查看更多>>摘要：Ceramic aerogels are attractive for their low density,high porosity,large surface area as well as vari-ous applications in areas of thermal insulation,catalysis,filtration,and lightweight structural materials.Conventional ceramic aerogels are usually assembled by oxides nanoparticles.Due to the inefficient neck-like connections between the nanoparticles and the volume shrinkage at elevated temperatures,ceramic aerogels fail easily caused by the brittleness and high-temperature structural collapse.To overcome these drawbacks,a class of resilient ceramic aerogels with highly porous architectures that are composed of one-or two-dimensional nanostructures has been prepared.Benefiting from the unique microstruc-tures and/or the high-temperature stability of their building blocks,these aerogels exhibit reversible compressibility,high-temperature stability,thermal insulation,and various functions.In this review,we introduced the preparation methods,microstructures,mechanical properties,high-temperature stabil-ity,thermal insulation and various functions of these resilient ceramic aerogels.We have also discussed the relationships between their microstructures and properties,including mechanical properties and thermal insulation performance.Finally,perspectives for the further development of resilient ceramic aerogels are presented.
查看更多>>摘要：Low dimensional semiconductors can be used for various electronic and optoelectronic devices because of their unique structure and property.In this work,one-dimensional Sb2S3 nanowires(NWs)with high crystallinity were grown via chemical vapor deposition(CVD)technique on SiO2/Si substrates.The Sb2S 3 NWs exhibited needle-like structures with inclined cross-sections.The lengths of Sb2S3 nanowires changed from 7 to 13 pm.The photodetection properties of Sb2S3 nanowires were comprehensively and systematically characterized.The Sb2S3 photodetectors show a broadband photoresponse ranging from ultraviolet(360 nm)to near-infrared(785 nm).An excellent specific detectivity of 2.1×1014 Jones,high external quantum efficiency of 1.5×104％,sensitivity of 2.2×104 cm2W-1 and short response time of less than 100 ms was achieved for the Sb2S3 NW photodetectors.Moreover,the Sb2S3 NWs showed out-standing switch cycling stability that was beneficial to the practical applications.The high-quality Sb2S3 nanowires fabricated by CVD have great application potential in semiconductor and optoelectronic fields.
查看更多>>摘要：Compared with the growing applications of peritectic alloy,none research on the freckle formation during peritectic solidification has been reported before.Observation on the dendritic mushy zone of Sn-36 at.％Ni peritectic alloy during directional solidification at different growth velocities shows that the freckles are formed in two different regions:region Ⅰ before peritectic reaction and region Ⅱ after peritectic reaction.In addition,more freckles can be observed at lower growth velocities.Examination on the experimental results demonstrates that both the temperature gradient zone melting(TGZM)and Gibbs-Thomson(G-T)effects have obvious influences on the morphology of dendritic network during directional solidification.The current theories onKI Rayleigh number Ra characterizing the thermoso-lutal convection of dendritic mushy zone to predict freckle formation through the maximum of Ra can only explain the existence of region Ⅰ while the appearance of region Ⅱ after peritectic reaction cannot be predicted.Thus,a new Rayleigh number RaP is proposed in consideration of evolution of dendritic mushy zone by both effects and peritectic reaction.Theoretical prediction of RaP also shows a maximum after peritectic reaction in addition to that before peritectic reaction,thus,agreeing well with the freckle formation in region Ⅱ.In addition,more severe thermosolutal convection can be predicted by the new Rayleigh number RaP at lower growth velocities,which further demonstrates the reliability of RaP in describing the dependence of freckle formation on growth velocity.
查看更多>>摘要：Microstructural evolution and deformation mechanism of a metastable β alloy(Ti-10V-2Fe-3Al)pro-cessed by rotationally accelerated shot peening(RASP)were systematically investigated with optical microscopy,X-ray diffraction,electron backscatter diffraction and transmission electron microscopy.Different gradient hierarchical microstructures(gradients in α"martensite and β phase,and hierarchical twins range from the nanoscale to microscale)can be fabricated by RASP via changing the shot peening time.The hardening behavior and tensile mechanical properties of gradient hierarchical microstructure were systematically explored.Novel deformation twinning systems of{112}α:and{130}〈310〉α"in the kinked α"martensite were revealed during the tensile deformation.It was found that stress-induced martensitic transformation,twinned α"martensite and the related dynamic grain refinement contribute to hardness and work hardening ability.Simultaneous improvement of strength and ductility of the metastable β titanium alloy can be achieved by introducing a gradient hierarchical microstructure.
查看更多>>摘要：High ultraviolet(UV)stability and low dark current(Idark)are necessary for high-quality perovskite photodetectors(PDs).TiO2 thin film is known as effective electron-transport-layer(ETL)for perovskite devices.However,common spin-coated TiO2 ETLs endow many surface defects and have strong UV pho-tocatalytic effect to decompose perovskite materials,resulting in inferior stability of devices.In this work,TiO2 bilayer film(Bi-TiO2)has been fabricated by combining spin-coating and atomic-layer-deposition process and its positive effects on UV stability and Idark of Cs2AgBiBr6-based PDs have been revealed for the first time.It is demonstrated that Bi-TiO2 possesses fewer surface defects and smoother morphology with type Ⅱ band alignment,which is beneficial to suppress photocatalytic activity of TiO2 and reduce carrier recombination at the interface.After accelerated strong UV aging treatment,the PD with Bi-TiO2 maintains excellent performance,whereas the PD with spin-coated TiO2 film dramatically deteriorate with on-off ratio drops from～102 to～2.Besides,the Idark of PD remarkably decreases from～10-8 A to～10-10 A after bilayer optimization.Furthermore,we have integrated the corresponding PDs into a self-built imaging system adopting diffuse reflection mode.This work suggests a feasible approach to fabricate TiO2/Cs2AgBiBr6-based PDs with remarkable UV tolerance for imaging applications.
