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Sample records for carbon nanotube-supported tungsten

  1. States of Carbon Nanotube Supported Mo-Based HDS Catalysts

    Institute of Scientific and Technical Information of China (English)

    Hongyan Shang; Chenguang Liu; Yongqiang Xu; Jieshan Qiu; Fei Wei

    2006-01-01

    The dispersion of the active phase and loading capacity of the Mo species on carbon nanotube (CNT) was studied by the XRD technique. The reducibility properties of Co-Mo catalysts in the oxide state over CNTs were investigated by TPR, while the sulfided Co-Mo/CNT catalysts were characterized by means of the XRD and LRS techniques. The activity and selectivity with respect to the hydrodesulfurization (HDS) performances on carbon nanotube supported Co-Mo catalysts were evaluated. It was found that the main active molybdenum species in the oxide state MoO3/CNT catalysts were MoO2, but not MoO3, as generally expected. The maximum loading before the formation of the bulk phase was lower than 6% (percent by mass, based on MoO3). TPR studies revealed that the active species in the oxide state Co-Mo/CNT catalysts were reduced more easily at relatively lower temperatures in comparison to those of the Co-Mo/γ-Al2O3 catalysts, indicating that the CNT support promoted or favored the reduction of the active species. The active species of a Co-Mo-0.7/CNT catalyst were more easily reduced than those of the Co-Mo/CNT catalysts with Co/Mo atomic ratios of 0.2, 0.35, and 0.5, respectively, suggesting that the Co/Mo atomic ratio has a great effect on the reducibility of the active species. It was found that the incorporation of cobalt improved the dispersion of the molybdenum species on the support, and a phenomenon of mobilization and re-dispersion had occurred during the sulfurization process, resulting in low valence state Mo3S4 and Co-MoS2.17 active phases. HDS measurements showed that the Co-Mo/CNT catalysts were more active than the Co-Mo/γ-Al2O3 ones for the desulfurization of DBT, and the hydrogenolysis/hydrogenation selectivity of the Co-Mo/CNT catalysts was also much higher than those of the Co-Mo/γ-Al2O3. The Co-Mo/CNT catalyst with a Co/Mo atomic ratio of 0.7 showed the highest activity, whereas the catalyst with a Co/Mo atomic ratio of 0.35 had the highest selectivity.

  2. Preparation of Multiwall Carbon Nanotubes-supported High Loading Platinum for Vehicular PEMFC Application

    Institute of Scientific and Technical Information of China (English)

    Bing ZHANG; Li Juan CHEN; Kai Yong GE; Yan Chuan GUO; Bi Xian PENG

    2005-01-01

    Multiwall carbon nanotube-supported Pt (Pt/MWNTs) catalysts with high dispersion and high loading of Pt were prepared by chemical reduction method and the loading of Pt got to 40wt%. The average diameter of Pt nanoparticles on MWNTs was about 3.5 nm. When the hydrogen and air were used as reactant gases for PEMFC, Pt/MWNTs catalysts showed significantly higher performance than the Pt/XC-72 (carbon black) catalysts.

  3. The study on carbon nanotubes-supported Pt catalysts for PEMFC

    Institute of Scientific and Technical Information of China (English)

    朱捷; 朱红; 康晓红; 葛奉娟; 杨玉国

    2004-01-01

    Carbon nanotube-supported-platinum (Pt/CNTs) and carbon-supported-platinum (Pt/C) catalysts were prepared by in situ chemical reduction method and analyzed by TEM and XRD. Then the experiments were carried out to test the performance of PEMFCs with the Pt electrodes. The results showed that in both catalyst, Pt was of small particle size (about 4 nm) and Pt/CNTs exhibited higher catalytic activity than Pt/C.

  4. Polyaniline-functionalized carbon nanotube supported platinum catalysts.

    Science.gov (United States)

    He, Daping; Zeng, Chao; Xu, Cheng; Cheng, Niancai; Li, Huaiguang; Mu, Shichun; Pan, Mu

    2011-05-03

    Electrocatalytically active platinum (Pt) nanoparticles on a carbon nanotube (CNT) with enhanced nucleation and stability have been demonstrated through introduction of electron-conducting polyaniline (PANI) to bridge the Pt nanoparticles and CNT walls with the presence of platinum-nitride (Pt-N) bonding and π-π bonding. The Pt colloids were prepared through ethanol reduction under the protection of aniline, the CNT was dispersed well with the existence of aniline in the solution, and aniline was polymerized in the presence of a protonic acid (HCl) and an oxidant (NH(4)S(2)O(8)). The synthesized PANI is found to wrap around the CNT as a result of π-π bonding, and highly dispersed Pt nanoparticles are loaded onto the CNT with narrowly distributed particle sizes ranging from 2.0 to 4.0 nm due to the polymer stabilization and existence of Pt-N bonding. The Pt-PANI/CNT catalysts are electroactive and exhibit excellent electrochemical stability and therefore promise potential applications in proton exchange membrane fuel cells.

  5. States of carbon nanotube supported Mo-based HDS catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Shang, Hongyan; Liu, Chenguang; Xu, Yongqiang [Key Laboratory of Catalysis, CNPC, College of Chemistry and Chemical Engineering, University of Petroleum, Dongying 257061 (China); Qiu, Jieshan [Carbon Research Laboratory, Center for Nano Materials and Science, Dalian University of Technology, 158 Zhongshan Road, P. O. Box 49, Dalian 116012 (China); Wei, Fei [Department of Chemical Engineering, Tsinghua University, Being, 100084 (China)

    2007-02-15

    As HDS catalysts, the supported catalysts including oxide state Mo, Co-Mo and sulfide state Mo on carbon nanotube (CNT) were prepared, while the corresponding supported catalysts on {gamma}-Al{sub 2}O{sub 3} were prepared as comparison. Firstly, the dispersion of the active phase and loading capacity of Mo species on CNT was studied by XRD and the reducibility properties of Co-Mo catalysts in oxide state over CNTs were investigated by TPR while the sulfide Co-Mo/CNT catalysts were characterized by XRD and LRS techniques. Secondly, the activity and selectivity of hydrodesulfurization (HDS) of dibenzothiophene with Co-Mo/CNT and Co-Mo/{gamma}-Al{sub 2}O{sub 3} were studied. It has been found that the main active molybdenum species in the oxide state MoO{sub 3}/CNT catalysts were MoO{sub 2}, rather than MoO{sub 3} as generally expected. The maximum loading before formation of the bulk phase was lower than 6%m (calculated in MoO{sub 3}). The TPR studies revealed that that active species in oxide state Co-Mo/CNT catalysts were more easily reduced at relatively lower temperatures in comparison to those in Co-Mo/{gamma}-Al{sub 2}O{sub 3}, indicating that the CNT support promoted the reduction of active species. Among 0-1.0 Co/Mo atomic ratio on Co-Mo/CNT, 0.7 has the highest reducibility. It shows that the Co/Mo atomic ratio has a great effect on the reducibility of active species on CNT and their HDS activities and that the incorporation of cobalt improved the dispersion of molybdenum species on CNT and mobilization. It was also found that re-dispersion could occur during the sulfiding process, resulting in low valence state Mo{sub 3}S{sub 4} and Co-MoS{sub 2.17} active phases. The HDS of DBT showed that Co-Mo/CNT catalysts were more active than Co-Mo/{gamma}-Al{sub 2}O{sub 3} and the hydrogenolysis/hydrogenation selectivity of Co-Mo/CNT catalyst was also much higher than Co-Mo/{gamma}-Al{sub 2}O{sub 3}. For the Co-Mo/CNT catalysis system, the catalyst with Co/Mo atomic

  6. Nitrogen-Doped Carbon Nanotube-Supported Pd Catalyst for Improved Electrocatalytic Performance toward Ethanol Electrooxidation

    Science.gov (United States)

    Wei, Ying; Zhang, Xinyuan; Luo, Zhiyong; Tang, Dian; Chen, Changxin; Zhang, Teng; Xie, Zailai

    2017-07-01

    In this study, hydrothermal carbonization (HTC) was applied for surface functionalization of carbon nanotubes (CNTs) in the presence of glucose and urea. The HTC process allowed the deposition of thin nitrogen-doped carbon layers on the surface of the CNTs. By controlling the ratio of glucose to urea, nitrogen contents of up to 1.7 wt% were achieved. The nitrogen-doped carbon nanotube-supported Pd catalysts exhibited superior electrochemical activity for ethanol oxidation relative to the pristine CNTs. Importantly, a 1.5-fold increase in the specific activity was observed for the Pd/HTC-N1.67%CNTs relative to the catalyst without nitrogen doping (Pd/HTC-CNTs). Further experiments indicated that the introduction of nitrogen species on the surface of the CNTs improved the Pd(0) loading and increased the binding energy.

  7. A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

    Institute of Scientific and Technical Information of China (English)

    Yan Ju; Fengyi Li

    2006-01-01

    A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.

  8. FT-IR Study of Carbon Nanotube Supported Co-Mo Catalysts

    Institute of Scientific and Technical Information of China (English)

    Hongyan Shang; Chenguang Liu1; Fei Wei

    2004-01-01

    In this paper, adsorption properties of dibenzothiophene (DBT) on carbon nanotube, carbon nanotube supported oxide state and sulfide state CoMo catalysts are studied by using thermal gravimetric analysis (TGA) technique and FT-IR spectroscopy. Activated carbon support, γ-Al2O3 support and supported CoMo catalysts are also subjected to studies for comparison. It was found that sulfide state CoMoS/MWCNT, CoMoS/AC and CoMoS/γ-Al2O3 catalysts adsorbed much more DBT molecules than their corresponding oxide state catalysts, as well as their corresponding supports. The chemically adsorbed DBT aromatic molecules did not undergo decomposition on the surface of supports, supported oxide state CoMo catalysts and sulfide state CoMo catalysts when out-gassing at 373 K. FT-IR results indicated that DBT molecules mainly stand upright on the active sites (acid sites and/or transition active phases) of CoMoS/MWCNT catalyst. However, DBT aromatic molecules mainly lie flat on MWCNT and CoMoO/MWCNT.

  9. Heterogeneous catalytic ozonation of ciprofloxacin in water with carbon nanotube supported manganese oxides as catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Sui, Minghao, E-mail: suiminghao.sui@gmail.com [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Xing, Sichu; Sheng, Li; Huang, Shuhang; Guo, Hongguang [State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Ciprofloxacin in water was degraded by heterogeneous catalytic ozonation. Black-Right-Pointing-Pointer MnOx were supported on MWCNTs to serve as catalyst for ozonation. Black-Right-Pointing-Pointer MnOx/MWCNT exhibited highly catalytic activity on ozonation of ciprofloxacin in water. Black-Right-Pointing-Pointer MnOx/MWCNT resulted in effective antibacterial activity inhibition on ciprofloxacin. Black-Right-Pointing-Pointer MnOx/MWCNT promoted the generation of hydroxyl radicals. - Abstract: Carbon nanotube-supported manganese oxides (MnOx/MWCNT) were used as catalysts to assist ozone in degrading ciprofloxacin in water. Manganese oxides were successfully loaded on multi-walled carbon nanotube surfaces by simply impregnating the carbon nanotube with permanganate solution. The catalytic activities of MnOx/MWCNT in ciprofloxacin ozonation, including degradation, mineralization effectiveness, and antibacterial activity change, were investigated. The presence of MnOx/MWCNT significantly elevated the degradation and mineralization efficiency of ozone on ciprofloxacin. The microbiological assay with a reference Escherichia coli strain indicated that ozonation with MnOx/MWCNT results in more effective antibacterial activity inhibition of ciprofloxacin than that in ozonation alone. The effects of catalyst dose, initial ciprofloxacin concentration, and initial pH conditions on ciprofloxacin ozonation with MnOx/MWCNT were surveyed. Electron spin resonance trapping was applied to assess the role of MnOx/MWCNT in generating hydroxyl radicals (HO{center_dot}) during ozonation. Stronger 5,5-dimethyl-1-pyrroline-N-oxide-OH signals were observed in the ozonation with MnOx/MWCNT compared with those in ozonation alone, indicating that MnOx/MWCNT promoted the generation of hydroxyl radicals. The degradation of ciprofloxacin was studied in drinking water and wastewater process samples to gauge the potential effects of water background matrix on

  10. 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.

  11. Multi-wall carbon nanotubes supported on carbon fiber paper synthesized by simple chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ya-hao [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Zhengzhou Research Institute of Chalco, Zhengzhou 450041 (China); Gao, Hong-quan [Zhengzhou Research Institute of Chalco, Zhengzhou 450041 (China); Yang, Jian-hong, E-mail: zyy_yjh@rilm.com.cn [Zhengzhou Research Institute of Chalco, Zhengzhou 450041 (China); Gao, Wen-liang; Xiang, Jia [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Li, Qing-yu, E-mail: 13975808173@126.com [School of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin, Guangxi 541004 (China)

    2014-09-15

    Highlights: • We deposited multi-wall carbon nanotubes on carbon fiber paper with a simple CVD. • We investigated the inherent mechanism of Ni particle's self-dispersion. • The MWCNTs/CFP composite possesses wonderful electrical conductivity. - Abstract: Aiming at developing a novel carbon/carbon composite as an electrode in the electrochemical capacitor applications, multi-wall carbon nanotubes (MWCNTs)/carbon fiber paper (CFP) composite has been synthesized using a simple chemical vapor deposition, in which different metal catalysts such as Fe, Ni and Cu are used. However, randomly oriented MWCNTs were only obtained on Ni particles. The mechanism for this unique phenomenon is investigated in this article. The physical and electrochemical properties of as-prepared MWCNTs/CFP composite are characterized and the results show that the as-prepared composite is a promising substrate for electrochemical capacitor applications.

  12. Highly efficient bimetal synergetic catalysis by a multi-wall carbon nanotube supported palladium and nickel catalyst for the hydrogen storage of magnesium hydride.

    Science.gov (United States)

    Yuan, Jianguang; Zhu, Yunfeng; Li, Liquan

    2014-06-25

    A multi-wall carbon nanotube supported Pd and Ni catalyst efficiently catalyzes the hydrogen storage of magnesium hydride prepared by HCS + MM. Excellent hydrogen storage properties were obtained: hydrogen absorption - 6.44 wt% within 100 s at 373 K, hydrogen desorption - 6.41 wt% within 1800 s at 523 K and 6.70 wt% within 400 s at 573 K.

  13. Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide:A facile method for the synthesis of tetrasubstituted olefins

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lei; ZHANG WeiDe; JIANG HuanFeng

    2008-01-01

    A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the cata-lyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of di-bromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.

  14. Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide: A facile method for the synthesis of tetrasubstituted olefins

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the catalyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of dibromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.

  15. Modified Sol-Gel Synthesis of Carbon Nanotubes Supported Titania Composites with Enhanced Visible Light Induced Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Quanjie Wang

    2016-01-01

    Full Text Available Multiwalled carbon nanotube (MWCNT enhanced MWCNT/TiO2 nanocomposites were synthesized by surface coating of carbon nanotube with mixed phase of anatase and rutile TiO2 through a modified sol-gel approach using tetrabutyl titanate as raw material. The morphological structures and physicochemical properties of the nanocomposites were characterized by FT-IR, XRD, DTA-TG, TEM, and UV-Vis spectra. The results show that TiO2 nanoparticles with size of around 15 nm are closely attached on the sidewall of MWCNT. The nanocomposites possess good absorption properties not only in the ultraviolet but also in the visible light region. Under irradiation of ultraviolet lamp, the prepared composites have the highest photodegradation efficiency of 83% within 4 hours towards the degradation of Methyl Orange (MO aqueous solution. The results indicate that the carbon nanotubes supported TiO2 nanocomposites exhibit high photocatalytic activity and stability, showing great potentials in the treatment of wastewater.

  16. CO selective methanation in hydrogen-rich gas mixtures over carbon nanotube supported Ru-based catalysts

    Institute of Scientific and Technical Information of China (English)

    Jun Xiong; Xinfa Dong; Lingling Li

    2012-01-01

    Series of carbon nanotube supported Ru-based catalysts were prepared by impregnation method and applied successfully for complete removal of CO by CO selective methanation from H2-rich gas stream conducted in a fixed-bed quartz tubular reactor at ambient pressure.It was found that the metal promoter,reduction temperature and metal loading affected the catalytic properties significantly.The most excellent performance was presented by 30 wt% Ru-Zr/CNTs catalyst reduced at 350 ℃.Since it decreased CO concentration to below 10 ppm from 12000 ppm by CO selective methanation at the temperature range of 180-240 ℃,and kept CO selectivity higher than 85% at the temperature below 200 ℃.Characterization using XRD,TEM,H2-TPR and XPS suggests that Zr modification of Ru/CNTs results in the weakening of the interaction between Ru and CNTs,a higher Ru dispersion and the oxidization of surface Ru.Amorphous and high dispersed Ru particles with small size were obtained for 30 wt% Ru-Zr/CNTs catalyst reduced at 350 ℃,leading to excellent catalytic performance in CO selective methanation.

  17. Novel Carbon Nanotubes-supported NiB Amorphors Alloy Catalyst for Benzene Hydrogenation

    Institute of Scientific and Technical Information of China (English)

    Mei Hua YANG; Rong Bin ZHANG; Feng Yi LI

    2004-01-01

    The NiB amorphous alloy catalysts supported on CNTs and alumina were prepared by impregnation and chemical reduction. The gas-phase benzene hydrogenation was used as a probe reaction to evaluate the catalytic activity. The result showed that the NiB amorphous alloy catalyst supported on carbon nanotubes exhibited higher activity than that supported on alumina.

  18. Multi-walled carbon nanotube supported CdS-DETA nanocomposite for efficient visible light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Jiali; Li, Dongpei [College of Physics and Electronic Information, Anhui Key Laboratory of Energetic Materials, Huaibei Normal University, Huaibei, 235000 (China); Dai, Kai, E-mail: daikai940@chnu.edu.cn [College of Physics and Electronic Information, Anhui Key Laboratory of Energetic Materials, Huaibei Normal University, Huaibei, 235000 (China); Liang, Changhao, E-mail: chliang@issp.ac.cn [College of Physics and Electronic Information, Anhui Key Laboratory of Energetic Materials, Huaibei Normal University, Huaibei, 235000 (China); Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Jiang, Dequan [College of Physics and Electronic Information, Anhui Key Laboratory of Energetic Materials, Huaibei Normal University, Huaibei, 235000 (China); Lu, Luhua [Faculty of Material Science and Chemical Engineering, China University of Geosciences, Wuhan, 430074 (China); Zhu, Guangping [College of Physics and Electronic Information, Anhui Key Laboratory of Energetic Materials, Huaibei Normal University, Huaibei, 235000 (China)

    2017-01-15

    Designing high performance functional nanomaterials by tuning their dimension at nanoscale and constructing novel interface has been a hot topic in recent years. In this work, multi-walled carbon nanotube (MWCNT)/CdS-diethylenetriamine (DETA) composite photocatalyst was synthesized via hydrothermal method. The structure, morphology, optical property and core level analysis of MWCNT/CdS-DETA nanocomposite were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy spectra (EDS), UV–Vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectrum (XPS). CdS-DETA can be uniformly dispersed on the surface of MWCNT. Photocatalytic properties of as-prepared photocatalysts were investigated under 410 nm LED light irradiation for photodegradation of methylene bule (MB). The k{sub app} of MWCNT/CdS-DETA is 0.034 min{sup −1}, which is about 6 times more than pure CdS-DETA. Photostability test indicated that MWCNT/CdS-DETA hybrid can be reused for degradation of organic pollution, suggesting the possible application of MWCNT/CdS-DETA hybrid is the most promising strategy for advanced photocatalyst material design. - Highlights: • Novel MWCNT/CdS-DETA photocatalyst was prepared. • MWCNT/CdS-DETA showed high photocatalytic activity. • MWCNT/CdS-DETA showed long reusable life.

  19. Laser irradiation of carbon-tungsten materials

    Science.gov (United States)

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

    2014-09-01

    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 sp3 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 sp2-sp3 transitions with the number of laser pulses just for nanometric layer thicknesses.

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

    NARCIS (Netherlands)

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

    2007-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    LU Hongzhi; YAN Taining

    2009-01-01

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

  2. High activity of carbon nanotubes supported binary and ternary Pd-based catalysts for methanol, ethanol and formic acid electro-oxidation

    Science.gov (United States)

    Zhu, Fuchun; Ma, Guanshui; Bai, Zhongchao; Hang, Ruiqiang; Tang, Bin; Zhang, Zhonghua; Wang, Xiaoguang

    2013-11-01

    In this study, we have synthesized a series of multi-walled carbon nanotubes supported Pd, PdCu(molar ratio 1:1), PdSn(1:1) and PdCuSn(1:1:1) catalysts by chemical reduction with NaBH4 as a reducing agent. These catalysts are characterized using X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and chronoamperometry. During the potential cycling activation, it is found that the additive Cu is prone to suffer leaching while the dissolution of Sn rarely occurs. Electrochemical measurements demonstrate that, the co-alloying of Pd with Cu and Sn can trigger the best catalytic activity enhancement as compared with the binary PdCu/CNTs, PdSn/CNTs and mono-component Pd/CNTs catalysts. The PdCuSn/CNTs reveals the most excellent activities toward methanol, ethanol and formic acid electro-oxidation and the corresponding mass activity can attain to 395.94, 872.70 and 534.83 mA mg-1 Pd, respectively. The possible promotion effect of additive Sn or/and Cu on the electrocatalytic activity improvement is also analyzed.

  3. Strain-driven and ultrasensitive resistive sensor/switch based on conductive alginate/nitrogen-doped carbon-nanotube-supported Ag hybrid aerogels with pyramid design.

    Science.gov (United States)

    Zhao, Songfang; Zhang, Guoping; Gao, Yongju; Deng, Libo; Li, Jinhui; Sun, Rong; Wong, Ching-Ping

    2014-12-24

    Flexible strain-driven sensor is an essential component in the flexible electronics. Especially, high durability and sensitivity to strain are required. Here, we present an efficient and low-cost fabrication strategy to construct a highly sensitive and flexible pressure sensor based on a conductive, elastic aerogel with pyramid design. When pressure is loaded, the contact area between the interfaces of the conductive aerogel and the copper electrode as well as among the building blocks of the nitrogen-doped carbon-nanotube-supported Ag (N-CNTs/Ag) aerogel monoliths, changes in reversible and directional manners. This contact resistance mechanism enables the hybrid aerogels to act as strain-driven sensors with high sensitivity and excellent on/off swithching behavior, and the gauge factor (GF) is ∼15 under strain of 3%, which is superior to those reported for other aerogels. In addition, robust, elastomeric and conductive nanocomposites can be fabricated by injecting polydimethylsiloxane (PDMS) into alginate/N-CNTs/Ag aerogels. Importantly, the building blocks forming the aerogels retain their initial contact and percolation after undergoing large-strain deformation, PDMS infiltration, and cross-linking of PDMS, suggesting their potential applications as strain sensors.

  4. Synthesis and utilization of a novel carbon nanotubes supported nanocables for the adsorption of dyes from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wei; Jiang, Xinyu [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Chen, Xiaoqing, E-mail: xqchen@csu.edu.cn [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Collaborative Innovation Center of Resource-conserving & Environment-friendly Society and Ecological Civilization (China)

    2015-09-15

    Using multiwalled carbon nanotubes(MWCNTs) as mechanical support and glucose as carbon resource, a hydrothermal carbonization route was designed for the synthesis of MWCNTs@carbon nanocables with tunable diameter and length. MWCNTs are firstly used as templates for the formation of carbon-rich composite nanocables, and the diameter of the nanocables could be tailored through adjusting the hydrothermal time or the ratio of MWCNTs and glucose. Owing to abundant superficial oxygen-containing functional groups, porous surface and remarkable reactivity, the as-synthesized nanocables are capable of efficiently adsorbing cationic dye methylene blue (MB) and crystal violet (CV). Furthermore, the optimum adsorption conditions, kinetics, adsorption isotherms and adsorption thermodynamics of dyes were studied systematically. Additionally, the maximum adsorption capacities calculated from data analysis (298.5 mg/g for MB and 228.3 mg/g for CV) are significant higher than those of raw MWCNTs and some other adsorbents reported previously, which provides strong evidence for using MWCNTs@carbon nanocables as adsorbent to remove dyes from aqueous solutions. - Graphical abstract: MWCNTs@carbon nanocables has been successfully fabricated by a hydrothermal carbonization method. The as-synthesized novel samples were used as adsorbents and exhibited high adsorption capacity on MB and CV. - Highlights: • A simple, cost-effective and “green” method for the synthesis of the material. • The diameter and length of the material are relatively easy to control. • The surface has large oxygen-containing groups and preferable chemical reactivity. • Compared with raw MWCNTs and some other adsorbents, the adsorption capacity is much high.

  5. Investigation on the formation of tungsten carbide in tungsten-containing diamond like carbon coatings

    NARCIS (Netherlands)

    Strondl, C.; Carvalho, N.M.; Hosson, J.Th.M. De; Kolk, G.J. van der

    2003-01-01

    A series of tungsten-containing diamond-like carbon (Me-DLC) coatings have been produced by unbalanced magnetron sputtering using a Hauzer HTC-1000 production PVD system. Sputtering from WC targets has been used to form W-C:H coatings. The metal to carbon ratio has been varied to study changes in th

  6. Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

    Directory of Open Access Journals (Sweden)

    Alicja Schlange

    2011-10-01

    Full Text Available In this contribution we present for the first time a continuous process for the production of highly active Pt catalysts supported by carbon nanotubes by use of an electrically heated tubular reactor. The synthesized catalysts show a high degree of dispersion and narrow distributions of cluster sizes. In comparison to catalysts synthesized by the conventional oil-bath method a significantly higher electrocatalytic activity was reached, which can be attributed to the higher metal loading and smaller and more uniformly distributed Pt particles on the carbon support. Our approach introduces a simple, time-saving and cost-efficient method for fuel cell catalyst preparation in a flow reactor which could be used at a large scale.

  7. Carbon Nanotubes Supported Pt-Ru-Ni as Methanol Electro-Oxidation Catalyst for Direct Methanol Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    Fei Ye; Shengzhou Chen; Xinfa Dong; Weiming Lin

    2007-01-01

    Carbon nanotubes (CNTs) supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy (EIS), linear sweep voltammetries (LSV), and chronoamperometry (CA). The results show that the catalysts exhibit face-centered cubic (fcc) structure.The particle size of Pt-Ru-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.

  8. Multi-walled carbon nanotube-supported metal-doped ZnO nanoparticles and their photocatalytic property.

    Science.gov (United States)

    Chen, C S; Liu, T G; Lin, L W; Xie, X D; Chen, X H; Liu, Q C; Liang, B; Yu, W W; Qiu, C Y

    2013-01-01

    A simple and versatile approach has been developed to synthesize multi-walled carbon nanotubes/metal-doped ZnO nanohybrid materials (MWNT/M-doped ZnO) by means of the co-deposition method. The experimental results illuminate that MWNTs can be modified by metal-doped ZnO nanoparticles at 450 °C, such as Mn, Mg, and Co elements. Furthermore, the MWNT/Mg-doped ZnO hybrids have been proven to have a high photocatalytic ability for methyl orange (MO), in which the degraded rate for MO reaches 100 % in 60 min. The enhancement in photocatalytic activity is attributed to the excellent electriconal property of MWNTs and Mg-doping. The resultant MWNT/Mg-doped ZnO nanohybrids have potential applications in photocatalysis and environmental protection.

  9. Electrochemical Deposition of Platinum and Palladium on Gold Nanoparticles Loaded Carbon Nanotube Support for Oxidation Reactions in Fuel Cell

    Directory of Open Access Journals (Sweden)

    Surin Saipanya

    2014-01-01

    Full Text Available Pt and Pd sequentially electrodeposited Au nanoparticles loaded carbon nanotube (Au-CNT was prepared for the electrocatalytic study of methanol, ethanol, and formic acid oxidations. All electrochemical measurements were carried out in a three-electrode cell. A platinum wire and Ag/AgCl were used as auxiliary and reference electrodes, respectively. Suspension of the Au-CNT, phosphate buffer, isopropanol, and Nafion was mixed and dropped on glassy carbon as a working electrode. By sequential deposition method, PdPtPt/Au-CNT, PtPdPd/Au-CNT, and PtPdPt/Au-CNT catalysts were prepared. Cyclic voltammograms (CVs of those catalysts in 1 M H2SO4 solution showed hydrogen adsorption and hydrogen desorption reactions. CV responses for those three catalysts in methanol, ethanol, and formic acid electrooxidations studied in 2 M CH3OH, CH3CH2OH, and HCOOH in 1 M H2SO4 show characteristic oxidation peaks. The oxidation peaks at anodic scan contribute to those organic substance oxidations while the peaks at cathodic scan are related with the reoxidation of the adsorbed carbonaceous species. Comparing all those three catalysts, it can be found that the PdPtPt/Au-CNT catalyst is good at methanol oxidation; the PtPdPt/Au-CNT effectively enhances ethanol oxidation while the PtPdPd/Au-CNT exceptionally catalyzes formic acid oxidation. Therefore, a different stoichiometry affects the electrochemical active surface area of the catalysts to achieve the catalytic oxidation reactions.

  10. In situ FT-IR spectroscopy investigations of carbon nanotubes supported Co-Mo catalysts for selective hydrodesulfurization of FCC gasoline

    Institute of Scientific and Technical Information of China (English)

    Jingcheng Zhang; Wenkun Yin; Hongyan Shang; Chenguang Liu

    2008-01-01

    To better understand the nature of carbon nanotubes supported Co-Mo catalysts (Co-Mo/CNTs) for selective hy-drodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline, studies are carried out using in situ Fourier transform infrared spectroscopy (FT-IR). The catalytic performances of Co-Mo/CNTs catalysts were evaluated with a mixture of cy-clohexane, diisobutylene, cyclohexene, 1-octene (60 : 30 : 5 : 5, volume ratio) and thiophene (0.5%, ratio of total weight) as model compounds to simulate FCC gasoline. The HDS experimental results suggested that the HDS activity and selectivity of Co-Mo/CNTs catalysts were affected by Co/Mo ratio; the optimal Co/Mo atomic ratio is about 0.4, and the optimum reaction temperature is 260 ℃. The in situ FT-IR studies revealed that 1-octene can be completely saturated at 200 ℃. In the FT-IR spectra of diisobutylene, the characteristic absorption peak around 3081 cm-1 for the stretching vibration peak of=C-H bond was still clear at 320℃, indicating that diisobutylene is difficult to be hydrogenated. As for the thiophene, no characteristic absorption peak could be found around 3092 cm-1 and 835 cm-1 when the reaction temperature was raised to 280 ℃, indi-cating that thiophene had been completely hydrodesulfurized. On the basis of FT-IR results, it can be deduced that thiopbene HDS reaction occurred mainly through direct hydrogenolysis route, whereas thiophene HDS and diisobutylene hydrogenation reaction over Co-Mo/CNTs catalysts might occur on two different kinds of active sites.

  11. Methanol Oxidation over TiO2-modified Multi-walled Carbon Nanotubes Supported Pt-Mo Electrocatalyst

    Institute of Scientific and Technical Information of China (English)

    WANG Xiu-yu; JIANG Yuan-sheng; ZHU Hong; ZHANG Jing-chang

    2011-01-01

    In order to develop a novel and high-performance catalytic material for direct methanol fuel cells(DMFC),molybdenum oxide as a co-catalyst with Pt on multi-walled carbon nanotubes which were modified by titanium dioxide(denoted as CNTs@TiO2) was investigated. The physicochemical characterizations of the catalysts were carried out via X-ray diffraction(XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS).Cyclic voltammetry(CV) showed that the CO-tolerance performance increased in the sequence of Pt/CNTs<Pt/CNTs@TiO2<Pt-Mo/CNTs@TiO2. The improved CO-tolerance performance of the Pt-Mo/CNTs@TiO2 catalyst can be attributed to the combined beneficial effects of highly dispersed Pt nanoparticles on the CNTs, the existence of oxygen holes in the MoO3 layer structure and the oxidation capability of TiO2.

  12. Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Gentil, Solène [Univ. Grenoble Alpes, CNRS, DCM UMR 5250, 38000 Grenoble France; Laboratoire de Chimie et Biologie des Métaux, Univ. Grenoble Alpes, CNRS UMR5249, CEA, 38000 Grenoble France; Lalaoui, Noémie [Univ. Grenoble Alpes, CNRS, DCM UMR 5250, 38000 Grenoble France; Dutta, Arnab [Pacific Northwest National Laboratory, Richland WA 99532 USA; Current address: Chemistry Department, IIT Gandhinagar, Gujarat 382355 India; Nedellec, Yannig [Univ. Grenoble Alpes, CNRS, DCM UMR 5250, 38000 Grenoble France; Cosnier, Serge [Univ. Grenoble Alpes, CNRS, DCM UMR 5250, 38000 Grenoble France; Shaw, Wendy J. [Pacific Northwest National Laboratory, Richland WA 99532 USA; Artero, Vincent [Laboratoire de Chimie et Biologie des Métaux, Univ. Grenoble Alpes, CNRS UMR5249, CEA, 38000 Grenoble France; Le Goff, Alan [Univ. Grenoble Alpes, CNRS, DCM UMR 5250, 38000 Grenoble France

    2017-01-12

    A biomimetic nickel bis-diphosphine complex incorporating the amino-acid arginine in the outer coordination sphere, was immobilized on modified single-wall carbon nanotubes (SWCNTs) through electrostatic interactions. The sur-face-confined catalyst is characterized by a reversible 2-electron/2-proton redox process at potentials close to the equibrium potential of the H+/H2 couple. Consequently, the functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2/2H+ interconversion over a broad range of pH. This system exhibits catalytic bias, analogous to hydrogenases, resulting in high turnover frequencies at low overpotentials for electrocatalytic H2 oxida-tion between pH 0 and 7. This allowed integrating such bio-inspired nanomaterial together with a multicopper oxi-dase at the cathode side in a hybrid bioinspired/enzymatic hydrogen fuel cell. This device delivers ~2 mW cm–2 with an open-circuit voltage of 1.0 V at room temperature and pH 5, which sets a new efficiency record for a bio-related hydrogen fuel cell with base metal catalysts.

  13. In Situ Synthesis and Characterization of Polyethyleneimine-Modified Carbon Nanotubes Supported PtRu Electrocatalyst for Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Xi Geng

    2015-01-01

    Full Text Available PtRu bimetallic nanoparticles were successfully synthesized on polyethyleneimine- (PEI- functionalized multiwalled carbon nanotubes (MWCNTs via an effective and facile polyol reduction approach. Noncovalent surface modification of MWCNTs with PEI was confirmed by FTIR and zeta potential measurements. The morphology, crystalline structure, and composition of the hybrid material were characterized by transmission electron microscopy (TEM, scanning electron microscopy (SEM, X-ray powder diffraction (XRD, and energy dispersive X-ray spectroscopy (EDX, respectively. According to SEM and TEM observations, PtRu nanoparticles with narrow size distribution were homogeneously deposited on PEI-MWCNTs. Cyclic voltammetry tests demonstrated that the as-prepared PtRu/PEI-MWCNTs nanocomposite had a large electrochemical surface area and exhibited enhanced electrocatalytic activity towards methanol oxidation in comparison with oxidized MWCNTs as catalyst support. PEI-functionalized CNTs, as useful building blocks for the assembly of Pt-based electrocatalyst, may have great potential for applications such as direct methanol fuel cell (DMFC.

  14. Carbon-Nanotubes-Supported Pd Nanoparticles for Alcohol Oxidations in Fuel Cells: Effect of Number of Nanotube Walls on Activity.

    Science.gov (United States)

    Zhang, Jin; Lu, Shanfu; Xiang, Yan; Shen, Pei Kang; Liu, Jian; Jiang, San Ping

    2015-09-07

    Carbon nanotubes (CNTs) are well known electrocatalyst supports due to their high electrical conductivity, structural stability, and high surface area. Here, we demonstrate that the number of inner tubes or walls of CNTs also have a significant promotion effect on the activity of supported Pd nanoparticles (NPs) for alcohol oxidation reactions of direct alcohol fuel cells (DAFCs). Pd NPs with similar particle size (2.1-2.8 nm) were uniformly assembled on CNTs with different number of walls. The results indicate that Pd NPs supported on triple-walled CNTs (TWNTs) have the highest mass activity and stability for methanol, ethanol, and ethylene glycol oxidation reactions, as compared to Pd NPs supported on single-walled and multi-walled CNTs. Such a specific promotion effect of TWNTs on the electrocatalytic activity of Pd NPs is not related to the contribution of metal impurities in CNTs, oxygen-functional groups of CNTs or surface area of CNTs and Pd NPs. A facile charge transfer mechanism via electron tunneling between the outer wall and inner tubes of CNTs under electrochemical driving force is proposed for the significant promotion effect of TWNTs for the alcohol oxidation reactions in alkaline solutions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cells.

    Science.gov (United States)

    Gentil, Solène; Lalaoui, Noémie; Dutta, Arnab; Nedellec, Yannig; Cosnier, Serge; Shaw, Wendy J; Artero, Vincent; Le Goff, Alan

    2017-02-06

    A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2 /2 H(+) interconversion from pH 0 to 9, with catalytic preference for H2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm(-2) , only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm(-2) , a new efficiency record for a hydrogen biofuel cell with base metal catalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine

    Energy Technology Data Exchange (ETDEWEB)

    Kutluay, Aysegul; Aslanoglu, Mehmet, E-mail: maslanoglu@harran.edu.tr

    2014-08-11

    Highlights: • A GCE was modified with carbon nanotubes and cobalt nanoparticles. • The composite material was obtained using an ultrasonic chemical deposition method. • The CoNPs/MWCNT/GCE was applied for the simultaneous determination of PAR and DA. • The presence of AA and UA did not affect the responses of PAR and DA. • Lower detection limits were obtained using the CoNPs/MWCNT/GCE. - Abstract: Multi-walled carbon nanotubes (MWCNTs) functionalized by cobalt nanoparticles were obtained using a single step chemical deposition method in an ultrasonic bath. The composite material was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The electroactivity of the cobalt-functionalized MWCNTs was assessed in respect to the electrooxidation of paracetamol (PAR) and dopamine (DA). It was found that the carbon nanotube supported cobalt nanoparticles have significantly higher catalytic properties. The proposed electrode has been applied for the simultaneous determination of PAR and DA. The modified electrode could resolve the overlapped voltammetric waves of PAR and DA into two well-defined voltammetric peaks with peak to peak separation of about 203 mV. On the other hand, the presence of potential drug interfering compounds AA and UA did not affect the voltammetric responses of PAR and DA. The current of oxidation peaks showed a linear dependent on the concentrations of PAR and DA in the range of 5.2 × 10{sup −9}–4.5 × 10{sup −7} M (R{sup 2} = 0.9987) and 5.0 × 10{sup −8}–3.0 × 10{sup −6} M (R{sup 2} = 0.9999), respectively. The detection limits of 1.0 × 10{sup −9} M and 1.5 × 10{sup −8} M were obtained for PAR and DA, respectively. The proposed electrode showed good stability (peak current change: 4.9% with and RSD of 2.6% for PAR; 5.5% with and RSD of 3.0% for DA over 3 weeks), reproducibility (RSD 2.3% for PAR and RSD 1.5% for DA), repeatability (RSD 2.25% for PAR and RSD 2.50% for DA) and

  17. An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine.

    Science.gov (United States)

    Kutluay, Aysegul; Aslanoglu, Mehmet

    2014-08-11

    Multi-walled carbon nanotubes (MWCNTs) functionalized by cobalt nanoparticles were obtained using a single step chemical deposition method in an ultrasonic bath. The composite material was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The electroactivity of the cobalt-functionalized MWCNTs was assessed in respect to the electrooxidation of paracetamol (PAR) and dopamine (DA). It was found that the carbon nanotube supported cobalt nanoparticles have significantly higher catalytic properties. The proposed electrode has been applied for the simultaneous determination of PAR and DA. The modified electrode could resolve the overlapped voltammetric waves of PAR and DA into two well-defined voltammetric peaks with peak to peak separation of about 203 mV. On the other hand, the presence of potential drug interfering compounds AA and UA did not affect the voltammetric responses of PAR and DA. The current of oxidation peaks showed a linear dependent on the concentrations of PAR and DA in the range of 5.2×10(-9)-4.5×10(-7) M (R(2)=0.9987) and 5.0×10(-8)-3.0×10(-6) M (R(2)=0.9999), respectively. The detection limits of 1.0×10(-9) M and 1.5×10(-8) M were obtained for PAR and DA, respectively. The proposed electrode showed good stability (peak current change: 4.9% with and RSD of 2.6% for PAR; 5.5% with and RSD of 3.0% for DA over 3 weeks), reproducibility (RSD 2.3% for PAR and RSD 1.5% for DA), repeatability (RSD 2.25% for PAR and RSD 2.50% for DA) and high recovery (99.7% with an RSD of 1.3% for PAR; 100.8% with an RSD of 1.8% for DA). The proposed method was successfully applied to the determination of PAR and DA in pharmaceuticals. Copyright © 2014. Published by Elsevier B.V.

  18. Effect of multi-wall carbon nanotubes supported nano-nickel and TiF{sub 3} addition on hydrogen storage properties of magnesium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Su, Wei; Zhu, Yunfeng, E-mail: yfzhu@njtech.edu.cn; Zhang, Jiguang; Liu, Yana; Yang, Yang; Mao, Qifeng; Li, Liquan

    2016-06-05

    Multi-wall carbon nanotubes supported nano-nickel (Ni/MWCNTs) with superior catalytic effects was introduced to magnesium hydride by the process of hydriding combustion synthesis (HCS) and mechanical milling (MM). The effect of different Ni/MWCNTs contents (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%) on the hydrogenation and dehydrogenation properties of the composite was investigated systematically. It is revealed that Mg{sub 85}-(Ni/MWCNTs){sub 15} composite shows the best comprehensive hydrogen storage properties, which absorbs 5.68 wt.% hydrogen within 100 s at 373 K and releases 4.31 wt.% hydrogen within 1800 s at 523 K under initial hydrogen pressures of 3.0 and 0.005 MPa, respectively. The in situ formed nano-Mg{sub 2}Ni and MWCNTs have excellent catalytic effect on the hydrogenation and dehydrogenation performances of MgH{sub 2}. To further improve the hydrogen absorption/desorption properties, TiF{sub 3} was added to the Mg–Ni/MWCNTs system. The result shows that TiF{sub 3} addition has little influence on the thermodynamic performance, but affects greatly the kinetic properties. The Mg{sub 85}-(Ni/MWCNTs){sub 15}-TiF{sub 3} composite exhibits an appreciably enhanced hydrogen desorption performance at low temperature, and the hydrogen desorption capacity within 1800 s at 473 K for the TiF{sub 3}-added composite is approximately four times the capacity of Mg{sub 85}-(Ni/MWCNTs){sub 15} under the same condition. The catalytic effects during hydrogenation and dehydrogenation have been discussed in the study. - Highlights: • The nanosized Ni/MWCNTs catalyst was successfully prepared. • Ni/MWCNTs shows superior catalytic effect on H absorption/desorption of Mg. • Mg{sub 85}-(Ni/MWCNTs){sub 15} composite shows the best hydrogen storage properties. • Ni/MWCNTs coupling with TiF{sub 3} improves the hydriding/dehydriding properties largely.

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

    NARCIS (Netherlands)

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

    2009-01-01

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

  20. Vacuum arc melting of tungsten-hafnium-carbon alloy

    Science.gov (United States)

    Ammon, R. L.; Buckman, R. W., Jr.

    1974-01-01

    The vacuum arc casting of tungsten alloys, which contain carbon as an alloy addition, require special melting procedures in order to produce melts of consistent controlled levels of alloy content. A melting procedure will be described in which elemental components of a tungsten 0.35% HfC alloy are assembled to form an electrode for ac vacuum arc melting to produce 3-in.-diam ingots. Melting procedures and analytical chemistry are discussed and compared with data for ingots produced by other techniques.

  1. Template-free formation of carbon nanotube-supported cobalt sulfide@carbon hollow nanoparticles for stable and fast sodium ion storage

    Science.gov (United States)

    Han, Fei; Jun Tan, Clara Yi; Gao, Zhiqiang

    2017-01-01

    Carbon-coated cobalt sulfide (CoS) hollow nanoparticles on carbon nanotube (CNT) networks are synthesized by combining three simple approaches: direct growth of Co3O4 nanocrystals on the CNT backbones, chemical conversion of the Co3O4 nanocrystals to CoS hollow nanoparticles, and the spatial introduction of conformal surface modification by carbon. It is noteworthy that the CoS hollow nanoparticles with inner cavity of <50 nm and an average wall thickness of 6-8 nm are derived from a template-free method. Such a template-free-derived multifunctional nanostructure design achieves the amalgamation of the favorite traits of one-dimensional conducting networks, hollow nanoparticles, and surface modification, thus resulting in much enhanced charge transfer, ion transport, and upholding the integrity of the electrode and electrode/electrolyte interface. When applied the synthesized CoS-based material as anodes in sodium-ion batteries (SIBs), excellent performance is observed. For instance, a reversible specific capacity of 562 mAh g-1 at 100 mA g-1 and a capacity retention rate of 90% after 200 cycles at a higher current density of 500 mA g-1 are obtained. Moreover, a superior rate capability is observed with reversible specific capacities of 341 and 276 mAh g-1 at 2000 and at 5000 mA g-1, respectively.

  2. Synthesis of Propylene Carbonate from Epoxide and CO2 Catalyzed by Carbon Nanotubes Supported Fe1.5PMo12O40

    Directory of Open Access Journals (Sweden)

    Tahani Al-Garni

    2017-01-01

    Full Text Available Carbon nanotubes (CNTs were functionalized and were then used as supports of Fe1.5PMo12O40 (FePMo Keggin heteropolyanions catalysts. The characterization of the resulting catalysts was investigated by inductively coupled plasma spectrometry (ICP, Fourier transform infrared (FTIR spectra, X-ray diffraction (XRD, ultraviolet-visible (UV-Vis light spectroscopy, and transmission electron microscopy (TEM. FTIR and XRD results confirmed that FePMo was bounded on CNTs successfully and the Keggin structure was preserved. Characterization by TEM showed that solids with high FePMo content exhibited aggregation of FePMo in large particles. The as-prepared catalysts were tested in the synthesis of propylene carbonate (PC from CO2 and propylene oxide (PO in a solvent-free reaction and under mild conditions. Effects of various parameters, such as reaction temperature, reaction time, FePMo content on the support, and catalyst loading on the reaction, were investigated. It has been found that CNTs supported FePMo achieved 57.7% PO conversion and 99.0% PC selectivity, whereas unsupported FePMo led only to 8.5% conversion and 48.6% selectivity. The remarkable enhancement of the catalytic activity over the supported catalyst can be attributed mainly to the better dispersion and reactivity of the FePMo catalyst in the supported material.

  3. Simple preparation of tungsten supported carbon nanoreactors for specific applications: Adsorption, catalysis and electrochemical activity

    Energy Technology Data Exchange (ETDEWEB)

    Mayani, Vishal J.; Mayani, Suranjana V.; Kim, Sang Wook, E-mail: swkim@dongguk.ac.kr

    2015-08-01

    Graphical abstract: - Highlights: • Tungsten carbon composites have shown great recognition in catalysis and electrochemistry. • W-carbon composites are prepared by template replication and W-doping on carbon cage. • Nanocomposites offer enormous assurance as adsorbent, electrode and heterogeneous catalyst. - Abstract: Porous carbon supported tungsten carbide nanoreactors, two sizes (∼25 and 170 nm), were designed using economical petroleum pitch residue followed by tungsten (W) doping. X-ray diffractions showed both carbon tungsten composites (CTC-25 and CTC-170) contained tungsten subcarbide (W{sub 2}C) and monocarbide (WC) as the major and minor crystalline phases, respectively. The present study provides a multiple perspective of carbon tungsten composites (CTCs) for methanol oxidation (as an electrode), adsorption (as an adsorbent) and degradation (as a solid catalyst) of methylene blue (MB). The operational electrodes were designed from both CTCs and used as a catalyst in an electrocatalysis process. The electrocatalysts exhibited high and stable catalytic performance (CTCE-25 > CTCE-170) in methanol electro-oxidation. The newly synthesized W-doped carbon nanoreactors were used successfully as an adsorbent for MB and a heterogeneous catalyst for MB oxidation. Ordered CTC-25 and CTC-170 exhibited dynamic MB adsorption within 15 min and complete oxidation of MB in 25–40 min. A synergetic effect between tungsten carbide and the carbon cage framework was noted.

  4. Platinum nanoparticles on carbon-nanotube support prepared by room-temperature reduction with H2 in ethylene glycol/water mixed solvent as catalysts for polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Zheng, Yuying; Dou, Zhengjie; Fang, Yanxiong; Li, Muwu; Wu, Xin; Zeng, Jianhuang; Hou, Zhaohui; Liao, Shijun

    2016-02-01

    Polyol approach is commonly used in synthesizing Pt nanoparticles in polymer electrolyte membrane fuel cells. However, the application of this process consumes a great deal of time and energy, as the reduction of precursors requires elevated temperatures and several hours. Moreover, the ethylene glycol and its oxidizing products bound to Pt are difficult to remove. In this work, we utilize the advantages of ethylene glycol and prepare Pt nanoparticles through a room-temperature hydrogen gas reduction in an ethylene glycol/water mixed solvent, which is followed by subsequent harvesting by carbon nanotubes as electrocatalysts. This method is simple, facile, and time-efficient, as the entire room-temperature reduction process is completed in a few minutes. As the solvent changes from water to an ethylene glycol/water mix, the size of Pt nanoparticles varies from 10 to 3 nm and their shape transitions from polyhedral to spherical. Pt nanoparticles prepared in a 1:1 volume ratio mixture of ethylene glycol/water are uniformly dispersed with an average size of ∼3 nm. The optimized carbon nanotube-supported Pt electrocatalyst exhibits excellent methanol oxidation and oxygen reduction activities. This work demonstrates the potential use of mixed solvents as an approach in materials synthesis.

  5. Au-Pd/石墨烯和 Au-Pd/碳纳米管催化电化学氧化甲酸%Effect of graphene and carbon nanotubes supported Au-Pd nanoparticles for electrocatalytic oxidation of formic acid

    Institute of Scientific and Technical Information of China (English)

    高丽; 吕逍雨; 杨海堂; 杨敬贺; 毛立群

    2015-01-01

    利用化学还原法合成了石墨烯和碳纳米管负载的 Au‐Pd 纳米粒子.石墨烯负载的 Au‐Pd 纳米粒子(Au‐Pd/G)的粒径远小于碳纳米管负载的 Au‐Pd 纳米粒子(Au‐Pd/CNTs)的粒径,且 Au‐Pd 纳米粒子在复合材料上分布均匀.与碳纳米管负载的 Au‐Pd 纳米粒子催化剂相比,石墨烯负载的 Au‐Pd 催化剂对甲酸的催化显示出更好的电催化活性,结果表明作为 Au‐Pd 纳米粒子的基底,石墨烯可以明显提高 Au‐Pd 纳米粒子的电催化活性.在0.1 mol/L H2 SO4中,该纳米修饰电极对甲酸有良好的电催化作用,甲酸在电极上的氧化动力学过程为扩散控制过程.%Graphene and carbon nanotubes supported Au‐Pd nanoparticles are synthesized by a chemical reduction method .The particle size of graphene supported Au‐Pd nanoparticles (Au‐Pd/G) is much smaller than that of carbon nanotubes supported Au‐Pd nanoparticles (Au‐Pd/CNTs) .There is a relatively high degree of nanoparticles dispersion on Au‐Pd/G .The Au‐Pd/G catalyst shows a higher electrocatalytic activity for the formic acid electrooxidation compared to the Au‐Pd/CNTs catalyst indicating the substrate graphene can obviously enhance the cata‐lytic activity of Au‐Pd nanoparticles .In 0 .1 mol/L H2 SO4 solution ,the modified electrode ex‐hibited good electrocatalytic activity on the oxidation of formic acid ,and the electrode reaction of formic acid was a diffusion control process .

