查看更多>>摘要：Molybdenum (Mo),with its high chemical stability and resistance to neutron irradiation,has wide appli-cation prospects in the nuclear industry;however,the embrittlement of welded Mo joints limits its further application.In this study,the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone (FZ) during laser welding.In the FZ of the Mo joints,carbon mainly existed as Mo2C,and some free C atoms,and MoC and MoOxCy phases were also present.The distribution of Mo2C directly influenced the bonding strength of the grain boundaries.As Mo2C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo,it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength.However,the Mo2C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate,thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength.The emergence of the MoOxCy phase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.
查看更多>>摘要：Two-dimensional (2D) hierarchical Mn2O3@graphene composite is synthesized by a one-step solid-phase reaction.The nanosheets of Mn2O3 are vertically grown on few-layered graphene,constructing a unique 2D hierarchical structure.As an anode material for lithium-ion batteries (LIBs),this hierarchical composite displays excellent electrochemical performances,showing an extraordinary reversible discharge capacity of 2125.9 mA h g-1.Moreover,a record high reversible capacity of 1746.8 mA h g-1 is maintained after 100 cycles at a current density of 100 mA g-1,which retains 82.2 ％ of the initial capacity.Such an outstanding performance could be attributed to its novel structure and the synergistic effects between the Mn2O3 and graphene.
查看更多>>摘要：Electrochemical reduction of CO2 is a promising strategy to manage the global carbon balance by trans-forming CO2 into chemicals.The efficiency of CO2 electroreduction is largely dependent on the design of hybrid electrode where both support and catalyst govern the performance of the electrolyzer.In this work,TiO2 calcined at different temperatures,was used as a support for immobilization of cobalt tetraphenyl porphyrin (CoTPP) and its effect on CO2 reduction was studied.It is demonstrated that the crystalline phase of TiO2 and doping of TiO2 apparently affecting CO2 electroreduction.It is found that anatase phase exhibits higher activity and selectivity compared to futile due to the enhanced conductivity which in turn enables faster electron transfer between the support and CoTPP.As for dopants,the carbon dop-ing in anatase TiO2 is proven to further enhance its conductivity,consequently resulting in the enhanced performance.This study implies that the rational design of supports is important for the performance of the hybrid electrode towards electrochemical CO2 reduction.
查看更多>>摘要：In this paper,microstructure,micromagnetic structure,texture,together with magnetic properties of the hot-deformed (HD) Nd-Fe-B magnets were systematically studied to understand the deformation process and the formation mechanism of c-axis texture.The results show that the platelet grains are formed in the fine-grain regions at the initial stage of the deformation.As the amount of deformation increases,the proportion of platelet grains increases and arranges gradually,causing the formation of c-axis texture,till the grain merging occurres when the deformation is excessive.It should be noted that the rare earth-rich phase in the fine-grained region slowly diffuses to the coarse-grained region where only grain growth can be observed during deformation.The deformation mechanism and formation of c-axis texture in HD Nd-Fe-B magnets can be deduced to be accomplished by the processes of dissolution-precipitation diffusion,grain rotation and grain arrangement,based on the characterization of microstructure and texture evolution.Also,approaches to optimize the preparation process and magnetic properties of the hot-deformed Nd-Fe-B magnets were discussed.
查看更多>>摘要：Dopamine (DA),one type of mussel-inspired biological molecules with adhesive nature and corrosion inhibitor property,are often used to functionalize the surfaces of various materials.Herein,we report the application of polydopamine (PDA) microcapsules as novel nanocontainers for the purpose,loading corrosion inhibitor (benzotriazole) in its shell structure,and then were embedded into epoxy coatings to provide self-healing and anti-corrosion protection for carbon steel.Fast release of benzotriazole in acidic environment caused by local corrosion and the chelating effect of PDA-Fe3+ can synergistically promote the formation of protective film on bare steel surface,which endows coatings with self-healing func-tionality.Electrochemical impedance spectroscopy (EIS),local electrochemical impedance spectroscopy(LEIS),and spray tests were conducted to evaluate the active inhibition and corrosion resistance of the loaded coatings.The scratched coating with incorporation of nanocontainers presented better protection performance,exhibiting increased Ro (oxide layer resistance) and Rct (charge transfer resistance) during initial immersion periods.The EIS tests in long-term immersion were also performed to confirm the anti-corrosion effect of composited coatings.These results demonstrated that benzotriazole-decorated PDA capsules dramatically enhanced the self-healing properties and anti-corrosion performance of epoxy coatings with the synergistic help of PDA and benzotriazole.
查看更多>>摘要：In order to improve mechanical and corrosion properties of biodegradable pure Zn,a knowledge-based microstructure design is performed on Zn-Li alloy system composed of hard β-LiZn4 and soft Zn phases.Precipitation and multi-modal grain structure are designed to toughen β-LiZn4 while strengthen Zn,resulting in high strength and high ductility for both the phases.Needle-like secondary Zn precipi-tates form in β-LiZn4,while fine-scale networks of string-like β-LiZn4 precipitates form in Zn with a tri-modal grain structure.As a result,near-eutectic Zn-0.48Li alloy with an outstanding combination of high strength and high ductility has been fabricated through hot-warm rolling,a novel fabrication process to realize the microstructure design.The as-rolled alloy has yield strength (YS) of 246 MPa,the ultimate tensile strength (UTS) of 395 MPa and elongation to failure (EL) of 47 ％.Immersion test in simulated body fluid (SBF) for 30 days reveals that Li-rich products form preferentially at initial stage,followed by Zn-rich products with prolonged time.Aqueous insoluble Li2CO3 forms a protective passivation film on the alloy surface,which suppresses the average corrosion rate from 81.2 μm/year at day one down dramatically to 18.2 μm/year at day five.Afterwards,the average corrosion rate increases slightly with decrease of Li2CO3 content,which undulates around the clinical requirements on corrosion resistance(i.e.,20 μm/year) claimed for biodegradable metal stents.
