Yazar "Sahin, O. S." seçeneğine göre listele

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    The mechanical properties of composite materials recycled from waste metallic chips under different pressures
    (Springer, 2019) Aslan, A.; Salur, E.; Gunes, A.; Sahin, O. S.; Karadag, H. B.; Akdemir, A.
    The purpose of this study is to produce composite materials by utilizing the waste metallic chips. In this context, the metal matrix composite materials (MMCs) were produced at different production pressures and the effects of the different pressures on mechanical properties of MMCs were investigated. In the present investigation, spheroidal graphite cast iron (GGG-40) was used as reinforcement material in bronze (CuSn10) matrix system. The MMCs were produced by hot press with 20 wt% GGG-40 reinforcement ratio. The total time required for the production of one specimen was selected as 25 min and temperature was settled at 400 degrees C. In order to determine mechanical properties and consolidation mechanism of MMCs, Brinell and micro-Vickers hardness, porosity, compression and X-ray diffraction tests were conducted. In addition, microstructure views were examined to determine the consolidation quality of metallic chips. According to experimental results, it was observed that waste metallic chips can be successfully recycled into MMC final parts with approximately 40% porosity and almost 100% strength and 150% hardness with respect to bulk CuSn10 materials. Most of the presented studies in the literature present information about properties of MMCs fabricated by conventional production methods. However, no available data are found about the recycling of bronze-based MMCs which make this study more original. It is also shown in this study that waste metallic chips can be utilized by proposed recycling methodology, which is environmentally friendly in comparison with conventional recycling methods producing harmful gases for earth atmosphere.
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    Production and thermal characterization of MWCNT reinforced polimethyl methacrylate (PMMA) nanofibers by electrospinning
    (Univ Larbi Ben Mhidi, 2021) Ekrem, M.; Ozten, U.; Sahin, O. S.
    In this study, the production of weight ratio of 1% multi-walled carbon nanotubes (MWCNT) reinforced / unreinforced Polymethyl Methacrylate (PMMA) nanofiber mats was carried out by electrospinning. PMMA concentration of 10, 12.5 and 15% weight in Dimethylformamide (DMF) solvent used in order to reach optimized electrospinning conditions. PMMA solutions with higher concentration ratio leading to higher viscosity and conductivity properties eliminates defects and imperfections and results improved quality of the products. In addition, different feed rates of 0.25, 0.50 and 0.75 ml/hour with 10 kV applied voltage power were compared for given MWCNT reinforced PMMA solutions electrospinning at specified concentration rate of solution were analyzed. Higher feed rates result thicker nanofiber diameters. Furthermore, Scanning Electron Microscope (SEM) images were investigated to determine the morphological properties of PMMA with MWCNT nanofibers and the average diameter of nanofibers. Optimum production parameters for 15 % wt. ratio and 0.5 ml/hr feed rate for electrospinning of PMMA-MWCNT solution were determined after comparison of results of alternative production options. We produced high quality bead-free nanofibers during electrospinning of PMMA fibers with MWCNT by manipulating dispersion methods, composition rates and electrospinning conditions. Thermal analysis of nanofibers was done by using Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) in order to obtain Glass Transition Temperature (Tg), Melting Temperature (Tm) and Decomposition Temperatures (Td) with respect to mass loss.