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

    Science.gov (United States)

    Tlustochowicz, Marcin

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

  7. Catalytic acceleration of graphitisation of amorphous carbon during synthesis of tungsten carbide from tungsten and excess amorphous carbon in a solar furnace

    Energy Technology Data Exchange (ETDEWEB)

    Shohoji, N. [Inst. Nacional de Engenharia e Tecnologia Industrial, Lisbon (Portugal); Guerra Rosa, L.; Cruz Fernandes, J. [Instituto Superior Tecnico, Departamento de Engenharia de Materiais, Av. Rovisco Pais, 1049-001, Lisbon (Portugal); Martinez, D.; Rodriguez, J. [Plataforma Solar de Almeria, Centro Europeo de Ensayos de Energia Solar, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, P.O. Box 22, 04200, Tabernas (Spain)

    1999-03-25

    Amorphous carbon is one of the allotropes of carbon possessing carbon activity a(C) higher than that of graphite (standard state with a(C) = 1). Amorphous carbon is in a metastable state but, under normal circumstances, it takes several hours to be graphitised to an extent detectable by X-ray diffraction even at temperature higher than 1500 C. In the present work, we report the accelerated graphitisation of amorphous carbon induced apparently by the catalytic action of tungsten (W) or tungsten carbide (WC) during synthesis of WC started from W and active carbon in solar furnace under controlled atmosphere (Ar or N{sub 2}). This degree of graphitisation of amorphous carbon did not proceed by the similar reaction undertaken in the traditional laboratory furnace under the comparable conditions. (orig.) 14 refs.

  8. High pressure organic colloid method for the preparation of high performance carbon nanotube-supported Pt and PtRu catalysts for fuel cell applications

    Institute of Scientific and Technical Information of China (English)

    WANG; KateNing; Viola; BIRSS

    2010-01-01

    Highly dispersed,high performance Pt and PtRu catalysts,supported on multiwalled carbon nanotubes(CNTs),were prepared by a high pressure organic colloid method.The particle sizes of the active components were as small as 1.2 nm for Pt and 1.1 nm for PtRu,and the active Pt surface areas were 295 and 395 m2/g,respectively.The catalysts showed very high activities toward the anodic oxidation of methanol,evaluated by cyclic voltammetry,being up to 4 times higher than that of commercial Johnson Matthey Hispec 2000 Pt/XC-72R and 5 times better than Hispec 5000 PtRu/XC-72R catalysts.In a full air/hydrogen fuel cell,a membrane-electrode assembly prepared using our Pt/CNT and PtRu/CNT catalysts showed 50% and 100% higher performances than those prepared with commercial Johnson Matthey Pt/XC-72R and PtRu/XC-72R catalysts for the same Pt loading and operating conditions.

  9. L-H power threshold studies with tungsten/carbon divertor on the EAST tokamak

    DEFF Research Database (Denmark)

    Chen, L.; Xu, G. S.; Gao, W.

    2016-01-01

    The power threshold for low (L) to high (H) confinement mode transition achieved by radio-frequency heating and molybdenum first wall with lithium coating has been experimentally investigated on the EAST tokamak for two sets of divertor geometries and materials: tungsten/carbon divertor and full...... configuration, with the ion grad-B drift direction away from the primary X-point, a lower normalized power threshold is observed in EAST with the tungsten/carbon divertor, compared to the carbon divertor after intensive lithium wall coating. A newly installed cryopump increasing the pumping efficiency also...

  10. Hydrofluoric-nitric-sulphuric-acid surface treatment of tungsten for carbon fibre-reinforced composite hybrids in space applications

    Science.gov (United States)

    Kanerva, M.; Johansson, L.-S.; Campbell, J. M.; Revitzer, H.; Sarlin, E.; Brander, T.; Saarela, O.

    2015-02-01

    Hybrid material systems, such as combinations of tungsten foils and carbon fibre-reinforced plastic (CFRP), are replacing metal alloy concepts in spacecraft enclosures. However, a good adhesion between the tungsten oxide scale and the epoxy resin used is required. Here, the effects of a hydrofluoric-nitric-sulphuric-acid (HFNS) treatment on tungsten oxides and subsequent adhesion to CFRP are analysed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fracture testing. The work shows that HFNS treatment results in decreased oxygen content, over 50% thinner tungsten trioxide (WO3) layer and increased nano-roughness on thin tungsten foils. Fracture testing established a 39% increase in the average critical strain for tungsten-CFRP specimens after HFNS treatment was carried out on tungsten. The effect of the oxide scale modification regarding the critical strain energy release rate was ΔGc≈ 8.4 J/m2.

  11. Microstructure and tribological behavior of tungsten-containing diamondlike carbon coated rubbers

    NARCIS (Netherlands)

    Pei, Y.T.; Bui, X.L.; Zhou, Xiao; Hosson, J.Th.M. De

    2008-01-01

    Tungsten-containing diamondlike carbon (W-DLC) coatings have been deposited on FKM (fluorocarbon), ACM (acrylate), and HNBR (hydrogenated nitrile butadiene) rubbers via unbalanced magnetron reactive sputtering from a WC target in C2H2/Ar plasma. The surface morphology and, fracture cross sections of

  12. Effect of Multi-Wall Carbon Nanotubes Supported Nickel on Hydrogen Storage Properties of Mg-Based Alloy%多壁碳纳米管载镍对镁基合金储氢性能影响

    Institute of Scientific and Technical Information of China (English)

    杨阳; 朱云峰; 卫灵君; 宦清清; 李李泉

    2013-01-01

    Mg85-Nix/MWNTs15-x (x=3,6,9,12,mass fraction) alloys were prepared from Mg and multi-wall carbon nanotubes supported nickel (Ni/MWNTs) by the combined methods of hydriding combustion synthesis (HCS) and mechanical milling (MM).The crystal structures,surface morphologies and hydriding/dehydriding properties of the products were investigated by means of X-ray diffraction (XRD),transmission electron microscopy (TEM),scanning electron microscopy (SEM) and gas reaction controller (GRC),respectively.The results show that the Mg85-Ni9/MWNTs6 alloy possesses the best hydriding/dehydriding properties,which absorbs nearly the saturated hydrogen capacity of 5.68 wt% within 100 s at 373 K,and desorbs 4.31 wt% hydrogen within 1800 s at 523 K.The addition of Ni/MWNTs plays a catalytic role,and it takes the effect on nano-confinement of the Mg2NiH4 particles in the product.There is synergic catalysis between Ni and MWNTs,and when the mass ratio ofNi/MWNTs =3/2,the hydriding/dehydriding properties of the Mg-Ni/MWNTs system reach the best.%采用化学法制备多壁碳纳米管载镍催化剂(Ni/MWNTs),并将其加入到镁粉中,结合氢化燃烧合成(Hydriding Combustion Synthesis,HCS)和机械球磨(Mechanical Milling,MM),即HCS+MM复合技术制备Mg85-Ni经x/MWNTs15-x(x代表质量百分数,x=3,6,9,12)合金.通过X射线衍射仪、透射电子显微镜、扫描电镜以及气体反应控制器研究了材料的晶体结构、微观形貌和吸放氢性能.结果表明:Mg85-Ni9/MWNTs6合金具有最佳综合吸放氢性能,其在373 K,吸氢量达到5.68%(质量分数,下同),且在100 s内就基本达到饱和吸氢量;在523 K,1800 s内的放氢量达到4.31%.Ni/MWNTs催化剂的添加,不但起到催化的作用,而且MWNTs具有优异的纳米限制作用,使得催化剂的粒径限制在纳米级,有利于限制产物中Mg2NiH4颗粒的长大.另外Ni与MWNTs存在协同催化作用,当它们达到一定比例时,对合金的吸放氢促进作用达到最优

  13. Erosion and Modifications of Tungsten-Coated Carbon and Copper Under High Heat Flux

    Institute of Scientific and Technical Information of China (English)

    Liu Xiang(刘翔); S.Tamura; K.Tokunaga; N.Yoshida; Zhang Fu(张斧); Xu Zeng-yu(许增裕); Ge Chang-chun(葛昌纯); N.Noda

    2003-01-01

    Tungsten-coated carbon and copper was prepared by vacuum plasma spraying (VPS)and inert gas plasma spraying (IPS), respectively. W/CFC (Tungsten /Carbon Fiber-Enhancedmaterial) coating has a diffusion barrier that consists of W and Re multi-layers pre-deposited byphysical vapor deposition on carbon fiber-enhanced materials, while W/Cu coating has a gradedtransition interface. Different grain growth processes of tungsten coatings under stable and tran-sient heat loads were observed, their experimental results indicated that the recrystallizing tem-perature of VPS-W coating was about 1400 ℃ and a recrystallized columnar layer of about 30μmthickness was formed by cyclic heat loads of 4 ms pulse duration. Erosion and modifications ofW/CFC and W/Cu coatings under high heat load, such as microstructure changes of interface,surface plastic deformations and cracks, were investigated, and the erosion mechanism erosionproducts) of these two kinds of tungsten coatings under high heat flux was also studied.

  14. Mesoporous carbon nitride-tungsten oxide composites for enhanced photocatalytic hydrogen evolution.

    Science.gov (United States)

    Kailasam, Kamalakannan; Fischer, Anna; Zhang, Guigang; Zhang, Jinshui; Schwarze, Michael; Schröder, Marc; Wang, Xinchen; Schomäcker, Reinhard; Thomas, Arne

    2015-04-24

    Composites of mesoporous polymeric carbon nitride and tungsten(VI) oxide show very high photocatalytic activity for the evolution of hydrogen from water under visible light and in the presence of sacrificial electron donors. Already addition of very small amounts of WO3 yields up to a twofold increase in the efficiency when compared to bulk carbon nitrides and their composites and more notably even to the best reported mesoporous carbon nitride-based photocatalytic materials. The higher activity can be attributed to the high surface area and synergetic effect of the carbon nitrides and the WO3 resulting in improved charge separation through a photocatalytic solid-state Z-scheme mechanism.

  15. Influence of tungsten on the carbon nanotubes growth by CVD process

    Energy Technology Data Exchange (ETDEWEB)

    Escobar, Mariano [Instituto de Fisicoquimica de Materiales, Ambiente y Energia, CONICET-UBA, Pabellon II, Ciudad Universitaria (1428) Bs As (Argentina); LP and MC, Dep. De Fisica, FCEyN-UBA, Pabellon 1, Ciudad Universitaria (1428) Bs As (Argentina)], E-mail: mescobar@qi.fcen.uba.ar; Rubiolo, Gerardo H. [LP and MC, Dep. De Fisica, FCEyN-UBA, Pabellon 1, Ciudad Universitaria (1428) Bs As (Argentina); Unidad de Actividad Materiales, CNEA, Av. Gral. Paz 1499, San Martin (1650), Bs As (Argentina); Moreno, M. Sergio [Centro Atomico Bariloche, (8400) S.C. de Bariloche, Rio Negro (Argentina); Goyanes, Silvia [LP and MC, Dep. De Fisica, FCEyN-UBA, Pabellon 1, Ciudad Universitaria (1428) Bs As (Argentina); Candal, Roberto [Instituto de Fisicoquimica de Materiales, Ambiente y Energia, CONICET-UBA, Pabellon II, Ciudad Universitaria (1428) Bs As (Argentina)

    2009-06-24

    The effect of tungsten (W) on the growth of multi-walled carbon nanotubes (MWNTs) using the chemical vapour deposition (CVD) process over a metal Fe-W catalyst incorporated into a silica matrix is reported. A W molar content in Fe/SiO{sub 2} up to 10% was studied. The incorporation of only 2% of W substantially modifies the crystalline phases and the crystalline degree of the catalyst during the MWNTs synthesis. This fact seems to have a strong influence on the type and yield of the carbonaceous species obtained by the CVD of acetylene, at 600 deg. C and 180 Torr, over each catalyst. Tungsten interacts with iron within the matrix, diminishing the catalytic activity of the metal nanoparticles, and both, carbon nanotubes and carbon nanofibers, are obtained when tungsten is present. The results obtained support the hypothesis of a base growth model for carbon nanotubes indicating a strong interaction between silica matrix and Fe/W nanoparticles, independently of the content of W.

  16. Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

    Science.gov (United States)

    Douglas, F. C.; Paradis, E. L.; Veltri, R. D.

    1973-01-01

    A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed.

  17. 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.

  18. Hydrofluoric–nitric–sulphuric-acid surface treatment of tungsten for carbon fibre-reinforced composite hybrids in space applications

    Energy Technology Data Exchange (ETDEWEB)

    Kanerva, M., E-mail: Mikko.Kanerva@aalto.fi [Aalto University, School of Engineering, Department of Applied Mechanics, P.O.B. 14300, FI-00076 Aalto (Finland); Johansson, L.-S.; Campbell, J.M. [Aalto University, School of Chemical Technology, Department of Forest Products Technology, P.O.B. 16300, FI-00076 Aalto (Finland); Revitzer, H. [Aalto University, School of Chemical Technology, Department of Chemistry, P.O.B. 16300, FI-00076 Aalto (Finland); Sarlin, E. [Tampere University of Technology, Department of Materials Science, P.O.B. 589, FI-33101 Tampere (Finland); Brander, T.; Saarela, O. [Aalto University, School of Engineering, Department of Applied Mechanics, P.O.B. 14300, FI-00076 Aalto (Finland)

    2015-02-15

    Highlights: • XPS and AFM analysis of the effect of hydrofluoric–nitric–sulphuric-acid on tungsten. • Dreiling's model established 54.4% thinning of WO{sub 3} due to 67 s treatment. • Strain energy release rate increased ≈8.4 J/m{sup 2} at the interface. • Failure loci analysis expressed the oxide and carbon fibre surfaces as weak points. - Abstract: Hybrid material systems, such as combinations of tungsten foils and carbon fibre-reinforced plastic (CFRP), are replacing metal alloy concepts in spacecraft enclosures. However, a good adhesion between the tungsten oxide scale and the epoxy resin used is required. Here, the effects of a hydrofluoric–nitric–sulphuric-acid (HFNS) treatment on tungsten oxides and subsequent adhesion to CFRP are analysed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and fracture testing. The work shows that HFNS treatment results in decreased oxygen content, over 50% thinner tungsten trioxide (WO{sub 3}) layer and increased nano-roughness on thin tungsten foils. Fracture testing established a 39% increase in the average critical strain for tungsten–CFRP specimens after HFNS treatment was carried out on tungsten. The effect of the oxide scale modification regarding the critical strain energy release rate was ΔG{sub c}≈ 8.4 J/m{sup 2}.

  19. Tungsten-Carbon X-ray Multilayered Mirror Prepared by Photo-Chemical Vapor Deposition

    Science.gov (United States)

    Suzuki, Yoshihiko

    1989-05-01

    A tungsten-carbon(W/C) X-ray multilayered mirror was prepared by photoinduced chemical vapor deposition (photo-CVD) using a low-pressure mercury lamp and an argon-fluoride (ArF) excimer laser. The 40% reflectivity of this mirror was measured using a small-angle X-ray diffractometer with Cu-Kα radiation. This reflectivity is lower than the theoretical reflectivity of 80%. From observations of the transmission electron micrograph from this multilayered mirror, it seems that the reduction of the reflectivity was caused by the indistinct interfaces of the diffused films, and by the roughness of the films introduced by partial crystallization of the tungsten films.

  20. Escape of carbon element in surface ablation of cobalt cemented tungsten carbide with pulsed UV laser

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 30 ns XeCl excimer laser. The surface phase transformation on different pulse number of laser shots has been investigated by means of XRD and microphotography as well as AES at laser fluence of 2.5 J/cm 2. The experimental results showed that the phase structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. It is suggested that the formation of non-stoichiometric tungsten carbide should result from the escaping of carbon element due to accumulated heating of surface by pulsed laser irradiation.

  1. Comparison on heat flux deposition between carbon and tungsten wall – Investigations on energy recycling

    Energy Technology Data Exchange (ETDEWEB)

    Bufferand, H., E-mail: hugo.bufferand@cea.fr [CEA, IRFM, 13108 St Paul-Lez-Durance (France); Bucalossi, J.; Ciraolo, G.; Fedorczak, N. [CEA, IRFM, 13108 St Paul-Lez-Durance (France); Genesio, P. [PIIM, CNRS, Aix-Marseille Université, 13397 Marseille (France); Ghendrih, Ph.; Gunn, J. [CEA, IRFM, 13108 St Paul-Lez-Durance (France); Marandet, Y.; Martin, C.; Mellet, N. [PIIM, CNRS, Aix-Marseille Université, 13397 Marseille (France); Serre, E. [M2P2, CNRS, Aix-Marseille Université, 13451 Marseille (France); Tamain, P. [CEA, IRFM, 13108 St Paul-Lez-Durance (France)

    2015-08-15

    The influence of the plasma facing components material on the scrape-off layer plasma is investigated. In particular, the energy recycling is found to be more pronounced for tungsten wall compared with carbon wall. Edge plasma simulations performed with the transport code SOLEDGE2D-EIRENE show that this enhanced energy recycling in the tungsten case leads to an increase of the scrape-off layer temperature. Moreover, the energy recycling depends on the ion angle of incidence with the wall. A PIC code has been used to model the ion acceleration in the magnetic pre-sheath and determine the later angle of incidence. These simulations show that ions mostly impact the wall with rather shallow incident angles leading to a further increase of the energy recycling.

  2. Tungsten disulphide coated multi-walled carbon nanotubes

    Science.gov (United States)

    Whitby, R. L. D.; Hsu, W. K.; Boothroyd, C. B.; Kroto, H. W.; Walton, D. R. M.

    2002-06-01

    Multi-walled carbon nanotubes (MWCNs), coated with ordered WS 2 mono- or multi-layers, are generated by pyrolysing H 2S/N 2 over MWCNs thinly coated with WO 3. High-resolution transmission electron microscopy (HRTEM) reveals the presence of hexagonal WS 2 arrays in the tube surface, consistent with the WS 2 simulated structure.

  3. Tungsten Promoted Ni/Al2O3 Catalysts for Carbon Dioxide Reforming of Methane to Synthesis Gas

    Institute of Scientific and Technical Information of China (English)

    XIAO Tian-cun; Thomas Suhartanto; Andrew P. E. York; Malcolm L. H. Green

    2004-01-01

    A series of tungsten promoted alumina supported nickel catalysts has been prepared for the carbon dioxide reforming of methane to synthesis gas. The catalysts have been characterized by means of XRD, TEM,and Laser Raman spectroscopy. It is shown that the addition of tungsten to the nickel catalyst can stabilize the catalyst and increase the resistance to carbon deposition. Adding a suitable amount of tungsten can also increase the catalyst activity to be close to that of supported noble metal catalysts. The carburisation of the tungsten modified nickel catalyst decreases the catalyst activity at lower reaction temperatures(<1123K),but has no effect on the catalyst performance at higher reaction temperatures. The alumina supported nickel catalyst modified by 0. 67 % (mass fraction)WOs has the equivalent equilibrium constant of the dry reforming reaction to that of alumina supported 5% (mass fraction) Ru at 873 K, and also has a lower activation energy for dry reforming than the latter.

  4. The Erosion and Erosion Products of Tungsten and Carbon Based Materials Bombarded by High Energy Pulse Electron Beam

    Institute of Scientific and Technical Information of China (English)

    LIUXiang; N.Yoshida; N.Noda; ZHANGFu; XUZengyu; LIUYong

    2001-01-01

    High Z and low Z materials are both the candidate plasma facing materials (PFM), up to now, the typical representative of high Z materials is tungsten, and the representatives of low Z materials are carbon materials (such as graphite, C/C composite) and beryllium. Most of these materials have been used as PFM limiters and diverter armor tiles of tokamak machines, tungsten, molybdenum and C/C composite are always used as high heat flux components.

  5. Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

    OpenAIRE

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity ...

  6. Electrochemical properties of tungsten sulfide-carbon composite microspheres prepared by spray pyrolysis.

    Science.gov (United States)

    Choi, Seung Ho; Boo, Sung Jin; Lee, Jong-Heun; Kang, Yun Chan

    2014-01-01

    Tungsten sulfide (WS2)-carbon composite powders with superior electrochemical properties are prepared by a two-step process. WO3-carbon composite powders were first prepared by conventional spray pyrolysis, and they were then sulfidated to form WS2-carbon powders. Bare WS2 powders are also prepared by sulfidation of bare WO3 powders obtained by spray pyrolysis. Stacked graphitic layers could not be found in the bare WS2 and WS2-carbon composite powders. The amorphous bare WS2 and WS2-carbon composite powders have Brunauer-Emmett-Teller (BET) surface areas of 2.8 and 4 m(2) g(-1), respectively. The initial discharge and charge capacities of the WS2-carbon composite powders at a current density of 100 mA g(-1) are 1055 and 714 mA h g(-1), respectively, and the corresponding initial Coulombic efficiency is 68%. On the other hand, the initial discharge and charge capacities of the bare WS2 powders are 514 and 346 mA h g(-1), respectively. The discharge capacities of the WS2-carbon composite powders for the 2(nd) and 50(th) cycles are 716 and 555 mA h g(-1), respectively, and the corresponding capacity retention measured after first cycle is 78%.

  7. Microstructure and Texture Changes of Tungsten-Rhenium coated on Carbon Fiber Composite during Annealing

    Institute of Scientific and Technical Information of China (English)

    LIUXiang; XUZengyu; S.Tamura; N.Yoshida

    2002-01-01

    Since tungsten was chose as the divertor tiles of 1TER, the investigation of tungsten and its coating as plasma facing material (PFM) have been paid more attentions by fusion scientists all over the world. Recent years, tungsten coatings have been successfully

  8. Residual stresses in boron/tungsten and boron/carbon fibers

    Science.gov (United States)

    Behrendt, D. R.

    1977-01-01

    Longitudinal residual stress distribution is determined for 102-micron diam B/W and B/C fibers. The 102-micron diam B/W fibers are deposited on a 12.7-micron diam tungsten wire resistively heated in a BCl3-H2 reactor. The 102-micron diam B/C fibers are made by deposition of boron on a pyrolytic graphite-coated carbon fiber. The longitudinal residual stress distribution is calculated from measurements of the change in length of the fiber produced by removal of the surface through electropolishing. It is found that for both types of fibers, the residual stress vary from a compressive stress at the surface to a tensile stress in the boron near the core. Closer to the core and in the core, significant differences in the residual stresses are observed for the B/W and B/C fibers.

  9. Density function theory study of the adsorption and dissociation of carbon monoxide on tungsten nanoparticles.

    Science.gov (United States)

    Weng, Meng-Hsiung; Ju, Shin-Pon; Chen, Hsin-Tsung; Chen, Hui-Lung; Lu, Jian-Ming; Lin, Ken-Huang; Lin, Jenn-Sen; Hsieh, Jin-Yuan; Yang, Hsi-Wen

    2013-02-01

    The adsorption and dissociation properties of carbon monoxide (CO) molecule on tungsten W(n) (n = 10-15) nanoparticles have been investigated by density-functional theory (DFT) calculations. The lowest-energy structures for W(n) (n = 10-15) nanoparticles are found by the basin-hopping method and big-bang method with the modified tight-binding many-body potential. We calculated the corresponding adsorption energies, C-O bond lengths and dissociation barriers for adsorption of CO on nanoparticles. The electronic properties of CO on nanoparticles are studied by the analysis of density of state and charge density. The characteristic of CO on W(n) nanoparticles are also compared with that of W bulk.

  10. Target particle and heat loads in low-triangularity L-mode plasmas in JET with carbon and beryllium/tungsten walls

    NARCIS (Netherlands)

    Groth, M.; Brezinsek, S.; Belo, P.; Corrigan, G.; Harting, D.; Wiesen, S.; Beurskens, M. N. A.; Brix, M.; Clever, M.; Coenen, J. W.; Eich, T.; Flanagan, J.; Giroud, C.; Huber, A.; Jachmich, S.; Kruezi, U.; Lehnen, M.; Lowry, C.; Maggi, C. F.; Marsen, S.; Meigs, A. G.; Sergienko, G.; Sieglin, B.; Silva, C.; Sirinelli, A.; Stamp, M. F.; van Rooij, G. J.

    2013-01-01

    Divertor radiation profiles, and power and particle fluxes to the target have been measured in attached \\{JET\\} L-mode plasmas with carbon and beryllium/tungsten wall materials. In the beryllium/tungsten configuration, factors of 2–3 higher power loads and peak temperatures at the low field side tar

  11. Mineral resource of the month: tungsten

    Science.gov (United States)

    Shedd, Kim B.

    2012-01-01

    The article offers information on tungsten. It says that tungsten is a metal found in chemical compounds such as in the scheelite and ore minerals wolframite. It states that tungsten has the highest melting point and it forms a compound as hard as diamond when combined with carbon. It states that tungsten can be used as a substitute for lead in fishing weights, ammunition, and hunting shot. Moreover, China started to export tungsten materials and products instead of tungsten raw materials.

  12. Tungsten disulfide-multiwalled carbon nanotube hybrid anode for lithium-ion battery.

    Science.gov (United States)

    Kartick, B; Srivastava, Suneel Kumar; Mahanty, Sourindra

    2014-05-01

    The present work is focused on the preparation of tungsten disulfide-multiwalled carbon nanotube (WS2-MWCNT) hybrids by simple dry grinding of WS2 and MWCNT in different proportion by weight (1:3, 1:1, 3:1). The as prepared hybrids have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Raman analyses. XRD results indicated complete exfoliation of MWCNT among WS2 particles in WS2-MWCNT (3:1) and (1:1) hybrids. FESEM images showed the formation of a 3-D network in WS2-MWCNT (1:1) hybrid with uniform dispersion of MWCNT being evident from HRTEM images. Raman analysis also suggested significant interaction between WS2 and MWCNT. WS2-MWCNT (1:1) hybrid, when used as anode material in lithium ion battery, exhibited a high initial charge capacity (483 mA h g(-1)) and an improved cycling stability with over 80% retention of the first cycle capacity after 20 cycles compared to only 40% capacity retention in pristine WS2. Such enhanced electrochemical performance of WS2-MWCNT (1:1) hybrid has been attributed to synergistic effect of WS2 and MWCNT.

  13. Interconversion between formate and hydrogen carbonate by tungsten-containing formate dehydrogenase-catalyzed mediated bioelectrocatalysis

    Directory of Open Access Journals (Sweden)

    Kento Sakai

    2015-09-01

    Full Text Available We have focused on the catalytic properties of tungsten-containing formate dehydrogenase (FoDH1 from Methylobacterium extorquens AM1 to construct a bioelectrochemical interconversion system between formate (HCOO− and hydrogen carbonate (HCO3−. FoDH1 catalyzes both of the HCOO oxidation and the HCO3− reduction with several artificial dyes. The bi-molecular reaction rate constants between FoDH1 and the artificial electron acceptors and NAD+ (as the natural electron acceptor show the property called a linear free energy relationship (LFER, indicating that FoDH1 would have no specificity to NAD+. Similar LFER is also observed for the catalytic reduction of HCO3−. The reversible reaction between HCOO− and HCO3− through FoDH1 has been realized on cyclic voltammetry by using methyl viologen (MV as a mediator and by adjusting pH from the thermodynamic viewpoint. Potentiometric measurements have revealed that the three redox couples, MV2+/MV·−+, HCOO−/HCO3−, FoDH1 (ox/red, reach an equilibrium in the bulk solution when the two-way bioelectrocatalysis proceeds in the presence of FoDH1 and MV. The steady-state voltammograms with two-way bioelectrocatalytic properties are interpreted on a simple model by considering the solution equilibrium.

  14. Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

    Directory of Open Access Journals (Sweden)

    Adisorn Tuantranont

    2010-08-01

    Full Text Available In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT-doped tungsten oxide (WO3 thin films by means of the powder mixing and electron beam (E-beam evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method.

  15. Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.

    Science.gov (United States)

    Wongchoosuk, Chatchawal; Wisitsoraat, Anurat; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Kerdcharoen, Teerakiat

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO(3)) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO(3) thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO(3) hydrogen sensor prepared by the E-beam method.

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

    Science.gov (United States)

    Zhang, Jie; Chen, Jinwei; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin

    2016-12-01

    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 Fe3C and Co3C 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, Fe3C, and Co3C. 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.

  17. INVESTIGATION OF AES AND XPS FOR THE ION BOMBARDED CARBON FILMS ON THE SURFACE OF TUNGSTEN ALLOY%离子束轰击钨合金表面碳膜的AES和XPS分析

    Institute of Scientific and Technical Information of China (English)

    李俊; 高剑; 张一云; 吴丽萍; 黄宁康; 赵纯培

    2000-01-01

    Tungsten alloy with special properties is a useful material in medical and weapon devices. Surface modification of ion technique is used to improve the surface hardness and wear resistance of tungsten alloy, where carbon films deposited with magnetron sputtering on the surface of tungsten alloy were bombarded by ion beam with different species AES and XPS analyses for these speciment show that tungsten carbide and tungsten nitride were formed due to N+ bombardment. Which is beneficial to the Surface hardness and wear resistance of tungsten alloy,but no carbide or no nitride as above with other ion species. Again,ion bombardness leads to mixing between the carbon and tungsten alloy hence improve the adhere of carbon film to the substrate.

  18. Characterizing Carbon Nanotube Supported Platinum Catalyst by Electrochemistry

    DEFF Research Database (Denmark)

    Veltzé, Sune; Andersen, Shuang Ma; Skou, Eivind Morten

    Den metode for hvorved forskellige platinbærende katalysatormaterialebærende kulstofunderlag vil blive testet elektrokemisk beskrives, hvor Elektrokemisk Masse Spektrometri nævnes som en mulighed sammen med mikroskopi....

  19. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

  20. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

  1. Tungsten toxicity.

    Science.gov (United States)

    Witten, Mark L; Sheppard, Paul R; Witten, Brandon L

    2012-04-05

    There is emerging evidence that tungsten has toxic health effects. We summarize the recent tungsten toxicity research in this short review. Tungsten is widely used in many commercial and military applications because it has the second highest melting temperature of any element. Consequently, it is important to elucidate the potential health effects of tungsten.

  2. Target particle and heat loads in low-triangularity L-mode plasmas in JET with carbon and beryllium/tungsten walls

    Energy Technology Data Exchange (ETDEWEB)

    Groth, M., E-mail: mathias.groth@aalto.fi [Aalto University, Association EURATOM-Tekes, Espoo (Finland); Brezinsek, S. [Institute for Energy and Climate Research, Association EURATOM-FZJ Jülich (Germany); Belo, P. [Institute of Plasmas and Nuclear Fusion, Association EURATOM-IST, Lisbon (Portugal); Corrigan, G. [Culham Centre of Fusion Energy, EURATOM-Association, Culham Science Centre, Abingdon (United Kingdom); Harting, D.; Wiesen, S. [Institute for Energy and Climate Research, Association EURATOM-FZJ Jülich (Germany); Beurskens, M.N.A.; Brix, M. [Culham Centre of Fusion Energy, EURATOM-Association, Culham Science Centre, Abingdon (United Kingdom); Clever, M.; Coenen, J.W. [Institute for Energy and Climate Research, Association EURATOM-FZJ Jülich (Germany); Eich, T. [Max-Planck Institute for Plasma Physics, EURATOM-Association, Garching (Germany); Flanagan, J.; Giroud, C. [Culham Centre of Fusion Energy, EURATOM-Association, Culham Science Centre, Abingdon (United Kingdom); Huber, A. [Institute for Energy and Climate Research, Association EURATOM-FZJ Jülich (Germany); Jachmich, S. [Association “EURATOM Belgium State”, Laboratory for Plasma Physics, Brussels (Belgium); Kruezi, U.; Lehnen, M. [Institute for Energy and Climate Research, Association EURATOM-FZJ Jülich (Germany); Lowry, C. [EFDA Close Support Unit, Culham Science Centre, Abingdon (United Kingdom); Maggi, C.F. [Max-Planck Institute for Plasma Physics, EURATOM-Association, Garching (Germany); Marsen, S. [Max-Planck-Institut for Plasma Physics, EURATOM-Association, Greifswald (Germany); and others

    2013-07-15

    Divertor radiation profiles, and power and particle fluxes to the target have been measured in attached JET L-mode plasmas with carbon and beryllium/tungsten wall materials. In the beryllium/tungsten configuration, factors of 2–3 higher power loads and peak temperatures at the low field side target were observed in high-recycling scrape-off layer conditions, whilst in close-to-sheath-limited conditions almost identical plasmas were obtained. The 30% reduction in total radiation with the beryllium/tungsten wall is consistent with a reduction of carbon as the dominant impurity radiator; however similar ion current to the plates, emission from recycling neutrals and neutral pressures in the pumping plenum were measured. Simulations with the EDGDE2/EIRENE code of these plasmas indicate a reduction of the total divertor radiation when carbon is omitted, but significantly higher power loads in high-recycling and detached conditions are predicted than measured.

  3. Deposition and Coating Properties on CVD Tungsten

    Institute of Scientific and Technical Information of China (English)

    DU Ji-hong; LI Zheng-xiang; LIU Gao-jian; ZHOU Hui-Huang; CHUN liang

    2004-01-01

    Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.

  4. Residual stresses in boron/tungsten and boron/carbon fibers

    Science.gov (United States)

    Behrendt, D. R.

    1977-01-01

    By measuring the change in fracture stress of 203 micrometer diameter fibers of boron on tungsten (B/W) as a function of fiber diameter as reduced by chemical etching, it is shown that the flaws which limit B/W fiber strength are located at the surface and in the tungsten boride core. After etching to a diameter of 188 micrometers m virtually all fiber fractures were caused by core flaws, the average strength being 4.50 GN/sq m. If both the surface and core flaws are removed, the fracture strength, limited by flaws in the boron itself, is approximately 6.89 GN/sq m. This was measured on B/W fibers which were split longitudinally and had their cores removed by chemical etching. The longitudinal residual stress distribution was determined for 102 micrometer diameter B/W and B/C fibers.

  5. 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.

  6. Investigation of interactions of intense plasma streams with tungsten and carbon fibre composite targets in the PF-1000 facility

    Science.gov (United States)

    Kubkowska, Monika; Skladnik-Sadowska, Elzbieta; Kwiatkowski, Roch; Malinowski, Karol; Kowalska-Strzęciwilk, Ewa; Paduch, Marian; Sadowski, Marek J.; Pisarczyk, Tadeusz; Chodukowski, Tomasz; Kalinowska, Zofia; Zielinska, Ewa; Scholz, Marek

    2014-05-01

    This paper presents the results of research on interactions of pulsed plasma streams, as generated by the PF-1000 facility, with solid targets made of tungsten or carbon fibre composite. The device was equipped with a modified inner electrode with a central tungsten insert of 50 mm in diameter. The PF-1000 experimental chamber was filled with pure deuterium at p0 = 1.47 hPa. At the charging voltage U0 = 24 kV, the maximum current amounted to 1.8 MA in about 5.5 μs after the discharge initiation. The investigated targets were located on the z-axis, at a distance of 9 cm from the inner electrode end. For plasma diagnostics, optical emission spectroscopy, 16-frame laser interferometry and a soft x-ray measuring system of four silicon pin diodes were used. It was observed that plasma streams reached the target about 100 ns after the maximum compression and generated a plasma pillow at the sample surface, as proved from time-resolved optical spectra.

  7. Efficient degradation of methylene blue dye over tungsten trioxide/multi-walled carbon nanotube system as a novel photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Dinari, Mohammad; Momeni, Mohamad Mohsen; Ahangarpour, Marzieh [Isfahan University of Technology, Department of Chemistry, Isfahan (Iran, Islamic Republic of)

    2016-10-15

    Combination of acid-functionalized multi-walled carbon nanotube/tungsten trioxide (MWCNT/WO{sub 3}) with different MWCNT's weight percentages as visible light-induced photocatalysts for photodegradation of methylene blue (MB) dye was synthesized. These photocatalysts were characterized by Fourier transform infrared, X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, field emission scanning electron microscopy and transmission electron microscopy techniques. Their photocatalytic activities were tested by using MB as a model compound. The results show that the MWCNT/WO{sub 3} hybrid nanostructures exhibit higher photocatalytic activity than pure WO{sub 3} or MWCNTs due to their higher absorption enhancement in visible light region and effective separation of electrons and holes. The stability of the hybrid was characterized through cyclic photocatalytic test. (orig.)

  8. Efficient degradation of methylene blue dye over tungsten trioxide/multi-walled carbon nanotube system as a novel photocatalyst

    Science.gov (United States)

    Dinari, Mohammad; Momeni, Mohamad Mohsen; Ahangarpour, Marzieh

    2016-10-01

    Combination of acid-functionalized multi-walled carbon nanotube/tungsten trioxide (MWCNT/WO3) with different MWCNT's weight percentages as visible light-induced photocatalysts for photodegradation of methylene blue (MB) dye was synthesized. These photocatalysts were characterized by Fourier transform infrared, X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, field emission scanning electron microscopy and transmission electron microscopy techniques. Their photocatalytic activities were tested by using MB as a model compound. The results show that the MWCNT/WO3 hybrid nanostructures exhibit higher photocatalytic activity than pure WO3 or MWCNTs due to their higher absorption enhancement in visible light region and effective separation of electrons and holes. The stability of the hybrid was characterized through cyclic photocatalytic test.

  9. Characteristics of a high brightness gaseous field ion source employing tungsten-carbon doped NiAl needles

    Energy Technology Data Exchange (ETDEWEB)

    Mousa, Marwan S., E-mail: mmousa@mutah.edu.jo [Department of Physics, Mu' tah University, P.O. Box 7, Al-Karak (Jordan)

    2011-05-15

    We report on the characterization of a high brightness gaseous field ion source using an emitter made of a NiAl needle containing tiny spherical tungsten-carbon precipitates. By field evaporation of such a multiphase alloy, a surface protrusion is formed out of a precipitate, which can act as a small source size field ion emitter. The emission current-voltage characteristics of this emitter were recorded for a variety of parameters. The results obtained suggest that its application as a stable ion source is possible even on long term operation. -- Research highlights: {yields} High brightness gaseous field ion source of precipitation hardened NiAl+W+C emitter. {yields} Emission current-voltage characteristics are recorded for a variety of parameters. {yields} Very small virtual source sizes and energy spreads can be attained. {yields} Results suggest that application as long term stable ion source is possible.

  10. Cytochrome c oxidase in proteoliposomes visualised by platinum-carbon and by tungsten-tantalum shadowing: image analysis.

    Science.gov (United States)

    Tihova, M; Tattrie, B; Nicholls, P

    1994-08-30

    Beef heart cytochrome c oxidase complexes incorporated into phospholipid liposomes were examined by freeze-fracture electron microscopy. Enzyme molecules are inserted into the membrane asymmetrically, with larger projections on the 'C' side, where cytochrome c binding occurs, than on the 'M' (matrix-facing) side. Visualisation of the complexes was improved by: (i) image analysis, to determine details of size and shape, and (ii) tungsten-tantalum (W/Ta) rather than platinum-carbon (Pt/C) shadowing, which permits examination of smaller entities. Enzyme molecules are incorporated as dimers in the proteoliposomes. Some surface structural details of the embedded molecules can be discerned. Around each complex is seen a small area of modified lipid, the frozen annulus whose existence has been predicted with other methods.

  11. Photodecolorization of Rhodamine B on tungsten-doped TiO2/activated carbon under visible-light irradiation.

    Science.gov (United States)

    Li, Youji; Zhou, Xiaoming; Chen, Wei; Li, Leiyong; Zen, Mengxiong; Qin, Shidong; Sun, Shuguo

    2012-08-15

    Tungsten-doped TiO(2)/activated carbon catalysts have been prepared by a supercritical-pretreatment-assisted sol-gel process. The structural features of the photocatalysts have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV/Vis diffuse-reflectance spectroscopy (DRS), electron dispersive X-ray (EDX), photoluminescence spectroscopy, and Brunauer-Emmett-Teller (BET) analysis. The results revealed that a W-TiO(2) layer was coated on the AC surface, and had higher surface area and smaller crystallite size than TiO(2)/AC obtained by a similar route. The W dopant was responsible for narrowing the band gap of TiO(2) and shifting its optical response from the ultraviolet (UV) to the visible-light region. The photocatalytic performances of the supported catalysts have been evaluated for the degradation of Rhodamine B (RhB) solution under visible-light irradiation. Compared with bulk W-TiO(2), the photoactivity was obviously enhanced when it was coated onto AC. In addition, it was found that the reactivity showed a significant relationship with the amount of W dopant, and the photoactivity order of the catalysts from weak to strong showed good agreement with their PL intensities. The effects of TiO(2) content, tungsten ion content, catalyst amount, pH, and initial RhB concentration have been examined as operational parameters. The photocatalytic reactions followed pseudo-first-order kinetics and are discussed in terms of the Langmuir-Hinshelwood model.

  12. Studies of the composition and reactivity of carbon species generated through laser vaporization of graphite, tantalum carbide and tungsten carbide

    Energy Technology Data Exchange (ETDEWEB)

    Ortman, B.J.

    1987-01-01

    Vapor compositions above graphite, tantalum carbide, and tungsten carbide together with the chemical reactions of C/sub 1/, C/sub 2/ and C/sub 3/ were studied by the techniques of CW laser vaporization, matrix isolation, and FTIR spectroscopy. The carbon species were scavenged by cocondensing reactive gases (N/sub 2/, H/sub 2/, O/sub 2/, CO and H/sub 2/O) with the vapors of graphitic samples in argon or nitrogen matrices. Products were identified from their infrared spectra. Photolysis and annealing studies were also conducted to detect reaction intermediates, formation of carbon clusters, and metastable C/sub 1/, C/sub 2/, and C/sub 3/ adducts with the added reactants. From these experiments, CO was shown to be potentially the most useful scavenger molecule, since it reacted with both C/sub 1/ and C/sub 2/ to form C/sub 2/O and C/sub 3/O, respectively. CO also reacted with C/sub 3/ to form an adduct, which rearranges upon photolysis to form C/sub 4/O, a previously unknown molecule. Its identity was confirmed by isotopic studies and comparison of its vibrations to those of related molecules, C/sub 3/O, C/sub 2/O, and CO.

  13. A novel composite electrode based on tungsten oxide nanoparticles and carbon nanotubes for the electrochemical determination of paracetamol.

    Science.gov (United States)

    Baytak, Aysegul Kutluay; Duzmen, Sehriban; Teker, Tugce; Aslanoglu, Mehmet

    2015-12-01

    An electrochemical sensor was prepared by the modification of a glassy carbon electrode (GCE) with a composite of nanoparticles of tungsten oxide (WO3) and carbon nanotubes (CNTs) for the quantification of paracetamol (PR). Energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were performed for the characterization of the nanocomposite layer. Compared with a bare GCE and a GCE modified with CNTs, the proposed electrode (WO3NPs/CNTs/GCE) exhibited a well-defined redox couple for PR and a marked enhancement of the current response. The experimental results also showed that ascorbic acid (AA) did not interfere with the selective determination of PR. The proposed electrode was used for the determination of PR in 0.1M phosphate buffer solution (PBS) at pH7.0 using square wave voltammetry (SWV). The peak current increased linearly with the concentration of PR in the range of 1.0×10(-9)-2.0×10(-7)M. The detection limit (LOD) was 5.54×10(-11)M (based on 3Sb/m). The proposed voltammetric sensor provided long-time stability, improved voltammetric behavior and good reproducibility for PR. The selective, accurate and precise determination of PR makes the proposed electrode of great interest for monitoring its therapeutic use.

  14. Dual catalytic purpose of the tungsten filament during the synthesis of single-helix carbon microcoils by hot-wire CVD.

    Science.gov (United States)

    Oliphant, C J; Arendse, C J; Malgas, G F; Motaung, D E; Muller, T F G; Knoesen, D

    2009-10-01

    We report on the deposition of crystalline single-helix carbon microcoils, in the as-deposited state, by the hot-wire chemical vapor deposition process without any special preparation of nano-sized transition metal catalysts and subsequent post-deposition annealing. Tungsten, originating from the heated tungsten filament, is identified as the catalyst material responsible for the growth of the microcoils. High-resolution transmission spectroscopy, combined with Raman spectroscopy, confirm that the as-deposited microcoils are crystalline, which is induced by the high deposition temperature in the vicinity of the heated filament. These results suggest a simplified, less tedious deposition process for the growth of carbon microcoils, once the process has been optimized.

  15. Tungsten trioxide as a visible light photocatalyst for volatile organic carbon removal.

    Science.gov (United States)

    Wicaksana, Yossy; Liu, Sanly; Scott, Jason; Amal, Rose

    2014-10-31

    Tungsten trioxide (WO3) has been demonstrated to possess visible light photoactivity and presents a means of overcoming the UV-light dependence of photocatalysts, such as titanium dioxide. In this study, WO3 nanostructures have been synthesised by a hydrothermal method using sodium tungstate (Na2WO4·2H2O), sulphate precursors and pH as structure-directing agents and parameters, respectively. By altering the concentration of the sulphate precursors and pH, it was shown that different morphologies and phases of WO3 can be achieved. The effect of the morphology of the final WO3 product on the visible light photoactivity of ethylene degradation in the gas phase was investigated. In addition, platinum (Pt) was photodeposited on the WO3 structures with various morphologies to enhance the photocatalytic properties. It was found that the photocatalytic properties of the WO3 samples greatly depend on their morphology, chemical composition and surface modification. WO3 with a cuboid morphology exhibited the highest visible light photoactivity compared to other morphologies, while adding Pt to the surface improved the performance of certain WO3 structures.

  16. Comparison of the Structural Configuration of Cobalt Nanoparticles on Titania and Titania Nanotube Supports

    Directory of Open Access Journals (Sweden)

    E. Muzenda

    2012-03-01

    Full Text Available In this study, two cobalt based catalyst samples were prepared on titania and titania nanotubes supports using the deposition precipitation method. Their structural configurations were characterized and compared using BET, and TRP analyses. The BET analysis showed that the surface area of TiO2 is much higher than that of TNT which was due to their structural differences. Analyses of the results obtained revealed that the surface area of the 10 % Co/TNT catalyst sample is higher than that of the 10 % Co/TiO2. The TPR analysis showed that it is much easier to reduce 10 % Co/TiO2, than 10 % Co/TNT. This is attributed to be due to the fact that the cobalt particles were adsorbed on the surface of the TiO2, and formed covalent bonds with TNT. Therefore reduction temperature was higher with TNT than TiO2. The investigation of structural changes of these catalysts when they were coated with carbon, using chemical vapour deposition method was also conducted. The catalyst prepared on TNT support showed better properties in terms of average pore diameter, pore volume and surface area than the catalyst sample prepared on TiO2 support when the two samples were exposed to carbon environment for the same period of time. In this study, two cobalt based catalyst samples were prepared on titania and titania nanotubes supports using the deposition precipitation method. Their structural configurations were characterized and compared using BET, and TRP analyses. The BET analysis showed that the surface area of TiO2 is much higher than that of TNT which was due to their structural differences. Analyses of the results obtained revealed that the surface area of the 10 % Co/TNT catalyst sample is higher than that of the 10 % Co/TiO2. The TPR analysis showed that it is much easier to reduce 10 % Co/TiO2, than 10 % Co/TNT. This is attributed to be due to the fact that the cobalt particles were adsorbed on the surface of the TiO2, and formed covalent bonds

  17. Direct imaging of the structure, relaxation, and sterically constrained motion of encapsulated tungsten polyoxometalate lindqvist ions within carbon nanotubes.

    Science.gov (United States)

    Sloan, Jeremy; Matthewman, Gemma; Dyer-Smith, Clare; Sung, A-Young; Liu, Zheng; Suenaga, Kazu; Kirkland, Angus I; Flahaut, Emmanuel

    2008-05-01

    The imaging properties and observation of the sterically regulated translational motion of discrete tungsten polyoxometalate Linqvist ions (i.e., [W(6)O(19)](2-)) within carbon nanotubes of specific internal diameter are reported. The translational motion of the nonspheroidal anion within the nanotube capillary is found to be impeded by its near-perfect accommodation to the internal van der Waals surface of the nanotube wall. Rotational motion of the anion about one remaining degree of freedom permits translational motion of the anion along the nanotube followed by locking in at sterically favorable positions in a mechanism similar to a molecular ratchet. This steric locking permits the successful direct imaging of the constituent octahedral cation template of individual [W(6)O(19)](2-) anions by high resolution transmission electron microscopy thereby permitting meterological measurements to be performed directly on the anion. Direct imaging of pairs of equatorial W(2) atoms within the anion reveal steric relaxation of the anion contained within the nanotube capillary relative to the bulk anion structure.

  18. EBSD analysis of tungsten-filament carburization during the hot-wire CVD of multi-walled carbon nanotubes.

    Science.gov (United States)

    Oliphant, Clive J; Arendse, Christopher J; Camagu, Sigqibo T; Swart, Hendrik

    2014-02-01

    Filament condition during hot-wire chemical vapor deposition conditions of multi-walled carbon nanotubes is a major concern for a stable deposition process. We report on the novel application of electron backscatter diffraction to characterize the carburization of tungsten filaments. During the synthesis, the W-filaments transform to W2C and WC. W-carbide growth followed a parabolic behavior corresponding to the diffusion of C as the rate-determining step. The grain size of W, W2C, and WC increases with longer exposure time and increasing filament temperature. The grain size of the recrystallizing W-core and W2C phase grows from the perimeter inwardly and this phenomenon is enhanced at filament temperatures in excess of 1,400°C. Cracks appear at filament temperatures >1,600°C, accompanied by a reduction in the filament operational lifetime. The increase of the W2C and recrystallized W-core grain size from the perimeter inwardly is ascribed to a thermal gradient within the filament, which in turn influences the hardness measurements and crack formation.

  19. Influence of carbon and metal oxide nanomaterials on aqueous concentrations of the munition constituents cyclotrimethylenetrinitramine (RDX) and tungsten.

    Science.gov (United States)

    Brame, Jonathon A; Kennedy, Alan J; Lounds, Christopher D; Bednar, Anthony J; Alvarez, Pedro J J; Scott, Andrea M; Stanley, Jacob K

    2014-05-01

    There is an increasing likelihood of interactions between nanomaterials and munitions constituents in the environment resulting from the use of nanomaterials as additives to energetic formulations and potential contact in waste streams from production facilities and runoff from training ranges. The purpose of the present research was to determine the ability of nano-aluminum oxide (Al(2)O(3)) and multiwalled carbon nanotubes (MWCNTs) to adsorb the munitions constituents cyclotrimethylenetrinitramine (RDX) and tungsten (W) from aqueous solution as a first step in determining the long-term exposure, transport, and bioavailability implications of such interactions. The results indicate significant adsorption of RDX by MWCNTs and of W by nano-Al(2)O(3) (but not between W and MWCNT or RDX and nano-Al(2)O(3)). Kinetic sorption and desorption investigations indicated that the most sorption occurs nearly instantaneously (<5 min), with a relatively slower, secondary binding leading to statistically significant but relatively smaller increases in adsorption over 30 d. The RDX sorption that occurred during the initial interaction was irreversible, with long-term, reversible sorption likely the result of a secondary interaction; as interaction time increased, however, the portion of W irreversibly sorbed onto nano-Al(2)O(3) also increased. The present study shows that strong interactions between some munitions constituents and nanomaterials following environmental release are likely. Time-dependent binding has implications for the bioavailability, migration, transport, and fate of munitions constituents in the environment.

