katsunori

    This paper presents a multifunctional sensor with novel structure, which is capable of directly sensing temperature and two physical parameters of solutions, namely ultrasonic velocity and conductivity. By combined measurement of these three measurable parameters, the concentrations of various components in a ternary solution can be simultaneously determined. The structure and operation principle of the sensor are described, and a regression algorithm based on natural cubic spline interpolation and the least square method is adopted to estimate the concentrations. The performances of the proposed sensor are experimentally tested by the use of ternary aqueous solution of sodium chloride and sucrose, which is widely involved in food and beverage industries. This sensor could prove valuable as a process control sensor in industry fields.

  7. Cohesion energy calculations for ternary ionic novel crystals

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez P, G.; Cabrera, E. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A.P. 20-364, 01000 Mexico D.F. (Mexico); Mijangos, R.R. [Centro de Investigacion en Fisica, Universidad de Sonora, A.P. 5-88, 83190 Hermosillo, Sonora (Mexico); Valdez, E. [Escuela Nacional de Estudios Profesionales Acatlan, Universidad Nacional Autonoma de Mexico, Santa Cruz Acatlan, Naucalpan (Mexico); Duarte, C. [Departamento de Geologia, Universidad de Sonora, 83000 Hermosillo, Sonora (Mexico)

    2001-07-01

    The present work calculates the value of the link energy of a crystalline ternary structure newly formed by alkali halides. The ternary structure prepared with different concentrations of KCl{sub x}KBrRbCl{sub 2} maintains a very good miscibility and stability. The calculation is based on the use of a generalization of the Vegard law (which generally is valid for binary compounds) for calculating the values of the lattice constant and the repulsive m exponent. The value of the lattice parameter given by X-ray diffractometry agrees with the close approximation of the calculated value of the method used. It also compares the value of energy cohesion obtained by the Born expression with more complex approximations. (Author)

  8. Hydrogen evolution activity and electrochemical stability of selected transition metal carbides in concentrated phosphoric acid

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Jensen, Jens Oluf; Bjerrum, Niels J.

    2014-01-01

    Alternative catalysts based on carbides of Group 5 (niobium and tantalum) and 6 (chromium, molybdenum and tungsten) metals were prepared as films on the metallic substrates. The electrochemical activities of these carbide electrodes towards the hydrogen evolution reaction (HER) in concentrated...... phosphoric acid were investigated in a temperature range from 80 to 170°C. A significant dependence of the activities on temperature was observed for all five carbide samples. Through the entire temperature range Group 6 metal carbides showed higher activity than that of the Group 5 metal carbides...

  9. Optical Properties of Silver Aluminium Sulphide Ternary Thin Films ...

    African Journals Online (AJOL)

    Ternary thin films of Silver Aluminium Sulphide (AgAlS2) have been prepared by chemical bath deposition techniques. Aqueous solution of 41.5 mls containing AgNO3, Al2(SO4)3, thiourea and EDTA was used, where AgNO3, Al2(SO4)3, thiourea were the source of Ag+, Al+ and S- respectively and EDTA was used as a ...

  10. Evaluation of Griseofulvin Binary and Ternary Solid Dispersions with HPMCAS

    OpenAIRE

    Al-Obaidi, Hisham; Buckton, Graham

    2009-01-01

    The stability and dissolution properties of griseofulvin binary and ternary solid dispersions were evaluated. Solid dispersions of griseofulvin and hydroxypropyl methylcellulose acetate succinate (HPMCAS) were prepared using the spray drying method. A third polymer, poly[N-(2-hydroxypropyl)methacrylate] (PHPMA), was incorporated to investigate its effect on the interaction of griseofulvin with HPMCAS. In this case, HPMCAS can form H bonds with griseofulvin directly; the addition of PHPMA to t...

  11. Some new quasi-twisted ternary linear codes

    Directory of Open Access Journals (Sweden)

    Rumen Daskalov

    2015-09-01

    Full Text Available Let [n, k, d]_q code be a linear code of length n, dimension k and minimum Hamming distance d over GF(q. One of the basic and most important problems in coding theory is to construct codes with best possible minimum distances. In this paper seven quasi-twisted ternary linear codes are constructed. These codes are new and improve the best known lower bounds on the minimum distance in [6].

  12. Theoretical prediction of topological insulator in ternary rare earth chalcogenides

    OpenAIRE

    Yan, Binghai; Zhang, Hai-Jun; Liu, Chao-Xing; Qi, Xiao-Liang; Frauenheim, Thomas; Zhang, Shou-Cheng

    2010-01-01

    A new class of three-dimensional topological insulator, ternary rare earth chalcogenides, is theoretically investigated with ab initio calculations. Based on both bulk band structure analysis and the direct calculation of topological surface states, we demonstrate that LaBiTe3 is a topological insulator. La can be substituted by other rare earth elements, which provide candidates for novel topological states such as quantum anomalous Hall insulator, axionic insulator and topological Kondo ins...

  13. Phase equilibria of the Mo-Al-Ho ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yitai; Chen, Xiaoxian; Liu, Hao [Guangxi Univ., Nanning (China). College of Materials Science and Engineering; Guangxi Univ., Nanning (China). Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials; Zhan, Yongzhong [Guangxi Univ., Nanning (China). College of Materials Science and Engineering; Guangxi Univ., Nanning (China). Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials; Guangxi Univ., Nanning (China). Center of Ecological Collaborative Innovation for Aluminum Industry

    2017-08-15

    Investigation into the reactions and phase equilibria of transition metal elements (i.e. Mo, Zr, Cr, V and Ti), Al and rare earths is academically and industrially important for the development of both refractory alloys and lightweight high-temperature materials. In this work, the equilibria of the Mo-Al-Ho ternary system at 773 K have been determined by using X-ray powder diffraction and scanning electron microscopy equipped with energy dispersive X-ray analysis. A new ternary phase Al{sub 4}Mo{sub 2}Ho has been found and the other ternary phase Al{sub 43}Mo{sub 4}Ho{sub 6} is observed. Ten binary phases in the Al-Mo and Al-Ho systems, including Al{sub 17}Mo{sub 4} rather than Al{sub 4}Mo, have been determined to exist at 773 K. The homogeneity ranges of AlMo{sub 3} and Al{sub 8}Mo{sub 3} phase are 7.5 at.% and 1 at.%, respectively. According to the phase-disappearing method, the maximum solubility of Al in Mo is about 16 at.%.

  14. Ternary Ag/epoxy adhesive with excellent overall performance.

    Science.gov (United States)

    Ji, Yan-Hong; Liu, Yu; Huang, Gui-Wen; Shen, Xiao-Jun; Xiao, Hong-Mei; Fu, Shao-Yun

    2015-04-22

    Excellent electrical conductivity (EC) generally conflicts with high lap shear strength (LSS) for electrically conductive adhesives (ECAs) since EC increases while LSS decreases with increasing conductive filler content. In this work, the ECAs with the excellent overall performance are developed based on the ternary hybrid of Ag microflakes (Ag-MFs), Ag nanospheres (Ag-NSs), and Ag nanowires (Ag-NWs). First, a low silver content adhesive system is determined. Then, the effects of the relative contents of Ag fillers on the EC and the LSS are studied. It is shown that a small amount of Ag-NSs or Ag-NWs can dramatically improve the EC for the Ag-MF/epoxy adhesives. The Ag-NSs and Ag-NWs with appropriate contents have a synergistic effect in improving the EC. Meanwhile, the LSS of the as-prepared adhesive with the appropriate Ag contents reaches an optimal value. Both the EC and the LSS of the as-prepared ternary hybrid ECA with a low content of 40 wt % Ag are higher than those of the commercial ECAs filled with the Ag-MF content over 60 wt %. Finally, the ternary hybrid ECA with the optimal formulation is shown to be promising for printing the radio frequency identification tag antennas as an immediate application example.

  15. Valence band electronic structure of Pd based ternary chalcogenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lohani, H. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India); Mishra, P. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Goyal, R.; Awana, V.P.S. [National Physical Laboratory(CSIR), Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sekhar, B.R., E-mail: sekhar@iopb.res.in [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India)

    2016-12-15

    Highlights: • VB Photoemission study and DFT calculations on Pd based ternary superconductors are presented. • Nb{sub 2}Pd{sub 0.95}S{sub 5} shows a temperature dependent pseudogap. • VB spectral features of ternary superconductors are correlated to their structural geometry. - Abstract: We present a comparative study of the valence band electronic structure of Pd based ternary chalcogenide superconductors Nb{sub 2}Pd{sub 0.95}S{sub 5}, Ta{sub 2}Pd{sub 0.97}S{sub 6} and Ta{sub 2}Pd{sub 0.97}Te{sub 6} using experimental photoemission spectroscopy and density functional based theoretical calculations. We observe a qualitatively similarity between valence band (VB) spectra of Nb{sub 2}Pd{sub 0.95}S{sub 5} and Ta{sub 2}Pd{sub 0.97}S{sub 6}. Further, we find a pseudogap feature in Nb{sub 2}Pd{sub 0.95}S{sub 5} at low temperature, unlike other two compounds. We have correlated the structural geometry with the differences in VB spectra of these compounds. The different atomic packing in these compounds could vary the strength of inter-orbital hybridization among various atoms which leads to difference in their electronic structure as clearly observed in our DOS calculations.

  16. Realizing Ternary Logic in FPGAs for SWL DSP Systems

    Directory of Open Access Journals (Sweden)

    Tayeb Din

    2013-07-01

    Full Text Available Recently SWL (Short Word Length DSP (Digital Signal Processing applications has been proposed to overcome multiplier complexity that is evident in most of the digital applications. These SWL applications have been processed through sigma-delta modulation as a key element. For such applications, adder design plays vital role and can impact upon the chip area and its performance. In this paper, a ternary approach for adder tree has been proposed instead of binary that can accommodate more data with less chip-area at the cost of extra pin. The proposed ternary adder tree has been designed and developed in Quartus-II using three different design strategies namely T-gate (Ternary gate, LUT (Look Up Table and algebraic equations. Through rigorous simulation it was found that T-gate technique results in superior performance, an average of 23.5 and 33% improvement compared to the same adder structure based on Boolean Algebraic Equation and LUT, respectively. The proposed adder design would benefit the efficient implementation of SWL applications.

  17. Growth stress in tungsten carbide-diamond-like carbon coatings

    NARCIS (Netherlands)

    Pujada, B.R.; Tichelaar, F.D.; Arnoldbik, W.M.; Sloof, W.G.; Janssen, G.C.A.M.

    2009-01-01

    Growth stress in tungsten carbide-diamond-like carbon coatings, sputter deposited in a reactive argon/acetylene plasma, has been studied as a function of the acetylene partial pressure. Stress and microstructure have been investigated by wafer curvature and transmission electron microscopy (TEM)

  18. Highly permeable and mechanically robust silicon carbide hollow fiber membranes

    NARCIS (Netherlands)

    de Wit, Patrick; Kappert, Emiel; Lohaus, T.; Wessling, Matthias; Nijmeijer, Arian; Benes, Nieck Edwin

    2015-01-01

    Silicon carbide (SiC) membranes have shown large potential for applications in water treatment. Being able to make these membranes in a hollow fiber geometry allows for higher surface-to-volume ratios. In this study, we present a thermal treatment procedure that is tuned to produce porous silicon

  19. stabilization of ikpayongo laterite with cement and calcium carbide ...

    African Journals Online (AJOL)

    PROF EKWUEME

    Laterite obtained from Ikpayongo was stabilized with 2-10 % cement and 2-10 % Calcium Carbide waste, for use as pavement material. Atterberg's limits test, California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were conducted on the natural laterite and the treated soil specimens. The plasticity ...

  20. Erratum to: Synthesis and investigation of silicon carbide nanowires ...

    Indian Academy of Sciences (India)

    Bull. Mater. Sci., Vol. 39, No. 4, August 2016, p. 961. c Indian Academy of Sciences. DOI 10.1007/s12034-016-1267-y. Erratum to: Synthesis and investigation of silicon carbide nanowires by. HFCVD method. S H MORTAZAVI. ∗. , M GHORANNEVISS, M DADASHBABA and R ALIPOUR. Plasma Physics Research Center, ...

  1. Influence of nanometric silicon carbide on phenolic resin composites ...

    Indian Academy of Sciences (India)

    Department of Polymer Science & Rubber Technology,. Cochin University of Science and Technology. [32] Perez J M, Echeverria J M, Oliet M, Alonso M V and. Rodriguez F 2007 BioResources 2 270. [33] Janz S 2006 Amorphous silicon carbide for photovoltaic applications (Masters Thesis). Fakultät für Physik Universität.

  2. Effect of tempering after cryogenic treatment of tungsten carbide ...

    Indian Academy of Sciences (India)

    #Department of Industrial and Production Engineering, National Institute of Technology, Jalandhar 144 001, India. MS received 10 ... Tungsten carbide is the most commonly used cutting tool material in the industry and the tech- nique can also be ..... in the WC-Co inserts and was present in the form of clusters of particles ...

  3. Erratum to: Synthesis and investigation of silicon carbide nanowires ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 4. Erratum to: Synthesis and investigation of silicon carbide nanowires by HFCVD method. S H MORTAZAVI M GHORANNEVISS M DADASHBABA R ALIPOUR. Volume 39 Issue 4 August 2016 pp 961-961 ...

  4. On Measurement and Interpretation of Toughness Behaviour of Carbide Tools

    NARCIS (Netherlands)

    Kals, H.J.J.

    1981-01-01

    The actual significance of any definition of toughness behaviour of carbide tools depends on the existence of an interrelation between the quality as defined and the occurrence of chipping and premature failure in cutting. While at present there is no adequate analysis available and the existing

  5. Synthesis and investigation of silicon carbide nanowires by HFCVD ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 4. Synthesis and investigation of silicon carbide nanowires by HFCVD ... Also Mountains Map Premium (64-bit version)software is used to investigate morphological features of samples. In this context, the analysis of the motifs, depth histograms, statistical ...

  6. Indentation fatigue in silicon nitride, alumina and silicon carbide ...

    Indian Academy of Sciences (India)

    Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 m and 25 m, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker's ...

  7. Stabilization of Ikpayongo laterite with cement and calcium carbide ...

    African Journals Online (AJOL)

    Laterite obtained from Ikpayongo was stabilized with 2-10 % cement and 2-10 % Calcium Carbide waste, for use as pavement material. Atterberg's limits test, California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were conducted on the natural laterite and the treated soil specimens. The plasticity ...

  8. RICE-HUSK ASH-CARBIDE-WASTE STABILIZATION OF ...

    African Journals Online (AJOL)

    This paper present results of the laboratory evaluation of the characteristics of carbide waste and rice husk ash stabilized reclaimed asphalt pavement waste with a view to determine its suitability for use as flexible pavement material. The mixtures were subjected to British Standard heavy compactive effort to determine the ...

  9. Carbide-fluoride-silver self-lubricating composite

    Science.gov (United States)

    Sliney, Harold E. (Inventor)

    1987-01-01

    A self-lubricating, friction and wear reducing composite material is described for use over a wide temperature spectrum from cryogenic temperature to about 900 C in a chemically reactive environment comprising silver, barium fluoride/calcium fluoride eutectic, and metal bonded chromium carbide.

  10. Carbide/fluoride/silver self-lubricating composite

    Science.gov (United States)

    Sliney, Harold E. (Inventor)

    1988-01-01

    A self-lubricating, friction and wear reducing composite material for use over a wide temperature spectrum from cryogenic temperature to about 900.degree. C. in a chemically reactive environment comprising silver, barium fluoride/calcium fluoride eutectic, and metal bonded chromium carbide.

  11. SEM investigation of minor constituents of carbide materials ...

    Indian Academy of Sciences (India)

    It is revealed that the noble metals phases occur as separate microsized grains, most of which have been indicated as Au–Ag–Hg amalgam and rarely as Pt-rich compounds. The obtained data can be mainly used to advance technologies for manufacturing carbide-based composite materials from natural carbonaceous ...

  12. Sintering of nano crystalline o silicon carbide doping with

    Indian Academy of Sciences (India)

    Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by ...

  13. Protective infrared antireflection coating based on sputtered germanium carbide

    Science.gov (United States)

    Gibson, Des; Waddell, Ewan; Placido, Frank

    2011-09-01

    This paper describes optical, durablility and environmental performance of a germanium carbide based durable antireflection coating. The coating has been demonstrated on germanium and zinc selenide infra-red material however is applicable to other materials such as zinc sulphide. The material is deposited using a novel reactive closed field magnetron sputtering technique, offering significant advantages over conventional evaporation processes for germanium carbide such as plasma enhanced chemical vapour deposition. The sputtering process is "cold", making it suitable for use on a wide range of substrates. Moreover, the drum format provide more efficient loading for high throughput production. The use of the closed field and unbalanced magnetrons creates a magnetic confinement that extends the electron mean free path leading to high ion current densities. The combination of high current densities with ion energies in the range ~30eV creates optimum thin film growth conditions. As a result the films are dense, spectrally stable, supersmooth and low stress. Films incorporate low hydrogen content resulting in minimal C-H absorption bands within critical infra-red passbands such as 3 to 5um and 8 to 12um. Tuning of germanium carbide (Ge(1-x)Cx) film refractive index from pure germanium (refractive index 4) to pure germanium carbide (refractive index 1.8) will be demonstrated. Use of film grading to achieve single and dual band anti-reflection performance will be shown. Environmental and durability levels are shown to be suitable for use in harsh external environments.

  14. Silicon Carbide and Magnetorresistive Technologies for Solid State Power Controllers

    Directory of Open Access Journals (Sweden)

    Garrigós A.

    2017-01-01

    Full Text Available The aim of this paper is to make an introduction, review and preliminary investigation tasks of the application of Silicon Carbide (SiC power semiconductors and magnetoresistive (MR current sensors for Solid State Power Controllers (SSPCs and controlled switches, especially for high temperature environment and/or high voltage applications.

  15. Influence of nanometric silicon carbide on phenolic resin composites ...

    Indian Academy of Sciences (India)

    ... tribological performance, improving their strength, stiffness and abrasive properties. The best results were obtained for 1 wt% nSiC, proving that this value is the optimum nanometric silicon carbide content. The results indicate that these materials could be effectively used to obtain ablative or carbon–carbon composites in ...

  16. Effect of tempering after cryogenic treatment of tungsten carbide ...

    Indian Academy of Sciences (India)

    Cryogenic treatment is a recent advancement in the field of machining to improve the properties of cutting tool materials. Tungsten carbide is the most commonly used cutting tool material in the industry and the technique can also be extended to it. Although the importance of tempering after cryogenic treatment has been ...

  17. PECVD silicon carbide surface micromachining technology and selected MEMS applications

    NARCIS (Netherlands)

    Rajaraman, V.; Pakula, L.S.; Yang, H.; French, P.J.; Sarro, P.M.

    2011-01-01

    Attractive material properties of plasma enhanced chemical vapour deposited (PECVD) silicon carbide (SiC) when combined with CMOS-compatible low thermal budget processing provides an ideal technology platform for developing various microelectromechanical systems (MEMS) devices and merging them with

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

    Energy Technology Data Exchange (ETDEWEB)

    Z. Zak Fang, H. Y. Sohn

    2009-03-10

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

  19. Synthesis of carbon fibre-reinforced, silicon carbide composites by ...

    Indian Academy of Sciences (India)

    pyrolysis (PIP), liquid silicon infiltration (LSI), sol–gel, reaction hot-pressing, have been used for ... resin matrix and is then infiltrated with molten silicon (Krenkel 2001); but the presence of free silicon may act as a ... and (iv) finally carbothermal reduction of oxides to carbides/borides at 1873 and 1973 K for 3 h as shown by ...

  20. Influence of Blending Canola, Palm, Soybean, and Sunflower Oil Methyl Esters on Fuel Properties of Bioiesel

    Science.gov (United States)

    Single, binary, ternary, and quaternary mixtures of canola (low erucic acid rapeseed), palm, soybean, and sunflower (high oleic acid) oil methyl esters (CME, PME, SME, and SFME, respectively) were prepared and important fuel properties measured, such as oil stability index (OSI), cold filter pluggin...

  1. Microprobe investigations of irradiated uranium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Kleykamp, H.

    1973-12-01

    A shielded Cameca microprobe, MS 46, was used to examine a UC sample canned in SAP and irradiated to a burnup of 0.7%. An annular zone at about 40% of the outer sample radius was seen to contain precipitates loaded with fission products; microprobe analysis showed the precipitates to be U/sub 2/ (Tc, Ru, Rh)C/sub 2/. Small amounts of palladium can be stabilized in this phase. Zirconium and molybdenum were verified in homogeneous distribution in the fuel. The Vickers hardness of the irradiated UC is 1000 to 1200 kg/mm/sup 2/. No signs of incompatibility with the canning material were detected. (auth)

  2. Heat-Resistance of the Powder Cobalt Alloys Reinforced by Niobium or Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Cherepova, T.S.

    2016-01-01

    Full Text Available The characteristics of heat-resistance of powder cobalt alloys at 1100 °C were investigated. These alloys were developed for the protection of workers banding shelves GTE blades from wear. The alloys were prepared by hot pressing powders of cobalt, chromium, aluminum, iron and niobium or titanium carbides. The values of heat resistance alloys containing carbides between 30 and 70% (vol. depend on the type made of carbide alloys: alloys with titanium carbide superior in heat-resistant alloy of niobium carbide. The most significant factor affecting on the heat-resistant alloys, is porosity: with its increase the parameters decline regardless of the type and content of carbide. The optimum composition of powder heat resisting alloys of titanium carbide with a melting point above 1300 °C were determined for use in the aircraft engine.

  3. Formation mechanism of spheroidal carbide in ultra-low carbon ductile cast iron

    Directory of Open Access Journals (Sweden)

    Bin-guo Fu

    2016-09-01

    Full Text Available The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.

  4. Synthesis, Characterization, and Enhanced Magnetic Properties of Iron Carbide Nanomaterials

    Science.gov (United States)

    Williams, Brent M.

    Permanent magnets are classified as hard magnetic materials with the main purpose of generating flux for applications such as electric motors, turbines, and hard drives. High coercivity, magnetic remanence, and saturation values with high stability are some of the requirements for permanent magnets. Rare-earth magnets including neodymium and samarium based magnets are known to have superior magnetic properties due to their high magnetocrystalline anisotropy. However, due to the price of rare-earth materials development of alternate permanent magnets composed of inexpensive materials is an ongoing process. Previously cobalt carbide (CoxC) have shown promise as a potential rare-earth free magnet alternative with magnetic properties comparable to that of hexaferrite materials. Unfortunately, CoxC magnets have a low magnetic saturation (50 emu g-1) which drastically lowers its energy product. Alternatively, iron carbide has a rather high bulk magnetization value of 140 emu g-1 and is composed of naturally abundant materials. The sole issue of iron carbide is that it is considered an intermediate magnet with properties between those of a hard and a soft magnetic material. The main focus of this work is the enhancement of the hard magnetic properties of iron carbide through size effect, shape anisotropy, magnetocrystalline anisotropy and exchange anisotropy. First a wet synthesis method was developed which utilized hexadecyltrimethylammonium chloride to control particle size, shape, and crystal structure to manipulate the magnetic properties of iron carbide. With this method a semi-hard 50 nm orthorhombic Fe3C phase and a magnetically soft single crystal hexagonal Fe7C3 structure with texture-induced magnetic properties were developed. The properties for both materials were further enhanced through formation of exchange bias Fe3C/CoO nanoaggregates and spring exchange coupling of the ferromagnetically hard and soft phases of Fe7C3/SrFe 12O19. A 33% increase in coercivity

  5. Coarsening of carbides during different heat treatment conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Kai, E-mail: miaok21@126.com; He, Yanlin, E-mail: ylhe@staff.shu.edu.cn; Zhu, Naqiong; Wang, Jingjing; Lu, Xiaogang; Li, Lin

    2015-02-15

    Highlights: • Coarsening of M{sub 7}C{sub 3} and V{sub 4}C{sub 3} carbides was quantitatively described in detail. • Cooling mode is a key factor to the simulation for the coarsening of carbides. • Coarsening of above spherical carbides can be calculated by Ostwald ripening model. • The interfacial energy between the γ matrix with M{sub 7}C{sub 3} and V{sub 4}C{sub 3} carbides are 0.7 J/m{sup 2}. - Abstract: Coarsening of carbides in 1# Fe-5.96Cr-0.35C (wt.%) alloy and 2# Fe-0.5V-0.53C (wt.%) alloy during different heat treatment conditions was investigated by carbon replica, high-resolution transmission electron microscopy (HRTEM) , X-ray diffraction (XRD) and SEM techniques. The equilibrium phases at 850 °C constitute of austenitic matrix (γ) + M{sub 7}C{sub 3} and austenite matrix (γ) + V{sub 4}C{sub 3} for 1# and 2# alloy respectively. Morphology of M{sub 7}C{sub 3} and V{sub 4}C{sub 3} carbides was mainly determined by cooling mode due to the different nucleation sites and growth mechanisms. Under directly aging condition, most carbides nucleate in the grain boundaries and grow into rod-shaped or flake-shaped particles by discontinuous growth mechanism. These particles turn out to be excluded during coarsening simulation using Oswald ripening model to give a more reasonable result. In addition, interfacial energy between M{sub 7}C{sub 3}/γ and V{sub 4}C{sub 3}/γ for the coarsening of M{sub 7}C{sub 3} and V{sub 4}C{sub 3} during aging at 850 °C is evaluated by fitting experimental data using thermodynamic and kinetic calculations. The interfacial energy is determined to be 0.7 J/m{sup 2} for the coarsening of M{sub 7}C{sub 3} and V{sub 4}C{sub 3} in austenitic matrix.

  6. Comparison of diffusion coefficients and activation energies for Ag diffusion in silicon carbide

    Directory of Open Access Journals (Sweden)

    Bong Goo Kim

    2015-08-01

    Full Text Available The migration of silver (Ag in silicon carbide (SiC and 110mAg through SiC of irradiated tri-structural isotropic (TRISO fuel has been studied for the past three to four decades. However, there is no satisfactory explanation for the transport mechanism of Ag in SiC. In this work, the diffusion coefficients of Ag measured and/or estimated in previous studies were reviewed, and then pre-exponential factors and activation energies from the previous experiments were evaluated using Arrhenius equation. The activation energy is 247.4 kJ·mol−1 from Ag paste experiments between two SiC layers produced using fluidized-bed chemical vapor deposition (FBCVD, 125.3 kJ·mol−1 from integral release experiments (annealing of irradiated TRISO fuel, 121.8 kJ·mol−1 from fractional Ag release during irradiation of TRISO fuel in high flux reactor (HFR, and 274.8 kJ·mol−1 from Ag ion implantation experiments, respectively. The activation energy from ion implantation experiments is greater than that from Ag paste, fractional release and integral release, and the activation energy from Ag paste experiments is approximately two times greater than that from integral release experiments and fractional Ag release during the irradiation of TRISO fuel in HFR. The pre-exponential factors are also very different depending on the experimental methods and estimation. From a comparison of the pre-exponential factors and activation energies, it can be analogized that the diffusion mechanism of Ag using ion implantation experiment is different from other experiments, such as a Ag paste experiment, integral release experiments, and heating experiments after irradiating TRISO fuel in HFR. However, the results of this work do not support the long held assumption that Ag release from FBCVD-SiC, used for the coating layer in TRISO fuel, is dominated by grain boundary diffusion. In order to understand in detail the transport mechanism of Ag through the coating layer, FBCVD

  7. 1976 scientific progress report. [Fuel and coating materials for HTGR]; Wissenschaftlicher Ergebnisberict 1976

    Energy Technology Data Exchange (ETDEWEB)

    Nickel, H.

