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    Modeling and optimization for adsorption of thorium (IV) ions using nano Gd:ZnO: application of response surface methodology (RSM) and artificial neural network (ANN)
    (Taylor & Francis Inc, 2022) Kaynar, Ümit Hüseyin
    The waste problem created by nuclear materials both in nuclear reactors and after their medical and industrial use is evaluated differently from other wastes because they can harm human and environmental health. In this study, it is aimed to study the adsorption properties of Gd ions doped nano ZnO (Gd/nano-ZnO) material synthesized by microwave assisted ignition method for the adsorption of Thorium (IV) from aqueous medium. We tested how pH (3-8), temperature (20-60 degrees C), Th (IV) concentration (25-125 mg/L) and adsorbent amount (0.005-0.08 g) affect adsorption efficiency. The best possible combinations of these parameters were examined by Response Surface Methodology (RSM) and Artificial Neural Network (ANN). R-2 values for RSM and ANN were 0.9970 and 0.9666, respectively. According to the models, the experimental adsorption capacity under the optimum conditions determined for the RSM and ANN model was found to be 192.62 mg/g and 218.47 mg/g, respectively.
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    Structural and temperature-dependent luminescence of Terbium doped YAl3(BO3)4 phosphor synthesized by the combustion method
    (Elsevier Sci Ltd, 2022) Hakami, Jabir Wali; Kaynar, Ümit Hüseyin; Ayvacıklı, Mehmet; Çoban, Mustafa Burak; Garcia-Guinea, J.; Townsend, Peter David; Oğlakçı, Mehmet
    A series of Y1-xAl3(BO3)4:x Tb3+ (x = 0.5 to 7 wt%) phosphors synthesized by a gel combustion method have been systemically investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive spectroscopy (EDS), and photoluminescence (PL) as a function of temperature from 300 K to 10 K and 300 K-550 K. An XRD analysis confirms that the phosphors crystallized, and its crystal structure was analysed. The synthesized phosphor matches the XRD pattern provided in the ICSD File No 96-152-6006. The FTIR analysis indicates that nitrates and organic matter have been completely removed and the BO3 groups are present. The broad PL band peaked at 420 nm with a shoulder circa 460 nm of YAl3(BO3)4 is associated with hydrous components which attached to the sample in environmental conditions after synthesis. The PL spectra of YAl3(BO3):Tb3+ phosphors exhibit a bright and narrow green main emission peak at 543 nm corresponding to the 5D4 -> 7F5 transition under 359 nm excitation. The PL intensity increases with increasing Tb3+ ion concentration up to 5 wt %, followed by evidence for concentration quenching. There is a possibility that higher concentration quenching could be from confinement effects of localised resonant energy transfer. PL data revealed that acti-vation energies for thermal quenching at 485 nm and 543 nm were found to be 0.659 and 0.092 eV, and 0.585 and 0.087 eV, respectively.
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    Thermoluminescence characterization and kinetic parameters of Dy3+ activated Ca3Y2B4O12
    (Elsevier, 2022) Hakami, J.; Sonsuz, M.; Kaynar, Ümit Hüseyin; Ayvacikli, M.; Oğlakçı, Mehmet; Topaksu, M.; Can, N.
    In this study, thermoluminescence (TL) characteristics of Ca3Y2B4O12:xDy (0 < x < 0.07) phosphor samples were studied. The samples were exposed to beta irradiation in the dose range from 0.1 Gy to 100 Gy to investigate TL dose response. The concentration of Dy3+ in Ca3Y2B4O12 phosphor was optimized and found to be 1 mass % in terms of TL signal quality. The TL glow curve appears to be consisted of three peaks which were discernible at 72 degrees C, 280 C and 376 degrees C. The trapping parameters (E, b, and s) were calculated using initial rise (IR), and variable heating rate (VHR) techniques. The trapping parameters, order of kinetics, frequency factor, and figure of merit have been all determined by means of the Glow Curve Deconvolution (GCD) method (tgcd:An R package). Ca3Y2B4O12:Dy phosphor displays efficient thermoluminescence properties.
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    Thermoluminescence glow curve analysis and kinetic parameters of Eu doped Li2MoO4 ceramic phosphors
    (Elsevier Sci Ltd, 2022) Souadi, G.; Oğlakçı, M.; Kaynar, Ümit Hüseyin; Correcher, V.; Benavente, J. F.; Bulcar, K.; Ayvacıklı, M.
    LiMoO4: x Eu ceramic phosphors with x = 0.5, 1, 2, 3, 5, and 7 mol% were synthesized using a gel combustion method. X-ray diffraction (XRD) measurements confirmed a rhombohedral structure (space group R-3) of synthesized compounds. Following irradiation with 50 Gy beta dose, the sample doped with 5 mol% Eu exhibited the highest integrated thermoluminescence (TL) intensity. In order to evaluate dose-response, samples were irradiated with beta radiation for 10-1000 Gy. TL intensity with 1000 Gy dose without saturation yielded the highest integrated value. Different methods were employed to determine the number of peaks, the trap structure, and the kinetic parameters of the thermoluminescence glow curve of Eu doped Li2MoO4: the Hoogenstraaten method, the Booth-Bohun-Parfianovitch method, the initial rise method (IR), combined with the T-M-T-stop experiment, various heating rates (VHR), and glow curve fitting with two different software packages. Based on the glow curve deconvolution obtained using both software packages, the component TL glow peaks present in the complex glow curve are composed of well-isolated nine overlapping glow peaks. Two software packages have shown quite similar activation energies and frequency factors.