With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite h...With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.展开更多
As the proportion of composite materials used in aircraft continues to increase, the electromagnetic Shielding Effectiveness (SE) of these materials becomes a critical factor in the electromagnetic safety design of ai...As the proportion of composite materials used in aircraft continues to increase, the electromagnetic Shielding Effectiveness (SE) of these materials becomes a critical factor in the electromagnetic safety design of aircraft structures. The assessment of electromagnetic SE for Slotted Composite Structures(SCSs) is particularly challenging due to their complex geometries and there remains a lack of suitable models for accurately predicting the SE performance of these intricate configurations. To address this issue, this paper introduces SCS-Net, a Deep Neural Network (DNN) method designed to accurately predict the SE of SCS. This method considers the impacts of various structural parameters, material properties and incident wave parameters on the SE of SCSs. In order to better model the SCS, an improved Nicolson-Ross-Weir (NRW) method is introduced in this paper to provide an equivalent flat structure for the SCS and to calculate the electromagnetic parameters of the equivalent structure. Additionally, the prediction of SE via DNNs is limited by insufficient test data, which hinders support for large-sample training. To address the issue of limited measured data, this paper develops a Measurement-Computation Fusion (MCF) dataset construction method. The predictions based on the simulation results show that the proposed method maintains an error of less than 0.07 dB within the 8–10 GHz frequency range. Furthermore, a new loss function based on the weighted L1-norm is established to improve the prediction accuracy for these parameters. Compared with traditional loss functions, the new loss function reduces the maximum prediction error for equivalent electromagnetic parameters by 47%. This method significantly improves the prediction accuracy of SCS-Net for measured data, with a maximum improvement of 23.88%. These findings demonstrate that the proposed method enables precise SE prediction and design for composite structures while reducing the number of test samples needed.展开更多
The rapid development of 5G communication technology and smart electronic and electrical equipment will inevitably lead to electromagnetic radiation pollution.Enriching heterointerface polarization relaxation through ...The rapid development of 5G communication technology and smart electronic and electrical equipment will inevitably lead to electromagnetic radiation pollution.Enriching heterointerface polarization relaxation through nanostructure design and interface modifica-tion has proven to be an effective strategy to obtain efficient electromagnetic wave absorption.Here,this work implements an innovative method that combines biomimetic honeycomb superstructure to constrain hierarchical porous heterostructure composed of Co/CoO nano-particles to improve the interfacial polarization intensity.The method effectively controlled the absorption efficiency of Co^(2+)through de-lignification modification of bamboo,and combined with the bionic carbon-based natural hierarchical porous structure to achieve uniform dispersion of nanoparticles,which is conducive to the in-depth construction of heterogeneous interfaces.In addition,the multiphase struc-ture brought about by high-temperature pyrolysis provides the best dielectric loss and impedance matching for the material.Therefore,the obtained bamboo-based Co/CoO multiphase composite showed excellent electromagnetic wave absorption performance,achieving excel-lent reflection loss(RL)of-79 dB and effective absorption band width of 4.12 GHz(6.84-10.96 GHz)at low load of 15wt%.Among them,the material’s optimal radar cross-section(RCS)reduction value can reach 31.9 dB·m^(2).This work provides a new approach to the micro-control and comprehensive optimization of macro-design of microwave absorbers,and offers new ideas for the high-value utiliza-tion of biomass materials.展开更多
In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity ca...Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity caused by heterogeneous structures in the magnesium matrix composite remains unclear.In this study,a dual-heterogeneous TiC/AZ61 composite exhibits significantly improved plastic elongation(PEL)by nearly one time compared to uniform FG composite,meanwhile maintaining a high strength(UTS:417 MPa).This is because more severe deformation inhomogeneity in heterogeneous structure leads to more geometrically necessary dislocations(GNDs)accumulation and stronger HDI stress,resulting in higher HDI hardening compared to FG and CG composites.During the early stage of plastic deformation,the pile-up types of GND in the FG zone and CG zone are significantly different.GNDs tend to form substructures in the FG zone instead of the CG zone.They only accumulate at grain boundaries of the CG region,thereby leading to obviously increased back stress in the CG region.In the late deformation stage,the elevated HDI stress activates the new〈c+a〉dislocations in the CG region,resulting in dislocation entanglements and even the formation of substructures,further driving the high hardening in the heterogeneous composite.However,For CG composite,〈c+a〉dislocations are not activated even under large plastic strains,and only〈a〉dislocations pile up at grain boundaries and twin boundaries.Our work provides an in-depth understanding of dislocation variation and HDI hardening in heterogeneous magnesium-based composites.展开更多
The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in ...The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices.Hence,a composite with three-dimensional network(Ho/U-BNNS/WPU)is developed by simultaneously incorporating magnetically modified boron nitride nanosheets(M@BNNS)and non-magnetic organo-grafted BNNS(U-BNNS)into waterborne polyurethane(WPU)to synchronous molding under a horizontal magnetic field.The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction,combined with the bridging structure established by U-BNNS,enable Ho/U-BNNS/WPU to exhibit exceptional in-plane(λ//)and through-plane thermal conductivities(λ_(⊥)).In particular,with the addition of 30 wt%M@BNNS and 5 wt%U-BNNS,theλ//andλ_(⊥)of composites reach 11.47 and 2.88 W m^(-1) K^(-1),respectively,which representing a 194.2%improvement inλ_(⊥)compared to the composites with a single orientation of M@BNNS.Meanwhile,Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips.The composites also demonstrate excellent flame retardancy,with a peak heat release and total heat release reduced by 58.9%and 36.9%,respectively,compared to WPU.Thus,this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites,presenting broad application potential in electronic packaging fields.展开更多
