Fabrication and characterization of single layer and multi-layer anodic alumina membranes

• Published in: Journal of membrane science 1999-05, Vol.157 (2), p.147-158
• Main Authors: Shawaqfeh, Ahmad T, Baltus, Ruth E
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Composite membranes; Exact sciences and technology; General and physical chemistry; Inorganic membranes; Membrane preparation and structure; Membranes; Microporous and porous membranes
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/S0376-7388(98)00314-7

Porous alumina films containing parallel capillary pores of uniform size were fabricated by anodically oxidizing high purity aluminum films in phosphoric acid and sulfuric acid solutions. These films were formed into membranes by post-oxidation processing that removes unoxidized aluminum as well as a barrier layer of alumina from the base of the pores. Symmetric membranes were made by oxidizing at constant current density conditions. Two layer composite membranes were made by changing current density during the oxidation process. The thickness, pore density and porosity of each membrane were predicted from the relationships between structural characteristics and processing conditions that were developed in previously reported kinetic studies of anodic oxidation of aluminum. Each membrane was then characterized using permeability measurements. The hydraulic permeability of membranes formed in phosphoric acid and the diffusive permeability of membranes formed in sulfuric acid were measured. A comparison of the measured permeability values to those predicted using the structural characteristics calculated using relationships developed in the kinetic studies shows excellent agreement. These results illustrate that porous alumina membranes can be fabricated with transport characteristics that can be predicted from the processing conditions used during membrane formation.