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    A comparison on physical, structural, and photocatalytical properties of TiO2 nanopowders produced using sol-gel and flame spray pyrolysis
    (2013) Erol, Mustafa; Sancakoğlu, Orkut; Yurddaşkal, Murat; Yıldırım, Serdar; Çelik, Erdal
    In this study, nanoscale photocatalyst TiO2 powders were synthesized via sol-gel and flame spray pyrolysis (FSP). Phase structures and ratios were analyzed by X-ray diffractometer (XRD). Size, specific surface area, and morphologies were determined using particle size analyzer, Brunauer-Emmett-Teller theory, and scanning electron microscope, respectively. Anatase phase with some rutile together was obtained in XRD analysis. The degradation rates of aqueous methylene blue (MB) by TiO2 nanopowders were calculated using UV-vis spectrophotometer. It was found that MB decomposition was successfully achieved with significantly high efficiencies for both sol-gel and FSP-derived powders with small differences. © 2013 The American Ceramic Society.
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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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    Degradation of contaminated industrial waste water using sol-gel derived Ru-doped TiO2 photocatalytic films
    (Foundation for Environmental Protection and Research (FEPR), 2013) Erol, Mustafa; Sancakoğlu, Orkut; Mermer, Ömer; Çelik, Erdal
    In this study, Ru-TiO2 films were deposited on glass substrates with a sol-gel route for degradation of contaminated industrial water. A solution with the Ru/Ti molar ratio of 0.05 was prepared using ruthenium and titanium based precursors. Solution characterizations were made using a turbidimeter and pH meter. The gel films, prepared by the sol-gel drop casting method, were dried at 300°C for 10 minutes and subsequently heat-treated at 500°C for 5 minutes in air. After that, the oxide thin films were annealed at 600°C for 60 minutes in air. In order to evaluate the phase structure, microstructure, optical, and photocatalytic properties of the coatings, they were investigated using XRD, SEM, and UV/Vis spectrophotometer, respectively. The obtained phase was mostly anatase TiO2. Photo-oxidation experiments were performed to obtain the photocatalytic activity of the films on impure water using an UV light source. The absorption spectrum of the water samples taken from Cigli Industrial Plant and Gediz River in Izmir/Turkey showed that they have absorbance bands in the range of 300 nm and 500 nm. The Ru doped TiO2 films exhibited highly photocatalytic activity to decompose organic species in contaminated waters. The degradation percentage ratios were calculated as 75% and 62% for two different industrial water samples.
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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.