Effect of Fluoride-containing Electrolyte on the Growth of TiO₂ Nanotube Arrays

TiO₂ nanotube arrays were fabricated on the Ti substrate in an ethylene glycol solution of NH₄F via anodic oxidation method. The morphology of TiO₂ nanotube arrays was characterized by scanning electron microscope (SEM). At the same time, the growth mechanism of TiO₂ nanotube arrays was analyzed. The results show that the TiO₂ nanotube displays a cone-shaped structure with one end closed. H⁺ and F^– ions are key to the formation of TiO₂ nanotube arrays . By reusing the fluoride-containing electrolyte, the F^– ions can be completely converted into TiF₆^2– ions, so as to reduce the harm to the environment. The fluoride-containing electrolyte can be used for 6 times continuously. The characteristic sizes of TiO₂ nanotubes can be effectively controlled with the usage count of electrolyte. The length of TiO₂ nanotubes increases first and then decreases, which can be adjusted freely within 20 μm, and the diameter of the nanotubes can reach up to about 110 nm.