纳米颗粒和纳米柱体的力学行为研究

Nanoparticles and nanopillars are the fundamental building blocks of advanced nanosystems and nanocomposites. Owing to the greately increased ratio of surface area to volume, their mechanical properties like elastic modulus, yield stress and plastic deformation mechanism display evident size dependence, which are clearly distinct from their macroscopic counterparts. In this porject, theoretical analysis,atomic simulation and nanoscale elaborate experiment will be performed to investigate the elastic and plastic deformation of nanoparticles and nanopillars. Based on the surface elasticity and crystal anisotropicity, we will analyze the elastic response of nanoparticles and nanopillars. It is expected to found the dependence of the yield stress on the intrinsic cystalline structure, extrinsic geometry and loading direction. Atomic simulations will be employed to explore the micro-mechanism of plasticity of nanoparticles and nanopillars. We will also investigate the fatigure characteristics of nanoparticles and nanopillars under cycle loading. Based on AFM and STM, the compression of nanoparticles and nanopillars, as well as the fatigure curve, will be measured. These works will be helpful to measure and evaluate the mechanical properties of nanoparticles and nanopillars, and describe their elasti and plastic deformation precisely, thus is of importance to the manufacture and design of reliable and durable nanocomponents and nanosystems.

纳米颗粒和纳米柱体是组装纳米器件和合成纳米材料的基本单元。由于表面所占比例显著增加，纳米颗粒和纳米柱体的弹性模量、屈服应力和塑性变形机制等明显不同于宏观块体材料，表现出显著的尺度相关性。本项目将采用理论分析、分子动力学模拟和微纳米尺度实验相结合的方法来研究纳米颗粒和纳米柱体的弹塑性力学行为。我们将基于表面弹性和晶体各向异性来研究单晶纳米颗粒和纳米柱体的弹性变形。建立纳米颗粒和纳米柱体的屈服应力与晶体结构、外在尺寸和加载方向的定量关系。采用分子动力学模拟方法揭示纳米颗粒和纳米柱体的塑性变形机制。研究周期载荷作用下纳米颗粒和纳米柱体的疲劳特性。利用AFM和STM等开展纳米尺度实验，测试纳米颗粒和纳米柱体的压缩变形过程和疲劳曲线。本项目的开展将能够用于纳米颗粒和纳米柱体力学性能的测试和评估、及其弹塑性力学响应的描述，对纳米器件和系统的设计与制备提供重要的指导意义。

纳米颗粒是组装纳米器件和合成纳米材料的基本单元。由于表面所占比例显著增加，纳米颗粒的弹性模量、屈服应力和塑性变形机制等明显不同于宏观块体材料，表现出显著的尺度相关性。本项目采用理论分析、分子动力学模拟和微纳米尺度实验相结合的方法来研究纳米颗粒的弹塑性力学行为。我们研究了表面能和表面台阶对纳米颗粒弹性压缩的影响，发展了相应的理论模型，能够准确表征纳米颗粒的弹性响应。采用分子动力学模拟揭示了金属纳米颗粒的塑形变形机制和空心硅纳米颗粒的三种典型失效模式。结合尺寸影响和表面形貌，提出了一个理论公式，能够准确预测金纳米颗粒的屈服应力。此外，我们也研究了表面张力对微纳米尺度接触问题的影响等。相关成果能够用于纳米颗粒力学性能的测量和评估、及其弹塑性力学响应的准确描述，对纳米器件和系统的设计与制备提供重要指导。