It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites incl...It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.展开更多
The formation of periodic layered structure in Ni3Si/Zn diffusion couples with Zn in vapor or liquid state was investigated by SEM-EDS, FESEM and XRD. The results show that the diffusion path in solid-liquid reaction ...The formation of periodic layered structure in Ni3Si/Zn diffusion couples with Zn in vapor or liquid state was investigated by SEM-EDS, FESEM and XRD. The results show that the diffusion path in solid-liquid reaction is Ni3Si/（T＋γ）/γ/…T/γ/Ni4Zn12Si3/γ/…Ni4Zn12Si3/γ/Ni4Zn12Si3/δ…/Ni4Zn12Si3/δ/liquid-Zn, and the diffusion path in solid-vapor reaction is Ni3Si/θ/（T＋γ）/γ/…/T/γ/…T/γ/vapor-Zn. With increasing Zn diffusion flux, the diffusion reaction path moves toward the Zn-rich direction, and the distance from the Ni3Si substrate to the periodic layer pair nearest to the interface decreases. In the initial stage of both reactions,γphase nucleates and grows within T matrix phase at first, and then conjuncts together to form a band to reduce the surface energy. Based on the experimental results and diffusion kinetics analysis, the microstructure differences were compared and the formation mechanism of the periodic layered structure in Ni3Si/Zn system was discussed.展开更多
Dissimilar high-energy beam(HEB)welding is necessary in many industrial applications.Different composition of heat-affected zone(HAZ)and weld metal(WM)lead to variation in mechanical properties within the dissimilar j...Dissimilar high-energy beam(HEB)welding is necessary in many industrial applications.Different composition of heat-affected zone(HAZ)and weld metal(WM)lead to variation in mechanical properties within the dissimilar joint,which determines the performance of the welded structure.In the present study,appropriate filler material was used during electron beam welding(EBW)to obtain a reliable dissimilar joint between reduced-activation ferritic-martensitic(RAFM)steel and 316L austenitic stainless steel.It was observed that the layered structure occurred in the weld metal with 310S filler(310S-WM),which had the inferior resistance to thermal disturbance,leading to severe hardening of 310S-WM after one-step tempering treatment.To further ameliorate the joint inhomogeneity,two-step heat treatment processes were imposed to the joints and optimized.δ-ferrite in the layered structure transformed intoγ-phase in the first-step normalizing and remained stable during cooling.In the second-step of tempering,tempered martensite was obtained in the HAZ of the RAFM steel,while the microstructure of 310S-WM was not affected.Thus,the optimized properties for HAZ and 310S-WM in dissimilar welded joint was both obtained by a two-step heat treatment.The creep failure position of two dissimilar joints both occurred in CLAM-BM.展开更多
This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The exp...This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.展开更多
The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedint...The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedinterlayer with a crack perpendicular to the boundaries. The impact load is applied on the face of the crack. Fourier transform and Laplace transform methods are used to formulate the present problem in terms of a singular integral equation in Laplace transform domain. Considering variations of parameters such as the nonhomogeneity constant, the thickness ratio and the crack length, the dynamic stress intensity factors （DSIFs） in time domain are studied and some meaningful conclusions are obtained.展开更多
Investigation of infiltration through unsaturated zone which consists of both porous and fractured media is important for comprehensively understanding water circulation and effectively man- aging groundwater resource...Investigation of infiltration through unsaturated zone which consists of both porous and fractured media is important for comprehensively understanding water circulation and effectively man- aging groundwater resources and contamination control. Infiltration experiments for three kinds of porous-fractured layered structures were conducted with application of a rainfall simulator in this in- vestigation. During experiments, the volumetric water contents of porous media and on the interface of porous-fractured media were monitored by moisture sensors （TDT）. The infiltration rate, water amount in the profile and on the interface between the soil and the fractured bedrock, and outflow from the layered structures were analyzed to identify the effects of porous-fractured interface on water movement in the upper porous media and the effects of various kinds of porous media on infiltration in fractured rocks. It has been observed from the experiment results that the porous media and the frac- tured rock bear considerable reciprocal impact each other on infiltration processes and water content distribution. The results showed fractured rock prevented vertical water movement in the layered structure, and it decreases infiltration rate of layered structure and slows the process for upper porous media saturation.展开更多
