In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been ...In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been attempts at minimizing the machining time by considering the kinematic capacities of the machine tool and/or the physical constraints such as the cutting force, they all target independently at either the finishing or the roughing process alone and are based on the simple premise of an offset interface surface. Conceivably, since the total machining time should count that of both roughing and finishing process and both of them crucially depend on the interface surface, it is natural to ask if, under the same kinematic capacities and the same physical constraints, there is a nontrivial interface surface whose corresponding total machining time will be the minimum among all the possible（infinite） choices of interface surfaces, and this is the motivation behind the work of this paper. Specifically, with respect to the specific type of iso-planar milling for both roughing and finishing, we present a practical algorithm for determining such an optimal interface surface for an arbitrary freeform surface. While the algorithm is proposed for iso-planar milling, it can be easily adapted to other types of milling strategy such as contour milling. Both computer simulation and physical cutting experiments of the proposed method have convincingly demonstrated its advantages over the traditional simple offset method.展开更多
In this paper, the shape problem of interface of bicomponent flows between two concentric rotating cylinders is investigated. With tensor analysis, the problem is reduced to an energy functional isoperimetric problem ...In this paper, the shape problem of interface of bicomponent flows between two concentric rotating cylinders is investigated. With tensor analysis, the problem is reduced to an energy functional isoperimetric problem when neglecting the effects of the dissipative energy caused by viscosity. We derive the associated Euler-Lagrangian equation, which is a nonlinear elliptic boundary value problem of the second order. Moreover, by considering the effects of the dissipative energy, we propose another total energy functional to characterize the geometric shape of the interface, and obtain the corresponding Euler-Lagrangian equation, which is also a nonlinear elliptic boundary value problem of the second order. Thus, the problem of the geometric shape is converted into a nonlinear boundary value problem of the second order in both cases.展开更多
As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal...As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal materials at various scales and dimensions.Conventional methods make it difficult to quantitatively describe the relationship between the regular characteristics and properties of metal material surfaces and interfaces.However,fractal analysis can be used to quantitatively describe the shape characteristics of metal materials and to establish the quantitative relationships between the shape characteristics and various properties of metal materials.From the perspective of two-dimensional planes and three-dimensional curved surfaces,this paper reviews the current research status of the fractal analysis of metal precipitate interfaces,metal grain boundary interfaces,metal-deposited film surfaces,metal fracture surfaces,metal machined surfaces,and metal wear surfaces.The relationship between the fractal dimensions and properties of metal material surfaces and interfaces is summarized.Starting from three perspectives of fractal analysis,namely,research scope,image acquisition methods,and calculation methods,this paper identifies the direction of research on fractal analysis of metal material surfaces and interfaces that need to be developed.It is believed that revealing the deep influence mechanism between the fractal dimensions and properties of metal material surfaces and interfaces will be the key research direction of the fractal analysis of metal materials in the future.展开更多
For emerging renewable and sustainable energy technologies,single crystal materials have become key materials to enhance electrocatalytic performance because of their atomic-level ordered structures and tailorable sur...For emerging renewable and sustainable energy technologies,single crystal materials have become key materials to enhance electrocatalytic performance because of their atomic-level ordered structures and tailorable surface and interfacial properties.Various single crystal types,including metals,semiconductors,ceramics,organics,and nanocrystals,exhibit superior catalytic selectivity and stability in reactions such as water splitting and carbon/nitrogen cycles,benefiting from high electrical conductivity,tunable energy bands,and active sites with high surface energy.Through surface modification,interfacial atomic doping,and heterostructure construction,the distribution of active sites,electronic structure,and mass transport can be precisely regulated,significantly optimizing the catalytic kinetics of single crystal materials.In situ characterizations elucidate catalytic mechanisms at the atomic scale,while emerging methods like AI-assisted synthesis and bio-template directed growth offer pathways to overcome bottlenecks in the precision and cost of single crystal preparation.In addressing stability challenges in complex environments,strategies such as organic-inorganic hybridization and gradient interface design effectively mitigate interfacial instability.Future research should focus on cross-scale structural regulation and multidisciplinary integration to facilitate the transition of single crystal electrocatalysts from fundamental research to industrial applications,enabling efficient energy conversion.展开更多
Organic-inorganic hybrid metal halide perovskite solar cells(PSCs)have attracted much attention due to their high photoelectric conversion efficiency(PCE)and low cost.The certificated PCE of small active area(below 0....Organic-inorganic hybrid metal halide perovskite solar cells(PSCs)have attracted much attention due to their high photoelectric conversion efficiency(PCE)and low cost.The certificated PCE of small active area(below 0.1 cm^(2))device has reached 26.7%[1].However,when considering the scaled-up commercialization of PSCs,an obvious efficiency drop exists for the translation to large-area perovskite submodules(PSMs)with areas more than 200 cm^(2),thus limiting the practical commercialization[2].The major PCE gap between small area cells and large area modules arises the drop of open-circuit voltage(VOC)and fill factor(FF).Formamidinium lead iodide(FAPbI_(3))is now the mostly widely used and highly efficient perovskite composition.However,the photo-active black α-FAPbI_(3) phase will spontaneously transform into photo-inactive yellowδ-FAPbI_(3) phase at room temperature[3].展开更多
