Wiley Acta Medica Okayama 1086-9379 59 6 2024 Wetting property of Fe‐S melt in solid core: Implication for the core crystallization process in planetesimals 1314 1328 EN Shiori Matsubara Department of Earth Sciences, Graduate School of Science and Technology, Okayama University Hidenori Terasaki Department of Earth Sciences, Graduate School of Science and Technology, Okayama University Takashi Yoshino Institute for Planetary Materials, Okayama University Satoru Urakawa Department of Earth Sciences, Graduate School of Science and Technology, Okayama University Daisuke Yumitori Department of Earth Sciences, Graduate School of Science and Technology, Okayama University In differentiated planetesimals, the liquid core starts to crystallize during secular cooling, followed by the separation of liquid–solid phases in the core. The wetting property between liquid and solid iron alloys determines whether the core melts are trapped in the solid core or they can separate from the solid core during core crystallization. In this study, we performed high-pressure experiments under the conditions of the interior of small bodies (0.5–3.0 GPa) to study the wetting property (dihedral angle) between solid Fe and liquid Fe-S as a function of pressure and duration. The measured dihedral angles are approximately constant after 2 h and decrease with increasing pressure. The dihedral angles range from 30° to 48°, which are below the percolation threshold of 60° at 0.5–3.0 GPa. The oxygen content in the melt decreases with increasing pressure and there are strong positive correlations between the S + O or O content and the dihedral angle. Therefore, the change in the dihedral angle is likely controlled by the O content of the Fe-S melt, and the dihedral angle tends to decrease with decreasing O content in the Fe-S melt. Consequently, the Fe-S melt can form interconnected networks in the solid core. In the obtained range of the dihedral angle, a certain amount of the Fe-S melt can stably coexist with solid Fe, which would correspond to the “trapped melt” in iron meteorites. Excess amounts of the melt would migrate from the solid core over a long period of core crystallization in planetesimals. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0342-1791 50 3 2023 Sound velocity and elastic properties of Fe–Ni–S–Si liquid: the effects of pressure and multiple light elements 19 EN Iori Yamada Department of Earth and Space Science, Osaka University Hidenori Terasaki Department of Earth Sciences, Okayama University Satoru Urakawa Department of Earth Sciences, Okayama University Tadashi Kondo Department of Earth and Space Science, Osaka University Akihiko Machida Synchrotron Radiation Research Center, National Institutes for Quantum Science and Technology (QST) Yoshinori Tange Japan Synchrotron Radiation Research Institute Yuji Higo Japan Synchrotron Radiation Research Institute Fe–Ni–S–Si alloy is considered to be one of the plausible candidates of Mercury core material. Elastic properties of Fe–Ni–S–Si liquid are important to reveal the density profile of the Mercury core. In this study, we measured the P-wave velocity (VP) of Fe–Ni–S–Si (Fe73Ni10S10Si7, Fe72Ni10S5Si13, and Fe67Ni10S10Si13) liquids up to 17 GPa and 2000 K to study the effects of pressure, temperature, and multiple light elements (S and Si) on the VP and elastic properties.<br> The VP of Fe–Ni–S–Si liquids are less sensitive to temperature. The effect of pressure on the VP are close to that of liquid Fe and smaller than those of Fe–Ni–S and Fe–Ni–Si liquids. Obtained elastic properties are KS0 = 99.1(9.4) GPa, KS’ = 3.8(0.1) and ρ0 =6.48 g/cm3 for S-rich Fe73Ni10S10Si7 liquid and KS0 = 112.1(1.5) GPa, KS’ = 4.0(0.1) and ρ0=6.64 g/cm3 for Si-rich Fe72Ni10S5Si13 liquid. The VP of Fe–Ni–S–Si liquids locate in between those of Fe–Ni–S and Fe–Ni–Si liquids. This suggests that the effect of multiple light element (S and Si) on the VP is suppressed and cancel out the effects of single light elements (S and Si) on the VP. The effect of composition on the EOS in the Fe–Ni–S–Si system is indispensable to estimate the core composition combined with the geodesy data of upcoming Mercury mission. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2075-163X 10 1 2020 X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa 84 EN Satoru Urakawa Department of Earth Sciences, Okayama University Toru Inoue Department of Earth and Planetary Systems Science, Hiroshima University Takanori Hattori J-PARC Center, Japan Atomic Energy Agency Asami Sano-Furukawa J-PARC Center, Japan Atomic Energy Agency Shinji Kohara Research Center for Advanced Measurement and Characterization, National Institute for Materials Science (NIMS) Daisuke Wakabayashi Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tomoko Sato Department of Earth and Planetary Systems Science, Hiroshima University Nobumasa Funamori Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) Ken-ichi Funakoshi Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 angstrom. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si-OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra. No potential conflict of interest relevant to this article was reported.