Interference colors of TiO₂ nanotube arrays grown by anodic oxidation

The study describes the interference color of anodic TiO₂ nanotube arrays on titanium foil. TiO₂ nanotube arrays are prepared by oxidizing titanium foil in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 wt.%). The morphologies of the oxide film are characterized by FESEM. The empirical color properties are obtained using the L*a*b* system. The different interference colors of oxidized Ti samples are obtained depending on the anodization time. The anodization time clearly indicates a strong effect on the reflectance at the visible wavelength region, thus confirming the observed color differences. Consequently, the interference colors can be controlled by the anodization time. By observing the coloration of Ti during the anodization, the interference colors can be utilized to identify the thickness of oxide layer and the formation of nanotubes on Ti sheet.