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Öğe A comparative approach to enhance the electrical performance of PEDOT:PSS as transparent electrode for organic solar cells(Sage Publications Ltd, 2020) Borazan, Ismail; Bedeloğlu, Ayşe; Demir, AliIn this article, the improvement in electrical performance of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the transparent electrode doped with different additives (ethylene glycol (EG), isopropyl alcohol) or treatment of sulfuric acid was enhanced that organic solar cells (OSCs) were produced by using poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C-61 butyric acid methyl ester. OSCs were fabricated by the doped or treated PEDOT:PSS films as transparent electrodes. The photoelectrical measurements were carried out and the effects of doping or treatment were compared. As a result, EG-added PEDOT:PSS electrode showed the best power conversion efficiency value of 1.87% among the PEDOT:PSS anodes.Öğe A photovoltaic textile design with a stainless steel mesh fabric(Sage Publications Inc, 2022) Borazan, Ismail; Bedeloğlu, Ayşe; Demir, AliSolar energy is one of the most popular energy sources among the other renewable energies. Photovoltaic technology is a clean way to generate electricity from sunlight. Flexible photovoltaics enable portable electronic devices to power at off-grid conditions. Stainless steel mesh fabric was used as a substrate and electrode allowing the light to reach the photoactive layer. The photoactive layer and hole transport layer were deposited by the means of dip-coating like in the textile industry. The metal back electrode was evaporated in a thermal evaporator under vacuum. Promising results were obtained from photovoltaic measurements. About 0.69% power conversion efficiency was obtained from textile-based solar cells in this study. The textile-based metal fabric enables a flexible photovoltaic structure that can be integrated on non-planar surfaces to generate electricity, and also mesh structure allows the light to reach the photoactive layer.Öğe Applications of polyimide coatings: a review(Springer International Publishing Ag, 2021) Hicyilmaz, Ayse Sezer; Bedeloğlu, AyşePolyimides, high-performance polymers with superior properties such as high temperature stability, resistance to solvents and high strength, can be used in high-tech applications of the aerospace and aviation, medical or electronics industry in different forms (film, fiber, nanofiber, membrane, foam, adhesive or coating). Among these applications, coating has a special place and is used to develop advanced structures having high temperature resistance, flame retardancy and etc. for high tech industries via an economical and feasible way. Therefore, in this review, we aimed to report the broad application status of polyimide coatings by reviewing publications, patents and commercial products. Thus, this study can assist in selecting suitable polyimide types and production methods for polyimide coating applications and in understanding their applicability for future products.Öğe Characterization of organic solar cells using semiconducting polymers with different bandgaps(Walter De Gruyter Gmbh, 2019) Borazan, Ismail; Altin, Yasin; Demir, Ali; Bedeloğlu, AyşePolymer-based organic solar cells are of great interest as they can be produced with low-cost techniques and also have many interesting features such as flexibility, graded transparency, easy integration, and lightness. However, conventional wide bandgap polymers used for the light-absorbing layer significantly affect the power conversion efficiency of organic solar cells because they collect sunlight in a given spectrum range and due to their limited stability. Therefore, in this study, polymers with different bandgaps were used, which could allow for the production of more stable and efficient organic solar cells: P3HT as the wide bandgap polymer, and PTB7 and PCDTBT as low bandgap polymers. These polymers with different bandgaps were combined with PCBM to obtain increased efficiency and optimum photoactive layer in the organic solar cell. The obtained devices were characterized by measuring optical, photoelectrical, and morphological properties. Solar cells using the PTB7 and PCDTBT polymers had more rough surfaces than the reference cell using P3HT. The use of low-bandgap polymers improved I-sc significantly, and when combined with P3HT, a higher V-oc was obtained.