Thermal decomposition and structural reconstruction effect on Mg–Fe-based hydrotalcite compounds
- 作者：Ferreira ; Odair P. ; Alves ; Oswaldo L. ; Gouveia ; Daniel X. ; Souza Filho ; Antonio G. ; de Paiva ; José ; A.C. ; et. al.
- 关键词：Layered double hydroxides ; Hydrotalcite-like compounds ; Pyroaurite ; Anionic clays ; Thermal decomposition ; Mixed oxides ; Spinel ; Rehydration ; Structural reconstruction ; Memory Effect ; Mö ; ssbauer spectroscopy ; Iron
- 刊名：Journal of Solid State Chemistry
- 出版年：2004
- 期刊代码：130_00224596
- 类别：ch
- 出版时间：September, 2004
- 卷：177
- 期：9
- 页码：3058-3069
- 文件大小：2.04 M
摘要
The thermal decomposition and structural reconstruction of Mg–Fe-based hydrotalcites (HT) have been studied through thermogravimetric analyses, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy and Mössbauer spectroscopy. The destruction of the layered structure took place at about 300°C. 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 500°C, the formation of the MgO and MgFe2O4 spinel phases is observed. 57Fe Mössbauer spectroscopy was employed to monitor the Fe chemical environment for the samples annealed at different temperatures (100–900°C). In situ XRD experiments revealed that the HTs start an interlayer contraction at about 180°C. 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.