S. MIRAGHAEL - Department of Materials Engineering, Isfahan University of Technology Isfahan ۸۴۱۵۶, Iran
F. ASHIRAFIZADEH - Department of Materials Engineering, Isfahan University of Technology Isfahan ۸۴۱۵۶, Iran,
M. SANTAMARIA - Electrochemical Materials Science Lab. Faculty of Engineering, University of Palermo Palermo ۹۰.۱۲۸, Italy monica.
F. DI QUARTO - Electrochemical Materials Science Lab. Faculty of Engineering, University of Palermo Palermo ۹۰.۱۲۸, Italy monica.

In the present study, TiO, nanotubes (TNTs) were formed via anodization of titanium within fluoride containing ethylene glycol solution. It has been shown that as-formed nanotubes are not stable on the substrate due to dissolution of TiF layer between and beneath them resulting in formation of a new barrier layer between TNTs and metal substrate by re-anodization in aqueous solutions. This new anodic barrier layer has an important role in controlling the electrochemical and photoelectrochemical behavior of the whole system. Annealing nanotubes in air transforms amorphous TiO, to crystalline polymorphs and forms a thermal barrier layer on the surface of titanium which noticeably changes the electrochemical and photo-electrochemicial behavior of TNTs. The new thermally formed barrier layer has important effects on the electrical connection between nanotubes and the substrate which provides better charge transfer from nanotubes to the substrate. Crystalline structure of tube walls causes different formation, separation and transportation of charges in contrast to the as-formed nanotubes.

TiO, nanotubes; Anodization; Photo-electrochemical; Barrier layer, Annealing