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What are Carbon Nanotubes ?
Carbon nano tubes are fullerene-related
structures which consist of graphene cylinders
closed at either end with caps containing
pentagonal rings
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What are Carbon Nanotubes ?
Carbon nanotubes are fullerene-related
structures which consist of graphenecylinders closed at either end with capscontaining pentagonal rings
http://www.rdg.ac.uk/~scsharip/Tubecap.htmhttp://www.rdg.ac.uk/~scsharip/Tubecap.htm8/3/2019 What Are Carbon Nanotubes
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Discovery
They were discovered in 1991 by the Japaneseelectron microscopist Sumio Iijima who was
studying the material deposited on the cathodeduring the arc-evaporation synthesis of fullerenes.He found that the central core of the cathodicdeposit contained a variety of closed graphitic
structures including nanoparticles and nanotubes,of a type which had never previously beenobserved
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Carbon Nanotubes: This is a nanoscopic structure made of carbon atoms in the
shape of a hollow cylinder. The cylinders are typically closedat their ends by semi-fullerene-like structures. There are threetypes of carbon nanotubes: armchair, zig-zag and Chiral(helical) nanotubes. These differ in their symmetry. Namely,the carbon nanotubes can be thought of as graphene planes'rolled up' in a cylinder (the closing ends of carbon nanotubescannot be obtained in this way). Depending on how the
graphene plane is 'cut' before rolled up, the three types ofcarbon nanotubes are obtained. Within a particular type,carbon nanotubes with many different radii can be found(depending on how large is the graphene area that is foldedonto a cylinder). These tubes can be extremely long (several
hundreds of nanometers and more). Some consider them asspecial cases of fullerenes. When produced in materials,carbon nanotubes pack either in bundles (one next to anotherwithin a triangular lattice) - single-walled carbon nanotubes, orone of smaller radius inside others of larger radii - multi-walled carbon nanotubes.. Carbon nanotubes were discovered
by Sumio Ijima in 1991.
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The way to findout how thecarbon atomsare arranged in
a molecule canbe done byjoining thevectorcoordinates of
the atoms. Bythis way it canbe identifiedwhether if thecarbon atomsare arranged ina zig-zag,armchair or in ahelical shape.
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Nanotubes are formed by
rolling up a graphene sheet
into a cylinder and capping
each end with half of a
fullerene molecule. Shown
here is a (5, 5) armchair
nanotube (top), a (9, 0)
zigzag nanotube (middle)and a (10, 5) chiral
nanotube. The diameter of
the nanotubes depends on
the values ofn and m.
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Discovery
They were discovered in 1991 by the Japaneseelectron microscopist Sumio Iijima who wasstudying the material deposited on the cathode
during the arc-evaporation synthesis offullerenes. He found that the central core of thecathodic deposit contained a variety of closedgraphitic structures including nanoparticles
and nanotubes, of a type which had never
previously been observed
S h i
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SynthesisArc discharge method Chemical vapor
deposition
Laser ablation
(vaporization)
Connect two graphite rods
to a power supply, placethem millimeters apart, and
throw switch. At 100 amps,
carbon vaporizes in a hot
plasma.
Place substrate in oven,
heat to 600 C, and slowlyadd a carbon-bearing gas
such as methane. As gas
decomposes it frees up
carbon atoms, which
recombine in the form of
NTs
Blast graphite with intense
laser pulses; use the laserpulses rather than
electricity to generate
carbon gas from which the
NTs form; try various
conditions until hit on one
that produces prodigiousamounts of SWNTs
Can produce SWNT and
MWNTs with few
structural defects
Easiest to scale to industrial
production; long length
Primarily SWNTs, with a
large diameter range that
can be controlled byvarying the reaction
temperature
Tubes tend to be short with
random sizes and directions
NTs are usually MWNTs
and often riddled with
defects
By far the most costly,
because requires expensive
lasers
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Uses of Carbon NanoTubes carbon nanotubes, which exhibit electrical conductivity as high
as copper, thermal conductivity as high as diamond, and as
much as 100 times the strength of steel at one-sixth the weight.In order to capitalize on these properties, researchers andengineers need a set of tools -- in this case, chemical processeslike pyrolytic fluorination -- that will allow them to cut, sort,dissolve and otherwise manipulate nanotubes.
Molecular and Nanotube Memories Nanotubes hold promisefor non-volatile memory; with a commercial prototypenanotube-based RAM predicted in 1-2 years, and terabitcapacity memories ultimately possible. Similar promises havebeen made of molecular memory from several companies, with
one projecting a low-cost memory based on molecule-sizedcylinders by end 2004 that will have capacities appropriate forthe flash memory market. These approaches offer non-volatilememory and if the predicted capacities of up to 1Tb can beachieved at appropriate cost then hard drives may no longer benecessary in PCs.
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Future Uses of CNTs
Nano-Electronics
Nanotubes can be conducting or insulatingdepending on their properties
Diameter, length, chirality/twist,
and number of walls
Joining multiple nanotubes together to make
nanoscale diodes Max Current Density: 10^13 A/cm^2
Future Uses of CNTs
Nano-Electronics
Nanotubes can be conducting or insulatingdepending on their properties
Diameter, length, chirality/twist,
and number of walls
Joining multiple nanotubes together to make
nanoscale diodes Max Current Density: 10^13 A/cm^2
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The Space Elevator
The Idea To create a tether from earth to
some object in a geosynchronous
orbit. Objects can then crawl upthe tether into space.
Saves time and money
The Problem 62,000-miles (100,000-
kilometers)
20+ tons
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The Space Elevator
The Solution: Carbon Nanotubes
10x the tensile strengh (30GPa)
1 atm = 101.325kPA
10-30% fracture strain
Further Obstacles
Production of Nanofibers
Record length 4cm
Investment Capital: $10 billion
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