Porous mullite composite with controlled pore structure processed using a freeze casting of TBA-based coal fly ash slurries

Porous ceramic composite with controlled “designer” pore structure has been prepared by a freeze casting route using a tertiary-butyl alcohol (TBA)/coal fly slurry system. Unidirectional aligned macropore channels were developed by controlling the solidification direction. Simultaneously, small sized dendrite-like pores formed in the outer walls of the pore channels. The compressive strength of the sintered porous composite increased as the porosity decreased, i.e. low porosity gave a high compressive strength. After sintering at 1500 °C, the mullite composite with a porosity of 67% exhibited a compressive strength of ∼23 MPa.