Inhomogeneity and low efficiency are two important factors that limit the application of laser-induced periodic surface structures(LIPSSs),especially on glass surfaces.In this study,two-beam interference(TBI)of femtos...Inhomogeneity and low efficiency are two important factors that limit the application of laser-induced periodic surface structures(LIPSSs),especially on glass surfaces.In this study,two-beam interference(TBI)of femtosecond lasers was used to produce large-area straight LIPSSs on fused silica using cylindrical lenses.Compared with those produced us-ing a single circular or cylindrical lens,the LIPSSs produced by TBI are much straighter and more regular.Depending on the laser fluence and scanning velocity,LIPSSs with grating-like or spaced LIPSSs are produced on the fused silica sur-face.Their structural colors are blue,green,and red,and only green and red,respectively.Grating-like LIPSS patterns oriented in different directions are obtained and exhibit bright and vivid colors,indicating potential applications in surface coloring and anti-counterfeiting logos.展开更多
Femtosecond laser pulses with GHz burst mode that consist of a series of trains of ultrashort laser pulses with a pulse interval of several hundred picoseconds offer distinct features in material processing that canno...Femtosecond laser pulses with GHz burst mode that consist of a series of trains of ultrashort laser pulses with a pulse interval of several hundred picoseconds offer distinct features in material processing that cannot be obtained by the conventional irradiation scheme of femtosecond laser pulses(single-pulse mode).However,most studies using the GHz burst mode femtosecond laser pulses focus on ablation of materials to achieve high-efficiency and high-quality material removal.In this study,we explore the ability of the GHz burst mode femtosecond laser processing to form laser-induced periodic surface structures(LIPSS)on silicon.It is well known that the direction of LIPSS formed by the single-pulse mode with linearly polarized laser pulses is typically perpendicular to the laser polarization direction.In contrast,we find that the GHz burst mode femtosecond laser(wavelength:1030 nm,intra-pulse duration:220 fs,intra-pulse interval time(intra-pulse repetition rate):205 ps(4.88 GHz),burst pulse repetition rate:200 kHz)creates unique two-dimensional(2D)LIPSS.We regard the formation mechanism of 2D LIPSS as the synergetic contribution of the electromagnetic mechanism and the hydrodynamic mechanism.Specifically,generation of hot spots with highly enhanced electric fields by the localized surface plasmon resonance of subsequent pulses in the bursts within the nanogrooves of one-dimensional LIPSS formed by the preceding pulses creates 2D LIPSS.Additionally,hydrodynamic instability including convection flow determines the final structure of 2D LIPSS.展开更多
Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much ...Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much simpler and cost effective.In this work,LIPSS on Si surfaces were generated using femtosecond laser pulses of 800 nm wavelength.Photocatalytic substrates were prepared by depositing TiO2 thin films on top of the structured and unstructured Si wafer.The coatings were produced by sputtering from a Ti target in two different types of oxygen atmospheres.In first case,the oxygen pressure within the sputtering chamber was chosen to be high(3×10^–2 mbar)whereas it was one order of magnitude lower in second case(2.1×10^–3 mbar).In photocatalytic dye decomposition study of Methylene blue dye it was found that in the presence of LIPSS the activity can be enhanced by 2.1 and 3.3 times with high pressure and low pressure grown TiO2 thin films,respectively.The increase in photocatalytic activity is attributed to the enlargement of effective surface area.In comparative study,the dye decomposition rates of TiO2 thin films grown on LIPSS are found to be much higher than the value for standard reference thin film material Pilkington Activ^TM.展开更多
Electrochemical oxidation/reduction of radicals is a green and environmentally friendly approach to generating fuels.These reactions,however,suffer from sluggish kinetics due to a low local concentration of radicals a...Electrochemical oxidation/reduction of radicals is a green and environmentally friendly approach to generating fuels.These reactions,however,suffer from sluggish kinetics due to a low local concentration of radicals around the electrocatalyst.A large applied electrode potential can enhance the fuel generation efficiency via enhancing the radical concentration around the electrocatalyst sites,but this comes at the cost of electricity.Here,we report about a~45%saving in energy to achieve an electrochemical hydrogen generation rate of 3×10^(16) molecules cm^(–2)s^(–1)(current density:10 mA/cm^(2))through localized electric field-induced enhancement in the reagent concentration(LEFIRC)at laser-induced periodic surface structured(LIPSS)electrodes.The finite element model is used to simulate the spatial distribution of the electric field to understand the effects of LIPSS geometric parameters in field localization.When the LIPSS patterned electrodes are used as substrates to support Pt/C and RuO_(2) electrocatalysts,the η_(10) overpotentials for HER and OER are decreased by 40.4 and 25%,respectively.Moreover,the capability of the LIPSS-patterned electrodes to operate at significantly reduced energy is also demonstrated in a range of electrolytes,including alkaline,acidic,neutral,and seawater.Importantly,when two LIPSS patterned electrodes were assembled as the anode and cathode into a cell,it requires 330 mVs of lower electric potential with enhanced stability over a similar cell made of pristine electrodes to drive a current density of 10 mA/cm^(2).This work demonstrates a physical and versatile approach of electrode surface patterning to boost electrocatalytic fuel generation performance and can be applied to any metal and semiconductor catalysts for a range of electrochemical reactions.展开更多
The interactions between ultrafast lasers and materials reveal a range of nonlinear transient phenomena that are crucial in advanced manufacturing.Understanding these interactions during ultrafast laser ablation requi...The interactions between ultrafast lasers and materials reveal a range of nonlinear transient phenomena that are crucial in advanced manufacturing.Understanding these interactions during ultrafast laser ablation requires detailed measurements of material properties and structural changes with high temporal and spatial resolutions.Traditional spatiotemporal imaging techniques relying on reflective imaging often fail to capture comprehensive information,resulting in predominantly qualitative theoretical models of these interactions.To overcome this limitation,we propose a dual-modal ultrafast microscopy system that combines two-dimensional reflectivity and three-dimensional topography imaging.By integrating pump-probe techniques with an interferometric imaging system,impressive spatiotemporal resolutions of 236 nm and 256 fs were achieved.Furthermore,using this system,we successfully examined the dynamics of laser-induced periodic surface structure formation,strengthening,and erasure on Si surfaces.The results demonstrate that the dual-modal spatiotemporal imaging technique can serve as a robust tool for the comprehensive analysis of ablation dynamics,facilitating a deeper understanding of the fundamental physics involved and enabling more accurate optimisation of ultrafast laser fabrication processes.展开更多
