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Öğe Comparison of Tafel Extrapolation and Linear Polarization Resistance Readings for TRC 8006 Aluminium Alloys in 3.5 wt.% NaCI Aqueous Solution(Bursa Teknik Üniversitesi, 2018) Eken, Taha Yasin; Sarıoğlu, Cevat; Küçük, İsrafilCorrosion behaviour of the twin-roll casting (TRC) 8006 Al alloys has been investigated as a function of foil thickness by two different polarization techniques; Tafel extrapolation and linear polarization resistance. Polarization curve changes depending on foil thickness for the TRC 8006 Al alloys have been achieved using both the polarization techniques, respectively. The measurements were performed using a three-electrode electrochemical cell system. Tafel slopes, polarization resistance, density of corrosion current, corrosion potential and corrosion rate values have been calculated based on the data collected from both method’s outcomes and compared with those of each techniques used. For these two polarization curves, the corrosion rate values obtained for TRC 8006 Al alloy with a thickness of 180 µm is remarkably lower than the obtained results of TRC 8006 Al alloy with a thickness of 150 µm. This specifies that a decrease in foil thickness of the TRC 8006 Al alloys increased corrosion rate of the TRC 8006 Al alloys and thus the two techniques used in the present study to determine corrosion rate appears to be reliable methods for a long-term corrosion behaviour.Öğe Corrosion behaviour of twin-roll cast 8006 aluminium alloy foil with different thicknesses for the food packaging industry(Emerald Group Holdings Ltd., 2021) Eken, Taha Yasin; Sarioglu C.; Kucuk I.Design/methodology/approach: The 8006 aluminium alloys are mostly used for the food packaging industry, as they are corrosion resistant, lightweight and shapable materials. The present work investigates the surface and corrosion behaviours of 8006 aluminium alloys at different thicknesses. TRC aluminium alloys were cold-rolled at two different reduction rates before investigation. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX) tests were used to examine the phase and elemental analyses. FE-SEM and 3D profilometry also used to observe surface morphology. Open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy tests (EIS) were carried out to find out corrosion behaviours. The results show that the more cold rolling reduction (CRR), the more corrosion rate and surface affection of the TRC 8006 aluminium alloys. Findings: According to the electrochemical tests (OCP, potentiodynamic polarization test and EIS) and surface morphology results (such as SEM, 3D profilometry and XRD) the more the rolling rate the less the corrosion resistance. Originality/value: First corrosion behaviour investigation of twin-rolled 8006 Al alloys using electrochemical techniques. First investigation of CRR effects on electrochemical corrosion behaviour of 8006 Al alloys with 3.5 wt.% NaCl solution using EIS. First investigation of 8006 Al alloys as a food packaging material with electrochemical ways.Öğe Effect of curvature and stacking sequence on flexural strength in glass fiber reinforced composites(Walter De Gruyter Gmbh, 2023) Kaboglu, Cihan; Eken, Taha Yasin; Guney, SukranMost of the structures in vehicles used in the automotive, aviation, and marine industries are exposed to different loads. It is seen that these structures are more exposed to flexural stress. Structures can sustain dangerous damage over time under the effects of flexural loads. The resistance of curved glass fiber reinforced polymer composites to flexural force is very important. In this study, the diameters of curved composites of 760 mm, 380 mm, and 304mm are studied. Also, fiber stacking sequences were determined as [0/0/-45/+45/90/90](S) and [90/90/-45/+45/0/0](S) and compared. All specimens were produced by vacuum infusion method. Three-point flexural tests were performed according to the ASTM D7264 standard at 1mm.min(-1) punch speed. Among all composites, 760mm diameter and Type 2 stacking were found to have the highest flexural strength. Hence, it was observed that the flexural strength decreased with the increase in curvature, and Type 2 fiber layer sequencing is more durable than Type 1 sequencing. This is because the 90 degrees fiber direction in the substrate has a damping effect on the applied force.