    1976-07-01

    Activities at the Institute for Reactor Materials in the production and properties of high temperature gas cooled reactor fuel and coating materials are summarized. Major emphasis was placed on investigations of pyrocarbon, BISO and TRISO coatings, uranium and thorium oxides and carbides, and graphite and matrix materials. A list of publications is included. (HDR)

  8. Effect of tungsten carbide in carbon Pt catalyst support on electrochemical oxygen reduction in acid solution

    Directory of Open Access Journals (Sweden)

    Obradović Maja D.

    2013-01-01

    Full Text Available Tungsten carbide was synthesized by calcination of carbon cryogel with embedded tungsten in a form of metatungstate. This material was used as a support for Pt nanoparticles. XRD pattern of W-C support indicates the presence of WC, W2C, and unreacted W, as well as graphitized carbon. According to the previous TEM analysis of W-C support, it contains particles with core-shell structure, where W particle was covered with the shell of a mixture of WC and W2C. The average Pt grain size calculated from XRD pattern was about 6 nm. Cyclic voltammogram of W-C support was recorded within potential range relevant for its application as a catalyst support in fuel cells. Pair of anodic/cathodic peaks close to the negative potential limit could be ascribed to the intercalation of hydrogen within hydrous tungsten oxide, which is always present on the surface of WC in aqueous solutions. Cyclic voltammogram of Pt/W-C indicated that tungsten oxide species are present on tungsten carbide shell as well as on the surface of Pt nanoparticles. Pt surface is only partially covered by hydrous tungsten oxide. Hydrogen intercalation in hydrous tungsten oxide is enhanced in the presence of Pt nanoparticles. Also, the presence of hydrated tungsten oxide leads to the decrease of OH chemisorbed on Pt surface. Stripping of underpotentially deposited copper was used for the assessment of Pt surface area and the specific surface area of Pt was estimated to 41 m2 g-1. Electrochemical oxygen reduction reaction was examined on the synthesized Pt/W-C catalyst and compared with the results on the commercial Pt/C catalyst. It was found that the current densities at Pt/W-C are almost double as those on Pt/C. The Tafel plots for both catalysts are characterized with two Tafel slopes: -0.060 V dec-1 at low current densities, and -0.120 V dec-1 at high current densities. From the rotational dependence of the reaction rate, it was found that oxygen reduction on both Pt/W-C and Pt

  9. Information on individual interfaces in ternary polymer blends from positron annihilation lifetime studies

    Science.gov (United States)

    Meghala, D.; Ramya, P.; Pasang, T.; Ravikumar, H. B.; Ranganathaiah, C.

    2012-06-01

    Positron Annihilation Lifetime Spectroscopy has been used to determine the free volume content in the ternary blends of SAN/EVA/PVC. The method of deriving hydrodynamic interaction parameter (α) in binary polymer blends was modified for ternary polymer blend system characterized by three distinct interfaces. Each interface characterized, is associated with an α and its assertion for the ternary blend are compared with available literature data.

  10. Nuclear fuels

    Energy Technology Data Exchange (ETDEWEB)

    Beauvy, M.; Berthoud, G.; Defranceschi, M.; Ducros, G.; Guerin, Y.; Limoge, Y.; Madic, Ch.; Santarini, G.; Seiler, J.M.; Sollogoub, P.; Vernaz, E.; Guillet, J.L.; Ballagny, A.; Bechade, J.L.; Bonin, B.; Brachet, J.Ch.; Delpech, M.; Dubois, S.; Ferry, C.; Freyss, M.; Gilbon, D.; Grouiller, J.P.; Iracane, D.; Lansiart, S.; Lemoine, P.; Lenain, R.; Marsault, Ph.; Michel, B.; Noirot, J.; Parrat, D.; Pelletier, M.; Perrais, Ch.; Phelip, M.; Pillon, S.; Poinssot, Ch.; Vallory, J.; Valot, C.; Pradel, Ph.; Bonin, B.; Bouquin, B.; Dozol, M.; Lecomte, M.; Vallee, A.; Bazile, F.; Parisot, J.F.; Finot, P.; Roberts, J.F

    2009-07-01

    Fuel is one of the essential components in a reactor. It is within that fuel that nuclear reactions take place, i.e. fission of heavy atoms, uranium and plutonium. Fuel is at the core of the reactor, but equally at the core of the nuclear system as a whole. Fuel design and properties influence reactor behavior, performance, and safety. Even though it only accounts for a small part of the cost per kilowatt-hour of power provided by current nuclear power plants, good utilization of fuel is a major economic issue. Major advances have yet to be achieved, to ensure longer in-reactor dwell-time, thus enabling fuel to yield more energy; and improve ruggedness. Aside from economics, and safety, such strategic issues as use of plutonium, conservation of resources, and nuclear waste management have to be addressed, and true technological challenges arise. This Monograph surveys current knowledge regarding in-reactor behavior, operating limits, and avenues for R and D. It also provides illustrations of ongoing research work, setting out a few noteworthy results recently achieved. Content: 1 - Introduction; 2 - Water reactor fuel: What are the features of water reactor fuel? 9 (What is the purpose of a nuclear fuel?, Ceramic fuel, Fuel rods, PWR fuel assemblies, BWR fuel assemblies); Fabrication of water reactor fuels (Fabrication of UO{sub 2} pellets, Fabrication of MOX (mixed uranium-plutonium oxide) pellets, Fabrication of claddings); In-reactor behavior of UO{sub 2} and MOX fuels (Irradiation conditions during nominal operation, Heat generation, and removal, The processes involved at the start of irradiation, Fission gas behavior, Microstructural changes); Water reactor fuel behavior in loss of tightness conditions (Cladding, the first containment barrier, Causes of failure, Consequences of a failure); Microscopic morphology of fuel ceramic and its evolution under irradiation; Migration and localization of fission products in UOX and MOX matrices (The ceramic under

  11. Role of alloying elements and carbides in the chlorine-induced corrosion of steels and alloys

    Directory of Open Access Journals (Sweden)

    Hans Jürgen Grabke

    2004-03-01

    Full Text Available The high temperature corrosion of steels and Ni-base alloys in oxidizing and chloridizing environments is of practical interest in relation to problems in waste incineration plants and power plants using Cl containing fuels. The behaviour of the most important alloying elements Fe, Cr, Ni, Mo, Mn, Si, Al upon corrosion in an oxidizing and chloridizing atmosphere was elucidated: the reactions and kinetics can be largely understood on the base of thermodynamic data, i.e. free energy of chloride formation, vapor pressure of the chlorides and oxygen pressure pO2 needed for the conversion chlorides -> oxides. The mechanism is described by 'active oxidation', comprising inward penetration of chlorine into the scale, formation of chlorides at the oxide/metal interface, evaporation of the chlorides and conversion of the evaporating chlorides into oxides, which occurs in more or less distance from the surface (depending on pO2. This process leads to loose, fragile, multilayered oxides which are unprotective (therefore: active oxidation. Fe and Cr are rapidly transferred into such scale, Ni and Mo are relatively resistant. In many cases, the grain boundaries of the materials are strongly attacked, this is due to a susceptibility of chromium carbides to chloridation. In contrast the carbides Mo2C, TiC and NbC are less attacked than the matrix. Alloys on the basis Fe-Cr-Si proved to be rather resistant, and the alloying elements Ni and Mo clearly retard the attack in an oxidizing and chloridizing environment.

  12. Crystalline SiCO: Implication on structure and thermochemistry of ternary silicon oxycarbide ceramics

    Science.gov (United States)

    Bodiford, Nelli

    The need for innovative refractory materials---materials that can sustain extreme temperatures---has been constantly growing within the modern industries. Basic requirements for usage at ultra-high-temperatures have been considered such as high melting point, high structural strength, exceptional resistance to oxidation, zero or almost zero creep. Monolithic ceramics alone cannot provide these properties, therefore, composite materials are sought to fulfill the demand. For example, silicon nitride and silicon carbide based ceramics have long been leading contenders for structural use in gas turbine engines. In the course of this work we are investigating amorphous SiCO formed via polymer-to-ceramic route. Previously a considerable amount of work has been done on structures of stoichiometric amorphous SiCO and a "perfect" random network was obtained (experimentally as well as supported by computational work) up to the phase content of 33 mol-% SiC. By "perfect" one assumes to have four fold coordinated Si atoms bonded to C and O; C atoms bond to Si atoms only and O is two fold connected to Si. Beyond 33 mol-% SiC within SiCO phase the structural imperfections and defects start to develop. Aside from the stoichiometric form of SiCO, the polymer-to-ceramic route allows for the incorporation of high molar amounts of carbon to create SiCO ceramic with excess carbon. The incorporation of carbon into silica glass improves high-temperature mechanical properties and increases resistance to crystallization of the amorphous material. The amount of 'free carbon' can be controlled through the choice of precursors used during synthesis. There were no ternary crystalline phases of SiCO observed. However, in systems such as MgO-SiO2, Na2O-Al2O 3-SiO2 there are ternary crystalline compounds (MgSiO 3, Mg2SiO4, NaAlSiO4, NaAlSi3 O8) that are of a greater energetic stability than glasses of the same composition. What makes the SiCO system different? In the approach proposed in this

  13. Liquid-liquid equilibria for binary and ternary polymer solutions with PC-SAFT

    DEFF Research Database (Denmark)

    Lindvig, Thomas; Michelsen, Michael Locht; Kontogeorgis, Georgios

    2004-01-01

    are used for investigating the correlative and predictive capabilities of the thermodynamic model PC-SAFT. The investigation shows that the model correlates well experimental LLE data for binary as well as ternary systems but further predicts the behavior of the ternary systems with reasonably good......Two algorithms for evaluating liquid-liquid equilibria (LLE) for binary and ternary polymer solutions are presented. The binary algorithm provides the temperature versus concentration cloud-point curve at fixed pressure, whereas the ternary algorithm provides component 1 versus component 2...

  14. Selective-area laser deposition (SALD) Joining of silicon carbide with silicon carbide filler

    Science.gov (United States)

    Harrison, Shay Llewellyn

    Selective Area Laser Deposition (SALD) is a gas-phase, solid freeform fabrication (SFF) process that utilizes a laser-driven, pyrolytic gas reaction to form a desired solid product. This solid product only forms in the heated zone of the laser beam and thus can be selectively deposited by control of the laser position. SALD Joining employs the SALD method to accomplish 'welding' of ceramic structures together. The solid reaction product serves as a filler material to bond the two parts. The challenges involved with ceramic joining center around the lack of a liquid phase, little plastic deformation and diffusivity and poor surface wetting for many ceramic materials. Due to these properties, traditional metal welding procedures cannot be applied to ceramics. Most alternative ceramic welding techniques use some form of a metal addition to overcome these material limitations. However, the metal possesses a lower ultimate use temperature than the ceramic substrate and therefore it decreases the temperature range over which the joined part can be safely used. SALD Joining enjoys several advantages over these ceramic welding procedures. The solid filler material chemistry can be tailored to match the type of ceramic substrate and therefore fabricate monolithic joints. The SALD filler material bonds directly to the substrate and the joined structure is made in a one step process, without any post-processing. The research documented in this dissertation focused on SALD Joining of silicon carbide structures with silicon carbide filler material. A historical progression of gas-phase SFF research and a literature review of the most prominent ceramic joining techniques are provided. A variety of SiC substrates were examined, as were various conditions of gas precursor pressures and mixtures, laser beam scan speed and joint configuration. The SALD material was characterized for composition and structure by x-ray diffraction, transmission electron microscopy and nuclear magnetic

  15. Combustion synthesis and thermal expansion measurements of the rare earth-uranium ternary oxides RE 6UO 12 (RE=La, Nd and Sm)

    Science.gov (United States)

    Jena, Hrudananda; Asuvathraman, R.; Govindan Kutty, K. V.

    2000-08-01

    Rare earth-uranium ternary oxides were synthesized by a solution combustion route. The starting materials were the corresponding metal nitrates and urea. In these preparations, the metal nitrates act as oxidizer and urea as fuel. Highly exothermic decomposition of the metal nitrate-urea complexes on heating at about 500 K leads to a combustion process yielding RE 6UO 12 fine powders. Thermal expansion measurements of these compounds were carried out in the temperature range of 298-1173 K by high temperature X-ray powder diffractometry. The observed axial thermal expansion behaviour is explained on the basis of the crystal chemistry of the compounds.

  16. The Lattice Compatibility Theory: Arguments for Recorded I-III-O2 Ternary Oxide Ceramics Instability at Low Temperatures beside Ternary Telluride and Sulphide Ceramics

    Directory of Open Access Journals (Sweden)

    K. Boubaker

    2013-01-01

    Full Text Available Some recorded behaviours differences between chalcopyrite ternary oxide ceramics and telluride and sulphides are investigated in the framework of the recently proposed Lattice Compatibility Theory (LCT. Alterations have been evaluated in terms of Urbach tailing and atomic valence shell electrons orbital eigenvalues, which were calculated through several approximations. The aim of the study was mainly an attempt to explain the intriguing problem of difficulties of elaborating chalcopyrite ternary oxide ceramics (I-III-O2 at relatively low temperatures under conditions which allowed crystallization of ternary telluride and sulphides.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-09-01

    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.

  18. Precipitation and Evolution Behavior of Carbide During Heat Treatments of GCr15 Bearing Steel

    Directory of Open Access Journals (Sweden)

    MA Chao

    2017-06-01

    Full Text Available The evolution behavior of carbides in GCr15 bearing steels after spheroidization annealing, austenitization quenching and low temperature tempering was investigated by the method of quantitative metallography. Numerical simulations on the dissolution kinetics of carbide size and composition during austenitization were performed by ThermoCalc software. The results indicate that the carbide particles formed after spheroidization annealing have a multimodal distribution whilst their size distribution changes to have a single peak after austenitization and tempering, and Cr content increases slightly after austenitization; the carbide particles appear to have larger size with higher Cr content; C rich austenite is formed during austenitization through solid solution by carbides after spheroidization annealing, and then high carbon martensite is formed after quenching and results in the high hardness; Cr atoms can partition from austenite to carbide during the dissolution of carbide, lead to the increasing Cr content of rest carbide particles; the numerical simulations indicate that the carbide particles with the diameter of 200nm cannot completely be dissolved during austenitization even if its Cr content is close to the nominal Cr content of steel, and the undissolved ones may affect the precipitation of carbides during the subsequent tempering.

  19. Development and Processing of Nickel Aluminide-Carbide Alloys

    Science.gov (United States)

    Newport, Timothy Scott

    1996-01-01

    With the upper temperature limit of the Ni-based superalloys attained, a new class of materials is required. Intermetallics appear as likely candidates because of their attractive physical properties. With a relatively low density, high thermal conductivity, excellent oxidation resistance, high melting point, and simple crystal structure, nickel aluminide (NiAl) appears to be a potential candidate. However, NiAl is limited in structural applications due to its low room temperature fracture toughness and poor elevated temperature strength. One approach to improving these properties has been through the application of eutectic composites. Researchers have shown that containerless directional solidification of NiAl-based eutectic alloys can provide improvement in both the creep strength and fracture toughness. Although these systems have shown improvements in the mechanical properties, the presence of refractory metals increases the density significantly in some alloys. Lower density systems, such as the carbides, nitrides, and borides, may provide NiAl-based eutectic structure. With little or no information available on these systems, experimental investigation is required. The objective of this research was to locate and develop NiAl-carbide eutectic alloys. Exploratory arc-melts were performed in NiAl-refractory metal-C systems. Refractory metal systems investigated included Co, Cr, Fe, Hf, Mo, Nb, Ta, Ti, W, and Zr. Systems containing carbides with excellent stability (i.e.,HfC, NbC, TaC, TiC, and ZrC) produced large blocky cubic carbides in an NiAl matrix. The carbides appeared to have formed in the liquid state and were randomly distributed throughout the polycrystalline NiAl. The Co, Cr, Fe, Mo, and W systems contained NiAl dendrites with a two-phase interdendritic microconstituent present. Of these systems, the NiAl-Mo-C system had the most promising microstructure for in-situ composites. Three processing techniques were used to evaluate the NiAl-Mo-C system

  20. Fossil Fuels.

    Science.gov (United States)

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with fossil fuels. Some topics covered are historic facts, development of fuels, history of oil production, current and future trends of the oil industry, refining fossil fuels, and environmental problems. Material in each unit may…

  1. Efficient hydrogen evolution by ternary molybdenum sulfoselenide particles on self-standing porous nickel diselenide foam

    Science.gov (United States)

    Zhou, Haiqing; Yu, Fang; Huang, Yufeng; Sun, Jingying; Zhu, Zhuan; Nielsen, Robert J.; He, Ran; Bao, Jiming; Goddard, William A., III; Chen, Shuo; Ren, Zhifeng

    2016-09-01

    With the massive consumption of fossil fuels and its detrimental impact on the environment, methods of generating clean power are urgent. Hydrogen is an ideal carrier for renewable energy; however, hydrogen generation is inefficient because of the lack of robust catalysts that are substantially cheaper than platinum. Therefore, robust and durable earth-abundant and cost-effective catalysts are desirable for hydrogen generation from water splitting via hydrogen evolution reaction. Here we report an active and durable earth-abundant transition metal dichalcogenide-based hybrid catalyst that exhibits high hydrogen evolution activity approaching the state-of-the-art platinum catalysts, and superior to those of most transition metal dichalcogenides (molybdenum sulfide, cobalt diselenide and so on). Our material is fabricated by growing ternary molybdenum sulfoselenide particles on self-standing porous nickel diselenide foam. This advance provides a different pathway to design cheap, efficient and sizable hydrogen-evolving electrode by simultaneously tuning the number of catalytic edge sites, porosity, heteroatom doping and electrical conductivity.

  2. Efficient hydrogen evolution catalysis using ternary pyrite-type cobalt phosphosulphide

    KAUST Repository

    Cabán-Acevedo, Miguel

    2015-09-14

    The scalable and sustainable production of hydrogen fuel through water splitting demands efficient and robust Earth-abundant catalysts for the hydrogen evolution reaction (HER). Building on promising metal compounds with high HER catalytic activity, such as pyrite structure cobalt disulphide (CoS 2), and substituting non-metal elements to tune the hydrogen adsorption free energy could lead to further improvements in catalytic activity. Here we present a combined theoretical and experimental study to establish ternary pyrite-type cobalt phosphosulphide (CoPS) as a high-performance Earth-abundant catalyst for electrochemical and photoelectrochemical hydrogen production. Nanostructured CoPS electrodes achieved a geometrical catalytic current density of 10 mA cm at overpotentials as low as 48mV, with outstanding long-term operational stability. Integrated photocathodes of CoPS on n -p-p silicon micropyramids achieved photocurrents up to 35 mA cm at 0 V versus the reversible hydrogen electrode (RHE), onset photovoltages as high as 450 mV versus RHE, and the most efficient solar-driven hydrogen generation from Earth-abundant systems.

  3. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    Energy Technology Data Exchange (ETDEWEB)

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm{sup -3} (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial Si

  4. Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment

    Science.gov (United States)

    Su, Ching-Hua

    2014-01-01

    A low gravity material experiment will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). There are two sections of the flight experiment: (I) crystal growth of ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, by physical vapor transport (PVT) and (II) melt growth of CdZnTe by directional solidification. The main objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the grown crystals as results of buoyancy-driven convection and growth interface fluctuations caused by irregular fluid-flows on Earth. The investigation consists of extensive ground-based experimental and theoretical research efforts and concurrent flight experimentation. This talk will focus on the ground-based studies on the PVT crystal growth of ZnSe and related ternary compounds. The objectives of the ground-based studies are (1) obtain the experimental data and conduct the analyses required to define the optimum growth parameters for the flight experiments, (2) perfect various characterization techniques to establish the standard procedure for material characterization, (3) quantitatively establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low-gravity environment and (4) develop theoretical and analytical methods required for such evaluations. ZnSe and related ternary compounds have been grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals have been characterized extensively by various techniques to correlate the grown crystal properties with the growth conditions.

  5. Quantifying the energetics of cooperativity in a ternary protein complex

    DEFF Research Database (Denmark)

    Andersen, Peter S; Schuck, Peter; Sundberg, Eric J

    2002-01-01

    and mathematical modeling to describe the energetics of cooperativity in a trimolecular protein complex. As a model system for quantifying cooperativity, we studied the ternary complex formed by the simultaneous interaction of a superantigen with major histocompatibility complex and T cell receptor, for which...... a structural model is available. This system exhibits positive and negative cooperativity, as well as augmentation of the temperature dependence of binding kinetics upon the cooperative interaction of individual protein components in the complex. Our experimental and theoretical analysis may be applicable...... to other systems involving cooperativity....

  6. Implementation of DFT application on ternary optical computer

    Science.gov (United States)

    Junjie, Peng; Youyi, Fu; Xiaofeng, Zhang; Shuai, Kong; Xinyu, Wei

    2018-03-01

    As its characteristics of huge number of data bits and low energy consumption, optical computing may be used in the applications such as DFT etc. which needs a lot of computation and can be implemented in parallel. According to this, DFT implementation methods in full parallel as well as in partial parallel are presented. Based on resources ternary optical computer (TOC), extensive experiments were carried out. Experimental results show that the proposed schemes are correct and feasible. They provide a foundation for further exploration of the applications on TOC that needs a large amount calculation and can be processed in parallel.

  7. A review on ternary vanadate one-dimensional nanomaterials.

    Science.gov (United States)

    Pei, Li Z; Wang, Shuai; Liu, Han D; Pei, Yin Q

    2014-01-01

    Ternary vanadate one-dimensional nanomaterials exhibit great application potential in the fields of lithium ion batteries, photocatalysis and electrochemical sensors owing to their good electrochemical and photocatalytic properties. The article reviews the recent progress and patents on the vanadate one-dimensional nanomaterials. The synthesis of the vanadate nanorods, nanobelts and nanotubes by hydrothermal method, template method and room temperature wet chemical process is demonstrated. The application of the vanadate one-dimensional nanomaterials for lithium ion batteries, electrochemical sensors and photocatalysis is discussed. The possible development direction of the vanadate one-dimensional nanomaterials for the synthesis and application is also analyzed.

  8. PREPARATION OF TANTALUM CARBIDE FROM AN ORGANOMETALLIC PRECURSOR

    Directory of Open Access Journals (Sweden)

    SOUZA C. P.

    1999-01-01

    Full Text Available In this work we have synthesized an organometallic oxalic precursor from tantalum oxide. This oxide was solubilized by heating with potassium hydrogen sulfate. In order to precipitate Ta2O5.nH2O, the fused mass obtained was dissolved in a sulfuric acid solution and neutralized with ammonia. The hydrated tantalum oxide precipitated was dissolved in an equimolar solution of oxalic acid/ammonium oxalate. The synthesis and the characterization of the tantalum oxalic precursor are described. Pyrolysis of the complex in a mixture of hydrogen and methane at atmospheric pressure was studied. The gas-solid reaction made it possible to obtain tantalum carbide, TaC, in the powder form at 1000oC. The natural sintering of TaC powder in an inert atmosphere at 1400°C during 10 hours, under inert atmosphere made it possible to densify the carbide to 96% of the theoretical value.

  9. Linear electro-optic effect in cubic silicon carbide

    Science.gov (United States)

    Tang, Xiao; Irvine, Kenneth G.; Zhang, Dongping; Spencer, Michael G.

    1991-01-01

    The first observation is reported of the electrooptic effect of cubic silicon carbide (beta-SiC) grown by a low-pressure chemical vapor deposition reactor using the hydrogen, silane, and propane gas system. At a wavelength of 633 nm, the value of the electrooptic coefficient r41 in beta-SiC is determined to be 2.7 +/- 0.5 x 10 (exp-12) m/V, which is 1.7 times larger than that in gallium arsenide measured at 10.6 microns. Also, a half-wave voltage of 6.4 kV for beta-SiC is obtained. Because of this favorable value of electrooptic coefficient, it is believed that silicon carbide may be a promising candidate in electrooptic applications for high optical intensity in the visible region.

  10. Scalable Quantum Photonics with Single Color Centers in Silicon Carbide.

    Science.gov (United States)

    Radulaski, Marina; Widmann, Matthias; Niethammer, Matthias; Zhang, Jingyuan Linda; Lee, Sang-Yun; Rendler, Torsten; Lagoudakis, Konstantinos G; Son, Nguyen Tien; Janzén, Erik; Ohshima, Takeshi; Wrachtrup, Jörg; Vučković, Jelena

    2017-03-08

    Silicon carbide is a promising platform for single photon sources, quantum bits (qubits), and nanoscale sensors based on individual color centers. Toward this goal, we develop a scalable array of nanopillars incorporating single silicon vacancy centers in 4H-SiC, readily available for efficient interfacing with free-space objective and lensed-fibers. A commercially obtained substrate is irradiated with 2 MeV electron beams to create vacancies. Subsequent lithographic process forms 800 nm tall nanopillars with 400-1400 nm diameters. We obtain high collection efficiency of up to 22 kcounts/s optical saturation rates from a single silicon vacancy center while preserving the single photon emission and the optically induced electron-spin polarization properties. Our study demonstrates silicon carbide as a readily available platform for scalable quantum photonics architecture relying on single photon sources and qubits.

  11. Functionalization and cellular uptake of boron carbide nanoparticles

    DEFF Research Database (Denmark)

    Mortensen, M. W.; Björkdahl, O.; Sørensen, P. G.

    2006-01-01

    In this paper we present surface modification strategies of boron carbide nanoparticles, which allow for bioconjugation of the transacting transcriptional activator (TAT) peptide and fluorescent dyes. Coated nanoparticles can be translocated into murine EL4 thymoma cells and B16 F10 malignant...... melanoma cells in amounts as high as 0.3 wt. % and 1 wt. %, respectively. Neutron irradiation of a test system consisting of untreated B16 cells mixed with B16 cells loaded with boron carbide nanoparticles were found to inhibit the proliferative capacity of untreated cells, showing that cells loaded...... with boron-containing nanoparticles can hinder the growth of neighboring cells upon neutron irradiation. This could provide the first step toward a T cell-guided boron neutron capture therapy....

  12. Scalable Quantum Photonics with Single Color Centers in Silicon Carbide

    Science.gov (United States)

    Radulaski, Marina; Widmann, Matthias; Niethammer, Matthias; Zhang, Jingyuan Linda; Lee, Sang-Yun; Rendler, Torsten; Lagoudakis, Konstantinos G.; Son, Nguyen Tien; Janzén, Erik; Ohshima, Takeshi; Wrachtrup, Jörg; Vučković, Jelena

    2017-03-01

    Silicon carbide is a promising platform for single photon sources, quantum bits (qubits) and nanoscale sensors based on individual color centers. Towards this goal, we develop a scalable array of nanopillars incorporating single silicon vacancy centers in 4H-SiC, readily available for efficient interfacing with free-space objective and lensed-fibers. A commercially obtained substrate is irradiated with 2 MeV electron beams to create vacancies. Subsequent lithographic process forms 800 nm tall nanopillars with 400-1,400 nm diameters. We obtain high collection efficiency, up to 22 kcounts/s optical saturation rates from a single silicon vacancy center, while preserving the single photon emission and the optically induced electron-spin polarization properties. Our study demonstrates silicon carbide as a readily available platform for scalable quantum photonics architecture relying on single photon sources and qubits.

  13. Alternative catalytic materials: carbides, nitrides, phosphides and amorphous boron alloys.

    Science.gov (United States)

    Alexander, Anne-Marie; Hargreaves, Justin S J

    2010-11-01

    Catalysts generated by the addition of carbon, nitrogen or phosphorus to transition metals have interesting properties and potential applications. The addition of carbon, nitrogen or phosphorus can lead to substantial modification of the catalytic efficacy of the parent metal and some carbides and nitrides are claimed to be comparable to noble metals in their behaviour. Amorphous boron transition metal alloys are also a class of interesting catalyst, although their structures and phase composition are more difficult to define. In this critical review, the preparation of these catalysts is described and brief details of their application given. To date, attention has largely centred upon the application of these materials as alternatives for existing catalysts. However, novel approaches towards their utilisation can be envisaged. For example, the extent to which it is possible to utilise the "activated" carbon and nitrogen species within the host lattices of carbides and nitrides, respectively, as a reactant remains largely unexplored (195 references).

