Directional dependence of electrical and thermal properties in graphene-nanoplatelet-based composite materials

Abstract

Graphene nanoplatelets have emerged as an efficient filler in matrices due to their remarkable thermal conductivity and electrical conductivity. What is not entirely clear, however, is how the physical properties of the derived composite materials are directionally dependent. The primary focus of this study was on determining this dependence. The electrical and thermal properties of the composite materials were studied to understand what causes anisotropy and how to control this phenomenon effectively. The results indicated that graphene-nanoplatelet-based composite materials can possess a high degree of anisotropy with respect to electrical and thermal conductivity. Electrical and thermal anisotropy in the derived composite materials arise due to the alignment of graphene nanoplatelets in the matrices resulting from very high compression. This allows a thermal management system to be designed to preferentially transfer energy in selected directions. The physical properties are very different, by up to three orders of magnitude with respect to electrical conductivity and five times with respect to thermal conductivity, in different directions. The degree of anisotropy increases with decreasing the viscosity of the matrix. Implications of the results on thermal management applications were discussed, and recommendations were also presented on the development of graphene-nanoplatelet-based thermal interface materials.