Navegando por Autor "Cela, Beatriz"

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Effect of a zirconia interlayer on the morphological properties of LaSrMnO3- 4YSZ composite films obtained by spin coating
(Journal of Ceramic Processing Research, 2011-12-31) Macedo, Daniel Araújo de; Souza, Graziele L.; Cesário, Moises Rômolos; Cela, Beatriz; Martinelli, Antonio Eduardo; Paskocimas, Carlos Alberto; Nascimento, Rubens Maribondo do
In this study, a chemical route was adopted to obtain strontium-doped lanthanum manganite (LaSrMnO3 or LSM) powders in order to prepare LaSrMnO3-4YSZ (4 mol% Y2O3) composite films by the suspension spin coating method onto 4YSZ and 8YSZ/8YSZ-NiO substrates with or without the application of a zirconia interlayer in the film/substrate interface. The multilayers were sintered at 1150 o C for 6 h and the effect of the interlayer on the morphological properties of the films has been investigated by scanning electron microscopy. The results show that in the less roughn substrates the application of the interlayer (~500 nm) not only improved the adhesion in the film/substrate interface, but also avoided new coating failures. All the films were porous, crack-free and with a thickness below 30 μm, desirable features for application as SOFC cathodes
Influence of polymerizing agent on structure and spectroscopic properties of nano‐crystalline La0.8Sr0.2MnO3 powders
(Wiley-VCH Verlag, 2010-10-20) Macedo, Daniel Araújo de; Cesário, Moises Rômolos; Cela, Beatriz; Melo, Dulce Maria de Araújo; Paskocimas, Carlos Alberto; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do
Strontium‐doped lanthanum manganite (La1‐xSrxMnO3 or LSM) is the material most widely used on solid oxide fuel cells cathode. In this work, nano‐scale La0.8Sr0.2MnO3 powders have been synthesized by polymeric precursor‐based methods using different polymerizing agents with the aim of evaluating the influence of this change in the final powder. The powders calcined at 700 °C for 2 h have been characterized by X‐ray diffraction (XRD), scanning electron microscopy (FE‐SEM) and Fourier transform infrared spectroscopy (FTIR) in order to investigate the quality of both synthesis routes. It is shown that the crystal structure and morphology of the particles are significantly dependent on the preparation conditions. Single phase and La0.8Sr0.2MnO3 nano‐crystalline particles less than 30 nm were obtained using ethylene glycol as polymerizing agent. FTIR results have been indicated that only the powder obtained using gelatin presented small traces of hydroxyl groups on its surface. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
NiO-CGO Composite for SOFC Anode: Synthesis and Characterization
(Journal of Materials Science and Engineering, 2010) Cela, Beatriz; Macedo, Daniel Araújo de; Souza, Graziele Lopes de; Miranda, Auristela Carla de; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do; Paskocimas, Carlos Alberto
In this work compounds of gadolinium-doped ceria, Ce0.9Gd0.1O1.95 (CGO) and NiO were synthesized by polymeric precursor method. NiO-Ce0.9Gd0.1O1.95 composite was attained by mixture of the powders of the both phases calcinated already. The precursor powders were characterized by simultaneous thermogravimetry-differential thermal analysis and the calcined materials were studied by X-ray diffraction, scanning electronic microscopy, Fourier transform infrared spectroscopy and dilatometry. The refinement of the diffraction data indicated that the powders were crystallized in the wanted phases. All the produced powders had nanometric and sub micrometric features. The produced composite showed good characteristics for the use as anode for SOFC.
NiO–CGO in situ nanocomposite attainment: one step synthesis
(Elsevier, 2011-03-01) Cela, Beatriz; Macedo, Daniel Araújo de; Souza, Graziele Lopes de; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do; Paskocimas, Carlos Alberto
The CeO2-based electrolyte low temperature SOFCs require special electrodes with a higher performance and compatibility. The performance of the CeO2-based composite anodes depends on microstructural features such as particle size, tripe phase boundaries (TPB), surface area, and percolation. Some of the primary parameter can be manipulated during the materials synthesis. In this work the compound NiO–Ce0.9Gd0.1O1.95 (NiO–CGO), used as anode in SOFC, was synthesized by two different processes. Both of them are based on the polymeric precursormethod. Characterized by simultaneous thermogravimetry-differential thermal analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and dilatometry. The refinement of the XRD data indicated that the composite sample synthesized by the process called “one step synthesis” produced smaller crystallite size in comparison to the sample attained by the two steps process. Simple preliminary performance tests were done with single cells in which such I–V curves indicated that the cell with one step anode had better performance. “One step synthesis” product, in situ nanocomposite, presented similar fine grained particle sizes for both phases Ni and CGO, which would be beneficial to the electrochemical activity, also indicated by first performance tests
A versatile route for the preparation of Ni–CGO cermets from nanocomposite powders
(Elsevier, 2013-05) Macedo, Daniel Araújo de; Souza, Graziele L.; Cela, Beatriz; Paskocimas, Carlos Alberto; Martinelli, Antonio Eduardo; Figueiredo, Filipe Miguel Henriques Lebre Ramos; Marques, Fernando M. B.; Nascimento, Rubens Maribondo do
A comparative microstructural study between Ni–Ce0.9Gd0.1O1.95 (Ni–CGO) anodes obtained from NiO–CGO nanocomposite powders prepared by in situ one-step synthesis and by mechanical mixture (two-step synthesis) of NiO and CGO powders is reported. The open porosity and microstructure of sintered and reduced pellets were investigated as a function of the citric acid content used as pore forming agent. Nanosized crystallites for the one-step and two-step routes were around 18 nm and 24 nm against 16 nm and 37 nm, for CGO and NiO, respectively. Overall results show that both routes provided suitable microstructures either for anode-support, or for functional anodes for solid oxide fuel cells (SOFCs), with more versatile characteristics in the case of the one-step route. The electrical characterization of selected NiO–CGO samples, carried out between 90 and 260 °C by impedance spectroscopy, confirms electrical percolation of both phases in the composites. However, based on combined microstructural and impedance data, it seems clear that the one-step processing route is the best approach to make SOFC anodes with improved performance

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Navegando por Autor "Cela, Beatriz"