Colloidal clusters conduct heat more efficiently compared to fully dispersed particles at the same volume fraction. Here we present a predictive model to calculate the thermal conductivity of clusters by extending Maxwell’s theory to non-spherical particles. We treat clusters as spheres with effective thermal conductivity kc and volume fraction ϕc. We calculate the conductivity of the cluster from the upper bound of Maxwell’s theory and the conductivity of a dispersion of such clusters from the lower limit of the theory. We find that structure effects can be represented by a single parameter and provide a method to obtain this parameter from numerical simulations. We test the theory against a system of colloidal clusters produced by controlled aggregation of silica spheres 39 nm in diameter and obtain good agreement. The results suggest that the variability of literature data and the unusually high values of thermal conductivity that have been reported in the literature can be explained quantitatively by the presence of clusters.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Modeling and Simulation
- Materials Science(all)
- Condensed Matter Physics