Preparation of porous silica ceramics with relatively high strength by a TBA-based gel-casting method

Porous silica ceramics with relatively high mechanical strength can be successfully fabricated via a novel tert-butyl alcohol-based gel-casting method. The microstructure similar to stone arch bridges and the sintering neck can be easily observed due to the evaporation of tert-butyl alcohol (TBA) during the drying process. The porosity of samples with different solid loading sintered at 1150 °C varied within the range of 56.4% and 70.1%, as the bulk density from 0.67 to 1.04 g/cm3. The compressive strength of sintered silica ceramics increased from 4.32 MPa to 8.82 MPa, which was attributed to the 3D-framework structure and the connection of silica particles. By setting the solid loading (15 wt.%) and changing the sintering temperature from 1050 to 1200 °C, the porosity of the sintered samples varied within the range of 51% and 72.4%, as the bulk density remarkably varied from 0.59 to 1.18 g/cm3 and pore sizes from 3.31 to 2.89 nm.

► Porous silica ceramics with relatively high strength were fabricated by a new gel-casting.
► Comparing with water-based gel-casting, TBA-based gel-casting can be used in slurries with ultra low solid loading.
► The raw silica powders were extracted directly from coal fly ash.