This study demonstrates for the first time,to the best of our knowledge,that femtosecond laser-induced periodic surface structures(LIPSSs)enhance diamond's visible-light transmittance.Using cylindrical-lens-shaped...This study demonstrates for the first time,to the best of our knowledge,that femtosecond laser-induced periodic surface structures(LIPSSs)enhance diamond's visible-light transmittance.Using cylindrical-lens-shaped beams for highspeed scanning and secondary defocused low-energy laser treatment,uniform nanogratings with a period of 105 nm(12μm×24μm)were fabricated within 3 s.Optimized scanning speeds and pulse energies improved structural quality,achieving up to 10%transmittance enhancement at 625±750 nm.This approach offers a novel strategy for anti-reflective diamond optoelectronic devices.展开更多
Triply periodic minimal surface(TPMS)-based bone implants are an innovative approach in orthopedic implantology,offering customized solutions for bone defect repair and regeneration.This review comprehensively examine...Triply periodic minimal surface(TPMS)-based bone implants are an innovative approach in orthopedic implantology,offering customized solutions for bone defect repair and regeneration.This review comprehensively examines the current research landscape of TPMS-based bone implants,addressing key challenges and proposing future directions.It explores design strategies aimed at optimizing mechanical strength and enhancing biological integration,with a particular emphasis on TPMS structures.These design strategies include graded,hierarchical,and hybrid designs,each contributing to the overall functionality and performance of the implants.This review also highlights state-of-the-art fabrication technologies,particularly advancements in additive manufacturing(AM)techniques for creating metal-based,polymer-based,and ceramic-based bone implants.The ability to precisely control the architecture of TPMS structures using AM techniques is crucial for tailoring the mechanical and biological properties of such implants.Furthermore,this review critically evaluates the biological performance of TPMS implants,focusing on their potential to promote bone ingrowth and regeneration.Key factors,such as mechanical properties,permeability,and biocompatibility,are examined to determine the effectiveness of these implants in clinical applications.By synthesizing existing knowledge and proposing innovative research directions,this review underscores the transformative potential of TPMS-based bone implants in orthopedic surgery.The objective is to improve clinical outcomes and enhance patient care through advanced implant designs and manufacturing techniques.展开更多
The pore structure of porous scaffolds plays a crucial role in bone repair.The prevalent bone implant structure in clinical practice is the traditional cubic structure.However,the traditional cubic structure exhibits ...The pore structure of porous scaffolds plays a crucial role in bone repair.The prevalent bone implant structure in clinical practice is the traditional cubic structure.However,the traditional cubic structure exhibits sharp edges and junctions that are not conducive to cell adhesion or growth.In this study,a double gyroid(DG)Ti6Al4V scaffold based on a triply periodic minimal surface(TPMS)structure was devised,and the osseointegration performance of DG structural scaffolds with varying porosities was investigated.Compression tests revealed that the elastic modulus and compressive strength of DG structural scaffolds were sufficient for orthopedic implants.In vitro cellular experiments demonstrated that the DG structure significantly enhanced cell proliferation,vascularization,and osteogenic differentiation compared to the cubic structure.The DG structure with 55%porosity exhibited the most favorable outcomes.In vivo experiments in rabbits further demonstrated that DG scaffolds could promote neovascularization and bone regeneration and maturation;those with 55%porosity performed best.Comparing the surface area,specific surface area per unit volume,and internal flow distribution characteristics of gyroid and DG structure scaffolds,the latter are more conducive to cell adhesion and growth within scaffolds.This study underscored the potential of DG scaffolds based on the TPMS structure in optimizing the pore structure design of titanium scaffolds,inducing angiogenesis,and advancing the clinical application of titanium scaffolds for repairing bone defects.展开更多
Magnesium(Mg)-based materials are promising for lightweight structural applications.However,their widespread adoption is significantly constrained by inherent limitations in mechanical properties.To address this chall...Magnesium(Mg)-based materials are promising for lightweight structural applications.However,their widespread adoption is significantly constrained by inherent limitations in mechanical properties.To address this challenge,this study introduces a novel Mg-based interpenetratingphase composite reinforced with a nickel-titanium(NiTi)scaffold featuring a triply periodic minimal surface(TPMS)configuration.By combining experimental investigations with finite element simulations,we systematically elucidate the dual impact of the scaffold’s unit cell size(a)on manufacturing viability and mechanical enhancement.To compensate for compromised infiltration dynamics induced by decreasing a,a critical permeability threshold of 1×10^(-8) m^(2) is proposed for achieving successful composite fabrication.Mechanically,reducing a strengthens the interaction between the scaffold and matrix:the TPMS-configured NiTi scaffolds improve stress transfer,deflect crack propagation,and facilitate damage delocalization,whereas the Mg matrix preserves structural integrity and enables load redistribution.Consequently,the composites significantly outperform pure Mg,and lowering a leads to more substantial enhancements in compressive strength,energy dissipation,and deformation recoverability.This study offers valuable insight into the design and fabrication of highperformance Mg-based materials for structural and biomedical applications.展开更多
This study uses numerical and analytical schemes to consider the wave propagation behavior of a triply periodic minimal surface sandwich cylindrical system(TPMS-SCS)for the first time.Although these structures exhibit...This study uses numerical and analytical schemes to consider the wave propagation behavior of a triply periodic minimal surface sandwich cylindrical system(TPMS-SCS)for the first time.Although these structures exhibit outstanding physical and mechanical properties,their dynamic and acoustic features have not been reported yet.This study addresses this gap by calculating the sound transmission loss(STL)coefficient within the framework of the wave approach across various architectures,including the primitive(P),Schoen gyroid(G),and wrapped package-graph(IWP)of a TPMS lattice structure.To determine an analytical STL,a third-order approach is used to precisely capture the stress-strain distribution based on the thickness coordinate,thereby providing a simultaneous solution to the general characteristic relations along with fluid-structure coupling.Given the lack of studies for frequency and STL comparisons,the structure is modeled considering a finite element(FE)design,which is a challenging and time-consuming process because of the complex topological TPMS configurations incorporated within a sandwich cylinder.In fact,achieving convincing computational accuracy requires fine mesh discretization,which significantly increases computational costs during vibroacoustic analysis.Using the numerical results from the COMSOL software Multiphysics,the accuracy of the analytical STL spectrum is verified for different configurations,including P,G,and IWP.The effective acoustic specifications of a TPMS-SCS in the frequency domain are examined by the comparison of the STL with that of a simple cylinder of the same mass.In this context,it would also be beneficial to examine the effect of TPMS thickness,which can demonstrate the importance of the present results.The findings of this approach can be beneficial for scholars working on the numerical and analytical sound insulation characteristics of metamaterial-based cylindrical systems.展开更多
