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Deep decarburization of molybdenum and tungsten powders by wet hydrogen

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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Deposition of tungsten by reduction of its hexafluoride with hydrogen

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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Deep decarburization of molybdenum and tungsten powders by wet hydrogen

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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Regulation of particle size and morphology of tungsten powders in

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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Novel process for preparing tungsten powder by hydrogen …

A novel process is proposed for the preparation of tungsten powder by the hydrogen reduction of tungsten trioxide. The process changes the traditional method of flow of …

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Hydrogen Reduction of Tungsten Oxides

PREVIOUS work1 has shown that hydrogen reduction of tungsten trioxide 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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Hydrogen Reduction of Tungsten Oxides

PREVIOUS work1 has shown that hydrogen reduction of tungsten trioxide 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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Novel process for preparing tungsten powder by hydrogen reduction …

The production of tungsten powder was mainly obtained by the hydrogen reduction of tungsten trioxide [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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Study on hydrogen adsorption on WO3(001) surface by density

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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Evolution of reduction process from tungsten oxide to ultrafine

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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Effect of Water Vapor Partial Pressure on the Structure of Blue

A novel process is proposed for the preparation of tungsten powder by the hydrogen reduction of tungsten trioxide. The process changes the traditional method of flow of hydrogen from the surface ...

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Hydrogen Plasma for Low-Carbon Extractive Metallurgy: Oxides Reduction

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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Hydrogen reduction characteristics of WO3 based on density …

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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Hydrogen Reduction

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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(PDF) Hydrogen as a reducing agent: State-of-the-art …

The reduction of tungsten yellow oxide (WO 3) or tungsten blue oxide (WO 3-x) can be controlled by temperature and. ... Hydrogen reduction of model steam reforming catalysts, comprising about 10 ...

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Vapor Deposition of Tungsten by Hydrogen Reduction of Tungsten

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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Unraveling grain growth of metallic tungsten: Investigating the

In the first step of the hydrogen reduction process, the vapor phase product water vapor generated by the combination of hydrogen and oxygen atoms reacts with tungsten oxide, and vapor phase migration deposition is carried out in the form of WO2(OH)2 on the W nucleus, resulting in the abnormal growth of W particles [29–31].

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High-pressure hydrogen annealing for resistivity reduction of …

High-pressure hydrogen annealing for resistivity reduction of ultrathin tungsten electrodes. Author links open overlay panel Seunghyun Park a, Sungjun Kim b, Changyu Park a, Hyoungsub Kim a. Show more. Add to Mendeley. ... Reduction of tungsten oxides with hydrogen. Ind. Eng. Chem., 48 (1956), p. 318, 10.1021/ie50554a042. Google Scholar

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A new pathway for preparing ultrafine tungsten powder via non …

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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Environmentally safe fluoride cycle in tungsten technology

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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Novel process for preparing tungsten powder by hydrogen reduction …

A novel process is proposed for the preparation of tungsten powder by the hydrogen reduction of tungsten trioxide. The process changes the traditional method of flow of hydrogen from the surface ...

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Hydrogen reduction of tungsten oxides: Alkali additions, their …

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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Regulation of particle size and morphology of tungsten powders in

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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Mechanism of technical reduction of tungsten. Pt. 2. Hydrogen reduction

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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(PDF) Mechanism of technical reduction of tungsten: …

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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Deposition of tungsten by reduction of its hexafluoride with hydrogen

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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(PDF) Mechanism of technical reduction of tungsten: …

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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Study of the formation of tungsten powder by hydrogen reduction …

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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Kinetics of the hydrogen reduction of tungsten oxides

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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Metals Production and Metal Oxides Reduction Using Hydrogen: …

Tungsten is industrially produced by reducing tungsten trioxide 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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