Effects of anodization parameters on the formation of titania nanotubes in ethylene glycol

The effects of fluoride concentration, anodization temperature, and anodization applied potential difference on the formation and dimensions of the titania nanotubes in ethylene glycol/water systems were investigated. It was found that fluoride concentration and anodization temperature were the two critical parameters for controlling the nanotube formation whilst anodization applied potential difference mainly contributes to tuning the dimension of the nanotubes. Electrolytes containing a low fluoride concentration are beneficial for initiating nanotube formation, whilst a higher anodization temperature is helpful to the rapid growth of the nanotubes. It is shown that the current–time curve obtained during the anodization can be used as an effective tool to predict the morphology of titania nanotubes. A model based on the competition between electrochemical oxidation of the titanium and chemical dissolution by fluoride ions is developed to explain the experimental observations.