查看更多>>摘要：Vanadium redox flow battery(VRFB)is a kind of battery with wide application prospect.Electrode mate-rial is one of the key components of VRFB,and its stability directly affects the performance of battery.Among all kinds of electrode materials,carbon-based material has the best comprehensive properties.However,carbon-based electrodes still have disadvantages such as poor hydrophilicity and low electro-chemical activity which need to be improved.One of the effective ways to improve the performance of electrode is to modify carbon-based material with metals and metal oxides.The metal catalysts have excellent electrical conductivity and high catalytic activity.The metal oxide catalysts have the advan-tages of low cost,wide variety and strong oxidizing properties.This work introduced the application of metal and metal oxide modified electrodes in VRFB in recent years,classified the catalysts,studied their catalytic performance and mechanism.The metal catalysts were reviewed from precious metals and base metals.The metal oxide catalysts were classified and discussed according to the similar proper-ties of the same group elements.This work compared different modification methods,summarized the research progress of metal and metal oxide modification,and proposes the future development direction of electrodes and catalysts.
查看更多>>摘要：Transition metal oxides as anode materials for high-performance lithium-ion batteries suffer from severe capacity decay,originating primarily from particle pulverization upon volume expansion/shrinkage and the intrinsically sluggish electron/ion transport.Herein,in-situ encapsulation of α-Fe2O3 nanoparticles into micro-sized ZnFe2O4 capsules is facilely fulfilled through a co-precipitation process and followed by heat-treatment at optimal calcination temperature.The porous ZnFe2C4 scaffold affords a synergistic confinement effect to suppress the grain growth of α-Fe2O3 nanocrystals during the calcination process and to accommodate the stress generated by volume expansion during the charge/discharge process,leading to an enhanced interfacial conductivity and inhibit electrode pulverization and mechanical failure in the active material.With these merits,the prepared α-Fe2O3/ZnFe2O4 composite delivers prolonged cycling stability and improved rate capability with a higher specific capacity than sole α-Fe2O3 and ZnFe2O4.The discharge capacity is retained at 700 mAh g-1 after 500 cycles at 200 mA g-1 and 940 mAh g-1 after 50 cycles at 100 mA g-1.This work provides a new perspective in designing transition metal oxides for advanced lithium-ion batteries with superior electrochemical properties.
查看更多>>摘要：Ge2Sb2Tes is the most widely utilized chalcogenide phase-change material for non-volatile photonic applications,which undergoes amorphous-cubic and cubic-hexagonal phase transition under external excitations.However,the cubic-hexagonal optical contrast is negligible,only the amorphous-cubic phase transition of Ge2Sb2Te5 is available.This limits the optical switching states of traditional active dis-plays and absorbers to two.We find that increasing structural disorder difference of cubic-hexagonal can increase optical contrast close to the level of amorphous-cubic.Therefore,an amorphous-cubic-hexagonal phase transition with high optical contrast is realized.Using this phase transition,we have developed display and absorber with three distinct switching states,improving the switching perfor-mance by 50％.Through the combination of first-principle calculations and experiments,we reveal that the key to increasing structural disorder difference of amorphous,cubic and hexagonal phases is to intro-duce small interstitial impurities(like N)in Ge2Sb2Tes,rather than large substitutional impurities(like Ag)previously thought.This is explained by the formation energy and lattice distortion.Based on the impurity atomic radius,interstitial site radius and formation energy,C and B are also potential suit-able impurities.In addition,introducing interstitial impurities into phase-change materials with van der Waals gaps in stable phase such as GeSb4Te7,GeSb2Te4,Ge3Sb2Te6,Sb2Te3 will produce high optical con-trast amorphous-metastable-stable phase transition.This research not only reveals the important role of interstitial impurities in increasing the optical contrast between metastable-stable phases,but also proposes varieties of candidate matrices and impurities.This provides new phase-change materials and design methods for non-volatile optical devices with multi-switching states.
