不同长径比纳米银线合成机理及变形机理

Synthesis Mechanism and Deformation Mechanism of Silver Nanowires with Different Aspect Ratios

摘要:

采用液相还原法，通过调节聚乙烯吡咯烷酮（PVP）摩尔浓度制备不同长径比的纳米银线。采用X射线衍射仪、扫描电子显微镜、紫外-可见光分光光度计、同步热分析仪及透射电子显微镜对纳米银线的物相组成、微观形貌、光吸收性能、热分解、晶体结构进行表征，并使用分子动力学模拟单晶纳米银线的拉伸和熔化过程。结果表明：纳米银线主要由面心立方银构成。PVP与AgNO₃的摩尔比由1.5变为7.5，纳米银线直径先减小后增加；当摩尔比为6.0时，纳米银线直径最小，为77.7 nm。纳米银线直径由106.1 nm减小为77.7 nm，熔化温度随之减小，最低为281.2 ℃。单晶纳米银线长径比由6变为72时，屈服强度逐渐由0.63 GPa提升至0.83 GPa。单晶纳米银线熔化温度随长径比增加而减小，由690 K变为657 K。PVP与AgNO₃的摩尔比为6.0是合成银线的最佳条件，长径比大的纳米银线具有良好的抵抗变形的能力。

Abstract:

Silver nanowires with different aspect ratios were prepared by adjusting the molar content of polyvinylpyrrolidone (PVP) through the liquid-phase reduction method. X-ray diffractometer, scanning electron microscope, UV-Vis spectrophotometer, simultaneous thermal analyzer, and transmission electron microscope were used to characterize the phase composition, microstructure, light absorption properties, thermal decomposition, and crystal structures of the silver nanowires, and the molecular dynamics was used to simulate the stretching and melting processes of single-crystal silver nanowires. Result shows that the silver nanowires are mainly composed of face-centered cubic silver. When the molar ratio of PVP to AgNO₃ changes from 1.5 to 7.5, the diameter of silver nanowires firstly decreases and then increases, and the minimum diameter of nanowires is 77.7 nm when the molar ratio is 6.0. With decreasing the diameter of silver nanowires from 106.1 nm to 77.7 nm, the melting temperature is decreased, and the lowest melting temperature is 281.2 °C. The yield strength is gradually increased from 0.63 GPa to 0.83 GPa with increasing the aspect ratios of silver nanowires from 6 to 72. The melting temperature of single-crystal silver nanowires is decreased from 690 K to 657 K with increasing the aspect ratio. Therefore, the molar ratio of 6.0 is the optimal condition to synthesize silver nanowires, and the silver nanowires with a large aspect ratio have good resistance to deformation.