Preparation and characterisation of carbon nanotube films and composites

Abstract

A simple method of carbon nanotube (NT) composite preparation has been demonstrated that produces wide ranging and extremely high carbon nanotube mass fraction, mf, composites with minimal reagregation of the nanotubes (up to 81 wt% NTs). High mass fraction polystyrene-nanotube composite films were fabricated using this method from very low concentration dispersions of N-MethyI-2-pyrrolidone by vacuum filtration. These films displayed conductivities between 100S/m and 10 4S/m with densities in the region of 400kg/m3. Taking into account their porous nature, the conductivity, δ , was plotted as a function of the true nanotube volume fraction, p. The conductivity scaled according to a percolation scaling law: δ ∝ pt right up to the nanotube only sample. This unexpected result shows that, in these systems at least, percolation scaling persists even at very high volume fractions. This indicates that the conductivity is limited only by the properties of the nanotube junctions of which the network is comprised, not by polymer tunnelling barriers. Mechanical analyses were also preformed on these films and prompted investigation into the factors that control the mechanical properties of nanotube films.