查看更多>>摘要：The antibacterial polyamide 6(PA6)material has attracted great research interest due to its wide ap-plication in food packaging,biomedical fields,functional textiles,and other fields.However,it is still a challenge to prepare intrinsically antibacterial PA6 with highly efficient and durably antibacterial activity via polymerization.Herein,the antibacterial imidazolium ionic liquid of 3-carboxymethyl-1-decyl imida-zole chloride was designed and synthesized for adapting the polymerization and processing temperature of PA6.Then antibacterial PA6(PA6-IL)was synthesized through hydrolyzed ring-opening copolymeriza-tion with imidazolium at the end of the backbones.Compared to physical blending or post-modification methods,antibacterial agents as end-capping reagents of polymer backbones endowed PA6 with intrin-sic antibacterial activity.As expected,the obtained PA6-IL exhibited not just comparable physicochemical and mechanical properties to conventional PA6 but excellent antibacterial activity of low antibacterial time to 60 min and durability for 28 days.Additionally,the corresponding electrospun PA6-IL nanofi-brous membranes showed homogenous morphology and remarkable hydrophilicity of 7.7° as well as the high-efficient antibacterial activity.Melt-spun PA6-IL microfibers revealed a smooth surface as well as enhanced tensile strength and increased breaking elongation compared to those of conventional PA6.The PA6-IL microfibers also behaved with excellent antibacterial efficiency and durability.Accordingly,this work provides a feasible and straightforward strategy to prepare durably and intrinsically antibacterial PA6 materials especially PA6 fibers,which can be widely applied in the textiles field.
查看更多>>摘要：Improving the low-cycle fatigue(LCF)properties of additively manufactured Ti-5.6Al-3.8V alloy is critical in ensuring its service safety and represents a significant research challenge.This work discusses a so-lution that optimizes the alloy's microstructure and ductility by precisely controlling the over-saturated strengthening elements and heat treatment.This was accomplished using selective laser melting(SLM),heat treatment at 800 ℃ for 2 h,and furnace cooling on a Ti-5.6Al-3.8V alloy with tightly controlled Al,V,and O concentrations in a lower range.The results showed that the SLM-fabricated Ti-5.6Al-3.8V alloy,post-heat treatment,exhibited α laths with a width of～1.4 μm and β columnar grains with a diameter of～126 μm,without experiencing coarsening or variant selection phenomena.The alloy bal-anced strength and ductility post-heat treatment with a UTS of 1015 MPa and an EL of 16.5％relative to the as-deposited state(UTS of 1199 MPa and EL of 11.9％).Notably,the LCF properties of the heat-treated SLM Ti-5.6Al-3.8V alloy are superior to those of other Ti-6Al-4V alloys produced by additive manu-facturing and comparable to traditional forgings.At high strain amplitudes(1-1.5％),the fatigue life of this alloy was twice that of the Ti-6Al-4V forgings.Furthermore,we comprehensively analyzed the mi-crostructure,strength,and ductility of the SLM Ti-5.6Al-3.8V alloy to elucidate the factors influencing its LCF properties.These findings provide a solid foundation for improving the LCF properties of additively manufactured Ti-6Al-4V alloy,thereby contributing to its safe and reliable use in critical applications.
