Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Acid concentration and temperature dependent self-ordering conditions of anodic porous alumina formed by anodization of aluminum in oxalic acid are quantitatively characterized by a new technique involving the distribution of the angular orientation of the triangles formed by neighboring pore centers, in order to detect the self-ordering domains in each porous pattern. This technique is found to be more sensitive in quantifying ordering of the patterns than the radial distribution function and angle distribution function. Using this technique, the optimal acid concentration which can result in the best self-ordering of the porous alumina under a given temperature is established. The optimal acid concentration is found to be approximately linearly increasing with temperature. The oxide growth rate increases approximately exponentially with acid concentration and also with temperature. The results suggest that anodization conducted at relatively higher temperatures at the corresponding optimal acid concentrations can enable fast production of self-ordered anodic porous alumina for industrial applications.