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Öğe ALÜMİNYUM MATRİSLİ FARKLI SERAMİK TAKVİYELİ KOMPOZİTLERE GRAFEN İLAVESİNİN TERMAL VE MEKANİK ÖZELLİKLERE ETKİSİNİN İNCELENMESİ(2020-06) Polat, SafaBu çalışmada, basınçlı infiltrasyon yöntemi ile alüminyum matrisli seramik ve nano partikül takviyeli hibrit kompozitler üretilmiştir. Matris malzemesi olarak AA2024, Al-Si ve AA6061 olmak üzere üç farklı alaşım kullanılmıştır. Takviye olarak mikron boyutunda titanyum diborür (TiB2) ve bor karbür (B4C) kullanılırken, nano boyutta ise grafen (GNP) partikülleri kullanılmıştır. Bu kompozitlerde matris ve takviyelerin bileşenleri hacimce %50-%50 olarak ayarlanmıştır. Grafenin miktarı ise hacimce %0, 0,25, 0,5 ve 1 olarak ayarlanmıştır. Üretilen kompozitlerin karakterizasyonları için ilk olarak yoğunluk ölçümü daha sonra XRD, SEM ve TEM analizleri gerçekleştirilmiştir. Mekanik dayanımlarını deneysel olarak belirlemek için sertlik, basma ve aşınma testleri uygulanmıştır. Termal özelliklerini tespit etmek için ise her bir kompozitin termal genleşme katsayısı, ısı yayınımı, ısı kapasitesi ve termal iletkenlik katsayısı testleri yapılmıştır. Deneysel olarak tespit edilen bu sonuçlar aynı zamanda bazı teorik modeller kullanılarak hesaplanan teorik sonuçlarla da kıyaslanmıştır. Mekanik özelliklerin teorik olarak tespit edilebilmesi için yük aktarım mekanizması, Orowan-Looping mekanizması, termal uyumsuzluk mekanizması ve geometrik deformasyon gradyan mekanizmaları kullanılmıştır. Termal ilektenliğin teorik olarak hesaplanması için Hasselman-Jhonson modeli, Maxwell yaklaşımları ve akustik uyumsuzluk modelleri kullanılmıştır. Termal genleşme katsayılarının teorik olarak belirlenmesi için ise Kerner ve Turner modelleri kullanılmıştır. Elde edilen sonuçlara göre seramik partiküller arasında bor karbürün mekanik özellikler bakımından oldukça üstün bir davranış gösterdiği anlaşılmıştır. Öte yandan termal özellikler bakımından seramik partikül takviyesi ile alaşımların genleşme katsayılarının ve iletkenliklerinin önemli oranda düştüğü, grafen takviyesi ile iletkenlik değerlerinin arttığı gözlenmiştir. Teorik ve deneysel sonuçların ise nispeten birbiriyle uyumlu olduğu gözlenmiştir. Uyumsuz sonuçların ise genel olarak poroziteden kaynaklandığı sonucuna varılmıştır.Öğe Chemical synthesis of single-layer graphene by using ball milling compared with NaBH4 and hydroquinone reductants(Inst Engineering Technology-Iet, 2018) Niftaliyeva, Aysel; Pehlivan, Erol; Polat, Safa; Avci, AhmetGraphene materials especially single-layer graphene have been identified as a new generation of nanomaterials having various potential applications in material industries. However, the synthesis procedure of single-layer graphene to improve its quality, size and amount has been still under research for commercial applications. The graphene oxide (GO) is synthesised from graphite by Hummer's spontaneous approach which is the most suitable reaction for a large-scale production. For the single-layer graphene, in this work, GO was exfoliated by using a ball milling in an inert atmosphere. Owing to using ball milling as intermediate treatment degreased oxygen functional groups and number of layers, it facilitates to synthesise graphene. Sodium borohydride (NaBH4) and hydroquinone were used as a reductant for the chemical conversion of the exfoliated GO to graphene. The results showed that due to the strong reduction feature, both reducing agents can be applied in the graphene production. As a preferred reductant, hydroquinone can be successfully applied for the synthesis of the single-layer graphene compared to NaBH4. The obtained graphene particles by two different chemicals were characterised by various analytical techniques. The big difference in the structure of GO and graphene was observed in transmission electron microscope analysis.