Diamond is a wide-bandgap semiconductor with a variety of crystal configurations,and has the potential applications in the field of high-frequency,radiation-hardened,and high-power devices.There are several important ...Diamond is a wide-bandgap semiconductor with a variety of crystal configurations,and has the potential applications in the field of high-frequency,radiation-hardened,and high-power devices.There are several important polytypes of diamonds,such as cubic diamond,lonsdaleite,and nanotwinned diamond(NTD).The thermal conductivities of semiconductors in high-power devices at different temperatures should be calculated.However,there has been no reports about thermal conductivities of cubic diamond and its polytypes both efficiently and accurately based on molecular dynamics(MD).Here,using interatomic potential of neural networks can provide obvious advantages.For example,comparing with the use of density functional theory(DFT),the calculation time is reduced,while maintaining high accuracy in predicting the thermal conductivities of the above-mentioned three diamond polytypes.Based on the neuroevolution potential(NEP),the thermal conductivities of cubic diamond,lonsdaleite,and NTD at 300 K are respectively 2507.3 W·m^(-1)·K^(-1),1557.2 W·m^(-1)·K^(-1),and 985.6 W·m^(-1)·K^(-1),which are higher than the calculation results based on Tersoff-1989 potential(1508 W·m^(-1)·K^(-1),1178 W·m^(-1)·K^(-1),and 794 W·m^(-1)·K^(-1),respectively).The thermal conductivities of cubic diamond and lonsdaleite,obtained by using the NEP,are closer to the experimental data or DFT data than those from Tersoff-potential.The molecular dynamics simulations are performed by using NEP to calculate the phonon dispersions,in order to explain the possible reasons for discrepancies among the cubic diamond,lonsdaleite,and NTD.In this work,we propose a scheme to predict the thermal conductivity of cubic diamond,lonsdaleite,and NTD precisely and efficiently,and explain the differences in thermal conductivity among cubic diamond,lonsdaleite,and NTD.展开更多
SnSe has attracted extensive attention due to its ultralow thermal conductivity and excellent thermoelectric properties.In this work,pressure-induced thermoelectric properties of Pnma SnSe are investigated via first-p...SnSe has attracted extensive attention due to its ultralow thermal conductivity and excellent thermoelectric properties.In this work,pressure-induced thermoelectric properties of Pnma SnSe are investigated via first-principles calculations.We uncover distinct energy isosurfaces topology transition of conduction band by applying pressure.The newly created conduction band valley caused by pressure has a distinct anisotropic shape compared to the old one.Inducing pressure can greatly enhance the anisotropy of electronic transport properties of the n-type Pnma SnSe.Furthermore,the lattice thermal conductivity also exhibits anisotropic behavior under pressure due to a special collaged phonon mode.The pressure-induced lattice thermal conductivity along the a-axis shows a slower growth trend than that along the b-axis and c-axis.The optimal ZT value of the n-type Pnma SnSe along the a-axis can reach 1.64 at room temperature.These results would be helpful for designing the Pnma SnSe-based materials for the potential thermoelectric and valleytronic applications.展开更多
Dielectric laser accelerators(DLAs)are considered promising candidates for on-chip particle accelerators that can achieve high acceleration gradients.This study explores various combinations of dielectric materials an...Dielectric laser accelerators(DLAs)are considered promising candidates for on-chip particle accelerators that can achieve high acceleration gradients.This study explores various combinations of dielectric materials and accelerated structures based on the inverse Cherenkov effect.The designs utilize conventional processing methods and laser parameters currently in use.We optimize the structural model to enhance the gradient of acceleration and the electron energy gain.To achieve higher acceleration gradients and energy gains,the selection of materials and structures should be based on the initial electron energy.Furthermore,we observed that the variation of the acceleration gradient of the material is different at different initial electron energies.These findings suggest that on-chip accelerators are feasible with the help of these structures and materials.展开更多
Non-noble metal electrocatalysis has witnessed rapid and profound performance improvements owing to the emergence of advanced nanosynthetic techniques.Integration of these nanotechniques can lead to synergistic perfor...Non-noble metal electrocatalysis has witnessed rapid and profound performance improvements owing to the emergence of advanced nanosynthetic techniques.Integration of these nanotechniques can lead to synergistic performance enhancement,but such system-engineering strategies are difficult to achieve because of the lack of effective synthesis method.We hereby demonstrate an integrated approach that combines most of the existing nanotechniques in a facile one-pot synthesis.Material characterization reveals that the product shows key features intended by techniques including morphological,structural,doping,heterointerface,and surface wetting engineering.The as-obtained nitrogen-doped hierarchical heterostructured MoS_(x)/Ni_(3)S_(2)nanowires show an overpotential that is only50 mV higher than commercial Pt/C for hydrogen evolution reaction over current densities from 10 to 150 mA cm^(-2).Correlations between the adopted nanotechniques and the electrochemical reaction rates are established by evaluating the impacts of individual techniques on the activation energy,pre-exponential factor,and transfer coefficient.This indepth analysis provides a full account of the synergistic effects and the overall improvement in electrocatalytic performance of hydrogen evolution reaction.This work manifests a generic strategy for multipurpose material design in non-noble metal electrocatalysis.展开更多
The use of mechanical drilling in accessing energy resources stored in deep and hard rock formations is becoming increasingly challenging.Thus,laser irradiation has emerged as a novel drilling method with considerable...The use of mechanical drilling in accessing energy resources stored in deep and hard rock formations is becoming increasingly challenging.Thus,laser irradiation has emerged as a novel drilling method with considerable in this context.This study examines the variation of rock fracture length,fracture tortuosity,hole size,and rock breaking efficiency for a different number of holes and laser power,based on the constant total energy of laser irradiation.As indicated by the results,increasing the laser power increases the laser intensity,which helps increase the hole diameter and depth.Moreover,for the same laser power,increasing the number of irradiated holes reduces the laser energy absorbed by each hole,which is not conducive to increasing the hole depth.As the number of holes increases,the mass loss of the rock also increases,while both specific energy(SE)and modified specific energy(MSE)decrease.When the number of holes remains the same,the mass of the shale removed by low power is less than that removed by high power,while SE and MSE have an inverse relation with power.Therefore,high laser power and multiple-hole irradiation are more conducive to rock breaking.Besides,the fracture length and fracture tortuosity of the rock irradiated by the low laser power will increase first and then decrease with the increase in the number of holes,and reach the peak value when the irradiation takes place through three holes.When a high-power laser irradiates the rock,the fracture length and tortuosity will increase with the increase in the number of irradiation holes.This is because a rock irradiated by low power dissipates more energy,with the result that the energy absorbed by the sample with four irradiation holes is not enough to break the rock quickly.This study is expected to provide some guidance to break rock for drilling deep reservoirs and hard rock formations using laser irradiation.展开更多
