Multiple-wall carbon nanotube method

A number of methods have been developed to produce single- and multiple-wall carbon nanotubes. The most prominent are laser ablation, arc discharge, and catalytic growth (vapor deposition (CVD) and high pressure carbon monoxide (HipCO) process). 

The electronic properties of single-walled carbon nanotubes have been studied theoretically using different methods[4-12. It is found that if n — wr is a multiple of 3, the nanotube will be metallic otherwise, it wiU exhibit a semiconducting behavior. Calculations on a 2D array of identical armchair nanotubes with parallel tube axes within the local density approximation framework indicate that a crystal with a hexagonal packing of the tubes is most stable, and that intertubule interactions render the system semiconducting with a zero energy gap[35]. 

Carbon nanotubes represent a second form of polymeric carbon that is being explored for multiple applications ranging from electronics to health care. These materials come in two forms multiwalled carbon nanotubes (MWNT) and single-walled carbon nanotubes (SWNT). Growth is very important and only recently has large-scale produaion been possible. Details of growth methods are described and include arc discharge methods, chemical vapor deposition (CVD), and laser ablation. Each method produces different types of nanotubes and so may be preferred for certain applications. 

Nanotubes. If the ends of the nanotube shown in Figure 8-16 are uncapped, the result is a hollow tube of very small dimension. Such ilanombes have been synthesized both with single and multiple walls (multiple layers built up on the outside of the innermost tube). One of the most promising potential applications of such structures is in the electronics industry. Extensive work has been done to devise methods for constructing computer circuits that use carbon nanotubes, and the nanombes have been cited as the leading candidate to replace silicon when the size limit on miniaturization of silicon chips has been reached. ... 

Both single-walled nanotubes (Figure 8.18) and multiple-walled nanotubes with multiple, concentric layers of carbons have been studied extensively. Commercially they are prepared by a variety of methods, including application of electric arcs to graphite... 

---