Material investigation on Core-Mantle Boundary

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In this research, we investigated the properties on some major mantle minerals under high pressure and high temperature using an improved double-sided laser heated diamond anvil cell (LHDAC). The results of this research are followings;(1)We newly developed a laser heating system at Tohoku University, which enable to heat the larger sample stably under pressure. The technical essences were feed backed to construction of in-situ X-ray diffraction system using LHDAC in both Photon Factory and SPring-8.(2) The reaction between iron and silicate perovskite was examined for the pressure range of 30 - 60 GPa. A possibility of reaction which produce iron silicide was detected in the recovered sample after laser heating at 30 GPa. The texture recovered from 60 GPa and 2800 K show a percolation of molten iron into the grain boundary of silicate perovskite.(3) High pressure and high temperature behavior of (Mg,Fe)O was examined using in-situ X-ray diffraction method with synchrotron radiation. A rhombohedral distortion was observed in all compositions. High temperature phase at around 100 GPa has rock salt structure and no NiAs-structured phase was observed except for the end member of FeO. Therefore, the stable phase under the lowermost mantle condition should have rock salt structure.(4) Post stishovite phase of Si0_2 was examined using in-situ X-ray diffraction method. CaCl2-structured phase was observed above 55 GPa, which was stable up to 80 GPa and 2000 K. The results show that the Clausius-Clapeyron slope of this transition is slightly positive.(5) Iron-water reaction was examined using in-situ X-ray diffraction method. The bcc iron directly reacted with water to produce iron hydrate and showed successive transition to iron hydride and wustite at higher temperature. The fcc iron reacted to produce iron hydride and wustite after laser heating. These iron hydride were unquenchable to ambient condition.