A numerical model is presented in this article to investigate the interactions between laser generated ultrasonic and the microdefects(0.01 to 0.1 mm),which are on the surface of the laser powder bed fusion additive m...A numerical model is presented in this article to investigate the interactions between laser generated ultrasonic and the microdefects(0.01 to 0.1 mm),which are on the surface of the laser powder bed fusion additive manufactured 316L stainless steel.Firstly,the influence of the transient sound field and detection positions on Rayleigh wave signals are investigated.The interactions between the varied microdefects and the laser ultrasonic are studied.It is shown that arrival time of reflected Rayleigh(RR)waves wave is only related to the location of defects.The depth can be checked from the feature point Q,the displacement amplitude and time delay of converted transverse(RS)wave,while the width information can be evaluated from the RS wave time delay.With the aid of fitting curves,it is found to be linearly related.This simulation study provides a theoretical basis for quantitative detection of surface microdefects of additive manufactured 316L stainless steel components.展开更多
The mechanisms for oxygen reduction reaction(ORR)on the naturally exposed(110)and(111)surfaces of Co_(3)O_(4)have been investigated with density functional theory(DFT)calculations.Depending on the vertical cutting pla...The mechanisms for oxygen reduction reaction(ORR)on the naturally exposed(110)and(111)surfaces of Co_(3)O_(4)have been investigated with density functional theory(DFT)calculations.Depending on the vertical cutting place,there are type A and B surfaces for each of the(110)and(111)surfaces of Co_(3)O_(4).Our DFT calculations reveal that the Co_(3)O_(4)(110)type B and(111)type B surfaces have ORR catalytic activities.In addition,the ORR activity on the(110)type B surface is better than the(111)type B surface.The ratedetermining step on both surfaces is thermodynamically depending on the^(*)OH desorption process.If the solvation effects are taken into accounts,the chemically adsorbed water molecules enhance the ORR activity.According to the barrier heights calculations,O_(2)→^(*)O_(2)→^(*)OOH→^(*)O+H_(2)O→^(*)OH→H_(2)O route is the most favorable ORR pathway.展开更多
1. Introduction The Lithium-sulfur battery(LSB) shows promise as a highdensity energy source, with a theoretical energy density of approximately 2600 W h kg^(-1)[1]. However, practical application of the LSB has been ...1. Introduction The Lithium-sulfur battery(LSB) shows promise as a highdensity energy source, with a theoretical energy density of approximately 2600 W h kg^(-1)[1]. However, practical application of the LSB has been hindered by the “shuttle effect” and Li anode corrosion [2,3]. Highly concentrated electrolytes(HCEs) have been proposed as a solution, as they can inhibit the dissolution of lithium polysulfide and promote homogeneous lithium deposition [4].展开更多
We present a first on-chip positron accelerator based on dielectric laser acceleration.This innovative approach significantly reduces the physical dimensions of the positron acceleration apparatus,enhancing its feasib...We present a first on-chip positron accelerator based on dielectric laser acceleration.This innovative approach significantly reduces the physical dimensions of the positron acceleration apparatus,enhancing its feasibility for diverse applications.By utilizing a stacked acceleration structure and far-infrared laser technology,we are able to achieve a seven-stage acceleration structure that surpasses the distance and energy gain of using the previous dielectric laser acceleration methods.Additionally,we are able to compress the positron beam to an ultrafast sub-femtosecond scale during the acceleration process,compared with the traditional methods,the positron beam is compressed to a greater extent.We also demonstrate the robustness of the stacked acceleration structure through the successful acceleration of the positron beam.展开更多
Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits,but also the weak spots in reliability tests.Most of failures in power devices are caused ...Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits,but also the weak spots in reliability tests.Most of failures in power devices are caused by the malfunction of interconnections,including failure of bonding wire as well as cracks of solder layer.In fact,the interconnection failure of power devices is the result of a combination of factors such as electricity,temperature,and force.It is significant to investigate the failure mechanisms of various factors for the failure analysis of interconnections in power devices.This paper reviews the main failure modes of bonding wire and solder layer in the interconnection structure of power devices,and its failure mechanism.Then the reliability test method and failure analysis techniques of interconnection in power device are introduced.These methods are of great significance to the reliability analysis and life prediction of power devices.展开更多
Currently,wire bonding is the most popular first-level interconnection technology used between the die and package terminals,but even with its long-term and excessive usage,the mechanism of wire bonding has not been c...Currently,wire bonding is the most popular first-level interconnection technology used between the die and package terminals,but even with its long-term and excessive usage,the mechanism of wire bonding has not been completely evaluated.Therefore,fundamental research is still needed.In this study,the mechanism of microweld formation and breakage during Cu-Cu wire bonding was investigated by using molecular dynamics simulation.The contact model for the nanoindentation process between the wire and substrate was developed to simulate the contact process of the Cu wire and Cu substrate.Elastic contact and plastic instability were investigated through the loading and unloading processes.Moreover,the evolution of the indentation morphology and distributions of the atomic stress were also investigated.It was shown that the loading and unloading curves do not coincide,and the unloading curve exhibited hysteresis.For the substrate,in the loading process,the main force changed from attractive to repulsive.The maximum von Mises stress increased and shifted from the center toward the edge of the contact area.During the unloading process,the main force changed from repulsive to attractive.The Mises stress reduced first and then increased.Stress concentration occurs around dislocations in the middle area of the Cu wire.展开更多