A review of the periodic layered structure （PLS） formed during reactive diffusion was presented. The formation of PLS is a very interesting and complex phenomenon during the reactive diffusion process. It was firstl...A review of the periodic layered structure （PLS） formed during reactive diffusion was presented. The formation of PLS is a very interesting and complex phenomenon during the reactive diffusion process. It was firstly discovered occasionally. The formation of PLS has been reported in various solid state diffusion couples such as Zn/ Ni3 Si, Mg/SiO2, Zn/Cux Tiy and so on, and some controversial theoretical models and formation mechanism of PLS were put forward. However, there have been few reports about the PLS formed during hot dip. The development of PLS was reviewed, and the recent progress referring to the formation of PLS during the hot dip aluminizing of a no- vel Fe-Cr-B cast steel was especially introduced. However, not all of the borides could form PLS in their interracial reaction with molten Al. PLS only formed at the Cr-rich Fe2B/Al interface, while Mo-rich Fe2B fractured. A general qualitative description for the interracial reaction of Fe-Cr-B cast steel with molten Al was represented. Further inves- tigation on the constituents of the alternating phases and formation mechanism of PLS needs to be done. At last, the development trends of PLS were proposed.展开更多
Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-l...Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.展开更多
Hydrodeoxygenation（HDO） is an effective alternative to produce value-added chemicals and liquid fuels by removing oxygen from lignin-derived compounds. Sulfide catalysts have been proved to have good activity for th...Hydrodeoxygenation（HDO） is an effective alternative to produce value-added chemicals and liquid fuels by removing oxygen from lignin-derived compounds. Sulfide catalysts have been proved to have good activity for the HDO and particularly high selectivity to phenolic products. Herein, we presented a novel way to prepare the layered structure sulfide catalysts（MgFeMo-S） derived from MgFe hydrotalcites via the intercalation of Mo in consideration of the memory effect of the calcined hydrotalcite. By varying the Mg/Fe mole ratio, a series of MgFeMo-S catalysts were successfully prepared and characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction（XRD）, transmission electron microscopy（TEM）,and inductively coupled plasma optical emission spectrometer（ICP-OES）. The characterization results indicated that the MgFeMo-S catalyst has retained the unique layered structure, which can facilitate uniform dispersion of the MoS2 species on both the surface and interlayer of the catalysts. For the HDO of eugenol, the Mg1Fe2Mo-S catalysts exhibited the best HDO activity among all the catalysts due to its higher active metal contents and larger pore size. The HDO conversion was 99.6% and the yield of phenolics was 63.7%, under 5 MPa initial H2 pressure（measured at RT） at 300 ℃ for 3 h. More importantly,MoS2 species deposited on the interlayer galleries in the MgFeMo-S catalysts resulted in dramatically superior HDO activity to MoS2/Mg1Fe2-S catalyst. Based on the mechanism investigation for eugenol, the HDO reaction route of eugenol under sulfide catalytic system has been proposed for the first time. Further applicability of the catalyst on HDO of more lignin-derived compounds was operated, which showed good HDO activity and selectivity to produce aromatic products.展开更多
Thin-film bulk acoustic resonators(FBARs)operating with essentially thickness-extensional mode have been widely used in communication fields.In this paper,we provide a convenient means for analyzing FBARs with sandwic...Thin-film bulk acoustic resonators(FBARs)operating with essentially thickness-extensional mode have been widely used in communication fields.In this paper,we provide a convenient means for analyzing FBARs with sandwich-layered structure by appropriately neglecting the high-order terms from 3D elasticity equations.First,for straight-crested waves,an approximate method is proposed,which can accurately describe the dispersion relation near the operating frequency range of an FBAR.Using the approximation,the optimum lateral size of a 2D model of frame-like FBAR is obtained,and the results are in good agreement with that obtained by commercial FEM software COMSOL.The approximation is further extended to variablecrested waves in order to analyze the 3D plate models for real devices.The mode shapes of 3D FBARs with and without frame-like structures are obtained.The results show that the approximation presented in this paper is of sufficient accuracy and can be used as an efficient tool for the analysis and design of FBARs.展开更多
The anisotropy of magnetostatic surface wave （MSSW） propagating in finite width YIG /dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell...The anisotropy of magnetostatic surface wave （MSSW） propagating in finite width YIG /dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell equation and the appropriate transmission Green＇s function matrix G. From the relationship of Green＇s function matrixes of dielectric layer and ferrite layer, the dispersion equation is obtained. The MSSW filter is designed to verify the dispersion characteristics. The experiment results are in good agreement with the calculating data from the model.展开更多
Layered structure oxides have emerged as highly promising cathode materials for lithium-ion batteries.In these cathode materials,volume variation related to anisotropic lattice strain during Li^(+)insertion/extraction...Layered structure oxides have emerged as highly promising cathode materials for lithium-ion batteries.In these cathode materials,volume variation related to anisotropic lattice strain during Li^(+)insertion/extraction,however,can induce critical structural instability and electrochemical degradation upon cycling.Despite extensive research efforts,solving the issues of lattice strain and mechanical fatigue remains a challenge.This perspective aims to establishthe"structure-property relationship"between the degradation mechanism of the layered oxide cathode due to lattice strain and the structural evolution during cycling.By addressing these issues,we aim to guide the improvement of electrochemical performance,thereby facilitating the widespread adoption of these materials in future high-energy density lithium-ion batteries.展开更多
