Pile foundation in alternate layered liquefiable and non-liquefiable soil deposits subjected to earthquake loading

Pile foundations are still the preferred foundation system for high-rise structures in earthquake-prone regions.Pile foundations have experienced failures in past earthquakes due to liquefaction.Research on pile foundations in liquefiable soils has primarily focused on the pile foundation behavior in two or three-layered soil profiles.However,in natural occurrence,it may occur in alternative layers of liquefiable and non-liquefiable soil.However,the experimental and/or numerical studies on the layered effect on pile foundations have not been widely addressed in the literature.Most of the design codes across the world do not explicitly mention the effect of sandwiched non-liquefiable soil layers on the pile response.In the present study,the behavior of an end-bearing pile in layered liquefiable and non-liquefiable soil deposit is studied numerically.This study found that the kinematic bending moment is higher and governs the design when the effect of the sandwiched non-liquefied layer is considered in the analysis as opposed to when its effect is ignored.Therefore,ignoring the effect of the sandwiched non-liquefied layer in a liquefiable soil deposit might be a nonconservative design approach.

High‑Entropy Layered Oxide Cathode Enabling High‑Rate for Solid‑State Sodium‑Ion Batteries

Na-ion O3-type layered oxides are prospective cathodes for Na-ion batteries due to high energy density and low-cost.Nevertheless,such cathodes usually suffer from phase transitions,sluggish kinetics and air instability,making it difficult to achieve high performance solid-state sodium-ion batteries.Herein,the high-entropy design and Li doping strategy alleviate lattice stress and enhance ionic conductivity,achieving high-rate performance,air stability and electrochemically thermal stability for Na_(0.95)Li_(0.06)Ni_(0.25)Cu_(0.05)Fe_(0.15)Mn_(0.49)O_(2).This cathode delivers a high reversible capacity(141 mAh g^(−1)at 0.2C),excellent rate capability(111 mAh g^(−1)at 8C,85 mAh g^(−1)even at 20C),and long-term stability(over 85%capacity retention after 1000 cycles),which is attributed to a rapid and reversible O3–P3 phase transition in regions of low voltage and suppresses phase transition.Moreover,the compound remains unchanged over seven days and keeps thermal stability until 279℃.Remarkably,the polymer solid-state sodium battery assembled by this cathode provides a capacity of 92 mAh g^(−1)at 5C and keeps retention of 96%after 400 cycles.This strategy inspires more rational designs and could be applied to a series of O3 cathodes to improve the performance of solid-state Na-ion batteries.

Probabilistic analysis of tunnel face seismic stability in layered rock masses using Polynomial Chaos Kriging metamodel

Face stability is an essential issue in tunnel design and construction.Layered rock masses are typical and ubiquitous;uncertainties in rock properties always exist.In view of this,a comprehensive method,which combines the Upper bound Limit analysis of Tunnel face stability,the Polynomial Chaos Kriging,the Monte-Carlo Simulation and Analysis of Covariance method(ULT-PCK-MA),is proposed to investigate the seismic stability of tunnel faces.A two-dimensional analytical model of ULT is developed to evaluate the virtual support force based on the upper bound limit analysis.An efficient probabilistic analysis method PCK-MA based on the adaptive Polynomial Chaos Kriging metamodel is then implemented to investigate the parameter uncertainty effects.Ten input parameters,including geological strength indices,uniaxial compressive strengths and constants for three rock formations,and the horizontal seismic coefficients,are treated as random variables.The effects of these parameter uncertainties on the failure probability and sensitivity indices are discussed.In addition,the effects of weak layer position,the middle layer thickness and quality,the tunnel diameter,the parameters correlation,and the seismic loadings are investigated,respectively.The results show that the layer distributions significantly influence the tunnel face probabilistic stability,particularly when the weak rock is present in the bottom layer.The efficiency of the proposed ULT-PCK-MA is validated,which is expected to facilitate the engineering design and construction.

Layered Structural PBAT Composite Foams for Efficient Electromagnetic Interference Shielding

The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.

