查看更多>>摘要：Laser powder bed fusion(LPBF)is a promising method for manufacturing functional and structural inte-grated Cu-Cr-Zr components.However,the LPBF-processed Cu-Cr-Zr alloys still suffer from the strength-ductility trade-off dilemma,while maintaining high conductivity.Here,LPBF-processed Cu-Cr-Zr alloy with a hierarchical structure was obtained by increasing the Cr and Zr content simultaneously.After ag-ing treatment,the hierarchical structure was composed of melt tracks at the macroscale,coarse grains(31.9±0.1 μm)and fine grains(5.6±0.2 μm)at the microscale,high-density of dislocations and dual precipitates at the nanoscale.The direct aged sample exhibited an excellent combination of strength and ductility(tensile strength was enhanced to 626±1 MPa and uniform elongation of 16.2％±1.1％),which is superior to the traditionally wrought and LPBF-processed Cu-Cr-Zr alloys reported previously.Meantime,a good electrical conductivity of 71.1％±0.3％IACS was also achieved.In addition,the hetero-geneous deformation-induced stress caused by the hierarchical structure not only led to a large increase in yield strength but also promoted tensile ductility.
查看更多>>摘要：Microscale stray grains(MSGs),which are composed of misoriented and fragmented high-ordered den-drite arms,small-sized equiaxed grains,and columnar grains,are a novel grain defect that occurs within the shrouds of single-crystal(SC)blades made from Ni-based superalloy.State-of-the-art non-destructive testing methods are incapable of detecting this defect,resulting in a high-risk application of SC blades.This study aims to control this defect by systematically investigating directional solidification process-ing parameters,shroud dimensions,and rhenium(Re)content in the formation of MSG defects.The re-sults reveal that the defect forms exclusively at the overhanging extremities of the upper shrouds on the back side of the blades that face the heater.Increasing the withdrawal rate reduces the occurrence of MSG defects.As the shroud dimensions increase,MSG defects appear in the transition area between the downward suspended extremity of the blade shroud and the side of the blade body,as well as near the corner of the downward suspended extremity of the shroud.The occurrence of MSG defects increases with increasing shroud dimensions.Varying Re content sharply decreases the formation of MSG defects.A concentration-attached Rayleigh-Taylor instability(RTI)superheating(CARTISH)model,considering solid-ification shrinkage,was proposed to comprehend the formation of MSG defects.Simulation results based on this model are consistent with the experimentally observed distribution and degree of MSG defects under different conditions.Effective control of the CARTISH is critical to managing MSG defects.
查看更多>>摘要：Laser powder bed fusion(LPBF)is a popular additive manufacturing(AM)technique to fabricate metal components.LPBF Ti alloys often exhibit high strength but poor ductility.In this study,we report that trace Y2O3 nanoparticles added to a pre-alloyed Ti-4Al-4V(Ti44)powder provides an excellent feedstock for LPBF.As-built Ti44-Y2O3 materials exhibited a strength-ductility combination that is slightly better than heat-treated LPBF Ti64.Some Y2O3 particles may have melted or decomposed during LPBF.From electron microscopy,the addition of Y2O3 refined α'martensite laths and weakened variant preference during β→α'transformation.Based on in situ synchrotron X-ray diffraction and elastic-viscoplastic self-consistent(EVPSC)modeling,<c+a>slip was more active in as-built Ti44-Y2O3 than in as-built Ti64 or Ti44.This work demonstrates that LPBF can be an excellent method to fabricate metal-nanoparticle composite materials.
Lucas SpessatoLucas H.S.CrespoMarcela C.SilvaMariana S.Gibin...
157-167页
查看更多>>摘要：Carbon quantum dots(CQD)were employed as dopants to enhance the photocatalytic efficiency of Nb2O5 by decreasing the bandgap energy and prolonging the lifetime of the photogenerated exciton by in-creasing conductivity.X-ray diffraction(XRD),N2 porosimetry,scanning electron microscopy(SEM),elec-trochemical impedance spectroscopy(EIS),photoacoustic spectroscopy(PAS),X-ray photoelectron spec-troscopy(XPS),Dynamic Light Scattering(DLS),zeta potential,and atomic force microscopy(AFM)were used to characterize the synthesized nanostructures.The residues from acerola processing were converted into CQD with an average size of 2.56 nm,as confirmed by AFM and the high fluorescence quantum yield of 43.32％.N2 physisorption results showed that the CQD were deposited on the surface of Nb2O5,re-ducing the specific surface area(SBET)from 122±2.0 to 29±1.3 m2 g-1.The photocatalytic performance of CQD/Nb2O5 was superior to that of the control materials under UV-vis light irradiation,as there was a decrease in the bandgap energy(Eg)from 2.78 to 1.93 eV.This decrease in Eg led to a significant increase in the apparent rate constant(kapp)of the MG dye from 1.90 ×10-3 s-1 to 42.2 ×10-3 s-1,demonstrating that the presence of CQD can effectively separate the photogenerated charge carriers,as it was observed from the increase in conductivity showed by Nyquist diagram.
