PREPARATION OF TUNGSTEN AND TUNGSTEN CARBIDE SUBMICRON POWDERS IN A CHLORINE-HYDROGEN FLAME BY THE CHEMICAL VAPOR-PHASE REACTION

A hydrogen-chlorine flame chemical vapor deposition reactor has been developed to synthesize ultrafine powders of refractory compounds (e.g. carbides and nitrides). At the laboratory scale, synthesis of tungsten and tungsten carbides (both (WC)1-itx and α-W2C) gave encouraging results. The collected refractory powders do not have internal porosity, they exhibit spherical shape and have a very narrow size distribution. The size of the particles and the crystalline structure depends on the flame temperature, flow rate of the reactants and residence time of particles. In short, they depend on the flame characteristics. Thermochemical calculations were carried out to obtain the optimum conditions for different carbide powder synthesis. The flame is completely characterized and the temperature distribution within the reactor is obtained. © 1990.