查看更多>>摘要：Microstructural and mechanical behavior of heat treatable Al-4.6Cu binary alloy reinforced with graphene nanoplates(GNPs)in different heat treatment status were investigated in this paper.The addition of GNPs significantly enhanced the yield strength and tensile strength of Al-Cu alloy regardless of the heat-treatment conditions.It was also found that GNPs accelerated the formation of precipitates,leading to a greatly shortened aging time for GNPs/Al-4.6Cu composite to reach the peak hardness.However,aging treatment enhanced the strength of GNPs/Al-Cu composite very little,which could be explained by the interaction between GNPs,precipitates and dislocations.This work inspires us that the heat treatment process of aluminum alloy matrix composites should be designed independently with the matrix in quest of an optimum performance.
查看更多>>摘要：In K4750 alloy,the evolution of grain boundary(GB)precipitates,including the degradation of blocky MC carbide particles and the precipitation of granular/needle-like η phase particles,were observed after long-term aging(LA)at 750℃for 8000 h.During MC degradation,the Ti and C released from the MC carbide combined with Ni and Cr,respectively,in the γ matrix to form η-Ni3Ti phase and Cr-rich M23C6 carbide.Large amounts of granular η phase precipitated at GBs and the needle-like η phase grew gradually from GBs toward the grain interior.Because of the growth of the η phase through absorbing γ'phase,γ'-depleted zones were formed around the η phase.The evolution of the MC carbide and η phase was primarily responsible for the decrease of the stress rupture life and the increase of elongation.After an LA sample was tested at 750℃and 360 MPa,the residual strain distribution was investigated by electron backscatter diffraction(EBSD).The results showed that the residual strain mainly distributed at GBs,especially in the region of MC degradation and at the edges of η phases,which was closely related to the appearance of phase interfaces.Microvoids/cracks easily initiated at phase interfaces,then easily extended along the γ'-depleted zones,thus the stress rupture life of LA samples was substantially shorter than that of samples subjected to the standard treatment.In particular,because of large amounts of fine degraded MC,granular M23C6 and granular η phase particles distributed at GBs after 750℃/8000 h LA and microvoid/crack formation could be hindered by the formation of dimples,which led to an increase of elongation.
查看更多>>摘要：Perovskite solar cells(PSCs)have become a promising alternative to sustainable energy due to their high power conversion efficiency(PCE)and low-cost processing.However,the practical applications of PSCs are still limited by the trade-off between high performance and poor stability under operation.Here,a 2D@3D perovskite with quasi core-shell architecture linking the superiorities of both two-dimensional(2D)and three-dimensional(3D)perovskite is prepared through a novel upgraded antisolvent approach.The basic properties as well as the phase distribution and the charge transport behavior of the 2D@3D perovskite were systematically elucidated.A high PCE of 21.60％for 2D@3D PSCs is achieved due to the enhanced surface and grain boundaries passivation,improved energy level alignment and efficient holes transport.The 2D@3D perovskite device without encapsulation shows significantly improved stability at the room temperature(90％of initial PCE for 45 d with a relative humidity of 50％±5％)and relative thermal conditions(83％of initial PCE for 200 h under 85℃).Compared with traditional 3D PSCs,it proved that such 2D@3D perovskite configuration is an effective architecture for enhancing efficiency and improving stability and therefore will facilitate the further industrialization of PSCs.
查看更多>>摘要：Acoustic emission(AE)of 316L stainless steel with of low Ni content shows,under tension,simultane-ously three avalanche processes.One avalanche process relates to the movement of dislocations,the oth-ers to martensitic transformations and detwinning/twinning.Detwinning/twinning occurs predominantly at the early stage of the plastic deformation while martensitic transformations only become observable after large plastic deformation.All processes coincide during deformation with variable effect on AE.An excellent fingerprint for the detection of the coincidence between the several mechanisms is the ob-servation of multivalued E～A2 correlations.AE signals from moving dislocations decay more slowly(～7×10-3s)and show long avalanche durations.In contrast,AE signals during martensitic transformations and detwinning/twinning decay rapidly(＜4×10-4s)and show short avalanche durations.They can be distinguished by different energy exponents of their avalanches.The energy distributions of the mech-anisms differ because energies are defined as the integral over the squared AE amplitudes,where the integration extends over the avalanche durations.A combination of statistical analysis with Convolutional Neural Network calculations provides an accurate and straightforward method for online,non-destructive avalanche monitoring of strain-induced martensitic transformations in 316L steel under high strain.
查看更多>>摘要：The degradation of acid orange Ⅱ(AO Ⅱ)by a nanoporous Fe-Si-B(NP-FeSiB)electrode under the pulsed square-wave potential has been investigated in this research.Defect-enriched NP-FeSiB electrode was fab-ricated through dealloying of annealed Fe76Si9B15 amorphous ribbons.The results of UV-vis spectra and FTIR indicated that AO Ⅱ solution was degraded efficiently into unharmful molecules H2O and CO2 on NP-FeSiB electrode within 5 mins under the square-wave potential of±1.5 V.The degradation efficiency of the NP-FeSiB electrode remains 98.9％even after 5-time recycling.The large amount of active surface area of the nanoporous FeSiB electrode with lattice disorders and stacking faults,and alternate electrochemical redox reactions were mainly responsible for the excellent degradation performance of the NP-FeSiB elec-trode.The electrochemical pulsed square-wave process accelerated the redox of Fe element in Fe-based nanoporous electrode and promoted the generation of hydroxyl radicals(·OH)with strong oxidizability as predominant oxidants for the degradation of azo dye molecules,which was not only beneficial to improv-ing the catalytic degradation activity,but also beneficial to enhancing the reusability of the nanoporous electrode.This work provides a highly possibility to efficiently degrade azo dyes and broadens the appli-cation fields of nanoporous metals.
