研究者詳細 - 寺﨑　英紀

論文 - 寺﨑　英紀

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形成期の惑星内部における鉄合金メルトとケイ酸塩の分離過程査読

岸本俊八, 浦川啓, 寺﨑英紀, 桑原荘馬, 西田圭佑, 坂巻竜也, 竹内晃久, 上杉健太朗

SPring-8/SACLA利用研究成果集 25 208 - 211 2018年

高温高圧下での鉄-珪素合金の弾性波速度測定査読

坂巻竜也, 寺﨑英紀, 柴﨑裕樹, 戸邉宙, 下山裕太, 肥後祐司, 鈴木昭夫

日本鉱物科学会年会講演要旨集 2017 ( 0 ) 103 - 103 2017年

記述言語：日本語出版者・発行元：一般社団法人日本鉱物科学会

惑星核を模擬した鉄-珪素合金に対して、圧力6 GPa、温度1873 Kまでの条件下で物性（密度・弾性波速度）測定に成功し、その温度・圧力依存性を決定した。本実験で用いたFe-10at%Si系では、体心立方格子構造(bcc)のみ1相と面心立方格子構造(fcc)のみ1相、bcc+fccの2相共存の3つの状態が観察された。bcc単相とfcc単相の物性比較から、結晶構造由来による違いを明らかにした。bcc構造においては同じ密度条件で純鉄とも比べ、珪素の付加による弾性波速度の上昇を確認した。また、fcc構造は水星や火星核条件下で安定であると考えられるため、本研究で得られた弾性特性と将来観測されるデータの比較から惑星核に対する新しい知見を得られることが期待される。

DOI： 10.14824/jakoka.2017.0_103

Simultaneous sound velocity and density measurements of iron-silicon alloys under core conditions of Mercury and Mars

Sakamaki, T, Terasaki, H, Shibazaki, Y, Suzuki, A, Tobe, H, Higo, Y, Kurokawa, F, Maki, M, Shimoyama, Y, Saito, R

SPring-8 User Experiment Report 2016B 2016B1111 2017年

Thermoelastic properties of liquid Fe-C revealed by sound velocity and density measurements at high pressure 査読

Yuta Shimoyama, Hidenori Terasaki, Satoru Urakawa, Yusaku Takubo, Soma Kuwabara, Shunpachi Kishimoto, Tetsu Watanuki, Akihiko Machida, Yoshinori Katayama, Tadashi Kondo

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 121 ( 11 ) 7984 - 7995 2016年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER GEOPHYSICAL UNION

Carbon is one of the possible light elements in the cores of the terrestrial planets. The P wave velocity (V-P) and density (rho) are important factors for estimating the chemical composition and physical properties of the core. We simultaneously measured the V-P and rho of Fe-3.5 wt % C up to 3.4 GPa and 1850 K by using ultrasonic pulse-echo method and X-ray absorption methods. The V-P of liquid Fe-3.5 wt % C decreased linearly with increasing temperature at constant pressure. The addition of carbon decreased the V-P of liquid Fe by about 2% at 3 GPa and 1700 K and decreased the Fe density by about 2% at 2 GPa and 1700 K. The bulk modulus of liquid Fe-C and its pressure (P) and temperature (T) effects were precisely determined from directly measured rho and V-P data to be K-0,K-1700 K = 83.9 GPa, dK(T)/dP = 5.9(2), and dK(T)/dT = -0.063(8) GPa/K. The addition of carbon did not affect the isothermal bulk modulus (K-T) of liquid Fe, but it decreased the dK/dT of liquid Fe. In the rho-V-P relationship, V-P increases linearly with rho and can be approximated as V-P (m/s) = -6786(506) + 1537(71) x rho (g/cm(3)), suggesting that Birch's law is valid for liquid Fe-C at the present P-T conditions. Our results imply that at the conditions of the lunar core, the elastic properties of an Fe-C core are more affected by temperature than those of Fe-S core.

