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Journal Articles

Anomalous magnetic anisotropy and magnetic nanostructure in pure Fe induced by high-pressure torsion straining

Oba, Yojiro; Adachi, Nozomu*; Todaka, Yoshikazu*; Gilbert, E. P.*; Mamiya, Hiroaki*

Physical Review Research (Internet), 2(3), p.033473_1 - 033473_6, 2020/11

Journal Articles

Local structure investigations of accumulated damage in irradiated MgAl$$_{2}$$O$$_{4}$$

Yoshioka, Satoru*; Tsuruta, Konosuke*; Yamamoto, Tomokazu*; Yasuda, Kazuhiro*; Matsumura, Sho*; Sugiyama, Takeharu*; Oba, Yojiro; Ishikawa, Norito; Kobayashi, Eiichi*; Okudaira, Koji*

Journal of the American Ceramic Society, 103(8), p.4654 - 4663, 2020/08

 Times Cited Count:0 Percentile:100(Materials Science, Ceramics)

X-ray absorption near edge structure (XANES) and small-angle X-ray scattering (SAXS) reveal the damaged structures in MgAl$$_{2}$$O$$_{4}$$ spinel induced by swift heavy ions. SAXS indicates the formation of ion tracks with cylindrical shape with a diameter of 5 nm. XANES indicates the cationic disordering between tetrahedral and octahedral sites by the irradiation. Quantitative analysis of XANES also reveals that cations preferably occupy the octahedral sites at high fluence.

Journal Articles

Nanostructural characterization of oleyl acid phosphate in poly-$$alpha$$-olefin using small-angle X-ray scattering

Oba, Yojiro; Motokawa, Ryuhei; Hino, Masahiro*; Adachi, Nozomu*; Todaka, Yoshikazu*; Inoue, Rintaro*; Sugiyama, Masaaki*

Chemistry Letters, 49(7), p.823 - 825, 2020/07

 Times Cited Count:0 Percentile:100(Chemistry, Multidisciplinary)

Journal Articles

Neutron scattering and imaging using neutron transmission spectra

Oba, Yojiro

Hamon, 30(2), p.90 - 93, 2020/05

no abstracts in English

Journal Articles

Neutron transmission spectrum of liquid lead bismuth eutectic

Oba, Yojiro; Ito, Daisuke*; Saito, Yasushi*; Onodera, Yohei*; Parker, J. D.*; Shinohara, Takenao; Oikawa, Kenichi

Materials Research Proceedings, Vol.15, p.160 - 164, 2020/02

Lead Bismuth eutectic (LBE) is a promising candidate of the coolant for accelerator driven system (ADS) and fast breeder reactor. Neutron transmission imaging is a powerful technique to investigate the LBE in flow channel. However, previous studies have focused on the analysis of the neutron transmission spectra due to Bragg diffraction (Bragg edge transmission) from the solid phase of the LBE. If the neutron transmission spectra due to the diffraction from a liquid phase can be observed, it is useful to study the behavior of the molten LBE in the flow channel. Therefore, the energy-resolved neutron transmission imaging measurements of the molten LBE was carried out. The observed neutron transmission spectra can be explained by those calculated from the scattering profiles of the molten LBE. This indicates that the structure of the molten LBE can be characterized and mapped using the neutron transmission imaging.

Journal Articles

Anomalous small-angle X-ray scattering (ASAXS) study of irradiation-induced nanostructure change in Fe-ion beam irradiated oxide dispersion-strengthened (ODS) steel

Kumada, Takayuki; Oba, Yojiro; Motokawa, Ryuhei; Morooka, Satoshi; Tominaga, Aki; Tanida, Hajime; Shobu, Takahisa; Konno, Azusa; Owada, Kenji*; Ono, Naoko*; et al.

Journal of Nuclear Materials, 528, p.151890_1 - 151890_7, 2020/01

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

We have developed an anomalous small-angle X-ray scattering (ASAXS) diffractometer in SPring-8 to investigate irradiation-induced nanostructural change in ion-beam irradiated stainless steel. A thermally-aged MA956 stainless steel sample displays power-law scattering that follows the Porod law at the magnitude of scattering vector, Q, below 0.5 nm$$^-1$$ and an overlapped shoulder around 0.7 nm$$^-1$$. After the ion-beam irradiation, the intensity of the shoulder remained unchanged, whereas that of the power-law scattering nearly doubled. This result indicates that none of the structural parameters of the Cr-rich nanoprecipitates, such as the number density, size, and interface roughness, were changed by the irradiation.

