Effect of annealing temperature on wettability of TiO2 nanotube array films.

Lei Yang,Miao Zhang,Jianguo Lv,Shiwei Shi,Zhaoqi Sun,Gang He,Xueping Song

doi:10.1186/1556-276x-9-621

Lei Yang, Miao Zhang + Show 5 more

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https://doi.org/10.1186/1556-276x-9-621

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Abstract

Highly ordered TiO2 nanotube array (TN) films were prepared by anodization of titanium foil in a mixed electrolyte solution of glycerin and NH4F and then annealed at 200°C, 400°C, 600°C, and 800°C, respectively. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), water contact angle (WCA), and photoluminescence (PL). It was found that low temperature (below 600°C) has no significant influence on surface morphology, but the diameter of the nanotube increases from 40 to 50 nm with increasing temperature. At 800°C, the nanotube arrays are completely destroyed and only dense rutile film is observed. Samples unannealed and annealed at 200°C are amorphous. At 400°C, anatase phase appears. At 600°C, rutile phase appears. At 800°C, anatase phase changes into rutile phase completely. The wettability of the TN films shows that the WCAs for all samples freshly annealed at different temperatures are about 0°. After the annealed samples have been stored in air for 1 month, the WCAs increase to 130°, 133°, 135°, 141°, and 77°, respectively. Upon ultraviolet (UV) irradiation, they exhibit a significant transition from hydrophobicity to hydrophilicity. Especially, samples unannealed and annealed at 400°C show high photoinduced hydrophilicity.

Highlights

In 1997, Wang et al [1] reported that ultraviolet (UV) illumination of TiO2 surfaces could produce a highly hydrophilic surface which was named as super-hydrophilicity
It is obvious that only the diffraction peaks of the titanium substrate can be found when the annealing temperature is 200°C (JCPDS No 44-1294); it is suggested that these TiO2 nanotube array (TN) are amorphous
In summary, TN films have been prepared by anodization on a pure titanium foil

Summary

Introduction

In 1997, Wang et al [1] reported that ultraviolet (UV) illumination of TiO2 surfaces could produce a highly hydrophilic surface which was named as super-hydrophilicity. It is necessary to investigate the effects of the preparation process and annealing conditions on the wettability of the films. In 1999, Zwilling and co-workers grew the first highly ordered TiO2 nanotube array (TN) films by anodization of titanium foil in a HF-containing electrolyte, which has attracted wide interest [12]. Thermal treatment of TiO2 and TiO2 nanotubes provides a facile route to control grain size, particle morphology, microstructures, phase composition, and surface photoelectrochemical properties via adjusting experimental parameters such as temperature, time, and atmospheres [13,14,15,16,17]. By changing the annealing temperature, the effects of phase transition combined with nanotubular morphology on the wettability of TN films were investigated and discussed

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Results

Conclusion