Jiaqi Zhang ^a, Akifumi Iwamoto ^a,b, Keisuke Shigemori ^a , Masanori Hara ^c , Kohei Yamanoi ^a

a Institute of Laser Engineering, Osaka University, Osaka 5650871, Japan
b National Institute for Fusion Science, National Institutes of Natural Sciences, Gifu 509-5202, Japan
c Academic Assembly, University of Toyama, Toyama 9308555, Japan

Abstract
A typical inertial confinement fusion target comprises a central deuterium-tritium (D-T) gas surrounded by a solid D-T layer inside an outer ablator shell. However, because of the isotope effect, fractionation of the hydrogen isotopologues can occur during the solidification process. This inhomogeneity in the solid D-T layer may lead to a deterioration in the fusion reaction. Thus, effective methods are required to characterize isotopologue distribution and homogeneity in solid D-T layers. The distribution of isotopologues in a solid hydrogen mixture can be simulated numerically using computational fluid dynamics. In this study, thermofluid simulations of the mixture’s solidification process were performed to investigate the mechanism behind component distribution and to analyze the factors affecting the homogeneity. A numerical simulation was conducted to model inhomogeneity formation during the solidification of hydrogen isotopologue mixtures in a 3D wedge-shaped cavity. The simulations revealed inhomogeneities in H₂-D₂, D₂-T₂, and D₂-DT-T₂ mixtures during solidification. For an H₂-D₂ mixture, the simulation showed good agreement with experimental results, validating the computational model. These simulation methods will be used for homogeneity analysis of the solid D-T layer in fuel pellets.

https://doi.org/10.1016/j.fusengdes.2025.114827
Accepted: 23 January 2025

Satoshi Akamaru, Kyosuke Miyake

Abstract
This study investigated the giant magnetoresistance (GMR) effect of a Fe/V(001) multilayer under different hydrogen concentrations in a hydrogen–nitrogen gas mixture to elucidate the effect of hydrogen absorption in the V layer on the exchange interactions between each Fe layer. The resistance against hydrogen concentration in the gas mixture revealed a phase boundary that was dependent on the V thickness in Fe/V, between hydrogen dissolved in the V metal and V hydride phases. The magnetoresistance in Fe/V with a V thickness of 1.7–2.0 nm demonstrated a GMR effect, which was reduced under low hydrogen concentration in the gas mixture, corresponding to the hydrogen dissolved phase in the V layer. However, Fe/V samples with V thicknesses within the range of 2.2–2.7 nm exhibited the GMR effect during the formation of the V hydride phase, although these samples did not display any GMR behavior under nitrogen gas. These behaviors were reversible to hydrogen concentration in the gas mixture. The dependence of the exchange coupling coefficient on the V layer thickness was estimated from the GMR behavior, revealing that the exchange coupling coefficient was governed by the change in the crystalline phase from the V metal to the hydride and not by the thickness of the V layer. In the V hydride phase, the GMR effect was gradually reduced following hydrogen absorption, suggesting that the induced structural disorder and/or stress in the V layer due to excess hydrogen absorption inhibited the exchange interactions between each Fe layer.

https://doi.org/10.1063/5.0250577
Published Online: 10 February 2025

Hidehisa Hagiwara,* Katsuaki Hayakawa, Kazuki Ishitsuka, Keisuke Awaya, Kazuto Hatakeyama,and Shintaro Ida

Abstract
To make full use of sunlight for water splitting reactions for hydrogen production, a visible-light-driven photocatalyst was developed by modifying TiO₂ nanosheets with Co(OH)₂. By adding an aqueous Co(NO₃)₂·6H₂O solution to a TiO₂ nanosheet suspension, the TiO₂ nanosheets aggregated and Co(OH)₂ was formed. In the ultraviolet−visible (UV−vis) diffuse reflectance spectrum of the photocatalyst, new absorption bands attributable to Co(OH)₂ and the interfacial charge transfer between Co(OH)₂ and the TiO₂ nanosheets appeared at around 600 and 400 nm, respectively. The photocatalytic activity of Co(OH)₂/TiO₂ nanosheets was evaluated in terms of the O₂ evolution reaction in an aqueous AgNO₃ solution, finding that the reaction proceeds under visible light. Furthermore, the investigation of the wavelength dependence of the photocatalytic activity revealed that the photocatalytic reaction on Co(OH)₂/TiO₂ nanosheets proceeds via Co(OH)₂ photocatalysis and interfacial charge transfer between Co(OH)₂ and the TiO₂ nanosheets under visible light irradiation.