DOI： 10.1002/2016JB012968

Towards a consensus on the pressure and composition dependence of sound velocity in the liquid Fe-S system 査読

Keisuke Nishida, Akio Suzuki, Hidenori Terasaki, Yuki Shibazaki, Yuji Higo, Souma Kuwabara, Yuta Shimoyama, Moe Sakurai, Masashi Ushioda, Eiichi Takahashi, Takumi Kikegawa, Daisuke Wakabayashi, Nobumasa Funamori

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 257 230 - 239 2016年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Recent advances in techniques for high-pressure and high-temperature experiments enable us to measure the velocity of sound in liquid Fe alloys. However, reported velocities in liquid Fe S differ among research groups (e.g., by >10% at 5 GPa), even when similar methods are used (i.e., the ultrasonic pulse echo overlap method combined with a large volume press). To identify the causes of the discrepancies, we reanalyzed previous data and conducted additional sound velocity measurements for liquid Fe S at 2-7 GPa, and evaluated the potential error sources. We found that the discrepancy cannot be explained by errors in the sound velocity measurements themselves, but by inaccuracies in determining the temperature, pressure, and chemical composition in each experiment. Of particular note are the significant errors introduced when determining pressures from the unit-cell volume of MgO, which is a temperature-sensitive pressure standard, using inaccurate temperatures. To solve the problem, we additionally used h-BN as a pressure standard, which is less sensitive to temperature. The pressure dependence of the sound velocity became smaller than that of the original data because of the revised pressure values. Our best estimate for the seismic velocity of the Moon's liquid outer core is 4.0 +/- 0.1 km/s, given a chemical composition Fe83S17. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2016.06.009

Compressional and shear wave velocities for polycrystalline bcc-Fe up to 6.3 GPa and 800 K 査読

Yuki Shibazaki, Keisuke Nishida, Yuji Higo, Mako Igarashi, Masaki Tahara, Tatsuya Sakamaki, Hidenori Terasaki, Yuta Shimoyama, Soma Kuwabara, Yusaku Takubo, Eiji Ohtani

AMERICAN MINERALOGIST 101 ( 5-6 ) 1150 - 1160 2016年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MINERALOGICAL SOC AMER

The cores of the Earth and other differentiated bodies are believed to be comprised of iron and various amounts of light elements. Measuring the densities and sound velocities of iron and its alloys at high pressures and high temperatures is crucial for understanding the structure and composition of these cores. In this study, the sound velocities (v(P) and v(S)) and density measurements of body-centered cubic (bcc)-Fe were determined experimentally up to 6.3 GPa and 800 K using ultrasonic and X-ray diffraction methods. Based on the measured v(P), v(S), and density, we obtained the following parameters regarding the adiabatic bulk K-S and shear G moduli of bcc-Fe: K-50 = 163.2(15) GPa, partial derivative K-S/partial derivative P = 6.75(33), partial derivative K-S/partial derivative T = -0.038(3) GPa/K, G(0) = 81.4(6) GPa, partial derivative G/partial derivative P = 1.66(14), and partial derivative G/partial derivative T = -0.029(1) GPa/K. Moreover, we observed that the sound velocity-density relationship for bcc-Fe depended on temperature in the pressure and temperature ranges analyzed in this study and the effect of temperature on vs was stronger than that on vp at a constant density, e.g., 6.0% and 2.7% depression for v(S) and v(P), respectively, from 300 to 800 K at 8000 kg/m(3). Furthermore, the effects of temperature on both v(P) and vs at a constant density were much greater for bcc-Fe than for epsilon-FeSi (cubic B20 structure), according to previously obtained measurements, which may be attributable to differences in the degree of thermal pressure. These results suggest that the effects of temperature on the sound velocity density relationship for Fe alloys strongly depend on their crystal structures and light element contents in the range of pressure and temperature studied.

