THE OBSERVATION OF ANODIC OXIDE-FILMS ON ALUMINUM BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

High resolution electron microscopy has been used for the study of internal structure of porous anodic films with relate to the incorporated species such as electrolyte anions and water. The observation of the crystallization process of ion thinned porous films under a strong electron beam with the change of diffraction patterns and lattice images revealed that the rate of crystallization decreased in the order of the films formed in chromic acid > phosphoric acid > sulfuric acid solutions, which was correlated to the electrolyte anion content in each films. Transformation from amorphous to crystalline oxide was observed in a few minutes for the film formed in chromic acid solution which contains little chromium. Incorporated species and water inhibit crystallization because they lower the regularity of the oxide structure. Furthermore, morphological changes suggested the substantial nature of the anodic oxide films. © 1990.