  14. Fuel distribution

    Energy Technology Data Exchange (ETDEWEB)

    Tison, R.R.; Baker, N.R.; Blazek, C.F.

    1979-07-01

    Distribution of fuel is considered from a supply point to the secondary conversion sites and ultimate end users. All distribution is intracity with the maximum distance between the supply point and end-use site generally considered to be 15 mi. The fuels discussed are: coal or coal-like solids, methanol, No. 2 fuel oil, No. 6 fuel oil, high-Btu gas, medium-Btu gas, and low-Btu gas. Although the fuel state, i.e., gas, liquid, etc., can have a major impact on the distribution system, the source of these fuels (e.g., naturally-occurring or coal-derived) does not. Single-source, single-termination point and single-source, multi-termination point systems for liquid, gaseous, and solid fuel distribution are considered. Transport modes and the fuels associated with each mode are: by truck - coal, methanol, No. 2 fuel oil, and No. 6 fuel oil; and by pipeline - coal, methane, No. 2 fuel oil, No. 6 oil, high-Btu gas, medium-Btu gas, and low-Btu gas. Data provided for each distribution system include component makeup and initial costs.

  15. Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

    Science.gov (United States)

    Mcalister, A. J.

    1981-01-01

    Tungsten carbide, which is active for hydrogen oxidation, is CO tolerant and has a hexagonal structure is discussed. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys W sub x-1Ti sub XC sub 1-y were found to be active and CO tolerant. When the activities of these cubic alloys are weighted by the reciprocal of the square to those of highly forms of WC. They offer important insight into the nature of the active sites on W-C anode catalysts for use in phosphoric acid fuel cells.

  16. Ternary System with Controlled Structure: A New Strategy toward Efficient Organic Photovoltaics.

    Science.gov (United States)

    Cheng, Pei; Wang, Rui; Zhu, Jingshuai; Huang, Wenchao; Chang, Sheng-Yung; Meng, Lei; Sun, Pengyu; Cheng, Hao-Wen; Qin, Meng; Zhu, Chenhui; Zhan, Xiaowei; Yang, Yang

    2018-02-01

    Recently, a new type of active layer with a ternary system has been developed to further enhance the performance of binary system organic photovoltaics (OPV). In the ternary OPV, almost all active layers are formed by simple ternary blend in solution, which eventually leads to the disordered bulk heterojunction (BHJ) structure after a spin-coating process. There are two main restrictions in this disordered BHJ structure to obtain higher performance OPV. One is the isolated second donor or acceptor domains. The other is the invalid metal-semiconductor contact. Herein, the concept and design of donor/acceptor/acceptor ternary OPV with more controlled structure (C-ternary) is reported. The C-ternary OPV is fabricated by a sequential solution process, in which the second acceptor and donor/acceptor binary blend are sequentially spin-coated. After the device optimization, the power conversion efficiencies (PCEs) of all OPV with C-ternary are enhanced by 14-21% relative to those with the simple ternary blend; the best PCEs are 10.7 and 11.0% for fullerene-based and fullerene-free solar cells, respectively. Moreover, the averaged PCE value of 10.4% for fullerene-free solar cell measured in this study is in great agreement with the certified one of 10.32% obtained from Newport Corporation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Fullerene alloy formation and the benefits for efficient printing of ternary blend organic solar cells

    DEFF Research Database (Denmark)

    Angmo, Dechan; Bjerring, Morten; Nielsen, Niels Chr.

    2015-01-01

    with a third polymer component, the system exhibits pseudo-binary phase behaviour instead of the expected ternary phase behaviour. Our results experimentally confirm the earlier hypothesis that the unexpected composition average dependent IV-behaviour for these supposed ternary mixtures are indeed due to them...

  18. Using a Ternary Diagram to Display a System's Evolving Energy Distribution

    Science.gov (United States)

    Brazzle, Bob; Tapp, Anne

    2016-01-01

    A ternary diagram is a graphical representation used for systems with three components. They are familiar to mineralogists (who typically use them to categorize varieties of solid solution minerals such as feldspar) but are not yet widely used in the physics community. Last year the lead author began using ternary diagrams in his introductory…

  19. Visible and near-infrared light emitting calix[4]arene-based ternary lanthanide complexes

    NARCIS (Netherlands)

    Hebbink, G.A.; Klink, S.I.; Oude Alink, Patrick G.B.; van Veggel, F.C.J.M.

    2001-01-01

    In this article ternary lanthanide complexes consisting of a calix[4]arene unit and dibenzoylmethane (dbm) as the antenna are described. In the europium complex [(Eu)2]NO3 two solvent molecules are still coordinated to the ion, making substitution of them by the dbm antenna possible. In the ternary

  20. Calculated site substitution in ternary gamma'-Ni3Al: Temperature and composition effects

    DEFF Research Database (Denmark)

    Ruban, Andrei; Skriver, Hans Lomholt

    1997-01-01

    The temperature and composition dependence of the site substitution behavior of ternary additions to Ni3Al is examined on the basis of first-principles calculations of the total energies of ternary, partially ordered (gamma') alloys. The calculations are performed by means of the linear muffin...

  1. INTERVAL-VALUED INTUITIONISTIC FUZZY BI-IDEALS IN TERNARY SEMIRINGS

    Directory of Open Access Journals (Sweden)

    D. KRISHNASWAMY

    2016-04-01

    Full Text Available In this paper we introduce the notions of interval-valued fuzzy bi-ideal, interval-valued anti fuzzy bi-ideal and interval-valued intuitionistic fuzzy bi-ideal in ternary semirings and some of the basic properties of these ideals are investigated. We also introduce normal interval-valued intuitionistic fuzzy ideals in ternary semirings.

  2. Ternary-fission dynamics and asymmetries in reactions with polarized neutrons

    CERN Document Server

    Bunakov, V E

    2002-01-01

    Experimental results of measuring various asymmetries of charged-particles emission in ternary fission induced by polarized neutrons, namely parity nonconserving asymmetries, left-right asymmetries and triple-odd correlations are presented. It is demonstrated what kind of new information about the mechanism of ternary fission can be obtained from their analysis

  3. Anodic etching of p-type cubic silicon carbide

    Science.gov (United States)

    Harris, G. L.; Fekade, K.; Wongchotigul, K.

    1992-01-01

    p-Type cubic silicon carbide was anodically etched using an electrolyte of HF:HCl:H2O. The etching depth was determined versus time with a fixed current density of 96.4 mA/sq cm. It was found that the etching was very smooth and very uniform. An etch rate of 22.7 nm/s was obtained in a 1:1:50 HF:HCl:H2O electrolyte.

  4. Silicon Carbide as a Material for Biomedical Microsystems

    OpenAIRE

    Zorman, Ch.,

    2009-01-01

    ISBN: 978-2-35500-009-6; Silicon Carbide (SiC) is emerging as an enabling material for biomedical microsystems due to its uniquecombination of electrical, mechanical and chemical properties combined with its compatibility with Simicromachining techniques. This paper presents an overview of the latest advancements in this areaincluding on-going research to develop SiC for biosensing, bio-microdevice packaging, bio-filtering,biomedical imaging and other related biomedical applications.

  5. Method of making carbide/fluoride/silver composites

    Science.gov (United States)

    Sliney, Harold E. (Inventor); Dellacorte, Christopher (Inventor)

    1991-01-01

    A composition containing 30 to 70 percent chromium carbide, 5 to 20 percent soft noble metal, 5 to 20 percent metal fluorides, and 20 to 60 percent metal binder is used in a powdered metallurgy process for the production of self-lubricating components, such as bearings. The use of the material allows the self-lubricating bearing to maintain its low friction properties over an extended range of operating temperatures.

  6. Progress in Studies on Carbon and Silicon Carbide Nanocomposite Materials

    Directory of Open Access Journals (Sweden)

    Peng Xiao

    2010-01-01

    Full Text Available 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 microstructure of pyrocarbon and induce the deposition of pyrocarbon with high text in carbon/carbon composites. So the carbon/carbon composites modified by CNT/CNF have more excellent properties.

  7. Catalytic Conversion of Syngas into Higher Alcohols over Carbide Catalysts

    DEFF Research Database (Denmark)

    Christensen, Jakob Munkholt; Duchstein, Linus Daniel Leonhard; Wagner, Jakob Birkedal

    2012-01-01

    This work investigates the use of the bulk carbides Mo2C, WC, and NbC as catalysts for the conversion of syngas into higher alcohols. K2CO3/WC produces mainly CH3OH and CH4 with a low activity. NbC has a very low activity in CO hydrogenation. K2CO3/Mo2C produces mixed alcohols with a reasonable...

  8. Epitaxial Growth of Silicon Carbide by Chemical Vapor Deposition

    Science.gov (United States)

    Bhat, Ishwara B.

    The properties of silicon carbide materials are first reviewed, with special emphasis on properties related to power device applications. Epitaxial growth methods for SiC are then discussed with emphasis on recent results for epitaxial growth by the hot-wall chemical vapor deposition method. The growth mechanism for maintaining the polytype, namely step-controlled epitaxy, is discussed. Also described is the selective epitaxial growth carried out on SiC at the author's laboratory, including some unpublished work.

  9. Production of boron carbide powder by carbothermal synthesis of ...

    Indian Academy of Sciences (India)

    Boron carbide (B4C) powder has been produced by carbothermal reduction of boric acid–citric acid gel. Initially a gel of boric acid–citric acid is prepared in an oven at 100°C. This gel is pyrolyzed in a high temperature furnace over a temperature range of 1000–1800°C. The reaction initiation temperature range for B4C ...

  10. Phonon spectrum, mechanical and thermophysical properties of thorium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Pérez Daroca, D., E-mail: pdaroca@tandar.cnea.gov.ar [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Consejo Nacional de Investigaciones Cientı´ficas y Técnicas (Argentina); Jaroszewicz, S. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA (Argentina); Llois, A.M. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Consejo Nacional de Investigaciones Cientı´ficas y Técnicas (Argentina); Mosca, H.O. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA (Argentina)

    2013-06-15

    In this work, we study, by means of density functional perturbation theory and the pseudopotential method, mechanical and thermophysical properties of thorium carbide. These properties are derived from the lattice dynamics in the quasi-harmonic approximation. The phonon spectrum of ThC presented in this article, to the best authors’ knowledge, have not been studied, neither experimentally, nor theoretically. We compare mechanical properties, volume thermal expansion and molar specific capacities with previous results and find a very good agreement.

  11. Adhesion of CVD coatings on new cemeted carbides

    OpenAIRE

    Bojestig, Eric

    2016-01-01

    Steel turning inserts cemented carbides have a binder phase consisting of cobalt (Co). However, in recent years a study from the United States National Toxicity Program (NTP) found that cobalt powder is carcinogenic upon inhalation. The European Union's REACH have therefore also classified cobalt powder as carcinogenic upon inhalation. The worldwide search to find a replacement has therefore lately intensified. It is important that the alternative binder phase has no negative effects on the p...

  12. Microstructural studies of carbides in MAR-M247 nickel-based superalloy

    Science.gov (United States)

    Szczotok, A.; Rodak, K.

    2012-05-01

    Carbides play an important role in the strengthening of microstructures of nickel-based superalloys. Grain boundary carbides prevent or retard grain-boundary sliding and make the grain boundary stronger. Carbides can also tie up certain elements that would otherwise promote phase instability during service. Various types of carbides are possible in the microstructure of nickel-based superalloys, depending on the superalloy composition and processing. In this paper, scanning electron and scanning transmission electron microscopy studies of carbides occurring in the microstructure of polycrystalline MAR-M247 nickel-based superalloy were carried out. In the present work, MC and M23C6 carbides in the MAR-M247 microstructure were examined.

  13. Effect of Cement Replacement with Carbide Waste on the Strength of Stabilized Clay Subgrade

    Directory of Open Access Journals (Sweden)

    Muntohar A.S.

    2016-03-01

    Full Text Available Cement is commonly used for soil stabilization and many other ground improvement techniques. Cement is believed to be very good to improve the compressive and split-tensile strength of clay subgrades. In some application cement could be partly or fully replaced with carbide waste. This research is to study the effectiveness of the cement replacement and to find the maximum carbide waste content to be allowed for a clay subgrade. The quantities of cement replaced with the carbide waste were 30, 50, 70, 90, and 100% by its mass. The results show that replacing the cement with carbide waste decreased both the compressive and split tensile strength. Replacing cement content with carbide waste reduced its ability for stabilization. The carbide waste content should be less than 70% of the cement to provide a sufficient stabilizing effect on a clay subgrade.

  14. Frictional Performance Assessment of Cemented Carbide Surfaces Textured by Laser

    Science.gov (United States)

    Fang, S.; Llanes, L.; Klein, S.; Gachot, C.; Rosenkranz, A.; Bähre, D.; Mücklich, F.

    2017-10-01

    Cemented carbides are advanced engineering materials often used in industry for manufacturing cutting tools or supporting parts in tribological system. In order to improve service life, special attention has been paid to change surface conditions by means of different methods, since surface modification can be beneficial to reduce the friction between the contact surfaces as well as to avoid unintended damage. Laser surface texturing is one of the newly developed surface modification methods. It has been successfully introduced to fabricate some basic patterns on cemented carbide surfaces. In this work, Direct Laser Interference Patterning Technique (DLIP) is implemented to produce special line-like patterns on a cobalt (Co) and nickel (Ni) based cemented tungsten carbide grade. It is proven that the laser-produced patterns have high geometrical precision and quality stability. Furthermore, tribology testing using a nano-tribometer unit shows that friction is reduced by the line-like patterns, as compared to the polished one, under both lubricated and dry testing regimes, and the reduction is more pronounced in the latter case.

  15. Nanoscale fullerene compression of an yttrium carbide cluster.

    Science.gov (United States)

    Zhang, Jianyuan; Fuhrer, Tim; Fu, Wujun; Ge, Jiechao; Bearden, Daniel W; Dallas, Jerry; Duchamp, James; Walker, Kenneth; Champion, Hunter; Azurmendi, Hugo; Harich, Kim; Dorn, Harry C

    2012-05-23

    The nanoscale parameters of metal clusters and lattices have a crucial influence on the macroscopic properties of materials. Herein, we provide a detailed study on the size and shape of isolated yttrium carbide clusters in different fullerene cages. A family of diyttrium endohedral metallofullerenes with the general formula of Y(2)C(2n) (n = 40-59) are reported. The high field (13)C nuclear magnetic resonance (NMR) and density functional theory (DFT) methods are employed to examine this yttrium carbide cluster in certain family members, Y(2)C(2)@D(5)(450)-C(100), Y(2)C(2)@D(3)(85)-C(92), Y(2)C(2)@C(84), Y(2)C(2)@C(3v)(8)-C(82), and Y(2)C(2)@C(s)(6)-C(82). The results of this study suggest that decreasing the size of a fullerene cage with the same (Y(2)C(2))(4+) cluster results in nanoscale fullerene compression (NFC) from a nearly linear stretched geometry to a constrained "butterfly" structure. The (13)C NMR chemical shift and scalar (1)J(YC) coupling parameters provide a very sensitive measure of this NFC effect for the (Y(2)C(2))(4+) cluster. The crystal structural parameters of a previously reported metal carbide, Y(2)C(3) are directly compared to the (Y(2)C(2))(4+) cluster in the current metallofullerene study.

  16. Carbide-Derived Carbon Films for Integrated Electrochemical Energy Storage

    Science.gov (United States)

    Heon, Min

    Active RFID tags, which can communicate over tens or even hundreds of meters, MEMS devices of several microns in size, which are designed for the medical and pharmaceutical purposes, and sensors working in wireless monitoring systems, require microscale power sources that are able to provide enough energy and to satisfy the peak power demands in those applications. Supercapacitors have not been an attractive candidate for micro-scale energy storage, since most nanoporous carbon electrode materials are not compatible with micro-fabrication techniques and have failed to meet the requirements of high volumetric energy density and small form factor for power supplies for integrated circuits or microelectronic devices or sensors. However, supercapacitors can provide high power density, because of fast charging/discharging, which can enable self-sustaining micro-modules when combined with energy-harvesting devices, such as solar cell, piezoelectric or thermoelectric micro-generators. In this study, carbide-derived carbon (CDC) films were synthesized via vacuum decomposition of carbide substrates and gas etching of sputtered carbide thin films. This approach allowed manufacturing of porous carbon films on SiC and silicon substrates. CDC films were studied for micro-supercapacitor electrodes, and showed good double layer capacitance. Since the gas etching technique is compatible with conventional micro-device fabrication processes, it can be implemented to manufacture integrated on-chip supercapacitors on silicon wafers.

  17. Palladium-defect complexes in diamond and silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Abiona, A. A., E-mail: adurafimihan.abiona@gmail.com; Kemp, W.; Timmers, H. [University of New South Wales, Canberra, School of Physical, Environmental and Mathematical Sciences (Australia); Bharuth-Ram, K. [Durban University of Technology, Physics Department (South Africa)

    2015-04-15

    Time Differential Perturbed Angular Correlations (TDPAC) studies, supported by Density Functional Theory (DFT) modelling, have shown that palladium atoms in silicon and germanium pair with vacancies. Building on these results, here we present DFT predictions and some tentative TDPAC results on palladium-defect complexes and site locations of palladium impurities in diamond and silicon carbide. For both diamond and silicon carbide, the DFT calculations predict that a split-vacancy V-PdBI-V complex is favoured, with the palladium atom on a bond-centred interstitial site having a nearest-neighbour semi-vacancy on either side. Consistent with experimental results, this configuration is also assigned to palladium complexes in silicon and germanium. For silicon carbide, the DFT modelling predicts furthermore that a palladium atom in replacing a carbon atom moves to a bond-centred interstitial site and pairs with a silicon vacancy to form a complex that is more stable than that of a palladium atom which replaces a silicon atom and then moves to a bond-centred interstitial site pairings with a carbon vacancy. These two competing alternatives differ by 8.94 eV. The favourable pairing with a silicon vacancy is also supported independently by TRIM Monte Carlo calculations, which predict that more silicon vacancies than carbon vacancies are created during heavy ion. implantation.

  18. Synthesis of a Mo/Nb mixed carbide

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira da Silva, V.L. [NUCAT/PEQ/COPPE/Universidade Federal do Rio de Janeiro, Caixa Postal 68502, Rio de Janeiro, RJ-21945-970 (Brazil)]|[Environmental Catalysis and Materials Laboratory, Department of Chemical Engineering, Virginia Polytechnic Institute State University, Blacksburg, Virginia 24061 (United States); Schmal, M. [NUCAT/PEQ/COPPE/Universidade Federal do Rio de Janeiro, Caixa Postal 68502, Rio de Janeiro, RJ-21945-970 (Brazil); Schwartz, V.; Oyama, S.T. [Environmental Catalysis and Materials Laboratory, Department of Chemical Engineering, Virginia Polytechnic Institute State University, Blacksburg, Virginia 24061 (United States)

    1998-07-01

    Molybdenum and niobium carbides ({beta}{endash}Mo{sub 2}C, NbC), as well as mixed carbides of molybdenum and niobium, were synthesized by the temperature-programmed carburization method (TPC) using a 20 vol.thinsp{percent} CH{sub 4}/H{sub 2} gas mixture. The starting materials were MoO{sub 3}, B-Nb{sub 2}O{sub 5}, and physical mixtures of B-Nb{sub 2}O{sub 5}/MoO{sub 3} with Nb/(Nb+Mo) atomic ratios varying from 0.2 to 0.8, respectively. Results from catalytic and temperature-programmed oxidation (TPO) measurements indicate that during the carburization of the Nb{sub 2}O{sub 5}/MoO{sub 3} physical mixture with Nb/(Nb+Mo)=0.8 there is, besides {beta}{endash}Mo{sub 2}C and NbC formation, the appearance of a carbidic phase not detectable by x-ray diffraction (XRD). This phase appears to be highly active and selective for the dibenzothiophene hydrodesulfurization (HDS) reaction. {copyright} {ital 1998 Materials Research Society.}

  19. Factoring with qutrits: Shor's algorithm on ternary and metaplectic quantum architectures

    Science.gov (United States)

    Bocharov, Alex; Roetteler, Martin; Svore, Krysta M.

    2017-07-01

    We determine the cost of performing Shor's algorithm for integer factorization on a ternary quantum computer, using two natural models of universal fault-tolerant computing: (i) a model based on magic state distillation that assumes the availability of the ternary Clifford gates, projective measurements, classical control as its natural instrumentation set; (ii) a model based on a metaplectic topological quantum computer (MTQC). A natural choice to implement Shor's algorithm on a ternary quantum computer is to translate the entire arithmetic into a ternary form. However, it is also possible to emulate the standard binary version of the algorithm by encoding each qubit in a three-level system. We compare the two approaches and analyze the complexity of implementing Shor's period-finding function in the two models. We also highlight the fact that the cost of achieving universality through magic states in MTQC architecture is asymptotically lower than in generic ternary case.

  20. High-performance ternary blend polymer solar cells involving both energy transfer and hole relay processes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Luyao; Chen, Wei; Xu, Tao; Yu, Luping

    2015-06-04

    The integration of multiple materials with complementary absorptions into a singlejunction device is regarded as an efficient way to enhance the power conversion efficiency (PCE) of organic solar cells (OSCs). However, due to increased complexity with one more component, only limited high performance ternary systems have been demonstrated previously. Here, we report an efficient ternary blend OSC with a PCE of 9.2%. We show for the first time that the third component can reduce surface trap densities in the ternary blend. Detailed studies unravel that the improved performance results from synergistic effects of enlarged open circuit voltage, suppressed trap assisted recombination, enhanced light absorption, increased hole extraction, efficient energy transfer, and better morphology. The novel working mechanism and high device performance demonstrate new insights and design guidelines for high performance ternary blend solar cells and suggest that ternary structure is a promising platform to boost the efficiency of OSCs.

  1. Review on Sintering Process of WC-Co Cemented Carbide in Metal Injection Molding Technology

    Science.gov (United States)

    Prathabrao, M.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

    2017-01-01

    The objective of this paper is to give an overview on sintering process of WC-Co cemented carbides in metal injection molding technology. Metal injection molding is an advanced and promising technology in producing cemented nanostructured carbides. Cemented tungsten carbide (WC-Co) hard metal is known for its high hardness and wear resistance in various applications. Moreover, areas include fine grained materials, alternative binders, and alternative sintering techniques has been discussed in this paper.

  2. Local Directional Ternary Pattern for Facial Expression Recognition.

    Science.gov (United States)

    Ryu, Byungyong; Rivera, Adin Ramirez; Kim, Jaemyun; Chae, Oksam

    2017-07-11

    This paper presents a new face descriptor, local directional ternary pattern (LDTP), for facial expression recognition. LDTP efficiently encodes information of emotion-related features (i.e., eyes, eyebrows, upper nose, and mouth) by using the directional information and ternary pattern in order to take advantage of the robustness of edge patterns in the edge region while overcoming weaknesses of edge-based methods in smooth regions. Our proposal, unlike existing histogram-based face description methods that divide the face into several regions and sample the codes uniformly, uses a two level grid to construct the face descriptor while sampling expression-related information at different scales. We use a coarse grid for stable codes (highly related to non-expression), and a finer one for active codes (highly related to expression). This multi-level approach enables us to do a finer grain description of facial motions, while still characterizing the coarse features of the expression. Moreover, we learn the active LDTP codes from the emotionrelated facial regions. We tested our method by using persondependent and independent cross-validation schemes to evaluate the performance. We show that our approaches improve the overall accuracy of facial expression recognition on six datasets.

  3. Genetic Synthesis of New Reversible/Quantum Ternary Comparator

    Directory of Open Access Journals (Sweden)

    DEIBUK, V.

    2015-08-01

    Full Text Available Methods of quantum/reversible logic synthesis are based on the use of the binary nature of quantum computing. However, multiple-valued logic is a promising choice for future quantum computer technology due to a number of advantages over binary circuits. In this paper we have developed a synthesis of ternary reversible circuits based on Muthukrishnan-Stroud gates using a genetic algorithm. The method of coding chromosome is presented, and well-grounded choice of algorithm parameters allowed obtaining better circuit schemes of one- and n-qutrit ternary comparators compared with other methods. These parameters are quantum cost of received reversible devices, delay time and number of constant input (ancilla lines. Proposed implementation of the genetic algorithm has led to reducing of the device delay time and the number of ancilla qutrits to 1 and 2n-1 for one- and n-qutrits full comparators, respectively. For designing of n-qutrit comparator we have introduced a complementary device which compares output functions of 1-qutrit comparators.

  4. Enhanced Light Absorption in Fluorinated Ternary Small-Molecule Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Eastham, Nicholas D. [Department; Dudnik, Alexander S. [Department; Harutyunyan, Boris [Department; Aldrich, Thomas J. [Department; Leonardi, Matthew J. [Department; Manley, Eric F. [Department; Chemical; Butler, Melanie R. [Department; Harschneck, Tobias [Department; Ratner, Mark A. [Department; Chen, Lin X. [Department; Chemical; Bedzyk, Michael J. [Department; Department; Melkonyan, Ferdinand S. [Department; Facchetti, Antonio [Department; Chang, Robert P. H. [Department; Marks, Tobin J. [Department; Department

    2017-06-14

    Using small-molecule donor (SMD) semiconductors in organic photovoltaics (OPVs) has historically afforded lower power conversion efficiencies (PCEs) than their polymeric counterparts. The PCE difference is attributed to shorter conjugated backbones, resulting in reduced intermolecular interactions. Here, a new pair of SMDs is synthesized based on the diketopyrrolopyrrole-benzodithiophene-diketopyrrolopyrrole (BDT-DPP2) skeleton but having fluorinated and fluorinefree aromatic side-chain substituents. Ternary OPVs having varied ratios of the two SMDs with PC61BM as the acceptor exhibit tunable open-circuit voltages (Vocs) between 0.833 and 0.944 V due to a fluorination-induced shift in energy levels and the electronic “alloy” formed from the miscibility of the two SMDs. A 15% increase in PCE is observed at the optimal ternary SMD ratio, with the short-circuit current density (Jsc) significantly increased to 9.18 mA/cm2. The origin of Jsc enhancement is analyzed via charge generation, transport, and diffuse reflectance measurements, and is attributed to increased optical absorption arising from a maximum in film crystallinity at this SMD ratio, observed by grazing incidence wide-angle X-ray scattering.

