Preparation of in-situ TiO₂/O′-Sialon multiphase ceramics by selective-oxidation

On the basis of thermodynamic and thermal analysis, in-situ TiO₂/O′-Sialon multiphase ceramics were prepared from TiN/O′-Sialon materials by selective-oxidation at 800-1000 °C in air. The samples were characterized by XRD and EPMA. Selective-oxidation kinetics and effect of partial pressure of oxygen on oxidation process were studied. The results indicate that the increase of oxidation temperature and partial pressure of oxygen in the atmosphere accelerates the selective-oxidation of the materials. Logarithm rule, i.e., Δm/A = k log t + C can describe the selective-oxidation process perfectly with an apparent activation energy of 56.1 kJ/mol. There is no protective scale formed on the surface of the materials and diffusion of gas through gradually closed pores is believed to be the rate-limiting step.