Size and shape of graphene layers in commercial carbon blacks established by Debye refinement

The size and the shape of graphene layers in commercial conductive carbon blacks, Super P and Super S, have been determined from powder X-ray diffraction data. Using a refinement procedure based on the fundamental diffraction equation of Debye, it is shown that the ordered regions within the layers of both materials are of elliptical shape, curved in a cylindrical fashion along the longer axis of the ellipse. The regions are greater in Super P, ellipse axes 5.4 and 2.2 nm, than in Super S, 4.6 and 2.1 nm, and less curved (curvature radii 12.7 and 11.7 nm, respectively). There is no crystallographic registry between layers, which are equidistantly stacked into concentric groups of six or seven, on average.