Öğe Comparison of microwave absorption properties between BaTiO3/Epoxy and NiFe2O4/Epoxy composites(Wiley, 2018) Akinay, Yuksel; Hayat, Fatih; Kanbur, Yasin; Gokkaya, Hasan; Polat, SafaMicrowave absorption properties of Epoxy/Nickel Ferrite (NiFe2O4) and Epoxy/Barium Titanate (BaTiO3) composites were investigated and compared in the 1-14 GHz. Epoxy/filler particles (NiFe2O4 and BaTiO3) composites were prepared with 85/15 mixture ratios via Ultrasonic Probe Sonicator method in solution. The complex permittivity (e '-e '') and permeability (mu '-mu '') of the composites have been measured at different microwave frequencies in 1-14 GHz via vector network analyzer (Keysight N9926A). The reflection loss (R-L) of composites was calculated and evaluated from camplex permitivity and permeability. The obtained results show that both composites exhibit the large R-L and broadband within the frequency range from 1 to 14 GHz for different thickness. Epoxy/BaTiO3 showed a better microwave absorption at the range of 6-7.2 GHz for 7 and 6 mm, at the range of 7.4-9.1 GHz for 5 mm. However, the Epoxy/NiFe2O4 exhibits the largest R-L and the widest bandwidth than those obtained from Epoxy/BaTiO3 composite. POLYM. COMPOS., 39:E2143-E2148, 2018. (c) 2017 Society of Plastics EngineersÖğe Dielectric properties of gnps@mgo/cuo@pvdf composite films(2021) Polat, SafaIn this study, it is aimed to develop dielectric materials with highdielectric coefficient for flexible capacitors. For this purpose, MgO/CuO nanoparticles were first synthesized by precipitation reactions. Then, theseparticles were added together with graphene nanoplates (GNPs) into PVDF indifferent compositions to form a composite mixture. After this process, flexiblecomposite films of 30 ?m thickness were formed with doctor blade and phaseinversion methods. In the characterization processes, it was determined thatMgO/CuO particles were successfully produced with an average size of 282 nm. Onthe other hand, the highest capacitance and dielectric coefficient values of thecomposite films were determined in the GNPs@MgO/CuO@PVDF sample as 2.8 nFand 42.6 at 100 Hz frequency, respectively. As a result, it was concluded that thedielectric properties were significantly improved with the use of graphene andmetal oxides together, and PVDF was very successful in terms of flexibility andbinding role.Öğe Dry Sliding Wear Behavior of Experimental Low-Cost Titanium Alloys(Taylor & Francis Inc, 2024) Rundora, Nicola R.; Klenam, Desmond E. P.; Polat, Safa; Mathabathe, Ntsoaki M.; van der Merwe, Josias; Bodunrin, Michael O.The high cost and potential toxicity associated with the common commercial Ti-6Al-4V alloy are major concerns against its continued use in the biomedical industry. Low-cost, less toxic titanium alloys have been developed as a possible alternative to Ti-6Al-4V. Because of the various wear processes that take place in the human body, it is imperative to have a good understanding of the wear properties and wear resistance of these alloys. This study, therefore, investigated the resistance to wear of the low-cost Ti-3Fe, Ti-4.5Al-1V-3Fe, and Ti-4.5Al-1V-3Fe alloys under dry sliding conditions in contrast to the common commercial alloy, Ti-6Al-4V. The findings revealed that among the tested alloys, Ti-3Fe exhibited the lowest resistance to wear as it displayed the highest coefficient of friction (0.55) and wear rate (5.55E-06 mm3/Nm). The Ti-4.5Al-1V-3Fe alloy demonstrated superior wear resistance compared to the rest of the alloys, including Ti-6Al-4V, as it had the lowest wear rate (4.27E-06 mm3/Nm) and wear volume (0.0026 mm3). Overall, the experimental alloys displayed very similar wear resistance to Ti-6Al-4V, making them promising commercial alloys that can replace Ti-6Al-4V in bioimplant applications. Abbreviations: COF: Coefficient of Friction; EDS: Energy Dispersive X-ray Spectroscopy; FEG-SEM: Field Emission Gun Scanning Electron MicroscopyÖğe Evaluation of thermal conductivity of GNPs-doped B4C/Al-Si composites in terms of interface interaction and electron mobility(Elsevier Science Sa, 2019) Polat, Safa; Sun, Yavuz; Cevik, Engin; Colijn, HendrikThe examination of the interactions between graphene and other components commonly used in thermal applications is an