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Li, C.*; Fang, W.*; Yu, H. Y.*; Peng, T.*; Yao, Z. T.*; Liu, W. G.*; Zhang, X.*; 徐 平光; Yin, F.*
Materials Science & Engineering A, 892, p.146096_1 - 146096_11, 2024/02
被引用回数:0 パーセンタイル:0.04(Nanoscience & Nanotechnology)The quasi-static superelastic responses and hierarchical martensite transformation from body-centered cubic (BCC) to face-centered cubic (FCC) under dynamic impact in FeMnAlNiTi alloys were investigated. Polycrystalline and oligocrystalline alloys were produced through solution heat treatment and cyclic heat treatment processes, respectively. The results show the volume fraction of residual martensite for oligocrystalline alloys is lower, which exhibits better superelastic responses compared with polycrystalline alloys. Dynamic impact tests indicate that, despite the weakening of the grain boundary strengthening effect, the ultimate strength of the oligocrystalline alloys closely matches that of the polycrystalline alloys under dynamic impact. The martensite transformation of the FeMnAlNiTi alloy is characterized as hierarchical under dynamic impact, and increasing strain rates and grain sizes can enhance the BCC FCC martensite transformation, resulting in higher martensite phase fractions for oligocrystalline alloys. The increase in ultimate strength is attributed to the dynamic Hall-Petch effect introduced by more martensite phase interfaces under dynamic impact.
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
被引用回数:41 パーセンタイル:95.34(Chemistry, Multidisciplinary)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.
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:40.81(Materials Science, Multidisciplinary)We use neutron scattering to study Vanadium (hole)-doped LiFeVAs. 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 LiFeV, the transverse incommensurate spin excitations in LiFeAs transform into longitudinally elongated ones in a similar fashion to that of potassium (hole)-doped BaKFeAs but with dramatically enhanced magnetic scattering and elimination of superconductivity. This is different from the suppression of the overall magnetic excitations in hole-doped BaFeAs 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.
Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.
Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05
被引用回数:5 パーセンタイル:42.69(Physics, Multidisciplinary)We report neutron scattering measurements of single-crystalline YFeGe in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFeGe does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFeGe displays anisotropic stripe-type antiferromagnetic spin fluctuations at (). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector (). These ferromagnetic spin fluctuations are isotropic in the () plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFeGe and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.
Yin, J. H.*; 谷田 聖; Belle Collaboration*; 他189名*
Physical Review D, 98(9), p.091102_1 - 091102_9, 2018/11
被引用回数:4 パーセンタイル:23.83(Astronomy & Astrophysics)We report searches for the processes and (J=1,2) in the vicinity of the resonance using energy scan data collected by the Belle experiment at the KEKB collider. We observe and find evidence for processes for data with center-of-mass energies from 10.96 to 11.05~GeV for the first time. The statistical significance for and are and , respectively. We investigate energy dependence of the cross section and find that it is consistent with production of and resonances without significant non-resonant contribution. Assuming proceeds via and , the branching fraction is measured for the first time, where the first error is statistical, the second is systematic, and the third from the branching fraction of . The signals for are not significant, and the upper limits of the Born cross sections at the 90% confidence level are and ~pb for and , respectively, for center-of-mass energies from 10.96 to 11.05 GeV.
Yin, H.*; Chung, B.*; Chen, F.*; 大内 隆成*; Zhao, J.*; 田中 伸幸; Sadoway, D. R.*
Nature Energy (Internet), 3(2), p.127 - 131, 2018/02
被引用回数:55 パーセンタイル:87.54(Energy & Fuels)リチウムイオン選択性を有する多孔質伝導膜を用い、正極と負極の電極金属を分離することで、性能劣化が小さく、高い充放電効率が得られるこれまでにない概念の溶融塩蓄電池の開発を行った。多孔質伝導膜にセラミックスの窒化チタン焼結体を、正・負極材に、それぞれ鉛及びリチウム鉛を使用した蓄電池を作製し、作動温度410Cにおける100サイクル試験を行った。初期の100サイクル平均の性能で、充放電効率が90%以上と優れた性能を達成するとともに、その間の充放電効率の低下速度は1サイクル当たり0.0017%が得られた。これは10年経過後も充放電効率の劣化は10%以下と高寿命であることを示している。また、多孔質状金属(ステンレス及びチタン)に窒化チタンをコーティングした多孔質伝導膜を使用した場合においても、同様の充放電効率を示すことを明らかにした。このように本開発で導入した金属を基盤とする多孔質伝導膜は、低電気抵抗が可能な薄膜化かつ工業的スケールアップに向けた大型化が期待できるものである。
Tam, D. M.*; Song, Y.*; Man, H.*; Cheung, S. C.*; Yin, Z.*; Lu, X.*; Wang, W.*; Frandsen, B. A.*; Liu, L.*; Gong, Z.*; et al.
Physical Review B, 95(6), p.060505_1 - 060505_6, 2017/02
被引用回数:23 パーセンタイル:71.49(Materials Science, Multidisciplinary)We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on the antiferromagnetic (AF) orthorhombic phase in BaFeTAs and its Co- and Ni-substituted members near optimal superconductivity. In the low-temperature AF ordered state, uniaxial pressure necessary to detwin the orthorhombic crystals also increases the magnetic ordered moment, reaching an 11% increase under 40 MPa for BaFeCoAs, and a 15% increase for BaFeNiAs. We also observe an increase of the AF ordering temperature () of about 0.25 K/MPa in all compounds, consistent with density functional theory calculations that reveal better Fermi surface nesting for itinerant electrons under uniaxial pressure. The doping dependence of the magnetic ordered moment is captured by combining dynamical mean field theory with density functional theory, suggesting that the pressure-induced moment increase near optimal superconductivity is closely related to quantum fluctuations and the nearby electronic nematic phase.
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
被引用回数:16 パーセンタイル:59.36(Materials Science, Multidisciplinary)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。
Zanino, R.*; Bagnasco, M.*; Baker, W.*; Bellina, F.*; Bruzzone, P.*; della Corte, A.*; Ilyin, Y.*; Martovetsky, N.*; Mitchell, N.*; Muzzi, L.*; et al.
IEEE Transactions on Applied Superconductivity, 16(2), p.886 - 889, 2006/06
被引用回数:7 パーセンタイル:40.69(Engineering, Electrical & Electronic)那珂核融合研究所においてITERポロイダル磁場コイル導体インサート(PFCI)の実験が予定されている。このため、PFCIの適切な実験プログラムを作成することを目的として、NbTi短尺導体サンプル実験から得られた結果の解析を行った。特に、次の項目について検討を行った;(1)巻線内の導体ジョイントがクエンチする前に導体自身の分流開始温度Tcsを測定できる可能性に関する検討。(2)解析コードMithrandirを用いて短尺導体サンプルの実験結果を解析し、いわゆる突然の又は早期のクエンチの可能性に関する検討。(3)PFCI実験における熱量法によるACロス測定の可能性。検討の結果、Tcs及びACロスの測定は可能であることがわかった。しかし、突然のクエンチについては今後のこれらの検討が必要である。