Master Degree / Yüksek Lisans Tezleri

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Access Right: Open AccessSubject: search.filters.subject.Solid oxide fuel cells

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  • Master Thesis
    Coating of La0.3sr0.7fe0.7cr0.3o3-Δ and La0.3ca0.7fe0.7cr0.3o3-Δ Cathode Layers on Gdc Ceramics by Electrospray Deposition (esd)
    (01. Izmir Institute of Technology, 2023) Erğen, Emre; Akkurt, Sedat; Ahmetoğlu, Çekdar Vakıf; Akkurt, Sedat; Ahmetoğlu, Çekdar Vakıf; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    High temperatures are needed to rapidly transfer of oxygen ions between layers during the chemical energy to electrical energy conversion in solid oxide fuel cells (SOFC). Nevertheless, intermediate-temperature SOFCs are preferred to increase their lifetime and reduce maintenance and production costs. The performance of IT-SOFCs depends particularly on the microstructure and electrochemical properties of the cathode layer. In this study, cobalt-free La0.3Sr0.7Fe0.7Cr0.3O3-δ and La0.3Ca0.7Fe0.7Cr0.3O3-δ cathode layers were coated on GDC ceramic pellets by ESD method. The aim of the thesis was to have better structural and electrochemical properties of coatings than the literature. ESD provides the atomization of liquids with the help of electrical forces. ESD is an effective method for forming coatings with desired compositions. By changing ESD parameters, different structural properties such as reticular, cracked, and dense were obtained. Reticular structures are useful for easier oxygen transfer with increased surface area. Effects of parameters were examined by Plackett-Burman design, and the most effective parameter was found as flow rate. The quality of the coatings was evaluated by quantitative scoring. The 16th sample, which was coated with solution E, got the best score. Parameters of 16th sample were used in the investigation of the effects of different solutions on the coatings. 8 different solutions named A to H were prepared with different solvents and precursor salts. Coating by solution E shows better EIS results than the literature as 0.22 Ω.cm2. Coatings by solution G and A show close values to the literature as 0.29 Ω.cm2, and 0.34 Ω.cm2, respectively.
  • Master Thesis
    Investigation of the Formation of La1-Xsrxc1 Cathode Materials and Their Interaction With Electrolyte Substrates for Potential It-Sofc Applications
    (Izmir Institute of Technology, 2013) Sındıraç, Can; Akkurt, Sedat; Akkurt, Sedat; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Cathode layers of IT-SOFC (Intermediate Temperature Solid Oxide Fuel Cell) materials are investigated to find out the reactions leading to the formation of La0.6Sr0.4Co0.8Fe0.2O3 and La0.6Sr0.4Co0.2Fe0.8O3 on the surface of either ZrO2 or CGO (Cerium-Gadolinium Oxide) electrolyte substrates. Precursor salt powders were blended, compressed and placed on discs of sintered ceramic electrolytes before being heated in a laboratory furnace at 800oC for 1h. Almost all combinations of LSCF salt mixtures were prepared and analyzed by SEM-EDS, XRD and DTA-TGA to see if all solid state reactions are completed and what new phases eventually formed in LSCF combinations. Most of the transformation was complete after 1050oC heat treatment to yield oxides. According to XRD analysis it was observed that La plays a significant role to enable the formation of new phases. In the absence of La, other salts had significant difficulty to react to form new phases. Also, Sr tends to swap its chloride with nitrate of other salts in salt mixtures after drying in oven. SEM-EDS analysis of the interface between the electrolyte and LSCF showed that there was weak mutual diffusion of the constituent elements between the cathode layer and the electrolyte. The cathode layer was usually in porous form but was found to spread well over the substrate. Uneven diffusion of La, Sr, Co or Fe into the substrate had little influence on the stoichiometry of the resulting coating layer. Unlike 6428 samples, it was possible to form stoichiometric LSCF in 6482 samples.