The role of initial hexagonal self-ordering in anodic nanotube growth in ionic liquid

The surface of titanium displays the areas with hexagonal structures (cells) and the areas with grown nanotubes upon anodic treatment in 1-butyl-3-methylimidazolium bis(triflate)imide ionic liquid (IL) in the presence of propylene glycol (1:1 volume ratio) at a constant current The hexagonal cells presumably serve as a matrix for the further growth of the nanotubes. The mechanism of the formation of the hexagonal cells is supposed to be the same as that one proposed earlier for nickel and steel. The presence of different types of the surface structures is related to the non -uniform distribution of the current density along the surface near the critical regime, i.e. at the boundary between the parameters corresponding to the electropolishing and anodization. (C) 2017 Elsevier B.V. All rights reserved.