查看更多>>摘要：Designing and synthesizing cost-effective bifunctional catalysts for overall alkaline water/seawater split-ting is still a huge challenge for hydrogen production.Herein,Co/Ni/Fe/Mn based-amorphous high-entropy phosphoxide self-standing electrode(CNFMPO)is synthesized by the facile and fast elec-trodeposition method.CNFMPO exhibits excellent bifunctional electrocatalytic performances on alka-line water/seawater electrolysis.The hydrogen evolution reaction(HER)and oxygen evolution reac-tion(OER)overpotentials of CNFMPO in alkaline water/seawater are as low as 43/73 and 252/282 mV to reach a current density of 10 mA cm-2,respectively.Additionally,two-electrode electrolyzers with CNFMPO||CNFMPO successfully achieve the current density of 10 mA cm-2 at low voltages of 1.54 and 1.56 V for overall alkaline water/seawater splitting,respectively.CNFMPO exhibits satisfactory long-term stability on overall alkaline water/seawater splitting for the surface reconstruction into active metal hy-droxide/(oxy)hydroxide,phosphite,and phosphate.Moreover,no hypochlorite is detected during seawater electrolysis for the beneficial chlorite oxidation inhibition of the reconstructed phosphite and phosphate.The excellent catalytic performances of CNFMPO are due to the unique amorphous structure,multi-component synergistic effect,beneficial electronic structure modulation,and surface reconstruction dur-ing the catalytic reaction process.Therefore,CNFMPO has shown potential promotion to the development of the water/seawater splitting industry as a promising substituent for noble-metal electrocatalysts.This work provides new insights into the design of efficient bifunctional catalysts for overall water/seawater splitting.
查看更多>>摘要：Semiconductor/metal junctions are widely discussed in photocatalysis.However,there is a notable scarcity of systematic studies focusing on photogenerated charge carrier transfer in such junctions.Herein,CdS/Pt,CdS/Au,and CdS/Ag are synthesized to serve as model systems for investigating the charge carrier transfer in semiconductor/metal junctions.Kelvin probe force microscopy is employed to visualize the transfer of photogenerated carriers in these materials.The results show that the electron transfer be-havior under illumination is related to the conduction band position of CdS and the Fermi level position of the metal.Moreover,Schottky junctions hinder the transfer of photogenerated electrons from CdS to Pt and Au,whereas ohmic contacts facilitate the transfer of photogenerated electrons from CdS to Ag.This work provides novel insights into the mechanisms governing the transfer of photogenerated carriers in semiconductor/metal junctions.
查看更多>>摘要：The single-phase high-entropy alloy film is difficult to meet severe friction conditions due to its low hardness and high friction coefficient.Nano-composite structure film is composed of at least two sep-arated phases,showing the properties of strength and toughness integration and excellent wear resis-tance.The design of nanocomposite structures can effectively improve the mechanical properties and tribological properties of high-entropy alloy films.In this study,the(CuNiTiNbCr)Cx nanocomposite high-entropy films(HEFs)integrated with high hardness,high toughness,and self-lubrication were synthesized by the double-target co-sputtering method.The effect of carbon content on microstructure,mechanical properties,and tribological properties of(CuNiTiNbCr)Cx films was studied.With the increase of car-bon content in the HEFs,the carbon atoms preferentially react with Ti,Nb,and Cr to form a(TiNbCr)C ceramic-reinforced phase,and then the excess carbon atoms precipitate in the form of amorphous carbon(a-C)lubricating phase in the HEFs.The structure of the HEFs changes from an amorphous structure to a nanocomposite structure of amorphous(amorphous CuNiTiNbCr phase+a-C phase)/nanocrystalline(TiN-bCr)C phase.When the carbon content is about 21.2 at.％,the carbide phase in the film reaches saturation and the hardness and modulus of the films are highest,which are 18 GPa and 228 GPa,respectively.The HEFs with a carbon content of 44.0 at.％show the best toughness and tribological properties with a friction coefficient of 0.16 and a wear rate of 2.4 × 10-6 mm3/(N m),which is mainly attributed to the excellent resistance to fatigue crack growth and the interfacial lubricating layer formed in the friction process.The nanocomposite(CuNiTiNbCr)Cx HEFs show very promising application prospect in the field of friction protection.
