Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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.