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Öğe A comparative assessment of artificial neural network and regression models to predict mechanical properties of continuously cooled low carbon steels: an external data analysis approach(2024) Alan, Emre; Ayhan, Ismail Irfan; Ogel, Bilgehan; Uzunsoy, DenizIn this study, mechanical properties of continuously cooled low carbon steels were predicted via Artificial Neural Network (ANN) and Multiple Linear Regression (MLR) models. Unlike the previous studies, laboratory scaled self-generated data that consists of chemical compositions and cooling rates were used as input while yield strength (YS), ultimate tensile strength (UTS) and total elongation (TE) were served as target data. The prediction performances of the models were compared by applying new data set extracted from external sources like previously studied research papers, thesis or dissertations. A better agreement between predicted and actual data was achieved with ANN model. Additionally, the response of ANN model to new external data resulted in lower prediction errors even the data has one or more input value that is not included in the range of training data set. Unlike ANN model, MLR model shows a significant decrease in prediction accuracy when input data has non-uniform distribution or target data takes place in relatively narrow range. In general, it was shown that ANN model trained with self-generated data can be used as an efficient tool to estimate mechanical properties of continuously cooled low carbon steels that are produced with various conditions, even for the phenomena between input and output is complex and data distribution is non-uniform.Öğe A comparative study about corrosion resistance and biocompatibility of Ti6Al4V samples produced by wrought and additive manufacturing methods(Elsevier Science Sa, 2026) Gurkan, Doruk; Sagbas, Binnur; Uzunsoy, Deniz; Dalbayrak, Basak; Arisan, Elif DamlaTi6Al4V is widely used in biomedical applications due to its excellent mechanical properties and biocompatibility. Conventional manufacturing techniques, such as plastic deformation processes, have long been employed to produce Ti6Al4V implants and prosthetics. Recently, the advent of additive manufacturing (AM), which allows the generation of complex geometries and customized implants, has introduced a new dimension to the production of these biomedical devices. However, examining the effects of newly developed manufacturing methods on material and sample properties is extremely important to obtain successful products. In this study, additive manufactured and wrought Ti6Al4V samples were implemented for their corrosion resistance and biocompatibility as orthopedic implant material. Three different post processes such as sandblasting, acid etching and bioactive coating (hydroxyapatite-chitosan composite via electrophoretic deposition (EPD)) were applied on the additive manufactured sample surfaces, while only the bioactive coating was applied on the wrought sample surfaces and their effects on the corrosion and biocompatibility were evaluated with the reference of untreated control samples. Corrosion resistance properties were examined with open circuit potential (OCP) measurement, electrochemical impedance spectroscopy (EIS) and Tafel extrapolation, respectively. Electrochemical impedance spectroscopy and Tafel extrapolation showed similar results. Biocompatibility tests were carried out as mouse embryonic fibroblast (MEF) cell culture and cellular viability tests with mouse embryonic fibroblast cells. Coating and sandblasting were the best post-processing methods for anti-corrosion and biocompatibility applications. AM sandblasted samples are the most suitable samples for both application areas.Öğe A comparison and identification study of dry sliding wear behaviour of Al/B4CP and Mg/B4CP composites for automobile disk brakes(SAE International, 2014) Isin, O.; Istif, I.; Uzunsoy, Deniz; Guleryuz, F.The brake friction materials in an automotive brake system play an important role in the overall braking performance of a vehicle. Metal Matrix Composites (MMCs) have been widely investigated and applied due to their advantages of improved strength, stiffness and increased wear resistance over the monolithic alloys in automobile industries. In this paper, Al/B 4CP and Mg/B4CP composites were compared to find a suitable candidate material for automotive disk brake application, in terms of wear behavior results of the materials. In addition, the experimental data was also used to model this behavior by identification. The measured tangential force was considered as the input parameter, whereas the weight loss as the output parameter. Preliminary results of this work showed that B4CP addition improved wear resistance of both aluminum and magnesium matrix composites. Additionally, the study pointed out that identified models provide a reliable and cost effective tool for wear prediction. Copyright © 2014 SAE International.