Influence of the Reinforcement Distribution and Interface on the Electronic Transport Properties of MWCNT-Reinforced Metal Matrix Composites

Abstract

The transition towards an electricity-driven world is testing electrical contact materials to their limits. Specifically, new alternatives are needed where composites that sacrificed conductivity in exchange for reduced weldability and higher heat dissipation sufficed. Carbon nanotubes (CNT) have the potential to close the gap as ideal fillers due to their outstanding intrinsic properties, pushing the application limits further. However, the reported electrical conductivity measurements showed no clear tendency. In the present study we attempt to shed some light on this matter by focusing on the causes behind those results. We observed that the addition of 1 wt. % CNT improves the conductivity of nickel, followed by a drop for higher concentrations, measured by 4-point probe testing. Six nanotube orientation models describing different CNT arrangements were contrasted to the experimental data. Corrected values for nickel and CNT resistivities effectively place that of the composites close to the models, providing indications of a preferential orientation. We conclude that, in contrast to what is widely reported, the main contributing factors to the resistivity are inter-tube coupling, porosity and interfacial scattering, whereas clustering marginally influences the behaviour.