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Öğe CNT-PAN hybrid nanofibrous mat interleaved carbon/epoxy laminates with improved Mode I interlaminar fracture toughness(ELSEVIER SCI LTD, 2018) Eskizeybek, Volkan; Yar, Adem; Avci, AhmetInterleaving laminated composites with electrospun nanofibrous mats comes out as a promising micro scale strategy to strengthen interlaminar regions of laminated composites. The aim of this study is to evaluate the synergetic contribution of nano- and micro-scale mechanisms on interlaminar delamination. For this, carbon nanotubes (CNTs) reinforced polyacrylonitrile (PAN) electrospun hybrid mats were successfully fabricated and utilized as interleaves within the interlaminar region of carbon/epoxy laminated composites. The Mode I interlaminar fracture toughness values were enhanced up to 77% by introducing CNTPAN nanofibrous interleaves. Specifically, the nano-scale toughening mechanisms such as CNTs bridging, CNTs pull-out, and sword-sheath increased the Mode I fracture toughness by 45% with respect to neat PAN nanofibrous interleaves. The related micro- and nano-scale toughening mechanisms were evaluated based on the fracture surface analysis. Atomic force microscopy was also utilized to quantify the magnitude of surface roughness changes on the interlaminar region with respect to multi scale interleaving reinforcement and correlate surface roughness changes due to crack deflection to increased fracture toughness. (C) 2018 Elsevier Ltd. All rights reserved.Öğe Earth-Abundant Cu2CoSnS4 Nanofibers for Highly Efficient H-2 Evolution at Soft Interfaces(WILEY-V C H VERLAG GMBH, 2015) Ozel, Faruk; Yar, Adem; Aslan, Emre; Arkan, Emre; Aljabour, Abdalaziz; Can, Mustafa; Patir, Imren HatayCu2CoSnS4 (CCTS) nanofibers have been fabricated by electrospinning and exhibit an excellent morphology with an average nanofiber diameter of 150 nm. Polyacrylonitrile (PAN) was used as templating polymer that leads to a decrease in imperfections in the crystalline nanofibers. CCTS and Cu2ZnSnS4 (CZTS) nanofibers, based on abundant and environmental friendly elements, efficiently enhanced the rates of biphasic proton reduction in the presence of an organic solubilized electron donor, decamethylferrocene (DMFc). This work paves the way for the exploration of copper-based chalcogenides as electrocatalysts for the hydrogen evolution reaction to replace noble metal Pt.Öğe Electrospinning of Cu2ZnSnSe4-xSx nanofibers by using PAN as template(ELSEVIER SCIENCE BV, 2015) Ozel, Faruk; Kus, Mahmut; Yar, Adem; Arkan, Emre; Yigit, M. Zeliha; Aljabour, Abdalaziz; Buyukcelebi, SumeyraWe firstly demonstrate the synthesis of Cu2ZnSnSe4-xSx (CZTSeS) nanofibers through versatile electrospinning technique. Polyacrylonitrile (PAN) was used as templating polymer that leads to decrease in imperfections on crystal fibers and yields outstanding structure including a few defects with diameter around 250 nm. Sulfurization and/or selenization processes were carried out separately and simultaneously depending upon the demanded chemical structure. Detailed characterization and electrochemical response indicate their potential application for solar cells as p-type semiconductors. (C) 2014 Elsevier B.V. All rights reserved.Öğe Electrospun TiO2/ZnO/PAN hybrid nanofiber membranes with efficient photocatalytic activity(ROYAL SOC CHEMISTRY, 2017) Yar, Adem; Haspulat, Bircan; Ustun, Tugay; Eskizeybek, Volkan; Avci, Ahmet; Kamis, Handan; Achour, SlimaneElectrospun polyacrylonitrile (PAN) nanofibers were decorated with TiO2, ZnO and TiO2/ZnO nanoparticles for the first time to prepare flexible multifunctional nanofibrous membranes. First, the arc-discharge process was utilized to prepare TiO2, ZnO and TiO2/ZnO nanoparticles and then the hybrid electrospun nanofibers were spun from PAN/nanoparticle colloids. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to characterize the resulting nanoparticles and nanofiber loaded nanoparticles. The microscopic investigations revealed that the specifically TiO2 nanoparticles tend to agglomerate within the PAN nanofiber resulting increased surface roughness; however, ZnO nanorods with 1D morphology are aligned as parallel to the fiber axis. Photocatalytic activity of the hybrid nanofibers was performed by pursuing the degradation of malachite green (MG) dye under UV light irradiation. The fabricated TiO2/ZnO/PAN hybrid nanofibers showed excellent photocatalytic efficiency with at least two times higher reaction rates compared to the bare PAN nanofibers. The results suggest that the photocatalytically active TiO2/ZnO/PAN hybrid nanofibers can be considered as filtering materials for a variety of applications in the fields of wastewater systems without the need of post processing stages for separating catalysts from the liquid medium.