Öğe ALUMINIUM OXIDE (Al2O3)-FEW LAYER GRAPHENE (FLG) REINFORCED ALUMINIUM HYBRID COMPOSITES(POLISH SOC COMPOSITE MATERIALS, 2022) Kaykılarlı, Cantekin; Altinisik, Zehra; Kilic, E. Can; Uzunsoy, Deniz; Yeprem, H. AygulThe present study investigates the microstructural and mechanical properties of few layer graphene (FLG, 0.1 to 5 wt.%) and aluminium oxide (Al2O3, 4 to 20 wt.%) reinforced Al6061 matrix composites prepared via mechanical alloying (MA), uniaxial pressing and pressureless sintering. The effects of the amounts of Al2O3 and FLG were studied. MA was carried out at 300 rpm for 3 h in a planetary ball mill in argon atmosphere. The mechanically alloyed (MAed) powders were compacted via uniaxial pressing (400 MPa) and sintering (620 degrees C, 2 h). The microstructural and mechanical properties of the Al-xAl(2)O(3)-yFLG powders and bulk samples were investigated via X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), the Archimedes' method and a hardness test. In the XRD analysis, the aluminium carbide (Al4C3) phase was not detected. The SEM, LM micrographs and EDS results show that the produced composites have a homogeneous structure. Based on the Archimedes' method, the densification rates of the rein-forced samples were higher than the unreinforced sample. The Al-20Al(2)O(3)-3FLG sample exhibited the highest relative density, 99.25%. According to the hardness measurements, the highest hardness value was 87.28 HV for the Al-20Al(2)O(3)-1FLG composite and increased twofold compared to Al6061.Öğe Boron and nitrogen doping in graphene: an experimental and density functional theory (DFT) study(IOP Publishing, 2020) Kaykılarlı, Cantekin; Uzunsoy, Deniz; Şam Parmak, Ebru Devrim; Fellah, Mehmet Ferdi; Çakır, Özgen ÇolakBoron (B) and Nitrogen (N) doped few layer graphene (BNG) is directly synthesized via electric arc discharge (EAD) method. NH3 and BCl3 gas mixtures are used in the synthesis atmosphere. Raman spectroscopy is used to determine graphene's purity and number of layers. The investigation of structure and morphology of pristine graphene and BNG are carried out via Transmission Electron Microscopy (TEM). The presence of B and N in the structure of graphene is detected by Energy Dispersive X-ray Spectroscopy (EDS) analysis. Elemental mapping show that N and B are distributed homogeneously in the graphene structure. It is observed that doping process did not affect the positions of the D, G and 2D bands in the Raman spectroscopy. The effect of doping on the number of layers of graphene is found negligible. TEM results exhibit that pristine graphene and BNG have 5 to 6 layers. Besides, the theoretical calculations based on Density Functional Theory (DFT) are employed to support experimental studies. Theoretical results based on DFT showed that bonding of B and N is favorable.Öğe Characterization of the Microstructure and Mechanical Properties of a Novel Functionally Graded Material Based on Al-Zn-Cu-Mg Alloy Matrix Reinforced with Few-Layered Graphene(Wiley-V C H Verlag Gmbh, 2025) Borand, Gokce; Uzunsoy, DenizComposite materials satisfactorily suit the needs of industrial applications. However, with the advancement of modern technology, functionally graded materials (FGMs) are becoming increasingly important in order to meet evolving customer demands. The reinforcement material in FGMs varies in quantity and arrangement across different regions, resulting in continuously changing properties and a non-uniform microstructure. Various industries widely employ aluminum (Al) alloys due to their favorable features, which include excellent stiffness, ductility, a high strength to weight ratio, and corrosion resistance. The current study facilitates the powder metallurgy (P/M) production of a novel generation of a six-layer Al-Zn-Cu-Mg alloy material graded according to increasing few-layered graphene (FLG) reinforcement. The increase in the FLG content between the layers, from the first to the last layer, results in an increase in the hardness value (HV) of the FGM by approximate to 39.13%. The most effective strengthening mechanism for FGM is grain size reduction, which is a result of the FLG content present in each layer. Moreover, the load transfer and reinforcing effect of graphene are enhanced by the strong interface bond that occurs between FLG and the matrix.