碳纳米管内气体吸附与扩散的分子模拟研究

气体在纳米管中的输运具有非连续性的特点,这与宏观条件下稀薄气体的输运类似,同时考虑到纳米管的比表面积非常大,那么吸附气体对输运的贡献就不可忽略。本文基于平衡分子动力学和巨正则蒙特卡洛方法,模拟了不同气体分子在不同直径碳纳米管内的扩散和吸附行为。运用通量相关函数计算了气体的输运扩散系数,并结合稀薄气体动力学推导出了气体的表面扩散系数。结果表明,气体在碳纳米管中的输运扩散系数比克努森公式计算出的结果高数倍甚至十数倍,碳纳米管内吸附分子的表面扩散是气体快速输运的原因,表面扩散系数随表面覆盖度的增大而增大。

Adsorption and Diffusion Properties of Gas in Carbon Nanotubes Based on Molecular Simulation

The gas transport in nanotubes is discontinuous, which is similar to that of rarefied gas in macro-scopic conditions. Meanwhile, considering the large specific surface area of the nanotube, the contribution of ad-sorbed gas to transport cannot be ignored. Based on the equilibrium molecular dynamics and the grand canonicalMonte Carlo method, the diffusion and adsorption of different gas molecules in carbon nanotubes with different diam-eters were simulated. The diffusion coefficient is calculated by using the flux correlation function, and the surfacediffusion coefficient of gas is deduced by combining rarefied gas dynamics. The results show that the diffusion coeffi-cient of the gas in carbon nanotubes is several times or even an order of magnitude higher than that calculated byKnudsen formula, and the surface diffusion of adsorbed molecules is the reason for the rapid transport, and the sur-face diffusion coefficient increases with the surface coverage.