Electrical Properties of Nanostructured Materials
Nanotubes are extremely conductive, displaying current capacity far in excess of any other material. In addition, their one dimensional nature means that only very small amounts of nanotubes need to be added to a polymer to render it conductive. The formation of a conducting network is known as percolation threshold and the minimum amount of filler required, known as the percolation threshold. The ability to disperse nanotubes in a range of solvents (see “Dispersion of nanotubes”) allows us to add nanotubes to a very large number of polymers to form conductive composites.
Figure 4 Variation of composite electrical conductivity as a function of filler content using nanotubes and nanodisks as fillers.
In addition to fabricating conductive composites we can actually make conductive thin films of nanotubes alone. This is done by dispersing nanotubes on a solvent and then removing the solvent by vacuum filtration. These films of “Buckypaper” are porous and have conductivities approaching those of poor metals. We are investigating the fabrication of these films for applications as flexible electrodes.
Figure 5 Graph of conductivity versus volume fraction for very high volume fraction composites of SWNT in polystyrene