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Journal Articles

Crystal and magnetic structures of double hexagonal close-packed iron deuteride

Saito, Hiroyuki*; Machida, Akihiko*; Iizuka, Riko*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*

Scientific Reports (Internet), 10, p.9934_1 - 9934_8, 2020/06

 Times Cited Count:0 Percentile:100(Multidisciplinary Sciences)

Neutron powder diffraction profiles were collected for iron deuteride (FeDx) while the temperature decreased from 1023 to 300 K for a pressure range of 4-6 GPa. The $$varepsilon$$' deuteride with a double hexagonal close-packed (dhcp) structure, which coexisted with other stable or metastable deutrides at each temperature and pressure condition, formed solid solutions with a composition of FeD$$_{0.68(1)}$$ at 673 K and 6.1 GPa and FeD$$_{0.74(1)}$$ at 603 K and 4.8 GPa. Upon stepwise cooling to 300 K, the D-content x increased to a stoichiometric value of 1.0 to form monodeuteride FeD$$_{1.0}$$. In the dhcp FeD$$_{1.0}$$ at 300 K and 4.2 GPa, dissolved D atoms fully occupied the octahedral interstitial sites, slightly displaced from the octahedral centers in the dhcp metal lattice, and the dhcp sequence of close-packed Fe planes contained hcp-stacking faults at 12%. Magnetic moments with 2.11 $$pm$$ 0.06 B/Fe-atom aligned ferromagnetically in parallel on the Fe planes.

Journal Articles

Hexagonal close-packed iron hydride behind the conventional phase diagram

Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*

Scientific Reports (Internet), 9(1), p.12290_1 - 12290_9, 2019/08

 Times Cited Count:3 Percentile:29.04(Multidisciplinary Sciences)

Hexagonal close-packed iron hydride, hcp FeHx, is absent from the conventional phase diagram of the Fe-H system, although hcp metallic Fe exists stably over extensive temperature ($$T$$) and pressure ($$P$$) conditions, including those corresponding to the Earth's inner core. ${{it In situ}}$ X-ray and neutron diffraction measurements at temperatures ranging from 298 to 1073 K and H pressures ranging from 4 to 7 GPa revealed that the hcp hydride was formed for FeH$$_{x}$$ compositions when $$x < 0.6$$. Hydrogen atoms occupied the octahedral interstitial sites of the host metal lattice both partially and randomly. The hcp hydride exhibited a H-induced volume expansion of 2.48(5) $AA $^{3}$$/H-atom, which was larger than that of the face-centered cubic (fcc) hydride. The hcp hydride showed an increase in $$x$$ with $$T$$, whereas the fcc hydride showed a corresponding decrease. The present study provides guidance for further investigations of the Fe-H system over an extensive $$x$$-$$T$$-$$P$$ region.

Journal Articles

High-pressure structure and electronic properties of YbD$$_{2}$$ to 34 GPa

Klotz, S.*; Casula, M.*; Komatsu, Kazuki*; Machida, Shinichi*; Hattori, Takanori

Physical Review B, 100(2), p.020101_1 - 020101_5, 2019/07

 Times Cited Count:4 Percentile:27.63(Materials Science, Multidisciplinary)

Ytterbium dihydride (YbH$$_{2}$$) shows a well-known transition at $$approx$$16 GPa from a CaH$$_{2}$$-type structure to a high-pressure (high-$$P$$) phase with Yb at hcp sites and unknown H-positions. Here, we report its complete structure determination by neutron diffraction at 34 GPa. Hydrogen(deuterium) is located at 2$$a$$ and 2$$d$$ positions of space group $$P6_{3}/mmc$$, thus forming a high-symmetry "collapsed" close-packed lattice. The transition is sluggish and can be seen as a transfer of 1/2 of the hydrogen atoms from strongly corrugated H-layers to interstitial sites of the Yb-lattice. We demonstrate by first-principles calculations that the transition is related to a change from a completely filled $$f$$-electron configuration to a fractional $$f$$-hole ($$approx$$0.25 h) occupation in the high-$$P$$ phase. The $$f$$ $$to$$ $$d$$ charge transfer closes the gap at the transition and leads to a metallic ground state with sizeable electron-phonon interaction involving out-of-plane vibrational modes of interstitial hydrogen.

