Nanostructure Transition on Anodic Titanium: Structure Control via a Competition Strategy between Electrochemical Oxidation and Chemical Etching

Synthesis of various nanostructures on anodic metals such as Al and Ti attracts much attention in recent years. In this paper, we investigate in detail the nanostructure transition on anodic Ti and put forward a novel physical model to systematically explain the formation mechanism and discuss the relevant influential factors. Our physical model reveals that the available nanostructures are dominated by a competition 11) strategy between electrochemical oxidation and chemical etching ( reactions. Depending on the ratio of initial rates of these two reactions, four types of nanostructures including compact oxide layer, ordered TiO2 nanotube/nanopore, ordered Ti nanorod/nanoflake, and disordered Ti nanostructure can be obtained. To verify this physical model, we fabricate various nanostructures via controlling the influential factors of the reaction rates, and the resulting morphologies are in good agreement with the physical model This also answers the question why the totally different self-organized ID nanostructure (TiO2 nanotube and Ti nanorod) can be synthesized under similar conditions.