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Sn
by time resolved X-ray diffractionMachida, Akihiko; Higuchi, Kensuke*; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
Nihon Kinzoku Gakkai-Shi, 79(3), p.124 - 130, 2015/03
Times Cited Count：4 Percentile：22.66(Metallurgy & Metallurgical Engineering)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 La
Ni(Ni,Sn) octahedron and La(Ni,Sn) tetrahedron in the intermediate phase.
Nagashio, Kosuke*; Adachi, Masayoshi*; Higuchi, Kensuke*; Mizuno, Akitoshi*; Watanabe, Masahito*; Kuribayashi, Kazuhiko*; Katayama, Yoshinori
Journal of Applied Physics, 100(3), p.033524_1 - 033524_6, 2006/08
Times Cited Count：14 Percentile：47.09(Physics, Applied)Grain refined microstructure is often obtained spontaneously in the solidification of metals and semiconductors from the undercooled melt without any external forces. Although it has been reported that the grain refinement is mainly caused by the fragmentation of the dendrites, the dynamic process of the fragmentation of dendrites has not been fully understood because the microstructure after the solidification has been analyzed. Here, we present a time-resolved 2- dimensional X-ray diffraction experiment on the solidification of Si from the undercooled melt. The number of diffraction spots observed at low undercoolings (
100K) did not increase at the plateau stage, while the diffraction pattern at medium undercoolings (100K
200K) changed from the spots with the tail to rings with the lapse of time. Both this result and high speed video imaging suggested that the high-order arms of the dendrites mostly detached from the main stems because nucleation could not be expected at the melting point after recalescence. The several spots observed at low undercoolings drastically changed to rings at high undercoolings (
200K), which indicated the complete fragmentation of dendrite main stem as well as high-order arms. This complete fragmentation resulted in the grain refined microstructure.
Higuchi, Kensuke*; Kimura, Kakuryo*; Mizuno, Akitoshi*; Watanabe, Masahito*; Katayama, Yoshinori; Kuribayashi, Kazuhiko*
Measurement Science and Technology, 16(2), p.381 - 385, 2005/02
Times Cited Count：43 Percentile：87.03(Engineering, Multidisciplinary)X-ray diffraction and density measurements have been simultaneously performed to investigate the atomic structure of molten silicon in wide temperature range including undercooling region by using the electromagnetic levitation technique. The density was obtained from the mass and the shape of levitated sample by non-contact method based on the image analysis technique. X-ray diffraction experiments were performed by using the synchrotron radiation at SPring8, Japan. From structural analysis of undercooled molten silicon, first nearest neighbour coordination numbers and interatomic distances were about 5 and 2.48
with no dependence on temperature in the range of 1900-1550 K. We conclude as a result that the short-range order based on tetrahedral bonds of undercooled molten silicon does not change with the degree of undercoolings but medium-range order changes by the degree of undercoolings.
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JAERI-M 87-050, 391 Pages, 1987/03
no abstracts in English
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JAERI-M 87-049, 325 Pages, 1987/03
no abstracts in English
Higuchi, Kensuke; Machida, Akihiko; Katayama, Yoshinori; Sakaki, Koji*; Nakamura, Yumiko*
no journal, ,
no abstracts in English
Higuchi, Kensuke; Machida, Akihiko; Katayama, Yoshinori; Sakaki, Koji*; Nakamura, Yumiko*
no journal, ,
no abstracts in English
Al
alloy on hydrogen absorption processHiguchi, Kensuke; Machida, Akihiko; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
no journal, ,
no abstracts in English
Al alloy on hydrogen absorbing processHiguchi, Kensuke; Machida, Akihiko; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
no journal, ,
no abstracts in English
Machida, Akihiko; Higuchi, Kensuke*; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
no journal, ,
We have investigated the structural properties of the hydrogen absorbing alloys on the hydrogen absorbing process. In-situ measurements are essential to elucidate the mechanism of the hydrogen storage because the hydrogen absorbing state usually keeps under the pressurized hydrogen gas environment. And then, the time-resolved measurements are one of the powerful tools for studying the gas-solid reaction processes. We have constructed the time-resolved X-ray diffraction system at BL22XU, SPring-8 in order to measure the X-ray diffraction patterns with higher time-resolution and higher quality. To demonstrate the performance of the constructed system, we have performed the time-resolved X-rays diffraction experiments for La(Ni,Al)
. We have found the formation of the transient intermediate phase on hydrogen absorbing reaction process from solid solution phase to known hydride phase.
Machida, Akihiko; Higuchi, Kensuke*; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
no journal, ,
To improve performance of hydrogen storage materials, it is essential to understand detailed mechanism of hydrogenation and dehydrogenation reactions. In-situ powder diffraction measurements provide direct information about structural changes accompanying the reactions. We therefore installed a time-resolved X-ray diffraction (XRD) system at a beamline BL22XU at the SPrign-8, a synchrotron radiation facility in Japan. The system equipped area detectors. A sample cell was connected to a hydrogen supply system. The pressure of hydrogen gas was limited to 1 MPa. To demonstrate the performance of the system, we have performed time-resolved XRD experiments for LaNiAl. LaNi exhibits the significant broadening of the diffraction peaks by hydrogen absorption; however, LaNiAl shows the no significant broadening. We have succeeded in the measurements of the structural change from the solid solution phase to the hydride phase and have found the formation of the transient intermediate phase on this reaction process. The system is currently used to study several materials.
M
on hydrogen absorption processMachida, Akihiko; Higuchi, Kensuke*; Watanuki, Tetsu; Katayama, Yoshinori; Sakaki, Koji*; Kim, H.*; Nakamura, Yumiko*
no journal, ,
no abstracts in English
