1H, 29Si and 27Al NMR study of the destabilization process of a paracrystalline opal from Mexico

This is the first NMR study of the destabilization through whitening of paracrystalline opal-CT (SiO 2, nH 2O). The aim of this study is to understand the process leading to the degradation, particularly any changes in the structure and bonding of this material. 29Si and 27Al NMR signals are not sig...

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Bibliographic Details
Published in:Journal of non-crystalline solids 2007-06, Vol.353 (16), p.1650-1656
Main Authors: Paris, Michaël, Fritsch, Emmanuel, Aguilar Reyes, Bertha O.
Format: Article
Language:English
Subjects:
Crystalline rocks
Earth sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Geophysics. Techniques, methods, instrumentation and models
Hydration
NMR, MAS–NMR and NQR
Short-range order
Silica
Water
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Summary:This is the first NMR study of the destabilization through whitening of paracrystalline opal-CT (SiO 2, nH 2O). The aim of this study is to understand the process leading to the degradation, particularly any changes in the structure and bonding of this material. 29Si and 27Al NMR signals are not significantly modified. In contrast, using for the first time 1H as a probe in opal, we show that a comprehensive understanding can be obtained on both the local structure of the opal-CT and the destabilization process. Thus, we propose the latter is related to some changes in 1H speciation (loss of strongly ‘bound’ water and appearance of new species) which induce structural reorganizations on the surface and in the rim of the silica nanograins constituting opal-CT.
ISSN:0022-3093
1873-4812
DOI:10.1016/j.jnoncrysol.2006.12.111