12 c-nanotubes

8/12/2019 12 C-Nanotubes

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Main interest:

1. Prototypes for a one-dimensional quantum wire.

2. Strength


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1970: Morinobu Endo-- First carbon filaments of nanometer

dimensions, as part of his PhD studies at the University ofOrleans in France. He grew carbon fibers about 7 nm in

diameter using a vapor-growth technique. Filaments were not

recognized as nanotubes and were not studied.

1991:Sumio Iijima-- NEC Laboratory in Tsukuba-- used high-

resolution transmission electron microscopy to observe carbon

nanotubes.


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Hexagonal graphite:

I. Graphite has a structure containing layers of atoms

arranged at the corners of contiguous hexagons.

II. (not to be confused with hexagonal close packed).

III. The ease with which layers slide against each other is

consistent with the much larger distance between carbon

atoms in different layers (335 pm) than between carbon

atoms in the same layer (142 pm).

IV. The lattice constant a = 246.6 pm

V. C=669 pm


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An ideal nanotube can be thought of as a hexagonal network

of carbon atoms that has been rolled up to make a cylinder.

width: nanometer: "capped" with half of a fullerene

molecule.

length: microns


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1. A carbon nanotube is

based on a two-

dimensional graphenesheet.

2. The chiral vector is

defined on the

hexagonal lattice asCh= n1+ m2,

3. Chiral angle

4. Role/cap off


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(n, 0) or (0, m) and

have a chiral angle of0, armchair

nanotubes have (n, n)

and a chiral angle of

30, while chiral

nanotubes have

general (n, m) values

and a chiral angle of

between 0 and 30.


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1. Diameter of nanotube

2. Chiral angle

Both depend on n and m.

Diameter=length of chiral vector divided by 4

(has to do with the capping)


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Quote: Since each unit cell of a nanotube contains a number of hexagons,

each of which contains two carbon atoms, the unit cell of a nanotube contains

many carbon atoms. If the unit cell of a nanotube isNtimes larger than that of

a hexagon, the unit cell of the nanotube in reciprocal space is 1/Ntimessmaller than that of a single hexagon.

Let us break this down!


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Then in reciprocal space:

(pi/L) = (pi/a N) = (pi/a)(1/N)For k space


14/185,5 9,0 10,0


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E(kx, ky)

Then because we have a cylinder:

E(kxn , ky)

Where

Kxn = ((2*pi) /P) * n

n=1,2,3 (1-D bands)


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Rice University group (1996)-- produce bundles of ordered single-wall

nanotubes :

1. Prepared by the laser vaporization of a carbon target in a furnace at 1200

C.

2. Cobalt-nickel catalyst helps the growth of the nanotubes, presumably

because it prevents the ends from being "capped" during synthesis.

3. By using two laser pulses 50 ns apart, growth conditions can be maintained

over a larger volume and for a longer time. This scheme provides moreuniform vaporization and better control of the growth conditions.

4. Flowing argon gas sweeps the nanotubes from the furnace to a water-cooled

copper collector just outside of the furnace.

Catherine Journet, Patrick Bernier and colleagues at the University of MontpellierinFrance: carbon-arc method to grow arrays of single-wall nanotubes.
http://univ-montp2.fr/http://univ-montp2.fr/


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Scanning electron microscope: looks like a mat of carbon ropes

Ropes are between 10 and 20 nm across and 100 m long.

Transmission electron microscope: each rope is found to consistof a bundle of single-wall carbon nanotubes aligned along a

single direction.

X-ray diffraction, which views many ropes at once, shows that

the diameters of the single-wall nanotubes have a narrowdistribution with a strong peak.


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12 c-nanotubes

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