Journal Articles

The Effect of final heat treatment at fabrication on the terminal solid solubility of hydrogen in Zry-4

Yamauchi, Akihiro*; Amaya, Masaki

Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 7 Pages, 2018/10

Differential scanning calorimetry (DSC) measurements on pre-hydrided cold worked, stress relieved and recrystallized Zry-4 cladding were performed in a temperature range between 50 and 600$$^{circ}$$C in order to elucidate the effect of final heat treatment at fabrication of Zircaloy-4 (Zry-4) cladding on the terminal solid solubility during the dissolution of zirconium hydrides at heating up (TSSD). Obtained DSC curves and Metallography indicate that the initial state of hydrides affects the dissolution behavior of hydride. The Arrhenius plots of the TSSD temperatures and hydrogen contents obtained from this study revealed that cold worked samples exhibited the largest TSSD and followed by stress relieved and recrystallized samples. The results of this study indicated that the difference in microstructure due to final heat treatment at fabrication of Zry-4 cladding affects the dissolution behavior of hydrides.

JAEA Reports

Deuterated Materials Enhancing Neutron Science for Structure Function Applications; October 19th-20th, 2017, Ibaraki Quantum Beam Research Center

Akutsu, Kazuhiro*; Adachi, Motoyasu*; Kawakita, Yukinobu

JAEA-Review 2018-002, 36 Pages, 2018/03


Since J-PARC started operation for user programs with high-intensity pulsed neutron beams, many material and life science studies have been carried out at J-PARC. Since partial or complete deuteration of organic compounds for contrast variation in the scattering length densities of materials is one of the most effective techniques in the application of neutron scattering analysis, deuterated materials have led to significant progress in our understanding of the structure of novel organic materials. Aiming at accelerating development of deuteration activities in our country, an international workshop "Deuterated Materials Enhancing Neutron Science for Structure Function Applications" was held as a J-PARC Workshop at Ibaraki Quantum Beam Research Center from 19th October to 20th October in 2017. In this workshop, the chemical/biological deuteration activities and recent scientific results of deuterated materials enhancing neutron study in Japan and other countries were discussed by domestic/foreign deuteration and neutron scientists. This is a report of the workshop summarized by organizers.

Journal Articles

${{it In situ}}$ neutron diffraction of iron hydride in iron-silicate-water system under high pressure and high temperature condition

Iizuka, Riko*; Yagi, Takehiko*; Goto, Hirotada*; Okuchi, Takuo*; Hattori, Takanori; Sano, Asami

Hamon, 27(3), p.104 - 108, 2017/08

Hydrogen is the most abundant element in the solar system and is considered to be one of the promising candidates of the light elements in the Earth's core. However, the amount of hydrogen dissolved in the core and its process are still unknown because hydrogen cannot be detected by X ray and easily escapes from iron at ambient conditions. In this study, we have conducted high-pressure and high-temperature in-situ neutron diffraction experiments on the iron-hydrous mineral system using PLANET in J-PARC. We observed that the water, which was dissociated from a hydrous mineral, reacted with iron to form both iron oxide and iron hydride at about 4 GPa. Iron hydride remained stable after further increase in temperature. This formation occurred at 1000K, where no materials melted. This suggests that hydrogen dissolved into iron before any other light elements dissolved in the very early stage of the Earth's evolution.

Journal Articles

True Boundary for the formation of homoleptic transition-metal hydride complexes

Takagi, Shigeyuki*; Iijima, Yuki*; Sato, Toyoto*; Saito, Hiroyuki; Ikeda, Kazutaka*; Otomo, Toshiya*; Miwa, Kazutoshi*; Ikeshoji, Tamio*; Aoki, Katsutoshi*; Orimo, Shinichi*

Angewandte Chemie; International Edition, 54(19), p.5650 - 5653, 2015/05

 Times Cited Count:23 Percentile:28.59(Chemistry, Multidisciplinary)

Journal Articles

Site occupation state of deuterium atoms in fcc Fe

Aoki, Katsutoshi*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami

Hamon, 25(1), p.26 - 31, 2015/02

The deuterization process of fcc Fe to form solid1solution fcc FeD$$_{x}$$ was investigated by ${{it in situ}}$ neutron diffraction measurements at high temperature and high pressure. In a completely deuterized specimen at 988 K and 6.3 GPa, deuterium atoms occupy the octahedral and tetrahedral interstitial sites with an occupancy of 0.532(9) and 0.056(5), respectively, giving a deuterium composition $$x$$ of 0.64(1). During deuterization, the metal-lattice expands approximately linearly with deuterium composition at a rate of 2.21 $AA${}^{3}$$ per deuterium atom. The minor occupation of tetrahedral site is likely driven by the intersite movement of deuterium atoms along the $$<$$111$$>$$ direction in the fcc metal lattice. These results provide implications for the light elements in the Earth's core and the mechanism of hydrogen embrittlement of ferrous metals.

