Estimation of the diffusion coefficient of water evolved during the non-isothermal dehydration of Australian sedimentary opal

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Journal Article
Journal of Thermal Analysis and Calorimetry, 2007, 88 (1), pp. 231 - 235
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The dehydration of an opal specimen was investigated by thermogravimetric analysis (TG) in powder and bulk forms. The change in geometry resulted in a significant difference in the temperature range in which dehydration occurred with peak temperatures in the differential TG (DTG) curve for the hand ground opal at 203°C and for the bulk opal at 340°C. This difference was attributed to time taken for diffusion of free water in the bulk opal to the specimen surface prior to evolution as a registered mass loss. A model was proposed to account for the diffusion of water and was used to estimate the diffusion coefficient. © Springer-Verlag 2007.
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