查看更多>>摘要：Al-Cu binary alloys are important and interesting industry materials.Up to date,the formation mecha-nisms of the key strengthening precipitates,named θ'-phase,in the alloys are still controversial.Here,we report that for non-deformed bulk Al-Cu alloys the θ'-phase actually has its own direct precursors that can form only at elevated aging temperature(＞ca.200℃).These high-temperature precursors have the same plate-like morphology as the θ'-phase precipitates but rather different structures.Atomic-resolution imaging reveals that they have a tetragonal structure with a = 0.405 nm and c = 1.213 nm,and an average composition of Al5-xCui+x(0≤x＜1),being fully coherent with the Al-lattice.This precur-sor phase may initiate with a composition of Al5Cu and evolve locally towards Al4Cu2 in composition,eventually leading to a consequent structural transformation into the θ'-phase(Al4Cu2=Al2Cu).There are evidences that because of their genetic links in structure,such a high-temperature precursor may transform to the θ'-phase without having to change their morphology and interface structure.Our study reveals a well-defined and previously hidden precipitation scenario for the θ'-phase to form in Al-Cu alloys at an elevated aging temperature.
查看更多>>摘要：A good combination of ultimate tensile strength(UTS)up to 1365 MPa and total strain to failure(StF)to 15.5％has been achieved due to deformable martensite in the invented vanadium-microalloyed dual-phase(DP)steel,which was manufactured by two-stage annealing of cold rolled steel strip.The employed extensive characterizations revealed that the ductile martensitic phase in this DP steel differ-entiated from ordinarily low-carbon martensitic lath in both morphology and lattice structure.Complex coherent orientation relationships between ferrite,reverse austenite,martensitic phase and vanadium carbide(VC)do exist,leading to a new martensitic transformation mechanism and resultant dual-phase microstructure.Besides,a detailed characterization including essential phase transformation analysis in combination with in situ TEM observation,shows that,all the essential processing including recrystal-lization,reverse austenitic and martensitic transformation,in debt to the particular effects of VC,can be recognized as phase transformations with higher thermodynamic driving force and higher kinetic energy barrier as compared to previously common processing,which actually changes the microstructure and,indirectly leads to higher strength and higher ductility.This synergy of thermodynamics and kinetics can be generalized to improve mechanical properties of present steels.
查看更多>>摘要：As one of the most effective mechanisms,precipitation-hardening is widely used to strengthen high-entropy alloys.Yet,heavy precipitation-hardened high-entropy alloys usually exhibit serious embrittlement.How to effectively achieve ultra-high strength and maintain reliable ductility remains a challenge.Here,we report a study of doping extremely little boron to meet this target.We found that adding of 30 ppm boron into the heavy Ti and Al alloyed FCC FeCoNiCr high-entropy,(FeCoNiCr)88Ti6Al6 HEA(at.％)which is strengthened mainly by both coarse BCC-based(Ni,Co)2TiAl Heusler and fine L12-type FCC-based(Ni,Co)3TiAl precipitates and shows ultrahigh strength but poor ductility,could significantly change the original microstructure and consequently improve mechanical performance,owing to the well-known effect of boron on reducing the energy of grain boundaries.The boron addition can(1)eliminate microcavities formed at Heusler precipitate-matrix interfaces;(2)suppress the formation and segregation of coarse BCC Heusler precipitates;(3)promote the formation of L12 nanoparticles.This changes of microstructure substantially improve the tensile ductility more than by～86％and retain comparable or even better ultimate tensile strength.These findings may provide a simple and cost-less solution to produce heavy precipitation-strengthened HEAs with ultrahigh strength and prevent accidental brittleness.
查看更多>>摘要：Ag-Mo-O ternary oxide has attracted growing attention because of its potential as a solid lubricant at high temperatures.This work designs and prepares NiCoCrAlYTa/Ag/Mo composite coating,performed using high velocity oxy-fuel(HVOF)spraying technology.The environment temperature plays an important role in the microstructure and phases as well as lubricant properties of NiCoCrAlYTa/Ag/Mo coatings.When the environment temperature is above 600C,the outer diffusion and oxidation of Ag and Mo lead to the formation of Ag2MoO4 on the coating surface.Layer-like Ag2MoO4 could form a continuous lubricant film at 800℃and consequently let the composite coating present the best tribological properties.Meanwhile,a small number of hard particles could play a good bearing role during friction and improve the tribological properties of the composite coating.
