Carbon Nanotubes and Graphene - Research and Applications

Multi-walled carbon nanotube / polyethylene (MWCNT/PE) composites with several concentrations (0.5, 1, 2.5, 5, 7 wt %) of CVD grown nanotubes have been prepared by melt mixing. Melt rheological investigations indicate that the percolation threshold in polyethylene/carbon nanotube composites is between 1 and 2.5 wt% of CNTs for high density polyethylene (HDPE) and low density polyethylene (LDPE) matrix. A better CNT dispersion was obtained in the HDPE matrix. For both HDPE/CNT and LDPE/CNT samples researchers found a similar percolation threshold also in conductance, with a six orders of magnitude increase in electrical conductivity at room temperature between 1 and 2.5 wt% CNTs. Electrical bistability and reproducible rectification behaviour has been found for a HDPE/CNT composite below percolation threshold. Raman line shifts confirm the strong compressive forces associated with PE chains on MWCNT.
Source: PHYSICA E (2008), article in press.