Öğe Effect of Few-Layered Graphene on the Corrosion Behaviour of the Al-Cu Matrix Composites(Springer, 2025) Kaykilarli, Cantekin; Eken, Taha Yasin; Kucukelyas, Burak; Uzunsoy, DenizIn the transportation, maritime and aviation industries, aluminum alloys - particularly those in the 2xxx series (Al-Cu type) - are frequently used because they offer an ideal combination of properties, including toughness, a high strength-to-weight ratio and fatigue resistance. Graphene, a two-dimensional material with a single-atom thickness composed of carbon atoms arranged in a hexagonal lattice, attracts interest due to its remarkable properties and is commonly utilized as a reinforcement in composite materials. Few-layered graphene (FLG) reinforced Al-4 wt.% Cu matrix composites were prepared via mechanical alloying (MA, 500 rpm, ball-to-powder ratio 7 : 1), uniaxial pressing (300 MPa), and conventional sintering (59 degrees C, 3 hours, argon gas flow). The present work investigates corrosion behaviors of FLG (0.25 and 0.5 wt.%) reinforced Al-4 wt.% Cu composites with different MA durations. Open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) measurements were carried out in a 3.5% NaCl solution to determine the corrosion behavior. Following the corrosion test, X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis were performed on the specimen that exhibited the optimum results. The data obtained before and after the test were compared to investigate the structural changes that occurred as a result of the corrosion test. The analysis demonstrated that the sample reinforced with 0.5 wt.% FLG and subjected to 7 hours of MA had the highest corrosion resistance.Öğe Electrochemical characterization of poly(thiophene-3-boronic acid) for aqueous environments(Elsevier, 2024) Eken, Taha Yasin; Gumus, Omer Yunus; Uzunsoy, DenizPoly(thiophene-3-boronic acid) (PTBA) was studied as a promising active material for aqueous environments in this paper. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the solubility and electrochemical behavior of it was studied in a range of aqueous solutions. Fourier Transform Infrared Spectrometry (FTIR) results verify the successful synthesis. PTBA shows promising solubility qualities in certain pH ranges, especially in alkaline solutions. However, among alkaline, neutral, and acidic environments the best environment for redox properties of aqueous 1 mM PTBA is the neutral one. The peak current (ip) of 1 mM PTBA for 100 mV/s in the neutral environment is 0.01 mA and half peak potential (Ep/2) is _ 0.1 V (vs Ag/AgCl). Diffusion coefficient of PTBA is found as 4.97 x 10_8 cm2/s. The impedance tests also confirm that the neutral solvent decreases the charge transfer resistance.Öğe Electrochemical Performance of a New Triazole Functionalized Ferrocene in Aqueous Redox Flow Batteries(Wiley, 2025) Eken, Taha Yasin; Gonzalez, Gabriel; Peljo, Pekka; Koz, GamzeA new 1,2,3-triazole functionalized ferrocene (1,2,3-TAFc) produced by Cu(I)-catalyzed click reaction was investigated as positive electrolyte for aqueous organic flow batteries (AOFBs). The molecule is highly soluble in 1 M hydrochloric acid and displays high electrochemical reversibility. 