Anodic films EXAFS studies

Forty and co-workers have used electron yield EXAFS to study (ex-situ) anodic films on aluminum prepared in tartrate and phosphoric acid electrolytes. The A1—O distance is different for the two film preparations. They conclude from these studies that in the tartrate formed film 80% of the aluminum ions are in octahedral sites and 20% in tetrahedral sites whereas for the films formed in phosphoric acid all of the aluminum ions appear to be located at tetrahedral sites. In addition, immersion of the phosphoric acid generated films into water at 85° C for 4 hr. gave rise to dramatic changes in the structure which were ascribed to hydration. (Fig. 13) No such changes were noted for the films generated in tartrate electrolyte. 

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