1. PRESENTED BY:
JUSTIN GEORGE
University of Antwerpen
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2. Allotropic forms of carbon
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3. why carbon naotubes are so special?
 Electrical properties depend on geometry of nanotube
 Tremendous current carrying capacity
1 billion Amps/cm2
 Excellent heat conductor
twice as good as diamond
 High strength
much higher than high-strength steel
 Young Modulus ~ 1 TPa (SWNT) and 1.25 TPa (MWNT) (Steel: 230 Gpa)
 High Aspect Ratio: 1000 – 10,000
 Density: 1.3 – 1.4 g/cm3
 Maximum Tensile Strength: 30 GPa
 Thermal Conductivity: 2000 W/m.K (Copper has 400 W/m.K)
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4. What is carbon nanotubes?
 Carbon nanotubes are a hexagonal shaped
arrangement of carbon atoms that has been rolled into
tubes.
Composites Science and Technology 61
(2001) 1899–1912
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5. Carbon naotube family
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6. Classification of carbon nanotubes
 Single walled carbon nanotubes (SWNT) (0.4 -2 nm)
 Multiwalled carbon nanotubes (MWNT) (2-100 nm)
 Metallic (n =m or n-m =3i, i is an interger)
 Semiconductor (all other cases)
Depends on the geometry
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7. Diameter of the tube and chiral vector.
 The diameter d of the carbon nanubes are given by
Where is the nearest carbon-carbon bond
length and C is the chiral vector or roll-up vector.
where the chiral angle
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8. Carbon nanotube synthesis
 Arc discharge
 Laser ablation
 CVD (chemical vapour deposition)
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9. Arc discharge method
 cathode gets
consumed, CNTs in
cathodic soot
 structure of CNTs
depends on: current
I, voltage V, He gas
pressure, anode
material, distance
between the
electrodes
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10. Arc discharge method
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11. Laser vaporization
 Laser vaporizes the graphite target at high
temperature in an inert atmosphere
 nanotubes formed at the cooler surface of the
chamber as the vaporized carbon condenses.
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12. Catalytic method
 Hydrocarbon in contact with hot metal nano particles
and decompose into hydrogen and carbon
 If the interaction with catalytic substrate is weak the
carbon diffuses down and push the nano particle up
“tip-growth model”
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13. Characterization of CNT’s
 STM (Scanning tunneling
microscopy )
 AFM (Atomic force
microscopy)
 TEM (transmission
electron microscopy)
 SEM (scanning electron
microscopy)
 Raman spectroscopy
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14. Quantum Effect
 Conductance appears to be ballistic over micron scales,
even at room temperature.
 Ballistic = no dissipation in the tube itself = very high
current densities are possible.
 Conductance increase with more CNTs are in contact with
liquid metal.
 Frank et al., Science 280, 1744 (1998).
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15. Energy
Rayleigh
Scattering
(elastic)
The Raman effect comprises a very small fraction,
about 1 in 107 of the incident photons.
Stokes
Scattering
Anti-Stokes
Scattering
h 0
h 0
h 0
h 0 h 0 h m
h 0+h m
E0
E0+h m
Raman
(inelastic)
Virtual State

