Yazar "Madkhli, A. Y." seçeneğine göre listele

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    Adsorption of thorium (IV) ions using a novel borate-based nano material Ca3Y2B4O12: Application of response surface methodology and Artificial Neural Network
    (Pergamon-Elsevier Science Ltd, 2023) Kaynar, Umit H.; Kaptanoglu, I. . Gozde; Cam-Kaynar, Sermin; Ugurlu, Onur; Yusan, Sabriye; Aytas, Sule; Madkhli, A. Y.
    Since nuclear wastes are the most important wastes in terms of health and the environment, they are evaluated differently within nuclear reactors as well as in terms of their use in medical and industrial applications. In some cases, emergency intervention is necessary due to the amount of radioactivity or the physical and/or chemical conditions. . The purpose of this study is to investigate the adsorption properties of nano Ca3Y2B4O12 (CYBO) material synthesized by the sol-gel combustion method for the adsorption of Thorium (IV) from an aqueous medium. We tested how pH (3???8), the concentration of Th (IV) (25???125 mg/L), amount of adsorbent value (0.005???0.08 g) and temperature (20???60 ???C), affect adsorption efficiency. The best possible combinations of these parameters were examined by Response Surface Methodology (RSM) and Artificial Neural Network (ANN). R2 values for RSM and ANN were 0.9964 and 0.9666, respectively. According to the models, the adsorption capacity under the optimum conditions determined for the RSM and ANN model was found to be 134.62 mg/g and 125.12 mg/g, respectively.
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    Beta irradiation-induced thermoluminescence: Glow curve analysis and kinetic parameters in combustion-synthesized undoped Ca4YO(BO3)3
    (Pergamon-Elsevier Science Ltd, 2024) Madkhli, A. Y.; Jabali, D. A.; Souadi, G.; Sonsuz, M.; Kaynar, U. H.; Akca-Ozalp, S.; Ayvacikli, M.
    This study examines the thermoluminescent (TL) properties of undoped Ca4YO(BO3)3 phosphor, focusing on how it behaves under a variety of experimental conditions. The IRSL-TL 565 nm was chosen as the appropriate detection filter among various optical detection filter combinations. During the preheating trials conducted at a rate of 2 degrees C/s, the TL peak exhibited increased intensity, particularly around 200 degrees C. The experimental outcomes demonstrated a reliable linear relationship (R2 = 0.996 and b = 1.015) in the dose response of undoped preheated Ca4YO(BO3)3 within the range of 1-200 Gy. The investigation encompasses a range of techniques, including the TM-Tstop method, computerized glow curve deconvolution (CGCD) analysis, and theoretical modelling. The application of the TM-Tstop method to samples irradiated with a 5 Gy dose revealed distinct zones on the TM versus Tstop diagram, signifying the presence of at least two discernible components within the TL glow curve, specifically, a single general order kinetics peak and a continuous distribution. The analysis of activation energy versus preheated temperature exhibited a stepwise curve, indicating five trap levels with depths ranging between 1.13 eV and 1.40 eV. The CGCD method also revealed the superposition of at least five distinct TL glow peaks. It was observed that their activation energies were consistent with the Tm-Tstop experiment. Furthermore, the low Figure of Merit (FOM) value of 1.18% indicates high reliability in the goodness-of-fit measure. These findings affirm the reliability and effectiveness of the employed methods in characterizing the TL properties of the Ca4YO(BO3)3 phosphor under investigation. Theoretical models, including the semi-localized transition model, were introduced to explain anomalous observations in TL glow peak intensities and heating rate patterns. While providing a conceptual framework, these models may require adjustments to accurately capture the specific characteristics uncovered through CGCD analysis. As a potential application, the study suggests that the characterized TL properties of Ca4YO(BO3)3 phosphor could be utilized in dosimetric applications, such as radiation dose measurements, owing to its reliable linear response within a broad dose range.
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    Characterization, room and low temperature photoluminescence of yttrium aluminium borate activated with Sm3+ions
    (Pergamon-Elsevier Science Ltd, 2023) Madkhli, A. Y.; Kaynar, U. H.; Coban, M. B.; Ayvacikli, M.; Canimoglu, A.; Can, N.
