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Thermodynamics of the Various High Temperature Transformations of Kaolinite

Published online by Cambridge University Press:  01 January 2024

N. C. Schieltz  and
M. R. Soliman
N. C. Schieltz
Affiliation:
Colorado School of Mines, Golden, Colorado, USA
M. R. Soliman
Affiliation:
Geological Survey and Mineral Research Department, Ministry of Industry, Cairo, Egypt
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Abstract

Thermodynamic calculations of ΔG for all possible transformations of metakaolin at the temperature of the first DTA exothermic peak indicates that the most stable transformation is the one that yields mullite rather than γ-alumina.

The energy of crystallization of γ-alumina is quite small—36,513 cal per mol, compared with the energy of crystallization of mullite—336,180 cal per mol. Furthermore, the crystallization of γ-alumina is very slow, and the crystal growth never produces crystallite sizes much larger than the lower end of the colloidal region. Hence, the gradual release of the small amounts of energy liberated during the crystallization of γ-alumina would be extremely difficult to detect by DTA methods.

Information

Type
General Session
Information
Clays and Clay Minerals (National Conference on Clays and Clay Minerals) , Volume 13 , February 1964 , pp. 419 - 428
Copyright
Copyright © Clay Minerals Society 1964

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