Synthesis of tungsten carbide through gas–solid reaction at low temperatures

Conventionally, WC powders are produced heating a mixture of W powder and carbon black. This method is based on solid state reaction controlled by diffusion and phase transformations. Thus high temperatures (>1400°C) and long times are necessary. This paper presents a method able to synthesize WC at low temperatures (∼850°C) in 2 h. It is based on a gas–solid reaction between a W source and a C-containing gas. The gas phase is a mixture of H2 and CH4. Ammonium paratungstate and tungsten blue oxide are used as the tungsten source. The higher reactivity of the precursor material and the better contact between the gas–solid reactants explain the lower temperatures and higher reaction rates of this method compared to the conventional one. Very fine WC crystallites (<1 μm) can be produced, but the particle size, shape and porosity depend on the precursor type and particle size.