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Öğe Effect of grinding time of synthesized gadolinium doped ceria (GDC10) powders on the performance of solid oxide fuel cell(Elsevier B.V., 2014) Aydin F.; Demir I.; Mat M.D.Ceria-based materials are prospective electrolytes for low and intermediate temperature solid oxide fuel cells. In the present work, fully dense CeO2 ceramics doped with 10 mol% gadolinium (Gd0.1Ce0.9O1.95) were prepared with a sol–gel method and commercially purchased GDC10 electrolyte powders were processed. Particle sizes of synthesized electrolyte powders were minimized by ball-milling method. Grinding of the samples were performed in different times intervals (12 h, 15 h, 18 h, 20 h, 25 h, 30 h, 35 h, 40 h and 45 h). Then, these powders were prepared to obtain of solid oxide fuel cells (SOFCs). Performances of these cells having an active area of 1 cm2 were tested using a fuel cell test station that measured in different temperatures (650 and 700 °C). In the present study, gadolinium doped ceria (GDC10) synthesiszed powders were investigated by using XRD and SEM images. Performance values of synthesized GDC10's in different temperature were compared to by commercial GDC10. Commercial GDC10's performance at 650 °C were tested, and maximum current density of 0.413 W/cm2 and maximum current density of 0.949 A/cm2 were obtained. Commercial GDC10 at 650 °C has better result. However, synthesized GDC10's performance at 700 °C demonstrated better results than commercial GDC10's. The performance tests of samples which are 20 h mill showed that they have the maximum power density of was obtained as 0.480 W/cm2 and maximum current density of as 1.231 A/cm2. © 2014 Karabuk UniversityÖğe Magma interaction processes inferred from Fe-Ti oxide compositions in the Dölek and Sariçiçek plutons, Eastern Turkey(2008) Karsli O.; Aydin F.; Uysal I.; Sadiklar M.B.Magnetite-ulvöspinel and ilmenite-hematite solid solution intergrowths from the high-K calc-alkaline Dölek and Sar?çiçek plutons, Eastern Turkey, were investigated using microprobe analyses. Compositions of twenty-eight samples from the host rocks and their enclaves' in the plutons were used to estimate the oxygen fugacity and temperature. The ilmenite and ulvöspinel component exsolves out along certain preferred crystallographic planes in the titanomagnetite of the host rocks, while they are always absent in those of the mafic-microgranular enclaves. The titanomagnetite and ilmenite show variations as Mt98-70Usp02-30 and Ilm99-65Hm01-35 in composition, respectively. Estimations of oxygen fugacity and temperature using the titanomagnetite-ilmenite thermometry/oxygen barometry range from log/O2 of -15.30 to -20.48 in host rocks, log/O2 of -15.39 to -20.80 in the mafic microgranular enclaves and 617±6 to 758±23 °C in host rocks, 622±6 to 735±24 °C in the mafic microgranular enclaves, possibly indicating crystallisation temperature. Applying magnetite-ilmenite thermometry/ oxygen barometry to the granitoid rocks also involves microprobe analyses of ilmenite lamellae in titanomagnetite and this method yielded mean temperatures of 679±18 °C. The specific forms and chemical properties of Fe-Ti oxides, and similarities in crystallization temperature and oxygen fugacity of the host rocks and the mafic microgranular enclaves (MME) obtained from the Fe-Ti oxide pairs imply that thermal equilibrium probably occurred between two contrasted magmas, which mixed invarious proportion so that possibly a felsic and a more mafic magma interaction occurred in a convectively dynamic magma chamber during crystallization of the plutons. Probably, underplating may be responsible for genesis of the hybrid plutons. Thus, for mixing of coeval magmas derived from a lithospheric upper mantle (mafic end-member) and lower crust (felsic end-member), a thermal anomaly should be supplied. Upwelling of hot asthenospheric material result in thermal perturbation and melting of lithospheric mantle. Intrusion of hot lithospheric mantle-derived mafic magma then induced lower crustal melting, producing felsic melt. Mixing of the lower crust-derived melt and lithospheric mantle-derived magma formed the hybrid pluton. This process requires a post-collisional extensional tectonic setting during the Eocene in the Eastern Pontides. Copyright © TÜBİTAK.