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Abe, Yosuke; Kubo, Atsushi; Ukai, Shigeharu; Tsuru, Tomohito
Journal of Nuclear Materials, 618, p.156221_1 - 156221_11, 2026/01
Understanding the stability of Cr-rich precipitates (CrRPs) is key to developing radiation-resistant ODS Fe-Cr-Al alloys. This study uses first-principles-based equilibrium Monte Carlo simulations to assess how Al content and irradiation-induced vacancies affect CrRP formation and atomic-scale structure. CrRP formation peaks at around 12 at.% Al, showing a non-monotonic trend. Higher Al levels cause segregation at CrRP-matrix interfaces and internal Al incorporation, leading to structural disorder and reduced stability. Vacancies alone have limited impact but co-segregate with Al near interfaces, potentially affecting diffusion and interfacial integrity under irradiation. These findings provide atomic-level insights for designing advanced Fe-Cr-Al alloys and guiding mesoscale modeling.
-PuO
-PuO systemVinograd, V. L.*; Vauchy, R.
Journal of Nuclear Materials, 619, p.156244_1 - 156244_16, 2026/01
Thermodynamic properties of (U
Pu
)O
fluorite (FCC) and (UPuz)O
bixbyite (BCC) in the UO-PuO-PuO system are assessed by considering phase equilibrium constraints and data on the variation of oxygen to metal ratio (O/M) as a function of the chemical potential of O. Thermodynamically, both BCC and FCC are described as ordered solid solutions allowing for a decrease in the configurational entropy of their oxygen/vacancy distributions at the specific values of 
= -0.5 and = -0.375 (O/M = 1.5 and O/M = 1.625). With this approach, fluorite/bixbyite equilibria in PuO-PuO and in UO-PuO-PuO are reproduced well with little effort. Moreover, we show that a large manifold of experimental data on the UO-PuO-PuO system is consistent with the assumption that Pu/(Pu+U) ratios in individual phases remain equal to the total Pu/(Pu+U) ratio in the system, i.e., no inter-phase U/Pu-partitioning occurs.
Chong, Y.*; Tsuru, Tomohito; Gholizadeh, R.*; Minor, A. M.*; Tsuji, Nobuhiro*
Acta Materialia, 301, p.121523_1 - 121523_12, 2025/12
Twinning is essential for achieving large ductility in hexagonal close-packed (HCP) titanium alloys that inherently lack independent slip systems due to an asymmetrical HCP crystal structure. Unfortunately, twinning is in principle suppressed by a trace amount of interstitial oxygen, resulting in a substantially deteriorated ductility in titanium. However, the underlying mechanism remains in dispute so far. Here, we report a systematic multiscale study on the twinning/detwinning behaviors of Ti-O alloys that provides a clear mechanistic view of how interstitial oxygen inhibits twinning. We reveal for the first time that oxygen atoms segregate to both {10
2}
2} compression twin boundaries using atom probe tomography. Combined with theoretical simulations that unravel a strong pinning effect of oxygen atoms on twin boundary due to an oxygen shuffling mechanism, we explain the distinctive migration abilities of twin boundaries in Ti-O alloys at different temperatures. The insights from our experimental and computational work provide a rationale for the design of titanium alloys with increased tolerance to variations in interstitial impurity content, with significant implications for more widespread use of this high strength, light weight material.
