Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Carbon-Free Zinc-Air Batteries(01. Izmir Institute of Technology, 2024) Ebil, Özgenç; Ebil, Özgenç; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyZinc-air batteries are thought to be among the greatest substitutes for present energy storage systems because of their high energy densities (~1000 Wh/kg), affordability, and safety. However, zinc-air batteries face several problems, such as carbon corrosion, pore-clogging, and electrode passivation. The main cause of these problems is carbon in the air electrode. Therefore, carbon should be eliminated from the air electrode to enhance its performance. This thesis aims to synthesize an electrocatalyst for air electrodes for secondary carbon-free zinc-air batteries within the scope of the M-Era.NET 'AMAZE' project. Initially, manganese oxide was selected as an electrocatalyst and synthesized using a co-precipitation method with different parameters such as concentration, pH, temperature, and precursor materials. The best MnxOy was obtained with a solution pH and temperature of 9.5 and 60°C, respectively. The main precursor for the catalyst was KMnO4, with a ratio of KMnO4:HCl as 20:4 by volume. α-MnO2 with a surface area of 85.68 m2g-1 was obtained. In addition, onset overpotentials for oxygen reduction and oxygen evolution reactions with 650mV and 271mV, respectively, and a maximum current density of 10.5 mA.cm-2 were obtained. Nickel and cobalt additions were evaluated to improve ORR and OER activity. Catalyst with MnxNiyCozOt(1:0.5:0.5) composition performed better than other samples and had the highest surface area (172.06 m2g-1), ORR and OER potentials of 463mV and 700mV, respectively, and current density of 96 mA.cm-2.Master Thesis Doping Effect on the Anode Material Capability of 2d Bn Nanosheets(01. Izmir Institute of Technology, 2024) Elmacı Irmak, Nuran; Özdemir, Mustafa Coşkun; Irmak, Nuran Elmacı; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this thesis, the potential of BNN surfaces doped with Al, Cl, Co, Fe, Ga, O, P, and S atoms as anode materials in K, Li, Mg, and Na ion batteries was investigated. Semi-empirical tight-binding combined with meta-dynamics methods and density functional theory were utilized to discover these properties. The effects of doping atoms on the electronic structure and geometry of BNN surfaces were also studied. Changes in the electronic structure and conductivity were reported by examining the HOMO-LUMO orbitals and the energy differences between these orbitals. Using previously reported experimental data and examining similar studies from the literature, the atoms to be doped were chosen. While vacancies at the sites of boron atoms in single-layer boron-nitride nanosheets were observed, vacancies formed by nitrogen atoms were not observed, indicating that boron vacancies are much more likely for the doping position. So that doping was performed on the boron atom. The level of quantum calculations used in this work was validated using experimental data. B3LYP/def2-SVP/D4/gCP level of theory is used for all calculations for BNN-nanosheets studied in this thesis. The bond lengths and the HOMO-LUMO energy difference were found to be nearly the same as the experimental data. The conductivity of the BNN surface was increased with the doping process. However, significant improvements are followed by doping of cobalt, iron, and sulfur atoms with 35%, 34%, and 26% alteration, respectively. For a suitable battery manufacture, the potential anode material should offer structures with high theoretical specific capacity, low anode electrode voltage, and minimal volume change between charged/discharged states. It was observed that none of the doped-BNN surfaces involved in this study were suitable for the use of anode material in magnesium ion batteries. On the other hand, they can be used as a negative electrode for potassium, lithium, and sodium batteries. Their capacity in lithium is better than Na and K batteries. Our results suggest that most of the doped BNN surface with ions studied in this thesis could be used as anode materials. However, none of them owns a better battery capacity than classic lithium batteries.Master Thesis An Investigation of Electrochemical Stability of Zinc Electrodes for Battery Applications(Izmir Institute of Technology, 2014) Payer, Gizem; Çiftçioğlu, Muhsin; Ebil, Özgenç; Ebil, Özgenç; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyEnergy is the most important and inevitable requirement for humankind. The increasing energy demand has been connected with technological advances and the population growth. One of the most serious problems of the world is to provide sustainable energy. New alternative energy sources and renewable energy technologies have become notable research subjects due to wide availability of renewable energy sources in the world. However, most renewable energy sources do not provide uninterrupted energy to consumers. An economic, efficient and reliable energy storage technology is desperately needed. Therefore, academic research has focused on improving the capacity of electrochemical energy storage technologies. The main goal of this study is the preparation and characterization of zinc electrodes for battery applications using different zinc oxide powders with various morphologies and additives. Zinc oxide powders were synthesized with chemical precipitation method under different conditions (precursors, temperatures and aging times) in order to investigate their effects on ZnO morphology and on the performance of nickel-zinc battery. It was found out that the initial morphology of ZnO powder was not crucial for the electrochemical performance. Nickel-Zinc batteries with zinc electrodes prepared from commercial ZnO powder had discharge capacities around 247 mAhg-1 and showed slightly better performance compared to nickel-zinc batteries with zinc electrodes prepared from ZnO powders synthesized via chemical precipitation method. It was also determined that zinc electrode morphology was greatly affected by battery additives (PVA and PEG) and charging current density. The effects of some selected electrode additives (Ca(OH)2, PbO and PEG) on battery performance were also investigated. Zinc electrode with all additives showed improved electrochemical properties, such as higher discharge capacity (322 mAhg-1) and utilization ratio (48.86 %.)Master Thesis Development of Lead Foams for Automobile Batteries(Izmir Institute of Technology, 2012) Savacı, Umut; Güden, Mustafa; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyOpen cell lead foam samples with, 48, 55, 60, 65 and 74% porosity, were successfully prepared by powder metallurgy and casting using ammonium bicarbonate, silica beads and salt particles as space holder filler. Additionally electrowinning and powder compact foaming methods were tried. The resulting foam samples resembled open foam cell structure; each cell had interconnections with neighboring cells. Small size lead (II) fluoride precipitates were observed interior of cells in the foam samples prepared using silica beads, resulting from the reaction between silica and HF acid during space holder removal. The compression stress-strain curve of foam samples prepared by powder metallurgy showed a brittle behavior following the initial elastic, while foam samples prepared by casting showed elastic-plastic characteristic metal foam deformation; crushing of cell edges on the bent cell walls and tearing of thin cell walls. The collapse stresses of the prepared foams were fitted with scaling relations. The imperfections such as curved, wrinkled and missing cell walls, voids on the cell edges and cell walls and non-uniform density lead to discrepancy between experimental and theoretical scaling parameters.