16. Raman scattering of CNT
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17. Raman signals in SWNT’s
 Radial breathing mode (observed
up to 3 nm in SWNTs and
MWNTs )
 D-band (1350 ) –Resonant
nature.
 G-band (1530 -1620 )
 G’ band (depends on diameter of
CNTs)
 Other weak features.
 Resonance is diameter selective.
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18. Significance of Raman signals
 RBM is useful to identify the presence of SWNT’s in
the carbon material and to determine the diameter of
SWNT’s.
 G-mode corresponds to planar vibrations of carbon
naotubes and is present in graphite like material
( carbon materials )
 D-mode generate from the structural defects of
graphite like carbon.
 G/D ratio is used to find quality of carbon nanotubes
(higher ratio, higher quality)
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19. Radial-Breathing Mode
Diameter of the carbon
nanotube
Breathing mode : 100 – 350
The growth
temperature,
Diameter of nanotube increases with
increase in growth temperature
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20. RBM as a function of diameter
 A particular diameter
is excited at a given
laser frequency
(Resonance Raman
effect)
 In a range of laser
frequency the RBM
frequency –diameter
plot can be made
which agree well with
the theory.
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21. Temperature dependence of G-band
 Intensity of G-band
decreases exponentially with
temperature.
 The intensity is independent
of surface morphology and
preparation method.
 This can be used to measure
the temperature of the
sample.
 A shift in the G+ peak can
also be observed as the
temperature increases.
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22. Distinction of SWNTs, DWNTs and
MWNTs using Raman spectroscopy
 Can distinguish
SWNT, DWNT
and MWNT from
a mixture of sample .
 G/D ratio show
MWNTs are low
quality.
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23. Identify metallic and semiconductor
SWNT using Raman spectra.
 Frequency is independent of diameter but
depends on diameter and metallic and semiconductor
nature of SWNT .
 The frequency downshift of metallic SWNT is more
than semiconductor SWNT.
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24. Characterization of water filled CNT using
Raman spectroscopy
 Resonance Raman
spectra of SWNT (a) S1
raw sample (c) air
oxidized and acid
treated sample (used to
open the SWNT).
 (b) and (d) are S1 and S2
respectively with empty
(0) and filled
nanotubes.

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25. Nanotube elecronics
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26. CNT gas sensors
 Chemical doping induces
a strong change in the
conductance.
 Detect small
concentration gas with
high sensitivity at room
temperature.
 Can detect NO2, NH3 etc.
with fast response time.
(Shu Peng and Kyeongjae Cho,
Department of Mechanical
Engineering, Stanford University)
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27. AFM (atomic force microscopy )
 1. Laser
 2. Mirror
 3. Photodetector
 4. Amplifier
 5. Register
 6. Sample
 7. Probe
 8. Cantilever
 Uses van der Waals force
between the tip and the
surface
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28. Nanotube as AFM tip
 Exceptional mechanical strength and large aspect ratio
 Survive tip crash due to accidental contact with
observation surface
 Slender and well defined tip, so higher resolution.
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29. CNT mechanical sensors
 Conductance decreases as
the AFM tip pushes the
nanotube down, but recovers
as the tip retracts.
 Full reversibility of
conductance, so can be used
as a mechanical sensor.
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30. CNT Nanothermometer
•Continuous, uni-dimensional column of Gallium in CNT
•Gallium has greatest liquid range (30 – 2,403 °C) and low vapour
pressure at high temperature.
• Height of liquid gallium varies linearly and reversibly with
temperature
• Expansion coefficient same as macroscopic gallium.
• Gallium meniscus perpendicular to inner surface of CNT
• Easy to read and suitable for microenvironment.
Gao and Bando, Nature (2002)
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31. CNT nanobalance
 Nanobalance can measure a mass
small as 22 fg (femtogram)
 Time dependent voltage applied
cause time dependent force and
dynamic deflection, by adjusting the
frequency resonance excitation can
be achieved
 E, modulaus , L -length, t -
thickness, desnsity , effective mass
Most sensitive and smallest balance in the
world
Poncharal et al., Science (1999) 31

32. CNT infrared detector
 SWNT based IR
detectors have excellent
sensitivity, response
time, dark current
characteristics.
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33. Applications of carbon nanotubes
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34. Blacker than black
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35. Electron field emission of CNT
 Electric field lines
concentrated on sharp
regions, since CNT have
sharp tip the geometry is
favorable for field
emission.
 Electron emission can
be observed with about
100 V on single CNT.
 Application in field
emission display.
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36. Novel hard disk
 A novel data storage system
capable of 1015 bytes/cm2 is
being explored.
In this system, H atoms
would be designated as 0
and F atoms as 1.
A tip that can distinguish
between 0 and 1 rapidly and
unambiguously
is being investigated.
 http://www.ipt.arc.nasa.go
v/datastorage.html
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37. Other applications
 Gas storage – as CNT has very large surface area gases
like Hydrogen can be absorbed and stored
 Super capacitor- can store large amount of energy and
can deliver very high peak power (CNT supercapacitor
have 7 times more energy density than commercial
activated carbon based supercapacitor)
 Nanomachines- CNT based nanogear with benzene
molecule bonded as teeth.
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38. Thank you
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