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Cao, T.*; Wei, D.*; Gong, W.; 川崎 卓郎; Harjo, S.; 他10名*
Materials Science and Engineering A, 940, p.148534_1 - 148534_16, 2025/09
The thermal stability of microstructure and mechanical performance is crucial for the industrial application of laser powder bed fusion (LPBF) superalloy components in gas turbines and jet engines. This work investigated the microstructural evolution and strengthening mechanism of LPBF Mar-M509 cobalt-based superalloy before and after thermal exposure at 1200 C using multi-scale microstructural characterization and in situ neutron diffraction tensile testing. The as-built Mar-M509 superalloy exhibited a heterogeneous microstructural features with coarse columnar and fine equiaxed grains, both containing dendritic and cellular substructures enriched with nanoscale carbides and high-density dislocations. The ultra high strength of the as-built sample was primarily attributed to dislocation-precipitation synergistic strengthening. After thermal exposure at 1200
C for 4 h, the dendritic and cellular substructures disappeared and the dislocation density decreased significantly. This study reveals the microstructural evolution and instability of LPBF Mar-M509 superalloy under high-temperature exposure and the impacts on mechanical properties, which provides critical support for the development of cobalt-based superalloys in high-temperature application fields.
Fine, L.*; Lavn, R.*; Wei, Z.*; 津森 竜也*; 陰山 洋*; 梶本 亮一; Jimen
z-Ruiz, M.*; Koza, M. M.*; Karlsson, M.*
Chemistry of Materials, 37(1), p.489 - 496, 2024/12
被引用回数:0 パーセンタイル:0.00(Chemistry, Physical)We report results on the configuration and vibrational dynamics of hydride-ions (H) in the novel nitridehydride catalyst Ca
CrN
H, by means of variable temperature inelastic neutron scattering (INS) experiments, harmonic phonon calculations, and machine-learning molecular dynamics (MLMD) calculations. The combined analyses of experimental and theoretical data show that the vibrational dynamics of H
are manifested as a broad, asymmetric vibrational band between 80 and 130 meV. Crucially, these modes are polarized along the crystallographic
axis, and their dispersive character reveals significant interactions between neighbouring H
in the material. We find that most H
are surrounded by two other H
and that the H
sites of the studied sample have an occupancy of at least 95%. We argue that this high H
occupancy may be related to the material's high efficiency as a catalyst for ammonia synthesis.
小泉 光生; 伊藤 史哲*; Lee, J.; 弘中 浩太; 高橋 時音; 鈴木 敏*; 有川 安信*; 安部 勇輝*; Wei, T.*; 余語 覚文*; et al.
第45回日本核物質管理学会年次大会会議論文集(インターネット), 4 Pages, 2024/11
Neutron resonance transmission analysis (NRTA) is a non-destructive method applicable for measuring nuclear material using a time-of-flight (TOF) technique with a pulsed neutron source. To realize a high resolution compact NRTA system, use of a short-pulsed neutron source is essential. Laser-driven neutron sources (LDNSs) are well-suit for generating such neutron beams due to their short pulse width. The advances in laser technology will further reduce the system's size and improve practicality. In this study, we demonstrate the measurement of a neutron transmission TOF spectrum of a sample containing indium and silver using the LDNS of the Osaka University. The obtained spectrum was analyzed using the least-square nuclear-resonance fitting program, REFIT, showcasing for the first time the potential of an LDNS for nondestructive areal-density material characterization.
小泉 光生; 伊藤 史哲*; Lee, J.; 弘中 浩太; 高橋 時音; 鈴木 敏*; 有川 安信*; 安部 勇輝*; Lan, Z.*; Wei, T.*; et al.