Triply periodic minimal surface(TPMS)structures,characterized by special repeating 3D surface periodically with an average curvature of zero in threedimensional directions,have a wide range of applications.Laser powde...Triply periodic minimal surface(TPMS)structures,characterized by special repeating 3D surface periodically with an average curvature of zero in threedimensional directions,have a wide range of applications.Laser powder bed fusion(LPBF)technique,as a type of additive manufacturing techniques,provides the capability to fabricate such complex-shaped porous TPMS structures.In this study,Ti6Al4V G-sheet TPMS structures with various unit cell sizes were fabricated using LPBF to investigate the structural and material anisotropy and their effects on the anisotropy in energy absorption capacity by combining the finite element simulations and experimental analysis.The results showed that the TPMS structures can be successfully fabricated using LPBF,although the sheet thickness exceeds the designed values,with deviation decreasing as the unit cell size increases from 2 to 4 mm.The inherent anisotropy during the LPBF process results in variations in structural dimension,materials characteristics,and energy absorption capacity between directions parallel and perpendicular to the build direction.The anisotropic ratio of the LPBFed Ti6Al4V G-sheet TPMS structures increases from 1.5 to 2.2 in the structural dimension and from 2.8 to 3.3 in specific energy absorption per unit mass(SEA_(m))respectively with decreasing the unit cell size from 4 to 2 mm.The anisotropy of SEA_(m) primarily originates from the coupling effects of anisotropic dimensions and material properties in the LPBFed G-sheet TPMS structure.Among these factors,anisotropic material properties play a more significant role compared to dimensional anisotropy.展开更多
Titanium alloys have a wide application in aerospace industries as it has greater strength and low density, but it has poor tribological properties. To improve its friction and wear performance, in present work, a fem...Titanium alloys have a wide application in aerospace industries as it has greater strength and low density, but it has poor tribological properties. To improve its friction and wear performance, in present work, a femtosecond laser is used to directly irradiate the Ti6Al4V titanium alloy surface in air conditioning, which results in localized ablation and the formation of periodic microstructures but also a strong pressure wave, propagating the material inside. Through the optimization of processing parameters, surface modification and periodic micropatterning with effective anti-friction properties were successfully induced on the surface. After a treatment of femtosecond laser-induced surface modification(FsLSM), the surface microhardness was improved by 16.6% and compressive residual stress reached-746 MPa. Besides, laser-induced periodic surface structures(LIPSS) with a titanium oxide outer coating were fabricated uniformly on the titanium alloy surface. Rotary ball-on-disk wear experiments revealed that the average coefficient of friction(COF) and wear mass loss of the specimen with Fs LSM treatment were largely reduced by 68.9% and 90% as compared to that of untreated specimens, respectively. It was analyzed that the reason for the remarkable wear resistance was attributed to the comprehensive action of the generation of LIPSS, the titanium oxide outer coating, high amplitude compressive residual stress and gradient grain size distribution on the subsurface during the laser surface treatment. Since the findings here are broadly applicable to a wide spectrum of engineering metals and alloys, the present results offer unique pathways to enhancing the tribological performance of materials.展开更多
Hard and brittle materials have high hardness,excellent optical stability,chemical stability,and high thermal stability.Hence,they have huge application potential in various fields,such as optical components,substrate...Hard and brittle materials have high hardness,excellent optical stability,chemical stability,and high thermal stability.Hence,they have huge application potential in various fields,such as optical components,substrate materials,and quantum information,especially under harsh conditions,such as high temperatures and high pressures.Femtosecond laser direct writing technology has greatly promoted the development of femtosecond laser-induced periodic surface structure(Fs-LIPSS or LIPSS by a femtosecond laser)applications of hard and brittle materials due to its high precision,controllability,and three-dimensional processing ability.Thus far,LIPSSs have been widely used in material surface treatment,optoelectronic devices,and micromechanics.However,a consensus has not been reached regarding the formation mechanism of LIPSSs on hard and brittle materials.In this paper,three widely accepted LIPSS formation mechanisms are introduced,and the characteristics and applications of LIPSSs on diamonds,silicon,silicon carbide,and fused silica surfaces in recent years are summarized.In addition,the application prospects and challenges of LIPSSs on hard and brittle materials by a femtosecond laser are discussed.展开更多
Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,mak...Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,making it difficult to machine functional surface structures through mechanical and chemical methods.This study investigated the fundamental characteristics of laser-induced periodic surface structures(LIPSSs)on RB-SiC via femtosecond pulsed laser irradiation at a wavelength of 1028 nm.Low-spatial-frequency LIPSS(LSFL)and high-spatial-frequency LIPSS(HSFL)formed on the surface along directions perpendicular to the laser polarization.SiC grains surrounded by a large amount of Si show a reduced threshold for LIPSS formation.By varying laser fluence and scanning speed,HSFL-LSFL hybrid structures were generated on the SiC grains.Transmission electron microscopy observations and Raman spectroscopy were carried out to understand the formation mechanism of the hybrid LIPSS.A possible mechanism based on the generation of multiple surface electromagnetic waves due to the nonlinear response of SiC was proposed to explain the hybrid structure formation.Furthermore,the direction of laser scanning with respect to laser polarization affects the uniformity of the generated LIPSS.展开更多
Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these...Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these materials.Periodic patterns of covalent functionalization can lead to pericxJic potentials in the monolayer;however,creating such superstructures is very challenging.Here,we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser.Laser-induced periodic surface structures(LIPSS)are produced on silicon wafers with thermally-grown oxide layers.The irradiation conditions for the formation of UPSS confined at the SiO2/Si interface have been unravelled.LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level.This method is clean,straightforward and scalable with high spatial resolution.展开更多
Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than t...Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than the diffraction limit,making it a useful method for efficient nanomanufacturing.However,compared with the low-spatial-frequency LIPSS(LSFL),the structure size of the HSFL is smaller,and it is more easily submerged.Therefore,the formation mechanism of HSFL is complex and has always been a research hotspot in this field.In this study,regular LSFL with a period of 760 nm was fabricated in advance on a silicon surface with two-beam interference using an 800 nm,50 fs femtosecond laser.The ultrafast dynamics of HSFL formation on the silicon surface of prefabricated LSFL under single femtosecond laser pulse irradiation were observed and analyzed for the first time using collinear pump-probe imaging method.In general,the evolution of the surface structure undergoes five sequential stages:the LSFL begins to split,becomes uniform HSFL,degenerates into an irregular LSFL,undergoes secondary splitting into a weakly uniform HSFL,and evolves into an irregular LSFL or is submerged.The results indicate that the local enhancement of the submerged nanocavity,or the nanoplasma,in the prefabricated LSFL ridge led to the splitting of the LSFL,and the thermodynamic effect drove the homogenization of the splitting LSFL,which evolved into HSFL.展开更多
High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for femtosecond laser-induced subwavelength periodic surface structures on silicon.Femtosecond laser micromach...High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for femtosecond laser-induced subwavelength periodic surface structures on silicon.Femtosecond laser micromachining is no longer a nonthermal process,as long as the repetition rate reaches up to 100 kHz due to heat accumulation.Moreover,a higher repetition rate generates much better defined ripple structures on the silicon surface,based on the fact that accumulated heat raises lattice temperature to the melting point of silicon(1687 K),with more intense surface plasmons excited simultaneously.Comparison of the surface morphology on repetition rate and on the overlapping rate confirms that repetition rate and pulse overlapping rate are two competing factors that are responsible for the period of ripple structures.Ripple period drifts longer because of a higher repetition rate due to increasing electron density;however,the period of laser structured surface is significantly reduced with the pulse overlapping rate.The Maxwell–Garnett effect is confirmed to account for the ripple period-decreasing trend with the pulse overlapping rate.展开更多
Inspired by natural porous architectures,numerous attempts have been made to generate porous structures.Owing to the smooth surfaces,highly interconnected porous architectures,and mathematical controllable geometry fe...Inspired by natural porous architectures,numerous attempts have been made to generate porous structures.Owing to the smooth surfaces,highly interconnected porous architectures,and mathematical controllable geometry features,triply periodic minimal surface(TPMS)is emerging as an outstanding solution to constructing porous structures in recent years.However,many advantages of TPMS are not fully utilized in current research.Critical problems of the process from design,manufacturing to applications need further systematic and integrated discussions.In this work,a comprehensive overview of TPMS porous structures is provided.In order to generate the digital models of TPMS,the geometry design algorithms and performance control strategies are introduced according to diverse requirements.Based on that,precise additive manufacturing methods are summarized for fabricating physical TPMS products.Furthermore,actual multidisciplinary applications are presented to clarify the advantages and further potential of TPMS porous structures.Eventually,the existing problems and further research outlooks are discussed.展开更多
The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of...The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.展开更多
Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties.In this work,a mathematical design approach for functionally graded(FG)and helicoidal l...Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties.In this work,a mathematical design approach for functionally graded(FG)and helicoidal lattice structures with triply periodic minimal surfaces is proposed.Four types of lattice structures including uniform,helicoidal,FG,and combined FG and helicoidal are fabricated by the additive manufacturing technology.The deformation behaviors,mechanical properties,energy absorption,and acoustic properties of lattice samples are thoroughly investigated.The load-bearing capability of helicoidal lattice samples is gradually improved in the plateau stage,leading to the plateau stress and total energy absorption improved by over 26.9%and 21.2%compared to the uniform sample,respectively.This phenomenon was attributed to the helicoidal design reduces the gap in unit cells and enhances fracture resistance.For acoustic properties,the design of helicoidal reduces the resonance frequency and improves the peak of absorption coefficient,while the FG design mainly influences the peak of absorption coefficient.Across broad range of frequency from 1000 to 6300 Hz,the maximum value of absorption coefficient is improved by18.6%-30%,and the number of points higher than 0.6 increased by 55.2%-61.7%by combining the FG and helicoidal designs.This study provides a novel strategy to simultaneously improve energy absorption and sound absorption properties by controlling the internal architecture of lattice structures.展开更多
文摘Inhomogeneity and low efficiency are two important factors that limit the application of laser-induced periodic surface structures(LIPSSs),especially on glass surfaces.In this study,two-beam interference(TBI)of femtosecond lasers was used to produce large-area straight LIPSSs on fused silica using cylindrical lenses.Compared with those produced us-ing a single circular or cylindrical lens,the LIPSSs produced by TBI are much straighter and more regular.Depending on the laser fluence and scanning velocity,LIPSSs with grating-like or spaced LIPSSs are produced on the fused silica sur-face.Their structural colors are blue,green,and red,and only green and red,respectively.Grating-like LIPSS patterns oriented in different directions are obtained and exhibit bright and vivid colors,indicating potential applications in surface coloring and anti-counterfeiting logos.
基金supported by MEXT Quantum Leap Flagship Program(MEXT Q-LEAP)Grant Number JPMXS0118067246.
文摘Femtosecond laser pulses with GHz burst mode that consist of a series of trains of ultrashort laser pulses with a pulse interval of several hundred picoseconds offer distinct features in material processing that cannot be obtained by the conventional irradiation scheme of femtosecond laser pulses(single-pulse mode).However,most studies using the GHz burst mode femtosecond laser pulses focus on ablation of materials to achieve high-efficiency and high-quality material removal.In this study,we explore the ability of the GHz burst mode femtosecond laser processing to form laser-induced periodic surface structures(LIPSS)on silicon.It is well known that the direction of LIPSS formed by the single-pulse mode with linearly polarized laser pulses is typically perpendicular to the laser polarization direction.In contrast,we find that the GHz burst mode femtosecond laser(wavelength:1030 nm,intra-pulse duration:220 fs,intra-pulse interval time(intra-pulse repetition rate):205 ps(4.88 GHz),burst pulse repetition rate:200 kHz)creates unique two-dimensional(2D)LIPSS.We regard the formation mechanism of 2D LIPSS as the synergetic contribution of the electromagnetic mechanism and the hydrodynamic mechanism.Specifically,generation of hot spots with highly enhanced electric fields by the localized surface plasmon resonance of subsequent pulses in the bursts within the nanogrooves of one-dimensional LIPSS formed by the preceding pulses creates 2D LIPSS.Additionally,hydrodynamic instability including convection flow determines the final structure of 2D LIPSS.
