Master Degree / Yüksek Lisans Tezleri

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

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Publisher: search.filters.publisher.01. Izmir Institute of TechnologySubject: search.filters.subject.Fuel cells

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Now showing 1 - 3 of 3
  • Master Thesis
    Electrocatalytic isopropanol oxidation for direct organic fuel cells
    (01. Izmir Institute of Technology, 2024) Çetin, Yağmur; Çağlar, Başar; Şeker, Erol
    Dünya üzerinde sürekli artan nüfus yoğunluğu ve buna eşlik eden enerji tüketim oranları nedeniyle, yenilenebilir enerji kaynaklarını bulma, bunları erişilebilir ve kullanıma hazır hale getirme ihtiyacı önemli konular gelmiştir. Son yıllarda, hidrojen taşıyıcıları ve yakıt hücresi sistemleri, geleneksel fosil yakıt türlerine bağlı enerji üretim sistemlerine iyi alternatifler olarak öne çıkmıştır. Bu çalışma için, hidrojen taşıyıcısı olarak izopropanol-aseton çifti seçilmiş ve reaksiyon kinetiği incelenmiştir. İzopropanolün elektrokimyasal oksidasyonu, yakıt hücresi uygulamaları ve enerji depolama cihazlarındaki önemi nedeniyle oldukça ilgi görmüştür. Bu tez içeriğinde, Pt/C, Cu/C, Pt-Cu(1:1)/C, Pt-Cu(3:1)/C ve Pt-Ru/C ticari katalizörleri kullanılarak izopropanolün elektrokimyasal oksidasyon davranışına odaklanılmıştır. Oksidasyon reaksiyonunun performansını iyileştirmeyi amaçlarken, her bir elektrokimyasal katalizörün aktivitesi, seçiciliği ve reaksiyon koşullarındaki kararlılığı farklı ortamların etkisi altında, alkali koşullarda incelenmiştir. Bu katalizörlerin elektrokimyasal performansı Döngülü Voltametri, Elektrokimyasal Empedans Spektroskopi ve Kronoamperometri analizleri ile değerlendirilmiştir. Sonuçlar, diğer Platin bazlı katalizörlere kıyasla daha yüksek katalitik aktivite ve daha düşük kinetik direnç gösteren Pt-Cu/C katalizörünün üstünlüğünü göstermektedir. Bu gelişmiş performans, Bakır'ın OH- türlerine olan güçlü afinitesine atfedilir ve bu da izopropanol oksidasyon hızını artırır ve genel elektrokimyasal aktiviteyi teşvik eder. Genel olarak, bu çalışma izopropanol elektrooksidasyonunun kinetiğine dair değerli bilgiler sağlayarak ve Pt-Cu alaşımının çeşitli elektrokimyasal sistemlerde verimli alkol oksidasyonu için umut verici bir katalizör olarak potansiyelini vurgular.
  • 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
    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
    Sintering and Densification Behavior of Gdc Infiltrated Porous Gdc Electrolyte
    (01. Izmir Institute of Technology, 2021) Tekin, Sinem; Akkurt, Sedat; Ebil, Özgenç
    It is desired that the electrolytes used in solid oxide fuel cells have a dense structure. Ceria-based electrolytes require temperatures of 1400-1500oC to densify. High densification temperatures make this material less in demand despite its good ionic conductivity. In this study, it was aimed to sinter and densify porous GDC scaffolds made of GDC (Gd0.10Ce0.90O1.95) material at low temperatures using infiltration technique. A porous GDC scaffold is first produced by sintering the GDC pellet around 1000oC to obtain an intermediate product ready to be infiltrated by a GDC-bearing solution. Multiple infiltration and drying cycles were intended to fill the pores by GDC nanoparticles which are expected to densify at lower temperatures. Two different groups (infiltrated and non-infiltrated) were formed and their densification behaviors with temperature and infiltration repetition cycles were investigated using a vertical dilatometer. The porous GDC scaffold was infiltrated with a polymeric solution prepared from Ce(NO3)3.6H2O and Gd(NO3)3.6H2O. The prepared samples were sintered at 1400oC. As a result of the experiments, it was observed that the densification decreased with the increase in temperature and infiltration cycles. This is thought to be because the porous scaffold could not be completely dried during the infiltration cycles. This led to the formation of a dense outer layer of GDC and porous inner layer. This dense layer inhibited shrinkage of the pellet during dilatometric analysis. Further studies need to be conducted to fully evaporate the solvent during drying of the infiltrated pellets.