The oxidation of TiC in dry oxygen, wet oxygen, and water vapor

Isothermal oxidation of TiC was studied using powder sample at 300-400degreesC in Ar/O-2 = 95/5 kPa (dry oxidation) and Ar/O-2/H2O = 90/5/5-10 kPa (wet oxidation), and at 520-650degreesC in Ar/H2O = 95/5-15 kPa (H2O oxidation) by monitoring weight changes. The phases produced were identified by X-ray analysis and the oxidized sample was observed by scanning and transmission electron microscopy. The dry, wet and H2O oxidation of TiC was found to be described by a one-dimensional diffusion-controlling equation. It was revealed that the oxidation was divided into three steps, slow step I, fast step II, and slow step III. Water vapor in the wet oxidation accelerated these three steps, particularly step II. Non-isothermal oxidation of TiC was also performed to simultaneously monitor the evolved gases (CO/CO2, H-2, CH4) with weight changes by thermogravimetry and mass analysis. The accelerating effect of water vapor on oxidation of TiC was discussed from kinetic and thermoanalytical viewpoints. (C) 2004 Kluwer Academic Publishers.