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論文

Structural and thermal confinement of Schwarz crystals

Huang, D.*; Fu, H.*; Lyu, M.*; Feng, Y.*; 梶本 亮一; 中村 充孝; 本田 孝志*; Liu, E.*; Li, B.*; Li, X.*; et al.

Physical Review Research (Internet), 8(3), p.033017_1 - 033017_7, 2026/07

As a nontrivial state of solid, Schwarz crystal manifests itself in extremely refined nanograins and triply periodic minimal surface (TPMS) grain boundaries, and therefore exceptional thermal and mechanical stability. However, it remains unexploited how the structural units interact and thermal transport is influenced by such complex atomic structures. Here, we investigate Schwarz crystals of Cu and Pt using neutron scattering and thermal transport measurements. Pair distribution function analysis reveals the coexistence of compressed grains and expanded TPMS grain-boundary regions, forming a spatially confined atomic environment. This leads to an unusual phonon hardening suggested by inelastic neutron scattering. As bulk materials, Schwarz crystals exhibit a quasilinear temperature dependence of thermal conductivity, which was previously only observed in low-dimensional materials. This contrast indicates that the spatial confinement of the Schwarz crystals plays a crucial role in determining the unique thermal conductivity, which also provides an emergent route to regulate thermal properties in bulk materials.

論文

Assessing and tackling the barocaloric fatigue for applicable solid-state refrigeration

Xue, J.*; Huang, D.*; 服部 高典; Li, L.*; Feng, Y.*; Wang, H.*; Fan, X.*; Yao, J.*; Wang, Y.*; Liu, Z.*; et al.

Applied Physics Letters, 128(20), p.201903_1 - 201903_8, 2026/05

 被引用回数:0 パーセンタイル:0.00(Physics, Applied)

NH$$_4$$Iのサイクル疲労およびバロカロリック応答は、最大100MPaの応力を伴う加圧・減圧サイクル下で直接評価され、100サイクルの後に断熱温度変化($$Delta T_{mathrm{ad}}$$)は15Kから約0.8Kまで減少した。emphその場X線回折、ラマン分光法、および中性子回折を併用した解析により、最初の荷重除去後であっても残留高圧相が存在することが明らかになり、その割合は100サイクル目までに急速に90%まで増加した。この疲労挙動を解明するために現象論的モデルが構築され、実験データとの良好な一致が得られた。粒界応力を緩和し、結晶粒の移動性を高めるため、NH$$_4$$I粒子とシリコーンオイルからなる複合体を、3Dプリントされたポリマーシェルに封入した。このような構造設計により、バロカロリック効果のサイクル安定性が著しく向上し、100サイクル後でも$$Delta T_{mathrm{ad}}$$は約4.6Kまで上昇した。我々の結果は、気圧熱効果の疲労挙動に関する基礎的な理解を確立するとともに、実用的な気圧熱冷却技術への実現可能な道筋を示すものである。

論文

Spin excitation continuum from degenerate states in the mixed ferro-antiferromagnetic exchange system CeMgAl$$_{11}$$O$$_{19}$$

Gao, B.*; Chen, T.*; Liu, C.*; Klemm, M. L.*; Zhang, S.*; Ma, Z.*; Xu, X.*; Won, C.*; McCandless, G. T.*; Rao, K.*; et al.

Science Advances (Internet), 12(10), p.eaed7778_1 - eaed7778_7, 2026/03

 被引用回数:2 パーセンタイル:76.89(Multidisciplinary Sciences)

In the search for unconventional magnetism, exotic quantum states are characterized by a lack of order and a broad spin excitation continuum approaching zero temperature. We study the two-dimensional triangular-lattice effective spin-system CeMgAl$$_{11}$$O$$_{19}$$, which shows slight disorder but no magnetic ordering down to 100 millikelvin. Spin-wave analysis in the magnetic-field-polarized state determines the spin Hamiltonian featuring a mixed ferromagnetic-antiferromagnetic nearest-neighbor exchange interaction. This places the system near an exactly solvable point of the spin-triangular-lattice XXZ model with extensive ground-state degeneracy. In zero field, neutron spectroscopy reveals a prominent continuum; we show that this arises from an ensemble average of spin-wave spectra across the degenerate ground-state manifold. This demonstrates that the role of weak quenched disorder can be quantitatively constrained: It inhibits unique ground-state selection and stabilizes a local distribution within the degenerate manifold, yielding continuum-like spectra that necessitate a critical reevaluation of the experimental signatures of exotic quantum states.

