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Sample records for tungsten carbide precursors

  1. Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Novotny, K. [Laboratory of Atomic Spectrochemistry, Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic)], E-mail: codl@sci.muni.cz; Stankova, A. [Laboratory of Atomic Spectrochemistry, Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic); Haekkaenen, H.; Korppi-Tommola, J. [Department of Chemistry, University of Jyvaeskylae, P.O. BOX 35, FIN-40014 (Finland); Otruba, V.; Kanicky, V. [Laboratory of Atomic Spectrochemistry, Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic)

    2007-12-15

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation. Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r{sup 2} > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r{sup 2} = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

  2. Effect of precursor mass on product phase composition in plasma dynamic synthesis of tungsten carbide

    Science.gov (United States)

    Shatrova, K. N.; Sivkov, A. A.; Shanenkov, I. I.; Saigash, A. S.

    2017-05-01

    An interest in WC1-x cubic tungsten carbide results from its catalytic properties similar to those of platinum group metals and the synergistic effect between WC1-x and Pt in reactions of hydrogen evolution and hydrogen oxidation. However, according to the phase diagram of the W-C system, the cubic phase WC1-x only exists in a narrow range of temperature stability (about 2798-3058 K), which makes it difficult for being obtained. To date, there are different methods for synthesizing tungsten carbide powder with a low content of cubic phase that complicates the study of WC1-x properties. A direct plasma dynamic synthesis is known as one of the promising methods to produce WC1-x. The aim of this work is to find the optimal amount of tungsten precursor to obtain cubic tungsten carbide with a high purity by plasma dynamic method. The synthesized products were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns showed that the main phase was cubic tungsten carbide with negligible content of hexagonal tungsten carbide W2C and pure tungsten W. According to a quantitative analysis of synthesized products, which were obtained using masses of initial tungsten equal to 1.0, 0.7, 0.6 and 0.5 gram, the yield of WC1-x phase was 84, 89, 95 and 92 wt%, respectively. The results of TEM displayed that the synthesized powders consist of crystallites, having the size less than 100 nm (WC1-x), and a carbon matrix. This carbon was not detected in XRD due to its presence as an amorphous phase.

  3. Electrocatalysis on tungsten carbide

    International Nuclear Information System (INIS)

    Fleischmann, R.

    1975-01-01

    General concepts of electrocatalysis, the importance of the equilibrium rest potential and its standardization on polished WC-electrodes, the influence of oxygen in the catalysts upon the oxidation of hydrogen, and the attained results of the hydrogen oxidation on tungsten carbide are treated. (HK) [de

  4. Preparation method of tungsten carbide

    International Nuclear Information System (INIS)

    Jenkins, T.R.

    1976-01-01

    A method is described for the preparation of tungsten carbide in powder form from tungsten oxide powder in which the tungsten oxide is heated to 800-1,050 0 C, preferably to 850 0 C, and is reduced by the addition of carbon monoxide. The partial pressure of the CO 2 then formed must be kept below a necessary equilibrium value for the formation of the carbide. The waste gas (with max. 20 Vol% CO 2 ) is hardly reduced and is recycled in the circuit. (UWI) [de

  5. Toxicity of tungsten carbide and cobalt-doped tungsten carbide nanoparticles in mammalian cells in vitro.

    Science.gov (United States)

    Bastian, Susanne; Busch, Wibke; Kühnel, Dana; Springer, Armin; Meissner, Tobias; Holke, Roland; Scholz, Stefan; Iwe, Maria; Pompe, Wolfgang; Gelinsky, Michael; Potthoff, Annegret; Richter, Volkmar; Ikonomidou, Chrysanthy; Schirmer, Kristin

    2009-04-01

    Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobalt-doped tungsten carbide (WC-Co) nanoparticle suspensions in an array of mammalian cells. We examined acute toxicity of WC and of WC-Co (10% weight content Co) nanoparticles in different human cell lines (lung, skin, and colon) as well as in rat neuronal and glial cells (i.e., primary neuronal and astroglial cultures and the oligodendrocyte precursor cell line OLN-93). Furthermore, using electron microscopy, we assessed whether nanoparticles can be taken up by living cells. We chose these in vitro systems in order to evaluate for potential toxicity of the nanoparticles in different mammalian organs (i.e., lung, skin, intestine, and brain). Chemical-physical characterization confirmed that WC as well as WC-Co nanoparticles with a mean particle size of 145 nm form stable suspensions in serum-containing cell culture media. WC nanoparticles were not acutely toxic to the studied cell lines. However, cytotoxicity became apparent when particles were doped with Co. The most sensitive were astrocytes and colon epithelial cells. Cytotoxicity of WC-Co nanoparticles was higher than expected based on the ionic Co content of the particles. Analysis by electron microscopy demonstrated presence of WC nanoparticles within mammalian cells. Our findings demonstrate that doping of WC nanoparticles with Co markedly increases their cytotoxic effect and that the presence of WC-Co in particulate form is essential to elicit this combinatorial effect.

  6. Toxicity of Tungsten Carbide and Cobalt-Doped Tungsten Carbide Nanoparticles in Mammalian Cells in Vitro

    Science.gov (United States)

    Bastian, Susanne; Busch, Wibke; Kühnel, Dana; Springer, Armin; Meißner, Tobias; Holke, Roland; Scholz, Stefan; Iwe, Maria; Pompe, Wolfgang; Gelinsky, Michael; Potthoff, Annegret; Richter, Volkmar; Ikonomidou, Chrysanthy; Schirmer, Kristin

    2009-01-01

    Background Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. Objective We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobaltdoped tungsten carbide (WC-Co) nanoparticle suspensions in an array of mammalian cells. Methods We examined acute toxicity of WC and of WC-Co (10% weight content Co) nanoparticles in different human cell lines (lung, skin, and colon) as well as in rat neuronal and glial cells (i.e., primary neuronal and astroglial cultures and the oligodendro cyte precursor cell line OLN-93). Furthermore, using electron microscopy, we assessed whether nanoparticles can be taken up by living cells. We chose these in vitro systems in order to evaluate for potential toxicity of the nanoparticles in different mammalian organs (i.e., lung, skin, intestine, and brain). Results Chemical–physical characterization confirmed that WC as well as WC-Co nanoparticles with a mean particle size of 145 nm form stable suspensions in serum-containing cell culture media. WC nanoparticles were not acutely toxic to the studied cell lines. However, cytotoxicity became apparent when particles were doped with Co. The most sensitive were astrocytes and colon epithelial cells. Cytotoxicity of WC-Co nanoparticles was higher than expected based on the ionic Co content of the particles. Analysis by electron microscopy demonstrated presence of WC nanoparticles within mammalian cells. Conclusions Our findings demonstrate that doping of WC nanoparticles with Co markedly increases their cytotoxic effect and that the presence of WC-Co in particulate form is essential to elicit this combinatorial effect. PMID:19440490

  7. Ultrasonic ranking of toughness of tungsten carbide

    Science.gov (United States)

    Vary, A.; Hull, D. R.

    1983-01-01

    The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.

  8. 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.

  9. Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

    KAUST Repository

    Garcia Esparza, Angel T.

    2012-12-17

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting.

    Science.gov (United States)

    Garcia-Esparza, Angel T; Cha, Dongkyu; Ou, Yiwei; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

    2013-01-01

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C(3)N(4) (mpg-C(3)N(4)) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W(2)C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H(2) and O(2) in a stoichiometric ratio from H(2)O decomposition when supported on a Na-doped SrTiO(3) photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Indian Academy of Sciences (India)

    Keywords. Cryogenic treatment; tungsten carbide–cobalt; SEM; XRD; microhardness. 1. Introduction. Tungsten carbide tools can machine metals at speeds that cause the cutting edge to become red hot, without losing its hardness or sharpness. It exhibits about 2–3 times the produc- tivity and 10 times the life of high-speed ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-15

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

  13. Plasma spraying of zirconium carbide – hafnium carbidetungsten cermets

    Czech Academy of Sciences Publication Activity Database

    Brožek, Vlastimil; Ctibor, Pavel; Cheong, D.-I.; Yang, S.-H.

    2009-01-01

    Roč. 9, č. 1 (2009), s. 49-64 ISSN 1335-8987 Institutional research plan: CEZ:AV0Z20430508 Keywords : Plasma spraying * cermet coatings * microhardness * zirconium carbide * hafnium carbide * tungsten * water stabilized plasma Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  14. 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)

  15. Hollow microspheres with a tungsten carbide kernel for PEMFC application.

    Science.gov (United States)

    d'Arbigny, Julien Bernard; Taillades, Gilles; Marrony, Mathieu; Jones, Deborah J; Rozière, Jacques

    2011-07-28

    Tungsten carbide microspheres comprising an outer shell and a compact kernel prepared by a simple hydrothermal method exhibit very high surface area promoting a high dispersion of platinum nanoparticles, and an exceptionally high electrochemically active surface area (EAS) stability compared to the usual Pt/C electrocatalysts used for PEMFC application.

  16. 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.

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

    Indian Academy of Sciences (India)

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

  18. Synthesis and characterization of tungsten carbide doped cobalt via gas-solid reaction in rotary bed reactor

    International Nuclear Information System (INIS)

    Tertuliano, R.S.C.; Araujo, C.P.B. de; Frota, A.V.V.M.; Moriyama, A.L.L.; Souza, C.P. de

    2016-01-01

    The search for materials with high added value, high applicability and sustainability, motivates innovations in all areas of engineering. In this context, so-called doped carbides, ceramic and metal compounds are included. This work proposes the synthesis and characterization of tungsten carbide doped cobalt (WC-Co) through the gas-solid reaction in a rotating bed reactor. The production stages of the material are: precursor synthesis by wetting, drying at 80 deg C, characterization of the precursor by MEV, DRX and FRX, gas-solid reaction at 750 deg C in a reducing atmosphere of CH 4 / H 2 in a rotary reactor at 34 rpm and characterization of the reaction product by the techniques already mentioned. The results showed that tungsten carbide powders were produced with cobalt inserted into the structure, with high surface area, nanometric grains and with potential for applications in the areas of catalysis, reactors and fuel cells, showing the relevance of this type of research

  19. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    Science.gov (United States)

    Airapetov, A. A.; Begrambekov, L. B.; Buzhinskiy, O. I.; Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A.

    2015-12-01

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400-1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  20. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    Energy Technology Data Exchange (ETDEWEB)

    Airapetov, A. A.; Begrambekov, L. B., E-mail: lbb@plasma.mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Buzhinskiy, O. I. [State Research Center Troitsk Institute for Innovation and Fusion Research (TRINITI) (Russian Federation); Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation)

    2015-12-15

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  1. Development of tungsten carbide-cobalt coatings

    Science.gov (United States)

    Fitzsimmons, Mark

    1999-09-01

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

  2. Pipe bend wear - is tungsten carbide the answer?

    International Nuclear Information System (INIS)

    Freinkel, D.

    1988-01-01

    The purpose of the investigation was to compare the relative wear resistance of various grades of sintered tungsten carbide liners against a mild steel standard in a full-scale pneumatic conveying testing rig. Speciments ranging in cobalt content from 6 to 30 per cent and in grain size from 0,56 to 2,98 microns, including a mild steel standard, were placed on a specially designed holder which fitted into a tee type 100 mm diameter bend. The specimens were tested under various operating conditions, ie air velocity ranging from 28m/s to 52m/s, impact angles of 30 0 to 70 0 mass flow rates of 35kg/min to 83kg/min and phase densities of 1,2 to 2,9, using a 4 mm nominal size crushed granite rock. The experimental results show that the ultrafine-grained, low cobalt (6 per cent) tungsten carbide displays little sensitivity to varying velocities, impact angles, mass flow rates or phase densities, and consistently gave the best wear resistance under all testing conditions. It consistently showed the least wear resistance under all testing conditions and performed only slightly better than mild steel. The effect of the carbide grain size was found to be small, although the finer grain sizes displayed greater wear resistance than the coarse grains. The effect of cobalt content was such that the lower cobalt specimens (6 per cent range) consistently performed better than the higher cobalt contents (10 per cent, 15 per cent, 30 per cent) under all testing conditions; the wear resistance decreasing with increasing cobalt content. An empirical model for the prediction of wear for each type of material tested has been proposed, given the particular operating conditions. Microstructurally it has been shown that there is a definite relationship between erosion resistance and the inverse of the magnetic coercivity of the tungsten carbide alloys

  3. Preparation and performance of nanosized tungsten carbides for electrocatalysis

    International Nuclear Information System (INIS)

    Shen Peikang; Yin Shibin; Li Zihui; Chen Chan

    2010-01-01

    The principle of the intermittent microwave heating (IMH) method and the details on the working procedure for prepare nanosized materials were presented along with the comparison to the traditional continuous microwave heating (CMH) method. The nanosized tungsten carbides were synthesized as an example by this novel method. It produced WC with the average particle size of 21.4 nm at the procedure of 15 s-on and 15 s-off for 20 times, however, the particle size increased to 35.7 nm by CMH method for 5 min. The pure WC was obtained by post-treating the sample in NaOH solution, which gave the better performance as support. The nanosized WC was used as support for the Pt nanoparticles (Pt-WC/C(IMH)) for alcohol oxidation and oxygen reduction. It was proved that the Pt-WC/C(IMH) electrocatalysts gave the better performance than that prepared by CMH method (Pt-WC/C(CMH)) or Pt/C electrocatalysts in terms of the activity and CO-tolerance. The intermittent microwave heating method is easier to scale-up for mass production of the nanosized tungsten carbides and other nanosized materials as well.

  4. High Surface Area Tungsten Carbides: Synthesis, Characterization and Catalytic Activity towards the Hydrogen Evolution Reaction in Phosphoric Acid at Elevated Temperatures

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Li, Qingfeng; Jensen, Jens Oluf

    2014-01-01

    Tungsten carbide powders were synthesized as a potential electrocatalyst for the hydrogen evolution reaction in phosphoric acid at elevated temperatures. With ammonium metatungstate as the precursor, two synthetic routes with and without carbon templates were investigated. Through the intermediate...... nitride route and with carbon black as template, the obtained tungsten carbide samples had higher BET area. In 100% H3PO4 at temperatures up to 185°C, the carbide powders showed superior activity towards the hydrogen evolution reaction. A deviation was found in the correlation between the BET area...... and catalytic activity; this was attributed to the presence of excess amorphous carbon in the carbide powder. TEM imaging and TGA-DTA results revealed a better correlation of the activity with the carbide particle size....

  5. Dissimilar Brazed Joints Between Steel and Tungsten Carbide

    Science.gov (United States)

    Voiculescu, I.; Geanta, V.; Binchiciu, H.; Iovanas, D.; Stefanoiu, R.

    2017-06-01

    Brazing is a joining process used to obtain heterogeneous assemblies between different materials, such as steels, irons, non-ferrous metals, ceramics etc. Some application, like asphalt cutters, require quick solutions to obtain dissimilar joints at acceptable costs, given the very short period of operation of these parts. This paper presents some results obtained during the brazing of dissimilar joints between steel and tungsten carbide by using different types of Ag-Cu system filler materials alloyed with P and Sn. The brazing techniques used were oxygen-gas flame and induction joining. The brazing behaviour was analysed in cross sections by optical and electron microscopy. The metallographic analysis enhanced the adhesion features and the length of penetration in the joining gap. The melting range of the filler materials was measured using thermal analysis.

  6. Dynamic SEM wear studies of tungsten carbide cermets

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined. Etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the WC and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation. The wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  7. Biological responses of isolated macrophages to cobalt metal and tungsten carbide-cobalt powders.

    Science.gov (United States)

    Lison, D; Lauwerys, R

    1991-10-01

    A previous study from this laboratory, using morphological and biochemical (LDH release) parameters, has shown that tungsten carbide-cobalt dust exhibits a greater cytotoxicity toward isolated macrophages than cobalt metal powder alone. The present study extends this comparison by examining additional biological parameters. Glucose uptake and superoxide anion production by isolated macrophages were significantly more depressed by the tungsten carbide-cobalt mixture (WC-Co) than by cobalt alone (Co) while pure tungsten carbide (WC) had no effect or even stimulated the cells. For glucose-6-phosphate dehydrogenase and cell-associated plasminogen activator (PA) activities, no difference between Co and WC-Co dusts was observed. These observations add further evidence to our previous findings regarding the different biological reactivity of cobalt metal alone or mixed with tungsten carbide.

  8. Structure-performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

    NARCIS (Netherlands)

    Stellwagen, D.R.; Bitter, J.H.

    2015-01-01

    This work demonstrates for the first time that carbide particle size is a critical factor for the activity and stability of carbon supported tungsten- and molybdenum carbide catalysts in (hydro-)deoxygenation reactions. The stability of the catalyst was shown to increase for larger particles due to

  9. Enhancing the adhesion of diamond films on cobalt-cemented tungsten carbide substrate using tungsten particles via MPCVD system

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Wen Chi [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Wu, Yu-Shiang, E-mail: yswu@cc.cust.edu.tw [Department of Mechanical Engineering, China University of Science and Technology, 245, Sec. 3, Yen-Chiu-Yuan Road, Nankang, Taipei 11581, Taiwan (China); Chang, Hou-Cheng [Department of Electronic Engineering, China University of Science and Technology, Taipei 11581, Taiwan (China); Lee, Yuan-Haun [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

    2011-03-24

    Graphical abstract: Display Omitted Research highlights: > Larger particles of tungsten led to larger diamond particles with improved crystallinity, covering the specimen with increased speed. > Adhesion was indicated to be a function of the gaps between the tungsten particles. > Diamond films pretreated with tungsten particles of 2.0 {mu}m showed the highest hardness of 27.78 GPa with good crystalline. - Abstract: To increase the adhesion of diamond films and avoid the negative effects of using cobalt, previous treatments have employed tungsten particles to cover the surface of the 6 wt.% cobalt-cemented tungsten carbide (WC-Co) substrate. The surface of the tungsten particles is transformed into W{sub 2}C and WC, which attracts and traps carbon. Through the process of nucleation, the carbon forms around the tungsten particles, thereby satisfying the conditions necessary for the formation of diamond film. Using Raman spectroscopy, we determined that diamond films of good quality with excellent adhesive properties and a hardness level as high as 27.78 GPa could be produced following pretreatment with 2.0 {mu}m tungsten particles. Rockwell indentation tests indicate that addition of tungsten particles promotes the interfacial adhesion of diamond films with WC-Co substrates. We determined that using smaller tungsten particles decreased the number of gaps and cavities on the surface of the substrate, thereby enhancing the adhesion of the diamond film.

  10. Simulation study on retention and reflection from tungsten carbide under high fluence of helium ions

    International Nuclear Information System (INIS)

    Ono, T.; Yamamura, Y.; Kawamura, T.; Kenmotsu, T.

    2000-08-01

    We have studied, by a Monte Carlo simulation code ACAT-DIFFUSE, the fluence-dependence of the amount of retained helium atoms in tungsten carbide at room temperature under helium ion bombardment. The retention behavior may be understood qualitatively in terms of irradiation-dependent diffusion coefficient assumed and range. The emission processes from tungsten carbide under helium ion irradiation derived were compared with each other. We have discussed the retention curves for incident energy of 5 keV at incident angles of 0deg and 80deg and of 500 eV at 0deg. The energy spectra of helium atoms reflected from tungsten carbide for incident energy of 500 eV at 0deg and 80deg were compared with those from graphite and tungsten. (author)

  11. PREPARATION OF TANTALUM CARBIDE FROM AN ORGANOMETALLIC PRECURSOR

    Directory of Open Access Journals (Sweden)

    C. P. SOUZA

    1999-03-01

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

  12. Characterization of Tungsten Carbide coatings deposited on AISI 1020 steel

    International Nuclear Information System (INIS)

    Santos, A; Gonzalez, C; Ramirez, Z Y

    2017-01-01

    In order to determine the variation in the mechanical properties of AISI 1020 standardized steel, heat treated by a quenching and tempering process and with a Tungsten Carbide coating, was performed a microstructural and chemical characterization of the coating material through electron microscopy scanning and X-ray energy dispersive spectroscopy. The steel received a heat treatment of quenching performed by heating to 850°C, followed by cooling in water and tempering at a temperature of 450°C with air cooling. Tests of a) microhardness with a Wilson-Wolpert Tukon 2100B micro durometer and b) resistance to adhesive and abrasive wear following the ASTM G99-05 “Standard test method for wear testing with a pin-on-disk machine” and ASTM G65-04 “standard test method for measuring abrasion using dry sand and rubber Wheel” standards respectively. The results show that the microhardness of the steel do not vary with the load used to perform the test; in addition, the heat treatment of quenching and tempering improves by 5.5% the property while the coating increase it by 124.2%. Regarding the abrasive wear resistance, it is observed that the amount of material lost increases linearly with the distance covered. It was determined that the heat treatment decreased on average by 17.5% the volume of released material during the tests while the coating recued it by 66.7%. The amount volume of material lost during the adhesive wear tests increases linearly with the distance covered while the heat treatment decreased on average by 10.5% the volume of released material during the trial and the coating reduced it by 66.5%. (paper)

  13. 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.

  14. Carbide formation in tungsten coatings on carbon-fibre reinforced carbon substrates

    International Nuclear Information System (INIS)

    Rasinski, M.; Maier, H.; Ruset, C.; Lewandowska, M.; Kurzydlowski, K.J.

    2013-01-01

    Tungsten coatings with molybdenum interlayer deposited on carbon-fibre reinforced carbon (CFC) substrates were selected as the first wall material for the divertor in the Wall Project at Joint European Torus (similar to the International Thermonuclear Experimental Reactor). For such a layered structure, diffusion of carbon from the CFC substrate towards the Mo and W deposits is expected during the operation of the reactor. As both molybdenum and tungsten form stable carbides, brittle compounds may form at the interface, thus strongly affecting the thermomechanical performance of the coated tiles. For the purpose of prediction of the operation time of such coated tiles, carbon diffusion and carbide formation kinetics need to be determined. In the present study, W/Mo/CFC samples were subjected to heat treatment at 1470 K for various annealing times. The Focused Ion Beam technique was used for sample preparation for electron microscopy examinations. Transmission electron microscopy observations supported with diffraction pattern analyses revealed the both W 2 C and WC carbides in the W coating, as well as that of Mo 2 C carbide in the Mo layer. The results were used to estimate the kinetics of coatings degradation. - Highlights: ► Thin Mo/W layers system on carbon-fibre reinforced carbon divertor tile ► Heat treatment at 1470 K results in two tungsten carbide creation — W 2 C and WC ► The total tungsten carbide creation is limited by carbon diffusion ► WC carbide creation is limited by W 2 C–WC reaction rate

  15. Ultrasonically Assisted Single Point Diamond Turning of Optical Mold of Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Zhanjie Li

    2018-02-01

    Full Text Available To realize high efficiency, low/no damage and high precision machining of tungsten carbide used for lens mold, a high frequency ultrasonic vibration cutting system was developed at first. Then, tungsten carbide was precisely machined with a polycrystalline diamond (PCD tool assisted by the self-developed high frequency ultrasonic vibration cutting system. Tool wear mechanism was investigated in ductile regime machining of tungsten carbide. The cutter back-off phenomenon in the process was analyzed. The subsequent experimental results of ultra-precision machining with a single crystal diamond tool showed that: under the condition of high frequency ultrasonic vibration cutting, nano-scale surface roughness can be obtained by the diamond tool with smaller tip radius and no defects like those of ground surface were found on the machined surface. Tool wear mechanisms of the single crystal diamond tool are mainly abrasive wear and micro-chipping. To solve the problem, a method of inclined ultrasonic vibration cutting with negative rake angle was put forward according to force analysis, which can further reduce tool wear and roughness of the machined surface. The investigation was important to high efficiency and quality ultra-precision machining of tungsten carbide.

  16. Tungsten carbide promoted Pd and Pd–Co electrocatalysts for formic acid electrooxidation

    DEFF Research Database (Denmark)

    Yin, Min; Li, Qingfeng; Jensen, Jens Oluf

    2012-01-01

    Tungsten carbide (WC) promoted palladium (Pd) and palladium–cobalt (Pd–Co) nanocatalysts are prepared and characterized for formic acid electrooxidation. The WC as the dopant to carbon supports is found to enhance the CO tolerance and promote the activity of the Pd-based catalysts for formic acid...

  17. Synthesis of ordered mesoporous carbon/tungsten carbides as a replacement of platinum-based electrocatalyst for methanol oxidation

    International Nuclear Information System (INIS)

    Zheng, Huajun; Chen, Zuo; Li, Yang; Ma, Chun’an

    2013-01-01

    The mesoporous material ordered mesoporous carbon/tungsten carbide (OMC/WC) was prepared and used as electrocatalyst for methanol electro-oxidation. WC embedded OMCs was synthesized through carbothermal reactions with a blow of argon and hydrogen by employing ammonium metatungstate as a precursor. In this method, because OMC acted both as the support and the carbon sources, not only the surface area of materials is enlarged, but also the generation of deposit carbon which covers the active sites can be effectively avoided. The characterization, which carried out by X-ray diffraction, Transmission electron microscopy and N 2 adsorption–desorption measurement showed a homogeneous distribution of WC throughout the surface of the mesoporous carbon and the surface area of OMC/WCs was up to 344 m 2 /g. Electro-catalytic properties and mechanism of methanol oxidation on the OMC/WCs electrode has been investigated using cyclic voltammetry and in situ FTIR technique. The results showed that there was only one characteristic methanol oxidation peak during the whole potential scan on the OMC/WCs electrode surface, it also showed an improved CO tolerance of the WC surface. It proved that tungsten carbide had good electro-catalytic property close to that of the Pt-based materials for methanol oxidation and provided a new idea for developing electrode materials in the future

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

    Science.gov (United States)

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

    2017-12-01

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

  19. Nanosized tungsten carbide synthesized by a novel route at low temperature for high performance electrocatalysis

    OpenAIRE

    Yan, Zaoxue; Cai, Mei; Shen, Pei Kang

    2013-01-01

    Tungsten carbide (WC) is a widely used engineering material which is usually prepared at high temperature. A new mechanism for synthesizing nanoscaled WC at ultralow temperature has been discovered. This discovery opens a novel route to synthesize valuable WC and other carbides at a cost-efficient way. The novel formation mechanism is based on an ion-exchange resin as carbon source to locally anchor the W and Fe species. As an intermediate, FeWO4 can be formed at lower temperature, which can ...

  20. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Hola, Marketa [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Otruba, Vitezslav [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Kanicky, Viktor [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic)]. E-mail: viktork@chemi.muni.cz

    2006-05-15

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm{sup 3}) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between {+-} 3% and {+-} 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed

  1. Influence of high power density plasma irradiation on the boron carbide coating on tungsten

    Science.gov (United States)

    Begrambekov, L. B.; Grunin, A. V.; Puntakov, N. A.; Sadovskiy, Ya A.; Utkov, N. S.

    2017-05-01

    The paper considers an influence of T-10 tokamak plasma disruption on boron carbide (B4C) coating on tungsten. The power density of coating irradiation reached 100 MW/m2. The relief and composition of the boron carbide coating sample areas heated up to different temperature due to influence of disruption is determined. Conclusion is made that B4C does not change integrity, when heated to temperatures of up to 2000 K. Local melting was observed in areas heated up to 2500 K. In the range of 2500-3600 K most of the coating was melted and collected into droplets. Composition rate is reduced to B:C = 1:1. In all temperature ranges the coating remained continuous and provided protection of tungsten from direct plasma irradiation.

  2. Manufacturing of a micro-tungsten carbide electrode using a supersonic-aided electrolysis process

    International Nuclear Information System (INIS)

    Weng, Feng-Tsai; Ho, Chi-Ting

    2008-01-01

    In this study, a novel micromachining technology for fabricating micro parts was described. The original diameter of a tungsten carbide rod was 3 mm, and it was first processed to a rod with a diameter of 50 µm by a precision-grinding process. It could then be machined to the desired diameter by a supersonic-aided electrolysis process. A high-aspect ratio of the micro-tungsten carbide rod was easily obtained by this process. The surface roughness of the sample that was processed by electrolysis with supersonic-aided agitation was compared with that of the sample obtained without agitation. The machined surface of the sample was smooth, and the reason may be that ionized particles in the anode could be removed by supersonic-aided agitation during the electrolysis process. A microelectrode with a tip of approximately 1 µm could be obtained by this process. (technical note)

  3. Studies on Mechanical Alloying of Copper-Tungsten Carbide Composite for Spot Welding Electrode

    Science.gov (United States)

    Zuhailawati, H.; Jamaludin, S. B.

    2009-12-01

    This article presents a study on the properties and performance of copper-based composite reinforced with recycled tungsten carbide powder as spot welding electrode. The copper-tungsten carbide composite electrode was prepared by mechanical alloying and powder forging before being machined into truncated cone-face geometry. The welding operation was conducted on galvanized steel using a pedestal-type spot welding machine. Composites with higher density and electrical conductivity were obtained after mechanical alloying for shorter time. In contrast, a higher hardness is shown in the composite, which was mechanically alloyed to longer time. The strength of the welded steel coupon was found to increase with decreasing milling time due to an increase in density and electrical conductivity. The wear behavior of the composite revealed that the deformation of the spot weld electrode increased with increasing milling time.

  4. Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  5. Dry Sliding Wear behaviour of Aluminium-Red mud- Tungsten Carbide Hybrid metal matrix composites

    Science.gov (United States)

    Devi Chinta, Neelima; Selvaraj, N.; Mahesh, V.

    2016-09-01

    Red mud is an industrial waste obtained during the processing of alumina by Bayer's process. An attempt has been made to utilize the solid waste by using it as the reinforcement material in metal matrix composites. Red mud received from NALCO has been subjected for sieve analysis and milled to 42 nanometers using high energy ball mill. Red mud is used as a reinforcement material in Pure Aluminium matrix composite at 2%, 4%, and 6% weight at 100 microns level as well as 42 nano meters along with 4%Tungsten carbide by weight. Micro and Nano structured red mud powders, Tungsten carbide powder and Aluminium is mixed in a V-Blender, compacted at a pressure of 40 bar and samples are prepared by conventional sintering with vacuum as medium. In this current work, dry sliding wear characteristics at normal and heat treatment conditions are investigated with optimal combination of Aluminium, Tungsten carbide and different weight fractions of micro and nano structured red mud powder.

  6. Durable and self-hydrating tungsten carbide-based composite polymer electrolyte membrane fuel cells.

    Science.gov (United States)

    Zheng, Weiqing; Wang, Liang; Deng, Fei; Giles, Stephen A; Prasad, Ajay K; Advani, Suresh G; Yan, Yushan; Vlachos, Dionisios G

    2017-09-04

    Proton conductivity of the polymer electrolyte membranes in fuel cells dictates their performance and requires sufficient water management. Here, we report a simple, scalable method to produce well-dispersed transition metal carbide nanoparticles. We demonstrate that these, when added as an additive to the proton exchange Nafion membrane, provide significant enhancement in power density and durability over 100 hours, surpassing both the baseline Nafion and platinum-containing recast Nafion membranes. Focused ion beam/scanning electron microscope tomography reveals the key membrane degradation mechanism. Density functional theory exposes that OH• and H• radicals adsorb more strongly from solution and reactions producing OH• are significantly more endergonic on tungsten carbide than on platinum. Consequently, tungsten carbide may be a promising catalyst in self-hydrating crossover gases while retarding desorption of and capturing free radicals formed at the cathode, resulting in enhanced membrane durability.The proton conductivity of polymer electrolyte membranes in fuel cells dictates their performance, but requires sufficient water management. Here, the authors report a simple method to produce well-dispersed transition metal carbide nanoparticles as additives to enhance the performance of Nafion membranes in fuel cells.

  7. Physical and Mechanical Properties of W-Ni-Fe-Co Metal Foam Modified by Titanium Tungsten Carbide Alloying

    Science.gov (United States)

    Ishchenko, A. N.; Tabachenko, A. N.; Afanas'eva, S. A.; Belov, N. N.; Biryukov, Yu. A.; Burkin, V. V.; D'yachkovskii, A. S.; Rogaev, K. S.; Skosyrskii, A. B.; Yugov, N. T.

    2018-02-01

    The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the liquid phase sintering of powder materials, including those containing tungsten nanopowders. High porosity metal foams are prepared through varying the porosity of powder specimens and the content of filling material. The penetration capability of cylinder projectiles made of new alloys is explored in this paper. It is shown that their penetration depth exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron alloy, other factors being equal.

  8. Densification rate and interfacial adhesion of bilayer cemented tungsten carbide and steel

    Energy Technology Data Exchange (ETDEWEB)

    Ojo-kupoluyi, Oluwatosin Job; Tahir, Suraya Mohd; Ariff, Azmah Hanim Mohamed; Baharudin, B.T. Hang Tuah [Univ. Putra Malaysia, Selangor (Malaysia). Dept. of Mechanical and Manufacturing Engineering; Matori, Khamirul Amin [Univ. Putra Malaysia, Selangor (Malaysia). Dept. of Physics; Univ. Putra Malaysia, Selangor (Malaysia). Inst. of Advanced Technology (ITMA); Shamsul Anuar, Mohd [Univ. Putra Malaysia, Selangor (Malaysia). Dept. of Process and Food Engineering

    2017-12-15

    Manufacturing tailored materials is commonly faced with the challenge of shrinkage mismatch between layers resulting in delamination. The effects of sintering temperature and carbon variation on the densification and interfacial bond strength of bilayer cemented tungsten carbide and steel processed through powder metallurgy are analyzed. It is revealed through field-emission scanning electron microscopy images that inter-layer diffusion induced by liquid-phase sintering plays a major role in the densification and bonding of layers. Through dimensional analysis of sintered bilayer specimens, the strain rate of cemented tungsten carbide is observed to surpass that of steel. An enhanced densification rate of 6.1 % and M{sub 6}C (eta carbide) reduction with increased carbon level results in strong interfacial bonding in specimens sintered at 1 280 C. At 1 295 C, diffusion accelerates and the axial and radial shrinkage increase by 14.05 % and 13.35 %, respectively, in 93.8 wt.% WC - 6 wt.% Fe - 0.2 wt.% C and 93.2 wt.% Fe - 6 wt.% WC - 0.8 wt.% C, thereby increasing the tendency for complete delamination.

  9. PARTITIONING TUNGSTEN BETWEEN MATRIX PRECURSORS AND CHONDRULE PRECURSORS THROUGH RELATIVE SETTLING

    International Nuclear Information System (INIS)

    Hubbard, Alexander

    2016-01-01

    Recent studies of chondrites have found a tungsten isotopic anomaly between chondrules and matrix. Given the refractory nature of tungsten, this implies that W was carried into the solar nebula by at least two distinct families of pre-solar grains. The observed chondrule/matrix split requires that the distinct families were kept separate during the dust coagulation process, and that the two families of grain interacted with the chondrule formation mechanism differently. We take the co-existence of different families of solids in the same general orbital region at the chondrule-precursor size as given, and explore the requirements for them to have interacted with the chondrule formation process at significantly different rates. We show that this sorting of families of solids into chondrule- and matrix-destined dust had to have been at least as powerful a sorting mechanism as the relative settling of aerodynamically distinct grains at least two scale heights above the midplane. The requirement that the chondrule formation mechanism was correlated in some fashion with a dust-grain sorting mechanism argues strongly for spatially localized chondrule formation mechanisms such as turbulent dissipation in non-thermally ionized disk surface layers, and argues against volume-filling mechanisms such as planetesimal bow shocks.

  10. Analysis of crystallite size and microdeformation crystal lattice the tungsten carbide milling in mill high energy

    International Nuclear Information System (INIS)

    Silva, F.T. da; Nunes, M.A.M.; Souza, C.P. de; Gomes, U.U.

    2010-01-01

    The tungsten carbide (WC) has wide application due to its properties like high melting point, high hardness, wear resistance, oxidation resistance and good electrical conductivity. The microstructural characteristics of the starting powders influences the final properties of the carbide. In this context, the use of nanoparticle powders is an efficient way to improve the final properties of the WC. The high energy milling stands out from other processes to obtain nanometric powders due to constant microstructural changes caused by this process. Therefore, the objective is to undertake an analysis of microstructural characteristics on the crystallite size and microdeformations of the crystal lattice using the technique of X-ray diffraction (XRD) using the Rietveld refinement. The results show an efficiency of the milling process to reduce the crystallite size, leading to a significant deformation in the crystal lattice of WC from 5h milling. (author)

  11. Characteristics of deposited boron doping diamond on tungsten carbide insert by MPECVD

    Science.gov (United States)

    Kim, Jong Seok; Park, Yeong Min; Kim, Jeong Wan; Tulugan, Kelimu; Kim, Tae Gyu

    2015-03-01

    Diamond-coated cutting tools are used primarily for machining non-ferrous materials such as aluminum-silicon alloys, copper alloys, fiber-reinforced polymers, green ceramics and graphite. Because the tool life of cemented carbide cutting tool is greatly improved by diamond coating, and typically more than 10 times of the tool life is obtained. However, research of boron-doped diamond (BDD) coating tool has not been fully researched yet. In this study, we have succeeded to make boron-doped microcrystalline and nanocrystalline diamond-coated Co-cemented tungsten carbide (WC-Co) inserts. Microcrystalline BDD thin film is deposited on WC-Co insert by using microwave plasma enhanced chemical vapor deposition (MPECVD) method. Scanning electron microscope (SEM) and Raman spectroscopy are used to characterize the as-deposited diamond films.1,2

  12. The enhancement of wear resistance for nitrogen-implanted tungsten carbide

    Science.gov (United States)

    Yeo, Sunmog; Kim, Yong-Gi

    2015-02-01

    The enhancement of the wear resistance for tungsten carbide (WC-Co) is investigated by using an ion implantation technique. A ball-on-disc-type tribometer confirmed that the wear resistance was systematically increased with increasing dose and implantation energy of the nitrogen ions. In accordance with the increase in the wear resistance, the nano-indentation measurements showed that the hardness for the nitrogen-implanted WC-Co with an energy of 120 keV (dose: 1 × 1018 ions/cm2) was increased by about 2.8 times compared to that for as-received WC-Co.

  13. Single-Crystal Tungsten Carbide in High-Temperature In-Situ Additive Manufacturing Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kolopus, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Boatner, Lynn A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-18

    Nanoindenters are commonly used for measuring the mechanical properties of a wide variety of materials with both industrial and scientific applications. Typically, these instruments employ an indenter made of a material of suitable hardness bonded to an appropriate shaft or holder to create an indentation on the material being tested. While a variety of materials may be employed for the indenter, diamond and boron carbide are by far the most common materials used due to their hardness and other desirable properties. However, as the increasing complexity of new materials demands a broader range of testing capabilities, conventional indenter materials exhibit significant performance limitations. Among these are the inability of diamond indenters to perform in-situ measurements at temperatures above 600oC in air due to oxidation of the diamond material and subsequent degradation of the indenters mechanical properties. Similarly, boron carbide also fails at high temperature due to fracture. [1] Transition metal carbides possess a combination of hardness and mechanical properties at high temperatures that offer an attractive alternative to conventional indenter materials. Here we describe the technical aspects for the growth of single-crystal tungsten carbide (WC) for use as a high-temperature indenter material, and we examine a possible approach to brazing these crystals to a suitable mount for grinding and attachment to the indenter instrument. The use of a by-product of the recovery process is also suggested as possibly having commercial value.

  14. Metal modified tungsten carbide (WC) for catalytic and electrocatalytic applications

    Science.gov (United States)

    Mellinger, Zachary J.

    One of the major challenges in the commercialization of proton exchange membrane fuel cells (PEMFC) is the cost, and low CO tolerance of the anode electrocatalyst material. The anode typically requires a high loading of precious metal electrocatalyst (Pt or Pt--Ru) to obtain a useful amount of electrical energy from the electrooxidation of methanol (CH3OH) or ethanol (C2H5OH). The complete electro--oxidation of methanol or ethanol on these catalysts produces strongly adsorbed CO on the surface, which reduces the activity of the Pt or Pt--Ru catalysts. Another major disadvantage of these electrocatalyst components is the scarcity and consequently high price of both Pt and Ru. Tungsten monocarbide (WC) has shown similar catalytic properties to Pt, leading to the utilization of WC and metal modified WC as replacements to Pt and Pt--Ru. In this thesis we investigated WC and Pt--modified WC as a potentially more CO--tolerant electrocatalysts as compared to pure Pt. These catalysts would reduce or remove the high loading of Pt used industrially. The binding energy of CO, estimated using temperature programmed desorption, is weaker on WC and Pt/WC than on Pt, suggesting that it should be easier to oxidize CO on WC and Pt/WC. This hypothesis was verified using cyclic voltammetry to compare the electro--oxidation of CO on WC, Pt/WC, and Pt supported on carbon substrates, which showed a lower voltage for the onset of oxidation of CO on WC and Pt/WC than on Pt. After observing these improved properties on the Pt/WC catalysts, we decided to expand our studies to investigate Pd--modified WC as Pd is less expensive than Pt and has shown more ideal properties for alcohol electrocatalysis in alkaline media. Pd/WC showed a lower binding energy of CO than both its parent metal Pd as well as Pt. Then, density functional theory (DFT) calculations were performed to determine how the presence of Pd affected the bonding of methanol and ethanol on the WC surface. The DFT studies showed

  15. Effects of lower cobalt binder concentrations in sintering of tungsten carbide

    International Nuclear Information System (INIS)

    Li Tao; Li Qingfa; Fuh, J.Y.H.; Yu, P.C.; Wu, C.C.

    2006-01-01

    Cemented tungsten carbides have received much attention because of their superior characteristics. Traditional cemented tungsten carbides usually contain 3-30 wt% binder phase. In this paper, WC with low Co concentration less than 3 wt% is studied using traditional powder metallurgy. The binder phase has tremendous effect on sinterability of WC. High sinterability and high hardness can be achieved for the WC (0.7 μm) with 0.5 wt% Co. Abnormal grain growth (AGG) is often observed in sintering WC with small amount of Co. It seems that AGG is affected by the concentration of Co and a range of Co concentrations may exist for the large amount of AGG. To control the grain size, VC is added to inhibit the grain growth of WC. It is observed that the hardness is affected by the amount of addition of VC. Controlling the ratio of C/W less than unity at low Co concentrations will result in the production of W 2 C phase. The hardness of WC-Co is affected by the amount of W 2 C phase in the sample and W 2 C is stable during the normal cooling process

  16. Formation of tungsten carbide nanoparticles on graphitized carbon to facilitate the oxygen reduction reaction

    Science.gov (United States)

    Yan, Zaoxue; He, Guoqiang; Cai, Mei; Meng, Hui; Shen, Pei Kang

    2013-11-01

    Tungsten carbide nanoparticles with the average size less than 5 nm uniformly dispersed on the graphitized carbon matrix have been successfully synthesized by a one-step ion-exchange method. This route is to locally anchor the interested species based on an ionic level exchange process using ion-exchange resin. The advantage of this method is the size control of targeted nanomaterial as well as the graphitization of resin at low temperatures catalyzed by iron salt. The Pt nanoparticles coupled with tungsten carbide nanoparticles on graphitized carbon nanoarchitecture form a stable electrocatalyst (Pt/WC-GC). The typical Pt/WC-GC electrocatalyst gives a Pt-mass activity of 247.7 mA mgPt-1, which is much higher than that of commercial Pt/C electrocatalyst (107.1 mA mgPt-1) for oxygen reduction reaction due to the synergistic effect between Pt and WC. The presented method is simple and could be readily scaled up for mass production of the nanomaterials.

  17. Recent Advances in the Deposition of Diamond Coatings on Co-Cemented Tungsten Carbides

    Directory of Open Access Journals (Sweden)

    R. Polini

    2012-01-01

    Full Text Available Co-cemented tungsten carbides, namely, hard metals are largely used to manufacture high wear resistant components in several manufacturing segments. Coating hard metals with superhard materials like diamond is of utmost interest as it can further extend their useful lifespan. The deposition of diamond coatings onto WC-Co can be extremely complicated as a result of poor adhesion. This can be essentially ascribed to (i the mismatch in thermal expansion coefficients between diamond and WC-Co, at the typical high temperatures inside the chemical vapour deposition (CVD chamber, generates large residual stresses at the interface; (ii the role of surface Co inside the WC-Co matrix during diamond CVD, which promotes carbon dissolution and diffusion. The present investigation reviews the techniques by which Co-cemented tungsten carbides can be treated to make them prone to receive diamond coatings by CVD. Further, it proposes interesting ecofriendly and sustainable alternatives to further improve the diamond deposition process as well as the overall performance of the coated hard metals.

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

    Science.gov (United States)

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

    2016-12-01

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

  19. Natural precursor based hydrothermal synthesis of sodium carbide for reactor applications

    Science.gov (United States)

    Swapna, M. S.; Saritha Devi, H. V.; Sebastian, Riya; Ambadas, G.; Sankararaman, S.

    2017-12-01

    Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.

  20. Atomic layer deposition synthesis of platinum-tungsten carbide core-shell catalysts for the hydrogen evolution reaction.

    Science.gov (United States)

    Hsu, Irene J; Kimmel, Yannick C; Jiang, Xiaoqiang; Willis, Brian G; Chen, Jingguang G

    2012-01-25

    Pt was deposited onto tungsten carbide powders using atomic layer deposition to produce core-shell catalysts for the hydrogen evolution reaction (HER). The Pt loading on these catalysts was reduced nearly ten-fold compared to a bulk Pt catalyst while equivalent HER activities were observed. This journal is © The Royal Society of Chemistry 2012

  1. Application of Deep Cryogenic Treatment to Uncoated Tungsten Carbide Inserts in the Turning of AISI 304 Stainless Steel

    Science.gov (United States)

    Özbek, Nursel Altan; Çİçek, Adem; Gülesİn, Mahmut; Özbek, Onur

    2016-12-01

    This study investigated the effects of deep cryogenic treatment (DCT) on the wear performance of uncoated tungsten carbide inserts. AISI 304 austenitic stainless steel, widely used in industry, was selected as the workpiece material. Cutting experiments showed that the amount of wear significantly increased with increasing cutting speed. In addition, it was found that DCT contributed to the wear resistance of the turning inserts. The treated turning inserts were less worn by 48 and 38 pct in terms of crater wear and notch wear, respectively, whereas they exhibited up to 18 pct superior wear performance in terms of flank wear. This was attributed to the precipitation of new and finer η-carbides and their homogeneous distribution in the microstructure of the tungsten carbide material after deep cryogenic treatment. Analyses via image processing, hardness measurements, and SEM observations confirmed these findings.

  2. Optimization of Tungsten Carbide Opposite Anvils Used in the In Situ High-Pressure Loading Apparatus

    Directory of Open Access Journals (Sweden)

    Zhang Ying

    2014-01-01

    Full Text Available In order to optimize the structure of anvils, finite element method is used to simulate two kinds of structures, one of which has a support ring but the other one does not. According to the simulated results, it is found that the maximum value of pressure appears at the center of culet when the bevelled angle is about 20°. Comparing the results of these two kinds of structures, we find that the efficiency of pressure transformation for the structure without support ring is larger than that for the structure with support ring. Considering the effect of von Mises stress, two kinds of tungsten carbide opposite anvils have been manufactured with bevelled angle of 10°. The experimental results for these two anvils are in good agreement with the simulation.

  3. Selective Production of Renewable para-Xylene by Tungsten Carbide Catalyzed Atom-Economic Cascade Reactions.

    Science.gov (United States)

    Dai, Tao; Li, Changzhi; Li, Lin; Zhao, Zongbao Kent; Zhang, Bo; Cong, Yu; Wang, Aiqin

    2018-02-12

    Tungsten carbide was employed as the catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA). This intermediate is the product of the Diels-Alder reaction between the two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization-hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W 2 C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio-based building blocks, thus potentially providing a petroleum-independent solution to valuable aromatic compounds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Evaluation of Analysis Conditions for Laser-Pulsed Atom Probe Tomography: Example of Cemented Tungsten Carbide.

    Science.gov (United States)

    Peng, Zirong; Choi, Pyuck-Pa; Gault, Baptiste; Raabe, Dierk

    2017-04-01

    Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAPTM 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAPTM 5000 XS system.

  5. Simulation on Mechanical Properties of Tungsten Carbide Thin Films Using Monte Carlo Model

    Directory of Open Access Journals (Sweden)

    Liliam C. Agudelo-Morimitsu

    2012-12-01

    Full Text Available The aim of this paper is to study the mechanical behavior of a system composed by substrate-coating using simulation methods. The contact stresses and the elastic deformation were analyzed by applying a normal load to the surface of the system consisting of a tungsten carbide (WC thin film, which is used as a wear resistant material and a stainless steel substrate. The analysis is based on Monte Carlo simulations using the Metropolis algorithm. The phenomenon was simulated from a fcc facecentered crystalline structure, for both, the coating and the substrate, assuming that the uniaxial strain is taken in the z-axis. Results were obtained for different values of normal applied load to the surface of the coating, obtaining the Strain-stress curves. From this curve, the Young´s modulus was obtained with a value of 600 Gpa, similar to the reports.

  6. Removal of a tungsten carbide wedding ring with a diamond tipped dental drill.

    Science.gov (United States)

    Ricks, Rupert

    2010-09-01

    Tungsten carbide (WC) is an incredibly hard inorganic compound that has recently become fashionable in the manufacture of men's jewellery, particularly wedding rings. It is a common misconception that these rings are unable to be cut and emergency treatment to remove them necessitates the amputation of the finger trapped within. We present a case of such a ring being successfully removed with the use of a diamond tipped dental drill with restoration of function and preservation of the finger. This is a previously undocumented method of removal of this type of ring in the English language literature. Copyright 2010 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  7. Comparative study of the acute lung toxicity of pure cobalt powder and cobalt-tungsten carbide mixture in rat.

