Microstructure and properties of hierarchical porous ZrO2/Al2O3 ceramics prepared by gel-foaming method

Hierarchical porous ZrO₂/Al₂O₃ ceramics with controllable pore structure were fabricated by gel-foaming method using nontoxic sodium alginate as gelling agent. Both the rheological property of ceramic slurry and the curing mechanism of gelatin system were studied. The effects of ZrO₂ content and sintering temperature on the pore structure and properties were also investigated. The three-dimensional net structure forms between calcium ion and sodium alginate molecule; then, the ceramic powder can realize in situ solidification. The porosity changes from 33 to 74% with different ZrO₂ content and sintering temperature. The macropores can be controlled through adjusting the foaming agent and ZrO₂ contents. The mesopores are mainly regulated by sintering temperature. The porosity and pore structure can be tailored through optimizing the gel-foaming and sintering process parameters. The sintering temperature has important influence on the mechanical properties. The porous ceramics with 25% ZrO₂ content sintered at 1550°C shows the highest compressive strength of 130MPa. The mechanical properties are improved with the micro-crack toughening and phase transformation mechanisms of ZrO₂ phases. Hierarchical porous ceramics with more inter-connective pores, high specific surface area, and suitable strength are promising for filtration and catalyst support applications.