查看更多>>摘要：The intrinsic heterogeneity of an amorphous structure originates from composition,and the structure de-termines the magnetic properties and crystallization models of amorphous magnets.Based on classical Fe-B binary magnetic amorphous alloys,the relationship between the structure and magnetic properties was extensively studied.The stacking structure of Fe-B binary amorphous alloys exhibit discontinuous changes within the range of 74-87 at.％Fe.The structural feature can be expressed as Amor.Fe3B ma-trix+Fe atoms are transforming into Amor.Fe matrix+B atoms with the increase of Fe content.The so-lute atoms are uniformly distributed in the amorphous matrix holes,similar to a single-phase solid solu-tion structure.The transition point corresponds to the eutectic crystallization model composition(Fe82B18 to Fe83B17).A high Fe content will amplify magnetic moment sensitivity to temperature.Under a given service temperature,the disturbance effect of magnetic moment self-spinning will offset the beneficial effect of increasing Fe content and induce the saturation magnetization(Ms)value to decrease.Binary amorphous Fe-B alloys obtain the maximum Curie temperature near 75 at.％Fe,which is slightly smaller than that of the corresponding metastable Fe3B phase,i.e.,the amorphous short-range order structure maintains the highest similarity to the Fe3B phase.The chemical short-range ordering(SRO)structure of amorphous alloys exhibits heredity to corresponding(meta)stable crystal phases.The unique spatial orientation structure of the metastable Fe3B phase is the structural origin of the amorphous nature.This study can guide the composition design of Fe-metalloid magnetic amorphous alloys.The design of ma-terials with excellent magnetic properties originates from a deep understanding of precise composition control and temperature disturbance mechanism.
查看更多>>摘要：Converting hydrocarbons into aldehydes in a green and environmentally benign way is of great signif-icance in fine chemistry.In this work,all-inorganic Cs3Bi2Br9 perovskite nanoparticles were uniformly loaded on BiOBr nanosheets via an in-situ growth method,which can selectivity photoactivate aromatic C(sp3)-H bond of toluene to generate benzaldehyde.According to the in-situ X-ray photoelectron spec-troscopy characterization,the photogenerated electrons of BiOBr transfer to Cs3Bi2Br9 enforced by the in-ternal electric field under light irradiation,resulting in S-scheme heterojunction.Furthermore,theoretical calculations indicate that toluene molecules are inclined to adsorb on the BiOBr surface,subsequently in-volving the oxidation reaction to generate benzyl radical(PhCH2·)by using the energetic holes of BiOBr,while the remaining photoinduced electrons in the conduction band(CB)of Cs3Bi2Br9 with powerful reduction ability reduce O2 into·O2-,which is the vital oxidative active species working on toluene selective oxidation process.Such an unexceptionable charge carrier utilization mode and tendentious ad-sorption behavior of reactants contribute to the optimized Cs3Bi2Br9/BiOBr heterojunction with excellent photocatalytic performance,achieving a maximum of 22.5％toluene conversion and 96.2％selectivity to-wards benzaldehyde formation.This work provides a rational photocatalyst heterojunction construction protocol for the selective oxidation of saturated aromatic C-H bonds.
查看更多>>摘要：Dissimilar welding of NiTi and stainless steel(SS)for multifunctional device fabrication is challenging due to the brittle nature of intermetallic compounds(IMCs)that are formed in the weld zone.In this work,Ni and Nb interlayers were applied for the resistance spot welding(RSW)of NiTi and SS to replace the harmful Fe2Ti phase and to restrict the mixing of dissimilar molten metals,respectively.Microstructural evolution and mechanical properties of the joints were investigated.It was shown that a conventional weld nugget was created in the absence of any interlayer in the welded joint suffering from traversed cracks due to the formation of brittle IMCs network in the fusion zone(FZ).By the addition of Ni from the interlayer,Fe2Ti dominated weld nugget was efficaciously replaced by Ni3Ti phase;however,the presence of the large pore and cracks reduced the effective joining area.The use of a Nb interlayer resulted in a fundamentally different joint,in which FZs at NiTi and SS sides separated by the unmolten Nb would suppress the mixing of dissimilar molten metals.Nb-containing eutectic structures with low brittleness formed at the interfaces,contributing to the enhancement of joint strength(increased by 38％on fracture load and 460％on energy absorption).A high-melting-point interlayer showed great potential to realize a reliable and high-performing RSWed NiTi-SS joint.