Scientific Reports (Internet), 14, p.21916_1 - 21916_9, 2024/09
被引用回数:2 パーセンタイル:64.46(Multidisciplinary Sciences)Laser-driven neutron sources (LDNSs) can generate strong short-pulse neutron beams, which are valuable for scientific studies and engineering applications. Neutron resonance transmission analysis (NRTA) is a nondestructive technique used for determining the areal density of each nuclide in a material sample using pulsed thermal and epithermal neutrons. Herein, we report the first successful NRTA performed using an LDNS driven by the Laser for Fast Ignition Experiment at the Institute of Laser Engineering, Osaka University. The key challenge was achieving a well-resolved resonance transmission spectrum for material analysis using an LDNS with a limited number of laser shots in the presence of strong background noise. We addressed this by employing a time-gated Li-glass scintillation neutron detector to measure the transmission spectra, reducing the impact of electromagnetic noise and neutron and gamma-ray flashes. Output waveforms were recorded for each laser shot and analyzed offline using a counting method. This approach yielded a spectrum with distinct resonances, which were attributed to
In and
Ag, as confirmed through neutron transmission simulation. The spectrum was analyzed using the least-square nuclear-resonance fitting program, REFIT, demonstrating the possibility of using an LDNS for nondestructive areal-density material characterization.
Lan, Z.*; 有川 安信*; Mirfayzi, S. R.*; Morace, A.*; 早川 岳人*; 佐藤 博隆*; 加美山 隆*; Wei, T.*; 巽 湧太*; 小泉 光生; et al.
Nature Communications (Internet), 15, p.5365_1 - 5365_7, 2024/07
被引用回数:5 パーセンタイル:75.95(Multidisciplinary Sciences)The temperature measurement of material inside of an object is one of the key technologies for control of dynamical processes. For this purpose, various techniques such as laser-based thermography and phase-contrast imaging thermography have been studied. However, it is, in principle, impossible to measure the temperature of an element inside of an object using these techniques. One of the possible solutions is measurements of Doppler brooding effect in neutron resonance absorption (NRA). Here we present a method to measure the temperature of an element or an isotope inside of an object using NRA with a single neutron pulse of approximately 100 ns width provided from a high-power laser. We demonstrate temperature measurements of a tantalum (Ta) metallic foil heated from the room temperature up to 617 K. Although the neutron energy resolution is fluctuated from shot to shot, we obtain the temperature dependence of resonance Doppler broadening using a reference of a silver (Ag) foil kept to the room temperature. A free gas model well reproduces the results. This method enables element(isotope)-sensitive thermometry to detect the instantaneous temperature rise in dynamical processes.
Zeng, Z.*; Zhou, C.*; Zhou, H.*; Han, L.*; Chi, R.*; Li, K.*; 古府 麻衣子; 中島 健次; Wei, Y.*; Zhang, W.*; et al.
Nature Physics, 20(7), p.1097 - 1102, 2024/07
被引用回数:12 パーセンタイル:94.31(Physics, Multidisciplinary)Emergent quasiparticles with a Dirac dispersion in condensed matter systems can be described by the Dirac equation for relativistic electrons, in analogy with Dirac particles in high-energy physics. For example, electrons with a Dirac dispersion have been intensively studied in electronic systems such as graphene and topological insulators. However, charge is not a prerequisite for Dirac fermions, and the emergence of Dirac fermions without a charge degree of freedom has been theoretically predicted to be realized in Dirac quantum spin liquids. These quasiparticles carry a spin of 1/2 but are charge-neutral and so are called spinons. Here we show that the spin excitations of a kagome antiferromagnet, YCu(OD)
Br
[Br
(OD)
], are conical with a spin continuum inside, which is consistent with the convolution of two Dirac spinons. The predictions of a Dirac spin liquid model with a spinon velocity obtained from spectral measurements are in agreement with the low-temperature specific heat of the sample. Our results, thus, provide spectral evidence for a Dirac quantum spin liquid state emerging in this kagome lattice antiferromagnet. However, the locations of the conical spin excitations differ from those calculated by the nearest-neighbor Heisenberg model, suggesting the Dirac spinons have an unexpected origin.
Wang, S.*; Wang, J.*; Zhang, S.*; Wei, D.*; Chen, Y.*; Rong, X.*; Gong, W.; Harjo, S.; Liu, X.*; Jiao, Z.*; et al.
