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Report No.

In situ X-ray observations of the decomposition of brucite and the graphite-diamond conversion in aqueous fluid at high pressure and temperature

Okada, Taku; Utsumi, Wataru; Kaneko, Hiroshi*; Yamakata, Masaaki*; Shimomura, Osamu

An experimental technique to make real-time observations at high pressure and temperature of the diamond forming process in candidate material of mantle fluids as a catalyst has been established for the first time. In situ X-ray diffraction experiments using synchrotron radiation have been performed upon a mixture of brucite (Mg(OH)$$_{2}$$) and graphite as starting material. Brucite decomposes into periclase (MgO) and H$$_{2}$$O at 3.6 GPa and 1050$$^{circ}$$C while no periclase is formed after the decomposition of brucite at 6.2 GPa and 1150$$^{circ}$$C, indicating that the solubility of the MgO component in H$$_{2}$$O greatly increases with increasing pressure. The conversion of graphite to diamond in aqueous fluid has been observed at 7.7 GPa and 1835$$^{circ}$$C. Time-dependent X-ray diffraction profiles for this transformation have been successfully obtained.



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Category:Materials Science, Multidisciplinary



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