  20. A novel composite electrode based on tungsten oxide nanoparticles and carbon nanotubes for the electrochemical determination of paracetamol

    Energy Technology Data Exchange (ETDEWEB)

    Baytak, Aysegul Kutluay; Duzmen, Sehriban; Teker, Tugce; Aslanoglu, Mehmet, E-mail: maslanoglu@harran.edu.tr

    2015-12-01

    An electrochemical sensor was prepared by the modification of a glassy carbon electrode (GCE) with a composite of nanoparticles of tungsten oxide (WO{sub 3}) and carbon nanotubes (CNTs) for the quantification of paracetamol (PR). Energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were performed for the characterization of the nanocomposite layer. Compared with a bare GCE and a GCE modified with CNTs, the proposed electrode (WO{sub 3}NPs/CNTs/GCE) exhibited a well-defined redox couple for PR and a marked enhancement of the current response. The experimental results also showed that ascorbic acid (AA) did not interfere with the selective determination of PR. The proposed electrode was used for the determination of PR in 0.1 M phosphate buffer solution (PBS) at pH 7.0 using square wave voltammetry (SWV). The peak current increased linearly with the concentration of PR in the range of 1.0 × 10{sup −9}–2.0 × 10{sup −7} M. The detection limit (LOD) was 5.54 × 10{sup −11} M (based on 3 S{sub b}/m). The proposed voltammetric sensor provided long-time stability, improved voltammetric behavior and good reproducibility for PR. The selective, accurate and precise determination of PR makes the proposed electrode of great interest for monitoring its therapeutic use. - Highlights: • A voltammetric nanosensor was prepared using nanoparticles of WO{sub 3} and CNTs. • A selective quantification of paracetamol was carried out in the presence of AA. • A linear plot was obtained for current responses versus concentrations over the range from 1.0 × 10{sup −9} to 2.0 × 10{sup −7} M. • A detection limit of 554 pM was obtained for paracetamol using the proposed nanosensor. • An accurate quantification makes the proposed nanosensor of great interest for public health.

  1. Hydrogen retention and erosion behaviour of tungsten-doped carbon films (a-C:W); Wasserstoffrueckhaltung und Erosionsverhalten von wolframdotierten Kohlenstofffilmen (a-C:W)

    Energy Technology Data Exchange (ETDEWEB)

    Sauter, Philipp Andre

    2012-06-13

    In this study tungsten-doped carbon films (a-C:W) were investigated with respect on hydrogen retention and erosion under deuterium (D) impact. a-C:W was used as model system for mixed layers, which will be deposited on the inner wall of the fusion reactor ITER. The erosion is lowered by the successive enrichment of tungsten at the surface and only mildly depends on the dopant concentration and the temperature. The hydrogen retention is determined by the diffusion of D into depth, which increases with temperature. The resulting successive accumulation of D in a-C:W is insensitive on enrichment for high fluences and in line with the accumulation of D in C.

  2. Tungsten carbide modified high surface area carbon as fuel cell catalyst support

    Science.gov (United States)

    Shao, Minhua; Merzougui, Belabbes; Shoemaker, Krista; Stolar, Laura; Protsailo, Lesia; Mellinger, Zachary J.; Hsu, Irene J.; Chen, Jingguang G.

    Phase pure WC nanoparticles were synthesized on high surface area carbon black (800 m 2 g -1) by a temperature programmed reaction (TPR) method. The particle size of WC can be controlled under 30 nm with a relatively high coverage on the carbon surface. The electrochemical testing results demonstrated that the corrosion resistance of carbon black was improved by 2-fold with a surface modification by phase pure WC particles. However, the WC itself showed some dissolution under potential cycling. Based on the X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis, most of the WC on the surface was lost or transformed to oxides after 5000 potential cycles in the potential range of 0.65-1.2 V. The Pt catalyst supported on WC/C showed a slightly better ORR activity than that of Pt/C, with the Pt activity loss rate for Pt/WC/C being slightly slower compared to that of Pt/C. The performance and decay rate of Pt/WC/C were also evaluated in a fuel cell.

  3. Microstructure and abrasive wear properties of M(Cr,Fe7C3 carbides reinforced high-chromium carbon coating produced by gas tungsten arc welding (GTAW process

    Directory of Open Access Journals (Sweden)

    Soner BUYTOZ

    2010-01-01

    Full Text Available In the present study, high-chromium ferrochromium carbon hypereutectic alloy powder was coated on AISI 4340 steel by the gas tungsten arc welding (GTAW process. The coating layers were analyzed by optical microscopy, X-ray diffraction (XRD, field-emission scanning electron microscopy (FE-SEM, X-ray energy-dispersive spectroscopy (EDS. Depending on the gas tungsten arc welding pa-rameters, either hypoeutectic or hypereutectic microstructures were produced. Wear tests of the coatings were carried out on a pin-on-disc apparatus as function of contact load. Wear rates of the all coating layers were decreased as a function of the loading. The improvement of abrasive wear resistance of the coating layer could be attributed to the high hardness of the hypereutectic M7C3 carbides in the microstruc-ture. As a result, the microstructure of surface layers, hardness and abrasive wear behaviours showed different characteristics due to the gas tungsten arc welding parameters.

  4. Growth of carbon nanofiber coatings on nickel thin films on fused silica by catalytic thermal chemical vapor deposition: On the use of titanium, titanium–tungsten and tantalum as adhesion layers

    NARCIS (Netherlands)

    Thakur, D.B.; Tiggelaar, R.M.; Gardeniers, J.G.E.; Lefferts, L.; Seshan, K.

    2009-01-01

    Coatings of carbon nanofiber (CNF) layers were synthesized on fused silica substrates using a catalytic thermal chemical vapor deposition process (C-TCVD). The effects of various adhesion layers–titanium, titanium–tungsten and tantalum–under the nickel thin film on the attachment of carbon nanofiber

  5. On the microstructure of tungsten disulfide films alloyed with carbon and nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Nossa, A. [Escola Superior de Tecnologia e Gestao, Instituto Politecnico da Guarda, Guarda (Portugal); Cavaleiro, A. [ICEMS, Departamento de Engenharia Mecanica, Faculdade de Ciencias e Tecnologia, Universidade de Coimbra, Engenharia Mecnica-GEMS, Polo II - Pinhal de Marrocos, 3030201, Coimbra (Portugal)]. E-mail: albano.cavaleiro@dem.uc.pt; Carvalho, N.J.M. [Department of Applied Physics, Materials Science Centre and Netherlands Institute for Metals Research, University of Groningen (Netherlands); Kooi, B.J. [Department of Applied Physics, Materials Science Centre and Netherlands Institute for Metals Research, University of Groningen (Netherlands); Hosson, J.Th.M. de [Department of Applied Physics, Materials Science Centre and Netherlands Institute for Metals Research, University of Groningen (Netherlands)

    2005-07-22

    This work aimed at studying the effect of a Ti interlayer and the alloying with carbon and nitrogen of W-S-C(N) films on the mechanical and tribological properties. The W-S-C and W-S-N films were deposited by r.f. magnetron reactive sputtering with CH{sub 4} or N{sub 2} as reactive gases and analysed by high resolution electron microscopy techniques. The hardness showed an improvement with the addition of the alloying element, which was attributed to the densification of the morphology, the decrease of the grain size, and the precipitation of new phases harder than WS{sub 2}. The formation of either TiC or TiN at the interface between the Ti interlayer and the W-S-C(N) films promoted the enhancement of adhesion in the alloyed films. These improvements led to an enhanced tribological behaviour, in particularly the lowering of the wear coefficients.

  6. Synthesis and Performance of Tungsten Disulfide/Carbon (WS2/C) Composite as Anode Material

    Science.gov (United States)

    Yuan, Zhengyong; Jiang, Qiang; Feng, Chuanqi; Chen, Xiao; Guo, Zaiping

    2017-09-01

    The precursors of an amorphous WS2/C composite were synthesized by a simple hydrothermal method using Na2WO4·2H2O and CH3CSNH2 as raw materials, polyethylene glycol as dispersant, and glucose as the carbon source. The as-synthesized precursors were further annealed at a low temperature in flowing argon to obtain the final materials (WS2/C composite). The structure and morphology of the WS2/C composite were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. The electrochemical properties were tested by galvanostatic charge/discharge testing and alternating current (AC) impedance measurements. The results show that the as-prepared amorphous WS2/C composite features both high specific capacity and good cycling performance at room temperature within the potential window from 3.0 V to 0.01 V (versus Li+/Li) at current density of 100 mAg-1. The achieved initial discharge capacity was 1080 mAhg-1, and 786 mAhg-1 was retained after 170 cycles. Furthermore, the amorphous WS2/C composite exhibited a lower charge/discharge plateau than bare WS2, which is more beneficial for use as an anode. The cyclic voltammetry and AC impedance testing further confirmed the change in the plateau and the decrease in the charge transfer resistance in the WS2/C composite. The chemical formation process and the electrochemical mechanism of the WS2/C composite are also presented. The amorphous WS2/C composite can be used as a new anode material for future applications.

  7. Dual catalytic purpose of the tungsten filament during the synthesis of single-helix carbon microcoils by hot-wire CVD

    CSIR Research Space (South Africa)

    Oliphant, CJ

    2009-10-01

    Full Text Available post-deposition annealing. Tungsten, originating from the heated tungsten filament, is identified as the catalyst material responsible for the growth of the microcoils. High-resolution transmission spectroscopy, combined with Raman spectroscopy, confirm...

  8. Mineral of the month: tungsten

    Science.gov (United States)

    Shedd, Kim B.

    2006-01-01

    Tungsten has the highest melting point of all metals, one of the highest densities and, when combined with carbon, is almost as hard as diamond. These and other properties make it useful in a wide variety of important commercial, industrial and military applications.

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

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

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

  10. Silica-templated synthesis of ordered mesoporous tungsten carbide/graphitic carbon composites with nanocrystalline walls and high surface areas via a temperature-programmed carburization route.

    Science.gov (United States)

    Wu, Zhangxiong; Yang, Yunxia; Gu, Dong; Li, Qiang; Feng, Dan; Chen, Zhenxia; Tu, Bo; Webley, Paul A; Zhao, Dongyuan

    2009-12-01

    Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

  11. Preparation of Carbon Nanotubes Supporting Bismuth Oxide Nanometer Particle and Its Catalysis on Thermal Decomposition of Ammonium Dinitramide%碳纳米管负载氧化铋的制备及催化二硝酰胺铵热分解的研究

    Institute of Scientific and Technical Information of China (English)

    李晓东; 杨燕; 杨荣杰

    2007-01-01

    采用微波辐射法制备了沉积于碳纳米管(CNTs)表面的氧化铋(Ri2O3)纳米粒子(Bi2O3/CNTs),用扫描电子显微镜(SEM)、光电子能谱(XPS)和X射线衍射(XRD)对制备的Bi2OO3CNTs纳米粒子进行了表征.研究了Bi2O3/CNTs纳米粒子对二硝酰胺铵(ADN)的催化热分解.结果表明,纳米Bi2O3均匀沉积在CNTs表面,平均粒径为8nm;添加3%Bi2O3/CNTs纳米粒子的ADN的初始热分解温度降低了12.8℃,热分解终止温度降低了29.3℃;NH4N(NO2)2→NH4NO3+N2O为ADN初始热分解的主导反应.%Carbon nanotubes (CNTs) supporting bismuth oxide ( Bi2O3 ) nanometer particle ( Bi2O3/CNTs) was prepared by the microwave radiation method. Bi2O3/CNTs nanometer particle was determined by means of scan electron microscopy ( SEM ), X-ray photoelectron spectroscopy ( XPS ) and X-ray diffraction (XRD). The catalytic property of Bi2O3/CNTs nanometer particle on thermal decomposition of ammonium dinitramide (AND) was investigated by TG and DSC. The results show that nanometer Bi2O3 was coated uniformly on the surface of CNTs. Average size of nanometer Bi2O3 is 8nm. Initial thermal decomposition temperature and ending thermal decomposition temperature of AND decrease 12.8℃ and 29.3℃, respectively when addition amount of Bi2O3/CNTs nanometer particle is 3%. NwH4N(NO2 )2→ NH4NO3 + N2O is dominant reaction of initial thermal decomposition of AND.

  12. Metallic Tungsten Nanostructures and Highly Nanostructured Thin Films by Deposition of Tungsten Oxide and Subsequent Reduction in a Single Hot-Wire CVD Process

    NARCIS (Netherlands)

    Harks, P.P.R.M.L.; Houweling, Z.S.; de Jong, M.M.; Kuang, Y; Geus, J.W.; Schropp, R.E.I.

    2012-01-01

    The synthesis of metallic tungsten nanostructures and highly nanostructured thin films is presented. Crystalline tungsten oxide nanostructures are deposited on glassy carbon substrates kept at 700 100 8C by oxidizing resistively heated tungsten filaments in an air flow under subatmospheric pressures

  13. XPS Characterization of Carbon Nanotube Supported CoMo Hydrodesulfurization Catalysts

    Institute of Scientific and Technical Information of China (English)

    SHANG, Hong-Yan(商红岩); LIU, Chen-Guang(刘晨光); ZHAO, Rui-Yu(赵瑞玉); WU, Ming-Bo(吴明铂); WEI, Fei(魏飞)

    2004-01-01

    In this paper, the effect of catalytic support and sulfiding method on the chemical state of supported Co-Mo catalysts is studied by XPS. After sulfidation with in-situ method, the majority of molybdenum in CNT supported CoMo catalyst is transferred to a species with a formal chemical state Mo(Ⅳ) in MoS2 phase, and the rest to Mo(Ⅴ)which consists of Mo coordinated both to O and S, such as MoO2S22- and MoO3S2-. In case of CoMo/γ-Al2O3 catalyst sulfided with in-situ method, a fraction of molybdenum is transferred to formal state Mo(Ⅳ) in the form of MoS2, but there is still a mount of unreduced Mo(Ⅵ) phase which is difficult to be sulfided. In CoMo/CNT catalytic system sulfided with ex-situ method, Mo(Ⅳ) in the form of MoS2 is detected along with a portion of unreduced Mo(Ⅵ) phase, suggesting that not all the Mo phases are reduced and sulfided by ex-situ method. As for CoMo/γ-Al2O3, a portion of molybdenum is sulfided to intermediate reduced state Mo(Ⅴ) which consists of Mo coordinated both to O and S, such as MoO2S22- and MoO3S2-, in addition, there is still a fraction of unreduced Mo(Ⅵ)phase. XPS analyses results suggest that CNT support facilitates the reduction and sulfidation of active species to a large extent, and that alumina support strongly interacts with active species, hereby producing a fraction of phase which resists complete sulfiding. Catalytic measurements of catalysts in the HDS of dibenzothiophene (DBT) show that CoMo/CNT catalysts are of higher HDS activity and selectivity than CoMo/γ-Al2O3 catalyst, which is in good relation with the sulfiding behavior of the corresponding catalyst.

  14. 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.

  15. Free energies of formation of WC and WzC and the thermodynamic properties of carbon in solid tungsten

    Science.gov (United States)

    Gupta, D. K.; Seigle, L. L.

    1974-01-01

    The activity of carbon in the two-phase regions - W + WC and W + W2C was obtained from the carbon content of iron rods equilibrated with mixtures of metal plus carbide powders. From this activity data the standard free energies of formation of WC and W2C were calculated. The temperature of the invariant reaction W2C = W + WC was fixed at 1570 + or - 5K. Using available solubility data for C in solid W, the partial molar free energy of C in the dilute solid solution was also calculated. The heat of solution of C in W, and the excess entropy for the interstitial solid solution, were computed, assuming that the carbon atoms reside in the octahedral interstices of bcc W.

  16. High-strength tungsten alloy with improved ductility

    Science.gov (United States)

    Klopp, W. D.; Raffo, P. L.; Rubenstein, L. S.; Witzke, W. R.

    1967-01-01

    Alloy combines superior strength at elevated temperatures with improved ductility at lower temperatures relative to unalloyed tungsten. Composed of tungsten, rhenium, hafnium, and carbon, the alloy is prepared by consumable electrode vacuum arc-melting and can be fabricated into rod, plate, and sheet.

  17. Halloysite nanotube supported Ag nanoparticles heteroarchitectures as catalysts for polymerization of alkylsilanes to superhydrophobic silanol/siloxane composite microspheres.

    Science.gov (United States)

    Li, Cuiping; Li, Xueyuan; Duan, Xuelan; Li, Guangjie; Wang, Jiaqiang

    2014-12-15

    Halloysite nanotube supported Ag nanoparticles heteroarchitectures have been prepared through a very simple electroless plating method. Robust Ag nanocrystals can be reproducibly fabricated by soaking halloysite nanotubes in ethanolic solutions of AgNO3 and butylamine. By simply adjusting the molar ratio of AgNO3 and butylamine, Ag nanoparticles with tunable size and quantity on halloysite nanotube are achieved. It reveals that the Ag nanoparticles are well-dispersed on the surface of halloysite nanotubes. The halloysite nanotube supported Ag nanoparticles heteroarchitectures can serve as active catalysts for the polymerization of an alkylsilane C18H37SiH3 with water to form silanol/siloxane composite microspheres and exhibit interesting superhydrophobicity ascribed to the micro/nanobinary structure.

  18. EBSD analysis of tungsten-filament carburization during the hot-wire CVD of multi-walled carbon nanotubes

    CSIR Research Space (South Africa)

    Oliphant, CJ

    2014-02-01

    Full Text Available -scale synthesis of multi-walled carbon nanotubes ~MWCNTs! using HWCVD ~Dillon et al., 2003!. Despite the efforts to reduce filament aging, the fila- ment alloying process is still being investigated. Previous studies have focused primarily on linking microscopy, X... pyrometer. At Received August 23, 2013; accepted November 26, 2013 *Corresponding author. E-mail: coliphant@nmisa.org Microsc. Microanal. Page 1 of 10 doi:10.1017/S1431927613014001 MicroscopyAND Microanalysis © MICROSCOPY SOCIETY OF AMERICA 2013 each...

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

    Science.gov (United States)

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

    1974-01-01

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

  20. 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…

  1. 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...

  2. 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 ...

  3. MECHANICAL PROPERTIES OF WROUGHT TUNGSTEN

    Science.gov (United States)

    Mechanical properties of wrought tungsten vol. II. Creep rupture test data from 1500 to 5000 F, and tensile test data from room temperature to 5000 F at various strain rates for tungsten sheet material.

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

    National Research Council Canada - National Science Library

    J.-H. Pee; G.H. Kim; H.Y. Lee; Y.J. Kim

    2015-01-01

    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...

  5. 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.

  6. Studing Tungsten-containing Electroerosion Powders and Alloys Synthesized from Them

    Directory of Open Access Journals (Sweden)

    E.V. Ageev

    2014-07-01

    Full Text Available The results of the X-ray spectral microanalysis of the powder obtained using electroerosion dispersion of tungsten-containing wastes in distilled water, and the alloy powder synthesized from this powder are presented in the article. It is shown that the basic elements both in the powder obtained using electroerosion dispersion of tungsten-containing wastes in distilled water and in the synthesized alloy are tungsten, molybdenum, iron, oxygen and carbon.

  7. Tungsten diffusion in olivine

    Science.gov (United States)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  8. 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.

  9. OPAL Silicon Tungsten Luminometer

    CERN Multimedia

    OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. The Silicon Tungsten Luminometer was part of OPAL's calorimeter which was used to measure the energy of particles. Most particles end their journey in calorimeters. These detectors measure the energy deposited when particles are slowed down and stopped.

  10. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kost, Florian

    2009-05-25

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

  12. Thermal decomposition and cobalt species transformation of carbon nanotubes supported cobalt catalyst for Fischer-Tropsch synthesis

    Institute of Scientific and Technical Information of China (English)

    Jing Lü; Chengdu Huang; Suli Bai; Yunhui Jiang; Zhenhua Li

    2012-01-01

    The effect of calcination condition on the cobalt species and Fischer-Tropsch synthesis (FTS) was studied.It was found that higher calcination temperature resulted in decreased FTS activities because CNTs were consumed by oxidation in air at temperature higher than 230 ℃.Cobalt species went through transformation from Co3O4 to metallic Co in Ar by autoreduction at temperature over 500 ℃.The autoreduction route might be Co3O4→CoO→Co or Co3O4→Co2C→Co.Reduction at temperature higher than 500 ℃ also resulted in decreased FTS activities due to the methanation of CNTs in hydrogen.

  13. Dynamics of Gold Nanoparticles on Carbon Nanostructures Driven by van der Waals and Electrostatic Interactions.

    Science.gov (United States)

    La Torre, Alessandro; Gimenez-Lopez, Maria del Carmen; Fay, Michael W; Lucas, Carlos Herreros; Brown, Paul D; Khlobystov, Andrei N

    2015-06-01

    Transmission electron microscopy studies on the assembly and growth of gold nanoparticles on carbon nanotubes supported on few-layer graphene and amorphous carbon reveal a competition between van der Waals forces and electrostatic interactions, enabling controlled positioning and sizing of adsorbed nanoparticles at the nanochannels formed between the carbon nanotube and the few-layer graph-ene surface.

  14. Controlled nanostructuration of polycrystalline tungsten thin films

    Energy Technology Data Exchange (ETDEWEB)

    Girault, B. [Institut P' (UPR 3346 CNRS), Universite de Poitiers, ENSMA, Bd Pierre et Marie Curie, 86962 Futuroscope Cedex (France); Institut de Recherche en Genie Civil et Mecanique (UMR CNRS 6183), LUNAM Universite, Universite de Nantes, Centrale Nantes, CRTT, 37 Bd de l' Universite, BP 406, 44602 Saint-Nazaire Cedex (France); Eyidi, D.; Goudeau, P.; Guerin, P.; Bourhis, E. Le; Renault, P.-O. [Institut P' (UPR 3346 CNRS), Universite de Poitiers, ENSMA, Bd Pierre et Marie Curie, 86962 Futuroscope Cedex (France); Sauvage, T. [CEMHTI/CNRS (UPR 3079 CNRS), Universite d' Orleans, 3A rue de la Ferollerie, 45071 Orleans Cedex 2 (France)

    2013-05-07

    Nanostructured tungsten thin films have been obtained by ion beam sputtering technique stopping periodically the growing. The total thickness was maintained constant while nanostructure control was obtained using different stopping periods in order to induce film stratification. The effect of tungsten sublayers' thicknesses on film composition, residual stresses, and crystalline texture evolution has been established. Our study reveals that tungsten crystallizes in both stable {alpha}- and metastable {beta}-phases and that volume proportions evolve with deposited sublayers' thicknesses. {alpha}-W phase shows original fiber texture development with two major preferential crystallographic orientations, namely, {alpha}-W<110> and unexpectedly {alpha}-W<111> texture components. The partial pressure of oxygen and presence of carbon have been identified as critical parameters for the growth of metastable {beta}-W phase. Moreover, the texture development of {alpha}-W phase with two texture components is shown to be the result of a competition between crystallographic planes energy minimization and crystallographic orientation channeling effect maximization. Controlled grain size can be achieved for the {alpha}-W phase structure over 3 nm stratification step. Below, the {beta}-W phase structure becomes predominant.

  15. The microstructure of chromium-tungsten steels

    Science.gov (United States)

    Klueh, R. L.; Maziasz, P. J.

    1989-03-01

    Chromium-tungsten steels are being developed to replace the Cr-Mo steels for fusion-reactor applications. Eight experimental steels were produced and examined by optical and electron microscopy. Chromium concentrations of 2.25, 5, 9 and 12 pct were used. Steels with these chromium compositions and with 2 pct W and 0.25 pct V were produced. To determine the effect of tungsten and vanadium, three other 2.25Cr steels were produced as follows: an alloy with 2 pct W and 0 pct V and alloys with 0 and 1 pct W and 0.25 pct V. A 9Cr steel containing 2 pct W, 0.25 pct V, and 0.07 pct Ta also was studied. For all alloys, carbon was maintained at 0.1 pct. Two pct tungsten was required in the 2.25Cr steels to produce 100 pct bainite (no polygonal ferrite). The 5Cr and 9Cr steels were 100 pct martensite, but the 12Cr steel contained about 25 pct delta-ferrite. Precipitate morphology and precipitate types varied, depending on the chromium content. For the 2.25Cr steels, M3C and M7C3 were the primary precipitates; for the 9Cr and 12Cr steels, M23C6 was the primary precipitate. The 5Cr steel contained M7C3 and M23C6. All of the steels with vanadium also contained MC.

  16. Plasma thermal performance of a dual-process PVD/PS tungsten coating on carbon-based panels for nuclear fusion application

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyunmyung; Lee, Ho Jung; Kim, Sung Hwan; Jang, Changheui, E-mail: chjang@kaist.ac.kr

    2016-11-01

    Highlights: • Plasma thermal performance of a dual-process PVD/PS W coating was evaluated. • Steady-state heat fluxes of 1–3 MW/m{sup 2} were applied to the W coated specimens. • Less micro-pores and grain growth were observed for the dual-process coating. • Loss of coating thickness was observed for the simple PS W coating. • Dual-process PVD/PS W coating was resistant to erosion due to the surface PVD layer. - Abstract: Various tungsten (W) coating techniques have been used for the application of plasma facing material in nuclear fusion devices, which resulted in limited success. In this study, a dual-process W coating structure was developed on a graphite substrate to improve the thermal performance of the coating structure. The dual-process coating structure consisted of a thin (∼7 μm) multilayer W/Mo physical vapor deposition (PVD) coating layer deposited on top of the relatively thick (∼160 μm) plasma spray (PS) W coating on a graphite substrate panel. Then the coated sample was exposed to plasma heat flux of 1–3 MW/m{sup 2} for 300 s. With addition of a thin surface PVD coating layer, the microstructure change in underlying PS W coating was substantially reduced compared to the simple PS W coating structure. The thickness of overall coating structure was maintained for the dual-process PVD/PS coated samples after the thermal loading tests, while a significant reduction in thickness due to surface erosion was observed for the simple PS W coated samples. The improvement in surface erosion resistance in the dual-process coating structure was discussed in view of the characteristics of PVD and PS coating layers.

  17. Development of Tungsten Based Composites

    Science.gov (United States)

    1992-02-01

    W-3.0% Ni-1.6% Fe and a zirconium foil (2 mils ) laminate. In addition, a GTE tungsten alloy (tungsten blended with 8% nickel and 2% iron) was...vescide.Wolframbleche sollten des- direction. i.e. the longitudinal direction. qu’elles sont lonaitudinales ou transver- ’AIM 1btakeristalliso tion noch 1 Stunde

  18. New tungsten alloy has high strength at elevated temperatures

    Science.gov (United States)

    1966-01-01

    Tungsten-hafnium-carbon alloy has tensile strengths of 88,200 psi at 3000 deg F and 62,500 psi at 3500 deg F. Possible industrial applications for this alloy would include electrical components such as switches and spark plugs, die materials for die casting steels, and heating elements.

  19. Preparation of tungsten oxide

    Science.gov (United States)

    Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee

    2009-09-22

    Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

  20. TUNGSTEN BASE ALLOYS

    Science.gov (United States)

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  1. L-SHELL IONIZATION MEASUREMENT OF TUNGSTEN BY ELECTRON IMPACT

    Institute of Scientific and Technical Information of China (English)

    PENG XIU-FENG; HE FU-QING; LONG XIAN-GUAN

    2000-01-01

    L-shell partial production cross sections of Lα- , Lβ-, Lγ- rays by electron impact were measured by observing the counts of X-ray from impacted thin tungsten target. Total production cross sections and mean ionization cross sections were deduced from these measured results. The electron beam energy range was from 11 to 36 keV. Tungsten was sputtered onto a carbon backing to reduce bremsstrahlung of the backing. The effect of electrons reflected by the backing has been corrected. Comparison with two theoretical calculations has performed. The experimental results agree rather well with the theoretical predications.

  2. 49 CFR 173.338 - Tungsten hexafluoride.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service. [ 74 FR 16143, Apr. 9,...

  3. 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

  4. RECOVERY OF URANIUM FROM TUNGSTEN

    Science.gov (United States)

    Newnam, K.

    1959-02-01

    A method is presented for the rccovery of uranium which has adhered to tungsten parts in electromagnetic isotope separation apparatus. Such a tungsten article is dissolved electrolytically in 20% NaOH by using the tungsten article as the anode. The resulting solution, containing soluble sodium lungstate and an insoluble slime, is then filtered. The slime residue is ignited successively with sodium nitrate and sodium pyrosulfate and leashed, and the resulting filtrates are combined with the original filtrate. Uranium is then recovered from the combined flltrates by diuranate precipitation.

  5. Tungsten resources of Brazil

    Science.gov (United States)

    White, Max Gregg

    1974-01-01

    Brazilian tungsten production, 85 percent of which is exported, comes almost entirely from scheelite-bearing tactites in northeast Brazil, and has reached an annual rate of about 2,000 metric tons (2,200 short tons) of scheelite concentrate with 70 percent WO3. Scheelite ore reserves, located principally in the State of Rio Grande do Norte, are estimated to be as high as 8,300,000 tons (9,100,000 short tons) containing 0.7 percent WO3. Minor deposits (or those about which only minimal information is available) of wolframite, with which some cassiterite is associated, are located in Sao Paulo, Santa Catarina, and Rio Grande do Sul. Both the scheelite and the wolframite deposits are considered . to be late Precambrian A (620 to 900 m.y.) or early Cambrian in age.

  6. Tungsten Toxicity in Plants

    Science.gov (United States)

    Adamakis, Ioannis-Dimosthenis S.; Panteris, Emmanuel; Eleftheriou, Eleftherios P.

    2012-01-01

    Tungsten (W) is a rare heavy metal, widely used in a range of industrial, military and household applications due to its unique physical properties. These activities inevitably have accounted for local W accumulation at high concentrations, raising concerns about its effects for living organisms. In plants, W has primarily been used as an inhibitor of the molybdoenzymes, since it antagonizes molybdenum (Mo) for the Mo-cofactor (MoCo) of these enzymes. However, recent advances indicate that, beyond Mo-enzyme inhibition, W has toxic attributes similar with those of other heavy metals. These include hindering of seedling growth, reduction of root and shoot biomass, ultrastructural malformations of cell components, aberration of cell cycle, disruption of the cytoskeleton and deregulation of gene expression related with programmed cell death (PCD). In this article, the recent available information on W toxicity in plants and plant cells is reviewed, and the knowledge gaps and the most pertinent research directions are outlined. PMID:27137642

  7. Tungsten chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kiichi; Takeda, Nobuo.

    1993-07-13

    A tungsten chemical vapor deposition method is described, comprising: a first step of selectively growing a first thin tungsten film of a predetermined thickness in a desired region on the surface of a silicon substrate by reduction of a WF[sub 6] gas introduced into an atmosphere of a predetermined temperature containing said silicon substrate; and a second step of selectively growing a second tungsten film of a predetermined thickness on said first thin tungsten film by reduction of said WF[sub 6] with a silane gas further introduced into said atmosphere, wherein the surface state of said substrate is monitored by a pyrometer and the switching from said first step to said second step is performed when the emissivity of infrared light from the substrate surfaces reaches a predetermined value.

  8. Global Tungsten Demand and Supply Forecast

    Science.gov (United States)

    Dvořáček, Jaroslav; Sousedíková, Radmila; Vrátný, Tomáš; Jureková, Zdenka

    2017-03-01

    An estimate of the world tungsten demand and supply until 2018 has been made. The figures were obtained by extrapolating from past trends of tungsten production from1905, and its demand from 1964. In addition, estimate suggestions of major production and investment companies were taken into account with regard to implementations of new projects for mining of tungsten or possible termination of its standing extraction. It can be assumed that tungsten supply will match demand by 2018. This suggestion is conditioned by successful implementation of new tungsten extraction projects, and full application of tungsten recycling methods.

  9. China’s Tungsten Resources Supply and Demand Situation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>China’s production of tungsten products mainly includes tungsten ore concentrates and a series of intermediate tungsten products such as ferro-tungsten, tungstic acid, sodium tungstate, calcium tungstate, tungsten trioxide, tungsten blue oxide, ammonium paratungstate, ammonium metatungstate, tungsten powder etc. During the period between 1949-1997, China produced 1.85 million tons of tungsten ore concentrates, in which 873,000 tons were exported with US$3.1 billion in value.

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

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

  11. Further development of the tungsten-fibre reinforced tungsten composite

    Energy Technology Data Exchange (ETDEWEB)

    Gietl, Hanns; Hoeschen, Till; Riesch, Johann [Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany); Aumann, Martin; Coenen, Jan [Forschungszentrum Juelich, IEK4, 52425 Juelich (Germany); Huber, Philipp [Lehrstuhl fuer Textilmaschinenbau und Institut fuer Textiltechnik (ITA), 52062 Aachen (Germany); Neu, Rudolf [Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany); Technische Universitaet Muenchen, 85748 Garching (Germany)

    2016-07-01

    For the use in a fusion device tungsten has a unique property combination. The brittleness below the ductile-to-brittle transition temperature and the embrittlement during operation e.g. by overheating, neutron irradiation are the main drawbacks for the use of pure tungsten. Tungsten fibre-reinforced tungsten composites utilize extrinsic mechanisms to improve the toughness. After proofing that this idea works in principle the next step is the conceptual proof for the applicability in fusion reactors. This will be done by producing mock-ups and testing them in cyclic high heat load tests. For this step all constituents of the composite, which are fibre, matrix and interface, and all process steps need to be investigated. Tungsten fibres are investigated by means of tension tests to find the optimum diameter and pretreatment. New interface concepts are investigated to meet the requirements in a fusion reactor, e.g. high thermal conductivity, low activation. In addition weaving processes are evaluated for their use in the fibre preform production. This development is accompanied by an extensive investigation of the materials properties e.g. single fibre tension tests.

  12. The tungsten metallome of Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M.; Pinkse, M.; Bol, E.; Krijgen, G.; Wolterbeek, H.; Verhaert, P.D.E.M.; Hagedoorn, P.L.; Hagen, W.R.

    2009-01-01

    The tungsten metallome of the hyperthermophilic archaeon Pyrococcus furiosus has been investigated using electroanalytical metal analysis and native–native 2D-PAGE with the radioactive tungsten isotope W-187 (t1/2 = 23.9 h). P. furiosus cells have an intracellular tungsten concentration of 29 mM, of

  13. The tungsten metallome of Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M.; Pinkse, M.W.H.; Bol, E.; Krijger, G.C.; Wolterbeek, H.T.; Verhaert, P.; Hagedoorn, P.L.; Hagen, W.R.

    2009-01-01

    The tungsten metallome of the hyperthermophilic archaeon Pyrococcus furiosus has been investigated using electroanalytical metal analysis and native-native 2D-PAGE with the radioactive tungsten isotope W-187 (t(1/2) = 23.9 h). P. furiosus cells have an intracellular tungsten concentration of 29 mu M

  14. Tungsten:Balance between Demand and Supply

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>In 2011,the tungsten market remained basically consistent with macro economic trends. In the first half of 2011, under the backdrop of upward economic situation,tungsten export and domestic consumption grew significantly and tungsten enterprises achieved remarkable economic benefits. However, as European debt crisis deepened in the second half of 2011, the global economic growth slowed down and

  15. Tungsten:Value Regression Is Inevitable Trend

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>China boasts rich reserve of tungsten resources,which accounts for about 65% of proved global tungsten mineral resource reserve,ranking top in the world.Judging from global production in the past five years,China’s tungsten production also far outstrips those of other countries,about

  16. Tungsten: A Preliminary Environmental Risk Assessment

    Science.gov (United States)

    2011-05-01

    Bioaccumulation of Tungsten in Plants Natural Sources • Trees & shrubs in Rocky Mountain region, USA • Siberian pine, willows, mosses & lichen in tungsten...Transitional metal ion binding • Peptidase activity • DNA & protein binding BUILDING STRONG® Geochemistry: • Aging of tungsten in soil results in

  17. 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.

  18. Process Of Bonding Copper And Tungsten

    Science.gov (United States)

    Slattery, Kevin T.; Driemeyer, Daniel E.

    1999-11-23

    Process for bonding a copper substrate to a tungsten substrate by providing a thin metallic adhesion promoting film bonded to a tungsten substrate and a functionally graded material (FGM) interlayer bonding the thin metallic adhesion promoting film to the copper substrate. The FGM interlayer is formed by thermal plasma spraying mixtures of copper powder and tungsten powder in a varied blending ratio such that the blending ratio of the copper powder and the tungsten powder that is fed to a plasma torch is intermittently adjusted to provide progressively higher copper content/tungsten content, by volume, ratio values in the interlayer in a lineal direction extending from the tungsten substrate towards the copper substrate. The resulting copper to tungsten joint well accommodates the difference in the coefficient of thermal expansion of the materials.

  19. 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

  20. 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.

  1. Thermal response of nanostructured tungsten

    NARCIS (Netherlands)

    Kajita, Shin; De Temmerman, G.; Morgan, Thomas; van Eden, Stein; de Kruif, Thijs; Ohno, Noriyasu

    2014-01-01

    The thermal response of nanostructured tungsten, which was fabricated in the linear divertor simulator NAGDIS-II, was investigated using pulsed plasma in the MAGNUM-PSI device and by using high powered laser pulses. The temperature evolution in response to the pulses was measured with an infrared fa

  2. Tungsten biochemistry of Pyrococcus furiosus

    NARCIS (Netherlands)

    Bevers, L.E.

    2008-01-01

    Tungsten is the heaviest element that exhibits biological activity (atomic number 74), when it is present in an enzyme. It is taken up by cells in the form of tungstate, and it is subsequently processed into an organic cofactor referred to as tungstopterin, which is found as active center in several

  3. Tungsten/Platinum Hybrid Nanowire Growth via Field Emission Using Nanorobotic Manipulation

    Directory of Open Access Journals (Sweden)

    Zhan Yang

    2011-01-01

    Full Text Available This paper reports tungsten-platinum hybrid nanowire growth via field emission, based on nanorobotic manipulation within a field emission scanning electron microscope (FESEM. A multiwalled carbon nanotube (MWCNT was used as the emitter, and a tungsten probe was used as the anode at the counterposition, by way of nanomanipulation. By independently employing trimethylcyclopentadienyl platinum (CpPtMe3 and tungsten hexacarbonyl (W(CO6 as precursors, the platinum nanowire grew on the tip of the MWCNT emitter. Tungsten nanowires then grew on the tip of the platinum nanowire. The hybrid nanowire length wascontrolled by nanomanipulation. Their purity was evaluated using energy-dispersive X-ray spectroscopy (EDS. Thus, it is possible to fabricate various metallic hybrid nanowires by changing the precursor materials. Hybrid nanowires have various applications in nanoelectronics, nanosensor devices, and nanomechanical systems.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-04-30

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

  5. Tungsten coatings electro-deposited on CFC substrates from oxide molten salt

    Science.gov (United States)

    Sun, Ningbo; Zhang, Yingchun; Lang, Shaoting; Jiang, Fan; Wang, Lili

    2014-12-01

    Tungsten is considered as plasma facing material in fusion devices because of its high melting point, its good thermal conductivity, its low erosion rate and its benign neutron activation properties. On the other hand, carbon based materials like C/C fiber composites (CFC) have been used for plasma facing materials (PFMs) due to their high thermal shock resistance, light weight and high strength. Tungsten coatings on CFC substrates are used in the JET divertor in the frame of the JET ITER-like wall project, and have been prepared by plasma spray (PS) and other techniques. In this study, tungsten coatings were electro-deposited on CFC from Na2WO4-WO3 molten salt under various deposition parameters at 900 °C in air. In order to obtain tungsten coatings with excellent performance, the effects of pulse duration ratio and pulse current density on microstructures and crystal structures of tungsten coatings were investigated by X-ray diffraction (XRD, Rigaku Industrial Co., Ltd., D/MAX-RB) and a scanning electron microscope (SEM, JSM 6480LV). It is found that the pulsed duration ratio and pulse current density had a significant influence on tungsten nucleation and electro-crystallization phenomena. SEM observation revealed that intact, uniform and dense tungsten coatings formed on the CFC substrates. Both the average grain size and thickness of the coating increased with the pulsed current density. The XRD results showed that the coatings consisted of a single phase of tungsten with the body centered cubic (BCC) structure. The oxygen content of electro-deposited tungsten coatings was lower than 0.05%, and the micro-hardness was about 400 HV.

  6. Synthesis of nanosized tungsten carbide from phenol formaldehyde resin coated precursors

    Institute of Scientific and Technical Information of China (English)

    LUO Ji; GUO Zhimeng; GAO Yuxi; LIN Tao

    2008-01-01

    Nanosized tungsten carbide was synthesized from phenol formaldehyde resin (PF) coated tungsten precursors.The process has three steps in which nanosized tungsten particles were first coated with PF,then the precursors were carburized at 950℃,and finally the carburized powders were treated in flowing wet hydrogen atmosphere at 940℃ to remove the uncombined carbon.The obtained powders were characterizedusing X-ray diffraction analysis (XRD),field-emission scanning electron microscopy (FESEM),small angle X-ray scattering (SAXS),andcombustion-gas-volume method.The results indicated that single-phase WC could be synthesized using excessive PF as carburizer at a muchlower temperature compared with using mixed carbon black.After wet hydrogen treating,the mean size of the obtained WC particles was 94.5nm and the total carbon content was 6.18 wt.%.

  7. A Review of the Application and Performance of Carbon Nanotubes in Fuel Cells

    Directory of Open Access Journals (Sweden)

    Chong Luo

    2015-01-01

    Full Text Available The fuel cell has the nature of high energy conversion efficiency and low pollutant emission. Carbon nanotubes used for fuel cells can decrease the needs of noble metals which are used for catalyst and improve the performance of fuel cells. The application of carbon nanotubes in fuel cells is summarized and discussed. The following aspects are described in this paper: the method used to reduce the platinum, the effect of carbon nanotubes on the fuel cell, improving the performance of fuel cell catalysts, the interaction between catalyst and carbon nanotube support, and the synthetic conditions of carbon nanotube supported catalyst. We summarize some of the results of previous studies and raise expectations for the microscopic state study of carbon nanotubes in the future.

  8. Laser cleaning of tungsten ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Aniruddha, E-mail: nontee65@rediffmail.com [Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur, Maharashtra, 401504 (India); Sonar, V.R.; Das, D.K.; Bhatt, R.B.; Behere, P.G.; Afzal, Mohd.; Kumar, Arun [Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur, Maharashtra, 401504 (India); Nilaya, J.P.; Biswas, D.J. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, 400085 (India)

    2014-07-01

    Removal of a thin oxide layer from a tungsten ribbon was achieved using the fundamental, second and third harmonic radiation from a Q- switched Nd-YAG laser. It was found that beyond the threshold, oxide removal was achieved at all wavelengths for a wide range of fluence values. The removal mechanism of the oxide layer was found to be critically dependent on both wavelength and fluence of the incident radiation and has been identified as ejection or sublimation. The un-cleaned and cleaned surfaces were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and atomic force microscopy (AFM). Laser cleaned tungsten ribbons were used in a thermal ionization mass spectrometer (TIMS) to determine isotopic composition of Neodymium atoms.

  9. Synthesis of nanosized tungsten powder

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Nanosized tungsten powder was synthesized by means of different methods and under different conditions with nanosized WO3 powder. The powder and the intermediate products were characterized using XRD, SEM, TEM, BET (Brunauer Emmett Teller Procedure) and SAXS (X-ray diffracto-spectrometer/Kratky small angle scattering goniometer). The results show that nanosized WO3 can be completely reduced to WO2 at 600℃ after 40 min, and WO2 can be reduced to W at 700℃ after 90 min, moreover, the mean size of W particles is less than 40 nm. Furthermore, the process of WO3→WO2→W excelled that of WO3→W in getting stable nanosized tungsten powder with less grain size.

  10. Does speciation matter for tungsten ecotoxicology?

    Science.gov (United States)

    Strigul, Nikolay

    2010-09-01

    Tungsten is a widely used transition metal that has not been thoroughly investigated with regards to its ecotoxicological effects. Tungsten anions polymerize in environmental systems as well as under physiological conditions in living organisms. These polymerization/condensation reactions result in the development of several types of stable polyoxoanions. Certain chemical properties (in particular redox and acidic properties) differentiate these polyanions from monotungstates. However, our current state of knowledge on tungsten toxicology, biological and environmental effects is based entirely on experiments where monotungstates were used and assumed by the authors to be the form of tungsten that was present and that produced the observed effect. Recent discoveries indicate that tungsten speciation may be important to ecotoxicology. New results obtained by different research groups demonstrate that polytungstates develop and persist in environmental systems, and that polyoxotungstates are much more toxic than monotungstates. This paper reviews the available toxicological information from the standpoint of tungsten speciation and identifies knowledge gaps and pertinent future research directions.

  11. Fine grain tungsten produced with nanoscale powder

    Institute of Scientific and Technical Information of China (English)

    Tao Lin; Fang Zhao; Liying Zhang; Chengyi Wu; Zhimeng Guo

    2005-01-01

    Nanoscale tungsten powder was prepared by reducing nanoscale tungsten trioxide in hydrogen to WO2.90 and further to W powder. After compacted with a rubber die, the nanoscale tungsten powder was sintered in a high-temperature dilatometer to investigate its shrinkage process. The results show that the compact of the nanoscale tungsten powder starts to shrink at 1050℃ and ends at 1500℃. The shrinkage rate reaches the maximum value at 1210℃. The relative density of sintered samples is 96.4%, and its grain size is about 5.8 μm.

  12. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Science.gov (United States)

    2010-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  13. Thermal shock behaviour of different tungsten grades under varying conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wirtz, Oliver Marius

    2012-07-19

    Thermonuclear fusion power plants are a promising option to ensure the energy supply for future generations, but in many fields of research enormous challenges have to be faced. A major step on the way to the prototype fusion reactor DEMO will be ITER which is build in Cadarache, southern France. One of the most critical issues is the field of in-vessel materials and components, in particular the plasma facing materials (PFM). PFMs that will be used in a device like ITER have to withstand severe environmental conditions in terms of steady state and transient thermal loads as well as high particle fluxes such as hydrogen, helium and neutrons. Candidate wall materials are beryllium, tungsten and carbon based materials like CFC (carbon fibre composite). Tungsten is the most promising material for an application in the divertor region with very severe loading conditions and it will most probably also be used as PFM for DEMO. Hence, this work focuses on the investigation of the thermal shock response of different tungsten grades in order to understand the damage mechanisms and to identify material parameters which influence this behaviour under ITER and DEMO relevant operation conditions. Therefore the microstructure and the mechanical and thermal properties of five industrially manufactured tungsten grades were characterised. All five tungsten grades were exposed to transient thermal events with very high power densities of up to 1.27 GWm{sup -2} at varying base temperatures between RT and 600 C in the electron beam device JUDITH 1. The pulse numbers were limited to a maximum of 1000 in order to avoid immoderate workload on the test facility and to have enough time to cover a wide range of loading conditions. The results of this damage mapping enable to define different damage and cracking thresholds for the investigated tungsten grades and to identify certain material parameters which influence the location of these thresholds and the distinction of the induced

  14. Thermal shock behaviour of different tungsten grades under varying conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wirtz, Oliver Marius

    2012-07-19

    Thermonuclear fusion power plants are a promising option to ensure the energy supply for future generations, but in many fields of research enormous challenges have to be faced. A major step on the way to the prototype fusion reactor DEMO will be ITER which is build in Cadarache, southern France. One of the most critical issues is the field of in-vessel materials and components, in particular the plasma facing materials (PFM). PFMs that will be used in a device like ITER have to withstand severe environmental conditions in terms of steady state and transient thermal loads as well as high particle fluxes such as hydrogen, helium and neutrons. Candidate wall materials are beryllium, tungsten and carbon based materials like CFC (carbon fibre composite). Tungsten is the most promising material for an application in the divertor region with very severe loading conditions and it will most probably also be used as PFM for DEMO. Hence, this work focuses on the investigation of the thermal shock response of different tungsten grades in order to understand the damage mechanisms and to identify material parameters which influence this behaviour under ITER and DEMO relevant operation conditions. Therefore the microstructure and the mechanical and thermal properties of five industrially manufactured tungsten grades were characterised. All five tungsten grades were exposed to transient thermal events with very high power densities of up to 1.27 GWm{sup -2} at varying base temperatures between RT and 600 C in the electron beam device JUDITH 1. The pulse numbers were limited to a maximum of 1000 in order to avoid immoderate workload on the test facility and to have enough time to cover a wide range of loading conditions. The results of this damage mapping enable to define different damage and cracking thresholds for the investigated tungsten grades and to identify certain material parameters which influence the location of these thresholds and the distinction of the induced

  15. Degradation of thin tungsten filaments at high temperature in HWCVD

    Energy Technology Data Exchange (ETDEWEB)

    Frigeri, P.A., E-mail: pfrigeri@phys.ethz.ch; Nos, O.; Bertomeu, J.

    2015-01-30

    The degradation of the filaments is usually studied by checking the silicidation or carbonization status of the refractory metal used as catalysts, and their effects on the structural stability of the filaments. In this paper, it will be shown that the catalytic stability of a filament heated at high temperature is much shorter than its structural lifetime. The electrical resistance of a thin tungsten filament and the deposition rate of the deposited thin film have been monitored during the filament aging. It has been found that the deposition rate drops drastically once the quantity of dissolved silicon in the tungsten reaches the solubility limit and the silicides start precipitating. This manuscript concludes that the catalytic stability is only guaranteed for a short time and that for sufficiently thick filaments it does not depend on the filament radius. - Highlights: • A model for the electrical resistance of a tungsten filament during aging is presented. • Catalytic activity of the filament drops when W5Si3 precipitation takes place at its surface. • The catalytic stability of the filament does not depend on its radius in most practical situations.

  16. 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.).

  17. Some features of sintering of tungsten powders

    Directory of Open Access Journals (Sweden)

    Andreiev Igor Viktorovich

    2016-01-01

    Full Text Available A method of activating the sintering process for tungsten powders using a closed reaction space and hydrogen, steam-saturated water was observed. This sintering process is allowed to activate super coarse-grained (1000μm tungsten powder sat relatively low temperatures (1000-1200°C.

  18. 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.

  19. Fabrication of a tantalum-clad tungsten target for LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A.T., E-mail: atnelson@lanl.gov [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); O' Toole, J.A.; Valicenti, R.A. [Accelerator Operations and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maloy, S.A. [Civilian Nuclear Program Office, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2012-12-15

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 Degree-Sign C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta{sub 2}O{sub 5} surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO{sub 2}, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  20. Fabrication of a tantalum-clad tungsten target for LANSCE

    Science.gov (United States)

    Nelson, A. T.; O'Toole, J. A.; Valicenti, R. A.; Maloy, S. A.

    2012-12-01

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 °C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta2O5 surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO2, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  1. Tribological properties of sputtered tungsten and tungsten nitride thin films

    Institute of Scientific and Technical Information of China (English)

    Wong; K.M.; ShenY.G.; Wong; P.L.

    2001-01-01

    The surface roughness, hardness and tribological properties of tungsten (W) and tung-sten nitride (WNx) thin films prepared by dc magnetron sputtering and reactive magnetron sputter-ing in Ar-N2 gas mixtures have been studied using atomic force microscopy (AFM), nanoindenta-tion measurements and ball-on-disc wear testing. A pronounced surface roughness was observedonly for films under compressive strains. The surface was flat under tension but rough under com-pression. Similar hardness with value about 20 GPa were observed in the W and WNx (x=0.3)films. This is thought to be due to the fact the grains are restricted to a very small size in the coat-ings. The higher coefficients of friction (0.4 for W and 0.9 for WN0.3) suggest that WN0.3 is not theoptimum phase. Finally, discussions are made with tribological test results.

