摘要
最近的实验研究表明,一维冰纳米线具有与体相冰截然不同的力学性质,但其微观机理尚不明晰.本文采用分子动力学模拟研究了冰纳米线拉伸力学性质及其微观结构演化.结果表明,冰纳米线的弹性极限和最大弹性应变分别可达0.93 GPa和10.32％.冰纳米线发生断裂后,其断裂区域冰晶格产生大量融化,导致该区域具有与非断裂区域明显不同的氢键结构.此外,相较于体相冰,冰纳米线对温度和应变率的变化更加敏感,其力学性能随着温度的升高或应变率的下降而显著降低.不同取向的冰纳米线具有不同的失效方式,且[0001]取向的冰纳米线具有最强的力学性能.
Abstract
In recent years,human activities in sea ice-covered regions have frequently confronted serious challenges with the development of marine transportation,polar exploration,and other related fields.Therefore,the structural and mechanical properties of ice have become increasingly important.Under external forces,bulk ice(characterized by macroscopic dimensions in all three directions)typically exhibits brittle fracture,and experiments have demonstrated that its maximum strain rarely exceeds 0.3％(ranging from 100 to 260 K).However,in 2021,Xu and colleagues successfully synthesized one-dimensional single-crystal ice nanowires with diameters in the nanometer range and a near-perfect internal structure.Based on bending tests,they observed an impressive elastic strain of approximately 11％,which approaches the theoretical limit for ice(ranging from 14％to 17％).Furthermore,these nanowires possess a uniform surface with minimal waveguide loss,presenting potential applications in optical signal transmission and sensing.Nonetheless,despite their promising potential,research on these novel ice nanowires remains limited.Accurate characterization of their nanoscale microstructures poses a challenge for experimental techniques,leaving uncertainties in understanding their microscopic structure and mechanical behavior during tensile deformation.To bridge this gap,we employed molecular dynamics simulations,which can provide atomic and molecular-level insights into system structures and properties,to investigate the mechanical properties of ice nanowires under tensile loading.In this study,we specifically simulated an ice nanowire with a radius of 3 nm at 150 K.Our findings revealed a linear relationship between stress and strain in the initial stage,with an elastic limit and maximum elastic strain of 0.93 GPa and 10.32％,respectively.Upon further straining,the nanowire fractured,accompanied by significant lattice melting in the fracture region,resulting in distinct hydrogen bonding changes as compared to the non-fractured zone.Moreover,our simulations indicated that the mechanical properties of ice nanowires,including elastic limit,maximum elastic strain,Young's modulus,and Poisson's ratio,all decrease with increasing temperature.Compared to bulk ice,ice nanowires are more sensitive to temperature changes.This is because there is a melting layer at the edges of ice nanowires.As the temperature rises,the number of melting water molecules at the edges increases,further reducing the mechanical properties of the ice nanowires.Additionally,as the strain rate increases,the elastic limit and maximum elastic strain increase.Furthermore,we found distinct failure modes for nanowires with different orientations,with the[0001]orientation exhibiting the strongest mechanical performance.As microfibers,ice nanowires can find applications in optical sensing.For practical use,their properties may be affected by applying tensile loads.This work significantly expands the understanding of the structural and mechanical properties of ices,particularly ice nanowires.Moreover,the present findings provide a solid theoretical foundation for further exploration and application of ice nanowires,paving the way for their potential utilization in various fields.
维普
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