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：The weldability of twin-induced plasticity(TWIP)steel with ultra-high strength via friction stir welding(FSW)technique was investigated,and microstructural evolution and deformation behavior of whole and micro-zones of FSW TWIP joint were studied for the first time.The results showed that the content of recrystallized grains in the stir zone(SZ)increased from 10.5％of basal material(BM)to 14.2％,and that of heat affected zone(HAZ)increased to 78.6％.The percentage of annealing twins decreased from 26.8％in BM to 11％in SZ,while increased to 35％in HAZ.Compared with the BM,the ultimate tensile strength and yield strength of the FSW joint increased to 1036 and 550 MPa,respectively,reaching 106.7％and 110.9％of BM,respectively.The elongation of the entire joint was 50.5％,which was lower than that of BM due to the nonuniform deformation during the tensile test.The engineering strain was mainly concentrated in BM and SZ and transferred to each other during the tensile test,while the engineering strain in HAZ was always the lowest.Finally,the tensile fracture occurred in the SZ.The order of ultimate tensile strength of micro-zones in the FSW joint was as follows:HAZ＞BM ≈ SZ.The order of yield strength was as follows:HAZ＞BM＞SZ.
查看更多>>摘要：As an ideal secondary energy source,hydrogen has the title of clean energy and the product of its com-plete combustion is only water,which is not polluting to the environment.Photocatalytic hydrogen pro-duction technology is an environmentally friendly,safe,and low-cost strategy that requires only an inex-haustible amount of solar energy and water as feedstock.This paper provides a detailed and detailed re-view of S-scheme heterojunction photocatalysts for photocatalytic hydrogen production,mainly including Ti02-based,Perovskite-based,CdS-based,Graphitic phase carbon nitride-based,COF-based graphdiyne-based,ZnO-based,and ZnIn2S4-based S-scheme heterojunction photocatalysts.The classification of S-scheme heterojunctions is summarized.What's more,various characterizations for direct verification of the charge migration mechanism of S-scheme heterojunctions are outlined.Based on the present study,the future potential challenges and future research trends for S-scheme heterojunctions in photocat-alytic hydrogen evolution technology are pointed out,which provides feasible strategies for the devel-opment and design of S-scheme heterojunction photocatalysts in the field of photocatalytic hydrogen evolution.
查看更多>>摘要：The sluggish redox reaction kinetics of lithium polysulfides(LiPSs)are considered the main obstacle to the commercial application of lithium-sulfur(Li-S)batteries.To accelerate the conversion by catalysis and inhibit the shuttling of soluble LiPSs in Li-S batteries,a solution is proposed in this study.The solution involves fabrication of N,S co-doped carbon coated In2O3/In2S3 heterostructure(In2O3-In2S3@NSC)as a multifunctional host material for the cathode.The In2O3-In2S3@NSC composite can reduce the Gibbs free energy for the conversion reactions of LiPSs,which results in superior performance.The synergy between different components in In2O3-In2S3@NSC and the unique 3D structure facilitate ion and electron transport in Li-S batteries.The In2O3-In2S3@NSC/Li2S6 cathode exhibits excellent rate capacity,with a capacity of 599 mAh g-1 at 5.5 C,and good cycle stability,with a capacity of 436 mAh g-1 after 1000 cycles at 1 C.Overall,this study proposes a promising solution to improve the energy storage properties of Li-S batteries,which could potentially facilitate the commercialization of Li-S batteries.
查看更多>>摘要：Chemical short-range orders(CSROs),as the built-in sub-nanoscale entities in a high-/medium-entropy alloy(H/MEA),have aroused an ever-increasing interest.With multi-principal elements in an H/MEA to form a complex concentrated solution,a variety of sub-systems of species exist to induce the metastable ordered compounds as candidates for ultimate CSROs.The issues remain pending on the origin of CSROs as to how to judge if CSRO will form in an H/MEA and particularly,what kind of CSROs would be stably produced if there were multiple possibilities.Here,the first-principles method,along with the proposed local formation energy calculation in allusion to the atomic-scale chemical heterogeneities,is used to predict the CSRO formation based on the mechanical stability,thermodynamic formation energy,and electronic characteristics.The simulations are detailed in an equiatomic ternary VCoNi MEA with three kinds of potential compounds,i.e.,L11,L12,and B2,in the face-centered cubic matrix.It turns out that L11 is stable but hard to grow up so as to become the final CSRO.L11 is further predicted as CSROs in CrCoNi,but unable to form in FeCoNi and CrMnFeCoNi alloys.These predictions are consistent with the experimental observations.Our findings shed light on understanding the formation of CSROs.This method is applicable to other H/MEAs to design and tailor CSROs by tuning chemical species/contents and thermal processing for high performance.
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