The role of precursor modification on the production of graphite foam

Abstract

A high-conductivity graphite foam developed at Oak Ridge National Laboratory (ORNL) exhibits properties indicative of highly graphitic structure. Similar to highly-ordered natural flake graphite, the foam exhibits a peak in thermal conductivity at temperatures approaching liquid nitrogen. This is due to its highly-aligned graphitic structure along the cell walls. This paper explores the manufacturing process to identify processing conditions that most affect the properties of the foam, such that the production of the foam can be easily tailored to different applications. This paper also examines processing conditions for the precursor's preparation as well as additives to the precursor (such as graphene) on the resulting foam structure and thermal properties. It was found that heat treating the precursor mesophase to increase melt viscosity and decrease off gassing during foaming decreased the thermal conductivity of the final foams, however, it resulted in smaller pores. Additions of graphene platelets decreases the thermal conductivity of the foams while simultaneously decreasing the pore size as well. These tradeoffs are evident and present the manufacturer options to tailor the foams.