The porous structure in pomelo peel is believed to be responsible for the protection of its fruit from damage during the free falling from a tree.The quantitative understanding of the relationship between the deformat...The porous structure in pomelo peel is believed to be responsible for the protection of its fruit from damage during the free falling from a tree.The quantitative understanding of the relationship between the deformation behavior and the porous structure could pave the way for the design of porous structures for efficient energy absorption.Here,a universal feature of pore distribution in pomelo peels along the radial direction is extracted from three varieties of pomelos,which shows strong correlation to the deformation behavior of the peels under compression.Guided by the porous design found in pomelo peels,porous polyether-ether-ketone(PEEK)cube is additively manufactured and possesses the highest ability to absorb energy during compression as compared to the non-pomelo-inspired geometries,which is further confirmed by the finite element simulation.The nature-optimized porous structure revealed here could guide the design of lightweight and high-energy-dissipating materials/devices.展开更多
Batteries are the most widely used energy storage devices, and the lithiumion battery is the most heavily commercialized and most widely used battery type in the industry. However, the current rapid development of soc...Batteries are the most widely used energy storage devices, and the lithiumion battery is the most heavily commercialized and most widely used battery type in the industry. However, the current rapid development of society requires a major advancement in battery materials to achieve high capacity,long life cycle, low cost, and reliable safety. Therefore, many new efficient energy storage materials and battery systems are being developed and explored, and their working mechanisms must be clearly understood before industrial application. In recent years, density functional theory (DFT) has been employed in the energy storage field and has made significant contributions to the understanding of electrochemical reaction mechanisms and to virtual screening of promising energy storage materials. In this review,the applications of DFT to battery materials are summarized and exemplified by some representative and up-to-date studies in the literature. The main focuses in this review include the following:1) structural stability estimation by cohesive energy, formation energy, Gibbs free energy, and phonon dispersion spectra calculations;2) the Gibbs free energy calculations for electrochemical reactions, corresponding open-circuit voltage, and theoretical capacity predictions of batteries;3) the analyses of molecule orbitals, band structures, density of states (DOS), and charge distribution of battery materials;4) ion transport kinetics in battery materials;5) simulations of adsorption processes. We conclude the review with the discussion of the assessments and validation of the popular functionals against several benchmarks, and a few suggestions have been given for the selection of density functionals for battery material systems.展开更多
High entropy alloys(HEAs)with multi-component solid solution microstructures have the potential for large-scale industrial applications due to their excellent mechanical and functional properties.However,the mechanica...High entropy alloys(HEAs)with multi-component solid solution microstructures have the potential for large-scale industrial applications due to their excellent mechanical and functional properties.However,the mechanical properties of HEAs limit the selection of processing technologies.Additive manufacturing technology possesses strong processing adaptability,making itthe best candidate method to overcome this issue.This comprehensive review examines the current state of selective laser melting(SLM)of HEAs.Introducing SLM to HEAs processing is motivated by its high quality for dimensional accuracy,geometric complexity,surface roughness,and microstructure.This review focuses on analyzing the current developments and challenges in SLM of HEAs,including defects,microstructures,and properties,as well as strengthing prediction models of fabricated HEAs.This review also offers directions for future studies to address existing challenges and promote technological advancement.展开更多
Hybrid supercapacitors have shown great potentials to fulfill the demand of future diverse applications such as electric vehicles and portable/wearable electronics.In particular,aqueous zinc-ion hybrid supercapacitors...Hybrid supercapacitors have shown great potentials to fulfill the demand of future diverse applications such as electric vehicles and portable/wearable electronics.In particular,aqueous zinc-ion hybrid supercapacitors(ZHSCs)have gained much attention due to their low-cost,high energy density,and environmental friendliness.Nevertheless,typical ZHSCs use Zn metal anode and normal liquid electrolyte,causing the dendrite issue,restricted working temperature,and inferior device flexibility.Herein,a novel flexible Zn-ion hybrid supercapacitor(FZHSC)is developed by using activated carbon(AC)anode,δ-MnO_(2) cathode,and innovative PVA-based gel electrolyte.In this design,heavy Zn anode and its dendrite issue are avoided and layered cathode with large interlayer spacing is employed.In addition,flexible electrodes are prepared and integrated with an anti-freezing,stretchable,and compressible hydrogel electrolyte,which is attained by simultaneously using glycerol additive and freezing/thawing technique to regulate the hydrogen bond and microstructure.The resulting FZHSC exhibits good rate capability,high energy density(47.86 Wh kg^(−1);3.94 mWh cm^(−3)),high power density(5.81 kW kg^(−1);480 mW cm^(−3)),and excellent cycling stability(~91%capacity retention after 30000 cycles).Furthermore,our FZHSC demonstrates outstanding flexibility with capacitance almost unchanged even after various continuous shape deformations.The hydrogel electrolyte still maintains high ionic conductivity at ultralow temperatures(≤−30℃),enabling the FZHSC cycled well,and powering electronic timer robustly within an all-climate temperature range of−30~80℃.This work highlights that the promising Zn metal-free aqueous ZHSCs can be designed with great multifunctionality for more practical application scenarios.展开更多
