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surface diffusion on Stressed Solid surface

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Communications in Computational Physics 2007年第1期2卷 73-86页

作者： Xiaofan Li Qing Nie Department of Applied Mathematics Illinois Institute of TechnologyChicagoIL 60616USA Center for Mathematical and Computational Biology Department of MathematicsUniversity of CaliforniaIrvineCA 92697-3875USA

The surface diffusion of an axi-symmetric solid,a whisker,subject to applied uniaxial stress,is studied numerically based on a new boundary integral formulation for periodic stress configurations.An efficient semi-implicit time-stepping scheme is developed to treat the serve stiffness due to high-order derivatives.When the initial perturbation is small the effect of the stress on the motion of the whisker is found to agree with the linear stability analysis.Numerical simulations of a fully nonlinear case are also presented,and a potential break-up of the whisker is observed.

关键词： surface diffusion elastic stress boundary integral method semi-implicit scheme.

Numerical Simulation on Intergranular Microcracks in Interconnect Lines Due to surface diffusion Induced by Stress-,Electro-and Thermo-migration

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第6期36卷 1004-1017页

作者： ZHOU Linyong HUANG Peizhen State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics

Based on the weak formulation for combined surface diffusion and evaporation-condensation,a governing equation of the finite element is derived for simulating the evolution of intergranular microcracks in copper interconnects induced simultaneously by stressmigration,electromigration and thermomigration.Unlike previously published works,the effect of thermomigration is considered.The results show that thermomigration can contribute to the microcrack splitting and accelerate the drifting process along the direction of the electric field.The evolution of the intergranular microcracks depends on the mechanical stress field,the temperature gradient field,the electric field,the initial aspect ratio and the linewidth.And there exists a critical electric fieldχ_c,a critical stress field■,a critical aspect ratioβ_c and a critical linewidth■.When■or■,the intergranular microcrack will split into two or three small intergranular microcracks.Otherwise,the microcrack will evolve into a stable shape as it migrates along the interconnect line.The critical stress field,the critical electric field and the critical aspect ratio decrease with a decrease in the linewidth,and the critical linewidth increases with an increase in the electric field and the aspect ratio.The increase of the stress field,the electric field or the aspect ratio and the decrease of the linewidth are not only beneficial for the intergranular microcrack to split but also accelerate the microcrack splitting process.

关键词： stressmigration electromigration thermomigration surface diffusion finite element method intergranular microcrack

First-principles study of diffusion behaviour of point defects in the O-terminated (0001) surface in wurtzite ZnO

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Chinese Physics B 2010年第1期19卷 257-261页

作者：黄贵洋王崇愚王建涛 Department of Physics Tsinghua University Institute of Physics Chinese Academy of Sciences

A detailed first-principles study of the diffusion behaviour of point defects in the O-terminated （0001） surface in wnrtzite ZnO was performed. The 0 vacancy and interstitial are found to diffuse much more easily in surface than in bulk. The Zn vacancy has a similar migration barrier for both bulk and surface, but has much smaller barrier for the diffuse-in process. The Zn interstitial is difficult to diffuse in the surface directly, but it can diffuse into the bulk relatively easily. Specific values of corresponding migration barriers are obtained.

关键词： semiconductor surface diffusion first-principles calculation

A Kinetic Monte Carlo Approach for Self-diffusion of Pt Atom Clusters on a Pt(111)surface

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Communications in Computational Physics 2011年第9期10卷 920-939页

作者： R.Deak Z.Neda P.B.Barna Department of Theoretical and Computational Physics Babes-Bolyai UniversityRO-400084Cluj-NapocaRomania Department of Materials Physics Eotvos Lorand UniversityH-1117BudapestHungary KFKI-MFA Research Institute for Technical Physics and Materials ScienceH-1525BudapestHungary.

A lattice Kinetic Monte Carlo(KMC)approach is considered to study the statistical properties of the diffusion of Pt atom clusters on a Pt(111)surface.The interatomic potential experienced by the diffusing atoms is calculated by the embedded atom method and the hopping barrier for the allowed atomic movements are calculated using the Nudged Elastic Band method.The diffusion coefficient is computed for various cluster sizes and system temperatures.The obtained results are in agreement with the ones obtained in previous experimental and theoretical works.A simple scaling argument is proposed for the size dependence of the diffusion coefficient’s prefactor.A detailed statistical analysis of the event by event KMC dynamics reveals two important and co-existing mechanisms for the diffusion of the cluster’s center of mass.At low temperatures(below T=400K)the dominating mechanism responsible for the displacement of the cluster’s center of mass is the periphery(or edge)diffusion of the atoms.At high temperatures(above T=800K)the dissociation and recombination of the clusters becomes more and more important.

