An X-ray and neutron scattering study of aqueous MgCl solution in the gigapascal pressure range

Yamaguchi, Toshio*; Fukuyama, Nami*; Yoshida, Koji*; Katayama, Yoshinori*; Machida, Shinichi*; Hattori, Takanori

Liquids, 3(3), p.288 - 302, 2023/09

https://doi.org/10.3390/liquids3030019

We report the structure of an aqueous 2 mol/kg MgCl solution at pressures from 0.1 MPa to 4 GPa and temperatures from 300 to 500 K revealed by X-ray and neutron scattering measurements. The scattering data are analyzed by empirical potential structure refinement (EPSR) modeling to derive the pair distribution functions, coordination number distributions, angle distributions, and spatial density functions as a function of pressure and temperature. Mg forms rigid solvation shells extended to the third shell; the first solvation shell of six-fold octahedral coordination with about six water molecules at 0 GPa transforms into about five water molecules and one Cl due to the formation of the contact ion pairs in the GPa pressure range. The Cl solvation shows a substantial pressure dependence; the coordination number of a water oxygen atom around Cl increases from 8 at 0.1 MPa/300 K to 10 at 4 GPa/500 K. The solvent water transforms the tetrahedral network structure at 0.1 MPa/300 K to a densely packed structure in the GPa pressure range; the number of water oxygen atoms around a central water molecule gradually increases from 4.6 at 0.1 MPa/298 K to 8.4 at 4 GPa/500 K.

Design and performance of high-pressure PLANET beamline at pulsed neutron source at J-PARC

Hattori, Takanori; Sano, Asami; Arima, Hiroshi*; Komatsu, Kazuki*; Yamada, Akihiro*; Inamura, Yasuhiro; Nakatani, Takeshi; Seto, Yusuke*; Nagai, Takaya*; Utsumi, Wataru; et al.

Nuclear Instruments and Methods in Physics Research A, 780, p.55 - 67, 2015/04

https://doi.org/10.1016/j.nima.2015.01.059

PLANET is a time-of-flight (ToF) neutron beamline dedicated to high-pressure and high-temperature experiments. The large six-axis multi-anvil high-pressure press designed for ToF neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10 GPa and 2000 K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators to eliminate parasitic scattering from the high-pressure cell assembly. The high performance of the diffractometer for the resolution ( / 0.6%) and the accessible -spacing range (0.2-8.4 ) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.

Observation of transient structural changes on hydrogen absorption process of LaNiSn by time resolved X-ray diffraction

Machida, Akihiko; Higuchi, Kensuke*; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*

Nihon Kinzoku Gakkai-Shi, 79(3), p.124 - 130, 2015/03

https://doi.org/10.2320/jinstmet.JC201407

Structural changes on hydrogen absorption process of hydrogen absorbing alloy LaNiSn have been investigated by time-resolved X-ray diffraction measurements using synchrotron radiation source. We have found the transient intermediate phase between the solid solution and hydride phases of LaNiSn under non-equilibrium hydrogen pressure condition at room temperature. LaNiSn has transformed into the hydride through three phase co-existing state. The hydrogen content of the intermediate phase estimated from the unit cell volume is independent of the induced hydrogen gas pressure. The variation of lattice constants indicate that the hydrogen atoms are located at the LaNi(Ni,Sn) octahedron and La(Ni,Sn) tetrahedron in the intermediate phase.

Site occupancy of interstitial deuterium atoms in face-centred cubic iron

Machida, Akihiko; Saito, Hiroyuki; Sugimoto, Hidehiko*; Hattori, Takanori; Sano, Asami; Endo, Naruki*; Katayama, Yoshinori; Iizuka, Riko*; Sato, Toyoto*; Matsuo, Motoaki*; et al.

Nature Communications (Internet), 5, p.5063_1 - 5063_6, 2014/09

https://doi.org/10.1038/ncomms6063

Iron hydride FeH, is thermodynamically stable only at high hydrogen pressure of several GPa. To investigate the hydrogenation process and hydrogen state in iron hydride, it is necessary to carry out the in-situ measurement under high pressure and high temperature. In this study, we performed the in-situ neutron diffraction measurement of Fe-D system using the high pressure neutron diffractometer PLANET in the MLF, J-PARC, and determined the deuterium occupying sites and occupancies in fcc-FeD. We found the minor occupation of tetrahedral sites under high pressure and high temperature. We considered the mechanism of the minor occupation based on the Quantum-mechanical calculation.