Miniaturized sound generators are attractive to realize intriguing functions.Thermoacoustic device’s application is seriously limited due to the frequency-doubling phenomenon.To address this issue,photoacoustic sound...Miniaturized sound generators are attractive to realize intriguing functions.Thermoacoustic device’s application is seriously limited due to the frequency-doubling phenomenon.To address this issue,photoacoustic sound generator is considered as a promising alternative.Here,based on vertical single-wall carbon nanotubes(CNTs)array,we introduce a photoacoustic sound generator with internal nano-Helmholtz cavity.Different from traditional device that generates sound by periodically heating up the open space air around material,this sound generator produces an audio signal by forming a forced vibration of the air inside the CNTs.Interestingly,anomalous photoacoustic behavior is observed that the sound pressure level(SPL)curve has a resonance peak,the corresponding frequency of which is inversely proportional to the CNTs array’s height.Furthermore,the energy conversion efficiency of this photoacoustic device is 1.64 times as large as that of a graphene sponge-based photoacoustic device.Most importantly,this device can be employed for music playing,bringing a new clew for the development of musical instruments in the future.展开更多
Two-dimensional transition metal chalcogenides(2D-TMDs)have attracted much attention because of their unique layered structure and physical properties for transistor applications.Mechanically transferred metal contact...Two-dimensional transition metal chalcogenides(2D-TMDs)have attracted much attention because of their unique layered structure and physical properties for transistor applications.Mechanically transferred metal contacts on these low-dimensional materials or their homogeneous and heterogeneous multilayers have generated huge interest to avoid deposition damages.In this paper,we show that there are large physical gaps at both the edge contact and surface contact between the transferred electrodes and the 2D materials.A method called laser shock induced superplastic deformation(LSISD)is proposed to tackle this issue and enhance the performance of the transistors.The enhancement mechanism was investigated by molecular dynamics(MD)simulations of the nanoforming process,atomic force microscopy(AFM),scanning electron microscopy(SEM),transmission electron microscopy(TEM)characterizations of the interfaces,and density functional theory(DFT)modeling.The force effect of laser shock can reduce the contact gap between metals and semiconductors.The electrical performances of the transistors before and after LSISD,along with MD simulations,are used to find the optimal process parameters.In addition,this paper applies the LSISD method to the short-channel MoS_(2)/graphene vertical transistors to show potential improvement in interface contact and electrical properties.This paper demonstrates the first report on using mechanical force induced by laser shock to enhance metal–semiconductor interfaces and transistor performances.展开更多
The development of perovskite photoelectric devices with excellent performance is largely dependent on the defects in the perovskite films.To address this issue,a specific drug,leflunomide(LF,C_(12)H_(9)F_(3)N_(2)O_(2...The development of perovskite photoelectric devices with excellent performance is largely dependent on the defects in the perovskite films.To address this issue,a specific drug,leflunomide(LF,C_(12)H_(9)F_(3)N_(2)O_(2)),was incorporated into the perovskite to reduce defects and improve its photoelectric properties.It is believed that the C=O bond on LF molecule can interact with the uncoordinated Pb2+of the perovskite,thereby reducing non-radiative recombination.This novel approach of incorporating LF into perovskite films has the potential to revolutionize the development of high-performance perovskite photoelectric devices.The trifluoromethyl functional(–CF_(3))group on LF can form a protective layer on the surface of the perovskite film,shielding it from water erosion.Moreover,LF can be utilized to alter the nucleation position of perovskite,thus minimizing the number of defects and optimizing the film quality.Consequently,the LF-doped perovskite film displays low trap density and high photoelectric performance.The LF-doped perovskite film showed a trap density of 8.28×10^(11),which is notably lower than the 2.04×10^(12) of the perovskite film without LF.The responsivity and detectivity of the LF-doped perovskite photodetector were 0.771 A/W and 2.81×10^(11) Jones,respectively,which are much higher than the 0.23 A/W and 1.06×10^(10) Jones of the LF-undoped perovskite photodetector.Meanwhile,the LF-doped photodetector maintained an initial photocurrent of 86%after 30 days of storage in air,indicating drastically increased environmental stability.This strongly suggests that LF is an effective additive for perovskites utilized in optoelectronic devices with high performance.展开更多
Nitrogen(N_(2))fixation at ambient condition by electrochemical N_(2)reduction reaction(NRR)is energy-efficient and eco-friendly as compared to the traditional Harber–Bosch process,but it is extremely challenging.Dev...Nitrogen(N_(2))fixation at ambient condition by electrochemical N_(2)reduction reaction(NRR)is energy-efficient and eco-friendly as compared to the traditional Harber–Bosch process,but it is extremely challenging.Development and design of high-performance NRR electrocatalysts are indispensable to achieve the goal.In this work,a strongly coupled hybrid of nano-Fe3O4 with reduced graphene oxide(rGO)is synthesized via an in situ redox hydrothermal approach,and the synthesized Fe_(3)O_(4)@r GO hybrid has excellent activity,selectivity,and stability as an NRR catalyst.The NH_(3) yield rate of 28.01μg h^(-1)mg^(-1)at-0.3 V and the Faradaic efficiency(FE)of 19.12%at-0.1 V are obtained in 0.1 M Na_(2)SO_(4) solutions at ambient conditions.The superior NRR performance is attributed to the chemical coupling effect between r GO and nano-Fe_(3)O_(4) particles,which leads to the enhancement of the binding affinity to N_(2) molecules,improvement of the conductivity,and lowering the free energy of reaction for the limiting reaction step.This work provides a facile route in fabricating hybrid NRR catalysts with superior performance and shed lights on the reaction mechanism with theoretical mechanistic calculations.展开更多
