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Nanostructures of the montmorillonite-derived restructured clays K10®, HMO and the Mg2+ exchanged analogue Mg-HMO. A SANS, N2 sorption and XRPD study

Small angle neutron scattering (SANS) of the montmorillonite (MO)-derived acid-restructured clays K10, HMO and the Mg2+ exchanged congener of the latter, Mg-HMO, has been investigated. K10 is a strong acid-treated clay, HMO a new, mild-acid treated material with different X-ray powder diffraction (X...

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Bibliographic Details
Published in:Journal of materials chemistry 2003-04, Vol.13 (5), p.1145-1148
Main Authors: De Stefanis, A., Tomlinson, A. A. G., Steriotis, Th. A., Stefanopoulos, K. L., Keiderling, U.
Format: Article
Language:English
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Summary:Small angle neutron scattering (SANS) of the montmorillonite (MO)-derived acid-restructured clays K10, HMO and the Mg2+ exchanged congener of the latter, Mg-HMO, has been investigated. K10 is a strong acid-treated clay, HMO a new, mild-acid treated material with different X-ray powder diffraction (XRPD) characteristics and Mg-HMO a Mg2+ exchanged derivative; the scattering curve of the latter exhibits a peak at Q = 5.46 nm-1 ascribed to intra-layer Mg2-Mg2+ distances. Analysis of the mid-Q region (0.2-2.6 nm -1) of the curves demonstrates that K10 and HMO differ in nanostructure. In particular, the solid matrix of K10 exhibits a mass fractal dimension, Dm = 2.53 which is absent from HMO but which is characteristic for sepiolites prepared via prolonged acid treatment. For Mg-HMO, recently found to be an efficient base catalyst for fine chemicals production, both XRPD and SANS point to a more ordered "parallel-plate in primary particle" shape. This is ascribed to both intercalation of Mg2+N between aluminosifcate sheets and enhanced correlation between platelets due to surface Mg2+ cations acting to bind clay platelet packets together face to face in agreement with the high Mg2+ loading level of HMO (10% w/w). The presence of the Mg2+ cations reduces the surface roughness and results in an increase of the length of the platelet packets in line with this enhanced ordering.
ISSN:0959-9428
1364-5501
DOI:10.1039/b300292f