Yazar "Apaydin, Gokhan" seçeneğine göre listele

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    Determination of L-shell fluorescence parameters of thallium in thallium compounds
    (Taylor & Francis Inc, 2021) Cengiz, Erhan; Tirasoglu, Engin; Apaydin, Gokhan; Koksal, Oguz Kagan
    The L-i (i = l, alpha, beta, and gamma) production cross-sections, L-shell average fluorescence yields, and Coster-Kronig vacancy transfer factors for L-3 subshell X-rays of thallium in some thallium compounds were determined using Energy Dispersive X-ray Fluorescence spectrometer. The compounds were excited by 59.5 keV gamma-rays from an Americium-241 annular radioactive source, and the L X-rays emitted by the compounds were counted using an ultra-low energy germanium detector with a resolution of 150 eV at 5.9 keV. The production cross-sections, average fluorescence yields, and Coster-Kronig vacancy transfer factors of thallium in these compounds were compared with theoretical calculations and available experimental values of the pure thallium.
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    Investigation of radiation shielding properties of CeO2 thin films prepared at different molarities
    (Iop Publishing Ltd, 2025) Kanmaz, Imran; Koksal, Oguzkagan; Apaydin, Gokhan; Tomakin, Murat; Cengiz, Erhan
    In this study, CeO2 thin films were produced using the spin coting method, which is one of the sol-gel methods, in six different molarities. X-ray diffraction (XRD) patterns revealed the characteristic peaks of the films, while Field Emission Scanning Electron Microscopy (FESEM) confirmed their homogeneous structure. Then, radiation shielding parameters like linear absorption coefficient (LAC), mass absorption coefficient (MAC), tent value layer (TVL), mean free path (MFP), and half value layer (HVL) were thoroughly examined. The results showed that increasing molarity had a significant effect on the thickness values of thin films and the absorption parameters were found to improve with increasing molarity. Both LAC and MAC values decrease as the energy level increases, but the increase in CeO2 molarity leads to a strong increase on these coefficients. The HVL value was also found to be 0.42 cm at the lowest energy of 14.957 keV and to be around 10 cm at the greatest energy of 59.543 keV (0.05 M). When the radiation energy applied to the material was raised from 14.957 keV to 59.543 keV, it was found that the MFP values of 0.05 M CeO2 thin films grew gradually from 0.61 cm to 14.51 cm. High energy radiation of 59.543 keV and a low density (0.05 M) medium resulted in peak TVL values of 33.423 cm, allowing the radiation to pass through the material with minimal interaction.
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    Spatiotemporal distribution, source identification and risk assessment of potentially toxic elements in sediments along the Alanya/Antalya coastline, Mediterranean Sea
    (Springer, 2025) Cengiz, Erhan; Sirin, Murat; Yesilkanat, Cafer Mert; Apaydin, Gokhan
    This study investigates the concentrations of potentially toxic elements (PTEs), ecological risks, and human health effects in sediment samples from 11 points along the Alanya coastline, influenced by industrial, agricultural, and tourism activities. Energy dispersive X-ray fluorescence spectroscopy was used for analysis. The mean concentrations of Mn, Fe, Ni, Cu, Zn, Cr, and As were 281, 14, 30, 34, 66, 60, and 12 mg/kg, respectively. The enrichment factor values were ranked as follows: As (3.94), Zn (2.94), Cu (2.83), Cr (2.45), Ni (1.29), and Mn (1.19), indicating moderate enrichment for Cu, Zn, Cr, and As, and minimal enrichment for Ni and Mn. The geo-accumulation index indicated minimal contamination, supporting the conclusion that Alanya is not heavily impacted by the PTEs studied. The contamination factor values were highest for As (0.90) and lowest for Fe (0.30), indicating generally low levels of pollution. Seasonal variation was observed, with the highest degree of contamination in winter (7.09) and the lowest in autumn (5.39). The pollution load index ranged from 0.411 in autumn to 0.622 in winter, with an annual average of 0.468, indicating no pollution. The ecological risk factor values, ranging from 0.30 for Fe to 8.97 for As, did not show a significant ecological risk, with As contributing most to the risk. The potential ecological risk index averaged 15.4, which means a very low ecological risk. Additionally, the study confirmed that the overall potential human health risks remained within acceptable limits.
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    The K?/K? X-ray intensity ratios of Cu and Ag in Cu-Ag thin alloy films
    (Pergamon-Elsevier Science Ltd, 2023) Sogut, Omer; Cengiz, Erhan; Ayaz, Durdu Hayrettin; Apaydin, Gokhan
    K & beta;/K & alpha; X-ray intensity ratio values of Cu and Ag in CuxAg1-x (x = 53.5, 67.6, 76.9, 85.4, 89.6) thin alloy films produced from two different sources by the physical vapour deposition method have been determined by the Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) method. The changes in the crystal structures of CuxAg1-x thin alloy films caused by the changes in the Cu and Ag concentrations, which affect the valence electronic structure have been investigated by the X-ray Diffraction (XRD) techniques. The obtained values were compared with the theoretical and fitted values for pure Cu and Ag elements.
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    Thickness-Dependent Structural and Electronic Properties of HfO2 Thin Films Probed by XRD and XAFS
    (Springer, 2025) Ozkendir, Osman Murat; Cengiz, Erhan; Kanmaz, Imran; Gunaydin, Selen; Apaydin, Gokhan; Harfouche, Messaoud
    Hafnium dioxide (HfO2) thin films have garnered significant attention due to their exceptional dielectric, mechanical, and thermal properties, making them ideal for applications in microelectronics, optoelectronics, and energy storage. However, despite extensive research, a comprehensive understanding of their thickness-dependent structural and electronic properties remains incomplete. In this study, we systematically investigate HfO2 thin films (13-115 nm) synthesized via spin coating and characterized using synchrotron-based x-ray absorption fine structure (XAFS) spectroscopy and x-ray diffraction (XRD). High-resolution XRD confirms the monoclinic P2(1)/c phase with high crystallinity and minimal strain, while XAFS analysis reveals thickness-dependent variations in local atomic coordination and electronic structure. XANES spectra demonstrate a systematic shift in the Hf L-3-edge white line, indicating modifications in unoccupied Hf 5d states due to changes in oxygen coordination. EXAFS fitting further quantifies bond distances and coordination numbers, revealing enhanced structural ordering in thicker films. Density functional theory (DFT) calculations corroborate experimental findings, confirming the bandgap (similar to 4.4 eV) and orbital contributions to valence and conduction bands. Our results provide critical insights into defect states, interfacial effects, and thickness-dependent structural modifications, advancing the optimization of HfO2 for next-generation electronic devices.