This paper theoretically investigates the influence of a cylindrical PN junction on the propagation characteristics of shear cylindrical waves(SCWs)in an infinitely long piezoelectric semiconductor(PS)concentric cylin...This paper theoretically investigates the influence of a cylindrical PN junction on the propagation characteristics of shear cylindrical waves(SCWs)in an infinitely long piezoelectric semiconductor(PS)concentric cylinder structure.This PS concentric cylinder structure is composed of three regions:an inner PS cylinder,an outer PS cylindrical shell,and a cylindrical PN junction at the interface between the two aforementioned regions.First,the basic equations of the PS concentric cylinder structure are derived,taking into account the coupling of the mechanical displacement,electric potential,and charge carrier perturbation in the cylindrical coordinate system.Next,a mathematical model for the SCWs in this PS concentric cylinder structure is established,utilizing the spectral method and considering the physical characteristics of the cylindrical PN junction.Finally,the dispersion and attenuation curves of the SCWs are numerically calculated to discuss the influence of the interface effect resulting from the cylindrical PN junction.It is found that the existence of a cylindrical PN junction can either reduce or enhance the mechanical-to-electrical energy conversion,which is closely related to the doping mode,doping concentration,and curvature radius of the cylindrical interface.A reasonable design of the aforementioned parameters can optimize the wave motion in acoustic equipment formed by PS media with different frequencies or wavelengths.The construction and resolution of the mathematical model as well as the analysis of physical mechanisms can offer theoretical guidance for improving the efficiency of energy conversion from mechanical energy to electrical energy and optimizing the acoustic performance of energy harvesting devices.展开更多
This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mini...This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simulations,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the roadways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.展开更多
Carbonaceous material has attracted much attention in the application of sodium-ion batteries(SIBs)anode.However,sluggish reaction kinetics and structure stability impede the application.Therefore,a stacked layered su...Carbonaceous material has attracted much attention in the application of sodium-ion batteries(SIBs)anode.However,sluggish reaction kinetics and structure stability impede the application.Therefore,a stacked layered sulfur-carbon complex with long-chain C–S_(x)–C bond(M-SC-S)is prepared.The layered structure ensures structural stability,and long-chain C–S_(x)–C bond expanding interlayer spacing boosts facile Na+diffusion.When assembled into cells,a high-quality solid-electrolyte interphase film would be formed due to a good match between the M-SC-S electrode and ether electrolyte.Moreover,an electrochemical activation process would happen between the Cu current collector and proper S-doped electrode material to in-situ form Cu_(2)S.The formation of Cu_(2)S in active material can not only provide more active sites for sodium storage and enhance pseudo-capacitance,but also reinforce the electrode/current collector interface and decrease the interfacial transfer resistance for rapid Na+kinetics.The synergistic effect of structure design and interface engineering optimizes the sodium storage system.Thus,the M-SC-S electrode delivers an excellent cyclic performance(321.6 mAh g^(−1)after 1000 cycles at 2 A g^(−1)with a capacity retention rate of 97.4%)and good rate capability(282.8 mAh g^(−1)after 4000 cycles even at a high current density of 10 A g^(−1)).The full cell also has an impressive cyclic performance(151.4 mAh g^(−1)after 500 cycles at 0.5 A g^(−1)).展开更多
The recently reported silicon/graphite(Si/Gr)composite electrode with a layered structure is a promising approach to achieve high capacity and stable cycling of Si-based electrodes in lithium-ion batteries.However,the...The recently reported silicon/graphite(Si/Gr)composite electrode with a layered structure is a promising approach to achieve high capacity and stable cycling of Si-based electrodes in lithium-ion batteries.However,there is still a need to clarify why particular layered structures are effective and why others are ineffective or even detrimental.In this work,an unreported mechanism dominated by the porosity evolution of electrodes is proposed for the degradation behavior of layered Si/Gr electrodes.First,the effect of layering sequence on the overall electrode performance is investigated experimentally,and the results suggest that the cycling performance of the silicon-on-graphite(SG)electrode is much superior to that of the graphite-on-silicon electrode.To explain this phenomenon,a coupled mechanical-electrochemical porous electrode model is developed,in which the porosity is affected by the silicon expansion and the local constraints.The modeling results suggest that the weaker constraint of the silicon layer in the SG electrode leads to a more insignificant decrease in porosity,and consequently,the more stable cycling performance.The findings of this work provide new insights into the structural design of Si-based electrodes.展开更多
Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica a...Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica aerogels decreased greatly caused by transparency to heat radiation.Opacifiers introduced into silica sol can block heat radiation yet destroy the uniformity of aerogels.Herein,we designed and prepared a silica aerogel composite with oriented and layered silica fibers(SFs),SiC nanowires(SiC_(NWs)),and silica aerogels,which were prepared by papermaking,chemical vapor infiltration(CVI),and sol-gel respectively.Firstly,oriented and layered SFs made still air a wall to block heat transfer by the solid phase.Secondly,SiC_(NWs) were grown in situ on the surface of SFs evenly to weave into the network,and the network reduced the gaseous thermal conductivity by dividing cracks in SFs/SiC_(NWs)/SA.Thirdly,SiC_(NWs) weakened the heat transfer by radiation at high temperatures.Therefore,SFs/SiC_(NWs)/SA presented remarkable thermal insulation(0.017 W(m K)^(-1) at 25℃,0.0287 W(m K)^(-1) at 500℃,and 0.094 W(m K)^(-1) at 1000℃).Besides,SFs/SiC_(NWs)/SA exhibited remarkable thermal stability(no size transform after being heat treated at 1000℃ for 1800 s)and tensile strength(0.75 MPa).These integrated properties made SFs/SiC_(NWs)/SA a promising candidate for highly efficient thermal insulators.展开更多
The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electrom...The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electromagnetic component regulation,layered arrangement structure,and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss.On the microscale,the incorporation of magnetic Ni nanoparticles into MXene nanosheets(Ni@MXene)endows suitable intrinsic permittivity and permeability.On the macroscale,the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves,inducing multiple reflection/scattering effects.On this basis,according to the analysis of absorption,reflection,and transmission(A-R-T)power coefficients of layered composites,the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer,electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer.Consequently,the layered gradient composite(LG5-10-15)achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL_(min) of-68.67 dB at 9.85 GHz in 2.05 mm,which is 199.0%,12.6%,and 50.6%higher than non-layered,layered and layered descending gradient composites,respectively.Therefore,this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.展开更多
Multi-layer riveted structures are widely applied to aircraft.During the service,cracks may appear within these structures due to stress concentration of the riveted holes.The guided wave monitoring has been proved to...Multi-layer riveted structures are widely applied to aircraft.During the service,cracks may appear within these structures due to stress concentration of the riveted holes.The guided wave monitoring has been proved to be an effective tool to deal with this problem.However,there is a lack of understanding of the wave propagation process across such kinds of structures.This study proposes a piezoelectric guided wave simulation method to reveal the propagation of guided waves in multi-layer riveted structures.Effects of pretension force,friction coefficient,and cracks that might influence wave characteristics are studied.The guided wave simulation data is compared with the experimental results and the results verify the simulation model.Then the guided wave propagation in a more complex long-beam butt joint structure is further simulated.展开更多
Selective Laser Melting(SLM),one of the metal additive manufacturing methods in the powder bed,is frequently used in the production of 316L stainless steel biomaterial.In this study,the effect of duplex surface modifi...Selective Laser Melting(SLM),one of the metal additive manufacturing methods in the powder bed,is frequently used in the production of 316L stainless steel biomaterial.In this study,the effect of duplex surface modification(metal additive manufacturing and plasma oxidizing)on the corrosion resistance of 316L was investigated.Ti6Al4V layer was formed by additive manufacturing on 316L produced by selective laser melting method.The obtained layered Ti6Al4V/316L samples were oxidized by plasma at 650℃–750℃ and 1 h–4 h parameter conditions.TiO_(2)ceramic layer was formed on the Ti6Al4V/316L structure by plasma oxidation process in several layer thicknesses.Corrosion properties of the TiO_(2)layer were determined by Open Circuit Potential(OCP),potentiodynamic polarization,and Electrochemical Impedance Spectroscopy(EIS)tests in Simulated Body Fluid(SBF)solution.Also,the surface characterizations of the samples were determined by the Vickers micro-hardness tester,Scanning Electron Microscopy(SEM),and X-Ray Diffractometer(XRD)analysis.From the results,it was obtained that the corrosion resistance of the plasma oxidized was higher than the untreated 316L and layered Ti6Al4V/316L samples.The best corrosion resistance was obtained under the 750℃ and 4 h parameter conditions because of the increasing plasma oxidizing time and temperature.展开更多
基金supported by the Guangdong Basic and Applied Basic Research Foundation (2020B1515120013,2022B1515120066)National Natural Science Foundation of China (Nos.U2001218, 51875215)+1 种基金Key-Area Research and Development Program of Guangdong Province (2020B090923001)Special Support Foundation of Guangdong Province (No.2019TQ05Z110)。
文摘It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.
