Particle Size and Shape
The particle size can be adjusted by the conditioning process like mechanical grinding, classification, and sieving. Particle size distribution is typically measured by laser diffraction (ISO 13320:2009) for powders <100 pm, whereas coarser
Fig. 4 Schematic of two graphite particle models with an extremely isotropic and an anisotropic graphite texture (from Spahr 2010) powders are analyzed by vibrating sieving. The particle shape is a consequence of the graphite type and the conditioning process and can be analyzed by optical and electron microscopes. The particle aspect ratio increases with decreasing particle thickness.
One can distinguish between two surface types in graphite: basal plane surface (the outer graphite layers of the graphite single crystal) and the edge surface (the exposed graphite layers form the higher energetic prismatic surfaces); see Fig. 3. The fraction of prismatic, basal plane surfaces is a key material parameter that correlates to different performance of graphite materials in the various applications. In particular, the surface chemistry at prismatic edges is relevant for polymer compounds. The sp2 carbons terminating the graphite layers at the edges have free valences, which are typically saturated by surface groups (hydrogen, oxygen groups) and can be functionalized to improve compatibility to specific polymer types.