Modeling thermal transport in nanoparticle composites

In this paper, the heat transfer in three-dimensional nanoparticle composites is simulated using the Boltzmann transport equation for phonon intensity. Several semiconductor materials are considered, with the emphasis placed on Bi₂Te₃-Sb₂Te₃ nanoparticle composite, due to its high thermoelectric conversion efficiency at room temperature. A unit-cell approach is used to model the periodic distribution of nanoparticles in the host. Both cubic and noncubic nanoparticle composites are considered. The phonon properties are based upon the phonon dispersion model, and the interfaces are assumed to be diffusely transmitting and reflecting. The thermal conductivity of nanocomposites is found to exhibit the classical size effect and is also found to be dependent on the atomic percentage of the particle. The three-dimensional nanoparticles exhibit values of thermal conductivity similar to the lowerdimensional nanostructures such as the superlattice and nanowire. A detailed comparison of the thermal field with the classical Fourier model indicates significant underprediction by the Fourier model in regions of high temperature around the interface of the particle. The scattering interfacial area per unit volume is found to be a useful parameter for comparing the values of thermal conductivity in different types of nanocomposites.