W-Cu 산화물 복합분말의 환원 기구에 관한 연구

Abstract

The reduction mechanism of the composite powders mixed with WO3 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 200℃ to 300℃. Then, WO3 powder is reduced to WO2 via WO2.9 and WO2.72 at higher temperature region. Finally, the gaseous phase of WO2(OH)2 formed by reaction of WO2 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 WO3 powder.