Lityum hava pilleri için Ag/Mg katkılı anot malzemelerinin geliştirilmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Benzinle kıyaslanabilir bir spesifik enerji yoğunluğu olan, oksijen kütlesi hariç 11,5 kWhkg-1 teorik spesifik enerjiye sahip lityum-hava pilleri büyük ilgi çekmektedir. Bu değerde yüksek bir enerji yoğunluğuna sahip piller, gelişmiş elektrikli araçlar için güç kaynağı olma potansiyeline sahiptirler. Ancak lityum anot yüzeyinde dendrit oluşması nedeniyle çevrim verimliliğinin az olması gibi birçok zorlukla karşılaşılmaktadır. Bu tezde lityum-hava pillerinde kullanılan lityumun gümüş ve magnezyum ile alaşımlandırılarak dendrit oluşumunu önlemek ve çevrim ömrünü ve kararlılığını artırmak amaçlanmıştır. Lityum hava pillerinde kullanılan lityum anoda eklenen gümüş ve magnezyum miktarlarının elektrokimyasal davranışa etkisi özellikle incelenmiştir. Başlangıç malzemesi olarak ultra ince Li tozları ile gümüş ve magnezyum metalleri kullanılmıştır. Mekanik alaşımla yöntemi kullanılarak Li-Ag ve Li-Mg alaşımları üretilmiştir. Yüksek enerjili bilyalı öğütme oda sıcaklığında ve argon atmosferi altında yapılmıştır. Üretilen numunelerin fiziksel özellikleri X-ışınları kırınımı (XRD) ve taramalı elektron mikroskobu (SEM) ile incelenmiştir. Lityumun ve lityum alaşımlarının elektrokimyasal analizleri de Swagelok tipi hücrede elektrolit olarak TEGDME içerisinde 1 M LiPF6 tuzu, katot olarak GDL (gaz difüzyon tabakası) ve anot olarak üretilmiş olan Li-Ag ve Li-Mg tozları kullanılmıştır.Lithium-air batteries have attracted great interest due to theoretical specific energy of Li-air excluding oxygen is 11.5 kWhkg−1, the value of which is comparable with that of gasoline/air device. This kind of battery which has as high as this energy density has the potential to be the power source for the advanced electric vehicles. However there are a lot of challenges, one of which is low cycleability of lithium-air batteries because of dendrite formation on top of the lithium anode. The aim of this thesis is to alloy lithium with silver and magnesium powders mechanically for suppressing dendrite formation and enhancing the cycleability and stability of lithium air batteries. The effect amount of adding the silver and magnesium into the lithium anode especially on the electrochemical behavior of lithium anode for lithium-air batteries is investigated. Ultra-fine powders of the Li and silver or magnesium metals were used as starting materials. Li-Ag or Li-Mg alloys were synthesized as an anode material using mechanical alloying process. The high energy ball milling was performed under an argon atmosphere at room temperature. The physical characterizations of the produced anodes were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. Electrochemical analysis of the lithium and lithium alloys were carried out by using a Swagelok-type cell with 1 M LiPF6 in TEGDME as electrolyte and GDL (gas diffusion layer) as cathode and produced Li-Ag and Li-Mg powders as anode

Structural and sliding wear properties of Ag/Graphene/WC hybrid nanocomposites produced by electroless co-deposition

The main objective of this work has been the deposition of hybrid silver/WC/Graphene nanocomposites and characterization of their tribological behaviors. Graphene as a conductive solid lubricant additive was introduced into Ag matrix from the electrolytes in which submicron WC particles and Graphene nanosheets were suspended. The main purpose for two different reinforcements is to improve both wear and friction properties. The friction and wear behaviors of Ag/WC/Graphene coatings on the metal substrates against M50 steel ball were tested under dry sliding wear conditions. Comprehensive characterizations were performed using Scanning Electron Microscopy, X-Ray Diffraction analysis, Raman spectroscopy and 3D profilometry facilities. Tribological test results have revealed that even small amounts of Graphene addition are able to drastically improve the antifriction and antiwear properties of hybrid nano Ag matrix composites. A possible explanation for these results is that the co-deposition of Graphene not only provides an enhanced effect for nanocomposites to produce better wear resistance, but also forms a local protective layer on the contact surfaces to reduce the friction. The investigation shown that hybrid reinforcements of sub-micron WC and Graphene hold great potential applications as effective load bearing and solid lubrication for Ag matrix composites and possibly for similar alloys. (C) 2015 Elsevier B.V. All rights reserved

A novel approach for wear and corrosion resistance in the electroless Ni-P-W alloy with CNFs co-depositions

Electroless nickel-based depositions have been considered as one of the industrially effective methods because of their deposition uniformity, good corrosion properties, high wear resistance and good electrical properties. In this study, Ni-P-W-CNF composite depositions were performed by electroless method on an aluminum substrate from an acidic hypophosphite at different sodium tungstate and CNFs contents. The main aim of this study was to deposit Ni-P-W-CNF composites and characterization of their morphology, tribological and corrosion behaviors. The Ni-P-W-CNF composite depositions were characterized using Scanning Electron Microscopy, X-Ray Diffraction analysis and Raman spectroscopy. The tribological behaviors of the Ni-P-W-CNF composite depositions were evaluated with reciprocating ball-on-disk test in dry conditions. The corrosion resistance behavior of the Ni-P-W-CNF composite depositions carried out by means of Tafel Polarization methods in 3.5% NaCl solution. The effects of CNFs and tungsten on the tribological and corrosion behaviors of the composite depositions were discussed. It was found that the best wear and corrosion resistance has been obtained Ni-P-W-CNF electroless co-deposition containing 100 g/L Na2WO4 and 0.2 g/L CNFs in the deposition bath