    Science.gov (United States)

    Lasfargues, G; Lison, D; Maldague, P; Lauwerys, R

    1992-01-01

    Alveolitis progressing to lung fibrosis has been reported in workers exposed to cobalt containing dust (e.g., tungsten carbide-cobalt mixture as produced by the hard metal industry) but rarely following exposure to pure cobalt dust (e.g., in cobalt-producing factories). We have previously demonstrated that tungsten carbide-cobalt mixture is more toxic toward rat alveolar macrophages in vitro than pure cobalt metal powder. The present study was undertaken to compare in female rats the acute pulmonary response (lung weight, lung histology, cellular and biochemical analyses of bronchoalveolar lavage fluid, and mortality) following the intratracheal instillation of pure cobalt (Co) particles (median particle size, d50:4 microns), pure tungsten carbide (WC) particles (d50:2 microns), tungsten carbide-cobalt (WC-Co) powder (d50:2 microns; cobalt 6.3%, tungsten 84%, carbon 5.4%) and crystalline silica (d50 less than 5 micron) used as pneumotoxic reference material. WC alone (15.67 mg/100 g body wt) behaves as an inert dust producing only a mild accumulation of macrophages in the alveolar duct walls. Co alone (1.0 mg/100 g) only causes a moderate inflammatory response. An identical amount of Co given as WC-Co mixture (16.67 mg/100 g; corresponding to 1.0 mg Co/100 g) produces a severe alveolitis and fatal pulmonary edema. Cellular and biochemical characteristics of bronchoalveolar lavage fluid collected 24 hr after the intratracheal instillation of WC (1.0 mg/100 g) or Co (0.06 mg/100 g) are not significantly different from those of control animals instilled with sterile saline. On the contrary, bronchoalveolar lavage fluid changes following administration of the WC-Co mixture (1.0 mg/100 g; corresponding to 0.06 mg Co/100 g) are very similar to those induced by crystalline silica (1.0 mg/100 g). The amount of cobalt excreted in urine is significantly higher when the animals are exposed to WC-Co powder as compared to an equivalent amount of pure cobalt particles

  8. Nanosized tungsten carbide synthesized by a novel route at low temperature for high performance electrocatalysis

    Science.gov (United States)

    Yan, Zaoxue; Cai, Mei; Shen, Pei Kang

    2013-04-01

    Tungsten carbide (WC) is a widely used engineering material which is usually prepared at high temperature. A new mechanism for synthesizing nanoscaled WC at ultralow temperature has been discovered. This discovery opens a novel route to synthesize valuable WC and other carbides at a cost-efficient way. The novel formation mechanism is based on an ion-exchange resin as carbon source to locally anchor the W and Fe species. As an intermediate, FeWO4 can be formed at lower temperature, which can be directly converted into WC along with the carbonization of resin. The size of WC can be less than 2 nm. The catalyst made with Pt nanoparticles supported on nanosized WC-GC (WC-graphitized carbon) shows enhanced electrocatalytic activity for oxygen reduction reaction. The result also indicates that the Pt nanoparticles deposited on WC-GC are dominated by Pt (111) plane and shows a mass activity of 257.7 mA mg-1Pt@0.9 V.

  9. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Igor Konyashin

    2018-03-01

    Full Text Available Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures.

  10. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide.

    Science.gov (United States)

    Konyashin, Igor; Zaitsev, Alexander; Meledin, Alexander; Mayer, Joachim; Loginov, Pavel; Levashov, Evgeny; Ries, Bernd

    2018-03-09

    Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures.

  11. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide

    Science.gov (United States)

    Konyashin, Igor; Zaitsev, Alexander; Mayer, Joachim; Loginov, Pavel; Levashov, Evgeny; Ries, Bernd

    2018-01-01

    Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures. PMID:29522437

  12. Mechanical Properties and Microstructure of Biomorphic Silicon Carbide Ceramics Fabricated from Wood Precursors

    Science.gov (United States)

    Singh, Mrityunjay; Salem, J. A.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Silicon carbide based, environment friendly, biomorphic ceramics have been fabricated by the pyrolysis and infiltration of natural wood (maple and mahogany) precursors. This technology provides an eco-friendly route to advanced ceramic materials. These biomorphic silicon carbide ceramics have tailorable properties and behave like silicon carbide based materials manufactured by conventional approaches. The elastic moduli and fracture toughness of biomorphic ceramics strongly depend on the properties of starting wood preforms and the degree of molten silicon infiltration. Mechanical properties of silicon carbide ceramics fabricated from maple wood precursors indicate the flexural strengths of 3441+/-58 MPa at room temperature and 230136 MPa at 1350C. Room temperature fracture toughness of the maple based material is 2.6 +/- 0.2 MPa(square root of)m while the mahogany precursor derived ceramics show a fracture toughness of 2.0 +/- 0.2 Mpa(square root of)m. The fracture toughness and the strength increase as the density of final material increases. Fractographic characterization indicates the failure origins to be pores and chipped pockets of silicon.

  13. Surface modification of the hard metal tungsten carbide-cobalt by boron ion implantation

    International Nuclear Information System (INIS)

    Mrotchek, I.

    2007-01-01

    In the present thesis ion beam implantation of boron is studied as method for the increasement of the hardness and for the improvement of the operational characteristics of cutting tools on the tungsten carbide-cobalt base. For the boron implantation with 40 keV energy and ∼5.10 17 ions/cm 2 fluence following topics were shown: The incoerporation of boron leads to a deformation and remaining strain of the WC lattice, which possesses different stregth in the different directions of the elementary cell. The maximum of the deformation is reached at an implantation temperature of 450 C. The segregation of the new phases CoWB and Co 3 W was detected at 900 C implantation temperature. At lower temperatures now new phases were found. The tribological characteristics of WC-Co are improved. Hereby the maxiaml effect was measured for implantation temperatures from 450 C to 700 C: Improvement of the microhardness by the factor 2..2.5, improvement of the wear resistance by the factor 4. The tribological effects extend to larger depths than the penetration depth of the boron implantation profile. The detected property improvements of the hard metal H3 show the possibility of a practical application of boron ion implantation in industry. The effects essential for a wer decreasement are a hardening of the carbide phase by deformation of the lattice, a hardening of the cobalt binding material and the phase boundaries because of the formation of a solid solution of the implanted boron atoms in Co and by this a blocking of the dislocation movement and the rupture spreading under load

  14. Contribution to the quantum study of neutral tungsten carbide WC and ionized (WCq+, q=1 and 2)

    International Nuclear Information System (INIS)

    Sabor, Said

    2015-01-01

    Metal carbides and oxides are more interesting in catalytic and industrial domains. Tungsten carbide WC has been detected as serious substituent of platinum Pt catalytic. The ultimate goal of this thesis is theoretical studies of electronic structure, stability and the bound nature on WC, WO and its cations. Our preliminary research were motivated by the available spectroscopic data on W, W + , W 2+ , WC and WC 2+ . We used the methodology (CASSCF/MRCI/MRCI+Q/aug-cc-pV5Z(-PP)) implemented on MOLPRO package to perform quantum calculations with high accuracy taking into account the correlation and relativistic effects with a specific treatment of spin orbit coupling for some low lying excited electronic states of WC n+ , (n=0, 1 et 2). Our results are shown in good agreement with those available in the literature. Furthermore, in this work for the first time we demonstrated that a carbide dication (WC 2+ ) is thermodynamically stable. (author) [fr

  15. Atomic layer deposited nanocrystalline tungsten carbides thin films as a metal gate and diffusion barrier for Cu metallization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun Beom; Kim, Soo-Hyun, E-mail: soohyun@ynu.ac.kr [School of Materials Science and Engineering, Yeungnam University, Gyeongsan-si 712-749 (Korea, Republic of); Han, Won Seok [UP Chemical 576, Chilgoedong, Pyeongtaek-si, Gyeonggi-do 459-050 (Korea, Republic of); Lee, Do-Joong [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States)

    2016-07-15

    Tungsten carbides (WC{sub x}) thin films were deposited on thermally grown SiO{sub 2} substrates by atomic layer deposition (ALD) using a fluorine- and nitrogen-free W metallorganic precursor, tungsten tris(3-hexyne) carbonyl [W(CO)(CH{sub 3}CH{sub 2}C ≡ CCH{sub 2}CH{sub 3}){sub 3}], and N{sub 2} + H{sub 2} plasma as the reactant at deposition temperatures between 150 and 350 °C. The present ALD-WC{sub x} system showed an ALD temperature window between 200 and 250 °C, where the growth rate was independent of the deposition temperature. Typical ALD characteristics, such as self-limited film growth and a linear dependency of the film grown on the number of ALD cycles, were observed, with a growth rate of 0.052 nm/cycle at a deposition temperature of 250 °C. The ALD-WC{sub x} films formed a nanocrystalline structure with grains, ∼2 nm in size, which consisted of hexagonal W{sub 2}C, WC, and nonstoichiometric cubic β-WC{sub 1−x} phase. Under typical deposition conditions at 250 °C, an ALD-WC{sub x} film with a resistivity of ∼510 μΩ cm was deposited and the resistivity of the ALD-WC{sub x} film could be reduced even further to ∼285 μΩ cm by further optimizing the reactant pulsing conditions, such as the plasma power. The step coverage of ALD-WC{sub x} film was ∼80% on very small sized and dual trenched structures (bottom width of 15 nm and aspect ratio of ∼6.3). From ultraviolet photoelectron spectroscopy, the work function of the ALD-WC{sub x} film was determined to be 4.63 eV. Finally, the ultrathin (∼5 nm) ALD-WC{sub x} film blocked the diffusion of Cu, even up to 600 °C, which makes it a promising a diffusion barrier material for Cu interconnects.

  16. Synthesis and characterization of tungsten carbide doped cobalt via gas-solid reaction in rotary bed reactor; Sintese e caracterizacao de carbeto de tungstenio dopado com cobalto via reacao gas-solido em reator de leito rotativo

    Energy Technology Data Exchange (ETDEWEB)

    Tertuliano, R.S.C.; Araujo, C.P.B. de; Frota, A.V.V.M.; Moriyama, A.L.L.; Souza, C.P. de, E-mail: ruasavio@hotmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Departamento de Engenharia Quimica

    2016-07-01

    The search for materials with high added value, high applicability and sustainability, motivates innovations in all areas of engineering. In this context, so-called doped carbides, ceramic and metal compounds are included. This work proposes the synthesis and characterization of tungsten carbide doped cobalt (WC-Co) through the gas-solid reaction in a rotating bed reactor. The production stages of the material are: precursor synthesis by wetting, drying at 80 deg C, characterization of the precursor by MEV, DRX and FRX, gas-solid reaction at 750 deg C in a reducing atmosphere of CH{sub 4} / H{sub 2} in a rotary reactor at 34 rpm and characterization of the reaction product by the techniques already mentioned. The results showed that tungsten carbide powders were produced with cobalt inserted into the structure, with high surface area, nanometric grains and with potential for applications in the areas of catalysis, reactors and fuel cells, showing the relevance of this type of research.

  17. Chemical vapour deposition diamond coating on tungsten carbide dental cutting tools

    International Nuclear Information System (INIS)

    Sein, H; Ahmed, W; Rego, C A; Jones, A N; Amar, M; Jackson, M; Polini, R

    2003-01-01

    Diamond coatings on Co cemented tungsten carbide (WC-Co) hard metal tools are widely used for cutting non-ferrous metals. It is difficult to deposit diamond onto cutting tools, which generally have a complex geometry, using a single step growth process. This paper focuses on the deposition of polycrystalline diamond films onto dental tools, which possess 3D complex or cylindrical shape, employing a novel single step chemical vapour deposition (CVD) growth process. The diamond deposition is carried out in a hot filament chemical vapour deposition (HFCVD) reactor with a modified filament arrangement. The filament is mounted vertically with the drill held concentrically in between the filament coils, as opposed to the commonly used horizontal arrangement. This is a simple and inexpensive filament arrangement. In addition, the problems associated with adhesion of diamond films on WC-Co substrates are amplified in dental tools due to the very sharp edges and unpredictable cutting forces. The presence of Co, used as a binder in hard metals, generally causes poor adhesion. The amount of metallic Co on the surface can be reduced using a two step pre-treatment employing Murakami etching followed by an acid treatment. Diamond films are examined in terms of their growth rate, morphology, adhesion and cutting efficiency. We found that in the diamond coated dental tool the wear rate was reduced by a factor of three as compared to the uncoated tool

  18. Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses

    International Nuclear Information System (INIS)

    Oliveira, Eduardo Spinelli

    2017-01-01

    Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

  19. The high performance of tungsten carbides/porous bamboo charcoals supported Pt catalysts for methanol electrooxidation

    Science.gov (United States)

    Ma, Chun-an; Xu, Chenbin; Shi, Meiqin; Song, Guanghui; Lang, Xiaoling

    2013-11-01

    In this paper, a kind of environmental friendly and cost-effective bamboo charcoal (BC) is used as catalyst support in DMFCs instead of carbon nanotubes (CNTs), which is toxic and expensive. After special treatments, we obtain a sponge-like three-dimensional (3D) BC, which can provide high specific surface area (1264.5 m2 g-1) and porous matrices. Then, tungsten carbide (WC) and Pt are loaded on the BCs with microwave-assisted technique and 3D structural Pt/WC/BCs electro-catalyst is finally fabricated. Subsequently, the catalyst is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the further electrochemical investigation, it was found that Pt/WC/BCs catalyst has higher performance (2.76 mA cm-2) and better CO-tolerance for methanol oxidation compared with Pt/WC/CNTs and commercial Pt/C. Herein, we believe that the as-synthesized 3D Pt/WC/BCs catalyst has great promising application in DMFCs.

  20. Direct deposition of cubic boron nitride films on tungsten carbide-cobalt.

    Science.gov (United States)

    Teii, Kungen; Matsumoto, Seiichiro

    2012-10-24

    Thick cubic boron nitride (cBN) films in micrometer-scale are deposited on tungsten carbide-cobalt (WC-Co) substrates without adhesion interlayers by inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD) using the chemistry of fluorine. The residual film stress is reduced because of very low ion-impact energies (a few eV to ∼25 eV) controlled by the plasma sheath potential. Two types of substrate pretreatment are used successively; the removal of surface Co binder using an acid solution suppresses the catalytic effect of Co and triggers cBN formation, and the surface roughening using mechanical scratching and hydrogen plasma etching increases both the in-depth cBN fraction and deposition rate. The substrate surface condition is evaluated by the wettability of the probe liquids with different polarities and quantified by the apparent surface free energy calculated from the contact angle. The surface roughening enhances the compatibility in energy between the cBN and substrate, which are bridged by the interfacial sp(2)-bonded hexagonal BN buffer layer, and then, the cBN overlayer is nucleated and evolved easier.

  1. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Jamin M.; Catledge, Shane A., E-mail: catledge@uab.edu

    2016-02-28

    Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W{sub 2}CoB{sub 2}. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W{sub 2}CoB{sub 2} with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  2. Tungsten Carbide Grain Size Computation for WC-Co Dissimilar Welds

    Science.gov (United States)

    Zhou, Dongran; Cui, Haichao; Xu, Peiquan; Lu, Fenggui

    2016-06-01

    A "two-step" image processing method based on electron backscatter diffraction in scanning electron microscopy was used to compute the tungsten carbide (WC) grain size distribution for tungsten inert gas (TIG) welds and laser welds. Twenty-four images were collected on randomly set fields per sample located at the top, middle, and bottom of a cross-sectional micrograph. Each field contained 500 to 1500 WC grains. The images were recognized through clustering-based image segmentation and WC grain growth recognition. According to the WC grain size computation and experiments, a simple WC-WC interaction model was developed to explain the WC dissolution, grain growth, and aggregation in welded joints. The WC-WC interaction and blunt corners were characterized using scanning and transmission electron microscopy. The WC grain size distribution and the effects of heat input E on grain size distribution for the laser samples were discussed. The results indicate that (1) the grain size distribution follows a Gaussian distribution. Grain sizes at the top of the weld were larger than those near the middle and weld root because of power attenuation. (2) Significant WC grain growth occurred during welding as observed in the as-welded micrographs. The average grain size was 11.47 μm in the TIG samples, which was much larger than that in base metal 1 (BM1 2.13 μm). The grain size distribution curves for the TIG samples revealed a broad particle size distribution without fine grains. The average grain size (1.59 μm) in laser samples was larger than that in base metal 2 (BM2 1.01 μm). (3) WC-WC interaction exhibited complex plane, edge, and blunt corner characteristics during grain growth. A WC ( { 1 {bar{{1}}}00} ) to WC ( {0 1 1 {bar{{0}}}} ) edge disappeared and became a blunt plane WC ( { 10 1 {bar{{0}}}} ) , several grains with two- or three-sided planes and edges disappeared into a multi-edge, and a WC-WC merged.

  3. Study on the Tribological Properties of Porous Titanium Sliding against Tungsten Carbide YG6

    Directory of Open Access Journals (Sweden)

    Zhiqiang Liu

    2017-01-01

    Full Text Available In the metal cutting process, the friction and wear behavior between the cutting tool and machined surface is the most important factor that affects the surface quality and the service life of the cutter. The irregular pore structure of porous titanium alloy has changed its mechanical properties and the processing technology. The friction and wear mechanism of the cutting tool and the machined surface is greatly different from the traditional dense metal processing because of the crumbling at the edges, tearing phenomenon and the pore agglomeration effect of chips. In this paper, the tribological characteristics and the wear mechanism of friction pair which was formed by porous titanium alloy material and hard alloy cutter were studied from cutting force, cutting speed and temperature in micro-cutting condition, and the influence of porosity on the wear rate and friction coefficient was analyzed. Results show that the main factor which influences the friction coefficient and wear rate is the porosity. The wear mechanisms of porous titanium materials were abrasive and oxidation wear while the wear mechanism of tungsten carbide YG6 was abrasive wear. The friction coefficient and wear rate of the relatively stable state are beneficial to improve the surface quality and tool life. As a result, in the micro-cutting process of porous titanium alloys, the best choice of machining parameters for different porosity materials are as follows: the load is about 8 N, the sliding speed is about 400 r/min and the temperature is about 300 °C.

  4. Stability of the tungsten diselenide and silicon carbide heterostructure against high energy proton exposure

    Science.gov (United States)

    Walker, Roger C.; Shi, Tan; Jariwala, Bhakti; Jovanovic, Igor; Robinson, Joshua A.

    2017-10-01

    Single layers of tungsten diselenide (WSe2) can be used to construct ultra-thin, high-performance electronics. Additionally, there has been considerable progress in controlled and direct growth of single layers on various substrates. Based on these results, high-quality WSe2-based devices that approach the limit of physical thickness are now possible. Such devices could be useful for space applications, but understanding how high-energy radiation impacts the properties of WSe2 and the WSe2/substrate interface has been lacking. In this work, we compare the stability against high energy proton radiation of WSe2 and silicon carbide (SiC) heterostructures generated by mechanical exfoliation of WSe2 flakes and by direct growth of WSe2 via metal-organic chemical vapor deposition (MOCVD). These two techniques produce WSe2/SiC heterostructures with distinct differences due to interface states generated during the MOCVD growth process. This difference carries over to differences in band alignment from interface states and the ultra-thin nature of the MOCVD-grown material. Both heterostructures are not susceptible to proton-induced charging up to a dose of 1016 protons/cm2, as measured via shifts in the binding energy of core shell electrons and a decrease in the valence band offset. Furthermore, the MOCVD-grown material is less affected by the proton exposure due to its ultra-thin nature and a greater interaction with the substrate. These combined effects show that the directly grown material is suitable for multi-year use in space, provided that high quality devices can be fabricated from it.

  5. Effect of CVD-diamond coatings on the tribological performance of cemented tungsten carbide substrates

    Directory of Open Access Journals (Sweden)

    Kaleem Ahmad Najar

    2016-06-01

    Full Text Available A comparison has been documented between nanocrystalline diamond (NCD and microcrystalline diamond (MCD coatings deposited on cemented tungsten carbide (WC-Co substrates with architectures of WC-Co/NCD & WC-Co/MCD, using hot filament chemical vapor deposition (HFCVD technique. In the present work, the frictional characteristics were studied using ball-on-disc type linear reciprocating micro-tribometer, under the application of 1–10N normal loads, when sliding against smooth alumina (Al2O3 ceramic ball for the total duration of 15min, under dry sliding conditions. Nanoindentation tests were also conducted using Berkovich nanoindenter for the purpose of measurement of hardness and elastic modulus values. The average coefficients of friction of MCD and NCD coatings decrease from 0.37 – 0.32 and 0.3 – 0.27 respectively, when the load is increased from 1–10N. However, for conventional WC-Co substrate the average coefficient of friction increases from 0.60–0.75, under the same input operating conditions. The wear tracks formed on the surfaces of CVD-diamond coatings and WC-Co substrate, after friction measurement were characterised using Raman spectroscopy and scanning electron microscopy (SEM techniques. However, the compositional analysis for the formation of tribo-layer observed on the wear tracks of CVD-diamond coatings was confirmed using energy dispersive spectroscopy (EDS technique. Therefore, maintaining an appropriate level of normal load and using appropriate type of diamond coating, friction may be kept to some lower value to improve mechanical processes.

  6. Tungsten carbide-cobalt as a nanoparticulate reference positive control in in vitro genotoxicity assays.

    Science.gov (United States)

    Moche, Hélène; Chevalier, Dany; Barois, Nicolas; Lorge, Elisabeth; Claude, Nancy; Nesslany, Fabrice

    2014-01-01

    With the increasing human exposure to nanoparticles (NP), the evaluation of their genotoxic potential is of significant importance. However, relevance for NP of the routinely used in vitro genotoxicity assays is often questioned, and a nanoparticulate reference positive control would therefore constitute an important step to a better testing of NP, ensuring that test systems are really appropriate. In this study, we investigated the possibility of using tungsten carbide-cobalt (WC-Co) NP as reference positive control in in vitro genotoxicity assays, including 2 regulatory assays, the mouse lymphoma assay and the micronucleus assay, and in the Comet assay, recommended for the toxicological evaluation of nanomedicines by the French Agency of Human Health Products (Afssaps). Through these assays, we were able to study different genetic endpoints in 2 cell types commonly used in regulatory genotoxicity assays: the L5178Y mouse lymphoma cell line and primary cultures of human lymphocytes. Our results showed that the use of WC-Co NP as positive control in in vitro genotoxicity assays was conceivable, but that different parameters have to be considered, such as cell type and treatment schedule. L5178Y mouse lymphoma cells did not provide satisfactory results in the 3 performed tests. However, human lymphocytes were more sensitive to genotoxic effects induced by WC-Co NP, particularly after a 24-h treatment in the in vitro micronucleus assay and after a 4-h treatment in the in vitro Comet assay. Under such conditions, WC-Co could be used as a nanoparticulate reference positive control in these assays.

  7. Superficial roughness on composite surface, composite enamel and composite dentin junctions after different finishing and polishing procedures. Part I: roughness after treatments with tungsten carbide vs diamond burs.

    Science.gov (United States)

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The aim of this study is to investigate different instruments for finishing composite restorations, as well as examining different surfaces and interfaces of the same restoration. The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations finishing between tungsten carbide and diamond burs, furthermore the null hypothesis is that there are no significant differences on roughness between finishing on composite surfaces (C), compositeenamel (CE) and composite-dentin (CD) interfaces. The study was performed on 28 teeth, and class V cavities were prepared on the extracted teeth. Restorations were done in Filtek XTE nanofilled composite (3M Espe) in a standardized method, to then be finished. A comparison was made in the phase 1 between tungsten carbide burs (16 blades), diamond burs (46 μm), with a similar shape by the same manufacturer (Komet). Each surface received 5 bur applications. Consequently, an analysis with a profilometer was performed. Phase 2 involved further confrontation of ulterior finishing with ultrafine tungsten carbide burs (30 blades) and with extra and ultrafine diamond burs (25 and 8 μm) (the same shape as previously mentioned). A second analysis was then performed with a profilometer. All measurements were taken on C surfaces, CE and CD interfaces. Statistical analyses were carried out with c2 test (a = 0.05). The finishing procedures with fine grit or toothing burs gave a better smoothness with tungsten carbide burs compared to diamond burs. While with the ultrafine grit no significant differences were noted between tungsten carbide and diamond burs on the CE and CD interfaces, the diamond bur left less superficial roughness on the C surfaces. With regards to the superficial roughness of the different areas of restoration, it can be concluded that: minor roughness was detected on C surfaces, while the CD interface had the most superficial roughness, regardless of whether the

  8. Tungsten

    International Nuclear Information System (INIS)

    Eschnauer, H.

    1978-01-01

    There is no substitute for tungsten in its main field of application so that the demand will not decrease, but there is a need for further important applications. If small variations are left out of account, a small but steady increase in the annual tungsten consumption can be expected. The amount of tungsten available will increase due to the exploritation of new deposits and the extension of existing mines. This tendency will probably be increased by the world-wide prospection. It is hard to make an assessment of the amount of tungsten are obtained in the People's Republic of china, the purchases of Eastern countries in the West, and the sales policy of the USA; pice forecasts are therefore hard to make. A rather interesting subject with regard to the tungsten cycle as a whole is the reprocessing of tungsten-containing wastes. (orig.) [de

  9. Experimental study of the diamond turning characteristics of tungsten carbide (Co 0.5%) when using a chamfered diamond bite

    Science.gov (United States)

    Kim, Min Jae; Lee, June Key; Hwang, Yeon; Cha, Du Hwan; Kim, Hye Jeong; Kim, Jeong Ho

    2012-11-01

    Tungsten carbide (WC) is a widely used as a mold material for fabrication of glass lens because of its superior properties. Due to its extremely high hardness (R c > 90), an abrasive machining process, although unproductive and expensive, is used to fabricate the mold. In this research, the authors investigated the machining possibility of tungsten carbide by single-point diamond turning (SPDT) for fabricating high-quality optical surfaces directly. A finite element analysis (FEA) was carried out in order to investigate the effects of the chamfered length on the cutting forces and the strain rate of single-crystal diamond tools. The obtained FEA results showed that a smaller chamfered length decreased the bite strain rate. The performance characteristics in terms of surface roughness (R a ) and tool wear (VB max ) of a conventional bite and a chamfered bite under same machining conditions were studied, the results were compared. Experimental results suggest that the chamfered bite wased a better performance than the conventional bite in terms of tool wear resistance. The WC surface machined by using the chamfered bite showed a 2.26 nm roughness (R a ), which is suitable for the fabrication of glass lenses.

  10. Evaluation of the apoptogenic potential of hard metal dust (WC-Co), tungsten carbide and metallic cobalt.

    Science.gov (United States)

    Lombaert, Noömi; De Boeck, Marlies; Decordier, Ilse; Cundari, Enrico; Lison, Dominique; Kirsch-Volders, Micheline

    2004-12-01

    The present study aimed at comparing in vitro the apoptogenic properties of metallic cobalt (Co), tungsten carbide (WC) and tungsten carbide-cobalt (WC-Co) in conditions known to cause genotoxicity. Human peripheral blood mononucleated cells were incubated with 2.0-6.0 microg/ml of Co alone or mixed with WC particles and 33.3-100.0 microg/ml WC alone for up to 24 h. Under these culture conditions the majority (60%) of the cobalt metal particles were almost immediately solubilised in the culture medium, while WC remained under the form of particles that were progressively phagocytosed by monocytes. Apoptosis was assessed by Annexin-V staining, flow cytometry and analysis of DNA fragmentation by ELISA. Metallic Co-particles induced apoptosis in vitro. Furthermore, although so far considered as biologically inert, WC particles also induced apoptosis. When compared with its individual components WC-Co displayed an additive apoptotic effect in the DNA fragmentation assay. Apoptosis induced by WC particles was found largely dependent on caspase-9 activation and occurred presumably in monocytes, while that induced by Co involved both caspase-9 and -8 activation. The data suggest that apoptosis induced by the tested WC-Co mixture results from the additive effects of WC apoptosis induced in monocytes and Co-specific apoptosis in both monocytes and lymphocytes. The apoptogenic properties of these metals may be important in the mechanism of lung pathologies induced by the cobalt-containing particles.

  11. Microstructural and Mechanical Study of Inconel 625 – Tungsten Carbide Composite Coatings Obtained by Powder Laser Cladding

    Directory of Open Access Journals (Sweden)

    Huebner J.

    2017-06-01

    Full Text Available This study focuses on the investigation of fine (~0.54 μm tungsten carbide particles effect on structural and mechanical properties of laser cladded Inconel 625-WC composite. Three powder mixtures with different Inconel 625 – WC weight ratio (10, 20 and 30 weight % of WC were prepared. Coatings were made using following process parameters: laser beam diameter ø ≈ 500 μm, powder feeder rotation speed – 7 m/min, scanning velocity – 10 m/min, laser power – 220 W changed to 320 W, distance between tracks – 1 mm changed to 0.8 mm. Microstructure and hardness were investigated. Coatings produced by laser cladding were crack and pore free, chemically and structurally homogenous. High cooling rate during cladding process resulted in fine microstructure of material. Hardness improved with addition of WC from 396.3 ±10.5 HV for pure Inconel 625, to 469.9 ±24.9 HV for 30 weight % of WC. Tungsten carbide dissolved in Inconel 625 which allowed formation of intergranular eutectic that contains TCP phases.

  12. The effect of vanadium-carbon monolayer on the adsorption of tungsten and carbon atoms on tungsten-carbide (0001 surface

    Directory of Open Access Journals (Sweden)

    Moitra A.

    2011-01-01

    Full Text Available We report a first-principles calculations to study the effect of a vanadium-carbon (VC monolayer on the adsorption process of tungsten (W and carbon (C atoms onto tungsten-carbide (WC (0001 surface. The essential configuration for the study is a supercell of hexagonal WC with a (0001 surface. When adding the VC monolayer, we employed the lowest energy configuration by examining various configurations. The total energy of the system is computed as a function of the W or C adatoms’ height from the surface. The adsorption of a W and C adatom on a clean WC (0001 surface is compared with that of a W and C adatom on a WC (0001 surface with VC monolayer. The calculations show that the adsorption energy increased for both W and C adatoms in presence of the VC monolayer. Our results provide a fundamental understanding that can explain the experimentally observed phenomena of inhibited grain growth during sintering of WC or WC-Co powders in presence of VC.

  13. Investigation on the Tribological Behavior of Arc-Sprayed and Hammer-Peened Coatings Using Tungsten Carbide Cored Wires

    Science.gov (United States)

    Tillmann, W.; Hagen, L.; Schröder, P.

    2017-01-01

    Due to their outstanding properties, WC-W2C iron-based cermet coatings are widely used in the field of wear protection. Regarding commonly used WC-W2C reinforced coating systems, it has been reported that their tribological behavior is mainly determined by the carbide grain size fraction. Although the manufacturing route for arc-sprayed WC-W2C cermet coatings is in an advanced state, there is still a lack of knowledge concerning the performance of cored wires with tungsten carbides as filling material and their related coating properties when post-treatment processes are used such as machine hammer peening (MHP). A major objective was to characterize WC-W2C FeCMnSi coatings, deposited with different carbide grain size fractions as a filling using cored wires, with respect to their tribological behavior. Moreover, deposits derived from cored wires with a different amount of hard phases are investigated. According to this, polished MHP surfaces are compared to as-sprayed and polished samples by means of metallographic investigations. With the use of ball-on-disk and dry rubber wheel tests, dry sliding and rolling wear effects on a microscopic level are scrutinized. It has been shown that the MHP process leads to a densification of the microstructure formation. For dry sliding experiments, the MHP coatings obtain lower wear resistances, but lower coefficients of friction than the conventional coatings. In view of abrasion tests, the MHP coatings possess an improved wear resistance. Strain hardening effects at the subsurface area were revealed by the mechanical response using nanoindentation. However, the MHP process has caused a cracking of embedded carbides, which favor breakouts, leading to advanced third-body wear.

  14. Contribution to the study of atmospheric projection and under partial vacuum of tungsten carbide particles with cobalt or nickel binder. Application to fretting coatings on steel

    International Nuclear Information System (INIS)

    Vinayo, Maria-Elena

    1985-01-01

    This research thesis addresses the plasma spraying (atmospheric, under controlled atmosphere, and under reduced pressure) of tungsten carbides with a metallic binder (WC/Co, WC/Ni; W 2 C/Co). This work comprised an optimisation of the spraying process under reduced pressure, the study of the influence of the powder production process on the physicochemical and micro-structural characteristics as well as on coating fretting properties, and a correlation between spraying parameters in a controlled atmosphere (power and pressure) and coating physico-chemical and micro-structural properties. Results show a high decarburization-oxidation of tungsten carbides during atmospheric spraying, as well as an important evaporation of cobalt. Under reduced pressure, high losses of carbides are noticed. These both phenomena strongly depend on the powder production process. Fretting results highlight remarkable performance of coatings obtained by atmospheric spraying [fr

  15. Study on tribological behavior and cutting performance of CVD diamond and DLC films on Co-cemented tungsten carbide substrates

    International Nuclear Information System (INIS)

    Zhang Dongcan; Shen Bin; Sun Fanghong

    2010-01-01

    The tribological behaviors of diamond and diamond-like carbon (DLC) films play a major role on their machining and mechanical applications. In this study, diamond and diamond-like carbon (DLC) films are deposited on the cobalt cemented tungsten carbide (WC-Co) substrate respectively adopting the hot filament chemical vapor deposition (HFCVD) technique and the vacuum arc discharge with a graphite cathode, and their friction properties are evaluated on a reciprocating ball-on-plate tribometer with counterfaces of silicon nitride (Si 3 N 4 ) ceramic, cemented tungsten carbide (WC) and ball-bearing steel materials, under the ambient air without lubricating condition. Moreover, to evaluate their cutting performance, comparative turning tests are conducted using the uncoated WC-Co and as-fabricated CVD diamond and DLC coated inserts, with glass fiber reinforced plastics (GFRP) composite materials as the workpiece. The as-deposited HFCVD diamond and DLC films are characterized with energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Raman spectroscopy and 3D surface topography based on white-light interferometry. Furthermore, Rocwell C indentation tests are conducted to evaluate the adhesion of HFCVD diamond and DLC films grown onto WC-Co substrates. SEM and 3D surface topography based on white-light interferometry are also used to investigate the worn region on the surfaces of diamond and DLC films. The friction tests suggest that the obtained friction coefficient curves that of various contacts exhibit similar evolution tendency. For a given counterface, DLC films present lower stable friction coefficients than HFCVD diamond films under the same sliding conditions. The cutting tests results indicate that flank wear of the HFCVD diamond coated insert is lower than that of DLC coated insert before diamond films peeling off.

  16. Tungsten carbide cobalt nanoparticles exert hypoxia-like effects on the gene expression level in human keratinocytes.

    Science.gov (United States)

    Busch, Wibke; Kühnel, Dana; Schirmer, Kristin; Scholz, Stefan

    2010-01-27

    Tungsten carbide (WC) and tungsten carbide cobalt (WC-Co) nanoparticles are of occupational health relevance because of the increasing usage in hard metal industries. Earlier studies showed an enhanced toxic potential for WC-Co compared to WC or cobalt ions alone. Therefore, we investigated the impact of these particles, compared to cobalt ions applied as CoCl(2), on the global gene expression level in human keratinocytes (HaCaT) in vitro. WC nanoparticles exerted very little effects on the transcriptomic level after 3 hours and 3 days of exposure. In contrast, WC-Co nanoparticles caused significant transcriptional changes that were similar to those provoked by CoCl(2). However, CoCl(2) exerted even more pronounced changes in the transcription patterns. Gene set enrichment analyses revealed that the differentially expressed genes were related to hypoxia response, carbohydrate metabolism, endocrine pathways, and targets of several transcription factors. The role of the transcription factor HIF1 (hypoxia inducible factor 1) is particularly highlighted and aspects of downstream events as well as the role of other transcription factors related to cobalt toxicity are considered. This study provides extensive data useful for the understanding of nanoparticle and cobalt toxicity. It shows that WC nanoparticles caused low transcriptional responses while WC-Co nanoparticles are able to exert responses similar to that of free cobalt ions, particularly the induction of hypoxia-like effects via interactions with HIF1alpha in human keratinocytes. However, the enhanced toxicity of WC-Co particles compared to CoCl(2) could not be explained by differences in gene transcription.

  17. Tungsten carbide cobalt nanoparticles exert hypoxia-like effects on the gene expression level in human keratinocytes

    Science.gov (United States)

    2010-01-01

    Background Tungsten carbide (WC) and tungsten carbide cobalt (WC-Co) nanoparticles are of occupational health relevance because of the increasing usage in hard metal industries. Earlier studies showed an enhanced toxic potential for WC-Co compared to WC or cobalt ions alone. Therefore, we investigated the impact of these particles, compared to cobalt ions applied as CoCl2, on the global gene expression level in human keratinocytes (HaCaT) in vitro. Results WC nanoparticles exerted very little effects on the transcriptomic level after 3 hours and 3 days of exposure. In contrast, WC-Co nanoparticles caused significant transcriptional changes that were similar to those provoked by CoCl2. However, CoCl2 exerted even more pronounced changes in the transcription patterns. Gene set enrichment analyses revealed that the differentially expressed genes were related to hypoxia response, carbohydrate metabolism, endocrine pathways, and targets of several transcription factors. The role of the transcription factor HIF1 (hypoxia inducible factor 1) is particularly highlighted and aspects of downstream events as well as the role of other transcription factors related to cobalt toxicity are considered. Conclusions This study provides extensive data useful for the understanding of nanoparticle and cobalt toxicity. It shows that WC nanoparticles caused low transcriptional responses while WC-Co nanoparticles are able to exert responses similar to that of free cobalt ions, particularly the induction of hypoxia-like effects via interactions with HIF1α in human keratinocytes. However, the enhanced toxicity of WC-Co particles compared to CoCl2 could not be explained by differences in gene transcription. PMID:20105288

  18. Nitrides and carbides of molybdenum and tungsten with high specific-surface area: their synthesis, structure, and catalytic properties

    International Nuclear Information System (INIS)

    Volpe, L.

    1985-01-01

    Temperature-programmed reactions between trioxides of molybdenum or tungsten and ammonia provide a new method to synthesize dimolybdenum and ditungsten nitrides with specific surface areas to two-hundred-and-twenty and ninety-one square meters per gram, respectively. These are the highest values on record for any unsupported metallic powders. They correspond to three-four nonometer particles. The reaction of molybdenum trioxide with ammonia is topotactic in the sense that one-zero-zero planes of dimolybdenum nitride are parallel to zero-one-zero planes of molybdenum trioxide. As the trioxide transforms, it passes through an oxynitride intermediate with changing bulk structure and increasing surface area and extent of reduction. The nitride product consists of platelets, pseudomorphous with the original trioxide, which can be regarded as highly porous defect single crystals. By treating small particles of dimolybdenum or ditungsten nitride with methane-dihydrogen mixtures it is possible to replace interstitial nitrogen atoms by carbon atoms, without sintering, and thus to prepare carbides of molybdenum and tungsten with very high specific surface areas. Molybdenum nitride powders catalyze ammonia synthesis. A pronounced increase in the catalytic activity with increasing particle size confirms the structure-sensitive character of this reaction

  19. Ultraviolet-Diode Pump Solid State Laser Removal of Titanium Aluminium Nitride Coating from Tungsten Carbide Substrate

    Science.gov (United States)

    See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

    2017-09-01

    This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

  20. Cobalt exposure and lung disease in tungsten carbide production. A cross-sectional study of current workers

    International Nuclear Information System (INIS)

    Sprince, N.L.; Oliver, L.C.; Eisen, E.A.; Greene, R.E.; Chamberlin, R.I.

    1988-01-01

    A cross-sectional study of 1,039 tungsten carbide (TC) production workers was carried out. The purposes were (1) to evaluate the prevalence of interstitial lung disease (ILD) and work-related wheezing, (2) to assess correlations between cobalt exposure and pulmonary disease, (3) to compare lung disease in grinders of hard carbide versus nongrinders, and (4) to evaluate the effects of new and previous threshold limit values for cobalt of 50 and 100 micrograms/m3. We obtained medical and occupational histories, flow-volume loops, single breath carbon monoxide diffusing capacity (DLCO), and chest radiographs. Time-weighted average cobalt levels were determined at every step in the production process. Work-related wheeze occurred in 113 participants (10.9%). Profusion greater than or equal to 1/0 occurred in 26 (2.6%) and interstitial lung disease (defined as profusion greater than or equal to 1M, FVC or DLCO less than or equal to 70%, and FEV1/FVC% greater than or equal to 75) in 7 (0.7%). The relative odds of work-related wheeze was 2.1 times for present cobalt exposures exceeding 50 micrograms/m3 compared with exposures less than or equal to 50 micrograms/m3. The relative odds of profusion greater than or equal to 1/0 was 5.1 times for average lifetime cobalt exposures exceeding 100 micrograms/m3 compared with exposures less than or equal to 100 micrograms/m3 in those with latency exceeding 10 yr. ILD was found in three workers with very low average lifetime exposures (less than 8 micrograms/m3) and shorter latencies. Grinders of hard carbide had lower mean DLCO than nongrinders, even though their cobalt exposures were lower

  1. Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

    International Nuclear Information System (INIS)

    Jiang, Liming; Fu, Honggang; Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong

    2014-01-01

    Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: • The WC/PC composite with high specific surface area was prepared by a simple way. • The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. • The current density for methanol electro-oxidation is as high as 595.93 A g −1 Pt. • The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. • The performance of Pt/WC/PC is superior to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 °C, exhibited a specific surface area (S BET ) of 457.92 m 2 g −1 . After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g −1 Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance

  2. Effect of fabrication process on physical and mechanical properties of tungsten carbide - cobalt composite: A review

    Science.gov (United States)

    Mahaidin, Ahmad Aswad; Jaafar, Talib Ria; Selamat, Mohd Asri; Budin, Salina; Sulaiman, Zaim Syazwan; Hamid, Mohamad Hasnan Abdul

    2017-12-01

    WC-Co, which is also known as cemented carbide, is widely used in metal cutting industry and wear related application due to their excellent mechanical properties. Manufacturing industries are focusing on improving productivity and reducing operational cost with machining operation is considered as one of the factors. Thus, machining conditions are becoming more severe and required better cutting tool bit with improved mechanical properties to withstand high temperature operation. Numerous studies have been made over the generation for further improvement of cemented carbide properties to meet the constant increase in demand. However, the results of these studies vary due to different process parameters and manufacturing technology. This paper summarizes the studies to improve the properties of WC-Co composite using different consolidation (powder size, mixing method, formulation, etc) and sintering parameters (temperature, time, atmosphere, etc).

  3. Exploration on Wire Discharge Machining Added Powder for Metal-Based Diamond Grinding Wheel on Wire EDM Dressing and Truing of Grinding Tungsten Carbide Material

    Science.gov (United States)

    Chow, H. M.; Yang, L. D.; Lin, Y. C.; Lin, C. L.

    2017-12-01

    In this paper, the effects of material removal rate and abrasive grain protrusion on the metal-based diamond grinding wheel were studied to find the optimal parameters for adding powder and wire discharge. In addition, this kind of electric discharge method to add powder on the metal-based diamond grinding wheel on line after dressing and truing will be applied on tungsten carbide to study the grinding material removal rate, grinding wheel wear, surface roughness, and surface micro-hardness.

  4. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

    OpenAIRE

    Armstead, Andrea L.; Arena, Christopher B.; Li, Bingyun

    2014-01-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity usin...

  5. Nanogravimetric studies of tungsten oxide thin films obtained by the polymeric precursor method

    International Nuclear Information System (INIS)

    Fernandes, V.C.; Santos, M.C.; Bulhoes, L.O.S.

    2007-01-01

    In this work, the intercalation/de-intercalation process of Li + ions in the tungsten oxide matrix was investigated. The reaction mechanism involved was also investigated. The WO 3 films, prepared by the polymeric precursor method, were deposited on a Pt covered quartz crystal using the dip-coating technique. The electrolyte was 0.1 mol L -1 LiClO 4 in acetonitrile. The morphology and structure of the deposit was accomplished by scanning electron microscopy and X-ray diffraction, respectively. In the electrochemical quartz crystal nanobalance results, it was observed that the mass transport as well as the kinetic processes involved are facilitated in the films cycled at lower potential sweep-rates. The mass variation data as a function of the charge variations in the anodic and cathodic regions indicate the participation of solvent molecules (acetonitrile) during the Li + ion intercalation/de-intercalation process. This was confirmed by the development of a model of the species flux as a function of the potential

  6. Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten-hafnium carbide bulk composite

    International Nuclear Information System (INIS)

    Rea, K.E.; Viswanathan, V.; Kruize, A.; Hosson, J.Th.M. de; O'Dell, S.; McKechnie, T.; Rajagopalan, S.; Vaidyanathan, R.; Seal, S.

    2008-01-01

    Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured thermo-mechanical components. Spray drying of powder feedstock appears to have a significant effect on the improved mechanical properties of the bulk nanocomposite. The reported elastic modulus of the nanocomposite nearly doubles due to the presence of HfC nano particulates in the W matrix. High resolution transmission electron microscopy (HRTEM) revealed the retention of nanostructures at the select process conditions and is correlated with the enhanced mechanical properties of the nanocomposite

  7. Preparation of porous silicon carbide from molecular precursors; Preparation de carbure de silicium poreux a partir de precurseurs moleculaires

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, J

    2008-02-15

    The preparation of Porous Silicon Carbide (SiC) from molecular precursors is described in this work. Firstly, poly-silane and poly-carbo-silane were synthesised from targeted molecular precursors TSCH and TCDSCB. The pyrolysis of these polymers under inert conditions gave the SiC. Secondly, the preparation of functional poly-silane was explored. It was shown that Cp{sub 2}Ti(OPh){sub 2} was a suitable catalyst for the preparation of such functional poly-silane in a one-pot process. Finally, macroporous SiC were prepared from hard templating method by using a commercial silica. (author)

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

    Science.gov (United States)

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

    2015-10-14

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

  9. Experimental investigations of the frictional and wear behavior of tungsten carbide cermet ball bearings under axial load in liquid sodium

    International Nuclear Information System (INIS)

    Kleefeldt, K.W.

    1976-01-01

    The paper describes part of the R and D work performed on ball bearings operated in a liquid sodium environment and tested under conditions which are felt to be representative for high precision mechanisms in LMFBR's. After a short introduction, mainly dealing with the experimental results of other authors, a description will be given of the test facility, the test procedure, the ball bearings and the basis for the selection of the materials. The paper covers the experimental phase, which has been carried out in two steps. In the first phase material screening tests demonstrated the tungsten-carbide-cobalt cermet to be superior to the other materials tested with respect to friction and wear. This material, therefore, was selected for a more detailed parameter test programme during phase 2. Up to now a series of tests have been performed with bearing load and speed as parameters, indicating that fatigue is the life limiting factor. It shows that a life-load relationship, similar to that known for conventional ball bearing technology, also seems appropriate for the test conditions and environment investigated here

  10. Genotoxicity of tungsten carbide-cobalt (WC-Co) nanoparticles in vitro: mechanisms-of-action studies.

    Science.gov (United States)

    Moche, Hélène; Chevalier, Dany; Vezin, Hervé; Claude, Nancy; Lorge, Elisabeth; Nesslany, Fabrice

    2015-02-01

    We showed previously that tungsten carbide-cobalt (WC-Co) nanoparticles (NP) can be used as a nanoparticulate positive control in some in vitro mammalian genotoxicity assays. Here, we investigate the mechanisms of action involved in WC-Co NP genotoxicity in L5178Y mouse lymphoma cells and primary human lymphocytes, in vitro. Data from the micronucleus assay coupled with centromere staining and from the chromosome-aberration assay show the involvement of both clastogenic and aneugenic events. Experiments with the formamidopyrimidine DNA glycosylase (FPG)-modified comet assay showed a slight (non-significant) increase in FPG-sensitive sites in the L5178Y mouse lymphoma cells but not in the human lymphocytes. Electron paramagnetic resonance spin-trapping results showed the presence of hydroxyl radicals (•OH) in WC-Co NP suspensions, with or without cells, but with time-dependent production in the presence of cells. However, a significant difference in •OH production was observed between human lymphocytes from two different donors. Using H2O2, we showed that WC-Co NP can participate in Fenton-like reactions. Thus, •OH might be produced either via intrinsic generation by WC-Co NP or through a Fenton-like reaction in the presence of cells. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Chemical vapor deposition of highly adherent diamond coatings onto co-cemented tungsten carbides irradiated by high power diode laser.

    Science.gov (United States)

    Barletta, M; Rubino, G; Valle, R; Polini, R

    2012-02-01

    The present investigation deals with the definition of a new eco-friendly alternative to pretreat Co-cemented tungsten carbide (WC-Co) substrates before diamond deposition by hot filament chemical vapor deposition (HFCVD). In particular, WC-5.8 wt %Co substrates were submitted to a thermal treatment by a continuous wave-high power diode laser to reduce surface Co concentration and promote the reconstruction of the WC grains. Laser pretreatments were performed both in N(2) and Ar atmosphere to prevent substrate oxidation. Diamond coatings were deposited onto the laser pretreated substrates by HFCVD. For comparative purpose, diamond coatings were also deposited on WC-5.8 wt %Co substrates chemically etched by the well-known two-step pretreatment employing Murakami's reagent and Caro's acid. Surface morphology, microstructure, and chemical composition of the WC-5.8 wt %Co substrates after the different pretreatments and the deposition of diamond coatings were assessed by surface profiler, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. Wear performance of the diamond coatings was checked by dry sliding linear reciprocating tribological tests. The worn volume of the diamond coatings deposited on the laser pretreated substrates was always found lower than the one measured on the chemically etched substrates, with the N(2) atmosphere being particularly promising.

  12. Tungsten Carbide-Cobalt Nanoparticles Induce Reactive Oxygen Species, AKT, ERK, AP-1, NF-κB, VEGF, and Angiogenesis.

    Science.gov (United States)

    Liu, Ling-Zhi; Ding, Min; Zheng, Jenny Z; Zhu, Yingxue; Fenderson, Bruce A; Li, Bingyun; Yu, Jing J; Jiang, Bing-Hua

    2015-07-01

    Powder mixtures of tungsten carbide and metallic cobalt (WC-Co) are widely used in various products. Nanoparticles are engineered structures with at least one dimension of 100 nm or smaller. WC-Co is known to be associated with lung injury and diseases. Angiogenesis is a key process during vasculature, carcinogenesis, recovery of injury, and inflammatory diseases. However, the cellular effects of WC-Co nanoparticles on angiogenesis remain to be elucidated. In this study, we investigated angiogenic response and relative mechanisms after exposure to WC-Co nanoparticles. Our results showed that WC-Co nanoparticles at 5 μg/cm(2) induced ROS production which activated AKT and ERK1/2 signaling pathways in lung epithelial cells by reactive oxygen species (ROS) staining and immunoblotting; WC-Co treatment also increased transcriptional activation of AP-1, NF-κB, and VEGF by reporter assay. Further studies demonstrated that ROS are upstream molecules of AKT and ERK signaling pathways; the activation of AP-1, NF-κB, and VEGF was through ROS generation, AKT and ERK1/2 activation. In addition, WC-Co nanoparticles affected the cells to induce angiogenesis by chicken chorioallantoic membrane (CAM) assay. These results illustrate that exposure to WC-Co nanoparticles induces angiogenic response by activating ROS, AKT, and ERK1/2 signaling pathways and the downstream molecules and elucidate the potential molecular mechanisms during this process. This information may be useful for preventing potential damage from nanoparticle exposure in the future.

