纳米多孔银力学性能表征分子动力学模拟

纳米多孔金属拥有优异的物理、化学性能,在众多领域中极具应用前景.相关力学性能的认知是实现其功能化应用的重要基础之一.基于分子动力学模拟,以三种拓扑结构(立方体结构、金刚石结构、螺旋体结构)的纳米多孔银为对象,研究了单轴拉伸下的力学响应,探讨了拓扑结构和相对密度与其力学性能的内在联系.仿真结果表明,纳米多孔银的极限强度和杨氏模量随相对密度增大而增大的同时,还紧密地依赖于拓扑结构.其中,金刚石结构与螺旋体结构的模量随相对密度的变化趋势较为相近,而螺旋体结构中螺旋形式的孔棱在受力拉直的过程中抵抗变形,表现出相对较好的塑性.立方体结构中,孔棱分布形式单一,抵抗变形的能力较弱,模量值较低.同一相对密度下,金刚石结构的强度最大,立方体结构次之,螺旋体结构最小.金刚石结构中,交错的孔棱间形成三角骨架结构,具有一定的稳定性,表现出相对较高的强度.

Characterization of nanoporous silver mechanical properties by molecular dynamics simulation

Nanoporous metals (NPMs) have great potential applications in many technological areas, such as catalysis, sensing, actuation, and fuel cells, because of their unique physical and chemical properties. The cognition of related mechanical properties is one of the important bases for achieving functionalized applications. A series of large-scale molecular dynamics (MD) simulations is performed to study the mechanical properties of nanoporous sliver (NPS) under uniaxial tension. Three different topology architectures of NPS, including cube, gyroid and diamond structures, are constructed and investigated. The effects of topology architecture and relative density on the mechanical properties are discussed. The LAMMPS is used to perform MD simulations and the embedded atom method potential is utilized to describe the interatomic interactions. The applied strain rate is 10⁹ s^-1 and the applied strain increment is 0.001 in each loading step. The results show that the plastic properties of NPS mainly depend on those of ligaments and the breakage of NPS mainly occurs in ligament areas. Meanwhile, the gyroid structure has better plasticity than other structures, due to the existence of ligament in spiral form. For one structure, the ultimate strength and the Young's modulus increase with the increase of relative density. Analysis shows that the basic mechanical properties of NPS largely depend on the relative density, similar to those of porous materials. The modulus as a function of relative density displays a power-law relation and the exponents depend on the topology architectures. The exponents of three structures are in a range between 1 and 2, showing that the bending of ligament and the tension of ligament are both included during the deformation. The variation trends of modulus of diamond and gyroid structures are similar to the variation of relative density, whose possible reason is that diamond and gyroid structures are both constructed by triply periodic minimal surfaces. With the same relative density, the modulus of diamond structure is in good agreement with that of gyroid structure, and the modulus of cube structure is the minimum. The strength shows a linear relation with the relative density, indicating that the yielding behavior of NPS is dominated by the axial yielding of ligament. When three types of NPSs have the same relative density, the strength of diamond structure is the maximum, cube structure second, and gyroid structure is the minimum. In diamond structure NPS, the structure of triangular framework is formed between ligaments, resulting in a relatively higher strength. The present study will provide an atomistic insight into the understanding of deformation mechanisms of nanoporous metals, and it will provide data support for designing NPMs with optimal mechanical properties by controlling geometric structure.