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Carbon nanotube

Carbon nanotube. Present to. Asst. Prof. Dr. Purit Thanakijkasem. By Papob lertapanon 5310755748 J ittaporn songprakob 5310755524. Overview.

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Carbon nanotube

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  1. Carbon nanotube

  2. Present to Asst. Prof. Dr. Purit Thanakijkasem

  3. By Papob lertapanon 5310755748 Jittaporn songprakob 5310755524

  4. Overview • Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1.These cylindrical carbon molecules have novel properties, making them potentially useful in many applications.

  5. Structure • Carbon Nanotubes are considered to be a curved graphene sheet. Graphene sheets are seamless cylinders derived from a honeycomb lattice, representing a single atomic layer of crystalline graphite.

  6. Types of carbon nanotube Multi-walled Single-walled

  7. Nanobud Cup stacked carbon nanotubes Torus

  8. Properties of carbon nanotube • StrengthCarbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp2 bonds formed between the individual carbon atoms. • HardnessStandard single walled carbon nanotubes can withstand a pressure up to 24GPa without deformation.Maximum pressures measured using current experimental techniques are around 55GPa.

  9. Thermal : All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction", but good insulators laterally to the tube axis. Electrical : Because of the symmetry and unique electronic structure of graphene,thestructure of a nanotube strongly affects its electrical properties. Themetallic nanotubes can carryan electric current density that are limited by electromigration.

  10. Defects : the existence of a crystallographic defect affects the material properties.Defectscan occur in the form of atomic vacancies.Highlevels of Such defects canlower the tensile strength by up to 85%.Another form of Carbonnanotube defect isthe Stone Wales defect,whichcreates a pentagon andheptagon pair byrearrangement of the bonds.

  11. Toxicity : Results of rodent studies collectively show that CNTs were capable of producing inflammation, epithelioid granulomas (microscopic nodules), fibrosis, and biochemical/toxicological changes in the lungs.Comparative toxicity studies in which mice were given equal weights of test materials showed that SWCNTs were more toxic than quartz, which is considered a serious occupational health hazard when chronically inhaled.

  12. Applications Arc discharge : Nanotubes were observed in 1991 in the carbon soot of graphite electrodes during an arc discharge, by using a current of 100 amps, that was intended to produce fullerenes. Powder of carbon nanotube

  13. Laser ablation : In thisprocess, a pulsed laser vaporizes a graphite target in ahigh-temperature reactor while an inert gas is bled into the chamber.Nanotubesdevelop on the cooler surfaces of the reactor as the Vaporizedcarbon condenses.Awater-cooled surface may be included in the Systemto collect the nanotubes.

  14. Super-growth CVD (water-assisted chemical vapour deposition) this process was developed by Kenji Hata, SumioIijima and co-workers at AIST, Japan.In this process, the activity and lifetime of the catalyst are enhanced by addition of water into the CVD reactor.

  15. Thank You Very Much !!!

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