1,2,3-TAFc demonstrated good stability during cycling with a low capacity decay (0.011%/cyc, 3.0%/day) and high Coulombic efficiency (99.4%) over 280 cycles when tested in a flow battery at low concentration. This low capacity decay was attributed to the instability of ferrocene. These findings indicate that a stable and water-soluble catholyte for AOFBs can be obtained with structural modifications of 1,2,3-TAFc. A new type of ferrocene catholyte for AOFBs based on a 1,2,3-triazole moiety was introduced. 1,2,3-TAFc was prepared easily via click chemistry with a one-pot, two steps reaction sequence with 73% overall yield. The CV and flow battery experiments demonstrated the reversible and stable nature of the material. The cycling battery tests show a high stability of 1,2,3-TAFc in acidic electrolyte with low capacity decay (0.011%/cyc) and high Coulombic efficiency (99.4%).imageÖğe Electromagnetic Shielding Effectiveness and Impact Test Performance of Carbon Fiber Reinforced Polymer Composites with Hematite and Goethite(John Wiley and Sons Inc, 2024) Eken, Taha Yasin; Kaykilarli, Cantekin; Kucukelyas, Burak; Tabakcioglu, Mehmet BarisCarbon fibers (CFs) are versatile materials widely employed in carbon fiber-reinforced polymer (CFRP) composites, known for their superior mechanical properties and electromagnetic interference (EMI) shielding capabilities. This study focuses on the successful production of 2-layer CFRP composites reinforced with hematite (Fe2O3) particles, in two different sizes (?44 µm (325 mesh) and 50 nm), and goethite (FeO(OH)), utilizing the hand lay-up method. The investigation encompasses EMI shielding effectiveness (SE) within a frequency range of 700 to 6000 MHz, and the drop-impact strength resistance properties (under a 6 J load). Results indicate that the highest EMI SE value, 60.19 dB at 5900 MHz, is achieved with 5 wt.% goethite reinforcements, while with a reduction in drop-impact strength. For hematite-reinforced composites, the highest EMI SE, measuring 57.85 dB at 5800 MHz, is observed for samples containing 15 wt.% hematite particles with a size of 50 nm, which exhibited an overall improvement in impact strength compared to non-reinforced samples. This research highlights the potential of these CFRP composites for EMI shielding applications, with considerations for their impact on mechanical properties, providing valuable insights for applications demanding both EMI protection and structural integrity. © 2023 The Authors. Macromolecular Materials and Engineering published by Wiley-VCH GmbH.Öğe Electromagnetic shielding effectiveness performance of carbon fiber reinforced polymer (CFRP) composites with hematite and goethite in far-field(Pamukkale Univ, 2024) Erbas, Ugur; Kaykilarli, Cantekin; Eken, Taha Yasin; Kucukelyas, Burak; Tabakcioglu, Mehmet BarisCarbon fibers (CFs) are indispensable materials in our daily life. The excellent bearing capacity, remarkable dielectric property, ease of production, and corrosion resistance of CFRP composites distinguish them from all other options in addition to them, CFRPs may also shield from electromagnetic interference (EMI). In this study, two-layer CF reinforced epoxy composites reinforced with two different hematite (alpha- Fe2O3) and goethite (FeO(OH)) particle sizes of 50 nm and 45 mu m (325 mesh) were produced using the manual lay-up method. Then, far field electromagnetic shielding effectiveness (SE) with 700 MHz- 6000 MHz range were examined. The maximum shielding effectiveness was determined to be at 5200 MHz with 39.28 dB for 5 wt.% FeO(OH), at 4700 MHz with 38.38 dB for 10 wt.% Fe2O3(325 mesh), at 3800 MHz with 37.15 dB for 15 wt.% Fe2O3(50 nm).