查看更多>>摘要：Large 2219 Al-Cu alloy aerospace integral components suffer from long-term stress relaxation aging(SRA)due to complex temperature and stress loads during aging treatment/forming and service process,which makes it difficult to ensure their appropriate residual stress and excellent mechanical and service prop-erties.However,the research is limited to a thorough understanding of macroscopic and microscopic features and underlying mechanisms of the long-term SRA under multivariable aging conditions.There-fore,this study investigated macroscopic and microscopic features of long-term SRA under different tem-peratures(120 ℃ to 190 ℃),initial stress levels(100 MPa to 250 MPa)and durations(0 h to 50 h)through stress relaxation curves,metallographic traits,Vickers hardness,tensile performance,disloca-tions and phases of precipitation.On the basis of experimental outcomes,the comprehensive mecha-nisms beneath SRA were unraveled through dislocation theory,multiphase strengthening mechanisms and thermodynamics,where the interplays of stress relaxation behavior with age-hardening response were taken into consideration.The results showed elevations in the rate of stress reduction as the tem-perature and initial stress rose.At an initial stress greater than the yield stress of alloy,a marked in-crease in stress relaxation was found,and the mechanisms transform from the intragranular motion of dislocations and diffusion of grain boundaries to the intragranular and intergranular motion of disloca-tions and migration of grain boundaries.The stress reduction rate rose sharply when the temperature exceeded 175 ℃,and the dislocation movement mechanisms transform from gliding to climbing of dislo-cations.Stress relaxation is in nature progressive transformation of strain from elastic into a permanently inelastic state via the motion of dislocations,leading to the decrease of movable dislocations and the increase of immovable dislocations with more stable configurations.The age hardening is mainly deter-mined by precipitation strengthening,supplementarily by dislocation strengthening,and obvious stress orientation effect(SOE)of G.P.zones and θ"phases degenerates strengthening effect.The interplay be-tween stress relaxation behavior and age-hardening response influences the thermal-mechanical coupling SRA of 2219 Al-Cu alloy,which depends fundamentally on the motion of dislocations and their interplay with precipitated phases.This is a thermal activation process concerning the interplay between internal(age-hardening resistance)stress and external(initial)stress.The initial energy of elastic strain offers Gibbs free energy as the SRA driver,and a steady state of stress relaxation is attained with the lowest energy of elastic strain.These findings provide valuable insights into exploring innovative aging treat-ment/forming for optimizing residual stress,mechanical performance and service property in a synergistic manner.
查看更多>>摘要：Developing high-efficiency photocatalysts for tetracycline hydrochloride(TCH)degradation is of great sig-nificance to ecosystems and human beings.In this work,a two-step process of exfoliation and re-stacking was performed to prepare re-stacked HTiNbO5 nanosheets(R-HTNS)and then coupled with Ti3C2 MXene to construct Ti3C2 MXene/R-HTNS(MX/RTS)with a 2D/2D Schottky heterojunction.These 2D/2D het-erostructures between Ti3C2 MXene and R-HTNS can produce an internal electric field and provide max-imum interface area for efficient charge transfer across the intimate interface.The photocatalytic perfor-mance of samples was evaluated by TCH degradation under simulated sunlight.The MX/RTS composites,with an optimal sample of 3-MX/RTS,show enhanced photocatalytic activity for TCH degradation com-pared with R-HTNS.The characterization results reveal that the introduction of Ti3C2 MXene can signif-icantly increase specific surface area for providing more reactive sites and broaden the light absorption region.Besides,the incident light energy is absorbed by the Ti3C2 MXene component in MX/RTS compos-ites to generate photothermal energy(heat),which facilitates the charge carrier separation and surface reaction kinetics.Thus,the enhanced TCH photodegradation activity for MX/RTS composites is due to the introduction of Ti3C2 MXene,which possesses the synergistic effect of the increased specific surface area,improved light-harvesting capacity,2D/2D Schottky heterojunction,and photothermal energy effect.Additionally,the TCH photodegradation behavior is deliberated with a detailed discussion on various co-existing ions.During TCH photodegradation,the active radical species are determined for 3-MX/RTS.Ac-cording to the characterization results,the possible TCH photodegradation pathway and mechanism over 3-MX/RTS are explored.This work may offer a novel insight for constructing MXene-based heterostruc-tured photocatalysts with high efficiency.