Öğe Design and fabrication of auxetic PCL nanofiber membranes for biomedical applications(Elsevier, 2017) Bhullar, Sukhwinder Kaur; Rana, Deepti; Lekesiz, Hüseyin; Bedeloğlu, Ayşe; Ko, Junghyuk; Cho, YonghyunThe main objective of this study was to fabricate poly (e-caprolactone) (PCL)-based auxetic nanofiber membranes and characterize them for their mechanical and physicochemical properties. As a first step, the PCL nanofibers were fabricated by electrospinning with two different thicknesses of 40 pm (called PCL thin membrane) and 180 pm (called PCL thick membrane). In the second step, they were tailored into auxetic patterns using femtosecond laser cut technique. The physicochemical and mechanical properties of the auxetic nanofiber membranes were studied and compared with the conventional electrospun PCL nanofibers (non-auxetic nano fiber membranes) as a control. The results showed that there were no significant changes observed among them in terms of their chemical functionality and thermal property. However, there was a notable difference observed in the mechanical properties. For instance, the thin auxetic nanofiber membrane showed the magnitude of elongation almost ten times higher than the control, which clearly demonstrates the high flexibility of auxetic nanofiber membranes. This is because that the auxetic nanofiber membranes have lesser rigidity than the control nanofibers under the same load which could be due to the rotational motion of the auxetic structures. The major finding of this study is that the auxetic PCL nanofiber membranes are highly flexible (10-fold higher elongation capacity than the conventional PCL nanofibers) and have tunable mechanical properties. Therefore, the auxetic PCL nanofiber membranes may serve as a potent material in various biomedical applications, in particular, tissue engineering where scaffolds with mechanical cues play a major role.Öğe Development of thermo-regulating fabrics with enhanced heat dissipation via graphene-modified n-octadecane microcapsules(Wiley, 2021) Hiçyılmaz, Ayşe Sezer; Teke, Sengul; Islek Cin, Zeynep; Bedeloğlu, AyşePhase change materials (PCMs) are of great importance in thermal regulation applications, but low thermal conductivity is the most critical disadvantage of these materials. Especially in the textile field, while there are many studies on the production of PCM-coated fabrics, studies on improving heat dissipation are quite limited. Therefore, in this study, first, n-octadecane was encapsulated with melamine formaldehyde shell modified with graphene as a thermal conductivity enhancer, and then, synthesized PCM microcapsules were coated on polyester fabrics. Chemical, morphological, thermal properties, as well as phase change behavior of microcapsules and coated fabrics were analyzed. The thermal conductivity of the PCM microcapsule-coated PET fabrics was increased by 31% with the addition of very low amount of graphene (0.1%).Öğe DIELECTRIC PROPERTIES OF POLYANILINE-FUNCTIONALIZED CARBON NANOTUBE/PDMS NANOCOMPOSITES(Bursa Uludağ Üniversitesi, 2020) Ünsal, Ömer Faruk; Altın, Yasin; Bedeloğlu, AyşeIn recent years, carbon nanotubes (CNTs) have emerged as materials that are often used in the preparation of polymer nanocomposites with conductive or advanced dielectric properties due to their unique properties including high temperature and electrical conductivity, which allows the production of very light and robust materials with a very high length-to-diameter ratio. However, during the preparation of polymeric nanocomposites with these materials, some problems are encountered. One of the major problems is that after preparing these conductivematerials or adding them into the polymer, they tend to aggregate, forming agglomerate, due to their conductive structures. Therefore, in this study, firstly, multi-walled carbon nanotubes (MWCNTs) were functionalized with conductive form of polyaniline (PANI) and subsequently, the poly (dimethyl siloxane) (PDMS) polymer nanocomposite films with different concentrations of functionalized multi-walled carbon nanotubes were prepared. Then, the structural, morphological, electrical and dielectric properties of the films were characterized. As a result, with the addition of only 1.5% PANI-CNT, the dielectric constant of PDMS was increased by 47-fold at 1 Hz. The dielectric films like presented here can be used in capacitors, flexible electronics, dielectric elastomers and artificial muscle applications.