查看更多>>摘要：Low-temperature fired ferrites or ceramics are usually processed by using low-melting materials(e.g.,glasses,oxides,and eutectics)as sintering aids to obtain compact and uniform microstructures.Herein,a dual-strategy of co-doping with V2O5 and Sb2O3 oxides and forming a eutectic liquid phase has been employed to reduce the melting point of LiZn ferrite ceramics in an effective way.The results indi-cate that miniscule amounts of V2O5 and Sb2O3 co-doping contribute in producing dense and uniform microstructures with enhanced magnetic performance by low-temperature firing.The phase structural and microstructural evolutions have been studied in detail.Thereafter their correlations with magnetic properties have been revealed.Enhanced magnetic performance(Bs=475.4 mT,Ms=82.51 emu/g,Br/Bs=0.85,Hc=2.2 Oe,△H=153.8 Oe)of the LiZn-based ferrite ceramics is achieved by optimized composition and microstructure,which shows great potential for microwave applications including phase shifters and radars.More importantly,such a co-doping strategy can be also extended to other material systems,like dielectric ceramics,hexagonal ferrites or piezoelectric ceramics.
查看更多>>摘要：Developing new electrode materials with a high specific capacity for excellent lithium-ion storage proper-ties is very desirable.The MnCO3/Mn3O4 nanoparticles with uniform size(about 50 nm)and shape which are wrapped with graphene have been successfully synthesized via the one-step method for anode mate-rial of lithium-ion batteries.The as-prepared graphene-wrapped MnCO3/Mn3O4 nanocomposite exhibits remarkable electrochemical performance,including high reversible specific capacity,outstanding cycling stability,and excellent rate capability in comparison with the bare MnCO3 and MnCO3/Mn3O4 nanocom-posite.This is because the synergistic effect of MnCO3 and Mn3O4 nanoparticles and graphene nanosheets act as both electron conductors and volume buffer layers.From the scanning electron microscopy(SEM)analysis,we confirmed that the morphology and structure of the composite are preserved after 200 cy-cles.This further confirms that graphene-wrapped MnCO3/Mn3O4 nanocomposite acts as a stable tem-plate for reversible lithium-ion intercalation/deintercalation.
查看更多>>摘要：A Co-free as-cast AlCrFe2Ni2 medium entropy alloy(MEA)with multi-phases was remelted by fiber laser in this study.The effect of laser remelting on the microstructure,phase distribution and mechanical prop-erties was investigated by characterizing the as-cast and the remelted AlCrFe2Ni2 alloy.The laser remelt-ing process resulted in a significant decrease of grain size from about 780 μm to 58.89 μm(longitudinal section)and 15.87 μm(transverse section)and an increase of hardness from 4.72±0.293 GPa to 6.40±0.147 GPa(longitudinal section)and 7.55±0.360 GPa(transverse section).It was also found that the long side plate-like microstructure composed of FCC phase,ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases.The mechanical properties were evaluated by the derived stress-strain relationship obtained from nano-indentation tests data.The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa(longitudinal section)and 1647.2 MPa(transverse section)after remelting.The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated,including grain boundary strengthening,dislocation strengthening,solid solution strengthening and precipitation strengthening.The calculation results indi-cated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA.
查看更多>>摘要：The lamellar structure has an important impact on the mechanical properties of dissimilar laminated metal composites(LMCs),including the thickness ratio of dissimilar metal constituent layers and the number of layers.AA1100 and AA7075 with thickness ratios of 1∶4 and 3∶4 were fabricated for multilayer AA1100/AA7075 LMCs by hot accumulative roll bonding(ARB)technology.The bending fracture charac-teristics of AA1100/AA7075 LMCs with different thickness ratios and numbers of constituent layers were investigated.The research results indicated that AA1100/AA7075 LMCs with a low thickness ratio exhib-ited better bending ductility and toughness than those with a high thickness ratio,which was attributed to the crack growth resistance caused by the thickness of the soft AA1100 layer.The toughening mech-anism introduced by crack deflection or arresting contributed to the enhancement in the toughness of the LMCs compared with that of the single 7075Al layer.The bonding interfaces of AA1100/AA7075 LMCs with different numbers of layers are continuous and straight due to the high ARB temperature.A decrease in bending toughness was observed as the number of layers increased.Unlike LMCs with a low number of layers,crack deflection or interface delamination is also considered a main toughening mechanism in dissimilar LMCs in addition to the thickness effect.
查看更多>>摘要：Evolution of deformation and relaxation behaviors of a prototypical Cu46Zr46Al8 metallic glass was ex-plored by extensive creep tests under both physical aging and cyclic loading.Deep insights into the microstructure-induced dynamic heterogeneity which accommodates creep deformation were succes-sively revealed via experimental measurements and spectral analyses.An annihilation of local defects within metallic glass with increasing annealing time and cyclic numbers was observed through the re-duction of amplitude in both activation energy spectra and relaxation-time spectra,which were also ac-companied by an ascending value of βKWW.It is further found that the corresponding deformation units within the metallic glass do not disappear permanently,but are recoverable over the course of cyclic loading.The apparent suppressed relaxation process can be gradually alleviated with increasing resum-ing time between two consecutive cycles,behaving differently from physical aging,which indicates a notable discrepancy between thermal treatment and mechanical treatment.