DOI： 10.2138/am-2016-5545

Sound velocity and elastic properties of Fe-Ni and Fe-Ni-C liquids at high pressure 査読

Soma Kuwabara, Hidenori Terasaki, Keisuke Nishida, Yuta Shimoyama, Yusaku Takubo, Yuji Higo, Yuki Shibazaki, Satoru Urakawa, Kentaro Uesugi, Akihisa Takeuchi, Tadashi Kondo

PHYSICS AND CHEMISTRY OF MINERALS 43 ( 3 ) 229 - 236 2016年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

The sound velocity (V (P)) of liquid Fe-10 wt% Ni and Fe-10 wt% Ni-4 wt% C up to 6.6 GPa was studied using the ultrasonic pulse-echo method combined with synchrotron X-ray techniques. The obtained V (P) of liquid Fe-Ni is insensitive to temperature, whereas that of liquid Fe-Ni-C tends to decrease with increasing temperature. The V (P) values of both liquid Fe-Ni and Fe-Ni-C increase with pressure. Alloying with 10 wt% of Ni slightly reduces the V (P) of liquid Fe, whereas alloying with C is likely to increase the V (P). However, a difference in V (P) between liquid Fe-Ni and Fe-Ni-C becomes to be smaller at higher temperature. By fitting the measured V (P) data with the Murnaghan equation of state, the adiabatic bulk modulus (K (S0)) and its pressure derivative (K (S) (') ) were obtained to be K (S0) = 103 GPa and K (S) (') = 5.7 for liquid Fe-Ni and K (S0) = 110 GPa and K (S) (') = 7.6 for liquid Fe-Ni-C. The calculated density of liquid Fe-Ni-C using the obtained elastic parameters was consistent with the density values measured directly using the X-ray computed tomography technique. In the relation between the density (rho) and sound velocity (V (P)) at 5 GPa (the lunar core condition), it was found that the effect of alloying Fe with Ni was that rho increased mildly and V (P) decreased, whereas the effect of C dissolution was to decrease rho but increase V (P). In contrast, alloying with S significantly reduces both rho and V (P). Therefore, the effects of light elements (C and S) and Ni on the rho and V (P) of liquid Fe are quite different under the lunar core conditions, providing a clue to constrain the light element in the lunar core by comparing with lunar seismic data.

DOI： 10.1007/s00269-015-0789-y

Physical Properties of the Outer Core 査読

Hidenori Terasaki

Deep Earth: Physics and Chemistry of the Lower Mantle and Core 129 - 142 2015年1月

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：wiley

The physical properties of liquid Fe alloys are important for understanding the characteristics of the molten outer core. The possible core composition can be constrained by matching the observed seismic data with the measured sound velocity and density of liquid Fe alloys. The transport properties of liquid Fe alloys strongly influence the convection behavior of the outer core. This chapter reviews the latest results on the elastic and transport properties of liquid Fe alloys obtained based on experimental and numerical approaches. Three variables of pressure (P), temperature (T), and specific volume (V), which are indispensable for understanding the structure and properties of Earth's interior, are linked by an equation of state (EOS). Convectional motion of the outer core is controlled by core magneto hydrodynamics. The viscosity of liquid Fe, Fe-S, and Fe-C at high pressures has been measured using the falling sphere method combined with in situ X-ray radiography.

DOI： 10.1002/9781118992487.ch11

Equation of state of Fe3S at room temperature up to 2 megabars 査読

Seiji Kamada, Eiji Ohtani, Hidenori Terasaki, Takeshi Sakai, Suguru Takahashi, Naohisa Hirao, Yasuo Ohishi

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 228 106 - 113 2014年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The equation of state of Fe3S was investigated up to 200 GPa at room temperature using a diamond anvil cell. Fe3S adopts a tetragonal structure up to 200 GPa and no phase transition was observed. The fourth-order Birch-Murnaghan equation of state (EOS) was fitted to present compression data at room temperature. The elastic parameters, such as bulk modulus (K-0), its pressure derivative (K-0'), and K-0 ''(dK'/dP) were determined to be 122.4(50) GPa, 5.36(48), and -0.066(30) GPa(-1), respectively by fixing the zero pressure volume, V-0, to be 377 angstrom(3). Based on fourth-order Birch-Murnaghan EOS of Fe3S, the maximum amount of S in the inner core was estimated to be 11.4(14) at.% based on the density deficit of the inner core. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.11.001

