Paper NS+EM+EN-TuM11
Ultrahigh Thermal Conductivity Gold Nanowire-Filled Polymer Composites and Interfaces

Tuesday, October 29, 2013, 11:20 am, Room 203 B

Realizing high thermal conductivity nanocomposites is a major challenge because of difficulties in incorporating high fractions of uniformly dispersed nanofillers and countering low filler-matrix interfacial conductance. Here, we obviate these issues by using < 3 volume% ultrathin sub-10-nm gold nanowire fillers to obtain a unprecedented 30-fold increase in polydimethylsiloxane [1] thermal conductivity to ~5 Wm^-1K^-1 that is 6-fold higher than any previously reported nanocomposite filler including graphene, carbon nanotubes and silver nanowires, at lower filler loadings, and exceeds theoretical predictions. The nanowire diameter and aspect ratio are key to obtaining cold-welded networks that enhance thermal conductivity, while fostering low modulus and electrical conductivity. The nanocomposites exhibit high compliance with a low elastic modulus of ~5 MPa conducive for conformal formation of interface contacts. However, the interfacial thermal contact conductance of the nanocomposites interfaced with copper is low, e.g., ~1.5 kWm^-2K^-1. Rheology measurements reveal that the low conductance is due to a liquid-solid transition that is sensitive to the nanowire loading fraction. In particular, the filler loading corresponding to the formation of a percolation network and maximizing the nanocomposite thermal conductivity also corresponds to a large increase in the polymer pre-cure viscosity. These results provide insights on designing processes to increase the thermal contact conductance at interfaces where efficient heat transport is of importance, e.g., in device packaging applications.

1. N. Balachander, I. Seshadri, R.J. Mehta, L.S. Schadler, T. Borca-Tasciuc, P. Keblinski, and G. Ramanath, “Nanowire-filled polymer composites with ultrahigh thermal conductivity,” Applied Physics Letters, vol. 102, 2013, pp 093117 – 093117-3.