  2. Structural and electrical properties in tungsten/tungsten oxide multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cacucci, Arnaud [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Potin, Valérie, E-mail: valerie.potin@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Imhoff, Luc [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Martin, Nicolas [Institut FEMTO-ST, UMR 6174 CNRS, Université de Franche-Comté, ENSMM, UTBM, 32 Avenue de l' observatoire, F-25044, BESANCON Cedex (France)

    2014-02-28

    Tungsten and tungsten oxide periodic nanometric multilayers have been deposited by DC reactive sputtering using the reactive gas pulsing process. Different pulsing periods have been used for each deposition to produce metal-oxide periodic alternations ranging from 3.3 to 71.5 nm. The morphology, crystallinity and chemical composition of these films have been investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy techniques. The produced multilayers exhibited an amorphous structure and the composition stability of WO{sub 3} sub-layers has been pointed out. Moreover, electrical properties have also been studied by the van der Pauw technique. It revealed a clear stability of resistivity versus temperature for almost all samples and an influence of the multilayered structure on the resistivity behavior. - Highlights: • W/WO{sub 3} multilayers with nanometric periods are produced by gas pulsing. • Multilayers are mainly amorphous and the oxide sub-layers composed of WO{sub 3}. • Crystallized inclusions of β-W and β-W{sub 3}O phases in metallic sub-layers • Metallic-like behavior with low temperature coefficient of resistance.

  3. Seed growth of tungsten diselenide nanotubes from tungsten oxides.

    Science.gov (United States)

    Kim, Hyun; Yun, Seok Joon; Park, Jin Cheol; Park, Min Ho; Park, Ji-Hoon; Kim, Ki Kang; Lee, Young Hee

    2015-05-13

    We report growth of tungsten diselenide (WSe2) nanotubes by chemical vapor deposition with a two-zone furnace. WO3 nanowires were first grown by annealing tungsten thin films under argon ambient. WSe2 nanotubes were then grown at the tips of WO3 nanowires through selenization via two steps: (i) formation of tubular WSe2 structures on the outside of WO3 nanowires, resulting in core (WO3)-shell (WSe2) and (ii) growth of WSe2 nanotubes at the tips of WO3 nanowires. The observed seed growth is markedly different from existing substitutional growth of WSe2 nanotubes, where oxygen atoms are replaced by selenium atoms in WO3 nanowires to form WSe2 nanotubes. Another advantage of our growth is that WSe2 film was grown by simply supplying hydrogen gas, where the native oxides were reduced to thin film instead of forming oxide nanowires. Our findings will contribute to engineer other transition metal dichacogenide growth such as MoS2, WS2, and MoSe2.

  4. 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

  5. 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...

  6. Tungsten carbide laser alloying of a low alloyed steel

    Science.gov (United States)

    Cojocaru, Mihai; Taca, Mihaela

    1996-10-01

    Laser alloying is a way to change the composition of metal surfaces in order to improve their corrosion-resistance, high-temperature strength and hardness. The results of a structural and phase analysis of a tungsten carbide based surface layer prepared by laser alloying of a low carbon steel substrate are presented. Structure, phase composition and microhardness of surface alloyed layers have been investigated. The surface of the samples exhibited a thin layer with a different chemical and phase composition. An increase in alloyed surface hardness and wear-resistance was observed.

  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. 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...

  9. Fracture behaviour of polycrystalline tungsten

    Science.gov (United States)

    Gaganidze, Ermile; Rupp, Daniel; Aktaa, Jarir

    2014-03-01

    Fracture behaviour of round blank polycrystalline tungsten was studied by means of three point bending Fracture-Mechanical (FM) tests at temperatures between RT and 1000 °C and under high vacuum. To study the influence of the anisotropic microstructure on the fracture toughness (FT) and ductile-to-brittle transition (DBT) the specimens were extracted in three different, i.e. longitudinal, radial and circumferential orientations. The FM tests yielded distinctive fracture behaviour for each specimen orientation. The crack propagation was predominantly intergranular for longitudinal orientation up to 600 °C, whereas transgranular cleavage was observed at low test temperatures for radial and circumferentially oriented specimens. At intermediate test temperatures the change of the fracture mode took place for radial and circumferential orientations. Above 800 °C all three specimen types showed large ductile deformation without noticeable crack advancement. For longitudinal specimens the influence of the loading rate on the FT and DBT was studied in the loading rate range between 0.06 and 18 MPa m1/2/s. Though an increase of the FT was observed for the lowest loading rate, no resolvable dependence of the DBT on the loading rate was found partly due to loss of FT validity. A Master Curve approach is proposed to describe FT vs. test temperature data on polycrystalline tungsten. Fracture safe design space was identified by analysis compiled FT data.

  10. Deuterium blistering in tungsten and tungsten vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Arshad, Kameel; Yuan, Yue; Cheng, Long; Wang, Jun [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Zhou, Zhang-Jian [School of Materials Science and Engineering, University of Science and Technology Beijing (USTB), Beijing 100083 (China); De Temmerman, Gregory [FOM Institute for Plasma Physics, Edisonbaan 14, 3439 MN, Nieuwegein (Netherlands); ITER Organization, Route de Vinon-sur-Verdon, CS90 046, 13067 St Paul Lez Durance Cedex (France); Lu, Guang-Hong, E-mail: lgh@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)

    2016-06-15

    In order to evaluate D blistering behavior in W based plasma facing materials, rolled W and different grades of W-V targets were exposed to high flux of 1.2 × 10{sup 24} m{sup −2} s{sup −1}, low energy (38 eV) D plasma at two different surface temperatures. The blistering behavior was investigated by means of scanning electron microscopy, accompanied by electron back-scattering diffraction. Highest numbers of blisters were observed on the surface of rolled tungsten. The addition of V precursor to W suppressed D blister formation. In the case of W-V alloys, comparatively submicron V-containing materials have shown high tendency but small size blisters formation than micron V-containing samples. A high density of blisters was observed near the (111) plane on the surface of both V-containing alloys. Nano-sized blisters were also observed on V enriched surface.

  11. Defect-induced loading of Pt nanoparticles on carbon nanotubes

    Science.gov (United States)

    Kim, Sung Jin; Park, Yong Jin; Ra, Eun Ju; Kim, Ki Kang; An, Kay Hyeok; Lee, Young Hee; Choi, Jae Young; Park, Chan Ho; Doo, Seok Kwang; Park, Min Ho; Yang, Cheol Woong

    2007-01-01

    Carbon nanotubes-supported Pt nanoparticles were loaded using a microwave oven on the defective carbon nanotubes generated by an additional oxidant during acid treatment. The authors' Raman spectra and x-ray diffraction analysis demonstrated that defects created during oxidation and microwave treatment acted as nucleation seeds for Pt adsorption. The generated Pt nanoparticles had the size distributions of 2-3nm and were uniformly distributed on the defects of carbon nanotubes. The authors' density functional calculations showed that the adsorption of Pt atom on the vacancy of nanotube was significantly stronger by s-p hybridization with carbon atoms near the defect site.

  12. Electrochromic performance of hybrid tungsten oxide films with multiwalled-CNT additions

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chung-Kwei, E-mail: cklin@fcu.edu.tw [Department of Materials Science and Engineering, Feng Chia University, Taichung, Taiwan (China); Tseng, Sheng-Chung; Cheng, Chin-Hua; Chen, Chin-Yi [Department of Materials Science and Engineering, Feng Chia University, Taichung, Taiwan (China); Chen, Chien-Chon [Department of Energy and Resources, National United University, Miaoli, Taiwan (China)

    2011-12-30

    In this study, tungsten oxide films were prepared by sol-gel technique. Various amounts of multiwalled carbon nanotubes (MWCNTs) were added during sol-gel process to obtain hybrid WO{sub 3}/MWCNT films. The original and hybrid films were characterized by thermogravimetric analysis, X-ray diffraction analysis, and scanning electron microscopy analysis, whereas the electrochromic performance was evaluated by measuring changes in the optical transmittance caused by potentiostatic charge-discharge intercalation. The influence on the structure and properties of tungsten oxide film due to MWCNT addition was also investigated. The results showed that all of the films were amorphous and exhibited porous microstructure. The electrochromic performance of pristine WO{sub 3} film was improved by adding MWCNTs that served as a template for the growth of WO{sub 3} and resulted in more porous microstructure. The hybrid tungsten oxide films with 0.1 wt.% MWCNT addition exhibited the best electrochromic performance.

  13. Material and gas-sensing properties of tungsten oxide nanorod thin-films.

    Science.gov (United States)

    Kim, Yong Shin; Lee, Kwangyeol

    2009-04-01

    Tungsten oxide thin-films were deposited simply by drop-casting a solution containing single-crystalline and monodispersed W18O49 nanorods prepared by a large-scale colloidal synthesis route. They were verified to be highly porous, nonstoichiometric, and monoclinic crystal structure only with little carbon impurities. These material properties heavily reflect relevant nanostructural characteristics of the nanorods acting as a basic building block. It could be comprehended by the observed structure of randomly arranged tungsten oxide agglomerates formed by favorable parallel alignment of individual nanorod units. Tungsten oxide nanorod sensors exhibit sensitive detection capability even at room temperature to various reducing volatile organic compounds (VOCs). This anomalous performance seems to result from unique nanostructural features of the thin-films, allowing a high surface-to-volume ratio and a considerable amount of active sensing sites due to the highly anisotropic, nonstoichiometric structure of W18O49 nanorods.

  14. Dielectronic recombination of tungsten ions

    Science.gov (United States)

    Li, Bowen; O'Sullivan, Gerry; Dong, Chenzhong; Chen, Ximeng

    2016-08-01

    Ab initio calculations of dielectronic recombination rate coefficients of Ne-, Pd- and Ag-like tungsten have been performed. Energy levels, radiative transition probabilities and autoionization rates were calculated using the Flexible Atomic Code. The contributions from different channels to the total rate coefficients are discussed. The present calculated rate coefficients are compared with other calculations where available. Excellent agreement has been found for Ne-like W while a large discrepancy was found for Pd-like W, which implies that more ab initio calculations and experimental measurements are badly needed. Further calculations demonstrated that the influence of configuration interaction is small while nonresonant radiative stabilizing (NRS) contribution to doubly excited non-autoionizing states are vital. The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community, which makes experimental verification even more essential.

  15. The electron affinity of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Lindahl, A.O.; Andersson, P.; Klason, P.; Hanstorp, D. [Department of Physics, University of Gothenburg (Sweden); Diehl, C. [Institut fur Physik, Johannes Gutenberg-Universitat, Mainz (Germany); Present Address: Max-Planck-Institut fur Kernphysik, Heidelberg (Germany); Forstner, O. [Faculty of Physics, University of Vienna, Wien (Austria)

    2010-11-15

    The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm{sup -1} by observing the onset of the process when W{sup -} ions in the 5d{sup 5}6s{sup 2} {sup 6}S{sub 5/2} ground state are photo-detached producing neutral W atoms in the 5d{sup 4}6s{sup 2} {sup 5}D{sub 0} ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W{sup -}. (authors)

  16. Viscosity of liquid undercooled tungsten

    Science.gov (United States)

    Paradis, Paul-François; Ishikawa, Takehiko; Yoda, Shinichi

    2005-05-01

    Knowledge of the viscosity and its temperature dependence is essential to improve metallurgical processes as well as to validate theoretical and empirical models of liquid metals. However, data for metals with melting points above 2504K could not be determined yet due to contamination and containment problems. Here we report the viscosity of tungsten, the highest melting point metal (3695K), measured by a levitation technique. Over the 3350-3700-K temperature range, which includes the undercooled region by 345K, the viscosity data could be fitted as η(T )=0.108exp[1.28×105/(RT)](mPas). At the melting point, the datum agrees with the proposed theoretical and empirical models of liquid metals but presents atypical temperature dependence, suggesting a basic change in the mechanism of momentum transfer.

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

    Science.gov (United States)

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

    2017-02-01

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

  18. Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

    Energy Technology Data Exchange (ETDEWEB)

    Ghasempour, Fariba [Plasma Physics Research Centre, Science and Research Branch, Islamic Azad University, P.O. Box 147789-3855, Tehran (Iran, Islamic Republic of); Azimirad, Rouhollah [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Amini, Abbas [School of Computing, Engineering and Mathematics, University of Western Sydney, Kingswood, NSW 2751 (Australia); Akhavan, Omid, E-mail: oakhavan@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of)

    2015-05-30

    Highlights: • Synthesis of tungsten oxide nano/micro-structures on W foils using KOH as a catalyst. • Strong antibacterial activity of tungsten oxide nanorods under visible light irradiation. • Decrease in photoinactivation of bacteria on tungsten oxide nano/micro-rods doped by potassium. - Abstract: Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400–800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50–90 nm and crystalline phase of WO{sub 3}) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K{sub 2}W{sub 6}O{sub 19} crystalline phase were formed on the foils. The WO{sub 3} nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K{sub 2}W{sub 6}O{sub 19} microrods formed at 800 °C could inactivate only ∼45% of the bacteria at the same conditions.

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

    Science.gov (United States)

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

    2016-10-01

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

  20. 氧化钨纳米线-单壁碳纳米管复合型气敏元件的室温NO_2敏感性能与机理%Room temperature NO2-sensing properties and mechanism of the sensors based on tungsten oxide nanowires/single-wall carbon nanotubes composites

    Institute of Scientific and Technical Information of China (English)

    秦玉香; 王飞; 沈万江; 胡明

    2012-01-01

    One-dimensional tungsten oxide nanowires are synthesized by the solvothermal method. The sensors based on tungsten oxide nanowires/single-wall carbon nanotubes (SWNTs) composites are fabricated by introducing SWNT, and their NO2 sensing properties are evaluated at room temperature. X-ray diffraction and field emission scanning electron microscope characterizations indicate that the as-synthesized nanowires are monoclinic WlsO49, and SWNTs are embedded within the nanowire matrix in the prepared tungsten oxide nanowires/SWNT composites. The tungsten oxide nanowires/SWNT composites-based sensors show high sensitivity, good selectivity and super fast response to NO2 gas at room temperature. The NO2 sensing properties of the sensors increase with the decrease of SWNT content. The sensing mechanism of the composites-based sensor is discussed and it is thought that the introduction of SWNT induces the formation of a large number of p-n hetero junctions and cross-linked diffusion channels in the structure of the composites, which are responsible for the good NO2 sensing properties at room temperature.%利用溶剂热法合成了一维的氧化钨纳米线,通过掺入适量单壁碳纳米管(SWNT)制备了基于氧化钨纳米线-SWNT复合结构的室温气敏元件并评价了其对NO_2气体的室温敏感性能.利用X射线与扫描电子显微镜表征了材料的微结构,结果表明,合成的氧化钨纳米线具有单斜的W_(18)O_(49)结构,复合材料中SWNT被包埋在氧化钨纳米线中间.气敏性能测试结果表明,氧化钨纳米线-SWNT复合结构气敏元件在室温下对NO_2气体表现出了高的灵敏度和超快的响应特性;较低的SWNT掺入量对获得好的气敏性能有利.分析了基于复合结构材料气敏元件的可能的气敏机理,认为元件良好的室温敏感性能与SWNT掺入在复合结构材料中引入大量的贯穿气孔和p-n异质结有关.

  1. 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...... is to act both as a diffusion barrier for chromium and provide better protection against high temperature oxidation than a pure cobalt coating. This work presents a characterization of a cobalt-tungsten alloy coating electrodeposited on the ferritic steel Crofer 22 H which subsequently was oxidized in air...... of oxidation time. The coating had completely oxidized during the 300 h oxidation time. GDOES measurements showed that the tungsten was located in an inner zone in the coating/substrate interface. The outer layer of the coating did not contain any tungsten after oxidation but consisted mainly of cobalt...

  2. SINTERED REFRACTORY TUNGSTEN ALLOYS. Gesinterte hochschmelzende wolframlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Kieffer, R.; Sedlatschek, K.; Braun, H.

    1971-12-15

    Dependence of the melting point of the refractory metals on their positions in the periodic system - alloys of tungsten with other refractory metals - sintering of the alloys - processing of the alloys - technological properties.

  3. Thermal stability of warm-rolled tungsten

    DEFF Research Database (Denmark)

    Alfonso Lopez, Angel

    Pure tungsten is considered as armor material for the most critical parts of fusion reactors (thedivertor and the blanket first wall), mainly due to its high melting point (3422 °C). This is becauseboth the divertor and the first wall have to withstand high temperatures during service which...... and recrystallization occur in tungsten, and quantifying the kinetics and microstructuralaspects of these restoration processes. Two warm-rolled tungsten plates are annealed attemperatures between 1100 °C and 1350 °C, under vacuum conditions or argon atmosphere. Theeffects of annealing on the microstructure...... on these activation energies) to lower annealingtemperatures allows predicting the lifespan of these tungsten plates under fusion reactor conditions.A much longer lifetime at normal operating temperatures was found for the plate W67 (e.g. at least1 million years at 800 °C) as compared to the plate W90 (e.g 71 years...

  4. Synthesis of tungsten carbide nanocrystals and their electrochemical properties

    Institute of Scientific and Technical Information of China (English)

    Jianghua ZENG; Dingsheng YUAN; Yingliang LIU; Jingxing CHEN; Sanxiang TAN

    2009-01-01

    Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO3 and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spec-troscopy and electrochemical methods. Hexagonal close-packed WC was successfully synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic ability for the oxygen reduction reaction.

  5. 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.

  6. 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

  7. Scandia doped tungsten matrix for impregnated cathode

    Institute of Scientific and Technical Information of China (English)

    WANG Jinshu; WANG Yanchun; LIU Wei; LI Hongyi; ZHOU Meiling

    2008-01-01

    As a matrix for Sc-type impregnated cathode,scandia doped tungsten with a uniform ldistribution of SC2O3 was obtained by powder metallurgy combined with the liquid-solid doping method.The microstructure and composition of the powder and the anti-ion bombardment behavior of scandium in the matrix were studied by means of SEM,EDS,XRD,and in-situ AES methods.Tungsten powder covered with scandium oxide,an ideal scandium oxide-doped tungsten powder for the preparation of Sc-type impregnated cathode,was obtained using the liquid-solid doping method.Compared with the matrix prepared with the mechanically mixed powder of tungsten and scandium oxide,SC2O3-W matrix prepared with this kind of powder had smaller grain size and uniform distribution of scandium.Sc on the surface of Sc2O3 doped tungsten mauix had good high temperature stability and good anti-ion bombardment capability.

  8. Ultrasonic drawing of tungsten wire for incandescent lamps production.

    Science.gov (United States)

    Mordyuk, B N; Mordyuk, V S; Buryak, V V

    2004-04-01

    An influence of ultrasonic treatment (drawing) on structure, high temperature durability, evaporation and creep behaviours of tungsten single crystal and wires were investigated. A relation of tungsten wires properties with dislocation distribution was determined.

  9. Electroanalytical determination of tungsten and molybdenum in proteins.

    Science.gov (United States)

    Hagedoorn, P L; van't Slot, P; van Leeuwen, H P; Hagen, W R

    2001-10-01

    Recent crystal structure determinations accelerated the progress in the biochemistry of tungsten-containing enzymes. In order to characterize these enzymes, a sensitive determination of this metal in protein-containing samples is necessary. An electroanalytical tungsten determination has successfully been adapted to determine the tungsten and molybdenum content in enzymes. The tungsten and molybdenum content can be measured simultaneously from 1 to 10 microg of purified protein with little or no sample handling. More crude protein samples require precipitation of interfering surface active material with 10% perchloric acid. This method affords the isolation of novel molybdenum- and tungsten-containing proteins via molybdenum and tungsten monitoring of column fractions, without using radioactive isotopes. A screening of soluble proteins from Pyrococcus furiosus for tungsten, using anion-exchange column chromatography to separate the proteins, has been performed. The three known tungsten-containing enzymes from P. furiosus were recovered with this screening.

  10. Process for the recovery of tungsten in a pure form from tungsten-containing materials

    Energy Technology Data Exchange (ETDEWEB)

    Fruchter, M.; Moscovici, A.

    1986-12-16

    A process is described for the recovery of tungsten from tungsten-containing materials which comprises the steps of (i) admixing the tungsten-containing material with a melt at a temperature of between 680/sup 0/C and 750/sup 0/C. The melt consists of a salt selected from the group consisting of sodium nitrate, sodium nitrite and mixtures thereof in a substantially stoichiometrical amount to the tungsten constituent of the tungsten-containing material. This is done to disintegrate the tungsten-containing material and to form sodium tungstate, cooling the melt, and leaching the cooled melt with water to obtain an aqueous solution of sodium tungstate; (ii) admixing a solution of calcium chloride with the aqueous solution of sodium tungstate at a temperature of between 40/sup 0/C and 95/sup 0/C to form a calcium tungstate precipitate and separating the calcium tungstate; (iii) admixing the calcium tungstate with a preheated concentrated hydrochloric acid solution to form a tungstic acid precipitate and a CaCl/sub 2/ solution having a concentration of between 80 g/l and 180 g/l free HCl and separating the tungstic acid precipitate and obtaining tungstic acid which is substantially free of calcium ions, and (iv) calcining the tungstic acid to convert it to tungstic oxide and reducing the tungstic oxide to form metallic tungsten.

  11. The Newly Released Export Quota for Tungsten Products

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>China’s Ministry of Commerce recently announced the second lot of export quota for tungsten products in 2005. Based on the new quota, the second lot for Ammonium Paratung-state (APT) and Ammonium Metatungstate (AMT) will be 1,232 tons. The second lot for tungsten trioxide and blue tungsten oxide will be 1,480 tons and the second lot for tungsten powder and its products will be 428 tons.

  12. Tungsten effect over co-hydrotalcite catalysts to produce hydrogen from bio-ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, J.L.; Ortiz, M.A.; Luna, R.; Nuno, L. [Univ. Autonoma Metropolitana-Azcapozalco, Mexico City (Mexico). Dept. de Energia; Fuentes, G.A. [Univ. Autonoma Metropolitana-Iztapalapa, Mexico City (Mexico). Dept. de IPH; Salmones, J.; Zeifert, B. [Inst. Politecnico Nacional, Mexico City (Mexico); Vazquez, A. [Inst. Mexicano del Petroleo, Mexico City (Mexico)

    2010-07-15

    The use of bioethanol has been considered for generating hydrogen via catalytic reforming. The reaction of ethanol with stream is strongly endothermic and produces hydrogen (H{sub 2}) and carbon dioxide (CO{sub 2}). However, undesirable products such as carbon monoxide (CO) and methane (CH{sub 4}) may also form during the reaction. This paper reported on the newly found stabilization effect of tungsten over the Co-hydrotalcite catalysts to produce H{sub 2} from ethanol in steam reforming. The catalysts were characterized by nitrogen (N{sub 2}) physisorption (BET area), X-ray diffraction, Infrared, Raman and UV-vis spectroscopies. Catalytic evaluations were determined using a fixed bed reactor with a water/ethanol mol ratio of 4 at 450 degrees C. The tungsten concentration studied was from 0.5 to 3 wt percent. The intensity of crystalline reflections of the Co-hydrotalcite catalysts decreased as tungsten concentration increased. Infrared spectroscopy was used to determine the superficial chemical groups, notably -OH, H{sub 2}O, Al-OH, Mg-OH, W-O-W and CO{sub 3}{sup 2.} The highest H{sub 2} production and the best catalytic stability was found in catalysts with low tungsten. The smallest pore volume of this catalyst could be related with long residence times of ethanol in the pores. Tungsten promoted the conversion for the Co-hydrotalcite catalysts. The reaction products were H{sub 2}, CO{sub 2}, CH{sub 3}CHO, CH{sub 4} and C{sub 2}H{sub 4} and the catalysts did not produce CO. 33 refs., 2 tabs., 10 figs.

  13. Study of tungsten based positron moderators

    Energy Technology Data Exchange (ETDEWEB)

    Lucio, O.G. de; Pérez, M.; Mendoza, U.; Morales, J.G.; Cruz, J.C. [Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México DF (Mexico); DuBois, R.D. [Missouri University of Science and Technology, Rolla, MO 65409 (United States)

    2015-07-01

    Positrons and how they interact with matter has a growing interest in many fields. Most of their uses require the production of slow positron beams with a well-defined energy, but since these particles are usually generated by means of a radioactive source, they are fast and with a broad distribution of energies. For this reason it is necessary to moderate them to lower energies via inelastic collisions. Then, they can be accelerated to the desired energies. This requires the use of a moderator. Tungsten is one of the most commonly used moderator materials because of its reasonable efficiency and relatively low cost. In this work we present different methods of producing transmission tungsten-based moderators, with particular interest in a combination of tungsten thin foils and grids. We also show results about the characterization of these moderators by ion beam analysis and microscopy techniques along with their relative moderation efficiencies.

  14. 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.

  15. Raman scattering from rapid thermally annealed tungsten silicide

    Science.gov (United States)

    Kumar, Sandeep; Dasgupta, Samhita; Jackson, Howard E.; Boyd, Joseph T.

    1987-01-01

    Raman scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films have been formed by rapid thermal annealing of thin tungsten films sputter deposited on silicon substrates. The Raman data are interpreted by using data from resistivity measurements, Auger and Rutherford backscattering measurements, and scanning electron microscopy.

  16. 40 CFR 721.10168 - Cesium tungsten oxide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  17. Tungsten carbide promoted Pd and Pd-Co electrocatalysts for formic acid electrooxidation

    Science.gov (United States)

    Yin, Min; Li, Qingfeng; Jensen, Jens Oluf; Huang, Yunjie; Cleemann, Lars N.; Bjerrum, Niels J.; Xing, Wei

    2012-12-01

    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 oxidation. Alloying of Pd with Co further improves the electrocatalytic activity and stability of the WC supported catalysts, attributable to a synergistic effect of the carbide support and PdCo alloy nanoparticles.

  18. The WEST project: Current status of the ITER-like tungsten divertor

    Energy Technology Data Exchange (ETDEWEB)

    Missirlian, M., E-mail: marc.missirlian@cea.fr; Bucalossi, J.; Corre, Y.; Ferlay, F.; Firdaouss, M.; Garin, P.; Grosman, A.; Guilhem, D.; Gunn, J.; Languille, P.; Lipa, M.; Richou, M.; Tsitrone, E.

    2014-10-15

    Highlights: • We presented the ITER-like W components occurred for the WEST divertor. • The main features including key elements of the design were detailed. • The main results of studies investigating the integration constraints or issues were reported. • The WEST ITER-like divertor design reached a mature stage to enable the launching of the procurement phase. - Abstract: The WEST (W – for tungsten – Environment in Steady-state Tokamak) project is an upgrade of Tore Supra from a limiter based tokamak with carbon PFCs into an X-point divertor tokamak with full-tungsten armour while keeping its long discharge capability. The WEST project will primarily offer the key capability of testing for the first time the ITER technology in real plasma environment. In particular, the main divertor (i.e. the lower divertor) of the WEST project will be based on actively cooled tungsten monoblock components and will follow as closely as possible the design and the assembling technology, foreseen for the ITER divertor units. The current design of WEST ITER-like tungsten divertor has now reached a mature stage following the 2013 WEST Final Design Review. This paper presents the key elements of the design, reports the technological requirements and reviews the main design and integration issues.

  19. Preparation of tungsten carbide nanoparticles by ion implantation and electrochemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Kato, S. [Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yamaki, T., E-mail: yamaki.tetsuya@jaea.go.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yamamoto, S.; Hakoda, T. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kawaguchi, K. [Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Kobayashi, T. [RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 350-0198 (Japan); Suzuki, A.; Terai, T. [Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2013-11-01

    Glassy carbon (GC) substrates were implanted with 100 keV tungsten ions at retained fluences of 4 × 10{sup 16} and 6 × 10{sup 16} ions/cm{sup 2} and surface-etched electrochemically in order to prepare tungsten-carbide (WC) nanoparticles on their topmost layers. The calculated current efficiency for the electrochemical etching was nearly the same for the two samples implanted at different fluences, suggesting the controllability of the etched depth using the consumed electric charge. The etching front reached the buried tungsten-implanted layer and increased the tungsten concentration at the surface. No oxidation of WC was observed, even under anodic potential application during electrochemical etching. The voltammogram response of the topmost nanoparticle layer was too small to be observed, probably due to the limited activity of the WC itself and the remaining low concentration. It was demonstrated that this technique could, in principle, be applied to various types of nanoparticle catalysts implanted in GC substrates.

  20. Thermal cycling and high power density hydrogen ion beam irradiation of tungsten layers on tungsten substrate

    Science.gov (United States)

    Airapetov, A. A.; Begrambekov, L. B.; Gretskaya, I. Yu; Grunin, A. V.; Dyachenko, M. Yu; Puntakov, N. A.; Sadovskiy, Ya A.

    2016-09-01

    Tungsten layers with iron impurity were deposited on tungsten substrates modeling re-deposited layers in a fusion device. The samples were tested by thermocycling and hydrogen ion beam tests. Thermocycling revealed globule formation on the surface. The size of the globules depended on iron impurity content in the coating deposited. Pore formation was observed which in some cases lead to exfoliation of the coatings. Hydrogen ion irradiation lead to formation of blisters on the coating and finally its exfoliation.

  1. Aluminum-tungsten fiber composites with cylindrical geometry and controlled architecture of tungsten reinforcement

    OpenAIRE

    Lucchese, Carl Joesph

    2010-01-01

    A aluminum matrix-W rod/wire structural material in support of DARPA initiative BAA 08-23 was developed and its density and mechanical strength ascertained, both being part of the DARPA matrices. Aluminum tubes and four 90 degree cross-ply tungsten fiber layers were arranged such that under extreme static pressure conditions the aluminum would viscoplastically flow into the tungsten arrangement to create a metal matrix composite. It was found that a cold isostatic process induced "Brazilian" ...

  2. 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.

  3. A Study of Scandia Doped Tungsten Nano-Powders

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The particle size of doped tungsten and distribution of scandia and rhenium were studied by SEM, EDS, XRD and granularity analysis. Experimental results showed that scandia distributed evenly on the surface of tungsten particles. Addition of scandia and rhenium decreased the particle size of doped tungsten, and the more the content of scandia and rhenium, the smaller the doped tungsten particles. Tungsten powders doped with 3% Sc2O3 and 3% Re (mass fraction) had an average size of about 80 nm in diameter. The mechanism of the decrease in the tungsten particle size was discussed.

  4. Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

    Science.gov (United States)

    Ghasempour, Fariba; Azimirad, Rouhollah; Amini, Abbas; Akhavan, Omid

    2015-05-01

    Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400-800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50-90 nm and crystalline phase of WO3) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K2W6O19 crystalline phase were formed on the foils. The WO3 nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K2W6O19 microrods formed at 800 °C could inactivate only ∼45% of the bacteria at the same conditions.

  5. Deuterium implantation into tungsten at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Johannes [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Physik-Department E28, Technische Universitaet Muenchen, James-Franck-Str. 1, D-85748 Garching (Germany); Schwarz-Selinger, Thomas; Balden, Martin; Schmid, Klaus [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

    2016-07-01

    To study the interaction of hydrogen isotopes with tungsten many experiments are conducted in linear plasma devices, which provide high enough hydrogen fluxes to supersaturate the tungsten sample and create defects such as blister. Here an alternative approach is presented. Instead of achieving a high deuterium concentration via high flux exposure, the sample temperature is reduced and the implantation energy of deuterium into tungsten is increased. The lower temperature associated with a reduction in diffusivity as well as the deeper implantation of deuterium lead to an increase of deuterium concentration within the implantation zone. Deuterium is stepwise implanted into polycrystalline tungsten up to a fluence of 1 x 10{sup 22} D/m{sup 2} with an energy of 3.0 keV/D at a sample temperature of 134 K. The retained deuterium is measured in-situ by nuclear reaction analysis. For low fluence approximately 100 % of the implanted deuterium is retained, while for higher fluence the retention saturates. Close to the surface deuterium concentrations up to 64 % are reached. This leads to massive grain orientation dependent blistering with blister sizes between 100-1000 nm at depths between 30-150 nm. Besides the characterization of the blisters their influence on deuterium transport is studied.

  6. OPAL Example Segment of Silicon Tungsten Luminometer

    CERN Multimedia

    OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. The Silicon Tungsten Luminometer was part of OPAL's calorimeter which was used to measure the energy of particles. Most particles end their journey in calorimeters. These detectors measure the energy deposited when particles are slowed down and stopped.

  7. Gas tungsten arc welder with electrode grinder

    Science.gov (United States)

    Christiansen, David W.; Brown, William 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 axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  8. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 2.64E11 protons @ 440 GeV are impinging on the target.

  9. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    HiRadMat facility of CERN/SPS

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 1.7E11 protons @ 440 GeV are impinging on the target.

  10. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 1.85E11 protons @ 440 GeV are impinging on the target.

  11. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 2E11 protons @ 440 GeV are impinging on the target.

  12. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 1.3E11 protons @ 440 GeV are impinging on the target.

  13. 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

  14. Indication of worn WC/C surface locations of a dry-running twin-screw rotor by the oxygen incorporation in tungsten-related Raman modes

    Science.gov (United States)

    Debus, J.; Schindler, J. J.; Waldkirch, P.; Goeke, S.; Brümmer, A.; Biermann, D.; Bayer, M.

    2016-10-01

    By comparing the worn and untouched locations of a tungsten-carbide/carbon surface of a dry-running twin-screw rotor, we demonstrate that tungsten-oxide Raman modes become observable only at worn locations and the integral intensity of the Raman line at 680 cm-1, which is related to the incipient oxidation of the tungsten-carbide stretching mode, is enhanced. Its frequency and width moreover change significantly, thus indicating the mechanical distortion of the bonding that has been occurred during the wearing process. The shape of the tungsten-oxide Raman lines, resembling the Voigt function, hints at a surface morphology that is a characteristic for an amorphous solid environment. Our Raman scattering results may be exploited to characterize the degree of wear of coated surfaces and to identify signatures of a tribological layer.

  15. Enhancement of hydrogen isotope retention capacity for the impurity deposited tungsten by long-term plasma exposure in LHD

    Energy Technology Data Exchange (ETDEWEB)

    Oya, Yasuhisa, E-mail: syoya@ipc.shizuoka.ac.jp [Radioscience Research Laboratory, Faculty of Science, Shizuoka University, Shizuoka 422-8529 (Japan); Masuzaki, Suguru; Tokitani, Masayuki [National Institute for Fusion Science, Gifu 509-5292 (Japan); Yoshida, Naoaki; Watanabe, Hideo [Kyushu University, Fukuoka 816-8580 (Japan); Yamauchi, Yuji; Hino, Tomoaki [Hokkaido University, Sapporo 060-8628 (Japan); Miyamoto, Mitsutaka [Shimane University, Shimane 690-8504 (Japan); Hatano, Yuji [University of Toyama, Toyama 930-8555 (Japan); Okuno, Kenji [Radioscience Research Laboratory, Faculty of Science, Shizuoka University, Shizuoka 422-8529 (Japan)

    2013-10-15

    Highlights: • The carbon-dominant mixed-material layer was formed on the tungsten surface after 15{sup th} plasma exposure in LHD. • The largest enhancement of deuterium retention was found to be about 21. • The major deuterium desorption temperature was shifted toward higher temperature side. -- Abstract: The stress relieved tungsten samples were placed at three positions, PI (sputtering erosion dominated area), DP (deposition dominated area) and HL (Higher heat load area) during 15th plasma experiment campaign in Large Helical Device (LHD) at National Institute for Fusion Science (NIFS), Japan and were exposed to ∼ 6700 shots of hydrogen plasma in a 15th long-term experiment campaign in LHD. Thereafter, the additional deuterium ion implantation to these tungsten samples was performed to evaluate the change of hydrogen isotope retention capacity in the samples by long-term plasma exposure. It was found that the carbon-dominant mixed-material layer with more than 100 nm thickness was formed on a wide area of the tungsten surface. The thicker mixed-material layer was formed on the DP sample, where the deuterium retention was about 21 times as high as that for pure W. The major desorption temperature of deuterium was shifted toward higher temperature side, which was comparable to the trapping characteristic of carbon or irradiation damages.

  16. Microstructure and properties of liquid-phase sintered tungsten heavy alloys by using ultra-fine tungsten powders

    Institute of Scientific and Technical Information of China (English)

    于洋; 王尔德

    2004-01-01

    The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquidphase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.

  17. 碳化钨和Vulcan XC-72炭黑载钯催化剂对甲酸氧化的电催化性能%Electrocatalytic Performance of Tungsten Carbide and Vulcan XC-72 Carbon Supported Pd Catalyst for Formic Acid Oxidation

    Institute of Scientific and Technical Information of China (English)

    沈娟章; 季芸; 陈赵杨; 马淳安; 陆天虹

    2012-01-01

    研究了碳化钨(WC)和Vulcan XC-72炭黑(XC)作混合载体的Pd/WC-XC催化剂对甲酸氧化的电催化性能.发现Pd/WC-XC催化剂对甲酸氧化的电催化性能优于Pd/XC催化剂.而且,Pd/WC-XC催化剂的电催化性能与WC和XC的质量比有关,当质量比为3:1时,催化剂对甲酸氧化的电催化活性最好,当质量比为2:1时,催化剂对甲酸氧化的电催化稳定性性最好.%This work investigated the elecrocatalytic performance of tungsten carbide(WC) and Vulcan XC-72 carbon (XC) supported Pd(Pd/WC-XC) catalysts for formic acid oxidation.It is found that the electrocatalytic performance of the Pd/WC-XC catalysts for formic acid oxidation is better than that of the Pd/XC catalyst.Furthermore,the electrocatalytic performance of the Pd/WC-XC catalyst is related to the mass ratio of WC and XC.When the mass ratio of WC and XC is 3:1,the electrocatalytic activity of the catalyst is best.When the mass ratio of WC and XC is 2:1,the electrocatalytic stability of the catalyst is best.

  18. Gas-driven permeation of deuterium through tungsten and tungsten alloys

    Energy Technology Data Exchange (ETDEWEB)

    Buchenauer, Dean A., E-mail: dabuche@sandia.gov [Sandia National Laboratories, Energy Innovation Department, Livermore, CA 94550 (United States); Karnesky, Richard A. [Sandia National Laboratories, Energy Innovation Department, Livermore, CA 94550 (United States); Fang, Zhigang Zak; Ren, Chai [University of Utah, Department of Metallurgical Engineering, Salt Lake City, UT 84112 (United States); Oya, Yasuhisa [Shizuoka University, Graduate School of Science, Shizuoka (Japan); Otsuka, Teppei [Kyushu University, Department of Advanced Energy Engineering Science, Fukuoka (Japan); Yamauchi, Yuji [Hokkaido University, Third Division of Quantum Science and Engineering, Faculty of Engineering, Sapporo (Japan); Whaley, Josh A. [Sandia National Laboratories, Energy Innovation Department, Livermore, CA 94550 (United States)

    2016-11-01

    Highlights: • We have designed and performed initial studies on a high temperature gas-driven permeation cell capable of operating at temperatures up to 1150 °C and at pressures between 0.1–1 atm. • Permeation measurements on ITER grade tungsten compare well with past studies by Frauenfelder and Zahkarov in the temperature range from 500 to 1000 °C. • First permeation measurements on Ti dispersoid-strengthened ultra-fine grained tungsten show higher permeation at 500 °C, but very similar permeation with ITER tungsten at 1000 °C. Diffusion along grain boundaries may be playing a role for this type of material. - Abstract: To address the transport and trapping of hydrogen isotopes, several permeation experiments are being pursued at both Sandia National Laboratories (deuterium gas-driven permeation) and Idaho National Laboratories (tritium gas- and plasma-driven tritium permeation). These experiments are in part a collaboration between the US and Japan to study the performance of tungsten at divertor relevant temperatures (PHENIX). Here we report on the development of a high temperature (≤1150 °C) gas-driven permeation cell and initial measurements of deuterium permeation in several types of tungsten: high purity tungsten foil, ITER-grade tungsten (grains oriented through the membrane), and dispersoid-strengthened ultra-fine grain (UFG) tungsten being developed in the US. Experiments were performed at 500–1000 °C and 0.1–1.0 atm D{sub 2} pressure. Permeation through ITER-grade tungsten was similar to earlier W experiments by Frauenfelder (1968–69) and Zaharakov (1973). Data from the UFG alloy indicates marginally higher permeability (< 10×) at lower temperatures, but the permeability converges to that of the ITER tungsten at 1000 °C. The permeation cell uses only ceramic and graphite materials in the hot zone to reduce the possibility for oxidation of the sample membrane. Sealing pressure is applied externally, thereby allowing for elevation

  19. Microwave synthesis of ultrafine and nanosized powders of tungsten oxide and carbide

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaenko, Irina; Kedin, Nikolay; Shveikin, Gennadii; Polyakov, Evgenii [Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Solid State Chemistry

    2014-03-15

    A new method of synthesis of nanosized and ultrafine tungsten oxide and carbide powders is offered, which combines carbon carrier supported classical liquid-phase precipitation and low-temperature microwave treatment. The full range of intermediate substances obtained during thermolysis, reduction and carburization of precursors to final products is presented. It is shown that cooling of ammonium tungstate solution to 4 C and the use of carbon carrier at the precipitation stage can increase the specific surface area from 20 to 100 m{sup 2} g{sup -1}. (orig.)

  20. Immobilization of Platinum Nanoparticles on 3,4-diaminobenzoyl-Functionalized Multi-Walled Carbon Nanotube and its Electrocatalytic Activity

    Science.gov (United States)

    2012-01-01

    650 C was 48 wt%, which is attributed to thermo-oxidative stripping of the DAB moiety (Fig. 2b). The value agreed well with the feed ratio of DAB...1979b) The use of linear potential sweep voltammetry and of ac voltammetry for the study of the surface electro- chemical reaction of strongly adsorbed...Xin Q (2003) Preparation and characterization of multiwalled carbon nanotube-supported platinum for cathode catalysts of direct methanol fuel cells

  1. 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)

  2. 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...

  3. Compatibility of ITER scenarios with full tungsten wall in ASDEX Upgrade

    Science.gov (United States)

    Gruber, O.; Sips, A. C. C.; Dux, R.; Eich, T.; Fuchs, J. C.; Herrmann, A.; Kallenbach, A.; Maggi, C. F.; Neu, R.; Pütterich, T.; Schweinzer, J.; Stober, J.; ASDEX Upgrade Team

    2009-11-01

    The transition of ASDEX Upgrade (AUG) from a graphite device to a full tungsten device is demonstrated with a reduction by an order of magnitude in both the carbon deposition and deuterium retention. The tungsten source is dominated by sputtering from intrinsic light impurities, and the tungsten influxes from the outboard limiters are the main source for the plasma. In H-mode discharges, central heating (neutral beams, ECRH) is used to increase turbulent outward transport avoiding tungsten accumulation. ICRH can only be used after boronization as its application otherwise results in large W influxes due to light impurities accelerated by electrical fields at the ICRH antennas. ELMs are important in reducing the inward transport of tungsten in the H-mode edge barrier and are controlled by gas puffing. Even without boronization, stationary, ITER baseline H-modes (confinement enhancement factor from ITER 98(y, 2) scaling H98 ~ 1, normalized beta βN ~ 2), with W concentrations below 3 × 10-5 were routinely achieved up to 1.2 MA plasma current. The compatibility of high performance improved H-modes with unboronized W wall was demonstrated, achieving H98 = 1.1 and βN up to 2.6 at modest triangularities δ cooled by N2 seeding. N2 seeding does not only protect the divertor tiles but also considerably improves the performance of improved H-mode discharges. The energy confinement increased to H98-factors of 1.25 (βN ~ 2.7) and thereby exceeded the best values in a carbon-dominated AUG machine under similar conditions. Recent investigations show that this improvement is due to higher temperatures rather than to peaking of the electron density profile. Further ITER discharge scenario tests include the demonstration of ECRF assisted low voltage plasma start-up and current rise to q95 = 3 at toroidal electric fields below 0.3 V m-1, to achieve a ITER compatible range of plasma internal inductance of 0.71-0.97. The results reported here strongly support tungsten as a first

  4. Laser surface infiltration of tungsten-carbide in steel and aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dahotre, N.B.; Mukherjee, K. (Michigan State Univ., East Lansing (USA))

    It has been demonstrated that surface modification in metals and alloys can be achieved by laser melting in conjunction with injection of particulate alloying elements in the heated zone. In our current experiments the authors have successfully implanted tungsten-carbide particles on the surface of several grades of carbon-steels as well as on the surface of a structural aluminum alloy. In both cases a significant increase in microhardness has been detected. Hardness profile from the interaction zone to the heat affected zone (HAZ) has been determined. The microstructural features of both the implanted zone and HAZ also have been determined. Effect of laser input energy, nature of tungsten-carbide particle size, size distribution and method of powder injection on the hardness profile have been investigated. Some preliminary examination of surface wear of such implanted material is also conducted. These results are discussed in detail.

  5. Femtosecond fiber laser additive manufacturing of tungsten

    Science.gov (United States)

    Bai, Shuang; Liu, Jian; Yang, Pei; Zhai, Meiyu; Huang, Huan; Yang, Lih-Mei

    2016-04-01

    Additive manufacturing (AM) is promising to produce complex shaped components, including metals and alloys, to meet requirements from different industries such as aerospace, defense and biomedicines. Current laser AM uses CW lasers and very few publications have been reported for using pulsed lasers (esp. ultrafast lasers). In this paper, additive manufacturing of Tungsten materials is investigated by using femtosecond (fs) fiber lasers. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, microstructural and mechanical properties of the processed components. Fully dense Tungsten part with refined grain and increased hardness was obtained and compared with parts made with different pulse widths and CW laser. The results are evidenced that the fs laser based AM provides more dimensions to modify mechanical properties with controlled heating, rapid melting and cooling rates compared with a CW or long pulsed laser. This can greatly benefit to the make of complicated structures and materials that could not be achieved before.

  6. 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.

  7. Epitaxial growth of tungsten nanoparticles on alumina and spinel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T; Lopez-Esteban, S; Pecharroman, C; Esteban-Cubillo, A; Moya, J S [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz 3, 28049, Cantoblanco, Madrid (Spain); Diaz, L A; Torrecillas, R [Nanomaterials and Nanotechnology Research Center (CINN), Consejo Superior de Investigaciones CientIficas (CSIC), C/ Francisco Pintado Fe 26, 33011, Oviedo, Asturias (Spain); Gremillard, L [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)], E-mail: jsmoya@icmm.csic.es

    2008-05-28

    Isolated tungsten nanoparticles ({alpha}-W and {beta}-W phase) were synthesized and epitaxially grown on alumina and spinel particle surfaces with an average tungsten size of {<=}20 nm for a low tungsten content (of {<=}1.5 vol%). Using tungsten (VI) ethoxide alcoholic solutions, tungsten trioxide hydrated precursors were attached to a ceramic grains surface as a nanoparticle coating. High-resolution transmission electron microscopy (HRTEM) micrographs showed epitaxial interfaces between alumina, spinel and metallic tungsten. This epitaxial growth is assumed to be due to the effect of water vapour on the sublimation of ortho-tungstic acid during the reduction process in a hydrogen atmosphere. The planes involved in the epitaxy were found to be (22-bar 0){sub Al2O3} parallel (121){sub W} and (311){sub MgAl2O4} parallel (110){sub W}.

  8. Induction plasma spheroidization of tungsten and molybdenum powders

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.

  9. Synthesis and electrical characterization of tungsten oxide nanowires

    Institute of Scientific and Technical Information of China (English)

    Huang Rui; Zhu Jing; Yu Rong

    2009-01-01

    Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition (CVD) method with vapour-solid (VS) mechanism. Tin powders are used to control oxygen concentration in the furnace, thereby assisting the growth of the tungsten oxide nanowires. The grown tungsten oxide nanowires are determined to be of crystalline W18O49. Ⅰ-Ⅴ curves are measured by an in situ transmission electron microscope (TEM) to investigate the electrical properties of the nanowires. All of the Ⅰ-Ⅴ curves observed are symmetric, which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I V curves by using a metal-semiconductor-metal (MSM) model give some intrinsic parameters of the tungsten oxide nanowires, such as the carrier concentration, the carrier mobility and the conductivity.

  10. Tungsten Speciation in Firing Range Soils

    Science.gov (United States)

    2011-01-01

    thus are composed of single minerals. Iron minerals used in fitting included ferrihydrite, hematite , goethite, biotite, hornblende, and pyrite, which...tungstate adsorbing on ferrihy- drite. Ferrihydrite was selected for these tests as earlier X-ray microprobe studies indicated that this was the primary ...Camp Edwards soil profile 31T as a function of depth. The spectra all indicate that the primary coordination sphere of tungsten is dominated by

  11. Luminescence of carbon nanotube bulbs

    Institute of Scientific and Technical Information of China (English)

    LI ChuanGang; WU DeHai; WANG KunLin; WEI JinQuan; WEI BingQing; ZHU HongWei; WANG ZhiCheng; LUO JianBin; LIU WenJin; ZHENG MingXin

    2007-01-01

    Carbon nanotube (CNT) bulbs made of decimeter-scale double-walled carbon nanotube (DWCNT) strands and films were fabricated and their luminescence properties, including the lighting efficiency, voltage-current relation and thermal stability were investigated. The results show that the DWCNT bulb has a comparable spectrum of visible light with tungsten bulb and its average efficiency is 40% higher than that of a tungsten filament at the same temperature (1400-2300 K). The nanotube filaments show both resistance and thermal stability over a large temperature region. No obvious damage was found for a nanotube bulb illuminating at 2300 K for more than 24 hours in vacuum.

  12. Defect and electrical properties of nanocrystalline tungsten trioxide

    Institute of Scientific and Technical Information of China (English)

    Yang Xin-Sheng; Wang Yu; Dong Liang; Qi Li-Zhen; Zhang Feng

    2004-01-01

    Nanocrystalline tungsten trioxide particles were prepared by a wet-chemical method. Transmission electron microscope (TEM) analysis shows that the average grain size is about 15nm. The oxygen deficiency of nanometre-sized sample is higher than that of ordinary tungsten trioxide. The electric conductivity increases because of high oxygen deficiency. Ironic relaxation polarization and crystallographic shear (CS) planes theory were used to explain the unusual dielectric characteristic of nanocrystalline tungsten trioxide.

  13. Powder Processing of Amorphous Tungsten-bearing Alloys and Composites

    Science.gov (United States)

    2015-03-01

    8725 John J. Kingman Road, MS-6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-14-73 Powder Processing of Amorphous Tungsten ...Technology, Boise State University, Army Research Laboratory Project Title: Powder Processing of Amorphous Tungsten -bearing Alloys and Composites...strength, we made them better suited to study the mechanical alloying of tungsten -transition metal couples in which interdiffusion during mechanical

  14. The Tungsten Demand and Supply Situation in Recent Years

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>Tungsten is an important and valuable resource listed by the State as a kind of special minerals under the State protection. By the end of 2005, China had 310 tungsten mining areas with the total tungsten deposit amounting to 5.69 million tons. Among the total deposit, wolframite accounts for approximately 20.8 per cent and scheelite accounts for about 70 per cent with

  15. Chemical vapour deposition of tungsten and tungsten silicide layers for applications in novel silicon technology

    CERN Document Server

    Li, F X

    2002-01-01

    This work was a detailed investigation into the Chemical Vapour Deposition (CVD) of tungsten and tungsten silicide for potential applications in integrated circuit (IC) and other microelectronic devices. These materials may find novel applications in contact schemes for transistors in advanced ICs, buried high conductivity layers in novel Silicon-On-Insulator (SOI) technology and in power electronic devices. The CVD techniques developed may also be used for metal coating of recessed or enclosed features which may occur in novel electronic or electromechanical devices. CVD of tungsten was investigated using the silicon reduction reaction of WF sub 6. W layers with an optimum self-limiting thickness of 100 nm and resistivity 20 mu OMEGA centre dot cm were produced self-aligned to silicon. A hydrogen passivation technique was developed as part of the wafer pre-clean schedule and proved essential in achieving optimum layer thickness. Layers produced by this approach are ideal for intimate contact to shallow junct...

