| 研究実績の概要 |
This study aims to obtain complementary information of bonding geometry and diffusion dynamics of structurally-bound hydrogen in the most-major water reservoir minerals existing in the Earth's deep mantle. In particular, we focus to analyze hydrous wadsleyite, hydrous ringwoodite, dense hydrous magnesium silicate (DHMS) phase E, and hydrous bridgmamite for obtaining the described information. In the last year, we successfully synthesized chemically-homogenous single crystals of DHMS phase E of more than 0.7 mm sizes at high pressure and temperature condition; these crystals were proved to be ideal samples for single crystal neutron diffraction (SCND). Their SCND analysis for determining bonding geometry of hydrogen were successfully carried out at BL 18 at Materials and Life Science Experimental Facility (MLF), Japan Proton Accelerator Research Complex (J-PARC), in February 2018. We measured two crystals at temperatures of 300 K and at 470 K, respectively. By conducting preliminary structure refinement, we successfully found the position of hydrogen and its bonding geometry in the structure of DHMS phase E. In addition, we had started independent synthesis experiments of hydrous ringwoodite to be analyzed by quasielastic neutron scattering.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
For the moment, we are successfully analyzing the SCND datasets of DHMS phase E obtained at room and high temperture conditions without any problem. We already found approximate hydrogen position and bonding geometry in the crystal structure of DHMS phase E. Meanwhile, the synthesis of hydrous ringwoodite powder sample is still proceeding. We were using 18/10 cell for the synthesis of hydrous ringwoodite, and obtained up to 80 mg of homogeneous sample after conducting each run. After three testing experiments, we successfully determined proper synthesis condition of the hydrous ringwoodite powders.
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| 今後の研究の推進方策 |
The first measurement of quasielastic neutron scattering of hydrous ringwoodite has been scheduled to be conducted in June 2018 at BL 02, MLF, J-PARC. The synthesis of hydrous ringwoodite powder samples will be finishing within May 2018. The sample will be characterized along with the synthesis experiments; we will conduct powder x-ray diffraction for phase identification and thermogravimetry for water content estimation of the synthesized samples. The quasielastic neutron scattering analysis is designed for observing diffusion dynamics of hydrogen in ringwoodite structure at high temperature conditions. In addition, we will soon start working for the synthesis of hydrous bridgmanite single crystals to be analysed by SCND, as well as writing the manuscript on the structure refinement results of DHMS phase E.
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