Electrochemical anodizing, structural and mechanical characterization of nanoporous alumina templates

Abstract

Highly ordered Anodic Aluminum Oxide (AAO) structures produced from aluminum by using an electrochemical anodizing method were developed towards its application for the next generation of micro/nano medical and energy devices. In addition of analyzing the anodizing current profile, the surface morphology was characterized by using Scanning Electron Microscopy (SEM), the crystalline structure by X-Ray Diffraction (XRD) and the mechanical properties by nanoindentation experiments. The anodizing time and applied potential determines the nanopores regularity and their size, although the effect of the potential is more pronounced than the effect of temperature in the transformation from crystalline alumina to amorphous alumina. Optimum pore growth was achieved with an applied potential of 17 V which led to a pore fraction - P(f) - of about 17.5%. The experimental Berkovich nanoindentation method was used to determine the AAO hardness as a function of the indenter depth, during the loading stage, using mechanical response and deformation behaviour of the nanopores structure. From the experimental data of the loaddisplacement curves, this method allows the calculation of the indenter contact depth at each reloading point, thus leading to the estimation of the material’s hardness. The results reveal that the hardness depends on the processing conditions used for the production of the AAO samples that also strongly influences the organization and pore size uniformity.