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Sample records for carbide electronics developed

  1. PYROLYTIC CARBIDE DEVELOPMENT PROGRAM

    Science.gov (United States)

    and injector design changes were made to improve the quality of the carbide produced. Niobium carbide and tantalum carbide coated nozzles are described...Additional data for pyrolytic niobium carbide and hafnium carbide is also presented. (Author)

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    FAN; ChangZeng

    2007-01-01

    The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.……

  7. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.

  8. Electronic transport properties of the armchair silicon carbide nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Song Jiuxu; Yang Yintang; Liu Hongxia [Key Laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Guo Lixin [School of Science, Xidian University, Xi' an 710071 (China); Zhang Zhiyong, E-mail: songjiuxu@126.com [Information Science and Technology Institution, Northwest University, Xi' an 710069 (China)

    2010-11-15

    The electronic transport properties of the armchair silicon carbide nanotube (SiCNT) are investigated by using the combined nonequilibrium Green's function method with density functional theory. In the equilibrium transmission spectrum of the nanotube, a transmission valley of about 2.12 eV is discovered around Fermi energy, which means that the nanotube is a wide band gap semiconductor and consistent with results of first principle calculations. More important, negative differential resistance is found in its current voltage characteristic. This phenomenon originates from the variation of density of states caused by applied bias voltage. These investigations are meaningful to modeling and simulation in silicon carbide nanotube electronic devices.

  9. Development and characterization of solid solution tri-carbides

    Science.gov (United States)

    Knight, Travis; Anghaie, Samim

    2001-02-01

    Solid-solution, binary uranium/refractory metal carbide fuels have been shown to be capable of performing at high temperatures for nuclear thermal propulsion applications. More recently, tri-carbide fuels such as (U, Zr, Nb)C1+x with less than 10% metal mole fraction uranium have been studied for their application in ultra-high temperature, high performance space nuclear power systems. These tri-carbide fuels require high processing temperatures greater than 2600 K owing to their high melting points in excess of 3600 K. This paper presents the results of recent studies involving hypostoichiometric, single-phase tri-carbide fuels. Processing techniques of cold uniaxial pressing and sintering were investigated to optimize the processing parameters necessary to produce high density (low porosity), single phase, solid solution mixed carbide nuclear fuels for testing. Scanning electron microscopy and xray diffraction were used to analyze samples. Liquid phase sintering with UC1+x at temperatures near 2700 K was shown to be instrumental in achieving good densification in hyper- and near-stoichiometric mixed carbides. Hypostoichiometric carbides require even higher processing temperatures greater than 2800 K in order to achieve liquid phase sintering with a UC liquid phase and good densification of the final solid solution, tri-carbide fuel. .

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

    Science.gov (United States)

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

    2015-11-01

    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 Ti3C2T2 (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 contributing most to the conduction. The conduction is also significantly anisotropic due to the fact that the effective masses of carriers including electrons and holes are remarkably direction-dependent. Such an anisotropic electronic conduction is evidenced by the I-V curves of an individual Ti3C2T2 particulate, which demonstrates that the in-plane electrical conduction is at least one order of magnitude higher than that vertical to the basal plane.

  11. Crystal structure and electron density distribution in niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Will, G.; Platzbecker, R. [Bonn Univ. (Germany). Abt. fuer Mineralogie und Kristallographie

    2001-09-01

    In this paper the bonding properties, e. g. the charge distribution between the atoms and the deformation of niobium carbide densities have been studied. The crystal studied had the composition NbC{sub 0.98}. Careful and redundant data collection (74 unique reflections out of 2087 reflections measured) gave the basis for a detailed study. IAM models (independent atom model), high order and multipole refinements were made resulting in R values of R=0.4% and R=0.07%. In the corresponding deformation density maps electron accumulations between the niobium atoms were detected, but no bonding to the carbon atoms. (orig.)

  12. 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

  13. Developments in silicon carbide for aircraft propulsion system applications

    Science.gov (United States)

    Przybylko, Stephen J.

    1993-06-01

    The physical and electrical properties of silicon carbide make it the foremost semiconductor material for high-temperature, radiation-resistant, and high-power electronic devices. These attributes make SiC particularly suitable for application to aircraft engines. Recent proof-of-concept efforts have verified SiC's potential. Field-effect transistors have shown high-temperature operating capability from 350 C to 650 C. JFETs, MOSFETs, and MESFETs have been fabricated. Ultraviolet photodiodes with high quantum efficiencies and extremely low dark currents have been fabricated and tested. Blue light-emitting diodes are for sale in production quantities as are one-inch diameter wafers. These developments have established a sufficient level of confidence to pursue the development of devices for aircraft-engine applications.

  14. 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.

  15. Applications of Silicon Carbide for High Temperature Electronics and Sensors

    Science.gov (United States)

    Shields, Virgil B.

    1995-01-01

    Silicon carbide (SiC) is a wide bandgap material that shows great promise in high-power and high temperature electronics applications because of its high thermal conductivity and high breakdown electrical field. The excellent physical and electronic properties of SiC allows the fabrication of devices that can operate at higher temperatures and power levels than devices produced from either silicon or GaAs. Although modern electronics depends primarily upon silicon based devices, this material is not capable of handling may special requirements. Devices which operate at high speeds, at high power levels and are to be used in extreme environments at high temperatures and high radiation levels need other materials with wider bandgaps than that of silicon. Many space and terrestrial applications also have a requirement for wide bandgap materials. SiC also has great potential for high power and frequency operation due to a high saturated drift velocity. The wide bandgap allows for unique optoelectronic applications, that include blue light emitting diodes and ultraviolet photodetectors. New areas involving gas sensing and telecommunications offer significant promise. Overall, the properties of SiC make it one of the best prospects for extending the capabilities and operational regimes of the current semiconductor device technology.

  16. Field electron emission enhancement of amorphous carbon through a niobium carbide buffer layer

    Science.gov (United States)

    Xu, L.; Wang, C.; Hu, C. Q.; Zhao, Z. D.; Yu, W. X.; Zheng, W. T.

    2009-01-01

    We investigate the field electron emission for amorphous carbon (a-C) films deposited on Si (100) substrates through a niobium carbide buffer layer with different structures and find that the niobium carbide buffer layer can substantially improve the electron field emission properties of a-C films, which can be attributed to an increase in the enhancement factor β on the surface of a-C films after the insertion of the niobium carbide layer in between a-C film and substrate. Moreover, a phase transition for niobium carbide layer from hexagonal (Nb2C) to cubic (NbC) structure, revealed by x-ray diffraction, further enhances the electron field emission. The first-principles calculated results show that the work function of NbC is lower than that of Nb2C, which is the reason why the electron emission of a-C is further enhanced.

  17. 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.

  18. Role of silicon dangling bonds in the electronic properties of epitaxial graphene on silicon carbide.

    Science.gov (United States)

    Ridene, Mohamed; Kha, Calvin S; Flipse, Cees F J

    2016-03-29

    In this paper, we study the electronic properties of epitaxial graphene (EG) on silicon carbide by means of ab initio calculations based on the local spin density approximation + U method taking into account the Coulomb interaction between Si localized electrons. We show that this interaction is not completely suppressed but is screened by carbon layers grown on-top of silicon carbide. This finding leads to a good qualitative understanding of the experimental results reported on EG on silicon carbide. Our results highlight the presence of the Si localized states and might explain the anomalous Hanle curve and the high values of spin relaxation time in EG.

  19. Development of a silicon carbide sewing thread

    Science.gov (United States)

    Sawko, Paul M.; Vasudev, Anand

    1989-01-01

    A silicon carbide (SiC) sewing thread has been designed which consists of a two-ply yarn in a 122 turns-per-meter-twist construction. Two processing aids in thread construction were evaluated. Prototype blankets were sewn using an SiC thread prepared either with polytetrafluoroethylene sizing or with an overwrap of rayon/dacron service yarn. The rayon/dacron-wrapped SiC thread was stronger, as shown by higher break-strength retention and less damage to the outer-mold-line fabric. This thread enables thermal protection system articles to be sewn or joined, or have perimeter close-out of assembled parts when using SiC fabric for high-temperature applications.

  20. High Power Silicon Carbide (SiC) Power Processing Unit Development

    Science.gov (United States)

    Scheidegger, Robert J.; Santiago, Walter; Bozak, Karin E.; Pinero, Luis R.; Birchenough, Arthur G.

    2015-01-01

    NASA GRC successfully designed, built and tested a technology-push power processing unit for electric propulsion applications that utilizes high voltage silicon carbide (SiC) technology. The development specifically addresses the need for high power electronics to enable electric propulsion systems in the 100s of kilowatts. This unit demonstrated how high voltage combined with superior semiconductor components resulted in exceptional converter performance.

  1. Measurement of electron spin transport in graphene on 6H-silicon carbide(0001)

    Science.gov (United States)

    Abel, Joseph

    The focus of this thesis is to demonstrate the potential of wafer scale graphene spintronics. Graphene is a single atomic layer of sp 2-bonded carbon atoms that has high carrier mobilities, making it a desirable material for future nanoscale electronic devices. The vision of spintronics is to utilize the spin of the electron to produce novel high-speed low power consuming devices. Materials with long spin relaxation times and spin diffusion lengths are needed to realize these goals. Graphene is an ideal material as it meets these requirements and is amenable to planar device geometries. In this thesis, spin transport in wafer scale epitaxial graphene grown on the silicon face of silicon carbide is demonstrated. Non-local Hanle spin precession measurement devices were fabricated using graphene with and without a hafnium oxide interface layer between the ferromagnetic metal and graphene. The structural properties of the devices were investigated with Raman spectroscopy, x-ray photoelectric spectroscopy, Rutherford backscattering spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The electrical properties of the graphene were measured utilizing Hall transport measurements. The magnetic properties of the contacts were investigated with vibrating sample magnetometery. The processes developed to fabricate the Hanle measurement devices are presented as well. A custom Hanle measurement setup was developed and utilized for the Hanle spin precession measurements. Spin precession is observed in the epitaxial graphene on silicon carbide, with improved spin transport properties with the utilization of a hafnium oxide barrier between the ferromagnetic contacts and graphene. The charge transport and spin transport properties are compared to determine the relevant spin relaxation mechanism in the devices. These results demonstrate that graphene has great potential for wafer scale production of future spintronic devices.

  2. Development and Processing of Nickel Aluminide-Carbide Alloys

    Science.gov (United States)

    Newport, Timothy Scott

    1996-01-01

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

  3. 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.

  4. Permanent Electron Electric Dipole Moment Search in the X^3Δ_1 Ground State of Tungsten Carbide Molecules

    Science.gov (United States)

    Lee, Jeongwon; Chen, Jinhai; Leanhardt, Aaron

    2011-06-01

    We are developing an experiment to search for the permanent electric dipole moment (EDM) of the electron using the valence electrons in the X^3Δ_1 ground state of Tungsten Carbide (WC) molecules. Currently, we are detecting the molecules by Laser Induced Fluorescence spectroscopy at ˜75cm downstream of a pulsed ablation beam source. We have a detection rate of ˜10 182W12C molecules/second in X^3Δ_1, v"=0, J"=1 state with geometric detection efficiency of 0.004. A continuous WC molecular beam is under development. Additionally, preliminary measurements of the 183W12C hyperfine structure will be presented.

  5. 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.

  6. Small cluster models of the surface electronic structure and bonding properties of titanium carbide, vanadium carbide, and titanium nitride.

    Science.gov (United States)

    Didziulis, Stephen V; Butcher, Kristine D; Perry, Scott S

    2003-12-01

    Density functional theory (DFT) calculations on stoichiometric, high-symmetry clusters have been performed to model the (100) and (111) surface electronic structure and bonding properties of titanium carbide (TiC), vanadium carbide (VC), and titanium nitride (TiN). The interactions of ideal surface sites on these clusters with three adsorbates, carbon monoxide, ammonia, and the oxygen atom, have been pursued theoretically to compare with experimental studies. New experimental results using valence band photoemission of the interaction of O(2) with TiC and VC are presented, and comparisons to previously published experimental studies of CO and NH(3) chemistry are provided. In general, we find that the electronic structure of the bare clusters is entirely consistent with published valence band photoemission work and with straightforward molecular orbital theory. Specifically, V(9)C(9) and Ti(9)N(9) clusters used to model the nonpolar (100) surface possess nine electrons in virtually pure metal 3d orbitals, while Ti(9)C(9) has no occupation of similar orbitals. The covalent mixing of the valence bonding levels for both VC and TiC is very high, containing virtually 50% carbon and 50% metal character. As expected, the predicted mixing for the Ti(9)N(9) cluster is somewhat less. The Ti(8)C(8) and Ti(13)C(13) clusters used to model the TiC(111) surface accurately predict the presence of Ti 3d-based surface states in the region of the highest occupied levels. The bonding of the adsorbate species depends critically on the unique electronic structure features present in the three different materials. CO bonds more strongly with the V(9)C(9) and Ti(9)N(9) clusters than with Ti(9)C(9) as the added metal electron density enables an important pi-back-bonding interaction, as has been observed experimentally. NH(3) bonding with Ti(9)N(9) is predicted to be somewhat enhanced relative to VC and TiC due to greater Coulombic interactions on the nitride. Finally, the interaction with

  7. 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}.

  8. Thermal Enhancement of Silicon Carbide (SiC) Power Electronics and Laser Bars: Statistical Design Optimization of a Liquid-Cooled Power Electronic Heat Sink

    Science.gov (United States)

    2015-08-01

    AFRL-RQ-WP-TR-2015-0138 THERMAL ENHANCEMENT OF SILICON CARBIDE (SiC) POWER ELECTRONICS AND LASER BARS: Statistical Design Optimization of a Liquid...Cooled Power Electronic Heat Sink James D. Scofield Electrical Systems Branch Power and Control Division AUGUST2015 Final Report Approved for...CARBIDE (SiC) POWER ELECTRONICS AND LASER BARS: Statistical Design Optimization of a Liquid-Cooled Power Electronic Heat Sink 5a. CONTRACT NUMBER

  9. Development of an Extreme High Temperature n-type Ohmic Contact to Silicon Carbide

    Science.gov (United States)

    Evans, Laura J.; Okojie, Robert S.; Lukco, Dorothy

    2011-01-01

    We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 -cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 C while potentially extending operations to 1000 C. Introduction Silicon Carbide (SiC) is widely recognized as one of the materials of choice for high temperature, harsh environment sensors and electronics due to its ability to survive and continue normal operation in such environments [1]. Sensors and electronics in SiC have been developed that are capable of operating at temperatures of 600 oC. However operating these devices at the upper reliability temperature threshold increases the potential for early degradation. Therefore, it is important to raise the reliability temperature ceiling higher, which would assure increased device reliability when operated at nominal temperature. There are also instances that require devices to operate and survive for prolonged periods of time above 600 oC [2, 3]. This is specifically needed in the area of hypersonic flight where robust sensors are needed to monitor vehicle performance at temperature greater than 1000 C, as well as for use in the thermomechanical characterization of high temperature materials (e.g. ceramic matrix composites). While SiC alone can withstand these temperatures, a major challenge is to develop reliable electrical contacts to the device itself in order to facilitate signal extraction

  10. Compton scattering study on the electronic properties of niobium carbide and niobium nitride

    Science.gov (United States)

    Deb, A.; Chatterjee, A. K.

    2000-02-01

    The electronic structure, experimental Compton profile and the chemical bonding mechanism of niobium carbide and niobium nitride are studied on the basis of the band structure calculations, using a self-consistent, all-electron, linear combination of Gaussian orbitals (LCGO) calculation based on density functional theory. Isotropic Compton profiles of niobium carbide have been measured, using a conventional technique based on 59.54 keV gamma-radiation with a solid state detector. The agreement between the experimental and the theoretical momentum density is very good. It is shown that the anisotropies at low momentum are heavily influenced by the particular shape of the Fermi surface. The charge distributions resulting from valence bands in different regions of the unit cell are discussed. The limitations of the rigid band structure model are illustrated and general trends in the chemical bonding are discussed.

  11. 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.

  12. Electron heat conductivity of epitaxial graphene on silicon carbide

    Science.gov (United States)

    Alisultanov, Z. Z.; Meilanov, R. P.

    2016-08-01

    The diagonal component of the electron heat conductivity tensor of epitaxial graphene formed in a semiconductor has been investigated within a simple analytical model. It is shown that the heat conductivity sharply changes at a chemical potential close to the substrate band gap edge. Low-temperature expressions for the heat conductivity are derived.

  13. Elastic and Electronic Properties of Point Defects in Titanium Carbide

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Daebok [Kyungsung Univ., Busan (Korea, Republic of)

    2013-12-15

    A theoretical study of the electronic structures of TiC{sub 1-x} and Ti{sub -1-x}W{sub x}C (x = 0, 0.25) is presented. The density of states and crystal orbital overlap population calculations were used to interpret variations of elastic properties induced by carbon vacancies and alloying substitutions. Our results show why the introduction of vacancies into TiC reduces bulk moduli, while W substitution at a Ti site increases the elastic modulus. The effect of the point defects on the bonding in TiC is investigated by means of extended Huckel tight-binding band calculations.

  14. 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

  15. Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Behzad, Somayeh, E-mail: somayeh.behzad@gmail.co [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physical Science Research Laboratory, Department of Nano Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Chegel, Raad [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)

    2010-12-01

    The effects of boron doping on the structural and electronic properties of (6,0)-(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

  16. 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.

  17. 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.

  18. The repopulation of electronic states upon vibrational excitation of niobium carbide clusters

    Science.gov (United States)

    Chernyy, V.; Logemann, R.; Bakker, J. M.; Kirilyuk, A.

    2016-07-01

    We study the infrared (IR) resonant heating of neutral niobium carbide clusters probed through ultraviolet photoionization spectroscopy. The IR excitation not only changes the photoionization spectra for the photon energies above the ionization threshold, but also modulates ion yield for energies significantly below it. An attempt to describe the experimental spectra using either Fowler's theory or thermally populated vibrational states was not successful. However, the data can be fully modeled by vibrationally and rotationally broadened discrete electronic levels obtained from Density Functional Theory (DFT) calculations. The application of this method to spectra with different IR pulse energies not only yields information about the excited electronic states in the vicinity of the HOMO level, populated by manipulation of the vibrational coordinates of a cluster, but also can serve as an extra indicator for the cluster isomeric structure and corresponding DFT-calculated electronic levels.

  19. The repopulation of electronic states upon vibrational excitation of niobium carbide clusters.

    Science.gov (United States)

    Chernyy, V; Logemann, R; Bakker, J M; Kirilyuk, A

    2016-07-14

    We study the infrared (IR) resonant heating of neutral niobium carbide clusters probed through ultraviolet photoionization spectroscopy. The IR excitation not only changes the photoionization spectra for the photon energies above the ionization threshold, but also modulates ion yield for energies significantly below it. An attempt to describe the experimental spectra using either Fowler's theory or thermally populated vibrational states was not successful. However, the data can be fully modeled by vibrationally and rotationally broadened discrete electronic levels obtained from Density Functional Theory (DFT) calculations. The application of this method to spectra with different IR pulse energies not only yields information about the excited electronic states in the vicinity of the HOMO level, populated by manipulation of the vibrational coordinates of a cluster, but also can serve as an extra indicator for the cluster isomeric structure and corresponding DFT-calculated electronic levels.

  20. Atomic and electronic structure of molybdenum carbide phases: bulk and low Miller-index surfaces.

    Science.gov (United States)

    Politi, José Roberto dos Santos; Viñes, Francesc; Rodriguez, Jose A; Illas, Francesc

    2013-08-14

    The geometric and electronic structure of catalytically relevant molybdenum carbide phases (cubic δ-MoC, hexagonal α-MoC, and orthorhombic β-Mo2C) and their low Miller-index surfaces have been investigated by means of periodic density functional theory (DFT) based calculations with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. Comparison to available experimental data indicates that this functional is particularly well suited to study these materials. The calculations reveal that β-Mo2C has a stronger metallic character than the other two polymorphs, both β-Mo2C and δ-MoC have a large ionic contribution, and δ- and α-MoC exhibit the strongest covalent character. Among the various surfaces explored, the calculations reveal the high stability of the δ-MoC(001) nonpolar surface, Mo- and C-terminated (001) polar surfaces of α-MoC, and the nonpolar (011) surface of β-Mo2C. A substantially low work function of only 3.4 eV is predicted for β-Mo2C(011), suggesting that this system is particularly well suited for (electro)catalytic processes where surface → adsorbate electron transfer is essential. The overall implications for heterogeneously catalysed reactions by these molybdenum carbide nanoparticles are also discussed.

  1. Electronic stopping for protons and α particles from first-principles electron dynamics: The case of silicon carbide

    Science.gov (United States)

    Yost, Dillon C.; Kanai, Yosuke

    2016-09-01

    We present the first-principles determination of electronic stopping power for protons and α particles in a semiconductor material of great technological interest: silicon carbide. The calculations are based on nonequilibrium simulations of the electronic response to swift ions using real-time, time-dependent density functional theory (RT-TDDFT). We compare the results from this first-principles approach to those of the widely used linear response formalism and determine the ion velocity regime within which linear response treatments are appropriate. We also use the nonequilibrium electron densities in our simulations to quantitatively address the longstanding question of the velocity-dependent effective charge state of projectile ions in a material, due to its importance in linear response theory. We further examine the validity of the recently proposed centroid path approximation for reducing the computational cost of acquiring stopping power curves from RT-TDDFT simulations.

  2. 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.

  3. Model creation and electronic structure calculation of amorphous hydrogenated boron carbide

    Science.gov (United States)

    Belhadj Larbi, Mohammed

    Boron-rich solids are of great interest for many applications, particularly, amorphous hydrogenated boron carbide (a-BC:H) thin films are a leading candidate for numerous applications such as: heterostructure materials, neutron detectors, and photovoltaic energy conversion. Despite this importance, the local structural properties of these materials are not well-known, and very few theoretical studies for this family of disordered solids exist in the literature. In order to optimize this material for its potential applications the structure property relationships need to be discovered. We use a hybrid method in this endeavor---which is to the best of our knowledge the first in the literature---to model and calculate the electronic structure of amorphous hydrogenated boron carbide (a-BC:H). A combination of classical molecular dynamics using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) and ab initio quantum mechanical simulations using the Vienna ab initio simulation package (VASP) have been conducted to create geometry optimized models that consist of a disordered hydrogenated twelve-vertex boron carbide icosahedra, with hydrogenated carbon cross-linkers. Then, the density functional theory (DFT) based orthogonalized linear combination of atomic orbitals (OLCAO) method was used to calculate the total and partial density of states (TDOS, PDOS), the complex dielectric function epsilon, and the radial pair distribution function (RPDF). The RPDF data stand as predictions that may be compared with future experimental electron or neutron diffraction data. The electronic structure simulations were not able to demonstrate a band gap of the same nature as that seen in prior experimental work, a general trend of the composition-properties relationship was established. The content of hydrogen and boron was found to be directly proportional to the decrease in the number of available states near the fermi energy, and inversely proportional to the

  4. 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.

  5. Thermal Transport in Refractory Carbides.

    Science.gov (United States)

    Thermal energy transport mechanisms in titanium carbide and zirconium carbide have been studied. Several compositions of vanadium carbide alloyed...with titanium carbide were used. The electronic component of the thermal conductivity exceeded the values computed using the classical value for L in

  6. Structural feature and electronic property of an (8, 0)carbon-silicon carbide nanotube heterojunction

    Institute of Scientific and Technical Information of China (English)

    Liu Hong-Xia; Zhang He-Ming; Hu Hui-Yong; Song Jiu-Xu

    2009-01-01

    A supercell of a nanotube heterojunction formed by an (8, 0) carbon nanotube (CNT) and an (8, 0) silicon carbide nanotube (SiCNT) is established, in which 96 C atoms and 32 Si atoms are included. The geometry optimization and the electronic property of the heterojunction are implemented through the first-principles calculation based on the density functional theory (DFT). The results indicate that the structural rearrangement takes place mainly on the interface and the energy gap of the heterojunetion is 0.31 eV, which is narrower than those of the isolated CNT and the isolated SiCNT. By using the average bond energy method, the valence band offset and the conduction band offset axe obtained as 0.71 and -0.03eV, respectively.

  7. Ab initio density functional theory investigation of structural and electronic properties of silicon carbide nanotube bundles

    Energy Technology Data Exchange (ETDEWEB)

    Moradian, Rostam [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Department of Nano Science, Computational Physical Science Research Laboratory, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: moradian.rostam@gmail.com; Behzad, Somayeh; Chegel, Raad [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)

    2008-10-01

    By using ab initio density functional theory the structural and electronic properties of isolated and bundled (8,0) and (6,6) silicon carbide nanotubes (SiCNTs) are investigated. Our results show that for such small diameter nanotubes the inter-tube interaction causes a very small radial deformation, while band splitting and reduction of the semiconducting energy band gap are significant. We compared the equilibrium interaction energy and inter-tube separation distance of (8,0) SiCNT bundle with (10,0) carbon nanotube (CNT) bundle where they have the same radius. We found that there is a larger inter-tube separation and weaker inter-tube interaction in the (8,0) SiCNT bundle with respect to (10,0) CNT bundle, although they have the same radius.

  8. Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics.

    Science.gov (United States)

    Hertel, S; Waldmann, D; Jobst, J; Albert, A; Albrecht, M; Reshanov, S; Schöner, A; Krieger, M; Weber, H B

    2012-07-17

    Graphene is an outstanding electronic material, predicted to have a role in post-silicon electronics. However, owing to the absence of an electronic bandgap, graphene switching devices with high on/off ratio are still lacking. Here in the search for a comprehensive concept for wafer-scale graphene electronics, we present a monolithic transistor that uses the entire material system epitaxial graphene on silicon carbide (0001). This system consists of the graphene layer with its vanishing energy gap, the underlying semiconductor and their common interface. The graphene/semiconductor interfaces are tailor-made for ohmic as well as for Schottky contacts side-by-side on the same chip. We demonstrate normally on and normally off operation of a single transistor with on/off ratios exceeding 10(4) and no damping at megahertz frequencies. In its simplest realization, the fabrication process requires only one lithography step to build transistors, diodes, resistors and eventually integrated circuits without the need of metallic interconnects.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Yuri, E-mail: yufi55@mail.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 2/3 Akademicheskiy Ave. Tomsk, 634055 (Russian Federation); National Research Tomsk State University, 36 Lenina Str., Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenina Str., Tomsk, 634050 (Russian Federation); Tolkachev, Oleg, E-mail: ole.ts@mail.ru; Petyukevich, Maria, E-mail: petukevich@tpu.ru; Polisadova, Valentina, E-mail: polis@tpu.ru [National Research Tomsk Polytechnic University, 30 Lenina Str., Tomsk, 634050 (Russian Federation); Teresov, Anton, E-mail: tad514@sibmail.com [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 2/3 Akademicheskiy Ave. Tomsk, 634055 (Russian Federation); National Research Tomsk State University, 36 Lenina Str., Tomsk, 634050 (Russian Federation); Ivanova, Olga, E-mail: ivaov@mail.ru; Ikonnikova, Irina, E-mail: irina-ikonnikova@yandex.ru [Tomsk State University of Architecture and Building, 2 Solyanaya Sq., Tomsk, 634003 (Russian Federation)

    2016-01-15

    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/cm{sup 2}, 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.

  10. 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.

  11. 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.

  12. Electronic fine structure in the nickel carbide superconductor Th2NiC2

    Science.gov (United States)

    Quan, Y.; Pickett, W. E.

    2013-07-01

    The recently reported nickel carbide superconductor body centered tetragonal I4/mmm Th2NiC2 with Tc=8.5 K increasing to 11.2 K upon alloying Th with Sc is found to have very fine structure in its electronic spectrum, according to density functional based first-principles calculations. The filled Ni 3d band complex is hybridized with C 2p and Th character to and through the Fermi level (EF), and a sharply structured density of states arises only when spin-orbit coupling is included, which splits a zone-center degeneracy, leaving a very flat band edge lying at the Fermi level. The flat part of the band corresponds to an effective mass mz*→∞ with large and negative mx*=my*. Although the region over which the effective mass characterization applies is less than 1% of the zone volume, it supplies on the order of half the states at (or just above) the Fermi level. The observed increase of Tc by hole doping is accounted for if the reference as-synthesized sample is minutely hole doped, which decreases the Fermi level density of states and will provide some stabilization. In this scenario, electron doping will increase the Fermi level density of states and the superconducting critical temperature. Vibrational properties are presented, and enough coupling to the C-Ni-C stretch mode at 70 meV is obtained to imply that superconductivity is electron-phonon mediated.

  13. 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...

  14. Tunable electronic and optical behaviors of two-dimensional germanium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhuo; Li, Yangping, E-mail: liyp@nwpu.edu.cn; Li, Chenxi; Liu, Zhengtang

    2016-03-30

    Graphical abstract: In-plane and biaxial strain effects can provide a wide band gap engineering and new options of interband transitions for 2d-GeC in application of optoelectronic devices. - Highlights: • Tunable band structures when in-plane strain is applied on monolayer GeC. • Tunable electronic and optical properties of bilayer under strain along the c axis. • Tunable band structures are observed in multilayer GeC. - Abstract: The electronic and optical properties of two-dimensional graphene-like germanium carbide (2D-GeC) are calculated using first-principle calculation based on density functional theory. Monolayer GeC has a direct band gap of 2.19 eV. The imaginary part of the dielectric function shows a wide energy range of absorption spectrum for monolayer GeC. Tunable band structures are found for monolayer GeC through in-plane strain. In addition, the band structures and optical properties of bilayer GeC under strain along the c axis are analyzed. Multilayer GeC exhibits a direct band gap like monolayer GeC, and new options of interband transitions are found between layers. The results suggest that 2D-GeC could be a good candidate for optoelectronic such as light-emitting diodes, photodiodes, and solar cells.

  15. 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:

  16. 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...

  17. Silicon carbide, an emerging high temperature semiconductor

    Science.gov (United States)

    Matus, Lawrence G.; Powell, J. Anthony

    1991-01-01

    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.

  18. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-11-15

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

  1. Development and characterization of nickel based tungsten carbide laser cladded coatings

    Science.gov (United States)

    Rombouts, Marleen; Persoons, Rosita; Geerinckx, Eric; Kemps, Raymond; Mertens, Myrjam; Hendrix, Willy; Chen, Hong

    Laser cladded coatings consisting of various types of tungsten carbides embedded in a NiCrBSiCFe matrix are characterized. At optimal process parameters crack-free coatings with a thickness of 0.85-1 mm, excellent bonding with the substrate, carbide concentrations up to 60 wt% and a hardness in the range of 40-55 HRC are obtained. During laser cladding the carbides have partly dissolved in the matrix as indicated by the presence of dispersed carbides in the matrix and by a carbide phase growing into the matrix along the edges of the particles. The wear coefficient during sliding contact decreases logarithmically with increasing carbide concentration.

  2. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cappelli, E., E-mail: emilia.cappelli@imip.cnr.it [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Bellucci, A. [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Orlando, S. [CNR-IMIP sez. Potenza, 85050 Tito Scalo, Potenza (Italy); Trucchi, D.M. [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Mezzi, A. [CNR-ISMN, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Valentini, V. [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy)

    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 (CH{sub 4}/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.

  4. The bainite transformation and the carbide precipitation of 4.88% aluminium austempered ductile iron investigated using electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kiani-Rashid, A.R. [Department of Materials Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, P.O. Box 91775-1111, Mashhad (Iran, Islamic Republic of)], E-mail: fkiana@yahoo.com

    2009-04-17

    The transformation to a bainitic microstructure during austempering under different conditions was examined for the most successful of the experimental casts. Austenitising temperature of 920 deg. C and austempering temperature of 350 deg. C for different holding times have been used. Microstructures have been examined by SEM and transmission electron microscopy (TEM). It was found that isothermal transformation at 350 deg. C for different soaking times gave a typical bainitic microstructure that increased with increasing austempering time. Extension of isothermal transformation time leads to precipitation of carbides which also depended on the bainitic phase transformation.

  5. Development of boron carbide-copper cermets. Status report

    Energy Technology Data Exchange (ETDEWEB)

    1979-09-01

    The status of a program to develop a B/sub 4/C-Cu cermet for Breeder Reactor spent-fuel shipping cask neutron shields is presented. It is shown that inspectable 6 to 7 cm thick 60 to 70 volume percent B/sub 4/C cermets can be fabricated using hot isostatic powder processing procedures. An alternative manufacturing method, rheocasting, also appears to be a promising, perhaps more cost-effective method for producing these cermets. Recommendations for further development of these manufacturing processes are given.

  6. Titanium Carbide: Nanotechnology, Properties, Application

    OpenAIRE

    Galevsky, G. V.; Rudneva, V. V.; Garbuzova, A. K.; Valuev, Denis Viktorovich

    2015-01-01

    The paper develops scientific and technological bases for fabrication of titanium carbide which is a nanocomponent of composite materials. The authors determine optimum technology specifications and the main titanium carbide properties: fineness of titaniferous raw materials, carbide-forming agent quantity, set temperature of plasma flow, tempering temperature, titanium carbide yield, productivity, specific surface, size and shape of particles. The paper includes equations to describe how the...

  7. Growth and Characterization of Silicon Carbide (SiC) Nanowires by Chemical Vapor Deposition (CVD) for Electronic Device Applications

    Science.gov (United States)

    Moore, Karina

    In recent years nanowires have gained a generous amount of interest because of the possible application of nanowires within electronic devices. A nanowire is a one dimensional semiconductor nanostructure with a diameter less than 100 nm. Nanowires have the potential to be a replacement for the present day complimentary metal oxide semiconductor (CMOS) technology; it is believed by 2020, a 5--6 nm gate length within field effect transistors (FET) would be realized and cease further miniaturization of electronic devices. SiC processes several unique chemical and physical properties that make it an attractive alternative to Si as a semiconductor material. Silicon carbide's properties make it a perfect candidate for applications such as high temperature sensors, x-ray emitters and high radiation sensors. The main objective of this thesis is to successfully grow silicon carbide nanowires on silicon substrates with the assistance of a metal catalyst, by the process of chemical vapor deposition (CVD). The contributions made by the work carried out in this thesis are broad. This is the first study that has carried out a comprehensive investigation into a wide range of metal catalyst for the growth of SiC nanowires by the process of chemical vapor deposition. The study proved that the surface tension interactions between the silicon substrate and the metal catalyst are the controlling factor in the determination of the diameter of the nanowires grown. This study also proved that the silicon substrate orientation has no impact on the growth of the nanowires, similar growth patterns occurred on both Si and Si substrates. The nanowires grown were characterized by a variety of different methods including scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and raman spectroscopy. The effect of temperature, growth temperature, growth time and the catalyst type used are investigated to determine the most suitable conditions necessary for SiC nanowire

  8. 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.

  9. Interface structure of niobium carbide-encapsulating carbon nanocapsules studied by high-resolution transmission electron microscopy.

    Science.gov (United States)

    Kizuka, Tokushi; Koizumi, Haruki

    2014-04-01

    Carbon nanocapsules (CNCs) encapsulating niobium carbide (NbC) crystals with a sodium chloride structure were synthesized via a gas-evaporation method by arc-discharge heating. CNCs were observed by high-resolution transmission electron microscopy, and the atomic configurations at the graphene/NbC interfaces were investigated. The NbC crystals within the nanospaces of CNCs were truncated by the {100}, {110}, and (111} facets and were coated with several graphene layers. It was found that the interlayer spacings for the graphene{0001}/NbC{100} and graphene{0001}/NbC{110} interfaces were 0.33 +/- 0.05 nm, whereas those for the graphene{0001}/{111}NbC interfaces were 0.28 +/- 0.05 nm.

  10. Small signal modeling of high electron mobility transistors on silicon and silicon carbide substrate with consideration of substrate loss mechanism

    Science.gov (United States)

    Sahoo, A. K.; Subramani, N. K.; Nallatamby, J. C.; Sylvain, L.; Loyez, C.; Quere, R.; Medjdoub, F.

    2016-01-01

    In this paper, we present a comparative study on small-signal modeling of AlN/GaN/AlGaN double hetero-structure high electron mobility transistors (HEMTs) grown on silicon (Si) and silicon carbide (SiC) substrate. The traditional small signal equivalent circuit model is modified to take into account the transmission loss mechanism of coplanar waveguide (CPW) line which cannot be neglected at high frequencies. CPWs and HEMTs-on-AlN/GaN/AlGaN epitaxial layers are fabricated on both the Si and SiC substrates. S-parameter measurements at room temperature are performed over the frequency range from 0.5 GHz to 40 GHz. Transmission loss of CPW lines are modeled with a distributed transmission line (TL) network and an equivalent circuit model is included in the small-signal transistor model topology. Measurements and simulations are compared and found to be in good agreement.

