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Carbon Nanotubes Structure and Synthesis Techniques

Structure of carbon nanotubes

Carbon nanotubes are cylindrical structured wrapped graphene sheets. They may be single walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). SWCNTs are cylinders of single graphene sheets and usually there are only 10 atoms in the circumference of single walled carbon nanotubes. A nanotube can be composed of millions of atoms and is considered as single molecule. Due to very high length to diameter ratio (~1000) nanotubes are considered as one-dimensional molecule. MWCNTs are the cylinders of multiple graphene sheets concentric about a common axis having separation almost 0.34 nm with increasing diameters. The name multiwalled carbon nanotube is specifically used for nanotubes having diameter less than 15 nm. Multi walled carbon nanotubes which have diameter 1-2 nm are usually curved instead of straight structure (Fig. 1.1a, c) (Balasubramanian et al., 2005). Double wall carbon nanotube (DWCNT) also exists, but in recent times among all types of carbon nanotubes the MWCNT received the great attention due their excellent promising features.


Carbon Nanotubes Structure and Synthesis Techniques

TEM image of SWCNTs                                         TEM image of MWCNTs

Carbon Nanotubes Structure and Synthesis Techniques

Schematic Molecular Representation of SWCNTs and MWCNTs

Carbon nanotubes synthesis techniques

There are different techniques have been introduced for the synthesis of MWCNTs and SWCNTs at laboratory level with different morphology and structures. But three methods have been widely used for synthesis of CNTs: chemical vapor deposition (CVD)(Su at al., 2000), arc discharge (Journet at al., 1997) and laser ablation (Thess at al., 1996). Sufficient amount of energy, source of carbon and catalyst are basic elements which are required for the synthesis of CNTs. Similarity among these three methods is to provide energy to the source of carbon which results in the formation of fragments (single carbon atom or groups carbon atoms). Recombination of these fragments results in the formation CNTs. The source of energy may be high-intensity light from a laser (laser ablation), electricity for arc discharge and heat from a furnace (900C) for CVD.

Arc Discharge 

Arc Discharge

Chemical Vapour Deposition (CVD)

Chemical Vapour Deposition (CVD)

Laser Ablation


Laser Ablation

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