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Sample records for carbide electronics developed

  1. An Overview of Wide Bandgap Silicon Carbide Sensors and Electronics Development at NASA Glenn Research Center

    Science.gov (United States)

    Hunter, Gary W.; Neudeck, Philip G.; Beheim, Glenn M.; Okojie, Robert S.; Chen, Liangyu; Spry, D.; Trunek, A.

    2007-01-01

    A brief overview is presented of the sensors and electronics development work ongoing at NASA Glenn Research Center which is intended to meet the needs of future aerospace applications. Three major technology areas are discussed: 1) high temperature SiC electronics, 2) SiC gas sensor technology development, and 3) packaging of harsh environment devices. Highlights of this work include world-record operation of SiC electronic devices including 500?C JFET transistor operation with excellent properties, atomically flat SiC gas sensors integrated with an on-chip temperature detector/heater, and operation of a packaged AC amplifier. A description of the state-of-the-art is given for each topic. It is concluded that significant progress has been made and that given recent advancements the development of high temperature smart sensors is envisioned.

  2. Thermally Stable Ohmic Contacts on Silicon Carbide Developed for High- Temperature Sensors and Electronics

    Science.gov (United States)

    Okojie, Robert S.

    2001-01-01

    The NASA aerospace program, in particular, requires breakthrough instrumentation inside the combustion chambers of engines for the purpose of, among other things, improving computational fluid dynamics code validation and active engine behavioral control (combustion, flow, stall, and noise). This environment can be as high as 600 degrees Celsius, which is beyond the capability of silicon and gallium arsenide devices. Silicon-carbide- (SiC-) based devices appear to be the most technologically mature among wide-bandgap semiconductors with the proven capability to function at temperatures above 500 degrees Celsius. However, the contact metalization of SiC degrades severely beyond this temperature because of factors such as the interdiffusion between layers, oxidation of the contact, and compositional and microstructural changes at the metal/semiconductor interface. These mechanisms have been proven to be device killers. Very costly and weight-adding packaging schemes that include vacuum sealing are sometimes adopted as a solution.

  3. Anomalous electronic transport in boron carbides

    Science.gov (United States)

    Emin, D.; Samara, G. A.; Wood, C.

    The boron carbides are composed of icosahedral units, B12 and B11C1, linked together by strong intericosahedral bonds. With such distributions of icosahedral and intericosahedral compositions, boron carbides, B/sub 1-x/C/sub x/, are single phase over 0.1 less than or equal to x less than or equal to 0.2. The electronic transport properties of the boron carbides were examined within this single-phase region. Results are inconsistent with conventional analyses of both itinerant and hopping transport. Most striking are Seebeck coefficients which are both large and rapidly increasing functions of temperature despite thermally activated dc conductivities. These results manifest the hopping of small bipolaronic holes between carbon-containing icosahedral that are inequivalent in energy and electron-lattice coupling strength. Under hydrostatic pressures up to approx. 25 kbar, the dc conductivities increase with pressure. This anomalous behavior for hopping conduction reflects the distinctive structure and bonding of these materials.

  4. Electron-Spin Resonance in Boron Carbide

    Science.gov (United States)

    Wood, Charles; Venturini, Eugene L.; Azevedo, Larry J.; Emin, David

    1987-01-01

    Samples exhibit Curie-law behavior in temperature range of 2 to 100 K. Technical paper presents studies of electron-spin resonance of samples of hot pressed B9 C, B15 C2, B13 C2, and B4 C. Boron carbide ceramics are refractory solids with high melting temperatures, low thermal conductives, and extreme hardnesses. They show promise as semiconductors at high temperatures and have unusually large figures of merit for use in thermoelectric generators.

  5. Electronic properties of disordered silicon carbides

    International Nuclear Information System (INIS)

    The disorder effects on the electronic properties of silicon carbide were studied at the atomic or micro-structural scale. We have investigated a great variety of materials: silicon carbide fibers, carbonated amorphous silicon films, single crystals and amorphous or crystalline SiC powders. The DC and AC conductivity measurements on the SiC fibers point out the major role of their micro-structure at the nanometric scale, which leads to large dielectric constants. Hopping of polaronic carriers is the dominant conduction mechanism. An electrons spin resonance study of all the materials was performed: sp2 hybridized carbon is always present, in diluted form in the amorphous systems or as free carbon in the crystalline one. Some irradiation defects of SiC were identified: silicon or carbon vacancy and carbon complexes with sp2 hybridization. Such a carbon is responsible of the low paramagnetic stability of the silicon dangling bonds. It is believed to induce the polaronic behavior of the localized carriers. (Author). refs., figs., tabs

  6. Characterization of boron carbide with an electron microprobe

    Science.gov (United States)

    Matteudi, G.; Ruste, J.

    1983-01-01

    Within the framework of a study of heterogeneous materials (Matteudi et al., 1971: Matteudi and Verchery, 1972) thin deposits of boron carbide were characterized. Experiments using an electronic probe microanalyzer to analyze solid boron carbide or boron carbide in the form of thick deposits are described. Quantitative results on boron and carbon are very close to those obtained when applying the Monte Carlo-type correction calculations.

  7. Analysis of boron carbides' electronic structure

    Science.gov (United States)

    Howard, Iris A.; Beckel, Charles L.

    1986-01-01

    The electronic properties of boron-rich icosahedral clusters were studied as a means of understanding the electronic structure of the icosahedral borides such as boron carbide. A lower bound was estimated on bipolaron formation energies in B12 and B11C icosahedra, and the associated distortions. While the magnitude of the distortion associated with bipolaron formation is similar in both cases, the calculated formation energies differ greatly, formation being much more favorable on B11C icosahedra. The stable positions of a divalent atom relative to an icosahedral borane was also investigated, with the result that a stable energy minimum was found when the atom is at the center of the borane, internal to the B12 cage. If incorporation of dopant atoms into B12 cages in icosahedral boride solids is feasible, novel materials might result. In addition, the normal modes of a B12H12 cluster, of the C2B10 cage in para-carborane, and of a B12 icosahedron of reduced (D sub 3d) symmetry, such as is found in the icosahedral borides, were calculated. The nature of these vibrational modes will be important in determining, for instance, the character of the electron-lattice coupling in the borides, and in analyzing the lattice contribution to the thermal conductivity.

  8. Silicon Carbide Sensors and Electronics for Harsh Environment Applications

    Science.gov (United States)

    Evans, Laura J.

    2007-01-01

    Silicon carbide (SiC) semiconductor has been studied for electronic and sensing applications in extreme environment (high temperature, extreme vibration, harsh chemical media, and high radiation) that is beyond the capability of conventional semiconductors such as silicon. This is due to its near inert chemistry, superior thermomechanical and electronic properties that include high breakdown voltage and wide bandgap. An overview of SiC sensors and electronics work ongoing at NASA Glenn Research Center (NASA GRC) will be presented. The main focus will be two technologies currently being investigated: 1) harsh environment SiC pressure transducers and 2) high temperature SiC electronics. Work highlighted will include the design, fabrication, and application of SiC sensors and electronics, with recent advancements in state-of-the-art discussed as well. These combined technologies are studied for the goal of developing advanced capabilities for measurement and control of aeropropulsion systems, as well as enhancing tools for exploration systems.

  9. Free electron laser annealing of silicon carbide

    International Nuclear Information System (INIS)

    We have studied the application of FEL for the semiconductor processing on the practical device fabrication. FEL annealing at a variety of wavelengths (10.0-13.0 μm) have been performed under room temperature for amorphous silicon carbide (a-SiC) and Nitrogen implanted cubic silicon carbide (3C-SiC) films. Infrared absorption spectroscopy indicated that the annealing at 12.6 μm, corresponding to the absorption peak of Si-C stretch mode, was effective for recrystallization. On the other hand, Hall effect measurements showed the increase of carrier density for N-implanted 3C-SiC films at around 10.4 μm, whereas the absorption was weak at this wavelength. The present results demonstrated that the direct excitation of the lattice vibration with FEL can induce the reconstruction of disordered atoms and activating dopants even at room temperature. (author)

  10. Anisotropic electronic conduction in stacked two-dimensional titanium carbide

    OpenAIRE

    Tao Hu; Hui Zhang; Jiemin Wang; Zhaojin Li; Minmin Hu; Jun Tan; Pengxiang Hou; Feng Li; Xiaohui Wang

    2015-01-01

    Stacked two-dimensional titanium carbide is an emerging conductive material for electrochemical energy storage which requires an understanding of the intrinsic electronic conduction. Here we report the electronic conduction properties of stacked Ti3C2 T 2 (T = OH, O, F) with two distinct stacking sequences (Bernal and simple hexagonal). On the basis of first-principles calculations and energy band theory analysis, both stacking sequences give rise to metallic conduction with Ti 3d electrons c...

  11. 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.

  12. The Development of Silicon Carbide Based Hydrogen and Hydrocarbon Sensors

    Science.gov (United States)

    Liu, Chung-Chiun

    1994-01-01

    Silicon carbide is a high temperature electronic material. Its potential for development of chemical sensors in a high temperature environment has not been explored. The objective of this study is to use silicon carbide as the substrate material for the construction of chemical sensors for high temperature applications. Sensors for the detection of hydrogen and hydrocarbon are developed in this program under the auspices of Lewis Research Center, NASA. Metal-semiconductor or metal-insulator-semiconductor structures are used in this development. Specifically, using palladium-silicon carbide Schottky diodes as gas sensors in the temperature range of 100 to 400 C are designed, fabricated and assessed. The effect of heat treatment on the Pd-SiC Schottky diode is examined. Operation of the sensors at 400 C demonstrate sensitivity of the sensor to hydrogen and hydrocarbons. Substantial progress has been made in this study and we believe that the Pd-SiC Schottky diode has potential as a hydrogen and hydrocarbon sensor over a wide range of temperatures. However, the long term stability and operational life of the sensor need to be assessed. This aspect is an important part of our future continuing investigation.

  13. Electronic structure of Pu carbides: photoelectron spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Gouder, T.; Havela, L.; Shick, Alexander; Huber, F.

    2008-01-01

    Roč. 403, č. 5-9 (2008), s. 852-853. ISSN 0921-4526 R&D Projects: GA AV ČR(CZ) IAA100100530 Grant ostatní: EU(XE) RITA-CT-2006-026176 Institutional research plan: CEZ:AV0Z10100520 Keywords : photoemission * electronic structure * plutonium Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.822, year: 2008

  14. Electronic properties of finite-length silicon carbide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Alfieri, G. [Department of Electronic Science and Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto (Japan); Kimoto, T. [Department of Electronic Science and Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto (Japan); Photonics and Electronics Science and Engineering Center (PESEC), Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto (Japan)

    2009-02-15

    The electronic properties of silicon carbide nanotubes (SiCNT) as a function of length, were investigated by means of density functional theory (DFT). We found that the increasing nanotube length yields a higher localization of the lowest unoccupied and highest occupied molecular orbitals (LUMO and HOMO), thus affecting the behavior of the band gap and chemical reactivity of the SiCNTs. It is also found that structural stability increases for longer and larger nanotubes. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Electron microscopy study of radiation effects in boron carbide

    International Nuclear Information System (INIS)

    Boron carbide is a disordered non-stoechiometric material with a strongly microtwinned polycristallyne microstructure. This ceramic is among the candidate materials for the first wall coating in fusion reactor and is used as a neutron absorber in the control rods of fast breeder reactors. The present work deals with the nature of radiation damage in this solid. Because of helium internal production, neutron irradiated boron carbide is affected by swelling and by a strong microcracking which can break up a pellet in fine powder. These processes are rather intensitive to the irradiation parameters (temperature, flux and even neutron spectrum). Transmission electron microscopy of samples irradiated by the fast neutrons of a reactor, the electrons of a high voltage electron microscope and of samples implanted with helium ions was used to understand the respective roles of helium and point defects in the processes of swelling and microcracking. The design of an irradiation chamber for helium implantation at controlled temperature from 600 to 17000C was an important technical part of this work

  16. 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

  17. Electronic and vibrational properties of vanadium-carbide nanowires

    Science.gov (United States)

    Singh, Poorva; Nautiyal, Tashi; Auluck, Sushil

    2012-09-01

    We have made an effort to understand the properties of transition metal carbide nanowires (NWs) and studied vanadium-carbide (VC) nanowires as a specific case. Different structures have been considered and their electronic and vibrational properties studied employing density functional theory. The effect of dimensionality is very well brought forth by these NWs, narrow/thinner structures have clear preference for magnetic state with sizeable magnetic moment at the V sites. As the thickness/width increases, the margin decreases and the magnetic moment disappears altogether for structures like square and rectangular NWs. The cohesive energy per atom increases with the increase in lateral dimensions of the NW, and it is about 88% of the bulk value for the rectangular NW, while it is only 50% for the linear chain. All the wires are conducting in nature, with the linear and zigzag wires having half-metallic character. Our calculations show that the V atoms decide the electronic and magnetic properties in these while compressibility, a mechanical property, is governed by the C atoms. The electron localization function beautifully illustrates the closeness of thicker/wider NWs to the bulk. It also reveals that electrons are highly localized around C atoms; however, the amount of charge transferred depends strongly on the structure of wire. The optical properties unfurl the impact of different spatial expanse in the cross section of NW in a nice way, e.g., ɛ2xx > ɛ2yy (ɛ2 is imaginary part of dielectric function) for all those with a larger expanse along X compared to Y and vice-versa. Thicker nanowires seem to be more suitable for optical applications. Site-resolved phonon density of states shows that presence of C atoms is responsible for high frequency branches. The heat capacity variation for various structures closely follows the magnitude of respective phonon density of states.

  18. Electron-energy-loss spectroscopy of transition-metal carbides

    International Nuclear Information System (INIS)

    Electron-energy-loss spectroscopy (EELS) was applied to several problems dealing with the transition-metal carbides. First, narrow (200A) precipitates of TiC were identified in a single crystal of titanium diboride. Second, the carbon concentration in individual stacking faults of TaC was determined to be less than in the surrounding matrix, and the implications of this finding for crystal structure and mechanical properties were discussed. Next, thin films of amorphous carbon and TiO were studied with EELS. Experimental cross sections for C and Ti were obtained from these spectra and used for quantitative analysis of a material of known stoichiometry, V6C5 (by assuming V and Ti cross sections equal), and one of unknown stoichiometry, a cemented carbide composed of 1 to 5 μm grains of TiC/sub x/ embedded in a Ni-Mo binder. These experimental cross sections gave a C/V ratio of 0.84, very close to the expected value of 0.833, and a C/Ti ratio of 0.81 for a grain of TiC/sub x/, a reasonable value of x in these materials. Two other methods of determining cross sections were applied: calculated cross sections based on a hydrogenic model gave inaccurate results, perhaps due to the inadequacy of the model for these transition metals; and efficiency factors applied to the Bethe cross section gave reasonable results, but inferior to those from the experimental cross sections

  19. Silicon carbide, a semiconductor for space power electronics

    Science.gov (United States)

    Powell, J. A.; Matus, Lawrence G.

    1991-01-01

    After many years of promise as a high temperature semiconductor, silicon carbide (SiC) is finally emerging as a useful electronic material. Recent significant progress that has led to this emergence has been in the area of crystal growth and device fabrication technology. High quality of single-crystal SiC wafers, up to 25 mm in diameter, can now be produced routinely from boules grown by a high temperature (2700 K) sublimation process. Device fabrication processes, including chemical vapor deposition (CVD), in situ doping during CVD, reactive ion etching, oxidation, metallization, etc. have been used to fabricate p-n junction diodes and MOSFETs. The diode was operated to 870 K and the MOSFET to 770 K.

  20. 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.

  1. Formation Energies and Electronic Properties of Vanadium Carbides Found in High Strength Steel Alloys

    Science.gov (United States)

    Limmer, Krista; Medvedeva, Julia

    2013-03-01

    Carbide formation and stabilization in steels is of great interest owing to its effect on the microstructure and properties of the Fe-based alloys. The appearance of carbides with different metal/C ratios strongly depends on the carbon concentration, alloy composition as well as the heat treatment. Strong carbide-forming elements such as Ti, V, and Nb have been used in microalloyed steels; with VC showing an increased solubility in the iron matrix as compared with TiC and NbC. This allows for dissolution of the VC into the steel during heating and fine precipitation during cooling. In addition to VC, the primary vanadium carbide with cubic structure, a wide range of non-stoichiometric compositions VCy with y varying from 0.72 to 0.88, has been observed. This range includes two ordered compounds, V8C7 and V6C5. In this study, first-principles density functional theory (DFT) is employed to examine the stability of the binary carbides by calculating their formation energies. We compare the local structures (atomic coordination, bond distances and angles) and the density of states in optimized geometries of the carbides. Further, the effect of alloying additions, such as niobium and titanium, on the carbide stabilization is investigated. We determine the energetically preferable substitutional atom location in each carbide and study the impurity distribution as well as its role in the carbide formation energy and electronic structure.

  2. Reactive infiltration in fabricating silicon carbide composites for electronic packaging

    Science.gov (United States)

    Xiao, Liming

    The silicon carbide (SiC) composite is a promising material to improve thermal dissipation and thermal expansion matching for electronic packaging, but its wide application has been greatly hindered by the high fabrication cost. To address this cost issue, two new reactive infiltration methods have been proposed and developed to fabricate SiC composite in a net-shape manner. They are Method 1--locally magnesium-enhanced infiltration and Method 2--globally carbon-enhanced infiltration. In Method 1, a magnesium wetting agent was strategically inserted at the interface between SiC powder and Al-Si alloy. The molten Al-Si alloy was assisted by chemical reaction to infiltrate into the porous SiC powder in an inert atmosphere sealed in a quartz tube or a steel cup. The infiltration kinetics was characterized by measuring the infiltration weight gain with respect to time. It was found that the infiltration kinetics could be divided into three stages: infiltration initiation, rapid infiltration, and slow infiltration, and most of the weight gain occurred in the rapid infiltration stage. The rapid infiltration was due to the magnesium-silicon oxide reaction and the magnesium accumulation at the infiltration front. Modeling of the infiltration kinetics showed the magnesium dilution increased the dynamic contact angle, which in turn decreased the infiltration rate. The SiC oxidation, Mg content and temperature were shown to be important factors affecting the infiltration. In Method 2, a carbon wetting agent is coated globally on every SiC particle. To accomplish this coating, a slip casting, drying, curing and carbonization process was developed. A crucibleless infiltration method was designed to fabricate SiC composites in an open atmosphere protected by nitrogen. The temperature change of SiC preform during infiltration was monitored to determine the infiltration kinetics. The silicon-carbon reaction was found to create a spontaneous infiltration of molten Si or molten Al

  3. The invention of graphene electronics and the physics of epitaxial graphene on silicon carbide

    International Nuclear Information System (INIS)

    Graphene electronics was officially invented at the Georgia Institute of Technology in 2003 after experimental and theoretical research on graphene properties starting from 2001. This paper focuses on the motivation and events leading to the invention of graphene electronics, as well as on recent developments. Graphene electronics was originally conceived as a new electronics paradigm to incorporate the room-temperature ballistic and coherent properties of carbon nanotubes in a patternable electronic material. Graphene on silicon carbide was chosen as the most suitable material. Other electronics schemes, involving transferred (exfoliated and chemical vapor deposition-produced) graphitic materials, that operate in the diffusive regime may not be competitive with standard methods and may therefore not significantly impact electronics. In recent years, epitaxial graphene has improved to the point where graphene electronics according to the original concept appears to be within reach. Beyond electronics, epitaxial graphene research has led to important developments in graphene physics in general and has become a leading platform for graphene science as well.

  4. Temperature-induced phase development in titanium-implanted silicon carbide

    International Nuclear Information System (INIS)

    Silicon carbide has been implated with titanium at three different doses. Transmission electron microscopy and Rutherford back-scattering (RBS) have been used to follow changes resulting from post-implantation heat treatment. The as-implanted layer is amorphous, and after a low temperature anneal a fine, non-equilibrium titanium carbide precipitate appears in the amorphous matrix. At higher temperatures, first the ternary phase Ti3SiC2 and the SiC crystallizes. RBS measurements show that the initial Gaussian titanium concentration profile changes near the ternary phase precipitation temperature, developing side peaks at the area of maximum initial concentration gradient. Thermodynamic and kinetic factors in the observed phase development are discussed, and the need for a metastable phase diagram is considered. (orig.)

  5. Tuning the electronic band-gap of fluorinated 3C-silicon carbide nanowires

    Science.gov (United States)

    Miranda Durán, Álvaro; Trejo Baños, Alejandro; Pérez, Luis Antonio; Cruz Irisson, Miguel

    The possibility of control and modulation of the electronic properties of silicon carbide nanowires (SiCNWs) by varying the wire diameter is well known. SiCNWs are particularly interesting and technologically important, due to its electrical and mechanical properties, allowing the development of materials with specific electronic features for the design of stable and robust electronic devices. Tuning the band gap by chemical surface passivation constitutes a way for the modification of the electronic band gap of these nanowires. We present, the structural and electronic properties of fluorinated SiCNWs, grown along the [111] crystallographic direction, which are investigated by first principles. We consider nanowires with six diameters, varying from 0.35 nm to 2.13 nm, and eight random covering schemes including fully hydrogen- and fluorine terminated ones. Gibbs free energy of formation and electronic properties were calculated for the different surface functionalization schemes and diameters considered. The results indicate that the stability and band gap of SiCNWs can be tuned by surface passivation with fluorine atoms This work was supported by CONACYT infrastructure project 252749 and UNAM-DGAPA-PAPIIT IN106714. A.M. would like to thank for financial support from CONACyT-Retención. Computing resources from proyect SC15-1-IR-27 of DGTIC-UNAM are acknowledged.

  6. On electronic structure of polymer-derived amorphous silicon carbide ceramics

    Science.gov (United States)

    Wang, Kewei; Li, Xuqin; Ma, Baisheng; Wang, Yiguang; Zhang, Ligong; An, Linan

    2014-06-01

    The electronic structure of polymer-derived amorphous silicon carbide ceramics was studied by combining measurements of temperature-dependent conductivity and optical absorption. By comparing the experimental results to theoretical models, electronic structure was constructed for a carbon-rich amorphous silicon carbide, which revealed several unique features, such as deep defect energy level, wide band-tail band, and overlap between the band-tail band and defect level. These unique features were discussed in terms of the microstructure of the material and used to explain the electric behavior.

  7. Development of the SOFIA silicon carbide secondary mirror

    Science.gov (United States)

    Fruit, Michel; Antoine, Pascal; Varin, Jean-Luc; Bittner, Hermann; Erdmann, Matthias

    2003-02-01

    The SOFIA telescope is ajoint NASA-DLR project for a 2.5 m airborne Stratospheric Observatory for IR Astronomy to be flown in a specially adapted Boeing 747 SP plane, Kayser-Threde being resopinsible for the development of the Telescope Optics. The φ 352 mm Secondary Mirror is mounted ona chopping mechanism to allow avoidance of background noise during IR observations. Stiffness associated to lightness is a major demand for such a mirror to achieve high frequency chopping. This leads to select SIlicon Carbide for the mirror blank. Its development has been run by the ASTRIUM/BOOSTEC joint venture SiCSPACE, taking full benefit of the instrinsic properties of the BOOSTEC SiC-100 sintered material, associated to qualified processes specifically developed for space borne mirrors by ASTRIUM. Achieved performances include a low mass of 1.97 kg, a very high stiffness with a first resonant frequency of 1865 Hz and a measured optical surface accuracy of 39 nm rms, using Ion Beam Figuring. It is proposed here to present the major design features of the SOFIA Secondary Mirror, highlighting the main advantages of using Silicon Carbide, the main steps of its development and the achieved optomechanical performances of the developed mirror.

  8. Sintering of oxide and carbide ceramics by electron beam at forevacuum pressure

    Science.gov (United States)

    Dvilis, E.; Tolkachev, O.; Burdovitsin, V.; Khasanov, A.; Petyukevich, M.

    2016-02-01

    Novel approaches for electron beam sintering of zirconia and silicon carbide ceramics have been investigated: application of forevacuum pressure plasma-cathode to compensate the charge induced by the electron beam on the green compact surface, and previous dry powder compaction under powerful ultrasound assistance. Dense YSZ ceramics with submicron and micron grains have been consolidated by electron beam sintering after powder compaction using ultrasound.

  9. Silicon Carbide Being Developed for High-Definition Television (HDTV) Transmitter Modules

    Science.gov (United States)

    Costello, Donald E.

    1999-01-01

    Through a Space Act Agreement, the NASA Lewis Research Center has helped develop the base silicon carbide (SiC) epitaxial growth technology for Westinghouse's efforts to bring silicon carbide products to the marketplace. SiC is a high-temperature, high-voltage semiconductor that can deliver greater than three times the power of conventional silicon devices. The technology was initially disclosed in the 1994 R&T report. NASA Lewis High Temperature Integrated Electronics and Sensors (HTIES) team is developing SiC as a material for advanced semiconductor electronic device applications because SiC-based electronics and sensors can operate in hostile environments where conventional silicon-based electronics cannot function. SiC transmitters hold great promise for television stations because they can convert broadcasts from analog to digital signals. A modular solid-state design provides broadcasters with an option to gradually add modules, increasing the power of their transmitters as they expand their high-definition television (HDTV) coverage. Using these high-power transistors will significantly reduce the space needed for high-power transmitters at television stations and will offer a solid-state solution, reducing long-term maintenance costs. Thus, transmitter manufacturers will be able to abandon their reliance on tube-based technology for high-power transmitters and will be able to build smaller, high-power, solid-state transmitters.

  10. Structure, electronic, mechanical and optical properties of ternary YAl3C3 carbide

    Science.gov (United States)

    Hussain, Altaf; Javed, Athar; Mehmood, Salman; Rasool, M. Nasir; Khan, Muhammad Azhar; Iqbal, Faisal

    2016-05-01

    The electronic structure, mechanical and optical properties of ternary yttrium aluminum carbide (YAl3C3) has been studied by first principles approach. The crystal structure and elastic properties are studied by using Vienna ab initio simulation package (VASP). An orthogonalized linear combination of atomic orbitals (OLCAO) method based on the density functional theory (DFT) is implemented to elucidate the electronic structure and optical properties of ternary YAl3C3 carbide. The YAl3C3 carbide exhibits a narrow indirect band gap, Eg=0.12 eV which shows its poor metallic and/or semiconductor behavior. The effective charge (Q*) calculation reveals more charge transfer from Al-sites as compared to Y-sites which indicates dominant ionic character of Al-sites. The analysis of structure and bond order (BO) calculations show that the Al-C bonds in the basal plane are much stronger as compared to Al-C bonds along the c-axis. The Al-C bonds lying in the basal plane have main contribution into the overall stiffness of YAl3C3 carbide. The effective mass of charge carriers (electrons and holes) and inter-band optical properties (complex dielectric function and optical conductivity) are also studied which show high degree of anisotropy in YAl3C3.

  11. Development of Processing Windows for HVOF Carbide-Based Coatings

    Science.gov (United States)

    Ang, Andrew Siao Ming; Howse, Hugo; Wade, Scott A.; Berndt, Christopher C.

    2016-01-01

    Optimized processing windows for spraying high-quality metal carbide-based coatings are developed using particle diagnostic technology. The cermet coatings were produced via the high-velocity oxygen fuel (HVOF) spray process and are proposed for service applications such as marine hydraulics. The traditional "trial and error" method for developing coating process parameters is not technically robust, as well as being costly and time consuming. Instead, this contribution investigated the use of real-time monitoring of parameters associated with the HVOF flame jets and particles using in-flight particle diagnostics. Subsequently, coatings can be produced with knowledge concerning the molten particle size, temperature, and velocity profile. The analytical results allow identification of optimized coating process windows, which translate to coatings of lower porosity and improved mechanical performance.

  12. Electronic states and potential energy surfaces of rhodium carbide (RhC)

    Science.gov (United States)

    Tan, Hang; Liao, Muzhen; Balasubramanian, K.

    1997-12-01

    Potential energy curves and spectroscopic constants of 23 electronic states of the rhodium carbide (RhC) have been studied using the complete-active-space multi-configuration self-consistent field (CASMCSCF) followed by first-order configuration interaction (FOCI) calculations. Multi-reference singles + doubles configuration interaction (MRSDCI) were used to determine the properties of low-lying electronic states. The nature of chemical bond formation in different states is discussed in terms of their wave function and Mulliken populations.

  13. Electronic structure of cobalt carbide, CoC.

    Science.gov (United States)

    Tzeli, Demeter; Mavridis, Aristides

    2006-07-20

    The ground and 18 low lying excited states of the diatomic molecule cobalt carbide, CoC, have been examined by multireference variational methods (MRCI) combined with quantitative basis sets. All calculated states are bound and correlate adiabatically to the ground-state atoms, Co(a4F) + C(3P). We report complete potential energy curves, equilibrium bond distances, dissociation energies (De), spectroscopic constants, electric dipole moments and spin-orbit splittings. The bonding character of certain states is also discussed with the help of Mulliken distributions and valence-bond-Lewis diagrams. We are practically certain that the ground state is of 2Sigma+ symmetry with a state of 2Delta symmetry lying less than 3 kcal/mol higher, in agreement with the relevant experimental findings. Our best estimate of the X 2Sigma+ dissociation energy is De(D0) = 83(82) kcal/mol at r(e) = 1.541 A, 0.02 A shorter than the experimental bond length. PMID:16836459

  14. Electronic properties of intrinsic and doped amorphous silicon carbide films

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, M. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain)]. E-mail: mvetter@eel.upc.edu; Voz, C. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Ferre, R. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Martin, I. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Orpella, A. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Puigdollers, J. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain); Andreu, J. [Departament de Fisica Aplicada i Optica, Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona (Spain); Alcubilla, R. [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, Gran Capita s/n, Modul C4, E-08034 Barcelona (Spain)

    2006-07-26

    Hydrogenated amorphous silicon carbide (a-SiC{sub x} : H) films have shown excellent surface passivation of crystalline silicon. With the aim of large area deposition of these films the influence of the rf plasma power was investigated. It is found that homogenous deposition with effective surface recombination velocity lower than 100 cms{sup -1} is possible up to 6'' diameter in a simple parallel plate reactor by optimizing deposition parameters. For application in solar cell processes the conductivity of these a-SiC{sub x} : H films might become of importance since good surface passivation results from field-effect passivation which needs an insulating dielectric layer. Therefore, the temperature dependence of the dark dc conductivity of these films was investigated in the temperature range from - 20 to 260 deg. C. Two transition temperatures, T {sub s}{approx}80 deg. C and T {sub s}{approx}170 deg. C, were found where conductivity increases, resp. decreases over-exponential. From Arrhenius plots activation energy (E {sub a}) and conductivity pre-factor ({sigma} {sub 0}) were calculated for a large number of samples with different composition. A correlation between E {sub a} and {sigma} {sub 0} was found giving a Meyer-Neldel relation with a slope of 59 mV, corresponding to a material characteristic temperature T {sub m} = 400 deg. C, and an intercept at {sigma} {sub 00} = 0.1 {omega}{sup -1}cm{sup -1}.

  15. Electronic properties of intrinsic and doped amorphous silicon carbide films

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon carbide (a-SiCx : H) films have shown excellent surface passivation of crystalline silicon. With the aim of large area deposition of these films the influence of the rf plasma power was investigated. It is found that homogenous deposition with effective surface recombination velocity lower than 100 cms-1 is possible up to 6'' diameter in a simple parallel plate reactor by optimizing deposition parameters. For application in solar cell processes the conductivity of these a-SiCx : H films might become of importance since good surface passivation results from field-effect passivation which needs an insulating dielectric layer. Therefore, the temperature dependence of the dark dc conductivity of these films was investigated in the temperature range from - 20 to 260 deg. C. Two transition temperatures, T s∼80 deg. C and T s∼170 deg. C, were found where conductivity increases, resp. decreases over-exponential. From Arrhenius plots activation energy (E a) and conductivity pre-factor (σ 0) were calculated for a large number of samples with different composition. A correlation between E a and σ 0 was found giving a Meyer-Neldel relation with a slope of 59 mV, corresponding to a material characteristic temperature T m = 400 deg. C, and an intercept at σ 00 = 0.1 Ω-1cm-1

  16. Transition metals and their carbides and nitrides: Trends in electronic and structural properties

    International Nuclear Information System (INIS)

    A study of the structural and electronic properties of selected transition metals and their carbides and nitrides is presented. We focus on assessing trends of possible importance for understanding their hardness. Lattice constants, bulk moduli (Bo), and charge densities are calculated using the local density approximation with a pseudopotential plane wave approach. An fcc lattice is employed for the transition metal elements in order to make comparisons and study trends relateable to their carbides and nitrides. Our results show that both increasing the number of valence d electrons and the presence of f electrons in the core lead to larger (Bo). Charge density plots and histograms enable us to explain the nature of the charge distribution in the interstitial region for the different compounds considered. In addition, we include the heavier elements seaborgium, bohrium, and hasnium in order to test further trends. Surprisingly, the calculated Bo for Hs is comparable to that of diamond. copyright 1999 The American Physical Society

  17. Transition metals and their carbides and nitrides: Trends in electronic and structural properties

    Science.gov (United States)

    Grossman, Jeffrey C.; Mizel, Ari; Côté, Michel; Cohen, Marvin L.; Louie, Steven G.

    1999-09-01

    A study of the structural and electronic properties of selected transition metals and their carbides and nitrides is presented. We focus on assessing trends of possible importance for understanding their hardness. Lattice constants, bulk moduli (Bo), and charge densities are calculated using the local density approximation with a pseudopotential plane wave approach. An fcc lattice is employed for the transition metal elements in order to make comparisons and study trends relateable to their carbides and nitrides. Our results show that both increasing the number of valence d electrons and the presence of f electrons in the core lead to larger (Bo). Charge density plots and histograms enable us to explain the nature of the charge distribution in the interstitial region for the different compounds considered. In addition, we include the heavier elements seaborgium, bohrium, and hasnium in order to test further trends. Surprisingly, the calculated Bo for Hs is comparable to that of diamond.

  18. Development of refractory armored silicon carbide by infrared transient liquid phase processing

    Science.gov (United States)

    Hinoki, Tatsuya; Snead, Lance L.; Blue, Craig A.

    2005-12-01

    Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m 2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m 2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing.

  19. Development of refractory armored silicon carbide by infrared transient liquid phase processing

    International Nuclear Information System (INIS)

    Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing

  20. Electronic structure and shearing in nanolaminated ternary carbides

    Science.gov (United States)

    Music, Denis; Sun, Zhimei; Voevodin, Andrey A.; Schneider, Jochen M.

    2006-07-01

    We have studied shearing in M 2AlC phases (M=Sc,Y,La,Ti,Zr,Hf,V,Nb,Ta,Cr,Mo,W) using ab initio calculations. We propose that these phases can be classified into two groups based on the valence electron concentration induced changes in C 44. One group comprises M=V B and VIB, where the C 44 values are approximately 170 GPa and independent of the corresponding MC. The other group includes M=IIIB and IVB, where the C 44 shows a linear dependency with the corresponding MC. This may be understood based on the electronic structure: shear resistant bands are filled in M 2AlC phases with M=V B and VIB, while they are not completely filled when M=IIIB and IVB. This notion is also consistent with our stress-strain analysis. These valence electron concentration induced changes in shear behaviour were compared to previously published valence electron concentration induced changes in compression behaviour [Z. Sun, D. Music, R. Ahuja, S. Li, J.M. Schneider, Phys. Rev. B 70 (2004) 092102]. These classification proposals exhibit identical critical valence electron concentration values for the group boundary. However, the physical mechanisms are not identical: the classification proposal for the bulk modulus is based on MC-A coupling, while shearing is based on MC-MC coupling.

  1. Electronic Structure Studies of Silicon Carbide Anionic Nanoclusters

    Science.gov (United States)

    Pradhan, Prachi

    2005-03-01

    As a continuation of our studies on the high stabilities and electronic structure properties of Si8C2 to Si14C2 clusters and Si60Cn (n=3-6) clusters,^1 we report here ab initio studies of small SimCn^- (1Gaussian03 suite of programs^2 with an all electron 6-311++G** basis set has been used. Complete geometry optimizations of different possible structures have been carried out. Carbon-rich and silicon rich species show distinctly different patterns with respect to the vertical detachment energies. For carbon-rich aggregates, the VDE's show an even odd alternation, similar to that of the carbon anions. We present results on binding energies, relative energies, fragmentation energies, vertical detachment energies, vibrational frequencies, and adiabatic electron affinities^3 for the optimized clusters. Detailed comparisons with published data in the literature will also be presented. * Work supported, in part, by the Welch Foundation, Houston, Texas (Grant No. Y-1525). ^1M. N. Huda and A. K. Ray, Phys. Rev. A (R) 69, 011201 (2004); Eur. Phys. J. D 31, 63 (2004). ^2 Gaussian03, Revision A.1, M. J. Frisch et al., Gaussian Inc., Pittsburgh, PA , 2003. ^3 P. Pradhan and A. K. Ray, J. Mol. Structure (Theochem), in press.

  2. Study of the machining of uranium carbide rods obtained by continuous casting under electronic bombardment

    International Nuclear Information System (INIS)

    The authors consider the various methods of machining uranium mono-carbide and compare them critically in the case of their application to uranium carbide obtained by fusion under an electronic bombardment and continuous casting. This study leads them to propose two mechanical machining methods: cylindrical rectification and center-less rectification, preceded by a preliminary roughing out of a cylinder, the latter appearing more suitable. A study of the machining yields as a function of the diameter of the rough bars and of the diameter of the finished rods has shown that an optimum value of the rough bar diameter exists for each value of the finished rod diameter. It is found that the yield increases as the diameter itself increases, this yield rising from 45 per cent to around 70 per cent as the diameter of the rough bars increases from 25-26 mm to 37-38 mm. (authors)

  3. Electronic structure analyses of the interface between a high refractive index optical glass and carbides

    International Nuclear Information System (INIS)

    High refractive index aspheric glass lenses are often used in digital still cameras. However, in manufacturing, adhesion of softened glass to carbide mold causes various defects on the lens surface. We performed experimental transmission electron microscopy (TEM) observations and molecular dynamics/orbital calculations to investigate the glass-carbide adhesion mechanism. TEM revealed island-shaped glass adhesion on the surface of carbide (glassy carbon: GC). TEM-energy dispersion spectra (EDS) showed reduced atomic ratio of oxygen in adhered glass compared with bulk, indicating adhered glass could undergo reduction. From DV-Xα calculations focused on the oxygen atom on the surface of the glass; OI, as Nb-OI bonds at the glass surface approach GC, an overlap population between OI and C increases while that of the Nb-OI bonds decreases. This suggests that, in agreement with TEM-EDS results, OI of the Nb-OI bond forms no bridging bond such as Nb-OI-C at the glass-GC interface, while the C-OI bonding unit could be isolated at the GC surface, and supports our assumption that reduction of the glass induces adhesion to the GC mold.

  4. Structural and electronic studies of metal carbide clusterfullerene Sc2C2@Cs-C72

    Science.gov (United States)

    Feng, Yongqiang; Wang, Taishan; Wu, Jingyi; Feng, Lai; Xiang, Junfeng; Ma, Yihan; Zhang, Zhuxia; Jiang, Li; Shu, Chunying; Wang, Chunru

    2013-07-01

    We present a metal carbide clusterfullerene Sc2C2@Cs(10528)-C72, whose structure has been baffling for many years. A motional endohedral Sc2C2 cluster, special molecule geometry and electronic structure were found in Sc2C2@Cs(10528)-C72. The paramagnetic Sc2C2@Cs-C72 anion radical was successfully prepared by a chemical reduction method and hyperfine couplings in the ESR spectrum were observed.We present a metal carbide clusterfullerene Sc2C2@Cs(10528)-C72, whose structure has been baffling for many years. A motional endohedral Sc2C2 cluster, special molecule geometry and electronic structure were found in Sc2C2@Cs(10528)-C72. The paramagnetic Sc2C2@Cs-C72 anion radical was successfully prepared by a chemical reduction method and hyperfine couplings in the ESR spectrum were observed. Electronic supplementary information (ESI) available: Experimental details, HPLC chromatogram, and DFT calculations. CCDC 917712. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3nr01739g

  5. Electronic transport properties of an (8,0) carbon/silicon-carbide nanotube heterojunction

    Institute of Scientific and Technical Information of China (English)

    Liu Hongxia; Zhang Heming; Zhang Zhiyong

    2009-01-01

    A two-probe system of the heterojunction formed by an (8,0) carbon nanotube(CNT) and an (8,0)silicon carbide nanotube (SiCNT) was established based on its optimized structure. By using a method combining nonequilibrium Green's function (NEGF) with density functional theory (DFT), the transport properties of the heterojunction were investigated. Our study reveals that the highest occupied molecular orbital (HOMO) has a higher electron density on the CNT section and the lowest unoccupied molecular orbital (LUMO) mainly concentrates on the interface and the SiCNT section. The positive and negative threshold voltages are1.8 and-2.2 V, respectively.

  6. Silicon carbide nanorodes on SiC bulk substrates: synthesis and field electron emission properties

    International Nuclear Information System (INIS)

    Full text: Earlier, we prepared SiC nanowires by a catalyst-assisted process at elevated temperatures from commercially SiC powders. In the study, silicon carbide (SiC) nanorodes were directly grown on the flat surface of commercially SiC bulk substrates. Their structure and chemical composition were studied by Raman spectroscopy and high-resolution transmission electron microscopy. A transparent anode technique was used to examine the field emission properties of the samples. The total current-voltage characteristics were recorded and a current density of 69.29 mA/cm2 was recorded at a field of 4 MV/m. Ref. 1 (author)

  7. Transition metals and their carbides and nitrides: Trends in electronic and structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Grossman, J.C.; Mizel, A.; Cote, M.; Cohen, M.L.; Louie, S.G. (Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States) Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States))

    1999-09-01

    A study of the structural and electronic properties of selected transition metals and their carbides and nitrides is presented. We focus on assessing trends of possible importance for understanding their hardness. Lattice constants, bulk moduli (B[sub o]), and charge densities are calculated using the local density approximation with a pseudopotential plane wave approach. An fcc lattice is employed for the transition metal elements in order to make comparisons and study trends relateable to their carbides and nitrides. Our results show that both increasing the number of valence d electrons and the presence of f electrons in the core lead to larger (B[sub o]). Charge density plots and histograms enable us to explain the nature of the charge distribution in the interstitial region for the different compounds considered. In addition, we include the heavier elements seaborgium, bohrium, and hasnium in order to test further trends. Surprisingly, the calculated B[sub o] for Hs is comparable to that of diamond. [copyright] [ital 1999] [ital The American Physical Society

  8. Electronic properties of a silicon carbide nanotube under uniaxial tensile strain: a density function theory study

    International Nuclear Information System (INIS)

    The electronic properties of an armchair (4,4) single-walled silicon carbide nanotube (SWSiCNT) with the length and diameter of 22.4 and 6.93 A, respectively under different tensile strains are investigated by density functional theory (DFT) calculation. The change of highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gap of the nanotube has been observed during the elongation process. Our results show that the gap will significantly decrease linearly with the increase of axial strain. Two different slopes are found before and after an 11% strain in the profiles of the HOMO-LUMO gap. The radial buckling has been performed to investigate the radial geometry of nanotube. The partial density of states (PDOS) of two neighboring Si and C atoms of the nanotube are further studied to demonstrate the strain effect on the electronic structure of SiC nanotube. The PDOS results exhibit that the occupied states of Si atom and the unoccupied states of C atom are red-shifted and blue-shifted under stretching, respectively. Mulliken charge analysis reveals that Si and C atoms will become less ionic under the larger strain. The electron differences of silicon carbide nanotube (SiCNT) on tensile loading are also studied.

  9. 2H-SiC Dendritic Nanocrystals In Situ Formation from Amorphous Silicon Carbide under Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Under electron beam irradiation, the in-situ formation of 2H-SiC dentritic nanocrystals from amorphous silicon carbide at room temperature was observed. The homogenous transition mainly occurs at the thin edge and on the surface of specimen where the energy obtained from electron beam irradiation is high enough to cause the amorphous crystallizing into 2H-SiC.

  10. Silicon carbide based one-dimensional nanostructure growth: towards electronics and biology perspectives

    International Nuclear Information System (INIS)

    One-dimensional (1D) nanostructures such as nanowires or nanotubes have attracted great interest in fundamental research as well as potential breakthrough applications. Among many materials, silicon carbide (SiC) has very interesting physical, chemical and electronic properties. This is why silicon carbide based 1D nanostructures, which combine excellent intrinsic properties with low dimensionality, have great potential. In this topical review, the growth of SiC 1D nanostructures is addressed as well as the potential applications of these peculiar nano-objects. This subject is first introduced by the interest in this material and by a summing up of the state of the art of SiC nanowire growth. In the second part, Si–SiC core–shell nanowire synthesis is described, followed by the growth of SiC nanotubes. In particular, these two kinds of nanostructures can be obtained via Si nanowire carburization. The third part is dedicated to the control of the synthesis from Si–SiC core–shell nanowires to SiC nanotubes using this original technique. Then, an alternative top-down approach to synthesize SiC 1D nanostructures is described. Finally, preliminary results towards integration for biology, energy and electronics are provided. (topical review)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-01

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

  12. Development and Characterization of the Bonding and Integration Technologies Needed for Fabricating Silicon Carbide Based Injector Components

    Science.gov (United States)

    Halbig,Michael C.; Singh, Mrityunjay

    2008-01-01

    Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding technology, titanium interlayers (coatings and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness, and processing time were investigated. Electron microprobe analysis was used to identify the reaction formed phases. In the diffusion bonds, an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner interlayers of pure titanium and/or longer processing times resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Nondestructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

  13. Modulation of electronic properties of silicon carbide nanotubes via sulphur-doping: An ab initio study

    Science.gov (United States)

    Singh, Ram Sevak; Solanki, Ankit

    2016-03-01

    Silicon carbide nanotubes (SiCNTs) have received a great deal of scientific and commercial interest due to their intriguing properties that include high temperature stability and electronic properties. For their efficient and widespread applications, tuning of electronic properties of SiCNTs is an attractive study. In this article, electronic properties of sulphur doped (S-doped) zigzag (9 , 0) SiCNT is investigated by ab initio calculations based on density functional theory (DFT). Energy band structures and density of states of fully optimized undoped and doped structures with varying dopant concentration are calculated. S-doped on C-site of the nanotube exhibits a monotonic reduction of energy gap with increase in dopant concentration, and the nanotube transforms from semiconductor to metal at high dopant concentration. In case of S-doped on Si-site doping has less influence on modulating electronic structures, which results in reduction of energy gap up to a moderate doping concentration. Importantly, S preferential substitutes of Si-sites and the nanotube with S-doped on Si-site are energetically more stable as compared to the nanotube with S-doped on C-site. The study of tunable electronic properties in S-doped SiCNT may have potential in fabricating nanoelectronic devices, hydrogen storage and gas sensing applications.

  14. The electron-ion dynamics in ionization of lithium carbide molecule under femtosecond laser pulses

    Science.gov (United States)

    Zhang, Xiaoqin; Wang, Feng; Hong, Xuhai; Su, Wenyong; Gou, Bingcong; Chen, Huimin

    2016-08-01

    The electron-ion dynamics of the linear lithium carbide molecule under femtosecond laser pulses have been investigated in the framework of Ehrenfest molecular dynamics, in which valence electrons are treated quantum mechanically by time-dependent density functional theory (TDDFT) and ions are described classically. The on- and off-resonant multiphoton ionization processes have been induced by regulating laser frequency and laser intensity. The laser pulse with on-resonant frequency induces pronounced enhancement in electron ionization, bond length vibration, and energy absorption. Moreover, the coulomb explosion is preferred to occur in the on-resonant case, which is in qualitative agreement with previous theoretical investigations. The subtle relations between escaped electron number and absorbed photon number are well discussed with the increasing of laser intensity. Finally, the effect of self-interaction error is analyzed by comparing escaped electron number calculated with LDA and LDA-ADSIC. And the revTPSS-meta-GGA, a currently more accurate nonempirical exchange-correlation energy functional from a point of static density functional theory, is introduced to display its capability for the description of ionization process within nonlinear and the nonperturbative regime of isolated systems.

  15. Effect of radiation-thermal treatment with focused electron beam on fine atomic structure and carbide formation in roll steel

    International Nuclear Information System (INIS)

    Using nuclear physics methods - positron annihilation and nuclear gamma-resonance vacancy type point defects concentration and distribution changes as well as carbide phase precipitation in steel surface layers were studied. Steel for color deformation rolls was irradiated with focused 1.5 MeV electron beam at 400-550 deg C

  16. Electronic and magnetic properties of yttrium-doped silicon carbide nanotubes: Density functional theory investigations

    Energy Technology Data Exchange (ETDEWEB)

    Khaira, Jobanpreet S., E-mail: joban10173@gmail.com [Department of Nanotechnology, Sri Guru Granth Sahib World University, Fatehgarh Sahib, Punjab -202002 (India); Jain, Richa N. [Indian Institute Of Science, Bangalore, 560012 (India); Chakraborty, Brahmananda; Ramaniah, Lavanya M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2015-06-24

    The electronic structure of yttrium-doped Silicon Carbide Nanotubes has been theoretically investigated using first principles density functional theory (DFT). Yttrium atom is bonded strongly on the surface of the nanotube with a binding energy of 2.37 eV and prefers to stay on the hollow site at a distance of around 2.25 Å from the tube. The semi-conducting nanotube with chirality (4, 4) becomes half mettalic with a magnetic moment of 1.0 µ{sub B} due to influence of Y atom on the surface. There is strong hybridization between d orbital of Y with p orbital of Si and C causing a charge transfer from d orbital of the Y atom to the tube. The Fermi level is shifted towards higher energy with finite Density of States for only upspin channel making the system half metallic and magnetic which may have application in spintronic devices.