Tribological Properties of TiO2 Reinforced Nickel Based MMCs Produced by Pulse Electrodeposition Technique

Nickel-TiO2 composite coatings were prepared under pulse current conditions by co-deposition of TiO2 particles and nickel from a Watts type bath. The effect of TiO2 particle concentration was studied on microhardness, friction coefficient and wear resistance. The morphological features and the structures were studied by scanning electron microscope, X-ray diffraction analysis and 3D profilometry facilities. A wide particle size range (between 95 and 140 nm) was chosen to provide a high dispersion and load bearing ability for the co-deposited layers. It was determined that increasing the particle concentration in the electrolyte dramatically increased the co-deposited TiO2 particles in the coating. The results showed that the high concentration of TiO2 particles in the electrolyte yielded the highest amount of particles co-deposited in the plating layer. The influence of the co-deposited TiO2 volume on microstructure and tribological properties in the coating were investigated. The wear tests were carried out using a constant load by a reciprocating ball-on disk configuration. Wear loss and friction coefficients of Ni/TiO2 composites were decreased by increasing TiO2 content in the electrolyte because of the increasing content of TiO2 in the deposited layer. The change in wear mechanisms by changing TiO2 content was also determined

Improved Electrochemical Performance of Lithium Oxygen Batteries with N-methyl-2-pyrrolidone Based Composite Polymer Electrolytes

The stability and reversibility of the electrolytes is a significant limitation for cycle life performance of Lithium oxygen (Li-O-2) batteries. Therefore, the traditionally used ionic/liquid electrolytes need to be modified with ceramic or polymer fillers to reach stable and reversible polymer composite electrolytes. Here, to increase reversibility and stability of the N-methyl-2-pyrrodione (NMP) based electrolytes, which is known as an ideal candidate to overcome electrolyte difficulties due to its attractive properties such as low flammability, viscosity and comparatively low toxicity, polymer supported liquid composites were synthesized using poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) polymers and aluminum oxide (Al2O3) nano ceramic powders. By preparing a suitable composite polymer electrolyte using a NMP aprotic solvent, we demonstrate a Li-O-2 battery which is capable of operating over 35 cycles with a capacity of 2.54 mAh. This study proved that ionic conductivity and over potential of the cell was greatly improved with the addition of polymer and ceramic additive in NMP based electrolyte. Moreover, our composite polymer electrolytes provided highly reversible Li-O-2 reaction during charging/discharging and prevented clogging of the porous structure of the cathode which is beneficial to increase the cycle performance. (C) 2016 The Electrochemical Society. All rights reserved

Electrolytic coating of Sn nano-rods on nickel foam support for high performance lithium ion battery anodes

In this study, Sn was electrodeposited onto the porous nickel foam substrate under pulse electrodeposition conditions. Pulse electrodeposition was carried out at three different peak current densities of 10, 20 and 40 mA/cm(2) for 5 min in a pyrophosphate bath containing 40 g/L SnCl2 center dot 2H(2)O,164 g/L K4P2O7 and 19 g/L Glycin. Surface morphology of Sn-Ni foam electrodes were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to understand the elemental surface composition of composites. X-ray diffraction (XRD) analysis was carried out to investigate the crystal structure of Sn-Ni foam electrode. The electrochemical performances of electrodes were investigated by charge/discharge tests, cyclic voltammetry experiments and the ac impedance technique. The results yielded encouraging discharge capacities since Ni foam behaves as a stress buffering layer as well as an electronic conductivity component. (C) 2016 Elsevier B.V. All rights reserved

Optimization of pulsed electro co-deposition for Ni-B-TiN composites and the variation of tribological and corrosion behaviors

In this study, novel Ni-B-TiN metal matrix composite (MMC) coatings were successfully deposited using a nickel Watts bath containing TiN nanoparticles by Pulse Electrodeposition (PED) method. The main purpose is to provide the deposition optimization of Ni-B-TiN and its morphology, mechanical, tribological and corrosion properties of composite coatings. The suspension of the TiN particles in the electrolyte has been studied by zeta potential technique. Deposition morphologies on the coating surface and cross sections, worn surfaces were analyzed with scanning electron microscopy (SEM). Phase structures of the deposited layers were analyzed with X-ray diffraction (XRD), nanoindentation hardness tests were performed on the cross-sections of the depositions and reciprocating ball-on disk tests were carried out for tribological measurements. Corrosion properties of the depositions were studied in 3.5 wt% NaCl solution and electrochemical impedance spectroscopy (EIS) was also applied. Microstructures, coating thickness, mechanical properties, tribological and corrosion tests have demonstrated that the-co-depositions of Ni-B-TiN composite coating mechanisms have governed by Gugliemi's absorption model. According to this model and experimental results, it has been demonstrated that the particle content in the electrolyte of 15 g/L is the optimum concentration to obtain best properties

Graphene oxide/alpha-MnO2 nanocomposite electrodes produced using planetary ball milling for Li-O-2 batteries

Graphene Oxide (GO)/alpha-MnO2 nanocomposite air breathing cathodes were prepared using mechanical alloying method. For preparation of GO/alpha-MnO2 nanocomposite cathodes, GO was produced by Hummer's method and alpha-MnO2 nanowires were synthesized using microwave hydrothermal synthesis. In order to investigate effect of GO on the electrochemical performance of the GO/alpha-MnO2 cathodes, different amounts of GO (10wt.%, 30wt.%, 50wt.%) were dispersed in the composite cathode. Electrochemical performances of the composite cathodes were tested using ECC-Air test cell. Among the produced composite cathodes, GO/alpha-MnO2 composite cathode containing 50 wt.% alpha-MnO2 showed 380 mAh/g discharge capacity after 30 cycles. (C) 2015 Elsevier Ltd. All rights reserved