查看更多>>摘要：To acquire efficient photocatalysts,it is necessary to make effective use of visible light/Near Infrared(NIR)light,which takes up a large percentage of sunlight.Integrating upconversion materials with visible light active photocatalysts has attracted much attention in this regard.The interface contact between upcon-version material and photocatalyst has potential influence on the properties and thus the performance of the system.In this work,NaYF4∶Yb,Er/CdS composites of the upconversion material NaYF4∶Yb,Er nanorods and CdS nanoparticles were synthesized by ion adsorption/precipitation process and were then annealed in an argon atmosphere at different temperatures to modulate the microstructures.The annealing pro-cess endows the crystal transformation of cubic CdS with low crystallinity to hexagonal CdS with high crystallinity and,importantly,good interface contact between NaYF4∶Yb,Er and CdS.Consequently,the hy-drogen evolution activity greatly increases from 171 to 2539 μmol h-1 g-1 under the light irradiation ofλ＞400 nm,and from 0 to 19 μmol h-1 g-1 under the light irradiation of λ＞600 nm.This work might provide a useful reference for the rational design of promising photocatalyst involving upconversion ma-terials.
查看更多>>摘要：Layered structure MoS2 nanosheets have shown great potential for energy storage applications.However,the methodology for elaborately controllable growth of MoS2 onto carbonaceous matrix for promoting the electrochemical performance is highly desirable.Herein,a high-effective,all-in-one in-situ conversion growth strategy has been proposed to construct a stable sandwich-type nanostructure.The formation of the optimized C-MoS2/NCNTs product undergoes a dissolution-recrystallization process,in which ultra-thin carbon layer-coated MoS2 nanosheets densely assembled onto the surface of polyimide(PI)derived N-doped carbon nanotubes(CNTs).Theoretical simulation reveals that MoS2 nanosheets possessing an expanded interlayer spacing of 0.92 nm can greatly reduce the barrier energy of Na ions mitigation.Ac-cordingly,the as-made C-MoS2/NCNTs anode delivers superior cycling stability(82％capacity retention after 400 cycles at 1 A g-1)and rate performance(348 mAh g-1 at 2 A g-1).The results demonstrate that the expanded MoS2 interlayer distance,ultrathin outer carbon coating,and N-doped CNTs matrix together accounts for the outstanding sodium storage capability for the C-MoS2/NCNTs electrode.
查看更多>>摘要：To improve the strength and ductility of TiAl alloys by second phase,Ti46Al4Nb1Mo alloys doped with different B content(0.4％,0.8％,1.2％,1.6％and 2.0％,atomic percent,hereafter in at.％,referred to as TNM-xB)were prepared.Macro/microstructure evolution,mechanical properties and deformation mechanisms of the alloys were studied systematically.Results showed that the microstructure of TNM-0.4B and TNM-0.8B alloy remained columnar dendrites,and the secondary dendritic arms of columnar grains were more obvious.When the content of B is 1.2％,the columnar dendrites transformed to equiaxed grains,and theα2/γ lamellae colony size was further refined in TNM-1.6B and TNM-2.0B alloy.The morphologies and kinds of the borides were changed with increasing B content,XRD results showed that TiB phase ap-peared with 1.6％B content,and both TiB and TiB2 phase formed in TNM-2.0B alloy.There were straight and curved TiB phases located around grain boundaries in TNM-0.4B and TNM-0.8B alloy,and when the content of B increased to 1.2％,the curved TiB phases were reduced,while the tiny and straight TiB phases increased.With further increasing B content to 1.6％and 2.0％,the tiny and straight TiB phases were coarser.Compressive testing results showed that the mechanical properties of the TNM alloy were enhanced with increasing B content.The maximum strength and strain of TNM alloy were 2339MPa and 33.7％with 1.6％B addition.The compressive strength and strain were mainly enhanced via refinement of lamellar colony and formation of TiB,and it is found that pile-up of dislocations and deformed twins promoted by TiB are predominant in improving the mechanical properties of TNM alloys with higher strength and strain.
查看更多>>摘要：Till now,fewer literatures have investigated the corrosion resistance of microwave absorbers,especially mental@C/carbon matrix derived from MOF composites,although it is known that carbon shells possess a protective effect.Herein,three kinds of morphology-controlled CoNi/C-N doped architectures were suc-cessfully fabricated via a sequence of processing,namely coprecipitation for ZIF-67,subsequent Ni2+ex-change and ultimate carbonization.Apart from composition characterization,the effects of microstructure tailoring and temperature controlling on electromagnetic response as well as attenuation performance were revealed,where dodecahedron-shaped composites possessed the highest permittivity.By contrast,rod-shaped composites(CoNi/C-r-550 and CoNi/C-r-700)were endowed with superior comprehensive ab-sorption properties,e.g.,RLmin:-49.8 dB and-64.0 dB;EAB:5.7 GHz and 4.8 GHz,respectively.Besides,samples CoNi/C-d-700 and CoNi/C-r-700 present higher corrosion potential(Ecorr)and lower corrosion current(Icorr).Hence,these corrosion-resistant microwave absorbers with outstanding absorption stabil-ity,wetting effect as well as environmental adaptability,can be used as a candidate/raw material for intelligent devices.
