Oxidation of tungsten carbide powders in air

The behavior of hexagonal tungsten monocarbide powders with the average particle size from 20 to 6000 nm in air in the temperature interval 323-1173 it is studied by differential thermal and thermogravimetric analyses, X-ray and laser diffraction methods and scanning electron microscopy. It is established that WC powders are oxidized, irrespective of their dispersity, to higher oxide WO3. It is shown that the decrease in the particle size of WC powders leads to a decrease in the exothermic peak temperature of oxidation and growth of the oxidation rate. The functional dependences of the temperature of the exothermic peak and the activation energy of oxidation on the particle size are determined. The estimated activation energy for WC powder with the average particle size from 20 nm to 10 pm changes from similar to 90 to similar to 120 kj.mol(-1). (C) 2013 Elsevier Ltd. All rights reserved.