Controlled photocatalytic conversion of CO_(2) into premium fuel such as methane(CH4)offers a sustainable pathway towards a carbon energy cycle.However,the photocatalytic efficiency and selectivity are still unsatisfa...Controlled photocatalytic conversion of CO_(2) into premium fuel such as methane(CH4)offers a sustainable pathway towards a carbon energy cycle.However,the photocatalytic efficiency and selectivity are still unsatisfactory due to the limited availability of active sites on the current photocatalysts.To resolve this issue,the design of oxygen vacancies(OVs)in metal-oxide semiconductors is an effective option.Herein,in situ deposition of TiO_(2) onto SiO_(2) nanospheres to construct a SiO_(2)@TiO_(2) core-shell structure was performed to modulate the oxygen vacancy concentrations.Meanwhile,charge redistribution led to the formation of abundant OV-regulated Ti-Ti(Ti-OV-Ti)dual sites.It is revealed that Ti-OV-Ti dual sites served as the key active site for capturing the photogenerated electrons during light-driven CO_(2) reduction reaction(CO_(2)RR).Such electron-rich active sites enabled efficient CO_(2) adsorption and activation,thus lowering the energy barrier associated with the rate-determining step.More importantly,the formation of a highly stable*CHO intermediate at Ti-OV-Ti dual sites energetically favored the reaction pathway towards the production of CH4 rather than CO,thereby facilitating the selective product of CH_(4).As a result,SiO_(2)@TiO_(2)-50 with an optimized oxygen vacancy concentration of 9.0% showed a remarkable selectivity(90.32%)for CH_(4) production with a rate of 13.21μmol g^(-1) h^(-1),which is 17.38-fold higher than that of pristine TiO_(2).This study provides a new avenue for engineering superior photocatalysts through a rational methodology towards selective reduction of CO_(2).展开更多
Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four plan...Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four planar N-coordination and one axial P-coordination(Co-N_(4)P_(1))are decorated on the lateral edges of nanorod-like crystalline g-C_(3)N_(4)(CCN)photocatalysts.Significantly,the electronic structures of central Co as active sites for O_(2) reduction reaction(ORR)and planar N-coordinator as active sites for H_(2)O oxidation reaction(WOR)in Co-N_(4)P_(1) can be well regulated by the synergetic effects of introducing axial P-coordinator,in contrast to the decorated Co single-atoms with only four planar N-coordination(Co-N_(4)).Specifically,directional photoelectron accumulation at central Co active sites,induced by an introduced midgap level in Co-N_(4)P_(1),mediates the ORR active sites from 4e–-ORR-selective terminal–NH_(2) sites to 2e–-ORR-selective Co sites,moreover,an elevated d-band center of Co 3d orbital strengthens ORR intermediate*OOH adsorption,thus jointly facilitating a highly selective and active 2e^(–)-ORR pathway to H_(2)O_(2) photosynthesis.Simultaneously,a downshifted p-band center of N_(2)p orbital in Co-N_(4)P_(1) weakens WOR intermediate*OH adsorption,thus enabling a preferable 2e^(–)-WOR pathway toward H_(2)O_(2) photosynthesis.Subsequently,Co-N_(4)P_(1) exhibits exceptional H_(2)O_(2) photosynthesis efficiency,reaching 295.6μmol g^(-1) h^(-1) with a remarkable solar-to-chemical conversion efficiency of 0.32%,which is 15 times that of Co-N_(4)(19.2μmol g^(-1) h^(-1))and 10 times higher than CCN(27.6μmol g^(-1) h^(-1)).This electronic structure modulation on single-atom catalysts offers a promising strategy for boosting the activity and selectivity of H_(2)O_(2) photosynthesis.展开更多
The damage distribution of the same type of aircraft in similar service environments should be similar. Based on this assumption, to perform the maintenance and repair of aircraft composite structures, the damage of c...The damage distribution of the same type of aircraft in similar service environments should be similar. Based on this assumption, to perform the maintenance and repair of aircraft composite structures, the damage of composite structures in a certain type of aircraft were investigated. The time-varying damage distribution model was established and verified based on the damage of a 16-aircraft fleet. The results show that the quantitative proportions of structural damage are 74% for skin delamination, 22% for stringer delamination and 3% for stringer-skin interface debonding. The amount of structural damages increases linearly with service time while the proportion of different damages does not change. As the service time increases, the geometric parameter distribution of damage for the same type of aircraft gradually converges, which can be approximated using the same function. There are certain differences in the proportion and geometric parameter distribution of damages among different components and locations, and the differences do not change over time.展开更多
Rare earth elements(REEs) are associated with phosphorite,which is an important strategic reserve resource.During sorting process of phosphorite,REEs may move with specific host minerals,however,occurrence state and m...Rare earth elements(REEs) are associated with phosphorite,which is an important strategic reserve resource.During sorting process of phosphorite,REEs may move with specific host minerals,however,occurrence state and moving pattern of REEs from rock to products are still unclear,which limits separation and enrichment of REEs from phosphorite.Mappings of scanning electron microscope(SEM) and electron probe X-ray micro-analyzer(EPMA) of REEs are highly consistent with those of calcium and phosphorus,and complementary with that of magnesium,which indicates that fluorapatite(Fap) is the main host mineral of REEs.The results of flotation and leaching experiments further indicate that REEs are enriched along with Fap from phosphorite to products.Occupied sites and occupation number of REEs were obtained by X-ray diffraction(XRD) refinement based on the Rietveld method.La,Ce,Nd,and Y can occupy both Ca1 and Ca2 sites.The ratios of La,Ce,Nd,and Y at Ca2 and Cal sites are 4.20,3.70,3.00,and 1.33,showing a decreasing trend,indicating that La,Ce,and Nd tend to occupy Ca2 sites,while Y tends to occupy Ca1 sites.X-ray absorption fine structure(XAFS) shows that REEs mainly form coordinate structures with oxygen and fluorine,which is a direct evidence that REEs replace calcium(Ⅱ) in phosphorite in an isomorphism form.Coordination structure and polyhedral configuration analysis indicate that substitution degree of La,Ce,Nd,and Y is Y> La> Ce≈Nd from easy to difficult at Cal and Ca2 sites.The research enriches the mineralization theory of REEs-bearing phosphorite and provides certain theoretical guidance for selective enrichment of REEs from phosphorite.展开更多
Engineering the local electronic structure of atomic-dispersed catalytic sites plays a critical role in selective photocatalysis.Here,we show the regulation of local electronic structure of atomic-dispersed Ni sites b...Engineering the local electronic structure of atomic-dispersed catalytic sites plays a critical role in selective photocatalysis.Here,we show the regulation of local electronic structure of atomic-dispersed Ni sites by forming oxygen-bridged diatomic Ni-O-Ni confined in MOF-derived TiO_(2)(O-Ni_(2)/TiO_(2))via oxalic acid chelation.Among them,MOF-derived TiO_(2)scaffold provides a highly porous structure,supporting highly exposed active sites of Ni-O-Ni dimers linked by oxygen bridges.Density functional theory calculations show that the Ni-O-Ni sites regulate the local electronic structure of Ni sites,promoting the adsorption and activation of reactant molecules.Ultrafast spectroscopy shows that,in comparison with monomeric Ni/TiO_(2),the strong interaction in dimeric O-Ni_(2)/TiO_(2)tends to bring forth a more pronounced suppression of photogenerated electron-hole recombination,beneficial for achieving better charge separation and transfer as desired.As a direct outcome,the O-Ni_(2)/TiO_(2)photocatalyst has shown enhanced photocatalytic activity and selectivity in glycerol reforming reaction,with the average rates of H_(2)and CO evolution attaining as high as 2542.6 and 361.7μmol g^(-1)h^(-1),respectively,along with a remarkable selectivity of96.1%towards the syngas production(under a 365-nm light irradiation).Notably,the H_(2)and CO yields of the O-Ni_(2)/TiO_(2)photocatalyst are 3.9 and 6.7 times higher than those of the Ni/TiO_(2)photocatalyst,respectively.This study highlights the beneficial role of engineering the local electronic structure of atomicdispersed catalytic sites and provides an effective way for selective photocatalytic biomass conversion.展开更多
