Abstract
Thermal oxide films grown on electropolished aluminum specimens have been investigated by transmission electron microscopy of stripped oxide films and ultramicrotomed sections. Particular attention has been focused on the nucleation sites γ-Al 2 O 3 crystals and the relationship of such sites to surface features on the electropolished aluminum surface. It is evident that “easy paths” for the diffusion of oxygen, or the nucleation sites of γ-Al 2 O 3 crystals, are not distributed randomly over the electropolished aluminum surface, but form preferentially in the amorphous oxide layer grown over preexisting metal ridges. Thus, the diffusion of molecular oxygen through cracks in the amorphous oxide layer represents the most realistic and acceptable basis for explaining the local growth of the γ-Al 2 O 3 crystals in thermal oxide films on aluminum, although the cracks have not yet been observed directly.
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Present address: Alcan International, Ltd., Banbury Laboratories, Banbury, Oxford, OX16 7SP, United Kingdom.
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Shimizu, K., Furneaux, R.C., Thompson, G.E. et al. On the nature of “easy paths” for the diffusion of oxygen in thermal oxide films on aluminum. Oxid Met 35, 427–439 (1991). https://doi.org/10.1007/BF00664713
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DOI: https://doi.org/10.1007/BF00664713