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Journal Articles

Detection of hydroxyl and hydride functional groups in a ceria crystal under hydrogen reduction

Matsukawa, Takeshi*; Iida, Kazuki*; Nakamura, Mitsutaka; Ishigaki, Toru*

CrystEngComm (Internet), 23(12), p.2355 - 2359, 2021/03

https://doi.org/10.1039/d1ce00130b
 Times Cited Count：4 Percentile：55.82(Chemistry, Multidisciplinary)

Journal Articles

Local disorder in proton conductor BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ analyzed by neutron diffraction/ atomic pair distribution function

Igawa, Naoki; Kodama, Katsuaki; Taguchi, Tomitsugu*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Hoshikawa, Akinori*; Ishigaki, Toru*

Transactions of the Materials Research Society of Japan, 43(6), p.329 - 332, 2018/12

https://doi.org/10.14723/tmrsj.43.329

For the understanding of the crystal structural effect on the electrical properties, the local disorder in BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ which is one of the excellent proton conductors for solid oxide fuel cells was estimated by using the Atomic Pair Distribution Function (PDF) analysis method with the neutron diffraction. The local structure is almost the same as the average structure which was estimated by the Rietveld analysis using the cubic crystal structure (space group, $${it Pm}$$$$overline{3}$$$${it m}$$) in the atomic distance range of ${it r}$ $$>$$ 6${AA}$. The PDF profile was fitted better using the tetragonal crystal structure with the space group of ${it P}$4/${it mmm}$ than those with $${it Pm}$$$$overline{3}$$$${it m}$$ in the range ${it r}$ $$<$$ 6${AA}$. Those results indicate the presence of the local disorder in the lattice. In this work, the relationship between the average and local structures of BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ will be discussed.

Journal Articles

Time-of-flight elastic and inelastic neutron scattering studies on the localized 4d electron layered perovskite La$$_5$$Mo$$_4$$O$$_{16}$$

Iida, Kazuki*; Kajimoto, Ryoichi; Mizuno, Yusuke*; Kamazawa, Kazuya*; Inamura, Yasuhiro; Hoshikawa, Akinori*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Ishigaki, Toru*; Kawamura, Yukihiko*; et al.

Journal of the Physical Society of Japan, 86(6), p.064803_1 - 064803_6, 2017/06

https://doi.org/10.7566/JPSJ.86.064803
 Times Cited Count：1 Percentile：12.03(Physics, Multidisciplinary)

Journal Articles

The Two-step nucleation of G-phase in ferrite

Matsukawa, Yoshitaka*; Takeuchi, Tomoaki; Kakubo, Yuta*; Suzudo, Tomoaki; Watanabe, Hideo*; Abe, Hiroaki*; Toyama, Takeshi*; Nagai, Yasuyoshi*

Acta Materialia, 116, p.104 - 113, 2016/09

https://doi.org/10.1016/j.actamat.2016.06.013
 Times Cited Count：73 Percentile：95.76(Materials Science, Multidisciplinary)

Atom probe tomography (APT) and TEM were combined for identifying the stage at which solute clusters transform into compounds crystallographically distinct from the matrix, in the precipitation of the G-phase (Ni$$_{16}$$Si$$_{7}$$Mn$$_{6}$$) from ferrite solid solution subjected to isothermal annealing at 673 K. Based on a systematic analysis of solute clusters as a function of annealing time, the nucleation of the G-phase was found to occur via a two-step process. Moreover, the structural change was found to occur via another two-step process. There was a time lag between the end of cluster growth to become a critical size and the start of the structural change. During the incubation period solute enrichment occurred inside the clusters without further size growth, indicating that the nucleation of the G-phase occurs at the critical size with a critical composition. Judging from the results of APT, TEM and the simulation of electron diffraction patterns, the critical composition was estimated to be Ni$$_{16}$$Si$$_{3.5}$$(Fe,Cr)$$_{3.5}$$Mn$$_{6}$$.

Journal Articles

Effects of thermal aging on microstructure and hardness of stainless steel weld-overlay claddings of nuclear reactor pressure vessels

Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio; et al.

Journal of Nuclear Materials, 452(1-3), p.235 - 240, 2014/09

https://doi.org/10.1016/j.jnucmat.2014.04.003
 Times Cited Count：40 Percentile：95.16(Materials Science, Multidisciplinary)

Microstructures and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the thermal aging at 400 $$^{circ}$$C for 100-10,000 h were investigated using atom probe tomography and nanoindentation technique. The Cr concentration fluctuation in the $$delta$$-ferrite phase caused by spinodal decomposition rapidly progressed by the 100 h aging while NiSiMn clusters increased in number density at 2,000 h and coarsened at 10,000 h. The hardness of the $$delta$$-ferrite phase also rapidly increased at the short aging time. The Cr concentration fluctuation and the hardness were in good correlation with the degree of the Cr concentration fluctuation rather than the formation of the NiSiMn clusters. These results strongly suggested that the dominant factor of the hardening of the $$delta$$-ferrite phase by the thermal aging was Cr spinodal decomposition.

