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Öğe Blend membranes of sulfonated poly (ether ether ketone) and thermoplastic poly (urethane) for fuel cells(Springer, 2019) Dönmez, Göknur; Okutan, Merve; Deligöz, HüseyinMembranes used in polymer electrolyte membrane fuel cells (PEMFCs) have critical importance because their properties directly affect the performance of fuel cell. For this purpose, blend membranes based on sulfonated poly (ether ether ketone) (sPEEK)-thermoplastic poly (urethane) (TPU) were prepared by solution casting method in different compositions. Generally, sPEEK-TPU blend membranes were thermally resistant up to 190 degrees C due to the presence of sulfonic acid groups regardless blend composition. The proton conductivity (sigma) of blend membranes significantly increased compared to TPU100. After 24h in water, sigma values of blend membranes were found to be 3.9-18.7 mS cm(-1) and rose with sPEEK content. A similar trend was also observed for water uptake (WU %), sulfonation degree (DS%) and ion exchange capacity (IEC). While sPEEK100 membrane has a fragile structure, blending with TPU led to dense, uniform and defect-free membrane surface. Further, all the blend membranes had no obvious phase separation. sPEEK80-TPU20 showed good mechanical properties to be used in PEMFCs with good compatibility. Preliminarily, the methanol permeability of blend membrane containing 40% of sPEEK was found to be 1x10(-11)cm(2)s(-1). Unlike, the blend membranes deteriorated with methanol if sPEEK content was more than 40% in composition. The membrane selectivity value of sPEEK40-TPU60 was found to be 4.7x10(8) S s/cm(3).Öğe Effect of external salt addition on the structural, morphological and electrochemical properties of flexible PEDOT:PSS based LbL multilayered films(Elsevier, 2019) Okutan, Merve; Deligöz, HüseyinThis article concerns with the effect of external salt addition on the structural, morphological and electrochemical properties of linear poly(ethylene imine) (LPEI) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) based LbL assembled films that is a cathodic color changing electrode for electrochromic device. For this purpose, cationic and anionic commercial polyelectrolytes (PEs) with/without 0.3 M NaCl were deposited on PET-ITO with automatized dip coating system. From QCM-D, it was found that the multilayer deposition became larger for LbL assembled films obtained from salt-free PEs. While the dissipation change (Delta D) of (LPEI/PEDOT:PSS)(10/NaCl) (150 x 10(-6)) exhibited relatively soft/flexible structure compared to the (LPEI/PEDOT:PSS)(10) (110 x 10(-6)), AD changes became more obvious during PEDOT:PSS adsorption. Furthermore, it was determined that the film thickness and surface roughness values were highly dependent on the number of deposited bilayers whereas they dropped with the addition of salt to LPEI. The root mean square roughness (R-q) of (LPEI/PEDOT:PSS)(10), (LPEI/PEDOT:PSS)(20) and (LPEI/ PEDOT:PSS)(40) were found to be 28 nm, 41.7 nm and 61.5 nm, respectively, while R-q of (LPEI/PEDOT:PSS)(20)(/NaCl) was 14.2 nm. All LbL mutilayered films had hydrophilic character and the average contact angle value of (LPEI/PEDOT:PSS)(20)(/NaCl) was found to be 66 degrees due to the presence of salt within the multilayers. In addition, ion transport rate increased if the external salt was added to PE. Concerning the salt effect on colorancy of LbL multilayers, all films showed reversible color changes between blue and transparent/pale blue and (LPEI/PEDOT:PSS)(20) exhibited darker blue in the colored state whereas (LPEI/PEDOT:PSS)(20/NaCl) had more translucent in the bleached state.