We considered adding different amounts(1%,2%,3%,and 4%)of EMR to prepare manganese residue polymer magnesium phosphate cement composite(EMR-PMPC).The influence mechanism of EMR doping on the early macroscopic and micr...We considered adding different amounts(1%,2%,3%,and 4%)of EMR to prepare manganese residue polymer magnesium phosphate cement composite(EMR-PMPC).The influence mechanism of EMR doping on the early macroscopic and microscopic pore structure properties of composites was studied by combining macroscopic and microscopic testing methods.The experimental results show that the addition of EMR can improve the working performance of the slurry and enhance the strength in the later stage,the 28 d compressive strength value of the slurry doped with EMR can reach 49.5 MPa.The Mn element and NH4_(+)^(-)N in EMR react with MgO in the raw material to produce Struvite and Mn(OH)_(2)and Mn_(3)(PO_(4))·6H_(2)O gel,the hydration products coexist with each other and lap each other to form a dense microfine structure and effectively refine the pores.The hydration process consists of five stages,mainly concentrated in the first 10 h or less to exothermic mainly,infrared spectral absorption band is mainly composed of O-H bond,H-O-H bond,PO_(4)bond and metal oxygen bond 3 parts,EMR makes the wave number of the absorption band from the ground wave number to the high wave number.EMR doping T_(2)spectral relaxation time will lag behind,the pore size distribution changes.The total porosity and bound fluid saturation decrease with increasing,the free fluid saturation shows the opposite trend,the permeability decreases and then increases.展开更多
The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts,reducing the vibration effect on the structure.Explosion tests were conducted using several...The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts,reducing the vibration effect on the structure.Explosion tests were conducted using several composite structure models,including a concrete lining structure(CLS)without foam geopolymer and six foam geopolymer composite structures(FGCS)with different backfill parameters,to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading.Pressure,strain,and vibration responses at different locations were synchronously tested.The damage modes and dynamic responses of different models were compared,and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed.The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading,reducing the strain in the liner structure by 52%and increasing the pressure attenuation rate by 28%.Additionally,the foam geopolymer backfill reduced structural vibration and liner deformation,with the FGCS structure showing 35%less displacement and 70%less acceleration compared to the CLS.The FGCS model with thicker,less dense foam geopolymer backfill,having more pores and higher porosity,demonstrated better compression and energy absorption under dynamic impact,increasing stress wave attenuation efficiency.By analyzing the stress wave propagation and the compression characteristics of the porous medium,it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77%lower than that of CLS,and the transmitted wave energy was 90%lower.The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.展开更多
Hydrogen production coupled with small molecule oxidation derived by renewable energy power has been widely studied as an effective method to reduce energy consumption and prepare added value production.Here,the coppe...Hydrogen production coupled with small molecule oxidation derived by renewable energy power has been widely studied as an effective method to reduce energy consumption and prepare added value production.Here,the copper-cobalt phosphide with a multilevel structure has been designed based on the hard and soft acids and bases theory.The nanocone composed of lamellas presented a sharp tip,which a positive effect on the mass transfer enhanced by a local electric field,and the nanolamellas contain CoP/Cu_(3)P interface provide the highly selective active site for the gluconic acid(GNA)synthesis and hydrogen evolution.The catalyst can drive hydrogen evolution at 5 A·cm^(-2)up to 437 h without active decay,and the electrocatalytic glucose oxidation at anode presents high efficiency due to Cu(I)introduction and the synergetic effect between interfaces.Density functional theory(DFT)calculation shows that water splitting more readily occurs at the CoP,which provides adsorbed H and-OH for hydrogen evolution and glucose oxidation,respectively,and glucose adsorption more readily occurs at the Cu_(3)P,which presents lower conversion energy for high value-added GNA.Efficient hydrogen evolution and glucose conversion indicate its high intrinsic activity and synergetic effect.This work provides a special interface construction strategy for the catalytic conversion of hydrogen and small molecules.展开更多
TiC/Ti_(2)AlC core-shell structure reinforced Ti-based composite coating was prepared by laser cladding technology.The effect of Ti_(2)AlC content on the microstructure and mechanical behavior of the coating was studi...TiC/Ti_(2)AlC core-shell structure reinforced Ti-based composite coating was prepared by laser cladding technology.The effect of Ti_(2)AlC content on the microstructure and mechanical behavior of the coating was studied.The results showed that the reinforced phase was mainly TiC/Ti_(2)AlC MAX phase core-shell structure at 20%Ti_(2)AlC content.According to the synthesis mechanism,Ti_(2)AlC nucleated on TiC through the diffusion of Al atoms to further generate the core-shell structure.The friction and wear test results showed that the wear resistance of the coating was significantly improved under the load distribution effect of the core-shell structure.The friction coefficient decreased to 0.342,and the wear rate reached 8.19×10^(−5)mm^(3)/(N·m),which was only 47.07%of TC4 substrate.展开更多