https://doi.org/10.1021/acsomega.4c10161
Accepted:January 8, 2025

Kazuyuki Shimizu ^a,* , Masatake Yamaguchi ^b , Satoshi Akamaru ^c , Katsuhiko Nishimura ^d,Rion Abe ^e, Taisuke T. Sasaki ^f , Yafei Wang ^g, Hiroyuki Toda ^g

a Faculty of Engineering, Tottori University, Tottori 680-8552, Japan b Center for Computational Science and e-Systems, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan
c Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555, Japan
d Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan
e Department of Physical Science and Materials Engineering, Iwate University, Iwate 020-8551, Japan
f Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Ibaraki 305-0047, Japan
g Department of Mechanical Engineering, Kyushu University, Fukuoka 819-0395, Japan

Abstract
The approximant crystal Mg₃₂(Al, Zn)₄₉ (T-phase in Al-Zn-Mg alloys) holds the potential for enhancing both strength and hydrogen embrittlement resistance in aluminum alloys when present as nano-precipitates. Our previous computational exploration indicated strong hydrogen trapping but neglected the inherent chemical disorder of this approximant crystal. This study revisits hydrogen trapping in Mg₃₂(Al, Zn)₄₉, directly including chemical disorder via special quasirandom structures. Density functional theory calculations reveal that, while chemical disorder introduces variations in trapping energies, the overall trend of strong trapping persists. Tetrahedral sites coordinated by Mg atoms exhibit particularly strong trapping, with smaller tetrahedral volumes correlating with stronger trapping due to enhanced Mg-H interactions. Multiple hydrogen occupation of these sites is also calculated, resulting in high hydrogen densities. Experimental validation using thermal desorption spectroscopy on a bulk Mg₃₂(Al, Zn)₄₉ sample confirms hydrogen trapping, reinforcing the potential of this phase for designing advanced, hydrogen-resistant aluminum alloys.

Accepted: 22 April 2025
https://doi.org/10.1016/j.scriptamat.2025.116730

Norihiro Ikemoto,^a,b* Hironori Shiraishi,^a Akira Tsuguchi,^a Mutsumi Nakamura,^a Naoki Mizuniwa,^a Satoshi Akamaru,^c and Masanori Hara^c

aKAKEN Incorporated, 1044 Horicho, Mito City, Ibaraki 310-0903, Japan
bUniversity of Toyama, Graduate School of Science and Engineering for Education, 3190 Gofuku, Toyama 930-8555, Japan
cUniversity of Toyama, Faculty of Science, Academic Assembly, 3190 Gofuku, Toyama 930-8555, Japan

Abstract
A tritium removal system (TRS) has been designed and installed. The TRS can remove tritium leaked into a workspace (100 m³). The tritium removal process in the TRS is a wet method in which leaked tritium compounds are oxidized to tritiated water by a catalyst, and the tritiated water is captured by a molecular sieve bed. The tritium removal performance (TRP) of the TRS was evaluated using H₂ and CH₄.The TRP is expressed by the relationship between the tritium oxidation efficiency of the catalyst bed and the water-capturing efficiency of the molecular sieve bed. The oxidation efficiency of CH₄ increased with increasing the catalyst temperature, and it reached to 0.75 around 280°C. The water-capturing efficiency was found to be 0.97 during the operation. The relationship between the oxidation efficiency and the water-capturing efficiency was reconstructed to chart and evaluate the tritium removal time. The chart evaluating the TRP of the TRS satisfied the design requirements. The design and evaluation method of this TRS can be applied to other TRSs using the wet method.

DOI: https://doi.org/10.1080/15361055.2025.2456894
Accepted for Publication: January 10, 2025