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 degrees C to 1300 degrees C, the bulk density (1.78-2.05 g/cm(3)) and linear shrinkage (1.98-4.23%) were increased, but the flexural strength was only enhanced within 1275 degrees C with a maximum of 20.69 MPa, since excess fused silica crystallized into cristobalite at 1300 degrees C, which deteriorated mechanical properties. (C) 2019 Elsevier B.V. All rights reserved.