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    Contrasting effects of metal oxide dopants on the superconductivity of YBa2Cu3O7-? ceramics
    (Springer, 2019) Ozabaci, Murat
    Bulk superconductor samples of YBa2Cu3O7-delta (YBCO or Y-123), with additions of 0.15 wt% MoO3, TiO2, RuO2 and two different types of Al2O3 compounds, are synthesized by a solid state reaction route. Structural, magnetic and transport properties of the samples are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), magnetic (M-H, M-T) and magneto-resistivity (MR-T) measurements. SEM investigations show that the addition of the Al2O3 obtained from the alumina crucible (Al2O3-cru) decreases the grain size of the sample which, in turn, degrades the transition temperatures (T-c) and magnetic critical current densities (Jcmag). On the contrary, the addition of the other metal oxides enhances of the samples by a few times and also increases T-c by up to 3 K. EDX analyses of the samples exhibit homogeneous distribution of additions, except for Ru-heterogeneities located around superconducting Y-123 grains. The highest J(c) and T-c values obtained on the RuO2 added sample were attributed to the agglomeration of the Ru-particles, which led to the optimal porosity that supports oxygenation process and intergrain coupling of the structure. From the DC magnetization data, we estimated Jcmagf 3.1 x 10(5) A/cm(2), 2.3 x 10(5) A/cm(2), 2 x 10(5) A/cm(2), 1.5 x 10(5) A/cm(2), 10(5) A/cm(2) and 5.1 x 10(4) A/cm(2) for the RuO2, TiO2, MoO3, Al2O3, undoped and Al2O3-cru added samples at 5 K under 0.25 T, respectively.
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    Enhancement of magnetic relaxation behavior by texturing in Bi-2212 superconducting rods
    (Elsevier Sci Ltd, 2016) Ozabaci, Murat; Kizilaslan, Olcay; Kirat, Gokhan; Aksan, Mehmet A.; Madre, Maria A.; Sotelo, Andres; Yakinci, Mehmet E.
    Time decay of magnetization, known as magnetic relaxation, is crucial for both fundamental and applied point of view in bulk high temperature superconductors (HTS) by setting the limits to the HTS devices stability. Melt-processed Bi2Sr2Ca1Cu2-xGa8+delta rods (Bi-2212, x=0,0.1) were used to study the effect of both grain alignment and substitution on the samples critical current density, relaxation and pinning behavior. The magnetic field has been applied both perpendicular and parallel to the rods growth axis to determine the effect of grain alignment. It has been found that Ga substitution reduces grains orientation and sizes leading to lower magnetic properties. The peaks of the curves, which indicate the temperature dependence of the samples magnetic relaxation rate (S), have been observed in the 7-35 K temperature range. Characteristic pinning energy (U-e/k(B)) of samples was determined using the formalism developed by Maley. The change of pinning energy as a function of magnetization has been found to be exponential between 3 and 60 K, which is in agreement with the collective creep theory. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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    Microstructure and wear analysis of CoWC alloy layers deposited by PTA process
    (Edp Sciences S A, 2023) Ozabaci, Murat; Teker, Tanju; Yilmaz, S. Osman
    CoWC composite coatings were produced on AISI 430 steel by the plasma transfer arc cladding. Three different powder mixtures containing WC (90%, 85% and 80%) and Co (10%, 15% and 20%) were used. Phase composition, microstructural characterization and coating properties were investigated by using scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), elemental mapping, hardness and wear test. The wear shape morphology of coatings was determined by SEM. The increased ratio of WC in CoWC powders reduced the degradation of CoWC. The substrate hardness of 180 HV gained a coating hardness value of approximately 462 HV. An increase in the hardness of the coating alloy compared to the substrate was achieved. W2C, WC, CoC and Co6W6C phases were determined on the coating surface. The high levels of WC concentration on the coating surface increased the wear resistance.
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    The Superconductivity and Structural Properties in FeSe0.5Te0.5 with Sb and Sm Additions
    (Springer, 2023) Ozabaci, Murat
    Single crystals of FeSe0.5Te0.5 with additions of 4 wt.% Sb and 4 wt.% Sm were grown by self-flux synthesis method in order to study their influence on the superconducting characteristics. Scanning electron microscope and energy-dispersive x-ray spectroscopy (SEM/EDX) analyses show that the added Sm atoms mostly precipitate at the bottom and outer surfaces of the solidified ingot and could not be detected in the structure within the resolution limit of the EDX, while the Sb atoms lead to Sb precipitation regions on the boundary outlines of the lamellas. X-ray diffraction (XRD) patterns approve the presence of single tetragonal phase of FeSe0.5Te0.5 without any other impurity phases. Electrotransport and magnetic measurements reveal that the Sm-saturated FeSe0.5Te0.5 gives rise to significantly better superconducting performance in comparing with the undoped and Sb added samples. From electrical resistivity measurements, the onset (T-c(onset)) and zero-resistivity temperatures (T(c)z(ero)) appear at T-c(onset)=14.65, 14.36, and 15.2 K and T-c(zero)= 11.57, 12.05, and 13.79 K with corresponding transition widths of T=3.08, 2.31, and 1.41 K for the undoped and Sb and Sm doped samples, respectively. These values indicate the positive effects of the Sm saturation in critical transition temperatures with similar to 2.22 K increase in Tczero and 1.67 K decrease in T. The estimated magnetic critical current densities, Jcmag, through the Bean model and transport critical current densities, J(c)(trans), of the samples demonstrate that the Sm added sample produces up to similar to 7 times higher j(c) values with respect to those for the other two samples. The calculated Jcmag values are 3.8x10(4), 1.9x10(4), and 2.7x10(5) A/cm(2) at 5 K under 0.1 T for the undoped and Sb and Sm added samples, respectively.
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    Synthesis and characterization of NiFe2O4 piezoelectric nanoparticles: a comprehensive study on the influence of natural surfactants, kinetics, and thermodynamics
    (Springer, 2024) Babakr, Karukh Ali; Qader, Ibrahim Nazem; Amiri, Omid; Ozabaci, Murat; Aspoukeh, Peyman; Hamad, Samir Mustafa
    Using piezoelectric nanoparticles created with natural surfactants to remove dyes from water is a promising, environmentally friendly approach with potential benefits in sustainability, efficiency, cost-effectiveness, and innovation in water treatment technologies. This study investigates the influence of natural surfactants on the synthesis of hydrothermal-based Ni ferrite nanoparticles designed for dye removal. Three fruit juices-grape, orange, and peach-were employed in the preparation process, and their properties were scrutinized through X-ray diffraction (XRD), scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDAX). The research also explores the effects of varying time and temperature parameters on dye removal. Results indicate that Ni-ferrite nanoparticles synthesized with grape juice exhibit enhanced efficacy in degrading crystal violet dye. Moreover, the morphology of these nanoparticles diverges from those produced through alternative methods documented in the literature. The study's findings suggest that the degradation of Crystal Violet (CV) by a NiFe2O4 catalyst through piezoelectric means adheres to pseudo-second-order kinetics. Thermodynamic analyses reveal that CV piezo degradation is an endothermic process. The presence of nearly spherical nanoparticles in all samples is accompanied by the remarkable identification of bar-shaped crystalline particles with piezoelectric properties with a length of around 3 mu m and a diameter of 300 nm in samples synthesized with grape juice. This unique morphological characteristic, which has not been previously reported for nickel ferrite, represents a novel finding. In conclusion, we posit that natural surfactants, exemplified by grape juice, exert a substantial influence on the microstructure of nanoparticles, thereby influencing their potential applications.