查看更多>>摘要：The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the bench-mark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed"fast decay"and"slow decay"have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80 ℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the"fast decay"in the initial 15 h is immune to the various operating parameters,while the"slow decay"highly depends on the applied temperature and pressure.According to the X-ray absorp-tion spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the"slow decay"and accounts for the catalyst decay after the demetallation process.
查看更多>>摘要：VS2 has attracted increasing attention as a cathode material for aqueous zinc ion batteries because of its proper large layer spacing,weak interlayer interactions,multiple valence states of V,and excellent electrical conductivity,but its large volume change during charging and discharging leads to poor cycling stability.Herein,we report a one-step hydrothermal synthesis of VS2 microflowers with proper lamel-lar spacing,which provides a stable framework for the insertion/deinsertion of zinc ions and enhances the cycling stability,delivering an initial charge capacity of 128.3 mAh g-1 at 3 A g-1 and maintains a charge capacity of 100.1 mAh g-1 after 900 cycles.In addition,the optimized VS2 cathode shows specific capacities of 215.7 and 150.5 mAh g-1 at the current densities of 0.1 and 2 A g-1,respectively,demon-strating that the microflower structure with a high specific surface area and a short diffusion distance also significantly enhances the rate performance.
查看更多>>摘要：Layer-by-layer(LBL)assembly shows great potential in fabrication of flexible conductive cotton fabrics(FCCF)with carbon nanotubes(CNT)as conductive components but is limited because complicated chem-ical modification of CNT is usually required.Herein,we reported a facile and eco-friendly LBL approach to fabricating FCCF by dipping in chitosan(CS)aqueous solution and poly(sodium 4-styrenesulfonate)(PSS)wrapped CNT aqueous dispersion alternately.The FCCF with electrical conductivity higher than 30 S/m was achieved when 4 layers of CNT were coated on the cotton fabric(CF).The obtained FCCF possessed outstanding mechanical stability with electrical resistivity almost unchanged after exposure to 500 times mechanical abrasion and 500 circles of tape peeling.The FCCF showed excellent strain sensing perfor-mance with high sensitivity(with a gauge factor up to 35.1)and a fast response time(70 ms).It can be used as a strain sensor to accurately detect various human deformations such as finger bending and joint movements.The FCCF could be used as a temperature sensor in that it exhibited stable and reproducible negative temperature sensing behavior in the temperature range of 30-100 ℃.
查看更多>>摘要：Although extremely challenging,it is highly desirable to develop self-healing materials that exhibit high efficiency under environmental conditions for marine protection applications.In this work,polyurethane elastomers with hydrogen bond and dimethylglyoxime-urethane(DOU)coordination complex were com-bined with in-situ dual-functional BiOI@Bi2S3 to synthesize high-efficiency photothermal cyclic self-healing antibacterial coating.The photothermal efficiency of BiOI@Bi2S3 is improved by 38％through in-terfacial regulation.BiOI@Bi2S3/PU rapidly rises by 50.2 ℃ within 300 s under near-infrared(NIR)light,which can trigger the hydrogen bond of polyurethane coating and recover the barrier properties of the coating through self-healing.Density functional theory was used to simulate and analyze the generation of multiple electron transfer paths after the vulcanization of BiOI,which improves the interfacial mobility of photogenerated carriers and generates more heat.Importantly,molecular dynamics verified the self-healing mechanism of hydrogen bond and the photothermal lifting mechanism of the coating.After 5th scratches and self-healing cycle tests,the coating has a self-healing efficiency of more than 80％,which can ensure the self-healing and anticorrosion protection performance of the coating for multiple cycles.The photocatalytic and photothermal properties of BiOI@Bi2S3 enhance the antibacterial rate of the coat-ing up to 99％.This work provides heuristic perspectives for the design of coatings with anti-corrosion,antibacterial and self-healing properties.
查看更多>>摘要：The charge carrier separation efficiency and the adsorption capacity of the photocatalyst usually affect the degradation rate of antibiotics.Herein,Cerium-doped leaf-like CdS(Ce-CdS)modified with ultrathin N-doped rGO(N-rGO)composites were successfully constructed(Ce-CdS/N-rGO)to investigate the re-moval efficiency of tetracycline(TC).X-ray photoelectron spectroscopy(XPS)and photoelectrochemical results revealed that Ce ions doped in CdS acting as the electron capture sites facilitated the interfacial charge transfer.Theoretical calculation(DFT)results indicated that the interfacial effect between Ce-CdS and ultrathin N-rGO promoted the transfer of photogenerated electrons under the synergistic effect be-tween the doping and interface modification strategy.The optimized Ce5-CdS/N-rGO20 composites had the maximum TC removal capability(94.5％)and maintained a stable cycling performance.In addition,the adsorption-driven photocatalytic degradation pathway of TC was studied through mass spectrometry(MS)and in-situ Fourier transform infrared spectroscopy(in-situ FTIR).This study will provide an effective strategy for the construction of efficient photocatalytic composites for wastewater treatment.
查看更多>>摘要：The precipitation of topologically close-packed(TCP)phases is the result of microstructure instabilities of Ni-based superalloys.This review seeks to comprehensively collate all the available information on TCP phases in SX superalloys based on the latest findings.First,the thermodynamics and kinetics of the TCP phase precipitation are introduced.Meanwhile,the morphology,composition and orientation of TCP phases and their sequential transformation are summarized in detail.Further,the factors affecting the precipitation of these phases are sorted out.Besides,the proposed damage mechanisms of TCP phases are listed.Finally,several control and prediction methods of the TCP phase precipitation are reviewed,so the alloy designer can better balance the relationship between microstructure stabilities and properties of the superalloy.
