Preparation and Properties of Porous α‐Al ₂ O ₃ Membrane Supports

Strong and permeable macro‐porous α‐Al 2 O 3 membrane supports are made by colloidal filtration of 20 vol% dispersions of α‐Al 2 O 3 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 ξ potential measurements. Slight sintering of dense‐packed α‐Al 2 O 3 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 α‐Al 2 O 3 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.