Difficulties, strategies, and recent research and development of layered sodium transition metal oxide cathode materials for high-energy sodium-ion batteries

Energy-storage systems and their production have attracted significant interest for practical applications.Batteries are the foundation of sustainable energy sources for electric vehicles(EVs),portable electronic devices(PEDs),etc.In recent decades,Lithium-ion batteries(LIBs) have been extensively utilized in largescale energy storage devices owing to their long cycle life and high energy density.However,the high cost and limited availability of Li are the two main obstacles for LIBs.In this regard,sodium-ion batteries(SIBs) are attractive alternatives to LIBs for large-scale energy storage systems because of the abundance and low cost of sodium materials.Cathode is one of the most important components in the battery,which limits cost and performance of a battery.Among the classified cathode structures,layered structure materials have attracted attention because of their high ionic conductivity,fast diffusion rate,and high specific capacity.Here,we present a comprehensive review of the classification of layered structures and the preparation of layered materials.Furthermore,the review article discusses extensively about the issues of the layered materials,namely(1) electrochemical degradation,(2) irreversible structural changes,and(3) structural instability,and also it provides strategies to overcome the issues such as elemental phase composition,a small amount of elemental doping,structural design,and surface alteration for emerging SIBs.In addition,the article discusses about the recent research development on layered unary,binary,ternary,quaternary,quinary,and senary-based O3-and P2-type cathode materials for high-energy SIBs.This review article provides useful information for the development of high-energy layered sodium transition metal oxide P2 and O3-cathode materials for practical SIBs.

Enhancing the stability of Ni Fe-layered double hydroxide nanosheet array for alkaline seawater oxidation by Ce doping

Electrocatalytic hydrogen production from seawater holds enormous promise for clean energy generation.Nevertheless,the direct electrolysis of seawater encounters significant challenges due to poor anodic stability caused by detrimental chlorine chemistry.Herein,we present our recent discovery that the incorporation of Ce into Ni Fe layered double hydroxide nanosheet array on Ni foam(Ce-Ni Fe LDH/NF)emerges as a robust electrocatalyst for seawater oxidation.During the seawater oxidation process,CeO_(2)is generated,effectively repelling Cl^(-)and inhibiting the formation of Cl O-,resulting in a notable enhancement in the oxidation activity and stability of alkaline seawater.The prepared Ce-Ni Fe LDH/NF requires only overpotential of 390 m V to achieve the current density of 1 A cm^(-2),while maintaining long-term stability for 500 h,outperforming the performance of Ni Fe LDH/NF(430 m V,150 h)by a significant margin.This study highlights the effectiveness of a Ce-doping strategy in augmenting the activity and stability of materials based on Ni Fe LDH in seawater electrolysis for oxygen evolution.

Enhancing layered perovskite ferrites with ultra-high-density nanoparticles via cobalt doping for ceramic fuel cell anode

Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural configuration.Herein,we employ controlled Co doping to effectively enhance the nanoparticle exsolution process in layered perovskite ferrites materials.CoFe alloy nanoparticles with ultra-high-density are exsolved on the(PrBa)_(0.95)(Fe_(0.8)Co_(0.1)Nb_(0.1))2O_(5+δ)(PBFCN_(0.1))surface under reducing atmosphere,providing significant amounts of reaction sites and good durability for hydrocarbon catalysis.Under a reducing atmosphere,cobalt facilitates the reduction of iron cations within PBFCN_(0.1),leading to the formation of CoFe alloy nanoparticles.This formation is accompanied by a cation exchange process,wherein,with the increase in temperature,partial cobalt ions are substituted by iron.Meanwhile,Co doping significantly enhance the electrical conductivity due to the stronger covalency of the Cosingle bondO bond compared with Fesingle bondO bond.A single cell with the configuration of PBFCN_(0.1)-Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)|SDC|Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF)-SDC achieves an extremely low polarization resistance of 0.0163Ωcm^(2)and a high peak power density of 740 mW cm^(−2)at 800℃.The cell also shows stable operation for 120 h in H_(2)with a constant current density of 285 mA cm^(−2).Furthermore,employing wet C_(2)H_(6)as fuel,the cell demonstrates remarkable performance,achieving peak power densities of 455 mW cm^(−2)at 800℃and 320 mW cm^(−2)at 750℃,marking improvements of 36%and 70%over the cell with(PrBa)_(0.95)(Fe_(0.9)Nb_(0.1))_(2)O_(5+δ)(PBFN)-SDC at these respective temperatures.This discovery emphasizes how temperature influences alloy nanoparticles exsolution within doped layered perovskite ferrites materials,paving the way for the development of high-performance ceramic fuel cell anodes.

