Figure 3. Scanning electron micrographs of the graphitic carbon
nanofibers that represent a class of nanostructured carbon fibers having
atomic structures uniquely different from that of carbon nanotubes.
The scanning electron micrographs are illustrated in Figure 4 for the
catalytically-grown multi-walled carbon nanotube-reinforced epoxy
composite. Carbon nanotubes differ physically and chemically from
continuous carbon fibers which are commercially available as
reinforcement materials, and from other forms of carbon such as standard
graphite and carbon black. Standard graphite, because of its structure,
can undergo oxidation to almost complete saturation. Moreover, carbon
black is amorphous carbon generally in the form of spheroidal particles
having a graphene structure, carbon layers around a disordered nucleus.
The differences make graphite and carbon black poor predictors of carbon
nanotube chemistry. Carbon nanotubes exist in a variety of forms and
have been prepared through the catalytic decomposition of various
carbon-containing gases at metal surfaces [51, 52]. Such vermicular
carbon deposits have been observed almost since the advent of electron
microscopy [53, 54]. Carbon nanotubes are known to have
extraordinary tensile strength, including high strain to failure and
relatively high tensile modulus [55, 56]. Carbon nanotubes may also
be highly resistant to fatigue, radiation damage, and heat [57, 58].
To this end, the addition of carbon nanotubes to composites can increase
tensile strength and stiffness. Unfortunately, adding even a small
amount of carbon nanotubes to, for instance, a resin matrix to
subsequently generate the desired composite can increase the viscosity
of the matrix significantly. Moreover, continuous carbon nanotubes are
not yet readily available, so as to permit the creation of a
substantially continuous carbon nanotube composite, or a substantially
continuous composite reinforced with the continuous carbon nanotubes.
The availability of either or both composites can allow for a variety of
interesting commercial applications. Accordingly, it would be
advantageous to provide a substantially continuous composite material
reinforced with substantially continuous carbon nanotubes, such that the
composite material can be provided with a low density while having high
modulus and strength. In addition, it would be advantageous to provide a
method for manufacturing such composite materials.