Evaluation of Effective Heat Transport and Temperature Gradients in Thermally Anisotropic Particulate Arrangements

Abstract

New materials are often designed to possess anisotropic properties to meet the specific demands of challenging applications. Thermally anisotropic materials are particularly important in the thermal management of electronics. Using anisotropic fillers is a common strategy to tailor the thermal transport properties of macroscopic materials. Various studies have demonstrated the role of filler concentration on the effective material properties. Strikingly, little is known about the contribution of the filler microstructure. Here, we study anisotropic filler particles in a 2D composite material. We determined the two main effects caused by the anisotropy. First, we show that the thermal percolation behavior changes drastically depending on the particle orientation. This enables the design of granular composites with widely adjustable effective thermal conductivities governed by composition and orientation. Second, we observe strong differences in local temperature distributions between isotropic and anisotropic mixtures. The admixture of anisotropic constituents leads to strong internal temperature gradients. These are unfavorable for many thermal management applications. Consequently, anisotropy can control the effective heat transport in composite materials, but adverse temperature gradients need to be considered.