important approach for the development of materials with high thermal conductivity. For this purpose, graphene-doped boron carbide reinforced Al Si matrix composites were produced using semi-powder and pressure infiltration methods together. These composites were then characterized by SEM, TEM and XRD analysis. Thermal conductivity coefficients of these composites were determined experimentally by Laser Flash method. In order to examine the effect of phonon transfer on the experimental data, the interacting components were simulated, and the interfacial thermal conductivity was calculated with the acoustic mismatch model. Then, theoretical thermal conductivity of composites was calculated by Hasselman-Johnson model and Maxwell's approach. The electrical conductivity of the composites was measured by four-point probe method for electron mobility. As a result, experimental results were found to be slightly lower than the theoretical ones. This was affected by several different factors but the most important one is thought to be related to porosity.Öğe Evaluation of Weight, area, and Volumetric Specific Capacitance Performance of high Graphene Content ZnFe2O4 Electrode for Supercapacitors(Springer, 2024) Polat, Safa; Mashrah, Muwafaq; Maksur, AbdulganiThe main purpose of this study is to synthesize ZnFe2O4 (ZFO) on a nickel foam along with a high amount of graphene. For this purpose, the productions were carried out with high amounts of graphene by hydrothermal method. According to the characterization results, it has been observed that a high amount of graphene nanosheets (GNPs) were successfully adhered to the current collector surface without agglomeration using this method. The electrochemical results have demonstrated a 97% enhancement in the performance of the ZFO electrode with the addition of GNPs, reaching 622 mF/cm(2) at a current density of 1 mA/cm(2). Additionally, the weight and volumetric specific capacitances of this electrode were calculated as 415 F/g and 519 F/cm(3), respectively. Regarding the charging mechanism of this electrode, it was found to be 82% capacitive and 18% diffusion-controlled according to the Dunn method. The abundance of GNPs compared to those in the literature has increased the effectiveness of the diffusion-controlled charging mechanism.Öğe Fabrication of CuFe2O4@g-C3N4@GNPs nanocomposites as anode material for supercapacitor applications(Elsevier Sci Ltd, 2022) Polat, Safa; Faris, DanaThe aim of this study was to synthesize CuFe2O4 together with g-C3N4 and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe2O4 was successfully synthesized together with g-C3N4 and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm(2) at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm(2) and 300 mW/cm(2), respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications. The aim of this study was to synthesize CuFe2O4 together with g-C3N4 and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe2O4 was successfully synthesized together with g-C3N4 and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm(2) at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm(2) and 300 mW/cm(2), respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications.Öğe Fatigue behavior of composite to aluminum single lap joints reinforced with graphene doped nylon 66 nanofibers(Elsevier Sci Ltd, 2018) Polat, Safa; Avci, Ahmet; Ekrem, MurselIt is an important approach to prevent the damage mechanisms that cause sudden fractures during fatigue loading in bonding joints by modifying the matrix with nanostructured materials. The aim of this study is to examine the effect of graphene nanoplates (GNPs) doped nylon 66 (N66) nanofiber mats reinforcement on the fatigue life of composite to aluminum single lap joint. For this purpose, 1 wt%, 3 wt% and 5 wt% GNPs doped N66 nanofibers were produced by electrospinning method. The morphological characteristics, chemical bond structures and % crystallinity of these nanofiber mats was investigated by SEM, TEM, FTIR, DSC analysis. The fatigue tests of the bonding joints with single axis periodic cycle loading were performed at five different load levels as 20%, 30%, 40%, 50% and 60% of the maximum shear strength of each samples. Fatigue life of bonding joints was assessed by S-N curves plotted according to the fatigue results. Damage mechanisms of fractured surface in the bonding joints were investigated with the macro and micro images. The results show that, these composite nanofiber mats have increased the fatigue life of bonding joints in all case.