Structures of amorphous anodic alumina films have been investigated by the X-ray radial distrubution function and the correlation method. The amorphous anodic alumina films are considered to contain AlO5 coordination polyhedra as well as AlO4 tetrahedra and AlO6 octahedra. Two types of conformation are taken into account by the correlation method; one (model A) is the conformation in which the above coordination polyhedra are arranged in a similar way to that found in the crystalline modifications of γ-Al2O3 within a short range of r A and the other (model B) is the conformation in which coordination polyhedra are randomly arranged. The final model formed by mixing these two conformations (model A and B) in 1 : 1 ratio describes quantitatively the observed scattering intensity curves of the amorphous anodic alumina films.

Structural analysis of anodic alumina films

Alumina is classified as an intermediate oxide that cannot form a glass and is industrially used as a multifunctional material. Intensive studies on the atomistic structure of amorphous alumina have been conducted because a fundamental understanding of its structure can be meaningful to the design of new materials and devices. Here we focused on anodic alumina as a model material for clarifying the atomistic structure of amorphous alumina and prepared anion-free and anion-incorporated porous-type amorphous alumina by anodization using chromic acid electrolyte and typical electrolytes (e.g., sulfuric acid, oxalic acid, and phosphoric acid), respectively. The local structure around aluminum atoms in the anodic alumina was investigated by nuclear magnetic resonance spectroscopy. We found that the structure of anodic amorphous alumina comprises AlO4, AlO5, and AlO6 units with predominant fractions of AlO5. We also observed that the fraction of each unit was 37.7, 54.3, and 8.0%, with an average coordination n...

NMR Spectroscopic Analysis of the Local Structure of Porous-Type Amorphous Alumina Prepared by Anodization

In the preceding report, the authors discussed the co-ordination numbers of aluminum and sulfur in anodic oxide coatings of aluminum, which had been prepared from sulfo-salicylic acid or sulfuric acid electrolyte, by fluorescent X-ray method.The results suggested that the aluminum atoms in the anodic oxide coatings consist of both of 4 and 6 ligands.The dispersion in measurements of the co-ordination numbers would be due to the contamination of the test piece with aluminum metal, which had been mixed into the test piece during its folding for preparation.Therefore, this paper reports the results of determination of co-ordination numbers of aluminum atoms in various coatings by means of E.P.M.A, method.The following 8 kinds of electrolytes were used in these experiments:Sulfuric acid (for 2 kinds of test pieces), oxalic acid, chromic acid, sulfo-salicylic acid, p-phenol sulfonic acid, sodium phosphate, and ematal solution.The displacement of the Kα peak of aluminum was calculated by the following equation:Δλ=λ(aluminum metal)-λ(anodic oxide coating of aluminum)The following results were obtained:The co-ordination numbers of aluminum atoms in the anodic oxide coatings prepared from the various electrolytes were considered to be the both of 4 and 6 ligands.The above results quite agreed with those obtained by the fluorescent X-ray method and it was believed that there were no significances among the various kinds of coatings.

https://www.jstage.jst.go.jp/article/sfj1950/22/8/22_8_400/_pdf

池ケ谷正志

Papers

X線マイクロアナライザー (epma) によるアルミニウム陽極酸化皮膜中のアルミニウムの配位数に関する研究

池ケ谷 正志

Papers

X線マイクロアナライザー (epma) によるアルミニウム陽極酸化皮膜中のアルミニウムの配位数に関する研究

池ケ谷正志