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Gu, G. H.*; Jeong, S. G.*; Heo, Y.-U.*; Harjo, S.; Gong, W.; Cho, J.*; Kim, H. S.*; 他4名*
Journal of Materials Science & Technology, 223, p.308 - 324, 2025/07
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)Face-centered cubic (FCC) equi-atomic multi-principal element alloys (MPEAs) exhibit excellent mechanical properties from cryogenic to room temperatures. At room temperature, deformation is dominated by dislocation slip, while at cryogenic temperatures (CTs), reduced stacking fault energy enhances strain hardening with twinning. This study uses in-situ neutron diffraction to analyze the temperature-dependent deformation behavior of Al
(CoNiV)
, a dual-phase (FCC/BCC) medium-entropy alloy (MEA). At liquid nitrogen temperature (LNT), deformation twinning in the FCC matrix leads to additional strain hardening through the dynamic Hall-Petch effect, giving the appearance of improved strengthening at LNT. In contrast, BCC precipitates show dislocation slip at both 77 K and 298 K, with temperature-dependent lattice friction stress playing a significant role in strengthening. The study enhances understanding of deformation behaviors and provides insights for future alloy design.
浪江 将成; 斉藤 淳一; 岡 涼太郎*; Kim, J.-H.*
Vacuum, 234, p.114038_1 - 114038_9, 2025/04
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)Wettability of titanium (Ti) and surface-modified (Oxidized or Fluorinated) Ti with liquid sodium (Na) were investigated via experiments and theoretical calculations. From the experimental results, a sliding angle of Na droplet on oxidized Ti was smaller than that on untreated Ti, indicating the worsening of wettability by oxidation. In contrast, the sliding angle of Na droplet on fluoridated Ti was larger than that on untreated Ti, indicating an improvement in wettability by fluorination. Additionally, the cluster models for the interface between Na droplets and treated or untreated Ti were constructed for theoretical calculations of electronic states at the interface, covalent and ionic bonds at the interface were evaluated from the calculation results. The sliding angles obtained in the wettability tests and the strength of covalent bonding at the interface showed no correlation, but good correlation was observed between the sliding angles and ionic bonding at the interface. Thus, the wettability of surface-modified Ti with liquid Na can be theoretically understood based on the atomic interactions at the interface.
Chung, J.-H.*; Kwangwoo, S.*; Yokoo, Tetsuya R.; 植田 大地*; 今井 正樹; Kim, H.-S.; Kiem, D. H.; Han, M. J.*; 社本 真一
Scientific Reports (Internet), 15, p.5978_1 - 5978_10, 2025/02
被引用回数：0 パーセンタイル：0.00(Multidisciplinary Sciences)Two dimensional honeycomb ferromagnets host massless Dirac magnons which are a bosonic analogue of Dirac fermions in graphene. The Dirac magnons may become massive and topological when the time-reversal symmetry breaks and an energy gap opens up at the Dirac point, which was experimentally observed in Cr
-based van der Waals magnets. Here, we investigate the spin wave excitations in the 
magnetic oxide FeTiO with Fe
electrons (
). Using inelastic neutron scattering, we observe two magnon bands separated by a 1.2-meV gap at the Dirac points indicating that its Dirac magnons are massive. Using the linear spin-wave and density functional theory calculations, we find that the spin-orbit-coupled antisymmetric Dzyaloshinskii-Moriya exchanges can best account for the observed Dirac gap opening. The associated Berry curvature and Chern number (
) indicate that FeTiO hosts topological spin excitations via time-reversal symmetry breaking of Dirac magnons.
Cho, S. H.*; Cho, S. W.*; Lv, Z.*; 関根 由莉奈; Liu, S.*; Zhou, M.*; Nuxoll, R. F.*; Kanatzidis, E. E.*; Ghaffari, R.*; Kim, D.*; et al.
