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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 Investigation of structural, electrical and photoresponse properties of composite based Al/NiO:CdO/p-Si/Al photodiodes(Elsevier, 2022) Gurgenc, Ezgi; Dikici, Aydin; Aslan, FehmiIn the present study, different molar ratios of (1:0, 0:1, 3:1, 1:1, and 1:3) NiO:CdO composite thin films were coated on p-Si by a dynamic sol-gel spin coating method. Structural characterizations of NiO:CdO thin films were performed by XRD, FE-SEM, and EDX analysis. The photoresponse and electrical behavior of the fabricated photodiodes were determined by current-voltage (I-V), transient photocurrent-time (I-t), capacitance-voltage (C-V), conductivity-voltage (G-V), and transient photocapacitance-time (C-t) measurements. All fabricated photodiodes were exhibited rectifying properties and the photocurrent values increased as the light intensity was increased. All photodiodes are sensitive to light and it was determined that the NiO photodiode exhibited the highest photosensitivity value. Photocapacitance and photoconductance values of photodiodes were affected by light. Photoresponse and electrical behavior were affected by the interface states and the NiO:CdO ratio. The results show that Al/NiO:CdO/p-Si/Al photodiodes can be used as photosensors or photocapacitors in optoelectronic applications.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 Performance enhancement of Hitec molten salt through TiB2 and ZrB2 nanoadditives for High-Temperature TES and CSP applications(Elsevier B.V., 2026) Gurgenc, Ezgi; Yamaç, Halil İbrahim; Öztop, Mesut; Özabacı, Murat; Canbay, Canan Aksu; Gurgenc, Turan; Gür, MuhammedHitec molten salt (7NaNO3–53KNO3–40NaNO2) is widely considered for high-temperature heat transfer and thermal energy storage, yet its relatively limited heat storage capacity and thermal transport performance constrain energy density and charging-discharging efficiency in CSP-TES systems. To address this limitation, Hitec was modified with TiB2 and ZrB2 nanoparticles at loadings of 0.5, 1, 1.5, and 2 wt% and investigated through a comprehensive experimental framework. Phase integrity and chemical stability were examined by X-ray diffraction and Fourier transform infrared spectroscopy. Microstructural features, nanoparticle distribution, and elemental homogeneity were evaluated using FE-SEM/EDX. Thermophysical behavior was characterized by DSC to determine specific heat capacity and melting–solidification characteristics, while thermal stability was assessed by TGA. Thermal conductivity was measured using the transient plane source method. ZrB2 provided the strongest heat storage enhancement. Solid-phase Cp increased from 1.44 to 2.22 J g−1 °C−1 and liquid-phase Cp increased from 1.51 to 2.47 J g−1 °C−1 at 1 wt% ZrB2, corresponding to improvements of 54.68% and 63.30%. TiB2 delivered the largest heat-transfer improvement, increasing thermal conductivity from 0.951 to 1.664 W m−1 K−1 at 2 wt% (74.97%). Melting enthalpy increased by up to 16.93% for TiB2 and 21.13% for ZrB2. Thermal stability improved substantially, shifting the decomposition onset from 612 °C (Hitec) to 661 °C and 673 °C for 2 wt% TiB2 and ZrB2, respectively. Overall, TiB2 and ZrB2 exhibit complementary performance profiles, enabling tailored Hitec-based media for higher energy density, improved heat transfer, and extended high-temperature operation in CSP-TES and related thermal management applications. © 2026 Elsevier B.V.