Designing highly efficient bifunctional electrocatalysts for oxygen reduction and evolution reaction(ORR/OER)is extremely important for developing regenerative fuel cells and metal-air batteries.Single-atom catalysts(...Designing highly efficient bifunctional electrocatalysts for oxygen reduction and evolution reaction(ORR/OER)is extremely important for developing regenerative fuel cells and metal-air batteries.Single-atom catalysts(SACs)have gained considerable attention in recent years because of their maximum atom utilization efficiency and tunable coordination environments.Herein,through density functional theory(DFT)calculations,we systematically explored the ORR/OER performances of nitrogencoordinated transition metal carbon materials(TM-N_(x)-C(TM=Mn,Fe,Co,Ni,Cu,Pd,and Pt;x=3,4))through tailoring the coordination environment.Our results demonstrate that compared to conventional tetra-coordinated(TM-N_(4)-C)catalysts,the asymmetric tri-coordinated(TM-N_(3)-C)catalysts exhibit stronger adsorption capacity of catalytic intermediates.Among them,Ni-N_(3)-C possesses optimal adsorption energy and the lowest overpotential of 0.29 and 0.28 V for ORR and OER,respectively,making it a highly efficient bifunctional catalyst for oxygen catalysis.Furthermore,we find this enhanced effect stems from the additional orbital interaction between newly uncoordinated d-orbitals and p-orbitals of oxygenated species,which is evidently testified via the change of d-band center and integral crystal orbital Hamilton population(ICOHP).This work not only provides a potential bifunctional oxygen catalyst,but also enriches the knowledge of coordination engineering for tailoring the activity of SACs,which may pave the way to design and discover more promising bifunctional electrocatalysts for oxygen catalysis.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.62004141 and 52202045)the Fundamental Research Funds for the Central Universities,China (Grant Nos.2042022kf1028 and 2042023kf0112)+2 种基金the Knowledge Innovation Program of Wuhan-Shuguang,China (Grant Nos.2023010201020243 and 2023010201020255)the Natural Science Foundation of Hubei Province,China (Grant No.2022CFB606)the Guangdong Basic and Applied Basic Research Fund:Guangdong–Shenzhen Joint Fund,China (Grant No.2020B1515120005)。
文摘Diamond is a wide-bandgap semiconductor with a variety of crystal configurations,and has the potential applications in the field of high-frequency,radiation-hardened,and high-power devices.There are several important polytypes of diamonds,such as cubic diamond,lonsdaleite,and nanotwinned diamond(NTD).The thermal conductivities of semiconductors in high-power devices at different temperatures should be calculated.However,there has been no reports about thermal conductivities of cubic diamond and its polytypes both efficiently and accurately based on molecular dynamics(MD).Here,using interatomic potential of neural networks can provide obvious advantages.For example,comparing with the use of density functional theory(DFT),the calculation time is reduced,while maintaining high accuracy in predicting the thermal conductivities of the above-mentioned three diamond polytypes.Based on the neuroevolution potential(NEP),the thermal conductivities of cubic diamond,lonsdaleite,and NTD at 300 K are respectively 2507.3 W·m^(-1)·K^(-1),1557.2 W·m^(-1)·K^(-1),and 985.6 W·m^(-1)·K^(-1),which are higher than the calculation results based on Tersoff-1989 potential(1508 W·m^(-1)·K^(-1),1178 W·m^(-1)·K^(-1),and 794 W·m^(-1)·K^(-1),respectively).The thermal conductivities of cubic diamond and lonsdaleite,obtained by using the NEP,are closer to the experimental data or DFT data than those from Tersoff-potential.The molecular dynamics simulations are performed by using NEP to calculate the phonon dispersions,in order to explain the possible reasons for discrepancies among the cubic diamond,lonsdaleite,and NTD.In this work,we propose a scheme to predict the thermal conductivity of cubic diamond,lonsdaleite,and NTD precisely and efficiently,and explain the differences in thermal conductivity among cubic diamond,lonsdaleite,and NTD.
基金support of the project from the National Natural Science Foundation of China(Grant No.91963207,12122408,12074292)National Key R&D Program of China(Grant No.2021YFA0718700)Suzhou Key Industrial Technology Innovation project(Grant No.SYG201921).
文摘SnSe has attracted extensive attention due to its ultralow thermal conductivity and excellent thermoelectric properties.In this work,pressure-induced thermoelectric properties of Pnma SnSe are investigated via first-principles calculations.We uncover distinct energy isosurfaces topology transition of conduction band by applying pressure.The newly created conduction band valley caused by pressure has a distinct anisotropic shape compared to the old one.Inducing pressure can greatly enhance the anisotropy of electronic transport properties of the n-type Pnma SnSe.Furthermore,the lattice thermal conductivity also exhibits anisotropic behavior under pressure due to a special collaged phonon mode.The pressure-induced lattice thermal conductivity along the a-axis shows a slower growth trend than that along the b-axis and c-axis.The optimal ZT value of the n-type Pnma SnSe along the a-axis can reach 1.64 at room temperature.These results would be helpful for designing the Pnma SnSe-based materials for the potential thermoelectric and valleytronic applications.
基金the National Natural Science Foundation of China(Grant No.11975214)。
文摘Dielectric laser accelerators(DLAs)are considered promising candidates for on-chip particle accelerators that can achieve high acceleration gradients.This study explores various combinations of dielectric materials and accelerated structures based on the inverse Cherenkov effect.The designs utilize conventional processing methods and laser parameters currently in use.We optimize the structural model to enhance the gradient of acceleration and the electron energy gain.To achieve higher acceleration gradients and energy gains,the selection of materials and structures should be based on the initial electron energy.Furthermore,we observed that the variation of the acceleration gradient of the material is different at different initial electron energies.These findings suggest that on-chip accelerators are feasible with the help of these structures and materials.
基金financial support from the NSFC(Grant No.21403119)the Science and Technology Bureau of Shenzhen(Grant No.JCYJ20170306171540744)
文摘Non-noble metal electrocatalysis has witnessed rapid and profound performance improvements owing to the emergence of advanced nanosynthetic techniques.Integration of these nanotechniques can lead to synergistic performance enhancement,but such system-engineering strategies are difficult to achieve because of the lack of effective synthesis method.We hereby demonstrate an integrated approach that combines most of the existing nanotechniques in a facile one-pot synthesis.Material characterization reveals that the product shows key features intended by techniques including morphological,structural,doping,heterointerface,and surface wetting engineering.The as-obtained nitrogen-doped hierarchical heterostructured MoS_(x)/Ni_(3)S_(2)nanowires show an overpotential that is only50 mV higher than commercial Pt/C for hydrogen evolution reaction over current densities from 10 to 150 mA cm^(-2).Correlations between the adopted nanotechniques and the electrochemical reaction rates are established by evaluating the impacts of individual techniques on the activation energy,pre-exponential factor,and transfer coefficient.This indepth analysis provides a full account of the synergistic effects and the overall improvement in electrocatalytic performance of hydrogen evolution reaction.This work manifests a generic strategy for multipurpose material design in non-noble metal electrocatalysis.