  11. 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.

  12. 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.

  13. Titanium Carbide: Nanotechnology, Properties, Application

    Science.gov (United States)

    Galevsky, G. V.; Rudneva, V. V.; Garbuzova, A. K.; Valuev, D. V.

    2015-09-01

    The paper develops scientific and technological bases for fabrication of titanium carbide which is a nanocomponent of composite materials. The authors determine optimum technology specifications and the main titanium carbide properties: fineness of titaniferous raw materials, carbide-forming agent quantity, set temperature of plasma flow, tempering temperature, titanium carbide yield, productivity, specific surface, size and shape of particles. The paper includes equations to describe how the major specifications of the fabrication technique influence the content of titanium carbide and free carbon in the end product.

  14. Thermal degradation study of silicon carbide threads developed for advanced flexible thermal protection systems

    Science.gov (United States)

    Tran, Huy Kim; Sawko, Paul M.

    1992-01-01

    Silicon carbide (SiC) fiber is a material that may be used in advanced thermal protection systems (TPS) for future aerospace vehicles. SiC fiber's mechanical properties depend greatly on the presence or absence of sizing and its microstructure. In this research, silicon dioxide is found to be present on the surface of the fiber. Electron Spectroscopy for Chemical Analysis (ESCA) and Scanning Electron Microscopy (SEM) show that a thin oxide layer (SiO2) exists on the as-received fibers, and the oxide thickness increases when the fibers are exposed to high temperature. ESCA also reveals no evidence of Si-C bonding on the fiber surface on both as-received and heat treated fibers. The silicon oxide layer is thought to signal the decomposition of SiC bonds and may be partially responsible for the degradation in the breaking strength observed at temperatures above 400 C. The variation in electrical resistivity of the fibers with increasing temperature indicates a transition to a higher band gap material at 350 to 600 C. This is consistent with a decomposition of SiC involving silicon oxide formation.

  15. Microstructure and mechanical properties of WC-Ni-Al based cemented carbides developed for engineering applications

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Edmilson O.; Santos, Julio N. [Universidade Federal de Itajuba, Minas Gerais (Brazil). Inst. de Engenharia Mecanica; Klein, Aloisio N. [Universidade Federal de Santa Catarina, Florianopolis (Brazil). Dept. de Engenharia de Materiais

    2011-11-15

    In this paper the influence of the Ni binder metal and Al as an additional alloying element on the microstructure and mechanical properties of WC-based cemented carbides processed by conventional powder metallurgy was studied. Microstructural examinations of the cemented carbides with 3 and 5 wt.% of Al in the binder metal indicated the presence of a very low and evenly distributed porosity as well as the presence of islands of metal binder in the microstructure. With the cemented carbide with 7 wt.% of Al in the metal binder, the presence of brittle needle-like regions was observed. The WC particles inside these regions were rounded and had a larger mean free path. Vickers hardness and flexural strength tests indicated that the cemented carbide WC-Ni - Al with addition of 5 wt.% of Al in the binder metal presented bulk hardness similar to the conventional WC-Co cemented carbides as well as superior flexure strength and fracture toughness. (orig.)

  16. Valance electron structure of carbide-diamond interface and catalytic mechanism for diamond synthesis under high-pressure and high-temperature

    Institute of Scientific and Technical Information of China (English)

    GONG Jianhong; XU Bin; YIN Longwei; QI Yongxin; LI Li; SU Qingcai; LI Musen

    2006-01-01

    The metallic films surrounding a synthetic diamond formed under high-pressure and high-temperature (HPHT) in the presence of Fe-based and Ni-based catalysts were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was showed that the carbide was the primary carbon source for the nucleation and growth of diamond. Based on the EET (empirical electron theory in solid and molecules) theory, the valence electron structure of interface between carbide (Fe3C, Ni3C, (Fe, Ni)3C) and diamond was calculated using the bonding length difference (BLD) method. The boundary criterion of Thomas-Fermi-Dirac-Cheng (TFDC): "the electron density being equal on the contacting surfaces of atoms" was applied to analyze the valence structure of carbide-diamond interface. The result based on the calculation valance electron structure is in good accordance with the experimental result. This study is very helpful to reveal the catalytic mechanism of diamond nucleation and growth and design the new catalyst for diamond synthesis.

  17. Single-Event Effects in Silicon Carbide Power Devices

    Science.gov (United States)

    Lauenstein, Jean-Marie; Casey, Megan C.; LaBel, Kenneth A.; Ikpe, Stanley; Topper, Alyson D.; Wilcox, Edward P.; Kim, Hak; Phan, Anthony M.

    2015-01-01

    This report summarizes the NASA Electronic Parts and Packaging Program Silicon Carbide Power Device Subtask efforts in FY15. Benefits of SiC are described and example NASA Programs and Projects desiring this technology are given. The current status of the radiation tolerance of silicon carbide power devices is given and paths forward in the effort to develop heavy-ion single-event effect hardened devices indicated.

  18. 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

  19. Paste development and co-sintering test of zirconium carbide and tungsten in freeze-form extrusion fabrication

    Science.gov (United States)

    Li, Ang

    Ultra-high temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as oxidation resistance, at temperatures above 2000°C. However, their brittle properties make them susceptible to thermal shock failure. Components fabricated as functionally graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal by fabricating graded composites. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGMs parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and W were developed and utilized in the FEF process to fabricate test bars graded from 100%ZrC to 50%W-50%ZrC (volume percent). Following FEF processing the test bars were co-sintered at 2300°C and characterized to determine their resulting density and micro-structure. Four-point bending tests were performed to assess the strength of test bars made using the FEF process, compared to test bars prepared using conventional powder processing and isostatic pressing techniques, for five distinct ZrC-W compositions. Scanning electron microscopy (SEM) was used to verify the inner structure of composite parts built using the FEF process.

  20. Tailoring the Electronic and Magnetic Properties of Two-Dimensional Silicon Carbide Sheets and Ribbons by Fluorination

    KAUST Repository

    Shi, Zhiming

    2016-07-12

    Fluorination has been instrumental for tuning the properties of several two-dimensional (2D) materials, including graphene, h-BN, and MoS2. However, its potential application has not yet been explored in 2D silicon carbide (SiC), a promising material for nanoelectronic devices. We investigate the structural, electronic, and magnetic properties of fully and partially fluorinated 2D SiC sheets and nanoribbons by means of density functional theory combined with cluster expansion calculations. We find that fully fluorinated 2D SiC exhibits chair configurations and a nonmagnetic semiconducting behavior. Fluorination is shown to be an efficient approach for tuning the band gap. Four ground states of partially fluorinated SiC, SiCF2x with x = 0.0625, 0.25, 0.5, 0.75, are obtained by cluster expansion calculations. All of them exhibit nanoroad patterns, with the x = 0.5 structure identified as the most stable one. The x = 0.0625 structure is a nonmagnetic metal, while the other three are all ferromagnetic half-metals, whose properties are not affected by the edge states. We propose an effective approach for modulating the electronic and magnetic behavior of 2D SiC, paving the way to applications of SiC nanostructures in integrated multifunctional and spintronic nanodevices. © 2016 American Chemical Society.

  1. Electronic Portfolios for Faculty Development.

    Science.gov (United States)

    Heath, Marilyn; Cockerham, Steve

    This paper examines the conceptual process of creating an electronic professional portfolio for faculty development. The characteristics of electronic professional portfolios and the benefits of electronic portfolio development are discussed. Additional topics covered include: collection and selection of portfolio contents; reflection on portfolio…

  2. Development of a model of silicon carbide thermodestruction for preparation of graphite layers

    Science.gov (United States)

    Davydov, S. Yu.; Lebedev, A. A.; Smirnova, N. Yu.

    2009-03-01

    A three-stage scheme of the silicon carbide thermodestruction resulting in surface graphitization, which was proposed earlier (based on structural studies), is discussed. A theoretical analysis shows, however, that this process occurs in two stages, namely, thermodesorption of silicon atoms from the two outer Si-C bilayers followed by condensation of carbon atoms on the Si(0001) face of silicon carbide, thus giving rise to the formation of a two-dimensional graphite structure (graphene).

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

    Energy Technology Data Exchange (ETDEWEB)

    Shannon M. Bragg-Sitton

    2013-09-01

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

  4. 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.

  5. Ab initio electronic transport study of two-dimensional silicon carbide-based p–n junctions

    Science.gov (United States)

    Zhou, Hanming; Lin, Xiao; Guo, Hongwei; Lin, Shisheng; Sun, Yiwei; Xu, Yang

    2017-03-01

    Two-dimensional silicon carbide (2d-SiC) is a viable material for next generation electronics due to its moderate, direct bandgap with huge potential. In particular, its potential for p–n junctions is yet to be explored. In this paper, three types of 2d-SiC-based p–n junctions with different doping configuration are modeled. The doping configurations refer to partially replacing carbon with boron or nitrogen atoms along the zigzag or armchair direction, respectively. By employing density functional theory, we calculate the transport properties of the SiC based p–n junctions and obtain negative differential resistance and high rectification ratio. We also find that the junction along the zigzag direction with lower doping density exhibits optimized rectification performance. Our study suggests that 2d-SiC is a promising candidate as a material platform for future nano-devices. Project supported by the National Science Foundation of China (Nos. 61474099, 61674127) and the ZJ-NSF (No. Z17F04003).

  6. 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.

  7. Mechanical and electronic properties of P4{sub 2}/mnm silicon carbides

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Quan; Fan, Qingyang; Zhang, Junqin [Xidian Univ., Xi' an (China). School of Microelectronics; Wei, Qun; Zhu, Xuanmin [Xidian Univ., Xi' an (China). School of Physics and Optoelectronic Engineering; Yan, Haiyan [Univ. of Arts and Sciences, Baoji (China). School of Chemistry and Chemical Engineering; Zhang, Dongyun [National Supercomputing Center, Shenzhen (China)

    2016-08-01

    Two new phases of Si{sub 8}C{sub 4} and Si{sub 4}C{sub 8} with the P4{sub 2}/mnm symmetry are proposed. Using first principles calculations based on density functional theory, the structural, elastic, and electronic properties of Si{sub 8}C{sub 4} and Si{sub 4}C{sub 8} are studied systematically. Both Si{sub 8}C{sub 4} and Si{sub 4}C{sub 8} are proved to be mechanically and dynamically stable. The elastic anisotropies of Si{sub 8}C{sub 4} and Si{sub 4}C{sub 8} are studied in detail. Electronic structure calculations show that Si{sub 8}C{sub 4} and Si{sub 4}C{sub 8} are indirect semiconductors with the band gap of 0.74 and 0.15 eV, respectively.

  8. Stacking disorder in silicon carbide supported cobalt crystallites: an X-ray diffraction, electron diffraction and high resolution electron microscopy study.

    Science.gov (United States)

    du Plessis, H E; de Villiers, J P R; Tuling, A; Olivier, E J

    2016-11-21

    Supported cobalt Fischer-Tropsch catalysts are characteristically nanoparticulate and the reduced SiC supported catalyst was found to contain both HCP and FCC polymorphs. This is reflected in the powder XRD patterns and generally there is a poor fit between the experimental and calculated diffractograms. This was ascribed to small crystallite sizes and the occurrence of disorder, manifested as peak broadening and peak shifts. Selected area electron diffraction data of suitably oriented cobalt catalyst grains on silicon carbide supports show non-periodic disorder in the zone axis orientations that contain the common (001) (HCP) and (111) (FCC) reciprocal lattice planes. Both FCC and HCP polymorphs are present in the same grains and these show disorder mainly in the HCP component. The disorder is further examined using high angle annular dark field (HAADF) scanning transmission electron microscopy at atomic resolution and the stacking sequences elucidated. Random sequences of mainly FCC are interrupted by HCP sequences and twin surfaces with reverse stacking sequences are also present. This study highlights the presence of significant disorder in cobalt catalyst grains confirmed by HAADF microscopy.

  9. 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.

  10. 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...

  11. 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

  12. 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.

  13. 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....

  14. 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...

  15. Tribological performance evaluation of tungsten carbide-based cermets and development of a fracture mechanics wear model

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, R.B. [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.; Conway, J.C. Jr. [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.; Amateau, M.F. [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.; Brezler, R.A. III [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.

    1996-12-15

    Tungsten carbide tools may exhibit sudden brittle fracture at high stresses such as are encountered in shear and slitter knives. This has limited the use of tungsten carbide tools to certain applications in spite of their high hardness and wear resistance. The objective of this investigation is to evaluate the tribological performance of selected cermets and develop a fracture mechanics wear model. Six compositions of WC-Co materials (Co ranging from 4 to 30% by weight) with or without TiC, NbC, TaC, or Mo{sub 2}C were selected for relating wear modes of these tool materials to pertinent mechanical properties such as fracture toughness and hardness. The influence of mechanical properties such as Young`s modulus, hardness, fracture toughness, modulus of rupture, and Weibull modulus on wear rates and wear modes of the selected materials is presented and discussed. The major mechanisms of wear in WC-Co materials are discussed as they apply to the development of suitable relationships between wear and mechanical properties. The wear process is by the transfer of steel from the ring to the cemented carbide block specimens, initiation of mode I cracks normal to the mating surface, propagation of mode II cracks parallel to the wear surfaces and the subsequent separation of platelets with adhered WC and Co particles through adhesive forces with the steel ring. The wear rates of the cermets do not show a consistent relationship with mode I or mode II fracture toughness, but a general trend of decreasing wear rate with hardness is seen. This suggests that the tribological performance of these cermets depends on certain specific functions of pertinent parameters including fracture toughness, hardness, applied load, coefficient of friction and microstructural characteristics. A fracture mechanics-based wear model has been developed to relate the steady state wear rate (W{sub ss}) to hardness, mode II fracture toughness, coefficient of friction, and applied load. (orig./MM)

  16. 钢结硬质合金的研究进展%Latest development of steel bonded cemented carbide

    Institute of Scientific and Technical Information of China (English)

    周书助; 兰登飞; 鄢玲利; 尹绍峰

    2015-01-01

    The relationship of the composition, microstructures and performance has been systematically elaborated. The main preparation technology of steel bonded carbide is summarized, and it is pointed that the powder metallurgy has been widely adopted to produce steel bonded carbide. However, due to the lower cost and better performance, electroslag melting and casting, self-propagating high temperature synthesis (SHS) and carbothermal reduction methods are full of vitality. In addition, forging and heat treatment can effectively improve the structure and performance of the alloy; Boriding, boron-sulphurizing treating process and laser cladding process can improve the surface hardness, reduce the friction coefficient and increase the service life. Finally, the development trend of steel bonded carbide is prospected.%该文较系统地阐述钢结硬质合金的成分、组织和性能之间的关系,综述钢结硬质合金的主要制备方法,指出粉末冶金法是最常用的制备方法,而电冶熔铸、自蔓延高温合成(SHS)和碳热还原法等工艺因更低的成本和更优的性能而展现出蓬勃生机.此外,锻造和热处理能够有效改善组织,提高合金性能;渗硼、硼?硫复合渗和激光熔覆等表面处理能提高合金的表面硬度,减小摩擦因数,提高使用寿命.最后,展望钢结硬质合金的发展方向.

  17. 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

  18. 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.

  19. 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......, 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 considered TMC(111......C, 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 results...

  20. Studies of silicon carbide and silicon carbide nitride thin films

    Science.gov (United States)

    Alizadeh, Zhila

    Silicon carbide semiconductor technology is continuing to advance rapidly. The excellent physical and electronic properties of silicon carbide recently take itself to be the main focused power device material for high temperature, high power, and high frequency electronic devices because of its large band gap, high thermal conductivity, and high electron saturation drift velocity. SiC is more stable than Si because of its high melting point and mechanical strength. Also the understanding of the structure and properties of semiconducting thin film alloys is one of the fundamental steps toward their successful application in technologies requiring materials with tunable energy gaps, such as solar cells, flat panel displays, optical memories and anti-reflecting coatings. Silicon carbide and silicon nitrides are promising materials for novel semiconductor applications because of their band gaps. In addition, they are "hard" materials in the sense of having high elastic constants and large cohesive energies and are generally resistant to harsh environment, including radiation. In this research, thin films of silicon carbide and silicon carbide nitride were deposited in a r.f magnetron sputtering system using a SiC target. A detailed analysis of the surface chemistry of the deposited films was performed using x-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy whereas structure and morphology was studied atomic force microscopy (AFM), and nonoindentation.

  1. The effects of the formation of Stone-Wales defects on the electronic and magnetic properties of silicon carbide nanoribbons: a first-principles investigation.

    Science.gov (United States)

    Guan, Jia; Yu, Guangtao; Ding, Xiuling; Chen, Wei; Shi, Zhiming; Huang, Xuri; Sun, Chiachung

    2013-08-26

    Detailed first-principles density functional theory (DFT) computations were performed to investigate the geometries, the electronic, and the magnetic properties of both armchair-edged silicon carbide nanoribbons (aSiCNRs) and zigzag-edged silicon carbide nanoribbons (zSiCNRs) with Stone-Wales (SW) defects. SW defects in the center of aSiCNRs can remarkably reduce their band gaps, irrespective of the orientation of the defect, whereas zSiCNRs with SW defects in the center or at the edges exhibit degenerate energies of their ferromagnetic (FM) and antiferromagnetic (AFM) states, in which metallic and half-metallic behavior can be observed, respectively; half-metallic behavior can even be observed in both the FM and AFM states simultaneously. Further, it was shown that the formation energies of the SW defects in SiCNRs are orientation dependent, and the formation of edge defects is always favored over the formation of interior defects in zSiCNRs. The possible existence of SW defects in SiCNRs was further validated through exploring the kinetic process of their formation. These findings can be anticipated to provide valuable information in promoting the potential applications of SiC-based nanomaterials in multifunctional and spintronic nanodevices.

  2. 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.

  3. 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.

  4. Development of a Silicon Carbide Molecular Beam Nozzle for Simulation Planetary Flybys and Low-Earth Orbit

    Science.gov (United States)

    Patrick, E. L.; Earle, G. D.; Kasprzak, W. T.; Mahaffy, Paul R.

    2008-01-01

    From commercial origins as a molybdenum molecular beam nozzle, a ceramic nozzle of silicon carbide (SiC) was developed for space environment simulation. The nozzle is mechanically stable under extreme conditions of temperature and pressure. A heated, continuous, supersonically-expanded hydrogen beam with a 1% argon seed produced an argon beam component of nearly 4 km/s, with an argon flux exceeding 1x1014 /cm2.s. This nozzle was part of a molecular beam machine used in the Atmospheric Experiments Branch at NASA Goddard Space Flight Center to characterize the performance of the University of Texas at Dallas Ram Wind Sensor (RWS) aboard the Air Force Communications/Navigation Outage Forecasting System (C/NOFS) launched in the Spring of 2008.

  5. Q-Band (45 GHz) Microwave Integrated Circuit Power Amplifier Designs Submitted to TriQuint Semiconductor for Fabrication with 0.15-micron High-Electron-Mobility Transistors (HEMT) Using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC)

    Science.gov (United States)

    2013-09-01

    Electron-Mobility Transistors (HEMT) Using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC) by John E. Penn ARL-TN-0574 September 2013...µm High-Electron-Mobility Transistors (HEMT) Using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC) John E. Penn Sensors and Electron Devices...with 0.15-µm High- Electron-Mobility Transistors (HEMT) Using 2-mil Gallium Nitride (GaN) on Silicon Carbide (SiC) 5a. CONTRACT NUMBER 5b. GRANT

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-01-15

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

  7. Development of high current electron beam generator

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byeong Cheol; Lee, Jong Min; Kim, Sun Kook [and others

    1997-05-01

    A high-current electron beam generator has been developed. The energy and the average current of the electron beam are 2 MeV and 50 mA, respectively. The electron beam generator is composed of an electron gun, RF acceleration cavities, a 260-kW RF generator, electron beam optics components, and control system, etc. The electron beam generator will be used for the development of a millimeter-wave free-electron laser and a high average power infrared free-electron laser. The machine will also be used as a user facility in nuclear industry, environment industry, semiconductor industry, chemical industry, etc. (author). 15 tabs., 85 figs.

  8. 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.

  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. Titanium Carbide-Graphite Composites

    Science.gov (United States)

    1991-11-08

    titanium carbide , titanium carbide with free graphite, titanium carbide /vanadium carbide alloy with free graphite, and titanium carbide with...from melts. The test pins were drawn across hot pressed titanium carbide wear plates with 5 newtons of normal force. The lowest friction coefficient at...22 C was 0.12 obtained with pure titanium carbide . The lowest friction coefficient at 900 C was 0.19 obtained with titanium carbide with boron and

  11. 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.

  12. Delivering carbide ligands to sulfide-rich clusters.

    Science.gov (United States)

    Reinholdt, Anders; Herbst, Konrad; Bendix, Jesper

    2016-02-01

    The propensity of the terminal ruthenium carbide Ru(C)Cl2(PCy3)2 (RuC) to form carbide bridges to electron-rich transition metals enables synthetic routes to metal clusters with coexisting carbide and sulfide ligands. Electrochemical experiments show the Ru≡C ligand to exert a relatively large electron-withdrawing effect compared with PPh3, effectively shifting redox potentials.

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

    Science.gov (United States)

    Kunz, Peter; Bricault, Pierre; Dombsky, Marik; Erdmann, Nicole; Hanemaayer, Vicky; Wong, John; Lützenkirchen, Klaus

    2013-09-01

    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 UC2/C targets was developed. It includes the preparation of UC2 by carbothermal reduction of UO2, the slip-casting of fine-grained UC2/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 LIII-edge densitometry. The results confirm that the properties of the UC2/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.

  14. Laser melting of uranium carbides

    Science.gov (United States)

    Utton, C. A.; De Bruycker, F.; Boboridis, K.; Jardin, R.; Noel, H.; Guéneau, C.; Manara, D.

    2009-03-01

    In the context of the material research aimed at supporting the development of nuclear plants of the fourth Generation, renewed interest has recently arisen in carbide fuels. A profound understanding of the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents. In this context, the main goal of the present paper is to demonstrate the feasibility of laser induced melting experiments on stoichiometric uranium carbides; UC, UC1.5 and UC2. Measurements were performed, at temperatures around 3000 K, under a few bars of inert gas in order to minimise vaporisation and oxidation effects, which may occur at these temperatures. Moreover, a recently developed investigation method has been employed, based on in situ analysis of the sample surface reflectivity evolution during melting. Current results, 2781 K for the melting point of UC, 2665 K for the solidus and 2681 K for the liquidus of U2C3, 2754 K for the solidus and 2770 K for the liquidus of UC2, are in fair agreement with early publications where the melting behaviour of uranium carbides was investigated by traditional furnace melting methods. Further information has been obtained in the current research about the non-congruent (solidus-liquidus) melting of certain carbides, which suggest that a solidus-liquidus scheme is followed by higher ratio carbides, possibly even for UC2.

  15. 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.

  16. 硬质合金孔加工刀具的技术进展%Technical Development of Cemented Carbide Cutting Tools for Hole Machining

    Institute of Scientific and Technical Information of China (English)

    王弢; 柯亚仕; 周一丹

    2011-01-01

    The types of cutting tools for hole machining commonly used in modem manufacturing techniques, carbide cutting tool materials and preparations were introduced briefly. Taking drill as an example, the influences of tool parameters design, edge grinding and cutting edge preparation technology on cutting performance were analyzed. The developing trends of cemented carbide cutting tools for hole machining were summarized.%简要介绍了现代制造技术中常用孔加工刀具的种类、硬质合金刀具的材料与制备.以钻头为例,分析了刀具参数、刃磨、刃口钝化技术对切削性能的影响,综述了硬质合金孔加工刀具技术的发展趋势.

  17. Quantitative evaluation of carbides in nickel-base superalloy MAR-M247

    Science.gov (United States)

    Szczotok, A.

    2011-05-01

    It has been established that carbides in superalloys serve three functions. Fine carbides precipitated in the matrix give strengthening results. Carbides also can tie up certain elements that would otherwise promote phase instability during service. Grain boundary carbides prevent or retard grain-boundary sliding and strengthen the grain boundary, which depends significantly on carbide shape, size and distribution. Various types of carbides are possible, depending on superalloy composition and processing. In the paper optical and scanning electron microscopy investigations of carbides occurring in specimens of the polycrystalline nickel-base superalloy MAR-M247 were carried out. Conditions of carbides revealing and microstructure images acquisition have been described. Taking into consideration distribution and morphology of the carbides in matrix a method of quantitative description of Chinese script-like and blocky primary carbides on the basis of image analysis was proposed.

  18. The Development of Molecular-Based Materials for Electrical and Electronic Applications

    Science.gov (United States)

    Babalola, P. O.; Inegbenebor, A. O.; Bolu, C. A.; Inegbenebor, A. I.

    2015-04-01

    Aluminum silicon carbide (AlSiC) metal matrix composite materials have a unique set of material properties that are ideally suited for electronics, hence the development of molecular-based materials (MBM) for the electrical and electronic industries. The low material density of AlSiC (3 g/cm3) makes it ideal for weight-sensitive applications such as portable devices over traditional thermal management materials like copper molybdenum (10 g/cm3) and copper tungsten (16 g/cm3). The aim of this work is to develop MBM for electrical and electronic industries. Aluminum (99.66% C.P.) and silicon carbide (SiC) particulates of 240 grit (45 µm), 320 grit (29 µm), 600 grit (9 µm) and 1200 grit (3 µm) at 2.5% weight fraction were used to achieve the objective. The aluminum was melted at 750°C for 25 min in a graphite crucible tilting furnace designed for this work using oil as a firing medium. After melting, a two-step mixing method of stir casting technique was adopted. The cast samples were further analyzed for mechanical and electrical properties. The electrical properties were carried out by using a 4-point probe machine. The result showed that hardness increases at lower grit level, while the electrical properties marginally increased at higher grit. It is therefore recommended that, to make AlSiC composite materials for electrical industries, the higher grit of SiC should be preferred.

  19. Development of high temperature materials for solid propellant rocket nozzle applications. [tantalum carbides-tungsten fiber composites

    Science.gov (United States)

    Manning, C. R., Jr.; Honeycutt, L., III

    1974-01-01

    Evaluation of tantalum carbide-tungsten fiber composites has been completed as far as weight percent carbon additions and weight percent additions of tungsten fiber. Extensive studies were undertaken concerning Young's Modulus and fracture strength of this material. Also, in-depth analysis of the embrittling effects of the extra carbon additions on the tungsten fibers has been completed. The complete fabrication procedure for the tantalum carbide-tungsten fiber composites with extra carbon additions is given. Microprobe and metallographic studies showed the effect of extra carbon on the tungsten fibers, and evaluation of the thermal shock parameter fracture strength/Young's Modulus is included.

  20. 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.

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

    Science.gov (United States)

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

    2017-02-24

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

  2. 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.

  3. 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

    2016-01-18

    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.

  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

    2016-08-01

    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.

  5. 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.

  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. Future developments in instrumentation for electron crystallography.

    Science.gov (United States)

    Downing, Kenneth H

    2013-01-01

    Advances in instrumentation have proceeded at an impressive rate since the invention of the electron microscope. These advances have produced a continuous expansion of the capabilities and range of application of electron microscopy. In order to provide some insights on how continuing advances may enhance cryo-electron microscopy and electron crystallography, we review some of the active areas of instrumentation development. There is strong momentum in areas including detectors, phase contrast devices, and aberration correctors that may have substantial impact on the productivity and expectations of electron crystallographers.

  8. LETTER TO THE EDITOR: Electronic structure and bonding properties in layered ternary carbide Ti3SiC2

    Science.gov (United States)

    Zhou, Yanchun; Sun, Zhimei

    2000-07-01

    Ab initio calculations based on the density-functional pseudopotential approach have been used to study the electronic structure and chemical bonding in layered machinable Ti3SiC2 ceramic. The calculations reveal that all three types of bonding - metallic, covalent and ionic - contribute to the bonding in Ti3SiC2. The high electric conductivity is attributed to the metallic bonding parallel to the basal plane and the high modulus and high melting point are attributed to the strong Ti-C-Ti-C-Ti covalent bond chains in the structure.

  9. 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.

  10. Epitaxial and bulk growth of cubic silicon carbide on off-oriented 4H-silicon carbide substrates

    OpenAIRE

    Norén, Olof

    2015-01-01

    The growth of bulk cubic silicon carbide has for a long time seemed to be something for the future. However, in this thesis the initial steps towards bulk cubic silicon carbide have been taken. The achievement of producing bulk cubic silicon carbide will have a great impact in various fields of science and industry such as for example the fields of semiconductor technology within electronic- and optoelectronic devices and bio-medical applications. The process that has been used to grow the bu...

  11. Recent development of organic electron transport materials

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This article reviews the recent development of organic electron transport materials applied in the fields of organic photoconductors, light-emitting diodes, field-effect transistors and solar cells. Several technologies for charge carrier mobility measurement are summarized and compared, and a series of basic principles for designing high-performance organic electron transport materials are suggested as well.

  12. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  13. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  14. SILICON CARBIDE FOR SEMICONDUCTORS

    Science.gov (United States)

    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  15. Silicon Carbide Shapes.

    Science.gov (United States)

    Free-standing silicon carbide shapes are produced by passing a properly diluted stream of a reactant gas, for example methyltrichlorosilane, into a...reaction chamber housing a thin walled, hollow graphite body heated to 1300-1500C. After the graphite body is sufficiently coated with silicon carbide , the...graphite body is fired, converting the graphite to gaseous CO2 and CO and leaving a silicon carbide shaped article remaining.

  16. Developing scandium and zirconium containing aluminum boron carbide metal matrix composites for high temperature applications

    Science.gov (United States)

    Lai, Jing

    The study presented in this thesis focuses on developing castable, precipitation-strengthened Al--B4C metal matrix composites (MMCs) for high temperature applications. In the first part, B4C plates were immersed in liquid aluminum alloyed with Sc, Zr and Ti to investigate the interfacial reactions between B4C and liquid aluminum The influences of Sc, Zr and Ti on the interfacial microstructure in terms of individual and combined additions were examined. Results reveal that all three elements reacted with B4C and formed interfacial layers that acted as a diffusion barrier to limit the decomposition of B4C in liquid aluminum. The interfacial reactions and the reaction products in each system were identified. With the combined addition of Sc, Zr and Ti, most of the Ti was found to enrich at the interface, which not only offered appropriate protection of the B4C but also reduced the consumption of Sc and Zr at the interface. In the second part, Sc and Zr were introduced into Al-15vol.% B 4C composites presaturated by Ti, and eight experimental composites with different Sc and Zr levels were prepared via a conventional casting technique. It was found that Sc was involved in the interfacial reactions with B 4C that partially consume Sc. The Sc addition yielded considerable precipitation strengthening in the as-cast and peak aged conditions. To achieve an equivalent strengthening effect of Sc in binary Al-Sc alloys, approximately double the amount of Sc is required in Al-B4C composites. On the contrary, no major Zr reaction products were found at the interfaces and the major part of Zr remained in the matrix for the precipitation strengthening. The combination of Sc and Zr enhanced sthe precipitation strengthening. Two kinds of nanoscale precipitates, Al3Sc and Al3(Sc, Zr), were found in the as-cast microstructure and contributed to the increase in the matrix hardness. In the third part, all the experimental composites were isothermally aged at 300, 350, 400 and 450

  17. Synthesis of silicon carbide nanocrystals from waste polytetrafluoroethylene.

    Science.gov (United States)

    Wang, Liangbiao; Cheng, Qinglin; Qin, Hengfei; Li, Zhongchun; Lou, Zhengsong; Lu, Juanjuan; Zhang, Junhao; Zhou, Quanfa

    2017-02-28

    Resource utilization of waste plastic could solve the problem of environmental pollution and simultaneously relieve energy shortages, achieving sustainable development. In this study, the conversion of waste polytetrafluoroethylene (PTFE) to cubic silicon carbide (SiC) nanoparticles has been described. The structures and morphologies of the obtained SiC were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, the FTIR spectrum of the obtained SiC sample suggests that the waste PTFE was completely converted into SiC in our approach.

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

    Science.gov (United States)

    Vojvodic, A; Ruberto, C; Lundqvist, B I

    2010-09-22

    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 of surface resonances (SRs) on them and because of their technological importance in growth processes. Also, TM compounds have shown potential in catalysis applications. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, δ-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH(2), and NH(3). 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 results are rationalized by use of a concerted-coupling model (CCM), which has previously been applied successfully to the description of adsorption on TiC(111) and TiN(111) surfaces (Ruberto et al 2007 Solid State Commun. 141 48). First, the clean TMC(111) surfaces are characterized by calculating 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 considered TMC(111) surfaces. The spatial extent and the dangling bond nature of these SRs are supported by real-space analyses of the calculated Kohn-Sham wavefunctions. Then, atomic and molecular adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOSs reveals a presence of both adsorbate-TMSR and adsorbate-CSRs interactions, of varying strengths depending on the surface and the adsorbate. These variations are

  19. Nonlinear optical imaging of defects in cubic silicon carbide epilayers.

    Science.gov (United States)

    Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Matei, Alecs; Stanciu, George A

    2014-06-11

    Silicon carbide is one of the most promising materials for power electronic devices capable of operating at extreme conditions. The widespread application of silicon carbide power devices is however limited by the presence of structural defects in silicon carbide epilayers. Our experiment demonstrates that optical second harmonic generation imaging represents a viable solution for characterizing structural defects such as stacking faults, dislocations and double positioning boundaries in cubic silicon carbide layers. X-ray diffraction and optical second harmonic rotational anisotropy were used to confirm the growth of the cubic polytype, atomic force microscopy was used to support the identification of silicon carbide defects based on their distinct shape, while second harmonic generation microscopy revealed the detailed structure of the defects. Our results show that this fast and noninvasive investigation method can identify defects which appear during the crystal growth and can be used to certify areas within the silicon carbide epilayer that have optimal quality.

  20. Synthesis of titanium carbide by induction plasma reactive spray

    Institute of Scientific and Technical Information of China (English)

    JIANG Xian-Liang(蒋显亮); M.Boulos

    2004-01-01

    A novel method capable of sufficient mixing of titanium powder and methane of carbon source was developed in the synthesis of titanium carbide by induction plasma reactive spray. X-ray diffraction analysis, optical microscopy, scanning electron microscopy, and microhardness test were used to characterize the spray-formed deposit.The experimental results show that both primary carburization of the titanium particles inside the plasma flame and secondary carburization of the growing deposit on high temperature substrate contribute to the forming of titanium carbide. The transitional phase of TiC1-x has the same crystal structure as TiC, but has a slightly low lattice constant. The deposit consists of fine grain structure and large grain structure. The fine grain structure, harder than large grain structure, shows grain boundary fracture.

  1. Development of a nanoindenter for in-situ transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stach, Eric A.; Freeman, Tony; Minor, Andrew M.; Owen, Doug K.; Cumings, John; Wall, Mark A.; Chraska, Tomas; Hull, Robert; Morris Jr., J.W.; Zettl, A.; Dahmen, Ulrich

    2001-01-30

    In-situ transmission electron microscopy is an established experimental technique that permits direct observation of the dynamics and mechanisms of dislocation motion and deformation behavior. In this paper, we detail the development of a novel specimen goniometer that allows real time observations of the mechanical response of materials to indentation loads. The technology of the scanning tunneling microscope is adopted to allow nanometer scale positioning of a sharp, conductive diamond tip onto the edge of an electron transparent sample. This allows application of loads to nanometer-scale material volumes couple with simultaneous imaging of the material response. The emphasis in this paper is experimental and descriptive, with particular attention given to sample geometry and other technical requirements. Examples of the deformation of aluminum and titanium carbide as well as the fracture of silicon will be presented.

  2. 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.

  3. 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

  4. 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...

  5. SILICON CARBIDE DATA SHEETS

    Science.gov (United States)

    These data sheets present a compilation of a wide range of electrical, optical and energy values for alpha and beta- silicon carbide in bulk and film...spectrum. Energy data include energy bands, energy gap and energy levels for variously-doped silicon carbide , as well as effective mass tables, work

  6. Development of Scanning Ultrafast Electron Microscope Capability.

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Kimberlee Chiyoko [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Talin, Albert Alec [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Chandler, David W. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Michael, Joseph R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-11-01

    Modern semiconductor devices rely on the transport of minority charge carriers. Direct examination of minority carrier lifetimes in real devices with nanometer-scale features requires a measurement method with simultaneously high spatial and temporal resolutions. Achieving nanometer spatial resolutions at sub-nanosecond temporal resolution is possible with pump-probe methods that utilize electrons as probes. Recently, a stroboscopic scanning electron microscope was developed at Caltech, and used to study carrier transport across a Si p-n junction [ 1 , 2 , 3 ] . In this report, we detail our development of a prototype scanning ultrafast electron microscope system at Sandia National Laboratories based on the original Caltech design. This effort represents Sandia's first exploration into ultrafast electron microscopy.

