关键词: 阳极化, 介电膜, 超薄切片技术, 穿透式电子显微镜

Abstract: The thickness, morphology, chemical composition, and crystallinity of the anodized film formed on aluminum were examined in a transmission electron microscope (TEM). Thin foil for TEM analysis was prepared by ultramicrotomy. The relationship between the microstructure and the electrochemical characteristics of the alumina film forming on the pure aluminum was discussed in this investigation. At the forming voltage less than 100V, the anodized films formed at 85 ℃in aqueous ammonium adipate electrolyte was amorphous in nature. Although the film resistance was increased with the forming voltage, its dielectric constant was not changed significantly. As the forming voltage exceeded 100V, crystalline γ′_Al2O3 was present in the film. The amount of crystalline γ′_Al2O3 and the flaws accompanied with the crystallization process were found to increase with the forming voltage. The crystalline alumina seemed to be beneficial in raising the dielectric constant of the oxide film. As the forming voltage reached 200V, the oxide film was composed of an inner amorphous layer and an outer crystalline γ′_Al2O3 layer. The crystalline layer had a lower resistance but a higher dielectric constant than the amorphous layer.