查看更多>>摘要：In this work,a novel biochar decorated Bi4O5Br2/g-C3N4 S-scheme heterojunction was successfully pre-pared for Norfloxacin(NOR)degradation,and it was found that the 5％-Bi4O5Br2/g-C3N4/C heterojunction exhibited the excellent photocatalytic degradation activity toward NOR,degrading 92.5％of NOR within 72 min under visible light irradiation.The effects of pH,dosage,and concentration of the NOR on the photocatalytic activity were also systematically investigated.The mechanism studies revealed that the active species like hole(h+),hydroxyl radical(·OH),and superoxide radical(·O2-)play a predominant role in the NOR degradation,and the enhanced removal rate of Bi4O5Br2/g-C3N4/C heterojunction can be attributed to the synergistic effect of adsorption and photocatalytic process.In addition,an S-scheme transfer channel in the interface of the Bi4O5Br2/g-C3N4/C heterojunction is proposed,which can effec-tively improve the separation of the photogenerated carriers and enhance the photocatalytic performance.This research provides inspiration for designing S-scheme heterojunction for wastewater treatment.
查看更多>>摘要：Ternary Pb-Bi-S compounds emerge as potential thermoelectric materials owing to low thermal conduc-tivity,but the origin of their intrinsic low lattice thermal conductivities lacks further investigation.Herein,a series of ternary PbmBi2S3+m(m=1-10)compounds are synthesized and their crystal structure evolu-tions with increasing m values are clearly unclosed.The room-temperature lattice thermal conductivities in PbBi2S4,Pb3Bi2S6 and Pb6Bi2S9 can reach at 0.57,0.56 and 0.80 W m-1 K-1,respectively,outperform-ing other ternary sulfur-based compounds.Theoretical calculations show that the low lattice thermal conductivities in PbmBi2S3+m(m=1-10)mainly originate from soft phonon dispersion caused by strong lattice anharmonicity,and both asymmetric chemical bond and lone pair electrons(Pb 6s2 and Bi 6s2)can favorably block phonon propagation.Furthermore,the elastic measurements also confirm relatively low sound velocities and shear modulus,and the Grüneisen parameter(y)calculated by sound velocities can reach at 1.67,1.85 and 1.94 in PbBi2S4,Pb3Bi2S6 and Pb6Bi2S9,respectively.Finally,the intrinsic low lattice thermal conductivities in PbmBi2S3+m(m=1-10)contribute to promising thermoelectric perfor-mance,and the maximum ZT values of 0.47,0.38 and 0.45 can be achieved in undoped PbBi2S4,Pb3Bi2S6 and Pb6Bi2S9,respectively.
查看更多>>摘要：Developing high-temperature metallic glass thin films(MGTFs)with excellent combination properties is crucial for extending the practical applications of metallic glasses.A high-temperature multicomponent Mo-based MGTF with tunable microstructure prepared by single-target magnetron sputtering was pre-sented in this study.Corresponding mechanical behaviors and thermal stability of MGTFs related to mi-crostructure are systemically explored.By adjusting deposition parameters(pressure and power),the mi-crostructure of as-deposited MGTFs can be altered from the dense homogeneous type to the loose nano-glass type.Such structure evolution can be explained by the competition between the surface diffusion and geometric shadowing effect.MGTFs with dense microstructure possess smaller surface roughness,higher hardness,higher Young's modulus,and better wear resistance.Moreover,they also possess higher thermal stability where the fully amorphous structure and smooth surface can be well maintained after vacuum annealing at 1123 K for 30 min.By contrast,the MGTF with nanoglass microstructure shows infe-rior mechanical properties and thermal stability due to plentiful loose interface regions,providing abun-dant free volumes during deformation and acting as favorable crystal nucleation sites during annealing.The correlation between the microstructure and properties of as-deposited MGTFs is clarified with the universal scaling law of glasses.The annealing treatment distinctly increases the hardness and Young's modulus of MGTFs.Meanwhile,after annealing,pop-in behaviors occur in the as-annealed MGTFs with dense microstructure but not in the as-annealed MGTF with nanoglass microstructure during the nanoin-dentation.These phenomena can be rationalized by the annihilation of free volumes during annealing and the evolution of the dynamical variable,shear transition zone,for the plastic deformation in MGTFs.
