查看更多>>摘要：Conventionally,interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites.In this study,we found that interface effects between different fillers have similar behavior.BN and BaTi03 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes (BT-fiber/BN ＜ BT-fiber@BN ＜ BT-fiber&BN),and introduced into a polyimide (PI)matrix to form composite films.Considerably enhanced breakdown strength and energy storage density were obtained in BT-fiber&BN/PI composites owing to strong interface bonding,compared to other two composite fillers,which are well supported by the data from the finite element simulation.Specifically,PI composites with only 3 wt％ BT-fiber&BN possess an optimized energy storage density of approximately 4.25 J/cm3 at 4343 kV/cm.These results provide an effective way for adjusting and improving the energy storage properties of polymer-based composites.
查看更多>>摘要：In this work,a Janus-type dual-ligand metal-organic frameworks derived bimetallic (Fe,Co)P nanoparticles embedded carbon nanotube (CNT) skeleton (DLD-FeCoP@CNT) is presented and synthesized via a facile "co-coordination synthesis" strategy.The DLD-FeCoP@CNT hybrid shows much better performances for OER and HER with much lower Tafel slope of 39.6 (57.1) mV dec-1,an overpotential of 286 (166) mV@10 mA cm-2 and better stability for OER (HER) in 1 M KOH.Being both cathode and anode for water splitting,it requires only a low voltage of 1.67 V to obtain 10 mAcm-2 with nearly 100％ faradaic efficiency,which is close to Pt/C//RuO2 cell.Density functional theory calculations based on the bimetallic phosphide (Fe0.3Co0.7P) model reveal that,compared with the monometallic FeP or CoP,the enhanced catalytic activities of Fe0.3Co0.7P is mainly manifested in its free energy of H adsorption (△GH*) closer to zero,larger binding strength for H2O and higher electrical conductivity.
查看更多>>摘要：Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni-Mn-based multiferroic alloys.Recently,experimental studies on B alloying shed new light on this issue.However,the knowledge related to B alloying is limited until now.More importantly,the mechanism of the improved ductility,which is intrinsically related to the chemical bond that is difficult to reveal by routine experiments,is still unclear.In this context,by first-principles calculations,the impact and the correlated mechanism of B alloying were systemically studied by investigating four alloying systems,i.e.,(Ni2-xBx)MnGa,Ni2(Mn1-xBx)Ga,Ni2Mn(Ga1-xBx) and (Ni2MnGa)1-xBx.Results show that B prefers the direct occupation manner when it replaces Ni,Mn and Ga.For interstitial doping,B tends to locate at octahedral rather than tetrahedral interstice.Calculations show that the replacement of B for Ga can effectively improve (reduce) the inherent ductility (inherent strength) due to the weaker covalent strength of Ni(Mn)-B compared with Ni(Mn)-Ga.In contrast,B staying at octahedral interstice will lead to the formation of new chemical bonds between Ni(Mn) and B,bringing about a significantly improved strength and a greatly reduced ductility.Upon the substitutions for Ni and Mn,they affect both the inherent ductility and strength insignificantly.For phase transition,the replacement of B for Ga tends to destabilize the austenite,which can be understood in the picture of the band Jahn-Teller effect.Besides,the substitution for Ga would not lead to an obvious reduction of magnetization.
查看更多>>摘要：Components of Ti and Al dissimilar alloys were obtained by wire and arc additive manufacturing using two cold metal transfer (CMT) modes.Direct current CMT (DC-CMT) mode was used for Ti alloy deposition,and DC-CMT or CMT plus pulse (CMT + P) mode was used for the Al alloy deposition.During deposition of the first Al alloy layer,little and a significant amount of Ti alloy were melted using DC-CMT and CMT +P mode,respectively.TiAl3 formed in the reaction layer when DC-CMT mode was used,while TiAl3,TiAl,and Ti3Al formed in the reaction layer when CMT + P mode was used.Compared to using DC-CMT mode,more cracks occurred when using CMT + P.The nanohardness of the reaction layer was between that of the Al and Ti alloys,irrespective of the CMT modes.The average tensile strengths of the samples us ingDC-CMT and CMT + P mode were 108 MPa and 24 MPa,respectively.DC-CMT mode was more suitable for the wire and arc additive manufacturing of Ti/Al dissimilar alloys.
查看更多>>摘要：The Ni43.75Mn37.5In12.5Co6.25 alloy was obtained by using the spark plasma sintering (SPS) technique.The martensitic transformation,magnetic and mechanical properties of the SPS alloy were investigated.Key findings demonstrate that the martensitic transformation temperature of this alloy is about 10 K lower than that of the as-cast one.Both SPS and as-cast alloys show a 7 layered modulated martensite (7M) at room temperature.The compressive fracture strength and strain of the SPS alloy increase by 176.92％ and 33.33％ compared with the as-cast alloy,achieving 1440 MPa and 14％,respectively.The maximum magnetic entropy change △Sm is 17.1 J kg-1 K-1 for the SPS alloy at the magnetic field of 5 T.
