Effect of trace alumina on mechanical, dielectric, and ablation properties of fused silica ceramics

The effect of a small amount of alumina on the mechanical strength, thermal shock resistance, room temperature and high-temperature dielectric, and ultra-high temperature ablation properties of fused silica ceramics prepared by aqueous gelcasting was investigated. Alumina addition promoted the dissolution of silica during slurry preparation. Compared to a pure fused silica sample, the flexural strength and thermal shock residual strength of fused silica ceramics with 0.5 wt% alumina (sintered at 1250 °C) reached 79.9 MPa and 82.0 MPa, showing increases of 19.3% and 19.9%, respectively. In addition, the ablation resistance increased. The mass loss rate and linear recession rate of fused silica ceramics with 0.5 wt% alumina were 0.018 g/s and 0.133 mm/s at 10 s and 0.026 g/s and 0.089 mm/s at 60 s ablation time, respectively. Importantly, the presence of alumina did not decrease the excellent room temperature and high-temperature dielectric properties of fused silica ceramics.