Journal Articles

Effects of ion irradiation on hydriding rate of Mm based hydrogen storage alloy

Abe, Hiroshi; Morimoto, Ryo*; Sato, Fumiatsu*; Azuma, Yorito*; Uchida, Hirohisa*

Journal of Alloys and Compounds, 408-412, p.348 - 350, 2006/02

 Times Cited Count:10 Percentile:41.43(Chemistry, Physical)

Mm(misch metal) based hydrogen storage alloys are applied to the negative electrode of the Ni-H battery and other hydrogen storage systems. In such pratical applications, various surface processes of hydrogen molecules often become rate contolling. Therefore, the improvement of the alloy surface is of great importance to promote the initial activation and hydriding rate. We have reported that the alkaline pretreatment of an alloy surfece exhibits a high durability against CO attack. Since low energy ion irradiation is quite useful for surface modification of materials, the hydriding proerties of a Mm is expected on electrochemical hydriding rate of the alloy. As a result, the ion irradiation Mm was found to induce a higher hydriding rate than that of the un-irradiation one.

Journal Articles

Intelligible seminar on fusion reactors, 8; Fuel cycling system for tritium recovery

Fukada, Satoshi*; Hayashi, Takumi

Nippon Genshiryoku Gakkai-Shi, 47(9), p.623 - 629, 2005/09

no abstracts in English

Journal Articles

Band gap closing in yttrium hydride at high pressures

Omura, Ayako; Machida, Akihiko; Watanuki, Tetsu; Aoki, Katsutoshi; Nakano, Satoshi*; Takemura, Kenichi*

Proceedings of Joint 20th AIRAPT - 43rd EHPRG International Conference on High Pressure Science and Technology (CD-ROM), 3 Pages, 2005/06

Yttrium hydride shows a structural change from a cubic dihydride to a hexagonal trihydride by hydrogenation. This is accompanied by the metal-insulator transition. The theoretical calculation of yttrium hydride speculates that the hybridization between 4d-Y and 1s-H leads to the opening of a large energy gap. They also predict that a transition from insulator to metal occurs when the volume is reduced to about 85% of the equilibrium volume in yttrium trihydride. Recently, we performed an infrared spectroscopy of yttrium trihydride to investigate pressure-induced metallization under high pressure. The insulator-metal transition occurred with an abrupt disappearance of the optical gap of $$sim$$1 eV at 23 GPa. There is a possibility of the electronic transition because no structural changes occur above 20 GPa. The electronic transition can be attributed to the delocalization of the 1s electrons bound to the H+ core ions or the rearrangement of hydrogen atoms.

Journal Articles

Conformational changes of troponin C within the thin filaments detected by neutron scattering

Matsumoto, Fumiko*; Makino, Koji*; Maeda, Kayo*; Patzelt, H.*; Maeda, Yuichiro*; Fujiwara, Satoru

Journal of Molecular Biology, 342(4), p.1209 - 1221, 2004/09

 Times Cited Count:17 Percentile:70.53(Biochemistry & Molecular Biology)

Regulation of skeletal and cardiac muscle contraction is associated with the thin filament-based proteins, troponin C (TnC), TnI, TnT, tropomyosin, and actin. Knowledge of ${it in situ}$ structures of these proteins is indispensable for elucidating the molecular mechanism of this Ca$$^{2+}$$-sensitive regulation. Here the structure of TnC within the thin filaments was investigated with neutron scattering, combined with selective deuteration and the contrast matching technique. Deuterated TnC was prepared, reconstituted into the native thin filaments, and neutron scattering patterns of these reconstituted thin filaments containing deuterated TnC were measured under the condition where non-deuterated components were rendered 'invisible' to neutrons. The obtained scattering curves arising only from deuterated TnC were analyzed by model calculations using the Monte Carlo method. The results showed that upon binding of Ca$$^{2+}$$, ${it in situ}$ radius of gyration of TnC changed from 23 AA to 24 AA , and the radial position of TnC within the thin filament changed from 53 AA to 49 AA .

