Ni／Al层合结构热传导性能的非平衡分子动力学研究

Heat transfer in the Ni/Al laminated structure via nonequilibrium molecular dynamics

采用非平衡分子动力学方法研究了[111]方向的Ni/Al层合结构的热传导性能.首先模拟了温度为300 K下[111]方向Ni/Al层合结构的热传导,通过分析界面处的声子态密度,发现交换热冷浴位置之后,层合结构的热参数基本没有变化,说明热冷浴的位置对结果影响不大.其次讨论了300 K下单层的Ni/Al层合结构的尺寸效应,计算结果表明随着系统尺寸的增大,界面热阻值逐渐减小并趋于平缓,并分别讨论了Ni和Al的热导率的尺寸效应;采用外推法计算了无限大系统下Ni和Al的声子热导率以及声子平均自由程,结合Wiedeman-Franz定律计算了Al和Ni的电子热导率,得到了Al和Ni的总热导率,并与实验值进行比较,结果与实验值在同一量级.然后讨论了传导方向为[001]和[110]时层合结构的界面热传导性,并和[111]方向的结果对比,发现界面热阻具有明显的各向异性.最后讨论了双周期层的Ni/Al层合结构的热传导性能,结果表明最靠近热浴的界面温度跳跃值最大,对应的界面热阻值最大,即对层合结构的热传导性能影响最大;与相同长度的单周期层结构对比,发现双周期层结构的热导率明显要小,因此可以通过增加材料的层数来提高隔热效果.

The nonequilibrium molecular dynamics method is employed to study the thermal properties of the Ni/AI laminated structure along the [111] direction. Firstly, we simulate the heat conduction process of a Ni/A1 laminated structure along the [111] direction at 300 K, by analyzing the phonon density of states at the interface, and find that the heat parameters of laminate structure do not change substantially after exchanging the location of the hot bath and cold bath, which means that the location of the hot/cold bath has no effect on the results. Secondly, we study the size effect of monolayer Ni/A1 laminated structure at 300 K, the calculation results show that the interracial thermal resistance decreases gradually as the system size increase. We also discuss the size effect of the thermal conductivity for A1 and Ni respectively, the phonon thermal conductivity and mean free path of Ni and A1 in the infinite system are obtained respectively. Then, the Wiedeman-Franz law is used to calculate the electronic thermal conductivity and the total thermal conductivity of A1 and Ni, we compare the results with the experimental ones, and they are in the same order of magnitude. Moreover, we discuss the thermal properties of the laminated structure along the [001] direction and the [110] direction and compare the results with those of [111] direction. The results show a significant anisotropy. Finally, we investigate the thermal properties of a bilayer Ni/A1 laminated structure, the results show that the nearest interface to hot bath had the most significant effect on the thermal properties of the laminate structure. The comparison between these results and the thermal conductivity of monolayer laminated structure with the same length shows that the former is significantly small, which implies that we can improve the insulating capacity by increasing the number of layers of the laminated structure.