Highly closed porosity and high strength alumina ceramic foams fabricated by colloidal hydrophobic modification

Alumina slurries with high solids loading were hydrophobically modified by triethanolamine lauryl sulfate (TLS) to prepare ceramic foams with highly closed porosity and high strength. After optimizing solids loading, pH value, and TLS concentration, alumina slurries with as high as 50 vol% solids loading were used to prepare ceramic foams, and the resultant foams exhibited 65.4%–69.6% total porosity. The ratio of the closed porosity to the total porosity was up to 91.5%–94.1%. Average cell sizes were as small as 44–51 μm, and cell walls were dense and smooth. As a result, compressive strength of the foams was as high as 90–128 MPa, much higher than that of the closed-cell ceramic foams fabricated by other methods.