Effect of in-situ synthesized calcium hexaluminate on the structure and properties of porous corundum materials

To balance the contradiction of mechanical strength and air permeability of porous corundum materials, the calcium hexaluminate was in-situ synthesized in the porous materials by using pure calcium aluminate cement as the calcium source. The effects of in-situ synthesized calcium hexaluminate on the microstructure, phase composition, and mechanical properties of the porous corundum materials were investigated. The results show that, the plate-like calcium hexaluminate particles can be in-situ synthesized in the specimens added with pure calcium aluminate cement after treated at 1700 for 3 h. When the mass fraction of pure calcium℃aluminate cement is no more than 3%, the in-situ synthesized calcium hexaluminate not only improves the cold compressive strength and the high-temperature bending strength (1400℃×0.5 h) of the porous material, but also improves the air permeability of specimens. With further increase of pure calcium aluminate cement additions, the above properties of the specimens turn to a reversed trend. The cold compressive strength of specimen added with 3% pure calcium aluminate cement by mass is 33.6 MPa, the highest high-temperature bending strength is 6.2 MPa, and the Darcian permeability and non-Darcian permeability constant are 2.54×10^-10 m²and 1.46×10^-6 m, respectively.