Fabrication of Porous Al<sub>2</sub>O<sub>3</sub> Ceramics by Freeze Drying Technique and Annealing Treatment

Abstract

Porous Al2O3 ceramics were fabricated by directional freezing and low pressure drying with sucrose solution as the cryogenic medium. The pore structure of the porous ceramics was changed by annealing in the environment of higher than the glass transition temperature of sucrose solution after directional freezing because of changing the size and distribution of crystalline solid. The effects of the annealing time on the pore structure, open porosity and mechanical property of porous ceramics were investigated. The results showed that the pore size of porous ceramics increased substantially with the increase of annealing time. The open porosity of porous ceramics changed slightly with the increase of annealing time, while the compressive strength of porous ceramics showed a trend of decrease. The pore size range of porous Al2O3 ceramics fabricated is from 6.0μm to 110.2μm, the range of porosity was 40.35%-64.58%, the compressive strength range of porous Al2O3 ceramics was from 25.9MPa-126.6MPa. The porous Al2O3 ceramics with different pore structure can be obtained by changing the annealing time.