Yazar "Bulut, F." seçeneğine göre listele

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    A comparative neutron and gamma-ray radiation shielding investigation of molybdenum and boron filled polymer composites
    (Pergamon-Elsevier Science Ltd, 2023) Ogul, H.; Agar, O.; Bulut, F.; Kacal, M. R.; Dilsiz, K.; Polat, H.; Akman, F.
    This work presents a detailed radiation shielding study for polymer composites filled with Boron and Molyb-denum additives. The chosen novel polymer composites were produced at different percentages of the additive materials to provide a proper evaluation of their neutron and gamma-ray attenuation abilities. The effect of additive particle size on the shielding characteristics was further investigated. On the gamma-ray side, simula-tion, theoretical and experimental evaluations were performed in a wide range of photon energies varying from 59.5 keV to 1332.5 keV with help of MC simulations (GEANT4 and FLUKA), WinXCOM code, a High Purity Germanium Detector, respectively. A remarkable consistency was reported between them. On the neutron shielding side, the prepared samples produced with nano and micron particle size additives were additionally examined by providing fast neutron removal cross-section (sigma R) and the simulated neutron transmissions through the prepared samples. The samples filled with nano sized particles show better shielding capability than the one filled with micron sized particles. In other words, a new polymer shielding material that does not contain toxic content is introduced: the sample codded N-B0Mo50 exhibits superior radiation attenuation.
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    Characterization of the CoFe2O4/Cu displacement effect in the Y123 superconductor matrix on critical properties
    (Springer, 2020) Safran, S.; Bulut, F.; Nefrow, A. R. A.; Ada, H.; Ozturk, O.
    In this study, CoFe2O4(x = 0, 5, 10 and 20 wt%) doped YBa2Cu3-x(CoFe2O4)(x)O(7-delta)bulk samples were produced using solid state reaction (SSR) method and sol-gel(SG) methods. Oxide-form and acetate-form powders were preferred for SSR method and SG method, respectively. The heat treatment of the produced samples was carried out in two stages. Firstly, the samples were annealed at 950 degrees C for 24 h, after which they were kept in oxygen at 500 degrees C for 5 h and allowed to be cooled down to room temperature. Characterization of all samples was performed using methods such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent resistance measurement (R-T) and Vickers microhardness analysis. Superconducting behavior was observed in all the produced samples, but as a result of the addition, a decrease was observed with the increase of the doping ratio at the critical transition temperature. As a result of the characterization, it is concluded that the doping ions can be replaced with Cu atoms in Y123 structure. In addition, doping led to significant changes in Vickers microhardness results.
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    Comparison of the Dopant Effect and Sample Preparation Method on Y-123 Superconductors
    (Springer, 2021) Ozturk, O.; Nefrow, A. R. A.; Bulut, F.; Kurnaz, S.; Safran, S.
    The detailed comparison of the effects of Co and CoFe2O4 dopants and preparation methods (solid-state reaction method and sol-gel methods) have been studied on structural, electrical, superconducting, and mechanical properties of Y123 bulk superconductors. The doping amounts of Co and CoFe2O4 were chosen up to 0.10 wt. %. X-ray powder diffraction (XRD) method, temperature-dependent resistance measurement (R-T), and Vickers microhardness analyses were performed to characterize prepared samples. XRD analysis showed that all samples have Pmmm symmetry of orthorhombic crystal structure; intensities and width of the diffraction lines were affected by doping material, but, independent of the preparation method. Although all samples crystallize in orthorhombic structure and exhibit superconductivity behavior, with increasing doping rate the critical transition temperatures of the samples showed a significant decrease and broadened to superconducting temperature transition width. This is more evident in CoFe2O4-doped Y-123 samples produced by sol-gel method. As the applied force increased, it was observed that the microhardness values of the Co-doped samples increased while the CoFe2O4-doped samples decreased, regardless of the sample preparation method.
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    Evolution of fundamental mechanical properties with aliovalent Co/Cu partial substitution and preparation method for Y-123 system
    (Springer, 2024) Ozturk, O.; Safran, S.; Ada, H.; Bulut, F.; Seydioglu, T.; Nefrow, A. R. A.; Akkurt, B.
