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Using molecular dynamics simulations, we study the roles of geometry, boundary conditions, and nanotwinned structure on the mechanical response of Cu ⟨ 110 ⟩ cylindrical nanopillars under tensile loading. Specifically, we investigate the stress–strain responses, deformation mechanisms, and defect evolution in nanopillars of varying height-to-diameter ( H / D ) ratios, capped with rigid layers to resemble hard coatings, and with microstructures consisting of columnar grains with and without nanoscale coherent twin boundaries (CTBs). Our results indicate that the disk-shaped nanopillars (DPs) with low H / D ratios exhibit high yield strength, significant triaxial tension stress, and pronounced plastic deformation. This deformation is accompanied by high defect density near the Cu/rigid layer interfaces, driven by dislocation pile up from multiple activated slip systems. Conversely, the deformed rod-shaped nanopillars of large ratios exhibit localized plastic deformation characterized by necking phenomena. Our results reveal the dominant role of Shockley type dislocations in plastic deformation, particularly in DPs, which display higher dislocation densities due to reduced dislocation annihilation events at free surfaces and pile up at interfaces. Notably, deformed DPs exhibit a unique vacancy-induced nanovoid nucleation mechanism at interfaces, resulting from the coalescence of vacancies generated during shearing of jogs. Additionally, the results demonstrate that dislocations glide between CTBs forming wide stacking faults, or traverse CTBs in a zigzag pattern as perfect dislocations, confirming a recently hypothesized cross-slip-like transmission in a recent experimental observation. Our simulations indicate that nanometer-spaced CTBs in Cu ⟨ 110 ⟩ nanopillars act as weak barriers to dislocation motion during tensile loading, leading to only a marginal enhancement of mechanical properties. [ABSTRACT FROM AUTHOR]

Clean energy and green solvents have attracted wide attention due to their non-toxic, biodegradable, and recyclable properties. Deep eutectic solvent (DES), as a green solvent, has advantages in the formation of nanocellulose. To reveal the formation mechanism during cellulose nanocrystal (CNC) preparation, different carboxylic acid DESs are compared in the optimal experimental conditions. Experimental observations show that oxalic acid (OA) DESs can fabricate CNCs with higher yield, higher crystalline index than that of citric acid series. Moreover, crystal water molecules in DESs promote the reaction activity of DESs in the CNC formation. To understand the interaction among the DES/cellulose complex, molecular dynamics simulations and quantum chemical calculations were applied to investigate the arrangement of CNCs in the atomic scale. The radial distribution function and intermolecular interactions indicate that the non-covalent intermolecular interactions between DESs and cellulose are strong, which could be further enhanced by the crystal waters in DESs. Reaction pathways during the formation of CNCs were revealed by computational simulations, which show that OA is more prone to react with cellulose in esterification and acidolysis reactions. Both computational and experimental results demonstrate that the OA DESs are more beneficial in the production of CNCs. The synergistic effects of chemical reactions and non-covalent interactions favor the formation of CNCs by DESs. [ABSTRACT FROM AUTHOR]

Conductive hydrogels as promising material candidates for soft electronics have been rapidly developed in recent years. However, the low ionic conductivity, limited mechanical properties, and insufficient freeze‐resistance greatly limit their applications for flexible and wearable electronics. Herein, aramid nanofiber (ANF)‐reinforced poly(vinyl alcohol) (PVA) organohydrogels containing dimethyl sulfoxide (DMSO)/H2O mixed solvents with outstanding freeze‐resistance are fabricated through solution casting and 3D printing methods. The organohydrogels show both high tensile strength and toughness due to the synergistic effect of ANFs and DMSO in the system, which promotes PVA crystallization and intermolecular hydrogen bonding interactions between PVA molecules as well as ANFs and PVA, confirmed by a suite of characterization and molecular dynamics simulations. The organohydrogels also exhibit ultrahigh ionic conductivity, ranging from 1.1 to 34.3 S m−1 at −50 to 60 °C. Building on these excellent material properties, the organohydrogel‐based strain sensors and solid‐state zinc–air batteries (ZABs) are fabricated, which have a broad working temperature range. Particularly, the ZABs not only exhibit high specific capacity (262 mAh g−1) with ultra‐long cycling life (355 cycles, 118 h) even at −30 °C, but also can work properly under various deformation states, manifesting their great potential applications in soft robotics and wearable electronics. [ABSTRACT FROM AUTHOR]

