Preparation of porous alumina ceramic with ultra-high porosity and long straight pores by freeze casting

Abstract

Porous alumina ceramic was prepared by freeze casting method using tert-butyl alcohol as the solvent. The as–prepared porous alumina ceramic possessed long straight porous structure. The non-dendrite pore feature was quite distinguished from that prepared based on common solvents such as water and camphene. The porosity of the ceramic could be regulated through the solid loading. When the solid loading in the slurry was 20 vol%, the porosity of the alumina ceramic was 65%. With decreasing the solid loading, the porosity of the alumina ceramic increased linearly. The relationship between the total porosity (P) and initial solid loading (X) can be expressed as P = 98.8−1.7X. The ultra-high porosity of 82% could be achieved when the solid loading was 10 vol%. Moreover, the density of the porous alumina ceramic with the porosity of 82% was even lower than water’s. The compressive strength of the porous alumina ceramic with the porosity of 63 and 82% was determined to be 37.0 and 2.6 MPa, respectively.