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Estimation of the diffusion coefficient of water evolved during the non-isothermal dehydration of Australian sedimentary opal |
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| Authors: | P S Thomas P Šimon A Smallwood A S Ray |
| Institution: | (1) Department of Chemistry, Materials and Forensic Sciences, University of Technology Sydney, Sydney, Australia, NSW 20007, PO Box 123, Broadway;(2) Institute Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Bratislava, Slovak Republic, 812 37, Radlinského 9 |
| Abstract: | 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. |
| Keywords: | amorphous silica dehydration diffusion coefficient Fickian diffusion opal thermogravimetric analysis |
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