抄録
The oxidation of tungsten in powder form has been investigated at temperatures below 400°C under oxygen pressures ranging from 10 to 400 mm Hg. It has been found that the apparent oxidation rate increases with the increase of the oxygen pressure PO2. Applying the model of double oxide layers, as previously described, to the present experimental results, the following results are obtained: (1) For the growth of the thin barrier scale layer the parabolic rate constant kp increases with PO2n and the activation energy is 29.4 kcal/mol; (2) for the growth of the outer porous layer from the barrier scale, the linear rate constant kl increases with log PO2 and the activation energy is 18.9 kcal/mol. The kinetics of the formation of these layers are discussed and the obtained results are found to be in agreement with the theory.
