查看更多>>摘要：Conductive hydrogels have attracted extensive attention owing to their promising application prospects in flexible and wearable electronics.However,achieving both high sensitivity and mechanical robust-ness remains challenging.Herein,a novel and versatile conductive hydrogel based on the hybrid assem-bly of conductive cellulose nanofiber(CNF)networks has been designed and fabricated.Assisted by the templating effect of CNFs and stabilizing effect of negatively charged poly(styrene sulfonate)(PSS),con-ducting polymer poly(3,4-ethylenedioxythiophene)(PEDOT)was self-organized into three-dimensional nanostructures which constructed a robust conductive network after in-situ oxidative polymerization.The unique structure derived from CNF bio-template endowed polyacrylamide(PAM)hydrogels with improved electrical conductivity and excellent mechanical performance.As a result,the as-fabricated CNF/PEDOT:PSS/PAM hydrogel exhibited an ultimate tensile strain of 1881％and toughness of 3.72 MJ/m3,which were 4.07 and 8.27 times higher than the CNF-free hydrogel,respectively.More significantly,the resultant hydrogel sensor showed highly desirable sensing properties,including remarkable sensing range(1100％),high gauge factor(GF=5.16),fast response time(185 ms),and commendable durability,as well as good adhesiveness.Moreover,the hydrogel sensor was able to distinguish subtle physiological activ-ities including phonation and facial expression,and monitor large human body motions such as finger flexion and elbow blending.Besides,it was feasible to integrate the strain sensor on the joints of robots to recognize complicated machine motion signals,showing potential in advanced human-machine inter-actions.
查看更多>>摘要：Synthesizing bimetallic nanomaterials,with noble metals as the surface layers and inert metals as the substrates,has been proven to be an effective way to reduce the use of noble metals with maintained cat-alytic activity.However,an atomic diffusion from the inert substrate to the surface during the long-term operation has been reported to significantly decrease the activity.In this work,a series of catalysis-inert Cu-coated Ni foil were fabricated through electrodeposition and their activities for alkaline hydrogen evo-lution were investigated.Notably,the Ni/Cu-60 sample showed a similar catalytic property with pure Ni foil and only a slight decrease in HER activity was observed.The X-ray photoelectron spectroscopy(XPS)results indicated a decreased electron concentration of Cu in Ni/Cu-60,and theoretical calculations further demonstrated the electron transfer between the Ni substrate and Cu layer.Our results reveal that a spe-cific composition or structure of an inert metal layer might not significantly decrease the electrocatalytic activity of active metals.Moreover,there are more possibilities for the rational design of metal-based catalysts for electrocatalysis.
查看更多>>摘要：In this work,a variety of CuxNi2-xFe(CN)6(x=0,0.4,0.8,1.2,1.6,2)cathodes for ammonium ion bat-teries are prepared and their electrochemical performances are investigated.During the introduction of copper in nickel hexacyanoferrate,the electrochemical performance varies without changing the structure of nickel hexacyanoferrate.The increase of Cu content in nickel hexacyanoferrate leads to the enhance-ment of reaction potential and capacity.Electrochemical results suggest that the substitution of Cu for Ni has a positive effect on improving the cycling stability and rate capacity of nickel hexacyanoferrate when x in CuxNi2-xFe(CN)6 is less than 0.4.Therefore,Cu0.4Ni1.6Fe(CN)6 exhibits the best cycling per-formance(capacity retention of 97.54％at 0.3 C)and the highest rate capacity(41.4 mAh g-1 at 10 C)in CuxNi2-xFe(CN)6.Additionally,the X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)tests also reveal that the structural evolution of Cu0.4Ni1.6Fe(CN)6 is highly reversible upon NH4+storage.Therefore,this work proposes a candidate material for ammonium-ion batteries and offers a novel avenue for adjusting the operating potential of the material.