Battulga, B.*; Nakanishi, Takahiro; Ikenoue, Tsubasa; Atarashi-Andoh, Mariko; Koarashi, Jun
Journal of Hazardous Materials, 500, p.140593_1 - 140593_11, 2025/12
Odaira, Naoya*; Kodama, Katsuaki; Ito, Daisuke*; Saito, Yasushi*; Parker, J. D.*; Shinohara, Takenao
Nuclear Materials and Energy (Internet), 45, p.102005_1 - 102005_7, 2025/12
Hirota, Noriaki; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*
Nuclear Materials and Energy (Internet), 45, p.102009_1 - 402009_10, 2025/12
Using SUS304L stainless steel, which is employed in reactor structural components, the effects of grain refinement on stress corrosion cracking occurring under nuclear reactor operating conditions were investigated. As a result, after conducting slow strain rate testing (SSRT) in air and nuclear reactor operating environments, a comparison of the tensile properties of SUS304L with the same grain size revealed that elongation significantly decreased with increasing grain size under nuclear reactor operating conditions. In SSRT conducted in air, the 
-value obtained from the Hall-Petch relationship was lower than the conventional values. Observations showed the absence of cracks on SUS304L with 0.59 and 1.52 
m grains; however, SUS304L with larger grains exhibited rougher fracture surfaces and side cracks. Thin oxide films were formed on SUS304L with 0.59 m and 1.52 m grains, while SUS304L with coarse grains of 28.4 m or larger enabled the formation of oxide films with over 2 m thickness. CrO
films were formed on SUS304L with 0.59 m, 1.52 m, and 28.4 m, while CrO and Fe based oxides were formed on SUS304L with 39.5 m and 68.6 m. Crystal orientation analysis revealed linear surface layers without cracks in the 
-phase for SUS304L with 0.59 m and 1.52 m. In materials with Larger grain sizes, surface irregularities and cracks were observed in the -phase. In fine-grained SUS304L, lattice diffusion caused uniform O diffusion in the -phase, resulting in the formation of a thin CrO layer that suppressed cracks. In coarse-grained SUS304L, grain boundary diffusion caused Fe oxide formation at the grain boundaries, weakening them, and supersaturated O led to the formation of thick films comprising CrO and Fe-based oxides, resulting in peeling and cracking.
Chaerun, R. I.; Sato, Junya; Hiraki, Yoshihisa; Yoshida, Yukihiko; Sato, Tsutomu*; Osugi, Takeshi
Construction and Building Materials, 500, p.144270_1 - 144270_10, 2025/11
Alkali-activated materials (AAMs), particularly those derived from metakaolin, have gained significant attention as sustainable binders for hazardous waste immobilisation, owing to their dense microstructure and chemical durability. Their amorphous aluminosilicate framework enables effective encapsulation of hazardous materials and reduces environmental risks. However, maintaining the stability of this amorphous network is challenging, particularly when sodium (Na
)-rich precursors are used, as excess Na) promotes crystallisation and compromises matrix integrity. This study systematically investigates the influence of Na) concentration on the structural stability of metakaolin-based AAMs activated primarily with potassium (K)). The objective is to identify the threshold Na incorporation level that preserves the amorphous structure and maintains chemical stability. Transmission electron microscopy (TEM), Raman spectroscopy, and thermodynamic modelling were employed to examine the structural evolution of K-AAMs across a range of Na:K molar ratios. The results reveal that higher Na:K ratios induce nanopore formation and early crystallisation of Na-rich zeolitic phases, which can reduce matrix stability. In contrast, an optimal Na:K ratio was identified that maintains the amorphous network and preserves the aluminosilicate framework. These findings provide valuable insights into optimising K-AAMs for advanced, durable waste encapsulation technologies.
Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro
Scripta Materialia, 268, p.116887_1 - 116887_6, 2025/11
Times Cited Count：0 Percentile：0.00Yuhara, Junji*; Maeda, Shota*; Katsube, Daiki*; Suzuki, Seiya; Terasawa, Tomoo; Takakura, Shoichi*; Nakatake, Masashi*; Le Lay, G.*
2D Materials (Internet), 12(4), p.045023_1 - 045023_10, 2025/10
Suzuki, Kazuya; Kubota, Takahide*; Takanashi, Koki
APL Materials (Internet), 13(10), p.101108_1 - 101108_6, 2025/10
The structural, magnetic, and magneto-transport properties of ferromagnetic FeCoNiCuPd high-entropy alloy (HEA) thin films were investigated to assess the role of the heavy element Pd in magneto-transport. The FeCoNiCuPd films with varying composition ratios of Cu and Pd were fabricated by a co-sputtering process at ambient temperature, and the resulting films exhibited a face-centered cubic structure with a homogenous single phase. All the films exhibited ferromagnetic hysteresis curves with soft magnetic behavior at room temperature. The dependence of the anisotropic magnetoresistance effect and anomalous Hall effect on Pd suggests that heavy metals with large spin-orbit interactions play an important role in the magneto-transport of magnetic HEAs. This finding will facilitate the understanding of the magneto-transport phenomenon in magnetic HEAs for future spintronic materials.
Vauchy, R.; Horii, Yuta; Hirooka, Shun; Akashi, Masatoshi; Sunaoshi, Takeo*; Nakamichi, Shinya; Saito, Kosuke
Journal of Nuclear Materials, 616, p.156115_1 - 156115_16, 2025/10
Jeong, S. G.*; Kwon, J.*; Kim, E. S.*; Prasad, K.*; Harjo, S.; Gong, W.; Kawasaki, Takuro; Estrin, Y.*; Bouaziz, O.*; Hong, S. I.*; et al.