  17. Electronic and magnetic properties of yttrium-doped silicon carbide nanotubes: Density functional theory investigations

    International Nuclear Information System (INIS)

    The electronic structure of yttrium-doped Silicon Carbide Nanotubes has been theoretically investigated using first principles density functional theory (DFT). Yttrium atom is bonded strongly on the surface of the nanotube with a binding energy of 2.37 eV and prefers to stay on the hollow site at a distance of around 2.25 Å from the tube. The semi-conducting nanotube with chirality (4, 4) becomes half mettalic with a magnetic moment of 1.0 µB due to influence of Y atom on the surface. There is strong hybridization between d orbital of Y with p orbital of Si and C causing a charge transfer from d orbital of the Y atom to the tube. The Fermi level is shifted towards higher energy with finite Density of States for only upspin channel making the system half metallic and magnetic which may have application in spintronic devices

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

    Energy Technology Data Exchange (ETDEWEB)

    Nappe, J.C. [Ecole Nationale Superieure des Mines, SPIN/PMMC, LPMG UMR CNRS 5148, 158 cours Fauriel, 42023 Saint-Etienne cedex 2 (France)], E-mail: nappe@emse.fr; Grosseau, Ph. [Ecole Nationale Superieure des Mines, SPIN/PMMC, LPMG UMR CNRS 5148, 158 cours Fauriel, 42023 Saint-Etienne cedex 2 (France); Audubert, F. [CEA, DEN, DEC/SPUA/LTEC, Cadarache, 13108 St Paul lez Durance (France); Guilhot, B. [Ecole Nationale Superieure des Mines, Centre CIS, 158 cours Fauriel, 42023 Saint-Etienne cedex 2 (France); Beauvy, M. [CEA, DEN, DEC/SPUA/LTEC, Cadarache, 13108 St Paul lez Durance (France); Benabdesselam, M. [Universite de Nice - Sophia Antipolis, LPMC UMR CNRS 6622, Parc Valrose, 06108 Nice cedex 2 (France); Monnet, I. [GANIL/CIMAP/CIRIL, bd. Henri Becquerel, BP 55027, 14076 Caen cedex 5 (France)

    2009-03-31

    Thanks to their refractoriness, carbides are sensed as fuel coating for the IVth generation of reactors. Among those studied, the Ti{sub 3}SiC{sub 2} ternary compound can be distinguished for its noteworthy mechanical properties: the nanolamellar structure imparts to this material some softness as well as better toughness than other classical carbides such as SiC or TiC. However, under irradiation, its behaviour is still unknown. In order to understand this behaviour, specimens were irradiated with heavy ions of different energies, then characterised. The choice of energies used allowed separation of the effects of nuclear interactions from those of electronic ones.

  19. A study on the development of silicon carbide materials for nuclear application

    International Nuclear Information System (INIS)

    Silicon carbide was synthesized by reaction sintering process from carbon and silicon powders as starting materials. The effects of two processing parameters, i.e., heat treatment time and temperature, were examined (to characterize the reaction sintering process) in terms of the degree of reaction and phase developed during heat treatment. The final products after reaction of silicon and carbon powders were identified as β-SiC having ZnS crystal structure. Sintering of cordierite ceramics which was used as an high temperature inorganic binder to fabricate ceramically bound silicon carbide, and phase identification of the sintered ceramics by X-ray powder diffraction techniques. (Author)

  20. 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...

  1. Characterization of LPCVD amorphous silicon carbide (a-SiC) as material for electron transparent windows

    International Nuclear Information System (INIS)

    We investigate on the physical and chemical properties of non-stoichiometric amorphous silicon carbide (a-SiCx) thin layers deposited by low-pressure chemical vapor deposition (LPCVD). Characterizations are specifically tailored to understand the suitability of a-SiCx as electron transparent window material. The structure, composition, continuity, intrinsic stress, etch-rates and roughness of the layers are determined. The a-SiCx layers are highly uniform and continuous, showing tensile intrinsic stress and high chemical inertness. The layer with the lowest roughness (0.22 nm) and intrinsic stress (0.7 GPa) is employed to fabricate electron transparent windows of 16 nm for use in a Transmission Electron Microscope (TEM). The resulting windows are highly transparent, enabling the acquisition of TEM images down to the resolution limit of the microscope (0.12 nm). Moreover, the a-SiCx windows show a resistance to electron beam damage which is up to 9 times higher than that of the commonly employed low-stress LPCVD silicon nitride (SiNx). Therefore, the proposed a-SiCx is particularly suited for TEM experiments where high chemical inertness and/or long exposures to the TEM electron beam are required. In addition, the a-SiCx layer could advantageously be employed in the design of microelectromechanical systems (MEMS), especially those operating in harsh environments. - Highlights: ► Very thin non-stoichiometric amorphous SiC (a-SiCx) layers are deposited by LPCVD. ► Layers of 20 nm are continuous, show tensile stress and high chemical inertness. ► Electron transparent windows made of a-SiCx are fabricated. ► a-SiCx windows are highly transparent allowing TEM images with 0.12 nm resolution. ► a-SiCx windows show high resistance to TEM electron beam

  2. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    Science.gov (United States)

    Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

    2016-01-01

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  3. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    International Nuclear Information System (INIS)

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance

  4. Impact of Radiation Hardness and Operating Temperatures of Silicon Carbide Electronics on Space Power System Mass

    Science.gov (United States)

    Juhasz, Albert J.; Tew, Roy C.; Schwarze, Gene E.

    1998-01-01

    The effect of silicon carbide (SiC) electronics operating temperatures on Power Management and Distribution (PMAD), or Power Conditioning (PC), subsystem radiator size and mass requirements was evaluated for three power output levels (100 kW(e) , 1 MW(e), and 10 MW(e)) for near term technology ( i.e. 1500 K turbine inlet temperature) Closed Cycle Gas Turbine (CCGT) power systems with a High Temperature Gas Reactor (HTGR) heat source. The study was conducted for assumed PC radiator temperatures ranging from 370 to 845 K and for three scenarios of electrical energy to heat conversion levels which needed to be rejected to space by means of the PC radiator. In addition, during part of the study the radiation hardness of the PC electronics was varied at a fixed separation distance to estimate its effect on the mass of the instrument rated reactor shadow shield. With both the PC radiator and the conical shadow shield representing major components of the overall power system the influence of the above on total power system mass was also determined. As expected, results show that the greatest actual mass savings achieved by the use of SiC electronics occur with high capacity power systems. Moreover, raising the PC radiator temperature above 600 K yields only small additional system mass savings. The effect of increased radiation hardness on total system mass is to reduce system mass by virtue of lowering the shield mass.

  5. Mechanical, electronic, and thermodynamic properties of zirconium carbide from first-principles calculations

    Science.gov (United States)

    Yang, Xiao-Yong; Lu, Yong; Zheng, Fa-Wei; Zhang, Ping

    2015-11-01

    Mechanical, electronic, and thermodynamic properties of zirconium carbide have been systematically studied using the ab initio calculations. The calculated equilibrium lattice parameter, bulk modulus, and elastic constants are all well consistent with the experimental data. The electronic band structure indicates that the mixture of C 2p and Zr 4d and 4p orbitals around the Fermi level makes a large covalent contribution to the chemical bonds between the C and Zr atoms. The Bader charge analysis suggests that there are about 1.71 electrons transferred from each Zr atom to its nearest C atom. Therefore, the Zr-C bond displays a mixed ionic/covalent character. The calculated phonon dispersions of ZrC are stable, coinciding with the experimental measurement. A drastic expansion in the volume of ZrC is seen with increasing temperature, while the bulk modulus decreases linearly. Based on the calculated phonon dispersion curves and within the quasi-harmonic approximation, the temperature dependence of the heat capacities is obtained, which gives a good description compared with the available experimental data. Project supported by the National Natural Science Foundation of China (Grant No. 51071032).

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

    Energy Technology Data Exchange (ETDEWEB)

    baney, Ronald; Tulenko, James

    2012-11-20

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

  7. Investigation of electronic structure of hexagonal vanadium and niobium carbides and nitrides by MO LCAO method

    International Nuclear Information System (INIS)

    By the MO LCAO cluster method calculations of vanadium and niobium h.c.p. - carbides nitrides are performed. The problems of chemical bonds formation in these phases are investigated, the results are compared with the available spectra of X-ray emission of hexagonal V, Nb carbides and nitrides

  8. Pressure-induced variation of structural, elastic, vibrational, electronic, thermodynamic properties and hardness of Ruthenium Carbides

    Science.gov (United States)

    Gopalakrishna Pillai, Harikrishnan; Kulangara Madam, Ajith; Natarajan, Sathish; Chandra, Sharat; Mundachali Cheruvalath, Valsakumar

    2016-07-01

    Three of the five structures obtained from the evolutionary algorithm based structure search of Ruthenium Carbide systems in the stoichiometries RuC, Ru2C and Ru3C are relaxed at different pressures in the range 0-200 GPa and the pressure-induced variation of their structural, elastic, dynamical, electronic and thermodynamic properties as well as hardness is investigated in detail. No structural transition is present for these systems in this pressure range. RuC-Zinc blende is mechanically and dynamically unstable close to 100 GPa. RuC-Rhombohedral and Ru3C-Hexagonal retain mechanical and dynamical stability up to 200 GPa. For all three systems the electronic bands and density of states spread out with pressure and the band gap increases with pressure for the semiconducting RuC-Zinc blende. From the computed IR spectrum of RuC-Zinc blende at 50 GPa it is noted that the IR frequency increases with pressure. Using a semi-empirical model for hardness it is estimated that hardness of all three systems consistently increases with pressure. The hardness of RuC-Zinc blende increases towards the superhard regime up to the limiting pressure of its mechanical stability while that of RuC-Rhombohedral becomes 30 GPa at the pressure of 150 GPa.

  9. Role of the surface effect on the structural, electronic and mechanical properties of the carbide MXenes

    Science.gov (United States)

    Zha, Xian-Hu; Luo, Kan; Li, Qiuwu; Huang, Qing; He, Jian; Wen, Xiaodong; Du, Shiyu

    2015-07-01

    The two-dimensional material MXene has recently attracted interest for its excellent performance in diverse perspectives. Etched from the parental MAX phase with hydrofluoric acid, the synthesized MXene surface is normally functionalized by oxygen (-O), fluorine (-F) or hydroxyl (-OH) groups. Herein, using first-principles density functional calculations, we investigate the structural, mechanical and electronic properties of the carbide MXene M2CT2 (M=Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W; T=-O, -F, -OH). Both the M atom and the surface group T have a significant effect on the MXenes properties. Generally, oxygen functionalized MXenes present smaller lattice parameters and stronger mechanical strength compared to those functionalized by fluorine and hydroxyl groups. \\text{Sc}2\\text{CO}2 exhibits the smallest interlayer thickness and \\text{W}2\\text{CO}2 shows the strongest mechanical strength. In regard to electronic properties, five oxygen functionalized members M2CO2 (M=Sc, Ti, Zr, Hf, W), two fluorine functionalized members M2CF2 (M=Sc, Mo), and hydroxyl functionalized Sc2C(OH)2 present semiconducting characteristics, but only Sc2C(OH)2 exhibits a direct band gap.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nixdorf, R.D.

    2003-04-22

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

  11. Analysis of bonding and d-electron count in the transition-metal carbides and transition-metal-silicide carbides with discrete linear M-C-M units (M = Cr, Fe, Re) by electronic structure calculations

    International Nuclear Information System (INIS)

    Electronic structures of the silicide carbides Tm2Fe2Si2C, Th2Re2Si2C, and ThFe2SiC and the carbide Ho2Cr2C3 were calculated, using the extended Hueckel tight binding method, to probe the d-electron counts of their transition metal atoms M (Cr, Fe, Re) the bonding of their linear M-C-M (M = Cr, Fe, Re) units. The nature of the short interlayer X hor-ellipsis X (X = C, Si) bonds in Tm2Fe2Si2C, Th2Re2Si2C, and Ho2Cr2C3 was also examined. The study shows that the M-C bonds of the M-C-M units exist as double bonds. There is significant bonding in the interlayer Si hor-ellipsis Si contacts of the silicide carbides R2M2Si2C (M = Fe, Re). The transition-metal atoms exist as d10 ions in Tm2Fe2Si2C and Th2Re2Si2C. The d-electron count is slightly lower than d10 in ThFe2SiC and close to d5 in Ho2Cr2C3

  12. Experimental and ab initio study of enhanced resistance to amorphization of nanocrystalline silicon carbide under electron irradiation

    Science.gov (United States)

    Jamison, Laura; Zheng, Ming-Jie; Shannon, Steve; Allen, Todd; Morgan, Dane; Szlufarska, Izabela

    2014-02-01

    The crystalline-to-amorphous transition in nanocrystalline silicon carbide (ncSiC) has been studied using 1.25 MeV electron irradiation. When compared to literature values for single crystal silicon carbide under electron irradiation, an increase in the dose to amorphization (DTA) was observed, indicative of an increase in radiation resistance. Factors that contribute to this improvement are grain refinement, grain texture, and a high density of stacking faults (SFs) in this sample of ncSiC. To test the effect of SFs on the DTA, density functional theory simulations were conducted. It was found that SFs reduced the energy barriers for both Si interstitial migration and the rate-limiting defect recovery reaction, which may explain the increased DTA.

  13. 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...

  14. Electroextraction of boron from boron carbide scrap

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-10-15

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

  15. Electroextraction of boron from boron carbide scrap

    International Nuclear Information System (INIS)

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

  16. Silicon carbide, an emerging high temperature semiconductor

    Science.gov (United States)

    Matus, Lawrence G.; Powell, J. Anthony

    In recent years, the aerospace propulsion and space power communities have expressed a growing need for electronic devices that are capable of sustained high temperature operation. Applications for high temperature electronic devices include development instrumentation within engines, engine control, and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Other earth-based applications include deep-well drilling instrumentation, nuclear reactor instrumentation and control, and automotive sensors. To meet the needs of these applications, the High Temperature Electronics Program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. Research is focussed on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of silicon carbide electronic devices and integrated sensors. The progress made in developing silicon carbide is presented, and the challenges that lie ahead are discussed.

  17. Secondary electron yield and Auger electron spectroscopy measurements on oxides, carbide, and nitride of niobium

    International Nuclear Information System (INIS)

    Secondary electron yield measurements before and after Ar ion sputtercleaning were made on Nb and Nb compounds of interest for rf superconductingcavities. Total secondary electron yields (sigma) for primary energies 20--1500 eV were measured for solid Nb (sigma/sub max/ = 1.3 at 300 eV), anodized Nb2O5 (sigma/sub max/ = 1.2 at 300 eV), and powders of Nb(sigma/sub max/ = 1.0 at 400 eV), NbO (sigma/sub max/ = 0.9 at 400 eV), NbO2 (sigma/sub max/ = 1.0 at 400 eV), Nb2O5 (sigma/sub max/ = 0.95 at 400 eV), NbC(sigma/sub max/ = 0.8 at 400 eV), and NbN (sigma/sub max/ = 0.8 at 500 eV). Determinations were made for Auger elemental sensitivities, and the relationship between Auger peak heights and oxide stoichiometry is discussed. The sputter etch rate of anodized Nb2O5 was measured by depth profiling anodic coatings of known thickness

  18. Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

    International Nuclear Information System (INIS)

    The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm

  19. Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

    Energy Technology Data Exchange (ETDEWEB)

    Gromov, Victor E., E-mail: gromov@physics.sibsiu.ru; Budovskikh, Evgeniy A., E-mail: budovskikh-ea@physics.sibsiu.ru; Bashchenko, Lyudmila P., E-mail: gromov@physics.sibsiu.ru; Kobzareva, Tatyana Yu., E-mail: gromov@physics.sibsiu.ru; Semin, Alexander P., E-mail: gromov@physics.sibsiu.ru [Siberian State Industrial University, Novokuznetsk, 654007 (Russian Federation); Ivanov, Yurii F., E-mail: yufi55@mail.ru [Institute of High Current Electronics SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Wang, Xinli, E-mail: wangxl520@hotmail.com [Northeastern University, Liaoning, Shenyang 110819 China (China)

    2015-10-27

    The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm.

  20. Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

    Science.gov (United States)

    Gromov, Victor E.; Budovskikh, Evgeniy A.; Ivanov, Yurii F.; Bashchenko, Lyudmila P.; Wang, Xinli; Kobzareva, Tatyana Yu.; Semin, Alexander P.

    2015-10-01

    The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm.

  1. Dangling bond electron spin-lattice relaxation in rf-sputtered hydrogenated amorphous silicon and silicon carbide

    International Nuclear Information System (INIS)

    Electron spin resonance methods have been used to measure the temperature dependence of the spin-lattice relaxation time T1 of dangling bond electrons in hydrogenated amorphous silicon and silicon carbide samples prepared by radio frequency sputtering. The T1 measurements were made by a combination of continuous-wave absorption mode saturation and periodic adiabatic passage methods over the temperature range 100--400 K, yielding T/sup -1/1proportionalT2 behavior consistent with relaxation by two-level systems

  2. Development of an aluminum nitride-silicon carbide material set for high-temperature sensor applications

    Science.gov (United States)

    Griffin, Benjamin A.; Habermehl, Scott D.; Clews, Peggy J.

    2014-06-01

    A number of important energy and defense-related applications would benefit from sensors capable of withstanding extreme temperatures (>300°C). Examples include sensors for automobile engines, gas turbines, nuclear and coal power plants, and petroleum and geothermal well drilling. Military applications, such as hypersonic flight research, would also benefit from sensors capable of 1000°C. Silicon carbide (SiC) has long been recognized as a promising material for harsh environment sensors and electronics because it has the highest mechanical strength of semiconductors with the exception of diamond and its upper temperature limit exceeds 2500°C, where it sublimates rather than melts. Yet today, many advanced SiC MEMS are limited to lower temperatures because they are made from SiC films deposited on silicon wafers. Other limitations arise from sensor transduction by measuring changes in capacitance or resistance, which require biasing or modulation schemes that can with- stand elevated temperatures. We are circumventing these issues by developing sensing structures directly on SiC wafers using SiC and piezoelectric aluminum nitride (AlN) thin films. SiC and AlN are a promising material combination due to their high thermal, electrical, and mechanical strength and closely matched coefficients of thermal expansion. AlN is also a non-ferroelectric piezoelectric material, enabling piezoelectric transduction at temperatures exceeding 1000°C. In this paper, the challenges of incorporating these two materials into a compatible MEMS fabrication process are presented. The current progress and initial measurements of the fabrication process are shown. The future direction and the need for further investigation of the material set are addressed.

  3. Deep Etching Process Developed for the Fabrication of Silicon Carbide Microsystems

    Science.gov (United States)

    Beheim, Glenn M.

    2000-01-01

    Silicon carbide (SiC), because of its superior electrical and mechanical properties at elevated temperatures, is a nearly ideal material for the microminiature sensors and actuators that are used in harsh environments where temperatures may reach 600 C or greater. Deep etching using plasma methods is one of the key processes used to fabricate silicon microsystems for more benign environments, but SiC has proven to be a more difficult material to etch, and etch depths in SiC have been limited to several micrometers. Recently, the Sensors and Electronics Technology Branch at the NASA Glenn Research Center at Lewis Field developed a plasma etching process that was shown to be capable of etching SiC to a depth of 60 mm. Deep etching of SiC is achieved by inductive coupling of radiofrequency electrical energy to a sulfur hexafluoride (SF6) plasma to direct a high flux of energetic ions and reactive fluorine atoms to the SiC surface. The plasma etch is performed at a low pressure, 5 mtorr, which together with a high gas throughput, provides for rapid removal of the gaseous etch products. The lateral topology of the SiC microstructure is defined by a thin film of etch-resistant material, such as indium-tin-oxide, which is patterned using conventional photolithographic processes. Ions from the plasma bombard the exposed SiC surfaces and supply the energy needed to initiate a reaction between SiC and atomic fluorine. In the absence of ion bombardment, no reaction occurs, so surfaces perpendicular to the wafer surface (the etch sidewalls) are etched slowly, yielding the desired vertical sidewalls.

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

    International Nuclear Information System (INIS)

    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)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

  5. Development of transparent polycrystalline beta-silicon carbide

    Science.gov (United States)

    Bayya, Shyam S.; Villalobos, Guillermo R.; Hunt, Michael P.; Sanghera, Jasbinder S.; Sadowski, Bryan M.; Aggarwal, Ishwar D.; Cinibulk, Michael; Carney, Carmen; Keller, Kristin

    2013-09-01

    Transparent beta-SiC is of great interest because its high strength, low coefficient of thermal expansion, very high thermal conductivity, and cubic crystal structure give it a very high thermal shock resistance. A transparent, polycrystalline beta-SiC window will find applications in armor, hypersonic missiles, and thermal control for thin disc lasers. SiC is currently available as either small transparent vapor grown disks or larger opaque shapes. Neither of which are useful in window applications. We are developing sintering technology to enable transparent SiC ceramics. This involves developing procedures to make high purity powders and studying their densification behavior. We have been successful in demonstrating transparency in thin sections using Field Assisted Sintering Technology (FAST). This paper will discuss the reaction mechanisms in the formation of beta-SiC powder and its sintering behavior in producing transparent ceramics.

  6. PLD deposition of tungsten carbide contact for diamond photodiodes. Influence of process conditions on electronic and chemical aspects

    International Nuclear Information System (INIS)

    Tungsten carbide, WC, contacts behave as very reliable Schottky contacts for opto-electronic diamond devices. Diamond is characterized by superior properties in high-power, high frequency and high-temperature applications, provided that thermally stable electrode contacts will be realized. Ohmic contacts can be easily achieved by using carbide-forming metals, while is difficult to get stable Schottky contacts at elevated temperatures, due to the interface reaction and/or inter-diffusion between metals and diamond. Novel type of contacts, made of tungsten carbide, WC, seem to be the best solution, for their excellent thermal stability, high melting point, oxidation and radiation resistance and good electrical conductivity. Our research was aimed at using pulsed laser deposition for WC thin film deposition, optimizing experimental parameters, to obtain a final device characterized by excellent electronic properties, as a detector for radiation in deep UV or as X-ray dosimeter. We deposited our films by laser ablation from a target of pure WC, using different reaction conditions (i.e., substrate heating, vacuum or reactive atmosphere (CH4/Ar), RF plasma activated), to optimize both the stoichiometry of the film and its structure. Trying to obtain a material with the best electronic response, we used also two sources of laser radiation for target ablation, i.e., nano-second pulsed excimer laser ArF, and ultra-short fs Ti:Sapphire laser. The structure and chemical aspects have been evaluated by Raman and X-ray photoelectron spectroscopy (XPS), while the dosimeter photodiode response has been tested by the I–V measurements, under soft X-ray irradiation.

  7. PLD deposition of tungsten carbide contact for diamond photodiodes. Influence of process conditions on electronic and chemical aspects

    Science.gov (United States)

    Cappelli, E.; Bellucci, A.; Orlando, S.; Trucchi, D. M.; Mezzi, A.; Valentini, V.

    2013-08-01

    Tungsten carbide, WC, contacts behave as very reliable Schottky contacts for opto-electronic diamond devices. Diamond is characterized by superior properties in high-power, high frequency and high-temperature applications, provided that thermally stable electrode contacts will be realized. Ohmic contacts can be easily achieved by using carbide-forming metals, while is difficult to get stable Schottky contacts at elevated temperatures, due to the interface reaction and/or inter-diffusion between metals and diamond. Novel type of contacts, made of tungsten carbide, WC, seem to be the best solution, for their excellent thermal stability, high melting point, oxidation and radiation resistance and good electrical conductivity. Our research was aimed at using pulsed laser deposition for WC thin film deposition, optimizing experimental parameters, to obtain a final device characterized by excellent electronic properties, as a detector for radiation in deep UV or as X-ray dosimeter. We deposited our films by laser ablation from a target of pure WC, using different reaction conditions (i.e., substrate heating, vacuum or reactive atmosphere (CH4/Ar), RF plasma activated), to optimize both the stoichiometry of the film and its structure. Trying to obtain a material with the best electronic response, we used also two sources of laser radiation for target ablation, i.e., nano-second pulsed excimer laser ArF, and ultra-short fs Ti:Sapphire laser. The structure and chemical aspects have been evaluated by Raman and X-ray photoelectron spectroscopy (XPS), while the dosimeter photodiode response has been tested by the I-V measurements, under soft X-ray irradiation.

  8. Development of high strength hot rolled low carbon copper-bearing steel containing nanometer sized carbides

    International Nuclear Information System (INIS)

    A low carbon ferritic steel was alloyed with Ti, Mo and Cu with the intention of achieving greater increment in strength by multiple precipitate strengthening. The steel is hot rolled and subjected to interrupted cooling to enable precipitation of Ti–Mo carbides and copper. Thermodynamic calculations were carried out to determine equilibrium phase fractions at different temperatures. Microstructure characterization using transmission electron microscopy and composition analysis revealed that the steel contains ~5 nm size precipitates of (Ti,Mo)C. Precipitation kinetics calculations using MatCalc software showed that mainly body centered cubic copper precipitates of size < 5nm form under the cooling conditions in the present study. The steel has the high tensile strength of 853 MPa and good ductility. The yield strength increases by 420 MPa, which is more than that achieved in hot rolled low carbon ferritic steels with only copper precipitates or only carbide precipitates. The precipitation and strengthening contribution of copper and (Ti,Mo)C precipitates and their effect on the work hardening behavior is discussed

  9. PHERMEX electron gun development

    International Nuclear Information System (INIS)

    The PHERMEX facility is a 50-MHz standing-wave linear accelerator. Electrons are injected, accelerated, and transported to a tungsten target where bremsstrahlung x rays are generated for flash radiography of hydrodynamic systems. The purpose of this article is to describe the progress of PHERMEX electron gun development. The goal of this program is to generate and transport a 200-ns, 1-MV, 1-kA electron beam into the first PHERMEX accelerating cavity. The standard gun is operated at a pulse voltage of 550 kV, which is the limit determined by internal breakdown of the vacuum insulator. This insulator has been redesigned, and the gun has been pulsed at 750 kV without internal breakdown. At present, the current output is not limited by voltage but by a phenomenon called pulse shortening, which occurs at a pulse voltage of approximately 650 kV. The phenomenon has been investigated and the results are presented

  10. Effect of xenon on the structural phase state of the surface layer of cemented carbide under pulsed electron-beam irradiation

    Science.gov (United States)

    Ovcharenko, Vladimir E.; Ivanov, Yurii F.; Mohovikov, Alexey A.; Baohai, Yu; Cai, Xiaolong; Zhong, Lisheng; Xu, Yunhua

    2015-10-01

    A comparative analysis of the surface-layer microstructure of a tungsten-based cemented carbide modified with pulsed high-energy electron beams generated by gas-discharge plasmas and of the tool life of metal-cutting plates prepared from this alloy is performed. The choice of a plasma-forming gas providing for the emission of electrons out of the plasma-filled cathode is shown to have a profound influence both on the formation process of nano-sized structural-phase states in the surface layer of the cemented carbide and on the tool life of the metal-cutting plates prepared from this alloy.

  11. Effect of xenon on the structural phase state of the surface layer of cemented carbide under pulsed electron-beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ovcharenko, Vladimir E., E-mail: ove45@mail.ru [Institute of Strength physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Polytechnic University, Tomsk, 634050 (Russian Federation); Ivanov, Yurii F., E-mail: yufi55@mail.ru [National Research Polytechnic University, Tomsk, 634050 (Russian Federation); High-Current Electronics Institute SB RAS, Tomsk, 634055 (Russian Federation); Mohovikov, Alexey A., E-mail: maa28@rambler.ru [Technological Institute Branch of Tomsk Polytechnic University, Yurga, Kemerovo region, 652055 (Russian Federation); Baohai, Yu, E-mail: bhyu@imr.ac.cn; Cai, Xiaolong, E-mail: xiaolongcai2015@163.com; Zhong, Lisheng, E-mail: zhonglisheng1984@163.com; Xu, Yunhua, E-mail: yunhuaxu2013@163.com [School of Material Science and Engineering, Xi’an University of Technology, Xi’an Shaanxi, 710048 (China)

    2015-10-27

    A comparative analysis of the surface-layer microstructure of a tungsten-based cemented carbide modified with pulsed high-energy electron beams generated by gas-discharge plasmas and of the tool life of metal-cutting plates prepared from this alloy is performed. The choice of a plasma-forming gas providing for the emission of electrons out of the plasma-filled cathode is shown to have a profound influence both on the formation process of nano-sized structural-phase states in the surface layer of the cemented carbide and on the tool life of the metal-cutting plates prepared from this alloy.

  12. Effect of xenon on the structural phase state of the surface layer of cemented carbide under pulsed electron-beam irradiation

    International Nuclear Information System (INIS)

    A comparative analysis of the surface-layer microstructure of a tungsten-based cemented carbide modified with pulsed high-energy electron beams generated by gas-discharge plasmas and of the tool life of metal-cutting plates prepared from this alloy is performed. The choice of a plasma-forming gas providing for the emission of electrons out of the plasma-filled cathode is shown to have a profound influence both on the formation process of nano-sized structural-phase states in the surface layer of the cemented carbide and on the tool life of the metal-cutting plates prepared from this alloy

  13. Experimental studies of laser-ablated zirconium carbide plasma plumes: Fuel corrosion diagnostic development

    International Nuclear Information System (INIS)

    Understanding the corrosion behavior of nuclear fuel materials, such as refractory carbides, in a high temperature hydrogen environment is critical for several proposed nuclear thermal propulsion (NTP) concepts. Monitoring the fuel corrosion products is important not only for understanding corrosion characteristics, but to assess the performance of an actual, operating nuclear propulsion system as well. In this paper, we describe an experimental study initiated to develop, test, and subsequently utilize non-intrusive, laser-based diagnostics to characterize the gaseous product species which are expected to evolve during the exposure of representative fuel samples to hydrogen. Laser ablation is used to produce high temperature, vapor plumes from solid solution, uranium-free, zirconium carbide (ZrC) forms for probing by other laser diagnostic methods; predominantly laser-induced fluorescence (LIF). We discuss the laser ablation technique, results of plume emission measurements, as well as the use of planar LIF to image both the ZrC plumes and actual NTP fuel corrosion constituents

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

    Energy Technology Data Exchange (ETDEWEB)

    Nixdorf, R.D.

    1999-04-01

    container was coated with an iron catalyst and brought to 1200 C by the microwave field. A mixture of hydrogen and methyl trichlorosilane gases were fed to the fibril reaction container. Excellent silicon carbide fibrils were produced at a growth rate that was over four times greater than previously reported processes. The next phase of the development will be an optimization of operating parameters to improve fibril yield in the microwave growth process. The development activities will then move to the construction and testing of a pilot unit.

  15. Extreme-Environment Silicon-Carbide (SiC) Wireless Sensor Suite

    Science.gov (United States)

    Yang, Jie

    2015-01-01

    Phase II objectives: Develop an integrated silicon-carbide wireless sensor suite capable of in situ measurements of critical characteristics of NTP engine; Compose silicon-carbide wireless sensor suite of: Extreme-environment sensors center, Dedicated high-temperature (450 deg C) silicon-carbide electronics that provide power and signal conditioning capabilities as well as radio frequency modulation and wireless data transmission capabilities center, An onboard energy harvesting system as a power source.

  16. 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.

  17. Development of polishing methods for Chemical Vapor Deposited Silicon Carbide mirrors for synchrotron radiation

    International Nuclear Information System (INIS)

    Material properties of Chemical Vapor Deposited Silicon Carbide (CVD SiC) make it ideal for use in mirrors for synchrotron radiation experiments. We developed methods to grind and polish flat samples of CVD SiC down to measured surface roughness values as low as 1.1 Angstroms rms. We describe the processing details, including observations we made during trial runs with alternative processing recipes. We conclude that pitch polishing using progressively finer diamond abrasive, augmented with specific water based lubricants and additives, produces superior results. Using methods based on these results, a cylindrical and a toroidal mirror, each about 100 x 300mm, were respectively finished by Continental Optical and Frank Cooke, Incorporated. WYCO Interferometry shows these mirrors have surface roughness less than 5.7 Angstroms rms. These mirrors have been installed on the LLNL/UC X-ray Calibration and Standards Facility at the Stanford Synthrotron Radiation Laboratory

  18. Theoretical study of the channeling effect in the electronic stopping power of silicon carbide nanocrystal for low-energy protons and helium ions

    International Nuclear Information System (INIS)

    Excited-states ab initio molecular dynamics model is employed to study the electronic stopping power of cubic silicon carbide nanocrystal when low-energy protons and helium ions are hyperchanneling in the 〈1 0 0〉,〈1 1 0〉 and 〈1 1 1〉 major crystal axes. The energy transfer processes between the ions and the electronic subsystem of the cubic silicon carbide nanocrystalline are studied. The channeling effect in the electronic stopping power is determined by the unique electronic structure of these channels. The velocity-proportional stopping power is predicted for both protons and helium ions in the low-energy region. The calculated stopping power is in a quantitative agreement with the experimental data up to the stopping power maximum. The deviations of the stopping power of helium ions from the linear proportionality are attributed to the electron transfer at higher velocities

  19. 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.

  20. Combustion synthesis of boron carbide - a spectroscopic studies

    International Nuclear Information System (INIS)

    Boron Carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. It is the hardest material produced in tonnage quantities. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. Nuclear applications of boron carbide include shielding, control rod and shut down pellets. Within control rods, boron carbide is often powdered, to increase its surface area. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by X-ray diffraction (XRD). The carbide formation was ascertained using finger-print spectroscopy of Fourier transform infrared (FTIR). Samples of pyrolized/microwave heated powder were characterized for surface morphology using electron microscope (SEM). The present work shows the recent advances in understanding of structural and chemical variation in boron carbide and their influence on morphology, optical and vibrational property result discussed in details. (author)

  1. Site-specific electron-induced cross-linking of ortho-carborane to form semiconducting boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Pasquale, Frank L. [Department of Chemistry, University of North Texas, Denton, TX 76203 (United States); Kelber, Jeffry A., E-mail: kelber@unt.edu [Department of Chemistry, University of North Texas, Denton, TX 76203 (United States)

    2012-01-15

    Semiconducting boron carbide (B{sub 10}C{sub 2}H{sub x}) films have been formed by bombardment of condensed ortho-carborane (closo-1,2-dicarbadodecaborane) multilayers on polycrystalline copper substrates by 200 eV electrons under ultra-high vacuum conditions. The film formation process was characterized by X-ray and ultraviolet photoelectron spectroscopies. Electron bombardment results in the cross-linking of the icosahedral units. The cross-linking is accompanied by a shift in the B(1s) binding energy indicating site-specific cross-linking between two boron sites on adjacent carborane icosahedra. An additional shift in valence band binding energies attributed to the surface photovoltage effect is indicative of the formation of a p-type semiconductor. This is the first report of B{sub 10}C{sub 2}H{sub x} formation by electron bombardment of condensed films, and the data indicate that this method is a viable route towards formation of ultra-thin films of tailored composition and cross-linkages for emerging nanoelectronics and sensor applications.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nixdorf, RD

    2002-10-24

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

  3. 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

  4. Study of irradiation effects in the silicon carbide cubic polytype by photoluminescence and electron spin resonance spectroscopies

    International Nuclear Information System (INIS)

    This experimental work has consisted in the study of point defects induced by an electronic irradiation in the cubic crystallographic structure of silicon carbide with low temperature photoluminescence and electron spin resonance spectroscopies. The first one of these measurement tools has allowed to estimate the displacement threshold energy in the silicon sub-lattice and then to analyze the thermal stability of the irradiation defects in the low temperature range: (10-300 K) and then in the high temperature range: (300-1400 K). Besides, on the base of a recent theoretical model, this thesis has confirmed the proposition of the isolated silicon antisite for the D1 center whose running beyond the nominal running temperature of fission nuclear reactors (generation IV), for which SiC is in part intended, seems to be particularly problematic. Measurements carried out by ESR under lighting have at last allowed to detect a new defect in its metastable spin state S=1, possibly associated to a silicon interstitial configuration. (O.M.)

  5. 中国超细晶硬质合金及原料制备技术进展%Development on Preparation Technology of Ultrafine-Grained Cemented Carbides and Their Raw Materials in China

    Institute of Scientific and Technical Information of China (English)

    吴冲浒; 聂洪波; 肖满斗

    2012-01-01

    The sintered WC-Co with uhrafine grain sizes ( 〈 0. 5 rim) is called ultrafine cemented carbide, which pos- sesses optimized properties such as hardness and strength. Efficient tools prepared by uhrafine cemented carbides have been used in aerospace, nuclear energy, automotive, generating equipment, new energy and other fields of electronic communications. The development of uhrafine cemented carbides and raw materials was systematically introduced and reviewed, mainly in aspects of the preparation, property and characterization of uhrafine tungsten carbide powder, ultrafine cobalt powder, WC-Co composite powder and ultrafine cemented carbides in China. Prospects on technology of the ultra-fine cemented carbide were discussed finally.%超细晶硬质合金是WC晶粒度≤0.5μm的硬质合金,这类合金具有高强度和高硬度的优异性能。目前由超细晶硬质合金制备的高效刀具已经广泛用于航空航天、核能、汽车、发电设备、新能源和电子通讯等现代制造业。主要对中国超细晶硬质合金原料(例如超细碳化钨粉、钴粉、复合粉)和超细晶硬质合金制备技术、性能及表征方法作了系统的阐述。最后对超细晶硬质合金制备技术进行了展望。

  6. Effect of Cr on electronic and magnetic properties of χ-carbide (Fe,Cr){sub 5}C{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, B. [State Key Laboratory of Metastable Material Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, Q.; Zhang, Z.F. [College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Lv, Z.Q., E-mail: zqlv@ysu.edu.cn [College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Fu, W.T. [State Key Laboratory of Metastable Material Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-10-15

    From density-function theory calculation, the structural, electronic and magnetic properties of χ-carbides (Fe,Cr){sub 5}C{sub 2} are investigated. With the increase of Cr content in χ-carbides (Fe,Cr){sub 5}C{sub 2}, the formation energy of χ carbide gradually decrease and energy stability of them increase. The formation energy of Cr{sub 5}C{sub 2} is −0.354 eV/f.u, and the stability of Cr{sub 5}C{sub 2} is higher than other χ carbides (Fe,Cr){sub 5}C{sub 2}, Mn{sub 5}C{sub 2} and Fe{sub 5}C{sub 2}. There exists charges transfer from metal cation (Fe/Cr) to C atoms in χ-carbides, and this reveals an ionic contribution to the bonds. The addition of Cr decreases the magnetic moments of χ carbide, and the magnetic moments (Ms) of Cr{sub 2}Cr{sub 2}FeC{sub 2} and Cr{sub 5}C{sub 2} are 0 μ{sub B}/f.u., while it expresses opposite magnetic characters of the same atom at different sites in the other χ type (Fe,Cr){sub 5}C{sub 2} carbides. The 3d states of metal atoms in the majority states (up) move to above the Femi level and some metal atoms (Fe/Cr) in χ type (Fe,Cr){sub 5}C{sub 2} are undergone the anti-ferromagnetic transformation. - Highlights: • Energy stability of (Fe,Cr){sub 5}C{sub 2} increase with Cr, and the formation energy of Cr{sub 5}C{sub 2} is −0.354 eV/f.u. • Magnetic characters of the same atom at different sites in some χ (Fe,Cr){sub 5}C{sub 2} carbides are opposite. • Some metal atoms in χ (Fe,Cr){sub 5}C{sub 2} are undergone the anti-ferromagnetic transformation.

  7. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties. PMID:19687534

  8. Electronic and magnetic structure of carbides RRh{sub 3}C

    Energy Technology Data Exchange (ETDEWEB)

    Djermouni, Mostefa; Kacimi, Salima; Zaoui, Ali [Modelling and Simulation in Materials Science Laboratory, Djillali Liabes University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria)

    2011-08-15

    Ab initio calculations are performed to study the electronic and magnetic properties of the cubic inverse perovskite RRh{sub 3}C (R = rare earth) compounds. In this work, we used the accurate augmented plane-wave plus local orbital method to find the equilibrium structural parameters and to determine the magnetic stability of each material. We investigated the electronic structure with the spin-orbit interaction and on-site Coulomb potential for the R-derived 4f orbitals to obtain the correct ground state of RRh{sub 3}C. The exchange interaction between local f electrons and conduction electrons play an important role in the heavy fermions characters. The fully relativistic band structure scheme shows that spin-orbit coupling splits the 4f states into many manifolds. We confirm the results of recently synthesized cubic phases [Phys. Rev. B 80, 224404 (2009)]. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Mechanical properties and electronic structures of M{sub 23}C{sub 6} (M = Fe, Cr, Mn)-type multicomponent carbides

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yangzhen [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming, Yunnan, 650093 (China); State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an, Shaanxi, 710049 (China); Jiang, Yehua, E-mail: jiangyehua@kmust.edu.cn [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming, Yunnan, 650093 (China); Xing, Jiandong [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an, Shaanxi, 710049 (China); Zhou, Rong [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming, Yunnan, 650093 (China); Feng, Jing, E-mail: jfeng@seas.harvard.edu [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming, Yunnan, 650093 (China); School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02318 (United States)

    2015-11-05

    The mechanical and electronic properties of M{sub 23}C{sub 6}- (M = Fe, Cr, Mn) and M{sub 23}C{sub 6}-type multicomponent carbides are investigated systematically by first-principles calculations. The values of cohesive energy and formation enthalpy exhibited thermodynamically stable structures of these carbides. The stress–strain method and Voigt-Reuss-Hill approximation were used to calculate the elastic constants and moduli, respectively. The mechanical properties of the doped Fe or Mo in M{sub 23}C{sub 6} compounds are superior to the pure phases of Cr{sub 23}C{sub 6}, Mn{sub 23}C{sub 6} and Fe{sub 23}C{sub 6}. Mechanical anisotropy of these compounds was illustrated from the anisotropic index and different shapes of the surface contour by Young's modulus. Moreover, the total density of states of M{sub 23}C{sub 6} compounds indicated that the bonding behaviors of M{sub 23}C{sub 6} compounds were combinations of metallic and covalent bonds. - Graphical abstract: The crystal structure of M{sub 23}C{sub 6} (M = Cr, Mn, Fe, Mo, W), which formed in different heat treatment of many iron-based alloys can dramatically influence the mechanical properties of materials such as extreme hardness, high melting point, wear resistance, corrosion resistance and high thermal conductivity, etc. - Highlights: • The mechanical properties of M{sub 23}C{sub 6} (M = Fe, Cr, Mn) multicomponent carbides are estimated. • The anisotropy of M{sub 23}C{sub 6} carbides are discussed with regards to bonding and density of states. • M{sub 23}C{sub 6} (M = Fe, Cr, Mn) multicomponent carbides are thermodynamically stable.

  10. Development of a continuous spinning process for producing silicon carbide - silicon nitride precursor fibers

    Science.gov (United States)

    1985-01-01

    An apparatus was designed for the continuous production of silicon carbide - silicon nitride precursor fibers. The precursor polymer can be fiberized, crosslined and pyrolyzed. The product is a metallic black fiber with the composition of the type C sub x Si sub y n sub z. Little, other than the tensile strength and modulus of elasticity, is known of the physical properties.

  11. Development of tungsten carbide hardmetals using iron-based binder alloys

    International Nuclear Information System (INIS)

    The main work was carried out on hardmetals with 20 wt.% of iron rich binder alloys; the cobalt and nickel content of the alloys was varied upto 50 wt.%. The properties of the WC-Fe, WC-Co and WC-Ni hardmetals were measured for comparison. The influence of the carbon content, heat treatment and alloying with chromium andor molybdenum carbide was also evaluated. In addition to this, the effect of changes in the binder content and the carbide grain size on the properties of the hardmetals was determined. The structure of the WC-hardmetals with Fe-Co-Ni binders is similar to that of WC-Co, but the carbide grain size is somewhat smaller. The carbon content of the hardmetals has to be above the stoichiometric value of the tungsten carbide in order to obtain optimal hardmetal properties. The mechanical properties of the WC-Fe/Co/Ni hardmetals are strongly dependent on the binder composition and can be varied in a wide range. The optimal WC-Fe/Co/Ni hardmetals have at comparable transverse rupture strengths higher room temperature and hot hardness values, better fracture toughness and abrasive strength than the WC-Co hardmetals. Hardmetals whose binder is mainly martensitic have the best combination of all measured mechanical properties. (orig./IHOE)

  12. Development of Plasma-Sprayed Molybdenum Carbide-Based Anode Layers with Various Metal Oxides for SOFC

    Science.gov (United States)

    Faisal, N. H.; Ahmed, R.; Katikaneni, S. P.; Souentie, S.; Goosen, M. F. A.

    2015-12-01

    Air plasma-sprayed (APS) coatings provide an ability to deposit a range of novel fuel cell materials at competitive costs. This work develops three separate types of composite anodes (Mo-Mo2C/Al2O3, Mo-Mo2C/ZrO2, Mo-Mo2C/TiO2) using a combination of APS process parameters on Hastelloy®X for application in intermediate temperature proton-conducting solid oxide fuel cells. Commercially available carbide of molybdenum powder catalyst (Mo-Mo2C) and three metal oxides (Al2O3, ZrO2, TiO2) was used to prepare three separate composite feedstock powders to fabricate three different anodes. Each of the modified composition anode feedstock powders included a stoichiometric weight ratio of 0.8:0.2. The coatings were characterized by scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, nanoindentation, and conductivity. We report herein that three optimized anode layers of thicknesses between 200 and 300 µm and porosity as high as 20% for Mo-Mo2C/Al2O3 (250-µm thick) and Mo-Mo2C/TiO2 (300 µm thick) and 17% for Mo-Mo2C/ZrO2 (220-µm thick), controllable by a selection of the APS process parameters with no addition of sacrificial pore-forming material. The nanohardness results indicate the upper layers of the coatings have higher values than the subsurface layers in coatings with some effect of the deposition on the substrate. Mo-Mo2C/ZrO2 shows high electrical conductivity.

  13. Reliable Breakdown Obtained in Silicon Carbide Rectifiers

    Science.gov (United States)

    Neudeck, Philip G.

    1997-01-01

    The High Temperature Integrated Electronics and Sensor (HTIES) Program at the NASA Lewis Research Center is currently developing silicon carbide (SiC) for use in harsh conditions where silicon, the semiconductor used in nearly all of today's electronics, cannot function. Silicon carbide's demonstrated ability to function under extreme high-temperature, high-power, and/or high-radiation conditions will enable significant improvements to a far-ranging variety of applications and systems. These range from improved high-voltage switching for energy savings in public electric power distribution and electric vehicles, to more powerful microwave electronics for radar and cellular communications, to sensor and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines.

  14. Ab initio calculations of mechanical, thermodynamic and electronic structure properties of mullite, iota-alumina and boron carbide

    Science.gov (United States)

    Aryal, Sita Ram

    The alumino-silicate solid solution series (Al 4+2xSi2-2 xO10-x) is an important class of ceramics. Except for the end member (x=0), Al2 SiO5 the crystal structures of the other phases, called mullite, have partially occupied sites. Stoichiometric supercell models for the four mullite phases 3Al2O 3 · 2SiO2 · 2Al 2O3 · SiO2, 4 Al2O3· SiO 2, 9Al2O3 · SiO2, and iota-Al2 O3 (iota-alumina) are constructed starting from experimentally reported crystal structures. A large number of models were built for each phase and relaxed using the Vienna ab initio simulation package (VASP) program. The model with the lowest total energy for a given x was chosen as the representative structure for that phase. Electronic structure and mechanical properties of mullite phases were studied via first-principles calculations. Of the various phases of transition alumina, iota-Al 2O3 is the least well known. In addition structural details have not, until now, been available. It is the end member of the aluminosilicate solid solution series with x=1. Based on a high alumina content mullite phase, a structural model for iota- Al2O3 is constructed. The simulated x-ray diffraction (XRD) pattern of this model agrees well with a measured XRD pattern. The iota-Al2 O3 is a highly disordered ultra-low-density phase of alumina with a theoretical density of 2854kg/m3. Using this theoretically constructed model, elastic, thermodynamic, electronic, and spectroscopic properties of iota-Al2 O3 have been calculated and compared it with those of alpha- Al2O3 and gamma- Al2O3. Boron carbide (B4C) undergoes an amorphization under high velocity impacts. The mechanism of amorphization is not clear. Ab initio methods are used to carry out large-scale uniaxial compression simulations on two polytypes of stoichiometric boron carbide (B4C), B 11C-CBC, and B12- CCC where B11C or B12 is the 12-atom icosahedron and CBC or CCC is the three-atom chain. The simulations were performed on large supercells of 180 atoms

  15. Recent development of transient electronics

    Directory of Open Access Journals (Sweden)

    Huanyu Cheng

    2016-01-01

    Full Text Available Transient electronics are an emerging class of electronics with the unique characteristic to completely dissolve within a programmed period of time. Since no harmful byproducts are released, these electronics can be used in the human body as a diagnostic tool, for instance, or they can be used as environmentally friendly alternatives to existing electronics which disintegrate when exposed to water. Thus, the most crucial aspect of transient electronics is their ability to disintegrate in a practical manner and a review of the literature on this topic is essential for understanding the current capabilities of transient electronics and areas of future research. In the past, only partial dissolution of transient electronics was possible, however, total dissolution has been achieved with a recent discovery that silicon nanomembrane undergoes hydrolysis. The use of single- and multi-layered structures has also been explored as a way to extend the lifetime of the electronics. Analytical models have been developed to study the dissolution of various functional materials as well as the devices constructed from this set of functional materials and these models prove to be useful in the design of the transient electronics.

