Oxidation Kinetics of Zirconium Carbide at Relatively Low Temperatures

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Abstract
The isothermal oxidation of ZrC powders was carried out at relatively low temperatures of 380° to 550°C at oxygen pressures of 1.3, 2.6, and 7.9 kPa under a static total pressure of 39.5 kPa, achieved by mixing with argon, using an electromicrobalance. The oxidation kinetics are described by the diffusion‐controlled Jander's equation, following rapid oxidation in the early stage. Two activation energies were obtained: 138 kJ · mol−1 below about 470°C and 180 kJ · mol−1 above that temperature. The high‐ and low‐temperature oxidation mechanisms are discussed in connection with the crystallization of cubic ZrO2, accompanied by the generation of cracks, as well as the formation of carbon in the hexagonal diamond form in the product phase.