Effects of an anodizing solution and chemical etching on the shape of porous anodic alumina

We report here the effects of an anodizing solution and chemical etching on the shape of porous anodic alumina (PAA). aluminum in two mixed solutions: PAA was synthesized by using a conventional anodization method for (1) an oxalic acid and phosphoric acid mixture and (2) an oxalic acid and ethanol mixture. We prepared various samples of PAA anodized at various voltages from 40 to 120 V, various mixing ratios, and various etching times; then, we examined their pore morphologies. We found that the inter-pore distance of PAA grown in the oxalic acid and phosphoric acid solution could be controlled over a wide range from 192 nm to 282 nm. The fastest PAA growth rate of about 153.15 nm/min was found for the mixed anodizing solution of 95% oxalic acid and 5% ethanol. Also, the pore arrangement of PAA grown in the mixed solution of 90% oxalic acid and 10% ethanol was the best. The pore size, inter-pore distance, and pore arrangement of PAA can be controlled in various metal-oxide nanostructures.