Defective Nickel-Iron Layered Double Hydroxide for Enhanced Photocatalytic NO Oxidation with Significant Alleviation of NO2 Production

Photocatalysis offers a sustainable means for the oxidative removal of low concentrations of NOx(NO,NO2,N2O,N2O5,etc.)from the atmosphere.Layered double hydroxides(LDHs)are promising candidate photocatalysts owing to their unique layered and tunable chemical structures and abundant surface hydroxide(OH)moieties,which are hydroxyl radical(OH)precursors.However,the practical applications of LDHs are limited by their poor charge-separation ability and insufficient active sites.Herein,we developed a facile N_(2)H_(4)-driven etching approach to introduce dual Ni^(2+)and OHvacancies(Niv and OHv,respectively)into NiFe-LDH nanosheets(hereafter referred to as NiFe-LDH-et)to facilitate improved charge-carrier separation and active Lewis acidic site(Fe^(3+)and Ni^(2+)exposed at OHv)formation.In contrast to inert pristine LDH,NiFe-LDH-et actively removed NO under visible-light illumination.Specifically,Ni_(76)Fe_(24)-LDH-et etched with 1.50 mmol·L^(-1)N_(2)H_(4)solution removed 32.8%of the NO in continuously flowing air(NO feed concentration:500 parts per billion(ppb))under visible-light illumination,thereby outperforming most reported catalysts.Experimental and theoretical data revealed that the dual vacancies promoted the production of reactive oxygen species(O_(2)·^(-)andOH)and the adsorption of NO on the LDH.In situ spectroscopy demonstrated that NO was preferentially adsorbed at Lewis acidic sites,particularly exposed Fe^(3+)sites,converted into NO+,and subsequently oxidized to NO3without the notable formation of the more toxic intermediate NO2,thereby alleviating risks associated with its production and emission.

Impact of Transition Metal Layer Vacancy on the Structure and Performance of P2 Type Layered Sodium Cathode Material

This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na_(0.6)[Ni_(0.3)Ru_(0.3)Mn_(0.4)]O_(2)(NRM)cathode material.The incorporation of Ru,Ni,and vacancy enhances the structural stability during extensive cycling,increases the operation voltage,and induces a capacity increase while also activating oxygen redox,respectively,in Na_(0.7)[Ni_(0.2)V_(Ni0.1)Ru_(0.3)Mn_(0.4)]O_(2)(V-NRM)compound.Various analytical techniques including transmission electron microscopy,X-ray absorption near edge spectroscopy,operando X-ray diffraction,and operando differential electrochemical mass spectrometry are employed to assess changes in the average oxidation states and structural distortions.The results demonstrate that V-NRM exhibits higher capacity than NRM and maintains a moderate capacity retention of 81%after 100 cycles.Furthermore,the formation of additional lone-pair electrons in the O 2p orbital enables V-NRM to utilize more capacity from the oxygen redox validated by density functional calculation,leading to a widened dominance of the OP4 phase without releasing O_(2) gas.These findings offer valuable insights for the design of advanced high-capacity cathode materials with improved performance and sustainability in sodium-ion batteries.

