(a) Open-channel CNF
(b) Periodically closed CNF
(c) swCNT
(d) mwCNT
Figure 2: High-resolution images of particles, illustrating their internal structure. The herringbone CNFs consisted of graphite layers arranged at an angle to the axis of the filament structure ((a), (b)). The micrographs show the structure of a typical open-channel fiber found in all CNF samples (a) and a periodically closed fiber present in large amounts only in CNF B and CNF D (b). Many graphite layers in the periodically-closed type of fiber have closed ends at the surface, indicated by arrows in (b). A typical example of a swCNT, together with disordered graphitic material, is shown in (c). An example of a typical defect mwCNT is shown in (d); a defect in the wall is indicated by an arrow head.