  16. Ultra-Lightweight, High Efficiency Silicon-Carbide (SIC) Based Power Electronic Converters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business of Innovation Research Phase I proposal seeks to investigate and prove the feasibility of developing highly efficient, ultra-lightweight SiC...

  17. Development of the 900 second specific impulse carbide low enriched uranium nuclear thermal rocket

    International Nuclear Information System (INIS)

    This study presents the Carbide Low Enriched Uranium Nuclear Thermal Rocket (LEU-NTR) in its latest form. First, a background on the design methodology is given along with a summary of previous work on the mass optimization of the core. The issue of the rather large power peaking is then raised and addressed through the implementation of radial enrichment zoning and increasing the radial reflector thickness. The advantages and disadvantages of each variation are then addressed before the issue of how to raise the coolant exit temperature is raised. Two methods to do so are then discussed and combined to produce three configurations of the Carbide LEU-NTR that operate with a specific impulse of 900 sec. Finally, the new performance characteristics are presented and compared with previous iterations of the design. (author)

  18. Development of a process to recover boron carbide from nuclear reactor absorber rods

    International Nuclear Information System (INIS)

    Boron carbide enriched with 10B is used as a control rod in reactor engineering. At present spent rods are disposed of, although major amounts of 10B are still 'unused'. The objective was to recover 10B from the control rods by an energy and cost saving method in order to use it for making new control rods, thus saving raw materials and minimizing the radioactive waste volume. For this purpose, the well-known pyrohydrolysis process was taken and analysed for possible improvements. By mixing boron carbide with CO2 as an oxidation-supporting agent, a lowering of the reaction temperature by 300deg C, and an increase in the oxidation speed by 350% were achieved. Since C02 is not consumed and can be circulated, the method for reprocessing spent control rods presented in this paper is both an economy-priced an energy-saving one. (orig.) With 98 refs., 9 tabs., 14 figs

  19. Radiation tolerance of epitaxial silicon carbide detectors for electrons and γ-rays

    International Nuclear Information System (INIS)

    Particles detectors were made using semiconductor epitaxial 4H-SiC as the detection medium. The investigated detectors are formed by Schottky contact (Au) on the epitaxial layer and an ohmic contact on the backside of 4H-SiC substrates with different micropipe densities from CREE. For radiation hardness studies, the detectors have been irradiated with electrons (8.2 MeV) and γ-rays (60Co source) at fluences and doses ranging from 0 to 9.48x1014 e/cm2 and 40 Mrad, respectively. We present experimental data on the charge collection properties by using 4.14 MeV α-particles impinging on the Schottky contact. Hundred percent Charge Collection Efficiency, CCE, is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the α-particle projected range, even after the irradiation at the highest dose. By comparing measured CCE values with the outcomes of drift-diffusion simulations, values are inferred for the hole lifetime, τp, within the neutral region of the charge carrier generation layer. τp was found to decrease with increasing radiation levels, ranging from 300 ns in non-irradiated detectors to 3 ns in the most irradiated ones. The diffusion contribution of the minority charge carriers to CCE is pointed out

  20. Film formation of silicon carbide on steel by activation reaction ion plating with thermal electron

    International Nuclear Information System (INIS)

    The formation of SiC (amorphous) film on steel was performed by reaction ion plating with electron activating ionization. Acetylene was superior to methane as the reactant gas at low gas partial pressures, and the SiC produced in this experiment was amorphous. Film characteristics was controlled by regulating gas partial pressure and ionization current. The optimum condition for the production of a hard SiC amorphous film on steel were: reactant gas: acetylene of 5.2 x 10-2 Pa; bias voltage: -0.8kV; ion current: 23 - 28 mA; ionization voltage: -0.3kV. The maximum hardness of SiC films produced in this experiment was Hv 4260. For the SiC films produced in solutions without Cl- ion the anodic polarization curves showed good corrosion resistance, but values were less for solution with Cl- ion. Wear resistance was as good as that of TiC films. (author)

  1. Developments in electron gun simulation

    Energy Technology Data Exchange (ETDEWEB)

    Herrmannsfeldt, W.B.

    1994-05-01

    This paper will discuss the developments in the electron gun simulation programs that are based on EGUN and its derivatives and supporting programs. Much of the code development has been inspired by technology changes in computer hardware; the implications on EGN2 of this evolution will be discussed. Some examples and a review of the capabilities of the EGUN family will be described.

  2. Developments in electron gun simulation

    International Nuclear Information System (INIS)

    This paper will discuss the developments in the electron gun simulation programs that are based on EGUN and its derivatives and supporting programs. Much of the code development has been inspired by technology changes in computer hardware; the implications on EGN2 of this evolution will be discussed. Some examples and a review of the capabilities of the EGUN family will be described

  3. Effect of the formation conditions on the local density of electronic states of amorphous films of silicon carbide

    International Nuclear Information System (INIS)

    The method of ultrafine x-ray emission spectroscopy was used to examine the effect of the formation conditions (power of the rf discharge and substrate temperature) on the nature of energy distribution of the valency states of silicon in amorphous films of silicon carbide produced by rf sputtering a target made of polycrystalline carbide. The results show the existence of optimum conditions under which the coordination of silicon atoms is closest to their coordination in the crystal. Under these conditions, the density of occupied localised states is minimum. (author)

  4. The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

    Science.gov (United States)

    Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Purohit, Sudhaunshu S.; Li, Han; King, Sean W.; Dutta, Dhanadeep; Gidley, David; Lanford, William A.; Paquette, Michelle M.

    2015-07-01

    Because of its high electrical resistivity, low dielectric constant (κ), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-BxC:Hy) has garnered interest as a material for low-κ dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (EU), and Tauc parameter (B1/2)], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-BxC:Hy thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm3, Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 1010 to 1015 Ω cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above ˜1.3 g/cm3 (or below ˜35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters EU and B1/2, with increasing H concentration is explained by the release of strain in the network and associated decrease in structural disorder. All of these correlations in a-BxC:Hy are found to be very similar to those

  5. Development of electronic cinema projectors

    Science.gov (United States)

    Glenn, William E.

    2001-03-01

    All of the components for the electronic cinema are now commercially available. Sony has a high definition progressively scanned 24 frame per second electronic cinema camera. This can be recorded digitally on tape or film on hard drives in RAID recorders. Much of the post production processing is now done digitally by scanning film, processing it digitally, and recording it on film for release. Fiber links and satellites can transmit cinema program material to theaters in real time. RAID or tape recorders can play programs for viewing at a much lower cost than storage on film. Two companies now have electronic cinema projectors on the market. Of all of the components, the electronic cinema projector is the most challenging. Achieving the resolution, light, output, contrast ratio, and color rendition all at the same time without visible artifacts is a difficult task. Film itself is, of course, a form of light-valve. However, electronically modulated light uses other techniques rather than changes in density to control the light. The optical techniques that have been the basis for many electronic light-valves have been under development for over 100 years. Many of these techniques are based on optical diffraction to modulate the light. This paper will trace the history of these techniques and show how they may be extended to produce electronic cinema projectors in the future.

  6. Structural, electronic, and magnetic properties of iron carbide Fe7C3 phases from first-principles theory

    NARCIS (Netherlands)

    Fang, C.M.; Van Huis, M.A.; Zandbergen, H.W.

    2009-01-01

    The iron carbide Fe7C3 exhibits two types of basic crystal structures, an orthorhombic (o-) form and a hexagonal (h-) one. First-principles calculations have been performed for the basic Fe7C3 forms and for the related θ-Fe3C cementite phase. Accurate total-energy calculations show that the stabilit

  7. From Electronic Structure to Catalytic Activity: A Single Descriptor for Adsorption and Reactivity on Transition-Metal Carbides

    DEFF Research Database (Denmark)

    Vojvodic, A.; Hellman, Anders; Ruberto, C.;

    2009-01-01

    Adsorption and catalytic properties of the polar (111) surface of transition-metal carbides (TMC's) are investigated by density-functional theory. Atomic and molecular adsorption are rationalized with the concerted-coupling model, in which two types of TMC surface resonances (SR's) play key roles...

  8. 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 be...... delineated. Close to the interface further microstructural inhomogeneities were obsered, there being a clear dependence of TiC deposition mechanism on the chemical and crystallographic nature of the upper layers of the multiphase substrate....

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

    Energy Technology Data Exchange (ETDEWEB)

    Dinesh Agrawal; Rustum Roy

    2000-11-01

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

  10. Physical and bonding characteristics of N-doped hydrogenated amorphous silicon carbide films grown by PECVD and annealed by pulsed electron beam

    International Nuclear Information System (INIS)

    Nitrogen-doped amorphous silicon carbide films were grown by a plasma enhanced chemical vapour deposition (PE CVD) technique. The actual amount of nitrogen in the SiC films is determined by Rutherford backscattering spectrometry (RBS). For irradiation experiments we use electron beams with a kinetic energy 200 keV, a pulse duration of 300 ns, and a beam current of 150 A/cm2. It is found that with increased nitrogen doping and following activation of dopants the resistivity of the amorphous SiC films is substantially reduced

  11. Electronic dosemeter development - final stages

    International Nuclear Information System (INIS)

    An electronic personal dosimetry service has been described together with the procedure which is being adopted to gain approval in the UK for monitoring the exposure of classified workers. NRPB considers this to be the next logical development in personal dosimetry and it has been shown that the device offers a number of advantages for this purpose. (Author)

  12. Boron carbide nanowires: Synthesis and characterization

    Science.gov (United States)

    Guan, Zhe

    solid orthorhombic phase catalyst. The status of a catalyst depends mainly on temperature. (3) Observation of "invisible" defects in boron carbide nanowires. The planar defects can only be seen under a transmission electron microscope when the electron beam is within the defect plane. Furthermore, there are only two directions within that plane, along which the orientation of defect can be told and clear TEM results can be taken. The challenge is that the TEM sample holder is limited to tilt +/-30° in each direction. A theory was developed based on lattice calculation and simulation to tell the orientation of defect even not from those unique directions. Furthermore, it was tested by experimental data and proved to be successful. (4) Preliminary exploration of structure-transport property of as-synthesized boron carbide nanowires. In collaboration with experts in the field of thermal science, thermal transport properties of a few boron carbide nanowires were studied. All measured nanowires were either pre-characterized or post-characterized by TEM to reveal their structural information such as diameter, fault orientations and chemical composition. The obtained structural information was then analyzed together with measured thermal conductivity to establish a structure-transport property relation. Current data indicate that TF ones have a lower thermal conductivity, which is also diameter-dependent.

  13. Development of high toughness, high strength aluminide-bonded carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Becher, P.F.; Plucknett, K.P.; Tiegs, T.N. [Oak Ridge National Lab., TN (United States)] [and others

    1997-04-01

    Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that are retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.

  14. Development of a feedstock formulation based on PP for MIM of carbides reinforced M2

    Directory of Open Access Journals (Sweden)

    A. Várez

    2008-04-01

    Full Text Available Purpose: Influence of binder composition on some selected properties of feedstock contained powder of M2 with 10% of carbides powders are demonstrated in the paper.Design/methodology/approach: Torque-load test, rheological tests.Findings: Examination of the effect of the binder type and portion on structure and properties of the experimental tool materials with the cermets structure revealed that using the stearic acid reduces viscosity, thus improving technological properties of the feedstock. Employment of polyethylene instead of the high density polypropylene reduces viscosity and torque-load of the investigated feedstocks. Therefore, there is a possibility to increase the portion of the metallic or ceramic powder.Practical implications: It is expected that further investigations of these materials will make possible their injection moulding, as well as their heat treatment increasing hardness and strength of matrix and thereby of the whole tool material. The extrusion process or PIM (Powder Injection Moulding gives the possibility to manufacturing tools materials on the basis of high speed-steel which characterised very good properties with their final or near net shape.Originality/value: In the paper the using extruding of the polymer-powder mix gives the possibility to fabricate cermets which, with their structure and mechanical properties, fill the gap in tool materials between the high-speed steels and cemented carbides.

  15. The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Paquette, Michelle M., E-mail: paquettem@umkc.edu [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); Purohit, Sudhaunshu S. [Department of Chemistry, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); Li, Han; King, Sean W. [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States); Dutta, Dhanadeep; Gidley, David [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Lanford, William A. [Department of Physics, University at Albany, Albany, New York 12222 (United States)

    2015-07-21

    Because of its high electrical resistivity, low dielectric constant (κ), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-B{sub x}C:H{sub y}) has garnered interest as a material for low-κ dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (E{sub U}), and Tauc parameter (B{sup 1/2})], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-B{sub x}C:H{sub y} thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm{sup 3}, Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 10{sup 10} to 10{sup 15} Ω cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above ∼1.3 g/cm{sup 3} (or below ∼35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters E{sub U} and B{sup 1/2}, with increasing H concentration is explained by the release of strain in the network and associated decrease in

  16. DEVELOPING APPLICATIONS FOR ELECTRONIC BUSINESS

    Directory of Open Access Journals (Sweden)

    Georgeta Șoavă

    2012-12-01

    Full Text Available We are in the early 3rd millennium as companies face the need to exploit technology changing computer environments, in order to improve customer satisfaction and reduce costs. Thus, the development of e-business, the efficient use of new information technologies in business, by developing an alternative sales channel with relatively low costs, it manages to establish relationships with incomparably greater number of customers, to traditional approaches. Starting from these general considerations, we conducted this work we divided it into four parts. In the first part we present general context in which companies can achieve needs using new technologies, then we reviewed the basic elements in developing e-business type applications presenting their main benefits. Next, I approached refining models for e-business software development and use of distributed architectures for electronic commerce, concluding with a set of conclusions.

  17. Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: a trend study of surface electronic factors

    DEFF Research Database (Denmark)

    Vojvodic, Aleksandra; Ruberto, C.; Lundqvist, Bengt

    2010-01-01

    This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMCs) in NaCl structure by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC(111) surfaces, of interest because of the presence of different types......C, NbC, delta-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH2, and NH3. Trends in adsorption strength are explained in terms of surface electronic factors, by correlating the calculated adsorption-energy values with the calculated surface electronic structures. The...... surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOSs). Detailed comparisons between surface and bulk DOSs reveal the existence of transition-metal localized SRs (TMSRs) in the pseudogap and of several C-localized SRs (CSRs) in the upper valence band on all...

  18. Development of a Robust Tri-Carbide Fueled Reactor for Multi-Megawatt Space Power and Propulsion Applications

    International Nuclear Information System (INIS)

    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

  19. Influence of Rare Earth on Carbide in Weld Metal

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yuan-Bin; REN Deng-Yi

    2003-01-01

    The influence of rare earths (RE) on carbides in high carbon steel weld metal was studied by transmission electron microscope (TEM) and energy dispersive X-ray microanalysis (EDX). It is found that rare earth markedly affects the quantity, morphology and distribution of carbides. The precipitating mechanism of carbides was proposed in which rare earth compounds with high surface energy serve as the nucleation sites for carbides in superheated liquid metal and the induced carbides are precipitated extensively and distributed evenly. The preferential precipitation of carbides decreases the carbon content in matrix, which is transformed into low carbon lath martensite after welds are chilled to room temperature.

  20. Electronic, thermal, and superconducting properties of metal nitrides (MN) and metal carbides (MC) (M=V, Nb, Ta) compounds by first principles studies

    Energy Technology Data Exchange (ETDEWEB)

    Subhashree, G.; Sankar, S.; Krithiga, R. [Anna Univ., Chennai, Tamil Nadu (India). Condensed Matter Lab.

    2015-07-01

    Structural, electronic, and superconducting properties of carbides and nitrides of vanadium (V), niobium (Nb), and tantalum (Ta) (group V transition elements) have been studied by computing their electronic band structure characteristics. The electronic band structure calculations have been carried out based on the density functional theory (DFT) within the local density approximation (LDA) by using the tight binding linear muffin tin orbital method. The NaCl-type cubic structures of MN and MC (M=V, Nb, Ta) compounds have been confirmed from the electronic total energy minimum of these compounds. The ground state properties, such as equilibrium lattice constant (a{sub 0}), bulk modulus (B), and Wigner-Seitz radius (S{sub 0}) are determined and compared with available data. The electronic density of states reveals the metallic nature of the chosen materials. The electronic specific heat coefficient, Debye temperature, and superconducting transition temperature obtained from the band structure results are found to agree well with the earlier reported literature.

  1. Polytype distribution in circumstellar silicon carbide.

    Science.gov (United States)

    Daulton, T L; Bernatowicz, T J; Lewis, R S; Messenger, S; Stadermann, F J; Amari, S

    2002-06-01

    The inferred crystallographic class of circumstellar silicon carbide based on astronomical infrared spectra is controversial. We have directly determined the polytype distribution of circumstellar SiC from transmission electron microscopy of presolar silicon carbide from the Murchison carbonaceous meteorite. Only two polytypes (of a possible several hundred) were observed: cubic 3C and hexagonal 2H silicon carbide and their intergrowths. We conclude that this structural simplicity is a direct consequence of the low pressures in circumstellar outflows and the corresponding low silicon carbide condensation temperatures. PMID:12052956

  2. Development and Characterization of Carbon Nanotubes (CNTs) and Silicon Carbide (SiC) Reinforced Al-based Nanocomposites

    Science.gov (United States)

    Gujba, Kachalla Abdullahi

    Composites are engineered materials developed from constituent materials; matrix and reinforcements, to attain synergistic behavior at the micro and macroscopic level which are different from the individual materials. The high specific strength, low weight, excellent chemical resistance and fatigue endurance makes these composites superior than other materials despite anisotropic behaviors. Metal matrix composites (MMCs) have excellent physical and mechanical properties and alumium (Al) alloy composites have gained considerable interest and are used in multiple industries including: aerospace, structural and automotive. The aim of this research work is to develop an advanced Al-based nanocomposites reinforced with Carbon nanotubes (CNTs) and silicon carbide particulates (SiCp) nanophases using mechanical alloying and advanced consolidation procedure (Non-conventional) i.e. Spark Plasma Sintering (SPS) using two types of aluminum alloys (Al-7Si-0.3mg and Al-12Si-0.3Mg). Different concentrations of SiCp and CNTs were added and ball milled for different milling periods under controlled atmosphere to study the effect of milling time and the distribution of the second phases. Characterization techniques were used to investigate the morphology of the as received monolithic and milled powder using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive Spectroscopy (EDS), X-Ray Mapping, X-Ray Diffraction (XRD) and Particle Size Analyses (PSA). The results revealed that the addition of high concentrations of SiCp and CNTs in both alloys aided in refining the structure of the resulting powder further as the reinforcement particles acted like a grinding agent. Good distribution of reinforcing particles was observed from SEM and no compositional fluctuations were observed from the EDS. Some degree of agglomerations was observed despite the ethyl alcohol sonication effect of the CNTs before ball milling. From the XRD; continuous reduction in crystallite size and

  3. Long-term carbide development in high-velocity oxygen fuel/high-velocity air fuel Cr3C2-NiCr coatings heat treated at 900 °C

    Science.gov (United States)

    Matthews, S.; Hyland, M.; James, B.

    2004-12-01

    During the deposition of Cr3C2-NiCr coatings, compositional degradation occurs, primarily through the dissolution of the carbide phase into the matrix. Exposure at an elevated temperature leads to transformations in the compositional distribution and microstructure. While these have been investigated in short-term trials, no systematic investigations of the long-term microstructural development have been presented for high-velocity sprayed coatings. In this work, high-velocity air fuel (HVAF) and high-velocity oxygen fuel (HVOF) coatings were treated at 900 °C for up to 60 days. Rapid refinement of the supersaturated matrix phase occurred, with the degree of matrix phase alloying continuing to decrease over the following 20 to 40 days. Carbide nucleation in the HVAF coatings occurred preferentially on the retained carbide grains, while that in the HVOF coatings developed in the regions of greatest carbide dissolution. This difference resulted in a variation in carbide morphologies. Preferential horizontal growth was evident in both coatings over the first 20 to 30 days of exposure, beyond which spheroidization of the microstructure occurred. After 30 days, the carbide morphology of both coatings was comparable, tending toward an expansive structure of coalesced carbide grains. The development of the carbide phase played a significant role in the microhardness variation of these coatings with time.

  4. Hafnium carbide cermets

    Czech Academy of Sciences Publication Activity Database

    Brožek, Vlastimil; Ctibor, Pavel; Dong-Ik, Ch.; Eun-Pyo, K.

    Praha: Czechoslovak association for crystal growth, 2008 - (Nitsch, K.; Rodová, M.), s. 8-9 ISBN 978-80-254-0864-3. [Development of Materials Science in Research and Education/18th./. Hnanice (CZ), 02.09.2008-05.09.2008] Institutional research plan: CEZ:AV0Z20430508 Keywords : Hafnium carbide * tungsten * cermets * plasma spraying * hot pressing, Subject RIV: BL - Plasma and Gas Discharge Physics

  5. Silicon Carbide Junction Field Effect Transistor Digital Logic Gates Demonstrated at 600 deg. C

    Science.gov (United States)

    Neudeck, Philip G.

    1998-01-01

    The High Temperature Integrated Electronics and Sensors (HTIES) Program at the NASA Lewis Research Center is currently developing silicon carbide (SiC) for use in harsh conditions where silicon, the semiconductor used in nearly all of today's electronics, cannot function. The HTIES team recently fabricated and demonstrated the first semiconductor digital logic gates ever to function at 600 C.

  6. Electronic Commerce in Developing Countries

    OpenAIRE

    Mann, Catherine L.

    2000-01-01

    Electronic commerce and its related activities over the internet can be the engines that improve domestic economic well-being through liberalization of domestic services, more rapid integration into globalization of production, and leap-frogging of available technology. Electronic commerce integrates the domestic and global markets from its very inception. Negotiating on trade issues related to electronic commerce will demand self-inspection of key domestic policies, particularly in telecommu...

  7. Recent developments on electronic dosimeters

    International Nuclear Information System (INIS)

    Potential replacements of the aging Film and TLD by passive and active electronic dosimetry systems are emerging. Such devises offer, at equally high dosimetric performance, additional features, such as direct readout and dose rate warnings. Today, a large number of electronic dosimeters is commercially available, but only very few comply with international standards and national requirements. Nevertheless, the first electronic dosimetry systems for photon and beta radiation have recently been approved for legal dosimetry. In neutron dosimetry, research projects on electronic dosimeters are still going on and some devices are already commercially available. (author)

  8. Progress in development of coated indexable cemented carbide inserts for machining of iron based work piece materials

    Science.gov (United States)

    Czettl, C.; Pohler, M.

    2016-03-01

    Increasing demands on material properties of iron based work piece materials, e.g. for the turbine industry, complicate the machining process and reduce the lifetime of the cutting tools. Therefore, improved tool solutions, adapted to the requirements of the desired application have to be developed. Especially, the interplay of macro- and micro geometry, substrate material, coating and post treatment processes is crucial for the durability of modern high performance tool solutions. Improved and novel analytical methods allow a detailed understanding of material properties responsible for the wear behaviour of the tools. Those support the knowledge based development of tailored cutting materials for selected applications. One important factor for such a solution is the proper choice of coating material, which can be synthesized by physical or chemical vapor deposition techniques. Within this work an overview of state-of-the-art coated carbide grades is presented and application examples are shown to demonstrate their high efficiency. Machining processes for a material range from cast iron, low carbon steels to high alloyed steels are covered.

  9. Thermal conductivity of boron carbides

    Science.gov (United States)

    Wood, C.; Emin, D.; Gray, P. E.

    1985-01-01

    Knowledge of the thermal conductivity of boron carbide is necessary to evaluate its potential for high-temperature thermoelectric energy conversion applications. Measurements have been conducted of the thermal diffusivity of hot-pressed boron carbide BxC samples as a function of composition (x in the range from 4 to 9), temperature (300-1700 K), and temperature cycling. These data, in concert with density and specific-heat data, yield the thermal conductivities of these materials. The results are discussed in terms of a structural model that has been previously advanced to explain the electronic transport data. Some novel mechanisms for thermal conduction are briefly discussed.

  10. Influence of fabricating process on microstructure and properties of spheroidal cast tungsten carbide powder

    Institute of Scientific and Technical Information of China (English)

    DAI Yu; TAN Xing-long; LI Yu-xi; YANG Jian-gao; HUANG Bai-yun

    2005-01-01

    A super-high temperature furnace was developed to fabricate spheroidal cast tungsten carbide powder with excellent flowability and fine feathery structure in a large scale. Optical microscope and scanning electron microscope were taken to characterize the morphology and microstructure of cast tungsten carbide powder. X-ray diffractometry was used to analyze the phase composition of powders involved. It is found that the carbon potential in the furnace and feeding speed play an important role on the microstructure, morphology and properties of the spheroidal cast tungsten carbide powder. As carbon potential is between 0.3% and 0.9% in the furnace, cast tungsten carbide powder with hardness over 2800(HV0.5 ), flowability over 7. 1 s/50 g and tap density over 10.3 g/cm3 is obtained.

  11. Composite uranium carbide targets at TRIUMF: Development and characterization with SEM, XRD, XRF and L-edge densitometry

    Energy Technology Data Exchange (ETDEWEB)

    Kunz, Peter, E-mail: pkunz@triumf.ca [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 (Canada); Bricault, Pierre; Dombsky, Marik [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 (Canada); Erdmann, Nicole [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Hanemaayer, Vicky; Wong, John [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 (Canada); Lützenkirchen, Klaus [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany)

    2013-09-15

    The production of radioactive ion beams (RIB) from spallation targets by irradiation with a continuous 500 MeV proton beam, has been routine at TRIUMF for several years. Based on the experience with composite refractory carbide targets a procedure for the fabrication of UC{sub 2}/C targets was developed. It includes the preparation of UC{sub 2} by carbothermal reduction of UO{sub 2}, the slip-casting of fine-grained UC{sub 2}/C slurry on graphite foil under inert gas atmosphere and the cutting of composite target discs which are stacked up to a lamellar structure. The thermal properties of such an arrangement are adequate to withstand the high power deposition of an intense, continuous proton beam and also beneficial for the fast release of short-lived radioactive isotopes. Molecular structure, particle size and the impact of sintering of the target discs were investigated via XRD and SEM. Thickness and mass distribution were measured with position-sensitive L{sub III}-edge densitometry. The results confirm that the properties of the UC{sub 2}/C target material are well suited for RIB production at TRIUMF while there is still room for improvement with regard to uniformity of mass distribution in target disc thickness.

  12. Synthesis and properties of low-carbon boron carbides

    International Nuclear Information System (INIS)

    This paper reports on the production of boron carbides of low carbon content (3 and CCl4 at 1273-1673 K in a chemical vapor deposition (CVD) reactor. Transmission electron microscopy (TEM) revealed that phase separation had occurred, and tetragonal boron carbide was formed along with β-boron or α-boron carbide under carbon-depleted gas-phase conditions. At temperatures greater than 1390 degrees C, graphite substrates served as a carbon source, affecting the phases present. A microstructure typical of CVD-produced α-boron carbide was observed. Plan view TEM of tetragonal boron carbide revealed a blocklike structure

  13. The development of carbides in the phase boundary between delta ferrite and martensite in 9-14% chromium steels

    International Nuclear Information System (INIS)

    Materials with a sufficient toughness have to be used for safety-relevant components. In martensitic 12% chromium steels delta ferrite may occur, at higher contents (>0,5%) the fracture toughness of the material may be reduced considerably. This means that the DBTT (ductile to brittle transition temperature) is shifted towards higher temperatures during impact tests. In two-phase steels consisting of delta-ferrite and martensite, this behavior of brittle fracture is found to be caused by the massive dendritic carbide surrounding the delta-ferrite. The generation of this carbide is described by means of CCT diagrams (continuous cooling transformation diagrams). Carbide formation depends on both the chromium content and the cooling velocity. (orig.)

  14. Palladium interaction with silicon carbide

    International Nuclear Information System (INIS)

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC–5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation

  15. Palladium interaction with silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, M., E-mail: Marialuisa.Gentile@manchester.ac.uk [Centre for Nuclear Energy Technology (C-NET), School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom); Xiao, P. [Materials Science Centre, School of Materials, The University of Manchester, Manchester M13 9PL (United Kingdom); Abram, T. [Centre for Nuclear Energy Technology (C-NET), School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-07-15

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC–5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd{sub 3}Si and SiO{sub 2} phases, while the second peak and the third peak are correlated with the formation of Pd{sub 2}Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO{sub 2} phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiC{sub x}O{sub y} phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  16. Palladium interaction with silicon carbide

    Science.gov (United States)

    Gentile, M.; Xiao, P.; Abram, T.

    2015-07-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC-5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  17. Latest development on preparation of carbides and silicon carbide based composite powders%碳化物及碳化硅基复合粉体制备的新进展

    Institute of Scientific and Technical Information of China (English)

    尹月; 马北越

    2016-01-01

    The latest development on preparation of carbides (SiC,TiC,B4 C,ZrC,Mo2 C and Al8 B4 C7 )and silicon carbide based composite powders (SiC-Al2 O3 ,SiC-ZrO2 ,SiC-ZrB2 ,SiC-SiAlON,SiC-Al6 Si2 O13 , SiC-TiC and SiC-ZrC)by the carbothermal reduction of natural minerals,industrial solid wastes and pre-cursors was reviewed.The advantages and disadvantages as well as synthesis reaction mechanisms were analyzed.The development trend was prospected.%综述了采用碳热还原天然矿物、工业固体废弃物和前驱体制备碳化物(SiC、TiC、B4 C、ZrC 、Mo2 C 和Al8 B4 C7)及碳化硅基复合粉体(SiC-Al2 O3、SiC-ZrO2、SiC-ZrB2、SiC-SiAlON、SiC-Al6 Si2 O13、SiC-TiC、SiC-ZrC)的最新研究进展,分析了碳热还原法制备陶瓷粉体的优缺点及合成反应机制,并展望了由天然矿物、固体废弃物和前驱体制备碳化物及碳化硅基复合粉体的发展前景。

  18. Modern developments in electron-beam fluorescence

    Science.gov (United States)

    Cattolica, Robert J.

    Recent developments in the area of electron-beam fluorescence are discussed with special attention given to the experience in the use of the electron-beam fluorescence in flight research. A new measurement approach, called electron-photon fluorescence (EPF), is described, and it is shown that EPF offers the potential of overcoming some of the disadvantages of electron-beam fluorescence in high-density flows. Examples of using the EPF technique are presented.

  19. Development of multi-channel electron spectrometer

    International Nuclear Information System (INIS)

    In order to obtain the angular dependent electron energy distributions, we developed a multichannel electron spectrometer (MCESM) with high energy and angular resolutions. The MCESM consists of seven small electron spectrometers set in every 5 deg. on the basement, each of which detection range is up to 25 MeV. In the experiment, we successfully obtained electron spectra from imploded cone-shell target as well as gold plane target irradiated by ultraintense (300 J/5 ps) laser beam.

  20. Silicon Carbide Solar Cells Investigated

    Science.gov (United States)

    Bailey, Sheila G.; Raffaelle, Ryne P.

    2001-01-01

    The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.

  1. The ternary iron aluminum carbides

    International Nuclear Information System (INIS)

    Research highlights: → Carbides present in ternary Fe-Al-C were investigated. → Presence of carbides Fe3C, M23C6, and/or κ-Fe3AlC depends on the Al and C concentration. → The existence of M23C6 ternary carbide in the Fe-Al-C system is recognized for first time. → Solubility of Al in M23C6 is low and negligible in the cementite. - Abstract: Carbides present in ternary Fe-Al-C were investigated by the combined utilization of an X-ray diffractometer and a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. The alloys were prepared by arc melting and the microstructure was homogenised by a solution annealing treatment in the temperature range 950-1050 deg. C for 15 min. The diffraction patterns of resulting materials were analysed using a multiphase Rietveld refinement. The steel is composed of a ferritic matrix with carbides Fe3C, M23C6, and/or κ-Fe3AlC depending on the Al and C concentration. It is the first time that the existence of M23C6 ternary carbide in the Fe-Al-C system is recognized. Microprobe analyses performed revealed that the solubility of Al in M23C6 is low, with an Fe/Al ratio (in at.%) higher than 15. On the other hand, the amount of Al in the cementite is negligible and hence its lattice parameters do not depend on the Al concentration of the alloy.

  2. Recent Developments in Electronic Radiography

    Energy Technology Data Exchange (ETDEWEB)

    Fry, D.A.; Claytor, T.N.; Davis, A.W.; Jones, M.H.; Sheats, M.J.; Stupin, D.M.; Summa, D.A.; White, S.M.; Hefele, J.; Watson, S.A.; Kauppila, T.J.; Mueller, K.H.

    1999-07-18

    An overview of the radiographic capabilities with emphasis on electronic image detection and processing at the Los Alamos National Laboratory is presented. Fixed facilities and portable x-ray sources and imaging systems make up the Los Alamos capability. Examples of imaging with large area amorphous silicon imaging panels, a portable computed tomography system, high speed x-ray imaging applications and equipment, and small area, high resolution imagers are given. Radiographic simulation and reverse engineering from radiographic images to computer aided design files and solid models is also presented.

  3. Studies on Interfacial Phenomena in Titanium Carbide/Liquid Steel Systems for Development of Functionally Graded Material

    Science.gov (United States)

    Kiviö, Miia; Holappa, Lauri; Louhenkilpi, Seppo; Nakamoto, Masashi; Tanaka, Toshihiro

    2016-08-01

    In modern materials' applications, versatile, often contradictory requirements are set for properties like high strength, hardness, and toughness. However, e.g., in steel castings, typically only certain surfaces should be hard and wear resistant, whereas the other "bulk" might have only standard properties. Then the critical parts of the surface should be "locally reinforced" to get functionally graded material. Expensive alloying elements are saved, and manufacturing stages are minimized. Titanium carbide is an extremely hard material widely applied in carbide tools. It could be used to reinforce steel castings. When TiC particles are added to liquid steel, wettability, stability, and dissolution are key phenomena that should be understood to better design and control manufacturing processes. In this work, the interfacial phenomena and reactions between TiC and iron/steel melts were examined by wetting experiments with special emphasis on the influence of Cr, Ni, and Mo. No significant effect on wettability was observed by Ni or Mo. High Cr melts showed somewhat higher contact angles. Partial penetration of liquid metal took place in the substrate along the grain boundaries. Ni seemed to promote penetration. During longer experiments, re-precipitation of carbides occurred on the liquid droplet influencing the apparent wetting angle. Cr and Mo promoted carbide formation.

  4. Studies on Interfacial Phenomena in Titanium Carbide/Liquid Steel Systems for Development of Functionally Graded Material

    Science.gov (United States)

    Kiviö, Miia; Holappa, Lauri; Louhenkilpi, Seppo; Nakamoto, Masashi; Tanaka, Toshihiro

    2016-04-01

    In modern materials' applications, versatile, often contradictory requirements are set for properties like high strength, hardness, and toughness. However, e.g., in steel castings, typically only certain surfaces should be hard and wear resistant, whereas the other "bulk" might have only standard properties. Then the critical parts of the surface should be "locally reinforced" to get functionally graded material. Expensive alloying elements are saved, and manufacturing stages are minimized. Titanium carbide is an extremely hard material widely applied in carbide tools. It could be used to reinforce steel castings. When TiC particles are added to liquid steel, wettability, stability, and dissolution are key phenomena that should be understood to better design and control manufacturing processes. In this work, the interfacial phenomena and reactions between TiC and iron/steel melts were examined by wetting experiments with special emphasis on the influence of Cr, Ni, and Mo. No significant effect on wettability was observed by Ni or Mo. High Cr melts showed somewhat higher contact angles. Partial penetration of liquid metal took place in the substrate along the grain boundaries. Ni seemed to promote penetration. During longer experiments, re-precipitation of carbides occurred on the liquid droplet influencing the apparent wetting angle. Cr and Mo promoted carbide formation.

  5. Development of electronic commerce in Europe

    OpenAIRE

    Alin Daniel MUNTEANU

    2012-01-01

    Among the many potential benefits of electronic commerce include lower prices, access to a wider range of goods, development of innovative services and creating jobs. Online purchases represent about 3% of European retail trade. But the development of uniform electronic markets still face numerous obstacles.

  6. X2000 power system electronics development

    Science.gov (United States)

    Carr, Greg; Deligiannis, Frank; Franco, Lauro; Jones, Loren; Lam, Barbara; Nelson, Ron; Pantaleon, Jose; Ruiz, Ian; Treichler, John; Wester, Gene; Sauers, Jim; Giampoli, Paul; Haskell, Russ; Mulvey, Jim; Repp, John

    2005-01-01

    The X2000 Power System Electronics (PSE) is a Jet Propulsion Laboratory (JPL) task to develop a new generation of power system building blocks for potential use on future deep space missions. The effort includes the development of electronic components and modules that can be used as building blocks in the design of generic spacecraft power systems.

  7. Flexible Electronics Development Supported by NASA

    Science.gov (United States)

    Baumann, Eric

    2014-01-01

    The commercial electronics industry is leading development in most areas of electronics for NASA applications; however, working in partnership with industry and the academic community, results from NASA research could lead to better understanding and utilization of electronic materials by the flexible electronics industry. Innovative ideas explored by our partners in industry and the broader U.S. research community help NASA execute our missions and bring new American products and services to the global technology marketplace. [Mike Gazarik, associate administrator for Space Technology, NASA Headquarters, Washington DC] This presentation provides information on NASA needs in electronics looking towards the future, some of the work being supported by NASA in flexible electronics, and the capabilities of the Glenn Research Center supporting the development of flexible electronics.

  8. Stabilization of boron carbide via silicon doping.

    Science.gov (United States)

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping. PMID:25427850

  9. Stabilization of boron carbide via silicon doping

    Science.gov (United States)

    Proctor, J. E.; Bhakhri, V.; Hao, R.; Prior, T. J.; Scheler, T.; Gregoryanz, E.; Chhowalla, M.; Giulani, F.

    2015-01-01

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  10. Disorder and defects are not intrinsic to boron carbide

    Science.gov (United States)

    Mondal, Swastik; Bykova, Elena; Dey, Somnath; Ali, Sk Imran; Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Parakhonskiy, Gleb; van Smaalen, Sander

    2016-01-01

    A unique combination of useful properties in boron-carbide, such as extreme hardness, excellent fracture toughness, a low density, a high melting point, thermoelectricity, semi-conducting behavior, catalytic activity and a remarkably good chemical stability, makes it an ideal material for a wide range of technological applications. Explaining these properties in terms of chemical bonding has remained a major challenge in boron chemistry. Here we report the synthesis of fully ordered, stoichiometric boron-carbide B13C2 by high-pressure-high-temperature techniques. Our experimental electron-density study using high-resolution single-crystal synchrotron X-ray diffraction data conclusively demonstrates that disorder and defects are not intrinsic to boron carbide, contrary to what was hitherto supposed. A detailed analysis of the electron density distribution reveals charge transfer between structural units in B13C2 and a new type of electron-deficient bond with formally unpaired electrons on the C-B-C group in B13C2. Unprecedented bonding features contribute to the fundamental chemistry and materials science of boron compounds that is of great interest for understanding structure-property relationships and development of novel functional materials.

  11. Disorder and defects are not intrinsic to boron carbide.

    Science.gov (United States)

    Mondal, Swastik; Bykova, Elena; Dey, Somnath; Ali, Sk Imran; Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Parakhonskiy, Gleb; van Smaalen, Sander

    2016-01-01

    A unique combination of useful properties in boron-carbide, such as extreme hardness, excellent fracture toughness, a low density, a high melting point, thermoelectricity, semi-conducting behavior, catalytic activity and a remarkably good chemical stability, makes it an ideal material for a wide range of technological applications. Explaining these properties in terms of chemical bonding has remained a major challenge in boron chemistry. Here we report the synthesis of fully ordered, stoichiometric boron-carbide B13C2 by high-pressure-high-temperature techniques. Our experimental electron-density study using high-resolution single-crystal synchrotron X-ray diffraction data conclusively demonstrates that disorder and defects are not intrinsic to boron carbide, contrary to what was hitherto supposed. A detailed analysis of the electron density distribution reveals charge transfer between structural units in B13C2 and a new type of electron-deficient bond with formally unpaired electrons on the C-B-C group in B13C2. Unprecedented bonding features contribute to the fundamental chemistry and materials science of boron compounds that is of great interest for understanding structure-property relationships and development of novel functional materials. PMID:26777140

  12. Chemical Mechanical Polishing of Silicon Carbide

    Science.gov (United States)

    Powell, J. Anthony; Pirouz

    1999-01-01

    The High Temperature Integrated Electronics and Sensors (HTIES) team at the NASA Lewis Research Center is developing silicon carbide (SiC) as an enabling electronic technology for many aerospace applications. The Lewis team is focusing on the chemical vapor deposition of the thin, single-crystal SiC films from which devices are fabricated. These films, which are deposited (i.e., epitaxially "grown") on commercial wafers, must consist of a single crystal with very few structural defects so that the derived devices perform satisfactorily and reliably. Working in collaboration (NASA grant) with Professor Pirouz of Case Western Reserve University, we developed a chemical-mechanical polishing (CMP) technique for removing the subsurface polishing damage prior to epitaxial growth of the single-crystal SiC films.

  13. Mechanism of instability of carbides in Fe–TaC alloy under high energy electron irradiation at 673 K

    International Nuclear Information System (INIS)

    Highlights: • Fe–TaC alloy was fabricated as a model alloy for F82H steel. • Instability of TaC in Fe was observed under high energy electron irradiation at 673 K. • The rate of shrinkage depended on energy, flux, degree of beam focus. • Displacement of Ta in TaC, or radiation-enhanced diffusion of Ta are the mechanism of instability. - Abstract: Reduced activation ferritic/martensitic steels (RAFMs), such as F82H steel, are designed to enhance the high-temperature strength by formation of MX-type nanometer-scale precipitates, mainly TaC. However, their instability under irradiation was recently reported. The purpose of this work, therefore, is to clarify the mechanism employing simultaneous observations under electron irradiation at elevated temperature in a high voltage electron microscope. In this work, Fe-0.2 wt.% TaC was fabricated as a model alloy of F82H steel. The instability of the precipitates was observed under electron irradiation at 1 MeV or above. The remarkable shrinkage and disappearance were clearly observed under irradiation with 1.5 MeV and above. On the contrary, the precipitates were mostly stable below 0.75 MeV. Two kinds of mechanism of the irradiation-induced instability were deduced from the electron-energy dependence. One is the dissolution and diffusion of tantalum from precipitates in ferrite matrix. The other is the displacements of tantalum in precipitates that introduce dissolution of Ta into matrix

  14. Effect of atomic sites on electronic and mechanical properties of (Fe,Mo){sub 6}C carbides

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Z.Q., E-mail: zqlv@ysu.edu.cn [State Key Laboratory of Metastable Material Science and Technology, Yanshan University, Qinhuangdao 066004 (China); College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004 (China); Wang, B. [State Key Laboratory of Metastable Material Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Sun, S.H. [College of Science, Yanshan University, Qinhuangdao 066004 (China); Fu, W.T., E-mail: wtfu@ysu.edu.cn [State Key Laboratory of Metastable Material Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-11-15

    The phase stability of Fe{sub 3}Mo{sub 3}C-II (Mo at the 48f site) is higher than other phases in the present work. The formation enthalpies of Fe{sub 3}Mo{sub 3}C-II and Fe{sub 2}Mo{sub 4}C are −0.095 and −0.053 eV/atom, respectively. The 16d and 32e sites are comfortable for Fe atoms, and the Mo atoms tend to be at the 48f sites. The electronic characteristics of metal atoms are sensitive to the local short-range order in these crystals. Moreover, the nonmetal C atom is with negative charges (obtaining electrons), and this electronegative phenomenon is also present in some metal atoms (Fe or Mo) in M{sub 6}C. The hardness of Fe{sub 3}Mo{sub 3}C (13.6 GPa) is the highest in these phases, and the hardness of Fe{sub 2}Mo{sub 4}C is 11.7 GPa. The θ{sub D} of Fe{sub 3}Mo{sub 3}C-I (Fe at the 48f site) is 397 K, and that of Fe{sub 3}Mo{sub 3}C-II abruptly changes to 657 K when Mo in the 48f site. - Highlights: • The electronic characteristics of metal atoms are sensitive to the local short-range order in the crystal. • Besides C atom with negative charges, partial metal atoms exist the electronegative phenomenon. • The hardness of Fe{sub 3}Mo{sub 3}C (13.6 GPa) is the highest and Fe{sub 2}Mo{sub 4}C (11.7 GPa) is the second hardest.

  15. Wear resistance and electronic structure of cutting tool materials on a basis carbides of tungsten and titanium

    International Nuclear Information System (INIS)

    The tool materials durability problem, in particular shock and wear resistance, has allowed to formulate a set of requirements and also to stablish the dependence between physical properties and wear. However, for understanding the nature of the process, for example determining the tribological property of the cutting tool, it is necessary to consider the atom interactions in a crystal. A theoretical study of the physical properties of cutting tool materials (W-Ti-C) with varying concentration of titanium is presented. Total and partial local electronic density for each atom in such hard solutions were calculated. (nevyjel)

  16. Electro-explosive alloying of VT6 alloy surface by boron carbide powder with the subsequent electron-beam treatment

    Science.gov (United States)

    Romanov, D. A.; Raykov, S. V.; Gromov, V. E.; Ivanov, Yu F.

    2015-11-01

    The formation of electro-explosive alloying zone with the thickness up to 50 μm has been revealed. It has been shown that it has a gradient structure, characterized by the decrease of carbon and boron concentration with the increase of the distance up to the treatment surface. The subsequent electron-beam treatment of alloying zone leads to flattening of alloying surface relief and is accompanied by the formation of a multilevel structure at the depth up to 30 μm, characterized by the interchange of some layers with a different level of alloying, having structure of a submicro- and nanoscale level.

  17. Aluminum doped silicon carbide thin films prepared by hot-wire CVD: Investigation of defects with electron spin resonance

    International Nuclear Information System (INIS)

    Al-doped p-type μc-SiC:H is prepared in a wide range of HWCVD preparation parameters like Al-doping ratio, deposition pressure, substrate and filament temperatures. We investigate the structural and electrical properties, and focus on identification of paramagnetic defect states by electron spin resonance (ESR). Nominally undoped μc-SiC:H is of a high n-type conductivity (σD = 10-6-10-1 S/cm) and shows a narrow central ESR line (g ∼ 2.003, peak-to-peak linewidth ΔHpp ∼ 4 G) with two pairs of satellites and a spin density NS = 1019 cm-3. Al-doping results in the compensation of dark conductivity to as low as σD = 10-11 S/cm and at higher doping concentrations to effective p-type material. Increase of Al-doping results in reduction of crystallinity (ICIR), ESR line shifts to g ∼ 2.01 and becomes as broad as ΔHpp ∼ 30 G, not unlike to the resonance of singly occupied paramagnetic valence band tail states in a-Si:H. ESR spectrum of highly crystalline Al-doped μc-SiC:H however has a g-value very close to undoped μc-SiC:H. Electron spin density in compensated material decreases to 5 x 1017 cm-3 before it increases again for the highly doped material.

  18. Silicon carbide bodies

    International Nuclear Information System (INIS)

    A self-bonded silicon carbide body produced by siliconising a preformed mixture of particles (shaped by means other than slip-casting) of carbon and silicon carbide in the beta form has a mean grain size in the range of 0.1 to 5 microns. Such a body may be produced using silicon carbide particles having a mean surface area in the range 0.5 to 20 square metres per gram. The silicon carbide particles may be produced by heating a mixture of silica and silicon to generate silicon monoxide vapour and passing the vapour through a bed of particulate carbon. (author)

  19. Developing and managing electronic collections the essentials

    CERN Document Server

    Johnson, Peggy

    2014-01-01

    The complex issues associated with developing and managing electronic collections deserve special treatment, and library collection authority Peggy Johnson rises to the challenge with a book sure to become a benchmark for excellence. Providing comprehensive coverage of key issues and decision points, she offers advice on best practices for developing and managing these important resources for libraries of all types and sizes.

  20. Recent developments in electron photon angular correlations

    International Nuclear Information System (INIS)

    The application of the electron photon coincidence technique to evaluate the role of spin-orbit interactions in electron impact excitation of heavy atoms is reviewed. Excitation of the 63P1 level of Hg is described in detail. The use of polarized electrons in this excitation governed by the selection rule ΔMsub(L)=0 is discussed. Experiments in which the time evolution of excited states can be observed are described. A recent theoretical development is reviewed, in which experimental observables are linked to specific dynamical effects during the excitation. (Auth.)

  1. Transformations of Carbides During Tempering of D3 Tool Steel

    Science.gov (United States)

    Nykiel, Tadeusz; Hryniewicz, Tadeusz

    2014-06-01

    The studies were performed on D3 tool steel hardened after austenitizing at 1050 °C during 30 min and tempering at 200-700 °C. Based on the diffraction studies performed from the extraction replicas, using electron microscopy, it was found that after 120-min tempering in the consecutive temperatures, the following types of carbides occur: Apart from higher mentioned carbides, there are also big primary carbides and fine secondary M7C3 carbides occurring, which did not dissolve during austenitizing.

  2. Recent developments and on-line tests of uranium carbide targets for production of nuclides far from

    CERN Document Server

    V.N. Panteleev et al.

    The capacity of uranium carbide target materials of different structure and density for production of neutron-rich and heavy neutron-deficient isotopes have been investigated at the IRIS facility (PNPI) in the collaboration with Legnaro – GANIL – Orsay laboratories. The yields and release times of the species produced in the targets by the reactions induced by a 1 GeV proton beam of the PNPI synchrocyclotron have been measured. For the purpose to elaborate the most efficient and fast uranium carbide target prototype three kinds of the target materials were studied: a) a high density UC target material having ceramic-like structure with the density of 11 g/cm3 and the grain dimensions of about 200 microns; b) a high density UC target material with the density of 12 g/cm3 and the grain dimensions of about 20 microns prepared by the method of the powder metallurgy; c) a low density UCx target material with the density 3g/cm3 and the grain dimensions of about 20 microns prepared by the ISOLDE method. The comp...