A CuPc/SiO2 sample is fabricated. Its morphology is characterized by atomic force microscopy, and the electron states are investigated by X-ray photoelectron spectroscopy. In order to investigate these spectra in deta...A CuPc/SiO2 sample is fabricated. Its morphology is characterized by atomic force microscopy, and the electron states are investigated by X-ray photoelectron spectroscopy. In order to investigate these spectra in detail, all of these spectra are normalized to the height of the most intense peak,and each component is fitted with a single Gaussian function. Analysis shows that the O element has great bearing on the electron states and that SiO2 layers produced by spurting technology are better than those produced by oxidation technology.展开更多
To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surfa...To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surface/interface engineering is found to be effective in achieving novel physicochemical properties and synergistic effects in nanomaterials for electrocatalysis.Among various engineering strategies,heteroatom-doping has been regarded as a most promising method to improve the electrocatalytic performance via the regulation of electronic structure of catalysts,and numerous works were reported on the synthesis method and mechanism investigation of heteroatom-doping electrocatalysts,though the heteroatom-doping can only provide limited active sites.Engineering of other defects such as vacancies and edge sites and construction of heterostructure have shown to open up a potential avenue for the development of noble metal-free electrocatalysts.In addition,surface functionalization can attach various molecules onto the surface of materials to easily modify their physical or chemical properties,being as a promising complement or substitute for offering materials with catalytic properties.This paper gives the insights into the diverse strategies of surface/interface engineering of the highefficiency noble metal-free electrocatalysts for energy-related electrochemical reactions.The significant advances are summarized.The unique advantages and mechanisms for specific applications are highlighted.The current challenges and outlook of this growing field are also discussed.展开更多
Surface/interface engineering plays an important role in improving the performance and economizing the cost and usage of electrocatalysts.In recent years,substantial progress has been achieved in designing and develop...Surface/interface engineering plays an important role in improving the performance and economizing the cost and usage of electrocatalysts.In recent years,substantial progress has been achieved in designing and developing highly active electrocatalysts with the deepening understanding of surface and interface enhanced mechanism.In this review,recent development about optimizing the surface and interfacial structure in promoting the electrocatalytic activity of noble-metals and transition metal compounds is presented and the chemical enhancements are also described in detail.The relationship between the surface/interface structures(both atomic and electronic configuration)and the electrochemical behaviors has been discussed.Finally,personal perspectives have been proposed,highlighting the challenges and opportunities for future development in tuning the surface/interface active sites of electrocatalysts.We believe that this timely review will be beneficial to the construction of highly active and durable electrode materials through optimizing surface atomic arrangement and interfacial interaction,which can largely promote the development of next-generation clean energy conversion technologies.展开更多
Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunc...Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.展开更多
The polar interface optical （IO） and surface optical （SO） phonon modes and the corresponding Froehlich electron phonon-interaction Hamiltonian in a freestanding multi-layer wurtzite cylindrical quantum wire （QWR...The polar interface optical （IO） and surface optical （SO） phonon modes and the corresponding Froehlich electron phonon-interaction Hamiltonian in a freestanding multi-layer wurtzite cylindrical quantum wire （QWR） are derived and studied by employing the transfer matrix method in the dielectric continuum approximation and Loudon＇s uniaxial crystal model. A numerical calculation of a freestanding wurtzite GaN/AlN QWR is performed. The results reveal that for a relatively large azimuthal quantum number m or wave-number kz in the free z-direction, there exist two branches of IO phonon modes localized at the interface, and only one branch of SO mode localized at the surface in the system. The degenerating behaviours of the IO and SO phonon modes in the wurtzite QWR have also been clearly observed for a small kz or m. The limiting frequency properties of the IO and SO modes for large kz and m have been explained reasonably from the mathematical and physical viewpoints. The calculations of electron-phonon coupling functions show that the high-frequency IO phonon branch and SO mode play a more important role in the electron phonon interaction.展开更多
The interface and surface properties of nano-hydroxyapatite(n-HA) and poly( 1, 4-phenylene sulfide)-poly (2,4-phenylene sulfide acid)(PPS-PPSA) copolymer composite were investigated. The results show that there are so...The interface and surface properties of nano-hydroxyapatite(n-HA) and poly( 1, 4-phenylene sulfide)-poly (2,4-phenylene sulfide acid)(PPS-PPSA) copolymer composite were investigated. The results show that there are some strong interface combinations of calcium ion (Ca2+ ), car-boxyl (-COO- ) and phosphate radicle ion (PO_4~3- ) between copolymer and n-HA in the composite. The presence of the 2,4-phenylene sulfide acid in copolymer can increase the affinity to n-HA, which causes the formation of chemical bindings between the PPS-PPSA copolymer and n-HA. XRD analysis and IR surface analysis indicate that n-HA is not encapsulated by copolymer but exposed on the surface of the composite, and has same structure and properties with the origi-nal n-HA. The presence of the interface chemical bindings between the PPS-PPSA copolymer and n-HA can increase the content of n-HA in composite but does not cause the decrease of the composite mechanical strength.展开更多
