Anisotropic Thermal Transport in Spray-Coated Single-Phase Two-Dimensional Materials: Synthetic Clay Versus Graphene Oxide.

Directional control on material properties such as mechanical moduli or thermal conductivity are of paramount importance for the development of nanostructured next-generation devices. Two-dimensional materials are particularly interesting in this context owing to their inherent structural anisotropy. Here, we compare graphene oxide (GO) and synthetic clay sodium fluorohectorite (Hec) with respect to their thermal transport properties. The unique sheet structure of both allows preparation of highly ordered Bragg stacks of these pure materials. The thermal conductivity parallel to the platelets strongly exceeds that perpendicular to them. We find a significant difference in the performance between GO and synthetic clay. Our analysis of the textured structure, size of the platelets, and chemical composition shows that Hec is a superior two-dimensional component to GO. Consequently, synthetic clay is a promising material for thermal management applications in electronic devices where electrically insulating materials are prerequisites.