查看更多>>摘要：The effect of the axial static magnetic field on the macro-segregation and structure in the Al-Cu and Ni-Mn-Ga alloys during directional solidification is investigated experimentally and numerically.It is found that the ring-like segregation and structure in the above-mentioned two alloys form during directional solidification at a certain growth speed under a moderate magnetic field.For the Al-Cu and Ni-Mn-Ga alloys,the moderate values of the magnetic field under which the ring-like structure forms are about 0.5 T and 1.0 T at respective growth speed of 10 μm/s and 5 μm/s.Further,the distributions of the flow and solute in the Al-Cu alloy during directional solidification under the axial static magnetic field is numer-ically simulated.Numerical results reveal that the rotary thermoelectric(TE)magnetic convection forms in the mushy zone during directional solidification under an axial magnetic field.This flow will induce the formation of the ring-like macro-segregation and structure.Changes in structures under the mag-netic field in the experimental results are in good agreement with the distributions of the TE magnetic convection and solute in the numerical results.Therefore,the formation of the ring-like structure and segregation under the magnetic field should be attributed to the solute redistribution induced by the TE magnetic convection.
查看更多>>摘要：High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lat-tices,differing from traditional alloys.Here,we investigate the magnetic and thermal transport proper-ties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical proper-ties measurements and neutron scattering.Direct-current and alternating-current magnetizations mea-surements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic in-teractions below room temperature and three anomalies are found at about 80,40,and 20 K,which are related to the paramagnetic to antiferromagnetic transition,the antiferromagnetic to ferromagnetic transition,and the spin freezing,respectively.The electrical and thermal conductivities are significantly reduced compared to Ni,and the temperature dependence of lattice thermal conductivity exhibits a glass-like plateau.Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.
查看更多>>摘要：Correlation between precipitates evolution and mechanical properties of Al-Sc-Zr alloy with Er additions during isothermal ageing were investigated by microhardness measurements,transmission electron mi-croscopy,atom probe tomography and density functional theory-based simulations.The results demon-strate that the Er additions significantly improve the hardness during elevated temperature ageing,es-pecially at 400℃.This is mainly because Er additions increase the nucleation rate of the Al3(Er,Sc,Zr)precipitates,resulting in a higher density of fine and uniform dispersion of L12 structured nanoparticles.First-principles calculations demonstrate that the second nearest neighboring solute-solute interactions for the species Sc,Zr and Er are energetically favored-a key feature to rationalize the observed pre-cipitate structure and the underlying formation mechanism.The sequential formation of the core/shell precipitates in the Er-free alloy and core/double-shell precipitates in the Er-containing alloy arises due to the different solute-solute and solute-vacancy interaction energies,and the relative diffusivities of the Er,Sc and Zr species in Al.These results shed light on the beneficial effects of Er additions on the age-hardening behavior of Al-Sc-Zr alloy and provide guidance for designing the ageing treatments for the Al-Sc-Zr(-Er)alloys.
查看更多>>摘要：Designing of hetero-atomic doped carbon-based systems through pyrolysis of abundant element organic precursors is a novel approach to construct rational porous carbon materials.Herein,a highly-cross-linked triazine polymer is employed to fabricate N,P co-doped porous carbon(A-TDP-12)with tunable active ni-trogen in the carbon framework for simultaneous enhancement of CO2 capture capability and Supercapac-itance(SC).The synthesized A-TDP-12 possesses a typical hierarchically porous framework(micro-pores and meso-pores)with a large surface area(1332 m2 g-1)and a rich content of N(7.89 at.％)and P(0.74 at.％).It delivers a CO2 adsorption capacity of 1.52 and 5.68 mmol g-1 at 1 and 5 bar,respectively,with almost no decay after successive 8 recycles.In 6 M KOH aqueous electrolyte,A-TDP-12 exhibits a supe-rior specific capacitance of 172.7 F g-1 at a current density of 1 A g-1.Even at a high current density of 10 A g-1,80％of its initial capacity still remains.This work not only offers a novel strategy for fabricating promising adsorbents and electrodes for CO2 uptake and SCs,but also provides new insights into design of porous carbon material for related applications.
查看更多>>摘要：Bacterial adhesion and biofilm formation impose a heavy burden on the medical system.Bacterial ad-hesion on implant materials would induce inflammation and result in implant failure.The adhesion of bacteria on food-processing and handling equipment may lead to food-borne illness.To reduce and even prevent bacterial adhesion,some bacterial anti-adhesion surface designs have been developed.However,the effect of some surface properties(including surface patterning,roughness and wettability)on bac-terial adhesion has not been systematically summarized.In this review,a comprehensive overview of bacterial anti-adhesion surface design is presented.Modifying the surface pattern and roughness could reduce the contact area between bacteria and surfaces to weaken the initial adhesion force.Fabricating superhydrophobic surface or modifying hydrophilic functional groups could hinder the bacterial adhe-sion.The analysis and discussion about influencing factors of bacterial anti-adhesion surfaces provide basic guidelines on antibacterial surface design for future researches.
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