  3. Development of the doppler electron velocimeter: theory.

    Energy Technology Data Exchange (ETDEWEB)

    Reu, Phillip L.

    2007-03-01

    Measurement of dynamic events at the nano-scale is currently impossible. This paper presents the theoretical underpinnings of a method for making these measurements using electron microscopes. Building on the work of Moellenstedt and Lichte who demonstrated Doppler shifting of an electron beam with a moving electron mirror, further work is proposed to perfect and utilize this concept in dynamic measurements. Specifically, using the concept of ''fringe-counting'' with the current principles of transmission electron holography, an extension of these methods to dynamic measurements is proposed. A presentation of the theory of Doppler electron wave shifting is given, starting from the development of the de Broglie wave, up through the equations describing interference effects and Doppler shifting in electron waves. A mathematical demonstration that Doppler shifting is identical to the conceptually easier to understand idea of counting moving fringes is given by analogy to optical interferometry. Finally, potential developmental experiments and uses of a Doppler electron microscope are discussed.

  4. Predicted boron-carbide compounds: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, De Yu; Yan, Qian; Wang, Bing; Wang, Yuan Xu, E-mail: wangyx@henu.edu.cn; Yang, Jueming; Yang, Gui [Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng 475004 (China)

    2014-06-14

    By using developed particle swarm optimization algorithm on crystal structural prediction, we have explored the possible crystal structures of B-C system. Their structures, stability, elastic properties, electronic structure, and chemical bonding have been investigated by first-principles calculations with density functional theory. The results show that all the predicted structures are mechanically and dynamically stable. An analysis of calculated enthalpy with pressure indicates that increasing of boron content will increase the stability of boron carbides under low pressure. Moreover, the boron carbides with rich carbon content become more stable under high pressure. The negative formation energy of predicted B{sub 5}C indicates its high stability. The density of states of B{sub 5}C show that it is p-type semiconducting. The calculated theoretical Vickers hardnesses of B-C exceed 40 GPa except B{sub 4}C, BC, and BC{sub 4}, indicating they are potential superhard materials. An analysis of Debye temperature and electronic localization function provides further understanding chemical and physical properties of boron carbide.

  5. Predicted boron-carbide compounds: a first-principles study.

    Science.gov (United States)

    Wang, De Yu; Yan, Qian; Wang, Bing; Wang, Yuan Xu; Yang, Jueming; Yang, Gui

    2014-06-14

    By using developed particle swarm optimization algorithm on crystal structural prediction, we have explored the possible crystal structures of B-C system. Their structures, stability, elastic properties, electronic structure, and chemical bonding have been investigated by first-principles calculations with density functional theory. The results show that all the predicted structures are mechanically and dynamically stable. An analysis of calculated enthalpy with pressure indicates that increasing of boron content will increase the stability of boron carbides under low pressure. Moreover, the boron carbides with rich carbon content become more stable under high pressure. The negative formation energy of predicted B5C indicates its high stability. The density of states of B5C show that it is p-type semiconducting. The calculated theoretical Vickers hardnesses of B-C exceed 40 GPa except B4C, BC, and BC4, indicating they are potential superhard materials. An analysis of Debye temperature and electronic localization function provides further understanding chemical and physical properties of boron carbide. PMID:24929411

  6. Predicted boron-carbide compounds: A first-principles study

    International Nuclear Information System (INIS)

    By using developed particle swarm optimization algorithm on crystal structural prediction, we have explored the possible crystal structures of B-C system. Their structures, stability, elastic properties, electronic structure, and chemical bonding have been investigated by first-principles calculations with density functional theory. The results show that all the predicted structures are mechanically and dynamically stable. An analysis of calculated enthalpy with pressure indicates that increasing of boron content will increase the stability of boron carbides under low pressure. Moreover, the boron carbides with rich carbon content become more stable under high pressure. The negative formation energy of predicted B5C indicates its high stability. The density of states of B5C show that it is p-type semiconducting. The calculated theoretical Vickers hardnesses of B-C exceed 40 GPa except B4C, BC, and BC4, indicating they are potential superhard materials. An analysis of Debye temperature and electronic localization function provides further understanding chemical and physical properties of boron carbide

  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. Processing of solid solution, mixed uranium/refractory metal carbides for advanced space nuclear power and propulsion systems

    Science.gov (United States)

    Knight, Travis Warren

    Nuclear thermal propulsion (NTP) and space nuclear power are two enabling technologies for the manned exploration of space and the development of research outposts in space and on other planets such as Mars. Advanced carbide nuclear fuels have been proposed for application in space nuclear power and propulsion systems. This study examined the processing technologies and optimal parameters necessary to fabricate samples of single phase, solid solution, mixed uranium/refractory metal carbides. In particular, the pseudo-ternary carbide, UC-ZrC-NbC, system was examined with uranium metal mole fractions of 5% and 10% and corresponding uranium densities of 0.8 to 1.8 gU/cc. Efforts were directed to those methods that could produce simple geometry fuel elements or wafers such as those used to fabricate a Square Lattice Honeycomb (SLHC) fuel element and reactor core. Methods of cold uniaxial pressing, sintering by induction heating, and hot pressing by self-resistance heating were investigated. Solid solution, high density (low porosity) samples greater than 95% TD were processed by cold pressing at 150 MPa and sintering above 2600 K for times longer than 90 min. Some impurity oxide phases were noted in some samples attributed to residual gases in the furnace during processing. Also, some samples noted secondary phases of carbon and UC2 due to some hyperstoichiometric powder mixtures having carbon-to-metal ratios greater than one. In all, 33 mixed carbide samples were processed and analyzed with half bearing uranium as ternary carbides of UC-ZrC-NbC. Scanning electron microscopy, x-ray diffraction, and density measurements were used to characterize samples. Samples were processed from powders of the refractory mono-carbides and UC/UC 2 or from powders of uranium hydride (UH3), graphite, and refractory metal carbides to produce hypostoichiometric mixed carbides. Samples processed from the constituent carbide powders and sintered at temperatures above the melting point of UC

  9. Study and optimization of the carbothermic reduction process for obtaining boron carbide

    International Nuclear Information System (INIS)

    Boron carbide - B sub(4)C - is a ceramic material of technological importance due to its hardness and high chemical and thermal stabilities. Moreover, its high neutron capture cross section makes it suitable for application as neutron absorber in nuclear technology. The process for obtaining carbothermally derived boron carbide has been studied in two steps: firstly, the parameters of the boric acid → boron oxide dehydration reaction have been defined; secondly, the optimization of the carbothermal reduction reaction using boron oxide has been undertaken looking for boron carbide having low level of free carbon. The starting materials as well as the main products have been studied by chemical and spectrographic analyses, X-ray diffractometry, granulometric classification and scanning electron microscopy. The optimization of the carbothermic reduction process allowed for the development and set up of a fabrication procedure yielding high quality B sub(4) C powders, starting from low cost and easily available (in the Brazilian market) raw materials. (author)

  10. Electron Storage Ring Development for ICS Sources

    Energy Technology Data Exchange (ETDEWEB)

    Loewen, Roderick [Lyncean Technologies, Inc., Palo Alto, CA (United States)

    2015-09-30

    There is an increasing world-wide interest in compact light sources based on Inverse Compton Scattering. Development of these types of light sources includes leveraging the investment in accelerator technology first developed at DOE National Laboratories. Although these types of light sources cannot replace the larger user-supported synchrotron facilities, they offer attractive alternatives for many x-ray science applications. Fundamental research at the SLAC National Laboratory in the 1990’s led to the idea of using laser-electron storage rings as a mechanism to generate x-rays with many properties of the larger synchrotron light facilities. This research led to a commercial spin-off of this technology. The SBIR project goal is to understand and improve the performance of the electron storage ring system of the commercially available Compact Light Source. The knowledge gained from studying a low-energy electron storage ring may also benefit other Inverse Compton Scattering (ICS) source development. Better electron storage ring performance is one of the key technologies necessary to extend the utility and breadth of applications of the CLS or related ICS sources. This grant includes a subcontract with SLAC for technical personnel and resources for modeling, feedback development, and related accelerator physics studies.

  11. Development of Quantitative electron nano-diffraction

    NARCIS (Netherlands)

    Kumar, V.

    2009-01-01

    This thesis is a step towards development of quantitative parallel beam electron nano-diffraction (PBED). It is focused on the superstructure determination of zig-zag and zig-zig NaxCoO2 and analysis of charge distribution in the two polymorphs Nb12O29 using PBED. It has been shown that quantitative

  12. Development of plasma cathode electron guns

    Science.gov (United States)

    Oks, Efim M.; Schanin, Peter M.

    1999-05-01

    The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

  13. Micro-physical properties of cemented carbides via OOF computer simulations

    International Nuclear Information System (INIS)

    Full text: Simulations of micro-physical properties in complex, heterogeneous systems are easily handled by commercial finite element codes. An object oriented finite element analysis, OOF, developed at the National Institute of Standards and Technology, allows a microstructure-based analysis to elucidate select micro-physical properties of various heterogeneous systems. In this paper, we have applied OOF to cemented carbides, i.e., a metal matrix composite consisting of tungsten carbide particles in a cobalt matrix. A conventional cemented carbide microstructure and a double cemented carbide structure (DCC) were examined In DCC microstructures, granules of conventional cemented carbides are distributed within a continuous cobalt matrix. OOF was applied to actual digitized images obtained from scanning electron microscopy by using gray levels and Boolean operations to identify and assign materials properties at the pixel level. An adaptive meshing procedure by phase was used to create the finite element mesh. Temperature changes and/or mechanical strains were then applied to the mesh and equilibrated. Resultant strains and stresses were analyzed to calculate the coefficients of thermal expansion and Young's modulus. Computational results compared well to experimental values obtained from dilatometry and resonant ultrasound spectroscopy. Residual stress distributions were compared between the two microstructures. (author)

  14. Hafnium and silicon carbide multilayer coatings for the protection of carbon composites

    International Nuclear Information System (INIS)

    A solution to protect the surface of a carbon/carbon composite from oxidation at high temperature is to combine refractory carbides, such as hafnium and silicon carbides (HfC and SiC). Their depositions have been studied on flat substrates and present major protection against oxidation at high temperature (several minutes at 2000 C under air). The infiltration of these carbides layers has been observed inside the open porosities of the carbon substrate which enhance the adhesion of the protection. The low pressure chemical vapor deposition (LPCVD) process developed here allows multilayer HfC/SiC depositions. The HfC coatings have various morphologies and thicknesses depending on the experimental conditions (temperature, pressure, dilution). This carbide has been firstly deposited over flat graphite substrates and carbon single fibers. Secondly, the multilayer coating deposition over a C/C composite and over carbon single fibers is studied. Finally, HfC layers have been infiltrated inside carbon fiber tows. To avoid the notch effect on the carbon fibers, a thin layer of pyrocarbon (50 nm thick) has been deposited prior to the growth of the carbides. All the coatings were done in a hot wall CVD reactor and their morphologies and chemical compositions characterized by scanning electron microscopy. (authors)

  15. Development of Quantitative electron nano-diffraction

    OpenAIRE

    Kumar, V

    2009-01-01

    This thesis is a step towards development of quantitative parallel beam electron nano-diffraction (PBED). It is focused on the superstructure determination of zig-zag and zig-zig NaxCoO2 and analysis of charge distribution in the two polymorphs Nb12O29 using PBED. It has been shown that quantitative electron nano-diffraction (parallel beam) has the potential of solving superstructures as well as charge distribution by taking the dynamicity of the data to its advantage. The information contain...

  16. Development of the Antares electron gun

    International Nuclear Information System (INIS)

    Antares is the Los Alamos National Laboratory 40-kJ, 1-ns, CO2 laser system that is now operational. This laser system was developed for the Intertial Confinement Fusion (ICF) program and is beginning target experiments. The distributed circuit modeling, design and operation of the large electron gun developed for the final laser power amplifier are reviewed. This gun is significant because of the large electron current area, 9 m2; the number of emitter blades, 48; the dual cathode current return; and the coaxial geometry and grid control. The gun components and their development are discussed. These include the emitter blades, the coaxial grid (to maintain constant electron current during the 5-μs pulse), the bonded stacked-ring insulator (to electrically insulate the grid/cathode), the Kapton/aluminum electron transmission windows (to provide an interface between gun vacuum and laser gas) and the vacuum shell (operated at a vacuum of 10-6 torr). A unique pressure diagnostic is also discussed

  17. Synthesis and photoluminescence property of boron carbide nanowires

    International Nuclear Information System (INIS)

    Large scale, high density boron carbide nanowires have been synthesized by using an improved carbothermal reduction method with B/B2O3/C powder precursors under an argon flow at 1100°C. The boron carbide nanowires are 5–10 μm in length and 80–100 nm in diameter. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) characterizations show that the boron carbide nanowire has a B4C rhombohedral structure with good crystallization. The Raman spectrum of the as-grown boron carbide nanowires is consistent with that of a B4C structure consisting of B11C icosahedra and C-B-C chains. The room temperature photoluminescence spectrum of the boron carbide nanowires exhibits a visible range of emission centred at 638 nm. (condensed matter: structure, thermal and mechanical properties)

  18. Multikilowatt power electronics development for spacecraft

    Science.gov (United States)

    Decker, D. K.; Inouye, L. Y.; Rolandelli, D. L.

    1991-01-01

    Attention is given to several multikilowatt power electronic components developed by TRW for the Space Station Power Management and Distribution test bed at NASA Lewis Research Center. These components include a 12.5-kW DC-DC converter, a 6.25-kW battery charge/discharge regulator, an 82-channel sequential shunt unit, a 10-A remote power controllers, and three different types of 1-kW load converters. TRW is also monitoring the development of 120-V fuses for space applications. The authors discuss these developments and provide steady-state and dynamic performance parameters.

  19. Thermodynamic and kinetic study of uranium carbide pyrophoricity

    International Nuclear Information System (INIS)

    This research thesis concerns the development of nuclear reactors of fourth generation, and more particularly the use of carbide fuels instead of oxide fuels. An experimental part allows the investigation of mechanisms resulting in the pyrophoric reaction of a powder of uranium carbide, and addresses the determination of kinetic parameters intrinsic to the oxidation of powdered uranium carbide. Experimental results are then used to develop models of oxidation of powders of carbide uranium which are applied to a simplified mono-dispersed powder, and then introduced in a computation code. Simulation results are compared with experimental results

  20. Enamel Surface Evaluation after Removal of Orthodontic Composite Remnants by Intraoral Sandblasting Technique and Carbide Bur Technique: A Three-Dimensional Surface Profilometry and Scanning Electron Microscopic Study

    OpenAIRE

    Mhatre, Amol C; Tandur, Arundhati P; Reddy, Sumitra S; Karunakara, B C; Baswaraj, H

    2015-01-01

    Background: The purpose of this thesis is to present a practical and efficient clinical method of returning enamel to as near its original condition as possible following removal of bonded orthodontic attachments. The main objective of this study is to evaluate and compare the iatrogenic enamel damage caused by use of two different remnant removal techniques – sandblasting technique and carbide bur technique. Materials and Methods: 40 extracted premolar teeth were selected as sample. Premolar...

  1. Comment on "Combined experimental and computational study of the recrystallization process induced by electronic interactions of swift heavy ions with silicon carbide crystals"

    OpenAIRE

    Benyagoub, A.

    2014-01-01

    A combined experimental and computational study of the recrystallization process induced by swift heavy ions in pre-damaged silicon carbide crystals was reported in a recent paper by Debelle et al. [Phys. Rev. B 86, 100102(R) (2012)]. In this study, the authors tried to mimic by means of molecular dynamic simulations both damage production induced by low energy ion irradiation in SiC and the recrystallization effect generated by subsequent swift heavy ion irradiation. Here we show that the si...

  2. Low-Temperature Electronic Components Being Developed

    Science.gov (United States)

    Patterson, Richard L.; Hammond, Ahmad

    1999-01-01

    In many future NASA missions, such as deep space planetary exploration and the Next Generation Space Telescope, electrical components and systems must operate reliably and efficiently in extremely low temperature environments. Most modern electronic components cannot operate below moderately low operating temperatures (-40 to -55 C). The low-temperature electronics program at the NASA Lewis Research Center is focusing on the development and characterization of low-temperature components and the integration of the developed devices into demonstrable very low-temperature (-200 C) power systems such as dc-dc converters. Such low-temperature electronics will not only tolerate hostile environments but also will reduce system size and weight by eliminating radioisotope heating units, thereby reducing launch cost, improving reliability and lifetime, and increasing energy densities. Low-temperature electronic components will also have a great influence on terrestrial applications such as medical instrumentation, magnetic levitation transportation systems, and arctic and antarctic exploration. Lewis researchers are now performing extensive evaluations of commercially available as well as custom-made devices. These include various types of energy storage and signal capacitors, power switching devices, magnetic and superconducting materials, and primary lithium batteries, to name a few.

  3. Electronic logbook development for the KSTAR commissioning

    International Nuclear Information System (INIS)

    During the commissioning of the KSTAR device, electronic logbook has been developed to record participant's opinions regarding experimental procedures and results. The experimental logbook, a kind of the electronic logbooks inserts principal experimental parameters by itself and gets the experimenter's comments. Since it usually takes long time to surf around raw experimental data, a summarized comment on the experimental logbook helps physicists to analyze the results. The operation logbook, the other part of electronic logbook records history about system's abnormality, including their management history. Records on the operation logbook for components provide the criteria to validate the device's stability and the basis to complement the device operation procedure. Since a large majority of readers is interested in the information on the electronic logbook, the data is manipulated to be searched and read on the web-site which is accessible by the authenticated users. The web-site also includes a formatting function to report the logbook data as a document using Java Document Object Model (DOM) and Java Simple API for XML (SAX) API. Because there were difficulties to make an action scenario on the events due to insufficient experience of tokamak operation, it was developed in parallel during the commissioning. By training operators to write comments on every detail of the experimental results and operation events, it could be more valuable data source for the next experiments.

  4. Cryogenic Electronics Being Developed for Space Operation

    Science.gov (United States)

    Patterson, Richard L.; Hammoud, Ahmad; Gerber, Scott S.

    2002-01-01

    Planetary exploration missions and deep space probes require electrical power management and control systems that can operate efficiently and reliably in very low temperature environments. Presently, spacecraft operating in the cold environment of deep space carry a large number of radioisotope heating units to maintain the surrounding temperature of the onboard electronics at approximately 20 C. Electronics capable of operation at cryogenic temperatures would not only tolerate the hostile environment of deep space but also reduce system size and weight by eliminating or reducing the radioisotope heating units and their associate structures. Thereby, such electronics would reduce system development as well as launch costs. In addition, power electronic circuits designed for operation at low temperatures are expected to result in more efficient systems than those at room temperature. This improvement results because semiconductor and dielectric materials have better behavior and tolerance in their electrical and thermal properties at low temperatures. The Low Temperature Electronics Program at the NASA Glenn Research Center is focusing on the research and development of electrical components, circuits, and systems suitable for applications in the aerospace environment and in deep space exploration missions. Research is being conducted on devices and systems for reliable use down to cryogenic temperatures. Some of the commercial off-the-shelf as well as developed components that are being characterized include semiconductor switching devices, resistors, magnetics, and capacitors. Semiconductor devices and integrated circuits including digital-to-analog and analog-to-digital converters, dc-dc converters, operational amplifiers, and oscillators are also being investigated for potential use in low-temperature applications. For example, the output response of an advanced oscillator at room temperature and at -190 C is shown. Most oscillators can operate at temperatures

  5. Development and Implementation of Star Tracker Electronics

    OpenAIRE

    Lindh, Marcus

    2014-01-01

    Star trackers are essential instruments commonly used on satellites. They provide precise measurement of the orientation of a satellite and are part of the attitude control system. For cubesats star trackers need to be small, consume low power and preferably cheap to manufacture. In this thesis work the electronics for a miniature star tracker has been developed. A star detection algorithm has been implemented in hardware logic, tested and verified. A platform for continued work is presented ...

  6. Zirconium carbide recrystallization

    Energy Technology Data Exchange (ETDEWEB)

    Lanin, A.G.; Erin, O.N.; Sul' Yanov, S.N.; Turchin, V.N.

    1986-02-01

    This paper studies the primary recrystallization process of the sintered polycrystalline zirconium carbide with a composition of ZrC /SUB 0.98/ . The properties of zirconium carbide samples deformed under compression are presented; the selected degree of deformation ensures a lower scatter of grain sizes at relative error of +/- 5% in the final deformation measurement. The established mechanisms of structural changes in zirconium carbide during plastic deformation and subsequent high temperature treatment indicate the possibility of using thermomechanical methods for the direct control of the structure of these mechanical methods for the direct control of the structure of these and obviously othe group IV and V carbides obtained by powder metallurgical methods.

  7. Indigenous development of scanning electron microscope

    International Nuclear Information System (INIS)

    Scanning electron microscope (SEM) is a precision instrument and plays very important role in scientific studies. Bhabha Atomic Research Centre has taken up the job of development of SEM indigenously. Standard and commercially available components like computer, high voltage power supply, detectors etc. shall be procured from market. Focusing and scanning coils, vacuum chamber, specimen stage, control hardware and software etc. shall be developed at BARC with the help of Indian industry. Procurement, design and fabrication of various parts of SEM are in progress. (author)

  8. History of development of electronic personal dosemeters

    International Nuclear Information System (INIS)

    The nuclear and accelerator facilities are now increasingly used, especially high-energy accelerators for various purposes such as nuclear physics, medical science, and engineering research. It is very important to monitor the personal dose equivalent of workers in such facilities by using a real-time personal dosemeter. As real-time personal dosemeter, the silicon semiconductor detectors are world-widely used in nuclear and accelerator facilities. We have developed the real-time personal dosemeters using GM-tube and silicon semiconductor detector from about 40 years before. This report describes the history of development of electronic personal dosemeters using at atomic power plants in Japan. (author)

  9. Joining of boron carbide using nickel interlayer

    International Nuclear Information System (INIS)

    Carbide ceramics such as boron carbide due to their unique properties such as low density, high refractoriness, and high strength to weight ratio have many applications in different industries. This study focuses on direct bonding of boron carbide for high temperature applications using nickel interlayer. The process variables such as bonding time, temperature, and pressure have been investigated. The microstructure of the joint area was studied using electron scanning microscope technique. At all the bonding temperatures ranging from 1150 to 1300degC a reaction layer formed across the ceramic/metal interface. The thickness of the reaction layer increased by increasing temperature. The strength of the bonded samples was measured using shear testing method. The highest strength value obtained was about 100 MPa and belonged to the samples bonded at 1250 for 75 min bonding time. The strength of the joints decreased by increasing the bonding temperature above 1250degC. The results of this study showed that direct bonding technique along with nickel interlayer can be successfully utilized for bonding boron carbide ceramic to itself. This method may be used for bonding boron carbide to metals as well.

  10. Inverse free-electron laser accelerator development

    International Nuclear Information System (INIS)

    The study of the Inverse Free-Electron Laser, as a potential mode of electron acceleration, has been pursued at Brookhaven National Laboratory for a number of years. More recent studies focused on the development of a low energy (few GeV), high gradient, multistage linear accelerator. The authors are presently designing a short accelerator module which will make use of the 50 MeV linac beam and high power (2 x 1011 W) CO2 laser beam of the Accelerator Test Facility (ATF) at the Center for Accelerator Physics (CAP), Brookhaven National Laboratory. These elements will be used in conjunction with a fast excitation (300 μsec pulse duration) variable period wiggler, to carry out an accelerator demonstration stage experiment

  11. Development of Surface Acoustic Wave Electronic Nose

    Directory of Open Access Journals (Sweden)

    S.K. Jha

    2010-07-01

    Full Text Available The paper proposes an effective method to design and develop surface acoustic wave (SAW sensor array-based electronic nose systems for specific target applications. The paper suggests that before undertaking full hardware development empirically through hit and trial for sensor selection, it is prudent to develop accurate sensor array simulator for generating synthetic data and optimising sensor array design and pattern recognition system. The latter aspects are most time-consuming and cost-intensive parts in the development of an electronic nose system. This is because most of the electronic sensor platforms, circuit components, and electromechanical parts are available commercially-off-the-shelve (COTS, whereas knowledge about specific polymers and data analysis software are often guarded due to commercial or strategic interests. In this study, an 11-element SAW sensor array is modelled to detect and identify trinitrotoluene (TNT and dinitrotoluene (DNT explosive vapours in the presence of toluene, benzene, di-methyl methyl phosphonate (DMMP and humidity as interferents. Additive noise sources and outliers were included in the model for data generation. The pattern recognition system consists of: (i a preprocessor based on logarithmic data scaling, dimensional autoscaling, and singular value decomposition-based denoising, (ii principal component analysis (PCA-based feature extractor, and (iii an artificial neural network (ANN classifier. The efficacy of this approach is illustrated by presenting detailed PCA analysis and classification results under varied conditions of noise and outlier, and by analysing comparative performance of four classifiers (neural network, k-nearest neighbour, naïve Bayes, and support vector machine.Defence Science Journal, 2010, 60(4, pp.364-376, DOI:http://dx.doi.org/10.14429/dsj.60.493

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

    International Nuclear Information System (INIS)

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

  13. Growth characteristics of primary M7C3 carbide in hypereutectic Fe-Cr-C alloy.

    Science.gov (United States)

    Liu, Sha; Zhou, Yefei; Xing, Xiaolei; Wang, Jibo; Ren, Xuejun; Yang, Qingxiang

    2016-01-01

    The microstructure of the hypereutectic Fe-Cr-C alloy is observed by optical microscopy (OM). The initial growth morphology, the crystallographic structure, the semi-molten morphology and the stacking faults of the primary M7C3 carbide are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The in-suit growth process of the primary M7C3 carbide was observed by confocal laser microscope (CLM). It is found that the primary M7C3 carbide in hypereutectic Fe-Cr-C alloy is irregular polygonal shape with several hollows in the center and gaps on the edge. Some primary M7C3 carbides are formed by layers of shell or/and consist of multiple parts. In the initial growth period, the primary M7C3 carbide forms protrusion parallel to {} crystal planes. The extending and revolving protrusion forms the carbide shell. The electron backscattered diffraction (EBSD) maps show that the primary M7C3 carbide consists of multiple parts. The semi-molten M7C3 carbide contains unmelted shell and several small-scale carbides inside, which further proves that the primary M7C3 carbide is not an overall block. It is believed that the coalescence of the primary M7C3 carbides is ascribed to the growing condition of the protrusion and the gap filling process. PMID:27596718

  14. The development of an electronic dosemeter

    International Nuclear Information System (INIS)

    The National Radiological Protection Board (NRPB) and Siemens Plessey Controls Ltd are in the process of developing an electronic dosemeter suitable for use by an approved dosimetry service for classified workers. Pre-production dosemeters and readers have now been produced and trials in conjunction with the Health and Safety Executive will commence shortly with the aim of setting up an approved dosimetry service at NRPB based on the use of the dosemeter. The way it is proposed to organise the service will be discussed. (Author)

  15. Sintering of nano crystalline silicon carbide by doping with boron carbide

    Indian Academy of Sciences (India)

    M S Datta; A K Bandyopadhyay; B Chaudhuri

    2002-06-01

    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 with carbon of 1 wt% at 2050°C at vacuum (3 mbar) for 15 min. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by scanning electron microscopy and transmission electron microscopy. This study shows that the mechanism is a solid-state sintering process. Polytype transformation from 6H to 4H was observed.

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

    International Nuclear Information System (INIS)

    Highlights: • The hydrogen evolution activity (HER) on five transition metal carbides was studied in concentrated phosphoric acid at different temperatures. • Carbides of Group 6 metals (Cr, Mo, W) showed significant HER activity; the Volmer-Heyrovsky mechanism was proposed for the HER reaction on these materials. • The electrochemical stability towards oxidation was studied in concentrated phosphoric acid, with Cr, Ta and W carbides showing passivating behavior, while Nb and Mo carbides showed corrosion. - Abstract: 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, attributable to the different electronic structures. Tungsten carbide among the studied electrode samples exhibited the highest HER activity. Upon anodic potential scans in the presence of oxygen, chromium, tantalum and tungsten carbides displayed passivation due to the formation of stable surface layers whereas niobium and molybdenum carbides seemed to undergo corrosion

  17. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    OpenAIRE

    Luo Xiaogang; Ma Wenhui; Zhou Yang; Liu Dachun; Yang Bin; Dai Yongnian

    2009-01-01

    Abstract Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core–shell structure and gr...

  18. Reverse Flotation of Titanium Carbide from Garnet Mineral Using Cationic Surfactants

    OpenAIRE

    M.A. Abdel Khalek; B.K. Parekh

    2013-01-01

    For cutting garnet rocks Titanium carbide (TiC) blades are used, which produces a fine waste material, a mixture of garnet and a few percent of Titanium carbide. In the present study, a reverse flotation technique was developed to recover the valuable Titanium carbide as tailings from the waste mixture using cationic surfactants such as, DA-1618 (Diethyl Amine ether) or DDAB (Dioctyl Dimethyl Ammonium Bromide) and poly-propylenimine (PPI) as a depressant for Titanium carbide. The effect of co...

  19. Silicon carbide thyristor

    Science.gov (United States)

    Edmond, John A. (Inventor); Palmour, John W. (Inventor)

    1996-01-01

    The SiC thyristor has a substrate, an anode, a drift region, a gate, and a cathode. The substrate, the anode, the drift region, the gate, and the cathode are each preferably formed of silicon carbide. The substrate is formed of silicon carbide having one conductivity type and the anode or the cathode, depending on the embodiment, is formed adjacent the substrate and has the same conductivity type as the substrate. A drift region of silicon carbide is formed adjacent the anode or cathode and has an opposite conductivity type as the anode or cathode. A gate is formed adjacent the drift region or the cathode, also depending on the embodiment, and has an opposite conductivity type as the drift region or the cathode. An anode or cathode, again depending on the embodiment, is formed adjacent the gate or drift region and has an opposite conductivity type than the gate.

  20. Effect of strong carbide forming elements in hardfacing weld metal

    Institute of Scientific and Technical Information of China (English)

    Yuanbin Zhang; Dengyi Ren

    2004-01-01

    To achieve high carbon hard-facing weld metals with both high hardness and crack resistance, strong carbide forming elements Ti, Nb and V were alloyed into the weld metals, and their effect on the formation of carbides and the matrix microstructure were studied. Electron Probe Microanalysis (EPMA), Energy Dispersive Spectroscopy(EDS) and Transmission Electron Microscopy(TEM) were adopted to investigate the microstructure, then thermodynamics of the formation of carbides was calculated and their effect on the matrix was further discussed. It is revealed that Nb, Ti and V influence strongly the distribution and existing state of carbon, inducing precipitation of carbides accompanying with the depletion of carbon in matrix. But when only V are alloyed as carbide forming element, the carbides are scarce and distributed along grain boundaries, and the hard-facing alloy is too hard, while the using of only Nb or Ti could not reinforce the weld metals effectively. The hard-facing alloy reinforced with Nb, V and Ti can form dispersive fine carbides and low carbon martensite matrix.

  1. Recrystallization of zirconium carbide

    International Nuclear Information System (INIS)

    Temperature and deformation rate are studied for their effect on the structure and mechanical properties of polycrystalline sintered zirconium carbide. A decrease of the deformation rate from 10-2 to 5x10-4 s-1 and an increase of the deformation temperature from 0.5 Tsub(melt.) to 0.65 Tsub(melt.) are shown to activate a formation of integranular cavities and to decrease a degree of the structure distortion due to the diminishing intragranular deformation. Kinetics of the initial recrystallization in zirconium carbide is studied after plastic deformation and subsequent high-temperature annealing beginning from 0.72 Tsub(melt.)

  2. Thermal Conductivity of Uranium Nitride and Carbide

    Directory of Open Access Journals (Sweden)

    B. Szpunar

    2014-01-01

    Full Text Available We investigate the electronic thermal conductivity of alternative fuels like uranium nitride and uranium carbide. We evaluate the electronic contribution to the thermal conductivity, by combining first-principles quantum-mechanical calculations with semiclassical correlations. The electronic structure of UN and UC was calculated using Quantum Espresso code. The spin polarized calculations were performed for a ferromagnetic and antiferromagnetic ordering of magnetic moments on uranium lattice and magnetic moment in UC was lower than in UN due to stronger hybridization between 2p electrons of carbon and 5f electrons of uranium. The nonmagnetic electronic structure calculations were used as an input to BolzTrap code that was used to evaluate the electronic thermal conductivity. It is predicted that the thermal conductivity should increase with the temperature increase, but to get a quantitative agreement with the experiment at higher temperatures the interaction of electrons with phonons (and electron-electron scattering needs to be included.

  3. Front-end electronics development at BNL

    International Nuclear Information System (INIS)

    AT BNL the monolithic front-end electronics development effort is an outgrowth of work in discrete and hybrid circuits over the past 30 years. BNL's area of specialization centers on circuits for precision amplitude measurement, with signal-to-noise ratios of 100:1 and calibration to the same level of precision. Circuits are predominantly classical, continuous-time implementation of the functions now performed by hybrids, with little or no loss of performance. Included in this category are charge and current-sensitive preamplifiers, pulse shapers, sample/hold, multiplexing, and associated calibration and control circuits. Presently integration densities are limited to 16 channels per chip. Two examples are presented to illustrate the techniques needed to adopt hybrid circuits to the constraints of monolithic CMOS technology. They are programmable pulse shapes and a charge-sensitive preamp for very low detector capacitance

  4. Development of Electron Guns for Linacs and DC Accelerator

    International Nuclear Information System (INIS)

    Electrons guns for RF linacs and DC Accelerators are designed and developed at Electron Beam Centre (EBC)/APPD/BARC. Planar geometry grid and Pierce geometry grid configuration diode and triode guns with LaB6 cathode are developed. The cathode assembly consists of cups and heat shields made out of Tantalum and Rhenium sheets. The cathode assembly and the electron guns are tested on a test bench for beam characterization. The paper presents the development of the electron guns.

  5. The manufacturing method of boron carbide

    International Nuclear Information System (INIS)

    The new method for manufacturing of boron carbide as powder with controlled purity and surface development has been described. The suspension of boric acid aqueous solution and carbon black in alcohol has been homogenized mechanically. Water and alcohol are then evaporated during mixing. After drying homogenous mixture is heated in temperature range of 1270-1870 C during one hour

  6. Uranium-plutonium carbide as an LMFBR advanced fuel

    International Nuclear Information System (INIS)

    Uranium-plutonium carbide offers an improved fuel system for advanced breeder reactors. The high thermal conductivity and density of carbide fuels permit superior breeding performance and high specific power operation. These advantages combine to increase plutonium production, reduce fuel cycle and power costs, and lower plant capital costs. The carbide advantages are obtained at conservative fuel sytem design and operating conditions. Carbide fabrication technology has been demonstrated by the production of quality-assured fuel elements for irradiation testing. The carbide irradiation test program has demonstrated that high burnup can be achieved with several designs and that the consequences of postulated off-normal operating events are benign. Design bases to support helium- and sodium-bonded carbide fuel pin test irradiations in the Fast Flux Test Facility have been developed in the Experimental Breeder Reactor-II and the Transient Reactor irradiation experiments. Important issues regarding safety, reprocessing, and commercial-scale fabrication remain to be addressed in the continuing development of carbide fuels. Fiscal and historical circumstances have combined to preclude this development. This report reviews these circumstances and the state of the technology in general and advances a rationale for why development should be continued

  7. Center for Space Power and Advanced Electronics, Auburn University

    Science.gov (United States)

    Deis, Dan W.; Hopkins, Richard H.

    1991-01-01

    The union of Auburn University's Center for Space Power and Advanced Electronics and the Westinghouse Science and Technology Center to form a Center for the Commercial Development of Space (CCDS) is discussed. An area of focus for the CCDS will be the development of silicon carbide electronics technology, in terms of semiconductors and crystal growth. The discussion is presented in viewgraph form.

  8. Electronic transport in boron carbides: temperature (4K-300K), frequency (0-1 GHz) and composition (B13C2-B4C) effects

    International Nuclear Information System (INIS)

    Boron carbide is a light ceramics of industrial interest. The equilibrium diagram reveals a large compositional range (B9C to B4C). The compositions close to the boundary B4C are obtained by pressing directly in graphite dies while the other compositions were obtained by using boron nitride lined graphite dies and boron additions to the commercial powders. The starting point of the present study was the idea to use the electrical transport properties as possible ways of characterising the industrial materials. We were thus led to measure at low temperatures dc and ac conductivity, dielectric constant and thermopower. The successful study of a measurement method for ac measurements between 10 KHz and 1 GHz and between 4 K and 300 K was one of the main experimental points of the present work. ac measurements have permitted a clear separation between bulk and grain boundary effects on the transport. The bulk results were analysed in terms of the usual conduction models in disordered solids (hopping, polarons...)

  9. Recent developments in electron beam machine technology

    International Nuclear Information System (INIS)

    Electron beam accelerator provides ionisation energy for industrial processing. Electron beam accelerators are increasingly used for decontamination, conservation and disinfestation of food, for sterilization of medical products, and for polymerisation of materials. These machines are easy to install into a production factory as the radiation stops as soon as the machine is switched off. This safety advantage, together with the flexibility of use of these highly automated machines, has allowed the electron beam accelerator to become an important production tool. (author). 23 refs., 6 figs., 2 tabs

  10. Electronic dosimeter characteristics and new developments

    International Nuclear Information System (INIS)

    Electronic dosimeters are very much more versatile than existing passive dosimeters such as TLDs and film badges which have previously been the only type of dosimeters approved by national authorities for the legal measurement of doses to occupationally exposed workers. Requirements for the specifications and testing of electronic dosimeters are given in the standards produced by the International Electrotechnical Commission Working Group IEC SC45B/B8. A description is given of these standards and the use of electronic dosimeters as legal dosimeters is discussed. (author)

  11. Electrophysical properties and structure of niobium and tantalum carbide coatings on graphite

    International Nuclear Information System (INIS)

    Variation of electric resistance and thermoelectromotive force of tantalum and niobium carbides depending on composition and temperature is studied. Electric resistance of carbides is shown to grow with increase of carbon deficit, while thermoelectromotive force - accepts more negative values. Electro- and thermophysical properties are determined to be closely interrelated with electron structure of carbide coatings. In particular, results of X-ray photoelectron spectroscopy prove the fact

  12. Ion age transport: developing devices beyond electronics

    Science.gov (United States)

    Demming, Anna

    2014-03-01

    There is more to current devices than conventional electronics. Increasingly research into the controlled movement of ions and molecules is enabling a range of new technologies. For example, as Weihua Guan, Sylvia Xin Li and Mark Reed at Yale University explain, 'It offers a unique opportunity to integrate wet ionics with dry electronics seamlessly'. In this issue they provide an overview of voltage-gated ion and molecule transport in engineered nanochannels. They cover the theory governing these systems and fabrication techniques, as well as applications, including biological and chemical analysis, and energy conversion [1]. Studying the movement of particles in nanochannels is not new. The transport of materials in rock pores led Klinkenberg to describe an analogy between diffusion and electrical conductivity in porous rocks back in 1951 [2]. And already in 1940, Harold Abramson and Manuel Gorin noted that 'When an electric current is applied across the living human skin, the skin may be considered to act like a system of pores through which transfer of substances like ragweed pollen extract may be achieved both by electrophoretic and by diffusion phenomena' [3]. Transport in living systems through pore structures on a much smaller scale has attracted a great deal of research in recent years as well. The selective transport of ions and small organic molecules across the cell membrane facilitates a number of functions including communication between cells, nerve conduction and signal transmission. Understanding these processes may benefit a wide range of potential applications such as selective separation, biochemical sensing, and controlled release and drug delivery processes. In Germany researchers have successfully demonstrated controlled ionic transport through nanopores functionalized with amine-terminated polymer brushes [4]. The polymer nanobrushes swell and shrink in response to changes in temperature, thus opening and closing the nanopore passage to ionic

  13. Electronic Business Development as a Sustainable Competitive Advantage Model

    OpenAIRE

    Narimantas Kazimieras Paliulis; Jolanta Sabaitytė

    2012-01-01

    The paper examines the practical usefulness of information technologies in business reviewing electronic business concepts provided in science literature and also the newest tendencies of electronic business development. The paper offers a review of various authors works on e-strategies and IT influence on companies’ functionality. An analysis of disadvantages in various electronic business development models is provided. On the basis of analyses done on the theory of electronic business deve...

  14. High-temperature electronics

    Science.gov (United States)

    Matus, Lawrence G.; Seng, Gary T.

    1990-02-01

    To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.

  15. Microwave synthesis of phase-pure, fine silicon carbide powder

    International Nuclear Information System (INIS)

    Fine, monophasic silicon carbide powder has been synthesized by direct solid-state reaction of its constituents namely silicon and carbon in a 2.45 GHz microwave field. Optimum parameters for the silicon carbide phase formation have been determined by varying reaction time and reaction temperature. The powders have been characterized for their particle size, surface area, phase composition (X-ray diffraction) and morphology (scanning electron microscope). Formation of phase-pure silicon carbide can be achieved at 1300 deg. C in less than 5 min of microwave exposure, resulting in sub-micron-sized particles. The free energy values for Si + C → SiC reaction were calculated for different temperatures and by comparing them with the experimental results, it was determined that phase-pure silicon carbide can be achieved at around 1135 deg. C

  16. Sintered silicon carbide

    International Nuclear Information System (INIS)

    A sintered silicon carbide body having a predominantly equiaxed microstructure consists of 91 to 99.85% by weight of silicon carbide at least 95% of which is the alpha phase, up to 5.0% by weight carbonized organic material, 0.15 to 3.0% of boron, and up to 1.0% by weight additional carbon. A mixture of 91 to 99.85 parts by weight silicon carbide having a surface area of 1 to 100 m2/g, 0.67 to 20 parts of a carbonizable organic binder with a carbon content of at least 33% by weight, 0.15 to 5 parts of a boron source containing 0.15 to 3.0 parts by weight boron and up to 15 parts by weight of a temporary binder is mixed with a solvent, the mixture is then dried, shaped to give a body with a density of at least 1.60 g/cc and fired at 1900 to 22500C to obtain an equiaxed microstructure. (author)

  17. Development of beam diagnostic devices for characterizing electron guns

    International Nuclear Information System (INIS)

    The electron guns for the DC accelerators and RF Linacs are designed and developed at EBC/APPD/BARC, Kharghar. These electron guns need to be characterized for its design and performance. Two test benches were developed for characterizing the electron guns. Various beam diagnostic devices for measuring beam currents and beam sizes were developed. Conical faraday cup, segmented faraday cup, slit scanning bellows movement arrangement, multi-plate beam size measurement setup, multi- wire beam size measurement setup, Aluminum foil puncture assembly etc. were developed and used. The paper presents the in-house development of various beam diagnostics for characterizing electron guns and their use. (author)

  18. New methods for trigger electronics development

    Energy Technology Data Exchange (ETDEWEB)

    Cleland, W.E.; Stern, E.G. [Univ. of Pittsburgh, PA (United States)

    1991-12-31

    The large and complex nature of RHIC experiments and the tight time schedule for their construction requires that new techniques for designing the electronics should be employed. This is particularly true of the trigger and data acquisition electronics which has to be ready for turn-on of the experiment. We describe the use of the Workview package from VIEWlogic Inc. for design, simulation, and verification of a flash ADC readout system. We also show how field-programmable gate arrays such as the Xilinx 4000 might be employed to construct or prototype circuits with a large number of gates while preserving flexibility.

  19. The valve effect of the carbide interlayer of an electric resistance plug

    International Nuclear Information System (INIS)

    The welded electric resistance plug (ERP) usually contains a carbide interlayer at the plug-carbon material interface. The interlayer forms during welding the contact metallic alloy with the carbon material when the oxide films of the alloy are reduced on the interface surface by carbon to the formation of carbides and the surface layer of the plug material dissolves carbon to saturation. Subsequently, during solidification of the plug material it forms carbides with the alloy components. The structural composition of the carbide interlayer is determined by the chemical composition of the contact alloy. In alloys developed by the author and his colleagues the carbide forming elements are represented in most cases by silicon and titanium and, less frequently, by chromium and manganese. Therefore, the carbide interlayers in the ERP consisted mainly of silicon and titanium carbides

  20. Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics

    International Nuclear Information System (INIS)

    Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice

  1. Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics

    Science.gov (United States)

    Jannotti, Phillip; Subhash, Ghatu; Zheng, James Q.; Halls, Virginia; Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K.

    2015-01-01

    Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

  2. Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jannotti, Phillip; Subhash, Ghatu, E-mail: subhash@ufl.edu [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States); Zheng, James Q.; Halls, Virginia [Program Executive Office—Soldier Protection and Individual Equipment, US Army, Fort Belvoir, Virginia 22060 (United States); Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K. [M-Cubed Technologies, Inc., Newark, Delaware 19711 (United States)

    2015-01-26

    Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

  3. Material properties of silicon and silicon carbide foams

    Science.gov (United States)

    Jacoby, Marc T.; Goodman, William A.

    2005-08-01

    Silicon and silicon carbide foams provide the lightweighting element for Schafer Corporation's silicon and silicon carbide lightweight mirror systems (SLMSTM and SiC-SLMSTM). SLMSTM and SiC-SLMSTM provide the enabling technology for manufacturing lightweight, athermal optical sub-assemblies and instruments. Silicon and silicon carbide foam samples were manufactured and tested under a Schafer-funded Internal Research and Development program in various configurations to obtain mechanical and thermal property data. The results of the mechanical tests that are reported in this paper include Young's modulus, compression strength, tensile strength, Poisson's ratio and vibrational damping. The results of the thermal tests include thermal conductivity and coefficient of thermal expansion.

  4. Silver diffusion through silicon carbide in microencapsulated nuclear fuels TRISO

    International Nuclear Information System (INIS)

    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. Study Regarding Development of Electronic Commerce in Romania

    OpenAIRE

    Moraru Camelia; Popovici Norina

    2011-01-01

    Over time, trade has undergone profound changes gaining new features and valent forms as a result of trade and technology development. Electronic commerce is the use of value-added in a network applications such as electronic transfer of documents (EDI), the fax communication, bar codes, file transfer and electronic mail.

  6. Behavior of Disordered Boron Carbide under Stress

    Science.gov (United States)

    Fanchini, Giovanni; McCauley, James W.; Chhowalla, Manish

    2006-07-01

    Gibbs free-energy calculations based on density functional theory have been used to determine the possible source of failure of boron carbide just above the Hugoniot elastic limit (HEL). A range of B4C polytypes is found to be stable at room pressure. The energetic barrier for shock amorphization of boron carbide is by far the lowest for the B12(CCC) polytype, requiring only 6GPa≈P(HEL) for collapse under hydrostatic conditions. The results clearly demonstrate that the collapse of the B12(CCC) phase leads to segregation of B12 and amorphous carbon in the form of 2 3 nm bands along the (113) lattice direction, in excellent agreement with recent transmission electron microscopy results.

  7. Process for microwave sintering boron carbide

    International Nuclear Information System (INIS)

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy

  8. Chemical Analysis Methods for Silicon Carbide

    Institute of Scientific and Technical Information of China (English)

    Shen Keyin

    2006-01-01

    @@ 1 General and Scope This Standard specifies the determination method of silicon dioxide, free silicon, free carbon, total carbon, silicon carbide, ferric sesquioxide in silicon carbide abrasive material.

  9. Bright Single Photon Emitter in Silicon Carbide

    Science.gov (United States)

    Lienhard, Benjamin; Schroeder, Tim; Mouradian, Sara; Dolde, Florian; Trong Tran, Toan; Aharonovich, Igor; Englund, Dirk

    Efficient, on-demand, and robust single photon emitters are of central importance to many areas of quantum information processing. Over the past 10 years, color centers in solids have emerged as excellent single photon emitters. Color centers in diamond are among the most intensively studied single photon emitters, but recently silicon carbide (SiC) has also been demonstrated to be an excellent host material. In contrast to diamond, SiC is a technologically important material that is widely used in optoelectronics, high power electronics, and microelectromechanical systems. It is commercially available in sizes up to 6 inches and processes for device engineering are well developed. We report on a visible-spectrum single photon emitter in 4H-SiC. The emitter is photostable at both room and low temperatures, and it enables 2 million photons/second from unpatterned bulk SiC. We observe two classes of orthogonally polarized emitters, each of which has parallel absorption and emission dipole orientations. Low temperature measurements reveal a narrow zero phonon line with linewidth < 0.1 nm that accounts for more than 30% of the total photoluminescence spectrum. To our knowledge, this SiC color emitter is the brightest stable room-temperature single photon emitter ever observed.

  10. Development of the electron gun control system of SSRF

    International Nuclear Information System (INIS)

    An electron gun is the key part of a linac, the beam quality of which depends on beam quality of the electron gun, hence the need of a stable control system of the electron gun to ensure its safe operation.In this paper, we report our progresses in developing the linac's electron gun control system of Shanghai Synchrotron Radiation Facility (SSRF). It uses PLC as the device controllers, with the monitoring software developed on EPICS. The whole system is connected by Ethernet. The PLC and Ethernet technology ensures good reliability and easy maintenance of the electron gun control system. (authors)

  11. Development of an expert system for interpreting electron diffraction patterns

    International Nuclear Information System (INIS)

    A laboratory prototype of the expert system Electron for the automatic interpretation of electron diffraction patterns has been described. A high-level language providing storage and processing of knowledge is developed as well as user's interface for work with images. The Electron expert system can play the part of a consultant and also serve as a text-book on electron diffraction in teaching crystallography

  12. Large area electron beam diode development

    International Nuclear Information System (INIS)

    A large area annular electron beam diode has been tested at Physics International Co. on the multi-terawatt PITHON generator. A twelve element post hole convolute converted the coaxial MITL into a triaxial arrangement of anode current return structures both inside and outside the cathode structure. The presence of both inner and outer current return paths provide magnetic pressure balance for the beam, as determined by diode current measurements. X-ray pinhole photographs indicated uniform emission with intensity maxima between the post positions. Current losses in the post hole region were negligible, as evidenced by the absence of damage to the aluminum hardware. Radial electron flow near the cathode ring however did damage the inner anode cylinder between the post positions. Cutting away these regions prevented further damage of the transmission lines

  13. Method Developed for the High-Temperature Nondestructive Evaluation of Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites

    Science.gov (United States)

    Goldsby, Jon C.