  16. Secondary electron emission from plasma-generated nanostructured tungsten fuzz

    Science.gov (United States)

    Patino, M.; Raitses, Y.; Wirz, R.

    2016-11-01

    Recently, several researchers [e.g., Yang et al., Sci. Rep. 5, 10959 (2015)] have shown that tungsten fuzz can grow on a hot tungsten surface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facing tungsten components. This work reports the direct measurements of the total effective secondary electron emission (SEE) from tungsten fuzz. Using dedicated material surface diagnostics and in-situ characterization, we find two important results: (1) SEE values for tungsten fuzz are 40%-63% lower than for smooth tungsten and (2) the SEE values for tungsten fuzz are independent of the angle of the incident electron. The reduction in SEE from tungsten fuzz is most pronounced at high incident angles, which has important implications for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively higher sheath potential difference that reduces plasma electron energy loss to the confining wall. Thus, the presence or self-generation in a plasma of a low SEE surface such as tungsten fuzz can be desirable for improved performance of many plasma devices.

  17. Tungsten-induced carcinogenesis in human bronchial epithelial cells

    Science.gov (United States)

    Laulicht, Freda; Brocato, Jason; Cartularo, Laura; Vaughan, Joshua; Wu, Feng; Kluz, Thomas; Sun, Hong; Oksuz, Betul Akgol; Shen, Steven; Paena, Massimilano; Medici, Serenella; Zoroddu, Maria Antonietta; Costa, Max

    2015-01-01

    Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten (W), remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. Here, for the first time, we demonstrate tungsten’s ability to induce carcinogenic related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer related pathways in transformed clones as determined by RNA seq. Human bronchial epithelial cell line (Beas-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA-sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten. Taken together, our data shows the carcinogenic potential of tungsten. Further tests are needed, including in vivo and human studies, in order to validate tungsten as a carcinogen to humans. PMID:26164860

  18. Toxicologic evaluation of tungsten: 28-day inhalation study of tungsten blue oxide in rats.

    Science.gov (United States)

    Rajendran, Narayanan; Hu, Shu-Chieh; Sullivan, Dennis; Muzzio, Miguel; Detrisac, Carol J; Venezia, Carmen

    2012-12-01

    The toxicity and toxicokinetics of tungsten blue oxide (TBO) were examined. TBO is an intermediate in the production of tungsten powder, and has shown the potential to cause cellular damage in in vitro studies. However, in vivo evidence seems to indicate a lack of adverse effects. The present study was undertaken to address the dearth of longer-term inhalation toxicity studies of tungsten oxides by investigating the biological responses induced by TBO when administered via nose-only inhalation to rats at levels of 0.08, 0.325, and 0.65 mg TBO/L of air for 6 h/day for 28 consecutive days, followed by a 14-day recovery period. Inhaled TBO was absorbed systemically and blood levels of tungsten increased as inhaled concentration increased. Among the tissues analyzed for tungsten levels, lung, femur and kidney showed increased levels, with lung at least an order of magnitude greater than kidney or femur. By exposure day 14, tungsten concentration in tissues had reached steady-state. Increased lung weight was noted for both terminal and recovery animals and was attributed to deposition of TBO in the lungs, inducing a macrophage influx. Microscopic evaluation of tissues revealed a dose-related increase in alveolar pigmented macrophages, alveolar foreign material and individual alveolar foamy macrophages in lung. After a recovery period there was a slight reduction in the incidence and severity of histopathological findings. Based on the absence of other adverse effects, the increased lung weights and the microscopic findings were interpreted as nonadverse response to exposure and were not considered a specific reaction to TBO.

  19. 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.

  20. 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.

  1. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    Energy Technology Data Exchange (ETDEWEB)

    Li, T. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Optics and Fine Mechanics; Northwest Institute of Nuclear Technology, Xi' an (China); Lou, Q.; Dong, J.; Wei, Y. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Optics and Fine Mechanics; Liu, J. [Northwest Institute of Nuclear Technology, Xi' an (China)

    2001-09-01

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm{sup 2}. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 {mu}m to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 {mu}m with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to {beta}WC{sub 1-x}, then to {alpha}W{sub 2}C and CW{sub 3}, and finally to W crystal. It is suggested that the undulating 'hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation. (orig.)

  2. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    Science.gov (United States)

    Li, T.; Lou, Q.; Dong, J.; Wei, Y.; Liu, J.

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm2. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to βWC1-x, then to αW2C and CW3, and finally to W crystal. It is suggested that the undulating `hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation.

  3. Covalent attachment of diamondoid phosphonic acid dichlorides to tungsten oxide surfaces.

    Science.gov (United States)

    Li, Fei Hua; Fabbri, Jason D; Yurchenko, Raisa I; Mileshkin, Alexander N; Hohman, J Nathan; Yan, Hao; Yuan, Hongyuan; Tran, Ich C; Willey, Trevor M; Bagge-Hansen, Michael; Dahl, Jeremy E P; Carlson, Robert M K; Fokin, Andrey A; Schreiner, Peter R; Shen, Zhi-Xun; Melosh, Nicolas A

    2013-08-06

    Diamondoids (nanometer-sized diamond-like hydrocarbons) are a novel class of carbon nanomaterials that exhibit negative electron affinity (NEA) and strong electron-phonon scattering. Surface-bound diamondoid monolayers exhibit monochromatic photoemission, a unique property that makes them ideal electron sources for electron-beam lithography and high-resolution electron microscopy. However, these applications are limited by the stability of the chemical bonding of diamondoids on surfaces. Here we demonstrate the stable covalent attachment of diamantane phosphonic dichloride on tungsten/tungsten oxide surfaces. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy revealed that diamondoid-functionalized tungsten oxide films were stable up to 300-350 °C, a substantial improvement over conventional diamondoid thiolate monolayers on gold, which dissociate at 100-200 °C. Extreme ultraviolet (EUV) light stimulated photoemission from these diamondoid phosphonate monolayers exhibited a characteristic monochromatic NEA peak with 0.2 eV full width at half-maximum (fwhm) at room temperature, showing that the unique monochromatization property of diamondoids remained intact after attachment. Our results demonstrate that phosphonic dichloride functionality is a promising approach for forming stable diamondoid monolayers for elevated temperature and high-current applications such as electron emission and coatings in micro/nano electromechanical systems (MEMS/NEMS).

  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. Behavior of tungsten fiber-reinforced tungsten based on single fiber push-out study

    Directory of Open Access Journals (Sweden)

    B. Jasper

    2016-12-01

    Full Text Available To overcome the intrinsic brittleness of tungsten (W, a tungsten fiber-reinforced tungsten-composite material (Wf/W is under development. The composite addresses the brittleness of W by extrinsic toughening through the introduction of energy dissipation mechanisms. These mechanisms allow the reduction of stress peaks and thus improve the materials resistance against crack growth. They do not rely on the intrinsinc material properties such as ductility. By utilizing powder metallurgy (PM one could benefit from available industrialized approaches for composite production and alloying routes. In this contribution the PM method of hot isostatic pressing (HIP is used to produce Wf/W samples containing W fibers coated with an Er2O3 interface. Analysis of the matrix material demonstrates a dense tungsten bulk, a deformed fiber and a deformed, but still intact interface layer. Metallographic analysis reveals indentations of powder particles in the interface, forming a complex 3D structure. Special emphasis is placed on push-out tests of single fiber HIP samples, where a load is applied via a small indenter on the fiber, to test the debonding and frictional properties of the Er2O3 interface region enabling the energy dissipation mechanisms. Together with the obtained experimental results, an axisymmetric finite element model is discussed and compared to existing work. In the HIP Wf/W composites the matrix adhesion is rather large and can dominate the push-out behavior. This is in contrast to the previously tested CVD produced samples.

  6. On the onset of void swelling in pure tungsten under neutron irradiation: An object kinetic Monte Carlo approach

    Science.gov (United States)

    Castin, N.; Bakaev, A.; Bonny, G.; Sand, A. E.; Malerba, L.; Terentyev, D.

    2017-09-01

    We propose an object kinetic Monte Carlo (OKMC) model for describing the microstructural evolution in pure tungsten under neutron irradiation. We here focus on low doses (under 1 dpa), and we neglect transmutation in first approximation. The emphasis is mainly centred on an adequate description of neutron irradiation, the subsequent introduction of primary defects, and their thermal diffusion properties. Besides grain boundaries and the dislocation network, our model includes the contribution of carbon impurities, which are shown to have a strong influence on the onset of void swelling. Our parametric study analyses the quality of our model in detail, and confronts its predictions with experimental microstructural observations with satisfactory agreement. We highlight the importance for an accurate determination of the dissolved carbon content in the tungsten matrix, and we advocate for an accurate description of atomic collision cascades, in light of the sensitivity of our results with respect to correlated recombination.

  7. Preparation and Electrocatalytic Activity of Tungsten Carbide Nanorod Arrays

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    High density tungsten carbide nanorod arrays have been prepared by magnetron sputtering (MS) using the aluminum lattice membrane (ALM) as template. Electrocatalytic properties of nitromethane electroreduction on the tungsten carbide nanorod arrays electrode were investigated by electrochemical method, and their electrocatalytic activity is approached to that of the Pt foil electrode.

  8. Tungsten and other refractory metals for VLSI applications II

    Energy Technology Data Exchange (ETDEWEB)

    Broadbent, E.K.

    1987-01-01

    This book presents papers on tungsten and other refractory metals for VLSI applications. Topics include the following: Selectivity loss and nucleation on insulators, fundamental reaction and growth studies, chemical vapor deposition of tungsten, chemical vapor deposition of molybdenum, reactive ion etching of refractory metal films; and properties of refractory metals deposited by sputtering.

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

    Science.gov (United States)

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

    2016-10-01

    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/m2 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.

  10. 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…

  11. 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…

  12. Microstructure and tensile properties of tungsten at elevated temperatures

    Science.gov (United States)

    Shen, Tielong; Dai, Yong; Lee, Yongjoong

    2016-01-01

    In order to support the development of the 5 MW spallation target for the European Spallation Source, the effect of fabrication process on microstructure, ductile-to-brittle transition temperature (DBTT), tensile and fracture behaviour of powder-metallurgy pure tungsten materials has been investigated. A hot-rolled (HR) tungsten piece of 12 mm thickness and a hot-forged (HF) piece of about 80 mm thickness were used to simulate the thin and thick blocks in the target. The two tungsten pieces were characterized with metallography analysis, hardness measurement and tensile testing. The HR piece exhibits an anisotropic grain structure with an average size of about 330 × 140 × 40 μm in rolling, long transverse and short transverse (thickness) directions. The HF piece possesses a bimodal grain structure with about 310 × 170 × 70 μm grain size in deformed part and about 25 μm sized grains remained from sintering process. Hardness (HV0.2) of the HR piece is slightly greater than that of the HF one. The ductility of the HR tungsten specimens is greater than that of the HF tungsten. For the HF tungsten piece, specimens with small grains in gauge section manifest lower ductility but higher strength. The DBTT evaluated from the tensile results is 250-300 °C for the HR tungsten and about 350 °C for the HF tungsten.

  13. Tungsten disulfide nanotubes reinforced biodegradable polymers for bone tissue engineering.

    Science.gov (United States)

    Lalwani, Gaurav; Henslee, Allan M; Farshid, Behzad; Parmar, Priyanka; Lin, Liangjun; Qin, Yi-Xian; Kasper, F Kurtis; Mikos, Antonios G; Sitharaman, Balaji

    2013-09-01

    In this study, we have investigated the efficacy of inorganic nanotubes as reinforcing agents to improve the mechanical properties of poly(propylene fumarate) (PPF) composites as a function of nanomaterial loading concentration (0.01-0.2 wt.%). Tungsten disulfide nanotubes (WSNTs) were used as reinforcing agents in the experimental group. Single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs) were used as positive controls, and crosslinked PPF composites were used as the baseline control. Mechanical testing (compression and three-point bending) shows a significant enhancement (up to 28-190%) in the mechanical properties (compressive modulus, compressive yield strength, flexural modulus and flexural yield strength) of WSNT-reinforced PPF nanocomposites compared to the baseline control. In comparison to the positive controls, significant improvements in the mechanical properties of WSNT nanocomposites were also observed at various concentrations. In general, the inorganic nanotubes (WSNTs) showed mechanical reinforcement better than (up to 127%) or equivalent to that of carbon nanotubes (SWCNTs and MWCNTs). Sol fraction analysis showed significant increases in the crosslinking density of PPF in the presence of WSNTs (0.01-0.2 wt.%). Transmission electron microscopy (TEM) analysis on thin sections of crosslinked nanocomposites showed the presence of WSNTs as individual nanotubes in the PPF matrix, whereas SWCNTs and MWCNTs existed as micron-sized aggregates. The trend in the surface area of nanostructures obtained by Brunauer-Emmett-Teller (BET) surface area analysis was SWCNTs>MWCNTs>WSNTs. The BET surface area analysis, TEM analysis and sol fraction analysis results taken together suggest that chemical composition (inorganic vs. carbon nanomaterials), the presence of functional groups (such as sulfide and oxysulfide) and individual dispersion of the nanomaterials in the polymer matrix (absence of aggregation of the reinforcing agent) are the key parameters

  14. High Heat Load Properties of Ultra Fine Grain Tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Z.; Du, J.; Ge, C. [Lab. of Special Ceramic and P/M, University of Science and Technology, 100083 Beijing (China); Linke, J.; Pintsuk, G. [FZJ-Forschungszentrum Juelich GmbH, Association Euratom-FZJ, Institut fur Plasmaphysik, Postfach 1913, D-52425 Juelich (Germany); Song, S.X. [Research Center on Fusion Materials (RCFM), University of Science and Technology Beijing (USTB), 100083 Beijing (China)

    2007-07-01

    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 {mu}m, 1 {mu}m and 3 {mu}m 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{sup 2} respectively. Horizontal cracks formed for all tungsten samples at 0.44 GW/m{sup 2}. Particle erosions occurred for tungsten with 3 {mu}m size at 0.33 GW/m{sup 2} and for tungsten with 0.2 and 1 {mu}m size at 0.55 GW/m{sup 2}. The weight loss of tungsten with 0.2, 1 and 3 {mu}m size are 2,0.1,0.6 mg respectively at 0.88 GW/m{sup 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 {mu}m size has

  15. Low temperature photoresponse of monolayer tungsten disulphide

    Directory of Open Access Journals (Sweden)

    Bingchen Cao

    2014-11-01

    Full Text Available High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup, while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  16. Double phase conjugation in tungsten bronze crystals.

    Science.gov (United States)

    Sharp, E J; Clark Iii, W W; Miller, M J; Wood, G L; Monson, B; Salamo, G J; Neurgaonkar, R R

    1990-02-20

    In this paper we report a new method for double phase conjugation particularly suited to the tungsten bronze crystal strontium barium niobate. It has also been observed to produce conjugate waves in BaTiO(3) and BSKNN. This new arrangement is called the bridge conjugator because the two beams enter opposing [100] crystal faces and fan together to form a bridge without reflection off a crystal face. Our measurements indicate that the bridge conjugator is competitive with previously reported double phase conjugate mirrors in reflectivity, response time, ease of alignment, and fidelity.

  17. Electrical properties of complex tungsten bronze ceramics

    Science.gov (United States)

    Padhee, R.; Das, Piyush R.

    2014-09-01

    This paper highlights the electrical properties of two new complex tungsten bronze ceramics (K2Pb2Eu2W2Ti4Nb4O30 and K2Pb2Pr2W2Ti4Nb4O30) which were prepared by high temperature mixed oxide method. Variation of impedance parameters with temperature (27-500 °C) and frequency (1 kHz to 5 MHz) shows the grain and grain boundary effects in the samples. The variation of dielectric parameters with frequency is also studied. The ac conductivity variation with temperature clearly exhibits that the materials have thermally activated transport properties of Arrhenius type.

  18. CALICE silicon-tungsten electromagnetic calorimeter

    Indian Academy of Sciences (India)

    G Mavromanolakis

    2007-12-01

    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 layers and depth of 7.2 0 at normal incidence, having in total 3024 channels of 1 cm2, was tested recently with - beam. We describe the prototype and discuss some preliminary testbeam results on its performance with respect to position resolution, response inhomogeneity and transverse containment.

  19. A study on consumable aided tungsten indirect arc welding

    Institute of Scientific and Technical Information of China (English)

    Wang Jun; Wang Yuxin; Feng Jicai

    2009-01-01

    A consumable aided tungsten indirect arc welding method has been studied. This method is different from the traditional TIG welding because it introduces an MIG welding torch into the traditional TIG welding system. An indirect arc is generated between the consumable electrode of the MIG welding torch and the tungsten electrode of the TIG welding torch, but not generated between the tungsten electrode of the welding torch and the base metal. Welding current flows from the consumable electrode to the tungsten electrode in the free-burning indirect arc. The consumable aided tungsten indirect arc welding not only rapidly melts the welding wire but also effectively restrains the excessive fusion of the base metal. The welding experiment and the theoretical analysis confirm that this method can obtain a high deposition rate and a low dilution ratio during the welding process.

  20. Plasma spray forming of tungsten coatings on copper electrodes

    Institute of Scientific and Technical Information of China (English)

    JIANG Xian-liang(蒋显亮); F.Gitzhofer; M.I.Boulos

    2004-01-01

    Both direct current dc plasma and radio frequency induction plasma were used to deposit tungsten coatings on copper electrodes. Fine tungsten powder with mean particle size of 5μm and coarse tungsten powder with particle size in the range from 45 μm to 75 μm were used as plasma spray feedstock. It is found that dc plasma is only applicable to spray the fine tungsten powder and induction plasma can be used to spray both the coarse powder and the fine powder. The tungsten coating deposited by the induction plasma spraying of the coarse powder is extremely dense. Such a coating with an interlocking structure and an integral interface with the copper substrate demonstrates high cohesion strength and adhesion strength.

  1. Tungsten recycling in the United States in 2000

    Science.gov (United States)

    Shedd, Kim B.

    2011-01-01

    This report, which is one of a series of reports on metals recycling, defines and quantifies the flow of tungsten-bearing materials in the United States from imports and stock releases through consumption and disposition in 2000, with particular emphasis on the recycling of industrial scrap (new scrap) and used products (old scrap). Because of tungsten's many diverse uses, numerous types of scrap were available for recycling by a wide variety of processes. In 2000, an estimated 46 percent of U.S. tungsten supply was derived from scrap. The ratio of tungsten consumed from new scrap to that consumed from old scrap was estimated to be 20:80. Of all the tungsten in old scrap available for recycling, an estimated 66 percent was either consumed in the United States or exported to be recycled.

  2. Homogenous Silver-Tungsten Composite Production for Electrical Contacts

    Directory of Open Access Journals (Sweden)

    Shahid M. Azhar

    2015-03-01

    Full Text Available Silver-tungsten composite materials have been widely used as medium duty electrical contacts since they offer the advantages of both refractory tungsten (welding and erosion resistance and silver (efficient electro-thermal conductivities. Since there is no alloying between the two elements (Ag and W, the properties of the composite depends on their composition. So for any particular application, a balance must be struck between the desirable properties of the two metals. Both welding and erosion resistance properties of silver-tungsten contacts depend on particle size, morphology and distribution of both elements within the composite, with finer W particles in Ag matrix give better performance. The main objective of this study is to produce an intimately mixed silver-tungsten powder with homogeneous distribution of both phases (silver and tungsten in the composite. Thus, to produce homogenous elemental silver-tungsten powder, the reduction behavior of each tungstate is studied at various reduction temperatures using TGA technique. Based on the results obtained from TGA, the reduction of silver tungstate carried out in two stage reduction process for producing elemental silver-tungsten powder with controlled particle size of tungsten. Also, small quantities of Fe and Co as sinter aids are introduced into tungstates by co-precipitation technique. However, the precipitated Fe and Co doped silver tungstates are reduced to yield Iron and cobalt doped silver-tungsten powders. The effect of Fe and Co on the morphology and particle size of the tungsten is studied using SEM. The reduced products will be used for subsequent sintering experiments to produce high density sintered compact for contact fabrication.

  3. Microstructural characterization and field emission properties of tungsten oxide and titanium-oxide-doped tungsten oxide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Su, Chia-Hsiang [Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan (China); Su, Cherng-Yuh, E-mail: cysu@ntut.edu.tw [Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Lin, Yan-Fu [Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China)

    2015-03-01

    Tungsten oxide and titanium-oxide-doped tungsten oxide nanowires were synthesized by using the DC magnetron sputtering and infrared furnace annealing processes. Scanning election microscopy (SEM) and transmission electron microscopy (TEM) were utilized to evaluate the topography and sizes. X-ray diffraction (XRD), grazing incidence X-ray diffraction (GI-XRD), and high-resolution transmission electron microscopy (HRTEM) were used to analyze the composition and structure. From the results of HRTEM, it was discovered that the prepared nanowires have a monoclinic single-crystal phase of W{sub 18}O{sub 49} with lattice growth along the (010) lattice plane, and the lattice spacing is 0.378 nm, which agrees with XRD and GI-XRD results. The prepared tungsten oxide and titanium-oxide-doped tungsten oxide nanowires have turn-on voltage of 3.06 V/μm and 1.46 V/μm respectively. They also possess superior field enhancement factors of 5103 and 10667 respectively. Their behavior thus follows the Fowler-Nordheim expression for tunneling. - Highlights: • A simple method to prepare tungsten oxide nanowires by annealing tungsten film. • High aspect ratio of the 1D titanium-oxide-doped tungsten oxide nanowires. • High field enhancement factor of titanium-oxide-doped tungsten oxide nanowires.

  4. Three-dimensional tungsten nitride nanowires as high performance anode material for lithium ion batteries

    Science.gov (United States)

    Zhang, Min; Qiu, Yongfu; Han, Yi; Guo, Yan; Cheng, Faliang

    2016-08-01

    Nanostructure materials often achieve low capacity when the active material mass loading is high. In this communication, high mass-loading tungsten nitride nanowires (WNNWs) were fabricated on a flexible carbon cloth by hydrothermal method and post annealing. The prepared electrode exhibited remarkable cyclic stability and attractive rate capability for lithium storage. It delivers at a current density of 200 mA g-1, a high capacity of 418 mAh g-1, which is higher than that of conventional graphite. This research opens more opportunity for the fabrication of three-dimensional metal nitrides as negative electrode material for flexible lithium ion batteries.

  5. Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

    Science.gov (United States)

    De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

    2012-09-01

    Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

  6. Bibliography on Metallurgy of High-Purity Tungsten, January 1911 through February 1959

    Science.gov (United States)

    1960-01-01

    acid, but univ., Istanbul 14-A, 1949, pp. 7-19; Chem. Abs., voL this usually is not necessary. The suspension is di- 44, 1950, p. 7179. luted with...crystallized form swept out. of the suspension changes. The yield of filtered, Tests on ore held on shallow trays showed that not washed, and air-dried...Hydrogen and Oxy- Carbon Monoxide. Cong. Materiaux RIsistants f gen on Tungsten. Jour. Chem. Phys., vol. 24, Janu- Chaud. AURA, 1951, pp. 307-331; Chem. Abs

  7. Study on in-situ WC particles/tungsten wire reinforced iron matrix composites under electromagnetic field

    Directory of Open Access Journals (Sweden)

    Niu Libin

    2010-05-01

    Full Text Available By applying electromagnetic field to a system consisting of tungsten wires and grey cast iron melt, the grey cast iron matrix composite reinforced by either in-situ WC particles or the combination of in-situ WC particles and the residual tungsten wire was obtained. By means of differential thermal analysis (DTA, the pouring temperature of iron melt was determined at 1,573 K. The microstructures of the composites were analyzed by using of X-ray diffraction (XRD, scanning electron microscopy (SEM equipped with an energy dispersive spectrum (EDS and pin-on-disc abrasive wear test. The obtained results indicated that, with the enhancing frequency of electromagnetic field, the amount of in-situ WC particles gradually increases, leading to continuous decrease of the residual tungsten wires. When the electromagnetic field frequency was up to 4 kHz, tungsten wires reacted completely with carbon atoms in grey cast iron melt, forming WC particals. The electromagnetic field appeared to accelerate the elemental diffusion in the melt, to help relatively quick formation of a series of small Fe-W-C ternary zones and to improve the kinetic condition of in-situ WC fabrication. As compared with the composite prepared without the electromagnetic field, the composite fabricated at 4 kHz presented good wear resistance.

  8. Carbon Fiber and Tungsten Disulfide Nanoscale Architectures for Armor Applications

    Science.gov (United States)

    2012-06-01

    Vickers, and the flat end cone , also known as a flat punch. The Berkovich and Vickers tips are three and four-sided pyramidal structures...respectively, while the flat punch is a cone with a removed tip (Figure 21). While the diameters of contact for the pyramidal tips are dependent on the depth...of a certain size, the pane of glass will shatter under loading far below what is expected of the material [32]. Depending on the future inclusions of

  9. Phase Transformations upon Doping in Tungsten Trioxide

    Science.gov (United States)

    Wang, Wennie; Janotti, Anderson; van de Walle, Chris G.

    Tungsten trioxide (WO3) is an emerging semiconductor material, with a growing number of applications in Li-ion batteries, photocatalysis, gas sensors and electrochromic devices. As an electrochromic material, WO3 turns from transparent to blue upon doping with monovalent species. Due to it having an empty A-site in the ABO3 perovskite structure, high doping concentrations are possible through intercalation. Tungsten trioxide has been experimentally shown to transform from the ground-state monoclinic symmetry to cubic symmetry with increasing monovalent doping. We use first-principles calculations to understand this transformation. Our calculations show that the addition of electrons to the conduction band is a primary driver of the phase transformation. We quantify the energetics and structural aspects of this transformation using density functional theory, allowing us to elucidate the mechanism. Comparison with experiment, role of the dopant species, and implications of structural changes for device applications will be discussed. This work is supported by the DOE and NSF GRFP.

  10. Concentration dependent hydrogen diffusion in tungsten

    Science.gov (United States)

    Ahlgren, T.; Bukonte, L.

    2016-10-01

    The diffusion of hydrogen in tungsten is studied as a function of temperature, hydrogen concentration and pressure using Molecular Dynamics technique. A new analysis method to determine diffusion coefficients that accounts for the random oscillation of atoms around the equilibrium position is presented. The results indicate that the hydrogen migration barrier of 0.25 eV should be used instead of the presently recommended value of 0.39 eV. This conclusion is supported by both experiments and density functional theory calculations. Moreover, the migration volume at the saddle point for H in W is found to be positive: ΔVm ≈ 0.488 Å3, leading to a decrease in the diffusivity at high pressures. At high H concentrations, a dramatic reduction in the diffusion coefficient is observed, due to site blocking and the repulsive H-H interaction. The results of this study indicates that high flux hydrogen irradiation leads to much higher H concentrations in tungsten than expected.

  11. Dynamic compaction of tungsten carbide powder.

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-04-01

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

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

    Science.gov (United States)

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

    2016-10-14

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

  13. Hexagonal tungsten oxide nanoflowers as enzymatic mimetics and electrocatalysts

    Science.gov (United States)

    Park, Chan Yeong; Seo, Ji Min; Jo, Hongil; Park, Juhyun; Ok, Kang Min; Park, Tae Jung

    2017-01-01

    Tungsten oxide (WOx) has been widely studied for versatile applications based on its photocatalytic, intrinsic catalytic, and electrocatalytic properties. Among the several nanostructures, we focused on the flower-like structures to increase the catalytic efficiency on the interface with both increased substrate interaction capacities due to their large surface area and efficient electron transportation. Therefore, improved WOx nanoflowers (WONFs) with large surface areas were developed through a simple hydrothermal method using sodium tungstate and hydrogen chloride solution at low temperature, without any additional surfactant, capping agent, or reducing agent. Structural determination and electrochemical analyses revealed that the WONFs have hexagonal Na0.17WO3.085·0.17H2O structure and exhibit peroxidase-like activity, turning from colorless to blue by catalyzing the oxidation of a peroxidase substrate, such as 3,3′,5,5′-tetramethylbenzidine, in the presence of H2O2. Additionally, a WONF-modified glassy carbon electrode was adopted to monitor the electrocatalytic reduction of H2O2. To verify the catalytic efficiency enhancement by the unique shape and structure of the WONFs, they were compared with calcinated WONFs, cesium WOx nanoparticles, and other peroxidase-like nanomaterials. The results indicated that the WONFs showed a low Michaelis-Menten constant (km), high maximal reaction velocity (vmax), and large surface area. PMID:28128306

  14. Hexagonal tungsten oxide nanoflowers as enzymatic mimetics and electrocatalysts

    Science.gov (United States)

    Park, Chan Yeong; Seo, Ji Min; Jo, Hongil; Park, Juhyun; Ok, Kang Min; Park, Tae Jung

    2017-01-01

    Tungsten oxide (WOx) has been widely studied for versatile applications based on its photocatalytic, intrinsic catalytic, and electrocatalytic properties. Among the several nanostructures, we focused on the flower-like structures to increase the catalytic efficiency on the interface with both increased substrate interaction capacities due to their large surface area and efficient electron transportation. Therefore, improved WOx nanoflowers (WONFs) with large surface areas were developed through a simple hydrothermal method using sodium tungstate and hydrogen chloride solution at low temperature, without any additional surfactant, capping agent, or reducing agent. Structural determination and electrochemical analyses revealed that the WONFs have hexagonal Na0.17WO3.085·0.17H2O structure and exhibit peroxidase-like activity, turning from colorless to blue by catalyzing the oxidation of a peroxidase substrate, such as 3,3‧,5,5‧-tetramethylbenzidine, in the presence of H2O2. Additionally, a WONF-modified glassy carbon electrode was adopted to monitor the electrocatalytic reduction of H2O2. To verify the catalytic efficiency enhancement by the unique shape and structure of the WONFs, they were compared with calcinated WONFs, cesium WOx nanoparticles, and other peroxidase-like nanomaterials. The results indicated that the WONFs showed a low Michaelis-Menten constant (km), high maximal reaction velocity (vmax), and large surface area.

  15. 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.

  16. Synthesis and structures of bis(dithiolene)tungsten(IV,VI) thiolate and selenolate complexes: approaches to the active sites of molybdenum and tungsten formate dehydrogenases.

    Science.gov (United States)

    Groysman, Stanislav; Holm, R H

    2007-05-14

    Formate dehydrogenases are molybdenum- or tungsten-containing enzymes that catalyze the oxidation of formate to carbon dioxide. Among the significant characteristics of the mononuclear active sites are coordination of two pyranopterindithiolene ligands and selenocysteinate to the metal in oxidation states IV-VI. The first detailed investigation of the synthesis and structures of bis(dithiolene)tungsten selenolate and analogous thiolate complexes of relevance to formate dehydrogenases has been undertaken. Some 17 complexes of the types [WIV(QR)(S2C2Me2)2]-, [WVIO(QR)(S2C2Me2)2]-, and [WVIS(QR)(S2C2Me2)2]- (Q = S, Se; R = tert-butyl, 1-adamantyl) and the desoxo species [WVI(SR)(OSiR'3)(S2C2Me2)2] (R' = Me, Ph) were prepared. Ten structures of representative members of these types were determined; WIV complexes are square-pyramidal and WVI complexes are six-coordinate, with geometries intermediate between octahedral and trigonal-prismatic. Selenolate complexes are less stable than similar thiolate species; decomposition products were identified as [WV2(mu2-Q)2(S2C2Me2)2]2- and [WIV,V2(mu2-Se)(S2C2Me2)4]-. The several [MoIV(QR)(S2C2Me2)2]- complexes prepared earlier and the tungsten compounds synthesized in this work form a family of molecules whose overall stereochemistry and metric features are those expected in the absence of protein structural constraints.

  17. Synthesis of carbon nanotubes with Ni/CNTs catalyst

    Institute of Scientific and Technical Information of China (English)

    李春华; 姚可夫; 阮殿波; 梁吉; 徐才录; 吴德海

    2003-01-01

    Carbon nanotubes (CNTs), owing to their large specific area, good chemical stability and modifiable surface properties after acidic or basic treatment, can be used as catalytic support materials. In this paper, the activities and selectivities of two catalysts, i. e. Ni catalyst supported by carbon nanotubes (Ni/CNTs) and that supported by diatomite (Ni/SiO2), are compared. It is found that the quality of the carbon nanotubes synthesized by the two catalysts is similar, but the yield of the former is 1.5 times higher than that of the latter. The excellent performance of the Ni/CNTs catalyst should be ascribed to the larger specific surface area and proper pore distribution and the structure of the carbon nanotube support.

  18. 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.

  19. 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.

  20. COMPUTER NUMERICAL SIMULATION OF MECHANICAL PROPERTIES OF TUNGSTEN HEAVY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A microstructure model of tungsten heavy alloys has been developed. On the basis of the model and several assumptions, the macro-mechanical properties of 90 W heavy alloy under quasi-static tensile deformation and the effects of microstructural parameters (mechanical properties of the matrix phase and tungsten content) on them have been analyzed by computer numerical simulation. The mechanical properties of the alloy have been found to be dependent on the mechanical parameters of the matrix phase. As the elastic modulus and yield strength of the matrix phase increase, the tensile strength of the alloy increases, while the elongation decreases. If the mechanical parameters except the tensile strength of the matrix phase are constant, both the tensile strength and the elongation of the alloy increase linearly with the increase of tensile strength of the matrix phase. The properties of the alloy are very sensitive to the hardening modulus of the matrix phase. As the hardening modulus increases, both the tensile strength and the elongation of the alloy exponentially decrease. The elongation of the alloys monotonically decreases with the increase of tungsten content, while the decrease of tensile strength is not monotonic. When the tungsten content < 85 %, the strength of tungsten heavy alloys increases with the increase of tungsten content, while decreases when the tungsten content >85 %. The maximum of tensile strength of the alloys appears at the tungsten content of 85 %. The results showed that the binder phase with a higher strength and a lower hardening modulus is advantageous to obtaining an optimum combination of mechanical properties of tungsten heavy alloys.

  1. Analysis of a tungsten sputtering experiment in DIII-D and code/data validation of high redeposition/reduced erosion

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, J.N., E-mail: brooksjn@purdue.edu [Purdue University, West Lafayette, IN (United States); Elder, J.D. [University of Toronto Institute for Aerospace Studies, Toronto (Canada); McLean, A.G. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Rudakov, D.L. [University of California San Diego, San Diego, CA (United States); Stangeby, P.C. [University of Toronto Institute for Aerospace Studies, Toronto (Canada); Wampler, W.R. [Sandia National Laboratories, Albuquerque, NM (United States)

    2015-05-15

    We analyze a DIII-D tokamak experiment where two tungsten spots on the removable DiMES divertor probe were exposed to 12 s of attached plasma conditions, with moderate strike point temperature and density (∼20 eV, ∼4.5 × 10{sup 19} m{sup −3}), and 3% carbon impurity content. Both very small (1 mm diameter) and small (1 cm diameter) deposited samples were used for assessing gross and net tungsten sputtering erosion. The analysis uses a 3-D erosion/redeposition code package (REDEP/WBC), with input from a diagnostic-calibrated near-surface plasma code (OEDGE), and with focus on charge state resolved impinging carbon ion flux and energy. The tungsten surfaces are primarily sputtered by the carbon, in charge states +1 to +4. We predict high redeposition (∼75%) of sputtered tungsten on the 1 cm spot—with consequent reduced net erosion—and this agrees well with post-exposure DiMES probe RBS analysis data. This study and recent related work is encouraging for erosion lifetime and non-contamination performance of tokamak reactor high-Z plasma facing components.

  2. Obtaining of films of tungsten trioxide (WO3) by resistive heating of a tungsten filament

    OpenAIRE

    2008-01-01

    Thin film of tungsten oxide (WO3) has been studied extensively as an electrochromic material and has numerous applications in electrochromic devices, smart windows, gas sensors and optical windows. In order to explore the possibility of using it in electrochromic devices, thorough study the optical properties of the WO3 is an important step. The WO3 layers have been grown by hot-filament metal oxide deposition technique under atmospheric pressure and an oxygen atmosphere. By FTIR and Raman sc...

  3. 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.

  4. The preparation, characterisation and catalytic activity of tungsten bronzes

    OpenAIRE

    Stevenson, Sheena

    1987-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. The structure and catalytic aspects of tungsten bronzes have been considered. A series of potassium tungsten bronzes, KxW03, 0.05 =< x =< 0.8, and the corresponding series of sodium tungsten bronzes, NaxW03, 0.05 =< x =< 0.8 were prepared by a thermal method. The thermal stability of the prepared samples was studied in the presence of both an oxidising and a reducing gas. The number and...

  5. Electrode potentials of tungsten in fused alkali chlorides

    Science.gov (United States)

    Ivanov, A. B.; Volkovich, V. A.; Poskryakov, D. A.; Vasin, B. D.; Griffiths, T. R.

    2016-09-01

    Anodic dissolution of tungsten was studied at 823-1173 K in the melts based on NaCl-CsCl, NaCl-KCl-CsCl and LiCl-KCl-CsCl eutectic mixtures. The process results in the formation of W(IV) ions. Prolonged contact with silica results in oxidation W(IV) ions and decreasing tungsten concentration in the electrolyte due to formation of volatile higher oxidation state chloro- and oxychloro-species. Tungsten electrode potentials were measured in NaCl-CsCl and NaCl-KCl-CsCl based melts using potentiometry.

  6. Preparation of nanocomposite thoriated tungsten cathode by swaging technique

    Institute of Scientific and Technical Information of China (English)

    王发展; 诸葛飞; 张晖; 丁秉钧

    2002-01-01

    By using the high energy ball milling method,the nanosized ThO2 powders were obtained.Through mixing powders,sintering and hot swaging processing,a nanocomposite thoriated tungsten cathode was fabricated.The relative density of the nanocomposite material is near 100%.The microstructure of nanocomposite cathode is quite different from that of conventional thoriated tungsten cathode.Most of thoria particles are less than 100 nm in diameter,and distribute on the boundaries of tungsten grains.The nanocomposite cathode shows a much lower arc starting field than that of conventional cathode,which will improve the performance of the cathode significantly.

  7. Tungsten Export Price Raised Due to Customs Tax Regulations

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>Affected by the export tax rise, China’s tungsten export price rose by about 40 per cent in the first 10 months of 2006. The average price of Ammonium Paratungstate (APT) was US$23,000/MT, up by 43.5 per cent year-on-year, and that of ferro-tungsten, blue tungsten oxide as well as yellow oxide also increased by 32.4 per cent to US$24,000/MT, 27.4 per cent to US$25,000/MT and 42.6 per cent to US$26,000/MT respectively.

  8. Low-Temperature Strengths and Ductility of Various Tungsten Sheets

    Directory of Open Access Journals (Sweden)

    Yutaka Hiraoka

    2011-01-01

    Full Text Available We used three kinds of tungsten sheets in this study. First, we examined microstructure such as grain size distribution using an optical microscope. Secondly, we carried out three-point bend tests at temperatures between about 290 and 500 K. Then, we examined fracture surface of a failed specimen using a scanning electron microscope. Lastly, by analyzing all these results, we evaluated apparent intergranular and transgranular fracture strengths and discussed strengths and ductility of tungsten. Additionally, we compared mechanical properties of tungsten with those of molybdenum.

  9. Tensile behavior of tungsten and tungsten-alloy wires from 1300 to 1600 K

    Science.gov (United States)

    Hee, Man Yun

    1988-01-01

    The tensile behavior of a 200-micrometer-diameter tungsten lamp (218CS-W), tungsten + 1.0 atomic percent (a/o) thoria (ST300-W), and tungsten + 0.4 a/o hafnium carbide (WHfC) wires was determined over the temperature range 1300 t0 1600 K at strain rates of 3.3 X 10 to the -2 to 3.3 X 10 to the -5/sec. Although most tests were conducted on as-drawn materials, one series of tests was undertaken on ST300-W wires in four different conditions: as-drawn and vacuum-annealed at 1535 K for 1 hr, with and without electroplating. Whereas heat treatment had no effect on tensile properties, electropolishing significantly increased both the proportional limit and ductility, but not the ultimate tensile strength. Comparison of the behavior of the three alloys indicates that the HfC-dispersed material possesses superior tensile properties. Theoretical calculations indicate that the strength/ductility advantage of WHfC is due to the resistance to recrystallization imparted by the dispersoid.

  10. 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.

  11. Density-functional studies of tungsten trioxide, tungsten bronzes, and related systems

    CERN Document Server

    Ingham, B; Chong, S V; Tallon, J L

    2005-01-01

    Tungsten trioxide adopts a variety of structures which can be intercalated with charged species to alter the electronic properties, thus forming `tungsten bronzes'. Similar optical effects are observed upon removing oxygen from WO_3, although the electronic properties are slightly different. Here we present a computational study of cubic and hexagonal alkali bronzes and examine the effects on cell size and band structure as the size of the intercalated ion is increased. With the exception of hydrogen (which is predicted to be unstable as an intercalate), the behaviour of the bronzes are relatively consistent. NaWO_3 is the most stable of the cubic systems, although in the hexagonal system the larger ions are more stable. The band structures are identical, with the intercalated atom donating its single electron to the tungsten 5d valence band. Next, this was extended to a study of fractional doping in the Na_xWO_3 system (0 < x < 1). A linear variation in cell parameter, and a systematic change in the po...

  12. Magneto photoluminescence measurements of tungsten disulphide monolayers

    Science.gov (United States)

    Kuhnert, Jan; Rahimi-Iman, Arash; Heimbrodt, Wolfram

    2017-03-01

    Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K‧, respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS2) monolayers at temperatures of 2 K. By applying magnetic fields up to 7 T in Faraday geometry, a splitting of the photoluminescence peaks can be observed. The magnetic field dependence of the A-exciton, the trion and three bound exciton states is discussed and the corresponding g-factors are determined.

  13. Tungsten-doped thin film materials

    Science.gov (United States)

    Xiang, Xiao-Dong; Chang, Hauyee; Gao, Chen; Takeuchi, Ichiro; Schultz, Peter G.

    2003-12-09

    A dielectric thin film material for high frequency use, including use as a capacitor, and having a low dielectric loss factor is provided, the film comprising a composition of tungsten-doped barium strontium titanate of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3, where X is between about 0.5 and about 1.0. Also provided is a method for making a dielectric thin film of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3 and doped with W, where X is between about 0.5 and about 1.0, a substrate is provided, TiO.sub.2, the W dopant, Ba, and optionally Sr are deposited on the substrate, and the substrate containing TiO.sub.2, the W dopant, Ba, and optionally Sr is heated to form a low loss dielectric thin film.

  14. Xiamen Tungsten Co.,Ltd Verified the Largest Tungsten Mine Worldwide with a Potential Value Topping 300 Billion Yuan

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>On June 5,the Ministry of Land and Resources announced that,in Dahutang area of Wuning County,Jiujiang City.Jiangxi Province,a tungsten mine with a reserve of 1.06 million tonnes has been prospected;it is the largest tungsten mine in the world today.One of the investors of this prospecting activity is Xiamen Tungsten Co.,Ltd,a public listed company from Fujian Province.According to data of The Ministry of Land and Resources,

  15. Enhanced toughness and stable crack propagation in a novel tungsten fibre-reinforced tungsten composite produced by chemical vapour infiltration

    Science.gov (United States)

    Riesch, J.; Höschen, T.; Linsmeier, Ch; Wurster, S.; You, J.-H.

    2014-04-01

    Tungsten is a promising candidate for the plasma-facing components of a future fusion reactor, but its use is strongly restricted by its inherent brittleness. An innovative concept to overcome this problem is tungsten fibre-reinforced tungsten composite. In this paper we present the first mechanical test of such a composite material using a sample containing multiple fibres. The in situ fracture experiment was performed in a scanning electron microscope for close observation of the propagating crack. Stable crack propagation accompanied with rising load bearing capacity is observed. The fracture toughness is estimated using the test results and the surface observation.

  16. Underwater explosive welding of thin tungsten foils and copper

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, P., E-mail: manikandan_exp@yahoo.com [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Lee, J.O.; Mizumachi, K. [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Mori, A. [Department of Mechanical Engineering, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082 (Japan); Raghukandan, K. [Department of Manufacturing Engineering, Annamalai University, Annamalainagar, Cuddalore District, Tamilnadu 608 002 (India); Hokamoto, K. [Shock Wave and Condensed Matter Research Center, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan)

    2011-11-15

    Highlights: > Underwater explosive welding was used to clad tungsten and copper. > The preset inclination was varied and the microstructure was observed. > Microstructure reveals a clear wavy interface for higher preset inclination. > High pressure and high strain rate leads to plastic flow of tungsten. - Abstract: This study demonstrates the ability to clad pure tungsten foils on copper plate using underwater shock waves generated by the detonation of explosive. Microstructural characterization revealed that a higher preset inclination results in wavy morphology. Weld formed at lower inclination exhibit a planar interfacial layer comprising fine grained particles of both components. The plastic flow of tungsten is ascribed to the synergistic influence of high pressure and high strain rate at the collision point.

  17. Advances in Thermionic Cathode of Tungsten and Molybdenum

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Several kinds of tungsten thermonic cathodes have been introduced. As a promising alternative for thoriated tungsten, rare earth doped molybdenum cathode has been studied. Compared with the traditional thoriated tungsten, La-Mo cathode has higher emission current density at lower temperature, but it has poor emission stability. In order to improve the emission stability, systematical study on the emission mechanism of La-Mo cathode has been carried out. The life of La-Mo cathode has been improved and has achieved 1400 h, which exceeds the minimum life for practical uses (1000 h). As another alternative for thoriated tungsten cathode, Y-Mo cathode has shown better performance. The thermionic emission capability of Y-Mo cathode is between that of La-Mo cathode and Th-W cathode.

  18. Preparation and catalytic properties of tungsten oxides with different morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Bi Yunfei, E-mail: beiyf2003@yahoo.com.cn [Research Institute of Petroleum Processing, SINOPEC, 18 Xue Yuan Road, 100083 Beijing (China); Li Dadong; Nie Hong [Research Institute of Petroleum Processing, SINOPEC, 18 Xue Yuan Road, 100083 Beijing (China)

    2010-09-01

    Tungsten oxides with different morphologies including platelet-like sheets, nanobelts, and nanoparticles have been successfully prepared by changing the ions in the synthetic solution. Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared analysis and N{sub 2} adsorption were employed to reveal the morphological evolution, and results show that the morphological evolution can be attributed to the alteration of coordination environment of tungstenic cations contained in the synthetic solution. Furthermore, these products have been applied into hydrodesulfurization measurement to investigate the relationship between the morphologies of tungsten oxides and their catalytic properties. It is concluded that the catalysts originating from nanobelt-like tungsten oxides have highest catalytic activity and excellent selectivity due to their scrolled character and strong metallic edges.

  19. Calibration and temperature profile of a tungsten filament lamp

    Energy Technology Data Exchange (ETDEWEB)

    De Izarra, Charles [Groupe de Recherche sur l' Energetique des Milieux Ionises, UMR6606 Universite d' Orleans, CNRS, Faculte des Sciences, Site de Bourges, rue Gaston Berger, BP 4043, 18028 Bourges Cedex (France); Gitton, Jean-Michel, E-mail: Charles.De_Izarra@univ-orleans.f [College Littre, 10 rue Littre, Bourges (France)

    2010-07-15

    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 lamp (lamp used in automotive lighting) and then tested on a standard tungsten ribbon lamp. The calibration procedure developed was checked by determining the calibration point of the tungsten ribbon lamp with an accuracy of 2%. In addition, for low current intensity, it was observed that the temperature of the filament was not uniform; an explanation is proposed by considering a simple heat transfer model.

  20. 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.)

  1. Tungsten-nickel-cobalt alloy and method of producing same

    Science.gov (United States)

    Dickinson, James M.; Riley, Robert E.

    1977-03-15

    An improved tungsten alloy having a tungsten content of approximately 95 weight percent, a nickel content of about 3 weight percent, and the balance being cobalt of about 2 weight percent is described. A method for producing said tungsten-nickel-cobalt alloy is further described and comprises (a) coating the tungsten particles with a nickel-cobalt alloy, (b) pressing the coated particles into a compact shape, (c) heating said compact in hydrogen to a temperature in the range of 1400.degree. C and holding at this elevated temperature for a period of about 2 hours, (d) increasing this elevated temperature to about 1500.degree. C and holding for 1 hour at this temperature, (e) cooling to about 1200.degree. C and replacing the hydrogen atmosphere with an inert argon atmosphere while maintaining this elevated temperature for a period of about 1/2 hour, and (f) cooling the resulting alloy to room temperature in this argon atmosphere.

  2. INDUCTION PLASMA REACTIVE DEPOSITION OF TUNGSTENCARBIDE FROM TUNGSTEN METAL POWDER

    Institute of Scientific and Technical Information of China (English)

    X.L. Jiang; M.I. Boulos

    2001-01-01

    Experimental results are reported on the primary carburization reaction between the tungsten powder and methane in the induction plasma, and the secondary carburization of the deposit on substrate at high temperature. Optical microscopy and scanning electron microscopy were used to examine the microstructures of starting tungsten powder, carburized powder, and deposit. X-ray diffraction analysis, thermal gravimetric analysis and microhardness measurement were used to characterize the structures and properties of the powder and the deposit. It is found that the primary carburization reaction in the induction plasma starts from the surface of tungsten particles when the particles are melted. Tungsten particles are partially carburized inside the reactive plasma. Complete carburization is achieved through the secondary carburization reaction of the deposit on substrate at high temperature.``

  3. Underwater explosive welding of thin tungsten foils and copper

    Science.gov (United States)

    Manikandan, P.; Lee, J. O.; Mizumachi, K.; Mori, A.; Raghukandan, K.; Hokamoto, K.

    2011-11-01

    This study demonstrates the ability to clad pure tungsten foils on copper plate using underwater shock waves generated by the detonation of explosive. Microstructural characterization revealed that a higher preset inclination results in wavy morphology. Weld formed at lower inclination exhibit a planar interfacial layer comprising fine grained particles of both components. The plastic flow of tungsten is ascribed to the synergistic influence of high pressure and high strain rate at the collision point.

  4. Hydrodynamic Analysis to Process of Hydrostatic Extrusion for Tungsten Alloy

    Institute of Scientific and Technical Information of China (English)

    Fuchi WANG; Zhaohui ZHANG; Shukui LI

    2001-01-01

    The hydrodynamic analysis to the process of the hydrostatic extrusion for tungsten alloy is carried through the hydrodynamic lubrication theory and Reynolds equation in this paper. The critical velocity equation when the hydrodynamic lubrication conditions appear between the surfaces of the work- piece and the die is obtained, and the relationship between the critical velocity and the extrusion parameters is discussed, which build the theoretical bases to the application of the hydrostatic extrusion for tungsten alloy.