基金supported by the National Natural Science Foundation of China(No.52174004 and No.51804318)the National Key Research and Development Program of China(No.2018YFC0808401)
文摘The use of mechanical drilling in accessing energy resources stored in deep and hard rock formations is becoming increasingly challenging.Thus,laser irradiation has emerged as a novel drilling method with considerable in this context.This study examines the variation of rock fracture length,fracture tortuosity,hole size,and rock breaking efficiency for a different number of holes and laser power,based on the constant total energy of laser irradiation.As indicated by the results,increasing the laser power increases the laser intensity,which helps increase the hole diameter and depth.Moreover,for the same laser power,increasing the number of irradiated holes reduces the laser energy absorbed by each hole,which is not conducive to increasing the hole depth.As the number of holes increases,the mass loss of the rock also increases,while both specific energy(SE)and modified specific energy(MSE)decrease.When the number of holes remains the same,the mass of the shale removed by low power is less than that removed by high power,while SE and MSE have an inverse relation with power.Therefore,high laser power and multiple-hole irradiation are more conducive to rock breaking.Besides,the fracture length and fracture tortuosity of the rock irradiated by the low laser power will increase first and then decrease with the increase in the number of holes,and reach the peak value when the irradiation takes place through three holes.When a high-power laser irradiates the rock,the fracture length and tortuosity will increase with the increase in the number of irradiation holes.This is because a rock irradiated by low power dissipates more energy,with the result that the energy absorbed by the sample with four irradiation holes is not enough to break the rock quickly.This study is expected to provide some guidance to break rock for drilling deep reservoirs and hard rock formations using laser irradiation.
基金supported by the National Key Research and Development Program of China(No.2017YFB1103900)the National Natural Science Foundation of China(No.51605340)。
文摘A numerical model is presented in this article to investigate the interactions between laser generated ultrasonic and the microdefects(0.01 to 0.1 mm),which are on the surface of the laser powder bed fusion additive manufactured 316L stainless steel.Firstly,the influence of the transient sound field and detection positions on Rayleigh wave signals are investigated.The interactions between the varied microdefects and the laser ultrasonic are studied.It is shown that arrival time of reflected Rayleigh(RR)waves wave is only related to the location of defects.The depth can be checked from the feature point Q,the displacement amplitude and time delay of converted transverse(RS)wave,while the width information can be evaluated from the RS wave time delay.With the aid of fitting curves,it is found to be linearly related.This simulation study provides a theoretical basis for quantitative detection of surface microdefects of additive manufactured 316L stainless steel components.
基金supported by the Excellent Dissertation Cultivation Funds of Wuhan University of Technology(2018-YS-013)
文摘The mechanisms for oxygen reduction reaction(ORR)on the naturally exposed(110)and(111)surfaces of Co_(3)O_(4)have been investigated with density functional theory(DFT)calculations.Depending on the vertical cutting place,there are type A and B surfaces for each of the(110)and(111)surfaces of Co_(3)O_(4).Our DFT calculations reveal that the Co_(3)O_(4)(110)type B and(111)type B surfaces have ORR catalytic activities.In addition,the ORR activity on the(110)type B surface is better than the(111)type B surface.The ratedetermining step on both surfaces is thermodynamically depending on the^(*)OH desorption process.If the solvation effects are taken into accounts,the chemically adsorbed water molecules enhance the ORR activity.According to the barrier heights calculations,O_(2)→^(*)O_(2)→^(*)OOH→^(*)O+H_(2)O→^(*)OH→H_(2)O route is the most favorable ORR pathway.
文摘1. Introduction The Lithium-sulfur battery(LSB) shows promise as a highdensity energy source, with a theoretical energy density of approximately 2600 W h kg^(-1)[1]. However, practical application of the LSB has been hindered by the “shuttle effect” and Li anode corrosion [2,3]. Highly concentrated electrolytes(HCEs) have been proposed as a solution, as they can inhibit the dissolution of lithium polysulfide and promote homogeneous lithium deposition [4].
基金supported by the National Natural Science Foundation of China(Grant No.11975214).
文摘We present a first on-chip positron accelerator based on dielectric laser acceleration.This innovative approach significantly reduces the physical dimensions of the positron acceleration apparatus,enhancing its feasibility for diverse applications.By utilizing a stacked acceleration structure and far-infrared laser technology,we are able to achieve a seven-stage acceleration structure that surpasses the distance and energy gain of using the previous dielectric laser acceleration methods.Additionally,we are able to compress the positron beam to an ultrafast sub-femtosecond scale during the acceleration process,compared with the traditional methods,the positron beam is compressed to a greater extent.We also demonstrate the robustness of the stacked acceleration structure through the successful acceleration of the positron beam.
基金supported by the National Natural Science Foundation of China(Grant No.61904127 and 62004144)Guangdong Basic and Applied Basic Research Foundation(Grant No.2021A1515010651)+2 种基金Fundamental Research Funds for the Central Universities(Grant No.202401002,203134004,20212VA100 and 2021VB006)Hubei Provincial Natural Science Foundation of China(Grant No.2020CFA032)National Key R&D Program of China(Grant No.2019YFB1704600)。
文摘Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits,but also the weak spots in reliability tests.Most of failures in power devices are caused by the malfunction of interconnections,including failure of bonding wire as well as cracks of solder layer.In fact,the interconnection failure of power devices is the result of a combination of factors such as electricity,temperature,and force.It is significant to investigate the failure mechanisms of various factors for the failure analysis of interconnections in power devices.This paper reviews the main failure modes of bonding wire and solder layer in the interconnection structure of power devices,and its failure mechanism.Then the reliability test method and failure analysis techniques of interconnection in power device are introduced.These methods are of great significance to the reliability analysis and life prediction of power devices.
基金the National Key R&D Program of China(Grant No.2019YFB1704600)the Hubei Provincial Natural Science Foundation of China(Grant No.2020CFA032).
文摘Currently,wire bonding is the most popular first-level interconnection technology used between the die and package terminals,but even with its long-term and excessive usage,the mechanism of wire bonding has not been completely evaluated.Therefore,fundamental research is still needed.In this study,the mechanism of microweld formation and breakage during Cu-Cu wire bonding was investigated by using molecular dynamics simulation.The contact model for the nanoindentation process between the wire and substrate was developed to simulate the contact process of the Cu wire and Cu substrate.Elastic contact and plastic instability were investigated through the loading and unloading processes.Moreover,the evolution of the indentation morphology and distributions of the atomic stress were also investigated.It was shown that the loading and unloading curves do not coincide,and the unloading curve exhibited hysteresis.For the substrate,in the loading process,the main force changed from attractive to repulsive.The maximum von Mises stress increased and shifted from the center toward the edge of the contact area.During the unloading process,the main force changed from repulsive to attractive.The Mises stress reduced first and then increased.Stress concentration occurs around dislocations in the middle area of the Cu wire.
