Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 54Citation - Scopus: 58Sintering and Microstructural Investigation of Gamma–alpha Alumina Powders(Elsevier Ltd., 2014) Yalamaç, Emre; Trapani, Antonio; Akkurt, SedatSintering behaviors of commercially available alumina powders were investigated using constant-heating rate dilatometric experiments. Each powder had different proportion of alpha/gamma alumina. Densification behaviors of powders were studied up to 1600 °C with three different heating rates of 1, 3.3 and 6.6 °C/min. Compacts of different gamma content alumina powders exhibited systematic anomalous second peaks in the densification rate curves at certain heating rates and temperatures. At 3.3 °C/min heating rate experiments, densification curves of 10% gamma phase alumina powder compacts reached a plateau after 1450 °C, and did not increase any further at higher temperatures. This phenomenon was double checked to understand powder behavior during sintering. 10% gamma phase alumina powder compacts showed the highest density for each heating rate. It reached 94% theoretical density with 1 °C/min heating rate. But 20% gamma phase alumina powder compacts had the finest grain size of about 1.40 ?m. Final density and porosity of compacts were also tested by image analysis and the results were coherent with Archimedes results. © 2014 Karabuk UniversityArticle Citation - WoS: 25Citation - Scopus: 26Lowering the Sintering Temperature of Solid Oxide Fuel Cell Electrolytes by Infiltration(Elsevier Ltd., 2019) Sındıraç, Can; Çakırlar, Seda; Büyükaksoy, Aligül; Akkurt, SedatA dense electrolyte with a relative density of over 95% is vital to prevent gas leakage and thus the achievement of high open circuit voltage in solid oxide fuel cells (SOFCs). The densification process of ceria based electrolyte requires high temperatures heat treatment (i.e. 1400-1500 degrees C). Thus, the minimum co-sintering temperatures of the anode-electrode bilayers are fixed at these values, resulting in coarse anode microstructures and consequently poor performance. The main purpose of this study is to densify gadolinia doped ceria (GDC), a common SOFC electrolyte, at temperatures lower than 1400 degrees C. By this aim, an approach involving the infiltration of polymeric precursors into porous electrolyte scaffolds, a method commonly used for composite SOFC electrodes, is proposed. By infiltrating polymeric precursors of GDC into porous GDC scaffolds, a reduction in the sintering temperature by at least 200 degrees C is achieved with no additives that might affect the electrical properties. Energy dispersive x-ray spectroscopy line scan analyses performed on porous GDC scaffolds infiltrated by a marker solution (polymeric FeOx precursor in this case) reveals a homogeneous infiltrated phase distribution, demonstrating the effectiveness of polymeric precursors.