Preparation and Characterization of TiO2 Nanotube Arrays by Anodic Oxidation Method

Thin films of TiO2 nanotube arrays were fabricated by anodic oxidation method in different electrolyte solution. The morphology of the film and the diameter of the nanotubes were observed by scanning electronic microscope (SEM). The crystal type of the film before and after heattreatment were characterized by X-ray diffraction (XRD) and Laser Raman.The results show that the electrolyte solution and applied votage have great effect on microstructure of the films. High order-aligned TiO2 nanotube arrays of 110nm in outer diameter are prepared at 20V in the 0.24wt% HF aqueous solution. Films of nanotube arrays of 100nm in outer diameter are prepared at 20V in 0.5wt％NaF+2.7wt% Na2SO4 aqueous solution and 0.88wt% NH4F glycerol-water (vol ratio 1∶1) mixture solution. The outer diameter (d) of nanotubes increase linearly with applied voltage (U) in the range of 0-25V which can be described as d=k×U+b with k=5.2nm/V and b=2.2nm. TiO2 nanotube arrays with amorphous structure is transformed to anatase after annealed at 450℃ for 2h.