Investigation of roughness and specular quality of commercial aluminum (6061 alloy) for fabrication of nanoporous anodic alumina films

Abstract

Nanoporous anodic alumina (NAA), obtained via aluminum anodization, have been used as template for fabrication of nanostructure materials and photonic devices. In order to promote the formation of regular porous and to control the desired properties, high-purity aluminum and pretreatment of Al surfaces are mandatory. This procedure consists in electrochemically removing the external irregular layer of the metal promoting a flat, bright and smooth metallic surface. In this study, the effect of electropolishing parameters on commercial aluminum samples (6061 alloy, 97%) was investigated. This procedure was performed at constant potential in a mixture of perchloric acid and ethyl alcohol solution in different experimental conditions. A factorial design was used to investigate the effect of applied potential, electropolishing time and electrolyte temperature on roughness and specularity of Al substrates. These samples were characterized by Atomic Force Microscopy (AFM) and Diffuse Reflectance Spectroscopy (DRS). All variables presented significant effects on roughness of Al substrates, although electropolishing time presented the most important effect on specularity of these samples. After galvanostatic anodization in oxalic acid solution, the results showed the influence of Al surface roughness on morphology of NAA films. Since all Al samples were anodized under same conditions, the differences observed in micrographs of NAA films were related to roughness of Al substrates, which was affected by electropolishing parameters, mainly the applied potential and electropolishing time.