  7. Development of high power and energy density microsphere silicon carbide-MnO2 nanoneedles and thermally oxidized activated carbon asymmetric electrochemical supercapacitors.

    Science.gov (United States)

    Kim, Myeongjin; Kim, Jooheon

    2014-06-21

    In order to achieve high energy and power densities, a high-voltage asymmetric electrochemical supercapacitor has been developed, with activated carbon (AC) as the negative electrode and a silicon carbide-MnO2 nanoneedle (SiC-N-MnO2) composite as the positive electrode. A neutral aqueous Na2SO4 solution was used as the electrolyte. SiC-N-MnO2 was prepared by packing growing MnO2 nanoneedle crystal species in only one direction on the silicon carbide surface. AC was oxidized by thermal treatment in order to introduce oxygen-containing functional groups. Owing to the high capacitance and excellent rate performance of SiC-N-MnO2 and AC, as well as the synergistic effects of the two electrodes, a constructed asymmetric supercapacitor exhibited superior electrochemical performance. The optimized asymmetric supercapacitor could be cycled reversibly in the voltage range from 0 to 1.9 V, and it exhibited a specific capacitance of 59.9 F g(-1) at a scan rate of 2 mV s(-1) and excellent energy density and power density (30.06 W h kg(-1) and 113.92 W kg(-1), respectively) with a specific capacitance loss of less than 3.1% after 1000 charge-discharge cycles, indicating excellent electrochemical stability. These encouraging results show great potential in terms of developing energy storage devices with high energy and power densities for practical applications.

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    Alternative catalysts based on carbides of Group 5 (niobium and tantalum) and 6 (chromium, molybdenum and tungsten) metals were prepared as films on the metallic substrates. The electrochemical activities of these carbide electrodes towards the hydrogen evolution reaction (HER) in concentrated......, 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...

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

    CERN Document Server

    Panteleev, V.N; Barzakh, A.E; Fedorov, D.V; Ionan, A.M; Ivanov, V.S; Mezilev, K.A; Molkanov, P.L; Moroz, F.V; Orlov, S.Yu; Volkov, Yu.M; Alyakrinskiy, O; Lanchais, A; Lau, C; Lhersonneau, G; Rizzi, V; Stroe, L; Tecchio, L.B; Dubois, M; Eleon, C; Gaubert, G; Jardin, P; Saint Laurent, M.G; Villari, A.C.C; Essabaa, S; O. Bajeat; Mhamed, C; Leroy, R

    2007-01-01

    The capacity of uranium carbide target materials of different structure and density for production of neutron-rich and heavy neutron-deficient nuclides have been investigated. The yields of Cs and Fr produced by a 1 GeV proton beam of the PNPI synchrocyclotron and release properties of different targets have been measured. The comparison of the yields and release efficiencies of Cs and Fr produced from a high density UC target material and from low density UCx prepared by the ISOLDE method at IRIS in the collaboration with PARRNe group from Orsay are presented. The yields from ISOLDE original target are presented for comparison as well.

  10. 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.

  11. Interfacial Engineering of Silicon Carbide Nanowire/Cellulose Microcrystal Paper toward High Thermal Conductivity.

    Science.gov (United States)

    Yao, Yimin; Zeng, Xiaoliang; Pan, Guiran; Sun, Jiajia; Hu, Jiantao; Huang, Yun; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2016-11-16

    Polymer composites with high thermal conductivity have attracted much attention, along with the rapid development of electronic devices toward higher speed and better performance. However, high interfacial thermal resistance between fillers and matrix or between fillers and fillers has been one of the primary bottlenecks for the effective thermal conduction in polymer composites. Herein, we report on engineering interfacial structure of silicon carbide nanowire/cellulose microcrystal paper by generating silver nanostructures. We show that silver nanoparticle-deposited silicon carbide nanowires as fillers can effectively enhance the thermal conductivity of the matrix. The in-plane thermal conductivity of the resultant composite paper reaches as high as 34.0 W/m K, which is one order magnitude higher than that of conventional polymer composites. Fitting the measured thermal conductivity with theoretical models qualitatively demonstrates that silver nanoparticles bring the lower interfacial thermal resistances both at silicon carbide nanowire/cellulose microcrystal and silicon carbide nanowire/silicon carbide nanowire interfaces. This interfacial engineering approach provides a powerful tool for sophisticated fabrication of high-performance thermal-management materials.

  12. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    Science.gov (United States)

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  13. 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...

  14. 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.

  15. Synthesis and photoluminescence property of boron carbide nanowires

    Institute of Scientific and Technical Information of China (English)

    Bao Li-Hong; Li Chen; Tian Yuan; Tian Ji-Fa; Hui Chao; Wang Xing-Jun; Shen Cheng-Min; Gao Hong-Jun

    2008-01-01

    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.

  16. 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.

  17. 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.

  18. Electronic structure of cubic Hf{sub x}Ta{sub 1-x}C{sub y} carbides from X-ray spectroscopy studies and cluster self-consistent calculations

    Energy Technology Data Exchange (ETDEWEB)

    Lavrentyev, A.A.; Gabrelian, B.V.; Vorzhev, V.B.; Nikiforov, I.Ya. [Department of Physics, Don State Technical University, Gagarin Sq. 1, Rostov-on-Don (Russian Federation); Khyzhun, O.Yu. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Str., UA-03142 Kyiv (Ukraine)], E-mail: khyzhun@ipms.kiev.ua; Rehr, J.J. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States)

    2008-08-25

    X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were employed in the present work to investigate the electronic structure of almost stoichiometric cubic (NaCl structure) Hf{sub x}Ta{sub 1-x}C{sub y} carbides. The XPS valence-band and core-level spectra, the XES bands reflecting energy distributions of mainly the Ta 5d- and C 2p-like states as well as the XAS Ta L{sub III} edges (unoccupied Ta d-like states) were derived and compared on a common energy scale for cubic HfC{sub 0.95}, Hf{sub 0.5}Ta{sub 0.5}C{sub 0.94} and TaC{sub 0.98} compounds. To investigate the influence of substitution of tantalum atoms for hafnium atoms in the Hf{sub x}Ta{sub 1-x}C{sub y} carbides, cluster self-consistent calculations of total and partial densities of states were carried out with the FEFF8 code for HfC, Hf{sub 0.5}Ta{sub 0.5}C and TaC compounds possessing the NaCl-type structure. In the present work a rather good agreement of the experimental and theoretical results for the electronic structure of the Hf{sub x}Ta{sub 1-x}C{sub y} system under study was obtained. The results indicate that a strong hybridization of the Hf(Ta) 5d- and C 2p-like states is characteristic for the Hf{sub x}Ta{sub 1-x}C{sub y} carbides. It has been established that, substitution of hafnium atoms by tantalum atoms in the Hf{sub x}Ta{sub 1-x}C{sub y} system reveals increasing the half-width of the XES C K{alpha} band. When going from HfC{sub 0.95} to TaC{sub 0.98} through the carbide of intermediate composition, the main maximum of the XPS valence-band spectrum shifts in the direction opposite to the position of the Fermi level. In the above sequence of compounds the asymmetry index of the C K{alpha} bands decreases significantly.

  19. Combustion synthesis of novel boron carbide

    Science.gov (United States)

    Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

    2013-02-01

    The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. 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. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

  20. 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.

  1. 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

    2016-09-01

    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.

  2. Influence of electronegativity on the electronic structures and stabilities of microclusters of carbides MC_n (M : transition, rare-earth or normal element, n < 10)

    Science.gov (United States)

    Leleyter, M.

    1991-10-01

    MC_n, clusters (n rare-earth metals, on the positions of the dσ and degenerate dδ levels due to the M atom, which are governed by Pauling's electronegativity (EN) of atom M. For transition or lanthanide metals, the alternations are “even" if EN le 1.7 (deficient d electron-elements: columns IIIA to VIIA; empty dσ and δ levels) or “odd" in the reverse case (rich d electron elements: column VIIIA bonding dσ and δ levels). For normal elements, the limit of EN seems to be the EN of C (2.5) and the alternations are “even" if EN le 2.5 or “odd" in the other case. Thus it is possible to infer a likely electronic configuration of the MC_n clusters and 2 tables give the compared electronic structures of these clusters for normal or transition elements. Such a kind of structure is only able to explain the parity effect origin of the MC_n clusters and even enable to foreknow for transition or rare-earth metal carbides which are not studied yet if the alternations will be “even" (EN le 1.7) or “odd". Les agrégats MC_n obtenus à partir de carbures par diverses méthodes expérimentales (SIMS, SSMS, vaporisation laser, effusion de Knudsen à haute température, etc.) présentent des alternances dans leurs intensités d'émission I(MC^+_n) avec maximums pour n impair si M = H, F, CI ou Fe, Ni, Rh, Ir, Pt ou au contraire pour n pair si M = B, Si, Ba, Ge ou Sc, Ti, V, Cr, Y, Zr, La, Ce, W, Th, U ou même n'existent que pour n pair (Nd, Dy, Ho, Er). D'autre part, seuls sont connus CO, C_3O, CN et C_3N pour l'oxygène et l'azote. Ces phénomènes sont interprétés tout d'abord à l'aide de la règle bien connue de correspondance qui relie de fortes (resp. faibles) intensités ou fréquences d'émissions d'ions MC^+_n à de fortes (resp. faibles) stabilités des amas correspondants. En second lieu, ces résultats s'expliquent dans le cadre du modèle de Pitzer et Clementi (hybridation sp en théorie de Hückel) corroboré par des calculs CNDO: on suppose que les

  3. 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.

  4. 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...

  5. 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

  6. Research Status and Developing Trend of Silicon Carbide foam Ceramic%碳化硅泡沫陶瓷的制备工艺研究进展

    Institute of Scientific and Technical Information of China (English)

    陈璐; 黎阳; 刘卫

    2011-01-01

    本文概述了碳化硅泡沫陶瓷的主要应用领域,着重介绍了近年来碳化硅泡沫陶瓷的制备工艺,并评述了其优缺点,最后针对目前的不足提出了碳化硅泡沫陶瓷未来的发展方向.%This article has described the main applications of silicon carbide foam ceramics. The traditional and new preparation methods of silicon carbide foam ceramics are introduced. The prospects for silicon carbide foam ceramics are explored.

  7. Mirror Surface Grinding of Steel Bonded Carbides

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The steel bonded carbide, a composite material, is very difficult to be machined to a fine finish mirror surface. In this paper, an electrolytic in-process dressing (ELID) grinding with metallic bond super-hard abrasive wheel was developed for grinding steel bonded carbide GT35. Factors affecting ELID grinding performance were analyzed by an atomic force microscope (AFM). Based on the analysis of AFM topography of the fine ground mirror surface of the steel bonded carbide, a schematic diagram of the mechanism of micro-removal of the ground surface was described. The AFM topography also shows that the hard brittle carbide particles, on the surface of steel bonded carbide, were machined out by ductile cutting. Since the grinding cracks in the ground surface are due to temperature gradient, temperature distribution in the grinding area was analyzed by finite element method (FEM). Experimental results indicate that a good mirror surface with Ra<0.02pm can be obtained by the developed ELID grinding system.

  8. Development of Electron Magnetic Spectrometer and Application

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The interaction between ultra-short pulse laser and solid plasma produces hot electron. Thereare many methods to study hot electron spectrum and space distribution. But the way of electron magnetic spectrometer is the most directional method. Particles with charge act circle movement in spare magnetic field. Different energy electrons have different whirl radius. So along whirl diameter direction electron spectrum can be obtained. Actually, electron is affected by gravity excursion and magnetic grads and curvature excursion besides lawrence power. The direction of

  9. Probing Field Emission from Boron Carbide Nanowires

    Institute of Scientific and Technical Information of China (English)

    TIAN Ji-Fa; GAO Hong-Jun; BAO Li-Hong; WANG Xing-Jun; HUI Chao; LIU Fei; LI Chen; SHEN Cheng-Min; WANG Zong-Li; GU Chang-Zhi

    2008-01-01

    High density boron carbide nanowires are grown by an improved carbon thermal reduction technique. Transmission electron microscopy and electron energy lose spectroscopy of the sample show that the synthesized nanowires are B4 C with good crystallization. The field emission measurement for an individual boron nanowire is performed by using a Pt tip installed in the focused ion beam system. A field emission current with enhancement factor of 106 is observed and the evolution process during emission is also carefully studied. Furthermore, a two-step field emission with stable emission current density is found from the high-density nanowire film. Our results together suggest that boron carbide nanowires are promising candidates for electron emission nanodevices.

  10. 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......-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....

  11. Ionisation Potentials of Metal Carbide Clusters

    Science.gov (United States)

    Dryza, Viktoras; Addicoat, M.; Gascooke, Jason; Buntine, Mark; Metha, Gregory

    2006-03-01

    Photo-Ionisation Efficiency (PIE) experiments have been performed on gas phase niobium and tantalum carbide clusters to determine their ionisation potentials (IPs). For TanCm (n = 3-4, m = 0-4) clusters an oscillatory behaviour is observed such that clusters with an odd number of carbon atoms have higher IPs and clusters with an even number of carbons have lower IPs. Excellent agreement is found with relative IPs calculated using density functional theory for the lowest energy structures, which are consistent with the development of a 2x2x2 face-centred nanocrystal. For the niobium carbide clusters we observe the species Nb4C5 and Nb4C6. Initial calculations suggest that these clusters contain carbon-carbon bonding. Interestingly, the stoichiometry for Nb4C6 is half that of a metcar, M8C12. Preliminary data will also be shown on bimetallic-carbide clusters.

  12. Silicon carbide reinforced silicon carbide composite

    Science.gov (United States)

    Lau, Sai-Kwing (Inventor); Calandra, Salvatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    2001-01-01

    This invention relates to a process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  13. Machining studies of die cast aluminum alloy-silicon carbide composites

    Science.gov (United States)

    Sornakumar, Thambu; Kathiresan, Marimuthu

    2010-10-01

    Metal matrix composites (MMCs) with high specific stiffness, high strength, improved wear resistance, and thermal properties are being increasingly used in advanced structural, aerospace, automotive, electronics, and wear applications. Aluminum alloy-silicon carbide composites were developed using a new combination of the vortex method and the pressure die-casting technique in the present work. Machining studies were conducted on the aluminum alloy-silicon carbide (SiC) composite work pieces using high speed steel (HSS) end-mill tools in a milling machine at different speeds and feeds. The quantitative studies on the machined work piece show that the surface finish is better for higher speeds and lower feeds. The surface roughness of the plain aluminum alloy is better than that of the aluminum alloy-silicon carbide composites. The studies on tool wear show that flank wear increases with speed and feed. The end-mill tool wear is higher on machining the aluminum alloy-silicon carbide composites than on machining the plain aluminum alloy.

  14. Rapid cost-effective silicon carbide optical component manufacturing technique

    Science.gov (United States)

    Casstevens, John M.; Plummer, Ronald; Jarocki, Jim

    1999-10-01

    Silicon carbide may well be the best known material for the manufacture of high performance optical components. A combination of extremely high specific stiffness (r/E), high thermal conductivity and outstanding dimensional stability make silicon carbide superior overall to beryllium and low- expansion glass ceramics. A major impediment to wide use of silicon carbide in optical systems has been the costs of preliminary pressing, casting, shaping and final finishing of silicon carbide. Diamond grinding of silicon carbide is a slow and expensive process even on machines specially designed for the task. The process described here begins by machining the component from a special type of graphite. This graphite is easily machined with multi-axis CNC machine tools to any level of complexity and lightweighting required. The graphite is then converted completely to silicon carbide with very small and very predictable dimensional change. After conversion to silicon carbide the optical surface is coated with very fine grain silicon carbide which is easily polished to extreme smoothness using conventional optical polishing techniques. The fabrication process and a 6 inch diameter development mirror is described.

  15. Characterization of Silicon Carbide.

    Science.gov (United States)

    The various electrical and structural measurement techniques for silicon carbide are described. The electrical measurements include conductivity, resistivity, carrier concentration, mobility, doping energy levels, and lifetime. The structural measurements include polytype determination and crystalline perfection. Both bulk and epitaxial films are included.

  16. Composition Comprising Silicon Carbide

    Science.gov (United States)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  17. Development Trends of Electronic Chemicals in China

    Institute of Scientific and Technical Information of China (English)

    Zheng Jinhong; Hou Hongsen

    2007-01-01

    @@ The annual growth of the electronic chemicals business in China exceeded 20% during the Tenth Five-year Plan period (2001-2005). The market volume of electronic chemicals in China is expected to exceed RMB20 billion in 2010.

  18. 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.

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

    Directory of Open Access Journals (Sweden)

    Matus K.

    2016-06-01

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

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

    Science.gov (United States)

    Szczotok, A.; Rodak, K.

    2012-05-01

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

  1. Hydrogen adsorption in metal-decorated silicon carbide nanotubes

    Science.gov (United States)

    Singh, Ram Sevak; Solanki, Ankit

    2016-09-01

    Hydrogen storage for fuel cell is an active area of research and appropriate materials with excellent hydrogen adsorption properties are highly demanded. Nanotubes, having high surface to volume ratio, are promising storage materials for hydrogen. Recently, silicon carbide nanotubes have been predicted as potential materials for future hydrogen storage application, and studies in this area are ongoing. Here, we report a systematic study on hydrogen adsorption properties in metal (Pt, Ni and Al) decorated silicon carbide nanotubes (SiCNTs) using first principles calculations based on density functional theory. The hydrogen adsorption properties are investigated by calculations of adsorption energy, electronic band structure, density of states (DOS) and Mulliken charge population analysis. Our findings show that hydrogen adsorptions on Pt, Ni and Al-decorated SiCNTs undergo spontaneous exothermic reactions with significant modulation of electronic structure of SiCNTs in all cases. Importantly, according to the Mulliken charge population analysis, dipole-dipole interaction causes chemisorptions of hydrogen in Pt, Ni and Al decorated SiCNTs with formation of chemical bonds. The study is a platform for the development of metal decorated SiCNTs for hydrogen adsorption or hydrogen storage application.

  2. Evaluation of Bidirectional Silicon Carbide Solid-State Circuit Breaker v3.2

    Science.gov (United States)

    2013-07-01

    Evaluation of Bidirectional Silicon Carbide Solid-State Circuit Breaker v3.2 by D. Urciuoli ARL-MR-0845 July 2013...Evaluation of Bidirectional Silicon Carbide Solid-State Circuit Breaker v3.2 D. Urciuoli Sensors and Electron Devices Directorate, ARL...2012 to 20 March 2013 4. TITLE AND SUBTITLE Evaluation of Bidirectional Silicon Carbide Solid-State Circuit Breaker v3.2 5a. CONTRACT NUMBER 5b

  3. Development of a spinodal decomposition model for the example of a heterostructure based on silicon carbide polytypes

    Science.gov (United States)

    Davydov, S. Yu.; Lebedev, A. A.; Lebedev, S. P.; Sitnikova, A. A.; Sorokin, L. M.

    2016-12-01

    The transition region of a 3C-SiC/4 H-SiC heterostructure constituted by layers of the 3 C and 4 H polytypes has been studied. A previously proposed spinodal decomposition model was used to estimate the thickness ratio of 4 H and 3 C layers in comparison with the image furnished by transmission electron microscopy.

  4. CHARACTERIZATION OF PRECIPITATES IN CUBIC SILICON CARBIDE IMPLANTED WITH 25Mg+ IONS

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin; Spurgeon, Steven R.; Liu, Jia; Edwards, Danny J.; Schreiber, Daniel K.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2016-09-26

    The aim of this study is to characterize precipitates in Mg+ ion implanted and high-temperature annealed cubic silicon carbide using scanning transmission electron microscopy, electron energy loss spectroscopy and atom probe tomography.

  5. Ion implantation phenomena in 4H-silicon carbide

    CERN Document Server

    Phelps, Gordon James

    2003-01-01

    Silicon Carbide is a promising wide band gap semiconductor with many new properties yet to be established and investigated. Ion implantation is the dominant method of incorporating dopant materials into the Silicon Carbide crystalline structure for electronic device fabrication. The implantation process of dopants into Silicon Carbide, both theoretical and practical, is described in this Thesis. Additional fabrication process steps, such as annealing, and their implications are also described. To gain further insight into the process of ion implantation into Silicon Carbide, the detailed design of a special test die is discussed. The aim of the special test die was to obtain general information such as implanted dopant sheet resistivity and to test a novel bipolar transistor design. The fabrication steps involved for the special test die are discussed in detail. The results from the special test die take the form of specific electrical measurements, together with detailed visual observations provided by a sca...

  6. A New Approach for Refining Carbide Dimensions in M42 Super Hard High-speed Steel

    Institute of Scientific and Technical Information of China (English)

    Xue-feng ZHOU; Wang-long ZHU; Hong-bing JIANG; Feng FANG; Yi-you TU; Jian-qing JIANG

    2016-01-01

    Obtaining small carbides is crucial but difficult for high-speed steels.A new approach for refining carbide dimensions in M42 super hard high-speed steel by increasing cooling rate and spheroidizing treatment was proposed. The morphologies and properties of eutectic carbides formed at different cooling rates were investigated by means of scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS),X-ray diffraction (XRD),transmis-sion electron microscopy (TEM),electron back-scattered diffraction (EBSD)and differential scanning calorimeter (DSC).The results show that eutectic carbides change from a lamellar shape into a curved-rod shape as cooling rate increases.Despite different morphologies,the two carbides are both of M2 C type with a hexagonal close-packed structure and display a single crystal orientation in one eutectic colony.The morphology of M2 C mainly depends on the growing process of eutectic carbides,which is strongly influenced by cooling rate.Compared with lamellar car-bides,M2 C carbides with curved-rod shapes are less stable,and decompose into M6 C and MC at lower temperatures. They are more inclined to spheroidize during heating,which ultimately and distinguishably refines the carbide dimen-sions.As small carbides are much easier to dissolve into matrices during austenization,the process described herein improves the supersaturation of alloying elements in martensite,which leads to an increment of hardness in M42 steel.

  7. Development of scientific and technological bases for application of brown coal semi coke in the technology of non- milled silicon carbide

    Science.gov (United States)

    Anikin, A. E.; Galevsky, G. V.; Rudneva, V. V.; Nozdrin, E. V.; Galevsky, S. G.

    2016-09-01

    Thermodynamics is investigated, and the optimum temperature and time modes of carbonization of a briquetted silica fume batch- brown coal semi coke are defined. The complete carbonization of the batch in the conditions of heat treatment is achieved at a temperature of 1923 - 1973 K within 15 - 20 minutes. The conditions and indicators of the chemical enrichment of carbonization products are established. After enrichment, the carbide content is more than 90%. Silicon carbide micro-powder is obtained with a specific surface area 8000 - 9000 m2/kg.

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

    Directory of Open Access Journals (Sweden)

    Cherepova, T.S.

    2016-01-01

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

  9. 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.

  10. Developing Assessment Techniques for Statewide Electronic Networks.

    Science.gov (United States)

    McClure, Charles R.; Bertot, John Carlo

    1996-01-01

    Explores several methods through which to evaluate statewide electronic networks, and discusses key issues and preliminary findings that affect the successful evaluation of statewide networked services. (Author/AEF)

  11. Behavior of disordered boron carbide under stress.

    Science.gov (United States)

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

    2006-07-21

    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 6 GPa approximately = 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.

  12. 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.

  13. 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

  14. Mass production of beta-silicon carbide nanofibers by the novel method of Forcespinning

    Science.gov (United States)

    Salinas, Alfonso

    Non-oxide Ceramics such as silicon carbide have very unique properties, for example high toughness, thermal stability, wear resistant, and thermal shock resistance these properties make these ceramic fibers excellent for high temperature applications. Here we present the development of Silicon Carbide nanofibers utilizing a Polystyrene/Polycarbomethylsilane solution as the precursor materials. The ForcespinningRTM was performed under a controlled nitrogen environment to prevent fiber oxidation. Characterization was conducted using scanning electron microscopy, x-ray diffraction, and thermogravimetric analysis. The results show successful formation of high yield, long continuous bead-free nanofibers with diameters ranging from 280nm to 2 micron depending on the selected processing parameters. The sintered precursors show formation of SiC nanofibers with a beta phase crystalline structure and oxygen content below 15%.

  15. Probing Structure and Composition of Nickel/Titanium Carbide Hybrid Interfaces at the Atomic Scale (Preprint)

    Science.gov (United States)

    2010-01-01

    The transition in structure and composition across the titanium carbide /nickel hybrid interface has been determined at near atomic resolution by...coupling high-resolution transmission electron microscopy with three-dimensional atom probe tomography. The titanium carbide phase adopts a rocksalt-type

  16. Zirconium carbide as an electrocatalyst for the chromous-chromic redox couple

    Science.gov (United States)

    Gahn, R. F.; Reid, M. A.; Yang, C. Y. (Inventor)

    1981-01-01

    Zirconium carbide is used as a catalyst in a REDOX cell for the oxidation of chromous ions to chromic ions and for the reduction of chromic ions to chromous ions. The zirconium carbide is coated on an inert electronically conductive electrode which is present in the anode fluid of the cell.

  17. 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.

  18. Development of high quality electron beam accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kando, Masaki; Dewa, Hideki; Kotaki, Hideyuki; Kondo, Shuji; Hosokai, Tomonao; Kanazawa, Shuhei; Yokoyama, Takashi; Nakajima, Kazuhisa [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Institute, Kizu, Kyoto (Japan)

    2000-03-01

    A design study on a high quality electron beam accelerator is described. This accelerator will be used for second generation experiments of laser wakefield acceleration, short x-ray generation, and other experiments of interaction of high intensity laser with an electron beam at Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Institute. The system consists of a photocathode rf gun and a race-track microtron (RTM). To combine these two components, injection and extraction beamlines are designed employing transfer matrix and compute codes. A present status of the accelerator system is also presented. (author)

  19. Iron carbide nanoparticles growth in room temperature ionic liquids [C{sub n}-MIM][BF{sub 4}] (n = 12, 16)

    Energy Technology Data Exchange (ETDEWEB)

    Lartigue, Lenaiec; Long, Jerome; Dumail, Xavier [Universite Montpellier II, Institut Charles Gerhardt Montpellier, UMR5253, Chimie Moleculaire et Organisation du Solide (France); Nikitenko, Sergey I.; Cau, Camille [Institut de Chimie Separative de Marcoule, UMR 5257, Centre de Marcoule (France); Guari, Yannick, E-mail: yannick.guari@um2.fr [Universite Montpellier II, Institut Charles Gerhardt Montpellier, UMR5253, Chimie Moleculaire et Organisation du Solide (France); Stievano, Lorenzo; Sougrati, Moulay T. [Universite Montpellier II, Institut Charles Gerhardt Montpellier, UMR 5253, Agregats, Interfaces et Materiaux pour l' Energie (France); Guerin, Christian [Universite Montpellier II, Institut Charles Gerhardt Montpellier, UMR5253, Chimie Moleculaire et Organisation du Solide (France); Sangregorio, Claudio [CNR-ISTM (Italy); Larionova, Joulia [Universite Montpellier II, Institut Charles Gerhardt Montpellier, UMR5253, Chimie Moleculaire et Organisation du Solide (France)

    2013-04-15

    The thermal decomposition of Fe{sub x}(CO){sub y} precursors for the synthesis of nanoparticles of iron carbides and their superstructures with sizes ranging from 2.8 to 15.1 nm is developed using imidazolium-based ionic liquids as solvents, stabilizers, and carbon source. A study of the influence of some synthesis parameters such as the heating temperature, nature, and concentration of the iron carbonyl precursor and chain length of the N-alkyl substituent on the imidazolium ring on the size and organization of the iron carbide nanoparticles is presented. These iron carbides nano-objects were characterized by infra-red spectroscopy, transmission electronic microscopy, powder X-ray diffraction, Mossbauer spectroscopy, and magnetic analyses.

  20. 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.

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2017-02-01

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

  3. Growth kinetics of cubic carbide free layers in graded cemented carbides

    Science.gov (United States)

    Shi, Liu-Yong; Liu, Yi-Min; Huang, Ji-Hua; Zhang, Shou-Quan; Zhao, Xing-Ke

    2012-01-01

    In order to reveal the formation mechanism of cubic carbide free layers (CCFL), graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA), respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

  4. Silicon carbide sewing thread

    Science.gov (United States)

    Sawko, Paul M. (Inventor)

    1995-01-01

    Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

  5. 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

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

    Science.gov (United States)

    Grady, Dennis E.

    2015-04-01

    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 mechanistic

  7. Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum

    Science.gov (United States)

    Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.

    2017-01-01

    Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.

  8. Epitaxial graphene electronic structure and transport

    Energy Technology Data Exchange (ETDEWEB)

    De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N [School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Stroscio, Joseph A [Center for Nanoscale Science and Technology, NIST, Gaithersburg, MD 20899 (United States); Haddon, Robert [Center for Nanoscale Science and Engineering, Departments of Chemistry and Chemical and Environmental Engineering, University of California, Riverside, CA 92521 (United States); Piot, Benjamin; Faugeras, Clement; Potemski, Marek [LNCMI -CNRS, Grenoble, 38042 Cedex 9 (France); Moon, Jeong-Sun, E-mail: walt.deheer@physics.gateh.ed [HRL Laboratories LLC, Malibu, CA 90265 (United States)

    2010-09-22

    Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.

  9. Engineering scale development of the vapor-liquid-solid (VLS) process for the production of silicon carbide fibrils. Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Ohnsorg, R.W.; Hollar, W.E. Jr.; Lau, S.K. [Carborundum Co., Niagara Falls, NY (United States). Technology Div.; Ko, F.K.; Schatz, K. [Advanced Product Development, Bristol, PA (United States)

    1995-04-01

    As reinforcements for composites, VLS SiC fibrils have attractive mechanical properties including high-strength, high modulus, and excellent creep resistance. To make use of their excellent mechanical properties in a composite, a significant volume fraction (>10%) of aligned, long fibrils (>2 mm) needs to be consolidated in the ceramic matrix. The fibrils must be processed into an assembly that will allow for composite fabrication while maintaining fibril alignment and length. With Advanced Product Development (APD) as the yam fabrication subcontractor, Carborundum investigated several approaches to achieve this goaL including traditional yam-forming processes such as carding and air-vortex spinning and nontraditional processes such as tape forming and wet casting. Carborundum additionally performed an economic analysis for producing 500 and 10,000 pounds of SiC fibrils annually using both conservative and more aggressive processing parameters. With the aggressive approach, the projected costs for SiC fibril production for 500 and 10,000 pounds per year are $1,340/pound and $340/pound, respectively.

  10. 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.

  11. 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

    2009-11-11

    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.

  12. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ugur

    2004-07-15

    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 Nb{sub 2}C 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 {mu}m 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{sup -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.

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

    Science.gov (United States)

    Debelle, A.; Backman, M.; Thomé, L.; Weber, W. J.; Toulemonde, M.; Mylonas, S.; Boulle, A.; Pakarinen, O. H.; Juslin, N.; Djurabekova, F.; Nordlund, K.; Garrido, F.; Chaussende, D.

    2012-09-01

    The healing effect of intense electronic energy deposition arising during swift heavy ion (SHI) irradiation is demonstrated in the case of 3C-SiC damaged by nuclear energy deposition. Experimental (ion channeling experiments) and computational (molecular dynamics simulations) studies provide consistent indications of disorder decrease after SHI irradiation. Furthermore, both methods establish that SHI-induced recrystallization takes place at amorphous-crystalline interfaces. The recovery process is unambiguously accounted for by the thermal spike phenomenon.

  15. Technology of Iron Carbide Synthesis

    Institute of Scientific and Technical Information of China (English)

    M.Bahgat

    2006-01-01

    Iron carbides are very promising metallurgical products and can be used for steelmaking process, where it plays as an alternative raw material with significant economic advantages. Also it has many other applications,e.g. catalysts, magnets, sensors. The present review investigates the different properties and uses of the iron carbides. The commercial production and the different varieties for the iron carbides synthesis (gaseous carburization, mechanochemical synthesis, laser pyrolysis, plasma pyrolysis, chemical vapor deposition and ion implantation) were reviewed. Also the effect of different factors on the carburization process like gas composition, raw material, temperature, reaction time, catalyst presence and sulfur addition was indicated.

  16. Microstructures and Wear Performance of PTAW Deposited Ni-Based Coatings with Spherical Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Dewei Deng

    2015-10-01

    Full Text Available The Ni-based coatings with different content of spherical tungsten carbide were deposited by plasma transfer arc welding (PTAW method on 304 austenitic stainless steel sheets in this study. The microstructure and wear property of spherical tungsten carbide particle reinforced composite coatings were investigated by means of optical microscope, scanning electron microscope (SEM, X-ray diffraction (XRD, electron probe microanalysis (EPMA and sliding wear test. It is shown that the fraction of spherical tungsten carbides has an important influence on microstructure of Ni-based overlay. The Ni40 overlay consists of γ-Ni dendrites with interdendritic Ni-based eutectics, borides and carbides improving the wear resistance. In the case of composite coatings with different content of tungsten carbide, many new phases are observed, such as Ni2W4C and NiW. In addition, there are a large number of irregular structures in composite coatings, such as acicular structure and irregular stripe organization. The results of sliding wear test indicate that the mass loss of coatings is influenced by the content of tungsten carbide. The mass loss decreases with the increase of tungsten carbide fraction. At high load, the abrasive resistance of composite coating with 60 wt. % tungsten carbide is improved about 50-fold compared to that of Ni40 overlay.

  17. Ballistic Evaluation of rolled Homogeneous Steel Armor with Tungsten Carbide and Titanium Carbide Facing.

    Science.gov (United States)

    1960-12-01

    LABORATORIES BALLISTIC EVALUATION OF ROLLED HMtOGE14EOUS STEEL ASWKR f VITH TUNGSTEN CARBIDE AND TITANIUM CARBIDE FACING (U) TECHNICAL REPORT NO. WAL...carbide steel and titanium carbide steel composite armor when attacked by cal. .40 H19B WC cores, cal. .0 AP W2 projectiles, ZOIN fragment simulating...determine the effectiveness of tungsten car- bide (WC) and titanium carbide (TIC) facing on steel armor for the defeat of steel and tungsten carbide

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

    NARCIS (Netherlands)

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

    2009-01-01

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

  19. 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.

  20. Single-Event Effects in Silicon and Silicon Carbide Power Devices

    Science.gov (United States)

    Lauenstein, Jean-Marie; Casey, Megan C.; LaBel, Kenneth A.; Topper, Alyson D.; Wilcox, Edward P.; Kim, Hak; Phan, Anthony M.

    2014-01-01

    NASA Electronics Parts and Packaging program-funded activities over the past year on single-event effects in silicon and silicon carbide power devices are presented, with focus on SiC device failure signatures.

  1. 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.

  2. Shock-induced localized amorphization in boron carbide.

    Science.gov (United States)

    Chen, Mingwei; McCauley, James W; Hemker, Kevin J

    2003-03-01

    High-resolution electron microscope observations of shock-loaded boron carbide have revealed the formation of nanoscale intragranular amorphous bands that occur parallel to specific crystallographic planes and contiguously with apparent cleaved fracture surfaces. This damage mechanism explains the measured, but not previously understood, decrease in the ballistic performance of boron carbide at high impact rates and pressures. The formation of these amorphous bands is also an example of how shock loading can result in the synthesis of novel structures and materials with substantially altered properties.

  3. 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.

  4. Carbide Dissolution during Intercritical Austenitization in Bearing Steel

    Institute of Scientific and Technical Information of China (English)

    LI Hui; MI Zhenli; ZHANG Xiaolei; TANG Di; WANG Yide

    2014-01-01

    In order to investigate the carbide dissolution mechanism of high carbon-chromium bearing steel during the intercritical austenitization, the database of TCFE7 of Thermo-calc and MOBFE of DICTRA software were used to calculate the elements diffusion kinetic and the evolution law of volume fraction of carbide. DIL805A dilatometer was used to simulate the intercritical heat treatment. The microstructure was observed by scanning electron microscopy(SEM), and the micro-hardness was tested. The experimental results indicate that the dissolution of carbide is composed of two stages:initial austenite growth governed by carbon diffusion which sharply moves up the micro-hardness of quenched martensite, and subsequent growth controlled by diffusion of Cr elements in M3C. The volume fraction of M3C decreases with the increasing holding time, and the metallographic analysis shows a great agreement with values calculated by software.

