*2.1.4 Procedure for synthesis of CNTs by Electric arc discharge method*

In this method, a potential of 20–25 V is applied across the pure graphite electrodes separated by 1 mm distance and maintained at 500 torr pressure of flowing helium gas filled inside the quartz chamber **Figure 2**. When the electrodes are made to strike each other under these conditions it produces an electric arc. The energy produced in the arc is transferred to the anode which ionizes the carbon atoms of pure graphite anode and produces C+ ions and forms plasma (Plasma is atoms or

**31**

**Figure 3.**

*Laser ablation method—schematic representation.*

*Carbon Nanotubes: Synthesis, Properties and Applications*

molecules in vapor state at high temperature). These positively charged carbon ions moves towards cathode, gets reduced and deposited and grow as CNTs on the cathode. As the CNTs grow, the length of the anode decreases, but the electrodes are adjusted and always maintain a gap of 1 mm between the two electrodes. If proper cooling of electrodes are achieved uniform deposition of CNTs are formed on the cathode which is achieved by inert gas maintained at proper pressure [25]. By this method multi-walled carbon nanotubes are synthesized and to synthesize singlewalled carbon nanotubes catalyst nanoparticles of Fe, Co, and Ni are incorporated in the central portion of the positive electrode. The obtained CNTs are further

**Physical vapor deposition (PVD):** PVD is a technique by which a material can be vaporized into gaseous form and then deposited on the surface of a substrate. **Target source:** The most common carbon source target used is solid graphite

**Laser source:** Laser source used for vaporization of target material into target

**Substrate used:** The substrate used in this method is the water cooled copper

**Inert gas atmosphere:** Argon gas is commonly used as inert gas which flows at a

Laser Ablation method is a Physical Vapor Deposition method in which graphite target is vaporized by laser source **Figure 3**. In this method the graphite target is placed at the center of quartz chamber filled with argon gas and maintained at 1200°C. The graphite target is vaporized by either continuous laser source or pulsed laser source. The vaporized target atoms (carbon) are sweeped toward cooled copper collector by the flow of argon gas. The carbon atoms are deposited and grown as CNTs on cooled copper collector. In case of continuous laser beam, the carbon atoms are continuously vaporized whereas in case of pulsed laser beam the amount of CNTs produced can be monitored as each shot of pulsed laser beam is directly proportional to the amount of carbon atoms vaporized [26]. By this method multiwalled carbon nanotubes are synthesized and to synthesize single-walled carbon

which is irradiated by laser source and vaporized into vapor carbon atoms.

vapor atoms can be continuous laser source such as CO2 laser or pulsed laser source such as Nd:YAG laser (Neodymium doped Yttrium Aluminum Garnet,

collector on which the vaporized carbon atoms deposit and grow as CNTs.

constant flow rate towards the water cooled copper collector.

*2.1.6 Procedure for synthesis of CNTs by Laser Ablation method*

*DOI: http://dx.doi.org/10.5772/intechopen.92995*

purified to get the pure form of CNTs.

*2.1.5 Laser ablation method*

Nd:Y3Al5O12) .

**Figure 2.** *Electric arc method.*

#### *Carbon Nanotubes: Synthesis, Properties and Applications DOI: http://dx.doi.org/10.5772/intechopen.92995*

molecules in vapor state at high temperature). These positively charged carbon ions moves towards cathode, gets reduced and deposited and grow as CNTs on the cathode. As the CNTs grow, the length of the anode decreases, but the electrodes are adjusted and always maintain a gap of 1 mm between the two electrodes. If proper cooling of electrodes are achieved uniform deposition of CNTs are formed on the cathode which is achieved by inert gas maintained at proper pressure [25]. By this method multi-walled carbon nanotubes are synthesized and to synthesize singlewalled carbon nanotubes catalyst nanoparticles of Fe, Co, and Ni are incorporated in the central portion of the positive electrode. The obtained CNTs are further purified to get the pure form of CNTs.