查看更多>>摘要：While manganese-based cathodes have been intensively studied for zinc-ion batteries (ZIBs),the limited rate capability and cycle life have always been a difficult problem to be solved.Here,we report a mixed valent manganese oxide (MnOx) cathode with superior electrochemical performance,which exhibits a high specific capacity of 450 mA h/g at 0.2 C and a satisfactory specific capacity of 158.3 mA h/g at a high rate of 5 C.The mixed cathode system reduces the charge transfer resistance,and show good surface stability and adsorption properties,so it is beneficial for the storage of Zn2+.Meanwhile,coaxial fiber ZIBs (CFZIBs) with splendid flexibility are assembled utilizing the elaborately prepared cathode material.The CFZIBs achieve a reversible capacity of 255.8 mA h/g and the capacity retention rate is as high as 80 ％ after 1000 bending deformations.This study provides new opportunities for designing ZIBs with high performance and high flexibility.
查看更多>>摘要：As a new class of lithium rich cathodes,disordered rock-salt cathodes have been of primary interest,because of their ability to deliver a promisingly high capacity up to 300 mA h/g.Nevertheless,some fundamental issues are yet to be fully understood and a comprehensive mastering of their solid-state chemistry,kinetics and thermal stability is required.Here,we select a high capacity cation-disordered positive electrode-Li1.2Ni0.4Nb0.4O2 as a model compound to study intrinsic reaction mechanism,including charge compensation mechanism,kinetics,thermal stability,and structural evolution.By combining soft and hard X-ray absorption spectroscopy (XAS),X-ray photoelectron spectroscopy (XPS) with operando and exsitu differential scanning calorimetry (DSC),galvanostatic intermittent titration technique (GITr),cyclic voltammetry (CV),and X-ray diffraction (XRD),we present holistic information on disordered rock-salt cathode.This work provides beneficial insights into designing and tailoring new positive electrodes with disordered rock-salt structure.
查看更多>>摘要：Due to the demands for high performance and ecological and economical alternatives to conventional lithium-ion batteries (LiBs),the development of lithium-sulfur (Li-S) batteries with remarkably higher theoretical capacity (1675 mA h g-1) has become one of the extensive research focus directions world-wide.However,poor conductivity of sulfur,critical cyclability problems due to shuttle of polysulfides as intermediate products of the cathodic reaction,and large volume variation of the sulfur composite cathode upon operation are the major bottlenecks impeding the implementation of the next-generation Li-S batteries.In this work,a unique three-dimensional (3D) interconnected macrocellular porous carbon (PC) architecture decorated with metal Ni nanopatticles was synthesized by a simple and facile strategy.The as-fabricated Ni/PC composite combines the merits of conducting carbon skeleton and highly adsorptive abilities of Ni,which resulted in efficient trapping of lithium polysulfides (LiPSs) and their fast conversion in the electrochemical process.Owing to these synergistic advantageous features,the composite exhibited good cycling stability (512.3 mA h g-1 after 1000 cycles at 1 C with an extremely low capacity fading rate 0.03 ％ per cycle),and superior rate capability (747.5 mAh g-1 at 2 C).Accordingly,such Ni nanoparticles embedded in a renewable puffed corn-derived carbon prepared via a simple and effective route represent a promising active type of sulfur host matrix to fabricate high-performance Li-S batteries.
查看更多>>摘要：This study used the pseudo-spinodal mechanism to obtain the ultrafine α phase for designing high-strength titanium alloy.Diffusion multiple experiments were designed to find the composition range of TM-xMo-yV alloy (TM: Ti-4.5Al-2Cr-2.5Nb-2Zr-1Sn) for obtaining ultrafine α phase.CALPHAD results confirm that when the alloy composition is located near the intersection of the α and β phase free energy curves,the alloy will undergo pseudo-spinodal transformation and obtain the ultrafine α phase.The designed TM-6Mo-3V alloy has a yield strength of 1411 MPa and an elongation of 6.5 ％.The strength of the alloy depends on the thickness,fraction of the α phase and the solid solution strengthening effect of the alloying elements.The deformation mechanism of the alloy is the dislocation slip of the α and β phases and the twin deformation of the α phase.The large number of α/β interfaces produced by the fine α phase is the main reason for limiting the ductility of the alloy.The use of the pseudo-spinodal mechanism combined with diffusion multiple experiments and CALPHAD is an effective method fordesigning high-strength titanium alloys.
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