Degradation of Materials by High-Energy Atomic Oxygen

Abstract

The degradation of materials exposed in LEO (low earth orbit) is one of the most important problems in space technology because the predominant component of the atmosphere in LEO is AO (atomic oxygen) which degrades some kinds of materials. This paper presents an experimental simulation on the ground for the degradation of carbon-based materiais. In the experiment, AO produced at a plasma torch is accelerated fluid-dynamically with working gas. Graphite, C/C (carbon/carbon) composite and Si -C.C. (silicon impregnated C/C composite) were used as the target materials. The mass loss per unit area depends strongly on the temperature of the material surface. The eroded surfaces of materials were observed with SEM (scanning electron microscope) and laser fucus displacement meter. In case of C/C composite, the matrix region erodes more than carbon fiber. The mass loss of Si-C.C. is less than that of corresponding C/C composite and only the C/C region erodes deeply with almost no erosion in Si and SiC regions. In order to investigate the degradation caused by the impact of AO, numerical simulation was also conducted for graphite using MD (molecular dynamics) method.