Surface flashover performance of chemically etched polycrystalline alumina

The surface flashover behavior of SiC and diamond-polished alumina samples is examined before and after chemical etching in molten borax. The etching parameters (e.g., crucible type, etching time, and temperature) are initially optimized to obtain a uniformly etched surface possessing minimum damages. The etching in molten borax at 850°C for 2 hours displayed a satisfactory surface condition, including minimum contamination. The surface flashover behavior of both the SiC- and the diamond-polished sampled to found to improve significantly after a controlled etching. The observed improvement in the surface flashover behavior is discussed in relation to the surface defects that are introduced during mechanical polishing