Formation and mechanistic study of self-ordered TiO₂ nanotubes on Ti substrate

다국어 초록 (Multilingual Abstract)

The formation of anatase TiO<SUB>2</SUB> nanotubes by anodic oxidation on a pure titanium substrate in an aqueous solution containing 0.5wt.% NaF was investigated. Nanotubes with a length of 3μm in a nanotubular TiO<SUB>2</SUB> film were obtained in the pH 4.2 electrolyte. In strong acidic solution (pH 1.5), TiO<SUB>2</SUB> nanotubes of short length were formed due to the fast chemical dissolution rate. In this case, there was no variation of the average pore diameter and wall thickness of the TiO<SUB>2</SUB> nanotubes. From this experiment, it was again confirmed that the pH value of the electrolyte controls the thickness of the well-aligned TiO<SUB>2</SUB> nanotubes. A mechanistic study of the formation of the TiO<SUB>2</SUB> nanotubes was performed based on the observation of the surface morphology (top-view and cross-sectional view) using FE-SEM and the analysis of the current density-time curves. Furthermore, the morphology of the anodized TiO<SUB>2</SUB> film shows a rough surface and irregular wall thickness, since the anodic reaction was performed in an aqueous solution containing F<SUP>-</SUP> ions. The origin of this morphology was dealt with in detail in the FE-SEM study. The crystal structure of the TiO<SUB>2</SUB> nanotubes was confirmed using XRD and Raman analyses.