論文

Microscopic insights into the mechanical behavior of a Ni-Co-based superalloy through ${it in-situ}$ neutron diffraction

Liu, Y.*; Yan, Z.*; Gao, Y.*; Li, Y.*; Gan, B.*; Harjo, S.; Gong, W.; 川崎 卓郎; Li, S.*; Wang, Y.-D.*

Microstructures (Internet), 5(4), p.2025096_1 - 2025096_15, 2025/10

The micromechanical behaviors and dislocation evolution in a polycrystalline Ni-Co-based superalloy were systematically investigated by ${it in situ}$ neutron diffraction tensile testing combined with line profile analysis. The results reveal the sequential activation of $$gamma$$' shearing and Orowan looping mechanisms, with interphase load partitioning governed by strain-dependent interactions of dislocation and precipitate. During the initial plastic deformation, the $$gamma$$ and $$gamma$$' phases undergo co-deformation through dislocation shearing without load transfer, while the Orowan looping facilitates the load transfer from $$gamma$$ to $$gamma$$' phase at a higher strain level. Furthermore, the low stacking fault energy leads to a rising fraction of screw dislocations by suppressing cross-slip. Crucially, the pinning effect of $$gamma$$' precipitates hinders the rearrangement of these dislocations into low-energy structures, resulting in the formation of high-energy, weakly screened dislocation configurations. These findings provide new evidence for the planar slip dominance in Ni-Co-based superalloys, enabling quantitative assessment of microstructural evolution and micromechanical responses.

論文

All-temperature barocaloric effects at pressure-induced phase transitions

Zhao, X.*; Zhang, Z.*; 服部 高典; Wang, J.*; Li, L.*; Jia, Y.*; Li, W.*; Xue, J.*; Fan, X.*; Song, R.*; et al.

Nature Communications (Internet), 16, p.7713_1 - 7713_8, 2025/08

 被引用回数:10 パーセンタイル:85.19(Multidisciplinary Sciences)

熱効果は、固体状態の冷凍技術の一つの解決策の基盤を成すもので、通常は固体状態の相転移付近で発生し、冷凍温度範囲が限定されている。ここでは、前例のない概念である「全温度帯バロカロリック効果」を導入し実現する。すなわち、KPF$$_6$$において77.5Kから300Kの極めて広い温度範囲(潜在的に4Kまで)で観測される顕著なバカカロリック効果である。この温度範囲は、一般的な室温、液体窒素、液体水素、液体ヘリウムの冷却領域をカバーしている。直接測定されたバーカロリック断熱温度変化は、250MPaの圧力を解放した際に、室温で12K、77.5Kで2.5Kに達する。この効果は、圧力依存性の中性子粉末回折、ラマン散乱解析、第一原理計算により示されるように、菱面体高圧相への持続的な相転移に起因する。構造的不安定性を考慮した熱力学的エネルギーランドスケープを記述する。この独自の全温度帯バロカロリック効果は、従来の多段式シナリオを超えた、高度に適用可能な固体状態冷凍技術への新たなアプローチを提供する。

論文

Complementary layer thickness effects of Q235 and SUS304 layers of multilayered steels for improving of tensile strength and plasticity simultaneously

Lin, Z. M.*; Liu, B. X.*; Ming, K. S.*; 徐 平光; Yin, F. X.*; Zheng, S. J.*

Scripta Materialia, 263, p.116692_1 - 116692_7, 2025/07

 被引用回数:3 パーセンタイル:56.20(Nanoscience & Nanotechnology)

