5.3 Nanostructures Related to Compounds with Layered Structures 93
From the explanations above, it is evident that forming a tube can reduce the
energy stored in a graphene layer, too. From simple geometrical considerations,
(think of the different possibilities of forming a tube from a sheet of paper) one
realizes different possibilities of rolling up a sheet of graphene. Interestingly, the
properties, especially electrical properties, depend strongly on the angle of coiling.
Similar to the case of fullerenes, carbon nanotubes can exist in concentric multilayers, multiwall nanotubes, too. Figure 5.14 displays these two possibilities.
Most of the production processes deliver primarily multiwall nanotubes; generally, single-wall nanotubes are the exception. As for the discussion of nanotubes,
there remain a series of dangling bonds at each end. Therefore, they have to be
closed; closing is performed by an endcap, which is similar to a moiety of a fullerene. Figure 5.15 displays an electron micrograph of a multiwall nanotube and
its endcaps. The contrast at the caps is, compared to the body of the nanotubes,
Figure 5.14 Models of carbon nanotubes. A
single-wall nanotube of the armchair type
with the chirality vector (10,10) (a). The
diameter of this tube is 1.35 nm (Reproduced
with permission, http://www.jcrystal.com/
steffenweber/pb/swpb1.pdf). The multiwalled
carbon nanotube of the zig-zag type depicted
in (b) has the chirality vectors (see Box 5.6)
[7,0], [10,0], [13,0] and [16,0]. The outer
diameter is 1.25 nm.
Figure 5.15 Multiwall carbon nanotube with endcaps (Ritschel, M., and Leonhardt, A. (2007),
IFE Dresden, Germany, unpublished results. http://www.ifw-dresden.de/institutes/iff/
research/Carbon/CNT/ferromagnetic-filled-cnts-by-cvd).
4 nm
From the explanations above, it is evident that forming a tube can reduce the
energy stored in a graphene layer, too. From simple geometrical considerations,
(think of the different possibilities of forming a tube from a sheet of paper) one
realizes different possibilities of rolling up a sheet of graphene. Interestingly, the
properties, especially electrical properties, depend strongly on the angle of coiling.
Similar to the case of fullerenes, carbon nanotubes can exist in concentric multilayers, multiwall nanotubes, too. Figure 5.14 displays these two possibilities.
Most of the production processes deliver primarily multiwall nanotubes; generally, single-wall nanotubes are the exception. As for the discussion of nanotubes,
there remain a series of dangling bonds at each end. Therefore, they have to be
closed; closing is performed by an endcap, which is similar to a moiety of a fullerene. Figure 5.15 displays an electron micrograph of a multiwall nanotube and
its endcaps. The contrast at the caps is, compared to the body of the nanotubes,
Figure 5.14 Models of carbon nanotubes. A
single-wall nanotube of the armchair type
with the chirality vector (10,10) (a). The
diameter of this tube is 1.35 nm (Reproduced
with permission, http://www.jcrystal.com/
steffenweber/pb/swpb1.pdf). The multiwalled
carbon nanotube of the zig-zag type depicted
in (b) has the chirality vectors (see Box 5.6)
[7,0], [10,0], [13,0] and [16,0]. The outer
diameter is 1.25 nm.
Figure 5.15 Multiwall carbon nanotube with endcaps (Ritschel, M., and Leonhardt, A. (2007),
IFE Dresden, Germany, unpublished results. http://www.ifw-dresden.de/institutes/iff/
research/Carbon/CNT/ferromagnetic-filled-cnts-by-cvd).
4 nm