Lab on a Chip, 9 Pages, 2025/00
被引用回数：0 パーセンタイル：0.00(Biochemical Research Methods)アミノ酸は体内のタンパク質合成と代謝プロセスに不可欠な物質である。本研究では、運動中の汗からのアミノ酸損失について定量的に調べることを目的とした。汗中のアミノ酸含有量をリアルタイムで分析するため、測定のための技術基盤としてウェアラブルなマイクロ流体システムを構築した。定量分析を実現するため、ウェアラブルデバイスに蛍光アッセイを組み込み、さらにスマートフォンベースの画像化技術を統合させたシステムを開発した。
signatures in two-dimensional cone beam interferometrySarenac, D.*; Gorbet, G.*; Clark, C. W.*; Cory, D. G.*; Ekinci, H.*; Henderson, M. E.*; Huber, M. G.*; Hussey, D. S.*; Kapahi, C.*; Kienzle, P. A.*; et al.
Physical Review Research (Internet), 6(3), p.L032054_1 - L032054_8, 2024/09
Neutron interferometry has played a distinctive role in fundamental science and characterization of materials. Moir neutron interferometers are candidate next-generation instruments: they offer microscopy-like magnification of the signal, enabling direct camera recording of interference patterns across the full neutron wavelength spectrum. Here we demonstrate the extension of phase-grating moir interferometry to two-dimensional geometries. Our measurements of phase topologies and gravitationally induced phase shifts are in good agreement with theory.
浪江 将成; 斉藤 淳一; 池田 明日香; 岡 涼太郎*; Kim, J.-H.*
Surfaces (Internet), 7(3), p.550 - 559, 2024/09
The iron (Fe) specimens selected as the substrate metal for this study were surface-treated using fluorine gas, and their wettability with liquid sodium (Na) was evaluated using the sliding angle. Additionally, the surface morphology and binding state were analyzed, and the applicability of wettability control with liquid sodium by fluorination was discussed using the analysis results. Fluorination formed a fluoride layer comprising FeF
and FeF
bonds on the iron surface. The composition of the fluoride layer varied, depending on the treatment conditions. The surface of the specimen that contains a lot of FeF bonds had a small sliding angle for the liquid sodium droplet and was harder to wet than the untreated specimen. In contrast, the surface of the specimen that contains a lot of FeF bonds had a large sliding angle for the liquid sodium droplet and was easier to wet than the untreated specimen. These results indicate that fluorination is an effective surface modification technique that can be applied to control the wettability of iron with liquid sodium.
Nguyen, T.-D.*; Singh, C.*; Kim, Y. S.*; Han, J. H.*; Lee, D.-H.*; Lee, K.*; Harjo, S.; Lee, S. Y.*
Journal of Materials Research and Technology, 31, p.1547 - 1556, 2024/07
被引用回数：3 パーセンタイル：41.92(Materials Science, Multidisciplinary)This study investigates the mechanical properties of a friction-stir-welded (FSW) AA6061-T6 aluminum alloy at ultra-low temperature (ULT) of 20 K. In-situ neutron diffraction and orientation imaging microscopy were employed to compare the tensile deformation behavior of the base metal (BM) and heat-affected zone (HAZ) in the FSW aluminum plate. The results demonstrate that compared to room-temperature (RT), ULT induces a significant improvement in tensile strength and ductility in both the BM and HAZ. The enhanced mechanical properties in BM at ULT result from a more homogeneous deformation than occurs at RT. On the other hand, HAZ at ULT exhibits an even lower yield strength than at RT, but the strain hardening rate (SHR) is the most significant among the alloys, leading to a tensile strength of 346 MPa and the highest ductility of 46.8%. The lowest yield strength corresponds to the lowest-hardness zones in HAZ, caused by dissolved/coarsened precipitates during the FSW process.
Kim, Y. S.*; Chae, H.*; Lee, D.-Y.*; Han, J. H.*; Hong, S.-K.*; Na, Y. S.*; Harjo, S.; 川崎 卓郎; Woo, W.*; Lee, S.-Y.*
Materials Science & Engineering A, 899, p.146453_1 - 146453_7, 2024/05
被引用回数：4 パーセンタイル：63.37(Nanoscience & Nanotechnology)This work focused on the mechanical properties and serration-involved deformation behavior of advanced alloys at 15 K. Evolution of stacking faults and 
-martensite improved the mechanical performance of CoCrNi alloys, and significant strain-induced martensite transformation of DED-SS316L led to superior strength and strain hardening. A magnitude in stress drop was governed by dislocation density, phase type, and lattice defects, irrespective of processing method. FCC {200} notably was influenced recovery behavior after stress drop, and the contribution of strain energy density by serration on tensile toughness was the greatest for HR-CoCrNi.