    1998-01-01

    Ceramic matrix composites have emerged as candidate materials to allow higher operating temperatures (1000 to 1400 C) in gas turbine engines. A need, therefore, exists to develop nondestructive methods to evaluate material integrity at the material operating temperature by monitoring thermal and mechanical fatigue. These methods would also have potential as quality inspection tools. The goal of this investigation at the NASA Lewis Research Center is to survey and correlate the temperature-dependent damping and stiffness of advanced ceramic composite materials with imposed thermal and stress histories that simulate in-service turbine engine conditions. A typical sample size of 100 by 4 by 2 cubic millimeters, along with the specified stiffness and density, placed the fundamental vibration frequencies between 100 and 2000 Hz. A modified Forster apparatus seemed most applicable to simultaneously measure both damping and stiffness. Testing in vacuum reduced the effects of air on the measurements. In this method, a single composite sample is vibrated at its fundamental tone; then suddenly, the mechanical excitation is removed so that the sample's motion freely decays with time. Typical results are illlustrated in this paper.

  14. Friction and surface chemistry of implantation-modified metal-carbide composites

    International Nuclear Information System (INIS)

    Dry sliding friction measurements were performed on model carbide-metal composite samples containing 24-42 vol.% carbide. Wear debris, located preferentially on the carbides, were analyzed using scanning electron microscopy-energy dispersive X-ray analysis and Auger scanning microscopy. The friction and wear of the composite samples were found to be influenced by the compatibility (degree of mutual solubility) of the carbides with the steel counterface, as well as by local inhomogeneities in the carbide distribution. Friction tests were also made on the samples following high fluence titanium implantation. Implantation resulted in increased friction and wear, possibly owing to an implantation-induced softening or degradation of the carbides. (orig.)

  15. Conductivities and Seebeck coefficients of boron carbides: Softening bipolaron hopping

    Science.gov (United States)

    Aselage, T. L.; Emin, D.; McCready, S. S.

    2001-08-01

    The electrical conductivities and Seebeck coefficients of boron carbides B12+xC3-x with 0.06function of the composition x. This strong sensitivity to composition indicates that percolation effects, arising from boron carbides having carbon atoms in inequivalent locations, influence the conductivity at low temperature. With x holes per unit cell, boron carbides have very large Seebeck coefficients that depend only weakly on x. The magnitudes and temperature dependences of the Seebeck coefficients are consistent with large contributions from carrier-induced softening of local vibrations. Softening effects can be exceptionally large when singlet bipolarons are stabilized among degenerate electronic energy levels by their softening of symmetry-breaking vibrations: ``softening bipolarons.'' The boron carbide transport properties are generally consistent with those expected of softening bipolarons. Finally, two high-temperature effects are observed in the boron carbide conductivities. The conductivities of samples having high carrier densities, x~1, are suppressed above 700 K. This suppression can arise when the rapid hopping of nearby carriers disrupts the energy coincidence required for a carrier's hop. At even higher temperatures, a sharp increase in the boron carbide conductivities (σ~T4) suggests a radiation-induced excitation of mobile charge carriers.

  16. Research and development in the Irish electronics industry

    OpenAIRE

    Madden, Joe

    1993-01-01

    The electronics industry is a rapidly changing technology driven industry. Intensive research and development activity in electronics has been partly responsible for the emergence of Japan as an economic superpower and the rapid development of the Korean economy. Following the publication of the Telesis Review of Industrial Policy in 1982, the Irish Government undertook a gradually more interventionist policy towards the indigenous electronics industry. In the ten years since Telesis ther...

  17. Front-end electronics development for the SSC

    International Nuclear Information System (INIS)

    This is a status report on electronics development undertaken by the Front-End Electronics Collaboration. The overall goal of the collaboration remains the development by 1992 of complete, architecturally compatible, front end electronic systems for calorimeter, wire drift chamber, and silicon strip readout. We report here a few highlights to give a brief overview of the work underway. Performance requirements and capabilities, selected architectures, circuit designs and test results are presented. 13 refs., 21 figs., 1 tab

  18. Ternary rare earth metal boride carbides containing two-dimensional boron-carbon network: The crystal and electronic structure of R2B4C (R=Tb, Dy, Ho, Er)

    International Nuclear Information System (INIS)

    The ternary rare earth boride carbides R2B4C (R=Tb, Dy, Ho, Er) have been synthesized by reacting the elements at temperatures between 1800 and 2000K. The crystal structure of Dy2B4C has been determined from single-crystal X-ray diffraction data. It crystallizes in a new structure type in the orthorhombic space group Immm (a=3.2772(6) A, b=6.567(2) A, c=7.542(1) A, Z=2, R1=0.035 (wR2=0.10) for 224 reflections with Io>2σ(Io)). Boron atoms form infinite chains of fused B6 rings in [100] joined with carbon atoms into planar, two-dimensional networks which alternate with planar sheets of rare earth metal atoms. The electronic structure of Dy2B4C was also analyzed using the tight-binding extended Hueckel method. - Graphical abstract: Dy2B4C crystallizes a new structure type where planar 63-Dy metal atom layers alternate with planar non-metal layers consisting of ribbons of fused B6 hexagons bridged by carbon atoms. Isostructural analogues with Tb, Ho and Er have also been characterized

  19. Structure and single-phase regime of boron carbides

    Science.gov (United States)

    Emin, David

    1988-09-01

    The boron carbides are composed of twelve-atom icosahedral clusters which are linked by direct covalent bonds and through three-atom intericosahedral chains. The boron carbides are known to exist as a single phase with carbon concentrations from about 8 to about 20 at. %. This range of carbon concentrations is made possible by the substitution of boron and carbon atoms for one another within both the icosahedra and intericosahedral chains. The most widely accepted structural model for B4C (the boron carbide with nominally 20% carbon) has B11C icosahedra with C-B-C intericosahedral chains. Here, the free energy of the boron carbides is studied as a function of carbon concentration by considering the effects of replacing carbon atoms within B4C with boron atoms. It is concluded that entropic and energetic considerations both favor the replacement of carbon atoms with boron atoms within the intericosahedral chains, C-B-C-->C-B-B. Once the carbon concentration is so low that the vast majority of the chains are C-B-B chains, near B13C2, subsequent substitutions of carbon atoms with boron atoms occur within the icosahedra, B11C-->B12. Maxima of the free energy occur at the most ordered compositions: B4C,B13C2,B14C. This structural model, determined by studying the free energy, agrees with that previously suggested by analysis of electronic and thermal transport data. These considerations also provide an explanation for the wide single-phase regime found for boron carbides. The significant entropies associated with compositional disorder within the boron carbides, the high temperatures at which boron carbides are formed (>2000 K), and the relatively modest energies associated with replacing carbon atoms with boron atoms enable the material's entropy to be usually important in determining its composition. As a result, boron carbides are able to exist in a wide range of compositions.

  20. Similarities and distinctions of defect production by fast electron and proton irradiation: Moderately doped silicon and silicon carbide of n-type

    International Nuclear Information System (INIS)

    Effects of irradiation with 0.9 MeV electrons as well as 8 and 15 MeV protons on moderately doped n-Si grown by the floating zone (FZ) technique and n-SiC (4H) grown by chemical vapor deposition are studied in a comparative way. It has been established that the dominant radiation-produced defects with involvement of V group impurities differ dramatically in electron- and proton-irradiated n-Si (FZ), in spite of the opinion on their similarity widespread in literature. This dissimilarity in defect structures is attributed to a marked difference in distributions of primary radiation defects for the both kinds of irradiation. In contrast, DLTS spectra taken on electron- and proton-irradiated n-SiC (4H) appear to be similar. However, there are very much pronounced differences in the formation rates of radiation-produced defects. Despite a larger production rate of Frenkel pairs in SiC as compared to that in Si, the removal rates of charge carriers in n-SiC (4H) were found to be considerably smaller than those in n-Si (FZ) for the both electron and proton irradiation. Comparison between defect production rates in the both materials under electron and proton irradiation is drawn.

  1. Electronic Business Development as a Sustainable Competitive Advantage Model

    Directory of Open Access Journals (Sweden)

    Narimantas Kazimieras Paliulis

    2012-07-01

    Full Text Available The paper examines the practical usefulness of information technologies in business reviewing electronic business concepts provided in science literature and also the newest tendencies of electronic business development. The paper offers a review of various authors works on e-strategies and IT influence on companies’ functionality. An analysis of disadvantages in various electronic business development models is provided. On the basis of analyses done on the theory of electronic business development and on disadvantages of e-business models, the main aspects of e-business development as sustainable competitive advantage are identified. A fully – formed model of electronic business development as sustainable competitive advantage is presented. Conclusions are provided.Article in Lithuanian

  2. Structure and properties of the gradient tool materials based on a high-speed steel HS6-5-2 reinforced with WC or VC carbides

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2009-12-01

    Full Text Available Purpose: This paper concerns manufacturing and researching a new group of the gradient tool materials, manufactured by a conventional powder metallurgy method, consisting in compacting a powder in a closed die and sintering it.Design/methodology/approach: The materials were obtained by mixing the powders of the HS6-5-2 high-speed steel, tungsten carbide (WC, and vanadium carbide (VC. The mixes were poured one by one into the die, yielding layers with the gradually changing volume ratio of carbides within the high-speed steel matrix. Structural research by using the scanning and transmission electron microscopes, x-ray microanalysis and density, hardness and porosity tests, were performed. Structure and hardness of selected materials after heat treatment were also investigated.Findings: On the basis of the results of the research, it was found that it was possible to obtain gradient materials by the powder metallurgy methods, in order to ensure the required properties and structure of the designed material. It was shown that the new sintered graded materials were characterized by a multiphase structure, consisting of ferrite, primary carbides of the high speed steel, of the MC and M6C type, and dependently of the reinforcement phase, of the tungsten carbide WC or the vanadium carbide VC, which were introduced into the material, in the form of powder. Additionally in the structure of the WC-reinforced materials the W2C phase occurs. The gradient tool materials reinforced with the WC carbide were characterized by a higher hardness, and a lower porosity in relation to the materials reinforced with the VC carbide. It was found that the desired structure and properties (density, porosity and hardness had the material containing 25% of the WC carbide in the surface layer, after sintering at the temperature 1210oC, for 30 minutes. The heat treatment application causes a significant increase of the surface layer hardness of the material. The highest

  3. Synthesis of high quality superfine structural powders of silicium carbide

    International Nuclear Information System (INIS)

    We have synthesized and studied the experimental samples of silicium carbide, which were produced of mechanically activized elemental fine-disperse silicium and pyrolitical soot according to the technology developed by the authors. We have shown that, as a result of synthesis, it is possible to produce the powder of silicium carbide (α- and β-phases) with high purity, nanodimensional fractional composition, and silicium dioxide content not more then 1- 2 mass %

  4. Application of electron beam irradiation, (1). Development and application of electron beam processors

    International Nuclear Information System (INIS)

    This paper deals with characteristics, equipment (principle and kinds), present conditions, and future issues in the application of electron beam irradiation. Characteristics of electron beams are described in terms of the following: chemical and biological effects of radiation; energy and penetrating power of electron beams; and principle and kinds of electron beam accelerator. Industrial application of electron beam irradiation has advantages of high speed procedure and producibility, less energy, avoidance of poisonous gas, and extreme reduction of organic solvents to be used. The present application of electron beam irradiation cen be divided into the following: (1) hardening of resin or coated membrane; (2) improvement of macromolecular materials; (3) environmental protection; (4) sterilization; (5) food sterilization. The present equipment for electron beam irradiation is introduced according to low energy, medium energy, and high energy equipment. Finally, future issues focuses on (1) the improvement of traceability system and development of electron dosimetric techniques and (2) food sterilization. (N.K.)

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

    International Nuclear Information System (INIS)

    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

  6. 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

  7. The atomic configuration of graphene/vanadium carbide interfaces in vanadium carbide-encapsulating carbon nanocapsules.

    Science.gov (United States)

    Yazaki, Gaku; Matsuura, Daisuke; Kizuka, Tokushi

    2014-03-01

    Carbon nanocapsules (CNCs) encapsulating vanadium carbide (VC) nanocrystals with a NaCI structure were synthesized by a gas-evaporation method using arc-discharge heating. The CNCs were observed by high-resolution transmission electron microscopy. The VC nanocrystals within the nanospaces of CNCs were truncated by low-index facets and were coated with several graphene layers, forming graphene/VC interfaces. The atomic configuration and interlayer spacings at the interfaces were found. PMID:24745251

  8. Development of modulated electron beam for intensity modulated radiation therapy (IMRT) on a photocathode electron gun

    International Nuclear Information System (INIS)

    Radiation therapy of cancer is developing to un-uniform irradiation, for concentrating dose to a cancer tumor and reducing dose to normal tissue. As a step toward the Intensity modulated radiation therapy, we examined dynamic optical modulation of electron beam produced by a photocathode electron gun. Images on photo-masks were transferred onto a photocathode by relay imaging. Electron beam could be controlled by a remote mirror. Modulated electron beam maintained its shape on acceleration, had a fine spatial resolution, and could be moved dynamically by optical methods. As a second step, optical modulation of electron beam and dynamic control succeeded by a digital micro mirror device (DMD). (author)

  9. Nuclear fuel management and boron carbide coating

    International Nuclear Information System (INIS)

    In recent years one way of introducing burnable absorber is to coat the fuel pellets by a thin layer of burnable absorber so called integral fuel burnable absorber (IFBA). In this method the fuel is coated with boron nitride or boron carbide. Boron has low absorption cross-section and when it exists on the surface of the fuel, it interacts with thermalized neutron. B4C is a boron compound, which can be used for coating the nuclear fuel. It has high thermal stability and withstands high pressure and temperatures. High technology product of boron carbide has different ratio of B: C. But in nuclear reactor when boron carbide is used, it must be rich with boron. In this research chemical vapor decomposition (CVD) has been using boron trichloride and carbon tetra chloride for reactant materials. The experiments were carried out at high temperatures (1050 degree Celsius, 1225 degree Celsius and 1325 degree Celsius). The coated samples were analyzed using X-Ray diffractometer (XRD), scanning electron microscopy (SEM) and will be presented in this paper. It was seen that decreasing the reaction temperature caused an increase on the quality and thickness of the coating

  10. Methods of producing continuous boron carbide fibers

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  11. The Electronic Nose Training Automation Development

    Science.gov (United States)

    Schattke, Nathan

    2002-01-01

    The electronic nose is a method of using several sensors in conjunction to identify an unknown gas. Statistical analysis has shown that a large number of training exposures need to be performed in order to get a model that can be depended on. The number of training exposures needed is on the order of 1000. Data acquisition from the noses are generally automatic and built in. The gas generation equipment consists of a Miller-Nelson (MN) flow/temperature/humidity controller and a Kin-Tek (KT) trace gas generator. This equipment has been controlled in the past by an old data acquisition and control system. The new system will use new control boards and an easy graphical user interface. The programming for this is in the LabVIEW G programming language. A language easy for the user to make modifications to. This paper details some of the issues in selecting the components and programming the connections. It is not a primer on LabVIEW programming, a separate CD is being delivered with website files to teach that.

  12. Microstructural characterisation of silicon nitride-bonded silicon carbide

    International Nuclear Information System (INIS)

    The microstructure of a commercial silicon nitride-bonded silicon carbide ceramic composite, formed via the nitridation of Si powder-SiC preforms, has been characterised by transmission electron microscopy. A mechanism combining reaction bonding and liquid-phase sintering is proposed to describe the development and observed morphology of the microstructure of the bonding matrix, which comprises predominantly phases based on Si2N2O and β-Si3N4 and an amorphous phase. Qualitative microanalysis of amorphous matrix regions has revealed significant concentrations of oxygen, aluminium and calcium, with Al also being detected in both of the surrounding cyrstalline phases. It is thus suggested that the principal constituents of the matrix are in fact O' and β' sialons. (orig.)

  13. Development of environmental guidelines for electronic appliances

    DEFF Research Database (Denmark)

    Legarth, Jens Brøbech; Alting, Leo; Erichsen, Hanne K. Linnet; Gregersen, Johan Chr; Jørgensen, Jørgen

    This paper presents a general method for the development of environmental guidelines for complex products. The method is based on the life cycle concept. The application of life cycle assessment methods reveals the peak environmental impacts, and their source resulting in environmental guidelines...

  14. Development of archetypes of radiology for electronic health record

    International Nuclear Information System (INIS)

    This paper presents a proposal to develop archetypes for electronic patient records system based the openEHR Foundation model. Archetypes were developed specifically for the areas of radiology and diagnostic imaging, as for the early implementation of an electronic health records system. The archetypes developed are related to the examinations request, their execution and report, corresponding to both the administrative as diagnostic workflow inside a diagnostic imaging sector. (author)

  15. Emission-adsorption properties of carbide and boride phase of coatings obtained by the method of direct electron-beam evaporation in the barium-containing flow

    International Nuclear Information System (INIS)

    Emission-adsorption properties of TiCsub(0.72), TiB2 and Nb2C coatings on molybdenum obtained by direct electron-beam evaporation are studied by the thermoemission method in the flow of the standard saturated aluminate cathode evaporation products. The Mo-electrode emission is suppressed most of all when applying the TiCsub(0.72) coating

  16. A transmission electron microscope characterization of sodium sulfate hot corrosion of silicon carbide fiber-reinforced lithium aluminosilicate glass-ceramic matrix composite

    OpenAIRE

    Hunt, Richard K.

    1994-01-01

    Sodium Sulfate hot corrosion of a SiC/LAS composite was studied using conventional transmission electron microscopy and selected area diffraction. Changes in the morphology, composition and crystallography of the phases in the glass-ceramic matrix and the fiber/matrix interface were studied. Microchemical analysis using energy dispersive x-ray spectroscopy (EDS) was also performed on all phases detected. Three samples were studied: (1) as-received, (2) no salt coating and annealed in argon, a...

  17. Plasma Spray Deposition of Boron Carbide

    Czech Academy of Sciences Publication Activity Database

    Brožek, Vlastimil; Hofman, R.; Ctibor, Pavel; Hrabovský, Milan

    Praha : MAXDORF, s.r.o., 2002 - (Nitsch, K.; Rodová, M.). s. 11-12 [Development of Materials Science in Research and Education.. 10.09.2002-12.09.2002, Ostravice] R&D Projects: GA ČR GA104/01/0149; GA ČR GA202/01/1563 Institutional research plan: CEZ:AV0Z2043910 Keywords : plasma spray, boron carbide Subject RIV: BL - Plasma and Gas Discharge Physics

  18. TEM investigation of aluminium containing precipitates in high aluminium doped silicon carbide

    International Nuclear Information System (INIS)

    Full text: Silicon carbide is a promising semiconductor material for applications in high temperature and high power devices. The successful growth of good quality epilayers in this material has enhanced its potential for device applications. As a novel semiconductor material, there is a need for studying its basic physical properties and the role of dopants in this material. In this study, silicon carbide epilayers were grown on 4H-SiC wafers of (0001) orientation with a miscut angle of 8 deg at a temperature of 1550 deg C. The epilayers contained regions of high aluminium doping well above the solubility of aluminium in silicon carbide. High temperature annealing of this material resulted in the precipitation of aluminium in the wafers. The samples were analysed by secondary ion mass spectrometry and transmission electron microscopy. Selected area diffraction studies show the presence of aluminium carbide and aluminium silicon carbide phases. Copyright (2002) Australian Society for Electron Microscopy Inc

  19. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica.

    Science.gov (United States)

    Luo, Xiaogang; Ma, Wenhui; Zhou, Yang; Liu, Dachun; Yang, Bin; Dai, Yongnian

    2009-01-01

    Silicon carbide nanowires have been synthesized at 1400 degrees C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core-shell structure and grow along direction. The diameter of silicon carbide nanowires is about 50-200 nm and the length from tens to hundreds of micrometers. The vapor-solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core-shell interface. PMID:20651911

  20. Synthesis and Photoluminescence Property of Silicon Carbide Nanowires Via Carbothermic Reduction of Silica

    Directory of Open Access Journals (Sweden)

    Luo Xiaogang

    2009-01-01

    Full Text Available Abstract Silicon carbide nanowires have been synthesized at 1400 °C by carbothermic reduction of silica with bamboo carbon under normal atmosphere pressure without metallic catalyst. X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy and Fourier transformed infrared spectroscopy were used to characterize the silicon carbide nanowires. The results show that the silicon carbide nanowires have a core–shell structure and grow along <111> direction. The diameter of silicon carbide nanowires is about 50–200 nm and the length from tens to hundreds of micrometers. The vapor–solid mechanism is proposed to elucidate the growth process. The photoluminescence of the synthesized silicon carbide nanowires shows significant blueshifts, which is resulted from the existence of oxygen defects in amorphous layer and the special rough core–shell interface.

  1. Design, Fabrication and Performance of Boron-Carbide Control Elements

    International Nuclear Information System (INIS)

    A control blade design, incorporating boron-carbide (B4C) in stainless-steel tubes, was introduced into service in boiling water reactors in April 1961. Since that time this blade has become the standard reference control element in General Electric boiling-water reactors, replacing the 2% boron-stainless-steel blades previously used. The blades consist of a sheathed, cruciform array of small vertical stainless-steel tubes filled with compácted boron-carbide powder. The boron-carbide powder is confined longitudinally into several independent compartments by swaging over ball bearings located inside the tubes. The development and use of boron-carbide control rods is discussed in five phases: 1. Summary of experience with boron-steel blades and reasons for transition to boron-carbide control; 2. Design of the boron-carbide blade, beginning with developmental experiments, including early measurements performed in the AEC ''Control Rod Material and Development Program'' at the Vallecitos Atomic Laboratory, through a description of the final control blade configuration; 3. Fabrication of the blades and quality control procedures; 4. Results of confirmatory pre-operational mechanical and reactivity testing; and 5. Post-operational experience with the blades, including information on the results of mechanical inspection and reactivity testing after two years of reactor service. (author)

  2. Deformation site-specific nature of transgranular carbide precipitation in 304 stainless steels

    International Nuclear Information System (INIS)

    This research was developed to identify the nature of transgranular carbide precipitation and chromium-depletion in heavily deformed 304 SS, and to examine the correlation between carbide precipitation and strain-induced martensite in the SS. Observations have indicated that: (1) Transgranular carbides form on twin-fault intersections in 304 SS. This causes linear-TG attack within the SS. (2) There was no observed correlation between strain-induced martensite and TG carbides in this work, except that both form at micro-shear band intersections, but not at the same intersection. (3) Lath martensite and fine-austenite form during heat treatment of deformed, 304 SS. (4) Transgranular carbides precipitate on martensite lath/fine-austenite boundaries in 304 SS, and produce extensive, random TG attack in the SS. (5) Lattice imaging of carbides has shown the presence of dislocations within the carbides and at the carbide-matrix interface, and changes in the carbide lattice orientation across a boundary, which may be indicators of key mechanisms of carbide nucleation on grain boundaries in SS

  3. Regulation and electronic commerce in developing countries

    OpenAIRE

    Mansell, Robin

    2005-01-01

    This report is the result of dialogue and research focusing on the World Dialogue on Regulation (WDR) theme Stimulating Investment in Network Development: Roles for Regulators. The World Dialogue on Regulation for Network Economies (WDR) is an infoDev-funded project that is helping to facilitate infoDev’s objectives to broaden the reach and affordability of ICTs for all through its program of applied research, web-based dialogue, expert forum meetings with policymakers and regulators, and pub...

  4. Kinetics of niobium carbide coating produced on AISI 1040 steel by thermo-reactive deposition technique

    International Nuclear Information System (INIS)

    There are a lot of technologically interesting characteristics of niobium carbide coating deposited by pack method which is the production of hard, wear-resistant, oxidation and corrosion resistant coating layer on the steel substrates. In the present study, the growth kinetics of niobium carbide layer deposited by thermo-reactive diffusion techniques in a solid medium on steel samples was reported. Niobium carbide coating treatment was performed on AISI 1040 steels in the powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 1073, 1173 and 1273 K for 1-4 h. The presence of NbC and Nb2C phases formed on the surface of the steel substrates was confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analyses. Niobium carbide layer thickness ranges from 3.42±0.52 to 11.78±2.29 μm depending upon the treatment time and temperature. Layer growth kinetics was analyzed by measuring the depth of niobium carbide layer as a function of time and temperature. The kinetics of niobium carbide coating by pack method shows a parabolic relationship between carbide layer thickness and treatment time, and the activation energy for the process is estimated to be 91.257 kJ mol-1. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of niobium carbide layer variation and to establish some empirical relationships between process parameters and niobium carbide layer thickness

  5. Determination of carbides generation parameters in corium ant its effect on meltdown removing

    International Nuclear Information System (INIS)

    Object of examination in the work is chemical reactions velocities of uranium dioxide with graphite under high temperatures. The method of study is conducting of calculations complex by numerical techniques and comparison its results with experimental data. Result of this study is mathematical model of uranium carbides and zirconium carbides formation in accidental processes courses. Results of study are allowing to create conditions for development or prevention of carbides formation reactions, so this methodics is suitable for ensuring of nuclear reaction safety

  6. Twelve tips for the development of electronic study guides.

    Science.gov (United States)

    Montemayor, Luz Leticia Elizondo

    2002-09-01

    With recent advances in technology, electronic study guides are becoming extraordinary management, learning and assessment tools in the teaching-learning process, replacing printed study guides. The educational advantages they offer are listed here. During the elaboration of an electronic study guide, there are important issues to consider, such as the student's capabilities in the use of electronic media, the type of software to be used, proper authorizations and accessibility, the inclusion of all information and links needed, as well as a clear explanation on the use of the software. This paper offers twelve useful tips for the development of electronic study guides. PMID:12450466

  7. Structural relaxation of amorphous silicon carbide

    International Nuclear Information System (INIS)

    We have examined amorphous structures of silicon carbide (SiC) using both transmission electron microscopy and a molecular-dynamics approach. Radial distribution functions revealed that amorphous SiC contains not only heteronuclear (Si-C) bonds but also homonuclear (Si-Si and C-C) bonds. The ratio of heteronuclear to homonuclear bonds was found to change upon annealing, suggesting that structural relaxation of the amorphous SiC occurred. Good agreement was obtained between the simulated and experimentally measured radial distribution functions

  8. Structural relaxation of amorphous silicon carbide.

    Science.gov (United States)

    Ishimaru, Manabu; Bae, In-Tae; Hirotsu, Yoshihiko; Matsumura, Syo; Sickafus, Kurt E

    2002-07-29

    We have examined amorphous structures of silicon carbide (SiC) using both transmission electron microscopy and a molecular-dynamics approach. Radial distribution functions revealed that amorphous SiC contains not only heteronuclear (Si-C) bonds but also homonuclear (Si-Si and C-C) bonds. The ratio of heteronuclear to homonuclear bonds was found to change upon annealing, suggesting that structural relaxation of the amorphous SiC occurred. Good agreement was obtained between the simulated and experimentally measured radial distribution functions. PMID:12144449

  9. Highly thermal conductive carbon fiber/boron carbide composite material

    International Nuclear Information System (INIS)

    In a composite member for use in walls of a thermonuclear reactor, if carbon fibers and boron carbide are mixed, since they are brought into contact with each other directly, boron is reacted with the carbon fibers to form boron carbide to lower thermal conductivity of the carbon fibers. Then, in the present invention, graphite or amorphous carbon is filled between the carbon fibers to provide a fiber bundle of not less than 500 carbon fibers. Further, the surface of the fiber bundle is coated with graphite or amorphous carbon to suppress diffusion or solid solubilization of boron to carbon fibers or reaction of them. Then, lowering of thermal conductivity of the carbon fibers is prevented, as well as the mixing amount of the carbon fiber bundles with boron carbide, a sintering temperature and orientation of carbon fiber bundles are optimized to provide a highly thermal conductive carbon fiber/boron carbide composite material. In addition, carbide or boride type short fibers, spherical graphite, and amorphous carbon are mixed in the boron carbide to prevent development of cracks. Diffusion or solid solubilization of boron to carbon fibers is reduced or reaction of them if the carbon fibers are bundled. (N.H.)

  10. Sliding wear of cemented carbides

    International Nuclear Information System (INIS)

    Cemented carbides are known to be very hard and wear resistant and are therefor often used in applications involving surface damage and wear. The wear rate of cemented carbides is often measured in abrasion. In such tests it has been shown that the wear rate is inversely dependent on the material hardness. The sliding wear is even more of a surface phenomenon than a abrasion, making it difficult to predict friction and wear from bulk properties. This paper concentrates on the sliding wear of cemented carbides and elucidates some wear mechanisms. It is especially shown that a fragmenting wear mechanism of WC is very important for the description of wear of cemented carbides. (author)

  11. Advances in Electronic-Nose Technologies Developed for Biomedical Applications

    OpenAIRE

    Wilson, Alphus D.; Manuela Baietto

    2011-01-01

    The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and futu...

  12. 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...

  13. Determination of structural changes and phase transformations in boron carbide by static and dynamic studies

    Science.gov (United States)

    Gupta, Varun

    Recent transmission electron microscopy results demonstrate that the failure of B4C is commensurate with the segregation of boron icosahedra embedded in amorphous carbon in 2--3 nm wide amorphous bands along the (113) lattice direction, in good agreement with our recent theoretical results. Boron carbide is generally composed of multiple polytypes of B4C which have the same primitive lattice parameters but differ from each other by the location of the boron and carbon atoms in the unit cells. The unit cells are formed by a 12-atom B12-nCn icosahedron and a 3-atom (C3-nBn) chain. Our theoretical results indicate that one polytype, B12(C3), whose formation is responsible for the failure of the entire material. This anomalous and poorly understood glass-like behavior in boron carbide has been the subject of research since its discovery over 70 years ago. The characterization of disorder in hot pressed and powder boron carbide samples is therefore of primary interest. The research work has focused on characterization techniques which can be used at a micrometric sampling size so that individual powder grains of the material can be utilized. Specifically, micro-Raman and electrical conductivity measurements can be used with micrometric gap cells to understand the disorder in B4C. The results also demonstrate that it is possible to induce transformations in boron carbide using electric fields that are comparable with those obtained under shock and nanoindentation. Our calculations present a hypothesis which can provide a solution to prevent the premature failure of B4C. A route to achieve suppression of the B12(CCC) polytype without significantly affecting the elastic constants is via low concentration Silicon (Si) doping of B4C. Suppression of B12(CCC) by Si doping has implications towards development of boron carbide armor with improved properties for protection against high velocity threats. In order to achieve this, nanostructures (nanowires, nanorods, etc.) of Si

  14. Nanofibre growth from cobalt carbide produced by mechanosynthesis

    International Nuclear Information System (INIS)

    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 μm in length and 20-200 nm in diameter and 0.6-1.2 μm in length were obtained after heating at 800 and 1000 deg. C, respectively, by means of this process

  15. 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.

  16. Development of Semi—Graphite Carbon—Silicon Carbide Brick and Its Application in Slag Forming Zone of Large—sized Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    HAOYun-zhong; CHENQian-wan

    1994-01-01

    Based on the damage mechanism of the lining at the slag forming zone of the blast furnace and the charactieristics of various refractory ma-terials,the methods to increase the service life of the lining at the slag forming zone have been found:(1) to improve the capacity of the blast furnace brick lining subjet to heat impact;(2) to reduce the working side temperature of the brick lining.On this basis,the semi-graphitized ,high temperature electrically calcined anthracite and silicon carbide etc ,were used as the main raw materials,Through a lot of experiments the proper raw material mix and grain size compo-sition were determined,In addition ,a suitable amount of additives and binders was added.After high pressur forming,high temperature firing and grinding ,the semi-graphitic carbon-silicon carbide bricks with close dimension tler-ances and ideal physical and chemical properties have been made.They have been applied in some blast furnaces,such as No.11(2580 m3) and No.6(1050 m3) blast furnaces etc.at Anshan Iron and Steel Company,and the problem of short service life at slag forming zone of blast furnace has been solved.

  17. Development of a high power free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Min; Lee, Byung Chul; Kim, Sun Kook; Jung, Yung Wook; Cho, Sung Oh [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-01-01

    A millimeter-wave free electron laser (FEL) driven by a recirculating electrostatic accelerator has been developed. The wavelength of the FEL is tunable in the range of 3 - 12 mm by tuning the energy of the electron beam. The output power is estimated to be 1 kW. The electrostatic accelerator is composed of high-current electron gun, acceleration tube, high-voltage generator, high-voltage terminal, deceleration tube, electron collator, and vacuum pumps. Two types of LaB{sub 6}-based thermionic electron guns (triode gun and diode gun) and their power supplies have been developed. The voltage of the guns is 30 kV and the output current is - 2 A. A beam-focusing planar undulator and a permanent-magnet helical undulator have been developed and 3D trajectories of electron beam in the undulators have been calculated to find optimal input condition of electron beam. 135 figs, 15 pix, 17 tabs, 98 refs. (Author).

  18. Doping of silicon carbide by ion implantation

    International Nuclear Information System (INIS)

    It appeared that in some fields, as the hostile environments (high temperature or irradiation), the silicon compounds showed limitations resulting from the electrical and mechanical properties. Doping of 4H and 6H silicon carbide by ion implantation is studied from a physicochemical and electrical point of view. It is necessary to obtain n-type and p-type material to realize high power and/or high frequency devices, such as MESFETs and Schottky diodes. First, physical and electrical properties of silicon carbide are presented and the interest of developing a process technology on this material is emphasised. Then, physical characteristics of ion implantation and particularly classical dopant implantation, such as nitrogen, for n-type doping, and aluminium and boron, for p-type doping are described. Results with these dopants are presented and analysed. Optimal conditions are extracted from these experiences so as to obtain a good crystal quality and a surface state allowing device fabrication. Electrical conduction is then described in the 4H and 6H-SiC polytypes. Freezing of free carriers and scattering processes are described. Electrical measurements are carried out using Hall effect on Van der Panw test patterns, and 4 point probe method are used to draw the type of the material, free carrier concentrations, resistivity and mobility of the implanted doped layers. These results are commented and compared to the theoretical analysis. The influence of the technological process on electrical conduction is studied in view of fabricating implanted silicon carbide devices. (author)

  19. The pyrolysis of a tungsten alkyne complex as a low temperature route to tungsten carbide

    International Nuclear Information System (INIS)

    The synthesis of designed organometallic compounds and their selective activation and transformation into materials of high purity (for electronic applications), high strength and/or high temperature stability (for refractory or structural applications), represents a potential area of extreme growth in organometallic chemistry. Research in this area could provide entirely new, inexpensive, fabrication methods for common and exotic materials. In this paper, the authors develop design principles for the preparation of organometallic precursors, ''premetallics'' that can be selectively converted, in high yields, to a desired refractory metal. They also describe preliminary efforts to prepare tungsten carbides (WC/sub x/) from a prematallic

  20. Quantitative analysis of WC grain shape in sintered WC-Co cemented carbides.

    Science.gov (United States)

    Christensen, Mikael; Wahnström, Göran; Allibert, Colette; Lay, Sabine

    2005-02-18

    The morphology of WC grains is examined by ab initio calculations, and by transmission electron microscopy in a WC-Co cemented carbide. Two compositions are studied to determine the effect of carbon chemical potential on the shape development. The WC grains are found to be truncated triangles, and the grain morphology is adequately reproduced by the ab initio calculations. The energy difference between the two types of grain facets is shown to be due to the formation of stronger bonds with more covalent character between low coordinated W and Co atoms at one type of facet. PMID:15783755

  1. 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....

  2. Atomic structure of amorphous shear bands in boron carbide.

    Science.gov (United States)

    Reddy, K Madhav; Liu, P; Hirata, A; Fujita, T; Chen, M W

    2013-01-01

    Amorphous shear bands are the main deformation and failure mode of super-hard boron carbide subjected to shock loading and high pressures at room temperature. Nevertheless, the formation mechanisms of the amorphous shear bands remain a long-standing scientific curiosity mainly because of the lack of experimental structure information of the disordered shear bands, comprising light elements of carbon and boron only. Here we report the atomic structure of the amorphous shear bands in boron carbide characterized by state-of-the-art aberration-corrected transmission electron microscopy. Distorted icosahedra, displaced from the crystalline matrix, were observed in nano-sized amorphous bands that produce dislocation-like local shear strains. These experimental results provide direct experimental evidence that the formation of amorphous shear bands in boron carbide results from the disassembly of the icosahedra, driven by shear stresses. PMID:24052052

  3. In situ-grown hexagonal silicon nanocrystals in silicon carbide-based films

    OpenAIRE

    Kim, Tae-Youb; Huh, Chul; Park, Nae-Man; Choi, Cheol-Jong; Suemitsu, Maki

    2012-01-01

    Silicon nanocrystals (Si-NCs) were grown in situ in carbide-based film using a plasma-enhanced chemical vapor deposition method. High-resolution transmission electron microscopy indicates that these nanocrystallites were embedded in an amorphous silicon carbide-based matrix. Electron diffraction pattern analyses revealed that the crystallites have a hexagonal-wurtzite silicon phase structure. The peak position of the photoluminescence can be controlled within a wavelength of 500 to 650 nm by ...

  4. Polarized Electron Gun Development at the Brookhaven National Laboratory

    International Nuclear Information System (INIS)

    Development of two different polarized electron guns is ongoing at BNL. One aims at extremely high brightness at a moderate beam current. This design uses a superconducting RF gun and a test setup is built to show that a Gallium-Arsenide cathode with negative affinity has a sufficiently long quantum efficiency lifetime in such an environment. An electron injector using this technology may eliminate the need of the electron damping ring and a long transport line at the International Linear Collider. The other project aims at producing a high beam current with moderate emittance requirements, dubbed the 'Gatling gun'. In this DC gun, bunches are extracted from 20 separate cathodes and merged into a single beam using a rotating magnetic field. Such an electron gun could serve as an injector for the electron-ion collider eRHIC, which is planned at BNL. We will report on the status of these projects.

  5. Evolution of carbides in cold-work tool steels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hoyoung [Department of Materials Science and Engineering, Pusan National University, 2 Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Korea Institute of Materials Science, 797 Changwon-daero, Seongsan-gu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Kang, Jun-Yun, E-mail: firice@kims.re.kr [Korea Institute of Materials Science, 797 Changwon-daero, Seongsan-gu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Son, Dongmin [Seah Changwon Special Steel, 147 Jeokhyeon-ro, Seongsan-gu, Changwon, Gyeongnam 642-370 (Korea, Republic of); Lee, Tae-Ho [Korea Institute of Materials Science, 797 Changwon-daero, Seongsan-gu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Cho, Kyung-Mox, E-mail: chokm@pusan.ac.kr [Department of Materials Science and Engineering, Pusan National University, 2 Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan 609-735 (Korea, Republic of)

    2015-09-15

    This study aimed to present the complete history of carbide evolution in a cold-work tool steel along its full processing route for fabrication and application. A sequence of processes from cast to final hardening heat treatment was conducted on an 8% Cr-steel to reproduce a typical commercial processing route in a small scale. The carbides found at each process step were then identified by electron diffraction with energy dispersive spectroscopy in a scanning or transmission electron microscope. After solidification, MC, M{sub 7}C{sub 3} and M{sub 2}C carbides were identified and the last one dissolved during hot compression at 1180 °C. In a subsequent annealing at 870 °C followed by slow cooling, M{sub 6}C and M{sub 23}C{sub 6} were added, while they were dissolved in the following austenitization at 1030 °C. After the final tempering at 520 °C, fine M{sub 23}C{sub 6} precipitated again, thus the final microstructure was the tempered martensite with MC, M{sub 7}C{sub 3} and M{sub 23}C{sub 6} carbide. The transient M{sub 2}C and M{sub 6}C originated from the segregation of Mo and finally disappeared due to attenuated segregation and the consequent thermodynamic instability. - Highlights: • The full processing route of a cold-work tool steel was simulated in a small scale. • The carbides in the tool steel were identified by chemical–crystallographic analyses. • MC, M{sub 7}C{sub 3}, M{sub 2}C, M{sub 6}C and M{sub 23}C{sub 6} carbides were found during the processing of the steel. • M{sub 2}C and M{sub 6}C finally disappeared due to thermodynamic instability.

  6. Wettability of boron carbide

    International Nuclear Information System (INIS)

    The wettability of boron carbide has been examined by means of the sessile drop method, using the following candidate alloys: (96wt%AG-4wt%Ti), (Ag-26.5wt%Cu-3wt%Ti), (Sn-10wt%Ag-4wt%Ti), Sn(99.95wt%) and Al(99.99wt%). The results show that B4C is completely wetted by the Ag-based alloys. Sn-10wt%Ag-4wt%Ti alloy and pure Al partly wet the B4C surface, while pure Sn does not wet B4C at all. For all the alloys used, except pure Sn, a reaction layer was observed at the interface between the ceramic part and the metal drop. Although the spreading kinetics of the Al-drop was much slower compared with the Ti-containing alloys, the reaction rate was considerably higher in the former case. This suggests that aluminium is an attractive candidate material for brazing of B4C. Formation of the low melting B2O3 at the B4C surface may cause oxidation of the filler metal during joining, which, in turn, leads to a low bond strength

  7. Development of the electron gun control system for LEBRA

    International Nuclear Information System (INIS)

    The control system of the electron gun was replaced at LEBRA. This system was developed using EPICS. EPICS is de-fact standard control framework. Device Support for the high voltage station controller and high frequency grid pulser was developed. (author)

  8. Development of a high current short pulse electron gun

    International Nuclear Information System (INIS)

    Dielectric wall accelerator (DWA), towards high gradient acceleration field (30 MeV/m-100 MeV/m), is under development at Institute of Modern Physics. A prototype was designed and constructed to prove the principle. This needs a short pulse high current electron source to match the acceleration field generated by the Blumlein-type pulse forming lines (PFLs). In this paper, we report the design and test of a new type short pulse high current electron gun based on principle of vacuum arc discharge. Electron beams of 100 mA with pulse width of 10 ns were obtained. (authors)

  9. Electronic Developments for the Hades RPC Wall Overview and Progress

    CERN Document Server

    Gil, A; Cabanelas, P; Castro, E; Díaz, J; Garzón, J A; Gonzales-Diaz, D; König, W; Lange, J S; May, G; Traxler, M

    2007-01-01

    This contribution presents the current status and progress of the electronics developed for the Resistive Plate Chamber detector of HADES. This new detector for the time-of-flight detection system will contain more than 1000 RPC modules, covering a total active area of around 7 m2. The Front-End electronics consist of custom-made boards that exploit the benefit of the use of commercial components to achieve time resolutions below 100 ps. The Readout electronics, also custom-made, is a multipurpose board providing a 128- channel Time to Digital Converter (TDC) based on the HPTDC chip.

  10. High temperature intermetallic binders for HVOF carbides

    International Nuclear Information System (INIS)

    Gas turbines technology has a long history of employing the desirable high temperature physical attributes of ceramic-metallic (cermet) materials. The most commonly used coatings incorporate combinations of WC-Co and Cr3C2-NiCr, which have also been successfully utilized in other non-turbine coating applications. Increased turbine operating temperatures and other high temperature service conditions have made apparent the attractive notion of increasing the temperature capability and corrosion resistance of these coatings. In this study the intermetallic binder NiAl has been used to replace the cobalt and NiCr constituents of conventional WC and Cr3C2 cermet powders. The composite carbide thermal spray powders were fabricated for use in the HVOF coating process. The structure of HVOF deposited NiAl-carbide coatings are compared directly to the more familiar WC-Co and Cr3C2-NiCr coatings using X-ray diffraction, back-scattered electron imaging (BEI) and electron dispersive spectroscopy (EDS). Hardness variations with temperature are reported and compared between the NiAl and Co/NiCr binders

  11. The Development Model Electronic Commerce of Regional Agriculture

    Science.gov (United States)

    Kang, Jun; Cai, Lecai; Li, Hongchan

    With the developing of the agricultural information, it is inevitable trend of the development of agricultural electronic commercial affairs. On the basis of existing study on the development application model of e-commerce, combined with the character of the agricultural information, compared with the developing model from the theory and reality, a new development model electronic commerce of regional agriculture base on the government is put up, and such key issues as problems of the security applications, payment mode, sharing mechanisms, and legal protection are analyzed, etc. The among coordination mechanism of the region is discussed on, it is significance for regulating the development of agricultural e-commerce and promoting the regional economical development.

  12. Development of the inner tracker detector electronics for LHCb

    CERN Document Server

    Vollhardt, A

    2002-01-01

    This paper describes the development and testing of the Inner Tracker detector modules including the silicon sensors and the electronic readout hybrid with the Beetle frontend chip. Testbeam measurements on the sensor performance including signal-to-noise and efficiency are discussed. We also present preformance studies on the digital optical transmission line. Talk presented at 8th workshop on Electronics for LHCb Experiments, Colmar, September 9-13, 2002

  13. INTERNET USAGE AND ELECTRONIC BUSINESS DEVELOPMENT IN KOSOVA

    OpenAIRE

    Mihane Berisha Namani; Myrvete Badivuku Pantina

    2008-01-01

    Worldwide, more and more companies are using the Internet as a medium for the development of business through electronic means. Internet usage has changed the business process in many companies, whereas electronic business has been accepted as a new form for the realization of digital business transactions, without use of hard copy documents and direct contacts in the business process. While the economies of western countries have started to utilize new forms of business through the Internet,...

  14. Research, Development and Innovation at the Section of Electronics

    International Nuclear Information System (INIS)

    The main task of the Section of Electronics is to solve electronic measurement problems emerging in the various fields of experimental research of the institute. Beside this, the section has its own research and development activities. We study new methods to improve measurement accuracy and take part in several projects from CERN to space applications and nuclear medical imaging. The Computational Group of this section takes care of the computing resources of the institute.

  15. The Study of Heat Treatment Effects on Chromium Carbide Precipitation of 35Cr-45Ni-Nb Alloy for Repairing Furnace Tubes

    Directory of Open Access Journals (Sweden)

    Nakarin Srisuwan

    2016-01-01

    Full Text Available This paper presents a specific kind of failure in ethylene pyrolysis furnace tubes. It considers the case in which the tubes made of 35Cr-45Ni-Nb high temperature alloy failed to carburization, causing creep damage. The investigation found that used tubes became difficult to weld repair due to internal carburized layers of the tube. The microstructure and geochemical component of crystallized carbide at grain boundary of tube specimens were characterized by X-ray diffractometer (XRD, scanning electron microscopy (SEM with back-scattered electrons mode (BSE, and energy dispersive X-ray spectroscopy (EDS. Micro-hardness tests was performed to determine the hardness of the matrix and the compounds of new and used tube material. The testing result indicated that used tubes exhibited a higher hardness and higher degree of carburization compared to those of new tubes. The microstructure of used tubes also revealed coarse chromium carbide precipitation and a continuous carbide lattice at austenite grain boundaries. However, thermal heat treatment applied for developing tube weld repair could result in dissolving or breaking up chromium carbide with a decrease in hardness value. This procedure is recommended to improve the weldability of the 35Cr-45Ni-Nb used tubes alloy.

  16. Development of an (e,2e) electron momentum spectroscopy apparatus using an ultrashort pulsed electron gun

    International Nuclear Information System (INIS)

    An (e,2e) apparatus for electron momentum spectroscopy (EMS) has been developed, which employs an ultrashort-pulsed incident electron beam with a repetition rate of 5 kHz and a pulse duration in the order of a picosecond. Its instrumental design and technical details are reported, involving demonstration of a new method for finding time-zero. Furthermore, EMS data for the neutral Ne atom in the ground state measured by using the pulsed electron beam are presented to illustrate the potential abilities of the apparatus for ultrafast molecular dynamics, such as by combining EMS with the pump-and-probe technique.

  17. Cubic Silicon Carbide: a promising material for automotive application

    OpenAIRE

    Attolini, Giovanni; Bosi, Matteo; Rossi, Francesca; Watts, Bernard Enrico; Salviati, Giancarlo

    2008-01-01

    carbide is a material that possesses properties that make it desirable in electronic, structural and sensor applications. As a wide band gap semiconductor it can be used in high power, high temperature electronics and harsh environments. Its hardness, wear resistance, chemical inertness, and thermal conductivity find uses ranging from disc brakes to micron scale sensors and actuators. The automotive industry faces some important challenges since it has obligations to manufacture safe, clean, ...

