Dr. Mei-Jiau Huang
Professor, Department of Mechanical Engineering, National Taiwan University, Taiwan, China.

Speech title: Effective-medium-approximation models for the thermal conductivities of nanocomposite materials

Abstract: The EMA (effective-medium-approximation) models treat a composite material as a new homogeneous material and estimate its effective transport properties based on the macro properties of the ingredients. With these models, the analysis of systems made of complicated materials and/or structures becomes much easier. In this work, the model proposed by Hasselman and Johnson (called HJ model herein) which predicts the effective thermal conductivity of particle-embedded-in-host composite materials under the assumption of dilute particle concentrations is introduced first. Followed is a description about how this model is extended to arbitrarily large concentrations and to porous materials. A combination of the modified HJ model with the triple-bond-percolation theory for even more complicated materials is discussed at last. The model predictions of thermal conductivities associated with several silicon and germanium composites as well as bismuth telluride nanoprism-assembled films are compared with the results of Monte-Carlo simulations which solve the phonon Boltzmann transport equation under the grey medium approximation. The agreement is satisfactory.