Quantitative Analysis of Nanoporous Anodic Alumina Ordering Obtained at Different Anodizing Potentials

Context: Nanoporous anodic alumina is a material of great interest due to its low density, high aspect ratio and because it is possible to obtain highly ordered structures. In the last decades, researchers have focused in controlling the morphological characteristics of the fabricated porous structures leading to the need for proper tools to quantify the ordering level of the obtained arrangements. Recently, characterization of the ordering level started to migrate from the qualitative to quantitative methods, leading to the development of more precise characterizations tools. Method: In the present work, the ordering of the nanoporous anodic alumina (NAA) fabricated in oxalic acid 0.3 M was evaluated. Fast Fourier transform was used to analyze the effect of anodizing potential in porous ordering. The regularity ratio was calculated based on the Fast Fourier Transformed images generated from the top SEM images of the obtained NAA samples. Results: It was observed that increasing the anodizing potential decreases the regularity ratio values for the evaluated potentials. Additionally, morphological characteristics such as pore diameter and interpore distance increase with anodizing potential. Conclusions: Highly ordered structures can be obtained by pure aluminum anodizing in 0,3 M oxalic acid at 40 V, 50 V y 55 V. The regularity ratio is a useful instrument for the quantitative characterization of the ordering level of nanoporous anodic alumina (NAA) structures. The NAA ordering level can be related with its properties and then with NAA applications. The understanding of the anodizing potential effect on porous alumina ordering provides tools to improve the design of NAA-based devices.