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Desordre a courte distance dans les phases transitoires resultant de l'activation thermique des montmorillonites

Published online by Cambridge University Press:  09 July 2018

A. Delmastro
Affiliation:
Politecnico di Torino, Dipartimento di Scienza dei Materiali e Ingegnieria Chimica, Corso Duca degli Abruzzi, 24 10129 Torino, Italia
A. Bachiorrini
Affiliation:
Politecnico di Torino, Dipartimento di Scienza dei Materiali e Ingegnieria Chimica, Corso Duca degli Abruzzi, 24 10129 Torino, Italia
M. Murat
Affiliation:
Politecnico di Torino, Dipartimento di Scienza dei Materiali e Ingegnieria Chimica, Corso Duca degli Abruzzi, 24 10129 Torino, Italia

Résumé

Des phases transitoires ont été préparées par activation thermique de deux montmorillonites, l'une calcique et l'autre sodique, dans le domaine de température 650–950°C, puis étudiées par spectroscopie infrarouge. Le coefficient de désordre à courte distance, défini à partir de l'élargissement et l'intensité de certaines bandes caracteristiques, présente ses valeurs maximales avec les phases transitoires obtenues à 800°C et 820–850°C respectivement pour la couche de silice et la couche d'alumine. Ce résultat a pu être corrélé à plusieurs données expérimentales concernant la cinétique de dissolution de ces phases transitoires dans l'acide fluorhydrique dilué ou dans des solutions saturées d'hydroxyde de calcium. En outre, l'accroissement particulièrement marqué du désordre à courte distance mis en évidence au niveau de la transition V→IV de la coordinance de l'aluminium, confirme l'hypothèses émise antérieurement par d'autres auteurs pour expliquer le troisième effet endothermique de faible intensité observé sur les courbes ATD des montmorillonites entre 800° et 900°C.

Abstract

Abstract

Transitory phases have been prepared by thermal activation of Ca- and Na-montmorillonites from 650 to 950°C, and investigated by IR spectroscopy. The short-range disorder index, defined from both the broadening and the intensity of characteristic bands, reaches its maximum value with transitory phases obtained at 800°C and 820–850°C for the silica layer and the alumina one, respectively. This result has been correlated with data dealing with the dissolution of transitory phases either in dilute hydrofluoric acid or in a saturated calcium hydroxide solution. In addition, the particularly large increase in short-range disorder observed when the Al(V)→Al(IV) transition occurs, experimentally confirms a previous hypothesis to explain the third endothermic effect observed on the DTA curve of montmorillonite between 800° and 900°C.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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