Although the kinetics of the dehydroxylation of kaolinite have been widely studied, there is no definitive explanation of its mechanism due to its dependence on a variety of parameters. In this study, the dehydroxylation of kaolinite has been studied using controlled-transformation rate thermal analysis (CRTA), allowing precise control of the reaction rate, and thus of both the temperature and pressure above the sample. Modelling of the experimental results obtained by CRTA as well as those from TEM and MAS-NMR show that two elementary processes (diffusion and firstorder) can occur in competition. At the start of the decomposition the diffusion mechanism is predominant, but as the reaction progresses, the first-order mechanism prevails. It would seem that the importance of each process depends, in particular, on the presence of defects as well as on the local vapour pressure.
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Document Type: Research Article
Centre de Recherche sur la Matière Divisée, CNRS, F-45071 Orléans cedex 2, France
Instituto de Ciencia de Materiales y Departamento de Quimica Inorganica, Universidad de Sevilla, Spain
Centre de Thermodynamique et de Microcalorimétrie du CNRS, 26 rue du 141è RIA, F-13331 Marseille cedex 3, France
Publication date: 1998-06-01
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