• A novel Janus hydrogel was prepared as solar steam generation evaporator. • The Janus hydrogel worked stably with an evaporation rate of 3.53 kg m−2 h−1 under 1 sun. • The desalination and purification performance of the Janus hydrogel was evaluated. • Dye could be effectively removed by PDA/TiO 2 nanoparticles in Janus hydrogel. Solar-powered water distillation is one of the effective and promising ways of water purification. However, new high-efficiency evaporators are especially needed to reduce the energy requirement and improve water yields under natural sunlight. In this study, a Janus structured hydrogel with an interpenetrating double network was formed by polyvinyl alcohol and natural polysaccharide to speed up solar water purification. Due to its unique pore structure, water molecules can quickly escape from the surface of Janus hydrogel by molecular dynamics simulations. The Janus evaporator worked stably and the evaporation rate was achieved to 3.53 kg·m−2·h−1 under 1 sun illumination, which was attributed to the outstanding water transport capacity and thermal localization capacity. Meanwhile, the Janus-based solar evaporator exhibited excellent durability in wide acid–base range (pH 1–13) and salinity range (0–350‰), and long term (30 days). The daily yield of the Janus hydrogel reached 24.5 kg·m−2·h−1 in outdoor tests. The Janus evaporator enables efficient desalination and purification of other unconventional water sources, and can degrade more than 95% of organic dyes (trypan blue and Congo red) as a result of the synergistic effect of Polydopamine (PDA) /TiO 2 nanoparticles. This Janus structured hydrogel evaporator opens up potential applications in desalination and wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Devised a molecular dynamics/time-stamped force-bias Monte Carlo (MD/tfMC) simulation method. • Discovered a new FCC-Cu[110]//TiN[001] orientation relationship via UHV sputter deposition. • MD/tfMC simulations showed that Cu grows on TiN(001) initially as BCC-Cu[001]//TiN[001] • BCC-Cu transforms to nanotwinned FCC-Cu[110] via a Nishiyama-Wasserman type shear mechanism. • Investigated Cu growth on N- and Ti- terminated TiN(111) surfaces in detail via simulation. Using a sequential molecular dynamics (MD)/time-stamped force-bias Monte Carlo (tfMC) algorithm to simulate the deposition of Cu species onto a TiN(001) substrate at 600 K, it is shown for the first time that at the very early stage of growth, BCC-Cu grows pseudomorphically on the TiN(001) substrate as a very thin continuous film with the BCC-Cu[001]//TiN[001] growth direction. By increasing the thickness of the Cu thin film, however, the film transforms through the Nishiyama-Wasserman mechanism from BCC into predominantly FCC-Cu with abundant nanotwins, which is the same type of structure obtained in the experiment conducted here via a dc magnetron sputter deposition technique to grow Cu on TiN(001) at 105 °C. In agreement with the experimental observations in the literature, the devised MD/tfMC is employed further to reveal that on the N-terminated TiN(111), Cu shows a very poor wettability, and FCC-Cu(111) grows vertically in the form of tall 3D islands. On Ti-terminated TiN(111) surface, however, FCC-Cu(111) initially grows in the form of 2D islands with high wettability. With additional Cu deposition, a triangular misfit dislocation network is generated at the Cu(111)//Ti-terminated TiN(111) interface with subsequent formation of a two-layer nanotwin with its twinning plane parallel to the surface substrate. [ABSTRACT FROM AUTHOR]