Electrochemical fabrication and formation mechanism of TiO2 nanotube arrays on metallic titanium surface

High density, well ordered and uniform titanium oxide nanotube arrays were fabricated by electrochemical anodic oxidation on a pure titanium sheet. A number of synthesis parameters for the preparation of titanium oxide nanotube arrays in hydrofluoric-acid have been investigated. The results show that voltage is the most important fator to control the appearance and sizes of TiO2 nanotube arrays. The average tubes diameter increases with increasing anodizing voltage. XRD and SEM techniques have been used to characterize the TiO2 nanotubes. It is showed that the TiO2 structure depends on the heating condition, amorphous phase is found at room temperature, the anatase phase is the predominant phase at 450 degreesC, and further heating to 600 degreesC the rutile phase of TiO2 appears in the XRD pattern. The SEM shows that average diameter of the TiO2 nanotubes is about 80 similar to 90 nm at 20 V anodizing voltage. A possible growth mechanism for the nanotubes formation has been proposed. Moreover, the I-V of TiO2/Ti interface has been characterized. It is demonstrated that the intense rectifying characterization of TiO2/Ti interface is attributed to the presence of a thick barrier layer between TiO2 nanotubes and the Ti substrate.