Linh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Duguet, T.*; G
mez-Ramos, M.*; Holt, J. D.*; Hu, B. S.*; et al.
Physical Review C, 109(3), p.034312_1 - 034312_15, 2024/03
被引用回数：2 パーセンタイル：58.81(Physics, Nuclear)理化学研究所RIビームファクトリーにて中性子過剰核
Arビームからの1中性子ノックアウト反応実験を行い、
Arのエネルギー準位および分光学的因子を導出した。特に、第一励起状態の
への分光学的因子が大きいことから、始状態のArの基底状態において中性子が
軌道を多く占めていることがわかった。これは、中性子数32がよい魔法数として知られる
Caとは異なった性質であり、カルシウムからアルゴンへと陽子が2個減ることで閉殻構造が大きく崩れることが明らかになった。
TaSPark, P.*; Cho, W.*; Kim, C.*; An, Y.*; Kang, Y.-G.*; Avdeev, M.*; Sibille, R.*; 飯田 一樹*; 梶本 亮一; Lee, K. H.*; et al.
Nature Communications (Internet), 14, p.8346_1 - 8346_9, 2023/12
被引用回数：21 パーセンタイル：84.93(Multidisciplinary Sciences)The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120
structure. However, a new triple-
chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF CoTaS as the first example of tetrahedral triple- magnetic ordering with the associated topological Hall effect (non-zero 
). We also present a theoretical framework that describes the emergence of this magnetic ground state, which is further supported by the electronic structure measured by angle-resolved photoemission spectroscopy. Additionally, our measurements of the inelastic neutron scattering cross section are consistent with the calculated dynamical structure factor of the tetrahedral triple- state.
Yang, D. S.*; Wu, Y.*; Kanatzidis, E. E.*; Avila, R.*; Zhou, M.*; Bai, Y.*; Chen, S.*; 関根 由莉奈; Kim, J.*; Deng, Y.*; et al.
Materials Horizons, 10(11), p.4992 - 5003, 2023/09
被引用回数：12 パーセンタイル：79.80(Chemistry, Multidisciplinary)本論文では、ハード及びソフトハイブリッド材料システムでの3Dプリントによって形成されたマイクロ流体ネットワーク、統合バルブ、およびマイクロスケール光学キュベットにより、汗成分に対してその場で分光および蛍光分析した成果を紹介する。一連の試験により、これらのマイクロキュベットシステムが汗中の銅、塩化物、グルコースの濃度と汗のpHを実験室レベルの精度と感度で評価できることが実証された。
O近藤 洋介*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; 馬場 秀忠*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
被引用回数：27 パーセンタイル：94.86(Multidisciplinary Sciences)非常に中性子が過剰な原子核Oは、陽子、中性子ともに魔法数であることから古くからその性質に興味が持たれていたが、酸素の最後の束縛核
Oよりも中性子が4個も多いため、これまで観測されてこなかった。この論文では、理化学研究所RIBFにて
Fからの1陽子ノックアウト反応によってOを生成し、そこから放出される中性子を測定することによって初めてその観測に成功した。核構造の観点からは、Oでは二重閉殻が保たれているか興味が持たれていたが、実験で得られた分光学的因子が殻模型計算で予言されて程度の大きいことから、閉殻構造をもたない可能性が高いことがわかった。
Ca cast doubt on a doubly magic 
CaChen, S.*; Browne, F.*; Doornenbal, P.*; Lee, J.*; Obertelli, A.*; 角田 佑介*; 大塚 孝治*; 茶園 亮樹*; Hagen, G.*; Holt, J. D.*; et al.
