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Journal Articles

Performance tests of catalysts for the safe conversion of hydrogen inside the nuclear waste containers in Fukushima Daiichi

Reinecke, E.-A.*; Takenaka, Keisuke*; Ono, Hitomi*; Kita, Tomoaki*; Taniguchi, Masashi*; Nishihata, Yasuo; Hino, Ryutaro; Tanaka, Hirohisa*

International Journal of Hydrogen Energy, 46(23), p.12511 - 12521, 2021/03

 Times Cited Count:5 Percentile:21.34(Chemistry, Physical)

The safe decommissioning as well as decontamination of the radioactive waste resulting from the nuclear accident in Fukushima Daiichi represents a huge task for the next decade. At present, research and development on long-term safe storage containers has become an urgent task with international cooperation in Japan. One challenge is the generation of hydrogen and oxygen in significant amounts by means of radiolysis inside the containers, as the nuclear waste contains a large portion of sea water. The generation of radiolysis gases may lead to a significant pressure build-up inside the containers and to the formation of flammable gases with the risk of ignition and the loss of integrity. In the framework of the project "R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers" funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context, a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification, and is characterized by having a self-healing function of precious metals (Pd, Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.

Journal Articles

Research on hydrogen safety technology utilizing the automotive catalyst

Ono, Hitomi*; Takenaka, Keisuke*; Kita, Tomoaki*; Taniguchi, Masashi*; Matsumura, Daiju; Nishihata, Yasuo; Hino, Ryutaro; Reinecke, E.-A.*; Takase, Kazuyuki*; Tanaka, Hirohisa*

E-Journal of Advanced Maintenance (Internet), 11(1), p.40 - 45, 2019/05

Journal Articles

Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates

Torigoe, Shuhei*; Ishimoto, Yutaro*; Aoishi, Yuhei*; Murakawa, Hiroshi*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo; Kodama, Katsuaki; Tomiyasu, Keisuke*; et al.

Physical Review B, 93(8), p.085109_1 - 085109_5, 2016/02

 Times Cited Count:5 Percentile:25.78(Materials Science, Multidisciplinary)

Journal Articles

Role of cerium oxide in the enhancement of activity for the oxygen reduction reaction at Pt-CeO$$_{x}$$ nanocomposite electrocatalyst; An in situ electrochemical X-ray absorption fine structure study

Masuda, Takuya*; Fukumitsu, Hitoshi*; Fugane, Keisuke*; Togasaki, Hirotaka*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Yoshikawa, Hideki*; Kobayashi, Keisuke*; Mori, Toshiyuki*; et al.

Journal of Physical Chemistry C, 116(18), p.10098 - 10102, 2012/05

 Times Cited Count:118 Percentile:93.69(Chemistry, Physical)

In situ electrochemical X-ray absorption fine structure (XAFS) measurements were performed at the Pt L$$_{3}$$ and Ce L$$_{3}$$ edges of the Pt-CeO$$_{x}$$/C catalyst, which was prepared by a combined process of precipitation and coimpregnation methods, as well as at the Pt L$$_{3}$$ edge of the conventional Pt/C catalyst in oxygen-saturated H$$_{2}$$SO$$_{4}$$ solution to clarify the role of CeO$$_{x}$$ in the reduction of the overpotential for the oxygen reduction reaction (ORR) at the Pt-CeO$$_{x}$$ nanocomposite compared with the conventional Pt/C catalyst. XAFS measurements clearly show that the enhancement of ORR activity is attributed to the inhibition of Pt oxide formation by the CeO$$_{x}$$ layer, of which Ce$$^{3+}$$ was oxidized to Ce$$^{4+}$$ instead of Pt at the Pt oxide formation potential.