基金Projects(51271040,51171031)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘The formation of periodic layered structure in Ni3Si/Zn diffusion couples with Zn in vapor or liquid state was investigated by SEM-EDS, FESEM and XRD. The results show that the diffusion path in solid-liquid reaction is Ni3Si/（T＋γ）/γ/…T/γ/Ni4Zn12Si3/γ/…Ni4Zn12Si3/γ/Ni4Zn12Si3/δ…/Ni4Zn12Si3/δ/liquid-Zn, and the diffusion path in solid-vapor reaction is Ni3Si/θ/（T＋γ）/γ/…/T/γ/…T/γ/vapor-Zn. With increasing Zn diffusion flux, the diffusion reaction path moves toward the Zn-rich direction, and the distance from the Ni3Si substrate to the periodic layer pair nearest to the interface decreases. In the initial stage of both reactions,γphase nucleates and grows within T matrix phase at first, and then conjuncts together to form a band to reduce the surface energy. Based on the experimental results and diffusion kinetics analysis, the microstructure differences were compared and the formation mechanism of the periodic layered structure in Ni3Si/Zn system was discussed.
基金supported financially by the National Magnetic Confinement Fusion Program of China (Nos.2014GB120000 and2014GB104003)the National Natural Science Foundation of China (No.51571026)
文摘Dissimilar high-energy beam(HEB)welding is necessary in many industrial applications.Different composition of heat-affected zone(HAZ)and weld metal(WM)lead to variation in mechanical properties within the dissimilar joint,which determines the performance of the welded structure.In the present study,appropriate filler material was used during electron beam welding(EBW)to obtain a reliable dissimilar joint between reduced-activation ferritic-martensitic(RAFM)steel and 316L austenitic stainless steel.It was observed that the layered structure occurred in the weld metal with 310S filler(310S-WM),which had the inferior resistance to thermal disturbance,leading to severe hardening of 310S-WM after one-step tempering treatment.To further ameliorate the joint inhomogeneity,two-step heat treatment processes were imposed to the joints and optimized.δ-ferrite in the layered structure transformed intoγ-phase in the first-step normalizing and remained stable during cooling.In the second-step of tempering,tempered martensite was obtained in the HAZ of the RAFM steel,while the microstructure of 310S-WM was not affected.Thus,the optimized properties for HAZ and 310S-WM in dissimilar welded joint was both obtained by a two-step heat treatment.The creep failure position of two dissimilar joints both occurred in CLAM-BM.
基金supported by the National Natural Science Foundation of China (Nos.10672108,10572069 and 10820101048)
文摘This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.
基金the National Science Foundation for Excellent Young Investigators(10325208)the National Natural Science Foundation of China(10432030)the China Postdoctoral Science Foundation(2004036018)
文摘The transient fracture behavior of a functionally graded layered structure subjected to an in-plane impact load is investigated. The studied structure is composed of two homogeneous layers and a functionally gradedinterlayer with a crack perpendicular to the boundaries. The impact load is applied on the face of the crack. Fourier transform and Laplace transform methods are used to formulate the present problem in terms of a singular integral equation in Laplace transform domain. Considering variations of parameters such as the nonhomogeneity constant, the thickness ratio and the crack length, the dynamic stress intensity factors （DSIFs） in time domain are studied and some meaningful conclusions are obtained.
基金supported by the Major State Basic Research Development Program of China(973 Program)(No.2010CB428804)the National Natural Science Foundation of China(No.40972166)the Major Science and Technology Program for Water Pollution Control and Treatment of China(No.2009ZX07212-003)
文摘Investigation of infiltration through unsaturated zone which consists of both porous and fractured media is important for comprehensively understanding water circulation and effectively man- aging groundwater resources and contamination control. Infiltration experiments for three kinds of porous-fractured layered structures were conducted with application of a rainfall simulator in this in- vestigation. During experiments, the volumetric water contents of porous media and on the interface of porous-fractured media were monitored by moisture sensors （TDT）. The infiltration rate, water amount in the profile and on the interface between the soil and the fractured bedrock, and outflow from the layered structures were analyzed to identify the effects of porous-fractured interface on water movement in the upper porous media and the effects of various kinds of porous media on infiltration in fractured rocks. It has been observed from the experiment results that the porous media and the frac- tured rock bear considerable reciprocal impact each other on infiltration processes and water content distribution. The results showed fractured rock prevented vertical water movement in the layered structure, and it decreases infiltration rate of layered structure and slows the process for upper porous media saturation.