查看更多>>摘要：Ferroelectric capacitors hold great promise for non-volatile memory applications.However,the challenge lies in fabricating resistive switching devices with a high on/off ratio,excellent non-volatility,and a simple manufacturing process.Here,a novel approach is introduced by demonstrating the efficacy of the coupling effect between ferroelectric polarization and oxygen vacancy-based conductive filaments in Hf0.5Zr0.5O2(HZO)films for the creation of non-volatile resistive switching memory devices,achiev-ing an impressive on/off ratio of 6.8 x 103 at+1.8 V.An in-depth exploration of the resistive switching mechanism is provided and subsequently the outstanding durability and retention characteristics of these devices for resistive switching is validated.Furthermore,the device's capacity to emulate non-volatile synaptic functionalities is assessed.Our results reveal that under pulsed conditions of 1 V/-2 V with 1 ps pulses spaced 50 ms apart,the device can robustly achieve potentiation/depression synaptic plasticity,while exhibiting energy consumption(0.16 fJ for potentiation,0.12 f]for depression)reduced by 1-2 or-ders of magnitude compared to biological synapses.This work holds significant value as a reference for the fabrication of energy-efficient,non-volatile memory and synaptic devices.
查看更多>>摘要：The strain rate(ε)dependence of ultra-low temperature strength and ductility was investigated systemat-ically on a cryogenic near alpha titanium alloy Ti-3Al-3Mo-3Zr-0.2Y additively manufactured by electron beam selective melting(EBSM).As e increases under quasi-static tension at 77 and 20 K,ductility mono-tonically decreases when yield strength(YS)keeps ascending.As ε increases from 5.6 × 10-4 s-1 once by one order of magnitude,elongation-to-fracture declines from 20.0％to 16.5％and 15.7％at 20 K.However,unlike the regular monotone increase at 298 and 77 K,ultimate tensile strength(UTS)at 20 K rises to 1460 MPa first then drops to 1320 MPa.This study further examined how strain rate affects slipping,twinning and strain hardening behavior.The monotone increase in YS is primarily attributed to the increased CRSS for slips and the enhanced tendency of pyramidal<a>and<c+a>slipping and<10(1)0>34° twinning at 20 K.On the other hand,the monotone decrease of ductility is essentially as-cribed to the intensified deformation localization characterized by micro shear bands,multiple necking and single necking.More importantly,the mechanisms of abnormal UTS variation and disappearance of serration flow at 20 K are discussed in terms of strain hardening levels,degree of shear deformation lo-calization and the interaction of slips and twins.This study provides deep insights into strain rate effect on cryogenic mechanical behavior of EBSM-built titanium alloy.
查看更多>>摘要：The low work hardening is a prominent deficiency for high-strength titanium(Ti)alloys.The gradient de-sign of oxygen content was adopted to realize the coupling deformation of {332}<113>twinning and dis-location slip in the Ti-15Mo alloy.This oxygen gradient alloy exhibited an optimal balance of yield/tensile strength(700 and 848 MPa)and elongation(25％),with remarkable work hardening behavior.The dom-inated dislocation slip deformation and the solution strengthening of oxygen atoms in the oxygen-rich region resulted in a remarkable increase in yield strength.The successive formation of {332)<113>twins and piled-up geometrically necessary dislocations around the twin boundaries in the oxygen-free region induced remarkable back stress strengthening,maintaining the high work hardening rate,which resulted in a stable increase in strength.The twins and dislocations formed at the crack tips effectively hindered the cracking behavior,avoiding premature necking.The present study provides a novel idea for designing oxygen layer-distributed Ti alloys,which further improves the strength-ductility tradeoff.
查看更多>>摘要：High/medium entropy alloys(HEAs/MEAs)with high electrocatalytic activity have attracted great atten-tion in water electrolysis applications.However,facile synthesis of self-supporting high/medium entropy alloys electrocatalysts with rich active sites through classical metallurgical methods is still a challenge.Here,a self-supporting porous FeCoNi MEA electrocatalyst with nanosheets-shaped surface for oxygen evolution reaction(OER)was prepared by a one-step electrochemical process from the metal oxides in molten CaCl2.The formation of the FeCoNi MEA is attributed to the oxides electro-reduction,high-temperature diffusion and solid solution.Additionally,the morphology and structure of the FeCoNi MEA can be precisely controlled by adjusting the electrolysis time and temperature.The electronic structure regulation and the reduced energy barrier of OER from the"cocktail effect",the abundant exposed ac-tive sites brought by surface ultrathin nanosheets,the good electronic conductivity and electrochemical stability from the self-supporting structure enable the FeCoNi MEA electrode shows high-performance OER electrocatalysis,exhibiting a low overpotential of 233 mV at a current density of 10 mA cm-2,a low Tafel slope of 29.8 mV dec-1,and an excellent stability for over 500 h without any obvious structural de-struction.This work demonstrates a facile one-step electrochemical metallurgical approach for fabricating self-supporting HEAs/MEAs electrocatalysts with nanosized surface for the application in water electroly-sis.
