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Carbon Nanotubes
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History of Nanotubes
Discovery ofbuckminsterfullerene in 1985sparked interest in other stablecarbon structures
In 1991 Sumio Iijima discovered
multi-walled carbon nanotubesand created first protocol for purenanotubes
Carbon fibers were seen asbyproducts of catalyticexperiments since 1976
In 1993 Iijima produced single-walled nanotubes with diameter~1nm
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History of nanotubes
M. Endo used a catalytic
chemical vapor deposition
method (1976)
Not industrially feasible
Iijima used an arc-
evaporation method
Purer product
Efforts to control diameter,
number of layers and purity
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Producing multi-walled nanotubes
The arc-evaporator apparatus produces the highest-quality nanotubes
The first nanotubes had two layers with diameter
ranging from 3 to 30 nanometers
Pass 50 amps of current between two graphite
electrodes in a cloud of helium
Some of the graphite vaporizes on the cathode,
containing carbon nanotubes
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Producing single-walled nanotubes
Pass a carbon-containing gas, like a hydrocarbon,
over a nano-sized metal catalyst (Fe, Ni, or Co)
Metal particles catalyze the break down of gaseous
molecules into carbon Nanotube begins to grow with the metal at one end
Poorer quality but better for volume production
Third method comes from vaporizing a metal-graphite target with a laser
Results in high yield of single-walled nanotubes
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Physical Properties of Carbon Nanotubes
Consists of 6-Membered
Carbon Rings that Form
Long, Thin, Tubular
Structures
Similar to Graphite
Three Different
ConformationsArm Chair
Zig-Zag
Chiral
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Physical Properties of Nanotubes II
The properties of CNTs areunparalleled by any substance.
Strength
Conductivity and Ballistic Transport
Electrical
Fouriers Law
H=(Q/t)=k*A*(T/x)
Thermal conductivity
k=(Q/T)*(1/A)*(x/T) Optical
CTNs will replace common
infrastructures in modern
technology
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Applications of CNTsCommercial
Commercial applications for CNTs are not really applicable because
of the high cost of CNT production
Analysts in 2004 originally thought CNT prices would drop to a
reasonable price by the present, but this was far too optimistic
Theres little doubt that once the purification and assemblycosts go down, CNTs will be wildly used
In February, a company was able to make relatively large sheets
(6x3) and are looking to mass produce by 2012
There are also some issues with the toxicity of CNTsThey are normally made with heavy metal catalysts and if they
are not purified properly this can lead to poisoning in biological
systems
It is still useful to examine its possible functions on a smaller scale
(following slides)
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Electronics The high thermal conductivity and low current resistance
makes CNTs very valuable to the future of electronics Many developers are making smaller and smaller devices and
overheating is a large problem
They can also be used in electronics for electromagneticshielding because it has good electrostatic dissipation properties
CNTs may also revolutionize the way speakers are
produced. A team in China created speakers using CNTs that were
functional over a wide range of sounds including the range ofhuman hearing
The CNT film a only a few nanometers thick and is used to make
the sound using an alternating current.
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Medicine
CNTs have many potential applications in the medicalworld They can be used to generate heat (via radio waves) or as
drug vectoring agents
Have major implications for tissue engineering Can be used for improved tracking of cells, sensing of
microenvironments, delivering of transfection agents andscaffolding for incorporating with the hosts body
CNTs are ideal for working in nano environments from 1-100 nm.
Graph below shows how drastically CNT research in the biomedical
field has increased CNTs will be most useful as structural supports as tissue
scaffolding, making these tissues stronger and their conductivitycan be used for directed cell growth
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Other Applications Preposterous
Space Elevator
Not Crazy
Tennis rackets, bikes, handlebars, hockey and lacrosse sticks
New ultra-light, ultra-strong body armor for soldiers
CNTs have been used to develop Ultra Capacitors
Swapping conventional capacitor materials with
sheets of CNTs greatly maximizes surface area and
creates a much more potent capacitor in a smaller
space
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