Journal Articles

Structural and electrochemical features of (Li$$_{2}$$S)$$_{x}$$(SiS$$_{2}$$)$$_{100-x}$$ superionic glasses

Mori, Kazuhiro*; Iwase, Kenji*; Oba, Yojiro; Ikeda, Kazutaka*; Otomo, Toshiya*; Fukunaga, Toshiharu*

Solid State Ionics, 344, p.115141_1 - 115141_10, 2020/01

 Times Cited Count:0 Percentile:100(Chemistry, Physical)

no abstracts in English

Journal Articles

Characterization of BaZrO$$_{3}$$ nanocolumns in Zr-added (Gd,Y)Ba$$_{2}$$Cu$$_{3}$$Ox superconductor tape by anomalous small-angle X-ray scattering

Oba, Yojiro; Sasaki, Hirokazu*; Yamazaki, Satoshi*; Nakasaki, Ryusuke*; Onuma, Masato*

Superconductor Science and Technology, 32(5), p.055011_1 - 055011_5, 2019/05

 Times Cited Count:0 Percentile:100(Physics, Applied)

Journal Articles

Advanced analysis technology for new material and product development

Sasaki, Hirokazu*; Nishikubo, Hideo*; Nishida, Shinsuke*; Yamazaki, Satoshi*; Nakasaki, Ryusuke*; Isomatsu, Takemi*; Minato, Ryuichiro*; Kinugawa, Kohei*; Imamura, Akihiro*; Otomo, Shinya*; et al.

Furukawa Denko Jiho, (138), p.2 - 10, 2019/02

no abstracts in English

Journal Articles

Imaging measurement of neutron attenuation by small-angle neutron scattering using soller collimator

Oba, Yojiro; Shinohara, Takenao; Sato, Hirotaka*; Onodera, Yohei*; Hiroi, Kosuke; Su, Y.; Sugiyama, Masaaki*

Journal of the Physical Society of Japan, 87(9), p.094004_1 - 094004_5, 2018/09

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Characterization of spin superstructures using neutron transmission spectra

Mamiya, Hiroaki*; Oba, Yojiro; Oikawa, Kenichi

Shiki, 39, P. 4, 2018/06

no abstracts in English

Journal Articles

Magnetic Bragg dip and Bragg edge in neutron transmission spectra of typical spin superstructures

Mamiya, Hiroaki*; Oba, Yojiro; Terada, Noriki*; Watanabe, Norimichi*; Hiroi, Kosuke; Shinohara, Takenao; Oikawa, Kenichi

Scientific Reports (Internet), 7(1), p.15516_1 - 15516_8, 2017/11

 Times Cited Count:1 Percentile:89.48(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

Energy-resolved small-angle neutron scattering from steel

Oba, Yojiro*; Morooka, Satoshi; Oishi, Kazuki*; Suzuki, Junichi*; Takata, Shinichi; Sato, Nobuhiro*; Inoue, Rintaro*; Tsuchiyama, Toshihiro*; Gilbert, E. P.*; Sugiyama, Masaaki*

Journal of Applied Crystallography, 50(2), p.334 - 339, 2017/04

 Times Cited Count:2 Percentile:67.97(Chemistry, Multidisciplinary)

Journal Articles

Quantitative analysis of tempering microstructure via ${it in-situ}$ synchrotron X-ray diffraction during heating

Morooka, Satoshi; Kanata, Hiroyuki*; Oba, Yojiro*; Sato, Masugu*

Heisei-28-Nendo SPring-8 Sangyo Shinbunya Shien Kadai, Ippan Kadai (Sangyo Bunya) Jisshi Hokokusho, p.95 - 98, 2017/00

no abstracts in English

Journal Articles

Characterization of microstructure using Bragg edge and energy-resolved small-angle neutron scattering

Oba, Yojiro; Morooka, Satoshi; Oishi, Kazuki*; Suzuki, Junichi*; Tsuchiyama, Toshihiro*; Gilbert, E. P.*

Proceedings of 5th International Symposium on Steel Science (ISSS 2017), p.151 - 154, 2017/00

Small-angle neutron scattering and neutron diffraction are powerful tools to characterize microstructures in steels. Several new experimental techniques such as Bragg edge transmission analysis and energy-resolved small-angle neuron scattering have been recently developed with the opening of new-generation pulsed neutron sources. In this talk, the combined use of these diffraction and small-angle scattering techniques are discussed for the total characterization of the microstructures in steels.