Öğe Graphene nanoplatelet-coated electrodes with cellulose binders for 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl-based aqueous proselyte(Taylor & Francis Inc, 2025) Eken, Taha Yasin; Kaykilarli, Cantekin; Tuna, Ali; Parmak, Ebru Devrim Sam; Uzunsoy, Deniz; Peljo, PekkaThis study investigates the development of cellulose-bonded graphene nanoplatelet-coated electrodes for organic flow batteries (OFBs) utilizing 4-Hydroxy-2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPOL) as the active material. Graphite felt electrodes were coated via an optimized dip-coating process, varying the number of dips (1, 5 and 10). Cyclic voltammetry (CV) showed a 150% increase in oxidation peak current and a 250% increase in reduction peak current for the 10-dipped electrodes compared to pristine ones. Electrochemical impedance spectroscopy (EIS) revealed a 35% reduction in charge transfer resistance (Rp) for the 5-dipped electrodes, indicating enhanced ion transfer efficiency. Surface characterization analyses, including SEM, XRD and Raman spectroscopy, confirmed uniform graphene coatings and structural integrity, while contact angle measurements demonstrated a transition from hydrophobic (157 degrees) to hydrophilic (0 degrees) surfaces, improving wettability and electrolyte interaction. These findings establish cellulose as a sustainable, cost-effective binder, with potential scalability for large-scale energy storage applications.Öğe High entropy alloy reinforcement for superior electromagnetic interference shielding performance in carbon fiber-reinforced polymer composites(Wiley, 2025) Kucukelyas, Burak; Kaykilarli, Cantekin; Eken, Taha Yasin; Erbas, Ugur; Tabakcioglu, Mehmet BarisThis study explores the enhancement of electromagnetic interference (EMI) shielding effectiveness (SE) in carbon fiber-reinforced polymer (CFRP) composites through the integration of equatomic CoCuFeNi high entropy alloy (HEA) particles. Employing mechanical alloying (MA), CoCuFeNi HEA powders were synthesized, revealing a face-centered cubic structure with crystallite and particle sizes of 14.7 nm and 11.62 mu m, respectively. The integration of these HEA particles at concentrations of 5%, 10%, and 15% by weight into epoxy resin, followed by the fabrication of composites using the hand lay-up technique. Detailed structural analysis of HEA particles confirmed the successful synthesis of equatomic HEAs via MA. Structural analysis of the HEA integrated composites revealed vacancy regions at 5% concentration, a uniform distribution at 10%, and particle agglomeration causing inhomogeneity and vacancies at 15%. The composites demonstrated significant improvements in EMI SE, with the 10% HEA sample showing superior performance compared to the other samples. Specifically, the 10% HEA composite achieved a peak SE of 73.09 dB at 4.72 GHz, attributed to the optimized distribution of HEA particles that enhanced electrical conductivity and reflective properties.Highlights CoCuFeNi HEA particles were successfully synthesized via MA. HEA particles were added to epoxy at 5, 10, and 15 wt% for composite fabrication. Voids were observed in HEA5, uniformity in HEA10, and clustering in HEA15. EMI shielding was assessed using VNA, SE, dielectric permittivity, and magnetic permeability. The HEA10 composite achieved peak EMI shielding, 73.09 dB at 4.72 GHz.Öğe İkiz merdane sürekli döküm tekniği ile üretilen hadde alüminyum alaşımlarının korozyon davranışı ve yüzey özelliklerinin incelenmesi(Bursa Teknik Üniversitesi, 2018) Eken, Taha Yasin; Küçük, İsrafil; Sarıoğlu, CevatYüksek korozyon dayanımı, kolay şekil verilebilmesi ve hafifliği gibi avantajlarından dolayı alüminyum malzemeler, son yıllarda gıda paketleme endüstrisinde yaygın olarak tercih edilir hale gelmiştir. Alüminyum alaşımlarının gıda endüstrisinde kullanılmasının temel nedeni gıdaların kimyasal yapısının korozif özelliği ve bu ortam nedeniyle gıda paket ve ambalajlarının özelliklerini