Transition of thermal rectification in silicon nanocones
Transition of thermal rectification in silicon nanocones
复制标题
硅纳米锥中热整流的转变
DOI：
10.1016/j.applthermaleng.2016.03.083
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发表时间：
2016
影响因子：
6.4
通讯作者：
Zhang Shengbai
中科院分区：
文献类型：
--
作者：
Zhang Zhongwei;Chen Yuanping;Xie Yuee;Zhang Shengbai
目前对热整流的理解认为，衡量纳米结构两端之间相对热通量的整流比（R）由其几何不对称性决定。不对称性越高，R值越高。然而，用非平衡态分子动力学方法计算了Si纳米锥中的热输运，结果表明这种理解可能是错误的，R可能并不随几何不对称性单调增加.相反，当纳米锥的顶角（θ）约为90°时，R表现出急剧的反转。换句话说，当θ>90°时，R减小，而不是增加。我们表明，这种异常的行为起源于热输运机制的变化。在小θs时，声子输运主要由局域模控制，特别是从顶端到底部的输运。当θs较大时，这些局域模消失，导致R减小。
Current understanding of thermal rectification asserts that the rectification ratio (R), which measures the relative heat flux between two ends of a nanostructure, is determined by its geometric asymmetry. The higher the asymmetry, the higher theR. However, by using nonequilibrium molecular dynamics method we have calculated thermal transport in Si nanocones as an example, the results show that such an understanding may be incorrect andRmay not increase monotonically with geometric asymmetry. Rather,Rexhibits a sharp reverse when the vertex angle (θ) of the nanocone is approximately 90°. In other words, whenθ>90°,Rdecreases, rather than increasing. We show that this abnormal behavior is originated from a change in the thermal transport mechanism. At smallθs, phonon transport is dominated by localized modes, especially for transport from tip to bottom. At largeθs, however, these localized modes disappear, leading toRdecrease.