Comparison of the Diffusion Control Models for Isothermal Oxidation of SiAlON Powders

Two kinetic diffusion control models (the parabolic rate law and Chou model) have been used to investigate the oxidation kinetic mechanism of SiAlON powder (beta-SiAlON (7 = 2.45), O'-SiAlON and x phase) based on the data available in literatures. The analysis shows that when the rate-controlling step is in the diffusion step. though both models can be used to describe the experimental data, Chou model is preferred. It is because, not only Chou model can give a clear physical meaning in expressing all parameters that will be convenient for theoretical discussion, but it will also perform a simple calculation. Besides, the most significant thing is that Chou model will lead to a more accurate calculation result.