查看更多>>摘要：Highly sensitive and stable acetylcholinesterase detection is critical for diagnosing and treating various neurotransmission-related diseases.In this study,a novel colorimetric-fluorescent dual-mode biosen-sor based on highly dispersive trimetal-modified graphite-phase carbon nitride nanocomposites for acetylcholinesterase detection was designed and synthesized by phosphorus doping and a mixed-metal MOF strategy.The specific surface area of trimetal-modified graphite-phase carbon nitride nanocom-posites increased from 15.81 to 96.69 g m-2,and its thermal stability,interfacial charge transfer,and oxidation-reduction capability were enhanced compared with those of graphite-phase carbon ni-tride.First-principles density functional theory calculations and steady-state kinetic analysis are ap-plied to investigate the electronic structures and efficient peroxidase-mimicking properties of trimetal-modified graphite-phase carbon nitride nanocomposites.The oxidation of 3,3',5,5'-tetramethylbenzidin was inhibited by thiocholine,which originates from the decomposition of thiocholine iodide by Acetyl-cholinesterase(AChE),resulting in changes in fluorescence and absorbance intensity.Due to the indepen-dence and complementarity of the signals,a highly precise colorimetric-fluorescent dual-mode biosensor with a linear range for detecting AChE of 4-20 μU mL-1 and detection limits of 0.13 μU mL-1(colori-metric)and 0.04 µU mL-1(fluorescence)was developed.The spiking recovery of AChE in actual samples was 99.0％-100.4％.Therefore,a highly accurate,specific,and stable dual-mode biosensor is available for AChE detection,and this biosensor has the potential for the analysis of other biomarkers.
查看更多>>摘要：For advanced conductive hydrogels,adaptable mechanical properties and high conductivity are essential requirements for practical application,e.g.,soft electronic devices.Here,a straightforward strategy to de-velop a mechanically robust hydrogel with high conductivity by constructing complicated 3D structures composed of covalently cross-linked polymer network and two nanofillers with distinguishing dimensions is reported.The combination of one-dimensional quaternized cellulose nanofibrils(QACNF)and two-dimensional MXene nanosheets not only provides prominent and tunable mechanical properties modu-lated by materials composition,but results in electronically conductive path with high conductivity(1281 mS m-1).Owing to the uniform interconnectivity of network structure attributed to the strong macro-molecular interaction and nano-reinforced effect,the resultant hydrogel exhibits a balanced mechanical feature,i.e.,high tensile strength(449 kPa),remarkable stretchability(＞1700％),and ultra-high tough-ness(5.46 MJ m-3),outperforming those of virgin one.Additionally,the enhanced conductive characteris-tic with the aid of QACNF enables hydrogels with impressive electromechanical behavior,containing high sensitivity(maximum gauge factor:2.24),wide working range(0-1465％),and fast response performance(response time:141 ms,recover time:140 ms).Benefiting from the excellent mechanical performance,a flexible strain sensor based on such conductive hydrogel can deliver an appealing sensing performance of monitoring multi-scale deformations,from large and monotonous mechanical deformation to tiny and complex physiological motions(e.g.,joint movement and signature/vocal recognition).Together,the hy-drogel material in this work opens up opportunities in the design and fabrication of advanced gel-based materials for emerging wearable electronics.
查看更多>>摘要：Redox-active organic electrode materials have emerged as a promising alternative to inorganic counter-parts in view of their low cost and easily tunable chemical/electrical/mechanical properties.However,practical issues of using these materials remain as a consequence of their electrically insulating character,limited specific capacity and cyclability.Porphyrin,a highly conjugated macrocyclic organic compound,is an appealing candidate due to its multi-electron transfer mechanism and its small energy barrier for rapid electron transfer.Here,a new class of copper(Ⅱ)meso-tetra(4-pyridyl)porphyrin(CuTPyP)was ob-tained by introducing copper ions into free-base H2TPyP for regulation of redox activity and prevention of material dissolution,and was further hosted on conducting reduced graphene oxide(rGO)to enhance the redox activity.The resultant CuTPyP/rGO composites hence demonstrated a high reversible discharge capacity of 152 mAh g-1 after 200 cycles,with a capacity retention rate of 84.5％at 0.5 C,vastly superior to the bare CuTPyP(113 mAh g-1)and free-base H2TPyP(62 mAh g-1).A deep insight into the chemical states showed that electron-donating N atoms in the tetrapyridyl subunits behaved as the main charge storage sites during the charge and discharge state along with part contribution from the Cu(Ⅱ)/Cu(Ⅰ)conversion center.The high and stable electrochemical performance makes porphyrins a potential choice for real-use cathodes for long-term organic alkali metal batteries.
