Fabrication of porous silica ceramics by gelation-freezing of diatomite slurry

Diatomite-derived porous silica ceramics with high porosities of up to 90% were fabricated using a gelation-freezing method, which resulted in unidirectional cellular or random microstructure with micrometer-sized cells. The ice crystals that were formed during freezing of a diatomite powder dispersed gel were removed by sublimation during vacuum drying, and the green bodies were sintered at 1150-1350 °C for 2 h in air. The thermal conductivity of the porous ceramics prepared with initial solid loadings of 5 and 10 vol% ranged from 0.09 to 0.16 W/(mK) at room temperature. The proposed method is therefore promising for the preparation of ceramic thermal insulators with very low thermal conductivity.