    This study investigates the effect of aliovalent Co/Cu replacement and preparation method on fundamental mechanical performance features of YBa2Cu3-xCoxO7-delta (Y-123) ceramic system depending on the crack propagation mechanism by Vickers hardness measurements (H-v) and mechanical investigation models for the first time. All the findings are verified by the scanning electron microscopy (SEM) examinations. Besides, the electron-dispersive X-ray (EDX) technique verifies the successful substitution mechanism. Besides, the Vickers hardness parameters improve systematically with the increment in the Co/Cu partial substitution (serving as a barrier) level due to formation of operable slip systems, ionic bond formations, and decrement of stress-amplified strain fields. Moreover, the Y-123 ceramic produced by solid-state reaction method and molecular weight of 0.20% presents the densest and smoothest surface morphology with the largest particle distributions and well-linked cobblestone-like grains. On the other hand, the Y-123 ceramic compounds produced by the sol-gel method are more sensitive and responsive to the indentation test loads. All the findings are wholly supported by the mechanical performance properties, including the shear modulus, resilience, and degree of granularity. Furthermore, the mechanical models indicate that every compound prepared exhibits the untypical reverse indentation size effect (RISE). Additionally, the modeling studies display that the induced cracking (IIC) approach is found to be the most appropriate method to examine true Vickers hardness parameters in the plateau limit regions. All in all, this comprehensive study reports efficiently exploiting the process-structure-property relationships in Y-123 ceramic material design for physical science and mechanical application fields using the aliovalent partial substitution and preparation condition.
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    Gamma and Neutron Shielding Parameters of Polyester-based composites reinforced with boron and tin nanopowders
    (Pergamon-Elsevier Science Ltd, 2022) Ogul, H.; Polat, H.; Akman, F.; Kacal, M. R.; Dilsiz, K.; Bulut, F.; Agar, O.
    The usage of composites as the shielding materials are highly recommended since they could be used in order to attenuate the undesired radiation with unique properties and advantages in the areas where the radiation is prevalent. In this context, not only are their radiation shielding properties important but also their flexibility, durability and low cost. Due to the mentioned superior characteristics, the polyester based composites are among the most preferred materials. With the aim of creating unique and novel radiation shielding materials, this study investigates gamma and neutron shielding capabilities of the polyester composites reinforced with Boron and Tin nanopowders at different proportions (0-50%, 10-40%, 20-30%, 30-20% and 40-10%, 50-0%). The gamma shielding abilities of the prepared polyester composite materials were evaluated using an HPGe detector system, WinXCOM computer program and different simulation tools (FLUKA and GEANT4) at the energies varying from 59.5 to 1332.5 keV. The experimental, theoretical and simulation results showed remarkable agreement between each other, and the addition of Sn enhances the gamma attenuation performance of the chosen polyester composite materials. In addition to gamma analysis results, neutron shielding properties of the proposed com-posites are further determined. On this purpose, the transmitted neutron numbers through the samples (as functions of neutron energy and the sample thickness) and effective neutron removal cross sections were eval-uated. The neutron shielding performance of the samples showed that the prepared composites could be alter-native materials to the existing neutron shields in the literature.
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    Investigation of structural, superconducting and mechanical properties of Co/Cu substituted YBCO-358 ceramic composites
    (Springer, 2019) Ozturk, O.; Arebat, R. A. M.; Nefrow, A. R. A.; Bulut, F.; Guducu, G.; Asikuzun, E.; Celik, S.
    In this study, we have examined the structural, superconducting and mechanical properties of Y3Ba5Cu8-xCoxO18- system (x=0, 0.05, 0.1, 0.15, 0.2 and 0.5), which is produced by conventional solid-state reaction method. Produced samples have been examined using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Vicker's hardness (H-v) and electrical resistance measurement (R-T). According to the XRD patterns, we have obtained that the Co nanopowder doping has been caused some changes on the average grain size, characteristic peak intensities and lattice parameters of the Y3Ba5Cu8O18- crystal system. Furthermore, according to the electrical resistance measurements, the critical temperature (T-c) values of all the samples have tended to decrease constantly with the increment in the doping ratio in the Y358 crystal structure. As for the variation in the microhardness parameters of superconducting materials, the H-v parameters and other related computations (Young's modulus and yield strengths) have been found to increase regularly with the Co/Cu substitution level. Besides, the characteristic H-v curves have confirmed that the whole bulk of Bi-2212 samples showed untypical reverse indentation size effect (RISE) behavior.