Formation of Al2O3–TiO2 composite oxide films on aluminum foil by cathodic electrodeposition and anodizing

Titanium dioxide (TiO2) thin films were deposited on aluminum foils by cathodic electrodeposition, and then Al2O3–TiO2 (Al–Ti) composite oxide films were formed on aluminum foils by anodizing in 15 wt% ammonium adipate solution. The composition and structure of TiO2 coating layer were investigated by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The morphologies of specimens at different stages in the preparation process were characterized by atomic force microscope (AFM). The growth mechanism of the Al–Ti composite oxide film was discussed. It was found that TiO2 coating layer with anatase structure was obtained on aluminum foil after heat treatment. The TiO2 film showed an island growth pattern, which favored the growth of Al2O3 from uneven channel in the coating layer, thus promoting the formation of the Al–Ti composite oxide film. The anodic oxidation efficiency of specimens increased with the current density of cathodic electrodeposition increasing. The specimen with the Al–Ti composite oxide film exhibited about 26.3% higher product of specific capacitance and withstanding voltage than that with pure aluminum oxide film.