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Journal Articles

Identification of hydrogen trapping in aluminum alloys $$via$$ muon spin relaxation method and first-principles calculations

Tsuru, Tomohito; Nishimura, Katsuhiko*; Matsuda, Kenji*; Nunomura, Norio*; Namiki, Takahiro*; Lee, S.*; Higemoto, Wataru; Matsuzaki, Teiichiro*; Yamaguchi, Masatake; Ebihara, Kenichi; et al.

Metallurgical and Materials Transactions A, 54(6), p.2374 - 2383, 2023/06

Although hydrogen embrittlement susceptibility of high-strength Al alloys is recognized as a critical issue in the practical use of Al alloys, identifying the hydrogen trapping or distribution has been challenging. In the present study, an effective approach based on experiment and simulation is proposed to explore the potential trap sites in Al alloys. Zero-field muon spin relaxation experiments were carried out for Al-0.5%Mg, Al-0.2%Cu, Al-0.15%Ti, Al-0.011%Ti, Al-0.28%V, and Al-0.015%V (at.%) in the temperature range from 5 to 300 K. The temperature variations of the dipole field widths have revealed three peaks for Al-0.5%Mg, four peaks for Al-0.2%Cu, three peaks for Al-0.011%Ti and Al-0.015%V. Atomic configurations of the muon trapping sites corresponding to the observed $$Delta$$ peaks are well assigned using the first-principles calculations for the trap energies of hydrogen around a solute and solute-vacancy pair. The extracted linear relationship between the muon $$Delta$$ peak temperature and the trap energy enables us to explore the potential alloying elements and their complex that have strong binding energies with hydrogen in Al alloys.

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

Abnormally enhanced diamagnetism in Al-Zn-Mg alloys

Nishimura, Katsuhiko*; Matsuda, Kenji*; Lee, S.*; Nunomura, Norio*; Shimano, Tomoki*; Bendo, A.*; Watanabe, Katsumi*; Tsuchiya, Taiki*; Namiki, Takahiro*; Toda, Hiroyuki*; et al.

Journal of Alloys and Compounds, 774, p.405 - 409, 2019/02

 Times Cited Count:3 Percentile:18.28(Chemistry, Physical)

Journal Articles

Superconducting properties of Pr-based filled skutterudite PrRu$$_4$$As$$_{12}$$

Namiki, Takahiro*; Aoki, Yuji*; Sato, Hideyuki*; Sekine, Chihiro*; Shirotani, Ichimin*; Matsuda, Tatsuma; Haga, Yoshinori; Yagi, Takehiko*

Journal of the Physical Society of Japan, 76(9), p.093704_1 - 093704_4, 2007/09

 Times Cited Count:31 Percentile:77.39(Physics, Multidisciplinary)

Journal Articles

Development and operation of nuclear material accounting system of JAERI

Obata, Takashi; Numata, Kazuyoshi; Namiki, Shinji; Suzuki, Tsuneo*; Yamauchi, Takahiro*

Dai-24-Kai Kaku Busshitsu Kanri Gakkai Nihon Shibu Nenji Taikai Rombunshu, p.65 - 70, 2003/00

For the nuclear material accounting system, the mainframe computer had been used in Japan Atomic Energy Research Institute (JAERI). For the purpose of more flexible use and easy operation, the PC base accounting system has been developed since 1999, and operation started from October, 2002. This system consists of the server with the database software and the client PC with original application software. The functions of this system are the input and edit of data, the creation of inspection correspondence data, and creation of a report to the states. Furthermore, it is also possible to create the Web application which used accounting data on a user level by using the programming language. Now, this system is being specialized in JAERI, but it is during a plan to develop as a system which can be also used at other institutions and organization. In the paper, the outline and operating situation of the nuclear material accounting system of JAERI are presented.

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