Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
2 results
Search Results
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, SedatCathode 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.Master Thesis Coating of La1-Xsrxco1 Films on Zirconia and Cgo (cerium Gadolinium Oxide) by Electrostatic Spray Deposition (esd)(Izmir Institute of Technology, 2010) Büyükkebabçı, Hande; Akkurt, SedatIn this study preparation and characterization of coating of La0.6Sr0.4Co0.8Fe0.2O3-δ and La0.6Sr0.4Co0.2Fe0.8O3-δ materials on TZ-3Y (3 mol % doped yttria) and CGO (Ce0.9Gd0.1Oxide) ceramic electrolytes was studied. Electrostatic spray deposition (ESD) was used for depositing the coatings on ceramic electrolytes to develop a well bonded electrolyte-cathode material for potential IT-SOFCs (intermediate temperature solid oxide fuel cells) applications. Precursor solutions having La0.6Sr0.4Co0.8Fe0.2O3-δ or La0.6Sr0.4Co0.2Fe0.8O3-δ stoichiometry were prepared from various salts before being sprayed on a heated ceramic substrate which rapidly evaporated the solvent in the salts and the droplets struck and covered its surface. A high voltage was maintained to accelerate the droplets to high speeds. A coating with a minimal 1 µm of thickness was successfully produced. Effects of experimental parameters like the flow rate of the solution (0.3-1.5 ml/h), distance between the nozzle and substrate (15-45 mm), temperature of the substrate (250-375 °C), post heat treatment temperature (900-1300 °C) of the coated substrate and applied voltage on the quality of the coating were studied. Analytical tools like DTA/TGA, Scanning Electron Microscopy (SEM) and Xray Diffraction (XRD) were used to investigate the samples to check for the quality of the coating. Coating microstructures ranged from dense to porous depending on the deposition parameters. Sample with 30 mm distance and 0.7 ml/h of flow rate produced the best reticulated structure of the coating. No preferential landing effect was observed on any of the samples studied. Zirconia was not an effective substrate for formation of La0.6Sr0.4Co0.8Fe0.2O3-δ or La0.6Sr0.4Co0.2Fe0.8O3-δ. Cerium gadolinium oxide, however, was effective for La0.6Sr0.4Co0.8Fe0.2O3-δ but not for La0.6Sr0.4Co0.2Fe0.8O3-δ.