Department of Mechanical Engineering & Engineering Science, University of North Carolina at Charlotte, Charlotte, NC 28223, United States of America.
Nanotechnology. 2020 Jan 17;31(3):035705. doi: 10.1088/1361-6528/ab4834. Epub 2019 Sep 26.
Reverse nonequilibrium molecular dynamics (RNEMD) is employed to study the phononic thermal transport properties of CN nanotubes. We study the effect of nanotube length and diameter on the thermal conductivity and investigate the phonon transport transition from ballistic to diffusive regime in CN nanotubes. It is found that the thermal conductivity of CN nanotubes is significantly lower than those of carbon nanotubes across the entire ballistic-diffusive range. In addition, significantly lower ballistic to diffusive transition length (72-80 nm) is observed in CN nanotubes compared to carbon nanotubes. The inspection of phonon dispersion curves shows that carbon nanotubes have stiffer acoustic modes than CN nanotubes which results in lower group velocities for CN nanotubes. Due to the presence of nitrogen atoms, the phonon mean free paths and relaxation times of CN nanotubes are shorter than those of the carbon nanotubes. The combined effect of lower group velocities and relaxation times leads to the lower thermal conductivity of CN nanotubes.
采用反向非平衡分子动力学（RNEMD）方法研究了 CN 纳米管的声子热输运性质。我们研究了纳米管长度和直径对热导率的影响，并研究了 CN 纳米管中从弹道到扩散区的声子输运转变。结果表明，在整个弹道-扩散范围内，CN 纳米管的热导率明显低于碳纳米管。此外，与碳纳米管相比，CN 纳米管中观察到的弹道到扩散的转变长度明显更短（72-80nm）。声子色散曲线的分析表明，碳纳米管的声学模比 CN 纳米管更硬，导致 CN 纳米管的群速度更低。由于氮原子的存在，CN 纳米管的声子平均自由程和弛豫时间比碳纳米管短。较低的群速度和弛豫时间的综合影响导致 CN 纳米管的热导率较低。
