Damage behavior of atomic oxygen on CVD SiC coating-modified carbon/carbon composite in low earth orbit environment

In this work, samples of carbon/carbon (C/C) and chemical vapor deposited (CVD) SiC-coated C/C samples were investigated to understand the AO damage mechanism in low Earth orbit (LEO) environment. The ground-based simulated atomic oxygen (AO) generator was employed. Results indicate that the CVD SiC coating exhibited improved radiation resistance properties against AO radiation as evidenced by a 16% better strength retention ratio, 60% less mass ablation, and increased strength stability. The magnitude of these influences affected the surface morphology, as observed by scanning electron microscopy (SEM) and surface resistance meter test results. The variations in the surface constituents were confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results. The main products left on surface after AO exposure are SiO₂ and SiC_xO_y film. Additionally, Si atoms are found to be the preferential reacting element in the SiC coating, and this process is accompanied by graphite precipitation, grain growth, and crack necking. Also, the damage mechanism of the AO-exposed SiC coating was revealed and is discussed.