Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Access type: Open accessSubject: search.filters.subject.Electrochemical Impedance Spectroscopy

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  • Master Thesis
    Investigation of Microbial Biofilm Formation Using Electrochemical Impedance Spectroscopy and Equivalent Circuit Modelling
    (01. Izmir Institute of Technology, 2021) Kuş, Anılcan; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 01. Izmir Institute of Technology; 04. Faculty of Science
    Bacterial biofilm is like a cooperative form of planktonic bacteria that colonize to acquire more nutritious and become resistant to surroundings. The communal organization results from the connection of bacteria by polysaccharides, lipids, or the extracellular matrix, which can provide a protective environment for living cells and communicate between them or allow specific types of chemicals inside through the matrix. 60%-80% of the infections are known to be biofilm-related. Bacterial biofilms are more resistant to antibiotics, and treating them with the wrong antibiotics might result in a thicker biofilm. In order to overcome these difficulties and researching new treatments for biofilm inflammation understanding the formation process is essential. For this manner, Electrochemical Impedance Spectroscopy (EIS) has potential uses in various fields such as biosensors, corrosion studies, healthcare owing to its facile operation and affordable devices to conduct electroanalysis. EIS calculates the excitation voltage and current generated with the oscillating frequency. Developing impedimetric methods are gaining attention due to the operation being label-free. Considering its label-free nature, EIS is a possible candidate to explain the electrodynamics of living systems such as cell-matrix interaction, biofilm formation in vitro. Detection of those is essential to prevent infections and to develop medical needs to cure them. The thesis focuses on understanding the electrodynamics of bacterial biofilm formation via electrochemical methods such as square wave voltammetry (SWV), Open Circuit Potential (OCP), and EIS. After carrying out the experiments, time-dependent circuit models for EIS were built, and the data were extracted to demonstrate changes in the bacterial system.
  • Master Thesis
    Effect of Aging Electrolyte and Organic Coating Type on the Corrosion Mechanism of Tinplate
    (Izmir Institute of Technology, 2019) Yıldırım, Koray; Çağlar, Başar; Kızılkaya, Ali Can; Kızılkaya, Ali Can; Çağlar, Başar; 03.06. Department of Energy Systems Engineering; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Market share of the can coating industry was 2 billion dollars in 2018 globally. A large portion of this market is focused on protecting valuable goods such as foods and cosmetics. Recent bans on the Bisphenol A(BPA) created a BPA-free coating demand due to the high portion of BPA based coatings in the industry such as epoxy. A conventional epoxy based (EP) can coating was compared with a new design of BPAfree polyester coating(PE). Atomic Force Microscopy(AFM), Scanning Electron Microscopy(SEM), Electron Dispersive Spectroscopy(EDX), Electrochemical Impedance Spectroscopy(EIS), Direct Current(DC) Polarization were used to investigate degradation. Industrial and model tinplate samples are compared with surface investigation methods. AFM results indicate the surface composition difference. To investigate bare tinplate corrosion, a mixture of acidic electrolyte was prepared and compared with other conventional aging electrolytes, containing mono acids. The electrolyte prepared from mixed acids was found to have the highest detinning abilities. Therefore, coated samples were aged with this mixed acid solution electrolyte. EIS results indicated that the type of electrolyte alters the corrosion mechanism, indicated by the observance of different time constants at different time scales. During immersion tests, EP based coatings showed better corrosion resistance as shown by higher impedance at low frequency, higher coating resistance and lower capacitance values. However, after sterilization, polyester coated samples showed better corrosion protective abilities (indicated by lower amount of corrosion products and higher impedance values) compared to the epoxy sample even though AFM measurements indicated that it had larger pore sizes after aging compared to epoxy sample. These results are attributed to the larger electrochemical area and higher diffusion properties of EP coatings, obtained after modelling of EIS data.