  5. Stable field emission from nanoporous silicon carbide.

    Science.gov (United States)

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

    2013-02-15

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

  6. Electrocatalytic Activity of Tungsten Trioxide Micro-spheres, Tungsten Carbide Microspheres and Multi-walled Carbon Nanotube-tungsten Carbide Composites

    Institute of Scientific and Technical Information of China (English)

    LU Hongzhi; YAN Taining

    2009-01-01

    Tungsten trioxide micropheres were prepared by spray pyrolysis, and tungsten carbidemicrospheres were produced by spray pyrolysis-low temperature reduction and carbonization technology.Multi-walled carbon nanotube-tungsten carbide composites were prepared by the continuous reductionand carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO_3 precursor by mo-lecular level mixing and calcination. The morphology and structure of the samples were characterized byscanning electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction. The electrocatalytic activity of the sample was analyzed by means of me-thanol oxidation. Tungsten carbide microspheres were catalytic active for methanol oxidation reaction.Nevertheless tungsten trioxide microspheres and multi-walled carbon nanotube-tungsten carbide compos-ites were not catalytic active for methanol oxidation reaction. These results indicate that tungsten carbide micropheres are promising catalyst for methanol oxidation.

  7. 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.

  8. Crystal structure and electronic properties of the new compounds, U 6Fe 16Si 7 and its interstitial carbide U 6Fe 16Si 7C

    Science.gov (United States)

    Berthebaud, D.; Tougait, O.; Potel, M.; Lopes, E. B.; Gonçalves, A. P.; Noël, H.

    2007-10-01

    The new compounds U6Fe16Si7 and U6Fe16Si7C were prepared by arc-melting and subsequent annealing at 1500 °C. Single-crystal X-ray diffraction showed that they crystallize in the cubic space group Fm3¯m (No. 225), with unit-cell parameters at room temperature a=11.7206(5) Å for U6Fe16Si7 and a=11.7814(2) Å for U6Fe16Si7C. Their crystal structures correspond to ordered variants of the Th6Mn23 type. U6Fe16Si7 adopts the Mg6Cu16Si7 structure type, whereas U6Fe16Si7C crystallizes with a novel "filled" quaternary variant. The inserted carbon is located in octahedral cages formed by six U atoms, with U-U interatomic distances of 3.509(1) Å. Insertion of carbon in the structure of U6Fe16Si7 has a direct influence on the U-Fe and Fe-Fe interatomic distances. The electronic properties of both compounds were investigated by means of DC susceptibility, electrical resistivity and thermopower. U6Fe16Si7 is a Pauli paramagnet. Its electrical resistivity and thermopower point out that it cannot be classified as a simple metal. The magnetic susceptibility of U 6Fe 16Si 7C is best described over the temperature range 100-300 K by using a modified Curie-Weiss law with an effective magnetic moment of 2.3(2) μB/U, a paramagnetic Weiss temperature, θp=57(2) K and a temperature-independent term χ0=0.057(1) emu/mol. Both the electrical resistivity and thermopower reveal metallic behavior.

  9. Directions for Research and Development on Electronic Portfolios

    Directory of Open Access Journals (Sweden)

    Philip Abrami

    2005-10-01

    Full Text Available This lead article for the special issue of the Canadian Journal of Learning and Technology explores directions for research and development on electronic portfolios, which are digital containers capable of storing visual and auditory content; software for which may also be designed to support a variety of pedagogical processes and assessment purposes. The paper is organized around several key questions: What are the types and characteristics of electronic portfolios? What are the outcomes and processes that electronic portfolios support for their creators? What are the contexts in which EPs are most effective and worthwhile? Who are electronic portfolio users/viewers and how do we provide appropriate professional development to encourage correct adoption and widespread and sustained use? What do we know and need to know about technical and administrative issues? What is evidence of electronic portfolio success? How do we move forward with funding and infrastructure?

  10. Development of High Power Electron Beam Measuring and Analyzing System for Microwave Vacuum Electron Devices

    Science.gov (United States)

    Ruan, C. J.; Wu, X. L.; Li, Q. S.; Li, C. S.

    The measurement and analysis of high power electron beam during its formation and transmission are the basic scientific problems and key techniques for the development of high performance microwave vacuum electron devices, which are widely used in the fields of military weapon, microwave system and scientific instruments. In this paper, the dynamic parameters measurement and analysis system being built in Institute of Electronics, Chinese Academy of Sciences (IECAS) recently are introduced. The instrument are designed to determine the cross-section, the current density, and the energy resolution of the high power electron beam during its formation and transmission process, which are available both for the electron gun and the electron optics system respectively. Then the three dimension trajectory images of the electron beam can be rebuilt and display with computer controlled data acquisition and processing system easily. Thus, much more complicated structures are considered and solved completely to achieve its detection and analysis, such as big chamber with 10-6 Pa high vacuum system, the controlled detector movement system in axis direction with distance of 600 mm inside the vacuum chamber, the electron beam energy analysis system with high resolution of 0.5%, and the electron beam cross-section and density detector using the YAG: Ce crystal and CCD imaging system et al. At present, the key parts of the instrument have been finished, the cross-section experiment of the electron beam have been performed successfully. Hereafter, the instrument will be used to measure and analyze the electron beam with the electron gun and electron optics system for the single beam and multiple beam klystron, gyrotron, sheet beam device, and traveling wave tube etc. thoroughly.

  11. Single crystalline boron carbide nanobelts:synthesis and characterization

    Institute of Scientific and Technical Information of China (English)

    Bao Li-Hong; Li Chen; Tian Yuan; Tian Ji-Fa; Hui Chao; Wang Xing-Jun; Shen Cheng-Min; Gao Hong-Jun

    2008-01-01

    This paper reports that the large-scale single crystalline boron carbide nanobelts have been fabricated through a simple carbothermal reduction method with B/B203/C/Fe powder as precursors at ll00~C.Transmission electron microscopy and selected area electron diffraction characterizations show that the boron carbide nanobelt has a B4C rhomb-centred hexagonal structure with good crystallization.Electron energy loss spectroscopy analysis indicates that the nanobelt contains only B and C,and the atomic ratio of B to C is close to 4:1.High resolution transmission electron microscopy results show that the preferential growth direction of the nanobelt is [101].A possible growth mechanism is also discussed.

  12. 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.

  13. High temperature stability of Cr-carbides in an experimental Co-Re-based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Mukherji, Debashis; Klauke, Michael; Roesler, Joachim [Technische Universitaet Braunschweig (Germany). Institut fuer Werkstoffe; Strunz, Pavel [Nuclear Physics Institute and Research Center Rez (Czech Republic); Zizak, Ivo [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung, Berlin (Germany); Schumacher, Gerhard; Wiedenmann, Albrecht [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Berlin (Germany)

    2010-03-15

    The stability of the microstructure at high temperatures was studied in an experimental Co-Re-based alloy. The experimental alloy is mainly strengthened by Cr-carbides, particularly by those in the form of thin lamellar plates. Electron microscopic investigation on samples exposed for up to 1000 h to temperatures of 1000 and 1200 C showed that Cr{sub 23}C{sub 6} type carbides present in the alloy in different morphologies are unstable at these temperatures. It was also observed that the alloy hardness dropped after exposing the samples to elevated temperatures and much of this loss occurred within the first 100 h. In-situ diffraction measurements with synchrotron radiation showed that carbide dissolution started as early as 3 h of holding at 1000 C. Moreover, in-situ small angle neutron scattering results indicated that the carbides at the grain boundaries and the blocky carbides dissolve first and then the thin lamellar carbides. Further, the enrichment of Cr in the Co-matrix phase, which took place due to the dissolution of Cr-carbides, stabilized a Cr-Re-rich {sigma} phase. Although the dissolution of lamellar carbides results in a significant loss of strength, the formation of {sigma} phase with extremely high hardness partly compensated the for loss. The {sigma} phase is stable even at 1200 C. (orig.)

  14. Sintering of nano crystalline silicon carbide doping with aluminium nitride

    Indian Academy of Sciences (India)

    M S Datta; A K Bandyopadhyay; B Chaudhuri

    2002-04-01

    Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by scanning electron microscopy and transmission electron microscopy. This study shows that the mechanism is a solid sintering process.

  15. 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.

  16. First-principles study of structural and bonding properties of vanadium carbide and niobium carbide

    Science.gov (United States)

    Joshi, K. B.; Paliwal, U.

    2009-11-01

    An ab initio linear combination of atomic orbitals method founded on density functional theory is applied to study the structural and bonding properties of vanadium carbide and niobium carbide. We present structural properties, namely, first-principles total energies, equilibrium lattice constants, bulk moduli and their pressure derivatives, together with the x-ray structure factors. Two generalized correction schemes—P86 and PW92—are applied to treat correlation. P86 gives a favourable ground state compared with the PW92. The computed equilibrium lattice constants and bulk moduli of the two compounds are compared with available experimental data. The x-ray structure factors for a few reflection planes are also reported. Comparison with experiment could be done only for niobium carbide. More refined measurements on x-ray structure factors for both compounds are required. We also present the autocorrelation functions derived from the ground-state momentum density. The electronic behaviour and bonding properties are discussed in terms of absolute and anisotropies in the directional autocorrelation functions. Our findings on structural and bonding parameters are well in accordance with the experimental data.

  17. First-principles study of structural and bonding properties of vanadium carbide and niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, K B; Paliwal, U [Department of Physics, University College of Science, M L Sukhadia University, Udaipur - 313001 (India)], E-mail: k_joshi@yahoo.com

    2009-11-15

    An ab initio linear combination of atomic orbitals method founded on density functional theory is applied to study the structural and bonding properties of vanadium carbide and niobium carbide. We present structural properties, namely, first-principles total energies, equilibrium lattice constants, bulk moduli and their pressure derivatives, together with the x-ray structure factors. Two generalized correction schemes-P86 and PW92-are applied to treat correlation. P86 gives a favourable ground state compared with the PW92. The computed equilibrium lattice constants and bulk moduli of the two compounds are compared with available experimental data. The x-ray structure factors for a few reflection planes are also reported. Comparison with experiment could be done only for niobium carbide. More refined measurements on x-ray structure factors for both compounds are required. We also present the autocorrelation functions derived from the ground-state momentum density. The electronic behaviour and bonding properties are discussed in terms of absolute and anisotropies in the directional autocorrelation functions. Our findings on structural and bonding parameters are well in accordance with the experimental data.

  18. A Study of the Pickup of Abrasive Particles during Abrasion of Annealed Aluminum on Silicon Carbide Abrasive Papers,

    Science.gov (United States)

    annealed aluminium during abrasion on silicon carbide abrasive papers. Neither optical nor scanning electron microscopy adequately characterises the...despite its limitations when examining rough surfaces. The present results show that the pickup of silicon carbide particles increases with increase in

  19. Theoretical descriptions of electron transport through single molecules: Developing design tools for molecular electronic devices

    Science.gov (United States)

    Carroll, Natalie R.

    There are vast numbers of organic compounds that could be considered for use in molecular electronics. Hence there is a need for efficient and economical screening tools. Here we develop theoretical methods to describe electron transport through individual molecules, the ultimate goal of which is to establish design tools for molecular electronic devices. To successfully screen a compound for its use as a device component requires a proper representation of the quantum mechanics of electron transmission. In this work we report the development of tools for the description of electron transmission that are: Charge self-consistent, valid in the presence of a finite applied potential field and (in some cases) explicitly time-dependent. In addition, the tools can be extended to any molecular system, including biosystems, because they are free of restrictive parameterizations. Two approaches are explored: (1) correlation of substituent parameter values (sigma), (commonly found in organic chemistry textbooks) to properties associated with electron transport, (2) explicit tracking of the time evolution of the wave function of a nonstationary electron. In (1) we demonstrate that the a correlate strongly with features of the charge migration process, establishing them as useful indicators of electronic properties. In (2) we employ a time-dependent description of electron transport through molecular junctions. To date, the great majority of theoretical treatments of electron transport in molecular junctions have been of the time-independent variety. Time dependence, however, is critical to such properties as switching speeds in binary computer components and alternating current conductance, so we explored methods based on time-dependent quantum mechanics. A molecular junction is modeled as a single molecule sandwiched between two clusters of close-packed metal atoms or other donor and acceptor groups. The time dependence of electron transport is investigated by initially

  20. Development of the electron cooling simulation program for JLEIC

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, He [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Chen, Jie [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Li, Rui [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Zhang, Yuhong [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Huang, He [Old Dominion Univ., Norfolk, VA (United States); Luo, Li-Shi [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-05-01

    In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during collision at the collider ring. A new electron cooling process simulation program has been developed to fulfill the requirements of the JLEIC electron cooler design. The new program allows the users to calculate the electron cooling rate and simulate the cooling process with either DC or bunched electron beam to cool either coasting or bunched ion beam. It has been benchmarked with BETACOOL in aspect of accuracy and efficiency. In typical electron cooling process of JLEIC, the two programs agree very well and we have seen a significant improvement of computational speed using the new one. Being adaptive to the modern multicore hardware makes it possible to further enhance the efficiency for computationally intensive problems. The new program is being actively used in the electron cooling study and cooler design for JLEIC. We will present our models and some simulation results in this paper.

  1. 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.

  2. MICROSTRUCTURE AT THE INTERFACE OF TITANIUM CARBIDE AND NICKEL ALUMINIDES

    Institute of Scientific and Technical Information of China (English)

    Shen Dian-hong; Wu Xing-fang; Lu Hua; N.Froumin; M.Polak

    2000-01-01

    Microstructure at the interface of titanium carbide and nickelaluminides in the samples obtained by infiltration of molten Ni3Al alloyhas studied by a scanning electron microscopy (SEM) and an analyticaltransmission electron microscopy (ATEM) with an energy dispersivespectrometer (EDS). It is found that the morphology at the interfacesbetween hard phase skeleton of TiC{0.7 and metallic phases depends on theratio of Ti/C in carbide. Some periodic zigzag fringes are observed ata smooth interface between metallic phase and carbides in the sampleof Ni3Al/TiC0.7. The results of analysis using EDS show that Ti inTiC0.7 carbide is easier than that in TiC0.9 to dissolve into the moltenalloy during solid-liquid reaction. The formation of this periodic zigzagfringe,which may be a growth zone of a new Ti-Ni-Al phase,in the interfaceof TiC0.7/Ni3Al would occur during the initial stage of solidification.

  3. 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..

  4. Developing Effective Case Scenarios for Interprofessional Electronic Health Record Research.

    Science.gov (United States)

    McDonald, Kristie; Courtney, Karen L; Frisch, Noreen

    2017-01-01

    In the last decade, there have been numerous calls for research in interprofessional communication and documentation. Some of the limitations of research in this area have been proprietary user interfaces that may not be generalizable and impact varying adoption rates of electronic documentation among different health disciplines. In order to address these concerns, researchers need to create standardized case scenarios as research instruments. This paper outlines the process for developing a case scenario instrument for use in interprofessional electronic documentation research.

  5. Development and characterization of advanced electron beam resists

    Science.gov (United States)

    Agrawal, Ankur

    Over the past twenty years, the amount of research and development work for electron beam resists has seriously lagged that performed for optical resists. This has been due mainly to the relatively low volume use of electron beam lithography for production purposes. However, as electron beam lithography is now becoming the primary solution for achieving future critical dimension requirements in mask making and appears to be a promising NGL technology, interest in electron beam resist development has increased in recent years. The primary issue in electron beam resist design centers around finding a single resist system that combines the required sensitivity and etch resistance that is needed to enable high volume production. In this work, the primary goal was to explore the development of a novel two-component non-chemically amplified electron beam resist material for high keV (>10 keV) patterning for mask-making with: (1) high contrast, (2) high sensitivity, (3) high resolution, and, (4) high etch resistance. Poly (2-methyl-1-pentene co 2-ethoxyethyl-methallyl ether sulfone) was used as a polymeric e-beam sensitive material conjunction with a series of commercial novolac resins to formulate electron beam resists. These two-component resists have been termed sulfone-novolac system (SNS) resists. The approach used in this project is to develop a suite of experimental tools and simulation models that can be used to aid in the rational design, formulation, and characterization of new electron beam resists. The main tasks that have been addressed are: (1) development of the electron beam resist characterization tool set, (2) understanding the fundamental material behavior of a non-chemically amplified polysulfone-novolac (SNS) e-beam resist for next generation mask making, (3) lithographic process development and optimization for the SNS resists, (4) evaluation of the lithographic performance of the SNS resists using the optimized processing conditions, and (5) develop

  6. Fullerene freejets-based synthesis of silicon carbide: heteroepitaxial growth on Si(111) at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Aversa, L.; Verucchi, R.; Boschetti, A.; Podesta, A.; Milani, P.; Iannotta, S

    2003-08-15

    The growth of silicon carbide (SiC), a large band-gap semiconductor, on Si is very promising for applications to sensors, electronics and optoelectronics. However, difficulties in controlling the growth of the material and the interface have inhibited the production of SiC based devices. We have developed a new technique (Supersonic Molecular Beam Epitaxy, SuMBE) for the heteroepitaxial growth of SiC on Si by means of supersonic molecular beams of fullerene (C{sub 60}). The carbide synthesis can be induced by the kinetic activation of the process due to the kinetic energy released in C{sub 60}-Si collision. This has made possible a reduction of the growth substrate temperature and an improvement of electronic and structural properties of the SiC film. We present a study of the processes governing the growth of very thin SiC film by C{sub 60} supersonic beam. Two films were grown in Ultra High Vacuum (UHV) on Si(111)-7x7, at substrate temperature of 800 deg. C, using the same fullerene beam but selecting C{sub 60} particles having different characteristics. Surface electronic and structural characterizations were done both in situ and ex situ. The results show that strongly different growth processes can be achieved by controlling the precursor kinetic energy.

  7. New catalysts for coal processing: Metal carbides and nitrides

    Energy Technology Data Exchange (ETDEWEB)

    S. Ted Oyama; David F. Cox

    1999-12-03

    The subject of this research project was to investigate the catalytic properties of a new class of materials, transition metal carbides and nitrides, for treatment of coal liquid and petroleum feedstocks. The main objectives were: (1) preparation of catalysts in unsupported and supported form; (2) characterization of the materials; (3) evaluation of their catalytic properties in HDS and HDN; (4) measurement of the surface properties; and (5) observation of adsorbed species. All of the objectives were substantially carried out and the results will be described in detail below. The catalysts were transition metal carbides and nitrides spanning Groups 4--6 in the Periodic Table. They were chosen for study because initial work had shown they were promising materials for hydrotreating. The basic strategy was first to prepare the materials in unsupported form to identify the most promising catalyst, and then to synthesize a supported form of the material. Already work had been carried out on the synthesis of the Group VI compounds Mo{sub 2}C, Mo{sub 2}N, and WC, and new methods were developed for the Group V compounds VC and NbC. All the catalysts were then evaluated in a hydrotreating test at realistic conditions. It was found that the most active catalyst was Mo{sub 2}C, and further investigations of the material were carried out in supported form. A new technique was employed for the study of the bulk and surface properties of the catalysts, near edge x-ray absorption spectroscopy (NEXAFS), that fingerprinted the electronic structure of the materials. Finally, two new research direction were explored. Bimetallic alloys formed between two transition metals were prepared, resulting in catalysts having even higher activity than Mo{sub 2}C. The performance of the catalysts in hydrodechloration was also investigated.

  8. 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.

  9. Handbook of refractory carbides and nitrides properties, characteristics, processing and applications

    CERN Document Server

    Pierson, Hugh O

    1996-01-01

    Refractory carbides and nitrides are useful materials with numerous industrial applications and a promising future, in addition to being materials of great interest to the scientific community. Although most of their applications are recent, the refractory carbides and nitrides have been known for over one hundred years. The industrial importance of the refractory carbides and nitrides is growing rapidly, not only in the traditional and well-established applications based on the strength and refractory nature of these materials such as cutting tools and abrasives, but also in new and promising fields such as electronics and optoelectronics.

  10. Production of copper-niobium carbide nanocomposite powders via mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Marques, M.T. [INETI-DMTP, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal)]. E-mail: tmarques@ineti.pt; Livramento, V. [INETI-DMTP, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Correia, J.B. [INETI-DMTP, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Almeida, A. [IST-Dep. Eng. de Materiais, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Vilar, R. [IST-Dep. Eng. de Materiais, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)

    2005-06-15

    Nanocrystalline niobium carbide was synthesed in situ in a copper matrix during high-energy milling of elemental powders. Three powder batches were produced with nominal compositions of 5, 10 and 20 vol.% NbC. Characterisation by X-ray diffraction and scanning electron microscopy indicates that early during the milling process a carbide dispersion is formed within a nanostructured copper matrix. After annealing at 873 K, the carbide structure and particle size are maintained, reflecting the ability of the microstructure to resist to coarsening. The hardness levels attained are more than twice those of nanostructured copper.

  11. Effect of process parameters on induction plasma reactive deposition of tungsten carbide from tungsten metal powder

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Tungsten carbide deposit was made directly from tungsten metal powder through the reaction with methane in radio frequency induction plasma. Effect of major process parameters on the induction plasma reactive deposition of tungsten carbide was studied by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, water displacement method, and microhardness test. The results show that methane flow rate, powder feed rate, particle size, reaction chamber pressure and deposition distance have significant influences on the phase composition, density, and microhardness of the deposit. Extra carbon is necessary to ensure the complete conversion of tungsten metal into the carbide.

  12. Development of High Performance Electron Beam Switching System for Swiss Free Electron Laser at PSI

    CERN Document Server

    Paraliev, M

    2012-01-01

    A compact X-ray Free Electron Laser (SwissFEL) is under development at the Paul Scherrer Institute. To increase facility efficiency the main linac will operate in two electron bunch mode. The two bunches are separated in time by 28 ns and sent to two undulator lines. The combination of two beam lines should produce short X-ray pulses covering wavelength range from 1 to 70 {\\AA} with submicron position stability. To separate the two bunches, a novel electron beam switching system is being developed. The total deflection is achieved with a combination of high Q-factor resonant deflector magnet, followed by a DC septum magnet. The shot-to-shot deflection stability of the entire switching system should be <+/-10 ppm in amplitude and +/-100 ps in time, values which present severe measurement difficulties. Deflection magnets requirements, development and results of the kicker prototype are presented.

  13. 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

  14. 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.

  15. 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...

  16. Ultracapacitor/battery electronic interface development. Final report

    Energy Technology Data Exchange (ETDEWEB)

    King, R.D.; Salasoo, L.; Schwartz, J.; Cardinal, M.

    1998-06-30

    A flexible, highly efficient laboratory proof-of-concept Ultracapacitor/Battery Interface power electronic circuit with associated controls was developed on a cost-shared contract funded by the US Department of Energy (DOE), the New York State Energy Research and Development Authority (NYSERDA), and the General Electric Company (GE). This power electronic interface translates the varying dc voltage on an ultracapacitor with bi-directional power flow to the dc bus of an inverter-supplied ac propulsion system in an electric vehicle application. In a related application, the electronic interface can also be utilized to interface a low-voltage battery to a dc bus of an inverter supplied ac propulsion system. Variations in voltage for these two intended applications occur (1) while extracting energy (discharge) or supplying energy (charge) to an ultracapacitor, and (2) while extracting energy (discharge) or supplying energy (charge) to a low-voltage battery. The control electronics of this interface is designed to be operated as a stand-alone unit acting in response to an external power command. However, the interface unit`s control is not configured to provide any of the vehicle system control functions associated with load leveling or power splitting between the propulsion battery and the ultracapacitor in an electric or hybrid vehicle application. A system study/preliminary design effort established the functional specification of the interface unit, including voltage, current, and power ratings, to meet the program objectives and technical goals for the development of a highly efficient ultracapacitor/battery electronic interface unit; and performed a system/application study of a hybrid-electric transit bus including an ultracapacitor and appropriate electronic interface. The maximum power capability of the ultracapacitor/battery electronic interface unit is 25 kW.

  17. Boron carbide coating deposition on tungsten substrates from atomic fluxes of boron and carbon

    Science.gov (United States)

    Sadovskiy, Y.; Begrambekov, L.; Ayrapetov, A.; Gretskaya, I.; Grunin, A.; Dyachenko, M.; Puntakov, N.

    2016-09-01

    A device used for both coating deposition and material testing is presented in the paper. By using lock chambers, sputtering targets are easily exchanged with sample holder thus allowing testing of deposited samples with high power density electron or ion beams. Boron carbide coatings were deposited on tungsten samples. Methods of increasing coating adhesion are described in the paper. 2 μm boron carbide coatings sustained 450 heating cycles from 100 to 900 C. Ion beam tests have shown satisfactory results.

  18. Wear resistant steels and casting alloys containing niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Theisen, W.; Siebert, S.; Huth, S. [Lehrstuhl Werkstofftechnik, Ruhr-Univ. Bochum (Germany)

    2007-12-15

    Niobium, like titanium and vanadium, forms superhard MC carbides that remain relatively pure in technical alloys on account of their low solubility for other metallic alloying elements. However, because they have a greater hardness than the precipitated chromium carbides commonly used in wear-resistant alloys, they are suitable as alternative hard phases. This contribution deals with new wear-resistant steels and casting alloys containing niobium carbide. These include a secondary hardening hardfacing alloy, a composite casting alloy for wear applications at elevated temperatures, a white cast iron as well as two variants of a corrosion-resistant cold-work tool steel produced by melt metallurgy and by powder metallurgy. A heat-resistant casting alloy is also discussed. Based on equilibrium calculations the microstructures developing during production of the alloys are analysed, and the results are discussed with respect to important properties such as abrasive wear and corrosion resistance. (orig.)

  19. Nanoporous molybdenum carbide wires as an active electrocatalyst towards the oxygen reduction reaction.

    Science.gov (United States)

    Liao, Lei; Bian, Xiaojun; Xiao, Jingjing; Liu, Baohong; Scanlon, Micheál D; Girault, Hubert H

    2014-06-01

    A non-precious metal electrocatalyst has been developed for the oxygen reduction reaction based on nanoporous molybdenum carbide (nano-Mo2C) wires through a facile calcination of sub-nanometer periodic organic-inorganic hybrid nanowires. The highly dispersed Mo2C wires were composed of 10-15 nm nanocrystals with a mesopore size of 3.3 nm. The properties of nano-Mo2C wires were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N2 adsorption/desorption porosimetry. The highly active surface area and enriched nanoporosity for nano-Mo2C wires are unique features that make them a high-performance electrocatalyst for oxygen reduction in an alkaline medium. The electrocatalysis and reaction kinetics results show that nano-Mo2C-based materials can be developed as new catalysts with high activity at low cost for electrochemical energy conversion applications.

  20. Characterization and refinement of carbide coating formation rates and dissolution kinetics in the Ta-C system

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Patrick James [Univ. of New Mexico, Albuquerque, NM (United States)

    1996-10-01

    The interaction between carbide coating formation rates and dissolution kinetics in the tantalum-carbon system was investigated. The research was driven by the need to characterize carbide coating formation rates. The characterization of the carbide coating formation rates was required to engineer an optimum processing scheme for the fabrication of the ultracorrosion-resistant composite, carbon-saturated tantalum. A packed-bed carburization process was successfully engineered and employed. The packed-bed carburization process produced consistent, predictable, and repeatable carbide coatings. A digital imaging analysis measurement process for accurate and consistent measurement of carbide coating thicknesses was developed. A process for removing the chemically stable and extremely hard tantalum-carbide coatings was also developed in this work.

  1. Electronic money in russia: current state and problems of development

    Directory of Open Access Journals (Sweden)

    T. G. Bondarenko

    2016-01-01

    Full Text Available Article is devoted to urgent problems of non-cash methods of calculation development by using electronic money – as one of the modern economically developed state strategic tasks. On modern economic science strong influence appears informatization process. The control expansion tendency, influence and distribution of commerce due to informatization of society led to emergence of the new phenomenon – information economy. Information economy brought new economic events which owing to their novelty are insufficiently studied to life. It is possible to carry electronic money to such phenomena of modern network economy Relevance and, in our opinion, timeliness of this scientific work, consisting in novelty of this non-cash payment method, its prospects and innovation within non-cash methods of calculations. Authors set as the purpose – studying of problems and the prospects of development of electronic money in the Russian Federation. In article theoretical bases of electronic money functioning are described. Determinations and classifications dismissed non-cash a method, and also the principles of electronic money functioning are considered, the questions of their historical development are raised.Authors analyzed statistical data on development of electronic services and channels of their using. Features, benefits and shortcomings of the current state of the market of electronic money are studied. The emphasis on that fact that in modern conditions considerable number of economic actors perform the activities, both in the real environment of economy, and within the virtual environment that promotes expansion of methods of their customer interaction by means of technical devices of personal computers, mobile phones is placed. In article common problems and tendencies of payments with using an electronic money are designated, the research on assessment of the current state and the prospects of electronic money

  2. Development of maskless electron-beam lithography using nc-Si electron-emitter array

    Science.gov (United States)

    Kojima, A.; Ikegami, N.; Yoshida, T.; Miyaguchi, H.; Muroyama, M.; Nishino, H.; Yoshida, S.; Sugata, M.; Cakir, S.; Ohyi, H.; Koshida, N.; Esashi, M.

    2013-03-01

    This study demonstrated our prototyped Micro Electro Mechanical System (MEMS) electron emitter which is a nc-Si (nanocrystalline silicon) ballistic electron emitter array integrated with an active-matrix driving LSI for high-speed Massively Parallel Electron Beam Direct Writing (MPEBDW) system. The MPEBDW system consists of the multi-column, and each column provides multi-beam. Each column consists of emitter array, a MEMS condenser lens array, an MEMS anode array, a stigmator, three-stage deflectors to align and to scan the multi beams, and a reduction lens as an objective lens. The emitter array generates 100x100 electron beams with binary patterns. The pattern exposed on a target is stored in one of the duplicate memories in the active matrix LSI. After the emission, each electron beam is condensed into narrow beam in parallel to the axis of electron optics of the system with the condenser lens array. The electrons of the beams are accelerated and pass through the anode array. The stigmator and deflectors make fine adjustments to the position of the beams. The reduction lens in the final stage focuses all parallel beams on the surface of the target wafer. The lens reduces the electron image to 1%-10% in size. Electron source in this system is nc-Si ballistic surface electron emitter. The characteristics of the emitter of 1:1 projection of e-beam have been demonstrated in our previous work. We developed a Crestec Surface Electron emission Lithography (CSEL) for mass production of semiconductor devices. CSEL system is 1:1 electron projection lithography using surface electron emitter. In first report, we confirmed that a test bench of CSEL resolved below 30 nm pattern over 0.2 um square area. Practical resolution of the system is limited by the chromatic aberration. We also demonstrated the CSEL system exposed deep sub-micron pattern over full-field for practical use. As an interim report of our development of MPEBDW system, we evaluated characteristics of the

  3. Sintering behavior of alumina-niobium carbide ceramics from polymer-filler mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Acchar, W.; Wolff, D.M.B. [Programa de Doutorado em Engenharia e Ciencia dos Materiais-UFRN, Univ. Federal do Rio Grande do Norte, Natal, RN (Brazil); S. Dantas, A.C. da [Programa de Pos-graduacao em Engenharia Mecanica-UFRN, Univ. Federal do Rio Grande do Norte - Natal, RN (Brazil)

    2003-07-01

    Studies have been developed in the literature to obtain alternative ceramic cutting tools with better properties as tungsten carbide and silicon nitride. Results have showed that the addition of titanium carbide, tungsten carbide or niobium carbide has improved the wear resistance and hardness of alumina. This work presents a study about preparation and characterization of an alumina reinforced with niobium carbide. The composite material is produced using polymer-filler mixtures. Samples with 60 wt.% polysiloxane and a mixture of 40 wt.% of niobium and alumina powder were mixed, uniaxially pressed at 200 C and sintered in flowing argon at 1200 C, 1400 C and 1600 C. The composite materials were characterized by X-ray diffraction (XRD), density measurements, fracture strength and microstructural analysis. The 60 wt% polymer+40 wt% Nb showed the presence of new crystalline phases such as NbC, Nb{sub 5}Si{sub 3} and Nb{sub 3}Si. (orig.)

  4. 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.

  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. Optimization of companies’ activity on development of electronic product

    Directory of Open Access Journals (Sweden)

    K.V. Nalivaychenko

    2012-02-01

    Full Text Available The article considers modern processes of informatization of activity for business companies. There are generalized the makes of world companies, which create information technologies in global information environment: the electronic information product containing an universal development algorithm for it, is most effective. It is found that companies prefer opened program codes.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Min; Lee, Byung Cheol; Kim, Sun Kook; Jeong, Young Uk; Cho, Sung Oh

    2000-10-01

    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 2x10{sup 9} at 2.5K, and 8x10{sup 9} 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.

  8. An Exploration of Neutron Detection in Semiconducting Boron Carbide

    Science.gov (United States)

    Hong, Nina

    The 3He supply problem in the U.S. has necessitated the search for alternatives for neutron detection. The neutron detection efficiency is a function of density, atomic composition, neutron absorption cross section, and thickness of the neutron capture material. The isotope 10B is one of only a handful of isotopes with a high neutron absorption cross section---3840 barns for thermal neutrons. So a boron carbide semiconductor represents a viable alternative to 3He. This dissertation provides an evaluation of the performance of semiconducting boron carbide neutron detectors grown by plasma enhance chemical vapor deposition (PECVD) in order to determine the advantages and drawbacks of these devices for neutron detection. Improved handling of the PECVD system has resulted in an extremely stable plasma, enabling deposition of thick films of semiconducting boron carbide. A variety of material and semiconducting characterization tools have been used to investigate the structure and electronic properties of boron carbide thin films, including X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, infrared/Raman spectroscopy, current-voltage measurements and capacitance-voltage measurements. Elemental concentrations in the boron carbide films have been obtained from Rutherford backscattering and elastic recoil detection analysis. Solid state neutron detection devices have been fabricated in the form of heterostructured p-n diodes, p-type boron carbide/n-type Si. Operating conditions, including applied bias voltage, and time constants, have been optimized for maximum detection efficiency and correlated to the semiconducting properties investigated in separate electronic measurements. Accurate measurements of the neutron detection efficiency and the response of the detector to a wide range of neutron wavelengths have been performed at a well calibrated, tightly collimated, "white" cold neutron beam source using time-of-flight neutron detection technique

  9. The synthesis of titanium carbide-reinforced carbon nanofibers.

    Science.gov (United States)

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

    2009-06-24

    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.

  10. 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.

  11. 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.

  12. Semiconducting boron carbides with better charge extraction through the addition of pyridine moieties

    Science.gov (United States)

    Echeverria, Elena; Dong, Bin; Peterson, George; Silva, Joseph P.; Wilson, Ethiyal R.; Sky Driver, M.; Jun, Young-Si; Stucky, Galen D.; Knight, Sean; Hofmann, Tino; Han, Zhong-Kang; Shao, Nan; Gao, Yi; Mei, Wai-Ning; Nastasi, Michael; Dowben, Peter A.; Kelber, Jeffry A.

    2016-09-01

    The plasma-enhanced chemical vapor (PECVD) co-deposition of pyridine and 1,2 dicarbadodecaborane, 1,2-B10C2H12 (orthocarborane) results in semiconducting boron carbide composite films with a significantly better charge extraction than plasma-enhanced chemical vapor deposited semiconducting boron carbide synthesized from orthocarborane alone. The PECVD pyridine/orthocarborane based semiconducting boron carbide composites, with pyridine/orthocarborane ratios ~3:1 or 9:1 exhibit indirect band gaps of 1.8 eV or 1.6 eV, respectively. These energies are less than the corresponding exciton energies of 2.0 eV-2.1 eV. The capacitance/voltage and current/voltage measurements indicate the hole carrier lifetimes for PECVD pyridine/orthocarborane based semiconducting boron carbide composites (3:1) films of ~350 µs compared to values of  ⩽35 µs for the PECVD semiconducting boron carbide films fabricated without pyridine. The hole carrier lifetime values are significantly longer than the initial exciton decay times in the region of ~0.05 ns and 0.27 ns for PECVD semiconducting boron carbide films with and without pyridine, respectively, as suggested by the time-resolved photoluminescence. These data indicate enhanced electron-hole separation and charge carrier lifetimes in PECVD pyridine/orthocarborane based semiconducting boron carbide and are consistent with the results of zero bias neutron voltaic measurements indicating significantly enhanced charge collection efficiency.

  13. Kinetics and Mechanisms of Creep in Sintered Alpha Silicon Carbide and Niobium Carbide.

    Science.gov (United States)

    1985-09-18

    CARBIDE AND NIOBIUM CARBIDE Supported by 30 F (DMR-812-0804) and ARO (MIPR’s 43-48, 127-83, 141-84) U August, 1985 NCSU .LET tow A CL School of Engineering...SILICON CARBIDE AND NIOBIUM CARBIDE Supported by NSF (DMR-812-0804) and ARO (MIPR’s 43-48, 127-83, 141-84) August, 1985 L. U. 1’ ’’ b b MASTER COPY - FOR...and Mechanisms of Creep in Sintered May 1, 1982-June 15, 1985 Alpha Silicon Carbide and Niobium Carbide 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(*) 11

  14. 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).

