RAFAEL MORGADO BATISTA

RAFAEL MORGADO BATISTA

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Phase transformation/stabilization and ionic conductivity in tantalum oxide co‑doped zirconia‑scandia solid electrolyte
2022 - SOUZA, J.P.; FUJIMOTO, T.G.; BATISTA, R.M.; STEIL, M.C.; MUCCILLO, R.; MUCCILLO, E.N.S.
The influence of small amounts of tantalum oxide as co-dopant on phase transformation and stabilization, microstructure and ionic conductivity of zirconia-10 mol% scandia is reported in this work. Cylindrical pellets were prepared by solid state synthesis with sintering at 1500 °C for 5 h. High relative density values (> 95%) were achieved. Reduction of the enthalpy for the cubic ⇌β-rhombohedral phase transformation was found for increasing amounts of the co-dopant. Full stabilization of the cubic structure at room temperature was obtained with only 0.45 mol% tantalum oxide addition. The ionic conductivity of sintered specimens was investigated as a function of the temperature and oxygen partial pressure by impedance spectroscopy. The fully stabilized co-doped system revealed a pure ionic conduction behavior up to 800 °C with wide electrolytic domain. In the 700–800 °C range, the ionic conductivity of co-doped specimens is similar to that of pure zirconia-scandia.
Analysis of the sintering process in gadolinia-doped ceria by thermodilatometry and correlation with microstructure evolution
2018 - BATISTA, RAFAEL M.; MUCCILLO, E.N.S.
The non-isothermal sintering process of cerium dioxide containing gadolinium sesquioxide powders within a wide range of specific surface area was investigated by dilatometry. Linear shrinkage data of powder compacts were recorded under several constant rates of heating. Dilatometry data were analyzed by two methodologies enabling to preview the relative density for any temperature/time profile, and determination of the apparent activation energy for sintering. Correlation of dilatometry results with microstructure evolution was also carried out. Remarkable differences in sintering powders with different specific surface areas were found. The apparent activation energy for sintering increases with decreasing specific surface area and, in most cases, it does not change significantly in the approximately 70-85% range of relative density.
Um programa de computação versátil para a construção da curva mestra de sinterização
2016 - MUCCILLO, ELIANA N. dos S.; BATISTA, RAFAEL M.; MARANJO, JUAN F.R.
O modelo da curva mestra de sinterização foi desenvolvido para prever a evolução da microestrutura durante a sinterização de pós cerâmicos. A obtenção da curva mestra de sinterização de uma cerâmica específica envolve cálculos complexos e repetitivos, que despendem várias horas de trabalho e podem resultar em imprecisões. Assim, neste trabalho foi desenvolvido um programa computacional capaz de realizar a determinação da curva mestra de sinterização num tempo bastante reduzido e com boa precisão. O programa foi elaborado tal que permite também calcular dados importantes da cinética de sinterização, como a energia de ativação pelo método de Arrhenius. Neste trabalho, é mostrado o funcionamento do programa desenvolvido tendo como material de estudo a céria contendo 10% mol gadolínia.
Sintering and electrical conductivity of gadolinia-doped ceria
2016 - BATISTA, R.M.; FERREIRA, A.M.D.C.; MUCCILLO, E.N.S.
Bulk specimens of Ce0.9Gd0.1O2-delta prepared with powders within a range of specific surface area were sintered in oxidizing, inert, and reducing atmospheres. The aim of this work is to investigate the effects of the sintering atmosphere on the microstructure and grain and grain boundary conductivities of the solid electrolyte. The lattice parameter determined by Rietveld refinement is 0.5420(1) nm, and the microstrain was found negligible in the powder materials. Specimens sintered in the Ar/4 % H-2 mixture display larger average grain sizes independent on the particle size of the starting powders. The grain and grain boundary conductivities of specimens sintered under reducing atmosphere are remarkably lower than those sintered under oxidizing and inert atmospheres. The activation energy (similar to 0.90 eV) for total electrical conductivity remains unchanged with both the initial particle size and the sintering atmosphere.
Caracterização da céria-gadolínia preparada com pós nanométricos
2012 - BATISTA, R.M.; MUCCILLO, E.N.S.
Influence of small amount of NiO on the Electrical conductivity of 8YSZ
2011 - BATISTA, R.M.; MUCCILLO, E.N.S.
Densification and grain growth of 8YSZ containing NiO
2011 - BATISTA, R.M.; MUCCILLO, E.N.S.
Structure, microstructure and electrical conductivity of 8YSZ containing NiO
2011 - BATISTA, R.M.; MUCCILLO, E.N.S.
Influence of small amount of NiO on the Electrical conductivity of 8YSZ
2011 - BATISTA, R.M.; MUCCILLO, E.N.S.