Figure 1. Scanning electron micrographs of the multi-walled carbon
nanotubes for the preparation of epoxy matrix composite materials.
The transmission electron micrographs of the multi-walled carbon
nanotubes are illustrated in Figure 2 for the preparation of epoxy
matrix composite materials. Multi-walled carbon nanotubes as used herein
refers to carbon nanotubes which are substantially cylindrical,
graphitic nanotubes of substantially constant diameter and comprise
cylindrical graphitic sheets or layers whose c-axes are substantially
perpendicular to the cylindrical axis. Single-walled carbon nanotube
structures can have smaller effective pore size than multi-walled carbon
nanotube structures. Having smaller effective pore size may be
beneficial in many applications, and undesirable in other circumstances.
For example, smaller pores result in catalyst supports having higher
specific surface. Conversely, smaller pores are subject to diffusion
limitations and plugging. Thus, the advantages of smaller pore size need
to be balanced against other considerations. Parameters, like total
porosity and pore size distribution, become important qualifiers of
effective pore size. Generally, single-walled carbon nanotubes are more
expensive and less pure than multi-walled carbon nanotubes, and are
harder to disperse and more difficult to functionalize. As such,
multi-walled carbon nanotube structures are easier to prepare.
Multi-walled carbon nanotubes are attracting increasing interest as
constituents of novel nanoscale materials and device structures.
Defect-free multi-walled carbon nanotubes are expected to have
remarkable mechanical, electronic, and magnetic properties that will be
tunable by varying the diameter, number of concentric shells, and
chirality of the tube. The multi-walled carbon nanotubes aggregated into
ropes in which many tubes are held together by van der Waals forces. The
multi-walled carbon nanotubes produced are remarkably uniform in
diameter.