Ordered film of carbon nanotubes

It is necessary to form a stable dispersion of nanotubes in order to properly integrate them into polymeric systems. This can be achieved by treating them with acid to oxidise the tube surfaces. The tubes will then spontaneously disperse in an aqueous medium. The viscosity of these suspensions is analogous to that of polymers; it increases gradually with concentration up to a critical point (at about 0.7vol%) where entanglement occurs. A solid nanotube film has been formed by filtering the suspension through a 0.2mm membrane filter. Suspensions of relatively high concentration (>0.3vol%) yield films with random tube orientations but at lower concentrations (as in this sample), liquid crystal aggregation occurs and there is noticeable mutual alignment. The films exhibiting such alignment are tougher. This image was taken using a field emission gun scanning electron microscope (FEGSEM)