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    Magnesia Stabilized Zirconia Doped With Boron, Ceria and Gadolinia
    (Elsevier Sci Ltd, 2012) Aytimur, A.; Uslu, I.; Koçyiğit, S.; Özcan, F.
    In this study, magnesia stabilized zirconia based nanocrystalline ceramics were produced through a polymer precursor route using gadolinium and boron. The powders were characterized during the various steps by structural and morphological techniques (FT-IR, XRD, and SEM). XRD results proved that a tetragonal phase is predominant for all samples with varying magnesium contents and no monoclinic zirconia solid solution appears. The crystallite sizes of the samples were calculated using Scherrer equation. The smallest crystallite size was obtained for the sample containing Zr/Mg/Ce/Gd/B ratio of 82/0/10/8/0. The lattice parameters were calculated for cubic, tetragonal, hexagonal, and orthorhombic structures. SEM results show all the samples have spherical grains. The average grain diameters were calculated for all the samples. The smallest average grain diameter was obtained for the sample containing Zr/Mg/Ce/Gd/B ratio of 82/0/10/8/0.
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    Synthesis and characterization of erbia and ceria doped calcia stabilized nanocrystalline zirconia based ceramics
    (SPRINGER, 2013) Uslu, I.; Aytimur, A.; Kocyigit, S.; Ozcan, F.; Ozturk, M. K.; Colak, U.
    Er2O3 doped calcia stabilized zirconia based inert matrix fuel containing CeO2 as a surrogate for PuO2 was fabricated for a wide range of concentration using the polymer-to-ceramic conversion technique via metal acetate preceramic hybrid polymer solutions. Samples were characterized by XRD, SEM and AFM techniques. Nanocrystallite size variation in the samples was evaluated using peak broadening values by means of the Scherrer formula. The smallest lattice constant was obtained for the sample containing Zr/Ca/Ce/Er atomic weight ratio of 74/11/10/5. The average grain diameters varied between 64 nm and 129 nm. SEM results show that, the smallest grain size was obtained for the sample containing Zr/Ce/Er atomic weight ratio of 22/2/1. Moreover, surface roughness characteristics of the samples were evaluated by different definitions using intermittent contact mode AFM.
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    Synthesis and Properties of Boron Doped NaxCo2O4 Nanocrystalline Ceramics
    (SPRINGER, 2012) Uslu, I.; Cetin, Saime Sebnem; Aytimur, A.; Yuceyurt, S.; Erdal, M. O.
    Sodium cobalt oxide (NaCo2O4) nanofibers with diameters ranging between 20 and 200 nm were prepared by electrospinning a precursor mixture of PVA/(Na-Co) acetate. This was the first time any such attempt was made. Afterwards, the electrospun nanofibers were subjected to calcination treatment. The characteristics of the fibers were investigated using a Fourier transform infrared spectroscopy, a X-ray diffractometer, and a scanning electron microscopy. The boron doped and undoped NaCo2O4 nanofibers calcined at 850 A degrees C were polycrystalline of the gamma NaxCo2O4 phase having diameters ranging between 20 and 60 nm with grain sizes of 5-10 nm, and the nanofibers calcined at 800 A degrees C were single crystals having linked particles or crystallites with particle sizes ranging between 60 and 200 nm. The results indicated a significant effect of calcination temperature on the crystalline phase and morphology of the nanofibers. It could be seen in the SEM micrograph of the fibers that when boron was added, this resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123 nm, respectively. The grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118 nm, respectively.