Growth study and photocatalytic properties of Co-doped tungsten oxide mesocrystals

Energy Technology Data Exchange (ETDEWEB)

Sun, Shibin [College of Logistics Engineering, Shanghai Maritime University, Shanghai 200135 (China); College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061 (China); Chang, Xueting, E-mail: xuetingchang@yahoo.cn [College of Logistics Engineering, Shanghai Maritime University, Shanghai 200135 (China); Li, Zhenjiang [College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061 (China)

2012-11-15

Cobalt-doped tungsten oxide mesocrystals with different morphologies have been successfully generated using a solvothermal method with tungsten hexachloride and cobalt chloride salts as precursors. The resulting mesocrystals were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmet-Teller analysis of nitrogen sorptometer, and UV-vis diffuse reflectance spectroscopy. The photocatalytic properties of the cobalt-doped tungsten oxide mesocrystals were evaluated on the basis of their ability to degrade methyl orange in an aqueous solution under simulated sunlight irradiation. Results showed that the cobalt doping had obvious effect on the morphologies of the final products, and lenticular and blocky cobalt-doped tungsten oxide mesocrystals could be obtained with 1.0 wt.% and 2.0 wt.% cobalt doping, respectively. The cobalt-doped tungsten oxides exhibited superior photocatalytic activities to that of the undoped tungsten oxide. - Graphical abstract: Schematic illustrations of the growth of the bundled nanowires, lenticular mesocrystals, and blocky mesocrystals. Highlights: Black-Right-Pointing-Pointer Co-doped W{sub 18}O{sub 49} mesocrystals were synthesized using a solvothermal method. Black-Right-Pointing-Pointer The Co doping has obvious effect on the morphology of the final mesocrystals. Black-Right-Pointing-Pointer The Co-doped W{sub 18}O{sub 49} exhibited superior photocatalytic activity to the undoped W{sub 18}O{sub 49}.

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.

Development of wear-resistant coatings for cobalt-base alloys

International Nuclear Information System (INIS)

Cockeram, B.V.

1999-01-01

The costs and hazards resulting from nuclear plant radiation exposure with activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. However, the hardnesses of many cobalt-base wear alloys are significantly lower than conventional PVD hard coatings, and mechanical support of the hard coating is a concern. Four approaches have been taken to minimize the hardness differences between the substrate and PVD hard coating: (1) use a thin Cr-nitride hard coating with layers that are graded with respect to hardness, (2) use a thicker, multilayered coating (Cr-nitride or Zr-nitride) with graded layers, (3) use nitriding to harden the alloy subsurface followed by application of a multilayered coating of Cr-nitride, and (4) use of nitriding alone. Since little work has been done on application of PVD hard coatings to cobalt-base alloys, some details on process development and characterization of the coatings is presented. Scratch testing was used to evaluate the adhesion of the different coatings. A bench-top rolling contact test was used to evaluate the wear resistance of the coatings. The test results are discussed, and the more desirable coating approaches are identified

In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys

Energy Technology Data Exchange (ETDEWEB)

Schuster, B.E. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Roszell, L.E. [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010‐5403 (United States); Murr, L.E.; Ramirez, D.A. [Department of Metallurgical and Materials Engineering, University of Texas, El Paso, TX 79968 (United States); Demaree, J.D. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Klotz, B.R. [Dynamic Science Inc., Aberdeen Proving Ground, MD 21005‐5609 (United States); Rosencrance, A.B.; Dennis, W.E. [U.S. Army Center for Environmental Health Research, Department of Chemistry, Ft. Detrick, MD 21702‐5010 (United States); Bao, W. [SAS Institute, Inc. SAS Campus Drive, Cary, NC 27513 (United States); Perkins, E.J. [U.S. Army Engineer Research and Development Center, 3909 Hall Ferry Road, Vicksburg MS 39180 (United States); Dillman, J.F. [U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010‐5400 (United States); Bannon, D.I., E-mail: desmond.bannon@us.army.mil [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010‐5403 (United States)

2012-11-15

Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up‐regulated and those involved with muscle development and differentiation significantly down‐regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin‐dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. -- Highlights: ► Tungsten/nickel/cobalt, tungsten/nickel/iron, and pure tungsten were studied. ► Male Fischer rats implanted with

In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys

International Nuclear Information System (INIS)

Schuster, B.E.; Roszell, L.E.; Murr, L.E.; Ramirez, D.A.; Demaree, J.D.; Klotz, B.R.; Rosencrance, A.B.; Dennis, W.E.; Bao, W.; Perkins, E.J.; Dillman, J.F.; Bannon, D.I.

2012-01-01

Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up‐regulated and those involved with muscle development and differentiation significantly down‐regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin‐dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. -- Highlights: ► Tungsten/nickel/cobalt, tungsten/nickel/iron, and pure tungsten were studied. ► Male Fischer rats implanted with

In vitro profiling of epigenetic modifications underlying heavy metal toxicity of tungsten-alloy and its components

International Nuclear Information System (INIS)

Verma, Ranjana; Xu, Xiufen; Jaiswal, Manoj K.; Olsen, Cara; Mears, David; Caretti, Giuseppina; Galdzicki, Zygmunt

2011-01-01

Tungsten-alloy has carcinogenic potential as demonstrated by cancer development in rats with intramuscular implanted tungsten-alloy pellets. This suggests a potential involvement of epigenetic events previously implicated as environmental triggers of cancer. Here, we tested metal induced cytotoxicity and epigenetic modifications including H3 acetylation, H3-Ser10 phosphorylation and H3-K4 trimethylation. We exposed human embryonic kidney (HEK293), human neuroepithelioma (SKNMC), and mouse myoblast (C2C12) cultures for 1-day and hippocampal primary neuronal cultures for 1-week to 50-200 μg/ml of tungsten-alloy (91% tungsten/6% nickel/3% cobalt), tungsten, nickel, and cobalt. We also examined the potential role of intracellular calcium in metal mediated histone modifications by addition of calcium channel blockers/chelators to the metal solutions. Tungsten and its alloy showed cytotoxicity at concentrations > 50 μg/ml, while we found significant toxicity with cobalt and nickel for most tested concentrations. Diverse cell-specific toxic effects were observed, with C2C12 being relatively resistant to tungsten-alloy mediated toxic impact. Tungsten-alloy, but not tungsten, caused almost complete dephosphorylation of H3-Ser10 in C2C12 and hippocampal primary neuronal cultures with H3-hypoacetylation in C2C12. Dramatic H3-Ser10 dephosphorylation was found in all cobalt treated cultures with a decrease in H3 pan-acetylation in C2C12, SKNMC and HEK293. Trimethylation of H3-K4 was not affected. Both tungsten-alloy and cobalt mediated H3-Ser10 dephosphorylation were reversed with BAPTA-AM, highlighting the role of intracellular calcium, confirmed with 2-photon calcium imaging. In summary, our results for the first time reveal epigenetic modifications triggered by tungsten-alloy exposure in C2C12 and hippocampal primary neuronal cultures suggesting the underlying synergistic effects of tungsten, nickel and cobalt mediated by changes in intracellular calcium homeostasis and

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.).

Tungsen--nickel--cobalt alloy and method of producing same

International Nuclear Information System (INIS)

Dickinson, J.M.; Riley, R.E.

1977-01-01

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 this tungsten--nickel--cobalt alloy is further described and comprises coating the tungsten particles with a nickel--cobalt alloy, pressing the coated particles into a compact shape, heating the compact in hydrogen to a temperature in the range of 1400 0 C and holding at this elevated temperature for a period of about 2 hours, increasing this elevated temperature to about 1500 0 C and holding for 1 hour at this temperature, cooling to about 1200 0 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 cooling the resulting alloy to room temperature in this argon atmosphere

Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

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Rachana Gupta

2015-09-01

Full Text Available Cobalt nitride (Co-N thin films prepared using a reactive magnetron sputtering process are studied in this work. During the thin film deposition process, the relative nitrogen gas flow (RN2 was varied. As RN2 increases, Co(N, Co4N, Co3N and CoN phases are formed. An incremental increase in RN2, after emergence of Co4N phase at RN2 = 10%, results in a linear increase of the lattice constant (a of Co4N. For RN2 = 30%, a maximizes and becomes comparable to its theoretical value. An expansion in a of Co4N, results in an enhancement of the magnetic moment, to the extent that it becomes even larger than pure Co. Such larger than pure metal magnetic moment for tetra-metal nitrides (M4N have been theoretically predicted. Incorporation of N atoms in M4N configuration results in an expansion of a (relative to pure metal and enhances the itinerary of conduction band electrons leading to larger than pure metal magnetic moment for M4N compounds. Though a higher (than pure Fe magnetic moment for Fe4N thin films has been evidenced experimentally, higher (than pure Co magnetic moment is evidenced in this work.

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

International Nuclear Information System (INIS)

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

1988-01-01

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

Development of wear-resistant coatings for cobalt-base alloys

International Nuclear Information System (INIS)

Cockeram, B.V.

1999-01-01

The level of nuclear plant radiation exposure due to activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. Laboratory pin-on-disc and rolling contact wear tests were used to evaluate the wear performance of several coatings. Based on the results of these tests, multilayer Cr-nitride coatings and ion nitriding are the most promising approaches

Amorphous Metal Tungsten Nitride and its Application for Micro and Nanoelectromechanical Applications

KAUST Repository

Mayet, Abdulilah M.

2016-05-01

The objective of this doctoral thesis is to develop, engineer and investigate an amorphous metal tungsten nitride (aWNx) and to study its functionality for applications focused on electromechanical system at the nano-scale. Charge transport based solid state device oriented complementary metal oxide semiconductor (CMOS) electronics have reached a level where they are scaled down to nearly their fundamental limits regarding switching speed, off state power consumption and the on state power consumption due to the fundamental limitation of sub-threshold slope (SS) remains at 60 mV/dec. NEM switch theoretically and practically offers the steepest sub-threshold slope and practically has shown zero static power consumption due to their physical isolation originated from the nature of their mechanical operation. Fundamental challenges remain with NEM switches in context of their performance and reliability: (i) necessity of lower pull-in voltage comparable to CMOS technology; (ii) operation in ambient/air; (iii) increased ON current and decreased ON resistance; (iv) scaling of devices and improved mechanical and electrical contacts; and (v) high endurance. The “perfect” NEM switch should overcome all the above-mentioned challenges. Here, we show such a NEM switch fabricated with aWNx to show (i) sub-0.3-volt operation; (ii) operation in air and vacuum; (iii) ON current as high as 0.5 mA and ON resistance lower than 5 kΩ; (iv) improved mechanical contact; and the most importantly (v) continuous switching of 8 trillion cycles for more than 10 days with the highest switching speed is 30 nanosecond without hysteresis. In addition, tungsten nitride could be the modern life vine by fulfilling the demand of biodegradable material for sustainable life regime. Transient electronics is a form of biodegradable electronics as it is physically disappearing totally or partially after performing the required function. The fabricated aWNx suites this category very well, despite not

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

Non-carbon titanium cobalt nitride nanotubes supported platinum catalyst with high activity and durability for methanol oxidation reaction

Science.gov (United States)

Chen, Xiaoxiang; Li, Wuyi; Pan, Zhanchang; Xu, Yanbin; Liu, Gen; Hu, Guanghui; Wu, Shoukun; Li, Jinghong; Chen, Chun; Lin, Yingsheng

2018-05-01

Titanium cobalt nitride nanotubes (Ti0.95Co0.05N NTs) hybrid support, a novel robust non-carbon support material prepared by solvothermal and post-nitriding processes, is further decorated with Pt nanoparticles for the electrooxidation of methanol. The catalyst is characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The morphology, structure and composition of the synthesized Ti0.95Co0.05N NTs suggest that the nanotube wall is porous and consists of homogeneous cohesively attached nitrides nanocube particles. Notable, Ti0.95Co0.05N NTs supported Pt catalyst exhibits significantly improved catalytic activity and durability for methanol electrooxidation compared with the conventional JM Pt/C catalyst. The experimental data indicate that enhanced catalytic activity and stability of Pt/Ti0.95Co0.05N NTs towards methanol electrooxidation might be mainly attributed to the tubular nanostructures and synergistic effect introduced by the Co doping. Both of them are playing an important role in improving the activity and durability of the Ti0.95Co0.05N NTs catalyst.

Chemical vapor deposition of refractory ternary nitrides for advanced diffusion barriers

Energy Technology Data Exchange (ETDEWEB)

Custer, Jonathan S.; Fleming, James G.; Roherty-Osmun, Elizabeth; Smith, Paul Martin

1998-09-22

Refractory ternary nitride films for diffusion barriers in microelectronics have been grown using chemical vapor deposition. Thin films of titanium-silicon-nitride, tungsten-boron-nitride, and tungsten-silicon-nitride of various compositions have been deposited on 150 mm Si wafers. The microstructure of the films are either fully amorphous for the tungsten based films, or nauocrystalline TiN in an amorphous matrix for titanium-silicon-nitride. All films exhibit step coverages suitable for use in future microelectronics generations. Selected films have been tested as diffusion barriers between copper and silicon, and generally perform extremely weH. These fiIms are promising candidates for advanced diffusion barriers for microelectronics applications. The manufacturing of silicon wafers into integrated circuits uses many different process and materials. The manufacturing process is usually divided into two parts: the front end of line (FEOL) and the back end of line (BEOL). In the FEOL the individual transistors that are the heart of an integrated circuit are made on the silicon wafer. The responsibility of the BEOL is to wire all the transistors together to make a complete circuit. The transistors are fabricated in the silicon itself. The wiring is made out of metal, currently aluminum and tungsten, insulated by silicon dioxide, see Figure 1. Unfortunately, silicon will diffuse into aluminum, causing aluminum spiking of junctions, killing transistors. Similarly, during chemical vapor deposition (CVD) of tungsten from ~fj, the reactivity of the fluorine can cause "worn-holes" in the silicon, also destroying transistors. The solution to these problems is a so-called diffusion barrier, which will allow current to pass from the transistors to the wiring, but will prevent reactions between silicon and the metal.

Conducting metal oxide and metal nitride nanoparticles

Science.gov (United States)

DiSalvo, Jr., Francis J.; Subban, Chinmayee V.

2017-12-26

Conducting metal oxide and nitride nanoparticles that can be used in fuel cell applications. The metal oxide nanoparticles are comprised of for example, titanium, niobium, tantalum, tungsten and combinations thereof. The metal nitride nanoparticles are comprised of, for example, titanium, niobium, tantalum, tungsten, zirconium, and combinations thereof. The nanoparticles can be sintered to provide conducting porous agglomerates of the nanoparticles which can be used as a catalyst support in fuel cell applications. Further, platinum nanoparticles, for example, can be deposited on the agglomerates to provide a material that can be used as both an anode and a cathode catalyst support in a fuel cell.

Variation of intrinsic magnetic parameters of single domain Co-N interstitial nitrides synthesized via hexa-ammine cobalt nitrate route

Energy Technology Data Exchange (ETDEWEB)

Ningthoujam, R.S. [Department of Chemistry, Indian Institute of Technology, Kanpur 208016 (India); Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Panda, R.N., E-mail: rnp@bits-goa.ac.in [Chemistry Group, Birla Institute of Technology and Science-Pilani, Goa Campus, Zuari Nagar, Goa 403726 (India); Gajbhiye, N.S. [Department of Chemistry, Indian Institute of Technology, Kanpur 208016 (India)

2012-05-15

Highlights: Black-Right-Pointing-Pointer Variation of intrinsic magnetic parameters of Co-N. Black-Right-Pointing-Pointer Synthesis by hexa-ammine cobalt complex route. Black-Right-Pointing-Pointer Tuning of coercivity by variation of size. - Abstract: We report the variation of Curie temperature (T{sub c}) and coercivity (H{sub c}) of the single domain Co-N interstitial materials synthesized via nitridation of the hexa-ammine Cobalt(III) nitrate complex at 673 K. Co-N materials crystallize in the fcc cubic structure with unit cell parameter, a = 3.552 Angstrom-Sign . The X-ray diffraction (XRD) peaks are broader indicating the materials to be nano-structured with crystallite sizes of 5-14 nm. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies confirm the nanocrystalline nature of the materials. TEM images show chain-like clusters indicating dipolar interactions between the particles. Magnetic studies focus on the existence of giant magnetic Co atoms in the Co-N lattice that are not influenced by the thermal relaxation. The values of the H{sub c} could be tuned with the dimension of the particles. The values of T{sub c} of the nitride materials are masked by the onset of the ferromagnetic to superparamagnetic transition at higher temperatures. Thermomagnetic studies show an increasing trend in the Curie temperature, T{sub c}, with decrease in particle dimension. This result has been explained qualitatively on the basis of ferromagnetic to superparamagnetic transition and finite size scaling effects.

Pipe bend wear - is tungsten carbide the answer?

International Nuclear Information System (INIS)

Freinkel, D.

1988-01-01

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

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

Directory of Open Access Journals (Sweden)

Esmar Budi

2015-02-01

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

Tissue distribution patterns of solubilized metals from internalized tungsten alloy in the F344 rat

Directory of Open Access Journals (Sweden)

Vernieda B. Vergara

2016-06-01

Full Text Available Because of its unique physical and chemical properties, tungsten has been increasingly utilized in a variety of civilian and military applications. This expanded use also raises the risk of human exposure through internalization by various routes. In most cases the toxicological and carcinogenic properties of these tungsten-based compounds are not known nor are the dissolution biokinetics and ultimate fate of the associated metals. Using a laboratory rodent model system designed to assess the health effects of embedded metals, and a tungsten alloy comprised of tungsten (91.1%, nickel (6.0%, and cobalt (2.9%, we investigated the tissue distribution patterns of the metals over a six month period. Despite its perceived insolubility, tungsten rapidly solubilized from the implanted metal fragments, as did nickel and cobalt. All three metals distributed systemically over time with extremely elevated levels of all three metals found in kidney, liver, and spleen. Unexpectedly, tungsten was found to cross the blood-brain and blood-testis barriers and localize in those tissues. These results, along with recent reports suggesting that tungsten is a tumor promoter, raises serious concerns as to the long-term health effects of exposure to tungsten and tungsten-based compounds.

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

International Nuclear Information System (INIS)

Mrotchek, I.

2007-01-01

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

Influence of structures on fracture and fracture toughness of cemented tungsten carbides

International Nuclear Information System (INIS)

Zhao, W.; Zhang, X.

1987-01-01

A study was made of the influence of structures on fracture and fracture toughness of cemented tungsten carbides with different compositions and grain sizes. The measurement of the fracture toughness of cemented tungsten carbide was carried out using single edge notched beam. The microstructural parameters and the proportion for each fracture mode on the fracture surface were obtained. The brittle fracture of the alloy is mainly due to the interfacial decohesion fracture following the interface of the carbide crystals. It has been observed that there are localized fractures region ahead of the crack tip. The morphology of the crack propagation path as well as the slip structure in the cobalt phase of the deformed region have been investigated. In addition, a study of the correlation between the plane strain fracture toughness and microstructural parameters, such as mean free path of the cobalt phase, tungsten carbide grain size and the contiguity of tungsten carbide crystals was also made

Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane

Directory of Open Access Journals (Sweden)

Yu Fu

2017-04-01

Full Text Available Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4, was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet–visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(IIN bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0% of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated. Keywords: Selective oxidation of cyclohexane, Oxygen oxidant, Carbon nitride, Co-doping

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

Science.gov (United States)

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

2018-04-01

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

Study of the temperature dependent nitrogen retention in tungsten surfaces by XPS-analysis

Energy Technology Data Exchange (ETDEWEB)

Plank, Ulrike [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Fakultaet fuer Physik der Ludwig-Maximilians-Universitaet Muenchen, Schellingstrasse 4, D-80799 Muenchen (Germany); Meisl, Gerd; Hoeschen, Till [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany)

2016-07-01

To reduce the power load on the divertor of fusion experiments, nitrogen (N) is puffed into the plasma. As a side effect, nitrogen gets implanted into the tungsten (W) walls of the reactor and forms nitride layers. Their formation and, therefore, the N accumulation in W showed an unexpected temperature dependence in previous experiments. To study the nitrogen retention, we implanted N ions with an energy of 300 eV into W and observed the evolution of the surface composition by X-ray photoelectron spectroscopy (XPS). We find that the N content does not change when the sample is annealed up to 800 K after implantation at lower temperatures. In contrast, the N concentration decreases with increasing implantation temperature. At 800 K implantation temperature, the N saturation level is about 5 times lower compared to 300 K implantation. A possible explanation for this difference is an enhanced diffusion during ion bombardment due to changes in the structure or in the chemical state of the tungsten nitride system. Ongoing tungsten nitride erosion experiments shall help to clarify whether the strong temperature dependence is the result of enhanced diffusion or of phase changes.

Adhesion of non-selective CVD tungsten to silicon dioxide

International Nuclear Information System (INIS)

Woodruff, D.W.; Wilson, R.H.; Sanchez-Martinez, R.A.

1986-01-01

Adhesion of non-selective, CVD tungsten to silicon dioxide is a critical issue in the development of tungsten as a metalization for VLSI circuitry. Without special adhesion promoters, tungsten deposited from WF/sub 6/ and H/sub 2/ has typically failed a standard tape test over all types of silicon oxides and nitrides. The reasons for failure of thin films, and CVD tungsten in particular are explored along with standard techniques for improving adhesion of thin films. Experiments are reported which include a number of sputtered metals as adhesion promoters, as well as chemical and plasma treatment of the oxide surface. Sputtered molybdenum is clearly the superior adhesion promoting layer from these tests. Traditional adhesion layers such as chromium or titanium failed as adhesion layers for CVD tungsten possibly due to chemical reactions between the WF/sub 6/ and Cr or Ti

Cobalt as chemical modifier to improve chromium sensitivity and minimize matrix effects in tungsten coil atomic emission spectrometry

Energy Technology Data Exchange (ETDEWEB)

Silva, Sidnei G. [Group of Applied Instrumental Analysis, Department of Chemistry, Federal University of São Carlos, P.O. Box 676, São Carlos, SP 13560-970 (Brazil); Donati, George L., E-mail: georgedonati@yahoo.com.br [Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109 (United States); Santos, Luana N. [Group of Applied Instrumental Analysis, Department of Chemistry, Federal University of São Carlos, P.O. Box 676, São Carlos, SP 13560-970 (Brazil); Jones, Bradley T. [Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109 (United States); Nóbrega, Joaquim A. [Group of Applied Instrumental Analysis, Department of Chemistry, Federal University of São Carlos, P.O. Box 676, São Carlos, SP 13560-970 (Brazil)

2013-05-30

Graphical abstract: -- Highlights: •Charge transfer reactions increase the population of Cr{sup +}. •Chromium ions and electrons recombine to form excited-state Cr atoms. •A 10-fold improvement in LOD is observed for Cr emission measurements. •The two-step ionization/excitation mechanism improves sensitivity and accuracy. •High concentrations of Co also minimize matrix effects. -- Abstract: Cobalt is used as chemical modifier to improve sensitivity and minimize matrix effects in Cr determinations by tungsten coil atomic emission spectrometry (WCAES). The atomizer is a tungsten filament extracted from microscope light bulbs. A solid-state power supply and a handheld CCD-based spectrometer are also used in the instrumental setup. In the presence of 1000 mg L{sup −1} Co, WCAES limit of detection for Cr (λ = 425.4 nm) is calculated as 0.070 mg L{sup −1}; a 10-fold improvement compared to determinations without Co modifier. The mechanism involved in such signal enhancement is similar to the one observed in ICP OES and ICP-MS determinations of As and Se in the presence of C. Cobalt increases the population of Cr{sup +} by charge transfer reactions. In a second step, Cr{sup +}/e{sup −} recombination takes place, which results in a larger population of excited-state Cr atoms. This alternative excitation route is energetically more efficient than heat transfer from atomizer and gas phase to analyte atoms. A linear dynamic range of 0.25–10 mg L{sup −1} and repeatability of 3.8% (RSD, n = 10) for a 2.0 mg L{sup −1} Cr solution are obtained with this strategy. The modifier high concentration also contributes to improving accuracy due to a matrix-matching effect. The method was applied to a certified reference material of Dogfish Muscle (DORM-2) and no statistically significant difference was observed between determined and certified Cr values at a 95% confidence level. Spike experiments with bottled water samples resulted in recoveries between 93% and

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

Science.gov (United States)

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

1975-01-01

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

Thermal conductivity of nitride films of Ti, Cr, and W deposited by reactive magnetron sputtering

International Nuclear Information System (INIS)

Jagannadham, Kasichainula

2015-01-01

Nitride films of Ti, Cr, and W were deposited using reactive magnetron sputtering from metal targets in argon and nitrogen plasma. TiN films with (200) orientation were achieved on silicon (100) at the substrate temperature of 500 and 600 °C. The films were polycrystalline at lower temperature. An amorphous interface layer was observed between the TiN film and Si wafer deposited at 600 °C. TiN film deposited at 600 °C showed the nitrogen to Ti ratio to be near unity, but films deposited at lower temperature were nitrogen deficient. CrN film with (200) orientation and good stoichiometry was achieved at 600 °C on Si(111) wafer but the film deposited at 500 °C showed cubic CrN and hexagonal Cr 2 N phases with smaller grain size and amorphous back ground in the x-ray diffraction pattern. An amorphous interface layer was not observed in the cubic CrN film on Si(111) deposited at 600 °C. Nitride film of tungsten deposited at 600 °C on Si(100) wafer was nitrogen deficient, contained both cubic W 2 N and hexagonal WN phases with smaller grain size. Nitride films of tungsten deposited at 500 °C were nonstoichiometric and contained cubic W 2 N and unreacted W phases. There was no amorphous phase formed along the interface for the tungsten nitride film deposited at 600 °C on the Si wafer. Thermal conductivity and interface thermal conductance of all the nitride films of Ti, Cr, and W were determined by transient thermoreflectance technique. The thermal conductivity of the films as function of deposition temperature, microstructure, nitrogen stoichiometry and amorphous interaction layer at the interface was determined. Tungsten nitride film containing both cubic and hexagonal phases was found to exhibit much higher thermal conductivity and interface thermal conductance. The amorphous interface layer was found to reduce effective thermal conductivity of TiN and CrN films

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-01

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

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

International Nuclear Information System (INIS)

Vinayo, Maria-Elena

1985-01-01

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

Cobalt phosphate-modified barium-doped tantalum nitride nanorod photoanode with 1.5% solar energy conversion efficiency

KAUST Repository

Li, Yanbo

2013-10-03

Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min. © 2013 Macmillan Publishers Limited. All rights reserved.

In situ thermal imaging and three-dimensional finite element modeling of tungsten carbide-cobalt during laser deposition

International Nuclear Information System (INIS)

Xiong Yuhong; Hofmeister, William H.; Cheng Zhao; Smugeresky, John E.; Lavernia, Enrique J.; Schoenung, Julie M.

2009-01-01

Laser deposition is being used for the fabrication of net shapes from a broad range of materials, including tungsten carbide-cobalt (WC-Co) cermets (composites composed of a metallic phase and a hard refractory phase). During deposition, an unusual thermal condition is created for cermets, resulting in rather complex microstructures. To provide a fundamental insight into the evolution of such microstructures, we studied the thermal behavior of WC-Co cermets during laser deposition involving complementary results from in situ high-speed thermal imaging and three-dimensional finite element modeling. The former allowed for the characterization of temperature gradients and cooling rates in the vicinity of the molten pool, whereas the latter allowed for simulation of the entire sample. By combining the two methods, a more robust analysis of the thermal behavior was achieved. The model and the imaging results correlate well with each other and with the alternating sublayers observed in the microstructure.

Precipitation and ion floatation of molybdenum, tungsten, copper, and cobalt compounds by cetyltrimethylammonium bromide and sodium diethyldithiocarbamate

International Nuclear Information System (INIS)

Strizhko, V.S.; Shekhirev, D.V.; Ignatkina, V.A.; Alimova, R.Eh.

1996-01-01

Experimental data are presented on application of ion-flotation in purification of low-concentration (less than 10 -3 M) acid solutions from molybdenum, tungsten, copper and cobalt ions. Two collectors, i.e. DEDC and CTMAB have been tested, their optimal consumption is determined. It is shown that CTMAB provides for selective purification from Mo and W ions and allows foam product with little water on flotation in a column to be obtained. But the achieved residual W and Mo concentration of 20 to 10 mg/l require deeper finishing purification in order to meet a sanitary permissible limiting concentration value employing other methods. DEDC provides for sufficient purification from nonferrous metal ions but does not possess selectivity with respect to some metals. The obtained results have shown the possibility to apply ion-flotation in concentration of metal ions in foam product in the process of waste water purification with further finishing purification up to a sanitary permissible limiting concentration value. 14 refs.; 3 figs.; 1 tab

Improvement of creep-rupture properties by serrated grain boundaries in high-tungsten cobalt-base superalloys

International Nuclear Information System (INIS)

Tanaka, Manabu

1993-01-01

The improvement of creep-rupture properties by serrated grain boundaries was investigated using cobalt-base superalloys containing about 14 to 20 wt.% tungsten at 1089 and 1311 K. Serrated grain boundaries improved both the rupture life and the ductility, especially under lower stresses at 1089 K. The increase in rupture life was larger in the alloys containing a larger amount of W. Ductile grain boundary fracture surfaces, which involved dimple patterns and grain boundary ledges, were observed in the specimens with serrated grain boundaries whereas brittle grain boundary facets were observed in the specimens with normal straight grain boundaries ruptured at 1089 K. The strengthening by serrated grain boundaries was also effective at 1311 K, but there was little difference in rupture life between the specimens with serrated grain boundaries and those with straight grain boundaries under lower stresses, since serrated grain boundaries developed also in the specimens with straight grain boundaries according to grain boundary precipitates forming during creep at 1311 K. The increase in W content of the alloys led to the increase in rupture life of the specimens with serrated grain boundaries at 1089 and 1311 K. (orig.) [de

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

Science.gov (United States)

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

2015-02-01

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

Refining waste hardmetals into tungsten oxide nanosheets via facile method

Energy Technology Data Exchange (ETDEWEB)

Li, Zhifei; Zheng, Guangwei; Wang, Jinshu, E-mail: wangjsh@bjut.edu.cn; Li, Hongyi, E-mail: lhy06@bjut.edu.cn; Wu, Junshu; Du, Yucheng [Beijing University of Technology, Key Laboratory of Advanced Functional Materials, School of Materials Science and Engineering (China)

2016-04-15

A new hydrothermal system has been designed to recycle waste WC–Co hardmetal with low cobalt (Co) content (3 %). In the solution system, nitric acid was designed to dissolve Co, H{sub 2}O{sub 2} served as oxidant to accelerate the oxidation of the WC–Co hardmetals, and fluorine (F{sup −}) was designed to dissolve and recrystallize generated tungsten oxides, which were found to possess a layered structure using scanning electron microscopy and transmission electron microscopy. The obtained tungsten oxides were identified as WO{sub 3}·0.33H{sub 2}O by X-ray diffraction and their specific surface area was measured as 89.2 m{sup 2} g{sup −1} via N{sub 2} adsorption–desorption techniques. The present layered structure tungsten oxides exhibited a promising capability for removing lead ion (Pb{sup 2+}) and organic species, such as methyl blue. The adsorption model was found to be in agreement with Langmuir isotherm model. Given the facile synthesis procedure and promising properties of final products, this new approach should have great potential for refining some other waste hardmetals or tungsten products.Graphical AbstractA new hydrothermal system was designed to recycle waste hardmetal with low cobalt content. Through this method, waste hardmetal was refined into WO{sub 3}·0.33H{sub 2}O nanosheets which shows excellent adsorption capacities toward methylene blue and lead ion (Pb{sup 2+}).

Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

DEFF Research Database (Denmark)

Meyer, Simon; Beyer, Hans; Köhler, Klaus

2015-01-01

For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of ...

A quantitative analysis of aerosols inside an armored vehicle perforated by a kinetic energy penetrator containing tungsten, nickel, and cobalt.

Science.gov (United States)

Gold, Kenneth; Cheng, Yung Sung; Holmes, Thomas D

2007-04-01

These tests were conducted to develop a database that could be used to assess risks to soldiers from exposure to aerosolized metallic particulates when the crew compartment of an Abrams tank is perforated by a kinetic energy penetrator. Quantitative data are reported for aerosols produced by kinetic energy penetrators containing tungsten, nickel, and cobalt. The following are addressed: (1) concentrations and rates of particle settling inside the vehicle, (2) particle size distribution, (3) inhalable and respirable particulates, (4) distribution of aerosol particles by mass, and (5) particle shapes. The scenario described in this report simulates a rare occurrence. The lessons learned, however, highlight a requirement for developing protocols for analyses of metals in body fluids and urine as soon as practical, and also for implementing targeted postdeployment medical surveillance programs that monitor both body burden for respired metals and pulmonary function.

Strain aging in tungsten heavy alloys

International Nuclear Information System (INIS)

Dowding, R.J.; Tauer, K.J.

1991-01-01

This paper reports on tungsten heavy alloys which are two-phase mixtures of body center cubic (BCC) tungsten surrounded by a face center cubic (FCC) matrix. The matrix is most often composed of nickel and iron in a ratio of 70:30 but, occasionally, the matrix may also contain cobalt or copper. Nickel, however, is always the primary matrix component. The tungsten heavy alloy is fabricated through powder metallurgy techniques. Elemental powders are blended, pressed to shape, and sintered. Depending upon the tungsten content, the sintering temperatures are usually in the range of 1450 degrees C to 1525 degrees C. These temperatures are high enough that, as a result, the matrix is at the liquid phase and the process is known as liquid phase sintering. At the liquid phase temperature, the matrix becomes saturated with tungsten, but this does not change the FCC character of the matrix. The sintering is usually done in a hydrogen atmosphere furnace in order to reduce the oxides on the tungsten powder surfaces and create clean, active surfaces which will enhance the adherence between the tungsten and the matrix. The hydrogen atmosphere also creates the presence of excess dissolved hydrogen in the alloy. It has been shown that the hydrogen degrades the toughness and ductility of the heavy alloy. A post-sintering vacuum heat treatment is generally required to insure that there is no residual hydrogen present. The as-sintered tensile strength of a 90% tungsten, 7% nickel, 3% iron alloy (90W) is in the range of 800 to 940 MPa and can be increased significantly by cold working, usually rolling or swaging. Swaging to reductions in area of 20% can result in tensile strengths of 1250 MPa or more. As the strength increases, the elongation, which may have been 30% or more, decreases to less than 5%

Dynamic SEM wear studies of tungsten carbide cermets

Science.gov (United States)

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

1975-01-01

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

Effect of tungsten-187 in primary coolant on dose rate build-up in Vandellos 2

International Nuclear Information System (INIS)

Fernandez Lillo, E.; Llovet, R.; Boronat, M.

1994-01-01

The present work proposes a relationship between the Cobalt-60 piping deposited activity and the relatively high levels of Tungsten-187 in the coolant of Vandellos 2. The conclusions of this work can be applicable to other plants, since it proposes a tool to estimate and quantify the contribution of stellite to the generation of Cobalt-60 and the radiation dose build-up. (authors). 7 figs., 6 refs

Morphological characterisation and spectroscopic studies of the corrosion behaviour of tungsten heavy alloys

International Nuclear Information System (INIS)

Ogundipe, A.; Greenberg, B.; Braida, W.; Christodoulatos, C.; Dermatas, D.

2006-01-01

Tungsten-based alloys have been used in a wide variety of industrial and military applications. These alloys are composed mainly of tungsten (88-95%) with various combinations of nickel, cobalt, iron and copper usually making up the remaining fraction. The corrosion behaviours of five munitions grade tungsten alloys of interest have been examined using immersion tests and wet-dry cycle tests to determine the mechanisms involved in the release of the metallic components. Analyses carried out using SEM, EDS and grazing incidence XRD techniques, show the release of tungsten as well as alloying elements due to galvanic corrosion resulting from the difference in electrode potential between the tungsten phase and the binder phase in all cases studied. The extent of corrosion was directly related with the dissolution of tungsten in the binder phase during the sintering stage of manufacture. In W-Ni-Co-Fe alloys binder phase corrosion was observed while the relatively noble tungsten phase was less affected. The reverse was observed for a W-Cu alloy

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

International Nuclear Information System (INIS)

Oliveira, Eduardo Spinelli

2017-01-01

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

Syntheses, Characterization and Kinetics of Nickel-Tungsten Nitride Catalysts for Hydrotreating of Gas Oil

Science.gov (United States)

Botchwey, Christian

This thesis summarizes the methods and major findings of Ni-W(P)/gamma-Al 2O3 nitride catalyst synthesis, characterization, hydrotreating activity, kinetic analysis and correlation of the catalysts' activities to their synthesis parameters and properties. The range of parameters for catalyst synthesis were W (15-40 wt%), Ni (0-8 wt%), P (0-5 wt%) and nitriding temperature (TN) (500-900 °C). Characterization techniques used included: N2 sorption studies, chemisorption, elemental analysis, temperature programmed studies, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, infrared spectroscopy, transmission electron microscopy and x-ray absorption near edge structure. Hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) were performed at: temperature (340-380 °C), pressure (6.2-9.0 MPa), liquid hourly space velocity (1-3 h-1) and hydrogen to oil ratio (600 ml/ml, STP). The predominant species on the catalyst surface were Ni3N, W2N and bimetallic Ni2W3N. The bimetallic Ni-W nitride species was more active than the individual activities of the Ni3N and W2N. P increased weak acid sites while nitriding temperature decreased amount of strong acid sites. Low nitriding temperature enhanced dispersion of metal particles. P interacted with Al 2O3 which increased the dispersion of metal nitrides on the catalyst surface. HDN activity increased with Ni and P loading but decreased with increase in nitriding temperature (optimum conversion; 60 wt%). HDS and HDA activities went through a maximum with increase in the synthesis parameters (optimum conversions; 88. wt% for HDS and 47 wt% for HDA). Increase in W loading led to increase in catalyst activity. The catalysts were stable to deactivation and had the nitride structure conserved during hydrotreating in the presence of hydrogen sulfide. The results showed good correlation between hydrotreating activities (HDS and HDN) and the catalyst nitrogen content, number of exposed

The influence of cobalt, tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys

Science.gov (United States)

Nathal, M. V.; Ebert, L. J.

1985-01-01

The influence of composition on the tensile and creep strength of 001-line oriented nickel-base superalloy single crystals at temperatures near 1000 C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247. For alloys with the baseline refractory metal level of 3 wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta-plus-W totals, strength was independent of Co level. The effects of composition on properties were related to the microstructural features of the alloys. In general, high creep strength was associated with high levels of gamma-prime volume fraction, gamma-gamma-prime lattice mismatch, and solid solution hardening.

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

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

Science.gov (United States)

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

2014-01-01

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

Discontinuous precipitation in cobalt-tungsten alloys

International Nuclear Information System (INIS)

Zieba, P.; Cliff, G.; Lorimer, G.W.

1997-01-01

Discontinuous precipitation in a Co32 wt% W alloy aged in the temperature range from 875 K to 1025 K has been investigated. Philips EM 430 STEM has been used to characterize the microstructure and to measure the composition profiles across individual lamellae of ε Co and Co 3 W phases in partially transformed specimens. Two kinds of cellular precipitates have been found in the alloy. The initial transformation product, identified as primary lamellae with spacing of a few nanometers is replaced during prolonged ageing by secondary lamellae with a much larger interlamellar spacing, typically a few tens of nm. Line scans across cell boundaries of the primary lamellae revealed that, just behind the advancing cell boundary, the solute content is far from the equilibrium state. This solute excess within the cells is quickly removed at the ageing temperature. Calculations show that the diffusion process was too rapid to be identified as ordinary volume diffusion. Investigation of the kinetics showed that discontinuous precipitation is controlled by diffusion processes at the advancing cell boundary. This proposal has been confirmed by STEM analysis of tungsten profiles in the depleted ε Co lamellae

Direct growth of hexagonal boron nitride/graphene heterostructures on cobalt foil substrates by plasma-assisted molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhongguang; Khanaki, Alireza; Tian, Hao; Zheng, Renjing; Suja, Mohammad; Liu, Jianlin, E-mail: jianlin@ece.ucr.edu [Quantum Structures Laboratory, Department of Electrical and Computer Engineering, University of California, Riverside, California 92521 (United States); Zheng, Jian-Guo [Irvine Materials Research Institute, University of California, Irvine, California 92697-2800 (United States)

2016-07-25

Graphene/hexagonal boron nitride (G/h-BN) heterostructures have attracted a great deal of attention because of their exceptional properties and wide variety of potential applications in nanoelectronics. However, direct growth of large-area, high-quality, and stacked structures in a controllable and scalable way remains challenging. In this work, we demonstrate the synthesis of h-BN/graphene (h-BN/G) heterostructures on cobalt (Co) foil by sequential deposition of graphene and h-BN layers using plasma-assisted molecular beam epitaxy. It is found that the coverage of h-BN layers can be readily controlled on the epitaxial graphene by growth time. Large-area, uniform-quality, and multi-layer h-BN films on thin graphite layers were achieved. Based on an h-BN (5–6 nm)/G (26–27 nm) heterostructure, capacitor devices with Co(foil)/G/h-BN/Co(contact) configuration were fabricated to evaluate the dielectric properties of h-BN. The measured breakdown electric field showed a high value of ∼2.5–3.2 MV/cm. Both I-V and C-V characteristics indicate that the epitaxial h-BN film has good insulating characteristics.

Composites having an intermetallic containing matrix

International Nuclear Information System (INIS)

Nagle, D.C.; Brupbacher, J.M.; Christodoulou, L.

1990-01-01

This paper describes a composite material. It comprises: a dispersion of in-situ precipitated second phase particles selected from the group consisting of borides, carbides, nitrides, and sulfides, in an intermetallic containing matrix selected from the group consisting of the aluminides, silicides, and beryllides of nickel, copper, titanium, cobalt, iron, platinum, gold, silver, niobium, tantalum, zinc, molybdenum, hafnium, tin, tungsten, lithium, magnesium, thorium, chromium, vanadium, zirconium, and manganese

An electrochemical process for the recycling of tungsten carbide scrap

International Nuclear Information System (INIS)

Johns, M.W.

1984-01-01

An account is given of the development of a number of designs for electrochemical cells, and the subsequent construction and operation of a vibrating-plate cell capable of oxidizing 15 kilograms of tungsten carbide a day to a crude tungstic acid precipitate, with similtaneous recovery of cobalt metal on the cathode. The effects on the process of the reagent concentration, temperature, current density, and cathode material are discussed

Thermomagnetic method to determine cobalt content in solid WC-Co alloys

International Nuclear Information System (INIS)

Tumanov, V.I.; Loshakov, A.L.; Korchakova, E.A.