Physics Letters B, 843, p.138025_1 - 138025_7, 2023/08
被引用回数：9 パーセンタイル：85.35(Astronomy & Astrophysics)
Scからの1陽子ノックアウト反応を用いて、
Caと
Caのガンマ崩壊を観測した。Caでは1456(12)keVの
線遷移が、Caでは1115(34)keVの遷移が観測された。どちらの遷移も暫定的に
と割り当てられた。有効核子間相互作用をわずかに修正した広い模型空間での殻模型計算では、
準位エネルギー、2中性子分離エネルギー、反応断面積が実験とよく一致し、N=34閉殻の上に新しい殻が形成されていることを裏付けた。その構成要素である
と
軌道はほぼ縮退しており、これはCaが二重魔法核である可能性を排除し、Ca同位体のドリップラインを
Caあるいはそれ以上にまで広げる可能性がある。
Ne at the transition into the island of inversion; Detailed structure study of NeWang, H.*; 安田 昌弘*; 近藤 洋介*; 中村 隆司*; Tostevin, J. A.*; 緒方 一介*; 大塚 孝治*; Poves, A.*; 清水 則孝*; 吉田 数貴; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
被引用回数：4 パーセンタイル：69.46(Astronomy & Astrophysics)Neからの1中性子除去反応を用いて、Neの詳細な線分光を行った。平行運動量分布の解析に基づき、Neの準位構造とスピンパリティを決定し、初めて負のパリティ状態を同定した。測定された断面積と運動量分布から、N=20とN=28のシェルギャップの消失の証拠となる有意なintruder p-wave強度が明らかになった。束縛状態については、弱いf-waveの可能性のある強度が観測された。いくつかの有効相互作用を用いた大規模殻模型計算では、実験的に観測された大きなp-wave強度と小さなf-wave強度は再現されず、Ne同位体に沿った反転の島への遷移の完全な理論的記述への挑戦が続いていることを示している。
Mun, M.-H.*; Shin, I. J.*; Paeng, W.-G.*; 原田 正康*; Kim, Y.*
European Physical Journal A, 59(7), p.149_1 - 149_6, 2023/07
被引用回数：4 パーセンタイル：60.26(Physics, Nuclear)Using an extended parity doublet model with the hidden local symmetry, we study some properties of nuclei in the mean field approximation to see if the parity doublet model could reproduce nuclear properties and also to estimate the value of the chiral invariant nucleon mass 
preferred by nuclear structure. We first determine our model parameters using the inputs from free space and from nuclear matter properties. Then, we study some basic nuclear properties such as the nuclear binding energy with several different choices of the chiral invariant mass. We observe that our results approach the experimental values as is increased until = 700 MeV and start to deviate more from the experiments afterwards with m0 larger than = 700 MeV. From this observation, we conclude that = 700 MeV is preferred by nuclear properties. We then calculate some properties of several selected nuclei with = 700 MeV and compare them with experiments. Finally, we study the neutron-proton mass difference in some nuclei.
Kwon, H.*; Sathiyamoorthi, P.*; Gangaraju, M. K.*; Zargaran, A.*; Wang, J.*; Heo, Y.-U.*; Harjo, S.; Gong, W.; Lee, B.-J.*; Kim, H. S.*
Acta Materialia, 248, p.118810_1 - 118810_12, 2023/04
被引用回数：48 パーセンタイル：99.21(Materials Science, Multidisciplinary)Maraging steels, known for ultrahigh strength and good fracture toughness, derive their superior properties from lath martensite structure with high-density nanoprecipitates. In this work, we designed a novel Fe-based medium-entropy alloy with a chemical composition of Fe
Co
Ni
Mo
in atomic% by utilizing the characteristics of the maraging steels. By a single-step aging of only 10 min at 650 C, the alloy showed microstructures consisting of a very high number density of (Fe, Co, Ni)
Mo
-type nanoprecipitates in lath martensite structure and reverted FCC phase, which led to ultrahigh yield strength higher than 2 GPa. This work demonstrates a novel direction to produce strong and ductile materials by expanding the horizons of material design with the aid of high-entropy concept and overcoming the limits of conventional materials.
100 MeV/nucleonPohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; Gmez-Ramos, M.*; 緒方 一介*; 吉田 数貴; Cai, B. S.*; Yuan, C. X.*; Brown, B. A.*; et al.
Physical Review Letters, 130(17), p.172501_1 - 172501_8, 2023/04
被引用回数：12 パーセンタイル：88.25(Physics, Multidisciplinary)大きなフェルミ面非対称性を持つ陽子過剰な
O原子核からの100MeV/nucleonでの陽子による陽子・中性子除去反応について報告した。この結果は、quasi-freeノックアウト反応、非弾性散乱、核子移行反応を含む複数の反応機構の定量的寄与を初めて示すものである。このようなエネルギー領域では通常無視される非弾性散乱と核子移行の寄与が、弱束縛陽子と強束縛中性子の除去反応断面積にそれぞれ約50%と30%寄与していることが示された。
Woo, W.*; Kim, Y. S.*; Chae, H. B.*; Lee, S. Y.*; Jeong, J. S.*; Lee, C. M.*; Won, J. W.*; Na, Y. S.*; 川崎 卓郎; Harjo, S.; et al.
