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REU

February 3, 2006

FRONTIERS IN MATERIALS SCIENCE
VINSE COLLOQUIUM SERIES

Dr. Byron Pipes
John L. Bray Distinguished Professor of Engineering
Schools of Aeronautics and Astronautics
Materials and Chemical Engineering
Purdue University
"Van der Waal’s Interactions in Carbon Nanotubes"

Abstract.  Van der Waal’s interactions at the nanoscale can play a dominant role in the interactions of single walled carbon nanotubes in arrays and in the interaction of the single atomic layers in the multiwalled carbon nanotube.  Further, as carbon nanotubes are employed as engineering elements for the creation of nano devices and nano machines, it is important that their behavior, when subjected to van der Waal’s forces, be well understood. 

Single walled nanotube arrays exhibiting hexagonal symmetry have been observed experimentally and physical measurement of the arrays have been measured with atomic force microscopy.  Properties of multiwalled carbon nanotube have also been measured, and in both cases, the observed properties differ significantly from those predicted by the assumption of perfect bonding between the graphene surfaces.  In the present study, a model for imperfect bonding is developed and exercised in applications such as the static flexural properties and resonant frequencies of single wall carbon nanotube arrays and for single walled carbon nanotubes containing the fullerene, C60.  In addition, the load transfer by van der Waals interactions for multiwalled carbon nanotubes are shown to be responsible for observed elastic moduli less than predicted for perfect bonding.

Finally, the comminution of carbon nanotube arrays to yield uniform mixtures with second phases such as polymeric solutions requires that the mechanisms for separation be developed and exercised. Determination the energy density necessary for the separation two single walled carbon nanotubes due to peeling action is the first step in developing this understanding for array comminution.  The present model utilizes the universal graphitic potential and the double cantilever geometry to determine the energy density for peeling and results are presented for a variety of carbon nanotube chiralities.  

 
 
Vanderbilt University