查看更多>>摘要：A series of silicates with double shell hollow sphere morphology were prepared by hydrothermal method with ultra-high temperature calcined,and used in the field of electromagnetic(EM)wave absorption.By characterizing the chemical composition,crystal structure,micro morphology and EM parameters of the several materials,the evaluation results of EM wave absorption capacity of the materials were obtained.In the discussion section,we will discuss the reasons for the differences in EM wave absorption capa-bilities of the several silicates from multiple aspects such as EM wave absorption mechanism in detail.Especially for iron-based silicate(HGMs@Fe2SiO4)materials,after reasonable composition and morphol-ogy design,the minimum reflection loss(RLmin)reached up to-41.14 dB with a matching thickness(d)of 3.4 mm,and the corresponding effective absorption bandwidth(fE,RL＜-10 dB)was 6.80 GHz.Because of the wide EM wave absorption bandwidth,light weight and low water absorption,this kind of double shell silicate material has gained huge application potential in the EM wave absorption field.
查看更多>>摘要：Magnetic liquid metal droplets(MLMDs)have been proven to be very important in many fields such as flexible electronics and soft robotics.Usually,soft magnetic particles such as nickel(Ni)and iron(Fe)are mixed or suspended into the liquid metal to obtain soft MLMDs(S-LMDs),which can be easily manipu-lated under the magnetic field due to the favorable deformability and flexibility.In addition,hard mag-netic particles such as neodymium iron boron(NdFeB)with a high residual magnetization can also be dispersed into the liquid metal and the hard MLMDs(H-LMDs)become more compact due to the inter-action between internal particles induced by remanence.This work reports a kind of H-LMDs with high surface tension,high flexibility and mechanical robustness,whose electrical conductivity and strength are better than the S-LMDs.Under the magnetic field,the H-LMDs have a faster response time(0.58 s)and a larger actuating velocity(4.45 cm/s)than the S-LMDs.Moreover,the H-LMDs show excellent magnetic controllability,good elasticity and favorable mobility,as demonstrated by magnetically actuated locomo-tion,bounce tests and rolling angle measurements.Finally,the droplets can be further applied in wheel-driven motors and micro-valve switches,which demonstrates their high application potential in robotic manipulation and microfluidic devices.
查看更多>>摘要：In the present investigation,the growth kinetics of interfacial reaction layer products between cubic boron nitride(CBN)and Cu-Sn-Ti filler metal has been thoroughly investigated.Detailed morphological and compositional features of respective compounds have been demonstrated for a wide brazing tem-perature ranging from 1153 K to 1223 K.It is found that within 30 minutes brazing holding time,the reaction layer growth is largely determined by the population of TiN via effective Ti diffusion with an activation energy of 223.51 kJ/mol,leading to parabolic growth patterns.It is further revealed that TiN grows both in axial and length dimensions,which eventually extends to the forefront and covers the reaction layer.
查看更多>>摘要：Recyclable thermosets and thermoset composites with covalent adaptable networks(CANs,or dynamic covalent networks)have attracted considerable attention in recent years due to the combined merits of excellent mechanical and thermal properties,and chemical stabilities of traditional thermosets and recy-clable,remoldable,and reprocessable attributes of thermoplastics.In this paper,we present an overview of the current strategies for synthesizing recyclable thermosets based on CANs,which involve recycla-bility,reprocessability,and possible rehealability.The recent literature examples are categorized based on the underlying controlled-cleavable linkages such as transesterification,DA/retro-DA chemistry,imine bonds,disulfide metathesis,dynamic B-O bonds,hemiaminals/hexahydrotriazines,and acetal linkages.Various degradation and malleability methods and resulting mechanical properties of the recycled ther-mosets and thermoset composites are presented.The emerging applications of recyclable thermosets and thermoset composites,with emphasis on their usage in adhesives,biomedical materials,wearable de-vices,coatings,and 3D printing materials,are also illustrated.Finally,a perspective on the challenges and future perspectives is briefly summarized.
查看更多>>摘要：The creep inconsistency between dendrite core and interdendritic region is investigated in a nickel-based single crystal superalloy under 1373 K and 137 MPa.Two specimens with higher and lower degree of el-emental inhomogeneity on dendritic structures are compared.For specimen with higher inhomogeneity,stronger segregation of refractory elements reinforces the local strength in dendrite core,but damages the strength in interdendritic region.Creep strain is accumulated faster in interdendritic region giving rise to promoted dislocation shearing in γ'phase,faster degradation of dislocation networks and facili-tated topological inversion of rated structures.Although the segregation of refractory elements produces a high density of topologically close-packed(TCP)phase in dendrite core,faster accumulation of creep strain forms microcracks prior in interdendritic region that gives rise to final rupture of the specimen.In another specimen,increased solid solution time gives rise to overall reduced inhomogeneity.Creep in-consistency is relieved to show more uniform evolution of dislocation substructures and rafting between dendrite core and interdendritic region.The second specimen is ruptured by formation and extension of microcracks along TCP phase although the precipitation of TCP phase is relatively restricted under re-duced inhomogeneity.Importantly,the balance of local strength between dendrite core and interdendritic region results in over 40％increase of creep rupture life of the second specimen.
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