二元凝胶法制备Al₂O₃多孔陶瓷及其表面强化层

Porous alumina ceramics were fabricated by a foam-gelcasting technology with acrylamide system and gelatin as binary gelling agents. The effects of acrylamide system and gelatin content on the viscosity of the slurries, foaming, green strength and microstructures were investigated. Also, the apparent porosities and mechanical properties of porous alumina ceramics were characterized. The results show that the use of acrylamide can decrease the viscosity of the slurries and increase the foaming volumes. The porous green bodies prepared by the binary gel system have an uniform pore size distribution and a good strength for simple machining. The porous alumina ceramics with high porosities ranging from 70% to 90% are obtained after the green samples are sintered at 1600℃ for 2h. For the sample with an apparent porosity of 90.8%, its compressive strength is 3.3MPa. Moreover, the surface reinforcement layers of porous ceramics were obtained by a tape-casting method. The porous layers with a relatively high strength increase the bending strength of the whole porous alumina ceramics from 6.4 to 10.8MPa, and improve the surface strength and the thermal ablation resistance of the porous materials.