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Archimedean lattices emerge in template-directed eutectic solidification 期刊论文
NATURE, 2020, 577 (7790) : 355-+
作者:  Subbaraman, Nidhi;  Viglione, Giuliana
收藏  |  浏览/下载:29/0  |  提交时间:2020/07/03

Template-directed assembly has been shown to yield a broad diversity of highly ordered mesostructures(1),(2), which in a few cases exhibit symmetries not present in the native material(3-5). However, this technique has not yet been applied to eutectic materials, which underpin many modern technologies ranging from high-performance turbine blades to solder alloys. Here we use directional solidification of a simple AgCl-KCl lamellar eutectic material within a pillar template to show that interactions of the material with the template lead to the emergence of a set of microstructures that are distinct from the eutectic'  s native lamellar structure and the template'  s hexagonal lattice structure. By modifying the solidification rate of this material-template system, trefoil, quatrefoil, cinquefoil and hexafoil mesostructures with submicrometre-size features are realized. Phase-field simulations suggest that these mesostructures appear owing to constraints imposed on diffusion by the hexagonally arrayed pillar template. We note that the trefoil and hexafoil patterns resemble Archimedean honeycomb and square-hexagonal-dodecagonal lattices(6), respectively. We also find that by using monolayer colloidal crystals as templates, a variety of eutectic mesostructures including trefoil and hexafoil are observed, the former resembling the Archimedean kagome lattice. Potential emerging applications for the structures provided by templated eutectics include non-reciprocal metasurfaces(7), magnetic spin-ice systems(8,9), and micro- and nano-lattices with enhanced mechanical properties(10,11).


  
General synthesis of two-dimensional van der Waals heterostructure arrays 期刊论文
NATURE, 2020: 368-+
作者:  Bloch, Joel S.;  Pesciullesi, Giorgio;  Boilevin, Jeremy;  Nosol, Kamil;  Irobalieva, Rossitza N.;  Darbre, Tamis;  Aebi, Markus;  Kossiakoff, Anthony A.;  Reymond, Jean-Louis;  Locher, Kaspar P.
收藏  |  浏览/下载:84/0  |  提交时间:2020/07/03

Two-dimensional van der Waals heterostructures (vdWHs) have attracted considerable interest(1-4). However, most vdWHs reported so far are created by an arduous micromechanical exfoliation and manual restacking process(5), which-although versatile for proof-of-concept demonstrations(6-16) and fundamental studies(17-30)-is clearly not scalable for practical technologies. Here we report a general synthetic strategy for two-dimensional vdWH arrays between metallic transition-metal dichalcogenides (m-TMDs) and semiconducting TMDs (s-TMDs). By selectively patterning nucleation sites on monolayer or bilayer s-TMDs, we precisely control the nucleation and growth of diverse m-TMDs with designable periodic arrangements and tunable lateral dimensions at the predesignated spatial locations, producing a series of vdWH arrays, including VSe2/WSe2, NiTe2/WSe2, CoTe2/WSe2, NbTe2/WSe2, VS2/WSe2, VSe2/MoS2 and VSe2/WS2. Systematic scanning transmission electron microscopy studies reveal nearly ideal vdW interfaces with widely tunable moire superlattices. With the atomically clean vdW interface, we further show that the m-TMDs function as highly reliable synthetic vdW contacts for the underlying WSe2 with excellent device performance and yield, delivering a high ON-current density of up to 900 microamperes per micrometre in bilayer WSe2 transistors. This general synthesis of diverse two-dimensional vdWH arrays provides a versatile material platform for exploring exotic physics and promises a scalable pathway to high-performance devices.


A general strategy for the synthesis of two-dimensional van der Waals heterostructure arrays is used to produce high-performance electronic devices, showing the potential of this scalable approach for practical technologies.


  
Strain-hardening and suppression of shear-banding in rejuvenated bulk metallic glass 期刊论文
NATURE, 2020, 578 (7796) : 559-+
作者:  Papai, Gabor;  Frechard, Alexandre;  Kolesnikova, Olga;  Crucifix, Corinne;  Schultz, Patrick;  Ben-Shem, Adam
收藏  |  浏览/下载:36/0  |  提交时间:2020/07/03

Strain-hardening (the increase of flow stress with plastic strain) is the most important phenomenon in the mechanical behaviour of engineering alloys because it ensures that flow is delocalized, enhances tensile ductility and inhibits catastrophic mechanical failure(1,2). Metallic glasses (MGs) lack the crystallinity of conventional engineering alloys, and some of their properties-such as higher yield stress and elastic strain limit(3)-are greatly improved relative to their crystalline counterparts. MGs can have high fracture toughness and have the highest known '  damage tolerance'  (defined as the product of yield stress and fracture toughness)(4) among all structural materials. However, the use of MGs in structural applications is largely limited by the fact that they show strain-softening instead of strain-hardening  this leads to extreme localization of plastic flow in shear bands, and is associated with early catastrophic failure in tension. Although rejuvenation of an MG (raising its energy to values that are typical of glass formation at a higher cooling rate) lowers its yield stress, which might enable strain-hardening(5), it is unclear whether sufficient rejuvenation can be achieved in bulk samples while retaining their glassy structure. Here we show that plastic deformation under triaxial compression at room temperature can rejuvenate bulk MG samples sufficiently to enable strain-hardening through a mechanism that has not been previously observed in the metallic state. This transformed behaviour suppresses shear-banding in bulk samples in normal uniaxial (tensile or compressive) tests, prevents catastrophic failure and leads to higher ultimate flow stress. The rejuvenated MGs are stable at room temperature and show exceptionally efficient strain-hardening, greatly increasing their potential use in structural applications.


Bulk metallic glasses can acquire the ability to strain-harden through a mechanical rejuvenation treatment at room temperature that retains their non-crystalline structure.


  
Point stresses during reproductive stage rather than warming seasonal temperature determine yield in temperate rice 期刊论文
GLOBAL CHANGE BIOLOGY, 2017, 23 (10)
作者:  Espe, Matthew B.;  Hill, Jim E.;  Hijmans, Robert J.;  McKenzie, Kent;  Mutters, Randall;  Espino, Luis A.;  Leinfelder-Miles, Michelle;  van Kessel, Chris;  Linquist, Bruce A.
收藏  |  浏览/下载:18/0  |  提交时间:2019/04/09
climate change  cold sterility  respiration  rice  temperature  yield potential