1. GROWTH OF
CARBON NANOTUBES
SUMIT KUMAR
20120959
MANGALAYATAN UNIVERSITY
2. Carbon nanotubes ???
• Discovered in 1991 by Lijima
• It has Unique material properties
• They are nearly One-dimensional
structures
• There are two types Single-walled and
Multi-walled
4. Definition
• Carbon nanotubes are nothing but
rolled up graphene sheets in armchair
structure, zigzag structure and chiral
structure.
• Carbon nanotubes, composed of
interlocking carbon atoms, are 1000x
thinner than an average human hair –
but can be 200x stronger than steel.
• Carbon nanotubes are hexagonally
shaped arrangements of carbon atoms
that have been rolled into tubes.
5. • These tiny straw-like cylinders of pure
carbon have useful electrical
properties. They have already been
used to make tiny transistor and one-dimensional
copper wire.
6.
7. If:
m=0 , the nanotubes are called zigzag
n=m ,the nanotubes are called armchair
Otherwise ,they are called chiral.
8. The upper view of folded
sheets
• Armchair
• Zigzag
• Chiral
9. Types
• Single Wall CNT (SWCNT)
• Multiple Wall CNT (MWCNT)
• Can be metallic or semiconducting
depending on their geometry.
10. Single Wall CNT(SWCNT)
• Most single-walled nanotubes (SWNTs)
have a diameter close to 1 nanometer,
with a tube length that can be many
millions of time longer.
• The structure of a SWNTs can be
conceptualized by wrapping a one-atom-thick
layer of graphite called graphene
in to a seamless cylinder.
12. Multiple Wall CNT
(MWCNT)
Multi-walled nanotubes (MWNTs) consist
of multiple rolled layer( concentric
tubes) of graphene
13. • In the Russian Doll model, sheets of
graphite are arranged in concentric
cylinders, e.g., a (0,8) single-walled
nanotube (SWNT) within a larger (0,17)
single-walled nanotube.
• In the Parchment model, a single sheet
of graphite is rolled in around itself,
resembling a scroll of parchment or a
rolled newspaper.
• The interlayer distance in multi-walled
nanotubes is approximately 3.4 Å. Its
individual shells can be described as
SWNTs, which can be metallic or
semiconducting.
14. Comparison
• Single –walled CNTs exhibit electric
properties that are not shared by the
multi-walled CNTs.
• SWNTs is useful in the development of
the first intramolecular field effect
transistors (FET).
16. Chemical Vapor
Deposition
• A substrate is prepared with a layer of
metal catalyst particles, most commonly
nickel, cobalt, iron , or a combination.
• The substrate is heated to
approximately 700°C.
17. • Two gases are bled into the reactor: a
process gas (such as ammonia ,
nitrogen or hydrogen ) and a carbon-containing
gas (such as acetylene ,
ethylene , ethanol or methane ).
• Nanotubes grow at the sites of the metal
catalyst; the carbon-containing gas is
broken apart at the surface of the
catalyst particle, and the carbon is
transported to the edges of the particle,
where it forms the nanotubes.
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23. Laser Ablation
• Use of very strong laser
• Expensive (energy costs)
• Commonly applied
24. Another method to grow SWNTs using
laser ablation was demonstrated in
1996 by Smalley's group and has
prompted a lot of interest.
The synthesis could be carried out in a
horizontal flow tube under a flow of
inert gas at controlled pressure.
In this set-up the flow tube is heated to
~1200°C by a tube furnace. Laser pulses
enter the tube and strike a target
consisting of a mixture of graphite and
a metal catalyst such as Co or Ni.
SWNTs condense from the laser
vaporization and are deposited on a
collector outside the furnace zone.
27. Arc-Discharge Process
• The carbon arc discharge method, is the
most common and perhaps easiest way
to produce CNTs, as it is rather simple.
• However, it is a technique that
produces a complex mixture of
components, and requires further
purification - to separate the CNTs from
the soot and the residual catalytic
metals present in the crude product.
28. • This method creates CNTs through arc-vaporization
of two carbon rods placed
end to end, separated by approximately
1mm, in an enclosure that is usually
filled with inert gas at low pressure.
• A direct current of 50 to 100A, driven
by a potential difference of
approximately 20 V, creates a high
temperature discharge between the two
electrodes.
• The discharge vaporizes the surface of
one of the carbon electrodes, and forms
a small rod-shaped deposit on the other
electrode.
29. • Producing CNTs in high yield depends
on the uniformity of the plasma arc,
and the temperature of the deposit
forming on the carbon electrode.
30.
31. Purification
• The main impurities :graphite (wrapped
up) sheets, amorphous carbon, metal
catalyst and the smaller fullerenes…
• Rules : - separate the SWNTs from the
impurities
give a more homogeneous diameter or
size distribution.
• The techniques that will be discussed
are oxidation, acid treatment,
annealing, ultrasonication, micro
filtration, ferromagnetic separation,
cutting, functionalisation and
chromatography techniques.
32. Properties
• CNTs have High Electrical Conductivity
• CNTs have Very High Tensile Strength
• CNT are Highly Flexible- can be bent
considerably without damage
• CNTs are Very Elastic ~18% elongation
to failure
• CNTs have High Thermal Conductivity
• CNTs have a Low Thermal Expansion
Coefficient
• CNTs are Good Electron Field Emitters
• CNTs have a High Aspect Ratio (length
= ~1000 x diameter
33. Applications
• Thermal Conductivity of CNTs
• Field Emission of CNTs
• Conductive Plastics with CNTs
• Energy Storage using CNTs
• Conductive Connectors with CNTs
• Molecular Electronics based on CNTs
• Thermal Materials with CNTs
• Structural Composites with CNTs
• Fibers and Fabrics with CNTs
34. Summary
• Carbon nanotubes have very different
properties compared to the other
carbon allotropes
- these unique properties offer huge
potential in product development.