查看更多>>摘要：To solve the electromagnetic pollution problem,the reasonable structure design and component control of the electromagnetic absorber is prominent.In this work,three-dimensional(3D)pyrolytic branched hollow architecture carbon PBHAC/MoS2 composites were prepared via a hydrothermal and calcina-tion two-step strategy.The narrow-gap nano-size MoS2 acquired after vulcanization and micro-size 3D branched carbon skeleton PBHAC possess intensified conduction losses.Particularly,the presence of po-tential differences between different phases creates a space charge region at the heterogeneous interface,resulting in strong interfacial polarization.The resulting 3D branched hollow PBHAC/MoS2 composites exhibit optimized impedance matching and multiple loss mechanisms.Finally,the 3D branched hollow carbon PBHAC/MoS2 composites have the best electromagnetic wave(EMW)absorption performance.The minimum reflection loss(RLmin)is-57.8 dB at 1.93 mm and the maximum effective absorption bandwidth(EABmax)is 6.08 GHz at 2 mm,which indicates the excellent EMW absorption performance of the com-posites.Accordingly,this composite is expected to be a microwave absorber with the characteristics of"thin,light,wide,and strong".
查看更多>>摘要：The inferior conductivity and drastic volume expansion of silicon still remain the bottleneck in achieving high energy density Lithium-ion Batteries(LIBs).The design of the three-dimensional structure of elec-trodes by compositing silicon and carbon materials has been employed to tackle the above challenges,however,the exorbitant costs and the uncertainty of the conductive structure persist,leaving ample room for improvement.Herein,silicon nanoparticles were innovatively composited with eco-friendly biochar sourced from cotton to fabricate a 3D globally consecutive conductive network.The network serves a dual purpose:enhancing overall electrode conductivity and serving as a scaffold to maintain electrode in-tegrity.The conductivity of the network was further augmented by introducing P-doping at the optimum doping temperature of 350 ℃.Unlike the local conductive sites formed by the mere mixing of silicon and conductive agents,the consecutive network can affirm the improvement of the conductivity at a macro level.Moreover,first-principle calculations further validated that the rapid diffusion of Li+is attributed to the tailored electronic microstructure and charge rearrangement of the fiber.The prepared consecutive conductive Si@P-doped carbonized cotton fiber anode outperforms the inconsecutive Si@Graphite anode in both cycling performance(capacity retention of 1777.15 mAh g-1 vs.682.56 mAh g-1 after 150 cy-cles at 0.3 C)and rate performance(1244.24 mAh g-1 vs.370.28 mAh g-1 at 2.0 C).The findings of this study may open up new avenues for the development of globally interconnected conductive networks in Si-based anodes,thereby enabling the fabrication of high-performance LIBs.
查看更多>>摘要：The effect of hydrogen and helium interaction,especially H-He ratio,on the irradiation behavior of nu-clear materials has not yet been resolved.However,this is an important basis for evaluating the irra-diation properties of nuclear materials and developing high irradiation resistant materials.Here,30 keV H2+and He+dual beams with four H-He ratios of 0:10,3:10,15:10,and 30:10 were used to irradiate the newly developed Fe9Cr1.5W0.4Si F/M steel in TEM to in-situ study the interaction and ratio effect of hydrogen and helium.The addition of H atoms significantly promoted the nucleation of dislocation loops and bubbles.In the early stage of irradiation,the average size and density of dislocation loops increased with the increase of H-He ratio.Meanwhile,the larger the H-He ratio,the easier it was to form a com-plex dislocation network.Furthermore,the final saturation size of bubbles increased with the increase of H-He ratio.It was first found that the swelling was affected by H concentrations,with high H concentra-tions slowing down the increase in swelling.For a certain irradiation dose,a specific H-He ratio would lead to a swelling peak of Fe9Cr1.5W0.4Si F/M steel.The super-sized bubbles at grain boundaries(GBs)were found after H addition,resulting in a bigger swelling of GBs than the matrix.Both the swelling of the GBs and the matrix show a dependence on the H-He ratio.The current work is of great significance for understanding the interaction between hydrogen and helium in nuclear materials.
查看更多>>摘要：In the conventional melt preparation of magnesium rare-earth(Mg-RE)alloys,the repeated heat-ing/cooling process involved in grain refinement and flux refining usually prolongs the preparation period and aggravates melt oxidation.In this work,the purification and grain refinement of Mg-9Gd-3Y(GW93)alloy was simultaneously realized by one-step refining at 740 ℃ by using a self-developed compound flux.The results show that,only after holding for 10 min,the inclusion content of the alloy is reduced by 81％to 0.29％,while the grain size is reduced by 84％to 119 μm.A physical model depicting the in-teractions between compound flux and alloy melt was proposed based on thermodynamic calculation and microstructure observation.The grain refinement mechanism has been analyzed by considering the presence of Zr particle(Zrp)and Zr solute(Zrs).In addition,the generated REC13 was found to be read-ily absorbed by the flux,decreasing the surface tension and promoting the purification efficacy of the flux,which plays an important role in the promoted elongation of the as-cast Mg-9Gd-3Y-0.5Zr(GW93K)alloy.This work presents a unique prospect in simplifying the melt preparation of Mg-RE alloy with a promoted quality.
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