Preparation of ?-alumina foams of high surface area employing the polyurethane sponge replica method

Abstract

Single phase γ-Al2O3 ceramic foams with high surface area (~180 m 2 /g) and porosity (67%) were prepared by the polyurethane sponge method from slurries containing γ-Al2O3 (~40 wt % of solids). Different commercial polyurethane sponges were tested as templates for the ceramic foams, and the better results were obtained with a hydrophilated polyester polyurethane with pore den- sity of 122 ppi, and thermal behavior that suggested the presence of fire retardant and smoke suppressor additives. The mechanical strength of the ceramic foams depended on several factors, such as the chemical nature of the sponge employed as template, composi- tion of the slurry, and the heating rate during calci- nation. It was found that at least four cycles of re- coating followed by drying were required before cal- cination to prevent collapse of the ceramic foams.