105 原子状酸素によるグラファイトの劣化の照射方向依存性

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Spacecraft structures in low earth orbit (LEO) encounter a degradation problem caused by atomic oxygen in the space environment. This study presents an experiment of degradation due to atomic oxygen on the ground. The experiment was carried out in a vacuum space chamber. Atomic oxygen produced at a plasma torch was accelerated fluid-dynamically with argon working gas. As target materials, isotropic high density graphite and highly oriented pyrolytic graphite (HOPG) were used. In this study, the effect of the bombardment direction is investigated. The macroscopic mass loss was measured and the microscopic degradation mode was observed. The mass loss of isotropic graphite depends on bombardment direction; however, the effect of the bombardment direction is not large considering the reduction of the bombardment area due to the inclination of the surface of the target material. The mass loss of HOPG is negligible compared with that of isotropic graphite. The eroded surfaces of both materials were observed with SEM. In case of isotropic graphite, the erosion occurred mainly at grain boundary area. On the other hand, the surface of HOPG after bombardment remains flat. It suggests that degradation of HOPG occurs by not only each atom but also by grain.
社団法人日本機械学会の論文
2003-10-17