Synthesis and morphology of TiO2 nanotube arrays by anodic oxidation using modified glycerol-based electrolytes

Titanium dioxide (TiO2) nanotube arrays were prepared by electrochemical anodization of titanium sheets in the glycerol 176 mL/H2O 44 mL/NH4F 0.5 wt% electrolytes modified with H2SO4 and NaAc addition. The surface morphologies, average inner diameter, and the length of the nanotube arrays changed with the solution pH in the range from 5.6 to 4.0 by adding H2SO4. A uniform surface morphology of the nanotubes; with average inner diameter of similar to 80 nm and a length of similar to 1000 nm was obtained when the solution pH was 5.0. The growth rates of the nanotubes; were remarkably enhanced by NaAc addition in the range of 0.04-0.14M. With NaAc addition of 0.10M, the length of the nanotube arrays reached 4.16 mu m after an 8-h anodization, increasing 3.23 mu m compared with no NaAc addition. The relationship between solution pH and growth of TiO2 nanotubes was analyzed by current-time curves, solution electrical conductivities, and scanning electron microscopy (SEM), and the role of NaAc was also discussed based on SEM and solution electrical conductivities.