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Öğe Brush-type surface modification of kapton with a new approach(Wiley, 2018) Vural, Sema; Seckin, TurgayIn this study, polystyrene- and poly(methyl methacrylate)-grafted polyimide films were prepared successfully using click chemistry and the ATRP technique. Firstly, kapton films were prepared from stepwise thermal imidization of polyamic acid. Surface modification of kapton films was then achieved by chloromethylation followed by the azide decoration process. For surface grafting of kapton films, polystyrene and poly(methyl methacrylate) as alkyne functional polymers were prepared with alkyne and bromine double functionality using propargyl-2-bromopropionate as an initiator. A coupling reaction with azide-decorated PI surface and alkyne functional polymers was achieved via the Huisgen-1,3-dipolar cycloaddition reaction. FTIR spectroscopy, contact angle measurement, thermogravimetry (TG) and differential scanning calorimetry (DSC), energy dispersive X-ray analysis (EDX) and GPC techniques were used to characterize the grafted polyimides. According to the TG analysis, kapton film was modified at the rate of 8% and 10% with PS and PMMA, respectively.Öğe Hydrothermal Synthesis of Polyoxometalate Containing Cobalt Ion, and Its Polyurethane Composites for Dielectric Material Applications(Taylor & Francis Inc, 2020) Kucuk, Ilhan; Vural, Sema; Kivilcim, Nilufer; Adiguzel, Ibrahim; Koytepe, Suleyman; Seckin, TurgayPolyurethane (PU) composites were prepared with different diisocyanate and diol compounds by adding cobalt ion-based polyoxometalate (Co-POM) as reinforcement. For the determination of using potential in microelectronic applications, the dielectric behavior and dielectric constant of these PU composites were investigated and compared to pure polyurethane structures. For this aim, firstly, Co-POM with Keggin structure was obtained from ammonium heptamolybdate, 1,10-phenanthroline ligand and a cobalt (II) salt by hydrothermal synthesis technique. Then, polyurethane/Co-POM composites (PU/Co-POM) were prepared with ethylene glycol, nonaromatic diisocyanate and different amounts of Co-POM reinforcement (1%, 3%, 5% and 10%, w/w) by in situ polymerization and mix-blend technique. Obtained PU/Co-POM composites were characterized in detail by infrared spectroscopy, Elemental Mapping, Energy-dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD) spectroscopy. The surface structure, morphology and roughness of PU/Co-POM composites were investigated by SEM and AFM analysis. The elemental maps of the PU/Co-POM surface were examined by EDX elemental mapping analysis methods. Thermal stability, Tg values and thermal decomposition temperatures of PU/Co-POM structures were determined by different thermal analysis techniques. Thermal analysis results showed that the PU/Co-POM composites are thermally stable up to approximately 200 degrees C and Tg values of synthesized PU composites are seen between 54.72 degrees C and 75.15 degrees C. The dielectric properties and dielectric constants of the PU/Co-POM composites were determined in the frequency range 1 Hz to 1000 kHz at room temperature using impedance analyzer. Dielectric constants of these composites were ranged from 5.50 to 9.26 according to their polarizability and H-bonding ability of PU matrix structure. According to the dielectric measurements, the dielectric constants of the PU/Co-POM structures were significantly decreased compared to the pure PU structures.Öğe Investigation of lime usage impacts on bauxite processability at ETI Aluminyum Plant(Springer Heidelberg, 2019) Arikan, Hueseyin; Demir, Gokhan K.; Vural, SemaETI Aluminyum A.S., the primary aluminium manufacturer of Turkey, is also one of the major integrated plants of the world capable of performing production from mining until end product. The alumina refinery was designed on a certain boehmitic bauxite quality basis. However, bauxite properties have changed over the years, resulting in the urgent need for process optimization to not only keep the refinery cost efficient, but also prevent serious bottlenecks in the near future. Lime can be used to overcome problems when using bauxites with specific and variable chemical and mineralogical characteristics. Although lime is extensively used when processing diasporic bauxites, the studies on boehmitic bauxites and the overall effects on the process are limited. In this paper, lime impact was investigated at all stages of the Bayer process including the effect on alumina quality, energy and raw material consumptions. The results showed significant improvements in the product quality as well as recordable savings on consumptions.