  18. Silicon Carbide High-Temperature Power Rectifiers Fabricated and Characterized

    Science.gov (United States)

    1996-01-01

    The High Temperature Integrated Electronics and Sensors (HTIES) team at the NASA Lewis Research Center is developing silicon carbide (SiC) for use in harsh conditions where silicon, the semiconductor used in nearly all of today's electronics, cannot function. Silicon carbide's demonstrated ability to function under extreme high-temperature, high power, and/or high-radiation conditions will enable significant improvements to a far ranging variety of applications and systems. These improvements range from improved high-voltage switching for energy savings in public electric power distribution and electric vehicles, to more powerful microwave electronics for radar and cellular communications, to sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. In the case of jet engines, uncooled operation of 300 to 600 C SiC power actuator electronics mounted in key high-temperature areas would greatly enhance system performance and reliability. Because silicon cannot function at these elevated temperatures, the semiconductor device circuit components must be made of SiC. Lewis' HTIES group recently fabricated and characterized high-temperature SiC rectifier diodes whose record-breaking characteristics represent significant progress toward the realization of advanced high-temperature actuator control circuits. The first figure illustrates the 600 C probe-testing of a Lewis SiC pn-junction rectifier diode sitting on top of a glowing red-hot heating element. The second figure shows the current-versus voltage rectifying characteristics recorded at 600 C. At this high temperature, the diodes were able to "turn-on" to conduct 4 A of current when forward biased, and yet block the flow of current ($quot;turn-off") when reverse biases as high as 150 V were applied. This device represents a new record for semiconductor device operation, in that no previous semiconductor electronic device has ever simultaneously demonstrated 600 C functionality

  19. Development of total-skin electron therapy at two energies

    International Nuclear Information System (INIS)

    Total-Skin Electron Therapy (TSET) modalities have been developed at two energies on a Varian Clinac 1800. The physical criteria for the beams were determined mainly from the requirement of continuing the Stanford treatment technique, which was 12 Total-Skin Electron Therapy portals combined in six pairs. The penetration of the lower energy mode matches that previously obtained at Stanford on the Varian Clinac 10, (about 4 mm for the 80% isodose contour in the 12-field treatment). The penetration of the higher energy mode is about 8 mm at the 80% contour. The Total-Skin Electron Therapy modes necessarily use electrons produced by the two standard electron-beam modes of lowest energy, nominally 6 and 9 MeV. Measurements to verify the beam specifications were carried out with diodes, a variety of ionization chambers, and a specially constructed circular phantom for film dosimetry. Initially, the penetration of the Total-Skin Electron Therapy beams was too large to match our criteria, so two methods of reducing it were explored: (a) the energies of the electron beams produced by the machine were reduced (which also reduced the energies of the corresponding standard electron modes) and (b) a large polymethylmethacrylate degrader (2.4 m X 1.2 m) 1 cm thick was placed just in front of the patient plane. Acceptable Total-Skin Electron Therapy beams could be produced by either method and the latter was finally used. The use of the standard dose monitoring system for the Total-Skin Electron Therapy modes considerably simplifies the daily treatment delivery as well as the implementation. However, the need for reasonable dose rates at the treatment plane (3.5 meters beyond the isocenter) requires dose rates of 24 Gy/min at the isocenter. Nevertheless, it is possible to use the internal dose monitor provided the problems associated with high dose rates are addressed

  20. APT analysis of WC-Co based cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Weidow, Jonathan, E-mail: jonathan.weidow@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden); Andren, Hans-Olof [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)

    2011-05-15

    A method for quickly producing sharp and site-specific atom probe specimens from WC-Co based cemented carbides was developed using a combination of electropolishing, controlled back-polishing and FIB milling. Also, a method for measuring the amount of segregated atoms to an interface between two phases with a big difference in field needed for field evaporation was developed. Using atom probe tomography, the interface chemistry of WC/WC grain boundaries, WC/(M,W)C phase boundaries and WC/binder phase boundaries was analysed. In addition, the transition metal solubility in WC was determined. -- Research highlights: {yields} We develop a method for producing specimens from WC-Co based cemented carbides. {yields} Measure segregated atoms to an interface between phases with different field evaporation field. {yields} The interface chemistry in cemented carbides. {yields} The transition metal solubility in WC.

  1. APT analysis of WC-Co based cemented carbides

    International Nuclear Information System (INIS)

    A method for quickly producing sharp and site-specific atom probe specimens from WC-Co based cemented carbides was developed using a combination of electropolishing, controlled back-polishing and FIB milling. Also, a method for measuring the amount of segregated atoms to an interface between two phases with a big difference in field needed for field evaporation was developed. Using atom probe tomography, the interface chemistry of WC/WC grain boundaries, WC/(M,W)C phase boundaries and WC/binder phase boundaries was analysed. In addition, the transition metal solubility in WC was determined. -- Research highlights: → We develop a method for producing specimens from WC-Co based cemented carbides. → Measure segregated atoms to an interface between phases with different field evaporation field. → The interface chemistry in cemented carbides. → The transition metal solubility in WC.

  2. Advances in Electronic-Nose Technologies Developed for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Alphus D. Wilson

    2011-01-01

    Full Text Available The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry.

  3. Development and characterization of electron sources for diffraction applications

    Energy Technology Data Exchange (ETDEWEB)

    Casandruc, Albert

    2015-12-15

    The dream to control chemical reactions that are essential to life is now closer than ever to gratify. Recent scientific progress has made it possible to investigate phenomena and processes which deploy at the angstroms scale and at rates on the order femtoseconds. Techniques such as Ultrafast Electron Diffraction (UED) are currently able to reveal the spatial atomic configuration of systems with unit cell sizes on the order of a few nanometers with about 100 femtosecond temporal resolution. Still, major advances are needed for structural interrogation of biological systems like protein crystals, which have unit cell sizes of 10 nanometers or larger, and sample sizes of less than one micrometer. For such samples, the performance of these electron-based techniques is now limited by the quality, in particular the brightness, of the electron source. The current Ph.D. work represents a contribution towards the development and the characterization of electron sources which are essential to static and time-resolved electron diffraction techniques. The focus was on electron source fabrication and electron beam characterization measurements, using the solenoid and the aperture scan techniques, but also on the development and maintenance of the relevant experimental setups. As a result, new experimental facilities are now available in the group and, at the same time, novel concepts for generating electron beams for electron diffraction applications have been developed. In terms of existing electron sources, the capability to trigger and detect field emission from single double-gated field emitter Mo tips was successfully proven. These sharp emitter tips promise high brightness electron beams, but for investigating individual such structures, new engineering was needed. Secondly, the influence of the surface electric field on electron beam properties has been systematically performed for flat Mo photocathodes. This study is very valuable especially for state

  4. Development and characterization of electron sources for diffraction applications

    International Nuclear Information System (INIS)

    The dream to control chemical reactions that are essential to life is now closer than ever to gratify. Recent scientific progress has made it possible to investigate phenomena and processes which deploy at the angstroms scale and at rates on the order femtoseconds. Techniques such as Ultrafast Electron Diffraction (UED) are currently able to reveal the spatial atomic configuration of systems with unit cell sizes on the order of a few nanometers with about 100 femtosecond temporal resolution. Still, major advances are needed for structural interrogation of biological systems like protein crystals, which have unit cell sizes of 10 nanometers or larger, and sample sizes of less than one micrometer. For such samples, the performance of these electron-based techniques is now limited by the quality, in particular the brightness, of the electron source. The current Ph.D. work represents a contribution towards the development and the characterization of electron sources which are essential to static and time-resolved electron diffraction techniques. The focus was on electron source fabrication and electron beam characterization measurements, using the solenoid and the aperture scan techniques, but also on the development and maintenance of the relevant experimental setups. As a result, new experimental facilities are now available in the group and, at the same time, novel concepts for generating electron beams for electron diffraction applications have been developed. In terms of existing electron sources, the capability to trigger and detect field emission from single double-gated field emitter Mo tips was successfully proven. These sharp emitter tips promise high brightness electron beams, but for investigating individual such structures, new engineering was needed. Secondly, the influence of the surface electric field on electron beam properties has been systematically performed for flat Mo photocathodes. This study is very valuable especially for state

  5. Comparative study on discharge conditions in micro-hole electrical discharge machining of tungsten carbide (WC-Co) material

    Institute of Scientific and Technical Information of China (English)

    Hyun-Seok TAK; Chang-Seung HA; Dong-Hyun KIM; Ho-Jun LEE; Hae-June LEE; Myung-Chang KANG

    2009-01-01

    WC-Co is used widely in die and mold industries due to its unique combination of hardness, strength and wear-resistance. For machining difficult-to-cut materials, such as tungsten carbide, micro-electrical discharge machining(EDM) is one of the most effective methods for making holes because the hardness is not a dominant parameter in EDM. This paper describes the characteristics of the discharge conditions for micro-hole EDM of tungsten carbide with a WC grain size of 0.5μm and Co content of 12%. The EDM process was conducted by varying the condenser and resistance values. A R-C discharge EDM device using arc erosion for micro-hole machining was suggested. Furthermore, the characteristics of the developed micro-EDM were analyzed in terms of the electro-optical observation using an oscilloscope and field emission scanning electron microscope.

  6. EELS analysis of the nitrogen content of carbide particles in a commercial γ′-strengthened nickel-base superalloy

    International Nuclear Information System (INIS)

    Carbide particles contribute to the high strength of nickel-base superalloys. It is a long standing question whether these carbide particles contain nitrogen. Here we examine the nitrogen content of the titanium–molybdenum-carbide in the commercial superalloy NIMONIC PE16 using a combination of electron energy loss spectroscopy (EELS) with energy dispersive X-ray (EDX) analysis. Careful examination of the molybdenum M3- and M2-edges, which overlap with the nitrogen K-edge, leads to an upper limit for the nitrogen content of the carbide: 1.8 at.%

  7. Selection of methods for etching carbides in MAR-M509 cobalt-base superalloy and acquisition of their images

    International Nuclear Information System (INIS)

    The paper summarizes results of research into conditions for selectively revealing carbides and carbide eutectics occurring in the structure of MAR-M509 cobalt-base alloy as well as conditions for their detection. Also discussed are the various conditions for acquisition and registration of structural images (by means of light and scanning electron microscopes) to ensure the selective detection of carbides and carbide eutectics. In particular, the influence of accelerating voltage on the possibility of automating the detection process is analyzed. Very good results were obtained on images registered by applying very low accelerating voltages (0.5 to 1 kV)

  8. Porous silicon carbide (SIC) semiconductor device

    Science.gov (United States)

    Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

    1996-01-01

    Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

  9. Development of laser heated high current DC electron gun

    International Nuclear Information System (INIS)

    The paper deals with the development of a Laser heated cathode for Electron Accelerator. The electron gun is meant for Megawatt-class DC Accelerator for Electron Beam Flue Gas Treatment applications. Conventionally, LaB6 cathode is indirectly heated by tungsten filaments whereas in the newly proposed gun, Laser is utilized for heating. A Nd:YAG Laser is used to heat the LaB6 cathode to emission temperatures. The characterization of cathode heating at various Laser powers has been carried out. In initial trials, it has been observed that with 125 W of Laser power, the LaB6 pellet was heated to 1315 ° C. Based on these experimental results, an electron gun rated for 30 kV, 350 mA CW has been designed. The optimization of gun electrode geometry has been done using CST Particle Studio in order to tune the various electron gun parameters. The beam diameter obtained in simulation is 8 mm at 100 mm from the LaB6 cathode. The perveance obtained is 7.1 x 10-8 A/V3/2 . The Laser heated cathode has the advantages of eliminating the magnetic field effects of filament on the electron beam, electrical isolation needed for gun filament power supplies and better electron beam emittances. (author)

  10. Development of the OPU electron linac system for advanced applications

    International Nuclear Information System (INIS)

    In Radiation Research Center, Osaka Prefecture University (OPU) 18 MeV electron linear accelerator has been used for scientific and industrial researches in various fields. This accelerator was constructed 48 years ago. For supplying stable beams to many users the accelerator components have been improved. For performing the characteristic quantum beam applications ultra-low intensity beams and coherent THz light sources have been developed. The recent development of the accelerator system for the application researches of the electron beams is reported. (author)

  11. Electronic Commerce in Poland - Present State and Prospects of Development

    OpenAIRE

    Gregor, Bogdan; Stawiszyński, Marcin

    2003-01-01

    Article concentrates on explanation of essence of electronic commerce, its current condition and prospects of development. The aim of the article is to explain basic notions such as e-commerce, e-business, e-economy. It analyses e-commerce conditions and evolution in B2C and B2B sectors. Forecast of development of e-commerce in Poland does not seem to be comforting. 2006-2008 is expected to become an era of e-commerce. Electronic business will go out from phase of experiment and it will pr...

  12. Innovative Mobile Platform Developments for Electronic Services Design and Delivery

    DEFF Research Database (Denmark)

    Scupola, Ada

    In the ever-growing world of technology, it is becoming more important to understand the developments of new electronic services and mobile applications. Innovative Mobile Platform Developments for Electronic Services Design, and Delivery is a comprehensive look at all aspects of production...... management, delivery and consumption of e-services, self services, and mobile communication including business-to-business, business-to-consumer, government-to-business, government-to-consumer, and consumer-to-consumer e-services. This volume is perfect for the interest of professionals, academic educators...

  13. Developing electron beam bunching technology for improving light sources

    International Nuclear Information System (INIS)

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project was to develop a new electron bunch compression technology, experimentally demonstrate subpicosecond compression of bunches with charges on the order of 1 nC, and to theoretically investigate fundamental limitations to electron bunch compression. All of these goals were achieved, and in addition, the compression system built for this project was used to generate 22 nm light in a plasma-radiator light source

  14. Recent developments of low-emittance electron gun for accelerator

    International Nuclear Information System (INIS)

    Recent developments of low-emittance electron guns for accelerator are reviewed. In the accelerator field, DC biased triode thermionic gun (Pierce type gun) has been widely used and is still conventional. On the other hand, because of strong demands on the high brightness electron beam by FEL and other advanced accelerator concepts based on linear accelerator, the low emittance beam generation becomes one of the most important issue in the accelerator science. The R and D effort is 'accelerated' by two technological innovations, photo-cathode and RF gun. They made a large improvement on the beam emittance. After the explanations on the technical and physical aspects of the low emittance electron beam generation, advanced electron sources for accelerators are reviewed. (author)

  15. Production of titanium carbide from ilmenite

    Directory of Open Access Journals (Sweden)

    Sutham Niyomwas

    2008-03-01

    Full Text Available The production of titanium carbide (TiC powders from ilmenite ore (FeTiO3 powder by means of carbothermal reduction synthesis coupled with hydrochloric acid (HCl leaching process was investigated. A mixture of FeTiO3 and carbon powders was reacted at 1500oC for 1 hr under flowing argon gas. Subsequently, synthesized product of Fe-TiC powders were leached by 10% HCl solutions for 24 hrs to get final product of TiC powders. The powders were characterized using X-ray diffraction, scanning electron and transmission electron microscopy. The product particles were agglomerated in the stage after the leaching process, and the size of this agglomerate was 12.8 μm with a crystallite size of 28.8 nm..

  16. Research and development of high-temperature operating photocathode electron source for high brightness electron gun

    International Nuclear Information System (INIS)

    We have been developing a novel photocathode RF gun system with an advanced RF cavity structure and a new photocathode material for the SuperKEKB electron linac. This injector is required to obtain a low emittance and high charge electron beams in order to achieve the highest luminosity in the world. The required beam parameters are 5 nC and 20 mm·mrad from the RF gun. Moreover, 10 nC electron beams for positron production will be also generated by the same RF gun. In order to obtain extremely high charge electron beams, Yb-based laser system is being upgraded for higher power and a high temperature photocathode system for a quantum efficiency (QE) enhancement will be introduced to the new RF gun system. This paper reports on the research and development of the system of high temperature photocathode for QE enhancement to be able to generate high charge electron beams (∼10 nC) at the RF gun in SuperKEKB electron linac. (author)

  17. Metal-carbide multilayers for molten Pu containment

    International Nuclear Information System (INIS)

    Multilayers composed of nine or ten alternating layers of Ta or W and TaC were studied for the feasibility of their use in containing molten plutonium (Pu) at 1200 degrees C. Single layers of W and TaC were also investigated. A two-source electron beam evaporation process was developed to deposit these coatings onto the inside surface of hemispherical Ta cups about 38 mm in diameter. Pu testing was done by melting Pu in the coated hemispherical cups and holding them under vacuum at 1200 degrees C for two hours. Metallographic examination and microprobe analysis of cross sections showed that Pu had penetrated to the Ta substrate in all cases to some extent. Full penetration to the outer surface of the Ta substrate, however, occurred in only a few of the samples. The fact that full penetration occurred in any of the samples suggests that it would have occurred in uncoated Ta under these testing conditions which in turn suggests that the multilayer coatings do afford some protection against Pu attack. The TaC used for these specimens was wet by Pu under these testing conditions, and following testing, Pu was found uniformly distributed throughout the carbide layers which appeared to be rather porous. Pu was seen in the W and Ta layers only when exposed directly to molten Pu during testing or near defects suggesting that Pu penetrated the multilayers at defects in the coating and traveled parallel to the layers along the carbide layers. These results indicate that the use of alternating metal and ceramic layers for Pu containment should be possible through the use of nonporous ceramic that is not wet by molten Pu and defect-free films

  18. Transition metal carbide and boride abrasive particles

    International Nuclear Information System (INIS)

    Abrasive particles and their preparation are discussed. The particles consist essentially of a matrix of titanium carbide and zirconium carbide, at least partially in solid solution form, and grains of crystalline titanium diboride dispersed throughout the carbide matrix. These abrasive particles are particularly useful as components of grinding wheels for abrading steel. 1 figure, 6 tables

  19. 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...

  20. Palladium interaction with silicon carbide

    OpenAIRE

    M. Gentile, P. Xiao, T. Abram

    2015-01-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide...

  1. Influence of electron irradiation on optical properties of inorganic materials

    International Nuclear Information System (INIS)

    Influence of electron radiation on optical properties and structure parameters of compound inorganic compositions (silicon nitrides, bor carbide, mono aluminates of rare-earth elements, high-temperature superconducting ceramics) was investigated. Mechanism of radiation defect formation was determined as a consequent development of lattice disorders and diffusion mass transfer of the substance

  2. Internet payments and the development of electronic business in Ukraine

    OpenAIRE

    Mereshenko, K.

    2006-01-01

    The article deals with the problems of the development of Internet payments in Ukraine. The author of the article examines the Internet payment like effective co-operation of the user and salesman. The author analyses the features of the use of electronic payments such as WebMoney, PayCash, PayPal and credits-cards.

  3. Development and evaluation of new electronic seals at the IAEA

    International Nuclear Information System (INIS)

    During the recent 5 years a wide program for evaluation of existing and development of new tamper-indicating devices was started at the IAEA. The purpose of this program is to assess functionality, usability and possible vulnerabilities of seals already in use, to define the requirements and enhanced features of new devices and systems and to test them appropriately. Emphasis was given to the development and assessment of electronic seals, which represent the family of multiple use, multiple verification tamper-indicating devices with the capability to store internally substantial information about the history of their handling. This information can be retrieved, transferred, processed and evaluated later allowing to establish conclusions about possible tampering of the protected object as well as assurance about the 'state of health' of the tamper-indicating device and its components. The present paper describes the main features of the currently used VACOSS-S seal as well as the needs for its replacement, and the most important Agency's requirements for the newly developed electronic seals. The implementation of these requirements is being shown on the examples of new developments mainly supported by the Member States Support Programmes for the IAEA Safeguards. The main technical data of the presented electronic seals are compared. Short description of the necessary steps for the IAEA acceptance testing and authorization procedure for new electronic seals including lab functional tests, usability check, environmental and EMC qualification tests, radiation tests, safety and vulnerability assessments as well as field tests completes the presentation. (author)

  4. Development of fiber laser for photo cathode electron gun

    International Nuclear Information System (INIS)

    We develop L-band photocathode RF gun which is conducted by the collaborations with the groups of Osaka University, KEK and Hiroshima University. For the photocathode, we uniquely develop laser at Osaka University. At the first laser system, we have developed passive mode lock Yb fiber laser at repetition rate of 108MHz. on the other hand, thermionic cathode electron gun generates electron with sub harmonic buncher with the repetition of 27MHz now in addition to 108MHz. For this reason, we started to develop passive mode lock Yb fiber laser at repetition rate of 27MHz uniquely. The mean power at pulse is 35∼70mW, and Max energy at a pulse is 2.7nJ. (author)

  5. DELSY project: status and development Dubna Electron Synchrotron

    CERN Document Server

    Balalykin, N; Bykovsky, V

    2003-01-01

    The DELSY (Dubna Electron Synchrotron) project is under development at the Joint Institute for Nuclear Research. It is based on an acceleration facility donated to the Joint Institute for Nuclear Research by the Institute for Nuclear and High Energy Physics (NIKHEF, Amsterdam). The NIKHEF accelerator facility consists of the linear electron accelerator MEA, which has an electron energy of 700 MeV, and the electron storage ring AmPS, with a maximum energy of 900 MeV and a beam current of 200 mA. There are three phases to the construction of the DELSY facility. Phase I will be accomplished with the construction of a complex of free-electron lasers covering continuously the spectrum from the far infrared down to the ultraviolet (approx 150 nm). Phase II will be accomplished with the commissioning of the storage ring DELSY. Complete commissioning of the DELSY project will take place after finishing Phase III, the construction of an X-ray free-electron laser. This phase is considered as the ultimate goal of the pr...

  6. New developments in transmission electron microscopy for nanotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.L. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States)

    2003-09-16

    High-resolution transmission electron microscopy (HRTEM) is one of the most powerful tools used for characterizing nanomaterials, and it is indispensable for nanotechnology. This paper reviews some of the most recent developments in electron microscopy techniques for characterizing nanomaterials. The review covers the following areas: in-situ microscopy for studying dynamic shape transformation of nanocrystals; in-situ nanoscale property measurements on the mechanical, electrical and field emission properties of nanotubes/nanowires; environmental microscopy for direct observation of surface reactions; aberration-free angstrom-resolution imaging of light elements (such as oxygen and lithium); high-angle annular-dark-field scanning transmission electron microscopy (STEM); imaging of atom clusters with atomic resolution chemical information; electron holography of magnetic materials; and high-spatial resolution electron energy-loss spectroscopy (EELS) for nanoscale electronic and chemical analysis. It is demonstrated that the picometer-scale science provided by HRTEM is the foundation of nanometer-scale technology. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  7. New developments in transmission electron microscopy for nanotechnology

    International Nuclear Information System (INIS)

    High-resolution transmission electron microscopy (HRTEM) is one of the most powerful tools used for characterizing nanomaterials, and it is indispensable for nanotechnology. This paper reviews some of the most recent developments in electron microscopy techniques for characterizing nanomaterials. The review covers the following areas: in-situ microscopy for studying dynamic shape transformation of nanocrystals; in-situ nanoscale property measurements on the mechanical, electrical and field emission properties of nanotubes/nanowires; environmental microscopy for direct observation of surface reactions; aberration-free angstrom-resolution imaging of light elements (such as oxygen and lithium); high-angle annular-dark-field scanning transmission electron microscopy (STEM); imaging of atom clusters with atomic resolution chemical information; electron holography of magnetic materials; and high-spatial resolution electron energy-loss spectroscopy (EELS) for nanoscale electronic and chemical analysis. It is demonstrated that the picometer-scale science provided by HRTEM is the foundation of nanometer-scale technology. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  8. The development of technology for recycling of electronic scrap

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hyo-Shin; Kim, Won-Baek; Sohn, Yong-Uhn [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

    1999-12-01

    Electronic devices, especially computer becomes an essential tools for home and industries entering the information era. The number of computers exceed over 100 million, hence, the amount of end of life(EOL) computer and electronic scrap is increasing. These wastes and scraps include products rejected from manufacturing processes and obstacle computers. Owing to a short life cycle of electronic products and rapid growth of electronic industries, the number of domestic EOL computers goes beyond a million and its disposal causes an environmental problems. Therefore, this recycling is considered to play an important role from the viewpoint of environmental preservation as well as reusable resources. The process development for the recovery of valuable materials and minimization of waste from electronic scrap has been carried out. In the first year of three year project, physical separation such as shredding, crushing, and magnetic separation is established to reclaim valuable materials effectively. Then, hydro- and pyrometallurgical processes are employed to recover valuable metals from electronic scrap. First, metallic and nonmetallic portion are separated from PCBs by a newly designed shredder to prevent hazardous organic materials from further chemical treatment. The optimum conditions for each unit process were found in terms of separation ratio, energy consumption, recovery rate, etc. (author). 92 refs., 24 tabs., 39 figs.

  9. Development of electron cyclotron resonance heavy ion source

    International Nuclear Information System (INIS)

    A multiply charged heavy ion (MCHI) beam is a major scientific ingredient to explore many new fields of research over a wide energy range (from a few eV to a few TeV). The basic requirement is to have an ion source that will produce highly charged (Z) high intensity ion beam with low emittance over the entire mass range and will work stably over a long time and having 100% duty cycle. These are very useful requirements in accelerator applications in particular. Performance of present day Electron Cyclotron Resonance Ion Source (ECRIS) has almost fulfilled all the above conditions. In ECRIS, high-Z ions are produced by subjecting low-Z ions in a plasma to successive impact of hot electrons, which are efficiently energized by rf power, the frequency of which equals the cyclotron frequency of the electrons in the magnetic field. The emphasis on ECRIS development has been to increase electron temperature Te and nτ factor, where n is electron density and τ is the ion confinement time, which in turn is related to plasma confinement and stability. In this paper the development on ECRIS and the experiences with the 6.4 GHz ECRIS indigenously built at the VEC centre will be briefly presented. (author). 32 refs., 9 figs., 2 tabs

  10. Development of superconducting acceleration cavity technology for free electron lasers

    International Nuclear Information System (INIS)

    As a result of the cooperative research between the KAERI and Peking University, the key technologies of superconducting acceleration cavity and photoelectron gun have been developed for the application to high power free electron lasers. A 1.5-GHz, 1-cell superconducting RF cavity has been designed and fabricated by using pure Nb sheets. The unloaded Q values of the fabricated superconducting cavity has been measured to be 2x109 at 2.5K, and 8x109 at 1.8K. The maximum acceleration gradient achieved was 12 MeV/m at 2.5K, and 20MV/m at 1.8 K. A cryostat for the 1-cell superconducting cavity has been designed. As a source of electron beam, a DC photocathode electron gun has been designed and fabricated, which is composed of a photocathode evaporation chamber and a 100-keV acceleration chamber. The efficiency of the Cs2Te photocathode is 3% nominally at room temperature, 10% at 290 deg C. The superconducting photoelectron gun system developed has been estimated to be a good source of high-brightness electron beam for high-power free electron lasers

  11. Trends in the chemical properties in early transition metal carbide surfaces: A density functional study

    DEFF Research Database (Denmark)

    Kitchin, J.R.; Nørskov, Jens Kehlet; Barteau, M.A.;

    2005-01-01

    In this paper we present density functional theory (DFT) investigations of the physical, chemical and electronic structure properties of several close-packed surfaces of early transition metal carbides, including beta-Mo2C(0 0 0 1), and the (1 1 1) surfaces of TiC, VC, NbC, and TaC. The results are...... closest-packed pure metal surfaces, due to the tensile strain induced in the carbide surfaces upon incorporation of carbon into the lattice. Hydrogen atoms were found to adsorb more weakly on carbide surfaces than on the corresponding closest-packed pure metal surfaces only when there were surface carbon...

  12. Critical cooling rate on carbide precipitation during quenching of austenitic manganese steel

    Directory of Open Access Journals (Sweden)

    Youn-Soo Ham

    2010-05-01

    Full Text Available Critical cooling rate to avoid carbide precipitation during quenching of austenitic manganese steel was investigated by means of optical microscopy, image analyzer and numerical analysis. An efficient heat treatment analysis program including temperature-dependent material properties was developed for the prediction of cooling rate and probability of carbide precipitation during quenching by finite difference method. Time-dependent heat transfer coefficient was adopted to achieve more precise results. Area ratio of carbide precipitation was measured by image analyzer to determine the critical point of carbide precipitation. Temperature-dependent critical cooling rate at that point was calculated by the developed numerical program. Finally, the probability of carbide precipitation on the whole area of specimen can be predicted by the proposed numerical program and the numerical result of a specimen was compared with the experimental result.

  13. Development of pierce type high-brightness electron gun

    International Nuclear Information System (INIS)

    A Pierce type electron gun has been developed. High voltage of 200kV DC is effective for the purpose of high brightness. A compact insulation gas tank of 600mmx600mmφ, and a very simple structure of high voltage feeding is realized by insulation designing using an electric field analysis. At the test bench experiments, high voltage of 200kV was achieved, which justifies our design. After a measurement of electron beam characteristics, the gun has been installed into linac system and operated stably. (author)

  14. Development and evaluation of new electronic seals at the IAEA

    International Nuclear Information System (INIS)

    Full text: The International Atomic Energy Agency, Vienna, is using world-wide a variety of seals to attain its safeguards objective in the area of Nuclear Non-Proliferation. During the recent 5 years a wide program for evaluation of existing and development of new tamper-indicating devices was started at the IAEA. The purpose of this program is to assess functionality, usability and possible vulnerabilities of seals already in use, to define the requirements and enhanced features of new devices and systems and to test them appropriately. Emphasis was given to the development and assessment of electronic seals, which represent the family of multiple use, multiple verification tamper-indicating devices with the capability to store internally substantial information about the history of their handling. This information can be retrieved, transferred, processed and evaluated later allowing to establish conclusions about possible tampering of the protected object as well as assurance about the 'state of health' of the tamper-indicating device and its components. The electronic seals represent the most sophisticated and user-friendly type of security seals, which can be easily integrated in small or large unattended automated data acquisition systems for C/S including also Remote Monitoring Systems at nuclear facilities and elsewhere. The present paper describes the main features of the currently used VACOSS-S seal as well as the needs for its replacement, and the most important Agency's requirements for the newly developed electronic seals. The implementation of these requirements is being shown on the examples of new developments like the modified enhanced VACOSS 5 seal developed by Aquila Technology Group, the Electro-Optical Sealing System (EOSS) under development by the German Support Programme, the Integrable Reusable Electronic Seal (IRES) under development by the French Support Programme, the Two-way Radio Frequency Sealing System with wireless information

  15. Homogeneous nanocrystalline cubic silicon carbide films prepared by inductively coupled plasma chemical vapor deposition.

    Science.gov (United States)

    Cheng, Qijin; Xu, S; Long, Jidong; Huang, Shiyong; Guo, Jun

    2007-11-21

    Silicon carbide films with different carbon concentrations x(C) have been synthesized by inductively coupled plasma chemical vapor deposition from a SiH(4)/CH(4)/H(2) gas mixture at a low substrate temperature of 500 °C. The characteristics of the films were studied by x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared absorption spectroscopy, and Raman spectroscopy. Our experimental results show that, at x(C) = 49 at.%, the film is made up of homogeneous nanocrystalline cubic silicon carbide without any phase of silicon, graphite, or diamond crystallites/clusters. The average size of SiC crystallites is approximately 6 nm. At a lower value of x(C), polycrystalline silicon and amorphous silicon carbide coexist in the films. At a higher value of x(C), amorphous carbon and silicon carbide coexist in the films. PMID:21730481

  16. Power Electronics Being Developed for Deep Space Cryogenic Applications

    Science.gov (United States)

    Patterson, Richard L.; Hammoud, Ahmad

    2003-01-01

    Electronic circuits and systems designed for deep space missions need to operate reliably and efficiently in harsh environments that include very low temperatures. Spacecraft that operate in such cold environments carry a large number of heaters so that the ambient temperature for the onboard electronics remains near 20 C. Electronics that can operate at cryogenic temperatures will simplify system design and reduce system size and weight by eliminating the heaters and their associated structures. As a result, system development and launch cost will be reduced. At the NASA Glenn Research Center, an ongoing program is focusing on the development of power electronics geared for deep space low-temperature environments. The research and development efforts include electrical components design, circuit design and construction, and system integration and demonstration at cryogenic temperatures. Investigations are being carried out on circuits and systems that are targeted for use in NASA missions where low temperatures will be encountered: devices such as ceramic and tantalum capacitors, metal film resistors, semiconductor switches, magnetics, and integrated circuits including dc/dc converters, operational amplifiers, voltage references, and motor controllers. Test activities cover a wide range of device and circuit performance under simple as well as complex test conditions, such as multistress and thermal cycling. The effect of low-temperature conditions on the switching characteristics of an advanced silicon-on-insulator field effect transistor is shown. For gate voltages (VGS) below 2.6 V, drain currents at -190 C are lower than drain currents at room temperature (20 C).

  17. Architectural development of an advanced EVA Electronic System

    Science.gov (United States)

    Lavelle, Joseph

    1992-01-01

    An advanced electronic system for future EVA missions (including zero gravity, the lunar surface, and the surface of Mars) is under research and development within the Advanced Life Support Division at NASA Ames Research Center. As a first step in the development, an optimum system architecture has been derived from an analysis of the projected requirements for these missions. The open, modular architecture centers around a distributed multiprocessing concept where the major subsystems independently process their own I/O functions and communicate over a common bus. Supervision and coordination of the subsystems is handled by an embedded real-time operating system kernel employing multitasking software techniques. A discussion of how the architecture most efficiently meets the electronic system functional requirements, maximizes flexibility for future development and mission applications, and enhances the reliability and serviceability of the system in these remote, hostile environments is included.

  18. A study of silicon carbide synthesis from waste serpentine.

    Science.gov (United States)

    Cheng, T W; Hsu, C W

    2006-06-01

    There are 60000 tons of serpentine wastes produced in year 2004 in Taiwan. This is due to the well-developed joints in the serpentine ore body as well as the stringent requirements of the particle size and chemical composition of serpentine by iron making company. The waste also creates considerable environmental problems. The purpose of this study is reutilization of waste serpentine to produce a high value silica powder after acid leaching. These siliceous microstructure products obtained from serpentine would be responsible for high reactivity and characteristic molecular sieving effect. In this study, the amorphous silica powder was then synthesized to silicon carbide with the C/SiO(2) molar ratio of 3. The experiment results show that silicon carbide can be synthesized in 1550 degrees C. The formed silicon carbide was whisker beta type SiC which can be used as raw materials for industry. PMID:16405956

  19. Development of applicators for intraoperative electron beam irradiation

    International Nuclear Information System (INIS)

    A set of applicator units for intraoperative electron beam irradiation has been developed, and is utilized for clinical practice. The applicator system includes a lead tube, a lead containing acrylic cone, and attachment devices. The lead tube is attached to a commercially available electron tube, and the acrylic cone is placed at the tip of the lead tube for better visualization of treatment fields. Measurements before clinical applications revealed that the system provides clinically acceptable dose distribution for intraoperative electron beam irradiation. Clinical utilization suggests the following advantages of the applicator: 1) Sterilization is easy. 2) It is inexpensive and easy to handle. 3) Treatment fields are clearly visualized using endoscopy. The acrylic cone is useful to verify relations between treatment fields and outer structures. 4) It is safe since collision inter-locking is available. (author)

  20. Development of scanning electron and x-ray microscope

    Energy Technology Data Exchange (ETDEWEB)

    Matsumura, Tomokazu, E-mail: tomokzau.matsumura@etd.hpk.co.jp; Hirano, Tomohiko, E-mail: tomohiko.hirano@etd.hpk.co.jp; Suyama, Motohiro, E-mail: suyama@etd.hpk.co.jp [Hamamatsu Photonics K.K., 314-5, Shimokanzo, Iwata City, Shizuoka-Pref. (Japan)

    2016-01-28

    We have developed a new type of microscope possessing a unique feature of observing both scanning electron and X-ray images under one unit. Unlike former X-ray microscopes using SEM [1, 2], this scanning electron and X-ray (SELX) microscope has a sample in vacuum, thus it enables one to observe a surface structure of a sample by SEM mode, to search the region of interest, and to observe an X-ray image which transmits the region. For the X-ray observation, we have been focusing on the soft X-ray region from 280 eV to 3 keV to observe some bio samples and soft materials. The resolutions of SEM and X-ray modes are 50 nm and 100 nm, respectively, at the electron energy of 7 keV.

  1. Development of scanning electron and x-ray microscope

    International Nuclear Information System (INIS)

    We have developed a new type of microscope possessing a unique feature of observing both scanning electron and X-ray images under one unit. Unlike former X-ray microscopes using SEM [1, 2], this scanning electron and X-ray (SELX) microscope has a sample in vacuum, thus it enables one to observe a surface structure of a sample by SEM mode, to search the region of interest, and to observe an X-ray image which transmits the region. For the X-ray observation, we have been focusing on the soft X-ray region from 280 eV to 3 keV to observe some bio samples and soft materials. The resolutions of SEM and X-ray modes are 50 nm and 100 nm, respectively, at the electron energy of 7 keV

  2. Fuels for space nuclear power systems. 1. Tri-Carbide Nuclear Fuel Processing and Characterization for Space Nuclear Applications

    International Nuclear Information System (INIS)

    Tri-carbide fuels fabricated from uranium and refractory metal carbides have been proposed for advanced nuclear thermal propulsion (NTP) applications. These fuels are particularly desirable for space nuclear applications because of their high melting points and high thermal conductivity and their thermochemical stability with the flowing hot hydrogen propellant. This study examined the processing methods for fabricating low-porosity, single-phase solid-solution tri-carbides of (U, Zr,Nb)C. Binary carbides of (U, Zr)C for NTP were first studied at the end of the Rover/NERVA program, a joint effort between the National Aeronautics and Space Administration (NASA) and the Atomic Energy Commission from 1955 to 1973. This advanced fuel was proposed to reduce the mass losses experienced by earlier graphite matrix and composite fuels due to corrosion by the flowing hot hydrogen propellant. However, insufficient tests were completed before the program was canceled in 1973. Results of this study revealed the difficulty to extrude this very hard material in the desired geometry for NTP applications and a susceptibility to fracture during operation. Preliminary indication of higher melting points and improvements in thermochemical stability led to work on tri-carbides of (U, Zr,Nb)C and (U, Zr, Ta)C in the former Soviet Union. A joint effort with the Russian research institute LUTCH and INSPI from 1993 to 1997 studied the mass losses from these fuels, which were extruded in a simple, twisted-ribbon geometry compatible with Russian core designs. The melting temperature of the tri-carbides is influenced by the carbon-to-metal ratio (C/M) and the uranium metal mole fraction (U/M).A target C/M of 0.88 to 0.95 was maintained during the Rover/NERVA program to avoid the development of a second phase, carbon, which leads to significantly lower, eutectic, melting temperatures. Recent efforts at INSPI have been directed toward optimizing the processing methods and parameters for

  3. Magnetron sputter deposition of boron and boron carbide

    International Nuclear Information System (INIS)

    The fabrication of X-ray optical coatings with greater reflectivity required the development of sputter deposition processes for boron and boron carbide. The use of high density boron and boron carbide (B4C) and a vacuum-brazed target design was required to achieve the required sputter process stability and resistance to the thermal stress created by high rate sputtering. Our results include a description of the target fabrication procedures and sputter process parameters necessary to fabricate B4C and boron modulated thin film structures. (orig.)

  4. Hot-press fabrication and joining of boron carbide

    International Nuclear Information System (INIS)

    A method has been developed for fabricating long, cylindrical rubber-mill rolls of boron carbide for use with abrasive materials. The technique consisted of initially hot pressing the boron carbide (to 90% of the theoretical density) to short, hollow cylinders having a length-to-diameter ratio of about one. This initial hot-press operation was followed by a second hot press to join or bond, and further densify, the short sections into a final compact having a length-to-diameter ratio of three. Flexural-strength data show that the integrity of the bond is comparable to that of the base material

  5. Fracture and fatigue behavior of WC-Co and WC-CoNi cemented carbides

    OpenAIRE

    Tarragó Cifre, Jose María; Roa Rovira, Joan Josep; Valle, Vladimir; Marsahll, J. M.; Llanes Pitarch, Luis Miguel

    2015-01-01

    The fracture and fatigue characteristics of several cemented carbide grades are investigated as a function of their microstructure. In doing so, the influence of binder chemical nature and content (Co and 76 wt.% Co-24 wt.% Ni), as well as carbide grain size on hardness, flexural strength, fracture toughness and fatigue crack growth (FCG) behavior is evaluated. Mechanical testing is combined with a detailed inspection of crack-microstructure interaction, by means of scanning electron microsco...

  6. Development of BPM Electronics at the JLAB FEL

    Science.gov (United States)

    Sexton, D.; Evtushenko, P.; Jordan, K.; Yan, J.; Dutton, S.; Moore, W.; Evans, R.; Coleman, J.

    2006-11-01

    A new version of BPM electronics based on the AD8362 RMS detector, which is a direct RF to DC converter, is under development at the JLAB FEL. Each of these new BPM electronics utilizes an embedded ColdFire Microprocessor for data processing and communication with the EPICS control system via TCP/IP. The ColdFire runs RTEMS, which is an open source real-time operating system. The JLAB FEL is a SRF Energy Recovery LINAC capable of running up to 10 mA CW beam with a 74.85 MHz micropulse frequency. For diagnostic reasons and for machine tune up, the micropulse frequency can be reduced to 1.17 MHz, which corresponds to about 160 μA of beam current. It is required that the BPM system would be functional for all micropulse frequencies. By taking into account the headroom for the beam steering and current variations the dynamic range of the RF front end is required to be about 60 dB. A BPM resolution of at least 100 μm is required, whereas better resolution is very desirable to make it possible for more accurate measurements of the electron beam optics. Some results of the RF front end development are presented as well as the first measurements made with an electron beam.

  7. Alumina Based 500 C Electronic Packaging Systems and Future Development

    Science.gov (United States)

    Chen, Liang-Yu

    2012-01-01

    NASA space and aeronautical missions for probing the inner solar planets as well as for in situ monitoring and control of next-generation aeronautical engines require high-temperature environment operable sensors and electronics. A 96% aluminum oxide and Au thick-film metallization based packaging system including chip-level packages, printed circuit board, and edge-connector is in development for high temperature SiC electronics. An electronic packaging system based on this material system was successfully tested and demonstrated with SiC electronics at 500 C for over 10,000 hours in laboratory conditions previously. In addition to the tests in laboratory environments, this packaging system has more recently been tested with a SiC junction field effect transistor (JFET) on low earth orbit through the NASA Materials on the International Space Station Experiment 7 (MISSE7). A SiC JFET with a packaging system composed of a 96% alumina chip-level package and an alumina printed circuit board mounted on a data acquisition circuit board was launched as a part of the MISSE7 suite to International Space Station via a Shuttle mission and tested on the orbit for eighteen months. A summary of results of tests in both laboratory and space environments will be presented. The future development of alumina based high temperature packaging using co-fired material systems for improved performance at high temperature and more feasible mass production will also be discussed.

  8. Development of BPM Electronics at the JLAB FEL

    Energy Technology Data Exchange (ETDEWEB)

    Daniel Sexton; Pavel Evtushenko; Kevin Jordan; Jianxun Yan; Steven Dutton; Steven Moore; Richard Evans; James Coleman

    2006-05-01

    A new version of BPM electronics based on the AD8362 RMS detector, which is a direct RF to DC converter, is under development at the JLAB FEL. Each of these new BPM electronics utilizes an embedded ColdFire Microprocessor for data processing and communication with the EPICS control system via TCP/IP. The ColdFire runs RTEMS, which is an open source real-time operating system. The JLAB FEL is a SRF Energy Recovery LINAC capable of running up to 10 mA CW beam with the micropulse up to 74.85 MHz. For diagnostic reasons and for the machine tune up, the micropulse frequency can be reduced to 1.17 MHz, which corresponds to about 160 ?A of beam current. It is required that the BPM system would be functional for all micropulse frequencies. By taking into account the headroom for the beam steering and current variations the dynamic range of the RF front end is required to be about 60 dB. A BPM resolution of at least 100 ?m is required, whereas better resolution is very desirable to make it possible for more accurate measurements of the electron beam optics. Some results of the RF front end development are presented as well as the first measurements made with an electron beam.

  9. Development of BPM Electronics at the JLAB FEL

    International Nuclear Information System (INIS)

    A new version of BPM electronics based on the AD8362 RMS detector, which is a direct RF to; DC-- converter, is under development at the JLAB FEL. Each of these new BPM electronics utilizes an embedded ColdFire Microprocessor for data processing and communication with the EPICS control system via TCP/IP. The ColdFire runs RTEMS, which is an open source real-time operating system. The JLAB FEL is a SRF Energy Recovery LINAC capable of running up to 10 mA CW beam with the micropulse up to 74.85 MHz. For diagnostic reasons and for the machine tune up, the micropulse frequency can be reduced to 1.17 MHz, which corresponds to about 160 ?A of beam current. It is required that the BPM system would be functional for all micropulse frequencies. By taking into account the headroom for the beam steering and current variations the dynamic range of the RF front end is required to be about 60 dB. A BPM resolution of at least 100 ?m is required, whereas better resolution is very desirable to make it possible for more accurate measurements of the electron beam optics. Some results of the RF front end development are presented as well as the first measurements made with an electron beam

  10. Surface chemistry and friction behavior of the silicon carbide (0001) surface at temperatures to 1500 deg C

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1981-01-01

    X-ray photoelectron and Auger electron spectroscopy analyses and friction studies were conducted with a silicon carbide (0001) surface in contact with iron at various temperatures to 1200 or 1500 C in a vacuum of 10 to the minus 8th power Pa. The results indicate that there is a significant temperature influence on both the surface chemistry and friction properties of silicon carbide. The principal contaminant of adsorbed amorphous carbon on the silicon carbide surface in the as received state is removed by simply heating to 400 C. Above 400 C, graphite and carbide type carbine are the primary species on the silicon carbide surface, in addition to silicon. The coefficients of friction of polycrystalline iron sliding against a single crystal silicon carbide (0001) surface were high at temperatures to 800 C. Similar coefficients of friction were obtained at room temperature after the silicon carbide was preheated at various temperatures up 800 C. When the friction experiments were conducted above 800 C or when the specimens were preheated to above 800 C, the coefficients of friction were dramatically lower. At 800 C the silicon and carbide type carbon are at a maximum intensity in the XPS spectra. With increasing temperature above 800 C, the concentration of the graphite increases rapidly on the surface, whereas those of the carbide type carbon and silicon decrease rapidly.

  11. Influence of nanometric silicon carbide on phenolic resin composites properties

    Indian Academy of Sciences (India)

    GEORGE PELIN; CRISTINA-ELISABETA PELIN; ADRIANA STEFAN; ION DINC\\u{A}; ANTON FICAI; ECATERINA ANDRONESCU; ROXANA TRUSC\\u{A}

    2016-06-01

    This paper presents a preliminary study on obtaining and characterization of phenolic resin-based composites modified with nanometric silicon carbide. The nanocomposites were prepared by incorporating nanometric silicon carbide (nSiC) into phenolic resin at 0.5, 1 and 2 wt% contents using ultrasonication to ensure uniform dispersion of the nanopowder, followed by heat curing of the phenolic-based materials at controlled temperature profile up to 120$^{\\circ}$C. The obtained nanocomposites were characterized by FTIR spectroscopy and scanning electron microscopy analysis and evaluated in terms of mechanical, tribological and thermal stability under load. The results highlight the positive effect of the nanometric silicon carbide addition in phenolic resin on mechanical, thermo-mechanical and 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 future studies.

  12. Modification of optical surfaces employing CVD boron carbide coatings

    International Nuclear Information System (INIS)

    Non-reflective or high emissivity optical surfaces require materials with given roughness or surface characteristics wherein interaction with incident radiation results in the absorption and dissipation of a specific spectrum of radiation. Coatings have been used to alter optical properties, however, extreme service environments, such as experienced by satellite systems and other spacecraft, necessitate the use of materials with unique combinations of physical, chemical, and mechanical properties. Thus, ceramics such as boron carbide are leading candidates for these applications. Boron carbide was examined as a coating for optical baffle surfaces. Boron carbide coatings were deposited on graphite substrates from BCl3, CH4, and H2 gases employing chemical vapor deposition (CVD) techniques. Parameters including temperature, reactant gas compositions and flows, and pressure were explored. The structures of the coatings were characterized using electron microscopy and compositions were determined using x-ray diffraction. The optical properties of the boron carbide coatings were measured, and relationships between processing conditions, deposit morphology, and optical properties were determined

  13. The synthesis of titanium carbide-reinforced carbon nanofibers

    Science.gov (United States)

    Zhu, Pinwen; Hong, Youliang; Liu, Bingbing; Zou, Guangtian

    2009-06-01

    Tailoring hard materials into nanoscale building blocks can greatly extend the applications of hard materials and, at the same time, also represents a significant challenge in the field of nanoscale science. This work reports a novel process for the preparation of carbon-based one-dimensional hard nanomaterials. The titanium carbide-carbon composite nanofibers with an average diameter of 90 nm are prepared by an electrospinning technique and a high temperature pyrolysis process. A composite solution containing polyacrylonitrile and titanium sources is first electrospun into the composite nanofibers, which are subsequently pyrolyzed to produce the desired products. The x-ray diffraction pattern and transmission electron microscopy results show that the main phase of the as-synthesized nanofibers is titanium carbide. The Raman analyses show that the composite nanofibers have low graphite clusters in comparison with the pure carbon nanofibers originating from the electrospun polyacrylonitrile nanofibers. The mechanical property tests demonstrate that the titanium carbide-carbon nanofiber membranes have four times higher tensile strength than the carbon nanofiber membranes, and the Young's modulus of the titanium carbide-carbon nanofiber membranes increases in direct proportion to the titanium quantity.

  14. The synthesis of titanium carbide-reinforced carbon nanofibers

    International Nuclear Information System (INIS)

    Tailoring hard materials into nanoscale building blocks can greatly extend the applications of hard materials and, at the same time, also represents a significant challenge in the field of nanoscale science. This work reports a novel process for the preparation of carbon-based one-dimensional hard nanomaterials. The titanium carbide-carbon composite nanofibers with an average diameter of 90 nm are prepared by an electrospinning technique and a high temperature pyrolysis process. A composite solution containing polyacrylonitrile and titanium sources is first electrospun into the composite nanofibers, which are subsequently pyrolyzed to produce the desired products. The x-ray diffraction pattern and transmission electron microscopy results show that the main phase of the as-synthesized nanofibers is titanium carbide. The Raman analyses show that the composite nanofibers have low graphite clusters in comparison with the pure carbon nanofibers originating from the electrospun polyacrylonitrile nanofibers. The mechanical property tests demonstrate that the titanium carbide-carbon nanofiber membranes have four times higher tensile strength than the carbon nanofiber membranes, and the Young's modulus of the titanium carbide-carbon nanofiber membranes increases in direct proportion to the titanium quantity.

