Ethanol-based electrolyte for nanotubular anodic TiO2 formation

We report fabrication of anodic titanium oxide nanotubes with rippled sidewalls using anodization of titanium foil in an ethanol-based electrolyte containing ammonium fluoride and water. The electrolyte was tested at 40 °C and at potential in the 30-60 V range. The internal diameter of nanotubes grows linearly from 88 nm for 30 V up to 124 nm for 50 V and next drops to 105 nm for 60 V. The thickness of anodic titanium oxide layer exceeds 1 μm. Presence of NH4F crystals in electrolyte is favorable for formation of nanotubes. The unusual shape of current curves during anodization was observed.