The tungsten industrial production is mostly based on the hydrogen reduction of tungsten oxides, ammonium paratungstate (APT) or ammonium tungsten oxide bronze (ATOB) obtaining high purity tungsten specimens. In the first reduction step occurs the formation of WO 2, and the incorporation of additives is more efficient [9–13].
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Selective dissolution of a tungsten (85 wt.%)–rhenium (15 wt.%) alloy with rhenium in hydrochloric acid at the temperature of 298 K and anodic polarization modes was carried out to develop a porous catalytic substrate and to recycle rare metals. The parameters of the effective selective anodic dissolution of the tungsten–rhenium alloy, including the differences in applied …
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This investigation shows how alkali compounds act during the reduction of doped tungsten oxides, making their effects "visible" in XRD and SEM investigations by using both heterogeneous and homogeneous additions. Alkali metals react at the very beginning of …
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The action of aluminum traces on tungsten reduction by hydrogen is examined. A detailed description of the morphological changes which occur during the reduction of the tungsten oxide to metal ...
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This study undertakes a comprehensive review of prior research on the use of hydrogen plasma for metal oxides reduction and reviewing state-of-the-art techniques for its use in extractive metallurgy applications. ... The authors reported that to produce tungsten powder, the hydrogen plasma route consumed 1.5 times less hydrogen and 1.8 times ...
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Hexagonal ammonium tungsten bronze (ATB, (NH 4)xWO 3) and tungsten xide obtained by the thermal decomposition from monoclinic ammonium paratungstate (APT) and tungstic acid were reduced in dry hydrogen.Monoclinic WO 2.90, tetragonal WO 2.90, monoclinic WO 2, and cubic β-W (i.e. W 3 O) for intermediate were produced. The decomposition of β-W …
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The tungsten oxides react with the water vapor released by the hydrogen reduction to form a volatile tungsten oxide WO 2 (OH) 2. Subsequently, WO 2 (OH) 2 tends to be reduced to W deposited on the surface of low-valent tungsten oxides or tungsten grains, resulting in the growth and heterogeneity of tungsten powders [[15], [16], [17], [18]].
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The reduction of WF 6 with hydrogen on a heated surface under atmospheric pressure, temperatures of 500–600°C, and a stoichiometric ratio of components with the subsequent additional reduction of tungsten hexafluoride at t = 800°C and condensation of formed HF is described. The method of calculation of the completeness (α) of reduction of WF 6 and …
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This paper deals with the reduction experiments, carried out during the past few years, with special regard to this «low temperature» range of 500 to 750 o C. Several hundred experiments were evaluated, using pure tungsten yellow oxide (WO 3 ), WO 2.72 and WO 2
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The industrial production of tungsten powder is carried out by the reduction of tungsten oxide powder via hydrogen. In this process, the size of the W particles is limited to particle sizes larger than 100 nm. To get below this limit, alternative processes are needed. In the current work, the possibility of preparing W powder below 100 nm via a vapour phase …
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Reduction of tungsten oxides with hydrogen and with hydrogen and carbon. Thermochim. Acta, 285 (1996), pp. 361-382. View PDF View article View in Scopus Google Scholar [41] L. Wang, G.H. Zhang, K.C. Chou. Mechanism and kinetic study of hydrogen reduction of ultra-fine spherical MoO 3 to MoO 2.
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A novel process is proposed for the preparation of tungsten powder by the hydrogen reduction of tungsten xide. The process changes the traditional method of flow of hydrogen from the surface ...
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With a high N 2 plasma flux, the W-N bond can be formed on the tungsten oxide surface, which contributes to the promotion of the hydrogen evolution reaction (HER) activity, and an overpotential of 93 mV @ 10 mA cm −2 in 1.0 M KOH is exhibited, and the Tafel slope largely reduced to 76 mV dec-1. Such a facile strategy provides an engineering ...
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PREVIOUS work1 has shown that hydrogen reduction of tungsten xide gave the β-oxide (W20O58)2, which was then apparently reduced both to β-tungsten (a = 5.04 A.) and to tungsten dioxide or ...
