Erosion of Carbon-Based Materials Under High-Fluence Heavy-Ion Irradiation

Abstract

Carbon-based materials are widely used in aerospace industry due to their strength, heat shielding properties, and a number of other specific characteristics [1]. To trace the radiation damage influence on the erosion regularities the sputtering yields Y of highly-oriented pyrolytic graphite (HOPG), polycrystalline graphites and one-dimensional composite material under high-fluence (10 – 10 ion/cm) 30 keV N2 and Ar ions at the incidence angles from θ = 0 (normal incidence) to θ = 80, developed morphology and crystalline phase state from low temperatures (T ~ −180C) till elevated ones (T ~ 400C) have been studied. At normal and near normal ion incidence Reflection High Energy Electron Diffraction has shown that diffraction patterns correspond to a high degree of disorder (diffuse halo) at the temperatures less the defect annealing temperature Ta. At elevated temperatures (T > Ta) the patterns have been found similar to those for the non-irradiated surfaces. It has been found that Ta is easy determined by a step-like behavior of a temperature dependence of ion-electron emission yield γ. This γ-jump has been explained by the dependence of secondary electron path length λ on changes in lattice structure (transition from strongly disordered surface layer under ion irradiation at T Ta) [2]. The Y(θ) dependences measured at T Ta, due to the ion-induced diffusion processes, causing three-fold suppression of sputtering in comparison with irradiation at T < Ta. The Ar irradiation at the room temperature results to strong sputtering suppressing in comparison with the isotropic polycrystalline graphites at the same conditions.