碳纳米管纱在应力下的压阻效应:现象和影响因素

摘要

碳纳米管因机械应力敏感特性而成为传感器的理想材料.单原子层厚度的石墨烯片卷曲而成的单壁碳纳米管具有大约1 nm的管径.碳纳米管纺丝形成纱,使其能够用于结构组份中.本文研究了碳纳米管纱的几何尺寸、力学性能和准静态应力加载速率对其压阻效应的影响.应力加载速率影响碳纳米管纱的失效机理和机电特性.高应力加载速率导致拉伸强度的增加和正压阻效应,而低应力加载速率引起较高的应力失效与负压阻效应.碳纳米管纱的压阻传感器系数随应力加载速率基本不变,但其对于应力水平和碳纳米管纱的几何尺寸具有高度依赖性.作为传感器所需的线性压阻关系在高应力加载速率下相关系数为0.995,而在低应力加载速率下相关系数只有0.832.%Carbon nanotubes(CNTs) are inherently sensitive to mechanical strain,making them ideal for sensing in composites. Because of this they were purposefully spun into macroscopic yarns to permit their utilization in structural components. This experi-mental study aims to determine the effect of quasi-static strain rate, mechanical properties and geometry of the CNT yarns on their piezoresistivity. Strain rates affect the failure mechanisms and electromechanical properties of CNT yarns, with high strain rates showing increased tensile strength and a positive piezoresistivity with low strain rates favoring a higher strain-to-failure and a negative piezoresistivity. The sensitivity or gauge factor (GF) of the free CNT yarn remains relatively unchanged with varying strain rates (GFs between 0.12-0.20 at 2.5% strain) but is strongly dependent on the strain level(GFs:0.2,0.5,0.4 and 0.2 at 0.5,1,1. 5 and 2.5% strains,respectively) and diameter(GFs:0.16 and 0.29 at 3% strain for ~25 μm and 50 μm diameter yarns,respec-tively). The linearity needed for a robust sensor is favored at higher strain rates with correlation coefficients more than 0.995 com-pared to values less than 0.832 at lower strain rates.