The preparation of tungsten carbides and tungsten powders by reaction of tungsten trioxide with methanol

摘要

In the present study, a new and simple method to prepare tungsten and tungsten carbides powders was proposed by using WO3 powders as the raw material and CH3OH vapor as the reduction and carbonization agent. Both thermodynamic and experimental studies were carried out, and based on the results, the reaction routes were obtained. It was found that at low and moderate temperatures, the final product of WC was formed via intermediates of W18O49, WO2, partial metallic W and W2C; while at high temperature, WO3 was first reduced to WO2 with the intermediate phase of W18O49, and then reduced to W. The morphology of final products almost retained the same shape as that of raw materials WO3 at low temperature, however, the large particles with blocky shape disappeared and the products were all small W particles with polyhedral shape at high temperature. Furthermore, the reaction mechanisms were proposed: the pseudomorphic transformation mechanism dominated the reaction at low temperature, but at high temperature, the reduction obeyed the chemical vapor transport mechanism, which is beneficial for grain refining of final product.