Ion sputtering resistance of dense h-BN thick film prepared via a chemical vapor deposition technique

Abstract

Hexagonal boron nitride (h-BN) ceramics are promising materials for Hall thruster acceleration channel walls due to their high heat resistance, low thermal expansion, superior thermal shock resistance, and appropriate secondary electron emission coefficients. Nevertheless, its utility is considerably curtailed by a limited service life due to inadequate densification and suboptimal ion sputtering resistance. In this work, dense h-BN ceramics were fabricated through hot-press sintering utilizing Y₂O₃-Al₂O₃ as a sintering additive. A chemical vapor deposition (CVD) technique was then employed to create a dense h-BN thick film on the ceramic surface. Furthermore, an assessment of the sputtering resistance of the obtained h-BN ceramic and the dense h-BN thick film is conducted through focused ion beam sputtering. Results show that the sputtering depth of the dense h-BN thick film is only 50% of that of the h-BN ceramics under identical conditions. Following the depletion of the thick film, the sputtering loss rate of the h-BN ceramics with the film matches that of those without. These results underscore the efficacy of depositing a dense h-BN thick film through CVD, offering a potent strategy for substantially enhancing the ion sputtering resistance of h-BN ceramics without necessitating alterations in composition.