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中国物理学会期刊

碳纳米管和碳化硅纳米管热导率的分子动力学研究

CSTR: 32037.14.aps.71.20210969

Molecular dynamics study of thermal conductivity of carbon nanotubes and silicon carbide nanotubes

CSTR: 32037.14.aps.71.20210969
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  • 采用Tersoff势测试和研究了反向非平衡分子动力学中的Müller-Plathe法和Jund法在一维纳米管热传导中的应用. 在相同的模拟步数中, Müller-Plathe法可以得到很好的结果, 热导率在交换频率大于50时对参数的选择并不敏感. 然而, Jund法并不能得到良好的线性温度梯度, 其热导率在一定程度上依赖于选择的热流大小. 在此基础上, 运用Müller-Plathe法进一步研究了碳纳米管和碳化硅纳米管的长度、直径和温度对热导率的影响. 结果表明, 无论是碳纳米管还是碳化硅纳米管, 其长度、直径和温度对热导率的影响是一致的. 只要长度增加, 纳米管的热导率相应增大, 但增长速率不断降低. 直径对热导率的影响很大程度上还取决于温度, 在高温时, 直径对热导率几乎没有影响. 除此之外, 纳米管的热导率随着温度的增加总体上也是不断降低的, 但峰值现象的出现还受纳米管长度的影响.

     

    In this paper, the application of Muller-Plathe method and Jund method in reverse nonequilibrium molecular dynamics to the heat conduction of one-dimensional nanotubes are tested and studied. The results show that the Jund method cannot obtain a good linear temperature gradient and its thermal conductivity is also dependent on the choice of heat flux. When the exchange frequency is 50, the thermal conductivity obtained by the Muller-Plathe method converges to a stable value. This method can be well applied to the study of thermal conductivity of nanotubes. The Muller-Plathe method is a good option when the number of atoms exchanged is 1 and the exchange frequency is 100. On this basis, we further investigate the effect of length, diameter and temperature of carbon nanotubes and silicon carbide nanotubes on the thermal conductivity. The thermal conductivity of carbon nanotubes is obviously higher than that of silicon carbide nanotubes, and their effects of length, diameter and temperature on the thermal conductivity are consistent. The thermal conductivity of nanotubes increases with the rise of temperature, but the increase rate decreases and the length dependence also weakens. Therefore, when carbon nanotubes and silicon carbide nanotubes reach certain lengths, their values of thermal conductivity will converge and no longer change with length, which is completely consistent with the results of previous studies. Comparing with carbon nanotubes, the convergence rate of thermal conductivity of SiC nanotubes is significantly lower. When the temperature is low, the diameter has a certain effect on the thermal conductivity; however, with the increase of temperature, the diameter has almost no effect on the thermal conductivity at high temperature. The effect of temperature on the thermal conductivity of nanotubes shows that the thermal conductivity of nanotubes generally decreases with the rise of temperature, but the occurrence of the peak phenomenon is also affected by the length of nanotubes. When the length of carbon nanotubes is 10 nm, the influence of temperature and diameter on the thermal conductivity are irregular. However, when the length of carbon nanotubes is 100 nm, the thermal conductivity of carbon nanotubes decreases continuously with the rise of temperature, and there occurs no peak phenomenon. Besides, when the tube length is 10 nm, the peak of SiC nanotubes appears at about 100 K. However, when the tube length is 100 nm, the thermal conductivity of SiC nanotubes decreases with the rise of temperature, but no peak phenomenon occurs.

     

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