关键词： Kinetic Monte Carlo methods surface diffusion diffusion coefficient

Evolution of stellated gold nanoparticles:New conceptual insights into controlling the surface processes

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Nano Research 2022年第2期15卷 1260-1268页

作者： Gurvinder Singh Hesamodin Jami Pooria Lesani Shubhayan B.hattacharya Yogambha Ramaswamy Prem BBisht Hala Zreiqat ARC Centre for Innovative BioEngineering Tissue Engineering and Biomaterials Research UnitSydney Nano Institute and the School oj Biomedical EngineeringThe University of SydneyNSW 2008Australia Department of Physics Indian Institute of Technology MadrasChennaiIndia

Understanding the surface processes(deposition and surface diffusion)that occur at or close to the surface of growing nanoparticles is important for fabricating reproducibly stellated or branched gold nanoparticles with precise control over arm length and spatial orientation of arms around the core.By employing a simple seed-mediated strategy,we investigate the key synthetic variables for precise tuning of in situ surface processes(competition between the deposition and surface diffusion).These variables include the reduction rate of a reaction,the packing density of molecules/ions on the high surface energy facets,and temperature.As a result,the thermodynamically stabilized nanoparticles(cuboctahedron and truncated cube)and kinetic products(cube,concave cube,octapod,stellated octahedron,and rhombic dodecahedron)in different sizes with high quantitative shape yield(>80%)can be obtained depending on the reduction rate of reaction and the packing density of molecules/ions.With computer simulation,we studied the stability of stellated(branched structure)and non-stellated(non-branched structure)gold nanoparticles at high temperature.We construct a morphology phase diagram by varying different synthetic parameters,illustrating the formation of both stellated and non-stellated gold nanoparticles in a range of reaction conditions.The stellated gold nanoparticles display shape-dependent optical properties and can be self-assembled into highly ordered superstructures to achieve an enhanced plasmonic response.Our strategy can be applied to other metal systems,allowing for the rational design of advanced new stellated metal nanoparticles with fascinating symmetry dependent plasmonic,catalytic,and electronic properties for technological applications.

关键词： surface diffusion shape control stellated nanoparticles self-assembly nanoplasmonics octapod stellated octahedron

Morphological transformation of elongated MnS inclusions in non-quenched and tempered steel during isothermal heating

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Journal of Iron and Steel Research(International) 2023年第3期30卷 525-536页

作者： Jun-yu Liu Cheng-song Liu Rui-juan Bai Wei Wang Qing-bo Wang Hua Zhang Hong-wei Ni The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan 430081HubeiChina Henan Jiyuan Iron&Steel(Group)Co. Ltd.Jiyuan 459000HenanChina

Elongated MnS inclusions in rolled non-quenched and tempered steel tend to cause the mechanical anisotropy of steel,deteriorate the mechanical properties and degrade the quality and service life of the steel products.To reveal the mechanisms of morphological transformation of strip-shaped MnS inclusions during isothermal heating,the effects of heat treatment time and temperature on the morphology,number density and size distribution of elongated MnS inclusions were systematically studied and discussed.A diffusion couple experiment was also conducted to clarify the diffusion mode of MnS inclusions.The experimental results showed that with the increase in isothermal heating time(from 0 to 10 h at 1473 K)and temperature(from 1173 to 1573 K for 3.0 h),the number density and average aspect ratio of MnS inclusions generally showed an increase and decrease trend,respectively,while the area fraction remained stable and only slightly fluctuated around 0.4%.In the diffusion couple,after the isothermal heating at 1473 K for 3.0 h,the elements Mn and S in the steel near the steel-MnS interface were very stable without any concentration gradient.The morphology change sequence of the elongated MnS inclusions in the rolled non-quenched and tempered steel during the isothermal heating was strip→cylinderization→spindle→spheroidization.Relationship between the diameter of MnS inclusion and the spacing between two MnS inclusions after splitting,and the fitting goodness of different n values under different experimental time and temperature confirmed that the driving force for the transformation of MnS inclusions during the isothermal heating was surface diffusion,instead of volume diffusion.

关键词： Non-quenched and tempered steel MnS inclusion Isothermal heating surface diffusion Morphological transformation

Electrochemical hydrogen-storage capacity of graphene can achieve a carbon-hydrogen atomic ratio of 1:1

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Science China Chemistry 2022年第2期65卷 318-321页

作者： Quanfeng He Lanping Zeng Lianhuan Han Juan Peng Matthew M.Sartin Yuan-Zhi Tan Dongping Zhan Zhong-Qun Tian State Key Laboratory of Physical Chemistry of Solid surfaces Fujian Science&Technology Innovation Laboratory for Energy Materials of ChinaEngineering Research Center of Electrochemical Technologies of Ministry of EducationGraphene Industry and Engineering Research InstituteDepartment of ChemistryCollege of Chemistry and Chemical EngineeringDepartment of Mechanical and Electrical EngineeringSchool of Aerospace EngineeringXiamen UniversityXiamen 361005China Department of Chemistry College of Chemistry and Chemical EngineeringNingxia UniversityYinchuan 750021China

