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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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 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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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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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 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 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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The purpose of this work is to add further details to the course of the hydrogen reduction reaction from tungsten-VI-oxide to tungsten powder. The investigations have been carried out under conditions far away from technical processes. The reduction has been studied by thermogravimetry forcing a thermodynamic reaction control by the use of tiny ...
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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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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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This study focuses on the operando unveiling of platinum-induced hydrogen spillover on monoclinic tungsten xide (γ-WO 3), employing ambient pressure X-ray photoelectron …
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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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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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Phase transformation of WO3/Y2O3 powder was observed during the hydrogen reduction process in the temperature range of 400–800 °C for up to 5 h. The reduction behavior was investigated by...
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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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A fluoride cycle in tungsten technology is based on three processes: (i) electrochemical decomposition of HF in the KHF 2 + HF melt at 80–100°C with the separate evolution of gaseous fluorine and hydrogen; (ii) fluorination of the tungsten powder with evoluated fluorine at 300–350°C with the condensation of formed WF 6 in a liquid form at t = 2.5–3.0°C, …
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An alternate method of producing metallic tungsten from WO 3 via hydrogen reduction is the use of a rotary furnace (Lassner & Schubert, 1999). The primary benefit of using a rotary furnace is the removal of the static powder bed. The powder in the rotary furnace tube is constantly tumbled as it progresses through the furnace, constantly ...
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The control of residual carbon content is an urgent problem to be solved for the preparations of molybdenum and tungsten powders by method of carbothermic reduction of their oxides.In this paper, finer Mo (W) powder with a low residual carbon content was prepared by a two-step reduction process consisting of carbothermal pre-reduction of MoO 3 (WO 3) at 1050 …
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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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Catalyzing hydrogen evolution reaction (HER) is a key process in high-efficiency proton exchange membrane water electrolysis (PEMWE) devices. To replace the use of Pt-based HER catalyst, tungsten carbide (W2C) is one of the most promising non-noble-metal-based catalysts with low cost, replicable catalytic performance, and durability. However, the …
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The reduction of oxide films on the surface of tungsten was studied. The oxide films were created by briefly exposing smooth W foils to oxygen plasma generated using a microwave discharge at 500 W and an oxygen pressure of 40 Pa. Oxidation resulted in the formation of a WO 3 film with a thickness of approximately 1700 nm. The oxidised samples …
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Uniform tungsten powders were prepared by an improved wet hydrogen reduction method. Explored the relationship between dew point, reduction temperature and particle size …
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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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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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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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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 …
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Tungsten fabricated by hydrogen reduction of WF6 and thermolysis of WCl6 has 100 -preferred columnar microstructures. However, the latter exhibits larger columnar grains and preferred 100 less. ...
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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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1 Introduction. Tungsten is widely used in products across the high density alloy [1,2], shielding material [3,4], photocatalyst [], and cemented carbides [].WC-Co-cemented carbides with ultrafine or nanocrystalline grains are widely employed in the precision machining field [7,8,9].The reduction step from tungsten oxide to pure tungsten powder is critical to determine the final …
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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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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 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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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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Hydrogen reduction of tungsten blue oxide to tungsten powder} author = {Haubner, R, Schubert, W D, Hellmer, H, Lassner, E, and Lux, B} abstractNote = {The purpose of this work was to ascertain the mechanism of the hydrogen reduction of tungsten oxide (WO/sub 3/, WOsub(2.9), WOsub(2.72) and WO/sub 2/) to tungsten powder and to clarify ...
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Ultrafine tungsten (W) powder was prepared by a non-contact carbon reduction followed by hydrogen reduction method. In this process, WO 3 and activated carbon were separated by a porous plate and the reduction of tungsten oxide was achieved by carbon atoms diffusion at high temperature. This method can stably prepare violet tungsten oxide powder …
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Hydrogen reduction of tungsten oxide has the widest application in many tungsten powder preparation for its series of advantages (simple equipment, mature technics, and less introducing impurities) [14]. However, as far as we know, the studies on the mechanism of hydrogen reduction have seldom been reported and are still unclear [15]. As a ...
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