Öğe Hydrothermal synthesis and electrochemical performance of GNPs-doped MgFe2O4 electrodes for supercapacitors(Elsevier, 2023) Mashrah, Muwafaq; Polat, SafaThis study sought to determine the effect of graphene on the electrochemical performance of MgFe2O4. The electrode preparation was done directly on the nickel foam surface using a hydrothermal technique. The crys-tallographic, morphological, and chemical configurations of the electrode components were investigated using XRD, FTIR, XPS, SEM, and TEM. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electro-chemical impedance spectrometry (EIS) were used to evaluate its electrochemical characteristics. The findings of the characterization demonstrate that MgFe2O4 was successfully synthesized with GNPs in a porous structure on a Ni foam surface. The electrochemical experiments show that the greatest specific capacitance (Cs) value found is 828 mF/cm2 at 1 mA current. At the same time, its stability after 1500 cycles at 4 mA was observed to be 136%, and its energy-power densities were calculated to be 28.75 mWh/cm2 and 200 mW/cm2. The Cs value in this study is roughly 242% higher than pure MgFe2O4 and 95% higher than MgFe2O4/GNPs in the literature, which is a significant effect of GNPs.Öğe Investigating the oxidation behavior of Mg-Zn alloy: Effects of heating rates, gas flow, protective atmosphere, and alloy composition(Chulalongkorn Univ, Metallurgy & Materials Science Research Inst, 2024) Saracoglu, Tugce Nur; Polat, Safa; Koc, Erkan; Mashra, Muwafaq; Najah Saud, Amir; Michalska-domanska, MartaMagnesium-zinc alloys offer promising lightweight properties but are prone to oxidation during high-temperature processing and usage. In this study, the oxidation behavior of Mg-Zn alloy was examined according to the inert gas type flow rate, heating rate and alloy amount. Initially, alloys were produced by adding zinc at weight percentages of 0.5%, 1.5%, and 2% using the casting method. The alloys were characterized using X-ray fluorescence (XRF), X-ray Diffraction (XRD), and scanning electron microscope (SEM) analyses, revealing the formation of dendritic Mg-Zn intermetallic within the alloy. The oxidation behavior of these alloys was examined via differential thermal analysis (DTA) and thermogravimetric analysis (TGA), considering factors such as heating rate, gas flow rate, type of protective atmosphere, and amount of alloying element. The results indicated that the onset temperature of oxidation decreased with increasing heating rate. The effect of gas flow rate varied depending on the heating rate and the type of gas. Under a nitrogen atmosphere, conditions with a heating rate of 20 degrees C center dot min-1 and a gas flow rate of 5 cm3 center dot min-1 resulted in the least oxidation. In an argon atmosphere, a gas flow rate of 5 cm3 center dot min-1 was found to be sufficient to prevent oxidation. However, at a gas flow rate of 1 cm3 center dot min-1, a heating rate of 20 degrees C center dot min-1 was more effective in preventing oxidation. The alloying element (zinc) likely reduced oxidation, particularly at the 1.5% addition level, possibly due to the formation of intermetallic compounds.Öğe Investigation of wear and corrosion behavior of graphene nanoplatelet-coated B4C reinforced Al-Si matrix semi-ceramic hybrid composites(Sage Publications Ltd, 2019) Polat, Safa; Sun, Yavuz; Cevik, Engin; Colijn, Hendrik; Turan, M. EmreThe present study aims to produce graphene nanoplatelet-coated B4C ceramic particle using semi-powder method and to investigate the effect of graphene nanoplatelets on wear and corrosion performance of Al-Si-based metal matrix hybrid composites. For this purpose, first graphene nanoplatelets at different ratios (0.25, 0.5, and 1 vol.