查看更多>>摘要：Engineering polyamide 6(PA6)is preferred for its superior mechanical properties,yet the intrinsic flammability restricts its industrial applications.As one of the biomass phosphorus-containing chemicals,phytic acid(PA)is favorable for its high phosphorus content and aggregation ability,making it expected to enhance the fire retardancy of PA6.Herein,a melamine-phytate aggregate(MPA)is prepared by elec-trostatic interaction in aqueous solution,and applied as a synergist for aluminum diethylphosphinate(ADP)in PA6.The strong synergistic effect exists between ADP and MPA towards PA6,especially when their mass ratio is 3:1 and the total loading is 18 wt％.Compared to the neat PA6,this formula allows for remarkable decreases in peak heat release rate(PHRR),total heat release(THR),and maximum average heat release rate(MARHE)by～48％,～27％,and～30％,respectively,as well as a high synergistic efficiency of～43％in PHRR.This PA6 composite also presents a V-0 rating in the vertical burning(UL-94)test and a high limiting oxygen index(LO1)of 29.7％.This work offers an eco-friendly strategy for developing bio-based P/N fire-retardant aggregates for fabricating PA6 materials with high fire safety.
查看更多>>摘要：17-4 precipitation hardening(PH)stainless steel is a multi-purpose engineering alloy offering an excel-lent trade-off between strength,toughness,and corrosion properties.It is commonly employed in additive manufacturing via laser powder bed fusion owing to its good weldability.However,there are remaining gaps in the processing-structure-property relationships for AM 17-4 PH that need to be addressed.For instance,discrepancies in literature regarding the as-built microstructure,subsequent development of the matrix phase upon heat treatment,as well as the as-built residual stress should be addressed to enable reproducible printing of 17-4 builds with superior properties.As such,this work applies a comprehensive characterisation and testing approach to 17-4 PH builds fabricated with different processing parameters,both in the as-built state and after standard heat treatments.Tensile properties in as-built samples both along and normal to the build direction were benchmarked against standard wrought samples in the so-lution annealed and quenched condition(CA).When testing along the build direction,higher ductility was observed for samples produced with a higher laser power(energy density)due to the promotion of interlayer cohesion and,hence,reduction of interlayer defects.Following the CA heat treatment,the austenite volume fraction increased to～35％,resulting in a lower yield stress and greater work hard-ening capacity than the as-built specimens due to the transformation induced plasticity effect.Neutron diffraction revealed a slight reduction in the magnitude of residual stress with laser power.A concentric scanning strategy led to a higher magnitude of residual stress than a bidirectional raster pattern.
查看更多>>摘要：Composition/structure-dependent superconductivity for FeSe-based superconductors attracted great at-tention not only due to their high superconducting transition temperatures(Tc),but also for under-standing the origin of iron-based superconductivity.Here,we report a new Fe-poor organic-inorganic hybrid material Fe14Se16(tepa)0.8 with a paramagnetic-diamagnetic transition at～42 K grown by a high-temperature organic-solution-phase method with soluble iron/selenium sources in a tepa solution,alter-native to previous intercalation strategies.The Fe14Se16(tepa)0.8 phase is in a tetragonal layered hybrid structure with a nanoplate shape.Composition analyses reveal a Fe-poor characteristic of the hybrid in contrast to previous FeSe-intercalated superconductor,and selected area electron diffraction pattern is featured by Fe3Se4 superstructures with a √2 × √2 of Fe vacancy order.Ab initio density functional cal-culations show that minus Fe3Se4 ions are stable in the hybrid and～0.25e-/Fe0.7sSe is obviously larger than the reported values of approximately 0.2e-/FeSe in other FeSe-intercalated superconductors.Typ-ical hysteresis loops and temperature dependence of dc/ac susceptibilities of the Fe14Se16(tepa)0.8 mea-sured below～42 K suggest a presence of the Meissner effect in this material.Effects of synthesis condi-tions on structures and magnetic properties of the hybrids show a magnetic evolution from a long-range ferrimagnetic(FIM)order of Fe14Se16(tepa)to a coexistence of FIM and superconducting(SC)orders of Fe14Se16(tepa)0.9 and an SC order of Fe14Se16(tepa)0.8.X-ray absorption spectrum(XAS)confirms the pres-ence of ferric/ferrous irons.Mössbauer studies reveal that the high-Tc superconductivity originates from a suppression of the FIM order through tuning the spin states of irons from high-spin Fe3+(S=5/2)and Fe2+(S=2)in the Fe14Se16(tepa)to low-spin Fe3+(S=1/2)and Fe2+(S=0)in the Fe14Se16(tepa)0.8.Although no zero resistance is detected even at a temperature of 2 K,the resistivity at 2 K decreases by more than 1600 times compared to that in a normal state calculated by a variable range hopping(VRH)model,suggesting that the high-Tc superconductivity of Fe14Se16(tepa)0.8 is possible.
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