Öğe Mineralogical, geochemical and thermobarometrical aspects of volcanic rocks in the Central Anatolia(Nova Science Publishers, Inc., 2011) Aydin F.This chapter focuses on the tectonic and geological settings, analytical methods, petrographical characteristics, geochemical features, mineralogy and mineral chemistry, crystallization conditions, and magmatic processes (mixing, evolution, etc.) of the Neo-Quaternary calc-alkaline and alkaline rocks in Nigde Volcanic Province from Central Anatolia, Turkey. First, in this regard, tectonic and geological settings of the Neo-Quaternary calc-alkaline and alkaline volcanic rocks have been generally presented after the introduction section. Then, analytical methods used for the studied volcanics have been briefly given. Second, the petrographical characteristics and phenocryst assemblages of the calc-alkaline and alkaline volcanic rock types are presented. In such a way that, the Nigde Volcanic Province consists of several stratovolcanoes and monogenetic cones activated in Neogene and Quaternary times. The Neo-Quaternary volcanic rocks are generally andesitic in composition and are characterized by their high phenocryst contents. They show porphyritic, glomeroporphyric and seriate texture and contain wide variety of phenocrysts consisting of plagioclase, orthopyroxene, clinopyroxene, amphibole, biotite. However, the Quaternary volcanic rocks related to the monogenetic cones are alkaline basalts with microlitic-porphyritic texture, and they have lower phenocrysts contents of olivine and clinopyroxene and lesser Ca-rich plagioclase. Third, geochemical features and classifications of the calc-alkaline and alkaline volcanic rocks have been determined. In such a way that, the SiO2 contents of the calc-alkaline rocks change from 55 to 65 wt%, called as basaltic andesite-andesite, and they define medium to high-K calc-alkaline affinities. Their MgO and TiO2 contents are generally lower than 4 and 1 wt%, respectively. The calc-alkaline volcanics show enrichment of LIL elements such as K, Rb, Th and U, depletion in HFSE with negative Nb, Ta, P and Ti anomalies, suggesting an enriched lithospheric mantle source metazomatized by a subduction-related process. On the other hand, the Quaternary volcanic rocks are alkaline in character. Compared to the Neo-Quaternary calc-alkaline andesites, they have lower SiO2 (49-51 wt %), and K2O (0.5-1.7 wt %), and higher MgO (5.1-7.2 wt %) and TiO2 (> 1 % wt) contents, and are classified as basalt. Fourth, mineral chemical features and crystallization conditions of these rock types have been determined and estimated, respectively. As follows, the crystallization conditions range from approximately 750 to 1100 oC and 2.5-8.0 kbars for the calc-alkaline andesitic magma, 885 to 944 oC and 2.0-7.5 kbars for alkaline basaltic magma, which correspond to a depth of 6-24 km for storage region of the Central Anatolian crust. Finally, the magmatic processes (mixing, evolution, etc.) of the calc-alkaline and alkaline volcanic rocks have been discussed. As follows, disequilibrium textures, geochemical characteristics and the compositional variations of the phenocrysts indicate that the calc-alkaline Neo-Quaternary volcanites have a complex evolutionary history. However, mineralogical and geochemical data from the Quaternary alkaline volcanic rocks show a relatively simple evolutionary history. © 2010 by Nova Science Publishers, Inc. All rights reserved.Öğe Mineralogy and geochemistry of the Kiziltepe (Çamardi-Niğde) Mn prospect in central Anatolia, Turkey(International Multidisciplinary Scientific Geoconference, 2016) Lermi A.; Sönmez M.; Aydin F.This paper is to investigate ore-alteration mineralogy and geochemical changes of wall rocks in Kızıltepe Mn mineralization (Çamardı, SE-Niğde), which is located in Ulukışla Basin from the central part of the Turkey. Kızıltepe prospect, a fault controlled hydrothermal-type Mn mineralization, is hosted predominantly by Late Cretaceous to Early Tertiary volcanic and volcanoclastic rock series, which are submarine in character with trachytic to rhyolitic composition. After all samples were systematically collected from surface outcrops and the mineralized zones, they were investigated by petrographical and geochemical analysis. The results obtained from the microscopic and XRD analysis showed that the mineralization contained oxi-hydroxide Mn minerals such as manganite, pyrolusite, psilomelane, and manganese phosphate. Quartz, carbonates, sericite, clay minerals and barite are the gangue minerals. Quartz is ubiquitous and occurs both in the ore zone and in the wall rocks. Alteration mineralogy usually was formed fault-related to alteration zones. Alterations were characterized by presence of quartz and sericite, and locally extensively overprinted by kaolinite. Mass change calculations revealed that Al, Ti, and Y behaved as the least mobile elements during alteration and that footwall felsic rocks gained Fe, Si, K, Ca and ore forming constituents, respectively. The most characteristic chemical changes near the ore bodies were the Na depletion, mainly due to plagioclase destruction by the hydrothermal fluids. The REE contents varied considerably depending on mass change effects related to alteration. An average grade of Mn in the fault zone has been reached about 22.47 %. © SGEM2016.
