As a kind of heat insulating material, alumina foam ceramics have many advantages such as low thermal conductivity, high thermostable performance, good wear resistance, high hardness and excellent resistance to chemical corrosion. In this paper, a high-alumina foam ceramic was prepared by the gel-foaming method using water as dispersing medium, aluminum dihydrogen phosphate as gel and alumina fiber as reinforcing component, and the effects of alumina fiber content on the slurry viscosity as well as the porosity, phase composition, microstructure and mechanical properties of the prepared ceramic were studied. It was found that the viscosity of the slurry increased with the increase of fiber content. After sintering, there were C-AlPO4, T-AlPO4 and α-Al2O3 phases in the prepared samples; with the increase of fiber content, the porosity increased first and then decreased, whereas the compressive strength presented an opposite variation trend. In addition, the fracture toughness was also improved owing to the bridging effect of alumina fibers, the crack deflection and the fiber pulling-out mechanism.

Keywords: Foam ceramics, Alumina fibers, Microstructure, Compressive strength.