基金Deutsche Forschungsgemeinschaft (DFG), Germany (Grant number GR 1782/12)Science and Engineering Research Board (SERB), India (Grant number EMR/2015/001175)
文摘Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much simpler and cost effective.In this work,LIPSS on Si surfaces were generated using femtosecond laser pulses of 800 nm wavelength.Photocatalytic substrates were prepared by depositing TiO2 thin films on top of the structured and unstructured Si wafer.The coatings were produced by sputtering from a Ti target in two different types of oxygen atmospheres.In first case,the oxygen pressure within the sputtering chamber was chosen to be high(3×10^–2 mbar)whereas it was one order of magnitude lower in second case(2.1×10^–3 mbar).In photocatalytic dye decomposition study of Methylene blue dye it was found that in the presence of LIPSS the activity can be enhanced by 2.1 and 3.3 times with high pressure and low pressure grown TiO2 thin films,respectively.The increase in photocatalytic activity is attributed to the enlargement of effective surface area.In comparative study,the dye decomposition rates of TiO2 thin films grown on LIPSS are found to be much higher than the value for standard reference thin film material Pilkington Activ^TM.
基金National Natural Science Foundation of China (grant nos.62134009,62121005)the Innovation Grant of Changchun Institute of Optics,Fine Mechanics and Physics (CIOMP),Jilin Provincial Science and Technology Development Project (grant no:YDZJ202102CXJD002)Bill&Melinda Gates Foundation (grant no:OPP1157723)
文摘Electrochemical oxidation/reduction of radicals is a green and environmentally friendly approach to generating fuels.These reactions,however,suffer from sluggish kinetics due to a low local concentration of radicals around the electrocatalyst.A large applied electrode potential can enhance the fuel generation efficiency via enhancing the radical concentration around the electrocatalyst sites,but this comes at the cost of electricity.Here,we report about a~45%saving in energy to achieve an electrochemical hydrogen generation rate of 3×10^(16) molecules cm^(–2)s^(–1)(current density:10 mA/cm^(2))through localized electric field-induced enhancement in the reagent concentration(LEFIRC)at laser-induced periodic surface structured(LIPSS)electrodes.The finite element model is used to simulate the spatial distribution of the electric field to understand the effects of LIPSS geometric parameters in field localization.When the LIPSS patterned electrodes are used as substrates to support Pt/C and RuO_(2) electrocatalysts,the η_(10) overpotentials for HER and OER are decreased by 40.4 and 25%,respectively.Moreover,the capability of the LIPSS-patterned electrodes to operate at significantly reduced energy is also demonstrated in a range of electrolytes,including alkaline,acidic,neutral,and seawater.Importantly,when two LIPSS patterned electrodes were assembled as the anode and cathode into a cell,it requires 330 mVs of lower electric potential with enhanced stability over a similar cell made of pristine electrodes to drive a current density of 10 mA/cm^(2).This work demonstrates a physical and versatile approach of electrode surface patterning to boost electrocatalytic fuel generation performance and can be applied to any metal and semiconductor catalysts for a range of electrochemical reactions.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030009)National Natural Science Foundation of China(62175157,62375177,and 92150301)+2 种基金Shenzhen Science and Technology Program(JCYJ20210324120403011,RCJC20210609103232046)Research Team Cultivation Program of Shen Zhen University(2023QNT014)Shenzhen University 2035 Initiative(2023B004).
文摘The interactions between ultrafast lasers and materials reveal a range of nonlinear transient phenomena that are crucial in advanced manufacturing.Understanding these interactions during ultrafast laser ablation requires detailed measurements of material properties and structural changes with high temporal and spatial resolutions.Traditional spatiotemporal imaging techniques relying on reflective imaging often fail to capture comprehensive information,resulting in predominantly qualitative theoretical models of these interactions.To overcome this limitation,we propose a dual-modal ultrafast microscopy system that combines two-dimensional reflectivity and three-dimensional topography imaging.By integrating pump-probe techniques with an interferometric imaging system,impressive spatiotemporal resolutions of 236 nm and 256 fs were achieved.Furthermore,using this system,we successfully examined the dynamics of laser-induced periodic surface structure formation,strengthening,and erasure on Si surfaces.The results demonstrate that the dual-modal spatiotemporal imaging technique can serve as a robust tool for the comprehensive analysis of ablation dynamics,facilitating a deeper understanding of the fundamental physics involved and enabling more accurate optimisation of ultrafast laser fabrication processes.
基金supported by the 173 Project Technical Fund(No.2022-JCJQ-JJ-0416)the Central Government Guides Local Funds for Scientific and Technological Development(No.236Z1813G)+2 种基金the Natural Science Foundation of Hebei Province(Nos.F2024202086 and F2024202083)the Science Fund for Excellent Young Scholars of Shijiazhuang(No.241791207A)the Science and Technology Cooperation Special Project of Shijiazhuang(No.SJZZXA24007)。
文摘This study demonstrates for the first time,to the best of our knowledge,that femtosecond laser-induced periodic surface structures(LIPSSs)enhance diamond's visible-light transmittance.Using cylindrical-lens-shaped beams for highspeed scanning and secondary defocused low-energy laser treatment,uniform nanogratings with a period of 105 nm(12μm×24μm)were fabricated within 3 s.Optimized scanning speeds and pulse energies improved structural quality,achieving up to 10%transmittance enhancement at 625±750 nm.This approach offers a novel strategy for anti-reflective diamond optoelectronic devices.
基金funded by the National Natural Science Foundation of China(No.52275343)the Natural Science Foundation of Zhejiang Province(No.LY23E050003)+1 种基金Ningbo Youth Science and Technology Innovation Leading Talent Project(No.2023QL021)Smart Medicine and Engineering Interdisciplinary Innovation Project of Ningbo University(No.ZHYG001).
