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Titanium thin films were deposited on glass and indium tin oxide (ITO) coated glass substrates by radio-frequency (RF) magnetron sputtering under varying sputtering parameters as: power, pressure, substrate temperature and target-substrate distance. The crystalline structure, crystallite size and texture coefficients of the films were evaluated in detail. As the evaluation points out, 100 W, 1.33 Pa ambient temperature and 70 mm were determined as the optimum sputtering parameters for intended crystalline structures. Subsequently, electrochemical anodization experiments were performed via varied electrolytes and under various anodization parameters (voltage, time and electrolyte type) in a two-electrode electrochemical cell using the films obtained through the optimized sputtering parameters. The anodized samples were annealed at 450 °C for 1 h in air in order to obtain anatase transformation and the desired crystalline structure. The surface morphologies and the crystalline structures of the anodized films were evaluated through x-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. Finally, the anodization parameters for the formation of TiO2 nanotube arrays were determined as: 35 V and 35 min. in an electrolyte composed of 0.3 wt.-% NH4F – 2 wt.-% water – ethylene glycol.

Porous titanium dioxide (TiO2) coatings were prepared on the pure titanium substrate by anodic spark oxidation (ASO) method in electrolytes containing various concentrations of sulfuric acid. The crystal phase, surface morphology, chemical composition, and optical property of the TiO2 films were analyzed by using XRD, SEM, XPS, and UV-vis spectroscopy. The photocatalytic activity is evaluated by the decomposition of methylene blue (MB) aqueous solution under UV light irradiation. It is found that the electrolyte concentration plays an important role in the properties and characteristics of the TiO2 coatings. The results show that TiO2 films consist of primarily the rutile phase with altering fraction depending on the electrolyte concentration without any heat treatment. The results demonstrated that there were formed too many sub-micron and nanopores of TiO2 neighboring to the micropores. TiO2 layer anodized in 0.75 M H2SO4 exhibited much higher photocatalytic activity than the other films. The results imply that anatase-rutile mixed TiO2 coatings can be successfully used for the photocatalytic degradation of organic pollutants.

In the present work, nanostructured TiO2 films were prepared by electrochemical anodization process of titanium in fluoride-containing electrolytes using an innovative approach. After anodization, the TiO2 films were annealed at 480 degrees C for 2 h in air in order to acquire anatase phase transformation and increase its crystallinity. The effects of anodization voltage, electrolyte concentration and anodization time on the formation of TiO2 films and the photocatalytic degradation of methylene blue (MB) were discussed in details. The phase structure and surface morphology of the samples characterized by means of X-ray diffraction and scanning electron microscope. The as-prepared nanostructured TiO2 film anodized in 0.5% HF electrolyte at 15 V for 240 min showed excellent photocatalytic degradation of MB and is promising for environmental purification.