查看更多>>摘要：Manganese oxides have received extensive attention in Oxygen Reduction Reaction(ORR)research.How-ever,the poor electrical conductivity and oxygen adsorption capacity of manganese oxides limit their development,so it is necessary to prepare catalysts with highly active surfaces.We propose a method to introduce an ionically conductive medium and induce structural distortion via thermodynamics,re-sulting in novel peak-splitting highly active structures for enhanced oxygen reduction activity.With the aid of refined structural analysis,High-angle annular dark-field(HAADF-STEM)imaging,and theoretical calculations,it is elucidated that this peak-splitting structure results from thermodynamically induced structural distortions and atomic displacements.The introduction of the ionically conductive medium promotes the formation of Ag-O-Mn conductive bond bridges,which regulate the energy level matching of manganese oxides and oxygen intermediates.The thermodynamically induced structural distortion ex-poses new atomic planes in the material,and the creation of this highly active surface is accompanied by a redistribution of surface charges,which modulates the adsorption of manganese active sites with oxy-gen intermediates and greatly enhances the oxygen reduction activity.Specifically,this Ag-OMS-2 with a novel split structure exhibits excellent activity at 0.836 V,superior to Pt/C kinetics and good stability.The preparation of such highly active structures is instructive for the development of manganese oxides.
查看更多>>摘要：Combining two-dimensional materials and high-k gate dielectrics offers a promising way to enhance the device performance of tunneling field-effect transistor(TFET).In this work,the device performance of WSe2/SnSe2 TFET with various gate dielectric materials is investigated based on quantum transport sim-ulation.Results show that TFETs with high-κ gate dielectric materials exhibit improved on-off ratio and enhanced transconductance.The optimized WSe2/SnSe2 TFET with TiO2 gate dielectrics achieves an on-state current of 1560 μA/µm and a subthreshold swing(SS)of 48 mV/dec.The utilization of high-κ gate dielectric materials results in shorter tunneling length,higher transmission efficiency,and increased elec-tron tunneling probability.The performance of the WSe2/SnSe2 TFET would be affected by the presence of the underlap region.Moreover,WSe2/SnSe2 TFETs with La2O3 dielectric can be scaled down to 3 nm while meeting high-performance(HP)device requirements according to the International Technology Roadmap for Semiconductors(ITRS).This research presents a practical solution for designing advanced logic devices in the sub-5 nm technology node.
查看更多>>摘要：Electrochemical oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)are two impor-tant half-cell reactions for overall water splitting.The rational design and fabrication of efficient electro-catalysts involving nonprecious-metals and carbon matrix is highly attractive.Herein,a series of N-doped carbon nanotubes encapsulated FeNi alloy nanoparticles(FeNi@NCNTs)are synthesized via a simple py-rolysis treatment of Fe-doped Ni(OH)2 precursors under the assistance of dicyandiamine source.The re-sults reveal that the Fe/Ni ratio has an obvious influence on the morphology and phase composition of FeNi@NCNTs series,thus affecting the electrocatalytic performance.The highest electrocatalytic activity is achieved for the Fe1Ni4@NCNTs product with a Fe/Ni molar ratio of 1:4,which delivers low overpoten-tials of 278 and 279 mV for OER and HER at 10 mA cm-2 in 1.0 mol/L KOH,respectively.The intriguing electrocatalytic performance is mainly ascribed to the advantageous integration of rambutan-like hier-archically porous structure and composition optimization,significantly facilitating the fast mass/charge transfer as well as promoting the adsorption ability for intermediates.The present method may open a facile avenue for developing cost-effective,high-activity,and stable electrocatalysts for the application of overall water splitting.