查看更多>>摘要：Laser powder bed fusion(LPBF)yields unique advantages during the fabrication of titanium alloys.In the present work,Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy specimens with excellent mechanical performances were fabricated by LPBF.The as-built specimens displayed relatively high strength and ductility under modest volume energy densities(VEDs),whereas they manifested high strength with low ductility under high VEDs.To investigate the key reason of this phenomenon,the specimens were designed with two VEDs ranges of 60 J/mm3 and 85J/mm3.Special attention was paid to the influences of residual stress and micro-deformation on microstructures and mechanical properties for the first time.The results indicated that the residual stresses and relative density of the 60 J/mm3 range specimens were higher than that of the 85 J/mm3 range specimens.Dislocation multiplication and dislocation movement promoted by the residual stress were hindered by the initial α'phase grain boundary(prior-α'GB),leading to the formation of α'metastable structures.The mean tensile strength and elongation of the 60 J/mm3 range specimens were 1248.1 MPa and 12.3％,respectively,whereas the corresponding values for the 85 J/mm3 range specimens were 1405.3 MPa,5.0％,respectively.During deformation,the strength and ductility of the specimens were first improved by lamellar structures generated from prior-α'phases,and then effectively enhanced by the interaction between the{10-12}twins and dislocations.However,pores significantly reduced the ductility;hence,high VED specimens with large twins and numerous large pores increased the strength and reduce the ductility.
查看更多>>摘要：The precipitation evolutions of Mg-Al-Zn alloys play essential roles in their mechanical properties,corro-sion performance,formability,plastic deformation mechanisms and texture development.In the present work,the precipitation evolutions of AZ80 magnesium alloy during both non-isothermal and isothermal processes were unraveled by utilizing in situ electrical resistivity monitoring,hardness testing,differen-tial scanning calorimetry and microstructural characterization.The results showed that discontinuous precipitation(DP)and continuous precipitation(CP)occurred competitively during non-isothermal and isothermal processes.The precipitation of dominant 3-Mgi7Ali2 phase during non-isothermal processes was highly dependent on the thermal history.During isothermal processes,the precipitation behavior of AZ80 magnesium alloy could be considered as the functions of holding temperature and time.At lower temperatures,massive DP and CP were gradually formed to equally strengthen the alloy.At higher tem-peratures,the Ostwald coarsening was characterized in the later stages and indicated to slightly soften the alloy.Isothermal time-temperature-precipitation curves and quantitative precipitate evolution were estimated to unravel precipitation characteristics and their strengthening functions.
Muhammad Imran SaleemShangyi YangAttia BatoolMuhammad Sulaman...
196-204页
查看更多>>摘要：Heterojunction is regarded as a crucial step toward realizing high-performance devices,particularly,forming gradient energy band between heterojunctions benefits self-powered photodetectors.There-fore,in this paper,the synthesis of CsPbI3 nanorods(NRs)and its application as the interfacial layer in high-performance,all-solution-processed self-powered photodetectors are presented.For the bilayer photodetector ITO/ZnO(100 nm)/PbS-TBAI(150 nm)/Au,a responsivity of 3.6 A/W with a specific detec-tivity of 9.8×1012 Jones was obtained under 0.1 mW/cm2 white light illumination at zero bias(i.e.in self-powered mode).Meanwhile,the photocurrent was enhanced to an On/Off current ratio of 10s at zero bias with an open circuit voltage of 0.53 V for trilayer photodetector ITO/ZnO(100 nm)/PbS-TBAI(150 nm)/CsPbI3(250 nm)/Au,in which the CsPbI3 NRs layer works as the interfacial layer.As a result,a specific detectivity of 4.5×1013 Jones with a responsivity of 11.12 A/W was obtained under 0.1 mW/cm2 white light illumination,as well as the rising/decaying time of 0.57 s/0.41 s with excellent stability and reproducibility upto four weeks in air.The enhanced-performance is ascribed to the mis-match bandgap between PbS-TBAI/CsPbI3 interface,which can suppress the carrier recombination and provide efficient transport passages for charge carriers.Thus,it provides a feasible and efficient method for high-performance photodetectors.
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