As a promising hydrogen-storage material,graphene is expected to have a theoretical capacity of 7.7 wt%,which means a carbon-hydrogen atomic ratio of 1:1.However,it has not been demonstrated yet by experiment,and the aim of the U.S.Department of Energy is to achieve 5.5 wt%in 2025.We designed a spatially-confined electrochemical system and found that the storage capacity of hydrogen adatoms on single layer graphene(SLG)is as high as 7.3 wt%,which indicates a carbon-hydrogen atomic ratio of 1:1 by considering the sp^(3) defects of SLG.First,SLG was deposited on a large-area polycrystalline platinum(Pt)foil by chemical vapor deposition(CVD);then,a micropipette with reference electrode,counter electrode and electrolyte solution inside was impacted on the SLG/Pt foil(the working electrode)to construct the spatially-confined electrochemical system.The SLG-uncovered Pt atoms act as the catalytic sites to convert protons(H^(+))to hydrogen adatoms(H_(ad)),which then spill over and are chemically adsorbed on SLG through surface diffusion during the cathodic scan.Because the electrode processes are reversible,the H_(ad) amount can be measured by the anodic stripping charge.This is the first experimental evidence for the theoretically expected hydrogen-storage capacity on graphene at ambient environment,especially by using H+rather than hydrogen gas(H_(2))as the hydrogen source,which is of significance for the practical utilization of hydrogen energy.

关键词： graphene hydrogen storage surface electrochemistry adsorption desorption spillover surface diffusion

AN ENERGY-STABLE PARAMETRICFINITE ELEMENT METHOD FOR SIMULATING SOLID-STATE DEWETTING PROBLEMS INTHREE DIMENSIONS

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Journal of Computational Mathematics 2023年第4期41卷 771-796页

作者： Weizhu Bao Quan Zhao Department of Mathematics National University of SingaporeSingapore119076

We propose an accurate and energy-stable parametric finite element method for solving the sharp-interface continuum model of solid-state dewetting in three-dimensional space.The model describes the motion of the film/vapor interface with contact line migration and is governed by the surface diffusion equation with proper boundary conditions at the contact line.We present a weak formulation for the problem,in which the contact angle condition is weakly enforced.By using piecewise linear elements in space and backward Euler method in time,we then discretize the formulation to obtain a parametric finite element approximation,where the interface and its contact line are evolved simultaneously.The resulting numerical method is shown to be well-posed and unconditionally energystable.Furthermore,the numerical method is generalized to the case of anisotropic surface energies in the Riemannian metric form.Numerical results are reported to show the convergence and efficiency of the proposed numerical method as well as the anisotropic effects on the morphological evolution of thin films in solid-state dewetting.

关键词： Solid-state dewetting surface diffusion Contact line migration Contact angle Parametric finite element method Anisotropic surface energy

Deterministic Synthesis of Pd Nanocrystals Enclosed by High-Index Facets and Their Enhanced Activity toward Formic Acid Oxidation

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Precision Chemistry

Precision Chemistry 2023年第6期1卷 372-381页

作者： Maochang Liu Siyu Zhou Sang-Il Choi Younan Xia The Wallace H.Coulter Department of Biomedical Engineering Georgia Institute of Technology and Emory UniversityAtlantaGeorgia 30332United States International Research Center for Renewable Energy State Key Laboratory of Multiphase FlowXi’an Jiaotong UniversityXi’anShanxi 710049P.R.China School of Chemical and Biomolecular Engineering Georgia Institute of TechnologyAtlantaGeorgia 30332United States School of Chemistry and Biochemistry and School of Chemical and Biomolecular Engineering Georgia Institute of TechnologyAtlantaGeorgia 30332United States

Noble-metal nanocrystals enclosed by high-index facets are of growing interest due to their enhanced catalytic performance in a variety of reactions.Herein,we report the deterministic synthesis of Pd nanocrystals encased by high-index facets by controlling the rate of deposition(V_(deposition))relative to that of surface diffusion(V_(diffusion)).For octahedral seeds with truncated corners,a reduction rate(and thus deposition rate)faster than that of surface diffusion(i.e.,V_(deposition)/V_(diffusion)>1)led to the formation of concave trisoctahedra(TOH)with high-index facets.When the reduction was slowed down,in contrast,surface diffusion dominated the growth pathway.In the case of V_(deposition)/V_(diffusion)≈1,truncated octahedra with enlarged sizes were produced.When the reduction rate was between these two extremes,we obtained concave tetrahexahedra(THH)without or with truncation.Similar growth patterns were also observed for the cuboctahedral seeds.When the Pd octahedra,concave TOH,and concave THH were tested for electrocatalyzing the formic acid oxidation(FAO)reaction,those with high-index facets were advantageous over the conventional Pd octahedra enclosed by{111}facets.This work not only contributes to the understanding of surface diffusion and its role in nanocrystal growth but also offers a general protocol for the synthesis of nanocrystals enclosed by high-index facets.

关键词： palladium surface diffusion high-index facet unconventional morphology kinetic control