查看更多>>摘要：Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160 pm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with 307Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.
查看更多>>摘要：Constructing noble-metal-free loaded catalyst with high-efficiency photocatalytic activity by a simple and scalable method is of profound significance for fundamental research and practical application.Herein,a simple one-pot method was used to synthesize novel samples of array-like sulfur-doped graphitic carbon nitride(SCN)nanosheets with ultrathin MoS2 loading(MS/SCN-x％).The ultrathin MoS2 cocatalyst was evenly distributed on the surface of SCN and was linked to the main catalyst by covalent chemical bonds.Benefited from the multiple advantages of the array-like porous nanosheets structure with rich exposed surface,covalent cross-linking structure,and enhanced visible light absorption,the MS/SCN-2.5％composites drastically improve hydrogen evolution performance,which is superior to orig-inal MoS2 nanosheet modified by two-step mixing method,and also rivals with Pt/SCN.The designing strategy of photocatalyst modified by noble-metal-free cocatalyst with covalent bond structure provides fascinating insights into enhanced photocatalytic hydrogen evolution.
查看更多>>摘要：The microstructural evolution in Re-containing Ni-based single crystal superalloys with different Tan-talum(Ta)content(2Ta,5Ta and 8Ta in wt％)was investigated.Ta addition significantly affected the γ'precipitate morphology,γ/γ'lattice misfit and microstructural stability during long-term aging.Results showed that the partitioning behaviors of solutes were enhanced by Ta addition,meanwhile,the reversal partitioning behavior of W was triggered which partitioned from γ'precipitate to y matrix.The elemental concentration redistribution caused variations in lattice misfit from positive to negative,the values of lat-tice misfit were measured to be 0.16％for 2Ta alloy,then decreased to-0.07％for 5Ta alloy and negatively increased to-0.23％for 8Ta alloy.These variations in the lattice misfit were reflected on the transition of γ'morphology from round-cornered cuboidal shape to cuboidal with sharp corners,accomplished with increasing shape parameter ratio η.Consequently,the optimal γ'shape could be obtained at lattice misfit of approximately 0.3％.The γ'coarsening investigation at 900℃(up to 2000 h)indicated that Ta addition was beneficial for improving the microstructural stability by reducing the coarsening rate and interfacial energy,accompanied by the enhanced capability of resisting γ'coalescence.By incorporating the calculated interfacial energy,computational modeling,Thermo-Calc and PrecipiCalc,were employed to elucidate the γ'kinetic pathways,the simulation results agreed with experiments,indicating that the model and parameters were reasonable.Additionally,it was found that there was no overlap between γ'nucleation and coarsening when the γ/γ'interfacial energy increased to a critical value.
查看更多>>摘要：In this work,the local structure and transport properties of three typical alkali chlorides(LiCl,NaCl,and KCl)were investigated by our newly trained deep potentials(DPs).We extracted datasets from ab initio molecular dynamics(AIMD)calculations and used these to train and validate the DPs.Large-scale and long-time molecular dynamics simulations were performed over a wider range of temperatures than AIMD to confirm the reliability and generality of the DPs.We demonstrated that the generated DPs can serve as a powerful tool for simulating alkali chlorides;the DPs also provide results with accuracy that is comparable to that of AIMD and efficiency that is similar to that of empirical potentials.The partial radial distribution functions and angle distribution functions predicted using the DPs are in close agreement with those derived from AIMD.The estimated densities,self-diffusion coefficients,shear viscosities,and electrical conductivities also matched well with the AIMD and experimental data.This work provides confidence that DPs can be used to explore other systems,including mixtures of chlorides or entirely different salts.
查看更多>>摘要：Biofilm plays an important role on microbial corrosion and biofouling in marine environments.Inhibiting biofilm formation on construction surfaces is of great importance.Photocatalytic material with visible-light response,especially BiVO4,is regarded as a promising material for biofilm inhibition due to its green biocidal effect and high antibacterial efficiency.Approaches which can immobilize the photocatalytic par-ticles onto metal surfaces with high mechanical strength are requisite.In this study,zinc matrixes were served as carriers for BiVO4 particles.The BiVO4-inserted zinc matrixes were successfully obtained by ultrasound assisted electrodeposition.The insertion content of BiVO4 showed positive correlation with ultrasound power.Highly enhanced biofilm inhibition properties were obtained by BiVO4 inserted zinc matrixes with an over 95％decreased bacterial coverage.It was proved that·O2-(chief)and *OH(sub-ordinate)radicals were responsible for the high biocidal performance.Possible antibacterial mechanism was proposed,indicating that the photoinduced holes would both attack zinc crystals to generate active electrons to form·O2-radicals,and react with H2O to generate *OH,finally.Furthermore,corrosion resistance of the matrixes was proved to be stable due to the insertion of BiVO4.This study provides a potential application for photocatalyst in marine antifouling and anti-biocorrosion aspects.
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