  5. Synthesis, characterization and thermoelectric properties of metal borides, boron carbides and carbaborides; Synthese, Charakterisierung und thermoelektrische Eigenschaften ausgewaehlter Metallboride, Borcarbide und Carbaboride

    Energy Technology Data Exchange (ETDEWEB)

    Guersoy, Murat

    2015-07-06

    This work reports on the solid state synthesis and structural and thermoelectrical characterization of hexaborides (CaB{sub 6}, SrB{sub 6}, BaB{sub 6}, EuB{sub 6}), diboride dicarbides (CeB{sub 2}C{sub 2}, LaB{sub 2}C{sub 2}), a carbaboride (NaB{sub 5}C) and composites of boron carbide. The characterization was performed by X-ray diffraction methods and Rietveld refinements based on structure models from literature. Most of the compounds were densified by spark plasma sintering at 100 MPa. As high-temperature thermoelectric properties the Seebeck coefficients, electrical conductivities, thermal diffusivities and heat capacities were measured between room temperature and 1073 K. ZT values as high as 0.5 at 1273 K were obtained for n-type conducting EuB{sub 6}. High-temperature X-ray diffraction also confirmed its thermal stability. The solid solutions Ca{sub x}Sr{sub 1-x}B{sub 6}, Ca{sub x}Ba{sub 1-x}B{sub 6} and Sr{sub x}Ba{sub 1-x}B{sub 6} (x = 0, 0.25, 0.5, 0.75, 1) are also n-type but did not show better ZT values for the ternary compounds compared to the binaries, but for CaB{sub 6} the values of the figure of merit (ca. 0.3 at 1073 K) were significantly increased (ca. 50 %) compared to earlier investigations which is attributed to the densification process. Sodium carbaboride, NaB{sub 5}C, was found to be the first p-type thermoelectric material that crystallizes with the hexaboride-structure type. Seebeck coefficients of ca. 80 μV . K{sup -1} were obtained. Cerium diboride dicarbide, CeB{sub 2}C{sub 2}, and lanthanum diboride dicarbide, LaB{sub 2}C{sub 2}, are metallic. Both compounds were used as model compounds to develop compacting strategies for such layered borides. Densities obtained at 50 MPa were determined to be higher than 90 %. A new synthesis route using single source precursors that contain boron and carbon was developed to open the access to new metal-doped boron carbides. It was possible to obtain boron carbide, but metal-doping could not be

  6. Chitosan: a green carbon source for the synthesis of graphitic nanocarbon, tungsten carbide and graphitic nanocarbon/tungsten carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Wang Baoli; Tian Chuigui; Wang Lei; Wang Ruihong; Fu Honggang, E-mail: fuhg@vip.sina.com [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Heilongjiang University, Harbin 150080 (China)

    2010-01-15

    In this paper, a simple approach was proposed to fabricate graphitic carbon nanocapsules, tungsten carbide and tungsten carbides/graphitic carbon composites by using chitosan, a green and renewable biopolymer, as a carbon source. The route includes, first, fabrication of the precursors that consist of chitosan coordinated with a certain metal ion (or metal complex anion) followed by carbonizing the precursors under N{sub 2} atmosphere. The composition of the final products could be regulated by changing the type and ratio of the metal source (cations or complex anions) combined with the chitosan in the precursors. The experimental results showed that uniform carbon nanocapsules could be obtained when Ni{sup 2+} was introducing in the precursors, while incorporating [PW{sub 12}O{sub 40}]{sup 3-} (PW{sub 12}) with chitosan led to the formation of WC nanoparticles. As the Ni{sup 2+} and PW{sub 12} are simultaneously coordinated with chitosan, the composites of tungsten carbide/graphitic carbon were successfully produced. Transmission electron microscopy (TEM) analysis revealed that the graphitic carbon nanocapsules are about 45 nm in diameter; uniform WC nanoparticles with a average size of 40 nm are observed. Moreover, the particle size of WC in the tungsten carbide/graphitic carbon composite is about 10 nm, which is smaller than that of the pure WC particles. Furthermore, the performance of the sample-loaded Pt nanoparticles for methanol electro-oxidation was studied in detail. The results indicated that the samples could act as good carriers for Pt in the methanol electro-oxidation reaction with high effectivity and improved stability.

  7. Active carbon supported molybdenum carbides for higher alcohols synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Chiarello, Gian Luca; Christensen, Jakob Munkholt

    This work provides an investigation of the high pressure CO hydrogenation to higher alcohols on K2CO3 promoted active carbon supported molybdenum carbide. Both activity and selectivity to alcohols over supported molybdenum carbides increased significantly compared to bulk carbides in literatures....... The optimal loadings of both molybdenum carbide and the K2CO3 promoter on active carbon have been investigated. The catalysts were characterized using BET surface area measurements, transmission electron microscopy and X-ray diffraction. Additionally, in-situ X-ray diffraction and in-situ X-ray absorption...

  8. Photoluminescence and Raman spectroscopy characterization of boron- and nitrogen-doped 6H silicon carbide

    DEFF Research Database (Denmark)

    Ou, Yiyu; Jokubavicius, Valdas; Liu, Chuan

    2011-01-01

    Boron - and nitrogen-doped 6H silicon carbide epilayers grown on low off-axis 6H silicon carbide substrates have been characterized by photoluminescence and Raman spectroscopy. Combined with secondary ion mass spectrometry results, preferable doping type and optimized concentration could be propo......Boron - and nitrogen-doped 6H silicon carbide epilayers grown on low off-axis 6H silicon carbide substrates have been characterized by photoluminescence and Raman spectroscopy. Combined with secondary ion mass spectrometry results, preferable doping type and optimized concentration could...

  9. The effects of applying silicon carbide coating on core reactivity of pebble-bed HTR in water ingress accident

    Energy Technology Data Exchange (ETDEWEB)

    Zuhair, S.; Setiadipura, Topan [National Nuclear Energy Agency of Indonesia, Serpong Tagerang Selatan (Indonesia). Center for Nuclear Reactor Technology and Safety; Su' ud, Zaki [Bandung Institute of Technology (Indonesia). Dept. of Physics

    2017-03-15

    Graphite is used as the moderator, fuel barrier material, and core structure in High Temperature Reactors (HTRs). However, despite its good thermal and mechanical properties below the radiation and high temperatures, it cannot avoid corrosion as a consequence of an accident of water/air ingress. Degradation of graphite as a main HTR material and the formation of dangerous CO gas is a serious problem in HTR safety. One of the several steps that can be adopted to avoid or prevent the corrosion of graphite by the water/air ingress is the application of a thin layer of silicon carbide (SiC) on the surface of the fuel element. This study investigates the effect of applying SiC coating on the fuel surfaces of pebble-bed HTR in water ingress accident from the reactivity points of view. A series of reactivity calculations were done with the Monte Carlo transport code MCNPX and continuous energy nuclear data library ENDF/B-VII at temperature of 1200 K. Three options of UO{sub 2}, PuO{sub 2}, and ThO{sub 2}/UO{sub 2} fuel kernel were considered to obtain the inter comparison of the core reactivity of pebble-bed HTR in conditions of water/air ingress accident. The calculation results indicated that the UO{sub 2}-fueled pebble-bed HTR reactivity was slightly reduced and relatively more decreased when the thickness of the SiC coating increased. The reactivity characteristic of ThO{sub 2}/UO{sub 2}-fueled pebble-bed HTR showed a similar trend to that of UO{sub 2}, but did not show reactivity peak caused by water ingress. In contrast with UO{sub 2}- and ThO{sub 2}-fueled pebble-bed HTR, although the reactivity of PuO{sub 2}-fueled pebble-bed HTR was the lowest, its characteristics showed a very high reactivity peak (0.33 Δk/k) and this introduction of positive reactivity is difficult to control. SiC coating on the surface of the plutonium fuel pebble has no significant impact. From the comparison between reactivity characteristics of uranium, thorium and plutonium cores with 0

  10. High-activity PtRuPd/C catalyst for direct dimethyl ether fuel cells.

    Science.gov (United States)

    Li, Qing; Wen, Xiaodong; Wu, Gang; Chung, Hoon T; Gao, Rui; Zelenay, Piotr

    2015-06-22

    Dimethyl ether (DME) has been considered as a promising alternative fuel for direct-feed fuel cells but lack of an efficient DME oxidation electrocatalyst has remained the challenge for the commercialization of the direct DME fuel cell. The commonly studied binary PtRu catalyst shows much lower activity in DME than methanol oxidation. In this work, guided by density functional theory (DFT) calculation, a ternary carbon-supported PtRuPd catalyst was designed and synthesized for DME electrooxidation. DFT calculations indicated that Pd in the ternary PtRuPd catalyst is capable of significantly decreasing the activation energy of the CO and CH bond scission during the oxidation process. As evidenced by both electrochemical measurements in an aqueous electrolyte and polymer-electrolyte fuel cell testing, the ternary catalyst shows much higher activity (two-fold enhancement at 0.5 V in fuel cells) than the state-of-the-art binary Pt50 Ru50 /C catalyst (HiSPEC 12100). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Thermal Analysis of Tantalum Carbide-Hafnium Carbide Solid Solutions from Room Temperature to 1400 °C

    Directory of Open Access Journals (Sweden)

    Cheng Zhang

    2017-07-01

    Full Text Available The thermogravimetric analysis on TaC, HfC, and their solid solutions has been carried out in air up to 1400 °C. Three solid solution compositions have been chosen: 80TaC-20 vol % HfC (T80H20, 50TaC-50 vol % HfC (T50H50, and 20TaC-80 vol % HfC (T20H80, in addition to pure TaC and HfC. Solid solutions exhibit better oxidation resistance than the pure carbides. The onset of oxidation is delayed in solid solutions from 750 °C for pure TaC, to 940 °C for the T50H50 sample. Moreover, T50H50 samples display the highest resistance to oxidation with the retention of the initial carbides. The oxide scale formed on the T50H50 sample displays mechanical integrity to prevent the oxidation of the underlying carbide solid solution. The improved oxidation resistance of the solid solution is attributed to the reaction between Ta2O5 and HfC, which stabilizes the volume changes induced by the formation of Ta2O5 and diminishes the generation of gaseous products. Also, the formation of solid solutions disturbs the atomic arrangement inside the lattice, which delays the reaction between Ta and O. Both of these mechanisms lead to the improved oxidation resistances of TaC-HfC solid solutions.

  12. Simultaneous measurement of neutron and gamma-ray radiation levels from a TRIGA reactor core using silicon carbide semiconductor detectors

    Science.gov (United States)

    Dulloo, A. R.; Ruddy, F. H.; Seidel, J. G.; Davison, C.; Flinchbaugh, T.; Daubenspeck, T.

    1999-06-01

    The ability of a silicon carbide radiation detector to measure neutron and gamma radiation levels in a TRIGA reactor's mixed neutron/gamma field was demonstrated. Linear responses to epicadmium neutron fluence rate (up to 3/spl times/10/sup 7/ cm/sup -2/ s/sup -1/) and to gamma dose rate (0.6-234 krad-Si h/sup -1/) were obtained with the detector. Axial profiles of the reactor core's neutron and gamma-ray radiation levels were successfully generated through sequential measurements along the length of the core. The SiC detector shows a high level of precision for both neutrons and gamma rays in high-intensity radiation environments-1.9% for neutrons and better than 0.6% for gamma rays. These results indicate that SiC detectors are well suited for applications such as spent fuel monitoring where measurements in mixed neutron/gamma fields are desired.

  13. Synthesis of Ternary Nitrides From Intermetallic Precursors: Modes of Nitridation in Model Cr3Pt Alloys to Form Cr3PtN Perovskite and Applications to Other Systems

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P [ORNL; Wrobel, Sarah [University of Tennessee, Knoxville (UTK); Lograsso, Tom [Ames Laboratory; Payzant, E Andrew [ORNL; Hoelzer, David T [ORNL; Horton Jr, Joe A [ORNL; Walker, Larry R [ORNL

    2004-01-01

    The use of intermetallic alloy precursors is explored as a new means to synthesize complex transition and refractory metal nitrides, carbides, and related phases. The conditions under which model single-phase Cr{sub 3}Pt and two-phase Cr{sub 3}Pt-dispersed Cr alloys form Cr{sub 3}PtN antiperovskite when thermally nitrided were studied. Phenomenological experiments suggest that the key variable to achieving single-phase Cr{sub 3}PtN surface layers is the Cr{sub 3}Pt phase composition. In two-phase {beta}-Cr-Cr{sub 3}Pt alloys, the formation of single-phase Cr{sub 3}PtN at Cr{sub 3}Pt precipitates by in-place internal nitridation was found to be a strong function of the size of the Cr{sub 3}Pt dispersion in the microstructure. Nanoscale Cr{sub 3}Pt dispersions were readily converted to near single-phase Cr{sub 3}PtN, whereas nitridation of coarse Cr{sub 3}Pt particles resulted in a cellular or discontinuous-type reaction to form a lath mixture of Cr{sub 3}PtN and a more Cr-rich Cr{sub 3}Pt or {beta}-Cr. The potential for using such external/internal oxidation phenomena as a synthesis approach to layered or composite surfaces of ternary ceramic phases (nitrides, carbides, borides, etc.) of technological interest such as the Ti{sub 3}AlC{sub 2} phase, bimetallic nitride, and carbide catalysts (Co{sub 3}Mo{sub 3}N and Co{sub 3}Mo{sub 3}C and related phases), and magnetic rare earth nitrides (Fe{sub 17}Sm{sub 2}N{sub x} or Fe{sub 17}Nd{sub 2}N{sub x}) is discussed.

  14. Fuel Cells

    DEFF Research Database (Denmark)

    Smith, Anders; Pedersen, Allan Schrøder

    2014-01-01

    Fuel cells have been the subject of intense research and development efforts for the past decades. Even so, the technology has not had its commercial breakthrough yet. This entry gives an overview of the technological challenges and status of fuel cells and discusses the most promising applications...... of the different types of fuel cells. Finally, their role in a future energy supply with a large share of fluctuating sustainable power sources, e.g., solar or wind, is surveyed....

  15. Study on fragmentation and dissolution behavior of carbide in a hot-rolled hypereutectic high chromium cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fei; Jiang, Yehua, E-mail: jiangyehua@kmust.edu.cn; Xiao, Han; Tan, Jun

    2015-01-05

    Highlights: • The method to prepare Carbon steel/High chromium iron is totally new. • High chromium iron can achieve small plastic deformation during hot rolling process. • Carbides in high chromium irons are crushed, refined obviously and becoming isolated, which is benefit to improve the impact toughness. • The carbide fragmentation and dissolution behavior of the hot-rolled HCCI were analyzed. - Abstract: A sandwich-structured composite containing a hypereutectic high chromium cast iron (HCCI) and low carbon steel (LCS) claddings was newly fabricated by centrifugal casting, then the blank was hot-rolled into composite plate. The carbide fragmentation and dissolution behavior of the hot-rolled HCCI were analyzed. During hot rolling, significant refinement of carbides was discovered in hot-rolled HCCI specimens. The carbides were broken and partly dissolved into the austenite matrix. The results show that carbides are firstly dissolved under the action of stress. There are grooves appeared at the boundaries of the carbides. The grooves reduce the cross section of the carbide. When the cross section of the carbide reaches to the required minimum critical cross section, the carbide breaks through the tensile force. After break, carbides continue to dissolve since more interfaces between the matrix and carbides are generated. The secondary carbides precipitated due to the dissolution are index as fcc and stacking faults parallel to the {1 1 1} are observed.

  16. Evaluation of ternary blended cements for use in transportation concrete structures

    Science.gov (United States)

    Gilliland, Amanda Louise

    This thesis investigates the use of ternary blended cement concrete mixtures for transportation structures. The study documents technical properties of three concrete mixtures used in federally funded transportation projects in Utah, Kansas, and Michigan that used ternary blended cement concrete mixtures. Data were also collected from laboratory trial batches of ternary blended cement concrete mixtures with mixture designs similar to those of the field projects. The study presents the technical, economic, and environmental advantages of ternary blended cement mixtures. Different barriers of implementation for using ternary blended cement concrete mixtures in transportation projects are addressed. It was concluded that there are no technical, economic, or environmental barriers that exist when using most ternary blended cement concrete mixtures. The technical performance of the ternary blended concrete mixtures that were studied was always better than ordinary portland cement concrete mixtures. The ternary blended cements showed increased durability against chloride ion penetration, alkali silica reaction, and reaction to sulfates. These blends also had less linear shrinkage than ordinary portland cement concrete and met all strength requirements. The increased durability would likely reduce life cycle costs associated with concrete pavement and concrete bridge decks. The initial cost of ternary mixtures can be higher or lower than ordinary portland cement, depending on the supplementary cementitious materials used. Ternary blended cement concrete mixtures produce less carbon dioxide emissions than ordinary portland cement mixtures. This reduces the carbon footprint of construction projects. The barriers associated with implementing ternary blended cement concrete for transportation projects are not significant. Supplying fly ash returns any investment costs for the ready mix plant, including silos and other associated equipment. State specifications can make

  17. Exposure to fibres, crystalline silica, silicon carbide and sulphur dioxide in the norwegian silicon carbide industry.

    Science.gov (United States)

    Føreland, S; Bye, E; Bakke, B; Eduard, W

    2008-07-01

    The aim of this study was to assess personal exposure to fibres, crystalline silica, silicon carbide (SiC) and sulphur dioxide in the Norwegian SiC industry. Approximately 720 fibre samples, 720 respirable dust samples and 1400 total dust samples were collected from randomly chosen workers from the furnace, processing and maintenance departments in all three Norwegian SiC plants. The respirable dust samples were analysed for quartz, cristobalite and non-fibrous SiC content. Approximately 240 sulphur dioxide samples were collected from workers in the furnace department. The sorting operators from all plants, control room and cleaning operators in Plant A and charger, charger/mix and payloader operators in Plant C had a geometric mean (GM) of fibre exposure above the Norwegian occupational exposure limit (OEL) (0.1 fibre cm(-3)). The cleaner operators in Plant A had the highest GM exposure to respirable quartz (20 mug m(-3)). The charger/mix operators in Plant C had the highest GM exposure to respirable cristobalite (38 mug m(-3)) and the refinery crusher operators in Plant A had the highest GM exposure to non-fibrous SiC (0.65 mg m(-3)). Exposure to the crystalline silica and non-fibrous SiC was generally low and between 0.4 and 2.1% of the measurements exceeded the OELs. The cleaner operators in Plant A had the highest GM exposure to respirable dust (1.3 mg m(-3)) and total dust (21 mg m(-3)). GM exposures for respirable dust above the Norwegian SiC industry-specific OEL of 0.5 mg m(-3) were also found for refinery crusher operators in all plants and mix, charger, charger/mix and sorting operators in Plant C. Only 4% of the total dust measurements exceeded the OEL for nuisance dust of (10 mg m(-3)). Exposure to sulphur dioxide was generally low. However, peaks in the range of 10-100 p.p.m. were observed for control room and crane operators in Plants A and B and for charger and charger/mix operators in Plant C. Workers in the SiC industry are exposed to a mixture of

  18. Oxygen Reduction Reaction Activity and Durability of Pt Catalysts Supported on Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Morio Chiwata

    2015-06-01

    Full Text Available We have prepared Pt nanoparticles supported on titanium carbide (TiC (Pt/TiC as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, and transmission electron microscopy (TEM. Hemispherical Pt nanocrystals were found to be dispersed uniformly on the TiC support after heat treatment at 600 °C in 1% H2/N2 (Pt/TiC-600 °C. The electrochemical properties (cyclic voltammetry, electrochemically active area (ECA, and oxygen reduction reaction (ORR activity of Pt/TiC-600 °C and a commercial Pt/carbon black (c-Pt/CB were evaluated by the rotating disk electrode (RDE technique in 0.1 M HClO4 solution at 25 °C. It was found that the kinetically controlled mass activity for the ORR on Pt/TiC-600 °C at 0.85 V (507 A g−1 was comparable to that of c-Pt/CB (527 A g−1. Moreover, the durability of Pt/TiC-600 °C examined by a standard potential step protocol (E = 0.9 V↔1.3 V vs. RHE, holding 30 s at each E was much higher than that for c-Pt/CB.

  19. Mechanical Behavior and Sliding Wear Studies on Iron Aluminide Coatings Reinforced with Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Mahdi Amiriyan

    2017-05-01

    Full Text Available Wear-resistant iron aluminide-based composites were coated on steel substrates with the High-Velocity Oxy-Fuel (HVOF technique using ball milled Fe3Al and TiC powders as feedstock. The phase composition, microstructure, microhardness, elastic modulus and dry sliding wear performance of unreinforced Fe3Al and Fe3Al–TiC composite coatings (reinforced with 30 and 50 vol. % TiC particles were evaluated in order to reveal the relationship between the mechanical and tribological behaviors. Compared to the unreinforced coatings, the composite coating with 30 vol. % TiC particles exhibited much greater hardness and higher elastic modulus. The increase of the elastic modulus of the composite coatings did not result in deterioration of sliding wear behavior. The addition of 50 vol. % TiC resulted in a further increase in hardness, however, both composite coatings showed the same elastic modulus. The fractured cross sectional surface of the unreinforced coating showed a weakly bonded microstructure promoting delamination in wear tests, whereas the composite fractured surface showed strong mechanical bonding between the matrix and carbide particles, leading to better cohesion. The Fe3Al–TiC coatings showed almost three orders of magnitude higher wear resistance under the dry sliding wear test compared to the unreinforced coatings.

  20. Au ion irradiation of various silicon carbide fiber-reinforced SiC matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Chaâbane, Nihed, E-mail: nihed.chaabane@cea.fr [CEA, INSTN/UEPTN, F-91191 Gif-sur-Yvette (France); Flem, Marion Le [CEA, DEN/DMN/SRMA, F-91191 Gif-sur-Yvette (France); Tanguy, Morgane [CEA, INSTN/UEPTN, F-91191 Gif-sur-Yvette (France); Urvoy, Stéphane [CEA, DEN/DMN/SRMA, F-91191 Gif-sur-Yvette (France); Sandt, Christophe; Dumas, Paul [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Serruys, Yves [CEA, DEN/DMN/SRMP, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France)

    2013-08-15

    Silicon carbide fiber-reinforced SiC matrix composites are promising candidates as fuel cladding for several concepts of Generation IV reactors and as structural materials for fusion reactors. The composites used in this study were composed of a SiC matrix obtained by chemical vapor infiltration associated with various fiber types (Tyranno Type-S, Tyranno SA Grade-3 and Hi-Nicalon Type-S) and with a PyC layer as the interphase. 12 MeV Au ions were used for irradiation up to 0.05 and 1 displacement per atom (dpa) fluences at room temperature and 800 °C. Analysis of both microstructure and composition of composites were performed by scanning electron microscopy (SEM), electron probe microanalysis and Raman spectroscopy. At room temperature and low fluence, Raman spectroscopy results showed that irradiation induces a disordered/distorted state into fibers and matrix. With increasing fluence, a total amorphization of these constituents occurs. The increase in the irradiation temperature leads to a damage recovery and partial recrystallization of samples. Image analysis performed from SEM micrographs highlights no significant change in fiber diameter and shape. However, SEM analysis suggests a longitudinal shrinkage of Tyranno Type-S fibers for the composite irradiated at 1 dpa at room temperature and 800 °C. These results are in complete agreement with conclusions from neutron irradiations suggesting an appropriate relevance of irradiations with 12 MeV Au.

  1. Selective deoxygenation of aldehydes and alcohols on molybdenum carbide (Mo{sub 2}C) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Ke [Catalysis Center for Energy Innovation, Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716 (United States); Yu, Weiting [Chemical Engineering, Columbia University, New York, NY 10027 (United States); Chen, Jingguang G., E-mail: jgchen@columbia.edu [Chemical Engineering, Columbia University, New York, NY 10027 (United States)

    2014-12-30

    Highlights: • Mo{sub 2}C surface can deoxygenate propanal and 1-propanol to produce propene through a similar intermediate (propoxide or η{sup 2}(C,O)-propanal). • Mo{sub 2}C surface can deoxygenate furfural and furfuryl alcohol to make 2-methylfuran through a 2-methylfuran-like intermediate. • The presence of furan ring modifies the selectivity between deoxygenation and hydrogenation/dehydrogenation pathways. - Abstract: The selective deoxygenation of aldehydes and alcohols without cleaving the C-C bond is crucial for upgrading bio-oil and other biomass-derived molecules to useful fuels and chemicals. In this work, propanal, 1-propanol, furfural and furfuryl alcohol were selected as probe molecules to study the deoxygenation of aldehydes and alcohols on molybdenum carbide (Mo{sub 2}C) prepared over a Mo(1 1 0) surface. The reaction pathways were investigated using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). The deoxygenation of propanal and 1-propanol went through a similar intermediate (propoxide or η{sup 2}(C,O)-propanal) to produce propene. The deoxygenation of furfural and furfuryl alcohol produced a surface intermediate similar to adsorbed 2-methylfuran. The comparison of these results revealed the promising deoxygenation performance of Mo{sub 2}C, as well as the effect of the furan ring on the selective deoxygenation of the C=O and C-OH bonds.

  2. Additive Manufacturing of Silicon Carbide-Based Ceramic Matrix Composites: Technical Challenges and Opportunities

    Science.gov (United States)

    Singh, Mrityunjay; Halbig, Michael C.; Grady, Joseph E.

    2016-01-01

    Advanced SiC-based ceramic matrix composites offer significant contributions toward reducing fuel burn and emissions by enabling high overall pressure ratio (OPR) of gas turbine engines and reducing or eliminating cooling air in the hot-section components, such as shrouds, combustor liners, vanes, and blades. Additive manufacturing (AM), which allows high value, custom designed parts layer by layer, has been demonstrated for metals and polymer matrix composites. However, there has been limited activity on additive manufacturing of ceramic matrix composites (CMCs). In this presentation, laminated object manufacturing (LOM), binder jet process, and 3-D printing approaches for developing ceramic composite materials are presented. For the laminated object manufacturing (LOM), fiber prepreg laminates were cut into shape with a laser and stacked to form the desired part followed by high temperature heat treatments. For the binder jet, processing optimization was pursued through silicon carbide powder blending, infiltration with and without SiC nano powder loading, and integration of fibers into the powder bed. Scanning electron microscopy was conducted along with XRD, TGA, and mechanical testing. Various technical challenges and opportunities for additive manufacturing of ceramics and CMCs will be presented.

  3. A theoretical study of ternary indole-cation-anion complexes.

    Science.gov (United States)

    Carrazana-García, Jorge A; Cabaleiro-Lago, Enrique M; Campo-Cacharrón, Alba; Rodríguez-Otero, Jesús

    2014-12-07

    The simultaneous interactions of an anion and a cation with a π system were investigated by MP2 and M06-2X theoretical calculations. Indole was chosen as a model π system for its relevance in biological environments. Two different orientations of the anion, interacting with the N-H and with the C-H groups of indole, were considered. The four cations (Na(+), NH4(+), C(NH2)3(+) and N(CH3)4(+)) and the four anions (Cl(-), NO3(-), HCOO(-) and BF4(-)) included in the study are of biological interest. The total interaction energy of the ternary complexes was calculated and separated into its two- and three-body components and all of them are further divided into their electrostatic, exchange, repulsion, polarization and dispersion contributions using the local molecular orbital-energy decomposition analysis (LMO-EDA) methodology. The binding energy of the indole-cation-anion complexes depends on both ions, with the cation having the strongest effect. The intense cation-anion attraction determines the geometric and energetic features in all ternary complexes. These structures, with both ions on the same side of the π system, show an anti-cooperative interaction. However, the interaction is not only determined by electrostatics, but also the polarization contribution is important. Specific interactions like the one established between the anion and the N-H group of indole or the proton transfer between an acidic cation and a basic anion play a significant role in the energetics and the structure of particular complexes. The presence of the polar solvent as modelled with the polarizable continuum model (PCM) does not seem to have a significant effect on the geometry of the ternary complexes, but drastically weakens the interaction energy. Also, the strength of the interaction is reduced at a faster rate when the anion is pushed away, compared to the results obtained in the gas phase. The combination of PCM with the addition of one water molecule indicates that the PCM

  4. Multi-modal fission in collinear ternary cluster decay of 252Cf(sf, fff

    Directory of Open Access Journals (Sweden)

    W. von Oertzen

    2015-06-01

    Full Text Available We discuss the multiple decay modes of collinear fission in 252Cf(sf, fff, with three fragments as suggested by the potential energy surface (PES. Fission as a statistical decay is governed by the phase space of the different decay channels, which are suggested in the PES-landscape. The population of the fission modes is determined by the minima in the PES at the scission points and on the internal potential barriers. The ternary collinear decay proceeds as a sequential process, in two steps. The originally observed ternary decay of 252Cf(sf into three different masses (e.g. 132–140Sn, 52–48Ca, 68–72Ni, observed by the FOBOS group in the FLNR (Flerov Laboratory for Nuclear Reactions of the JINR (Dubna the collinear cluster tripartition (CCT, is one of the ternary fission modes. This kind of “true ternary fission” of heavy nuclei has often been predicted in theoretical works during the last decades. In the present note we discuss different ternary fission modes in the same system. The PES shows pronounced minima, which correspond to several modes of ternary fragmentations. These decays have very similar dynamical features as the previously observed CCT-decays. The data obtained in the experiments on CCT allow us to extract the yields for different decay modes using specific gates on the measured parameters, and to establish multiple modes of the ternary fission decay.