%) were coated to the surfaces of B4C particles and then the Al-Si alloy was infiltrated into the reinforcements by gas pressure infiltration method. The characterization of graphene nanoplatelet-coated B4C powders and its composites was carried out by X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and transmission electron microscope analysis. Tribological properties were investigated by reciprocating ball-on-flat method under three different loads (10-20-40 N) in a dry environment. The corrosion resistance was carried out with Tafel polarization method in 3.5% NaCl solution. Characterization results show that graphene coated on the B4C surface was successfully achieved by semi-powder method. After infiltration process, a new phase formation was not observed, but porosity increased with the increase of graphene content. When the boron carbide surface was coated with 0.5vol.% graphene, it was determined that the specific wear resistance increased by 55% and the corrosion resistance decreased by 12%.Öğe Microstructure and synergistic reinforcing activity of GNPs-B4C dual-micro and nano supplements in Al-Si matrix composites(Elsevier Science Sa, 2019) Polat, Safa; Sun, Yavuz; Cevik, Engin; Colijn, HendrikThe aim of this study is to investigate the mechanical effect of graphene nanoparticles and boron carbide microparticles together on Al-17Si alloy. For this purpose, graphene nanoparticles were firstly attached to boron carbide surfaces by semi-powder method. The Al-17Si alloy was then infiltrated into these particles. Systematic characterization of produced composites, microstructure investigations, strengthening mechanisms were investigated respectively. The composites were systematically characterized by XRD, DSC, SEM and TEM. Their mechanical strength was determined experimentally by compression test. In addition, the contribution of these reinforcements to strength by using some models has been calculated theoretically and the results have been associated with the microstructure. According to these results, the yield strength of pure matrix was increased from 185 MPa to 547 MPa by increasing 195% with the reinforcement of 0.5 vol% GNPs thorn B4C at most. This result is also the case where the theoretical and experimental are the most compatible. In this case, it is thought that load transfer mechanism and dislocations make the most positive contribution while porosity makes the most negative effect. (C) 2019 Elsevier B.V. All rights reserved.Öğe Production of znfe2o4 doped carbon cloth-based flexible composite electrodes for supercapacitors(2021) Polat, SafaIn this study, it is aimed to develop carbon cloth-based (CC) ZnFe2O4 doped super capacitor electrode. For this purpose, cotton fabric was first carbonized in a nitrogen atmosphere at 800 °C and turned into a conductive substrate. Then, metal oxide with ZnFe2O4 spinel structure was synthesized from the chlorinated compounds of Zn and Fe elements by hydrothermal method on carbon fabric surfaces. In the results of the XRD analysis of the produced electrodes, it was determined that the ZnFe2O4 structure was successfully synthesized, but some Fe3O4 and ZnO structures were formed. In the SEM analysis, it was observed that the synthesized structures were formed to completely cover the CC surfaces. Three-electrode system and 3 M KOH were used for the electrochemical performance of the electrodes. Specific capacitance measurements were performed starting from 5 mV/s scanning speed to 100 mV/s scanning speed. According to the results obtained, it was determined that the highest capacitance value was 66 F/g at 5 mV/s speed, the energy density was 2.95 Wh/kg, and the amount of stored charge was 159 C. As a result, it can be said that flexible supercapacitors have been successfully developed, but higher capacitance values can be achieved by optimizing the production conditions.