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.