In this paper, we present an analytical solution of the interaction of the nanotube （NT） with a wedge disclination dipole in nanotube-based composites. The corresponding boundary value problem is solved exactly by u...In this paper, we present an analytical solution of the interaction of the nanotube （NT） with a wedge disclination dipole in nanotube-based composites. The corresponding boundary value problem is solved exactly by using complex potential functions. The explicit expression of the force exerted on disclination dipole is given by using the generalized Peach- Koehler formula. As a numerical illustration, both the equilibrium position and the stability of the disclination dipole are evaluated for different material combinations, relative thickness of an NT, surface/interface effects, and the features of the disclination dipole. The results show that as the thickness of the NT layer increases, the NT has a relatively major role in the force acting on the disclination dipole in the NT-based composite. The cooperative effect of surface/interface stresses and the NT becomes considerable as the increase of NT layer thickness. The equilibrium position may occur, even more than one, due to the influences of the surface/interface stress and the NT thickening. The influences of the surface/interface stresses and the thickness of the NT layer on the force are greatly dependent on the disclination angle.展开更多
Based on the first-principles method, the structural stability and the contribution of point defects such as O, Sr or Ti vacancies on two-dimensional electron gas of n- and p-type LaAlO3/SrTiO3 interfaces are investig...Based on the first-principles method, the structural stability and the contribution of point defects such as O, Sr or Ti vacancies on two-dimensional electron gas of n- and p-type LaAlO3/SrTiO3 interfaces are investigated. The results show that O vacancies at p-type interfaces have much lower formation energies, and Sr or Ti vacancies at n-type interfaces are more stable than the ones at p-type interfaces under O-rich conditions. The calculated densities of states indicate that O vacancies act as donors and give a significant compensation to hole carriers, resulting in insulating behavior at p-type interfaces. In contrast, Sr or Ti vacancies tend to trap electrons and behave as acceptors. Sr vacancies are the most stable defects at high oxygen partial pressures, and the Sr vacancies rather than Ti vacancies are responsible for the insulator-metal transition of n-type interface. The calculated results can be helpful to understand the tuned electronic properties of LaAlO3 /SrTiO3 heterointerfaces.展开更多
This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements, including nanoparticles, nanowires, nanobeams, and nanofilms, and heterogeneous materials containing na...This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements, including nanoparticles, nanowires, nanobeams, and nanofilms, and heterogeneous materials containing nanoscale inhomogeneities. It begins with the fundamental formulations of surface mechanics of solids, including the definition of surface stress as a surface excess quantity, the surface constitutive relations, and the surface equilibrium equations. Then, it depicts some theoretical and experimental studies of the mechanical properties of nanostructured elements, as well as the static and dynamic behaviour of cantilever sensors caused by the surface stress which is influenced by adsorption. Afterwards, the article gives a summary of the analytical elasto-static and dynamic solutions of a single as well as multiple inhomogeneities embedded in a matrix with the interface stress prevailing. The effect of surface elasticity on the diffraction of elastic waves is elucidated. Due to the difficulties in the analytical solution of inhomogeneities of complex shapes and configurations, finite element approaches have been developed for heterogeneous materials with the surface stress. Surface stress and surface energy are inherently related to crack propagation and the stress field in the vicinity of crack tips. The solutions of crack prob- lems taking into account surface stress effects are also included. Predicting the effective elastic and plastic responses of heterogeneous materials while taking into account surface and interface stresses has received much attention. The advances in this topic are inevitably delineated. Mechanics of rough surfaces appears to deserve special attention due to its theoretical and practical implications. Some most recent work is reviewed. Finally, some challenges are pointed out. They include the characterization of surfaces and interfaces of real nanomaterials, experimental mea- surements and verification of mechanical parameters of complex surfaces, and the effects of the physical and chemical processes on the surface properties, etc.展开更多
This work deals with the influences of nano-heterogeneities in the form of voids/cavities or cracks on the elastic (please confirm which word is correct. effective or elastic? According to the title of paper, I choose...This work deals with the influences of nano-heterogeneities in the form of voids/cavities or cracks on the elastic (please confirm which word is correct. effective or elastic? According to the title of paper, I choose elastic.) properties of a host medium. With a relatively large ratio of apparent-surface to volume and particularly strong physical interactions with the surrounding medium at nano-scale, nano-heterogeneities can potentially affect the elastic(effective or elastic?) properties of the parent medium (matrix) containing them in a significant manner. This has been reported by various theoretical and experimental studies, some of them are discussed in the present paper. To describe the positive (reinforcement) or negative (degradation) effect of the nano-heterogeneities from the modeling perspective, it is necessary to take into account the energy of interfaces/surfaces between nano-heterogeneities and the matrix which, by the fact of the relatively large extent of their apparent surface and their strong physical interaction with their neighborhood, can no longer be neglected compared to those of the volume energy. Thus, to account for the effects of interfaces/surfaces in a nanostructured heterogeneous medium, the coherent interface model is considered in the present investigation within a periodic homogenization procedure. In this interface/surface model, the displacement vector is assumed to be continuous across the interface while the stress vector is considered to be discontinuous and satisfying the Laplace-Young equations. To solve these equations coupled to the classical mechanical equilibrium problem, a numerical simulation tool is developed in a two-dimensional (2D) context using the eXtended Finite Element Method (XFEM) and the Level-Set functions. The developed numerical tool is then used to carry out a detailed analysis about the effect of nano-heterogeneities on the overall mechanical properties of a medium. The nano-heterogeneities are present in the medium initially as cylindrical cavities (circular in 2D) before being reduced to plane cracks (line in 2D) by successive flattenings.展开更多
Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic compo- nents with high heat flux in microgravity, and was verified by experiments performed utilizing the drop...Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic compo- nents with high heat flux in microgravity, and was verified by experiments performed utilizing the drop tower Beijing. Micro-pin-fins with tile dimensions of 50 × （30 μm2 （thickness × height） and the space of 50 μm were fabricated on the chip surface by the dry etching technique. FC-72 was used as the working fluid. Nucleate pool boiling of FC-72 on a smooth surface was also tested for comparison. Unlike much obvious deterioration of heat transfer of nucleate pool boiling on the smooth surface in microgravity, constant heater surface temperature of nucleate pool boiling for the micro-pin-finned surface was observed, even though a large coalesced bubble completely covered the surface under microgravity condition. The performance of high efficient heat transfer on micro-pin-finned surface is independent of the gravity, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary forces.展开更多
BL02U2 of the Shanghai Synchrotron Radiation Facility is a surface diffraction beamline with a photon flux of 5.5×10^(12) photons/s at 10 keV and a beam size of 160µm×80µm at the sample site.It is ...BL02U2 of the Shanghai Synchrotron Radiation Facility is a surface diffraction beamline with a photon flux of 5.5×10^(12) photons/s at 10 keV and a beam size of 160µm×80µm at the sample site.It is dedicated to studying surfaces(solid-vacuum,solid-gas)and interfaces(solid-solid,solid-liquid,and liquid-liquid)in nanoscience,condensed matter,and soft matter systems using various surface scattering techniques over an energy range of 4.8-28 keV with transmission and reflection modes.Moreover,BL02U2 has a high energy resolution,high angular resolution,and low beam divergence,which can provide excellent properties for X-ray diffraction experiments,such as grazing incident X-ray diffraction,X-ray reflectivity,crystal truncation rods,and liquid X-ray scattering.Diversity of in situ environments can also be provided for the samples studied.This paper describes the setup of the new beamline and its applications in various fields.展开更多
6H-SiC （1010） surface and Si （220）/6H-SIC （1010） interface with different stacking sites are investigated using first-principles calculations. Surface energies of 6H-SiC （1010） （case I, case II, and case III...6H-SiC （1010） surface and Si （220）/6H-SIC （1010） interface with different stacking sites are investigated using first-principles calculations. Surface energies of 6H-SiC （1010） （case I, case II, and case III） are firstly studied and the surface calculation results show that case II and case III are more stable than case I. Then, the adhesion energies, fracture toughness values, interfacial energies, densities of states, and electronic structures of Si （220）/6H-SIC （1010） interfaces for three stacking models （AM, BM, and CM） are calculated. The CM model has the highest adhesion energy and the lowest interracial energy, suggesting that the CM is stronger and more thermodynamically stable than AM and BM. Densities of states and the total charge densities give evidence that interfacial bonding is formed at the interface and that Si-Si and Si-C are induced due to the hybridization of C-2p and Si-3p. Moreover, the Si-C is much stronger than Si-Si at the interface, implying that the contribution of the interfacial bonding mainly comes from Si-C rather than Si-Si.展开更多
In order to restore the degraded ultrasonic C-scan image for testing surfacing inteoface, a method based on support vector regression （SVR） network is proposed. By using the image of a simulating defect, the network...In order to restore the degraded ultrasonic C-scan image for testing surfacing inteoface, a method based on support vector regression （SVR） network is proposed. By using the image of a simulating defect, the network is trained and a mapping relationship between the degraded and restored image is founded. The degraded C-scan image of Cu-Steel surfacing inteoface is processed by the trained network and improved image is obtained. The result shows that the method can effectively suppress the noise and deblur the defect edge in the image, and provide technique support for quality and reliability evaluation of the surfacing weld.展开更多
Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompa...Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.展开更多
文摘In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been attempts at minimizing the machining time by considering the kinematic capacities of the machine tool and/or the physical constraints such as the cutting force, they all target independently at either the finishing or the roughing process alone and are based on the simple premise of an offset interface surface. Conceivably, since the total machining time should count that of both roughing and finishing process and both of them crucially depend on the interface surface, it is natural to ask if, under the same kinematic capacities and the same physical constraints, there is a nontrivial interface surface whose corresponding total machining time will be the minimum among all the possible（infinite） choices of interface surfaces, and this is the motivation behind the work of this paper. Specifically, with respect to the specific type of iso-planar milling for both roughing and finishing, we present a practical algorithm for determining such an optimal interface surface for an arbitrary freeform surface. While the algorithm is proposed for iso-planar milling, it can be easily adapted to other types of milling strategy such as contour milling. Both computer simulation and physical cutting experiments of the proposed method have convincingly demonstrated its advantages over the traditional simple offset method.