Öğe Reciprocating dry sliding wear behaviour of BN@MXene@AA7075 composites(Sage Publications Ltd, 2024) Karaca, Muhammet Mevlut; Polat, Safa; Esen, IsmailAluminium alloys are preferred in various fields, especially in the aviation and automotive sectors, due to their lightweight and durable nature. However, their usage is limited due to weak tribological properties such as low hardness and high adhesion tendency against steel. In order to overcome this deficiency, this study aimed to develop AA7075 matrix composites reinforced with BN and MXene. The productions were conducted by powder metallurgy method with these reinforcements in different ratios, both together and separately. The produced composites were characterized primarily by XRD and SEM analyses, followed by measurement of density and porosity values. Wear tests were conducted using the reciprocating ball-on-flat method, at a frequency of 3 Hz, a sliding distance of 100 m, and a stroke distance of 5 mm, with Inox steel ball. The highest improvement in wear rate was realized under 5 N load at 5 wt.% reinforcement ratios of 48% and 42% for BN and MXene, respectively. When 2 wt% BN and MXene reinforcements were applied together, the improvement rate remained around 34%. It can be said that BN and MXene show promising results by providing significant improvements compared to their counterparts in the literature, with MXene especially warranting further investigation.Öğe Spring assisted triboelectric nanogenerator based on sepiolite doped polyacrylonitrile nanofibers(Elsevier, 2021) Ozen, Abdurrahman; Ozel, Faruk; Kinas, Zeynep; Karabiber, Abdulkerim; Polat, SafaTriboelectric nanogenerators (TENGs) are suitable devices for converting small mechanical movements into electrical power. TENGs are inexpensive, easy to manufacture, and have a wide range of uses, but their energy efficiency is low for use in commercial products. In this study, sepiolite doped polyacrylonitrile (PAN) and ethyl cellulose/Polyvinylpyrrolidone nanofibers are tested as negative and positive dielectric layers, respectively, to improve output performance of TENGs. In the experiments, spring assisted TENG was employed to obtain higher power density and electrospun technique was used to produce flexible nanofiber dielectrics. According to the results, different sepiolite contents (1, 3, and 5 wt%) increase tribo-potential of PAN nanofiber by expanding the surface area and dielectric constant of the dielectric layers. The optimized electrical performance are 486 V open circuit voltage and 45 mW (28.125 W/m(2)) maximum power density for 3 wt% sepiolite doped PAN nanofiber. The proposed nanofibers can be efficiently used as the dielectric layers of contact mode TENGs to supply self-powered electronic devices.Öğe Sustainable Cauliflower-Patterned CuFe2O4 Electrode Production from Chalcopyrite for Supercapacitor Applications(Mdpi, 2023) Mbebou, Moctar; Polat, Safa; Zengin, HuseyinThe primary purpose of this study was to produce an ore-based high-capacity supercapacitor electrode. For this, chalcopyrite ore was first leached with nitric acid, and then metal oxide synthesis was carried out immediately on nickel foam using a hydrothermal technique from the solution. Cauliflower-patterned CuFe2O4 with a wall thickness of about 23 nm was synthesized on the Ni foam surface, characterized by XRD, FTIR, XPS, SEM, and TEM investigations. The produced electrode also displayed a feature of a battery-like charge storage mechanism with a specific capacity of 525 mF cm(-2) at 2 mA cm(-2) current density, energy of 8.9 mWh cm(-2), and a power density of 233 mW cm(-2). Additionally, even after 1350 cycles, this electrode still performed at 109% of its original capacity. The performance of this finding is 255% higher than that of the CuFe2O4 in our earlier investigation; despite being pure, it performs far better than some of its equivalents in the literature. Obtaining such performance from an electrode made from ore indicates that the use of ore has a lot of potential for supercapacitor production and property improvement.