The electronic transport properties and microstructure of carbon nanofiber/epoxy composites

摘要

Carbon nanofibres (CNF) were dispersed into an epoxy resin using acombination of ultrasonication and mechanical mixing. The electronic transportproperties of the resulting composites were investigated by means of impedancespectroscopy. It was found that a very low critical weight fraction (pc = 0.064wt %) which may be taken to correspond to the formation of a tunnelingconductive network inside the matrix. The insulator-to-conductor transitionregion spanned about one order of magnitude from 0.1 to 1 wt %. Far from thetransition, the conductivity increased by two orders of magnitude. Thisincrease and the low value of the conductivity were explained in terms of thepresence of an epoxy film at the contact between CNF. A simple model based onthe CNF-CNF contact network inside the matrix was proposed in order to evaluatethe thickness of that film.