Öğe Effect of molar ratio of PVP/AgNO3 and molecular weight of PVP on the synthesis of silver nanowires(Old City Publishing, 2017) Sağlam, Gökçenur; Borazan, I.; Hoşgün, Halit Levent; Demir, A.; Bedeloğlu, AyşeIn this paper, the effect of different parameters including the molar ratio of PVP/AgNO3 and the molecular weight of PVP on the silver nanowires synthesized by polyol method was investigated. The polyol method was performed in the presence of glycerol to obtain silver nanowires with optimum shape and therefore, experiments were repeated using different molecular weights of PVP and aspect ratios of PVP/AgNO3. Optical, structural and morphological characterizations were carried out to understand the effect of parameters on formation of silver nanowires. The results indicated that both molar ratio and molecular weight have influence on silver nanowire synthesis reaction. Silver nanowires with desired shape and high aspect ratio were obtained when PVP with low molecular weight and low molar ratio of PVP/AgNO3 were used. ©2017 Old City Publishing, Inc.Öğe Electrical, electromagnetic shielding, and some physical properties of hybrid yarn-based knitted fabrics(Taylor & Francis Ltd, 2013) Bedeloğlu, AyşeRecently, increasing number of studies are performed on protective fabrics containing metal wires for electromagnetic shielding purposes. In the present paper, the hybrid fabrics in plain and rib structures were knitted by using single and double ply hybrid yarns obtained by acrylic (PAC) yarns plied with stainless steel wires having two different diameters. The physical properties including conductivity, air permeability, pilling, and abrasion resistance as well as electromagnetic shielding effectiveness (EMSE) were measured. The variations in EMSE as well as reflection, absorption, and transmission and in other physical properties of knitted hybrid fabrics were investigated considering wire content and weave structure. It was seen that an increase in the wire content significantly increased the conductivity. Rib fabrics exhibited better EMSE values as compared with plain fabrics. Fabrics using two-folded yarns exhibited better EMSE values. Fabrics using thinner wire exhibited higher EMSE values. The highest EMSE value was obtained for rib-knitted fabric with 35 micrometer (m) stainless steel wire.Öğe Fabrication and characterization of polyaniline functionalized graphene nanosheets (GNSs)/polydimethylsiloxane (PDMS) nanocomposite films(SAGE Publications Ltd, 2021) Altın, Yasin; Ünsal, Ömer Faruk; Bedeloğlu, AyşeIn this study, graphene nanosheets (GNSs)/poly(dimethylsiloxane) (PDMS) nanocomposites and the novel polyaniline (PANI)-functionalized graphene nanosheets (GNSs)/poly(dimethylsiloxane) (PDMS) nanocomposites were fabricated successfully. GNSs and PANI-functionalized GNSs were dispersed in PDMS matrix at different nanofiller concentration and nanocomposites were prepared via solution casting method. PANI functionalization were performed by in-situ polymerization of aniline in the presence of GNSs and was used in order to be dispersed homogenously and efficiently in the PDMS matrix. Besides graphene layers were also isolated to hinder aggregation in the polymeric matrix. The effect of PANI functionalization of GNSs and filler concentration on dielectric, electrical and mechanical properties of nanocomposite films were investigated. According to dielectric measurements, the dielectric constant of polymer nanocomposites highly dependant on frequency, so dielectric constant was characterized in a wide frequency range (1 Hz–10 MHz) at room temperature, in this study. The dielectric constant of PDMS nanocomposites containing 1.50% GNSs and 1.50% PANI-GNSs increased by 111 times and 24 times, at 1 Hz, compared to pure PDMS, respectively. Besides, electrical conductivity increased 6868 and 1474 times with the addition of GNSs and PANI-GNSs, respectively. Optimized GNSs/PDMS and PANI-functionalized GNSs/PDMS nanocomposites can be candidate for soft actuators to be used in artificial muscle applications, in the future.