Journal Articles

Effects of neutron irradiation on microstructures and hardness of stainless steel weld-overlay cladding of nuclear reactor pressure vessels

Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio

Journal of Nuclear Materials, 449(1-3), p.273 - 276, 2014/06

https://doi.org/10.1016/j.jnucmat.2014.01.004
 Times Cited Count：19 Percentile：81.57(Materials Science, Multidisciplinary)

Microstructural changes and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the neutron irradiation with a dose of 7.2 $$times$$ 10$$^{19}$$n cm$$^{-2}$$ (E $$>$$ 1 MeV) and a flux of 1.1 $$times$$ 10$$^{13}$$n cm$$^{-2}$$ s$$^{-1}$$ at 290$$^{circ}$$C were investigated by atom probe tomography and with nanoindentation technique. In order to isolate the effect of the irradiation, we compared the results of the measurements of the irradiated sample with that of the aged one at 300$$^{circ}$$C for the time equivalent to the irradiation. The Cr concentration fluctuation was enhanced in the $$delta$$-ferrite phase of the irradiated sample. In addition, the enhancement of the concentration fluctuation of Si, which was not observed in the aged sample, was observed. The hardening at the $$delta$$-ferrite phase was occurred by both the irradiation and the aging. However, the former was more than that expected from the Cr concentration fluctuation, which suggested that the Si concentration fluctuation and irradiation-induced defects were possible origins of the additional hardening.

Journal Articles

First test results for the ITER central solenoid model coil

Kato, Takashi; Tsuji, Hiroshi; Ando, Toshinari; Takahashi, Yoshikazu; Nakajima, Hideo; Sugimoto, Makoto; Isono, Takaaki; Koizumi, Norikiyo; Kawano, Katsumi; Oshikiri, Masayuki*; et al.

Fusion Engineering and Design, 56-57, p.59 - 70, 2001/10

https://doi.org/10.1016/S0920-3796(01)00235-6
 Times Cited Count：17 Percentile：74.85(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Progress of the ITER central solenoid model coil programme

Tsuji, Hiroshi; Okuno, Kiyoshi*; Thome, R.*; Salpietro, E.*; Egorov, S. A.*; Martovetsky, N.*; Ricci, M.*; Zanino, R.*; Zahn, G.*; Martinez, A.*; et al.

Nuclear Fusion, 41(5), p.645 - 651, 2001/05

https://doi.org/10.1088/0029-5515/41/5/319
 Times Cited Count：57 Percentile：83.02(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Analysis of the current distortion factor of 3-phase, 3-wire system

Nakano, Hirotami*; Tanabe, Takeshi*; Naito, Masanobu*; Kubota, Yoshiki*; Morita, Tsuyoshi*; Kimura, Toyoaki; Matsukawa, Makoto; Miura, Yushi

Electrical Engineering in Japan, 131(4), p.1 - 10, 2000/04

https://doi.org/10.1002/(SICI)1520-6416(200006)131:4<1::AID-EEJ1>3.0.CO;2-0
 Times Cited Count：8 Percentile：48.65(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Analysis method of current distortion factor of 3-phase 3-wire system

*; Tanabe, Takeshi*; Naito, Masanobu*; Kubota, Yoshiki*; Morita, Tsuyoshi*; Kimura, Toyoaki; Matsukawa, Makoto; Miura, Yushi

Denki Gakkai Rombunshi, A, 119(3), p.279 - 285, 1999/03

no abstracts in English

Journal Articles

High triangularity discharges with improved stability and confinement in JT-60U

Kamada, Yutaka; Yoshino, Ryuji; Ushigusa, Kenkichi; Neyatani, Yuzuru; Oikawa, Toshihiro; Naito, Osamu; Tokuda, Shinji; Shirai, Hiroshi; Takizuka, Tomonori; Ozeki, Takahisa; et al.

