Yazar "Dorozhkin, Sergey V." seçeneğine göre listele

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    Mg-Dopant Effects on Band Structures of Zn-Based Hydroxyapatites: A Theoretical Study
    (Springer Int Publ Ag, 2023) Bulut, Niyazi; Kaygili, Omer; Hssain, Ala Hamd; Dorozhkin, Sergey V.; Abdelghani, Benahmed; Orek, Cahit; Kareem, Rebaz Obaid
    The band structures of Zn-based hydroxyapatites co-doped with Mg at varying amounts from 0 to 2.0 at. % have been investigated theoretically in more detail. The calculations were done to obtain the band structure, density of states, and band gap for all the modeled structures to study their electronic properties. It was seen that the co-doping has an effect on the structural and electronic properties of all the as-investigated structures. The bandgap energy for all samples in each group was found to be reduced gradually with varying doping rates of Mg into Zn-doped HAp. The band gap decreased from 4.54 to 3.84 eV for samples of 0.4Zn-0.4 Mg-HAp and 2.0Zn-0.4 Mg-HAp with the same amount of Mg, respectively, as a result of increasing the doping levels of Zn from 0.4 to 2.0 at.%. The lattice parameters, unit cell volume, and density decrease with increase in doping of Zn-containing HAp and in addition of second dopant Mg at varying amounts 0.4, 0.8, 1.2, 1.6, and 2.0 at. % in all of the modeled sample group. Furthermore, it is observed that the declining values of the aforementioned parameters are significantly impacted by the increasing Zn doping rates.
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    Theoretical and experimental characterization of Pr/Ce co-doped hydroxyapatites
    (Elsevier, 2021) İbrahimzade, Lala; Kaygılı, Ömer; Dündar, Serkan; Ateş, Tankut; Dorozhkin, Sergey V.; Bulut, Niyazi; Köytepe, Süleyman; Ercan, Filiz; Gürses, Canbolat; Ercan, Filiz; Hssain, Ala Hamd
    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 (?-TCP) as the minor one. The amount of ?-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.