查看更多>>摘要：In order to efficiently explore the nearly infinite composition space in multicomponent solid solution alloys for reaching higher mechanical performance,it is important to establish predictive design strate-gies using computation-aided methods.Here,using ab initio calculations we systematically study the effects of magnetism and chemical composition on the generalized stacking fault energy surface (γ-surface) of Cr-Co-Ni medium entropy alloys and show that both chemistry and the coupled magnetic state strongly affect the γ-surface,consequently,the primary deformation modes.The relations among various stable and unstable stacking fault energies are revealed and discussed.The present findings are useful for studying the deformation behaviors of Cr-Co-Ni alloys and facilitate a density functional the-ory based design of transformation-induced plasticity and twinning-induced plasticity mechanisms in Cr-Co-Ni alloys.
查看更多>>摘要：The electron mediator can effectively improve the performance of the direct Z-scheme heterojunction photocatalysts.However,it is still a great challenge to select cheap and efficient electron mediators and to design them into the Z-scheme photocatalytic system.In the present paper,the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst was prepared using carbon nanotubes (CNTs) as the electron mediators,and its photocatalytic hydrogen production performance was studied.Compared with single-phase g-C3N4,CdZnS and biphasic g-C3 N4/CdZnS photocatalysts,the photocatalytic hydrogen production performance of the prepared g-C3N4/CNTs/CdZnS has been significantly enhanced.Meanwhile,g-C3N4/CNTs/CdZnS possesses very good photocatalytic hydrogen production stability.The enhanced photocatalytic hydrogen production performance of g-C3 N4/CNTs/CdZnS is attributed to the fact that CNTs,as an electron mediator,can accelerate the recombination of the photogenerated holes in the valence band of g-C3N4 and the photogenerated electrons in the conduction band of CdZnS,which makes the g-C3N4/CNTs/CdZnS Z-scheme photocatalyst be easier to escape the photogenerated electrons,increases the concentration of the photogenerated carriers and prolongs the lifetime of the photogenerated carriers.This work provides a theoretical basis for the further development and design of CNTs as the intermediate electron mediator of the Z-scheme heterojunction photocatalyst.
查看更多>>摘要：Plate-like Fe-rich intermetallic phases directly influence the mechanical properties of recycled Al alloys;thus,many attempts have been made to modify the morphology of these phases.Through synchrotron X-ray imaging and electron microscopy,the underlying nucleation and growth mechanisms of Fe-rich phases during the solidification of Al-5Ti-1B-modified Al-2Fe alloys were revealed in this study.The results showed that the Al-5Ti-1 B grain refiner as well as the applied pressure both resulted in reduction of the size and number of primary Al3Fe phases and promoted the formation of eutectic Al6Fe phases.The tomography results demonstrated that Al-5Ti-1B changed the three-dimensional (3D) morphology of primary Fe-rich phases from rod-like to branched plate-like,while a reduction in their thickness and size was also observed.This was attributed to the fact that Ti-containing solutes in the melts inhibit the diffusion of Fe atoms and the Al3Fe twins produce re-entrant corner on the twin boundaries along the growth direction.Moreover,the TiB2 provides possible nucleation sites for Al6Fe phases.The nucleation mechanism of Fe-rich phases is discussed in terms of experimental observations and crystallography calculations.The decrease in the lattice mismatch between TiB2 and Al6Fe phases was suggested,which promoted the transformation of Al3Fe to Al6Fe phases.
查看更多>>摘要：Combining dissimilar materials in a single component is an effective solution to integrate diverse material properties into a single part.Copper-stainless steel hybrid components are attracting more and more attention since the high thermal conductivity of copper can greatly enhance the thermal performance of stainless steel,which benefits its applications in many industries.However,direct joining of copper and stainless steel such as SS316 L is challenging since they preserve significant dissimilarities in physical,chemical,and thermo-mechanical properties.This paper aims to fabricate well-bonded copper-SS316 L hybrid parts using a laser-aided directed energy deposition (DED) process.A nickel-based alloy Deloro 22 (D22) is introduced between copper and SS316 L to address the detrimental issues in copper-SS316 L direct joints.Using this technique,defect-free interfaces are achieved at both the D22-SS316 L and copper-D22 transition zones.Tensile testing of Cu-D22-SS316 L and D22-SS316 L hybrid parts shows the fracture occurs at pure copper and SS316 L region,respectively,indicating an excellent bonding at the interfaces.Ascending in the building direction,a transition of grain structure is observed.A significant diffusion zone is obtained at both the D22-SS316 L and the Cu-D22 interfaces.The large diffusion distance results in a smooth variation in microhardness over the dissimilar materials.The microhardness increases from SS316 L to D22 with the highest value of 240 HV and then decreases from D22 to Cu with the lowest value of 63 ± 4 HV.Testing of thermophysical properties of the Cu-D22-SS316 L system indicates there is a ～300 ％ increase in thermal diffusivity and a ～200 ％ increase in thermal conductivity when compared to pure SS316 L.The significant increase in thermal diffusivity and conductivity validates the enhanced thermal performance of SS316 L when it is joined with pure copper.
NETL
NSTL
维普
万方数据