Öğe Fabrication and properties of graphene oxide and reduced graphene oxide reinforced Poly(Vinyl alcohol) nanocomposite films for packaging applications(SAGE Publications Ltd, 2022) Doğan Yılmaz, Hazal; Altın, Yasin; Bedeloğlu, AyşePetroleum-based polymers have a wide range of uses in the packaging industry, including films, food packaging, rigid containers, foamed containers, medical products, etc. This study focuses on improving the properties of polyvinyl alcohol (PVA) based material systems, one of the most popular water-soluble biopolymers, to reduce the waste of petroleum-based plastics, which are widely used. Polyvinyl alcohol (PVA) nanocomposite films containing low concentrations (0.05-1%) of graphene oxide (GO) and reduced graphene oxide (rGO) were produced via the solution casting method. When electrical properties of nanocomposite films were evaluated, the addition of 1 wt% GO and rGO resulted in a 36% and 45% decrease in the volumetric resistance of the films as well as a decrease in surface resistance of 24.5% and 34.9%, respectively. The maximum tensile strength of 1% GO and rGO-reinforced PVA nanocomposites was found to be similar to 59 MPa and similar to 68 MPa with an increase of 20% and 38% compared to neat PVA films, respectively. The average Young's modulus of 1% GO and rGO-reinforced PVA nanocomposites also increased from 2561 MPa to 3515 MPa and 4219 MPa with an increase of 37% and 65%, respectively. As a result, the electrical conductivity, Young's modulus, maximum tensile strength, thermal properties, and optical absorption of nanocomposite films increased by adding GO and rGO to PVA. The results show that the produced nanocomposite film may be a promising material for packaging applications.Öğe Fabrication of Unilateral Conductive and Transparent Polymer Thin Films Decorated With Nanomaterials for Flexible Electrodes(Wiley, 2018) Taş, Mahmut; Cin, Zeynep İşlek; Şam Parmak, Ebru Devrim; Bedeloğlu, AyşeRecently, electrically conductive, flexible, and transparent nanocomposite thin films consisting of nanomaterials on insulating polymer layers are of particular interest to scientific and industrial experts and have promising applications in energy, electronic, and environment areas, due to their remarkable properties. In this study, nanomaterials including silver nanowires, reduced graphene oxide, and carbon nanotubes, and also, conducting polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate were embedded onto insulating polyamide 6-based polymer layer to form unilateral (one-sided) conductive nanocomposite thin film with advanced optical, electrical, and mechanical properties. Spin coating technique was used to fabricate these flexible, conductive, and transparent thin film layers. Thin conductive films decorated with silver nanowires exhibited sufficiently low sheet resistance of 105 Omega/sq with a transparency of similar to 85%. The maximum measured stress and elongation was obtained as 2.24 N/mm(2) and 12.5%, respectively. (C) 2016 Society of Plastics EngineersÖğe Farklı Punta Sayılarının Poliester Kumaş Özellikleri Üzerindeki Etkilerinin İncelenmesi(2021) Garip, Beysim; Yüksel Yılmaz, Ayten Nur; Er, Necati; Bedeloğlu, AyşePoliester (PES) diğer bir deyişle polietilen tereftalat (PET) tekstil sektöründe önemli yere sahip olansentetik polimerlerden biridir. Poliester iplik ve kumaşlar, gerilmeye karşı yüksek dayanım, bakterilere veısıya karşı direnç, elastiklik, bakım kolaylığı ve yıkama sonrası çabuk kuruma gibi üstün özellikleresahiptir. Bu çalışmada, aynı iplik numaralarına sahip (167/48 dtex/filament) tam çekimli (fully drawn yarn)(FDY) ve tekstüre kısmen çekilmiş poliester iplikler (partially oriented) (POY), hava ile kaplama (aircovering) yöntemiyle farklı punta sayılarında (8, 29, 54, 75, 85 adet/metre) birleştirilerek filament şeklindeüretilmiştir. Daha sonra bu filamentler kullanılarak örme kumaş yüzeyleri oluşturulmuş ve boyamayapılmıştır. Punta sayısının, poliester iplik ve kumaş üzerine etkileri, görsel ve fiziksel performansözellikleri ile değerlendirilmiştir. Farklı punta sayısına sahip ipliklerde, en yüksek ve en düşükmukavemet değeri, sırasıyla 29 punta (3,41 cN/ dtex) ve 8 punta (3,23 cN/ dtex ) sayısına sahip ipliklerdeelde edilmiştir. Genel olarak, boyalı kumaşlarda punta sayısının artması sonucunda kumaş kalınlığıartarken hava geçirgenliğinin azaldığı gözlenmiştir.