Imaging of conductive filler networks in heterogeneous materials by scanning Kelvin microscopy

This article reports a novel application of scanning Kelvin microscopy for exclusively revealing the distribution of a percolated conductive filler network in heterogeneous materials. The materials under investigation are carbon black and carbon nanotube-filled epoxies with a highly inhomogeneous conductivity distribution due to their fabrication. The Kelvin method is demonstrated to be especially suitable for resolving the resistive particle network in these kinds of composite materials with sample resistance levels in the megaohm range. Transmission optical microscopy reveals matches between the scanning Kelvin images and the sample morphologies, whereas the percolating backbone cannot be distinguished in the optical micrographs.