  5. He and Be ternary spontaneous fission of sup 2 sup 5 sup 2 Cf

    CERN Document Server

    Hwang, J K; Ramayya, A V; Hamilton, J H

    2002-01-01

    Ternary and binary fission studies of sup 2 sup 5 sup 2 Cf have been carried out by using the Gammasphere detector array with light charged particle (LCD) detectors. The relative sup 4 He and sup 5 He ternary fission yields were determined. The kinetic energies of the sup 5 He and sup 4 He ternary particles were found to be approximately 11 and 16 MeV, respectively. The sup 5 He particles contribute 10-20 % to the total observed alpha ternary yield. The data indicate that in nuclei with octupole deformations the population for the negative parity bands might be enhanced in the alpha ternary fission. >From LCP-gamma double gated spectra, neutron multiplicity distributions for alpha ternary fission pairs were measured. The average neutron multiplicity decreases about 0.7 AMU in going from the binary to alpha ternary fission in the approximately same mass splittings (104-146). From the analysis of the gamma-gamma matrix gated on the sup 1 sup 0 Be particles, the two fragment pairs of sup 1 sup 3 sup 8 Xe - sup 1...

  6. Fuel cells:

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2013-01-01

    A brief overview of the progress in fuel cell applications and basic technology development is presented, as a backdrop for discussing readiness for penetration into the marketplace as a solution to problems of depletion, safety, climate or environmental impact from currently used fossil...... and nuclear fuel-based energy technologies....

  7. Hardware emulation of Memristor based Ternary Content Addressable Memory

    KAUST Repository

    Bahloul, Mohamed A.

    2017-12-13

    MTCAM (Memristor Ternary Content Addressable Memory) is a special purpose storage medium in which data could be retrieved based on the stored content. Using Memristors as the main storage element provides the potential of achieving higher density and more efficient solutions than conventional methods. A key missing item in the validation of such approaches is the wide spread availability of hardware emulation platforms that can provide reliable and repeatable performance statistics. In this paper, we present a hardware MTCAM emulation based on 2-Transistors-2Memristors (2T2M) bit-cell. It builds on a bipolar memristor model with storing and fetching capabilities based on the actual current-voltage behaviour. The proposed design offers a flexible verification environment with quick design revisions, high execution speeds and powerful debugging techniques. The proposed design is modeled using VHDL and prototyped on Xilinx Virtex® FPGA.

  8. Normal freezing of ideal ternary systems of the pseudobinary type

    Science.gov (United States)

    Li, C. H.

    1972-01-01

    Perfect liquid mixing but no solid diffusion is assumed in normal freezing. In addition, the molar compositions of the freezing solid and remaining liquid, respectively, follow the solidus and liquidus curves of the constitutional diagram. For the linear case, in which both the liquidus and solidus are perfectly straight lines, the normal freezing equation giving the fraction solidified at each melt temperature and the solute concentration profile in the frozen solid was determined as early as 1902, and has since been repeatedly published. Corresponding equations for quadratic, cubic or higher-degree liquidus and solidus lines have also been obtained. The equation of normal freezing for ideal ternary liquid solutions solidified into ideal solid solutions of the pseudobinary type is given. Sample computations with the use of this new equation were made and are given for the Ga-Al-As system.

  9. Nonequilibrium patterns in phase-separating ternary membranes

    Science.gov (United States)

    Gómez, Jordi; Sagués, Francesc; Reigada, Ramon

    2009-07-01

    We present a nonequilibrium approach for the study of a two-dimensional phase-separating ternary mixture. When the component that promotes phase separation is dynamically exchanged with the medium, the separation process is halted and actively maintained finite-size segregation domains appear in the system. In addition to this effect, already reported in our earlier work [J. Gómez, F. Sagués, and R. Reigada, Phys. Rev. E 77, 021907 (2008)], the use of a generic Ginzburg-Landau formalism and the inclusion of thermal fluctuations provide a more dynamic description of the resulting domain organization. Its size, shape, and stability properties are studied. Larger and more circular and stable domains are formed when decreasing the recycling rate, increasing the mobility of the exchanged component, and the mixture is quenched deeper. We expect this outcome to be of applicability in raft phenomenology in plasmatic cell membranes.

  10. A high-throughput search for new ternary superalloys

    Science.gov (United States)

    Nyshadham, Chandramouli; Hansen, Jacob; Oses, Corey; Curtarolo, Stefano; Hart, Gus

    In 2006 an unexpected new superalloy, Co3[Al,W], was discovered. This new alloy is cobalt-based, in contrast to conventional superalloys, which are nickel-based. Inspired by this new discovery, we performed first-principles calculations, searching through 2224 ternary metallic systems of the form A3[B0.5C0.5], where A = Ni/Co/Fe and [B, C] = all binary combinations of 40 different elements chosen from the periodic table. We found 175 new systems that are better than the Co3[Al, W] superalloy. 75 of these systems are brand new--they have never been reported in experimental literature. These 75 new potential superalloys are good candidates for further experiments. Our calculations are consistent with current experimental literature where data exists. Work supported under: ONR (MURI N00014-13-1-0635).

  11. Hardness and Microstructure of Binary and Ternary Nitinol Compounds

    Science.gov (United States)

    Stanford, Malcolm K.

    2016-01-01

    The hardness and microstructure of twenty-six binary and ternary Nitinol (nickel titanium, nickel titanium hafnium, nickel titanium zirconium and nickel titanium tantalum) compounds were studied. A small (50g) ingot of each compound was produced by vacuum arc remelting. Each ingot was homogenized in vacuum for 48 hr followed by furnace cooling. Specimens from the ingots were then heat treated at 800, 900, 1000 or 1100 degree C for 2 hr followed by water quenching. The hardness and microstructure of each specimen was compared to the baseline material (55-Nitinol, 55 at.% nickel - 45 at.% titanium, after heat treatment at 900 degC). The results show that eleven of the studied compounds had higher hardness values than the baseline material. Moreover, twelve of the studied compounds had measured hardness values greater 600HV at heat treatments from 800 to 900 degree C.

  12. Comprehensive characterization of chitosan/PEO/levan ternary blend films.

    Science.gov (United States)

    Bostan, Muge Sennaroglu; Mutlu, Esra Cansever; Kazak, Hande; Sinan Keskin, S; Oner, Ebru Toksoy; Eroglu, Mehmet S

    2014-02-15

    Ternary blend films of chitosan, PEO (300,000) and levan were prepared by solution casting method and their phase behavior, miscibility, thermal and mechanical properties as well as their surface energy and morphology were characterized by different techniques. FT-IR analyses of blend films indicated intermolecular hydrogen bonding between blend components. Thermal and XRD analysis showed that chitosan and levan suppressed the crystallinity of PEO up to nearly 25% of PEO content in the blend, which resulted in more amorphous film structures at higher PEO/(chitosan+levan) ratios. At more than 30% of PEO concentration, contact angle (CA) measurements showed a surface enrichment of PEO whereas at lower PEO concentrations, chitosan and levan were enriched on the surfaces leading to more amorphous and homogenous surfaces. This result was further confirmed by atomic force microscopy (AFM) images. Cell proliferation and viability assay established the high biocompatibility of the blend films. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Designing and analysing parallel control for multifeed ternary systems

    Directory of Open Access Journals (Sweden)

    Rocío Solar-González

    2010-06-01

    Full Text Available This paper explores a parallel control structure for improving the behaviour of a chemical plant having recycling and multi- ple feed streams; a ternary system is taken as an example,having an A + B → C second-order irreversible reaction. Material recycling dynamics can induce the so-called snowball effect in the presence of disturbance in the feed stream. The snowball effect can be prevented by distributing load through the parallel control scheme. A control structure was thus pro- posed where product composition was regulated by means of simultaneous feedback manipulation of final column vapour boilup rate and reactor temperature. An extension was made for one reactor, one distillation column and recycle stream configuration. Nonlinear simulations showed that effective composition control could be obtained with moderate vapour boilup control efforts.

  14. Morphological Control Agent in Ternary Blend Bulk Heterojunction Solar Cells

    Directory of Open Access Journals (Sweden)

    Hsueh-Chung Liao

    2014-11-01

    Full Text Available Bulk heterojunction (BHJ organic photovoltaic (OPV promise low cost solar energy and have caused an explosive increase in investigations during the last decade. Control over the 3D morphology of BHJ blend films in various length scales is one of the pillars accounting for the significant advance of OPV performance recently. In this contribution, we focus on the strategy of incorporating an additive into BHJ blend films as a morphological control agent, i.e., ternary blend system. This strategy has shown to be effective in tailoring the morphology of BHJ through different inter- and intra-molecular interactions. We systematically review the morphological observations and associated mechanisms with respect to various kinds of additives, i.e., polymers, small molecules and inorganic nanoparticles. We organize the effects of morphological control (compatibilization, stabilization, etc. and provide general guidelines for rational molecular design for additives toward high efficiency and high stability organic solar cells.

  15. Ternary gypsum-based materials: Composition, properties and utilization

    Science.gov (United States)

    Doleželová, M.; Svora, P.; Vimmrová, A.

    2017-10-01

    In spite of the fact that gypsum is one of the most environmentally friendly binders, utilization of gypsum products is relatively narrow. The main problem of gypsum materials is their low resistance to the wet environment and radical decrease of mechanical properties with increasing moisture. The solution of the problem could be in use of composed gypsum-based binders, usually ternary, comprising gypsum, pozzolan and alkali activator of pozzolan reaction. These materials have a better moisture resistance and often also better mechanical properties. Paper provides literature survey of the possible compositions, properties and ways of utilization of the composed gypsum-based binders with latent hydraulic and pozzolan materials together with some results of present research performed by authors.

  16. Issues Affecting the Synthetic Scalability of Ternary Metal Ferrite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Lauren Morrow

    2015-01-01

    Full Text Available Ternary Mn-Zn ferrite (MnxZn1-xFe2O4 nanoparticles (NPs have been prepared by the thermal decomposition of an oleate complex, sodium dodecylbenzenesulfonate (SDBS mediated hydrazine decomposition of the chloride salts, and triethylene glycol (TREG mediated thermal decomposition of the metal acetylacetonates. Only the first method was found to facilitate the synthesis of uniform, isolable NPs with the correct Mn : Zn ratio (0.7 : 0.3 as characterized by small angle X-ray scattering (SAXS, transmission electron microscopy (TEM, and inductively coupled plasma-optical emission spectroscopy (ICP-OES. Scaling allowed for retention of the composition and size; however, attempts to prepare Zn-rich ferrites did not result in NP formation. Thermogravimetric analysis (TGA indicated that the incomplete decomposition of the metal-oleate complexes prior to NP nucleation for Zn-rich compositions is the cause.

  17. Ternary cobalt-molybdenum-zirconium coatings for alternative energies

    Science.gov (United States)

    Yar-Mukhamedova, Gulmira; Ved', Maryna; Sakhnenko, Nikolay; Koziar, Maryna

    2017-11-01

    Consistent patterns for electrodeposition of Co-Mo-Zr coatings from polyligand citrate-pyrophosphate bath were investigated. The effect of both current density amplitude and pulse on/off time on the quality, composition and surface morphology of the galvanic alloys were determined. It was established the coating Co-Mo-Zr enrichment by molybdenum with current density increasing up to 8 A dm-2 as well as the rising of pulse time and pause duration promotes the content of molybdenum because of subsequent chemical reduction of its intermediate oxides by hydrogen ad-atoms. It was found that the content of the alloying metals in the coating Co-Mo-Zr depends on the current density and on/off times extremely and maximum Mo and Zr content corresponds to the current density interval 4-6 A dm-2, on-/off-time 2-10 ms. Chemical resistance of binary and ternary coatings based on cobalt is caused by the increased tendency to passivity and high resistance to pitting corrosion in the presence of molybdenum and zirconium, as well as the acid nature of their oxides. Binary coating with molybdenum content not less than 20 at.% and ternary ones with zirconium content in terms of corrosion deep index are in a group ;very proof;. It was shown that Co-Mo-Zr alloys exhibits the greatest level of catalytic properties as cathode material for hydrogen electrolytic production from acidic media which is not inferior a platinum electrode. The deposits Co-Mo-Zr with zirconium content 2-4 at.% demonstrate high catalytic properties in the carbon(II) oxide conversion. This confirms the efficiency of materials as catalysts for the gaseous wastes purification and gives the reason to recommend them as catalysts for red-ox processes activating by oxygen as well as electrode materials for red-ox batteries.

  18. Cohesion energy calculations for ternary ionic novel crystals

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez Polo, G; Valdes, E. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico); Mijngos, R. R; Duarte, D. [Universidad de Sonora, Hermosillo, Sonora (Mexico)

    2001-12-01

    The present work calculates the value of the link energy of a crystalline ternary structure newly formed by alkali halides. The ternary structure prepared with different concentrations of KCI{sub x}KBr{sub y}RbCl{sub z} maintains a very good miscibility and stability. The calculation is based on the use of a generalization of the Vegard's law (which generally is valid for binary compounds) for calculating the values of the lattice constant and the repulsive m exponent. The values of the lattice parameter given X-ray diffractometry agrees with the close approximation of the calculated value of the method used. It also compares the value of energy cohesion obtained by the Born expression with more complex approximations. [Spanish] En el presente trabajo se calcula el valor de la energia de amarre de una estructura ternaria cristalina nueva formada por halogenuros alcalinos. La estructura ternaria preparada con diferentes concentraciones KCI{sub x}KBr{sub y}RbCl{sub z} mantiene una muy buena estabilidad y miscibilidad. El calculo se basa en el uso de una generalizacion de la ley de Vegard (que en general es valida para compuestos binarios) para calcular los valores de la constante de red y de exponente repulsivo m. El valor del parametro de red medido por difractometria de rayos X, concuerda en buena aproximacion con el valor calculado por el metodo usado. Tambien se compara el valor de la energia de cohesion obtenido por la expresion de Born con aproximaciones mas complejas.

  19. Boron-Based Hydrogen Storage: Ternary Borides and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Vajo, John J. [HRL Laboratories, LLC, Malibu, CA (United States)

    2016-04-28

    DOE continues to seek reversible solid-state hydrogen materials with hydrogen densities of ≥11 wt% and ≥80 g/L that can deliver hydrogen and be recharged at moderate temperatures (≤100 °C) and pressures (≤100 bar) enabling incorporation into hydrogen storage systems suitable for transportation applications. Boron-based hydrogen storage materials have the potential to meet the density requirements given boron’s low atomic weight, high chemical valance, and versatile chemistry. However, the rates of hydrogen exchange in boron-based compounds are thus far much too slow for practical applications. Although contributing to the high hydrogen densities, the high valance of boron also leads to slow rates of hydrogen exchange due to extensive boron-boron atom rearrangements during hydrogen cycling. This rearrangement often leads to multiple solid phases occurring over hydrogen release and recharge cycles. These phases must nucleate and react with each other across solid-solid phase boundaries leading to energy barriers that slow the rates of hydrogen exchange. This project sought to overcome the slow rates of hydrogen exchange in boron-based hydrogen storage materials by minimizing the number of solid phases and the boron atom rearrangement over a hydrogen release and recharge cycle. Two novel approaches were explored: 1) developing matched pairs of ternary borides and mixed-metal borohydrides that could exchange hydrogen with only one hydrogenated phase (the mixed-metal borohydride) and only one dehydrogenated phase (the ternary boride); and 2) developing boranes that could release hydrogen by being lithiated using lithium hydride with no boron-boron atom rearrangement.

  20. Monolayer Iron Carbide Films on Au(111) as a Fischer–Tropsch Model Catalyst

    DEFF Research Database (Denmark)

    Mannie, Gilbère; Lammich, Lutz; Li, Yong-Wang

    2014-01-01

    Using scanning tunneling microscopy (STM), we characterize the atomic-scale details of ultrathin films of iron carbide (FexCy) on Au(111) synthesized as a potential model system for the active iron carbide phase in iron Fischer–Tropsch synthesis (FTS) catalysts. The experiments show that room...

  1. Microstructural evaluation of the NbC-20Ni cemented carbides during sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, D. [BRATS Sintered Filters and Metallic Powders, Cajamar, SP (Brazil); Cannizza, E. [EHT Cannizza Consultoria Em Engenharia Ltda, Sao Paulo, SP (Brazil)

    2016-07-01

    Full text: Fine carbides in a metallic matrix (binder) form the microstructure of the cemented carbides. Grain size and binder content are the main variables to adjust hardness and toughness. These products are produced by Powder Metallurgy, and traditional route involves mixing carbides with binder by high energy milling, pressing and sintering. During sintering, a liquid phase promotes densification, and a final relative density higher than 99% is expected. Sintering is carried out at high temperatures, and dissolution of the carbides changes the chemical composition of the binder. To control grain growth of the main carbide, which reduces hardness, small quantities of secondary carbides are used. These additives limit dissolution and precipitation of the main carbides reducing the final grain size. This paper focused the structural and chemical evolution during sintering using NbC-20Ni cermets. Mixtures of very fine NbC carbides and carbonyl Ni powders were produce by intense milling. These mixtures were pressed using uniaxial pressures from 50 to 200MPa. Shrinkage was evaluated using dilatometric measurements under an atmosphere of dynamic argon. Samples were also sintered under vacuum in high temperature industrial furnace. The sintered samples were characterized in terms of density hardness, toughness and microstructure. DRX was the main tool used to evaluate the structural evolution of the binder. In situ chemical analysis helped to understand the dissolution mechanisms. (author)

  2. Plasma-Chemical Synthesis of Nanosized Powders-Nitrides, Carbides, Oxides, Carbon Nanotubes and Fullerenes

    Science.gov (United States)

    Katerina, Zaharieva; Gheorghi, Vissokov; Janis, Grabis; Slavcho, Rakovsky

    2012-11-01

    In this article the plasma-chemical synthesis of nanosized powders (nitrides, carbides, oxides, carbon nanotubes and fullerenes) is reviewed. Nanosized powders - nitrides, carbides, oxides, carbon nanotubes and fullerenes have been successfully produced using different techniques, technological apparatuses and conditions for their plasma-chemical synthesis.

  3. Natural precursor based hydrothermal synthesis of sodium carbide for reactor applications

    Science.gov (United States)

    Swapna, M. S.; Saritha Devi, H. V.; Sebastian, Riya; Ambadas, G.; Sankararaman, S.

    2017-12-01

    Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.

  4. Properties and characterization of multilayers of carbides and diamond-like carbon

    NARCIS (Netherlands)

    Strondl, C.; Kolk, G.J. van der; Hurkmans, T.; Fleischer, W.; Trinh, T.; Marcolino Carvalho, Nuno; Hosson, J.Th.M. de

    Metal containing diamond-like carbon (Me-DLC) coatings are widely applied in industrial applications. Normally, the coatings are produced with small inclusions of carbide forming elements like the 3d, 4d or 5d metals, or Si or B. The small carbide islands have sizes of approximately 2-20 nm. The

  5. Microstructures and Wear Performance of PTAW Deposited Ni-Based Coatings with Spherical Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Dewei Deng

    2015-10-01

    Full Text Available The Ni-based coatings with different content of spherical tungsten carbide were deposited by plasma transfer arc welding (PTAW method on 304 austenitic stainless steel sheets in this study. The microstructure and wear property of spherical tungsten carbide particle reinforced composite coatings were investigated by means of optical microscope, scanning electron microscope (SEM, X-ray diffraction (XRD, electron probe microanalysis (EPMA and sliding wear test. It is shown that the fraction of spherical tungsten carbides has an important influence on microstructure of Ni-based overlay. The Ni40 overlay consists of γ-Ni dendrites with interdendritic Ni-based eutectics, borides and carbides improving the wear resistance. In the case of composite coatings with different content of tungsten carbide, many new phases are observed, such as Ni2W4C and NiW. In addition, there are a large number of irregular structures in composite coatings, such as acicular structure and irregular stripe organization. The results of sliding wear test indicate that the mass loss of coatings is influenced by the content of tungsten carbide. The mass loss decreases with the increase of tungsten carbide fraction. At high load, the abrasive resistance of composite coating with 60 wt. % tungsten carbide is improved about 50-fold compared to that of Ni40 overlay.

  6. Stereological parameters of carbides on section of casting made from modified chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2011-07-01

    Full Text Available The analysis of stereological parameters of carbides on the section of the model castingmade from modified (the mixture FeNb+FeV+RE wear resistance chromium cast iron was introduced in the article. The jump change of some stereological parameters of carbides in certain distance from the surface of the casting was observed.

  7. Synthesis of nanoparticles of vanadium carbide in the ferrite of nodular cast iron

    CERN Document Server

    Fras, E; Guzik, E; Lopez, H

    2005-01-01

    The synthesis method of nanoparticles of vanadium carbide in nodular cast iron is presented. After introduction of this method, the nanoparticles with 10-70 nm of diameter was obtained in the ferrite. The diffraction investigations confirmed that these particles are vanadium carbides of type V/sub 3/C/sub 4/.

  8. Calcium carbide (CaC2): Effect on fruit set and yield of mango ...

    African Journals Online (AJOL)

    Calcium carbide (CaC2): Effect on fruit set and yield of mango ( Mangifera indica L.) cv. ... photosynthetic rate, final fruit drop, yield per plant, fruit weight, fruit volume, pulp weight, peel weight, juice weight and fruit skin color were significantly affected by the calcium carbide treatment while number of new flushes per branch, ...

  9. Synthesis of functional acetylene derivatives from calcium carbide.

    Science.gov (United States)

    Lin, Zhewang; Yu, Dingyi; Sum, Yin Ngai; Zhang, Yugen

    2012-04-01

    AHA Erlebnis: CaC(2), used to produce acetylene until several decades ago, is re-emerging as a cheap, sustainable resource synthesized from coal and lignocellulosic biomass. We report efficient catalytic protocols for the synthesis of functional acetylene derivatives from CaC(2) through aldehyde, alkyne, and amine (AAA) as well as alkyne, haloalkane, and amine (AHA) couplings, and in addition demonstrate its use in click and Sonogashira chemistry, showing that calcium carbide is a sustainable and cost-efficient carbon source. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Method of fabricating silicon carbide coatings on graphite surfaces

    Science.gov (United States)

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

    1994-07-26

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

  11. Temperature Induced Voltage Offset Drifts in Silicon Carbide Pressure Sensors

    Science.gov (United States)

    Okojie, Robert S.; Lukco, Dorothy; Nguyen, Vu; Savrun, Ender

    2012-01-01

    We report the reduction of transient drifts in the zero pressure offset voltage in silicon carbide (SiC) pressure sensors when operating at 600 C. The previously observed maximum drift of +/- 10 mV of the reference offset voltage at 600 C was reduced to within +/- 5 mV. The offset voltage drifts and bridge resistance changes over time at test temperature are explained in terms of the microstructure and phase changes occurring within the contact metallization, as analyzed by Auger electron spectroscopy and field emission scanning electron microscopy. The results have helped to identify the upper temperature reliable operational limit of this particular metallization scheme to be 605 C.

  12. Surface coating metrology of carbides of cutting tools

    Science.gov (United States)

    Parfenov, V. D.; Basova, G. D.

    2017-10-01

    The coatings were studied by their main sign of the micrometric thickness by means of coating destruction and electron microscopical study of cleavage surfaces. Shock stress ruptures of heated carbides of cutting tools were performed. The discovery of the coating technology and creation of the coating structure for nonuniform and nonequilibrium conditions of the cutting process were dealt with. Multifracture microdestruction of nitride coatings, caused by complex external influences, was analysed to reveal the mechanism of interaction of elementary failures. Positive results were obtained in the form of improving the strength and wear resistance of the product, crack resistance increasing.

  13. Improvement of contact resistances on plasma-exposed silicon carbide

    Science.gov (United States)

    Cheung, R.; Hay, J.; van der Drift, E.; Gao, W.

    2000-11-01

    We demonstrate improvements in the specific contact resistance of unannealed ohmic contacts by at least one order of magnitude on undoped 6H-SiC (silicon carbide, SiC). The improved contacts with a specific resistance of 0.3 Ω cm 2 have been fabricated on SiC surfaces exposed to an argon plasma at -80 V for 2.5 min. Under these plasma conditions, the top monolayers of the plasma-exposed SiC surface is silicon rich as revealed by X-ray photoelectron spectroscopy, and the surface roughness is decreased by a factor of 2 from atomic force microscopy analysis.

  14. Growth of Vanadium Carbide by Halide-Activated Pack Diffusion

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Dahl, Kristian Vinter

    The present work investigates growth of vanadium carbide (VC) layers by the pack diffusion method on a Vanadis 6 tool steel. The VC layers were produced by pack diffusion at 1000°C for 1, 4 and 16 hours. The VC layers were characterized with optical and electron microscopy, Vickers hardness tests...... and X-ray diffraction. Homogeneous VC mono-phase layers with Vickers hardness of more than 2400 HV were obtained. Hardening and tempering of the vanadized Vanadis 6 steel did not affect the VC layers....

  15. High-Temperature Electronic Materials: Silicon Carbide and Diamond

    Science.gov (United States)

    Willander, Magnus; Friesel, Milan; Wahab, Qamar-Ul; Straumal, Boris

    The physical and chemical properties of wide-band-gap semiconductors make these materials an ideal choice for device fabrication for applications in many different areas, e.g. light emitters, high-temperature and high-power electronics, high-power microwave devices, micro-electromechanical system (MEM) technology, and substrates for semiconductor preparation. These semiconductors have been recognized for several decades as being suitable for these applications, but until recently the low material quality has not allowed the fabrication of high-quality devices. In this chapter, we review the wide-band-gap semiconductors, silicon carbide and diamond.

  16. Characterization of plastic and boron carbide additive manufactured neutron collimators

    Science.gov (United States)

    Stone, M. B.; Siddel, D. H.; Elliott, A. M.; Anderson, D.; Abernathy, D. L.

    2017-12-01

    Additive manufacturing techniques allow for the production of materials with complicated geometries with reduced costs and production time over traditional methods. We have applied this technique to the production of neutron collimators for use in thermal and cold neutron scattering instrumentation directly out of boron carbide. We discuss the design and generation of these collimators. We also provide measurements at neutron scattering beamlines which serve to characterize the performance of these collimators. Additive manufacturing of parts using neutron absorbing material may also find applications in radiography and neutron moderation.

  17. Fuel cell-fuel cell hybrid system

    Science.gov (United States)

    Geisbrecht, Rodney A.; Williams, Mark C.

    2003-09-23

    A device for converting chemical energy to electricity is provided, the device comprising a high temperature fuel cell with the ability for partially oxidizing and completely reforming fuel, and a low temperature fuel cell juxtaposed to said high temperature fuel cell so as to utilize remaining reformed fuel from the high temperature fuel cell. Also provided is a method for producing electricity comprising directing fuel to a first fuel cell, completely oxidizing a first portion of the fuel and partially oxidizing a second portion of the fuel, directing the second fuel portion to a second fuel cell, allowing the first fuel cell to utilize the first portion of the fuel to produce electricity; and allowing the second fuel cell to utilize the second portion of the fuel to produce electricity.