1980-01-01

A thermomagnetic method of cobalt amount determination in tungsten solid alloys is suggested. The method consists in the following: a sample of solid alloy is placed in a magnetic field sufficient to achieve technical saturation (not less than 10 kOe), and specific magnetization of saturation of the alloy σ is determined, then the sample is heated and according to the curves of magnetic permeability dependence on the temperature the Curie point of the alloy THETA is determined and cobalt amount is calculated by the formula qsub(Co)=σ100/(kTHETA+b). The analysis duration is approximately 30 min. Comparative data of cobalt amount determination in solid alloys WC-Co using thermonagnetic and potentiometric methods are presented. Results obtained by thermomagnetic and chemical method are in good agreement. Efficiency of the thermomagnetic method is much higher

EFFECT OF NICKEL AND COBALT ADDITIONS ON INFILTRATION BEHAVIOR, MICROSTRUCTURE AND HARDNESS OF W-AG COMPOSITES

Directory of Open Access Journals (Sweden)

N Parvin

2014-12-01

Full Text Available In this research, infiltration behavior of W-Ag composite compacts with Nickel and Cobalt as additives has been investigated. Nickel and Cobalt were added to Tungsten powder by two distinct methods: mixing elementally and reduction of salt solution. The coated Tungsten powders were compacted under controlled pressures to make porous skeleton with 32-37 vol. % porosity. Infiltration process was carried out at 1100 ̊C under a reducing atmosphere for 1h. The effect of additives on infiltration of Ag and density were evaluated by SEM and Archimedes methods. Properties of the specimens were compared following two distinct processes namely: I sintering simultaneously with infiltration process and II sintering prior to infiltration (pre-sintering process. It was found that specimens which were pre-sintered and then infiltrated with molten silver represent higher hardness and finer microstructure than the specimens infiltrated simultaneously with sintering.

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

Energy Technology Data Exchange (ETDEWEB)

Mrotchek, I.

2007-09-07

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

Effects of lower cobalt binder concentrations in sintering of tungsten carbide

International Nuclear Information System (INIS)

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

2006-01-01

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

Hot tungsten plate based ionizer for cesium plasma in a multi-cusp field experiment

International Nuclear Information System (INIS)

Patel, Amitkumar D.; Sharma, Meenakshee; Ramasubramanian, Narayanan; Chattopadhyay, Prabal K.

2015-01-01

In a newly proposed basic experiment, contact-ionized cesium ions will be confined by a multi cups magnetic field configuration. The cesium ion will be produced by impinging collimated neutral atoms on an ionizer consisting of the hot tungsten plate. The temperature of the tungsten plate will also be made high enough (∼2700 K) such that it will contribute electrons also to the plasma. It is expected that at this configuration the cesium plasma would be really quiescent and would be free from even the normal drift waves observed in the classical Q-machines. For the ionizer a design based on F. F. Chen's design was made. This ionizer is very fine machining and exotic material like Tungsten plate, Molybdenum screws, rings, and Boron Nitride ceramics etc. The fine and careful machining of these materials was very hard. In this paper, the experience about to join the tungsten wire to molybdenum plate and alloy of tantalum and molybdenum ring is described. In addition experimental investigations have been made to measure 2D temperature distribution profile of the Tungsten hot plate using infrared camera and the uniformity of temperature distribution over the hot plate surface is discussed. (author)

Method of activating an article of passive ferrous or non-ferrous metal prior to carburising, nitriding and /or nitrocarburising

DEFF Research Database (Denmark)

2011-01-01

Source: US2012111456A A method of activating an article of passive ferrous or non-ferrous metal by heating at least one compound containing nitrogen and carbon, wherein the article is treated with gaseous species derived from the compound. The activated article can be subsequently carburised......, nitrided or nitrocarburised in shorter time at lower temperature and resulting superior mechanical properties compared with non-activated articles and even articles of stainless steel, nickel alloy, cobalt alloy or titanium based material can be carburised, nitrided or nitrocarburised....

Cobalt-60 production in CANDU power reactors

International Nuclear Information System (INIS)

Slack, J.; Norton, J.L.; Malkoske, G.R.

2003-01-01

MDS Nordion has been supplying cobalt-60 sources to industry for industrial and medical purposes since 1946. These cobalt-60 sources are used in many market and product segments. The major application is in the health care industry where irradiators are used to sterilize single use medical products. These irradiators are designed and built by MDS Nordion and are used by manufacturers of surgical kits, gloves, gowns, drapes and other medical products. The irradiator is a large shielded room with a storage pool for the cobalt-60 sources. The medical products are circulated through the shielded room and exposed to the cobalt-60 sources. This treatment sterilizes the medical products which can then be shipped to hospitals for immediate use. Other applications for this irradiation technology include sanitisation of cosmetics, microbial reduction of pharmaceutical raw materials and food irradiation. The cobalt-60 sources are manufactured by MDS Nordion in their Cobalt Operations Facility in Kanata. More than 75,000 cobalt-60 sources for use in irradiators have been manufactured by MDS Nordion. The cobalt-60 sources are double encapsulated in stainless steel capsules, seal welded and helium leak tested. Each source may contain up to 14,000 curies. These sources are shipped to over 170 industrial irradiators around the world. This paper will focus on the MDS Nordion proprietary technology used to produce the cobalt-60 isotope in CANDU reactors. Almost 55 years ago MDS Nordion and Atomic Energy of Canada developed the process for manufacturing cobalt-60 at the Chalk River Labs, in Ontario, Canada. A cobalt-59 target was introduced into a research reactor where the cobalt-59 atom absorbed one neutron to become cobalt-60. Once the cobalt-60 material was removed from the research reactor it was encapsulated in stainless steel and seal welded using a Tungsten Inert Gas weld. The first cobalt-60 sources manufactured using material from the Chalk River Labs were used in cancer

Pulmonary toxicity after exposure to military-relevant heavy metal tungsten alloy particles

International Nuclear Information System (INIS)

Roedel, Erik Q.; Cafasso, Danielle E.; Lee, Karen W.M.; Pierce, Lisa M.

2012-01-01

Significant controversy over the environmental and public health impact of depleted uranium use in the Gulf War and the war in the Balkans has prompted the investigation and use of other materials including heavy metal tungsten alloys (HMTAs) as nontoxic alternatives. Interest in the health effects of HMTAs has peaked since the recent discovery that rats intramuscularly implanted with pellets containing 91.1% tungsten/6% nickel/2.9% cobalt rapidly developed aggressive metastatic tumors at the implantation site. Very little is known, however, regarding the cellular and molecular mechanisms associated with the effects of inhalation exposure to HMTAs despite the recognized risk of this route of exposure to military personnel. In the current study military-relevant metal powder mixtures consisting of 92% tungsten/5% nickel/3% cobalt (WNiCo) and 92% tungsten/5% nickel/3% iron (WNiFe), pure metals, or vehicle (saline) were instilled intratracheally in rats. Pulmonary toxicity was assessed by cytologic analysis, lactate dehydrogenase activity, albumin content, and inflammatory cytokine levels in bronchoalveolar lavage fluid 24 h after instillation. The expression of 84 stress and toxicity-related genes was profiled in lung tissue and bronchoalveolar lavage cells using real-time quantitative PCR arrays, and in vitro assays were performed to measure the oxidative burst response and phagocytosis by lung macrophages. Results from this study determined that exposure to WNiCo and WNiFe induces pulmonary inflammation and altered expression of genes associated with oxidative and metabolic stress and toxicity. Inhalation exposure to both HMTAs likely causes lung injury by inducing macrophage activation, neutrophilia, and the generation of toxic oxygen radicals. -- Highlights: ► Intratracheal instillation of W–Ni–Co and W–Ni–Fe induces lung inflammation in rats. ► W–Ni–Co and W–Ni–Fe alter expression of oxidative stress and toxicity genes. ► W�

Determination of tungsten in high-alloy steels and heat resisting alloys by isotope dilution-spark source mass spectrometry

International Nuclear Information System (INIS)

Saito, Morimasa; Yamada, Kei; Okochi, Haruno; Hirose, Fumio

1983-01-01

Tungsten in high-alloy steels and heat-resisting alloys was determined by isotope dilution method combined with spark source mass spectrometry by using 183 W enriched tungsten. The spike solution was prepared by fusing tungsten trioxide in sodium carbonate. A high-alloy steel sample was dissolved in the mixture of sulfuric acid and phosphoric acid together with the spike solution; a sample of heat resisting alloy was similarly dissolved in the mixture of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid. The solution was evaporated to give dense white fumes. Tungsten was separated from the residue by a conventional cinchonine salt-precipitation method. The salt was ignited, and the residue was mixed with graphite powder and pressed into electrodes. The isotope 183 W and 184 W were measured. The method was applied to the determination of tungsten in JSS and NBS standard high-alloy steels and JAERI standard nickel- and NBS standard cobalt-base heat resisting alloys containing more than 0.05% tungsten. The results were obtained with satisfactory precision and accuracy. However, the results obtained for JSS standard high- speed steels containing molybdenum tended to be significantly lower than the certified values. (author)

Comparative tribological studies of duplex surface treated AISI 1045 steels fabricated by combinations of plasma nitriding and aluminizing

International Nuclear Information System (INIS)

Haftlang, Farahnaz; Habibolahzadeh, Ali; Sohi, Mahmoud Heydarzadeh

2014-01-01

Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Aluminizing of pre-nitrided specimen provides the highest surface hardness. • The lowest wear rate was obtained via aluminizing of pre-nitrided specimen. • Wear mechanism of the modified layer consists of oxidative and spallung wear. - Abstract: Duplex surface treatments via aluminizing and plasma nitriding were carried out on AISI 1045 steel. A number of work pieces were aluminized and subsequently plasma nitrided (Al–PN) and other work pieces were plasma nitrided and then aluminized (PN–Al). Aluminizing was carried out via pack process at 1123 K for 5 h and plasma nitriding was performed at 823 K for 5 h. The fabricated steels were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and microhardness testing. Tribological behaviors of the duplex treated AISI 1045 steels were examined against tungsten carbide pin using a pin-on-disc apparatus at room temperature. The PN–Al specimen showed higher surface hardness, lower wear rate and coefficient of friction than the Al–PN one. It was noticed from the worn surfaces that tribo-oxidation plays an important role in wear behavior of both specimens

Toughness behaviour of tungsten-carbide-cobalt alloys

International Nuclear Information System (INIS)

Sigl, L.S.

1985-05-01

In the present work the mechanisms of crack propagation in technically important WC-Co alloys are investigated and a model describing the influence of microstructural parameters and of the mechanical properties of the constituents is developed. An energy concept is used for modelling fracture toughness. The energies dissipated in the four crack-paths (trans- and intergranular carbide fracture, fracture across the binder-ligaments, fracture in the binder close to the carbide/binder interface) are summed up using the experimentally determined area-fractions of the crack-paths, the specific energy of brittle fracture in the carbide and of ductile fracture is calculated by integrating the energy to deform a volume element over the plastically deformed region. In contrast to all earlier models, this concept describes fracture toughness of WC-Co alloys only with physically meaningful parameters. The excellent agreement with experimental toughness values and with qualitative observations of crack propagation show that the new model includes all effects which influence toughness. As demonstrated with WC-based hardmetals with a cobalt-nickel binder, the results open new possibilities for optimizing the toughness of composites in which a small amount of a tough phase is embedded in a brittle matrix. (Author, shortened by G.Q.)

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

International Nuclear Information System (INIS)

Zhang Dongcan; Shen Bin; Sun Fanghong

2010-01-01

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

Tungsten

International Nuclear Information System (INIS)

Eschnauer, H.

1978-01-01

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

Cobalt

Science.gov (United States)

Slack, John F.; Kimball, Bryn E.; Shedd, Kim B.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Cobalt is a silvery gray metal that has diverse uses based on certain key properties, including ferromagnetism, hardness and wear-resistance when alloyed with other metals, low thermal and electrical conductivity, high melting point, multiple valences, and production of intense blue colors when combined with silica. Cobalt is used mostly in cathodes in rechargeable batteries and in superalloys for turbine engines in jet aircraft. Annual global cobalt consumption was approximately 75,000 metric tons in 2011; China, Japan, and the United States (in order of consumption amount) were the top three cobalt-consuming countries. In 2011, approximately 109,000 metric tons of recoverable cobalt was produced in ores, concentrates, and intermediate products from cobalt, copper, nickel, platinum-group-element (PGE), and zinc operations. The Democratic Republic of the Congo (Congo [Kinshasa]) was the principal source of mined cobalt globally (55 percent). The United States produced a negligible amount of byproduct cobalt as an intermediate product from a PGE mining and refining operation in southeastern Montana; no U.S. production was from mines in which cobalt was the principal commodity. China was the leading refiner of cobalt, and much of its production came from cobalt ores, concentrates, and partially refined materials imported from Congo (Kinshasa).The mineralogy of cobalt deposits is diverse and includes both primary (hypogene) and secondary (supergene) phases. Principal terrestrial (land-based) deposit types, which represent most of world’s cobalt mine production, include primary magmatic Ni-Cu(-Co-PGE) sulfides, primary and secondary stratiform sediment-hosted Cu-Co sulfides and oxides, and secondary Ni-Co laterites. Seven additional terrestrial deposit types are described in this chapter. The total terrestrial cobalt resource (reserves plus other resources) plus past production, where available, is calculated to be 25.5 million metric tons. Additional resources of

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

Science.gov (United States)

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

2014-07-01

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

Electrochemical properties of lanthanum nitride with calcium nitride additions

International Nuclear Information System (INIS)

Lesunova, R.P.; Fishman, L.S.

1986-01-01

This paper reports on the electrochemical properties of lanthanum nitride with calcium nitride added. The lanthanum nitride was obtained by nitriding metallic lanthanum at 870 K in an ammonia stream. The product contained Cl, Pr, Nd, Sm, Fe, Ca, Cu, Mo, Mg, Al, Si, and Be. The calcium nitride was obtained by nitriding metallic calcium in a nitrogen stream. The conductivity on the LaN/C 3 N 2 system components are shown as a function of temperature. A table shows the solid solutions to be virtually electronic conductors and the lanthanum nitride a mixed conductor

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

Science.gov (United States)

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

2012-06-01

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

Standard specification for cobalt-chromium-nickel-molybdenum-tungsten alloy (UNS R31233) plate, sheet and strip. ASTM standard

International Nuclear Information System (INIS)

1998-09-01

This specification is under the jurisdiction of ASTM Committee B-2 on Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee B02.07 on Refined Nickel and Cobalt, and Alloys Containing Nickel or Cobalt or Both as Principal Constituents. Current edition approved Apr. 10, 1998 and published September 1998. Originally published as B 818-91. Last previous edition was B 818-93

Superconducting structure with layers of niobium nitride and aluminum nitride

International Nuclear Information System (INIS)

Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

1989-01-01

A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs

Tungsten and tungsten alloys by powder metallurgy

International Nuclear Information System (INIS)

Belhadjhamida, A.; German, R.M.

1991-01-01

Tungsten has a historical link with powder metallurgy and there is continued progress in expanding the available compositions and processing options. This paper starts with an introduction to the history of tungsten powder metallurgy and use this as a basis for analyzing some of the current trends. The literature base in tungsten processing is expanding and includes new alloys, microstructures, and processing routes. A few examples will be emphasize here to produce a frame work for this program, including description of sintering mechanisms for tungsten, liquid phase sintering advances, hot consolidation fundamentals, and options for complex shaping using powder injection modeling. For this base, subsequent presentations will expand on these fundamental advances

Tungsten nitride coatings obtained by HiPIMS as plasma facing materials for fusion applications

Czech Academy of Sciences Publication Activity Database

Tiron, V.; Velicu, I. L.; Porosnicu, C.; Burducea, I.; Dinca, P.; Malinský, Petr

Roč. 416, SEP (2017), s. 878-884 ISSN 0169-4332 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015056 Institutional support: RVO:61389005 Keywords : Tugensten nitride layers * m-HIPIMS * deuterium retention * deuterium plasma jet * thermal desorption spectrometry Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Nuclear physics Impact factor: 3.387, year: 2016

40 CFR 421.316 - Pretreatment standards for new sources.

Science.gov (United States)

2010-07-01

... GUIDELINES AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Secondary Tungsten and Cobalt... 87.800 (k) Cobalt hydroxide filter cake wash. PSNS for the Secondary Tungsten and Cobalt Subcategory...

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.

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

International Nuclear Information System (INIS)

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

2016-01-01

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. (paper)

Tungsten foil laminate for structural divertor applications - Joining of tungsten foils

Science.gov (United States)

Reiser, Jens; Rieth, Michael; Möslang, Anton; Dafferner, Bernhard; Hoffmann, Jan; Mrotzek, Tobias; Hoffmann, Andreas; Armstrong, D. E. J.; Yi, Xiaoou

2013-05-01

This paper is the fourth in our series on tungsten laminates. The aim of this paper is to discuss laminate synthesis, meaning the joining of tungsten foils. It is obvious that the properties of the tungsten laminate strongly depend on the combination of (i) interlayer and (ii) joining technology, as this combination defines (i) the condition of the tungsten foil after joining (as-received or recrystallised) as well as (ii) the characteristics of the interface between the tungsten foil and the interlayer (wettability or diffusion leading to a solid solution or the formation of intermetallics). From the example of tungsten laminates joined by brazing with (i) an eutectic silver copper brazing filler, (ii) copper, (iii) titanium, and (iv) zirconium, the microstructure will be discussed, with special focus on the interface. Based on our assumptions of the mechanism of the extraordinary ductility of tungsten foil we present three syntheses strategies and make recommendations for the synthesis of high temperature tungsten laminates.

Development and characterisation of a tungsten-fibre reinforced tungsten composite

International Nuclear Information System (INIS)

Riesch, Johann

2012-01-01

In tungsten-fibre reinforced tungsten, tungsten wire is combined with a tungsten matrix. The outstanding ductility of the fibres and extrinsic mechanisms of energy dissipation lead to an intense toughening. With extensive analytical and experimental investigations a manufacturing method based on chemical vapour infiltration is developed and first material is produced. The toughening mechanisms are shown by means of sophisticated mechanical experiments i.a. X-ray microtomography.

Changes In Mechanical Properties Of Heat Resisting Alloy For A Satellite Propulsion System After A Nitriding Process

Science.gov (United States)

Kagawa, Hideshi; Fujii, Go; Kajiwara, Kenichi; Kuroda, Daisuke; Suzuki, Takuya; Yamabe-Mitarai, Yoko; Murakami, Hideyuki; Ono, Yoshinori

2012-07-01

Haynes25 (L-605) is a common heat resistant alloy used in mono-propellant structures and screen materials for catalyst beds. The lifetime requirements for thrusters have expanded dramatically after studies conducted in the 1970s on mono-propellant materials used to extend the service life. The material design had long remained unchanged, and the L-605 was still used as thruster material due to its good heritage. However, some important incidents involving degradation were found during the test-unit break-up inspection following the thruster life tests. The Japanese research team focused on the L-605 degradations found on the catalyst bed screen mesh used for mono-propellant thruster and analysed the surface of the wire material and the cross- section of the wire screen mesh used in the life tests. The investigation showed that the degradation was caused by nitriding L-605 component elements. The team suggested that the brittle fracture was attributable to tungsten (W) carbides, which formed primarily in the grain boundaries, and chromium (Cr) nitride, which formed mainly in the parts in contact with the hot firing gas. The team also suggested the installation of a platinum coating on the material surface as a countermeasure L-605 nitric degradation. Inconel 625 is now selected as a mono-propellant structure material due to its marginal raw material characters and cost. The team believes that Inconel 625 does not form W carbides since it contains no tungsten component, but does contain Cr and Fe, which form nitrides easily. Therefore, the team agreed that for the Inconel 625, there was a need to evaluate changes in the microstructure and mechanical properties following exposure to hot nitrogen gases. This paper will describe these changes of Inconel 625.

Plasma-spray synthesis and characterization of ti-based nitride and oxide nanogranules

Energy Technology Data Exchange (ETDEWEB)

Antipas, Georgios S.E., E-mail: gantipas@metal.ntua.gr [School of Mining Engineering and Metallurgy, National Technical University of Athens, Athens (Greece)

2014-09-15

The synthesis of nanosized Ti-based nanogranules via plasma spraying is reported. The synthesis route involved use of both nitrogen and oxygen gases with varying results. In the case of nitrogen, a mixture of titanium nitrides were produced, yielding both the Ti2N and the sub-stoichiometric TiN0.61 compounds. In the case of oxygen, both the stoichiometric rutile and TiO ceramic phases were indexed. Based on EDS analysis, even fractional oxygen concentrations caused tungsten impurities which originated from the cathode electrode. The method yielded particle mass median sizes of the order of 15nm and the smallest particles detected were 5nm. (author)

Tungsten foil laminate for structural divertor applications – Joining of tungsten foils

Energy Technology Data Exchange (ETDEWEB)

Reiser, Jens, E-mail: jens.reiser@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP) (Germany); Rieth, Michael; Möslang, Anton; Dafferner, Bernhard; Hoffmann, Jan [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP) (Germany); Mrotzek, Tobias; Hoffmann, Andreas [PLANSEE SE, Reutte (Austria); Armstrong, D.E.J.; Yi, Xiaoou [University of Oxford, Department of Materials (United Kingdom)

2013-05-15

This paper is the fourth in our series on tungsten laminates. The aim of this paper is to discuss laminate synthesis, meaning the joining of tungsten foils. It is obvious that the properties of the tungsten laminate strongly depend on the combination of (i) interlayer and (ii) joining technology, as this combination defines (i) the condition of the tungsten foil after joining (as-received or recrystallised) as well as (ii) the characteristics of the interface between the tungsten foil and the interlayer (wettability or diffusion leading to a solid solution or the formation of intermetallics). From the example of tungsten laminates joined by brazing with (i) an eutectic silver copper brazing filler, (ii) copper, (iii) titanium, and (iv) zirconium, the microstructure will be discussed, with special focus on the interface. Based on our assumptions of the mechanism of the extraordinary ductility of tungsten foil we present three syntheses strategies and make recommendations for the synthesis of high temperature tungsten laminates.

Process for improving the low temperature ductility of tungsten-base composites

International Nuclear Information System (INIS)

Zukas, E.G.

1975-05-01

At temperatures below about 100 0 C, liquid-phase-sintered tungsten-base composites fail in a brittle manner because of the formation of cleavage cracks in the tungsten spheroids. Improving the ductility, then, would require some alloying addition or treatment which would improve the ductility of these spheroids, or some method of changing the stress distribution, such as putting the surface in compression, which would reduce stress concentrations and thereby require a higher load to initiate fracture. The ductilizing process used here consists of coating the composite with a ductile metal followed by heat treating at a high enough temperature to insure sufficient diffusion so that the coat and base become integral. The ductile coat is now the 'piece' surface, and the initiation of cleavage cracks requires much greater stresses. Coats of copper, nickel, gold, and cobalt have been used successfully. A possible added advantage is that the surface properties can now be controlled if certain reflective properties or corrosion resistance are needed. Also soldering or low temperature brazing operations are feasible, allowing the construction or assembly of intricate shapes which could not be accomplished previously. (U.S.)

Nitride alloy layer formation of duplex stainless steel using nitriding process

Science.gov (United States)

Maleque, M. A.; Lailatul, P. H.; Fathaen, A. A.; Norinsan, K.; Haider, J.

2018-01-01

Duplex stainless steel (DSS) shows a good corrosion resistance as well as the mechanical properties. However, DSS performance decrease as it works under aggressive environment and at high temperature. At the mentioned environment, the DSS become susceptible to wear failure. Surface modification is the favourable technique to widen the application of duplex stainless steel and improve the wear resistance and its hardness properties. Therefore, the main aim of this work is to nitride alloy layer on the surface of duplex stainless steel by the nitriding process temperature of 400°C and 450°C at different time and ammonia composition using a horizontal tube furnace. The scanning electron microscopy and x-ray diffraction analyzer are used to analyse the morphology, composition and the nitrided alloy layer for treated DSS. The micro hardnesss Vickers tester was used to measure hardness on cross-sectional area of nitrided DSS. After nitriding, it was observed that the hardness performance increased until 1100 Hv0.5kgf compared to substrate material of 250 Hv0.5kgf. The thickness layer of nitride alloy also increased from 5μm until 100μm due to diffusion of nitrogen on the surface of DSS. The x-ray diffraction results showed that the nitride layer consists of iron nitride, expanded austenite and chromium nitride. It can be concluded that nitride alloy layer can be produced via nitriding process using tube furnace with significant improvement of microstructural and hardness properties.

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

Microstructural characteristics of new type γ-γ` Co-9Al-9W cobalt-based superalloys in as-cast state

Directory of Open Access Journals (Sweden)

A. Tomaszewska

2018-01-01

Full Text Available The paper presented deals primary with the structure characteristics of a new type of cobalt-based superalloys Co-9Al-9W type, casted via induction melting process with partially dosing of Common problems described in literature are focused on difficulties in obtaining uniform distribution of tungsten, particularly in interdendritic areas. That was the reason for the modified casting process to be applied. The method of tungsten dosing into liquid melts of Co and Al allows to obtain microstructure characterized by considerably decreased microsegregation. The material obtained was analyzed by standard methods such as light and scanning microscopy with analysis of chemical composition in micro-areas. Additionally, the detailed analysis of the sub-grain level was made by S/TEM on thin foils collected from equiaxed grains zone of the ingot.

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

International Nuclear Information System (INIS)

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

2009-01-01

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

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.

Deuterium trapping in tungsten

Science.gov (United States)

Poon, Michael

Tungsten is one of the primary material candidates being investigated for use in the first-wall of a magnetic confinement fusion reactor. An ion accelerator was used to simulate the type of ion interaction that may occur at a plasma-facing material. Thermal desorption spectroscopy (TDS) was the primary tool used to analyze the effects of the irradiation. Secondary ion mass spectroscopy (SIMS) was used to determine the distribution of trapped D in the tungsten specimen. The tritium migration analysis program (TMAP) was used to simulate thermal desorption profiles from the D depth distributions. Fitting of the simulated thermal desorption profiles with the measured TDS results provided values of the D trap energies. Deuterium trapping in single crystal tungsten was studied as a function of the incident ion fluence, ion flux, irradiation temperature, irradiation history, and surface impurity levels during irradiation. The results show that deuterium was trapped at vacancies and voids. Two deuterium atoms could be trapped at a tungsten vacancy, with trapping energies of 1.4 eV and 1.2 eV for the first and second D atoms, respectively. In a tungsten void, D is trapped as atoms adsorbed on the inner walls of the void with a trap energy of 2.1 eV, or as D2 molecules inside the void with a trap energy of 1.2 eV. Deuterium trapping in polycrystalline tungsten was also studied as a function of the incident fluence, irradiation temperature, and irradiation history. Deuterium trapping in polycrystalline tungsten also occurs primarily at vacancies and voids with the same trap energies as in single crystal tungsten; however, the presence of grain boundaries promotes the formation of large surface blisters with high fluence irradiations at 500 K. In general, D trapping is greater in polycrystalline tungsten than in single crystal tungsten. To simulate mixed materials comprising of carbon (C) and tungsten, tungsten specimens were pre-irradiated with carbon ions prior to D

Deuterium trapping in tungsten

International Nuclear Information System (INIS)

Poon, M.

2004-01-01

Tungsten is one of the primary material candidates being investigated for use in the first-wall of a magnetic confinement fusion reactor. An ion accelerator was used to simulate the type of ion interaction that may occur at a plasma-facing material. Thermal desorption spectroscopy (TDS) was the primary tool used to analyze the effects of the irradiation Secondary ion mass spectroscopy (SIMS) was used to determine the distribution of trapped D in the tungsten specimen. The tritium migration analysis program (TMAP) was used to simulate thermal desorption profiles from the D depth distributions. Fitting of the simulated thermal desorption profiles with the measured TDS results provided values of the D trap energies. . Deuterium trapping in single crystal tungsten was studied as a function of the incident ion fluence, ion flux, irradiation temperature, irradiation history, and surface impurity levels during irradiation The results show that deuterium was trapped at vacancies and voids. Two deuterium atoms could be trapped at a tungsten vacancy, with trapping energies of 1.4 eV and 1.2 eV for the first and second D atoms, respectively. In a tungsten void, D is trapped as atoms adsorbed on the inner walls of the void with a trap energy of 2.1 eV, or as D 2 molecules inside the void with a trap energy of 1.2 eV. . Deuterium trapping in polycrystalline tungsten was also studied as a function of the incident fluence, irradiation temperature, and irradiation history. Deuterium trapping in polycrystalline tungsten also occurs primarily at vacancies and voids with the same trap energies as in single crystal tungsten; however, the presence of grain boundaries promotes the formation of large surface blisters with high fluence irradiations at 500 K. In general, D trapping is greater in polycrystalline tungsten than in single crystal tungsten. To simulate mixed materials comprising of carbon (C) and tungsten, tungsten specimens were pre-irradiated with carbon ions prior to D

Deuterium trapping in tungsten

Energy Technology Data Exchange (ETDEWEB)

Poon, M

2004-07-01

Tungsten is one of the primary material candidates being investigated for use in the first-wall of a magnetic confinement fusion reactor. An ion accelerator was used to simulate the type of ion interaction that may occur at a plasma-facing material. Thermal desorption spectroscopy (TDS) was the primary tool used to analyze the effects of the irradiation Secondary ion mass spectroscopy (SIMS) was used to determine the distribution of trapped D in the tungsten specimen. The tritium migration analysis program (TMAP) was used to simulate thermal desorption profiles from the D depth distributions. Fitting of the simulated thermal desorption profiles with the measured TDS results provided values of the D trap energies. . Deuterium trapping in single crystal tungsten was studied as a function of the incident ion fluence, ion flux, irradiation temperature, irradiation history, and surface impurity levels during irradiation The results show that deuterium was trapped at vacancies and voids. Two deuterium atoms could be trapped at a tungsten vacancy, with trapping energies of 1.4 eV and 1.2 eV for the first and second D atoms, respectively. In a tungsten void, D is trapped as atoms adsorbed on the inner walls of the void with a trap energy of 2.1 eV, or as D{sub 2} molecules inside the void with a trap energy of 1.2 eV. . Deuterium trapping in polycrystalline tungsten was also studied as a function of the incident fluence, irradiation temperature, and irradiation history. Deuterium trapping in polycrystalline tungsten also occurs primarily at vacancies and voids with the same trap energies as in single crystal tungsten; however, the presence of grain boundaries promotes the formation of large surface blisters with high fluence irradiations at 500 K. In general, D trapping is greater in polycrystalline tungsten than in single crystal tungsten. To simulate mixed materials comprising of carbon (C) and tungsten, tungsten specimens were pre-irradiated with carbon ions prior to D

Mechanism of the electrochemical hydrogen reaction on smooth tungsten carbide and tungsten electrodes

International Nuclear Information System (INIS)

Wiesener, K.; Winkler, E.; Schneider, W.

1985-01-01

The course of the electrochemical hydrogen reaction on smooth tungsten-carbide electrodes in hydrogen saturated 2.25 M H 2 SO 4 follows a electrochemical sorption-desorption mechanism in the potential range of -0.4 to +0.1 V. At potentials greater than +0.1 V the hydrogen oxidation is controlled by a preliminary chemical sorption step. Concluding from the similar behaviour of tungsten-carbide and tungsten electrodes after cathodic pretreatment, different tungsten oxides should be involved in the course of the hydrogen reaction on tungsten carbide electrodes. (author)

Plasma nitriding of steels

CERN Document Server

Aghajani, Hossein

2017-01-01

This book focuses on the effect of plasma nitriding on the properties of steels. Parameters of different grades of steels are considered, such as structural and constructional steels, stainless steels and tools steels. The reader will find within the text an introduction to nitriding treatment, the basis of plasma and its roll in nitriding. The authors also address the advantages and disadvantages of plasma nitriding in comparison with other nitriding methods. .

Recovery of Cobalt as Cobalt Oxalate from Cobalt Tailings Using Moderately Thermophilic Bioleaching Technology and Selective Sequential Extraction

Directory of Open Access Journals (Sweden)

Guobao Chen

2016-07-01

Full Text Available Cobalt is a very important metal which is widely applied in various critical areas, however, it is difficult to recover cobalt from minerals since there is a lack of independent cobalt deposits in nature. This work is to provide a complete process to recover cobalt from cobalt tailings using the moderately thermophilic bioleaching technology and selective sequential extraction. It is found that 96.51% Co and 26.32% Cu were extracted after bioleaching for four days at 10% pulp density. The mean compositions of the leach solutions contain 0.98 g·L−1 of Co, 6.52 g·L−1 of Cu, and 24.57 g·L−1 of Fe (III. The copper ion was then recovered by a solvent extraction process and the ferric ions were selectively removed by applying a goethite deironization process. The technological conditions of the above purification procedures were deliberately discussed. Over 98.6% of copper and 99.9% of ferric ions were eliminated from the leaching liquor. Cobalt was finally produced as cobalt oxalate and its overall recovery during the whole process was greater than 95%. The present bioleaching process of cobalt is worth using for reference to deal with low-grade cobalt ores.

Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

International Nuclear Information System (INIS)

Ramesh, Thimmasandra Narayan

2010-01-01

The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co 3 O 4 . The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co 3 O 4 phase.

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.

Comparative evaluation of particle properties, formation of reactive oxygen species and genotoxic potential of tungsten carbide based nanoparticles in vitro

Energy Technology Data Exchange (ETDEWEB)

Kuehnel, Dana, E-mail: dana.kuehnel@ufz.de [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Scheffler, Katja [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Department of Cell Techniques and Applied Stem Cell Biology, University of Leipzig, Deutscher Platz 5, 04103 Leipzig (Germany); Wellner, Peggy [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Meissner, Tobias; Potthoff, Annegret [Fraunhofer-Institute for Ceramic Technologies and Systems (IKTS), Winterbergstr. 28, 01277 Dresden (Germany); Busch, Wibke [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Springer, Armin [Centre for Translational Bone, Cartilage and Soft Tissue Research, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstrasse 74, 01307 Dresden (Germany); Schirmer, Kristin [Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Duebendorf (Switzerland); EPF Lausanne, School of Architecture, Civil and Environmental Engineering, 1015 Lausanne (Switzerland); ETH Zuerich, Institute of Biogeochemistry and Pollutant Dynamics, 8092 Zuerich (Switzerland)

2012-08-15

Highlights: Black-Right-Pointing-Pointer Assessment of toxic potential of tungsten carbide-based nanoparticles. Black-Right-Pointing-Pointer Evaluation of ROS and micronuclei induction of three hard metal nanomaterials. Black-Right-Pointing-Pointer Dependency of observed toxic effects on the materials physical-chemical properties. Black-Right-Pointing-Pointer Differences in several particle properties seem to modulate the biological response. - Abstract: Tungsten carbide (WC) and cobalt (Co) are constituents of hard metals and are used for the production of extremely hard tools. Previous studies have identified greater cytotoxic potential of WC-based nanoparticles if particles contained Co. The aim of this study was to investigate whether the formation of reactive oxygen species (ROS) and micronuclei would help explain the impact on cultured mammalian cells by three different tungsten-based nanoparticles (WC{sub S}, WC{sub L}, WC{sub L}-Co (S: small; L: large)). The selection of particles allowed us to study the influence of particle properties, e.g. surface area, and the presence of Co on the toxicological results. WC{sub S} and WC{sub L}/WC{sub L}-Co differed in their crystalline structure and surface area, whereas WC{sub S}/WC{sub L} and WC{sub L}-Co differed in their cobalt content. WC{sub L} and WC{sub L}-Co showed neither a genotoxic potential nor ROS induction. Contrary to that, WC{sub S} nanoparticles induced the formation of both ROS and micronuclei. CoCl{sub 2} was tested in relevant concentrations and induced no ROS formation, but increased the rate of micronuclei at concentrations exceeding those present in WC{sub L}-Co. In conclusion, ROS and micronuclei formation could not be associated with the presence of Co in the WC-based particles. The contrasting responses elicited by WC{sub S} vs. WC{sub L} appear to be due to large differences in crystalline structure.

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

International Nuclear Information System (INIS)

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

2017-01-01

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

Blood doping by cobalt. Should we measure cobalt in athletes?

Directory of Open Access Journals (Sweden)

Guidi Gian

2006-07-01

Full Text Available Abstract Background Blood doping is commonplace in competitive athletes who seek to enhance their aerobic performances through illicit techniques. Presentation of the hypothesis Cobalt, a naturally-occurring element with properties similar to those of iron and nickel, induces a marked and stable polycythemic response through a more efficient transcription of the erythropoietin gene. Testing the hypothesis Although little information is available so far on cobalt metabolism, reference value ranges or supplementation in athletes, there is emerging evidence that cobalt is used as a supplement and increased serum concentrations are occasionally observed in athletes. Therefore, given the athlete's connatural inclination to experiment with innovative, unfair and potentially unhealthy doping techniques, cobalt administration might soon become the most suited complement or surrogate for erythropoiesis-stimulating substances. Nevertheless, cobalt administration is not free from unsafe consequences, which involve toxic effects on heart, liver, kidney, thyroid and cancer promotion. Implications of the hypothesis Cobalt is easily purchasable, inexpensive and not currently comprehended within the World Anti-Doping Agency prohibited list. Moreover, available techniques for measuring whole blood, serum, plasma or urinary cobalt involve analytic approaches which are currently not practical for antidoping laboratories. Thus more research on cobalt metabolism in athletes is compelling, along with implementation of effective strategies to unmask this potentially deleterious doping practice

X-ray reflectivity of cobalt and titanium in the vicinity of the Lsub(2,3) absorption edges

International Nuclear Information System (INIS)

Bremer, J.; Kaihola, L.; Keski-Kuha, R.

1980-01-01

X-ray reflectivity across cobalt and titanium Lsub(2,3) absorption edges was measured as a function of energy by means of continuous radiation from a tungsten anode in a grating spectrometer. The real and imaginary parts of the refractive index were obtained from the absorption curves and an exact Kramers-Kronig analysis. A measured fine structure in the reflected intensities was interpreted as an effect of white lines in the absorption spectra. The x-ray intensity was calculated as a function of energy by means of the Fresnel formula. (author)

Thermodynamics of the hydrogen-carbon-oxygen-tungsten system, as applied to the manufacture of tungsten and tungsten carbide

International Nuclear Information System (INIS)

Schwenke, G.K.

2001-01-01

The thermodynamics of the quaternary hydrogen-carbon oxygen-tungsten system and its binary and ternary sub-systems are reviewed. Published thermodynamic data are evaluated, and expression for free energies of formation are chosen. These expressions are integrated with and equilibrium-calculating algorithm, producing a powerful tool for understanding and improving the manufacture of tungsten and tungsten carbide. Three examples are presented: reduction/carburization of tungstic oxide with hydrogen, carbon, and methane. (author)

Tungsten foil laminate for structural divertor applications – Analyses and characterisation of tungsten foil

International Nuclear Information System (INIS)

Reiser, Jens; Rieth, Michael; Dafferner, Bernhard; Hoffmann, Andreas; Yi Xiaoou; Armstrong, David E.J.

2012-01-01

It has been attempted for several years to synthesise a tungsten material with a low brittle-to-ductile transition temperature and a high fracture toughness that can be used for structural parts. It was shown in our previous work that tungsten foil is ductile at room temperature and that this ductility can be transformed to bulk by synthesising a tungsten laminate. In this work we want to focus on tungsten foil and assess the microstructure as well as the mechanical properties of the foil. The assessment of the microstructure of 0.1 mm tungsten foil will be performed using electron microscopy. It will be shown that the grains of the tungsten foil have a dimension of 0.5 μm × 3 μm × 15 μm and a clear texture in (1 0 0) 〈0 1 1〉. This texture becomes even more pronounced by annealing. Three-point-bending tests with tungsten foil, as-received, will define the barriers: ductile at room temperature and brittle in liquid nitrogen (−196 °C). This shows that the ductility is a thermally activated process. Recrystallised tungsten foil (annealed for 1 h/2700 °C) shows ductile material behaviour at 200 °C. The paper closes with a discussion on the reasons of the ductility of 0.1 mm tungsten foil. These might be the ultra fine grained (UFG) microstructure or, in other words, a nano microstructure (see tungsten foil as-received), the high amount of mobile edge dislocations, and/or the foil effect, which means that dislocations can move to the surface and are annihilated (see tungsten foil recrystallised).

Adherent diamond coatings on cemented tungsten carbide substrates with new Fe/Ni/Co binder phase

International Nuclear Information System (INIS)

Polini, Riccardo; Delogu, Michele; Marcheselli, Giancarlo

2006-01-01

WC-Co hard metals continue to gain importance for cutting, mining and chipless forming tools. Cobalt metal currently dominates the market as a binder because of its unique properties. However, the use of cobalt as a binder has several drawbacks related to its hexagonal close-packed structure and market price fluctuations. These issues pushed the development of pre-alloyed binder powders which contain less than 40 wt.% cobalt. In this paper we first report the results of extensive investigations of WC-Fe/Ni/Co hard metal sintering, surface pretreating and deposition of adherent diamond films by using an industrial hot filament chemical vapour deposition (HFCVD) reactor. In particular, CVD diamond was deposited onto WC-Fe/Ni/Co grades which exhibited the best mechanical properties. Prior to deposition, the substrates were submitted to surface roughening by Murakami's etching and to surface binder removal by aqua regia. The adhesion was evaluated by Rockwell indentation tests (20, 40, 60 and 100 kg) conducted with a Brale indenter and compared to the adhesion of diamond films grown onto Co-cemented tungsten carbide substrates, which were submitted to similar etching pretreatments and identical deposition conditions. The results showed that diamond films on medium-grained WC-6 wt.% Fe/Ni/Co substrates exhibited good adhesion levels, comparable to those obtained for HFCVD diamond on Co-cemented carbides with similar microstructure

Potentiometric determination of the tungsten content of tantalum-tungsten alloys with chromium II

International Nuclear Information System (INIS)

Gavra, Z.; Ronen, S.; Levin, R.

1977-05-01

A method was developed for the potentiometric determination of the tungsten content of tantalum-tungsten alloys of different compositions. These were dissolved under conditions that enabled the tungsten content to be determined with chromium (II). Phosphoric acid was selected as a suitable complexing agent for the prevention of the precipitation of tungsten and tantalum compounds. The use of chromium (II) required an oxygen-tight system and therefore the work was carried out in suitable vessels for storage and tritation

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-07-01

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

High temperature diffusion of hafnium in tungsten and a tungsten-hafnium carbide alloy

International Nuclear Information System (INIS)

Ozaki, Y.; Zee, R.H.

1994-01-01

Refractory metals and ceramics are used extensively in energy systems due to their high temperature properties. This is particularly important in direct conversion systems where thermal to electric conversion efficiency is a direct function of temperature. Tungsten, which has the highest melting temperature among elemental metals, does not possess sufficient creep resistance at temperature above 1,600 K. Different dispersion strengthened tungsten alloys have been developed to extend the usefulness of tungsten to higher temperatures. One of these alloys, tungsten with 0.4 mole percent of finely dispersed HfC particles (W-HfC), has the optimum properties for high temperature applications. Hafnium carbide is used as the strengthening agent due to its high chemical stability and its compatibility with tungsten. The presence of HfC particles retards the rate of grain growth as well as restricting dislocation motion. Both of which are beneficial for creep resistance. The long term behavior of this alloy depends largely on the evolution of its microstructure which is governed by the diffusion of its constituents. Data on the diffusion of carbon in tungsten and tungsten self-diffusion are available, but no direct measurements have been made on the diffusion of hafnium in tungsten. The only diffusion data available are estimated from a coarsening study and these data are highly unreliable. In this study, the diffusion behavior of hafnium in pure tungsten and in a W-HfC alloy was directly measured by means of Secondary Ion Mass Spectroscopy (SIMS). The selection of the W-HfC alloy is due to its importance in high temperature engineering applications, and its higher recrystallization temperature. The presence of HfC particles in tungsten restricts grain growth resulting in better high temperature creep resistance. The higher recrystallization temperature allows measurements to be made over a wider range of temperatures at a relatively constant grain size

Ion nitriding of aluminium

International Nuclear Information System (INIS)

Fitz, T.

