Yazar "Dorozhkin, Sergey V." seçeneğine göre listele

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    Structural and dielectric properties of yttrium-substituted hydroxyapatites
    (Elsevier, 2015) Kaygili, Omer; Dorozhkin, Sergey V.; Ates, Tankut; Gursoy, N. Canan; Keser, Serhat; Yakuphanoglu, Fahrettin; Selcuk, A. Birkan
    Hydroxyapatite (HAp) samples doped with 0,2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FOR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FOR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content (C) 2014 Elsevier B.V. All rights reserved.
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    Structural and Dielectrical Properties of Ag- and Ba-Substituted Hydroxyapatites
    (Springer, 2014) Kaygili, Omer; Keser, Serhat; Dorozhkin, Sergey V.; Yakuphanoglu, Fahrettin; Al-Ghamdi, Ahmed A.; Kirbag, Sevda; Sertkaya, Duygu
    Ag- and Ba-doped hydroxyapatite (HAp) samples were synthesized by sol-gel method. The crystallite sizes for all the samples were found to vary from 26 to 39 nm. Neither Ag nor Ba did result in dramatic changes in the morphology of all the samples, and the Ca/P molar ratio was varied. The dielectric parameters of the samples were changed with the dopant content. The maximum and minimum values of the dielectric constant were observed for 2.0 %Ba-HAp and 0.5 %Ba-HAp samples. The alternating current conductivity indicates that all the samples exhibit the insulator behavior. The results of the biological tests revealed that Ag-containing samples have an antimicrobial activity, while no antimicrobial activity was detected for both HAp and Ba-doped HAp samples.
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    Theoretical and experimental characterization of Pr/Ce co-doped hydroxyapatites
    (Elsevier, 2021) Ibrahimzade, Lala; Kaygili, Omer; Dundar, Serkan; Ates, Tankut; Dorozhkin, Sergey V.; Bulut, Niyazi; Koytepe, Suleyman
    This study presents a more extensive report on the experimental and theoretical characterization of the Ce-doped hydroxyapatite (HAp) samples additionally doped with Pr at varying amounts. To achieve this goal, four Ce-containing (a constant amount of 0.35 at.%) HAps additionally doped with Pr at various amounts (0.35, 0.70, 1.05, and 1.40 at.%) were synthesized via a combustion method. Besides, all these samples were modeled theoretically by using a density functional theory (DFT). Theoretical results showed that the bandgap energy decreased continuously from 4.5156 to 4.3097 eV. For all samples, the linear attenuation (or absorption) coefficient increased with the increasing amount of Pr and this parameter had a decreasing trend with the increase in the photon energy. An increase in the theoretical density and the lattice parameter c and a decrease of both the lattice parameter a and the unit cell volume were found. After analyzing the experimental data, the following results were observed: X-ray diffraction (XRD) and Fourier transform infrared (FTIR) data verified the formation of HAp phase (above 94% for all the samples) as the major phase and beta-tricalcium phosphate (beta-TCP) as the minor one. The amount of beta-TCP phase was found to increase from 3.4 to 5.9% with the addition of Pr. Similar to the theoretical findings, an increasing trend for the density and decreasing one for the unit cell volume were detected. Both a decrease in the crystallinity and an increase in the anisotropic energy density were found. The results of the thermal analysis supported the thermal stability of all the samples. The cell viability was found to be affected by Pr-content. (C) 2021 Elsevier B.V. All rights reserved.