文摘Triply periodic minimal surface(TPMS)-based bone implants are an innovative approach in orthopedic implantology,offering customized solutions for bone defect repair and regeneration.This review comprehensively examines the current research landscape of TPMS-based bone implants,addressing key challenges and proposing future directions.It explores design strategies aimed at optimizing mechanical strength and enhancing biological integration,with a particular emphasis on TPMS structures.These design strategies include graded,hierarchical,and hybrid designs,each contributing to the overall functionality and performance of the implants.This review also highlights state-of-the-art fabrication technologies,particularly advancements in additive manufacturing(AM)techniques for creating metal-based,polymer-based,and ceramic-based bone implants.The ability to precisely control the architecture of TPMS structures using AM techniques is crucial for tailoring the mechanical and biological properties of such implants.Furthermore,this review critically evaluates the biological performance of TPMS implants,focusing on their potential to promote bone ingrowth and regeneration.Key factors,such as mechanical properties,permeability,and biocompatibility,are examined to determine the effectiveness of these implants in clinical applications.By synthesizing existing knowledge and proposing innovative research directions,this review underscores the transformative potential of TPMS-based bone implants in orthopedic surgery.The objective is to improve clinical outcomes and enhance patient care through advanced implant designs and manufacturing techniques.
基金supported bythe National Natural Science Foundation of China(Nos.U23A20523,82272504,and 82072456)the Department of Science and Technology of Jilin Province,China(Nos.20210101439JC,20210101321JC,20220204119YY,202201ZYTS131,202201ZYTS129,20230204114YY,YDZJ202201ZYTS505,and YDZJ202301ZYTS076)+4 种基金the Special Program for Science and Technology Personnel of Changchun(No.ZKICKJJ2023015)the Key Training Plan for Outstanding Youth of Jilin University(No.419070623036)the Research Fund of the First Hospital of Jilin University(No.2021-zl-01)the Graduate Innovation Fund of Jilin University(No.2024CX125)the Foun-dation of National Center for Translational Medicine(Shanghai)SHU Branch,China(No.SUITM-202405).
文摘The pore structure of porous scaffolds plays a crucial role in bone repair.The prevalent bone implant structure in clinical practice is the traditional cubic structure.However,the traditional cubic structure exhibits sharp edges and junctions that are not conducive to cell adhesion or growth.In this study,a double gyroid(DG)Ti6Al4V scaffold based on a triply periodic minimal surface(TPMS)structure was devised,and the osseointegration performance of DG structural scaffolds with varying porosities was investigated.Compression tests revealed that the elastic modulus and compressive strength of DG structural scaffolds were sufficient for orthopedic implants.In vitro cellular experiments demonstrated that the DG structure significantly enhanced cell proliferation,vascularization,and osteogenic differentiation compared to the cubic structure.The DG structure with 55%porosity exhibited the most favorable outcomes.In vivo experiments in rabbits further demonstrated that DG scaffolds could promote neovascularization and bone regeneration and maturation;those with 55%porosity performed best.Comparing the surface area,specific surface area per unit volume,and internal flow distribution characteristics of gyroid and DG structure scaffolds,the latter are more conducive to cell adhesion and growth within scaffolds.This study underscored the potential of DG scaffolds based on the TPMS structure in optimizing the pore structure design of titanium scaffolds,inducing angiogenesis,and advancing the clinical application of titanium scaffolds for repairing bone defects.
基金supported by the Mainland-Hong Kong Joint Funding Scheme(MHKJFS)(Project No:MHP/040/22)RGC Theme-based Research Scheme AoE/M-402/20+1 种基金National Natural Science Foundation of China/Hong Kong Research Grants Council Joint Research Scheme(Project No:N_CityU151/23)Hong Kong Innovation and Technology Commission via the Hong Kong Branch of National Precious Metals Materials Engineering Research Center.
文摘Magnesium(Mg)-based materials are promising for lightweight structural applications.However,their widespread adoption is significantly constrained by inherent limitations in mechanical properties.To address this challenge,this study introduces a novel Mg-based interpenetratingphase composite reinforced with a nickel-titanium(NiTi)scaffold featuring a triply periodic minimal surface(TPMS)configuration.By combining experimental investigations with finite element simulations,we systematically elucidate the dual impact of the scaffold’s unit cell size(a)on manufacturing viability and mechanical enhancement.To compensate for compromised infiltration dynamics induced by decreasing a,a critical permeability threshold of 1×10^(-8) m^(2) is proposed for achieving successful composite fabrication.Mechanically,reducing a strengthens the interaction between the scaffold and matrix:the TPMS-configured NiTi scaffolds improve stress transfer,deflect crack propagation,and facilitate damage delocalization,whereas the Mg matrix preserves structural integrity and enables load redistribution.Consequently,the composites significantly outperform pure Mg,and lowering a leads to more substantial enhancements in compressive strength,energy dissipation,and deformation recoverability.This study offers valuable insight into the design and fabrication of highperformance Mg-based materials for structural and biomedical applications.
文摘This study uses numerical and analytical schemes to consider the wave propagation behavior of a triply periodic minimal surface sandwich cylindrical system(TPMS-SCS)for the first time.Although these structures exhibit outstanding physical and mechanical properties,their dynamic and acoustic features have not been reported yet.This study addresses this gap by calculating the sound transmission loss(STL)coefficient within the framework of the wave approach across various architectures,including the primitive(P),Schoen gyroid(G),and wrapped package-graph(IWP)of a TPMS lattice structure.To determine an analytical STL,a third-order approach is used to precisely capture the stress-strain distribution based on the thickness coordinate,thereby providing a simultaneous solution to the general characteristic relations along with fluid-structure coupling.Given the lack of studies for frequency and STL comparisons,the structure is modeled considering a finite element(FE)design,which is a challenging and time-consuming process because of the complex topological TPMS configurations incorporated within a sandwich cylinder.In fact,achieving convincing computational accuracy requires fine mesh discretization,which significantly increases computational costs during vibroacoustic analysis.Using the numerical results from the COMSOL software Multiphysics,the accuracy of the analytical STL spectrum is verified for different configurations,including P,G,and IWP.The effective acoustic specifications of a TPMS-SCS in the frequency domain are examined by the comparison of the STL with that of a simple cylinder of the same mass.In this context,it would also be beneficial to examine the effect of TPMS thickness,which can demonstrate the importance of the present results.The findings of this approach can be beneficial for scholars working on the numerical and analytical sound insulation characteristics of metamaterial-based cylindrical systems.
