Raman spectroscopy of graphitic foams

Abstract

The recently developed pitch-based graphitic foams have a very high thermal conductivity to weight ratio. This property allows graphitic foams to be used in several thermal management applications, especially in the aeronautics and aerospace industries. Raman spectroscopy studies were performed on the different structural regions of the foam, yelding important information on the structural properties of the graphitic foams, as well as on the physical properties of graphite. The graphitic foam was found to be composed of two intermixed graphitic structures, one with stacked planes and one with a turbostratic structure. This special structure allowed for a simultaneous study of the properties of two-dimensional (2D) and three-dimensional (3D) graphitic structures. The dispersion of the ${G}^{\ensuremath{'}}$ band was found to be different for 2D and 3D graphite. The intensity of the $D$-band Raman feature was used to probe the density of defects in the structure, leading to the conclusion that the defects are mainly localized in the 2D structures. A simple model is proposed to explain the origin of the two different structures within the graphitic foam. Also, the dependence of the ${G}^{\ensuremath{'}}$ band on polarization is addressed.