Öğe Enhancement of dispersion stability of inorganic additives via poly(sodium-4- styrenesulfonate) treatment geared to hydrogel applications(TUBITAK, 2021) Boran, Filiz; Okutan, MerveThis study reports the preparation of poly(sodium-4-styrene sulfonate) (PSS) treated bentonite and clinoptilolite to prevent the agglomeration and sedimentation of these inorganic fillers during the preparation of hydrogel. For this purpose PSS treated fillers were prepared by using various techniques (dip and dry, hydrothermal, one-step ball milling and ultrasonication methods). The most suitable technique for preparing these PSS treated inorganic fillers (abbreviated as BP-dip and CP-dip) was the dip and dry method. BP-dip and CP-dip based polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) composite hydrogels were prepared using the freeze/ thawing method after the addition of one of BP-dip and CP-dip inorganic fillers in various amounts. The swelling properties, stability behaviors and Rhodamine B (RhB) adsorption of the composite hydrogels were studied. It was found that the swelling degrees of CP-dip and BP-dip based composite hydrogels with 25 mg of filler were higher than that of all other samples. The kinetic mechanism of RhB adsorption process and the related characteristic kinetic parameters were investigated by Pseudo kinetic models. The adsorption kinetics results for RhB adsorption were found best fitted with pseudo-second-order kinetics model. The maximum RhB adsorption capacity was determined to be for PVA/PVP-CP-dip25, which was 3.3 times higher than that of the unfilled PVA/PVP hydrogel. © 2021 TUBITAK. All rights reserved.Öğe Hydrophobic surface modification and characterization of melamine foam(TUBİTAK, 2023) Okutan, Merve; Boran, Filiz; Ergün, Ayça; Kanca, Yusuf; Özkahraman, Bengi; Deligöz, HüseyinAbstract: Superhydrophobic and oleophilic modification of commercial acoustic melamine foam (MF) was made in this study. The modification was carried out with chitosan (CHI) and silica particles (SiO2 ), by using both a layer-by-layer-like approach (LbL) and dip coating technique. Subsequently, 1-octadecanethiol was used as a secondary modification agent. QCM-D, SEM, and FTIR analyses confirmed that the coating was successfully performed. After the modification, the column wall thicknesses increased than that of MF and they ranged from 25% to 48% for modified MF with an LbL-like approach (MMF) and modified MF via dip coating technique (MMFd), respectively. The sorption experiments showed that modified MFs, which had a water contact angle (WCA) above 160°, could sorb several model pollutants (vegetable oil, chloroform, ethanol, and toluene) up to 76–130 times their original weight. It had been determined that MMF protects its open-pore structure better than that of MMFd, which indicated that MF has a more uniform pore structure after modification. Furthermore, after 10 cycles of the sorption and release process, there was no significant change in sorption capacity, and they preserved their mechanical stability and flexibilityÖğe Influence of epoxy addition on the thermal, mechanical, and dielectrical properties of polycyanurate films(John Wiley and Sons Inc., 2018) Okutan, Merve; Sarıboğa, Vedat; Yıldırım, Saffettin; Deligöz, HüseyinIn the study, polycyanurate (PCN)/epoxy resin (ER) blends are prepared to enhance the physical properties of cyanate ester resins. The effects of curing schedule and blend composition on their thermal, mechanical, and dielectrical properties of cured PCN/epoxy blend films are examined. FTIR analysis of the cured blend films exhibits the expected cyanurate and oxazolidinone peaks in all blend compositions except the film thermally treated for 1 h in the presence of 1% phenol. TGA results show that the thermal stability decreases with epoxy content in the blend film. From SEM analyses, it is observed that all films have very dense, smooth, and bubble free surface without phase separation. For the pure PCN, the dielectric constants are found to be 3.54–5.91 in the range of 10?1–107 Hz between 20°C and 200°C. PCN/epoxy blends up to 50% epoxy resin show a good stability of dielectric constant in this frequency band for 200°C, which is close to the dielectric constant of the homopolymerized PCN. Beyond this percentage of epoxy resin, dielectric constants of PCN/epoxy blends greatly increase at low-frequency region (0.1–103 Hz) due to the interfacial polarization governed by Maxwell–Wagner–Sillars effect. POLYM. ENG. SCI., 58:820–829, 2018. © 2017 Society of Plastics Engineers. © 2017 Society of Plastics EngineersÖğe Investigating the effect of electrolyte types with various ionic liquids on the electrochromic performance of PEDOT:PSS based LbL multilayers(Elsevier, 