Browsing by Author "Bayram, Umit"

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Comparison of Photocatalytic and Adsorption Properties of ZnS@ZnO, CdS@ZnO, and PbS@ZnO Nanocomposites to Select the Best Material for the Bifunctional Removal of Methylene Blue
(AMER CHEMICAL SOC, 2025) Bayram, Umit; Ozer, Cigdem; Yilmaz, Erkan; 0000-0001-8760-8024; 0000-0001-8962-3199; AGÜ; Bayram, Umit
In this study, photocatalytic- and adsorption-based removal processes were conducted, which are frequently preferred in wastewater treatment due to their ease of control and high removal efficiency. An innovative method aimed at wastewater treatment was developed by combining the advantages of these two distinct approaches within the same material. The study synthesized ZnO, ZnS, CdS, PbS, and their composite structures (ZnS@ZnO, CdS@ZnO, and PbS@ZnO) using a hydrothermal synthesis method. Characterization of the samples was performed through field emission-scanning electron microscopy (FE-SEM), FE-SEM-energy dispersive X-ray (FE-SEM-EDX), X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR) measurement. Additionally, the optical properties of all samples (absorption spectra and band gap) were investigated by using absorbance measurements obtained from ultraviolet (UV)-visible absorption spectroscopy. Although ZnO nanoparticles are among the materials with high photocatalytic properties (exhibiting a photodegradation efficiency of 95.8% in a short duration of 90 min), their adsorption properties are low. Therefore, with the aim of enhancing both the low adsorption values and the photocatalytic properties of pure metal sulfides (ZnS, CdS, PbS), nanocomposites ZnS@ZnO, CdS@ZnO, and PbS@ZnO with different morphologies were synthesized, and their photocatalytic and adsorption-based removal performances on methylene blue (MB) dye were investigated. FE-SEM images indicated that ZnS nanoparticles exhibit a spherical morphology, CdS nanoparticles have a flower-like morphology, and PbS nanoparticles display a dendritic-like structure. The results obtained from experimental studies demonstrated that the highest efficiency in both photocatalytic- and adsorption-based removal was achieved with the ZnS@ZnO nanocomposite. The degradation rates of MB were found to be 95.3, 90.5, and 89.4% for the heterojunction composites ZnS@ZnO, CdS@ZnO, and PbS@ZnO, respectively, over a time range of 0-480 min. The optimal amount of photocatalyst that could effectively degrade MB was determined to be 100 mg, and the reusability studies revealed that the ability of the ZnS@ZnO semiconductor heterojunction photocatalyst to decompose MB into simpler molecules was limited after the fourth cycle. The adsorption-based removal rates were 96.0, 30.5, and 19.4% for the heterojunction composites ZnS@ZnO, CdS@ZnO, and PbS@ZnO, respectively. Finally, parameters influencing the adsorption-based removal of MB, such as pH, mass, and contact time, were examined, indicating that the adsorption capacity of ZnS@ZnO remained unchanged after reaching a value of 40 mgg-1.
Directional Solidification of Al-Si-Ti Irregular Ternary Eutectic Alloy and Thermophysical Properties
(SPRINGER, 2022) Bayram, Umit; 0000-0001-8760-8024; AGÜ; Bayram, Ümit
Directional solidification of Al–11.75 wt pct Si–2.15 wt pct Ti irregular eutectic alloy which has an 843.83 K melting point, was done with different growth rates (V = 8.51 to 2065.18 µm s−1) at a temperature gradient (G) of 8.36 K mm−1 using Bridgman-type directional solidification apparatus (BTDSA). Scanning electron microscopy (SEM)—Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were used to characterize all phases forming the alloy. The average values of interflake spacing (λT) were measured from transverse sections of the directionally solidified samples with standard techniques. The dependency of λT was experimentally obtained using linear regression analysis for low, high, and all growth rates. It was observed that the λT values tended to decrease with increasing V values; therefore, the interflake structures came closer. The fusion enthalpy (ΔHf) and specific heat difference between solid and liquid (ΔCp) for the Al–Si–Ti eutectic alloy were found as 376.12 J g−1and 0.659 J g−1 K−1, respectively, by the differential scanning calorimetry (DSC). All results obtained in the present work were compared with the eutectic theory and the Al-based similar experimental results in the literature.