    In this study, the combustion method assisted by urea that is ideally suited to economic and time saving was used for the synthesizing of reddish orange emitting YAl3(BO3)4 phosphor samples doped with various Sm3+ ions (from 0.01 wt% to 7wt%). A detailed study of the structural and luminescence properties at room/low tem-perature of the synthesized samples was performed. XRD analysis revealed a rhombohedral structure with an R32 space group (155). The particle size was determined by the Scherrer's method to be 48 nm. The visible PL emission spectra upon excitation at 359 nm are recorded and four emission peaks around 564, 599, 646, and 707 nm with transitions 4G5/2 -> 6H5/2, 4G5/2 -> 6H7/2, 4G5/2 -> 6H9/2 and 4G5/2 -> 6H11/2 are observed. Concentration quenching was mainly caused by dipole-dipole interactions between neighbouring trivalent Sm3+ ions. Through the CIE chroma coordinates (0.606, 0.382), the optimized sample (x = 0.03) demonstrates admirable luminous performance. YAl3(BO3)4:Sm3+ can be a good candidate for use as a red component for lighting applications.
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    Phase transition and luminescence characteristics of dysprosium doped strontium stannate phosphor synthesized using hydrothermal method
    (Elsevier Sci Ltd, 2023) Kaynar, Umit H.; Coban, M. B.; Madkhli, A. Y.; Ayvacikli, M.; Can, N.
    A series of strontium stannate (SrSnO3) doped with Dy3+ ions at various wt % concentrations (1, 2, 3 and 5) were synthesized via hydrothermal reaction and analysed using X-ray diffraction (XRD), energy dispersive spectros-copy (EDS), environmental electron scanning microscope (ESEM), photoluminescence (PL) and, cath-odoluminescence (CL). The XRD results confirmed that all samples were assigned to cubic perovskite-type SrSnO3 structured with the Pm3m space group. The PL emission spectrum of Dy3+ activated samples consisted of some characteristic peaks located at 481 nm, 572 nm, 660 nm and 753 nm, corresponding to (4F9/2 -> 6H15/2, blue), (4F9/2 -> 6H13/2, yellow), 660 nm (4F9/2 -> 6H11/2, red) and 753 nm (4F9/2 -> 6H9/2, red) transitions. The PL emission line intensity is gradually enhanced with an increase in doping concentration up to 3 wt %, followed by concentration quenching. The confinement effects of localized resonant energy transfer might cause higher concentration quenching. PL emission spectra were affected by the temperature range from 10 K to 300 K. PL emission anomalies at 270 K in SrSnO3:Dy3+ have been reported to be consistent with a structural phase tran-sition at this temperature. This work confirms Singh et al.'s observation, revealing that SrSnO3 has a phase transition at 270 K.
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    Photoluminescence properties and structural analysis of Tb3+-doped K3Gd (BO2)6: A first study on negative thermal quenching
    (Elsevier Science Sa, 2025) Souadi, G.; Madkhli, A. Y.; Kaynar, U. H.; Gok, C.; Aydin, H.; Coban, M. B.; Kaynar, S. Cam
    In this study, Tb3+-doped K3Gd(BO2)6 phosphors were synthesized using the microwave-assisted sol-gel method to explore their photoluminescence (PL) properties and thermal stability. XRD and Rietveld refinement confirmed the incorporation of Tb3+ions, without secondary phases. PL analysis revealed a strong green emission near 542 nm, attributed to the 5 D 4 -> 7 F 5 transition of Tb3+ions. An optimal Tb3+concentration of 3 wt% was identified, beyond which concentration quenching significantly reduced luminescence intensity. Radiative energy transfer, occurring via reabsorption, was observed at lower concentrations, facilitating efficient energy migration. Conversely, at higher concentrations, non-radiative processes such as cross-relaxation dominated. Remarkably, negative thermal quenching (NTQ) was observed up to 470 K, with an activation energy of 0.96 eV. Additionally, Na+ co- doping introduced lattice distortions that enhanced energy transfer between Tb3+ions and improved luminescence efficiency. The chromaticity diagram highlighted a shift towards the yellow-green region with increasing the Tb3+concentration, demonstrating tunable emission properties for solid-state lighting applications.