查看更多>>摘要：This study investigates the phase constitutions and transformations that occur in the mushy zone and in the adjacent phase fields of a directionally solidified Ti-44Al-8Nb-1Cr alloy via quenching technique.The results indicate that the mushy zone consists of unmelted β dendrites and interdendritic liquid,whose formation can be attributed to the difference in melting point aroused by local heterogeneity in solutecontent.The β dendrite is composed of numerous subgrains with various orientations.During quenching,the β dendrite transforms into Widmanstätten α via a precipitation reaction,owing to the decreasing cooling rate caused by heat transfer from the surrounding liquid.Additionally,after quenching,the interdendritic liquid is transformed into y plates.Within the single β phase field and the lower part of the mushy zone,a massive transformation of β to γ occurs.Conversely,in the β+α phase field,both β and α phases are retained to ambient temperature.During the heating process,the transformation of α → β gives rise to the formation of β variants,which affects the orientation of β dendrites in the mushy zone.The growth kinematics of the α → β transformation was elucidated,revealing the preferential growth directions of<111>and<112>for β variants.Furthermore,this study presents an illustration of the formation process of the mushy zone and the microstructural evolution during the heating and quenching process.
查看更多>>摘要：Sn/ENIG has recently been used in flexible interconnects to form a more stable micron-sized metallurgical joint,due to high power capability which causes solder joints to heat up to 200 ℃.However,Cu6Sn5 which is critical for a microelectronic interconnection,will go through a phase transition at temperatures between 186 and 189 ℃.This research conducted an in-situ TEM study of a micro Cu/ENIG/Sn solder joint under isothermal aging test and proposed a model to illustrate the mechanism of the microstructural evolution.The results showed that part of the Sn solder reacted with Cu diffused from the electrode to form η'-Cu6Sn5 during the ultrasonic bonding process,while the rest of Sn was left and enriched in a region in the solder joint.But the enriched Sn quickly diffused to both sides when the temperature reached 100 ℃,reacting with the ENIG coating and Cu to form(NixCu1-x)3Sn4,AuSn4,and Cu6Sn5 IMCs.After entering the heat preservation process,the diffusion of Cu from the electrode to the joint became more intense,resulting in the formation of Cu3Sn.The scallop-type Cu6Sn5 and the seahorse-type Cu3Sn constituted a typical two-layered structure in the solder joint.Most importantly,the transition between η and η'was captured near the phase transition temperature for Cu6Sn5 during both the heating and cooling process,which was accompanied by a volume shifting,and the transition process was further studied.This research is expected to serve as a reference for the service of micro Cu/ENIG/Sn solder joints in the electronic industry.
查看更多>>摘要：Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element(3D CPFE)simulations,co-deformation and instability of hetero-phase interface in different material sys-tems were herein studied for polycrystalline metal matrix composites(MMCs).Local stress and strain fields in two types of 31ayer MMCs such as fcc/fcc Cu-Ag and fcc/bcc Cu-Nb have been predicted un-der simple compressive deformations.Accordingly,more severe strain-induced interface instability can be observed in the fcc/bcc systems than in the fcc/fcc systems upon refining to metallic nanolayered composites(MNCs).By detailed analysis of stress and strain localization,it has been demonstrated that the interface instability is always accompanied by high-stress concentration,i.e.,thermodynamic char-acteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase interface.It then follows that the thermodynamic driving force △G and the kinetic energy barrier Q during dislocation and shear banding can be adopted to classify the deformation modes,following the so-called thermo-kinetic correlation.Then by inserting a high density of high-energy interfaces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interface allows a successful establishment of MMCs with the high △G-high Q deformation mode,which ensures high hardening and uniform strain distri-bution,thus efficiently suppressing the shear band,stabilizing the hetero-phase interface,and obtaining an exceptional combination in strength and ductility.Such hetero-phase interface chosen by a couple of thermodynamics and kinetics can be defined as breaking the thermo-kinetic correlation and has been proposed for artificially designing MNCs.
