查看更多>>摘要：Grain refinement to the nanocrystalline regime is the most effective way to strengthen materials but this often deteriorates the grain-size thermal stability and plasticity.Here we manufactured a nanocrystalline face centred cubic CrCoNi medium entropy alloy with columnar grains via magnetron sputtering.Com-pression of CrCoNi pillars with diameters of～1 μm revealed a record high yield strength of～5 GPa for pillars with face centred cubic structures and engineering plastic strain of＞30％.The alloy possessed an outstanding grain-size thermal stability even at 1073 K.Both nanocrystalline grain size and a high density of nanotwins/stacking faults are critical to the exceptional yield strength.Deformation twinning,grains refinement during deformation,grain boundary sliding and random grain orientation all contribute to the large plasticity.The outstanding thermal stability is attributed to the sluggish diffusion effect and the low energy of twin boundaries.
查看更多>>摘要：Interfacial solar-driven evaporators have presented great potential for water purification owing to their low energy consumption and high steam generation efficiency.However,their further applications are hindered by the high costs and complicated fabrication processes.Here,a scalable bilayer interfacial evap-orator was constructed via an affordable technique,in which carbon black deposited nonwoven fabric(CB@NF)was employed as the upper photothermal layer,as well as PVA/starch hybrid hydrogel for self-floating and water transport.Under simulated one sun irradiation,CB@NF layer displayed excellent pho-tothermal conversion performance,whose temperature could increase 30.4℃within 15 min.Moreover,the introduction of starch into PVA endowed the hybrid hydrogels with considerable water-absorption capability on the premise of ensuring mechanical properties.The resultant CB@NF/PVA/starch compos-ites achieved superior interfacial adhesion performance with interfacial toughness at about 200 J m-2.Combining with good evaporation performance,salt-rejection property and high purification efficiency on pollutants,this evaporation system would become a promising candidate to alleviate water shortage.
查看更多>>摘要：The Ni3Al-based alloy has been considered as a robust catalyst for oxygen evolution reaction(OER)due to its long-term durability and acceptable activity.However,related reports about understanding the cat-alytic mechanism are rare and desirable.Herein,the effect of γ/γ'phase lattice mismatch on the cat-alytic performance caused by various cooling rates after solution heat treatment was investigated.With decreasing cooling rate,the morphologies of y'precipitates transformed from sphere to cube and the lattice mismatch increased from-0.172％to-0.409％.The increased lattice mismatch facilitated the forma-tion of the active β-NiOOH phase and enhanced the intrinsic catalytic activity,resulting in the optimized OER overpotential of 240 mV at a current density of 10 mA cm-2 with a Tafel slope of 66.1 mV dec-1 and a stability of 200 h in 1 M KOH.This work reveals the lattice mismatch effect on OER and provides a potential candidate for OER.
查看更多>>摘要：Magnetically anisotropic nanoparticle monolayer films are of great interest for the development of ap-plications such as high-density data storage,sensors.However,the formation of large-scale magnetically anisotropic monolayer film is a challenging task.Here,we provide a new way to fabricate large-scale area of Fe3O4 nanoparticle monolayer films by vacuum deposition technique(matrix-assisted pulsed laser evaporation,MAPLE).During the deposition process,only interactions between nanoparticles influence nanoparticle self-assembly behaviors.A strong magnetic anisotropy,characterized by in-plane and out-of-plane coercivity and saturation field obtained by DCM(dynamic cantilever magnetometry),was obtained both in cubic and spherical Fe3O4 nanoparticle monolayer films.The inter-particle dipolar interaction but not crystal anisotropy is responsible for this effective magnetic anisotropy,which has been proved by Monte-Carlo simulations.
查看更多>>摘要：Body-centred cubic(BCC)metals are known to have unstable intrinsic stacking faults and high resis-tance to deformation twinning,which can strongly influence their twinning behaviour.Though twinning mechanisms of BCC metals have been investigated for more than 60 years,the atomistic level dynam-ics of twinning remains under debate,especially regarding its impact on competition between twinning and slip.Here,we investigate the atomistic level dynamics of twinning in BCC tungsten(W)nanowires using in situ nanomechanical testing.Quantitative experimental studies directly visualize that deforma-tion twins in W nanowires have a minimum size of six-layers and grow in increments of approximately three-layers at a time,in contrast to the layer-by-layer growth of deformation twins in face-centred cu-bic metals.These unique twinning dynamics induces a strong competition with ordinary dislocation slip,as exhibited by a size-dependent dislocation-to-twin transition in W nanowires,with a transition size of～40 nm.Our work provides physical insight into the dynamics of twinning at the atomic level,as well as a size-dependent dislocation-twinning competition,which have important implications for the plastic deformation in a broad class of BCC metals and alloys.
查看更多>>摘要：In this study,the inhomogeneous dealloying phenomenon during the liquid metal dealloying(LMD)was investigated using Fe50Ni50+Mg and(FeCo)50Ni50+Mg systems.For the Fe50Ni50+Mg system,the inhomo-geneous dealloying and wetting of Mg melt occurred along triple junction(TJ)and grain boundary(GB).Temperature increase enhances the inhomogeneous dealloying kinetics and leads to the formation of the plate-shaped abnormal ligaments at the GB region.The energy banlance between a GB energy(γGB)and solid-liquid interface energies(γsl)is the key factor governing the inhomogeneous dealloying and wetting.Particularly,the low-energy twin boundaries were unaffected by the inhomogeneous dealloying.Therefore,precursor microstructure is an important factor determining the final morphology of dealloyed material as well as its physical properties.In the case of the(FeCo)50Ni50 precursor,all TJ and GB were stable against the preferred penetration of Mg melt from 600℃to 800℃.It was concluded that a minor addition of alloying elements(V or Cr)changes GB characteristics as well as γsl of the precursor alloy.Consequently,this significantly influences dealloying mechanisms and final morphology of the dealloyed material.The current findings demonstrate the importance of GB engineering in the precursor materials for the technological application of liquid metal dealloying for the synthesis of advanced structural and functional materials.
