Tang Chun, Dávila Lilian P
School of Engineering, University of California, Merced, CA 95343, USA.
Nanotechnology. 2014 Oct 31;25(43):435702. doi: 10.1088/0957-4484/25/43/435702. Epub 2014 Oct 9.
Molecular dynamics simulations of amorphous silica nanowires under tension were analyzed for size and surface stress effects on mechanical properties and for structural modifications via bond angle distributions. Their fracture behavior was also investigated beyond the elastic limit. The Young's moduli of silica nanowires were predicted to be about 75-100 GPa, depending on the nanowire size. The ultimate strength was calculated to be ∼10 GPa, depending on the diameter, which is in excellent agreement with the experiments. The dependence of the Young's modulus on nanowire diameter is explained in terms of surface compressive stress effects. The fracture behavior of nanowires was also found to be influenced by surface compressive stresses. Bond angle distribution analysis of various nanowires reveals significant compressive surface states, as evidenced by the appearance of a secondary peak in the Si-O-Si bond angle distribution at ∼97°, which is absent in bulk silica. The strain rate was found to have a negligible effect on the Young's modulus of the silica nanowires, but it has a critical role in determining their fracture mode.
对非晶态二氧化硅纳米线在拉伸状态下的分子动力学模拟进行了分析，以研究尺寸和表面应力对其力学性能的影响，以及通过键角分布研究结构变化。还研究了其在弹性极限之外的断裂行为。二氧化硅纳米线的杨氏模量预计约为75 - 100 GPa，这取决于纳米线的尺寸。根据直径计算出的极限强度约为10 GPa，这与实验结果非常吻合。杨氏模量对纳米线直径的依赖性可以通过表面压应力效应来解释。还发现纳米线的断裂行为受表面压应力影响。对各种纳米线的键角分布分析揭示了显著的压缩表面状态，这在Si - O - Si键角分布中约97°处出现的二次峰中得到证明，而在块状二氧化硅中不存在此峰。发现应变速率对二氧化硅纳米线的杨氏模量影响可忽略不计，但在确定其断裂模式方面起着关键作用。
