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Characterization of Hexagonal and Lamellar Mesoporous Silicas, Aluminosilicates and Gallosilicates by Small-Angle X-ray Scattering by G. Van den Bossche; R. Sobry; F. Fontaine; J.-M. Clacens; Z. Gabelica is a Materials Science article available to read on EtoBox.

What is Characterization of Hexagonal and Lamellar Mesoporous Silicas, Aluminosilicates and Gallosilicates by Small-Angle X-ray Scattering about?

Various mesoporous silicas and the corresponding aluminosilicates or gallosilicates have been synthesized using a series of literature or 'home-made' recipes. The efficiency of AI or Ga incorporation into the siliceous walls of these materials depends markedly on the trivalent source and the evolution (ageing) of the soformed Si-A/an gel-type phases at different starting pH values and temperatures, alter adding the surfactantstructuring compounds. Crystallization at low temperature (e.g. <373 K) yielded mesoporous compounds with hexagonal topology (MCM-41 type), involving doublelayered Si walls possibly partly substituted by A1 or Ga. Such structures remain stable after calcination in air at 873 K. When the same gels are crystallized at 423 K for 2 d, lamellar frameworks (MCM-50 type) are preferentially stabilized. They readily collapse on heating. The ultra-small-angle X-ray scattering (USAXS) data and the first part of the SAXS data show a power behaviour that indicates a fractal interface before calcination. After calcination, in the case of MCM-50 type materials, the fractal dimension significantly increases, the fractality region being larger than in the precursor. By contrast

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Author

G. Van den Bossche; R. Sobry; F. Fontaine; J.-M. Clacens; Z. Gabelica

Publisher

International Union of Crystallography; Blackwell Publishing Inc.; International Union of Crystallography (IUCr) (ISSN 0021-8898)

Published

1997

Language

EN

Field

Materials Science (Physical Sciences)