查看更多>>摘要：Non-precious metal electrocatalyst molybdenum sulphide (MoS) and black phosphorus (BP) are highly promising catalysts for H2 evolution reaction (HER).However,BP is environmentally unstable and the basal planes of crystal MoS2 are inactive toward HER.Herein,amorphous molybdenum sulphide (MoSx) directly on BP/BiVO4 film dramatically improves the performance of photoelectrochemical water splitting compared with pure BiVO4.Additionally,we demonstrate that a BP layer,inserted between the MoSx and BiVO4,can enhance the photoelectrochemical performance and improve the stability of the electrodes.Finally,MoSx/BP/BVO electrode shows the excellent current density of 2.1 mA/cm2 at the potential of 1.2 V (vs Ag/AgCl),which is twice higher than that of pure BVO electrode.Our novel nanostructure materials will lead to a new class of non-precious metal photocatalysts for hydrogen production.
查看更多>>摘要：In recent years,oxygen storage materials (OSMs) have been widely used in many fields.It would be particularly important for researchers to design high-oxygen-uptake/release-rate materials.In this study,various synthesis processes were used to successfully synthesize YBaC04O7+δ and comprehensively investigate their potential applications.Compared with traditional solid-state reaction method and co-precipitation method,the results demonstrated that the utilization of mechanical ball milling treatment on co-precipitated precursors could lead to samples with reversible oxygen uptake/release under an oxidative atmosphere at low temperatures.The resultant materials exhibited fast oxygen absorption/desorption rate that could uptake/release oxygen directly to the equilibrium state within 9 min and 20 min,respectively.The mechanochemically ball-milled sample possessed outstanding oxygen storage performance,which could be attributed to their small particle size,the active outer surface of particles,large specific surface area,and relatively low activation energy.Moreover,the ball-milled sample also exhibited excellent cycling stability during relatively short time spacing.TG results also demonstrated that the ball-milled samples could reversibly uptake/release 2.90 wt.％ of excess oxygen (while only 0.70 wt.％ for solid-state samples) by adjusting the ambient temperature under pure O2 atmosphere,which would make them promising candidates in various applications.This research demonstrated that mechanical treatment could be an effective strategy to tune the properties and oxygen storage capacity(OSC) performances of YBaCo4O7+δ.
查看更多>>摘要：Metastable high entropy alloys (HEAs) and amorphous metallic glasses (MGs),with the chemical disordered character,are intensively studied due to their excellent performance.Here,we introduce Cu to separately constrain these two metastable materials and comparatively investigate their deformation behaviors and mechanical properties of Cu/HEA FeCoCrNi and Cu/MG CuZr nanolaminated micropillars in terms of intrinsic layer thickness h and extrinsic pillar diameter D.The metastable HEA layers,as the hard phase in Cu/HEA micropillars,are stable and dominate the deformation,while transformation (crystallization) occurs in MG which plays a minor role in deformation of Cu/MG micropillars.The h-controlled deformation mode transits from the D-independent homogenous-like deformation at large h to the D-dependent shear banding at small h in both Cu/HEA and Cu/MG micropillars.Although both Cu/HEA and Cu/MG micropillars exhibit a maximum strain hardening capability controlled by h,the former manifests much lower hardening capability compared with the latter.The intrinsic size h and extrinsic size D have a strong coupling effect on the strength of Cu/HEA and Cu/MG micropillars.The strength of strength of Cu/HEA micropillars exhibits the D-dependent transition from "smaller is stronger" to "smaller is weaker" with increasing h.By contrast,the strength of Cu/MG micropillars exhibits the transition from bulk-like D-independent behavior at large h to small volume D-dependent behavior (smaller is stronger) at small h.
查看更多>>摘要：Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration (GBM) process.The relationship between GBM and the orientations of nanograins relative to loading direction was established by using electron backscatter diffraction.GBM is found to be more pronounced in the grains with higher Schmid factors where dislocations are easier to slip.As a result,the fraction of high angle grain boundaries decreases and that of low angle grain boundaries increases after GBM.
查看更多>>摘要：In the present study,we offer an in-depth analysis over the microstructure,thickness and product composition of the interfacial reaction layer generated upon CBN/Cu-Sn-Ti active filler metal at 1223 K.Current findings demonstrate that adequate wettability and satisfactory bonding have been achieved via chemical reactions between Ti and N,B.More importantly,we report,for the first time,the formation of a three-layer juxtaposition of reaction products,namely,TiN,TiB2 and TiB,along the diffusion path of Ti.Meanwhile,we determine the average layer thickness to be 1.24 μm.Through deep etching,we unambiguously present morphologies of the newly formed TiN and TiB2,which are columnar and bulky,respectively,and constitute the formation of a high strength metallurgical interfacial bonding layer,and is crucial towards gaining enhanced grinding performance.Finally,we propose a possible reaction sequence and mechanism that govern the nucleation and growth of corresponding crystals.
