Morphological investigation of anodized TiO2 nanotubes fabricated using different voltage conditions

•Anodized TiO2 nanotube was fabricated by controlling various voltage conditions.•The surface morphology and layer structures were investigated.•The “worm-like” surface structures on the nanotube layers were observed.•The voltage retention time induced the well-defined pore structure.

The morphology of TiO2 nanotube layers fabricated by electrochemical anodization in an ethylene glycol solution containing 0.5 wt% NH4F was investigated as a function of several voltage conditions. The effects of voltage sweep rate, retention time, and initial sweep voltage on the surface pore structure and tube length were observed in detail by scanning electron microscopy (SEM). It was clearly seen that worm-like porous structures on the TiO2 nanotube layers were formed during the voltage sweep process. These porous structures changed to round-shaped individual pores with longer tubular layers under constant voltage conditions. The initial sweep voltage also affected the pore size, even when the same final voltage was applied. These findings indicate that voltage conditions are very important factors in determining the surface and layer structure of anodized TiO2 nanotubes.

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