基金financially supported by the Open Project Program of Chinese Scholar Tree Ridge State Key Laboratory(No.AF20240023)
文摘Triply periodic minimal surface(TPMS)structures,characterized by special repeating 3D surface periodically with an average curvature of zero in threedimensional directions,have a wide range of applications.Laser powder bed fusion(LPBF)technique,as a type of additive manufacturing techniques,provides the capability to fabricate such complex-shaped porous TPMS structures.In this study,Ti6Al4V G-sheet TPMS structures with various unit cell sizes were fabricated using LPBF to investigate the structural and material anisotropy and their effects on the anisotropy in energy absorption capacity by combining the finite element simulations and experimental analysis.The results showed that the TPMS structures can be successfully fabricated using LPBF,although the sheet thickness exceeds the designed values,with deviation decreasing as the unit cell size increases from 2 to 4 mm.The inherent anisotropy during the LPBF process results in variations in structural dimension,materials characteristics,and energy absorption capacity between directions parallel and perpendicular to the build direction.The anisotropic ratio of the LPBFed Ti6Al4V G-sheet TPMS structures increases from 1.5 to 2.2 in the structural dimension and from 2.8 to 3.3 in specific energy absorption per unit mass(SEA_(m))respectively with decreasing the unit cell size from 4 to 2 mm.The anisotropy of SEA_(m) primarily originates from the coupling effects of anisotropic dimensions and material properties in the LPBFed G-sheet TPMS structure.Among these factors,anisotropic material properties play a more significant role compared to dimensional anisotropy.
基金co-supported by the Key-Area Research and Development Program of Guangdong Province(No.2018B090906002)the National Natural Science Foundation of China(No.51875574)the National Science and Technology Major Project of China(No.2017-Ⅶ-0003-0096-1)。
文摘Titanium alloys have a wide application in aerospace industries as it has greater strength and low density, but it has poor tribological properties. To improve its friction and wear performance, in present work, a femtosecond laser is used to directly irradiate the Ti6Al4V titanium alloy surface in air conditioning, which results in localized ablation and the formation of periodic microstructures but also a strong pressure wave, propagating the material inside. Through the optimization of processing parameters, surface modification and periodic micropatterning with effective anti-friction properties were successfully induced on the surface. After a treatment of femtosecond laser-induced surface modification(FsLSM), the surface microhardness was improved by 16.6% and compressive residual stress reached-746 MPa. Besides, laser-induced periodic surface structures(LIPSS) with a titanium oxide outer coating were fabricated uniformly on the titanium alloy surface. Rotary ball-on-disk wear experiments revealed that the average coefficient of friction(COF) and wear mass loss of the specimen with Fs LSM treatment were largely reduced by 68.9% and 90% as compared to that of untreated specimens, respectively. It was analyzed that the reason for the remarkable wear resistance was attributed to the comprehensive action of the generation of LIPSS, the titanium oxide outer coating, high amplitude compressive residual stress and gradient grain size distribution on the subsurface during the laser surface treatment. Since the findings here are broadly applicable to a wide spectrum of engineering metals and alloys, the present results offer unique pathways to enhancing the tribological performance of materials.
基金This work was supported by the National Natural Science Foundation of China(Grant No.62004059)the Natural Science Research Foundation of Hebei University of Technology(Grant No.BKYXX2203)+2 种基金the Natural Science Foundation of Hebei Province(Grant Nos.F2021202047 and F2021202002)the Funding Projects for the Introduction of Overseas Staff of Hebei Province(Grant No.C20210334)the Key Laboratory Fund Project(Grant No.2021JCJQLB055004).
文摘Hard and brittle materials have high hardness,excellent optical stability,chemical stability,and high thermal stability.Hence,they have huge application potential in various fields,such as optical components,substrate materials,and quantum information,especially under harsh conditions,such as high temperatures and high pressures.Femtosecond laser direct writing technology has greatly promoted the development of femtosecond laser-induced periodic surface structure(Fs-LIPSS or LIPSS by a femtosecond laser)applications of hard and brittle materials due to its high precision,controllability,and three-dimensional processing ability.Thus far,LIPSSs have been widely used in material surface treatment,optoelectronic devices,and micromechanics.However,a consensus has not been reached regarding the formation mechanism of LIPSSs on hard and brittle materials.In this paper,three widely accepted LIPSS formation mechanisms are introduced,and the characteristics and applications of LIPSSs on diamonds,silicon,silicon carbide,and fused silica surfaces in recent years are summarized.In addition,the application prospects and challenges of LIPSSs on hard and brittle materials by a femtosecond laser are discussed.
文摘Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,making it difficult to machine functional surface structures through mechanical and chemical methods.This study investigated the fundamental characteristics of laser-induced periodic surface structures(LIPSSs)on RB-SiC via femtosecond pulsed laser irradiation at a wavelength of 1028 nm.Low-spatial-frequency LIPSS(LSFL)and high-spatial-frequency LIPSS(HSFL)formed on the surface along directions perpendicular to the laser polarization.SiC grains surrounded by a large amount of Si show a reduced threshold for LIPSS formation.By varying laser fluence and scanning speed,HSFL-LSFL hybrid structures were generated on the SiC grains.Transmission electron microscopy observations and Raman spectroscopy were carried out to understand the formation mechanism of the hybrid LIPSS.A possible mechanism based on the generation of multiple surface electromagnetic waves due to the nonlinear response of SiC was proposed to explain the hybrid structure formation.Furthermore,the direction of laser scanning with respect to laser polarization affects the uniformity of the generated LIPSS.
