The variation with temperature and oxygen concentration of the oxidation rate of large tubular specimens of graphite exposed to oxidising gas on the bore surface was examined. Temperatures in the range of 550 to 675C and oxygen concentrations of between 2.5 and 20.8% were studied. Under these conditions the overall rate of reaction was controlled by the rate of in-pore mass transport. A previously reported mathematical model was extended to interpret these results. The experimental results yield an apparent energy of activation of 25.0kcal/g-atom and an apparent order of 0.81. Calculations based on the extended model give a true energy of activation for the graphite-oxygen reaction of 48.6kcal/g-atom and an order of reaction of 0.62.

The Effect of Diffusion and Bulk Gas Flow on the Thermal Oxidation of Porous Carbons-II. Diffusional Effects in Graphite at High Temperatures. Hawtin, P., Gibson, J.A.: Carbon, 1966, 4[4], 489-500