  15. 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.

  16. Multifunctional composites containing molybdenum carbides as potential electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Weigert, Erich C. [Center for Catalytic Science and Technology, Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716 (United States); South, Joseph [Army Research Laboratory, Building 4600, Aberdeen Proving Ground, MD 21005 (United States); Rykov, Sergey A.; Chen, Jingguang G. [Center for Catalytic Science and Technology, Department of Chemical Engineering, University of Delaware, Newark, DE 19716 (United States)

    2005-01-30

    The aim of the current study is to determine the feasibility of introducing fuel cell functionality on the surfaces of carbon-based composite materials. This can potentially be achieved by the synthesis of molybdenum carbides on the surfaces of carbon foam, which is a light and rigid material that can be used as structural components in aircrafts and vehicles. The current study employed physical vapor deposition (PVD) to deposit molybdenum on the carbon foam substrate. The ratio of surface molybdenum and surface carbon was determined using X-ray photoelectron spectroscopy (XPS). The combination of PVD and in situ XPS allowed for the synthesis of molybdenum-coated carbon foam samples with desirable and reproducible Mo/C ratios. The coated films were then heated in vacuum to promote the reaction between molybdenum and carbon foam to produce surface molybdenum carbides. The carbide-coated samples were further characterized using XPS, near-edge X-ray absorption fine structure (NEXAFS), and scanning electron microscopy (SEM). Platinum metal was also deposited via PVD on carbon foam, both with and without the presence of molybdenum carbide on the foam surface. The electrochemical stability of Pt-coated foams was evaluated using cyclic voltammetry (CV)

  17. Investigating important factors influencing electronic banking for export development

    OpenAIRE

    Vahid Abbas Zadeh; Gholamreza Heydari Kord Zangeneh; Naser Azad

    2014-01-01

    Export is one of the most important indicators of a growing economy and it is the primary source of reaching sustainable growth on the market. This paper presents an empirical study to determine important factors influencing electronic banking in export development of Iranian organizations. The proposed study designs a questionnaire and distributes it among some regular customers who do internet banking with Parsian bank in city of Tehran, Iran. Cronbach alpha is calculated as 0.82, which is ...

  18. 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.

  19. Radiation damage of transition metal carbides

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, G.

    1991-01-01

    In this grant period we have investigated electrical properties of transition metal carbides and radiation-induced defects produced by low-temperature electron irradiation in them. Special attention has been given to the composition VC[sub 0.88] in which the vacancies on the carbon sublattice of this fcc crystal order to produce a V[sub 8]C[sub 7] superlattice. The existence of this superlattice structure was found to make the crystal somewhat resistant to radiation damage at low doses and/or at ambient temperature. At larger doses significant changes in the resistivity are produced. Annealing effects were observed which we believe to be connected with the reconstitution of the superlattice structure.

  20. Neutron irradiation induced amorphization of silicon carbide

    International Nuclear Information System (INIS)

    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 x 1025 n/m2. 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 critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C

  1. Microwave hybrid synthesis of silicon carbide nanopowders

    International Nuclear Information System (INIS)

    Nanosized silicon carbide powders were synthesised from a mixture of silica gel and carbon through both the conventional and microwave heating methods. Reaction kinetics of SiC formation were found to exhibit notable differences for the samples heated in microwave field and furnace. In the conventional method SiC nanopowders can be synthesised after 105 min heating at 1500 deg. C in a coke-bed using an electrical tube furnace. Electron microscopy studies of these powders showed the existence of equiaxed SiC nanopowders with an average particle size of 8.2 nm. In the microwave heating process, SiC powders formed after 60 min; the powder consisted of a mixture of SiC nanopowders (with two average particle sizes of 13.6 and 58.2 nm) and particles in the shape of long strands (with an average diameter of 330 nm)

  2. Preparation of Silicon Carbide with High Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to prepare silicon carbide with high properties, three kinds of SiC powders A, B, and C with different composition and two kinds of additives, which were Y2O3-Al2O3 system and Y2O3-La2O3 system, were used in this experiment. The properties of hot-pressed SiC ceramics were measured. With the same additives, different SiC powder resulted in different properties. On the other hand, with the same SiC powder, increasing the amount of the additive Y2O3-Al2O3 improved properties of SiC ceramics at room temperature, and increasing the amount of the additive Y2O3-La2O3 improved property SiC ceramics at elevated temperature. In addition, the microstructure of SiC ceramics was studied by scanning electron microscopy.

  3. 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

  4. Formation and characterization of titanium nitride and titanium carbide films prepared by reactive sputtering

    International Nuclear Information System (INIS)

    Titanium has been reactively r.f. sputtered in mixed Ar-N2 and Ar-CH4 discharges on to substrates held at 775 K. The films obtained have been characterized by scanning electron microscopy, X-ray diffraction and by measurements of hardness and electrical resistivity. The compositions of the films have been determined using Auger electron spectroscopy. The processes occurring both on substrates and target surfaces have been studied and it is shown that the latter is of great importance for the composition and structure of deposited films. Titanium nitride films of full density and with electrical resistivity and hardness values close to those of bulk TiN were only obtained in a narrow range close to the stoichiometric composition. Titanium carbide films grown on non-biased substrates were found to have an open structure and thus a low density. A bias applied to the substrate, however, improved the quality of the films. It is also shown that the heat of formation of the compounds plays an important role in the formation of carbides and nitrides. A large value promotes the development of large grains and dense structures. (Auth.)

  5. Simulation in Amorphous Silicon and Amorphous Silicon Carbide Pin Diodes

    OpenAIRE

    Gonçalves, Dora; Fernandes, Miguel; Louro, Paula; Fantoni, Alessandro; Vieira, Manuela

    2014-01-01

    Part 21: Electronics: Devices International audience Photodiodes are devices used as image sensors, reactive to polychromatic light and subsequently color detecting, and they are also used in optical communication applications. To improve these devices performance it is essential to study and control their characteristics, in fact their capacitance and spectral and transient responses. This study considers two types of diodes, an amorphous silicon pin and an amorphous silicon carbide pi...

  6. Development of mobile electron beam plant for environmental applications

    Science.gov (United States)

    Han, Bumsoo; Kim, Jinkyu; Kang, Wongu; Choi, Jang Seung; Jeong, Kwang-Young

    2016-07-01

    Due to the necessity of pilot scale test facility for continuous treatment of wastewater and gases on site, a mobile electron beam irradiation system mounted on a trailer has developed. This mobile electron beam irradiation system is designed for the individual field application with self-shielded structure of steel plate and lead block which will satisfy the required safety figures of International Commission on Radiological Protection (ICRP). Shielding of a mobile electron accelerator of 0.7 MeV, 30 mA has been designed and examined by Monte Carlo technique. Based on a 3-D model of electron accelerator shielding which is designed with steel and lead shield, radiation leakage was examined using the Monte Carlo N-Particle Transport (MCNP) Code. Simulations with two different versions (version 4c2 and version 5) of MCNP code showed agreements within statistical uncertainties, and the highest leakage expected is 5.5061×10-01 (1±0.0454) μSv/h, which is far below the tolerable radiation dose limit for occupational workers. This unit could treat up to 500 m3 of liquid waste per day at 2 kGy or 10,000 N m3 of gases per hour at 15 kGy.

  7. Ultrasonic characterization of microwave joined silicon carbide/silicon carbide

    International Nuclear Information System (INIS)

    High frequency (50--150 MHz), ultrasonic immersion testing has been used to characterize the surface and interfacial joint conditions of microwave bonded, monolithic silicon carbide (SiC) materials. The high resolution ultrasonic C-scan images point to damage accumulation after thermal cycling. Image processing was used to study the effects of the thermal cycling on waveform shape, amplitude and distribution. Such information is useful for concurrently engineering material fabrication processes and suitable nondestructive test procedures

  8. Preparation and application of cellular and nanoporous carbides.

    Science.gov (United States)

    Borchardt, Lars; Hoffmann, Claudia; Oschatz, Martin; Mammitzsch, Lars; Petasch, Uwe; Herrmann, Mathias; Kaskel, Stefan

    2012-08-01

    A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review. PMID:22344324

  9. Design and development of pulsed electron beam accelerator 'AMBICA - 600'

    Science.gov (United States)

    Verma, Rishi; Deb, Pankaj; Shukla, Rohit; Sharma, Surender; Shyam, Anurag

    2012-11-01

    Short duration, high power pulses with fast rise time and good flat-top are essentially required for driving pulsed electron beam diodes. To attain this objective, a dual resonant Tesla transformer based pulsed power accelerator 'AMBICA-600' has been developed. In this newly developed system, a coaxial water line is charged through single turn Tesla transformer that operates in the dual resonant mode. For making the accelerator compact, in the high power pulse forming line, water has been used as dielectric medium because of its high dielectric constant, high dielectric strength and high energy density. The coaxial waterline can be pulsed charged up to 600kV, has impedance of ~5Ω and generates pulse width of ~60ns. The integrated system is capable of producing intense electron beam of 300keV, 60kA when connected to impedance matched vacuum diode. In this paper, system hardware details and experimental results of gigawatt electron beam generation have been presented.

  10. Development of an irradiation device for electron beam wastewater treatment

    International Nuclear Information System (INIS)

    When domestic or industrial effluents with synthetic compounds are disposed without an adequate treatment, they impact negatively the environment with damages to aquatic life and for the human being. Both population and use of goods and services that contribute for the hazardous waste are growing. Hazardous regulations are becoming more restrictive and technologies, which do not destroy these products, are becoming less acceptable. The electron beam radiation process is an advanced oxidation process, that produces highly reactive radicals resulting in mineralization of the contaminant. In this work was developed an irradiation system in order to optimize the interaction of electron beam delivered from the accelerator with the processed effluent. It is composed by an irradiation device where the effluent presents to the electron beam in an up flow stream and a process control unit that uses the calorimetric principle. The developed irradiation device has a different configuration from the devices used by others researchers that are working with this technology. It was studied the technical and economic feasibility, comparing with the literature the results of the irradiation device demonstrated that it has a superior performance, becoming an process for use in disinfection and degradation of hazardous organic compounds of wastewater from domestic and industrial origin, contributing as an alternative technology for Sanitary Engineering. (author)

  11. INTERNET USAGE AND ELECTRONIC BUSINESS DEVELOPMENT IN KOSOVA

    Directory of Open Access Journals (Sweden)

    Mihane Berisha Namani

    2008-10-01

    Full Text Available Worldwide, more and more companies are using the Internet as a medium for the development of business through electronic means. Internet usage has changed the business process in many companies, whereas electronic business has been accepted as a new form for the realization of digital business transactions, without use of hard copy documents and direct contacts in the business process. While the economies of western countries have started to utilize new forms of business through the Internet, in Kosovo we have just started to talk about electronic business, and neither have the advantages of B2C business been yet discovered. New technologies and the increase of their usage, especially the Internet, have changed the traditional business manner and enabled the overcoming of time and space limitations in communications and business development, and have increased the efficiency of the business system work, creating new business forms and models, which meet the needs, desires and requests of the consumers. Firstly, such a paper aims to emphasize the opportunities of Internet usage for business purposes in Kosovo, and the need to raise the awareness amongst the business community so that they accept such new model of digital business if they intend to be competitive in the market.

  12. Carbide characterization in a Nb-microalloyed advanced ultrahigh strength steel after quenching-partitioning-tempering process

    International Nuclear Information System (INIS)

    Based on the observations of scanning electron microscopy and transmission electron microscopy, four kinds of carbides were identified in a Nb-microalloyed steel after quenching-partitioning-tempering treatment. In addition to transitional epsilon carbide that usually forms in silicon-free carbon steel, other three types of niobium carbides (NbC) formed at various treatment stages respectively. They are incoherent NbC inclusion that nucleated at solidification mainly, fine NbC that nucleated in lath martensite at tempering stage and regular polygonal NbC that nucleated in austenite before quenching. Their formation mechanisms on steel were discussed briefly based on thermodynamics.

  13. Existence and structure of rare-earth mono-carbides: study of their low-temperature magnetic properties

    International Nuclear Information System (INIS)

    There are two types of rare earth carbides, the first one is face-centered cubic, stable at high temperature, and very hypo-stoichiometric (formula MCx with 0.35 2C. These two carbides are magnetically ordered at low temperatures (ferro or ferri-magnetism). They are highly anisotropic. A great part of the electric and magnetic properties can be explained from the following ideas: the M3+ ions are coupled via the conduction electrons, there are more conduction electrons in the carbides than in the metals, and there is some local order around the transition temperatures. (author)

  14. Electronic Unit Pump Test Bench Development and Pump Properties Research

    Institute of Scientific and Technical Information of China (English)

    LIU Bo-lan; HUANG Ying; ZHANG Fu-jun; ZHAO Chang-lu

    2006-01-01

    A unit pump test bench is developed on an in-line pump test platform. The bench is composed of pump adapting assembly, fuel supply subsystem, lubricating subsystem and a control unit. A crank angle domain injection control method is given out and the control accuracy can be 0.1° crank degree. The bench can test bot h mechanical unit pump and electronic unit pump. A test model-PLD12 electronic unit pump is tested. Full pump delivery map and some influence factors test is d one. Experimental results show that the injection quantity is linear with the de livery angle. The quantity change rate is 15% when fuel temperature increases 30℃. The delivery quantity per cycle increases 30mg at 28V drive voltage. T he average delivery difference for two same type pumps is 5%. Test results show that the bench can be used for unit pump verification.

  15. New developments for high power electron beam equipment

    International Nuclear Information System (INIS)

    High power electron guns for industrial use work in the range of power of more than 10 kW up to 1200 kW. The only suitable principle for this purpose is that used in axial guns. Elements necessary for these EB guns and their design are described. The outstanding properties required for applications in production and R ampersand D can only be achieved if the equipment is supplemented by a high voltage supply, beam guidance supply, vacuum generator and the various devices for observation, measurement and control. Standard rules for both the technical demands in application and dimensioning of some of the necessary components are explained. Special developments, such as high speed deflection, observation by BSE-camera and arc-free electron beam systems are also presented

  16. Research and Development of Electronic and Optoelectronic Materials in China

    Institute of Scientific and Technical Information of China (English)

    王占国

    2000-01-01

    A review on the research and development of electronic and optoelectronic materials in China, including the main scientific activities in this field, is presented. The state-of-the-arts and prospects of the electronic and optoelectronic materials in China are briefly introduced, such as those of silicon crystals, compound semiconductors, synthetic crystals, especially nonlinear optical crystals and rare-earth permanent magnets materials, etc. , with a greater emphasis on Chinese scientist's contributions to the frontier area of nanomaterials and nanostructures in the past few years. A new concept of the trip chemistry proposed by Dr. Liu Zhongfan from Peking University has also been described. Finally the possible research grants and the national policy to support the scientific research have been discussed.

  17. Development of a Francium Electron Electric Dipole Moment Experiment

    Science.gov (United States)

    Munger, Charles T., Jr.; Feinberg, B.; Gould, Harvey; Kalnins, Juris; Nishimura, Hiroshi; Jentschura, Ulrich; Behr, John; Pearson, Matt

    2014-09-01

    An experiment to discover or rule out a permanent electric dipole moment (EDM) of the electron, at a sensitivity well beyond the present experimental limit, is being developed. The experiment will use 211Fr, obtainable online at TRIUMF at rates of 109/s, in a laser-cooled fountain. The experiment is done in free space and free fall, with an electric field, but no applied magnetic field, between optical state preparation and analysis. The relation between an electron EDM and an EDM of a francium atom has recently been recalculated using field theory alone (Blundell, Griffith & Sapirstein, Phys. Rev. D 86, 025023 [2012]), confirming previous atomic physics calculations and removing any ambiguity in the experimental interpretation.

  18. Laser micromachining of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Sciti, D.; Bellosi, A. [CNR-IRTEC, Faenza (Italy). Research Inst. for Ceramics Technology

    2002-07-01

    Two different laser processing procedures on silicon carbide are studied: i) surface treatment through a pulsed KrF excimer laser, with the aim of evaluating the surface microstructure modifications and variation the surface roughness in function of the processing parameters. In all the cases, the presence of a thin scale due to melting and solidification, crack formation and surface pores closure were observed. ii) A pulsed CO{sub 2} laser was used to form a micro-holes texture on the surface of silicon carbide. Holes dimensions in the range 80-100 {mu}m were obtained using a laser power of 0.5 kW and pulse duration of 1 ms. The possibility of producing a regular array of microholes was demonstrated. (orig.)

  19. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    L M Manocha; E Yasuda; Y Tanabe; S Manocha; D Vashistha

    2000-02-01

    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 has been used to prepare silicon based glasses, especially oxycarbides through organic–inorganic hybrid gels by hydrolysis–condensation reactions in silicon alkoxides, 1,4-butanediol and furfuryl alcohol with an aim to introduce Si–C linkages in the precursors at sol level. The incorporation of these linkages has been studied using IR and NMR spectroscopy. These bonds, so introduced, are maintained throughout the processing, especially during pyrolysis to high temperatures. In FFA–TEOS system, copolymerization with optimized mol ratio of the two results in resinous mass. This precursor on pyrolysis to 1000°C results in Si–O–C type amorphous solid black mass. XRD studies on the materials heated to 1400°C exhibit presence of crystalline Si–C and cristobalites in amorphous Si–O–C mass. In organic–inorganic gel system, the pyrolysed mass exhibits phase stability up to much higher temperatures. The carbidic materials so produced have been found to exhibit good resistance against oxidation at 1000°C.

  20. 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.

  1. Thermally Sprayed Silicon Carbide Coating

    OpenAIRE

    Mubarok, Fahmi

    2014-01-01

    Thermal spraying of silicon carbide (SiC) material is a challenging task since SiC tends to decompose during elevated temperature atmospheric spraying process. The addition of metal or ceramic binders as a matrix phase is necessary to facilitate the bonding of SiC particles, allowing SiC coatings to be deposited. In the conventional procedure, the matrix phase is added through mechanical mixing or mechanical alloying of the powder constituents, making it difficult to achieve homogeneous distr...

  2. Conduction mechanism in boron carbide

    Science.gov (United States)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  3. Sintering behavior of boron carbide

    International Nuclear Information System (INIS)

    Pressureless sintering behavior of boron carbide (B4C) in argon was studied, with change in time and temperature, using carbon as sintering aid. Carbon was added via fenolic resin, acting also as a binder. After isostatic pressing the specimens were sintered in a graphite furnace at 19600C/1h, 21600C/15 minutes and 1h and 22000C/1h. The achieved density was 97% of the theoretical. Some mechanical properties and microstructural aspects have been evaluated. (author)

  4. Raman and FTIR Studies of Silicon Carbide Surface Damage from Palladium Implantation in Presence of Hydrogen

    Science.gov (United States)

    Muntele, I.; Ila, D.; Muntele, C. J.; Poker, D. B.; Hensley, D. K.; Larkin, David (Technical Monitor)

    2001-01-01

    The ion implantation in a crystal such as silicon carbide will cause both damage in the ion track and in the substrate at the end of the ion track. We used both keV, and MeV Pd ions in fabricating electronic chemical sensors in silicon carbide, which can operate at elevated temperatures. In order to study the feasibility of fabricating an optical chemical sensor (litmus sensor), we need to understand the optical behavior of the embedded damage in the presence of hydrogen, as well as the potential chemical interaction of silicon carbide broken lattice bonds with the hydrogen dissociated from gas by palladium. Implanted samples of silicon carbide were studied using both Raman spectroscopy and FTIR (Fourier Transform-Infrared). The results of this work will be presented during the meeting.

  5. Formation of carbon nanostructures containing single-crystalline cobalt carbides by ion irradiation method

    Science.gov (United States)

    Wang, Zhipeng; Yusop, Zamri; Ghosh, Pradip; Hayashi, Yasuhiko; Tanemura, Masaki

    2011-02-01

    Carbon nanofibers (CNFs) with a diameter of 17 nm, and carbon nanoneedles (CNNs) with sharp tips have been synthesized on graphite substrates by ion irradiation of argon ions with the Co supplies rate of 1 and 3.4 nm/min, respectively. Energy dispersive X-ray spectrometry, combined with selected area electron diffraction patterns has been used to identify the chemical composition and crystallinity of these carbon nanostructures. The CNFs were found to be amorphous in nature, while the structures of the CNNs consisted of cubic CoCx, orthorhombic Co2C and Co3C depending on the cobalt content in the CNNs. The diameter of the carbide crystals was almost as large as the diameter of the CNN. Compared to the ion-induced nickel carbides and iron carbides, the formation of single-crystalline cobalt carbides might be due to the high temperature produced by the irradiation.

  6. Formation of carbon nanostructures containing single-crystalline cobalt carbides by ion irradiation method

    International Nuclear Information System (INIS)

    Carbon nanofibers (CNFs) with a diameter of 17 nm, and carbon nanoneedles (CNNs) with sharp tips have been synthesized on graphite substrates by ion irradiation of argon ions with the Co supplies rate of 1 and 3.4 nm/min, respectively. Energy dispersive X-ray spectrometry, combined with selected area electron diffraction patterns has been used to identify the chemical composition and crystallinity of these carbon nanostructures. The CNFs were found to be amorphous in nature, while the structures of the CNNs consisted of cubic CoCx, orthorhombic Co2C and Co3C depending on the cobalt content in the CNNs. The diameter of the carbide crystals was almost as large as the diameter of the CNN. Compared to the ion-induced nickel carbides and iron carbides, the formation of single-crystalline cobalt carbides might be due to the high temperature produced by the irradiation.

  7. Microwave sintering of boron carbide composites

    International Nuclear Information System (INIS)

    Boron carbide is an important ceramic material because of its high hardness and low specific gravity. it is used for applications involving impact and wear resistance. The disadvantages of boron carbide materials are difficulty in fabrication and sensitivity to brittle fracture. These problems are significantly reduced by production of cermets based on boron carbide and aluminum or aluminum alloys. Microwave heating of boron carbide materials results in ultrarapid heating and high temperatures. Therefore, a finer microstructure is obtained. The objective of this work was to define a technology that would allow the manufacture of boron carbide ceramics having mechanical properties similar to those exhibited by hot-pressed specimens. microwave heating would be used for the densification step. Mixtures of boron carbide and aluminum were considered for this research because aluminum simultaneously acts as a sintering aid and introduces phases that contribute to toughness enhancement

  8. Method to manufacture tungsten carbide

    International Nuclear Information System (INIS)

    The patent deals with an improved method of manufacturing tungsten carbide. An oxide is preferably used as initial product whose particle size and effective surface approximately corresponds to that of the endproduct. The known methods for preparing the oxide are briefly given. Carbon monoxide is passed over the thus obtained oxide particles whereby the reaction mixture is heated to a temperature at which tungsten oxide and carbon monoxide react and tungsten carbide is formed, however, below that temperature at which the tungsten-containing materials are caked or sintered together. According to the method the reaction temperature is about below 9000C. The tungsten carbide produced has a particle size of under approximately 100 A and an active surface of about 20 m2/g. It has sofar not been possible with the usual methods to obtain such finely divided material with such a large surface. These particles may be converted back to the oxide by heating in air at low temperature without changing particle size and effective surface. One thus obtains a tungsten oxide with smaller particle size and larger effective surface than the initial product. (IHOE)

  9. Advanced microstructure of boron carbide.

    Science.gov (United States)

    Werheit, Helmut; Shalamberidze, Sulkhan

    2012-09-26

    The rhombohedral elementary cell of the complex boron carbide structure is composed of B(12) or B(11)C icosahedra and CBC, CBB or B□B (□, vacancy) linear arrangements, whose shares vary depending on the actual chemical compound. The evaluation of the IR phonon spectra of isotopically pure boron carbide yields the quantitative concentrations of these components within the homogeneity range. The structure formula of B(4.3)C at the carbon-rich limit of the homogeneity range is (B(11)C) (CBC)(0.91) (B□B)(0.09) (□, vacancy); and the actual structure formula of B(13)C(2) is (B(12))(0.5)(B(11)C)(0.5)(CBC)(0.65)(CBB)(0.16) (B□B)(0.19), and deviates fundamentally from (B(12))CBC, predicted by theory to be the energetically most favourable structure of boron carbide. In reality, it is the most distorted structure in the homogeneity range. The spectra of (nat)B(x)C make it evident that boron isotopes are not randomly distributed in the structure. However, doping with 2% silicon brings about a random distribution. PMID:22945740

  10. Implementing electronic medical record systems in developing countries

    Directory of Open Access Journals (Sweden)

    Hamish Fraser

    2005-06-01

    Full Text Available The developing world faces a series of health crises including HIV/AIDS and tuberculosis that threaten the lives of millions of people. Lack of infrastructure and trained, experienced staff are considered important barriers to scaling up treatment for these diseases. In this paper we explain why information systems are important in many healthcare projects in the developing world. We discuss pilot projects demonstrating that such systems are possible and can expand to manage hundreds of thousands of patients. We also pass on the most important practical lessons in design and implementation from our experience in doing this work. Finally, we discuss the importance of collaboration between projects in the development of electronic medical record systems rather than reinventing systems in isolation, and the use of open standards and open source software.

  11. Silicon carbide as platform for energy applications

    OpenAIRE

    Syväjärvi, Mikael; Jokubavicius, Valdas; Sun, Jianwu; Liu, Xinyu; Løvvik, Ole Martin; Ou, Haiyan; Wellmann, Peter

    2015-01-01

    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 solar cells, and further pursue concepts in materials for thermoelectrics, biofuel cells and supercapacitor research proposals. In fact, there are a number of energy applications which can be based on...

  12. Crystallization of nodular cast iron with carbides

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2008-12-01

    Full Text Available In this paper a crystallization process of nodular cast iron with carbides having a different chemical composition have been presented. It have been found, that an increase of molybdenum above 0,30% causes the ledeburutic carbides crystallization after (γ+ graphite eutectic phase crystallization. When Mo content is lower, these carbides crystallize as a pre-eutectic phase. In this article causes of this effect have been given.

  13. Boron carbide nanolumps on carbon nanotubes

    Science.gov (United States)

    Lao, J. Y.; Li, W. Z.; Wen, J. G.; Ren, Z. F.

    2002-01-01

    Boron carbide nanolumps are formed on the surface of multiwall carbon nanotubes by a solid-state reaction between boron and carbon nanotubes. The reaction is localized so that the integrity of the structure of carbon nanotubes is maintained. Inner layers of multiwall carbon nanotubes are also bonded to boron carbide nanolumps. These multiwall carbon nanotubes with boron carbide nanolumps are expected to be the ideal reinforcing fillers for high-performance composites because of the favorable morphology.

  14. Development of an electronic system for signals amplification

    International Nuclear Information System (INIS)

    This paper presents the obtained results with a spectrometer for electromagnetic radiation whose detector, a Si PIN type diode, was directly coupled to a signal amplification system developed in this project for scientific initiation. The linearity conditions and the gain operational limits, constituted of two stages of amplification based on the employment of devices from AMTEK A225 and A206, were determined using a precision pulse generator. The obtained results shown that the developed system is stable and linear in the gain range of 50-150. The spectrometric response of the electronic system coupled to the Siemens SFH-00206 type diode, were studied in view of the register of the 59.5 keV gamma ray spectra proceeding from 241Am as function of the reversal polarization voltage. The influence pf the voltage and the electronic contribution in the energy resolution of the registered spectra under room temperature (22 degree Celsius) had also investigated considering the more adequate value of the coupling capacitance of the amplification system diode. Up to the present. the best energy resolution (FWHM = 4.85 keV) of the 59.5 keV line was obtained for the condition of the detector polarization at 16 V. This result proves that the signal amplification system developed coupled to the SFH00206 diode, besides the low cost, excellent operational condition for the detection and spectrometry or low energy electromagnetic radiation

  15. Development of superconducting RF electron gun in KEK

    International Nuclear Information System (INIS)

    A high-intensity electron gun is required for the next generation ERL or a high power FEL system. KEK started development of a superconducting RF electron gun in addition to the conventional DC electron gun. 1.3 GHz of the resonant frequency, 100 mA of the beam current, and 2 MeV of the energy in the exit of gun are made into the precondition. By combining electromagnetic field analysis and charged particle dynamics analysis, the optimal design of the cavity shape, where the maximum surface electric field of less than 50 MV/m, a low emittance of less than 1 mm mrad, and a low energy spread of less than 0.1% (2 keV)) can be filled with this precondition, was tried. The designed elliptical cavity is a 1.5-cell structure made of Nb material, and the three half cells are manufactured from one common die. Thermo-structural analysis under cryogenic temperature and vacuum environment was also carried out, and the resonance frequency change would be evaluated. (author)

  16. Developing a Records Management Programme in the Electronic Environment

    CERN Document Server

    Hare, Catherine

    2012-01-01

    A practical approach to developing and operating an effective programme to manage hybrid records within an organization. This title positions records management as an integral business function linked to the organization's business aims and objectives. The authors also address the records requirements of new and significant pieces of legislation, such as data protection and freedom of information, as well as exploring strategies for managing electronic records. Bullet points, checklists and examples assist the reader throughout, making this a one-stop resource for information in this area.

  17. Electrothermal gas generator: Development and qualification of the control electronics

    Science.gov (United States)

    Matthaeus, G.; Schmitz, H. D.

    1986-07-01

    The development and qualification of an electronic control circuitry for an electrothermal or catalytic hydrazine gas generator system is described. The circuitry, named manual override, controls the gas pressure in a tank using a pressure transducer and the gas generator to keep the pressure constant within narrow tolerances. The present pressure can be varied by ground command, enabling a variable thrust of the gas fed cold gas thrusters. The automatic loop can be switched off and the tank pressure be controlled by ground command. Two manual overrides SN01 and SN02 were qualified.

  18. Shock-wave strength properties of boron carbide and silicon carbide

    International Nuclear Information System (INIS)

    Time-resolved velocity interferometry measurements have been made on boron carbide and silicon carbide ceramics to assess dynamic equation-of-state and strength properties of these materials. Hugoniot precursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides. (orig.)

  19. Solid oxide membrane-assisted controllable electrolytic fabrication of metal carbides in molten salt.

    Science.gov (United States)

    Zou, Xingli; Zheng, Kai; Lu, Xionggang; Xu, Qian; Zhou, Zhongfu

    2016-08-15

    Silicon carbide (SiC), titanium carbide (TiC), zirconium carbide (ZrC), and tantalum carbide (TaC) have been electrochemically produced directly from their corresponding stoichiometric metal oxides/carbon (MOx/C) precursors by electrodeoxidation in molten calcium chloride (CaCl2). An assembled yttria stabilized zirconia solid oxide membrane (SOM)-based anode was employed to control the electrodeoxidation process. The SOM-assisted controllable electrochemical process was carried out in molten CaCl2 at 1000 °C with a potential of 3.5 to 4.0 V. The reaction mechanism of the electrochemical production process and the characteristics of these produced metal carbides (MCs) were systematically investigated. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses clearly identify that SiC, TiC, ZrC, and TaC carbides can be facilely fabricated. SiC carbide can be controlled to form a homogeneous nanowire structure, while the morphologies of TiC, ZrC, and TaC carbides exhibit porous nodular structures with micro/nanoscale particles. The complex chemical/electrochemical reaction processes including the compounding, electrodeoxidation, dissolution-electrodeposition, and in situ carbonization processes in molten CaCl2 are also discussed. The present results preliminarily demonstrate that the molten salt-based SOM-assisted electrodeoxidation process has the potential to be used for the facile and controllable electrodeoxidation of MOx/C precursors to micro/nanostructured MCs, which can potentially be used for various applications. PMID:27195950

  20. Silicon Carbide Lightweight Optics With Hybrid Skins for Large Cryo Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Optical Physics Company (OPC) has developed new silicon carbide (SiC) foam-based optics with hybrid skins that are composite, athermal and lightweight (FOCAL) that...

  1. 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...

  2. 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...

  3. The First JFET-Based Silicon Carbide Active Pixel Sensor UV Imager Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Solar-blind ultraviolet (UV) imaging is needed in the fields of astronomy, national defense, and bio-chemistry. United Silicon Carbide, Inc. proposes to develop a...

  4. Methods for producing silicon carbide fibers

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. SOLID SOLUTION CARBIDES ARE THE KEY FUELS FOR FUTURE NUCLEAR THERMAL PROPULSION

    Science.gov (United States)

    Panda, Binayak; Hickman, Robert R.; Shah, Sandeep

    2005-01-01

    Nuclear thermal propulsion uses nuclear energy to directly heat a propellant (such as liquid hydrogen) to generate thrust for space transportation. In the 1960 s, the early Rover/Nuclear Engine for Rocket Propulsion Application (NERVA) program showed very encouraging test results for space nuclear propulsion but, in recent years, fuel research has been dismal. With NASA s renewed interest in long-term space exploration, fuel researchers are now revisiting the RoverMERVA findings, which indicated several problems with such fuels (such as erosion, chemical reaction of the fuel with propellant, fuel cracking, and cladding issues) that must be addressed. It is also well known that the higher the temperature reached by a propellant, the larger the thrust generated from the same weight of propellant. Better use of fuel and propellant requires development of fuels capable of reaching very high temperatures. Carbides have the highest melting points of any known material. Efforts are underway to develop carbide mixtures and solid solutions that contain uranium carbide, in order to achieve very high fuel temperatures. Binary solid solution carbides (U, Zr)C have proven to be very effective in this regard. Ternary carbides such as (U, Zr, X) carbides (where X represents Nb, Ta, W, and Hf) also hold great promise as fuel material, since the carbide mixtures in solid solution generate a very hard and tough compact material. This paper highlights past experience with early fuel materials and bi-carbides, technical problems associated with consolidation of the ingredients, and current techniques being developed to consolidate ternary carbides as fuel materials.

  6. The effects of annealing temperature and cooling rate on carbide precipitation behavior in H13 hot-work tool steel

    International Nuclear Information System (INIS)

    Highlights: • Unexpected Mo carbides formed during slow cooling from low annealing temperatures. • Mo carbides formed during the migration of Mo for a transition of Cr-rich carbide. • Mo carbides were precipitated at the boundaries of M7C3 carbides and ferrite grains. • Annealing conditions for the precipitation of Mo carbides were discussed. - Abstract: The precipitation behavior of H13 hot-work tool steel was investigated as a function of both annealing temperature and cooling rate through thermodynamic calculations and microstructural analyses using transmission and scanning electron microscope and a dilatometer. The V-rich MC carbide and Cr-rich M7C3 and M23C6 carbides were observed in all annealed specimens regardless of annealing and cooling conditions, as expected from an equilibrium phase diagram of the steel used. However, Mo-rich M2C and M6C carbides were unexpectedly precipitated at a temperature between 675 °C and 700 °C during slow cooling at a rate of below 0.01 °C/s from the annealing temperatures of 830 °C and below. The solubility of Mo in both M7C3 and ferrite reduces with decreasing temperature during cooling. Mo atoms diffuse out of both M7C3 and ferrite, and accumulate locally at the interface between M7C3 and ferrite. Mo carbides were form at the interface of M7C3 carbides during the transition of Cr-rich M7C3 to stable M23C6

  7. The effects of annealing temperature and cooling rate on carbide precipitation behavior in H13 hot-work tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Minwoo, E-mail: aonia@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Park, Gyujin, E-mail: nanum01@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Jung, Jae-Gil, E-mail: jgjung@kims.re.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Light Metal Division, Korea Institute of Materials Science, Changwon 642-831 (Korea, Republic of); Kim, Byung-Hoon, E-mail: byung-hoon.kim@doosan.com [Doosan Heavy Industries & Construction, Changwon, Gyeongnam 642-792 (Korea, Republic of); Lee, Young-Kook, E-mail: yklee@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2015-04-05

    Highlights: • Unexpected Mo carbides formed during slow cooling from low annealing temperatures. • Mo carbides formed during the migration of Mo for a transition of Cr-rich carbide. • Mo carbides were precipitated at the boundaries of M{sub 7}C{sub 3} carbides and ferrite grains. • Annealing conditions for the precipitation of Mo carbides were discussed. - Abstract: The precipitation behavior of H13 hot-work tool steel was investigated as a function of both annealing temperature and cooling rate through thermodynamic calculations and microstructural analyses using transmission and scanning electron microscope and a dilatometer. The V-rich MC carbide and Cr-rich M{sub 7}C{sub 3} and M{sub 23}C{sub 6} carbides were observed in all annealed specimens regardless of annealing and cooling conditions, as expected from an equilibrium phase diagram of the steel used. However, Mo-rich M{sub 2}C and M{sub 6}C carbides were unexpectedly precipitated at a temperature between 675 °C and 700 °C during slow cooling at a rate of below 0.01 °C/s from the annealing temperatures of 830 °C and below. The solubility of Mo in both M{sub 7}C{sub 3} and ferrite reduces with decreasing temperature during cooling. Mo atoms diffuse out of both M{sub 7}C{sub 3} and ferrite, and accumulate locally at the interface between M{sub 7}C{sub 3} and ferrite. Mo carbides were form at the interface of M{sub 7}C{sub 3} carbides during the transition of Cr-rich M{sub 7}C{sub 3} to stable M{sub 23}C{sub 6}.

  8. Observation of 'hidden' planar defects in boron carbide nanowires and identification of their orientations.

    Science.gov (United States)

    Guan, Zhe; Cao, Baobao; Yang, Yang; Jiang, Youfei; Li, Deyu; Xu, Terry T

    2014-01-01

    The physical properties of nanostructures strongly depend on their structures, and planar defects in particular could significantly affect the behavior of the nanowires. In this work, planar defects (twins or stacking faults) in boron carbide nanowires are extensively studied by transmission electron microscopy (TEM). Results show that these defects can easily be invisible, i.e., no presence of characteristic defect features like modulated contrast in high-resolution TEM images and streaks in diffraction patterns. The simplified reason of this invisibility is that the viewing direction during TEM examination is not parallel to the (001)-type planar defects. Due to the unique rhombohedral structure of boron carbide, planar defects are only distinctive when the viewing direction is along the axial or short diagonal directions ([100], [010], or 1¯10) within the (001) plane (in-zone condition). However, in most cases, these three characteristic directions are not parallel to the viewing direction when boron carbide nanowires are randomly dispersed on TEM grids. To identify fault orientations (transverse faults or axial faults) of those nanowires whose planar defects are not revealed by TEM, a new approach is developed based on the geometrical analysis between the projected preferred growth direction of a nanowire and specific diffraction spots from diffraction patterns recorded along the axial or short diagonal directions out of the (001) plane (off-zone condition). The approach greatly alleviates tedious TEM examination of the nanowire and helps to establish the reliable structure-property relations. Our study calls attention to researchers to be extremely careful when studying nanowires with potential planar defects by TEM. Understanding the true nature of planar defects is essential in tuning the properties of these nanostructures through manipulating their structures. PMID:24423258

  9. Predicting Two-Dimensional Silicon Carbide Monolayers.

    Science.gov (United States)

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics. PMID:26394207

  10. 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.

  11. Power Electronics Development for the SPT-100 Thruster

    Science.gov (United States)

    Hamley, John A.; Hill, Gerald M.; Sankovic, John M.

    1994-01-01

    Russian electric propulsion technologies have recently become available on the world market. Of significant interest is the Stationary Plasma Thruster (SPT) which has a significant flight heritage in the former Soviet space program. The SPT has performance levels of up to 1600 seconds of specific impulse at a thrust efficiency of 0.50. Studies have shown that this level of performance is well suited for stationkeeping applications, and the SPT-100, with a 1.35 kW input power level, is presently being evaluated for use on Western commercial satellites. Under a program sponsored by the Innovative Science and Technology Division of the Ballistic Missile Defense Organization, a team of U.S. electric propulsion specialists observed the operation of the SPT-100 in Russia. Under this same program, power electronics were developed to operate the SPT-100 to characterize thruster performance and operation in the U.S. The power electronics consisted of a discharge, cathode heater, and pulse igniter power supplies to operate the thruster with manual flow control. A Russian designed matching network was incorporated in the discharge supply to ensure proper operation with the thruster. The cathode heater power supply and igniter were derived from ongoing development projects. No attempts were made to augment thruster electromagnet current in this effort. The power electronics successfully started and operated the SPT-100 thruster in performance tests at NASA Lewis, with minimal oscillations in the discharge current. The efficiency of the main discharge supply was measured at 0.92, and straightforward modifications were identified which could increase the efficiency to 0.94.

  12. Properties of boron-carbide based nanotubular structures

    International Nuclear Information System (INIS)

    Full text: One of the most important areas of search for a new generation of superconductors is amongst layered A1B2-type systems. One such structure, LiBC, which is isovalent with, and structurally similar to, the superconductor MgB2, has recently attracted attention due to the nature of its electronic structure. It was found by Rosner et al., that the character of the Fermi surface of hole-doped LiBC is very similar to the features which lead to superconductivity in MgB2 at TC ∼ 40 K. Exploration of the novel properties of tubular analogues of layered and crystalline structures is another promising trend in the search for novel superconductors. Carbon nanotubes, for example, have been found tp have a superconducting transition temperature, TC, of approximately 0.55 K. A number of interesting attempts to model the properties of hypothetical nanotubular modifications of layered A1B2 and A1B2 - type ternary suicides have also been performed recently. We have proposed a new class of charged Boron-Carbide nanotubes (BC(-)) which correspond to a charged backbone structure for the hypothetical LiBC nanotubes. In the present work we discuss the energetics and electronic structure of these charged Boron-Carbide nanotubes, and the effects of hole-doping of these structures. We also present some preliminary results of calculations of the vibrational properties of charged and hole-doped Boron-Carbide nanotubes

  13. A Blue Print for the Future Electronic Warfare Suite Development

    Directory of Open Access Journals (Sweden)

    R. Pitchammal

    2013-03-01

    Full Text Available Mastering increasing complexity of electronic warfare (EW airborne equipment systems needs new architectural concepts mainly based on modular design, generic resources and reliable communication buses. Less is more architectural concept replaces separate EW line replaceable units with fewer centralized processing units. This approach leads to a robust architecture for the next generation EW suite development in a unified fashion and thereby promising significant weight reduction and maintenance savings. In general, this approach is represented by a blanket term called integrated modular avionics (IMA. IMA architecture based EW suite development concentrates with the main goals of IMA such as technology transparency, resource sharing, incremental qualification, reduced maintenance cost, and so on.Defence Science Journal, 2013, 63(2, pp.192-197, DOI:http://dx.doi.org/10.14429/dsj.63.4263

  14. Open source cardiology electronic health record development for DIGICARDIAC implementation

    Science.gov (United States)

    Dugarte, Nelson; Medina, Rubén.; Huiracocha, Lourdes; Rojas, Rubén.

    2015-12-01

    This article presents the development of a Cardiology Electronic Health Record (CEHR) system. Software consists of a structured algorithm designed under Health Level-7 (HL7) international standards. Novelty of the system is the integration of high resolution ECG (HRECG) signal acquisition and processing tools, patient information management tools and telecardiology tools. Acquisition tools are for management and control of the DIGICARDIAC electrocardiograph functions. Processing tools allow management of HRECG signal analysis searching for indicative patterns of cardiovascular pathologies. Telecardiology tools incorporation allows system communication with other health care centers decreasing access time to the patient information. CEHR system was completely developed using open source software. Preliminary results of process validation showed the system efficiency.

  15. Boron carbide (B4C) coating. Deposition and testing

    International Nuclear Information System (INIS)

    Boron carbide was proposed as a material of in-situ protecting coating for tungsten tiles of ITER divertor. To prove this concept the project including investigation of regimes of plasma deposition of B4C coating on tungsten and tests of boron carbide layer in ITER-like is started recently. The paper contends the first results of the project. The results of B4C coating irradiation by the plasma pulses of QSPU-T plasma accelerator are presented. The new device capable of B4C film deposition on tungsten and testing of the films and materials with ITER-like heat loads and ion- and electron irradiation is described. The results of B4C coating deposition and testing of both tungsten substrate and coating are shown and discussed

  16. Diffusion Bonding of Silicon Carbide for MEMS-LDI Applications

    Science.gov (United States)

    Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, J. Douglas

    2007-01-01

    A robust joining approach is critically needed for a Micro-Electro-Mechanical Systems-Lean Direct Injector (MEMS-LDI) application which requires leak free joints with high temperature mechanical capability. Diffusion bonding is well suited for the MEMS-LDI application. Diffusion bonds were fabricated using titanium interlayers between silicon carbide substrates during hot pressing. The interlayers consisted of either alloyed titanium foil or physically vapor deposited (PVD) titanium coatings. Microscopy shows that well adhered, crack free diffusion bonds are formed under optimal conditions. Under less than optimal conditions, microcracks are present in the bond layer due to the formation of intermetallic phases. Electron microprobe analysis was used to identify the reaction formed phases in the diffusion bond. Various compatibility issues among the phases in the interlayer and substrate are discussed. Also, the effects of temperature, pressure, time, silicon carbide substrate type, and type of titanium interlayer and thickness on the microstructure and composition of joints are discussed.

  17. Thermal boundary conductance between refractory metal carbides and diamond

    International Nuclear Information System (INIS)

    The thermal boundary conductance (TBC) between thin films of Cr, Mo, Nb and W and diamond substrates has been measured using time domain thermoreflectance before and after a high-vacuum heat treatment at 800 °C for 2 h. While no signs of carbide formation could be detected in as-deposited layers by scanning transmission electron microscopy energy dispersive X-ray spectroscopy elemental analysis, the heat treatment led to partial (W, Mo) or full conversion (Cr, Nb) of the film into carbide. The measured TBC values on as-deposited samples of 315, 220, 220 and 205 MW m-2K-1 measured for, respectively, the Cr, Mo, Nb and W samples, were found to not be significantly altered by the heat treatment

  18. Amorphous silicon carbide coatings for extreme ultraviolet optics

    Science.gov (United States)

    Kortright, J. B.; Windt, David L.

    1988-01-01

    Amorphous silicon carbide films formed by sputtering techniques are shown to have high reflectance in the extreme ultraviolet spectral region. X-ray scattering verifies that the atomic arrangements in these films are amorphous, while Auger electron spectroscopy and Rutherford backscattering spectroscopy show that the films have composition close to stoichiometric SiC, although slightly C-rich, with low impurity levels. Reflectance vs incidence angle measurements from 24 to 1216 A were used to derive optical constants of this material, which are presented here. Additionally, the measured extreme ultraviolet efficiency of a diffraction grating overcoated with sputtered amorphous silicon carbide is presented, demonstrating the feasibility of using these films as coatings for EUV optics.

  19. Boron carbide (B4C) coating. Deposition and testing

    Science.gov (United States)

    Azizov, E.; Barsuk, V.; Begrambekov, L.; Buzhinsky, O.; Evsin, A.; Gordeev, A.; Grunin, A.; Klimov, N.; Kurnaev, V.; Mazul, I.; Otroshchenko, V.; Putric, A.; Sadovskiy, Ya.; Shigin, P.; Vergazov, S.; Zakharov, A.

    2015-08-01

    Boron carbide was proposed as a material of in-situ protecting coating for tungsten tiles of ITER divertor. To prove this concept the project including investigation of regimes of plasma deposition of B4C coating on tungsten and tests of boron carbide layer in ITER-like is started recently. The paper contends the first results of the project. The results of B4C coating irradiation by the plasma pulses of QSPU-T plasma accelerator are presented. The new device capable of B4C film deposition on tungsten and testing of the films and materials with ITER-like heat loads and ion- and electron irradiation is described. The results of B4C coating deposition and testing of both tungsten substrate and coating are shown and discussed.

  20. 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.

  1. Processes and applications of silicon carbide nanocomposite fibers

    International Nuclear Information System (INIS)

    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 1200deg. C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  2. 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.

  3. Chromium carbide coatings obtained by the hybrid PVD methods

    Directory of Open Access Journals (Sweden)

    M. Richert

    2010-11-01

    Full Text Available Purpose: With the use of the Arc-PVD and Arc-EB PVD hybrid method, the chromium carbide coatings were deposited on steel substrate. Two kinds of coatings were obtained. The nanostructure coatings were formed by deposition of chromium carbide films by Arc PVD evaporation technique. The multilayer coatings were produced by Arc-EB PVD hybrid technology. In the second case the amorphous phase in majority was found in samples, identified by X-ray investigations.Design/methodology/approach: The Arc PVD and combination Arc-EB PVD methods were used for carbide coatings deposition. The special hybrid multisource device, produced in the Institute for Sustainable Technologies – National Research Institute (ITeE –PIB in Radom, was used for sample deposition. The microstructures of coatings were investigated by JEM 20101 ARP transmission electron microscopy (TEM, TESLA BS500 scanning electron microscopy (SEM and Olympus GX50 optical microscopy (MO. The X-ray diffraction was utilized to identify phase configuration in coatingsFindings: The microstructure of deposited coatings differs depending on the deposition method used. The Arc PVD deposition produced nanometric coatings with the Cr3C2, Cr23C6, Cr7C3 and CrC carbides built from nanometric in size clusters. In the case of the Arc-EB PVD hybrid technology in majority of cases the amorphous microstructure of coatings was found. The hybrid coatings consist of alternating layers of Ni/Cr-Cr3C2.Practical implications: The performed investigations provide information, which could be useful in the industrial practice for the production of wear resistant coatings on different equipments and tools.Originality/value: It was assumed that by using different kinds of PVD methods the different microstructures of coatings could be formed.