Complementary layer thickness effects on strength and plasticity in Q235 and SUS304 steels provide a novel strategy to realize high strength and high plasticity of heterogeneous Q235/SUS304 multilayered steel. In this work, the tensile deformation behaviors and fracture characteristics of vacuum hot-rolled Q235/SUS304 multilayered steel with various layer thicknesses ranging from 223 $$mu$$m to 5 $$mu$$m were deeply investigated. The tensile strength improved with the reduction of layer thickness, and the uniform elongation were first increasing and then decreasing with the decrease of layer thickness, and the peak value appeared at the layer thickness of 20 $$mu$$m. Interestingly, the fracture elongation forms a high plateau value within the 10$$sim$$20 $$mu$$m range. Further analysis reveals that the severe strain localization in the brittle SUS304 thin layers is delayed by the ductile Q235 layers, which is mainly attributed to the different texture evolution and dislocation configuration characteristics during tensile deformation.

論文

Spin correlations in the nematic quantum disordered state of FeSe

Liu, R.*; Stone, M. B.*; Gao, S.*; 中村 充孝; 蒲沢 和也*; Krajewska, A.*; Walker, H. C.*; Cheng, P.*; Yu, R.*; Si, Q.*; et al.

Nature Communications (Internet), 16, p.5212_1 - 5212_8, 2025/06

 被引用回数:7 パーセンタイル:81.75(Multidisciplinary Sciences)

The quantum-disordered state in FeSe, intertwined with superconductivity and nematicity, has been a research focus in iron-based superconductors. Temperature-dependent differences between Q= (1, 0) and (0, 1) spin excitations above the structural transition unambiguously reveals the nematic quantum disordered state. Comparison with NaFeAs suggests the Neel excitations originate from enhanced 3dxy orbital correlations. Modeling the stripe dispersions using a J1-K-J2 Heisenberg Hamiltonian, we establish a spininteraction phase diagram, positioning FeSe near a crossover regime between the antiferroquadrupolar, Neel, and stripe orders. Our results provide key insights into themicroscopic spin interactions and their role in the intertwined orders in iron-based superconductors.

論文

Strong low-energy rattling modes enabled liquid-like ultralow thermal conductivity in a well-ordered solid

Liu, P.-F.*; Li, X.*; Li, J.*; Zhu, J.*; Tong, Z.*; 古府 麻衣子*; 楡井 真実; Xu, J.*; Yin, W.*; Wang, F.*; et al.

National Science Review, 11(12), p.nwae216_1 - nwae216_10, 2024/12

 被引用回数:31 パーセンタイル:91.47(Multidisciplinary Sciences)

Crystalline solids exhibiting inherently low lattice thermal conductivity ($$kappa_{rm L}$$) are of great importance in applications such as thermoelectrics and thermal barrier coatings. However, $$kappa_{rm L}$$ cannot be arbitrarily low and is limited by the minimum thermal conductivity related to phonon dispersions. In this work, we report the liquid-like thermal transport in a well-ordered crystalline CsAg$$_5$$Te$$_3$$, which exhibits an extremely low $$kappa_{rm L}$$ value of $$sim$$ 0.18 Wm$$^{-1}$$K$$^{-1}$$. On the basis of first-principles calculations and inelastic neutron scattering measurements, we find that there are lots of low-lying optical phonon modes at $$sim$$ 3.1 meV hosting the avoided-crossing behavior with acoustic phonons. These strongly localized modes are accompanied by weakly bound rattling Ag atoms with thermally induced large amplitudes of vibrations. Using the two-channel model, we demonstrate that coupling of the particle-like phonon modes and the heat-carrying wave-like phonons is essential for understanding the low $$kappa_{rm L}$$, which is heavily deviated from the $$1/T$$ temperature dependence of the standard Peierls theory. In addition, our analysis indicates that the soft structural framework with liquid-like motions of the fluctuating Ag atoms is the underlying cause that leads to the suppression of the heat conduction in CsAg$$_5$$Te$$_3$$. These factors synergistically account for the ultralow $$kappa_{rm L}$$ value. Our results demonstrate that the liquid-like heat transfer could indeed exist in a well-ordered crystal.