  5. China Limits the Mining Quantity of Tungsten and Rare Earth

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>Based on a notice issued by the Ministry of Land Resources, China’s tungsten mining quantity in 2006 will be controlled to 59,060 tons in concentrates form, which include 4,250 tons of recycled tungsten. And the rare earth mining quantity in 2006 will also be controlled to 86,620 tons (REO) including 8,320 tons of heavy rare earth and 78,200 tons of light rare earth.

  6. Effect of neutron irradiation on the microstructure of tungsten

    Directory of Open Access Journals (Sweden)

    M. Klimenkov

    2016-12-01

    Full Text Available Two grades of pure tungsten, single and polycrystalline, were irradiated for 282 days in the HFR reactor, Petten, at 900 °C to an average damage level of 1.6dpa. Each grade of tungsten was investigated using the transmission electron microscope (TEM to assess the effect of neutron irradiation on tungsten microstructure. Investigations revealed the formation of faceted cavities, whose diameter varies from 4 to 14nm in both materials. The cavities are homogeneously distributed only inside single crystalline tungsten. The local distribution of cavities in polycrystalline tungsten is strongly influenced by grain boundaries. The number densities of cavities were measured to be 4×1021 m−3 for polycrystalline and 2.5×1021 m−3 for single crystalline tungsten. This corresponds to volumetric densities of 0.45% and 0.33% respectively. High-resolution transmission electron microscopy (HRTEM revealed that faces of cavities are oriented in (110 plane. Analytical investigations showed precipitation of rhenium and osmium produced by a transmutation reaction around cavities and at grain boundaries.

  7. Degradation of tungsten under the action of a plasma jet

    Science.gov (United States)

    Voronin, A. V.; Sud'enkov, Yu. V.; Semenov, B. N.; Atroshenko, S. A.; Naumova, N. S.

    2014-07-01

    The degradation of the surface and structure of single-crystal tungsten and sintered powder tungsten during the action of a pulsed plasma jet is studied. It is shown that the degradation of a tungsten target during the action of a plasma jet with an energy flux density of 0.25-1 MJ/m2 is accompanied by surface evaporation and melting and the fracture of surface layers on scales of 150-250 μm. The results of a numerical simulation of the thermomechanical processes that occur in a tungsten target during the action of a plasma jet are presented. The degradation of tungsten during the action of a plasma jet is shown to proceed almost continuously from the action (evaporation, melting) to the times that are more than three orders of magnitude longer than the action time, which is caused by the thermomechanical processes occurring in the tungsten target. Moreover, the action of thermal stresses leads to structural and morphological changes throughout the sample volume, and these changes are accompanied by recrystallization in adiabatic shear bands.

  8. Irradiation effects in tungsten-copper laminate composite

    Science.gov (United States)

    Garrison, L. M.; Katoh, Y.; Snead, L. L.; Byun, T. S.; Reiser, J.; Rieth, M.

    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 × 1025 n/m2, 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.

  9. Irradiation effects in tungsten-copper laminate composite

    Energy Technology Data Exchange (ETDEWEB)

    Garrison, L. M.; Katoh, Y.; Snead, L. L.; Byun, T. S.; Reiser, J.; Rieth, M.

    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 0.02-9.0×1025 n/m2, 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.

  10. The fabrication of carbon-nanotube-coated electrodes and a field-emission-based luminescent device.

    Science.gov (United States)

    Agarwal, Sanjay; Yamini Sarada, B; Kar, Kamal K

    2010-02-10

    Tungsten substrates were coated with an Ni or Ni-Co catalyst by the electroless dip coating technique. Various carbon nanotubes were synthesized by the catalytic chemical vapor deposition (CVD) method under different growth conditions. It was observed that Ni-and Ni-Co-coated tungsten substrates give very good growth of carbon nanotubes (CNT) in terms of yield, uniformity and alignment at a growth temperature of 600 degrees C. We fabricated a field-emission-based luminescent light bulb where a tungsten wire coated with carbon nanotubes served as a cathode. Results show lower threshold voltage, better emission stability and higher luminescence for CNT cathodes in comparison with uncoated tungsten cathodes. We found that aligned-coiled carbon nanotubes are superior to straight CNTs in terms of field emission characteristics and luminescence properties.

  11. Refining Tungsten Purification by Electron Beam Melting Based on the Thermal Equilibrium Calculation and Tungsten Loss Control

    Science.gov (United States)

    Long, Luping; Liu, Wensheng; Ma, Yunzhu; Liu, Ye; Liu, Shuhua

    2015-10-01

    Electron beam melting (EBM) technology has been considered as one of the key steps for preparing high purity tungsten, and reasonable setting of process parameters is the premise. In this paper, the optimum process parameters obtained from thermal equilibrium calculation and evaporation loss control of tungsten are presented. Effective power is closely related to melting temperature, and the required power for maintaining the superheating melt linearly increases with the increase of melt superheat temperature. The evaporation loss behavior of tungsten is significantly influenced by melting rate and melting temperature. Analysis of experiments show that the best results are realized at melting rate of 1.82 g/s, melting temperature of 4200 K, and the corresponding melting power of 130 kW, in which the main impurity elements in tungsten, such as As, Cd, Mg and Sn, present high removal ratio of 90%, 95%, 85.7% and 90%, respectively.

  12. The Influence of Impurities in Tungsten and Matrix Composition on the Tungsten-Matrix Interfacial Properties of Heavy Metal Alloys.

    Science.gov (United States)

    1982-10-01

    Impurities in Tungsten and Nov 79 - Nov 82 Matrix Composition on the Tungsten-Matrix Interfacial Properties of Heavy Metal Alloys 6. PERFORMING ORG. REPORT...fundamental change both in structure of the heavy metal and in fracture behaviour: The samples which were merely pre-reduced or sintered for very short...features of a satisfactory heavy metal : mainly transgranular fracture, considerable binder deformation and only rather few and small sintering necks in

  13. Jiangxi Discovered a Large Tungsten Mine Which May Create the World’s Largest Tungsten Mineral Deposit Reserve Record

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    It has been learned from the Jiangxi Province Geological and Mineral Resource Bureau Work Conference for 2015 held on January 21 that,the Zhuxi Tungsten and Copper Mine Project confirmed by the bureau at Fuliang County in Jingdezhen,Jiangxi in 2014 might create the world’s largest tungsten deposit reserve record.According to Peng Zezhou,Director of Jiangxi Province Geological and Mineral Resource

  14. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  15. Causes Analysis for the Cracking of Tungsten Strip Cold Bending%钨带冷弯时断裂原因分析

    Institute of Scientific and Technical Information of China (English)

    丁丽; 刘立娜; 周智慧; 蔺娴; 章安辉; 李剑

    2011-01-01

    钨带在90°弯曲时发生断裂,通过分析发现,断裂钨带碳含量偏高,断口处分层并呈蜂窝式片状形貌,断口附近金相组织也显示出明显的带状组织,断口处组织呈纤维状,断口为脆性断口.建议将材料含量控制在0.0050%以下,在90°弯曲时加热,加热温度在650~800℃,以降低钨带的脆性,增加弯曲时的韧性,提高成品率.%The tungsten strip will crack with 90° of cold bending.. It's find that the carbon content is bit high of the crack tungsten strip. The fracture is delaminated, cellular and flaky. Nearby fracture metal-lographic structure also show obvious banded structure. Fracture appears fiber structure? And it is brittle fracture. It's suggested that carbon content should be controlled below 0. 005% in tungsten strip, heat the strip to 650~800℃ when bend to 90°. It will reduce friability of tungsten strip, improve bend ductility, and raise the rate of finished products.

  16. T-1018 UCLA Spacordion Tungsten Powder Calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Trentalange, Stephen; Tsai, Oleg; Igo, George; Huang, Huan; Pan, Yu Xi; Dunkelberger, Jay; Xu, Wen Qin; /UCLA; Soha, Aria; /Fermilab; Heppelmann, Steven; /Penn State U.; Gagliardi, Carl; /Texas A-M

    2011-11-16

    The present experiments at the BNL-RHIC facility are evolving towards physics goals which require the detection of medium energy electromagnetic particles (photons, electrons, neutral pions, eta mesons, etc.), especially at forward angles. New detectors will place increasing demands on energy resolution, hadron rejection and two-photon resolution and will require large area, high performance electromagnetic calorimeters in a variety of geometries. In the immediate future, either RHIC or JLAB will propose a facility upgrade (Electron-Ion Collider, or EIC) with physics goals such as electron-heavy ion collisions (or p-A collisions) with a wide range of calorimeter requirements. An R and D program based at Brookhaven National Laboratory has awarded the group funding of approximately $110,000 to develop new types of calorimeters for EIC experiments. The UCLA group is developing a method to manufacture very flexible and cost-effective, yet high quality calorimeters based on scintillating fibers and tungsten powder. The design and features of the calorimeter can be briefly stated as follows: an arbitrarily large number of small diameter fibers (< 0.5 mm) are assembled as a matrix and held rigidly in place by a set of precision screens inside an empty container. The container is then back-filled with tungsten powder, compacted on a vibrating table and infused with epoxy under vacuum. The container is then removed. The resulting sub-modules are extremely uniform and achieve roughly the density of pure Lead. The sub-modules are stacked together to achieve a final detector of the desired shape. There is no dead space between sub-modules and the fibers can be in an accordion geometry bent to prevent 'channeling' of the particles due to accidental alignment of their track with the module axis. This technology has the advantage of being modular and inexpensive to the point where the construction work may be divided among groups the size of typical university physics

  17. DYNAMIC STRENGTH AND STRAIN RATE EFFECTS ON FRACTURE BEHAVIOR OF TUNGSTEN AND TUNGSTEN ALLOYS

    OpenAIRE

    Zurek, A; G. Gray

    1991-01-01

    An investigation of the stress-strain response as a function of strain rate, spall strength, and dynamic fracture behavior of pure W, W-26Re, W-Ni- Fe and W-Ni-Fe-Co has been performed. Spall strength measurements, obtained in symmetric-impact tests, showed an increase in spall strength from 0.4 GPa for pure tungsten to 3.8 GPa for 90W-7Ni-3Fe. Concurrent with the increase in spall strength was a change in fracture mode from cleavage (for pure W) to a mixture of transgranular and intergranula...

  18. Annealing induced structural evolution and electrochromic properties of nanostructured tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ching-Lin [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Lin, Chung-Kwei [School of Dental Technology, Taipei Medical University, Taipei City 110, Taiwan, ROC (China); Wang, Chun-Kai [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Wang, Sheng-Chang [Department of Mechanical Engineering, Southern Taiwan University, Tainan 710, Taiwan, ROC (China); Huang, Jow-Lay, E-mail: JLH888@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan, ROC (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan, ROC (China)

    2013-12-31

    The effect of microstructure on the optical and electrochemical properties of nanostructured tungsten oxide films was evaluated as a function of annealing temperature. The films using block copolymer as the template were prepared from peroxotungstic acid (PTA) by spin-coating onto the substrate and post-annealed at 250–400 °C to form tungsten oxide films with nanostructure. The microstructure of the films was measured by X-ray diffraction and surface electron microscopy. The films annealed at temperatures below 300 °C are characterized by amorphous or nanocrystalline structures with a pore size of less than 10 nm. The evaluated annealing temperature caused a triclinic crystalline structure and microcracks. Cyclic voltammetry measurements were performed in a LiClO{sub 4}-propylene carbonate electrolyte. The results showed that the ion inserted capacity were maximized for films annealed at 300 °C and decreased with the increasing of annealing temperature. The electrochromic properties of the nanostructured tungsten oxide films were evaluated simultaneously by potentiostat and UV–vis spectroscopy. The films annealed at 300 °C exhibit high transmission modulation (∆T ∼ 40%) at λ = 633 nm and good kinetic properties. As a result, the correlation between the microstructure and kinetic properties was established, and the electrochromic properties have been demonstrated. - Highlights: • Surfactant-assisted WO{sub 3} films have been prepared by sol–gel method. • Nanostructure of porous WO{sub 3} film is retained after crystallization. • Kinetic properties of WO{sub 3} can be improved by nanostructure and crystallinity.

  19. Plasmons in doped finite carbon nanotubes and their interactions with fast electrons and quantum emitters

    Science.gov (United States)

    de Vega, Sandra; Cox, Joel D.; de Abajo, F. Javier García

    2016-08-01

    We study the potential of highly doped finite carbon nanotubes to serve as plasmonic elements that mediate the interaction between quantum emitters. Similar to graphene, nanotubes support intense plasmons that can be modulated by varying their level of electrical doping. These excitations exhibit large interaction with light and electron beams, as revealed upon examination of the corresponding light extinction cross-section and electron energy-loss spectra. We show that quantum emitters experience record-high Purcell factors, while they undergo strong mutual interaction mediated by their coupling to the tube plasmons. Our results show the potential of doped finite nanotubes as tunable plasmonic materials for quantum optics applications.

  20. The DAMPE silicon–tungsten tracker

    Energy Technology Data Exchange (ETDEWEB)

    Azzarello, P., E-mail: philipp.azzarello@unige.ch [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Ambrosi, G. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Asfandiyarov, R. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Bernardini, P. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare Sezione di Lecce, Lecce (Italy); Bertucci, B.; Bolognini, A. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Cadoux, F. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Caprai, M. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); De Mitri, I. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare Sezione di Lecce, Lecce (Italy); Domenjoz, M. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Dong, Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China); Duranti, M. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Fan, R. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China); and others

    2016-09-21

    The DArk Matter Particle Explorer (DAMPE) is a spaceborne astroparticle physics experiment, launched on 17 December 2015. DAMPE will identify possible dark matter signatures by detecting electrons and photons in the 5 GeV–10 TeV energy range. It will also measure the flux of nuclei up to 100 TeV, for the study of the high energy cosmic ray origin and propagation mechanisms. 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 composed of six tracking planes of 2 orthogonal layers of single-sided micro-strip detectors, for a total detector surface of ca. 7 m{sup 2}. The STK has been extensively tested for space qualification. Also, numerous beam tests at CERN have been done to study particle detection at silicon module level, and at full detector level. After description of the DAMPE payload and its scientific mission, we will describe the STK characteristics and assembly. We will then focus on some results of single ladder performance tests done with particle beams at CERN.

  1. Deuterium accumulation in tungsten at high fluences

    Energy Technology Data Exchange (ETDEWEB)

    Zibrov, Mikhail [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching (Germany); FOM Institute DIFFER, De Zaale 20, 5612 AJ Eindhoven (Netherlands); Balden, Martin; Matej, Matej [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching (Germany); Bystrov, Kirill; Morgan, Thomas [FOM Institute DIFFER, De Zaale 20, 5612 AJ Eindhoven (Netherlands)

    2016-07-01

    The data on the deuterium (D) retention in tungsten (W) at high fluences (≥ 10{sup 27} D/m{sup 2}) are scarce and the existing results are contradictory. Since retention in W is known to be flux-dependent, the laboratory experiments addressing this issue should be carried out in reactor-relevant conditions (high fluxes of low-energy ions). In this work the samples made of polycrystalline W were exposed to D plasmas in the linear plasma generator Pilot-PSI at temperatures ranging from 360 K to 1140 K to fluences in the range of 0.3-8.7 x 10{sup 27} D/m{sup 2}. It was observed that at exposure temperatures of 360 K and 580 K the D retention was only slightly dependent on the ion fluence. In addition, the presence of blister-like structures was found after the exposures, and their density and size distributions were also only weakly dependent on the fluence. In the case of exposure at 1140 K no surface modifications of the samples after plasma exposure were detected and the concentrations of retained D were very small. At all temperatures used the total amounts of retained D were smaller compared to those obtained by other researchers at lower ion flux densities, which indicates that the incident ion flux may play an important role in the total D retention in W.

  2. Anthocyanins facilitate tungsten accumulation in Brassica

    Energy Technology Data Exchange (ETDEWEB)

    Hale, K.L.

    2002-11-01

    Accumulation of molybdenum in Brassica was recently found to be correlated with anthocyanin content, involving the formation of a blue complex. Here the role of anthocyanins in tungsten sequestration was investigated using three species of Brassica: B. rapa (cv. Fast plants), B. juncea (Indian mustard) and B. oleracea (red cabbage). Seedlings of B. rapa and B. juncea turned blue when supplied with colourless tungstate. The blue compound co-localized with anthocyanins in the peripheral cell layers, and the degree of blueness was correlated with anthocyanin content. The direct involvement of anthocyanins in the blue coloration was evident when purified anthocyanins showed a colour change from pink to blue in vitro upon addition of tungstate, over a wide pH range. Anthocyanin production was upregulated 3-fold by W in B. juncea, possibly reflecting a function for anthocyanins in W tolerance or sequestration. The presence of anthocyanins facilitated W accumulation in B. rapa: anthocyanin-containing seedlings accumulated 3-fold more W than an anthocyaninless mutant. There was no correlation between anthocyanin content and W tolerance under these conditions. The nature of the interaction between anthocyanins and tungstate was investigated. X-ray absorption spectroscopy showed no change in the local chemical environment of Wupon uptake of tungstate by the plant; HPLC analysis of purified anthocyanin with or without tungstate showed no peak shift after metal treatment.

  3. Tungsten Oxides for Photocatalysis, Electrochemistry, and Phototherapy.

    Science.gov (United States)

    Huang, Zhen-Feng; Song, Jiajia; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

    2015-09-23

    The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx ≤3 ) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx ≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx ≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control.

  4. Growth of silicon on tungsten diselenide

    Science.gov (United States)

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

    2016-12-01

    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 silicon deposition, the flat WSe2 surface converts into a surface with a hill-and-valley structure. The lattice constant of the hill-and-valley structure is identical to the lattice constant of WSe2 and the transition from hills to valleys is very gradual, suggesting that the top layer is composed of pristine WSe2. In order to verify this conjecture, we have removed the height information from our scanning tunneling microscopy signal and obtained chemical contrast of the surface by recording dI/dz, rather than the conventional regulation voltage of the z-piezo. The spatially resolved dI/dz maps provide compelling evidence that the deposited silicon does indeed not reside on top of the WSe2 substrate.

  5. VARIATION OF RESOLVED PROPORTIONAL LIMIT WITH MOSAIC ANGLE FROM 77K TO 973K IN ZONE REFINED TUNGSTEN,

    Science.gov (United States)

    TUNGSTEN, *FRACTOGRAPHY), (*CRYSTAL SUBSTRUCTURE, TUNGSTEN), ZONE MELTING, DISLOCATIONS, GRAIN BOUNDARIES, ELECTRON BEAM MELTING , STRAIN(MECHANICS), IMPURITIES, TENSILE PROPERTIES, SINGLE CRYSTALS, CRYOGENICS, HIGH TEMPERATURE

  6. Tungsten Contact and Line Resistance Reduction with Advanced Pulsed Nucleation Layer and Low Resistivity Tungsten Treatment

    Science.gov (United States)

    Chandrashekar, Anand; Chen, Feng; Lin, Jasmine; Humayun, Raashina; Wongsenakhum, Panya; Chang, Sean; Danek, Michal; Itou, Takamasa; Nakayama, Tomoo; Kariya, Atsushi; Kawaguchi, Masazumi; Hizume, Shunichi

    2010-09-01

    This paper describes electrical testing results of new tungsten chemical vapor deposition (CVD-W) process concepts that were developed to address the W contact and bitline scaling issues on 55 nm node devices. Contact resistance (Rc) measurements in complementary metal oxide semiconductor (CMOS) devices indicate that the new CVD-W process for sub-32 nm and beyond - consisting of an advanced pulsed nucleation layer (PNL) combined with low resistivity tungsten (LRW) initiation - produces a 20-30% drop in Rc for diffused NiSi contacts. From cross-sectional bright field and dark field transmission electron microscopy (TEM) analysis, such Rc improvement can be attributed to improved plugfill and larger in-feature W grain size with the advanced PNL+LRW process. More experiments that measured contact resistance for different feature sizes point to favorable Rc scaling with the advanced PNL+LRW process. Finally, 40% improvement in line resistance was observed with this process as tested on 55 nm embedded dynamic random access memory (DRAM) devices, confirming that the advanced PNL+LRW process can be an effective metallization solution for sub-32 nm devices.

  7. Chemically deposited tungsten fibre-reinforced tungsten – The way to a mock-up for divertor applications

    Directory of Open Access Journals (Sweden)

    J. Riesch

    2016-12-01

    Full Text Available The development of advanced materials is essential for sophisticated energy systems like a future fusion reactor. Tungsten fibre-reinforced tungsten composites (Wf/W utilize extrinsic toughening mechanisms and therefore overcome the intrinsic brittleness of tungsten at low temperature and its sensitivity to operational embrittlement. This material has been successfully produced and tested during the last years and the focus is now put on the technological realisation for the use in plasma facing components of fusion devices. In this contribution, we present a way to utilize Wf/W composites for divertor applications by a fabrication route based on the chemical vapour deposition (CVD of tungsten. Mock-ups based on the ITER typical design can be realized by the implementation of Wf/W tiles. A concept based on a layered deposition approach allows the production of such tiles in the required geometry. One fibre layer after the other is positioned and ingrown into the W-matrix until the final sample size is reached. Charpy impact tests on these samples showed an increased fracture energy mainly due to the ductile deformation of the tungsten fibres. The use of Wf/W could broaden the operation temperature window of tungsten significantly and mitigate problems of deep cracking occurring typically in cyclic high heat flux loading. Textile techniques are utilized to optimise the tungsten wire positioning and process speed of preform production. A new device dedicated to the chemical deposition of W enhances significantly, the available machine time for processing and optimisation. Modelling shows that good deposition results are achievable by the use of a convectional flow and a directed temperature profile in an infiltration process.

  8. Accelerated Molecular Dynamics studies of He Bubble Growth in Tungsten

    Science.gov (United States)

    Uberuaga, Blas; Sandoval, Luis; Perez, Danny; Voter, Arthur

    2015-11-01

    Understanding how materials respond to extreme environments is critical for predicting and improving performance. In materials such as tungsten exposed to plasmas for nuclear fusion applications, novel nanoscale fuzzes, comprised of tendrils of tungsten, form as a consequence of the implantation of He into the near surface. However, the detailed mechanisms that link He bubble formation to the ultimate development of fuzz are unclear. Molecular dynamics simulations provide insight into the He implantation process, but are necessarily performed at implantation rates that are orders of magnitudes faster than experiment. Here, using accelerated molecular dynamics methods, we examine the role of He implantation rates on the physical evolution of He bubbles in tungsten. We find that, as the He rate is reduced, new types of events involving the response of the tungsten matrix to the pressure in the bubble become competitive and change the overall evolution of the bubble as well as the subsequent morphology of the tungsten surface. We have also examined how bubble growth differs at various microstructural features. These results highlight the importance of performing simulations at experimentally relevant conditions in order to correctly capture the contributions of the various significant kinetic processes and predict the overall response of the material.

  9. Ambient Pressure Synthesis of Nanostructured Tungsten Oxide Crystalline Films

    Directory of Open Access Journals (Sweden)

    H. X. Zhang

    2008-01-01

    Full Text Available We report the results of the ambient pressure synthesis of tungsten oxide nanowires and nanoparticles on AlN substrates using the hot filament CVD techniques. The morphologic surface, crystallographic structures, chemical compositions, and bond structures of the obtained samples have been investigated using scanning electron microscopy (SEM, X-ray diffraction (XRD, energy dispersive X-ray spectroscopy (EDX, and Raman scattering, respectively. Different morphologies were observed for different substrate temperatures, but otherwise identical growth conditions. The experimental measurements reveal the evolutions of the crystalline states and bond structures following the substrate temperatures. Besides, different substrate materials also affected the tungsten oxide nanostructures. Bundles of wire-type tungsten oxide nanowires with a length of up to 5 mm were obtained on Al2O3 substrate. Furthermore, the sensitive properties of the super long nanowires to the gas and different temperature were investigated. The dependence of the sensitivity of tungsten oxide nanowires to the methane as a function of the time was obtained. The sensitive properties of the tungsten oxide nanowires have almost linear relationship with the temperature.

  10. Measurements and modelling of hydrogen dynamics in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Johannes [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Technische Universitaet Muenchen, James-Franck-Str. 1, D-85748 Garching (Germany); Schwarz-Selinger, Thomas; Schmid, Klaus; Toussaint, Udo von; Jacob, Wolfgang [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

    2015-05-01

    Although hydrogen retention in defect free tungsten is low it can be significantly altered by plasma wetting. Thus understanding the interaction and dynamics of hydrogen in tungsten becomes an important issue. Present understanding distinguishes between solute and trapped hydrogen inventory. The solute hydrogen is located in the tetrahedral interstitial sites of bbc tungsten and can diffuse rapidly due to the low activation energy of 0.2-0.4 eV. The trapped hydrogen inventory resides at defects like vacancies, grain boundaries or dislocations, with de-trapping energies between 0.8-2.0 eV and is therefore less mobile. Common ex-situ experiments only allow the investigation of hydrogen retained in traps, while the solute is out of experimental reach due to its fast out-gassing at ambient temperatures. In this study the dynamics of the solute hydrogen in tungsten is measured in-situ for the first time. Diffusion/trapping simulations reveal that for low temperature e.g. 200 K, the solute hydrogen dominates the total inventory and its out-gassing after implantation is slowed down to the timescale of hours. Therefore in-situ hydrogen implantation and nuclear reaction analysis of tungsten samples are conducted at temperatures down to 140 K investigating experimentally the dynamics of solute hydrogen.

  11. A Conceptual Multi-Megawatt System Based on a Tungsten CERMET Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Jonathan A. Webb; Brian Gross

    2011-02-01

    Abstract. A conceptual reactor system to support Multi-Megawatt Nuclear Electric Propulsion is investigated within this paper. The reactor system consists of a helium cooled Tungsten-UN fission core, surrounded by a beryllium neutron reflector and 13 B4C control drums coupled to a high temperature Brayton power conversion system. Excess heat is rejected via carbon reinforced heat pipe radiators and the gamma and neutron flux is attenuated via segmented shielding consisting of lithium hydride and tungsten layers. Turbine inlet temperatures ranging from 1300 K to 1500 K are investigated for their effects on specific powers and net electrical outputs ranging from 1 MW to 100 MW. The reactor system is estimated to have a mass, which ranges from 15 Mt at 1 MWe and a turbine inlet temperature of 1500 K to 1200 Mt at 100 MWe and a turbine temperature of 1300 K. The reactor systems specific mass ranges from 32 kg/kWe at a turbine inlet temperature of 1300 K and a power of 1 MWe to 9.5 kg/kW at a turbine temperature of 1500 K and a power of 100 MWe.

  12. Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

    Energy Technology Data Exchange (ETDEWEB)

    De Bonis, A. [Dipartimento di Chimica ' A.M. Tamburro' , Universita della Basilicata, Via dell' Ateneo Lucano 10, 85100 Potenza (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali - INSTM, Via G. Giusti 9, 00121 Florence (Italy); Teghil, R., E-mail: roberto.teghil@unibas.it [Dipartimento di Chimica ' A.M. Tamburro' , Universita della Basilicata, Via dell' Ateneo Lucano 10, 85100 Potenza (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali - INSTM, Via G. Giusti 9, 00121 Florence (Italy); Santagata, A. [Istituto Metodologie Inorganiche e Plasmi, CNR, Unita di Potenza, via S. Loja, 85050 Tito Scalo PZ (Italy); Galasso, A. [Dipartimento di Chimica ' A.M. Tamburro' , Universita della Basilicata, Via dell' Ateneo Lucano 10, 85100 Potenza (Italy); Rau, J.V. [Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Rome (Italy)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer We have deposited amorphous tungsten carbide films by ultra-short PLD. Black-Right-Pointing-Pointer In the films different W-C phases are present. Black-Right-Pointing-Pointer The films are formed mainly by particles with nanometric size. Black-Right-Pointing-Pointer We propose that the particles are directly ejected from the target. - Abstract: Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

  13. 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.

  14. Numerical analyses of JT-60SA tokamak with tungsten divertor by COREDIV code

    Science.gov (United States)

    Gałązka, K.; Ivanova-Stanik, I.; Stępniewski, W.; Zagórski, R.; Neu, R.; Romanelli, M.; Nakano, T.

    2017-04-01

    An analysis of radiative power exhaust for the JT-60SA tokamak with a tungsten divertor is performed with the help of the self-consistent, core-edge integrated COREDIV code. Two scenarios of operation (low and high density) were investigated in the scope of different parameters (electron density at the separatrix and the perpendicular transport in the scrape-off layer) with impurity seeding (Ne and Kr). The calculations show that in the case of the tungsten divertor the power load to the divertor plate is mitigated and the central plasma dilution is smaller compared to the carbon divertor. In the most cases the energy flux through the separatrix is above the L–H transition threshold. For the high density case with neon seeding operation in full detachment mode is observed. Changing the diffusion coefficient in the SOL has a strong influence on the result of the calculations as increased radial transport causes stronger screening effect. Also by changing the electron density on the separatrix the influx of heavy impurities (W, Kr) into the core region can be reduced. The results demonstrate that it is easier to achieve sustainable conditions in the divertor region for the high density scenario, whereas for the low density one reducing the auxiliary heating power seems unavoidable to prevent damaging of the target plate, even for strong seeding gas influx.

  15. 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.

  16. 75 FR 75694 - Certain Semiconductor Integration Circuits Using Tungsten Metallization and Products Containing...

    Science.gov (United States)

    2010-12-06

    ... COMMISSION Certain Semiconductor Integration Circuits Using Tungsten Metallization and Products Containing... United States after importation of certain semiconductor integrated circuits using tungsten metallization... following six respondents ] remained in the investigation: Tower Semiconductor, Ltd. of Israel;...

  17. Mechanical-property evaluation of a series of commercial tungsten alloys. Memorandum report

    Energy Technology Data Exchange (ETDEWEB)

    Bruchey, W.J.; Montiel, D.M.

    1987-06-01

    A series of commercially available tungsten alloys ranging in tungsten content from 75% to 95% were evaluated. Typical tensile and compressive engineering properties are reported. These tests were conducted in support of penetrator ballistic-test programs.

  18. Largest domestic tungsten and molybdenum deep processing project finding its home in Luan-chuan

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>Recently, a tungsten and molybdenum deep processing project was formally executed with a joint investment of 300 million yuan from Luanchuan Molybdenum Mining & Smelting Co., Ltd, Beijing Tian-Long Tungsten & Mo-

  19. Mathematical Modelling of the Process of Tungsten Fluorides Reduction by Hydrogen

    OpenAIRE

    Brendakov Roman; Shvab Alexander; Brendakov Vladimir

    2016-01-01

    The process of tungsten fluorides reduction by hydrogen is a component part of Fluoride technology of tungsten conversion. Nowadays the researchers are definitely interested in studying this process. It is connected with common use of metal tungsten products in different sectors of the economy, which is the result of unique qualities of this metal. With the help of physical and mathematical modelling of the process of tungsten hexafluoride reduction by hydrogen, it becomes possible to create ...

  20. Properties of drawn W wire used as high performance fibre in tungsten fibre-reinforced tungsten composite

    Science.gov (United States)

    Riesch, J.; Almanstötter, J.; Coenen, J. W.; Fuhr, M.; Gietl, H.; Han, Y.; Höschen, T.; Linsmeier, Ch; Travitzky, N.; Zhao, P.; Neu, R.

    2016-07-01

    High strength and creep resistance also at high temperature, combined with a high thermal conductivity and high melting point make tungsten (W) an ideal material for highly loaded areas in future fusion reactors. However, as a typical bcc metal tungsten features an intrinsic brittleness up to very high temperature and is prone to operational embrittlement. Tungsten fibre-reinforced tungsten composite (Wf/W) utilizes extrinsic toughening mechanisms similar to ceramic fibre-reinforced ceramics and therefore overcomes the brittleness problem. The properties of the composite are to a large extend determined by the properties of the drawn tungsten wire used as reinforcement fibres. W wire exhibits a superior strength and shows ductile behaviour with exceptional local plasticity. Beside the typical mechanisms observed for ceramic composites the ductile deformation of the fibres is therefore an additional very effective toughening mechanism. Tension tests were used to investigate this phenomenon in more detail. Results show that there is a region of enhanced localized plastic deformation. The specific energy consumption in this region was estimated and used to suggest optimisation options for Wf/W composites.

  1. 3D-microscopy of hydrogen in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Peeper, K., E-mail: katrin.peeper@unibw.de [Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85577 München (Germany); Moser, M.; Reichart, P. [Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85577 München (Germany); Markina, E.; Mayer, M.; Lindig, S.; Balden, M. [Max-Planck-Institute for Plasma Physics, EURATOM Association, Boltzmannstraße 2, D-85748 Garching (Germany); Dollinger, G. [Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85577 München (Germany)

    2013-07-15

    The mapping of hydrogen distributions in 3 dimensions and its correlation with structural features allow further insight into mechanisms of hydrogen trapping in tungsten. We studied hydrogen distributions in 25 μm thick polycrystalline tungsten foils by 3D hydrogen microscopy using a proton–proton-scattering method. Two types of tungsten samples were prepared: (i) at 1200 K annealed foils and using 1.8 MeV implantation energy (ii) at 2000 K annealed foils using 200 eV implantation energy. It has been found that large variations of surface hydrogen contamination occur within different samples. Nevertheless, a statistically significant variation of the hydrogen content across grain boundaries has been observed.

  2. Field-emission spectroscopy of beryllium atoms adsorbed on tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Czyzewski, J.J.; Grzesiak, W.; Krajniak, J. (Politechnika Wroclawska (Poland))

    1981-01-01

    Field emission energy distributions (FEED) have been measured for the beryllium-tungsten (023) adsorption system over the 78-450 K temperature range. A temperature dependence of the normalized half-width, ..delta../d, of FEED peaks changed significantly due to beryllium adsorption; and the curve, ..delta../d vs p, for the Be/W adsorption system was identical in character to the calculated curve based on the free electron model in contrast to the curve for the clean tungsten surface. In the last part of this paper Gadzuk's theory of the resonance-tunneling effect is applied to the beryllium atom on tungsten. Experimental and theoretical curves of the enhancement factor as a function of energy have been discussed.

  3. Tungsten-microdiamond composites for plasma facing components

    Science.gov (United States)

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

    2011-09-01

    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.

  4. Recombination of open-f-shell tungsten ions

    Science.gov (United States)

    Krantz, C.; Badnell, N. R.; Müller, A.; Schippers, S.; Wolf, A.

    2017-03-01

    We review experimental and theoretical efforts aimed at a detailed understanding of the recombination of electrons with highly charged tungsten ions characterised by an open 4f sub-shell. Highly charged tungsten occurs as a plasma contaminant in ITER-like tokamak experiments, where it acts as an unwanted cooling agent. Modelling of the charge state populations in a plasma requires reliable thermal rate coefficients for charge-changing electron collisions. The electron recombination of medium-charged tungsten species with open 4f sub-shells is especially challenging to compute reliably. Storage-ring experiments have been conducted that yielded recombination rate coefficients at high energy resolution and well-understood systematics. Significant deviations compared to simplified, but prevalent, computational models have been found. A new class of ab initio numerical calculations has been developed that provides reliable predictions of the total plasma recombination rate coefficients for these ions.

  5. Effect of neon plasma pre-irradiation on surface morphology and deuterium retention of tungsten

    NARCIS (Netherlands)

    Cheng, L.; De Temmerman, G.; van Emmichoven, P. A. Zeijlma; Ji, G.; Zhou, H. B.; Wang, B.; Yuan, Y.; Zhang, Y.; Lu, G. H.

    2015-01-01

    Neon and deuterium plasma irradiation of polycrystalline tungsten targets have been performed at high fluxes of ∼1024 ions m−2 s−1 to study the interaction of neon with tungsten and the influence of neon on deuterium retention. Tungsten exposure to neon plasma leads to the

  6. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Science.gov (United States)

    2010-07-01

    ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the secondary tungsten and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting from...

  7. 40 CFR 440.60 - Applicability; description of the tungsten ore subcategory.

    Science.gov (United States)

    2010-07-01

    ... tungsten ore subcategory. 440.60 Section 440.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORE MINING AND DRESSING POINT SOURCE CATEGORY Tungsten Ore Subcategory § 440.60 Applicability; description of the tungsten ore subcategory. The provisions of...

  8. 75 FR 39678 - Bishop Tungsten Development, LLC; Notice of Application Accepted for Filing and Soliciting...

    Science.gov (United States)

    2010-07-12

    ... Energy Regulatory Commission Bishop Tungsten Development, LLC; Notice of Application Accepted for Filing....: 13163-000. c. Date filed: April 3, 2008. d. Applicant: Bishop Tungsten Development, LLC. e. Name of.... Hicks, Bishop Tungsten Development, LLC, 9050 Pine Creek Road, Bishop, CA 93514, phone (760) 387-2080....

  9. Loss of Balance between Tungsten Reserve and Mining, China’s Resource Advantage Is Weakening

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    <正>China’s tungsten reserve, product output, export trade volume and consumption all rank top in the world. By offering supply for more than 80% global tungsten consumption with less than 50% of global tungsten ore resource, China has made significant contribution to the development of

  10. 75 FR 66082 - Bishop Tungsten Development, LLC; Notice of Preliminary Permit Application Accepted for Filing...

    Science.gov (United States)

    2010-10-27

    ... Federal Energy Regulatory Commission Bishop Tungsten Development, LLC; Notice of Preliminary Permit... October 20, 2010. On November 9, 2009, Bishop Tungsten Development, LLC filed an application for a... Tungsten Development, LLC, 725 9050 Pine Creek Road, Bishop, CA 93514; phone: (706) 387-2080. FERC...

  11. 75 FR 66079 - Bishop Tungsten Development, LLC; Notice of Preliminary Permit Application Accepted for Filing...

    Science.gov (United States)

    2010-10-27

    ... Energy Regulatory Commission Bishop Tungsten Development, LLC; Notice of Preliminary Permit Application..., 2010. On November 9, 2009, Bishop Tungsten Development, LLC filed an application for a preliminary... be 26,300,000 kilowatt-hours. Applicant Contact: Douglas A. Hicks, Bishop Tungsten Development,...

  12. The WiZard/CAPRICE silicon-tungsten calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Bocciolini, M. [Florence Univ. (Italy). Dipt. di Fisica; Celletti, F. [Florence Univ. (Italy). Dipt. di Fisica; Finetti, N. [Florence Univ. (Italy). Dipt. di Fisica; Grandi, M. [Florence Univ. (Italy). Dipt. di Fisica; Papini, P. [Florence Univ. (Italy). Dipt. di Fisica; Perego, A. [Florence Univ. (Italy). Dipt. di Fisica; Piccardi, S. [Florence Univ. (Italy). Dipt. di Fisica; Spillantini, P. [Florence Univ. (Italy). Dipt. di Fisica; Bidoli, V. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); Candusso, M. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); Casolino, M. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); De Pascale, M.P. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); Morselli, A. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); Picozza, P. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); Sparvoli, R. [Dipartimento di Fisica dell`Universita `Tor Vergata`, and Sezione INFN di Roma 1I (Italy); Basini, G. [Laboratori Nazionali INFN, Frascati (Italy); Mazzenga, G. [Laboratori Nazionali INFN, Frascati (Italy); Ricci, M. [Laboratori Nazionali INFN, Frascati (Italy); Bronzini, F. [Dipartimento di Fisica dell`Universita `La Sapienza`, and Sezione INFN di Roma (Italy); Barbiellini, G. [Dipartimento di Fisica dell`Universita, Trieste and Sezione INFN di Trieste, Trieste (Italy); Boezio, M. [Dipartimento di Fisica dell`Universita, Trieste and Sezione INFN di Trieste, Trieste (Italy); Bravar, U. [Dipartimento di Fisica dell`Universita, Trieste and Sezione INFN di Trieste, Trieste (Italy); Fratnik, F. [Dipartimento di Fisica dell`Universita, Trieste and Sezione INFN di Trieste, Trieste (Italy); Schiavon, P. [Dipartimento di Fisica dell`Universita, Trieste and Sezione INFN di Trie (Italy)

    1996-02-21

    A silicon-tungsten calorimeter has been developed to be flown in the WiZard/CAPRICE balloon borne experiment to measure the flux of antiprotons, positrons and light nuclei in the cosmic radiation. The calorimeter is composed of 8 x,y silicon sampling planes [active area (48 x 48) cm{sup 2}] interleaved with 7 tungsten absorbers (7 radiation lengths); it provides the topology of the interacting events together with an independent measurement of the deposited energy. Details of the front-end electronics and of the read-out system are given and the overall performances during pre-flight ground operations are described as well. (orig.).

  13. The WiZard/CAPRICE silicon-tungsten calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    Bocciolini, M.; Celletti, F.; Finetti, N.; Grandi, M.; Papini, P.; Perego, A.; Piccardi, S.; Spillantini, P. [Florence Univ. (Italy). Dip. di Fisica]|[INFN, Florence (Italy); Bidoli, V.; Candusso, M. [Rome Univ. `Tor Vergata` (Italy). Dip. di Fisica]|[INFN, Sezione di Roma II (Italy)

    1995-09-01

    A silicon-tungsten calorimeter has been developed to be flown in the WiZard/ CAPRICE balloon borne experiment to measure the flux of antiprotons, positrons and light nuclei in the cosmic radiation. The calorimeter is composed of 8 x, y silicon sampling planes (active area (48x48) cm{sup 2}) interleaved with 7 tungsten absorbers (7 radiation lengths); it provides the topology of the interacting events together with an independent measurement of the deposited energy. Details of the front-end electronics and of the read-out system are given and the overall performances during pre-flight ground operations are described as well.

  14. Temperature and distortion transients in gas tungsten-arc weldments

    Energy Technology Data Exchange (ETDEWEB)

    Glickstein, S.S.; Friedman, E.

    1979-10-01

    An analysis and test program to develop a fundamental understanding of the gas tungsten-arc welding process has been undertaken at the Bettis Atomic Power Laboratory to develop techniques to determine and control the various welding parameters and weldment conditions so as to result in optimum weld response characteristics. These response characteristics include depth of penetration, weld bead configuration, weld bead sink and roll, distortion, and cracking sensitivity. The results are documented of that part of the program devoted to analytical and experimental investigations of temperatures, weld bead dimensions, and distortions for moving gas tungsten-arc welds applied to Alloy 600 plates.

  15. Effects of laser ablation on cemented tungsten carbide surface quality

    Energy Technology Data Exchange (ETDEWEB)

    Tan, J.L.; Butler, D.L.; Sim, L.M.; Jarfors, A.E.W. [Singapore Institute of Manufacturing Technology, Singapore (Singapore)

    2010-11-15

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable. (orig.)

  16. Effects of laser ablation on cemented tungsten carbide surface quality

    Science.gov (United States)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  17. Electronic transport and scattering times in tungsten-decorated graphene

    Science.gov (United States)

    Elias, Jamie A.; Henriksen, Erik A.

    2017-02-01

    The electronic transport properties of a monolayer graphene device have been studied before and after the deposition of a dilute coating of tungsten adatoms on the surface. For coverages up to 2.5% of a monolayer, we find tungsten adatoms simultaneously donate electrons to graphene and reduce the carrier mobility, impacting the zero- and finite-field transport properties. Two independent transport analyses suggest the adatoms lie nearly 1 nm above the surface. The presence of adatoms is also seen to impact the low-field magnetoresistance, altering the signatures of weak localization.

  18. Quantum-Accurate Molecular Dynamics Potential for Tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Mitchell; Thompson, Aidan P.

    2017-03-01

    The purpose of this short contribution is to report on the development of a Spectral Neighbor Analysis Potential (SNAP) for tungsten. We have focused on the characterization of elastic and defect properties of the pure material in order to support molecular dynamics simulations of plasma-facing materials in fusion reactors. A parallel genetic algorithm approach was used to efficiently search for fitting parameters optimized against a large number of objective functions. In addition, we have shown that this many-body tungsten potential can be used in conjunction with a simple helium pair potential1 to produce accurate defect formation energies for the W-He binary system.

  19. Polaron transitions in charge intercalated amorphous tungsten oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Saenger, M.F.; Hofmann, T.; Schubert, M. [Department of Electrical Engineering, and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln (United States); Hoeing, T. [Flabeg GmbH and Co. KG, Furth im Wald (Germany)

    2008-04-15

    We present a parametric dielectric function model in dependence of the intercalated charge per tungsten ion ratio x, which excellently describes the ellipsometric experimental data, and allows the identification of two polaron modes corresponding to transitions between W{sup 4+} and W{sup 5+} and between W{sup 5+} and W{sup 6+} tungsten ion sites. A competitive relation between the two polaron transitions is found. An empirical relation for the amplitude of the polaron transitions is found useful to provide a good description of the polaron transition dependence on x. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. [Murine peritoneal neutrophil activation upon tungsten nanoparticles exposure in vivo].

    Science.gov (United States)

    Martinova, E A; Baranov, V I

    2014-01-01

    Two examples of tungsten carbide nanoparticles (d = 15 nm, 50 nm) and tungsten carbide nanoparticles with 8% cobalt (d = 50 nm) have been found to induce the neutrophil activation 3 h and 36 h after intraperitoneal administration in the doses 0.005; 0.025; 0.05; 0.25; 0.5; 1; 2.5 and 5 microgram per 1 gram body weight to FVB mice. Neutrophil activation was calculated based on the CD11b and S100 antigen expression. Effect of nanoparticles is bimodal for all tested examples.

  1. Dislocation mechanism of deuterium retention in tungsten under plasma implantation.

    Science.gov (United States)

    Dubinko, V I; Grigorev, P; Bakaev, A; Terentyev, D; van Oost, G; Gao, F; Van Neck, D; Zhurkin, E E

    2014-10-01

    We have developed a new theoretical model for deuterium (D) retention in tungsten-based alloys on the basis of its being trapped at dislocations and transported to the surface via the dislocation network with parameters determined by ab initio calculations. The model is used to explain experimentally observed trends of D retention under sub-threshold implantation, which does not produce stable lattice defects to act as traps for D in conventional models. Saturation of D retention with implantation dose and effects due to alloying of tungsten with, e.g. tantalum, are evaluated, and comparison of the model predictions with experimental observations under high-flux plasma implantation conditions is presented.

  2. Engineered Surface Properties of Porous Tungsten from Cryogenic Machining

    Science.gov (United States)

    Schoop, Julius Malte

    Porous tungsten is used to manufacture dispenser cathodes due to it refractory properties. Surface porosity is critical to functional performance of dispenser cathodes because it allows for an impregnated ceramic compound to migrate to the emitting surface, lowering its work function. Likewise, surface roughness is important because it is necessary to ensure uniform wetting of the molten impregnate during high temperature service. Current industry practice to achieve surface roughness and surface porosity requirements involves the use of a plastic infiltrant during machining. After machining, the infiltrant is baked and the cathode pellet is impregnated. In this context, cryogenic machining is investigated as a substitutionary process for the current plastic infiltration process. Along with significant reductions in cycle time and resource use, surface quality of cryogenically machined un-infiltrated (as-sintered) porous tungsten has been shown to significantly outperform dry machining. The present study is focused on examining the relationship between machining parameters and cooling condition on the as-machined surface integrity of porous tungsten. The effects of cryogenic pre-cooling, rake angle, cutting speed, depth of cut and feed are all taken into consideration with respect to machining-induced surface morphology. Cermet and Polycrystalline diamond (PCD) cutting tools are used to develop high performance cryogenic machining of porous tungsten. Dry and pre-heated machining were investigated as a means to allow for ductile mode machining, yet severe tool-wear and undesirable smearing limited the feasibility of these approaches. By using modified PCD cutting tools, high speed machining of porous tungsten at cutting speeds up to 400 m/min is achieved for the first time. Beyond a critical speed, brittle fracture and built-up edge are eliminated as the result of a brittle to ductile transition. A model of critical chip thickness ( hc ) effects based on cutting

  3. Structural, electrochemical and optical comparisons of tungsten oxide coatings derived from tungsten powder-based sols

    Energy Technology Data Exchange (ETDEWEB)

    Isik, Dilek, E-mail: e145342@metu.edu.t [Department of Metallurgical and Materials Engineering, METU, 06531 Ankara (Turkey); Ak, Metin, E-mail: metinak@pamukkale.edu.t [Department of Chemistry, Pamukkale University, 20017 Denizli (Turkey); Durucan, Caner, E-mail: cdurucan@metu.edu.t [Department of Metallurgical and Materials Engineering, METU, 06531 Ankara (Turkey)

    2009-11-02

    Tungsten trioxide (WO{sub 3}) electrochromic coatings have been formed on indium tin oxide-coated glass substrates by aqueous routes. Coating sols are obtained by dissolving tungsten powder in acetylated (APTA) or plain peroxotungstic acid (PTA) solutions. The structural evolution and electrochromic performance of the coatings as a function of calcination temperature (250 {sup o}C and 400 {sup o}C) have been reported. Differential scanning calorimetry and X-ray diffraction have shown that amorphous WO{sub 3} films are formed after calcination at 250 {sup o}C for both processing routes; however, the coatings that calcined at 400 {sup o}C were crystalline in both cases. The calcination temperature-dependent crystallinity of the coatings results in differences in optical properties of the coatings. Higher coloration efficiencies can be achieved with amorphous coatings than could be seen in the crystalline coatings. The transmittance values (at 800 nm) in the colored state are 35% and 56% for 250 {sup o}C and 400 {sup o}C-calcined coatings, respectively. The electrochemical properties are more significantly influenced by the method of sol preparation. The ion storage capacities designating the electrochemical properties are found in the range of 1.62-2.74 x 10{sup -3} (mC cm{sup -2}) for APTA coatings; and 0.35-1.62 x 10{sup -3} (mC cm{sup -2}) for PTA coatings. As a result, a correlation between the microstructure and the electrochromic performance has been established.

  4. Surface damage characteristics of CFC and tungsten with repetitive ELM-like pulsed plasma irradiation

    Science.gov (United States)

    Kikuchi, Y.; Nishijima, D.; Nakatsuka, M.; Ando, K.; Higashi, T.; Ueno, Y.; Ishihara, M.; Shoda, K.; Nagata, M.; Kawai, T.; Ueda, Y.; Fukumoto, N.; Doerner, R. P.

    2011-08-01

    Surface damage of carbon fiber composite (CFC) and tungsten (W) due to repetitive ELM-like pulsed plasma irradiation has been investigated by using a magnetized coaxial plasma gun. CX2002U CFC and stress-relieved W samples were exposed to repetitive pulsed deuterium plasmas with duration of ˜0.5 ms, incident ion energy of ˜30 eV, and surface absorbed energy density of ˜0.3-0.7 MJ/m2. Bright spots on a CFC surface during pulsed plasma exposures were clearly observed with a high-speed camera, indicating a local surface heating. No melting of a W surface was observed under a single plasma pulse exposure at energy density of ˜0.7 MJ/m2, although cracks were formed. Cracking of the W surface grew with repetitive pulsed plasma exposures. Subsequently, the surface melted due to localized heat absorption.

  5. Video analysis of dust events in full-tungsten ASDEX Upgrade

    Science.gov (United States)

    Brochard, F.; Shalpegin, A.; Bardin, S.; Lunt, T.; Rohde, V.; Briançon, J. L.; Pautasso, G.; Vorpahl, C.; Neu, R.; The ASDEX Upgrade Team

    2017-03-01

    Fast video data recorded during seven consecutive operation campaigns (2008-2012) in full-tungsten ASDEX Upgrade have been analyzed with an algorithm developed to automatically detect and track dust particles. A total of 2425 discharges have been analyzed, corresponding to 12 204 s of plasma operation. The analysis aimed at precisely identifying and sorting the discharge conditions responsible of the dust generation or remobilization. Dust rates are found to be significantly lower than in tokamaks with carbon PFCs. Significant dust events occur mostly during off-normal plasma phases such as disruptions and particularly those preceded by vertical displacement events (VDEs). Dust rates are also increased but to a lower extent during type-I ELMy H-modes. The influences of disruption energy, heating scenario, vessel venting and vessel vibrations are also presented.

