Fabrication of enhanced anodic aluminum oxide performance at room temperatures using hybrid pulse anodization with effective cooling

Conventional anodic aluminum oxide (AAO) template was performed using potentiostatic method of direct-current anodization (DCA) on costly high-purity (99.997%) aluminum foils at low temperatures of 0–10 °C to avoid dissolution effects which occurred frequently at room temperatures (RT) of 20–30 °C. In this paper, we show the hybrid pulse anodization (HPA) method with pulsing normal-positive and small-negative potential differences at RT for enhancing performance of AAO structure for both the cheap low-purity (99%) and costly high-purity (99.997%) aluminum foils. The HPA mainly takes advantages of effective cooling that arise from the nearly zero cathodic current and high-thermal-conductivity liquid electrolyte on the foils. The HPA is different from the traditional pulse anodization with alternating both high and low positive potential differences (/currents) or both one-positive and one-zero potential differences. The HPA not only merits manufacturing convenience and cost reduction but also promotes pore distribution uniformity of AAO at severe conditions of cheap low-purity Al foils and relatively high room temperature. The pore distribution uniformity can be improved by HPA in a suitable duration compared with the DCA. Very good AAO distribution uniformity (91%) was achieved in high-purity aluminum foil by HPA because it can suppress the Joule's heat to diminish the dissolution reaction. The evolution of AAO distribution uniformity for both the HPA and DCA on Al foil purities and process durations were comparatively investigated.