碳纳米管中点缺陷对热导率影响的正交试验模拟分析

在碳纳米管的制备过程中, 各种点缺陷不可避免地存在于其晶格结构中, 对于碳管的热输运性质造成不可忽视的影响. 使用非平衡分子动力学方法, 选用反应经验键序势能, 模拟计算含有缺陷的碳纳米管的热导率. 尝试采用正交试验方法设计算例, 不但减少了计算量, 并且利于分析缺陷类型、 管长和管径三种结构因素对缺陷造成的热导率下降影响的主次和趋势. 重点研究了掺杂、 吸附和空位三类点缺陷的影响, 与无缺陷完整碳纳米管进行比较, 开展缺陷效应分析, 并进一步考察了环境温度等因素的影响. 模拟结果表明, 相对完整无缺陷碳管, 含有点缺陷的碳管热导率显着下降; 在有缺陷存在的情况下, 缺陷的类型对碳管热导率的影响最大, 管径次之, 管长影响相对最小; 缺陷类型对热导率影响力从大到小依次为: 空位 > 掺杂 > 吸附; 不同环境温度下, 点缺陷对碳管热导率的影响不尽相同.

Research on the influences of point defects on the thermal conductivity of carbon nanotube by simulation with orthogonal array testing strategy

In the preparation process of carbon nanotubes, various point defects inevitably come into being in the lattice structures. The defects strongly affect the thermal transport properties of carbon nanotubes. Thermal conduction in carbon nanotube is simulated by using nonequilibrium molecular dynamics method with reactive bond order (REBO) potential. Thermal conductivities of carbon nanotubes with and without defects are calculated for comparison. An orthogonal array testing strategy is employed. In the calculation it greatly saves the experimental effort and identifies the degrees of influence of such structural factors as defect type, tube length, tube radius, etc. on thermal conductivity of tube. The effects of three types of point defects: vacancy, doping and adsorption are primarily studied, and the ambient temperature factor is also analyzed. Simulation results show that the thermal conductivity of carbon nanotubes with defects decreases significantly due to point defects compared with that of perfect carbon nanotubes. The defect type has the first greatest influence on the decrease of thermal conductivity, and hvae the second third greatest infuluences respeetively the radius and the length of carbon nanotubes. The degrees of influence of the above types of point defect are in the order of vacancy>doping>adsorption. Different types of point defects have different effects on tubes at different ambient temperatures.