Öğe Comparison of fatigue crack growth rate of selective laser sintered Rapid Steel via computational fracture mechanics(Carl Hanser Verlag, 2014) Okyar, Ali Fethi; Uzunsoy, Deniz; Qzsoy, BurakThe fatigue-crack growth behavior of materials manufactured by means of selective laser sintering was studied. In the process, specimens were prepared from metal powders (316 steel) into the desired shape by additive manufacturing technology, followed by sintering and infiltration in a suitable molten metal. The latter process was aimed at eliminating the inherent porosity associated with powder metallurgy. Porosity is known to adversely affect the fatigue-crack growth rate behavior of powder metallurgy components. Carefully conducted fatigue-crack growth rate tests (single-edge-notch four-point bending type) were carried out on RapidSteel (TM) and the results were compared with data of infiltrated low carbon steel in the literature. Finite element analysis was carried out as an intermediate step in order to validate the geometry factor calculations provided by empirical formulae. It was found that the fracture resistance of Rapid Steel was higher compared with low-carbon copper infiltrated steel tempered at 177 degrees C and 428 degrees C, and same as that tempered at 704 degrees C.Öğe Comprehensive Optimization of Selective Laser Melting Process Parameters for Microstructure, Density, Hardness, and Tribological Performance of Pure Copper(Int Inst Science Sintering (I I S S), 2024) Ozkan, Burcu Asli; Dilsiz, Yusuf; Kucukelyas, Burak; Sever, Ahmet; Bademlioglu, Ali Husnu; Kaboglu, Cihan; Uzunsoy, DenizThis study is concerned with the optimisation of the processing parameters for the selective laser melting (SLM) of pure copper. The influence of these parameters on the microstructure, density and mechanical properties of copper samples produced by SLM is investigated in detail. Taguchi analysis is used to assess the importance of key building parameters including layer thickness, laser spot size and hatch distance on density. In addition, ANOVA is used to describe the contribution of each parameter to the density. The results reveal that layer thickness is the most effective parameter on density with an impact rate of 88.86%. Contrary to this situation, it appears that the effect of laser spot size and hatch distance on the density is quite limited, with an impact rate of 2.57% and 0.10%, respectively. Optimum results, including a relative density of 95.4% and a hardness of 63 HV, are achieved under specific parameters: a layer thickness of 0.03 mm, a hatch distance of 110 mm and a laser spot size of 70 mu m. This study provides a valuable insight into SLM processing of pure copper and offers practical recommendations for optimising the parameters used.Öğe Determination of Production Parameters of CuCrZr Alloy by Selective Laser Melting Process(2025) Özkan, Burcu Aslı; Dilsiz, Yusuf; Ozates, Cem; Sevinç, Enes Furkan; Kaykılarlı, Cantekin; Kaboglu, Cihan; Uzunsoy, DenizCuCrZr alloy is a widely preferred material in the space, defense, and electronics industries with its high thermal and electrical conductivity properties. There are limited publications on the investigation of the tribological properties of CuCrZr alloys produced via the selective laser melting (SLM) method. In this study, it was aimed to optimize the process parameters and examine the effect of process parameters on density, hardness, microstructure, and tribological properties of domestically produced CuCrZr powder to be produced by the SLM method, which allows the production of complex structured parts. The optimum process parameters of the CuCrZr alloy were determined as laser power of 435 W, scanning speed of 350 mm/s, layer thickness of 0.02 mm, laser diameter of 0.1 mm, hatch distance of 0.1 mm, and energy density of 621.42 J/mm3. The relative density, hardness, COF, and wear values of the samples produced with the optimized SLM process parameters were obtained as 99% and 96 HV, 0.5520 ±0.1648, and 1.17x 10-4 (mm3/N.m), respectively.Öğe Development of High Purity, Few-Layer Graphene Synthesis by Electric Arc Discharge Technique(Polish Acad Sciences Inst Physics, 2018) Çotul, Uğur; Şam Parmak, Ebru Devrim; Kaykilarli, C.; Saray, O.; Colak, O.; Uzunsoy, DenizIn this study, high purity graphene nanoflakes (GNF) were synthesized by electric arc discharge technique. The arc discharge method is more advantageous than other graphene synthesis methods for producing cheap and good-quality graphene with minimum defects and not including dangerous chemicals. Because of this advantages, the arc discharge method is one step ahead of all graphene synthesis methods. In order to synthesize GNF, a DC electric arc discharge reactor was designed by our team. Electric