  15. The CECAM Electronic Structure Library: community-driven development of software libraries for electronic structure simulations

    Science.gov (United States)

    Oliveira, Micael

    The CECAM Electronic Structure Library (ESL) is a community-driven effort to segregate shared pieces of software as libraries that could be contributed and used by the community. Besides allowing to share the burden of developing and maintaining complex pieces of software, these can also become a target for re-coding by software engineers as hardware evolves, ensuring that electronic structure codes remain at the forefront of HPC trends. In a series of workshops hosted at the CECAM HQ in Lausanne, the tools and infrastructure for the project were prepared, and the first contributions were included and made available online (http://esl.cecam.org). In this talk I will present the different aspects and aims of the ESL and how these can be useful for the electronic structure community.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. On carbide dissolution in an as-cast ASTM F-75 alloy.

    Science.gov (United States)

    Caudillo, M; Herrera-Trejo, M; Castro, M R; Ramírez, E; González, C R; Juárez, J I

    2002-02-01

    The solution treatment of an as-cast ASTM F-75 alloy was investigated. Microstructural evolution was followed during thermal processing, in particular with regard to the content and type of carbides formed. To evidence any probable carbide transformations occurring during the heating stage, as well as to clarify their effect on the carbide dissolution kinetics, three heating rates were studied. Image analysis and scanning electron microscopy techniques were used for microstructural characterization. For the identification of precipitates, these were electrolytically extracted from the matrix and then analyzed by X-ray diffraction. It was found that the precipitates in the as-cast alloy were constituted by both a M(23)C(6) carbide and a sigma intermetallic phase. The M(23)C(6) carbide was the only phase identified in solution-treated specimens, regardless of the heating rate employed, which indicated that this carbide dissolved directly into the matrix without being transformed first into an M(6)C carbide, as reported in the literature. It was found that the kinetics of dissolution for the M(23)C(6) carbide decreased progressively during the solution treatment, and that it was sensitive to the heating rate, decreasing whenever the latter was decreased. Because the M(23)C(6) carbide was not observed to suffer a phase transformation prior to its dissolution into the matrix, the effect of the heating rate was associated to the morphological change occurred as the specimens were heated. The occurrence of the observed phases was analyzed with the aid of phase diagrams computed for the system Co-Cr-Mo-C.

  1. 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.

  2. Effect of Heating Rate on Accelerated Carbide Spheroidisation (ASR in 100CrMnSi6-4 Bearing Steel

    Directory of Open Access Journals (Sweden)

    Hauserova D.

    2014-10-01

    Full Text Available Typical processing routes for bearing steels include a soft annealing stage, the purpose of which is to obtain a microstructure containing globular carbides in ferritic matrix. A newly developed process called ASR cuts the carbide spheroidisation times several fold, producing considerably finer globular carbides than conventional soft annealing. The present paper explores the effect of the heating rate and temperature on the accelerated carbide spheroidisation process and on the resulting hardness. Accelerated spheroidisation was achieved by thermal cycling for several minutes around various temperatures close to the transformation temperature at various heating rates applied by induction heating.

  3. Tribological behaviors of graphite sliding against cemented carbide in CaCl2 solution

    Science.gov (United States)

    Guo, Fei; Tian, Yu; Liu, Ying; Wang, Yuming

    2015-12-01

    The tribological behaviors of graphite sliding against cemented carbide were investigated using a standard tribological tester Plint TE92 in a ring-on-ring contact configuration in both CaCl2 solution and deionized water. An interesting phenomenon occurred: as the CaCl2 solution concentration increased, the friction coefficient firstly decreased and was lower than that in the deionized water, and then gradually increased, exceeding the friction coefficient in the deionized water. The wear rate of the ,graphite also presented the same variation trend. According to the polarization curves of cemented carbide, contact angle measurements, Raman spectrum analysis and scanning electron microscope (SEM) images analysis, the above friction and wear behaviors of graphite sliding against cemented carbide were attributed to the graphite surface wettability and the cemented carbide surface corrosion property.

  4. Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation.

    Science.gov (United States)

    Ochedowski, Oliver; Osmani, Orkhan; Schade, Martin; Bussmann, Benedict Kleine; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika

    2014-06-06

    The controlled creation of defects in silicon carbide represents a major challenge. A well-known and efficient tool for defect creation in dielectric materials is the irradiation with swift (E(kin) ≥ 500 keV/amu) heavy ions, which deposit a significant amount of their kinetic energy into the electronic system. However, in the case of silicon carbide, a significant defect creation by individual ions could hitherto not be achieved. Here we present experimental evidence that silicon carbide surfaces can be modified by individual swift heavy ions with an energy well below the proposed threshold if the irradiation takes place under oblique angles. Depending on the angle of incidence, these grooves can span several hundreds of nanometres. We show that our experimental data are fully compatible with the assumption that each ion induces the sublimation of silicon atoms along its trajectory, resulting in narrow graphitic grooves in the silicon carbide matrix.

  5. Thermo-Mechanical Characterization of Silicon Carbide-Silicon Carbide Composites at Elevated Temperatures Using a Unique Combustion Facility

    Science.gov (United States)

    2009-09-10

    F THERMO-MECHANICAL CHARACTERIZATION OF SILICON CARBIDE - SILICON CARBIDE COMPOSITES AT ELEVATED...MECHANICAL CTERIZATION OF SILICON CARBIDE -SILIC BIDE COMPOSITES AT LEVATED TEMPER S USING A UNIQUE COMBUSTION FACILITY DISSERTATI N Ted T. Kim...THERMO-MECHANICAL CHARACTERIZATION OF SILICON CARBIDE - SILICON CARBIDE COMPOSITES AT ELEVATED TEMPERATURES USING A UNIQUE COMBUSTION FACILITY

  6. [Calcium carbide of different crystal formation synthesized by calcium carbide residue].

    Science.gov (United States)

    Lu, Zhong-yuan; Kang, Ming; Jiang, Cai-rong; Tu, Ming-jing

    2006-04-01

    To recycle calcium carbide residue effectively, calcium carbide of different crystal form, including global aragonite, calcite and acicular calcium carbide was synthesized. Both the influence of pretreatment in the purity of calcium carbide, and the influence of temperatures of carbonization reaction, release velocity of carbon dioxide in the apparition of calcium carbide of different crystal form were studied with DTA-TG and SEM. The result shows that calcium carbide residue can take place chemistry reaction with ammonia chlorinate straight. Under the condition that pH was above 7, the purity of calcium carbide was above 97%, and the whiteness was above 98. Once provided the different temperatures of carbonization reaction and the proper release velocity of carbon dioxide, global aragonite, calcite and acicular calcium carbide were obtained.

  7. 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.

  8. Nanotube field electron emission: principles, development, and applications

    Science.gov (United States)

    Li, Yunhan; Sun, Yonghai; Yeow, J. T. W.

    2015-06-01

    There is a growing trend to apply field emission (FE) electron sources in vacuum electronic devices due to their fast response, high efficiency and low energy consumption compared to thermionic emission ones. Carbon nanotubes (CNTs) have been regarded as a promising class of electron field emitters since the 1990s and have promoted the development of FE technology greatly because of their high electrical and thermal conductivity, chemical stability, high aspect ratio and small size. Recent studies have shown that FE from CNTs has the potential to replace conventional thermionic emission in many areas and that it exhibits advanced features in practical applications. Consequently, FE from nanotubes and applications thereof have attracted much attention. This paper provides a comprehensive review of both recent advances in CNT field emitters and issues related to applications of CNT based FE. FE theories and principles are introduced, and the early development of field emitters is related. CNT emitter types and their FE performance are discussed. The current situation for applications based on nanotube FE is reviewed. Although challenges remain, the tremendous progress made in CNT FE over the past ten years indicates the field’s development potential.

  9. Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide.

    Science.gov (United States)

    de Heer, Walt A; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward

    2011-10-11

    After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultrahigh vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The Georgia Tech team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high-quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the "furnace grown" graphene. Graphene multilayers grown on the carbon-terminated face of SiC, using the CCS method, were shown to consist of decoupled high mobility graphene layers. The CCS method is now applied on structured silicon carbide surfaces to produce high mobility nano-patterned graphene structures thereby demonstrating that EG is a viable contender for next-generation electronics. Here we present for the first time the CCS method that outperforms other epitaxial graphene production methods.

  10. Visualization issues in the development of electronic atlas in China

    Institute of Scientific and Technical Information of China (English)

    WANGYingjie; SUYing; CHENXiaogang; YUZhuoyuan; LiqiuMENG

    2005-01-01

    In this paper, we discuss the development of electronic atlas in China, with focus on the issues of visualization. We particularly categorise this development into four periods, and then analyse the characters in each period and discuss the visualization issues. The four periods are highlighted: 1)Infant period (2001) characterized as web mapping and adaptive map design with products of Internet maps and atlas as well as adaptive maps. It is obvious that the development follows the logical way from static to dynamic, and even real time visualization, from single user to multiple users, from presentation to exploration for effective communication and knowledge construction. Current research and development projects are focused on customisation of at/as information systems for real-time tasks, Internet operability, small displays and mobile environments. The major challenges involved in each of such customisation processes are identified and commented in relation to the further development of visualization.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Investigation of Infiltrated and Sintered Titanium Carbide

    Science.gov (United States)

    1952-04-01

    taneive investigations in this field during the ’time preceding this contract, and concentrated their effort® On titanium carbide as the’ refractospy...component • The Basic work of this investigation consisted of? X, KpälfiCÄVtloh and refinement of cOmätrcial grades of titanium carbide hj...facilitate a comparison between the different methods» an investigation was then carried out with composite bodies* consisting of titanium carbide asd

  16. 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.

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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

    2014-01-15

    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.

  2. Observation of ‘hidden’ planar defects in boron carbide nanowires and identification of their orientations

    Science.gov (United States)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Grady, D.E.

    1994-02-01

    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 pecursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides.

  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. Silicon carbide fibers and articles including same

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E; Griffith, George W

    2015-01-27

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

  6. 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.

  7. Electronic materials with a wide band gap: recent developments

    Directory of Open Access Journals (Sweden)

    Detlef Klimm

    2014-09-01

    Full Text Available The development of semiconductor electronics is reviewed briefly, beginning with the development of germanium devices (band gap Eg = 0.66 eV after World War II. A tendency towards alternative materials with wider band gaps quickly became apparent, starting with silicon (Eg = 1.12 eV. This improved the signal-to-noise ratio for classical electronic applications. Both semiconductors have a tetrahedral coordination, and by isoelectronic alternative replacement of Ge or Si with carbon or various anions and cations, other semiconductors with wider Eg were obtained. These are transparent to visible light and belong to the group of wide band gap semiconductors. Nowadays, some nitrides, especially GaN and AlN, are the most important materials for optical emission in the ultraviolet and blue regions. Oxide crystals, such as ZnO and β-Ga2O3, offer similarly good electronic properties but still suffer from significant difficulties in obtaining stable and technologically adequate p-type conductivity.

  8. Latest Diagnostic Electronics Development for the PROSCAN Proton Accelerator

    Science.gov (United States)

    Duperrex, P. A.; Frei, U.; Gamma, G.; Müller, U.; Rezzonico, L.

    2004-11-01

    New VME-based diagnostic electronics are being developed for PROSCAN, a proton accelerator for medical application presently under construction at PSI. One new development is a VME-based multi-channel logarithmic amplifier for converting current to voltage (LogIV). The LogIV boards are used for measuring current from the multiple wire (harp) profile monitors. The LogIV calibration method, current dependant bandwidth and temperature stability are presented. Another development is a BPM front end, based on the newest digital receiver techniques. Features of this new system are the remote control of the preamplifier stage and the continuous monitoring of each individual signal overall gain. Characteristics of the developed prototype are given.

  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.

  10. Electrochemical isolation of intermetallic and carbide phases from nickel-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shul' ga, A.V.; Nikishanov, V.V.; Ofitserov, A.V.

    1988-01-01

    Parameters of carbide phases were examined to find the optimum conditions for isolating intermetallic and carbide phases from complex nickel-base alloys. Conditions for an electrochemical isolation of the phases are chosen on the basis of polarization curves for the matrix and phases to be isolated. Electrochemical studies were performed with a potentiostat and data from x-ray analyses of the phases are tabulated. Two electrolytes were developed, the first for isolating carbide phases from nickel matrix and from nickel-base superalloys and the second electrolyte isolates intermetallic phases.

  11. 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.

  12. 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.

  13. 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.

  14. Barrier properties of nano silicon carbide designed chitosan nanocomposites.

    Science.gov (United States)

    Pradhan, Gopal C; Dash, Satyabrata; Swain, Sarat K

    2015-12-10

    Nano silicon carbide (SiC) designed chitosan nanocomposites were prepared by solution technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used for studying structural interaction of nano silicon carbide (SiC) with chitosan. The morphology of chitosan/SiC nanocomposites was investigated by field emission scanning electron microscope (FESEM), and high resolution transmission electron microscope (HRTEM). The thermal stability of chitosan was substantially increased due to incorporation of stable silicon carbide nanopowder. The oxygen permeability of chitosan/SiC nanocomposites was reduced by three folds as compared to the virgin chitosan. The chemical resistance properties of chitosan were enhanced due to the incorporation of nano SiC. The biodegradability was investigated using sludge water. The tensile strength of chitosan/SiC nanocomposites was increased with increasing percentage of SiC. The substantial reduction in oxygen barrier properties in combination with increased thermal stability, tensile strength and chemical resistance properties; the synthesized nanocomposite may be suitable for packaging applications.

  15. Electrical transport and thermoelectric properties of boron carbide nanowires

    Science.gov (United States)

    Kirihara, Kazuhiro; Mukaida, Masakazu; Shimizu, Yoshiki

    2017-04-01

    The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200–450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

  16. 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.

  17. 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.

  18. Room temperature quantum emission from cubic silicon carbide nanoparticles.

    Science.gov (United States)

    Castelletto, Stefania; Johnson, Brett C; Zachreson, Cameron; Beke, David; Balogh, István; Ohshima, Takeshi; Aharonovich, Igor; Gali, Adam

    2014-08-26

    The photoluminescence (PL) arising from silicon carbide nanoparticles has so far been associated with the quantum confinement effect or to radiative transitions between electronically active surface states. In this work we show that cubic phase silicon carbide nanoparticles with diameters in the range 45-500 nm can host other point defects responsible for photoinduced intrabandgap PL. We demonstrate that these nanoparticles exhibit single photon emission at room temperature with record saturation count rates of 7 × 10(6) counts/s. The realization of nonclassical emission from SiC nanoparticles extends their potential use from fluorescence biomarker beads to optically active quantum elements for next generation quantum sensing and nanophotonics. The single photon emission is related to single isolated SiC defects that give rise to states within the bandgap.

  19. Laser-induced phase separation of silicon carbide

    Science.gov (United States)

    Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

    2016-11-01

    Understanding the phase separation mechanism of solid-state binary compounds induced by laser-material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (~2.5 nm) and polycrystalline silicon (~5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system.

  20. Surface modification of titanium carbide with carbyne-containing nanocoatings.

    Science.gov (United States)

    Demyashev, G M; Taube, A L; Siores, E

    2002-04-01

    The aim of this research is to investigate a novel approach to surface engineering of biomaterials that are based on transition metals of the groups IVA-VIA. The approach taken relies on the fact that, during the electropolishing of TiC surfaces, the removal of Ti atoms from the TiC surface surpasses that of C atoms. This leads to enrichment of the TiC surface with carbon. Transmission electron microscopic investigation showed that carbon-based films contain carbynes in the form of nanorod-like clusters with lengths in the range of 5-100 nm. This carbyne-containing layer is 50-100 nm thick. It was generalized that carbyne-containing nanofilms are formed on the carbide surface of transition metals of groups IVA-VIA during electropolishing. Since carbynes, being one-dimensional chain-like structures [(-C identical to C-)n/(=C=C=)n] with sp1 carbon-carbon hybridization, have the highest degree of biocompatibility because of their biological activity, the development of such surface bioengineering with carbynes extends applications of biomaterials based on transition metals of the groups IVA-VIA.

  1. Processes and applications of silicon carbide nanocomposite fibers

    Energy Technology Data Exchange (ETDEWEB)

    Shin, D G; Cho, K Y; Riu, D H [Nanomaterials Team, Korea Institute of Ceramic Engineering and Technology, 233-5 Gasan-dong, Guemcheon-gu, Seoul 153-801 (Korea, Republic of); Jin, E J, E-mail: dhriu15@seoultech.ac.kr [Battelle-Korea Laborotary, Korea University, Anamdong, Seongbuk-gu, Seoul (Korea, Republic of)

    2011-10-29

    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 {gamma}-Al{sub 2}O{sub 3}. 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. 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.

  3. Lithium and calcium carbides with polymeric carbon structures.

    Science.gov (United States)

    Benson, Daryn; Li, Yanling; Luo, Wei; Ahuja, Rajeev; Svensson, Gunnar; Häussermann, Ulrich

    2013-06-01

    We studied the binary carbide systems Li2C2 and CaC2 at high pressure using an evolutionary and ab initio random structure search methodology for crystal structure prediction. At ambient pressure Li2C2 and CaC2 represent salt-like acetylides consisting of C2(2-) dumbbell anions. The systems develop into semimetals (P3m1-Li2C2) and metals (Cmcm-Li2C2, Cmcm-CaC2, and Immm-CaC2) with polymeric anions (chains, layers, strands) at moderate pressures (below 20 GPa). Cmcm-CaC2 is energetically closely competing with the ground state structure. Polyanionic forms of carbon stabilized by electrostatic interactions with surrounding cations add a new feature to carbon chemistry. Semimetallic P3m1-Li2C2 displays an electronic structure close to that of graphene. The π* band, however, is hybridized with Li-sp states and changed into a bonding valence band. Metallic forms are predicted to be superconductors. Calculated critical temperatures may exceed 10 K for equilibrium volume structures.

  4. On the Carbon Solubility in Expanded Austenite and Formation of Hägg Carbide in AISI 316 Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Ståhl, Kenny; Brink, Bastian;

    2016-01-01

    –420 °C and 465–470 °C, respectively. Hägg carbide (x-M5C2)develops when the carbon content in the expanded austenite exceeds the metastable solubility limit; the transformation of carbon expanded austenite into Hägg carbide occurs irrespective of carburizing temperature in the investigated temperature...

  5. 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.

  6. Tribology of carbide derived carbon films synthesized on tungsten carbide

    Science.gov (United States)

    Tlustochowicz, Marcin

    Tribologically advantageous films of carbide derived carbon (CDC) have been successfully synthesized on binderless tungsten carbide manufactured using the plasma pressure compaction (P2CRTM) technology. In order to produce the CDC films, tungsten carbide samples were reacted with chlorine containing gas mixtures at temperatures ranging from 800°C to 1000°C in a sealed tube furnace. Some of the treated samples were later dechlorinated by an 800°C hydrogenation treatment. Detailed mechanical and structural characterizations of the CDC films and sliding contact surfaces were done using a series of analytical techniques and their results were correlated with the friction and wear behavior of the CDC films in various tribosystems, including CDC-steel, CDC-WC, CDC-Si3N4 and CDC-CDC. Optimum synthesis and treatment conditions were determined for use in two specific environments: moderately humid air and dry nitrogen. It was found that CDC films first synthesized at 1000°C and then hydrogen post-treated at 800°C performed best in air with friction coefficient values as low as 0.11. However, for dry nitrogen applications, no dechlorination was necessary and both hydrogenated and as-synthesized CDC films exhibited friction coefficients of approximately 0.03. A model of tribological behavior of CDC has been proposed that takes into consideration the tribo-oxidation of counterface material, the capillary forces from adsorbed water vapor, the carbon-based tribofilm formation, and the lubrication effect of both chlorine and hydrogen.

  7. Effects of space exposure on ion-beam-deposited silicon-carbide and boron-carbide coatings.

    Science.gov (United States)

    Keski-Kuha, R A; Blumenstock, G M; Fleetwood, C M; Schmitt, D R

    1998-12-01

    Two recently developed optical coatings, ion-beam-deposited silicon carbide and ion-beam-deposited boron carbide, are very attractive as coatings on optical components for instruments for space astronomy and earth sciences operating in the extreme-UV spectral region because of their high reflectivity, significantly higher than any conventional coating below 105 nm. To take full advantage of these coatings in space applications, it is important to establish their ability to withstand exposure to the residual atomic oxygen and other environmental effects at low-earth-orbit altitudes. The first two flights of the Surface Effects Sample Monitor experiments flown on the ORFEUS-SPAS and the CRISTA-SPAS Shuttle missions provided the opportunity to study the effects of space exposure on these materials. The results indicate a need to protect ion-beam-deposited silicon-carbide-coated optical components from environmental effects in a low-earth orbit. The boron-carbide thin-film coating is a more robust coating able to withstand short-term exposure to atomic oxygen in a low-earth-orbit environment.

  8. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Du, Jun [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Li, Qianqian [Institute of Applied Mechanics, Zhejiang University, Hangzhou 310027 (China); Xia, Yang; Cheng, Xuejuan; Gan, Yongping; Huang, Hui [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Zhang, Wenkui, E-mail: msechem@zjut.edu.cn [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Tao, Xinyong, E-mail: tao@zjut.edu.cn [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China)

    2013-12-25

    Graphical abstract: B{sub 4}C 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.

  10. Influence of yttrium oxide doping on the microstructures of alumina-niobium carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Rumbao, A.H.; Bressiani, J.C.; Bressiani, A.H.A. [IPEN - Inst. de Pesquisas Energeticas e Nucleares, Cidade Univ. - Sao Paulo, SP (Brazil)

    2003-07-01

    Ceramic cutting tools have been developed as an alternative material to cemented carbides based ones with the goal of improving cutting speeds and productivity. Among the vast variety of ceramics considered for prospective use as cutting tools materials the preference is given to the composites containing carbides as a second component, i.e., such materials as Al{sub 2}O{sub 3}-SiC, and Al{sub 2}O{sub 3}-TiC. In the present work, the influence of Y{sub 2}O{sub 3} additives on microstructure of Al{sub 2}O{sub 3}-NbC composite is studied in order to evaluate the applicability of this material for as ceramic cutting tools manufacturing. The amount of Y{sub 2}O{sub 3} additives varied in the ranged, 0-3 wt% in the Al{sub 2}O{sub 3}-NbC 20 wt% composition. Specimens were produced by consequent uniaxial and isostatic pressing followed by pressureless sintering in the flowing argon at 1750 C for 15 min in a graphite resistance furnace. The achieved densities were up to 99% TD. Microstructure evaluation in terms of grain size distribution were achieved by mean of QUANTIKOV software applied to scanning electron microscope (SEM) micrographs. Optimization of the materials composition in regard of achieving the high densities without compromising the microstructure formation are discussed. (orig.)

  11. 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.

  12. 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.

  13. 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.

  14. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

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

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first exam...

  15. 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.

  16. Titanium Carbide Bipolar Plate for Electrochemical Devices

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-05-08

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

  17. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

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

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-15

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

  19. Cold Electronics Development for the LBNE LAr TPC

    Science.gov (United States)

    Thorn, C.; De Geronimo, Gianluigi; D'Andragora, Alessio; Li, Shaorui; Nambiar, Neena; Rescia, Sergio; Vernon, Emerson; Chen, Hucheng; Lanni, Francesco; Makowiecki, Don; Radeka, Veljko; Yu, Bo

    The LBNE Project is developing a design for multiple 20 kiloton liquid argon (LAr) time projection chambers to be used as the far detector for the Long Baseline Neutrino Experiment. An essential component of this design is a complete electronic readout system designed to operate in LAr (at 90K). This system is being implemented as a CMOS ASIC, in 180 nm commercial technology, that will provide low-noise readout of the signals induced on the TPC wires, digitization of those signals at 2 MS/s, zero-suppression, buffering and output multiplexing to a small number of cryostat feed-throughs. A resolution better than 1000 rms electrons at 200 pF input capacitance for an input range of 300 fC is required, along with low power (analog-only frontend has been successfully completed and fully evaluated, and will be used in the MicroBooNE LAr TPC. A prototype of the digital section has been fabricated and is being evaluated. The results demonstrate that CMOS transistors have lower noise and much improved dc characteristics at LAr temperature. We will describe the progress to date and plans for the remaining development.

  20. 电石液排放管理在线节能系统开发实践%DEVELOPMENT PRACTICE OF ONLINE ENERGY-SAV-ING CARBIDE LIQUID DISCHARGE MANAGE SYSTEM

    Institute of Scientific and Technical Information of China (English)

    王建领; 张建良; 金鑫; 王汝松; 薛廷超; 焦克新

    2015-01-01

    In order to achieve submerged arc furnace energy-saving and stable production, the physical parameters, electrode parameters, real-time production parameters of calcium carbide production as input, through a series of equilib-rium calculations and regression analysis, based on production of calcium carbide, calcium carbide liquid emissions man-agement model is built, the real yields derived liquid calcium carbide, calcium carbide liquid gas evolution, the time pre-dicted and tons of calcium carbide power consumption etc. parameters are given. By collecting and processing data as well as on-site production of calcium carbide furnace programming technology online, the calculation of is realized, and successfully applied, the information channel between calcium carbide furnace and the main control room is established, which could forecast and reflect the real-time conditions of calcium carbide production status. Practice shows that the op-timal solution of calcium carbide calcium carbide emissions management may be appropriate to increase the liquid gas evolution, increasing the production of calcium carbide production efficiency, while appropriate to reduce the tons of cal-cium carbide power consumption, realizes the high efficiency, energy saving, stable production purposes.%为实现矿热炉节能降耗、稳定生产,以电石生产的物性参数、电极参数、实时生产参数为输入量,通过一系列的平衡计算及回归分析,建立了基于电石液产量的电石液排放管理模型,实时得出电石液产量、电石液发气量、预测电石液排放时间及吨电石耗电量等参数指标。通过采集与处理现场电石炉生产数据以及编程技术实现了该模型的在线计算,并成功应用在电石炉与主控室之间建立起一条电石生产预测的信息通道,实时反映电石生产状态。实践表明,优化电石液排放管理可适当提高电石液发气量,增加电石生产的生产效率,

  1. Archetype Development Process of Electronic Health Record of Minas Gerais.

    Science.gov (United States)

    Abreu Maia, Thais; Fernandes De Muylder, Cristiana; Mendonça Queiroga, Rodrigo

    2015-01-01

    The Electronic Health Record (EHR) supports health systems and aims to reduce fragmentation, which will enable continuity of patient care. The paper's main objective is to define the steps, roles and artifacts for an archetype development process (ADP) for the EHR at the Brazilian National Health System (SUS) in the State of Minas Gerais (MG). This study was conducted using qualitative analysis based upon an applied case. It had an exploratory purpose metodologically defined in four stages: literature review; descriptive comparison; proposition of an archetype development process and proof of concept. The proof of concept showed that the proposed ADP ensures the archetype quality and supports the semantic interoperability in SUS to improve clinical safety and the continuity of patient care.

  2. 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.

  3. Fluorination of silicon carbide thin films using pure F{sub 2} gas or XeF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Batisse, Nicolas [Laboratoire des Materiaux Inorganiques UMR UBP-CNRS 6002, Clermont Universite, Universite Blaise Pascal, Clermont-Ferrand (France); Guerin, Katia, E-mail: Katia.guerin@univ-bpclermont.f [Laboratoire des Materiaux Inorganiques UMR UBP-CNRS 6002, Clermont Universite, Universite Blaise Pascal, Clermont-Ferrand (France); Dubois, Marc; Hamwi, Andre; Spinelle, Laurent; Tomasella, Eric [Laboratoire des Materiaux Inorganiques UMR UBP-CNRS 6002, Clermont Universite, Universite Blaise Pascal, Clermont-Ferrand (France)

    2010-09-30

    Two fluorination methods: direct fluorination using F{sub 2} gas and fluorination by the decomposition of fluorinating agent XeF{sub 2} have been applied to silicon carbide SiC thin films in order to form a composite of carbide derived carbon film together with residual silicon carbide. Before and after fluorination, the thin films have been characterized by Scanning Electron Microscopy, Rutherford Backscattering spectroscopy, Fourier Transformed InfraRed and Raman spectroscopies. Whereas direct fluorination leads to irreversible damages into the thin films, XeF{sub 2} method allows a progressive etching of the silicon atoms and the formation of non-fluorinated carbon.

  4. Process for making silicon carbide reinforced silicon carbide composite

    Science.gov (United States)

    Lau, Sai-Kwing (Inventor); Calandra, Salavatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    1998-01-01

    A process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  5. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    OpenAIRE

    Amado Paz, José Manuel; Tobar Vidal, María José; YAÑEZ CASAL, ARMANDO JOSE; Amigó Borrás, Vicente; Candel Bou, Juan Jose

    2011-01-01

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nomi...

  6. Physico-chemical properties and toxic effect of fruit-ripening agent calcium carbide

    OpenAIRE

    Mohammad Asif

    2012-01-01

    Ripening is the final stage of the maturation process, when the fruit changes color, softens and develops the flavor, texture and aroma that constitute optimum eating quality. This study was conducted to discuss the use of unsatisfactory calcium carbide to ripen fruits for domestic markets as well as their toxic effects on human health. The commonly used ripening agents are calcium carbide, acetylene, ethylene, propylene, ethrel (2-chloroethyl phosphonic acid), glycol, ethanol and some other ...

  7. Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development

    Science.gov (United States)

    2016-09-01

    ARL-TN-0779 ● SEP 2016 US Army Research Laboratory Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and...Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development by Neal Tesny Sensors and Electron Devices Directorate...TITLE AND SUBTITLE Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development 5a. CONTRACT NUMBER 5b

  8. Titanium carbide/carbon composite nanofibers prepared by a plasma process

    Energy Technology Data Exchange (ETDEWEB)

    El Mel, A A; Gautron, E; Angleraud, B; Granier, A; Tessier, P Y [Universite de Nantes, CNRS, Institut des Materiaux Jean Rouxel, UMR 6502, 2 rue de la Houssiniere BP 32229-44322 Nantes cedex 3 (France); Choi, C H [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

    2010-10-29

    The incorporation of metal or metal carbide nanoparticles into carbon nanofibers modifies their properties and enlarges their field of application. The purpose of this work is to report a new non-catalytic and easy method to prepare organized metal carbide-carbon composite nanofibers on nanopatterned silicon substrates prepared by laser interference lithography coupled with deep reactive ion etching. Titanium carbide-carbon composite nanofibers were grown on the top of the silicon lines parallel to the substrate by a hybrid plasma process combining physical vapor deposition and plasma enhanced chemical vapor deposition. The prepared nanofibers were analyzed by scanning electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. We demonstrate that the shape, microstructure and the chemical composition of the as-grown nanofibers can be tuned by changing the plasma conditions.

  9. Titanium carbide/carbon composite nanofibers prepared by a plasma process.

    Science.gov (United States)

    El Mel, A A; Gautron, E; Choi, C H; Angleraud, B; Granier, A; Tessier, P Y

    2010-10-29

    The incorporation of metal or metal carbide nanoparticles into carbon nanofibers modifies their properties and enlarges their field of application. The purpose of this work is to report a new non-catalytic and easy method to prepare organized metal carbide-carbon composite nanofibers on nanopatterned silicon substrates prepared by laser interference lithography coupled with deep reactive ion etching. Titanium carbide-carbon composite nanofibers were grown on the top of the silicon lines parallel to the substrate by a hybrid plasma process combining physical vapor deposition and plasma enhanced chemical vapor deposition. The prepared nanofibers were analyzed by scanning electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. We demonstrate that the shape, microstructure and the chemical composition of the as-grown nanofibers can be tuned by changing the plasma conditions.

  10. Initial Development of an Electronic Testis Rigidity Tester

    Directory of Open Access Journals (Sweden)

    Petros Mirilas

    2011-01-01

    Full Text Available We aimed to develop our previously presented mechanical device, the Testis Rigidity Tester (TRT, into an electronic system (Electronic Testis Rigidity Tester, ETRT by applying tactile imaging, which has been used successfully with other solid organs. A measuring device, located at the front end of the ETRT incorporates a tactile sensor comprising an array of microsensors. By application of a predetermined deformation of 2 mm, increased pressure alters linearly the resistance of each microsensor, producing changes of voltage. These signals were amplified, filtered, and digitized, and then processed by an electronic collector system, which presented them as a color-filled contour plot of the area of the testis coming into contact with the sensor. Testis models of different rigidity served for initial evaluation of ETRT; their evacuated central spaces contained different, increasing glue masses. An independent method of rigidity measurement, using an electric weight scale and a micrometer, showed that the more the glue injected, the greater the force needed for a 2-mm deformation. In a preliminary test, a single sensor connected to a multimeter showed similar force measurement for the same deformation in these phantoms. For each of the testis models compressed in the same manner, the ETRT system offered a map of pressures, represented by a color scale within the contour plot of the contact area with the sensor. ETRT found certain differences in rigidity between models that had escaped detection by a blind observer. ETRT is easy to use and provides a color-coded “insight“ of the testis internal structure. After experimental testing, it could be valuable in intraoperative evaluation of testes, so that the surgeon can decide about orchectomy or orcheopexy.

  11. TRANSFORMATIONS IN NANO-DIAMONDS WITH FORMATION OF NANO-POROUS SILICON CARBIDE AT HIGH PRESSURE

    Directory of Open Access Journals (Sweden)

    V. N. Kovalevsky

    2010-01-01

    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.

  12. 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...

  13. Module and Electronics Developments for the ATLAS ITK Pixel System

    CERN Document Server

    Rummler, Andr{e}; The ATLAS collaboration

    2016-01-01

    The entire tracking system of the ATLAS experiment will be replaced during the LHC Phase II shutdown around 2025 by an all-silicon detector (Inner Tracker, ITk). The pixel detector will be composed by the five innermost layers, instrumented with new sensor and readout electronics technologies to improve the tracking performance and cope with the severe HL-LHC environment in terms of occupancy and radiation. The total area of the new pixel system could measure up to 14 m^2, depending on the final layout choice that is expected to take place in early 2017. Different designs of planar, 3D, CMOS sensors are being investigated to identify the optimal technology for the different pixel layers. In parallel sensor-chip interconnection options are evaluated in collaboration with industrial partners to identify reliable technologies when employing 100-150 μm thin chips. While the new read-out chip is being developed by the RD53 Collaboration, the pixel off detector read-out electronics will be implemented in the frame...

  14. 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

  15. 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.

  16. 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.

  17. Electronic teaching files and continuing professional development in radiology.

    Science.gov (United States)

    Lim, Cct; Yang, Gl

    2006-04-01

    Education in diagnostic radiology employs medical images extensively, and case-based teaching files of actual patients are useful to illustrate pertinent teaching points. In the era of digital radiology, there is great potential to use the ready source of patient material from Picture Archive and Communication Systems (PACS) and initiatives such as Medical Imaging Resource Center (MIRC) on the World Wide Web for teaching and for Continuing Professional Development (CPD). As mandatory CPD becomes the reality in medical practice, computerised solutions that support the creation of electronic teaching files in the midst of busy clinical workflow would be very valuable. This paper will explore the features of image-based CPD, the various ways in which medical images can be used for self directed learning and the challenges that face the radiology profession.

  18. A system of electronic records developed by a children's hospice.

    Science.gov (United States)

    Menezes, Antoinette; Esplen, Polly; Bartlett, Paul; Turner, Bridget; Keel, Mike; Etherington, Veronica; Conisbee, Elaine; Plant, Antonia; Haslam, Val; England, Julie

    2007-05-01

    This paper describes the development, implementation and dissemination of an electronic data collection system for children's hospices in the UK. In 1999, CHASE Hospice Care for Children (CHASE) began providing support for life-limited children and their families in their own homes across south-west London, Surrey and West Sussex. CHASE community team is multidisciplinary and original members of the team had to create all of the necessary administrative systems for collecting and storing information about referrals and care provided to children and their families. The community team had the foresight to record activity statistics from day one of the service. The team worked together to identify information routinely collected that could usefully be stored on a computer database and a simple solution was created for this purpose using Microsoft Access version 2. CHASE was in a privileged position because the commitment to use information technology came from people providing care to children and their families.

