Abstract:

The non-equilibrium molecular dynamics method was used to simulate the normal thermal conductivity of the three-dimensional graphene-carbon nanotube composite structure. The structure is based on multi-layer graphene, and the graphene layers are connected with each other through nanotubes. In this way, it is expected to have both low contact thermal resistance and high normal thermal conductivity. In this paper, the out-of-plane thermal conductivity of 3D GCHs is simulated by non-equilibrium molecular dynamics method. The results show that the out-of-plane thermal conductivity increases by one order of magnitude compared with that of multi-layer graphene, and the interface resistance decreases by one order of magnitude in comparison with thermal contact resistance of CNTs. However, the interface between graphene and CNT hinders the heat transfer of GCHs enhancing further. The heat transfer and phonon localization of the GCHs are further investigated through its phonon vibrational density of states and overlap energy. The results show that the addition of carbon nanotubes stimulates more medium and high frequency phonons to participate in heat transfer, but the low frequency phonons still dominate. It is verified that the deformation at the interface is the main factor to prevent the out-of-plane thermal conductivity from further increasing. This paper provides some directional guidance for the improvement and development of high thermal conductivity materials: in the three-dimensional structure of the same element, the fewer types of structural atoms, the better the coordination of inter-atomic vibration, the fewer phonon scattering, the lower the degree of energy localization, and the higher the thermal conductivity

Key words: nano structure, composite material, thermal conductivity, molecular dynamics, vibrational density of states

摘要：

采用非平衡分子动力学方法模拟了三维石墨烯-碳纳米管复合结构的法向热导率。结果表明相比于多层石墨烯，其法向热导率提高了一个量级，其界面热阻相比碳纳米管的接触热阻降低了一个量级，但是石墨烯和碳纳米管的界面形变又阻碍了三维石墨烯-碳纳米管复合热导率的进一步提高。通过其振动态密度和重叠能进一步探究了三维石墨烯-碳纳米管复合结构结构能量的传递及声子的局域化情况。结果表明，碳管的添加激发了更多中高频声子振动参与传热，但是依然是低频声子占据主导；验证了界面处的形变是阻止法向热导率进一步提升的主要因素。

关键词: 纳米结构, 复合材料, 热传导, 分子动力学, 振动态密度