Homogeneously bulk porous calcium hexaaluminate (CaAl12O19): Reactive sintering and microstructure development

Porous CaAl12O19 ceramics attract much attention toward many potential applications, such as high-temperature filters, catalyst supports, and lightweight structural materials at high temperatures. In this study, we have focused on the reactive sintering and microstructure development of homogeneously bulk porous CaAl12O19. Boehmite AlOOH powders with different particle size [0.08 µm (C01) and 0.7 µm (C06)] were used as Al2O3 sources. CaCO3 and boehmite powders were wet-ball milled, and the green compacts were sintered in air at 520 °C, 750 °C, 1100 °C, 1200 °C, 1300 °C, 1400 °C, 1500 °C (3 h) and 1600 °C (3 h), in order to analyze the microstructure development. At 1500 °C (3 h), microstructure became macroscopically homogeneous. The porosities of the C01 and C06 samples sintered at 1500 °C were calculated to be 51% and 56%, respectively. Stacking of the plate-like grains and their card-house structures are observed. Such card-house structures stabilize the open-porous structure even at 1600 °C. Just by changing the size of starting boehmite AlOOH powders, the size of the CaAl12O19 plate-like particles was altered with keeping similar porosity.