Self-ordering of anodic porous alumina formed in organic acid electrolytes

• Published in: Electrochimica acta 2005-11, Vol.51 (5), p.827-833
• Main Authors: Ono, Sachiko, Saito, Makiko, Asoh, Hidetaka
• Format: Article
• Language: English
• Subjects: Anodic porous alumina; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; High-current-density; Materials science; Organic acid; Physics; Pre-treatment; Self-ordering; Surface treatments
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2005.05.058

New self-ordering porous alumina films were fabricated in organic acid electrolytes. Highly ordered cell arrangements of porous alumina films were realized in malonic acid at 120 V and tartaric acid at 195 V having 300 nm and 500 nm pore intervals, respectively. Self-organization was achieved at the maximum voltage required to induce high-current-density anodization while preventing burning, i.e., an extremely high-current flow concentrated at local points. The cells of the film grown at a high field must be pressed against each other, so that the self-ordering proceeds with the porous layer growth. When the self-ordering of cell arrangement proceeds, the cells became smaller. To improve the regularity of the cell configuration, a low electrolyte temperature and a relatively high electrolyte concentration were effective for maintaining a high-current-density to prevent burning. Surface flatness was an essential factor for self-ordering, however, the surface oxide film produced by electropolishing an aluminum substrate prevented quick pore growth in the organic acids having a low dissociation constant. It is confirmed that electropolishing followed by alkaline treatment was most appropriate as the pre-treatment in preparing flat surfaces.