查看更多>>摘要：In order to maintain the optimal operating temperature of the battery surface and meet the demand for thermal storage technology,battery thermal management system based on phase change materials has attracted increasing interest.In this work,a kind of core-shell structured microcapsule was synthesized by an in-situ polymerization,where paraffin was used as the core,while methanol was applied to mod-ify the melamine-formaldehyde shell to reduce toxicity and improve thermal stability.Moreover,three different types of heat conductive fillers with the same content of 10 wt.％,i.e.,nano-Al2O3,nano-ZnO and carbon nanotubes were added,generating composites.The microcapsules were uniform,and were not affected by the thermal fillers,which were evenly dispersed around.The composite sample with carbon nanotubes(10 wt.％)showed the highest thermal conductivity of 0.50 W/(m K)and latent heat of 139.64 J/g.Furthermore,according to the leakage testing and battery charge/discharge experiments,compared with Al2O3 and ZnO,the addition of carbon nanotubes remarkably enhances the heat storage ability as latent heat from 126.98 J/g for the prepared sample with Al2O3 and 125.86 J/g for the one with ZnO,then to 139.64 J/g,as well as dissipation performance as a cooling effect by decreasing the sur-face temperature of battery from 2％to 12％of microcapsule,composite sample with carbon nanotubes presents a broad application prospect in battery thermal management system and energy storage field.
查看更多>>摘要：In this work,we proposed a novel Cu/θ dual nanoparticles strategy to tailor the austenite characteris-tics of a medium Mn steel via a tempering-annealing process to optimize the mechanical properties.We explored the effects of Cu-rich particles and cementite precipitated in the tempering process on the austenite reversion during the subsequent annealing process.Both experiments and numerical simula-tions verified that the austenite inherited from cementite had a finer size and a higher Mn enrichment compared with the austenite originating from the tempered martensite matrix.In addition,quantitative evaluations revealed that the pinning effect exerted by the Cu-rich particles could significantly hinder the α/γ interface migration and the recrystallized grain growth,thereby further refining the final mi-crostructure.With contributions from the effects of dual nanoprecipitates on the austenite reversion,the heterogeneous austenite grains inherited from varying nucleation sites ensured the sustained and gradual deformation-induced martensite and twinning formation.Therefore,the Cu-added steels subjected to a tempering-annealing process achieved synergetic enhancement of the tensile strength from 1055 MPa to 1250 MPa and elongation from 33％to 45％.This strategy may provide new guidance for the development and alloy design of high-performance medium Mn steels.
查看更多>>摘要：Recently,S-scheme heterojunctions have gained considerable attention in the field of photocatalytic en-vironmental remediation as their potential to achieve efficient spatial charge separation coupled with strong redox capacities.Herein,this review provides an overview of the current state-of-the-art in the development of S-scheme-based photocatalysts for the purification of environmental contaminants.The review first covers the fundamentals of heterogeneous photocatalysis for environmental purification.Sub-sequently,an introduction to the background,mechanism,design principles,and characterization tech-niques of S-scheme heterojunctions is presented.Then,the review presents a comparison and summary of using various S-scheme photocatalysts for the removal of several target pollutants,such as bacteria,heavy metals,nitrogen oxides,antibiotics,and phenols.Additionally,the modification strategies of S-scheme heterojunction photocatalysts are also provided.Finally,a brief discussion of the challenges and prospects associated with S-scheme photocatalytic systems is demonstrated.
查看更多>>摘要：MXene-contained paper is a good choice to design ultrathin and flexible electromagnetic interference(EMI)shielding materials.However,the deficiencies in strength and stability of MXene-contained paper impede its practical applications.Herein,a composite paper was proposed to address the problems,in which a filter paper was modified with a three-layer structured surface via a facile layer-by-layer coat-ing procedure.Specifically,the TEMPO-oxidized cellulose nanofibers(TOCN)/cationic starch(CS)/MXene gel layer and TOCN/MXene nacre structure layer ensured the good EMI shielding and mechanical per-formances of the composite paper,while the uppermost TOCN/CS hydrogel film layer mainly protected MXene.The composite paper achieved an EMI SE of 40.3 dB at a thickness of merely 0.1894 mm(SE/t value of ca.212.8 dB mm-1,SSE/t values of ca.13216 dB cm2 g-1)and the total MXene dosage was 20 g m-2.Its tensile strength could be up to 11.7 MPa while the original filter paper was 6.4 MPa.Four pieces of this composite papers could be easily packed together to attain an EMI SE of nearly 70 dB.Importantly,the hydrogel film layer efficiently protected the MXene and maintained the EMI shielding performance of the composite paper when immersed in different liquids including water,HC1(1 M)and ethanol,due to the dense and compact structure of hydrogel film layer.This work provides a practical way to develop ultrathin,flexible and durable EMI shielding materials.
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