Characterization of nickel nanostrand nanocomposites through dielectric spectroscopy and nanoindentation

One particularly promising model of electrical properties of conductive nanocomposites involves a combined quantum tunneling/percolation approach. However, two key inputs to the model--the polymer matrix barrier height and the average gap between conductive filler particles--are difficult to determine experimentally. This article demonstrates improved methods for determining barrier height in polymer materials via conductive nanoindentation, with barrier heights measured between 0.4 and 1.7 eV for five different polymers. By using dielectric spectroscopy techniques, combined with the barrier height measurements, the average junction gap was determined for the first time for nickel-nanostrand nanocomposites with six different polymer matrices; the values range from 1.31 to 3.28 nm. Using those measured values for barrier height and junction gap distances in a simple model, we have tested predictions for bulk resistivity of six polymers. The model worked well for four of the six, which suggests that for a given volume fraction of filler, knowledge of the barrier height and the junction distance may in many cases be sufficient to provide an estimate of the bulk resistivity of the polymer-nanostrand blend, an important parameter in nanocomposite engineering. POLYM. ENG. SCI., 53:2666-2673, 2013. © 2013 Society of Plastics Engineers