基金supported by the National Key R&DProgram of China(2018YFB1105100)National Natural Science Foundation of China(51973165).
文摘The porous structure in pomelo peel is believed to be responsible for the protection of its fruit from damage during the free falling from a tree.The quantitative understanding of the relationship between the deformation behavior and the porous structure could pave the way for the design of porous structures for efficient energy absorption.Here,a universal feature of pore distribution in pomelo peels along the radial direction is extracted from three varieties of pomelos,which shows strong correlation to the deformation behavior of the peels under compression.Guided by the porous design found in pomelo peels,porous polyether-ether-ketone(PEEK)cube is additively manufactured and possesses the highest ability to absorb energy during compression as compared to the non-pomelo-inspired geometries,which is further confirmed by the finite element simulation.The nature-optimized porous structure revealed here could guide the design of lightweight and high-energy-dissipating materials/devices.
基金supported by the Excel ent Dissertation Cultivation Funds of Wuhan University of Technology(2018-YS-013)
文摘Batteries are the most widely used energy storage devices, and the lithiumion battery is the most heavily commercialized and most widely used battery type in the industry. However, the current rapid development of society requires a major advancement in battery materials to achieve high capacity,long life cycle, low cost, and reliable safety. Therefore, many new efficient energy storage materials and battery systems are being developed and explored, and their working mechanisms must be clearly understood before industrial application. In recent years, density functional theory (DFT) has been employed in the energy storage field and has made significant contributions to the understanding of electrochemical reaction mechanisms and to virtual screening of promising energy storage materials. In this review,the applications of DFT to battery materials are summarized and exemplified by some representative and up-to-date studies in the literature. The main focuses in this review include the following:1) structural stability estimation by cohesive energy, formation energy, Gibbs free energy, and phonon dispersion spectra calculations;2) the Gibbs free energy calculations for electrochemical reactions, corresponding open-circuit voltage, and theoretical capacity predictions of batteries;3) the analyses of molecule orbitals, band structures, density of states (DOS), and charge distribution of battery materials;4) ion transport kinetics in battery materials;5) simulations of adsorption processes. We conclude the review with the discussion of the assessments and validation of the popular functionals against several benchmarks, and a few suggestions have been given for the selection of density functionals for battery material systems.
基金This research is financially supported by the National Key Research and Development Program of China(Grant Nos.2017YFB1103900 and 2018YFB1107701)the Fundamental Research Funds for the Central Universities(Grant No.2042019kf0015)+1 种基金the Key R&D projects of Sichuan Province(Grant No.2020YFSY0054)the National Natural Science Foundation of China(Grant No.51605343).
文摘High entropy alloys(HEAs)with multi-component solid solution microstructures have the potential for large-scale industrial applications due to their excellent mechanical and functional properties.However,the mechanical properties of HEAs limit the selection of processing technologies.Additive manufacturing technology possesses strong processing adaptability,making itthe best candidate method to overcome this issue.This comprehensive review examines the current state of selective laser melting(SLM)of HEAs.Introducing SLM to HEAs processing is motivated by its high quality for dimensional accuracy,geometric complexity,surface roughness,and microstructure.This review focuses on analyzing the current developments and challenges in SLM of HEAs,including defects,microstructures,and properties,as well as strengthing prediction models of fabricated HEAs.This review also offers directions for future studies to address existing challenges and promote technological advancement.
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.52072136,51972257,51872104,and 52172229)the Ningxia Key R&D Program(2019BFG02018)the Fundamental Research Funds for the Central Universities(WUT:2021IVA115,2021IVA071).
文摘Hybrid supercapacitors have shown great potentials to fulfill the demand of future diverse applications such as electric vehicles and portable/wearable electronics.In particular,aqueous zinc-ion hybrid supercapacitors(ZHSCs)have gained much attention due to their low-cost,high energy density,and environmental friendliness.Nevertheless,typical ZHSCs use Zn metal anode and normal liquid electrolyte,causing the dendrite issue,restricted working temperature,and inferior device flexibility.Herein,a novel flexible Zn-ion hybrid supercapacitor(FZHSC)is developed by using activated carbon(AC)anode,δ-MnO_(2) cathode,and innovative PVA-based gel electrolyte.In this design,heavy Zn anode and its dendrite issue are avoided and layered cathode with large interlayer spacing is employed.In addition,flexible electrodes are prepared and integrated with an anti-freezing,stretchable,and compressible hydrogel electrolyte,which is attained by simultaneously using glycerol additive and freezing/thawing technique to regulate the hydrogen bond and microstructure.The resulting FZHSC exhibits good rate capability,high energy density(47.86 Wh kg^(−1);3.94 mWh cm^(−3)),high power density(5.81 kW kg^(−1);480 mW cm^(−3)),and excellent cycling stability(~91%capacity retention after 30000 cycles).Furthermore,our FZHSC demonstrates outstanding flexibility with capacitance almost unchanged even after various continuous shape deformations.The hydrogel electrolyte still maintains high ionic conductivity at ultralow temperatures(≤−30℃),enabling the FZHSC cycled well,and powering electronic timer robustly within an all-climate temperature range of−30~80℃.This work highlights that the promising Zn metal-free aqueous ZHSCs can be designed with great multifunctionality for more practical application scenarios.
文摘Miniaturized sound generators are attractive to realize intriguing functions.Thermoacoustic device’s application is seriously limited due to the frequency-doubling phenomenon.To address this issue,photoacoustic sound generator is considered as a promising alternative.Here,based on vertical single-wall carbon nanotubes(CNTs)array,we introduce a photoacoustic sound generator with internal nano-Helmholtz cavity.Different from traditional device that generates sound by periodically heating up the open space air around material,this sound generator produces an audio signal by forming a forced vibration of the air inside the CNTs.Interestingly,anomalous photoacoustic behavior is observed that the sound pressure level(SPL)curve has a resonance peak,the corresponding frequency of which is inversely proportional to the CNTs array’s height.Furthermore,the energy conversion efficiency of this photoacoustic device is 1.64 times as large as that of a graphene sponge-based photoacoustic device.Most importantly,this device can be employed for music playing,bringing a new clew for the development of musical instruments in the future.