2020) Okutan, Merve; Evecan, Dilek; Yıldırım, Saffettin; Özkan Zayim, Esra; Deligöz, HüseyinThe objective of the study is to investigate the electrochromic performances of layer-by-layer (LbL) multilayered thin film electrode prepared from linear polyethylene imine (LPEI) and poly(3,4-ethylenediox-ythiophene):polystyrene sulfonate (PEDOT:PSS) on PET-ITO substrate in the presence of different types of electrolytes. For this purpose, the electrochromic behaviors of (LPEI/PEDOT:PSS) 10 is performed in LiClO4/propylene carbonate (PC) and two different ionic liquids (IL) namely N-methylimidazolium tetrafluoroborate (Melm-BF4) and 2-hydroxy ethyl ammonium formate (2-HEAF), as a function of IL content and scanning rate. The optical contrast value of (LPEI/PEDOT:PSS) 10 film is determined as 58.4% in the existence of 10 wt% of 2-HEAF as the electrolyte. The coloration efficiency of this film is determined as 606.7 cm(2)/C, which this value was greater approximately four times than 1 M LiClO4/PC. According to the obtained results, 2-HEAF has been evaluated as a suitable electrolyte alternative for (LPEI/PEDOT:PSS) 10 film due to its better optical contrast and coloration efficiency compared to other electrolytes.Öğe Preparation, Characterization, and Separation Performances of Novel Surface Modified LbL Composite Membranes from Polyelectrolyte Blends and MWCNT(Wiley, 2020) Arslan, Merve; Dönmez, Göknur; Ergun, Ayça; Okutan, Merve; Albayrak Arı, Gülşen; Deligöz, HüseyinHere, it was aimed to modify the surface of NF90 with layer by layer (LbL) blended poly(allylamine hydrochloride) (PAH)-chitosan (CHI) and poly(acrylic acid) (PAA) with/without functionalized multiwalled carbon nanotube (fMWCNT) for reverse-osmosis applications. Using Quartz Crystal Microbalance Dissipation monitoring, it was observed that PAH-CHI/PAA LbL films grew linearly after a few bilayers and no LbL film degradation occurred during synthetic seawater treatment. Thermal degradation of all LbL blended membranes was similar. NF90 had a heterogeneous surface while the surface of LbL blend membranes exhibited some agglomerations due to the polyelectrolyte (PE) complex formation and fibrillary appearance depending on the use of fMWCNT. [(PAH50-CHI50/(PAA-fMWCNT)](30) indicated the highest flux with 14.5 L m(2) h(-1) at 40 bar. The sodium and chlorine ion rejections were 75% and 87%, respectively, for the same membrane. The use of fMWCNT led to a significant enhancement in flux with a slight decay in ion rejections. On the other hand, chlorine ion rejection of [(PAH50-CHI50/(PAA-fMWCNT)](30) decreased by 25% at 40 bar while 60 and 90 bilayers of [(PAH50-CHI50/(PAA-fMWCNT)] disintegrated after NaOCl treatment. Briefly, the flux and ion rejections of the LbL blended membranes can be controlled depending on the use of fMWCNT and different PE couples without multilayer decomposition against synthetic seawater. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics EngineersÖğe Smart glass electrochromic device fabrication of uniform tungsten oxide films from its powder synthesized by solution combustion method(Elsevier, 2019) Evecan, Dilek; Kaplan, Şevki Samet; Sönmez, M. Şeref; Yıldırım, Saffettin; Okutan, Merve; Deligöz, Hüseyin; Zayim, EsraRecently, there has been renewed interest in tungsten oxide based electrochromic (EC) materials. A variety of studies related to these materials have been reported, however, no serious studies so far have been reported on the electrochromic effect of tungsten oxide that is synthesized by solution combustion method. The major advantage of this process is the ease and simplicity with preparing nanosize oxides. Herein, the principal objective of this project was to produce uniform and adhesive tungsten oxide thin films from as-synthesized powder by solution combustion route for EC device. Although extensive research has been carried out on EC properties of tungsten oxide, limited study exists in e-beam evaporated tungsten oxide thin film studies for smart window application. Therefore, tungsten oxide thin films were deposited from our own produced powder by e-beam evaporation. To present the effect of new powder on the properties of the thin films, their physical and morphological properties were compared with