Zhang Lin, Ban Heng
Department of Engineering Mechanics, School of Civil Engineering, Shandong University, Jinan 250061, China.
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Nanomaterials (Basel). 2022 Aug 18;12(16):2855. doi: 10.3390/nano12162855.
The scattering of gases on solid surfaces plays a vital role in many advanced technologies. In this study, the scattering behavior of helium on graphene surfaces was investigated, including the thermal accommodation coefficient (TAC), outgoing zenith angle of helium, bounce number, and interaction time. First, we performed molecular dynamics simulations to describe the incident angle-resolved behaviors, and showed that the scattering is highly dependent on the zenith angle of incident helium but insensitive to the azimuthal angle. The contribution of the normal velocity component of the incident helium dominated the energy transfer. The nonlinear relationship of the parameters to the zenith angle of the incident helium could be suppressed by increasing the graphene temperature or decreasing the speed of the incident helium. Subsequently, the scattering performance considering all gas molecules in the hemispherical space was evaluated using the Monte Carlo method with angle-resolved results. The result showed that the TAC, its nominal components, and the zenith angle of the scattered helium increased with higher speeds of incident helium and lower temperatures of graphene. This study should provide a fundamental understanding of energy transfer between gas and two-dimensional materials and guidelines to tune the scattering behavior between them.
气体在固体表面的散射在许多先进技术中起着至关重要的作用。在本研究中，研究了氦气在石墨烯表面的散射行为，包括热适应系数（TAC）、氦气的出射天顶角、反弹次数和相互作用时间。首先，我们进行了分子动力学模拟以描述入射角分辨行为，并表明散射高度依赖于入射氦气的天顶角，但对方位角不敏感。入射氦气法向速度分量的贡献主导了能量转移。通过提高石墨烯温度或降低入射氦气速度，可以抑制参数与入射氦气天顶角之间的非线性关系。随后，使用具有角度分辨结果的蒙特卡罗方法评估了半球空间中所有气体分子的散射性能。结果表明，TAC、其标称分量以及散射氦气的天顶角随着入射氦气速度的提高和石墨烯温度的降低而增加。本研究应为理解气体与二维材料之间的能量转移提供基础认识，并为调节它们之间的散射行为提供指导。