查看更多>>摘要：Due to the rapid development of radar technology,the demand for absorbing stealth materials is increas-ing,and ultra-broadband absorption(effective absorption bandwidth＞8 GHz)has become an inevitable requirement.As a new type of two-dimensional material,MXene material possesses the characteristics of excellent wave absorbing material due to its easy preparation,easy modulation of defects and sur-face functional groups,and high conductivity.This work summarizes the absorbing theory and research progress on MXene-based absorbing materials in recent years,including pure MXene absorbing materials and MXene-based magnetic or dielectric composite materials with multiple losses.Some shortcomings and research directions of MXene-based materials were pointed out.Currently,research on MXene-based absorbent materials is thriving and in a state of vigorous development.Excellent absorbent materials have been reported,but their shortcomings are also apparent.The factors that affect the performance of MXene-based absorbent materials are complex,and the absorption mechanism is relatively simple.Further systematic and detailed research is needed to clarify these influencing mechanisms,broaden the absorption bandwidth,and reduce the matching thickness to meet practical usage requirements in the future.
查看更多>>摘要：The effect of precipitation aging on the fracture behavior of cast Mg-14.23Gd-0.45Zr(wt.％)alloy at room temperature has been studied in this work.Uniaxial tensile and three-point bending tests were conducted on samples peak-aged at 175,200,225,and 250 ℃.Notably,samples aged at 175 ℃ and 200 ℃ exhibited premature fracture during the uniaxial tensile test.Through fractographic observations of the tensile test samples and electron backscattered diffraction(EBSD)analysis on the samples sub-jected to three-point bending tests,a preferential formation of cleavage cracks in samples aged at 175 ℃ and 200 ℃ was identified as the reason for their premature fracture.The X-ray diffraction(XRD)results and transmission electron microscopy(TEM)observations of precipitates indicate that the dominant strengthening precipitates in all peak-aged samples are of theβ'phase,and their size significantly influences the formation of cleavage cracks.This phenomenon is attributed to the shearing mechanism of precipitates.Specifically,the smaller β'precipitates formed under the aging temperature of 175-200 ℃ are susceptible to dislocation shearing,leading to the formation of cleavage cracks.In contrast,the larger size of β'precipitates formed under the aging temperature of 225-250 ℃ provides resistance to shearing,resulting in the restrained formation of cleavage cracks and ultimately contributing to the enhancement of the ultimate tensile strength.
查看更多>>摘要：Design of electrode materials for stable and efficient electrocatalytic oxidation of As(Ⅲ)in arsenic-contaminated groundwater poses a great challenge due to the rapid deactivation of catalysts resulting from the high oxygen evolution potential(OEP)and considerable barrier to generating reactive oxygen species(ROS).Herein,an innovative TNAs/SnO2/PEDOT/Fe(Ⅲ)-RuO2 multilayer electrode was synthesized by utilizing a PEDOT-coated SnO2 interlayer as a supportive framework to combine Fe-doped amorphous RuO2 catalytic layer with TiO2 nanotube array substrate.Such electrode exhibited high activity and sta-bility for the oxidation of As(Ⅲ)to As(V)due to the large surface area provided by the TiO2 nanotube arrays and the SnO2/PEDOT interlayer for facilitating the growth of the catalytic layer.The electrochem-ically active surface area of the electrode reached as high as 31.7 mF/cm2.Impressively,the doping of Fe into RuO2 layer led to a remarkable increase in the OEP value to 3.12 V,which boosted the indirect oxidation process mediated by ROS at a lower potential to achieve the As(Ⅲ)oxidation ratio of 98.5％.DFT calculations revealed that the Fe-doped amorphous RuO2 weakened the adsorption strength of·OH and.SO4-intermediates and lowered the energy barrier for generating ROS.Combined with ESR results,the formation of·OH and·SC4-with strong oxidizing properties was fully verified,providing further evi-dence for the involvement of ROS as the main mediator of the oxidation mechanism of As(Ⅲ).This work may provide valuable perspectives into the design of catalytic layer structures and heteroatom doping modifications for composite-coated electrodes.
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