2002-09-01

The present study is devoted to the investigation of the mechanism of aluminium nitriding by a technique that employs implantation of low-energy nitrogen ions and diffusional transport of atoms. The nitriding of aluminium is investigated, because this is a method for surface modification of aluminium and has a potential for application in a broad spectrum of fields such as automobile, marine, aviation, space technologies, etc. However, at present nitriding of aluminium does not find any large scale industrial application, due to problems in the formation of stoichiometric aluminium nitride layers with a sufficient thickness and good quality. For the purposes of this study, ion nitriding is chosen, as an ion beam method with the advantage of good and independent control over the process parameters, which thus can be related uniquely to the physical properties of the resulting layers. Moreover, ion nitriding has a close similarity to plasma nitriding and plasma immersion ion implantation, which are methods with a potential for industrial application. (orig.)

Plasma etching of patterned tungsten

International Nuclear Information System (INIS)

Franssila, S.

1993-01-01

Plasma etching of tungsten is discussed from the viewpoint of thin film structure and integrated circuit process engineering. The emphasis is on patterned tungsten etching for silicon device and X-ray mask fabrication. After introducing tungsten etch chemistries and mechanisms, microstructural aspects of tungsten films (crystal structure, grain size, film density, defects, impurities) in relation to etching are discussed. Approaches to etch process optimization are presented, and the current state-of-the-art of patterned tungsten etching is reviewed. (orig.)

Cobalt release from inexpensive jewellery

DEFF Research Database (Denmark)

Thyssen, Jacob Pontoppidan; Jellesen, Morten Stendahl; Menné, Torkil

2010-01-01

. Conclusions: This study showed that only a minority of inexpensive jewellery purchased in Denmark released cobalt when analysed with the cobalt spot test. As fashion trends fluctuate and we found cobalt release from dark appearing jewellery, cobalt release from consumer items should be monitored in the future......Objectives: The aim was to study 354 consumer items using the cobalt spot test. Cobalt release was assessed to obtain a risk estimate of cobalt allergy and dermatitis in consumers who would wear the jewellery. Methods: The cobalt spot test was used to assess cobalt release from all items...

Three-terminal nanoelectromechanical switch based on tungsten nitride—an amorphous metallic material

KAUST Repository

Mayet, Abdulilah M.; Hussain, Aftab M.; Hussain, Muhammad Mustafa

2015-01-01

© 2016 IOP Publishing Ltd. Nanoelectromechanical (NEM) switches inherently have zero off-state leakage current and nearly ideal sub-threshold swing due to their mechanical nature of operation, in contrast to semiconductor switches. A challenge for NEM switches to be practical for low-power digital logic application is their relatively large operation voltage which can result in higher dynamic power consumption. Herein we report a three-terminal laterally actuated NEM switch fabricated with an amorphous metallic material: tungsten nitride (WNx). As-deposited WNx thin films have high Young's modulus (300 GPa) and reasonably high hardness (3 GPa), which are advantageous for high wear resistance. The first prototype WNx switches are demonstrated to operate with relatively low control voltage, down to 0.8 V for an air gap thickness of 150 nm.

Three-terminal nanoelectromechanical switch based on tungsten nitride—an amorphous metallic material

KAUST Repository

Mayet, Abdulilah M.

2015-12-04

© 2016 IOP Publishing Ltd. Nanoelectromechanical (NEM) switches inherently have zero off-state leakage current and nearly ideal sub-threshold swing due to their mechanical nature of operation, in contrast to semiconductor switches. A challenge for NEM switches to be practical for low-power digital logic application is their relatively large operation voltage which can result in higher dynamic power consumption. Herein we report a three-terminal laterally actuated NEM switch fabricated with an amorphous metallic material: tungsten nitride (WNx). As-deposited WNx thin films have high Young\\'s modulus (300 GPa) and reasonably high hardness (3 GPa), which are advantageous for high wear resistance. The first prototype WNx switches are demonstrated to operate with relatively low control voltage, down to 0.8 V for an air gap thickness of 150 nm.

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

Science.gov (United States)

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

2015-09-01

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

Cobalt release from inexpensive jewellery: has the use of cobalt replaced nickel following regulatory intervention?

Science.gov (United States)

Thyssen, Jacob Pontoppidan; Jellesen, Morten S; Menné, Torkil; Lidén, Carola; Julander, Anneli; Møller, Per; Johansen, Jeanne Duus

2010-08-01

Before the introduction of the EU Nickel Directive, concern was raised that manufacturers of jewellery might turn from the use of nickel to cobalt following the regulatory intervention on nickel exposure. The aim was to study 354 consumer items using the cobalt spot test. Cobalt release was assessed to obtain a risk estimate of cobalt allergy and dermatitis in consumers who would wear the jewellery. The cobalt spot test was used to assess cobalt release from all items. Microstructural characterization was made using scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS). Cobalt release was found in 4 (1.1%) of 354 items. All these had a dark appearance. SEM/EDS was performed on the four dark appearing items which showed tin-cobalt plating on these. This study showed that only a minority of inexpensive jewellery purchased in Denmark released cobalt when analysed with the cobalt spot test. As fashion trends fluctuate and we found cobalt release from dark appearing jewellery, cobalt release from consumer items should be monitored in the future. Industries may not be fully aware of the potential cobalt allergy problem.

Nitride stabilized core/shell nanoparticles

Science.gov (United States)

Kuttiyiel, Kurian Abraham; Sasaki, Kotaro; Adzic, Radoslav R.

2018-01-30

Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

Cobalt

International Nuclear Information System (INIS)

Stolyarova, I.A.; Bunakova, N.Yu.

1983-01-01

The neutron-activation method for determining cobalt in rocks, polymetallic and iron ores and rockforming minerals at 2x10 -6 -5x10 -3 % content is developed. Cobalt determination is based on the formation under the effect of thermal neutrons of nuclear reactor of the 60 Co radioactive isotope by the 59 Co (n, γ) 60 Co reaction with radiation energy of the most intensive line of 1333 keV. Cobalt can be determined by the scheme of the multicomponent analysis from the sample with other elements. Co is determined in the solution after separation of all determinable by the scheme elements. The 60 Co intensity is measured by the mUltichannel gamma-spectrometer with Ge(Li)-detector

Cobalt release from implants and consumer items and characteristics of cobalt sensitized patients with dermatitis

DEFF Research Database (Denmark)

Thyssen, Jacob Pontoppidan; Menne, Torkil; Liden, Carola

2012-01-01

-containing dental alloys and revised hip implant components.Results. Six of eight dental alloys and 10 of 98 revised hip implant components released cobalt in the cobalt spot test, whereas none of 50 mobile phones gave positive reactions. The clinical relevance of positive cobalt test reactions was difficult......-tested dermatitis patients in an attempt to better understand cobalt allergy.Materials and methods. 19 780 dermatitis patients aged 4-99 years were patch tested with nickel, chromium or cobalt between 1985 and 2010. The cobalt spot test was used to test for cobalt ion release from mobile phones as well as cobalt...

Fabrication of vanadium nitride by carbothermal nitridation reaction

International Nuclear Information System (INIS)

Wang Xitang; Wang Zhuofu; Zhang Baoguo; Deng Chengji

2005-01-01

Vanadium nitride is produced from V 2 O 5 by carbon-thermal reduction and nitridation. When the sintered temperature is above 1273 K, VN can be formed, and the nitrogen content of the products increased with the firing temperature raised, and then is the largest when the sintered temperature is 1573 K. The C/V 2 O 5 mass ratio of the green samples is the other key factor affecting on the nitrogen contents of the products. The nitrogen content of the products reaches the most when the C/V 2 O 5 mass ratio is 0.33, which is the theoretical ratio of the carbothermal nitridation of V 2 O 5 . (orig.)

Method for producing polycrystalline boron nitride

International Nuclear Information System (INIS)

Alexeevskii, V.P.; Bochko, A.V.; Dzhamarov, S.S.; Karpinos, D.M.; Karyuk, G.G.; Kolomiets, I.P.; Kurdyumov, A.V.; Pivovarov, M.S.; Frantsevich, I.N.; Yarosh, V.V.

1975-01-01

A mixture containing less than 50 percent of graphite-like boron nitride treated by a shock wave and highly defective wurtzite-like boron nitride obtained by a shock-wave method is compressed and heated at pressure and temperature values corresponding to the region of the phase diagram for boron nitride defined by the graphite-like compact modifications of boron nitride equilibrium line and the cubic wurtzite-like boron nitride equilibrium line. The resulting crystals of boron nitride exhibit a structure of wurtzite-like boron nitride or of both wurtzite-like and cubic boron nitride. The resulting material exhibits higher plasticity as compared with polycrystalline cubic boron nitride. Tools made of this compact polycrystalline material have a longer service life under impact loads in machining hardened steel and chilled iron. (U.S.)

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-02-28

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

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

International Nuclear Information System (INIS)

Johnston, Jamin M.; Catledge, Shane A.

2016-01-01

Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W_2CoB_2. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W_2CoB_2 with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

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

International Nuclear Information System (INIS)

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

2014-10-01

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

Preparation of uranium nitride

International Nuclear Information System (INIS)

Potter, R.A.; Tennery, V.J.

1976-01-01

A process is described for preparing actinide-nitrides from massive actinide metal which is suitable for sintering into low density fuel shapes by partially hydriding the massive metal and simultaneously dehydriding and nitriding the dehydrided portion. The process is repeated until all of the massive metal is converted to a nitride

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 ...

Toughness enhancement of tungsten reinforced with short tungsten fibres

Energy Technology Data Exchange (ETDEWEB)

Jiang, Y. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhang, L.H. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Fang, Q.F., E-mail: qffang@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Zhang, T.; Wang, X.P.; Hao, T.; Liu, C.S. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2017-04-06

The feasibility and toughening efficiency of the short tungsten fibre reinforcement on tungsten were investigated in W{sub f}/W composites fabricated by powder metallurgy method of spark plasma sintering. Fibres in the composites presented a Z-free laminar structure. Partial recrystallization of fibre grains occurred but fibre crack or damage was not detected. Fracture energy of W{sub f}/W composites was estimated in tensile tests, and the results indicated great toughness improvement over pure tungsten in virtue of frictional pullout and plastic deformation of fibres, and matrix-fibres interfacial debonding since 873 K. The specimen with mass fraction of 10% and fibre diameter of 100 µm exhibits the largest elongation of 9±1.1% and the highest ultimate strength of 482±13 MPa at 873 K.

Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

Science.gov (United States)

Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

1983-01-01

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

Process for recovering tungsten from alkaline leaching solution of tungsten ores

International Nuclear Information System (INIS)

Onozaki, S.; Nemoto, S.; Hazeyama, T.

1976-01-01

This invention relates to a process for recovering tungsten from an alkaline leaching solution of tungsten ores. This invention comprises adjusting the pH of an alkaline leaching solution which is obtained by lixiviating ore containing tungsten with an alkaline solution to 7--8 with acid to oxidize molybdic acid ions in the solution, adding a sulfide donor, then precipitating molybdenum sulfide compounds by adjusting the pH value of the solution to 2--3. Tungstic acid ions are recovered as calcium tungstate by the addition of a calcium ion donor after the molybdenum sulfide compounds are separated

Braze welding of cobalt with a silver–copper filler

Directory of Open Access Journals (Sweden)

Everett M. Criss

2015-01-01

Full Text Available A new method of joining cobalt by braze-welding it with a silver–copper filler was developed in order to better understand the residual stresses in beryllium–aluminum/silicon weldments which are problematic to investigate because of the high toxicity of Be. The base and filler metals of this new welding system were selected to replicate the physical properties, crystal structures, and chemical behavior of the Be–AlSi welds. Welding parameters of this surrogate Co–AgCu system were determined by experimentation combining 4-point bending tests and microscopy. Final welds are 5 pass manual TIG (tungsten inert gas, with He top gas and Ar back gas. Control of the welding process produces welds with full penetration melting of the cobalt base. Microscopy indicates that cracking is minimal, and not through thickness, whereas 4-point bending shows failure is not by base-filler delamination. These welds improve upon the original Be–AlSi welds, which do not possess full penetration, and have considerable porosity. We propose that utilization of our welding methods will increase the strength of the Be–AlSi weldments. The specialized welding techniques developed for this study may be applicable not only for the parent Be–AlSi welds, but to braze welds and welds utilizing brittle materials in general. This concept of surrogacy may prove useful in the study of many different types of exotic welds.

Plasmonic Titanium Nitride Nanostructures via Nitridation of Nanopatterned Titanium Dioxide

DEFF Research Database (Denmark)

Guler, Urcan; Zemlyanov, Dmitry; Kim, Jongbum

2017-01-01

Plasmonic titanium nitride nanostructures are obtained via nitridation of titanium dioxide. Nanoparticles acquired a cubic shape with sharper edges following the rock-salt crystalline structure of TiN. Lattice constant of the resulting TiN nanoparticles matched well with the tabulated data. Energy...

Hot pressing of uranium nitride and mixed uranium plutonium nitride

International Nuclear Information System (INIS)

Chang, J.Y.

1975-01-01

The hot pressing characteristics of uranium nitride and mixed uranium plutonium nitride were studied. The utilization of computer programs together with the experimental technique developed in the present study may serve as a useful purpose of prediction and fabrication of advanced reactor fuel and other high temperature ceramic materials for the future. The densification of nitrides follow closely with a plastic flow theory expressed as: d rho/ dt = A/T(t) (1-rho) [1/1-(1-rho)/sup 2/3/ + B1n (1-rho)] The coefficients, A and B, were obtained from experiment and computer curve fitting. (8 figures) (U.S.)

Passivation and corrosion behaviours of cobalt and cobalt-chromium-molybdenum alloy

International Nuclear Information System (INIS)

Metikos-Hukovic, M.; Babic, R.

2007-01-01

Passivation and corrosion behaviour of the cobalt and cobalt-base alloy Co30Cr6Mo was studied in a simulated physiological solution containing chloride and bicarbonate ions and with pH of 6.8. The oxido-reduction processes included solid state transformations occurring at the cobalt/electrolyte interface are interpreted using theories of surface electrochemistry. The dissolution of cobalt is significantly suppressed by alloying it with chromium and molybdenum, since the alloy exhibited 'chromium like' passivity. The structural and protective properties of passive oxide films formed spontaneously at the open circuit potential or during the anodic polarization were studied using electrochemical impedance spectroscopy in the wide frequency range

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…

Interactions between tungsten carbide (WC) particulates and metal matrix in WC-reinforced composites

International Nuclear Information System (INIS)

Lou, D.; Hellman, J.; Luhulima, D.; Liimatainen, J.; Lindroos, V.K.

2003-01-01

A variety of experimental techniques have been used to investigate the interactions between tungsten carbide (WC-Co 88/12) particulates and the matrix in some new wear resistant cobalt-based superalloy and steel matrix composites produced by hot isostatic pressing. The results show that the chemical composition of the matrix has a strong influence on the interface reaction between WC and matrix and the structural stability of the WC particulates in the composite. Some characteristics of the interaction between matrix and reinforcement are explained by the calculation of diffusion kinetics. The three-body abrasion wear resistance of the composites has been examined based on the ASTM G65-91 standard procedure. The wear behavior of the best composites of this study shows great potential for wear protection applications

Metal Nitrides for Plasmonic Applications

DEFF Research Database (Denmark)

Naik, Gururaj V.; Schroeder, Jeremy; Guler, Urcan

2012-01-01

Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications.......Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications....

Tungsten behaviour under anodic polarization

International Nuclear Information System (INIS)

Vas'ko, A.T.; Patsyuk, F.N.

1980-01-01

Electrochemical investigations have been carried out to identify the state of elements of the tungsten galvanic coating. Active zones on anode polarization curves in the hydrogen region of galvanic tungsten are established. The difference in the behaviour of monocrystal and galvanic tungsten electrodes is shown to be connected with the oxidation of hydrogen in the galvanic sediment

Characteristics of Au/PZT/TiO2/Nitride/Si structure capacitors with ICP nitride treatments

International Nuclear Information System (INIS)

Min, Hyung Seob; Kim, Tae Ho; Jeon, Chang Bae; Lee, Jae Gab; Kim, Ji Young

2002-01-01

In this study, the characteristics of PZT/TiO 2 ferroelectric gate stack capacitors with Inductively Coupled Plasma (ICP) nitridation were investigated for field effect transistor (FET)-type Ferroelectric Random Access Memory (FeRAM) applications. If a high accumulation capacitance is to be had, the ICP nitridation time needs to be optimized. While a short ICP treatment time results in thermal oxide growth due to lack of nitrogen, a long nitridation time causes a nitride layer which is too thick. Au/PZT(200 nm)/TiO 2 (40 nm)/Nitride/Si (MeFINS) structure capacitors show a memory window (ΔV) of 1.6 V under ±3-V operation while Au/PZT(200 nm)/TiO 2 (40 nm)/Si (MeFIS) capacitors without nitride treatment exhibit a small memory window of 0.6 V. At the same time, the capacitance of the MeFINS device is almost twice that of the MeFIS capacitor. This result implies that the ICP nitride treatment suppresses the formation of a low dielectric constant interfacial SiO x layer and alleviates the series capacitance problem

Helium bubble bursting in tungsten

International Nuclear Information System (INIS)

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

2013-01-01

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

Properties of minor actinide nitrides

International Nuclear Information System (INIS)

Takano, Masahide; Itoh, Akinori; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo

2004-01-01

The present status of the research on properties of minor actinide nitrides for the development of an advanced nuclear fuel cycle based on nitride fuel and pyrochemical reprocessing is described. Some thermal stabilities of Am-based nitrides such as AmN and (Am, Zr)N were mainly investigated. Stabilization effect of ZrN was cleary confirmed for the vaporization and hydrolytic behaviors. New experimental equipments for measuring thermal properties of minor actinide nitrides were also introduced. (author)

Elicitation threshold of cobalt chloride

DEFF Research Database (Denmark)

Fischer, Louise A; Johansen, Jeanne D; Voelund, Aage

2016-01-01

: On the basis of five included studies, the ED10 values of aqueous cobalt chloride ranged between 0.0663 and 1.95 µg cobalt/cm(2), corresponding to 30.8-259 ppm. CONCLUSIONS: Our analysis provides an overview of the doses of cobalt that are required to elicit allergic cobalt contactdermatitis in sensitized...

Scanning tunneling microscopy measurements of the spin Hall effect in tungsten films by using iron-coated tungsten tips

Science.gov (United States)

Xie, Ting; Dreyer, Michael; Bowen, David; Hinkel, Dan; Butera, R. E.; Krafft, Charles; Mayergoyz, Isaak

2018-05-01

Scanning tunneling microscopy experiments using iron-coated tungsten tips and current-carrying tungsten films have been conducted. An asymmetry of the tunneling current with respect to the change of the direction of the bias current through a tungsten film has been observed. It is argued that this asymmetry is a manifestation of the spin Hall effect in the current-carrying tungsten film. Nanoscale variations of this asymmetry across the tungsten film have been studied by using the scanning tunneling microscopy technique.

Scanning tunneling microscopy measurements of the spin Hall effect in tungsten films by using iron-coated tungsten tips

Directory of Open Access Journals (Sweden)

Ting Xie

2018-05-01

Full Text Available Scanning tunneling microscopy experiments using iron-coated tungsten tips and current-carrying tungsten films have been conducted. An asymmetry of the tunneling current with respect to the change of the direction of the bias current through a tungsten film has been observed. It is argued that this asymmetry is a manifestation of the spin Hall effect in the current-carrying tungsten film. Nanoscale variations of this asymmetry across the tungsten film have been studied by using the scanning tunneling microscopy technique.

Reduction of blue tungsten oxide

International Nuclear Information System (INIS)

Wilken, T.; Wert, C.; Woodhouse, J.; Morcom, W.

1975-01-01

A significant portion of commercial tungsten is produced by hydrogen reduction of oxides. Although several modes of reduction are possible, hydrogen reduction is used where high purity tungsten is required and where the addition of other elements or compounds is desired for modification of the metal, as is done for filaments in the lamp industry. Although several investigations of the reduction of oxides have been reported (1 to 5), few principles have been developed which can aid in assessment of current commercial practice. The reduction process was examined under conditions approximating commercial practice. The specific objectives were to determine the effects of dopants, of water vapor in the reducing atmosphere, and of reduction temperature upon: (1) the rate of the reaction by which blue tungsten oxide is reduced to tungsten metal, (2) the intermediate oxides associated with reduction, and (3) the morphology of the resulting tungsten powder

Micro-powder injection moulding of tungsten

International Nuclear Information System (INIS)

Zeep, B.

2007-12-01

For He-cooled Divertors as integral components of future fusion power plants, about 300000 complex shaped tungsten components are to be fabricated. Tungsten is the favoured material because of its excellent properties (high melting point, high hardness, high sputtering resistance, high thermal conductivity). However, the material's properties cause major problems for large scale production of complex shaped components. Due to the resistance of tungsten to mechanical machining, new fabrication technologies have to be developed. Powder injection moulding as a well established shaping technology for a large scale production of complex or even micro structured parts might be a suitable method to produce tungsten components for fusion applications but is not yet commercially available. The present thesis is dealing with the development of a powder injection moulding process for micro structured tungsten components. To develop a suitable feedstock, the powder particle properties, the binder formulation and the solid load were optimised. To meet the requirements for a replication of micro patterned cavities, a special target was to define the smallest powder particle size applicable for micro-powder injection moulding. To investigate the injection moulding performance of the developed feedstocks, experiments were successfully carried out applying diverse cavities with structural details in micro dimension. For debinding of the green bodies, a combination of solvent debinding and thermal debinding has been adopted for injection moulded tungsten components. To develop a suitable debinding strategy, a variation of the solvent debinding time, the heating rate and the binder formulation was performed. For investigating the thermal consolidation behaviour of tungsten components, sinter experiments were carried out applying tungsten powders suitable for micro-powder injection moulding. First mechanical tests of the sintered samples showed promising material properties such as a

Impact of residual by-products from tungsten film deposition on process integration due to nonuniformity of the tungsten film

CERN Document Server

Sidhwa, A; Gandy, T; Melosky, S; Brown, W; Ang, S; Naseem, H; Ulrich, R

2002-01-01

The effects of residual by products from a tungsten film deposition process and their impact on process integration due to the nonuniformity of the tungsten film were investigated in this work. The tungsten film deposition process involves three steps: nucleation, stabilization, and tungsten bulk fill. Six experiments were conducted in search for a solution to the problem. The resulting data suggest that excess nitrogen left in the chamber following the tungsten nucleation step, along with residual by products, causes a shift in the tungsten film uniformity during the tungsten bulk fill process. Data reveal that, due to the residual by products, an abnormal grain growth occurs causing a variation in the tungsten thickness across the wafer during the bulk fill step. Although several possible solutions were revealed by the experiments, potential integration problems limited the acceptable solutions to one. The solution chosen was the introduction of a 10 s pumpdown immediately following the nucleation step. Thi...

Irradiation effects in tungsten-copper laminate composite

Energy Technology Data Exchange (ETDEWEB)

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

2016-12-01

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

An investigation of tungsten by neutron activation techniques

International Nuclear Information System (INIS)

Svetsreni, R.

1978-01-01

This investigation used neutron from Plutonium-Beryllium source (5 curie) to analyse the amount of tungsten in tungsten oxide which was extracted from tungsten ores, slag and tungsten alloy of tungsten iron and carbon. The technique of neutron activation analysis with NaI(Tl) gamma detector 3'' x 3'' and 1024 multichannel analyzer. The dilution technique was used by mixing Fe 2 O 3 or pure sand into the sample before irradiation. In this study self shielding effect in the analysis of tungsten was solved and the detection limit of the tungsten in the sample was about 0.5%

Hydrogen permeation properties of plasma-sprayed tungsten

International Nuclear Information System (INIS)

Anderl, R.A.; Pawelko, R.J.; Hankins, M.R.; Longhurst, G.R.; Neiser, R.A.

1994-01-01

Tungsten has been proposed as a plasma-facing component material for advanced fusion facilities. This paper reports on laboratory-scale studies that were done to assess the hydrogen permeation properties of plasma-sprayed tungsten for such applications. The work entailed deuterium permeation measurements for plasma-sprayed (PS) tungsten coatings, sputter-deposited (SP) tungsten coatings, and steel substrate material using a mass-analyzed, 3 keV D + 3 ion beam with fluxes of similar 6.5x10 19 D/m 2 s. Extensive characterization analyses for the plasma-sprayed tungsten coatings were made using Auger spectrometry and scanning electron microscopy (SEM). Observed permeation rates through composite PS-tungsten/steel specimens were several orders of magnitude below the permeation levels observed for SP-tungsten/steel composite specimens and pure steel specimens. Characterization analyses indicated that the plasma-sprayed tungsten coating had a nonhomogeneous microstructure that consisted of splats with columnar solidification, partially-melted particles with grain boundaries, and void regions. Reduced permeation levels can be attributed to the complex microstructure and a substantial surface-connected porosity. ((orig.))

Hydrogen permeation properties of plasma-sprayed tungsten

Energy Technology Data Exchange (ETDEWEB)

Anderl, R.A. (Idaho National Engineering Lab., EG and G Idaho Inc., Idaho Falls, ID (United States)); Pawelko, R.J. (Idaho National Engineering Lab., EG and G Idaho Inc., Idaho Falls, ID (United States)); Hankins, M.R. (Idaho National Engineering Lab., EG and G Idaho Inc., Idaho Falls, ID (United States)); Longhurst, G.R. (Idaho National Engineering Lab., EG and G Idaho Inc., Idaho Falls, ID (United States)); Neiser, R.A. (Sandia National Laboratories, Albuquerque, NM 87185 (United States))

1994-09-01

Tungsten has been proposed as a plasma-facing component material for advanced fusion facilities. This paper reports on laboratory-scale studies that were done to assess the hydrogen permeation properties of plasma-sprayed tungsten for such applications. The work entailed deuterium permeation measurements for plasma-sprayed (PS) tungsten coatings, sputter-deposited (SP) tungsten coatings, and steel substrate material using a mass-analyzed, 3 keV D[sup +][sub 3] ion beam with fluxes of similar 6.5x10[sup 19] D/m[sup 2] s. Extensive characterization analyses for the plasma-sprayed tungsten coatings were made using Auger spectrometry and scanning electron microscopy (SEM). Observed permeation rates through composite PS-tungsten/steel specimens were several orders of magnitude below the permeation levels observed for SP-tungsten/steel composite specimens and pure steel specimens. Characterization analyses indicated that the plasma-sprayed tungsten coating had a nonhomogeneous microstructure that consisted of splats with columnar solidification, partially-melted particles with grain boundaries, and void regions. Reduced permeation levels can be attributed to the complex microstructure and a substantial surface-connected porosity. ((orig.))

Kinetics of low pressure chemical vapor deposition of tungsten silicide from dichlorocilane reduction of tungsten hexafluoride

International Nuclear Information System (INIS)

Srinivas, D.; Raupp, G.B.; Hillman, J.

1990-01-01

The authors report on experiments to determine the intrinsic surface reaction rate dependences and film properties' dependence on local reactant partial pressures and wafer temperature in low pressure chemical vapor deposition (LPCVD) of tungsten silicide from dichlorosilane reduction of tungsten hexafluoride. Films were deposited in a commercial-scale Spectrum CVD cold wall single wafer reactor under near differential, gradientless conditions. Over the range of process conditions investigated, deposition rate was found to be first order in dichlorosillane and negative second order in tungsten hexafluoride partial pressure. The apparent activation energy in the surface reaction limited regime was found to be 70-120 kcal/mol. The silicon to tungsten ratio of as deposited silicide films ranged from 1.1 to 2.4, and increased with increasing temperature and dichlorosillane partial pressure, and decreased with increasing tungsten hexafluoride pressure. These results suggest that the apparent silicide deposition rate and composition are controlled by the relative rates of at least two competing reactions which deposit stoichiometric tungsten silicides and/or silicon

The Effect of Constant and Pulsed Current Gas Tungsten Arc Welding on Joint Properties of 2205 Duplex Stainless Steel to 316L Austenitic Stainless Steel

Science.gov (United States)

Neissi, R.; Shamanian, M.; Hajihashemi, M.

2016-05-01

In this study, dissimilar 316L austenitic stainless steel/2205 duplex stainless steel (DSS) joints were fabricated by constant and pulsed current gas tungsten arc welding process using ER2209 DSS as a filler metal. Microstructures and joint properties were characterized using optical and electron scanning microscopy, tensile, Charpy V-notch impact and micro-hardness tests, and cyclic polarization measurements. Microstructural observations confirmed the presence of chromium nitride and delta ferrite in the heat-affected zone of DSS and 316L, respectively. In addition, there was some deviation in the austenite/ferrite ratio of the surface welding pass in comparison to the root welding pass. Besides having lower pitting potential, welded joints produced by constant current gas tungsten arc welding process, consisted of some brittle sigma phase precipitates, which resulted in some impact energy reduction. The tensile tests showed high tensile strength for the weld joints in which all the specimens were broken in 316L base metal.

Hydrogen retention properties of polycrystalline tungsten and helium irradiated tungsten

International Nuclear Information System (INIS)

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

1998-01-01

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

Elysia bangtawaensis Swennen (Nudibranch) from the mangrove habitat of Mandovi estuary, Goa (central west coast), India

Digital Repository Service at National Institute of Oceanography (India)

Jagtap, T.G.; Shenai-Tirodkar, P.S.; Savant, S.B.; Kulkarni, V.A.; Ansari, Z.A.

with the duration of the pulverization period. The study reveals that a good amount of tungsten and cobalt get transferred into the sample during pulverization from the tungsten-carbide cup. The con- tamination of tungsten and cobalt from the pulverizing cup... (Table 2). The popu- lation declined from mid-January 2008. The present form of Elysia was con- fined to the mid-reaches of estuarine Figure 1. Geographical positions of sampling stations. Figure 2. Elysia bangtawaensis from various...

Fractographic peculiarities of cermet tungsten fracture

International Nuclear Information System (INIS)

Stepanenko, V.A.; Babak, A.V.; Uskov, E.I.

1982-01-01

Effect of test temperature on fracture peculiarities of cermets tungsten with initial cellular structure of deformation is shown. Tungsten crack resistance increases at temperatures to Tsub(x) (ductile-brittle transition temperature) and decreases at temperatures above Tsub(x). The degree of ceramics tungsten plasticity realization depends on its crack resistance

40 CFR 421.315 - Pretreatment standards for existing sources.

Science.gov (United States)

2010-07-01

...) EFFLUENT GUIDELINES AND STANDARDS NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY Secondary Tungsten....346 68.543 Tungsten 197.1 87.8 (k) Cobalt hydroxide filter cake wash. PSES for the Secondary Tungsten...

Tungsten wire and tubing joined by nickel brazing

Science.gov (United States)

1965-01-01

Thin tungsten wire and tungsten tubing are brazed together using a contacting coil of nickel wire heated to its melting point in an inert-gas atmosphere. This method is also effective for brazing tungsten to tungsten-rhenium parts.

Surface modification of 17-4PH stainless steel by DC plasma nitriding and titanium nitride film duplex treatment

International Nuclear Information System (INIS)

Qi, F.; Leng, Y.X.; Huang, N.; Bai, B.; Zhang, P.Ch.

2007-01-01

17-4PH stainless steel was modified by direct current (DC) plasma nitriding and titanium nitride film duplex treatment in this study. The microstructure, wear resistance and corrosion resistance were characterized by X-ray diffraction (XRD), pin-on-disk tribological test and polarization experiment. The results revealed that the DC plasma nitriding pretreatment was in favor of improving properties of titanium nitride film. The corrosion resistance and wear resistance of duplex treatment specimen was more superior to that of only coated titanium nitride film

Micro creep mechanisms of tungsten

International Nuclear Information System (INIS)

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

2000-01-01

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

Influence of Chemical Composition on Rupture Properties at 1200 Degrees F. of Forged Chromium-Cobalt-Nickel-Iron Base Alloys in Solution-Treated and Aged Condition

Science.gov (United States)

Reynolds, E E; Freeman, J W; White, A E

1951-01-01

The influence of systematic variations of chemical composition on rupture properties at 1200 degrees F. was determined for 62 modifications of a basic alloy containing 20 percent chromium, 20 percent nickel, 20 percent cobalt, 3 percent molybdenum, 2 percent tungsten, 1 percent columbium, 0.15 percent carbon, 1.7 percent manganese, 0.5 percent silicon, 0.12 percent nitrogen and the balance iron. These modifications included individual variations of each of 10 elements present and simultaneous variations of molybdenum, tungsten, and columbium. Laboratory induction furnace heats were hot-forged to round bar stock, solution-treated at 2200 degrees F., and aged at 1400 degrees F. The melting and fabrication conditions were carefully controlled in order to minimize all variable effects on properties except chemical composition. Information is presented which indicates that melting and hot-working conditions play an important role in high-temperature properties of alloys of the type investigated.

Preparation of refractory cermet structures for lithium compatibility testing

Science.gov (United States)

Heestand, R. L.; Jones, R. A.; Wright, T. R.; Kizer, D. E.

1973-01-01

High-purity nitride and carbide cermets were synthesized for compatability testing in liquid lithium. A process was developed for the preparation of high-purity hafnium nitride powder, which was subsequently blended with tungsten powder or tantalum nitride and tungsten powders and fabricated into 3 in diameter billets by uniaxial hot pressing. Specimens were then cut from the billets for compatability testing. Similar processing techniques were applied to produce hafnium carbide and zirconium carbide cermets for use in the testing program. All billets produced were characterized with respect to chemistry, structure, density, and strength properties.

Recrystallization and embrittlement of sintered tungsten

International Nuclear Information System (INIS)

Bega, N.D.; Babak, A.V.; Uskov, E.I.

1982-01-01

The recrystallization of sintered tungsten with a cellular structure of deformation is studied as related to its embrittlement. It is stated that in case of preliminary recrystallization the sintered tungsten crack resistance does not depend on the testing temperature. The tungsten crack resistance is shown to lower with an increase of the structure tendency to primary recrystallization [ru

Tungsten-induced carcinogenesis in human bronchial epithelial cells

Energy Technology Data Exchange (ETDEWEB)

Laulicht, Freda; Brocato, Jason; Cartularo, Laura; Vaughan, Joshua; Wu, Feng; Kluz, Thomas; Sun, Hong [Department of Environmental Medicine, New York University Langone Medical Center, Tuxedo, NY 10987 (United States); Oksuz, Betul Akgol [Genome Technology Center, New York University Langone Medical Center, New York, NY 10016 (United States); Shen, Steven [Center for Health Informatics and Bioinformatics, New York University Langone Medical Center, New York, NY 10016 (United States); Peana, Massimiliano; Medici, Serenella; Zoroddu, Maria Antonietta [Department of Chemistry and Pharmacy, University of Sassari, Sassari (Italy); Costa, Max, E-mail: Max.Costa@nyumc.org [Department of Environmental Medicine, New York University Langone Medical Center, Tuxedo, NY 10987 (United States)

2015-10-01

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 sequencing. 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 show 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. - Highlights: • Tungsten (W) induces cell transformation and increases migration in vitro. • W increases xenograft growth in nude mice. • W altered the expression of cancer-related genes such as those involved in leukemia. • Some of the dysregulated leukemia genes include, CD74, CTGF, MST4, and HOXB5. • For the first time, data is presented that demonstrates tungsten's carcinogenic potential.

Nitriding of high speed steel

International Nuclear Information System (INIS)

Doyle, E.D.; Pagon, A.M.; Hubbard, P.; Dowey, S.J.; Pilkington, A.; McCulloch, D.G.; Latham, K.; DuPlessis, J.

2010-01-01

Current practice when nitriding HSS cutting tools is to avoid embrittlement of the cutting edge by limiting the depth of the diffusion zone. This is accomplished by reducing the nitriding time and temperature and eliminating any compound layer formation. However, in many applications there is an argument for generating a compound layer with beneficial tribological properties. In this investigation results are presented of a metallographic, XRD and XPS analysis of nitrided surface layers generated using active screen plasma nitriding and reactive vapour deposition using cathodic arc. These results are discussed in the context of built up edge formation observed while machining inside a scanning electron microscope. (author)

The Role of the Component Metals in the Toxicity of Military-Grade Tungsten Alloy

Directory of Open Access Journals (Sweden)

Christy A. Emond

2015-12-01

Full Text Available Tungsten-based composites have been recommended as a suitable replacement for depleted uranium. Unfortunately, one of these mixtures composed of tungsten (W, nickel (Ni and cobalt (Co induced rhabdomyosarcomas when implanted into the leg muscle of laboratory rats and mice to simulate a shrapnel wound. The question arose as to whether the neoplastic effect of the mixture could be solely attributed to one or more of the metal components. To investigate this possibility, pellets with one or two of the component metals replaced with an identical amount of the biologically-inert metal tantalum (Ta were manufactured and implanted into the quadriceps of B6C3F1 mice. The mice were followed for two years to assess potential adverse health effects. Implantation with WTa, CoTa or WNiTa resulted in decreased survival, but not to the level reported for WNiCo. Sarcomas in the implanted muscle were found in 20% of the CoTa-implanted mice and 5% of the WTa- and WCoTa-implanted rats and mice, far below the 80% reported for WNiCo-implanted mice. The data obtained from this study suggested that no single metal is solely responsible for the neoplastic effects of WNiCo and that a synergistic effect of the three metals in tumor development was likely.

Solvothermal synthesis: a new route for preparing nitrides

CERN Document Server

Demazeau, G; Denis, A; Largeteau, A

2002-01-01

Solvothermal synthesis appears to be an interesting route for preparing nitrides such as gallium nitride and aluminium nitride, using ammonia as solvent. A nitriding additive is used to perform the reaction and, in the case of gallium nitride, is encapsulated by melt gallium. The syntheses are performed in the temperature range 400-800 deg. C and in the pressure range 100-200 MPa. The synthesized powders are characterized by x-ray diffraction and scanning electron microscopy. Finely divided gallium nitride GaN and aluminium nitride AlN, both with wurtzite-type structure, can be obtained by this route.

Environmental fate of tungsten from military use

International Nuclear Information System (INIS)

Clausen, Jay L.; Korte, Nic

2009-01-01

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

Cobalt metabolism and toxicology—A brief update

International Nuclear Information System (INIS)

Simonsen, Lars Ole; Harbak, Henrik; Bennekou, Poul

2012-01-01

Cobalt metabolism and toxicology are summarized. The biological functions of cobalt are updated in the light of recent understanding of cobalt interference with the sensing in almost all animal cells of oxygen deficiency (hypoxia). Cobalt (Co 2+ ) stabilizes the transcriptional activator hypoxia-inducible factor (HIF) and thus mimics hypoxia and stimulates erythropoietin (Epo) production, but probably also by the same mechanism induces a coordinated up-regulation of a number of adaptive responses to hypoxia, many with potential carcinogenic effects. This means on the other hand that cobalt (Co 2+ ) also may have beneficial effects under conditions of tissue hypoxia, and possibly can represent an alternative to hypoxic preconditioning. Cobalt is acutely toxic in larger doses, and in mammalian in vitro test systems cobalt ions and cobalt metal are cytotoxic and induce apoptosis and at higher concentrations necrosis with inflammatory response. Cobalt metal and salts are also genotoxic, mainly caused by oxidative DNA damage by reactive oxygen species, perhaps combined with inhibition of DNA repair. Of note, the evidence for carcinogenicity of cobalt metal and cobalt sulfate is considered sufficient in experimental animals, but is as yet considered inadequate in humans. Interestingly, some of the toxic effects of cobalt (Co 2+ ) have recently been proposed to be due to putative inhibition of Ca 2+ entry and Ca 2+ -signaling and competition with Ca 2+ for intracellular Ca 2+ -binding proteins. The tissue partitioning of cobalt (Co 2+ ) and its time-dependence after administration of a single dose have been studied in man, but mainly in laboratory animals. Cobalt is accumulated primarily in liver, kidney, pancreas, and heart, with the relative content in skeleton and skeletal muscle increasing with time after cobalt administration. In man the renal excretion is initially rapid but decreasing over the first days, followed by a second, slow phase lasting several weeks, and

Preparation of aluminum nitride-silicon carbide nanocomposite powder by the nitridation of aluminum silicon carbide

NARCIS (Netherlands)

Itatani, K.; Tsukamoto, R.; Delsing, A.C.A.; Hintzen, H.T.J.M.; Okada, I.

2002-01-01

Aluminum nitride (AlN)-silicon carbide (SiC) nanocomposite powders were prepared by the nitridation of aluminum-silicon carbide (Al4SiC4) with the specific surface area of 15.5 m2·g-1. The powders nitrided at and above 1400°C for 3 h contained the 2H-phases which consisted of AlN-rich and SiC-rich

Development and kinetic analysis of cobalt gradient formation in WC-Co composites

Science.gov (United States)

Guo, Jun

2011-12-01

Functionally graded cemented tungsten carbide (FG WC-Co) is one of the main research directions in the field of WC-Co over decades. Although it has long been recognized that FG WC-Co could outperform conventional homogeneous WC-Co owing to its potentially superior combinations of mechanical properties, until recently there has been a lack of effective and economical methods to make such materials. The lack of the technology has prevented the manufacturing and industrial applications of FG WC-Co from becoming a reality. This dissertation is a comprehensive study of an innovative atmosphere heat treatment process for producing FG WC-Co with a surface cobalt compositional gradient. The process exploited a triple phase field in W-C-Co phase diagram among three phases (solid WC, solid Co, and liquid Co) and the dependence of the migration of liquid Co on temperature and carbon content. WC-Co with a graded surface cobalt composition can be achieved by controlling the diffusion of carbon transported from atmosphere during sintering or during postsintering heat treatment. The feasibility of the process was validated by the successful preparations of FG WC-Co via both carburization and decarburization process following conventional liquid phase sintering. A study of the carburization process was undertaken to further understand and quantitatively modeled this process. The effects of key processing parameters (including heat treating temperature, atmosphere, and time) and key materials variables (involving Co content, WC grain size, and addition of grain growth inhibitors) on the formation of Co gradients were examined. Moreover, a carbon-diffusion controlled kinetic model was developed for simulating the formation of the gradient during the process. The parameters involved in this model were determined by thermodynamic calculations and regression-fit of simulation results with experimental data. In summary, this research first demonstrated the principle of the approach

Cobalt metabolism and toxicology-A brief update

Energy Technology Data Exchange (ETDEWEB)

Simonsen, Lars Ole, E-mail: LOSimonsen@dadlnet.dk; Harbak, Henrik; Bennekou, Poul

2012-08-15

Cobalt metabolism and toxicology are summarized. The biological functions of cobalt are updated in the light of recent understanding of cobalt interference with the sensing in almost all animal cells of oxygen deficiency (hypoxia). Cobalt (Co{sup 2+}) stabilizes the transcriptional activator hypoxia-inducible factor (HIF) and thus mimics hypoxia and stimulates erythropoietin (Epo) production, but probably also by the same mechanism induces a coordinated up-regulation of a number of adaptive responses to hypoxia, many with potential carcinogenic effects. This means on the other hand that cobalt (Co{sup 2+}) also may have beneficial effects under conditions of tissue hypoxia, and possibly can represent an alternative to hypoxic preconditioning. Cobalt is acutely toxic in larger doses, and in mammalian in vitro test systems cobalt ions and cobalt metal are cytotoxic and induce apoptosis and at higher concentrations necrosis with inflammatory response. Cobalt metal and salts are also genotoxic, mainly caused by oxidative DNA damage by reactive oxygen species, perhaps combined with inhibition of DNA repair. Of note, the evidence for carcinogenicity of cobalt metal and cobalt sulfate is considered sufficient in experimental animals, but is as yet considered inadequate in humans. Interestingly, some of the toxic effects of cobalt (Co{sup 2+}) have recently been proposed to be due to putative inhibition of Ca{sup 2+} entry and Ca{sup 2+}-signaling and competition with Ca{sup 2+} for intracellular Ca{sup 2+}-binding proteins. The tissue partitioning of cobalt (Co{sup 2+}) and its time-dependence after administration of a single dose have been studied in man, but mainly in laboratory animals. Cobalt is accumulated primarily in liver, kidney, pancreas, and heart, with the relative content in skeleton and skeletal muscle increasing with time after cobalt administration. In man the renal excretion is initially rapid but decreasing over the first days, followed by a second, slow

Cobalt Fischer-Tropsch catalysts: influence of cobalt dispersion and titanium oxides promotion

Energy Technology Data Exchange (ETDEWEB)

Azib, H

1996-04-10

The aim of this work is to study the effect of Sol-Gel preparation parameters which occur in silica supported cobalt catalysts synthesis. These catalysts are particularly used for the waxes production in natural gas processing. The solids have been characterized by several techniques: transmission electron microscopy (TEM), X-ray absorption near edge spectroscopy (XANES), programmed temperature reduction (TPR), infrared spectroscopy (IR), ultraviolet spectroscopy (UV), Magnetism, thermodesorption of H{sub 2} (TPD). The results indicate that the control of the cobalt dispersion and oxide phases nature is possible by modifying Sol-Gel parameters. The catalytic tests in Fischer-Tropsch synthesis were conducted on a pilot unit under pressure (20 atm) and suggested that turnover rates were independent of Co crystallite size, Co phases in the solids (Co deg., cobalt silicate) and titanium oxide promotion. On the other methane, the C{sub 3}{sup +} hydrocarbon selectivity is increased with increasing crystallite size. Inversely, the methane production is favoured by very small crystallites, cobalt silicate increase and titanium addition. However, the latter, used as a cobalt promoter, has a benefic effect on the active phase stability during the synthesis. (author). 149 refs., 102 figs., 71 tabs.

