Longitudinal pore alignment in anodic alumina films grown on polycrystalline metal substrates

Abstract

A quantitative analysis of longitudinal pore alignment in anodic alumina films grown on polycrystalline metal substrates was performed on the basis of small-angle X-ray diffraction mapping. The very high sensitivity of the diffraction pattern to the orientation of the anodic alumina film allowed the average pore alignment within the irradiated area to be determined, with an accuracy better than 0.1°. It is shown that pores deviate from the orientation orthogonal to the metal surface by a small angle that is constant within a single-crystal grain. Strong correlation between the longitudinal pore alignment within the anodic alumina film and the grain structure of the aluminium substrate indicates the important role of the crystallographic orientation of the metal in the pore growth process.