Acta Materialia, 246, p.118699_1 - 118699_13, 2023/03
被引用回数：47 パーセンタイル：99.25(Materials Science, Multidisciplinary)In situ neutron diffraction experiments have been performed under loading in cast-wrought (CW) and additively manufactured (AM) equiatomic CoCrNi medium-entropy alloys. The diffraction line profile analysis correlated the faulting-embedded crystal structure to the dislocation density, stacking/twin fault probability, and stacking fault energy as a function of strain. The results showed the initial dislocation density of 1.8
10
m
in CW and 1.310 m in AM. It significantly increased up to 1.310
m- in CW and 1.710 m in AM near fracture. The dislocation density contributed to the flow stress of 470 MPa in CW and 600 MPa in AM, respectively. Meanwhile, the twin fault probability of CW (2.7%) was about two times higher than AM (1.3%) and the stacking fault probability showed the similar tendency. The twinning provided strengthening of 360 MPa in CW and 180 MPa in AM. Such a favorable strengthening via deformation twinning in CW and dislocation slip in AM was attributed to the stacking fault energy. It was estimated as 18.6 mJ/m
in CW and 37.5 mJ/m in AM by the strain field of dislocations incorporated model. Dense dislocations, deformation twinning, and atomic-scale stacking structure were examined by using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM).
synchrotron X-ray scattering and nanoindentation testIm, S.*; Jee, H.*; Suh, H.*; 兼松 学*; 諸岡 聡; Choe, H.*; 西尾 悠平*; 町田 晃彦*; Kim, J.*; Lim, S.*; et al.
Construction and Building Materials, 365, p.130034_1 - 130034_18, 2023/02
被引用回数：17 パーセンタイル：77.01(Construction & Building Technology)Nanocrystalline calcium-silicate-hydrate (C-S-H) is a typical heterogeneous material with a multiscale structure spanning a wide length scale from angstrom to micrometer, and whose structure is determined by the Ca/Si ratio. In this study, we directly applied compressive loads on synthetic C-S-H pastes with Ca/Si ratios of 0.6-1.2 and investigated their mechanical properties using the elastic modulus calculated at three length scale levels (i.e., angstrom to nanometer, micrometer, and millimeter) via in-situ synchrotron X-ray scattering, nanoindentation tests, and strain gauges, respectively. Further, Si nuclear magnetic resonance spectroscopy was conducted on the C-S-H pastes to elucidate the alterations in the silicate polymerization. The experimental results confirmed the deformation behavior of the C-S-H paste with different Ca/Si ratios under external loading, which was demonstrated to be transferred from the surface of the pastes to particles owing to the presence of multiscale pores.
Wei, D.*; Gong, W.; 都留 智仁; Lobzenko, I.; Li, X.*; Harjo, S.; 川崎 卓郎; Do, H.-S.*; Bae, J. W.*; Wagner, C.*; et al.
International Journal of Plasticity, 159, p.103443_1 - 103443_18, 2022/12
被引用回数：105 パーセンタイル：99.79(Engineering, Mechanical)Face-centered cubic single-phase high-entropy alloys (HEAs) containing multi-principal transition metals have attracted significant attention, exhibiting an unprecedented combination of strength and ductility owing to their low stacking fault energy (SFE) and large misfit parameter that creates severe local lattice distortion. Increasing both strength and ductility further is challenging. In the present study, we demonstrate via meticulous experiments that the CoCrFeNi HEA with the addition of the substitutional metalloid Si can retain a single-phase FCC structure while its yield strength (up to 65%), ultimate strength (up to 34%), and ductility (up to 15%) are simultaneously increased, owing to a synthetical effect of the enhanced solid solution strengthening and a reduced SFE. The dislocation behaviors and plastic deformation mechanisms were tuned by the addition of Si, which improves the strain hardening and tensile ductility. The present study provides new strategies for enhancing HEA performance by targeted metalloid additions.