基金The work was supported by project No.18-09055Y and 20-08633X awarded by Czech Science FoundationThe research of I.M.,J.S.,T.J.-Y.D.,and N.M.B.is financed by the European Regional Development Fund and the state budget of the Czech Republic(project BIATRI,No.CZ.02.1.01/0.0/0.0/15_003/0000445,project HiLASE CoE,No.CZ.02.1.01/0.0/0.0/15_006/0000674,programme NPU I,project No.LO1602)+3 种基金The work was further supported by European Regional Development Fund,OP RDE,Project:“Carbon allotropes with rationalized nanointerfaces and nanolinks for environmental and biomedical applications”(No.CZ.02.1.01/0.0/0.0/16_026/0008382)The authors also acknowledge the assistance provided by the Research Infrastructures NanoEnviCz(No.LM2015073)supported by the Ministry of EducationYouth and Sports of the Czech Republic and the project Pro-NanoEnviCz(No.CZ.02.1.01/0.0/0.0/16_013/0001821)supported by the Ministry of EducationYouth and Sports of the Czech Republic and the European Union-European Structural and Investments Funds in the frame of Operational Programme Research Development and Education.
文摘Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these materials.Periodic patterns of covalent functionalization can lead to pericxJic potentials in the monolayer;however,creating such superstructures is very challenging.Here,we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser.Laser-induced periodic surface structures(LIPSS)are produced on silicon wafers with thermally-grown oxide layers.The irradiation conditions for the formation of UPSS confined at the SiO2/Si interface have been unravelled.LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level.This method is clean,straightforward and scalable with high spatial resolution.
基金supports from the National Natural Science Foundation of China(12074123,12174108)the Foundation of‘Manufacturing beyond limits’of Shanghai‘Talent Program'of Henan Academy of Sciences.
文摘Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than the diffraction limit,making it a useful method for efficient nanomanufacturing.However,compared with the low-spatial-frequency LIPSS(LSFL),the structure size of the HSFL is smaller,and it is more easily submerged.Therefore,the formation mechanism of HSFL is complex and has always been a research hotspot in this field.In this study,regular LSFL with a period of 760 nm was fabricated in advance on a silicon surface with two-beam interference using an 800 nm,50 fs femtosecond laser.The ultrafast dynamics of HSFL formation on the silicon surface of prefabricated LSFL under single femtosecond laser pulse irradiation were observed and analyzed for the first time using collinear pump-probe imaging method.In general,the evolution of the surface structure undergoes five sequential stages:the LSFL begins to split,becomes uniform HSFL,degenerates into an irregular LSFL,undergoes secondary splitting into a weakly uniform HSFL,and evolves into an irregular LSFL or is submerged.The results indicate that the local enhancement of the submerged nanocavity,or the nanoplasma,in the prefabricated LSFL ridge led to the splitting of the LSFL,and the thermodynamic effect drove the homogenization of the splitting LSFL,which evolved into HSFL.
基金supported by the National Natural Science Foundation of China(Nos.52175377 and 12174411)。
文摘High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for femtosecond laser-induced subwavelength periodic surface structures on silicon.Femtosecond laser micromachining is no longer a nonthermal process,as long as the repetition rate reaches up to 100 kHz due to heat accumulation.Moreover,a higher repetition rate generates much better defined ripple structures on the silicon surface,based on the fact that accumulated heat raises lattice temperature to the melting point of silicon(1687 K),with more intense surface plasmons excited simultaneously.Comparison of the surface morphology on repetition rate and on the overlapping rate confirms that repetition rate and pulse overlapping rate are two competing factors that are responsible for the period of ripple structures.Ripple period drifts longer because of a higher repetition rate due to increasing electron density;however,the period of laser structured surface is significantly reduced with the pulse overlapping rate.The Maxwell–Garnett effect is confirmed to account for the ripple period-decreasing trend with the pulse overlapping rate.
基金financially supported by National Key R&D Program of China(No.2020YFC1107103)Key Research and Development Program of Zhejiang Province(No.2021C01107)+1 种基金China Postdoctoral Science Foundation(No.2020M681846)Science Fund for Creative Research Groups of National Natural Science Foundation of China(No.51821093).
文摘Inspired by natural porous architectures,numerous attempts have been made to generate porous structures.Owing to the smooth surfaces,highly interconnected porous architectures,and mathematical controllable geometry features,triply periodic minimal surface(TPMS)is emerging as an outstanding solution to constructing porous structures in recent years.However,many advantages of TPMS are not fully utilized in current research.Critical problems of the process from design,manufacturing to applications need further systematic and integrated discussions.In this work,a comprehensive overview of TPMS porous structures is provided.In order to generate the digital models of TPMS,the geometry design algorithms and performance control strategies are introduced according to diverse requirements.Based on that,precise additive manufacturing methods are summarized for fabricating physical TPMS products.Furthermore,actual multidisciplinary applications are presented to clarify the advantages and further potential of TPMS porous structures.Eventually,the existing problems and further research outlooks are discussed.
基金support from the National Natural Science Foundation of China(NSFC,Project Nos.91860136 and 51801231)the Key R&D Plan of Guangdong Province(Grant No.2018B090905001)the Key Science and Technology project of Shaanxi Province(Grant No.2018zdzx01-04-01).
文摘The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.
基金supported by the NUS R&G Postdoc Fellowship Program (No.A-0000065-76-00)the China Scholarship Council (No.202006050088)。
文摘Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties.In this work,a mathematical design approach for functionally graded(FG)and helicoidal lattice structures with triply periodic minimal surfaces is proposed.Four types of lattice structures including uniform,helicoidal,FG,and combined FG and helicoidal are fabricated by the additive manufacturing technology.The deformation behaviors,mechanical properties,energy absorption,and acoustic properties of lattice samples are thoroughly investigated.The load-bearing capability of helicoidal lattice samples is gradually improved in the plateau stage,leading to the plateau stress and total energy absorption improved by over 26.9%and 21.2%compared to the uniform sample,respectively.This phenomenon was attributed to the helicoidal design reduces the gap in unit cells and enhances fracture resistance.For acoustic properties,the design of helicoidal reduces the resonance frequency and improves the peak of absorption coefficient,while the FG design mainly influences the peak of absorption coefficient.Across broad range of frequency from 1000 to 6300 Hz,the maximum value of absorption coefficient is improved by18.6%-30%,and the number of points higher than 0.6 increased by 55.2%-61.7%by combining the FG and helicoidal designs.This study provides a novel strategy to simultaneously improve energy absorption and sound absorption properties by controlling the internal architecture of lattice structures.
