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What are Carbon

nanotubes.Carbon nanotubes(CNTs) are allotropes of carbon. Thesecylindrical carbon molecules have interesting properties thatmake them potentially useful in many applications innanotechnology, electronics, optics and other elds of materialsscience, as well as potential uses in architectural elds. Theyehibit etraordinary strength and uni!ue electrical properties,and are e"cient conductors of heat. Their nal usage, however,may be limited by their potential toicity.

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#roperties

$%&,''','''$ ength*To*+iameter atio

+iameter of % to - nm

engths in themillimeter range

"cient electricalconductors

Can act as boththermal conductorsand thermal insulators

http//brent.kearneys.ca/wp*content/uploads/&''0/'1/carbon2nanotube.3pg

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4ow C5Ts are made

Arc discharge CNTs Can be found in the carbon soot of graphite

electrodes during an arc discharge involving highcurrent. This process yields CNTs with lengths up to 50microns.

Laser Ablation In the laser ablation process a pulsed laser vapori!es a

graphite target in a high"temperature reactor while aninert gas is inserted into the reactor. Nanotubesdevelop on the cooler surfaces of the reactor as thevapori!ed carbon condenses.

#ther methods where CNTs are created$ " Chemical %apor &ecomposition

" Natural incidental and controlled 'ame environments

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#roperties

6trength

lectrical

Thermal +efects

Toicity

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6trength #roperties

Carbon nanotubes have thestrongest tensile strength of any

material known.

7t also has the highest modulus ofelasticity.

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lectrical #roperties

7f the nanotube structure isarmchair then the electricalproperties are metallic

7f the nanotube structure is

chiral then the electricalproperties can be eithersemiconducting with a verysmall band gap, otherwise thenanotube is a moderatesemiconductor

7n theory, metallic nanotubescan carry an electrical currentdensity of 89$'-:/cm&whichis more than $,''' timesgreater than metals such as

copper

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Thermal #roperties

:ll nanotubes are epected to be very good thermalconductors along the tube, but good insulators laterallyto the tube ais.

7t is predicted that carbon nanotubes will be able totransmit up to 0''' watts per meter per ;elvin at roomtemperature< compare this to copper, a metal well*knownfor its good thermal conductivity, which transmits %=1watts per meter per ;.

The temperature stability of carbon nanotubes isestimated to be up to &=''oC in vacuum and about >1'oCin air.

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+efects

+efects can occur in the form of atomicvacancies. 4igh levels of such defectscan lower the tensile strength by up to

=1?.

@ecause of the very small structure ofC5Ts, the tensile strength of the tube isdependent on its weakest segment in a

similar manner to a chain, where thestrength of the weakest link becomesthe maimum strength of the chain.

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4ealth 4aAards

According to scientists at the NationalInstitute of (tandards and Technologycarbon nanotubes shorter than about )00nanometers readily enter into human lungcells similar to the way asbestos does andmay pose an increased ris* to health.

Carbon nanotubes along with the ma+orityof nanotechnology are an une,ploredmatter and many of the possible healthha!ards are still un*nown.

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lectrical Bield emission in vacuum

electronics :pplication in electrodes,

capacitors

nergy storage ithium batteries 4ydrogen storage

@iological sensors :B tips +5: se!uencing

:pplications

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eferences

http//www.news*medical.net/news/&&>--.asp

Chae, 4.D.< ;umar, 6. (&''0). Eigid od #olymeric BibersE.Journal of Applied Polymer Science-00$/-"0) >-$.doi$'.$''&/app.&&0='.

4ong, 6eunghun< 6ung yung (&''>). E5anotubelectronics : Geible approach to mobilityE. NatureNanotechnology) &'>H&'=. doi$'.$'%=/nnano.&''>.=-

eo, 6.@.< :ndrews . (&''$). ECarbon 5anotubes6ynthesis, #roperties, and :pplicationsE. Crit. Rev. Solid

State Mater. Sci.)1234$-5")/ $81.doi$'.$'='/&''$8'-$$'8$=-.

;olosn3a3 I, 6Awarc 4, oussa B (&''>). EToicity studies ofcarbon nanotubesE.Adv Exp Med Biol.1)0 $=$H&'8. #7+$=&$>%88

bbesen, T. W.< :3ayan, #. . ($--&). Earge*scale synthesisof carbon nanotubesE. Nature35 &&'H&&&.

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