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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

https://doi.org/10.1016/j.calphad.2023.102641

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 transforms continuously to 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 phase, 138 GPa for the 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 2 and phases under high pressure.

論文

Optimizing TiO through water-soluble Ti complexes as raw material for controlling particle size and distribution of synthesized BaTiO nanocubes

中島光一*; 廣中航太*; 大内一真*; 味岡真央*; 小林芳男*; 米田安宏; Yin, S.*; 垣花眞人*; 関野徹*

ACS Omega (Internet), 6(48), p.32517 - 32527, 2021/12

https://doi.org/10.1021/acsomega.1c04013

被引用回数：6 パーセンタイル：34.61(Chemistry, Multidisciplinary)

水熱合成法によって合成されたBaTiOナノ粒子のサイズは原料となるTiOナノ結晶の粒子サイズに依存することを見出したため、TiOナノ結晶の最適化を行い、これを用いてBaTiOナノ結晶を合成することで粒度分布のそろった100nmサイズのナノキューブの合成に成功した。得られたBaTiOナノキューブはX線回折実験によって強誘電性を示す正方晶構造であることがわかった。また、電子線トモグラフィによって3次元構造を可視化することによってクリアな粒子外形の観察にも成功した。

論文

Stabilization of size-controlled BaTiO nanocubes via precise solvothermal crystal growth and their anomalous surface compositional reconstruction

中島光一*; 小名木海飛*; 小林芳男*; 石垣徹*; 石川喜久*; 米田安宏; Yin, S.*; 垣花眞人*; 関野徹*

ACS Omega (Internet), 6(14), p.9410 - 9425, 2021/04

https://doi.org/10.1021/acsomega.0c05878

被引用回数：11 パーセンタイル：53.29(Chemistry, Multidisciplinary)

チタン酸バリウムナノキューブを水熱合成法によって合成することに成功した。ナノキューブを走査型電子顕微鏡、パルス中性子、大型放射光を用いて詳細に調べたところ、表面に酸化チタンの再構成層が形成されていることを見出した。

論文

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

被引用回数：62 パーセンタイル：96.39(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.

論文

Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe $_{2}$ Ge $_{2}$

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

https://doi.org/10.1103/PhysRevLett.122.217003

被引用回数：6 パーセンタイル：44.53(Physics, Multidisciplinary)

We report neutron scattering measurements of single-crystalline YFe $_{2}$ Ge $_{2}$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe $_{2}$ Ge $_{2}$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe $_{2}$ Ge $_{2}$ 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 YFe $_{2}$ Ge $_{2}$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.

論文

Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe $_{2-x}$ T $_{x}$ As $_{2}$ ( = Co,Ni)

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

https://doi.org/10.1103/PhysRevB.95.060505

被引用回数：24 パーセンタイル：70.10(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 BaFe $_{2-x}$ T $_{x}$ As $_{2}$ 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 BaFe $_{1.9}$ Co $_{0.1}$ As, and a 15% increase for BaFe $_{1.915}$ Ni $_{0.085}$ As. 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.

論文

Spin excitations in optimally P-doped BaFe(As $_{0.7}$ P $_{0.3}$ ) 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

被引用回数：17 パーセンタイル：59.01(Materials Science, Multidisciplinary)

最適Pドープされた超伝導体BaFe(As $_{0.7}$ P $_{0.3}$ ) (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(As $_{0.7}$ P $_{0.3}$ )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。

論文

Tensile deformation behavior of hydrogen charged ultrahigh strength steel studied by in situ neutron diffraction

徐平光; Yin, J*; Zhang, S. Y.*

Acta Metallurgica Sinica, 51(11), p.1297 - 1305, 2015/11

http://www.ams.org.cn/EN/10.11900/0412.1961.2014.00541

The tensile deformation behavior of 1250 MPa ultra-high strength steels with and without hydrogen charging was comparably investigated using neutron diffraction together with the fracture morphology and microstructure observation. Before tensile loading, the (110) lattice spacing of hydrogen charged steel was found larger than that of non-charged sample while the (200) lattice spacing of the former was smaller than that of the latter, suggesting that the hydrogen atoms occupied the tetrahedral center promoted the increment of lattice plane spacing of (110) crystal planes while the balanced internal stress resulted in the proper decrement of (200) lattice plane spacing. In the non-charged sample, the non-linear elastic deformation was observed at 700 MPa in (200) planes, and then at 800 MPa in (110) planes. In the hydrogen charged sample, the non-linear elastic deformation was observed at 300 MPa in (110) planes, and then at 400 MPa in (200) planes. The microstructure observation confirmed the cleavage crack propagation and local crystal rotation in the hydrogen charged sample. Here, a concept about crystallographic orientation dependent micro-yielding was proposed, i.e. the hydrogen charging promoted the (110) preferable micro-yielding rather than (200) preferable micro-yielding, and resulted into a special deformation characteristics.

論文

Final results of an analytical round robin exercise to support constraint effects

Scibetta, M.*; Altstadt, E.*; Callejas, R.*; Lee, B.*; 三浦直樹*; 鬼沢邦雄; Paffumi, E.*; Serrano, M.*; Tatar, L.*; Yin, S.*

Proceedings of 2009 ASME Pressure Vessels and Piping Division Conference (PVP 2009) (CD-ROM), 11 Pages, 2009/07

国際原子力機関(IAEA)では、軽水型原子炉圧力容器への破壊靱性マスターカーブ法の適用に関する課題解決のため、国際協力研究(CRP)を行っている。このCRPにおける課題1では、マスターカーブ法により予き裂付シャルピー(PCC)試験片から参照温度T0を決定するための課題に着目し、破壊靱性試験及び解析を実施した。ラウンドロビン解析では、き裂先端近傍の応力・ひずみに着目して弾塑性有限要素法解析を用いた。ラウンドロビン解析には、9か国から10機関が参加し、浅いき裂と深いき裂を有する試験片の3次元モデルを作成して解析を行った。解析コードや解析者の相違の影響は比較的小さく、深いき裂と比較した場合、浅いき裂の試験片の方が拘束効果に対する感受性が高いことが示された。また、破壊靱性参照温度の観点では、き裂深さの影響は約40 $^{circ}$ Cとなることが示された。

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