High-pressure and high-temperature phase diagram for Fe0.9Ni0.1-H alloy 査読

Yuki Shibazaki, Hidenori Terasaki, Eiji Ohtani, Ryuji Tateyama, Keisuke Nishida, Ken-ichi Funakoshi, Yuji Higo

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 228 192 - 201 2014年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Planetary cores are considered to consist of an iron-nickel (Fe-Ni) alloy and light elements and hydrogen is one of plausible light elements in the core. Here we have performed in situ X-ray diffraction experiments on an Fe0.9Ni0.1-H system up to 15.1 GPa and 1673 K, and investigated the effect of Ni on phase relations of FeHx under high pressure and high temperature. The experimental system in the present work was oversaturated with hydrogen. We found a face-center-cubic (fcc) phase (with hydrogen concentration up to x similar to 1) and a body-center-cubic (bcc) phase (x < 0.1) as stable phases. The partial melting was observed below 6 GPa. We could not observe a double-hexagonal-close-packed (dhcp) phase because of limitations in pressure and temperature conditions. The stability field of each phase of Fe0.9Ni0.1Hx was almost same as that of FeHx. The solidus of Fe0.9Ni0.1Hx was 500-700 K lower than the melting curve of Fe and its liquidus was 400-600 K lower than that of Fe in the pressure range of this study. Both the solidus and liquidus of Fe0.9Ni0.1Hx were depressed at around 3.5 GPa, as was the solidus of FeHx. The hydrogen contents in fcc-Fe(0.9)Ni(0.1)Hx just below solidus were slightly lower than those of fcc-FeHx, which suggests that nickel is likely to prevent dissolution of hydrogen into iron. Due to the lower hydrogen solubilities in Fe0.9Ni0.1 compared to Fe, the solidus of Fe0.9Ni0.1Hx is about 100-150 K higher than that of FeHx. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.12.013

The sound velocity measurements of Fe3S 査読

Seiji Kamada, Eiji Ohtani, Hiroshi Fukui, Takeshi Sakai, Hidenori Terasaki, Suguru Takahashi, Yuki Shibazaki, Satoshi Tsutsui, Alfred Q. R. Baron, Naohisa Hirao, Yasuo Ohishi

AMERICAN MINERALOGIST 99 ( 1 ) 98 - 101 2014年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MINERALOGICAL SOC AMER

We measured the sound velocity of Fe3S at room temperature up to 85 GPa employing inelastic X-ray scattering to better constrain the constitution of the inner core. The density of Fe3S was also determined by X-ray diffraction under the same conditions. The relation of the P-wave velocity (v(P)) and density (rho) of Fe3S follows Birch's law, v(P)(m/s) = 1.14(5) x rho(kg/m(3)) - 2580(410). Based on Birch's law determined here for Fe3S and that for epsilon-Fe reported previously, we found that sulfur decreases both density and compressional velocity of hcp-Fe at the core pressure and 300 K.

DOI： 10.2138/am.2014.4463

Repulsive Nature for Hydrogen Incorporation to Fe3C up to 14 GPa 査読

Hidenori Terasaki, Yuki Shibazaki, Keisuke Nishida, Ryuji Tateyama, Suguru Takahashi, Miho Ishii, Yuta Shimoyama, Eiji Ohtani, Ken-ichi Funakoshi, Yuji Higo

ISIJ INTERNATIONAL 54 ( 11 ) 2637 - 2642 2014年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN

We have performed in situ X-ray diffraction measurements under high pressure and high temperature to study hydrogen solubility in Fe3C carbide. Hydrogen solubility can be estimated from a volume expansion associated with hydrogen incorporation into metal. The lattice volumes and phase relations of Fe3C H system and Fe3C were measured up to 14 GPa and 1 973 K. The lattice volumes of Fe3C measured in this study are well fitted using the 3rd order Birch Murnaghan equation of state with the reported elastic parameters of Fe3C. Obtained lattice volumes of Fe3C H are quite consistent with those of Fe3C. No difference between the melting temperatures of Fe3C H and Fe3C was observed. These results demonstrate that hydrogen incorporation into Fe3C does not occur and hydrogen is unlikely to coexist with carbon in iron-alloy up to 14 GPa.

DOI： 10.2355/isijinternational.54.2637

Ponded melt at the boundary between the lithosphere and asthenosphere 査読

Tatsuya Sakamaki, Akio Suzuki, Eiji Ohtani, Hidenori Terasaki, Satoru Urakawa, Yoshinori Katayama, Ken-ichi Funakoshi, Yanbin Wang, John W. Hernlund, Maxim D. Ballmer

NATURE GEOSCIENCE 6 ( 12 ) 1041 - 1044 2013年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

The boundary between Earth's rigid lithosphere and the underlying, ductile asthenosphere is marked by a distinct seismic discontinuity(1). A decrease in seismic-wave velocity and increase in attenuation at this boundary is thought to be caused by partial melt(2). The density and viscosity of basaltic magma, linked to the atomic structure(3,4), control the process of melt separation from the surrounding mantle rocks(5-9). Here we use high-pressure and high-temperature experiments and in situ X-ray analysis to assess the properties of basaltic magmas under pressures of up to 5.5 GPa. We find that the magmas rapidly become denser with increasing pressure and show a viscosity minimum near 4 GPa. Magma mobility-the ratio of the melt-solid density contrast to the magma viscosity-exhibits a peak at pressures corresponding to depths of 120150 km, within the asthenosphere, up to an order of magnitude greater than pressures corresponding to the deeper mantle and shallower lithosphere. Melts are therefore expected to rapidly migrate out of the asthenosphere. The diminishing mobility of magma in Earth's asthenosphere as the melts ascend could lead to excessive melt accumulation at depths of 80-100 km, at the lithosphere-asthenosphere boundary. We conclude that the observed seismic discontinuity at the lithosphere-asthenosphere boundary records this accumulation of melt.

DOI： 10.1038/NGEO1982

Density of Fe-3.5 wt% C liquid at high pressure and temperature and the effect of carbon on the density of the molten iron 査読

Yuta Shimoyama, Hidenori Terasaki, Eiji Ohtani, Satoru Urakawa, Yusaku Takubo, Keisuke Nishida, Akio Suzuki, Yoshinori Katayama

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 224 77 - 82 2013年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

Carbon is a plausible light element candidate in the Earth's outer core. We measured the density of liquid Fe-3.5 wt% C up to 6.8 GPa and 2200 K using an X-ray absorption method. The compression curve of liquid Fe-C was fitted using the third-order Birch-Murnaghan equation of state. The bulk modulus and its pressure derivative are K-0.1500K = 55.3 +/- 2.5 GPa and (dK(o)/dP)(T) = 5.2 +/- 1.5, and the thermal expansion coefficient is alpha = 0.86 +/- 0.04 x 10(-4) K-1. The Fe-C density abruptly increases at pressures between 4.3 and 5.5 GPa in the range of present temperatures. Compared with the results of previous density measurements of liquid Fe-C, the effect of carbon on the density of liquid Fe shows a nonideal mixing behavior. The abrupt density increase and nonideal mixing behavior are important factors in determining the light element content in the Earth's core. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2013.08.003

Phase relations in the carbon-saturated C-Mg-Fe-Si-O system and C and Si solubility in liquid Fe at high pressure and temperature: Implications for planetary interiors 査読

