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http://dx.doi.org/10.4150/KPMI.2003.10.6.422

A Study on the Reduction Mechanism of Tungsten and Copper Oxide Composite Powders  

Lee, Seong (Technical Research Center, Agency for Defense Development)
Hong, Moon-Hee (Technical Research Center, Agency for Defense Development)
Kim, Eun-Pyo (Technical Research Center, Agency for Defense Development)
Lee, Sung-Ho (Technical Research Center, Agency for Defense Development)
Noh, Joon-Woong (Technical Research Center, Agency for Defense Development)
Publication Information
Journal of Powder Materials / v.10, no.6, 2003 , pp. 422-429 More about this Journal
Abstract
The reduction mechanism of the composite powders mixed with $WO_3$ and CuO has been studied by using thermogravimetry (TG), X-ray diffraction, and microstructure analyses. The composite powders were made by simple Turbula mixing, spray drying, and ball-milling in a stainless steel jar with the ball to powder ratio of 32 to 1 at 80 rpm for 1 h without process controlling agents. It is observed that all the oxide composite powders are converted to W-coated Cu composite powder after reducing treatment under hydrogen atmosphere. For the formation mechanism of W-coated Cu composite powder, the sequential reduction steps are proposed as follows: CuO contained in the ball-milled composite powder is initially reduced to Cu at the temperature range from 20$0^{\circ}C$ to 30$0^{\circ}C$. Then, $WO_3$ powder is reduced to W $O_2$ via W $O_{2.9}$ and W $O_{2.72}$ at higher temperature region. Finally, the gaseous phase of $WO_3(OH)_2$ formed by reaction of $WO_2$ with water vapour migrates to previously reduced Cu and deposits on it as W reduced by hydrogen. The proposed mechanism has been proved through the model experiment which was performed by using Cu plate and $WO_3$ powder.
Keywords
W and Cu oxide composite powders; W-Cu composite powder; Reduction mechanism; Ball-milling;
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