論文

Enhancing mechanical properties of medium Mn steel by warm rolling based on laminated elemental segregation

Chen, H. F.*; Liu, B. X.*; 徐 平光; Fang, W.*; Tong, H. C.*; Yin, F. X.*

Journal of Materials Research and Technology, 32, p.3060 - 3069, 2024/09

 被引用回数:9 パーセンタイル:66.69(Materials Science, Multidisciplinary)

The hot-rolled microstructure of medium Mn steel has coarse grains and severe elemental segregation, resulting in low strength and plasticity. Constructing a multiphase structure, refining the microstructure, and regulating elemental segregation enhance the mechanical properties. In this study, liquid nitrogen treatment created a layered distribution of austenite and martensite. Warm rolling was then used to reduce layer thickness and refine grain structure. After liquid nitrogen and warm rolling treatments, the strength and plasticity of medium Mn steel increased to 1270 MPa and 23.3%, respectively, far exceeding the hot-rolled state (724 MPa, 12.8%). Warm rolling also triggers austenite reverted transformation (ART) and introduces high-density dislocations, further improving austenite stability. This strengthening effect is higher than that from intercritical annealing alone. Improved austenite stability delays the transformation induced plasticity (TRIP) effect, preventing brittle fracture and enhancing deformation coordination between layers, significantly increasing the plastic deformation capacity of medium Mn steel.

論文

Brightening triplet excitons enable high-performance white-light emission in organic small molecules via integrating n-$$pi^*/pi$$-$$pi^*$$ transitions

Yang, Q.*; Yang, X.*; Wang, Y.*; Fei, Y.*; Li, F.*; Zheng, H.*; Li, K.*; Han, Y.*; 服部 高典; Zhu, P.*; et al.

Nature Communications (Internet), 15, p.7778_1 - 7778_9, 2024/09

 被引用回数:47 パーセンタイル:94.53(Multidisciplinary Sciences)

明るい一重項励起子と三重項励起子を同時に発現する発光材料は、オプトエレクトロニクス、サイネージ、情報暗号化において大きな可能性を秘めている。しかしながら、高性能の白色発光を実現するためには、蛍光と燐光の寄与が不均衡であることが大きな障害となっている。ここでは、水素結合の協同効果による圧力処理エンジニアリングによって、n-$$pi^*/pi$$-$$pi^*$$遷移の混合を実現し、イソフタル酸(IPA)中で三重項状態の発光を7%から40%に高めることで、この課題に対処した。加圧処理したIPAでは、蛍光と燐光のハイブリッドに基づく優れた白色発光が得られ、フォトルミネッセンス量子収率は当初の19%(青色発光)から75%に増加した。その場での高圧IRスペクトル、X線回折、中性子回折から、圧力の上昇に伴い水素結合が連続的に強化されることが明らかになった。さらに、この強化された水素結合は、圧力処理後も常圧条件下まで保持され、バランスの取れた一重項/三重項励起子集団のための効率的な系間交差を目的としたIPAに与え、効率的な白色発光をもたらした。この研究は、有機低分子の三重項状態を明るくするルートを提案するだけでなく、一重項励起子と三重項励起子の比率を調節して、高性能の白色発光を構築するものである。

論文

Antiferromagnetism and phase stability of CrMnFeCoNi high-entropy alloy

Zhu, L.*; He, H.*; Naeem, M.*; Sun, X.*; Qi, J.*; Liu, P.*; Harjo, S.; 中島 健次; Li, B.*; Wang, X.-L.*