Öğe Preparation of the copper-based polyoxometalate/polyurethane composites and their dielectric properties(Sage Publications Ltd, 2020) Kucuk, Ilhan; Vural, Sema; Kivilcim, Nilufer; Adiguzel, Ibrahim; Koytepe, Suleyman; Seckin, TurgayThe aim of this study is synthesis of polyurethane (PU) composites from 4,4 '-methylenebis(cyclohexyl isocyanate), 1,2-ethanediol and different amounts of copper-based polyoxometalate (Cu-POM) and investigation of their dielectric properties. Firstly, Cu-POM structure as reinforcement was synthesized with ammonium heptamolybdate and Cu metal ion salt by a hydrothermal synthesis method. Then, Cu-POM-PU composites were prepared by in situ polymerization process. The prepared Cu-POM-PU composites were characterized by means of various techniques for their structure, morphology and thermal behaviour. The chemical structure, surface and morphological properties of the obtained composites were studied by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. Thermal properties of these Cu-POM-PU composites were determined by thermogravimetric analysis, differential thermal analysis and differential scanning calorimetry analysis techniques. Dielectric properties of the Cu-POM-PU composites were also determined. The dielectric measured results showed that the dielectric constants decreased with the increase of the Cu-POMs content. The Cu-POM-PU composites showed relatively low dielectric constant compared to pure PUs.Öğe Spinel ferrit nano-parçacıklarının hidrotermal sentez tekniği kullanılarak hazırlanması ve manyetik özelliklerinin araştırılması(2016) Vural, Sema; Alphan, Aysel; Köytepe, Süleyman; Seçkin, TurgayKobalt, nikel ve çinko ferrit nano parçacıkları hidrotermal sentez yöntemi kullanılarak sentezlenmiştir. Sentez koşullarının elde edilen spinel ferritlerin kristal yapısı, parçacık boyutu, örgü parametreleri, mikroyapı ve manyetik özellikler üzerine etkileri XIşını Kırınım Analizi (XRD), taramalı elektron mikroskopu (SEM), Enerji-dağılımlı X-ışınları spektroskopisi (EDX) ve Mapping yöntemleriyle belirlenmiştir. Hazırlanan ferritlerin parçacık boyutu 25-70 nm arasında değişmektedir. Ayrıca, nano parçacıkların manyetik özellikleri titreşimli örnek magnetometresi (VSM) kullanılarak araştırılmıştır. Manyetik özelliklerin sıcaklık ve Co, Ni ve Çinko iyon çeşidine şiddetle bağımlı olduğu gözlenmiştir. Bu örnekler yüksek yoğunluklu manyetik kayıtlama cihazlarında, yüksek kullanım potansiyeline sahiptir.Öğe Synthesis and characterization of SDS assistant -alumina structures and investigation of the effect of the calcination time on the morphology(Springer, 2019) Vural, Sema; Sari, OzlemIn this paper, -alumina structures were successfully prepared via hydrothermal synthesis supported with sodium dodecyl sulfonate anionic surfactant. The effect of the surfactant and the calcination time were investigated. The characterization of the samples calcinated at 1200 degrees C was performed using Raman spectroscopy, X-Ray Difraction analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy techniques. Experimental results showed that pure -Al2O3 structures were obtained with different morphologies.Öğe Synthesis, characterization and dielectric properties of nickel-based polyoxometalate/polyurethane composites(Taylor & Francis Inc, 2019) Kucuk, Ilhan; Vural, Sema; Koytepe, Suleyman; Seckin, TurgayThe aim of this study was to synthesis, characterization and investigation of the influence of the polyoxometalate concentrations (1, 3, 5 and 10 wt%) on chemical, thermal, physical and morphological properties of nickel-based polyoxometalate/polyurethane composite (Ni-POM/PU) materials. Firstly, nickel-based polyoxometalate (Ni-POM) compound has been synthesized and characterized through various spectroscopic techniques. Synthesized Ni-POM compounds have been used for preparation of polyurethane composites as a reinforcement. Three different Ni-POM/PU composites containing Ni-POM were prepared by solution mixing and casting techniques. The chemical structure and morphology of prepared Ni-POWPU composite samples were confirmed by Fourier transform infrared spectroscopy (FTIR), elemental analysis and SEM techniques. Effects of Ni-POM on thermal stability, glass transition temperature, optical transparency, hydrophilicity and physical properties of polyurethane composites were examined. Thermal stabilities and glass temperatures of the materials have been checked by differential thermal analysis (DTA), thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The SEM results confirmed the highly porous structure and the formation of Ni-POM structures in the polymer matrix. Synthesized composites showed high chemical stability, good processability, and low Tg values. The dielectric properties of the prepared Ni-POM/polyurethane composites were also investigated at room temperature. These results displayed that the dielectric constant of the POM/polyurethane composites decreased with the increase of the Ni-POM content in polymeric matrix. [GRAPHICS] .