Öğe Enhancing the Efficiency of Air-processed Organic Solar Cells by Pristine MWCNT Incorporation into the Active Layer(Selçuk Üniversitesi, 2014) Demir, Okan; Yar, Adem; Avci, AhmetOrganic solar cells (OSCs) with P3HT:PCBM active layer and 0.05% wt. MWCNT introduced P3HT:PCBM active layer were produced in ambient air atmosphere and the effect of MWCNT addition on the cell performance was investigated. We report open circuit voltage, short-circuit current density, power conversion efficiency, and fill factor of 0.5 V, 1.178 mA/cm2, 0.69, 0.293 respectively. Reference cells without MWCNTs exhibited lower performance. MWCNTs seem to be a low cost and promising candidate for the improvement of OSCs performance.Öğe Fabrication of quaternary Cu2FeSnS4 (CFTS) nanocrystalline fibers through electrospinning technique(SPRINGER, 2015) Ozel, Faruk; Kus, Mahmut; Yar, Adem; Arkan, Emre; Can, Mustafa; Aljabour, Abdalaziz; Varal, Nurhan MehmetCopper-based quaternary chalcogenide Cu2FeSnS4 (CFTS) is an important material due to its indium-free nature and presence of earth-abundant elements. Herein, CFTS nanofibers have been first fabricated via a facile two-step approach using a simple and inexpensive electrospinning technique. X-ray diffraction and scanning electron microscopy techniques were used to determine structural, morphological, and compositional features of the obtained films. Nanofibers annealed at 500 degrees C for 1 h were characterized by (112), (200), (220), (312) preferred orientations via X-ray diffraction method. Nanofibers showed well crystallization and tetragonal phase. The average diameters of obtained fibers were found to be 100 +/- 50 nm. Cyclic voltammograms showed that CFTS fibers showed p-type behavior.Öğe Preparation of nanoclay incorporated PAN fibers by electrospinning technique and its application for oil and organic solvent absorption(TAYLOR & FRANCIS INC, 2018) Kahraman, Havva Tutar; Yar, Adem; Avci, Ahmet; Pehlivan, ErolIn this work, polymer nanofibers (PAN/n-OMMT clay) were successfully produced by using an electrospinning process. The PAN/n-OMMT nanofibers were studied as an oil and solvent absorbent material due to their super hydrophobicity and super oleophilic properties. The generated composite nanofibers were found to have a very high oil and solvent absorption capacity in the case of 3% n-OMMT clay loading. It showed excellent absorption capacity up to 160 times its own weight for motor oil. The findings reported in this work might provide a fast and facile approach for the removal of oils and organic solvents on water surfaces.Öğe Removal of hexavalent chromium using polyacrylonitrile/titanium dioxide nanofiber membrane(TAYLOR & FRANCIS INC, 2016) Parlayici, Serife; Yar, Adem; Avci, Ahmet; Pehlivan, ErolPolyacrylonitrile/titanium dioxide nanofiber (PAN/T-nF) membrane was prepared with TiO2 nanoparticles which dispersed into polyacrylonitrile (PAN) matrix with ultrasonic probe in ultrasonic bath. The amount of TiO2 loaded in the membrane was 1 and 3wt% to explore the activity of membranes in the adsorption process. PAN/T-nF membrane was prepared by electrospinning technique. The potential of the prepared PAN/T-nF membrane was investigated for the removal of Cr(VI) from aqueous solutions. The adsorption equilibrium was investigated in the batch process. The adsorption process displayed pH dependence and the maximum Cr(VI) adsorption took place at pH 2. The equilibrium was attained at a contact time of 180min and Langmuir adsorption model was suitable for the adsorption isotherms. Maximum adsorption capacities 245.3 and 280.4mg Cr(VI)/g were calculated for 1 and 3% PAN/T-nF membrane, respectively. The adsorption of Cr(VI) on PAN/T-nF was related to the mechanism of surface complexation, coordination, and electrostatic attraction. This new fabrication method for PAN/T-nF membranes showed an excellent thermal stability that can persist up to 400 degrees C and has a big capacity for Cr(VI) ion.Öğe Tek cidarlı karbon nanotüp ve TiO2 tabaka ilavesinin P3Ht: PCBm organik güneş pillerinin performansına etkileri(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2011-07-07) Yar, Adem; Avcı, AhmetBu çalışmada tek cidarlı karbon nanotüp ve polimer P3HT:PCBM'den oluşan kompozit karışımın fotovoltaik özellikleri incelenmiştir. SWNT:P3HT:PCBM kompozit karışımı spin-coating tekniği kullanılarak kaplanmış ve daha sonra tavlanmıştır. Polimer ile SWNT arasındaki yapıyı ve yük transferini anlamak için, yapılan güneş pilleri AFM, SEM, absorbans ile karakterize edilmiştir. Düşük (% 0.025) karbon nanotüp konsantrasyonlu güneş pillerinin fotovoltaik karakteristiği incelenmiş olup kısa devre akımı 0.89 mA/cm2, açık devre gerilimi 500 mV, dolum faktörü 0.34 olarak belirlenmiş ve verimin % 0.61 olmasına yol açmıştır. SWNT'nin ilave edilmesi hem kısa devre akım yoğunluğunun hem de dolum faktörünün artmasına neden olmuştur. Kısa devre akım yoğunluğunun ve dolum faktörünün artması, verimin artmasını sağlamıştır. TiO2 tabakası boşluk bloke edici ve elektron seçici olmasına rağmen açık devre gerilimini, kısa devre akımını ve dolum faktörünü azalttığından dolayı güneş pilinin verimini düşürmüştür.
