529-551Carbon nanotubes are the closed tabular
structures consisting of nested cylindrical graphitic layers capped by
fullerene-like ends with a hollow internal cavity, which were first discovered
by Iijima in 1991. It consists of either one cylindrical graphene sheet, i.e.,
single-wall nanotube (SWNT)) or of several nested cylinders with an interlayer
spacing of 0.34-0.36 nm, i.e., multiwall nanotube (MWNT)). The lengths of SWNTs
and MWNTs are usually well over 1 m and
diameters range from ~1 nm (for SWNTs) to ~50 nm (for MWNTs). SWNTs are usually
closed at both ends by fullerene-like half spheres that contain both pentagons
and hexagons. Carbon nanotubes show exceptional electronic and mechanical
properties. They are flexible but very hard to stretch and have extremely low
turn-on fields and high current densities ranking them among the best electron
field emitters for future field emission displays. This article presents an
overview of current state of research on carbon nanotubes. In this review, we
have focused on different synthesis routes for carbon nanotubes growth, used
during last 12 years and possible future applications of carbon nanotubes
especially in fuel cell and field emission displays. We have also discussed
various parametric studies reported by several groups and extracted from their
observations the common factors, which seem to be important towards a
controlled production of carbon nanotubes. The limitations of these approaches,
compatibility between an up-scaled production, the quality of the grown
nanotube materials as well as the question of an economic production, have also
been addressed