Person: ARAT, REFİK
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Publication Preparation of Shape Stabilized Phase Change Materials by Coaxial Electrospinning(2018) Önder Karaoğlu, Emel; Boz, Ezgi Ceren; SARIER, NİHAL; ARAT, REFİK; 114920; 3551Publication Biodegradable Pectin Based Agrotextiles(2013) Özay, Seray; Ukuser, Gökçen; SARIER, NİHAL; ARAT, REFİK; ; 114920Publication Preparation of magnetite nanoparticle and fatty alcohol/acidincorporated poly(methacrylic acid-ethyl acrylate) nanowebs via electrospinning for magnetic hyperthermia application(RADIOMAG: Annual Action Conference and MC meeting, Bilbao, 2017) Önder Karaoğlu, Emel; SARIER, NİHAL; ARAT, REFİK; 114920; 10598Publication Synthesis of Biobased Oleocarbonates and Their Use in the Production of Thermally Enhanced Nanofibers by Electrospinning(2015) Boz, Ezgi Ceren; Önder Karaoğlu, Emel; SARIER, NİHAL; ARAT, REFİK; 114920; 10598Thermal management named as the dynamic heat-storage, has attracted more attention in the last decade because of the demand for developed energy conservation as well as improved thermal comfort. Phase change materials (PCMs), as thermally active materials, have a buffering effect against temperature changes. A PCM is capable of absorbing or releasing large amount of heat during phase transitions between two solid states and/or liquid and solid states. Various encapsulating and shape stabilizing methods for PCMs have been developed by researchers and industry prior to their application on the surfaces for reducing their reactivity with the outside environment, decreasing the evaporation and diffusion rates and promoting the ease of handling [1]. Fatty acids, fatty alcohols and their derivatives, obtained from fats and oils, serve as an important raw material for the oleochemical industry, since they are from biomass resources. Recently, fatty acids and their derivatives have attracted attention as potential biobased PCM candidates in consequence of their attractive thermal characteristics [2,3]. With the aim of spreading out the biobased PCMs away from fatty acids and fatty acid derivatives, this study concerns with the synthesis of two oleocarbonates, namely dihexadecyl carbonate and dioctadecyl carbonate, from fatty alcohols through a carbonate interchange reaction, and examines for their potential to be used as potential biobased PCM in dynamic thermal management of various composites such as clothing textiles and building envelopes. In the second part of the study, bicomponent nanofibers of those oleocarbonates have been produced using poly olefins as shell and oleocarbonates as core material by the coaxial electrospinning process. The thermal behaviors of dihexadecyl and dioctadecyl carbonates during heating and successive cooling in DSC analysis are given in Figure 1. The heat capacity of dihexadecyl carbonate was 192.8 Jg-1 between 33.9–47.8 C and of dioctadecyl carbonate was 178.2 Jg-1 at 47.4–51.1 C which were quite remarkable in terms of their contribution to the dynamic thermal management of PCM incorporated products. Electrospun nanofibers, carrying the thermal properties of corresponding oleocarbonate, were highly competitive with other existing strategies of encapsulating and shape-stabilizing PCMs.Publication Ethanol Sensing with Pure and Boric Acid Doped Eectrospun CuInS2 Nanofibers in the Presence of Relative Humidity(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2019-12) Yağcı, Özlem; Ömür, Birsel Can; Altındal, Ahmet; SARIER, NİHAL; ARAT, REFİKThe influence of boric acid doping on ethanol vapor sensing performance of electrospun copper indium disulfide (CuInS2) nanofibers in the presence of various levels of relative humidity was examined for the first time. Pure and boric doped CuInS2 nanofibers are prepared through electrospinning method and characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and Thermogravimetric analysis techniques. It was found that not only the ethanol sensing performance but also base line current of the CuInS2 nanofiber based sensors are greatly influenced by the boric acid doping level. Maximum sensitivity was obtained with pure CuInS2 under humid conditions. Kinetic studies indicated that ethanol vapor adsorption kinetics strongly depend on level of the relative humidity and the ethanol concentration.Publication Preparation of magnetite nanoparticle and fatty acid incorporated poly(methacrylic acid-ethyl acrylate) nanowebs via electrospinning for magnetic hyperthermia application(2018) Önder Karaoğlu, Emel; Carvalhoa, Maria M.; Liliana, P. Ferreria; Magdelena, M. Cruz; SARIER, NİHAL; ARAT, REFİK; 114920; 10598Magnetic hyperthermia has been arising as a promising approach for treatment of cancer. When magnetic nanoparticles (MNPs) are locally injected through cancerous tissues and subjected to an appropriate alternating magnetic field, they generate heat due to the rotation of the nanomagnets, causing the destruction of the cancer cells. For repeated applications of magnetic hyperthermia, it is highly preferred to keep the temperature constant at about 41-46 degrees C while preventing the leakage of MNPs, to minimize secondary effects on surrounding healthy tissues. In our study, we produced novel nanowebs provided with magnetic and thermal buffering