Journal of Materials Science & Technology, 185, p.245 - 258, 2024/06
被引用回数:17 パーセンタイル:98.00(Materials Science, Multidisciplinary)Nanoprecipitates and nanoscale retained austenite (RA) with suitable stability play crucial roles in determining the yield strength (YS) and ductility of ultrahigh strength steels (UHSSs). However, owing to the kinetics incompatibility between nanoprecipitation and austenite reversion, it is highly challenging to simultaneously introduce high-density nanoprecipitates and optimized RA in UHSSs. In this work, through the combination of austenite reversion treatment (ART) and subsequent flash austenitizing (FA), nanoscale chemical heterogeneity was successfully introduced into a low-cost UHSS prior to the aging process. This chemical heterogeneity involved the enrichment of Mn and Ni in the austenite phase. The resulting UHSS exhibited dual-nanoprecipitation of Ni(Al,Mn) and (Mo,Cr) C and nanoscale austenite stabilized via Mn and Ni enrichment. The hard martensitic matrix strengthened by high-density dual-nanoprecipitates constrains the plastic deformation of soft RA with a relatively low fraction, and the presence of relatively stable nanoscale RA with adequate Mn and Ni enrichment leads to a marginal loss in YS but keeps a persistent transformation-induced plasticity (TRIP) effect. As a result, the newly-developed UHSS exhibits an ultrahigh YS of 1.7 GPa, an ultimate tensile strength (UTS) of 1.8 GPa, a large uniform elongation (UE) of 8.5 percent, and a total elongation (TE) of 13 percent. The strategy of presetting chemical heterogeneity to introduce proper metastable phases before aging can be extended to other UHSSs and precipitation-hardened alloys.
余語 覚文*; Lan, Z.*; 有川 安信*; 安部 勇輝*; Mirfayzi, S. R.*; Wei, T.*; 森 隆人*; Golovin, D.*; 早川 岳人*; 岩田 夏弥*; et al.
Physical Review X, 13(1), p.011011_1 - 011011_12, 2023/01
被引用回数:28 パーセンタイル:96.01(Physics, Multidisciplinary)Neutrons are powerful tools for investigating the structure and properties of materials used in science and technology. Recently, laser-driven neutron sources (LDNS) have attracted the attention of different communities, from science to industry, in a variety of applications, including radiography, spectroscopy, security, and medicine. However, the laser-driven ion acceleration mechanism for neutron generation and for establishing the scaling law on the neutron yield is essential to improve the feasibility of LDNS. In this paper, we report the mechanism that accelerates ions with spectra suitable for neutron generation. We show that the neutron yield increases with the fourth power of the laser intensity, resulting in the neutron generation of in
at a maximum, with
Wcm
, 900 J, 1.5 ps lasers. By installing a "hand-size" moderator, which is specially designed for the LDNS, it is demonstrated that the efficient generation of epithermal (0.1-100 eV) neutrons enables the single-shot analysis of composite materials by neutron resonance transmission analysis (NRTA). We achieve the energy resolution of 2.3% for 5.19-eV neutrons 1.8 m downstream of the LDNS. This leads to the analysis of elements and isotopes within sub-
s times and allows for high-speed nondestructive inspection.
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:107 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.
Wei, D.*; Gong, W.; Wang, L.*; Tang, B.*; 川崎 卓郎; Harjo, S.; 加藤 秀実*
Journal of Materials Science & Technology, 129, p.251 - 260, 2022/12
被引用回数:37 パーセンタイル:95.41(Materials Science, Multidisciplinary)Owing to their attractive structure and mechanical properties, high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have attracted considerable research interest. The strength of HEAs/MEAs with a single face-centered cubic (FCC) phase, on the other hand, requires improvement. Therefore, in this study, we demonstrate a strategy for increasing the room-temperature strength of FCC-phase HEAs/MEAs by tuning cryo-pre-straining-induced crystal defects via the temperature-dependent stacking fault energy-regulated plasticity mechanism. Through neutron diffraction line profile analysis and electron microscope observation, the effect of the tuned defects on the tensile strength was clarified. This study discussed the possibility of developing single-phase high-performance HEAs by tuning pre-straining-induced crystal defects.
Wei, D.*; Gong, W.; 都留 智仁; 川崎 卓郎; Harjo, S.; Cai, B.*; Liaw, P. K.*; 加藤 秀実*
International Journal of Plasticity, 158, p.103417_1 - 103417_17, 2022/11
被引用回数:54 パーセンタイル:98.44(Engineering, Mechanical)In this study, we investigated the yielding and hardening behaviors of the Cantor alloy and FCC-phase Co-rich HEAs with different SFEs by in situ neutron diffraction combined with the first-principles method and electron-microscopy characterizations. The Co-rich HEAs exhibited a higher intrinsic yield strength than the Cantor alloy, mainly because of the larger shear modulus or modulus misfit, and grain refinement being more effective in improving the yield strength of low-SFE HEAs. Furthermore, higher flow stresses and better ductility of the Co-rich HEAs are attributed to the greater dislocation density and a larger number of stacking faults, which enhanced the strain-hardening rate during tensile deformation. The low SFE promoted mechanical twinning, and martensitic transformation contributed to higher strain-hardening rates.
