Effects of Plasma Exposure on Boron Nitride Ceramic Insulators for Hall-Effect Thrusters

摘要

Worn Hall-effect thrusters show a variety of unique microstructures and elemental compositions in the boron nitride thruster channel walls. Understanding the plasma conditions that lead to the formation of these microstructures and elemental changes can assist in the goal of creating new ceramic materials with desired plasma material interactions. Pristine and worn Hall-effect thruster channel samples of boron nitride were exposed to xenon plasma in a magnetron sputter device. Erosion rate was shown to depend on the grade of the boron nitride ceramic and the preparation of the surface before plasma exposure. Worn Hall-effect thruster thruster channel samples eroded up to 90% faster than their pristine counterparts. This result highlights the evolution and feedback of the plasma-material interaction within the Hall-effect thruster channel. Microscope images of the ceramic surface show that the magnetron plasma rounded the edges of the ceramic grains to closely match the worn Hall-effect thruster surface. This effect is absent from pure ion beam bombardment and appears to be unique to quasi-neutral plasma exposure.