Preparation of titanium dioxide films on etched aluminum foil by vacuum infiltration and anodizing

Al ₂ O ₃ –TiO ₂ (Al–Ti) composite oxide films are a promising dielectric material for future use in capacitors. In this study, TiO ₂ films were prepared on etched Al foils by vacuum infiltration. TiO ₂ films prepared using a sol–gel process were annealed at various temperatures (450, 500, and 550 °C) for different time durations (10, 30, and 60 min) for 4 cycles, and then anodized at 100 V. The specimens were characterized using X-ray diffraction, field emission scanning electron microscopy, and field emission transmission electron microscopy. The results show that the tunnels of the specimens feature a multi-layer structure consisting of an Al ₂ O ₃ outer layer, an Al–Ti composite oxide middle layer, and an aluminum hydrate inner layer. The electrical properties of the specimens, such as the withstanding voltage and specific capacitance, were also measured. Compared to specimens without TiO ₂ coating, the specific capacitances of the TiO ₂ -coated specimens are increased. The specific capacitance of the anode Al foil with TiO ₂ coating increased by 42% compared to that of a specimen without TiO ₂ coating when annealed at 550 °C for 10 min. These composite oxide films could enhance the specific capacitance of anode Al foils used in dielectric materials.