  18. ROLE OF GRAIN BOUNDARY CARBIDES IN CRACKING BEHAVIOR OF Ni BASE ALLOYS

    Directory of Open Access Journals (Sweden)

    SEONG SIK HWANG

    2013-02-01

    Full Text Available The primary water stress corrosion cracking (PWSCC of Alloy 600 in a PWR has been reported in the control rod drive mechanism (CRDM, pressurizer instrumentation, and the pressurizer heater sleeves. Recently, two cases of boric acid precipitation that indicated leaking of the primary cooling water were reported on the bottom head surface of steam generators (SG in Korea. The PWSCC resistance of Ni base alloys which have intergranular carbides is higher than those which have intragranular carbides. Conversely, in oxidized acidic solutions like sodium sulfate or sodium tetrathionate solutions, the Ni base alloys with a lot of carbides at the grain boundaries and shows less stress corrosion cracking (SCC resistance. The role of grain boundary carbides in SCC behavior of Ni base alloys was evaluated and effect of intergranular carbides on the SCC susceptibility were reviewed from the literature.

  19. Method of testing carbide inserts for premature fracture by face milling of cylindrical workpieces

    Science.gov (United States)

    Kitagawa, R.; Akasawa, T.; Okusa, K.

    1984-12-01

    Methods are proposed for face milling solid cylindrical workpieces or half-cut and hollow cylindrical workpieces prepared from rectangular blocks by continuously changing both or either of the angles of engagement and disengagement. Carbide inserts are tested for premature fracture before the onset of steady wear using these face-milling methods. The premature fracture indicates the insufficient toughness of carbides to perform a given machining job. As carbides of higher wear resistance have lower shock resistance in general, they must be tested for premature fracture due to the lack of toughness to select suitable carbides for specific cutting applications. The test results obtained under the present study show that the premature fracture of carbides, whose toughness was classified by static toughness tests, can be evaluated dynamically and easily by the proposed face-milling methods.

  20. Modular fabrication and characterization of complex silicon carbide composite structures Advanced Reactor Technologies (ART) Research Final Report (Feb 2015 – May 2017)

    Energy Technology Data Exchange (ETDEWEB)

    Khalifa, Hesham [General Atomics, San Diego, CA (United States)

    2017-08-03

    Advanced ceramic materials exhibit properties that enable safety and fuel cycle efficiency improvements in advanced nuclear reactors. In order to fully exploit these desirable properties, new processing techniques are required to produce the complex geometries inherent to nuclear fuel assemblies and support structures. Through this project, the state of complex SiC-SiC composite fabrication for nuclear components has advanced significantly. New methods to produce complex SiC-SiC composite structures have been demonstrated in the form factors needed for in-core structural components in advanced high temperature nuclear reactors. Advanced characterization techniques have been employed to demonstrate that these complex SiC-SiC composite structures provide the strength, toughness and hermeticity required for service in harsh reactor conditions. The complex structures produced in this project represent a significant step forward in leveraging the excellent high temperature strength, resistance to neutron induced damage, and low neutron cross section of silicon carbide in nuclear applications.

  1. A novel, efficient CNTFET Galois design as a basic ternary-valued logic field.

    Science.gov (United States)

    Keshavarzian, Peiman; Mirzaee, Mahla Mohammad

    2012-01-01

    This paper presents arithmetic operations, including addition and multiplication, in the ternary Galois field through carbon nanotube field-effect transistors (CNTFETs). Ternary logics have received considerable attention among all the multiple-valued logics. Multiple-valued logics are an alternative to common-practice binary logic, which mostly has been expanded from ternary (three-valued) logic. CNTFETs are used to improve Galois field circuit performance. In this study, a novel design technique for ternary logic gates based on CNTFETs was used to design novel, efficient Galois field circuits that will be compared with the existing resistive-load CNTFET circuit designs. In this paper, by using carbon nanotube technology and avoiding the use of resistors, we will reduce power consumption and delay, and will also achieve a better product. Simulation results using HSPICE illustrate substantial improvement in speed and power consumption.

  2. Serpentine diffusion trajectories and the Ouzo effect in partially miscible ternary liquid mixtures

    NARCIS (Netherlands)

    Krishna, R.

    2015-01-01

    This work investigates the transient equilibration process when partially miscible ternary liquid mixtures of two different compositions are brought into contact with each other. Diffusional coupling effects are shown to become increasingly significant as the mixture compositions approach the

  3. Thermodynamic optimization and phase equilibria in the ternary system Ni–Sn–Zn

    Energy Technology Data Exchange (ETDEWEB)

    Gandova, V., E-mail: gandova_71@abv.bg [University of Food Technologies, Inorganic and Physical Chemistry Department, 26 Mariza avenue, 4000 Plovdiv (Bulgaria); Vassilev, G.P. [University of Plovdiv, Faculty of Chemistry, 24 Tsar Asen str., 4000 Plovdiv (Bulgaria)

    2014-10-01

    Highlights: • Thermodynamic description of the Ni–Sn–Zn system was obtained. • Six isothermal sections were calculated. • Third constituents solubility in binary phases’ extensions were taken into account. • Good correlation between calculated and experimental data was obtained. - Abstract: Recent experimental results obtained by differential scanning calorimetry, Scanning Electron Microscopy and other methods were used to develop a thermodynamic description of the ternary system Ni–Sn–Zn. Four ternary non-stoichiometric compounds (T1–T4), mentioned in the literature, were described using three-sublattice models. Previously known optimizations of the binary subsystems were remodeled to comply with the new experimental data. The solubility of the respective ternary components, i.e., Zn in Ni–Sn phases and Sn in Ni–Zn phases, were taken into account and optimized ternary parameters were derived. Six isothermal sections were calculated using Thermo-Calc software.

  4. A novel ternary quantum-dot cell for solving majority voter gate problem

    Science.gov (United States)

    Tehrani, Mohammad A.; Bahrami, Safura; Navi, Keivan

    2014-03-01

    Since the complementary metal-oxide semiconductor (CMOS) technology has experienced many serious problems in fulfilling the need for more robust and efficient circuits, some emerging nanotechnologies have been introduced as the candidates for replacing CMOS. Quantum-dot cellular automata (QCA) is one of the promising nanotechnology candidates with majority function as its fundamental logic element. It has one implementation in binary QCA and several implantations in ternary QCA, but none of the ternary QCA implementations are as efficient as the binary one. In this paper, a new cell configuration for ternary QCA is proposed which works as well as previous cell configuration. Also, a new design for ternary QCA majority function is proposed which performs faster and occupies less area.

  5. Ternary and Multi-Bit FIR Filter Area-Performance Tradeoffs in FPGA

    Directory of Open Access Journals (Sweden)

    Khalil-Ur-Rahman Dayo

    2013-01-01

    Full Text Available In this paper, performance and area of conventional FIR (Finite Impulse Responce filters versus ternary sigma delta modulated FIR filter is compared in FPGA (Field Programmable Gate Arrays using VHDL (Verilog Description Language. Two different approaches were designed and synthesized at same spectral performance by obtaining a TIR (Target Impulse Response. Both filters were synthesized on adaptive LUT (Look Up Table FPGA device in pipelined and non-pipelined modes. It is shown that the Ternary FIR filter occupies approximately the same area as the corresponding multi-bit filter, but for a given specification, the ternary FIR filter has 32% better performance in non-pipelined and 72% in pipelined mode, compared to its equivalent Multi-Bit filter at its optimum 12-bit coefficient quantization. These promising results shows that ternary logic based (i.e. +1,0,-1 filters can be used for huge chip area savings and higher performance.

  6. Improved CVD Coatings for Carbide Based Nuclear Thermal Propulsion Fuel Elements Project

    Data.gov (United States)

    National Aeronautics and Space Administration — One of the great hurdles to further development and evaluation of nuclear thermal propulsion systems is the issue surrounding the release of radioactive material...

  7. Low-temperature synthesis of silicon carbide powder using shungite

    Energy Technology Data Exchange (ETDEWEB)

    Gubernat, A.; Pichor, W.; Lach, R.; Zientara, D.; Sitarz, M.; Springwald, M.

    2017-07-01

    The paper presents the results of investigation the novel and simple method of synthesis of silicon carbide. As raw material for synthesis was used shungite, natural mineral rich in carbon and silica. The synthesis of SiC is possible in relatively low temperature in range 1500–1600°C. It is worth emphasising that compared to the most popular method of SiC synthesis (Acheson method where the temperature of synthesis is about 2500°C) the proposed method is much more effective. The basic properties of products obtained from different form of shungite and in wide range of synthesis temperature were investigated. The process of silicon carbide formation was proposed and discussed. In the case of synthesis SiC from powder of raw materials the product is also in powder form and not requires any additional process (crushing, milling, etc.). Obtained products are pure and after grain classification may be used as abrasive and polishing powders. (Author)

  8. Low-temperature synthesis of silicon carbide powder using shungite

    Directory of Open Access Journals (Sweden)

    Agnieszka Gubernat

    2017-01-01

    Full Text Available The paper presents the results of investigation the novel and simple method of synthesis of silicon carbide. As raw material for synthesis was used shungite, natural mineral rich in carbon and silica. The synthesis of SiC is possible in relatively low temperature in range 1500–1600 °C. It is worth emphasising that compared to the most popular method of SiC synthesis (Acheson method where the temperature of synthesis is about 2500 °C the proposed method is much more effective. The basic properties of products obtained from different form of shungite and in wide range of synthesis temperature were investigated. The process of silicon carbide formation was proposed and discussed. In the case of synthesis SiC from powder of raw materials the product is also in powder form and not requires any additional process (crushing, milling, etc.. Obtained products are pure and after grain classification may be used as abrasive and polishing powders.

  9. A highly luminescent octanuclear gold(i) carbide cluster.

    Science.gov (United States)

    Feuerstein, Thomas J; Poß, Marieke; Seifert, Tim P; Bestgen, Sebastian; Feldmann, Claus; Roesky, Peter W

    2017-08-08

    The ligand [{Me3SiC[triple bond, length as m-dash]CC(NDipp)2}Li(thf)3] (Dipp = 2,6-diisopropylphenyl) was used for salt metathesis reactions with [AuCl(tht)] (tht = tetrahydrothiophene) to obtain the dinuclear alkyne functionalized bisamidinate [{Me3SiC[triple bond, length as m-dash]CC(NDipp)2}2Au2]. This compound serves as a building block for the polynuclear carbide bridged gold(i) amidinate complex [Au8{μ3-(η1:η2-C[triple bond, length as m-dash]C)}2(Me3SiC[triple bond, length as m-dash]CC(NDipp)2)4(tht)2], which is the first gold(i) complex with a μ3-η1:η2 carbide coordination. Both gold(i) compounds show distinct aurophilic interactions and are remarkably stable at ambient conditions. Photophysical investigations revealed intense luminescence with notable high quantum yields both in the solid state and in solution.

  10. The Local Physical Structure of Amorphous Boron Carbide Thin Films

    Science.gov (United States)

    Paquette, M. M.; Li, Wenjing; Driver, M. S.; Oyler, N. A.; Caruso, A. N.

    2011-03-01

    Thin-film amorphous hydrogenated boron carbide (a-B5 C:Hx) and technical boron carbide (B4 C:Cy) are important materials in next-generation solid-state neutron detectors and refractory electronics. Optimizing the electrical carrier transport and electronic structure of these films for the stated applications has been severely hindered by: (1) their lack of long-range periodicity; (2) the ability of boron-rich solids to form complex polyhedra; and, (3) the possibility that carbon atoms incorporate into the polyhedral structures in an intraicosahedral fashion or that they bridge polyhedral structures in an intericosahedral fashion. The use of traditional spectroscopies that are sensitive to local coordination environment have been inadequate in the determination of the local physical structure because of either poor resolution or very low interaction cross sections. However, magic spinning angle (MAS) solid-state nuclear magnetic resonance (SSNMR), does have the signal-to-noise and rigor to extract the local physical coordination structure of these materials, despite the challenges associated with deltahedra-based structures. This poster will describe the progress and challenges in structure determination through a comparison of unknown samples to known calibration standards using MAS techniques, in the context of furthering the general understanding of the electronic structure of a-B5 C:Hx and B4 C:Cy thin films.

  11. High Input Voltage, Silicon Carbide Power Processing Unit Performance Demonstration

    Science.gov (United States)

    Bozak, Karin E.; Pinero, Luis R.; Scheidegger, Robert J.; Aulisio, Michael V.; Gonzalez, Marcelo C.; Birchenough, Arthur G.

    2015-01-01

    A silicon carbide brassboard power processing unit has been developed by the NASA Glenn Research Center in Cleveland, Ohio. The power processing unit operates from two sources: a nominal 300 Volt high voltage input bus and a nominal 28 Volt low voltage input bus. The design of the power processing unit includes four low voltage, low power auxiliary supplies, and two parallel 7.5 kilowatt (kW) discharge power supplies that are capable of providing up to 15 kilowatts of total power at 300 to 500 Volts (V) to the thruster. Additionally, the unit contains a housekeeping supply, high voltage input filter, low voltage input filter, and master control board, such that the complete brassboard unit is capable of operating a 12.5 kilowatt Hall effect thruster. The performance of the unit was characterized under both ambient and thermal vacuum test conditions, and the results demonstrate exceptional performance with full power efficiencies exceeding 97%. The unit was also tested with a 12.5kW Hall effect thruster to verify compatibility and output filter specifications. With space-qualified silicon carbide or similar high voltage, high efficiency power devices, this would provide a design solution to address the need for high power electric propulsion systems.

  12. High Input Voltage, Silicon Carbide Power Processing Unit Performance Demonstration

    Science.gov (United States)

    Bozak, Karin E.; Pinero, Luis R.; Scheidegger, Robert J.; Aulisio, Michael V.; Gonzalez, Marcelo C.; Birchenough, Arthur G.

    2015-01-01

    A silicon carbide brassboard power processing unit has been developed by the NASA Glenn Research Center in Cleveland, Ohio. The power processing unit operates from two sources - a nominal 300-Volt high voltage input bus and a nominal 28-Volt low voltage input bus. The design of the power processing unit includes four low voltage, low power supplies that provide power to the thruster auxiliary supplies, and two parallel 7.5 kilowatt power supplies that are capable of providing up to 15 kilowatts of total power at 300-Volts to 500-Volts to the thruster discharge supply. Additionally, the unit contains a housekeeping supply, high voltage input filter, low voltage input filter, and master control board, such that the complete brassboard unit is capable of operating a 12.5 kilowatt Hall Effect Thruster. The performance of unit was characterized under both ambient and thermal vacuum test conditions, and the results demonstrate the exceptional performance with full power efficiencies exceeding 97. With a space-qualified silicon carbide or similar high voltage, high efficiency power device, this design could evolve into a flight design for future missions that require high power electric propulsion systems.

  13. High capacitance of coarse-grained carbide derived carbon electrodes

    Science.gov (United States)

    Dyatkin, Boris; Gogotsi, Oleksiy; Malinovskiy, Bohdan; Zozulya, Yuliya; Simon, Patrice; Gogotsi, Yury

    2016-02-01

    We report exceptional electrochemical properties of supercapacitor electrodes composed of large, granular carbide-derived carbon (CDC) particles. Using a titanium carbide (TiC) precursor, we synthesized 70-250 μm sized particles with high surface area and a narrow pore size distribution. Electrochemical cycling of these coarse-grained powders defied conventional wisdom that a small particle size is strictly required for supercapacitor electrodes and allowed high charge storage densities, rapid transport, and good rate handling ability. The material showcased capacitance above 100 F g-1 at sweep rates as high as 250 mV s-1 in organic electrolyte. 250-1000 micron thick dense CDC films with up to 80 mg cm-2 loading showed superior areal capacitances. The material significantly outperformed its activated carbon counterpart in organic electrolytes and ionic liquids. Furthermore, large internal/external surface ratio of coarse-grained carbons allowed the resulting electrodes to maintain high electrochemical stability up to 3.1 V in ionic liquid electrolyte. In addition to presenting novel insights into the electrosorption process, these coarse-grained carbons offer a pathway to low-cost, high-performance implementation of supercapacitors in automotive and grid-storage applications.

  14. Detonation Synthesis of Alpha-Variant Silicon Carbide

    Science.gov (United States)

    Langenderfer, Martin; Johnson, Catherine; Fahrenholtz, William; Mochalin, Vadym

    2017-06-01

    A recent research study has been undertaken to develop facilities for conducting detonation synthesis of nanomaterials. This process involves a familiar technique that has been utilized for the industrial synthesis of nanodiamonds. Developments through this study have allowed for experimentation with the concept of modifying explosive compositions to induce synthesis of new nanomaterials. Initial experimentation has been conducted with the end goal being synthesis of alpha variant silicon carbide (α-SiC) in the nano-scale. The α-SiC that can be produced through detonation synthesis methods is critical to the ceramics industry because of a number of unique properties of the material. Conventional synthesis of α-SiC results in formation of crystals greater than 100 nm in diameter, outside nano-scale. It has been theorized that the high temperature and pressure of an explosive detonation can be used for the formation of α-SiC in the sub 100 nm range. This paper will discuss in detail the process development for detonation nanomaterial synthesis facilities, optimization of explosive charge parameters to maximize nanomaterial yield, and introduction of silicon to the detonation reaction environment to achieve first synthesis of nano-sized alpha variant silicon carbide.

  15. Boron doping of silicon rich carbides: Electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Summonte, C., E-mail: caterina.summonte@cnr.it [Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e i Microsistemi, Bologna (Italy); Canino, M.; Allegrezza, M.; Bellettato, M.; Desalvo, A. [Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e i Microsistemi, Bologna (Italy); Shukla, R. [Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e i Microsistemi, Bologna (Italy); Centre of Non-Conventional Energy Resources, University of Rajasthan, Jaipur (India); Jain, I.P. [Centre of Non-Conventional Energy Resources, University of Rajasthan, Jaipur (India); Crupi, I. [Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e i Microsistemi, Catania (Italy); Milita, S.; Ortolani, L. [Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e i Microsistemi, Bologna (Italy); López-Conesa, L.; Estradé, S.; Peiró, F.; Garrido, B. [MIND – UB, Electronics Department, University of Barcelona, Barcelona (Spain)

    2013-05-15

    Boron doped multilayers based on silicon carbide/silicon rich carbide, aimed at the formation of silicon nanodots for photovoltaic applications, are studied. X-ray diffraction confirms the formation of crystallized Si and 3C-SiC nanodomains. Fourier Transform Infrared spectroscopy indicates the occurrence of remarkable interdiffusion between adjacent layers. However, the investigated material retains memory of the initial dopant distribution. Electrical measurements suggest the presence of an unintentional dopant impurity in the intrinsic SiC matrix. The overall volume concentration of nanodots is determined by optical simulation and is shown not to contribute to lateral conduction. Remarkable higher room temperature dark conductivity is obtained in the multilayer that includes a boron doped well, rather than boron doped barrier, indicating efficient doping in the former case. Room temperature lateral dark conductivity up to 10{sup −3} S/cm is measured on the multilayer with boron doped barrier and well. The result compares favorably with silicon dioxide and makes SiC encouraging for application in photovoltaic devices.

  16. Transformation-toughening in cemented carbides: Part II. Thermomechanical treatments

    Science.gov (United States)

    Viswanadham, R. K.; Lindquist, P. G.

    1987-12-01

    WC-(Fe, Ni, C) cemented carbides can be successfully transformation-toughened by careful control of binder composition and taking into consideration the effect of thermal residual stress on the transformation characteristics of the binder. An additional degree of control on the metastability of the binder phase can be achieved via thermomechanical treatments. These treatments consist of transforming an austenitic binder to martensite by cooling in liquid nitrogen followed by a suitable high temperature heat treatment to reaustenitize it. The in situ deformation of the binder caused by the large shape and volume changes that accompany its transformation to martensite thus provides the mechanical component of the thermomechanical treatment. Subsequent heat treatments not only reaustenitize the binder but also modify its susceptibility to undergo stress-induced transformation. It is shown that the hardness/fracture toughness behavior of WC-(Fe, Ni, C) cemented carbides can be significantly improved by the application of such treatments. A qualitative explanation for the enhancements in fracture toughness provided by thermomechanical treatments is offered based on a careful examination of the changes in phase constitution of the binder that occur during these treatments.

  17. Ion beam figuring of CVD silicon carbide mirrors

    Science.gov (United States)

    Gailly, P.; Collette, J.-P.; Fleury Frenette, K.; Jamar, C.

    2017-11-01

    Optical and structural elements made of silicon carbide are increasingly found in space instruments. Chemical vapor deposited silicon carbide (CVD-SiC) is used as a reflective coating on SiC optics in reason of its good behavior under polishing. The advantage of applying ion beam figuring (IBF) to CVD-SiC over other surface figure-improving techniques is discussed herein. The results of an IBF sequence performed at the Centre Spatial de Liège on a 100 mm CVD-SiC mirror are reported. The process allowed to reduce the mirror surface errors from 243 nm to 13 nm rms . Beside the surface figure, roughness is another critical feature to consider in order to preserve the optical quality of CVD-SiC . Thus, experiments focusing on the evolution of roughness were performed in various ion beam etching conditions. The roughness of samples etched at different depths down to 3 ≠m was determined with an optical profilometer. These measurements emphasize the importance of selecting the right combination of gas and beam energy to keep roughness at a low level. Kaufman-type ion sources are generally used to perform IBF but the performance of an end-Hall ion source in figuring CVD-SiC mirrors was also evaluated in this study. In order to do so, ion beam etching profiles obtained with the end-Hall source on CVD-SiC were measured and used as a basis for IBF simulations.

  18. FCRD Advanced Reactor (Transmutation) Fuels Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Janney, Dawn Elizabeth [Idaho National Lab. (INL), Idaho Falls, ID (United States); Papesch, Cynthia Ann [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-09-01

    alloys of two or three of these elements. It contains information about phase diagrams and related information (including phases and phase transformations); heat capacity, entropy, and enthalpy; thermal expansion; and thermal conductivity and diffusivity. In addition to presenting information about materials properties, the handbook attempts to provide information about how well the property is known and how much variation exists between measurements. Although it includes some results from models, its primary focus is experimental data. The Handbook is organized in two sections: one with information about the U-Pu-Zr ternary and one with information about other elements and binary and vi ternary alloys in the U-Np-Pu-Am-La-Ce-Pr-Nd-Zr system. Within each section, information about elements is presented first, followed by information about binary alloys, then information about ternary alloys. The order in which the elements in each alloy are mentioned follows the order in the first sentence of this paragraph. Much of the information on the U-Pu-Zr system repeats information from the FCRD Transmutation Fuels Handbook 2015. Most of the other data has been published elsewhere (although scattered throughout numerous references, some quite obscure); however, some data from Idaho National Laboratory is presented here for the first time. As the FCRD programmatic mission evolves, future editions of this handbook will begin to include other advanced reactor fuel designs and compositions. Hence, the title of the handbook will transition to the Advanced Reactor Fuels Handbook.

  19. Binary Ternary Based Nanolaminates Fabricated By Multi Stationary Target PLD (Preprint)

    Science.gov (United States)

    2017-04-04

    AFRL-RX-WP-JA-2017-0306 BINARY- TERNARY BASED NANOLAMINATES FABRICATED BY MULTI-STATIONARY TARGET PLD (PREPRINT) Steven R. Smith...December 2013 – 15 July 2016 4. TITLE AND SUBTITLE BINARY- TERNARY BASED NANOLAMINATES FABRICATED BY MULTI-STATIONARY TARGET PLD (PREPRINT) 5a...energy of 450 mJ per pulse, a galvanometer mirror system and a background pressure of oxygen. Trends in material properties were identified by

  20. Toward Multi Principal Component Alloy Discovery: Assessment of the CALPHAD Approach for Ternary (Preprint)

    Science.gov (United States)

    2016-09-15

    phase names such as “ sigma ” or “r- phase ” were disregarded. Of the ternaries evaluated, 14% of the systems have a phase that is only present with a...principal element systems. However, the uncertainty of phase equilibria predictions within these regions is unknown. This study assesses the current...capabilities of a commercially available CALPHAD databases to accurately predict phase equilibria within ternary phase space as a function of the number

  1. Ternary Organic Solar Cells Based on Two Compatible Nonfullerene Acceptors with Power Conversion Efficiency >10.

    Science.gov (United States)

    Liu, Tao; Guo, Yuan; Yi, Yuanping; Huo, Lijun; Xue, Xiaonan; Sun, Xiaobo; Fu, Huiting; Xiong, Wentao; Meng, Dong; Wang, Zhaohui; Liu, Feng; Russell, Thomas P; Sun, Yanming

    2016-12-01

    Two different nonfullerene acceptors and one copolymer are used to fabricate ternary organic solar cells (OSCs). The two acceptors show unique interactions that reduce crystallinity and form a homogeneous mixed phase in the blend film, leading to a high efficiency of ≈10.3%, the highest performance reported for nonfullerene ternary blends. This work provides a new approach to fabricate high-performance OSCs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Silk flame retardant finish by ternary silica sol containing boron and nitrogen

    Science.gov (United States)

    Zhang, Qiang-hua; Chen, Guo-qiang; Xing, Tie-ling

    2017-11-01

    A ternary flame retardant sol system containing Si, B and N was prepared via sol gel method using tetraethoxysilane (TEOS) as a precursor, boric acid (H3BO3) and urea (CO(NH2)2) as flame retardant additives and then applied to silk fabric flame retardant finish. The FT-IR and SEM results showed that the nitrogen-boron-silica ternary sol was successfully prepared and entrapped onto the surface of silk fibers. The limiting oxygen index (LOI) test indicated that the silk fabric treated with 24% boric acid and 6% urea (relative to the TEOS) doped ternary silica sol system performed excellent flame retardancy with the LOI value of 34.6%. Furthermore, in order to endow silk fabric with durable flame retardancy, the silk fabric was pretreated with 1,2,3,4-butanetetracarboxylic acid (BTCA) before the ternary sol system treatment. The BTCA pretreat ment applied to silk could effectively promote the washing durability of the ternary sol, and the LOI value of the treated sample after 10 times washing could still maintain at 30.8% compared with that of 31.0% before washing. Thermo gravimetric (TG), micro calorimeter combustion (MCC) and smoke density test results demonstrated that the thermal stability, heat release and smoke suppression of the nitrogen-boron-silica ternary system decreased somewhat compared with the boron-silica binary flame retardant system.

  3. Improving performance with accident tolerant-fuels

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Daniel S.; Muniz, Rafael O.R.; Giovedi, Claudia, E-mail: dsgomes@ipen.br, E-mail: rafael.orm@gmail.com, E-mail: claudia.giovedi@ctmsp.mar.mil.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Universidade de São Paulo (USP), SP (Brazil). Departamento de Engenharia Naval e Oceânica

    2017-07-01

    After the Fukushima reactor accident, efforts to improve risk management in nuclear operations have included the intensification of research on accident-tolerant fuels (ATFs). In this investigation, the physical properties of recently developed ATFs were compared with those of the current standard fuel, UO{sub 2} - Zr. The goals for innovative fuel design include a rigorous characterization of the thermal, mechanical, and chemical considerations. The intentions are to lengthen the burnup cycle, raise the power density, and improve safety. Fuels must have a high uranium density - above that supported by UO{sub 2} - and possess a coating that exhibits better oxidation resistance than Zircaloys. ATFs such as U{sub 3}Si{sub 2}, UN, and UC contain a higher uranium density and thermal conductivity than UO{sub 2}, providing significant benefits. The ideal combination of fuel and cladding must increase performance in a loss-of-coolant accident. However, U{sub 3}Si{sub 2}, UN, and UC have a disadvantage; their respective swelling rates are higher than that of UO{sub 2}. These ATFs also have thermal conductivities approximately four times higher than that of UO{sub 2}. A study was conducted investigating the hydrogen generated by the oxidation of zirconium alloys in contact with steam using cladding options such as Fe-Cr-Al and silicon carbide. It was confirmed that ferritic alloys offer a better response under severe conditions, because of their mechanical properties as creep rate. The findings of this study indicate that advanced fuels should replace UO{sub 2} - Zr as the fuel system of choice. (author)

  4. Reduced ternary molybdenum and tungsten sulfides and hydroprocessing catalysis therewith

    Science.gov (United States)

    Hilsenbeck, S.J.; McCarley, R.E.; Schrader, G.L.; Xie, X.B.