基金the National Natural Science Foundation of China(Nos.10571142,10771167)
文摘In this paper, the shape problem of interface of bicomponent flows between two concentric rotating cylinders is investigated. With tensor analysis, the problem is reduced to an energy functional isoperimetric problem when neglecting the effects of the dissipative energy caused by viscosity. We derive the associated Euler-Lagrangian equation, which is a nonlinear elliptic boundary value problem of the second order. Moreover, by considering the effects of the dissipative energy, we propose another total energy functional to characterize the geometric shape of the interface, and obtain the corresponding Euler-Lagrangian equation, which is also a nonlinear elliptic boundary value problem of the second order. Thus, the problem of the geometric shape is converted into a nonlinear boundary value problem of the second order in both cases.
基金financially supported by the National Key R&D Program of China(No.2022YFE0121300)the National Natural Science Foundation of China(No.52374376)the Introduction Plan for High-end Foreign Experts(No.G2023105001L)。
文摘As a mathematical analysis method,fractal analysis can be used to quantitatively describe irregular shapes with self-similar or self-affine properties.Fractal analysis has been used to characterize the shapes of metal materials at various scales and dimensions.Conventional methods make it difficult to quantitatively describe the relationship between the regular characteristics and properties of metal material surfaces and interfaces.However,fractal analysis can be used to quantitatively describe the shape characteristics of metal materials and to establish the quantitative relationships between the shape characteristics and various properties of metal materials.From the perspective of two-dimensional planes and three-dimensional curved surfaces,this paper reviews the current research status of the fractal analysis of metal precipitate interfaces,metal grain boundary interfaces,metal-deposited film surfaces,metal fracture surfaces,metal machined surfaces,and metal wear surfaces.The relationship between the fractal dimensions and properties of metal material surfaces and interfaces is summarized.Starting from three perspectives of fractal analysis,namely,research scope,image acquisition methods,and calculation methods,this paper identifies the direction of research on fractal analysis of metal material surfaces and interfaces that need to be developed.It is believed that revealing the deep influence mechanism between the fractal dimensions and properties of metal material surfaces and interfaces will be the key research direction of the fractal analysis of metal materials in the future.
基金supported by National Natural Science Foundation of China(No.52202366)Taishan Scholar Project of Shandong Province(tstp20240515,tsqn202312217)+1 种基金Natural Science Foundation of Shandong Province(China,No.2025HWYQ-050,ZR2021QE011,ZR2022QH072,ZR2021QE284)the King Abdullah University of Science and Technology,the Center of Excellence for Renewable Energy and Storage Technologies.
文摘For emerging renewable and sustainable energy technologies,single crystal materials have become key materials to enhance electrocatalytic performance because of their atomic-level ordered structures and tailorable surface and interfacial properties.Various single crystal types,including metals,semiconductors,ceramics,organics,and nanocrystals,exhibit superior catalytic selectivity and stability in reactions such as water splitting and carbon/nitrogen cycles,benefiting from high electrical conductivity,tunable energy bands,and active sites with high surface energy.Through surface modification,interfacial atomic doping,and heterostructure construction,the distribution of active sites,electronic structure,and mass transport can be precisely regulated,significantly optimizing the catalytic kinetics of single crystal materials.In situ characterizations elucidate catalytic mechanisms at the atomic scale,while emerging methods like AI-assisted synthesis and bio-template directed growth offer pathways to overcome bottlenecks in the precision and cost of single crystal preparation.In addressing stability challenges in complex environments,strategies such as organic-inorganic hybridization and gradient interface design effectively mitigate interfacial instability.Future research should focus on cross-scale structural regulation and multidisciplinary integration to facilitate the transition of single crystal electrocatalysts from fundamental research to industrial applications,enabling efficient energy conversion.
基金support from open fund of Fujian Provincial Key Laboratory of Functional Materials and Applications(Xiamen University of Technology,fma2024003)the National Key R&D Program of China(No.2021YFB3500400)the National Natural Science Foundation of China(Nos.52073286 and 22275185).
文摘Organic-inorganic hybrid metal halide perovskite solar cells(PSCs)have attracted much attention due to their high photoelectric conversion efficiency(PCE)and low cost.The certificated PCE of small active area(below 0.1 cm^(2))device has reached 26.7%[1].However,when considering the scaled-up commercialization of PSCs,an obvious efficiency drop exists for the translation to large-area perovskite submodules(PSMs)with areas more than 200 cm^(2),thus limiting the practical commercialization[2].The major PCE gap between small area cells and large area modules arises the drop of open-circuit voltage(VOC)and fill factor(FF).Formamidinium lead iodide(FAPbI_(3))is now the mostly widely used and highly efficient perovskite composition.However,the photo-active black α-FAPbI_(3) phase will spontaneously transform into photo-inactive yellowδ-FAPbI_(3) phase at room temperature[3].