  6. Tungsten Oxide and Polyaniline Composite Fabricated by Surfactant-Templated Electrodeposition and Its Use in Supercapacitors

    Directory of Open Access Journals (Sweden)

    Benxue Zou

    2014-01-01

    Full Text Available Composite nanostructures of tungsten oxide and polyaniline (PANI were fabricated on carbon electrode by electrocodeposition using sodium dodecylbenzene sulfonate (SDBS as the template. The morphology of the composite can be controlled by changing SDBS surfactant and aniline monomer concentrations in solution. With increasing concentration of aniline in surfactant solution, the morphological change from nanoparticles to nanofibers was observed. The nanostructured WO3/PANI composite exhibited enhanced capacitive charge storage with the specific capacitance of 201 F g−1 at 1.28 mA cm−2 in large potential window of -0.5~ 0.65 V versus SCE compared to the bulk composite film. The capacitance retained about 78% when the sweeping potential rate increased from 10 to 150 mV/s.

  7. Microcrystalline hexagonal tungsten bronze. 2. Dehydration dynamics.

    Science.gov (United States)

    Luca, Vittorio; Griffith, Christopher S; Hanna, John V

    2009-07-06

    Low-temperature (25-600 degrees C) thermal transformations have been studied for hydrothermally prepared, microcrystalline hexagonal tungsten bronze (HTB) phases A(x)WO(3+x/2).zH(2)O as a function of temperature, where A is an exchangeable cation (in this case Na(+) or Cs(+)) located in hexagonal structural tunnels. Thermal treatment of the as-prepared sodium- and cesium-exchanged phases in air were monitored using a conventional laboratory-based X-ray diffractometer, while thermal transformations in vacuum were studied using synchrotron X-ray and neutron diffraction. Concurrent thermogravimetric, diffuse reflectance infrared (DRIFT), and (23)Na and (133)Cs magic angle spinning (MAS) NMR spectroscopic studies have also been undertaken. For the cesium variant, cell volume contraction occurred from room temperature to about 350 degrees C, the regime in which water was "squeezed" out of tunnel sites. This was followed by a lattice expansion in the 350-600 degrees C temperature range. Over the entire temperature range, a net thermal contraction was observed, and this was the result of an anisotropic change in the cell dimensions which included a shortening of the A-O2 bond length. These changes explain why Cs(+) ions are locked into tunnel positions at temperatures as low as 400 degrees C, subsequently inducing a significant reduction in Cs(+) extractability under low pH (nitric acid) conditions. The changing Cs(+) speciation as detected by (133)Cs MAS NMR showed a condensation from multiple Cs sites, presumably associated with differing modes of Cs(+) hydration in the tunnels, to a single Cs(+) environment upon thermal transformation and water removal. While similar lattice contraction was observed for the as-prepared sodium variant, the smaller radius of Na(+) caused it to be relatively easily removed with acid in comparison to the Cs(+) variant. From (23)Na MAS NMR studies of the parent material, complex Na(+) speciation was observed with dehydrated and various

  8. Tailoring of fuzzy nanostructures on porous tungsten skeleton by helium plasma irradiation

    Science.gov (United States)

    Kajita, Shin; Tanaka, Hirohiko; Ohno, Noriyasu

    2017-03-01

    Porous tungsten skeleton, which was fabricated by sintering of tungsten powder, was exposed to helium plasmas, and the fuzzy nanostructures were tailored on the surface. The hemispherical optical reflectance of the samples was measured at the wavelength of 633 nm. It was shown that the optical reflectance of the porous tungsten skeleton was lower than that of flat tungsten samples. The minimum reflectance was ∼0.4%, suggesting that the darkest metallic material was fabricated. The advantage of the porous tungsten skeleton with nanostructures for optical application is discussed.

  9. Molybdenum incorporation in tungsten aldehyde oxidoreductase enzymes from Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M; Bevers, L.E.; Pinkse, M.W.H.; Krijger, G.C.; Wolterbeek, H.T.; Verhaert, P.D.E.M.; Hagen, W.R.; Hagedoorn, P.L.

    2010-01-01

    The hyperthermophilic archaeon Pyrococcus furiosus expresses five aldehyde oxidoreductase (AOR) enzymes, all containing a tungsto-bispterin cofactor. The growth of this organism is fully dependent on the presence of tungsten in the growth medium. Previous studies have suggested that molybdenum is no

  10. Recent Progress in Processing of Tungsten Heavy Alloys

    Directory of Open Access Journals (Sweden)

    Y. Şahin

    2014-01-01

    Full Text Available Tungsten heavy alloys (WHAs belong to a group of two-phase composites, based on W-Ni-Cu and W-Ni-Fe alloys. Due to their combinations of high density, strength, and ductility, WHAs are used as radiation shields, vibration dampers, kinetic energy penetrators and heavy-duty electrical contacts. This paper presents recent progresses in processing, microstructure, and mechanical properties of WHAs. Various processing techniques for the fabrication of WHAs such as conventional powder metallurgy (PM, advent of powder injection molding (PIM, high-energy ball milling (MA, microwave sintering (MW, and spark-plasma sintering (SPS are reviewed for alloys. This review reveals that key factors affecting the performance of WHAs are the microstructural factors such as tungsten and matrix composition, chemistry, shape, size and distributions of tungsten particles in matrix, and interface-bonding strength between the tungsten particle and matrix in addition to processing factors. SPS approach has a better performance than those of others, followed by extrusion process. Moreover, deformation behaviors of WHA penetrator and depleted uranium (DU Ti alloy impacting at normal incidence both rigid and thick mild steel target are studied and modelled as elastic thermoviscoplastic. Height of the mushroomed region is smaller for α=0.3 and it forms sooner in each penetrator as compared to that for α=0.2.

  11. Preparation of tungsten disulfide motor oil and its tribological characteristics

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Through using mineral oil and synthetic oil to deploy the semisynthesis base oil, modifying the surfaces of ultrafine tungsten disulfide grains by surface chemical embellishment and adsorption embellishment to make them suspended steadily in the base oil as solid lubricating additive, and adding some function additives, the tungsten disulfide motor oil was prepared. The tribological characteristics of this kind motor oil and the well-known motor oils in our country and overseas were studied. The results show that the oil film strength of this kind of motor oil is respectively 1.06 and 1.38 times of that of shell helix ultra motor oil and great wall motor oil, and its sintering load is 1.75 and 2.33 times of that of them, and when tested under 392 N, 1 450 r/min and 30 min, the friction coefficients of friction pairs lubricated by the tungsten disulfide motor oil decrease with the increase of time, meanwhile, the diameter of worn spot is small, and the surface of worn spot is smooth, and no obvious furrows appear. The experiments indicate that the tungsten disulfide motor oil has the better antiwear, antifriction and extreme pressure properties than the well-known motor oils.

  12. Helium effects on tungsten surface morphology and deuterium retention

    NARCIS (Netherlands)

    Ueda, Y.; H. Y. Peng,; H. T. Lee,; N. Ohno,; S. Kajita,; Yoshida, N.; Doerner, R.; De Temmerman, G.; V. Alimov,; G. Wright,

    2013-01-01

    Recent experimental results on tungsten surface morphology, especially nano-structure (fuzz), induced by helium plasma exposure at temperatures between 1000 K and 2000 K are reviewed. This structure was firstly reported in 2006. In this review, most of experimental results reported

  13. Technogenic hydrogeochemical anomalies of tungsten deposits in Kykylbey ore region

    Institute of Scientific and Technical Information of China (English)

    Leonid V.Zamana; Larisa P.Chechel

    2004-01-01

    Peculiarities of the tungsten deposits drainage flow chemical composition formation, the development of which was ceased almost 40 years ago, have been considered. Migration peculiarities of ore components have been covered, and forms of their migration have been calculated. Inertial characteristics of the surface flow contamination are shown.

  14. Thermal Neutron Capture onto the Stable Tungsten Isotopes

    Directory of Open Access Journals (Sweden)

    Nichols A.

    2012-02-01

    Full Text Available Thermal neutron-capture measurements of the stable tungsten isotopes have been carried out using the guided thermal-neutron beam at the Budapest Reactor. Prompt singles spectra were collected and analyzed using the HYPERMET γ-ray analysis software package for the compound tungsten systems 183W, 184W, and 187W, prepared from isotopically-enriched samples of 182W, 183W, and 186W, respectively. These new data provide both confirmation and new insights into the decay schemes and structure of the tungsten isotopes reported in the Evaluated Gamma-ray Activation File based upon previous elemental analysis. The experimental data have also been compared to Monte Carlo simulations of γ-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. Together, the experimental cross sections and modeledfeeding contribution from the quasi continuum, have been used to determine the total radiative thermal neutron-capture cross sections for the tungsten isotopes and provide improved decay-scheme information for the structural- and neutron-data libraries.

  15. Geochemistry of the Panasqueira tungsten-tin deposit, Portugal

    NARCIS (Netherlands)

    Bussink, R.W.

    1984-01-01

    Major tin-tungsten deposits in Portugal are related to intrusions of the Younger Series (300-280 Ma) of Hercynian granitoids. Mineralized granites are 'specialized' by a specific increase or decrease of major, minor and trace element contents in comparison with non-mineralized occurrences. Component

  16. Geochemistry of the Panasqueira tungsten-tin deposit, Portugal

    NARCIS (Netherlands)

    Bussink, R.W.

    1984-01-01

    Major tin-tungsten deposits in Portugal are related to intrusions of the Younger Series (300-280 Ma) of Hercynian granitoids. Mineralized granites are 'specialized' by a specific increase or decrease of major, minor and trace element contents in comparison with non-mineralized occurrences.

  17. Geochemistry of the Panasqueira tungsten-tin deposit, Portugal

    NARCIS (Netherlands)

    Bussink, R.W.

    1984-01-01

    Major tin-tungsten deposits in Portugal are related to intrusions of the Younger Series (300-280 Ma) of Hercynian granitoids. Mineralized granites are 'specialized' by a specific increase or decrease of major, minor and trace element contents in comparison with non-mineralized occurrences. Component

  18. Molybdenum incorporation in tungsten aldehyde oxidoreductase enzymes from Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M; Bevers, L.E.; Pinkse, M.W.H.; Krijger, G.C.; Wolterbeek, H.T.; Verhaert, P.D.E.M.; Hagen, W.R.; Hagedoorn, P.L.

    2010-01-01

    The hyperthermophilic archaeon Pyrococcus furiosus expresses five aldehyde oxidoreductase (AOR) enzymes, all containing a tungsto-bispterin cofactor. The growth of this organism is fully dependent on the presence of tungsten in the growth medium. Previous studies have suggested that molybdenum is no

  19. 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.

  20. Thermal Desorption of Helium Implanted in Tungsten at RT

    Institute of Scientific and Technical Information of China (English)

    ZHANGFu; XUZengyu; LIUXiang; CHENJiming; XUYing; N.Yoshida; H.Iwakiri

    2002-01-01

    Tungsten is envisaged as one of the main candidate materials for divertor plate of ITER and future fusion reactors. Due to D-T reaction, PFMs would suffer helium irradiation from plasma additional to the high heat loads. Helium retention and thermal desorption behavior are largely concerned.

  1. Gas Tungsten Arc Welding and Plasma Arc Cutting. Teacher Edition.

    Science.gov (United States)

    Fortney, Clarence; And Others

    This welding curriculum guide treats two topics in detail: the care of tungsten electrodes and the entire concept of contamination control and the hafnium electrode and its importance in dual-air cutting systems that use compressed shop air for plasma arc cutting activities. The guide contains three units of instruction that cover the following…

  2. Volume and surface photoemission from tungsten. II. Experiment

    DEFF Research Database (Denmark)

    Feuerbacher, B.; Egede Christensen, N.

    1974-01-01

    Energy-distribution spectra of photoelectrons emitted normal to three single-crystal faces of tungsten have been measured for photon energies between 7.7 and 21.2 eV. The results are interpreted in terms of one-dimensional electronic properties along the symmetry lines in k space that correspond...

  3. Tungsten-yttria carbide coating for conveying copper

    Science.gov (United States)

    Rothman, Albert J.

    1993-01-01

    A method is provided for providing a carbided-tungsten-yttria coating on the interior surface of a copper vapor laser. The surface serves as a wick for the condensation of liquid copper to return the condensate to the interior of the laser for revolatilization.

  4. Tungsten disrupts root growth in Arabidopsis thaliana by PIN targeting.

    Science.gov (United States)

    Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2014-08-15

    Tungsten is a heavy metal with increasing concern over its environmental impact. In plants it is extensively used to deplete nitric oxide by inhibiting nitrate reductase, but its presumed toxicity as a heavy metal has been less explored. Accordingly, its effects on Arabidopsis thaliana primary root were assessed. The effects on root growth, mitotic cell percentage, nitric oxide and hydrogen peroxide levels, the cytoskeleton, cell ultrastructure, auxin and cytokinin activity, and auxin carrier distribution were investigated. It was found that tungsten reduced root growth, particularly by inhibiting cell expansion in the elongation zone, so that root hairs emerged closer to the root tip than in the control. Although extensive vacuolation was observed, even in meristematic cells, cell organelles were almost unaffected and microtubules were not depolymerized but reoriented. Tungsten affected auxin and cytokinin activity, as visualized by the DR5-GFP and TCS-GFP expressing lines, respectively. Cytokinin fluctuations were similar to those of the mitotic cell percentage. DR5-GFP signal appeared ectopically expressed, while the signals of PIN2-GFP and PIN3-GFP were diminished even after relatively short exposures. The observed effects were not reminiscent of those of any nitric oxide scavengers. Taken together, inhibition of root growth by tungsten might rather be related to a presumed interference with the basipetal flow of auxin, specifically affecting cell expansion in the elongation zone.

  5. Information extraction from FN plots of tungsten microemitters

    Energy Technology Data Exchange (ETDEWEB)

    Mussa, Khalil O. [Department of Physics, Mu' tah University, Al-Karak (Jordan); Mousa, Marwan S., E-mail: mmousa@mutah.edu.jo [Department of Physics, Mu' tah University, Al-Karak (Jordan); Fischer, Andreas, E-mail: andreas.fischer@physik.tu-chemnitz.de [Institut für Physik, Technische Universität Chemnitz, Chemnitz (Germany)

    2013-09-15

    Tungsten based microemitter tips have been prepared both clean and coated with dielectric materials. For clean tungsten tips, apex radii have been varied ranging from 25 to 500 nm. These tips were manufactured by electrochemical etching a 0.1 mm diameter high purity (99.95%) tungsten wire at the meniscus of two molar NaOH solution. Composite micro-emitters considered here are consisting of a tungsten core coated with different dielectric materials—such as magnesium oxide (MgO), sodium hydroxide (NaOH), tetracyanoethylene (TCNE), and zinc oxide (ZnO). It is worthwhile noting here, that the rather unconventional NaOH coating has shown several interesting properties. Various properties of these emitters were measured including current–voltage (IV) characteristics and the physical shape of the tips. A conventional field emission microscope (FEM) with a tip (cathode)–screen (anode) separation standardized at 10 mm was used to electrically characterize the electron emitters. The system was evacuated down to a base pressure of ∼10{sup −8}mbar when baked at up to ∼180°C overnight. This allowed measurements of typical field electron emission (FE) characteristics, namely the IV characteristics and the emission images on a conductive phosphorus screen (the anode). Mechanical characterization has been performed through a FEI scanning electron microscope (SEM). Within this work, the mentioned experimental results are connected to the theory for analyzing Fowler–Nordheim (FN) plots. We compared and evaluated the data extracted from clean tungsten tips of different radii and determined deviations between the results of different extraction methods applied. In particular, we derived the apex radii of several clean and coated tungsten tips by both SEM imaging and analyzing FN plots. The aim of this analysis is to support the ongoing discussion on recently developed improvements of the theory for analyzing FN plots related to metal field electron emitters, which in

  6. Effect of Co in the efficiency of the methanol electrooxidation reaction on carbon supported Pt

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Fernandez, P.; Montiel, M.; Ocon, P. [Dpto. Quimica-Fisica Aplicada, Facultad de Ciencias, Universidad Autonoma de Madrid (UAM), C/Francisco Tomas y Valiente 7, 28049 Madrid (Spain); Fierro, J.L.G.; Rojas, S. [Grupo de Energia y Quimica Sostenibles, Instituto de Catalisis y Petroleoquimica (CSIC), C/ Marie Curie 2, 28049 Madrid (Spain); Wang, H.; Abruna, H.D. [Department of Chemistry and Chemical Biology, Cornell University. Ithaca, NY 14853 (United States)

    2010-12-15

    The effect of Co addition to carbon nanotubes supported Pt in the methanol oxidation reaction has been investigated by means of differential electrochemical mass spectrometry (DEMS). It has been observed that the CO{sub 2} efficiency increases in carbon nanotubes supported PtCo compared to its homologous Pt catalysts, especially at potentials lower than 0.55 V. Despite of this, the Faradaic current reached by the bimetallic catalysts in the methanol electrooxidation was lower than those recorded on the monometallic samples. This is because Co addition difficult finding enough Pt vicinal sites for methanol dehydrogenation. On the other hand, it has been found that alloying Pt with Co, shifts down the d-band center of the larger element, so the strength of the interaction with adsorbates decreases. Consequently, it will be easier to oxidize CO{sub ad} on the bimetallic surface. Furthermore, the necessary -OH{sub ad} species for the CO{sub ad} oxidation to CO{sub 2} will be provided by the CNTs themselves. (author)

  7. 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.

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

    Science.gov (United States)

    Novotný, K.; Staňková, A.; Häkkänen, H.; Korppi-Tommola, J.; Otruba, V.; Kanický, V.

    2007-12-01

    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 r2 > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r2 = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

  9. Aerosol-assisted chemical vapor deposition of tungsten oxide films and nanorods from oxo tungsten(VI) fluoroalkoxide precursors.

    Science.gov (United States)

    Kim, Hankook; Bonsu, Richard O; O'Donohue, Christopher; Korotkov, Roman Y; McElwee-White, Lisa; Anderson, Timothy J

    2015-02-04

    Aerosol-assisted chemical vapor deposition (AACVD) of WOx was demonstrated using the oxo tungsten(VI) fluoroalkoxide single-source precursors, WO[OCCH3(CF3)2]4 and WO[OC(CH3)2CF3]4. Substoichiometric amorphous tungsten oxide thin films were grown on indium tin oxide (ITO) substrates in nitrogen at low deposition temperature (100-250 °C). At growth temperatures above 300 °C, the W18O49 monoclinic crystalline phase was observed. The surface morphology and roughness, visible light transmittance, electrical conductivity, and work function of the tungsten oxide materials are reported. The solvent and carrier gas minimally affected surface morphology and composition at low deposition temperature; however, material crystallinity varied with solvent choice at higher temperatures. The work function of the tungsten oxide thin films grown between 150 and 250 °C was determined to be in the range 5.0 to 5.7 eV, according to ultraviolet photoelectron spectroscopy (UPS).

  10. Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles.

    Science.gov (United States)

    Stefaniak, Aleksandr B; Virji, M Abbas; Day, Gregory A

    2009-07-01

    As many as 30,000 workers in the United States of America are exposed to cemented tungsten carbides (CTC), alloys composed primarily of tungsten carbide and cobalt, which are used in cutting tools. Inhalation of cobalt-containing particles may be sufficient for the development of occupational asthma, whereas tungsten carbide particles in association with cobalt particles are associated with the development of hard metal disease (HMD) and lung cancer. Historical epidemiology and exposure studies of CTC workers often rely only on measures of total airborne cobalt mass concentration. In this study, we characterized cobalt- and tungsten-containing aerosols generated during the production of CTC with emphasis on (1) aerosol "total" mass (n=252 closed-face 37 mm cassette samples) and particle size-selective mass concentrations (n=108 eight-stage cascade impactor samples); (2) particle size distributions; and (3) comparison of exposures obtained using personal cassette and impactor samplers. Total cobalt and tungsten exposures were highest in work areas that handled powders (e.g., powder mixing) and lowest in areas that handled finished product (e.g., grinding). Inhalable, thoracic, and respirable cobalt and tungsten exposures were observed in all work areas, indicating potential for co-exposures to particles capable of getting deposited in the upper airways and alveolar region of the lung. Understanding the risk of CTC-induced adverse health effects may require two exposure regimes: one for asthma and the other for HMD and lung cancer. All sizes of cobalt-containing particles that deposit in the lung and airways have potential to cause asthma, thus a thoracic exposure metric is likely biologically appropriate. Cobalt-tungsten mixtures that deposit in the alveolar region of the lung may potentially cause HMD and lung cancer, thus a respirable exposure metric for both metals is likely biologically appropriate. By characterizing size-selective and co-exposures as well as

  11. Comparison of hydrogen isotope retention for tungsten probes in LHD vacuum vessel during the experimental campaigns in 2011 and 2012

    Energy Technology Data Exchange (ETDEWEB)

    Oya, Y., E-mail: syoya@ipc.shizuoka.ac.jp [Graduate School of Science, Shizuoka University, Shizuoka (Japan); Masuzaki, S.; Tokitani, M. [National Institute for Fusion Science, Gifu (Japan); Sato, M.; Toda, K.; Uchimura, H. [Graduate School of Science, Shizuoka University, Shizuoka (Japan); Yoshida, N.; Watanabe, H. [Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka (Japan); Yamauchi, Y.; Hino, T. [Graduate School of Engineering, Hokkaido University, Sapporo (Japan); Miyamoto, M. [Department of Material Science, Shimane University, Matsue, Shimane (Japan); Hatano, Y. [Hydrogen Isotope Research Center, University of Toyama, Toyama (Japan); Okuno, K. [Graduate School of Science, Shizuoka University, Shizuoka (Japan)

    2014-10-15

    Highlights: • Hydrogen isotope retention enhancement for W exposed to LHD 2011 and 2012 campaigns were evaluated. • Large hydrogen retention enhancement was derived for all the samples compared to that for pure W. • The carbon-dominated mixed-material layer would control the hydrogen isotope retention for all the area except for erosion-dominated area. • The chemical structure for carbon-dominant mixed-material layer may govern the H and D retention enhancement for most area. - Abstract: To evaluate hydrogen isotope retention enhancement in W by plasma exposure, the stress relieved tungsten samples were placed at three or four different positions, namely PI (sputtering erosion dominated area), DP (deposition dominated area), HL (Higher heat load area) and ER (erosion dominated area) during 2011 (15th) or 2012 (16th) plasma experiment campaign in Large Helical Device (LHD) at National Institute for Fusion Science (NIFS), Japan and were exposed to ∼6700 shots of hydrogen plasma in a 2011 plasma experiment campaign and ∼5000 shots in a 2012 plasma campaign. Thereafter, additional 1.0 keV deuterium ion implantation was performed to evaluate the change of hydrogen isotope retention capacity by plasma exposure. It was found that more than 50 times of hydrogen retention enhancement for DP sample was derived compared to that for pure W. In especially, the carbon-dominated mixed-material layer would control the hydrogen isotope retention for all the area except for erosion-dominated area, indicating that the chemical structure for carbon-dominant mixed-material layer would govern the H and D retention enhancement for most area by long-term plasma exposure. Therefore, the surface area for carbon material would be one of key issues for the determination of hydrogen isotope retention in first wall, even if all tungsten first walls will be used.

  12. Pitfalls of tungsten multileaf collimator in proton beam therapy

    Energy Technology Data Exchange (ETDEWEB)

    Moskvin, Vadim; Cheng, Chee-Wai; Das, Indra J. [Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202 (United States) and Indiana University Health Proton Therapy Center (Formerly Midwest Proton Radiotherapy Institute), Bloomington, Indiana 47408 (United States)

    2011-12-15

    Purpose: Particle beam therapy is associated with significant startup and operational cost. Multileaf collimator (MLC) provides an attractive option to improve the efficiency and reduce the treatment cost. A direct transfer of the MLC technology from external beam radiation therapy is intuitively straightforward to proton therapy. However, activation, neutron production, and the associated secondary cancer risk in proton beam should be an important consideration which is evaluated. Methods: Monte Carlo simulation with FLUKA particle transport code was applied in this study for a number of treatment models. The authors have performed a detailed study of the neutron generation, ambient dose equivalent [H*(10)], and activation of a typical tungsten MLC and compared with those obtained from a brass aperture used in a typical proton therapy system. Brass aperture and tungsten MLC were modeled by absorber blocks in this study, representing worst-case scenario of a fully closed collimator. Results: With a tungsten MLC, the secondary neutron dose to the patient is at least 1.5 times higher than that from a brass aperture. The H*(10) from a tungsten MLC at 10 cm downstream is about 22.3 mSv/Gy delivered to water phantom by noncollimated 200 MeV beam of 20 cm diameter compared to 14 mSv/Gy for the brass aperture. For a 30-fraction treatment course, the activity per unit volume in brass aperture reaches 5.3 x 10{sup 4} Bq cm{sup -3} at the end of the last treatment. The activity in brass decreases by a factor of 380 after 24 h, additional 6.2 times after 40 days of cooling, and is reduced to background level after 1 yr. Initial activity in tungsten after 30 days of treating 30 patients per day is about 3.4 times higher than in brass that decreases only by a factor of 2 after 40 days and accumulates to 1.2 x 10{sup 6} Bq cm{sup -3} after a full year of operation. The daily utilization of the MLC leads to buildup of activity with time. The overall activity continues to increase

  13. Root Cause Analysis of Tungsten-Induced Protein Aggregation in Pre-filled Syringes.

    Science.gov (United States)

    Liu, Wei; Swift, Rob; Torraca, Gianni; Nashed-Samuel, Yasser; Wen, Zai-Qing; Jiang, Yijia; Vance, Aylin; Mire-Sluis, Anthony; Freund, Erwin; Davis, Janice; Narhi, Linda

    2010-01-01

    Particles isolated from a pre-filled syringe containing a protein-based solution were identified as aggregated protein and tungsten. The origin of the tungsten was traced to the tungsten pins used in the supplier's syringe barrel forming process. A tungsten recovery study showed that the vacuum stopper placement process has a significant impact on the total amount of tungsten in solutions. The air gap formed in the syringe funnel area (rich in residual tungsten) becomes accessible to solutions when the vacuum is pulled. Leachable tungsten deposits that were not removed by the supplier's wash process are concentrated in this small area. Extraction procedures used to measure residual tungsten in empty syringes would under-report the tungsten quantity unless the funnel area is wetted during the extraction. Improved syringe barrel forming and washing processes at the supplier have lowered the residual tungsten content and significantly reduced the risk of protein aggregate formation. This experience demonstrates that packaging component manufacturing processes, which are outside the direct control of drug manufacturers, can have an impact on the drug product quality. Thus close technical communication with suppliers of product contact components plays an important role in making a successful biotherapeutic.

  14. 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)

  15. Surface modification of tungsten and tungsten-tantalum alloys exposed to high-flux deuterium plasma and its impact on deuterium retention

    NARCIS (Netherlands)

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

    2013-01-01

    Samples of tungsten and tungsten-tantalum alloy (with 5 mass per cent of Ta) were exposed to high-flux deuterium plasma at different fluences. The surface modification was studied with scanning electron microscopy, and deuterium retention was measured by thermal desorption spectroscopy (TDS). In the

  16. Mechanical properties of tantalum-tungsten interlayer between tungsten tile and thimble to prevent helium leak from He-cooled divertor

    Science.gov (United States)

    Zhang, Pingping; Shen, Weiping; Zhou, Yanan; Zhang, Qingling

    2013-03-01

    The tungsten parts made of pure tungsten tile and dispersion strengthened tungsten thimble with 3 mm interlayer of tantalum-tungsten alloy are fabricated by Spark Plasmas Sintering (SPS). The process of SPS is that the temperature is raised to 1700 °C at a rate of 100 °C/min and kept for 3 min, under a constant pressure of 50MPa along the Z-axis. The mechanical properties of the interlayer with different percent of tantalum are measured. The results show that with increasing percent of tantalum, the hardness first increases and then decreases; and as the indentation on the sample is closer to dispersion strengthened tungsten, the value of Vickers hardness is much higher. The Vickers hardness of interlayer is the highest when the content of tantalum is 50% and the indentation is next to dispersion strengthened tungsten. Bending strength drops with increasing content of tantalum, when the content of tantalum is 100% the value of bending strength is the lowest. The fracture toughness is highest as the content of tantalum is 25%, the value is 9.89MPa•m1/2. The toughening tungsten-tantalum interlayer between tungsten tile and thimble would better prevent helium leak from He-cooled divertor for DEMO.

  17. [Preparation and optical properties of tantalum tungsten bronze].

    Science.gov (United States)

    Mu, Wan-jun; Xie, Xiang; Li, Xing-liang; Zhang, Rui; Lü, Kai; Wei, Hong-yuan

    2015-01-01

    Tantalum tungsten bronze(TaxWO3)nanowires were successfully synthesized via hydrothermal method using TaCl5 and Na2WO4 . 2H20 as raw materials. The morphology, crystal structure and optical properties of synthesized products were characterized by means of XRD, TEM, SEM, UV-Vis and Raman technologies. The XRD results showed that TaxWO3 nanowire exhibited hexagonal structure. By increasing the doping content, the cell parameter was kept increasing gradually till Ta/W= 0. 04, then it remained almost constant. The UV-Vis diffraction spectrum analysis showed that the absorption peaks redshifted, the band gap energy decreased with increasing the doping content. The Raman peaks moved with a downshift, and the peak gradually became broader, which further proved the influence of the tantalum doping for tungsten oxide. The reactions of decomposing liquid rhodamine B solution showed that the nanosized TaxWO3 had a high photo-catalytic activity.

  18. Tungsten Scintillating Fibers Electromagnetic Calorimeters for sPHENIX upgrade

    Science.gov (United States)

    Li, Siyang; Loggins, Vera; Phipps, Michael; Sickles, Anne

    2015-10-01

    sPHENIX, a planned new detector at RHIC, features electromagnetic and hadronic calorimetry that covers | η| design is optimized for the study of jets in heavy ion collisions. The design includes a tungsten fiber EmCal that is made out of a tower array of plastic scintillating fiber embedded inside a mixture of tungsten powder and epoxy. For this calorimeter, silicon photomultipliers will be attached at the end of the module to convert scintillated optical photons into electrical signals. The sPHENIX group at Illinois is currently making samples of these modules to study the production process and achievable density. In addition, we have set up a silicon photomultiplier read out test system which will be used to evaluate the module performance. sPHENIX collaboration and Brookhaven National Laboratory.

  19. Development of positron annihilation spectroscopy for characterizing neutron irradiated tungsten

    Energy Technology Data Exchange (ETDEWEB)

    C.N. Taylor; M. Shimada; D.W. Akers; M.W. Drigert; B.J. Merrill; Y. Hatano

    2013-05-01

    Tungsten samples (6 mm diameter, 0.2 mm thick) were irradiated to 0.025 and 0.3 dpa with neutrons in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Samples were then exposed to deuterium plasma in the tritium plasma experiment (TPE) at 100, 200 and 500ºC to a total fluence of 1 x 1026 m-2. Nuclear reaction analysis (NRA) and Doppler broadening positron annihilation spectroscopy (DB-PAS) were performed at various stages to characterize damage and retention. We present the first known results of neutron damaged tungsten characterized by DB-PAS in order to study defect concentration. Two positron sources, 22Na and 68Ge, probe ~58 µm and through the entire 200 µm thick samples, respectively. DB-PAS results reveal clear differences between the various irradiated samples. These results, and the calibration of DB-PAS to NRA data are presented.

  20. Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

    Institute of Scientific and Technical Information of China (English)

    马淳安; 张文魁; 成旦红; 周邦新

    2002-01-01

    The tungsten carbide(WC) electrocatalysts with definite phase components and high specific surface area were prepared by gas-solid reduction method. The crystal structure, phase components and electrochemical properties of the as-prepared materials were characterized by XRD, BET(Brunauer Emmett and Teller Procedure) and electrochemical test techniques. It is shown that the tungsten carbide catalysts with definite phase components can be obtained by controlling the carburizing conditions including temperature, gas flowing rate and duration time. The electrocatalysts with the major phase of W2C show higher electrocatalytic activity for the hydrogen evolution reaction. The electrocatalysts with the major phase of WC are suitable to be used as the anodic electrocatalyst for hydrogen anodic oxidation, which exhibit higher hydrogen anodic oxidation electrocatalytic properties in HCl solutions.

  1. A comparison of interatomic potentials for modeling tungsten nanocluster structures

    Science.gov (United States)

    Hao, Jiannan; Shu, Xiaolin; Jin, Shuo; Zhang, Xuesong; Zhang, Ying; Lu, Guang-Hong

    2017-02-01

    Molecular dynamic simulation is utilized to study the nanocluster and the fuzz structure on the PFM surface of tungsten. The polyhedral and linear cluster structures based on the icosahedron, cuboctahedron and rhombic dodecahedron are built up. Three interatomic potentials are used in calculating the relationship between the cluster energy and the number of atoms. The results are compared with first-principles calculation to show each potential's best application scale. Furthermore, the transition between the icosahedral and the cuboctahedral clusters is observed in molecular dynamic simulation at different temperatures, which follows a critical curve for different numbers of atoms. The linear structures are proved to be stable at experimental temperatures by thermodynamics. The work presents a selection of interatomic potentials in simulating tungsten cluster systems and helps researchers understand the growth and evolution laws of clusters and the fuzz-like structure formation process in fusion devices.

  2. Preparation and characterization of tungsten diselenide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Pouzet, J.; Bernede, J.C. (Lab. de Physique des Materiaux pour l' Electronique, Faculte des Sciences et des Techniques, 44 - Nantes (France)); Khellil, A. (Lab. de Micro-Optoelectronique, Univ. d' Oran-Es-Senia (Algeria)); Essaidi, H.; Benhida, S. (Lab. de Physique des Materiaux pour l' Electronique, Faculte des Sciences et des Techniques, 44 - Nantes (France))

    1992-02-28

    WSe{sub 2} layers synthesized by annealing tungsten foils and r.f.-sputtered tungsten thin films under selenium pressure have been investigated by scanning electron microscopy, X-ray analysis, X-ray photoelectron spectroscopy (XPS), optical absorption and electrical resistance measurements. It has been found that stoichiometric layers are obtained after appropriate processing at a temperature lower than the glass melting temperature. The films crystallize in the hexagonal structure. The crystallites develop preferentially along the c axis. The binding energies deduced from the XPS lines were found to be in good agreement with those of the reference powder. The electrical resistance is governed by hopping conduction in the low temperature range (80-250 K) and by grain-boundary-scattering mechanisms at higher temperature. (orig.).

  3. Gas-tungsten arc welding of aluminum alloys

    Science.gov (United States)

    Frye, Lowell D.

    1984-01-01

    A gas-tungsten arc welding method for joining together structures formed of aluminum alloy with these structures disposed contiguously to a heat-damagable substrate of a metal dissimilar to the aluminum alloy. The method of the present invention is practiced by diamond machining the fay surfaces of the aluminum alloy structures to provide a mirror finish thereon having a surface roughness in the order of about one microinch. The fay surfaces are aligned and heated sufficiently by the tungsten electrode to fuse the aluminum alloy contiguous to the fay surfaces to effect the weld joint. The heat input used to provide an oxide-free weld is significantly less than that required if the fay surfaces were prepared by using conventional chemical and mechanical practices.

  4. Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

    Directory of Open Access Journals (Sweden)

    Siyuan Feng Chen

    2015-10-01

    Full Text Available We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM, X-ray diffraction (XRD, and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability.

  5. Synthesis of one-dimensional potassium tungsten bronze with excellent near-infrared absorption property.

    Science.gov (United States)

    Guo, Chongshen; Yin, Shu; Huang, Lijun; Sato, Tsugio

    2011-07-01

    Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat.

  6. STUDY OF PREPARATION PROCESS OF TUNGSTEN POWDER BY SHS WITH A MAGNESIUM THERMIT STAGE

    Institute of Scientific and Technical Information of China (English)

    T.A.Zhang; Y.L.Wang; Z.H.Dou; H.Yang

    2004-01-01

    Tungsten powder was fabricated from the system CaWO4-Mg by self-propagating high-temperature synthesis (SHS) with a magnesium thermit stage. The physic-chemical change during heating and the effects of pressure of sample and diluents (W powder) on product have been studied. The experimental results show that the porosity of combustion product and the particle size of final tungsten powder decrease with increasing pressure of sample. Addition of diluents could increase the particle size of final tungsten powder. The purity of tungsten is improved by leaching in NaOH solution. The results of spectral analysis and particle size distribution of final tungsten powder show that the final Tungsten powder has a median diameter of 0.87μn, specific surface area of 1.09m2/g and purity of above 99.0%.

  7. Structure and molecular modeling of tungsten borotellurate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Rada, S., E-mail: Simona.Rada@phys.utcluj.ro [Department of Physics and Chemistry, Technical University of Cluj-Napoca, Cluj-Napoca 400020 (Romania); Rada, M. [Nat. Inst. for R and D of Isotopic and Molec. Technologies, Cluj-Napoca 400293 (Romania); Culea, E., E-mail: eugen.culea@phys.utcluj.ro [Department of Physics and Chemistry, Technical University of Cluj-Napoca, Cluj-Napoca 400020 (Romania)

    2013-03-05

    Highlights: ► The [WO{sub 6}] structural units are highly deformed. ► EPR spectra reveal the existence of W{sup +5} ions situated in distorted octahedral positions and the oxygen ions defects. ► The presence of W{sup +5} ions confers to the glass colors that change with composition. -- Abstract: Glasses of the xWO{sub 3} (100−x)[3TeO{sub 2}·2B{sub 2}O{sub 3}] system where x = 0–40 mol% WO{sub 3} were synthesized and characterized by investigations on FTIR, UV–VIS, EPR spectroscopy and molecular modeling calculations in order to obtain information about the structural changes of the glass network determined by the evolution of tungsten ions states, glass composition and WO{sub 3} concentration. Our spectroscopic data show that the incorporation of WO{sub 3} into borate–tellurate glasses causes both the formation of Te–O–W as well as B–O–W linkages and the increase of the number of non-bridging oxygens. The accommodation of the network with the excess of oxygen and the higher capacity of migration of the tungsten ions inside the host network can be associated with a change of tungsten coordination, from [WO{sub 4}] to [WO{sub 6}] structural units. This conversion is accompaniment of a large displacement of the tungsten atom from the centre of the octahedral geometry. EPR spectra reveal the existence of two signals associated with the presence of W{sup +5} ions situated in distorted octahedral positions and the oxygen ions defects. The presence of W{sup +5} ions confers to the glass colors that change with composition.

  8. Electrochromic behavior in CVD grown tungsten oxide films

    Science.gov (United States)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Dimitrova, Zl; Gesheva, K.

    1999-03-01

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thin TiO 2 film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte.

  9. Electrochromic behavior in CVD grown tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Gesheva, K.; Dimitrova, Z. [Central Laboratory for Solar Energy and New Energy Sources at Bulgarian Academy of Science, 72 Tzarigradsko shossee Blvd., Sofia (Bulgaria)

    1999-03-15

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thinTiO{sub 2} film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte

  10. Beam tests with the CALICE tungsten analog hadronic calorimeter prototype

    CERN Document Server

    Dannheim, D; van der Kraaij, E

    2012-01-01

    The CALICE Analog Hadronic Calorimeter prototype has been equipped with layers of tungsten absorber. Together with the MICROMEGAS and T3B exper- iments the calorimeter was operated in test beams at the CERN PS and SPS with mixed beams of muons, electrons, pions, kaons and protons in an energy range from 1 to 300 GeV. This note describes the experimental configurations and data taking conditions.

  11. Blistering on tungsten surface exposed to high flux deuterium plasma

    NARCIS (Netherlands)

    Xu, H.Y.; Liu, W.; Luo, G. N.; Yuan, Y.; Jia, Y. Z.; Fu, B. Q.; De Temmerman, G.

    2016-01-01

    The blistering behaviour of tungsten surfaces exposed to very high fluxes (1–2 × 1024/m2/s) of low energy (38 eV) deuterium plasmas was investigated as a function of ion fluence (0.2–7 × 1026 D/m2) and surface temperature (423–873 K). Blisters were observed under all conditions, especially up to

  12. Brush Plating of Nickel-Tungsten Alloy for Engineering Application

    Science.gov (United States)

    2012-08-01

    12 8 Nickel-Tungsten deposit properties Property Test method Result Microstructure XRD Nanocrystalline Structure Microscopy Micro-cracked...Composition Chemical Analysis Ni 60 wt.%: W 40 wt.% Residual Stress Bent strip 12 ~ 16 kpsi tensile Hardness Microhardness (Vickers) 660 ~ 690 HV Hydrogen...embrittlement ASTM F519 1a.1 notched bar Pass without bake Ductility Bend test 1.6% Abrasive wear Taber 14 mg/1000 cycle Friction coefficient

  13. Computer Control For Gas/Tungsten-Arc Welding

    Science.gov (United States)

    Andersen, Kristinn; Springfield, James F.; Barnett, Robert J.; Cook, George E.

    1994-01-01

    Prototype computer-based feedback control system developed for use in gas/tungsten arc welding. Beyond improving welding technician's moment-to-moment general control of welding process, control system designed to assist technician in selecting appropriate welding-process parameters, and provide better automatic voltage control. Modular for ease of reconfiguration and upgrading. Modularity also reflected in software. Includes rack-mounted computer, based on VME bus, containing Intel 80286 and 80386 processors.

  14. Tungsten quasispherical wire loads with a profiled mass

    Energy Technology Data Exchange (ETDEWEB)

    Grabovskii, E. V.; Dzhangobegov, V. V., E-mail: jvv88@triniti.ru; Oleinik, G. M.; Rodionov, R. N. [State Research Center of the Russian Federation Troitsk Institute for Innovation and Fusion Research (TRINITI) (Russian Federation)

    2015-12-15

    Wire arrays made from micrometer tungsten wires with linear mass profiled along their height are developed for experiments on the generation of X-ray radiation upon pinch compression with a current of ∼3 MA at a pulse duration of ∼100 ns. Wires are imaged with a scanning electron microscope, and their diameter is determined. It is shown that the arrays have such a profile of height distribution of linear mass that allows for compact spherical compression upon current implosion.

  15. Improved fracture behavior and microstructural characterization of thin tungsten foils

    OpenAIRE

    Vladica Nikolic; Stefan Wurster; Daniel Firneis; Reinhard Pippan

    2016-01-01

    This study is focused towards the development of the technique for investigating the fracture behaviour of 100µm thick rolled tungsten foils, with a purity of 99.97%. Electron backscatter diffraction (EBSD) scans reveal that the grains are elongated along the rolling direction of the foil, which has a very strong {100} texture. The test specimens were fabricated by electrical discharge machining (EDM) and cracks were initiated by consecutively using a diamond wire saw, a razor blade and a foc...

  16. Low-Temperature Strengths and Ductility of Various Tungsten Sheets

    OpenAIRE

    Yutaka Hiraoka; Hiroaki Kurishita

    2011-01-01

    We used three kinds of tungsten sheets in this study. First, we examined microstructure such as grain size distribution using an optical microscope. Secondly, we carried out three-point bend tests at temperatures between about 290 and 500 K. Then, we examined fracture surface of a failed specimen using a scanning electron microscope. Lastly, by analyzing all these results, we evaluated apparent intergranular and transgranular fracture strengths and discussed strengths and ductility of tungs...

  17. Synthesis, characterization, and structure of reduced tungsten chalcogenide cluster complexes

    Energy Technology Data Exchange (ETDEWEB)

    Xiaobing, Xie

    1997-02-01

    Over the previous twenty years, ternary molybdenum chalcogenides of the general formula M{sub x}Mo{sub 6}Y{sub 8} (M = ternary metal cation; Y = chalcogenide), known as Chevrel phases, have been extensively studied. Many of these compounds have been found to have superconductivity, catalytic activity and ionic conductivity. The rich chemistry of the Chevrel phases raises considerable interest in finding the tungsten analogues of these phases. However, no such analogue has ever been synthesized, although the Chevrel phases are usually prepared directly from elements at high temperatures above 1000{degrees}C. The absence of the tungsten analogues may be caused by their thermodynamic instability at such high temperatures. Thus it might be necessary to avoid high-temperature synthetic procedures in order to establish the ternary and binary tungsten chalcogenides. A major focus of the McCarley research group has been on the preparation of M{sub 6}Y{sub 8}L{sub 6} (M = Mo, W; Y = S, Se, Te) cluster complexes as low temperature pathways to the Chevrel phases.

  18. Photoionization of the valence shells of the neutral tungsten atom

    CERN Document Server

    Ballance, Connor P

    2015-01-01

    Results from large-scale theoretical cross section calculations for the total photoionization of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom using the Dirac Coulomb R-matrix approximation (DARC: Dirac-Atomic R-matrix codes) are presented. Comparisons are made with previous theoretical methods and prior experimental measurements. In previous experiments a time-resolved dual laser approach was employed for the photo-absorption of metal vapours and photo-absorption measurements on tungsten in a solid, using synchrotron radiation. The lowest ground state level of neutral tungsten is $\\rm 5p^6 5d^4 6s^2 \\; {^5}D_{\\it J}$, with $\\it J$=0, and requires only a single dipole matrix for photoionization. To make a meaningful comparison with existing experimental measurements, we statistically average the large-scale theoretical PI cross sections from the levels associated with the ground state $\\rm 5p^6 5d^4 6s^2 \\; {^5}D_{\\it J}[{\\it J}=0,1,2,3,4]$ levels and the $\\rm 5d^56s \\; ^7S_3$ excited metastable...

  19. Tungsten fiber reinforced copper matrix composites: A review

    Science.gov (United States)

    Mcdanels, David L.

    1989-01-01

    Tungsten fiber reinforced copper matrix (W/Cu) composites have served as an ideal model system with which to analyze the properties of metal matrix composites. A series of research programs were conducted to investigate the stress-strain behavior of W/Cu composites; the effect of fiber content on the strength, modulus, and conductivity of W/Cu composites; and the effect of alloying elements on the behavior of tungsten wire and of W/Cu composites. Later programs investigated the stress-rupture, creep, and impact behavior of these composites at elevated temperatures. Analysis of the results of these programs as allows prediction of the effects of fiber properties, matrix properties, and fiber content on the properties of W/Cu composites. These analyses form the basis for the rule-of-mixtures prediction of composite properties which was universally adopted as the criteria for measuring composite efficiency. In addition, the analyses allows extrapolation of potential properties of other metal matrix composites and are used to select candidate fibers and matrices for development of tungsten fiber reinforced superalloy composite materials for high temperature aircraft and rocket engine turbine applications. The W/Cu composite efforts are summarized, some of the results obtained are described, and an update is provided on more recent work using W/Cu composites as high strength, high thermal conductivity composite materials for high heat flux, elevated temperature applications.

  20. Many-body central force potentials for tungsten

    Science.gov (United States)

    Bonny, G.; Terentyev, D.; Bakaev, A.; Grigorev, P.; Van Neck, D.

    2014-07-01

    Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2{1 1 0} and 1/2 {1 1 2} stacking fault energy profiles and the 1/2 screw dislocation core. We also provide the Peierls stress for the 1/2 edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials.

  1. Silicon and tungsten oxide nanostructures for water splitting

    Science.gov (United States)

    Reyes Gil, Karla R.; Spurgeon, Joshua M.; Lewis, Nathan S.

    2009-08-01

    Inorganic semiconductors are promising materials for driving photoelectrochemical water-splitting reactions. However, there is not a single semiconductor material that can sustain the unassisted splitting of water into H2 and O2. Instead, we are developing a three part cell design where individual catalysts for water reduction and oxidation will be attached to the ends of a membrane. The job of splitting water is therefore divided into separate reduction and oxidation reactions, and each catalyst can be optimized independently for a single reaction. Silicon might be suitable to drive the water reduction. Inexpensive highly ordered Si wire arrays were grown on a single crystal wafer and transferred into a transparent, flexible polymer matrix. In this array, light would be absorbed along the longer axial dimension while the resulting electrons or holes would be collected along the much shorter radial dimension in a massively parallel array resembling carpet fibers on a microscale, hence the term "solar carpet". Tungsten oxide is a good candidate to drive the water oxidation. Self-organized porous tungsten oxide was successfully synthesized on the tungsten foil by anodization. This sponge-like structure absorbs light efficiently due to its high surface area; hence we called it "solar sponge".

  2. The Partitioning of Tungsten bwtween Aqueous Fluids and Silicate Melts

    Institute of Scientific and Technical Information of China (English)

    许永胜; 张本仁; 等

    1993-01-01

    An experimental study has been carried out to determine the partition coefficients of tungsten between aqueous fluids and granitic melts at 800℃ and 1.5kb with natural granite as the starting material,The effects of the solution on the partition coefficients of tungsten show a wequence of P>co32->B>H2O.The effects are limited(generally KD<0.3)and the tungsten shows a preferential trend toward the melt over the aqueous fiuid.The value of KD increases with increasing concentration of phosphorus;the KD increases first and then reduces with the concentration of CO32-;when temperature decreases,the KD between the solution of CO32- and the silicate melt increases,and that between the solution of B4O72- and the silicate melt decreases.The partition coefficients of phosphorus and sodium between fluids and silicate melts have been calculated from the concentrations of the elements in the melts.The KD value for phosphorus is 0.38 and that for sodium is 0.56.Evidence shows that the elements tend to become richer and richer in the melts.

  3. Influence of particle flux on morphology changes of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta; Schweer, Bernd; Terra, Alexis; Unterberg, Bernhard [Institut fuer Energie- und Klimaforschung - Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Juelich (Germany); Temmerman, Greg de [FOM-DIFFER, Association EURATOM-FOM, Nieuwegein (Netherlands); Oost, Guido van [Department of Applied Physics, Ghent University (Belgium)

    2013-07-01

    Tungsten is currently considered as the main candidate material for high heat flux components of future fusion devices. Bombardment of tungsten surfaces by large fluences of low energy particles such as hydrogen isotopes and helium can lead to strong microstructural changes which are mechanically unstable. The occurrence of those effects is strongly dependent on the surface temperature and particle flux. In this contribution we present the experiments done at PSI-2 linear plasma device in order to generate surface modifications on tungsten. The power flux density delivered to the target at PSI-2 is up to 2 MWm{sup -2} and the ion flux density is of the order of 10{sup 22}-10{sup 23} m{sup -2}s{sup -1}. A dedicated actively heated sample holder was designed and tested in order to provide the required temperature range from 300 K to 1800 K. We present here the first measurements performed at PSI-2 whereas subsequent experiments are foreseen at Pilot-PSI and MAGNUM-PSI linear plasma devices with higher flux densities up to 10{sup 25} m{sup -2}s{sup -1}.

  4. Extraction Factor Of Pure Ammonium Paratungstate From Tungsten Scraps

    Directory of Open Access Journals (Sweden)

    Pee J.-H.

    2015-06-01

    Full Text Available Typical oxidation process of tungsten scraps was modified by the rotary kiln with oxygen burner to increase the oxidation rate of tungsten scraps. Also to accelerate the solubility of solid oxidized products, the hydrothermal reflux method was adapted. By heating tungsten scraps in rotary kiln with oxygen burner at around 900° for 2hrs, the scraps was oxidized completely. Then oxidized products (WO3 and CoWO4 was fully dissolved in the solution of NaOH by hydrothermal reflux method at 150° for 2hrs. The dissolution rate of oxidized products was increased with increasing the reaction temperature and concentration of NaOH. And then CaWO4 and H2WO4 could be generated from the aqueous sodium tungstate solution. Ammonium paratungstate (APT also could be produced from tungstic acid using by aqueous ammonium solution. The morphologies (cubic and plate types of APT was controlled by the stirring process of purified solution of ammonium paratungstate.