Fusion Energy 1996, Vol.1, p.247 - 258, 1997/00

no abstracts in English

Oral presentation

Study on microstructural changes in neutron-irradiated stainless steel weld-overlay cladding of nuclear reactor pressure vessels by atom probe tomography

Takeuchi, Tomoaki; Nishiyama, Yutaka; Katsuyama, Jinya; Onizawa, Kunio; Matsukawa, Yoshitaka*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Kameda, Jun*

no journal, , 

Microstructure evolution on stainless overlay cladding of reactor pressure vessel was quantitatively investigated by means of three-dimensional local electrode atom probe (3DAP) in nano-scale. The cladding material was neutron-irradiated up to 7$$times$$10$$^{19}$$n/cm$$^{2}$$ (E $$>$$ 1 MeV)at JMTR. In ferrite phases of cladding material, a 12% of Cr concentration fluctuation, which was arisen through a spinodal decomposition, observed before the irradiation was progressed to 20% after the irradiation while the wave length of the fluctuation was almost not changed about 8-10 nm before and after the irradiation. In addition, Ni, Si and Mn concentration fluctuations were also observed. Correlation between Cr concentration fluctuation and hardness, other elements concentration fluctuation and differences from the thermal aging will be reported in presentation.

Oral presentation

3DAP analysis of a neutron-irradiated stainless steel weld-overlay cladding of nuclear reactor pressure vessel

Takeuchi, Tomoaki; Nishiyama, Yutaka; Katsuyama, Jinya; Onizawa, Kunio; Nozawa, Yasuko*; Matsukawa, Yoshitaka*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Kameda, Jun*

no journal, , 

Microstructure evolution on stainless overlay cladding of reactor pressure vessel was quantitatively investigated by means of three-dimensional local electrode atom probe (3DAP) in nano-scale. The cladding material was neutron-irradiated up to 7$$times$$10$$^{19}$$ n/cm$$^{2}$$ (E $$>$$ 1 MeV) at JMTR. In ferrite phases of cladding material, a 12% of Cr concentration fluctuation, which was arisen through a spinodal decomposition, observed before the irradiation was progressed to 20% after the irradiation while the wave length of the fluctuation was almost not changed about 8-10 nm before and after the irradiation. In addition, Ni, Si and Mn concentration fluctuations were also observed. The concentration fluctuations of the elements other than Cr and differences from the thermal aging will be reported in presentation.

Oral presentation

Microstructural analysis of neutron-irradiated stainless steel weld-overlay claddings of nuclear reactor pressurevessel

Takeuchi, Tomoaki; Nishiyama, Yutaka; Katsuyama, Jinya; Onizawa, Kunio; Nozawa, Yasuko*; Matsukawa, Yoshitaka*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Kameda, Jun*

no journal, , 

Microstructure evolutions on two types, namely electroslag (ESW) and submerged-arc (SAW) welding, of stainless overlay claddings of reactor pressure vessel were quantitatively investigated by means of three-dimensional local electrode atom probe (3DAP) in nano-scale. The cladding materials were neutron-irradiated up to about 7$$times$$10$$^{19}$$n/cm$$^{2}$$ (E $$>$$ 1 MeV) at JMTR. In ferrite phases of cladding materials, a 12% of Cr concentration fluctuation, which was arisen through a spinodal decomposition, observed before the irradiation was progressed to 20% after the irradiation while the wave length of the fluctuation was almost not changed about 8-10 nm before and after the irradiation. In addition, Ni, Si and Mn concentration fluctuations were also observed. Correlation between Cr concentration fluctuation and hardness, other elements concentration fluctuation and differences between the neutron irradiation and the thermal aging, the ESW and SAW will be reported in presentation.

Oral presentation

Transmission electron microscopy crystal structure analysis of G-phase precipitates in an overlay-clad duplex stainless steel on a light-water pressure vessel steel

Matsukawa, Yoshitaka*; Kakubo, Yuta*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Takeuchi, Tomoaki; Yamaguchi, Yoshihito; Katsuyama, Jinya; Nishiyama, Yutaka

no journal, , 

The $$delta$$/$$gamma$$ duplex stainless steel overlay-welded on the inner wall of light-water reactor pressure vessels for protection from corrosion is known to exhibit a complex phase transformation under thermal aging. Our atom-probe tomography analysis revealed that in the $$delta$$-ferrite $$alpha$$/$$alpha$$' spinodal decomposition and precipitation of nanometer-sized Ni-Mn-Si clusters occur together at 673 K after 2000 hrs. The Ni-Mn-Si clusters visualized in the 3-D atom map are most likely G-phase, which is an intermetallic compound commonly observed in this type of duplex stainless steels; however, since crystallographic information is largely lost in atom-probe data, it is unknown if they are certainly G-phase accompanied with a specific supper-lattice structure or simple agglomerates of solute atoms without any crystal structure change. In the present study crystal structure of the Ni-Mn-Si nano-clusters has been analyzed by transmission electron microscopy to determine the fraction of G-phase over all clusters.

