Browsing by Author "Türk A."

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    Investigation of erosive wear behavior of granulated blast furnace slag on hard coated and uncoated steels; [Yüksek fırın granüle cürufunun sert kaplama uygulanmış ve uygulanmamış çeliklere karşı erozif aşındırma davranışının incelenmesi]
    (Gazi Universitesi Muhendislik-Mimarlik, 2019) Demirsöz R.; Polat R.; Türk A.; Erdoğan G.
    One of the biggest problems in industrial plants is wear that directly affects equipment life. In integrated plants such as blast furnaces, many types of wear are encountered, one of which is erosive wear. Slurry erosion is one of the effective types of erosive wear. During the transfer of the slag into the liquid medium, the transport equipment is exposed to slurry erosion. The high amount of erosion seriously shortens the life of the equipment where the transportation is carried out and increases the maintenance-repair costs. In this study, blast furnace slag was used in the slurry erosive wear test system and the abrasivity of the St 37-2 reference standard pipe material, Hardox 400 and W2C-NiCrBSi coating materials was investigated. The slag was sieved to an average particle size of 505 μm and slurry containing 10%, 20% and 30% by weight of slag was prepared. The experiments were carried out at 2 m/s and 4 m/s peripheral speed values at the partical normal impact angle (90°). It has been determined by these experimental studies that the abrasivity of the slag prepared at a certain grain size is directly related to the concentration and the rotation speed (material conveyance speed) and that the wear is also increased by increasing the concentration and rotation speed. The wear values of the materials used as specimens are determined from high to low respectively as St 37-2, Hardox 400 and W2C-NiCrBSi coating material. In addition, the morphological structures of the worn surfaces were examined using SEM(Scanning Electron Microscope) in order to understand the wear mechanisms. © 2019 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.
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    Synthesis and characterizations of sol–gel derived LaFeO3 perovskite powders
    (Springer, 2020) Çoban Özkan D.; Türk A.; Çelik E.
    In this study, LaFeO3 perovskite powders were prepared via the sol–gel method in two different annealing temperatures (500 and 850 °C-according to DTA/TG results) for use in dye-sensitized solar cell applications. The thermal, structural, microstructural, particle size, optical and magnetic properties of the samples were characterized by differential thermal analysis (DTA)/thermogravimetric analysis (TG), Fourier transforms infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), particle size analysis (PSA), UV–Vis spectrometer and vibrating sample magnetometer (VSM). Our XRD findings show that the as-synthesized powders have an excellent crystallinity, and Scherrer’s Equation is used for the estimation of crystallite sizes (within 26–29 nm). Samples were analyzed to reveal the valence states of elements through XPS. Survey scan XPS spectra and high-resolution XPS spectra of La-3d5 and Fe-2p for LaFeO3 samples are given. SEMs employed to observe surface morphologies of all xerogel and ceramic perovskite powder materials and SEM images were verified with PSA results. UV–Vis spectrometer analysis results show that the optical bandgap values (Eg) as measured on both particles were found 2.42 eV. In addition to all analyses, the powders show ferromagnetic behavior, and VSM analyses are used to determine ferromagnetic properties. These results, especially low bandgap, make LaFeO3 powders possible to further increase the performance and efficiency of perovskite-based cells. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
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    Synthesis and characterizations of LaMnO3 perovskite powders using sol–gel method
    (Springer, 2021) Çoban Özkan D.; Türk A.; Celik E.
    The present research demonstrates the synthesis and characterization of LaMnO3 perovskite powders using the sol–gel technique for solar cell applications. With this respect, LaMnO3 powders were synthesized at two different annealing temperatures by the sol–gel method using La- and Mn-based precursors. Thermal, structural, microstructural, optical and magnetic properties of the powders were characterized through differential thermal analysis-thermogravimetry (DTA-TG), Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Malvern zeta sizer (PSD), UV–Vis spectrometer and vibrating sample magnetometer (VSM). LaMnO3 was synthesized successfully at 500 °C and 850 °C synthesis temperatures, and the bandgap was determined as 1.27 eV for both. The analysis revealed that magnetic properties, crystalline and particle sizes change according to the heat of synthesis. The obtained results indicate promise, especially the low bandgap, that LaMnO3 powders can be used in solar cell applications and can positively affect performance and efficiency. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Synthesis and characterization of sol–gel derived LaFe0.5Mn0.5O3 perovskite powders for dye-sensitized solar cell applications
    (Springer, 2022) Çoban Özkan D.; Türk A.; Çelik E.
    In the present work, structural, microstructural, thermal, magnetic and optical properties of LaFe0.5Mn0.5O3 prepared perovskite powders were exclusively compared for processing temperatures for applications of dye-sensitized solar cells. In this framework, LaFe0.5Mn0.5O3 perovskite powders were synthesized with the sol–gel method at 500 °C and 850 °C (according to DTA/TG results). They were characterized through DTA/TGA (Thermogravimetric and Differential Thermal Analysis), FTIR (Fourier Transformed Infrared Spectroscopy), XRD (X-Ray Diffractometer), XPS (X-Ray Photoelectron Spectroscopy), PSA (Particle Size Analysis), SEM (Scanning Electron Microscopy), VSM (Vibrating Sample Magnetometer) and UV–Vis Spectrometer. In line with the obtained results, ferroelectric perovskite powders were successfully produced. These powders have crystallite sizes of 27.38–35.74 nm, bandgap values of 1.19–0.93 eV, particle sizes of 28–358 nm and ferromagnetic properties. In addition to the effect of synthesis temperature on LaFe0.5Mn0.5O3 synthesis with these characterization processes, it was found that the production of sustainable and applicable dye-sensitized solar cells using LaFe0.5Mn0.5O3 powders can be useful as innovative and futuristic approaches. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    The Role of Water on the Oxidation Process of Graphene Oxide Structures
    (Sakarya University, 2024) Kanbur K.; Birlik I.; Sargın F.; Funda Ak Azem N.; Türk A.
    Graphene oxide (GO) has recently attracted attention with its unique chemical and physical properties and serves as a raw material for graphene-based materials. GO has been produced for decades by the Hummers Method with the oxidation process of graphite. The properties and structure of GO are significantly affected by the production parameters of Hummers Method. In this study, the effect of the water content on the oxidation level of GO structure was investigated. GO was produced with different amounts of water in the oxidation stage of Hummers Method. The structural characterizations of produced GO were carried out by X-ray Diffraction Technique (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS), UV-Visible Spectroscopy (UV-Vis) and Raman Spectroscopy. Additionally, morphological and thermal characterization of the produced GO samples were performed by Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA)/Differential Thermal Analysis (DTA), respectively. According to XRD, FTIR, XPS, and EDS results, it was determined that the oxidation degree of GO decreased with increasing amount of water. Besides, it was revealed that the post-oxidation step generated more defects in the basal plane of graphene according to the results of the Raman Analysis. Also, it was observed that GO had a smoother surface and was found to have higher thermal stability with increasing amounts of water. The results show that the post-oxidation step reduces the oxidation degree of GO, increases the amount of the defect, provides a less wrinkled structure, and improves the thermal stability of GO. © 2024, Sakarya University. All rights reserved.