查看更多>>摘要：Nowadays,photovoltaic effect has been widely studied in various ferroelectric materials due to its ap-plications as optoelectronic devices.In this work,with BiFeO3(BFO)films as the photovoltaic materials,we report the effects of Eu3+doping content on the phase structure,ferroelectric and optical properties of BFO films grown on Ca0.96Ce0.04MnO3/YAlO3(001)substrate.We found that a small doping level of 0.05 could induce a phase change of BFO from tetragonal to rhombohedral,due to the shrinking of the lattice upon Eu3+doping and the breaking of surface terrace structure induced by Ca0.96Ce0.04Mn03 layer.This results in a sharp band gap reduction from 3.30 eV to 2.60 eV,and a decrease in the coercivity of ferroelectric polarization switching.Based on these findings,we investigate the photovoltaic effects of ITO/EuxBi1-xFeO3/Ca0.96Ce0.04MnO3 vertical capacitors.It is found that the short-circuit current density(Jsc)decreases with increasing Eu3+doping,whereas the open-circuit voltage(Voc)first increases to a level of 0.1 V and then decreases with further Eu3+doping.This could be explained by the combined ef-fect of Schottky-junction and depolarization field on the photovoltaic process.Our research suggests that a moderate Eu3+doping is helpful for enhancing the photovoltaic effect of BFO thin film devices.
查看更多>>摘要：As a semiconductor material with a 2D-laminate structure,g-C3N4(bandwidth 2.7 eV)has a similar struc-ture and excellent performance to graphene.However,high surface energy and photogenerated e-h re-combination of g-C3N4 seriously hinder its application in the field of marine anticorrosion and antifouling.To solve these problems,we synthesized the g-C3N4 nanosheets decorated with ZnO nanoring via chem-ical etching technology.Whether the NR ZnO-CNNs have surface protection performance among the pure EP on the corrosion protection for metal substrate were investigated.The antifouling properties NR ZnO-CNNs hybrid were also estimated through photocatalytic bacterial and algae resistance tests.Combined with the electrochemical results,it was found that the impedance modulus of NR ZnO-CNNs/EP within 45 days showed two orders of magnitude higher than that of pure EP in the 3.5 wt％NaCl solution.Be-sides,Local electrochemical impedance spectroscopy(LEIS)further explored the anticorrosion behavior of NR ZnO-CNNs/EP coating,which indicated that the NR ZnO-CNNs/EP coating with a scratch maintained an excellent corrosion resistance between 0-24 h.Under the visible light conditions,the lifetime of pho-togenerated e-h was prolonged due to the formation of NR ZnO-CNNs heterojunction structure,it was observed that the antibacterial rate against Bacillus subtilis reached 100％within 8 h.An Antialgae test was performed on chlorella seawater solution,which indicated that 5 mg/mL of NR ZnO-CNNs hybrid could make chlorella sharply reduce within 4 days.Simultaneously,the corrosion protection and photo-catalytic antifouling mechanisms of NR ZnO-CNNs were proposed,thus it provided a broader platform for the design of versatile marine protection materials.
查看更多>>摘要：Simultaneously achieving high energy product and high coercivity in the 2:17-type Sm-Co-Fe-Cu-Zr high temperature magnets has been closely relied on long-term isothermal aging to develop complete cellu-lar nanostructure.In this work,we report a novel stress-aging approach that can substantially shorten the aging time to fabricate high-performance Sm-Co-Fe-Cu-Zr magnets.As exhibited by a model magnet Sm25Co50.2Fe16.2Cu5.6Zr3,0(wt.％),applying 90 MPa compressive stress can shorten the aging time from 20 h for conventional isothermal aging to 10 h at the same aging temperature for achieving nearly equiv-alent magnetic performance.Further comparative study between the 10 h-aged samples under stress-containing and stress-free conditions revealed that the stress not only promotes the precipitation of the cell boundary phase that are essential for enhancing the coercivity but also accelerates the dissociation of the cell edge defects that are detrimental to squareness factor,without destroying the[001]crystal-lographic texture.Such microstructural improvements enable the achievement of high-performance with maximum energy product of～30 MGOe and coercivity above 35 kOe at reduced aging time.
查看更多>>摘要：Homogeneous crystal nucleation is prone to formation of defects and often experiences heterogeneities,the inferences of which are crucial in processing crystalline materials and controlling their physical prop-erties.It has been debated in literature whether the associated heterogeneities are an integral part of the homogenous nucleation.In this study by integrating a probabilistic approach with large-scale molecular dynamics simulations based on the most advanced high-temperature interatomic potentials,we attempt to address the ambiguity over the sources and mechanisms of heterogeneities in homogenous nucleation during solidification of pure melts.Different classes of structured metals are investigated for this purpose,including face-centered cubic aluminum,body-centered cubic iron,and hexagonal close-packed magne-sium.The results reveal,regardless of the element type or the solidified crystal structure,that the densi-fication process of liquid metals is accompanied by short-range orderings of atoms prior to the formation of crystals,controlling the heterogeneities during homogenous nucleation.
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