*2.1.3 Electric arc discharge method*

Carbon nanotubes are synthesized by electric arc discharge method which is also called Plasma Arcing method.

## *2.1.3.1 Description*

**Electrodes:** Pure graphite rods (both positive and negative electrode). The positive electrode is adjustable from outside to maintain the gap between the two electrodes.

```
Diameter of electrodes: 5–20 μm.
Gap between electrodes: 1 mm.
Current: 50–120 amperes.
Voltage: 20–25 V.
```
**Inert gas pressure:** 100–500 torr (No CNT formed below 100 torr). Inert gas is used for cooling and condensation of atoms to form the CNTs. Inert gas determines the structure of carbons to be present in CNTS. Commonly used inert gas is helium gas.