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In the industrial production, the tungsten powders are mainly produced by the hydrogen reduction of tungsten oxides [14].The temperature and the water vapor partial pressure are the main factors influencing the hydrogen reduction of tungsten oxides [5].The reduction process is accompanied by a chemical vapor transport process, especially at high temperature.
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An investigation of the variables involved in the deposition of tungsten from a mixture of tungsten hexafluoride and hydrogen has shown that the fastest rate of deposition (about 5 mils thickness in 2 min) was obtained at atmospheric pressure with a hydrogen/tungsten hexafluoride ratio of 1.5 (by volume) at a temperature of 800°–850°C.
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Hydrogen isotope retention of tungsten in nuclear fusion reactors is one of the hot research issues all along. In this paper, tungsten samples in different rolled surfaces were polished by mechanical processing, subsequently subjected to D 2 + irradiation and thermal desorption. To better understand the experimental observations, this study also performed …
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In the present investigation, we have explored the synthesis of tungsten powders by means of annealing treatments and hydrogen reduction of ammonium paratungstate, …
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Tungsten is industrially produced by reducing tungsten xide WO 3 or blue tungsten oxide WO 3À x with hydrogen [3] ... Hydrogen reduction at 900 °C for 30 min with 0.5 L/min H2 flowrate ...
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The production of tungsten powder was mainly obtained by the hydrogen reduction of tungsten xide [21]. In the reduction, the main factors affecting the reaction process can be attributed to temperature and H 2 O partial pressure [4]. Furthermore, it undergoes a multistage reaction and forms a series of oxides [[22], [23], [24]].
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The experiments confirmed that intermediately formed tungsten bronzes play an important role in the early stages of reduction. Further experiments showed that bronzes are formed from potassium containing compounds in equilibrium with mixtures of W and WO 2 or WO 2 and WO 2.72.Furthermore it is demonstrated that the kinetics of the reduction sequence …
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addition to the reduction characteristics of the WO x layer formed on the tungsten line surface using hydrogen plasmas. The surface oxidation of tungsten lines during the mask layer removal process could be minimized by using low-temperature (300K) plasma processing for the removal of the carbon-based material. Using this technique, the ...
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On the other hand, WO 2 and H 2 O can form volatile tungsten oxide-hydroxide during reduction, and then the tungsten grain grows through CVT (chemical vapour transport) reaction [13, 15]: 222 H3)g(OH)(WO O(g)H4W(s) 2 (1) When the p H 2 O /p H 2 in hydrogen atmosphere is high, the nucleation is limited; tungsten grain grows; and coarse-grain ...
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The industrial production of tungsten powder is carried out by the reduction of tungsten oxide powder via hydrogen. In this process, the size of the W particles is limited to particle sizes larger ...
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Reduction of tungsten oxide using a hydrogen plasma Rasulyaar, Parwez Award date: 2021 Link to publication Disclaimer This document contains a student thesis (bachelor's or master's), as authored by a student at Eindhoven University of Technology. Student theses are made available in the TU/e repository upon obtaining the required degree.
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A novel process is proposed for the preparation of tungsten powder by the hydrogen reduction of tungsten xide. The process changes the traditional method of flow of hydrogen from the surface ...
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Current commercial tungsten powder is dominantly produced via hydrogen reduction of the tungsten oxides. Carbothermic reduction is not preferred for producing pure …
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PREVIOUS work1 has shown that hydrogen reduction of tungsten xide gave the β-oxide (W20O58)2, which was then apparently reduced both to β-tungsten (a = 5.04 A.) and to …
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The process of reduction of tungsten oxide in hydrogen arc plasma using linear plasmatron (300 kW) and a direct-flow reactor has been developed on semi-industrial scale (INET, VNIITS, VNIIETO, USSR) . By rapid cooling (quenching) metallic tungsten powder as globular particulates with a specific surface of 10–12 m 2 /g was produced. After ...
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Hydrogen reduction of tungsten oxide is currently the most widely used technology to produce metal tungsten for its simplicity and pollution-free nature. The computer simulation is a powerful tool for exploring the mechanism of hydrogen reduction of tungsten oxide from a microscopic view. The density functional theory (DFT) is applied to investigate the adsorption …
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