查看更多>>摘要：Introducing minor alloying elements is an effective strategy to improve the corrosion and mechanical properties of zirconium alloys for nuclear applications.During in-reactor service,external environment and stress can affect the distribution of alloying elements,substantially changing the degradation process of zirconium alloys.To date,there is a lack of in-depth understanding of the interaction between creep and microchemistry changes.Here,we conducted systematic transmission electron microscopy(TEM)and atom probe tomography(APT)investigations to address creep-induced redistribution of alloying elements in CZ1(Zr-Sn-Nb-Fe-Cr-Cu)zirconium alloy with different initial microstructures.Nb,Fe,Sn,and Cu are found to co-segregate at grain boundaries.The higher the intermediate annealing temperature,the larger the Gibbsian interfacial excesses of solute elements are.We further demonstrate that creep can reduce the excess value of Fe at grain boundaries due to the coarsening of Zr-Fe-Cr second phase particles via grain boundary and dislocation pipe diffusion.At the same time,the excess value of Sn is increased by diffusing from the matrix to grain boundaries.Moreover,Cu as a minor element in the concentration range of 0.05-0.3 wt.％is found to segregate at dislocations to form the Cottrell atmosphere and develop Cu-rich nanoclusters for suppressing dislocation motion.The new understanding of the segregation and clustering of minor alloying elements provides guidance for developing zirconium alloys with enhanced creep resistance.
查看更多>>摘要：The interface healing mechanism of fine-grained Ni-Co-based superalloy during hot-compression bonding(HCB)is investigated.During HCB,the incompatibility of deformation between the γ and the primary γ'leads to a large number of dislocation pairs(DP),stacking faults(SF),and micro-twins(MT)in the pri-mary γ'.These defects act as fast channels for elemental diffusion,leading to supersaturation of the pri-mary γ'and promoting the growth of the γ-shell.On the one hand,the primary γ'with a γ-shell moves towards the bonding interface due to anomalous yielding phenomena of the primary γ'and plastic flow during HCB process.The increase in the number of defects leads to the growth of γ-γ'heterogeneous epitaxial recrystallization(HERX)grain with coherent structure at the bonding interface,which promotes the bulge of the interface grain boundaries(IGBs).On the other hand,the nucleation and growth of a necklace-like distribution of discontinuous dynamic recrystallization(DDRX)grain at the interface lead to the healing of IGBs.With the synergistic action of DDRX and HERX,the mechanical properties of Ni-Co-based superalloy joints through HCB achieve the same level as the base material.This finding further enriches the theory of interface healing in HCB.
查看更多>>摘要：Designing electrochemical catalysts has become a research hotspot due to their accelerating the polysul-fide conversion of the sulfur cathode to inhibit the"shuttle effect"in lithium-sulfur batteries.However,it is still a great challenge to design the heterogeneous selective electrochemical catalyst for inhibiting the"shuttle effect".Herein,nickel cobalt phosphide and cobalt phosphide as the heterogeneous catalyst ac-tive sites embedded in the nitrogen-doped hollow carbon nanocages(NiCoP@CoP/NC)are reported,used for multi-step and multi-phase sulfur electrode reaction,and it is found that metal-sulfur d-p hybridiza-tion can effectively indicate the intrinsic catalytic activity of metal site.Division of labor and cooperation of the bi-active NiCoP@CoP as heterogeneous catalysts propel the stepwise polysulfide conversion.NiCoP and CoP sites preferentially accelerate the long-chain polysulfide conversion reaction(S8⇄LiPSs)and the short-chain polysulfide conversion reactions(LiPSs⇄Li2S),respectively.Moreover,the hollow and porous N-doped carbon structure can successfully suppress the volume effect and improve the conductivity of the sulfur cathode.The unique design can obtain an effective inhibition of the shuttle effect and rapid electrode reaction.As a result,Li-S batteries demonstrate a high initial capacity of 1063 mAh g-1 and a low-capacity decay of 0.04％per cycle within 1000 cycles.Our work provides a feasible idea for the design of host materials in Li-S batteries.
