Moderate anisotropy in the electrical conductivity of bulk MWCNT/epoxy composites

Bulk aligned multi-walled carbon nanotube films and their epoxy composites were prepared and their DC and AC conductivity studied. Nanotube films of up to 2 mm thickness were grown by catalytic chemical vapor deposition. Composites of nanotubes were made by infiltrating the films with a commercial epoxy. DC electrical resistivities in the axial direction of as-grown and purified films were found to be similar to 1.2 Omega mm and similar to 3.4 Omega rnm, respectively. For the transverse direction the resistivity values were higher only with a factor of similar to 2. In the case of composites, anisotropy is more pronounced showing more than an order of magnitude higher resistivity in the transverse direction (similar to 71.4 Omega mm) as compared to the axial value (similar to 4.2 Omega mm). AC behavior of the films investigated between 1 MHz and 3 GHz shows the presence of inductive and capacitive components at frequencies above similar to 100 MHz. The moderate anisotropy for both DC and AC electrical properties are explained on the basis of the films' structure combined with percolation theory and equivalent circuit models. (C) 2010 Elsevier Ltd. All rights reserved.