Physical Review Letters, 133(12), p.126701_1 - 126701_6, 2024/09

 被引用回数:12 パーセンタイル:84.34(Physics, Multidisciplinary)

It has long been suspected that magnetism could play a vital role in the phase stability of multi- component high-entropy alloys. However, the nature of the magnetic order, if any, has remained elusive. Here, by using elastic and inelastic neutron scattering, we demonstrate evidence of antiferromagnetic order below $$sim$$80 K and strong spin fluctuations persisting to room temperature in a single-phase face-centered cubic (fcc) CrMnFeCoNi high-entropy alloy. Despite the chemical complexity, the magnetic structure in CrMnFeCoNi can be described as $$gamma$$-Mn-like, with the magnetic moments confined in alternating (001) planes and pointing toward the $$langle$$111$$rangle$$ direction. Combined with first-principles calculation results, it is shown that the antiferromagnetic order and spin fluctuations help stabilized the fcc phase in CrMnFeCoNi high-entropy alloy.

論文

Influence of interstitial carbon on bulk texture evolution of carbide-free high-entropy alloys during cold rolling using neutron diffraction

Fang, W.*; Liu, C.*; Zhang, J.*; 徐 平光; Peng, T.*; Liu, B.*; 諸岡 聡; Yin, F.*

Scripta Materialia, 249, p.116046_1 - 116046_6, 2024/08

 被引用回数:5 パーセンタイル:44.40(Nanoscience & Nanotechnology)

The influence of interstitial carbon on the texture evolution of high-entropy alloys during cold rolling was investigated. To prevent carbide formation, elements with weak carbon affinity were carefully selected in the (FeMnCoNi)$$_{96.5}$$C$$_{3.5}$$ alloy. Neutron diffraction, electron channeling contrast imaging, and electron backscatter diffraction were used to analyze the texture and microstructure evolution in alloys with and without carbon addition. Though their texture components are similar at the early stage of deformation, the Brass and Goss textures in the carbon-containing alloy at 50% cold rolling reduction are obviously higher than those in the carbon-free alloy, while Copper and S textures are lower. A large number of deformation twins induced in the carbon containing alloy is attributed as the significant reason for the texture differences. This work helps to understand the impact of interstitial carbon on the texture evolution of high-entropy alloys, providing valuable insights for microstructure and performance optimization.

論文

A Systematic approach for the adequacy analysis of a set of experimental databases; Application in the framework of the ATRIUM activity

Baccou, J.*; Glantz, T.*; Ghione, A.*; Sargentini, L.*; Fillion, P.*; Damblin, G.*; Sueur, R.*; Iooss, B.*; Fang, J.*; Liu, J.*; et al.

Nuclear Engineering and Design, 421, p.113035_1 - 113035_16, 2024/05

 被引用回数:12 パーセンタイル:92.28(Nuclear Science & Technology)

In the Best-Estimate Plus Uncertainty (BEPU) framework, the use of best-estimate code requires to go through a Verification, Validation and Uncertainty Quantification process (VVUQ). The relevance of the experimental data in relation to the physical phenomena of interest in the VVUQ process is crucial. Adequacy analysis of selected experimental databases addresses this problem. The outcomes of the analysis can be used to select a subset of relevant experimental data, to encourage designing new experiments or to drop some experiments from a database because of their substantial lack of adequacy. The development of a specific transparent and reproducible approach to analyze the relevance of experimental data for VVUQ still remains open and is the topic of this contribution. In this paper, the concept of adequacy initially introduced in the OECD/NEA SAPIUM (Systematic APproach for model Input Uncertainty quantification Methodology) activity is formalized. It is defined through two key properties, called representativeness and completeness, that allows considering the multifactorial dimension of the adequacy problem. A new systematic approach is then proposed to analyze the adequacy of a set of experimental databases. It relies on the introduction of two sets of criteria to characterize representativeness and completeness and on the use of multi-criteria decision analysis method to perform the analysis. Finally, the approach is applied in the framework of the new OECD/NEA ATRIUM activity which includes a set of practical IUQ exercises in thermal-hydraulics to test the SAPIUM guideline in determining input uncertainties and forward propagating them on an application case. It allows evaluating the adequacy of eight experimental databases coming from the Super Moby-dick, Sozzi-Sutherland and Marviken experiments and identifying the most adequate ones.

