Material investigation on Core-Mantle Boundary

本研究利用改进的双面激光加热金刚石对顶砧装置（LHDAC），对地幔中几种主要矿物在高温高压下的性质进行了研究。本研究的结果如下：（1）东北大学新开发的激光加热系统，可以在压力下稳定地加热较大的样品。这些技术精华已反馈到Photon Factory和SPring-8的LHDAC原位X射线衍射系统的构建中。(2)在30 - 60 GPa的压力范围内检查铁和硅酸盐钙钛矿之间的反应。在30 GPa激光加热后，在回收的样品中检测到产生铁硅化物的反应的可能性。从60 GPa和2800 K恢复的织构显示出熔融铁渗透到硅酸盐钙钛矿的晶界。(3)用同步辐射原位X射线衍射方法研究了（Mg，Fe）O的高温高压行为。在所有组合物中观察到菱面体畸变。在100 GPa左右的高温相为岩盐结构，除FeO端元外没有观察到NiAs结构相。因此，最低地幔条件下的稳定相应具有岩盐结构。(4)用原位X射线衍射方法研究了SiO_2的后斯铁橄榄石相。在55 GPa以上观察到CaCl 2结构相，其在80 GPa和2000 K下稳定。结果表明，该跃迁的Clausius-Clapeyron斜率为正。(5)用原位X射线衍射方法研究了铁-水反应。体心立方铁直接与水反应生成氢氧化铁，并在较高温度下依次转变为氢化铁和方铁矿。面心立方铁在激光加热后发生反应生成氢化铁和浮氏体。这些氢化铁在环境条件下是不能淬灭的。

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.