- phase diagram and structural transformations of molten PO under pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Lyapin, A. G.*; Saito, Hiroyuki

Physical Review B, 89(10), p.104203_1 - 104203_4, 2014/03

https://doi.org/10.1103/PhysRevB.89.104203

The PO compound is an archetypical glass-forming oxide. We present the in situ X-ray diffraction study of the pressure-temperature phase diagram of PO and of the liquid PO structure under high pressure up to 10 GPa. We found that structural transformation in the liquid PO under pressure is unique and includes three stages: first, the disappearance of the intermediate range order of the melt together with a slow increase in the average first-coordination number (P-O and O-P neighbors) up to 4 GPa; second, the "normal" compression almost without structural modification at higher pressures up to 8-9 GPa; and, finally, the abrupt change of the short-range order structure of the liquid with the jumplike increase at 9-10 GPa.

Mechanical properties of full austenitic welding joint at cryogenic temperature for the ITER toroidal field coil structure

Iguchi, Masahide; Saito, Toru; Kawano, Katsumi; Chida, Yutaka; Nakajima, Hideo; Ogawa, Tsuyoshi*; Katayama, Yoshinori*; Ogata, Hiroshige*; Minemura, Toshiyuki*; Tokai, Daisuke*; et al.

Fusion Engineering and Design, 88(9-10), p.2520 - 2524, 2013/10

https://doi.org/10.1016/j.fusengdes.2013.02.165

ITER TFC structures are large welding structures made of heavy thick stainless steels. JAEA plans to apply narrow gap TIG welding with FMYJJ1 which is full austenitic stainless filler material to manufacture TFC structure. FMYJJ1 is specified in "Codes for Fusion Facilities -Rules on Superconducting Magnet Structure (2008)". In order to evaluate effect of base material combinations and thickness of welded joint on tensile properties at 4 K, tensile tests were conducted at 4 K by using tensile specimens taken from 40 mm thickness weld joints of four combinations and 200 mm thickness ones of two combinations of base materials. These weld joints were manufactured by one side narrow gap TIG welding with FMYJJ1. As the results, it was confirmed that yield and tensile strengths of welded joint at 4K were decreased with decreasing of nitrogen of base material, and there were no large distribution of strengths at 4 K along the thickness of welded joints of 200 mm thickness.

Formation of NaCl-type lanthanum monohydride under high pressure; Discovery of novel rare-earth metal hydride using synchrotron radiation X-ray and neutron

Machida, Akihiko; Honda, Mitsunori*; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Oshita, Hidetoshi*; Ikeda, Kazutaka*; Otomo, Toshiya*

Hamon, 23(2), p.131 - 136, 2013/05

https://doi.org/10.5611/hamon.23.1_131

Recently, we have revealed formation of NaCl-type LaD using synchrotron radiation X-ray diffraction and neutron diffraction measurements under high pressure. Previously, we have found that LaH decomposes into two phases, which have different hydrogen compositions, the H-poor and H-rich phases, at 11 GPa at room temperature by synchrotron radiation X-ray diffraction. Recent neutron diffraction measurements on LaD confirmed the formation of a NaCl-type LaD as the D-poor phase. This is the first observation of a formation of the rare-earth metal monodeuteride. Present result indicates that that rare-earth metal can form a series of stoichiometric hydrides, such as mono-, di-, and trihydride with the fcc metal lattice.

Pressure-driven liquid-liquid transformations and corresponding bizarre viscosity behavior

Brazhkin, V. V.*; Katayama, Yoshinori; Kanzaki, Masami*; Lyapin, A. G.*

Advances in Chemical Physics, Vol.152, p.29 - 50, 2013/04

https://doi.org/10.1002/9781118540350.ch2

In recent years, transformations in the melts of elementary substances and oxides have been found under high pressure. These transformations are accompanied by structural changes and variations in physical properties. In this work, structure and viscosity of Se, AsS, AsS, AsS and BO were studied using synchrotron radiation. These substances exhibit changes in bonding in the crystalline state under high pressure. An X-ray diffraction measurements and falling sphere viscosity measurements using an X-ray radiography technique were carried out. Huge change in viscosity which accompanies structural change under compression was observed in each substance.

Structural and dynamical properties of water under high temperatures and pressures

Ikeda, Takashi; Katayama, Yoshinori

Teion Kagaku, 71, p.125 - 129, 2013/03

http://hdl.handle.net/2115/52363

Although liquid water is one of the most abundant materials on earth and most familiar to all of us, the present understanding of liquid water exhibiting various interesting properties depending on the environment is still far from satisfactory. Hence, it is still one of main subjects in vast research fields including physics, chemistry, and biology. In this contribution, we first describe the structural and dynamical properties of water under high temperatures and pressures revealed by combining advanced first principles molecular dynamics simulations and in situ X-ray diffraction experiments. Then, the future prospects for investigating water under higher pressures and temperatures are summarized.

Phase diagram and equation of state of TiH at high pressures and high temperatures

Endo, Naruki; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori; Aoki, Katsutoshi

Journal of Alloys and Compounds, 546, p.270 - 274, 2013/01

https://doi.org/10.1016/j.jallcom.2012.08.083