論文

Phase transformation and equation of state in Ti-45Al alloy under high pressure

Li, X.*; Zhu, R.*; Xin, J.*; Luo, M.*; Shang, S.-L.*; Liu, Z.-K.*; Yin, C.*; 舟越 賢一*; Dippenaar, R. J.*; 肥後 祐司*; et al.

CALPHAD; Computer Coupling of Phase Diagrams and Thermochemistry, 84, p.102641_1 - 102641_6, 2024/03

 被引用回数:0 パーセンタイル:0.00(Thermodynamics)

The phase transformations and pressure-volume dependencies of the Ti-45Al alloy with respect to pressure have been investigated by means of in-situ observation using multi anvil-type high-pressure devices and synchrotron radiation. Under hydrostatic compression from 0 to 10.1 GPa, about 2.3 vol. % of $$gamma$$ transforms continuously to $$alpha$$2. Lattice parameters as well as volume fractions of these two phases have been determined as a function of pressure. Bulk moduli estimated using Birch-Murnaghan's equation of state are 148 GPa for the $$gamma$$ phase, 138 GPa for the $$alpha$$2 phase, and 149 GPa for their two-phase mixture of Ti-45Al alloy. First-principles have also applied to investigate bulk moduli of two single phases, and the deviation between calculations and measurements is discussed and attributed to mainly phase transformation. The presently study provides useful insights into thermodynamics of $$alpha$$2 and $$gamma$$ phases under high pressure.

論文

Onset of collectivity for argon isotopes close to $$N=32$$

Linh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Duguet, T.*; G$'o$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:6 パーセンタイル:76.58(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$$^{50}$$Arビームからの1中性子ノックアウト反応実験を行い、$$^{49}$$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$$1/2^-$$への分光学的因子が大きいことから、始状態の$$^{50}$$Arの基底状態において中性子が$$p_{1/2}$$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$$^{52}$$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。

論文

Atomic structure and dynamics of organic-inorganic hybrid perovskite formamidinium lead iodide

Yu, C.*; 川北 至信; 菊地 龍弥*; 古府 麻衣子*; 本田 孝志*; Zhang, Z.*; Zhang, Z.*; Liu, Y.*; Liu, S. F.*; Li, B.*

Journal of Physical Chemistry Letters (Internet), 15(1), p.329 - 338, 2024/01

 被引用回数:2 パーセンタイル:22.06(Chemistry, Physical)

The atomic dynamic behaviors of formamidinium lead iodide [HC(NH$$_{2}$$)$$_{2}$$PbI$$_{3}$$] are critical for understanding and improving photovoltaic performances. However, they remain unclear. Here, we investigate the structural phase transitions and the reorientation dynamics of the formamidinium cation [HC(NH$$_{2}$$)$$_{2}^{+}$$, FA$$^{+}$$] of FAPbI$$_{3}$$ using neutron scattering techniques. Two structural phase transitions occur with decreasing temperature, from cubic to tetragonal phase at 285 K and then to another tetragonal at 140 K, accompanied by gradually frozen reorientation of FA cations. The nearly isotropic reorientation in the cubic phase is suppressed to reorientation motions involving a two-fold (C$$_{2}$$) rotation along the $${N cdots N}$$ axis and a four-fold (C$$_{4}$$) rotation along the C-H axis in the tetragonal phase, and eventually to local disordered motion as a partial C$$_{4}$$ along the C-H axis in another tetragonal phase, thereby indicating an intimate interplay between lattice and orientation degrees of freedom in the hybrid perovskite materials. The present complete atomic structure and dynamics provide a solid standing point to understand and then improve photovoltaic properties of organic-inorganic hybrid perovskites in the future.

