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The Effects of Trace Metal Cations on the High Temperature Reactions of an Halloysite Mineral

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posted on 2021-11-12, 15:37 authored by Maciver, Susan Margaret

This thesis describes a kinetic study of the high temperature solid state reactions of a well characterized halloysite mineral and five of its cation-saturated forms, the cations used being sodium, calcium, manganese, copper and iron (Ill). The reaction sequence may be represented by the idealised equations: The formation of mullite from metakaolinite has been studied in the temperature range 1020° - 1200°C, by X-ray analysis. Comparison of the experimental data with several theoretical models suggests that up to 90% conversion the reaction takes place by exponential nucleation followed by crystal growth. There is, however, some evidence for diffusion occurring as a rate controlling process, especially at high degrees of conversion to mullite. The rate constants and experimental thermodynamic functions have been evaluated for all halloysite samples. The free energies of activation (111-128 k cal.mole-1) and the rate constants are independent of the starting materials, but the enthalpies of activation (51-118 k cal.mole-1) and the entropies of activation (0 to -50 cal.deg.-1 mole-1) are not.


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Te Herenga Waka—Victoria University of Wellington

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Te Herenga Waka—Victoria University of Wellington

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Degree Name

Master of Science

Victoria University of Wellington Item Type

Awarded Research Masters Thesis



Victoria University of Wellington School

School of Chemical and Physical Sciences


Duncan, J. F.; Foster, P. K.