Improvement of pore distribution uniformity of nanoporous anodic aluminum oxide with pulse reverse voltage on low-and-high-purity aluminum foils

Many conventional anodic aluminum oxide (AAO) templates were performed using direct current anodization (DCA) at low temperature (0–5 °C) to avoid Joule-heat-dissolution effect at relatively high temperature of 20–25 °C. In this article, a small pulse reverse voltage added to normal-positive pulse anodization which is called hybrid pulse anodization (HPA) has been investigated for improving pore distribution uniformity of AAO at high temperature. The nanoporous AAO films were synthesized with both low-purity (99%) and high-purity (99.997%) aluminum (Al) foils in 0.3 M oxalic acid by different voltage modes of HPA and DCA for comparison. The pore distribution uniformity can be much improved by small pulse reverse voltage in 3 h duration anodization compared to DCA method. The small pulse reverse voltage presented the high uniformity of 88% and 91% for both low and high purity Al due to nearly zero cathodic current for reducing Joule-heat-dissolution. The effect of Al purity and voltage mode on uniformity improvement was further discussed.