Smooth anodic TiO2 nanotubes:: annealing and structure

The influence of an annealing process on the structure and the composition of smooth high aspect ratio TiO2 nanotube layers, grown by anodization of Ti in viscous glycerol electrolytes containing fluorides, is reported. XRD and HRTEM measurements demonstrate that the as-formed high aspect ratio TiO2 nanotubes have an amorphous structure that can be entirely transformed to single phase - anatase - upon thermal annealing at 450 degrees C for 3 hours. XPS and EDX analyses furthermore show that annealing process is accompanied with an elimination of fluoride ions (present in the structure after formation).