金纳米颗粒烧结的分子动力学模拟

采用分子动力学模拟方法研究了不同尺寸Au纳米颗粒在烧结过程中晶型转变及烧结颈长大机制.研究发现纳米颗粒的烧结颈生长主要分为两个阶段：初始烧结颈的快速形成阶段和烧结颈的稳定长大阶段.不同尺寸纳米颗粒烧结过程中烧结颈长大的主要机制不同：当颗粒尺寸为4 nm时，原子迁移主要受晶界（或位错）滑移、表面扩散和黏性流动控制；当尺寸在6nm左右时，原子迁移主要受晶界扩散、表面扩散和黏性流动控制；当颗粒尺寸为9 nm时，原子迁移主要受晶界扩散和表面扩散控制.烧结过程中Au颗粒的fcc结构会向无定形结构转变.此外，小尺寸的纳米颗粒在烧结过程中由于位错或晶界滑移、原子的黏性流动等因素会形成hcp结构.

Molecular dynamics simulation for the sintering process of Au nanoparticles

The sintering process of gold nanoparticles was investigated using molecular dynamics simulation, and the detailed crystal structure transformation and neck growth mechanisms were identified and analyzed for different particle sizes. It is found that the coalescence of two nanoparticles experiences two stages, which are the initial rapid neck formation and stable neck growth. Simulation results show that different particle sizes lead to different neck growth mechanisms. When the particle size is 4 nm, the major neck growth mechanisms are grain-boundary/dislocation slid, surface diffusion, and viscous flow. For the particles with the size of about 6 nm, the major neck growth mechanisms are grain-boundary diffusion, surface diffusion, and viscous flow. But when the particle size is 9 nm, the major neck growth mechanisms are grain-boundary diffusion and surface diffusion. During the sintering process, the fcc structure of the particles transforms to amorphous structure gradually. Besides, the hcp crystal structure forms in the small sized particles because of grain-boundary slid or viscous flow.