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 hexagonalgraphite molecules attached at the edges. Nanotubes look like a powder or black soot, but they'reactually 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 itsunique 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 afamily of processes whereby a solid material is deposited from a vapor by a chemical reaction occurringon or in the vicinity of a normally heated substrate surface. The resulting solid material is in the form ofa thin film, powder, or single crystal. Among these methods, the chemical vapor deposition method is acheap and simple method. Supercritical fluids, particularly supercritical CO2, have been used in variousareas such as nanoparticle and CNT synthesis. In this paper the CNT synthesis methods based onCVD and using supercritical fluids were studied.