Page 135 - Book Hosokawa Nanoparticle Technology Handbook

2.7 NANOTUBES (CNT) FUNDAMENTALS
Now, a kind of CVD called HiPCo method [28]
is used for mass production of SWNTs, by using high-
pressure CO gas and Fe catalyst. However, the crys-
tallinity of produced SWNTs is not so high. Recently,
Hata et al. [29] made film-like SWNT by CVD
method, using a control of moisture in the process. By
this method, SWNT of the diameter 2–3 nm and
2
specific surface of 1,000 m /g was produced.
On the contrary, SWNTs produced by arc method
have high crystallinity, because growth temperature is
higher than CVD method. By utilizing the feature, we
achieve [30] mass production of SWNTs by arc dis-
charge in hydrogen mixed gas using only Fe catalyst.
We call it FH-arc method. When we conduct evapora-
tion by FH-arc method, SWNTs are produced as
macroscopic net similar to the production of cotton
cake. The produced SWNT nets are just put in the
1-L bottle, and the mass [31] measured is to be only
1g as shown in Fig. 2.7.2. The green density is only
3
1mg/cm , but the specific surface area measured
2
by BET method is several 100m /g.
Low-magnification TEM image of as-grown
SWNT is shown [30] in Fig. 2.7.3(a). HRTEM of the
same specimen is shown in Fig. 2.7.3(b). Catalyst iron
particles are observed as dark spots uniformly dis-
persed on SWNT net in Fig. 2.7.3(a). The size of each
iron particle is less than 10 nm, and covered by thin
amorphous carbon (2–3 nm thick) as seen in Figure 2.7.2
Fig. 2.7.3(b). Purification of this SWNT can be easily SWNT produced by FH-arc method bottled in 1-L vessel
done by first thermal removing of amorphous carbon, [31]. Mass is only 1g.

Figure 2.7.3
Electron microscope images of SWNTs produced by FH-arc method [30]. (a) Low-magnification TEM image of as-grown
SWNT; (b) High-resolution TEM image of as-grown SWNT; (c) Low-magnification SEM image of purified SWNT;
(d) Low-magnification TEM image of purified SWNT.

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