Microstructures and mechanical properties of reactively sintered CaAl12O19/CaAl4O7 porous composites

Porous CaAl12O19 ceramics attract much attention as a light-weight structural material. In this study, CaAl12O19/ CaAl4O7 porous ceramic composites have been prepared by the reactive sintering, and their thermo-mechanical properties were evaluated by the three-point bending test, micro-Vickers hardness test to investigate the effect of the presence of CaAl4O7 second phase. The rod-shaped samples with 4 different compositions were heated at 5 degrees C/min and sintered at 1600 degrees C for 3 h to obtain sintered bodies. Microstructural observation confirmed that the composite materials with CaAl4O7 had larger particles than the CaAl12O19 single phase. Compositing with CaAl4O7, which has a low coefficient of thermal expansion, made it possible to reduce the coefficient of thermal expansion. The sample with a CaAl12O19/CaAl4O7 volume fraction of 65.2/34.8 exhibited the highest microVickers hardness.