Yazar "Ciftcioglu, Muhsin" seçeneğine göre listele

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    Inverse effects of lanthanide co-doping on the photocatalytic hydrogen production and dye degradation activities of Cu doped sol-gel TiO2
    (Elsevier, 2023) Yurtsever, Husnu Arda; Erzin, Kubilay; Ciftcioglu, Muhsin
    Copper doped and lanthanide-copper co-doped titania powders were prepared by sol-gel technique and the effects of co-doping on the photocatalytic reduction and oxidation activities of titania were investigated in this work. Characterization studies indicated that a reduced structure was formed due to the presence of Ti3+ species in copper doped titania powder and a more stable structure was formed when lanthanides were used as co-dopants. Copper doped powder had a significantly higher activity in photocatalytic hydrogen production (1037 mu mol/g/h) than the co-doped powders (similar to 400 mu mol/g/h). The oxidation activities of co-doped powders however were determined to be about 2 times higher than that of the copper doped powder. The decrease in the reduction activity was attributed to the decrease in the number of Ti3+ sites, whereas the increase in oxidation activity was probably a result of the increase in the surface area and dye adsorption due to lanthanide co-doping.
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    Preparation and characterization of hydroxyapatite reinforced polymeric scaffolds
    (National Institute of Science Communication and Information Resources-NISCAIR, 2025) Firata, Duygu Doga; Ersoz, Su Turku; Burcu Alp, Fatma; Cetin, Ali Emrah; Ciftcioglu, Muhsin
    Porous HA reinforced PLA/PCL scaffolds with polymer volume percentages in the 7.0-7.6 range have been prepared by solvent-casting/salt leaching technique. The scaffolds have been characterized by conducting gravimetric measurements, FTIR analysis, TGA, X-ray diffraction analysis, compression tests, cell viability tests, and thermal and hydrolytic degradation tests in order to investigate the effect of PLA/PCL, PLA/HA, PCL/HA and PLA/PCL/HA blending on scaffold properties. Porosity of the scaffolds has been determined to be in the 83-92 percent range. The scaffold porosity has decreased with HA content. The water absorption of the scaffolds has been found to be in between 400 and 750%. The yield strength and the elastic modulus of the scaffolds have been determined to be in the 0.001-0.02 and 5.6-10.6 MPa ranges, respectively. The yield strength of the scaffolds has increased by both PCL and HA contents whereas elastic modulus has increased with PCL content but has decreased with HA content. Mechanical test results have indicated that the addition of HA has increased the strength of the scaffolds while decreasing their flexibility. The activation energies for the thermal degradation of the scaffolds have been determined to be in the 130-398 kJ/mol range and have been shown to be a function of PCL, PLA, and HA content. The hydrolytic degradation behavior of the scaffolds in acetate buffer solutions (pH=4.5) during 127 days and XRD analysis have indicated that the hydrolytic degradation occurring in the amorphous part of the surface film has been diffusion-controlled. The diffusion coefficients of the degradation products in the scaffolds have been estimated to be in the 1.21-4.95x10(-13) m(2)/s range. Cell viability test results have indicated that the composition of the composite scaffold structure has played a determining role in the prepared scaffolds.
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    Öğe
    The effect of powder preparation method on the artificial photosynthesis activities of neodymium doped titania powders
    (Pergamon-Elsevier Science Ltd, 2018) Yurtsever, Husnu Arda; Ciftcioglu, Muhsin
    The effects of nanostructure on the artificial photosynthesis activities of undoped and Nd doped titania (TiO2) powders prepared by three different chemical co-precipitation methods were investigated. Substitutional/interstitial N and S doping was observed in powders due to the presence of high concentrations of HNO3 (NP) and H2SO4 (SP) in the powder preparation media, respectively. Nd, N and S doping caused anatase/rutile phase transformation inhibition and crystallite size reduction in the nanostructure. Light absorption was significantly enhanced by Nd doping and the residual SO42-/NOx species in the nanostructure. Photocatalytic hydrogen production activity of Nd doped NP powder was 4 times greater than undoped NP powder at 700 degrees C and had a high purity (CO:H-2 ratio similar to 0.00). CO was determined to be the main product in photocatalytic CO2 reduction. NP powders had the highest CO yields and Nd doping enhanced CO production. The powders with high crystallite sizes and rutile weight fractions had the highest artificial photosynthesis activities. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.