Suguru Takahashi, Eiji Ohtani, Hidenori Terasaki, Yoshinori Ito, Yuki Shibazaki, Miho Ishii, Ken ichi Funakoshi, Yuji Higo

Physics and Chemistry of Minerals 40 ( 8 ) 647 - 657 2013年9月

掲載種別：研究論文（学術雑誌）

The phase and melting relations of the C-saturated C-Mg-Fe-Si-O system were investigated at high pressure and temperature to understand the role of carbon in the structure of the Earth, terrestrial planets, and carbon-enriched extraterrestrial planets. The phase relations were studied using two types of experiments at 4 GPa: analyses of recovered samples and in situ X-ray diffractions. Our experiments revealed that the composition of metallic iron melts changes from a C-rich composition with up to about 5 wt.% C under oxidizing conditions (ΔIW = -1.7 to -1.2, where ΔIW is the deviation of the oxygen fugacity (fO2) from an iron-wüstite (IW) buffer) to a C-depleted composition with 21 wt.% Si under reducing conditions (ΔIW < -3.3) at 4 GPa and 1,873 K. SiC grains also coexisted with the Fe-Si melt under the most reducing conditions. The solubility of C in liquid Fe increased with increasing fO2, whereas the solubility of Si decreased with increasing fO2. The carbon-bearing phases were graphite, Fe3C, SiC, and Fe alloy melt (Fe-C or Fe-Si-C melts) under the redox conditions applied at 4 GPa, but carbonate was not observed under our experimental conditions. The phase relations observed in this study can be applicable to the Earth and other planets. In hypothetical reducing carbon planets (ΔIW < -6.2), graphite/diamond and/or SiC exist in the mantle, whereas the core would be an Fe-Si alloy containing very small amount of C even in the carbon-enriched planets. The mutually exclusive nature of C and Si may be important also for considering the light elements of the Earth's core. © 2013 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s00269-013-0600-x

Sound velocity measurements in liquid Fe-S at high pressure: Implications for Earth's and lunar cores 査読

Keisuke Nishida, Yoshio Kono, Hidenori Terasaki, Suguru Takahashi, Miho Ishii, Yuta Shimoyama, Yuji Higo, Ken-ichi Funakoshi, Tetsuo Irifune, Eiji Ohtani

EARTH AND PLANETARY SCIENCE LETTERS 362 182 - 186 2013年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The P-wave velocity (V-p) of liquid Fe57S43 was measured up to 5.4 GPa using an ultrasonic method combined with the synchrotron X-ray technique. The Vp of liquid Fe57S43 showed little change with temperature, but increased almost linearly from 3105 +/- 11 m/s to 3845 +/- 9 m/s with increasing pressure from 2.4 to 5.4 GPa. This can be approximated by Vp [m/s]=2664+205.4 x P, where P is the pressure in GPa. The V-P of liquid Fe57S43 at 2.4-5.4 GPa was significantly lower than that of pure liquid Fe. However, the pressure dependence of Vp of the liquid Fe57S43 was markedly higher than that of pure liquid Fe. The marked difference in the pressure dependences of VP between pure liquid Fe and liquid Fe57S43 may cause Vp crossover at around 7 GPa. As a result, the Vp of liquid Fe57S43 would become higher than that of pure liquid Fe at pressures higher than 7 GPa. Thus, S decreases Vp at low pressures such as those of the lunar outer core, but would increase it at the high pressures of the Earth's outer core. Assuming the lunar core consists of a liquid Fe-FeS outer core and a solid Fe inner core, the expected Vp in the lunar outer core ranges from 3756 to 4230 m/s. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2012.11.042

Melting relationships in the Fe-Fe3S system up to the outer core conditions 査読

Seiji Kamada, Eiji Ohtani, Hidenori Terasaki, Takeshi Sakai, Masaaki Miyahara, Yasuo Ohishi, Naohisa Hirao

EARTH AND PLANETARY SCIENCE LETTERS 359 26 - 33 2012年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

