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Atomic oxygen (AO) is considered the most erosive particle to spacecraft materials in low earth orbit (LEO). Carbon fiber, carbon/carbon (C/C), and some modified C/C composites were exposed to a simulated AO environment to investigate their behaviors in LEO. Scanning electron microscopy (SEM), AO erosion rate calculation, and mechanical property testing were used to characterize the material properties. Results show that the carbon fiber and C/C specimens undergo significant degradation under the AO bombing. According to the effects of AO on C/C-SiC and CVD-SiC-coated C/C, a condensed CVD-SiC coat is a feasible approach to protect C/C composites from AO degradation. [ABSTRACT FROM AUTHOR]

The reactivity of HO and the Si-terminated silicon carbide surface (001) was investigated on the triplet potential energy surface with the combined first principle and molecular mechanics ONIOM(CASSCF:AM1:UFF) method for the (SiC)·HO model. It was found that the HO molecule and the surface can form three physisorption complexes and follow five reaction paths to produce eight products, in which there are five main products having necessary energy barriers less than 300 kJ mol. Compared with that on the C-terminated surface, the interaction with the Si-terminated surface has stronger physisorption energy, smaller lowest necessary energy barrier, more main and more stable products. [ABSTRACT FROM AUTHOR]