  19. 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

  20. Precipitating Mechanism of Carbide in Cold-Welding Surfacing Metals

    Institute of Scientific and Technical Information of China (English)

    Yuanbin ZHANG; Dengyi REN

    2004-01-01

    Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different carbide-forming tendency, Nb and Ti could combine with C to form particulate carbide in liquid weld metal and depleted the carbon content in matrix, while V induced the carbide precipitated along grain boundary. But too much Nb or Ti alone resulted in coarse carbide and poor strengthened matrix. When suitable amount of Nb, Ti and V coexisted in weld metal, both uniformly distributed particulate carbide and well strengthened matrix could be achieved. It was proposed that the carbide nucleated on the oxide which dispersed in liquid weld metal, and then grew into multi-layer complex carbide particles by epitaxial growth. At different sites, carbide particles may present as different morphologies.

  1. 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.

  2. Hydrothermal synthesis of xonotlite from carbide slag

    Institute of Scientific and Technical Information of China (English)

    Jianxin Cao; Fei Liu; Qian Lin; Yu Zhang

    2008-01-01

    Carbide slag was used as the calcareous materials for the first time to prepare xonotlite via dynamic hydrothermal synthesis.The effects of influential factors including different calcination temperatures,pretreatment methods of the carbide slag and process param-eters of hydrothermal synthesis on the microstructure and morphology of xonotlite were explored using XRD and SEM techniques.The results indicate that the carbide slag after proper calcination could be used to prepare pure xonotlite;and different calcination tern-peratures have little effect on the crystallinity of synthesized xonotlitc,but have great impact on the morphology of secondary particles.The different pretreatment methods of the carbide slag pose great impact on the crystallinity and morphology of secondary particles of xonotlite.Xonotlite was also synthesized from pure CaO under the salne experimental conditions as that prepared from calcined carbide slag for comparison.Little amount of impurities in carbide slag has no effect on the mechanism of hydrothermal synthesizing xonotlite from carbide slag.

  3. Synthesis of refractory conductive niobium carbide nanowires within the inner space of carbon nanotube templates

    Science.gov (United States)

    Kobayashi, Keita; Kitaura, Ryo; Wang, Qing; Wakamori, Ikuya; Shinohara, Hisanori; Anada, Satoshi; Nagase, Takeshi; Saito, Takeshi; Kiyomiya, Masaharu; Yasuda, Hidehiro

    2014-01-01

    Conductive niobium carbide (NbC) nanowires with diameters of 1-3 nm were synthesized within the inner space of carbon nanotubes (CNTs) by exposing the CNTs to niobium (V) chloride vapor through hydrogen reduction. The NbC nanowires were found to have a NaCl-type crystal structure by transmission electron microscopy and transmission electron diffractometry. Results from electronic transport measurements imply that the electrical conductivity of the synthesized product was improved compared with that of empty CNTs.

  4. Formation of nanoscale titanium carbides in ferrite: an atomic study

    Science.gov (United States)

    Lv, Yanan; Hodgson, Peter; Kong, Lingxue; Gao, Weimin

    2016-03-01

    The formation and evolution of nanoscale titanium carbide in ferrite during the early isothermal annealing process were investigated via molecular dynamics simulation. The atomic interactions of titanium and carbon atoms during the initial formation process explained the atoms aggregation and carbides formation. It was found that the aggregation and dissociation of titanium carbide occurred simultaneously, and the composition of carbide clusters varied in a wide range. A mechanism for the formation of titanium carbide clusters in ferrite was disclosed.

  5. 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...

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

    OpenAIRE

    Matus K.; Pawlyta M.; Matula G.; Gołombek K.

    2016-01-01

    The aim of this article of this paper is to present issues related to characterization of nanometric-sized carbides, nitrides and/or carbonitrides formed during tempering of carbide-steel cermets. Closer examination of those materials is important because of hardness growth of carbide-steel cermet after tempering. The results obtained during research show that the upswing of hardness is significantly higher than for high-speed steels. Another interesting fact is the displacement of secondary ...

  7. The development of new generation electronic personal dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Aoyama, Kei; Nagase, Yoshiyuki; Suzuki, T. [Fuji Electric Co., Ltd., Tokyo (Japan); Watanabe, Shinichi; Taniguchi, Kazufumi; Muramatsu, Kunihiro; Fujita, Mikio; Fujii, Yutaka [Japan Atomic Power Company, Tokyo (Japan)

    2000-05-01

    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)

  8. RECENT DEVELOPMENTS IN ELECTRONICS UNDER NANOTECHNOLOGY-NANOELECTRONICS

    Directory of Open Access Journals (Sweden)

    Kritika Bhattacharya

    2012-09-01

    Full Text Available This paper presents an insight into some of the recent breakthroughs in nanotechnology which includes various traditional devices like transistors, light emitting diode, capacitors, integrated circuits to achieve efficiency resulting in lesser time and low power consumption. Nanotechnology can be applied to the field of electronics using carbon nanotubes, which when used on a polyamide substrate of a semiconductor wafer provides high mobility, flexibility, shock resistance, on off ratios and switching speeds, impossible to be achieved with glass plates as substrates. Its usage in Active Matrix Organic Light Emitting Diode displays results in high current driving capability unlike polycrystalline silicon in traditional Liquid Crystal Displays. Lately semiconductor nanowires have been developed, exhibiting transparency and highly uniform electrical performance. CNT FETs have come of age where single walled CNTs replace the silicon channel resulting in strong coupling thus shrinking the FET size. The latest area of development of CNTs have been in Super capacitors where CNT heterogeneous films are used to store high amount of energy catering to the needs of high power, energy density and long operation cycles. Thus this farsighted technology has helped in achieving unprecedented densities and speeds which is the need of the hour.

  9. In situ ion irradiation of zirconium carbide

    Science.gov (United States)

    Ulmer, Christopher J.; Motta, Arthur T.; Kirk, Mark A.

    2015-11-01

    Zirconium carbide (ZrC) is a candidate material for use in one of the layers of TRISO coated fuel particles to be used in the Generation IV high-temperature, gas-cooled reactor, and thus it is necessary to study the effects of radiation damage on its structure. The microstructural evolution of ZrCx under irradiation was studied in situ using the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory. Samples of nominal stoichiometries ZrC0.8 and ZrC0.9 were irradiated in situ using 1 MeV Kr2+ ions at various irradiation temperatures (T = 20 K-1073 K). In situ experiments made it possible to continuously follow the evolution of the microstructure during irradiation using diffraction contrast imaging. Images and diffraction patterns were systematically recorded at selected dose points. After a threshold dose during irradiations conducted at room temperature and below, black-dot defects were observed which accumulated until saturation. Once created, the defect clusters did not move or get destroyed during irradiation so that at the final dose the low temperature microstructure consisted only of a saturation density of small defect clusters. No long-range migration of the visible defects or dynamic defect creation and elimination were observed during irradiation, but some coarsening of the microstructure with the formation of dislocation loops was observed at higher temperatures. The irradiated microstructure was found to be only weakly dependent on the stoichiometry.

  10. Formation of titanium carbide coating with micro-porous structure

    Science.gov (United States)

    Luo, Yong; Ge, Shirong; Jin, Zhongmin; Fisher, John

    2010-03-01

    Micro-porous titanium carbide coating was successfully synthesized in a vacuum gas carburizing furnace by using a sequential diffusion technology. The composition and structure of the as-synthesized TiC were examined by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and glow discharge mass spectrometry (GDMS), and scanning electron microscopy (SEM). All of the XRD, XPS and GDMS analysis results indicate that carbon atoms effectively diffused into the titanium alloys and formed a uniform acicular TiC coating with micro-porous structure.

  11. Growth of Vanadium Carbide by Halide-Activated Pack Diffusion

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Dahl, Kristian Vinter;

    The present work investigates growth of vanadium carbide (VC) layers by the pack diffusion method on a Vanadis 6 tool steel. The VC layers were produced by pack diffusion at 1000°C for 1, 4 and 16 hours. The VC layers were characterized with optical and electron microscopy, Vickers hardness tests...... and X-ray diffraction. Homogeneous VC mono-phase layers with Vickers hardness of more than 2400 HV were obtained. Hardening and tempering of the vanadized Vanadis 6 steel did not affect the VC layers....

  12. 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.

  13. 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.

  14. Carbothermal synthesis of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-05-01

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

  15. 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.

  16. 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...

  17. Surface Layer States of Worn Uncoated and TiN-Coated WC/Co-Cemented Carbide Cutting Tools after Dry Plain Turning of Carbon Steel

    Directory of Open Access Journals (Sweden)

    Johannes Kümmel

    2013-01-01

    Full Text Available Analyzing wear mechanisms and developments of surface layers in WC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc., so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings on WC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM, and EDX analysis. The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses.

  18. Fabrication of hierarchical porous carbide-derived carbons by chlorination of mesoporous titanium carbides%氯气刻蚀中孔碳化钛制备分等级孔结构炭材料

    Institute of Scientific and Technical Information of China (English)

    成果; 龙东辉; 刘小军; 凌立成

    2009-01-01

    Mesoporous titanium carbides were prepared via carbothermal reduction of organic-inorganic gels using tita-nium n-butoxide as a Ti source and sucrose as a carbon precursor. The as-made titanium carbides were used as starting materials for producing carbide-derived carbons (CDCs) through thermochemical treatment in a chlorine environment. The influence of the ratio of titanium n-butoxide to sucrose (R) on the porous structure and physical properties of the mesoporous titanium carbide and the resulting CDCs were investigated using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and N2 adsorption. It was found that mesoporosity and macroporosity de-veloped in the course of the formation of the titanium carbides can be preserved and transmitted to the carbon material af-ter chlorine treatment, while microporosity was formed by extraction titanium atoms from the carbide. The obtained CDCs have a hierarchical structure of multiscaled pores, including uniform micropores produced from carbides, meso-pores with diameter of 3-4rim original from the residual free carbon and macropores formed by interconnection and over-lapping of the carbon particles. By changing the R, the Brunauer-Emmett-Teller specific surface areas and total pore vo-lumes of the CDCs could be adjusted in the range of 1479-1640 m2/g and 1.06-2.03 cm3/g, respectively. These hierar-chical porous carbons would have potential applications for use in catalysis, adsorption, gas separation, and electroche-mical energy storage.%以钛酸正丁酯为钛源、蔗糖为炭源,采用溶胶-凝胶法制得有机-无机复合干凝胶,后经高温炭热反应、氯气化学刻蚀分别得到中孔碳化钛及碳化物基炭材料(CDCS).通过XRD、Raman、SEM、TEM和氮气吸附等表征,考察了钛酸正丁酯/蔗糖摩尔比例(R)对所制碳化钛和CDCS的孔结构和物理特性的影响.结果表明:在碳热过程所形成的中孔和大孔孔隙能够在氯气刻蚀过程

  19. Calcium Carbide: A Unique Reagent for Organic Synthesis and Nanotechnology.

    Science.gov (United States)

    Rodygin, Konstantin S; Werner, Georg; Kucherov, Fedor A; Ananikov, Valentine P

    2016-04-01

    Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry. Several highly valuable processes have been developed based on this simplest alkyne and the development of acetylene chemistry has had a paramount impact on chemical science over the last few decades. However, in spite of numerous useful possible reactions, the application of gaseous acetylene in everyday research practice is rather limited. Moreover, the practical implementation of high-pressure acetylene chemistry can be very challenging, owing to the risk of explosion and the requirement for complex equipment; special safety precautions need to be taken to store and handle acetylene under high pressure, which limit its routine use in a standard laboratory setup. Amazingly, recent studies have revealed that calcium carbide, CaC2 , can be used as an easy-to-handle and efficient source of acetylene for in situ chemical transformations. Thus, calcium carbide is a stable and inexpensive acetylene precursor that is available on the ton scale and it can be handled with standard laboratory equipment. The application of calcium carbide in organic synthesis will bring a new dimension to the powerful acetylene chemistry.

  20. Bonding and Integration Technologies for 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, titanium interlayers (PVD and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness (10, 20, and 50 microns), processing time and temperature, and cooling rates were investigated. Microprobe analysis was used to identify the phases in the bonded region. For bonds that were not fully reacted 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 titanium interlayers and/or longer processing times resulted in stable and compatible phases that did not contribute to microcracking and resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Non-destructive 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.

  1. Structure, bonding and stability of semi-carbides M{sub 2}C and sub-carbides M{sub 4}C (M=V, Cr, Nb, Mo, Ta, W): A first principles investigation

    Energy Technology Data Exchange (ETDEWEB)

    Abderrahim, F.Z., E-mail: sara_ais@yahoo.fr [Unite de Recherche Materiaux et Energie Renouvelables, URMER, Universite de Tlemcen (Algeria); Faraoun, H.I. [Unite de Recherche Materiaux et Energie Renouvelables, URMER, Universite de Tlemcen (Algeria); Ouahrani, T. [Laboratoire de Physique Theorique, Universite de Tlemcen B.P. 230, 13000 Tlemcen (Algeria); Ecole Preparatoire en Sciences et Techniques, B.P. 230, 13000 Tlemcen (Algeria)

    2012-09-15

    Density functional theory within the generalized gradient approximation (GGA) is used to investigate the electronic structure and formation energies of semi-carbides M{sub 2}C and sub-carbides M{sub 4}C (where M=V, Cr, Nb, Mo, Ta and W). Our results show that M{sub 2}C carbides are more stable than M{sub 4}C. Total and partial densities of states were obtained and analyzed systematically for these phases. Moreover, the bonding nature of M{sub 2}C polymorphs is studied from the point of view of the Quantum Theory of Atoms in Molecules (QTAIM). It is found that inter-atomic interactions in these carbides are of mixed type including ionic, covalent and metallic components.

  2. Developing a Legal Framework for Remote Electronic Voting

    Science.gov (United States)

    Schmidt, Axel; Heinson, Dennis; Langer, Lucie; Opitz-Talidou, Zoi; Richter, Philipp; Volkamer, Melanie; Buchmann, Johannes

    This paper describes how to legally regulate remote electronic elections. Electronic voting systems have to respect the constitutional election principles. For technological solutions, this translates into security requirements that have to be fulfilled by the operational environment in which the voting takes place. Therefore [26] introduced the concept of providing the technical and organizational implementation of a remote electronic election by a qualified trustworthy third party. This paper adds legal regulation to support this concept. The legal framework addresses the secure operation of remote electronic voting services as well as their accreditation and supervision by an official authority.

  3. 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

  4. 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.

  5. Study of irradiation effects in the silicon carbide cubic polytype by photoluminescence and electron spin resonance spectroscopies; Etude des effets d'irradiation dans le polytype cubique du carbure de silicium par les techniques spectroscopiques de photoluminescence et de resonance paramagnetique electronique

    Energy Technology Data Exchange (ETDEWEB)

    Lefevre, J

    2008-01-15

    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.)

  6. Effects of gradient structure on the microstructures and properties of coated cemented carbides

    Institute of Scientific and Technical Information of China (English)

    Li Chen; Enxi Wu; Fei Yin; Jia Li

    2006-01-01

    The effects of gradient structure on the microstructure and properties of coated cemented carbides were researched with optical microscopy (OM), scanning electron microscopy (SEM), strength measurements, and cutting tests. It shows that vacuum sintering of WC-Ti(C, N)-TaC-Co cemented carbides results in the formation of a surface ductile zone. The ductile zone prevents crack propagation and leads to the increase of transverse rupture strength of the substrate. The impact resistance of coated gradient inserts was obviously improved on the basis of maintaining resistance to abrasion and the forming mechanism of the gradient structure was also analyzed.

  7. Synthesis of silicon carbide in a nitrogen plasma torch: rotational temperature determination and material analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Camacho, J; Castell, R [Universidad Simon BolIvar, Departamento de Fisica, Caracas (Venezuela, Bolivarian Republic of); Castro, A; Manrique, M [Universidad Simon BolIvar, Departamento de Ciencias de los Materiales, Caracas (Venezuela, Bolivarian Republic of)], E-mail: jgruiz@usb.ve

    2008-09-07

    Experiments on silicon carbide synthesis were performed using a dc nitrogen plasma torch. Measurements of rotational temperature of nitrogen molecules by emission spectroscopy were performed, based on the band (0, 1) of the first negative system of nitrogen N{sub 2}{sup +}(B{sup 2}{sigma}{sub u}{sup +}{yields}X{sup 2}{sigma}{sub g}{sup +}) for the R branch. Three different plasma torch powers were studied in order to optimize the production of silicon carbide with our experimental set-up. The synthesized products were characterized by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy.

  8. Synthesis of silicon carbide in a nitrogen plasma torch: rotational temperature determination and material analysis

    Science.gov (United States)

    Ruiz-Camacho, J.; Castell, R.; Castro, A.; Manrique, M.

    2008-09-01

    Experiments on silicon carbide synthesis were performed using a dc nitrogen plasma torch. Measurements of rotational temperature of nitrogen molecules by emission spectroscopy were performed, based on the band (0, 1) of the first negative system of nitrogen N_2^+ (B\\,{}^2\\Sigma_u^+ \\to X\\,{}^2\\Sigma _g^+) for the R branch. Three different plasma torch powers were studied in order to optimize the production of silicon carbide with our experimental set-up. The synthesized products were characterized by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy.

  9. Characterization of Transition Metal Carbide Layers Synthesized by Thermo-reactive Diffusion Processes

    DEFF Research Database (Denmark)

    Laursen, Mads Brink; Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin

    2015-01-01

    Hard wear resistant surface layers of transition metal carbides can be produced by thermo-reactive diffusion processes where interstitial elements from a steel substrate together with external sources of transition metals (Ti, V, Cr etc.) form hard carbide and/or nitride layers at the steel surface...... electron microscopy, X-ray diffraction and Vickers hardness testing. The study shows that porosityfree, homogenous and very hard surface layers can be produced by thermo-reactive diffusion processes. The carbon availability of the substrate influences thickness of obtained layers, as Vanadis 6 tool steel...

  10. Calcium carbide poisoning via food in childhood.

    Science.gov (United States)

    Per, Hüseyin; Kurtoğlu, Selim; Yağmur, Fatih; Gümüş, Hakan; Kumandaş, Sefer; Poyrazoğlu, M Hakan

    2007-02-01

    The fast ripening of fruits means they may contain various harmful properties. A commonly used agent in the ripening process is calcium carbide, a material most commonly used for welding purposes. Calcium carbide treatment of food is extremely hazardous because it contains traces of arsenic and phosphorous. Once dissolved in water, the carbide produces acetylene gas. Acetylene gas may affect the neurological system by inducing prolonged hypoxia. The findings are headache, dizziness, mood disturbances, sleepiness, mental confusion, memory loss, cerebral edema and seizures. We report the case of a previously healthy 5 year-old girl with no chronic disease history who was transferred to our Emergency Department with an 8-h history of coma and delirium. A careful history from her father revealed that the patient ate unripe dates treated with calcium carbide.

  11. Stabilization and strengthening effects of functional groups in two-dimensional titanium carbide

    Science.gov (United States)

    Fu, Z. H.; Zhang, Q. F.; Legut, D.; Si, C.; Germann, T. C.; Lookman, T.; Du, S. Y.; Francisco, J. S.; Zhang, R. F.

    2016-09-01

    Two-dimensional (2D) materials have attracted considerable interest due to their remarkable properties and potential applications for nanoelectronics, electrodes, energy storage devices, among others. However, many well-studied 2D materials lack appreciable conductivity and tunable mechanical strength, limiting their applications in flexible devices. Newly developed MXenes open up the opportunity to design novel flexible conductive electronic materials. Here, using density functional theory (DFT), we investigate systematically the effects of several functional groups on the stabilization, mechanical properties, and electronic structures of a representative MXene. It is found that oxygen possesses the largest adsorption energy as compared to other functional groups, indicating its good thermodynamic stabilization. In comparison with bare and other functionalized titanium carbides, the oxygen functionalized one exhibits the most superior ideal strength; however, the premature softening of the long-wave phonon modes might limit the intrinsic strength for T i3C2O2 . Furthermore, the introduction of functional groups can induce a strong anisotropy under tensile loading. By analyzing the deformation paths and the electronic instability under various loadings, we demonstrate that the unique strengthening by oxygen functional groups is attributed to a significant charge transfer from inner bonds to outer surface ones after functionalization. Our results shed a novel view into exploring a variety of MXenes for their potential applications in flexible electronic and energy storage devices.

  12. Histological preparation of developing vestibular otoconia for scanning electron microscopy

    Science.gov (United States)

    Huss, D.; Dickman, J. D.

    2003-01-01

    The unique nature of vestibular otoconia as calcium carbonate biominerals makes them particularly susceptible to chemical deformation during histological processing. We fixed and stored otoconia from all three otolith endorgans of embryonic, hatchling and adult Japanese quail in glutaraldehyde containing either phosphate or non-phosphate buffers for varying lengths of time and processed them for scanning electron microscopy. Otoconia from all age groups and otolith endorgans processed in 0.1 M phosphate buffer (pH 7.4) showed abnormal surface morphology when compared to acetone fixed controls. Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls. The degree of otoconial deformation was directly related to the time exposed to phosphate buffer. Short duration exposure produced particulate deformations while longer exposures resulted in fused otoconia that formed solid sheets. Otoconial surface deformation and fusing was independent of the glutaraldehyde component of the histological processing. These findings should help vestibular researchers to develop appropriate histological processing protocols in future studies of otoconia.

  13. Readout electronics development for the ATLAS silicon tracker

    Energy Technology Data Exchange (ETDEWEB)

    Borer, K. [Bern Univ. (Switzerland); Beringer, J. [Bern Univ. (Switzerland); Anghinolfi, F. [CERN, CH-1211 Geneva 23 (Switzerland); Aspell, P. [CERN, CH-1211 Geneva 23 (Switzerland); Chilingarov, A. [CERN, CH-1211 Geneva 23 (Switzerland)]|[Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Jarron, P. [CERN, CH-1211 Geneva 23 (Switzerland); Heijne, E.H.M. [CERN, CH-1211 Geneva 23 (Switzerland); Santiard, J.C. [CERN, CH-1211 Geneva 23 (Switzerland); Verweij, H. [CERN, CH-1211 Geneva 23 (Switzerland); Goessling, C. [Institut fur Physik, Univ. Dortmund, D-4600 Dortmund (Germany); Lisowski, B. [Institut fur Physik, Univ. Dortmund, D-4600 Dortmund (Germany); Reichold, A. [Institut fur Physik, Univ. Dortmund, D-4600 Dortmund (Germany); Bonino, R. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); Clark, A.G. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); Kambara, H. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); La Marra, D. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); Leger, A. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); Wu, X. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); Richeux, J.P. [DPNC, University of Geneva, CH-1211 Geneva 4 (Switzerland); Taylor, G.N. [School of Physics, University of Melbourne, Parkville, Victoria 3052 (Australia); Fedotov, M. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Kuper, E. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Velikzhanin, Yu. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Campbell, D. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Murray, P. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Seller, P. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)

    1995-06-01

    We present the status of the development of the readout electronics for the large area silicon tracker of the ATLAS experiment at the LHC, carried out by the CERN RD2 project. Our basic readout concept is to integrate a fast amplifier, analog memory, sparse data scan circuit and analog-to-digital convertor (ADC) on a single VLSI chip. This architecture will provide full analog information of charged particle hits associated unambiguously to one LHC beam crossing, which is expected to be at a frequency of 40 MHz. The expected low occupancy of the ATLAS inner silicon detectors allows us to use a low speed (5 MHz) on-chip ADC with a multiplexing scheme. The functionality of the fast amplifier and analog memory have been demonstrated with various prototype chips. Most recently we have successfully tested improved versions of the amplifier and the analog memory. A piecewise linear ADC has been fabricated and performed satisfactorily up to 5 MHz. A new chip including amplifier, analog memory, memory controller, ADC, and data buffer has been designed and submitted for fabrication and will be tested on a prototype of the ATLAS silicon tracker module with realistic electrical and mechanical constraints. (orig.).

  14. Module and Electronics Developments for the ATLAS ITK Pixel System

    CERN Document Server

    Nellist, Clara; The ATLAS collaboration

    2016-01-01

    ATLAS is preparing for an extensive modification of its detector in the course of the planned HL-LHC accelerator upgrade around 2025 which includes a replacement of the entire tracking system by an all-silicon detector (Inner Tracker, ITk). The five innermost layers of ITk will comprise of a pixel detector built of new sensor and readout electronics technologies to improve the tracking performance and cope with the severe HL-LHC environment in terms of occupancy and radiation. The total area of the new pixel system could measure up to 14 m$^{2}$, depending on the final layout choice that is expected to take place in early 2017. An intense R\\&D activity is taking place in the field of planar, 3D, CMOS sensors to identify the optimal technology for the different pixel layers. In parallel various sensor-chip interconnection options are explored to identify reliable technologies when employing 100-150~$\\mu$m thin chips. While the new read-out chip is being developed by the RD53 Collaboration, the pixel off de...

  15. 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.

  16. Selective etching of silicon carbide films

    Science.gov (United States)

    Gao, Di; Howe, Roger T.; Maboudian, Roya

    2006-12-19

    A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

  17. Developing Argumentation Strategies in Electronic Dialogs: Is Modeling Effective?

    Science.gov (United States)

    Mayweg-Paus, Elisabeth; Macagno, Fabrizio; Kuhn, Deanna

    2016-01-01

    The study presented here examines how interacting with a more capable interlocutor influences use of argumentation strategies in electronic discourse. To address this question, 54 young adolescents participating in an intervention centered on electronic peer dialogs were randomly assigned to either an experimental or control condition. In both…

  18. 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…

  19. Generation and Characteristics of IV-VI transition Metal Nitride and Carbide Nanoparticles using a Reactive Mesoporous Carbon Nitride

    KAUST Repository

    Alhajri, Nawal Saad

    2016-02-22

    Interstitial nitrides and carbides of early transition metals in groups IV–VI exhibit platinum-like electronic structures, which make them promising candidates to replace noble metals in various catalytic reactions. Herein, we present the preparation and characterization of nano-sized transition metal nitries and carbides of groups IV–VI (Ti, V, Nb, Ta, Cr, Mo, and W) using mesoporous graphitic carbon nitride (mpg-C3N4), which not only provides confined spaces for restricting primary particle size but also acts as a chemical source of nitrogen and carbon. We studied the reactivity of the metals with the template under N2 flow at 1023 K while keeping the weight ratio of metal to template constant at unity. The produced nanoparticles were characterized by powder X-ray diffraction, CHN elemental analysis, nitrogen sorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results show that Ti, V, Nb, Ta, and Cr form nitride phases with face centered cubic structure, whereas Mo and W forme carbides with hexagonal structures. The tendency to form nitride or carbide obeys the free formation energy of the transition metal nitrides and carbides. This method offers the potential to prepare the desired size, shape and phase of transition metal nitrides and carbides that are suitable for a specific reaction, which is the chief objective of materials chemistry.

  20. Preparation And Characterization Of Silicon Carbide Foam By Using In-Situ Generated Polyurethane Foam

    Directory of Open Access Journals (Sweden)

    Shalini Saxena

    2015-08-01

    Full Text Available Abstract The open cell silicon carbide SiC foam was prepared using highly crosslinked hybrid organic- inorganic polymer resin matrix. As inorganic polymer polycarbosilane was taken and organic resin was taken as a mixture of epoxy resin and diisocyanates. The resultant highly crosslinked hybrid resin matrix on heating and subsequently on pyrolysis yielded open cell silicon carbide foam. The hybrid resin matrix was characterized by Fourier transform Infrared Spectroscopy FT-IR and thermal properties i.e. Thermogravimetric analysis TGA amp Differential Scanning Calorimetry DSC were also studied. The morphological studies of silicon carbide ceramic foam were carried out using X-ray Spectroscopy XRD amp Scanning Electron Microscopy SEM.

  1. Generation and characterization of nano-tungsten carbide particles by wire explosion process

    Energy Technology Data Exchange (ETDEWEB)

    Debalina, B.; Kamaraj, M.; Murthy, B.S. [Dept. of Metallurgical and Materials Engg., IIT Madras, Chennai 600036 (India); Chakravarthi, S.R. [Dept. of Aerospace Engg, IIT Madras, Chennai 600036 (India); Sarathi, R., E-mail: rsarathi@iitm.ac.i [Dept. of Electrical Engineering, IIT Madras, Chennai 600036, Tamilnadu (India)

    2010-04-30

    The nano-tungsten carbide particles were produced by exploding tungsten conductor in different carburizing medium viz. carbon dioxide and methane atmosphere. The influence of gas pressure in explosion chamber on the size of the particles formed was analyzed. Methane gas was found to be a conducive medium to form tungsten carbide particles. Certain physico-chemical diagnostic studies such as wide angle X-ray diffraction (WAXD) and Fourier transform infra-red (FTIR) spectroscopy studies were carried out to characterize the nano-tungsten carbide powder produced by the wire explosion process. The size of the particles was measured by using transmission electron microscope (TEM) and its size distribution was analyzed by adopting log-normal distribution. Thermal conductivity of the gas plays a major role on the size of the particle formed by wire explosion process as observed in the present work.

  2. Superconductivity in boron carbide? Clarification by low-temperature MIR/FIR spectra.

    Science.gov (United States)

    Werheit, H; Kuhlmann, U

    2011-11-01

    The electronic structure and phonon density of B(13)B(2) boron carbide calculated by Calandra et al (2004 Phys. Rev. B 69 224505) defines this compound as metallic, and the authors predict superconductivity with T(C)s up to 36.7 K. Their results are affected by the same deficiencies as former band structure calculations on boron carbides based on hypothetical crystal structures deviating significantly from the real ones. We present optical mid IR/far IR (MIR/FIR) spectra of boron carbide with compositions between B(4.3)C and B(10.37)C, evidencing semiconducting behaviour at least down to 30 K. There is no indication of superconductivity. The spectra yield new information on numerous localized gap states close to the valence band edge.

  3. Synthesis of thermal and chemical resistant oxygen barrier starch with reinforcement of nano silicon carbide.

    Science.gov (United States)

    Dash, Satyabrata; Swain, Sarat K

    2013-09-12

    Starch/silicon carbide (starch/SiC) bionanocomposites were synthesized by solution method using different wt% of silicon carbide with starch matrix. The interaction between starch and silicon carbide was studied by Fourier transform infrared (FTIR) spectroscopy. The structure of the bionanocomposites was investigated by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). Thermal property of starch/SiC bionanocomposites was measured and a significant enhancement of thermal resistance was noticed. The oxygen barrier property of the composites was studied and a substantial reduction in permeability was observed as compared to the virgin starch. The reduction of oxygen permeability with enhancement of thermal stability of prepared bionanocomposites may enable the materials suitable for thermal resistant packaging and adhesive applications.

  4. Effect of silicon carbide ceramic coating process on the mirror surface quality

    Science.gov (United States)

    Wang, Peipei; Wang, Li; Wang, Gang; Bai, Yunli; Wang, Peng; Xiao, Zhenghang

    2016-10-01

    Silicon carbide, as a new reflector material, its excellent physical and chemical properties has been widely recognized by the industry. In order to make SiC mirror better used in space optical system, we used digital coating equipment during its coating process. By using ion-assisted electron evaporation method, we got a complete metal reflective film system on the surface of finely polished silicon carbide mirror. After automated coating process, by adjusting the coating parameters during the process, the surface roughness of silicon carbide improved from 7.8 nm to 5.1 nm, and the average optical reflectance of the surface reached 95% from visible to near-infrared. The metal reflective film system kept well after annealing and firmness test. As a result, the work of this paper will provide an important reference for high-precision coating process on large diameter SiC mirror.

  5. Test setup for long term reliability investigation of Silicon Carbide MOSFETs

    DEFF Research Database (Denmark)

    Baker, Nick; Munk-Nielsen, Stig; Beczkowski, Szymon

    2013-01-01

    Silicon Carbide MOSFETs are now widely available and have frequently been demonstrated to offer numerous advantages over Silicon based devices. However, reliability issues remain a significant concern in their realisation in commercial power electronic systems. In this paper, a test bench...... is designed that enables an accelerated power cycling test to be performed on packaged Silicon Carbide MOSFETs (TO-247) under realistic operating conditions. An accelerated power cycling test is then performed, with on-state resistance selected as the observed parameter to detect degradation. On......-state resistance is routinely monitored online through the use of an innovative voltage measurement system. The packaged Silicon Carbide MOSFET is shown to exhibit a 25% increase in on-state resistance as the device ages throughout its lifetime, with the test still on-going....

  6. Formation of austenite and dissolution of carbides in Fe-8.2Cr-C alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shtansky, D.; Nakai, K.; Ohmori, Y. [Ehime Univ., Matsuyama (Japan). Faculty of Engineering

    1999-01-01

    The mechanism of austenite formation and the kinetics of carbide dissolution have been studied in Fe-8.2Cr-0.2C and Fe-8.2Cr-0.96 C (numbers indicate mass%) alloys with ferrite lamellar carbide and ferrite spheroidized carbide initial structures. The morphology of austenite formation in the range of 850 to 900 C has been examined in detail by transmission electron microscopy. The mechanisms of austenite nucleation and growth have been distinguished as they depend on the composition, starting microstructure and austenitizing temperature. The effects of both austenitising temperature in the range of 850 to 1150 C and a time on the M{sub 23}C{sub 6} and M{sub 7}C{sub 3} carbide evolution have also been investigated. Different morphologies of transformation products have been observed. The orientation relationships between ferrite, austenite and carbides were determined. The observed results can be explained by assuming local equilibrium at the moving interfaces during the reactions. (orig.) 47 refs.

  7. Structural and electrical characterization of ohmic contacts to graphitized silicon carbide.

    Science.gov (United States)

    Maneshian, Mohammad H; Lin, Ming-Te; Diercks, David; Shepherd, Nigel D

    2009-12-09

    Titanium was deposited onto silicon carbide (6H-SiC) using the 248 nm line of an excimer laser in a vacuum of 10(-6) Torr, and ohmic contacts were formed by annealing the structure at approximately 1000 degrees C. Further anneals between 1350 and 1430 degrees C did not degrade the formed contacts, and Raman analysis confirmed that sublimation of silicon from the near surface layers of the silicon carbide between the contact pads resulted in graphene formation after 5 min, 1428 degrees C anneals. The graphene formation was accompanied by a significant enhancement of ohmic behavior, and, it was found to be sensitive to the temperature ramp-up rate and annealing time. High-resolution transmission electron microscopy showed that the interface between the metal and silicon carbide remained sharp and free of macroscopic defects even after 30 min, 1430 degrees C anneals. The interface was determined to be carbon rich by elemental analysis, which indicates metal carbide formation. The potential of this approach for achieving ohmic contacts and graphene formation on silicon carbide substrates is discussed. A mechanism for the sequential formation of ohmic contacts then graphene is proposed.

  8. Microstructure of reactive synthesis TiC/Cr18Ni8 stainless steel bonded carbides

    Institute of Scientific and Technical Information of China (English)

    Jiang Junsheng; Liu Junbo; Wang Limei

    2008-01-01

    TiC/Cr18Ni8 steel bonded carbides were synthesized by vacuum sintering with mixed powders of iron, ferrotitanium, ferrochromium, colloidal graphite and nickel as raw materials. The microstructure and microhardness of the steel bonded carbides were analyzed by scanning electron microscope (SEM),X-ray diffraction (XRD) and Rockwell hardometer. Results show that the phases of steel bonded carbides mainly consist of TiC and Fe-Cr-Ni solid solution. The synthesized TiC particles are fine. Most of them are not more than 1 μm With the increase of sintering temperature, the porosity of TiC/Cr18Ni8 steel bonded carbides decreases and the density and hardness increase, but the size of TiC panicles slightly increases. Under the same sintering conditions, the density and hardness of steel bonded carbides with C/Ti atomic ratio 0.9 are higher than those with C/Ti atomic ratio 1.0.The TiC particles with C/Ti atomic ratio 0.9 are much finer and more homogeneous.

  9. Nanosilicon carbide/hydroxyapatite nanocomposites: structural, mechanical and in vitro cellular properties.

    Science.gov (United States)

    Hesaraki, Saeed; Ebadzadeh, Touraj; Ahmadzadeh-Asl, Shaghayegh

    2010-07-01

    In this study, bioceramic nanocomposites were synthesized by sintering compacted bodies of hydroxyapatite (HA) mixed with 5 or 15 wt% nanosilicon carbide at 1,100 or 1,200 degrees C in a reducing atmosphere. Pure hydroxyapatite was also prepared for comparison. Phase compositions, structural and physical properties of the composites were studied using appropriate techniques. Some in vitro biological properties of the composites were also investigated by using newrat calvaria osteoblastic cells. X-ray diffraction analysis indicated that tricalcium phosphate (TCP) comprising negligible alpha-TCP and considerable beta-TCP were formed in composites during sintering meanwhile hydroxyapatite and silicon carbide (SiC) were also existed in the composition. Based on the results, that composite made of 5 wt% nanosilicon carbide exhibited higher bending strength, fracture toughness and bulk density than pure HA and composite with 15 wt% silicon carbide. The scanning electron microscopy coupled with energy dispersive X-ray analysis revealed that the addition of nanosilicon carbide suppressed the grain growth and yielded a feature of island-type clusters consisting of blistered calcium phosphate (HA and TCP) and SiC grains. Also, in this study, better proliferation rate and alkaline phosphatase activity were observed for the osteoblastic cells seeded on top of the composites compared to pure HA. Overall, the results indicated that the composite of 95 wt% hydroxyapatite and 5 wt% SiC exhibited better mechanical and biological properties than pure HA and further addition of SiC failed strength and toughness.