Journal Articles

Novel neutron scattering techniques using neutron transmission spectra

Oba, Yojiro*; Morooka, Satoshi; Sato, Hirotaka*; Sato, Nobuhiro*; Inoue, Rintaro*; Sugiyama, Masaaki*

Hamon, 26(4), p.170 - 173, 2016/11

Journal Articles

Magnetic scattering in the simultaneous measurement of small-angle neutron scattering and Bragg edge transmission from steel

Oba, Yojiro*; Morooka, Satoshi; Oishi, Kazuki*; Sato, Nobuhiro*; Inoue, Rintaro*; Adachi, Nozomu*; Suzuki, Junichi*; Tsuchiyama, Toshihiro*; Gilbert, E. P.*; Sugiyama, Masaaki*

Journal of Applied Crystallography, 49(5), p.1659 - 1664, 2016/10

 Times Cited Count:7 Percentile:38.97(Chemistry, Multidisciplinary)

Journal Articles

Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

Ikeda, Yoshimasa*; Taketani, Atsushi*; Takamura, Masato*; Sunaga, Hideyuki*; Kumagai, Masayoshi*; Oba, Yojiro*; Otake, Yoshie*; Suzuki, Hiroshi

Nuclear Instruments and Methods in Physics Research A, 833, p.61 - 67, 2016/10

 Times Cited Count:22 Percentile:2.8(Instruments & Instrumentation)

A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by the large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 minutes. The minimum resolution of the 110 reflection for RANS is approximately 2.5 % at 8 $$mu$$s of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 $$mu$$s, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenite phase was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS was proved to be capable for neutron engineering diffraction aiming for the easy access measurement of the texture and the amount of retained austenite.

Journal Articles

Non-destructive texture measurement of steel sheets with compact neutron source "RANS"

Takamura, Masato*; Ikeda, Yoshimasa*; Sunaga, Hideyuki*; Taketani, Atsushi*; Otake, Yoshie*; Suzuki, Hiroshi; Kumagai, Masayoshi*; Hama, Takayuki*; Oba, Yojiro*

Journal of Physics; Conference Series, 734(Part B), p.032047_1 - 032047_4, 2016/08

 Times Cited Count:2 Percentile:24.4

Neutron diffraction is well known to be a useful technique for measuring a bulk texture of metallic materials taking advantage of a large penetration depth of the neutron beam. However, this technique has not been widely utilized for the texture measurement because large facilities like a reactor or a large accelerator are required in general. In contrast, RANS (Riken Accelerator-driven Compact Neutron Source) has been developed as a neutron source which can be used easily in laboratories. In this study, texture evolution in steel sheets with plastic deformation was successfully measured using RANS. The results show the capability of the compact neutron source for the analysis of the crystal structure of metallic materials, which leads us to a better understanding of plastic deformation behavior.

Journal Articles

Hierarchical structure-property relationships in graft-type fluorinated polymer electrolyte membranes using small- and ultrasmall-angle X-ray scattering analysis

Tran Duy, T.*; Sawada, Shinichi; Hasegawa, Shin; Yoshimura, Kimio; Oba, Yojiro*; Onuma, Masato*; Katsumura, Yosuke*; Maekawa, Yasunari

Macromolecules, 47(7), p.2373 - 2383, 2014/04

 Times Cited Count:16 Percentile:36.85(Polymer Science)

The hierarchical structures of graft-type ETFE-based polymer electrolyte membranes (ETFE-PEMs) were investigated using small- and ultrasmall-angle X-ray cattering experiments. The ETFE-PEMs with IECs $$<$$ 2.4 mmol/g possessed conducting graft domains around lamellar crystals, with a d-spacing of 21.8-29.1 nm, and oriented crystallites with short and long correlation distances of 218-320 and 903-1124 nm, respectively. The membranes with IECs $$>$$ 2.7 mmol/g showed a new phase of crystallite network domains with a d-range of 225-256 nm, indicating a phase transition from oriented crystallite to crystallite network structures in the IEC range of 2.4-2.7 mmol/g. Noted that for the ETFE-PEMs with high IECs higher conductivity at 30% RH and compatible tensile strengths at 100% RH and 80 $$^{circ}$$ C, compared with Nafion, originated from the well-interconnected ion channels around the crystallites and the remaining lamellar crystals and crystallites, respectively.

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