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.

Microstructural characterization of an AISI-SAE 4140 steel without nitridation and nitrided

International Nuclear Information System (INIS)

Medina F, A.; Naquid G, C.

2000-01-01

It was micro structurally characterized an AISI-SAE 4140 steel before and after of nitridation through the nitridation process by plasma post-unloading microwaves through Optical microscopy (OM), Scanning electron microscopy (SEM) by means of secondary electrons and retrodispersed, X-ray diffraction (XRD), Energy dispersion spectra (EDS) and mapping of elements. (Author)

Cobalt accumulation and circulation by blackgum trees

International Nuclear Information System (INIS)

Thomas, W.A.

1975-01-01

Blackgum (Nyssa sylvatica Marsh.) trees accumulate far greater concentrations of cobalt in mature foliage than do other species on the same site (363 ppM in ash of blackgum, compared with about 3 ppM by mockernut hickory and about 1 ppM by red maple, tulip tree, and white oak). Cobalt concentrations in dormant woody tissues of blackgum also significantly exceed those in the other four species. Inoculation of six blackgums with 60 Co revealed that cobalt remains mobile in the trees for at least 3 years. Foliar concentrations of stable cobalt increase uniformly until senescence. In late August, foliage accounts for only 9 percent of total tree weight but 57 percent of total tree cobalt. Losses of cobalt from trees occur almost entirely by leaf abscission, and the loss rates of weight and cobalt from decomposing litter are similar. Retention of cobalt in the biologically active soil layers perpetuates zones of cobalt concentration created by this species in woodlands

Hydrogen permeation properties of plasma-sprayed tungsten*1

Science.gov (United States)

Anderl, R. A.; Pawelko, R. J.; Hankins, M. R.; Longhurst, G. R.; Neiser, R. A.

1994-09-01

Tungsten has been proposed as a plasma-facing component material for advanced fusion facilities. This paper reports on laboratory-scale studies that were done to assess the hydrogen permeation properties of plasma-sprayed tungsten for such applications. The work entailed deuterium permeation measurements for plasma-sprayed (PS) tungsten coatings, sputter-deposited (SP) tungsten coatings, and steel substrate material using a mass-analyzed, 3 keV D 3+ ion beam with fluxes of ˜6.5 × 10 19 D/m 2 s. Extensive characterization analyses for the plasma-sprayed tungsten coatings were made using Auger spectrometry and scanning electron microscopy (SEM). Observed permeation rates through composite PS-tungsten/steel specimens were several orders of magnitude below the permeation levels observed for SP-tungsten/steel composite specimens and pure steel specimens. Characterization analyses indicated that the plasma-sprayed tungsten coating had a nonhomogeneous microstructure that consisted of splats with columnar solidification, partially-melted particles with grain boundaries, and void regions. Reduced permeation levels can be attributed to the complex microstructure and a substantial surface-connected porosity.

Vapor-transport of tungsten and its geologic application

Energy Technology Data Exchange (ETDEWEB)

Shibue, Y [Hyogo Univ. of Teacher Education, Hyogo (Japan)

1988-11-10

The volatility of tungsten in a hydrous system at elevated temperatures and pressures was examined, and a tentative model for the enrichment of tungsten in hydrothermal solutions for the deposits related to granitic activities was proposed. To produce vapor-saturated solution, 17 or 15ml of 20wt% NaCl solution was introduced into an autoclave. Ca(OH){sub 2} for tungsten and H{sub 2}WO{sub 4} for base metals were used as vapor-captures, and run products were identified by X-ray powder diffractometry. The results suggested that the ratio of tungsten to base metals was higher in a vapor phase than in a liquid phase, and more enrichment of tungsten in the vapor phase occurred at higher temperature and pressure under the coexistence of the vapor and liquid phase. The tentative model emphasizing the vapor-transport of tungsten could explain the presence of tungsten deposits without large mineralization of base metals. Geological schematic model for the generation of the hydrothermal solution enriched in tungsten compared with base metals was illustrated based on above mentioned results. 21 refs., 3 figs.

Electroplated zinc-cobalt alloy

International Nuclear Information System (INIS)

Carpenter, D.E.O.S.; Farr, J.P.G.

2005-01-01

Recent work on the deposition and use of ectrodeposited zinc-cobalt alloys is surveyed. Alloys containing lower of Nuclear quantities of cobalt are potentially more useful. The structures of the deposits is related to their chemical and mechanical properties. The inclusion of oxide and its role in the deposition mechanism may be significant. Chemical and engineering properties relate to the metallurgical structure of the alloys, which derives from the mechanism of deposition. The inclusion of oxides and hydroxides in the electroplate may provide evidence for this mechanism. Electrochemical impedance measurements have been made at significant deposition potentials, in alkaline electrolytes. These reveal a complex electrode behaviour which depends not only on the electrode potential but on the Co content of the electrolyte. For the relevant range of cathodic potential zinc-cobalt alloy electrodeposition occurs through a stratified interface. The formation of an absorbed layer ZnOH/sup +/ is the initial step, this inhibits the deposition of cobalt at low cathodic potentials, so explaining its 'anomalous deposition'. A porous layer of zinc forms on the adsorbed ZnOH/sup +/ at underpotential. As the potential becomes more cathodic, cobalt co- deposits from its electrolytic complex forming a metallic solid solution of Co in Zn. In electrolytes containing a high concentration of cobalt a mixed entity (ZnCo)/sub +/ is assumed to adsorb at the cathode from which a CoZn intermetallic deposits. (author)

Environmental fate of tungsten from military use

Energy Technology Data Exchange (ETDEWEB)

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

2009-04-01

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

Precipitation of metal nitrides from chloride melts

International Nuclear Information System (INIS)

Slater, S.A.; Miller, W.E.; Willit, J.L.

1996-01-01

Precipitation of actinides, lanthanides, and fission products as nitrides from molten chloride melts is being investigated for use as a final cleanup step in treating radioactive salt wastes generated by electrometallurgical processing of spent nuclear fuel. The radioactive components (eg, fission products) need to be removed to reduce the volume of high-level waste that requires disposal. To extract the fission products from the salt, a nitride precipitation process is being developed. The salt waste is first contacted with a molten metal; after equilibrium is reached, a nitride is added to the metal phase. The insoluble nitrides can be recovered and converted to a borosilicate glass after air oxidation. For a bench-scale experimental setup, a crucible was designed to contact the salt and metal phases. Solubility tests were performed with candidate nitrides and metal nitrides for which there are no solubility data. Experiments were performed to assess feasibility of precipitation of metal nitrides from chloride melts

Cobalt allergy in hard metal workers

Energy Technology Data Exchange (ETDEWEB)

Fischer, T; Rystedt, I

1983-03-01

Hard metal contains about 10% cobalt. 853 hard metal workers were examined and patch tested with substances from their environment. Initial patch tests with 1% cobalt chloride showed 62 positive reactions. By means of secondary serial dilution tests, allergic reactions to cobalt were reproduced in 9 men and 30 women. Weak reactions could not normally be reproduced. A history of hand eczema was found in 36 of the 39 individuals with reproducible positive test reactions to cobalt, while 21 of 23 with a positive initial patch test but negative serial dilution test had never had any skin problems. Hand etching and hand grinding, mainly female activities and traumatic to the hands, were found to involve the greatest risk of cobalt sensitization. 24 individuals had an isolated cobalt allergy. They had probably been sensitized by hard metal work, while the individuals, all women, who had simultaneous nickel allergy had probably been sensitized to nickel before their employment and then became sensitized to cobalt by hard metal work. A traumatic occupation, which causes irritant contact dermatitis and/or a previous contact allergy or atopy is probably a prerequisite for the development of cobalt allergy.

Pharmacokinetics of inorganic cobalt and a vitamin B12 supplement in the Thoroughbred horse: Differentiating cobalt abuse from supplementation.

Science.gov (United States)

Hillyer, L L; Ridd, Z; Fenwick, S; Hincks, P; Paine, S W

2018-05-01

While cobalt is an essential micronutrient for vitamin B 12 synthesis in the horse, at supraphysiological concentrations, it has been shown to enhance performance in human subjects and rats, and there is evidence that its administration in high doses to horses poses a welfare threat. Animal sport regulators currently control cobalt abuse via international race day thresholds, but this work was initiated to explore means of potentially adding to application of those thresholds since cobalt may be present in physiological concentrations. To devise a scientific basis for differentiation between presence of cobalt from bona fide supplementation and cobalt doping through the use of ratios. Six Thoroughbred horses were given 10 mL vitamin B 12 /cobalt supplement (Hemo-15 ® ; Vetoquinol, Buckingham, Buckinghamshire, UK., 1.5 mg B 12 , 7 mg cobalt gluconate = 983 μg total Co) as an i.v. bolus then an i.v. infusion (15 min) of 100 mg cobalt chloride (45.39 mg Co) 6 weeks later. Pre-and post-administration plasma and urine samples were analysed for cobalt and vitamin B 12 . Urine and plasma samples were analysed for vitamin B 12 using an immunoassay and cobalt concentrations were measured via ICP-MS. Baseline concentrations of cobalt in urine and plasma for each horse were subtracted from their cobalt concentrations post-administration for the PK analysis. Compartmental analysis was used for the determination of plasma PK parameters for cobalt using commercially available software. On administration of a vitamin B 12 /cobalt supplement, the ratio of cobalt to vitamin B 12 in plasma rapidly increased to approximately 3 and then rapidly declined below a ratio of 1 and then back to near baseline over the next week. On administration of 100 mg cobalt chloride, the ratio initially exceeded 10 in plasma and then declined with the lower 95% confidence interval remaining above a ratio of 1 for 7 days. For two horses with extended sampling, the plasma ratio remained above one for

Tungsten Speciation in Firing Range Soils

Science.gov (United States)

2011-01-01

satisfactorily, such as: which tungsten mineral phase is present in soil and to what extent is adsorption important in regu- lating soil solution concentrations... soil solution rather than discrete mineral phases. Information provided in this report will assist the following organizations in future decision...the soil solution ERDC TR-11-1 43 must affect tungsten speciation in other ways. The precipitation of soil minerals also would limit tungsten

Effective Duration of Gas Nitriding Process on AISI 316L for the Formation of a Desired Thickness of Surface Nitrided Layer

Directory of Open Access Journals (Sweden)

Mahmoud Hassan R. S.

2014-07-01

Full Text Available High temperature gas nitriding performed on AISI 316L at the temperature of 1200°C. The microstructure of treated AISI 316L samples were observed to identify the formation of the microstructure of nitrided surface layer. The grain size of austenite tends to be enlarged when the nitriding time increases, but the austenite single phase structure is maintained even after the long-time solution nitriding. Using microhardness testing, the hardness values drop to the center of the samples. The increase in surface hardness is due to the high nitrogen concentration at or near the surface. At 245HV, the graph of the effective duration of nitriding process was plotted to achieve the maximum depth of nitrogen diffuse under the surface. Using Sigma Plot software best fit lines of the experimental result found and plotted to find out effective duration of nitriding equation as Y=1.9491(1-0.7947x, where Y is the thickness of nitrided layer below the surface and X is duration of nitriding process. Based on this equation, the duration of gas nitriding process can be estimated to produce desired thickness of nitrided layer.

COBALT SALTS PRODUCTION BY USING SOLVENT EXTRACTION

Directory of Open Access Journals (Sweden)

Liudmila V. Dyakova

2010-06-01

Full Text Available The paper deals with the extracting cobalt salts by using mixtures on the basis of tertiary amine from multicomponent solutions from the process of hydrochloride leaching of cobalt concentrate. The optimal composition for the extraction mixture, the relationship between the cobalt distribution coefficients and modifier’s nature and concentration, and the saltingout agent type have been determined. A hydrochloride extraction technology of cobalt concentrate yielding a purified concentrated cobalt solution for the production of pure cobalt salts has been developed and introduced at Severonikel combine.

Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

International Nuclear Information System (INIS)

Qi, B.; Andrew, J. S.; Arnold, D. P.

2017-01-01

This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe_6_6Co_3_4) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe_2O_4) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

Energy Technology Data Exchange (ETDEWEB)

Qi, B. [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States); Andrew, J. S. [University of Florida, Department of Materials Science and Engineering (United States); Arnold, D. P., E-mail: darnold@ufl.edu [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States)

2017-03-15

This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe{sub 66}Co{sub 34}) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

Separation of zirconium--hafnium by nitride precipitation

International Nuclear Information System (INIS)

Anderson, R.N.; Parlee, N.A.

1977-01-01

A method is described for the separation of a light reactive metal (e.g., zirconium) from a heavy reactive metal (e.g., hafnium) by forming insoluble nitrides of the metals in a molten metal solvent (e.g., copper) inert to nitrogen and having a suitable density for the light metal nitride to form a separate phase in the upper portion of the solvent and for the heavy metal nitride to form a separate phase in the lower portion of the solvent. Nitriding is performed by maintaining a nitrogen-containing atmosphere over the bath. The light and heavy metals may be an oxide mixture and carbothermically reduced to metal form in the same bath used for nitriding. The nitrides are then separately removed and decomposed to form the desired separate metals. 16 claims, 1 figure

Nitride fuels irradiation performance data base

International Nuclear Information System (INIS)

Brozak, D.E.; Thomas, J.K.; Peddicord, K.L.

1987-01-01

An irradiation performance data base for nitride fuels has been developed from an extensive literature search and review that emphasized uranium nitride, but also included performance data for mixed nitrides [(U,Pu)N] and carbonitrides [(U,Pu)C,N] to increase the quantity and depth of pin data available. This work represents a very extensive effort to systematically collect and organize irradiation data for nitride-based fuels. The data base has many potential applications. First, it can facilitate parametric studies of nitride-based fuels to be performed using a wide range of pin designs and operating conditions. This should aid in the identification of important parameters and design requirements for multimegawatt and SP-100 fuel systems. Secondly, the data base can be used to evaluate fuel performance models. For detailed studies, it can serve as a guide to selecting a small group of pin specimens for extensive characterization. Finally, the data base will serve as an easily accessible and expandable source of irradiation performance information for nitride fuels

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.

Simple process to fabricate nitride alloy powders

International Nuclear Information System (INIS)

Yang, Jae Ho; Kim, Dong-Joo; Kim, Keon Sik; Rhee, Young Woo; Oh, Jang-Soo; Kim, Jong Hun; Koo, Yang Hyun

2013-01-01

Uranium mono-nitride (UN) is considered as a fuel material [1] for accident-tolerant fuel to compensate for the loss of fissile fuel material caused by adopting a thickened cladding such as SiC composites. Uranium nitride powders can be fabricated by a carbothermic reduction of the oxide powders, or the nitriding of metal uranium. Among them, a direct nitriding process of metal is more attractive because it has advantages in the mass production of high-purity powders and the reusing of expensive 15 N 2 gas. However, since metal uranium is usually fabricated in the form of bulk ingots, it has a drawback in the fabrication of fine powders. The Korea Atomic Energy Research Institute (KAERI) has a centrifugal atomisation technique to fabricate uranium and uranium alloy powders. In this study, a simple reaction method was tested to fabricate nitride fuel powders directly from uranium metal alloy powders. Spherical powder and flake of uranium metal alloys were fabricated using a centrifugal atomisation method. The nitride powders were obtained by thermal treating the metal particles under nitrogen containing gas. The phase and morphology evolutions of powders were investigated during the nitriding process. A phase analysis of nitride powders was also part of the present work. KAERI has developed the centrifugal rotating disk atomisation process to fabricate spherical uranium metal alloy powders which are used as advanced fuel materials for research reactors. The rotating disk atomisation system involves the tasks of melting, atomising, and collecting. A nozzle in the bottom of melting crucible introduces melt at the center of a spinning disk. The centrifugal force carries the melt to the edge of the disk and throws the melt off the edge. Size and shape of droplets can be controlled by changing the nozzle size, the disk diameter and disk speed independently or simultaneously. By adjusting the processing parameters of the centrifugal atomiser, a spherical and flake shape

Microhardness and microplasticity of zirconium nitride

International Nuclear Information System (INIS)

Neshpor, V.S.; Eron'yan, M.A.; Petrov, A.N.; Kravchik, A.E.

1978-01-01

To experimentally check the concentration dependence of microhardness of 4 group nitrides, microhardness of zirconium nitride compact samples was measured. The samples were obtained either by bulk saturation of zirconium iodide plates or by chemical precipitation from gas. As nitrogen content decreased within the limits of homogeneity of zirconium nitride samples where the concentration of admixed oxygen was low, the microhardness grew from 1500+-100 kg/mm 2 for ZrNsub(1.0) to 27000+-100 kg/mm 2 for ZrNsub(0.78). Microplasticity of zirconium nitride (resistance to fracture) decreased, as the concentration of nitrogen vacancies was growing

Surface analysis in steel nitrides by using Moessbauer spectroscopy

International Nuclear Information System (INIS)

Figueiredo, R.S. de.

1991-07-01

The formation of iron nitride layer at low temperatures, 600-700 K, by Moessbauer spectroscopy is studied. These layers were obtained basically through two different processes: ion nitriding and ammonia gas nitriding. A preliminary study about post-discharge nitriding was made using discharge in hollow cathode as well as microwave excitation. The assembly of these chambers is also described. The analysis of the nitrided samples was done by CEMS and CXMS, aided by optical microscopy, and the CEMS and CXMS detectors were constructed by ourselves. We also made a brief study about these detectors, testing as acetone as the mixture 80% He+10% C H 4 as detection gases for the use of CEMS. The surface analysis of the samples showed that in the ammonia gas process nitriding the nitrided layer starts by the superficial formation of an iron nitride rich nitrogen. By thermal evolution this nitride promotes the diffusion of nitrogen and the formation of other more stable nitrides. (author)

Fabrication of tungsten wire needles

International Nuclear Information System (INIS)

Roder, A.

1983-02-01

Fine point needles for field emissoin are conventionally produced by electrolytically or chemically etching tungsten wire. Points formed in this manner have a typical tip radius of about 0.5 microns and a cone angle of some 30 degrees. The construction of needle matrix detector chambers has created a need for tungsten needles whose specifications are: 20 mil tungsten wire, 1.5 inch total length, 3 mm-long taper (resulting in a cone angle of about 5 degrees), and 25 micron-radius point (similar to that found on sewing needles). In the process described here for producing such needles, tungsten wire, immersed in a NaOH solution and in the presence of an electrode, is connected first to an ac voltage and then to a dc supply, to form a taper and a point on the end of the wire immersed in the solution. The process parameters described here are for needles that will meet the above specifications. Possible variations will be discussed under each approprite heading

Nickel acts as an adjuvant during cobalt sensitization

DEFF Research Database (Denmark)

Bonefeld, Charlotte Menne; Nielsen, Morten Milek; Vennegaard, Marie T.

2015-01-01

Metal allergy is the most frequent form of contact allergy with nickel and cobalt being the main culprits. Typically, exposure comes from metal-alloys where nickel and cobalt co-exist. Importantly, very little is known about how co-exposure to nickel and cobalt affects the immune system. We...... investigated these effects by using a recently developed mouse model. Mice were epicutaneously sensitized with i) nickel alone, ii) nickel in the presence of cobalt, iii) cobalt alone, or iv) cobalt in the presence of nickel, and then followed by challenge with either nickel or cobalt alone. We found...... that sensitization with nickel alone induced more local inflammation than cobalt alone as measured by increased ear-swelling. Furthermore, the presence of nickel during sensitization to cobalt led to a stronger challenge response to cobalt as seen by increased ear-swelling and increased B and T cell responses...

The tungsten powder study of the dispenser cathode

International Nuclear Information System (INIS)

Bao Jixiu; Wan Baofei

2006-01-01

The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes has been investigated for the different grain morphologies. It is shown that a fully cleaning step of the tungsten powder is so necessary that the tungsten powder will be reduction of oxide in hydrogen atmosphere above 700 deg. C. The porosity of the tungsten matrix distributes more even and the closed pore is fewer, the average granule size of the tungsten powder distributes more convergent. The porosity of the tungsten matrix and the evaporation of the activator are bigger and the pulse of the cathode is smaller when the granularity is bigger by the analysis of the electronic microscope and diode experiment

The tungsten powder study of the dispenser cathode

Science.gov (United States)

Bao, Ji-xiu; Wan, Bao-fei

2006-06-01

The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes has been investigated for the different grain morphologies. It is shown that a fully cleaning step of the tungsten powder is so necessary that the tungsten powder will be reduction of oxide in hydrogen atmosphere above 700 °C. The porosity of the tungsten matrix distributes more even and the closed pore is fewer, the average granule size of the tungsten powder distributes more convergent. The porosity of the tungsten matrix and the evaporation of the activator are bigger and the pulse of the cathode is smaller when the granularity is bigger by the analysis of the electronic microscope and diode experiment.

Leachability of nitrided ilmenite in hydrochloric acid

OpenAIRE

Swanepoel, J.J.; van Vuuren, D.S.; Heydenrych, M.

2011-01-01

Titanium nitride in upgraded nitrided ilmenite (bulk of iron removed) can selectively be chlorinated to produce titanium tetrachloride. Except for iron, most other components present during this low temperature (ca. 200°C) chlorination reaction will not react with chlorine. It is therefore necessary to remove as much iron as possible from the nitrided ilmenite. Hydrochloric acid leaching is a possible process route to remove metallic iron from nitrided ilmenite without excessive dissolution o...

Chemical and phase composition of powders obtained by electroerosion dispersion from alloys WC-Co

International Nuclear Information System (INIS)

Putintseva, M.N.

2004-01-01

A consideration is given to the dependence of chemical and phase compositions of dispersed powders on the conditions, the medium of electroerosion dispersing and the content of cobalt in an initial alloy. It is shown that dissociation of carbon from tungsten carbide proceeds even on dispersing in liquid hydrocarbon-containing media (kerosene and machine oil). The phase composition is determined to a large extent by a medium of dispersing and a cobalt content in the initial alloy. In all powders complex tungsten-cobalt carbides and even Co 7 W 6 intermetallic compounds are found [ru

Chemical and Phase Composition of Powders Obtained by Electroerosion Dispersion from WC - Co Alloys

Science.gov (United States)

Putintseva, M. N.

2004-03-01

The dependence of the chemical and phase composition of dispersed powders on the mode and medium of electroerosion dispersion and the content of cobalt in the initial alloy is considered. It is shown that the dissociation of carbon from tungsten carbide occurs even in dispersion in liquid hydrocarbon-bearing media (kerosene and industrial oils). The phase composition is primarily determined by the dispersion medium and the content of cobalt in the initial alloy. Compound tungsten-cobalt carbides and even a Co7W6 intermetallic are determined in all the powders.

Tungsten or Wolfram: Friend or Foe?

Science.gov (United States)

Zoroddu, Maria A; Medici, Serenella; Peana, Massimiliano; Nurchi, Valeria M; Lachowicz, Joanna I; Laulicht-Glickc, Freda; Costa, Max

2018-01-01

Tungsten or wolfram was regarded for many years as an enemy within the tin smelting and mining industry, because it conferred impurity or dirtiness in tin mining. However, later it was considered an amazing metal for its strength and flexibility, together with its diamond like hardness and its melting point which is the highest of any metal. It was first believed to be relatively inert and an only slightly toxic metal. Since early 2000, the risk exerted by tungsten alloys, its dusts and particulates to induce cancer and several other adverse effects in animals as well as humans has been highlighted from in vitro and in vivo experiments. Thus, it becomes necessary to take a careful look at all the most recent data reported in the scientific literature, covering the years 2001-2016. In fact, the findings indicate that much more attention should be devoted to thoroughly investigate the toxic effects of tungsten and the involved mechanisms of tungsten metal or tungsten metal ions. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Investigation of LMFBR prototype 7A heaters and the metallurgy of the platinum-8 weight percent tungsten alloy

International Nuclear Information System (INIS)

Ludwig, R.L.

1976-09-01

A Liquid Metal Fast Breeder Reactor 7A prototype heater failure was analyzed. The failure was due to melting of the platinum-8 weight percent tungsten alloy (Pt-8 W) alloy winding caused by a loss of contact with the inside boron nitride insulation. An attempt to simulate a failure revealed that elemental boron forms a low-melting mixture with Pt-8 W, but a means by which boron might be present in an actual heater was not determined. A time/temperature/grain size study of various Pt-8 W alloy samples resulted in behavior which would be expected from a single-phase, solid-solution alloy. The results of the study were useful in estimating the temperatures reached at various locations along the length of two failed 7A prototype heaters

Cobalt-60 production in CANDU reactors

International Nuclear Information System (INIS)

Ross, Michel; Lemire, Christian

2002-01-01

CANDU reactors can produce cobalt-60 very efficiently and with an interesting return on investment. This paper discusses what is needed to convert a CANDU reactor into a cobalt-60 producer: what are the different phases, the safety studies required, the physical modifications needed, and what is the minimum involvement of the utility owning the plant. The past ten years of experience of Hydro-Quebec as a cobalt-60 producer will be reviewed, including the management of the risk of both incident and electricity generation loss, and including the benefits for the utility and its personnel. Originally a simple metal used for centuries as a pigment, cobalt-59 today is transformed into cobalt-60, a radioactive element of unprecedented value. Well known in medicine for cancer treatment, cobalt-60 is also used to sterilize a wide range of disposable medical products used in hospitals and to sanitize pharmaceutical and cosmetic products. Cobalt-60 is proving to be a new and effective solution, in the food sector, for preserving harvests and controlling food-borne diseases, or to advantageously replace certain gases and chemical products which are suspected of being harmful or carcinogenic. There are also other applications, such as: hardening of some plastics, treatment of sewage sludge and elimination of harmful insect populations. With a half-life of 5,3 years, cobalt-60 is a metal not found in nature. It is a radioactive isotope produced by exposing stable nuclei of cobalt-59 to neutrons. One of the best places to find such an important neutron source is a nuclear reactor. High energy gamma rays are then emitted during the process of radioactive decay, where cobalt-60 seeks again its stable state

Nitriding behavior of Ni and Ni-based binary alloys

Energy Technology Data Exchange (ETDEWEB)

Fonovic, Matej

2015-01-15

Gaseous nitriding is a prominent thermochemical surface treatment process which can improve various properties of metallic materials such as mechanical, tribological and/or corrosion properties. This process is predominantly performed by applying NH{sub 3}+H{sub 2} containing gas atmospheres serving as the nitrogen donating medium at temperatures between 673 K and 873 K (400 C and 600 C). NH{sub 3} decomposes at the surface of the metallic specimen and nitrogen diffuses into the surface adjacent region of the specimen whereas hydrogen remains in the gas atmosphere. One of the most important parameters characterizing a gaseous nitriding process is the so-called nitriding potential (r{sub N}) which determines the chemical potential of nitrogen provided by the gas phase. The nitriding potential is defined as r{sub N} = p{sub NH{sub 3}}/p{sub H{sub 2}{sup 3/2}} where p{sub NH{sub 3}} and p{sub H{sub 2}} are the partial pressures of the NH{sub 3} and H{sub 2} in the nitriding atmosphere. In contrast with nitriding of α-Fe where the nitriding potential is usually in the range between 0.01 and 1 atm{sup -1/2}, nitriding of Ni and Ni-based alloys requires employing nitriding potentials higher than 100 atm{sup -1/2} and even up to ∞ (nitriding in pure NH{sub 3} atmosphere). This behavior is compatible with decreased thermodynamic stability of the 3d-metal nitrides with increasing atomic number. Depending on the nitriding conditions (temperature, nitriding potential and treatment time), different phases are formed at the surface of the Ni-based alloys. By applying very high nitriding potential, formation of hexagonal Ni{sub 3}N at the surface of the specimen (known as external nitriding) leads to the development of a compound layer, which may improve tribological properties. Underneath the Ni{sub 3}N compound layer, two possibilities exist: (i) alloying element precipitation within the nitrided zone (known as internal nitriding) and/or (ii) development of metastable and

Thermal Spray Coating of Tungsten for Tokamak Device

International Nuclear Information System (INIS)

Jiang Xianliang; Gitzhofer, F; Boulos, M I

2006-01-01

Thermal spray, such as direct current (d.c.) plasma spray or radio frequency induced plasma spray, was used to deposit tungsten coatings on the copper electrodes of a tokamak device. The tungsten coating on the outer surface of one copper electrode was formed directly through d.c. plasma spraying of fine tungsten powder. The tungsten coating/lining on the inner surface of another copper electrode could be formed indirectly through induced plasma spraying of coarse tungsten powder. Scanning electron microscopy (SEM) was used to examine the cross section and the interface of the tungsten coating. Energy Dispersive Analysis of X-ray (EDAX) was used to analyze the metallic elements attached to a separated interface. The influence of the particle size of the tungsten powder on the density, cracking behavior and adhesion of the coating is discussed. It is found that the coarse tungsten powder with the particle size of 45 ∼ 75 μm can be melted and the coating can be formed only by using induced plasma. The coating deposited from the coarse powder has much higher cohesive strength, adhesive strength and crack resistance than the coating made from the fine powder with a particle size of 5 μm

Chromium Elimination and Cannon Life Extension for Gun Tubes

Science.gov (United States)

2012-08-30

the use of hexavalent chromium (VI) in the production of cannon barrels by developing a cost effective environmentally friendly Explosive Bonding...erosion- resistant chrome cobalt alloy matrix with 15% tungsten. Stellite is used as M60 machine gun barrel liner. Tantalum Cobalt Tungsten...Grounds (YPG) Preliminary proof of principle endurance testing at YPG shows promising results when conducted side by side to a chrome plated

Operation of ASDEX Upgrade with tungsten coated walls

International Nuclear Information System (INIS)

Rohde, V.

2002-01-01

An alternative for low-Z materials in the main chamber of a future fusion device are high-Z materials, but the maximal tolerable concentration in the plasma core is restricted. A step by step approach to employ tungsten at the central column of ASDEX Upgrade was started in 1999. Meanwhile almost the whole central column is covered with tiles, which were coated by PVD with tungsten. Up to now 9000 s of plasma discharge covering all relevant scenarios were performed. Routine operation of ASDEX Upgrade was not affected by the tungsten. Typical concentrations below 10 -5 were found. The tungsten concentration is mostly connected to the transport into the core plasma, not to the tungsten erosion. It can be demonstrated, that additional central heating can eliminate the tungsten accumulation. These experiments demonstrate the compatibility of fusion plasmas with W plasma facing components under reactor relevant conditions. The erosion pattern found by post mortem analysis indicates that the main effect is ion sputtering. The main erosion of tungsten seems to occur during plasma ramp-up and ramp-down. (author)

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.

Alloy Effects on the Gas Nitriding Process

Science.gov (United States)

Yang, M.; Sisson, R. D.

2014-12-01

Alloy elements, such as Al, Cr, V, and Mo, have been used to improve the nitriding performance of steels. In the present work, plain carbon steel AISI 1045 and alloy steel AISI 4140 were selected to compare the nitriding effects of the alloying elements in AISI 4140. Fundamental analysis is carried out by using the "Lehrer-like" diagrams (alloy specific Lehrer diagram and nitriding potential versus nitrogen concentration diagram) and the compound layer growth model to simulate the gas nitriding process. With this method, the fundamental understanding for the alloy effect based on the thermodynamics and kinetics becomes possible. This new method paves the way for the development of new alloy for nitriding.

Ion nitridation - physical and technological aspects

International Nuclear Information System (INIS)

Elbern, A.W.

1980-01-01

Ion nitridation, is a technique which allows the formation of a controlled thickness of nitrides in the surface of the material, using this material as the cathode in a low pressure glow discharge, which presents many advantages over the conventional method. A brief review of the ion nitriding technique, the physical fenomena involved, and we discuss technological aspects of this method, are presented. (Author) [pt

Silicon nitride-fabrication, forming and properties

International Nuclear Information System (INIS)

Yehezkel, O.

1983-01-01

This article, which is a literature survey of the recent years, includes description of several methods for the formation of silicone nitride, and five methods of forming: Reaction-bonded silicon nitride, sintering, hot pressing, hot isostatic pressing and chemical vapour deposition. Herein are also included data about mechanical and physical properties of silicon nitride and the relationship between the forming method and the properties. (author)

Tungsten Targets the Tumor Microenvironment to Enhance Breast Cancer Metastasis

Science.gov (United States)

Bolt, Alicia M.; Sabourin, Valérie; Molina, Manuel Flores; Police, Alice M.; Negro Silva, Luis Fernando; Plourde, Dany; Lemaire, Maryse; Ursini-Siegel, Josie; Mann, Koren K.

2015-01-01

The number of individuals exposed to high levels of tungsten is increasing, yet there is limited knowledge of the potential human health risks. Recently, a cohort of breast cancer patients was left with tungsten in their breasts following testing of a tungsten-based shield during intraoperative radiotherapy. While monitoring tungsten levels in the blood and urine of these patients, we utilized the 66Cl4 cell model, in vitro and in mice to study the effects of tungsten exposure on mammary tumor growth and metastasis. We still detect tungsten in the urine of patients’ years after surgery (mean urinary tungsten concentration at least 20 months post-surgery = 1.76 ng/ml), even in those who have opted for mastectomy, indicating that tungsten does not remain in the breast. In addition, standard chelation therapy was ineffective at mobilizing tungsten. In the mouse model, tungsten slightly delayed primary tumor growth, but significantly enhanced lung metastasis. In vitro, tungsten did not enhance 66Cl4 proliferation or invasion, suggesting that tungsten was not directly acting on 66Cl4 primary tumor cells to enhance invasion. In contrast, tungsten changed the tumor microenvironment, enhancing parameters known to be important for cell invasion and metastasis including activated fibroblasts, matrix metalloproteinases, and myeloid-derived suppressor cells. We show, for the first time, that tungsten enhances metastasis in an animal model of breast cancer by targeting the microenvironment. Importantly, all these tumor microenvironmental changes are associated with a poor prognosis in humans. PMID:25324207

Synthesis of reduced carbon nitride at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O

Energy Technology Data Exchange (ETDEWEB)

Kharlamov, Alexey [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine); Bondarenko, Marina, E-mail: mebondarenko@ukr.net [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine); Kharlamova, Ganna [Taras Shevchenko National University of Kiev, Volodymyrs' ka St. 64, 01601 Kiev (Ukraine); Fomenko, Veniamin [Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev (Ukraine)

2016-09-15

For the first time at the reduction by hydroquinone of water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O reduced carbon nitride (or reduced multi-layer azagraphene) is obtained. It is differed from usually synthesized carbon nitride by a significantly large (on 0.09 nm) interplanar distance is. At the same time, the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. The samples of water-soluble carbon nitride oxide were synthesized under the special reactionary conditions of a pyrolysis of melamine and urea. We believe that reduced carbon nitride consists of weakly connected carbon-nitrogen monosheets (azagraphene sheets) as well as reduced (from graphene oxide) graphene contains weakly connected graphene sheets. - Graphical abstract: XRD pattern and schematic atomic model of one layer of reduced carbon nitride, carbon nitride oxide and synthesized carbon nitride. For the first time at the reduction by hydroquinone of the water-soluble carbon nitride oxide (g-C{sub 3}N{sub 4})O is obtained the reduced carbon nitride (or reduced multi-layer azagraphene). Display Omitted - Highlights: • First the reduced carbon nitride (RCN) at the reduction of the carbon nitride oxide was obtained. • Water-soluble carbon nitride oxide was reduced by hydroquinone. • The chemical bonds in a heteroatomic plane of RCN correspond to the bonds in a synthesized g-C{sub 3}N{sub 4}. • Reduced carbon nitride consists of poorly connected heteroatomic azagraphene layers.

Electrocatalytic performance evaluation of cobalt hydroxide and cobalt oxide thin films for oxygen evolution reaction

Science.gov (United States)

Babar, P. T.; Lokhande, A. C.; Pawar, B. S.; Gang, M. G.; Jo, Eunjin; Go, Changsik; Suryawanshi, M. P.; Pawar, S. M.; Kim, Jin Hyeok

2018-01-01

The development of an inexpensive, stable, and highly active electrocatalyst for oxygen evolution reaction (OER) is essential for the practical application of water splitting. Herein, we have synthesized an electrodeposited cobalt hydroxide on nickel foam and subsequently annealed in an air atmosphere at 400 °C for 2 h. In-depth characterization of all the films using X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) techniques, which reveals major changes for their structural, morphological, compositional and electrochemical properties, respectively. The cobalt hydroxide nanosheet film shows high catalytic activity with 290 mV overpotential at 10 mA cm-2 and 91 mV dec-1 Tafel slope and robust stability (24 h) for OER in 1 M KOH electrolyte compared to cobalt oxide (340 mV). The better OER activity of cobalt hydroxide in comparison to cobalt oxide originated from high active sites, enhanced surface, and charge transport capability.

SU-F-T-530: Characterization of a 60-Leaf Motorized MLC Designed for Cobalt-60 Units

International Nuclear Information System (INIS)

Xu, L; Smith, L; Ciresianu, A

2016-01-01

Purpose: In a continuing effort to improve conformal radiation therapy with Cobalt-60 units, a 60-leaf MLC was designed, manufactured, and released to market. This work describes the physics measurements taken to characterize the clinical performance of this MLC. Methods: A 60 leaf MLC was custom designed with tungsten leaves of 4.5 cm height, single focused, achieving field size of 30×30 cm^2 when mounted on a 100cm SAD Cobalt-60 unit. Leakage and output factor measurements were performed using a single ion chamber in a solid water phantom. Penumbra and surface dose were measured using scanning chambers and diodes in a water phantom. Radiation-light coincidence measurements were performed using radiographic films. Results: With MLC mounted, measured penumbras at all depths are smaller than with jaws only. Surface doses were not significantly affected by the presence of MLC, and remained below values recommended by regulatory bodies. Light-radiation coincidences were found to be better than 3 mm for all field sizes. Leakage through the MLC was found to be strongly dependent on field size, increasing from 1.0 % for a 10×10 cm field to 2.0% for a 30×30 cm field. Such results meet the requirements of IEC 60601-2-11. The MLC was found to have significant influence on the output factor, when field size defined by MLC is significantly smaller than field size defined by jaws. Such effect is also observed on linear accelerators, but it is more pronounced on Cobalt-60 units. A 10×10 “diamond” MLC shape inside a 14×14 cm jaw showed output factor that is 5.7% higher than 10×10 cm field defined by matching MLC and jaws. Conclusion: The MLC offers clinically acceptable performance in penumbra, surface dose, and light-radiation coincidence. Several units of this MLC have recently been installed and used clinically. Validation of Cobalt-60 based IMRT with this MLC is ongoing. The authors are employees of Best Theratrnics Ltd.

SU-F-T-530: Characterization of a 60-Leaf Motorized MLC Designed for Cobalt-60 Units

Energy Technology Data Exchange (ETDEWEB)

Xu, L; Smith, L; Ciresianu, A [Best Theratronics, Ottawa, ON (Canada)

2016-06-15

Purpose: In a continuing effort to improve conformal radiation therapy with Cobalt-60 units, a 60-leaf MLC was designed, manufactured, and released to market. This work describes the physics measurements taken to characterize the clinical performance of this MLC. Methods: A 60 leaf MLC was custom designed with tungsten leaves of 4.5 cm height, single focused, achieving field size of 30×30 cm^2 when mounted on a 100cm SAD Cobalt-60 unit. Leakage and output factor measurements were performed using a single ion chamber in a solid water phantom. Penumbra and surface dose were measured using scanning chambers and diodes in a water phantom. Radiation-light coincidence measurements were performed using radiographic films. Results: With MLC mounted, measured penumbras at all depths are smaller than with jaws only. Surface doses were not significantly affected by the presence of MLC, and remained below values recommended by regulatory bodies. Light-radiation coincidences were found to be better than 3 mm for all field sizes. Leakage through the MLC was found to be strongly dependent on field size, increasing from 1.0 % for a 10×10 cm field to 2.0% for a 30×30 cm field. Such results meet the requirements of IEC 60601-2-11. The MLC was found to have significant influence on the output factor, when field size defined by MLC is significantly smaller than field size defined by jaws. Such effect is also observed on linear accelerators, but it is more pronounced on Cobalt-60 units. A 10×10 “diamond” MLC shape inside a 14×14 cm jaw showed output factor that is 5.7% higher than 10×10 cm field defined by matching MLC and jaws. Conclusion: The MLC offers clinically acceptable performance in penumbra, surface dose, and light-radiation coincidence. Several units of this MLC have recently been installed and used clinically. Validation of Cobalt-60 based IMRT with this MLC is ongoing. The authors are employees of Best Theratrnics Ltd.

Cobalt sensitization and dermatitis

DEFF Research Database (Denmark)

Thyssen, Jacob P

2012-01-01

: This clinical review article presents clinical and scientific data on cobalt sensitization and dermatitis. It is concluded that cobalt despite being a strong sensitizer and a prevalent contact allergen to come up on patch testing should be regarded as a very complex metal to test with. Exposure...

Processing of tungsten scrap into powders by electroerosion disintegration

International Nuclear Information System (INIS)

Fominskii, L.P.; Leuchuk, M.V.; Myuller, A.S.; Tarabrina, V.P.

