Plasma-Induced Erosion on Ceramic Wall Structures in Hall-Effect Thrusters

摘要

A 60 wt% boron nitride (BN)-40 wt% silica (SiO_2) hot-pressed composite, denoted as M26, was used as the insulating chamber wall for a xenon plasma Hall-effect thruster operated for approximately 2000 h at power levels between 1.5 and 5 kW. The chamber wall showed a range of erosion microstructures. In the heavily eroded regions, striations in the surface topology were evident with surface protrusions in the generic shape of conical tips consisting of stratified BN and silica phases. Microcracking along the long axis of the BN basal plane was prevalent Through a two-dimensional finite element model, the microcracking has been determined to occur because of the anisotropic thermal expansion of BN in the amorphous silica matrix. Exfoliation accompanied the microcracking in BN and resulted in the preferential loss of BN as compared with silica in these heavily eroded regions.