  13. Study of the mechanism responsible for the elective toxicity of tungsten carbide-cobalt powder toward macrophages.

    Science.gov (United States)

    Lison, D; Lauwerys, R

    1992-04-01

    We have previously demonstrated that tungsten carbide-cobalt powder (WC-Co) is more toxic toward murine macrophages in vitro than pure cobalt metal particles and that the cellular uptake of cobalt is enhanced when the metal is present in the form of WC-Co mixture. The present study was undertaken to assess the possible mechanism(s) of this interaction. We found that solubilization of cobalt in the extracellular milieu was increased in the presence of WC. This phenomenon, however, is not the critical factor explaining the greater toxicity of the WC-Co mixture since increasing the amount of solubilized cobalt in the extracellular medium in the absence of WC did not result in increased toxicity. Moreover, the amount of cobalt solubilized from a toxic dose of WC-Co was insufficient to affect by itself macrophage viability. A toxic effect was only observed when the WC-Co mixture came directly in contact with the cells. The elective toxicity of WC-Co can also not be explained by stimulation of phagocytosis of cobalt metal particles due to the simultaneous presence of other particles (WC) in the extracellular fluid since stimulation of phagocytosis by latex beads or zymosan particles did not amplify the toxicity of cobalt metal particles. These results indicate that the toxicity of the WC-Co mixture does not simply result from an enhanced bioavailability of its cobalt component. This suggests that hard metal dust behaves as a specific toxic entity.

  14. Thermally induced defects in a polycrystalline diamond layer on a tungsten carbide substrate

    Energy Technology Data Exchange (ETDEWEB)

    Masina, B.N. [Department of Physics and Engineering, University of Zululand, Private Bag X1001, Kwadlangezwa 3886 (South Africa); CSIR National Laser Centre, P.O. Box 395, Pretoria 0001 (South Africa); Forbes, A., E-mail: aforbes1@csir.co.z [CSIR National Laser Centre, P.O. Box 395, Pretoria 0001 (South Africa); School of Physics, University of Kwazulu-Natal, Private Bag X54001, Durban 4000 (South Africa); Ndwandwe, O.M. [Department of Physics and Engineering, University of Zululand, Private Bag X1001, Kwadlangezwa 3886 (South Africa); Hearne, G. [School of Physics, University of the Witwatersrand, Private bag X3, P.O. Wits, Johannesburg 2050 (South Africa); Mwakikunga, B.W. [School of Physics, University of the Witwatersrand, Private bag X3, P.O. Wits, Johannesburg 2050 (South Africa); CSIR National Centre for Nano-Structured Materials, P.O. Box 395, Pretoria 0001 (South Africa); Department of Physics and Biochemical Sciences, University of Malawi-The Polytechnic, Private Bag 303, Chichiri, Blantyre 0003 (Malawi); Katumba, G. [CSIR National Laser Centre, P.O. Box 395, Pretoria 0001 (South Africa)

    2009-12-01

    In this study we make use of laser heating of HTHP industrial diamond, to study temperature induced changes to the diamond structure, both chemically and mechanically, in the absence of mechanical forces. This has relevance to the efficacy of diamond as a hard material in such applications as rock drilling and material processing. We report on the induced defects when the diamond is irradiated with high power CO{sub 2} and Nd:YAG lasers respectively, and show that the thermal induced stresses in the diamond are sufficient to radically alter its physical properties, resulting in critical fracture. Raman spectroscopy, X-ray diffraction and scanning electron microscopy indicate that the heating does not result in graphitisation of the diamond, but rather diffusion from the non-diamond base results in cobalt and tungsten oxides forming on the diamond surface. This has a deleterious effect on the diamond performance.

  15. Hydrothermal development and characterization of the wear-resistant boron carbide from Pandanus: a natural carbon precursor

    Science.gov (United States)

    Saritha Devi, H. V.; Swapna, M. S.; Ambadas, G.; Sankararaman, S.

    2018-04-01

    Boron carbide (B4C) is a prominent semiconducting material that finds applications in the field of science and technology. The excellent physical, thermal and electronic properties make it suitable as ceramic armor, wear-resistant, lens polisher and neutron absorber in the nuclear industry. The existing methods of synthesis of boron carbide involve the use of toxic chemicals that adversely affect the environment. In the present work, we report for the first time the use of the hydrothermal method, for converting the cellulose from Pandanus leaves as the carbon precursor for the synthesis of B4C. The carbon precursor is changed into porous functionalized carbon by treating with sodium borohydride (NaBH4), followed by treating with boric acid to obtain B4C. The samples are characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared, Raman, photoluminescent and Ultraviolet-Visible absorption spectroscopy. The formation of B4C from natural carbon source— Pandanus presents an eco-friendly, economic and non-toxic approach for the synthesis of refractory carbides.

  16. High temperature strengthening mechanism of hafnium carbide in a tungsten-rhenium matrix

    International Nuclear Information System (INIS)

    Luo, A.; Shin, K.S.; Jacobson, D.L.

    1991-01-01

    The interrelationship between the testing temperature and HfC strength increment of an arc-melted W-3.6Re-0.4HfC was determined from 1950 K to 2980 K in a vacuum of better than 1.3x10 -5 Pa (10 -7 torr). The present research was focused on the characteristic temperature at which the rapid coarsening of HfC particles occurred and the effect of the second-phase particle size on the high temperature strength properties of this material. It was found that the HfC particle strengthening was effective in a W-Re matrix up to a characteristic temperature of 2450 K in the short-term tensile test. Carbon was found to be the rate-limiting solute in the HfC particle growth. The strength of HfC strengthened alloy at temperature above 0.5 T m is proportional to the square root of particle volume fraction. The yield strengths of W-3.6Re-0.26HfC calculated based on the particle statistical distribution had good agreement with the experimental values from 1950 K to 2980 K. Besides, an addition of 0.26 percent HfC in tungsten resulted in about 28 percent increase in the activation energy of plastic deformation at high temperatures

  17. Comparison of nickel, cobalt, palladium, and tungsten Schottky contacts on n-4H-silicon carbide

    Science.gov (United States)

    Gora, V. E.; Chawanda, A.; Nyamhere, C.; Auret, F. D.; Mazunga, F.; Jaure, T.; Chibaya, B.; Omotoso, E.; Danga, H. T.; Tunhuma, S. M.

    2018-04-01

    We have investigated the current-voltage (I-V) characteristics of nickel (Ni), cobalt (Co), tungsten (W) and palladium (Pd) Schottky contacts on n-type 4H-SiC in the 300-800 K temperature range. Results extracted from I-V measurements of Schottky barrier diodes showed that barrier height (ФBo) and ideality factor (n) were strongly dependent on temperature. Schottky barrier heights for contacts of all the metals showed an increase with temperature between 300 K and 800 K. This was attributed to barrier inhomogeneities at the interface between the metal and the semiconductor, which resulted in a distribution of barrier heights at the interface. Ideality factors of Ni, Co and Pd decreased from 1.6 to 1.0 and for W the ideality factor decreased from 1.1 to 1.0 when the temperature was increased from 300 K to 800 K respectively. The device parameters were compared to assess advantages and disadvantages of the metals for envisaged applications.

  18. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel-tungsten composite coatings

    Science.gov (United States)

    Singh, Swarnima; Sribalaji, M.; Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G.; Singh, Raghuvir; Keshri, Anup Kumar

    2016-02-01

    Silicon carbide (SiC) reinforced nickel-tungsten (Ni-W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni-W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni-W-5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni-W-5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, Ecorr) compared to Ni-W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni-W-5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2.

  19. Factors determining the activity of catalysts of different chemical types in the oxidation of hydrogen. III. Oxidation and isotopic exchange of hydrogen on tungsten carbide

    International Nuclear Information System (INIS)

    Il'chenko, N.I.; Dolgikh, L.Y.; Golodets, G.I.

    1985-01-01

    It is explained how the oxidation of hydrogen on tungsten carbide at 653 K comes about via two basic mechanisms. In an excess of H 2 , the predominant mechanism involves the reaction of O 2 with dissociated, adsorbed hydrogen while at low concentrations of hydrogen it is the reaction of H 2 with adsorbed oxygen that makes the basic contribution to the observed rate. A model is proposed which also describes satisfactorily the rate of the simultaneously occurring isotopic exchange of hydrogen with deuterium

  20. Comparative evaluation of the in vitro micronucleus test and the alkaline single cell gel electrophoresis assay for the detection of DNA damaging agents: genotoxic effects of cobalt powder, tungsten carbide and cobalt-tungsten carbide.

    Science.gov (United States)

    Van Goethem, F; Lison, D; Kirsch-Volders, M

    1997-08-01

    Although it is well known that micronuclei may arise from either DNA breakage leading to acentric chromosome fragments or from chromosome/chromatid lagging in anaphase, the ratio between the amount of DNA breakage induced and the frequency of micronuclei expressed in the following interphase is unclear. With the development of the alkaline single cell gel electrophoresis assay, which measures single strand and/or double strand breaks in a cell by cell approach, it is new possible to address this question at the cellular level. We therefore compared the genotoxic potential of pure cobalt powder (Co) and a cobalt-containing alloy, cobalt-tungsten carbide (WC-Co), involved in specific lung disorders, in parallel with the alkaline single cell gel electrophoresis (SCGE) assay (comet assay) and the cytokinesis-blocked micronucleus (MN) test, both carried out in vitro on isolated human leukocytes. The comet assay indicated that the WC-Co mixture produced a higher level of DNA damage than Co alone; WC alone was not able to induce a dose-dependent DNA breakage effect as was seen for Co and WC-Co. Results from the MN test confirmed these observations. It was clear that the clastogenic property of Co-containing dust is significantly enhanced when the Co metal is mixed with WC and suggested that their physicochemical characteristics may act as one of the important parameters responsible for the increased incidence of lung cancers observed in the population of hard metal workers. In agreement with data obtained in the same laboratory on liposoluble chemicals (PCBs and chlorinated aliphatic hydrocarbons) and from the literature, the results indicate that both the comet assay and the micronucleus test were able to detect differences in the genotoxic potential of the compounds studied. Although the micronucleus test seemed to be less sensitive to assess a synergistic DNA damaging potential of the mixture involved, it detects chromosomal aberrations (chromosome/genome mutations

  1. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel–tungsten composite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Swarnima; Sribalaji, M. [Materials Science and Engineering, Indian Institute of Technology Patna, Navin Government Polytechnic Campus, Patliputra Colony, Patna, Bihar 800013 (India); Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G. [International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI) Hyderabad, Balapur P.O., Hyderabad, Andhra Pradesh 500005 (India); Singh, Raghuvir [CSIR-National Metallurgical Laboratory, Jamshedpur, Jharkhand 831007 (India); Keshri, Anup Kumar, E-mail: anup@iitp.ac.in [Materials Science and Engineering, Indian Institute of Technology Patna, Navin Government Polytechnic Campus, Patliputra Colony, Patna, Bihar 800013 (India)

    2016-02-28

    Graphical abstract: - Highlights: • Pulse electrodeposited Ni–W–SiC coating has been synthesized successfully. • Dome to turtle like structure has been observed on addition of SiC in Ni–W coating. • Formation of W(Ni) solid solution was observed on adding 5 g/l SiC in Ni–W coating. • Corrosion resistance improved for Ni–W–5 g/l SiC coating. • Texture formation and continuous barrier layer enhanced the corrosion resistance. - Abstract: Silicon carbide (SiC) reinforced nickel–tungsten (Ni–W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni–W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni–W–5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni–W–5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, E{sub corr}) compared to Ni–W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni–W–5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO{sub 4} and SiO{sub 2}.

  2. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel–tungsten composite coatings

    International Nuclear Information System (INIS)

    Singh, Swarnima; Sribalaji, M.; Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G.; Singh, Raghuvir; Keshri, Anup Kumar

    2016-01-01

    Graphical abstract: - Highlights: • Pulse electrodeposited Ni–W–SiC coating has been synthesized successfully. • Dome to turtle like structure has been observed on addition of SiC in Ni–W coating. • Formation of W(Ni) solid solution was observed on adding 5 g/l SiC in Ni–W coating. • Corrosion resistance improved for Ni–W–5 g/l SiC coating. • Texture formation and continuous barrier layer enhanced the corrosion resistance. - Abstract: Silicon carbide (SiC) reinforced nickel–tungsten (Ni–W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni–W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni–W–5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni–W–5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, E corr ) compared to Ni–W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni–W–5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO 4 and SiO 2 .

  3. Ethylene glycol assisted low-temperature synthesis of boron carbide powder from borate citrate precursors

    Directory of Open Access Journals (Sweden)

    Rafi-ud-din

    2014-09-01

    Full Text Available B4C powders were synthesized by carbothermal reduction of ethylene glycol (EG added borate citrate precursors, and effects of EG additions (0–50 mol% based on citric acid on the morphologies and yields of synthesized B4C powders were investigated. The conditions most suitable for the preparation of precursor were optimized and optimum temperature for precursor formation was 650 °C. EG additions facilitated low-temperature synthesis of B4C at 1350 °C, which was around 100–300 °C lower temperature compared to that without EG additions. The lowering of synthesis temperature was ascribed to the enlargement of interfacial area caused by superior homogeneity and dispersibility of precursors enabling the diffusion of reacting species facile. The 20% EG addition was optimal with free residual carbon lowered to 4%. For smaller EG additions, the polyhedral and rod-like particles of synthesized product co-existed. With higher EG additions, the morphology of synthesized product was transformed into needle and blade-like structure.

  4. Plasma Spraying and Characterization of Tungsten Carbide-Cobalt Coatings by the Water-Stabilized System WSP

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Kašparová, M.; Bellin, J.; Le Guen, E.; Zahálka, F.

    2009-01-01

    Roč. 2009, - (2009), s. 1-11 ISSN 1687-8434 R&D Projects: GA AV ČR 1QS200430560 Institutional research plan: CEZ:AV0Z20430508 Keywords : Tungsten karbide – cobalt, cermet * wear resistance * abrasion * plasma spraying Subject RIV: JG - Metallurgy http://www.hindawi.com/journals/amse/2009/254848.html

  5. Thermodynamic approach to the synthesis of silicon carbide using tetramethylsilane as the precursor at high temperature

    Science.gov (United States)

    Jeong, Seong-Min; Kim, Kyung-Hun; Yoon, Young Joon; Lee, Myung-Hyun; Seo, Won-Seon

    2012-10-01

    Tetramethylsilane (TMS) is commonly used as a precursor in the production of SiC(β) films at relatively low temperatures. However, because TMS contains much more C than Si, it is difficult to produce solid phase SiC at high temperatures. In an attempt to develop a more efficient TMS-based SiC(α) process, computational thermodynamic simulations were performed under various temperatures, working pressures and TMS/H2 ratios. The findings indicate that each solid phase has a different dependency on the H2 concentration. Consequently, a high H2 concentration results in the formation of a single, solid phase SiC region at high temperatures. Finally, TMS appears to be useful as a precursor for the high temperature production of SiC(α).

  6. Alkynyl substituted carboranes as precursors to boron carbide thin films, fibers and composites

    International Nuclear Information System (INIS)

    Johnson, S.E.; Yang, X.; Hawthorne, M.F.; Mackenzie, J.D.; Thorne, K.J.; Zheng, H.

    1992-01-01

    In this paper the use of alkynyl substituted derivatives of o-carborane as precursors to boron containing ceramics is described. These compounds undergo a thermally or photochemically induced polymerization to afford cross linked polyakynyl-o-carborane derivatives. The increase in molecular weight should allow for increased Tg's and the retention of modelled polymer preforms. In this report, these modification reactions are described. In addition, the retention of molded polymer preforms were analyzed after UV exposure and inert atmosphere pyrolysis

  7. Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells

    International Nuclear Information System (INIS)

    Ding, M.; Kisin, E.R.; Zhao, J.; Bowman, L.; Lu, Y.; Jiang, B.; Leonard, S.; Vallyathan, V.; Castranova, V.; Murray, A.R.; Fadeel, B.; Shvedova, A.A.

    2009-01-01

    Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-κB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P + ). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P + cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-κB more efficiently in JB6 +/+ cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6 +/+ cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

  8. Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells.

    Science.gov (United States)

    Ding, M; Kisin, E R; Zhao, J; Bowman, L; Lu, Y; Jiang, B; Leonard, S; Vallyathan, V; Castranova, V; Murray, A R; Fadeel, B; Shvedova, A A

    2009-12-15

    Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-kappaB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P(+)). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P(+) cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-kappaB more efficiently in JB6(+/+) cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6(+/+) cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

  9. Surface modification of the hard metal tungsten carbide-cobalt by boron ion implantation; Oberflaechenmodifikation des Hartmetalls Wolframkarbid-Kobalt durch Bor-Ionenimplantation

    Energy Technology Data Exchange (ETDEWEB)

    Mrotchek, I.

    2007-09-07

    In the present thesis ion beam implantation of boron is studied as method for the increasement of the hardness and for the improvement of the operational characteristics of cutting tools on the tungsten carbide-cobalt base. For the boron implantation with 40 keV energy and {approx}5.10{sup 17} ions/cm{sup 2} fluence following topics were shown: The incoerporation of boron leads to a deformation and remaining strain of the WC lattice, which possesses different stregth in the different directions of the elementary cell. The maximum of the deformation is reached at an implantation temperature of 450 C. The segregation of the new phases CoWB and Co{sub 3}W was detected at 900 C implantation temperature. At lower temperatures now new phases were found. The tribological characteristics of WC-Co are improved. Hereby the maxiaml effect was measured for implantation temperatures from 450 C to 700 C: Improvement of the microhardness by the factor 2..2.5, improvement of the wear resistance by the factor 4. The tribological effects extend to larger depths than the penetration depth of the boron implantation profile. The detected property improvements of the hard metal H3 show the possibility of a practical application of boron ion implantation in industry. The effects essential for a wer decreasement are a hardening of the carbide phase by deformation of the lattice, a hardening of the cobalt binding material and the phase boundaries because of the formation of a solid solution of the implanted boron atoms in Co and by this a blocking of the dislocation movement and the rupture spreading under load.

  10. Tungsten-coated nano-boron carbide as a non-noble metal bifunctional electrocatalyst for oxygen evolution and hydrogen evolution reactions in alkaline media.

    Science.gov (United States)

    Zhang, Yan; Wang, Yanhui; Han, Chan; Jia, Shaopei; Zhou, Shuyu; Zang, Jianbing

    2017-12-14

    Herein, tungsten-coated nano-boron carbide (W-WB 4 -WC x /B 4 C) particles were prepared by heating a mixture of B 4 C and W powder using a spark plasma coating (SPC) method. During the discharge treatment process, metal W in the mixture is activated and reacts with B 4 C to form WC x , WB 4 , and graphite nanoribbons. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance of W-WB 4 -WC x /B 4 C is tested in an alkaline solution, and the results show that the W-WB 4 -WC x /B 4 C composite electrocatalyst exhibits a low overpotential of 0.36 V at 10 mA cm -2 for the OER, a small overpotential of -0.19 V (j = 10 mA cm -2 ) for the HER, as well as good stability. The significantly enhanced electrocatalytic performance of the W-WB 4 -WC x /B 4 C composites is attributed to their unique structure, in which WC x and WB 4 not only improve the catalytic activity for the OER and HER, but also effectively anchor the W coating on the substrate.

  11. Effects of Increasing Feed Rate on Tool Deterioration and Cutting Force during End Milling of 718Plus Superalloy Using Cemented Tungsten Carbide Tool

    Directory of Open Access Journals (Sweden)

    Nurul H. Razak

    2017-10-01

    Full Text Available Understanding how feed rate (ft affects tool deterioration during milling of Ni-based superalloys is practically important, but this understanding is currently insufficient. In the present study using a 718Plus Ni-based alloy and cemented tungsten carbide tool inserts, milling experiments were conducted with ft = 0.10 mm/tooth under either dry or wet (with coolant conditions. The results are compared to those based on using ft = 0.05 mm/tooth from previous studies. The milling force (F was monitored, the cutting tool edge was examined and the flank wear (VBmax was measured. As would be expected, an increase in ft increased F. It was found that F correlated well with VBmax for the high ft (0.1 mm/tooth experiments, as opposed to the previously observed poor F-VBmax relationship for the lower ft (0.05 mm/tooth value. This is explained, supported by detailed failure analysis of the cutting tool edges, by the deterioration mode to be dominantly edge chipping with a low occurrence of fracturing along the flank face when the high ft was used. This dominancy of the deterioration mode means that the tool edge and workpiece contact was consistent and thus resulted in a clear F-VBmax relationship. A clear F-VBmax relationship should then mean monitoring VBmax through monitoring F is possible.

  12. Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kartal, Muhammet, E-mail: kartal@sakarya.edu.tr [Sakarya University, Engineering Faculty, Metallurgical & Materials Engineering Department, Esentepe Campus, 54187 Sakarya (Turkey); Uysal, Mehmet [Sakarya University, Engineering Faculty, Metallurgical & Materials Engineering Department, Esentepe Campus, 54187 Sakarya (Turkey); Gul, Harun [Duzce University, Gumusova Vocational School, 81850 Duzce (Turkey); Alp, Ahmet; Akbulut, Hatem [Sakarya University, Engineering Faculty, Metallurgical & Materials Engineering Department, Esentepe Campus, 54187 Sakarya (Turkey)

    2015-11-01

    Highlights: • Effect of surfactant concentration on the co-deposited WC was investigated. • In the Ni matrix significantly high hardness was achieved by WC co-deposition. • Optimum surfactant resulted in obtaining superior wear resistance in the Ni. • Friction coefficient was decreased by WC co-deposition in the Ni matrix. - Abstract: A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55–65%).

  13. Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

    Science.gov (United States)

    Kartal, Muhammet; Uysal, Mehmet; Gul, Harun; Alp, Ahmet; Akbulut, Hatem

    2015-11-01

    A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55-65%).

  14. Tungsten carbide-cobalt particles activate Nrf2 and its downstream target genes in JB6 cells possibly by ROS generation.

    Science.gov (United States)

    Zhang, Xing-Dong; Zhao, Jinshun; Bowman, Linda; Shi, Xianglin; Castranova, Vincent; Ding, Min

    2010-01-01

    Hard metal consisting of a mixture of tungsten carbide (WC) and metallic cobalt (Co) was evaluated as a possible carcinogen in humans by IARC in 2003. Studies have suggested that nuclear factor erythroid 2-related factor 2 (Nrf2) constitutes one of the chemical-sensing and transcription systems that play an essential role(s) in chemical toxicity, carcinogenesis, and pathological processes. To elucidate the mechanisms of health hazards of WC-Co, effects of nano-WC-Co particles on Nrf2 signaling pathway were investigated in the present study in a JB6 cell line. After a 5 h treatment with nano-WC-Co particles, Nrf2 was released from Keap1 in the cytoplasm and translocated into the nucleus. Enzymatic activities of Nrf2 target genes, including glutathione S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), increased at 24 and 48 h after the treatment. Studies using reactive oxygen species (ROS) sensitive dyes indicated that ROS were produced in nano-WC-Co particle-treated cells. Pretreatment of the cells with catalase, but not sodium formate, resulted in a significant inhibitory effect on nano-WC-Co particle-induced Nrf2 target gene activation. These findings suggest that activation of Nrf2 and its downstream genes may be initiated by ROS generation, and ROS may act as a major contributor in nano-WC-Co particle-induced adverse health effects.

  15. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro.

    Science.gov (United States)

    Armstead, Andrea L; Arena, Christopher B; Li, Bingyun

    2014-07-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause "hard metal lung disease" but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

    Science.gov (United States)

    Armstead, Andrea L.; Arena, Christopher B.; Li, Bingyun

    2014-01-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggests that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. PMID:24746988

  17. Hard coating of ultrananocrystalline diamond/nonhydrogenated amorphous carbon composite films on cemented tungsten carbide by coaxial arc plasma deposition

    Science.gov (United States)

    Naragino, Hiroshi; Egiza, Mohamed; Tominaga, Aki; Murasawa, Koki; Gonda, Hidenobu; Sakurai, Masatoshi; Yoshitake, Tsuyoshi

    2016-08-01

    Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were deposited on cemented carbide containing Co by coaxial arc plasma deposition. With decreasing substrate temperature, the hardness was enhanced accompanied by an enhancement in the sp3/(sp2 + sp3). Energy-dispersive X-ray and secondary ion mass spectrometry spectroscopic measurements exhibited that the diffusion of Co atoms from the substrates into the films hardly occurs. The film deposited at room temperature exhibited the maximum hardness of 51.3 GPa and Young's modulus of 520.2 GPa, which evidently indicates that graphitization induced by Co in the WC substrates, and thermal deformation from sp3 to sp2 bonding are suppressed. The hard UNCD/a-C films can be deposited at a thickness of approximately 3 μm, which is an order larger than that of comparably hard a-C films. The internal compressive stress of the 51.3-GPa film is 4.5 GPa, which is evidently smaller than that of comparably hard a-C films. This is a reason for the thick deposition. The presence of a large number of grain boundaries in the film, which is a structural specific to UNCD/a-C films, might play a role in releasing the internal stress of the films.

  18. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

    International Nuclear Information System (INIS)

    Armstead, Andrea L.; Arena, Christopher B.; Li, Bingyun

    2014-01-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. - Highlights: • Hard metal (WC-Co) particle toxicity was established in lung epithelial cells. • Nano-WC-Co particles caused greater toxicity than micro-WC-Co particles. • Nano- and micro-WC-Co particles were capable of inducing cellular apoptosis. • Nano-WC-Co particles were internalized by lung epithelial cells. • WC-Co particle internalization was mediated by actin dynamics

  19. Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Armstead, Andrea L. [Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Pharmaceutical and Pharmacological Sciences Graduate Program, School of Pharmacy, West Virginia University, Morgantown, WV 26506 (United States); Arena, Christopher B. [Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); E.J. Van Liere Research Program, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Li, Bingyun, E-mail: bili@hsc.wvu.edu [Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Pharmaceutical and Pharmacological Sciences Graduate Program, School of Pharmacy, West Virginia University, Morgantown, WV 26506 (United States); E.J. Van Liere Research Program, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Mary Babb Randolph Cancer Center, Morgantown, WV 26506 (United States)

    2014-07-01

    Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. - Highlights: • Hard metal (WC-Co) particle toxicity was established in lung epithelial cells. • Nano-WC-Co particles caused greater toxicity than micro-WC-Co particles. • Nano- and micro-WC-Co particles were capable of inducing cellular apoptosis. • Nano-WC-Co particles were internalized by lung epithelial cells. • WC-Co particle internalization was mediated by actin dynamics.

  20. Induction of miR-21-PDCD4 signaling by tungsten carbide-cobalt nanoparticles in JB6 cells involves ROS-mediated MAPK pathways.

    Science.gov (United States)

    Hou, Lichao; Bowman, Linda; Meighan, Terence G; Shi, Xianglin; Ding, Min

    2013-01-01

    Tungsten carbide-cobalt (WC-Co) nanoparticle composites have wide applications because of their hardness and toughness. WC-Co was classified as "probably carcinogenic" to humans by the International Agency for Research on Cancer (IARC) in 2003. It is believed that the toxicity and carcinogenesis of WC-Co is associated with particle size. Recent studies demonstrated that the tumor suppressor gene programmed cell death 4 (PDCD4) and its upstream regulator miR-21 have been considered as oncogenes for novel cancer prevention or anticancer therapies. The present study examined the effects of WC-Co nanoparticles on miR-21-PDCD4 signaling in a mouse epidermal cell line (JB6 P+). The results showed that (i) exposure of JB6 cells to WC-Co stimulated a increase of miR-21 generation; (ii) WC-Co also caused inhibition of PDCD4, a tumor suppressor protein and downstream target of miR-21, expression in JB6 cells; (iii) inhibition of ERKs with ERK inhibitor U0126 significantly reversed WC-Cominus;induced PDCD4 inhibition, but inhibition of p38 with p38 inhibitor SB203580 did not; and (iv) ROS scavengers, N-acetyl-L-cysteine and catalase, blocked the inhibitory effect of WC-Co on PDCD4 expression, while superoxide dismutase promoted the inhibitory effect. These findings demonstrate that WC-Co nanoparticles induce miR-21 generation, but inhibit PDCD4 production, which may be mediated through ROS, especially endogenous H2O2, and ERK pathways. Unraveling the complex mechanisms associated with these events may provide insights into the initiation and progression of WC-Co-induced carcinogenesis.

  1. Agglomeration of tungsten carbide nanoparticles in exposure medium does not prevent uptake and toxicity toward a rainbow trout gill cell line.

    Science.gov (United States)

    Kühnel, Dana; Busch, Wibke; Meissner, Tobias; Springer, Armin; Potthoff, Annegret; Richter, Volkmar; Gelinsky, Michael; Scholz, Stefan; Schirmer, Kristin

    2009-06-28

    Due to their increased production and use, engineered nanoparticles are expected to be released into the aquatic environment where particles may agglomerate. The aim of this study was to explore the role of agglomeration of nanoparticles in the uptake and expression of toxicity in the rainbow trout (Oncorhynchus mykiss) gill cell line, RTgill-W1. This cell line was chosen as model because it is known to be amenable to culture in complete as well as greatly simplified exposure media. Nano-sized tungsten carbide (WC) with or without cobalt doping (WC-Co), two materials relevant in the heavy metal industry, were applied as model particles. These particles were suspended in culture media with decreasing complexity from L15 with 10% fetal bovine serum (FBS) to L15 to L15/ex, containing only salts, galactose and pyruvate of the complete medium L15. Whereas the serum supplement in L15 retained primary nanoparticle suspensions, agglomerates were formed quickly in L15 and L15/ex. Nevertheless, scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) elemental analysis revealed an uptake of both WC and WC-Co nanoparticles into RTgill-W1 cells irrespective of the state of agglomeration of nanoparticles. The localisation seemed to be restricted to the cytoplasm, as no particles were observed in the nucleus of cells. Moreover, reduction in cell viability between 10 and 50% compared to controls were observed upon particle exposure in all media although the pattern of impact varied depending on the medium and exposure time. Short-term exposure of cells led to significant cytotoxicity at the highest nominal particle concentrations, irrespective of the particle type or exposure medium. In contrast, long-term exposures led to preferential toxicity in the simplest medium, L15/ex, and an enhanced toxicity by the cobalt-containing WC nanoparticles in all exposure media. The composition of the exposure media also influenced the toxicity of the cobalt ions, which may

  2. Singlet Diradical Complexes of Chromium, Molybdenum, and Tungsten with Azo Anion Radical Ligands from M(CO)6 Precursors

    Czech Academy of Sciences Publication Activity Database

    Sanyal, A.; Chatterjee, S.; Castineiras, A.; Sarkar, B.; Singh, P.; Fiedler, Jan; Záliš, Stanislav; Kaim, W.; Goswami, S.

    2007-01-01

    Roč. 46, č. 21 (2007), s. 8584-8593 ISSN 0020-1669 R&D Projects: GA ČR GA203/03/0822; GA MŠk OC 139; GA MŠk OC D15.10 Grant - others:Deutsche Forschungsgemeinschaft(DE) SR/S1/IC-24/2006 Institutional research plan: CEZ:AV0Z40400503 Source of funding: R - rámcový projekt EK Keywords : singlet diradical complexes * chromium * molybdenum * tungsten Subject RIV: CG - Electrochemistry Impact factor: 4.123, year: 2007

  3. 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.

  4. 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...

  5. Process for microwave sintering boron carbide

    Science.gov (United States)

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

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

  6. Extraction Factor Of Tungsten Sources From Tungsten Scraps By Zinc Decomposition Process

    Directory of Open Access Journals (Sweden)

    Pee J.-H.

    2015-06-01

    Full Text Available Decomposition promoting factors and extraction process of tungsten carbide and tungstic acid powders in the zinc decomposition process of tungsten scraps which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility was suppressed by the enclosed graphite crucible and zinc volatilization pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP (Zinc Decomposition Process. Decomposition reaction was done for 2hours at 650°, which 100% decomposed the tungsten scraps that were over 30 mm thick. Decomposed scraps were pulverized under 75μm and were composed of tungsten carbide and cobalt identified by the XRD (X-ray Diffraction. To produce the WC(Tungsten Carbide powder directly from decomposed scraps, pulverized powders were reacted with hydrochloric acid to remove the cobalt binder. Also to produce the tungstic acid, pulverized powders were reacted with aqua regia to remove the cobalt binder and oxidize the tungsten carbide. Tungsten carbide and tungstic acid powders were identified by XRD and chemical composition analysis.

  7. The effect of mixing methods and polymer infiltration and pyrolysis (PIP) cycles on the densification of silicon carbide inert matrix fuel through a polymer precursor route

    International Nuclear Information System (INIS)

    Shih Chunghao; Tulenko, J.S.; Baney, R.H.

    2011-01-01

    Highlights: ► A pre-ceramic polymer precursor route was utilized to fabricate SiC based inert matrix fuel (IMF). ► The effect of mixing and polymer infiltration and pyrolysis (PIP) cycles on the fabrication of the SiC IMF was investigated. ► A theoretical density of ∼86% has been achieved after one PIP cycle. ► Pore size distributions before and after PIP cycles have been determined. ► SEM images showed a “springback” effect for 600 MPa pressed pellets. - Abstract: The effect of mixing methods on the fabrication of silicon carbide (SiC) inert matrix fuel through a polymer precursor route was investigated in order to break up the agglomerates of the SiC particles observed in earlier studies. It was found that a high energy shaker mill could effectively break up the agglomerates and thereby achieve a higher pellet density. Moreover, it was found that the pellet density depended less on the pressing pressure, when the particles are well mixed. SEM images showed cracks caused by the springback effect on pellets with a high cold pressing pressure of 600 MPa, but no signs of springback effect were observed for the 200 MPa pressed pellets. The polymer infiltration and pyrolysis (PIP) cycles were used to further increase the pellet density and close the open pores. The first PIP cycle was found to increase the theoretical density of the pellets from 81.2% to 86.0% and close ∼50% of the open pores. The pore size distribution showed that most of the remaining open pores had diameters smaller than 10 nm. The successive second PIP cycle is not as effective on either the density or the pore size distribution because the small pores present before the second PIP cycle made the infiltration process difficult.

  8. High Purity Tungsten Spherical Particle Preparation From WC-Co Spent Hard Scrap

    Directory of Open Access Journals (Sweden)

    Han Chulwoong

    2015-06-01

    Full Text Available Tungsten carbide-cobalt hard metal scrap was recycled to obtain high purity spherical tungsten powder by a combined hydrometallurgy and physical metallurgy pathway. Selective leaching of tungsten element from hard metal scrap occurs at solid / liquid interface and therefore enlargement of effective surface area is advantageous. Linear oxidation behavior of Tungsten carbide-cobalt and the oxidized scrap is friable to be pulverized by milling process. In this regard, isothermally oxidized Tungsten carbide-cobalt hard metal scrap was mechanically broken into particles and then tungsten trioxide particle was recovered by hydrometallurgical method. Recovered tungsten trioxide was reduced to tungsten particle in a hydrogen environment. After that, tungsten particle was melted and solidified to make a spherical one by RF (Ratio Frequency thermal plasma process. Well spherical tungsten micro-particle was successfully obtained from spent scrap. In addition to the morphological change, thermal plasma process showed an advantage for the purification of feedstock particle.

  9. Diallyl disulphide as natural organosulphur friction modifier via the in-situ tribo-chemical formation of tungsten disulphide

    Science.gov (United States)

    Rodríguez Ripoll, Manel; Totolin, Vladimir; Gabler, Christoph; Bernardi, Johannes; Minami, Ichiro

    2018-01-01

    The present work shows a novel method for generating in-situ low friction tribofilms containing tungsten disulphide in lubricated contacts using diallyl disulphide as sulphur precursor. The approach relies on the tribo-chemical interaction between the diallyl disulphide and a surface containing embedded sub-micrometer tungsten carbide particles. The results show that upon sliding contact between diallyl disulphide and the tungsten-containing surface, the coefficient of friction drops to values below 0.05 after an induction period. The reason for the reduction in friction is due to tribo-chemical reactions that leads to the in-situ formation of a complex tribofilm that contains iron and tungsten components. X-ray photoelectron spectroscopy analyses indicate the presence of tungsten disulphide at the contact interface, thus justifying the low coefficient of friction achieved during the sliding experiments. It was proven that the low friction tribofilms can only be formed by the coexistence of tungsten and sulphur species, thus highlighting the synergy between diallyl disulphide and the tungsten-containing surface. The concept of functionalizing surfaces to react with specific additives opens up a wide range of possibilities, which allows tuning on-site surfaces to target additive interactions.

  10. The Mechanical and Tribology Properties of Sputtered Titanium Aluminum Nitride Coating on the Tungsten Carbide Insert Tool in the Dry Turning of Tool Steel

    Directory of Open Access Journals (Sweden)

    Esmar Budi

    2015-02-01

    Full Text Available The effect of the sputtering parameters on the mechanical tribology properties of Titanium Aluminum Nitride coating on the tungsten cabide insert tool in the dry turning of tool steel has been investigated. The coating was deposited using a Direct Current magnetron sputtering system with various substrate biases (-79 to -221 V and nitrogen flow rates (30 to 72 sccm. The dry turning test was carried out on a Computer Numeric Code machine using an optimum cutting parameter setting. The results show that the lowest flank wear (~0.4 mm was achieved using a Titanium Aluminum Nitride-coated tool that was deposited at a high substrate bias (-200 V and a high nitrogen flow rate (70 sccm. The lowest flank wear was attributed to high coating hardness.

  11. Selective formation of tungsten nanowires

    Directory of Open Access Journals (Sweden)

    Bien Daniel

    2011-01-01

    Full Text Available Abstract We report on a process for fabricating self-aligned tungsten (W nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

  12. Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials

    Czech Academy of Sciences Publication Activity Database

    Holá, M.; Mikuška, Pavel; Hanzlíková, Renáta; Kaiser, J.; Kanický, V.

    2010-01-01

    Roč. 80, č. 5 (2010), s. 1862-1867 ISSN 0039-9140 Institutional research plan: CEZ:AV0Z40310501; CEZ:AV0Z20650511 Keywords : laser ablation * inductively coupled plasma mass * ICP-MS spectrometry Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.722, year: 2010

  13. Surface composition of carburized tungsten trioxide and its catalytic activity

    International Nuclear Information System (INIS)

    Nakazawa, M.; Okamoto, H.

    1985-01-01

    The surface composition and electronic structure of carburized tungsten trioxide are investigated using x-ray photoelectron spectroscopy (XPS). The relationship between the surface composition and the catalytic activity for methanol electro-oxidation is clarified. The tungsten carbide concentration in the surface layer increases with the carburization time. The formation of tungsten carbide enhances the catalytic activity. On the other hand, the presence of free carbon or tungsten trioxide in the surface layer reduces the activity remarkably. It is also shown that, the higher the electronic density of states near the Fermi level, the higher the catalytic activity

  14. High-energy, high-rate consolidation of tungsten and tungsten-based composite powders

    Energy Technology Data Exchange (ETDEWEB)

    Raghunathan, S.K.; Persad, C.; Bourell, D.L.; Marcus, H.L. (Center for Materials Science and Engineering, Univ. of Texas, Austin (USA))

    1991-01-20

    Tungsten and tungsten-based heavy alloys are well known for their superior mechanical properties at elevated temperatures. However, unalloyed tungsten is difficult to consolidate owing to its very high melting temperature (3683 K). The additions of small amounts of low-melting elements such as iron, nickel, cobalt and copper, facilitate the powder processing of dense heavy alloys at moderate temperatures. Energetic high-current pulses have been used recently for powder consolidation. In this paper, the use of a homopolar generator as a power source to consolidate selected tungsten and tungsten-based alloys is examined. Various materials were consolidated including unalloyed tungsten, W-Nb, W-Ni, and tungsten heavy alloy with boron carbide. The effect of process parameters such as pressure and specific energy input on the consolidation of different alloy systems is described in terms of microstructure and property relationships. (orig.).

  15. Metal carbides

    International Nuclear Information System (INIS)

    Wells, A.F.

    1988-01-01

    From the viewpoint of general crystal chemistry principles and on the base of modern data the structural chemistry of metal carbides is presented. The classification deviding metal carbides into 4 groups depending on chemical and physical properties is presented. The features of the crystal structure of carbides of alkali alkaline earth, transition, 4 f- and 5f-elements and their effect on physical and chemical properties are considered

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

    Energy Technology Data Exchange (ETDEWEB)

    Rowcliff, D.J.

    1983-10-01

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

  17. Shock propagation in a cemented tungsten carbide

    NARCIS (Netherlands)

    Appleby-Thomas, G.J.; Hazell, P.J.; Stennett, C.; Cooper, G.; Herlaar, K.; Diederen, A.M.

    2009-01-01

    WC-based ceramic metal composites (cermets) are of great importance in both armor and munition design due to the combination of properties imparted by the presence of two different phases. WC-Co cermets are of interest in this area due to the hardness and strength imparted by the WC phase while the

  18. 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.

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

    Science.gov (United States)

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

    2017-01-01

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

  20. New doped tungsten cathodes. Applications to power grid tubes

    International Nuclear Information System (INIS)

    Cachard, J. de; Cadoret, K; Martinez, L.; Veillet, D.; Millot, F.

    2001-01-01

    Thermionic emission behavior of tungsten/tungsten carbide modified with rare earth (La, Ce, Y) oxides is examined on account of suitability to deliver important current densities in a thermo-emissive set up and for long lifetime. Work functions of potential cathodes have been determined from Richardson plots for La 2 O 3 doped tungsten and for tungsten covered with variable compositions rare earth tungstates. The role of platinum layers covering the cathode was also examined. Given all cathodes containing mainly lanthanum oxides were good emitters, emphasis was put on service lifetime. Comparisons of lifetime in tungsten doped with rare earth oxides and with rare earth tungstates show that microstructure of the operating cathodes may play the major role in the research of very long lifetime cathodes. Based on these results, tests still running show lifetime compatible with power grid tubes applications. (author)

  1. Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses; Ablação seletiva de um filme de nitreto de titânio em substrato de carboneto de tungstênio utilizando laser de pulsos ultracurtos

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Eduardo Spinelli

    2017-07-01

    Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

  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. 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.

  4. Systematic studies of the nucleation and growth of ultrananocrystalline diamond films on silicon substrates coated with a tungsten layer

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Yueh-Chieh; Jiang, Gerald [Institute of Microelectronics, No.1, University Road, Tainan 701, Taiwan (China); Tu, Chia-Hao [Institute of Nanotechnology and Microsystems Engineering, No.1, University Road, Tainan 701, Taiwan (China); Department of Materials Science and Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan (China); Chang Chi [Institute of Nanotechnology and Microsystems Engineering, No.1, University Road, Tainan 701, Taiwan (China); Liu, Chuan-pu; Ting, Jyh-Ming [Department of Materials Science and Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan (China); Lee, Hsin-Li [Industrial Technology Research Institute - South, Tainan 701, Taiwan (China); Tzeng, Yonhua [Institute of Microelectronics, No.1, University Road, Tainan 701, Taiwan (China); Advanced Optoelectronics Technology Center, No.1, University Road, Tainan 701, Taiwan (China); Auciello, Orlando [Argonne National Laboratory, Materials Science Division, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2012-06-15

    We report on effects of a tungsten layer deposited on silicon surface on the effectiveness for diamond nanoparticles to be seeded for the deposition of ultrananocrystalline diamond (UNCD). Rough tungsten surface and electrostatic forces between nanodiamond seeds and the tungsten surface layer help to improve the adhesion of nanodiamond seeds on the tungsten surface. The seeding density on tungsten coated silicon thus increases. Tungsten carbide is formed by reactions of the tungsten layer with carbon containing plasma species. It provides favorable (001) crystal planes for the nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the density of diamond seeds/nuclei. UNCD films grown at different gas pressures on tungsten coated silicon which is pre-seeded by nanodiamond along with heteroepitaxially nucleated diamond nuclei were characterized by Raman scattering, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy.

  5. Effect of CVD Tungsten and TaC Coatings on the Mechanical Behavior of SiC(C)

    Science.gov (United States)

    1979-12-01

    to infiltration. Compatibility studies made by the authors2 showed that tungsten and tantalum carbide could provide protection against cobalt base Mar...34Silicon Carbide Filaments as Reinforcements for High Temperature Superalloy Matrices," Proceedings of the International Conference on Composites, Geneva...was approximately two minutes. 19Ahmad, I., et al, "Silicon Carbide Filaments as Reinforcements for High Temperature Superalloy Matrices," Proceedings

  6. Structure and thermal expansion of NbC complex carbides

    International Nuclear Information System (INIS)

    Khatsinskaya, I.M.; Chaporova, I.N.; Cheburaeva, R.F.; Samojlov, A.I.; Logunov, A.V.; Ignatova, I.A.; Dodonova, L.P.

    1983-01-01

    Alloying dependences of the crystal lattice parameters at indoor temperature and coefficient of thermal linear exspansion within a 373-1273 K range are determined for complex NbC-base carbides by the method of mathematical expemental design. It is shown that temperature changes in the linear expansion coefficient of certain complex carbides as distinct from NbC have an anomaly (minimum) within 773-973 K caused by occurring reversible phase transformations. An increase in the coefficient of thermal linear expansion and a decrease in hardness of NbC-base tungsten-, molybdenum-, vanadium- and hafnium-alloyed carbides show a weakening of a total chemical bond in the complex carbides during alloying

  7. Tungsten Alloy Outgassing Measurements

    CERN Document Server

    Rutherfoord, John P; Shaver, L

    1999-01-01

    Tungsten alloys have not seen extensive use in liquid argon calorimeters so far. Because the manufacturing process for tungsten is different from the more common metals used in liquid argon there is concern that tungsten could poison the argon thereby creating difficulties for precision calorimetry. In this paper we report measurements of outgassing from the tungsten alloy slugs proposed for use in the ATLAS FCal module and estimate limits on potential poisoning with reasonable assumptions. This estimate gives an upper limit poisoning rate of tungsten slugs.

  8. Tungsten and refractory metals 3, proceedings

    International Nuclear Information System (INIS)

    Bose, A.; Dowding, R.J.

    1996-01-01

    The Third International Conference on Tungsten and Refractory Metals was held in Greater Washington DC at the McLean Hilton, McLean Virginia, on November 15--16, 1995. This meeting was the third in a series of conferences held in the Washington DC area. The first meeting was in 1992 and was entitled ''International Conference on Tungsten and Tungsten Alloys.'' In 1994, the scope of the meeting was expanded to include other refractory metals such as molybdenum, iridium, rhenium, tantalum and niobium. The tremendous success of that meeting was the primary motivation for this Conference. The broader scope (the inclusion of other refractory metals and alloys) of the Conference was kept intact for this meeting. In fact, it was felt that the developments in the technology of these materials required a common forum for the interchange of current research information. The papers presented in this meeting examined the rapid advancements in the technology of refractory metals, with special emphasis on the processing, structure, and properties. Among the properties there was emphasis on both quasi-static and dynamic rates. Another topic that received considerable interest was the area of refractory carbides and tungsten-copper composites. One day of concurrent session was necessary to accommodate all of the presentations

  9. Tungsten-nanodiamond composite powders produced by ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, D., E-mail: daniela.nunes@ist.utl.pt [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Livramento, V. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Mardolcar, U.V. [Departamento de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Centro de Ciencias Moleculares e Materiais, Faculdade de Ciencias da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Correia, J.B. [LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Carvalho, P.A. [ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Departamento de Bioengenharia, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2012-07-15

    The major challenge in producing tungsten-nanodiamond composites by ball milling lies in successfully dispersing carbon nanoparticles in the metallic matrix while keeping carbide formation at a minimum. Processing windows for carbide minimization have been established through systematic variation of the nanodiamond fraction, milling energy and milling time. Materials characterization has been carried out by X-ray diffraction, scanning and transmission electron microscopy and microhardness testing. Nanostructured matrices with homogeneously dispersed particles that preserved the diamond structure have been produced. Differential thermal analysis has been used to evaluate the composites thermal stability.

  10. Boron carbide (B{sub 4}C) coating. Deposition and testing

    Energy Technology Data Exchange (ETDEWEB)

    Azizov, E.; Barsuk, V. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Begrambekov, L., E-mail: lbb@plasma.mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Buzhinsky, O. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Evsin, A.; Gordeev, A.; Grunin, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Klimov, N. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Kurnaev, V. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Mazul, I. [Federal State Unitary Interprise Efremov Scientific Research Institute of Electrophysical Apparatus (NIIEFA Efremov), St-Peterburg (Russian Federation); Otroshchenko, V.; Putric, A. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Sadovskiy, Ya.; Shigin, P.; Vergazov, S.; Zakharov, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2015-08-15

    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 B{sub 4}C 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 B{sub 4}C coating irradiation by the plasma pulses of QSPU-T plasma accelerator are presented. The new device capable of B{sub 4}C 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 B{sub 4}C coating deposition and testing of both tungsten substrate and coating are shown and discussed.

  11. ELASTO-PLASTIC DEFORMATION OF COMPOSITE POWDERS WITH LAYERED CARBON AND CARBIDE-FORMING ELEMENT COATING

    Directory of Open Access Journals (Sweden)

    V. N. Kovalevsky

    2012-01-01

    Full Text Available Coating structure formation under magnetron spraying of titanium and carbon cathodes and combined cathodes, namely cobalt (EP 131 – nickel, tungsten – carbon have been investigated under conditions of carbide separate synthesis within the temperature range of 650–1200 °C. Usage of cobalt and nickel particles as matrix material leads to their rapid thermal expansion under heating during sintering process in the dilatometer. Subsequent plastic deformation of sintered samples provides obtaining a composite powder material that is a composite with framing structure of cobalt, titanium and tungsten carbides in the coatings.

  12. Tungsten Deposition on Graphite using Plasma Enhanced Chemical Vapour Deposition

    International Nuclear Information System (INIS)

    Sharma, Uttam; Chauhan, Sachin S; Sharma, Jayshree; Sanyasi, A K; Ghosh, J; Choudhary, K K; Ghosh, S K

    2016-01-01

    The tokamak concept is the frontrunner for achieving controlled thermonuclear reaction on earth, an environment friendly way to solve future energy crisis. Although much progress has been made in controlling the heated fusion plasmas (temperature ∼ 150 million degrees) in tokamaks, technological issues related to plasma wall interaction topic still need focused attention. In future, reactor grade tokamak operational scenarios, the reactor wall and target plates are expected to experience a heat load of 10 MW/m 2 and even more during the unfortunate events of ELM's and disruptions. Tungsten remains a suitable choice for the wall and target plates. It can withstand high temperatures, its ductile to brittle temperature is fairly low and it has low sputtering yield and low fuel retention capabilities. However, it is difficult to machine tungsten and hence usages of tungsten coated surfaces are mostly desirable. To produce tungsten coated graphite tiles for the above-mentioned purpose, a coating reactor has been designed, developed and made operational at the SVITS, Indore. Tungsten coating on graphite has been attempted and successfully carried out by using radio frequency induced plasma enhanced chemical vapour deposition (rf -PECVD) for the first time in India. Tungsten hexa-fluoride has been used as a pre-cursor gas. Energy Dispersive X-ray spectroscopy (EDS) clearly showed the presence of tungsten coating on the graphite samples. This paper presents the details of successful operation and achievement of tungsten coating in the reactor at SVITS. (paper)

  13. Tungsten-microdiamond composites for plasma facing components

    International Nuclear Information System (INIS)

    Livramento, V.; Nunes, D.; Correia, J.B.; Carvalho, P.A.; Mardolcar, U.; Mateus, R.; Hanada, K.; Shohoji, N.; Fernandes, H.; Silva, C.; Alves, E.