1985-01-01

Utilization of tungsten and tungsten alloy swarf and other waste and also of rejected and worn parts is a matter of great importance in view of the shortage of this metal. The authors examine the electroerosion (EE) disintegration of tungsten in water as a means of utilizing swarf and other loose waste. Unlike chemical methods, EE disintegration ensures ecological purity since there are no effluent waters or toxic discharges. Swarf and trimmings of rods of diameters up to 20 mm obtained after the lathe-turning of tungsten bars sintered from PVN and PVV tungsten powders were disintegrated in water at room temperature between tungsten electrodes. The phase composition of the powder was studied using FeK /SUB alpha/ radiation, by x-ray diffraction methods in a DRON-2 diffractometer with a graphite monochromator on the secondary beam. When tungsten is heated to boiling during EE disintegration, the impurities present in it can evaporate and burn out. Thus, tungsten powder produced by EE disintegration can be purer than the starting metal

Topotactic synthesis of vanadium nitride solid foams

International Nuclear Information System (INIS)

Oyama, S.T.; Kapoor, R.; Oyama, H.T.; Hofmann, D.J.; Matijevic, E.

1993-01-01

Vanadium nitride has been synthesized with a surface area of 120 m 2 g -1 by temperature programmed nitridation of a foam-like vanadium oxide (35 m 2 g -1 ), precipitated from vanadate solutions. The nitridation reaction was established to be topotactic and pseudomorphous by x-ray powder diffraction and scanning electron microscopy. The crystallographic relationship between the nitride and oxide was {200}//{001}. The effect of precursor geometry on the product size and shape was investigated by employing vanadium oxide solids of different morphologies

Solvent extraction in analytical chemistry of tungsten (Review)

International Nuclear Information System (INIS)

Ivanov, V.M.; Busev, A.I.; Sokolova, T.A.

1975-01-01

The use of extraction for isolating and concentrating tungsten with subsequent determination by various methods is considered. For tungsten extractants of all types are employed: neutral, basic and acidic. Neutral extractants are used for isolating and concentrating tungsten, basic and acidic ones are employed, as a rule, for the isolation and subsequent determination of tungsten. This type of extractants is highly promising, since, selectively extracting tungsten, they allow its simultaneous determination. Neutral extractants are oxygen-containing solvents, TBP; basic extractants are aniline, pyridine, 1-naphthylamine, trialkylbenzylammoniumanitrate. As acidic reagents use is made of 8-oxyquinoline and its derivatives, oximes and hydroxamic acids, β-diketones, carbaminates. In the extraction radioactive isotope 185 W is employed

Microstructure and mechanical properties of silicon nitride structural ceramics of silicon nitride

International Nuclear Information System (INIS)

Strohaecker, T.R.; Nobrega, M.C.S.

1989-01-01

The utilization of direct evaluation technic of tenacity for fracturing by hardness impact in silicon nitride ceramics is described. The microstructure were analysied, by Scanning Electron Microscopy, equiped with a microanalysis acessory by X ray energy dispersion. The difference between the values of K IC measure for two silicon nitride ceramics is discussed, in function of the microstructures and the fracture surfaces of the samples studied. (C.G.C.) [pt

Surface energy anisotropy of tungsten

Energy Technology Data Exchange (ETDEWEB)

Kumar, R; Grenga, H E [Georgia Inst. of Tech., Atlanta (USA). School of Chemical Engineering

1976-10-01

Field-ion microscopy was used to study the faceting behavior and/or surface energy anisotropy of tungsten in vacuum and in hydrogen. In vacuum below 1700 K the activation energy for (110) facet growth agreed with values previously reported for surface diffusion on tungsten. The observed anisotropy values at 0.5 Tsub(m), where Tsub(m) is the absolute melting temperature of tungsten (approximately 3680 K), were different from those previously reported at higher temperatures and more nearly agreed with broken bond calculations based on Mie potential using m=5, n=8, and a 1.5% lattice expansion. Hydrogen appeared to have a negligible effect on surface energy anisotropy, but did preferentially increase surface diffusion rates on (310) regions.

Cobalt 60 availability for radiation processing

International Nuclear Information System (INIS)

Fraser, F.M.

1986-01-01

In the last 20 years, the steady and significant growth in the application of radiation processing to industrial sterilization has been seen. The principal application of this technology is the sterilization of disposable medical products, food irradiation, the irradiation of personal care goods and so on. At present, more than 70 million curies of cobalt-60 supplied by Atomic Energy of Canada Ltd. have been used for gamma processing in these applications. This is estimated to be more than 80 % of the total cobalt-60 in service in the world. Commercial food irradiation has an exciting future, and as to the impact of food irradiation on the availability of cobalt-60 over the next ten years, two principal factors must be examined, namely, the anticipated demand for cobalt-60 in all radiation processing applications, and the supply of cobalt-60 to reliably meet the expected demand. As for the cobalt-60 in service today, 90 % is used for the sterilization of disposable medical products, 5 % for food irradiation, and 5 % for other application. The demand for up to 30 million curies of cobalt-60 is expected over the next 10 years. Today, it is estimated that over 150,000 tons of spices, fruit and fish are irradiated. The potential cobalt-60 production could exceed 110 million curies per year. Gamma processing application will demand nearly 50 million curies in 1990. (Kako, I.)

Anti corrosion layer for stainless steel in molten carbonate fuel cell - comprises phase vapour deposition of titanium nitride, aluminium nitride or chromium nitride layer then oxidising layer in molten carbonate electrolyte

DEFF Research Database (Denmark)

2000-01-01

Forming an anticorrosion protective layer on a stainless steel surface used in a molten carbonate fuel cell (MCFC) - comprises the phase vapour deposition (PVD) of a layer comprising at least one of titanium nitride, aluminium nitride or chromium nitride and then forming a protective layer in situ...

High Heat Load Properties of Ultra Fine Grain Tungsten

International Nuclear Information System (INIS)

Zhou, Z.; Du, J.; Ge, C.; Linke, J.; Pintsuk, G.; Song, S.X.

2007-01-01

Full text of publication follows: Tungsten is increasingly considered as a promising candidate armour materials facing the plasma in tokamaks for medium to high heat flux components (EAST, ASDEX, ITER). Fabrication tungsten with ultra fine grain size is considered as an effective way to ameliorate some disadvantages of tungsten, such as its brittleness at room temperature. But the research data on the performance of ultra fine grain tungsten is still very limit. In this work, high heat load properties of pure ultra-fine grain tungsten have been studied. The ultra fine grain tungsten samples with average grain size of 0.2 μm, 1 μm and 3 μm were fabricated by resistance sintering under ultra high pressure. The annealing experiments for the investigation of the material resistance against grain growth have been done by annealing samples in a vacuum furnace at different temperature holding for 2 hours respectively. It is found that recrystallization and grain growth occur at heating temperature of 1250 deg. c. The finer the initial grain sizes of tungsten, the smaller its grain growth grain. The effects of transient high thermal loads (off normal events like disruptions) on tungsten surface morphology have been performed in electron beam test facility JUDITH. The thermal loads tests have been carried out with 4 ms pulses at different power density of 0.22, 0.33, 0.44, 0.55 and 0.88 GW/m 2 respectively. Horizontal cracks formed for all tungsten samples at 0.44 GW/m 2 . Particle erosions occurred for tungsten with 3 μm size at 0.33 GW/m 2 and for tungsten with 0.2 and 1 μm size at 0.55 GW/m 2 . The weight loss of tungsten with 0.2, 1 and 3 μm size are 2,0.1,0.6 mg respectively at 0.88 GW/m 2 . The effects of a large number of very short transient repetitive thermal loads (ELM-like) on tungsten surface morphology also have been performed by using a fundamental wave of a YAG laser. It is found that tungsten with 0.2 μm size has the best performance. (authors)

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

The influence of Fe content on spreading ability of tungsten heavy alloys matrix on tungsten surface

Directory of Open Access Journals (Sweden)

A. Krzyńska

2011-07-01

Full Text Available The results of experimental study of tungsten spreading ability with W-Ni-Co-Fe matrix are presented. The aim of these investigations was to see how Fe concentration in W – Ni – Co matrix influences the wettability of tungsten grains during liquid phase sintering. Four green compact specimens containing 50%W, 10%Co and Ni + Fe = 40% but with different Ni to Fe ratio were prepared. The cylindrical specimen 5mm diameter and 5mm height were put on clean pure tungsten substrate and then 20 minutes heated at 1520oC in hydrogen atmosphere. After heating the specimens were carefully measured and then the specimens for structure observations were prepared. It was concluded, that increase of Fe content decrease the melting temperature of W – Ni – Co alloy. The melting point decrease caused by Fe content increase substantially the spreading ability of tungsten substrate with W – Ni – Co alloy. Metallography investigations showed some microstructure changes in “reaction zone” identified in tungsten substrate – (WNi40-xCo10Fex interface. The results of the study confirmed our earlier observations that even relative small Fe addition promotes Weight Heavy Alloys (WHA liquid phase sintering.

Tungsten--carbide critical assembly

International Nuclear Information System (INIS)

Hansen, G.E.; Paxton, H.C.

1975-06-01

The tungsten--carbide critical assembly mainly consists of three close-fitting spherical shells: a highly enriched uranium shell on the inside, a tungsten--carbide shell surrounding it, and a steel shell on the outside. Ideal critical specifications indicate a rather low computed value of k/sub eff/. Observed and calculated fission-rate distributions for 235 U, 238 U, and 237 Np are compared, and calculated leakage neutrons per fission in various energy groups are given. (U.S.)

The prospect of uranium nitride (UN) and mixed nitride fuel (UN-PuN) for pressurized water reactor

International Nuclear Information System (INIS)

Syarifah, Ratna Dewi; Suud, Zaki

2015-01-01

Design study of small Pressurized Water Reactors (PWRs) core loaded with uranium nitride fuel (UN) and mixed nitride fuel (UN-PuN), Pa-231 as burnable poison, and Americium has been performed. Pa-231 known as actinide material, have large capture cross section and can be converted into fissile material that can be utilized to reduce excess reactivity. Americium is one of minor actinides with long half life. The objective of adding americium is to decrease nuclear spent fuel in the world. The neutronic analysis results show that mixed nitride fuel have k-inf greater than uranium nitride fuel. It is caused by the addition of Pu-239 in mixed nitride fuel. In fuel fraction analysis, for uranium nitride fuel, the optimum volume fractions are 45% fuel fraction, 10% cladding and 45% moderator. In case of UN-PuN fuel, the optimum volume fractions are 30% fuel fraction, 10% cladding and 60% coolant/ moderator. The addition of Pa-231 as burnable poison for UN fuel, enrichment U-235 5%, with Pa-231 1.6% has k-inf more than one and excess reactivity of 14.45%. And for mixed nitride fuel, the lowest value of reactivity swing is when enrichment (U-235+Pu) 8% with Pa-231 0.4%, the excess reactivity value 13,76%. The fuel pin analyze for the addition of Americium, the excess reactivity value is lower than before, because Americium absorb the neutron. For UN fuel, enrichment U-235 8%, Pa-231 1.6% and Am 0.5%, the excess reactivity is 4.86%. And for mixed nitride fuel, when enrichment (U-235+Pu) 13%, Pa-231 0.4% and Am 0.1%, the excess reactivity is 11.94%. For core configuration, it is better to use heterogeneous than homogeneous core configuration, because the radial power distribution is better

The prospect of uranium nitride (UN) and mixed nitride fuel (UN-PuN) for pressurized water reactor

Science.gov (United States)

Syarifah, Ratna Dewi; Suud, Zaki

2015-09-01

Design study of small Pressurized Water Reactors (PWRs) core loaded with uranium nitride fuel (UN) and mixed nitride fuel (UN-PuN), Pa-231 as burnable poison, and Americium has been performed. Pa-231 known as actinide material, have large capture cross section and can be converted into fissile material that can be utilized to reduce excess reactivity. Americium is one of minor actinides with long half life. The objective of adding americium is to decrease nuclear spent fuel in the world. The neutronic analysis results show that mixed nitride fuel have k-inf greater than uranium nitride fuel. It is caused by the addition of Pu-239 in mixed nitride fuel. In fuel fraction analysis, for uranium nitride fuel, the optimum volume fractions are 45% fuel fraction, 10% cladding and 45% moderator. In case of UN-PuN fuel, the optimum volume fractions are 30% fuel fraction, 10% cladding and 60% coolant/ moderator. The addition of Pa-231 as burnable poison for UN fuel, enrichment U-235 5%, with Pa-231 1.6% has k-inf more than one and excess reactivity of 14.45%. And for mixed nitride fuel, the lowest value of reactivity swing is when enrichment (U-235+Pu) 8% with Pa-231 0.4%, the excess reactivity value 13,76%. The fuel pin analyze for the addition of Americium, the excess reactivity value is lower than before, because Americium absorb the neutron. For UN fuel, enrichment U-235 8%, Pa-231 1.6% and Am 0.5%, the excess reactivity is 4.86%. And for mixed nitride fuel, when enrichment (U-235+Pu) 13%, Pa-231 0.4% and Am 0.1%, the excess reactivity is 11.94%. For core configuration, it is better to use heterogeneous than homogeneous core configuration, because the radial power distribution is better.

Electrokinetic treatment of firing ranges containing tungsten-contaminated soils

International Nuclear Information System (INIS)

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

2007-01-01

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

Low temperature processing of tungsten-fibre high-strength composite

International Nuclear Information System (INIS)

Semrau, W.M.

2001-01-01

A tungsten nickel/iron compound with a high tungsten content up to over 90 percent by volume of tungsten and an ideal distribution of the nickel-iron multilayer-matrix avoiding tungsten - tungsten interfaces, has been processed without the use of any sintering process and thus resulted in avoiding temperatures of above 700 o C during the entire manufacturing process. An electrochemical coating of coarse tungsten powder with alternating layers of nickel and iron and a forging process at temperatures not exceeding 650 o C resulted in a high strength compound, which easily could be altered into a tungsten fiber compound with a fiber-length to fiber-diameter ratio of more than 10 3 . From the viewpoint of the metallurgist, easier handling systems are obtained when both a liquid phase and high temperatures with their risks for grain structures and grain boundaries are lacking. (author)

Structure of tungsten electrodeposited from oxide chloride-fluoride molten salts

International Nuclear Information System (INIS)

Pavlovskij, V.A.; Reznichenko, V.A.

1998-01-01

Investigation results on the influence of electrolysis parameters and electrolyte composition on tungsten cathode deposit structure are presented. The electrolysis was performed in NaCl-NaF-WO 3 molten salts using tungsten and tungsten coated molybdenum cathodes. Morphological and metallographic studies of tungsten crystals were carrier out. Tungsten deposits were obtained in the form of crystalline conglomerates, sponge and high dispersity powder

The relationship between structural evolution and electrical percolation of the initial stages of tungsten chemical vapor deposition on polycrystalline TiN

International Nuclear Information System (INIS)

Rozenblat, A.; Haimson, S.; Shacham-Diamand, Y.; Horvitz, D.

2012-01-01

This paper presents experimental results and a geometric model of the evolution of sheet resistance and surface morphology during the transition from nucleation to percolation of tungsten chemical vapor deposition over ultrathin polycrystalline titanium nitride (TiN). We observed two mechanisms of reduction in sheet resistance. At deposition temperatures higher than 310 deg. C, percolation effect is formed at ∼35% of surface coverage, θ, and characterized with a sharp drop in resistance. At temperature below 310 deg. C, a reduction in resistance occurs in two steps. The first step occurs when θ = 35% and the second step at θ = 85%. We suggest a geometric model in which the electrical percolation pass is modulated by the thickness threshold of the islands at the instant of collision.

Humidity-dependent stability of amorphous germanium nitrides fabricated by plasma nitridation

International Nuclear Information System (INIS)

Kutsuki, Katsuhiro; Okamoto, Gaku; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

2007-01-01

We have investigated the stability of amorphous germanium nitride (Ge 3 N 4 ) layers formed by plasma nitridation of Ge(100) surfaces using x-ray photoelectron spectroscopy and atomic force microscopy. We have found that humidity in the air accelerates the degradation of Ge 3 N 4 layers and that under 80% humidity condition, most of the Ge-N bonds convert to Ge-O bonds, producing a uniform GeO 2 layer, within 12 h even at room temperature. After this conversion of nitrides to oxides, the surface roughness drastically increased by forming GeO 2 islands on the surfaces. These findings indicate that although Ge 3 N 4 layers have superior thermal stability compared to the GeO 2 layers, Ge 3 N 4 reacts readily with hydroxyl groups and it is therefore essential to take the best care of the moisture in the fabrication of Ge-based devices with Ge 3 N 4 insulator or passivation layers

Tungsten carbide and tungsten-molybdenum carbides as automobile exhaust catalysts

International Nuclear Information System (INIS)

Leclercq, L.; Daubrege, F.; Gengembre, L.; Leclercq, G.; Prigent, M.

1987-01-01

Several catalyst samples of tungsten carbide and W, Mo mixed carbides with different Mo/W atom ratios, have been prepared to test their ability to remove carbon monoxide, nitric oxide and propane from a synthetic exhaust gas simulating automobile emissions. Surface characterization of the catalysts has been performed by X-ray photoelectron spectroscopy (XPS) and selective chemisorption of hydrogen and carbon monoxide. Tungsten carbide exhibits good activity for CO and NO conversion, compared to a standard three-way catalyst based on Pt and Rh. However, this W carbide is ineffective in the oxidation of propane. The Mo,W mixed carbides are markedly different having only a very low activity. 9 refs.; 10 figs.; 5 tabs

Detection and reduction of tungsten contamination in ion implantation processes

International Nuclear Information System (INIS)

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

2016-01-01

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

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)

Optical characterization of gallium nitride

NARCIS (Netherlands)

Kirilyuk, Victoria

2002-01-01

Group III-nitrides have been considered a promising system for semiconductor devices since a few decades, first for blue- and UV-light emitting diodes, later also for high-frequency/high-power applications. Due to the lack of native substrates, heteroepitaxially grown III-nitride layers are usually

Tungsten oxide nanowires grown on amorphous-like tungsten films

International Nuclear Information System (INIS)

Dellasega, D; Pezzoli, A; Russo, V; Passoni, M; Pietralunga, S M; Nasi, L; Conti, C; Vahid, M J; Tagliaferri, A

2015-01-01

Tungsten oxide nanowires have been synthesized by vacuum annealing in the range 500–710 °C from amorphous-like tungsten films, deposited on a Si(100) substrate by pulsed laser deposition (PLD) in the presence of a He background pressure. The oxygen required for the nanowires formation is already adsorbed in the W matrix before annealing, its amount depending on deposition parameters. Nanowire crystalline phase and stoichiometry depend on annealing temperature, ranging from W_1_8O_4_9-Magneli phase to monoclinic WO_3. Sufficiently long annealing induces the formation of micrometer-long nanowires, up to 3.6 μm with an aspect ratio up to 90. Oxide nanowire growth appears to be triggered by the crystallization of the underlying amorphous W film, promoting their synthesis at low temperatures. (paper)

Tungsten as First Wall Material in Fusion Devices

International Nuclear Information System (INIS)

Kaufmann, M.

2006-01-01

In the PLT tokamak with a tungsten limiter strong cooling of the central plasma was observed. Since then mostly graphite has been used as limiter or target plate material. Only a few tokamaks (limiter: FTU, TEXTOR; divertor: Alcator C-Mod, ASDEX Upgrade) gained experience with high-Z-materials. With the observed strong co- deposition of tritium together with carbon in JET and as a result of design studies of fusion reactors, it became clear that in the long run tungsten is the favourite for the first-wall material. Tungsten as a plasma facing material requires intensive research in all areas, i.e. in plasma physics, plasma wall-interaction and material development. Tungsten as an impurity in the confined plasma reveals considerable differences to carbon. Strong radiation at high temperatures, in connection with mostly a pronounced inward drift forms a particular challenge. Turbulent transport plays a beneficial role in this regard. The inward drift is an additional problem in the pedestal region of H-mode plasmas in ITER-like configurations. The erosion by low energy hydrogen atoms is in contrast to carbon small. However, erosion by fast particles from heating measures and impurity ions, accelerated in the sheath potential, play an important role in the case of tungsten. Radiation by carbon in the plasma boundary reduces the load to the target plates. Neon or Argon as substitutes will increase the erosion of tungsten. So far experiments have demonstrated that in most scenarios the tungsten content in the central plasma can be kept sufficiently small. The material development is directed to the specific needs of existing or future devices. In ASDEX Upgrade, which will soon be a divertor experiment with a complete tungsten first-wall, graphite tiles are coated with tungsten layers. In ITER, the solid tungsten armour of the target plates has to be castellated because of its difference in thermal expansion compared to the cooling structure. In a reactor the technical

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

Directory of Open Access Journals (Sweden)

V. N. Kovalevsky

2012-01-01

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

Hydrogen diffusion between plasma-deposited silicon nitride-polyimide polymer interfaces

International Nuclear Information System (INIS)

Nguyen, S.V.; Kerbaugh, M.

1988-01-01

This paper reports a nuclear reaction analysis (NRA) for hydrogen technique used to analyze the hydrogen concentration near plasma enhanced chemical vapor deposition (PECVD) silicon nitride-polyimide interfaces at various nitride-deposition and polyimide-polymer-curing temperatures. The CF 4 + O 2 (8% O 2 ) plasma-etch-rate variation of PECVD silicon nitride films deposited on polyimide appeared to correlate well with the variation of hydrogen-depth profiles in the nitride films. The NRA data indicate that hydrogen-depth-profile fluctuation in the nitride films is due to hydrogen diffusion between the nitride-polyimide interfaces during deposition. Annealing treatment of polyimide films in a hydrogen atmosphere prior to the nitride film deposition tends to enhance the hydrogen-depth-profile uniformity in the nitride films, and thus substantially reduces or eliminates variation in the nitride plasma-etch rate

Radiative capture of slow electrons by tungsten surface

International Nuclear Information System (INIS)

Artamonov, O.M.; Belkina, G.M.; Samarin, S.N.; Yakovlev, I.I.

1987-01-01

Isochromatic spectra of radiation capture of slow electrons by the surface of mono- and polycrystal tungsten recorded on 322 and 405 nm wave lengths are presented. The effect of oxygen adsorption on isochromates of the (110) face of tungsten monocrystal is investigated. The obtained isochromatic spectra are compared with energy band structure of tungsten. Based on the analysis of the obtained experimental results it is assumed that optical transition to the final state at the energy of 7.3 eV relatively to Fermi level is conditioned by surface states of the tungsten face (110)

Nucleation of iron nitrides during gaseous nitriding of iron; the effect of a preoxidation treatment

DEFF Research Database (Denmark)

Friehling, Peter B.; Poulsen, Finn Willy; Somers, Marcel A.J.

2001-01-01

grains. On prolonged nitriding, immediate nucleation at the surface of iron grains becomes possible. Calculated incubation times for the nucleation of gamma'-Fe4N1-x during nitriding are generally longer than those observed experimentally in the present work. The incubation time is reduced dramatically...

RF plasma nitriding of severely deformed iron-based alloys

International Nuclear Information System (INIS)

Ferkel, H.; Glatzer, M.; Estrin, Y.; Valiev, R.Z.; Blawert, C.; Mordike, B.L.

2003-01-01

The effect of severe plastic deformation by cold high pressure torsion (HPT) on radio frequency (RF) plasma nitriding of pure iron, as well as St2K50 and X5CrNi1810 steels was investigated. Nitriding was carried out for 3 h in a nitrogen atmosphere at a pressure of 10 -5 bar and temperatures of 350 and 400 deg. C. Nitrided specimens were analysed by scanning electron microscopy (SEM), X-ray diffraction and micro hardness measurements. It was found that HPT enhances the effect of nitriding leading almost to doubling of the thickness of the nitrided layer for pure iron and the high alloyed steel. The largest increase in hardness was observed when HPT was combined with RF plasma nitriding at 350 deg. C. In the case of pure iron, the X-ray diffraction spectra showed the formation of ε and γ' nitrides in the compound layer, with a preferential formation of γ' at the expense of the α-phase at the higher nitriding temperature. The corresponding surface hardness was up to 950 HV0.01. While the HPT-processed St2K50 exhibits both nitride phases after nitriding at 350 deg. C, only the γ'-phase was observed after nitriding at 400 deg. C. A surface hardness of up to 1050 HV0.01 was measured for this steel. The high alloyed steel X5CrNi1810 exhibited the highest increase in surface hardness when HPT was combined with nitriding at 350 deg. C. The surface hardness of this steel was greater than 1400 HV0.025. The XRD analyses indicate the formation of the expanded austenite (S-phase) in the surface layer as a result of RF plasma nitriding. Furthermore, after HPT X5CrNi1810 was transformed completely into deformation martensite which did not transform back to austenite under thermochemical treatment. However, in the case of nitriding of the HPT-processed high alloyed steel at 400 deg. C, the formation of the S-phase was less pronounced. In view of the observed XRD peak broadening, the formation of nitrides, such as e.g. CrN, cannot be ruled out

Development of pseudocapacitive molybdenum oxide–nitride for electrochemical capacitors

Energy Technology Data Exchange (ETDEWEB)

Ting, Yen-Jui Bernie [Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Wu, Haoran [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Kherani, Nazir P. [Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Lian, Keryn, E-mail: keryn.lian@utoronto.ca [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada)

2015-03-15

A thin film Mo oxide–nitride pseudocapacitive electrode was synthesized by electrodeposition of Mo oxide on Ti and a subsequent low-temperature (400 °C) thermal nitridation. Two nitridation environments, N{sub 2} and NH{sub 3}, were used and the results were compared. Surface analyses of these nitrided films showed partial conversion of Mo oxide to nitrides, with a lower conversion percentage being the film produced in N{sub 2}. However, the electrochemical analyses showed that the surface of the N{sub 2}-treated film had better pseudocapacitive behaviors and outperformed that nitrided in NH{sub 3}. Cycle life of the resultant N{sub 2}-treated Mo oxide–nitride was also much improved over Mo oxide. A two-electrode cell using Mo oxide–nitride electrodes was demonstrated and showed high rate performance. - Highlights: • Mo(O,N){sub x} was developed by electrodeposition and nitridation in N{sub 2} or NH{sub 3}. • N{sub 2} treated Mo(O,N){sub x} showed a capacitive performance superior to that treated by NH{sub 3}. • The promising electrochemical performance was due to the formation of γ-Mo{sub 2}N.

Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

Science.gov (United States)

Zelenay, Piotr; Wu, Gang

2014-04-29

A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

Morphology of Si/tungsten-silicides/Si interlayers

International Nuclear Information System (INIS)

Theodore, N.; Secco d'Aragona, F.; Blackstone, S.

1992-01-01

Tungsten and tungsten-silicides are of interest for semiconductor technology because of their refractory nature, low electrical-resistivity and high electromigration-resistance. This paper presents the first formation of buried tungsten-silicide layers in silicon, by proximity adhesion. The interlayers, created by a combination of chemical vapor-deposition (CVD) and proximity-adhesion were studied using transmission electron-microscopy (TEM). The behavior of the layers in the presence and absence of an adjacent silicon-dioxide interlayer was also investigated. Buried silicide layers were successfully formed with or without the adjacent silicon-dioxide. The silicide formed continuous layers with single grains encompassing the width of the interlayer. Individual grains were globular, with cusps at grain boundaries. This caused interlayer-thicknesses to be non-uniform, with lower thickness values being present at the cusps. Occasional voids were observed at grain-boundary cusps. The voids were smaller and less frequent in the presence of an adjacent oxide-layer, due to flow of the oxide during proximity adhesion. Electron-diffraction revealed a predominance of tungsten-disilicide in the interlayers, with some free tungsten being present. Stresses in the silicide layers caused occasional glide dislocations to propagate into the silicon substrate beneath the interlayers. The dislocations propagate only ∼100 nm into the substrate and therefore should not be detrimental to use of the buried layers. Occasional precipitates were observed at the end of glide-loops. These possibly arise due to excess tungsten from the interlayer diffusion down the glide dislocation to finally precipitate out as tungsten-silicide

Surface morphologies of He-implanted tungsten

Energy Technology Data Exchange (ETDEWEB)

Bannister, M.E., E-mail: bannisterme@ornl.gov [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6371 (United States); Meyer, F.W.; Hijazi, H. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6371 (United States); Unocic, K.A.; Garrison, L.M.; Parish, C.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

2016-09-01

Surface morphologies of tungsten surfaces, both polycrystalline and single-crystal [1 1 0], were investigated using SEM and FIB/SEM techniques after implantations at elevated surfaces temperatures (1200–1300 K) using well-characterized, mono-energetic He ion beams with a wide range of ion energies (218 eV–250 keV). Nanofuzz was observed on polycrystalline tungsten (PCW) following implantation of 100-keV He ions at a flux threshold of 0.9 × 10{sup 16} cm{sup −2} s{sup −1}, but not following 200-keV implantations with similar fluxes. No nanofuzz formation was observed on single-crystal [1 1 0] tungsten (SCW), despite fluxes exceeding those demonstrated previously to produce nanofuzz on polycrystalline tungsten. Pre-damaging the single-crystal tungsten with implanted C impurity interstitials did not significantly affect the surface morphologies resulting from the high-flux He ion implantations. The main factor leading to the different observed surface structures for the pristine and C-implanted single-crystal W samples appeared to be the peak He ion flux characterizing the different exposures. It was speculated that nanofuzz formation was not observed for any SCW target exposures because of increased incubation fluences required for such targets.

The gate oxide integrity of CVD tungsten polycide

International Nuclear Information System (INIS)

Wu, N.W.; Su, W.D.; Chang, S.W.; Tseng, M.F.

1988-01-01

CVD tungsten polycide has been demonstrated as a good gate material in recent very large scale integration (VLSI) technology. CVD tungsten silicide offers advantages of low resistivity, high temperature stability and good step coverage. On the other hand, the polysilicon underlayer preserves most characteristics of the polysilicon gate and acts as a stress buffer layer to absorb part of the thermal stress origin from the large thermal expansion coefficient of tungsten silicide. Nevertheless, the gate oxide of CVD tungsten polycide is less stable or reliable than that of polysilicon gate. In this paper, the gate oxide integrity of CVD tungsten polycide with various thickness combinations and different thermal processes have been analyzed by several electrical measurements including breakdown yield, breakdown fluence, room temperature TDDB, I-V characteristics, electron traps and interface state density

Synthesis of new cobalt aluminophosphate framework by opening a cobalt methylphosphonate layered material

Czech Academy of Sciences Publication Activity Database

Zaarour, M.; Pérez, O.; Boullay, P.; Martens, J.; Mihailova, B.; Karaghiosoff, K.; Palatinus, Lukáš; Mintova, S.

2017-01-01

Roč. 19, č. 34 (2017), s. 5100-5105 ISSN 1466-8033 Institutional support: RVO:68378271 Keywords : cobalt aluminophosphate * cobalt methylphosphonate * layered materials * crystallic structure * X-ray diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.474, year: 2016

New Routes to Lanthanide and Actinide Nitrides

Energy Technology Data Exchange (ETDEWEB)

Butt, D.P.; Jaques, B.J.; Osterberg, D.D. [Boise State University, 1910 University Dr., Boise, Idaho 83725-2075 (United States); Marx, B.M. [Concurrent Technologies Corporation, Johnstown, PA (United States); Callahan, P.G. [Carnegie Mellon University, Pittsburgh, PA (United States); Hamdy, A.S. [Central Metallurgical R and D Institute, Helwan, Cairo (Egypt)

2009-06-15

The future of nuclear energy in the U.S. and its expansion worldwide depends greatly on our ability to reduce the levels of high level waste to minimal levels, while maintaining proliferation resistance. Implicit in the so-called advanced fuel cycle is the need for higher levels of fuel burn-up and consequential use of complex nuclear fuels comprised of fissile materials such as Pu, Am, Np, and Cm. Advanced nitride fuels comprised ternary and quaternary mixtures of uranium and these actinides have been considered for applications in advanced power plants, but there remain many processing challenges as well as necessary qualification testing. In this presentation, the advantages and disadvantages of nitride fuels are discussed. Methods of synthesizing the raw materials and sintering of fuels are described including a discussion of novel, low cost routes to nitrides that have the potential for reducing the cost and footprint of a fuel processing plant. Phase pure nitrides were synthesized via four primary methods; reactive milling metal flakes in nitrogen at room temperature, directly nitriding metal flakes in a pure nitrogen atmosphere, hydriding metal flakes prior to nitridation, and carbo-thermically reducing the metal oxide and carbon mixture prior to nitridation. In the present study, the sintering of UN, DyN, and their solid solutions (U{sub x}, Dy{sub 1-x}) (x = 1 to 0.7) were also studied. (authors)

Radio cobalt in French rivers

International Nuclear Information System (INIS)

Lambrechts, A.; Baudin-Jaulent, Y.

1996-01-01

The isotopes 58 and 60 of cobalt present in liquid wastes from nuclear plants or from fuel reprocessing plant of Marcoule are fixed in the different compartments of French rivers. The activity levels of radio-cobalt vary according to the sampled compartments nature (bryophyta > immersed plants > sediment > fish). Elsewhere, laboratory experimentations show that the contamination of fish occurs essentially from the water way rather than from food. Cobalt is mainly fixed by kidneys; muscles is no more than 30 % of the total fish activity. (author)

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.

Molecular mechanics calculations on cobalt phthalocyanine dimers

NARCIS (Netherlands)

Heuts, J.P.A.; Schipper, E.T.W.M.; Piet, P.; German, A.L.

1995-01-01

In order to obtain insight into the structure of cobalt phthalocyanine dimers, molecular mechanics calculations were performed on dimeric cobalt phthalocyanine species. Molecular mechanics calculations are first presented on monomeric cobalt(II) phthalocyanine. Using the Tripos force field for the

A solid tungsten divertor for ASDEX Upgrade

International Nuclear Information System (INIS)

Herrmann, A; Greuner, H; Jaksic, N; Böswirth, B; Maier, H; Neu, R; Vorbrugg, S

2011-01-01

The conceptual design of a solid tungsten divertor for ASDEX Upgrade (AUG) is presented. The Div-III design is compatible with the existing divertor structure. It re-establishes the energy and heat receiving capability of a graphite divertor and overcomes the limitations of tungsten coatings. In addition, a solid tungsten divertor allows us to investigate erosion and bulk deuterium retention as well as test castellation and target tilting. The design criteria as well as calculations of forces due to halo and eddy currents are presented. The thermal properties of the proposed sandwich structure are calculated with finite element method models. After extensive testing of a target tile in the high heat flux test facility GLADIS, two solid tungsten tiles were installed in AUG for in-situ testing.

AN ELECTROPLATING METHOD OF FORMING PLATINGS OF NICKEL, COBALT, NICKEL ALLOYS OR COBALT ALLOYS

DEFF Research Database (Denmark)

1997-01-01

An electroplating method of forming platings of nickel, cobalt, nickel alloys or cobalt alloys with reduced stresses in an electrodepositing bath of the type: Watt's bath, chloride bath or a combination thereof, by employing pulse plating with periodic reverse pulse and a sulfonated naphthalene...

Plasma nitriding - an eco friendly surface hardening process

International Nuclear Information System (INIS)

Mukherjee, S.

2015-01-01

Surface hardening is a process of heating the metal such that the surface gets only hardened. This process is adopted for many components like gears, cams, and crankshafts, which desire high hardness on the outer surface with a softer core to withstand the shocks. So, to attain such properties processes like carburising, nitriding, flame hardening and induction hardening are employed. Amongst these processes nitriding is the most commonly used process by many industries. In nitriding process the steel material is heated to a temperature of around 550 C and then exposed to atomic nitrogen. This atomic nitrogen reacts with iron and other alloying elements and forms nitrides, which are very hard in nature. By this process both wear resistance and hardness of the product can be increased. The atomic nitrogen required for this process can be obtained using ammonia gas (gas nitriding), cyanide based salt bath (liquid nitriding) and plasma medium (plasma nitriding). However, plasma nitriding has recently received considerable industrial interest owing to its characteristic of faster nitrogen penetration, short treatment time, low process temperature, minimal distortion, low energy use and easier control of layer formation compared with conventional techniques such as gas and liquid nitriding. This process can be used for all ferrous materials including stainless steels. Plasma nitriding is carried out using a gas mixture of nitrogen and hydrogen gas at sub atmospheric pressures hence, making it eco-friendly in nature. Plasma nitriding allows modification of the surface layers and hardness profiles by changing the gas mixture and temperature. The wide applicable temperature range enables a multitude of applications, beyond the possibilities of gas or salt bath processes. This has led to numerous applications of this process in industries such as the manufacture of machine parts for plastics and food processing, packaging and tooling as well as pumps and hydraulic, machine

Advancing liquid metal reactor technology with nitride fuels

International Nuclear Information System (INIS)

Lyon, W.F.; Baker, R.B.; Leggett, R.D.; Matthews, R.B.

1991-08-01

A review of the use of nitride fuels in liquid metal fast reactors is presented. Past studies indicate that both uranium nitride and uranium/plutonium nitride possess characteristics that may offer enhanced performance, particularly in the area of passive safety. To further quantify these effects, the analysis of a mixed-nitride fuel system utilizing the geometry and power level of the US Advanced Liquid Metal Reactor as a reference is described. 18 refs., 2 figs., 2 tabs

Corrosion of high-density sintered tungsten alloys. Part 2

International Nuclear Information System (INIS)

Batten, J.J.; Moore, B.T.

1988-12-01

The behaviour of four high-density sintered tungsten alloys has been evluated and compared with that of pure tungsten. Rates of corrosion during the cyclic humidity and the salt mist tests were ascertained from weight loss measurements. Insight into the corrosion mechanism was gained from the nature of the corrosion products and an examination of the corroded surfaces. In the tests, the alloy 95% W, 2.5% Ni, 1.5% Fe was the most corrosion resistant. The data showed that copper as an alloying element accelerates corrosion of tungsten alloys. Both attack on the tungsten particles and the binder phase were observed together with tungsten grain loss. 6 refs., 3 tabs.,

Substructure and electrical resistivity analyses of pure tungsten sheet

International Nuclear Information System (INIS)

Trybus, C.L.; Sellers, C.H.; Anderl, R.A.

1991-01-01

The substructure of pure tungsten sheet (0.025 mm thick) is examined and quantified by transmission electron microscopy (TEM). Dislocation populations and arrangements are evaluated for as-worked and various annealed conditions of the tungsten sheet. The worked (rolled) tungsten substructure was nonhomogeneous, consisting of areas of very high and low dislocation densities. These results are correlated to resistivity measurements of the tungsten sheet following thermal cycling to 1200 degrees C to determine the substructural changes as a function of temperature. The comparison between the two characterization techniques is used to examine the relationship between structural and electronic properties in tungsten. 15 refs., 6 figs., 2 tabs

Study of complex formation of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel

International Nuclear Information System (INIS)

Ismailova, M.M.; Egorova, L.A.; Khamidov, B.O.

1993-01-01

Present article is devoted to study of complex formation of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel. The condition of cobalt in various rate of oxidation in acrylamide aqueous solutions was studied. The concentration conditions of stability of system Co(II)-Co(III) were defined. The composition of coordination compounds of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel was determined.

Exploring electrolyte preference of vanadium nitride supercapacitor electrodes

Energy Technology Data Exchange (ETDEWEB)

Wang, Bo; Chen, Zhaohui; Lu, Gang [Department of Electrical Engineering and Automation, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Wang, Tianhu [School of Electrical Information and Engineering, Jiangsu University of Technology, Changzhou 213001 (China); Ge, Yunwang, E-mail: ywgelit@126.com [Department of Electrical Engineering and Automation, Luoyang Institute of Science and Technology, Luoyang 471023 (China)

2016-04-15

Highlights: • Hierarchical VN nanostructures were prepared on graphite foam. • Electrolyte preference of VN supercapacitor electrodes was explored. • VN showed better capacitive property in organic and alkaline electrolytes than LiCl. - Abstract: Vanadium nitride hierarchical nanostructures were prepared through an ammonia annealing procedure utilizing vanadium pentoxide nanostructures grown on graphite foam. The electrochemical properties of hierarchical vanadium nitride was tested in aqueous and organic electrolytes. As a result, the vanadium nitride showed better capacitive energy storage property in organic and alkaline electrolytes. This work provides insight into the charge storage process of vanadium nitride and our findings can shed light on other transition metal nitride-based electrochemical energy storage systems.

Modeling the Gas Nitriding Process of Low Alloy Steels

Science.gov (United States)

Yang, M.; Zimmerman, C.; Donahue, D.; Sisson, R. D.

2013-07-01

The effort to simulate the nitriding process has been ongoing for the last 20 years. Most of the work has been done to simulate the nitriding process of pure iron. In the present work a series of experiments have been done to understand the effects of the nitriding process parameters such as the nitriding potential, temperature, and time as well as surface condition on the gas nitriding process for the steels. The compound layer growth model has been developed to simulate the nitriding process of AISI 4140 steel. In this paper the fundamentals of the model are presented and discussed including the kinetics of compound layer growth and the determination of the nitrogen diffusivity in the diffusion zone. The excellent agreements have been achieved for both as-washed and pre-oxided nitrided AISI 4140 between the experimental data and simulation results. The nitrogen diffusivity in the diffusion zone is determined to be constant and only depends on the nitriding temperature, which is ~5 × 10-9 cm2/s at 548 °C. It proves the concept of utilizing the compound layer growth model in other steels. The nitriding process of various steels can thus be modeled and predicted in the future.

Synthesis of Uranium nitride powders using metal uranium powders

International Nuclear Information System (INIS)

Yang, Jae Ho; Kim, Dong Joo; Oh, Jang Soo; Rhee, Young Woo; Kim, Jong Hun; Kim, Keon Sik

2012-01-01

Uranium nitride (UN) is a potential fuel material for advanced nuclear reactors because of their high fuel density, high thermal conductivity, high melting temperature, and considerable breeding capability in LWRs. Uranium nitride powders can be fabricated by a carbothermic reduction of the oxide powders, or the nitriding of metal uranium. The carbothermic reduction has an advantage in the production of fine powders. However it has many drawbacks such as an inevitable engagement of impurities, process burden, and difficulties in reusing of expensive N 15 gas. Manufacturing concerns issued in the carbothermic reduction process can be solved by changing the starting materials from oxide powder to metals. However, in nitriding process of metal, it is difficult to obtain fine nitride powders because metal uranium is usually fabricated in the form of bulk ingots. In this study, a simple reaction method was tested to fabricate uranium nitride powders directly from uranium metal powders. We fabricated uranium metal spherical powder and flake using a centrifugal atomization method. The nitride powders were obtained by thermal treating those metal particles under nitrogen containing gas. We investigated the phase and morphology evolutions of powders during the nitriding process. A phase analysis of nitride powders was also a part of the present work

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

The oxidation of titanium nitride- and silicon nitride-coated stainless steel in carbon dioxide environments

International Nuclear Information System (INIS)

Mitchell, D.R.G.; Stott, F.H.

