Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Properties of Thin Film Lixlaytio3 Electrolyte for All-Solid State Li-On Batteries(Izmir Institute of Technology, 2016) Gülen, Sena; Aygün, Gülnur; Aygün Özyüzer, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyOne of the requirements of daily life, the most preferred rechargeable batteries are Li-ion batteries because of high energy, long life cycle and eco-friendly properties. Having high energy density, no memory effect and slow energy losses, these batteries have applications in portable electronic devices, power source for space vehicles, electric cars etc. Furthermore, there is a strong interest in all solid-state rechargeable lithium-ion battery research, because these batteries will replace the conventional liquid electrolyte Li-ion batteries due to use of non-combustible inorganic solid electrolyte, which has high safety and reliability. While the bulk ionic conductivity of La0.5Li0.5TiO3 (LLTO) produced by solid-state reaction is 10-3 S/cm, the total ionic conductivity of LLTO is 10-5 S/cm. Another way to increase ionic property is to dope the solid electrolyte with transition metals. The substitution of transition metal leads to decrease of the lattice parameter because of reduced average ionic radius. This causes increase of Li-ion content and also ionic conductivity. In this study, initially pure and Al doped targets were fabricated by using solid-state reaction after that the available targets are placed to the sputtering gun. When the all optimizations of the system were completed, pure and Al doped LLTO thin films were deposited by RF (radio frequency) magnetron sputtering technique on ITO coated soda lime glass substrates. While the thin film was been deposited, the substrate was heated at approximately 220 oC. For ionic conductivity measurement of the Al doped LLTO electrolyte, small circular Al contact regions were created on Al doped LLTO thin films by thermal evaporation system. Afterword the impedance spectra of the sandwich structure in a frequency range of 1 Hz - 200 MHz was recorded by using probe station. Thickness, the crystal structure, optical transmission, chemical compositions, surfaces and porosity of the thin films are investigated by surface profilometer, XRD, UV-Visible Spectroscopy, XPS, and Raman Spectroscopy respectively.Master Thesis Co Gas Sensor Applications of Fe Doped Calix[4] Arene Molecules(Izmir Institute of Technology, 2013) Özbek, Cebrail; Aygün, Gülnur; Aygün Özyüzer, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyInvisible and odourless carbon monoxide (CO) is one of the most toxic gas for respiratory systems. Therefore, the concentration level of carbon monoxide in the environment is extremely vital. In this thesis study, Calixarene molecules have been synthesized and the carbon monoxide selectivity and sensitivity of bare and iron doped calixarene molecules were measured by quartz crystal microbalance QCM technique and interdigitated electrodes with 3 ï m spacing. Calixarenes are promising compounds for sensing studies due to the well-designed cyclic structure, easily derivatization at both p- position of phenolic ring (upper rim) and phenolic-O (lower rim) as well as having diversely cavities which are a straightforward platform to form complex with molecules and ions. Quartz Crystal Microbalance is a powerful technique for nano scale determining the sorption properties of materials. According to Sauerbrey relation, the mass change on quartz crystal electrode cause a certain shift in the resonant frequency of vibrating crystal oscillator. This shift can be monitored using QCM method. In this study, a computer controlled QCM measurement system was developed for toxic gas detection. Iron doped calixarene based sensors were fabricated using drop-casting method on an AT-cut QCM gold electrode and interdigitated gold electrodes. The sensitivity and reproducible detection performances of prepared calixarene-iron doped calixarene thin films were measured under exposure of varying carbon monoxide for nitrogen and dry air used as desorption gas, respectively. The analysis of carbon monoxide sensitivity of iron doped calixarene is a new study for literature. This thesis study will guide future studies on this topic.