SWCNT森林导热系数的应变工程研究
Strain Engineering for Thermal Conductivity of SWCNT Forests
摘要：
我们进行经典的分子动力学模拟，以调查的单壁碳纳米管（SWCNT）森林，其中单壁碳纳米管是紧密排列和平行于彼此的热导率的机械压缩效果。我们发现，热传导率可以线性增加压缩之前屈曲的单壁碳纳米管森林，但热传导率迅速下降，进一步增加压缩后屈曲森林。我们的声子模式分析表明，在屈曲之前，管间界面的光滑性保持在压缩过程中，和管间范德华相互作用的压缩被加强。因此，扭曲状模式（良好的热载体）被很好地保留，并且其群速度通过增加压缩而增加，从而导致热导率的增强。屈曲现象将单壁碳纳米管的圆形截面改变为椭圆形，这在管间界面处引起用于扭转运动的有效粗糙度。因此，在椭圆形单壁碳纳米管中，径向呼吸模式（差的热载体）成为最有利的运动，而不是扭曲状模式，导致导热率的快速降低，并在屈曲后进一步增加压缩。
英文摘要：
We perform classical molecular dynamics simulations to investigate the mechanical compression effect on the thermal conductivity of the single-walled carbon nanotube (SWCNT) forest, in which SWCNTs are closely aligned and parallel with each other. We find that the thermal conductivity can be linearly enhanced by increasing compression before the buckling of SWCNT forests, but the thermal conductivity decreases quickly with further increasing compression after the forest is buckled. Our phonon mode analysis reveals that, before buckling, the smoothness of the inter-tube interface is maintained during compression, and the inter-tube van der Waals interaction is strengthened by the compression. Consequently, the twisting-like mode (good heat carrier) is well preserved and its group velocity is increased by increasing compression, resulting in the enhancement of the thermal conductivity. The buckling phenomenon changes the circular cross section of the SWCNT into ellipse, which causes effective roughness at the inter-tube interface for the twisting motion. As a result, in ellipse SWCNTs, the radial breathing mode (poor heat carrier) becomes the most favorable motion instead of the twisting-like mode, leading to the quick decrease of the thermal conductivity with further increasing compression after buckling.
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