The controllable microstructure of porous Al2O3 ceramics prepared via a novel freeze casting route

In traditional aqueous slurry freezing casting processing, the growth method of ice crystals is hard to control, resulting in the uncontrollable poreʹs morphologies of the porous ceramics. In the experimental, the pure Al2O3 sol was used to substitute water as a medium for preparing ceramic slurry. With Al2O3 sol addition, it becomes easy to control the microstructure and poreʹs morphologies of the porous Al2O3 ceramics via adjusting of the solid loading, composition of the ceramic slurries, as well as the cooling methods. The SEM micrographs showed that the sol-contained ceramic slurry combined with freeze casting processing can easily prepare the porous Al2O3 ceramics with different pore sizes and different morphologies. The porous Al2O3 ceramics prepared from 70 wt.% to 90 wt.% solid loading sol-contained Al2O3 slurries and sintered at 1500 °C for 2 h have open porosities from 81.7% to 64.6%.