查看更多>>摘要：In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room temperature mechanical properties and creep behaviors at 423 K were investigated.The results show that Zn and Ca co-addition shows little influence on average grain size and texture in-tensity but changes the dispersive Mg3Bi2 into Mg2Bi2Ca particles in different sizes and a lower density.Twinning is largely activated during room-temperature deformation.Consequently,a slightly decreased proof strength but tripled elongation is shown at room temperature.Unexpectedly,large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy.Stress exponent n=4-5 indicates that the creep is a dislocation-climb controlled type.Post-mortem characterization on microstructure shows slip of dislocation<c+a>are also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy.Dynamic segregation and precipitation are also seen in both alloys.Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries.By contrast,Zn-rich needle-like precipitates are developed at most"ends"of<c+a>dislocations,which would hinder the further dislocation motions and thus improve the creep resistance.First-principles cal-culations were adopted and the results show that the thermal stability and thermomechanical properties of Mg2Bi2Ca are much better than that of Mg3Bi2.Stacking faults energy is lowered down with the co-addition of Ca and Zn,which could inhibit the rate of dislocation climb and cross-slip.As a result,the im-proved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys.Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition.These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.
查看更多>>摘要：In the context of abundant marine wind energy resources,offshore wind power presents an effective solution to the current energy crisis,however,the challenges of electromagnetic interference and corrosion faced by offshore wind power generation equipment demand urgent resolution.This study addresses these issues by employing a coordination strategy between deprotonated dopamine and tran-sition metal ions,utilizing compositional regulation and temperature engineering to synthesize a series of carbon/transition metal carbides(TMCs)composite materials.Compositional regulation introduces heterojunction interfaces to enhance dielectric loss,while temperature engineering effectively adjusts the material's impedance matching.WM@C,with an extremely thin thickness of 1.66 mm,demonstrates a remarkable effective absorption bandwidth(EAB)reaching 5.52 GHz,accompanied by a maximum reflection loss(RL)of-26.8 dB.Notably,attributed to the outstanding anti-chloride ion pitting ability of TMCs and the stacking effect of dense carbon nanosheets on the surface,the synthesized composite coatings demonstrate excellent corrosion protection capabilities.After 10 consecutive days of salt spray test,the EAB of the WM@C still maintains 5.01 GHz at 1.76 mm,a new idea of dual-function integrated materials for microwave absorption(MA)and corrosion protection has been developed,providing theoretical support for the construction of offshore wind power generation equipment.
查看更多>>摘要：Contemporary industrial sectors are experiencing a growing imperative for coatings that exhibit a multi-tude of functions.In this study,PBP-Ce(Ⅲ)nanosheets,characterized by robust structural stability,were synthesized using a one-pot method and incorporated into waterborne epoxy resin(WEP)to formu-late nanocomposite coatings.The findings demonstrate that the coating,containing 0.6 wt.％PBP-Ce(Ⅲ)nanosheets,exhibits superb anti-corrosion,flame-retardant,and wear-resistant properties.Upon 42 days of 3.5％NaCl solution immersion,the fb of the 6-PBTC coating was a mere 3.55 Hz,significantly lower than the 309.51 Hz measured for the pure WEP coating.Furthermore,the Peak heat release rate(PHRR)of the microscale combustion calorimeter(MCC)and the wear rate of the 6-PBTC coating were reduced by 41.63％and 84.65％,respectively,in comparison to the pure WEP coating.This work not only delves into the utilization of BP nanosheets but also presents a viable solution for advancing the development of multifunctional coatings.
查看更多>>摘要：The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectures.However,the development of heterogeneous ceramics is limited by low flexibil-ity of heterogeneity,geometrical complexity,structural resolution,manufacturing efficiency,and mate-rial diversity.In this study,we demonstrated flexible and rapid approaches for fabricating complicated and precise heterogeneous ceramics by shape-changing(4D)or shape-keeping(3D)additive-subtractive manufacturing(ASM)methods.The shape-changing strategy for heterogeneous ceramics was achieved by global ceramization of heterogeneous precursors,while the shape-keeping strategy for heterogeneous ceramics was achieved by local receramization of homogeneous ceramics.Finite element analysis(FEA)simulations of the influence of the thermal shrinkage dominant in the shape-changing strategy on the shape deformation of heterogeneous ceramics could be valuable predictions of the experimental results.The 3D/4D ASM methods are generic for high-temperature materials and extendable to metallic and dia-mond materials.
