Mechanochemical synthesis of nanocrystalline tungsten carbide powders

Nanocrystalline tungsten carbide powder mixtures of WC, W2C, and cubic WC1- z were prepared by the mechanochemical method of reactive high energy ball milling WO3-Mg mixtures containing graphite as a source of carbon for the W phase. The synthesis is completed in two steps, namely the explosive react ive synthesis of alpha-W by the reductive reaction of Mg with WO3 and the d iffusion reaction of high activity alpha-W with C. The chemical regularitie s of mechanochemical synthesis of the refractory compounds are given. After grinding for 50 h at a milling rate of 250 rev min(-1), all WO3 and C diff raction peaks disappeared and only diffraction peaks of tungsten carbides a nd MgO remained. The final product, with an average grain size of about 4-2 0 nm was obtained after MgO was removed by HCl solution.