JAEA Reports

Annual report on operation, utilization and technical development of Hot Laboratories; April 1, 2001 to March 31, 2002

Department of Hot Laboratories

JAERI-Review 2002-039, 106 Pages, 2003/01


no abstracts in English

Journal Articles

Research and development on the nuclear fuels

Sawa, Kazuhiro; Yamashita, Toshiyuki; Minato, Kazuo; Arai, Yasuo; Konashi, Kenji*

Nippon Genshiryoku Gakkai-Shi, 44(9), p.657 - 662, 2002/09

no abstracts in English

Journal Articles

Hydrogen analyses of titanium hydride by ERD and NRG methods

Tsuchiya, Bun*; Teshigawara, Makoto; Nagata, Shinji*; Konashi, Kenji*; Yasuda, Ryo; Nishino, Yasuharu; Nakagawa, Tetsuya*; Yamawaki, Michio*

Nuclear Instruments and Methods in Physics Research B, 190(1-4), p.699 - 703, 2002/05

 Times Cited Count:10 Percentile:41.77(Instruments & Instrumentation)

Practicability of Elastic Recoil Detection (ERD) and Neutron Radiography (NRG) methods for hydrogen concentration in titanium hydrides (d-TiHx : 1.6<x<2.0) is investigated. In ERD methods, the hydrogen concentration in the surface of TiHx is recognized. In NRG method, the hydrogen concentration over the balk was confirmed. These results show that both methods are effective means for estimating the hydrogen concentration in hydride materials.

Journal Articles

In-situ XAFS analysis of Y zeolite-supported Rh catalysts during high-pressure hydrogenation of CO$$_{2}$$

Bando, Kyoko*; Saito, Takeru; Sato, Koichi*; Tanaka, Tomoaki*; Dumeignil, F.*; Imamura, Motoyasu*; Matsubayashi, Nobuyuki*; Shimada, Hiromichi*

Topics in Catalysis, 18(1-2), p.59 - 65, 2002/01

no abstracts in English

Journal Articles

Fusion reactor design towards radwaste minimum with advanced shield material

Tobita, Kenji; Konishi, Satoshi; Nishio, Satoshi; Kosako, Kazuaki*; Tabara, Takashi*

Purazuma, Kaku Yugo Gakkai-Shi, 77(10), p.1035 - 1039, 2001/10

no abstracts in English

JAEA Reports

Evaluation of mechanical properties of hydrided cladding by usig modified ring tensile test

Kitano, Koji*; Fuketa, Toyoshi; Uetsuka, Hiroshi

JAERI-Research 2001-041, 24 Pages, 2001/08


no abstracts in English

JAEA Reports

Development of advanced neutron radiography for inspection on irradiated fuels and materials, 2; Observation of hydride and oxide film on zircaloy cladding using by neutron radiography

Yasuda, Ryo; Nakata, Masahito; Matsubayashi, Masahito; Harada, Katsuya; Ando, Hitoshi*

JAERI-Tech 2000-082, 38 Pages, 2001/02


no abstracts in English

JAEA Reports

Effect of magnetite as a corrosion product on the corrosion of carbon steel overpack

Taniguchi, Naoki; ; Kawasaki, Manabu*; *

JNC-TN8400 2001-001, 56 Pages, 2000/12


It is necessary to clear the effects of corrosion products on the corrosion life time of carbon steel overpack for geological isolation of high-level radioactive waste(HLW). Especially, it is important to understand the effects of magnetite because magnetite as a simulated corrosion product is reported to accelerate the corrosion rate of carbon steel. In this study, corrosion tests to reproduce the acceleration of corrosion due to magnetite was performed and the mechanism of the acceleration was investigated to evaluate the effects of magnetite as a corrosion product. Based on the results of experiments, following conclusions are obtained ; (1)Magnetite powder accelerates the corrosion rate of carbon steel. The main reaction of corrosion under the presence of magnetite is the reduction of Fe(III) in magnetite to Fe(II), but the reaction of hydrogen generation is also accelerated. The contribution of hydrogen generation reaction was estimated to be about 30% in the total corrosion reaction based on the experimental result of immersion test under the presence of magnetite. (2)Actual corrosion products containing magnetite generated by the corrosion of carbon steel protect the metal from the propagation of corrosion. The corrosion depth of carbon steel overpack due to magnetite was estimated to be about 1 mm based on the results of experiments. Even if the effect of magnetite is taken into the assessment of corrosion lifetime of overpack, total corrosion depth in 1000 years is estimated to be 33 mm, which is smaller than the corrosion allowance of 40 mm described in the second progress report on research and development for the geological disposal of HLM/ in Japan. It was concluded that the effect of magnetite on the corrosion life time of carbon steel overpack is negligible.

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