| 2051. |
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| 2052. |
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| 2053. |
- Zhang, B., et al.
(author)
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Magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism in FeCoNiZMnx (Z = Si, Al, Sn, Ge) high entropy alloys
- 2021
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In: Journal of Materials Science & Technology. - : Elsevier BV. - 1005-0302. ; 68, s. 124-131
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Journal article (peer-reviewed)abstract
- We design high entropy alloys (HEAs) with different induction elements (Si/Al/Sn). In order to keep the crystal structure invariant and to investigate how the increment in saturation magnetization (Ms) is caused only by the change of electron spin state, each set of HEAs contains a different amount of Mn. Synergistic effects among induction elements that induce the magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism are found. Ms of added Mn reduces when a particular induction element (Si0.4/Al0.4/Sn0.4) exists, while a larger increment of Ms appears when two induction elements coexist, Si0.4Al0.4 (25.79 emu/g) and Sn0.4Al0.4 (15.43 emu/g). This is reflected in the microcosmic magnetic structure for the emergence of closed domains due to large demagnetization energy, which is confirmed by the Lorentz transmission electron microscope (LTEM) data. The calculated magnetic moments and the exchange integral constants from density functional theory based on the Exact Muffin-Tin Orbits formalism reveal that the magnetic state and the strength of ferromagnetic and anti-ferromagnetic coupling determine the variation of Ms in different chemical environments. The difference in energy levels of coexisting multiple induction elements also leads to a larger increment of Ms, Si0.4Al0.4Sn0.4 (29.78 emu/g), and Si0.4Al0.4Ge0.4Sn0.4 (31.00 emu/g).
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| 2054. |
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| 2055. |
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| 2056. |
- Zhang, C., et al.
(author)
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Near Earth Vortices Driving of Field Aligned Currents Based on Magnetosphere Multiscale and Swarm Observations
- 2019
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In: Chinese Journal of Space Science. - : National Space Science Center, Chinese Academy of Sciences. - 0254-6124. ; 39:1, s. 9-17
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Journal article (peer-reviewed)abstract
- A long-standing mystery in the study of Field-Aligned Currents (FACs) has been that: how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere. Here we present two events of magnetotail FACs observed by the Magnetospheric Multiscale Spacecraft (MMS) on 1st July and 14th July 2016, to show how the Substorm Current Wedges (SCW) were formed. The results show that particles were transferred heading towards the Earth during the expansion phase of substorms. The azimuthal flow formed clockwise (counter-clockwise) vortex-like motion, and then generated downward (upward) FACs on the tailward/poleward side of the distorted field with opposite vorticity on their Earthward/equatorward side. We also analyzed the Region 1 FACs observed by the Earth Explorer Swarm spacecraft on 1st July 2016 and found that they were associated with FACs observed by MMS, although differing by a factor of 10. This difference suggests that either there was the closure of the currents at altitudes above 500 km or the currents were not strictly parallel to B and closed at longitudes away from where they were generated.
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| 2057. |
- Zhang, D. H., et al.
(author)
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Calculations of Dielectronic Recombination and Electron-impact Excitation Rate Coefficients of Highly Charged Sulfur Ions
- 2020
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In: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 247:1
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Journal article (peer-reviewed)abstract
- Connected to the experiment performed at the Stockholm electron beam ion trap, a systematic relativistic configuration-interaction calculation is carried out to compare with the experimental spectra. In particular, separate rate coefficients are calculated for dominant recombination and excitation processes in the range of the impact electron energy determined by the experiment. By means of the relevant experimental parameters, the presently calculated dielectronic recombination rate coefficients for and S14+ ions and electron-impact excitation ones for S15+, S14+, and S13+ ions are employed further to synthesize overall theoretical spectra for comparison with the experimentally measured spectra. Overall, very good agreements with the experimental results are found except for one missing excitation peak around the impact electron energy 2.52 keV, which cannot be explained by the present calculations and thus remains open.
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| 2058. |
- Zhang, H., et al.
(author)
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Application Prospects and Microstructural Features in Laser-Induced Rapidly Solidified High-Entropy Alloys
- 2014
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In: JOM. - : Springer Science and Business Media LLC. - 1543-1851 .- 1047-4838. ; 66:10, s. 2057-2066
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Research review (peer-reviewed)abstract
- Recently, high-entropy alloys (HEAs) have attracted much interest in the materials community, as they offer massive opportunities to observe new phenomena, explore new structure, and develop new materials. Particularly, it is attractive to prepare high-performance HEA coatings by laser-induced rapid solidification, which can be formed on the surface of components and parts in a variety of sizes and shapes with a lower cost in comparison with those bulk material fabrication methods. From the technical point of view, laser-induced rapid solidification could hamper the compositional segregation, improve the solubility in solid-solution phases, and lead to the strengthening effect by the grain refinement. This article reviews the recent work on the typical microstructural features and the mechanical and chemical properties in laser-induced rapidly solidified HEAs, and these data are compared with conventional Co- and Ni-based alloy coatings. The article concludes with suggestions for future research and development in HEAs, from considerations of their characteristic properties.
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| 2059. |
- Zhang, H., et al.
(author)
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Effect of High Configuration Entropy and Rare Earth Addition on Boride Precipitation and Mechanical Properties of Multi-principal-Element Alloys
- 2017
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In: Journal of Materials Engineering and Performance. - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 26:8, s. 3750-3755
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Journal article (peer-reviewed)abstract
- A series of multi-principal-element (MPE) alloys have been prepared by adding Ni, Mn, Al, Cu and Y into the reference CoCrFe-B alloy. The microstructure and mechanical properties of these MPE alloys have been investigated thoroughly. It is found that the addition of the elements can inhibit boride precipitation in the designed alloys and the solid solution strengthening effect induced by interstitial boron atoms is more significant than that by boride precipitation. The MPE alloys with the fcc phase as the main solid solution phase have a higher boron solubility and hence less boride precipitation, than those with the bcc phase as the main solid solution phase. The addition of yttrium can improve the boron solubility, decrease boride precipitation, control the boride morphology and, importantly, simultaneously improve the compressive strength and ductility of boron-containing MPE alloys.
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| 2060. |
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