Öğe Synthesis and electrochemical performance of MgFe2O4 with g-C3N4 on Ni-foam as composite anode material in supercapacitors(Springer, 2022) Polat, Safa; Mashrah, MuwafaqThis study aimed to improve the electrochemical performance of MgFe2O4 (MFO) by combining it with g-C3N4 (g-CN). The hydrothermal process was used to produce electrodes directly on the nickel foam surface. XRD, FTIR, SEM, and TEM analyses were made to describe the electrodes in detail. CV, GCD, and EIS measurements were performed electrochemically at various scanning rates and current densities. According to the findings, g-CN-MFO electrode was successfully synthesized in spongy structure on Ni-foams. The areal capacitance (Ca) of g-CN-MFO was measured as 600 mF/cm(2), which is 152% higher than MFO. At the same time, the energy and power densities of g-CN-MFO were calculated to be 13.3 mWh/cm(2) and 200 mW/cm(2) at 1 mA, respectively. EIS results showed that this increase was probably due to easier diffusion of electrolyte ions onto the electrode surface. As a result, the g-CN-MFO electrode can be considered a promising anode material for supercapacitors due to its low cost, ease of fabrication, and strong electrochemical performance.Öğe Synthesis of Zinc Oxide Nanorods from Zinc Borate Precursor and Characterization of Supercapacitor Properties(Mdpi, 2023) Lefdhil, Chikh; Polat, Safa; Zengin, HueseyinThe synthesis of zinc oxide (ZnO) was accomplished from zinc borate (Zn3B2O6) minerals to be used as electrodes in supercapacitor applications. The concentrations of obtained zinc (Zn) metal after treatment with hydrochloric acid (HCl) were determined by atomic absorption spectroscopy (AAS). Direct synthesis of ZnO on a nickel (Ni) foam surface was conducted by employing the hydrothermal technique using a solution with the highest Zn content. The results showed the successful synthesis of ZnO nanorods on the surface of Ni foam with an average wall size of approximately 358 nm. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements revealed that the synthesized electrode exhibited battery-type charge storage characteristics, reaching a maximum specific capacitance of approximately 867 mF & BULL;cm-(2) at a current density of 2 mA & BULL;cm-(2). Additionally, the energy and power densities of the electrode at a current density of 2 mA & BULL;cm-(2) were calculated as 19.3 mWh & BULL;cm-(2) and 200 mW & BULL;cm-(2), respectively. These results exhibited promising performance of the single-component electrode, outperforming the existing counterparts reported in the literature.Öğe Theoretical modeling and optimization of interface design to improve thermal conductivity in Mg-Dia composites(Elsevier Sci Ltd, 2022) Polat, SafaThis study aimed to theoretically optimize the Mg-Dia interface with components of different types and thicknesses to increase the thermal conductivity of diamond-doped magnesium matrix composites. Acoustic mismatch (AMM), diffusion mismatch model (DMM) and differential effective medium (DEM) models were used for TC calculations of the designed composites. According to the results, TiC, SiC, ZrC, and B4C carbides are the components that can increase the TC value up to 529 W/mK; however, most of (t)hem, except SiC, negatively affected the TC value with the increase in thickness. B and Cr elements also provided higher TC values compared to other elements. Except for the Cr-CrC3C2 conversion, all other carbide conversions had a positive effect on TC. MgO, Al2O3 and ZrO oxides alone or together with MgO increased the TC value up to 525 W/mK. Apart from this, MgO had a negative effect on all components except B or B4C. As a result, Mg-MgO-B-Dia was observed as the component providing the most stable TC value even if the thickness increased. This is thought to be due to less scattering during heat transfer between components with close Debye temperatures. It has also been understood that these results can deviate 29% from the experimental one even with the best method.