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Öğe B4C-based nanoenhancement on the thermophysical and stability performance of solar salt: a novel approach for high-temperature TES applications(Elsevier, 2025) Gurgenc, Ezgi; Oztop, Hakan F.; Yamac, Halil ibrahim; Canbay, Canan Aksu; Senocak, Safak Melih; Ozabaci, Murat; Gurgenc, TuranEnhancement of the thermophysical properties of molten salt-based nanofluids is essential for improving energy density and efficiency in high-temperature thermal energy storage (TES) systems. However, the mechanisms behind the anomalous increase in specific heat capacity upon nanoparticle addition remain unclear. In this study, solar salt (60 wt% NaNO3-40 wt% KNO3) was modified with boron carbide (B4C) nanoparticles at concentrations of 0.5, 1.0, 1.5, and 2.0 wt% using a wet dispersion method. The structural and thermal behaviors of the nanofluids were investigated through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FE-SEM/ EDX), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The DSC results from the second thermal cycle confirmed that the addition of B4C significantly enhanced the Cp of the base salt. Specifically, the 2.0 wt% B4C sample exhibited average enhancements of 31.5 % in the solid phase (100-220 degrees C) and 49.83 % in the liquid phase (250-400 degrees C) compared to pure solar salt, with a peak value of 2.11 J/g.K at 250 degrees C. FE-SEM analyses revealed more uniform nanoparticle distribution at lower concentrations, while higher loadings led to particle agglomeration. Thermal conductivity increased by 142.8 %, from 1.05 to 2.55 W/m.K. Although latent heat decreased with higher nanoparticle content (from 108.7 J/g to 97.2 J/g), thermal stability improved, with the decomposition onset temperature shifting from 607 degrees C to 644 degrees C at 1.5 wt% B4C. These results identify B4C as a promising non-oxide nanoadditive for TES applications, offering balanced improvements in thermal performance and stability.Öğe Contrasting effects of metal oxide dopants on the superconductivity of YBa2Cu3O7-? ceramics(Springer, 2019) Ozabaci, MuratBulk 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.Öğe 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.Öğe Microstructure and wear analysis of CoWC alloy layers deposited by PTA process(Edp Sciences S A, 2023) Ozabaci, Murat; Teker, Tanju; Yilmaz, S. OsmanCoWC 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.Öğe Novel boride-enhanced solar salts: Thermophysical and structural properties for thermal energy storage(Elsevier, 2026) Gurgenc, Ezgi; Oztop, Hakan F.; Yamac, Halil Ibrahim; Canbay, Canan Aksu; Senocak, Safak Melih; Ozabaci, Murat; Gur, MuhammedMolten nitrate salts, widely used as thermal energy storage (TES) media in concentrated solar power (CSP) systems, suffer from intrinsic drawbacks such as low thermal conductivity, moderate thermal stability, and limited heat capacity. Conventional oxide nanoparticles have been explored to mitigate these limitations, yet their improvements are often restricted by relatively low intrinsic conductivity and stability. In this context, boride-based nanoparticles (HfB2, TiB2, and ZrB2) have attracted increasing attention owing to their exceptional thermal conductivity, chemical inertness, and high-temperature stability. In this study, solar salt (60 wt% NaNO3-40 wt% KNO3) was modified with different weight fractions (0.5-2.0 wt%) of HfB2, TiB2, and ZrB2 nanoparticles, and their thermophysical properties were systematically investigated. The results revealed that boride addition significantly enhanced density, specific heat capacity (Cp), thermal conductivity, and thermal stability compared to pure solar salt. Specifically, Cp increased from 1.51 J/g.K (pure salt) to 2.68 J/g.K with 2 wt% HfB2 (77.8 % increase), while ZrB2 and TiB2 yielded 2.39 J/g.K (58.4 %) and 1.60 J/g & sdot;K (6.2 %), respectively. Thermal conductivity rose from 0.632 W/m.K (pure salt) to 1.53 W/m.K (HfB2), 1.60 W/m.K (TiB2), and 1.38 W/m.K (ZrB2) at 2 wt% loading. TGA confirmed improved decomposition stability, with TiB2 showing the highest thermal stability at 651 degrees C. Additionally, density measurements indicated systematic increases with additive concentration, with the highest value (2.2411 g/cm3) recorded for ZrB2 at 2 wt%. These findings demonstrate that boride nanoparticles, even at relatively low concentrations, can effectively enhance the thermophysical performance of solar salt, surpassing many conventional oxide-based additives. Among the additives, HfB2 is most promising for maximizing energy density, TiB2 for high-temperature stability and conductivity, and ZrB2 for balanced multipurpose performance. Such improvements highlight the potential of boride-based nanocomposite salts for next generation CSP and thermal energy storage applications, particularly in hightemperature operation regimes where both energy density and efficient heat transfer are critical.Öğe The Superconductivity and Structural Properties in FeSe0.5Te0.5 with Sb and Sm Additions(Springer, 2023) Ozabaci, MuratSingle 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.Öğe 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 MustafaUsing 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.