  5. Porous tungsten oxide nanoflakes for highly alcohol sensitive performance.

    Science.gov (United States)

    Xiao, J; Liu, P; Liang, Y; Li, H B; Yang, G W

    2012-11-21

    Porous tungsten oxide (WO(3)) nanoflakes have been synthesized by a simple and green approach in an ambient environment. As a precursor solution a polycrystalline hydrated tungstite (H(2)WO(4)·H(2)O) nanoparticles colloid was first prepared by pulsed-laser ablation of a tungsten target in water. The H(2)WO(4)·H(2)O nanoflakes were produced by 72 h aging treatment at room temperature. Finally, porous WO(3) nanoflakes were synthesized by annealing at 800 °C for 4 h. Considering the large surface-to-volume ratio of porous nanoflakes, a porous WO(3) nanoflake gas sensor was fabricated, which exhibits an excellent sensor response performance to alcohol concentrations in the range of 20 to 600 ppm under low working temperature. This high response was attributed to the highly crystalline and porous flake-like morphology, which leads to effective adsorption and desorption, and provides more active sites for the gas molecules' reaction. These findings showed that the porous tungsten oxide nanoflake has great potential in gas-sensing performance.

  6. Measurement of Neutron Transmission for Tungsten With 2.8 MeV Neutrons

    Institute of Scientific and Technical Information of China (English)

    REN; Jie; RUAN; Xi-chao; BAO; Jie; NIE; Yang-bo; ZHOU; Zu-ying

    2012-01-01

    <正>The neutron transmission for different thickness of tungsten plates for 2.8 MeV neutrons was measured with TOF technique using the d-D reaction neutron source at the 600 kV Cococroft-Walton accelerator at CIAE. The sensitivity for distinguishing the thickness of the tungsten plate was determined with this method. The tungsten plate was put at the beam direction and 1.7 m from the neutron source, and

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

    Science.gov (United States)

    1960-12-01

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

  8. Changing Conditions of Supply and Demand in the Tungsten Concentrate Market

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正> In January 2004,when Jiangxi Tungsten Indus-try Group,one of the major tungsten producersin China,made a quote of RMB 25,500 yuanper ton,the actual domestic market quotes hadalready risen above RMB 28,000 yuan per ton.In February,when the major tungsten produc-ers negotiated a quote of RMB 28,500 yuan perton,the actual domestic market quotes had

  9. Direct Growth of Crystalline Tungsten Oxide Nanorod Arrays by a Hydrothermal Process and Their Electrochromic Properties

    Science.gov (United States)

    Lu, Chih-Hao; Hon, Min Hsiung; Leu, Ing-Chi

    2016-12-01

    Transparent crystalline tungsten oxide nanorod arrays for use as an electrochromic layer have been directly prepared on fluorine-doped tin oxide-coated glass via a facile tungsten film-assisted hydrothermal process using aqueous tungsten hexachloride solution. X-ray diffraction analysis and field-emission scanning electron microscopy were used to characterize the phase and morphology of the grown nanostructures. Arrays of tungsten oxide nanorods with diameter of ˜22 nm and length of ˜240 nm were obtained at 200°C after 8 h of hydrothermal reaction. We propose a growth mechanism for the deposition of the monoclinic tungsten oxide phase in the hydrothermal environment. The tungsten film was first oxidized to tungsten oxide to provide seed sites for crystal growth and address the poor connection between the growing tungsten oxide and substrate. Aligned tungsten oxide nanorod arrays can be grown by a W thin film-assisted heterogeneous nucleation process with NaCl as a structure-directing agent. The fabricated electrochromic device demonstrated optical modulation (coloration/bleaching) at 632.8 nm of ˜41.2% after applying a low voltage of 0.1 V for 10 s, indicating the potential of such nanorod array films for use in energy-saving smart windows.

  10. Fully Relativistic Electron Impact Excitation Cross-Section and Polarization for Tungsten Ions

    Directory of Open Access Journals (Sweden)

    Priti

    2015-04-01

    Full Text Available Electron impact excitation of highly charged tungsten ions in the framework of a fully relativistic distorted wave approach is considered in this paper. Calculations of electron impact excitation cross-sections for the M- and L-shell transitions in the tungsten ions Wn+ (n = 44–66 and polarization of the decay of photons from the excited tungsten ions are briefly reviewed and discussed. New calculations in the wide range of incident electron energies are presented for M-shell transitions in the K-like through Ne-like tungsten ions.

  11. Solution and diffusion of hydrogen isotopes in tungsten-rhenium alloy

    Science.gov (United States)

    Ren, Fei; Yin, Wen; Yu, Quanzhi; Jia, Xuejun; Zhao, Zongfang; Wang, Baotian

    2017-08-01

    Rhenium is one of the main transmutation elements forming in tungsten under neutron irradiation. Therefore, it is essential to understand the influence of rhenium impurity on hydrogen isotopes retention in tungsten. First-principle calculations were used to study the properties of hydrogen solution and diffusion in perfect tungsten-rhenium lattice. The interstitial hydrogen still prefers the tetrahedral site in presence of rhenium, and rhenium atom cannot act directly as a trapping site of hydrogen. The presence of rhenium in tungsten raises the solution energy and the real normal modes of vibration on the ground state and the transition state, compared to hydrogen in pure tungsten. Without zero point energy corrections, the presence of rhenium decreases slightly the migration barrier. It is found that although the solution energy would tend to increase slightly with the rising of the concentration of rhenium, but which does not influence noticeably the solution energy of hydrogen in tungsten-rhenium alloy. The solubility and diffusion coefficient of hydrogen in perfect tungsten and tungsten-rhenium alloy have been estimated, according to Sievert's law and harmonic transition state theory. The results show the solubility of hydrogen in tungsten agrees well the experimental data, and the presence of Re would decrease the solubility and increase the diffusivity for the perfect crystals.

  12. Ion cyclotron resonance heating for tungsten control in various JET H-mode scenarios

    Science.gov (United States)

    Goniche, M.; Dumont, R. J.; Bobkov, V.; Buratti, P.; Brezinsek, S.; Challis, C.; Colas, L.; Czarnecka, A.; Drewelow, P.; Fedorczak, N.; Garcia, J.; Giroud, C.; Graham, M.; Graves, J. P.; Hobirk, J.; Jacquet, P.; Lerche, E.; Mantica, P.; Monakhov, I.; Monier-Garbet, P.; Nave, M. F. F.; Noble, C.; Nunes, I.; Pütterich, T.; Rimini, F.; Sertoli, M.; Valisa, M.; Van Eester, D.; Contributors, JET

    2017-05-01

    Ion cyclotron resonance heating (ICRH) in the hydrogen minority scheme provides central ion heating and acts favorably on the core tungsten transport. Full wave modeling shows that, at medium power level (4 MW), after collisional redistribution, the ratio of power transferred to the ions and the electrons vary little with the minority (hydrogen) concentration n H/n e but the high-Z impurity screening provided by the fast ions temperature increases with the concentration. The power radiated by tungsten in the core of the JET discharges has been analyzed on a large database covering the 2013-2014 campaign. In the baseline scenario with moderate plasma current (I p = 2.5 MA) ICRH modifies efficiently tungsten transport to avoid its accumulation in the plasma centre and, when the ICRH power is increased, the tungsten radiation peaking evolves as predicted by the neo-classical theory. At higher current (3-4 MA), tungsten accumulation can be only avoided with 5 MW of ICRH power with high gas injection rate. For discharges in the hybrid scenario, the strong initial peaking of the density leads to strong tungsten accumulation. When this initial density peaking is slightly reduced, with an ICRH power in excess of 4 MW,very low tungsten concentration in the core (˜10-5) is maintained for 3 s. MHD activity plays a key role in tungsten transport and modulation of the tungsten radiation during a sawtooth cycle is correlated to the fishbone activity triggered by the fast ion pressure gradient.

  13. The relationship between the microstructure and thermal diffusivity of plasma-sprayed tungsten coatings

    Energy Technology Data Exchange (ETDEWEB)

    Moreau, C. [National Research Council Canada, Boucherville, Quebec (Canada); Boire-Lavigne, S.; Saint-Jacques, R.G. [INRS-Energie et Materiaux, Varennes, Quebec (Canada)

    1994-12-31

    Tungsten and tungsten alloy coatings are candidate materials for plasma facing components of divertor plates in future fusion reactors. In normal operation, the sprayed coatings will be submitted to intense heat fluxes and particle bombardment. This work intends to investigate the relationship between the microstructure of plasma-sprayed tungsten coatings and their thermal diffusivity as determined by the laser flash method. The microstructural investigation was carried out on copper-infiltrated coatings. Such a preparation technique permitted the measurement of the total real contact area between the lamellae within the tungsten coatings. The spraying atmosphere was found to strongly influence the interfacial contact between lamellae and coating thermal diffusivity.

  14. Programming voltage reduction in phase change memory cells with tungsten trioxide bottom heating layer/electrode.

    Science.gov (United States)

    Rao, Feng; Song, Zhitang; Gong, Yuefeng; Wu, Liangcai; Feng, Songlin; Chen, Bomy

    2008-11-05

    A phase change memory cell with tungsten trioxide bottom heating layer/electrode is investigated. The crystalline tungsten trioxide heating layer promotes the temperature rise in the Ge(2)Sb(2)Te(5) layer which causes the reduction in the reset voltage compared to a conventional phase change memory cell. Theoretical thermal simulation and calculation for the reset process are applied to understand the thermal effect of the tungsten trioxide heating layer/electrode. The improvement in thermal efficiency of the PCM cell mainly originates from the low thermal conductivity of the crystalline tungsten trioxide material.

  15. Direct Growth of Crystalline Tungsten Oxide Nanorod Arrays by a Hydrothermal Process and Their Electrochromic Properties

    Science.gov (United States)

    Lu, Chih-Hao; Hon, Min Hsiung; Leu, Ing-Chi

    2017-04-01

    Transparent crystalline tungsten oxide nanorod arrays for use as an electrochromic layer have been directly prepared on fluorine-doped tin oxide-coated glass via a facile tungsten film-assisted hydrothermal process using aqueous tungsten hexachloride solution. X-ray diffraction analysis and field-emission scanning electron microscopy were used to characterize the phase and morphology of the grown nanostructures. Arrays of tungsten oxide nanorods with diameter of ˜22 nm and length of ˜240 nm were obtained at 200°C after 8 h of hydrothermal reaction. We propose a growth mechanism for the deposition of the monoclinic tungsten oxide phase in the hydrothermal environment. The tungsten film was first oxidized to tungsten oxide to provide seed sites for crystal growth and address the poor connection between the growing tungsten oxide and substrate. Aligned tungsten oxide nanorod arrays can be grown by a W thin film-assisted heterogeneous nucleation process with NaCl as a structure-directing agent. The fabricated electrochromic device demonstrated optical modulation (coloration/bleaching) at 632.8 nm of ˜41.2% after applying a low voltage of 0.1 V for 10 s, indicating the potential of such nanorod array films for use in energy-saving smart windows.

  16. Micro-mechanical behavior of porous tungsten/Zr-based metallic glass composite under cyclic compression

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.Q. [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Xue, Y.F., E-mail: xueyunfei@bit.edu.cn [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Wang, L.; Fan, Q.B.; Nie, Z.H. [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Zhang, H.F.; Fu, H.M. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2015-09-03

    The micro-mechanical behavior of porous tungsten/Zr-based metallic glass composites with different tungsten volume fraction was investigated under cyclic compression by synchrotron-based in-situ high-energy X-ray diffraction (HEXRD) and finite element modeling (FEM). During cyclic compression, the dislocation in the tungsten phase tangled near the interfaces, indicating that the elastic metallic glass phase restricted dislocation motion and obstructed the deformation of the tungsten phase because of the heterogeneity in stress. After the metallic glass phase yielded, the dislocation tended to propagate away from the interfaces, showing the decrease of the interphase stress affected the direction of motion in the dislocations. The tungsten phase exhibited increased yield strength with the increase of cyclic loading number. Yield stress of the tungsten phase decreased with increasing the tungsten volume fraction during cyclic compression, which was influenced by the elastic strain mismatch between the two phases. The stress heterogeneity and the stress distribution difference between the two phases resulted in that the yield strength of the metallic glass phase decreased with the increase of tungsten volume fraction, and accelerated the formation of shear bands in the metallic glass phase as well as cracks in the tungsten phase. The heterogeneity in stress also excessed the interface bonding strength, inducing interface fracture near interfaces.

  17. Molecular basis of carcinogenicity of tungsten alloy particles

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Robert M.; Williams, Tim D.; Waring, Rosemary H.; Hodges, Nikolas J., E-mail: n.hodges@bham.ac.uk

    2015-03-15

    The tungsten alloy of 91% tungsten, 6% nickel and 3% cobalt (WNC 91–6–3) induces rhabdomyosarcoma when implanted into a rat thigh muscle. To investigate whether this effect is species-specific human HSkMc primary muscle cells were exposed to WNC 91–6–3 particles and responses were compared with those from a rat skeletal muscle cell line (L6-C11). Toxicity was assessed by the adenylate kinase assay and microscopy, DNA damage by the Comet assay. Caspase 3 enzyme activity was measured and oligonucleotide microarrays were used for transcriptional profiling. WNC 91–6–3 particles caused toxicity in cells adjacent to the particles and also increased DNA strand breaks. Inhibition of caspase 3 by WNC 91–6–3 occurred in rat but not in human cells. In both rat and human cells, the transcriptional response to WNC 91–6–3 showed repression of transcripts encoding muscle-specific proteins with induction of glycolysis, hypoxia, stress responses and transcripts associated with DNA damage and cell death. In human cells, genes encoding metallothioneins were also induced, together with genes related to angiogenesis, dysregulation of apoptosis and proliferation consistent with pre-neoplastic changes. An alloy containing iron, WNF 97–2–1, which is non-carcinogenic in vivo in rats, did not show these transcriptional changes in vitro in either species while the corresponding cobalt-containing alloy, WNC 97–2–1 elicited similar responses to WNC 91–6–3. Tungsten alloys containing both nickel and cobalt therefore have the potential to be carcinogenic in man and in vitro assays coupled with transcriptomics can be used to identify alloys, which may lead to tumour formation, by dysregulation of biochemical processes. - Highlights: • Use of transcriptomics to identify likely carcinogenic tungsten alloys in vitro • Cobalt containing alloys cause oxidative stress, DNA-damage and perturb apoptosis. • Presence of cobalt causes changes in gene expression

  18. Residual carbon content in the initial ITER-Like Wall experiments at JET

    NARCIS (Netherlands)

    Brezinsek, S.; Jachmich, S.; Stamp, M. F.; Meigs, A. G.; Coenen, J. W.; Krieger, K.; Giroud, C.; Groth, M.; Philipps, V.; S. Grünhagen,; Smith, R.; van Rooij, G. J.; Ivanova, D.; Matthews, G. F.

    2013-01-01

    Abstract The residual carbon content and carbon edge flux in JET have been assessed by three independent diagnostic techniques after start of plasma operation with the ITER-Like Wall (ILW) with beryllium first wall and tungsten divertor: (i) in-situ measurements with optical spectroscopy on low

  19. Tungsten Promotes Sex-Specific Adipogenesis in the Bone by Altering Differentiation of Bone Marrow-Resident Mesenchymal Stromal Cells.

    Science.gov (United States)

    Bolt, Alicia M; Grant, Michael P; Wu, Ting Hua; Flores Molina, Manuel; Plourde, Dany; Kelly, Alexander D R; Negro Silva, Luis Fernando; Lemaire, Maryse; Schlezinger, Jennifer J; Mwale, Fackson; Mann, Koren K

    2016-04-01

    Tungsten is a naturally occurring metal that increasingly is being incorporated into industrial goods and medical devices, and is recognized as an emerging contaminant. Tungsten preferentially and rapidly accumulates in murine bone in a concentration-dependent manner; however the effect of tungsten deposition on bone biology is unknown. Other metals alter bone homeostasis by targeting bone marrow-derived mesenchymal stromal cell (MSC) differentiation, thus, we investigated the effects of tungsten on MSCsin vitroandin vivoIn vitro, tungsten shifted the balance of MSC differentiation by enhancing rosiglitazone-induced adipogenesis, which correlated with an increase in adipocyte content in the bone of tungsten-exposed, young, male mice. Conversely, tungsten inhibited osteogenesis of MSCsin vitro; however, we found no evidence that tungsten inhibited osteogenesisin vivo Interestingly, two factors known to influence adipogenesis are sex and age of mice. Both female and older mice have enhanced adipogenesis. We extended our study and exposed young female and adult (9-month) male and female mice to tungsten for 4 weeks. Although tungsten accumulated to a similar extent in young female mice, it did not promote adipogenesis. Interestingly, tungsten did not accumulate in the bone of older mice; it was undetectable in adult male mice, and just above the limit of detect in adult female mice. Surprisingly, tungsten enhanced adipogenesis in adult female mice. In summary, we found that tungsten alters bone homeostasis by altering differentiation of MSCs, which could have significant implications for bone quality, but is highly dependent upon sex and age.

  20. Black silicon maskless templates for carbon nanotube forests

    DEFF Research Database (Denmark)

    Wierzbicki, Rafal; Schmidt, Michael Stenbæk; Boisen, Anja

    2013-01-01

    We present here a proof of concept for a novel fabrication method of vertically aligned carbon nanotube forests, utilizing black silicon nanograss (a forest of silicon nanometer-sized spikes created with reactive ion etching) coated with titanium tungsten diffusion barrier as a template. The meth...

  1. Immobilization of redox mediators on functionalized carbon nanotube: A material for chemical sensor fabrication and amperometric determination of hydrogen peroxide

    Indian Academy of Sciences (India)

    D R Shobha Jeykumari; S Senthil Kumar; S Sriman Narayanan

    2005-10-01

    Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) on graphite electrode was achieved by gently rubbing the electrode surface on carbon nanotubes supported on a glass slide. The electrochemical behaviour of the modified electrodes was investigated by cyclic voltammetry. The SWNT-modified electrodes showed excellent electrocatalytic effect for the reduction of hydrogen peroxide. A decrease in overvoltage was observed as well as an enhanced peak current compared to a bare graphite electrode for the reduction of hydrogen peroxide. The catalytic current was found to be directly proportional to the amount of hydrogen peroxide taken.

  2. Stable Field Emitters for a Miniature X-ray Tube Using Carbon Nanotube Drop Drying on a Flat Metal Tip

    OpenAIRE

    Heo SungHwan; Ihsan Aamir; Yoo SeungHwa; Ali Ghafar; Cho SungOh

    2010-01-01

    Abstract Stable carbon nanotube (CNT) field emitters for a vacuum-sealed miniature X-ray tube have been fabricated. The field emitters with a uniform CNT coating are prepared by a simple drop drying of a CNT mixture solution that is composed of chemically modified multi-walled CNTs, silver nanoparticles, and isopropyl alcohol on flat tungsten tips. A highly thermal- and electrical-conductive silver layer strongly attaches CNTs to the tungsten tips. Consequently, the field emitters exhibit goo...

  3. A novel technique for production of nano-crystalline mono tungsten carbide single phase via mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Razavi, Mansour, E-mail: m-razavi@merc.ac.ir [Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran (Iran, Islamic Republic of); Rahimipour, Mohammad Reza; Yazdani-Rad, Rahim [Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran (Iran, Islamic Republic of)

    2011-06-09

    Highlights: > By adding WC to mixture of tungsten and carbon black unlike the system which does not contain any additive, it can lead to synthesized mono carbide tungsten. > However, the synthesize time has been reduced significantly. > Crystalline size of two systems were in nano-meter scale, this amount in system contain primary WC which was smaller than system without WC. - Abstract: Due to simultaneous synthesis of WC and W{sub 2}C phases in most of the synthesis processes and lower mechanical properties of W{sub 2}C than WC, in this work the possibility of production of nano-crystalline WC single phase as a useful refractory ceramic by means of mechanical alloying has been investigated. The raw materials containing W and C with WC were milled in a planetary ball mill. The sampling has been done in different times. As it was expected, XRD studies showed that after 75 h of milling the WC with W{sub 2}C were produced. By adding WC to the raw materials in the beginning of the process it led to the fact that after 50 h of milling WC was synthesized only without any other phases which remained stable at the higher times while milling. During broadening of XRD peaks, the size of synthesized crystalline WC was estimated in the order of nano-meter. Crystalline size and mean strain of synthesized WC in the system without additive were higher and lower than the system containing WC, respectively.

  4. Determination of tungsten target parameters for transmission X-ray tube: A simulation study using Geant4

    Energy Technology Data Exchange (ETDEWEB)

    Nasseri, Mohammad M. [School of Plasma Physics and Nuclear Fusion, Institute of Nuclear Science and Technology (AEOI), Tehran (Iran, Islamic Republic of)

    2016-06-15

    Transmission X-ray tubes based on carbon nanotube have attracted significant attention recently. In most of these tubes, tungsten is used as the target material. In this article, the well-known simulator Geant4 was used to obtain some of the tungsten target parameters. The optimal thickness for maximum production of usable X-rays when the target is exposed to electron beams of different energies was obtained. The linear variation of optimal thickness of the target for different electron energies was also obtained. The data obtained in this study can be used to design X-ray tubes. A beryllium window was considered for the X-ray tube. The X-ray energy spectra at the moment of production and after passing through the target and window for different electron energies in the 30-110 keV range were also obtained. The results obtained show that with a specific thickness, the target material itself can act as filter, which enables generation of X-rays with a limited energy.

  5. The KCaSrTa5O15 photocatalyst with tungsten bronze structure for water splitting and CO2 reduction.

    Science.gov (United States)

    Takayama, Tomoaki; Tanabe, Kentaro; Saito, Kenji; Iwase, Akihide; Kudo, Akihiko

    2014-11-28

    KCaSrTa5O15 with tungsten bronze structure and a band gap of 4.1 eV showed activity for water splitting without cocatalysts. The activity was improved by loading the NiO cocatalyst. The apparent quantum yield of optimized NiO-loaded KCaSrTa5O15 was 2.3% at 254 nm for water splitting. When CO2 gas was bubbled into the reactant aqueous solution, Ag cocatalyst-loaded KCaSrTa5O15 produced CO and H2 as reduction products of CO2 and H2O, respectively, and O2 as an oxidation product of H2O. The carbon source of CO was confirmed to be CO2 molecules by using (13)CO2. The ratio of the number of electrons to that of holes calculated from the amounts of products (CO, H2 and O2) was almost unity. Additionally, the ratio of the turnover number of electrons consumed for CO production to the total number of an Ag atom of the cocatalyst that was the active site for CO2 reduction was 8.6 at 20 h. These results indicate that water was consumed as an electron donor for this photocatalytic CO2 reduction in an aqueous medium. Thus, KCaSrTa5O15 with tungsten bronze structure has arisen as a new photocatalyst that is active for water splitting and CO2 reduction utilizing water as an electron donor.

  6. Direct determination of sodium, potassium, chromium and vanadium in biodiesel fuel by tungsten coil atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Dancsak, Stacia E. [Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109 (United States); Silva, Sidnei G.; Nóbrega, Joaquim A. [Group of Applied Instrumental Analysis, Department of Chemistry, Federal University of São Carlos, São Carlos, SP (Brazil); Jones, Bradley T. [Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109 (United States); Donati, George L., E-mail: georgedonati@yahoo.com.br [Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109 (United States)

    2014-01-02

    Graphical abstract: -- Highlights: •Direct analysis of biodiesel on a tungsten coil atomizer. •Determination of Na, K, Cr and V by tungsten coil atomic emission spectrometry. •Sample dilution with methanol or ethanol. •Ten-microliter sample aliquots and limits of detection between 20 and 90 μg kg{sup −1}. •Low consumption of reagents, samples and gases in a 140 s per run procedure. -- Abstract: High levels of sodium and potassium can be present in biodiesel fuel and contribute to corrosion, reduced performance and shorter engine lifetime. On the other hand, trace amounts of chromium and vanadium can increase the emission of pollutants during biodiesel combustion. Sample viscosity, immiscibility with aqueous solutions and high carbon content can compromise biodiesel analyzes. In this work, tungsten filaments extracted from microscope light bulbs are used to successively decompose biodiesel's organic matrix, and atomize and excite the analytes to determine sodium, potassium, chromium and vanadium by tungsten coil atomic emission spectrometry (WCAES). No sample preparation other than simple dilution in methanol or ethanol is required. Direct analysis of 10-μL sample aliquots using heating cycles with less than 150 s results in limits of detection (LOD) as low as 20, 70, 70 and 90 μg kg{sup −1} for Na, K, Cr and V, respectively. The procedure's accuracy is checked by determining Na and K in a biodiesel reference sample and carrying out spike experiments for Cr and V. No statistically significant differences were observed between reference and determined values for all analytes at a 95% confidence level. The procedure was applied to three different biodiesel samples and concentrations between 6.08 and 95.6 mg kg{sup −1} for Na and K, and between 0.22 and 0.43 mg kg{sup −1} for V were obtained. The procedure is simple, fast and environmentally friendly. Small volumes of reagents, samples and gases are used and no residues are generated

  7. Sinter-hardening of Ni-Mo pre-alloyed powders with tungsten addition

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-01-01

    Full Text Available Purpose: Purpose of this paper was to present the benefits of powder metallurgy technology and development ofsinter-hardening process. The mechanical properties, focusing in particular on hardness and wear resistance, oftwo different carbon levels pre-alloyed steel powders processed with sinter-hardening method, were described.Microstructure characteristic of produced sinter-hardened Ni-Mo steels with increasing amount of tungsten(from 0 to 0.3% wt. was taken under consideration.Design/methodology/approach: Different compositions have been tested in order to investigate the influenceof various tungsten additions into low (0.4% and high (0.6% carbon content of pre-alloyed steel powders.Powders, with addition of 0.7% lubricant, were pressed in a 2000kN hydraulic press. De-waxing process at550ºC for 60 minutes in a fully nitrogen atmosphere was performed before the sintering. Sintering was carriedout in vacuum furnace with argon backfilling. The furnace was equipped with a cooling zone to provideaccelerated cooling from the sintering temperature. Green compacts were sintered at the temperature 1120ºC for1 hour and rapidly cooled with a rate 2.5ºC/s.Findings: The applied sinter-hardening process resulted with achievement of material characterized by goodwear resistance. The investigation of Ni-Mo and Ni-Mo-W sinter-hardened steels with low and high carboncontent proved that applied process of sintering under vacuum and rapid cooling brought expected outcome.Research limitations/implications: Considering the achieved outcome, it was revealed that chemical compositionand applied process of steels preparation, sinter-hardening with the cooling rate 2.5ºC/s, results in achieving materialswith relatively high hardness and significant resistance to abrasion. Anyhow, further research should be performed.Originality/value: Sinter-hardening of Ni-Mo pre-alloyed powders with the addition of different additions oftungsten, especially in terms of

  8. Influences of sub-micrometer Ta and Co dopants on microstructure and properties of tungsten heavy alloys

    Institute of Scientific and Technical Information of China (English)

    谭兴龙; 冷邦义; 邱绍宇; 李强; 何文艳; 王传海; 雷代富

    2004-01-01

    Tungsten heavy alloys are aggregates of particles of tungsten bonded with Ni/Fe or Ni/Cu via liquidphase sintering. The sub-micrometer Ta Co powder was added to this aggregate to strengthen the bonding phase. It is found that the main fracture pattern of the alloys is cleavage of tungsten grains and ductile rupture of bond phase,leading to improved tensile strength and elongation. Dopant Ta can act as grain size inhibitor in tungsten heavy alloys.

  9. The effect of metal-contacts on carbon nanotube for high frequency interconnects and devices

    Directory of Open Access Journals (Sweden)

    George Chimowa

    2014-08-01

    Full Text Available High frequency characterisation of platinum and tungsten contacts on individual multi-walled carbon nanotubes (MWNT is performed from 10 MHz to 50 GHz. By measuring the scattering parameters of aligned individual MWNTs, we show that metal contacts enhance an inductive response due to the improved MWNT-electrode coupling reducing the capacitive effect. This behaviour is pronounced in the frequency below 10 GHz and strong for tungsten contacts. We explain the inductive response as a result of the interaction of stimulus current with the localized (or defects states present at the contact region resulting in the current lagging behind the voltage. The results are further supported by direct current measurements that show tungsten to significantly increase carbon nanotube-electrode coupling. The immediate consequence is the reduction of the contact resistance, implying a reduction of electron tunnelling barrier from the electrode to the carbon nanotube.

  10. Interaction between tungsten monocarbide and an iron-based metallic melt

    Science.gov (United States)

    Chumanov, I. V.; Anikeev, A. N.

    2015-12-01

    A technique and results of investigation of compacted tungsten carbide substrates by scanning microscopy are reported. Samples are prepared in the course of studies of the wettability of tungsten carbide substrates with the iron melt, which are performed in accordance with the sessile drop method using two different heating strategies, namely, contact and noncontact heating of metal.

  11. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    NARCIS (Netherlands)

    Buzi, L.; De Temmerman, G.; Unterberg, B.; M. Reinhart,; Litnovsky, A.; Philipps, V.; Van Oost, G.; Möller, S.

    2014-01-01

    Systematic study of deuterium irradiation effects on tungsten was done under ITER - relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER - like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux

  12. TiNi shape memory alloy coated with tungsten : A novel approach for biomedical applications

    NARCIS (Netherlands)

    Li, Huafang; Zheng, Yufeng; Pei, Y. T.; de Hosson, Jeff

    2014-01-01

    This study explores the use of DC magnetron sputtering tungsten thin films for surface modification of TiNi shape memory alloy (SMA) targeting for biomedical applications. SEM, AFM and automatic contact angle meter instrument were used to determine the surface characteristics of the tungsten thin fi

  13. Demonstration of Shear Localization in Ultrafine Grained Tungsten Alloys via Powder Metallurgy Processing Route

    Science.gov (United States)

    2012-09-01

    Hardness Vickers microhardness tests were performed to determine the hardness of the material. Indents were analyzed to determine basic information...shear banding observed in depleted uranium. Microhardness testing indicated that the boron containing sample had a higher propensity to shear...18 cm3) tungsten based alloy tested in the as-sintered state. 15. SUBJECT TERMS tungsten, shear localization, kinetic energy penetrator, depleted

  14. China’s Ministry of Commerce Set the Tungsten Export Quota for 2007

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>China’s ministry of commerce recently set the export quota for tungsten in 2007. According to the ministry’s report, China’s total tungsten export quota will be 15,400 tons metal content, which is 2.53 per cent less compared to that in 2006.

  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. The influence of high grain boundary density on helium retention in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Valles, G., E-mail: gonzalovallesalberdi@hotmail.es [Instituto de Fusión Nuclear UPM, José Gutiérrez Abascal 2, 28006 Madrid (Spain); González, C. [Departamento de Física, Universidad de Oviedo, C/ Calvo Sotelo, s/n, Oviedo (Spain); Martin-Bragado, I. [IMDEA Materials Institute, C/ Enric Kandel 2, 28906 Getafe, Madrid (Spain); Iglesias, R. [Departamento de Física, Universidad de Oviedo, C/ Calvo Sotelo, s/n, Oviedo (Spain); Perlado, J.M.; Rivera, A. [Instituto de Fusión Nuclear UPM, José Gutiérrez Abascal 2, 28006 Madrid (Spain)

    2015-02-15

    Highlights: • Comparison between monocrystalline and nanostructured irradiated tungsten. • OKMC parameterization published and new DFT data. • Important role of grain boundary density on defect evolution. • Cluster pressurization much lower in nanostructured tungsten. • Promising expectations on nanocrystalline tungsten in view of results. - Abstract: In order to study the influence of a high grain boundary density on the amount, size and distribution of defects produced by pulsed helium (625 keV) irradiation in tungsten, we have carried out Object Kinetic Monte Carlo (OKMC) simulations in both monocrystalline and nanocrystalline tungsten. The parameterization of the OKMC code (MMonCa) includes binding energies obtained with our in-house Density Functional Theory (DFT) calculations. In the interior of a grain in nanocrystalline tungsten the mixed He{sub n}V{sub m} clusters are larger and have a lower He/V ratio. Thus, they are less pressurized clusters. The total elastic strain energy remains almost constant with the increasing number of pulses, contrary to its increase in monocrystalline tungsten. A better response to helium irradiation is therefore expected in nanocrystalline tungsten, opening a new path to investigate these nanostructured materials for fusion purposes.

  17. Comparison of tungsten nano-tendrils grown in Alcator C-Mod and linear plasma devices

    NARCIS (Netherlands)

    Wright, G. M.; D. Brunner,; Baldwin, M. J.; Bystrov, K.; Doerner, R. P.; Labombard, B.; Lipschultz, B.; De Temmerman, G.; J.L. Terry,; Whyte, D. G.; Woller, K.B.

    2013-01-01

    Growth of tungsten nano-tendrils (“fuzz”) has been observed for the first time in the divertor region of a high-power density tokamak experiment. After 14 consecutive helium L-mode discharges in Alcator C-Mod, the tip of a tungsten Langmuir probe at the outer strike point was fully covered with a la

  18. Growth Process Conditions of Tungsten Oxide Thin Films Using Hot-Wire Chemical Vapor Deposition

    NARCIS (Netherlands)

    Houweling, Z.S.; Geus, J.W.; de Jong, M.; Harks, P.P.R.M.L.; van der Werf, C.H.M.; Schropp, R.E.I.

    2011-01-01

    We report the growth conditions of nanostructured tungsten oxide (WO3−x) thin films using hot-wire chemical vapor deposition (HWCVD). Two tungsten filaments were resistively heated to various temperatures and exposed to an air flow at various subatmospheric pressures. The oxygen partial pressure was

  19. Early stage damage of ultrafine-grained tungsten materials exposed to low energy helium ion irradiation

    NARCIS (Netherlands)

    El-Atwani, O.; Gonderman, S.; Suslov, S.; Efe, M.; De Temmerman, G.; Morgan, T.; Bystrov, K.; Hattar, K.; Allain, J. P.

    2015-01-01

    Tungsten is considered as a plasma facing component in the divertor region of the International Thermonuclear Experiment Reactor (ITER). High flux, high fluence helium (He) exposure of tungsten surfaces induces severe morphology changes and nanostructure formation, which may eventually erode tungste

  20. Phase II Tungsten Fate-and Transport Study for Camp Edwards

    Science.gov (United States)

    2010-02-01

    cubic meters degrees Fahrenheit (oF-32)/1.8 degrees Celsius (oC) feet 0.3048 meters gallons (U.S. liquid) 3.785412 E-03 liters inches 0.0254 meters...1 Desorption/dissolution of tungsten 451 39 8.1 2 Sorption of sodium tungstate and desorption/dissolution of tungsten and sodium tungstate 124

  1. Thermal shock behaviour of tungsten after high flux H-plasma loading

    NARCIS (Netherlands)

    Wirtz, M.; Linke, J.; Pintsuk, G.; De Temmerman, G.; Wright, G. M.

    2013-01-01

    Previous studies have shown that transient thermal shock loads induce crack networks on tungsten samples especially at low base temperatures. To achieve test conditions which are more relevant for the performance of tungsten-armoured plasma facing components in next step thermonuclear fusion devices

  2. Jiangxi Again Discovered Worldclass Tungsten Mine with Controlled Volume Topping 1 million tonnes

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    <正>The reporter recently learned from Jiangxi Province Geological Mineral Prospecting & Development Bureau that following the discovery of ultra large tungsten mine in northwestern Jiangxi in 2010, Jiangxi Province again discovered a world-class large tungsten mine in Zhuxi Mining Zone in Fuliang County in northeastern Jiangxi.

  3. Efficient emission of positronium atoms from an Na-coated polycrystalline tungsten surface

    Science.gov (United States)

    Terabe, H.; Iida, S.; Wada, K.; Hyodo, T.; Yagishita, A.; Nagashima, Y.

    2013-06-01

    Time-of-flight spectra for the ortho-positronium emitted from clean and Na-coated tungsten surfaces have been measured using the pulsed slow positron beam at KEK-IMSS slow positron facility. Emission efficiency of positronium from the Na-coated sample was found to be several times greater than that from uncoated tungsten surfaces.

  4. TiNi shape memory alloy coated with tungsten : A novel approach for biomedical applications

    NARCIS (Netherlands)

    Li, Huafang; Zheng, Yufeng; Pei, Y. T.; de Hosson, Jeff

    This study explores the use of DC magnetron sputtering tungsten thin films for surface modification of TiNi shape memory alloy (SMA) targeting for biomedical applications. SEM, AFM and automatic contact angle meter instrument were used to determine the surface characteristics of the tungsten thin

  5. Mathematical Modelling of the Process of Tungsten Fluorides Reduction by Hydrogen

    Directory of Open Access Journals (Sweden)

    Brendakov Roman

    2016-01-01

    Full Text Available The process of tungsten fluorides reduction by hydrogen is a component part of Fluoride technology of tungsten conversion. Nowadays the researchers are definitely interested in studying this process. It is connected with common use of metal tungsten products in different sectors of the economy, which is the result of unique qualities of this metal. With the help of physical and mathematical modelling of the process of tungsten hexafluoride reduction by hydrogen, it becomes possible to create an import substitution technology of metal tungsten conversion. Fluoride technology of tungsten conversion allows putting different coverings and make tungsten products of different shapes, which is impossible to get traditionally. The process of tungsten fluorides reduction by hydrogen can be referred to CVD processes (Chemical Vapor Deposition. Common use of CVD technologies for getting metal products and coverings is limited by definite problems, connected with access difficulties to initial components of research and the lack of information about their basic thermal characteristics. Therefore, mathematical description of the initial components mass-moving process, which provides with optimal value of their concentration in gas flow and in precipitation zone, is a question of current importance.

  6. pH-controllable synthesis of unique nanostructured tungsten oxide aerogel and its sensitive glucose biosensor.

    Science.gov (United States)

    Sun, Qiang-Qiang; Xu, Maowen; Bao, Shu-Juan; Li, Chang Ming

    2015-03-20

    This work presents a controllable synthesis of nanowire-networked tungsten oxide aerogels, which was performed by varying the pH in a polyethyleneimine (PEI)-assisted hydrothermal process. An enzyme-tungsten oxide aerogel co-modified electrode shows high activity and selectivity toward glucose oxidation, thus holding great promise for applications in bioelectronics.

  7. Optically Polarized Conduction-Band Electrons in Tungsten Observed by Spin-Polarized Photoemission

    DEFF Research Database (Denmark)

    Zürcher, P.; Meier, F.; Christensen, N. E.

    1979-01-01

    Along the (100) direction of tungsten, interband transitions induced by circularly polarized light of energy 1.5 eV......Along the (100) direction of tungsten, interband transitions induced by circularly polarized light of energy 1.5 eV...

  8. Jiangxi Tungsten Acquired 71.34% Shares of Jiangxi Golden Century New Materials Co., Ltd.

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>On June 22, 2010, the 71.34% equity change of Jiangxi Golden Century New Materials Co., Ltd. to Jiangxi Rare Earth & Rare Metals Tungsten Group Holding Co., Ltd. (Jiangxi Tungsten) was registered at Jiangxi Admini-stration for Industry and Commerce.

  9. The nitrate reductase inhibitor, tungsten, disrupts actin microfilaments in Zea mays L.

    Science.gov (United States)

    Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2014-05-01

    Tungsten is a widely used inhibitor of nitrate reductase, applied to diminish the nitric oxide levels in plants. It was recently shown that tungsten also has heavy metal attributes. Since information about the toxic effects of tungsten on actin is limited, and considering that actin microfilaments are involved in the entry of tungsten inside plant cells, the effects of tungsten on them were studied in Zea mays seedlings. Treatments with sodium tungstate for 3, 6, 12 or 24 h were performed on intact seedlings and seedlings with truncated roots. Afterwards, actin microfilaments in meristematic root and leaf tissues were stained with fluorescent phalloidin, and the specimens were examined by confocal laser scanning microscopy. While the actin microfilament network was well organized in untreated seedlings, in tungstate-treated ones it was disrupted in a time-dependent manner. In protodermal root cells, the effects of tungsten were stronger as cortical microfilaments were almost completely depolymerized and the intracellular ones appeared highly bundled. Fluorescence intensity measurements confirmed the above results. In the meristematic leaf tissue of intact seedlings, no depolymerization of actin microfilaments was noticed. However, when root tips were severed prior to tungstate application, both cortical and endoplasmic actin networks of leaf cells were disrupted and bundled after 24 h of treatment. The differential response of root and leaf tissues to tungsten toxicity may be due to differential penetration and absorption, while the effects on actin microfilaments could not be attributed to the nitric oxide depletion by tungsten.

  10. Antaike Estimates That the Demand for Tungsten will Increase by 18% in China

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    <正>Antaike estimates that the demand for tungsten will increase to 37,987 tons in China this year, up by 18% compared with the year 2012. According to the Antaike data, the consumption volume of tungsten in our country in 2012 was 32,082 tons, down by 21% compared with the year 2011. An analyst of Antaike said that due

  11. Room-Temperature Tensile Behavior of Oriented Tungsten Single Crystals with Rhenium in Dilute Solid Solution

    Science.gov (United States)

    1966-01-01

    SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION Sby M. Garfinkle Lewis Research Center Cleveland, Ohio 20060516196 NATIONAL AERONAUTICS AND...WITH RHENIUM IN DILUTE SOLID SOLUTION By M. Garfinkle Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by...ORIENTED TUNGSTEN SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION * by M. Garfinkle Lewis Research Center SUMMARY Tungsten single crystals

  12. Conjugated organometallic materials containing tungsten centers

    Science.gov (United States)

    Jones, Marya

    Our group is interested in the optical and electronic properties of organometallic analogues of conjugated organic compounds. Specifically, in this thesis we will discuss the properties of complexes in which W≡C moieties replace C≡C fragments within the framework of oligo(phenyleneethynylenes) and a C4-polyyne. A family of derivatives of the type Ph(C≡CC6H4 )m(L)4W≡C(C6H 4C≡C)nPh (m = 0, 1; n = 0, 1, 2) have been prepared and characterized by X-ray crystallography, electronic-absorption spectroscopy, and electrochemistry. This substitution has allowed us to directly compare the electronic and optical properties of these organometallic complexes with those of their organic analogues. We found that while these systems exhibit redox and spectroscopic properties similar to those of their organic counterparts they also exhibit new characteristics that are due to the incorporation of the metal center. The design of these compounds has also allowed us to address how the position of the metal within the backbone affects the electronic and optical properties of these compounds. We found that the position of the metal is important in controlling the electronic structure of the material, thus suggesting that the properties of these compounds can be further tuned by changing the position of the metal within the conjugated carbon chain. In addition, we have appended sulfur and isocyanide functionalities to oligo(phenyleneethynylene) analogues. A family of compounds of the type Cl(dppe) 2W(≡CC6H4-4-(C≡CC6H 4)m-4'-R) (m = l, 2; R = N≡C, SCH2CH 2Si(CH3)3) have been prepared and characterized by electronic-absorption spectroscopy and electrochemistry. Differences between the sulfur and isocyanide functionalities are examined, along with the effects of extending conjugation along the arylidyne chain. Evidence that the sulfur-containing arylidyne complexes form self-assembled monolayers on Au and Pt electrodes is presented. In addition, the electron-transfer rates for

  13. Helium segregation on surfaces of plasma-exposed tungsten.

    Science.gov (United States)

    Maroudas, Dimitrios; Blondel, Sophie; Hu, Lin; Hammond, Karl D; Wirth, Brian D

    2016-02-17

    We report a hierarchical multi-scale modeling study of implanted helium segregation on surfaces of tungsten, considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations based on a reliable interatomic interaction potential, including molecular-statics simulations to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile He n (1⩽  n  ⩽  7) clusters in the near-surface region are attracted to the surface due to an elastic interaction force that provides the thermodynamic driving force for surface segregation. This elastic interaction force induces drift fluxes of these mobile He n clusters, which increase substantially as the migrating clusters approach the surface, facilitating helium segregation on the surface. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, in the near-surface region at rates much higher than in the bulk material. These near-surface cluster dynamics have significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure. We integrate the findings of such atomic-scale simulations into a properly parameterized and validated spatially dependent, continuum-scale reaction-diffusion cluster dynamics model, capable of predicting implanted helium evolution, surface segregation, and its near-surface effects in tungsten. This cluster-dynamics model sets the stage for development of fully atomistically informed coarse-grained models for computationally efficient simulation predictions of helium surface segregation, as well as helium retention and surface morphological evolution, toward optimal design of plasma facing components.

  14. Progress of ITER full tungsten divertor technology qualification in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Ezato, K., E-mail: ezato.koichiro@jaea.go.jp [Japan Atomic Energy Agency, 801-1, Mukoyma, Naka-shi, Ibaraki (Japan); Suzuki, S.; Seki, Y.; Mohri, K.; Yokoyama, K. [Japan Atomic Energy Agency, 801-1, Mukoyma, Naka-shi, Ibaraki (Japan); Escourbiac, F.; Hirai, T. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Kuznetcov, V. [NIIEFA, 3 doroga na Metallostroy, Metallostroy, St. Petersburg 196641 (Russian Federation)

    2015-10-15

    Highlights: • JAEA has demonstrated tungsten monoblock technology for ITER divertor that needs to withstand the repetitive heat load as high as 20 MW/m{sup 2}. This includes as follows; • Bonding technologies between W and Cu interlayer, and between Cu interlayer and CuCrZr tube. • Non-destructive examination techniques, especially, ultrasonic testing method, and. • Load carrying capability of W monoblock attachment to support structure of ITER divertor. - Abstract: Japan Atomic Energy Agency (JAEA) is in progress for technology qualification toward full-tungsten (W) ITER divertor outer vertical target (OVT), especially, tungsten monoblock technology that needs to withstand the repetitive heat load as high as 20 MW/m{sup 2}. To demonstrate the armor heat sink bonding technology and heat removal capability, 6 small-scale W monoblock mock-ups manufactured by different bonding technologies using different W materials in addition to 4 full-scale prototype plasma-facing units (PFUs). After non-destructive test, the W components were tested under high heat flux (HHF) in ITER Divertor Test Facility (IDTF) at NIIEFA. Consequently, all of the W monoblocks endured the repetitive heat load at 20 MW/m{sup 2} for 1000 cycles (requirements 20 MW/m{sup 2} for 300 cycles) without any failure. In addition to the armor to heat sink joints, the load carrying capability test on the W monoblock with a leg attachment was carried out. In uniaxial tensile test, all of the W monoblock attachments with different bonding technologies such as brazing and HIPping withstand the tensile load exceeding 20 kN that is the value more than twice the design value. The failures occurred at the leg attachments or the W monoblocks, rather than the bonding interface of the W monoblocks to the leg attachment.

  15. Research on Diamond Enhanced Tungsten Carbide Composite Button

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    At the present, the cutters used in button bits and rock bits are mainly cobalt tungsten carbide in our country. Because of its low abrasive resistance, the bit service life and drilling efficiency was very low when the hard and extremely hard formations were being drilled. Owing to its high abrasive resistance, the diamond composite material is widely used in drilling operations. However, its toughness against impact is too low to be used in percussion drilling, only can it be used in rotary drilling. In ...

  16. Unified approach for determining tetragonal tungsten bronze crystal structures.

    Science.gov (United States)

    Smirnov, M; Saint-Grégoire, P

    2014-05-01

    Tetragonal tungsten bronze (TTB) oxides are one of the most important classes of ferroelectrics. Many of these framework structures undergo ferroelastic transformations related to octahedron tilting deformations. Such tilting deformations are closely related to the rigid unit modes (RUMs). This paper discusses the whole set of RUMs in an ideal TTB lattice and possible crystal structures which can emerge owing to the condensation of some of them. Analysis of available experimental data for the TTB-like niobates lends credence to the obtained theoretical predictions.

  17. L-Shell Ionization Study of Tungsten by Electron Impact

    Institute of Scientific and Technical Information of China (English)

    彭秀峰; 何福庆; 龙先灌; 安竹; 罗正明

    2001-01-01

    L-shell partial production cross sections of Lα-, Lβ- , Lγ- rays by electron impact were measured by observing the counts of x-rays from an impacted thin tungsten target. The total production cross sections and mean ionization cross sections were deduced from the measured results. The electron beam energy range was found to be 11-36 keV. The influence of electrons reflected by the backing on ionization cross sections has been corrected. The experimental results agree well with the theoretical predictions.

  18. Impact toughness of tungsten films deposited on martensite stainless steel

    Institute of Scientific and Technical Information of China (English)

    HUANG Ning-kang; YANG Bin; WANG De-zhi

    2005-01-01

    Tungsten films were deposited on stainless steel Charpy specimens by magnetron sputtering followed by electron beam heat treatment. Charpy impact tests and scanning electron microscopy were used to investigate the ductile-brittle transition behavior of the specimens. With decreasing test temperature the fracture mode was transformed from ductile to brittle for both kinds of specimens with and without W films. The data of the crack initiation energy, crack propagation energy, impact absorbing energy, fracture time and deflection as well as the fracture morphologies at test temperature of -70 ℃ show that W films can improve the impact toughness of stainless steel.

  19. Ablation study of tungsten-based nuclear thermal rocket fuel

    Science.gov (United States)

    Smith, Tabitha Elizabeth Rose

    The research described in this thesis has been performed in order to support the materials research and development efforts of NASA Marshall Space Flight Center (MSFC), of Tungsten-based Nuclear Thermal Rocket (NTR) fuel. The NTR was developed to a point of flight readiness nearly six decades ago and has been undergoing gradual modification and upgrading since then. Due to the simplicity in design of the NTR, and also in the modernization of the materials fabrication processes of nuclear fuel since the 1960's, the fuel of the NTR has been upgraded continuously. Tungsten-based fuel is of great interest to the NTR community, seeking to determine its advantages over the Carbide-based fuel of the previous NTR programs. The materials development and fabrication process contains failure testing, which is currently being conducted at MSFC in the form of heating the material externally and internally to replicate operation within the nuclear reactor of the NTR, such as with hot gas and RF coils. In order to expand on these efforts, experiments and computational studies of Tungsten and a Tungsten Zirconium Oxide sample provided by NASA have been conducted for this dissertation within a plasma arc-jet, meant to induce ablation on the material. Mathematical analysis was also conducted, for purposes of verifying experiments and making predictions. The computational method utilizes Anisimov's kinetic method of plasma ablation, including a thermal conduction parameter from the Chapman Enskog expansion of the Maxwell Boltzmann equations, and has been modified to include a tangential velocity component. Experimental data matches that of the computational data, in which plasma ablation at an angle shows nearly half the ablation of plasma ablation at no angle. Fuel failure analysis of two NASA samples post-testing was conducted, and suggestions have been made for future materials fabrication processes. These studies, including the computational kinetic model at an angle and the

  20. A study on twin-tungsten TIG welding method

    Institute of Scientific and Technical Information of China (English)

    Leng Xuesong; Zhang Guangjun; Gao Hongming; Wu Lin

    2006-01-01

    A new twin-tungsten TIG (T-TIG) welding method was studied. This method differs from the conventional TIG method, it places two electrodes insulated from each other in the same welding torch, and a coupling arc is generated from the two electrodes. The coupling arc pressure was measured and preliminary welding experiment was made. The results show that the coupling arc can keep arc pressure at a low level compared with conventional TIG arc, and welding can be achieved under higher current and high travel speed with sound appearance of weld. Therefore, this new method can applied widely in high efficiency welding.