Artículos de revistas
Thermal decomposition and structural reconstruction effect on Mg-Fe-based hydrotalcite compounds
Journal Of Solid State Chemistry. Academic Press Inc Elsevier Science, v. 177, n. 9, n. 3058, n. 3069, 2004.
de Paiva, JAC
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.177930583069