IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Nanotubes: Science and Applications Topical Conference Thursday Sessions
       Session NT+EL+NS-ThM

Paper NT+EL+NS-ThM3
Using Carbon Nanotube Materials to Separate Molecular Mixtures: Predictions from Molecular Dynamics Simulations

Thursday, November 1, 2001, 9:00 am, Room 133

Session: Nanotubes: Growth, Functionalization, and Sensors
Presenter: S.B. Sinnott, The University of Florida
Authors: S.B. Sinnott, The University of Florida
Z. Mao, The University of Kentucky
K.-H. Lee, The University of Florida
R. Andrews, The University of Kentucky
E.A. Grulke, The University of Kentucky
Correspondent: Click to Email
Carbon nanotubes have been proposed as good materials for separation membranes because of their hollow, cylindrical shape and growth in ordered, close-packed bundles. We have therefore studied the manner in which molecular mixtures separate after diffusion into individual carbon nanotubes or nanotube bundles. The mixed systems considered in our study are methane/n-butane, methane/isobutane, methane/ethane, nitrogen/oxygen, nitrogen/carbon dioxide and oxygen/carbon dioxide. The computational approach used is classical molecular dynamics simulations where the forces on the atoms are calculated using empirical potentials that vary with distance.@footnote 1@ Short-range interactions are calculated using a many-body, reactive empirical bond-order hydrocarbon potential and the long-range interactions are characterized with Lennard-Jones potentials. Some of these molecular mixtures separate within individual nanotubes while others do not. The mechanisms by which the molecules diffuse through the nanotubes are found to play an important role in the separation of some mixtures. Molecular structure also has a large effect on the separation of the molecular mixtures. The helical structure of the nanotube walls is predicted to have no effect on results while the nanotube diameter has a large effect. As the diameter of the nanotubes increases, the amount of separation between the molecules decreases. In nanotube bundles, the diffusion behavior and coefficients of binary molecular systems change relative to the diffusion behavior in individual nanotubes. This research is sponsored by the NASA Ames Research Center and the Advanced Carbon Materials Center through the NSF (DMR-9809686). @FootnoteText@ @footnote 1@S.B. Sinnott, L. Qi, O.A. Shenderova, D.W. Molecular Dynamics of Clusters, Surfaces, Liquids, and Interfaces, Ed. W. Hase (JAI Press, Inc., Stamford, CT, 1999, pp. 1-26.