Carbon Nanotube Reinforced Composites: Metal and Ceramic ...

Figure 5.3 SEM micrographs of (a) Fe-Al 2O 3/4.8 wt% CNT and
(b) Fe-Al 2O 3/5.7 wt% CNT composite powders. Reproduced with
permission from [59]. Copyright Ó (2000) Elsevier.
hot pressing at 1500 C, leading to the formation of disordered graphene sheets at
grain boundary junctions (Figure 5.4(a) and (b)). Obviously, dense alumina-CNT
nanocomposite cannot be achieved by hot-pressing in situ composite powders at
high temperatures. The low density of the resulting nanocomposites affects their
mechanical strength and fracture toughness dramatically.
In another study, Peigney et al. used high-temperature extrusion to consolidate the
in situ composite powders [39]. They demonstrated that the CNTs can withstand
extreme shear stresses during extrusion. The densification of the extruded composite
Figure 5.4 SEM images of the fracture surface of hot-pressed
Fe-Al2O3/4.8 wt% CNT nanocomposite showing formation of
disordered graphene sheets at grain junctions. Reproduced with
permission from [59]. Copyright Ó (2000) Elsevier.
5.4 Oxide-Based Nanocompositesj139