1992-01-01

A study has been undertaken into the effects of thin titanium nitride and silicon nitride coatings, deposited by physical vapour deposition and chemical vapour deposition processes, on the oxidation resistance of 321 stainless steel in a simulated advanced gas-cooled reactor carbon dioxide environment for long periods at 550 o C and 700 o C under thermal-cycling conditions. The uncoated steel contains sufficient chromium to develop a slow-growing chromium-rich oxide layer at these temperatures, particularly if the surfaces have been machine-abraded. Failure of this layer in service allows formation of less protective iron oxide-rich scales. The presence of a thin (3-4 μm) titanium nitride coating is not very effective in increasing the oxidation resistance since the ensuing titanium oxide scale is not a good barrier to diffusion. Even at 550 o C, iron oxide-rich nodules are able to develop following relatively rapid oxidation and breakdown of the coating. At 700 o C, the coated specimens oxidize at relatively similar rates to the uncoated steel. A thin silicon nitride coating gives improved oxidation resistance, with both the coating and its slow-growing oxide being relatively electrically insulating. The particular silicon nitride coating studied here was susceptible to spallation on thermal cycling, due to an inherently weak coating/substrate interface. (Author)

Surface modification of titanium by plasma nitriding

Directory of Open Access Journals (Sweden)

Kapczinski Myriam Pereira

2003-01-01

Full Text Available A systematic investigation was undertaken on commercially pure titanium submitted to plasma nitriding. Thirteen different sets of operational parameters (nitriding time, sample temperature and plasma atmosphere were used. Surface analyses were performed using X-ray diffraction, nuclear reaction and scanning electron microscopy. Wear tests were done with stainless steel Gracey scaler, sonic apparatus and pin-on-disc machine. The obtained results indicate that the tribological performance can be improved for samples treated with the following conditions: nitriding time of 3 h; plasma atmosphere consisting of 80%N2+20%H2 or 20%N2+80%H2; sample temperature during nitriding of 600 or 800 degreesC.

Synthesis of high purity tungsten nanoparticles from tungsten heavy alloy scrap by selective precipitation and reduction route

International Nuclear Information System (INIS)

Kamal, S.S. Kalyan; Sahoo, P.K.; Vimala, J.; Shanker, B.; Ghosal, P.; Durai, L.

2016-01-01

In this paper we report synthesis of tungsten nanoparticles of high purity >99.7 wt% from heavy alloy scrap using a novel chemical route of selective precipitation and reduction. The effect of Poly(vinylpyrrolidone) polymer on controlling the particle size is established through FTIR spectra and corroborated with TEM images, wherein the average size decreased form 210 to 45 nm with increasing PVP content from zero to 2 g under different experimental conditions. This process is economical as raw material is a scrap and the efficiency of the reaction is >95%. - Highlights: • Tungsten nanoparticles were synthesized from tungsten heavy alloy scrap. • A novel chemical route of precipitation and reduction with Poly(vinylpyrrolidone) polymer as stabilizer is reported. • The average size decreased form 210 to 45 nm with increasing PVP content from zero to 2 g. • High pure tungsten nanoparticles of >99.7% purity could be synthesized using this route. • Efficiency of the reaction is >95%.

Characterization of porous tungsten by microhardness

International Nuclear Information System (INIS)

Selcuk, C.; Wood, J.V.; Morley, N.; Bentham, R.

2001-01-01

One of the applications of tungsten is as high current density dispenser cathode in the form of porous tungsten. It is used as a cathode after being impregnated with an electron emissive material so pore distribution in the part is the most important parameter for its function as a uniform and controlled porosity will lead to a better performance. In this study, application of microhardness as a characterization method for uniformity of the pore distribution and homogeneity of the structure is introduced. Optical microscopy and SEM is used to relate the results and porous tungsten structure for a better understanding of the method applied. (author)

Electrochemical Solution Growth of Magnetic Nitrides

Energy Technology Data Exchange (ETDEWEB)

Monson, Todd C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pearce, Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2014-10-01

Magnetic nitrides, if manufactured in bulk form, would provide designers of transformers and inductors with a new class of better performing and affordable soft magnetic materials. According to experimental results from thin films and/or theoretical calculations, magnetic nitrides would have magnetic moments well in excess of current state of the art soft magnets. Furthermore, magnetic nitrides would have higher resistivities than current transformer core materials and therefore not require the use of laminates of inactive material to limit eddy current losses. However, almost all of the magnetic nitrides have been elusive except in difficult to reproduce thin films or as inclusions in another material. Now, through its ability to reduce atmospheric nitrogen, the electrochemical solution growth (ESG) technique can bring highly sought after (and previously inaccessible) new magnetic nitrides into existence in bulk form. This method utilizes a molten salt as a solvent to solubilize metal cations and nitrogen ions produced electrochemically and form nitrogen compounds. Unlike other growth methods, the scalable ESG process can sustain high growth rates (~mm/hr) even under reasonable operating conditions (atmospheric pressure and 500 °C). Ultimately, this translates into a high throughput, low cost, manufacturing process. The ESG process has already been used successfully to grow high quality GaN. Below, the experimental results of an exploratory express LDRD project to access the viability of the ESG technique to grow magnetic nitrides will be presented.

Phosphorus introduction mechanism in electrodeposited cobalt films

International Nuclear Information System (INIS)

Kravtchenko, Jean-Francois

1973-01-01

The cathodic reduction of hypophosphite, phosphite and phosphate ions was studied using chrono-potentiometry and voltammetry. Then cobalt was deposited at constant current from a bath containing one of these three compounds. The current, while giving an electrodeposition of cobalt, also enhances at the same time a chemical deposition of cobalt. It is shown that high coercive forces in cobalt films are much more related to this chemical deposition than to the simple fact that the films contain some phosphorus. (author) [fr

Microstructure and tensile properties of tungsten at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Shen, Tielong [Laboratory for Nuclear Materials, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Dai, Yong, E-mail: yong.dai@psi.ch [Laboratory for Nuclear Materials, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Lee, Yongjoong [European Spallation Source, Tunavägen 24, 223 63 Lund (Sweden)

2016-01-15

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. - Highlights: • This work was conducted 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 and tensile behaviour was studied with hot-rolled and hot-forged tungsten. • The tungsten materials were characterized with metallography analysis, hardness measurement and tensile test in a temperature range of 25–500 °C. • The results indicate that the HR tungsten has better mechanical properties in terms of greater ductility and lower ductile-to-brittle transition temperature.

Quenching and recovery experiments on tungsten

International Nuclear Information System (INIS)

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

1976-01-01

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

Simulation of the Nitriding Process

Science.gov (United States)

Krukovich, M. G.

2004-01-01

Simulation of the nitriding process makes it possible to solve many practical problems of process control, prediction of results, and development of new treatment modes and treated materials. The presented classification systematizes nitriding processes and processes based on nitriding, enables consideration of the theory and practice of an individual process in interrelation with other phenomena, outlines ways for intensification of various process variants, and gives grounds for development of recommendations for controlling the structure and properties of the obtained layers. The general rules for conducting the process and formation of phases in the layer and properties of the treated surfaces are used to create a prediction computational model based on analytical, numerical, and empirical approaches.

Process for separation of tungsten and molybdenum by extraction

International Nuclear Information System (INIS)

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

1976-01-01

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

Cobalt reduction of NSSS valve hardfacings for ALARA

Energy Technology Data Exchange (ETDEWEB)

Kim, Joo Hak; Lee, Sang Sub [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1994-07-01

This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author).

Cobalt reduction of NSSS valve hardfacings for ALARA

International Nuclear Information System (INIS)

Kim, Joo Hak; Lee, Sang Sub

1994-07-01

This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author)

The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model

Science.gov (United States)

Tagliabue, Alessandro; Hawco, Nicholas J.; Bundy, Randelle M.; Landing, William M.; Milne, Angela; Morton, Peter L.; Saito, Mak A.

2018-04-01

Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B12 and is a co-factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state-of-the-art three-dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom-water oxygen conditions. The basin-scale distribution of cobalt supplied from margins is facilitated by the activity of manganese-oxidizing bacteria being suppressed under low oxygen and low temperatures, which extends the residence time of cobalt. Overall, we find a residence time of 7 and 250 years in the upper 250 m and global ocean, respectively. Importantly, we find that the dominant internal resupply process switches from regeneration and recycling of particulate cobalt to dissolution of scavenged cobalt between the upper ocean and the ocean interior. Our model highlights key regions of the ocean where biological activity may be most sensitive to cobalt availability.

Characterization of plasma nitrided layers produced on sintered iron

Directory of Open Access Journals (Sweden)

Marcos Alves Fontes

2014-07-01

Full Text Available Plasma nitriding is a thermo-physical-chemical treatment process, which promotes surface hardening, caused by interstitial diffusion of atomic nitrogen into metallic alloys. In this work, this process was employed in the surface modification of a sintered ferrous alloy. Scanning electron microscopy (SEM, X-ray diffraction (XRD analyses, and wear and microhardness tests were performed on the samples submitted to ferrox treatment and plasma nitriding carried out under different conditions of time and temperature. The results showed that the nitride layer thickness is higher for all nitrided samples than for ferrox treated samples, and this layer thickness increases with nitriding time and temperature, and temperature is a more significant variable. The XRD analysis showed that the nitrided layer, for all samples, near the surface consists in a mixture of γ′-Fe4N and ɛ-Fe3N phases. Both wear resistance and microhardness increase with nitriding time and temperature, and temperature influences both the characteristics the most.

Accumulation of cobalt by cephalopods

International Nuclear Information System (INIS)

Nakahara, Motokazu

1981-01-01

Accumulation of cobalt by cephalopod mollusca was investigated by radiotracer experiments and elemental analysis. In the radiotracer experiments, Octopus vulgaris took up cobalt-60 from seawater fairly well and the concentration of the nuclide in whole body attained about 150 times the level of seawater at 25th day at 20 0 C. Among the tissues and organs measured, branchial heart which is the specific organ of cephalopods showed the highest affinity for the nuclide. The organ accumulated about 50% of the radioactivity in whole body in spite of its little mass as 0.2% of total body weight. On the other hand, more than 90% of the radioactivity taken up from food (soft parts of Gomphina melanaegis labelled with cobalt-60 previously in an aquarium) was accumulated in liver at 3rd day after the single administration and then the radioactivity in the liver seemed to be distributed to other organs and tissues. The characteristic elution profiles of cobalt-60 was observed for each of the organs and tissues in Sephadex gel-filtration experiment. It was confirmed by the gel-filtration that most of cobalt-60 in the branchial heart was combined with the constituents of low molecular weights. The average concentration of stable cobalt in muscle of several species of cephalopods was 5.3 +- 3.0 μg/kg wet and it was almost comparable to the fish muscle. On the basis of soft parts, concentration of the nuclide closed association among bivalve, gastropod and cephalopod except squid that gave lower values than the others. (author)

Cobalt-free nickel-base superalloys

International Nuclear Information System (INIS)

Koizumi, Yutaka; Yamazaki, Michio; Harada, Hiroshi

1979-01-01

Cobalt-free nickel-base cast superalloys have been developed. Cobalt is considered to be a beneficial element to strengthen the alloys but should be eliminated in alloys to be used for direct cycle helium turbine driven by helium gas from HTGR (high temp. gas reactor). The elimination of cobalt is required to avoid the formation of radioactive 60 Co from the debris or scales of the alloys. Cobalt-free alloys are also desirable from another viewpoint, i.e. recently the shortage of the element has become a serious problem in industry. Cobalt-free Mar-M200 type alloys modified by the additions of 0.15 - 0.2 wt% B and 1 - 1.5 wt% Hf were found to have a creep rupture strength superior or comparable to that of the original Mar-M200 alloy bearing cobalt. The ductility in tensile test at 800 0 C, as cast or after prolonged heating at 900 0 C (the tensile test was done without removing the surface layer affected by the heating), was also improved by the additions of 0.15 - 0.2% B and 1 - 1.5% Hf. The morphology of grain boundaries became intricated by the additions of 0.15 - 0.2% B and 1 - 1.5% Hf, to such a degree that one can hardly distinguish grain boundaries by microscopes. The change in the grain boundary morphology was considered, as suggested previously by one of the authors (M.Y.), to be the reason for the improvements in the creep rupture strength and tensile ductility. (author)

Surface studies of tungsten erosion and deposition in JT-60U

International Nuclear Information System (INIS)

Ueda, Y.; Fukumoto, M.; Nishikawa, M.; Tanabe, T.; Miya, N.; Arai, T.; Masaki, K.; Ishimoto, Y.; Tsuzuki, K.; Asakura, N.

2007-01-01

In order to study tungsten erosion and migration in JT-60U, 13 W tiles have been installed in the outer divertor region and tungsten deposition on graphite tiles was measured. Dense local tungsten deposition was observed on a CFC tile toroidally adjacent to the W tiles, which resulted from prompt ionization and short range migration of tungsten along field lines. Tungsten deposition with relatively high surface density was found on an inner divertor tile around standard inner strike positions and on an outer wing tile of a dome. On the outer wing tile, tungsten deposition was relatively high compared with carbon deposition. In addition, roughly uniform tungsten depth distribution near the upper edge of the inner divertor tile was observed. This could be due to lift-up of strike point positions in selected 25 shots and tungsten flow in the SOL plasma

Innovative boron nitride-doped propellants

Directory of Open Access Journals (Sweden)

Thelma Manning

2016-04-01

Full Text Available The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P. Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower flame temperatures for gun barrels. Further, boron can dope steel, which drastically improves its strength and wear resistance, and can block the formation of softer carbides. A scalable synthesis method for producing boron nitride nano-particles that can be readily dispersed into propellants has been developed. Even dispersion of the nano-particles in a double-base propellant has been demonstrated using a solvent-based processing approach. Stability of a composite propellant with the BN additive was verified. In this paper, results from propellant testing of boron nitride nano-composite propellants are presented, including closed bomb and wear and erosion testing. Detailed characterization of the erosion tester substrates before and after firing was obtained by electron microscopy, inductively coupled plasma and x-ray photoelectron spectroscopy. This promising boron nitride additive shows the ability to improve gun wear and erosion resistance without any destabilizing effects to the propellant. Potential applications could include less erosive propellants in propellant ammunition for large, medium and small diameter fire arms.

Cobalt-60 production in CANDU power reactors

International Nuclear Information System (INIS)

Malkoske, G.R.; Norton, J.L.; Slack, J.

2002-01-01

MDS Nordion has been supplying cobalt-60 sources to industry for industrial and medical purposes since 1946. These cobalt-60 sources are used in many market and product segments, but are primarily used to sterilize single-use medical products including; surgical kits, gloves, gowns, drapes, and cotton swabs. Other applications include sanitization of cosmetics, microbial reduction of pharmaceutical raw materials, and food irradiation. The technology for producing the cobalt-60 isotope was developed by MDS Nordion and Atomic Energy of Canada Limited (AECL) almost 55 years ago using research reactors at the AECL Chalk River Laboratories in Ontario, Canada. The first cobalt-60 source produced for medical applications was manufactured by MDS Nordion and used in cancer therapy. The benefits of cobalt-60 as applied to medical product manufacturing, were quickly realized and the demand for this radioisotope quickly grew. The same technology for producing cobalt-60 in research reactors was then designed and packaged such that it could be conveniently transferred to a utility/power reactor. In the early 1970's, in co-operation with Ontario Power Generation (formerly Ontario Hydro), bulk cobalt-60 production for industrial irradiation applications was initiated in the four Pickering A CANDU reactors. As the demand and acceptance of sterilization of medical products grew, MDS Nordion expanded its bulk supply by installing the proprietary Canadian technology for producing cobalt-60 in additional CANDU reactors. CANDU is unique among the power reactors of the world, being heavy water moderated and fuelled with natural uranium. They are also designed and supplied with stainless steel adjusters, the primary function of which is to shape the neutron flux to optimize reactor power and fuel bum-up, and to provide excess reactivity needed to overcome xenon-135 poisoning following a reduction of power. The reactor is designed to develop full power output with all of the adjuster

Experimental evidence for cobalt(III)-carbene radicals: key intermediates in cobalt(II)-based metalloradical cyclopropanation

NARCIS (Netherlands)

Lu, H.; Dzik, W.I.; Xu, X.; Wojtas, L.; de Bruin, B.; Zhang, X.P.

2011-01-01

New and conclusive evidence has been obtained for the existence of cobalt(III)-carbene radicals that have been previously proposed as the key intermediates in the underlying mechanism of metalloradical cyclopropanation by cobalt(II) complexes of porphyrins. In the absence of olefin substrates,

Tritium Decay Helium-3 Effects in Tungsten

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-01

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

Palladium-cobalt particles as oxygen-reduction electrocatalysts

Science.gov (United States)

Adzic, Radoslav [East Setauket, NY; Huang, Tao [Manorville, NY

2009-12-15

The present invention relates to palladium-cobalt particles useful as oxygen-reducing electrocatalysts. The invention also relates to oxygen-reducing cathodes and fuel cells containing these palladium-cobalt particles. The invention additionally relates to methods for the production of electrical energy by using the palladium-cobalt particles of the invention.

Tungsten metallizing alumina--yttria ceramics

International Nuclear Information System (INIS)

Cowan, R.E.; Stoddard, S.D.

1977-03-01

The ease with which high-alumina bodies may be metallized with tungsten is improved by additions of yttria to the alumina. Mechanisms of this bonding process were studied by use of optical and electron microscopy, electron microprobe, and tensile tests. Variables studied included yttria content of the body and the firing temperature during metallizing. The study showed that a reaction between the tungsten and the yttrogarnet grain boundary phase markedly improved adherence

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

KAUST Repository

Alhajri, Nawal Saad

2016-02-22

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

Removal of Cobalt Ions by Precipitate Foam Flotation

Energy Technology Data Exchange (ETDEWEB)

Jung, In Ha; Lee, Jung Won [Korea Atomic Energy Research Institute, Taejon (Korea)

1998-09-30

Simulated waste liquid containing 50 ppm cobalt ion was tested by precipitate flotation using a sodium lauryl sulfate as a collector. The effects of initial cobalt ion concentration, pH, surfactant concentration, flotation time, gas flow rate and foreign ions on removal efficiency of cobalt ion were studied. Pretreatment of the waste liquid with 35% H{sub 2}O{sub 2} prior to precipitate flotation made shift of optimal flotation pH from the strong alkalinity to weak alkaline range and made a favorable flotation of cobalt ion in wide range of pH. For the result of this experiment, 99.8% removal efficiency was obtained on the conditions of initial cobalt ion concentration 50 ppm, pH 9.5, gas flow rate 70 ml/min, flotation time 30 min. The simulate ion was formed to be the most harmful ion against removal of cobalt by precipitate flotation of the species which were tested. The presence of 0.1 M of SO{sub 4}{sup 2-} ion decreased removal efficiency of cobalt to 90% while the cobalt were almost entirely removed in the absence of sulfate ion. (author). 11 refs., 8 figs.

Physical metallurgy of tungsten. Metallovedenie vol'frama

Energy Technology Data Exchange (ETDEWEB)

Savitskii, E M; Povarova, K B; Makarov, P V

1978-01-01

The physico-chemical principles of the interaction between tungsten and the elements of the periodic chart are systematized and summarized, and a description is given of the physical and mechanical properties of tungsten and its alloys. An examination is made of the nature of cold brittleness and methods of increasing the plasticity of alloys, means of producing tungsten, methods of purification, alloying, thermal and mechanical processing, and a survey is made of the contemporary use of tungsten and its alloys in advanced sectors of modern technology. The book is designed for personnel at scientific-research institutes, design bureaus and plants, engaged in the development, technology, and use of alloys of refractory metals as well as for instructors, graduate students and senior students taking metal studies and machine building courses, and aeronautical institutions of higher learning. 431 references, 11 tables.

Selective CVD tungsten on silicon implanted SiO/sub 2/

International Nuclear Information System (INIS)

Hennessy, W.A.; Ghezzo, M.; Wilson, R.H.; Bakhru, H.

1988-01-01

The application range of selective CVD tungsten is extended by its coupling to the ion implantation of insulating materials. This article documents the results of selective CVD tungsten using silicon implanted into SiO/sub 2/ to nucleate the tungsten growth. The role of implant does, energy, and surface preparation in achieving nucleation are described. SEM micrographs are presented to demonstrate the selectivity of this process. Measurements of the tungsten film thickness and sheet resistance are provided for each of the experimental variants corresponding to successful deposition. RBS and XPS analysis are discussed in terms of characterizing the tungsten/oxide interface and to evaluate the role of the silicon implant in the CVD tungsten mechanism. Utilizing this method a desired metallization pattern can be readily defined with lithography and ion implantation, and accurately replicated with a layer of CVD tungsten. This approach avoids problems usually associated with blanket deposition and pattern transfer, which are particularly troublesome for submicron VLSI technology

Preparation and study of the nitrides and mixed carbide-nitrides of uranium and of plutonium

International Nuclear Information System (INIS)

Anselin, F.

1966-06-01

A detailed description is given of a simple method for preparing uranium and plutonium nitrides by the direct action of nitrogen under pressure at moderate temperatures (about 400 C) on the partially hydrogenated bulk metal. It is shown that there is complete miscibility between the UN and PuN phases. The variations in the reticular parameters of the samples as a function of temperature and in the presence of oxide have been used to detect and evaluate the solubility of oxygen in the different phases. A study has been made of the sintering of these nitrides as a function of the preparation conditions with or without sintering additives. A favorable but non-reproducible, effect has been found for traces of oxide. The best results were obtained for pure UN at 1600 C (96 per cent theoretical density) on condition that a well defined powder, was used. The criterion used is the integral width of the X-ray diffraction lines. The compounds UN and PuN are completely miscible with the corresponding carbides. This makes it possible to prepare carbide-nitrides of the general formula (U,Pu) (C,N) by solid-phase diffusion, at around 1400 C. The sintering of these carbide-nitrides is similar to that of the carbides if the nitrogen content is low; in particular, nickel is an efficient sintering agent. For high contents, the sintering is similar to that of pure nitrides. (author) [fr

Combustion of powdery tungsten in pyrotechnic mixtures

International Nuclear Information System (INIS)

Ivanov, G.V.; Reshetov, A.A.; Viktorenko, A.M.; Surkov, V.G.; Karmadonov, L.N.

1982-01-01

The basic regularities of tungsten burning (powder 2-5 μm) with oxidizers most typical for pyrotechnics: nitrates, lead and barium peroxides (powder, 2-8 μm) and potassium perchlorate (powder, 2-8 μm) are studied. Dependences of burning rate as a function of pressure and ratio of components are established. It is supposed that tungsten burning in mixtures with the mentioned nitrates is a complex and multistage process the rate of which is determined by tungsten dissolution in nitrate melts. Analysis of burning products using available methods is complex

An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

International Nuclear Information System (INIS)

Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap; Tanemura, Masaki

2016-01-01

The synthesis of large-area monolayer tungsten disulphide (WS 2 ) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS 2 crystals using tungsten hexachloride (WCl 6 ) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl 6 in ethanol was drop-casted on SiO 2 /Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS 2 crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS 2 single crystalline monolayer can be grown using the WCl 6 precursor. Our finding shows an easier and effective approach to grow WS 2 monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction

Tungsten-based composite materials for fusion reactor shields

International Nuclear Information System (INIS)

Greenspan, E.; Karni, Y.

1985-01-01

Composite tungsten-based materials were recently proposed for the heavy constituent of compact fusion reactor shields. These composite materials will enable the incorporation of tungsten - the most efficient nonfissionable inelastic scattering (as well as good neutron absorbing and very good photon attenuating) material - in the shield in a relatively cheap way and without introducing voids (so as to enable minimizing the shield thickness). It is proposed that these goals be achieved by bonding tungsten powder, which is significantly cheaper than high-density tungsten, with a material having the following properties: good shielding ability and relatively low cost and ease of fabrication. The purpose of this work is to study the effectiveness of the composite materials as a function of their composition, and to estimate the economic benefit that might be gained by the use of these materials. Two materials are being considered for the binder: copper, second to tungsten in its shielding ability, and iron (or stainless steel), the common fusion reactor shield heavy constituent

Cobalt: for strength and color

Science.gov (United States)

Boland, Maeve A.; Kropschot, S.J.

2011-01-01

Cobalt is a shiny, gray, brittle metal that is best known for creating an intense blue color in glass and paints. It is frequently used in the manufacture of rechargeable batteries and to create alloys that maintain their strength at high temperatures. It is also one of the essential trace elements (or "micronutrients") that humans and many other living creatures require for good health. Cobalt is an important component in many aerospace, defense, and medical applications and is a key element in many clean energy technologies. The name cobalt comes from the German word kobold, meaning goblin. It was given this name by medieval miners who believed that troublesome goblins replaced the valuable metals in their ore with a substance that emitted poisonous fumes when smelted. The Swedish chemist Georg Brandt isolated metallic cobalt-the first new metal to be discovered since ancient times-in about 1735 and identified some of its valuable properties.

Preparation and characteristics of various rare earth nitrides

International Nuclear Information System (INIS)

Imamura, H.; Imahashi, T.; Zaimi, M.; Sakata, Y.

2008-01-01

Active nanocrystalline nitrides of EuN and YbN with high surface areas were successfully prepared by the thermal decomposition of the rare earth amides (Eu(NH 2 ) 2 , Yb(NH 2 ) 2 and Yb(NH 2 ) 3 ). For the preparation of CeN, PrN and NdN, the direct reaction of the rare earth metals with ammonia was extensively studied to determine optimal conditions. In the reaction of rare earth metals with ammonia, hydrides besides the nitrides were competitively formed. The reaction conditions such as temperatures and ratios of ammonia to rare earth metal were crucial in preferential formation of nitride. The nanocrystalline YbN and EuN readily absorbed large amounts of ammonia even at room temperature upon contact with ammonia (13.3 kPa). The absorbed ammonia existed in at least two forms on/in the nitride; the one was surface-adsorbed ammonia and the other ammonia absorbed in the nitride in a decomposed state. The properties of ammonia absorbed by the nitride were further evaluated by temperature-programmed desorption (TPD), FT-IR and XRD techniques

Computer simulations for thorium doped tungsten crystals

International Nuclear Information System (INIS)

Eberhard, Bernd

2009-01-01

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

Effects of cobalt in nickel-base superalloys

Science.gov (United States)

Tien, J. K.; Jarrett, R. N.

1983-01-01

The role of cobalt in a representative wrought nickel-base superalloy was determined. The results show cobalt affecting the solubility of elements in the gamma matrix, resulting in enhanced gamma' volume fraction, in the stabilization of MC-type carbides, and in the stabilization of sigma phase. In the particular alloy studied, these microstructural and microchemistry changes are insufficient in extent to impact on tensile strength, yield strength, and in the ductilities. Depending on the heat treatment, creep and stress rupture resistance can be cobalt sensitive. In the coarse grain, fully solutioned and aged condition, all of the alloy's 17% cobalt can be replaced by nickel without deleteriously affecting this resistance. In the fine grain, partially solutioned and aged condition, this resistance is deleteriously affected only when one-half or more of the initial cobalt content is removed. The structure and property results are discussed with respect to existing theories and with respect to other recent and earlier findings on the impact of cobalt, if any, on the performance of nickel-base superalloys.

Cobalt: A vital element in the aircraft engine industry

Science.gov (United States)

Stephens, J. R.

1981-01-01

Recent trends in the United States consumption of cobalt indicate that superalloys for aircraft engine manufacture require increasing amounts of this strategic element. Superalloys consume a lion's share of total U.S. cobalt usage which was about 16 million pounds in 1980. In excess of 90 percent of the cobalt used in this country was imported, principally from the African countries of Zaire and Zambia. Early studies on the roles of cobalt as an alloying element in high temperature alloys concentrated on the simple Ni-Cr and Nimonic alloy series. The role of cobalt in current complex nickel base superalloys is not well defined and indeed, the need for the high concentration of cobalt in widely used nickel base superalloys is not firmly established. The current cobalt situation is reviewed as it applies to superalloys and the opportunities for research to reduce the consumption of cobalt in the aircraft engine industry are described.

Method of preparation of uranium nitride

Science.gov (United States)

Kiplinger, Jaqueline Loetsch; Thomson, Robert Kenneth James

2013-07-09

Method for producing terminal uranium nitride complexes comprising providing a suitable starting material comprising uranium; oxidizing the starting material with a suitable oxidant to produce one or more uranium(IV)-azide complexes; and, sufficiently irradiating the uranium(IV)-azide complexes to produce the terminal uranium nitride complexes.

Tungsten deposition by hydrogen-atom reaction with tungsten hexafluoride

International Nuclear Information System (INIS)

Lee, W.W.

1991-01-01

Using gaseous hydrogen atoms with WF 6 , tungsten atoms can be produced in a gas-phase reaction. The atoms then deposit in a near-room temperature process, which results in the formation of tungsten films. The W atoms (10 10 -10 11 /cm 3 ) were measured in situ by atomic absorption spectroscopy during the CVD process. Deposited W films were characterized by Auger electron spectroscopy, Rutherford backscattering, and X-ray diffraction. The surface morphology of the deposited films and filled holes was studied using scanning electron microscopy. The deposited films were highly adherent to different substrates, such as Si, SiO 2 , Ti/Si, TiN/Si and Teflon. The reaction mechanism and kinetics were studied. The experimental results indicated that this method has three advantages compared to conventional CVD or PECVD: (1) film growth occurs at low temperatures; (2) deposition takes place in a plasma-free environment; and (3) a low level of impurities results in high-quality adherent films

Modeling of hydrogen desorption from tungsten surface

Energy Technology Data Exchange (ETDEWEB)

Guterl, J., E-mail: jguterl@ucsd.edu [University of California, San Diego, La Jolla, CA 92093 (United States); Smirnov, R.D. [University of California, San Diego, La Jolla, CA 92093 (United States); Krasheninnikov, S.I. [University of California, San Diego, La Jolla, CA 92093 (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation); Uberuaga, B.; Voter, A.F.; Perez, D. [Los Alamos National Laboratory, Los Alamos, NM 8754 (United States)

2015-08-15

Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed.

Microstructural Characterization of Low Temperature Gas Nitrided Martensitic Stainless Steel

DEFF Research Database (Denmark)

Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.

2015-01-01

The present work presents microstructural investigations of the surface zone of low temperature gas nitrided precipitation hardening martensitic stainless steel AISI 630. Grazing incidence X-ray diffraction was applied to investigate the present phases after successive removal of very thin sections...... of the sample surface. The development of epsilon nitride, expanded austenite and expanded martensite resulted from the low temperature nitriding treatments. The microstructural features, hardness and phase composition are discussed with emphasis on the influence of nitriding duration and nitriding potential....

Feasibility Study for Cobalt Bundle Loading to CANDU Reactor Core

International Nuclear Information System (INIS)

Park, Donghwan; Kim, Youngae; Kim, Sungmin

2016-01-01

CANDU units are generally used to produce cobalt-60 at Bruce and Point Lepreau in Canada and Embalse in Argentina. China has started production of cobalt-60 using its CANDU 6 Qinshan Phase III nuclear power plant in 2009. For cobalt-60 production, the reactor’s full complement of stainless steel adjusters is replaced with neutronically equivalent cobalt-59 adjusters, which are essentially invisible to reactor operation. With its very high neutron flux and optimized fuel burn-up, the CANDU has a very high cobalt-60 production rate in a relatively short time. This makes CANDU an excellent vehicle for bulk cobalt-60 production. Several studies have been performed to produce cobalt-60 using adjuster rod at Wolsong nuclear power plant. This study proposed new concept for producing cobalt-60 and performed the feasibility study. Bundle typed cobalt loading concept is proposed and evaluated the feasibility to fuel management without physics and system design change. The requirement to load cobalt bundle to the core was considered and several channels are nominated. The production of cobalt-60 source is very depend on the flux level and burnup directly. But the neutron absorption characteristic of cobalt bundle is too high, so optimizing design study is needed in the future

Feasibility Study for Cobalt Bundle Loading to CANDU Reactor Core

Energy Technology Data Exchange (ETDEWEB)

Park, Donghwan; Kim, Youngae; Kim, Sungmin [KHNP Central Research Institute, Daejeon (Korea, Republic of)

2016-10-15

CANDU units are generally used to produce cobalt-60 at Bruce and Point Lepreau in Canada and Embalse in Argentina. China has started production of cobalt-60 using its CANDU 6 Qinshan Phase III nuclear power plant in 2009. For cobalt-60 production, the reactor’s full complement of stainless steel adjusters is replaced with neutronically equivalent cobalt-59 adjusters, which are essentially invisible to reactor operation. With its very high neutron flux and optimized fuel burn-up, the CANDU has a very high cobalt-60 production rate in a relatively short time. This makes CANDU an excellent vehicle for bulk cobalt-60 production. Several studies have been performed to produce cobalt-60 using adjuster rod at Wolsong nuclear power plant. This study proposed new concept for producing cobalt-60 and performed the feasibility study. Bundle typed cobalt loading concept is proposed and evaluated the feasibility to fuel management without physics and system design change. The requirement to load cobalt bundle to the core was considered and several channels are nominated. The production of cobalt-60 source is very depend on the flux level and burnup directly. But the neutron absorption characteristic of cobalt bundle is too high, so optimizing design study is needed in the future.

Pyrochemical reprocessing of nitride fuel

International Nuclear Information System (INIS)

Nakazono, Yoshihisa; Iwai, Takashi; Arai, Yasuo

2004-01-01

Electrochemical behavior of actinide nitrides in LiCl-KCl eutectic melt was investigated in order to apply pyrochemical process to nitride fuel cycle. The electrode reaction of UN and (U, Nd)N was examined by cyclic voltammetry. The observed rest potential of (U, Nd)N depended on the equilibrium of U 3+ /UN and was not affected by the addition of NdN of 8 wt.%. (author)

Nickel, cobalt, and their alloys

CERN Document Server

2000-01-01

This book is a comprehensive guide to the compositions, properties, processing, performance, and applications of nickel, cobalt, and their alloys. It includes all of the essential information contained in the ASM Handbook series, as well as new or updated coverage in many areas in the nickel, cobalt, and related industries.

Cobalt sorption onto Savannah River Plant soils

International Nuclear Information System (INIS)

Hoeffner, S.L.

1985-06-01

A laboratory study of cobalt-60 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that cobalt sorption is most strongly a function of pH. Over a pH range of 2 to 9, the distribution coefficient ranged from 2 to more than 10,000 mL/g. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence cobalt sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect on cobalt sorption. Ferrous ion, added to groundwater to simulate the condition of water at the bottom of the waste trenches, accounts for part of the decrease in cobalt sorption observed with trench waters. 17 refs., 3 figs., 4 tabs

Substitution of thoriated tungsten electrodes in Switzerland

International Nuclear Information System (INIS)

Kunz, H.; Piller, G.

2006-01-01

Thoriated tungsten electrodes are frequently used for inert gas welding (TIG/WIG). The use of these electrodes can lead to doses which are well above the limit for the general population (1mSv/year). This has been shown by different investigations, for example from the ''Berufsgenossenschaft''. With these findings in mind, the regulatory authorities (Swiss Federal Office of Public Health (SFOPH) and Swiss National Accident Insurance Association (Suva)) started in 1999 to examine the justification of thoriated tungsten electrodes and a possible substitution with products containing no radioactive material. Up to this time, the use of thoriated tungsten electrodes could be justified since no thorium-free products leading to comparable results were available on the market. This was also the reason why the SFOPH approved several types of these electrodes. Discussions with formation centers for welding and inquiries made at welding shops, trading companies and producers showed that in the mean-time thorium-free products with comparable welding specifications and results became available on the market. Since the 1 January 2004, thoriated tungsten electrodes can only be used if the user has obtained the corresponding license from the SFOPH. The use of thoriated tungsten electrodes is thus not completely forbidden, but very strict conditions have to be fulfilled. Up to now and due to the involvement of the relevant partners, the substitution process has not met any problem. Neither trading companies nor users made any opposition and no request for obtaining a license for thoriated tungsten electrodes was made. (orig.)

Titanium nitride deposition in titanium implant alloys produced by powder metallurgy

International Nuclear Information System (INIS)

Henriques, V.A.R.; Cairo, C.A.A.; Faria, J.; Lemos, T.G.; Galvani, E.T.

2009-01-01

Titanium nitride (TiN) is an extremely hard material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve wear resistance. Electron Beam Physical Vapor Deposition (EB-PVD) is a form of deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work are presented results of TiN deposition in targets and substrates of Ti (C.P.) and Ti- 13 Nb- 13 Zr obtained by powder metallurgy. Samples were produced by mixing of hydride metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900°C up to 1400 °C, in vacuum. The deposition was carried out under nitrogen atmosphere. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure, with ideal characteristics for an adequate deposition and adherence. The film layer presented a continuous structure with 15μm. (author)

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.

Manipulating radicals: Using cobalt to steer radical reactions

OpenAIRE

Chirilă, A.

2017-01-01

This thesis describes research aimed at understanding and exploiting metallo-radical reactivity and explores reactions mediated by square planar, low-spin cobalt(II) complexes. A primary goal was to uncover novel reactivity of discrete cobalt(III)-bound carbene radicals generated upon reaction of the cobalt(II) catalysts with carbene precursors. Another important goal was to replace cobalt(II)-porphyrin catalysts with cheaper and easier to prepare metallo-radical analogues. Therefore the cata...

Fusion bonding of silicon nitride surfaces

DEFF Research Database (Denmark)

Reck, Kasper; Østergaard, Christian; Thomsen, Erik Vilain

2011-01-01

While silicon nitride surfaces are widely used in many micro electrical mechanical system devices, e.g. for chemical passivation, electrical isolation or environmental protection, studies on fusion bonding of two silicon nitride surfaces (Si3N4–Si3N4 bonding) are very few and highly application...

EDITORIAL: Non-polar and semipolar nitride semiconductors Non-polar and semipolar nitride semiconductors

Science.gov (United States)

Han, Jung; Kneissl, Michael

2012-02-01

Throughout the history of group-III-nitride materials and devices, scientific breakthroughs and technological advances have gone hand-in-hand. In the late 1980s and early 1990s, the discovery of the nucleation of smooth (0001) GaN films on c-plane sapphire and the activation of p-dopants in GaN led very quickly to the realization of high-brightness blue and green LEDs, followed by the first demonstration of GaN-based violet laser diodes in the mid 1990s. Today, blue InGaN LEDs boast record external quantum efficiencies exceeding 80% and the emission wavelength of the InGaN-based laser diode has been pushed into the green spectral range. Although these tremenduous advances have already spurred multi-billion dollar industries, there are still a number of scientific questions and technological issues that are unanswered. One key challenge is related to the polar nature of the III-nitride wurtzite crystal. Until a decade ago all research activities had almost exclusively concentrated on (0001)-oriented polar GaN layers and heterostructures. Although the device characteristics seem excellent, the strong polarization fields at GaN heterointerfaces can lead to a significant deterioration of the device performance. Triggered by the first demonstration non-polar GaN quantum wells grown on LiAlO2 by Waltereit and colleagues in 2000, impressive advances in the area of non-polar and semipolar nitride semiconductors and devices have been achieved. Today, a large variety of heterostructures free of polarization fields and exhibiting exceptional electronic and optical properties have been demonstrated, and the fundamental understanding of polar, semipolar and non-polar nitrides has made significant leaps forward. The contributions in this Semiconductor Science and Technology special issue on non-polar and semipolar nitride semiconductors provide an impressive and up-to-date cross-section of all areas of research and device physics in this field. The articles cover a wide range of

Plasma nitridation optimization for sub-15 A gate dielectrics

NARCIS (Netherlands)

Cubaynes, F.N; Schmitz, Jurriaan; van der Marel, C.; Snijders, J.H.M.; Veloso, A.; Rothschild, A.; Olsen, C.; Date, L.

The work investigates the impact of plasma nitridation process parameters upon the physical properties and upon the electrical performance of sub-15 A plasma nitrided gate dielectrics. The nitrogen distribution and chemical bonding of ultra-thin plasma nitrided films have been investigated using

Diagnostic of corrosion–erosion evolution for [Hf-Nitrides/V-Nitrides]n structures

Energy Technology Data Exchange (ETDEWEB)

Escobar, C.; Villarreal, M. [Thin Film Group, Universidad del Valle, A.A. 25360, Cali (Colombia); Caicedo, J.C., E-mail: jcaicedoangulo1@gmail.com [Powder Metallurgy and Processing of Solid Recycled Research Group, Universidad del Valle, Cali (Colombia); Aperador, W. [Ingeniería Mecatrónica, Universidad Militar Nueva Granada, Bogotá (Colombia); Caicedo, H.H. [Department of Bioengineering, University of Illinois at Chicago, IL 60612 (United States); Department of Anatomy and Cell Biology, University of Illinois at Chicago, IL 60612 (United States); Prieto, P. [Thin Film Group, Universidad del Valle, A.A. 25360, Cali (Colombia); Center of Excellence for Novel Materials, CENM, Cali (Colombia)

2013-10-31

HfN/VN multilayered systems were grown on 4140 steel substrates with the aim to improve their electrochemical behavior. The multilayered coatings were grown via reactive r.f. magnetron sputtering technique by systematically varying the bilayer period (Λ) and the bilayer number (n) while maintaining constant the total coating thickness (∼ 1.2 μm). The coatings were characterized by X-ray diffraction (XRD), and electron microscopy. The electrochemical properties were studied by Electrochemical Impedance Spectroscopy and Tafel curves. XRD results showed preferential growth in the face-centered cubic (111) crystal structure for [HfN/VN]{sub n} multilayered coatings. The maximum corrosion resistance was obtained for coatings with (Λ) equal to 15 nm, corresponding to bilayer n = 80. Polarization resistance and corrosion rate was around 112.19 kΩ cm{sup 2} and 0.094*10{sup −3} mmy respectively; moreover, these multilayered system showed a decrease of 80% on mass loss due to the corrosive–erosive process, in relation to multilayered systems with n = 1 and Λ = 1200. HfN/VN multilayers have been designed and deposited on Si (100) and AISI 4140 steel substrates with bilayer periods (Λ) in a broad range, from nanometers to hundreds of nanometers to study the microstructural evolution and electrochemical progress with decreasing bilayer thickness. - Highlights: • Enhancements on surface electrochemical properties and response to surface corrosion attack. • Superficial phenomenon that occurs in corrosion surface of [Hf-Nitrides/V-Nitrides]n • Corrosion–erosion evolution for [Hf-Nitrides/V-Nitrides]n structures.

Diagnostic of corrosion–erosion evolution for [Hf-Nitrides/V-Nitrides]n structures

International Nuclear Information System (INIS)

Escobar, C.; Villarreal, M.; Caicedo, J.C.; Aperador, W.; Caicedo, H.H.; Prieto, P.

2013-01-01

HfN/VN multilayered systems were grown on 4140 steel substrates with the aim to improve their electrochemical behavior. The multilayered coatings were grown via reactive r.f. magnetron sputtering technique by systematically varying the bilayer period (Λ) and the bilayer number (n) while maintaining constant the total coating thickness (∼ 1.2 μm). The coatings were characterized by X-ray diffraction (XRD), and electron microscopy. The electrochemical properties were studied by Electrochemical Impedance Spectroscopy and Tafel curves. XRD results showed preferential growth in the face-centered cubic (111) crystal structure for [HfN/VN] n multilayered coatings. The maximum corrosion resistance was obtained for coatings with (Λ) equal to 15 nm, corresponding to bilayer n = 80. Polarization resistance and corrosion rate was around 112.19 kΩ cm 2 and 0.094*10 −3 mmy respectively; moreover, these multilayered system showed a decrease of 80% on mass loss due to the corrosive–erosive process, in relation to multilayered systems with n = 1 and Λ = 1200. HfN/VN multilayers have been designed and deposited on Si (100) and AISI 4140 steel substrates with bilayer periods (Λ) in a broad range, from nanometers to hundreds of nanometers to study the microstructural evolution and electrochemical progress with decreasing bilayer thickness. - Highlights: • Enhancements on surface electrochemical properties and response to surface corrosion attack. • Superficial phenomenon that occurs in corrosion surface of [Hf-Nitrides/V-Nitrides]n • Corrosion–erosion evolution for [Hf-Nitrides/V-Nitrides]n structures

Vaporization of tungsten-metal in steam at high temperatures

International Nuclear Information System (INIS)

Greene, G.A.; Finfrock, C.C.