yitirmesidir. Alüminyum alaşımları ise korozyona oldukça dayanıklı olup yerkabuğunda da bol miktarda bulunmaktadır. Günümüzde alüminyum ve alaşımlarının üretimi ve gıda paketleme endüstrisinde kullanımı oldukça kolay ve pratiktir. Özellikle 8006 grubu alüminyum alaşımları, hazır gıda ve asitli veya asitsiz içecek kutularının üretimi, sıvı ve katı gıda ambalajlama gibi gerek endüstri gerekse günlük hayatta yaygın olarak kullanılmaktadır. Sürekli döküm yöntemlerinden (CC) ikiz merdane sürekli döküm (TRC) tekniği ile üretilen 8006 serisi alüminyum alaşımlarının korozyon davranışlarının ve yüzey özelliklerinin incelendiği bu yüksek lisans tez çalışmasında, ilk olarak 8006 serisi alüminyum alaşımı ergiyik halde ikiz merdanelerin arasına kalıp yardımıyla dökülerek 8,5 mm kalınlığında levha halinde numuneler elde edildi. Daha sonra elde edilen bu levha halindeki alüminyum alaşım numunelerine 550 °C ila 600 °C sıcaklıkları arasında homojenleştirme tavlaması uygulandı. Haddeleme işlemlerinden sonra 400 °C ila 450 °C sıcaklıkları arasında normalizasyon tavlamasına tabi tutularak numuneler kullanıma hazır hale getirildi. Üretimi gerçekleştirilen numunelere elektrokimyasal korozyon testleri öncesi karakterizasyon testleri yapıldı. Öncelikle spektral analiz yöntemi ile numunelerin içerdiği elementlerin tespiti yapıldı. Ardından X-ışını difraktometresi (XRD) yöntemi kullanılarak alüminyum folyo alaşımlarının yüzeylerinde bulunan faz ve elementlerin tespiti gerçekleştirildi. Stereo mikroskop ile yüzeylerinde bulunan hadde izleri ve hadde yönleri gözlemlendi. Son olarak taramalı elektron mikroskobu (SEM) ile alaşımların yüzeyleri daha ayrıntılı olarak incelendi ve yüzeyde bulunan elementlerin yüzdece kütlelerini bulmak için enerji dağılım spektroskopisi (EDS) yöntemi kullanıldı. Korozyon öncesi karakterizasyon testleri yapıldıktan sonra %3,5 NaCl çözeltisi kullanılarak elektrokimyasal korozyon testlerinden açık devre potansiyeli (OCP), lineer polarizasyon (LP) ve elektrokimyasal empedans spektroskopisi (EIS) ölçümleri alüminyum folyo alaşım numunelerine uygulandı. Uygulanan bu elektrokimyasal korozyon testleri sonrasında tekrar X-ışını difraktometresi (XRD), stereo mikroskop, taramalı elektron mikroskobu (SEM) ve enerji dağılım spektroskopisi (EDS) yöntemleri kullanılarak TRC 8006 alüminyum folyo alaşım numunelerinin korozyon davranışı ile yüzey özelliklerinde meydana gelen değişimler incelendi. Bu çalışmalara ek olarak soğuk hadde ile ezme oranı %94 ve %98 olan iki alüminyum folyo alaşım numunesine de karakterizasyon ve elektrokimyasal testler uygularak ezme oranın etkisi incelenmiştir. Bu işlemler neticesinde, ikiz merdane sürekli döküm tekniği sonrasında uygulanan ezme oranı arttırıldığında, üretilen 8006 serisi alüminyum alaşımlarının korozyon hızının arttığı ve bu alaşımların gıda paketleme uygulamalarında kullanılmasının uygun olduğu sonucuna varılmıştır.Öğe Impact performances and failure modes of glass fiber reinforced polymers in different curvatures and stacking sequences(SAGE Publications Ltd, 2022) Kaboğlu, Cihan; Eken, Taha Yasin; Yürektürk, YakupRecently, glass fiber reinforced polymer composites have been increasingly used in applications which are exposed to impact loads due to their high strength, low weight, and corrosion resistance properties. Therefore, the effect of curvature of composite laminate on their impact resistance is important. In this study, the mechanical properties of three curvature diameters and two stacking sequences, which have not been compared before, were examined and compared. The diameter of curved composites is 760 mm, 380 mm, and 304 mm and flat designated as A, B, C, and D, respectively. The fiber stacking orders are [0/0/-45/+45/90/90]S and [90/90/-45/+45/0/0]S designated as Type 1 and Type 2, respectively. The drop-weight