Solvothermal synthesis and adsorption performance of layered boehmite using aluminum chloride and high-alumina fly ash

High alumina fly ash(FAHAl)is a kind of bulk solid waste unique to China,whose availability of high-value aluminum and the threat to the environment makes its high-value utilization urgent.In this work,the alumina containing leaching solution obtained from Na_(2)CO_(3) roasting and HCl leaching of FAHAl was used as the mother liquor to prepare layered boehmite in situ.The preparation process with AlCl_(3) as the raw material was also compared.The formation process and mechanism of boehmite,the choice of solvent,along with the adsorption capability of Congo red were analyzed by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,Brunauer-Emmett-Teller method and adsorption experiments.Results showed that during the preparation of layered boehmite,the precursor Al(OH)_(3) from the reaction of Al^(3+) and OH-is transformed into boehmiteγ-AlOOH.The existence of ethanol is beneficial to regulate and promote the growth of boehmite crystal effectively.When water and ethanol are mixed with a volume ratio of 2:1 and used as the solvent,the maximum specific surface area of the boehmite is obtained at 135.7 m^(2)·g^(-1),and 99.16%of Congo red can be absorbed after 10 min when AlCl3 is used as a raw material.As purified leaching solution is used as the mother liquid,the crystallinity of boehmite decreases slightly when the pH value decreases from 12.5 to 11.When pH is 11,the removal efficiency of Congo red reaches a maximum of 72.25%.This process not only achieves the extraction of aluminum and high-value utilization of FAHAl but also provides a thought to prepare layered boehmite with adsorption properties.

Cycling performance of layered oxide cathode materials for sodium-ion batteries

Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the application prospects of batteries.However,facing challenges,including phase transitions,ambient stability,side reactions,and irreversible anionic oxygen activity,the cycling performance of layered oxide cathode materials still cannot meet the application requirements.Therefore,this review proposes several strategies to address these challenges.First,bulk doping is introduced from three aspects:cationic single doping,anionic single doping,and multi-ion doping.Second,homogeneous surface coating and concentration gradient modification are reviewed.In addition,methods such as mixed structure design,particle engineering,high-entropy material construction,and integrated modification are proposed.Finally,a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.

Mg/Fe site-specific dual-doping to boost the performance of cobalt-free nickle-rich layered oxide cathode for high-energy lithium-ion batteries

Layer-type LiNi0.9Mn0.1O2is promising to be the primary cathode material for lithium-ion batteries(LIBs)due to its excellent electrochemical performance.Unfortunately,the cathode with high nickel content suffers from severely detrimental structural transformation that causes rapid capacity attenuation.Herein,site-specific dual-doping with Fe and Mg ions is proposed to enhance the structural stability of LiNi0.9Mn0.1O2.The Fe3+dopants are inserted into transition metal sites(3b)and can favorably provide additional redox potential to compensate for charge and enhance the reversibility of anionic redox.The Mg ions are doped into the Li sites(3a)and serve as O_(2)^(-)-Mg^(2+)-O_(2)^(-)pillar to reinforce the electrostatic cohesion between the two adjacent transition-metal layers,which further suppress the cracking and the generation of harmful phase transitions,ultimately improving the cyclability.The theoretical calculations,including Bader charge and crystal orbital Hamilton populations(COHP)analyses,confirm that the doped Fe and Mg can form stable bonds with oxygen and the electrostatic repulsion of O_(2)^(-)-O_(2)^(-)can be effectively suppressed,which effectively mitigates oxygen anion loss at the high delithiation state.This dual-site doping strategy offers new avenues for understanding and regulating the crystalline oxygen redox and demonstrates significant potential for designing high-performance cobalt-free nickel-rich cathodes.