properties by encapsulating MNPs and Lauric Acid in poly(methyl ethyl acrylate) matrix via uniaxial electrospinning. For the oleic acid functionalized magnetic nanoparticles, the magnetization for the corresponding nanowebs is higher by a factor of two for all concentrations than the ones with non-functionalized magnetic nanoparticles, indicating a more effective integration of the functionalized nanoparticles through the nanoweb. The heat absorption and release capacities of the nanowebs, incorporated with 1.25-2.50 % functionalized MNPs, vary between 70-75 Jg(-1) at 40-48 degrees C. They also demonstrate thermal cycling ability and thermal stability.Publication Synthesis and Electrospinning of Polyethylene Glycol Grafted Polyacrylonitrile Copolymers as Novel Solid-Solid Phase Change Materials(2016) Önder Karaoğlu, Emel; Boz Noyan, Ezgi Ceren; Menceloğlu, Yusuf Ziya; SARIER, NİHAL; ARAT, REFİK; 114920; 10598; 3329Publication PS/Silica Aerogel Nanofibers Production for Thermal Insulation(2019-08) ARAT, REFİKAerogels are fascinating solid materials made up with over 95% air and less than 5% skeletons [1], With the advantages of an extremely low density of 0.003-0.5 g/cm3, a low thermal conductivity of 0.017-0.021W/m-K and a high specific surface area of 500-1200 m2/g [1-3], aerogels have enormous application potential in various fields, such as thermal insulators, energy conservation, catalyst supports, biomedical engineering and aerospace applications [3- 9]- In this work, silica aerogels were synthesized as stated by Li at al. [10], Commercial polystyrene (PS) was used instead of polymerization of styrene monomers to obtain PS/silica aerogels nanocomposites. Furthermore, nanofiber structure was obtained by electrospinning. The specific surface area, pore volume and particle size of aerogels, which are 590 m2/g, 1.4 cm3/g and 10 nm, respectively, were determined by BET analysis. Thermal gravimetric analysis indicated that the maximum degradation temperature of PS shifted from 412 to 444 °C when silica aerogels content at 10wt%. Regards to improvement in thermal stability, PS/silica aerogels nanocomposites can be a promising candidate for thermal insulation applications.Publication Production of PEG grafted PAN copolymers and their electrospun nanowebs as novel thermal energy storage materials(Elsevier Science Bv, Po Box 211, 1000 AE Amsterdam, Netherlands, 2016-11-10) Menceloğlu, Yusuf; Önder Karaoğlu, Emel; Boz, Ezgi Ceren; Oğuz, Oğuzhan; SARIER, NİHAL; ARAT, REFİK; 114920; 10598; 198107This paper deals with the synthesis of poly(ethylene glycol) (PEG) grafted poly(acrylo nitrile) (PAN) copolymers as novel solid-solid phase change materials via two step free radical polymerization reaction. The structural and thermal characterizations of the synthesized copolymers, namely PEG1500-g-PAN, PEG2000-g-PAN, PEG4000-g-PAN, PEG10000-g-PAN and PEG35000-g-PAN, were performed by Fourier transform infrared spectroscopy, Nuclear magnetic resonance spectrometry, differential scanning calorimetry and thermogravimetry. They were thermally stable and had the capability of absorbing and releasing great amount of heat ranging between 70 and 126 Jg(-1) at the temperature interval of 40-65 degrees C during heating and successive cooling cycles. To transform the PEG-g-PAN copolymers into the assemblies appropriate for thermal energy storage (TES) systems, thermo-regulating PEG-g-PAN nanowebs were also produced by means of coaxial electrospinning. The SEM images of PEG-g-PAN nanowebs displayed that they were all composed of hollow cylindrical ultrafine fibers with the average diameters ranging in 175-277 nm. During the differential scanning calorimetry measurements, those nanowebs demonstrated repeatable solid-solid phase change with the heat storage capacities varying between 35 and 75 Jg-1 at the same temperature interval with the corresponding PEG-g-PAN copolymers. The PEG-g-PAN copolymers and their electrospun nanowebs can be promising TES materials and can have convenient industrial applications. (C) 2016 Elsevier B.V. All rights reserved.Publication Surface Modification of Nanoclays with Styrene-Maleic Anhydride Copolymers(Scientific Research, 2017) Uyanık, Nurseli; ARAT, REFİK; 5194This study presents the modification of surfaces of nanoclays, halloysite nanotubes (HNT) and sepiolite (SEP), with styrene-maleic anhydride copolymers (SMA) via esterification reaction between hydroxyl groups of the nanoclays and anhydride groups of SMA. The structural, thermal, and morphological analyses of the modified nanoclays were performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). All of these results suggested that the expected modification of HNT and SEP surfaces were performed. Although XRD patterns of HNT containing samples showed that the basal spacing shifted to higher distances, it was found that those of the crystalline structure of SEP remained unchanged. Thermal gravimetric analysis exhibited that SMA copolymers were grafted onto the surfaces of nanoclays varying amounts between 15 and 43 wt. % depending on the types of nanoclays and SMA copolymers. This modification indicates that these nanoclays can be added to the polystyrene matrix without any compatibilizers.
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