Volume 50

Cluster Evolution and Transition From Adsorption to Capillary Condensation in Nanostructure With Varying Wettability Jun-Feng Shen, Zhuan-Tao He, Qing Zhou, Chun-Mei Wu, You-Rong Li

Abstract

To capture the transformation mechanism from adsorption to capillary condensation in nanostructures,argon adsorption on regularly arranged nanostructures model is established based on Monte Carlo and molecular dynamics simulation in this work. The variation of clusters and the effect of surface wettability during adsorption and capillary condensation are examined. Results indicate that the adsorption starts with the filling of the adsorption site by the single molecular cluster. The atoms in the bulk vapor coalesce with a single molecular cluster to form the multi molecular cluster after the adsorption site is filled. And the coalesce of clusters induces the formation of liquid film. Subsequently, the bending of the liquid film brings a negative pressure to the bulk liquid, which induces the onset of capillary condensation. During this process, the number of single clusters decreases rapidly, while the number of multi molecular clusters increases. With the decrease of surface wettability, the argon atoms tend to gather at the bottom of nanostructures, directly forming into multi molecular clusters. Finally, the adsorption and capillary condensation map exhibit that the critical relative pressure decrease from 0.6 to 0.2 as the surface wettability parameter increase from 0.33 to 0.67. And the increase in spacing leads to an increase in critical relative pressure.

Keywords adsorption, capillary condensation, nanostructure, wettability, cluster evolution