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采用非平衡分子动力学方法研究了300K和1000K时(5,5)碳纳米管热导率随长度的变化.在室温下,碳纳米管长度小于40nm时热导率与长度呈线性关系,此时导热处于弹道输运阶段,单位面积弹道热导为5.88×109Wm-2K-1.随着碳纳米管长度的增加,其热导率逐渐增加,但增加速度随长度逐渐减小,此时导热处于弹道—扩散输运阶段,并随长度的增加从以弹道输运为主向以扩散输运为主转变.长度大于10μm时由于弹道输运可以忽略,导热近似达到完全扩散输运.模拟发现碳纳米管热导率随长度变化的幂指数随着碳纳米管长度的增加而成衰减指数的规律减小,与理想一维材料不同,在热力学极限下碳纳米管导热会出现完全扩散输运,其热导率将收敛到有限值.
The thermal conductivity of (5,5) carbon nanotubes at 300K and 1000K was investigated by using the non-equilibrium molecular dynamics method. At room temperature, there was a linear relationship between the thermal conductivity and the length of carbon nanotubes at a length of less than 40 nm When the thermal conductivity is in the ballistic transport stage, the thermal conductivity per unit area is 5.88 × 109Wm-2K-1. As the length of the carbon nanotubes increases, the thermal conductivity gradually increases, but the increasing speed decreases with the length. At this time, the thermal conductivity In the period of ballistic-diffusive transport, with the increase of the length, it mainly takes the ballistic transport as the predominant diffusion transport, and when it is longer than 10μm, it can be neglected due to the ballistic transport, and the thermal conductivity approximately reaches the complete diffusion transport. The thermal exponent of thermal conductivity of CNTs decreases with the length of carbon nanotubes and decreases with the increase of carbon nanotube length. Different from the ideal one-dimensional materials, thermal conductivity of CNTs will be completely diffused and transported , Its thermal conductivity will converge to a finite value.