Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 TechnologyHigh 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 Formation of Srtio3[tio2] Ceramic Composites at Low Temperatures(01. Izmir Institute of Technology, 2021) Adem, Umut; Karataş, Esin; Ahmetoğlu, Çekdar Vakıf; Adem, Umut; Ahmetoğlu, Çekdar Vakıf; 03.09. Department of Materials Science and Engineering; 01. Izmir Institute of Technology; 03. Faculty of EngineeringStrontium titanate ceramics are materials belonging to the perovskite material group with the formula ABO3. Strontium titanate ceramics have been a preferred material in many areas, such as the electroceramics industry, due to its high dielectric constant and high chemical stability and generally produced by manufacturing processes such as solid-state synthesis, hydrothermal method, and sol-gel. SrTiO3 ceramics have been produced in the literature with different temperatures, times, and starting materials. For ceramic products, a sintering step is required after the powder production step. Traditional sintering methods, which have been used for many years, are used to densify powders with high temperatures. Recently developed low-temperature densification methods enable the sintering process to be carried out at relatively lower temperatures. For this purpose, in this thesis, SrTiO3-TiO2 ceramic composites were produced at different reaction temperatures and times using the rHLPD method, which combines powder production and sintering steps in a single process. In the studies, the reaction temperature, time, and the effect of adding mineralizer to the prepared solution for the hydrothermal reaction on the final product were investigated. The aim of the thesis is to produce SrTiO3 from TiO2 green body using the rHLPD method. In addition, the production of SrTiO3-TiO2 ceramic composites with as high mole conversion and relative density values as possible was targeted with different parameters such as reaction temperature, reaction time, and addition of NaOH to the solution. As a result of the studies carried out with different parameters, SrTiO3-TiO2 ceramic composites with a final relative density value of approximately 81 % were produced. Consequently, in the XRD and Rietveld analysis, it was seen that the main phase was SrTiO3. In addition, there was a TiO2 phase in the structure. Finally, the SrCO3 phase was not detected in the structure.Master Thesis Optimisation of Organic Phase Pre-Neutralisation Stage in Purification Studies With Solvent Extraction for Mhp (mixed Hydroxide Precipitate) Produced From Gördes Laterite Ore and Investigation of Its Effect on Extraction(01. Izmir Institute of Technology, 2021) Ahmetoğlu, Çekdar Vakıf; Ahmetoğlu, Çekdar Vakıf; 03.09. Department of Materials Science and Engineering; 01. Izmir Institute of Technology; 03. Faculty of EngineeringIntermediate products such as MHP (Mixed Hydroxide Precipitate) are processed by solvent extraction which is a continuous process in industry for obtaining final product such as nickel metal or nickel sulphate. Nickel is used essentially in stainless steel industry and cobalt is used in super alloys. Both metals are used in lithium-ion battery technologies especially electrical vehicles. A preliminary stage of solvent extraction process is called as pre-neutralisation and it is based on partial neutralisation of the acidic organic reactant to prevent pH fluctuations in extraction due to the H+ ions release aqueous phase, and it provides an exchange mechanism to enable loading of the metals to the organic phase. In this thesis study, it is aimed to optimise the organic phase pre-neutralisation percent in further purification treatment of MHP leach solution (PLS-Pregnant Leach Solution) from Gordes nickel laterites and investigate its effect on extraction by D2EHPA and Cyanex 272 organic reactants. NaOH and Na2CO3 solutions were used in pre-neutralisation with 35%, 40% and 45% in D2EHPA and 30%, 35% and 40% in Cyanex 272. The optimum pre-neutralisation results were found as 35% for D2EHPA and 30% for Cyanex 272.