    2011-01-01

    Tungsten is considered as one of promising candidate materials for plasma facing component in nuclear fusion reactors due to its resistance to sputtering and high melting point. High thermal conductivity is also a prerequisite for plasma facing components under the unique service environment of fusion reactor characterised by the massive heat load, especially in the divertor area. The feasibility of mechanical alloying of nanodiamond and tungsten, and the consolidation of the composite powders with Spark Plasma Sintering (SPS) was previously demonstrated. In the present research we report on the use of microdiamond instead of nanodiamond in such composites. Microdiamond is more favourable than nanodiamond in view of phonon transport performance leading to better thermal conductivity. However, there is a trade off between densification and thermal conductivity as the SPS temperature increases tungsten carbide formation from microdiamond is accelerated inevitably while the consolidation density would rise.

  14. Tungsten Filament Fire

    Science.gov (United States)

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  15. Electrical and optical properties of mixed phase tungsten trioxide films grown by laser pyrolysis

    CSIR Research Space (South Africa)

    Govender, M

    2014-02-01

    Full Text Available Laser pyrolysis was chosen to synthesize tungsten trioxide starting with tungsten ethoxide precursor. The film was found to have a thickness that varied from 205 nm to 1 µm. X-ray diffraction and Raman spectroscopy confirmed the presence of a...

  16. Textbook tests with tungsten

    CERN Multimedia

    Barbara Warmbein

    2010-01-01

    CERN's linear collider detector group joins forces with CALICE in building the world's first tungsten hadronic calorimeter.   Hadronic calorimeter prototype made of tungsten for the linear collider detector being equipped with CALICE scintillators. In a hall for test beam experiments at CERN, next to the CLOUD climate experiment and an irradiation facility, sits a detector prototype that is in many ways a first. It's the first ever hadronic sandwich calorimeter (HCal) prototype made of tungsten. It's the first prototype for a detector for the Compact Linear Collider Study CLIC, developed by the linear collider detector R&D group (LCD group) at CERN. And it's the first piece of hardware that results directly from the cooperation between CLIC and ILC detector study groups. Now its makers are keen to see first particle showers in their detector. The tungsten calorimeter has just moved from a workshop at CERN, where it was assembled from finely polished tungsten squares and triangles, into the ...

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

    Indian Academy of Sciences (India)

    Department of Mechanical Engineering, Beant College of Engineering & Technology, Gurdaspur 143 521, India. †Department of Mechanical Engineering, National Institute of Technology, Hamirpur 173 742, India. #Department of Industrial and Production Engineering, National Institute of Technology, Jalandhar 144 001, ...

  18. Diode Laser Surface Alloying of Armor Steel with Tungsten Carbide

    OpenAIRE

    Janicki D.; Górka J.; Kwaśny W.; Gołombek K.; Kondracki M.; Żuk M.

    2017-01-01

    Metal matrix composite (MMC) surface layers reinforced by WC were fabricated on armor steel ARMOX 500T plates via a laser surface alloying process. The microstructure of the layers was assessed by scanning electron microscopy and X-ray diffraction.

  19. Diode Laser Surface Alloying of Armor Steel with Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Janicki D.

    2017-06-01

    Full Text Available Metal matrix composite (MMC surface layers reinforced by WC were fabricated on armor steel ARMOX 500T plates via a laser surface alloying process. The microstructure of the layers was assessed by scanning electron microscopy and X-ray diffraction.

  20. Friction and metal transfer for single-crystal silicon carbide in contact with various metals in vacuum

    International Nuclear Information System (INIS)

    Miyoshi, K.; Buckley, D.H.

    1978-04-01

    Sliding friction experiments were conducted with single-crystal silicon carbide in contact with transition metals (tungsten, iron, rhodium, nickel, titanium, and cobalt), copper, and aluminum. Results indicate the coefficient of friction for a silicon carbide-metal system is related to the d bond character and relative chemical activity of the metal. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to the surface of silicon carbide in sliding. The chemical activity of metal to silicon and carbon and shear modulus of the metal may play important roles in metal transfer and the form of the wear debris. The less active metal is, and the greater resistance to shear it has, with the exception of rhodium and tungsten, the less transfer to silicon carbide

  1. Laser irradiation of carbon–tungsten materials

    International Nuclear Information System (INIS)

    Marcu, A; Lungu, C P; Ursescu, D; Porosnicu, C; Grigoriu, C; Avotina, L; Kizane, G; Marin, A; Osiceanu, P; Grigorescu, C E A; Demitri, N

    2014-01-01

    Carbon–tungsten layers deposited on graphite by thermionic vacuum arc (TVA) were directly irradiated with a femtosecond terawatt laser. The morphological and structural changes produced in the irradiated area by different numbers of pulses were systematically explored, both along the spots and in their depths. Although micro-Raman and Synchrotron-x-ray diffraction investigations have shown no carbide formation, they have shown the unexpected presence of embedded nano-diamonds in the areas irradiated with high fluencies. Scanning electron microscopy images show a cumulative effect of the laser pulses on the morphology through the ablation process. The micro-Raman spatial mapping signalled an increased percentage of sp 3 carbon bonding in the areas irradiated with laser fluencies around the ablation threshold. In-depth x-ray photoelectron spectroscopy investigations suggested a weak cumulative effect on the percentage increase of the sp 2 -sp 3 transitions with the number of laser pulses just for nanometric layer thicknesses. (paper)

  2. Point Defect Calculations in Tungsten

    National Research Council Canada - National Science Library

    Danilowicz, Ronald

    1968-01-01

    .... The vacancy migration energy for tungsten was calculated. The calculated value of 1.73 electron volts, together with experimental data, suggests that vacancies migrate in stage III recovery in tungsten...

  3. High-gravity combustion synthesis and in situ melt infiltration: A new method for preparing cemented carbides

    International Nuclear Information System (INIS)

    Liu, Guanghua; Li, Jiangtao; Yang, Zengchao; Guo, Shibin; Chen, Yixiang

    2013-01-01

    A new method of high-gravity combustion synthesis and in situ melt infiltration is reported for preparing cemented carbides, where hot nickel melt is in situ synthesized from a highly exothermic combustion reaction and then infiltrated into tungsten carbide powder compacts. The as-prepared sample showed a homogeneous microstructure, and its relative density, hardness and flexural strength were 94.4%, 84 HRA and 1.49 GPa, respectively. Compared with conventional powder metallurgy approaches, high-gravity combustion synthesis offers a fast and furnace-free way to produce cemented carbides

  4. Reactive sintering and microstructure development of tungsten carbide-AISI 304 stainless steel cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, C.M. [Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); CEMUC-Mechanical Engineering Department, University of Coimbra, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra (Portugal); Oliveira, F.J. [Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Senos, A.M.R., E-mail: anamor@ua.pt [Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)

    2017-06-01

    Sintering of WC-stainless steel (SS) composites within a typical binder range from 6 up to 15 wt% SS was investigated through constant heating rate dilatometry, in vacuum conditions, complemented by differential thermal analysis and by the study of the high temperature wetting behavior of SS on WC. The densification starts ∼900 °C with a typical densification curve for all compositions, where three distinct regions are discernible: the first one with a slow densification rate, followed by a second region where a sharp increase in the densification rate up to a maximum value dependent on the binder amount is observed and, finally, a third one with a slowdown of the densification rate until the end of the thermal cycle. The attained final density at 1450 °C is dependent on the binder amount, increasing proportionally to its initial content. The final microstructure presents a normal grain size distribution and appreciable amounts of eta-phase, besides the major WC phase and residual iron rich phase. The reactive densification behavior and the role of the liquid phase are interpreted accordingly with structural and kinetic data. - Highlights: • Sintering of WC-AISI304 composites starts ∼900 °C and involves three stages. • Densification is largely dominated by a reactive liquid phase sintering process. • Eta-phase constitutes a transient liquid phase during sintering. • Sintering cycles are dependent on the initial binder content.

  5. High-temperature brazing for reliable tungsten-CFC joints

    International Nuclear Information System (INIS)

    Koppitz, Th; Pintsuk, G; Reisgen, U; Remmel, J; Hirai, T; Sievering, R; Rojas, Y; Casalegno, V

    2007-01-01

    The joining of tungsten and carbon-based materials is demanding due to the incompatibility of their chemical and thermophysical properties. Direct joining is unfeasible by the reason of brittle tungsten carbide formation. High-temperature brazing has been investigated in order to find a suitable brazing filler metal (BFM) which successfully acts as an intermediary between the incompatible properties of the base materials. So far only low Cr-alloyed Cu-based BFMs provide the preferential combination of good wetting action on both materials, tolerable interface reactions, and a precipitation free braze joint. Attempts to implement a higher melting metal (e.g. Pd, Ti, Zr) as a BFM have failed up to now, because the formation of brittle precipitations and pores in the seam were inevitable. But the wide metallurgical complexity of this issue is regarded to offer further joining potential

  6. Influence of Cooling Rate in High-Temperature Area on Hardening of Deposited High-Cutting Chrome-Tungsten Metal

    International Nuclear Information System (INIS)

    Malushin, N N; Valuev, D V; Valueva, A V; Serikbol, A; Borovikov, I F

    2015-01-01

    The authors study the influence of cooling rate in high-temperature area for thermal cycle of high-cutting chrome-tungsten metal weld deposit on the processes of carbide phase merging and austenite grain growth for the purpose of providing high hardness of deposited metal (HRC 64-66). (paper)

  7. Gas tungsten arc welder

    Science.gov (United States)

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  8. Utilization of geothermal energy in the mining and processing of tungsten ore. Quarterly report

    Energy Technology Data Exchange (ETDEWEB)

    Lane, C.K.; Erickson, M.V.; Lowe, G.D.

    1980-02-01

    The status of the engineering and economic feasibility study of utilizing geothermal energy for the mining and processing of tungsten ore at the Union Carbide-Metals Division Pine Creek tungsten complex near Bishop, Calfironia is reviewed. Results of geophysical data analysis including determination of assumed resource parameters are presented. The energy utilization evaluation identifies potential locations for substituting geothermal energy for fossil fuel energy using current technology. Preliminary analyses for local environmental and institutional barriers to development of a geothermal system are also provided.

  9. Synthesis of bundled tungsten oxide nanowires with controllable morphology

    International Nuclear Information System (INIS)

    Sun Shibin; Zou Zengda; Min Guanghui

    2009-01-01

    Bundled tungsten oxide nanowires with controllable morphology were synthesized by a simple solvothermal method with tungsten hexachloride (WCl 6 ) as precursor and cyclohexanol as solvent. The as-synthesized products were systematically characterized by using scanning electron microscopy, X-ray diffraction and transition electron microscopy. Brunauer-Emmett-Teller gas-sorption measurements were also employed. Accompanied by an apparent drop of specific surface area from 151 m 2 g -1 for the longer nanowires synthesized using a lower concentration of WCl 6 to 106 m 2 g -1 for the shorter nanowires synthesized using a higher concentration of WCl 6 , a dramatically morphological evolution was also observed. With increasing concentration of tungsten hexachloride (WCl 6 ) in cyclohexanol, the nanostructured bundles became larger, shorter and straighter, and finally a block-shape product occurred

  10. Synthesis of Tungsten Diselenide Nanoparticles by Chemical Vapor Condensation Method

    Directory of Open Access Journals (Sweden)

    Oleg V. Tolochko

    2015-09-01

    Full Text Available Crystalline tungsten diselenide (WSe2 nanoparticles have been synthesized by a gas phase reaction using tungsten hexacarbonyl and elemental selenium as precursors. The WSe2 nanoparticle morphology varies from the spherical shape to flake-like layered structures. Mean size in smaller dimension are less than 5 nm and the number of layers decreased linearly with decreasing of reaction time and concentration of carbonyl in the gas phase. The mean value of interlayer distance in <0001> direction is comparable with the microscopic values. The selenium-to-tungsten atomic ratios of 2.07, 2.19 and 2.19 were determined respectively, approach to the stoichiometric ratio of 2:1. Main impurities are oxygen and carbon and strongly interrelated with carbonyl concentration in the gas phase.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7356

  11. Effect of mechanical milling on the microstructure of tungsten under He{sup +} irradiation condition

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Xiao-Yue [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Li, Ping [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Luo, Lai-Ma, E-mail: luolaima@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Chen, Hong-Yu [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zan, Xiang; Zhu, Xiao-Yong [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Wu, Yu-Cheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China)

    2015-11-15

    “Pure” W was prepared through a powder metallurgy route by using hard alloy (WC–Co) milling tank and balls to mill WO{sub 3} powder, reducing with high purity H{sub 2}, and sintering with spark plasma sintering technique. XRD, SEM, and TEM were used to characterize the phase and phase structures. Results showed that the cobalt tungsten carbide (Co{sub 3}W{sub 10}C{sub 3.4}) phase was induced from the milling tank and balls. After the “pure” W bulk was exposed to helium ions for 2 h, the cobalt tungsten carbide phase was found to be surrounded by the lattice distortion phase of W, which showed high irradiation resistance.

  12. Helium bubble bursting in tungsten

    International Nuclear Information System (INIS)

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    2013-01-01

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz

  13. Synthesis of multifilament silicon carbide fibers by chemical vapor deposition

    Science.gov (United States)

    Revankar, Vithal; Hlavacek, Vladimir

    1991-01-01

    A process for development of clean silicon carbide fiber with a small diameter and high reliability is presented. An experimental evaluation of operating conditions for SiC fibers of good mechanical properties and devising an efficient technique which will prevent welding together of individual filaments are discussed. The thermodynamic analysis of a different precursor system was analyzed vigorously. Thermodynamically optimum conditions for stoichiometric SiC deposit were obtained.

  14. 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...

  15. Properties of multiple field ion emitters of tungsten and a simple method for improving their ionization efficiency

    International Nuclear Information System (INIS)

    Okuyama, F.; Beckey, H.D.

    1978-01-01

    The ion emission properties of the multiple tungsten emitters developed recently for field ionization mass spectrometry were investigated with the aid of a sector type mass spectrometer at emitter-cathode voltages of 10-15 kV using acetone, n-heptane and benzene as test substances. The emitters, which comprised a 10-μm tungsten filament bearing thickly arrayed microneedles of tungsten, produced very weak and unstable signals at voltages of about 10 kV, but increasing the voltage to 14 kV led to intensifying ion currents high enough to yield mass spectra of satisfactory quality. During the course of the experiments, it was observed that nucleating tungsten carbide particles on the emitter surface by means of a high-field chemical reaction with benzene vapours can significanlty promote the field ionization of gas molecules, presumably as a result of the field enhancement resulting from roughening of the surface. (Auth.)

  16. Self diffusion in tungsten

    International Nuclear Information System (INIS)

    Mundy, J.N.; Rothman, S.J.; Lam, N.Q.; Nowicki, L.J.; Hoff, H.A.

    1978-01-01

    The lack of understanding of self-diffusion in Group VI metals together with the wide scatter in the measured values of tungsten self-diffusion has prompted the present measurements to be made over a wide temperature range (1/2Tsub(m) to Tsub(m)). The diffusion coefficients have been measured in the temperature range 1430-2630 0 C. The present measurements show non-linear Arrhenius behavior but a reliable two-exponential fit of the data should await further measurements. (Auth.)

  17. Gas tungsten arc welder

    International Nuclear Information System (INIS)

    Christiansen, D.W.; Brown, W.F.

    1984-01-01

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable grinder, co-axial with the electrode, is provided in the enclosure for refurbishing the used electrode between welds. The specification also discloses means for loading of the cladding with fuel pellets and for placement of reflectors, gas capsules and end caps. Gravity feed conveyor and inerting means are also described. (author)

  18. Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

    Science.gov (United States)

    Halverson, Danny C.; Landingham, Richard L.

    1988-01-01

    A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.

  19. 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.

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

    Science.gov (United States)

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

    2017-10-01

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

  1. Improved silicon carbide for advanced heat engines

    Science.gov (United States)

    Whalen, T. J.; Winterbottom, W. L.

    1986-01-01

    Work performed to develop silicon carbide materials of high strength and to form components of complex shape and high reliability is described. A beta-SiC powder and binder system was adapted to the injection molding process and procedures and process parameters developed capable of providing a sintered silicon carbide material with improved properties. The initial effort has been to characterize the baseline precursor materials (beta silicon carbide powder and boron and carbon sintering aids), develop mixing and injection molding procedures for fabricating test bars, and characterize the properties of the sintered materials. Parallel studies of various mixing, dewaxing, and sintering procedures have been carried out in order to distinguish process routes for improving material properties. A total of 276 MOR bars of the baseline material have been molded, and 122 bars have been fully processed to a sinter density of approximately 95 percent. The material has a mean MOR room temperature strength of 43.31 ksi (299 MPa), a Weibull characteristic strength of 45.8 ksi (315 MPa), and a Weibull modulus of 8.0. Mean values of the MOR strengths at 1000, 1200, and 14000 C are 41.4, 43.2, and 47.2 ksi, respectively. Strength controlling flaws in this material were found to consist of regions of high porosity and were attributed to agglomerates originating in the initial mixing procedures. The mean stress rupture lift at 1400 C of five samples tested at 172 MPa (25 ksi) stress was 62 hours and at 207 MPa (30 ksi) stress was 14 hours. New fluid mixing techniques have been developed which significantly reduce flaw size and improve the strength of the material. Initial MOR tests indicate the strength of the fluid-mixed material exceeds the baseline property by more than 33 percent.

  2. Automated laser fabrication of cemented carbide components

    Science.gov (United States)

    Paul, C. P.; Khajepour, A.

    2008-07-01

    Automated Laser Fabrication (ALFa) is one of the most rapidly growing rapid-manufacturing technologies. It is similar to laser cladding at process level with different end applications. In general, laser cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn-out parts, while ALFa is capable of near net shaping the components by layer-by-layer deposition of the material directly from CAD model. This manufacturing method is very attractive for low volume manufacturing of hard materials, as near net shaping minimizes machining of hard material and subsequently brings significant savings in time and costly material. To date, many researchers have used this technology to fabricate components using various alloy steels, nickel-based alloys and cobalt-based alloys. In the present study, the work is extended to tungsten carbide cobalt (WC-Co) composites. A set of comprehensive experiments was carried out to study the effect of processing parameters during multi-layer fabrication. The process parameters were optimized for the component-level fabrication. Fabricated components were subjected to dye-penetrant testing, three-point flexural testing, hardness measurement, optical and scanning electron microscopy and X-ray diffraction analysis. The test results revealed that the laser-fabricated material was defect free and more ductile in nature. Thus, ALFa technology, not only produced the quality components, but also minimized machining of hard material and brought significant saving of time and costly WC-Co material.

  3. Methods of producing continuous boron carbide fibers

    Science.gov (United States)

    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.

  4. Thermoset precursor

    International Nuclear Information System (INIS)

    Yamamoto, Y.

    1983-04-01

    This invention pertains to a distinctive thermoset precursor which is prepared by mixing a resin composition (A) which can be hardened by ionizing radiation, and a resin composition (B) which can be hardened by heat but cannot be hardened by, or is resistant to, ionizing radiation, and by coating or impregnating a molding or other substrate with a sheet or film of this mixture and irradiating this with an ionizing radiation. The principal components of composition (A) and (B) can be the following: (1) an acrylate or methacrylate and an epoxy resin and an epoxy resin hardener; (2) an unsaturated polyester resin and epoxy resin and an epoxy resin hardener; (3) a diacrylate or dimethacrylate or polyethylene glycol and an epoxy resin; (4) an epoxy acrylates or epoxy methacrylate obtained by the addition reaction of epoxy resin and acrylic or methacrylic acid

  5. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

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

    2009-09-09

    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.

  6. Thermal response of plasma sprayed tungsten coating to high heat flux

    International Nuclear Information System (INIS)

    Liu, X.; Yang, L.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.; Xu, Z.

    2004-01-01

    In order to investigate the thermal response of tungsten coating on carbon and copper substrates by vacuum plasma spray (VPS) or inert gas plasma spray (IPS), annealing and cyclic heat load experiments of these coatings were conducted. It is indicated that the multi-layered tungsten and rhenium interface of VPS-W/CFC failed to act as a diffusion barrier at elevated temperature and tungsten carbides were developed after 1 h incubation time when annealing temperature was higher than 1600 deg. C. IPS-W/Cu and W/C without an intermediate bonding layer were failed by the detachment of the tungsten coating at 900 and 1200 deg. C annealing for several hours, respectively. Cyclic heat load of electron beam with 35 MW/m 2 and 3-s pulse duration indicated that IPS-W/Cu samples failed with local detachment of the tungsten coating within 200 cycles and IPS-W/C showed local cracks by 300 cycles, but VPS-W/CFC withstood 1000 cycles without visible damages. However, crack creation and propagation in VPS-W/CFC were also observed under higher heat load

  7. Production of propylene from 1-butene on highly active "bi-functional single active site" catalyst: Tungsten carbene-hydride supported on alumina

    KAUST Repository

    Mazoyer, Etienne

    2011-12-02

    1-Butene is transformed in a continuous flow reactor over tungsten hydrides precursor W-H/Al2O3, 1, giving a promising yield into propylene at 150 °C and different pressures. Tungsten carbene-hydride single active site operates as a "bi-functional catalyst" through 1-butene isomerization on W-hydride and 1-butene/2-butenes cross-metathesis on W-carbene. This active moiety is generated in situ at the initiation steps by insertion of 1-butene on tungsten hydrides precursor W-H/Al2O3, 1 followed by α-H and β-H abstraction. © 2011 American Chemical Society.

  8. Gleeble Testing of Tungsten Samples

    Science.gov (United States)

    2013-02-01

    length of the sample. Density measurements were also taken before and after testing using Archimedes principle . Samples were also tested at room...commonly seen in body centered cubic (BCC) metals and can be attributed to dislocation mobility theories (8). The basic principles are that the...processing of nano-tungsten and nano-tungsten alloys to achieve superior strength, ductility, and fracture toughness for room temperature applications

  9. Sliding wear of cemented carbides

    International Nuclear Information System (INIS)

    Engqvist, H.; Ederyd, S.; Uhrenius, B.; Hogmark, S.

    2001-01-01

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

  10. Micro creep mechanisms of tungsten

    International Nuclear Information System (INIS)

    Levoy, R.; Hugon, I.; Burlet, H.; Baillin, X.; Guetaz, L.

    2000-01-01

    Due to its high melting point (3410 deg C), tungsten offers good mechanical properties at elevated temperatures for several applications in non-oxidizing environment. The creep behavior of tungsten is well known between 1200 and 2500 deg C and 10 -3 to 10 -1 strain. However, in some applications when dimensional stability of components is required, these strains are excessive and it is necessary to know the creep behavior of the material for micro-strains (between 10 -4 and 10 -6 ). Methods and devices used to measure creep micro-strains are presented, and creep equations (Norton and Chaboche laws) were developed for wrought, annealed and recrystallized tungsten. The main results obtained on tungsten under low stresses are: stress exponent 1, symmetry of micro-strains in creep-tension and creep-compression, inverse creep (threshold stress), etc. TEM, SEM and EBSD studies allow interpretation of the micro-creep mechanism of tungsten under low stresses and low temperature (∼0.3 K) like the Harper-Dorn creep. In Harper-Dorn creep, micro-strains are associated with the density and the distribution of dislocations existing in the crystals before creep. At 975 deg C, the initial dislocation structure moves differently whether or not a stress is applied. To improve the micro-creep behavior of tungsten, a heat treatment is proposed to create the optimum dislocation structure. (authors)

  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. Low-chromium reduced-activation chromium-tungsten steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  13. Evaluation of the performance of coated and uncoated carbide tools in drilling thick CFRP/aluminium alloy stacks

    OpenAIRE

    MONTOYA , Maxime; CALAMAZ , Madalina; GEHIN , Daniel; GIROT , Franck

    2013-01-01

    This paper aims to establish the wear mechanisms of coated and uncoated tungsten carbide drills when drilling carbon fibre reinforced plastics (CFRP)/aluminium alloy (Al) stacks. During the drilling experiments, thrust forces were measured. A scanning electron microscope (SEM) and a numerical microscope, provided with a scanning device, were periodically used to analyse tool wear mechanisms and to measure wear progression of the tool cutting edges. For both coated and uncoated drills, abrasio...

  14. The high temperature impact response of tungsten and chromium

    Science.gov (United States)

    Zaretsky, E. B.; Kanel, G. I.

    2017-09-01

    The evolution of elastic-plastic shock waves has been studied in pure polycrystalline tungsten and chromium at room and elevated temperatures over propagation distances ranging from 0.05 to 3 mm (tungsten) and from 0.1 to 2 mm (chromium). The use of fused silica windows in all but one experiment with chromium and in several high temperature experiments with tungsten led to the need for performing shock and optic characterization of these windows over the 300-1200 K temperature interval. Experiments with tungsten and chromium samples showed that annealing of the metals transforms the initial ramping elastic wave into a jump-like wave, substantially increasing the Hugoniot elastic limits of the metals. With increased annealing time, the spall strength of the two metals slightly increases. Both at room and at high temperatures, the elastic precursor in the two metals decays in two distinct regimes. At propagation distances smaller than ˜1 mm (tungsten) or ˜0.5 mm (chromium), decay is fast, with the dislocation motion and multiplication being controlled by phonon viscous drag. At greater distances, the rate of decay becomes much lower, with control of the plastic deformation being passed to the thermally activated generation and motion of dislocation double-kinks. The stress at which this transition takes place virtually coincides with the Peierls stress τP of the active glide system. Analysis of the annealing effects in both presently and previously studied BCC metals (i.e., Ta, V, Nb, Mo, W, and Cr) and of the dependencies of their normalized Peierls stresses τP(θ) /τP(0 ) on the normalized temperature θ=T /Tm allows one to conclude that the non-planar, split into several glide planes, structure of the dislocation core in these metals is mainly responsible for their plastic deformation features.

  15. Elevated tungsten and cobalt in airborne particulates in Fallon, Nevada: Possible implications for the childhood leukemia cluster

    Energy Technology Data Exchange (ETDEWEB)

    Sheppard, Paul R. [Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 (United States)]. E-mail: sheppard@ltrr.arizona.edu; Ridenour, Gary [1055 S. Taylor St., Fallon, NV 89406 (United States); Speakman, Robert J. [Research Reactor Center, University of Missouri, Columbia, MO 65211 (United States); Witten, Mark L. [Department of Pediatrics, University of Arizona, Tucson, AZ 85721 (United States)

    2006-01-15

    Trace metal content was measured in airborne particulates in five towns located in west central Nevada with an emphasis on Fallon, where 16 cases of childhood leukemia were diagnosed recently. Airborne dust samples were collected using portable, high-volume particulate air samplers, and each filter was chemically analyzed by acid-dissolution, inductively coupled plasma mass spectroscopy. Tungsten was the most notable metal in Fallon dust, with cobalt of secondary but still important interest. Tungsten and cobalt were elevated in Fallon relative to comparison towns of west central Nevada, and within Fallon they co-varied closely temporally and spatially. These results were obtained and confirmed in two different collections during two different seasons of the year and using entirely different hardware and different types of filters. By weight of multiple lines of evidence, the source of tungsten and cobalt in airborne particulates in Fallon is probably not natural, but rather a hard-metal facility located in Fallon should tentatively be considered a candidate source of the airborne exposure of these metals within Fallon. Neither tungsten nor cobalt has yet to be definitively associated with childhood leukemia, but cobalt and tungsten carbide together are probably carcinogenic to humans. We concur with calls by others for more research in Fallon, and we recommend that cobalt be added into the toxicological studies, especially as an interactive factor with tungsten.

  16. Thermal reaction of SiC films with tungsten and tungsten-rhenium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Roger, J.; Le Petitcorps, Y. [Univ Bordeaux 1, Lab Composites Thermostruct, CNRS-SAFRAN-CEA-UB1, UMR 5801, F-33600 Pessac, (France); Roger, J.; Audubert, F. [CEA Cadarache, DEN/DEC/SPUA/LTEC, F-13108 St Paul Les Durance, (France)

    2008-07-01

    Solid-state reactions between SiC films and W-xRe (x = 0, 5 and 25 at%) substrates on thermal annealing between 1673 K and 1873 K for various durations have been investigated. SiC coatings were deposited on metallic wires by hot filament chemical vapour deposition (HFCVD) from a gas mixture of tetramethyl-silane (TMS) and hydrogen at 1373 K under normal pressure. The interface zones were characterized using scanning electron and optical microscopies, X-ray diffraction and electron microprobe microanalysis. All analyses reveal that SiC reacts with substrates. Various metal silicides and carbides were formed in layered reaction and the presence of these phases was confirmed by electron probe microanalysis. The effects of rhenium on the reactivity were established by the determination of growth kinetics deducted from the thicknesses of reaction zones as a function of annealing time. It has been found that an increase in the diffusion kinetics and activation energy with the quantity of rhenium in the tungsten wire. (authors)

  17. Synthesis and characterization of tungsten or calcium doped PZT ceramics

    International Nuclear Information System (INIS)

    Santos, D.M.; Caracas, L.B.; Noronha, R.G.; Santos, M.M.T. dos; Paiva-Santos, C.O.

    2009-01-01

    Pure and doped (tungsten or calcium) PZT ceramics were prepared by association of the polymeric precursor and partial oxalate method. The phase formation was investigated by thermal analysis (TG/DSC) and X-ray diffraction (XRD). The affect of W or Ca doping PZT and their electrical properties was evaluated. Substitution of W by Ti and Ca by Pb leads to an increase of Curie temperature and broadening of dielectric constant. A typical hysteresis loop was observed at room temperature and the remnant polarization was increased with the content of W and Ca. (author)

  18. Tungsten contamination in ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Polignano, M.L., E-mail: maria.polignano@st.com; Barbarossa, F.; Galbiati, A.; Magni, D.; Mica, I.

    2016-06-15

    In this paper the tungsten contamination in ion implantation processes is studied by DLTS analysis both in typical operating conditions and after contamination of the implanter by implantation of wafers with an exposed tungsten layer. Of course the contaminant concentration is orders of magnitude higher after contamination of the implanter, but in addition our data show that different mechanisms are active in a not contaminated and in a contaminated implanter. A moderate tungsten contamination is observed also in a not contaminated implanter, however in that case contamination is completely not energetic and can be effectively screened by a very thin oxide. On the contrary, the contamination due to an implantation in a previously contaminated implanter is reduced but not suppressed even by a relatively thick screen oxide. The comparison with SRIM calculations confirms that the observed deep penetration of the contaminant cannot be explained by a plain sputtering mechanism.

  19. A Review of Metal Injection Molding- Process, Optimization, Defects and Microwave Sintering on WC-Co Cemented Carbide

    Science.gov (United States)

    Shahbudin, S. N. A.; Othman, M. H.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

    2017-08-01

    This article is about a review of optimization of metal injection molding and microwave sintering process on tungsten cemented carbide produce by metal injection molding process. In this study, the process parameters for the metal injection molding were optimized using Taguchi method. Taguchi methods have been used widely in engineering analysis to optimize the performance characteristics through the setting of design parameters. Microwave sintering is a process generally being used in powder metallurgy over the conventional method. It has typical characteristics such as accelerated heating rate, shortened processing cycle, high energy efficiency, fine and homogeneous microstructure, and enhanced mechanical performance, which is beneficial to prepare nanostructured cemented carbides in metal injection molding. Besides that, with an advanced and promising technology, metal injection molding has proven that can produce cemented carbides. Cemented tungsten carbide hard metal has been used widely in various applications due to its desirable combination of mechanical, physical, and chemical properties. Moreover, areas of study include common defects in metal injection molding and application of microwave sintering itself has been discussed in this paper.

  20. Hydrogen chemisorption and oxidation of transition metal carbides

    International Nuclear Information System (INIS)

    Bethin, J.R.

    1979-01-01

    A study was made of the catalytic activity of WC, focusing on the possible influence of point defects. The chemisorption of H on WC and titanium oxycarbides was studied with differential scanning calorimetry. The catalytic activity of these materials for oxidation of H was determined by potentiostatic steady-state and potentiodynamic measurements in acid electrolyte. Compositions of WC surfaces were determined by x-ray photoemission and related to the catalytic behavior. Titanium oxycarbide surfaces were analyzed by Auger electron spectroscopy. Of the carbides tested only one WC preparation was able to chemisorb H. Both WC powders investigated catalyzed H oxidation with similar specific activities. Spectroscopic studies showed that the active surface of WC was a mixture of WO 3 and a carbon-deficient WC phase. This result indicates that carbon vacancies are the active sites in tungsten carbide. Theoretical models of a carbon vacancy surrounded by metal atoms suggested by calculations by other workers support this assignment and identify the important role of the W6s level. The measured value of the heat of chemisorption is consistent with the proposed model

  1. 49 CFR 173.338 - Tungsten hexafluoride.

    Science.gov (United States)

    2010-10-01

    ... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... shipped in an overpack that meets the provisions of § 173.40. (b) In place of the volumetric expansion... expansion test, must be condemned if removed from tungsten hexafluoride service. [ 74 FR 16143, Apr. 9, 2009...

  2. Compression and Associated Properties of Boron Carbide

    Science.gov (United States)

    2008-12-01

    Klandadze, G.I., and Eristavi, A.M., 1999: IR- Active Phonons and Structure Elements of Isotope - Enriched Boron Carbide, J. Sol. State Chem. 154, 79- 86...COMPRESSION AND ASSOCIATED PROPERTIES OF BORON CARBIDE D. P. Dandekar*and J. A. Ciezak Army Research Laboratory, APG, MD 21005 M. Somayazulu...of the observed loss of shear strength in boron carbide under plane shock wave compression to amorphization in boron carbide under triaxial stress

  3. Anodic oxide films on tungsten

    International Nuclear Information System (INIS)

    Di Paola, A.; Di Quarto, F.; Sunseri, C.

    1980-01-01

    Scanning electron microscopy was used to investigate the morphology of anodic oxide films on tungsten, obtained in various conditions of anodization. Studies were made of the growth of porous films, whose thickness increases with time and depends upon the current density. Temperature and electrolyte composition influence the film morphology. Gravimetric measurements of film dissolution at 70 0 C show that after a transient time, the rate of metal dissolution and that of film formation coincide. The porous films thicken because tungsten dissolves as WO 2 2+ and precipitates as WO 3 .H 2 O. (author)

  4. Method of synthesizing tungsten nanoparticles

    Science.gov (United States)

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  5. 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.

  6. New Icosahedral Boron Carbide Semiconductors

    Science.gov (United States)

    Echeverria Mora, Elena Maria

    Novel semiconductor boron carbide films and boron carbide films doped with aromatic compounds have been investigated and characterized. Most of these semiconductors were formed by plasma enhanced chemical vapor deposition. The aromatic compound additives used, in this thesis, were pyridine (Py), aniline, and diaminobenzene (DAB). As one of the key parameters for semiconducting device functionality is the metal contact and, therefore, the chemical interactions or band bending that may occur at the metal/semiconductor interface, X-ray photoemission spectroscopy has been used to investigate the interaction of gold (Au) with these novel boron carbide-based semiconductors. Both n- and p-type films have been tested and pure boron carbide devices are compared to those containing aromatic compounds. The results show that boron carbide seems to behave differently from other semiconductors, opening a way for new analysis and approaches in device's functionality. By studying the electrical and optical properties of these films, it has been found that samples containing the aromatic compound exhibit an improvement in the electron-hole separation and charge extraction, as well as a decrease in the band gap. The hole carrier lifetimes for each sample were extracted from the capacitance-voltage, C(V), and current-voltage, I(V), curves. Additionally, devices, with boron carbide with the addition of pyridine, exhibited better collection of neutron capture generated pulses at ZERO applied bias, compared to the pure boron carbide samples. This is consistent with the longer carrier lifetimes estimated for these films. The I-V curves, as a function of external magnetic field, of the pure boron carbide films and films containing DAB demonstrate that significant room temperature negative magneto-resistance (> 100% for pure samples, and > 50% for samples containing DAB) is possible in the resulting dielectric thin films. Inclusion of DAB is not essential for significant negative magneto

  7. Hydrogen retention properties of polycrystalline tungsten and helium irradiated tungsten

    International Nuclear Information System (INIS)

    Hino, T.; Koyama, K.; Yamauchi, Y.; Hirohata, Y.

    1998-01-01

    The hydrogen retention properties of a polycrystalline tungsten and tungsten irradiated by helium ions with an energy of 5 keV were examined by using an ECR ion irradiation apparatus and a technique of thermal desorption spectroscopy, TDS. The polycrystalline tungsten was irradiated at RT with energetic hydrogen ions, with a flux of 10 15 H cm -2 and an energy of 1.7 keV up to a fluence of 5 x 10 18 H cm -2 . Subsequently, the amount of retained hydrogen was measured by TDS. The heating temperature was increased from RT to 1000 C, and the heating rate was 50 C min -1 . Below 1000 C, two distinct hydrogen desorption peaks were observed at 200 C and 400 C. The retained amount of hydrogen was observed to be five times smaller than that of graphite, but the concentration in the implantation layer was comparable with that of graphite. Also, the polycrystalline tungsten was irradiated with 5 keV helium ions up to a fluence of 1.4 x 10 18 He cm -2 , and then re-irradiated with 1.7 keV hydrogen ions. The amount of retained hydrogen in this later experiment was close to the value in the case without prior helium ion irradiation. However, the amount of hydrogen which desorbed around the low temperature peak, 200 C, was largely enhanced. The desorption amount at 200 C saturated for the helium fluence of more than 5 x 10 17 He cm -2 . The present data shows that the trapping state of hydrogen is largely changed by the helium ion irradiation. Additionally, 5 keV helium ion irradiation was conducted on a sample pre-implanted with hydrogen ions to simulate a helium ion impact desorption of hydrogen retained in tungsten. The amount of the hydrogen was reduced as much as 50%. (orig.)

  8. Closed-cage tungsten oxide clusters in the gas phase.

    Science.gov (United States)

    Singh, D M David Jeba; Pradeep, T; Thirumoorthy, Krishnan; Balasubramanian, Krishnan

    2010-05-06

    During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) mass spectrometry, we observed several anionic W-O clusters. Three distinct species, W(6)O(19)(-), W(13)O(29)(-), and W(14)O(32)(-), stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W(13) and W(14) clusters were observed for the first time in the gas phase.

  9. High heat flux testing of TiC coated molybdenum with a tungsten intermediate layer

    International Nuclear Information System (INIS)

    Fujitsuka, Masakazu; Fukutomi, Masao; Okada, Masatoshi

    1988-01-01

    The use of low atomic number (Z) material coatings for fusion reactor first-wall components has proved to be a valuable technique to reduce the plasma radiation losses. Molybdenum coated with titanium carbide is considered very promising since it has a good capability of receiving heat from the plasma. An interfacial reaction between the TiC film and the molybdenum substrate, however, causes a severe deterioration of the film at elevated temperatures. In order to solve this problem a TiC coated molybdenum with an intermediate tungsten layer was developed. High temperature properties of this material was evaluated by a newly devised electron beam heating apparatus. TiC coatings prepared on a vacuum-heat-treated molybdenum with a tungsten intermediate layer showed good high temperature stability and survived 2.0 s pulses of heating at a power density as high as 53 MW/m 2 . The melt area of the TiC coatings in high heat flux testings also markedly decreased when a tungsten intermediate layer was applied. The melting mechanism of the TiC coatings with and without a tungsten intermediate layer was discussed by EPMA measurements. (author)

  10. HYDROGEN VACANCY INTERACTION IN TUNGSTEN

    NARCIS (Netherlands)

    FRANSENS, [No Value; ELKERIEM, MSA; PLEITER, F

    1991-01-01

    Hydrogen-vacancy interaction in tungsten was investigated by means of the perturbed angular correlation technique, using the isotope In-111 as a probe. Hydrogen trapping at an In-111-vacancy cluster manifests itself as a change of the local electric field gradient, which gives rise to an observable

  11. Vacuum Gas Tungsten Arc Welding

    Science.gov (United States)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  12. The effects of ion implantation upon the mechanical properties of metals and cemented carbides

    International Nuclear Information System (INIS)

    Dearnaley, G.

    1982-01-01

    Ion implantation has been successful in producing significant improvements in the wear resistance and fatigue endurance of metals such as steel, titanium, copper and electrodeposited chromium. Models to explain this behaviour in terms of the pinning of mobile dislocations are presented. Friction coefficients are also modified by ion implantation, and in the composite material cobalt-cemented tungsten carbide this effect is very strong, and is accompanied by a reduction in wear. Examples of the range of tools which have been improved by nitrogen ion implantation are given, and the review concludes with a description of the equipment developed for the industrial application of this process. (author)

  13. Determination of emissivity coefficient of heat-resistant super alloys and cemented carbide

    Directory of Open Access Journals (Sweden)

    Kieruj Piotr

    2016-12-01

    Full Text Available This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples’ temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.

  14. 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

    2016-04-05

    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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Tensile behaviour of drawn tungsten wire used in tungsten fibre-reinforced tungsten composites

    Science.gov (United States)

    Riesch, J.; Feichtmayer, A.; Fuhr, M.; Almanstötter, J.; Coenen, J. W.; Gietl, H.; Höschen, T.; Linsmeier, Ch; Neu, R.

    2017-12-01

    In tungsten fibre-reinforced tungsten composites (Wf/W) the brittleness problem of tungsten is solved by utilizing extrinsic toughening mechanisms. The properties of the composite are very much related to the properties of the drawn tungsten wire used as fibre reinforcements. Its high strength and capability of ductile deformation are ideal properties facilitating toughening of Wf/W. Tensile tests have been used for determining mechanical properties and study the deformation and the fracture behaviour of the wire. Tests of as-fabricated and straightened drawn wires with a diameter between 16 and 150 μm as well as wire electrochemically thinned to a diameter of 5 μm have been performed. Engineering stress–strain curves and a microscopic analysis are presented with the focus on the ultimate strength. All fibres show a comparable stress–strain behaviour comprising necking followed by a ductile fracture. A reduction of the diameter by drawing leads to an increase of strength up to 4500 MPa as a consequence of a grain boundary hardening mechanism. Heat treatment during straightening decreases the strength whereas electrochemical thinning has no significant impact on the mechanical behaviour.

  16. Bundled tungsten oxide nanowires under thermal processing

    International Nuclear Information System (INIS)

    Sun Shibin; Zhao Yimin; Xia Yongde; Zhu Yanqiu; Zou Zengda; Min Guanghui

    2008-01-01

    Ultra-thin W 18 O 49 nanowires were initially obtained by a simple solvothermal method using tungsten chloride and cyclohexanol as precursors. Thermal processing of the resulting bundled nanowires has been carried out in air in a tube furnace. The morphology and phase transformation behavior of the as-synthesized nanowires as a function of annealing temperature have been characterized by x-ray diffraction and electron microscopy. The nanostructured bundles underwent a series of morphological evolution with increased annealing temperature, becoming straighter, larger in diameter, and smaller in aspect ratio, eventually becoming irregular particles with size up to 5 μm. At 500 deg. C, the monoclinic W 18 O 49 was completely transformed to monoclinic WO 3 phase, which remains stable at high processing temperature. After thermal processing at 400 deg. C and 450 deg. C, the specific surface areas of the resulting nanowires dropped to 110 m 2 g -1 and 66 m 2 g -1 respectively, compared with that of 151 m 2 g -1 for the as-prepared sample. This study may shed light on the understanding of the geometrical and structural evolution occurring in nanowires whose working environment may involve severe temperature variations

  17. A Silica-Supported Monoalkylated Tungsten Dioxo Complex Catalyst for Olefin Metathesis

    KAUST Repository

    Maity, Niladri

    2018-02-15

    A well-defined silica-supported monoalkylated tungsten dioxo complex [(Si-O-)W(=O)(CH-Bu)] was prepared by treatment of highly dehydroxylated silica (SiO: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt][W(=O)(CH-Bu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.

  18. Metal Immiscibility Route to Synthesis of Ultrathin Carbides, Borides, and Nitrides.

    Science.gov (United States)

    Wang, Zixing; Kochat, Vidya; Pandey, Prafull; Kashyap, Sanjay; Chattopadhyay, Soham; Samanta, Atanu; Sarkar, Suman; Manimunda, Praveena; Zhang, Xiang; Asif, Syed; Singh, Abhisek K; Chattopadhyay, Kamanio; Tiwary, Chandra Sekhar; Ajayan, Pulickel M

    2017-08-01

    Ultrathin ceramic coatings are of high interest as protective coatings from aviation to biomedical applications. Here, a generic approach of making scalable ultrathin transition metal-carbide/boride/nitride using immiscibility of two metals is demonstrated. Ultrathin tantalum carbide, nitride, and boride are grown using chemical vapor deposition by heating a tantalum-copper bilayer with corresponding precursor (C 2 H 2 , B powder, and NH 3 ). The ultrathin crystals are found on the copper surface (opposite of the metal-metal junction). A detailed microscopy analysis followed by density functional theory based calculation demonstrates the migration mechanism, where Ta atoms prefer to stay in clusters in the Cu matrix. These ultrathin materials have good interface attachment with Cu, improving the scratch resistance and oxidation resistance of Cu. This metal-metal immiscibility system can be extended to other metals to synthesize metal carbide, boride, and nitride coatings. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Testing Boron Carbide and Silicon Carbide under Triaxial Compression

    Science.gov (United States)

    Anderson, Charles; Chocron, Sidney; Nicholls, Arthur

    2011-06-01

    Boron Carbide (B4C) and silicon carbide (SiC-N) are extensively used as armor materials. The strength of these ceramics depends mainly on surface defects, hydrostatic pressure and strain rate. This article focuses on the pressure dependence and summarizes the characterization work conducted on intact and predamaged specimens by using compression under confinement in a pressure vessel and in a thick steel sleeve. The techniques used for the characterization will be described briefly. The failure curves obtained for the two materials will be presented, although the data are limited for SiC. The data will also be compared to experimental data from Wilkins (1969), and Meyer and Faber (1997). Additionally, the results will be compared with plate-impact data.

  20. Tungsten monocrystal cutting without distortion

    International Nuclear Information System (INIS)

    Dudkin, A.Yu.; Matveev, I.V.; Cheremisin, S.M.

    1982-01-01

    Electrolyte with high electric current localization, containing 1-3 % KOH and 2-10 % NH 3 , is suggested to use for electrochemical cutting of tungsten. A cutting device is described which includes a cathode feed mechanism based on electric heating and a circuit of automatic control of an interelectrode gap. Laue patterns obtained from a cut surface are practically the same as ones from the initial monocrystal

  1. Adsorption and condensation of bismuth on tungsten

    International Nuclear Information System (INIS)

    Radon, T.; Sidorski, Z.

    1979-01-01

    The bismuth-tungsten system was studied by means of field emission microscopy. The average work function changes induced by the bismuth adsorption were measured for different amounts of adsorbed bismuth. It was found that the adsorption of bismuth changes the work function of tungsten only slightly. The penetration of bismuth into the tungsten substrate was observed. The growth of bismuth single crystals was studied when bismuth was deposited with a rate of about 6 monolayers per minute onto the tungsten substrate and kept at 470 K. Bismuth single crystals with two-fold symmetry occurred most often on the (100) tungsten planes. On the (111) tungsten plane bismuth crystals with three-fold symmetry were observed. An explanation of the observed phenomena is proposed. (Auth.)

  2. 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

  3. Anisotropic growth mechanism of tungsten diselenide domains using chemical vapor deposition method

    Science.gov (United States)

    Lee, Yoobeen; Jeong, Heekyung; Park, Yi-Seul; Han, Seulki; Noh, Jaegeun; Lee, Jin Seok

    2018-02-01

    Anisotropic transition metal dichalcogenide (TMDC) domains have stimulated a growing interest mainly due to their electronic properties that depend on the size, shape, and edge structures of the domains. In this work, we investigated the anisotropic morphogenesis and edge terminations of tungsten diselenide (WSe2) domains grown on sapphire substrates by chemical vapor deposition (CVD) using tungsten oxide (WO3) and selenium (Se) powders as precursors. We varied the amount of Se powder and growth temperature during the CVD process, which in turn caused variations in the growth mechanism and kinetic energies of precursors. We succeeded in synthesizing hexagonal, square, circular, and triangular anisotropic WSe2 domains. They were characterized using scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) analyses, and atomic force microscopy (AFM). Furthermore, we proposed the growth mechanism of anisotropic WSe2 domains with different edge terminations based on experimental observations through scanning tunneling microscope (STM).

  4. Bimetallic Carbides-Based Nanocomposite as Superior Electrocatalyst for Oxygen Evolution Reaction.

    Science.gov (United States)

    Tang, Yu-Jia; Liu, Chun-Hui; Huang, Wei; Wang, Xiao-Li; Dong, Long-Zhang; Li, Shun-Li; Lan, Ya-Qian

    2017-05-24

    The development of highly efficient and low-cost oxygen evolution electrocatalysts is extremely imperative for the new energy technology. Transition metal carbides have been investigated as remarkable hydrogen evolution reaction (HER) electrocatalysts but undesired oxygen evolution reaction (OER) electrocatalysts and need further study. Here, a cobalt-molybdenum-based bimetallic carbide coated by N-doped porous carbon and anchored on N-doped reduced graphene oxide film (Co 6 Mo 6 C 2 /NCRGO) is synthesized by directly carbonizing the Co-doped polyoxometalate/conductive polymer/graphene oxide (Co-PCG) precursors. The precise control of the Co/Mo molar ratio in the Co-PCG precursor is of critical importance to synthesize pure phase bimetallic carbide of Co 6 Mo 6 C 2 . As the highly active and robust OER electrocatalyst, the Co 6 Mo 6 C 2 /NCRGO composite exhibits excellent activity in alkaline solution, affording a low overpotential of 260 mV versus RHE at 10 mA cm -2 , a small Tafel slope of 50 mV dec -1 , as well as long-term stability. The superior OER performances are strongly associated with the active Co 6 Mo 6 C 2 particles, polypyrrole (PPy)-derived N-doped porous carbon, and the conductive RGO films. Remarkably, it is the first evidence that the bimetallic carbides were used as the OER catalysts with such high OER activity.

  5. 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.

  6. 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.

  7. Abrasive slurry composition for machining boron carbide

    Science.gov (United States)

    Duran, Edward L.

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  8. Influence of Carbon Content on the Crystallographic Structure of Boron Carbide Films

    OpenAIRE

    Conde, O.; Silvestre, A. J.; Oliveira, J. C.