查看更多>>摘要：To prolong the service lifetime of hot-section components used in marine environment at elevated tem-peratures,it is crucial to explore and develop high-temperature corrosion-resistant coatings.High-velocity oxygen fuel(HVOF)sprayed NiCoCrAlY,Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated.This study is concerned with the performance of three coat-ings in a simulated marine environment based on the phase composition of corrosion products and mi-crostructure evolution of coating samples combined with first-principles density functional theory.The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion,leading to premature coating failure.The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating.In contrast,the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance,which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.
查看更多>>摘要：The ultrasonic-assisted transient liquid phase(U-TLP)bonding process is extremely fast,which is a great challenge to reveal the inherent mechanisms.Understanding the joint formation mechanism of U-TLP is essential for the joining process design.In this study,the SiC ceramics and 6063Al alloys were joined by U-TLP using a Zn interlayer.The process of removing the oxide film on the base metal involved crack-ing,flaking off,suspending,and fragmenting.The migration of the eutectic liquid phases frontier was very fast(within 1 s).The relationship between the thickness of the liquid layer and the ultrasonic ac-tion time was a power function.The typical microstructure of the SiC/6063AI joints was SiC/amorphous Al2O3/Zn-Al eutectic/Zn-Al eutectoid/6063Al.The shear strength of SiC/6063Al joints increased with the interfacial bonding ratio and reached up to 27 MPa for the ultrasonic action time of 5 s.The metallurgical bonding at the SiC/bond metal interface was formed through the amorphous Al2O3 transition layer.The formation mechanism of the Al2O3 reaction layer was revealed based on the thermodynamics,kinetics,and acoustics cavitation theory.This will provide a guideline for the future U-TLP process design.
查看更多>>摘要：Nowadays,energy and environmental problems are becoming increasingly prominent in society,the de-velopment of clean and environmentally friendly energy is in line with the construction of ecological civilization and energy,which have attracted the attention of many researchers over the past decades.Narrow band gap semiconductor Sb2S3 is widely used in the area of solar cells because of its high light absorption coefficient and suitable bandgap width.However,numerous deep-level defects provide plen-tiful photogenerated carrier recombination sites,which restricts the improvement of photoelectrochem-ical properties seriously.In this work,S-scheme Sb2S3@CdSexS1-x core-shell quasi-one-dimensional het-erojunction photoanodes were prepared on the FTO substrate by a two-step vapor transport deposition(VTD)method,chemical bath deposition(CBD)and in-situ selenization method.The results showed that CdSexS1-x nanoparticles(NPs)were tightly coated on the Sb2S3 nanorods(NRs).The photocurrent den-sity of the Sb2S3@CdSexS1-x photoanodes was 1.61 mA cm-2 under 1.23 VRHE.Compared with the Sb2S3 photoanodes(0.61 mA cm-2),Sb2S3@CdSexS1-x photoanodes obtained a 2.64-fold improvement,and the dark current was effectively reduced.It showed excellent stability and fast photocurrent response in a 600 s optical stability test.It was concluded that:(1)The charge transfer mechanism of the S-scheme can avoid the problem of high recombination rate of photogenerated charge carriers due to the defects of Sb2S3 effectively,and realized spatial separation of photogenerated carriers.(2)The[hkl]oriented Sb2S3 NRs and the formed quasi-one-dimensional heterostructures promote efficient carrier transport.(3)The introduction of Se effectively regulated the band structure of CdS,slowed down the photocorrosion of S,and improved the stability of the photoelectrodes significantly.
NETL
NSTL
万方数据