The emerging interfacial polarization strategy exhibits applicative potential in piezoelectric enhancement.However,there is an ongoing effort to address the inherent limitations arising from charge bridging phenomena ...The emerging interfacial polarization strategy exhibits applicative potential in piezoelectric enhancement.However,there is an ongoing effort to address the inherent limitations arising from charge bridging phenomena and stochastic interface disorder that plague the improvement of piezoelectric performance.Here,we report a dual structure reinforced MXene/PVDF-TrFE piezoelectric composite,whose piezoelectricity is enhanced under the coupling effect of interfacial polarization and structural design.Synergistically,molecular dynamics simulations,density functional theory calculations and experimental validation revealed the details of interfacial interactions,which promotes the net spontaneous polarization of PVDF-TrFE from the 0.56 to 31.41 Debye.The oriented MXene distribution and porous structure not only tripled the piezoelectric response but also achieved an eightfold increase in sensitivity within the low-pressure region,along with demonstrating cyclic stability exceeding 20,000 cycles.The properties reinforcement originating from dual structure is elucidated through the finite element simulation and experimental validation.Attributed to the excellent piezoelectric response and deep learning algorithm,the sensor can effectively recognize the signals of artery pulse and finger flexion.Finally,a 3×3 sensor array is fabricated to monitor the pressure distribution wirelessly.This study provides an innovative methodology for reinforcing interfacial polarized piezoelectric materials and insight into structural designs.展开更多
The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and ...The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and toughness of PP.The low-temperature toughness of PP was improved by inserting high-density polyethylene(HDPE)between PP and polystyrene-b-ethylene-co-propyleneb-polystyrene(SEPS)to form an unusual SEPS@HDPE core–shell structure,with SEPS as the core and HDPE as the shell.Based on the microtopography and rheological behavior characterization,HDPE in PP/SEPS/HDPE composites was found to serve as an emulsifier,decrease the size of SEPS particles,and promote the homogeneous dispersion of dispersed phase particles in the matrix.An increase in the HDPE content shifted the toughening mechanism of PP composites from cavitation to matrix shear yielding.The reduction in the distance between the dispersed core–shell structure particles promoted shear yielding in the PP composites,leading to increased toughness.The creation of an intermediate HDPE layer with a moderate modulus was crucial for dispersing stress concentrations and significantly improving toughness without compromising the tensile strength.These findings will facilitate the fabrication of high-toughness PP products at low temperatures.展开更多
Advanced chemical engineering for simultaneous modulation of nanomaterial morphology, defects, interfaces, and structure to enhance electromagnetic and microwave absorption (MA) performance. However, accurately distin...Advanced chemical engineering for simultaneous modulation of nanomaterial morphology, defects, interfaces, and structure to enhance electromagnetic and microwave absorption (MA) performance. However, accurately distinguishing the MA contributions of different scale factors and tuning the optimal combined effects remains a formidable challenge. This study employs a synergistic approach combining template protection etching and vacuum annealing to construct a controlled system of micrometer-sized cavities and amorphous carbon matrices in metal-organic framework (MOF) derivatives. The results demonstrate that the spatial effects introduced by the hollow structure enhance dielectric loss but significantly weaken impedance matching. By increasing the proportion of amorphous carbon, the balance between electromagnetic loss and impedance matching can be effectively maintained. Importantly, in a suitable graphitization environment, the presence of oxygen vacancies in amorphous carbon can induce significant polarization to compensate for the reduced conductivity loss due to the absence of sp2 carbon. Through the synergistic effects of morphology and composition, the samples exhibit a broader absorption bandwidth (6.28 GHz) and stronger reflection loss (−61.64 dB) compared to the original MOF. In conclusion, this study aims to elucidate the multiscale impacts of macroscopic micro-nano structure and microscopic defect engineering, providing valuable insights for future research in this field.展开更多
In this study,the free vibration of a piezoelectric semiconductor(PS)composite structure composed of a PS layer,a fractional viscoelastic layer,and an elastic substrate with simply-supported boundary conditions is inv...In this study,the free vibration of a piezoelectric semiconductor(PS)composite structure composed of a PS layer,a fractional viscoelastic layer,and an elastic substrate with simply-supported boundary conditions is investigated.The fractional derivative Zener model is used to establish the constitutive relation of the viscoelastic layer.The first-order shear deformation theory and Hamilton's principle are used to derive the motion equations of the present problem.The frequency parameter is numerically resolved with the Newton-Raphson method through the eigenvalue equation.The effects of either geometric parameters,carrier density,and electric voltage applied on the surface of the composite structure or the fractional order of the Zener model on both the natural frequency and loss factor are discussed,and some interesting conclusions are drawn.This work will be helpful for designing and manufacturing PS materials and structures.展开更多
This paper presents a deep learning-based topology optimization method for the joint design of material layout and fiber orientation in continuous fiber-reinforced composite structure(CFRCS).The proposed method mainly...This paper presents a deep learning-based topology optimization method for the joint design of material layout and fiber orientation in continuous fiber-reinforced composite structure(CFRCS).The proposed method mainly includes three steps:(1)a ResUNet-involved generative and adversarial network(ResUNet-GAN)is developed to establish the end-to-end mapping from structural design parameters to fiber-reinforced composite optimized structure,and a fiber orientation chromatogram is presented to represent continuous fiber angles;(2)to avoid the local optimum problem,the independent continuous mapping method(ICM method)considering the improved principal stress orientation interpolated continuous fiber angle optimization(PSO-CFAO)strategy is utilized to construct CFRCS topology optimization dataset;(3)the well-trained ResUNet-GAN is deployed to design the optimal structural material distribution together with the corresponding continuous fiber orientations.Numerical simulations for benchmark structure verify that the proposed method greatly improves the design efficiency of CFRCS along with high design accuracy.Furthermore,the CFRCS topology configuration designed by ResUNet-GAN is fabricated by additive manufacturing.Compression experiments of the specimens show that both the stiffness structure and peak load of the CFRCS topology configuration designed by the proposed method have significantly enhanced.The proposed deep learning-based topology optimization method will provide great flexibility in CFRCS for engineering applications.展开更多
基金sponsored by National Natural Science Foundation of China(No.52302121,No.52203386)Shanghai Sailing Program(No.23YF1454700)+1 种基金Shanghai Natural Science Foundation(No.23ZR1472700)Shanghai Post-doctoral Excellent Program(No.2022664).
文摘With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.
基金supported by the National Natural Science Foundation of China(Nos.62101020 and 62141405)the Special Scientific Research Project of Civil Aircraft,China(No.MJZ5-2N22).