    2002-01-01

    Boron carbide thin films were synthesised by laser-assisted chemical vapour deposition (LCVD), using a CO2 laser beam and boron trichloride and methane as precursors. Boron and carbon contents were measured by electron probe microanalysis (EPMA). Microstructural analysis was carried out by Raman microspectroscopy and glancing incidence X-ray diffraction (GIXRD) was used to study the crystallographic structure and to determine the lattice parameters of the polycrystalline films. The rhombohedr...

  9. Natural cotton as precursor for the refractory boron carbide—a hydrothermal synthesis and characterization

    Science.gov (United States)

    Saritha Devi, H. V.; Swapna, M. S.; Raj, Vimal; Ambadas, G.; Sankararaman, S.

    2018-01-01

    Boron carbide (B4C) is an excellent covalent carbide that finds applications in industries and nuclear power plants. The present synthesis methods of boron carbide are expensive and involve the use of toxic chemicals that adversely affect environment. In the present work, we report for the first time the use of the hydrothermal method for converting the cellulose from cotton as the carbon precursor for B4C. The carbon precursor is converted into functionalized porous carbonaceous material by hydrothermal treatment followed by sodium borohydride. It is further treated with boric acid to make it a B4C precursor. The precursor is characterized by UV-visible diffuse reflectance, Raman, Fourier transform infrared, photoluminescent and energy dispersive spectroscopy. The morphology and structure analysis is carried out using field emission scanning electron microscopy and x-ray diffraction techniques. The results of structural and optical characterization of the sample synthesized are compared with the commercial B4C. The thermal stability of the sample is studied by thermogravimetric analysis. The sample annealed at 700 °C is found to be B4C devoid of amorphous carbon with a yield of 44.7%. The analysis reveals the formation of boron carbide from the sample.

  10. Effect of SiC Nanowhisker on the Microstructure and Mechanical Properties of WC-Ni Cemented Carbide Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Xiaoyong Ren

    2014-01-01

    Full Text Available Ultrafine tungsten carbide-nickel (WC-Ni cemented carbides with varied fractions of silicon carbide (SiC nanowhisker (0–3.75 wt.% were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC and tantalum carbide (TaC as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  11. Development of quantitative atomic modeling for tungsten transport study Using LHD plasma with tungsten pellet injection

    International Nuclear Information System (INIS)

    Murakami, I.; Sakaue, H.A.; Suzuki, C.; Kato, D.; Goto, M.; Tamura, N.; Sudo, S.; Morita, S.

    2014-10-01

    Quantitative tungsten study with reliable atomic modeling is important for successful achievement of ITER and fusion reactors. We have developed tungsten atomic modeling for understanding the tungsten behavior in fusion plasmas. The modeling is applied to the analysis of tungsten spectra observed from currentless plasmas of the Large Helical Device (LHD) with tungsten pellet injection. We found that extreme ultraviolet (EUV) lines of W 24+ to W 33+ ions are very sensitive to electron temperature (Te) and useful to examine the tungsten behavior in edge plasmas. Based on the first quantitative analysis of measured spatial profile of W 44+ ion, the tungsten concentration is determined to be n(W 44+ )/n e = 1.4x10 -4 and the total radiation loss is estimated as ∼4 MW, of which the value is roughly half the total NBI power. (author)

  12. Effect of metallic coating on the properties of copper-silicon carbide composites

    Science.gov (United States)

    Chmielewski, M.; Pietrzak, K.; Teodorczyk, M.; Nosewicz, S.; Jarząbek, D.; Zybała, R.; Bazarnik, P.; Lewandowska, M.; Strojny-Nędza, A.

    2017-11-01

    In the presented paper a coating of SiC particles with a metallic layer was used to prepare copper matrix composite materials. The role of the layer was to protect the silicon carbide from decomposition and dissolution of silicon in the copper matrix during the sintering process. The SiC particles were covered by chromium, tungsten and titanium using Plasma Vapour Deposition method. After powder mixing of components, the final densification process via Spark Plasma Sintering (SPS) method at temperature 950 °C was provided. The almost fully dense materials were obtained (>97.5%). The microstructure of obtained composites was studied using scanning electron microscopy as well as transmission electron microscopy. The microstructural analysis of composites confirmed that regardless of the type of deposited material, there is no evidence for decomposition process of silicon carbide in copper. In order to measure the strength of the interface between ceramic particles and the metal matrix, the micro tensile tests have been performed. Furthermore, thermal diffusivity was measured with the use of the laser pulse technique. In the context of performed studies, the tungsten coating seems to be the most promising solution for heat sink application. Compared to pure composites without metallic layer, Cu-SiC with W coating indicate the higher tensile strength and thermal diffusitivy, irrespective of an amount of SiC reinforcement. The improvement of the composite properties is related to advantageous condition of Cu-SiC interface characterized by well homogenity and low porosity, as well as individual properties of the tungsten coating material.

  13. Tungsten: A Preliminary Environmental Risk Assessment

    Science.gov (United States)

    2011-05-01

    Effects on Flora & Fauna • Geochemistry • Soil microbial communities • Plants • Soil invertebrates • Higher order animals • Additional studies BUILDING...Bioaccumulation of Tungsten in Plants Natural Sources • Trees & shrubs in Rocky Mountain region, USA • Siberian pine, willows, mosses & lichen in tungsten

  14. Structures and transitions in tungsten grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Frolov, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zhu, Q. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Marian, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rudd, R. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-02-07

    The objective of this study is to develop a computational methodology to predict structure, energies of tungsten grain boundaries as a function of misorientation and inclination. The energies and the mobilities are the necessary input for thermomechanical model of recrystallization of tungsten for magnetic fusion applications being developed by the Marian Group at UCLA.

  15. International strategic mineral issues summary report: tungsten

    Science.gov (United States)

    Werner, Antony B.T.; Sinclair, W. David; Amey, Earle B.

    1998-01-01

    Scheelite and wolframite are the principal minerals currently mined for tungsten. Both occur in hard-rock deposits; wolframite is also recovered from placer deposits. Most current mine production of tungsten is from vein/stockwork, skarn, porphyry, and strata-bound deposits. Minor amounts are produced from disseminated, pegmatite, breccia, and placer deposits.

  16. Quenching and recovery experiments on tungsten

    International Nuclear Information System (INIS)

    Rasch, K.D.; Siegel, R.W.; Schultz, H.

    1976-01-01

    A short summary is given of new results concerning transmission electron microscopy and resistivity measurements on quenched tungsten. These results give evidence for the first time that the quenching and annealing of high purity tungsten leads to vacancy--defect clustering resulting in small voids observable in the electron microscope. 21 references

  17. Development of Tungsten Based Composites

    Science.gov (United States)

    1992-02-01

    CONTENTS Section Title Page 1 INTRODUCTION & SUMMARY .............................. 1 2 MATERIAL SELECTION .................................. 3 3...Metallographic Examination .. 41 - iv - 1. INTRODUCTION & SUMMARY This is the. Final Report on a Phase I SBIR Program entitled "Development of Tungsten Based...m = - -𔃺 S (l- 1- =11 = (t) 011CU ’a . 4) woj .- :2 01w c L .0 u .-. 0C 0 goa - L 0d MCDM . 3 -X - z 1 m- L. S.1 MCDM -z3-2: S - m 1 o. 01 In 0,10Lnw

  18. Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition.

    Science.gov (United States)

    Walock, Michael J; Rahil, Issam; Zou, Yujiao; Imhoff, Luc; Catledge, Shane A; Nouveau, Corinne; Stanishevsky, Andrei V

    2012-06-01

    Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.

  19. Low temperature study of nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Tashmetov, M.Yu.

    2005-05-01

    By low temperature neutron diffraction method was studied structure in nonstoichiometric titanium carbide from room temperature up to 12K. It is found of low temperature phase in titanium carbide- TiC 0.71 . It is established region and borders of this phase. It is determined change of unit cell parameter. (author)

  20. 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.

  1. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    Unknown

    tions ranging from kiln furniture to membrane material. Keywords. Microwave sintering; biaxial flexure; silicon carbide. 1. Introduction. Silicon carbide (SiC) ceramics is a very well known candidate material for a structural application. However, due to (i) poor densification due to highly directional bonding, (ii) susceptibility of ...

  2. Compression and associated properties of boron carbide

    Science.gov (United States)

    Ciezak, Jennifer; Dandekar, Dattatraya

    2009-06-01

    The observed loss of shear strength of boron carbide around 22 GPa has been attributed to presence of amorphous material in the shock recovered, and statically indented and pressurized boron carbide. The present work presents a more direct association of the observed loss of shear strength in boron carbide under plane shock wave compression to amorphization in boron carbide under triaxial stress compression. This evidence is obtained from in-situ measurement of Raman, and infrared vibrational spectra of boron carbide confined in a Diamond Anvil Cell (DAC) under hydrostatic and non-hydrostatic pressures. X-ray-diffraction measurements do show a shift in the compression of boron carbide around 27 GPa. However, X-ray diffraction measurements indicate that the amorphization does not extend to micron scale, as there is no evidence of a loss of crystallinity in the recorded diffraction pattern of boron carbide to 47 GPa. Our work shows that shear plays a very dominant role in the stress-induced amorphization of boron carbide.

  3. 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...

  4. PIXE characterization of by-products resulting from the zinc recycling of industrial cemented carbides

    Science.gov (United States)

    Freemantle, C. S.; Sacks, N.; Topic, M.; Pineda-Vargas, C. A.

    2015-11-01

    By-product materials of the widely used zinc recycling process of cemented carbides have been studied. Scanning electron microscopy and micro-PIXE techniques have identified elemental concentrations, distributions and purity of by-product materials from an industrial zinc recycling plant. Cobalt surface enrichment, lamellar microstructures of varying composition, including alternating tungsten carbide (WC) grains and globular cobalt, and regions of excess zinc contamination were found in materials with incomplete zinc penetration. Liquid Co-Zn formation occurred above 72 wt.% Zn at the furnace temperature of 930 °C, and was extracted towards the surface of poorly zinc infiltrated material, primarily by the vacuum used for zinc distillation. Surface enrichment was not observed in material that was zinc infiltrated to the sample center, which was more friable and exhibited more homogeneous porosity and elemental concentrations. The result of incomplete zinc infiltration was an enriched surface zone of up to 60 wt.% Co, compared to an original sample composition of ∼10-15 wt.% Co. The impact on resulting powders could be higher or inhomogeneous cobalt content, as well as unacceptably high zinc concentrations. PIXE has proven it can be a powerful technique for solving industrial problems in the cemented carbide cutting tool industry, by identifying trace elements and their locations (such as Zn to 0.1 wt.% accuracy), as well as the distribution of major elements within WC-Co materials.

  5. PIXE characterization of by-products resulting from the zinc recycling of industrial cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Freemantle, C.S. [School of Chemical & Metallurgical Engineering and DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, P/Bag 3, Wits 2050 (South Africa); Pilot Tools (Pty) (Ltd), P.O. Box 27420, Benrose 2011 (South Africa); Sacks, N. [School of Chemical & Metallurgical Engineering and DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, P/Bag 3, Wits 2050 (South Africa); Topic, M. [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129 (South Africa); Pineda-Vargas, C.A. [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129 (South Africa); Faculty of Health & Wellness Sciences, CPUT, Bellville (South Africa)

    2015-11-15

    By-product materials of the widely used zinc recycling process of cemented carbides have been studied. Scanning electron microscopy and micro-PIXE techniques have identified elemental concentrations, distributions and purity of by-product materials from an industrial zinc recycling plant. Cobalt surface enrichment, lamellar microstructures of varying composition, including alternating tungsten carbide (WC) grains and globular cobalt, and regions of excess zinc contamination were found in materials with incomplete zinc penetration. Liquid Co–Zn formation occurred above 72 wt.% Zn at the furnace temperature of 930 °C, and was extracted towards the surface of poorly zinc infiltrated material, primarily by the vacuum used for zinc distillation. Surface enrichment was not observed in material that was zinc infiltrated to the sample center, which was more friable and exhibited more homogeneous porosity and elemental concentrations. The result of incomplete zinc infiltration was an enriched surface zone of up to 60 wt.% Co, compared to an original sample composition of ∼10–15 wt.% Co. The impact on resulting powders could be higher or inhomogeneous cobalt content, as well as unacceptably high zinc concentrations. PIXE has proven it can be a powerful technique for solving industrial problems in the cemented carbide cutting tool industry, by identifying trace elements and their locations (such as Zn to 0.1 wt.% accuracy), as well as the distribution of major elements within WC–Co materials.

  6. The DAMPE silicon tungsten tracker

    CERN Document Server

    Gallo, Valentina; Asfandiyarov, R; Azzarello, P; Bernardini, P; Bertucci, B; Bolognini, A; Cadoux, F; Caprai, M; Domenjoz, M; Dong, Y; Duranti, M; Fan, R; Franco, M; Fusco, P; Gargano, F; Gong, K; Guo, D; Husi, C; Ionica, M; Lacalamita, N; Loparco, F; Marsella, G; Mazziotta, M N; Mongelli, M; Nardinocchi, A; Nicola, L; Pelleriti, G; Peng, W; Pohl, M; Postolache, V; Qiao, R; Surdo, A; Tykhonov, A; Vitillo, S; Wang, H; Weber, M; Wu, D; Wu, X; Zhang, F; De Mitri, I; La Marra, D

    2017-01-01

    The DArk Matter Particle Explorer (DAMPE) satellite has been successfully launched on the 17th December 2015. It is a powerful space detector designed for the identification of possible Dark Matter signatures thanks to its capability to detect electrons and photons with an unprecedented energy resolution in an energy range going from few GeV up to 10 TeV. Moreover, the DAMPE satellite will contribute to a better understanding of the propagation mechanisms of high energy cosmic rays measuring the nuclei flux up to 100 TeV. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon-tungsten tracker-converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is made of twelve layers of single-sided AC-coupled silicon micro-strip detectors for a total silicon area of about 7 $m^2$ . To promote the conversion of incident photons into electron-positron pairs, tungsten foils are inserted into the supporting structure. In this document, a detailed description of the STK constructi...

  7. Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

    Science.gov (United States)

    Riesch, J.; Han, Y.; Almanstötter, J.; Coenen, J. W.; Höschen, T.; Jasper, B.; Zhao, P.; Linsmeier, Ch; Neu, R.

    2016-02-01

    For the next step fusion reactor the use of tungsten is inevitable to suppress erosion and allow operation at elevated temperature and high heat loads. Tungsten fibre-reinforced composites overcome the intrinsic brittleness of tungsten and its susceptibility to operation embrittlement and thus allow its use as a structural as well as an armour material. That this concept works in principle has been shown in recent years. In this contribution we present a development approach towards its use in a future fusion reactor. A multilayer approach is needed addressing all composite constituents and manufacturing steps. A huge potential lies in the optimization of the tungsten wire used as fibre. We discuss this aspect and present studies on potassium doped tungsten wire in detail. This wire, utilized in the illumination industry, could be a replacement for the so far used pure tungsten wire due to its superior high temperature properties. In tensile tests the wire showed high strength and ductility up to an annealing temperature of 2200 K. The results show that the use of doped tungsten wire could increase the allowed fabrication temperature and the overall working temperature of the composite itself.

  8. Effect of an intermediate tungsten layer on thermal properties of TiC coatings ion plated onto molybdenum

    International Nuclear Information System (INIS)

    Fukutomi, M.; Fujitsuka, M.; Shikama, T.; Okada, M.

    1985-01-01

    Among the various low-Z coating-substrate systems proposed for fusion reactor first-wall applications, molybdenum coated with titanium carbide is considered very promising since it has a good capability of receiving heat from the plasma. The thermal stabilities of TiC layers ion plated onto the molybdenum substrate are discussed with particular reference to the interfacial reaction between the TiC coating and molybdenum. The deposition of an intermediate tungsten layer was found to be very effective in suppressing the formation of reaction layers, resulting in a marked improvement in thermal stabilities of TiC--Mo systems. Thermal shock test using a pulsed electron beam showed that the TiC coatings remained adherent to the molybdenum substrates during energy depositions high enough to melt the substrates within the area of beam deposition. The melt area of the TiC coatings apparently decreased when a tungsten intermediate layer was applied

  9. Development of quantitative atomic modeling for tungsten transport study using LHD plasma with tungsten pellet injection

    Science.gov (United States)

    Murakami, I.; Sakaue, H. A.; Suzuki, C.; Kato, D.; Goto, M.; Tamura, N.; Sudo, S.; Morita, S.

    2015-09-01

    Quantitative tungsten study with reliable atomic modeling is important for successful achievement of ITER and fusion reactors. We have developed tungsten atomic modeling for understanding the tungsten behavior in fusion plasmas. The modeling is applied to the analysis of tungsten spectra observed from plasmas of the large helical device (LHD) with tungsten pellet injection. We found that extreme ultraviolet (EUV) emission of W24+ to W33+ ions at 1.5-3.5 nm are sensitive to electron temperature and useful to examine the tungsten behavior in edge plasmas. We can reproduce measured EUV spectra at 1.5-3.5 nm by calculated spectra with the tungsten atomic model and obtain charge state distributions of tungsten ions in LHD plasmas at different temperatures around 1 keV. Our model is applied to calculate the unresolved transition array (UTA) seen at 4.5-7 nm tungsten spectra. We analyze the effect of configuration interaction on population kinetics related to the UTA structure in detail and find the importance of two-electron-one-photon transitions between 4p54dn+1- 4p64dn-14f. Radiation power rate of tungsten due to line emissions is also estimated with the model and is consistent with other models within factor 2.

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

    Science.gov (United States)

    Kelly, Thomas Glenn

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

  11. Electron stimulated desorption study of oxygen adsorption on tungsten

    International Nuclear Information System (INIS)

    Prince, R.H.; Floyd, G.R.

    1978-01-01

    The adsorption of oxygen on a polycrystalline tungsten surface at approximately 800 K has been studied by means of electron stimulated desorption (ESD). Although precision gas dosing was not employed, the initial sticking probability for dissociative adsorption appears to be essentially unity, while the variation with coverage suggests that a high degree of order exists and that precursor state kinetics are significant. A most noticeable and reproducible discontinuity in ESD parameters occurs at a fractional coverage theta approximately 0.8 (exposure approximately 1.4 X 10 15 molecules/cm 2 incident) which is interpreted as an order-disorder transition within a single (β 1 ) chemisorption state, and results in an increase in the ionic desorption cross-section by a factor of approximately 1.26. A discussion of the adsorption kinetics and the disorder transition is given in terms of current models of dissociative adsoption which include the effects of nearest neighbour lateral interactions. (Auth.)

  12. Effects of heat treatment on mechanical properties and microstructure of tungsten fi ber reinforced grey cast iron matrix composites

    Directory of Open Access Journals (Sweden)

    Peng jianHong

    2009-11-01

    Full Text Available In this study, grey cast iron matrix composites reinforced by different volume fractions of tungsten fibers (Vr = 0.95 %, 1.90 %, 2.85 %, 3.80 % were investigated in as-cast and under the heat treatment temperatures of 1,000℃ and 1,100℃. The microstructure and mechanical properties of the composites were analyzed and tested by means of SEM, micro-hardness tester and three-point bend testing. The results show that with increasing of the volume fraction of tungsten fibers, the composites reinforced by the tungsten fiber have higher fl exural strength and modulus than that of cast iron without reinforcement, and the fl exural strength increases with the increasing of heat treatment temperatures. Due to diffusion reaction between matrix and reinforcing phases, the process of heat treatment, the number of graphite fl akes in the matrix seemingly becomes lower; and some hard carbide particles are formed around the residual tungsten fi bers. Not only does the hardness of both matrix and reinforcement change tremendously, but also the region of reinforcement is also extended from the original 0.11 mm to 0.19 mm in radius.

  13. Formation of carbide derived carbon coatings on silicon carbide

    Science.gov (United States)

    Cambaz, Zarife Goknur

    Control over the structure of materials on nanoscale can open numerous opportunities for the development of materials with controlled properties. Carbon, which is one of the most promising materials for nanotechnology, can be produced by many different methods. One of the most versatile, in terms of a variety of structures demonstrated (graphite, porous amorphous carbon, nanotubes, graphene and diamond), is selective etching of SiC and other carbides. Since the Si atoms are extracted layer by layer, atomic level control of the carbon structures can potentially be achieved without changing the size and shape of the sample. Carbon produced by this method is called Carbide-Derived Carbon (CDC). In this work, CDC formation was studied on single crystalline 3C-SiC whiskers and 6H-SIC wafers by chlorination and vacuum decomposition at high temperatures with the goals to better understand the mechanism of carbide-to-carbon transformation and determine conditions for synthesis of desired carbon structures. The reaction kinetics, morphology and shape conservation were investigated at nanoscale. The transformation mechanism of the SIC surface to carbon was discussed in detail accounting to the effects of processing parameters (temperature, and composition of the environment), and material parameters (surface conditions, surface chemistry, crystal face, etc.). The characterization of the carbon structures was performed by using scanning electron microscopy (SEM), Raman spectroscopy and transmission electron microscopy (TEM). We compared chlorination of SiC whiskers with wet etching and showed that chlorination revealed the dislocations, while wet etching resulted in pagoda-like 3-D nanostructures upon selective etching of stacking faults (SFs). The difference in etching mechanisms was discussed. We determined the processing conditions for controlled synthesis of carbon structures like graphene, graphite and carbon nanotubes (CNTs) on the surface of alpha-SiC wafers by

  14. Directional amorphization of boron carbide subjected to laser shock compression.

    Science.gov (United States)

    Zhao, Shiteng; Kad, Bimal; Remington, Bruce A; LaSalvia, Jerry C; Wehrenberg, Christopher E; Behler, Kristopher D; Meyers, Marc A

    2016-10-25

    Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B 4 C.

  15. Directional amorphization of boron carbide subjected to laser shock compression

    Science.gov (United States)

    Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; LaSalvia, Jerry C.; Wehrenberg, Christopher E.; Behler, Kristopher D.; Meyers, Marc A.

    2016-10-01

    Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45˜50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C.

  16. Self-Supported Biocarbon-Fiber Electrode Decorated with Molybdenum Carbide Nanoparticles for Highly Active Hydrogen-Evolution Reaction.

    Science.gov (United States)

    Xiao, Jian; Zhang, Yan; Zhang, Zheye; Lv, Qiying; Jing, Feng; Chi, Kai; Wang, Shuai

    2017-07-12

    Devising and facilely synthesizing an efficient noble metal-free electrocatalyst for the acceleration of the sluggish kinetics in the hydrogen-evolution reaction (HER) is still a big challenge for electrolytic water splitting. Herein, we present a simple one-step approach for constructing self-supported biocarbon-fiber cloth decorated with molybdenum carbide nanoparticles (BCF/Mo 2 C) electrodes by a direct annealing treatment of the Mo oxyanions loaded cotton T-shirt. The Mo 2 C nanoparticles not only serve as the catalytic active sites toward the HER but also enhance the hydrophilicity and conductivity of resultant electrodes. As an integrated three-dimensional HER cathode catalyst, the BCF/Mo 2 C exhibits outstanding electrocatalytic performance with extremely low overpotentials of 88 and 115 mV to drive a current density of 20 mA cm -2 in alkaline and acidic media, respectively. In addition, it can continuously work for 50 h with little decrease in the cathodic current density in both alkaline and acidic solutions. Even better, self-supported tungsten carbide and vanadium carbide based electrodes also can be prepared by a similar synthesis process. This work will illuminate an entirely new avenue for the preparation of various self-supported three-dimensional electrodes made of transition-metal carbides for various applications.

  17. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    Directory of Open Access Journals (Sweden)

    Genrong Zhang

    2016-03-01

    Full Text Available This study investigates the microstructure and mechanical properties of ultrafine tungsten carbide and cobalt (WC/Co cemented carbides with cubic boron nitride (CBN and chromium carbide (Cr₃C₂ fabricated by a hot pressing sintering process. This study uses samples with 8 wt% Co content and 7.5 vol% CBN content, and with different Cr₃C₂ content ranging from 0 to 0.30 wt%. Based on the experimental results, Cr₃C₂ content has a significant influence on inhibiting abnormal grain growth and decreasing grain size in cemented carbides. Near-full densification is possible when CBN-WC/Co with 0.25 wt% Cr₃C₂ is sintered at 1350°C and 20 MPa; the resulting material possesses optimal mechanical properties and density, with an acceptable Vickers hardness of 19.20 GPa, fracture toughness of 8.47 MPa.m1/2 and flexural strength of 564 MPa.u̇ Å k⃗

  18. Environmental fate of tungsten from military use

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Jay L. [Research and Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, New Hampshire, 03755 (United States)], E-mail: Jay.L.Clausen@erdc.usace.army.mil; Korte, Nic [1946 Clover Ct., Grand Junction, Colorado, 81506 (United States)

    2009-04-01

    This manuscript describes the distribution, fate and transport of tungsten used in training rounds at three small arms ranges at Camp Edwards on the Massachusetts Military Reservation (MMR), USA. Practice with tungsten/nylon rounds began in 2000 subsequent to a 1997 US Environmental Protection Agency ban on training with lead. Training with the tungsten rounds was halted in 2005 because of concerns regarding tungsten's environmental mobility and potential toxicity. This study, therefore, examines how tungsten partitions in the environment when fired on a small arms training range. Soil sampling revealed surface soil concentrations, highest at the berm face, up to 2080 mg/kg. Concentrations decreased rapidly with depth-at least by an order of magnitude by 25 cm. Nonetheless, tungsten concentrations remained above background to at least 150 cm. Pore-water samples from lysimeters installed in berm areas revealed a range of concentrations (< 1-400 mg/L) elevated with respect to background although there was no discernable trend with depth. Groundwater monitoring well samples collected approximately 30 m below ground surface showed tungsten (0.001-0.56 mg/L) attributable to range use.

  19. Nickel-promoted tungsten carbide catalysts for cellulose conversion: effect of preparation methods.

    Science.gov (United States)

    Ji, Na; Zheng, Mingyuan; Wang, Aiqin; Zhang, Tao; Chen, Jingguang G

    2012-05-01

    A series of Ni-promoted W(2) C catalysts was prepared by means of a post-impregnation method and evaluated for the catalytic conversion of cellulose into ethylene glycol (EG). Quite different from our previously reported Ni-W(2) C/AC catalysts, which were prepared by using the co-impregnation method, the introduction of Ni by the post-impregnation method did not cause catalyst sintering, but resulted in redispersion of the W component, which was identified and characterized by means of XRD, TEM, and CO chemisorption. The highly dispersed Ni-promoted W(2) C catalyst was very active and selective in cellulose conversion into EG, with a 100% conversion of cellulose and a 73.0% yield in EG. The underlying reason for the enhanced catalytic performance was most probably the significantly higher dispersion of active sites on the catalyst. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Inelastic deformation and failure of tungsten carbide under ballistic-loading conditions

    NARCIS (Netherlands)

    Hazell, P.J.; Appleby-Thomas, G.J.; Herlaar, K.; Painter, J.

    2010-01-01

    High-speed photography has been used to investigate the dynamic behaviour of similar grades of WC-Co hardmetals during ballistic impacts with velocities in the range of 28-484. m/s. Key features of the failure of similar grades of WC-Co materials during complimentary impacts have been observed and

  1. Precursors and BRST symmetry

    Science.gov (United States)

    de Boer, Jan; Freivogel, Ben; Kabir, Laurens; Lokhande, Sagar F.

    2017-07-01

    In the AdS/CFT correspondence, bulk information appears to be encoded in the CFT in a redundant way. A local bulk field corresponds to many different non-local CFT operators (precursors). We recast this ambiguity in the language of BRST symmetry, and propose that in the large N limit, the difference between two precursors is a BRST exact and ghost-free term. This definition of precursor ambiguities has the advantage that it generalizes to any gauge theory. Using the BRST formalism and working in a simple model with global symmetries, we re-derive a precursor ambiguity appearing in earlier work. Finally, we show within this model that the obtained ambiguity has the right number of parameters to explain the freedom to localize precursors within different spatial regions of the boundary order by order in the large N expansion.

  2. Study on plasma sprayed boron carbide coating

    Science.gov (United States)

    Zeng, Yi; Lee, Soo W.; Ding, Chuanxian

    2002-03-01

    The microstructure, phase composition, and mechanical properties of boron carbide coatings formed by atmospheric plasma spraying (APS) are studied in the present work. The boron carbide coating with high microhardness and low porosity could be produced by APS. The decomposition of boron carbide powder during the plasma spray process would result in the formation of the BxC phase and an increase of the carbon phase, which is confirmed by transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction results.

  3. Viscoelastic model of tungsten 'fuzz' growth

    International Nuclear Information System (INIS)

    Krasheninnikov, S I

    2011-01-01

    A viscoelastic model of fuzz growth is presented. The model describes the main features of tungsten fuzz observed in experiments. It gives estimates of fuzz growth rate and temperature range close to experimental ones.

  4. Room-temperature Electrochemical Synthesis of Carbide-derived Carbons and Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    Gogotsi, Yury [Drexel Univ., Philadelphia, PA (United States). Nanomaterials Group. Materials Science and Engineering Dept.

    2015-02-28

    This project addresses room-temperature electrochemical etching as an energy-efficient route to synthesis of 3D nanoporous carbon networks and layered 2D carbons and related structures, as well as provides fundamental understanding of structure and properties of materials produced by this method. Carbide-derived-carbons (CDCs) are a growing class of nanostructured carbon materials with properties that are desirable for many applications, such as electrical energy and gas storage. The structure of these functional materials is tunable by the choice of the starting carbide precursor, synthesis method, and process parameters. Moving from high-temperature synthesis of CDCs through vacuum decomposition above 1400°C and chlorination above 400°C, our studies under the previous DOE BES support led to identification of precursor materials and processing conditions for CDC synthesis at temperatures as low as 200°C, resulting in amorphous and highly reactive porous carbons. We also investigated synthesis of monolithic CDC films from carbide films at 250-1200°C. The results of our early studies provided new insights into CDC formation, led to development of materials for capacitive energy storage, and enabled fundamental understanding of the electrolyte ions confinement in nanoporous carbons.

  5. 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.

  6. Breaking the icosahedra in boron carbide.

    Science.gov (United States)

    Xie, Kelvin Y; An, Qi; Sato, Takanori; Breen, Andrew J; Ringer, Simon P; Goddard, William A; Cairney, Julie M; Hemker, Kevin J

    2016-10-25

    Findings of laser-assisted atom probe tomography experiments on boron carbide elucidate an approach for characterizing the atomic structure and interatomic bonding of molecules associated with extraordinary structural stability. The discovery of crystallographic planes in these boron carbide datasets substantiates that crystallinity is maintained to the point of field evaporation, and characterization of individual ionization events gives unexpected evidence of the destruction of individual icosahedra. Statistical analyses of the ions created during the field evaporation process have been used to deduce relative atomic bond strengths and show that the icosahedra in boron carbide are not as stable as anticipated. Combined with quantum mechanics simulations, this result provides insight into the structural instability and amorphization of boron carbide. The temporal, spatial, and compositional information provided by atom probe tomography makes it a unique platform for elucidating the relative stability and interactions of primary building blocks in hierarchically crystalline materials.

  7. Silicon Carbide Gate Driver, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA needs efficient, low mass, low volume power electronics for a wide variety of applications and missions. Silicon carbide (SiC) switches provide fast, low loss...

  8. Stabilization of boron carbide via silicon doping.

    Science.gov (United States)

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

    2015-01-14

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

  9. Earthquakes: hydrogeochemical precursors

    Science.gov (United States)

    Ingebritsen, Steven E.; Manga, Michael

    2014-01-01

    Earthquake prediction is a long-sought goal. Changes in groundwater chemistry before earthquakes in Iceland highlight a potential hydrogeochemical precursor, but such signals must be evaluated in the context of long-term, multiparametric data sets.

  10. Carbiding of the electrodes of electrovacuum devices

    Science.gov (United States)

    Pryalukhin, E. D.; Rikov, A. A.; Kostrin, D. K.; Lisenkov, A. A.

    2018-02-01

    Modification of the surface properties of the materials of electrodes or deposition of protective coatings on them are the most effective ways to increase the service life and reliability of electrovacuum devices. Very often for these tasks operations of the carbiding of details are used. In this work results of direct carbiding of W and Mo, carried out in a mixture of the hydrogen stream and the carbon-containing gas on a technological installation of a flow type, are discussed.

  11. Stable carbides in transition metal alloys

    International Nuclear Information System (INIS)

    Piotrkowski, R.

    1991-01-01

    In the present work different techniques were employed for the identification of stable carbides in two sets of transition metal alloys of wide technological application: a set of three high alloy M2 type steels in which W and/or Mo were total or partially replaced by Nb, and a Zr-2.5 Nb alloy. The M2 steel is a high speed steel worldwide used and the Zr-2.5 Nb alloy is the base material for the pressure tubes in the CANDU type nuclear reactors. The stability of carbide was studied in the frame of Goldschmidt's theory of interstitial alloys. The identification of stable carbides in steels was performed by determining their metallic composition with an energy analyzer attached to the scanning electron microscope (SEM). By these means typical carbides of the M2 steel, MC and M 6 C, were found. Moreover, the spatial and size distribution of carbide particles were determined after different heat treatments, and both microstructure and microhardness were correlated with the appearance of the secondary hardening phenomenon. In the Zr-Nb alloy a study of the α and β phases present after different heat treatments was performed with optical and SEM metallographic techniques, with the guide of Abriata and Bolcich phase diagram. The α-β interphase boundaries were characterized as short circuits for diffusion with radiotracer techniques and applying Fisher-Bondy-Martin model. The precipitation of carbides was promoted by heat treatments that produced first the C diffusion into the samples at high temperatures (β phase), and then the precipitation of carbide particles at lower temperature (α phase or (α+β)) two phase field. The precipitated carbides were identified as (Zr, Nb)C 1-x with SEM, electron microprobe and X-ray diffraction techniques. (Author) [es

  12. Amphibian tachykinin precursor.

    Science.gov (United States)

    Li, Jianxu; Liu, Tongguang; Xu, Xueqing; Wang, Xu; Wu, Min; Yang, Hailong; Lai, Ren

    2006-12-01

    The precursor of amphibian tachykinin has not been found although more than 30 tachykinins have been isolated from amphibians since 1964. In this report, two tachykinin-like peptides are identified from the skin secretions of the frog, Odorrana grahami. Their amino acid sequences are DDTEDLANKFIGLM-NH(2) (named tachykinin OG1) and DDASDRAKKFYGLM-NH(2) that is the same with ranamargarin found in Rana margaretae, respectively, with a conserved FXGLM-NH(2) C-terminal consensus motif. By cDNA cloning, their precursors were screened from the skin cDNA library of O. grahami. The precursors are composed of 61 amino acid (aa) residues including a signal peptide followed by an acidic spacer peptide and one copy of mature tachykinin-like peptide. Their overall structure is different from structures of other tachykinin precursors such as human protachykinin 1 precursor containing 143 aa including one copy of substance P (SP) and neurokinin A (NKA), and ascidian tachykinin 1 precursor containing 164 aa including two copies of tachykinin-like peptides. The current results demonstrate that the biosynthesis mode of tachykinins in amphibians is different from other animals.

  13. Influence of tungsten substitution and oxygen deficiency on the thermoelectric properties of CaMnO3−δ

    International Nuclear Information System (INIS)

    Thiel, Philipp; Eilertsen, James; Populoh, Sascha; Saucke, Gesine; Shkabko, Andrey; Sagarna, Leyre; Karvonen, Lassi; Döbeli, Max; Weidenkaff, Anke

    2013-01-01

    Polycrystalline tungsten-substituted CaMn 1−x W x O 3−δ (0.00 ≤ x ≤ 0.05) powders were synthesized from a polymeric precursor, pressed and sintered to high density. The impact of tungsten substitution on the crystal structure, thermal stability, phase transition, electronic and thermal transport properties is assessed. Tungsten acts as an electron donator and strongly affects high-temperature oxygen stoichiometry. Oxygen vacancies form in the high figure-of-merit (ZT)-region starting from about T = 1000 K and dominate the carrier concentration and electronic transport far more than the tungsten substitution. The analysis of the transport properties yields that in the investigated regime the band filling is sufficiently high to overcome barriers of polaron transport. Therefore, the Cutler-Mott approach describes the electrical transport more accurately than the Mott approach for small polaron transport. The lattice thermal conductivity near room temperature is strongly suppressed with increasing tungsten concentration due to mass-difference impurity scattering. A ZT of 0.25 was found for x = 0.04 at 1225 K

  14. Electronic Transitions of Tungsten Monosulfide

    Science.gov (United States)

    Tsang, L. F.; Chan, Man-Chor; Zou, Wenli; Cheung, Allan S. C.

    2017-06-01

    Electronic transition spectrum of the tungsten monosulfide (WS) molecule in the near infrared region between 725 nm and 885 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The WS molecule was produced by reacting laser - ablated tungsten atoms with 1% CS_{2} seeded in argon. Fifteen vibrational bands with resolved rotational structure have been recorded and analyzed, which were organized into seven electronic transition systems. The ground state has been identified to be the X^{3}Σ^{-}(0^{+}) state, and the determined vibrational frequency, ΔG_{1/2} and bond length, r_{0}, are respectively 556.7 cm^{-1} and 2.0676 Å. In addition, vibrational bands belong to another transition system involving lower state with Ω = 1 component have also been analyzed. Least-squares fit of the measured line positions yielded molecular constants for the electronic states involved. The low-lying Λ-S states and Ω sub-states of WS have been calculated using state-averaged complete active space self-consistent field (SA-CASSCF) and followed by MRCISD+Q (internally contracted multi-reference configuration interaction with singles and doubles plus Davidson's cluster correction). The active space consists of 10 electrons in 9 orbitals corresponding to the W 5d6s and S 3p shells. The lower molecular orbitals from W 5s5p and S 3s are inactive but are also correlated, and relativistic effective core potential (RECPs) are adopted to replace the core orbitals with 60 (W) and 10 (S) core electrons, respectively. Spin-orbit coupling (SOC) is calculated via the state-interaction (SI) approach with RECP spin-orbit operators using SA-CASSCF wavefunctions, where the diagonal elements in the SOC matrix are replaced by the corresponding MRCISD+Q energies calculated above. Spectroscopic constants and potential energy curves of the ground and many low-lying Λ-S states and Ω sub-states of the WS molecule are obtained. The calculated

  15. Deuterium retention in tungsten and tungsten-tantalum alloys exposed to high-flux deuterium plasmas

    NARCIS (Netherlands)

    Zayachuk, Y.; Hoen, M. H. J. 't; van Emmichoven, P. A. Zeijlma; Uytdenhouwen, I.; Van Oost, G.

    2012-01-01

    A direct comparison of deuterium retention in samples of tungsten and two grades of tungsten-tantalum alloys-W-1% Ta and W-5% Ta, exposed to deuterium plasmas (ion flux similar to 10(24) m(-2) s(-1), ion energy at the biased target similar to 50 eV) at the plasma generator Pilot-PSI was performed

  16. Process of making titanium carbide (TiC) nano-fibrous felts

    Science.gov (United States)

    Fong, Hao; Zhang, Lifeng; Zhao, Yong; Zhu, Zhengtao

    2015-01-13

    A method of synthesizing mechanically resilient titanium carbide (TiC) nanofibrous felts comprising continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix, comprising: (a) electrospinning a spin dope for making precursor nanofibers with diameters less than 0.5 J.Lm; (b) overlaying the nanofibers to produce a nanofibrous mat (felt); and then (c) heating the nano-felts first at a low temperature, and then at a high temperature for making electrospun continuous nanofibers or nano-ribbons with TiC crystallites embedded in carbon matrix; and (d) chlorinating the above electrospun nano-felts at an elevated temperature to remove titanium for producing carbide derived carbon (CDC) nano-fibrous felt with high specific surface areas.

  17. Engineering a novel material: Nanometric titanium carbide particles in a matrix of carbon nanotubes

    CERN Document Server

    BADIE, Sylvain

    2015-01-01

    New physics studies at ISOLDE are motivated by new beams available, especially beams of exotic nuclei located at the frontier of the nuclear chart. Such beams are often short lived (in the order of milliseconds) and decay before they can be extracted from the target material, where typical diffusion times are in the order of seconds or more. Novel nanostructured and nanocomposite target materials have been developed to increase the release efficiency by reducing the diffusion paths and so the diffusion times, allowing ISOLDE to deliver new and more intense beams of exotic nuclei. 35Ca (25 ms half-life) was attempted by developing a titanium carbide and carbon black nanocomposite, but such isotope could not be extracted. A different production method with different precursors - titanium oxide and multiwall carbon nanotubes - is here proposed and expected to yield a target material which will increase the release rates of such isotope. A novel material, very porous, consisting of titanium carbide particles disp...

  18. Catalytic activity of molybdenum carbide for hydrogen generation via diesel reforming

    Science.gov (United States)

    Cheekatamarla, Praveen K.; Thomson, William J.

    The activity of a bulk molybdenum carbide catalyst for the steam (SR) and oxidative-steam reforming (OSR) of hexadecane has been studied with and without the presence of aromatic coke precursors and sulfur compounds. It is shown that this catalyst can be stable under very low steam:carbon ratios at temperatures as low as 885 °C under OSR conditions, and 965 °C under SR conditions. Using benzo-thiophene as a model sulfur compound at concentrations as high as 500 ppmw, the degree of deactivation was found to be dependent on the sulfur concentration but was minimal at concentrations below 100 ppmw. Experiments confirmed that the sulfur poisoning is reversible and characterization studies suggested the formation of sulfur entities, which lead to carbide oxidation and subsequent coking. There was minimal effect of the aromatic species on the catalyst stability.

  19. Evaluation of surface, microstructure and phase modifications on various tungsten grades induced by pulsed plasma loading

    Czech Academy of Sciences Publication Activity Database

    Vilémová, Monika; Pala, Zdeněk; Jäger, Aleš; Matějíček, Jiří; Chernyshova, M.; Kowalska-Strzęciwilk, E.; Tonarová, Dana; Gribkov, V. A.

    2016-01-01

    Roč. 91, č. 3 (2016), č. článku 034003. ISSN 0031-8949. [PLASMA 2015 : International Conference on Research and Applications of Plasmas. Warsaw, 07.09.2015-11.09.2015] R&D Projects: GA ČR(CZ) GA14-12837S Institutional support: RVO:61389021 ; RVO:68378271 Keywords : tungsten * titanium carbide * yttrium oxide * plasma focus * damage Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (FZU-D) OBOR OECD: 1.3 Physical sciences; 1.3 Physical sciences (FZU-D) Impact factor: 1.280, year: 2016 http://iopscience.iop.org/article/10.1088/0031-8949/91/3/034003/meta

  20. Atomically thin heterostructures based on single-layer tungsten diselenide and graphene.

    Science.gov (United States)

    Lin, Yu-Chuan; Chang, Chih-Yuan S; Ghosh, Ram Krishna; Li, Jie; Zhu, Hui; Addou, Rafik; Diaconescu, Bogdan; Ohta, Taisuke; Peng, Xin; Lu, Ning; Kim, Moon J; Robinson, Jeremy T; Wallace, Robert M; Mayer, Theresa S; Datta, Suman; Li, Lain-Jong; Robinson, Joshua A

    2014-12-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green's function (NEGF).

  1. Evaluation of surface, microstructure and phase modifications on various tungsten grades induced by pulsed plasma loading

    Czech Academy of Sciences Publication Activity Database

    Vilémová, Monika; Pala, Zdeněk; Jäger, Aleš; Matějíček, Jiří; Chernyshova, M.; Kowalska-Strzęciwilk, E.; Tonarová, Dana; Gribkov, V. A.

    2016-01-01

    Roč. 91, č. 3 (2016), č. článku 034003. ISSN 0031-8949. [PLASMA 2015 : International Conference on Research and Applications of Plasmas. Warsaw, 07.09.2015-11.09.2015] R&D Projects: GA ČR(CZ) GA14-12837S Institutional support: RVO:61389021 ; RVO:68378271 Keywords : tungsten * titanium carbide * yttrium oxide * plasma focus * damage Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (FZU-D) OBOR OECD: 1.3 Physical sciences; 1.3 Physical sciences (FZU-D) Impact factor: 1.280, year: 2016 http://iopscience.iop.org/article/10.1088/0031-8949/91/3/034003/ meta

  2. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan

    2014-11-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green\\'s function (NEGF).

  3. Performance of biomorphic Silicon Carbide as particulate filter in diesel boilers.

    Science.gov (United States)

    Orihuela, M Pilar; Gómez-Martín, Aurora; Becerra, José A; Chacartegui, Ricardo; Ramírez-Rico, Joaquín

    2017-12-01

    Biomorphic Silicon Carbide (bioSiC) is a novel porous ceramic material with excellent mechanical and thermal properties. Previous studies have demonstrated that it may be a good candidate for its use as particle filter media of exhaust gases at medium or high temperature. In order to determine the filtration efficiency of biomorphic Silicon Carbide, and its adequacy as substrate for diesel particulate filters, different bioSiC-samples have been tested in the flue gases of a diesel boiler. For this purpose, an experimental facility to extract a fraction of the boiler exhaust flow and filter it under controlled conditions has been designed and built. Several filter samples with different microstructures, obtained from different precursors, have been tested in this bench. The experimental campaign was focused on the measurement of the number and size of particles before and after placing the samples. Results show that the initial efficiency of filters made from natural precursors is severely determined by the cutting direction and associated microstructure. In biomorphic Silicon Carbide derived from radially cut wood, the initial efficiency of the filter is higher than 95%. Nevertheless, when the cut of the wood is axial, the efficiency depends on the pore size and the permeability, reaching in some cases values in the range 70-90%. In this case, the presence of macropores in some of the samples reduces their efficiency as particle traps. In continuous operation, the accumulation of particles within the porous media leads to the formation of a soot cake, which improves the efficiency except in the case when extra-large pores exist. For all the samples, after a few operation cycles, capture efficiency was higher than 95%. These experimental results show the potential for developing filters for diesel boilers based on biomorphic Silicon Carbide. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. High temperature evaporation of titanium, zirconium and hafnium carbides

    International Nuclear Information System (INIS)

    Gusev, A.I.; Rempel', A.A.

    1991-01-01

    Evaporation of cubic nonstoichiometric carbides of titanium, zirconium and hafnium in a comparatively low-temperature interval (1800-2700) with detailed crystallochemical sample certification is studied. Titanium carbide is characterized by the maximum evaporation rate: at T>2300 K it loses 3% of sample mass during an hour and at T>2400 K titanium carbide evaporation becomes extremely rapid. Zirconium and hafnium carbide evaporation rates are several times lower than titanium carbide evaporation rates at similar temperatures. Partial pressures of metals and carbon over the carbides studied are calculated on the base of evaporation rates

  5. Photoelectron yield spectroscopy and inverse photoemission spectroscopy evaluations of p-type amorphous silicon carbide films prepared using liquid materials

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Tatsuya, E-mail: mtatsuya@jaist.ac.jp, E-mail: mtakashi@jaist.ac.jp [Center for Nano Materials and Technology, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Masuda, Takashi, E-mail: mtatsuya@jaist.ac.jp, E-mail: mtakashi@jaist.ac.jp; Inoue, Satoshi; Shimoda, Tatsuya [Green Device Research Center, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-1211 (Japan); Yano, Hiroshi; Iwamuro, Noriyuki [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennoudai, Tsukuba, Ibaraki 305-8573 (Japan)

    2016-05-15

    Phosphorus-doped amorphous silicon carbide films were prepared using a polymeric precursor solution. Unlike conventional polymeric precursors, this polymer requires neither catalysts nor oxidation for its synthesis and cross-linkage, providing semiconducting properties in the films. The valence and conduction states of resultant films were determined directly through the combination of inverse photoemission spectroscopy and photoelectron yield spectroscopy. The incorporated carbon widened energy gap and optical gap comparably in the films with lower carbon concentrations. In contrast, a large deviation between the energy gap and the optical gap was observed at higher carbon contents because of exponential widening of the band tail.

  6. Expanding the versatility of silicon carbide thin films and nanowires

    Science.gov (United States)

    Luna, Lunet

    Silicon carbide (SiC) based electronics and sensors hold promise for pushing past the limits of current technology to achieve small, durable devices that can function in high-temperature, high-voltage, corrosive, and biological environments. SiC is an ideal material for such conditions due to its high mechanical strength, excellent chemical stability, and its biocompatibility. Consequently, SiC thin films and nanowires have attracted interest in applications such as micro- and nano-electromechanical systems, biological sensors, field emission cathodes, and energy storage devices. However to fully realize SiC in such technologies, the reliability of metal contacts to SiC at high temperatures must be improved and the nanowire growth mechanism must be understood to enable strict control of nanowire crystal structure and orientation. Here, we present a novel metallization scheme, utilizing solid-state graphitization of SiC, to improve the long-term reliability of Pt/Ti contacts to polycrystalline n-type SiC films at high temperature. The metallization scheme includes an alumina protection layer and exhibits low, stable contact resistivity even after long-term (500 hr) testing in air at 450 ºC. We also report the crystal structure and growth mechanism of Ni-assisted silicon carbide nanowires using single-source precursor, methyltrichlorosilane. The effects of growth parameters, such as substrate and temperature, on the structure and morphology of the resulting nanowires will also be presented. Overall, this study provides new insights towards the realization of novel SiC technologies, enabled by advanced electron microscopy techniques located in the user facilities at the Molecular Foundry in Berkeley, California. This work was performed in part at the Molecular Foundry, supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  7. Fabrication and evaluation of chemically vapor deposited tungsten heat pipe.

    Science.gov (United States)

    Bacigalupi, R. J.

    1972-01-01

    A network of lithium-filled tungsten heat pipes is being considered as a method of heat extraction from high temperature nuclear reactors. The need for material purity and shape versatility in these applications dictates the use of chemically vapor deposited (CVD) tungsten. Adaptability of CVD tungsten to complex heat pipe designs is shown. Deposition and welding techniques are described. Operation of two lithium-filled CVD tungsten heat pipes above 1800 K is discussed.

