查看更多>>摘要：The ecological environment suffers from multiple pollution from many aspects,and the heavy metal ions(HMI)pose a significant threat to human health.Detecting these ions is challenging due to their trace amounts and diverse types.Optical fiber sensors offer numerous advantages over conventional tech-niques in HMI sensing,including small size,quick response,resistance to electromagnetic interference,and long-range monitoring capabilities.In this paper,several optical methods for HMI detection have been described,namely fluorescence,fiber grating,fiber modal interference,surface plasmon resonance,and optical absorbance.The principles,structures,and sensitive materials of these methods are discussed in detail.The advantages and disadvantages of each approach are illustrated to facilitate a better com-parison.Furthermore,the current status and future directions for the development of HMI optical fiber sensors are also discussed,which could enlighten the future HMI sensor design.
查看更多>>摘要：Metals and alloys with heterogeneous microstructures are an emerging class of materials that exhibit exceptional mechanical properties,owing to the novel scientific principle of hetero-deformation induced(HD1)strengthening and hardening.For magnesium alloys,due to their low recrystallization tempera-ture,poor ductility at room temperature,limited cold workability,and the tendency to generate strong basal texture during deformation,it is difficult to obtain heterostructures without relying on precipitation of the second phases.Here,three heterostructured Mg-2.9Y(wt.％)materials with varying accumulative equivalent true strains,i.e.,5％-5 cycles,7.5％-5 cycles,and 10％-5 cycles materials were fabricated via applying five complete triaxial compression cycles to the bulk alloy.The 5％-5 cycles material with an ac-cumulative equivalent true strain of 0.37 is featured with long twin lamellae embedded in coarse grains.When the accumulative true strain increases to 0.72,a heterogeneous structure composed of long and short twin lamellae is formed inside the 7.5％-5 cycles material.As the equivalent true strain further in-creases to 1.01,the 10％-5 cycles material exhibits a mixed structure with densely refined twin lamellae embedded in the coarse-grained matrix.The room-temperature uniaxial tensile tests show that the yield strength of the materials processed by triaxial cyclic compression(TCC)has been significantly improved compared to that at the initial state,whereas ductility was not significantly sacrificed without the sub-sequent heat treatment.The dense and refined twin lamellae that serve as hard domains in this material provide a high density of interfaces and impede dislocation motion effectively.This results in significant HDI strengthening and hardening.These findings provide new insight into the design of heterostructured hexagonal close-packed materials with both high strength and good ductility.
查看更多>>摘要：Photocatalytic reduction of CO2 to chemical fuels enables a sustainable way of reducing carbon emis-sions but faces a high reduction potential due to the high stability of CO2 molecules.Here,we prepared a SnO2/SnS2/Cu2SnS3 double Z-scheme heterojunction photocatalyst,in which SnO2,SnS2,and Cu2SnS3 absorb ultraviolet,visible,and near-infrared light,respectively.Based on the compre-hensive analysis of in-situ X-ray photoelectron spectroscopy and photo(chemical)characterizations,we find that the photogenerated electrons would transfer from SnO2 to SnS2 to Cu2SnS3.The optimized SnO2/SnS2/Cu2SnS3-0.3 double Z-scheme heterojunction could achieve 28.44 μmol g-1 h-1 ethanol yield and 92％selectivity,which is roughly 3 folds higher than SnO2/SnS2 single Z-scheme heterojunction.By using in-situ diffuse reflectance infrared Fourier-transform spectroscopy,we observe that ethanol is produced through a*COCOH pathway,in which Cu2SnS3 would decrease the activation energy barrier from*COOH to*CO.
查看更多>>摘要：Effective electromagnetic wave absorption is now possible thanks to the design of the dielectric-magnetic double loss mechanism and the rich heterogeneous structure.In this study,hollow carbon spheres with rich heterostructures were synthesized using an easy and effective in situ growing approach.In addition to improving impedance matching,the hollow structure also reduces material density and weight.By modifying the load,this system can alter the dielectric characteristics of MXene,which in turn affects the sample's ability to absorb electromagnetic waves.MXene and the carbon material create a thick con-ductive network during the whole electromagnetic wave absorption process,creating the ideal environ-ment for conduction loss.The sample's ability to attenuate electromagnetic waves is further improved by the interfacial polarization that the rich heterogeneous structure can produce.Co-magnetic nanoparticle nanoparticles are the main source of magnetic loss.The MXene@Co/C-100-800(MCC-100-800)exhibits excellent electromagnetic wave absorption performance under the synergy of multiple loss mechanisms,with the maximum effective absorption bandwidth(EABmax)reaching 7.20 GHz and the minimum reflec-tion loss(RLmin)being-53.99 dB at 2.10 mm.Finally,this work is guided by the coating engineering of MXene and provides new ideas for the rational design of heterostructures of nanomaterials.
查看更多>>摘要：The effect of electromagnetic vibration(EMV)on the solidification structure of Cu-15Ni-8Sn alloy during bulk solidification and the upward continuous casting was investigated experimentally and numerically.The bulk solidification results indicated that in the case of B=0.5 T and J=1.27 x 105 A/m2,the most effective grain refinement frequency was at f=10 Hz,where fine non-dendrites were obtained.The so-lidification structure became coarser at f=0.1 Hz and f=1 Hz compared to the case of f=10 Hz,while no grain refinement was observed at f=100 Hz.The numerical simulations showed that at f=10 Hz,the strong melt convection surrounding the primary solid phase promotes the diffusion of the rejected solute,consequently,resulting in a reduction of the solute boundary layer,which leads to the decrease in the nucleation-free zone(NFZ)and the grain refinement.Additionally,the most effective grain refinement frequency transformed to 1 Hz when the electromagnetic force was reduced by five times.Moreover,we proposed that the most effective grain refinement frequency range aligns with the EMV-induced rela-tive displacement in the range of 102-103 μm.Finally,the upward continuous casting was conducted to validate the relative displacement range,and the experimental results matched well.
