Metalloid substitution elevates simultaneously the strength and ductility of face-centered-cubic high-entropy alloys

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

https://doi.org/10.1016/j.actamat.2021.117571

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.

New -emitting isotope U and abnormal enhancement of -particle clustering in lightest uranium isotopes

Zhang, Z. Y.*; Yang, H. B.*; Andreyev, A. N.; Liu, M. L.*; Ma, L.*; 他37名*

Physical Review Letters, 126(15), p.152502_1 - 152502_6, 2021/04

https://doi.org/10.1103/PhysRevLett.126.152502

A new -emitting isotope U, produced by the fusion-evaporation reaction W(Ar,4n)U, was identified by employing the gas-filled recoil separator SHANS and the recoil- correlation technique. More precise -decay properties of even-even nuclei U were also measured in the reactions of Ar, Ca beams with W targets. By combining the experimental data, improved -decay reduced widths for the even-even Po-Pu nuclei in the vicinity of the magic neutron number = 126 are deduced. Their systematic trends are discussed in terms of the scheme in order to study the influence of proton-neutron interaction on decay in this region of nuclei. It is strikingly found that the reduced widths of U are significantly enhanced by a factor of two as compared with the systematics for the 84 90 and 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the 1 and 1 spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

Stacking fault driven phase transformation in CrCoNi medium entropy alloy

He, H.*; Naeem, M.*; Zhang, F.*; Zhao, Y.*; Harjo, S.; 川崎 卓郎; Wang, B.*; Wu, X.*; Lan, S.*; Wu, Z.*; et al.

Nano Letters, 21(3), p.1419 - 1426, 2021/02

https://doi.org/10.1021/acs.nanolett.0c04244

In CrCoNi, a so-called medium-entropy alloy, an fcc-to-hcp phase transformation has long been anticipated. Here, we report an in situ loading study with neutron diffraction, which revealed a bulk fcc-to-hcp phase transformation in CrCoNi at 15 K under tensile loading. By correlating deformation characteristics of the fcc phase with the development of the hcp phase, it is shown that the nucleation of the hcp phase was triggered by intrinsic stacking faults. The confirmation of a bulk phase transformation adds to the myriads of deformation mechanisms available in CrCoNi, which together underpin the unusually large ductility at low temperatures.

Extremely high dislocation density and deformation pathway of CrMnFeCoNi high entropy alloy at ultralow temperature

Naeem, M.*; He, H.*; Harjo, S.; 川崎 卓郎; Zhang, F.*; Wang, B.*; Lan, S.*; Wu, Z.*; Wu, Y.*; Lu, Z.*; et al.

Scripta Materialia, 188, p.21 - 25, 2020/11

https://doi.org/10.1016/j.scriptamat.2020.07.004

The deformation behavior of CrMnFeCoNi high entropy alloy was investigated by in situ neutron diffraction at an ultralow temperature of 15 K. Analysis of the diffraction peak widths showed an extremely high dislocation density at 15 K, reaching 10 m. In addition, the dislocation density was found to closely follow the development of texture caused by deformation. In contrast to deformation by dislocation slip at room temperature, the ultralow-temperature deformation also involved stacking faults, twinning and serrations. The deformation pathway at ultralow temperature is outlined which is responsible for the extraordinary strength-ductility combination.

Selective removal of radiocesium from micaceous clay for post-accident soil decontamination by temperature-controlled Mg-leaching in a column

Yin, X.; Zhang, L.*; Meng, C.*; 稲葉 優介*; Wang, X.*; 二田 郁子; 駒 義和; 竹下 健二*

Journal of Hazardous Materials, 387, p.121677_1 - 121677_10, 2020/04

https://doi.org/10.1016/j.jhazmat.2019.121677

The effective and efficient removal of radioactive Cs from contaminated soil is highly urgent for the nuclear post-accident remediation. In present study, we achieved rapid Cs desorption from both a typical micaceous clay (i.e., vermiculitized biotite, VB) and actually contaminated soil by high-speed ion exchange through temperature-controlled continuous leaching with Mg-solutions in a column reactor. Cs-sorbed VB was firstly employed as a soil surrogate to explore the macro-Cs desorption process and micro-mechanism in detail.

Fine structure in the decay of U

Sun, M. D.*; Liu, Z.*; Huang, T. H.*; Zhang, W. Q.*; Andreyev, A. N.; Ding, B.*; Wang, J. G.*; Liu, X. Y.*; Lu, H. Y.*; Hou, D. S.*; et al.

