The kinetics of dehydration and order-disorder of molecular H20 in Mg-cordierite
Giampaolo, Ciriaco; Putnis, Andrew
European Journal of Mineralogy Volume 1 Number 2 (1989), p. 193 - 202
published: May 3, 1989
manuscript accepted: Oct 6, 1988
manuscript received: Apr 9, 1988
ArtNo. ESP147050102005, Price: 29.00 €
Abstract The kinetics of water loss in synthetic, hydrated Mg-cordierite has been studied between 336 °C and 687 °C by thermogravimetry. Analysis of the rate data shows that water loss is controlled by two thermally activated processes, one with activation energy, Ea of 39 kJ/mole, the other with Ea 135.5 kJ/mole. The lower Ea process, which may be associated with the loss of disordered, loosely-bound H2O, operates in the early stages of the dehydration, the proportion of water being lost by this process increasing markedly with temperature. The higher Ea process, associated with the loss of ordered, strongly-bound H2O, decreases in importance at high temperatures where most of the channel water is disordered. The kinetic data is used to define the temperature dependence of the change in structural state of H2O molecules from ordered Type I (with H-H vector parallel to the c axis) to disordered.