論文

Level structures of $$^{56,58}$$Ca cast doubt on a doubly magic $$^{60}$$Ca

Chen, 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:23 パーセンタイル:93.47(Astronomy & Astrophysics)

$$^{57,59}$$Scからの1陽子ノックアウト反応を用いて、$$^{56}$$Caと$$^{58}$$Caのガンマ崩壊を観測した。$$^{56}$$Caでは1456(12)keVの$$gamma$$線遷移が、$$^{58}$$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$$2^{+}_{1} rightarrow 0^{+}_{gs}$$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、$$2^{+}_{1}$$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$$0_{f5/2}$$と$$0_{g9/2}$$軌道はほぼ縮退しており、これは$$^{60}$$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$$^{70}$$Caあるいはそれ以上にまで広げる可能性がある。

論文

Deformation mechanism of a strong and ductile maraging steel investigated using ${it in situ}$ X-ray synchrotron diffraction

Li, H.*; Liu, Y.*; Zhao, W.*; Liu, B.*; 冨永 亜希; 菖蒲 敬久; Wei, D.*

International Journal of Plasticity, 165, p.103612_1 - 103612_20, 2023/06

 被引用回数:51 パーセンタイル:97.37(Engineering, Mechanical)

コバルトフリーのマルエージング鋼の強度特性を明らかにするために、高エネルギー放射光X線回折法を利用したその場引張試験を行った。マルテンサイト相とオーステナイト相からの回折プロファイルが得られ、それらの強度及び幅が負荷に伴い変化している様子が観察された。回折プロファイルを解析した結果、時効(as-aged)材では、低応力レベルにてマルテンサイトの含有量が緩やかに減少し、高応力レベルでは急激に減少した。一方、熱処理(as-solution)材では、応力の増加とともにオーステナイト相がマルテンサイト相に著しく転移変態している結果が得られた。これらのことがそれぞれの強度特性に起因していることを明らかにした。

論文

Pressure-modulated magnetism and negative thermal expansion in the Ho$$_2$$Fe$$_{17}$$ intermetallic compound

Cao, Y.*; Zhou, H.*; Khmelevskyi, S.*; Lin, K.*; Avdeev, M.*; Wang, C.-W.*; Wang, B.*; Hu, F.*; 加藤 健一*; 服部 高典; et al.

Chemistry of Materials, 35(8), p.3249 - 3255, 2023/04

 被引用回数:9 パーセンタイル:47.78(Chemistry, Physical)

静水圧や化学圧力は、結晶構造を変化させる効率的な刺激であり、材料科学において電気的、磁気的特性のチューニングによく利用されている。しかし、化学圧力は定量化が困難であり、これら両者の定量的な対応関係はまだよくわかっていない。本研究では、負の熱膨張(NTE)を持つ永久磁石の候補である金属間化合物を調べた。放射光X線その場観察により、AlをドープしたHo$$_2$$Fe$$_{17}$$に負の化学圧力があることを明らかにし、単位セル体積の温度・圧力依存性を用いそれを定量的に評価した。また、磁化測定と中性子回折測定を組み合わせることで、磁気秩序に対する化学圧力と静水圧の違いを比較した。興味深いことに、圧力はNTEの抑制と増強を制御するために使用することができた。電子状態計算から、圧力がFermiレベル(EF)に対する主要バンドの上部に影響を与えたことを示しており、これは磁気安定性に影響を与え、それが磁気とNTEを調節する上で重要な役割を果たしていることがわかった。本研究は、圧力の影響を理解し、それを利用して機能性材料の特性を制御する良い例を示している。

論文

Multiple mechanisms in proton-induced nucleon removal at $$sim$$100 MeV/nucleon

Pohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; G$'o$mez-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:20 パーセンタイル:86.36(Physics, Multidisciplinary)

大きなフェルミ面非対称性を持つ陽子過剰な$$^{14}$$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。

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