A whole process damage constitutive model for layered sandstone under uniaxial compression based on Logistic function

Bedding structural planes significantly influence the mechanical properties and stability of engineering rock masses.This study conducts uniaxial compression tests on layered sandstone with various bedding angles(0°,15°,30°,45°,60°,75°and 90°)to explore the impact of bedding angle on the deformational mechanical response,failure mode,and damage evolution processes of rocks.It develops a damage model based on the Logistic equation derived from the modulus’s degradation considering the combined effect of the sandstone bedding dip angle and load.This model is employed to study the damage accumulation state and its evolution within the layered rock mass.This research also introduces a piecewise constitutive model that considers the initial compaction characteristics to simulate the whole deformation process of layered sandstone under uniaxial compression.The results revealed that as the bedding angle increases from 0°to 90°,the uniaxial compressive strength and elastic modulus of layered sandstone significantly decrease,slightly increase,and then decline again.The corresponding failure modes transition from splitting tensile failure to slipping shear failure and back to splitting tensile failure.As indicated by the modulus’s degradation,the damage characteristics can be categorized into four stages:initial no damage,damage initiation,damage acceleration,and damage deceleration termination.The theoretical damage model based on the Logistic equation effectively simulates and predicts the entire damage evolution process.Moreover,the theoretical constitutive model curves closely align with the actual stress−strain curves of layered sandstone under uniaxial compression.The introduced constitutive model is concise,with fewer parameters,a straightforward parameter determination process,and a clear physical interpretation.This study offers valuable insights into the theory of layered rock mechanics and holds implications for ensuring the safety of rock engineering.

Recent progress in Ni-rich layered oxides and related cathode materials for Li-ion cells

Undoubtedly,the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery(LIB)technology.The achieved improvements in the energy density,cyclability,charging speed,reduced costs,as well as safety and stability,already contribute to the wider adoption of LIBs,which extends nowadays beyond mobile electronics,power tools,and electric vehicles,to the new range of applications,including grid storage solutions.With numerous published papers and broad reviews already available on the subject of Ni-rich oxides,this review focuses more on the most recent progress and new ideas presented in the literature references.The covered topics include doping and composition optimization,advanced coating,concentration gradient and single crystal materials,as well as innovations concerning new electrolytes and their modification,with the application of Ni-rich cathodes in solid-state batteries also discussed.Related cathode materials are briefly mentioned,with the high-entropy approach and zero-strain concept presented as well.A critical overview of the still unresolved issues is given,with perspectives on the further directions of studies and the expected gains provided.

Microstructure control and hot cracking behavior of the new Ni-Co based superalloy prepared by electron beam smelting layered solidification technology

The prevention of hot cracking formation is of utmost importance in the production of the new Ni-Co based superalloys through the utilization of the electron beam smelting layered solidification technique(EBSL),as it ensures exceptional homogeneity and dependable consistency of the specimens.In contrast to previous studies that focused on minimizing the liquid film and solidification range,our methodology adopts a distinct approach.In this research,a novel methodology was employed to mitigate internal stresses through the implementation of equiaxed grain layers via an alternately reduced cooling method.This ultimately resulted in the elimination of hot cracking.To be more specific,the transition from a columnar to an equiaxed structure was observed during the layer-by-layer construction process in the fabrication of the new Ni-Co based superalloy in EBSL.The EBSL-Ni-Co superalloy,when subjected to the alternating reduction cooling method,exhibited an internal stress of 49 MPa.This value represents a significant reduction of 83.8%compared to the internal stress observed when employing the linear reduction cooling method.Additionally,the solvus temperature of theγ-γ’eutectic phases in EBSL-Ni-Co superalloys produced by the alternating reduction cooling method is significantly higher.Intriguingly,the Nth layer of the EBSL-Ni-Co based superalloys produced by EBSL simultaneously heats treated with the preceding layers.And the low melting point phase gradually dissolved back into the matrix.The implementation of an alternating reduced cooling method successfully mitigated the formation of the liquid film in theγ-γ’eutectic phase and the buildup of internal stresses in the EBSL-Ni-Co superalloy during its manufacturing process.These discoveries open up a novel preparation procedure pathway for the manufacture of crack-free superalloys with superior mechanical characteristics using EBSL.

Restraint effect of partition wall on the tunnel floor heave in layered rock mass

The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.

