Porous fused silica ceramics prepared by gelcasting using multigrade fused silica powders

Porous fused silica ceramics were successfully prepared by gelcasting using N, N–dimethylacrylamide (DMAA) as gelling agent and multigrade powders as starting materials. The results suggest that the ratio of fine–grained to coarse–grained mixed powders, solid loading and sintering temperature were highly correlated with microstructure and properties of fused silica ceramics. When the ratio was 0.8 and solid loading was 80 vol%, the resulting slurries had a relatively high viscosity, which ensured the excellent homogeneity and stability of slurries, ultimately endowing fused silica ceramics desirable microstructure and properties. As sintering temperature increased from 1225 °C to 1300 °C, the bulk density (1.78–2.05 g/cm³) and linear shrinkage (1.98–4.23%) were increased, but the flexural strength was only enhanced within 1275 °C with a maximum of 20.69 MPa, since excess fused silica crystallized into cristobalite at 1300 °C, which deteriorated mechanical properties.