VOLUME DIFFUSION OF ATOMIC OXYGEN IN alpha-SiO_2 PROTECTIVE COATING AT VARIOUS TEMPERATURES

摘要

The minimum thickness for an amorphous silicon dioxide (alpha-SiO_2) protective coating required to prevent volume diffusion of atomic oxygen in a low Earth orbit (LEO) was evaluated by measuring the oxide thickness formed on Si (001) wafers in a hyperthermal atomic oxygen beam. The thickness of oxide film was measured with X-ray photoelectron spectroscopy. The diffusion length of atomic oxygen in alpha-SiO_2 at temperatures between 297 K to 493 K, where exterior surfaces of a spacecraft may be heated in LEO, shows temperature and flux dependencies. The ground-based testing condition to evaluate performances of protective coatings will also be discussed.