查看更多>>摘要：This work intends to manipulate the internal flow units in Zr55Cu30Ni5Al10 bulk-metallic glasses(BMGs)through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity.Based on the cooperative shear model theory,serration-flow statistics during nanoindentation loading and creep tests during the holding stage were used to analyze the influence of hydrogen on the behavior of flow units in BMGs.Experimental observations showed that the hydrogen in the Zr55Cu30Ni5Al10 BMGs caused mechanical softening,plasticity improvement,and structural relaxation.Analysis also showed that the average volume,size,and activation energy of internal flow units in the BMGs all increased as a result of the increase in the hydrogen content,The hydrogenation in the BMGs was found to lead to a prolifera-tion of shear bands,which promoted plasticity.The aggregation of these internal flow units reduced the stress required for plastic deformation through shear bands,ultimately causing softening and structural relaxation.
查看更多>>摘要：Hollow nanostructures are extremely attractive in energy storage and show broad application prospects.But the preparation method is accompanied by a complicated process.In this article,the CoZn-based hol-low nanoboxes with electrochemical synergy are prepared in a simple way.This structure can effectively shorten the transmission distance of ions and electrons,and alleviate the volume expansion during the cycle.In particular,bimetallic oxides are rich in oxygen vacancies,providing more active sites for electro-chemical reactions.In addition,the stepwise oxidation-reduction reaction can also improve the volume change of the electrode material.According to the kinetic analysis and density functional theory(DFT)calculation,it is confirmed that the synergistic effect of the bimetallic oxide can accelerate the reaction kinetics.Based on these characteristics,the electrode exhibits stable cycle performance and long cycle life in alkali metal ion batteries,and can provide reversible capacities of 302.1(LIBs,2000 cycles),172.5(SIBs,10000 cycles)and 109.6(PIBs,5000 cycles)mA h g-1 at a current density of 1.0 A g-1,respectively.In ad-dition,by assembling(LiCoO2//CoZn-O2)and(Na3V2(PO4)3//CoZn-O2)full-cells,the practical application value is demonstrated.The sharing of this work introduces a simple way to synthesize hollow nanoboxes,and shows excellent electrochemical performance,which can also be expanded in other areas.
查看更多>>摘要：Epitaxial Ni-Mn-Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems.To date,large abrupt magnetization changes have been observed in some epitaxial Ni-Mn-Ga thin films,but their origin-either from magnetically induced martensite variant reorientation(MIR)or magnetic domain evolution-has been discussed controversially.In the present work,we inves-tigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni-Mn-Ga thin film through wide-field magneto-optical Kerr-microscopy.It is demonstrated that the abrupt magnetiza-tion changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.
查看更多>>摘要：Magnetic refrigeration(MR)by utilizing the magnetocaloric(MC)effect is recognized as one of the most potential promising solid state environmentally friendly and high efficiency alternative method to the well-used state-of-the-art gas compression cooling technique.In this work,a systematic investigation of quinary equi-atomic rare-earths(RE)based Er20Ho20Gd20Ni20Co20 high-entropy(HE)amorphous alloy in terms of the microstructure,magnetic and magnetocaloric(MC)properties have been reported.The Er20Ho20Gd20Ni20Co20 exhibits promising glass forming ability with an undercooled liquid region of 72 K.Excellent cryogenic MC performances can be found in wide temperature from～25 and～75 K,close to H2 and N2 liquefaction,respectively.Apart from the largest magnetic entropy change(-ΔSM)reaches 17.84 J/(kg K)with 0-7 T magnetic field change,corresponding refrigerant capacity(RC)attains a giant value of 1030 J/kg.The promising cryogenic MC performances together with the unique HE amorphous characterizations make the quinary Er20Ho20Gd20Ni20Co20 HE amorphous alloy attractive for cryogenic MR applications.
查看更多>>摘要：Anions in the electrolyte are usually ignored in conventional"rocking-chair"batteries because only cationic de-/intercalation is considered.An ingenious scheme combining LiMn0.7Fe0.3PO4(LMFP@C)and graphite as a hybrid cathode for lithium-ion batteries(LIBs)is elaborately designed in order to exploit the potential value of anions for battery performance.The hybrid cathode has a higher conductivity and energy density than any of the individual components,allowing for the co-utilization of cations and an-ions through the de-/intercalation of Li+and PF6-over a wide voltage range.The optimal compound with a weight mix ratio of LMFP@C∶ graphite=5∶ 1 can deliver the highest specific capacity of nearly 140 mA h/g at 0.1 C and the highest voltage plateau of around 4.95 V by adjusting the appropriate mixing ratio.In addition,cyclic voltammetry was used to investigate the electrode kinetics of Li+and PF6-dif-fusion in the hybrid compound at various scan rates.In situ X-ray diffraction is also performed to further demonstrate the structural evolution of the hybrid cathode during the charge/discharge process.
查看更多>>摘要：The mechanical properties of crystalline materials can be efficiently optimized using a hierarchical twinned structure.Conventional deformation mechanisms for coherent E3 boundaries generally involve three basic models:cross-slip,partial dislocation step,and full dislocation step.In this study,we report a novel deformation mechanism that allows the co-existence of twin-separation,phase transformations,grain rotation,and cracking,around a triple junction of twin boundaries in a hierarchical twinned high-entropy alloy.The deformation mechanisms in the reference high-entropy alloy(Fe-30Mn-10Co-10Cr at.％)were investigated using LAADF-STEM.The triple junction of the hierarchical twinned structure gradually deformed during in-situ strain and showed mechanisms significantly different from that observed in the purely twinned structures.These new mechanisms are referred to as"novel synergetic deformation mech-anisms of hierarchical twin boundaries".Understanding the fundamental mechanisms of the hierarchical twin boundaries under deformation could assist the design of strong and ductile bulk materials with hierarchical twinned structure.
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