    1999-02-16

    New amorphous molybdenum/tungsten sulfides with the general formula M{sup n+}{sub 2x/n}(L{sub 6}S{sub 8})S{sub x}, where L is molybdenum or tungsten and M is a ternary metal, has been developed. Characterization of these amorphous materials by chemical and spectroscopic methods (IR, Raman, PES) shows that the (M{sub 6}S{sub 8}){sup 0} cluster units are present. Vacuum thermolysis of the amorphous Na{sub 2x}(Mo{sub 6}S{sub 8})S{sub x}{hor_ellipsis}yMeOH first produces poorly crystalline NaMo{sub 6}S{sub 8} by disproportionation at 800 C and well-crystallized NaMo{sub 6}S{sub 8} at {>=} 900 C. Ion-exchange of the sodium material in methanol with soluble M{sup 2+} and M{sup 3+} salts (M=Sn, Co, Ni, Pb, La, Ho) produces the M{sup n+}{sub 2x/n}(Mo{sub 6}S{sub 8})S{sub x}{hor_ellipsis}yMeOH compounds. Additionally, the new reduced ternary molybdenum sulfides with the general formula M{sup n+}{sub 2x/n}Mo{sub 6}S{sub 8+x}(MeOH){sub y}[MMOS] (M=Sn, Co, Ni) is an effective hydrodesulfurization (HDS) catalyst both as-prepared and after a variety of pretreatment conditions. Under specified pretreatment conditions with flowing hydrogen gas, the SnMoS type catalyst can be stabilized, and while still amorphous, can be considered as ``Chevrel phase-like`` in that both contain Mo{sub 6}S{sub 8} cluster units. Furthermore, the small cation NiMoS and CoMoS type pretreated catalyst is shown to be very active HDS catalysts with rates that exceeded the model unpromoted and cobalt-promoted MoS{sub 2} catalysts. 9 figs.

  5. XPS, AES and friction studies of single-crystal silicon carbide

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    The surface chemistry and friction behavior of a single crystal silicon carbide surface parallel to the 0001 plane in sliding contact with iron at various temperatures to 1500 C in a vacuum of 3 x 10 nPa are investigated using X-ray photoelectron and Auger electron spectroscopy. Results show that graphite and carbide-type carbon are seen primarily on the silicon carbide surface in addition to silicon at temperatures to 800 C by both types of spectroscopy. The coefficients of friction for iron sliding against a silicon carbide surface parallel to the 0001 plane surface are found to be high at temperatures up to 800 C, with the silicon and carbide-type carbon at maximum intensity in the X-ray photoelectron spectroscopy at 800 C. The concentration of the graphite increases rapidly on the surface as the temperature is increased above 800 C, while the concentrations of the carbide-type carbon and silicon decrease rapidly and this presence of graphite is accompanied by a significant decrease in friction. Preheating the surfaces to 1500 C also gives dramatically lower coefficients of friction when reheating in the sliding temperature range of from room temperature to 1200 C, with this reduction in friction due to the graphite layer on the silicon carbide surface.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-08-01

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

  7. Fabrication and characterization of carbon and boron carbide nanostructured materials

    Science.gov (United States)

    Reynaud, Sara

    Carbon is present in nature in a variety of allotropes and chemical compounds. Due to reduced dimensionality, nanostructured carbon materials, i.e. single walled carbon nanotubes (SWNTs), are characterized by unique physical and chemical properties. There is a potential for SWNTs use as biological probes and assists for tunable tissue growth in biomedical applications. However, the presumed cytotoxicity of SWNTs requires investigation of the risks of their incorporation into living systems. Boron is not found in nature in elementary form. Boron based materials are chemically complex and exist in various polymorphic forms, i.e. boron carbide (BC). Because BC is a lightweight material with exceptional mechanical and elastic properties, it is the ideal candidate for armor and ballistic applications. However, practical use of BC as armor material is limited because of its anomalous glass-like behaviour at high velocity impacts, which has been linked to stress-induced structural instability in one of BC polymorphs, B12(CCC). Theoretical calculations suggest that formation of B12(CCC) in BC could be suppressed by silicon doping. In the first part of this thesis, biocompatibility of SWNTs is investigated. It is shown that under normal cell implantation conditions, the electrical conductivity of the SWNTs decreases due to an increase in structural disorder. This research suggests that SWNTs can be functionalized by protein and biological cells reducing the risk of cytotoxicity. In the second part of this thesis, boron carbide nanostructured materials are synthesized and investigated. Radio frequency sputtering deposition technique is employed for fabrication of BC (Si free) and BC:Si thin films. Variation of plasma conditions and temperature are found to affect chemical composition, adhesion to the substrate and morphology of the films. It is shown that BC films are predominantly amorphous and a small addition of Si largely improves their mechanical properties. In addition

  8. Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites

    Science.gov (United States)

    Williams, Brian E.; Bernander, Robert E.

    2007-01-01

    Composites of zirconium carbide matrix material reinforced with carbon fibers can be fabricated relatively rapidly in a process that includes a melt infiltration step. Heretofore, these and other ceramic matrix composites have been made in a chemical vapor infiltration (CVI) process that takes months. The finished products of the CVI process are highly porous and cannot withstand temperatures above 3,000 F (approx.1,600 C). In contrast, the melt-infiltration-based process takes only a few days, and the composite products are more nearly fully dense and have withstood temperatures as high as 4,350 F (approx.2,400 C) in a highly oxidizing thrust chamber environment. Moreover, because the melt- infiltration-based process takes much less time, the finished products are expected to cost much less. Fabrication begins with the preparation of a carbon fiber preform that, typically, is of the size and shape of a part to be fabricated. By use of low-temperature ultraviolet-enhanced chemical vapor deposition, the carbon fibers in the preform are coated with one or more interfacial material(s), which could include oxides. The interfacial material helps to protect the fibers against chemical attack during the remainder of the fabrication process and against oxidation during subsequent use; it also enables slippage between the fibers and the matrix material, thereby helping to deflect cracks and distribute loads. Once the fibers have been coated with the interfacial material, the fiber preform is further infiltrated with a controlled amount of additional carbon, which serves as a reactant for the formation of the carbide matrix material. The next step is melt infiltration. The preform is exposed to molten zirconium, which wicks into the preform, drawn by capillary action. The molten metal fills most of the interstices of the preform and reacts with the added carbon to form the zirconium carbide matrix material. The zirconium does not react with the underlying fibers because they

  9. Characterization of silicon carbide and diamond detectors for neutron applications

    Science.gov (United States)

    Hodgson, M.; Lohstroh, A.; Sellin, P.; Thomas, D.

    2017-10-01

    The presence of carbon atoms in silicon carbide and diamond makes these materials ideal candidates for direct fast neutron detectors. Furthermore the low atomic number, strong covalent bonds, high displacement energies, wide bandgap and low intrinsic carrier concentrations make these semiconductor detectors potentially suitable for applications where rugged, high-temperature, low-gamma-sensitivity detectors are required, such as active interrogation, electronic personal neutron dosimetry and harsh environment detectors. A thorough direct performance comparison of the detection capabilities of semi-insulating silicon carbide (SiC-SI), single crystal diamond (D-SC), polycrystalline diamond (D-PC) and a self-biased epitaxial silicon carbide (SiC-EP) detector has been conducted and benchmarked against a commercial silicon PIN (Si-PIN) diode, in a wide range of alpha (Am-241), beta (Sr/Y-90), ionizing photon (65 keV to 1332 keV) and neutron radiation fields (including 1.2 MeV to 16.5 MeV mono-energetic neutrons, as well as neutrons from AmBe and Cf-252 sources). All detectors were shown to be able to directly detect and distinguish both the different radiation types and energies by using a simple energy threshold discrimination method. The SiC devices demonstrated the best neutron energy discrimination ratio (E\\max (n=5 MeV)/E\\max (n=1 MeV)  ≈5), whereas a superior neutron/photon cross-sensitivity ratio was observed in the D-PC detector (E\\max (AmBe)/E\\max (Co-60)  ≈16). Further work also demonstrated that the cross-sensitivity ratios can be improved through use of a simple proton-recoil conversion layer. Stability issues were also observed in the D-SC, D-PC and SiC-SI detectors while under irradiation, namely a change of energy peak position and/or count rate with time (often referred to as the polarization effect). This phenomenon within the detectors was non-debilitating over the time period tested (> 5 h) and, as such, stable operation was

  10. Handbook of refractory carbides and nitrides properties, characteristics, processing and applications

    CERN Document Server

    Pierson, Hugh O

    1996-01-01

    Refractory carbides and nitrides are useful materials with numerous industrial applications and a promising future, in addition to being materials of great interest to the scientific community. Although most of their applications are recent, the refractory carbides and nitrides have been known for over one hundred years. The industrial importance of the refractory carbides and nitrides is growing rapidly, not only in the traditional and well-established applications based on the strength and refractory nature of these materials such as cutting tools and abrasives, but also in new and promising fields such as electronics and optoelectronics.

  11. Synthesis and characterization of transition metal carbides and their catalytic applications

    Science.gov (United States)

    Wan, Cheng

    Transition metal (both monometallic and bimetallic) carbides have been synthesized by an amine-metal oxide composite (AMOC) method. The composite reduces the diffusion distances among each element and allows the formation of carbides to take place as low as 610°C, which is significantly lower than traditional carbide synthesis methods (above 1500°C). Additionally, amines act not only as carbon sources and reducing agents, but also morphological templates which helps to make uniform transition metal carbide (TMC) nanocrystals with various shapes. Beyond morphology control, AMOC method can also help to synthesize multiple phases of monometallic carbides, which includes four phases of molybdenum carbides (alpha-MoC1-x, beta-Mo2C, eta-MoC, and gamma-MoC), two phases of tungsten carbides (W2C and WC), and three phases of chromium carbides (Cr3C2-x, Cr7C3, and Cr3C2). Molybdenum carbide has been proposed as a possible alternative to platinum for catalyzing the hydrogen evolution reaction (HER). Previous studies were limited to only one phase, which is beta-Mo2C with an Fe 2N structure. Here, four molybdenum carbide materials including gamma-MoC with a WC type structure which was stabilized for the first time as a phase pure nanomaterial. Moreover, a wide range of magnetic iron-doped molybdenum carbide (Mo2-xFexC) nanomaterials were also synthesized, which exhibits a better HER activity to non-doped beta-Mo2C. A group of (CrxFe1-x)7C3 (0.2nanomaterials via AMOC method, which demonstrate excellent catalytic activities for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Other carbides/nitrides made from AMOCs include WN1-x, Fe3C, Fe3-xN, Fe3Mo3C, N 2Mo3C, Ni3Mo3C, Ni6Mo 6C, and Mo0.5W0.5C.

  12. Synthesis and characterization of metal carbides nanoparticles produced by electrical explosion of wires.

    Science.gov (United States)

    Ilyin, Alexander P; Nazarenko, Olga B; Tikhonov, Dmitriy V

    2012-10-01

    Tungsten, titanium, tantalum, aluminum carbides nanoparticles were produced by electrical explosion of wires. The explosions were carried out in gaseous mixtures of argon and acetylene at different ratios, argon and propane, and in liquids such as benzene, toluene, decane. The effects of the synthesis conditions on the size and phase composition of metal carbide nanoparticles were investigated. The thermal activity of the prepared powders was studied by the method of differential thermal analysis at the heating in air. Thermodynamic analysis of carbides formation during the process of electrical explosion has been made. The output of the chemical compounds depends on their thermal stability: the more thermally stable they are, the higher their output.

  13. Effect of boron carbide on primary crystallization of chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2008-04-01

    Full Text Available In the paper results of the influence of boron carbide (B4C as inoculant of abrasion-resisting chromium cast iron (about 2,8% carbon and 18% chromium on primary crystallization researches are presented. Boron carbide dispersion was introduced at the bottom of pouring ladle before tap of liquid cast iron. In this investigations were used three different quantities of inoculant in amounts 0,1%; 0,2% and 0,3% with relation to bath weight. It has been demonstrated that such small additions of boron carbide change primary crystallization parameters, particularly temperature characteristic of process, their time and kinetics.

  14. Steel-bonded carbides for high reliability wear parts in aerospace

    Energy Technology Data Exchange (ETDEWEB)

    Mandalis, P.; Tarkan, S.E.; Kumar Mal, M.

    1975-01-01

    Properties and uses of Ferro-Tic cemented carbides are discussed. It is noted that owing to the unique combination of desirable mechanical properties, high strength, ability to resist corrosion by some of the most aggressive chemical environments, good oxidation resistance, wear resistance, and favorable strength-to-weight ratio, the steel-bonded carbides are increasingly being used for many severe-environment applications in the aerospace industries, but there is still a great untapped potential. Material engineers and designers are urged to consider steel/alloy bonded machinable and hardenable carbides for their more difficult wear applications. (JRD)

  15. Biocatalysis of immobilized chlorophyllase in a ternary micellar system.

    Science.gov (United States)

    Gaffar, R; Kermasha, S; Bisakowski, B

    1999-09-24

    The immobilization of chlorophyllase was optimized by physical adsorption on various inorganic supports, including alumina, celite, Dowex-1-chloride, glass beads and silica gel. The enzyme was also immobilized in different media, including water, Tris-HCl buffer solution and a ternary micellar system containing Tris-HCl buffer solution, hexane and surfactant. The highest immobilization efficiency (84.56%) and specific activity (0.34 mumol hydrolyzed chlorophyll mg protein-1 per min) were obtained when chlorophyllase was suspended in Tris-HCl buffer solution and adsorbed onto silica gel. The effect of different ratios of chlorophyllase to the support and the optimum incubation time for the immobilization of chlorophyllase were determined to be 1-4 and 60 min, respectively. The experimental results showed that the optimum pH and temperature for the immobilized chlorophyllase were 8.0 and 35 degrees C, respectively. The use of optimized amounts of selected membrane lipids increased the specific activity of the immobilized chlorophyllase by approximately 50%. The enzyme kinetic studies indicated that the immobilized chlorophyllase showed a higher affinity towards chlorophyll than pheophytin as substrate.

  16. Contribution to the aluminum–tin–zinc ternary system

    Science.gov (United States)

    Drápala, J.; Kostiuková, G.; Losertová, M.

    2017-11-01

    The Sn–Zn–Al alloys are one of significant candidates in the proposal of alternative lead-free solders for higher temperature soldering. This paper deals with the study of the aluminum–tin–zinc system. Twenty Sn–Zn–Al alloys together with six binary Sn–Zn alloys were prepared and studied experimentally. Alloys were prepared from pure Sn, Zn and Al (melting and cooling in a vacuum resistance furnace). The specimens were studied metallographically including the micro-hardness measurements, complete chemical analysis (ICP-AES, OES), X-ray micro-analysis of alloys by SEM and EDX in order to determine the composition and identification of individual phases. Significant temperatures and enthalpies of phase transformations were determined by DTA. After long-term annealing of selected alloys in vacuum followed by quenching the structural and chemical microanalyses of the present phases and their limit concentrations were carried out. The achieved results were compared with the thermodynamic modelling of the ternary Sn–Zn–Al system (computer programs THERMOCALC, MTDATA, PANDAT and databases CALPHAD, COST). Electrical resistivity, density, magnetic susceptibility and wettability of Sn–Zn–Al solders were measured as well.

  17. Dynamical simulation of sputtering and reflection from a ternary alloy

    Science.gov (United States)

    Ishida, M.; Yamaguchi, Y.; Yoshinaga, H.; Yamamura, Y.

    The sputtering and the reflection from a Tb0.2Fe0.7Co0.1 alloy due to Ar+ ion bombardment have been investigated by the Monte Carlo simulation code ACAT-DIFFUSE which include the compositional change induced by ion influence. In the Tb-Fe-Co system, Fe atoms are preferentially sputtered. The atomic size of a Tb atom is the largest of these three atoms, and so Tb atoms trap preferentially in vacancies. The steady-state concentration of Tb atoms at the topmost layer is larger than the bulk concentration for the low energy ions due to radiation-induced segregation and preferential sputtering of Fe atoms. As the ion fluence increases, the atomic fractions of sputtered atoms calculated by the ACAT-DIFFUSE code become those of the bulk concentration. The depth profiles of each element at the steady state depend on the incident energy. The total sputtering yield and the reflection coefficient from a Tb-Fe-Co alloy calculated by the ACAT-DIFFUSE code are larger than those by the ACAT code at near-threshold energies, where the ACAT code does not include the ion-influence effect. The energy spectra of back-scattered Ar atoms from the present ternary alloy have very similar profiles to those from a monoatomic Tb target, especially for low-energy Ar+ ions.

  18. Iron binary and ternary coatings with molybdenum and tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Yar-Mukhamedova, Gulmira, E-mail: gulmira-alma-ata@mail.ru [Institute Experimental and Theoretical Physics Al-Farabi Kazakh National University, 050038, Al-Farabi av., 71, Almaty (Kazakhstan); Ved, Maryna; Sakhnenko, Nikolay; Karakurkchi, Anna; Yermolenko, Iryna [National Technical University “Kharkov Polytechnic Institute”, Kharkov (Ukraine)

    2016-10-15

    Highlights: • High quality coatings of double Fe-Mo and ternary Fe-Mo-W electrolytic alloys can be produced both in a dc and a pulsed mode. • Application of unipolar pulsed current allows receiving an increased content of the alloying components and their more uniform distribution over the surface. • It is established that Fe-Mo and Fe-Mo-W coatings have an amorphous structure and exhibit improved corrosion resistance and microhardness as compared with the steel substrate due to the inclusion molybdenum and tungsten. - Abstract: Electrodeposition of Fe-Mo-W and Fe-Mo layers from a citrate solution containing iron(III) on steel and iron substrates is compared. The utilization of iron(III) compounds significantly improved the electrolyte stability eliminating side anodic redox reactions. The influence of concentration ratios and electrodeposition mode on quality, chemical composition, and functional properties of the alloys is determined. It has been found that alloys deposited in pulse mode have more uniform surface morphology and chemical composition and contain less impurities. Improvement in physical and mechanical properties as well as corrosion resistance of Fe-Mo and Fe-Mo-W deposits when compared with main alloy forming metals is driven by alloying components chemical passivity as well as by alloys amorphous structure. Indicated deposits can be considered promising materials in surface hardening technologies and repair of worn out items.

  19. Delay Insensitive Ternary CMOS Logic for Secure Hardware

    Directory of Open Access Journals (Sweden)

    Ravi S. P. Nair

    2015-09-01

    Full Text Available As digital circuit design continues to evolve due to progress of semiconductor processes well into the sub 100 nm range, clocked architectures face limitations in a number of cases where clockless asynchronous architectures generate less noise and produce less electro-magnetic interference (EMI. This paper develops the Delay-Insensitive Ternary Logic (DITL asynchronous design paradigm that combines design aspects of similar dual-rail asynchronous paradigms and Boolean logic to create a single wire per bit, three voltage signaling and logic scheme. DITL is compared with other delay insensitive paradigms, such as Pre-Charge Half-Buffers (PCHB and NULL Convention Logic (NCL on which it is based. An application of DITL is discussed in designing secure digital circuits resistant to side channel attacks based on measurement of timing, power, and EMI signatures. A Secure DITL Adder circuit is designed at the transistor level, and several variance parameters are measured to validate the efficiency of DITL in resisting side channel attacks. The DITL design methodology is then applied to design a secure 8051 ALU.

  20. Multistate Memristive Tantalum Oxide Devices for Ternary Arithmetic

    Science.gov (United States)

    Kim, Wonjoo; Chattopadhyay, Anupam; Siemon, Anne; Linn, Eike; Waser, Rainer; Rana, Vikas

    2016-11-01

    Redox-based resistive switching random access memory (ReRAM) offers excellent properties to implement future non-volatile memory arrays. Recently, the capability of two-state ReRAMs to implement Boolean logic functionality gained wide interest. Here, we report on seven-states Tantalum Oxide Devices, which enable the realization of an intrinsic modular arithmetic using a ternary number system. Modular arithmetic, a fundamental system for operating on numbers within the limit of a modulus, is known to mathematicians since the days of Euclid and finds applications in diverse areas ranging from e-commerce to musical notations. We demonstrate that multistate devices not only reduce the storage area consumption drastically, but also enable novel in-memory operations, such as computing using high-radix number systems, which could not be implemented using two-state devices. The use of high radix number system reduces the computational complexity by reducing the number of needed digits. Thus the number of calculation operations in an addition and the number of logic devices can be reduced.

  1. Alloy multilayers and ternary nanostructures by direct-write approach

    Science.gov (United States)

    Porrati, F.; Sachser, R.; Gazzadi, G. C.; Frabboni, S.; Terfort, A.; Huth, M.

    2017-10-01

    The fabrication of nanopatterned multilayers, as used in optical and magnetic applications, is usually achieved by two independent steps, which consist in the preparation of multilayer films and in the successive patterning by means of lithography and etching processes. Here we show that multilayer nanostructures can be fabricated by using focused electron beam induced deposition (FEBID), which allows the direct writing of nanostructures of any desired shape with nanoscale resolution. In particular, {[{{{Co}}}2{{Fe}}/{{Si}}]}n multilayers are prepared by the alternating deposition from the metal carbonyl precursors, {{{HFeCo}}}3{({{CO}})}12 and {{Fe}}{({{CO}})}5, and neopentasilane, {{{Si}}}5{{{H}}}12. The ability to fabricate nanopatterned multilayers by FEBID is of interest for the realization of hyperbolic metamaterials and related nanodevices. In a second experiment, we treated the multilayers by low-energy electron irradiation in order to induce atomic species intermixing with the purpose to obtain ternary nanostructured compounds. Transmission electron microscopy and electrical transport measurements indicate that in thick multilayers, (n = 12), the intermixing is only partial, taking place mainly in the upper part of the structures. However, for thin multilayers, (n = 2), the intermixing is such that a transformation into the L21 phase of the Co2FeSi Heusler compound takes place over the whole sample volume.

  2. The role of In in III-nitride ternary semiconductors

    CERN Multimedia

    Redondo cubero, A

    This proposal aims to study the role of In in the outstanding efficiency of luminescent devices based on group III-nitride ternary semiconductors. To study the microscopic environments of In in GaInN and AlInN, Perturbed Angular Correlation (PAC) experiments will be performed using the PAC-probes $^{111m}$Cd($^{111}$Cd), $^{115}$Cd($^{115}$In) and $^{117}$Cd($^{117}$In). Temperature dependent PAC measurements using the $^{111}$In($^{111}$Cd) probe indicated that In in GaN and AlN forms a complex with a defect, possibly a nitrogen vacancy (V$_{N}$), which is stable up to high temperatures and might be involved in the luminescence mechanisms. Analysing these results two questions arose: \\\\ \\\\1. Does the fact that the actual measurement is performed with the daughter nucleus $^{111}$Cd (being an acceptor) influence the probe-defect interaction? This question can be answered by performing measurements with the complementary probe $^{117}$Cd($^{117}$In). \\\\ \\\\ 2. What is the significance of $\\textit{a...

  3. Control mechanism of double-rotator-structure ternary optical computer

    Science.gov (United States)

    Kai, SONG; Liping, YAN

    2017-03-01

    Double-rotator-structure ternary optical processor (DRSTOP) has two characteristics, namely, giant data-bits parallel computing and reconfigurable processor, which can handle thousands of data bits in parallel, and can run much faster than computers and other optical computer systems so far. In order to put DRSTOP into practical application, this paper established a series of methods, namely, task classification method, data-bits allocation method, control information generation method, control information formatting and sending method, and decoded results obtaining method and so on. These methods form the control mechanism of DRSTOP. This control mechanism makes DRSTOP become an automated computing platform. Compared with the traditional calculation tools, DRSTOP computing platform can ease the contradiction between high energy consumption and big data computing due to greatly reducing the cost of communications and I/O. Finally, the paper designed a set of experiments for DRSTOP control mechanism to verify its feasibility and correctness. Experimental results showed that the control mechanism is correct, feasible and efficient.

  4. Internal oxidation of laminated ternary Ru-Ta-Zr coatings

    Science.gov (United States)

    Chen, Yung-I.; Lu, Tso-Shen

    2015-10-01

    Researchers have observed the internal oxidation phenomenon in binary alloy coatings when developing refractory alloy coatings for protective purposes by conducting annealing at high temperatures and in oxygen-containing atmospheres. The coatings were assembled using cyclical gradient concentration deposition during cosputtering by employing a substrate holder rotating at a slow speed. The internally oxidized zone demonstrated a laminated structure, comprising alternating oxygen-rich and oxygen-deficient layers stacked in a general orientation. In the current study, Ru-Ta-Zr coatings were prepared with various stacking sequences during cosputtering. The Ru-Ta-Zr coatings were annealed at 600 °C in an atmosphere continuously purged with 1% O2-99% Ar mixed gas for 30 min. A transmission electron microscope was used to examine the periods of the laminated layers and crystallinity of the annealed coatings. Depth profiles produced using an Auger electron spectroscope and X-ray photoelectron spectroscope were used to certify the periodic variation of the related constituents and chemical states of the elements, respectively. The results indicate that the internally oxidized ternary coatings are stacked of Ru-, Ta2O5-, and ZrO2-dominant sublayers and that the stacking sequences of the sublayers affect the crystalline structure of the coatings. Zr is oxidized preferentially in the Ru-Ta-Zr coatings, increasing the surface hardness of the oxidized coatings.

  5. Growth Mechanism of Nanowires: Binary and Ternary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Coriell, S. R.; Su, Ching-Hua; Hopkins, R. H.; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    Semiconductor nanowires exhibit very exciting optical and electrical properties including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here the mechanism of nanowire growth from the melt-liquid-vapor medium. We describe preliminary results of binary and ternary selenide materials in light of recent theories. Experiments were performed with lead selenide and thallium arsenic selenide systems which are multifunctional material and have been used for detectors, acousto-optical, nonlinear and radiation detection applications. We observed that small units of nanocubes and elongated nanoparticles arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places. Growth of lead selenide nanowires was performed by physical vapor transport method and thallium arsenic selenide nanowire by vapor-liquid-solid (VLS) method. In some cases very long wires (>mm) are formed. To achieve this goal experiments were performed to create situation where nanowires grew on the surface of solid thallium arsenic selenide itself.

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

    Science.gov (United States)

    Milewski, J.V.

    1982-06-18

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

  7. ELABORATION OF AN EPOXY COATING REINFORCED WITH ZIRCONIUM CARBIDE NANOSTRUCTURES

    Directory of Open Access Journals (Sweden)

    Lucia G. Díaz-Barriga

    2013-12-01

    Full Text Available This work shows the preparation of a transparent epoxy coating reinforced with 200 PPM of zirconium carbide nanostructures. The nanostructures of ZrC were prepared by mechanosynthesis. The additive characteristics analyzed by X-ray diffraction (XRD and scanning electron microscopy (SEM were presented. Epoxy coating adhesion on a steel plate was analyzed using MEB. Thermogravimetric analysis (TGA was performed to the reinforced paints between 20-700 °C. The reinforced enamel was compared with an enamel without nanostructures. There is not vaporization of reinforced enamel at a 95 y 100 °C with ZrC particles size of 10 µm y 120 nm respectively. The final enamel degradation is slower when there is a 14% by weight of the residue and 426 °C with 120nm diameter particles.

  8. Microstructural optimization of solid-state sintered silicon carbide

    Science.gov (United States)

    Vargas-Gonzalez, Lionel R.

