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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

New approach to understanding the experimental $$^{133}$$Cs NMR chemical shift of clay minerals via machine learning and DFT-GIPAW calculations

Okubo, Takahiro*; Takei, Akihiro*; Tachi, Yukio; Fukatsu, Yuta; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*

Journal of Physical Chemistry A, 127(4), p.973 - 986, 2023/02

 Times Cited Count:0 Percentile:0.01(Chemistry, Physical)

The identification of adsorption sites of Cs on clay minerals has been studied in the fields of environmental chemistry. The nuclear magnetic resonance (NMR) experiments allow direct observations of the local structures of adsorbed Cs. The NMR parameters of $$^{133}$$Cs, derived from solid-state NMR experiments, are sensitive to the local neighboring structures of adsorbed Cs. However, determining the Cs positions from NMR data alone is difficult. This paper describes an approach for identifying the expected atomic positions of Cs adsorbed on clay minerals by combining machine learning (ML) with experimentally observed chemical shifts. A linear ridge regression model for ML is constructed from the smooth overlap of atomic positions descriptor and gauge-including projector augmented wave (GIPAW) ab initio data. The $$^{133}$$Cs chemical shifts can be instantaneously calculated from the Cs positions on any clay layers using ML. The inverse analysis from the ML model can derive the atomic positions from experimentally observed chemical shifts.

Journal Articles

High-spin states in $$^{35}$$S

Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Aoi, Nori*; Azaiez, F.*; Furutaka, Kazuyoshi; Hatsukawa, Yuichi; Kimura, Atsushi; Kisamori, Keiichi*; Kobayashi, Motoki*; et al.

Physical Review C, 103(3), p.034327_1 - 034327_8, 2021/03

 Times Cited Count:4 Percentile:58.42(Physics, Nuclear)

Journal Articles

New insights into the Cs adsorption on montmorillonite clay from $$^{133}$$Cs solid-state NMR and density functional theory calculations

Okubo, Takahiro*; Okamoto, Takuya*; Kawamura, Katsuyuki*; Gu$'e$gan, R.*; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*; Tachi, Yukio; Iwadate, Yasuhiko*

Journal of Physical Chemistry A, 122(48), p.9326 - 9337, 2018/12

 Times Cited Count:14 Percentile:61.08(Chemistry, Physical)

The structures of Cs adsorption on montmorillonite were investigated by the nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Cs adsorbed on montmorillonite samples were measured under different Cs contents and relative humidity levels. NMR parameters were evaluated by the first principle calculations in order to identify the relationship between adsorbed Cs structures and NMR parameters. The comparisons between experimental and theoretical NMR spectra revealed that Cs is preferentially adsorbed at sites near Al for low Cs substituted montmorillonites, and that non-hydrated Cs present in partially Cs substituted samples, even after being hydrated under high relative humidity.

JAEA Reports

Measurements of Prompt Gamma-Ray Emission Probabilities for Determinations of Neutron Capture Cross Sections of Long Life Nuclides

Miyazaki, Itaru*; Shimizu, Toshiaki*; Shibata, Michihiro*; Kawade, Kiyoshi*; Furutaka, Kazuyoshi; Nakamura, Shoji; Sakane, Hitoshi

JNC TY8400 2005-002, 40 Pages, 2005/06

JNC-TY8400-2005-002.pdf:2.69MB

Accurate cross section data for the neutron capture of long-lived fission products (LLFP) are needed for developing a nuclear transmutation technology which reduces radioactive wastes by transmuting nuclides that have half-lives of as long as a few million years to other nuclides that have much shorter half-lives. There are some nuclides, whose cross sections cannot be measured in activation method. Utilization of prompt gamma-rays is expected to solve this problem. The aim of present study was twofold: (i) to measure emission probabilities of the high energy gamma-ray, up to 10MeV, emitted from$$^{14}$$N(n, gamma)$$^{15}$$N reaction, which are usually used as standards, in order to improve their accuracies and (ii) to develop a measurement method for neutron capture cross sections by using prompt gamma-rays. Emission probabilities of principal prompt gamma-rays from$$^{14}$$N(n, gamma)$$^{15}$$N reaction were determined with 0.2-0.9% errors. For ten nuclides,$$^{23}$$Na,$$^{27}$$Al,$$^{51V,sup}$$55 Mn,$$^{64}$$Ni,$$^{65}$$Cu,$$^{141}$$Pr,$$^{186}$$W, and$$^{197Au,}$$capture cross sections were measured by using prompt gamma-rays and gamma-rays following b-decay. By comparing both cross section values, it was found that emission probabilities of prompt gamma-rays reported in the literatures were systematically larger than those inferred from the cross sections that were determined in activation methods. The cross section of a$$^{104}$$Pd (n, gamma)$$^{105}$$Pd reaction at thermal energy was measured. Considering transmutation of the nuclide, the cross section of$$^{104}$$Pd(n, gamma), which is an isotope of palladium, is also necessary. A lower limit of the cross section was determined with 6% accuracy. Additionally, a method of estimating an upper limit was examined by noting similarity of nuclear structures to the neighboring nuclides. It was estimated that the observed lower limit of emission probabilities correspond to 79% of the cross section.

