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Abstract
Pyrophyllite gaskets heated up to 900 °C for 1 h and raw gaskets (without heating treatment) were characterized by X-ray diffraction and Raman spectroscopy. These gaskets were used in multi-anvil high-pressure experiments to investigate the effect of pre-heating on pressure generation in Kawai-type apparatus. The results show that the gaskets heated at low temperatures (200–500 °C) have no change in structure and those heated at higher temperatures (600–900 °C) dehydroxylate gradually. No structural OH is observed in 900 °C pre-heated gasket from Raman spectroscopy indicating a complete dehydroxylation. The low temperature (200–500 °C) pre-heated gasket causes a limited effect on pressure generation, and the high-temperature (600–900 °C) pre-heated gasket has a relatively large negative effect on pressure generation.
Acknowledgements
The authors thank M. Kanzaki for Raman spectroscopic analyses, T. Matsuzaki for technical support, and D. Yamazaki and T. Katsura for valuable discussions. This work was financially supported by the program of “Centre of Excellence (COE) for the 21st Century in Japan”, and National Natural Science Foundation of China (grant no. 40402006).