Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 24Citation - Scopus: 27Atomic–scale Investigations of Passive Film Formation on Ti-Nb Alloys(Elsevier, 2023) Çaha, İhsan; Alves, Alexandra C.; Chirico, Caterina; Maria Pinto, Ana; Tsipas, Sophia; Gordo, Elena; Bondarchuk, Oleksandr; Leonard Deepak, Francis; Toptan, FatihThis study extensively investigates the passive film formation mechanisms on Ti-xNb alloys by using several electrochemical techniques, including electrochemical impedance spectroscopy (EIS) before and after potentiostatic polarization at the passive zone, and Mott-Schottky (MS) measurements in 9 g/l NaCl electrolyte at 37 °C, together with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis. Overall, the Ti40Nb presented lower corrosion resistance due to a thinner passive film as compared to commercial pure Ti (grade 2) and Ti12Nb. The passive film formed on Ti12Nb and Ti40Nb alloys at a steady-state condition (+0.5 VAg/AgCl for 60 min) is composed of amorphous phases of TiO, Ti2O3, TiO2, Nb2O5 and crystalline phases of TiO2 (anatase) and Nb2O5. © 2022 Elsevier B.V.Article Citation - WoS: 3Citation - Scopus: 3Influence of Cation Size and Polarity on Charge Transport in Ionic Liquid Based Electrolytes(Wiley, 2022) Aydın, Banu; Öner, Saliha; Zafer, Ceylan; Varlıklı, CananImidazolium-based ionic liquids (ILs) with allyl and ether side chains were synthesized and characterized. Comprehensive structural and photoelectrochemical characterizations were performed, transport properties of ILs were also examined as electrolyte components in dye sensitized solar cells (DSSCs). The properties of synthesized materials and DSSC performances were compared with 1-propyl-3-methyl imidazolium iodide (PMII) and 1-allyl-3-ethyl imidazolium iodide (AEII) as reference ILs. Ionic conductivities, diffusion coefficients and charge transfer resistances of synthesized ionic liquids were investigated on DSSCs by Electrochemical Impedance Spectroscopy (EIS). The diffusion coefficient values of triiodide ions in different ionic liquid-based electrolytes were measured by the means of diffusion limited current density method and found to be 1.75×10−7 cm2 s−1 and 2.05×10−7 cm2 s−1 with corresponding photocurrent densities of 10.38 mAcm−2 and 12.13 mAcm−2 for the reference AEII and PMII based electrolytes, respectively. However, for the electrolytes of 1-(2-methoxyethyl)-3-allyl imidazolium iodide and 1-allyl-3-methyl imidazolium iodide ionic liquids, these values were found to be 0.86×10−7 cm2 s−1 and 0.57×10−7 cm2 s−1 with photocurrent densities of 9.53 mAcm−2 and 8.98 mAcm−2, respectively. Allyl and ether substituted imidazolium ILs exhibited promising results as potential alternative electrolyte materials for DSSCs.Article 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.Article Citation - WoS: 11Citation - Scopus: 12Electrical Properties of Gadolinia Doped Ceria Electrolytes Fabricated by Infiltration Aided Sintering(Elsevier Ltd., 2019) Sındıraç, Can; Büyükaksoy, Aligül; Akkurt, SedatCommon solid oxide fuel cell (SOFC) electrolyte materials (e.g., gadolinia doped ceria - GDC) demand temperatures exceeding 1400 degrees C for densification by conventional solid state sintering. It is very desirable to reduce the densification of the SOFC electroltytes to i) avoid microstructural coarsening of the composite anode layers, which are co-sintered with the electolyte layer in the anode supported SOFC fabrication scheme and ii) reduce energy consumption during SOFC manufacturing. We have recently demostrated a novel infiltration-aided sintering route to densify GDC ceramics at 1200 degrees C. In the present work, we present the electrical properties of GDC ceramics fabricated thusly. Comparison of high density (>= 95%) samples fabricated by conventional or infiltration-aided sintering reveal that at 700 degrees C, similar total electrical conductivities are obtained, while at 300 degrees C, specific grain boundary resistivity is smaller in the latter. Bulk (grain) conductivity is higher in porous GDC ceramics (relative density <= 90%) fabricated by infiltration-aided sintering than the conventionally sintered ones with similar porosities. Finally, open circuit voltage of 0.84 V at 700 degrees C, obtained under dilute hydrogen and stagnant air conditions suggests that GDC ceramics densified by infiltration-aided sintering are suitable for use as SOFC electrolytes.Article Citation - WoS: 9Citation - Scopus: 10Microstructural Investigation of the Effect of Electrospraying Parameters on Lscf Films(Elsevier Ltd., 2020) Sındıraç, Can; Akkurt, SedatIntermediate temperature solid oxide fuel cells (IT-SOFC) require an effectively functioning cathode layer whose performance depends largely on their microstructures. Improved electrochemical performance of the cathode layer can be possible by tailoring the microstructure to ensure that both the oxygen reduction reaction (ORR) occurs fast along the triple-phase boundaries (TPB) and the diffusion pathway is short enough for fast ion diffusion through the cathode layer. Electro spray deposition (ESD) method is a low-cost deposition method which allows the optimization of microstructure by changing the spraying parameters. In this study, gadolinium doped ceria (GDC) electrolyte layer is deposited with La1-xSrxCo1-yFeyO3-? (LSCF) derived from polymeric precursor salts, symmetrically. As a solvent couple, 2-butoxyethanol and ethylene glycol are used instead of the conventional solvent couples frequently employed in the literature. The use of the new type of solvents in the precursor solution leads to promising results on modifying the microstructure of the deposited layer. The effect of electrospraying parameters on the cell performance was also studied. Promising results were obtained as measured by impedance spectroscopy when this new solvent couple was employed. © 2020 Hydrogen Energy Publications LLCArticle Citation - WoS: 9Citation - Scopus: 10Novel Hybrid Process for the Conversion of Microcrystalline Cellulose To Value-Added Chemicals: Part 2: Effect of Constant Voltage on Product Selectivity(Springer Verlag, 2017) Akın, Okan; Yüksel, AslıIn this study, electrochemical degradation of microcrystalline cellulose (MCC) under hot-compressed water was investigated via application of constant voltage on reaction medium. Constant voltage ranges from 2.5 to 8.0 V was applied between anode (Titanium) and cathode (reactor wall). As an electrolyte and proton source 5–25 mM of H2SO4 was used. Reactions were carried out in a specially designed batch reactor (450 mL) made of T316 for 240 min at temperature of 200 °C.MCC decomposition products such as glucose, fructose, furfural, 5-HMF and levulinic acid were detected and quantified by High Performance Liquid Chromatography (HPLC). In the absence of electrolyte, applied voltage (2.5 and 4.0 V) decreased the total organic carbon (TOC) yield, in contrast at 8.0 V, TOC yield increased to 13%. Application of 8.0 V in hydrothermal conditions alter MCC decomposition pathway selectively to furfural (15%). Addition of electrolyte (5 mM, H2SO4) and application of 2.5 V potential increased TOC (54%) and changed the decomposition pathway in favor of 5-HMF (30%) and levulinic acid (21%). The structural changes in solid residues of electrochemically reacted MCC was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and found that MCC particles functionalized by carboxylic acid and sulfonated groups by the application of constant voltage to reaction medium. In the presence of electrolyte, under certain voltage (2.5 V), functionalization of solid particles became more obvious in FTIR spectrum results. Therefore, change in the selectivity values of degradation products were conducted with the functionalization of MCC particles due to applied voltage under sub-critical conditions.Article Citation - WoS: 6Citation - Scopus: 12Effect of Calcium Hydroxide on Slip Casting Behaviour(Elsevier Ltd., 2004) Şakar Deliormanlı, Aylin; Yayla, ZelihaThe effect of calcium hydroxide addition on the casting performance of ceramic slips for sanitary ware was studied. Powder composed of feldspar (24 wt.%), quartz (24 wt.%), kaolin (35 wt.%) and ball clay (17 wt.%) was mixed with water to contain 65 wt.% of solids (specific density 1800 g/l). Either Ca(OH)2 or Na2CO3 was added at concentrations ranging between 0.060 and 0.085 wt.% and the slurries were dispersed by the optimum addition of sodium silicate. Calcium hydroxide in presence of sodium silicate improved the casting behavior of the slips, lowering the viscosity, and water absorption, increasing bending strength and cake thickness, as compared to the addition of sodium carbonateArticle Citation - WoS: 89Citation - Scopus: 103Group 15 Quaternary Alkyl Bistriflimides: Ionic Liquids With Potential Application in Electropositive Metal Deposition and as Supporting Electrolytes(Royal Society of Chemistry, 2002) Bhatt, Anand I.; May, Iain; Volkovich, Vladimir A.; Hetherington, Melissa E.; Lewin, Bob G.; Thied, Robert C.; Ertok, NigarThe eletrochemical properties of Group 15 quaternary alkyl bistriflimides salts were reported. The ionic liquids with potential application in electropositive metal deposition when used as supporting electrolytes in MeCN was also discussed. It was found that the three Group 15 based ionic liquids that were prepared have extremely large electrochemical windows.