基金Item Sponsored by National Natural Science Foundation of China(51404084)Scientific Research Foundation of Hainan University of China(hyqd1629)Opening Project of Guangdong Key Laboratory for Advanced Metallic Materials Processing(South China University of Technology)of China(GJ201609)
文摘A review of the periodic layered structure （PLS） formed during reactive diffusion was presented. The formation of PLS is a very interesting and complex phenomenon during the reactive diffusion process. It was firstly discovered occasionally. The formation of PLS has been reported in various solid state diffusion couples such as Zn/ Ni3 Si, Mg/SiO2, Zn/Cux Tiy and so on, and some controversial theoretical models and formation mechanism of PLS were put forward. However, there have been few reports about the PLS formed during hot dip. The development of PLS was reviewed, and the recent progress referring to the formation of PLS during the hot dip aluminizing of a no- vel Fe-Cr-B cast steel was especially introduced. However, not all of the borides could form PLS in their interracial reaction with molten Al. PLS only formed at the Cr-rich Fe2B/Al interface, while Mo-rich Fe2B fractured. A general qualitative description for the interracial reaction of Fe-Cr-B cast steel with molten Al was represented. Further inves- tigation on the constituents of the alternating phases and formation mechanism of PLS needs to be done. At last, the development trends of PLS were proposed.
文摘Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.
基金supported by the National Natural Science Foundation of China (Grant nos. 21503144, 21406165, 51506147, 21376239)Major Projects of the National Natural Science Foundation of China (21690083)Tianjin Research Program of Application Foundation and Advanced Technique (Nos.16JCQNJC05400, 15JCQNJC08500)
文摘Hydrodeoxygenation（HDO） is an effective alternative to produce value-added chemicals and liquid fuels by removing oxygen from lignin-derived compounds. Sulfide catalysts have been proved to have good activity for the HDO and particularly high selectivity to phenolic products. Herein, we presented a novel way to prepare the layered structure sulfide catalysts（MgFeMo-S） derived from MgFe hydrotalcites via the intercalation of Mo in consideration of the memory effect of the calcined hydrotalcite. By varying the Mg/Fe mole ratio, a series of MgFeMo-S catalysts were successfully prepared and characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction（XRD）, transmission electron microscopy（TEM）,and inductively coupled plasma optical emission spectrometer（ICP-OES）. The characterization results indicated that the MgFeMo-S catalyst has retained the unique layered structure, which can facilitate uniform dispersion of the MoS2 species on both the surface and interlayer of the catalysts. For the HDO of eugenol, the Mg1Fe2Mo-S catalysts exhibited the best HDO activity among all the catalysts due to its higher active metal contents and larger pore size. The HDO conversion was 99.6% and the yield of phenolics was 63.7%, under 5 MPa initial H2 pressure（measured at RT） at 300 ℃ for 3 h. More importantly,MoS2 species deposited on the interlayer galleries in the MgFeMo-S catalysts resulted in dramatically superior HDO activity to MoS2/Mg1Fe2-S catalyst. Based on the mechanism investigation for eugenol, the HDO reaction route of eugenol under sulfide catalytic system has been proposed for the first time. Further applicability of the catalyst on HDO of more lignin-derived compounds was operated, which showed good HDO activity and selectivity to produce aromatic products.
基金supported by the National Natural Science Foundation of China(12061131013,11972276,12172171 and 12102183)the State Key Laboratory of Mechanics and Control of Mechanical Structures at NUAA(No.MCMS-E-0520K02)+5 种基金the Fundamental Research Funds for the Central Universities(NE2020002 and NS2019007)National Natural Science Foundation of China for Creative Research Groups(No.51921003)the Start-up Fund supported by NUAA,National Natural Science Foundation of Jiangsu Province(BK20211176)Local Science and Technology Development Fund Projects Guided by the Central Government(2021Szvup061)Jiangsu High-Level Innovative and Entrepreneurial Talents Introduction Plan(Shuangchuang Doctor Program,JSSCBS20210166)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Thin-film bulk acoustic resonators(FBARs)operating with essentially thickness-extensional mode have been widely used in communication fields.In this paper,we provide a convenient means for analyzing FBARs with sandwich-layered structure by appropriately neglecting the high-order terms from 3D elasticity equations.First,for straight-crested waves,an approximate method is proposed,which can accurately describe the dispersion relation near the operating frequency range of an FBAR.Using the approximation,the optimum lateral size of a 2D model of frame-like FBAR is obtained,and the results are in good agreement with that obtained by commercial FEM software COMSOL.The approximation is further extended to variablecrested waves in order to analyze the 3D plate models for real devices.The mode shapes of 3D FBARs with and without frame-like structures are obtained.The results show that the approximation presented in this paper is of sufficient accuracy and can be used as an efficient tool for the analysis and design of FBARs.
基金This work was supported by the National Basic Research Program of China (973) under Grant No. 2007CB31407the International S&T Cooperation Program of China under Grant No. 2006DFA53410.
文摘The anisotropy of magnetostatic surface wave （MSSW） propagating in finite width YIG /dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell equation and the appropriate transmission Green＇s function matrix G. From the relationship of Green＇s function matrixes of dielectric layer and ferrite layer, the dispersion equation is obtained. The MSSW filter is designed to verify the dispersion characteristics. The experiment results are in good agreement with the calculating data from the model.
