氮掺杂和空位对石墨烯纳米带热导率影响的分子动力学模拟

石墨烯是近年纳米材料研究领域的一个热点,其独特的热学性质受到了广泛关注,为了实现对石墨烯传热特性的预期与可控,利用氮掺杂和空位缺陷对石墨烯进行改性.采用非平衡态分子动力学方法研究了扶手形石墨烯纳米带中氮掺杂浓度、位置及空位缺陷对热导率影响并从理论上分析了热导率变化原因.研究表明氮掺杂后石墨烯纳米带热导率急剧下降,氮浓度达到30%时,热导率下降了75.8%;氮掺杂位置从冷浴向热浴移动过程中,热导率先近似的呈线性下降后上升;同时发现单原子三角形氮掺杂结构比多原子平行氮掺杂结构对热传递抑制作用强;空位缺陷的存在降低了石墨烯纳米带热导率,空位缺陷位置从冷浴向热浴移动过程中,热导率先下降后上升,空位缺陷距离冷浴边缘长度相对于整个石墨烯纳米带长度的3/10时,热导率达到最小.石墨烯纳米带热导率降低的原因主要源于结构中声子平均自由程和声子移动速度随着氮掺杂浓度、位置及空位缺陷位置的改变发生了明显变化.这些结果有利于纳米尺度下对石墨烯传热过程进行调控及为新材料的合成应用提供了理论支持.

The effect of doped nitrogen and vacancy on thermal conductivity of graphenenanoribbon from nonequilibrium molecular dynamics

Graphene has become one of the most exciting topics of nano-material research in recent years because of its unique thermal properties. Nitrogen doping and vacancy defects are utilized to modify the characteristics of graphene in order to understand and control the heat transfer process of graphene. We use nonequilibrium molecular dynamics to calculate the thermal conductivity of armchair graphenenanoribbon affected by nitrogen doping concentration and nitrogen doping location, and analyze theoretically the cause of the change of thermal conductivity. The research shows that the thermal conductivity drops sharply when graphenenanoribbon is doped by nitrogen. When nitrogen doping concentration is up to 30%, the thermal conductivity drops by 75.8%. When the location of nitrogen doping moves from the cold bath to the thermal bath, the thermal conductivity first decreases and then increases. And it is also found that the structure of triangular single-nitrogen-doped graphenenanoribbon is inhibited more strongly in the heat transfer process than that of parallel various-nitrogen-doped graphenenanoribbon. Vacancy defects reduce the thermal conductivity of graphenenanoribbon. When the location of vacancy moves from the cold bath to thermal bath, the thermal conductivity first decreases and then increases. When the vacancy position is located at 3/10 of the entire length relative to the edge of the cold bath, the thermal conductivity reaches a minimum value. This is because of the phonon velocity and phonon mean free path varying with the concentration and the location of nitrogen doping and the location of vacancy defect. These results are useful to control the heat transfer process of nanoscalegraphene and provide theoretical support for the synthesis of new materials.