Preparation and properties of porous α-Al2O3 membrane supports

Strong and permeable macro-porous alpha-Al2O3 membrane supports are made by colloidal filtration of 20 vol% dispersions of alpha-Al2O3 with an average particle size of 600 nm. Intact compacts with very good surface quality were obtained at an optimum pH of 9.5 and dosage of 0.2 wt% ammonium aurintricarboxylate (Aluminon), based on dry alumina. The colloidal stability of the aluminon-stabilized slurries is confirmed by xi potential measurements. Slight sintering of dense-packed alpha-Al2O3 compacts was found to result in > 67% packing density and a bimodal pore-size distribution as derived from shrinkage behavior and gas adsorption studies. Non-stationary single gas permeation measurements showed improved gas permeability, compared with alpha-Al2O3 compacts prepared using powder with a smaller particle size (300 nm). The strength of the disk-shaped alumina compacts within the porosity range of 30%-20% increased from 100 to 300 MPa with a standard deviation of 20 and 50 MPa, respectively.