Wei, D.*; Gong, W.; 川崎 卓郎; Harjo, S.; 加藤 秀実*
Scripta Materialia, 216, p.114738_1 - 114738_6, 2022/07
被引用回数:52 パーセンタイル:97.96(Nanoscience & Nanotechnology)Near-equiatomic single-phase twining-induced plasticity (TWIP) high-entropy alloys (HEAs) exhibit a good combination of strength and ductility, but their modest yield strength requires further improvement. Here, we propose a strategy for markedly enhancing their strength while retaining satisfactory ductility, taking advantage of the temperature dependence of the stacking fault energy. The room-temperature strength of a representative TWIP HEA was improved by the cryogenic pre-deformation-induced dislocations, martensite, nanotwins, and stacking faults. The tensile properties were further tuned by subsequent annealing to obtain partially recovered or recrystallized microstructures. The influence of regulated microstructures on the yield strength was clarified by neutron diffraction line profile analysis. This study presents possibilities for fabricating advanced HEAs by tuning the substructures.
Wei, D.*; Wang, L.*; Zhang, Y.*; Gong, W.; 都留 智仁; Lobzenko, I.; Jiang, J.*; Harjo, S.; 川崎 卓郎; Bae, J. W.*; et al.
Acta Materialia, 225, p.117571_1 - 117571_16, 2022/02
被引用回数:97 パーセンタイル:99.64(Materials Science, Multidisciplinary)Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have ex-tended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions.
Zheng, Y.*; Xiao, H.*; Li, K.*; Wang, Y.*; Li, Y.*; Wei, Y.*; Zhu, X.*; Li, H.-W.*; 松村 大樹; Guo, B.*; et al.
ACS Applied Materials & Interfaces, 12(37), p.42274 - 42284, 2020/09
被引用回数:27 パーセンタイル:70.49(Nanoscience & Nanotechnology)Interactions between the active components with the support are one of the fundamentally factors in determining the catalytic performance of a catalyst. In this study, we investigated the interaction between CeO and LaFeO
, the two important oxygen storage materials in catalysis area, by tuning the sizes of CeO
particles and highlight a two-fold effect of the strong oxide-oxide interaction in determining the catalytic activity and selectivity for preferential CO oxidation in hydrogen feeds. It is found that the anchoring of ultra-fine CeO
particles at the framework of three-dimensional-ordered macroporous LaFeO
surface results in a strong interaction between the two oxides that induces the formation of abundant uncoordinated cations and oxygen vacancy at the interface. This discovery demonstrates that in hybrid oxide-based catalysts, tuning the interaction among different components is essential for balancing the catalytic activity and selectivity.
Xu, Z.*; Dai, G.*; Li, Y.*; Yin, Z.*; Rong, Y.*; Tian, L.*; Liu, P.*; Wang, H.*; Xing, L.*; Wei, Y.*; et al.
npj Quantum Materials (Internet), 5(1), p.11_1 - 11_7, 2020/02
被引用回数:4 パーセンタイル:33.13(Materials Science, Multidisciplinary)We use neutron scattering to study Vanadium (hole)-doped LiFeV
As. In the undoped state, LiFeAs exhibits superconductivity at
K and transverse incommensurate spin excitations similar to electron overdoped iron pnictides. Upon Vanadium doping to form LiFe
V
, the transverse incommensurate spin excitations in LiFeAs transform into longitudinally elongated ones in a similar fashion to that of potassium (hole)-doped Ba
K
Fe
As
but with dramatically enhanced magnetic scattering and elimination of superconductivity. This is different from the suppression of the overall magnetic excitations in hole-doped BaFe
As
and the enhancement of superconductivity near optimal hole doping. These results are consistent with density function theory plus dynamic mean field theory calculations, suggesting that Vanadium doping in LiFeAs may induce an enlarged effective magnetic moment
with a spin crossover ground state arising from the inter-orbital scattering of itinerant electrons.