查看更多>>摘要：Microencapsulation of phase change materials(MPCM)is an effective way to achieve solar energy man-agement.However,the crystallization of phase change materials(PCMs)in microcapsules will produce supercooling,which will affect the energy storage efficiency of MPCM.The incorporation of TiO2 nanopar-ticles into MPCM can alleviate supercooling.In this work,octadecyltrimethoxysilane(ODTMS)was used to modify the solid nucleating agent TiO2(m-TiO2)to improve its compatibility with n-Octadecane.Then,MPCM based on m-TiO2 nucleating agent,melamine-formaldehyde resin(MF)shell material,and n-Octadecane core material was prepared.Differential scanning calorimetry(DSC)results demonstrate that the supercooling degree(ΔT)of MPCM(MPCM-02)decreases to 0 ℃ with a tiny level of 0.25 wt％m-TiO2,while the MPCM with unmodified TiO2 is 6.1 ℃ and the MPCM without nucleating agent is 4.1 ℃.Be-sides,the phase change enthalpy(ΔHm)and encapsulation efficiency(E)of MPCM-02 remain at 183.7 J/g and 95.3％,respectively.Finally,phase change composite materials with photothermal conversion capa-bilities were constructed by MXenes,MPCM,and polyurethane acrylate(PUA).When 1 wt％MXenes and 30 wt％MPCM were incorporated into PUA matrix,the thermal conductivity and surface temperature af-ter 1200s of infrared light irradiation were 48.8％and 8.2 ℃ higher than pure PUA matrix.These results demonstrate the good solar energy storage capabilities of the MPCM,which possesses promising applica-tion potential in the field of solar energy thermal management and human thermal regulation.
查看更多>>摘要：The progress of zinc(Zn)metal batteries(ZMBs)is greatly limited by poor cycling stability because of the mutual restrictions of dendrite growth,corrosion reactions,and passivation.In this work,an ultra-long lifespan(～7800 h),dendrite-free Zn metal anode is enabled via fabricating a functional hydrogel electrolyte out of polyacrylamide/graphene oxide(GO)/agarose(PGA)with a multifully cross-linked net-work.The synergetic integration of GO nanosheets and double-network structure endows the PGA hy-drogel electrolyte with high ionic conductivity and excellent mechanical performance.More importantly,the abundant hydrophilic groups and stable three-dimensional cross-linked network of PGA electrolyte effectively constrain Zn2+diffusion laterally along the Zn surface,which simultaneously prohibits water-induced corrosion and thus significantly enhances Zn anode reversibility.Both theoretical simulations and experiments reveal that the PGA electrolyte is capable of optimizing de-solvation kinetics and harmoniz-ing Zn2+flux at the electrolyte-electrode interface,ensuring uniform Zn2+deposition.Consequently,an ultra-long lifespan of 7800 h is achieved in the symmetric cell with the PGA electrolyte.Even at a high Zn utilization of 42.7％,it still delivers stable cycling over 1100 h.This work provides a practical and benefi-cial approach to dramatically extending the lifespan of the Zn anode and thus achieving high-performance ZMBs.
查看更多>>摘要：Micron-scale molybdenum(Mo)wires are vital in numerous technological applications,including micro-electromechanical systems and nanodevices.Understanding their mechanical behavior under cyclic tor-sion loading is critical in designing reliable and durable components.This work investigates the mechan-ical behavior and fracture characteristics of micron Mo wires under various torsional loading conditions,including monotonic,symmetric,and asymmetric cyclic torsion.The results reveal that the fractures ob-served in Mo wires exhibit a relatively planar characteristic with noticeable clockwise river-patterned cleavage steps under monotonic torsion,mirroring the direction of the torsional stress applied during the experiment.In terms of symmetric cyclic torsion,it is notable that cyclic softening becomes increasingly pronounced as the increase of strain amplitude.The fractures exhibit distinctive stratification,character-ized by the longitudinal cracks propagating radially.When the unloading strain is less than the loaded strain,the extent of the strain hysteresis effect amplifies with an increase in unloading strain.And the observed fracture characteristics are consistent with those under monotonic torsion.Differently,when the loading strain equals the unloading strain,a distinctive fracture pattern emerges in the Mo wire,characterized by a"peak"shape.This research provides valuable insights for optimizing the mechanical reliability of micron wires in microscale and nanoscale applications.
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