2000-01-01

The vaporization of tungsten from the APT spallation target dominates the radiological source term for unmitigated target overheating accidents. Chemical reactions of tungsten with steam which persist to tungsten temperatures as low as 800 C result in the formation of a hydrated tungsten-oxide which has a high vapor pressure and is readily convected in a flowing atmosphere. This low-temperature vaporization reaction essentially removes the oxide film that forms on the tungsten-metal surface as soon as it forms, leaving behind a fresh metallic surface for continued oxidation and vaporization. Experiments were conducted to measure the oxidative vaporization rates of tungsten in steam as part of the effort to quantify the MT radiological source term for severe target accidents. Tests were conducted with tungsten rods (1/8 inch diameter, six inches long) heated to temperatures from approximately 700 C to 1350 C in flowing steam which was superheated to 140 C. A total of 19 experiments was conducted. Fifteen tests were conducted by RF induction heating of single tungsten rods held vertical in a quartz glass retort. Four tests were conducted in a vertically-mounted tube furnace for the low temperature range of the test series. The aerosol which was generated and transported downstream from the tungsten rods was collected by passing the discharged steam through a condenser. This procedure insured total collection of the steam along with the aerosol from the vaporization of the rods. The results of these experiments revealed a threshold temperature for tungsten vaporization in steam. For the two tests at the lowest temperatures which were tested, approximately 700 C, the tungsten rods were observed to oxidize without vaporization. The remainder of the tests was conducted over the temperature range of 800 C to 1350 C. In these tests, the rods were found to have lost weight due to vaporization of the tungsten and the missing weight was collected in the downstream condensate

Transport of cobalt-60 industrial radiation sources

Science.gov (United States)

Kunstadt, Peter; Gibson, Wayne

This paper will deal with safety aspects of the handling of Cobalt-60, the most widely used industrial radio-isotope. Cobalt-60 is a man-made radioisotope of Cobalt-59, a naturally occurring non radioactive element, that is made to order for radiation therapy and a wide range of industrial processing applications including sterilization of medical disposables, food irradiation, etc.

Fabrication and evaluation of chemically vapor deposited tungsten heat pipe.

Science.gov (United States)

Bacigalupi, R. J.

1972-01-01

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

Comparison of four tungsten alloys for use as ultrasonic thermometer sensors

International Nuclear Information System (INIS)

Arave, A.E.

1975-06-01

Four tungsten alloy materials were evaluated for use as ultrasonic sensors: (a) tungsten, (b) tungsten-1 percent thoria, (c) tungsten-2 percent thoria, and (d) tungsten-26 percent rhenium. Four parameters were checked: (1) temperature sensitivity, (2) signal attenuation as a function of temperature, (3) temperature sensitivity as a function of frequency, and (4) relative signal attenuation as a function of frequency. The temperature sensors were designed for the Loss-of-Fluid Test (LOFT) and Power Burst Facility (PBF) reactors. (U.S.)

The physiological effect of cobalt on watermelon cultivation

International Nuclear Information System (INIS)

Yao Naihua; Jin Yafang; Sun Yaochen; Huang Yiming

1993-01-01

Cobalt has essential physiological action on both animals and plants. For the latter it can raise plant's nitrogen-fixing ability and saccharine content. Spray of cobalt mixed with other nutritive elements can improve the germinatit of seeds and the yield of fruit. For specifying the nutritive function of cobalt upon watermelon, isotope 60 Co was mixed into a complex leaf nutritive aqua and the regularity of transferring and absorbing cobalt in the watermelon's body was investigated

Relaxation resistance of heat resisting alloys with cobalt

International Nuclear Information System (INIS)

Borzdyka, A.M.

1977-01-01

Relaxation resistance of refractory nickel-chromium alloys containing 5 to 14 % cobalt is under study. The tests involve the use of circular samples at 800 deg to 850 deg C. It is shown that an alloy containing 14% cobalt possesses the best relaxation resistance exceeding that of nickel-chromium alloys without any cobalt by a factor of 1.5 to 2. The relaxation resistance of an alloy with 5% cobalt can be increased by hardening at repeated loading

Nano-particulate Aluminium Nitride/Al: An Efficient and Versatile Heterogeneous Catalyst for the Synthesis of Biginelli Scaffolds

Science.gov (United States)

Tekale, S. U.; Tekale, A. B.; Kanhe, N. S.; Bhoraskar, S. V.; Pawar, R. P.

2011-12-01

Nano-particulate aluminium nitride/Al (7:1) is reported as a new heterogeneous solid acid catalyst for the synthesis of 3, 4-dihydroxypyrimidi-2-(1H)-ones and their sulphur analogues using the Biginelli reaction. This method involves short reaction time, easy separation, high yields and purity of products.

New doped tungsten cathodes. Applications to power grid tubes

International Nuclear Information System (INIS)

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

2001-01-01

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

Deuterium transport and trapping in polycrystalline tungsten

International Nuclear Information System (INIS)

Anderl, R.A.; Holland, D.F.; Longhurst, G.R.; Pawelko, R.J.; Trybus, C.L.; Sellers, C.H.

1992-01-01

This paper reports that deuterium permeation studies for polycrystalline tungsten foil have been conducted to provide data for estimating tritium transport and trapping in tungsten-clad divertors proposed for advanced fusion-reactor concepts. Based on a detailed transmission electron microscopy (TEM) microstructural characterization of the specimen material and on analyses of permeation data measured at temperatures ranging form 610 to 823 K for unannealed and annealed tungsten foil (25 μm thick), the authors note the following key results: deuterium transport in tungsten foil is dominated by extensive trapping that varies inversely with prior anneal temperatures of the foil material, the reduction in the trapped fraction correlates with a corresponding elimination of a high density of dislocations in cell-wall structures introduced during the foil fabrication process, trapping behavior in these foils can be modelled using trap energies between 1.3 eV and 1.5 eV and trap densities ranging from 1 x 10 -5 atom fraction

Corrosion of high-density sintered tungsten alloys

International Nuclear Information System (INIS)

Batten, J.J.; Moore, B.T.

1989-01-01

In comparative corrosion tests, the corrosion resistance of an Australian tungsten alloy (95% W, 3.5% Ni, 1.5% Fe) was found to be superior to three other tungsten alloys and, under certain conditions, even more corrosion-resistant than pure tungsten. Corrosion resistance was evaluated after immersion in both distilled water and 5% sodium chloride solutions, and in cyclic humidity and salt mist environments. For all but the Australian alloy, the rate of corrosion in sodium chloride solution was markedly less than that in distilated water. In all cases, alloys containing copper had the greatest corrosion rates. Corrosion mechanisms were investigated using a scanning electron microscope, analysis of corrosion products and galvanic corrosion studies. For the alloys, corrosion was attributed primarily to a galvanic reaction. Whether the tungsten or binder phase of the alloy became anodic, and thus was attacked preferentially, depended upon alloy composition and corrosion environment. 16 refs., 4 tabs., 4 figs

Mesoporous coaxial titanium nitride-vanadium nitride fibers of core-shell structures for high-performance supercapacitors.

Science.gov (United States)

Zhou, Xinhong; Shang, Chaoqun; Gu, Lin; Dong, Shanmu; Chen, Xiao; Han, Pengxian; Li, Lanfeng; Yao, Jianhua; Liu, Zhihong; Xu, Hongxia; Zhu, Yuwei; Cui, Guanglei

2011-08-01

In this study, titanium nitride-vanadium nitride fibers of core-shell structures were prepared by the coaxial electrospinning, and subsequently annealed in the ammonia for supercapacitor applications. These core-shell (TiN-VN) fibers incorporated mesoporous structure into high electronic conducting transition nitride hybrids, which combined higher specific capacitance of VN and better rate capability of TiN. These hybrids exhibited higher specific capacitance (2 mV s(-1), 247.5 F g(-1)) and better rate capability (50 mV s(-1), 160.8 F g(-1)), which promise a good candidate for high-performance supercapacitors. It was also revealed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) characterization that the minor capacitance fade originated from the surface oxidation of VN and TiN.

Additive Manufacturing of Dense Hexagonal Boron Nitride Objects

Energy Technology Data Exchange (ETDEWEB)

Marquez Rossy, Andres E [ORNL; Armstrong, Beth L [ORNL; Elliott, Amy M [ORNL; Lara-Curzio, Edgar [ORNL

2017-05-12

The feasibility of manufacturing hexagonal boron nitride objects via additive manufacturing techniques was investigated. It was demonstrated that it is possible to hot-extrude thermoplastic filaments containing uniformly distributed boron nitride particles with a volume concentration as high as 60% and that these thermoplastic filaments can be used as feedstock for 3D-printing objects using a fused deposition system. Objects 3D-printed by fused deposition were subsequently sintered at high temperature to obtain dense ceramic products. In a parallel study the behavior of hexagonal boron nitride in aqueous solutions was investigated. It was shown that the addition of a cationic dispersant to an azeotrope enabled the formulation of slurries with a volume concentration of boron nitride as high as 33%. Although these slurries exhibited complex rheological behavior, the results from this study are encouraging and provide a pathway for manufacturing hexagonal boron nitride objects via robocasting.

Incorporation of tungsten metal fibers in a metal and ceramic matrix

Directory of Open Access Journals (Sweden)

V. Brozek

2017-01-01

Full Text Available Tungsten fibers have high tensile strength but a poor oxidation resistance at elevated temperatures. Using this first characteristic and to prevent oxidation of tungsten coated composite materials in which the primary requirement: reinforcement against destruction or deformation, was studied on tungsten fibers and tungsten wires which were coated by applying the metal and ceramic powders via plasma spraying device in plasma generator WSP®. Deposition took place in an atmosphere of Ar + 7 % H2, sufficient to reduce the oxidized trace amounts of tungsten.

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

Aluminum nitride insulating films for MOSFET devices

Science.gov (United States)

Lewicki, G. W.; Maserjian, J.

1972-01-01

Application of aluminum nitrides as electrical insulator for electric capacitors is discussed. Electrical properties of aluminum nitrides are analyzed and specific use with field effect transistors is defined. Operational limits of field effect transistors are developed.

Heating-induced inner-sphere substitution and reduction-oxidation reactions of the solid phenanthroline containing cobalt (2) and cobalt (3) complexes

International Nuclear Information System (INIS)

Palade, D.M.

1996-01-01

The results of the differential thermal and thermogravimetric analyses of solid phenanthroline-containing complexes of cobalt (2) and cobalt (3) in the atmosphere of the air have been analyzed. Mechanism of redox reactions occurring when cobalt (3) complexes are heated has been discussed. It is shown that some of gaseous products of the redox processes appear as a result of secondary reactions and not the processes of the ligands oxidation by Co 3+ . The influence of certain inner-sphere and coordinated anions (of I, inclusively) on cobalt (3) complexes behaviour during heating has been considered

Capacitive performance of molybdenum nitride/titanium nitride nanotube array for supercapacitor

Energy Technology Data Exchange (ETDEWEB)

Xie, Yibing, E-mail: ybxie@seu.edu.cn; Tian, Fang

2017-01-15

Highlights: • MoN{sub x}/TiN NTA is fully converted from MoO{sub 2}/TiO{sub 2} NTA by one-step nitridation process. • MoN{sub x}/TiN NTA is used as feasible electrode material of high-performance supercapacitor. • MoN{sub x}/TiN NTA shows high capacitance, rate capability and cycling stability. - Abstract: Molybdenum nitride (MoN{sub x}) depositing on titanium nitride nanotube array (TiN NTA) was designed as MoN{sub x}/TiN NTA for supercapacitor electrode material. MoN{sub x}/TiN NTA was fabricated by electrodepositing molybdenum oxide onto titanium dioxide NTA and one-step nitridation treatment in ammonia. MoN{sub x}/TiN NTA involved top-surface layer of MoN{sub x} nanoparticles and underlying layer of TiN NTA, which contributed to electric double layer capacitance in aqueous lithium-ion electrolyte solution. The specific capacitance was increased from 69.05 mF cm{sup −2} for TiN NTA to 121.50 mF cm{sup −2} for MoN{sub x}/TiN NTA at 0.3 mA cm{sup −2}, presenting the improved capacitance performance. MoN{sub x} exhibited the capacitance of 174.83 F g{sup −1} at 1.5 A g{sup −1} and slightly declined to 109.13 F g{sup −1} at 30 A g{sup −1}, presenting high rate capability. MoN{sub x}/TiN NTA exhibited the capacitance retention ratio of 93.8% at 3.0 mA cm{sup −2} after 1000 cycles, presenting high cycling stability. MoN{sub x}/TiN NTA could act as a promising electrode material of supercapacitor.

An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

Energy Technology Data Exchange (ETDEWEB)

Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp; Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2016-02-01

The synthesis of large-area monolayer tungsten disulphide (WS{sub 2}) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS{sub 2} crystals using tungsten hexachloride (WCl{sub 6}) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl{sub 6} in ethanol was drop-casted on SiO{sub 2}/Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS{sub 2} crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS{sub 2} single crystalline monolayer can be grown using the WCl{sub 6} precursor. Our finding shows an easier and effective approach to grow WS{sub 2} monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction.

Ab initio and DFT benchmarking of tungsten nanoclusters and tungsten hydrides

International Nuclear Information System (INIS)

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

2015-01-01

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

Nitride coating enhances endothelialization on biomedical NiTi shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Ion, Raluca [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Luculescu, Catalin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, 077125 Magurele-Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Marx, Philippe [AMF Company, Route de Quincy, 18120 Lury-sur-Arnon (France); Gordin, Doina-Margareta; Gloriant, Thierry [INSA Rennes, UMR CNRS 6226 ISCR, 20 Avenue des Buttes de Coësmes, 35708 Rennes Cedex 7 (France)

2016-05-01

Surface nitriding was demonstrated to be an effective process for improving the biocompatibility of implantable devices. In this study, we investigated the benefits of nitriding the NiTi shape memory alloy for vascular stent applications. Results from cell experiments indicated that, compared to untreated NiTi, a superficial gas nitriding treatment enhanced the adhesion of human umbilical vein endothelial cells (HUVECs), cell spreading and proliferation. This investigation provides data to demonstrate the possibility of improving the rate of endothelialization on NiTi by means of nitride coating. - Highlights: • Gas nitriding process of NiTi is competent to promote cell spreading. • Surface nitriding of NiTi is able to stimulate focal adhesion formation and cell proliferation. • Similar expression pattern of vWf and eNOS was exhibited by bare and nitrided NiTi. • Gas nitriding treatment of NiTi shows promise for better in vivo endothelialization.

Gleeble Testing of Tungsten Samples

Science.gov (United States)

2013-02-01

temperature on an Instron load frame with a 222.41 kN (50 kip) load cell . The samples were compressed at the same strain rate as on the Gleeble...ID % RE Initial Density (cm 3 ) Density after Compression (cm 3 ) % Change in Density Test Temperature NT1 0 18.08 18.27 1.06 1000 NT3 0...4.1 Nano-Tungsten The results for the compression of the nano-tungsten samples are shown in tables 2 and 3 and figure 5. During testing, sample NT1

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.

Control of carbon nanotube growth using cobalt nanoparticles as catalyst

International Nuclear Information System (INIS)

Huh, Yoon; Green, Malcolm L.H.; Kim, Young Heon; Lee, Jeong Yong; Lee, Cheol Jin

2005-01-01

We have controllably grown carbon nanotubes using uniformly distributed cobalt nanoparticles as catalyst. Cobalt nanoparticles with a uniform size were synthesized by chemical reaction and colloidal solutions including the cobalt nanoparticles were prepared. The cobalt nanoparticles were uniformly distributed on silicon substrates by a spin-coating method. Carbon nanotubes with a uniform diameter were synthesized on the cobalt nanoparticles by thermal chemical vapor deposition of acetylene gas. The density and vertical alignment of carbon nanotubes could be controlled by adjusting the density of cobalt (Co) nanoparticles

Novel hard compositions and methods of preparation

Science.gov (United States)

Sheinberg, H.

1983-08-23

Novel very hard compositions of matter are prepared by using in all embodiments only a minor amount of a particular carbide (or materials which can form the carbide in situ when subjected to heat and pressure); and no strategic cobalt is needed. Under a particular range of conditions, densified compositions of matter of the invention are prepared having hardnesses on the Rockwell A test substantially equal to the hardness of pure tungsten carbide and to two of the hardest commercial cobalt-bonded tungsten carbides. Alternately, other compositions of the invention which have slightly lower hardnesses than those described above in one embodiment also possess the advantage of requiring no tungsten and in another embodiment possess the advantage of having a good fracture toughness value. Photomicrographs show that the shapes of the grains of the alloy mixture with which the minor amount of carbide (or carbide-formers) is mixed are radically altered from large, rounded to small, very angular by the addition of the carbide. Superiority of one of these hard compositions of matter over cobalt-bonded tungsten carbide for ultra-high pressure anvil applications was demonstrated. 3 figs.

In-situ field-ion microscope study of the recovery behavior of heavy metal ion-irradiated tungsten, tungsten (rhenium) alloys and molybdenum

International Nuclear Information System (INIS)

Nielsen, C.H.

1977-06-01

Three field ion microscope (FIM) experiments were carried out to study the annealing behavior of heavy ion irradiated tungsten, tungsten (rhenium) alloys and molybdenum. The first experiment dealt with the stage I long-range migration of tungsten self interstitial atoms (SIAs) in high purity tungsten of resistivity ratio, R = 24,000 (R = rho 300 /rho 4 . 2 , where rho 300 and rho 4 . 2 are the room temperature and 0 0 C resistivities). The FIM specimens were irradiated in situ at 18 K with 30 keV W + ions to an average dose of 5 x 10 12 ions cm -2 and subsequently examined by the pulsed-field evaporation technique. The second experiment dealt with the phenomenon of impurity atom trapping of SIAs during long-range migration. It was shown that rhenium atoms in a tungsten matrix tend to capture tungsten SIAs and remain bound up to temperatures as high as 390 K. The final experiment was concerned with the low temperature annealing kinetics of irradiated molybdenum. High purity molybdenum of resistivity ratio R = 5700 was irradiated at 10 K with 30 keV Mo + ions to a dose of approximately 5 x 10 12 ions cm -2 . The results indicated that the electric field has only a minimal effect on the SIA annealing kinetics. This tends to strengthen the contention that the molybdenum SIA becomes mobile at 32 K

Electrochemical behavior of rare earth metals and their nitrides

International Nuclear Information System (INIS)

Ito, Yasuhiko; Goto, Takuya

2004-01-01

Pyrometallurgical recycle process using molten salts is considered to be a high potential in pyro-reprocess technologies for spent nitride fuels, and it is important to understand chemical and electro-chemical behavior of nitrides and metals in molten salts. In this study, cadmium nitrates deposited on the anode Cd plate in motlen salt (LiCl-KCl) with addition of Li 3 N are examined. The cadmium nitrates deposited have various compositions corresponding to polarization potentials and then, the relationship between the deposition potential of nitride Cd and their composition is cleared. Their standard chemical potential of CdN is estimated from electrochemical measurement. And then, potential-pH 3- diagram is drawn by voltametry examination of nitride resolution behavior with using thermochemical data of nitrides. (A. Hishinuma)

Dosing of anaerobic granular sludge bioreactors with cobalt: Impact of cobalt retention on methanogenic activity

KAUST Repository

Fermoso, Fernando G.

2010-12-01

The effect of dosing a metal limited anaerobic sludge blanket (UASB) reactor with a metal pulse on the methanogenic activity of granular sludge has thus far not been successfully modeled. The prediction of this effect is crucial in order to optimize the strategy for metal dosage and to prevent unnecessary losses of resources. This paper describes the relation between the initial immobilization of cobalt in anaerobic granular sludge cobalt dosage into the reactor and the evolution of methanogenic activity during the subsequent weeks. An operationally defined parameter (A0· B0) was found to combine the amount of cobalt immobilized instantaneously upon the pulse (B0) and the amount of cobalt immobilized within the subsequent 24. h (A0). In contrast with the individual parameters A0 and B0, the parameter A0· B0 correlated significantly with the methanogenic activity of the sludge during the subsequent 16 or 35. days. This correlation between metal retention and activity evolution is a useful tool to implement trace metal dosing strategies for biofilm-based biotechnological processes. © 2010.

Leachability of nitrided ilmenite in hydrochloric acid

CSIR Research Space (South Africa)

Swanepoel, JJ

2010-10-01

Full Text Available Titanium nitride in upgraded nitrided ilmenite (bulk of iron removed) can selectively be chlorinated to produce titanium tetrachloride. Except for iron, most other components present during this low temperature (ca. 200 °C) chlorination reaction...

Formation of carbon containing layers on tungsten test limiters

International Nuclear Information System (INIS)

Rubel, M.; Philipps, V.; Huber, A.; Tanabe, T.

1999-01-01

Tungsten test limiters of mushroom shape and a plasma facing area of approximately 100 cm 2 were exposed at the TEXTOR-94 tokamak to a number of deuterium fuelled discharges performed under various operation conditions. Two types of limiters were tested: a sole tungsten limiter and a twin limiter consisting of two halves, one made of tungsten and another of graphite. The exposed surfaces were examined with ion beam analysis methods and laser profilometry. The formation of some deposition zones was observed near the edges of the limiters. The deuterium-to-carbon concentration ratio was in the range from 0.04 to 0.11 and around 0.2 for the sole tungsten and the twin limiter, respectively. Significant amounts of the co-deposited tungsten and silicon atoms were found on the graphite part of the twin limiter indicating the formation of mixed W-C-Si compounds. (orig.)

Thermodynamics, kinetics and process control of nitriding

DEFF Research Database (Denmark)

Mittemeijer, Eric J.; Somers, Marcel A. J.

1999-01-01

As a prerequisite for predictability of properties obtained by a nitriding treatment of iron-based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present (even) the description of thermodynamic equilibrium...... of pure iron-nitrogen phases has not been achieved fully. It has been shown that taking into account ordering of nitrogen in the epsilon and gamma' iron-nitride phases, leads to an improved understanding of the Fe-N phase diagram. Although thermodynamics indicate the state the system strives for......, the nitriding result is determined largely by the kinetics of the process. The nitriding kinetics have been shown to be characterised by the occurring local near-equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data have...

Cobalt(II) and Cobalt(III) Coordination Compounds.

Science.gov (United States)

Thomas, Nicholas C.; And Others

1989-01-01

Presents a laboratory experiment which illustrates the formation of tris(phenanthroline)cobalt complexes in the 2+ and 3+ oxidation states, the effect of coordination on reactions of the ligand, and the use of a ligand displacement reaction in recovering the transformed ligand. Uses IR, UV-VIS, conductivity, and NMR. (MVL)

Residual Stress Induced by Nitriding and Nitrocarburizing

DEFF Research Database (Denmark)

Somers, Marcel A.J.

2005-01-01

The present chapter is devoted to the various mechanisms involved in the buildup and relief of residual stress in nitrided and nitrocarburized cases. The work presented is an overview of model studies on iron and iron-based alloys. Subdivision is made between the compound (or white) layer......, developing at the surfce and consisting of iron-based (carbo)nitrides, and the diffusion zone underneath, consisting of iron and alloying element nitrides dispersed in af ferritic matrix. Microstructural features are related directly to the origins of stress buildup and stres relief....

Cobalt-60 control in Ontario Hydro reactors

International Nuclear Information System (INIS)

Lacy, C.S.

1988-01-01

This paper discusses the impact of specifying reduced Cobalt-59 in the primary heat transport circuit materials of construction on the radiation fields developed around the primary circuit. An eight-fold reduction in steam generator radiation fields due to Cobalt-60 has been observed for two identical sets of reactors, one with and one without Cobalt-59 control. The comparison is between eight reactors at the Pickering Nuclear Generating Station (PNGS). Units 5 to 8 (PNGS-B) are identical to Units 1 to 4 (PNGS-A) except that PNGS-B has reduced impurity Cobalt-59 in the alloys of construction and a reduced use of stellite. The effects of chemistry control are also discussed

An elevator for cobalt-60 source

International Nuclear Information System (INIS)

Tang Zaimin; Liang Donghu

1990-07-01

The elevator used for cobalt-60 source is a key device in the irradiation industry. It plays an important role in the safety and control of irradiation operation as well as the utilization rate of radiation source. From 1983 to 1986, Beijing Institute of Nuclear Engineering undertook designing of various size irradiation projects for different uses. Since then a kind of cobalt-60 source elevator suited for the irradiator of wet-source-storage has been chosen. It is reliable in the operation and complete in the function. An automatic control circuit brings the systems of cobalt-60 source elevator into an interlock system which ensures the irradiation operation safety. Besides introducing the structural features and performance of this elevator, the conditions of safety interlocking in raising or lowering the cobalt-60 source is also discussed. The discussion is from the safety viewpoint of operating an irradiator and irradiation technology

3D-atom probe analysis of Cr and Cu added nitriding steels

International Nuclear Information System (INIS)

Takahashi, J.; Kawakami, K.; Sugiyama, M.; Kawasaki, K.

2004-01-01

Full text: Nitriding treatment is a very effective method for hardening the surface of steels and realizing improvement in wear-resistance. Although this technology has been performed for many years, the precipitation and hardening mechanisms are not completely clear. It was not easy to observe very fine precipitates which may be generated in nitriding steels. We performed a three-dimensional atom probe analysis of the nitriding steel plate in which two kinds of precipitates were generated. Hot-rolled steel plates, which mainly contained Cr 1.0wt.% and Cu 1.3wt.%, were nitrided by annealing (550-6000 o ) in a mainly NH 3 atmosphere. The material before the nitriding had a hardness of about 100 Hv. By the nitriding, the surface hardness increased to more than 700 Hv, and the inside hardness also increased to 200 Hv. The specimens were taken from 0.15 mm, 0.3 mm and 0.8 mm depth from the surface, which mostly correspond to the peak, the half and the inside hardness, respectively. In the specimen of 0.8 mm depth, prolate spheroidal Cu precipitates of more than 8 nm in diameter were observed. In the specimen of 0.3 mm depth, plate-shape nitride precipitates of 6-10 nm in diameter were observed in addition to the Cu precipitates. Each Cu precipitate made a pair with the nitride precipitate. In the 0.15 mm depth specimen, Cr nitride precipitates of high volume density in addition to the pairs consisting of a Cu precipitate and a Cr nitride precipitate were observed. The size of the nitride precipitate forming the pair was slightly larger than that of the single Cr nitride precipitates. Furthermore, the denuded zone where the nitride precipitate does not exist was observed around the pairs. From these results, it was concluded that three stages of precipitation arose as follows: By the heat treatment of nitriding processing, Cu precipitates were generated first. Then, Cr nitride nucleated at the surface of the Cu precipitates inhomogeneously, and surrounding solute Cr was

Experiments and procedures for bottom-heating heat-transfer experiments through UO2 debris beds in sodium

International Nuclear Information System (INIS)

Sowa, E.S.; Pedersen, D.R.; Pavlik, J.; Purviance, R.

1982-01-01

Real materials experiments in heat transfer through beds of UO 2 in sodium have been performed at Argonne National Laboratory over a period of years. The most recent method utilizes the resistive heating in a sheet tungsten filament located at the base of the debris container. A schematic diagram of the apparatus is shown. The tungsten is clamped between two water cooled copper electrodes. The filament is a sheet of tungsten 0.15 mm thick, 5 cm wide and 18 cm long. Two 6.5 mm thick sheets of boron nitride sandwich the filament. The upper face of the upper boron nitride sheet is in intimate contact with the bottom of the debris container. Temperatures are measured at various levels in the bed as well as in the boron nitride plate. In addition, the sodium pool temperature is measured by the thermocouple. The heat transferral through the bed is measured by the temperature difference and mass flowrate in a NaK condenser located above the debris bed. The NaK inlet and outlet temperatures are recorded individually, as well as, differentially

Tungsten Deposition on Graphite using Plasma Enhanced Chemical Vapour Deposition

International Nuclear Information System (INIS)

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

2016-01-01

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

Recovery of Tungsten and Molybdenum from Low-Grade Scheelite

Science.gov (United States)

Li, Yongli; Yang, Jinhong; Zhao, Zhongwei

2017-10-01

With most high-quality tungsten ores being exhausted, the enhancement of low-grade scheelite concentrates processing has attracted a great deal of attention. The objective of this study is to develop a method to maximize the recovery tungsten and molybdenum from a low-grade scheelite via a new acid leaching process followed by solvent extraction. Under optimal conditions (350 g/L H2SO4, 95°C, and 2 h), approximately 99.8% of tungsten and 98% of molybdenum were leached out. In the subsequent solvent extraction process, more than 99% of the tungsten and molybdenum were extracted with a co-extraction system (50% TBP, 30% HDEHP, and 10% 2-octanol in kerosene) using a three-stage cross-flow extraction. The raffinate can be recycled for the next leaching process after replenishing the H2SO4 to the initial value (approximately 350 g/L). Based on these results, a conceptual flowsheet is presented to recover tungsten and molybdenum from the low-grade scheelite.

21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining a...

Tungsten and refractory metals 3, proceedings

International Nuclear Information System (INIS)

Bose, A.; Dowding, R.J.

1996-01-01

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

Electrospark doping of steel with tungsten

International Nuclear Information System (INIS)

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

2016-01-01

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

Electrospark doping of steel with tungsten

Energy Technology Data Exchange (ETDEWEB)

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

2016-01-15

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

The Advanced Aluminum Nitride Synthesis Methods and Its Applications: Patent Review.

Science.gov (United States)

Shishkin, Roman A; Elagin, Andrey A; Mayorova, Ekaterina S; Beketov, Askold R

2016-01-01

High purity nanosized aluminum nitride synthesis is a current issue for both industry and science. However, there is no up-to-date review considering the major issues and the technical solutions for different methods. This review aims to investigate the advanced methods of aluminum nitride synthesis and its development tendencies. Also the aluminum nitride application patents and prospects for development of the branch have been considered. The patent search on "aluminum nitride synthesis" has been carried out. The research activity has been analyzed. Special attention has been paid to the patenting geography and the leading researchers in aluminum nitride synthesis. Aluminum nitride synthesis methods have been divided into 6 main groups, the most studied approaches are carbothermal reduction (88 patents) and direct nitridation (107 patents). The current issues for each group have been analyzed; the main trends are purification of the final product and nanopowder synthesis. The leading researchers in aluminum nitride synthesis have represented 5 countries, namely: Japan, China, Russia, South Korea and USA. The main aluminum nitride application spheres are electronics (59,1 percent of applications) and new materials manufacturing (30,9 percent). The review deals with the state of the art data in nanosized aluminum nitride synthesis, the major issues and the technical solutions for different synthesis methods. It gives a full understanding of the development tendencies and of the current leaders in the sphere.

Fabrication of Aluminum Gallium Nitride/Gallium Nitride MESFET And It's Applications in Biosensing

Science.gov (United States)

Alur, Siddharth

Gallium Nitride has been researched extensively for the past three decades for its application in Light Emitting Diodes (LED's), power devices and UV photodetectors. With the recent developments in crystal growth technology and the ability to control the doping there has been an increased interest in heterostructures formed between Gallium nitride and it's alloy Aluminium Gallium Nitride. These heterostructures due to the combined effect of spontaneous and piezoelectric effect can form a high density and a high mobility electron gas channel without any intentional doping. This high density electron gas makes these heterostructures ideal to be used as sensors. Gallium Nitride is also chemically very stable. Detection of biomolecules in a fast and reliable manner is very important in the areas of food safety and medical research. For biomolecular detection it is paramount to have a robust binding of the probes on the sensor surface. Therefore, in this dissertation, the fabrication and application of the AlGaN/GaN heterostructures as biological sensors for the detection of DNA and Organophosphate hydrolase enzyme is discussed. In order to use these AlGaN/GaN heterostructures as biological sensors capable of working in a liquid environment photodefinable polydimethyl-siloxane is used as an encapsulant. The immobilization conditions for a robust binding of thiolated DNA and the catalytic receptor enzyme organophosphate hydrolase on gold surfaces is developed with the help of X-ray photoelectron spectroscopy. DNA and OPH are detected by measuring the change in the drain current of the device as a function of time.

Joining of Tungsten Armor Using Functional Gradients

International Nuclear Information System (INIS)

John Scott O'Dell

2006-01-01

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

Cobalt release from inexpensive jewellery: has the use of cobalt replaced nickel following regulatory intervention?

DEFF Research Database (Denmark)

Thyssen, Jacob Pontoppidan; Jellesen, Morten S; Menné, Torkil

2010-01-01

Before the introduction of the EU Nickel Directive, concern was raised that manufacturers of jewellery might turn from the use of nickel to cobalt following the regulatory intervention on nickel exposure.......Before the introduction of the EU Nickel Directive, concern was raised that manufacturers of jewellery might turn from the use of nickel to cobalt following the regulatory intervention on nickel exposure....

Problems of tungsten crack resistance optimization

International Nuclear Information System (INIS)

Babak, A.V.; Uskov, E.I.

1986-01-01

Technically pure and precipitation-hardening tungsten is studied for its crack resistance in the initial and hardened states at the temperatures of 20...2000 deg C. Results of the study are presented. It is shown that hardening of tungsten base alloys in oil from the temperature corresponding to the upper boundary of the temperature region of ductile-brittle transition increases a crack propagation resistance of the studied materias at elevated and high temperatures

Characterization of plasma coated tungsten heavy alloy

International Nuclear Information System (INIS)

Bose, A.; Kapoor, D.; Lankford, J. Jr.; Nicholls, A.E.

1996-01-01

The detrimental environmental impact of Depleted Uranium-based penetrators have led to tremendous development efforts in the area of tungsten heavy alloy based penetrators. One line of investigation involves the coating of tungsten heavy alloys with materials that are prone to shear localization. Plasma spraying of Inconel 718 and 4340 steel have been used to deposit dense coatings on tungsten heavy alloy substrates. The aim of the investigation was to characterize the coating primarily in terms of its microstructure and a special push-out test. The paper describes the results of the push-out tests and analyzes some of the possible failure mechanisms by carrying out microstructural characterization of the failed rings obtained from the push out tests

Plasma nitriding of CA-6NM steel: effect of H2 + N2 gas mixtures in nitride layer formation for low N2 contents at 500 ºC

Directory of Open Access Journals (Sweden)

Angela Nardelli Allenstein

2010-12-01

Full Text Available This work aims to characterize the phases, thickness, hardness and hardness profiles of the nitride layers formed on the CA-6NM martensitic stainless steel which was plasma nitrided in gas mixtures containing different nitrogen amounts. Nitriding was performed at 500 ºC temperature, and 532 Pa (4 Torr pressure, for gas mixtures of 5% N2 + 95% H2, 10% N2 + 90% H2, and 20% N2 + 80% H2, and 2 hours nitriding time. A 6 hours nitriding time condition for gas mixture of 5% N2 + 95% H2 was also studied. Nitrided samples results were compared with non-nitrided condition. Thickness and microstructure of the nitrided layers were characterized by optical microscopy (OM, using Villela and Nital etchants, and the phases were identified by X-ray diffraction. Hardness profiles and hardness measured on surface steel were determined using Vickers hardness and nanoindentation tester, respectively. It was verified that nitrided layer produced in CA-6NM martensitc stainless steel is constituted of compound layer, being that formation of the diffusion zone was not observed for the studied conditions. The higher the nitrogen amounts in gas mixture the higher is the thickness of the nitrided layer and the probability to form different nitride phases, in the case γ'-Fe4N, ε-Fe2-3N and CrN phases. Intrinsic hardness of the nitrided layers produced in the CA-6NM stainless steel is about 12-14 GPa (~1200-1400 HV.

Ion nitriding in 316=L stainless steel

International Nuclear Information System (INIS)

Rojas-Calderon, E.L.

1989-01-01

Ion nitriding is a glow discharge process that is used to induce surface modification in metals. It has been applied to 316-L austenitic stainless steel looking for similar benefits already obtained in other steels. An austenitic stainless steel was selected because is not hardenable by heat treatment and is not easy to nitride by gas nitriding. The samples were plastically deformed to 10, 20, 40, 50 AND 70% of their original thickness in order to obtain bulk hardening and to observe nitrogen penetration dependence on it. The results were: an increase of one to two rockwell hardness number (except in 70% deformed sample because of its thickness); an increase of even several hundreds per cent in microhardness knoop number in nitrided surface. The later surely modifies waste resistance which would be worth to quantify in further studies. Microhardness measured in an internal transversal face to nitrided surface had a gradual diminish in its value with depth. Auger microanalysis showed a higher relative concentration rate C N /C F e near the surface giving evidence of nitrogen presence till 250 microns deep. The color metallography etchant used, produced faster corrosion in nitrited regions. Therefore, corrosion studies have to be done before using ion nitrited 316-L under these chemicals. (Author)

UN2−x layer formed on uranium metal by glow plasma nitriding

International Nuclear Information System (INIS)

Long, Zhong; Hu, Yin; Chen, Lin; Luo, Lizhu; Liu, Kezhao; Lai, Xinchun

2015-01-01

Highlights: • We used a very simple method to prepare nitride layer on uranium metal surface. • This modified layer is nitrogen-rich nitride, which should be written as UN 2−x . • TEM images show the nitride layer is composed of nano-sized grains. • XPS analysis indicates there is uranium with abnormal low valence in the nitride. - Abstract: Glow plasma nitriding is a simple and economical surface treatment method, and this technology was used to prepare nitride layer on the surface of uranium metal with thickness of several microns. The composition and structure of the nitride layer were analyzed by AES and XRD, indicating that this modified layer is nitrogen-rich uranium nitride, which should be written as UN 2−x . TEM images show the nitride layer is composed of nano-sized grains, with compact structure. And XPS analysis indicates there is uranium with abnormal low valence existing in the nitride. After the treated uranium storage in air for a long time, oxygen just entered the surface several nanometers, showing the nitride layer has excellent oxidation resistance. The mechanism of nitride layer formation and low valence uranium appearance is discussed

The role of cobalt on the creep of Waspaloy

Science.gov (United States)

Jarrett, R. N.; Chin, L.; Tien, J. K.

1984-01-01

Cobalt was systematically replaced with nickel in Waspaloy (which normally contains 13% Co) to determine the effects of cobalt on the creep behavior of this alloy. Effects of cobalt were found to be minimal on tensile strengths and microstructure. The creep resistance and the stress rupture resistance determined in the range from 704 to 760 C (1300 to 1400 C) were found to decrease as cobalt was removed from the standard alloy at all stresses and temperatures. Roughly a ten-fold drop in rupture life and a corresponding increase in minimum creep rate were found under all test conditions. Both the apparent creep activation energy and the matrix contribution to creep resistance were found to increase with cobalt. These creep effects are attributed to cobalt lowering the stacking fault energy of the alloy matrix. The creep resistance loss due to the removal of cobalt is shown to be restored by slightly increasing the gamma' volume fraction. Results are compared to a previous study on Udimet 700, a higher strength, higher gamma' volume fraction alloy with similar phase chemistry, in which cobalt did not affect creep resistance. An explanation for this difference in behavior based on interparticle spacing and cross-slip is presented.

Pulse current electrodeposition of tungsten coatings on V–4Cr–4Ti alloy

International Nuclear Information System (INIS)

Jiang, Fan; Zhang, Yingchun; Li, Xuliang

2015-01-01

Highlights: • Tungsten coatings were successfully electroplated on vanadium alloy substrate. • Tungsten coatings consisted of two sub-layers. • Tungsten coatings plated at lower duty cycle has a better surface quality. • High heat flux property of tungsten coatings was investigated. • Helium ion irradiation property of tungsten coatings was investigated. - Abstract: Tungsten coatings with high (2 2 0)-orientation were formed on V alloy substrate by pulse current electrodeposition in air atmosphere. The coatings’ microstructure, crystal structure and adhesive strength between coatings and substrates were investigated. It could be observed the tungsten coatings consisted of two sub-layers with the inner tooth-like layer, and the outer columnar layer. The tungsten coatings deposited at lower duty cycle have a better surface quality with a little change in the adhesive strength. The tungsten coating was exposed to electron beam with power density of 200 MW/m 2 in the thermal shock test, the tungsten crystal grain surface melt, the microcracks are found among the crystal grains. Exfoliation, flaking and dense needle-like holes were observed on the tungsten coating after irradiation with helium ions at an energy of 65 keV and an implanted dose of 22.67 × 10 18 cm −2

Nickel-cobalt hydroxide nanosheets: Synthesis, morphology and electrochemical properties.

Science.gov (United States)

Schneiderová, Barbora; Demel, Jan; Zhigunov, Alexander; Bohuslav, Jan; Tarábková, Hana; Janda, Pavel; Lang, Kamil

2017-08-01

This paper reports the synthesis, characterization, and electrochemical performance of nickel-cobalt hydroxide nanosheets. The hydroxide nanosheets of approximately 0.7nm thickness were prepared by delamination of layered nickel-cobalt hydroxide lactate in water and formed transparent colloids that were stable for months. The nanosheets were deposited on highly oriented pyrolytic graphite by spin coating, and their electrochemical behavior was investigated by cyclic voltammetry in potassium hydroxide electrolyte. Our method of electrode preparation allows for studying the electrochemistry of nanosheets where the majority of the active centers can participate in the charge transfer reaction. The observed electrochemical response was ascribed to mutual compensation of the cobalt and nickel response via electron sharing between these metals in the hydroxide nanosheets, a process that differentiates the behavior of nickel-cobalt hydroxide nanosheets from single nickel hydroxide or cobalt hydroxide nanosheets or their physical mixture. The presence of cobalt in the nickel-cobalt hydroxide nanosheets apparently decreases the time of electrochemical activation of the nanosheet layer, which for the nickel hydroxide nanosheets alone requires more potential sweeps. Copyright © 2017 Elsevier Inc. All rights reserved.

Tungsten/copper composite deposits produced by a cold spray

International Nuclear Information System (INIS)

Kang, Hyun-Ki; Kang, Suk Bong

2003-01-01

An agglomerated tungsten/copper composite powder was both cold sprayed and plasma sprayed onto a mild steel substrate for electronic package applications. Most pores resulting from the spraying were found in the vicinity of the tungsten-rich regions of the final product. The levels of porosity varied with the amount of tungsten present. No copper oxidation was found at the cold-sprayed deposit, but relatively high copper oxidation was observed at the plasma-sprayed deposit

Problems and possibilities of development of boron nitride ceramics

International Nuclear Information System (INIS)

Rusanova, L.N.; Romashin, A.G.; Kulikova, G.I.; Golubeva, O.P.

1988-01-01

The modern state of developments in the field of technology of ceramics produced from boron nitride is analyzed. Substantial difficulties in production of pure ceramics from hexagonal and wurtzite-like boron nitride are stated as related to the structure peculiarities and inhomogeneity of chemical bonds in elementary crystal cells of various modifications. Advantages and disadvantages of familiar technological procedures in production of boron nitride ceramics are compared. A new technology is suggested, which is based on the use of electroorganic compounds for hardening and protection of porous high-purity boron-nitride die from oxidation, and as high-efficient sintered elements for treatment of powders of various structures and further pyrolisis. The method is called thermal molecular lacing (TML). Properties of ceramics produced by the TML method are compared with characteristics of well-known brands of boron nitride ceramics

Behavior of porous tungsten under shock compression at room temperature

International Nuclear Information System (INIS)

Dandekar, D.P.; Lamothe, R.M.

