CARBON NANOTUBES (CNT’s)

1. Carbon particles as graphite sheets are made into tubular form calles as Carbon nanotubes.
2. They have diameter of few nanometers and their lengths are up to several micrometers.
3. They were discovered in 1991 by lijima.
4. Carbon nanotubes have very important future applications.

LASER METHOD OF PREPARATION OF CNT

1. In 1996 CNT’s were first synthesized using a dual-pulsed laser and achieved yields of >70 wt% purity.
2. In this method the sample were prepared by laser vaporization of graphite rods with a 1:1 catalyst mixture of Cobalt and Nickel at 1200 degree Celsius in flowing argon, followed by heat treatment in a vacuum at 1000 degree Celsius to get C60 and other fullerenes.
3. The use of two successive laser pulses minimizes the amount of carbon deposited as shoot.
4. The second laser pulses breaks up the larger particles ablated by the first one, and feeds them into growing nanotubes structure.
5. The material produced by this method appears as a mat of “ropes”, 10-20nm in diameter and up to 100um or more in length.
6. Each rope is found to consists primarily of a bundle of single walled nanotubes, aligned along a common axis.
7. By varying the temperature, the catalyst composition, and other process parameters, the average nanotube diameter and size distribution can be varied.
8. Arc-discharge and laser vaporization are currently the principles methods for obtaining small quantities of high quality CNT’s.