impact tests were performed and failure modes of composites were examined. It was observed that the impact resistance decreases with the increase of curvature, where 760 mm diameter and Type 2 composites had the highest strength in all of the composites. In addition, delamination, fiber breakage, and matrix cracking failure modes were observed in the composites after impact. The reason why the strength decreases as the curvature of the composite increases is that the curved areas create an effect that increases the external force applied. The reason why Type 2 stacking order is more durable than Type 1 stacking order is that the 90° fiber direction in the bottom layer has a damping effect on the applied force. According to the results of this study, composite materials with larger diameter and stacking order starting with 0° provides more mechanical strength. (Figure presented.)Öğe Organik esaslı akış bataryalarının geliştirilmesi, kimyasal/elektrokimyasal karakterizasyonu ve performanslarının belirlenmesi(Bursa Teknik Üniversitesi, 2024) Eken, Taha Yasin; Uzunsoy, Deniz; Koz, GamzeDünyada artan nüfus ve teknolojiye bağlı olarak her geçen gün enerji talebi artmaktadır. Artan enerji talebinin karşılanması için karbon ayak izi yüksek enerji kaynakları kullanılmakta, bu durum çevre ve atmosfer kirliliği olarak insanlığa geri dönmektedir. Kirliliği önleyerek çevreyi temiz tutmak ve canlıların yaşamına olumsuz etki etmesini engellemek amacıyla, ekonomik açıdan da cazip olan yenilenebilir enerji kaynakları (YEK) kullanımı artırılmaya çalışılmaktadır. Ancak YEK sürekli olmadığı için, örneğin güneş enerjisi panelleri ve rüzgar türbinleri gibi, üretilen enerjinin şebekeye entegrelerinde problemler olmakta ve üretilen enerji her zaman kullanılamamaktadır. Bu nedenle her alanda olduğu gibi yüksek enerji talebinin olduğu şehir şebeke elektrik enerjisinin de depolanmasına ihtiyaç duyulmaktadır. Böylece depolanan enerji şebekeye belirli akımlarda aktarılabilecek ve YEK ile üretilen enerjinin sürekli olmadığı saatlerde de şebekeye enerji verilebilecektir. Ülkemizde de YEK'e ve enerji depolamaya verilen önem dünyada olduğu gibi her geçen gün yükselmektedir. Bu tezde şehir elektriğini depolamak amacıyla organik redoks akış bataryalarının kullanılması çalışılmıştır. Redoks akış bataryaları yüksek elektrik enerjisi depolama özelliklerine sahip bataryalardır. Sıvı elektrolitin akışı yoluyla enerjinin depolanması prensibine dayanan bu bataryalarda, enerji depolama miktarını artırmak için elektrolit miktarını artırmak yeterlidir. Elektrolit ise sulu veya susuz çözücü kullanarak hazırlanabilmektedir. Çözünen ise redoks tepkimelerinin gerçekleştiği elektroaktif bir organik malzeme olmalıdır. Tez kapsamında çeşitli organik malzemeler incelenmiştir. Bu organik malzemeler polianilin boronik asit (PABA), politiyofen boronik asit (PTBA), ferrosen disülfonik asit (FcDS), ferrosen - 1,4-disübstitüe 1,2,3-triazol (1,2,3-TAFc), ve 2,2,6,6-tetrametilpiperidin (TEMPOL) bileşikleridir. PTBA, PABA, FcDS, 1,2,3-TAFc organik malzemelerinin akış bataryalarında elektroaktif malzeme olarak kullanım potansiyelleri incelenmiştir. Farklı pH seviyelerindeki çözeltilerde yapılan testler ile ilgili organik malzemelerin elektrokimyasal özellikleri incelenmiştir. Sulu ortamda yapılan testlerde 1,2,3-TAFc bileşiği ile akış bataryası sistemi kurularak şarj/deşarj davranışı araştırılmıştır. İlgili organik malzemenin son derece kararlı olduğu tespit edilerek literatürde ilk defa başarılı bir şekilde batarya testleri gerçekleştirilmiştir. TEMPOL bileşiği ise akış bataryalarında elektrot olarak kullanılan grafit keçelerin performans testlerini gerçekleştirmek amacıyla kullanılmıştır. Grafit keçe elektrotlar grafen ile kaplanarak TEMPOL malzemesi ile test edilmiş ve performans değişimleri incelenmiştir.