Physics Letters B, 800, p.135096_1 - 135096_5, 2020/01

https://doi.org/10.1016/j.physletb.2019.135096

Fine structure in the decay of U was observed in the fusion-evaporation reaction Re(Ar,p3n) by using fast digital pulse processing technique. Two -decay branches of U feeding the ground state and 244 keV excited state of Th were identified by establishing the decay chain UThRaRn. The -particle energy for the ground-state to ground-state transition of U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62s. Evolution of nuclear structure for =131 even- isotones from Po to U was discussed in the frameworks of nuclear mass and reduced -decay width, a weakening octupole deformation in the ground state of U relative to its lighter isotones Ra and Th was suggested.

Asymmetrically optimized structure in a high- single unit-cell FeSe superconductor

深谷 有喜; Zhou, G.*; Zheng, F.*; Zhang, P.*; Wang, L.*; Xue, Q.-K.*; 社本 真一

Journal of Physics; Condensed Matter, 31(5), p.055701_1 - 055701_6, 2019/02

https://doi.org/10.1088/1361-648X/aaf2d9

本研究では、SrTiO基板上の単層FeSeの構造が上下方向に非対称化していることを報告する。SrTiO基板上の単層FeSeは、鉄系超伝導体において最も高い転移温度(50K以上)を示す。全反射高速陽電子回折(TRHEPD)を用いた構造解析の結果、真空側と界面側のSe-Fe層間隔は異なり、上下方向に非対称な構造であることがわかった。これらの層間隔および結合角の平均値は、圧力下のバルクFeSeにおいて高い転移温度を示す最適値と一致している。したがって、SrTiO基板上の単層FeSeは非対称化することにより高い転移温度を発現するための最適構造を形成したと考えられる。

Liquid-like thermal conduction in intercalated layered crystalline solids

Li, B.; Wang, H.*; 川北 至信; Zhang, Q.*; Feygenson, M.*; Yu, H. L.*; Wu, D.*; 尾原 幸治*; 菊地 龍弥*; 柴田 薫; et al.

Nature Materials, 17(3), p.226 - 230, 2018/03

https://doi.org/10.1038/s41563-017-0004-2

As a generic property, all substances transfer heat through microscopic collisions of constituent particles. A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations. As a result, a solid is usually thermally more conductive than a liquid. In canonical viewpoints, such a difference also serves as the dynamic signature distinguishing a solid from a liquid. Here, we report liquid-like thermal conduction observed in the crystalline AgCrSe. The transverse acoustic phonons are completely suppressed by the ultrafast dynamic disorder while the longitudinal acoustic phonons are strongly scattered but survive, and are thus responsible for the intrinsically ultralow thermal conductivity. This scenario is applicable to a wide variety of layered compounds with heavy intercalants in the van der Waals gaps, manifesting a broad implication on suppressing thermal conduction. These microscopic insights might reshape the fundamental understanding on thermal transport properties of matter and open up a general opportunity to optimize performances of thermoelectrics.

Super-absorbent polymer valves and colorimetric chemistries for time-sequenced discrete sampling and chloride analysis of sweat via skin-mounted soft microfluidics

Kim, S. B.*; Zhang, Y.*; Won, S. M.*; Bandodkar, A. J.*; 関根 由莉奈; Xue, Y.*; Koo, J.*; Harshman, S. W.*; Martin, J. A.*; Park, J. M.*; et al.

Small, 14(12), p.1703334_1 - 1703334_11, 2018/03

https://doi.org/10.1002/smll.201703334

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.

Spin excitations in optimally P-doped BaFe(AsP) superconductor

Hu, D.*; Yin, Z.*; Zhang, W.*; Ewings, R. A.*; 池内 和彦*; 中村 充孝; Roessli, B.*; Wei, Y.*; Zhao, L.*; Chen, G.*; et al.

Physical Review B, 94(9), p.094504_1 - 094504_7, 2016/09

AA2016-0252.pdf:2.18MB

https://doi.org/10.1103/PhysRevB.94.094504

最適Pドープされた超伝導体BaFe(AsP) (T=30K)におけるスピン励起の温度及びエネルギー依存性が非弾性中性子散乱実験を使って調べられた。我々の実験結果は密度汎関数理論や動的平均場理論で予想される計算結果と矛盾しておらず、BaFe(AsP)における平均プニクトゲン高さの減少が、電子相関の強さを弱め、磁気励起の有効バンド幅の増加に寄与することを示唆している。