Öğe Functional sol-gel coated electrospun polyamide 6,6/ZnO composite nanofibers(Walter De Gruyter Gmbh, 2019) Bedeloğlu, Ayşe; Cin, Zeynep IslekPolymer-based nanofibers are good candidates for medical textiles due to their excellent properties including high surface area, breathability and flexibility. Doping polymer nanofibers with different nanoparticles enhances their existing properties. In this study, electrospun polyamide 6,6 (PA6,6) composite nanofibers containing ZnO nanoparticles (<50 nm) in different amounts (1%, 3% and 5%) were first produced by electrospinning technique; then, these nanofibers were coated with sol-gel ZnO solution (0.5 M) via dip coating method at 1000, 3000 and 5000 mu m/s speeds. The sol-gel coating process increased the breaking strength of nanofiber mats, while the incorporation of ZnO nanoparticles into the polymer nanofibers reduced. Compared to pure PA6,6 nanofiber mats, the ZnO sol-gel coated samples and doped nanofibers had lower reflectance values. In addition, the reflection values decreased as the additive and coating speed increased.Öğe Grafen ve Grafen Üretim Yöntemleri(2016) Bedeloğlu, Ayşe; Taş, Mahmut2010 yılı nobel fizik ödülünün grafen hakkındaki ''Çığır açan deneyleri'' dolayısıyla Hollandalı Andre Geim ve Rus kökenli İngiliz vatandaşı Konstantin Novoselov'a verilmesi dikkatleri ''mucize materyal'' olarak da bilinen bu malzeme üzerine çekmiştir. Grafen tek atom inceliğinde olduğundan dolayı iki boyutlu kabul edilen, kovalent bağ ile bağlı karbon atomlarının altılı balpeteği örgüsünde kusursuzca dizilmesiyle oluşturduğu üstün özelliklere sahip bir nanomateryal olarak tanınmaktadır. Grafen yapısında karbon-karbon arası bağ uzunluğu 0,142 nm'dir. Grafen içindeki elektronlar oda sıcaklığında kütlesiz rölativistik parçaçıklar gibi davranır, bu sayede grafen kuantum boşluğu etkisi gibi kendine has özellikler sergiler. Grafenin temel üstün özellikleri geniş yüzey alanı (2630 m 2 g - 1) yüksek elektron mobilitesi (200000 cm2/(V s) yüksek ısıl iletkenliği (5000 Wm-1K-1) ve yüksek young modülü (~1100 Gpa) olarak sıralanabilir. Bu malzeme sahip olduğu üstün özellikler nedeniyle bir çok uygulama alanı bulmaktadır bunların başlıcaları transparan elektrotlar, alan etkili transistörler, sensörler, temiz enerji cihazları, nanokompozitler ve organik fotovoltaik cihazlar olarak sayılabilir. Bu çalışmada üstün özellikleri ile ön plana çıkan grafen nanomateryalinin üretim yöntemleri ele alınacaktır.Öğe Graphene and graphene oxide-coated polyamide monofilament yarns for fiber-shaped flexible electrodes(Taylor & Francis Ltd, 2019) Tas, Mahmut; Altin, Yasin; Bedeloğlu, AyşeIn this study, polyamide monofilament yarn of 3000 tex was coated with graphene oxide (GO) nanomaterial using dip-coating method. The graphene oxide layer was then reduced with green chemical reduction method, resulting in a reduced graphene oxide-coated monofilament yarn. The properties of the graphene oxide and reduced graphene oxide-coated polyamide monofilament yarns were characterized by performing physical, electrical, optical, and morphological investigations. The lowest sheet resistance was measured from seven-layer graphene-coated polyamide monofilament yarn as 3.09 k omega/sq. Moreover, it was measured that 90 degrees and 180 degrees bent seven-layer graphene-coated polyamide monofilament yarns had 3.57 and 3.81 k omega/sq sheet resistance, respectively. Additionally, while PA monofilament yarn has 73.5% transmittance at 550 nm; seven-layer GO and seven-layer graphene have 18.8 and 4.5%, respectively, as expected. On the other hand, the contact angle increased with the reduction of graphene oxide layer on monofilament yarn. The fabricated graphene-coated polyamide monofilament yarns can be used in electrotextiles, solar cells, sensors, and OLEDs as fiber-shaped flexible electrodes.