thin film deposited by commercial tungsten oxide powder. Finally, electrochemical and optical characteristics of an all-solid-state EC device with a structure of glass/ITO/SCS-WO3/Nafion/ITO/glass with high optical transmittance modulation (63% at 550 nm) was fabricated. This study has been one of the first attempts to thoroughly examine in detail of tungsten oxide powder synthesized by solution combustion method for EC active layer. These findings contribute in several ways to our understanding of solution combustion synthesized powder to be used for production of EC active layer of thin film and provide a basis for developing and designing energy-efficient EC active materials and devices.Öğe Synthesis optimization of ZrO2 nanostructures for photocatalytic applications(Scientific and Technological Research Council Turkey, 2023) Boran, Filiz; Okutan, MerveAbstract: This study aims to optimize the synthesis of semiconductor zirconia (ZrO2 ) nanoparticles for future photocatalytic applications in degradation of pollutants in wastewater under ultraviolet (UV) light. The synthesis procedure of ZrO2 nanoparticles was optimized by examining the effects of synthesis methods (ultrasound-assisted, hydrothermal method in an autoclave and conventional precipitation), reaction time (2, 6, 10, and 18 h), ambient pH (3, 7, 10, 13), and surfactant type (anionic, cationic, and non-ionic), on the particle size and crystal phase of the nanomaterial. The characterization of the synthesized samples was performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), high-contrast transmission electron microscopy (HR-TEM), and transmission electron microscope (TEM) analysis. Consequently, to synthesize ZrO2 nanoparticles with the smallest particle size and monoclinic/tetragonal phase, the experimental conditions were optimized as ultrasound-assisted synthesis method, pH 10, and 6 h reaction time without surfactant. Moreover, percentage yield, particle size, crystallinity, monoclinic and tetragonal volumes of ZrO2 nanostructures synthesized under optimized conditions were determined as 39.40%, approximately 9 nm, 46.77, 79%, and 21%, respectively. It has been determined that the particle sizes can be kept under control by controlling the phase composition of ZrO2 nanostructures by optimizing the synthesis parameters. Structural and morphological characterization results can be correlated to the photocatalytic application, showing the potential of this material for the photodegradation of organic dye pollutants.Öğe Termal indirgenmiş grafen oksit ile elektrokimyasal olarak askorbik asit tayini(2020) Okutan, MerveBu çalışma, yüksek sıcaklıkta ani termal işlem ile indirgenmiş grafen oksitin (T-rGO) sentezi, SEM, XRD, Raman, FTIR, EDX teknikleriyle karakterizasyon analizi ve elektrokimyasal karakterizasyonu hakkındadır. T-rGO ve Nafion çözeltisi (N117) ile kaplanmış camsı karbon elektrot (GCE) doğrudan fosfat tampon çözeltisi (PBS) içerisindeki askorbik asit (AA) varlığının algılanması için kullanılmıştır. Modifiye GCE’nin elektrokimyasal davranışının değerlendirilmesi için dönüşümlü voltametri (CV), diferansiyel puls voltametri (DPV) ve amperometrik tekniklerden yararlanılmıştır. Bu amaçla başlangıç malzemesi olan sentetik grafitten modifiye Hummers yöntemi ile grafen oksit (GO) sentezlenmiştir. Ardından T-rGO, GO’nun inert gaz ortamında ve yüksek sıcaklıkta ani termal işlem uygulanarak indirgenmesi ile elde edilmiştir. XRD analiz verileri kullanılarak yaklaşık 3,32 tabaka sayısına sahip T-rGO sentezlendiği tespit edilmiştir. 5,0 mM AA içeren farklı pH değerlerine sahip (6, 7 ve 8) fosfat tampon çözeltileri (PBS) arasından pH değeri 8 olan çözeltide GCE/T-rGO elektrotu için en belirgin ve yüksek akıma sahip anodik yükseltgenme piki gözlenmiştir. Elde edilen sonuçlara göre hazırlanan GCE/T-rGO elektrotu, AA için yeniden üretilebilirlik (RSD=%6,25, n=3) ve tekrarlanabilirlikle (RSD=%2,14, n=3), yüksek hassasiyete (0,3 ?A mM-1) ve tayin limitine (0,61 ?M) sahiptir. Ayrıca, GCE/T-rGO elektrot ürik asit, dopamin, KCl, NaCl ve CaCl2’e karşı yüksek seçicilik sergilemiştir. Bu nedenlerle, hazırlanan GCE/T-rGO elektrotların AA molekülünün elektrokimyasal tayininde kullanılabileceği düşünülmektedir.
