Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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2 resultados
Resultados da Pesquisa
- Relationship between surface segregation and rapid propane electrical response in Cd-doped SnO2 nanomaterials(2008-07-05) Castro R. H. R.; Hidalgo P.; Perez H.E.M.; Ramirez-Fernandez F.J.; Gouvea D.Controlling the surface properties of nanoparticles using ionic dopants prone to be surface segregated has emerged as an interesting tool for obtaining highly selective and sensitive sensors. In this work, the surface segregation of Cd cations on SnO2 nanopowders prepared by the Pechini's method was studied by infrared spectroscopy, X-ray diffraction, and specific surface area analysis. We observed that the surface chemistry modifications caused by the surface segregation of Cd and the large specific surface area were closely responsible for a rapid and regular electrical response of 5 mol% Cd-doped SnO2 films to 100 ppm propane and NOx diluted in dry air at relatively low temperature (100 °C). © 2008 Elsevier B.V. All rights reserved.
- Surface modification of SnO 2 nanoparticles containing Mg or Fe: Effects on sintering(2007) Castro R.H.R.; Pereira G.J.; Gouvea D.Controlling the surface chemistry of oxide systems has emerged an effective tool to obtain desirable nanostructures and macro properties. A relatively simple way to achieve this is by using dopants that are prone to segregate to the surfaces of the powders. In this work, we delineate the effect of Mg and Fe on SnO 2 nanopowders focusing on the surface modifications caused by surface segregation. The effects of increasing the temperature of calcinations are particularly addressed to evaluate the surface modifications at high temperatures. The powders were studied by infrared spectroscopy, zeta potential measurements, X-ray diffraction, and specific surface area measurements. Since sintering is a high-temperature process strongly dependent on surface characteristics, we drawn a relationship between the final densities after sintering and the surface chemistry of the doped powders. Doped SnO 2 pellets were sintered to over 95% of the theoretical density within a few seconds (fast firing) when significant surface modifications were observed. © 2006 Elsevier B.V. All rights reserved.