文摘A CuPc/SiO2 sample is fabricated. Its morphology is characterized by atomic force microscopy, and the electron states are investigated by X-ray photoelectron spectroscopy. In order to investigate these spectra in detail, all of these spectra are normalized to the height of the most intense peak,and each component is fitted with a single Gaussian function. Analysis shows that the O element has great bearing on the electron states and that SiO2 layers produced by spurting technology are better than those produced by oxidation technology.
基金supported by the Natural Science Foundation of Shandong Province(ZR2019PB013)the Natural Science Foundation of Tianjin(19JCZDJC37700)the National Natural Science Foundation of China(21421001 and 21875118)。
文摘To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surface/interface engineering is found to be effective in achieving novel physicochemical properties and synergistic effects in nanomaterials for electrocatalysis.Among various engineering strategies,heteroatom-doping has been regarded as a most promising method to improve the electrocatalytic performance via the regulation of electronic structure of catalysts,and numerous works were reported on the synthesis method and mechanism investigation of heteroatom-doping electrocatalysts,though the heteroatom-doping can only provide limited active sites.Engineering of other defects such as vacancies and edge sites and construction of heterostructure have shown to open up a potential avenue for the development of noble metal-free electrocatalysts.In addition,surface functionalization can attach various molecules onto the surface of materials to easily modify their physical or chemical properties,being as a promising complement or substitute for offering materials with catalytic properties.This paper gives the insights into the diverse strategies of surface/interface engineering of the highefficiency noble metal-free electrocatalysts for energy-related electrochemical reactions.The significant advances are summarized.The unique advantages and mechanisms for specific applications are highlighted.The current challenges and outlook of this growing field are also discussed.
基金supported financially by the Joint Funds of National Natural Science Foundation of China and Guangdong Province(No.U1601216)the National Natural Science Foundation of China(Nos.51602216 and 51472178)+1 种基金Young Elite Scientists Sponsorship Program by CAST(No.2018QNRC001)Tianjin Natural Science Foundation(No.17JCQNJC02100).
文摘Surface/interface engineering plays an important role in improving the performance and economizing the cost and usage of electrocatalysts.In recent years,substantial progress has been achieved in designing and developing highly active electrocatalysts with the deepening understanding of surface and interface enhanced mechanism.In this review,recent development about optimizing the surface and interfacial structure in promoting the electrocatalytic activity of noble-metals and transition metal compounds is presented and the chemical enhancements are also described in detail.The relationship between the surface/interface structures(both atomic and electronic configuration)and the electrochemical behaviors has been discussed.Finally,personal perspectives have been proposed,highlighting the challenges and opportunities for future development in tuning the surface/interface active sites of electrocatalysts.We believe that this timely review will be beneficial to the construction of highly active and durable electrode materials through optimizing surface atomic arrangement and interfacial interaction,which can largely promote the development of next-generation clean energy conversion technologies.
基金financial support from the National Key Research and Development Program of China(2017YFB0102900)
文摘Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60276004 and 60390073） and the Natural Science Foundation of Guangzhou Education Bureau, China （Grant No 2060）. Acknowledgement The author would like to thank Professor J J Shi for detailed and valuable discussion.
文摘The polar interface optical （IO） and surface optical （SO） phonon modes and the corresponding Froehlich electron phonon-interaction Hamiltonian in a freestanding multi-layer wurtzite cylindrical quantum wire （QWR） are derived and studied by employing the transfer matrix method in the dielectric continuum approximation and Loudon＇s uniaxial crystal model. A numerical calculation of a freestanding wurtzite GaN/AlN QWR is performed. The results reveal that for a relatively large azimuthal quantum number m or wave-number kz in the free z-direction, there exist two branches of IO phonon modes localized at the interface, and only one branch of SO mode localized at the surface in the system. The degenerating behaviours of the IO and SO phonon modes in the wurtzite QWR have also been clearly observed for a small kz or m. The limiting frequency properties of the IO and SO modes for large kz and m have been explained reasonably from the mathematical and physical viewpoints. The calculations of electron-phonon coupling functions show that the high-frequency IO phonon branch and SO mode play a more important role in the electron phonon interaction.
