Porous silica ceramics with relatively high strength and novel bi-modal pore structure prepared by a TBA-based gel-casting method

Porous silica ceramics with relatively high strength and novel bi-modal pore structure can be successfully fabricated via a facile tert-butyl alcohol-based gel-casting process by use of silica extracted from coal fly ash. Based on the evaporating of tert-butyl alcohol (TBA) during the drying process, the microstructure with bi-modal pores was obtained. By setting the solid loading (15 wt.%) and changing the sintering temperature from 1050 to 1150 °C, the porosity of the porous silica ceramics varied within the range of 70.1% and 72.4%, as the bulk density varied from 0.59 to 0.67 g/cm3 and small pore sizes from 3.31 to 2.89 nm. The compressive strength of sintered silica ceramics increased from 4.38 MPa to 5.82 MPa, which was attributed to the 3D-framework structure and the connection of silica particles.