  8. In vitro genotoxic effects of different combinations of cobalt and metallic carbide particles.

    Science.gov (United States)

    De Boeck, Marlies; Lombaert, Noömi; De Backer, Sofie; Finsy, Robert; Lison, Dominique; Kirsch-Volders, Micheline

    2003-03-01

    Occupational exposure to hard metal dust, consisting of tungsten carbide (WC) and metallic cobalt particles (Co), is associated with an increased risk of lung cancer, while no increased risk was observed in workers exposed to Co alone. In vitro, in human peripheral blood mononucleated cells (PBMC), we previously demonstrated that WC-Co is more genotoxic than Co and WC alone. A possible mechanism underlying this higher genotoxicity is a specific physicochemical interaction between Co and WC particles leading to the enhanced short-term formation of active oxygen species. The aim of this study was to evaluate the in vitro genotoxicity of other combinations of Co with metal carbide particles in comparison with WC-Co. The ability of Cr(3)C(2), Mo(2)C and NbC and of their powder mixtures with Co to induce DNA strand breaks and alkali-labile sites was assessed by the alkaline Comet assay and their potential to induce chromosome(/genome) mutations by the cytokinesis-block micronucleus test on human PBMC from two donors. PBMC were treated in vitro for 15 min, 24 h after the onset of PHA stimulation. In the micronucleus test, while the metal carbides alone did not increase the micronucleus frequency, Co alone and the four tested carbide-Co mixtures induced a statistically significant concentration-dependent increase in micronucleated binucleates. In addition to WC, NbC and Cr(3)C(2) particles were able to interact with Co, producing a higher mutagenic effect than the individual metal particles. Mo(2)C particles did not display interactive mutagenicity with Co in the micronucleus test, possibly related to their small specific surface area, compactness and/or spherical shape. With the Comet assay, applied directly at the end of the treatment, less clear results, due to inter-experimental and inter-donor variation, were obtained. These data indicate that particular interaction of a metal carbide with Co leading to enhanced mutagenicity is not specific for WC.

  9. Process optimization for diffusion bonding of tungsten with EUROFER97 using a vanadium interlayer

    Science.gov (United States)

    Basuki, Widodo Widjaja; Aktaa, Jarir

    2015-04-01

    Solid-state diffusion bonding is a selected joining technology to bond divertor components consisting of tungsten and EUROFER97 for application in fusion power plants. Due to the large mismatch in their coefficient of thermal expansions, which leads to serious thermally induced residual stresses after bonding, a thin vanadium plate is introduced as an interlayer. However, the diffusion of carbon originated from EUROFER97 in the vanadium interlayer during the bonding process can form a vanadium carbide layer, which has detrimental influences on the mechanical properties of the joint. For optimal bonding results, the thickness of this layer and the residual stresses has to be decreased sufficiently without a significant reduction of material transport especially at the vanadium/tungsten interface, which can be achieved by varying the diffusion bonding temperature and duration. The investigation results show that at a sufficiently low bonding temperature of 700 °C and a bonding duration of 4 h, the joint reaches a reasonable high ductility and toughness especially at elevated test temperature of 550 °C with elongation to fracture of 20% and mean absorbed Charpy impact energy of 2 J (using miniaturized Charpy impact specimens). The strength of the bonded materials is about 332 MPa at RT and 291 MPa at 550 °C. Furthermore, a low bonding temperature of 700 °C can also help to avoid the grain coarsening and the alteration of the grain structure especially of the EUROFER97 close to the bond interface.

  10. Process optimization for diffusion bonding of tungsten with EUROFER97 using a vanadium interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Basuki, Widodo Widjaja; Aktaa, Jarir

    2015-04-15

    Solid-state diffusion bonding is a selected joining technology to bond divertor components consisting of tungsten and EUROFER97 for application in fusion power plants. Due to the large mismatch in their coefficient of thermal expansions, which leads to serious thermally induced residual stresses after bonding, a thin vanadium plate is introduced as an interlayer. However, the diffusion of carbon originated from EUROFER97 in the vanadium interlayer during the bonding process can form a vanadium carbide layer, which has detrimental influences on the mechanical properties of the joint. For optimal bonding results, the thickness of this layer and the residual stresses has to be decreased sufficiently without a significant reduction of material transport especially at the vanadium/tungsten interface, which can be achieved by varying the diffusion bonding temperature and duration. The investigation results show that at a sufficiently low bonding temperature of 700 °C and a bonding duration of 4 h, the joint reaches a reasonable high ductility and toughness especially at elevated test temperature of 550 °C with elongation to fracture of 20% and mean absorbed Charpy impact energy of 2 J (using miniaturized Charpy impact specimens). The strength of the bonded materials is about 332 MPa at RT and 291 MPa at 550 °C. Furthermore, a low bonding temperature of 700 °C can also help to avoid the grain coarsening and the alteration of the grain structure especially of the EUROFER97 close to the bond interface.

  11. Element 74, the Wolfram Versus Tungsten Controversy

    Energy Technology Data Exchange (ETDEWEB)

    Holden,N.E.

    2008-08-11

    Two and a quarter centuries ago, a heavy mineral ore was found which was thought to contain a new chemical element called heavy stone (or tungsten in Swedish). A few years later, the metal was separated from its oxide and the new element (Z=74) was called wolfram. Over the years since that time, both the names wolfram and tungsten were attached to this element in various countries. Sixty years ago, IUPAC chose wolfram as the official name for the element. A few years later, under pressure from the press in the USA, the alternative name tungsten was also allowed by IUPAC. Now the original, official name 'wolfram' has been deleted by IUPAC as one of the two alternate names for the element. The history of this controversy is described here.

  12. Electron work function of stepped tungsten surfaces

    International Nuclear Information System (INIS)

    Krahl-Urban, B.

    1976-03-01

    The electron work function of tungsten (110) vicinal faces was measured with the aid of thermionic emission, and its dependence on the crystallographic orientation and the surface structure was investigated. The thermionic measurements were evaluated with the aid of the Richardson plot. The real temperature of the emitting tungsten faces was determined with an accuracy of +- 0.5% in the range between 2,200 and 2,800 K. The vicinal faces under investigation have been prepared with an orientation exactness of +- 15'. In the tungsten (110) vicinal faces under investigation, a strong dependence of the temperature coefficient d PHI/dT of the work function on the crystallographic orientation was found. A strong influence of the edge structure as well as of the step density on the temperature coefficient was observed. (orig./HPOE) [de

  13. Determination of free carbon content in boron carbide ceramic powders

    International Nuclear Information System (INIS)

    Castro, A.R.M. de; Lima, N.B. de; Paschoal, J.O.A.

    1990-01-01

    Boron carbide is a ceramic material of technological importance due to its hardness and high chemical and thermal stabilities. Free carbon is always found as a process dependent impurity in boron carbide. The development of procedures for its detection is required because its presence leads to a degradation of the boron carbide properties. In this work, several procedures for determining free carbon content in boron carbide specimens are reported and discussed for comparison purposes. (author) [pt

  14. Precursor Additive Manufacturing Inventions

    Science.gov (United States)

    Roberts, C.; Bourell, D.

    2018-03-01

    Most modern Additive Manufacturing (AM) processes were invented and commercialized in a short period of time spanning 1984-2000. This paper reports on AM processes invented in the 1974-1987 time period, known as precursor AM processes. The critical difference between the two periods is public knowledge and utilization of distributed computing.

  15. Silicon carbide as platform for energy applications

    DEFF Research Database (Denmark)

    Syväjärvi, Mikael; Jokubavicius, Valdas; Sun, Jianwu

    and solar cells, and further pursue concepts in materials for thermoelectrics, biofuel cells and supercapacitor research proposals. In fact, there are a number of energy applications which can be based on the SiC materials.- Fluorescent SiC for white LED in general lighting - Cubic SiC for a highly...... efficient solar cell- Cubic SiC for water splitting to generate hydrogen.Further on, we have the following concepts that could be explored- Thermoelectric SiC for electricity generation from heat- Biofuels cells based on carbon electrodes on SiC- Supercapacitors based on sintered SiC and carbon materials......Silicon carbide is emerging as a novel material for a range of energy and environmental technologies. Previously, silicon carbide was considered as a material mainly for transistor applications. We have initiated the use of silicon carbide material towards optoelectronics in general lighting...

  16. Wear Characterization of Cemented Carbides (WC–CoNi Processed by Laser Surface Texturing under Abrasive Machining Conditions

    Directory of Open Access Journals (Sweden)

    Shiqi Fang

    2017-06-01

    Full Text Available Cemented carbides are outstanding engineering materials widely used in quite demanding material removal applications. In this study, laser surface texturing is implemented for enhancing, at the surface level, the intrinsic bulk-like tribological performance of these materials. In this regard, hexagonal pyramids patterned on the cutting surface of a tungsten cemented carbide grade (WC–CoNi have been successfully introduced by means of laser surface texturing. It simulates the surface topography of conventional honing stones for abrasive application. The laser-produced structure has been tested under abrasive machining conditions with full lubrication. Wear of the structure has been characterized and compared, before and after the abrasive machining test, in terms of changes in geometry aspect and surface integrity. It is found that surface roughness of the machined workpiece was improved by the laser-produced structure. Wear characterization shows that laser treatment did not induce any significant damage to the cemented carbide. During the abrasive machining test, the structure exhibited a high wear resistance. Damage features were only discerned at the contacting surface, whereas geometrical shape of pyramids remained unchanged.

  17. Fabrication of uranium carbide/beryllium carbide/graphite experimental-fuel-element specimens

    International Nuclear Information System (INIS)

    Muenzer, W.A.

    1978-01-01

    A method has been developed for fabricating uranium carbide/beryllium carbide/graphite fuel-element specimens for reactor-core-meltdown studies. The method involves milling and blending the raw materials and densifying the resulting blend by conventional graphite-die hot-pressing techniques. It can be used to fabricate specimens with good physical integrity and material dispersion, with densities of greater than 90% of the theoretical density, and with a uranium carbide particle size of less than 10 μm

  18. 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

  19. Mesoscale Modeling of Dynamic Compression of Boron Carbide Polycrystals

    Science.gov (United States)

    2013-05-01

    occurs in ballistic impact, and accompanies amorphization in diamond anvil cell (DAC) experiments (Yan et al., 2009). Fracture in boron carbide ...Mesoscale Modeling of Dynamic Compression of Boron Carbide Polycrystals by J. D. Clayton ARL-RP-440 May 2013...Ground, MD 21005-5069 ARL-RP-440 May 2013 Mesoscale Modeling of Dynamic Compression of Boron Carbide Polycrystals J. D. Clayton

  20. Synthesis of poly(dimethylsilylene-co-diphenylsilylene) polymers as precursors for SiC ceramics

    International Nuclear Information System (INIS)

    Bushnell-Watson, S.M.; Emsley, R.J.P.; Morris, M.J.; Sharp, J.H.

    1993-01-01

    Silicon carbide ceramics, especially fibres, are being fabricated via polymeric precursors. Although such fibres are commercially available, there is a demand for improved performance particularly at elevated temperatures. A range of copolymers has been synthesized from the monomers, dimethyldichlorosilane and diphenyldichlorosilane, by a Wurtz reaction involving dechlorination using sodium metal in xylene. The products of reaction were characterised by a range of techniques, including gel permeation chromatography (GPC), infra-red spectroscopy (IR), X-ray powder diffraction (XRD) and thermogravimetry (TG). (orig.)

  1. Thermal conductivity behavior of boron carbides

    Science.gov (United States)

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

    1983-01-01

    Knowledge of the thermal conductivity of boron carbides is necessary to evaluate its potential for high temperature thermoelectric energy conversion applications. The thermal diffusivity of hot pressed boron carbide B/sub 1-x/C/sub x/ samples as a function of composition, temperature and temperature cycling was measured. These data in concert with density and specific heat data yield the thermal conductivities of these materials. The results in terms of a structural model to explain the electrical transport data and novel mechanisms for thermal conduction are discussed.

  2. 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

  3. Morphology study of refractory carbide powders

    International Nuclear Information System (INIS)

    Vavrda, J.; Blazhikova, Ya.

    1982-01-01

    Refractory carbides were investigated using JSM-U3 electron microscope of Joelco company at 27 KV accelerating voltage. Some photographs of each powder were taken with different enlargements to characterise the sample upon the whole. It was shown that morphological and especially topographic study of powders enables to learn their past history (way of fabrication and treatment). The presence of steps of compact particle fractures and cracks is accompanied by occurence of fine dispersion of carbides subjected to machining after facrication. On the contrary, the character of crystallographic surfaces and features of surface growth testify to the way of crystallization

  4. Tritium Decay Helium-3 Effects in Tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Shimada, M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Merrill, B. J. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-06-01

    A critical challenge for long-term operation of ITER and beyond to a Demonstration reactor (DEMO) and future fusion reactor will be the development of plasma-facing components (PFCs) that demonstrate erosion resistance to steady-state/transient heat fluxes and intense neutral/ion particle fluxes under the extreme fusion nuclear environment, while at the same time minimizing in-vessel tritium inventories and permeation fluxes into the PFC’s coolant. Tritium will diffuse in bulk tungsten at elevated temperatures, and can be trapped in radiation-induced trap site (up to 1 at. % T/W) in tungsten [1,2]. Tritium decay into helium-3 may also play a major role in microstructural evolution (e.g. helium embrittlement) in tungsten due to relatively low helium-4 production (e.g. He/dpa ratio of 0.4-0.7 appm [3]) in tungsten. Tritium-decay helium-3 effect on tungsten is hardly understood, and its database is very limited. Two tungsten samples (99.99 at. % purity from A.L.M.T. Co., Japan) were exposed to high flux (ion flux of 1.0x1022 m-2s-1 and ion fluence of 1.0x1026 m-2) 0.5%T2/D2 plasma at two different temperatures (200, and 500°C) in Tritium Plasma Experiment (TPE) at Idaho National Laboratory. Tritium implanted samples were stored at ambient temperature in air for more than 3 years to investigate tritium decay helium-3 effect in tungsten. The tritium distributions on plasma-exposed was monitored by a tritium imaging plate technique during storage period [4]. Thermal desorption spectroscopy was performed with a ramp rate of 10°C/min up to 900°C to outgas residual deuterium and tritium but keep helium-3 in tungsten. These helium-3 implanted samples were exposed to deuterium plasma in TPE to investigate helium-3 effect on deuterium behavior in tungsten. The results show that tritium surface concentration in 200°C sample decreased to 30 %, but tritium surface concentration in 500°C sample did not alter over the 3 years storage period, indicating possible tritium

  5. Ab initio and DFT benchmarking of tungsten nanoclusters and tungsten hydrides

    International Nuclear Information System (INIS)

    Skoviera, J.; Novotny, M.; Cernusak, I.; Oda, T.; Louis, F.

    2015-01-01

    We present several benchmark calculations comparing wave-function based methods and density functional theory for model systems containing tungsten. They include W 4 cluster as well as W 2 , WH and WH 2 molecules. (authors)

  6. Solvothermally synthesized tungsten oxide nanowires/nanorods for NO2 gas sensor applications

    International Nuclear Information System (INIS)

    Qin Yuxiang; Li Xiao; Wang Fei; Hu Ming

    2011-01-01

    Highlights: → Tungsten oxide nanowires and nanorods were solvothermally synthesized by changing reaction solvent. → The sensing characteristics of the tungsten oxide nanowires and nanorods sensors to NO 2 gas were evaluated in detail. → The response time and recovery time for the nanowires or nanorods sensors are much shorter than the oxide nanoparticles or sputtered films. → The nanowires sensor shows a much shorter response time and a relative higher response value to NO 2 gas than the nanorods one. → The NO 2 -sensing mechanism and the possible reason for the better gas sensing properties of the nanowires are analyzed. - Abstract: One-dimensional nanorods or nanowires of W 18 O 49 were synthesized by solvothermal method at 200 deg. C with tungsten hexachloride (WCl 6 ) as precursor and cyclohexanol or 1-propanol as reaction solvent. Their morphology and structure properties were systematically characterized. The NO 2 -sensing properties of the sensors based on nanowires and nanorods were investigated at 100 deg. C up to 250 deg. C over NO 2 concentration ranging from 1 ppm to 20 ppm. The results indicate that both nanowires and nanorods exhibit reversible response to different concentrations of NO 2 , and the highest gas response is achieved at 150 deg. C. In comparison with nanorods, nanowires showed a much quicker response characteristic and a relative higher response value to the same concentration of NO 2 gas due to the smaller diameter and larger specific surface area.

  7. Monolayer Tungsten Disulfide (WS2) via Chlorine-Driven Chemical Vapor Transport.

    Science.gov (United States)

    Modtland, Brian J; Navarro-Moratalla, Efren; Ji, Xiang; Baldo, Marc; Kong, Jing

    2017-09-01

    Large-scale production of high-quality tungsten disulfide (WS 2 ) monolayers is a prerequisite for potential device applications using this promising transition metal dichalcogenide semiconductor. The most researched technique is chemical vapor deposition, typically involving the reaction of sulfur vapors with tungsten oxide. Other techniques such as physical vapor deposition have been explored with some success, but low vapor pressures make growth difficult. This study demonstrates a growth process that relies on halide-driven vapor transport commonly utilized in bulk crystal growth. Using a small amount of sodium chloride salt as a source of chlorine, nonvolatile WS 2 can react to form gaseous tungsten chloride and sulfur. With an open tube system, a controlled reaction generates mono and few-layer WS 2 crystals. Optical and physical characterization of the monolayer material shows good uniformity and triangular domains over 50 µm in length. Photoluminescence transient measurements show similar nonlinear exciton dynamics as exfoliated flakes, attributed to multiparticle physics. Requiring only the powder of the desired crystal and appropriate halide salt as precursors, the technique has the potential to realize other layered materials that are challenging to grow with current processes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    International Nuclear Information System (INIS)

    Nagle, Dennis; Zhang, Dajie

    2009-01-01

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

  9. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    Energy Technology Data Exchange (ETDEWEB)

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26

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

  10. Growth of silicon on tungsten diselenide

    NARCIS (Netherlands)

    Yao, Qirong; van Bremen, Rik; Zandvliet, Henricus J.W.

    2016-01-01

    Here, we report a scanning tunneling microscopy and spectroscopy study of the growth of silicon on a tungsten diselenide (WSe2) substrate. We have found convincing experimental evidence that silicon does not remain on the WSe2 substrate but rather intercalates between the top layers of WSe2. Upon

  11. Copper-Tungsten Composites Sprayed by HVOF

    Czech Academy of Sciences Publication Activity Database

    Matějíček, Jiří; Zahálka, F.; Bensch, Jan; Chi, W.; Sedláček, J.

    2008-01-01

    Roč. 17, č. 2 (2008), s. 177-180 ISSN 1059-9630 Institutional research plan: CEZ:AV0Z20430508 Keywords : Thermally sprayed coatings * tungsten * copper * HVOF Subject RIV: JG - Metallurgy Impact factor: 1.200, year: 2008 http://www.springerlink.com/content/120439/

  12. Joining of Tungsten Armor Using Functional Gradients

    International Nuclear Information System (INIS)

    John Scott O'Dell

    2006-01-01

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  13. Joining of Tungsten Armor Using Functional Gradients

    Energy Technology Data Exchange (ETDEWEB)

    John Scott O' Dell

    2006-12-31

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  14. CALICE silicon-tungsten electromagnetic calorimeter

    Indian Academy of Sciences (India)

    A highly granular electromagnetic calorimeter prototype based on tungsten absorber and sampling units equipped with silicon pads as sensitive devices for signal collection is under construction. The full prototype will have in total 30 layers and be read out by about 10000 Si cells of 1 × 1 cm2. A first module consisting of 14 ...

  15. Titanium tungsten coatings for bioelectrochemical applications

    DEFF Research Database (Denmark)

    Wierzbicki, Rafal; Amato, Letizia; Łopacińska, J.

    2011-01-01

    This paper presents an assessment of titanium tungsten (TiW) coatings and their applicability as components of biosensing systems. The focus is put on using TiW as an electromechanical interface layer between carbon nanotube (CNT) forests and silicon nanograss (SiNG) cell scaffolds. Cytotoxicity...

  16. Distribution of induced activity in tungsten targets

    International Nuclear Information System (INIS)

    Donahue, R.J.; Nelson, W.R.

    1988-09-01

    Estimates are made of the induced activity created during high-energy electron showers in tungsten, using the EGS4 code. Photon track lengths, neutron yields and spatial profiles of the induced activity are presented. 8 refs., 9 figs., 1 tab

  17. Electrospark doping of steel with tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Denisova, Yulia, E-mail: yukolubaeva@mail.ru; Shugurov, Vladimir, E-mail: shugurov@opee.hcei.tsc.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); Petrikova, Elizaveta, E-mail: elizmarkova@yahoo.com [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); Seksenalina, Malika, E-mail: sportmiss@bk.ru [National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation); Ivanova, Olga, E-mail: ivaov@mail.ru; Ikonnikova, Irina, E-mail: irinaikonnikova@yandex.ru [Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Kunitsyna, Tatyana, E-mail: kma11061990@mail.ru; Vlasov, Victor, E-mail: rector@tsuab.ru [National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Klopotov, Anatoliy, E-mail: klopotovaa@tsuab.ru [National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Ivanov, Yuriy, E-mail: yufi55@mail.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation)

    2016-01-15

    The paper is devoted to the numerical modeling of thermal processes and the analysis of the structure and properties of the surface layer of carbon steel subjected to electrospark doping with tungsten. The problem of finding the temperature field in the system film (tungsten) / substrate (iron) is reduced to the solution of the heat conductivity equation. A one-dimensional case of heating and cooling of a plate with the thickness d has been considered. Calculations of temperature fields formed in the system film / substrate synthesized using methods of electrospark doping have been carried out as a part of one-dimensional approximation. Calculations have been performed to select the mode of the subsequent treatment of the system film / substrate with a high-intensity pulsed electron beam. Authors revealed the conditions of irradiation allowing implementing processes of steel doping with tungsten. A thermodynamic analysis of phase transformations taking place during doping of iron with tungsten in equilibrium conditions has been performed. The studies have been carried out on the surface layer of the substrate modified using the method of electrospark doping. The results showed the formation in the surface layer of a structure with a highly developed relief and increased strength properties.

  18. Consolidation of tungsten disilicide by plasma spraying

    Czech Academy of Sciences Publication Activity Database

    Brožek, Vlastimil; Ctibor, Pavel; Matějíček, Jiří; Rohan, Pavel; Janča, J.

    2007-01-01

    Roč. 52, č. 3 (2007), s. 311-320 ISSN 0001-7043 R&D Projects: GA ČR(CZ) GA104/05/0540 Institutional research plan: CEZ:AV0Z20430508 Keywords : Water stabilized plasma * tungsten disilicide * plasma deposition * thermal spray coatings Subject RIV: JJ - Other Materials

  19. CALICE silicon–tungsten electromagnetic calorimeter

    Indian Academy of Sciences (India)

    A highly granular electromagnetic calorimeter prototype based on tungsten absorber and sampling units equipped with silicon pads as sensitive devices for signal collection is under construction. The full prototype will have in total 30 layers and be read out by about 10000 Si cells of 1 × 1 cm2. A first module consisting of 14 ...

  20. Superhard Rhenium/Tungsten Diboride Solid Solutions.

    Science.gov (United States)

    Lech, Andrew T; Turner, Christopher L; Lei, Jialin; Mohammadi, Reza; Tolbert, Sarah H; Kaner, Richard B

    2016-11-02

    Rhenium diboride (ReB 2 ), containing corrugated layers of covalently bonded boron, is a superhard metallic compound with a microhardness reaching as high as 40.5 GPa (under an applied load of 0.49 N). Tungsten diboride (WB 2 ), which takes a structural hybrid between that of ReB 2 and AlB 2 , where half of the boron layers are planar (as in AlB 2 ) and half are corrugated (as in ReB 2 ), has been shown not to be superhard. Here, we demonstrate that the ReB 2 -type structure can be maintained for solid solutions of tungsten in ReB 2 with tungsten content up to a surprisingly large limit of nearly 50 atom %. The lattice parameters for the solid solutions linearly increase along both the a- and c-axes with increasing tungsten content, as evaluated by powder X-ray and neutron diffraction. From micro- and nanoindentation hardness testing, all of the compositions within the range of 0-48 atom % W are superhard, and the bulk modulus of the 48 atom % solid solution is nearly identical to that of pure ReB 2 . These results further indicate that ReB 2 -structured compounds are superhard, as has been predicted from first-principles calculations, and may warrant further studies into additional solid solutions or ternary compounds taking this structure type.

  1. Electrospark doping of steel with tungsten

    International Nuclear Information System (INIS)

    Denisova, Yulia; Shugurov, Vladimir; Petrikova, Elizaveta; Seksenalina, Malika; Ivanova, Olga; Ikonnikova, Irina; Kunitsyna, Tatyana; Vlasov, Victor; Klopotov, Anatoliy; Ivanov, Yuriy

    2016-01-01

    The paper is devoted to the numerical modeling of thermal processes and the analysis of the structure and properties of the surface layer of carbon steel subjected to electrospark doping with tungsten. The problem of finding the temperature field in the system film (tungsten) / substrate (iron) is reduced to the solution of the heat conductivity equation. A one-dimensional case of heating and cooling of a plate with the thickness d has been considered. Calculations of temperature fields formed in the system film / substrate synthesized using methods of electrospark doping have been carried out as a part of one-dimensional approximation. Calculations have been performed to select the mode of the subsequent treatment of the system film / substrate with a high-intensity pulsed electron beam. Authors revealed the conditions of irradiation allowing implementing processes of steel doping with tungsten. A thermodynamic analysis of phase transformations taking place during doping of iron with tungsten in equilibrium conditions has been performed. The studies have been carried out on the surface layer of the substrate modified using the method of electrospark doping. The results showed the formation in the surface layer of a structure with a highly developed relief and increased strength properties

  2. Study of nano-metric silicon carbide powder sintering. Application to fibers processing

    International Nuclear Information System (INIS)

    Malinge, A.

    2011-01-01

    Silicon carbide ceramic matrix composites (SiCf/SiCm) are of interest for high temperature applications in aerospace or nuclear components for their relatively high thermal conductivity and low activation under neutron irradiation. While most of silicon carbide fibers are obtained through the pyrolysis of a poly-carbo-silane precursor, sintering of silicon carbide nano-powders seems to be a promising route to explore. For this reason, pressureless sintering of SiC has been studied. Following the identification of appropriate sintering aids for the densification, optimization of the microstructure has been achieved through (i) the analysis of the influence of operating parameters and (ii) the control of the SiC β a SiC α phase transition. Green fibers have been obtained by two different processes involving the extrusion of SiC powder dispersion in polymer solution or the coagulation of a water-soluble polymer containing ceramic particles. Sintering of these green fibers led to fibers of around fifty microns in diameter. (author) [fr

  3. ITER tungsten divertor design development and qualification program

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, T., E-mail: takeshi.hirai@iter.org [ITER Organization, Route de Vinon sur Verdon, F-13115 Saint Paul lez Durance (France); Escourbiac, F.; Carpentier-Chouchana, S.; Fedosov, A.; Ferrand, L.; Jokinen, T.; Komarov, V.; Kukushkin, A.; Merola, M.; Mitteau, R.; Pitts, R.A.; Shu, W.; Sugihara, M. [ITER Organization, Route de Vinon sur Verdon, F-13115 Saint Paul lez Durance (France); Riccardi, B. [F4E, c/ Josep Pla, n.2, Torres Diagonal Litoral, Edificio B3, E-08019 Barcelona (Spain); Suzuki, S. [JAEA, Fusion Research and Development Directorate JAEA, 801-1 Mukouyama, Naka, Ibaragi 311-0193 (Japan); Villari, R. [Associazione EURATOM-ENEA sulla Fusione, Via Enrico Fermi 45, I-00044 Frascati, Rome (Italy)

    2013-10-15

    Highlights: • Detailed design development plan for the ITER tungsten divertor. • Latest status of the ITER tungsten divertor design. • Brief overview of qualification program for the ITER tungsten divertor and status of R and D activity. -- Abstract: In November 2011, the ITER Council has endorsed the recommendation that a period of up to 2 years be set to develop a full-tungsten divertor design and accelerate technology qualification in view of a possible decision to start operation with a divertor having a full-tungsten plasma-facing surface. To ensure a solid foundation for such a decision, a full tungsten divertor design, together with a demonstration of the necessary high performance tungsten monoblock technology should be completed within the required timescale. The status of both the design and technology R and D activity is summarized in this paper.

  4. Electrokinetic treatment of firing ranges containing tungsten-contaminated soils

    International Nuclear Information System (INIS)

    Braida, Washington; Christodoulatos, Christos; Ogundipe, Adebayo; Dermatas, Dimitris; O'Connor, Gregory

    2007-01-01

    Tungsten-based alloys and composites are being used and new formulations are being considered for use in the manufacturing of different types of ammunition. The use of tungsten heavy alloys (WHA) in new munitions systems and tungsten composites in small caliber ammunition could potentially release substantial amounts of this element into the environment. Although tungsten is widely used in industrial and military applications, tungsten's potential environmental and health impacts have not been thoroughly addressed. This necessitates the research and development of remedial technologies to contain and/or remove tungsten from soils that may serve as a source for water contamination. The current work investigates the feasibility of using electrokinetics for the remediation of tungsten-contaminated soils in the presence of other heavy metals of concern such as Cu and Pb with aim to removing W from the soil while stabilizing in situ, Pb and Cu

  5. Computer simulations for thorium doped tungsten crystals

    Energy Technology Data Exchange (ETDEWEB)

    Eberhard, Bernd

    2009-07-17

    Tungsten has the highest melting point among all metals in the periodic table of elements. Furthermore, its equilibrium vapor pressure is by far the lowest at the temperature given. Thoria, ThO{sub 2}, as a particle dopant, results in a high temperature creep resistant material. Moreover, thorium covered tungsten surfaces show a drastically reduced electronic work function. This results in a tremendous reduction of tip temperatures of cathodes in discharge lamps, and, therefore, in dramatically reduced tungsten vapor pressures. Thorium sublimates at temperatures below those of a typical operating cathode. For proper operation, a diffusional flow of thorium atoms towards the surface has to be maintained. This atomic flux responds very sensitively on the local microstructure, as grain boundaries as well as dislocation cores offer ''short circuit paths'' for thorium atoms. In this work, we address some open issues of thoriated tungsten. A molecular dynamics scheme (MD) is used to derive static as well as dynamic material properties which have their common origin in the atomistic behavior of tungsten and thorium atoms. The interatomic interactions between thorium and tungsten atoms are described within the embedded atom model (EAM). So far, in literature no W-Th interaction potentials on this basis are described. As there is no alloying system known between thorium and tungsten, we have determined material data for the fitting of these potentials using ab-initio methods. This is accomplished using the full potential augmented plane wave method (FLAPW), to get hypothetical, i.e. not occurring in nature, ''alloy'' data of W-Th. In order to circumvent the limitations of classical (NVE) MD schemes, we eventually couple our model systems to external heat baths or volume reservoirs (NVT, NPT). For the NPT ensemble, we implemented a generalization of the variable cell method in combination with the Langevin piston, which results in a

  6. Computer simulations for thorium doped tungsten crystals

    International Nuclear Information System (INIS)

    Eberhard, Bernd

    2009-01-01

    Tungsten has the highest melting point among all metals in the periodic table of elements. Furthermore, its equilibrium vapor pressure is by far the lowest at the temperature given. Thoria, ThO 2 , as a particle dopant, results in a high temperature creep resistant material. Moreover, thorium covered tungsten surfaces show a drastically reduced electronic work function. This results in a tremendous reduction of tip temperatures of cathodes in discharge lamps, and, therefore, in dramatically reduced tungsten vapor pressures. Thorium sublimates at temperatures below those of a typical operating cathode. For proper operation, a diffusional flow of thorium atoms towards the surface has to be maintained. This atomic flux responds very sensitively on the local microstructure, as grain boundaries as well as dislocation cores offer ''short circuit paths'' for thorium atoms. In this work, we address some open issues of thoriated tungsten. A molecular dynamics scheme (MD) is used to derive static as well as dynamic material properties which have their common origin in the atomistic behavior of tungsten and thorium atoms. The interatomic interactions between thorium and tungsten atoms are described within the embedded atom model (EAM). So far, in literature no W-Th interaction potentials on this basis are described. As there is no alloying system known between thorium and tungsten, we have determined material data for the fitting of these potentials using ab-initio methods. This is accomplished using the full potential augmented plane wave method (FLAPW), to get hypothetical, i.e. not occurring in nature, ''alloy'' data of W-Th. In order to circumvent the limitations of classical (NVE) MD schemes, we eventually couple our model systems to external heat baths or volume reservoirs (NVT, NPT). For the NPT ensemble, we implemented a generalization of the variable cell method in combination with the Langevin piston, which results in a set of Langevin equations, i.e. stochastic

  7. Progress in silicon carbide semiconductor technology

    Science.gov (United States)

    Powell, J. A.; Neudeck, P. G.; Matus, L. G.; Petit, J. B.

    1992-01-01

    Silicon carbide semiconductor technology has been advancing rapidly over the last several years. Advances have been made in boule growth, thin film growth, and device fabrication. This paper wi11 review reasons for the renewed interest in SiC, and will review recent developments in both crystal growth and device fabrication.

  8. 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.

  9. Testing boron carbide under triaxial compression

    Science.gov (United States)

    Anderson, Charles; Chocron, Sidney; Dannemann, Kathryn A.; Nicholls, Arthur E.

    2012-03-01

    This article focuses on the pressure dependence and summarizes the characterization work conducted on intact and predamaged specimens of boron carbide under confinement in a pressure vessel and in a thick steel sleeve. The failure curves obtained are presented, and the data compared to experimental data from the literature.

  10. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

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

  11. Kinetic analysis of boron carbide sintering

    International Nuclear Information System (INIS)

    Borchert, W.; Kerler, A.R.

    1975-01-01

    The kinetics of the sintering of boron carbide were investigated by shrinkage measurements with a high-temperature dilatometer under argon atmosphere in dependence on temperature, grain size, and pressure. The activation energies and the reaction mechanisms of the different stages of sintering were determined. (orig.) [de

  12. Low temperature CVD deposition of silicon carbide

    International Nuclear Information System (INIS)

    Dariel, M.; Yeheskel, J.; Agam, S.; Edelstein, D.; Lebovits, O.; Ron, Y.

    1991-04-01

    The coating of graphite on silicon carbide from the gaseous phase in a hot-well, open flow reactor at 1150degC is described. This study constitutes the first part of an investigation of the process for the coating of nuclear fuel by chemical vapor deposition (CVD)

  13. Anomalous Seebeck coefficient in boron carbides

    International Nuclear Information System (INIS)

    Aselage, T.L.; Emin, D.; Wood, C.; Mackinnon, I.D.R.; Howard, I.A.

    1987-01-01

    Boron carbides exhibit an anomalously large Seebeck coefficient with a temperature coefficient that is characteristic of polaronic hopping between inequivalent sites. The inequivalence in the sites is associated with disorder in the solid. The temperature dependence of the Seebeck coefficient for materials prepared by different techniques provides insight into the nature of the disorder

  14. 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 catalysing

  15. Reaction of boron carbide with molybdenum disilicide

    International Nuclear Information System (INIS)

    Novikov, A.V.; Melekhin, V.F.; Pegov, V.S.

    1989-01-01

    The investigation results of interaction in the B 4 C-MoSi 2 system during sintering in vacuum are presented. Sintering of boron carbide with molybdenum disilicide is shown to lead to the formation of MoB 2 , SiC, Mo 5 Si 3 compounds, the presence of carbon-containing covering plays an important role in sintering

  16. Perfomance analysis of boron carbide in LMFBR

    International Nuclear Information System (INIS)

    Pitner, A.L.; Birney, K.R.

    1975-01-01

    Reactivity control in the FFTF and LMFBR's will be maintained by control elements utilizing boron carbide pellets contained in stainless steel pins. Computer performance codes predict irradiation service conditions of absorber pellets and identify required experimental testing. Test results are incorporated in the codes to improve performance prediction capabilities

  17. Growth and structure of carbide nanorods

    International Nuclear Information System (INIS)

    Lieber, C.M.; Wong, E.W.; Dai, H.; Maynor, B.W.; Burns, L.D.

    1996-01-01

    Recent research on the growth and structure of carbide nanorods is reviewed. Carbide nanorods have been prepared by reacting carbon nanotubes with volatile transition metal and main group oxides and halides. Using this approach it has been possible to obtain solid carbide nanorods of TiC, SiC, NbC, Fe 3 C, and BC x having diameters between 2 and 30 nm and lengths up to 20 microm. Structural studies of single crystal TiC nanorods obtained through reactions of TiO with carbon nanotubes show that the nanorods grow along both [110] and [111] directions, and that the rods can exhibit either smooth or saw-tooth morphologies. Crystalline SiC nanorods have been produced from reactions of carbon nanotubes with SiO and Si-iodine reactants. The preferred growth direction of these nanorods is [111], although at low reaction temperatures rods with [100] growth axes are also observed. The growth mechanisms leading to these novel nanomaterials have also been addressed. Temperature dependent growth studies of TiC nanorods produced using a Ti-iodine reactant have provided definitive proof for a template or topotactic growth mechanism, and furthermore, have yielded new TiC nanotube materials. Investigations of the growth of SiC nanorods show that in some cases a catalytic mechanism may also be operable. Future research directions and applications of these new carbide nanorod materials are discussed

  18. Processing and alloying of tungsten heavy alloys

    International Nuclear Information System (INIS)

    Bose, A.

    1993-01-01

    Tungsten heavy alloys are two-phase metal matrix composites with a unique combination of density, strength, and ductility. They are processed by liquid-phase sintering of mixed elemental powders. The final microstructure consists of a contiguous network of nearly pure tungsten grains embedded in a matrix of a ductile W-Ni-Fe alloy. Due to the unique property combination of the material, they are used extensively as kinetic energy penetrators, radiation shields. counterbalances, and a number of other applications in the defense industry. The properties of these alloys are extremely sensitive to the processing conditions. Porosity levels as low as 1% can drastically degrade the properties of these alloys. During processing, care must be taken to reduce or prevent incomplete densification, hydrogen embrittlement, impurity segregation to the grain boundaries, solidification shrinkage induced porosity, and in situ formation of pores due to the sintering atmosphere. This paper will discuss some of the key processing issues for obtaining tungsten heavy alloys with good properties. High strength tungsten heavy alloys are usually fabricated by swaging and aging the conventional as-sintered material. The influence of this on the shear localization tendency of a W-Ni-Co alloy will also be demonstrated. Recent developments have shown that the addition of certain refractory metals partially replacing tungsten can significantly improve the strength of the conventional heavy alloys. This development becomes significant due to the recent interest in near net shaping techniques such as powder injection moldings. The role of suitable alloying additions to the classic W-Ni-Fe based heavy alloys and their processing techniques will also be discussed in this paper

  19. Low temperature carbide precipitation in a nickel base superalloy

    Science.gov (United States)

    Garosshen, T. J.; McCarthy, G. P.

    1985-07-01

    A M23C6 carbide phase has been observed to precipitate at relatively low temperatures (732 to 760 °C) in a nickel base superalloy.* Transmission Electron Microscopy shows the low temperature carbide to reside at the grain boundaries in a continuous morphology. The continuous carbide has a typical width of 25 to 40 nm with aspect ratios on the order of 30:1. The structure of the carbide is face-centered cubic with a lattice parameter (α0) of approximately 1.063 nm, which is typical of the M23C6 carbides that form at higher temperatures. STEM analysis indicates the carbide to have a typical M23C6 chemistry, enriched in chromium with lesser amounts of molybdenum, cobalt, and nickel. The formation of the continuous carbide occurs readily around 760 °C; however, at temperatures 55 °C lower the precipitation kinetics are significantly reduced. The extent of the low temperature carbide reaction is observed to be dependent upon the duration of the low temperature exposure and the degree of prior M23C6 stabilization at an intermediate temperature. Alloy modifications, involving hafnium additions and lower carbon levels, were studied with the aim of reducing the extent of this carbide reaction. Despite these chemistry modifications, the low temperature carbide was still observed to form to an appreciable extent. The presence of the continuous carbide is also observed to reduce the stress-rupture life of the alloy.

  20. Boron carbide nanowires: Synthesis and characterization

    Science.gov (United States)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  1. Synthesis of tantalum carbide and nitride nanoparticles using a reactive mesoporous template for electrochemical hydrogen evolution

    KAUST Repository

    Alhajri, Nawal Saad

    2013-01-01

    Tantalum carbide and nitride nanocrystals were prepared through the reaction of a tantalum precursor with mesoporous graphitic (mpg)-C 3N4. The effects of the reaction temperature, the ratio of the Ta precursor to the reactive template (mpg-C3N4), and the selection of the carrier gas (Ar, N2 and NH3) on the resultant crystal phases and structures were investigated. The produced samples were characterized using powder X-ray diffraction (XRD), CHN elemental analyses, thermogravimetric analyses (TGA), nitrogen sorption, a temperature-programmed reaction with mass spectroscopy (MS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results indicate that the different tantalum phases with cubic structure, TaN, Ta2CN, and TaC, can be formed under a flow of nitrogen when formed at different temperatures. The Ta3N5 phase with a Ta5+ oxidation state was solely obtained at 1023 K under a flow of ammonia, which gasified the C 3N4 template and was confirmed by detecting the decomposed gaseous products via MS. Significantly, the formation of TaC, Ta2CN, and TaN can be controlled by altering the weight ratio of the C 3N4 template relative to the Ta precursor at 1573 K under a flow of nitrogen. The high C3N4/Ta precursor ratio generally resulted in high carbide content rather than a nitride one, consistent with the role of mpg-C3N4 as a carbon source. Electrochemical measurements revealed that the synthesized nanomaterials were consistently able to produce hydrogen under acidic conditions (pH 1). The obtained Tafel slope indicates that the rate-determining step is the Volmer discharge step, which is consistent with adsorbed hydrogen being weakly bound to the surface during electrocatalysis. © 2013 The Royal Society of Chemistry.

  2. Synergistic methods for the production of high-strength and low-cost boron carbide

    Science.gov (United States)

    Wiley, Charles Schenck

    2011-12-01

    Boron carbide (B4C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B4C make it a nearly ideal material for personnel and vehicular armor. B4C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B4C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B4C powders. The boron carbide powder examined in this study was a sub-micron (0.6 mum median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form of phenolic resin, and titanium additives in the form of 32 nm and 0.9 mum TiO2 powders were selected. Parametric studies of

  3. Polymer assisted deposition of electrochromic tungsten oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kalagi, S.S. [Govindram Seksaria Science College, Belgaum 590006, Karnataka (India); Dalavi, D.S.; Pawar, R.C.; Tarwal, N.L.; Mali, S.S. [Thin Films Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India); Patil, P.S., E-mail: psp_phy@unishivaji.ac.i [Thin Films Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India)

    2010-03-18

    We report the synthesis of structurally and uniformly deposited porous tungsten oxide (WO{sub 3}) thin films for the first time by the novel route of polymer assisted deposition (PAD) using ammonium tungstate as a precursor with polyvinyl alcohol (PVA) as an additive. The effect of deposition parameters on the morphological, optical and electrochemical performance of the thin films is investigated. WO{sub 3} thin films were characterized for their structural, morphological, optical and electrochromic properties. XRD result indicates monoclinic phase of WO{sub 2.92}. FT-Raman studies show high intensity peaks centered at 997 cm{sup -1}and 798 cm{sup -1}. SEM results indicate that there is uniform deposition of porous WO{sub 3}-PVA agglomerates on the transparent substrates. SEM data show low dense structure of an average grain size of about 1 {mu}m. Electrochromic studies reveal highly reversible and the stable nature of the thin films. Transmission data show an optical modulation density of 46.57% at 630 nm with an excellent reversibility of 89% and an electrochromic coloration efficiency of 36 cm{sup 2}/C.

  4. 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:

  5. In situ growth of silicon carbide nanowires from anthracite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.; Fox, J.T.; Cannon, F.S.; Komarneni, S. [Penn State University, University Park, PA (United States)

    2011-04-15

    Silicon carbide nanowires (SCNWs) were grown from anthracite fine surfaces through a simple one-step carbothermal process with silicon powder as the Si precursor. This straightforward and fast formation of SCNWs made it possible to maintain the binding of briquetted waste anthracite fines at very high temperatures as an alternative fuel in foundry cupola furnaces. This SCNW mechanism could thus provide the crucial hot crushing strength in the cupola heat zone and melt zone. Progressive thermal tests exhibited that the formation of the SCNWs started from 1100{sup o}C, and was favored at 1400{sup o}C. No extra metal catalyst was needed for the growth of the SCNWs. Characterizations were performed by XRD, SEM, EDS, TEM, and SAED. The SCNWs were 30-60 nm in diameter. Many non-epitaxial branches of the nanowires were also formed through this one-step process as observed by TEM. The results suggest that the SCNWs were most likely grown through the vapor solid mechanism.

  6. Synthesis of silicon carbide by carbothermal reduction of silica

    International Nuclear Information System (INIS)

    Abel, Joao Luis

    2009-01-01

    The production of silicon carbide (SiC) in an industrial scale still by carbothermal reduction of silica. This study aims to identify, in a comparative way, among the common reducers like petroleum coke, carbon black, charcoal and graphite the carbothermal reduction of silica from the peat. It is shown, that the peat, also occurs in nature together with high purity silica sand deposits, where the proximity of raw materials and their quality are key elements that determine the type, purity and cost of production of SiC. Tests were running from samples produced in the electric resistance furnace with controlled atmosphere at temperatures of 1550 degree C, 1600 degree C and 1650 degree C, both the precursors and products of reaction of carbothermal reduction were characterized by applying techniques of X-ray diffraction, scanning electron microscopy (SEM) and Energy-Dispersive X-ray analysis Spectroscopy (EDS). The results showed the formation of SiC for all common reducers, as well as for peat, but it was not possible to realize clearly the difference between them, being necessary, specific tests. (author)

  7. Irradiation effects in tungsten-copper laminate composite

    Energy Technology Data Exchange (ETDEWEB)

    Garrison, L.M., E-mail: garrisonlm@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Katoh, Y. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Snead, L.L. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Byun, T.S. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Reiser, J.; Rieth, M. [Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2016-12-01

    Tungsten-copper laminate composite has shown promise as a structural plasma-facing component as compared to tungsten rod or plate. The present study evaluated the tungsten-copper composite after irradiation in the High Flux Isotope Reactor (HFIR) at temperatures of 410–780 °C and fast neutron fluences of 0.02–9.0 × 10{sup 25} n/m{sup 2}, E > 0.1 MeV, 0.0039–1.76 displacements per atom (dpa) in tungsten. Tensile tests were performed on the composites, and the fracture surfaces were analyzed with scanning electron microscopy. Before irradiation, the tungsten layers had brittle cleavage failure, but the overall composite had 15.5% elongation at 22 °C. After only 0.0039 dpa this was reduced to 7.7% elongation, and no ductility was observed after 0.2 dpa at all irradiation temperatures when tensile tested at 22 °C. For elevated temperature tensile tests after irradiation, the composite only had ductile failure at temperatures where the tungsten was delaminating or ductile. - Highlights: • Fusion reactors need a tough, ductile tungsten plasma-facing material. • The unirradiated tungsten-copper laminate is more ductile than tungsten alone. • After neutron irradiation, the composite has significantly less ductility. • The tungsten behavior appears to dominate the overall composite behavior.

  8. Detection and reduction of tungsten contamination in ion implantation processes

    International Nuclear Information System (INIS)

    Polignano, M.L.; Galbiati, A.; Grasso, S.; Mica, I.; Barbarossa, F.; Magni, D.

    2016-01-01

    In this paper, we review the results of some studies addressing the problem of tungsten contamination in implantation processes. For some tests, the implanter was contaminated by implantation of wafers with an exposed tungsten layer, resulting in critical contamination conditions. First, DLTS (deep level transient spectroscopy) measurements were calibrated to measure tungsten contamination in ion-implanted samples. DLTS measurements of tungsten-implanted samples showed that the tungsten concentration increases linearly with the dose up to a rather low dose (5 x 10 10 cm -2 ). Tungsten deactivation was observed when the dose was further increased. Under these conditions, ToF-SIMS revealed tungsten at the wafer surface, showing that deactivation was due to surface segregation. DLTS calibration could therefore be obtained in the linear dose regime only. This calibration was used to evaluate the tungsten contamination in arsenic implantations. Ordinary operating conditions and critical contamination conditions of the equipment were compared. A moderate tungsten contamination was observed in samples implanted under ordinary operating conditions. This contamination was easily suppressed by a thin screen oxide. On the contrary, implantations in critical conditions of the equipment resulted in a relevant tungsten contamination, which could be reduced but not suppressed even by a relatively thick screen oxide (up to 150 Aa). A decontamination process consisting of high dose implantations of dummy wafers was tested for its efficiency to remove tungsten and titanium contamination. This process was found to be much more effective for titanium than for tungsten. Finally, DLTS proved to be much more sensitive that TXRF (total reflection X-ray fluorescence) in detecting tungsten contamination. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Detection and reduction of tungsten contamination in ion implantation processes

    Energy Technology Data Exchange (ETDEWEB)

    Polignano, M.L.; Galbiati, A.; Grasso, S.; Mica, I.; Barbarossa, F.; Magni, D. [STMicroelectronics, Agrate Brianza (Italy)

    2016-12-15

    In this paper, we review the results of some studies addressing the problem of tungsten contamination in implantation processes. For some tests, the implanter was contaminated by implantation of wafers with an exposed tungsten layer, resulting in critical contamination conditions. First, DLTS (deep level transient spectroscopy) measurements were calibrated to measure tungsten contamination in ion-implanted samples. DLTS measurements of tungsten-implanted samples showed that the tungsten concentration increases linearly with the dose up to a rather low dose (5 x 10{sup 10} cm{sup -2}). Tungsten deactivation was observed when the dose was further increased. Under these conditions, ToF-SIMS revealed tungsten at the wafer surface, showing that deactivation was due to surface segregation. DLTS calibration could therefore be obtained in the linear dose regime only. This calibration was used to evaluate the tungsten contamination in arsenic implantations. Ordinary operating conditions and critical contamination conditions of the equipment were compared. A moderate tungsten contamination was observed in samples implanted under ordinary operating conditions. This contamination was easily suppressed by a thin screen oxide. On the contrary, implantations in critical conditions of the equipment resulted in a relevant tungsten contamination, which could be reduced but not suppressed even by a relatively thick screen oxide (up to 150 Aa). A decontamination process consisting of high dose implantations of dummy wafers was tested for its efficiency to remove tungsten and titanium contamination. This process was found to be much more effective for titanium than for tungsten. Finally, DLTS proved to be much more sensitive that TXRF (total reflection X-ray fluorescence) in detecting tungsten contamination. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Precursor of color superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Kitazawa, M. [Kyoto Univ., Dept. of Physics, Kyoto (Japan); Koide, T.; Kunihiro, T. [Kyoto Univ., Yukawa Institute for Theoretical Physics, Kyoto (Japan); Nemoto, Y. [Brookhaven National Laboratory, RIKEN BNL Research Center, Upton, NY (United States)

    2002-09-01

    We investigate possible precursory phenomena of color superconductivity in quark matter at finite temperature T with use of a simple Nambu-Jona-Lasinio model. It is found that the fluctuating pair field exists with a prominent strength even well above the critical temperature T{sub c}. We show that the collective pair field has a complex energy located in the second Riemann sheet, which approaches the origin as T is lowered to T{sub c}. We discuss the possible relevance of the precursor to the observables to be detected in heavy ion collisions. (author)

  11. Surface characterization of alumina reinforced with niobium carbide obtained by polymer precursor

    Directory of Open Access Journals (Sweden)

    Wilson Acchar

    2006-09-01

    Full Text Available Active filler controlled pyrolysis of polymers (AFCOP is a recent method for obtaining near-net shaped ceramic bodies. Alumina based composites have been developed for use as cutting tools, so knowledge of the surface composition is extremely important because it is directly related to the hardness and wear resistance Samples containing a fixed concentration of 60 wt. (% of polysiloxane and a mixture of metallic niobium and alumina powder were homogenized, uniaxially warm pressed at 80 °C and subsequently pyrolyzed in flowing argon at 1200, 1400 and 1500 °C. Analysis of the surface composition was carried out by X ray photoelectron spectroscopy, infrared spectroscopy, X ray diffraction and scanning electron microscopy. The results have indicated that the formation of the phases on the surface depends strongly on the niobium/carbon ratio in the raw materials.