Oral presentation

Radiation effects of the boron nano-belt on the electronic conductivity

Kirihara, Kazuhiro*; Kawaguchi, Kenji*; Shimizu, Yoshiki*; Sasaki, Takeshi*; Koshizaki, Naoto*; Kimura, Kaoru*; Yamada, Yoichi; Yamamoto, Hiroyuki; Shamoto, Shinichi

no journal, , 

Radiation effects of the boron nano-belt on the electronic conductivity have been studied.

Oral presentation

Radiation detection using boron nanobelts

Kirihara, Kazuhiro*; Kawaguchi, Kenji*; Shimizu, Yoshiki*; Sasaki, Takeshi*; Koshizaki, Naoto*; Kimura, Kaoru*; Yamada, Yoichi; Yamamoto, Hiroyuki; Shamoto, Shinichi

no journal, , 

We discuss the effects of neutron and $$gamma$$-ray irradiation on electrical transport of single-crystalline boron nanobelts toward a nano-scale radiation sensor device. Changes of electrical conductance of individual nanobelt before and after thermal neutron irradiation with low (10$$^{8}$$ cm$$^{-2}$$ s$$^{-1}$$) or high (3$$times$$10$$^{13}$$ cm$$^{-2}$$ s$$^{-1}$$) flux are presented.

Oral presentation

Effect of neutron irradiation on the electrical transport of boron nanobelt devices

Kirihara, Kazuhiro*; Kawaguchi, Kenji*; Shimizu, Yoshiki*; Sasaki, Takeshi*; Koshizaki, Naoto*; Kimura, Kaoru*; Yamada, Yoichi; Yamamoto, Hiroyuki; Shamoto, Shinichi

no journal, , 

Isotopic $$^{10}$$B atom has large thermal neutron capture cross section. $$^{7}$$Li atom and $$alpha$$ particle as a product of the neutron reaction can change the electrical transport property of the boron-rich semiconductor because they provide carrier doping and lattice defects. We successfully synthesized catalyst-free single-crystalline boron nanobelts (BNBs) and clarified the electrical transport and photoconduction mechanism of individual nanobelt. The BNB device is promising candidates for solid-state neutron sensors with both high resolution and good discrimination performance between neutron and $$gamma$$-ray. In the presentation, we discuss the performance of thermal neutron detection of BNB devices. Isotopic $$^{10}$$B enriched BNBs was synthesized to detect thermal neutrons efficiently. Electrical conductance of a nanobelt increased to eight times after the thermal neutron irradiation with a dose of 1.8$$times$$10$$^{14}$$ cm$$^{-2}$$ by the neutron reaction of $$^{10}$$B.

Oral presentation

Structural analysis of Cs adsorption on Cs-montmorillonite using ab initio calculation and $$^{133}$$Cs solid state NMR, 2; $$^{133}$$Cs MAS and 3Q MAS NMR

Okamoto, Takuya*; Okubo, Takahiro*; Iwadate, Yasuhiko*; Deguchi, Kenzo*; Shimizu, Tadashi*; Oki, Shinobu*; Tachi, Yukio

no journal, , 

The structures of Cs adsorption on montmorillonite were investigated by the nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Cs adsorbed montmorillonite samples with different Cs contents were collected by $$^{133}$$Cs Magic Angle Spinning (MAS) NMR and $$^{133}$$Cs Triple Quantum (3Q) MAS NMR. The adsorbed Cs structures were evaluated based on the correlations between the structural characteristics and the values of the NMR parameters predicted by the first principal calculations.

Oral presentation

Structure of hydrated Cs on montmorillonite

Okamoto, Takuya*; Okubo, Takahiro*; Iwadate, Yasuhiko*; Deguchi, Kenzo*; Shimizu, Tadashi*; Oki, Shinobu*; Tachi, Yukio

no journal, , 

The structures of Cs adsorbed on montmorillonite were investigated by $$^{133}$$Cs Magic Angle Spinning (MAS) NMR spectroscopy. The NMR spectra of Cs adsorbed on montmorillonite samples were measured under different relative humidity levels and were analyzed to evaluate the change in the structure of hydrated Cs sorbed on montmorillonite.

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