| 1. |
- Ding, Haoming, et al.
(author)
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Chemical scissor-mediated structural editing of layered transition metal carbides
- 2023
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In: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 379:6637, s. 1130-1135
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Journal article (peer-reviewed)abstract
- Intercalated layered materials offer distinctive properties and serve as precursors for important two-dimensional (2D) materials. However, intercalation of non-van der Waals structures, which can expand the family of 2D materials, is difficult. We report a structural editing protocol for layered carbides (MAX phases) and their 2D derivatives (MXenes). Gap-opening and species-intercalating stages were respectively mediated by chemical scissors and intercalants, which created a large family of MAX phases with unconventional elements and structures, as well as MXenes with versatile terminals. The removal of terminals in MXenes with metal scissors and then the stitching of 2D carbide nanosheets with atom intercalation leads to the reconstruction of MAX phases and a family of metal-intercalated 2D carbides, both of which may drive advances in fields ranging from energy to printed electronics.
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| 2. |
- Li, Youbing, et al.
(author)
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Near-room temperature ferromagnetic behavior of single-atom-thick 2D iron in nanolaminated ternary MAX phases
- 2021
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In: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 8:3
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Journal article (peer-reviewed)abstract
- M(n+)(1)AX(n) (MAX) phases nanolaminated ternary carbides or nitrides possess a unique crystal structure in which single-atom-thick "A" sublayers are interleaved by alternative stacking of a "Mn+1Xn" sublayer; these materials have been investigated as promising high-safety structural materials for industrial applications because of their laminated structure and metal and ceramic properties. However, limited of A-site elements in the definition of M(n+)(1)AX(n) phases, it is a huge challenge for designing nanolaminated ferromagnetic materials with single-atom-thick two-dimensional iron layers occupying the A layers in the M(n+)(1)AX(n) phases. Here, we report three new ternary magnetic M(n+)(1)AX(n) phases (Ta2FeC, Ti2FeN, and Nb2FeC) with A sublayers of single-atom-thick two-dimensional iron through an isomorphous replacement reaction of M(n+)(1)AX(n) precursors (Ta2AlC, Ti2AlN, and Nb2AlC) with a Lewis acid salts (FeCl2). All these M(n+)(1)AX(n) phases exhibit ferromagnetic behavior. The Curie temperatures of the Ta2FeC and Nb2FeC M(n+)(1)AX(n) phases are 281 and 291K, respectively, i.e., close to room temperature. The saturation magnetization of these ternary magnetic MAX phases is almost two orders of magnitude higher than V-2(Sn,Fe)C, whose A-site is partially substituted by Fe. Theoretical calculations on magnetic orderings of spin moments of Fe atoms in these nanolaminated magnetic M(n+)(1)AX(n) phases reveal that the magnetism can be mainly ascribed to an intralayer exchange interaction of the two-dimensional Fe atomic layers. Owing to the richness in composition of M(n+)(1)AX(n) phases, our work provides a large imaginary space for constructing functional single-atom-thick two-dimensional layers in materials using these nanolaminated templates.
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| 3. |
- Telloni, Daniele, et al.
(author)
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Evolution of Solar Wind Turbulence from 0.1 to 1 au during the First Parker Solar Probe-Solar Orbiter Radial Alignment
- 2021
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 912:2
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Journal article (peer-reviewed)abstract
- The first radial alignment between Parker Solar Probe and Solar Orbiter spacecraft is used to investigate the evolution of solar wind turbulence in the inner heliosphere. Assuming ballistic propagation, two 1.5 hr intervals are tentatively identified as providing measurements of the same plasma parcels traveling from 0.1 to 1 au. Using magnetic field measurements from both spacecraft, the properties of turbulence in the two intervals are assessed. Magnetic spectral density, flatness, and high-order moment scaling laws are calculated. The Hilbert-Huang transform is additionally used to mitigate short sample and poor stationarity effects. Results show that the plasma evolves from a highly Alfvenic, less-developed turbulence state near the Sun, to fully developed and intermittent turbulence at 1 au. These observations provide strong evidence for the radial evolution of solar wind turbulence.
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| 4. |
- Telloni, Daniele, et al.
(author)
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Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations
- 2022
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In: Astrophysical Journal. - : IOP Publishing Ltd. - 0004-637X .- 1538-4357. ; 935:2
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Journal article (peer-reviewed)abstract
- The solar wind measured in situ by Parker Solar Probe in the very inner heliosphere is studied in combination with the remote-sensing observation of the coronal source region provided by the METIS coronagraph aboard Solar Orbiter. The coronal outflows observed near the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and 6.3 R (circle dot) above the eastern solar limb, can be associated with the streams sampled by PSP at 0.11 and 0.26 au from the Sun, in two time intervals almost 5 days apart. The two plasma flows come from two distinct source regions, characterized by different magnetic field polarity and intensity at the coronal base. It follows that both the global and local properties of the two streams are different. Specifically, the solar wind emanating from the stronger magnetic field region has a lower bulk flux density, as expected, and is in a state of well-developed Alfvenic turbulence, with low intermittency. This is interpreted in terms of slab turbulence in the context of nearly incompressible magnetohydrodynamics. Conversely, the highly intermittent and poorly developed turbulent behavior of the solar wind from the weaker magnetic field region is presumably due to large magnetic deflections most likely attributed to the presence of switchbacks of interchange reconnection origin.
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| 5. |
- Telloni, Daniele, et al.
(author)
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Observation of a Magnetic Switchback in the Solar Corona
- 2022
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In: Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205 .- 2041-8213. ; 936:2
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Journal article (peer-reviewed)abstract
- Switchbacks are sudden, large radial deflections of the solar wind magnetic field, widely revealed in interplanetary space by the Parker Solar Probe. The switchbacks' formation mechanism and sources are still unresolved, although candidate mechanisms include Alfvenic turbulence, shear-driven Kelvin-Helmholtz instabilities, interchange reconnection, and geometrical effects related to the Parker spiral. This Letter presents observations from the Metis coronagraph on board a Solar Orbiter of a single large propagating S-shaped vortex, interpreted as the first evidence of a switchback in the solar corona. It originated above an active region with the related loop system bounded by open-field regions to the east and west. Observations, modeling, and theory provide strong arguments in favor of the interchange reconnection origin of switchbacks. Metis measurements suggest that the initiation of the switchback may also be an indicator of the origin of slow solar wind.
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