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Simulation and experiment of substrate aluminum grain orientation dependent self-ordering in anodic porous alumina
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Cheng, Chuan, Ng, K. Y., Aluru, N. R. and Ngan, A. H. W. (2013) Simulation and experiment of substrate aluminum grain orientation dependent self-ordering in anodic porous alumina. Journal of Applied Physics, 113 (20). 204903. doi:10.1063/1.4807295 ISSN 0021-8979.
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Official URL: http://dx.doi.org/10.1063/1.4807295
Abstract
Recent experiments have indicated a strong influence of the substrate grain orientation on the self-ordering in anodic porous alumina. Anodic porous alumina with straight pore channels grown in a stable, self-ordered manner is formed on (001) oriented Al grain, while disordered porous pattern is formed on (101) oriented Al grain with tilted pore channels growing in an unstable manner. In this work, numerical simulation of the pore growth process is carried out to understand this phenomenon. The rate-determining step of the oxide growth is assumed to be the Cabrera-Mott barrier at the oxide/electrolyte (o/e) interface, while the substrate is assumed to determine the ratio β between the ionization and oxidation reactions at the metal/oxide (m/o) interface. By numerically solving the electric field inside a growing porous alumina during anodization, the migration rates of the ions and hence the evolution of the o/e and m/o interfaces are computed. The simulated results show that pore growth is more stable when β is higher. A higher β corresponds to more Al ionized and migrating away from the m/o interface rather than being oxidized, and hence a higher retained O:Al ratio in the oxide. Experimentally measured oxygen content in the self-ordered porous alumina on (001) Al is indeed found to be about 3% higher than that in the disordered alumina on (101) Al, in agreement with the theoretical prediction. The results, therefore, suggest that ionization on (001) Al substrate is relatively easier than on (101) Al, and this leads to the more stable growth of the pore channels on (001) Al.
Item Type: | Journal Article | ||||||
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Divisions: | Faculty of Science, Engineering and Medicine > Engineering > WMG (Formerly the Warwick Manufacturing Group) | ||||||
Journal or Publication Title: | Journal of Applied Physics | ||||||
Publisher: | American Institute of Physics | ||||||
ISSN: | 0021-8979 | ||||||
Official Date: | 22 May 2013 | ||||||
Dates: |
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Volume: | 113 | ||||||
Number: | 20 | ||||||
Article Number: | 204903 | ||||||
DOI: | 10.1063/1.4807295 | ||||||
Status: | Peer Reviewed | ||||||
Publication Status: | Published | ||||||
Access rights to Published version: | Restricted or Subscription Access |
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