Effect of Sn contents on thermodynamic, microstructure and mechanical properties in the Zn-90-Bi-10 and Bi-88-Zn-12 based ternary alloys
(SPRINGER, VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS, 2019) Esener, Pinar Ata; Altintas, Yemliha; Bayram, Umit; Ozturk, Esra; Marasli, Necmettin; Aksoz, Sezen; 0000-0002-1993-2655; 0000-0001-8760-8024; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
The thermal conductivity variations with temperature for Zn90-x-Sn-x-Bi10 (x=5,10, 40 and 85wt%) and Bi88-x-Sn-x-Zn-12 (x=1.39, 43.26 and 79.3wt%) alloys were measured by using the linear heat flow method. From thermal conductivity-temperature plots, the coefficients of thermal conductivity for the Zn-Sn-Bi alloys were calculated. The microstructures of Zn-Sn-Bi alloys were observed using scanning electron microscopy (SEM). The existing phases into microstructure were identified energy dispersive X-ray (EDX) analysis. The melting temperatures, the enthalpy of fusion and specific heat change between the liquid and solid phases in the Zn-Sn-Bi alloys were determined from Differential Scanning Calorimetry (DSC) trace. The tensile strength and microhardness of the alloys were measured using a Shimadzu Universal Testing Instrument (Type AG-10 KNG) and Future-Tech FM-700 model microhardness device.
Investigations of Electrical Resistivity and Thermal Conductivity Dependences on Growth Rate in the Al-Cu-Ti Eutectic Alloy
(SPRINGER/PLENUM PUBLISHERS233 SPRING ST, NEW YORK, NY 10013, 2021) Marasli, Necmettin; Bayram, Umit; AGÜ, Mühendislik Fakültesi, Mühendislik Bilimleri Bölümü; Bayram, Umit
Directional solidification of Al-Cu-Ti (Al-33wt%Cu-0.1wt%Ti) eutectic alloy was done with a growth rate range (V = 8.58 to 2038.65 mu m.s(-1)) at a temperature gradient of 6.45 K.mm(-1) using Bridgman-type directional solidification furnace. The measurements of thermal conductivity (K) and electrical resistivity (rho) for the Al-Cu-Ti alloy solidified with the different values of V were made by the longitudinal heat flow method (LHFM) and DC four-point probe technique (FPPT). While the highest values of K and rho were determined to be 236.04 W.K-1.m(-1) and 5.91 x 10(-8) omega m, respectively, at 8.58 mu m.s(-1), the lowest values of K and rho were obtained to be 199.82 W.K-1.m(-1) and 12.11 x 10(-8) omega m, respectively, at 2038.65 mu m.s(-1). The K and rho dependences on V were obtained to be K=259.96xV(-0.032) and rho=4.47x10(-8)V(0.13) from linear regression analysis. The fusion enthalpy ( increment H) and specific heat difference between solid and liquid ( increment C-P) for the Al-Cu-Ti were also determined to be 222.69 J.g(-1) and 0.266 Jg(-1).K-1, respectively, by means of differential scanning calorimetry (DSC).
The variations of electrical resistivity and thermal conductivity with growth rate for the Zn-Al-Cu eutectic alloy
(SPRINGERVAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS, 2021) Marasli, Necmettin; Bayram, Umit; Aksoz, Sezen; 0000-0001-8760-8024; AGÜ, Yaşam ve Doğa Bilimleri Fakültesi, Biyomühendislik Bölümü; Bayram, Umit
The Zn-Al-Cu alloy (Zn-5wt%Al-0.5wt%Cu) is solidified with different growth rates (V = 8.45-2087.15 mu m s(-1)) at a constant temperature gradient (G = 3.67 K mm(-1)) using Bridgman-type directional solidification apparatus (BTDSA). The thermal conductivity (K) and electrical resistivity (rho) for the Zn-Al-Cu alloy solidified with the different V values are measured by the longitudinal heat flow method (LHFM) and DC four-point probe technique (FPPT), respectively. The lambda and K decrease with the increasing V, while the q increases with increasing V in the Zn-Al-Cu eutectic alloy. The dependences of rho and K on lambda and V for the Zn-Al-Cu eutectic alloy are obtained as rho = 9.98 x 10(-8)lambda(-0.18), q = 7.03 x 10(-8) V-0.07, K = 110.91 lambda(0.104) and K = 144.59V(-0.040), respectively. The melting enthalpy (DHf) and specific heat difference between solid and liquid phases (Delta C-p) for the Zn-Al-Cu eutectic alloy are determined as 113.89 J g(-1) and 0.172 J g(-1) K-1, respectively, by the differential scanning calorimetry (DSC).