查看更多>>摘要：The rational design of metal-organic frameworks(MOFs)provides potential opportunities for improv-ing energy conversion efficiency.However,developing efficient MOF-based electrocatalysts remains highly challenging.Herein,a strategy involving strain engineering is developed to promote the electrocatalytic performance of MOFs by optimizing electronic configuration and improving the active site.As expected,the optimized CoFe-BDC-NO2 exhibits a low overpotential of 292 mV at 10 mA cm-2 and a small Tafel slope of 31.6 mV dec-1 as oxygen evolution reaction(OER)electrocatalyst.Notably,when CoFe-BDC-NO2 is prepared on Nickel foam(NF),the overpotential is only 345 mV at 1 A cm-2,which ensures efficient water oxidation properties.Integrating CoFe-BDC-NO2/NF anode in membrane electrode assembly(MEA)for overall water splitting and CO2 reduction reaction(CO2RR)tests,the results show that the cell volt-ages of CoFe-BDC-NO2/NF are 3.14 and 3.09 V at 300 mA cm-2(25 ℃),respectively,indicating that MOFs have various practical application prospects.The research of the structure-performance relationship re-veals the lattice oxygen oxidation mechanism(LOM)where the Co-O-Fe bond is formed during the OER process by changing the electronic environment and coordination structure of CoFe-BDC-NO2,and with high valence Co as active center,which provides a deep understanding of the structure design of MOFs and their structural transformation during OER.
查看更多>>摘要：We report the mechanical performance and microstructural characteristics of a Fe-Cr-Ni-Mn-N alloy at cryogenic temperatures.The exceptionally high yield strength of 1.5 GPa combined with a high strain-hardening rate and no deterioration in ductility at 4.2 K was displayed.The evolution of deformation mi-crostructure was examined using electron backscatter diffraction(EBSD),the transmission Kikuchi diffrac-tion(TKD),high-resolution transmission electron microscopy(HRTEM),and aberration-corrected scanning TEM(STEM).The deformation microstructure mainly consisted of dislocation slip with L-C locks,{111}stacking fault formation,{111} deformation nanotwinning,and FCC → HCP shear transformation at 4.2 K.The occurrence of FCC-HCP shear transformation inside/near {111} twins to form γ-γtw-ε dual-phase structure induces a dynamic Hall-Petch effect that promotes the strain-hardening rate and enhances the strength-ductility combination.We believe that this alloy displays outstanding damage tolerance through a progressive synergy of deformation mechanisms leading to exceptional strength which provides a new insight into the commercialized development of high-performance alloys for cryogenic applications.
查看更多>>摘要：Oxygen vacancies have been widely concerned with the facilitation effects of CO2 activation for CO2 methanation.However,little attention has been paid to the generation of active intermediate species induced by enriched oxygen vacancies.Herein,we discovered that CeNiO3-δ catalyst enriched oxygen va-cancies can efficiently activate CO2 and realize high activity for photothermal CO2 methanation.In situ dif-fuse reflectance infrared Fourier transform spectroscopy(DRIFTS)proved that oxygen vacancies are bene-ficial to the formation of reactive intermediate species of polydentate carbonate over CeNiO3-δ,which is crucial for efficient CO2 methanation.These results revealed mechanistic insights into how effective CO2 activation induced by oxygen vacancies can be manipulated by adjusting the adsorption intermediate species.
查看更多>>摘要：Eutectic high-entropy alloys(EHEAs),combining the advantages of both eutectic alloys and high-entropy alloys(HEAs),possess good castability and superior comprehensive mechanical properties which are re-garded as a revolutionary material system.In this paper,a current study of EHEAs is captured compre-hensively for the first time,including basic theory,microstructure and deformation behavior,and alloy design.An in-depth analysis of the formation of different microstructures of EHEAs and their mechani-cal properties is presented,and four methods of designing EHEAs are summarized.Due to their unique characteristics,EHEAs show great potential in materials processing engineering.Here we give a compre-hensive summary of their applications in welding,surface engineering,and additive manufacturing for the first time.Among them,EHEAs in welding are divided into three sections based on different welding techniques:fusion-based welding,solid-state welding,and diffusion reaction-based welding;EHEAs in surface engineering are separated into two parts:surface modification of bulk EHEAs and EHEA coatings;EHEAs in additive manufacturing are elaborated in two parts:laser powder bed fusion(LPBF)and laser direct energy deposition(LDED).Finally,a summary is given and a future outlook is prospected.
查看更多>>摘要：Grain boundary(GB)significantly influences the mechanical properties of metal structural materials,yet the effect of solutes on GB modification and the underlying atomic mechanisms of solute segregation and strengthening in iron-based alloys remain insufficiently explored.To address this research gap,we conducted a comprehensive investigation into the segregation and strengthening effect of 33 commonly occurring solutes in iron-based alloys,with a specific focus on the body-centered cubic(BCC)iron Σ5(310)GB,utilizing first-principle calculations.Our findings reveal a negative linear correlation between solute segregation energy and atomic radius,highlighting the crucial role of atomic radius and electronic structure in determining GB strength.Moreover,through analyzing the relationship between strength-ening energy and segregation energy,it was found that the elements Ni,Co,Ti,V,Mn,Nb,Cr,Mo,W,and Re are significant enhancers of GB strength upon segregation.This study aims to provide theoretical guidance for selecting optimal doping elements in BCC iron-based alloys.
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