Preparation of macroporous alumina ceramics by ice templating without freeze drying using natural rubber latex binder

Sublimation of ice crystals from the frozen ceramic powder suspension for the preparation of porous ceramics is energy and capital-intensive. Herein, we explored the removal of ice crystals from frozen ceramic powder suspensions by solvent exchange without the collapse of the pore structure using natural rubber as a binder. Thawing of frozen bodies in acetone and subsequent aging for exchange of water with acetone strengthened the alumina particle-rubber network that prevented the pore collapse during drying. Exchange of > 96% of the water present in the bodies with acetone by repeating the solvent exchange for a second time effectively prevented pore collapse due to the lower surface tension of acetone compared to that of water. The rubber concentration required to prevent pore collapse depended on alumina slurry concentration. 20 wt% (with respect to alumina) rubber prevented pore collapse at alumina slurry concentrations up to 25 vol% whereas 30 wt% is required to stabilize the pores at slurry concentrations in the range of 25 to 15 vol%. The ceramics prepared by rubber burnout followed by sintering at 1550 °C exhibited a porosity in the range of 44.5 to 71.12% at alumina slurry concentrations in the range of 42.74 to 15 vol%. The ceramics with lamellar pore structure exhibited compressive strength and Young’s modulus in the ranges of 3.84 to 35.3 MPa and 306.2 to 1486.5 MPa, respectively. The porosity was lower by nearly 10–15% whereas the pore structure similar to that of porous ceramics prepared by freeze drying followed by sintering.