查看更多>>摘要：LiBH4 containing 18.5 wt.％H2 is an attractive high-capacity hydrogen storage material,however,it suf-fers from high operation temperature and poor reversibility.Herein,a novel and low-cost bifunctional additive,waxberry-like Fe3O4 secondary nanospheres assembled from ultrafine primary Fe3O4 nanopar-ticles,is synthesized,which exhibits significant destabilization and bidirectional catalyzation towards(de)hydrogenation of LiBH4.With an optimized addition of 30 wt.％waxberry-like Fe3O4,the system initiated dehydrogenation below 100 ℃ and released a total of 8.1 wt.％H2 to 400 ℃.After 10 cycles,a capacity retention of 70％was achieved,greatly superior to previously reported oxides-modified sys-tems.The destabilizing and catalyzing mechanisms of waxberry-like Fe3O4 on LiBH4 were systematically analyzed by phase and microstructural evolutions during dehydrogenation and hydrogenation cycling as well as density functional theory(DFT)calculations.The present work provides new insights in develop-ing advanced nano-additives with unique structural and multifunctional designs towards LiBH4 hydrogen storage.
查看更多>>摘要：Mg-based amorphous alloys are one of the potential hydrogen storage materials but suffer from sluggish dehydrogenation/hydrogenation(de/hydrogenation)kinetics.In this work,as a new strategy,a hydrogen pump is built on the surface of amorphous alloys to solve this problem.By milling crystalline YFe2-xAlx hydrogen storage alloy with Mg60La10Ni20Cu10 amorphous alloy,fine crystalline particles were seeded on amorphous alloy powder to form a"strawberry"structure.According to the TEM observation,a metal-lurgical bonding boundary formed between the Mg-based amorphous matrix and the Y-Fe-Al crystalline alloy.By microstructure and de/hydrogenation kinetics investigation,the"hydrogen pump"effect of the seeded crystalline alloy was confirmed,which makes it much easier for the hydrogen to dissociate on and diffuse through the surface of the Mg-based amorphous alloy.With such effect,the H absorption rate of Mg60La10Ni20Cu10 amorphous alloy became almost eight times faster and it absorbs～2.8 wt.％in 1 h at 130 ℃ under 4.5 MPa-H2.Further,fast hydrogenation can even achieve at 70 ℃ and the low-temperature dehydrogenation kinetics of the amorphous hydride can be also greatly promoted.The present work proves that surface modification is of great importance for obtaining Mg-based amorphous alloy with ideal hydrogen storage performance.
查看更多>>摘要：A novel compliant spinal fixation designed based on the concept of compliant mechanisms can reduce the stress-shielding effect and adjacent segment degeneration(ASD)effectively,but propose higher re-quirements for the properties of the used materials.Bulk metallic glasses(BMGs),as a kind of young biomaterials,exhibiting excellent comprehensive properties,which are attractive for compliant spinal fix-ation.Here,according to the practical service condition of the basic elements in compliant spinal fixation,large deflection deformation behaviors of Zr61Ti2Cu25Al12(at.％,ZT1)BMG beam,including elastic,yielding and plastic were investigated systematically.It was shown that the theoretical nonlinear analytical solu-tion curve as the benchmark not only with the capacity to predict the nonlinear load-deflection relation within the elastic deformation regime,but also assists to capture the yielding event roughly,which can be used as a powerful design tool for engineers.To capture the beginning of the yielding event exactly,bending proof strength(σp,0.05％)accompanied with tiny permanent strain of 0.05％was proposed and de-termined for BMGs in biomedical implant applications,which is of significance for setting the allowable operating limits of the basic flexible elements.By approach of interrupted loading-unloading cycles,plas-tic deformation driven by the bending moment can be classified into two typical stages:the initial stage which mainly characterized by the nucleation and intense interaction of abundant shear bands when the plastic strain below the critical value,and the second stage which dominated by the progressive propa-gation of shear bands and coupled with the emergence of shear offsets on tensile side.The plasticity of BMG beam structures depends on the BMG's inherent plastic zone size(rp).When the half beam thick-ness less than that of the rp,the plastic deformation of BMGs will behave in a stable manner,which can be acted as the margin of safety effectively.
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