A novel decompress-freezing process for ultra-high porosity ZrO2 ceramics

The porous ZrO2 ceramics with ultra-high porosity were produced by combining phase change, heat exchange and freeze drying process of ZrO2 slurries during decompression environment. The prepared slurry was first cooled to near the supercooling point, and then the supercooled slurry was placed on decompression system to induce foaming and solidification until the decompress-freezing process of the slurry completed. After drying and sintering of the green part, an as-prepared ceramic with porosity more than 93% was obtained. It was shown that the porous ceramic was typically composed of large spherical cells, interconnected by near circular windows. Although the mechanical properties in obtained ceramics are not enough to resist high stress, porous ceramics with a number of pores in cell walls and struts may be expected to be applied in high thermal insulation process.

► ZrO2 ceramic with porosity more than 93% is prepared by decompress-freezing process.
► The foaming and foam setting steps of ceramic slurry can be organically combined.
► The glycerol promotes development of microstructure of ZrO2 porous ceramics.