Fig. 4 shows the surface morphology of the CF with the grafted
CNTs. The bright lines correspond to the carbon nanotubes attached
to the surface and the dark areas correspond to the bare carbon
fiber. The CNTs uniformly stick to the CF surface along the outer
edges of the grooves with different angles. The whole morphology
of the grafting CF can easily be controlled by this method to satisfy
different needs in engineering applications. On one hand, the long
CNTs form a flocculated structure which makes the carbon fiber
look like a branched fiber (Fig. 4b). The short CNTs are deposited as
individual nails (Fig. 4a). On the other hand, the CNT grafting
densities can be controlled by the PAMAM ration (Fig. 4c and d).
The saturated coverage rate of this method is about 30%. Whereas,
the ideal product is the fiber with a 15–20% grafting ratio which is
obtained by 1:1×10−4 feeding ratios. The influence of the grafting
length and ratio on the composite interfacial properties will be
access in the future study.