Self-organized growth mechanism for porous aluminum anodic oxide

Likely mechanisms of the self-organization observed in the growth of porous aluminum anodic oxide are discussed. A mechanism that includes physical and chemical processes occurring in the initial stage is put forward by considering the distribution of an applied voltage between three main components of the electrochemical system: a growing oxide layer; a Helmholtz layer at the oxide-electrolyte interface; and a Gouy-Chapman space-charge layer, which extends to the quasi-neutral electrolyte region. It is found that the transformation of the Helmholtz layer is due to self-organization effects in the Gouy-Chapman layer. The cell size of the porous oxide is shown to vary as Gouy-Chapman layer thickness, which in turn depends on the temperature, concentration, and composition of the electrolyte. The theoretical results obtained are in good agreement with previous experiments.