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Positron Annihilation Spectroscopy Study of Interfacial Defects Formed by Anodic Oxidation of Aluminum
Journal of the Electrochemical Society
  • Kurt R. Hebert, Iowa State University
  • Thomas Gessman, Washington State University
  • Kelvin Lynn, Washington State University
  • P. Asoka-Kumar, Lawrence Livermore National Laboratory
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Positron annihilation spectroscopy (PAS) measurements were carried out to characterize open-volume defects associated with anodic oxidation of aluminum. The annihilation fractions with low and high momentum electrons (S and W spectral lineshape parameters, respectively) of the annihilation photopeak were determined, as a function of the positron beam energy. A subsurface defect layer, containing nanometer-scale voids in the metal near the metal/oxide film interface, was found after oxide growth, and was shown to contain new voids created by anodizing. Such interfacial voids in the metal are of interest because of their possible role as corrosion initiation sites. The Sparameter characterizing the defect-containing layer (Sd) was obtained by simulation of the S-energy profiles. On samples with two different surface conditions, Sd remained constant at its initial value during anodizing. Because Sd is related to the void volume fraction in the interfacial metallic layer containing the voids, that result suggests that formation of metallic voids, and their subsequent incorporation into the growing oxide layer, occurred repeatedly at specific favored sites. © 2003 The Electrochemical Society. All rights reserved.

This article is from Journal of the Electrochemical Society 151 (2004): B22–B26, doi:10.1149/1.1631821. Posted with permission.

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ECS—The Electrochemical Society
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Kurt R. Hebert, Thomas Gessman, Kelvin Lynn and P. Asoka-Kumar. "Positron Annihilation Spectroscopy Study of Interfacial Defects Formed by Anodic Oxidation of Aluminum" Journal of the Electrochemical Society Vol. 151 Iss. 1 (2004) p. B22 - B26
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