Phase engineering of Ni-Mn binary layered oxide cathodes for sodiumion batteries

Nickel-manganese binary layered oxides with high working potential and low cost are potential candidates for sodium-ion batteries,but their electrochemical properties are highly related to compositional diversity.Diverse composite materials with various phase structures of P3,P2/P3,P2,P2/O3,and P2/P3/O3 were synthesized by manipulating the sodium content and calcination conditions,leading to the construction of a synthetic phase diagram for Na_(x)Ni_(0.25)Mn_(0.75)O_(2)(0.45≤x≤1.1).Then,we compared the electrochemical characteristics and structural evolution during the desodiation/sodiation process of P2,P2/P3,P2/03,and P2/P3/O3-Na_(x)Ni_(0.25)Mn_(0.75)O_(2).Among them,P2/P3-Na0.75Ni0.25Mn0.75O2exhibits the best rate capability of 90.9 mA h g^(-1)at 5 C,with an initial discharge capacity of 142.62 mA h g^(-1)at 0.1 C and a capacity retention rate of 78.25%after 100 cycles at 1 C in the voltage range of 2-4.3 V.The observed superior sodium storage performance of P2/P3 hybrids compared to other composite phases can be attributed to the enhanced Na^(+)transfer dynamic,reduction of the Jahn-teller effect,and improved reaction reversibility induced by the synergistic effect of P2 and P3 phases.The systematic research and exploration of phases in Na_(x)Ni_(0.25)Mn_(0.75)O_(2)provide new sights into high-performance nickel-manganese binary layered oxide for sodium-ion batteries.

A modified smoothed particle hydrodynamics method considering residual stress for simulating failure and its application in layered rock mass

Residual strength is an indispensable factor in evaluating rock fracture,yet the current Smoothed Particle Hydrodynamics(SPH)framework rarely considers its influence when simulating fracture.An improved cracking strategy considering residual stress in the base bond SPH method was proposed to simulate failures in layered rocks and slopes and verified by experimental results and other simulation methods(i.e.,the discrete element method).Modified Mohr–Coulomb failure criterion was applied to distinguish the mixed failure of tensile and shear.Bond fracture markψwas introduced to improve the kernel function after tensile damage,and the calculation of residual stress after the damage was derived after shear damage.Numerical simulations were carried out to evaluate its performance under different stress and scale conditions and to verify its effectiveness in realistically reproducing crack initiation and propagation and coalescence,even fracture and separation.The results indicate that the improved cracking strategy precisely captures the fracture and failure pattern in layered rocks and rock slopes.The residual stress of brittle tock is correctly captured by the improved SPH method.The improved SPH method that considers residual strength shows an approximately 13%improvement in accuracy for the safety factor of anti-dip layered slopes compared to the method that does not consider residual strength,as validated against analytical solutions.We infer that the improved SPH method is effective and shows promise for applications to continuous and discontinuous rock masses.

In-situ additive manufacturing of high strength yet ductility titanium composites with gradient layered structure using N_(2)

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.

Early-stage latent thermal failure of single-crystal Ni-rich layered cathode

High nickel content worsens the thermal stability of layered cathodes for lithium-ion batteries,raising safety concerns for their applications.Thoroughly understanding the thermal failure process can offer valuable guidance for material optimization on thermal stability and new opportunities in monitoring battery thermal runaway(TR).Herein,this work comprehensively investigates the thermal failure process of a single-crystal nickel-rich layered cathode and finds that the latent thermal failure starts at∼120℃far below the TR temperature(225℃).During this stage of heat accumulation,sequential structure transition is revealed by atomic resolution electron microscopy,which follows the layered→cation mixing layered→LiMn_(2)O_(4)-type spinel→disordered spinel→rock salt.This progression occurs as a result of the continuous migration and densification of transition metal cations.Phase transition generates gaseous oxygen,initially confined within the isolated closed pores,thereby not showing any thermal failure phenomena at the macro-level.Increasing temperature leads to pore growth and coalescence,and eventually to the formation of open pores,causing oxygen gas release and weight loss,which are the typical TR features.We highlight that latent thermal instability occurs before the macro-level TR,suggesting that suppressing phase transitions caused by early thermal instability is a crucial direction for material optimization.Our findings can also be used for early warning of battery thermal runaway.