Reactive Molecular Dynamics Simulation of Interfacial Evolution Behavior of Amorphous Silica under an Atomic Oxygen Impact.

Using reactive molecular dynamics simulations, the protective limit, erosion mechanism, and surface mechanical properties of amorphous silica material under an extreme atomic oxygen (AO) impact are studied in this paper. The results show that the AO erosion process consists of two distinct stages: the absorption stage and the sublimation stages, with the transition occurring at a surface temperature of about 4200 K. High-energy and high-flux AO impacts shorten the duration of the absorption stage due to increased penetration (30 eV AO penetrating up to 4 Å of material), a high heating rate (230 K/ps), and enhanced chemical reactivity, leading to a reduction in material's protective performance. Notably, amorphous silica demonstrates a superior protective capability against a high-energy (10 eV) AO impact with an oxygen particle erosion rate of only 27% after 100 ps. Nanoindentation simulations indicate that amorphous silica exhibits excellent vertical and lateral surface mechanical properties when the oxygen atoms on its surface reach a dynamic equilibrium state (approaching the absorption peak: n = 200). These findings provide valuable insights for the evaluation and design of an amorphous silica-protected protective coating for aerospace applications in a low-Earth orbit.