    Silicon carbide armor, manufactured through solid-state sintering, liquid-phase sintering, and hot-pressing, is being used by the United States Armed Forces for personal and vehicle protection. There is a lack of consensus, however, on which process results in the best-performing ballistic armor. Previous studies have shown that hot-pressed ceramics processed with secondary oxide and/or rare earth oxides, which exhibit high fracture toughness, perform well in handling and under ballistic impact. This high toughness is due to the intergranular nature of the fracture, creating a tortuous path for cracks and facilitating crack deflection and bridging. However, it has also been shown that higher-hardness sintered SiC materials might perform similarly or better to hot-pressed armor, in spite of the large fracture toughness deficit, if the microstructure (density, grain size, purity) of these materials are improved. In this work, the development of theoretically-dense, clean grain boundary, high hardness solid-state sintered silicon carbide (SiC) armor was pursued. Boron carbide and graphite (added as phenolic resin to ensure the carbon is finely dispersed throughout the microstructure) were used as the sintering aids. SiC batches between 0.25--4.00 wt.% carbon were mixed and spray dried. Cylindrical pellets were pressed at 13.7 MPa, cold-isostatically pressed (CIP) at 344 MPa, sintered under varying sintering soaking temperatures and heating rates, and varying post hot-isostatic pressing (HIP) parameters. Carbon additive amounts between 2.0--2.5 wt.% (based on the resin source), a 0.36 wt.% B4C addition, and a 2050°C sintering soak yielded parts with high sintering densities (˜95.5--96.5%) and a fine, equiaxed microstructure (d50 = 2.525 mum). A slow ramp rate (10°C/min) prevented any occurrence of abnormal grain growth. Post-HIPing at 1900°C removed the remaining closed porosity to yield a theoretically-dense part (3.175 g/cm3, according to rule of mixtures). These

  9. Linear integrated optics in 3C silicon carbide.

    Science.gov (United States)

    Martini, Francesco; Politi, Alberto

    2017-05-15

    The development of new photonic materials that combine diverse optical capabilities is needed to boost the integration of different quantum and classical components within the same chip. Amongst all candidates, the superior optical properties of cubic silicon carbide (3C SiC) could be merged with its crystalline point defects, enabling single photon generation, manipulation and light-matter interaction on a single device. The development of photonics devices in SiC has been limited by the presence of the silicon substrate, over which thin crystalline films are heteroepitaxially grown. By employing a novel approach in the material fabrication, we demonstrate grating couplers with coupling efficiency reaching -6 dB, sub-µm waveguides and high intrinsic quality factor (up to 24,000) ring resonators. These components are the basis for linear optical networks and essential for developing a wide range of photonics component for non-linear and quantum optics.

  10. Body of Knowledge for Silicon Carbide Power Electronics

    Science.gov (United States)

    Boomer, Kristen; Lauenstein, Jean-Marie; Hammoud, Ahmad

    2016-01-01

    Wide band gap semiconductors, such as silicon carbide (SiC), have emerged as very promising materials for future electronic components due to the tremendous advantages they offer in terms of power capability, extreme temperature tolerance, and high frequency operation. This report documents some issues pertaining to SiC technology and its application in the area of power electronics, in particular those geared for space missions. It also serves as a body of knowledge (BOK) in reference to the development and status of this technology obtained via literature and industry survey as well as providing a listing of the major manufacturers and their capabilities. Finally, issues relevant to the reliability of SiC-based electronic parts are addressed and limitations affecting the full utilization of this technology are identified.

  11. Mode Grüneisen parameters of boron carbide

    Science.gov (United States)

    Werheit, Helmut; Manghnani, Murli H.; Kuhlmann, Udo; Hushur, Anwar; Shalamberidze, Sulkhan

    2017-10-01

    IR- and Raman-active phonons of boron carbide and the mode Grüneisen parameters γ related are studied concerning their dependence on chemical composition, temperatures between 30 and 800 K and pressures up to ∼70 GPa. Most bulk phonons yield γ between +1.5 and - 1.5: those related to icosahedra yield γ = 0.8(3). Surface phonons are distinguished by considerably higher γ. Negative γ of chain bending modes supports the assumption that the chain center buckles out under pressure. Some striking specific mode Grüneisen parameters are explained. Pressure-dependent bond lengths suggest the reversible high-pressure phase transition to be second order.

  12. Hydrothermal corrosion of silicon carbide joints without radiation

    Science.gov (United States)

    Koyanagi, Takaaki; Katoh, Yutai; Terrani, Kurt A.; Kim, Young-Jin; Kiggans, James O.; Hinoki, Tatsuya

    2016-12-01

    Hydrothermal corrosion of four types of the silicon carbide (SiC) to SiC plate joints were investigated under pressurized water reactor and boiling water reactor relevant chemical conditions without irradiation. The joints were formed by metal diffusion bonding using molybdenum or titanium interlayer, reaction sintering using Ti-Si-C system, and SiC nanopowder sintering. Most of the joints withstood the corrosion tests for five weeks. The recession of the SiC substrates was limited. Based on the recession of the bonding layers, it was concluded that all the joints except for the molybdenum diffusion bond are promising under the reducing environments without radiation. The SiC nanopowder sintered joint was the most corrosion tolerant under the oxidizing environment among the four joints.

  13. New method for synthesis of metal carbides, nitrides and carbonitrides

    Energy Technology Data Exchange (ETDEWEB)

    Koc, R.; Folmer, J.S.; Kodambaka, S.K. [Southern Illinois Univ., Carbondale, IL (United States)] [and others

    1997-04-01

    The purpose of this work is to develop a novel synthesis method using a carbothermic reduction reaction of carbon coated precursors for producing high purity, submicron, non-agglomerated powders of metal carbide, metal nitride and metal boride systems. The authors also want to demonstrate the advantages of the process and provide information on the applicability of the process for synthesizing related advanced ceramic powders (e.g. SiC, WC, TiN, TiB{sub 2}, Si{sub 3}N{sub 4}). During the FY96 of the project, steps are taken to investigate the reaction mechanisms and phase evolution during the formation of TiC from carbon coated titania precursors and to produce submicron TiC powders with desired stoichiometries. Depending on the carbon content in the coated titania precursor, TiC powder was produced with different stoichiometries (different amount of oxygen and free carbon).

  14. Spin-photon entanglement interfaces in silicon carbide defect centers

    Science.gov (United States)

    Economou, Sophia E.; Dev, Pratibha

    2016-12-01

    Optically active spins in solid-state systems can be engineered to emit photons that are entangled with the spin in the solid. This allows for applications such as quantum communications, quantum key distribution, and distributed quantum computing. Recently, there has been a strong interest in silicon carbide defects, as they emit very close to the telecommunication wavelength, making them excellent candidates for long range quantum communications. In this work we develop explicit schemes for spin-photon entanglement in several SiC defects: the silicon monovacancy, the silicon divacancy, and the NV center in SiC. Distinct approaches are given for (i) single-photon and spin entanglement and (ii) the generation of long strings of entangled photons. The latter are known as cluster states and comprise a resource for measurement-based quantum information processing.

  15. Superconductivity in heavily boron-doped silicon carbide

    Directory of Open Access Journals (Sweden)

    Markus Kriener, Takahiro Muranaka, Junya Kato, Zhi-An Ren, Jun Akimitsu and Yoshiteru Maeno

    2008-01-01

    Full Text Available The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.

  16. Dissimilar Brazed Joints Between Steel and Tungsten Carbide

    Science.gov (United States)

    Voiculescu, I.; Geanta, V.; Binchiciu, H.; Iovanas, D.; Stefanoiu, R.

    2017-06-01

    Brazing is a joining process used to obtain heterogeneous assemblies between different materials, such as steels, irons, non-ferrous metals, ceramics etc. Some application, like asphalt cutters, require quick solutions to obtain dissimilar joints at acceptable costs, given the very short period of operation of these parts. This paper presents some results obtained during the brazing of dissimilar joints between steel and tungsten carbide by using different types of Ag-Cu system filler materials alloyed with P and Sn. The brazing techniques used were oxygen-gas flame and induction joining. The brazing behaviour was analysed in cross sections by optical and electron microscopy. The metallographic analysis enhanced the adhesion features and the length of penetration in the joining gap. The melting range of the filler materials was measured using thermal analysis.

  17. Diffusion in thorium carbide: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Pérez Daroca, D., E-mail: pdaroca@tandar.cnea.gov.ar [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, 1650, San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, 1025, Buenos Aires (Argentina); Llois, A.M. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, 1650, San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, 1025, Buenos Aires (Argentina); Mosca, H.O. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, Av. General Paz 1499, 1650, San Martín, Buenos Aires (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM–CNEA, Av. General Paz 1499, 1650, San Martín, Buenos Aires (Argentina)

    2015-12-15

    The prediction of the behavior of Th compounds under irradiation is an important issue for the upcoming Generation-IV nuclear reactors. The study of self-diffusion and hetero-diffusion is a central key to fulfill this goal. As a first approach, we obtained, by means of first-principles methods, migration and activation energies of Th and C atoms self-diffusion and diffusion of He atoms in ThC. We also calculate diffusion coefficients as a function of temperature. - Highlights: • Diffusion in thorium carbide by means of first-principles calculations is studied. • The most favorable migration event is a C atom moving through a C-vacancy aided path. • Calculated C atoms diffusion coefficients agree very well with the experimental data. • For He, the energetically most favorable migration path is through Th-vacancies.

  18. Silicon carbide: a versatile material for biosensor applications.

    Science.gov (United States)

    Oliveros, Alexandra; Guiseppi-Elie, Anthony; Saddow, Stephen E

    2013-04-01

    Silicon carbide (SiC) has been around for more than 100 years as an industrial material and has found wide and varied applications because of its unique electrical and thermal properties. In recent years there has been increased attention to SiC as a viable material for biomedical applications. Of particular interest in this review is its potential for application as a biotransducer in biosensors. Among these applications are those where SiC is used as a substrate material, taking advantage of its surface chemical, tribological and electrical properties. In addition, its potential for integration as system on a chip and those applications where SiC is used as an active material make it a suitable substrate for micro-device fabrication. This review highlights the critical properties of SiC for application as a biosensor and reviews recent work reported on using SiC as an active or passive material in biotransducers and biosensors.

  19. Chapter 19: Catalysis by Metal Carbides and Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Schaidle, Joshua A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nash, Connor P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Yung, Matthew M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Chen, Yuan [Pacific Northwest National Laboratory; Carl, Sarah [University of Michigan; Thompson, Levi [University of Michigan

    2017-08-09

    Early transition metal carbides and nitrides (ETMCNs), materials in which carbon or nitrogen occupies interstitial sites within a parent metal lattice, possess unique physical and chemical properties that motivate their use as catalysts. Specifically, these materials possess multiple types of catalytic sites, including metallic, acidic, and basic sites, and as such, exhibit reactivities that differ from their parent metals. Moreover, their surfaces are dynamic under reaction conditions. This chapter reviews recent (since 2010) experimental and computational investigations into the catalytic properties of ETMCN materials for applications including biomass conversion, syngas and CO2 upgrading, petroleum and natural gas refining, and electrocatalytic energy conversion, energy storage, and chemicals production, and attempts to link catalyst performance to active site identity/surface structure in order to elucidate the present level of understanding of structure-function relationships for these materials. The chapter concludes with a perspective on leveraging the unique properties of these materials to design and develop improved catalysts through a dedicated, multidisciplinary effort.

  20. High surface area silicon carbide-coated carbon aerogel

    Science.gov (United States)

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

    2014-01-14

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

  1. Deposition of tantalum carbide coatings on graphite by laser interactions

    Science.gov (United States)

    Veligdan, James; Branch, D.; Vanier, P. E.; Barietta, R. E.

    1994-01-01

    Graphite surfaces can be hardened and protected from erosion by hydrogen at high temperatures by refractory metal carbide coatings, which are usually prepared by chemical vapor deposition (CVD) or chemical vapor reaction (CVR) methods. These techniques rely on heating the substrate to a temperature where a volatile metal halide decomposes and reacts with either a hydrocarbon gas or with carbon from the substrate. For CVR techniques, deposition temperatures must be in excess of 2000 C in order to achieve favorable deposition kinetics. In an effort to lower the bulk substrate deposition temperature, the use of laser interactions with both the substrate and the metal halide deposition gas has been employed. Initial testing involved the use of a CO2 laser to heat the surface of a graphite substrate and a KrF excimer laser to accomplish a photodecomposition of TaCl5 gas near the substrate. The results of preliminary experiments using these techniques are described.

  2. Cryogenic Treatment of Carbide-free Bainite Steel After Carburizing

    Directory of Open Access Journals (Sweden)

    SUN Shi-qing

    2017-05-01

    Full Text Available The cryogenic treatment (CT process of carbide-free bainite steel after carburizing was optimized by the method combining thermal magnetic analysis, microhardness analysis and direct reading spectrometric analysis. The results show that cryogenic treatment temperature of the hardened layer should be lower than 134K by measuring thermal magnetic curve of the sample after carburizing at 1193K and air cooling (AC. After cryogenic treatment at 123K and tempering (T at 463K, retained austenite content of the hardened layer is about 12.2% (mass fraction. The near surface layer of carburized steel is hardened dramatically through the cryogenic treatment, and the hardness of near surface layer reaches about 810HV1.0 after low temperature tempering. The distribution of hardness gradient of carburized steel tends to be reasonable.

  3. Methods and systems for utilizing carbide lime or slag

    Energy Technology Data Exchange (ETDEWEB)

    Devenney, Martin; Fernandez, Miguel; Chen, Irvin; Calas, Guillaume; Weiss, Michael Joseph; Tester, Chantel Cabrera

    2018-02-27

    Provided herein are methods comprising a) treating a slag solid or carbide lime suspension with an ammonium salt in water to produce an aqueous solution comprising calcium salt, ammonium salt, and solids; b) contacting the aqueous solution with carbon dioxide from an industrial process under one or more precipitation conditions to produce a precipitation material comprising calcium carbonate and a supernatant aqueous solution wherein the precipitation material and the supernatant aqueous solution comprise residual ammonium salt; and c) removing and optionally recovering ammonia and/or ammonium salt using one or more steps of (i) recovering a gas exhaust stream comprising ammonia during the treating and/or the contacting step; (ii) recovering the residual ammonium salt from the supernatant aqueous solution; and (iii) removing and optionally recovering the residual ammonium salt from the precipitation material.

  4. Directional amorphization of boron carbide subjected to laser shock compression

    Science.gov (United States)

    Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; LaSalvia, Jerry C.; Wehrenberg, Christopher E.; Behler, Kristopher D.; Meyers, Marc A.

    2016-10-01

    Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45˜50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C.

  5. Reforming of fuel inside fuel cell generator

    Science.gov (United States)

    Grimble, Ralph E.

    1988-01-01

    Disclosed is an improved method of reforming a gaseous reformable fuel within a solid oxide fuel cell generator, wherein the solid oxide fuel cell generator has a plurality of individual fuel cells in a refractory container, the fuel cells generating a partially spent fuel stream and a partially spent oxidant stream. The partially spent fuel stream is divided into two streams, spent fuel stream I and spent fuel stream II. Spent fuel stream I is burned with the partially spent oxidant stream inside the refractory container to produce an exhaust stream. The exhaust stream is divided into two streams, exhaust stream I and exhaust stream II, and exhaust stream I is vented. Exhaust stream II is mixed with spent fuel stream II to form a recycle stream. The recycle stream is mixed with the gaseous reformable fuel within the refractory container to form a fuel stream which is supplied to the fuel cells. Also disclosed is an improved apparatus which permits the reforming of a reformable gaseous fuel within such a solid oxide fuel cell generator. The apparatus comprises a mixing chamber within the refractory container, means for diverting a portion of the partially spent fuel stream to the mixing chamber, means for diverting a portion of exhaust gas to the mixing chamber where it is mixed with the portion of the partially spent fuel stream to form a recycle stream, means for injecting the reformable gaseous fuel into the recycle stream, and means for circulating the recycle stream back to the fuel cells.

  6. Nanoporous Carbide-Derived Carbon Material-Based Linear Actuators

    Directory of Open Access Journals (Sweden)

    Janno Torop

    2009-12-01

    Full Text Available Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect in nanocomposite material actuators containing carbide-derived carbon (CDC and polytetrafluoroetylene polymer (PTFE. Transducers based on high surface area carbide-derived carbon electrode materials are suitable for short range displacement applications, because of the proportional actuation response to the charge inserted, and high Coulombic efficiency due to the EDL capacitance. The material is capable of developing stresses in the range of tens of N cm-2. The area of an actuator can be dozens of cm2, which means that forces above 100 N are achievable. The actuation mechanism is based on the interactions between the high-surface carbon and the ions of the electrolyte. Electrochemical evaluations of the four different actuators with linear (longitudinal action response are described. The actuator electrodes were made from two types of nanoporous TiC-derived carbons with surface area (SA of 1150 m2 g-1 and 1470 m2 g-1, respectively. Two kinds of electrolytes were used in actuators: 1.0 M tetraethylammonium tetrafluoroborate (TEABF4 solution in propylene carbonate and pure ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf. It was found that CDC based actuators exhibit a linear movement of about 1% in the voltage range of 0.8 V to 3.0 V at DC. The actuators with EMITf electrolyte had about 70% larger movement compared to the specimen with TEABF4 electrolyte.

  7. Fischer-Tropsch reaction on a thermally conductive and reusable silicon carbide support.

    Science.gov (United States)

    Liu, Yuefeng; Ersen, Ovidiu; Meny, Christian; Luck, Francis; Pham-Huu, Cuong

    2014-05-01

    The Fischer-Tropsch (FT) process, in which synthesis gas (syngas) derived from coal, natural gas, and biomass is converted into synthetic liquid fuels and chemicals, is a strongly exothermic reaction, and thus, a large amount of heat is generated during the reaction that could severely modify the overall selectivity of the process. In this Review, we report the advantages that can be offered by different thermally conductive supports, that is, carbon nanomaterials and silicon carbide, pure or doped with different promoters, for the development of more active and selective FT catalysts. This Review follows a discussion regarding the clear trend in the advantages and drawbacks of these systems in terms of energy efficiency and catalytic performance for this most-demanded catalytic process. It is demonstrated that the use of a support with an appropriate pore size and thermal conductivity is an effective strategy to tune and improve the activity of the catalyst and to improve product selectivity in the FT process. The active phase and the recovery of the support, which also represents a main concern in terms of the large amount of FT catalyst used and the cost of the active cobalt phase, is also discussed within the framework of this Review. It is expected that a thermally conductive support such as β-SiC will not only improve the development of the FT process, but that it will also be part of a new support for different catalytic processes for which high catalytic performance and selectivity are strongly needed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-01-07

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

  9. Fast Reactor Fuel Type and Reactor Safety Performance

    Energy Technology Data Exchange (ETDEWEB)

    R. Wigeland; J. Cahalan

    2009-09-01

    Fast Reactor Fuel Type and Reactor Safety Performance R. Wigeland , Idaho National Laboratory J. Cahalan, Argonne National Laboratory The sodium-cooled fast neutron reactor is currently being evaluated for the efficient transmutation of the highly-hazardous, long-lived, transuranic elements that are present in spent nuclear fuel. One of the fundamental choices that will be made is the selection of the fuel type for the fast reactor, whether oxide, metal, carbide, nitride, etc. It is likely that a decision on the fuel type will need to be made before many of the related technologies and facilities can be selected, from fuel fabrication to spent fuel reprocessing. A decision on fuel type should consider all impacts on the fast reactor system, including safety. Past work has demonstrated that the choice of fuel type may have a significant impact on the severity of consequences arising from accidents, especially for severe accidents of low probability. In this paper, the response of sodium-cooled fast reactors is discussed for both oxide and metal fuel types, highlighting the similarities and differences in reactor response and accident consequences. Any fast reactor facility must be designed to be able to successfully prevent, mitigate, or accommodate all consequences of potential events, including accidents. This is typically accomplished by using multiple barriers to the release of radiation, including the cladding on the fuel, the intact primary cooling system, and most visibly the reactor containment building. More recently, this has also included the use of ‘inherent safety’ concepts to reduce or eliminate the potential for serious damage in some cases. Past experience with oxide and metal fuel has demonstrated that both fuel types are suitable for use as fuel in a sodium-cooled fast reactor. However, safety analyses for these two fuel types have also shown that there can be substantial differences in accident consequences due to the neutronic and

  10. Influence of Heat Treatment on Content of the Carbide Phases in the Microstructure of High-Speed Steel

    Directory of Open Access Journals (Sweden)

    Jaworski J.

    2017-09-01

    Full Text Available This article presents the results of investigations of the effect of heat treatment temperature on the content of the carbide phase of HS3-1-2 and HS6-5-2 low-alloy high-speed steel. Analysis of the phase composition of carbides is carried out using the diffraction method. It is determined that with increasing austenitising temperature, the intensification of dissolution of M6C carbide increases. As a result, an increase in the grain size of the austenite and the amount of retained austenite causes a significant reduction in the hardness of hardened steel HS3-1-2 to be observed. The results of diffraction investigations showed that M7C3 carbides containing mainly Cr and Fe carbides and M6C carbides containing mainly Mo and W carbides are dissolved during austenitisation. During austenitisation of HS3-1-2 steel, the silicon is transferred from the matrix to carbides, thus replacing carbide-forming elements. An increase in a degree of tempering leads to intensification of carbide separation and this process reduce the grindability of tested steels.

  11. Structural Evolution of Molybdenum Carbides in Hot Aqueous Environments and Impact on Low-Temperature Hydroprocessing of Acetic Acid

    Directory of Open Access Journals (Sweden)

    Jae-Soon Choi

    2015-03-01

    Full Text Available We investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites were converted to oxidic sites. Water aging also induced changes to the non-carbidic carbon deposited during carbide synthesis and increased surface roughness, which in turn affected carbide pore volume and surface area. The extent of these structural changes was sensitive to the initial carbide structure and was lower under actual hydroprocessing conditions indicating the possibility of further improving the hydrothermal stability of Mo carbides by optimizing catalyst structure and operating conditions. Mo carbides were active in acetic acid conversion in the presence of liquid water, their activity being comparable to that of Ru/C. The results suggest that effective and inexpensive bio-oil hydroprocessing catalysts could be designed based on Mo carbides, although a more detailed understanding of the structure-performance relationships is needed, especially in upgrading of more complex reaction mixtures or real bio-oils.

  12. Investigation of a Tricarbide Grooved Ring Fuel Element for a Nuclear Thermal Rocket

    Science.gov (United States)

    Taylor, Brian D.; Emrich, Bill; Tucker, Dennis; Barnes, Marvin; Donders, Nicolas; Benensky, Kelsa

    2017-01-01

    Deep space exploration, especially that of Mars, is on the horizon as the next big challenge for space exploration. Nuclear propulsion, through which high thrust and efficiency can be achieved, is a promising option for decreasing the cost and logistics of such a mission. Work on nuclear thermal engines goes back to the days of the NERVA program. Currently, nuclear thermal propulsion is under development again in various forms to provide a superior propulsion system for deep space exploration. The authors have been working to develop a concept nuclear thermal engine that uses a grooved ring fuel element as an alternative to the traditional hexagonal rod design. The authors are also studying the use of carbide fuels. The concept was developed in order to increase surface area and heat transfer to the propellant. The use of carbides would also raise the temperature limitations of the reactor. It is hoped that this could lead to a higher thrust to weight nuclear thermal engine. This paper describes the modeling of neutronics, heat transfer, and fluid dynamics of this alternative nuclear fuel element geometry. Fabrication experiments of grooved rings from carbide refractory metals are also presented along with material characterization and interactions with a hot hydrogen environment.

  13. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR project, APEI, Inc. is proposing to develop a high efficiency, rad-hard 3.8 kW silicon carbide (SiC) Power Processing Unit (PPU) for Hall Effect...

  14. The Affordable Pre-Finishing of Silicon Carbide for Optical Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Creare proposes to develop a novel, laser-assisted, pre-finishing process for chemical vapor deposition (CVD) coated silicon-carbide ceramics. Our innovation will...

  15. CHARACTERIZATION OF PRECIPITATES IN CUBIC SILICON CARBIDE IMPLANTED WITH 25Mg+ IONS

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin; Spurgeon, Steven R.; Liu, Jia; Edwards, Danny J.; Schreiber, Daniel K.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2016-09-26

    The aim of this study is to characterize precipitates in Mg+ ion implanted and high-temperature annealed cubic silicon carbide using scanning transmission electron microscopy, electron energy loss spectroscopy and atom probe tomography.

  16. Combustion synthesis of nano-sized tungsten carbide powder and effects of sodium halides

    Science.gov (United States)

    Won, H. I.; Nersisyan, H. H.; Won, C. W.

    2010-02-01

    The synthesis of nano-size tungsten carbide powder has been investigated with a WO3 + Mg + C + carbonate system using alkali halides. The effects of different types of alkali halides on combustion temperature and tungsten carbide formation were discussed. Sodium fluoride had a notable effect on the particle size of the product and the degree of transformation from the initial mixture. A small amount of ammonium carbonate activated the carburization of tungsten carbide by the gas phase carbon transportation. X-ray diffraction data and particle analysis showed that the final product synthesized from a WO3-Mg-C-(NH4)2CO3-NaF system contains pure-phase tungsten carbide with a particle size of 50-100 nm.

  17. MUTUAL SOLUBILITY ОF CARBIDES WITHIN MULTICOMPONENT DIFFUSIVE COATINGS ОN HARD ALLOYS

    Directory of Open Access Journals (Sweden)

    A. A. Shmatov

    2008-01-01

    Full Text Available An optimization of powder mixtures has been performed with respect to wear resistance of  diffusive carbide coatings on hard alloy Т15К6 (79% WC, 15% TiC and 6% Co for four three-component systems, viz. Cr–Ti–V, Cr–V–Mo, Cr–Ti–Mo and Cr–V–Nb,. The «composition-properties» diagrams have been plotted using the obtained mathematical models. Optimum three-component diffusive saturation of a hard alloy using carbide-forming elements permits to increase its service life by the factor of 2.2–3.1 as compared with one-component saturation. This significant improvement of wear resistance of three-component diffusive carbide coatings is due to formation of heterogeneous microstructure containing complex alloyed carbides of IV-VI-group metals with 2–30% mutually soluble one- or two- saturating elements. 

  18. Ultra-Lightweight, High Efficiency Silicon-Carbide (SIC) Based Power Electronic Converters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In Phase I of this project, APEI, Inc. proved the feasibility of creating ultra-lightweight power converters (utilizing now emerging silicon carbide [SiC] power...

  19. The effects of stoichiometry on the mechanical properties of icosahedral boron carbide under loading.

    Science.gov (United States)

    Taylor, DeCarlos E; McCauley, James W; Wright, T W

    2012-12-19

    The effects of stoichiometry on the atomic structure and the related mechanical properties of boron carbide (B(4)C) have been studied using density functional theory and quantum molecular dynamics simulations. Computational cells of boron carbide containing up to 960 atoms and spanning compositions ranging from 6.7% to 26.7% carbon were used to determine the effects of stoichiometry on the atomic structure, elastic properties, and stress-strain response as a function of hydrostatic, uniaxial, and shear loading paths. It was found that different stoichiometries, as well as variable atomic arrangements within a fixed stoichiometry, can have a significant impact on the yield stress of boron carbide when compressed uniaxially (by as much as 70% in some cases); the significantly reduced strength of boron carbide under shear loading is also demonstrated.

  20. Novel Silicon Carbide Deep Ultraviolet Detectors: Device Modeling, Characterization, Design and Prototyping Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Silicon Carbide deep UV detectors can achieve large gains, high signal-to-noise ratios and solar-blind operation, with added benefits of smaller sizes, lower...