基金supported by the National Natural Science Foundation of China(no.52272241)the Zhejiang Provincial Natural Science Foundation of China under grant no.LR24E020001.
文摘Layered structure oxides have emerged as highly promising cathode materials for lithium-ion batteries.In these cathode materials,volume variation related to anisotropic lattice strain during Li^(+)insertion/extraction,however,can induce critical structural instability and electrochemical degradation upon cycling.Despite extensive research efforts,solving the issues of lattice strain and mechanical fatigue remains a challenge.This perspective aims to establishthe"structure-property relationship"between the degradation mechanism of the layered oxide cathode due to lattice strain and the structural evolution during cycling.By addressing these issues,we aim to guide the improvement of electrochemical performance,thereby facilitating the widespread adoption of these materials in future high-energy density lithium-ion batteries.
基金Project supported by the National Natural Science Foundation of China(Nos.12202039,52204085,and 52474123)。
文摘This paper theoretically investigates the influence of a cylindrical PN junction on the propagation characteristics of shear cylindrical waves(SCWs)in an infinitely long piezoelectric semiconductor(PS)concentric cylinder structure.This PS concentric cylinder structure is composed of three regions:an inner PS cylinder,an outer PS cylindrical shell,and a cylindrical PN junction at the interface between the two aforementioned regions.First,the basic equations of the PS concentric cylinder structure are derived,taking into account the coupling of the mechanical displacement,electric potential,and charge carrier perturbation in the cylindrical coordinate system.Next,a mathematical model for the SCWs in this PS concentric cylinder structure is established,utilizing the spectral method and considering the physical characteristics of the cylindrical PN junction.Finally,the dispersion and attenuation curves of the SCWs are numerically calculated to discuss the influence of the interface effect resulting from the cylindrical PN junction.It is found that the existence of a cylindrical PN junction can either reduce or enhance the mechanical-to-electrical energy conversion,which is closely related to the doping mode,doping concentration,and curvature radius of the cylindrical interface.A reasonable design of the aforementioned parameters can optimize the wave motion in acoustic equipment formed by PS media with different frequencies or wavelengths.The construction and resolution of the mathematical model as well as the analysis of physical mechanisms can offer theoretical guidance for improving the efficiency of energy conversion from mechanical energy to electrical energy and optimizing the acoustic performance of energy harvesting devices.
基金support of the National Natural Science Foundation of China(52374180,52327804).
文摘This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simulations,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the roadways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.
基金supported by the Key Research and Development Program of Wuhan(2025010102030005)the National Nature Science Foundation of Jiangsu Province(BK20221259)。
文摘Carbonaceous material has attracted much attention in the application of sodium-ion batteries(SIBs)anode.However,sluggish reaction kinetics and structure stability impede the application.Therefore,a stacked layered sulfur-carbon complex with long-chain C–S_(x)–C bond(M-SC-S)is prepared.The layered structure ensures structural stability,and long-chain C–S_(x)–C bond expanding interlayer spacing boosts facile Na+diffusion.When assembled into cells,a high-quality solid-electrolyte interphase film would be formed due to a good match between the M-SC-S electrode and ether electrolyte.Moreover,an electrochemical activation process would happen between the Cu current collector and proper S-doped electrode material to in-situ form Cu_(2)S.The formation of Cu_(2)S in active material can not only provide more active sites for sodium storage and enhance pseudo-capacitance,but also reinforce the electrode/current collector interface and decrease the interfacial transfer resistance for rapid Na+kinetics.The synergistic effect of structure design and interface engineering optimizes the sodium storage system.Thus,the M-SC-S electrode delivers an excellent cyclic performance(321.6 mAh g^(−1)after 1000 cycles at 2 A g^(−1)with a capacity retention rate of 97.4%)and good rate capability(282.8 mAh g^(−1)after 4000 cycles even at a high current density of 10 A g^(−1)).The full cell also has an impressive cyclic performance(151.4 mAh g^(−1)after 500 cycles at 0.5 A g^(−1)).
基金supported by the National Natural Science Foundation of China(Grant Nos.12072183,12472174,and 12421002).
文摘The recently reported silicon/graphite(Si/Gr)composite electrode with a layered structure is a promising approach to achieve high capacity and stable cycling of Si-based electrodes in lithium-ion batteries.However,there is still a need to clarify why particular layered structures are effective and why others are ineffective or even detrimental.In this work,an unreported mechanism dominated by the porosity evolution of electrodes is proposed for the degradation behavior of layered Si/Gr electrodes.First,the effect of layering sequence on the overall electrode performance is investigated experimentally,and the results suggest that the cycling performance of the silicon-on-graphite(SG)electrode is much superior to that of the graphite-on-silicon electrode.To explain this phenomenon,a coupled mechanical-electrochemical porous electrode model is developed,in which the porosity is affected by the silicon expansion and the local constraints.The modeling results suggest that the weaker constraint of the silicon layer in the SG electrode leads to a more insignificant decrease in porosity,and consequently,the more stable cycling performance.The findings of this work provide new insights into the structural design of Si-based electrodes.