1977-01-01

This work reports the results of room-temperature shock-compression experiments on porous tungsten. The porous tungsten was fabricated by sintering 1-μm tungsten particles. The initial density of the material was 15290 kg/m 3 . Around 97% of the pores in the material were interconnected. The main features of the results are as follows: (1) porous tungsten behaves as a linear elastic material to 1.43 GPa; (2) the shock wave following the elastic precursor is unstable in the material in the stress range 1.43--2.7 GPa; (3) a stable two-wave structure is established at and above 6.4 GPa; (4) the response of porous tungsten is accurately described by the Mie-Grueneisen equation of state at stresses above 4.9 GPa, the stress at which the voids suffer a complete extinction in the material; (5) the deformations induced in the material due to shock compression are irreversible; (6) the recentered Hugoniot of porous tungsten becomes stiffer with the increasing magnitude of initial compressive stress

Molecular dynamics study of grain boundary diffusion of hydrogen in tungsten

International Nuclear Information System (INIS)

Von Toussaint, U; Gori, S; Manhard, A; Höschen, T; Höschen, C

2011-01-01

Understanding the influence of the microstructure of tungsten on hydrogen transport is crucial for the use of tungsten as first-wall material in fusion reactors. Here, we report the results of molecular dynamics and transition state studies on the influence of grain boundaries in tungsten on the transport of hydrogen. An exhaustive mapping of possible minimum activation energy migration trajectories for hydrogen as the trace impurity reveals a strongly modified activation energy distribution in the neighborhood of grain boundaries together with an altered connectivity matrix. The results indicate that grain boundaries in polycrystalline tungsten may provide an important transport channel, especially for neutron-damaged tungsten.

Development of nitride fuel and pyrochemical process for transmutation of minor actinides

International Nuclear Information System (INIS)

Arai, Yasuo; Akabori, Mitsuo; Minato, Kazuo; Uno, Masayoshi

2010-01-01

Nitride fuel cycle for transmutation of minor actinides has been investigated under the double-strata fuel cycle concept. Mononitride solid solutions containing minor actinides have been prepared and characterised. Thermo-physical properties, such as thermal expansion, heat capacity and thermal diffusivity, have been measured by use of minor actinide nitride and burn-up simulated nitride samples. Irradiation behaviour of nitride fuel has been examined by irradiation tests. Pyrochemical process for treatment of spent nitride fuel has been investigated mainly by electrochemical measurements and nitride formation behaviour in pyrochemical process has been studied for recycled fuel fabrication. Recent results of experimental study on nitride fuel and pyrochemical process are summarised in the paper. (authors)

Corrosion fatigue behaviour of ion nitrided AISI 4140 steel

Energy Technology Data Exchange (ETDEWEB)

Genel, K. [Sakarya Univ., Adapazari (Turkey). Mech. Eng. Dept.; Demirkol, M.; Guelmez, T. [Faculty of Mechanical Engineering, Istanbul Technical University, Guemuessuyu, 80191, Istanbul (Turkey)

2000-08-31

Machine components suffer from corrosion degradation of fatigue characteristics and improvement can be attained by the application of a nitriding treatment, particularly to low alloy steels. In the present study, the effect of ion nitriding on corrosion fatigue performance of AISI 4140 steel has been investigated by conducting a series of rotary bending corrosion fatigue tests at 95 Hz, in 3% NaCl aqueous solution. Hourglass shaped, 4 mm diameter fatigue specimens were ion nitrided at 748 K for 1, 3, 8 and 16 h prior to the tests. It was observed that distinct fatigue limit behaviour of ion nitrided steel in air completely disappeared in corrosive environment besides severe degradation in fatigue characteristics. An improvement reaching to 60% in corrosion fatigue strength can be attained by successive ion nitriding practice based on a fatigue life of 10{sup 7} cycles. An attempt was made to establish an empirical relationship between corrosion fatigue strength and relative case depth, which considers the size of the ion nitrided specimen. It was also determined that a power relationship holds between corrosion fatigue strength and fatigue life of ion nitrided steel. The presence of white layer has resulted in additional improvement in corrosion fatigue resistance, and it was observed that corrosion fatigue cracks were initiated dominantly under the white layer by pit formation mechanism. (orig.)

Corrosion fatigue behaviour of ion nitrided AISI 4140 steel

International Nuclear Information System (INIS)

Genel, K.

2000-01-01

Machine components suffer from corrosion degradation of fatigue characteristics and improvement can be attained by the application of a nitriding treatment, particularly to low alloy steels. In the present study, the effect of ion nitriding on corrosion fatigue performance of AISI 4140 steel has been investigated by conducting a series of rotary bending corrosion fatigue tests at 95 Hz, in 3% NaCl aqueous solution. Hourglass shaped, 4 mm diameter fatigue specimens were ion nitrided at 748 K for 1, 3, 8 and 16 h prior to the tests. It was observed that distinct fatigue limit behaviour of ion nitrided steel in air completely disappeared in corrosive environment besides severe degradation in fatigue characteristics. An improvement reaching to 60% in corrosion fatigue strength can be attained by successive ion nitriding practice based on a fatigue life of 10 7 cycles. An attempt was made to establish an empirical relationship between corrosion fatigue strength and relative case depth, which considers the size of the ion nitrided specimen. It was also determined that a power relationship holds between corrosion fatigue strength and fatigue life of ion nitrided steel. The presence of white layer has resulted in additional improvement in corrosion fatigue resistance, and it was observed that corrosion fatigue cracks were initiated dominantly under the white layer by pit formation mechanism. (orig.)

Radiofrequency cold plasma nitrided carbon steel: Microstructural and micromechanical characterizations

International Nuclear Information System (INIS)

Bouanis, F.Z.; Bentiss, F.; Bellayer, S.; Vogt, J.B.; Jama, C.

2011-01-01

Highlights: → C38 carbon steel samples were plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge. → RF plasma treatment enables nitriding for non-heated substrates. → The morphological and chemical analyses show the formation of a uniform thickness on the surface of the nitrided C38 steel. → Nitrogen plasma active species diffuse into the samples and lead to the formation of Fe x N. → The increase in microhardness values for nitrided samples with plasma processing time is interpreted by the formation of a thicker nitrided layer on the steel surface. - Abstract: In this work, C38 carbon steel was plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge on non-heated substrates. General characterizations were performed to compare the chemical compositions, the microstructures and hardness of the untreated and plasma treated surfaces. The plasma nitriding was carried out on non-heated substrates at a pressure of 16.8 Pa, using N 2 gas. Surface characterizations before and after N 2 plasma treatment were performed by means of the electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS) and Vickers microhardness measurements. The morphological and chemical analysis showed the formation of a uniform structure on the surface of the nitrided sample with enrichment in nitrogen when compared to untreated sample. The thickness of the nitride layer formed depends on the treatment time duration and is approximately 14 μm for 10 h of plasma treatment. XPS was employed to obtain chemical-state information of the plasma nitrided steel surfaces. The micromechanical results show that the surface microhardness increases as the plasma-processing time increases to reach, 1487 HV 0.005 at a plasma processing time of 8 h.

Radiofrequency cold plasma nitrided carbon steel: Microstructural and micromechanical characterizations

Energy Technology Data Exchange (ETDEWEB)

Bouanis, F.Z. [Universite Lille Nord de France, F-59000 Lille (France); Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Bentiss, F. [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco); Bellayer, S.; Vogt, J.B. [Universite Lille Nord de France, F-59000 Lille (France); Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Jama, C., E-mail: charafeddine.jama@ensc-lille.fr [Universite Lille Nord de France, F-59000 Lille (France); Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France)

2011-05-16

Highlights: {yields} C38 carbon steel samples were plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge. {yields} RF plasma treatment enables nitriding for non-heated substrates. {yields} The morphological and chemical analyses show the formation of a uniform thickness on the surface of the nitrided C38 steel. {yields} Nitrogen plasma active species diffuse into the samples and lead to the formation of Fe{sub x}N. {yields} The increase in microhardness values for nitrided samples with plasma processing time is interpreted by the formation of a thicker nitrided layer on the steel surface. - Abstract: In this work, C38 carbon steel was plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge on non-heated substrates. General characterizations were performed to compare the chemical compositions, the microstructures and hardness of the untreated and plasma treated surfaces. The plasma nitriding was carried out on non-heated substrates at a pressure of 16.8 Pa, using N{sub 2} gas. Surface characterizations before and after N{sub 2} plasma treatment were performed by means of the electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS) and Vickers microhardness measurements. The morphological and chemical analysis showed the formation of a uniform structure on the surface of the nitrided sample with enrichment in nitrogen when compared to untreated sample. The thickness of the nitride layer formed depends on the treatment time duration and is approximately 14 {mu}m for 10 h of plasma treatment. XPS was employed to obtain chemical-state information of the plasma nitrided steel surfaces. The micromechanical results show that the surface microhardness increases as the plasma-processing time increases to reach, 1487 HV{sub 0.005} at a plasma processing time of 8 h.

COBALT COMPOUNDS AS ANTIDOTES FOR HYDROCYANIC ACID.

Science.gov (United States)

EVANS, C L

1964-12-01

The antidotal potency of a cobalt salt (acetate), of dicobalt edetate, of hydroxocobalamin and of cobinamide against hydrocyanic acid was examined mainly on mice and rabbits. All the compounds were active antidotes for up to twice the LD50; under some conditions for larger doses. The most successful was cobalt acetate for rabbits (5xLD50), which was effective at a molar cyanide/cobalt (CN/Co) ratio of 5, but had as a side-effect intense purgation. Hydroxocobalamin was irregular in action, but on the whole was most effective for mice (4.5xLD50 at a molar ratio of 1), and had no apparent side effects. Dicobalt edetate, at molar ratios of up to 2, was more effective for rabbits (3xLD50) than for mice (2xLD50), but had fewer side effects than cobalt acetate. The effect of thiosulphate was to augment the efficacy of dicobalt edetate and, in mice, that of hydroxocobalamin; but, apparently, in rabbits, to reduce that of hydroxocobalamin. Cobinamide, at a molar ratio of 1, was slightly more effective than hydroxocobalamin on rabbits and also less irregular in its action. Cobalt acetate by mouth was effective against orally administered hydrocyanic acid. The oxygen uptake of the body, reduced by cyanide, is rapidly reinstated when one of the cobalt antidotes has been successfully administered.

Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

Energy Technology Data Exchange (ETDEWEB)

Si, M. S.; Gao, Daqiang, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn; Yang, Dezheng; Peng, Yong; Zhang, Z. Y.; Xue, Desheng, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Liu, Yushen [Jiangsu Laboratory of Advanced Functional Materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500 (China); Deng, Xiaohui [Department of Physics and Electronic Information Science, Hengyang Normal University, Hengyang 421008 (China); Zhang, G. P. [Department of Physics, Indiana State University, Terre Haute, Indiana 47809 (United States)

2014-05-28

Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

Characterization of a Porous Carbon Material Functionalized with Cobalt-Oxide/Cobalt Core-Shell Nanoparticles for Lithium Ion Battery Electrodes

KAUST Repository

Anjum, Dalaver H.; Rasul, Shahid; Roldan-Gutierrez, Manuel A.; Da Costa, Pedro M. F. J.

2016-01-01

A nanoporous carbon (C) material, functionalized with Cobalt-Oxide/Cobalt (CoO/Co) core-shell nanoparticles (NPs), was structurally and chemically characterized with transmission electron microcopy (TEM) while its electrochemical response

Cobalt mineral exploration and supply from 1995 through 2013

Science.gov (United States)

Wilburn, David R.

2011-01-01

The global mining industry has invested a large amount of capital in mineral exploration and development over the past 15 years in an effort to ensure that sufficient resources are available to meet future increases in demand for minerals. Exploration data have been used to identify specific sites where this investment has led to a significant contribution in global mineral supply of cobalt or where a significant increase in cobalt production capacity is anticipated in the next 5 years. This report provides an overview of the cobalt industry, factors affecting mineral supply, and circumstances surrounding the development, or lack thereof, of key mineral properties with the potential to affect mineral supply. Of the 48 sites with an effective production capacity of at least 1,000 metric tons per year of cobalt considered for this study, 3 producing sites underwent significant expansion during the study period, 10 exploration sites commenced production from 1995 through 2008, and 16 sites were expected to begin production by 2013 if planned development schedules are met. Cobalt supply is influenced by economic, environmental, political, and technological factors affecting exploration for and production of copper, nickel, and other metals as well as factors affecting the cobalt industry. Cobalt-rich nickel laterite deposits were discovered and developed in Australia and the South Pacific and improvements in laterite processing technology took place during the 1990s and early in the first decade of the 21st century when mining of copper-cobalt deposits in Congo (Kinshasa) was restricted because of regional conflict and lack of investment in that country's mining sector. There was also increased exploration for and greater importance placed on cobalt as a byproduct of nickel mining in Australia and Canada. The emergence of China as a major refined cobalt producer and consumer since 2007 has changed the pattern of demand for cobalt, particularly from Africa and

Surface composition of carburized tungsten trioxide and its catalytic activity

International Nuclear Information System (INIS)

Nakazawa, M.; Okamoto, H.

1985-01-01

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

Study of tungsten based positron moderators

International Nuclear Information System (INIS)

Lucio, O.G. de; Pérez, M.; Mendoza, U.; Morales, J.G.; Cruz, J.C.; DuBois, R.D.

2015-01-01

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

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.

Wear resistance and microstructural properties of Ni–Al/h-BN/WC–Co coatings deposited using plasma spraying

International Nuclear Information System (INIS)

Hsiao, W.T.; Su, C.Y.; Huang, T.S.; Liao, W.H.

2013-01-01

Hexagonal boron nitride (h-BN) and tungsten carbide cobalt (WC–Co) were added to nickel aluminum alloy (Ni–Al) and deposited as plasma sprayed coatings to improve their tribological properties. The microstructure of the coatings was analyzed using a scanning electron microscope (SEM). Following wear test, the worn surface morphologies of the coatings were analyzed using a SEM to identify their fracture modes. The results of this study demonstrate that the addition of h-BN and WC–Co improved the properties of the coatings. Ni–Al/h-BN/WC–Co coatings with high hardness and favorable lubrication properties were deposited. - Highlights: • We mixed Ni–Al, h-BN and WC–Co powders and deposited them as composite coatings. • Adding WC–Co was found to increase the hardness and reduce the wear volume loss. • Adding h-BN was found to decrease the hardness and reduce the friction coefficient. • This composite coating was shown to have improved wear properties at 850 °C

Structure and electrochemical properties of plasma-nitrided low alloy steel

Energy Technology Data Exchange (ETDEWEB)

Chyou, S.D.; Shih, H.C. (Dept. of Materials Science and Engineering, National Tsing Hua Univ., Hsinchu (Taiwan))

1990-10-01

Plasma-nitrided SAE 4140 steel has been widely applied industrially because of its superior resistance to wear and fatigue. However, its corrosion behaviour in aqueous environments has not been completely explored. The effects of nitriding on corrosion were investigated by performing electrochemical tests on both nitrided and untreated SAE 4140. It was found that, by plasma nitriding, the corrosion resistance improved significantly in HNO{sub 3} and Na{sub 2}SO{sub 4} aqueous environments. A reaction model is proposed to explain the beneficial effect of nitride on corrosion resistance. It is concluded that nitrogen and chromium (an alloying element) act synergistically to form a dense protective layer which is responsible for the corrosion resistance. Characterization of the surface layers by Auger electron spectroscopy and X-ray photoelectron spectroscopy reveals that the protective layer is composed of (Fe, Cr){sub 4}N, (Fe, Cr){sub 2-3}N and CrN in the inner layer, Fe{sub 2}O{sub 3}, Cr{sub 2}O{sub 3} together with nitrides in the middle layer, and nitrides, {gamma}'-FeOOH, and Cr(OH){sub 3}.H{sub 2}O in the outermost layer. (orig.).

OEDGE modeling for the planned tungsten ring experiment on DIII-D

Directory of Open Access Journals (Sweden)

J.D. Elder

2017-08-01

Full Text Available The OEDGE code is used to model tungsten erosion and transport for experiments with toroidal rings of high-Z metal tiles in the DIII-D tokamak. Such modeling is needed for both experimental and diagnostic design to have estimates of the expected core and edge tungsten density and to understand the various factors contributing to the uncertainties in these calculations. OEDGE simulations are performed using the planned experimental magnetic geometries and plasma conditions typical of both L-mode and inter-ELM H-mode discharges in DIII-D. OEDGE plasma reconstruction based on specific representative discharges for similar geometries is used to determine the plasma conditions applied to tungsten plasma impurity simulations. A new model for tungsten erosion in OEDGE was developed which imports charge-state resolved carbon impurity fluxes and impact energies from a separate OEDGE run which models the carbon production, transport and deposition for the same plasma conditions as the tungsten simulations. These values are then used to calculate the gross tungsten physical sputtering due to carbon plasma impurities which is then added to any sputtering by deuterium ions; tungsten self-sputtering is also included. The code results are found to be dependent on the following factors: divertor geometry and closure, the choice of cross-field anomalous transport coefficients, divertor plasma conditions (affecting both tungsten source strength and transport, the choice of tungsten atomic physics data used in the model (in particular ionization rate for W-atoms, and the model of the carbon flux and energy used for calculating the tungsten source due to sputtering. Core tungsten density is found to be of order 1015m−3 (excluding effects of any core transport barrier and with significant variability depending on the other factors mentioned with density decaying into the scrape off layer. For the typical core density in the plasma conditions examined of 2 to 4�

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.

Atomic Resolution Microscopy of Nitrides in Steel

DEFF Research Database (Denmark)

Danielsen, Hilmar Kjartansson

2014-01-01

MN and CrMN type nitride precipitates in 12%Cr steels have been investigated using atomic resolution microscopy. The MN type nitrides were observed to transform into CrMN both by composition and crystallography as Cr diffuses from the matrix into the MN precipitates. Thus a change from one...

The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung fibroblast cells

Energy Technology Data Exchange (ETDEWEB)

Smith, Leah J.; Holmes, Amie L. [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Maine Center for Environmental Toxicology and Health, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Department of Applied Medical Science, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Kandpal, Sanjeev Kumar; Mason, Michael D. [Department of Chemical and Biological Engineering, University of Maine, Orono, ME (United States); Zheng, Tongzhang [Department of Environmental Health Sciences, Yale School of Public Health, New Haven, CT (United States); Wise, John Pierce, E-mail: John.Wise@usm.maine.edu [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Maine Center for Environmental Toxicology and Health, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Department of Applied Medical Science, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States)

2014-08-01

Cobalt exposure is increasing as cobalt demand rises worldwide due to its use in enhancing rechargeable battery efficiency, super-alloys, and magnetic products. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in human lung cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble cobalt was more cytotoxic than particulate cobalt while particulate and soluble cobalt induced similar levels of genotoxicity. However, soluble cobalt induced cell cycle arrest indicated by the lack of metaphases at much lower intracellular cobalt concentrations compared to cobalt oxide. Accordingly, we investigated the role of particle internalization in cobalt oxide-induced toxicity and found that particle-cell contact was necessary to induce cytotoxicity and genotoxicity after cobalt exposure. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung fibroblasts, and solubility plays a key role in cobalt-induced lung toxicity. - Highlights: • Particulate and soluble cobalt are cytotoxic and genotoxic to human lung cells. • Soluble cobalt induces more cytotoxicity compared to particulate cobalt. • Soluble and particulate cobalt induce similar levels of genotoxicity. • Particle-cell contact is required for particulate cobalt-induced toxicity.

Defects in dilute nitrides

International Nuclear Information System (INIS)

Chen, W.M.; Buyanova, I.A.; Tu, C.W.; Yonezu, H.

2005-01-01

We provide a brief review our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in dilute nitrides, i.e. Ga(In)NAs and Ga(Al,In)NP. Defect complexes involving intrinsic defects such as As Ga antisites and Ga i self interstitials were positively identified.Effects of growth conditions, chemical compositions and post-growth treatments on formation of the defects are closely examined. These grown-in defects are shown to play an important role in non-radiative carrier recombination and thus in degrading optical quality of the alloys, harmful to performance of potential optoelectronic and photonic devices based on these dilute nitrides. (author)

Making a robust carbon-cobalt(III) bond

DEFF Research Database (Denmark)

Larsen, Erik; Madsen, Anders Østergaard; Kofod, Pauli

2009-01-01

The coordination ion with a well-characterized carbon-cobalt(III) bond, the (1,4,7-triazacyclononane)(1,6-diamino-3-thia-4-hexanido)cobalt(III) dication, [Co(tacn)(C-aeaps)](2+) (aeaps, for aminoethylaminopropylsulfide), has been reacted with iodomethane, and the S-methyl thionium derivative has...... been isolated. The crystal structure of the resulting [Co(tacn)(C-aeaps-SCH(3))]Br(3) x 3 H(2)O at 122 K has been determined by X-ray diffraction techniques to verify the structure. The crystal structure determination shows that the carbon-cobalt bond length is even shorter (2.001(4) A) than in [Co......(tacn)(C-aeaps)](2+) participates in bonding to cobalt(III), having implications for the transformation between the carbon- and sulfur-bound forms of the aeaps ligand....

On the shear strength of tungsten nano-structures with embedded helium

International Nuclear Information System (INIS)

Smirnov, R.D.; Krasheninnikov, S.I.

2013-01-01

Modification of plastic properties of tungsten nano-structures under shear stress load due to embedded helium atoms is studied using molecular dynamics modelling. The modelling demonstrates that the yield strength of tungsten nano-structures reduces significantly with increasing embedded helium concentration. At high helium concentrations (>10 at%), the yield strength decreases to values characteristic to the pressure in helium nano-bubbles, which are formed in tungsten under such conditions and thought to be responsible for the formation of nano-fuzz on tungsten surfaces irradiated with helium plasma. It is also shown that tungsten plastic flow strongly facilitates coagulation of helium clusters to larger bubbles. The temperature dependencies of the yield strength are obtained. (letter)

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

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Eduardo Spinelli

2017-07-01

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

Total body irradiation with a reconditioned cobalt teletherapy unit.

Science.gov (United States)

Evans, Michael D C; Larouche, Renée-Xavière; Olivares, Marina; Léger, Pierre; Larkin, Joe; Freeman, Carolyn R; Podgorsak, Ervin B

2006-01-01

While the current trend in radiotherapy is to replace cobalt teletherapy units with more versatile and technologically advanced linear accelerators, there remain some useful applications for older cobalt units. The expansion of our radiotherapy department involved the decommissioning of an isocentric cobalt teletherapy unit and the replacement of a column-mounted 4-MV LINAC that has been used for total body irradiation (TBI). To continue offering TBI treatments, we converted the decommissioned cobalt unit into a dedicated fixed-field total body irradiator and installed it in an existing medium-energy LINAC bunker. This article describes the logistical and dosimetric aspects of bringing a reconditioned cobalt teletherapy unit into clinical service as a total body irradiator.

Superhard Rhenium/Tungsten Diboride Solid Solutions.

Science.gov (United States)

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

2016-11-02

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

Potential for cobalt recovery from lateritic ores in Europe

Science.gov (United States)

Herrington, R.

2012-04-01

Cobalt is one of the 'critical metals' identified under the EU Raw Materials Initiative. Annually the global mine production of cobalt is around 55,000 tonnes,with Europe's industries consuming around 30% of that figure. Currently Europe produces around 27 tonnes of cobalt from mines in Finland although new capacity is planned. Co-bearing nickel laterite ores being mined in Greece, Macedonia and Kosovo where the cobalt is currently not being recovered (ores have typical analyses of 0.055% Co and >1% Ni,). These ores are currently treated directly in pyrometallurgical plants to recover the contained nickel and this process means there is no separate cobalt product produced. Hydrometallurgical treatment of mineralogically suitable laterite ores can recover the cobalt; for example Cuba recovers 3,500 tonnes of cobalt from its laterite mining operations, which are of a similar scale to the current European operations. Implementation of hydrometallurgical techniques is in its infancy in Europe with one deposit in Turkey planning to use atmospheric heap leaching to recover nickel and copper from oxide-dominated ores. More widespread implementation of these methods to mineralogically suitable ore types could unlock the highly significant undeveloped resources (with metal contents >0.04% Co and >1% Ni), which have been defined throughout the Balkans eastwards into Turkey. At a conservative estimate, this region has the potential to supply up to 30% of the EU cobalt requirements.

Monte Carlo study of MLC fields for cobalt therapy machine

Directory of Open Access Journals (Sweden)

Komanduri M Ayyangar

2014-01-01

Full Text Available An automated Multi-Leaf Collimator (MLC system has been developed as add-on for the cobalt-60 teletherapy machines available in India. The goal of the present computational study is to validate the MLC design using Monte Carlo (MC modeling. The study was based on the Kirloskar-supplied Phoenix model machines that closely match the Atomic Energy of Canada Limited (AECL theratron-80 machine. The MLC is a retrofit attachment to the collimator assembly, with 14 non-divergent leaf pairs of 40 mm thick, 7 mm wide, and 150 mm long tungsten alloy plates with rounded edges and 20 mm tongue and 2 mm groove in each leaf. In the present work, the source and collimator geometry has been investigated in detail to arrive at a model that best represents the measured dosimetric data. The authors have studied in detail the proto-I MLC built for cobalt-60. The MLC field sizes were MC simulated for 2 × 2 cm 2 to 14 × 14 cm 2 square fields as well as irregular fields, and the percent depth dose (PDD and profile data were compared with ROPS† treatment planning system (TPS. In addition, measured profiles using the IMATRIXX system‡ were also compared with the MC simulations. The proto-I MLC can define radiation fields up to 14 × 14 cm΂ within 3 mm accuracy. The maximum measured leakage through the leaf ends in closed condition was 3.4% and interleaf leakage observed was 7.3%. Good agreement between MC results, ROPS and IMATRIXX results has been observed. The investigation also supports the hypothesis that optical and radiation field coincidence exists for the square fields studied with the MLC. Plots of the percent depth dose (PDD data and profile data for clinically significant irregular fields have also been presented. The MC model was also investigated to speed up the calculations to allow calculations of clinically relevant conformal beams.

Low temperature anodic bonding to silicon nitride

DEFF Research Database (Denmark)

Weichel, Steen; Reus, Roger De; Bouaidat, Salim

2000-01-01

Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bu...

Review of actinide nitride properties with focus on safety aspects

Energy Technology Data Exchange (ETDEWEB)

Albiol, Thierry [CEA Cadarache, St Paul Lez Durance Cedex (France); Arai, Yasuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2001-12-01

This report provides a review of the potential advantages of using actinide nitrides as fuels and/or targets for nuclear waste transmutation. Then a summary of available properties of actinide nitrides is given. Results from irradiation experiments are reviewed and safety relevant aspects of nitride fuels are discussed, including design basis accidents (transients) and severe (core disruptive) accidents. Anyway, as rather few safety studies are currently available and as many basic physical data are still missing for some actinide nitrides, complementary studies are proposed. (author)

Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications

DEFF Research Database (Denmark)

Guler, Urcan; Suslov, Sergey; Kildishev, Alexander V.

2015-01-01

Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal and photocatalytic applications via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average ...

Mechanistic, kinetic, and processing aspects of tungsten chemical mechanical polishing

Science.gov (United States)

Stein, David

This dissertation presents an investigation into tungsten chemical mechanical polishing (CMP). CMP is the industrially predominant unit operation that removes excess tungsten after non-selective chemical vapor deposition (CVD) during sub-micron integrated circuit (IC) manufacture. This work explores the CMP process from process engineering and fundamental mechanistic perspectives. The process engineering study optimized an existing CMP process to address issues of polish pad and wafer carrier life. Polish rates, post-CMP metrology of patterned wafers, electrical test data, and synergy with a thermal endpoint technique were used to determine the optimal process. The oxidation rate of tungsten during CMP is significantly lower than the removal rate under identical conditions. Tungsten polished without inhibition during cathodic potentiostatic control. Hertzian indenter model calculations preclude colloids of the size used in tungsten CMP slurries from indenting the tungsten surface. AFM surface topography maps and TEM images of post-CMP tungsten do not show evidence of plow marks or intergranular fracture. Polish rate is dependent on potassium iodate concentration; process temperature is not. The colloid species significantly affects the polish rate and process temperature. Process temperature is not a predictor of polish rate. A process energy balance indicates that the process temperature is predominantly due to shaft work, and that any heat of reaction evolved during the CMP process is negligible. Friction and adhesion between alumina and tungsten were studied using modified AFM techniques. Friction was constant with potassium iodate concentration, but varied with applied pressure. This corroborates the results from the energy balance. Adhesion between the alumina and the tungsten was proportional to the potassium iodate concentration. A heuristic mechanism, which captures the relationship between polish rate, pressure, velocity, and slurry chemistry, is presented

Helium-induced hardening effect in polycrystalline tungsten

Science.gov (United States)

Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

2017-09-01

In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

Microstructure and Hardness of High Temperature Gas Nitrided AISI 420 Martensitic Stainless Steel

Directory of Open Access Journals (Sweden)

Ibrahim Nor Nurulhuda Md.

2014-07-01

Full Text Available This study examined the microstructure and hardness of as-received and nitrided AISI 420 martensitic stainless steels. High temperature gas nitriding was employed to treat the steels at 1200°C for one hour and four hours using nitrogen gas, followed by furnace cooled. Chromium nitride and iron nitride were formed and concentrated at the outmost surface area of the steels since this region contained the highest concentration of nitrogen. The grain size enlarged at the interior region of the nitrided steels due to nitriding at temperature above the recrystallization temperature of the steel and followed by slow cooling. The nitrided steels produced higher surface hardness compared to as-received steel due to the presence of nitrogen and the precipitation of nitrides. Harder steel was produced when nitriding at four hours compared to one hour since more nitrogen permeated into the steel.

Influence of plastic deformation on nitriding of a molybdenum-hafnium alloy

International Nuclear Information System (INIS)

Lakhtin, Yu.M.; Kogan, Ya.D.; Shashkov, D.P.; Likhacheva, T.E.

1982-01-01

The influence of a preliminary plastic strain on the structure and properties of molybdenum alloy with 0.2 wt.% Hf upon nitriding in the ammonia medium at 900-1200 deg C during 1-6 h is investigated. The study of microhardness distribution across the nitrided layer thickness has shown that with increase of the degree of preliminary plastic strain up to 50 % the nitrided layer hardness decreases and with further reduction growth up to 90 % - increases. Nitriding sharply (hundred times) increases wear resistance of molybdenum alloy with hafnium addition. At the reduction degree 25 % the wear resistance is less than at other values of percentage reduction in area owing to the minimum thickness of the nitride zone. The alloy strained before nitriding by 25 % has shown the best results during heat resistance testing

A study of scandia and rhenium doped tungsten matrix dispenser cathode

Science.gov (United States)

Wang, Jinshu; Li, Lili; Liu, Wei; Wang, Yanchun; Zhao, Lei; Zhou, Meiling

2007-10-01

Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The experimental results show that scandia was distributed evenly on the surface of tungsten particles. The addition of scandia and rhenium could decrease the particle size of doped tungsten, for example, the tungsten powders doped with Sc 2O 3 and Re had the average size of about 50 nm in diameter. By using this kind of powder, scandia and rhenium doped tungsten matrix with the sub-micrometer sized tungsten grains was obtained. This kind of matrix exhibited good anti-bombardment insensitivity at high temperature. The emission property result showed that high space charge limited current densities of more than 60 A/cm 2 at 900 °C could be obtained for this cathode. A Ba-Sc-O multilayer about 100 nm in thickness formed at the surface of cathode after activation led to the high emission property.

Temperature dependent viscosity of cobalt ferrite / ethylene glycol ferrofluids

Science.gov (United States)

Kharat, Prashant B.; Somvanshi, Sandeep B.; Kounsalye, Jitendra S.; Deshmukh, Suraj S.; Khirade, Pankaj P.; Jadhav, K. M.

2018-04-01

In the present work, cobalt ferrite / ethylene glycol ferrofluid is prepared in 0 to 1 (in the step of 0.2) volume fraction of cobalt ferrite nanoparticles synthesized by co-precipitation method. The XRD results confirmed the formation of single phase spinel structure. The Raman spectra have been deconvoluted into individual Lorentzian peaks. Cobalt ferrite has cubic spinel structure with Fd3m space group. FT-IR spectra consist of two major absorption bands, first at about 586 cm-1 (υ1) and second at about 392 cm-1 (υ2). These absorption bands confirm the formation of spinel-structured cobalt ferrite. Brookfield DV-III viscometer and programmable temperature-controlled bath was used to study the relationship between viscosity and temperature. Viscosity behavior with respect to temperature has been studied and it is revealed that the viscosity of cobalt ferrite / ethylene glycol ferrofluids increases with an increase in volume fraction of cobalt ferrite. The viscosity of the present ferrofluid was found to decrease with increase in temperature.

Behavior of tungsten carbide in water stabilized plasma

Czech Academy of Sciences Publication Activity Database

Brožek, Vlastimil; Matějíček, Jiří; Neufuss, Karel

2007-01-01

Roč. 7, č. 4 (2007), s. 213-220 ISSN 1335-8987 R&D Projects: GA ČR(CZ) GA104/05/0540 Institutional research plan: CEZ:AV0Z20430508 Keywords : water stabilized plasma * tungsten carbide * tungsten hemicarbide * decarburization Subject RIV: BL - Plasma and Gas Discharge Physics

Synthesis of cobalt boride nanoparticles using radio frequency thermal plasma

International Nuclear Information System (INIS)

Lapitan, Jr. Lorico DS.; Ying Ying Chen; Seesoek Choe; Watanabe, Takayuki

2012-01-01

Nano size cobalt boride particles were synthesized from vapor phase using a 30 kw-4 MHz radio frequency (RF) thermal plasma. Cobalt and boron powder mixtures used as precursors in different composition and feed rate were evaporated immediately in the high temperature plasma and cobalt boride nanoparticles were produced through the quenching process. The x-ray diffractometry (XRD) patterns of cobalt boride nanoparticles prepared from the feed powder ratio of 1:2 and 1:3 for Co: B showed peaks that are associated with the Co 2 B and CoB crystal phases of cobalt boride. The XRD analysis revealed that increasing the powder feed rate results in a higher mass fraction and a larger crystalline diameter of cobalt boride nanoparticles. The images obtained by field emission scanning electron microscopy (FE-SEM) revealed that cobalt boride nanoparticles have a spherical morphology. The crystallite size of the particles estimated with XRD was found to be 18-22 nm. (author)

Study to use graded cobalt adjuster in 540 MWe PHWR

International Nuclear Information System (INIS)

Raj, Manish; Fernando, M.P.S.; Pradhan, A.S.; Kumar, A.N.

2007-01-01

Full text: There are 17 adjusters in 540 MWe PHWR, which are essentially provided for xenon override function. They also provide flux flattening being in the central region of the reactor core. The present design of adjusters consists of stainless steel tube. The adjuster rods are grouped into 8 banks for movement. Since adjusters are normally fully inserted during reactor operation, they are best suited for production of cobalt 60. The nickel-plated cobalt in the form of either slugs or pellet are used for the design of cobalt pencils. The number of pencils can be varied to optimize the reactivity load and cobalt 60 production requirement. The worth and activity of cobalt adjusters have been worked out considering different pin configuration for the adjuster assembly. To start with we have assumed all adjusters throughout its length are of the same configuration. The flux depression factors within the cobalt pencils have been considered in the estimations of the specific and total cobalt 60 activities. The option of using graded cobalt adjusters, where different pin configuration along the length is considered for better flux flattening

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

Energy Technology Data Exchange (ETDEWEB)

Sun, Ningbo; Zhang, Yingchun, E-mail: zycustb@163.com; Lang, Shaoting; Jiang, Fan; Wang, Lili

2014-12-15

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 Na{sub 2}WO{sub 4}–WO{sub 3} 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.

Antimicrobial and anti-biofilm properties of polypropylene meshes coated with metal-containing DLC thin films.

Science.gov (United States)

Cazalini, Elisa M; Miyakawa, Walter; Teodoro, Guilherme R; Sobrinho, Argemiro S S; Matieli, José E; Massi, Marcos; Koga-Ito, Cristiane Y

2017-06-01

A promising strategy to reduce nosocomial infections related to prosthetic meshes is the prevention of microbial colonization. To this aim, prosthetic meshes coated with antimicrobial thin films are proposed. Commercial polypropylene meshes were coated with metal-containing diamond-like carbon (Me-DLC) thin films by the magnetron sputtering technique. Several dissimilar metals (silver, cobalt, indium, tungsten, tin, aluminum, chromium, zinc, manganese, tantalum, and titanium) were tested and compositional analyses of each Me-DLC were performed by Rutherford backscattering spectrometry. Antimicrobial activities of the films against five microbial species (Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis) were also investigated by a modified Kirby-Bauer test. Results showed that films containing silver and cobalt have inhibited the growth of all microbial species. Tungsten-DLC, tin-DLC, aluminum-DLC, zinc-DLC, manganese-DLC, and tantalum-DLC inhibited the growth of some strains, while chromium- and titanium-DLC weakly inhibited the growth of only one tested strain. In-DLC film showed no antimicrobial activity. The effects of tungsten-DLC and cobalt-DLC on Pseudomonas aeruginosa biofilm formation were also assessed. Tungsten-DLC was able to significantly reduce biofilm formation. Overall, the experimental results in the present study have shown new approaches to coating polymeric biomaterials aiming antimicrobial effect.

Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

International Nuclear Information System (INIS)

Czarnowska, Elżbieta; Borowski, Tomasz; Sowińska, Agnieszka; Lelątko, Józef; Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał; Wierzchoń, Tadeusz

2015-01-01

Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications

Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

Energy Technology Data Exchange (ETDEWEB)

Czarnowska, Elżbieta [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Borowski, Tomasz [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Sowińska, Agnieszka [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Lelątko, Józef [Silesia University, Faculty of Computer Science and Materials Science, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Wierzchoń, Tadeusz, E-mail: twierz@inmat.pw.edu.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland)

2015-04-15

Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

Investigations on bioaccumulation of cobalt by fish eggs

International Nuclear Information System (INIS)

Harms, U.; Behringer, H.; Kunze, J.

1978-01-01

In ionized form cobalt is taken up by fish eggs directly from the water. Accumulation takes place on the chorion where the metal ions are reversibly bound to functional groups of the protein of the envelope of the egg or of the mycosa. To a small extent there occurs a transport of metal ions into the interior of the egg. It could not be clarified within the scope of the studies performed if this process is to be attributed to diffusion. Binding of the cobalt ions to the chorion leads, within hours, to a nearly uncharged final state, an apparent equilibrium, whose position is determined by the cobalt ion concentration of the breeding medium. Foreign ions (electrolytes like Ca 2+ ) lead to reduced uptake of cobalt ions, because they compete with the latter for binding places in the egg's envelope. Complex-forming substances (cysteine) result in lower absorption rates, too, the concentration of available cobalt ions in the water being reduced. (orig.) [de

Method of production of hollow silicon nitride articles

International Nuclear Information System (INIS)

Parr, N.L.; Brown, R.L.

1971-01-01

The hollow articles prepared according to the invention have a high density, exhibit no internal stresses and correspond to high demands of tolerance and surface quality. One obtains these by flame spraying silicon powder on a pre-heated form designed with separating agent - e.g. NaCl. After removing the form, the silicon is nitridated to silicon nitride by heating in N 2 or in an atmosphere of ammonia. This process can be interrupted if the article is also to be mechanically processed, and then the nitridation can be completed. (Hoe/LH) [de

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.

Precipitation formation in recrystallized nickel-plated non-sag tungsten wire

International Nuclear Information System (INIS)

Lai, Z.H.

1994-01-01

It is well established that some metals, such as palladium and nickel, can easily penetrate into tungsten by fast diffusion via crystal defects such as grain boundaries and dislocations. As a result of the fast penetration of these so called activators the recrystallization temperature of heavily drawn non-sag tungsten wire can be lower from about 2,000 C to about 1,000 C, thus the application of the tungsten wire, serving as reinforcement material in metal matrix composites used at high temperatures, is limited. An interesting question is in which form these activators exist in the recrystallized tungsten wire. It is generally believed that W-Ni intermediate compounds could form in the recrystallized material, presumably at grain boundaries. The free energy difference between the pure tungsten fibbers and the precipitating W(Ni) solid solution was suggested as the chemical driving force which governed the recrystallization process. The presence of nickel in small particles had also been observed in recrystallized grains of nickel plated tungsten wires using scanning electron microscopy (SEM) and secondary ion mass spectroscopy. These particles were considered to be nickel rich precipitates. However, a detailed investigation of the precipitation process has not been reported. In the present work an investigation of the structure, composition and distribution of nickel rich particles precipitated in recrystallized grains of nickel plated heavily drawn non-sage tungsten wires was carried out using analytical electron microscopy (AEM)

Crack resistance of tungsten strengthened by dispersed refractory oxides

International Nuclear Information System (INIS)

Babak, A.V.; Uskov, E.I.

1984-01-01

Investigation results are presented for crack resistance of commercial tungsten, obtained during specimen testing at temperatures of 20 deg C to Tsub(cr) (upper boundary of temperature range of ductile-brittle transition). Comparison of s-n diagrams and temperature dependences of crack resistance are conducted for commercial tungsten and tungsten strengthened by refractory oxides. It is shown that dispersion hardening increases crack resistance in the temperature range of 20 to 2000 deg C but the upper boundary of ductile-brittle shifts to the side of higher temperatures

Electron work function of stepped tungsten surfaces

International Nuclear Information System (INIS)

Krahl-Urban, B.

1976-03-01

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

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.

Ion beam induces nitridation of silicon

International Nuclear Information System (INIS)

Petravic, M.; Williams, J.S.; Conway, M.

1998-01-01

High dose ion bombardment of silicon with reactive species, such as oxygen and nitrogen, has attracted considerable interest due to possible applications of beam-induced chemical compounds with silicon. For example, high energy oxygen bombardment of Si is now routinely used to form buried oxide layers for device purposes, the so called SIMOX structures. On the other hand, Si nitrides, formed by low energy ( 100 keV) nitrogen beam bombardment of Si, are attractive as oxidation barriers or gate insulators, primarily due to the low diffusivity of many species in Si nitrides. However, little data exists on silicon nitride formation during bombardment and its angle dependence, in particular for N 2 + bombardment in the 10 keV range, which is of interest for analytical techniques such as SIMS. In SIMS, low energy oxygen ions are more commonly used as bombarding species, as oxygen provides stable ion yields and enhances the positive secondary ion yield. Therefore, a large body of data can be found in the literature on oxide formation during low energy oxygen bombardment. Nitrogen bombardment of Si may cause similar effects to oxygen bombardment, as nitrogen and oxygen have similar masses and ranges in Si, show similar sputtering effects and both have the ability to form chemical compounds with Si. In this work we explore this possibility in some detail. We compare oxide and nitride formation during oxygen and nitrogen ion bombardment of Si under similar conditions. Despite the expected similar behaviour, some large differences in compound formation were found. These differences are explained in terms of different atomic diffusivities in oxides and nitrides, film structural differences and thermodynamic properties. (author)

Plasmonic spectral tunability of conductive ternary nitrides