Yazar "Gurgenc, Ezgi" seçeneğine göre listele

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    Performance enhancement of Hitec molten salt through TiB2 and ZrB2 nanoadditives for High-Temperature TES and CSP applications
    (Elsevier, 2026) Gurgenc, Ezgi; Yamac, Halil ibrahim; Oztop, Mesut; Ozabaci, Murat; Canbay, Canan Aksu; Gurgenc, Turan; Oztop, Hakan F.
    Hitec 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 Xray 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 degrees C- 1 and liquid-phase Cp increased from 1.51 to 2.47 J g- 1 degrees 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 degrees C (Hitec) to 661 degrees C and 673 degrees 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.
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    Production and Characterization of AlNiOZnOp-SiAl Composite Photodiodes for Solar Energy Tracking Systems
    (2022) Gurgenc, Ezgi; Dikici, Aydın; ASLAN, Fehmi
    In present study, NiO:ZnO thin films in molar ratios of 1:0, 0:1, 3:1, 1:1 and 1:3 were formed on p-Si layers with aluminum (Al) bottom contact. Dynamic sol-gel spin coating method was used as coating method. Al top contacts were deposited on thin films and Al/NiO:ZnO/p-Si/Al photodiodes were fabricated. The structural and morphological properties of the photodiodes were determined by X-ray diffraction (XRD), emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDX). The photoresponse and electrical properties of the produced photodiodes were investigated by current–voltage (I–V) and capacitance-voltage (C-V) measurements. Al/NiO:ZnO/p-Si/Al photodiodes were successfully produced. It was determined that the thin films formed were composed of nanostructures. All photodiodes were found to be sensitive to light. It was seen that the photosensitivity of composite photodiodes was higher than the pure photodiodes and photosensitivity decreased as the ZnO ratio increased. It was determined that the most sensitive photodiode to light was the composite photodiode with a NiO:ZnO ratio of 3:1, and the highest photosensitivity was measured as 3.12 x 103 at 100 mW/cm2 light intensity in this photodiode. In all photodiodes, the capacitance values decreased as the frequency increased. The results show that by changing the NiO:ZnO ratio, the photoresponse and electrical parameters of the photodiodes can be controlled and the produced photodiodes can be used as a photosensor in solar tracking systems and optoelectronic applications.
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    Sol-Jel Yöntemi ile Sentezlenen La katkılı CdO Nanoparçacıkların, Yapısal Karakterizasyonu ve Dielektriksel Özelliklerinin Belirlenmesi
    (2022) Gurgenc, Ezgi; Dikici, Aydın; Biryan, Fatih; ASLAN, Fehmi; KORAN, Kenan
    Bu çalışmada, saf ve nadir toprak elementlerinden olan Lantan (La) katkılı kadmiyum oksit (CdO) nanoparçacıkları sol-jel yöntemi ile üretildi. Katkılama farklı mol yüzdelerinde (1%, 3%, 5% ve 7%) gerçekleştirildi. Üretilen nanoparçacıklar FE-SEM, EDX, XRD ve FT-IR analizleri ile karakterize edildi. Farklı oranlardaki La katkılı CdO nanoparçacıkların dielektrik sabiti, dielektrik kayıp faktörü ve ac iletkenlik değerleri oda sıcaklığında frekansın bir fonksiyonu olarak empedans analizör cihazı ile belirlendi. La katkılı nanoparçacıklar sol-jel yöntemi ile başarılı bir şekilde üretilmiştir. Üretilen nanoparçacıklar küre benzeri formdadır ve La katkılı nanoparçacıkların boyutları saf CdO’ ya göre daha yüksektir. Frekansın artması ile birlikte dielektrik özelliklerinde azalma olmuş ve daha yüksek frekanslarda sabit bir değere yaklaşmıştır. %1 La katkısı ile 6.87 olan dielektrik sabiti %7 La katksı ile 28.15’e yükselmiştir. Dielektrik kayıp değerleri La katkısı ile azalma göstermiştir. %1 La katkısı ile 9.799x10-5 S/cm olan iletkenlik değeri %7 La katkısı ile 6.110 x10-7 S/cm olarak ölçülmüştür.