In situ X-ray diffraction experiments in the Fe-Fe3S system were performed up to 175 GPa and 3500 K using a laser-heated diamond anvil cell to investigate melting relationships in the system. Partial melting in the Fe-Fe3S system was observed based on the disappearance of X-ray diffraction peaks of solid Fe3S and texture observation of the recovered samples. The melting relationship of the Fe-Fe3S system as a function of pressure is evaluated based on Kraut-Kennedy law. Our results of melting relationships suggest that the temperature at the inner core boundary is between 4700(160) and 4930(330) K if sulfur is the only light element in the Earth's core. Assuming the adiabatic temperature gradient in the outer core, the temperature at the core-mantle boundary is estimated to be in the range of 3600-3770 K. The present temperature profile of the core is consistent with the core-mantle boundary temperature that can explain the core heat flux to maintain the core dynamo and the seismic structure at the base of the lower mantle. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2012.09.038

高圧下におけるFe-FeO融体の密度と熱弾性特性の解明

寺崎英紀, 田窪勇作, 下山裕太, 鈴木昭夫, 西田圭佑, 大谷栄治, 浦川啓, 近藤忠, 片山芳則

SPring-8 User Experiment Report No.29 (2012A) 29 2012A3782 2012年11月

Interfacial tension of Fe-Si liquid at high pressure: Implications for liquid Fe-alloy droplet size in magma oceans 査読

Hidenori Terasaki, Satoru Urakawa, David C. Rubie, Ken-ichi Funakoshi, Tatsuya Sakamaki, Yuki Shibazaki, Shin Ozawa, Eiji Ohtani

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 202 1 - 6 2012年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The interfacial tension of Fe-Si liquid was measured using in situ X-ray radiography at high pressure and temperatures using the sessile drop method. The interfacial tension of Fe-Si liquid decreases (from 665 to 407 mN/m) with increasing temperature (1673-2173 K) at 1.5 GPa. The interfacial tension also decreases gradually with increasing Si content (0-25 at%), suggesting that Si behaves as a "moderately" surface-active element. Comparing the effects of different light elements on the interfacial tension of liquid iron, the most effective elements for reducing the interfacial tension lie in the order S > Si > P. although P has almost no effect. The droplet size of emulsified Fe-alloys in a magma ocean are estimated to be larger for Fe-Si and Fe-P liquids and smaller for Fe-S (S > 10 at%) liquid compared with that for pure Fe liquid. Therefore, if droplets in a magma ocean are enriched in S, chemical equilibrium between droplets and silicate melt is established faster in the magma ocean compared to Fe, Fe-Si and Fe-P liquids. (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2012.05.002

In-Situ Observations of Martensitic Transformation in Blast-Resistant Steel 査読

Xinghua Yu, Sudarsanam Suresh Babu, John C. Lippold, Hidenori Terasaki, Yu-ichi Komizo

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE 43A ( 5 ) 1538 - 1546 2012年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

A hybrid in-situ characterization system, which couples the laser scanning confocal microscopy (LSCM) with the time-resolved X-ray diffraction (TRXRD) measurement with synchrotron radiation, was used to characterize the microstructure evolution during heat-affected zone (HAZ) thermal cycling of high-strength and blast-resistant steel. The combined technique has a time resolution of 0.3 seconds that allows for high-fidelity measurements of transformation kinetics, lattice parameters, and morphological features. The measurements showed a significant reduction in the martensite start transformation temperature with a decrease in the prior austenite grain size. In addition, the LSCM images confirmed the concurrent refinement of martensite packet size with smaller austenite grain sizes. This is consistent with dilatometric observations. The austenite grain size also influenced the rate of transformation (df (m) /dT); however, the measurements from the hybrid (surface) and dilatometric (volume) measurements were inconsistent. Challenges and future directions of adopting this technique for comprehensive tracking of microstructure evolution in steels are discussed.

DOI： 10.1007/s11661-011-0746-4

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