Carbon Nanotube (CNT)

Carbon nanotubes (CNT) were discovered in 1991 by Sumio Iijima. Carbon nanotube is a thin cylindrical material made by carbon. Carbon nanotubes having many structure, different in shape and size. The thermal, electrical and structural properties of nanotubes quite depend upon shape and size of nanotube. A nanotube is about 10,000 times small than human hair. Due to small size of nanotube the bonding between the atoms is very strong. CNT are almost 100 times stronger than steel. CNT are already used in polymer to enhance conductivity. A nanotube looks like rolled-up chicken wire with a continuous unbroken hexagonal mesh and carbon molecules at the peak of the hexagons. Currently, the most popular use for carbon nanotubes is in structural reinforcement. The high strength and low weight of CNT increases the strength of structure.

Depending upon the number of layers, the CNT are classified as below:-
  • single-walled nanotube (SWNT):- 
  • It consists of a single graphene sheet rolled into a cylinder having hexagonal rings with double and single carbon carbon bonding. The diameter varry from 0.7–2.0 nm.

SWNT are of three types:-
  1. Armchair
  2. Zigzag and
  3. Chiralm
  • Multi-wallednanotubes(MWNT):-It consist of multiple layers of graphite rolled into a cylinder with different diameters. The layers of graphite having some distance between them. The diameter of MWNT is 30nm when compare to typical SWNT. The length of MWNT is much higher than diameter.

Properties of CNT:-
  • Strength and elasticity:- Carbon nanotubes have a higher tensile strength than steel. Under high pressure the bonding between the individual carbon must be strong. Carbon nanotubes are not only strong, they are also elastic. When force exerted on the top of the nanotube it will bend without damaging. Nanotube will returns back to its original shape when the force is removed. Elasticity work upto certain limit and under very Strong force it will permanentely deformed.
  • Thermal conductivity:- The strength between the atoms in carbon nanotubes allows them to withstand high temperature. Due to this property, carbon nanotubes working as a good thermal conductor. The thermal conductivity depends upon temperature of tube as well as outside environment.
  • Electrical conductivity:- The strong bonds  between carbon atoms allow carbon  nanotubes to withstand higher electric  currents than copper.

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