  10. IMPLEMENTING AND AUDITING ELECTRONIC RECORDKEEPING SYSTEMS USED IN SCIENTIFIC RESEARCH AND DEVELOPMENT

    Science.gov (United States)

    Electronic recordkeeping is increasingly replacing hadwritten records in the course of "normal business." As this trend continues, it is important that organizations develop and implement electronic recordkeeping policies and procedures. This is especially true for Research and...

  11. Scientists at Brookhaven contribute to the development of a better electron accelerator

    CERN Multimedia

    2004-01-01

    Scientists working at Brookhaven have developed a compact linear accelerator called STELLA (Staged Electron Laser Acceleration). Highly efficient, it may help electron accelerators become practical tools for applications in industry and medicine, such as radiation therapy (1 page)

  12. Electronic Business Helps Middle & Small Enterprises Develop International Trade

    Institute of Scientific and Technical Information of China (English)

    黎裕华

    2012-01-01

    Under the influence of the financial crisis, our international trade faces very serious challenge. During such a difficult period, electronic business brings us some new hope. Electronic business optimizes traditional process, saves large number of manpower and assets, decreases cost, breaks through the limit of time and space, makes deals more convenient and shortcut and strongly boosts efficiency. Our middle and small enterprises should make full use of such a tool of electronic business to hit out the international market actively, search more trading opportunities and living spaces and smoothly bridge such a difficult period due to the financial crisis.

  13. Metamagnetism of η-carbide-type transition-metal carbides and nitrides

    Science.gov (United States)

    Waki, T.; Terazawa, S.; Umemoto, Y.; Tabata, Y.; Sato, K.; Kondo, A.; Kindo, K.; Nakamura, H.

    2011-09-01

    η-carbide-type transition-metal compounds include the frustrated stella quadran-gula lattice. Due to characteristics of the lattice, we expect subtle transitions between frustrated and non-frustrated states. Here, we report metamagnetic transitions newly found in η-carbide-type compounds Fe3W3C, Fe6W6C and Co6W6C.

  14. FIB/FESEM experimental and analytical assessment of R-curve behavior of WC–Co cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Tarragó, J.M., E-mail: jose.maria.tarrago@upc.edu [CIEFMA, Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); Jiménez-Piqué, E. [CIEFMA, Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); Schneider, L. [Sandvik Hyperion, Coventry CV4 0XG (United Kingdom); Casellas, D. [Fundació CTM Centre Tecnològic, 08243 Manresa (Spain); Torres, Y. [Departamento de Ingeniería y Ciencia de los Materiales y del Transporte, ETSI, Universidad de Sevilla, 41092 Sevilla (Spain); Llanes, L. [CIEFMA, Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain)

    2015-10-01

    Exceptional fracture toughness levels exhibited by WC–Co cemented carbides (hardmetals) are due mainly to toughening derived from plastic stretching of crack-bridging ductile enclaves. This takes place due to the development of a multiligament zone at the wake of cracks growing in a stable manner. As a result, hardmetals exhibit crack growth resistance (R-curve) behavior. In this work, the toughening mechanics and mechanisms of these materials are investigated by combining experimental and analytical approaches. Focused Ion Beam technique (FIB) and Field-Emission Scanning Electron Microscopy (FESEM) are implemented to obtain serial sectioning and imaging of crack–microstructure interaction in cracks arrested after stable extension under monotonic loading. The micrographs obtained provide experimental proof of the developing multiligament zone, including failure micromechanisms within individual bridging ligaments. Analytical assessment of the multiligament zone is then conducted on the basis of experimental information attained from FIB/FESEM images, and a model for the description of R-curve behavior of hardmetals is proposed. It was found that, due to the large stresses supported by the highly constrained and strongly bonded bridging ligaments, WC–Co cemented carbides exhibit quite steep but short R-curve behavior. Relevant strength and reliability attributes exhibited by hardmetals may then be rationalized on the basis of such toughening scenario.

  15. A Novel Compact and Reliable Hybrid Silicon/Silicon Carbide Device Module for Efficient Power Conversion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — United Silicon Carbide, Inc. proposes to develop a novel compact, efficient and high-temperature power module, based on unique co-packaging approach of normally-off...

  16. Sample Development on Java Smart-Card Electronic Wallet Application

    Directory of Open Access Journals (Sweden)

    Toma Cristian

    2009-12-01

    Full Text Available In this paper, are highlighted concepts as: complete Java card application, life cycle of an applet, and a practical electronic wallet sample implemented in Java card technology. As a practical approach it would be interesting building applets for ID, Driving License, Health-Insurance smart cards, for encrypt and digitally sign documents, for E-Commerce and for accessing critical resources in government and military field. The end of this article it is presented a java card electronic wallet application.

  17. Catalytic synthesis of silicon carbide preceramic polymers: Polycarbosilanes

    Energy Technology Data Exchange (ETDEWEB)

    Berry, D.H.

    1991-11-01

    Polycarbosilanes are the most successful and widely studied class of polymer precursors for silicon carbide, but traditional methods for thier synthesis are inefficient and nonselective. This project is focused on developing transition metal catalysts for the synthesis of polycarbosilanes and other perceramic polymers. In recent work we have developed the first homogeneous transition metal catalysts for the dehydrogenative coupling of simple alkyl silanes to oligomeric and polymeric carbosilanes, H-(SiR{sub 2}CR{prime}{sub 2}){sub n}-SiR{sub 3}. Future work will help elucidate the mechanism of the catalytic process, explore the use of hydrogen acceptors as reaction accelerators, and develop new and more active catalysts.

  18. Microstructure Development in Electron Beam-Melted Inconel 718 and Associated Tensile Properties

    Science.gov (United States)

    Kirka, M. M.; Unocic, K. A.; Raghavan, N.; Medina, F.; Dehoff, R. R.; Babu, S. S.

    2016-03-01

    During the electron beam melting (EBM) process, builds occur at temperatures in excess of 800°C for nickel-base superalloys such as Inconel 718. When coupled with the temporal differences between the start and end of a build, a top-to-bottom microstructure gradient forms. Characterized in this study is a microstructure gradient and associated tensile property gradient common to all EBM Inconel 718 builds, the extent of which is dependent on build geometry and the specifics of a build's processing history. From the characteristic microstructure elements observed in EBM Inconel 718 material, the microstructure gradient can be classified into three distinct regions. Region 1 (top of a build) is comprised of a cored dendritic structure that includes carbides and Laves phase within the interdendritic regions. Region 2 is an intermediate transition zone characterized by a diffuse dendritic structure, dissolution of the Laves phase, and precipitation of δ needle networks within the interdendritic regions. The bulk structure (Region 3) is comprised of a columnar grain structure lacking dendritic characteristics with δ networks having precipitated within the grain interiors. Mechanically, at both 20°C and 650°C, the yield strength, ultimate tensile strength, and elongation at failure exhibit the general trend of increasing with increasing build height.

  19. Development of high-temperature resistant noncorrodible silicon-carbide components for gas turbine application. Follow-up-report. Entwicklung von hochwarmfesten, korrosionsbestaendigen Siliciumcarbid-Formkoerpern fuer die Verwendung im Gasturbinenbau. Fortschrittsbericht

    Energy Technology Data Exchange (ETDEWEB)

    Blecha, M.; Pohlmann, H.J.

    1985-03-01

    The report under review describes the work of phase 3 (1980 - 1983) of the project 'Ceramic Materials for Automobile Gas Turbines', which has been sponsored by the Ministry for Research and Technology of the Federal Republic of Germany since 1974. Special effort has been put on the improvement of different silicon carbide materials and suitable production techniques for the production of static gas turbine components and a heat exchanger prototype. Tight connection of production techniques, construction and testing in simulated application conditions made it possible to transfer improved material data from test specimens to structural components. Prototypes of combustion chambers, heat exchangers were produced and tested. The positive results of this R+D-project lead to the series production of silicon carbide components for engineering.

  20. Understanding the Irradiation Behavior of Zirconium Carbide

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-10-11

    Zirconium carbide (ZrC) is being considered for utilization in high-temperature gas-cooled reactor fuels in deep-burn TRISO fuel. Zirconium carbide possesses a cubic B1-type crystal structure with a high melting point, exceptional hardness, and good thermal and electrical conductivities. The use of ZrC as part of the TRISO fuel requires a thorough understanding of its irradiation response. However, the radiation effects on ZrC are still poorly understood. The majority of the existing research is focused on the radiation damage phenomena at higher temperatures (>450{degree}C) where many fundamental aspects of defect production and kinetics cannot be easily distinguished. Little is known about basic defect formation, clustering, and evolution of ZrC under irradiation, although some atomistic simulation and phenomenological studies have been performed. Such detailed information is needed to construct a model describing the microstructural evolution in fast-neutron irradiated materials that will be of great technological importance for the development of ZrC-based fuel. The goal of the proposed project is to gain fundamental understanding of the radiation-induced defect formation in zirconium carbide and irradiation response by using a combination of state-of-the-art experimental methods and atomistic modeling. This project will combine (1) in situ ion irradiation at a specialized facility at a national laboratory, (2) controlled temperature proton irradiation on bulk samples, and (3) atomistic modeling to gain a fundamental understanding of defect formation in ZrC. The proposed project will cover the irradiation temperatures from cryogenic temperature to as high as 800{degree}C, and dose ranges from 0.1 to 100 dpa. The examination of this wide range of temperatures and doses allows us to obtain an experimental data set that can be effectively used to exercise and benchmark the computer calculations of defect properties. Combining the examination of radiation

  1. The Effects of Thermal Cycling on Gallium Nitride and Silicon Carbide Semiconductor Devices for Aerospace Use

    Science.gov (United States)

    Patterson, Richard L.; Hammoud, Ahmad

    2012-01-01

    Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These Include radiation, extreme temperatures, thermal cycling, to name a few. Preliminary data obtained on new Gallium Nitride and Silicon Carbide power devices under exposure to radiation followed by long term thermal cycling are presented. This work was done in collaboration with GSFC and JPL in support of the NASA Electronic Parts and Packaging (NEPP) Program

  2. Structure of TiBN coatings deposited onto cemented carbides and sialon tool ceramics

    OpenAIRE

    L.A. Dobrzański; M. Staszuk; J. Konieczny; W. Kwaśny; M. Pawlyta

    2009-01-01

    Purpose: The aim of this paper was investigated structure of sintered carbides WC-Co type and sialon tool ceramics with wear resistance ternary coatings TiBN type deposited by cathodes arc evaporation process (CAE-PVD).Design/methodology/approach: Observation of fracture and topography studied coatings were done by scanning electron microscope. Chemical composition was determine by energy dispersive spectrometry (EDS) method. Thin foils of substrates and coatings by transmission electron micr...

  3. Pyrolytic deposition of nanostructured titanium carbide coatings on the surface of multiwalled carbon nanotubes

    Science.gov (United States)

    Kremlev, K. V.; Ob"edkov, A. M.; Ketkov, S. Yu.; Kaverin, B. S.; Semenov, N. M.; Gusev, S. A.; Tatarskii, D. A.; Yunin, P. A.

    2016-05-01

    Nanostructured titanium carbide coatings have been deposited on the surface of multiwalled carbon nanotubes (MWCNTs) by the MOCVD method with bis(cyclopentadienyl)titanium dichloride precursor. The obtained TiC/MWCNT hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is established that a TiC coating deposits onto the MWCNT surface with the formation of a core-shell (MWSNT-TiC) type structure.

  4. Synthesis of silicon carbide nanowires in a catalyst-assisted process

    Science.gov (United States)

    Deng, S. Z.; Wu, Z. S.; Zhou, Jun; Xu, N. S.; Chen, Jian; Chen, Jun

    2002-04-01

    At elevated temperatures, silicon carbide nanowires were synthesized in a catalyst-assisted process using aluminum as a catalyst. Transmission electron microscopy shows that the nanowires are around 20 nm in diameter and around 2 μm in length. High resolution transmission electron microscopy shows that the nanowires are crystalline β-SiC. Raman spectra show the typical features of nano-SiC. A model based on vapor-liquid-solid process is proposed to explain our finding.

  5. Nanostructured carbide catalysts for the hydrogen economy

    Energy Technology Data Exchange (ETDEWEB)

    Ram Seshadri, Susannah Scott, Juergen Eckert

    2008-07-21

    The above quote, taken from the executive summary of the Report from the US DOE Basic Energy Sciences Workshop held August 6–8, 2007,[1] places in context the research carried out at the University of California, Santa Barbara, which is reported in this document. The enormous impact of heterogeneous catalysis is exemplified by the Haber process for the synthesis of ammonia, which consumes a few % of the world’s energy supply and natural gas, and feeds as many as a third of the world’s population. While there have been numerous advances in understanding the process,[2] culminating in the awarding of the Nobel Prize to Gerhard Ertl in 2007, it is interesting to note that the catalysts themselves have changed very little since they were discovered heuristically in the the early part of the 20th century. The thesis of this report is that modern materials chemistry, with all the empirical knowledge of solid state chemistry, combined with cutting edge structural tools, can help develop and better heterogeneous catalysis. The first part of this report describes research in the area of early transition metal carbides (notably of Mo and W), potentially useful catalysts for water gas shift (WGS) and related reactions of use to the hydrogen economy. Although these carbides have been known to be catalytically useful since the 1970s,[3] further use of these relatively inexpensive materials have been plagued by issues of low surface areas and ill-defined, and often unreactive surfaces, in conjunction with deactivation. We have employed for the first time, a combination of constant-wavelength and time-of-flight neutron scattering, including a total scattering analysis of the latter data, to better understand what happens in these materials, in a manner that for the first time, reveals surface graphitic carbon in these materials in a quantitative manner. Problems of preparation, surface stability, and irreversible reactivity have become manifest in this class of materials

  6. Development of self-assembling nanowires containing electronically active oligothiophenes

    Science.gov (United States)

    Tsai, Wei-Wen

    This dissertation discusses the development of conductive one-dimensional nanowires from self-assembling oligothiophene molecules. Self-assembly has been demonstrated to be a promising alternative approach towards high performance, solution processable, and low-cost organic electronics. One of the many challenges in this field is the control of supramolecular morphologies of ordered structures containing pi-conjugated moieties. This research demonstrated several successful strategies to achieve self assembly of conductive nanowires using synergistic interactions combining pi stacking and hydrogen bonding. The first approach used was to develop a hairpin-shaped sexithiophene molecule, which features two arms of the conjugated structure. The diamidocyclohexyl headgroup of this molecule successfully directs the self-assembly from hydrogen bonding among the amides, forming high-aspect-ratio one-dimensional nanowires with well-defined diameters of 3.0 +/- 0.3 nm. The molecular orientation in the nanostructures promotes formation of sexithiophene H and J aggregates that facilitate efficient charge transport. Organic field-effect transistors were fabricated to reveal improved intrinsic hole mobility from films of the nanostructures, 3.46 x 10-6 cm2V-1s-1, which is one order of magnitude higher than films cast from unassembled molecules. Bulk heterojunction solar cells were developed from this molecule and fullerenes utilizing solution-phase fabrication methods. Intimate mix of the molecule and phenyl-C61-butyric acid methyl ester creates structured interfaces for efficient exciton splitting. The charge carrier mobilities of each material are improved by self-assembly in solution and thermal-energy assisted phase separation.The photovoltaic devices achieved the highest open-circuit voltage of 0.62 V, short-circuit current of 1.79 mA/cm2, fill factor of 35%, and power conversion efficiency of 0.48%. Another strategy to one-dimensional nanowires studied here involved the

  7. Present State of Electron Backscatter Diffraction and Prospective Developments

    Energy Technology Data Exchange (ETDEWEB)

    Schwarzer, R A; Field, D P; Adams, B L; Kumar, M; Schwartz, A J

    2008-10-24

    Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

  8. Development of a Drop Tester for Portable Electronic Products

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Portable electronic products are susceptible to accidental drop impact which can cause various functional and physical damage. This paper first presents a patent pending drop tester which allows portable electronic products free drop at any orientation and drop height, and then introduces the drop tester experiment setup and its design principle. Using a cellular phone as an experiment object, we obtain some data such as the impact forces, the impact accelerations, and the strain of an interested spot. By analyzing experiment data the influence of impact to products in various states is investigated with the aim to provide help for the design of products and improvement of reliability.

  9. On the Role of Carbides in the Formation of Hydrocarbons from Deep Carbon

    Science.gov (United States)

    Vecht, A.

    2012-12-01

    The origin of hydrocarbons found in rocks has been a matter of dispute for over a century. Scientists of the former Soviet Union favoured an inorganic origin, while in the west an organic origin was thought the most likely. Both hypotheses may be reconciled by considering the origin of carbon compounds from the core upwards or from the Earth surface downwards. Carbides are the key to understanding the development and distribution of global carbon compounds. They are precursors in the formation of hydrocarbons. It has been estimated that the Earth's core is composed of between 2-4% carbon. It is found in metallic form and is substantially denser that the surrounding mantle. Wood has proposed that the inner core is a carbide probably iron carbide(1). This conclusion is consistent with studies of meteorites, shock waves and densities Carbides can be divided into four groups:- (a) Interstitial: -Ti, V, Cr, Zr, Nb, Hf, Ta and W. (b) Covalent:- B and Si (c) Intermediate:- Ti, V, Cr, Mn, Fe, Co and Ni. (d) Salt like:- Groups I, II, and III. Groups (a) (b) and (c) should be included as candidates for carbides found in the inner core. Such carbides are stable at high temperature and will react with water and/or oxygen to form hydrocarbons and CO or CO2 respectively., carbides can be described as examples of a 'reactive minerals' as we suggested in 2007(2). Carbides which are stable at high temperatures react with water to yield hydrocarbons. This points to an abiotic origin for a range of natural hydrocarbons. A detailed review by Cataldo(3) analysed the relevant evidence for biological vs. inorganic origins. He suggests that metal carbides when hydrolysed yield organic 'matter'. Amongst the carbides suggested are (Cr, Fe, Ni, V, Mn and Co}. These carbides are correlated to the relative abundance of these elements in the solar system. We propose similar reactions based on carbides of calcium and aluminium for the formation of methane hydrate. The reactions are expected to

  10. Development of advanced electron holographic techniques and application to industrial materials and devices.

    Science.gov (United States)

    Yamamoto, Kazuo; Hirayama, Tsukasa; Tanji, Takayoshi

    2013-06-01

    The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: GaAs compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.

  11. The Development Methodology of the UML Electronic Guide

    Directory of Open Access Journals (Sweden)

    N.A. Magariu

    2006-09-01

    Full Text Available A technological model for realization of the electronic guide to UML language is considered. This model includes description of peculiarities of using the special graphic editor for constructing the UML diagrams, XML vocabularies (XMI, DocBook, SVG, XSLT for representing the text and diagrams and JavaScript code for constructing the tests.

  12. Electronic Publishing and Collection Development, a Subscription Agent's View.

    Science.gov (United States)

    Wallas, Philip

    Trends in publishing, advances in technology and pressures on library budgets have combined to put libraries and publishers at odds with each other. Research libraries expect broad, easy access to electronic information, greater convenience and faster delivery but at reduced cost. Publishers are exploring new channels for distributing their…

  13. Green development within product families, Electronics goes green 2000+ conference

    DEFF Research Database (Denmark)

    Lenau, Torben Anker; Willum, Ole; Frees, Niels

    2001-01-01

    , based on environ-mental and economical importance as well as the existence of several producers. Using this method, five families have been selected, namely mobile phones, vacuum cleaners, industrial valves with electronic controls, lighting and ventilation. Collaboration with 5 industrial companies has...

  14. Development of Boron Carbide Pellet for CEFR

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Many shielding subassemblies which contain B4C absorber material are arranged outside the reflecting subassemblies in China experimental fast reactor (CEFR). A hot press process has been adopted for preparing B4C pellet. The B4C powder is synthesized by boric acid and carbon black. The B4C pellet is fabricated by cold press, hot press and sintering, precision working, cleaning surface and drying. Among those processes, hot press process is very important because of its

  15. Mechanical and Tribological Properties of PVD-Coated Cemented Carbide as Evaluated by a New Multipass Scratch-Testing Method

    Directory of Open Access Journals (Sweden)

    M. Fallqvist

    2012-01-01

    Full Text Available A new test method based on multipass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by posttest scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N, and (Al0.7Cr0.32O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple, and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping, and spalling characteristics of different coating-substrate composites. The test method can be used as a virtually nondestructive test and, for example, be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests.

  16. Processing and characterization of in-situ aluminum bronze titanium carbide composites

    Science.gov (United States)

    Pillai, Balathandan S.

    The present study was carried out to develop a process for manufacturing in-situ aluminum bronze titanium carbide (TiC) friction drums using the centrifugal casting method and to characterize the material under optimum performance. The in-situ method of manufacturing is based on the reactive gas injection technique (RGI). The gas used in this study is high purity methane (CH 4). It was found that the methane gas injection time into the molten bath of aluminum bronze alloyed with titanium promotes the formation of titanium carbide (TiC) in the bronze matrix. The maximum amount of TiC incorporated in the matrix was 3.1 wt.%. This lead to 11.5 wt.% incorporation of TiC in the inner diameter of centrifugal castings as carbide particles drifted towards this region due to the centrifugal forces and their relatively low density. The hardness and strength of these composites when compared with the as cast condition was improved by heat treatment. However, the alloy ductility was decreased at the expense of the strength. It was found that the wear resistance properties of the composites were superior to those of pure cast and heat treated aluminum bronze currently in use. Optical and Scanning Electron Microscopy indicated that the composite surfaces did not scratch deeply when wearing against a hardened 4340 steel. The wear resistance of the as cast aluminum bronze was inferior to that of heat treated one. Moreover, the heat treated aluminum bronze showed a lack of high abrasion resistance. The frictional coefficient was relatively low for the as cast aluminum bronze as a result of adhesive wear behavior for the load and speed chosen in this present investigation. The corrosion studies showed that these composites do not lead to improved corrosion resistance in marine water environments. Apparently, there is a galvanic corrosion of TiC to bronze. In addition, pitting was observed on the corroded surfaces and increased with the volume fraction of TiC. Model validation was

  17. Evidence of amorphisation of B4C boron carbide under slow, heavy ion irradiation

    Science.gov (United States)

    Gosset, D.; Miro, S.; Doriot, S.; Victor, G.; Motte, V.

    2015-12-01

    Boron carbide is widely used either as armor-plate or neutron absorber. In both cases, a good structural stability is required. However, a few studies have shown amorphisation may occur in severe conditions. Hard impacts lead to the formation of amorphous bands. Some irradiations in electronic regime with H or He ions have also shown amorphisation of the material. Most authors however consider the structure is not drastically affected by irradiations in the ballistic regime. Here, we have irradiated at room temperature dense boron carbide pellets with Au 4 MeV ions, for which most of the damage is in the ballistic regime. This study is part of a program devoted to the behavior of boron carbide under irradiation. Raman observations have been performed after the irradiations together with transmission electron microscopy (TEM). Raman observations show a strong structural damage at moderate fluences (1014/cm2, about 0.1 dpa), in agreement with previous studies. On the other hand, TEM shows the structure remains crystalline up to 1015/cm2 then partially amorphises. The amorphisation is heterogeneous, with the formation of nanometric amorphous zones with increasing density. It then appears short range and long range disorder occurs at quite different damage levels. Further experiments are in progress aiming at studying the structural stability of boron carbide and isostructural materials (α-B, B6Si,…).

  18. Catastrophic degradation of the interface of epitaxial silicon carbide on silicon at high temperatures

    Science.gov (United States)

    Pradeepkumar, Aiswarya; Mishra, Neeraj; Kermany, Atieh Ranjbar; Boeckl, John J.; Hellerstedt, Jack; Fuhrer, Michael S.; Iacopi, Francesca

    2016-07-01

    Epitaxial cubic silicon carbide on silicon is of high potential technological relevance for the integration of a wide range of applications and materials with silicon technologies, such as micro electro mechanical systems, wide-bandgap electronics, and graphene. The hetero-epitaxial system engenders mechanical stresses at least up to a GPa, pressures making it extremely challenging to maintain the integrity of the silicon carbide/silicon interface. In this work, we investigate the stability of said interface and we find that high temperature annealing leads to a loss of integrity. High-resolution transmission electron microscopy analysis shows a morphologically degraded SiC/Si interface, while mechanical stress measurements indicate considerable relaxation of the interfacial stress. From an electrical point of view, the diode behaviour of the initial p-Si/n-SiC junction is catastrophically lost due to considerable inter-diffusion of atoms and charges across the interface upon annealing. Temperature dependent transport measurements confirm a severe electrical shorting of the epitaxial silicon carbide to the underlying substrate, indicating vast predominance of the silicon carriers in lateral transport above 25 K. This finding has crucial consequences on the integration of epitaxial silicon carbide on silicon and its potential applications.

  19. Dispersion of nonresonant third-order nonlinearities in Silicon Carbide

    Science.gov (United States)

    De Leonardis, Francesco; Soref, Richard A.; Passaro, Vittorio M. N.

    2017-01-01

    In this paper we present a physical discussion of the indirect two-photon absorption (TPA) occuring in silicon carbide with either cubic or wurtzite structure. Phonon-electron interaction is analyzed by finding the phonon features involved in the process as depending upon the crystal symmetry. Consistent physical assumptions about the phonon-electron scattering mechanisms are proposed in order to give a mathematical formulation to predict the wavelength dispersion of TPA and the Kerr nonlinear refractive index n2. The TPA spectrum is investigated including the effects of band nonparabolicity and the influence of the continuum exciton. Moreover, a parametric analysis is presented in order to fit the experimental measurements. Finally, we have estimated the n2 in a large wavelength range spanning the visible to the mid-IR region. PMID:28098223

  20. Synthesis of silicon carbide thin films with polycarbosilane (PCS)

    Energy Technology Data Exchange (ETDEWEB)

    Colombo, P. [Univ. di Padova (Italy). Dept. di Ingegneria Meccanica-Settore Materiali; Paulson, T.E.; Pantano, C.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

    1997-09-01

    Polycarbosilane (PCS) thin films were deposited on silicon (and other) substrates and heat treated under vacuum ({approximately}10{sup {minus}6} torr) at temperatures in the range of 200--1,200 C. At temperatures in the range of 1,000--1,200 C, the initially amorphous PCS films transformed to polycrystalline {beta}-silicon carbide ({beta}-SiC). Although PCS films could be deposited at thickness up to 2 {micro}m, the films with thicknesses >1 {micro}m could not be transformed to SiC without extensive cracking. The resulting SiC coatings were characterized using Fourier transform infrared spectroscopy, glancing-angle X-ray diffractometry, secondary-ion mass spectroscopy, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The temperature and time dependence of the amorphous-to-crystalline transition could be associated with the evolution of free carbon, oxygen, and hydrogen in the films.

  1. Dispersion of nonresonant third-order nonlinearities in Silicon Carbide

    Science.gov (United States)

    de Leonardis, Francesco; Soref, Richard A.; Passaro, Vittorio M. N.

    2017-01-01

    In this paper we present a physical discussion of the indirect two-photon absorption (TPA) occuring in silicon carbide with either cubic or wurtzite structure. Phonon-electron interaction is analyzed by finding the phonon features involved in the process as depending upon the crystal symmetry. Consistent physical assumptions about the phonon-electron scattering mechanisms are proposed in order to give a mathematical formulation to predict the wavelength dispersion of TPA and the Kerr nonlinear refractive index n2. The TPA spectrum is investigated including the effects of band nonparabolicity and the influence of the continuum exciton. Moreover, a parametric analysis is presented in order to fit the experimental measurements. Finally, we have estimated the n2 in a large wavelength range spanning the visible to the mid-IR region.

  2. Joining of Silicon Carbide Through the Diffusion Bonding Approach

    Science.gov (United States)

    Halbig, Michael .; Singh, Mrityunjay

    2009-01-01

    In order for ceramics to be fully utilized as components for high-temperature and structural applications, joining and integration methods are needed. Such methods will allow for the fabrication the complex shapes and also allow for insertion of the ceramic component into a system that may have different adjacent materials. Monolithic silicon carbide (SiC) is a ceramic material of focus due to its high temperature strength and stability. Titanium foils were used as an interlayer to form diffusion bonds between chemical vapor deposited (CVD) SiC ceramics with the aid of hot pressing. The influence of such variables as interlayer thickness and processing time were investigated to see which conditions contributed to bonds that were well adhered and crack free. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

  3. Trend of Energy Saving in Electronic Devices for Research and Development

    Directory of Open Access Journals (Sweden)

    Rahmayanti R.

    2016-01-01

    Full Text Available In electronic industry, energy saving is one of the performance indicators of competitiveness beside price, speed, bandwidth and reliability. This affects research and development (R&D activity in mechatronic systems which uses electronic components and electronic systems. A review of trend of electronic devices technology development has been conducted with focus on energy saving. This review includes electronic devices, semiconductor, and nanotechnology. It can be concluded that the trend in electronic devices is mainly dictated by semiconductor technology development. The trend can be concluded as smaller size, lower voltage leading to energy saving, less heat, higher speed, more reliable, and cheaper. In accordance to such technology development, R&D activities in mechatronics especially in Indonesia is being pushed to make proper alignment.Some of such alignment actions are surface mount technology (SMT for installing surface mount devices components (SMD, design layout and SMD troubleshooting tools as well as human resources training and development.

  4. Structural characterization of “carbide-free” bainite in a Fe–0.2C–1.5Si–2.5Mn steel

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, Christina, E-mail: christina.hofer@unileoben.ac.at [Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Leitner, Harald [Böhler Edelstahl GmbH & Co KG, Mariazeller Straße 25, 8605 Kapfenberg (Austria); Winkelhofer, Florian [voestalpine Stahl Linz GmbH, voestalpine-Straße 3, 4020 Linz (Austria); Clemens, Helmut; Primig, Sophie [Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria)

    2015-04-15

    Low-alloyed, low C containing carbide-free bainitic steels are attractive candidates for applications in the automotive industry due to their well-balanced combination of high strength and ductility achieved in an economic way. In this work, their complex microstructure consisting of a mixture of bainitic ferrite, austenite with different morphologies and stabilities, martensite, M/A constituent and a few carbides has been investigated with metallographic and high-resolution techniques. After specific isothermal heat treatments in a dilatometer, a combination of LePera and Nital etching was applied to distinguish between bainite and martensite. Site-specific atom probe tips were prepared by means of scanning electron microscopy, electron backscatter diffraction and focused ion beam, revealing that “carbide-free” bainite consists of C depleted bainitic ferrite, C enriched retained austenite and occasional ε-carbides. Furthermore, it was found that the M/A constituent is highly dislocated and mainly martensitic. Its C content is increased compared to the nominal composition, but below the values obtained for retained austenite, explaining the lower transformation resistance. - Highlights: • Detailed top-down characterization of low C “carbide-free” bainitic steel • APT of all constituents in “carbide-free” bainite • Identification of ε-carbide based on its C content determined by APT • M/A constituent is mainly martensitic with austenitic areas at the boundaries • Lower C content of M/A constituent explains its lower stability.

  5. Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi'an; DAI Haiyang; ZOU Yu

    2008-01-01

    TiC based steel bonded carbides with the addition of nano TiN were prepared by vicuum sintering techniques.The microstructure was investigated using scanning electron microscopy(SEM)and transmission electron microscopy (TEM),and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides.the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

  6. Chemical Modification Methods of Nanoparticles of Silicon Carbide Surface

    OpenAIRE

    Anton S. Yegorov; Vitaly S. Ivanov; Alexey V. Antipov; Alyona I. Wozniak; Kseniia V. Tcarkova.

    2015-01-01

    silicon carbide exhibits exceptional properties: high durability, high thermal conductivity, good heat resistance, low thermal expansion factor and chemical inactivity. Reinforcement with silicon carbide nanoparticles increases polymer’s tensile strength and thermal stability.Chemical methods of modification of the silicon carbide surface by means of variety of reagents from ordinary molecules to macromolecular polymers are reviewed in the review.The structure of silicon carbide surface layer...

  7. Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

    Science.gov (United States)

    Singh, M.

    2011-01-01

    During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

  8. Structural changes induced by heavy ion irradiation in titanium silicon carbide

    Science.gov (United States)

    Nappé, J. C.; Monnet, I.; Grosseau, Ph.; Audubert, F.; Guilhot, B.; Beauvy, M.; Benabdesselam, M.; Thomé, L.

    2011-02-01

    Carbide-type ceramics, which have remarkable thermomechanical properties, are sensed to manufacture the fuel cladding of Generation IV reactors that should work at high temperature. The MAX phases, and more particularly titanium silicon carbide, are distinguished from other materials by their ability to have some plasticity, even at room temperature. For this study, polycrystalline Ti 3SiC 2 was irradiated with ions of different energies, which allow to discriminate the effect of both electronic and nuclear interactions. After characterization by low-incidence X-ray diffraction and cross-sectional transmission electron microscopy, it appears that Ti 3SiC 2 is not sensitive to electronic excitations while nuclear shocks damage its structure. The results show the creation of many defects and disorder in the structure, an expansion of the hexagonal close-packed lattice along the c axis, and an increase in the microstrain yield.

  9. Fabrication of thorium bearing carbide fuels

    Science.gov (United States)

    Gutierrez, Rueben L.; Herbst, Richard J.; Johnson, Karl W. R.

    1981-01-01

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

  10. Titanium carbide nanocrystals in circumstellar environments.

    Science.gov (United States)

    von Helden, G; Tielens, A G; van Heijnsbergen, D; Duncan, M A; Hony, S; Waters, L B; Meijer, G

    2000-04-14

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that infrared wavelength spectra of gas-phase titanium carbide nanocrystals derived in the laboratory show a prominent feature at a wavelength of 20.1 micrometers, which compares well to a similar feature in observed spectra of postasymptotic giant branch stars. It is concluded that titanium carbide forms during a short (approximately 100 years) phase of catastrophic mass loss (>0.001 solar masses per year) in dying, low-mass stars.

  11. Carbides composite surface layers produced by (PTA)

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-12-16

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

  12. The Electronic Commerce Integrated Development Methodology For Small Firms

    OpenAIRE

    Stapleton, Larry; Woods, Jaqueline; McDonald, T.J.

    2005-01-01

    Electronic Commerce (EC) technologies have the ability to reshape industry structure, and in doing so modify the rules of competition, which, in turn, lead to new methods of competing (Thong, 1999; Hawkins et al., 1999). The technological shift from traditional methods to Internet-based methods of trading has facilitated cost and competitive advantage (Auger and Gallaugher, 1997). However, to maximise EC gains it is critical that organisations understand the phases of technological assimila...

  13. A Two-Dimensional, Finite-Difference Model of the Oxidation of a Uranium Carbide Fuel Pellet

    OpenAIRE

    Shepherd, J; Fairweather, M; Hanson, BC; Heggs, PJ

    2015-01-01

    The oxidation of spent uranium carbide fuel, a candidate fuel for Generation IV nuclear reactors, is an important process in its potential reprocessing cycle. However, the oxidation of uranium carbide in air is highly exothermic. A model has therefore been developed to predict the temperature rise, as well as other useful information such as reaction completion times, under different reaction conditions in order to help in deriving safe oxidation conditions. Finite difference-methods are used...

  14. Molybdenum carbide nanotubes: a novel multifunctional material for label-free electrochemical immunosensing.

    Science.gov (United States)

    Zhai, Qingfeng; Zhang, Xiaowei; Li, Jing; Wang, Erkang

    2016-08-18

    Herein, a multifunctional nanoarchitecture has been developed by integrating well-crystalline molybdenum carbide (Mo2C) nanotubes and an electrochemical indicator - thionin (TH). The Mo2C nanotubes were synthesized through the self-degradable template method and high-temperature calcination, and their structure and morphology were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Due to the high electrocatalytic properties, excellent conductivity and highly active surface area of Mo2C nanotubes, the Mo2C-based material was used as a nanocarrier to load TH molecules for the development of a label-free electrochemical immunosensor for α-fetoprotein (AFP) detection. The decorated TH probe on the Mo2C nanotubes not only acted as a bridging molecule to effectively capture and immobilize primary anti-AFP on the Mo2C nanotubes, but also acted as a signal indicator for the detection of AFP. The proposed immunosensor exhibited excellent selectivity (with a detection limit of 3 pg mL(-1)), high stability and good reproducibility by combining the unique structure and features of the Mo2C nanotubes. Furthermore, this sensing platform was finally used for the detection of AFP in human serum with satisfactory results. Therefore, the Mo2C nanotubes can be considered as a candidate carbon material for fabrication of simple, label-free and ultrasensitive electrochemical sensors, broadening the application of this material.

