Evaluation of the influence of synthesis conditions on the morphology of nanostructured anodic aluminum oxide coatings on Al 1050

Abstract

Currently, the use of nanostructured films of anodic aluminum oxide (AAO) arouses great interest for a variety of nanotechnological applications. Previous studies have shown that the most important parameters in the anodic synthesis of nanoporous AAO films are the pretreatment of the substrate, the anodization voltage, and the nature, concentration and temperature of the electrolyte. To advance the development of nanomaterials, which are increasingly specific according to their functionality, in a simple and inexpensive way, it is essential to study the combined effect of the synthesis variables on the morphological properties of the coatings. The objective of this work was to study and predict the combined effect of the concentration and temperature of oxalic acid and the anodization voltage in the ordering, the pore diameter, the interpore distance, the pore density and the thickness of nanostructured films of AAO synthesized at 20, 30, 40 and 60 V and 20, 30 and 40 °C in 0.3 and 0.9 M oxalic acid, from the Al 1050 alloy. For this, surface images were obtained by optical microscopy and scanning electron microscopy, the latter being processed through the Fast Fourier Transform, and non-linear regressions were performed with the data obtained. The results proved which anodic synthesis conditions have the greatest influence on the ordering and each of the morphological parameters of the AAO films. The optimum voltage and temperature of the self-ordering regime for both oxalic acid concentrations tested were 40 V and 20 °C. The combined effect of the synthesis variables allowed obtaining coatings with a pore diameter of 27–150 nm, an interpore distance of 51–160 nm, a pore density of 35 × 108 –390 × 108 and a thickness of 10–130 μm.