Reactive Molecular Dynamics Study of Silicon Carbide under Atomic Oxygen Exposure: Structural Dependence of Oxidation and Erosion Resistance
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Atomic oxygen (AO) in low Earth orbit (LEO) poses a severe erosion threat to silicon carbide (SiC) used in spacecraft thermal protection systems. In this work, large-scale reactive molecular dynamics (RMD) simulations are employed to systematically investigate the AO erosion behaviors of single-crystal SiC with different polytypes, surface terminations, and stacking sequences. The results reveal that surface termination and polytype predominantly control the AO erosion resistance of single-crystal SiC, whereas stacking sequence exerts only a minor influence. From the onset of AO bombardment, the surface termination plays a dominant role: the Si-terminated surface immediately forms a dense and stable SiO₂ passivation layer that drastically suppresses mass loss, whereas the C-terminated surface induces immediately CO/CO₂ release and rapid erosion. Notably, among Si-terminated polytypes, hexagonal 4H-SiC far outperforms cubic 3C-SiC, showing ~8% higher AO adsorption, ~50% lower erosion depth under extended exposure, and transient dynamic recrystallization that effectively heals lattice disorder and delays catastrophic collapse. These findings elucidate the coupled thermo-mechanical-chemical mechanisms underlying AO-induced SiC erosion and provide guidance for the design of spacecraft thermal protection components.
