Effect of pre-reduced Cu particles on hydrogen-reduction of W-oxide in WO3–CuO powder mixtures

The hydrogen-reduction behavior of W-oxides in ball-milled powder mixtures of W- and Cu-oxides was investigated by microstructural analysis and humidity change measurement in the reduction process. The refinement and homogeneous mixing of powders by the ball-milling process induced a decrease in hydrogen-reduction temperature of W-oxides and the resultant refinement of W particle size. In addition, it is suggested that the surface of previously hydrogen-reduced Cu particles acted as a nucleation site to be W particles by reduction including chemical vapor transport process of WO2 in hydrogen atmosphere. Decrease in reduction temperature of W-oxides in powder mixture was explained by the attribution of Cu particles in the hydrogen-reduction of WO2.