文摘The interface and surface properties of nano-hydroxyapatite(n-HA) and poly( 1, 4-phenylene sulfide)-poly (2,4-phenylene sulfide acid)(PPS-PPSA) copolymer composite were investigated. The results show that there are some strong interface combinations of calcium ion (Ca2+ ), car-boxyl (-COO- ) and phosphate radicle ion (PO_4~3- ) between copolymer and n-HA in the composite. The presence of the 2,4-phenylene sulfide acid in copolymer can increase the affinity to n-HA, which causes the formation of chemical bindings between the PPS-PPSA copolymer and n-HA. XRD analysis and IR surface analysis indicate that n-HA is not encapsulated by copolymer but exposed on the surface of the composite, and has same structure and properties with the origi-nal n-HA. The presence of the interface chemical bindings between the PPS-PPSA copolymer and n-HA can increase the content of n-HA in composite but does not cause the decrease of the composite mechanical strength.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11172094 and 11172095)the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-11-0122)the Hunan Provincial Natural Science Foundation for Creative Research Groups,China(Grant No.12JJ7001)
文摘In this paper, we present an analytical solution of the interaction of the nanotube （NT） with a wedge disclination dipole in nanotube-based composites. The corresponding boundary value problem is solved exactly by using complex potential functions. The explicit expression of the force exerted on disclination dipole is given by using the generalized Peach- Koehler formula. As a numerical illustration, both the equilibrium position and the stability of the disclination dipole are evaluated for different material combinations, relative thickness of an NT, surface/interface effects, and the features of the disclination dipole. The results show that as the thickness of the NT layer increases, the NT has a relatively major role in the force acting on the disclination dipole in the NT-based composite. The cooperative effect of surface/interface stresses and the NT becomes considerable as the increase of NT layer thickness. The equilibrium position may occur, even more than one, due to the influences of the surface/interface stress and the NT thickening. The influences of the surface/interface stresses and the thickness of the NT layer on the force are greatly dependent on the disclination angle.
基金Supported by the National Natural Science Foundation of China Under Grant No 61205180the Natural Science Foundation of Hebei Province under Grant No E2014201188+1 种基金the Hebei University Science Funds for Distinguished Young Scholars under Grant No 2012JQ01the Program for Top Young Talents of Hebei Province
文摘Based on the first-principles method, the structural stability and the contribution of point defects such as O, Sr or Ti vacancies on two-dimensional electron gas of n- and p-type LaAlO3/SrTiO3 interfaces are investigated. The results show that O vacancies at p-type interfaces have much lower formation energies, and Sr or Ti vacancies at n-type interfaces are more stable than the ones at p-type interfaces under O-rich conditions. The calculated densities of states indicate that O vacancies act as donors and give a significant compensation to hole carriers, resulting in insulating behavior at p-type interfaces. In contrast, Sr or Ti vacancies tend to trap electrons and behave as acceptors. Sr vacancies are the most stable defects at high oxygen partial pressures, and the Sr vacancies rather than Ti vacancies are responsible for the insulator-metal transition of n-type interface. The calculated results can be helpful to understand the tuned electronic properties of LaAlO3 /SrTiO3 heterointerfaces.
基金the support of the National Natural Science Foundation of China (NSFC) through grants Nos.10032010,10072002,10372004,10525209,10872003 and 10932001the Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD,Grant No.2007B2)+5 种基金Research Fund for the New Teacher Program of the State Education Ministry of China (Grant No.200800011011)Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry of Chinathe support of NSFC (Grants Nos.10772093 and 10732050)the support of NSFC (Nos.11072186,10902081 and 11021202)973-Program (Nos.2007CB936803 and 2010CB631005)973-Program (No.2007CB707702)
文摘This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements, including nanoparticles, nanowires, nanobeams, and nanofilms, and heterogeneous materials containing nanoscale inhomogeneities. It begins with the fundamental formulations of surface mechanics of solids, including the definition of surface stress as a surface excess quantity, the surface constitutive relations, and the surface equilibrium equations. Then, it depicts some theoretical and experimental studies of the mechanical properties of nanostructured elements, as well as the static and dynamic behaviour of cantilever sensors caused by the surface stress which is influenced by adsorption. Afterwards, the article gives a summary of the analytical elasto-static and dynamic solutions of a single as well as multiple inhomogeneities embedded in a matrix with the interface stress prevailing. The effect of surface elasticity on the diffraction of elastic waves is elucidated. Due to the difficulties in the analytical solution of inhomogeneities of complex shapes and configurations, finite element approaches have been developed for heterogeneous materials with the surface stress. Surface stress and surface energy are inherently related to crack propagation and the stress field in the vicinity of crack tips. The solutions of crack prob- lems taking into account surface stress effects are also included. Predicting the effective elastic and plastic responses of heterogeneous materials while taking into account surface and interface stresses has received much attention. The advances in this topic are inevitably delineated. Mechanics of rough surfaces appears to deserve special attention due to its theoretical and practical implications. Some most recent work is reviewed. Finally, some challenges are pointed out. They include the characterization of surfaces and interfaces of real nanomaterials, experimental mea- surements and verification of mechanical parameters of complex surfaces, and the effects of the physical and chemical processes on the surface properties, etc.
