|
|||||
|
|
A comparative study of the thermal behaviour of length-fast chalcedony, length-slow chalcedony (quartzine) and moganite |
|
| Authors: | Patrick Schmidt Aneta Slodczyk Vanessa Léa Anne Davidson Simon Puaud Philippe Sciau |
| Institution: | 1. Muséum national d’histoire naturelle, Dept. de Préhistoire UMR 7194, Centre de spectroscopie infrarouge, CP 57, 57, rue Cuvier, 75231, Paris Cedex 05, France 2. Laboratoire de dynamique, interactions et réactivité (LADIR), UMR 7075, CNRS, Université Pierre et Marie Curie (UPMC)-Paris 6, 4 Place Jussieu, 75252, Paris Cedex 05, France 3. TRACES, UMR 5608, Université Toulouse II le Mirail, Maison de la Recherche, 5, allée A. Machado, 31058, Toulouse CEDEX 9, France 4. Laboratoire de Réactivité de Surface (LRS), UMR 7197, CNRS, Université Pierre et Marie Curie (UPMC)-Paris 6, 3, rue Galilée, 94200, Ivry sur Seine, France 5. Muséum national d’histoire naturelle, Dpt. de Préhistoire UMR 7194 CNRS, 1, rue René-Panhard, 75013, Paris, France 6. CEMES, CNRS UPR 8011, Université de Toulouse, 29 rue Jeanne Marvig, 31055, Toulouse, France |
| Abstract: | The thermal behaviour of silica rocks upon heat treatment is dependent on the constituent minerals and petrographic texture types. These constituents can be shown to be mainly quartz in the form of two types of chalcedony (Length-fast (LF) chalcedony and Length-slow (LS) chalcedony, the latter also being termed quartzine) and moganite. Even though the thermal behaviour of LF-chalcedony is well understood, major uncertainties persist concerning the high-temperature behaviour of LS-chalcedony and moganite. We present here a comparative study of these three constituents of common silica rocks. Our results show that the chemical reaction is the same in all three, Si–OH + HO–Si → Si–O–Si + H2O, but that the reaction kinetics and activation temperatures are very different. LS-chalcedony begins to react from 200 °C upwards, that is at temperatures 50 °C below the ones observed in LF-chalcedony, and shows the fastest reaction kinetics of this ‘water’ loss. Chemically bound water (SiOH) in moganite is more stable at high temperatures and no specific activation temperature is necessary for triggering the temperature-induced ‘water’ loss. Moganite is also found to act as a stabilizer in silica rocks preventing them from temperature-induced fracturing. These findings have implications for the study of potential heat treatment temperatures of silica rocks (in industry and heritage studies), but they also shed light on the different structures of SiO2 minerals and the role of OH impurities therein. |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ | |