Processing and microstructure characterization of porous corundum–spinel ceramics prepared by in situ decomposition pore-forming technique

Porous corundum–spinel ceramics were prepared from Al(OH)3 and basic magnesium carbonate by an in situ decomposition pore-forming technique. Apparent porosity was detected by Archimedes’ Principle with water as medium. Pore size distribution and the volume percentage of micropores were measured by mercury intrusion porosimetry, and the microstructure was analyzed by SEM. The apparent porosity of the sintered sample decreased with increasing the Al(OH)3 content in the raw mixture. With increasing temperature from 1200 °C to 1300 °C the porosity of the sample increased rapidly, from 1300 °C to 1500 °C the apparent porosity increased slightly, while it decreased rapidly when the temperature increased from 1500 °C to 1600 °C. The pores in the samples consist of two groups. One group is composed of micropores whose diameter is mostly in the range from 150 nm to 300 nm while the other is composed of bigger pores whose diameter is in the range from 0.5 μm to 1 μm. It was found that the composition of the starting powders and the sintering temperature are responsible for the apparent porosity and the pore size distribution of the samples. However the spinel formation and sintering play a more important role on porosity and pore size distribution.