arc discharge method based on a principle that provides a constant current between two high purity graphite electrodes to vaporize. After the arc discharge, nanoparticles accumulate on the inner surface of the reactor. The voltage stabilizer DC power source is used to create a current in the environment and the discharge usually occurs in a range 20-60 V. This current can be adjusted depending on the diameter of electrodes, the distance between electrodes and arc current varies between 100 and 150 A. Different characterization techniques such as the Raman spectroscopy, scanning electron microscope and transmission electron microscope were used to characterize the graphene layers synthesized by the arc discharge method. The L-D / L-G ratio was calculated as 0.66 while the L-G / L-2D was determined as 1.31. These values show that the purity of the synthesized graphene is compatible to that of commercially supplied graphene. Besides, the synthesized graphene has fewer layer than commercially supplied one. Transmission electron microscope observations confirmed the typical wrinkled feature of graphene.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 Experimental investigation of oligo cyclic compression behavior of pure epoxy and graphene-epoxy nanocomposites(Springer, 2021) Colak, Ozgen U.; Uzunsoy, Deniz; Bahlouli, Nadia; Francart, CharlesThe loading-unloading compression behavior and the oligo cyclic behavior of pure epoxy and graphene-epoxy nanocomposites are investigated since the systematic evaluation of the mechanical behavior under cyclic loading is of great importance in the development of damage characterization and fatigue models for polymer composites. High purity graphene nanoflakes (GNF) are synthesized by electric arc discharge method, and the manufacturing of graphene epoxy nanocomposites is done using solution blending. The structural characterizations of produced GNF are performed using several techniques such as transmission electron microscopy (TEM), Raman spectroscopy and Brunauer-Emmett-Teller (BET). Oligo quasi-static strain-controlled cyclic tests are performed at the elastic (or viscoelastic) region, around yield and after softening at the viscoplastic region. Comparing the behavior under compression, loading-unloading and oligo (repeated) cycled reveals that prehistory does not have much effect on the subsequent behavior. The change in the elasticity modulus during repeated cyclic compression is determined. It is observed that elasticity modulus decreases initially, and then, it progressively increases with the increase in applied maximum strain. Compared to epoxy, the yield stresses of graphene-epoxy decrease in both strain rates and a small increase in the elasticity modulus of graphene-epoxy is observed at low strain rate (1.E-4 /s).Öğe Fabrication of functionally graded few-layered graphene reinforced Al-4.5Cu alloy by powder metallurgy(Elsevier Science Sa, 2022) Borand, Gokce; Uzunsoy, DenizFunctionally graded materials (FGMs) are a class of innovative materials designed for needs that conven-tional composite materials cannot provide. Potential application areas such as aerospace, automobile, biomedical, defence, electrical/electronics, energy have begun to increase for the use of FGMs. Aluminium and aluminium alloys are preferred in these potential application areas for their physical and mechanical properties such as lightweight, high specific strength, high specific modulus and low thermal expansion coefficient. Graphene, one of the allotropes of carbon, is of great interest worldwide due to its superior mechanical, electrical and thermal properties. In this study, functionally graded graphene reinforced Al-4.5Cu alloy was produced by powder metallurgy. Few-layered graphene (FLG) with high purity, which was synthesized by the electric arc discharge (EAD) was reinforced to the Al-4.5Cu alloy powders that were produced by mechanical alloying as 0,0.1,0.2,0.3,0.5 and 0.7 wt%. These FLG reinforced Al-4.5Cu alloy composite powders considering FGM design with six layers, were pressed by stacking according to their various FLG contents and subjected to sintering at 570 degrees C and 590 degrees C for 3 h. It was observed that the FLG, which was graded according to their contents acting as a barrier between grains, was homogeneously dispersed in the Al-4.5Cu alloy matrix in optical and scanning electron images. According to the design of each FGM, an increase in the hardness by 37.11 % and 24.71 % was observed in the last layer compared to the first layer for sintering at 570 degrees C and 590 degrees C, respectively. (c) 2022 Elsevier B.V. All rights reserved.