Anodic formation of ordered and bamboo-type TiO2 anotubes arrays with different electrolytes

TiO2 nanotubes with a highly ordered structure on titanium were grown by a self-organized electrochemical anodization in viscous organic electrolytes. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) were used to investigate the structure and morphology of the TiO2 nanotubes. The results show that the nanotubes morphology is much different obtained in different electrolytes under the constant 20 V. The aligned nanotubes with a “honeycomb” shape were obtained in ethylene glycol/water, but that of the “bamboo-type” nanotubes of 50 nm spacing obtained in glycerol/water. The nanotubes morphology is apparently influenced both by the viscosity and the water content of the electrolytes based on the experimental results, and the possible formation mechanism of different shape nanotubes was also further explored. It is found that TiO2 nanotubes are polycrystalline with anatase phase observed by the analysis of selected area electron diffraction (SAED) and HRTEM.