Ray absorption spectroscopy study of the incorporated copper species in anodic alumina films formed on an Al-2 wt % Cu alloy

Barrier anodic films, formed on an Al-2 wt % Cu binary alloy at a current density of 50 A m(-2) in ammonium pentaborate electrolyte, have been examined by analytical transmission electron microscopy, which revealed the presence of copper species across the amorphous film section, indicating incorporation and outward mobility under the electric field. From the position of the absorption edge, X-ray absorption spectroscopy revealed conclusively the presence of Cu(II) species within the alumina film. Analysis of the extended X-ray absorption fine structure showed further that each copper atom in the film is surrounded by 4 +/- 1 oxygen atoms at a mean distance of 1.92 +/- 0.01 angstrom, but with little long- range order. (c) 2005 The Electrochemical Society.