文摘As the proportion of composite materials used in aircraft continues to increase, the electromagnetic Shielding Effectiveness (SE) of these materials becomes a critical factor in the electromagnetic safety design of aircraft structures. The assessment of electromagnetic SE for Slotted Composite Structures(SCSs) is particularly challenging due to their complex geometries and there remains a lack of suitable models for accurately predicting the SE performance of these intricate configurations. To address this issue, this paper introduces SCS-Net, a Deep Neural Network (DNN) method designed to accurately predict the SE of SCS. This method considers the impacts of various structural parameters, material properties and incident wave parameters on the SE of SCSs. In order to better model the SCS, an improved Nicolson-Ross-Weir (NRW) method is introduced in this paper to provide an equivalent flat structure for the SCS and to calculate the electromagnetic parameters of the equivalent structure. Additionally, the prediction of SE via DNNs is limited by insufficient test data, which hinders support for large-sample training. To address the issue of limited measured data, this paper develops a Measurement-Computation Fusion (MCF) dataset construction method. The predictions based on the simulation results show that the proposed method maintains an error of less than 0.07 dB within the 8–10 GHz frequency range. Furthermore, a new loss function based on the weighted L1-norm is established to improve the prediction accuracy for these parameters. Compared with traditional loss functions, the new loss function reduces the maximum prediction error for equivalent electromagnetic parameters by 47%. This method significantly improves the prediction accuracy of SCS-Net for measured data, with a maximum improvement of 23.88%. These findings demonstrate that the proposed method enables precise SE prediction and design for composite structures while reducing the number of test samples needed.
基金supported by the National Key R&D Program of China(Nos.2023YFE0108300 and 2023YFD2202103)the National Natural Science Foundation of China(No.32371972)+2 种基金the Natural Science Foundation of Jiangsu Province,China(No.BK20221336)Jiangsu Agricultural Science and Technology Independent Innovation Fund,China(No.CX(23)3060)Jiangxi Forestry Bureau Forestry Science and Technology Innovation Special Project,China(No.202240).
文摘The rapid development of 5G communication technology and smart electronic and electrical equipment will inevitably lead to electromagnetic radiation pollution.Enriching heterointerface polarization relaxation through nanostructure design and interface modifica-tion has proven to be an effective strategy to obtain efficient electromagnetic wave absorption.Here,this work implements an innovative method that combines biomimetic honeycomb superstructure to constrain hierarchical porous heterostructure composed of Co/CoO nano-particles to improve the interfacial polarization intensity.The method effectively controlled the absorption efficiency of Co^(2+)through de-lignification modification of bamboo,and combined with the bionic carbon-based natural hierarchical porous structure to achieve uniform dispersion of nanoparticles,which is conducive to the in-depth construction of heterogeneous interfaces.In addition,the multiphase struc-ture brought about by high-temperature pyrolysis provides the best dielectric loss and impedance matching for the material.Therefore,the obtained bamboo-based Co/CoO multiphase composite showed excellent electromagnetic wave absorption performance,achieving excel-lent reflection loss(RL)of-79 dB and effective absorption band width of 4.12 GHz(6.84-10.96 GHz)at low load of 15wt%.Among them,the material’s optimal radar cross-section(RCS)reduction value can reach 31.9 dB·m^(2).This work provides a new approach to the micro-control and comprehensive optimization of macro-design of microwave absorbers,and offers new ideas for the high-value utiliza-tion of biomass materials.
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
基金support from the National Natural Science Foundation of China(No:52061040)China Postdoctoral Science Foundation(No:2021M692512)+1 种基金Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province(No:2023CL01)Open Projects of Key Laboratory of Advanced Technologies of Materials,Ministry of Education China,Southwest Jiaotong University(No:KLATM202003).
文摘Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity caused by heterogeneous structures in the magnesium matrix composite remains unclear.In this study,a dual-heterogeneous TiC/AZ61 composite exhibits significantly improved plastic elongation(PEL)by nearly one time compared to uniform FG composite,meanwhile maintaining a high strength(UTS:417 MPa).This is because more severe deformation inhomogeneity in heterogeneous structure leads to more geometrically necessary dislocations(GNDs)accumulation and stronger HDI stress,resulting in higher HDI hardening compared to FG and CG composites.During the early stage of plastic deformation,the pile-up types of GND in the FG zone and CG zone are significantly different.GNDs tend to form substructures in the FG zone instead of the CG zone.They only accumulate at grain boundaries of the CG region,thereby leading to obviously increased back stress in the CG region.In the late deformation stage,the elevated HDI stress activates the new〈c+a〉dislocations in the CG region,resulting in dislocation entanglements and even the formation of substructures,further driving the high hardening in the heterogeneous composite.However,For CG composite,〈c+a〉dislocations are not activated even under large plastic strains,and only〈a〉dislocations pile up at grain boundaries and twin boundaries.Our work provides an in-depth understanding of dislocation variation and HDI hardening in heterogeneous magnesium-based composites.
基金support from the National Natural Science Foundation of China(22268025,52473083,and 22475176)Key Research and Development Program of Yunnan Province(202403AP140036)+2 种基金Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)Applied Basic Research Program of Yunnan Province(202201AT070115 and 202201BE070001-031)supported by the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57).
文摘The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices.Hence,a composite with three-dimensional network(Ho/U-BNNS/WPU)is developed by simultaneously incorporating magnetically modified boron nitride nanosheets(M@BNNS)and non-magnetic organo-grafted BNNS(U-BNNS)into waterborne polyurethane(WPU)to synchronous molding under a horizontal magnetic field.The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction,combined with the bridging structure established by U-BNNS,enable Ho/U-BNNS/WPU to exhibit exceptional in-plane(λ//)and through-plane thermal conductivities(λ_(⊥)).In particular,with the addition of 30 wt%M@BNNS and 5 wt%U-BNNS,theλ//andλ_(⊥)of composites reach 11.47 and 2.88 W m^(-1) K^(-1),respectively,which representing a 194.2%improvement inλ_(⊥)compared to the composites with a single orientation of M@BNNS.Meanwhile,Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips.The composites also demonstrate excellent flame retardancy,with a peak heat release and total heat release reduced by 58.9%and 36.9%,respectively,compared to WPU.Thus,this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites,presenting broad application potential in electronic packaging fields.
基金supported by the National Natural Science Foundation of China(No.21773089,22202037)the Science and Technology Development Plan Project of Jilin Province,China(No.20240101192JC)the Fundamental Research Funds for the Central Universities(No.2412023QD019).
