Infiltration behaviour of water in a carbon nanotube under external pressure

Abstract

The wetting behaviour and associated pressure effect of water in single-walled carbon nanotubes (SWCNTs) are investigated through molecular dynamics (MD) simulations. It is found that water molecules can enter SWCNTs via surface diffusion, and the effective infiltration rate increases with pressure. The effect of pressure on infiltration rate is highly non-linear, exhibiting characteristics of both hydrophilic and hydrophobic surfaces. There exists a nominal infiltration pressure that is dependent on the SWCNT size, above which the water flux is significantly increased.

Keywords:

• carbon nanotube
• water infiltration
• simulation

Acknowledgement

The study was supported by The Army Research Office under Grant No. W911NF-05-1-0288 and by National Science Foundation CMMI-0643726.

Notes

Note

1. Using MD simulations, Hummer et al. 23 reported that it takes only a few ps for water molecules to infiltrate a CNT under ambient conditions. In the present work, not only is the tube radius much larger than that used in reference 23 but also an external pressure is applied; thus the water molecules are able to penetrate the tube within a few ps.