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प्रश्न
What are carbon nanotubes. what are its types. Discuss the laser method for its production.
उत्तर
Carbon nanotubes represents one of the best examples of the novel nanostructures derived by bottom-up chemical synthesis approaches. Nanotubes have the simplest chemical
composition and atomic bonding configuration but exhibit perhaps the most extreme diversity and richness among nanomaterial in structure and structure-property relations. The different types of carbon nanotubes are as follows;
1. SINGLE WALLED NANOTUBES.
2. MUL TIWALLED NANOTUBES.
LASER VAPORIZATION METHOD.
This method is used to produce CNT's with 70% purity. In this process, a graphite rod with so.· so catalyst mixtures of cobalt and nickel at 1200 oc in flowing argon is used to prepare sample. The uniform vaporization of the target can be achieved by using the initial laser vaporization pulse followed by a second pulse. The amount of deposition of carbon soot is primarily minimized by the usage of these two successive laser pulses. The large particles are broken by applying the second laser pulse. The CNT's produced through this process are 10- 20nm in dia and 1 0011m or more in length. The average nanotube diameter and size distribution can vary for different growth temperature, catalyst composition, and other process parametes.
DRAWBACKS.
1. This method involves evaporation of carbon source, so it is unclear to scale up the production to industria level .
2. Vaporisation methods grow CNT's in highly tangled form, mixed with unwanted forms of C and metal species.
3. CNT's produced are difficult to purify.