文摘Controlled photocatalytic conversion of CO_(2) into premium fuel such as methane(CH4)offers a sustainable pathway towards a carbon energy cycle.However,the photocatalytic efficiency and selectivity are still unsatisfactory due to the limited availability of active sites on the current photocatalysts.To resolve this issue,the design of oxygen vacancies(OVs)in metal-oxide semiconductors is an effective option.Herein,in situ deposition of TiO_(2) onto SiO_(2) nanospheres to construct a SiO_(2)@TiO_(2) core-shell structure was performed to modulate the oxygen vacancy concentrations.Meanwhile,charge redistribution led to the formation of abundant OV-regulated Ti-Ti(Ti-OV-Ti)dual sites.It is revealed that Ti-OV-Ti dual sites served as the key active site for capturing the photogenerated electrons during light-driven CO_(2) reduction reaction(CO_(2)RR).Such electron-rich active sites enabled efficient CO_(2) adsorption and activation,thus lowering the energy barrier associated with the rate-determining step.More importantly,the formation of a highly stable*CHO intermediate at Ti-OV-Ti dual sites energetically favored the reaction pathway towards the production of CH4 rather than CO,thereby facilitating the selective product of CH_(4).As a result,SiO_(2)@TiO_(2)-50 with an optimized oxygen vacancy concentration of 9.0% showed a remarkable selectivity(90.32%)for CH_(4) production with a rate of 13.21μmol g^(-1) h^(-1),which is 17.38-fold higher than that of pristine TiO_(2).This study provides a new avenue for engineering superior photocatalysts through a rational methodology towards selective reduction of CO_(2).
文摘Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four planar N-coordination and one axial P-coordination(Co-N_(4)P_(1))are decorated on the lateral edges of nanorod-like crystalline g-C_(3)N_(4)(CCN)photocatalysts.Significantly,the electronic structures of central Co as active sites for O_(2) reduction reaction(ORR)and planar N-coordinator as active sites for H_(2)O oxidation reaction(WOR)in Co-N_(4)P_(1) can be well regulated by the synergetic effects of introducing axial P-coordinator,in contrast to the decorated Co single-atoms with only four planar N-coordination(Co-N_(4)).Specifically,directional photoelectron accumulation at central Co active sites,induced by an introduced midgap level in Co-N_(4)P_(1),mediates the ORR active sites from 4e–-ORR-selective terminal–NH_(2) sites to 2e–-ORR-selective Co sites,moreover,an elevated d-band center of Co 3d orbital strengthens ORR intermediate*OOH adsorption,thus jointly facilitating a highly selective and active 2e^(–)-ORR pathway to H_(2)O_(2) photosynthesis.Simultaneously,a downshifted p-band center of N_(2)p orbital in Co-N_(4)P_(1) weakens WOR intermediate*OH adsorption,thus enabling a preferable 2e^(–)-WOR pathway toward H_(2)O_(2) photosynthesis.Subsequently,Co-N_(4)P_(1) exhibits exceptional H_(2)O_(2) photosynthesis efficiency,reaching 295.6μmol g^(-1) h^(-1) with a remarkable solar-to-chemical conversion efficiency of 0.32%,which is 15 times that of Co-N_(4)(19.2μmol g^(-1) h^(-1))and 10 times higher than CCN(27.6μmol g^(-1) h^(-1)).This electronic structure modulation on single-atom catalysts offers a promising strategy for boosting the activity and selectivity of H_(2)O_(2) photosynthesis.
文摘The damage distribution of the same type of aircraft in similar service environments should be similar. Based on this assumption, to perform the maintenance and repair of aircraft composite structures, the damage of composite structures in a certain type of aircraft were investigated. The time-varying damage distribution model was established and verified based on the damage of a 16-aircraft fleet. The results show that the quantitative proportions of structural damage are 74% for skin delamination, 22% for stringer delamination and 3% for stringer-skin interface debonding. The amount of structural damages increases linearly with service time while the proportion of different damages does not change. As the service time increases, the geometric parameter distribution of damage for the same type of aircraft gradually converges, which can be approximated using the same function. There are certain differences in the proportion and geometric parameter distribution of damages among different components and locations, and the differences do not change over time.
基金Project supported by Guizhou Provincial Basic Research Program (Natural Science)(Qian Ke He Basic-ZK 2024 General 626)National Natural Science Foundation of China (52164018)Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology (13210025)。
文摘Rare earth elements(REEs) are associated with phosphorite,which is an important strategic reserve resource.During sorting process of phosphorite,REEs may move with specific host minerals,however,occurrence state and moving pattern of REEs from rock to products are still unclear,which limits separation and enrichment of REEs from phosphorite.Mappings of scanning electron microscope(SEM) and electron probe X-ray micro-analyzer(EPMA) of REEs are highly consistent with those of calcium and phosphorus,and complementary with that of magnesium,which indicates that fluorapatite(Fap) is the main host mineral of REEs.The results of flotation and leaching experiments further indicate that REEs are enriched along with Fap from phosphorite to products.Occupied sites and occupation number of REEs were obtained by X-ray diffraction(XRD) refinement based on the Rietveld method.La,Ce,Nd,and Y can occupy both Ca1 and Ca2 sites.The ratios of La,Ce,Nd,and Y at Ca2 and Cal sites are 4.20,3.70,3.00,and 1.33,showing a decreasing trend,indicating that La,Ce,and Nd tend to occupy Ca2 sites,while Y tends to occupy Ca1 sites.X-ray absorption fine structure(XAFS) shows that REEs mainly form coordinate structures with oxygen and fluorine,which is a direct evidence that REEs replace calcium(Ⅱ) in phosphorite in an isomorphism form.Coordination structure and polyhedral configuration analysis indicate that substitution degree of La,Ce,Nd,and Y is Y> La> Ce≈Nd from easy to difficult at Cal and Ca2 sites.The research enriches the mineralization theory of REEs-bearing phosphorite and provides certain theoretical guidance for selective enrichment of REEs from phosphorite.
基金supported by the National Key R&D Program of China(2022YFA1503003)the National Natural Science Foundation of China(U24A20550,52273264,22173090)+2 种基金the Youth Scienceof China(22409056)the Innovation Program for Quantum Science and Technology(2021ZD0303303)the Key Project of the Heilongjiang Provincial Natural Science Foundation(ZD2024B001)。
文摘Engineering the local electronic structure of atomic-dispersed catalytic sites plays a critical role in selective photocatalysis.Here,we show the regulation of local electronic structure of atomic-dispersed Ni sites by forming oxygen-bridged diatomic Ni-O-Ni confined in MOF-derived TiO_(2)(O-Ni_(2)/TiO_(2))via oxalic acid chelation.Among them,MOF-derived TiO_(2)scaffold provides a highly porous structure,supporting highly exposed active sites of Ni-O-Ni dimers linked by oxygen bridges.Density functional theory calculations show that the Ni-O-Ni sites regulate the local electronic structure of Ni sites,promoting the adsorption and activation of reactant molecules.Ultrafast spectroscopy shows that,in comparison with monomeric Ni/TiO_(2),the strong interaction in dimeric O-Ni_(2)/TiO_(2)tends to bring forth a more pronounced suppression of photogenerated electron-hole recombination,beneficial for achieving better charge separation and transfer as desired.As a direct outcome,the O-Ni_(2)/TiO_(2)photocatalyst has shown enhanced photocatalytic activity and selectivity in glycerol reforming reaction,with the average rates of H_(2)and CO evolution attaining as high as 2542.6 and 361.7μmol g^(-1)h^(-1),respectively,along with a remarkable selectivity of96.1%towards the syngas production(under a 365-nm light irradiation).Notably,the H_(2)and CO yields of the O-Ni_(2)/TiO_(2)photocatalyst are 3.9 and 6.7 times higher than those of the Ni/TiO_(2)photocatalyst,respectively.This study highlights the beneficial role of engineering the local electronic structure of atomicdispersed catalytic sites and provides an effective way for selective photocatalytic biomass conversion.
