27Al and 29Si MAS NMR Study of Kaolinite Thermal Decomposition by Controlled Rate Thermal Analysis |
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| Authors: | Dominique Massiot,Pascal Dion,Jean Fran¸ ois Alcover,Faiza Bergaya |
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| Affiliation: | Centre de Recherche sur la Physique des Hautes Températures, CNRS, 45071 Orléans cedex 2, France;Centre de Recherche sur la Matière Divisée, CNRS, 45071 Orléans cedex 2, France |
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| Abstract: | The processing of kaolinite under controlled rate thermal analysis conditions (CRTA) provides homogeneously transformed samples at defined dehydroxylation rates. The kaolinite-to-metakaolinite transformation has been monitored by solid-state NMR and X-ray diffraction. The metakaolinite product is an amorphous material with no resolved XRD pattern and is based on a disordered polymerized silicon/aluminum network in which aluminum preferably occupies four- and five-fold structural positions in the ratio 60% AlVI, 30% AlV, and 10% AlVI. This complex dehydroxylation process has been viewed at different scales, with the aluminum NMR tracing a site-by-site destructon of the octahedral sheet and the silicon NMR and XRD following a more rapid destruction of the longrange order. |
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