Current research and development on the oxidation kinetics of nonoxide ceramics

Abstract

Nonoxide ceramics (NOCs) as representative high-temperature structural materials are widely applied in various key fields, such as metallurgy, electric power, and chemical industry, owing to combined excellent characteristics including high strength, lightweight, good thermal shock resistance, and erosion resistance. In practical applications, NOCs are often exposed to high temperatures containing oxygen; thus, they are inevitably confronted with the oxidation issue. In addition, NOCs are mostly used as lining materials for high-temperature containers and transmission components for high-temperature devices, in which they are also subjected to external loads. Simultaneously, internal stress will be generated inside the oxide film during oxidation, owing to the density difference and thermal expansion coefficient difference between the oxidation products and substrate. The coupled effect of oxidation and complex stresses accelerates the degradation of high-temperature performance and ultimately reduces the service life of NOCs, even causing severe industrial accidents. Therefore, studying the oxidation of NOCs under complex conditions is essential. However, limited by the high temperature and long serving time, an experimental approach to the oxidation of NOCs remains a challenge. By comparison, kinetic models based on specific reaction principles and different assumptions have become an effective tool for understanding and analyzing the oxidation of NOCs. This article compares the oxidation mechanism and corresponding kinetic models of NOCs under stressfree and stress conditions. Through comparing and analyzing the application effects of different models, the effect of stress on oxidation of NOCs is determined from a quantitative point, and the oxidation kinetic models of NOCs considering stress are preliminarily established, which can provide a scientific model for further recognition of service behavior of NOCs under complex conditions and provide effective theoretical guidance for improvement of the service life of materials.

Keywords

• nonoxide ceramics
• oxidation
• diffusion
• stress
• kinetic model