基金Funden by the National Natural Science Foundation of China(Nos.51868044 and 52178216)the Basic Research Program of Qinghai Province(No.2022-ZJ-921)+2 种基金the Innovation Star”Project for Excellent Postgraduates in Gansu Province(No.2022-CXZX-450)the Hongliu First-class Discipline Construction Program of Lanzhou University of TechnologyScience and Technology Project of Gansu Provincial Department of Transportation(No.2022-23)。
文摘We considered adding different amounts(1%,2%,3%,and 4%)of EMR to prepare manganese residue polymer magnesium phosphate cement composite(EMR-PMPC).The influence mechanism of EMR doping on the early macroscopic and microscopic pore structure properties of composites was studied by combining macroscopic and microscopic testing methods.The experimental results show that the addition of EMR can improve the working performance of the slurry and enhance the strength in the later stage,the 28 d compressive strength value of the slurry doped with EMR can reach 49.5 MPa.The Mn element and NH4_(+)^(-)N in EMR react with MgO in the raw material to produce Struvite and Mn(OH)_(2)and Mn_(3)(PO_(4))·6H_(2)O gel,the hydration products coexist with each other and lap each other to form a dense microfine structure and effectively refine the pores.The hydration process consists of five stages,mainly concentrated in the first 10 h or less to exothermic mainly,infrared spectral absorption band is mainly composed of O-H bond,H-O-H bond,PO_(4)bond and metal oxygen bond 3 parts,EMR makes the wave number of the absorption band from the ground wave number to the high wave number.EMR doping T_(2)spectral relaxation time will lag behind,the pore size distribution changes.The total porosity and bound fluid saturation decrease with increasing,the free fluid saturation shows the opposite trend,the permeability decreases and then increases.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52378401,12202494)the Fundamental Research Funds for the Central Universities(Grant No.30922010918)。
文摘The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts,reducing the vibration effect on the structure.Explosion tests were conducted using several composite structure models,including a concrete lining structure(CLS)without foam geopolymer and six foam geopolymer composite structures(FGCS)with different backfill parameters,to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading.Pressure,strain,and vibration responses at different locations were synchronously tested.The damage modes and dynamic responses of different models were compared,and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed.The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading,reducing the strain in the liner structure by 52%and increasing the pressure attenuation rate by 28%.Additionally,the foam geopolymer backfill reduced structural vibration and liner deformation,with the FGCS structure showing 35%less displacement and 70%less acceleration compared to the CLS.The FGCS model with thicker,less dense foam geopolymer backfill,having more pores and higher porosity,demonstrated better compression and energy absorption under dynamic impact,increasing stress wave attenuation efficiency.By analyzing the stress wave propagation and the compression characteristics of the porous medium,it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77%lower than that of CLS,and the transmitted wave energy was 90%lower.The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.
基金supported by the National Nature Science Foundation of China(No.22269021)Tianshan Talent Project of Xinjiang Uygur Autonomous Region(No.2023TSYCQNTJ0039)the Open project of Key Laboratory in Xinjiang Uygur Autonomous Region of China(No.2023D04027).
文摘Hydrogen production coupled with small molecule oxidation derived by renewable energy power has been widely studied as an effective method to reduce energy consumption and prepare added value production.Here,the copper-cobalt phosphide with a multilevel structure has been designed based on the hard and soft acids and bases theory.The nanocone composed of lamellas presented a sharp tip,which a positive effect on the mass transfer enhanced by a local electric field,and the nanolamellas contain CoP/Cu_(3)P interface provide the highly selective active site for the gluconic acid(GNA)synthesis and hydrogen evolution.The catalyst can drive hydrogen evolution at 5 A·cm^(-2)up to 437 h without active decay,and the electrocatalytic glucose oxidation at anode presents high efficiency due to Cu(I)introduction and the synergetic effect between interfaces.Density functional theory(DFT)calculation shows that water splitting more readily occurs at the CoP,which provides adsorbed H and-OH for hydrogen evolution and glucose oxidation,respectively,and glucose adsorption more readily occurs at the Cu_(3)P,which presents lower conversion energy for high value-added GNA.Efficient hydrogen evolution and glucose conversion indicate its high intrinsic activity and synergetic effect.This work provides a special interface construction strategy for the catalytic conversion of hydrogen and small molecules.
基金Project(52365020) supported by the National Natural Science Foundation of ChinaProject([2022]06) supported by the Special Fund for Special Posts of Guizhou University,China+2 种基金Project([2024]03) supported by the Guizhou University Fund,ChinaProject(ZK[2023]78) supported by the Guizhou Provincial Basic Research Program(Natural Science),ChinaProject(BQW[2024]011) supported by the Guizhou Province Science and Technology Foundation,China。
文摘TiC/Ti_(2)AlC core-shell structure reinforced Ti-based composite coating was prepared by laser cladding technology.The effect of Ti_(2)AlC content on the microstructure and mechanical behavior of the coating was studied.The results showed that the reinforced phase was mainly TiC/Ti_(2)AlC MAX phase core-shell structure at 20%Ti_(2)AlC content.According to the synthesis mechanism,Ti_(2)AlC nucleated on TiC through the diffusion of Al atoms to further generate the core-shell structure.The friction and wear test results showed that the wear resistance of the coating was significantly improved under the load distribution effect of the core-shell structure.The friction coefficient decreased to 0.342,and the wear rate reached 8.19×10^(−5)mm^(3)/(N·m),which was only 47.07%of TC4 substrate.