基金supported by the National Natural Science Foundation of China(No.51901162).
文摘Two-dimensional transition metal chalcogenides(2D-TMDs)have attracted much attention because of their unique layered structure and physical properties for transistor applications.Mechanically transferred metal contacts on these low-dimensional materials or their homogeneous and heterogeneous multilayers have generated huge interest to avoid deposition damages.In this paper,we show that there are large physical gaps at both the edge contact and surface contact between the transferred electrodes and the 2D materials.A method called laser shock induced superplastic deformation(LSISD)is proposed to tackle this issue and enhance the performance of the transistors.The enhancement mechanism was investigated by molecular dynamics(MD)simulations of the nanoforming process,atomic force microscopy(AFM),scanning electron microscopy(SEM),transmission electron microscopy(TEM)characterizations of the interfaces,and density functional theory(DFT)modeling.The force effect of laser shock can reduce the contact gap between metals and semiconductors.The electrical performances of the transistors before and after LSISD,along with MD simulations,are used to find the optimal process parameters.In addition,this paper applies the LSISD method to the short-channel MoS_(2)/graphene vertical transistors to show potential improvement in interface contact and electrical properties.This paper demonstrates the first report on using mechanical force induced by laser shock to enhance metal–semiconductor interfaces and transistor performances.
文摘The development of perovskite photoelectric devices with excellent performance is largely dependent on the defects in the perovskite films.To address this issue,a specific drug,leflunomide(LF,C_(12)H_(9)F_(3)N_(2)O_(2)),was incorporated into the perovskite to reduce defects and improve its photoelectric properties.It is believed that the C=O bond on LF molecule can interact with the uncoordinated Pb2+of the perovskite,thereby reducing non-radiative recombination.This novel approach of incorporating LF into perovskite films has the potential to revolutionize the development of high-performance perovskite photoelectric devices.The trifluoromethyl functional(–CF_(3))group on LF can form a protective layer on the surface of the perovskite film,shielding it from water erosion.Moreover,LF can be utilized to alter the nucleation position of perovskite,thus minimizing the number of defects and optimizing the film quality.Consequently,the LF-doped perovskite film displays low trap density and high photoelectric performance.The LF-doped perovskite film showed a trap density of 8.28×10^(11),which is notably lower than the 2.04×10^(12) of the perovskite film without LF.The responsivity and detectivity of the LF-doped perovskite photodetector were 0.771 A/W and 2.81×10^(11) Jones,respectively,which are much higher than the 0.23 A/W and 1.06×10^(10) Jones of the LF-undoped perovskite photodetector.Meanwhile,the LF-doped photodetector maintained an initial photocurrent of 86%after 30 days of storage in air,indicating drastically increased environmental stability.This strongly suggests that LF is an effective additive for perovskites utilized in optoelectronic devices with high performance.
基金Sichuan Science and Technology Program(2018GZ0459)Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-003)the Fundamental Research Funds for the Central Universities(WUT:2020Ⅲ029)
文摘Nitrogen(N_(2))fixation at ambient condition by electrochemical N_(2)reduction reaction(NRR)is energy-efficient and eco-friendly as compared to the traditional Harber–Bosch process,but it is extremely challenging.Development and design of high-performance NRR electrocatalysts are indispensable to achieve the goal.In this work,a strongly coupled hybrid of nano-Fe3O4 with reduced graphene oxide(rGO)is synthesized via an in situ redox hydrothermal approach,and the synthesized Fe_(3)O_(4)@r GO hybrid has excellent activity,selectivity,and stability as an NRR catalyst.The NH_(3) yield rate of 28.01μg h^(-1)mg^(-1)at-0.3 V and the Faradaic efficiency(FE)of 19.12%at-0.1 V are obtained in 0.1 M Na_(2)SO_(4) solutions at ambient conditions.The superior NRR performance is attributed to the chemical coupling effect between r GO and nano-Fe_(3)O_(4) particles,which leads to the enhancement of the binding affinity to N_(2) molecules,improvement of the conductivity,and lowering the free energy of reaction for the limiting reaction step.This work provides a facile route in fabricating hybrid NRR catalysts with superior performance and shed lights on the reaction mechanism with theoretical mechanistic calculations.
基金We thank the following funding agencies for supporting this work:Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(No.XHT2020-003)the China Postdoctoral Science Foundation(No.2021M692490)the Fundamental Research Funds for the Central Universities(No.WUT:2020Ⅲ029,2020IVA100).
文摘Designing highly efficient bifunctional electrocatalysts for oxygen reduction and evolution reaction(ORR/OER)is extremely important for developing regenerative fuel cells and metal-air batteries.Single-atom catalysts(SACs)have gained considerable attention in recent years because of their maximum atom utilization efficiency and tunable coordination environments.Herein,through density functional theory(DFT)calculations,we systematically explored the ORR/OER performances of nitrogencoordinated transition metal carbon materials(TM-N_(x)-C(TM=Mn,Fe,Co,Ni,Cu,Pd,and Pt;x=3,4))through tailoring the coordination environment.Our results demonstrate that compared to conventional tetra-coordinated(TM-N_(4)-C)catalysts,the asymmetric tri-coordinated(TM-N_(3)-C)catalysts exhibit stronger adsorption capacity of catalytic intermediates.Among them,Ni-N_(3)-C possesses optimal adsorption energy and the lowest overpotential of 0.29 and 0.28 V for ORR and OER,respectively,making it a highly efficient bifunctional catalyst for oxygen catalysis.Furthermore,we find this enhanced effect stems from the additional orbital interaction between newly uncoordinated d-orbitals and p-orbitals of oxygenated species,which is evidently testified via the change of d-band center and integral crystal orbital Hamilton population(ICOHP).This work not only provides a potential bifunctional oxygen catalyst,but also enriches the knowledge of coordination engineering for tailoring the activity of SACs,which may pave the way to design and discover more promising bifunctional electrocatalysts for oxygen catalysis.
