Comparison of two methods of carbon nanotube synthesis: CVD and supercritical process (A review)

A carbon nanotube (CNT) is a miniature cylindrical carbon structure that has hexagonal
graphite molecules attached at the edges. Nanotubes look like a powder or black soot, but they're
actually rolled-up sheets of graphene that form hollow strands with walls that are only one atom thick.
Carbon nanotube has been one of the most actively explored materials in recent year(s) due to its
unique properties and wide range of applications. Various methods have been adopted to produce CNT,
including laser ablation, arc discharge and CVD process. Chemical vapor deposition (CVD) is parent to a
family of processes whereby a solid material is deposited from a vapor by a chemical reaction occurring
on or in the vicinity of a normally heated substrate surface. The resulting solid material is in the form of
a thin film, powder, or single crystal. Among these methods, the chemical vapor deposition method is a
cheap and simple method. Supercritical fluids, particularly supercritical CO2, have been used in various
areas such as nanoparticle and CNT synthesis. In this paper the CNT synthesis methods based on
CVD and using supercritical fluids were studied.