Ultrafast oxide nanotube formation on TiNb, TiZr and TiTa alloys by rapid breakdown anodization

The present work demonstrates ultrafast formation of nanotube bundles on titanium-based alloys, namely TiNb, TiZr and TiTa, by so-called rapid breakdown anodization (RBA). In this process anodization is carried out in chloride–perchlorate based solution for a short period of time. Within seconds, initiation of tube growth appears randomly over the anodized surface, and within a few minutes the entire sample surface can be covered with bundles of nanotubes of several 10 μm in length and some 10 nm in diameter. For all three alloys, the tubes consist of mixtures of oxides of the alloying elements. In every case, the “as formed” oxide tubes are amorphous. By annealing, the oxide nanotube powders can be converted to crystalline mixed oxide in the case of TiNb and TiZr, and a mixture of the individual oxides in the case of TiTa.