Xie, T.*; Wei, Y.*; Gong, D.*; Fennell, T.*; Stuhr, U.*; 梶本 亮一; 池内 和彦*; Li, S.*; Hu, J.*; Luo, H.*
Physical Review Letters, 120(26), p.267003_1 - 267003_7, 2018/06
被引用回数:40 パーセンタイル:86.24(Physics, Multidisciplinary)We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFeAs
. In contrast to its quasi-two-dimensional electron structure, three strongly
-dependent modes of spin resonance are found below
= 35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper-pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high-
superconducting families share a common nature.
Wang, C.*; Daiwei, Y.*; Liu, X.*; Chen, R.*; Du, X.*; Hu, B.*; Wang, L.*; 飯田 一樹*; 蒲沢 和也*; 脇本 秀一; et al.
Physical Review B, 96(8), p.085111_1 - 085111_5, 2017/08
被引用回数:9 パーセンタイル:38.92(Materials Science, Multidisciplinary)This paper presents a systematic study of spin and lattice dynamics in the quasi-one-dimensional spiral magnet CuBr, using Raman scattering in conjunction with infrared and neutron spectroscopy. Along with the development of spin correlations upon cooling, we observe a rich set of broad Raman bands at energies that correspond to phonon-dispersion energies near the one-dimensional magnetic wave vector. The low-energy bands further exhibit a distinct intensity maximum at the spiral magnetic ordering temperature.
He, Z.*; Wei, J.*; 大崎 一哉*; 岡本 宏巳*; 野田 章*; 中尾 政夫*; 想田 光*; 百合 庸介; 神保 光一*
Proceedings of 25th North American Particle Accelerator Conference (NA-PAC '13) (Internet), p.1298 - 1300, 2013/09
The power of the cooling laser currently available in a compact ion cooler ring S-LSR, Kyoto University, is quite limited for generating ultralow-temperature ion beams. Therefore, parameters of laser cooling should be carefully determined in order to approach the lowest possible temperature in the experiment. This paper mainly concerns optimization of laser-cooling parameters and prediction of a possible lower limit of beam temperature in S-LSR, based on systematic molecular dynamics simulations. The adiabatic capture process of the ion beam was introduced to prevent the emittance from blowing up during bunching. The spot size of the laser was optimized with the total laser power limited. An optimum solenoid field strength was obtained for three-dimensional cooling. The lowest beam temperature achievable in S-LSR was predicted by choosing the parameters optimized.
池上 雅紀*; Fang, Z.*; 二ツ川 健太*; 宮尾 智章*; Liu, Y.*; 丸田 朋史; 佐甲 博之; 三浦 昭彦; 田村 潤; Wei, G.
Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.64 - 67, 2013/08
The beam operation of J-PARC linac was interrupted by the Tohoku earthquake in March 2011. After significant effort for its restoration, we have resumed the beam operation of J-PARC linac in December 2011. After resumption of beam operation, we have been suffering from beam losses which were not observed before the earthquake. Tackling with the beam loss issues, we have been reached the same beam power for user operation as before the earthquake. In this paper, we present the experience in the beam start-up tuning after the earthquake with emphasis on the beam loss mitigation efforts.
中嶋 秀夫; 辺見 努; 井口 将秀; 名原 啓博; 松井 邦浩; 千田 豊; 梶谷 秀樹; 高野 克敏; 礒野 高明; 小泉 徳潔; et al.
Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03
ITER機構及び6国内機関(中国,欧州,日本,韓国,ロシア,米国)は、協力してITERマグネット・システムを製作している。日本,ロシア,中国,韓国は既に実機の超伝導導体の製作を実施している。TFコイル用のラジアルプレートの製作では、欧州及び日本で品質検証が終了し、実機施策の準備が整った。日本は1/3サイズの試作ダミー巻線を実機大ダミー巻線試作の前に実施し、製作方法を検証した。欧州では、実機製作に必要な治具類の準備とその性能検証が進行中である。また、日本は、2個の実機大TF構造物を試作し、製作方法の最適化と工業化を実施した。コレクション・コイルの製作進捗はTFコイル同様に順調であり、巻線治具等の準備はほとんど終了し、品質検証が開始された。その他のマグネットにおいても、2020年の初期プラズマ点火達成に向けて、順調に製作が進んでいる。