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Öğe Production and characterization of CuCrO2 nanofibers(ELSEVIER SCIENCE SA, 2016) Cetin, Cagla; Akyildiz, HasanComposite nanofibers were prepared from homogeneously mixed copper chloride, chromium nitrate and polyvinylpyrrolidone solution by electrospinning and were subsequently heat treated under isochronal and isothermal annealing conditions. In the isochronal experiments, CuCrO2 formation began at 773 K. Annealing at 973 K yielded single-phase, highly porous CuCrO2 nanofibers accompanied by the formation of large quasi-hexagonal grains. In contrast, isothermal annealing at 973 K resulted in the formation of phase-pure CuCrO2 nanofibers with belt-like morphology and relatively higher density. A substantial decrease was observed in the size and number of plate-like grains in these nanofibers. When the fibers were annealed isothermally at 973 K for 1 h, the average width and specific surface area of the synthesized fibers were 150 nm and 7.85 m(2) g(-1), respectively, and the direct bandgap was 2.82 eV. The CuCrO2 behaved like a semiconductor, and the thermally activated energy was approximately 0.157 eV. A simple formation mechanism was proposed for the quasi-hexagonal grains. (C) 2015 Elsevier B.V. All rights reserved.Öğe Production of CuAlO2 in powder, bulk and nanofiber forms(KOREAN ASSOC CRYSTAL GROWTH, INC, 2015) Kaya, Ismail Cihan; Cetin, Cagla; Aydin, Hursit Safa; Katircioglu, Zeynep; Buyukbekar, Burak Zafer; Yavuz, Mustafa Selman; Uyaner, MesutA study was carried out on the production of CuAlO2 by using 3 different production routes namely, hydrothermal synthesis, conventional solid state reaction and electrospinning process. For hydrothermal synthesis, commercially available metal salts, Cu2O powder and chemically precipitated CuO nanoparticles were used as precursors. Bulk CuAlO2 samples were prepared via solid state reaction route by ball milling and high temperature sintering of CuO and Al2O3 powders. CuAlO2 ceramic mats were synthesized by electrospinning process with the assistance of polyvinylpyrolidone, as a template polymer. Highly crystalline mesh structured fibers were obtained after sintering of polymer/equal moles of copper chloride and aluminum nitrate composite in air. In the current work, solid state reaction and electrospinning processes yielded phase pure CuAlO2 in hexagonal symmetry. On the other hand, products obtained from hydrothermal synthesis were CuO, Cu2O and Al(OOH), which did not yield CuAlO2 under current experimental conditions. Detailed qualitative X-ray diffraction analysis revealed the need of specific ionic species in the solution within a narrow temperature-composition-pH window to obtain phase pure CuAlO2 employing hydrothermal conditions.