Öğe Few-layered graphene reinforced Al-10 wt% Si-2 wt% Cu matrix composites(Elsevier, 2022) Senyurt, Berk; Kucukelyas, Burak; Bellek, Mustafa; Kavak, Sina; Borand, Gokce; Uzunsoy, Deniz; Akcamli, NazliFew-layered graphene (FLG) reinforced Al-10 wt% Si-2 wt% Cu (Al10Si2Cu) matrix com-posites were fabricated via a powder metallurgical route. FLG powders were produced in an originally designed DC arc reactor via arc discharge method. Al, Si, Cu and FLG powders were subjected to high-energy ball milling at different durations to produce ternary Al alloy with homogeneously dispersed FLG, and bulk composites were fabricated via subsequent uni-axial compaction and pressureless sintering. The effects of varying FLG amounts and milling duration on the properties of the powder and bulk samples were investigated. The characterization of as-blended and mechanically alloyed (MAed) powders and their sin-tered forms were performed in terms of microstructural, thermal, mechanical, wear and corrosion properties. According to the results, the hardness values of the 4 h MAed Al10Si2Cu-xFLG composites were determined as 102, 154, 191 and 241 HV for x 1/4 0, 1, 2 and 5 wt%, respectively. Despite the greater hardness value of the Al10Si2Cu-5FLG-4h com-posite, its compressive strength was low due to its brittle structure. The highest compressive strength was shown by the Al10Si2Cu-1FLG as 463 MPa by an approximate increase of 53% compared to that of the Al10Si2Cu matrix. Moreover, the tribology tests showed that FLG addition (up to 2 wt%) improved the wear rate of the Al10Si2Cu matrix. However, a deteriorative effect of FLG on the corrosion resistance of the composites was determined.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Öğe Functionalized graphene-epoxy nanocomposites: experimental investigation of viscoelastic and viscoplastic behaviors(Springer, 2023) Colak, Ozgen U.; Birkan, Besim; Bakbak, Okan; Acar, Alperen; Uzunsoy, DenizIn this work, graphene-epoxy nanocomposites are produced for two different graphene fractions (0.1 and 0.5 wt%). Three-roll milling is used as the main strategy to achieve a homogeneous dispersion and prevent agglomeration. To improve the interfacial bonding between graphene nanoflakes (GNF) and epoxy matrix, GNFs are functionalized using Triton X-100 as a surfactant. The effectiveness of this functionalization is investigated using Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). These spectroscopy results show that the Triton X-100 molecules are successfully adsorbed on the surface of GNFs. To investigate the total viscoelastic-viscoplastic behavior of the nanocomposites, compression tests at three different quasistatic strain rates (1.E-1, 1.E-2, 1.E-3 /s), creep tests at two different stress levels and relaxation tests at two different strain levels are performed. The total time-dependent mechanical behavior of the produced nanocomposites is therefore characterized comprehensively. Elasticity-modulus values obtained from compression tests increased up to 29% and yield stress increased up to 18%. In creep tests, it is observed that the creep strain decreased 32% and 65% at 50 and 100 MPa stress levels, respectively, at 0.1 wt% functionalized graphene flakes (f-GNF)-epoxy nanocomposite. At the same time, with the addition of 0.1 wt% f-GNF to epoxy, during relaxation tests, the stress drop decreased up to 47% compared to pure epoxy at a 3.16% constant strain level. Both creep and relaxation resistance improved when compared to pure epoxy. This total improvement in the mechanical behaviors is explained with the effective dispersion of the GNFs and also a strong interface between the GNFs and the epoxy matrix.Öğe Grafen Nano Plaka Takviyeli Alüminyum Ve Alüminyum Alasım Esaslı Fonksiyonel Derecelendirilmis Malzemelerin Üretimi Ve Karakterizasyonu(2020) Uzunsoy, DenizFonksiyonel derecelendirilmis malzemeler (FDM); günümüzde modern teknolojinin yol açtıgı ihtiyaçlara göre, geleneksel kompozit malzemelerinin yeterli olmadıgı üstün performans özelliklerinin gerektirdigi durumlar için gelistirilmis ileri mühendislik malzemeleridir. Bu malzemelerin; havacılık, otomobil, biyomedikal, savunma, elektrik / elektronik, enerji, gibi potansiyel uygulama alanlarının mevcudiyeti giderek artmaya baslamıstır. Metal malzemeler içinde, Alüminyum ve Alüminyum alasımları; hafif, yüksek özgül mukavemet, yüksek özgül modül ve düsük termal genlesme katsayısı gibi fiziksel ve mekanik özellikleri için bu potansiyel uygulama alanlarda tercih edilmektedir. Karbonun allotroplarından biri olan grafen; üstün mekanik, elektriksel ve termal özelliklerinden dolayı, dünya çapında büyük ilgi görmektedir. Bu çalısmada; elektrik ark yöntemi ile saflıgı yüksek birkaç tabakalı grafenin üretimi