Journal Articles

Spin chirality and electric polarization in multiferroic compounds RMn$$_2$$O$$_5$$ ($$R$$ = Ho, Er)

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

Physica B; Condensed Matter, 404(17), p.2513 - 2516, 2009/09

 Times Cited Count:5 Percentile:25.54(Physics, Condensed Matter)

Oral presentation

Polarized neutron scattering study of spin chirality in multiferroic material HoMn$$_{2}$$O$$_{5}$$ under electric field

Kimura, Hiroyuki*; Wakimoto, Shuichi; Nishihata, Keisuke*; Noda, Yukio*; Kakurai, Kazuhisa; Kon, Keiichiro*

no journal, , 

Multiferroic materials are known to show gigantic magnetoelectric effects. One of the microscopic models for polarization in such systems is based on spin chirality. We have perfoermed polarized neutron scattering experiments using HoMn$$_{2}$$O$$_{5}$$ single crystal to study correlation between the spin chirality and ferroelectric polarization. We found that the spin chirality is absent in the high temperature paraelectric HT-ICM phase whereas it appears in the ferroelectric LT-ICM phase. This fact demonstrates a strong coupling between the spin chirality and the ferroelctric polarization.

Oral presentation

Linear relation between electric polarization and magnetic chirality in the commensurate phase of $$R$$Mn$$_{2}$$O$$_{5}$$ ($$R=$$Ho, Er)

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

no journal, , 

Polarized neutron scattering experiments have been performed on multiferroic materials $$R$$Mn$$_{2}$$O$$_{5}$$ ($$R=$$Ho, Er) under electric fields to study the direct relation between the electric polarization and the magnetic chiral structure of Mn spins. It is found that, after cooling in electric fields down to temperatures where the system has both commensurate magnetic order and ferroelectricity, the magnetic chiral order parameter is proportional to the polarization.

Oral presentation

Linear relation between magnetic chirality and spontaneous polarizatin in multiferroic $$R$$Mn$$_2$$O$$_5$$ ($$R$$=Ho, Er)

Wakimoto, Shuichi; Kimura, Hiroyuki*; Nishihata, Keisuke*; Fukunaga, Mamoru*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

no journal, , 

Polarized neutron scattering experiments have been performed on multiferroic materials $$R$$Mn$$_{2}$$O$$_{5}$$ ($$R=$$Ho, Er) under electric fields to study the direct relation between the electric polarization and the magnetic chiral structure of Mn spins. It is found that the magnetic chirality is proportional to the polarization, consisntent with the inverse-DM model.

Oral presentation

Polarized neutron scattering study of magnetic chirality in multiferroic compounds $$R$$Mn$$_2$$O$$_5$$ ($$R=$$Ho, Er)

Wakimoto, Shuichi; Takeda, Masayasu; Kakurai, Kazuhisa; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Noda, Yukio*; Tokura, Yoshinori*

no journal, , 

Polarized neutron diffraction experiments have been performed on multiferroic materials $$R$$Mn$$_{2}$$O$$_{5}$$ ($$R=$$Ho, Er) under electric fields in the ferroelectric commensurate (CM) and the low-temperature incommensurate (LT-ICM) phases. It is found that the magnetic chirality is proportional to the electric polarization and magnetic chirality can be switched by the polarity of the electric polarization in both the CM and LT-ICM phases. However, upon the transition from the CM to LT-ICM phase, the reduction of the electric polarization is not accompanied by any reduction of the magnetic chirality, implying that the CM and LT-ICM phases contain different mechanisms of the magnetoelectric coupling.

Oral presentation

Magnetic chirality and electric polarization in multiferroic $$R$$Mn$$_2$$O$$_5$$

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

no journal, , 

Polarized neutron diffraction experiments have been performed on multiferroic materials $$R$$Mn$$_{2}$$O$$_{5}$$ ($$R=$$Ho, Er) under electric fields in the ferroelectric commensurate (CM) and the low-temperature incommensurate (LT-ICM) phases. It is found that the magnetic chirality is proportional to the electric polarization and magnetic chirality can be switched by the polarity of the electric polarization in both the CM and LT-ICM phases. However, upon the transition from the CM to LT-ICM phase, the reduction of the electric polarization is not accompanied by any reduction of the magnetic chirality, implying that the CM and LT-ICM phases contain different mechanisms of the magnetoelectric coupling.

Oral presentation

R&D on reduction technology of hydrogen generation in long-term waste storage containers, 8; Reaction mechanism of hydrogen recombination catalysts studied by synchrotron X-ray absorption spectroscopy

Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Hino, Ryutaro; Taniguchi, Masashi*; Takenaka, Keisuke*; Ono, Hitomi*; Kita, Tomoaki*; Tanaka, Hirohisa*

no journal, , 

no abstracts in English

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