Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/57997
Type: Artigo de periódico
Title: Thermal decomposition and structural reconstruction effect on Mg-Fe-based hydrotalcite compounds
Author: Ferreira, OP
Alves, OL
Gouveia, DX
Souza, AG
de Paiva, JAC
Mendes, J
Abstract: The thermal decomposition and structural reconstruction of Mg-Fe-based hydrotalcites (FIT) have been studied through thermogravimetric analyses, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy and Mossbauer spectroscopy. The destruction of the layered structure took place at about 300degreesC. The broad peaks observed in the X-ray diffractograms suggest that the resultant oxides constitute a solid solution. For samples treated at temperatures higher than 500degreesC, the formation of the MgO and MgFe2O4 spinel phases is observed. Fe-57 Mossbauer spectroscopy was employed to monitor the Fe chemical environment for the samples annealed at different temperatures (100-900degreesC). In situ XRD experiments revealed that the HTs start an interlayer contraction at about 180degreesC. This phenomenon is identified as being due to a grafting process for which the interlamellar anions attach to the layers through a covalent bond. The reconstruction of the HTs was also investigated and its efficiency depends on the thermal annealing temperature and the Mg/Fe ratio. The structure of the reconstructed samples was found to be exactly the same as the parent structure. (C) 2004 Elsevier Inc. All rights reserved.
Subject: layered double hydroxides
hydrotalcite-like compounds
pyroaurite
anionic clays
thermal decomposition
mixed oxides
spinel
rehydration
structural reconstruction
Memory Effect
Mossbauer spectroscopy
iron
Country: EUA
Editor: Academic Press Inc Elsevier Science
Rights: fechado
Identifier DOI: 10.1016/j.jssc.2004.04.030
Date Issue: 2004
Appears in Collections:Unicamp - Artigos e Outros Documentos

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