Percolation conduction in vapour grown carbon fibre

We investigate the conductivity variation with density of compacted vapour-grown carbon fibre (VGCF). The results indicate a typical transition between a non-linear domain at low compaction conditions and a regime where the conductivity increases roughly linearly with density when the sample is subjected to higher pressures. From a simple scaling argument, we suggest that percolation theory can be consistently applied to represent the morphological changes of the disordered system during the compaction process. In addition, a characteristic percolating behaviour has been detected from the results of conductivity experiments with a polymer composite of VGCF and polypropylene. In this case, an observed percolation threshold below 1% in volume confirms the highly structured nature of the conducting filler material.