The mechanism of the hot water sealing of anodic alumina films was studied using electron microscopy and compositional analysis. The films dissolve in boiling water and boehmite precipitates as small flakes due to (100)-oriented growth with 3-nm average thickness and evenly dispersing in the pores and the surface. The quantity and size of flakes increase with increasing sealing time forming a densely intertwined boehmite structure. Eventually, a three-layered structure is formed, which is composed of an outer vertically grown coarse flaky layer, an intermediate dense flaky layer with 2:1 thickness ratio, and a porous layer filled with dense flaky boehmite.

中文翻译：

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铝上形成阳极膜的热水密封机理

利用电子显微镜和成分分析研究了阳极氧化铝膜的热水密封机理。薄膜溶解在沸水中，勃姆石沉淀成小薄片，这是由于（100）定向生长，平均厚度为3 nm，并均匀地分散在孔和表面中。薄片的数量和大小随密封时间的增加而增加，形成了紧密缠结的勃姆石结构。最终形成三层结构，该结构由垂直生长的外部粗鳞片层，厚度比为2：1的中间致密鳞片层和填充有致密鳞片勃姆石的多孔层组成。