  12. Spectroscopic modeling for tungsten EUV spectra

    International Nuclear Information System (INIS)

    Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A.; Suzuki, Chihiro; Morita, Shigeru; Goto, Motoshi; Sasaki, Akira; Nakamura, Nobuyuki; Yamamoto, Norimasa; Koike, Fumihiro

    2014-01-01

    We have constructed an atomic model for tungsten extreme ultraviolet (EUV) spectra to reconstruct characteristic spectral feature of unresolved transition array (UTA) observed at 4-7 nm for tungsten ions. In the tungsten atomic modeling, we considered fine-structure levels with the quantum principal number n up to 6 as the atomic structure and calculated the electron-impact collision cross sections by relativistic distorted-wave method, using HULLAC atomic code. We measured tungsten EUV spectra in Large Helical Device (LHD) and Compact Electron Beam Ion Trap device (CoBIT) and compared them with the model calculation. The model successfully explain series of emission peaks at 1.5-3.5 nm as n=5-4 and 6-4 transitions of W 24+ - W 32+ measured in CoBIT and LHD and the charge state distributions were estimated for LHD plasma. The UTA feature observed at 4-7 nm was also successfully reconstructed with our model. The peak at ∼5 nm is produced mainly by many 4f-4d transition of W 22+ - W 35+ ions, and the second peak at ∼6 nm is produced by 4f-4d transition of W 25+ - W 28+ ions, and 4d-4p inner-shell transitions, 4p 5 4d n+1 - 4p 6 4d n , of W 29+ - W 35+ ions. These 4d-4p inner-shell transitions become strong since we included higher excited states such as 4p 5 4d n 4f state, which ADAS atomic data set does not include for spectroscopic modeling with fine structure levels. (author)

  13. Laser induced white lighting of tungsten filament

    Science.gov (United States)

    Strek, W.; Tomala, R.; Lukaszewicz, M.

    2018-04-01

    The sustained bright white light emission of thin tungsten filament was induced under irradiation with focused beam of CW infrared laser diode. The broadband emission centered at 600 nm has demonstrated the threshold behavior on excitation power. Its intensity increased non-linearly with excitation power. The emission occurred only from the spot of focused beam of excitation laser diode. The white lighting was accompanied by efficient photocurrent flow and photoelectron emission which both increased non-linearly with laser irradiation power.

  14. Process for separation of tungsten and molybdenum by extraction

    International Nuclear Information System (INIS)

    Zelikman, A.N.; Voldman, G.M.; Rumyantsev, V.K.; Ziberov, G.N.; Kagermanian, V.S.

    1976-01-01

    A process for the separation of tungsten and molybdenum by extraction involves the addition of HCl or HNO 3 to an aqueous solution containing tungsten and molybdenum to obtain a pH from 0.5 to 4.3, and introduction of a stabilizer comprising water-soluble phosphorus salts and a complexing agent, hydrogen peroxide, in an amount from 1.5 to 2 mole per 1 g-atom of the total content of tungsten and molybdenum. Then molybdenum is selectively extracted from the resulting aqueous solution with tri-n-butylphosphate with equal volumetric proportioning of the aqueous and organic solutions. Re-extraction of molybdenum and partially tungsten is carried out from the organic extracting agent with an alkali or soda solution. The process makes possible the preparation of tungsten solution containing no more than 0.001 g/l of molybdenum, and an increase in the degree of extraction of tungsten and molybdenum

  15. Neutron irradiation damage in transition metal carbides

    International Nuclear Information System (INIS)

    Matsui, Hisayuki; Nesaki, Kouji; Kiritani, Michio

    1991-01-01

    Effects of neutron irradiation on the physical properties of light transition metal carbides, TiC x , VC x and NbC x , were examined, emphasizing the characterization of irradiation induced defects in the nonstoichiometric composition. TiC x irradiated with 14 MeV (fusion) neutrons showed higher damage rates with increasing C/Ti (x) ratio. A brief discussion is made on 'cascade damage' in TiC x irradiated with fusion neutrons. Two other carbides (VC x and NbC x ) were irradiated with fission reactor neutrons. The irradiation effects on VC x were not so simple, because of the complex irradiation behavior of 'ordered' phases. For instance, complete disordering was revealed in an ordered phase, 'V 8 C 7 ', after an irradiation dose of 10 25 n/m 2 . (orig.)

  16. 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.

  17. Seebeck effect of some thin film carbides

    International Nuclear Information System (INIS)

    Beensh-Marchwicka, G.; Prociow, E.

    2002-01-01

    Several materials have been investigated for high-temperature thin film thermocouple applications. These include silicon carbide with boron (Si-C-B), ternary composition based on Si-C-Mn, fourfold composition based on Si-C-Zr-B and tantalum carbide (TaC). All materials were deposited on quartz or glass substrates using the pulse sputter deposition technique. Electrical conduction and thermoelectric power were measured for various compositions at 300-550 K. It has been found, that the efficiency of thermoelectric power of films containing Si-C base composition was varied from 0.0015-0.034 μW/cmK 2 . However for TaC the value about 0.093 μW/cmK 2 was obtained. (author)

  18. Radiation stability of proton irradiated zirconium carbide

    International Nuclear Information System (INIS)

    Yang, Yong; Dickerson, Clayton A.; Allen, Todd R.

    2009-01-01

    The use of zirconium carbide (ZrC) is being considered for the deep burn (DB)-TRISO fuel as a replacement for the silicon carbide coating. The radiation stability of ZrC was studied using 2.6 MeV protons, across the irradiation temperature range from 600 to 900degC and to doses up to 1.75 dpa. The microstructural characterization shows that the irradiated microstructure is comprised of a high density of nanometer-sized dislocation loops, while no irradiation induced amorphization or voids are observed. The lattice expansion induced by point defects is found to increase as the dose increases for the samples irradiated at 600 and 800degC, while for the 900degC irradiation, a slight lattice contraction is observed. The radiation hardening is also quantified using a micro indentation technique for the temperature and doses studies. (author)

  19. Visible light emission from porous silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang

    2017-01-01

    Light-emitting silicon carbide is emerging as an environment-friendly wavelength converter in the application of light-emitting diode based white light source for two main reasons. Firstly, SiC has very good thermal conductivity and therefore a good substrate for GaN growth in addition to the sma...... by time-resolved photoluminescence. The ultrashort lifetime in the order of ~70ps indicates porous SiC is very promising for the application in the ultrafast visible light communications.......Light-emitting silicon carbide is emerging as an environment-friendly wavelength converter in the application of light-emitting diode based white light source for two main reasons. Firstly, SiC has very good thermal conductivity and therefore a good substrate for GaN growth in addition to the small...

  20. Structure of Boron Carbide: Where's the Carbon?

    Science.gov (United States)

    Marx, David; Seidler, Gerald; Fister, Timothy; Nagle, Kenneth; Segre, Carlo

    2008-03-01

    Although the structure of the boron carbide series, B12-xCx with 0.06 x x-ray scattering (LERIX) spectrometer on the PNC-CAT beamline at the Advanced Photon Source at Argonne National Lab has enabled differentiation of the boron and carbon absorption edge data for the various crystallographic sites. The structure (R-3m) consists of twelve-atom icosahedra and three-atom chains. Boron carbide may have a maximum of three carbon atoms, which may be located on the two end of chain sites and in one of two inequivalent sites on the icosahedra. At least one carbon atom must be present in the structure for it to be stable. In this presentation, structural results from non-resonant x-ray scattering for seven samples, ranging from B4C to B10.1C will be presented.

  1. HCl removal using cycled carbide slag from calcium looping cycles

    International Nuclear Information System (INIS)

    Xie, Xin; Li, Yingjie; Wang, Wenjing; Shi, Lei

    2014-01-01

    Highlights: • Cycled carbide slag from calcium looping cycles is used to remove HCl. • The optimum temperature for HCl removal of cycled carbide slag is 700 °C. • The presence of CO 2 restrains HCl removal of cycled carbide slag. • CO 2 capture conditions have important effects on HCl removal of cycled carbide slag. • HCl removal capacity of carbide slag drops with cycle number rising from 1 to 50. - Abstract: The carbide slag is an industrial waste from chlor-alkali plants, which can be used to capture CO 2 in the calcium looping cycles, i.e. carbonation/calcination cycles. In this work, the cycled carbide slag from the calcium looping cycles for CO 2 capture was proposed to remove HCl in the flue gas from the biomass-fired and RDFs-fired boilers. The effects of chlorination temperature, HCl concentration, particle size, presence of CO 2 , presence of O 2 , cycle number and CO 2 capture conditions in calcium looping cycles on the HCl removal behavior of the carbide slag experienced carbonation/calcination cycles were investigated in a triple fixed-bed reactor. The chlorination product of the cycled carbide slag from the calcium looping after absorbing HCl is not CaCl 2 but CaClOH. The optimum temperature for HCl removal of the cycled carbide slag from the carbonation/calcination cycles is 700 °C. The chlorination conversion of the cycled carbide slag increases with increasing the HCl concentration. The cycled carbide slag with larger particle size exhibits a lower chlorination conversion. The presence of CO 2 decreases the chlorination conversions of the cycled carbide slag and the presence of O 2 has a trifling impact. The chlorination conversion of the carbide slag experienced 1 carbonation/calcination cycle is higher than that of the uncycled calcined sorbent. As the number of carbonation/calcination cycles increases from 1 to 50, the chlorination conversion of carbide slag drops gradually. The high calcination temperature and high CO 2

  2. Influence of tungsten substitution and oxygen deficiency on the thermoelectric properties of CaMnO{sub 3−δ}

    Energy Technology Data Exchange (ETDEWEB)

    Thiel, Philipp; Eilertsen, James; Populoh, Sascha, E-mail: sascha.populoh@empa.ch; Saucke, Gesine; Shkabko, Andrey; Sagarna, Leyre; Karvonen, Lassi [Laboratory for Solid State Chemistry and Catalysis, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Döbeli, Max [Ion Beam Physics, Schafmattstrasse 20, ETH Hönggerberg, Swiss Federal Institute of Technology, CH-8093 Zürich (Switzerland); Weidenkaff, Anke [Laboratory for Solid State Chemistry and Catalysis, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Materials Chemistry, Institute for Materials Science, University of Stuttgart, Heisenbergstr. 3, DE-70569 Stuttgart (Germany)

    2013-12-28

    Polycrystalline tungsten-substituted CaMn{sub 1−x}W{sub x}O{sub 3−δ} (0.00 ≤ x ≤ 0.05) powders were synthesized from a polymeric precursor, pressed and sintered to high density. The impact of tungsten substitution on the crystal structure, thermal stability, phase transition, electronic and thermal transport properties is assessed. Tungsten acts as an electron donator and strongly affects high-temperature oxygen stoichiometry. Oxygen vacancies form in the high figure-of-merit (ZT)-region starting from about T = 1000 K and dominate the carrier concentration and electronic transport far more than the tungsten substitution. The analysis of the transport properties yields that in the investigated regime the band filling is sufficiently high to overcome barriers of polaron transport. Therefore, the Cutler-Mott approach describes the electrical transport more accurately than the Mott approach for small polaron transport. The lattice thermal conductivity near room temperature is strongly suppressed with increasing tungsten concentration due to mass-difference impurity scattering. A ZT of 0.25 was found for x = 0.04 at 1225 K.

  3. New high boron content polyborane precursors to advanced ceramic materials: New syntheses, new applications

    Science.gov (United States)

    Guron, Marta

    There is a need for new synthetic routes to high boron content materials for applications as polymeric precursors to ceramics, as well as in neutron shielding and potential medical applications. To this end, new ruthenium-catalyzed olefin metathesis routes have been devised to form new complex polyboranes and polymeric species. Metathesis of di-alkenyl substituted o-carboranes allowed the synthesis of ring-closed products fused to the carborane cage, many of which are new compounds and one that offers a superior synthetic method to one previously published. Acyclic diene metathesis of di-alkenyl substituted m-carboranes resulted in the formation of new main-chain carborane-containing polymers of modest molecular weights. Due to their extremely low char yields, and in order to explore other metathesis routes, ring opening metathesis polymerization (ROMP) was used to generate the first examples of poly(norbornenyl- o-carboranes). Monomer synthesis was achieved via a two-step process, incorporating Ti-catalyzed hydroboration to make 6-(5-norbornenyl)-decaborane, followed by alkyne insertion in ionic liquid media to achieve 1,2-R2 -3-norbornenyl o-carborane species. The monomers were then polymerized using ROMP to afford several examples of poly(norbornenyl- o-carboranes) with relatively high molecular weights. One such polymer, [1-Ph, 3-(=CH2-C5H7-CH2=)-1,2-C 2B10H10]n, had a char yield very close to the theoretical char yield of 44%. Upon random copolymerization with poly(6-(5-norbornenyl) decaborane), char yields significantly increased to 80%, but this number was well above the theoretical value implicating the formation of a boron-carbide/carbon ceramic. Finally, applications of polyboranes were explored via polymer blends toward the synthesis of ceramic composites and the use of polymer precursors as reagents for potential ultra high temperature ceramic applications. Upon pyrolysis, polymer blends of poly(6-(5-norbornenyl)-decaborane) and poly

  4. Electron-Spin Resonance in Boron Carbide

    Science.gov (United States)

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

    1987-01-01

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

  5. High resolution imaging of boron carbide microstructures

    International Nuclear Information System (INIS)

    MacKinnon, I.D.R.; Aselage, T.; Van Deusen, S.B.

    1986-01-01

    Two samples of boron carbide have been examined using high resolution transmission electron microscopy (HRTEM). A hot-pressed B 13 C 2 sample shows a high density of variable width twins normal to (10*1). Subtle shifts or offsets of lattice fringes along the twin plane and normal to approx.(10*5) were also observed. A B 4 C powder showed little evidence of stacking disorder in crystalline regions

  6. Low blow Charpy impact of silicon carbides

    Science.gov (United States)

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

    1978-01-01

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

  7. Electronic state of europium atoms on surface of oxidized tungsten

    CERN Document Server

    Davydov, S Y

    2001-01-01

    The energy scheme of the europium atoms adsorption system on the tungsten surface, coated with the oxygen monolayer, is considered. The evaluations of the europium adatoms charged state on the oxidized tungsten surface are performed. It is established, that europium, adsorbed at the oxidized tungsten surface, is a positive ion with the charge close to the unit. The zonal scheme of the Eu-O/W adsorption system for the europium low and high concentrations is proposed

  8. Electronic specific heat of transition metal carbides

    International Nuclear Information System (INIS)

    Conte, R.

    1964-07-01

    The experimental results that make it possible to define the band structure of transition metal carbides having an NaCI structure are still very few. We have measured the electronic specific heat of some of these carbides of varying electronic concentration (TiC, either stoichiometric or non-stoichiometric, TaC and mixed (Ti, Ta) - C). We give the main characteristics (metallography, resistivity, X-rays) of our samples and we describe the low temperature specific heat apparatus which has been built. In one of these we use helium as the exchange gas. The other is set up with a mechanical contact. The two use a germanium probe for thermometer. The measurement of the temperature using this probe is described, as well as the various measurement devices. The results are presented in the form of a rigid band model and show that the density of the states at the Fermi level has a minimum in the neighbourhood of the group IV carbides. (author) [fr

  9. Compressive creep of hot pressed silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Silva, C.R.M., E-mail: cosmeroberto@gmail.com [Universidade de Brasilia (UnB), Campus Darcy Ribeiro, Brasilia CEP 70736-020, DF (Brazil); Nono, M.C.A. [Instituto de Nacional de Pesquisas Espaciais (INPE-LAS) (Brazil); Reis, D.A.P.; Hwang, M.K. [Instituto de Aeronautica e Espaco (IAE) (Brazil)

    2010-07-15

    Silicon carbide has a good match of chemical, mechanical and thermal properties and therefore is considered an excellent structural ceramic for high temperature applications. The aim of the present work is compressive creep evaluation of liquid phase sintered silicon carbide with aluminum and rare earth oxide as sintering aids. Rare earth oxides are possible additives considering their highly refractory remnant grain-boundary phase and lower synthesis costs compared to high purity rare earth. Samples were prepared with silicon carbide powder (90 wt%) and aluminum oxide (5 wt%) plus rare earth oxide (5 wt%) additions. Powders were mixed, milled and hot pressed at 1800 deg. C in argon atmosphere. Compressive creep tests were carried out under stress from 150 to 300 MPa and temperatures from 1300 to 1400 deg. C. At lower creep test temperatures, the obtained stress exponent values were correlated to mechanisms based on diffusion. At intermediate temperatures, grain-boundary sliding becomes operative, accommodated by diffusion. At higher temperatures cavities are discernible. Oxidation reactions and ionic diffusion result on surface oxidized layer, grain-boundary amorphous and intergranular crystalline Al{sub 6}Si{sub 2}O{sub 13}, {delta}-Y{sub 2}Si{sub 2}O{sub 7} and YAG phases. In this case cavitation and amorphous phases redistribution enhance grain-boundary sliding, not accommodated by diffusion. Coalescence occurs at triple point and multigrain-junctions, with subsequent strain rate acceleration and cavitational creep.

  10. A fundamental study of industrial boron carbide

    International Nuclear Information System (INIS)

    Zuppiroli, L.; Kormann, R.; Lesueur, D.

    1983-09-01

    Some of the physical properties of boron carbide, before and after irradiation are reviewed on the basis of several new experiments performed in our laboratory. The layered aspect of the grains of this ceramic, due to a microtwinning of the rhomboedral structure, is emphasized first. Then, the location of free carbon in samples of composition close to B 4 C is discussed in relation with new sputtering experiments. Coupled studies of the electric conductivities and the electron spin resonance lines have demonstrated the important role of free carbon in the electronic properties of boron carbide and revealed the existence of a homogeneous short range disorder, the origin of which is not very clear (amorphous concept). The elementary processes responsible of the swelling and microcracking of neutron irradiated boron carbide are rather well understood. The role of the point defects in these processes is reported. The displacement threshold energies and formation volumes are discussed in relation with electron irradiation experiments, and displacement rates are calculated in different irradiation situations including neutron irradiations [fr

  11. Doping of silicon carbide by ion implantation

    International Nuclear Information System (INIS)

    Gimbert, J.

    1999-01-01

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

  12. Radiative capture of slow electrons by tungsten surface

    International Nuclear Information System (INIS)

    Artamonov, O.M.; Belkina, G.M.; Samarin, S.N.; Yakovlev, I.I.

    1987-01-01

    Isochromatic spectra of radiation capture of slow electrons by the surface of mono- and polycrystal tungsten recorded on 322 and 405 nm wave lengths are presented. The effect of oxygen adsorption on isochromates of the (110) face of tungsten monocrystal is investigated. The obtained isochromatic spectra are compared with energy band structure of tungsten. Based on the analysis of the obtained experimental results it is assumed that optical transition to the final state at the energy of 7.3 eV relatively to Fermi level is conditioned by surface states of the tungsten face (110)

  13. On tungsten technologies and qualification for DEMO

    International Nuclear Information System (INIS)

    Laan, J. van der; Hegeman, H.; Wouters, O.; Luzginova, N.; Jonker, B.; Van der Marck, S.; Opschoor, J.; Wang, J.; Dowling, G.; Stuivenga, M.; Carton, E.

    2009-01-01

    Tungsten alloys are considered prime candidates for the in-vessel components directly facing the plasma. For example, in the HEMJ helium cooled divertor design tiles may be operated at temperatures up to 1700 deg. C, supported by a structure partially consisting of tungsten at temperatures from 600 to 1000 deg. C, and connected to a HT steel structure. The tungsten armoured primary wall is operated at 500-900 deg. C. Irradiation doses will be few tens dpa at minimum, but FPR requirements for plants availability will stretch these targets. Recently injection moulding technology was developed for pure tungsten and representative parts were manufactured for ITER monobloc divertors and DEMO HEMJ thimbles. The major advantages for this technology are the efficient use of material feedstock/resources and the intrinsic possibility to produce near-finished product, avoiding machining processes that are costly and may introduce surface defects deteriorating the component in service performance. It is well suited for mass-manufacturing of components as well known in e.g. lighting industries. To further qualify this material technology various specimen types were produced with processing parameters identical to the components, and tested successfully, showing the high potential for implementation in (fusion) devices. Furthermore, the engineering approach can clearly be tailored away from conventional design and manufacturing technologies based on bulk materials. The technology is suitable for shaping of new W-alloys and W-ODS variants as well. Basically this technology allows a particular qualification trajectory. There is no need to produce large batches of material during the material development and optimization stage. For the verification of irradiation behaviour in the specific neutron spectra, there is a further attractive feature to use e.g. isotope tailored powders to adjust to available irradiation facilities like MTR's. In addition the ingrowth of transmutation

  14. Identified EM Earthquake Precursors

    Science.gov (United States)

    Jones, Kenneth, II; Saxton, Patrick

    2014-05-01

    Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for

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

    Science.gov (United States)

    Halverson, Danny C.; Pyzik, Aleksander J.; Aksay, Ilhan A.

    1986-01-01

    Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.

  16. Microhardness and grain size of disordered nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.

    1999-01-01

    Effect of the disordered nonstoichiometric titanium carbide on its microhardness and grain size is studied. It is established that decrease in defectiveness of carbon sublattice of disordered carbide is accompanied by microhardness growth and decrease in grain size. Possible causes of the TiC y microhardness anomalous behaviour in the area 0.8 ≤ y ≤ 0.9 connected with plastic deformation mechanism conditioned by peculiarities of the electron-energetic spectrum of nonstoichiometric carbide are discussed [ru

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

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

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

  18. 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.

  19. Impact scenarios in boron carbide: A computational study

    OpenAIRE

    Bell, R. G.; Sugden, I. J.; Plant, D. F.

    2016-01-01

    The effect of radiative impacts on the structure of boron carbide has been studied by both classical and ab initio simulations. As a part of this study, a new forcefield was developed for use in studying boron carbide materials. Impact scenarios in boron carbide were simulated in order to investigate the exceptional resistance of this material, and other icosahedral boron solids, to high-energy impact events. It was observed that interstitial defects created by radiative impacts are likely to...

  20. Carbides in Nodular Cast Iron with Cr and Mo

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2007-07-01

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

  1. Silicon Carbide Corrugated Mirrors for Space Telescopes, Phase I

    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...

  2. Preparation of dense zirconium carbides with controlled composition and microstructure; Elaboration de carbures de zirconium denses a composition et microstructure controlees

    Energy Technology Data Exchange (ETDEWEB)

    Gosset, D. [CEA Saclay, Direction de l Energie Nucleaire, Direction Deleguee aux Activites Nucleaires de Saclay, Departement des Materiaux pour le Nucleaire, Service de Recherches en Metallurgie Appliquee 91191 Gif-sur-Yvette Cedex (France); Legendre, F.; Chaffron, L. [CEA Saclay, Direction de l Energie Nucleaire, Direction Deleguee aux Activites Nucleaires de Saclay, Departement des Materiaux pour le Nucleaire, Service de Recherches de Metallurgie Physique 91191 Gif-sur-Yvette Cedex (France)

    2006-07-01

    A preparation process of zirconium carbide has been perfected. It includes a grinding of zirconium and carbon precursors leading to a reactive mixture. The sintering of this mixture leads to very dense products, with homogeneous microstructure and composition in conditions of pressure and temperature much softer than for the usual processes. Such a material could be used as matrix for fuels of high temperature reactors (Gen-IV). (O.M.)

  3. Development and characterization of powder metallurgically produced discontinuous tungsten fiber reinforced tungsten composites

    Science.gov (United States)

    Mao, Y.; Coenen, J. W.; Riesch, J.; Sistla, S.; Almanstötter, J.; Jasper, B.; Terra, A.; Höschen, T.; Gietl, H.; Bram, M.; Gonzalez-Julian, J.; Linsmeier, Ch; Broeckmann, C.

    2017-12-01

    In future fusion reactors, tungsten is the prime candidate material for the plasma facing components. Nevertheless, tungsten is prone to develop cracks due to its intrinsic brittleness—a major concern under the extreme conditions of fusion environment. To overcome this drawback, tungsten fiber reinforced tungsten (Wf/W) composites are being developed. These composite materials rely on an extrinsic toughing principle, similar to those in ceramic matrix composite, using internal energy dissipation mechanisms, such as crack bridging and fiber pull-out, during crack propagation. This can help Wf/W to facilitate a pseudo-ductile behavior and allows an elevated damage resilience compared to pure W. For pseudo-ductility mechanisms to occur, the interface between the fiber and matrix is crucial. Recent developments in the area of powder-metallurgical Wf/W are presented. Two consolidation methods are compared. Field assisted sintering technology and hot isostatic pressing are chosen to manufacture the Wf/W composites. Initial mechanical tests and microstructural analyses are performed on the Wf/W composites with a 30% fiber volume fraction. The samples produced by both processes can give pseudo-ductile behavior at room temperature.

  4. Comparative Investigation of Tungsten Fibre Nets Reinforced Tungsten Composite Fabricated by Three Different Methods

    Directory of Open Access Journals (Sweden)

    Linhui Zhang

    2017-07-01

    Full Text Available Tungsten fibre nets reinforced tungsten composites (Wf/W containing four net layers were fabricated by spark plasma sintering (SPS, hot pressing (HP and cold rolling after HP (HPCR, with the weight fraction of fibres being 17.4%, 10.5% and 10.5%, respectively. The relative density of the HPCRed samples is the highest (99.8% while that of the HPed composites is the lowest (95.1%. Optical and scanning electron microscopy and electron back scattering diffraction were exploited to characterize the microstructure, while tensile and hardness tests were used to evaluate the mechanical properties of the samples. It was found that partial recrystallization of fibres occurred after the sintering at 1800 °C. The SPSed and HPed Wf/W composites begin to exhibit plastic deformation at 600 °C with tensile strength (TS of 536 and 425 MPa and total elongation at break (TE of 11.6% and 23.0%, respectively, while the HPCRed Wf/W composites exhibit plastic deformation at around 400 °C. The TS and TE of the HPCRed Wf/W composites at 400 °C are 784 MPa and 8.4%, respectively. The enhanced mechanical performance of the Wf/W composites over the pure tungsten can be attributed to the necking, cracking, and debonding of the tungsten fibres.

  5. Synthesis and characterization of tungsten or calcium doped PZT ceramics; Sintese e caracterizacao do PZT dopado com W ou Ca

    Energy Technology Data Exchange (ETDEWEB)

    Santos, D.M.; Caracas, L.B.; Noronha, R.G.; Santos, M.M.T. dos [Universidade Federal do Maranhao (UFMA), Sao Luis, MA (Brazil). Dept. de Desenho e Tecnologia. Curso de Desenho Industrial; Paiva-Santos, C.O., E-mail: denilson@ufma.b [Universidade Estadual Paulista (IQ/UNESP), Araraquara, SP (Brazil). Inst. de Quimica

    2009-07-01

    Pure and doped (tungsten or calcium) PZT ceramics were prepared by association of the polymeric precursor and partial oxalate method. The phase formation was investigated by thermal analysis (TG/DSC) and X-ray diffraction (XRD). The affect of W or Ca doping PZT and their electrical properties was evaluated. Substitution of W by Ti and Ca by Pb leads to an increase of Curie temperature and broadening of dielectric constant. A typical hysteresis loop was observed at room temperature and the remnant polarization was increased with the content of W and Ca. (author)

  6. Tritium decay helium-3 effects in tungsten

    Directory of Open Access Journals (Sweden)

    M. Shimada

    2017-08-01

    Full Text Available Tritium (T implanted by plasmas diffuses into bulk material, especially rapidly at elevated temperatures, and becomes trapped in neutron radiation-induced defects in materials that act as trapping sites for the tritium. The trapped tritium atoms will decay to produce helium-3 (3He atoms at a half-life of 12.3 years. 3He has a large cross section for absorbing thermal neutrons, which after absorbing a neutron produces hydrogen (H and tritium ions with a combined kinetic energy of 0.76 MeV through the 3He(n,HT nuclear reaction. The purpose of this paper is to quantify the 3He produced in tungsten by tritium decay compared to the neutron-induced helium-4 (4He produced in tungsten. This is important given the fact that helium in materials not only creates microstructural damage in the bulk of the material but alters surface morphology of the material effecting plasma-surface interaction process (e.g. material evolution, erosion and tritium behavior of plasma-facing component materials. Effects of tritium decay 3He in tungsten are investigated here with a simple model that predicts quantity of 3He produced in a fusion DEMO FW based on a neutron energy spectrum found in literature. This study reveals that: (1 helium-3 concentration was equilibrated to ∼6% of initial/trapped tritium concentration, (2 tritium concentration remained approximately constant (94% of initial tritium concentration, and (3 displacement damage from 3He(n,HT nuclear reaction became >1 dpa/year in DEMO FW.

  7. 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.

  8. Calibration and Temperature Profile of a Tungsten Filament Lamp

    Science.gov (United States)

    de Izarra, Charles; Gitton, Jean-Michel

    2010-01-01

    The goal of this work proposed for undergraduate students and teachers is the calibration of a tungsten filament lamp from electric measurements that are both simple and precise, allowing to determine the temperature of tungsten filament as a function of the current intensity. This calibration procedure was first applied to a conventional filament…

  9. Gas Tungsten Arc Welding. Welding Module 6. Instructor's Guide.

    Science.gov (United States)

    Missouri Univ., Columbia. Instructional Materials Lab.

    This guide is intended to assist vocational educators in teaching a three-unit module in gas tungsten arc welding. The module has been designed to be totally integrated with Missouri's Vocational Instruction Management System. The basic principles involved in gas tungsten arc welding, supplies, and applications are covered. The materials included…

  10. Spectrophotometric determination of tungsten with salicylic acid

    International Nuclear Information System (INIS)

    Goncalves, Z.C.

    1976-10-01

    The method comprises the complexation of tungsten with salicylic acid in concentrated sulphuric acid yielding a reddish color. The maximum absorbance of the complex lies within 410-420 nm, 420 nm being the chosen wavelenght. The final concentration of salicylic acid is 0,080 g/ml. The sensitivity is 0,13 μg W(%T) -1 ml -1 . Titanium, vanadium, rhenium, niobium and molybdenum interferes and must be separated, titanium being the strongest interferent. The separation procedures, advantages of the process, stoichiometric relations and equilibrium constant are discussed. (Author) [pt

  11. Titanium tungsten coatings for bioelectrochemical applications

    DEFF Research Database (Denmark)

    Wierzbicki, Rafal; Amato, Letizia; Łopacińska, J.

    2011-01-01

    This paper presents an assessment of titanium tungsten (TiW) coatings and their applicability as components of biosensing systems. The focus is put on using TiW as an electromechanical interface layer between carbon nanotube (CNT) forests and silicon nanograss (SiNG) cell scaffolds. Cytotoxicity......, applicability to plasma-enhanced chemical vapor deposition (PECVD) of aligned CNT forests, and electrochemical performance are investigated. Experiments include culturing of NIH3T3 mouse embryonic fibroblast cells on TiW coated silicon scaffolds, CNT growth on TiW substrates with nickel catalyst, and cyclic...

  12. Characterization of a Cobalt-Tungsten Interconnect

    DEFF Research Database (Denmark)

    Harthøj, Anders; Holt, Tobias; Caspersen, Michael

    2012-01-01

    A ferritic steel interconnect for a solid oxide fuel cell must be coated in order to prevent chromium evaporation from the steel substrate. The Technical University of Denmark and Topsoe Fuel Cell have developed an interconnect coating based on a cobalt-tungsten alloy. The purpose of the coating...... for 300 h at 800 °C. The coating was characterized with Glow Discharge Optical Spectroscopy (GDOES), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The oxidation properties were evaluated by measuring weight change of coated samples of Crofer 22 H and Crofer 22 APU as a function...

  13. Dilatometric study on sintering mechanism of the WC-10wt%Co cemented carbide doped with tantalum carbide and niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Manuel, J.B. [Universidade Federal Rural de Pernambuco (UFRPE), PE (Brazil); Gomes, U.U.; Karimi, M.M. [Universidade Federal do Rio Grande do Norte (UFRN), RN (Brazil)

    2016-07-01

    Full text: Nanocrystalline WC-10wt.%Co powders were prepared by high energy milling and were liquid phase sintered. The powders were milled at 20 hours and characterized by X-ray diffraction, and Scanning electron microscopy. The particle size distribution and mean diameter analysis were characterized by Granulometro Cilas model 920 L and 1180. After sintering the WC-10wt.%Co cemented carbides doped with tantalum carbide and niobium carbide exhibited ultra fine grain sizes. dilatometer study on sintering mechanism detected phase transformations and degassing. (author)

  14. High Heat Load Properties of Ultra Fine Grain Tungsten

    International Nuclear Information System (INIS)

    Zhou, Z.; Du, J.; Ge, C.; Linke, J.; Pintsuk, G.; Song, S.X.

    2007-01-01

    Full text of publication follows: Tungsten is increasingly considered as a promising candidate armour materials facing the plasma in tokamaks for medium to high heat flux components (EAST, ASDEX, ITER). Fabrication tungsten with ultra fine grain size is considered as an effective way to ameliorate some disadvantages of tungsten, such as its brittleness at room temperature. But the research data on the performance of ultra fine grain tungsten is still very limit. In this work, high heat load properties of pure ultra-fine grain tungsten have been studied. The ultra fine grain tungsten samples with average grain size of 0.2 μm, 1 μm and 3 μm were fabricated by resistance sintering under ultra high pressure. The annealing experiments for the investigation of the material resistance against grain growth have been done by annealing samples in a vacuum furnace at different temperature holding for 2 hours respectively. It is found that recrystallization and grain growth occur at heating temperature of 1250 deg. c. The finer the initial grain sizes of tungsten, the smaller its grain growth grain. The effects of transient high thermal loads (off normal events like disruptions) on tungsten surface morphology have been performed in electron beam test facility JUDITH. The thermal loads tests have been carried out with 4 ms pulses at different power density of 0.22, 0.33, 0.44, 0.55 and 0.88 GW/m 2 respectively. Horizontal cracks formed for all tungsten samples at 0.44 GW/m 2 . Particle erosions occurred for tungsten with 3 μm size at 0.33 GW/m 2 and for tungsten with 0.2 and 1 μm size at 0.55 GW/m 2 . The weight loss of tungsten with 0.2, 1 and 3 μm size are 2,0.1,0.6 mg respectively at 0.88 GW/m 2 . The effects of a large number of very short transient repetitive thermal loads (ELM-like) on tungsten surface morphology also have been performed by using a fundamental wave of a YAG laser. It is found that tungsten with 0.2 μm size has the best performance. (authors)

  15. The high-flux effect on deuterium retention in TiC and TaC doped tungsten at high temperatures

    Science.gov (United States)

    Zibrov, Mikhail; Bystrov, Kirill; Mayer, Matej; Morgan, Thomas W.; Kurishita, Hiroaki

    2017-10-01

    Samples made of tungsten (W) doped either with titanium carbide (W-1.1TiC) or tantalum carbide (W-3.3TaC) were exposed to a low-energy (40 eV/D), high-flux (1.8-5 × 1023 D/m2s) deuterium (D) plasma at temperatures of about800 K, 1050 K, and 1250 K to a fluence of about1 × 1027 D/m2. The deuterium (D) inventory in the samples was examined by nuclear reaction analysis and thermal desorption spectroscopy. At 800 K the D bulk concentrations and total D inventories in W-1.1TiC and W-3.3TaC were more than one order of magnitude higher compared to that in pure polycrystalline W. At 1050 K and 1250 K the D concentrations in all types of samples were very low (≤10-5 at. fr.); however the D inventories in W-1.1TiC were significantly higher compared to those in W-3.3TaC and pure W. It is suggested that D trapping inside the carbide precipitates and at their boundaries is essential at high temperatures and high incident fluxes, especially in W-1.1TiC.

  16. Corrosion of high-density sintered tungsten alloys. Part 2

    International Nuclear Information System (INIS)

    Batten, J.J.; Moore, B.T.

    1988-12-01

    The behaviour of four high-density sintered tungsten alloys has been evluated and compared with that of pure tungsten. Rates of corrosion during the cyclic humidity and the salt mist tests were ascertained from weight loss measurements. Insight into the corrosion mechanism was gained from the nature of the corrosion products and an examination of the corroded surfaces. In the tests, the alloy 95% W, 2.5% Ni, 1.5% Fe was the most corrosion resistant. The data showed that copper as an alloying element accelerates corrosion of tungsten alloys. Both attack on the tungsten particles and the binder phase were observed together with tungsten grain loss. 6 refs., 3 tabs.,

  17. Observation of the Structure of Tungsten Films Prepared by MOCVD

    Science.gov (United States)

    Zhang, Xiaofeng; Liu, Weiliang; Yu, Lei; Li, Yujie; Guo, Shuangquan

    2013-09-01

    The tungsten films with ultra microstructure on CuCrZr alloy and China Low Activation Martensitic (CLAM) steel have been prepared by metal organic chemical vapor deposition (MOCVD). The films were produced by pyrolysing the tungsten hexacarbonyl at air or argon atmosphere. When formed at or below 400 °C, they were poorly crystalized and the films showed low quality in thickness, density, bonding performance etc. While above this temperature, the properties of tungsten films have been improved, all the films consist of tungsten in the β-W. And β-W can change into α-W after heat treatment. As in other variations of pyrolysis, oxygen and carbon were observed. When filled with argon, the oxygen and carbon content would reduce apparently. Tungsten films prepared by MOCVD have stable chemical composition and microstructure. Besides, the properties of films on CuCrZr alloy are better than that on CLAM steel.

  18. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    use as sub-base and base material. The addition of both cement and calcium carbide waste to Ikpayongo laterite improves its consistency indices, as the plasticity index reduced from. 14% to 5% when treated with a combination of 10 % cement plus 10 % calcium carbide waste. Variation of liquid limit, plastic limit and ...

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

    Indian Academy of Sciences (India)

    Abstract. This paper presents a preliminary study on obtaining and characterization of phenolic resin-based com- posites 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 ...

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

    African Journals Online (AJOL)

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

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

    African Journals Online (AJOL)

    In this paper, an attempt has been made to modify the micro sized Silicon carbide powder into nano structured Silicon carbide powder using High Energy Ball Mill. Ball milling was carried out for the total duration of 50 hours. The sample was taken out after every 5 hours of milling and it was characterized for its crystallite ...

  2. Process for the preparation of fine grain metal carbide powders

    International Nuclear Information System (INIS)

    Gortsema, F.P.

    1976-01-01

    Fine grain metal carbide powders are conveniently prepared from the corresponding metal oxide by heating in an atmosphere of methane in hydrogen. Sintered articles having a density approaching the theoretical density of the metal carbide itself can be fabricated from the powders by cold pressing, hot pressing or other techniques. 8 claims, no drawings

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

    Indian Academy of Sciences (India)

    TECS

    Production of boron carbide powder by carbothermal synthesis of gel material. A K KHANRA. Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721 302, India. MS received 21 August 2006; revised 29 January 2007. Abstract. Boron carbide (B4C) powder has been produced ...

  4. properties of cement paste and concrete containing calcium carbide

    African Journals Online (AJOL)

    user

    2017-01-01

    Jan 1, 2017 ... curves are shown in Figure 1. The grain size curve indicates that the sand used was classified as zone 2 based on British Standard classification [20] grading limits for fine aggregates and was well graded. 3.2 Cement and Calcium Carbide Waste. The oxide composition of calcium carbide waste (CCW).

  5. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    the stabilization of soil will ensure economy in road construction, while providing an effective way of disposing calcium carbide waste. KEYWORDS: Cement, Calcium carbide waste, Stabilization, Ikpayongo laterite, Pavement material. INTRODUCTION. Road building in the developing nations has been a major challenge to ...

  6. Role of carbon impurities on the surface morphology evolution of tungsten under high dose helium ion irradiation

    International Nuclear Information System (INIS)

    Al-Ajlony, A.; Tripathi, J.K.; Hassanein, A.

    2015-01-01

    The effect of carbon impurities on the surface evolution (e.g., fuzz formation) of tungsten (W) surface during 300 eV He ions irradiation was studied. Several tungsten samples were irradiated by He ion beam with a various carbon ions percentage. The presence of minute carbon contamination within the He ion beam was found to be effective in preventing the fuzz formation. At higher carbon concentration, the W surface was found to be fully covered with a thick graphitic layer on the top of tungsten carbide (WC) layer that cover the sample surface. Lowering the ion beam carbon percentage was effective in a significant reduction in the thickness of the surface graphite layer. Under these conditions the W surface was also found to be immune for the fuzz formation. The effect of W fuzz prevention by the WC formation on the sample surface was more noticeable when the He ion beam had much lower carbon (C) ions content (0.01% C). In this case, the fuzz formation was prevented on the vast majority of the W sample surface, while W fuzz was found in limited and isolated areas. The W surface also shows good resistance to morphology evolution when bombarded by high flux of pure H ions at 900 °C. - Highlights: • Reporting formation of W nanostructure (fuzz) due to low energy He ion beam irradiation. • The effect of adding various percentage of carbon impurity to the He ion beam on the trend of W fuzz formation was studied. • Mitigation of W fuzz formation due to addition of small percentage of carbon to the He ion beam is reported. • The formation of long W nanowires due to He ion beam irradiation mixed with 0.01% carbon ions is reported.

  7. Processing of boron carbide-aluminum composites

    International Nuclear Information System (INIS)

    Halverson, D.C.; Pyzik, A.J.; Aksay, I.A.

    1989-01-01

    The processing problems associated with boron carbide and the limitations of its mechanical properties can be significantly reduced when a metal phase (e.g., aluminum) is added. Lower densification temperatures and higher fracture toughness will result. Based on fundamental capillarity thermodynamics, reaction thermodynamics, and densification kinetics, we have established reliable criteria for fabricating B 4 C-Al particulate composites. Because chemical reactions cannot be eliminated, it is necessary to process B 4 C-Al by rapidly heating to near 1200 degrees C (to ensure wetting) and subsequently heat-treating below 1200 degrees C (for microstructural development)

  8. White light emission from engineered silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan

    Silicon carbide (SiC) is a wide indirect bandgap semiconductor. The light emission efficiency is low in nature. But this material has very unique physical properties like good thermal conductivity, high break down field etc in addition to its abundance. Therefore it is interesting to engineer its...... light emission property so that to take fully potential applications of this material. In this talk, two methods, i.e. doping SiC heavily by donor-acceptor pairs and making SiC porous are introduced to make light emission from SiC. By co-doping SiC with nitrogen and boron heavily, strong yellow emission...

  9. Boron carbide nanowires with uniform CNx coatings

    Science.gov (United States)

    Zhang, H. Z.; Wang, R. M.; You, L. P.; Yu, J.; Chen, H.; Yu, D. P.; Chen, Y.

    2007-01-01

    Boron carbide nanowires with uniform carbon nitride coating layers were synthesized on a silicon substrate using a simple thermal process. The structure and morphology of the as-synthesized nanowires were characterized using x-ray diffraction, scanning and transmission electron microscopy and electron energy loss spectroscopy. A correlation between the surface smoothness of the nanowire sidewalls and their lateral sizes has been observed and it is a consequence of the anisotropic formation of the coating layers. A growth mechanism is also proposed for these growth phenomena.

  10. Preparation and analysis of uranium carbides

    International Nuclear Information System (INIS)

    Sun Jichang; Song Dianwu; Yang Youqing; Guo Yibai; Cao Yenan

    1988-03-01

    The preparation process of uranium carbides is investigated by using the carbothermic reduction method of uranium dioxide in vacuum. The carbonisation reaction in the mixture of uranium dioxide with graphite begins to take place at the temperature of 1100 deg C. The temperature is measured by a W-Re thermocouple. Then the quantity of carbon, density, porosities and microstructure of the sintered pellets are examined. At the same time, in order to measure the content of uranium monocarbide, those sintered pellets are also indentified by means of X-ray diffraction

  11. Thin films by metal-organic precursor plasma spray

    International Nuclear Information System (INIS)

    Schulz, Douglas L.; Sailer, Robert A.; Payne, Scott; Leach, James; Molz, Ronald J.

    2009-01-01

    While most plasma spray routes to coatings utilize solids as the precursor feedstock, metal-organic precursor plasma spray (MOPPS) is an area that the authors have investigated recently as a novel route to thin film materials. Very thin films are possible via MOPPS and the technology offers the possibility of forming graded structures by metering the liquid feed. The current work employs metal-organic compounds that are liquids at standard temperature-pressure conditions. In addition, these complexes contain chemical functionality that allows straightforward thermolytic transformation to targeted phases of interest. Toward that end, aluminum 3,5-heptanedionate (Al(hd) 3 ), triethylsilane (HSi(C 2 H 5 ) 3 or HSiEt 3 ), and titanium tetrakisdiethylamide (Ti(N(C 2 H 5 ) 2 ) 4 or Ti(NEt 2 ) 4 ) were employed as precursors to aluminum oxide, silicon carbide, and titanium nitride, respectively. In all instances, the liquids contain metal-heteroatom bonds envisioned to provide atomic concentrations of the appropriate reagents at the film growth surface, thus promoting phase formation (e.g., Si-C bond in triethylsilane, Ti-N bond in titanium amide, etc.). Films were deposited using a Sulzer Metco TriplexPro-200 plasma spray system under various experimental conditions using design of experiment principles. Film compositions were analyzed by glazing incidence x-ray diffraction and elemental determination by x-ray spectroscopy. MOPPS films from HSiEt 3 showed the formation of SiC phase but Al(hd) 3 -derived films were amorphous. The Ti(NEt 2 ) 4 precursor gave MOPPS films that appear to consist of nanosized splats of TiOCN with spheres of TiO 2 anatase. While all films in this study suffered from poor adhesion, it is anticipated that the use of heated substrates will aid in the formation of dense, adherent films.

  12. Solvothermally synthesized tungsten oxide nanowires/nanorods for NO{sub 2} gas sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Qin Yuxiang, E-mail: qinyuxiang@tju.edu.cn [School of Electronics and Information Engineering, Tianjin University, No. 92, Weijin Road, Nankai District, Tianjin 300072 (China); Li Xiao; Wang Fei; Hu Ming [School of Electronics and Information Engineering, Tianjin University, No. 92, Weijin Road, Nankai District, Tianjin 300072 (China)

    2011-08-18

    Highlights: > Tungsten oxide nanowires and nanorods were solvothermally synthesized by changing reaction solvent. > The sensing characteristics of the tungsten oxide nanowires and nanorods sensors to NO{sub 2} gas were evaluated in detail. > The response time and recovery time for the nanowires or nanorods sensors are much shorter than the oxide nanoparticles or sputtered films. > The nanowires sensor shows a much shorter response time and a relative higher response value to NO{sub 2} gas than the nanorods one. > The NO{sub 2}-sensing mechanism and the possible reason for the better gas sensing properties of the nanowires are analyzed. - Abstract: One-dimensional nanorods or nanowires of W{sub 18}O{sub 49} were synthesized by solvothermal method at 200 deg. C with tungsten hexachloride (WCl{sub 6}) as precursor and cyclohexanol or 1-propanol as reaction solvent. Their morphology and structure properties were systematically characterized. The NO{sub 2}-sensing properties of the sensors based on nanowires and nanorods were investigated at 100 deg. C up to 250 deg. C over NO{sub 2} concentration ranging from 1 ppm to 20 ppm. The results indicate that both nanowires and nanorods exhibit reversible response to different concentrations of NO{sub 2}, and the highest gas response is achieved at 150 deg. C. In comparison with nanorods, nanowires showed a much quicker response characteristic and a relative higher response value to the same concentration of NO{sub 2} gas due to the smaller diameter and larger specific surface area.

  13. Supported molybdenum carbide for higher alcohol synthesis from syngas

    DEFF Research Database (Denmark)

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

    2013-01-01

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

  14. Tensile properties of irradiated TZM and tungsten

    International Nuclear Information System (INIS)

    Steichen, J.M.

    1975-04-01

    The effect of neutron irradiation on the elevated temperature tensile properties of TZM and tungsten has been experimentally determined. Specimens were irradiated at a temperature of approximately 720 0 F to fluences of 0.4 and 0.9 x 10 22 n/cm 2 (E greater than 0.1 MeV). Test parameters for both control and irradiated specimens included strain rates from 3 x 10 -4 to 1 s -1 and temperatures from 72 to 1700 0 F. The results of these tests were correlated with a rate-temperature parameter (T ln A/epsilon) to provide a concise description of material behavior over the range of deformation conditions of this study. The yield strength of the subject materials was significantly increased by decreasing temperature, increasing strain rate, and increasing fluence. Ductility was significantly reduced at any temperature or strain rate by increasing fluence. Cleavage fractures occurred in both unirradiated and irradiated specimens when the yield strength was elevated to the effective cleavage stress by temperature and/or strain rate. Neutron irradiation for the conditions of this study increased the ductile-to-brittle transition temperature of tungsten by approximately 300 0 F and TZM by approximately 420 0 F. (U.S.)

  15. Tungsten tetraboride, an inexpensive superhard material

    Science.gov (United States)

    Mohammadi, Reza; Lech, Andrew T.; Xie, Miao; Weaver, Beth E.; Yeung, Michael T.; Tolbert, Sarah H.; Kaner, Richard B.

    2011-01-01

    Tungsten tetraboride (WB4) is an interesting candidate as a less expensive member of the growing group of superhard transition metal borides. WB4 was successfully synthesized by arc melting from the elements. Characterization using powder X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) indicates that the as-synthesized material is phase pure. The zero-pressure bulk modulus, as measured by high-pressure X-ray diffraction for WB4, is 339 GPa. Mechanical testing using microindentation gives a Vickers hardness of 43.3 ± 2.9 GPa under an applied load of 0.49 N. Various ratios of rhenium were added to WB4 in an attempt to increase hardness. With the addition of 1 at.% Re, the Vickers hardness increased to approximately 50 GPa at 0.49 N. Powders of tungsten tetraboride with and without 1 at.% Re addition are thermally stable up to approximately 400 °C in air as measured by thermal gravimetric analysis. PMID:21690363

  16. Vaccum Gas Tungsten Arc Welding, phase 1

    Science.gov (United States)

    Weeks, J. L.; Krotz, P. D.; Todd, D. T.; Liaw, Y. K.

