Energy Dependence of Hyperthermal Oxygen Atom Erosion of a Fluorocarbon Polymer: Relevance to Space Environmental Effects

The origin of the inconsistency in the erosion phenomena of fluorocarbon polymers between a ground-based atomic-oxygen test environment and the low Earth orbital space environment has been investigated. A detailed experiment was performed in order to study the effect of the high-energy component in the atomic-oxygen beam pulses on the erosion. The experiment was carried out with the combination of a polymer-coated quartz crystal microbalance and a high-speed chopper wheel installed in a laser-detonation atomic-oxygen facility. It was clearly observed that the mass-loss rates of both polyimide and fluorocarbon polymers depend on the impact energy of atomic oxygen. However, the energy dependence is more significant on the fluorocarbon polymer compared with that on polyimide. Collisions of atomic oxygen with translational energies higher than ∼5 eV induce a significant mass loss on the fluorocarbon polymer. These experimental findings agree with earlier measurements of the volatile products released during hyperthermal O-atom bombardment, and they are consistent with theoretical calculations on related systems. It is concluded that the difference in the collision energy distribution of atomic oxygen between laboratory and space environments is the major reason for the difference in erosion yields measured in the two environments.