基金supported by the National Natural Science Foundation of China(No.52303328)the Postdoctoral Innovation Talents Support Program(No.BX20220257)the Sichuan Science and Technology Program(No.2023NSFSC0313).
文摘The emerging interfacial polarization strategy exhibits applicative potential in piezoelectric enhancement.However,there is an ongoing effort to address the inherent limitations arising from charge bridging phenomena and stochastic interface disorder that plague the improvement of piezoelectric performance.Here,we report a dual structure reinforced MXene/PVDF-TrFE piezoelectric composite,whose piezoelectricity is enhanced under the coupling effect of interfacial polarization and structural design.Synergistically,molecular dynamics simulations,density functional theory calculations and experimental validation revealed the details of interfacial interactions,which promotes the net spontaneous polarization of PVDF-TrFE from the 0.56 to 31.41 Debye.The oriented MXene distribution and porous structure not only tripled the piezoelectric response but also achieved an eightfold increase in sensitivity within the low-pressure region,along with demonstrating cyclic stability exceeding 20,000 cycles.The properties reinforcement originating from dual structure is elucidated through the finite element simulation and experimental validation.Attributed to the excellent piezoelectric response and deep learning algorithm,the sensor can effectively recognize the signals of artery pulse and finger flexion.Finally,a 3×3 sensor array is fabricated to monitor the pressure distribution wirelessly.This study provides an innovative methodology for reinforcing interfacial polarized piezoelectric materials and insight into structural designs.
基金supported by the Taiyuan Major Science and Technology Project Fund in 2021,Fund for Shanxi“1331 Project,”Key Research and Development Program of Shanxi Province(202102040201011)the Zhanjiang Marine Equipment and Marine Biological Industry Unveiled the Talent Team Project(2021E05034).
文摘The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and toughness of PP.The low-temperature toughness of PP was improved by inserting high-density polyethylene(HDPE)between PP and polystyrene-b-ethylene-co-propyleneb-polystyrene(SEPS)to form an unusual SEPS@HDPE core–shell structure,with SEPS as the core and HDPE as the shell.Based on the microtopography and rheological behavior characterization,HDPE in PP/SEPS/HDPE composites was found to serve as an emulsifier,decrease the size of SEPS particles,and promote the homogeneous dispersion of dispersed phase particles in the matrix.An increase in the HDPE content shifted the toughening mechanism of PP composites from cavitation to matrix shear yielding.The reduction in the distance between the dispersed core–shell structure particles promoted shear yielding in the PP composites,leading to increased toughness.The creation of an intermediate HDPE layer with a moderate modulus was crucial for dispersing stress concentrations and significantly improving toughness without compromising the tensile strength.These findings will facilitate the fabrication of high-toughness PP products at low temperatures.
基金supported by the National Natural Science Foundation of China(52172091,52172295)Defense Industrial Technology Development Program(JCKY2023605C002)+4 种基金Frontier Leading Technology Basic Research Major Project of Jiangsu Province(SBK2023050110)the National Key Laboratory on Electromagnetic Environmental Effects and Electro-optical Engineering(NO.61422062301)the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory(ZHD202305)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(ASMA202303)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0371).
文摘Advanced chemical engineering for simultaneous modulation of nanomaterial morphology, defects, interfaces, and structure to enhance electromagnetic and microwave absorption (MA) performance. However, accurately distinguishing the MA contributions of different scale factors and tuning the optimal combined effects remains a formidable challenge. This study employs a synergistic approach combining template protection etching and vacuum annealing to construct a controlled system of micrometer-sized cavities and amorphous carbon matrices in metal-organic framework (MOF) derivatives. The results demonstrate that the spatial effects introduced by the hollow structure enhance dielectric loss but significantly weaken impedance matching. By increasing the proportion of amorphous carbon, the balance between electromagnetic loss and impedance matching can be effectively maintained. Importantly, in a suitable graphitization environment, the presence of oxygen vacancies in amorphous carbon can induce significant polarization to compensate for the reduced conductivity loss due to the absence of sp2 carbon. Through the synergistic effects of morphology and composition, the samples exhibit a broader absorption bandwidth (6.28 GHz) and stronger reflection loss (−61.64 dB) compared to the original MOF. In conclusion, this study aims to elucidate the multiscale impacts of macroscopic micro-nano structure and microscopic defect engineering, providing valuable insights for future research in this field.
基金supported by the National Natural Science Foundation of China(No.12372153)the Funding by Guangdong Basic and Applied Basic Research Foundation(No.2023A1515012366)。
文摘In this study,the free vibration of a piezoelectric semiconductor(PS)composite structure composed of a PS layer,a fractional viscoelastic layer,and an elastic substrate with simply-supported boundary conditions is investigated.The fractional derivative Zener model is used to establish the constitutive relation of the viscoelastic layer.The first-order shear deformation theory and Hamilton's principle are used to derive the motion equations of the present problem.The frequency parameter is numerically resolved with the Newton-Raphson method through the eigenvalue equation.The effects of either geometric parameters,carrier density,and electric voltage applied on the surface of the composite structure or the fractional order of the Zener model on both the natural frequency and loss factor are discussed,and some interesting conclusions are drawn.This work will be helpful for designing and manufacturing PS materials and structures.
基金supported by the National Natural Science Foundation of China(Grant No.11872080)Beijing Natural Science Foundation(Grant No.3192005).
文摘This paper presents a deep learning-based topology optimization method for the joint design of material layout and fiber orientation in continuous fiber-reinforced composite structure(CFRCS).The proposed method mainly includes three steps:(1)a ResUNet-involved generative and adversarial network(ResUNet-GAN)is developed to establish the end-to-end mapping from structural design parameters to fiber-reinforced composite optimized structure,and a fiber orientation chromatogram is presented to represent continuous fiber angles;(2)to avoid the local optimum problem,the independent continuous mapping method(ICM method)considering the improved principal stress orientation interpolated continuous fiber angle optimization(PSO-CFAO)strategy is utilized to construct CFRCS topology optimization dataset;(3)the well-trained ResUNet-GAN is deployed to design the optimal structural material distribution together with the corresponding continuous fiber orientations.Numerical simulations for benchmark structure verify that the proposed method greatly improves the design efficiency of CFRCS along with high design accuracy.Furthermore,the CFRCS topology configuration designed by ResUNet-GAN is fabricated by additive manufacturing.Compression experiments of the specimens show that both the stiffness structure and peak load of the CFRCS topology configuration designed by the proposed method have significantly enhanced.The proposed deep learning-based topology optimization method will provide great flexibility in CFRCS for engineering applications.
