First, regarding the role of milling, it is believed that graphene
shells wrapping nano SiC particles can be in charge of the uniform
dispersion of these particles in the milled composite powder, as
shown in Fig. 2(c). From an energetic standpoint, the quasi-spherical
carbon and onions are the most stable form of carbon particles
[26]. When the highly curved graphene sheets are obtained as a
result of high flexibility of graphene sheets and impact forces
applied during ball milling, they are in a metastable state in the
light of the theory of minimization of surface area, so the need to
minimize the energy drives this curling up to spherical forms like
onions. Under this circumstance, nano SiC particles can be a
favourable substrate to be wrapped by highly curved graphene
sheets which in turn diminishes the total energy of system by alleviating
the agglomeration of nano SiC particles.