    1995-01-01

    This two year program will investigate Vacuum Gas Tungsten Arc Welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. VGTAW appears to offer a significant improvement in weldability because of the clean environment and lower heat input needed. The overall objective of the program is to develop the VGTAW technology and implement it into a manufacturing environment that will result in lower cost, better quality and higher reliability aerospace components for the space shuttle and other NASA space systems. Phase 1 of this program was aimed at demonstrating the process's ability to weld normally difficult-to-weld materials. Phase 2 will focus on further evaluation, a hardware demonstration and a plan to implement VGTAW technology into a manufacturing environment. During Phase 1, the following tasks were performed: (1) Task 11000 Facility Modification - an existing vacuum chamber was modified and adapted to a GTAW power supply; (2) Task 12000 Materials Selection - four difficult-to-weld materials typically used in the construction of aerospace hardware were chosen for study; (3) Task 13000 VGTAW Experiments - welding experiments were conducted under vacuum using the hollow tungsten electrode and evaluation. As a result of this effort, two materials, NARloy Z and Incoloy 903, were downselected for further characterization in Phase 2; and (4) Task 13100 Aluminum-Lithium Weld Studies - this task was added to the original work statement to investigate the effects of vacuum welding and weld pool vibration on aluminum-lithium alloys.

  17. Tungsten - Yttrium Based Nuclear Structural Materials

    Science.gov (United States)

    Ramana, Chintalapalle; Chessa, Jack; Martinenz, Gustavo

    2013-04-01

    The challenging problem currently facing the nuclear science community in this 21st century is design and development of novel structural materials, which will have an impact on the next-generation nuclear reactors. The materials available at present include reduced activation ferritic/martensitic steels, dispersion strengthened reduced activation ferritic steels, and vanadium- or tungsten-based alloys. These materials exhibit one or more specific problems, which are either intrinsic or caused by reactors. This work is focussed towards tungsten-yttrium (W-Y) based alloys and oxide ceramics, which can be utilized in nuclear applications. The goal is to derive a fundamental scientific understanding of W-Y-based materials. In collaboration with University of Califonia -- Davis, the project is designated to demonstrate the W-Y based alloys, ceramics and composites with enhanced physical, mechanical, thermo-chemical properties and higher radiation resistance. Efforts are focussed on understanding the microstructure, manipulating materials behavior under charged-particle and neutron irradiation, and create a knowledge database of defects, elemental diffusion/segregation, and defect trapping along grain boundaries and interfaces. Preliminary results will be discussed.

  18. Proton beam induced dynamics of tungsten granules

    Science.gov (United States)

    Caretta, O.; Loveridge, P.; O'Dell, J.; Davenne, T.; Fitton, M.; Atherton, A.; Densham, C.; Charitonidis, N.; Efthymiopoulos, I.; Fabich, A.; Guinchard, M.; Lacny, L. J.; Lindstrom, B.

    2018-03-01

    This paper reports the results from single-pulse experiments of a 440 GeV /c proton beam interacting with granular tungsten samples in both vacuum and helium environments. Remote high-speed photography and laser Doppler vibrometry were used to observe the effect of the beam on the sample grains. The majority of the results were derived from a trough containing ˜45 μ m diameter spheres (not compacted) reset between experiments to maintain the same initial conditions. Experiments were also carried out on other open and contained samples for the purposes of comparison both with the 45 μ m grain results and with a previous experiment carried out with sub-250 μ m mixed crystalline tungsten powder in helium [Phys. Rev. ST Accel. Beams 17, 101005 (2014), 10.1103/PhysRevSTAB.17.101005]. The experiments demonstrate that a greater dynamic response is produced in a vacuum than in a helium environment and in smaller grains compared with larger grains. The examination of the dynamics of the grains after a beam impact leads to the hypothesis that the grain response is primarily the result of a charge interaction of the proton beam with the granular medium.

  19. Deuterium desorption from tungsten using laser heating

    Directory of Open Access Journals (Sweden)

    J.H. Yu

    2017-08-01

    Full Text Available Retention and desorption of hydrogenic species need to be accurately modeled to predict the tritium inventory of next generation fusion devices, which is needed both for tritium fuel recovery and for tritium safety concerns. In this paper, experiments on thermal desorption of deuterium from intrinsic polycrystalline tungsten defects using laser heating are compared to TMAP-7 modeling. The samples during deuterium plasma exposure were at a temperature of 373K for this benchmark study with ion fluence of 0.7–1.0 ×1024Dm−2. Following plasma exposure, a fiber laser (λ= 1100nm heated the samples to peak surface temperatures ranging from ∼500 to 1400K with pulse widths from 10ms to 1s, and 1 to 10 pulses applied to each sample. The remaining deuterium retention was measured using temperature programmed desorption (TPD. Results show that > 95% of deuterium is desorbed when the peak surface temperature reached ∼950K for > 1s. TMAP-7 is used to predict deuterium desorption from tungsten for a range of surface temperatures and heating durations, and is compared to previous work on desorption from beryllium codeposits.

  20. Mechanical properties of tungsten alloys with Y2O3 and titanium additions

    International Nuclear Information System (INIS)

    Aguirre, M.V.; Martin, A.; Pastor, J.Y.; LLorca, J.; Monge, M.A.; Pareja, R.

    2011-01-01

    In this research the mechanical behaviour of pure tungsten (W) and its alloys (2 wt.% Ti-0.47 wt.% Y 2 O 3 and 4 wt.% Ti-0.5 wt.% Y 2 O 3 ) is compared. These tungsten alloys, have been obtained by powder metallurgy. The yield strength, fracture toughness and elastic modulus have been studied in the temperature interval of 25 deg. C to 1000 deg. C. The results have shown that the addition of Ti substantially improves the bending strength and toughness of W, but it also dramatically increases the DBTT. On the other hand, the addition of 0.5% Y 2 O 3 , is enough to improve noticeably the oxidation behaviour at the higher temperatures. The grain size, fractography and microstructure are studied in these materials. Titanium is a good grain growth inhibitor and effective precursor of liquid phase in HIP. The simultaneous presence of Y 2 O 3 and Ti permits to obtain materials with low pores presence.

  1. Development of silicon carbide composites for fusion

    International Nuclear Information System (INIS)

    Snead, L.L.

    1993-01-01

    The use of silicon carbide composites for structural materials is of growing interest in the fusion community. However, radiation effects in these materials are virtually unexplored, and the general state of ceramic matrix composites for nonnuclear applications is still in its infancy. Research into the radiation response of the most popular silicon carbide composite, namely, the chemically vapor-deposited (CVD) SiC-carbon-Nicalon fiber system is discussed. Three areas of interest are the stability of the fiber and matrix materials, the stability of the fiber-matrix interface, and the true activation of these open-quotes reduced activityclose quotes materials. Two methods are presented that quantitatively measure the effect of radiation on fiber and matrix elastic modulus as well as the fiber-matrix interfacial strength. The results of these studies show that the factor limiting the radiation performance of the CVD SiC-carbon-Nicalon system is degradation of the Nicalon fiber, which leads to a weakened carbon interface. The activity of these composites is significantly higher than expected and is dominated by impurity isotopes. 52 refs., 12 figs., 3 tabs

  2. High temperature intermetallic binders for HVOF carbides

    International Nuclear Information System (INIS)

    Shaw, K.G.; Gruninger, M.F.; Jarosinski, W.J.

    1994-01-01

    Gas turbines technology has a long history of employing the desirable high temperature physical attributes of ceramic-metallic (cermet) materials. The most commonly used coatings incorporate combinations of WC-Co and Cr 3 C 2 -NiCr, which have also been successfully utilized in other non-turbine coating applications. Increased turbine operating temperatures and other high temperature service conditions have made apparent the attractive notion of increasing the temperature capability and corrosion resistance of these coatings. In this study the intermetallic binder NiAl has been used to replace the cobalt and NiCr constituents of conventional WC and Cr 3 C 2 cermet powders. The composite carbide thermal spray powders were fabricated for use in the HVOF coating process. The structure of HVOF deposited NiAl-carbide coatings are compared directly to the more familiar WC-Co and Cr 3 C 2 -NiCr coatings using X-ray diffraction, back-scattered electron imaging (BEI) and electron dispersive spectroscopy (EDS). Hardness variations with temperature are reported and compared between the NiAl and Co/NiCr binders

  3. Methyldichloroborane evidenced as an intermediate in the chemical vapour deposition synthesis of boron carbide.

    Science.gov (United States)

    Reinisch, G; Patel, S; Chollon, G; Leyssale, J-M; Alotta, D; Bertrand, N; Vignoles, G L

    2011-09-01

    The most recent ceramic-matrix composites (CMC) considered for long-life applications as thermostructural parts in aerospace propulsion contain, among others, boron-rich phases like boron carbide. This compound is prepared by thermal Chemical Vapour Infiltration (CVI), starting from precursors like boron halides and hydrocarbons. We present a study aiming at a precise knowledge of the gas-phase composition in a hot-zone LPCVD reactor fed with BCl3, CH4 and H2, which combines experimental and theoretical approaches. This work has brought strong evidences of the presence of Methydichloroborane (MDB, BCl2CH3) in the process. It is demonstrated that this intermediate, the presence of which had never been formally proved before, appears for processing temperatures slightly lower than the deposition temperature of boron carbide. The study features quantum chemical computations, which provide several pieces of information like thermochemical and kinetic data, as well as vibration and rotation frequencies, reaction kinetics computations, and experimental gas-phase characterization of several species by FTIR, for several processing parameter sets. The main results are presented, and the place of MDB in the reaction scheme is discussed.

  4. Activated Carbon, Carbon Nanofiber and Carbon Nanotube Supported Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Guaiacol

    Directory of Open Access Journals (Sweden)

    Eduardo Santillan-Jimenez

    2015-03-01

    Full Text Available Molybdenum carbide was supported on three types of carbon support—activated carbon; multi-walled carbon nanotubes; and carbon nanofibers—using ammonium molybdate and molybdic acid as Mo precursors. The use of activated carbon as support afforded an X-ray amorphous Mo phase, whereas crystalline molybdenum carbide phases were obtained on carbon nanofibers and, in some cases, on carbon nanotubes. When the resulting catalysts were tested in the hydrodeoxygenation (HDO of guaiacol in dodecane, catechol and phenol were obtained as the main products, although in some instances significant amounts of cyclohexane were produced. The observation of catechol in all reaction mixtures suggests that guaiacol was converted into phenol via sequential demethylation and HDO, although the simultaneous occurrence of a direct demethoxylation pathway cannot be discounted. Catalysts based on carbon nanofibers generally afforded the highest yields of phenol; notably, the only crystalline phase detected in these samples was Mo2C or Mo2C-ζ, suggesting that crystalline Mo2C is particularly selective to phenol. At 350 °C, carbon nanofiber supported Mo2C afforded near quantitative guaiacol conversion, the selectivity to phenol approaching 50%. When guaiacol HDO was performed in the presence of acetic acid and furfural, guaiacol conversion decreased, although the selectivity to both catechol and phenol was increased.

  5. Molybdenum carbide-carbon nanocomposites synthesized from a reactive template for electrochemical hydrogen evolution

    KAUST Repository

    Alhajri, Nawal Saad

    2014-01-01

    Molybdenum carbide nanocrystals (Mo2C) with sizes ranging from 3 to 20 nm were synthesized within a carbon matrix starting from a mesoporous graphitic carbon nitride (mpg-C3N4) template with confined pores. A molybdenum carbide phase (Mo2C) with a hexagonal structure was formed using a novel synthetic method involving the reaction of a molybdenum precursor with the carbon residue originating from C3N4 under nitrogen at various temperatures. The synthesized nanocomposites were characterized using powder X-ray diffraction (XRD), temperature-programmed reaction with mass spectroscopy (MS), CHN elemental analyses, thermogravimetric analyses (TGA), nitrogen sorption, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results indicated that the synthesized samples have different surface structures and compositions, which are accordingly expected to exhibit different electrocatalytic activities toward the hydrogen evolution reaction (HER). Electrochemical measurements demonstrated that the sample synthesized at 1323 K exhibited the highest and most stable HER current in acidic media, with an onset potential of -100 mV vs. RHE, among the samples prepared in this study. This result is attributed to the sufficiently small particle size (∼8 nm on average) and accordingly high surface area (308 m2 g-1), with less oxidized surface entrapped within the graphitized carbon matrix. © 2014 the Partner Organisations.

  6. Guidelines for Synthesis and Processing of 2D Titanium Carbide (Ti3C2Tx MXene)

    KAUST Repository

    Alhabeb, Mohamed

    2017-08-25

    Two-dimensional (2D) transition metal carbides, carbonitrides and nitrides (MXenes) were discovered in 2011. Since the original discovery, more than 20 different compositions have been synthesized by the selective etching of MAX phase and other precursors and many more theoretically predicted. They offer a variety of different properties, making the family promising candidates in a wide range of applications, such as energy storage, electromagnetic interference shielding, water purification, electrocatalysis and medicine. These solution-processable materials have the potential to be highly scalable, deposited by spin, spray or dip coating, painted or printed, or fabricated in a variety of ways. Due to this promise, the amount of research on MXenes has been increasing, and methods of synthesis and processing are expanding quickly. The fast evolution of the material can also be noticed in the wide range of synthesis and processing protocols that determine the yield of delamination, as well as the quality of the 2D flakes produced. Here we describe the experimental methods and best practices we use to synthesize the most studied MXene, titanium carbide (Ti3C2Tx), using different etchants and delamination methods. We also explain effects of synthesis parameters on the size and quality of Ti3C2Tx and suggest the optimal processes for the desired application.

  7. Structure of superhard tungsten tetraboride: A missing link between MB2 and MB12 higher borides

    Science.gov (United States)

    Lech, Andrew T.; Turner, Christopher L.; Mohammadi, Reza; Tolbert, Sarah H.; Kaner, Richard B.

    2015-01-01

    Superhard metals are of interest as possible replacements with enhanced properties over the metal carbides commonly used in cutting, drilling, and wear-resistant tooling. Of the superhard metals, the highest boride of tungsten—often referred to as WB4 and sometimes as W1–xB3—is one of the most promising candidates. The structure of this boride, however, has never been fully resolved, despite the fact that it was discovered in 1961—a fact that severely limits our understanding of its structure–property relationships and has generated increasing controversy in the literature. Here, we present a new crystallographic model of this compound based on refinement against time-of-flight neutron diffraction data. Contrary to previous X-ray–only structural refinements, there is strong evidence for the presence of interstitial arrangements of boron atoms and polyhedral bonding. The formation of these polyhedra—slightly distorted boron cuboctahedra—appears to be dependent upon the defective nature of the tungsten-deficient metal sublattice. This previously unidentified structure type has an intermediary relationship between MB2 and MB12 type boride polymorphs. Manipulation of the fractionally occupied metal and boron sites may provide insight for the rational design of new superhard metals. PMID:25733870

  8. Fabrication and characterization of zirconium carbide (ZrC) nanofibers with thermal storage property

    International Nuclear Information System (INIS)

    Nam, Young Sik; Cui, Xue Mei; Jeong, Lim; Lee, Jae Yeol; Park, Won Ho

    2009-01-01

    Zirconium carbide (ZrC) nanofibers were fabricated by the electrospinning method and subsequent heat-treatment. The solution for electrospinning was prepared by dissolving zirconium acetyl acetonate and cellulose acetate in glacial acetic acid and 2,4-pentanedione as common solvents. The effects of the solution properties used for electrospinning, including the concentrations of the starting materials, the C/Zr ratio of the solutions, and soaking conditions, were investigated. The electrospinning process parameters and heat-treatment conditions were also investigated. The electrospun precursors and the heat-treated nanofibers were characterized by scanning electron microscopy, X-ray diffraction, elemental analysis, and Fourier transform infrared spectroscopy. ZrC nanofibers with a thermal emissivity above 90% have a great potential for thermal storage barrier membrane.

  9. Tungsten transport in the plasma edge at ASDEX upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Janzer, Michael Arthur

    2015-04-30

    The Plasma Facing Components (PFC) will play a crucial role in future deuterium-tritium magnetically confined fusion power plants, since they will be subject to high energy and particle loads, but at the same time have to ensure long lifetimes and a low tritium retention. These requirements will most probably necessitate the use of high-Z materials such as tungsten for the wall materials, since their erosion properties are very benign and, unlike carbon, capture only little tritium. The drawback with high-Z materials is, that they emit strong line radiation in the core plasma, which acts as a powerful energy loss mechanism. Thus, the concentration of these high-Z materials has to be controlled and kept at low levels in order to achieve a burning plasma. Understanding the transport processes in the plasma edge is essential for applying the proper impurity control mechanisms. This control can be exerted either by enhancing the outflux, e.g. by Edge Localized Modes (ELM), since they are known to expel impurities from the main plasma, or by reducing the influx, e.g. minimizing the tungsten erosion or increasing the shielding effect of the Scrape Off Layer (SOL). ASDEX Upgrade (AUG) has been successfully operating with a full tungsten wall for several years now and offers the possibility to investigate these edge transport processes for tungsten. This study focused on the disentanglement of the frequency of type-I ELMs and the main chamber gas injection rate, two parameters which are usually linked in H-mode discharges. Such a separation allowed for the first time the direct assessment of the impact of each parameter on the tungsten concentration. The control of the ELM frequency was performed by adjusting the shape of the plasma, i.e. the upper triangularity. The radial tungsten transport was investigated by implementing a modulated tungsten source. To create this modulated source, the linear dependence of the tungsten erosion rate at the Ion Cyclotron Resonance

  10. Co removal and phase transformations during high power diode laser irradiation of cemented carbide

    Energy Technology Data Exchange (ETDEWEB)

    Barletta, M., E-mail: barletta@ing.uniroma2.it [Dipartimento di Ingegneria Meccanica, Universita degli Studi di Roma Tor Vergata, Via del Politecnico, 1 - 00133 Roma (Italy); Rubino, G. [Dipartimento di Ingegneria Meccanica, Universita degli Studi di Roma Tor Vergata, Via del Politecnico, 1 - 00133 Roma (Italy); Gisario, A. [Dipartimento di Meccanica ed Aeronautica, Universita degli Studi di Roma La Sapienza, Via Eudossiana, 18 - 00184 Roma (Italy)

    2011-02-15

    The use of a continuous wave-high power diode laser for removing surface Co-binder from Co-cemented tungsten carbide (WC-Co (5.8 wt%.)) hardmetal slabs was investigated. Combined scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were performed in order to study the phase transformations and micro-structural modifications of the WC-Co substrates occurring during and after laser irradiation. The micro-structure of the WC-Co progressively transforms as energy density increased, exhibiting stronger removal of Co and WC grain growth. At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed, and the crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C (often referred to as the {eta}-phase). The latter can be detrimental to the mechanical properties of WC-Co. Therefore, the proper adjustment of the laser processing parameters plays a crucial role in surface treatments of WC-Co substrates prior to post-processing like diamond deposition.

  11. Advanced smart tungsten alloys for a future fusion power plant

    Science.gov (United States)

    Litnovsky, A.; Wegener, T.; Klein, F.; Linsmeier, Ch; Rasinski, M.; Kreter, A.; Tan, X.; Schmitz, J.; Mao, Y.; Coenen, J. W.; Bram, M.; Gonzalez-Julian, J.

    2017-06-01

    The severe particle, radiation and neutron environment in a future fusion power plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten-chromium-yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten-chroimium-titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.

  12. Microstructural development of tungsten and tungsten-rhenium alloys due to neutron irradiation in HFIR

    Science.gov (United States)

    Fukuda, Makoto; Yabuuchi, Kiyohiro; Nogami, Shuhei; Hasegawa, Akira; Tanaka, Teruya

    2014-12-01

    The microstructural development of pure tungsten (W) and tungsten-rhenium (Re) alloys due to neutron irradiation in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, TN, USA, was investigated in this work. The irradiation conditions were ∼1 displacements per atom (dpa) at 500 and 800 °C. After the neutron irradiation, microstructural observations were performed using a transmission electron microscope (TEM). Large amounts of precipitates identified as sigma- and chi-phases were observed in not only the W-Re alloys but also in the pure W after the neutron irradiation. The precipitates observed in the pure W were coarse and larger than those in the W-Re alloys. This was considered to be caused by the transmutation products of W and Re, namely, Re and osmium (Os), respectively, under irradiation in the HFIR with a higher contents of thermal neutron flux.

  13. An all optical system for studying temperature induced changes in polycrystalline diamond deposited on a tungsten carbide substrate

    CSIR Research Space (South Africa)

    Masina, BN

    2010-09-01

    Full Text Available In this poster the authors discussed the ability to heat an industrial diamond sample by means of optical absorption of a CO2 laser beam, and then measure the resulting temperature on the surface of the diamond optically by means of radiometry...

  14. Corrosion resistance of tungsten carbide based cermet coatings deposited by High Velocity Oxy-Fuel spray process

    Energy Technology Data Exchange (ETDEWEB)

    Aw, Poh Koon [Singapore Institute of Manufacturing Technology (Singapore)], E-mail: pkaw@SIMTech.a-star.edu.sg; Tan, Annie Lai Kuan [Singapore Institute of Manufacturing Technology (Singapore); Tan, Tai Phong [Hamilton Sundstrand Pacific Aerospace Pte Ltd (Singapore); Qiu, Jianhai [School of Materials Science and Engineering, Nanyang Technological University (Singapore)

    2008-06-30

    WC-17Ni and WC-17Co coatings were deposited on mild steel and stainless steel substrates by High Velocity Oxy-Fuel (HVOF) spray process. WC-17Ni and WC-17Co coatings were obtained by the spray process and the porosity of these coatings was measured. Polarization and electrochemical impedance spectroscopy (EIS) were performed on both uncoated substrates and coated samples immersed in 3% NaCl solution. WC-17Ni coating with a lower porosity, serve as a better barrier and effectively prevented corrosion attack when it was deposited on mild steel substrate. The nickel binder in the WC-17Ni coating was found to have a better corrosion resistance than the cobalt binder in the WC-17Co coating.

  15. Analysis of cobalt, tantalum, titanium, vanadium and chromium in tungsten carbide by inductively coupled plasma-optical emission spectrometry

    CSIR Research Space (South Africa)

    Archer, M

    2003-12-01

    Full Text Available standard laboratory glassware may used instead of PTFE vessels required for use with hydrofluoric acid. The method was found faster and more convenient, as well as less expensive than previous published methods. Only a few wavelengths were entirely...

  16. The Effect of pH on Slurry Erosion-Corrosion of Tungsten Carbide Overlays Alloyed with Ru

    Science.gov (United States)

    Nelwalani, Ndivhuwo B.; van der Merwe, Josias W.

    2018-01-01

    The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion-corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion-corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion-corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

  17. The Effect of pH on Slurry Erosion-Corrosion of Tungsten Carbide Overlays Alloyed with Ru

    Science.gov (United States)

    Nelwalani, Ndivhuwo B.; van der Merwe, Josias W.

    2018-02-01

    The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion-corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion-corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion-corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

  18. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    Science.gov (United States)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  19. Computational Studies of Physical Properties of Boron Carbide

    Energy Technology Data Exchange (ETDEWEB)

    Lizhi Ouyang

    2011-09-30

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

  20. Preparation and Fatigue Properties of Functionally Graded Cemented Carbides

    International Nuclear Information System (INIS)

    Liu Yong; Liu Fengxiao; Liaw, Peter K.; He Yuehui

    2008-01-01

    Cemented carbides with a functionally graded structure have significantly improved mechanical properties and lifetimes in cutting, drilling and molding. In this work, WC-6 wt.% Co cemented carbides with three-layer graded structure (surface layer rich in WC, mid layer rich in Co and the inner part of the average composition) were prepared by carburizing pre-sintered η-phase-containing cemented carbides. The three-point bending fatigue tests based on the total-life approach were conducted on both WC-6wt%Co functionally graded cemented carbides (FGCC) and conventional WC-6wt%Co cemented carbides. The functionally graded cemented carbide shows a slightly higher fatigue limit (∼100 MPa) than the conventional ones under the present testing conditions. However, the fatigue crack nucleation behavior of FGCC is different from that of the conventional ones. The crack nucleates preferentially along the Co-gradient and perpendicular to the tension surface in FGCC, while parallel to the tension surface in conventional cemented carbides

  1. Study on the performance of fuel elements with carbide and carbide-nitride fuel

    International Nuclear Information System (INIS)

    Golovchenko, Yu.M.; Davydov, E.F.; Maershin, A.A.

    1985-01-01

    Characteristics, test conditions and basic results of material testing of fuel elements with carbide and carbonitride fuel irradiated in the BOR-60 reactor up to 3-10% burn-up at specific power rate of 55-70 kW/m and temperatures of the cladding up to 720 deg C are described. Increase of cladding diameter is stated mainly to result from pressure of swelling fuel. The influence of initial efficient porosity of the fuel on cladding deformation and fuel stoichiometry on steel carbonization is considered. Utilization of carbide and carbonitride fuel at efficient porosity of 20% at the given test modes is shown to ensure their operability up to 10% burn-up

  2. Neutron irradiation effects on the microstructural development of tungsten and tungsten alloys

    Science.gov (United States)

    Hasegawa, Akira; Fukuda, Makoto; Yabuuchi, Kiyohiro; Nogami, Shuhei

    2016-04-01

    Data on the microstructural development of tungsten (W) and tungsten rhenium (Re) alloys were obtained after neutron irradiation at 400-800 °C in the Japan Materials Testing Reactor (JMTR), the experimental fast test reactor Joyo, and the High Flux Isotope Reactor (HFIR) for irradiation damage levels in the range of 0.09-1.54 displacement per atom (dpa). Microstructural observations showed that a small amount of Re (3-5%) in W-Re alloys is effective in suppressing void formation. In W-Re alloys with Re concentrations greater than 10%, acicular precipitates are the primary structural defects. In the HFIR-irradiated specimen, in which a large amount of Re was expected to be produced by the nuclear transmutation of W to Re because of the reactor's high thermal neutron flux, voids were not observed even in pure W. The synergistic effects of displacement damage and solid transmutation elements on microstructural development are discussed, and the microstructural development of tungsten materials utilized in fusion reactors is predicted.

  3. Tungsten as First Wall Material in Fusion Devices

    International Nuclear Information System (INIS)

    Kaufmann, M.

    2006-01-01

    In the PLT tokamak with a tungsten limiter strong cooling of the central plasma was observed. Since then mostly graphite has been used as limiter or target plate material. Only a few tokamaks (limiter: FTU, TEXTOR; divertor: Alcator C-Mod, ASDEX Upgrade) gained experience with high-Z-materials. With the observed strong co- deposition of tritium together with carbon in JET and as a result of design studies of fusion reactors, it became clear that in the long run tungsten is the favourite for the first-wall material. Tungsten as a plasma facing material requires intensive research in all areas, i.e. in plasma physics, plasma wall-interaction and material development. Tungsten as an impurity in the confined plasma reveals considerable differences to carbon. Strong radiation at high temperatures, in connection with mostly a pronounced inward drift forms a particular challenge. Turbulent transport plays a beneficial role in this regard. The inward drift is an additional problem in the pedestal region of H-mode plasmas in ITER-like configurations. The erosion by low energy hydrogen atoms is in contrast to carbon small. However, erosion by fast particles from heating measures and impurity ions, accelerated in the sheath potential, play an important role in the case of tungsten. Radiation by carbon in the plasma boundary reduces the load to the target plates. Neon or Argon as substitutes will increase the erosion of tungsten. So far experiments have demonstrated that in most scenarios the tungsten content in the central plasma can be kept sufficiently small. The material development is directed to the specific needs of existing or future devices. In ASDEX Upgrade, which will soon be a divertor experiment with a complete tungsten first-wall, graphite tiles are coated with tungsten layers. In ITER, the solid tungsten armour of the target plates has to be castellated because of its difference in thermal expansion compared to the cooling structure. In a reactor the technical

  4. Investigation of Tungsten and Beryllium Behaviour under Short Transient Events

    International Nuclear Information System (INIS)

    Pintsuk, G.; Kuehnlein, W.; Linke, J.; Roedig, M.

    2006-01-01

    The electron beam facility JUDITH is a rather versatile test facility for the simulation of high heat fluxes. One key issue is the simulation of the material performance under short transient events. The study of melting behaviour and crack formation, which occurs even for heat pulses below the melting threshold of the metals, is of huge importance for the qualification of materials for future nuclear devices. Heat load simulations at RT with a pulse length of 5 ms have been performed on beryllium (S65C), the ITER candidate material for the first wall, at power loads of 0.5 - 2 GW/m 2 . Crack formation, surface roughening and melt layer motion has been studied. Similar conditions during single and multiple shots below and above the melting threshold (∼50 MW·m-2·s 1 /2) have been applied to tungsten. Since its material properties are dependent on grain size and shape, 3 different grades have been tested in an as-delivered state: 1) deformed tungsten aligned in deformation direction, which corresponds to the actual ITER specification for tungsten used in the divertor; 2) deformed tungsten aligned perpendicular to the deformation direction; 3) sintered tungsten. Significant differences in the crack resistance and the crack pattern of the various tungsten grades below the melting threshold have been determined and further material degradation has been found after multiple shots. This is of importance also in regard to expected ELM loads in ITER, in which power densities below the melting threshold are applied at a high repetition rate (∼ 1 Hz). Crack formation for sintered tungsten starts at ∼20 MW·m -2 ·s -1 /2. The cracks are located across the loaded area and increase in number, length and width with increasing power load. In comparison to that for deformed tungsten cracking was first detected at ∼35 MW·m -2 ·s -1 /2. Whereas for tungsten aligned in deformation direction a crack pattern comparable to those of sintered tungsten was formed, tungsten

  5. Classification of tungsten powder by fluidization method and its application

    International Nuclear Information System (INIS)

    Li Khan-Guan'.

    1989-01-01

    Search for accessible in practice, the technological method to increase the level of control of the granulometric composition of tungsten powder and to increase quality of products and to prepare new materials is carried out. It is shown that the method of fluidization is effective and accessible in practice for tungsten powder (and other refractory metals and compounds) classification, that increases the level of control of the granulometric composition of the powder and thus - its quality, and that improves control of properties of tungsten and other refractory metal products

  6. Dense Pure Tungsten Fabricated by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Dianzheng Wang

    2017-04-01

    Full Text Available Additive manufacturing using tungsten, a brittle material, is difficult because of its high melting point, thermal conductivity, and oxidation tendency. In this study, pure tungsten parts with densities of up to 18.53 g/cm3 (i.e., 96.0% of the theoretical density were fabricated by selective laser melting. In order to minimize balling effects, the raw polyhedral tungsten powders underwent a spheroidization process before laser consolidation. Compared with polyhedral powders, the spherical powders showed increased laser absorptivity and packing density, which helped in the formation of a continuous molten track and promoted densification.

  7. 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.

  8. High precision tungsten cutting for optics

    International Nuclear Information System (INIS)

    Reglero, V.; Velasco, T.; Rodrigo, J.; Gasent, L.J.; Alamo, J.; Chato, R.; Ruiz Urien, I.; Santos, I.; Zarauz, J.; Clemente, G.; Sanz-Tudanca, C.; Lopez, J.L.

    2001-01-01

    The results obtained during the INTEGRAL masks development program an implementing the HURA and MURA codes on tungsten plates of different thickness are presented. Hard scientific requirements on pixels size and location tolerances (tenths of microns over large areas -1 m 2 - and thickness from 0.5 mm to 60 mm) required the set up of a dedicated program for testing cutting technologies: laser, photochemical milling, spark machining and electro discharge wire cutting. After a very intensive test campaign the wire cutting process was selected as the optimum technology for code manufacturing . Accuracies achieved an the code cutting fulfill scientific requirements. In fact, they are 5 times better than required. Pixel size and centroids location accuracies of 0.01 mm over a 1 m 2 area have been obtained for the 10,000 pixels on IBIS, 100 pixels on SPI and 24000 pixels on JEM-X masks. Comparative results among different cutting technologies are also discussed. (author)

  9. Modification of tungsten layers by arcing

    International Nuclear Information System (INIS)

    Laux, M.; Schneider, W.; Juettner, B.; Lindig, S.; Mayer, M.; Balden, M.; Beilis, I.; Djakov, B.

    2005-01-01

    Numerous traces of arcs have been found on W-covered graphite tiles of ASDEX Upgrade after exposure. The distributions of number density, lengths and orientation are calculated and compared to pure graphite tiles at comparable locations. It was established that arcs perforate a 1 μm tungsten layer down to the carbon substrate. The amount of removal should rise with arc current, but a surface fraction of about 8% is eroded at 10 A already. At tiles of the divertor baffle the layer is continuously removed along the entire track pointing to higher currents. The carbon of the stripped parts is subject to subsequent erosion processes. The distribution of materials in and around arc tracks was investigated by sputter depth profiling (SIMS and AES) and the characteristic geometry was studied using an electron microscope. Observations are interpreted using results from laboratory vacuum arcs on the same material

  10. The movement of screw dislocations in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Tian Xiaogeng; Woo Chungho

    2004-03-25

    Using Acland potential for tungsten, the movement of 1/2a<1 1 1> screw dislocation under shear stress was investigated by molecular dynamics simulation. Equilibrated core structure was obtained by relaxation of screw dislocation with proper boundary conditions. We found that the equilibrium dislocation core has three-fold symmetry and spread out in three <1 1 2> direction on {l_brace}1 1 0{r_brace} planes. The screw dislocation core could not keep the original shape when the shear stress applied. The dislocation could not move until the shear stress became large enough. The dislocation moved in zigzag when the shear stress neared the Peierls stress. When the shear stress became larger, the dislocation moved in zigzag at the beginning and than moved almost in straight line in [2-bar11] direction. The large shear stress applied, the long distance moved before the dislocation stilled in z-direction and the large velocity in y-direction.

  11. Electronic structure and Compton profiles of tungsten

    International Nuclear Information System (INIS)

    Lal Ahuja, Babu; Rathor, Ashish; Sharma, Vinit; Sharma, Yamini; Ramniklal Jani, Ashvin; Sharma, Balkrishna

    2008-01-01

    The energy bands, density of states and Compton profiles of tungsten have been computed using band structure methods, namely the spin-polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) approach as well as the linear combination of atomic orbitals with Hartree-Fock scheme and density functional theory. The full potential linearized augmented plane wave scheme to calculate these properties and the Fermi surface topology(except the momentum densities) have also been used to analyze the theoretical data on the electron momentum densities. The directional Compton profiles have been measured using a 100 mCi 241 Am Compton spectrometer. From the comparison, the measured anisotropies are found to be in good agreement with the SPR-KKR calculations. The band structure calculations are also compared with the available data. (orig.)

  12. Hydrogen generation from steam reaction with tungsten

    Science.gov (United States)

    Smolik, G. R.; McCarthy, K. A.; Petti, D. A.; Coates, K.

    1998-10-01

    A LOCA in a fusion reactor involving an ingress of steam presents a safety concern due to hydrogen generated from steam reactions with plasma facing components. Hydrogen concentrations must be maintained below explosive levels. To support safety evaluations we have experimentally determined hydrogen generation rates when a tungsten alloy is exposed to steam from 400°C to 1200°C. We studied effects of steam pressure between 2.8 × 10 4 and 8.5 × 10 4 Pa, i.e., (0.28-0.84 atm) and gas velocity between 0.011 and 0.063 m/s. We present relationships for the reaction rates, oxidation phases, and mechanisms associated with the hydrogen generation.

  13. Unveiling polytype transformation assisted growth mechanism in boron carbide nanowires

    Science.gov (United States)

    Song, Ningning; Li, Xiaodong

    2018-01-01

    We demonstrate direct evidence that the lattice distortion, induced by boron carbide (BxCy) stoichiometry, assists the growth of boron carbide nanowires. The transformation between different polytypic boron carbide phases lowers the energy barrier for boron diffusion, promoting boron migration in the nanowire growth. An atomistic mass transport model has been established to explain such volume-diffusion-induced nanowire growth which cannot be explained by the conventional surface diffusion model alone. These findings significantly advance our understanding of nanowire growth processes and mass transport mechanisms and provide new guidelines for the design of nanowire-structured devices.

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

    International Nuclear Information System (INIS)

    Baney, Ronald

    2008-01-01

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

  15. 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

  16. Colloidal characterization of ultrafine silicon carbide and silicon nitride powders

    Science.gov (United States)

    Whitman, Pamela K.; Feke, Donald L.

    1986-01-01

    The effects of various powder treatment strategies on the colloid chemistry of aqueous dispersions of silicon carbide and silicon nitride are examined using a surface titration methodology. Pretreatments are used to differentiate between the true surface chemistry of the powders and artifacts resulting from exposure history. Silicon nitride powders require more extensive pretreatment to reveal consistent surface chemistry than do silicon carbide powders. As measured by titration, the degree of proton adsorption from the suspending fluid by pretreated silicon nitride and silicon carbide powders can both be made similar to that of silica.

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

    International Nuclear Information System (INIS)

    Cancino T, F.; Lopez H, E.

    2013-10-01

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

  18. Fuzzy tungsten in a magnetron sputtering device

    Energy Technology Data Exchange (ETDEWEB)

    Petty, T.J., E-mail: tjpetty@liv.ac.uk [Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ (United Kingdom); Khan, A. [Pariser Building-G11, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester, M13 9PL (United Kingdom); Heil, T. [NiCaL, Block C Waterhouse Building, 1-3 Brownlow Street, Liverpool, L69 3GL (United Kingdom); Bradley, J.W., E-mail: j.w.bradley@liverpool.ac.uk [Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ (United Kingdom)

    2016-11-15

    Helium ion induced tungsten nanostructure (tungsten fuzz) has been studied in a magnetron sputtering device. Three parameters were varied, the fluence from 3.4 × 10{sup 23}–3.0 × 10{sup 24} m{sup −2}, the He ion energy from 25 to 70 eV, and the surface temperature from 900 to 1200 K. For each sample, SEM images were captured, and measurements of the fuzz layer thickness, surface roughness, reflectivity, and average structure widths are provided. A cross-over point from pre-fuzz to fully formed fuzz is found at 2.4 ± 0.4 × 10{sup 24} m{sup −2}, and a temperature of 1080 ± 60 K. No significant change was observed in the energy sweep. The fuzz is compared to low fluence fuzz created in the PISCES-A linear plasma device. Magnetron fuzz is less uniform than fuzz created by PISCES-A and with generally larger structure widths. The thicknesses of the magnetron samples follow the original Φ{sup 1/2} relation as opposed to the incubation fluence fit. - Highlights: • Fuzz has been created in a magnetron sputtering device. • Three parameters for fuzz formation have been swept. • A cross-over from pre-fuzz to fully formed fuzz is seen. • Evidence for annealing out at lower temperatures than has been seen before. • Evidence to suggest that fuzz grown in discrete exposures is not consistent with fuzz grown in one long exposure.

  19. Fuzzy tungsten in a magnetron sputtering device

    International Nuclear Information System (INIS)

    Petty, T.J.; Khan, A.; Heil, T.; Bradley, J.W.

    2016-01-01

    Helium ion induced tungsten nanostructure (tungsten fuzz) has been studied in a magnetron sputtering device. Three parameters were varied, the fluence from 3.4 × 10 23 –3.0 × 10 24  m −2 , the He ion energy from 25 to 70 eV, and the surface temperature from 900 to 1200 K. For each sample, SEM images were captured, and measurements of the fuzz layer thickness, surface roughness, reflectivity, and average structure widths are provided. A cross-over point from pre-fuzz to fully formed fuzz is found at 2.4 ± 0.4 × 10 24  m −2 , and a temperature of 1080 ± 60 K. No significant change was observed in the energy sweep. The fuzz is compared to low fluence fuzz created in the PISCES-A linear plasma device. Magnetron fuzz is less uniform than fuzz created by PISCES-A and with generally larger structure widths. The thicknesses of the magnetron samples follow the original Φ 1/2 relation as opposed to the incubation fluence fit. - Highlights: • Fuzz has been created in a magnetron sputtering device. • Three parameters for fuzz formation have been swept. • A cross-over from pre-fuzz to fully formed fuzz is seen. • Evidence for annealing out at lower temperatures than has been seen before. • Evidence to suggest that fuzz grown in discrete exposures is not consistent with fuzz grown in one long exposure.

  20. Electrodeposition of tungsten coatings on molybdenum substrates and deuterium irradiation effect

    International Nuclear Information System (INIS)

    Lian, Ziwei; Fang, Xianqin; Han, Wenjia; Yu, Jiangang; Wang, Zhanlei; Zhang, Ying; Zhu, Kaigui

    2016-01-01

    Highlights: • Tungsten coatings were successfully electroplated on molybdenum substrates. • The current density affected the performance of tungsten coatings. • Deuterium irradiation property of tungsten coatings was investigated. • Deuterium retention in the tungsten coating was less than that in the bulk tungsten. - Abstract: Tungsten coatings were prepared using pulse electrodeposition on the molybdenum substrates. Effects of variations in current density on surface morphology, thickness distribution and crystal orientation of the coatings were investigated. The results indicate that with the current density increasing, the grain size of tungsten coatings first decreases, then increases; while the deposited thickness increases all the time. And all of tungsten coatings exhibit the preferred orientation of (200) plane. Moreover, the polished tungsten coating and bulk tungsten were exposed to low energy (80 eV) and high flux (7.2 × 10 20 D/m 2 /s) deuterium plasma in a linear plasma device (Simulator of Tokamak Edge Plasma, STEP). Deuterium (D) retention was measured by thermal desorption spectroscopy (TDS). It is found that blisters on the tungsten coating are much fewer than that on the bulk tungsten. TDS spectroscopy of the tungsten coating reveals one D 2 release peak at 740 K, while the bulk tungsten has two D 2 release peaks at 500 K and 660 K. The amount of deuterium retention in the tungsten coating is lower.

  1. Ordering effects in nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.; Kottar, A.

    2000-01-01

    The effect of nonstoichiometry and ordering on crystalline structure and specific electric resistance (ρ) of TiC y (0.52≤y≤0.98) is studied within the temperature range of 300-1100 K. It is shown that the titanium carbide ordering in the areas 0.52≤y≤0.55, 0.56≤y≤0.58 and 0.62≤y≤0.68 leads to formation of the Ti 2 C cubic and trigonal ordered phase and the Ti 3 C 2 rhombic ordered phase correspondingly. Availability of hysteresis on the ρ(T) dependences in the area of the disorder-order reversible equilibrium transition points out to the fact that the TiC y ↔Ti 2 C and TiC y ↔Ti 3 C 2 transformations are the first order phase transitions [ru

  2. 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.

  3. Carbon in palladium catalysts: A metastable carbide

    International Nuclear Information System (INIS)

    Seriani, Nicola; Mittendorfer, Florian; Kresse, Georg

    2010-01-01

    The catalytic activity of palladium towards selective hydrogenation of hydrocarbons depends on the partial pressure of hydrogen. It has been suggested that the reaction proceeds selectively towards partial hydrogenation only when a carbon-rich film is present at the metal surface. On the basis of first-principles simulations, we show that carbon can dissolve into the metal because graphite formation is delayed by the large critical nucleus necessary for graphite nucleation. A bulk carbide Pd 6 C with a hexagonal 6-layer fcc-like supercell forms. The structure is characterized by core level shifts of 0.66-0.70 eV in the core states of Pd, in agreement with experimental x-ray photoemission spectra. Moreover, this phase traps bulk-dissolved hydrogen, suppressing the total hydrogenation reaction channel and fostering partial hydrogenation. (author)

  4. Silicon Carbide Nanotube Oxidation at High Temperatures

    Science.gov (United States)

    Ahlborg, Nadia; Zhu, Dongming

    2012-01-01

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

  5. Texaco, carbide form hydrogen plant venture

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

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

  6. 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..

  7. 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.

  8. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    Unknown

    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 ...

  9. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    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.

  10. Understanding metal–insulator transition in sodium tungsten bronze

    Indian Academy of Sciences (India)

    ARPES) and spectro- microscopy studies to understand the metal–insulator transition (MIT) observed in sodium tungsten bronzes, NaxWO3. The experimentally determined band structure is compared with the theoretical calculation based on ...

  11. A Compact Gas/Tungsten-Arc Welding Torch

    Science.gov (United States)

    Morgen, Gene E.

    1991-01-01

    Compact gas/tungsten-arc welding torch delivers 100-A current, yet used in confined spaces inaccessible to even smallest commercially available torch. Despite its extremely small size, torch contains all usual components and delivers high current.

  12. TIG (Tungsten Inert Gas) welding; Le soudage TIG

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2010-09-15

    After having recalled the Tungsten Inert Gas process principle and the different alternative TIG processes, the author explains the advantages and limits of this process. The applications and recent developments are given. (O.M.)

  13. Cold machining of high density tungsten and other materials

    Science.gov (United States)

    Ziegelmeier, P.

    1969-01-01

    Cold machining process, which uses a sub-zero refrigerated cutting fluid, is used for machining refractory or reactive metals and alloys. Special carbide tools for turning and drilling these alloys further improve the cutting performance.

  14. Microwave-assisted synthesis of WS2 nanowires through tetrathiotungstate precursors

    Directory of Open Access Journals (Sweden)

    Pravas Kumar Panigrahi and Amita Pathak

    2008-01-01

    Full Text Available Tungsten disulfide (WS2 nanowires have been synthesized through a microwave-assisted chemical route that uses tungstic acid, elemental sulfur and monoethanolamine as starting reagents for obtaining a precursor solution of tetrathiotungstate ions. Acidification of the precursor solution yields amorphous precipitates, which lead to the formation of nanowires of WS2 with thickness of about 5–10 nm when heated at 750 °C under argon atmosphere for 1.5 h. Phase and the microstructure of the prepared powders have been investigated through x-ray powder diffraction and high-resolution transmission electron microscopy, respectively. Optical absorption of the WS2 powders reveals a red shift of the exciton bands compared to bulk WS2.

  15. Nano-porous carbide derived carbon with tunable pore size: synthesis and energy-related applications

    International Nuclear Information System (INIS)

    Gleb Yushin; John Chmiola; Ranjan K Dash; Elisabeth Hoffman; Michel Barsoum; Yury Gogotsi; Giovanna Laudisio; John E Fischer

    2005-01-01

    The large surface area and adjustable internal surface chemistry of porous carbons are attractive for a wide range of energy applications, including gas separation and storage, high power super-capacitors and lithium ion batteries. Major efforts in the field have been directed toward control of pore size, shape and uniformity, and total pore volume. Here we demonstrate that pore size can be precisely tuned with sub-Angstroms accuracy over a 0.5-3.0 nm range by preferentially removing metals from metal carbides. This is achieved by 'burning out' the metals (and metalloids) in halogen atmospheres at modest temperatures. The resulting carbide-derived carbon (CDC) retains the original shape of the carbide and shows linear reaction kinetics, allowing conversion of a carbide surface to a CDC layer of any thickness, including the entire monolith, film or particle. CDCs produced from binary and ternary carbides have been investigated, and specific surface areas (SSA) in excess of 2000 m 2 /g have been achieved. Pore size is determined by the structure and chemistry of the precursor, and by process parameters including temperature and composition of the reaction mixture. Most CDCs show smaller and more uniform pores when processed below 400-800 C, while larger and less uniform pores are found at 600-1200 C. Some CDCs (e.g. from B 4 C) have relatively broad pore size distributions, including meso-pores, even when processed at low temperatures. In contrast, other CDCs, e.g from SiC maintain a narrow distribution up to 1200 C. CDC microstructures become more ordered, evolving from amorphous to graphitic, with increasing process temperature. Other carbon forms, e.g. nano-tubes, onions, and nanocrystalline diamonds have also been obtained as CDC. The ability to fine tune the pore size, and independently to control the microstructure and surface termination, offers unique opportunities for parametric studies of gas sorption and desorption phenomena. Our recent studies show that

  16. Radial furnace shows promise for growing straight boron carbide whiskers

    Science.gov (United States)

    Feingold, E.

    1967-01-01

    Radial furnace, with a long graphite vaporization tube, maintains a uniform thermal gradient, favoring the growth of straight boron carbide whiskers. This concept seems to offer potential for both the quality and yield of whiskers.

  17. On surface Raman scattering and luminescence radiation in boron carbide.

    Science.gov (United States)

    Werheit, H; Filipov, V; Schwarz, U; Armbrüster, M; Leithe-Jasper, A; Tanaka, T; Shalamberidze, S O

    2010-02-03

    The discrepancy between Raman spectra of boron carbide obtained by Fourier transform Raman and conventional Raman spectrometry is systematically investigated. While at photon energies below the exciton energy (1.560 eV), Raman scattering of bulk phonons of boron carbide occurs, photon energies exceeding the fundamental absorption edge (2.09 eV) evoke additional patterns, which may essentially be attributed to luminescence or to the excitation of Raman-active processes in the surface region. The reason for this is the very high fundamental absorption in boron carbide inducing a very small penetration depth of the exciting laser radiation. Raman excitations essentially restricted to the boron carbide surface region yield spectra which considerably differ from bulk phonon ones, thus indicating structural modifications.

  18. Properties of cemented carbides alloyed by metal melt treatment

    International Nuclear Information System (INIS)

    Lisovsky, A.F.

    2001-01-01

    The paper presents the results of investigations into the influence of alloying elements introduced by metal melt treatment (MMT-process) on properties of WC-Co and WC-Ni cemented carbides. Transition metals of the IV - VIll groups (Ti, Zr, Ta, Cr, Re, Ni) and silicon were used as alloying elements. It is shown that the MMT-process allows cemented carbides to be produced whose physico-mechanical properties (bending strength, fracture toughness, total deformation, total work of deformation and fatigue fracture toughness) are superior to those of cemented carbides produced following a traditional powder metallurgy (PM) process. The main mechanism and peculiarities of the influence of alloying elements added by the MMT-process on properties of cemented carbides have been first established. The effect of alloying elements on structure and substructure of phases has been analyzed. (author)

  19. Studies of Hafnium-Carbide Wafers Using a Thermogravimetric Analyzer

    National Research Council Canada - National Science Library

    Castillo, Domingo

    1993-01-01

    ...) over chemical propulsion systems. Solar thermal can accomplish this increased performance by absorbing concentrated solar energy with very high temperature materials which through conduction heat hydrogen (H2). Hafnium carbide (HfC...

  20. Process for preparing fine grain silicon carbide powder

    Science.gov (United States)

    Wei, G.C.

    Method of producing fine-grain silicon carbide powder comprises combining methyltrimethoxysilane with a solution of phenolic resin, acetone and water or sugar and water, gelling the resulting mixture, and then drying and heating the obtained gel.