基金supported by the National Natural Science Foun-dation of China(Grant No.U2167214).
文摘Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica aerogels decreased greatly caused by transparency to heat radiation.Opacifiers introduced into silica sol can block heat radiation yet destroy the uniformity of aerogels.Herein,we designed and prepared a silica aerogel composite with oriented and layered silica fibers(SFs),SiC nanowires(SiC_(NWs)),and silica aerogels,which were prepared by papermaking,chemical vapor infiltration(CVI),and sol-gel respectively.Firstly,oriented and layered SFs made still air a wall to block heat transfer by the solid phase.Secondly,SiC_(NWs) were grown in situ on the surface of SFs evenly to weave into the network,and the network reduced the gaseous thermal conductivity by dividing cracks in SFs/SiC_(NWs)/SA.Thirdly,SiC_(NWs) weakened the heat transfer by radiation at high temperatures.Therefore,SFs/SiC_(NWs)/SA presented remarkable thermal insulation(0.017 W(m K)^(-1) at 25℃,0.0287 W(m K)^(-1) at 500℃,and 0.094 W(m K)^(-1) at 1000℃).Besides,SFs/SiC_(NWs)/SA exhibited remarkable thermal stability(no size transform after being heat treated at 1000℃ for 1800 s)and tensile strength(0.75 MPa).These integrated properties made SFs/SiC_(NWs)/SA a promising candidate for highly efficient thermal insulators.
基金support for this work by Key Research and Development Project of Henan Province(Grant.No.241111232300)the National Natural Science Foundation of China(Grant.No.52273085 and 52303113)the Open Fund of Yaoshan Laboratory(Grant.No.2024003).
文摘The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electromagnetic component regulation,layered arrangement structure,and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss.On the microscale,the incorporation of magnetic Ni nanoparticles into MXene nanosheets(Ni@MXene)endows suitable intrinsic permittivity and permeability.On the macroscale,the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves,inducing multiple reflection/scattering effects.On this basis,according to the analysis of absorption,reflection,and transmission(A-R-T)power coefficients of layered composites,the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer,electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer.Consequently,the layered gradient composite(LG5-10-15)achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL_(min) of-68.67 dB at 9.85 GHz in 2.05 mm,which is 199.0%,12.6%,and 50.6%higher than non-layered,layered and layered descending gradient composites,respectively.Therefore,this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.
文摘Multi-layer riveted structures are widely applied to aircraft.During the service,cracks may appear within these structures due to stress concentration of the riveted holes.The guided wave monitoring has been proved to be an effective tool to deal with this problem.However,there is a lack of understanding of the wave propagation process across such kinds of structures.This study proposes a piezoelectric guided wave simulation method to reveal the propagation of guided waves in multi-layer riveted structures.Effects of pretension force,friction coefficient,and cracks that might influence wave characteristics are studied.The guided wave simulation data is compared with the experimental results and the results verify the simulation model.Then the guided wave propagation in a more complex long-beam butt joint structure is further simulated.
基金the Erzurum Technical University High Technology Research and Application Centre(ETÜ-YÜTAM)for their valuable contribution.
文摘Selective Laser Melting(SLM),one of the metal additive manufacturing methods in the powder bed,is frequently used in the production of 316L stainless steel biomaterial.In this study,the effect of duplex surface modification(metal additive manufacturing and plasma oxidizing)on the corrosion resistance of 316L was investigated.Ti6Al4V layer was formed by additive manufacturing on 316L produced by selective laser melting method.The obtained layered Ti6Al4V/316L samples were oxidized by plasma at 650℃–750℃ and 1 h–4 h parameter conditions.TiO_(2)ceramic layer was formed on the Ti6Al4V/316L structure by plasma oxidation process in several layer thicknesses.Corrosion properties of the TiO_(2)layer were determined by Open Circuit Potential(OCP),potentiodynamic polarization,and Electrochemical Impedance Spectroscopy(EIS)tests in Simulated Body Fluid(SBF)solution.Also,the surface characterizations of the samples were determined by the Vickers micro-hardness tester,Scanning Electron Microscopy(SEM),and X-Ray Diffractometer(XRD)analysis.From the results,it was obtained that the corrosion resistance of the plasma oxidized was higher than the untreated 316L and layered Ti6Al4V/316L samples.The best corrosion resistance was obtained under the 750℃ and 4 h parameter conditions because of the increasing plasma oxidizing time and temperature.