gerçeklestirilmistir. Bu grafen nano plakalar (GNP), daha sonra, mekanik alasımlama yöntemi ile; Alüminyum (Al), Alüminyum-Bakır (Al4,5Cu) ve Alüminyum-Çinko (Al6Zn) alasım esaslı kompozit tozlarına %0, %0,1; %0,2; %0,3; %0,5 ve %0,7 oranlarında takviye edilmistir. Nihai ürün olan FDM?lerin yapısal ve mekanik özellikleri için, Al esaslı malzemelere takviye edilecek GNP?lerin, matriste homojen olarak dagılması önemlidir. Gerçeklestirilen partikül boyutu, X-Isınları Difraksiyonu (XRD) ve Taramalı Elektron Mikroskobu (SEM) analizlerine göre; GNP?lerin Al esaslı matriste homojen bir sekilde dagıldıgı görülmüstür. Elde edilen bu GNP takviyeli kompozit tozları, FDM tasarımları düsünülerek, altı katman olacak sekilde; GNP içeriklerine göre sırasıyla istiflenerek sekillendirilmisler ve 590°C?de 3 saat boyunca sinterleme islemine tabi tutulmuslardır. Üretilmesi basarıyla gerçeklestirilen yedi adet GNP takviyeli Al, Al4,5Cu ve Al6Zn alasım esaslı FDM numunelerinin; mekanik, yapısal ve tribolojik özellikleri incelenmistir. Uygulanan optik ve SEM görüntülerinde, GNP?lerin içeriklerine göre matriste homojen bir sekilde derecelendirildigi görülmüs ve GNP?lerin bir nevi bariyer görevi görerek matrise iyi bir sekilde baglandıgı tespit edilmistir. Buna baglı olarak her FDM numunesi tasarımlarına göre, GNP içeriginin yogun oldugu katmanlara dogru, sertlikte yaklasık %16 ile %48 arasında; sürtünme katsayısında ise yaklasık %2 ile %12 arasında bir iyilesme gözlemlenmistir.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 strain rate behavior of graphene-epoxy nanocomposites(Elsevier Sci Ltd, 2020) Colak, Ozgen U.; Bahlouli, Nadia; Uzunsoy, Deniz; Francart, CharlesThis work consists of the synthesis of high purity graphene nanoflakes (GNF), the manufacturing of GNF-epoxy nanocomposites and the mechanical characterization of the nanocomposite at high and quasi static strain rates, (2750/s - 1.E 5/s). GNF were synthesized by using the electric arc discharge technique. Thermogravimetry/ Differential Thermal Analysis (TG/DTA) of synthesized graphene reveals high purity and high crystallinity. Raman spectra and the broad Brunauer-Emmet-Teller (BET) specific surface area indicate that the synthesized graphene has several layers. Following the solution mixing manufacturing process of GNF-epoxy nanocomposites, the influences of strain rate on the mechanical behaviors are investigated under quasi static and dynamic loadings. High strain rate uniaxial compression tests (1270-2750/s) using Split Hopkinson Pressure Bar (SHPB) and quasi static compression tests (1.E-3 and 1.E-5/s) of GNF-epoxy with two graphene contents (0.1 and 0.5 wt %) are performed at room temperature. The maximum elasticity modulus achieved by the GNF-epoxy with 0.5 wt% at the strain rate of 2350/s corresponds to a 68% increase compared to the neat epoxy. The yield strength of the material is doubled under dynamic loading conditions compared to the quasi static loading.Öğe Investigation of Mechanical Properties of Graphene and Reduced Graphene Oxide Reinforced Epoxy Matrix Composites(Amer Soc Testing Materials, 2016) Topal, Emre; Şam Parmak, Ebru Devrim; Uzunsoy, Deniz; Cakir, O. ColakGraphene has generated great excitement in the scientific community due its unique mechanical and electronic properties, and also the availability of bulk quantities of graphene as both colloidal dispersion and powder. With the development of relatively high yield and defect-free synthesis methods, this exciting material is ready for practical application in the preparation of polymer nanocomposites. Here, we reported on the mechanical performances of epoxy nanocomposites which have been reinforced with exfoliated graphene nano platelet (GNP) and reduced graphene oxide (RGO) at a loading of 0 to 0.5 wt. %. A soft molding method was used for the preparation of epoxy nanocomposites. The reinforcing effects of GNP and RGO on epoxy resin were examined by tensile testing and dynamic mechanical analysis (DMA). The morphology of the epoxy/GO and epoxy/RGO nanocomposites were investigated using a scanning electron microscope (SEM). A significant improvement on mechanical properties of epoxy/GO and epoxy/RGO nanocomposites was observed at low GNP and RGO loading. Contrary to the literature, the ultimate tensile strength values have mainly decreased, although the Young's modulus has improved. Dynamic mechanical analysis has shown that with the addition of both GNP and RGO, storage modulus was significantly enhanced at 40 degrees C. The loss factor was almost not affected by both RGO and GNP loading. SEM investigation of the fractured surface indicates that GNP and RGO fillers are dispersed uniformly in the epoxy matrix.
