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Mori, Yuichiro*; Kagi, Hiroyuki*; Aoki, Katsutoshi*; Takano, Masahiro*; Kakizawa, Sho*; Sano, Asami; Funakoshi, Kenichi*
Earth and Planetary Science Letters, 634, p.118673_1 - 118673_8, 2024/05
To investigate silicon effects on the hydrogen-induced volume expansion of iron, neutron diffraction and X-ray diffraction experiments were conducted to examine hcp-Fe
Si
under high pressures and high temperatures. Neutron diffraction experiments were performed on the deuterated hcp-FeSi at 13.5 GPa and 900 K, and at 12.1 GPa and 300 K. By combining the P-V-T equation of state of hcp-FeSi, present results indicate that the hydrogen-induced volume expansion of hcp-FeSi is 10% greater than that of pure hcp iron. Using the obtained values, we estimated the hydrogen content that would reproduce the density deficit in the inner core, which was 50% less than that without the effect of silicon. Possible hydrogen content, 
, in the inner core and the outer core was calculated to be 0.07 and 0.12-0.15, respectively, when reproducing the density deficit of the inner core with hcp-FeSiHx.
Ni
D
at high 
conditionsShito, Chikara*; Kagi, Hiroyuki*; Kakizawa, Sho*; Aoki, Katsutoshi*; Komatsu, Kazuki*; Iizuka, Riko*; Abe, Jun*; Saito, Hiroyuki*; Sano, Asami; Hattori, Takanori
American Mineralogist, 108(4), p.659 - 666, 2023/04
Times Cited Count：1 Percentile：64.83(Geochemistry & Geophysics)The phase relation and crystal structure of FeNiH (D) at high pressures and temperatures up to 12 GPa and 1000 K were clarified by in-situ X-ray and neutron diffraction measurements. Under conditions of the present study, no deuterium atoms occupied tetragonal (
) sites of face-centered cubic (fcc) FeNiD unlike fcc FeH(D). The deuterium-induced volume expansion per deuterium 
was determined as 2.45(4) 
and 3.31(6) for fcc and hcp phases, respectively, which were significantly larger than the corresponding values for FeD. The value slightly increased with increasing temperature. This study suggests that only 10% of nickel in iron drastically changes the behaviors of hydrogen in metal. Assuming that is constant regardless of pressure, the maximum hydrogen content in the Earth's inner core is estimated to be one to two times the amount of hydrogen in the oceans.
Sano, Asami; Kakizawa, Sho*; Shito, Chikara*; Hattori, Takanori; Machida, Shinichi*; Abe, Jun*; Funakoshi, Kenichi*; Kagi, Hiroyuki*
High Pressure Research, 41(1), p.65 - 74, 2021/03
Times Cited Count：2 Percentile：30.35(Physics, Multidisciplinary)We applied Kawai-type multi-anvil assemblies (MA6-8) for time-of-flight neutron-diffraction experiments to achieve high pressures and high temperatures simultaneously. To achieve sufficient signal intensities, the angular access to the sample was enlarged using slits and tapers on the first-stage anvils. Using SiC-binder sintered diamond for the second-stage anvils that transmits neutrons, sufficient signal intensities were achieved at a high-pressure of 
23.1 GPa. A high-temperature experiment was also conducted at 16.2 GPa and 973 K, validating the use of tungsten carbide for the second-stage anvils. The present study reveals the capability of the MA6-8 cells in neutron-diffraction experiments to attain pressures and temperatures beyond the limits of the conventional MA6-6 cells used in the high-pressure neutron diffractometer PLANET at the MLF, J-PARC.
Si at 14.7 GPa and 800 KMori, Yuichiro*; Kagi, Hiroyuki*; Kakizawa, Sho*; Komatsu, Kazuki*; Shito, Chikara*; Iizuka, Riko*; Aoki, Katsutoshi*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; et al.
Journal of Mineralogical and Petrological Sciences, 116(6), p.309 - 313, 2021/00
Times Cited Count：0 Percentile：0.02(Mineralogy)The Earth's core is believed to contain some light elements because it is 10% less dense than pure Fe under the corresponding pressure and temperature conditions. Hydrogen, a promising candidate among light elements, has phase relations and physical properties that have been investigated mainly for the Fe-H system. This study specifically examined an Fe-Si-H system using in-situ neutron diffraction experiments to investigate the site occupancy of deuterium of hcp-FezSi hydride at 14.7 GPa and 800 K. Results of Rietveld refinement indicate hcp-FeSi hydride as having deuterium (D) occupancy of 0.24(2) exclusively at the interstitial octahedral site in the hcp lattice. The effect on the site occupancy of D by addition of 2.6 wt% Si into Fe (FeSi) was negligible compared to results obtained from an earlier study of an Fe-D system (Machida et al., 2019).
Hattori, Takanori; Sano, Asami; Machida, Shinichi*; Abe, Jun*; Funakoshi, Kenichi*; Okazaki, Nobuo*; Kakizawa, Sho*
no journal, ,
PLANET is the neutron beamline dedicated to high-pressure experiments in J-PARC. One of most characteristic features is its ability to conduct diffraction measurements simultaneously at high pressures and high temperatures up to 24 GPa and 1200 K, respectively. Another characteristic feature is its ability to collect clean pattern without parasitic scattering from materials around sample by defining the diffraction gauge volume with narrow incident slits and radial collimators with a field of view of 0.8-3.0 mm at the sample position. This enables precise structure determination not only of crystals but also of liquids and amorphous solids. Furthermore, it also enables the use of smaller samples, which contributes to increase maximum available pressure. In this presentation, the performance and recent developments of the beamline will be introduced along with recent scientific results obtained at PLANET.
Sano, Asami; Kakizawa, Sho*; Mori, Yuichiro*; Kagi, Hiroyuki*; Abe, Jun*; Funakoshi, Kenichi*; Hattori, Takanori
no journal, ,
Neutron scattering with high sensitivity to hydrogen can be a powerful tool in the investigation of hydrogen in the Earth's material. In the high-pressure neutron diffractometer PLANET at MLF in J-PARC, a large volume 6-axis multi-anvil press, and precise optics have enabled stable neutron diffraction experiments at high pressure and high temperature. This sample environment has promoted unique research, as exemplified by determining the amount of hydrogen in the iron alloys that form the Earth's core. In this presentation, recent results of neutron experiments at PLANET will be presented, as well as the on-going developments.