Öğe Graphene oxide and zinc oxide decorated chitosan nanocomposite biofilms for packaging applications(Walter De Gruyter Gmbh, 2020) Terzioğlu, Pınar; Altin, Yasin; Kalemtaş, Ayşe; Bedeloğlu, AyşeRecently, due to sustainable development and environmental protection policies, there is increasing interest in the development of new biodegradable polymer-based multifunctional composites. Chitosan is one of the most remarkable and preferred biopolymers, which is environmentally friendly as well as renewable, biocompatible, and inexpensive. Though it has a wide range of potential applications, the major limitation of chitosan - the problem of poor mechanical performance needs to be solved. In this work, graphene oxide was first produced and then used to manufacture a chitosan/graphene oxide/zinc oxide composite film through a casting method. The properties of the chitosan film and the chitosan/graphene oxide/zinc oxide composite film were investigated using Fourier transform infrared spectroscopy, mechanical, thermal gravimetric, and ultraviolet (UV)-visible spectroscopy analyses. The results showed that the incorporation of graphene oxide and zinc oxide into the chitosan matrix resulted in enhanced mechanical properties and thermal stability of chitosan biocomposite films. The graphene oxide- and zinc oxide-reinforced chitosan film showed 2527 MPa and 55.72 MPa of Young's modulus and tensile strength, respectively, while neat chitosan showed only 1549 MPa and 37.91 MPa of Young's modulus and tensile strength, respectively. Conversely, the addition of graphene oxide decreased the transmittance, notably in the UV region.Öğe Graphene oxide modified carbon fiber reinforced epoxy composites(Walter De Gruyter Gmbh, 2020) Altin, Yasin; Yilmaz, Hazal; Unsal, Omer Faruk; Bedeloğlu, AyşeThe interfacial interaction between the fiber and matrix is the most important factor which influences the performance of the carbon fiber-epoxy composites. In this study, the graphitic surface of the carbon fibers was modified with graphene oxide nanomaterials by using a spray coating technique which is an easy, cheap, and quick method. The carbon fiber-reinforced epoxy matrix composites were prepared by hand layup technique using neat carbon fibers and 0.5, 1 and 2% by weight graphene oxide (GO) modified carbon fibers. As a result of SEM analysis, it was observed that GO particles were homogeneously coated on the surface of the carbon fibers. Furthermore, Young's modulus increased from 35.14 to 43.40 GPa, tensile strength increased from 436 to 672 MPa, and the elongation at break was maintained around 2% even in only 2% GO addition.Öğe İletken Polimer Esaslı Nanojeneratörler(2018) Ünsal, Ömer Faruk; Bedeloğlu, AyşeGerek doğada, gerekse şehir hayatında mekanik enerjiye di ğer enerji türl eri ne kıya s l a da ha kol a y ul a şılabilmektedir. Suyun yüksek debi de a ktığı bi r a ka rs u ya ta ğı, rüzgâ rın s a l l a dığı a ğa ç da l l a rı, üzeri nden araçların geçtiği bir köprü, yürüyen bir i nsanın eklem hareketleri ve zemine p eriyodik olarak uygul adığı basınç aslında birer a tık mekanik enerji kaynağıdırlar. Rüzgar enerjis i , hi drol i k enerji gi bi büyük mi ktarlarda mekanik enerji sağlana bi l en mecra l a rda uzun yıl l a rdır enerji dönüşüm i şl emi endüstriyel olarak gerçekleştirilmektedir. Son yıllarda daha küçük miktarlarda atık enerjinin dönüşümü ve kul l a nıma s unul ma s ı i çi n na nojenera törl er üzeri ne a ra ştırma l a r yoğunl a şmıştır.Öğe Improving the Water Repellency of Polyester Filament Yarn and Fabrics(Ege Üniversitesi, 2023) Garip, Beysim; Yüksel, Ayten; Ünal, Seda; Bedeloğlu, AyşeWater-repellent finishing is one of the most applied finishing processes by using materials that prevent the wetting of textile products and the passage of water drops. Fluorinated compounds are widely used in conventional methods applied for the development of water repellency, but the threats posed by these to humans and the environment have led to new searches for water repellency. Giving the water-repellent effect by reinforcing the masterbatch during fiber production can provide longer-lasting, homogeneously dispersed and environmentally friendly products. This reason, in this study, filament yarns containing fluorine-free water-repellent additives in three different weight percentages and fabrics coated with a water-repellent finishing without fluorine were produced. Then, the performance properties of the yarns were analyzed and water repellency, tensile and air permeability tests of the fabrics were performed. As coating repetition increased, the water repellency of the fabrics improved and air permeability decreased by approximately 80%.
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