Oral presentation

Thermal aging time dependence of nanostructural changes in an overlay-clad duplex stainless steel on a light-water pressure vessel steel

Kakubo, Yuta*; Nozawa, Yasuko*; Matsukawa, Yoshitaka*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Kameda, Jun; Takeuchi, Tomoaki; Yamaguchi, Yoshihito; Katsuyama, Jinya; Nishiyama, Yutaka; et al.

no journal, , 

no abstracts in English

Oral presentation

Transmission electron microscopy crystal-structure analysis of G-phase precipitates in a $$delta$$/$$gamma$$ duplex stainless steel weld overlay cladding of light-water reactor pressure vessel steels

Matsukawa, Yoshitaka*; Kakubo, Yuta*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Takeuchi, Tomoaki; Yamaguchi, Yoshihito; Katsuyama, Jinya; Nishiyama, Yutaka

no journal, , 

Crystal structure change and composition change of G-phase (Ni$$_{16}$$Si$$_{7}$$Mn$$_{6}$$) precipitates in a duplex stainless steel welded on an RPV steel were analyzed by transmission electron microscopy combined with atom-probe tomography. Based on TEM crystallographic analysis data and atom-probe composition analysis data, together with simulation results of electron diffraction patterns, it was found that those precipitates turned G-phase in structure-wise before they turned stoichiometric composition.

Oral presentation

Magnetic properties and crystal structure of honeycomb lattice system Li$$_{3}$$Ni$$_{2}$$SbO$$_{6}$$

Fukui, Akito*; Yasui, Yukio*; Igawa, Naoki; Matsukawa, Takeshi*; Yoshida, Yukihiko*; Hoshikawa, Akinori*; Ishigaki, Toru*

no journal, , 

The powder neutron crystal structure analysis and measurements of the magnetization and the specific heat have been carried out for the honeycomb lattice spin system Li$$_{3}$$Ni$$_{2}$$SbO$$_{6}$$. From the Rietveld analysis of the neutron diffraction data, we determined the crystal structure of Li$$_{3}$$Ni$$_{2}$$SbO$$_{6}$$, where the space group is ${it C}$ 2/${it m}$ monoclinic and the distortion from ideal honeycomb lattice is $$sim$$0.1 % only. The Weiss temperature $$theta_mathrm{w}$$ obtained from the temperature dependence of magnetic susceptibility is 12.2 K, indicating that dominant interaction between the Ni$$^{2+}$$ spins is ferromagnetic one. However, from the behavior of the magnetic susceptibility and the specific heat, Li$$_{3}$$Ni$$_{2}$$SbO$$_{6}$$ is found to exhibit an antiferromagnetic transition at $$T_mathrm{N}$$ = 13.5 K.

Oral presentation

Magnetic behavior and magnetic structure of CuO$$_{2}$$ ribbon system A$$_{2}$$Cu$$_{2}$$Mo$$_{3}$$O$$_{12}$$ (A=Rb, Cs)

Fujimura, Akio*; Yasui, Yukio*; Kono, Yohei*; Kittaka, Shunichiro*; Sakakibara, Toshiro*; Igawa, Naoki; Matsukawa, Takeshi*; Yoshida, Yukihiko*; Hoshikawa, Akinori*; Ishigaki, Toru*

no journal, , 

The magnetic behavior and magnetic structure of A$$_{2}$$Cu$$_{2}$$Mo$$_{3}$$O$$_{12}$$ (A=Rb, Cs) with CuO$$_{2}$$ ribbon chains have been studied by using specific heat measurement and neutron diffraction method. Cs$$_{2}$$Cu$$_{2}$$Mo$$_{3}$$O$$_{12}$$ showed collinear-antiferromagnetic structure analyzed by the neutron diffraction. The relation between magnetic behavior and magnetic for those materials are discussed.

Oral presentation

Average and local structures of BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ as electrolyte for solid oxide fuel cell analyzed by neutron diffraction

Igawa, Naoki; Kodama, Katsuaki; Taguchi, Tomitsugu*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Hoshikawa, Akinori*; Ishigaki, Toru*

no journal, , 

The average and local structures of BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ which is one of the excellent solid electrolytes for solid oxide fuel cells were analyzed by using the Rietveld method and the Atomic Pair Distribution Function (PDF) analysis method with the neutron diffraction to research the crystal structural effect on the electrical properties. PDF profile which was obtained from the neutron diffraction data of BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ was fitted by using the crystal structure with the space group, ${it Pm}$-3${it m}$ which corresponds with the average structure, and the fitting relatively good reproduces the observed data. In this work, the relationship between the average and local structures of hydrogen doped and undoped BaSn$$_{0.5}$$In$$_{0.5}$$O$$_{2.75}$$ will be discussed.

25 (Records 1-20 displayed on this page)