  15. Physico-chemical properties and toxic effect of fruit-ripening agent calcium carbide

    Directory of Open Access Journals (Sweden)

    Mohammad Asif

    2012-01-01

    Full Text Available Ripening is the final stage of the maturation process, when the fruit changes color, softens and develops the flavor, texture and aroma that constitute optimum eating quality. This study was conducted to discuss the use of unsatisfactory calcium carbide to ripen fruits for domestic markets as well as their toxic effects on human health. The commonly used ripening agents are calcium carbide, acetylene, ethylene, propylene, ethrel (2-chloroethyl phosphonic acid, glycol, ethanol and some other agents. The calcium carbide is one of the most commonly used ripening agent for fruits, while other calcium salts like calcium ammonium nitrate, calcium chloride and calcium sulfate are used to delay fruit ripening agents for local fruit industries. The use of calcium carbide is being discouraged worldwide, due to associated health hazards. Calcium carbide treatment of food is extremely hazardous because it contains traces of arsenic and phosphorous, and once dissolved in water, it produces acetylene gas. Arsenic, phosphorous and acetylene gas may affect the different body organs and causes various health problems like headache, dizziness, mood disturbances, sleepiness, mental confusion, memory loss, cerebral edema, seizures and prolonged hypoxia.

  16. Titanium Carbide and Silicon Carbide Thermal Conductivity under Heavy Ions Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Cabrero, J.; Weisbecker, P.; Pailler, R. [LCTS, F-33600 Pessac (France); Cabrero, J.; Audubert, F. [CEA Cadarache, DEN 13108 Saint Paul Iez Durance (France); Kusiak, A. [TREFLE, Esplanade des Arts et Metiers 33405 Talence Cedex (France)

    2010-07-01

    SiC(f)/SiC ceramic matrix composites (CMC) are considered as structural materials in next generation fission nuclear reactors. However, thermal conductivity of SiC is reduced on the one hand at the highest temperatures, but also under irradiation. Titanium carbide, because of its peculiar thermal properties is an attractive material to be used as a matrix in a CMC to enhance the thermal conductivity of CMC under irradiation and at high temperature. In this study, we performed irradiation experiments on TiC, TiC{sub x}SiC{sub 1-x} and SiC samples, with heavy ions at room temperature (74 MeV Kr, fluence from 10{sup 13} to 10{sup 15} ions/cm{sup 2}). This energy results in an irradiated layer of about 7 {mu}m for TiC. Thermal conductivity of the irradiated layer is measured using IR radiometry as a function of fluence and composition. The structural evolution of the irradiated samples was investigated by Raman micro spectroscopy and transmission electron microscopy. (authors)

  17. Ablation of carbide materials with femtosecond pulses

    Science.gov (United States)

    Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Sentis, Marc; Marine, Wladimir

    2003-01-01

    The response of cemented tungsten carbide and of titanium carbonitride was investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of significant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2. The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions.

  18. Ultrarapid microwave synthesis of superconducting refractory carbides

    Energy Technology Data Exchange (ETDEWEB)

    Vallance, Simon R. [Department of Chemical and Environmental Engineering, University of Nottingham (United Kingdom); School of Chemistry, University Nottingham (United Kingdom); Round, David M. [School of Chemistry, University Nottingham (United Kingdom); Ritter, Clemens [Institut Laue-Langevin, Grenoble (France); Cussen, Edmund J. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow (United Kingdom); Kingman, Sam [Department of Chemical and Environmental Engineering, University of Nottingham (United Kingdom); Gregory, Duncan H. [WestCHEM, Department of Chemistry, University of Glasgow (United Kingdom)

    2009-11-26

    Nb{sub 1-x}Ta{sub x}C Carbides can be synthesized by high power MW methods in less than 30 s. In situ and ex situ techniques probing changes in temperature and dielectric properties with time demonstrate that the reactions self-terminate as the loss tangent of the materials decreases. The resulting carbides are carbon deficient and superconducting; T{sub c} correlates linearly to unit cell volume, reaching a maximum at NbC. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  19. Development and calibration of mirrors and gratings for the soft x-ray materials science beamline at the Linac Coherent Light Source free-electron laser.

    Science.gov (United States)

    Soufli, Regina; Fernández-Perea, Mónica; Baker, Sherry L; Robinson, Jeff C; Gullikson, Eric M; Heimann, Philip; Yashchuk, Valeriy V; McKinney, Wayne R; Schlotter, William F; Rowen, Michael

    2012-04-20

    This work discusses the development and calibration of the x-ray reflective and diffractive elements for the Soft X-ray Materials Science (SXR) beamline of the Linac Coherent Light Source (LCLS) free-electron laser (FEL), designed for operation in the 500 to 2000 eV region. The surface topography of three Si mirror substrates and two Si diffraction grating substrates was examined by atomic force microscopy (AFM) and optical profilometry. The figure of the mirror substrates was also verified via surface slope measurements with a long trace profiler. A boron carbide (B4C) coating especially optimized for the LCLS FEL conditions was deposited on all SXR mirrors and gratings. Coating thickness uniformity of 0.14 nm root mean square (rms) across clear apertures extending to 205 mm length was demonstrated for all elements, as required to preserve the coherent wavefront of the LCLS source. The reflective performance of the mirrors and the diffraction efficiency of the gratings were calibrated at beamline 6.3.2 at the Advanced Light Source synchrotron. To verify the integrity of the nanometer-scale grating structure, the grating topography was examined by AFM before and after coating. This is to our knowledge the first time B4C-coated diffraction gratings are demonstrated for operation in the soft x-ray region.

  20. Android and PSoC Technology Applied to Electronic Tongue Development

    OpenAIRE

    2015-01-01

    Nowadays, in the food industry, analyzing the quality of alimentary products has become a necessity. As a result, producers have been searching for new accurate methods to analyze food quality. The development of bio-inspired devices (electronic nose and electronic tongue) is a potential alternative to supply this need. The current project shows the development of a prototype circuit based on PSoC technology, which is used as a signal processing stage in an electronic tongue device with the a...

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    of carbonaceous deposits on the catalyst. At the same general activity level Li, K, and Cs provide similar promotional effects for Mo2C, although K at a loading level of alkali metal/Mo = 0.164 mol/mol provides the better behavior at equal conditions. The effect of further additives on the K2CO3/Mo2C system......This work investigates the use of the bulk carbides Mo2C, WC, and NbC as catalysts for the conversion of syngas into higher alcohols. K2CO3/WC produces mainly CH3OH and CH4 with a low activity. NbC has a very low activity in CO hydrogenation. K2CO3/Mo2C produces mixed alcohols with a reasonable...... activity and selectivity. In a 94 h test the activity and the specific surface area of the K2CO3/Mo2C catalyst decreased significantly, but X-ray diffraction and transmission electron microscopy did not indicate a strong sintering of the carbide. A likely cause for the deactivation is the formation...

  2. Microstructural Evolution of Chloride-Cleaned Silicon Carbide Aluminum Composites

    Science.gov (United States)

    Adeosun, S. O.; Akpan, E. I.; Gbenebor, O. P.; Balogun, S. A.

    2016-02-01

    This study examines the synergy between reinforcement surface modifications on the evolution of microstructures of AA6011-silicon carbide particle (SiCp) composites in multidirectional solidification. Silicon carbide particles (SiCp) were cleaned with ammonium chloride, tin(II) chloride, sodium chloride, and palladium(II) chloride and used as reinforcement to cast AA6011-SiCp composites by applying the stir casting method. A scanning electron microscope and x-ray diffractometer were used to investigate the morphology and phases present, respectively, in the composite material. Results show that wetting agents were effective as they inhibited the formation of Al4C3 in all modified composites. The modified SiCp was found to have varying effects on the morphology, dendrite arm size and direction, size and configuration of AlFeSi, and the amount of eutectic silicon depending on the concentration of the reagent and cleaning time. The highest effect was shown by the use of 40 g/L of tin(II) chloride. The composites had short dendritic arms, good interfacial interaction, and only a few crystals of AlFeSi.

  3. Carbide Nanoparticles Encapsulated in the Caves of Carbon Nanotubes by an In Situ Reduction-Carbonization Route

    Directory of Open Access Journals (Sweden)

    Chunli Guo

    2011-01-01

    Full Text Available Carbides (TiC, WC, and NbC nanoparticles fully encapsulated in the caves of carbon nanotubes (CNTs were synthesized via an in situ reduction-carbonization route at 600∘C in an autoclave. The structural features and morphologies of as-obtained products were investigated using by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy (HRTEM. HRTEM studies showed that the average diameter of CNTs encapsulated with carbide nanoparticles are in the range of 15–40 nm. The reaction temperature, the reaction time, and the metal catalyst are found to play crucial roles to the product morphology. The growth mechanism of carbide nanoparticles encapsulated in CNTs was discussed in detail.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-12-05

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

  5. Developing an Electronic Infrastructure To Support Multimedia Telecomputing Resources.

    Science.gov (United States)

    Robin, Bernard; Miller, Robert

    1998-01-01

    The Houston Consortium of Urban Professional Development and Technology Schools project, developed to prepare teachers for urban, multicultural classrooms is continuing its development of a telecommunications infrastructure for its members--faculty, teachers, staff and students from colleges, public schools, and regional educational service…

  6. Quantum Monte Carlo for electronic structure: Recent developments and applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodriquez, Maria Milagos Soto [Lawrence Berkeley Lab. and Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-04-01

    Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined by the accuracy of the trial wave function`s nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C2H and C2H2. The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is

  7. Carbide Coatings for Nickel Alloys, Graphite and Carbon/Carbon Composites to be used in Fluoride Salt Valves

    Energy Technology Data Exchange (ETDEWEB)

    Nagle, Denis [Johns Hopkins Univ., Baltimore, MD (United States); Zhang, Dajie [Johns Hopkins Univ., Baltimore, MD (United States)

    2015-10-22

    The focus of this research was concerned with developing materials technology that supports the evolution of Generation IV Advanced High Temperature Reactor (AHTR) concepts. Specifically, we investigate refractory carbide coatings for 1) nickel alloys, and 2) commercial carbon-carbon composites (CCCs). Numerous compelling reasons have driven us to focus on carbon and carbide materials. First, unlike metals, the strength and modulus of CCCs increase with rising temperature. Secondly, graphite and carbon composites have been proven effective for resisting highly corrosive fluoride melts such as molten cryolite [Na₃AlF₆] at ~1000°C in aluminum reduction cells. Thirdly, graphite and carbide materials exhibit extraordinary radiation damage tolerance and stability up to 2000°C. Finally, carbides are thermodynamically more stable in liquid fluoride salt than the corresponding metals (i.e. Cr and Zr) found in nickel based alloys.

  8. Review of the literature for dry reprocessing oxide, metal, and carbide fuel: The AIROX, RAHYD, and CARBOX pyrochemical processes

    Energy Technology Data Exchange (ETDEWEB)

    Hoyt, R.C.; Rhee, B.W. [Rockwell International Corp., Canoga Park, CA (United States). Energy Systems Group

    1979-09-30

    The state of the art of dry processing oxide, carbide, and metal fuel has been determined through an extensive literature review. Dry processing in one of the most proliferation resistant fuel reprocessing technologies available to date, and is one of the few which can be exported to other countries. Feasibility has been established for oxide, carbide, and metal fuel on a laboratory scale, and large-scale experiments on oxide and carbide fuel have shown viability of the dry processing concept. A complete dry processing cycle has been demonstrated by multicycle processing-refabrication-reirradiation experiments on oxide fuel. Additional experimental work is necessary to: (1) demonstrate the complete fuel cycle for carbide and metal fuel, (2) optimize dry processing conditions, and (3) establish fission product behavior. Dry process waste management is easier than for an aqueous processing facility since wastes are primarily solids and gases. Waste treatment can be accomplished by techniques which have been, or are being, developed for aqueous plants.

  9. Development of a novel straining holder for transmission electron microscopy compatible with single tilt-axis electron tomography.

    Science.gov (United States)

    Sato, K; Miyazaki, H; Gondo, T; Miyazaki, S; Murayama, M; Hata, S

    2015-10-01

    We have developed a newly designed straining specimen holder for in situ transmission electron microscopy (TEM) compatible with high-angle single tilt-axis electron tomography. The holder can deform a TEM specimen under tensile stress with the strain rate between 1.5 × 10(-6) and 5.2 × 10(-3) s(-1). We have also confirmed that the maximum tilt angle of the specimen holder reaches ±60° with a rectangular shape aluminum specimen. The new specimen holder, termed as 'straining and tomography holder', will have wide range potential applications in materials science.

  10. Module and electronics developments for the ATLAS ITK pixel system

    CERN Document Server

    Nellist, Clara; The ATLAS collaboration

    2016-01-01

    Summary ATLAS is preparing for an extensive modification of its detector in the course of the planned HL‐ LHC accelerator upgrade around 2025 which includes a replacement of the entire tracking system by an all‐silicon detector (Inner Tracker, ITk). A revised trigger and data taking system is foreseen with triggers expected at lowest level at an average rate of 1 MHz. The five innermost layers of ITk will comprise of a pixel detector built of new sensor and readout electronics technologies to improve the tracking performance and cope with the severe HL‐LHC environment in terms of occupancy and radiation. The total area of the new pixel system could measure up to 14 m2, depending on the final layout choice that is expected to take place in early 2017. A new on‐detector readout chip is designed in the context of the RD53 collaboration in 65 nm CMOS technology. This paper will present the on‐going R&D within the ATLAS ITK project towards the new pixel modules and the off‐detector electronics. Pla...

  11. Production of carbide-free thin ductile iron castings

    Institute of Scientific and Technical Information of China (English)

    M. Ashraf Sheikh

    2008-01-01

    The fast cooling rate of thin ductile iron castings requires special consideration to produce carbide-free castings. Extraor-dinary care was taken to select the charge to produce castings of 100-mm long round bars with 16-ram diameter. The castings show the presence of carbides in the bars. Seven melts were made with different temperatures and with different compositions to get rid of carbides. After chemical analyses, it was found that the extra purity of the charge with less than 0.008wt% sulfur in the castings was the cause of carbides. To remove the carbides fi'om the castings, sulfur should be added to the charge.

  12. Ultra-rapid processing of refractory carbides; 20 s synthesis of molybdenum carbide, Mo2C.

    Science.gov (United States)

    Vallance, Simon R; Kingman, Sam; Gregory, Duncan H

    2007-02-21

    The microwave synthesis of molybdenum carbide, Mo(2)C, from carbon and either molybdenum metal or the trioxide has been achieved on unprecedented timescales; Ex- and in-situ characterisation reveals key information as to how the reaction proceeds.

  13. Room-temperature carbide-derived carbon synthesis by electrochemical etching of MAX phases.

    Science.gov (United States)

    Lukatskaya, Maria R; Halim, Joseph; Dyatkin, Boris; Naguib, Michael; Buranova, Yulia S; Barsoum, Michel W; Gogotsi, Yury

    2014-05-05

    Porous carbons are widely used in energy storage and gas separation applications, but their synthesis always involves high temperatures. Herein we electrochemically selectively extract, at ambient temperature, the metal atoms from the ternary layered carbides, Ti3 AlC2 , Ti2 AlC and Ti3 SiC2 (MAX phases). The result is a predominantly amorphous carbide-derived carbon, with a narrow distribution of micropores. The latter is produced by placing the carbides in HF, HCl or NaCl solutions and applying anodic potentials. The pores that form when Ti3 AlC2 is etched in dilute HF are around 0.5 nm in diameter. This approach forgoes energy-intensive thermal treatments and presents a novel method for developing carbons with finely tuned pores for a variety of applications, such as supercapacitor, battery electrodes or CO2 capture.

  14. The impact of thermal fatigue and carbidization on the W coatings deposited on CFC tiles for the ITER-like Wall project at JET

    Energy Technology Data Exchange (ETDEWEB)

    Ruset, C., E-mail: ruset@infim.ro [National Institute for Laser, Plasma and Radiation Physics, Bucharest, Euratom-MEdC Association Romania (Romania); Grigore, E.; Falie, D.; Gherendi, M. [National Institute for Laser, Plasma and Radiation Physics, Bucharest, Euratom-MEdC Association Romania (Romania); Maier, H. [Max-Plank Institut für Plasma Physik, Euratom Association, 85748 Garching (Germany); Rasinski, M. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Matthews, G.F. [Culham Centre for Fusion Energy, Euratom Association, Abingdon (United Kingdom); Zoita, V. [National Institute for Laser, Plasma and Radiation Physics, Bucharest, Euratom-MEdC Association Romania (Romania); EFDA Close Support Unit, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)

    2013-10-15

    Highlights: ► Degradation curves of the W coatings depend on temperature and number of pulses. ► Thermo-mechanical properties of the W coatings are associated with degradation curves. ► Thermal fatigue and carbidization affect the interface between CFC and W. ► A pore structure was detected at the interface by SEM examination. -- Abstract: Since August 2011 JET operates with the ITER-like wall comprising bulk Be tiles, bulk W tiles and W coated CFC tiles with a thickness of 10–15 μm and 20–25 μm. In order to evaluate behavior of the W coatings to a cyclic thermal loading relevant to JET operation, high heat flux (HHF) tests have been carried out up to 5100 pulses with an electron beam facility at peak temperatures of 1000 °C, 1250 °C and 1450 °C. The pulse duration was 24 s. Optical inspections of the W layer performed periodically by interrupting the test revealed small delaminations with the size of 50–500 μm. The dependence of the delamination percentage on the number of pulses can be seen as a degradation curve for each particular W coating. In this way the thermo-mechanical properties of the W coatings can be characterized quantitatively. Thermal fatigue and carbidization of the tungsten due to the diffusion of the carbon from the substrate have been recognized as mechanisms for degradation of the coatings. Tungsten carbides have been identified by using TEM (transmission electron microscopy) diffraction analysis on FIB (focused ion beam) prepared cross-section samples subjected to HHF tests. Nano-pores developed at the CFC–Mo and Mo–W interfaces during the tests might be also responsible for the degradation of the coating.

  15. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    Science.gov (United States)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  16. Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei;

    2014-01-01

    of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR......). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts....

  17. Carbide Dissolution/Carbon Loss as a Function of Spray Distance in Unshrouded/Shrouded Plasma Sprayed Cr3C2-NiCr Coatings

    Science.gov (United States)

    Matthews, S.

    2015-02-01

    Thermal spraying of Cr3C2-NiCr composites generates varying degrees of carbide dissolution into the Ni binder. During high-temperature exposure, the carbide dissolution zones precipitate high concentrations of small carbides which develop into finely structured networks. This raises the possibility of producing unique tailored carbide composite structures through the generation of controlled carbide dissolution and appropriate heat treatment. The first step in this process is to produce a supersaturated Ni-Cr-C solid solution from which the carbide phase could be precipitated. In a previous work, a broad range of plasma parameters were trialed to assess their effect on the degree of carbide dissolution at a fixed spray distance of 100 mm. The current two-part work builds on the most promising plasma parameters from those trials. In Part 1 of this two-part article series, the effect of spray distance on the extent of carbide dissolution and carbon loss during high energy plasma spraying was investigated. The effectiveness of solid shield and gas shrouding is contrasted, and the mechanisms by which they influence the degree of decarburization discussed.

  18. High-temperature carbidization of carboniferous rocks

    Science.gov (United States)

    Goldin, B. A.; Grass, V. E.; Nadutkin, A. V.; Nazarova, L. Yu.

    2009-08-01

    Processes of thermal metamorphism of carboniferous rocks have been studied experimentally. The conditions of high-temperature interaction of shungite carbon with components of the contained rocks, leading to formation of carbide compounds, have been determined. The results of this investigation contribute to the works on searching for new raw material for prospective material production.

  19. Titanium carbide nanocrystals in circumstellar environments

    NARCIS (Netherlands)

    von Helden, G; Tielens, ACGM; van Heijnsbergen, D; Duncan, MA; Hony, S; Waters, LBFM; Meijer, G.

    2000-01-01

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that i

  20. CLAD CARBIDE NUCLEAR FUEL, THERMIONIC POWER, MODULES.

    Science.gov (United States)

    The general objective is to evaluate a clad carbide emitter, thermionic power module which simulates nuclear reactor installation, design, and...performance. The module is an assembly of two series-connected converters with a single common cesium reservoir. The program goal is 500 hours

  1. Boron carbide morphology changing under purification

    Science.gov (United States)

    Rahmatullin, I. A.; Sivkov, A. A.

    2015-10-01

    Boron carbide synthesized by using coaxial magnetoplasma accelerator with graphite electrodes was purified by two different ways. XRD-investigations showed content changing and respectively powder purification. Moreover TEM-investigations demonstrated morphology changing of product under purification that was discussed in the work.

  2. Casimir force measurements from silicon carbide surfaces

    NARCIS (Netherlands)

    Sedighi, M.; Svetovoy, V. B.; Palasantzas, G.

    2016-01-01

    Using an atomic force microscope we performed measurements of the Casimir force between a gold-coated (Au) microsphere and doped silicon carbide (SiC) samples. The last of these is a promising material for devices operating under severe environments. The roughness of the interacting surfaces was mea

  3. Bioactivation of biomorphous silicon carbide bone implants.

    Science.gov (United States)

    Will, Julia; Hoppe, Alexander; Müller, Frank A; Raya, Carmen T; Fernández, Julián M; Greil, Peter

    2010-12-01

    Wood-derived silicon carbide (SiC) offers a specific biomorphous microstructure similar to the cellular pore microstructure of bone. Compared with bioactive ceramics such as calcium phosphate, however, silicon carbide is considered not to induce spontaneous interface bonding to living bone. Bioactivation by chemical treatment of biomorphous silicon carbide was investigated in order to accelerate osseointegration and improve bone bonding ability. Biomorphous SiC was processed from sipo (Entrandrophragma utile) wood by heating in an inert atmosphere and infiltrating the resulting carbon replica with liquid silicon melt at 1450°C. After removing excess silicon by leaching in HF/HNO₃ the biomorphous preform consisted of β-SiC with a small amount (approximately 6wt.%) of unreacted carbon. The preform was again leached in HCl/HNO₃ and finally exposed to CaCl₂ solution. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared analyses proved that oxidation of the residual carbon at the surface induced formation of carboxyl [COO⁻] groups, which triggered adsorption of Ca(2+), as confirmed by XPS and inductively coupled plasma optical emission spectroscopy measurements. A local increase in Ca(2+) concentration stimulated in vitro precipitation of Ca₅(PO₄)₃OH (HAP) on the silicon carbide preform surface during exposure to simulated body fluid, which indicates a significantly increased bone bonding activity compared with SiC.

  4. Method of preparing a porous silicon carbide

    NARCIS (Netherlands)

    Moene, R.; Tazelaar, F.W.; Makkee, M.; Moulijn, J.A.

    1994-01-01

    Abstract of NL 9300816 (A) Described is a method of preparing a porous silicon carbide suitable for use as a catalyst or as a catalyst support. Porous carbon is provided with a catalyst which is suitable for catalysing gasification of carbon with hydrogen, and with a catalyst suitable for cataly

  5. Silicon Carbide Technologies for Lightweighted Aerospace Mirrors

    Science.gov (United States)

    2008-09-01

    silicon carbide (SiC) based materials. It is anticipated that SiC can be utilized for most applications from cryogenic to high temperatures. This talk will focus on describing the SOA for these (near term) SiC technology solutions for making mirror structural substrates, figuring and finishing technologies being investigated to reduce cost time

  6. Boron Carbides As Thermo-electric Materials

    Science.gov (United States)

    Wood, Charles

    1988-01-01

    Report reviews recent theoretical and experimental research on thermoelectric materials. Recent work with narrow-band semiconductors demonstrated possibility of relatively high thermoelectric energy-conversion efficiencies in materials withstanding high temperatures needed to attain such efficiencies. Among promising semiconductors are boron-rich borides, especially boron carbides.

  7. Casimir forces from conductive silicon carbide surfaces

    NARCIS (Netherlands)

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

    2014-01-01

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

  8. Synthesis of nanostructured carbon by chlorination of calcium carbide at moderate temperatures and its performance evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Dai Chunling [School of Chemistry, Xiangtan University, Hunan 411105 (China); Wang, Xianyou [School of Chemistry, Xiangtan University, Hunan 411105 (China)], E-mail: wxianyou@yahoo.com; Wang Ying [School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Hubei 430073 (China); Li Na; Wei Jianliang [School of Chemistry, Xiangtan University, Hunan 411105 (China)

    2008-12-01

    A new type of one-step preparation technique for the calcium carbide-derived carbon (CaC{sub 2}-CDC) was developed. In this study, CaC{sub 2}-CDC was synthesized from CaC{sub 2} in a freshly prepared chlorine environment in the temperature range of 100-600 deg. C. The structure and morphology of as-prepared CaC{sub 2}-CDC were studied by X-ray diffraction, transmission electron microscopy and nitrogen sorption experiment. Analysis of X-ray diffraction and transmission electron microscopy showed that CaC{sub 2}-CDC is an amorphous nanoporous material, and the structure depended on the synthesis temperature. The resultant carbon demonstrated narrow pore size distribution (PSD) and specific surface area (SSA) close to 800 m{sup 2} g{sup -1} (for nitrogen sorption) at a synthesized temperature of 100 deg. C. Increasing the reaction temperature above 400 deg. C resulted in a lower SSA of CaC{sub 2}-CDC due to the beginning of graphitization tendency. The nanoporous structure and narrow PSD of CaC{sub 2}-CDC indicated potential application as electrode materials in supercapacitor. The CaC{sub 2}-CDC exhibited a specific capacitance of 127.7 F g{sup -1} measured from the three-electrode cyclic voltammetry experiment at 10 mV s{sup -1}.

  9. Coarsening behaviour of M23C6 carbides in creep-resistant steel exposed to high temperatures

    OpenAIRE

    M. Godec; Skobir Balantič, D. A.

    2016-01-01

    High operating temperatures can have very deleterious effects on the long-term performance of high-Cr, creep-resistant steels used, for example, in the structural components of power plants. For the popular creep-resistant steel X20CrMoV12.1 we analysed the processes of carbide growth using a variety of analytical techniques: transmission electron microscopy (TEM) and diffraction (TED), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The evolution of the micro...

  10. An experimental investigation of wire electrical discharge machining of hot-pressed boron carbide

    Directory of Open Access Journals (Sweden)

    Ravindranadh Bobbili

    2015-12-01

    Full Text Available The present work discusses the experimental study on wire-cut electric discharge machining of hot-pressed boron carbide. The effects of machining parameters, such as pulse on time (TON, peak current (IP, flushing pressure (FP and spark voltage on material removal rate (MRR and surface roughness (Ra of the material, have been evaluated. These parameters are found to have an effect on the surface integrity of boron carbide machined samples. Wear rate of brass wire increases with rise in input energy in machining of hot-pressed boron carbide. The surfaces of machined samples were examined using scanning electron microscopy (SEM. The influence of machining parameters on mechanism of MRR and Ra was described. It was demonstrated that higher TON and peak current deteriorate the surface finish of boron carbide samples and result in the formation of large craters, debris and micro cracks. The generation of spherical particles was noticed and it was attributed to surface tension of molten material. Macro-ridges were also observed on the surface due to protrusion of molten material at higher discharge energy levels.

  11. Micrometric rods grown by nanosecond pulsed laser deposition of boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Quintas, Ignacio; Oujja, Mohamed; Sanz, Mikel; Benitez-Cañete, Antonio [Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Chater, Richard J. [Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Cañamares, Maria Vega [Instituto de Estructura de la Materia, CSIC, Serrano 119, 28006 Madrid (Spain); Marco, José F. [Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain); Castillejo, Marta, E-mail: marta.castllejo@iqfr.csic.es [Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain)

    2015-02-15

    Highlights: • Micrometric rods obtained by ns pulsed laser deposition of boron carbide at 1064 and 266 nm. • At 1064 nm microrods display crystalline polyhedral shape with sharp edges and flat sides. • Microrods consist of a mixture of boron, boron oxide, boron carbide and aliphatic hydrocarbons. - Abstract: Micrometric size rods have been fabricated via pulsed laser deposition in vacuum from boron carbide targets using nanosecond pulses of 1064 and 266 nm and room temperature Si (1 0 0) substrates. Morphological, structural and chemical characterization of the microrods was made by applying scanning electron microscopy, focussed ion beam microscopy coupled to secondary ion mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Ablation at 1064 nm favours the formation of microrods with high aspect ratio, sharp edges and pyramidal tips, typically 10 μm long with a cross section of around 2 μm × 2 μm. Differently, at 266 nm the microrods are of smaller size and present a more globular aspect. The analyses of the microrods provide information about their crystalline nature and composition, based on a mixture which includes boron, boron oxide and boron carbide, and allows discussion of the wavelength dependent growth mechanisms involved.

  12. Development of compact gas treatment system using secondary emission electron gun

    CERN Document Server

    Watanabe, M; Okino, A; Ko, K C; Hotta, E; Watanabe, Masato; Wang, Yu; Okino, Akitoshi; Ko, Kwang-Cheol; Hotta, Eiki

    2004-01-01

    It is well known that the non-thermal plasma processes using electrical discharge or electron beam are effective for the environmental pollutant removal. Especially, the electron beam can efficiently remove pollutant, because a lot of radicals which are useful to remove pollutant can be easily produced by high-energy electrons. We have developed a compact 100kV secondary emission electron gun to apply NOX removal. The device offers several inherent advantages such as compact in size, wide and uniform electron beam. Besides, the device offers good capability in high repetition rate pulsed operation with easy control compared with glow discharge or field emission control cathode guns. In present study, the NOX removal characteristics have been studied under the increased gun voltage, varied pulsed electron beam parameters such as current density and pulse width as well as gas flow rate. The experimental results indicate a better NOX removal efficiency comparing to other high-energy electron beam and electrical ...

  13. Theoretical investigation of nano zirconium carbide sheet: A study of NMR, NBO, EPR and Polar

    Directory of Open Access Journals (Sweden)

    Roya Rouhani

    2015-09-01

    Full Text Available In this work, we have focused on the zirconium carbide (ZrC sheet. The result exhibited that ZrC exhibits various outstanding physical and chemical properties, such as high hardness (25 Gpa, high melting point (3420°C, high corrosion and wear resistance, solid-state phase stability as well as chemical stability. Hence, ZrC has been considered a good potential material for ultra-high temperature applications. Applications range from cutting tools, grinding wheels and abrasives for mechanical as well as structural components in chemical and electronic industries. Abinitio calculation was carried out for Zirconium carbide sheet (ZrC using Gaussian 09 program for the first time (Fig 1. We choose B3LYP for calculating natural bond orbital (NBO, Nuclear magnetic resonance (NMR, Electron paramagnetic resonance (EPR and polar.

  14. Identification of Mo-Rich M23C6 Carbides in Alloy 718

    Science.gov (United States)

    Aghajani, Ali; Tewes, Jürgen; Parsa, Alireza Basir; Hoffmann, Thorsten; Kostka, Alexander; Kloewer, Jutta

    2016-09-01

    In the present study, we systematically identify and characterize a (Nb, Mo)-rich M23C6 type of M23C6 carbide with a lattice parameter of 1.094 nm in alloy 718 for the first time using a combination of selected area electron diffraction pattern and powder X-ray diffraction analysis. The time-temperature-precipitation diagrams of the precipitates in both annealed and strained conditions are obtained by particle analysis using an automated scanning electron microscopy method. (Nb, Mo)-rich M23C6 carbides first precipitate after 24 hours at 1223 K (950 °C) annealing, while they form after 10 minutes at 1273 K (1000 °C) in the strained condition. This correlates with the excess dislocations produce during deformation.

  15. Using Electron Paramagnetic Resonance Spectroscopy To Facilitate Problem Solving in Pharmaceutical Research and Development.

    Science.gov (United States)

    Mangion, Ian; Liu, Yizhou; Reibarkh, Mikhail; Williamson, R Thomas; Welch, Christopher J

    2016-08-19

    As new chemical methodologies driven by single-electron chemistry emerge, process and analytical chemists must develop approaches to rapidly solve problems in this nontraditional arena. Electron paramagnetic resonance spectroscopy has been long known as a preferred technique for the study of paramagnetic species. However, it is only recently finding application in contemporary pharmaceutical development, both to study reactions and to track the presence of undesired impurities. Several case studies are presented here to illustrate its utility in modern pharmaceutical development efforts.

  16. STATUS OF THE RESEARCH AND DEVELOPMENT TOWARDS ELECTRON COOLING OF RHIC

    Energy Technology Data Exchange (ETDEWEB)

    BEN-ZVI,I.; OZAKI, T.; YOSHIDA, T.; NANKAWA, T.; KOZAI, N.; SAKAMOTO, F.; SUZUKI, Y.

    2007-06-25

    The physics interest in a luminosity upgrade of RHIC requires the development of a cooling-frontier facility. Detailed calculations were made of electron cooling of the stored RHIC beams. This has been followed by beam dynamics simulations to establish the feasibility of creating the necessary electron beam. The electron beam accelerator will be a superconducting Energy Recovery Linac (ERL). An intensive experimental R&D program engages the various elements of the accelerator, as described by 24 contributions to the 2007 PAC.

  17. Molybdenum Carbides, Active and In Situ Regenerable Catalysts in Hydroprocessing of Fast Pyrolysis Bio-Oil

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jae-Soon; Zacher, Alan H.; Wang, Huamin; Olarte, Mariefel V.; Armstrong, Beth L.; Meyer, Harry M.; Soykal, I. Ilgaz; Schwartz, Viviane

    2016-06-16

    We assessed molybdenum carbides as a potential catalyst for fast pyrolysis bio-oil hydroprocessing. Currently, high catalyst cost, short catalyst lifetime, and lack of effective regeneration methods are hampering the development of this otherwise attractive renewable hydrocarbon technology. A series of metal-doped bulk Mo carbides were synthesized, characterized and evaluated in sequential low-temperature stabilization and high-temperature deoxygenation of a pine-derived bio-oil. During a typical 60-h run, Mo carbides were capable of upgrading raw bio-oil to a level suitable for direct insertion into the current hydrocarbon infrastructure with residual oxygen content and total acid number of upgraded oils below 2 wt% and 0.01 mg KOH g-1, respectively. The performance was shown to be sensitive to the type of metal dopant, Ni-doped Mo carbides outperforming Co-, Cu-, or Ca-doped counterparts; a higher Ni loading led to a superior catalytic performance. No bulk oxidation or other significant structural changes were observed. Besides the structural robustness, another attractive property of Mo carbides was in situ regenerability. The effectiveness of regeneration was demonstrated by successfully carrying out four consecutive 60-h runs with a reductive decoking between two adjacent runs. These results strongly suggest that Mo carbides are promising catalytic materials which could lead to a significant cost reduction in hydroprocessing bio-oils. This paper highlights areas for future research which will be needed to further understand carbide structure-function relationships and help design practical bio-oil upgrading catalysts based on Mo carbides.

  18. Development of a high average current polarized electron source with long cathode operational lifetime

    Energy Technology Data Exchange (ETDEWEB)

    C. K. Sinclair; P. A. Adderley; B. M. Dunham; J. C. Hansknecht; P. Hartmann; M. Poelker; J. S. Price; P. M. Rutt; W. J. Schneider; M. Steigerwald

    2007-02-01

    Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2?105???C/cm2 and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.

  19. Synthesis of tungsten carbide nanocrystals and their electrochemical properties

    Institute of Scientific and Technical Information of China (English)

    Jianghua ZENG; Dingsheng YUAN; Yingliang LIU; Jingxing CHEN; Sanxiang TAN

    2009-01-01

    Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO3 and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spec-troscopy and electrochemical methods. Hexagonal close-packed WC was successfully synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic ability for the oxygen reduction reaction.

  20. Pulsed laser ablation and deposition of niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Sansone, M.; De Bonis, A. [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza (Italy); Santagata, A. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, UOS Tito Scalo, C.da Santa Loja, 85010 Tito, PZ (Italy); Rau, J.V. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100, 00133 Rome (Italy); Galasso, A. [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza (Italy); Teghil, R., E-mail: roberto.teghil@unibas.it [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza (Italy)

    2016-06-30

    Highlights: • We have deposited in vacuum niobium carbide films by fs and ns PLD. • We have compared PLD performed by ultra-short and short laser pulses. • The films deposited by fs PLD of NbC are formed by nanoparticles. • The structure of the films produced by fs PLD at 500 °C corresponds to NbC. - Abstract: NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation–deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.