Molecular insight of the interface evolution of silicon carbide under hyperthermal atomic oxygen impact

One of the key challenges faced by hypersonic flying is the complex thermal–mechanical–chemical coupling effect between thermal protection materials and non-equilibrium flow environment. Silicon carbide (SiC) has drawn much attention due to its superior physical and chemical characteristics, and its performance under hyperthermal atomic oxygen (AO) impact, however, is still little known. This work investigates the effects of various SiC crystalline polytypes, surface temperature, and crystal orientations on the SiC interface evolution by hyperthermal AO collisions via the reactive molecular dynamics method. The results showed that SiC surface erosion is highly dependent on the temperature and the presence of different interfacial structures. In the range of 500–2000 K, the proceeding of the passive oxidation advances the amorphous SiO2/SiC interface and the formation of SixOy phase weakens the surface catalytic characteristics and mechanical properties. The presence of defects, such as dangling bonds at the gas–solid interface, caused by different surface orientations affects the anti-erosion capabilities of SiC significantly, which may limit its further wide applications.