Oxidation behavior of SiC in dissociated oxygen environments

Abstract

Dissociated oxygen environments are typically encountered during the hyper-speed flight of vehicles. Silicon carbide (SiC) is a typical material used in the thermal protection systems of hyper-speed vehicles; therefore, its oxidation behavior under dissociated oxygen conditions is crucial to the safety of flights. In this study, a high-frequency plasma wind tunnel was used to generate the dissociated oxygen environments to investigate the oxidation behavior of SiC in such environments. During the experiments, growth of silica (SiO₂) was observed on the surface; however, the thickness of this oxide layer reduced simultaneously. A para-linear curve was used to fit the experimental data to distinguish between the growth and recession processes. By combining molecular dynamics simulations with aerodynamic calculations, it was found that the oxidation of SiC was governed by the diffusion of dissociated oxygen through the channels in the SiO₂ crystal, while the loss of surface SiO₂ was due to its sublimation. These findings establish a theoretical foundation for determining the failure boundaries of SiC materials during hyper-speed flight.