  4. Phase transitions in multicomponent interstitial alloys on the base of titanium and vanadium carbides

    International Nuclear Information System (INIS)

    ordered phase with cubic structure is found. Existence of cubic and trigonal ordered phases in Ti0.98Mo0.02C0.6, Ti1-xVxC0.6 and Ti0.8V0.2C0.62 is determined; it is related to preferred distribution of carbon over octahedral interstitial positions and to distortion of metal sublattice, accordingly. The ordered phases in Ti0.87Ta0.13C0.71, Ti0.8Ta0.1Nb0.1C0.7 and Ti0.85Nb0.15C0.71 are absent because the replacement of a part of titanium atoms by tantalum and niobium decreases the upper concentration limit of existence of carbon atoms ordering in titanium carbide. In Ti1-xTaxC0.6 and Ti1-xNbxC0.6 short-range order is found and the dependence of character of Ti-Ta interaction on carbon content is established in carbides Ti1-xTaxCy, at decreasing it from C/Ti=1 up to C/Ti=0.6 the short range parameter changes approaching to that of Ti1-xTax. The existence regions of orthorhombic and hexagonal ordered phases, characteristics of order - order phase transition in VC0.47, VC0.33N0.12 and VC0.36O0.06N0.07 are determined. Nucleation of orthorhombic phase in vanadium subcarbide and subcarbonitride occurs by the heterogeneous mechanism, and phase transformation occurs through nucleation of bidimensional domains. By low-temperature (from 300 K to 12 K) neutron diffraction study of structures of titanium carbide, carbonitride and complex carbide a new low-temperature phase is found in the temperature interval of 12 K- 40 K, due to nonstoichiometry and power non equivalence of positions. In TiC0.67 correlation between structure and thermal capacity is determined at low temperatures (from 100 K to 30 K), consisting in decreasing of a thermal capacity at ordering in comparison with disordered state that is connected by changing of spectrum of an electronic subsystem. Regular researches of thermal capacity of nonstoichiometric titanium carbonitrides, oxycarbonitrides and complex carbides are carried out at low temperatures. In titanium carbide decrease in degree of long-range order is

  5. Electrical and optical properties of amorphous silicon carbide, silicon nitride and germanium carbide prepared by the glow discharge technique

    International Nuclear Information System (INIS)

    Amorphous specimens of silicon carbide, silicon nitride and germanium carbide have been prepared by decomposition of suitable gaseous mixtures in a r.f. glow discharge. Substrates were held at a temperature Tsub(d) between 400 and 800 K during deposition. In all three of the above materials the results of optical absorption and of d.c. conductivity measurements show a systematic variation with Tsub(d) and with the volume ratio of the gases used. Electron microprobe results on silicon carbide specimens indicate that a wide range of film compositions can be prepared. The optical gap has a pronounced maximum at the composition Sisub(0.32)Csub(0.68) where it is 2.8 eV for a sample deposited at Tsub(d) = 500 K, but shifts to lower energies with increasing Tsub(d). The conductivity above about 400 K has a single activation energy approximately equal to half the optical gap and extended state conduction predominates if the silicon content exceeds 32%. If the latter is reduced, hopping transport takes over and it is suggested that the excess carbon in the network tends to bond in three-fold graphic coordination. Absence of any obvious feature in the electronic properties at the stoichiometric composition SiC implies that there is little tendency towards compound formation in the glow discharge films. The present results are discussed in relation to measurements on specimens prepared by different methods. (author)

  6. Development of an electron-temperature-dependent interatomic potential for molecular dynamics simulation of tungsten under electronic excitation

    International Nuclear Information System (INIS)

    Irradiation of a metal by lasers or swift heavy ions causes the electrons to become excited. In the vicinity of the excitation, an electronic temperature is established within a thermalization time of 10-100 fs, as a result of electron-electron collisions. For short times, corresponding to less than 1 ps after excitation, the resulting electronic temperature may be orders of magnitude higher than the lattice temperature. During this short time, atoms in the metal experience modified interatomic forces as a result of the excited electrons. These forces can lead to ultrafast nonthermal phenomena such as melting, ablation, laser-induced phase transitions, and modified vibrational properties. We develop an electron-temperature-dependent empirical interatomic potential for tungsten that can be used to model such phenomena using classical molecular dynamics simulations. Finite-temperature density functional theory calculations at high electronic temperatures are used to parametrize the model potential

  7. Dispersion of boron carbide in a tungsten carbide/cobalt matrix

    International Nuclear Information System (INIS)

    Particles of boron carbide (105-125 microns) were coated with a layer (10-12 microns) of titanium carbide in a fluidized bed. These coated particles have been successfully incorporated in a tungsten carbide--cobalt matrix by hot pressing at 1 tonf/in2, (15.44 MN/m2) at 13500C. Attempts to produce a similar material by a cold pressing and sintering technique were unsuccessful because of penetration of the titanium carbide layer by liquid cobalt. Hot-pressed material containing boron carbide had a static strength in bend of approximately 175,000 lbf/in2, (1206MN/m2) which compares favorably with the strength of conventionally produced tungsten carbide/cobalt. The impact strength of the material containing boron carbide was however considerably lower than tungsten carbide/cobalt. In rock drilling tests on Darley Dale sandstone at low speeds and low loads, the material containing boron carbide drilled almost ten times as far without seizure as tungsten carbide/cobalt. In higher speed and higher load rotary drilling tests conducted by the National Coal Board, the material containing boron carbide chipped badly compared with normal NCB hardgrade material

  8. Development of a new electronic neutron imaging system

    International Nuclear Information System (INIS)

    An electronic neutron imaging camera system was developed for use with thermal, epithermal, and fast neutrons in applications that include nondestructive inspection of explosives, corrosion, turbine blades, electronics, low Z components, etc. The neutron images are expected to provide information to supplement that available from X-ray tests. The primary camera image area was a 30x30 cm field-of-view with a spatial resolution approaching 1.6 line pairs/mm (lp/mm). The camera had a remotely changeable second lens to limit the field-of-view to 7.6x7.6 cm for high spatial resolution (at least 4 lp/mm) thermal neutron imaging, but neutron and light scatter will limit resolution for fast neutrons to about 0.5 lp/mm. Remote focus capability enhanced camera set-up for optimum operation. The 75 dB dynamic range camera system included 6Li-based screens for imaging of thermal and epithermal neutrons and ZnS(Ag)-based screens for fast neutron imaging. The fast optics was input to a Super S-25 Gen II image intensifier, fiber optically coupled to a 1134 (h)x486 (v) frame transfer CCD camera. The camera system was designed to be compatible with a Navy-sponsored accelerator neutron source. The planned neutron source is an RF quadrupole accelerator that will provide a fast neutron flux of 107 n/cm2-s (at a source distance of 1 m) at an energy of about 2.2 MeV and a thermal neutron flux of 106 n/cm2-s at a source L/D ratio of 30. The electronic camera produced good quality real-time images at these neutron levels. On-chip integration could be used to improve image quality for low flux situations. The camera and accelerator combination provided a useful non-reactor neutron inspection system

  9. Monitoring the thin film formation during sputter deposition of vanadium carbide

    International Nuclear Information System (INIS)

    The theoretical description and the experimental realisation of in situ X-ray reflectivity measurements during thin film deposition of polycrystalline vanadium carbide coatings are presented. The thin film formation of magnetron sputtered polycrystalline coatings was monitored by in situ X-ray reflectivity measurements. The measured intensity was analyzed using the Parratt algorithm for time-dependent thin film systems. Guidelines for the on-line interpretation of the data were developed. For thick coatings, the experimental resolution needs to be included in the data evaluation in order to avoid misinterpretations. Based on a simple layer model, the time-dependent mean electron density, roughness and growth velocity were extracted from the data. As an example, the method was applied to the hard coating material vanadium carbide. Both instantaneous and slowly varying changes of the coating could be detected. It was shown that the growth velocity is proportional to the DC power. Significant changes of the microstructure induced by the working gas pressure are mainly driven by the chemical composition

  10. Interfacial reactions of refractory metals niobium and tantalum with ceramics silicon carbide and alumina

    International Nuclear Information System (INIS)

    Recent interest in the development of advanced metal matrix composites has prompted research on interfacial reactions of Nb and Ta with candidate reinforcements such as silicon carbide and alumina. Formation of reaction layers as small as 0.1 μm can be detrimental to composite strength and ductility and in some instances to the corrosion behavior, which suggests the importance of understanding the early stages of interfacial reactions. Thin films of Nb and Ta were sputter deposited on single crystal and polycrystalline silicon carbide and on sapphire substrates, and the nature and extent of reaction evaluated using Auger depth profiling and electron microscopy. This paper reports that in the Nb/SiC system, NbCx is the first reaction product to form, but the overall extent of the reaction is dominated by the formation of the more stable NbCxSiy ternary phase. Little or no interfacial reaction was observed in the Nb/Al2O3 system for up to 4 hours at 1100 degrees C, which also suggests that Al2O3 may be a potential diffusion barrier to minimize reactions in the Nb/SiC system. Similar interesting observations were made in the Ta/SiC and Ta/Al2O3 systems

  11. Development of a new electronic neutron imaging system

    CERN Document Server

    Brenizer, J S; Gibbs, K M; Mengers, P; Stebbings, C T; Polansky, D; Rogerson, D J

    1999-01-01

    An electronic neutron imaging camera system was developed for use with thermal, epithermal, and fast neutrons in applications that include nondestructive inspection of explosives, corrosion, turbine blades, electronics, low Z components, etc. The neutron images are expected to provide information to supplement that available from X-ray tests. The primary camera image area was a 30x30 cm field-of-view with a spatial resolution approaching 1.6 line pairs/mm (lp/mm). The camera had a remotely changeable second lens to limit the field-of-view to 7.6x7.6 cm for high spatial resolution (at least 4 lp/mm) thermal neutron imaging, but neutron and light scatter will limit resolution for fast neutrons to about 0.5 lp/mm. Remote focus capability enhanced camera set-up for optimum operation. The 75 dB dynamic range camera system included sup 6 Li-based screens for imaging of thermal and epithermal neutrons and ZnS(Ag)-based screens for fast neutron imaging. The fast optics was input to a Super S-25 Gen II image intensifi...

  12. Boron carbide whiskers produced by vapor deposition

    Science.gov (United States)

    1965-01-01

    Boron carbide whiskers have an excellent combination of properties for use as a reinforcement material. They are produced by vaporizing boron carbide powder and condensing the vapors on a substrate. Certain catalysts promote the growth rate and size of the whiskers.

  13. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

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

    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 exam...

  14. Characterization of boron carbide particles and its shielding behavior against neutron radiation

    International Nuclear Information System (INIS)

    Highlights: • B4C was characterized by XRD, SEM, EDS, FT-IR and Raman Spectroscopy. • B4C was investigated for the neutron shielding behavior analysis. • Neutron permeability experiments were moderated in the Howitzer using Ra–Be source. • The pellet with 12.5 g B4C powder had the lowest neutron permeability rate. • Total macroscopic cross sections found between 1.491 ± 0.0074 and 0.722 ± 0.0071 cm-1. - Abstract: Boron minerals, considered future essential materials, can be used as raw materials in the production of boron carbide. In this study, boron carbide, the hardest material after diamond and cubic boron nitride, is characterized and the neutron shielding behavior is investigated. The characterization and structural evaluation of the boron carbide sample was performed using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FT-IR) and Raman Spectroscopy. In addition, a neutron Howitzer was used to measure the neutron permeability of boron carbide samples of various thicknesses. The sample composed of 12.5 g of boron carbide powder and 3 g of Wax® had the lowest neutron permeability rate (62.1%). Pellet 3 had the smallest total macroscopic cross section of boron carbide particles, 0.722 ± 0.0071 cm−1

  15. Synthesis of boron carbide nanoflakes via a bamboo-based carbon thermal reduction method

    International Nuclear Information System (INIS)

    Graphical abstract: B4C nanoflakes were synthesized via a facile and cost-effective bamboo-based carbon thermal reduction method. Highlights: •Boron carbide nanoflakes were successfully synthesized via a bamboo-based carbon thermal reduction method. •A fluoride-assisted VLS nucleation and VS growth mechanism were proposed. •We studied the resistivity of boron carbide nanoflakes via in situ TEM techniques for the first time. -- Abstract: Boron carbide nanoflakes have been successfully synthesized by a facile and cost-effective bamboo-based carbon thermal reduction method. The majority of the boron carbide products exhibited a flake-like morphology with lateral dimensions of 0.5–50 μm in width and more than 50 μm in length, while the thickness was less than 150 nm. The structural, morphological, and elemental analyses demonstrated that these nanoflakes grew via the fluoride-assisted vapor–liquid–solid combined with vapor–solid growth mechanism. The corresponding growth model was proposed. In addition, the electrical property of individual boron carbide nanoflake was investigated by an in situ two point method inside a transmission electron microscope. The resistivity of boron carbide nanoflakes was measured to be 0.14 MΩ cm

  16. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    International Nuclear Information System (INIS)

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer

  17. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Boccard, Mathieu; Holman, Zachary C. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States)

    2015-08-14

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  18. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    Science.gov (United States)

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-01

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  19. Nanostructures obtained from a mechanically alloyed and heat treated molybdenum carbide

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Barriga Arceo, L. [Programa de Ingenieria Molecular, I.M.P. Lazaro Cardenas 152, C.P. 07730 D.F. Mexico (Mexico) and ESIQIE-UPALM, IPN Apdo Postal 118-395, C.P. 07051 D.F. Mexico (Mexico)]. E-mail: luchell@yahoo.com; Orozco, E. [Instituto de Fisica UNAM, Apdo Postal 20-364, C.P. 01000 D.F. Mexico (Mexico)]. E-mail: eorozco@fisica.unam.mx; Mendoza-Leon, H. [ESIQIE-UPALM, IPN Apdo Postal 118-395, C.P. 07051 D.F. Mexico (Mexico)]. E-mail: luchell@yahoo.com; Palacios Gonzalez, E. [Programa de Ingenieria Molecular, I.M.P. Lazaro Cardenas 152, C.P. 07730 D.F. Mexico (Mexico)]. E-mail: epalacio@imp.mx; Leyte Guerrero, F. [Programa de Ingenieria Molecular, I.M.P. Lazaro Cardenas 152, C.P. 07730 D.F. Mexico (Mexico)]. E-mail: fleyte@imp.mx; Garibay Febles, V. [Programa de Ingenieria Molecular, I.M.P. Lazaro Cardenas 152, C.P. 07730 D.F. Mexico (Mexico)]. E-mail: vgaribay@imp.mx

    2007-05-31

    Mechanical alloying was used to prepare molybdenum carbide. Microstructural characterization of samples was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. Molybdenum carbide was heated at 800 {sup o}C for 15 min in order to produce carbon nanotubes. Nanoparticles of about 50-140 nm in diameter and nanotubes with diameters of about 70-260 nm and 0.18-0.3 {mu}m in length were obtained after heating at 800 {sup o}C, by means of this process.

  20. Hafnium carbide nanocrystal chains for field emitters

    International Nuclear Information System (INIS)

    A hafnium carbide (HfC) nanostructure, i.e., HfC nanocrystal chain, was synthesized by a chemical vapor deposition (CVD) method. X-ray diffractometer, field-emission scanning electron microscope, transmission electron microscope, and energy-dispersive X-ray spectrometer were employed to characterize the product. The synthesized one-dimensional (1D) nanostructures with many faceted octahedral nanocrystals possess diameters of tens of nanometers to 500 nm and lengths of a few microns. The chain-like structures possess a single crystalline structure and preferential growth direction along the [1 0 0] crystal orientation. The growth of the chains occurred through the vapor–liquid–solid process along with a negative-feedback mechanism. The field emission (FE) properties of the HfC nanocrystal chains as the cold cathode emitters were examined. The HfC nanocrystal chains display good FE properties with a low turn-on field of about 3.9 V μm−1 and a high field enhancement factor of 2157, implying potential applications in vacuum microelectronics.

  1. The development and demonstration of hybrid programmable attitude control electronics

    Science.gov (United States)

    Smith, L. S.; Kopf, E. H., Jr.

    1973-01-01

    In the course of extended life attitude control system (ELACS) research sponsored by NASA a hybrid programable attitude control electronics (HYPACE) concept was developed and demonstrated. The wide variety of future planetary missions demanded a new control approach to accommodate the automatic fault tolerance and long the life requirements of such missions. HYPACE provides an adaptable, analog/digital design approach that permits preflight and in-flight accommodation of mission changes, component performance variations, and spacecraft changes, through programing. This enabled broad multimission flexibility of application in a cost effective manner. Previously, flight control computers have not been not flown on planetary missions because of weight and power problems. These problems were resolved in the design of HYPACE. The HYPACE design, which was demonstrated in breadboard form on a single-axis gas-bearing spacecraft simulation, uses a single control channel to perform the attitude control functions sequentially, thus significantly reducing the number of component parts over hard-wired designs.

  2. Investigating important factors influencing electronic banking for export development

    Directory of Open Access Journals (Sweden)

    Vahid Abbas Zadeh

    2014-01-01

    Full Text Available Export is one of the most important indicators of a growing economy and it is the primary source of reaching sustainable growth on the market. This paper presents an empirical study to determine important factors influencing electronic banking in export development of Iranian organizations. The proposed study designs a questionnaire and distributes it among some regular customers who do internet banking with Parsian bank in city of Tehran, Iran. Cronbach alpha is calculated as 0.82, which is well above the minimum desirable limit of 0.70. In addition, Kaiser-Meyer-Olkin Measure of Sampling Adequacy and Approx. Chi-Square are 0.71 and 1955 with Sig. = 0.000, respectively. Using principal component analysis, the study has detected six factors including customer’s information, building trust, secure internet access, having good internet infrastructure and internet users.

  3. Mockup Didatic Set for Students Development in Automotive Electronic

    Directory of Open Access Journals (Sweden)

    Fabio Delatore

    2013-05-01

    Full Text Available The automotive engineering education area, specifically on internal combustion engine, requires the use of suitable systems, capable to simulate, test and obtain specifics data from its operation. Automotive engines are so complex due to it is a mix of engineering subjects, so, a mockup was created to help its study. The mockup is an exactly the same engine that equips a vehicle, but assembled in a mechanical base, equipped with all the necessary components for running it up. The objective of this work is to develop a mockup with a suitable Electronic Control Unit (ECU board, in order to obtain the sensors/actuators signals from the engine and control some important engine functions by using an external ECU, so that the students may test their own strategies, compare with the original ECU.

  4. Novosibirsk terahertz free electron laser: instrumentation development and experimental achievements

    International Nuclear Information System (INIS)

    Nowadays, the Novosibirsk free electron laser (NovoFEL) is the most intense radiation source in the terahertz spectral range. It operates in the continuous mode with a pulse repetition rate of up to 11.2 MHz (5.6 MHz in the standard mode) and an average power of up to 500 W. The radiation wavelength can be precisely tuned from 120 to 240 mm with a relative line width of 0.3–1%, which corresponds to the Fourier transform limit for a micropulse length of 40–100 ps. The laser radiation is plane-polarized and completely spatially coherent. The radiation is transmitted to six user stations through a nitrogen-filled beamline. Characteristics of the NovoFEL radiation differ drastically from those of conventional low-power (and often broadband) terahertz sources, which enables obtaining results impossible with other sources, but necessitates the development of special experimental equipment and techniques. In this paper, we give a review of the instrumentation developed for control and detection of high-power terahertz radiation and for the study of interaction of the radiation with matter. Quasi-optic elements and systems, one-channel detectors, power meters, real-time imagers, spectroscopy devices and other equipment are described. Selected experimental results (continuous optical discharge, material and biology substance ablation, real-time imaging attenuated total reflection spectroscopy, speckle metrology, polarization rotation by an artificial chiral structure, terahertz radioscopy and imaging) are also presented in the paper. In the near future, after commissioning another four electron racetracks and two optical resonators, intense radiation in the range from 5 to 240 µm will be available for user experiments

  5. Development of the Electron Drift Instrument (EDI) for Cluster

    Science.gov (United States)

    Quinn, Jack; Christensen, John L. (Technical Monitor)

    2001-01-01

    The Electron Drift Instrument (EDI) is a new technique for measuring electric fields in space by detecting the effect on weak beams of test electrons. This U.S. portions of the technique, flight hardware, and flight software were developed for the Cluster mission under this contract. Dr. Goetz Paschmann of the Max Planck Institute in Garching, Germany, was the Principle Investigator for Cluster EDI. Hardware for Cluster was developed in the U.S. at the University of New Hampshire, Lockheed Palo Alto Research Laboratory, and University of California, San Diego. The Cluster satellites carrying the original EDI instruments were lost in the catastrophic launch failure of first flight of the Arianne-V rocket in 1996. Following that loss, NASA and ESA approved a rebuild of the Cluster mission, for which all four satellites were successfully launched in the Summer of 2000. Limited operations of EDI were also obtained on the Equator-S satellite, which was launched in December, 1997. A satellite failure caused a loss of the Equator-S mission after only 5 months, but these operations were extremely valuable in learning about the characteristics and operations of the complex EDI instrument. The Cluster mission, satellites, and instruments underwent an extensive on-orbit commissioning phase in the Fall of 2000, carrying over through January 2001. During this period all elements of the instruments were checked and careful measurements of inter-experiments interferences were made. EDI is currently working exceptionally well in orbit. Initial results verify that all aspects of the instrument are working as planned, and returning highly valuable scientific information. The first two papers describing EDI on-orbit results have been submitted for publication in April, 2001. The principles of the EDI technique, and its implementation on Cluster are described in two papers by Paschmann et al., attached as Appendices A and B. The EDI presentation at the formal Cluster Commissioning

  6. The role of intergranular chromium carbides on intergranular oxidation of nickel based alloys in pressurized water reactors primary water

    Science.gov (United States)

    Gaslain, F. O. M.; Le, H. T.; Duhamel, C.; Guerre, C.; Laghoutaris, P.

    2016-02-01

    Alloy 600 is used in pressurized water reactors (PWRs) but is susceptible to primary water stress corrosion cracking (PWSCC). Intergranular chromium carbides have been found beneficial to reduce PWSCC. Focussed ion beam coupled with scanning electron microscopy (FIB/SEM) 3D tomography has been used to reconstruct the morphology of grain boundary oxide penetrations and their interaction with intergranular Cr carbides in Alloy 600 subjected to a PWR environment. In presence of intergranular Cr carbides, the intergranular oxide penetrations are less deep but larger than without carbide. However, the intergranular oxide volumes normalized by the grain boundary length for both samples are similar, which suggest that intergranular oxidation growth rate is not affected by carbides. Analytical transmission electron microscopy (TEM) shows that the intergranular oxide consists mainly in a spinel-type oxide containing nickel and chromium, except in the vicinity of Cr carbides where Cr2O3 was evidenced. The formation of chromium oxide may explain the lower intergranular oxide depth observed in grain boundaries containing Cr carbides.

  7. Engineering scale development of the vapor-liquid-solid (VLS) process for the production of silicon carbide fibrils and linear fibril assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Tenhover, M.; Biernacki, J. [Carborundum Co., Niagara Falls, NY (United States); Schatz, K.; Ko, F. [Advanced Product Development, Inc., Bristol, PA (United States)

    1995-08-01

    In order to exploit the superior thermomechanical properties of the VLS fibril, the feasibility of scaled-up production of the SiC fibril is demonstrated in this study. Through time series study and computer simulation, the parameters affecting the growth process and properties of the fibrils were examined. To facilitate translation of the superior mechanical properties into higher level preform structures, conventional and unconventional processing methods were evaluated. As revealed by scanning electron microscopic examination and X-ray diffractometry, high level alignment of the fibrils was achieved by the wet-laid process.

  8. Deposition from gas-phase of boron-carbide on graphite

    International Nuclear Information System (INIS)

    Deposition of boron-carbide on graphite was investigated, as a step in the development of carbon fibers/boron-carbide composite. Experiment were first conducted in a 'hot-wall' reactor, then in a 'cold-wall' reactor, which enables better process control and higher tempratures. Various susceptor configurations were utilized as to enable adequate characterization, good material yield, process simplicity, and reproducibility of the results

  9. Express methods for post-reactor research of cladding-free rod carbide fuel pins

    International Nuclear Information System (INIS)

    Brief descriptions of the following express methods of irradiated rod carbide fuel pins research were provided: the method of fuel pins bunch swirl angle evaluation in heating section, the method of fuel pin small-scale bending detection, the method of surface crack detection in fuel pin, the method of fuel pin swelling X-ray detection and the method of fuel carbide microhardness measuring in case of structure high porosity. Appliance boundaries of each developed method are pointed out. (author)

  10. Novel silicon carbide/polypyrrole composites; preparation and physicochemical properties

    International Nuclear Information System (INIS)

    Novel silicon carbide/polypyrrole (SiC/PPy) conducting composites were prepared using silicon carbide as inorganic substrate. The surface modification of SiC was performed in aqueous solution by oxidative polymerization of pyrrole using ferric chloride as oxidant. Elemental analysis was used to determine the mass loading of polypyrrole in the SiC/PPy composites. Scanning electron microscopy showed the surface modification of SiC by PPy. PPy in composites was confirmed by the presence of PPy bands in the infrared spectra of SiC/PPy containing various amounts of conducting polymer. The conductivity of SiC/PPy composites depends on PPy content on the surface. The composite containing 35 wt.% PPy showed conductivity about 2 S cm-1, which is in the same range as the conductivity of pure polypyrrole powder prepared under the same conditions using the same oxidant. PPy in the composites was clearly detected by X-ray photoelectron spectroscopy (XPS) measurements by its N1s and Cl2p peaks. High resolution scans of the C1s regions distinguished between silicon carbide and polypyrrole carbons. The fraction of polypyrrole at the composite surface was estimated from the silicon and nitrogen levels. The combination of XPS and conductivity measurements suggests that the surface of the SiC/PPy composites is polypyrrole-rich for a conducting polymer mass loading of at least 12.6 wt.%

  11. An investigation on gamma attenuation behaviour of titanium diboride reinforced boron carbide-silicon carbide composites

    Science.gov (United States)

    Buyuk, Bulent; Beril Tugrul, A.

    2014-04-01

    In this study, titanium diboride (TiB2) reinforced boron carbide-silicon carbide composites were investigated against Cs-137 and Co-60 gamma radioisotope sources. The composite materials include 70% boron carbide (B4C) and 30% silicon carbide (SiC) by volume. Titanium diboride was reinforced to boron carbide-silicon carbide composites as additive 2% and 4% by volume. Average particle sizes were 3.851 µm and 170 nm for titanium diboride which were reinforced to the boron carbide silicon carbide composites. In the experiments the gamma transmission technique was used to investigate the gamma attenuation properties of the composite materials. Linear and mass attenuation coefficients of the samples were determined. Theoretical mass attenuation coefficients were calculated from XCOM computer code. The experimental results and theoretical results were compared and evaluated with each other. It could be said that increasing the titanium diboride ratio causes higher linear attenuation values against Cs-137 and Co-60 gamma radioisotope sources. In addition decreasing the titanium diboride particle size also increases the linear and mass attenuation properties of the titanium diboride reinforced boron carbide-silicon carbide composites.

  12. The development of new generation electronic personal dosimeters

    International Nuclear Information System (INIS)

    We have developed two types of new small, light, electronic personal dosemeters (EPDs) which can be used for dose management of workers at nuclear power plants without additional dosemeters. The one is a card size dosemeter to measure gamma exposure dose and the other is a multi sensor dosemeter to measure gamma, beta and neutron dose respectively. With direct reading, alarm and instant readout, these EPDs have ruggedness and if failure happens, memory readout facility can read dose data in the dosemeter. These dosemeters have enough performance characteristics and reliability for use as a dose record dosemeter. The gamma dosemeter has a lightweight credit card size body to reduce workers' burden of wearing it. The multi sensor dosemeter has four hetero junction silicon detectors that detect gamma, beta, thermal and fast neutron respectively and it is smaller and lighter than conventional alarm dosemeters presently used at nuclear power plant. Thermal neutron detector has thin Boron layer deposited on silicon surface and fast neutron detector has polyethylene radiator in front of silicon wafer. These dosemeters with a rechargeable battery can operate more than 15 hours continuously. The data transmission can be made with radiofrequency wave in area smaller than 30 cm distance between dosemeter and readout system. These dosemeters were introduced into Tokai nuclear power plant on October 1997, Tsuruga nuclear power plant on December 1997 of Japan Atomic Power Company and have been operating satisfactorily. At now these EPD have been used as secondary dosemeters. The performance characteristics comparison between EPD and film badge(FB) have been continuing to assure EPD suitable for use as a primary dosemeter. Near future Japco will abolish FB and establish the radiation control system based on the electronic personal dosemeters as a dose record dosemeter. (author)

  13. Bioelectronic Learning: The Effects of Electronic Media on a Developing Brain.

    Science.gov (United States)

    Sylwester, Robert

    1997-01-01

    Considers the effects of electronic media on the developing brains of children. Topics include the attentional demands of electronic media; commercial sponsorship; brain development, including memory systems and response systems; and what a developing mind can bring to the electronic media. (LRW)

  14. 75 FR 18825 - Advantage Electronic Product Development Incorporated/Utility Crew Safety LLC

    Science.gov (United States)

    2010-04-13

    ... Advantage Electronic Product Development Incorporated/Utility Crew Safety LLC AGENCY: Department of Energy... intent to grant to: Advantage Electronic Product Development Incorporated/Utility Crew Safety LLC, of... enhanced. Advantage Electronic Product Development Incorporated/Utility Crew Safety LLC, of...

  15. In situ-grown hexagonal silicon nanocrystals in silicon carbide-based films.

    Science.gov (United States)

    Kim, Tae-Youb; Huh, Chul; Park, Nae-Man; Choi, Cheol-Jong; Suemitsu, Maki

    2012-01-01

    Silicon nanocrystals (Si-NCs) were grown in situ in carbide-based film using a plasma-enhanced chemical vapor deposition method. High-resolution transmission electron microscopy indicates that these nanocrystallites were embedded in an amorphous silicon carbide-based matrix. Electron diffraction pattern analyses revealed that the crystallites have a hexagonal-wurtzite silicon phase structure. The peak position of the photoluminescence can be controlled within a wavelength of 500 to 650 nm by adjusting the flow rate of the silane gas. We suggest that this phenomenon is attributed to the quantum confinement effect of hexagonal Si-NCs in silicon carbide-based film with a change in the sizes and emission states of the NCs. PMID:23171576

  16. Carbide formation in tungsten coatings on carbon-fibre reinforced carbon substrates

    International Nuclear Information System (INIS)

    Tungsten coatings with molybdenum interlayer deposited on carbon-fibre reinforced carbon (CFC) substrates were selected as the first wall material for the divertor in the Wall Project at Joint European Torus (similar to the International Thermonuclear Experimental Reactor). For such a layered structure, diffusion of carbon from the CFC substrate towards the Mo and W deposits is expected during the operation of the reactor. As both molybdenum and tungsten form stable carbides, brittle compounds may form at the interface, thus strongly affecting the thermomechanical performance of the coated tiles. For the purpose of prediction of the operation time of such coated tiles, carbon diffusion and carbide formation kinetics need to be determined. In the present study, W/Mo/CFC samples were subjected to heat treatment at 1470 K for various annealing times. The Focused Ion Beam technique was used for sample preparation for electron microscopy examinations. Transmission electron microscopy observations supported with diffraction pattern analyses revealed the both W2C and WC carbides in the W coating, as well as that of Mo2C carbide in the Mo layer. The results were used to estimate the kinetics of coatings degradation. - Highlights: ► Thin Mo/W layers system on carbon-fibre reinforced carbon divertor tile ► Heat treatment at 1470 K results in two tungsten carbide creation — W2C and WC ► The total tungsten carbide creation is limited by carbon diffusion ► WC carbide creation is limited by W2C–WC reaction rate

  17. 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

  18. Mechanical analysis of a boron carbide control rod for pressurized water reactor application

    International Nuclear Information System (INIS)

    A control rod using boron carbide as the neutron poison was analyzed for use in a pressurized water reactor. The motivation for this study stems from the increasing use of boron carbide in control rod elements for large commercial nuclear power stations and the potential safety hazard related to excessive inelastic cladding deformation due to pellet-cladding interaction. As such, the radiation induced dilatation of the boron carbide pellets and the ensuing pellet-cladding interaction phenomena were the dominant concerns of this investigation. Based on the small deformation theory of linear elasticity, the method developed herein can be used to predict that rod burnup which initiates the yielding of the cladding. The details of the physical properties of boron carbide and related design data required for the analysis are included

  19. TRANSFORMATIONS IN NANO-DIAMONDS WITH FORMATION OF NANO-POROUS SILICON CARBIDE AT HIGH PRESSURE

    Directory of Open Access Journals (Sweden)

    V. N. Kovalevsky

    2014-11-01

    Full Text Available The paper contains investigations on regularities of diamond - silicon carbide composite structure formation at impact-wave excitation. It has been determined that while squeezing a porous blank containing Si (SiC nano-diamond by explosive detonation products some processes are taking place such as diamond nano-particles consolidation, reverse diamond transition into graphite, fragments formation from silicon carbide. A method for obtaining high-porous composites with the presence of ultra-disperse diamond particles has been developed. Material with three-dimensional high-porous silicon-carbide structure has been received due to nano-diamond graphitation at impact wave transmission and plastic deformation. The paper reveals nano-diamonds inverse transformation into graphite and its subsequent interaction with the silicon accompanied by formation of silicon-carbide fragments with dimensions of up to 100 nm.

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

    International Nuclear Information System (INIS)

    The main objective of this research project was the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Since alumina has excellent resistance to corrosion but coefficient than silicon carbide, the key idea of this project has been to develop graded coatings with composition varying smoothly along their thickness between an inner (base) layer of mullite in contact with the silicon carbide component and an outer layer of pure alumina, which would function as the actual protective coating of the component. (Mullite presents very good adhesion towards silicon carbide and has thermal expansion coefficient very close to that of the latter.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Prof. Stratis V. Sotirchos

    2001-02-01

    The main objective of this research project was the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Since alumina has excellent resistance to corrosion but coefficient than silicon carbide, the key idea of this project has been to develop graded coatings with composition varying smoothly along their thickness between an inner (base) layer of mullite in contact with the silicon carbide component and an outer layer of pure alumina, which would function as the actual protective coating of the component. (Mullite presents very good adhesion towards silicon carbide and has thermal expansion coefficient very close to that of the latter.)

  2. Enhanced mechanical properties of nanocrystalline boron carbide by nanoporosity and interface phases.

    Science.gov (United States)

    Madhav Reddy, K; Guo, J J; Shinoda, Y; Fujita, T; Hirata, A; Singh, J P; McCauley, J W; Chen, M W

    2012-01-01

    Ceramics typically have very high hardness, but low toughness and plasticity. Besides intrinsic brittleness associated with rigid covalent or ionic bonds, porosity and interface phases are the foremost characteristics that lead to their failure at low stress levels in a brittle manner. Here we show that, in contrast to the conventional wisdom that these features are adverse factors in mechanical properties of ceramics, the compression strength, plasticity and toughness of nanocrystalline boron carbide can be noticeably improved by introducing nanoporosity and weak amorphous carbon at grain boundaries. Transmission electron microscopy reveals that the unusual nanosize effect arises from the deformation-induced elimination of nanoporosity mediated by grain boundary sliding with the assistance of the soft grain boundary phases. This study has important implications in developing high-performance ceramics with ultrahigh strength and enhanced plasticity and toughness. PMID:22968698

  3. Microstructure characterisation of chromium carbides coatings deposited by thermal spraying processes

    Directory of Open Access Journals (Sweden)

    M.W. Richert

    2012-11-01

    Full Text Available Purpose: The Cr3C2-NiCr coatings were deposited by plasma spraying (PS and high velocity oxy-fuel (HVOF processes. The objective of the work concerns characterization of microstructure of sprayed coatings. In the investigated samples, apart from Cr3C2 carbide particles, the carbides Cr7C3 were also present according to the reported through X-ray diffraction analyses. It is likely that Cr7C3 carbides were formed thorough decarburization of Cr3C2. The microstructure of the thermal sprayed Cr3C2-NiCr coatings was characterized by optical (MO, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The fine-grained and nano-crystalline microstructure was found in the investigated coatings. The microhardness of coatings was measured. It was found that the coatings deposited in HVOF process have higher microhardnes than the plasma spraying one. The formation of chromium carbide phases in the coatings was discussed based on the microstructure observation results.Design/methodology/approach: The investigations of coating microstructure by optical microscopy (MO Olympus GX51, scanning electron microscopy STEREOSCAN 420 and transmission electron microscopy JEM2010 ARP (TEM were performed. The examination of phase consistence was determined by Brucker D8 Discover - Advance diffractometer with copper tubing. The microhardness of coatings was measured by Vickers method.Findings: The microstructures of Cr3C2-NiCr coatings were observed and analyzed. On the base of the microstructure investigations and contend of the chromium carbides the mechanism of thermal sprayed coating formation was discussed.Practical implications: The performed investigations contribute to the improvement of microstructure and properties of thermal spraying coatings used in the industrial applications.Originality/value: It was assumed that thermal spraying processes are able to form nano-crystalline microstructure of the chromium carbide coatings.

  4. An electrochemical process for the recycling of tungsten carbide scrap

    International Nuclear Information System (INIS)

    An account is given of the development of a number of designs for electrochemical cells, and the subsequent construction and operation of a vibrating-plate cell capable of oxidizing 15 kilograms of tungsten carbide a day to a crude tungstic acid precipitate, with similtaneous recovery of cobalt metal on the cathode. The effects on the process of the reagent concentration, temperature, current density, and cathode material are discussed

  5. Development of hollow electron beams for proton and ion collimation

    CERN Document Server

    Stancari, G.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; Assmann, R.; Kabantsev, A.

    2010-01-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams

  6. Development of hollow electron beams for proton and ion collimation

    CERN Document Server

    Stancari, G; Kuznetsov, G; Shiltsev, V; Still, D A; Valishev, A; Vorobiev, L G; Assmann, R; Kabantsev, A

    2012-01-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

  7. Development of hollow electron beams for proton and ion collimation

    Energy Technology Data Exchange (ETDEWEB)

    Stancari, G.; Drozhdin, A.I.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; /Fermilab; Assmann, R.; /CERN; Kabantsev, A.; /UC, San Diego

    2010-06-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

  8. Development of electron temperature measuring system by silicon drift detector

    International Nuclear Information System (INIS)

    Soft X-ray spectroscopy with two channels Silicon Drift Detector (SDD) are adopted for electron temperature measuring on HL-2A tokamak in 2005. The working principle, design and first operation of the SDD soft X-ray spectroscopy are introduced. The measuring results of electron temperature are also presented. The results show that the SDD is very good detector for electron temperature measuring on HL-2A tokamak. These will become a solid basic work to establish SDD array for electron temperature profiling. (authors)

  9. Carbide and nitride fuels for advanced burner reactor

    International Nuclear Information System (INIS)

    Full text: Under the U.S. fast reactor program, reference and alternative 1000 MWth Advanced Burner Reactor (ABR) core concepts were developed using ternary metallic (U-TRU-Zr) and mixed oxide (UO2+TRUO2) fuels. Recently, mixed carbide and nitride fuels have been considered as fast reactor fuels on the basis of their high density, compatibility with coolant, high melting temperature, and excellent thermal conductivity although they are ceramic fuel like a mixed oxide fuel. Thus, the performance of the ABR core loaded with carbide and nitride fuels was evaluated in this study with an expectation that the carbide and nitride fuels can mitigate disadvantages of both metallic and oxide fuels in the ABR: favorable passive safety features in a severe accident compared to the oxide core, a higher discharge burnup compared to the metallic core, and a potential to increase thermal efficiency. All calculations performed in this study were focused on the neutronics characteristics, although the fabrication and irradiation experiences for carbide and nitride fuels are limited and some problems were observed in the reprocessing and irradiation of these fuels. The mixed monocarbide and mixed mononitride fuels were selected as the alternative fuel forms and the ABR core concepts with these fuels were developed based on the reference 1000 MWth ABR core concepts. For consistency, the potential design goals used in the reference ABR core concepts were also employed in this study: a 1000 MWth power rating, medium TRU conversion ratio of ∼0.75, a compact core, one-year operational cycle length at least with a capacity factor of 90%, sufficient shutdown margin with a limited maximum single control assembly fault, and possible use of either metallic or any ceramic fuels in the same core layout. The core layout and outer assembly dimensions of the reference 1000 MWth ABR core were kept, but the intra assembly design parameters were varied to maximize the discharge burnup within the

  10. Performance review of thermionic electron gun developed for RF linear accelerators at RRCAT

    International Nuclear Information System (INIS)

    RRCAT is engaged in development of RF electron linear accelerator for irradiation of industrial and agricultural products. Thermionic electron gun is primary source for this accelerator as beam current in the RF accelerator is modest and thermionic emission is most prevalent option for electron gun development. An electron gun has to meet high cathode emission capability, low filament power, good accessibility for cathode replacement and should provide short time for maintenance. Electron linear accelerator up to beam energy of 10 MeV require electron source of 45-50 keV beam energy and emission current of 1 A. Electron optics of gun and electron beam profile simulations were carried out using CST's particle tracking code and EGUN code. Triode type electron gun of cathode voltage 50 kV pulsed has been designed, developed and integrated with 10 MeV electron linear accelerators at RRCAT. Beam current of more than 600 mA has been measured with faraday cup in the test stand developed for characterizing the electron gun. Two accelerators one is imported and another one developed indigenously has been energized using this electron gun. Beam energy of 5-10 MeV has been achieved with beam current of 250-400 mA by integrating this electron gun with the linear accelerator. This paper reviews the performance of indigenously developed electron gun for both linear accelerators. (author)

  11. Development of an Electronic Claim System Based on an Integrated Electronic Health Record Platform to Guarantee Interoperability

    OpenAIRE

    Kim, Hwa Sun; Cho, Hune; Lee, In Keun

    2011-01-01

    Objectives We design and develop an electronic claim system based on an integrated electronic health record (EHR) platform. This system is designed to be used for ambulatory care by office-based physicians in the United States. This is achieved by integrating various medical standard technologies for interoperability between heterogeneous information systems. Methods The developed system serves as a simple clinical data repository, it automatically fills out the Centers for Medicare and Medic...

  12. Recent development in methods for electron optical computations

    Czech Academy of Sciences Publication Activity Database

    Lencová, Bohumila

    2001-01-01

    Roč. 93, č. 6 (2001), s. 434-435. ISSN 0248-4900 Institutional research plan: CEZ:AV0Z2065902 Keywords : electron optical computations * finite element method Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.829, year: 2001

  13. The Early Development of Electronic pH Meters

    Science.gov (United States)

    Hines, Wallis G.; de Levie, Robert

    2010-01-01

    A 19-year-old undergraduate at the University of Chicago, Kenneth Goode, in 1921 came up with the idea of an electronic pH meter, worked out some of its initial problems, and set in motion an international scientific effort that culminated in the current, wide availability of electronic pH meters. Except for the replacement of vacuum tubes by…

  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. Silicon carbide materials for LWR application: current status and issues

    International Nuclear Information System (INIS)

    Silicon carbide (SiC) is a very attractive engineering ceramic in particular for high-temperature use and nuclear application due to its high-temperature strength, oxygen resistance, chemical stability, low activation, radiation resistance, etc. Silicon carbide composites have pseudo ductile behaviour by de-bonding and sliding at fiber/matrix interphase. Fundamental mechanical properties of highly crystalline nuclear grade SiC composites are stable following neutron irradiation. Silicon carbide composites are promising materials for accident-tolerant fuel. The sophistication of the technology infrastructure for safety has been requested by the Ministry of Economy, Trade and Industry (METI) in Japan. The research and development of fuel such as SiC cladding are expected to be described in a new road map by METI. Silicon carbide is a promising material for LWR application in terms of excellent stability of dimension and strength under neutron irradiation and excellent resistance to high-temperature steam. Fundamental fabrication technique and joining technique have been established. Current SiC/SiC composites have C interphase and environmental coating is required to prevent oxidation. Novel porous SiC/SiC composites do not have C interphase and have excellent oxidation resistance, although hermetic coating is required. The issues of SiC composite development for LWR application are as follows: The SiC/SiC composites have impurities depending on fabrication methods. It is important to understand the effect of impurities on the resistance to high-temperature water under normal operation and the resistance to high-temperature steam in the case of severe accident. The synergetic effect of irradiation and high-temperature water is also important. The reaction with fuel under neutron irradiation needs to be clarified. As for material development, coating, joining technique and large scale fabrication should be considered as important issues. Material cost should be

  16. Oxidation of vanadium carbide in air

    International Nuclear Information System (INIS)

    It was studied the samples oxidation of vanadium carbide (V8C7), synterized and in powder, in order to know the temperature influence and the aggregation state in the kinetics and the oxidation products. The assays were realized in static air, at temperature between 600 y 750 Centigrade, between 6 and 24 hours periods. The gaseous products were analyzed through gas chromatography while the condensates ones were analyzed through optical microscopy and scanning electron microscopy, X-ray diffraction and chemical analysis by X-ray fluorescence analysis. It was found that in the V8C7 oxidation occurs two basic processes: the gaseous oxides production which results of the carbon oxidation, fundamentally CO2, and the vanadium condensate oxides production, fundamentally V2O5. In the synterized samples assayed under 650 Centigrade, the kinetics is lineal with loss of mass, suggesting a control by the formation of gaseous products in the sample surface, while in the synterized samples assayed over 650 Centigrade, it occurs a neat gain of mass, which is attributed to vanadium pentoxide fusion. These processes produce stratified layers of V2O5 although at higher temperatures also it was detected V2O4. The superficial area effect is revealed in what the powder samples always experiment a mass neat increase in all essay temperatures, being the condensate oxidation products, fundamentally V2O5 and V6O13. (Author)

  17. Surface group modification and carrier transport properties of layered transition metal carbides (Ti2CTx, T: -OH, -F and -O)

    Science.gov (United States)

    Lai, Shen; Jeon, Jaeho; Jang, Sung Kyu; Xu, Jiao; Choi, Young Jin; Park, Jin-Hong; Hwang, Euyheon; Lee, Sungjoo

    2015-11-01

    In spite of recent significant research into various two-dimensional (2D) materials after the emergence of graphene, the development of a new 2D material that provides both high mobility and an appropriate energy band gap (which are crucial for various device applications) remains elusive. In this report, we demonstrate that the carrier transport behaviour of 2D Ti2CTx, which belongs to the family of 2D transition metal carbides and nitrides, can be tuned by modifying the surface group Tx (-OH, -F, and -O). Our results show that 2D Ti2C(OH)xFy and Ti2COx films can be obtained via simple chemical treatment, thermal annealing, and mechanical exfoliation processes. For the first time, we study the carrier transport properties of 2D Ti2CTx field effect transistors (FETs), obtaining the high field effect carrier mobilities of 104 cm2 V-1 s-1 at room temperature. The temperature dependent resistivity of the Ti2COx film exhibits semiconductor like Arrhenius behaviour at zero gate voltage, from which we estimate the energy gap of 80 meV. One interesting feature of the FETs based on transition metal carbides is that the field effect mobility at room temperature is less sensitive to the measured transport gaps, which may arise from the dominant charge transport of activated carriers over the narrow energy gaps of the transition metal carbides. Our results open up the possibility that new 2D materials with high mobilities and appropriate band gaps can be achieved, and broaden the range of electronic device applications of Ti2CTx films.In spite of recent significant research into various two-dimensional (2D) materials after the emergence of graphene, the development of a new 2D material that provides both high mobility and an appropriate energy band gap (which are crucial for various device applications) remains elusive. In this report, we demonstrate that the carrier transport behaviour of 2D Ti2CTx, which belongs to the family of 2D transition metal carbides and nitrides

  18. Electron guns and collectors developed at INP for electron cooling devices

    Energy Technology Data Exchange (ETDEWEB)

    Sharapa, A.N.; Shemyakin, A.V. [Institute of Nuclear Physics, Novosibirsk (Russian Federation)

    1997-09-01

    Institute of Nuclear Physics (INP) has a rich experience in designing electron guns and collectors for electron cooling devices. This paper is a review of the experience of several INP research groups in this field. Some results obtained at INP for systems without a guiding magnetic field are also discussed.

  19. Indentation fatigue in silicon nitride, alumina and silicon carbide ceramics

    Indian Academy of Sciences (India)

    A K Mukhopadhyay

    2001-04-01

    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 microhardness tester at various loads in the range 1–20 N. Subsequently, the gradual evolution of the damage was characterized using an optical microscope in conjunction with the image analysing technique. The materials were classified in the order of the decreasing resistance against repeated indentation fatigue at the highest applied load of 20 N. It was further shown that there was a strong influence of grain size on the development of resistance against repeated indentation fatigue on the same spot. Finally, the poor performance of the sintered silicon carbide was found out to be linked to its previous thermal history.

  20. CALCIUM CARBIDE: AN EFFICIENT ALTERNATIVE TO THE USE OF ALUMINUM

    Directory of Open Access Journals (Sweden)

    Amilton Carlos Pinheiro Cardoso Filho

    2013-03-01

    Full Text Available The steel demand for fine applications have increased considerably in the last years, and the criteria for its production are even stricter, mainly in relation to the residual elements content and cleanness required. In relation to the steel cleanness, the main problem faced is the control of the amount and morphology of alumina inclusions, generated in the steel deoxidation with aluminum. Besides harming the products quality, the presence of non metallic inclusions can originate nozzle clogging, and consequently interruptions in the process flux. Aiming to improve the steel cleanness and to minimize nozzle clogging, this study is developed to evaluate the partial substitution of aluminum by calcium carbide in the steel deoxidation. Along the operational procedures, the calcium carbide was applied to 397 heats, through what the improvement in steel cleanness is confirmed, with consequent reduction in the nozzle clogging occurrence.