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    Characterization and photocatalytic properties of nanoporous titanium dioxide layer fabricated on pure titanium substrates by the anodic oxidation process
    (Elsevier Ltd, 2014) Dikici, Tuncay; Erol, Mustafa; Toparlı, Mustafa; Çelik, Erdal
    Nanoporous titanium oxide (TiO2) layers were fabricated on commercially pure titanium (Cp-Ti) substrates by the anodic oxidation method under a potentiostatic regime. Anodic oxidation was performed in an aqueous solution containing 1 wt% hydrofluoric acid at room temperature for 30 min. Subsequently one of the anodized samples was annealed at 480 C for 2 h in air in order to obtain anatase transformation and increased crystallinity. The average pore diameter of both anodized and anodized+annealed samples were found to be nearly 52 nm and 66 nm, whilst the average inter-pore distances were approximately 65 nm and 76 nm, respectively. Characterization of nanoporous TiO2 layers was carried out through X-ray diffractometer (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV visible spectroscopy. Effects of heat treatment on properties such as crystallinity, morphology and photocatalytic activity were investigated in details. Finally photocatalytic degradation ratios and changes in degradation kinetics under the presence of both anodized and anodized+annealed catalysts were calculated. Depending on the obtained results, the annealed film with anatase structure demonstrated highly efficient photacatalytic performance. © 2013 Elsevier Ltd and Techna Group S.r.l.
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    The effect of anodization parameters on the formation of nanoporous TiO2 layers and their photocatalytic activities
    (Elsevier B.V., 2014) Erol, Mustafa; Dikici, Tuncay; Toparlı, Mustafa; Çelik, Erdal
    In this work, nanoporous titanium dioxide (TiO2) layers were successfully formed by electrochemical anodization method on titanium (Ti) surface in fluorine containing electrolytes with different processing parameters. The effects of anodization voltages, electrolyte temperature and anodization time on the microstructure and photocatalytic performance of nanoporous TiO2 layers were investigated and compared in details. Nanoporous structures were annealed at 480 °C for 2 h in air in order to obtain anatase transformation and increase crystallinity. The phase structure and surface morphology of the samples characterized by means of X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. The photocatalytic activity tests of the samples were evaluated by the degradation of aqueous methylene blue (MB) solutions under UV light illumination for different periods of time. The results showed that the processing parameters on production of nanoporous TiO2 layers played important roles in the degradation of aqueous MB solutions. To sum up, the highest photocatalytical activity was obtained at the sample anodized under 30 V for 30 min at 20°C among the samples. © 2014 Elsevier B.V. All rights reserved.