Materials Science & Engineering A, 942, p.148712_1 - 148712_11, 2025/10
Okumura, Masahiko
Journal of Electronic Materials, 54(9), p.7015 - 7026, 2025/09
The machine learning molecular dynamics (MLMD) method enables simulations with high prediction accuracy at low computational cost by learning the results of first-principles calculations (quantum mechanical calculations) using artificial neural networks. This presentation will show how machine-learning molecular dynamics can simulate materials with complex structures. Our MLMD simulations succeeded in reproducing the experimental results of the phonon spectrum of the hydroxy groups of a clay mineral (kaolinite), the superionic transition of thorium dioxide, and the medium-range ordered structure of silica glass, which are difficult to accurately evaluate using other simulation methods, such as classical molecular dynamics.
Takahashi, Yoshio*; Miura, Hikaru*; Yamada, Shinya*; Sekizawa, Oki*; Nitta, Kiyofumi*; Hashimoto, Tadashi*; Yomogida, Takumi; Yamaguchi, Akiko; Okada, Shinji*; Itai, Takaaki*; et al.
Journal of Hazardous Materials, 495, p.139031_1 - 139031_19, 2025/09
In this presentation, we analyzed the chemical state of cesium in radiocesium-bearing microparticles (CsMPs) released during the 2011 Fukushima Daiichi Nuclear Power Plant accident using high-resolution X-ray absorption spectroscopy (XANES) and micro X-ray fluorescence (-XRF). The results identified two forms of cesium: one dissolved in glass and the other enriched on the surfaces of internal voids. The latter is considered to have originally existed as a gas and became concentrated during the cooling and solidification of the molten glass. These findings are crucial for understanding the formation process of CsMPs during the accident, as well as for future decommissioning and safety assessments.
Mn
N and Fe
Co
N filmsYin, W.*; Ito, Keita*; Tsubowa, Yusuke*; Tsujikawa, Masahito*; Shirai, Masafumi*; Umetsu, Rie*; Takanashi, Koki
Journal of Magnetism and Magnetic Materials, 628, p.173157_1 - 173157_8, 2025/09
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Tanaka, Nobuyuki; Sawada, Shinichi*; Koshikawa, Hiroshi*; Yamaki, Tetsuya*
Material Stage, 25(6), p.76 - 80, 2025/09
A thermochemical water-splitting iodine-sulfur process enables us to provide the Carbon-free hydrogen (H) at high-efficiency levels, and it uses high-temperature heat sources, including high-temperature gas-cooled reactors, solar heat, and more. The cation exchange membranes (CEMs) for the HI mediated electro-electrodialysis (EED) were developed using a radiation grafted polymerization method in order to improve the process efficiency of the IS process. High proton (H) conductivity and selectivity are required for the performance of CEMs to reduce the consumption energy for EED. The H conductivity of the radiation grafted CEMs were successfully improved by controlling the grafting amount, comparing with that of Nafion. Moreover, the H selectivity and water transport of the developed CEMs was improved by introducing the crosslinker. Currently, the further improvement of the membrane performance is underway by using the ion-track grafting technic.
Cao, T.*; Wei, D.*; Gong, W.; Kawasaki, Takuro; Harjo, S.; 10 of others*
Materials Science and Engineering A, 940, p.148534_1 - 148534_16, 2025/09
Times Cited Count：0 Percentile：0.00
neutron diffraction studyYamashita, Takayuki*; Koga, Norimitsu*; Mao, W.*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Fujii, Hidetoshi*; Umezawa, Osamu*
Materials Science and Engineering A, 941, p.148602_1 - 148602_11, 2025/09
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Karimi, V.*; Qvistgaard, C. H.*; Schmidt, S.*; Wolfertz, A.*; Parker, J. D.*; Kai, Tetsuya; Hayashida, Hirotoshi*; Shinohara, Takenao; Angelis, S. D.*; Tengattini, A.*; et al.
ACS Applied Materials & Interfaces, 17(36), p.50742 - 50752, 2025/08
Times Cited Count：0 Percentile：0.00Kubota, Takahide*; Suzuki, Kazuya; Hirayama, Yoshiyuki*; Takahashi, Shigeki*; Takanashi, Koki
Physical Review Materials (Internet), 9(8), p.084408_1 - 084408_7, 2025/08