查看更多>>摘要：Tensile properties at room temperature of a new casting Ni-base superalloy during aging at 800 ℃ for 0-1000 h were investigated.During aging,granular M23C6 carbides presented at grain boundaries and kept growing from dispersed particles to continuous networks.The γ'phase significantly coarsened,with the morphology of some γ'phase changed from spherical to rounded cubic shape after 1000 h.Three deformation mechanisms in relation to the γ'diameter (dγ') were identified: (i) weakly coupled dislocations (WCD) connected by anti-phase boundary (APB) traveled in pair across the γ/γ'structure when dγ'was small in the under-aged alloys;(ii) strongly coupled dislocations (SCD) with reduced spacing compared to (i) sheared γ'phase when dγ'increased in the over-aged alloys;(iii) dislocations occasionally by-passed γ'phase when dγ'was larger than 97 nm after aging for more than 300 h.The alloy obtained the peak strength when 20 h-aged with dγ'=44 nm which was in the transition between (i) and (ii).The aging-induced variation in yield strength was correlated to the coarsening of γ'phase using a theoretical model of precipitation strengthening in terms of the formation of APB.The calculated results suggested that the γ'phase with a volume fraction of 23％ contributed more than 61％ of the peak-aged yield strength.Observation after fracture revealed that the alloys usually fractured at grain boundaries.High stress concentration around carbides resulted in cracks by carbides self-cracking and the initiation of cavities.The undesirable agglomeration of M23C6 at grain boundaries was harmful to the properties of the overaged alloys.
查看更多>>摘要：The harsh melt-spinning and annealing processes of high saturation magnetization nanocrystalline soft-magnetic alloys are the biggest obstacles for their industrialization.Here,we proposed a novel strategy to enlarge the processing window by annealing the partially crystallized precursor ribbons via a heterostructured crystallization process.The heterostructured evolution of Fe84.75Si2B9P3C0.5Cu0.75 (at.％)alloy ribbons with different spinning rate were studied in detail,to demonstrate the gradient nucleation and grain refinement mechanisms.The nanocrystalline alloys made with industrially acceptable spinning rate of 25-30 m/s and normal annealing process exhibit excellent magnetic properties and fine nanostructure.The small quenched-in crystals/clusters in the free surface of the low spinning rate ribbons will not grow to coarse grains,because of the competitive grain growth and shielding effect of metalloid elements rich interlayer with a high stability.Avoiding the precipitation of quenched-in coarse grains in precursor ribbons is thus a new criterion for the composition and process design,which is more convenient than the former one with respect to the homogenous crystallization mechanism,and enable us to produce high performance nanocrystalline soft-magnetic alloys.This strategy is also suitable for improving the compositional adjustability,impurity tolerance,and enlarging the window of melt temperature,which is an important reference for the future development of composition and process.
查看更多>>摘要：To solve the electromagnetic pollution,herein,a CoFe204/C/PANI composite was developed by a green route,which was constructed with spinel of metal oxide,graphitized carbon and conductive polymer composites.Benefiting from the designable interfaces and increased dipoles,the microwave dielectric response capability can be boosted significantly and resulted in the enhanced microwave absorbing performance.As revealed by the reflection loss curve,the minimum reflection loss (RLmin) reached-51.81 dB at 12.4 GHz under a matched thickness of 2.57 mm.At 2.5 mm,the effective absorbing band covered 8.88 GHz,suggesting the desirable wideband feature.In our case,the method of utilization of a novel green way to fabricate multiple-component EM absorber can be a promising candidate for high-performance EM absorber.
查看更多>>摘要：In medium/high entropy alloys,their mechanical properties are strongly dependent on the chemical-elemental composition.Thus,searching for optimum elemental composition remains a critical issue to maximize the mechanical performance.However,this issue solved by traditional optimization process via "trial and error" or experiences of domain experts is extremely difficult.Here we propose an approach based on high-throughput simulation combined machine learning to obtain medium entropy alloys with high strength and low cost.This method not only obtains a large amount of data quickly and accurately,but also helps us to determine the relationship between the composition and mechanical properties.The results reveal a vital importance of high-throughput simulation combined machine learning to find best mechanical properties in a wide range of elemental compositions for development of alloys with expected performance.
查看更多>>摘要：Zinc (Zn) and its alloys have been proposed as biodegradable implant materials due to their unique combination of biodegradability,biocompatibility,and biofunctionality.However,the insufficient mechanical properties of pure Zn greatly limit its clinical application.Here,we report on the microstructure,mechanical properties,friction and wear behavior,corrosion and degradation properties,hemocompatibility,and cytocompatibility of Zn-3Cu and Zn-3Cu-0.2Ti alloys under three different conditions of as-cast (AC),hot-rolling (HR),and hot-rolling plus cold-rolling (HR + CR).The HR + CR Zn-3Cu-0.2Ti exhibited the best set of comprehensive properties among all the alloy samples,with yield strength of 211.0 MPa,ultimate strength of 271.1 MPa,and elongation of 72.1 ％.Immersion tests of the Zn-3Cu and Zn-3Cu-0.2Ti alloys in Hanks' solution for 3 months indicated that the AC samples showed the lowest degradation rate,followed by the HR samples,and then the HR + CR samples,while the HR + CR Zn-3Cu exhibited the highest degradation rate of 23.9 μm/a.Friction and wear testing of the Zn-3Cu and Zn-3Cu-0.2Ti alloys in Hanks' solution indicated that the AC samples showed the highest wear resistance,followed by the HR samples,and then the HR + CR samples,while the AC Zn-3Cu-0.2Ti showed the highest wear resistance.The diluted extracts of HR + CR Zn-3Cu and Zn-3Cu-0.2Ti at a concentration of ≤25 ％ exhibited non-cytotoxicity.Furthermore,both the HR + CR Zn-3Cu and Zn-3Cu-0.2Ti exhibited effective antibacterial properties against S.aureus.
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