Navegando por Autor "Borges, Kellen Cristina Mesquita"

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    Síntese e caracterização de cerâmicas do tipo BZYO e BCGO para uso em células a combustíveis
    (Universidade Federal de Goiás, 2014-04-11) Borges, Kellen Cristina Mesquita; Godinho Júnior, Mario; http://lattes.cnpq.br/8364676654739392; Godinho Junior, Mario; Simões, Fábio Ruiz; Santos, Maria Rita de Cássia
    The study of the synthesis of materials which have proton conductivity contributes to the production of solid electrolytes protonic conductors, used extensively in the operation of fuel cells. Materials doped barium zirconate yttrium (BZYO) and barium cerate doped with gadolinium (BCGO), were synthesized by the polymeric precursor method, which stands as an effective technique. The synthesized powders were characterized by thermal analysis (TG-DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM / FEG) and Zeta Potential. The sinterability of the powders was observed by dilatometric analysis, followed by XRD, SEM / FEG and density apparent. From the results obtained it was possible to verify the formation of BZYO phase at a temperature of 900 °C/ 2h. A higher dopant concentration (20% Y) promoted the formation of the phase in a temperature 800 °C/ 2h, and the formation of the phase BCGO at 950 °C/ 2h. The crystallite size calculated by Scherrer's equation, ranged from 20,8 to 15,2 nm and 38,2 to 30,5 nm for BZYO and BCGO respectively. This results depends on the amount of dopant and its capacity to form solid solution. The micrographs (SEM/FEG) confirmed the nanometric nature of the material with a spherical morphology. The zeta potential was -23,6 mV and -22,8 mV for BZYO and BCGO, respectively, which demonstrates a good stability in the formation of colloidal dispersions for thin film formation which are of interest for fuel cells. The pads BCGO showed a satisfactory densification (95,1%) at 1550 °C/ 4h, a result that shows its applicability as proton conductive solid electrolyte. For tablets BZYO the densification was lower than BCGO with a result of bulk density of 73,8% at 1600 °C/ 4h. This result shows the need for heat treatment at higher temperatures to obtain a higher densification of the pellets.