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Chemical Modification
of Nanotubes by Electron and Ion Beam Irradiation
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1. Mechanical
Properties of Chemically Functionalized Carbon Nanotubes
i) Why Chemically
Functionalize Nanotube Walls?
- Nanotube-polymer matrix materials fail by fiber
pull-out
- Chemical functionalization of the nanotube
walls increase the interaction of the nanotubes with the matrix and
toughen the composite
- Chemical functionalization would also create sp3
defects on the nanotube walls.
ii) Results
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2. Modification of
Multi-Walled Carbon Nanotubes
(a) Modification by Electron
and Ion-Beam Irradiation
Electron
Irradiation
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CF3+
Irradiation
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Ar Irradiation
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Electron beams are
found to induce the most uniform and consistent modification of the
multi-walled carbon nanotubes because of the high amount of energy they
impart to the atoms via the primary knock-on atom mechanism. Ar beams
similarly impart a great deal of energy, and induces a significant
amount of damage, to the multi-walled nanotube systems considered. In
contract, polyatomic fluorocarbon beams produce chemical modification
of primarily the exteriors of the multi-walled carbon nanotubes.
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(b) Mechanical Pullout
The
innermost shell of an irradiated multi-walled carbon nanotube was
pulled out via a "sword and sheath" mechanism at a rate of 40 m/s in
the direction of the nanotube length. A similar test was performed on
an unirradiated multi-walled nanotube. The inner shell pulled out
freely in the case of the bare multi-walled carbon nanotube. In
contrast, the inner shell of the irradiated nanotube had significantly
more difficulty in pulling out of the multi-walled tube, as shown in
the movie.
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3. Beam Deposition
on a Nanotube Bundle
Ion beam deposition has been shown
to be an effective way of modifying carbon nanotubes and producing
novel nanostructures.
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i) CF3+
Beam Deposition on a Single-Walled Nanotube Bundle
- 20 CF3+/beam,
incident energy = 80 eV/ion
- System temperature = 300 K
- Cross-links formed between adjacent
nanotubes
- Nanotubes distorted
- Most CF3+ ions
dissociate into CF fragments and individual F atoms.
ii) Results
| Events |
Percentage |
| Dissociation into C+3F |
55.0 |
| Dissociation into CF+2F |
45.0 |
| Scattering of C |
10.0 |
| Scattering of F |
5.0 |
| Adsorption of C on nanotube wall |
90.0 |
| Adsorption of F on nanotube wall |
81.7 |
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4. Deposition on
Nanopeapods
- Same conditions as for the empty single-walled
nanotube bundle
- Cross-links formed between
- nanotube walls and fullerene molecules
- adjacent nanotube walls
- Most CF3+ ions dissociate
into individual C atoms and F atoms
i) Results
| Events |
Percentage |
| Dissociation into C+3F |
80.0 |
| Dissociation into CF+2F |
19.0 |
| Dissociation into CF2+F |
1.0 |
| Scattering of C |
20.0 |
| Scattering of F |
10.0 |
| Adsorption of C on nanotube wall |
50.0 |
| Adsorption of F on nanotube wall |
61.7 |
| Incorporation of C with C60 |
15.0 |
| Incorporation of F with C60 |
20.0 |
| Cross-link formation between CNT and C60 |
15.0 |
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