文摘This work deals with the influences of nano-heterogeneities in the form of voids/cavities or cracks on the elastic (please confirm which word is correct. effective or elastic? According to the title of paper, I choose elastic.) properties of a host medium. With a relatively large ratio of apparent-surface to volume and particularly strong physical interactions with the surrounding medium at nano-scale, nano-heterogeneities can potentially affect the elastic(effective or elastic?) properties of the parent medium (matrix) containing them in a significant manner. This has been reported by various theoretical and experimental studies, some of them are discussed in the present paper. To describe the positive (reinforcement) or negative (degradation) effect of the nano-heterogeneities from the modeling perspective, it is necessary to take into account the energy of interfaces/surfaces between nano-heterogeneities and the matrix which, by the fact of the relatively large extent of their apparent surface and their strong physical interaction with their neighborhood, can no longer be neglected compared to those of the volume energy. Thus, to account for the effects of interfaces/surfaces in a nanostructured heterogeneous medium, the coherent interface model is considered in the present investigation within a periodic homogenization procedure. In this interface/surface model, the displacement vector is assumed to be continuous across the interface while the stress vector is considered to be discontinuous and satisfying the Laplace-Young equations. To solve these equations coupled to the classical mechanical equilibrium problem, a numerical simulation tool is developed in a two-dimensional (2D) context using the eXtended Finite Element Method (XFEM) and the Level-Set functions. The developed numerical tool is then used to carry out a detailed analysis about the effect of nano-heterogeneities on the overall mechanical properties of a medium. The nano-heterogeneities are present in the medium initially as cylindrical cavities (circular in 2D) before being reduced to plane cracks (line in 2D) by successive flattenings.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50806057 and 10972225, and the Key Laboratory of Mierogravity/CAS for experiments utilizing the drop tower Beijing.
文摘Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic compo- nents with high heat flux in microgravity, and was verified by experiments performed utilizing the drop tower Beijing. Micro-pin-fins with tile dimensions of 50 × （30 μm2 （thickness × height） and the space of 50 μm were fabricated on the chip surface by the dry etching technique. FC-72 was used as the working fluid. Nucleate pool boiling of FC-72 on a smooth surface was also tested for comparison. Unlike much obvious deterioration of heat transfer of nucleate pool boiling on the smooth surface in microgravity, constant heater surface temperature of nucleate pool boiling for the micro-pin-finned surface was observed, even though a large coalesced bubble completely covered the surface under microgravity condition. The performance of high efficient heat transfer on micro-pin-finned surface is independent of the gravity, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary forces.
基金National Natural Science Foundation of China(Nos.12275344,12304132)National Key Research and Development Program of China(No.2022YFA1603901).
文摘BL02U2 of the Shanghai Synchrotron Radiation Facility is a surface diffraction beamline with a photon flux of 5.5×10^(12) photons/s at 10 keV and a beam size of 160µm×80µm at the sample site.It is dedicated to studying surfaces(solid-vacuum,solid-gas)and interfaces(solid-solid,solid-liquid,and liquid-liquid)in nanoscience,condensed matter,and soft matter systems using various surface scattering techniques over an energy range of 4.8-28 keV with transmission and reflection modes.Moreover,BL02U2 has a high energy resolution,high angular resolution,and low beam divergence,which can provide excellent properties for X-ray diffraction experiments,such as grazing incident X-ray diffraction,X-ray reflectivity,crystal truncation rods,and liquid X-ray scattering.Diversity of in situ environments can also be provided for the samples studied.This paper describes the setup of the new beamline and its applications in various fields.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61076011 and 51177134)
文摘6H-SiC （1010） surface and Si （220）/6H-SIC （1010） interface with different stacking sites are investigated using first-principles calculations. Surface energies of 6H-SiC （1010） （case I, case II, and case III） are firstly studied and the surface calculation results show that case II and case III are more stable than case I. Then, the adhesion energies, fracture toughness values, interfacial energies, densities of states, and electronic structures of Si （220）/6H-SIC （1010） interfaces for three stacking models （AM, BM, and CM） are calculated. The CM model has the highest adhesion energy and the lowest interracial energy, suggesting that the CM is stronger and more thermodynamically stable than AM and BM. Densities of states and the total charge densities give evidence that interfacial bonding is formed at the interface and that Si-Si and Si-C are induced due to the hybridization of C-2p and Si-3p. Moreover, the Si-C is much stronger than Si-Si at the interface, implying that the contribution of the interfacial bonding mainly comes from Si-C rather than Si-Si.
文摘In order to restore the degraded ultrasonic C-scan image for testing surfacing inteoface, a method based on support vector regression （SVR） network is proposed. By using the image of a simulating defect, the network is trained and a mapping relationship between the degraded and restored image is founded. The degraded C-scan image of Cu-Steel surfacing inteoface is processed by the trained network and improved image is obtained. The result shows that the method can effectively suppress the noise and deblur the defect edge in the image, and provide technique support for quality and reliability evaluation of the surfacing weld.
基金supported by the Special Project of Shanghai Nano Technology (0852nm02400 and 0752nm012)Shaoxing Science and Technology Commission (2007A21015)+3 种基金Shanghai Rising-Star Program (07QA14026)the National Natural Science Foundation of China (10804072)the Key Fundamental Project of Shanghai (08JC1410400)Shanghai Education Commission (07zz143)
文摘Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.
