CARBON NANO TUBE -- PREPARATION – METHODS

1. CARBON NANO TUBE
PREPARATION – METHODS
Fathima.P.E
CBPST,KOCHI

2. INTRODUCTION:
 Carbon nanotubes are hexagonally shaped arrangements of carbon atoms
that have been rolled into tubes.
 These tiny straw-like cylinders of pure carbon have useful electrical
propeties. They have already been used to make tiny transistor and one-
dimentional copper wire
 Carbon nanotube properties depend on how you roll the sheet.
 In other words, even though all carbon nanotubes are made of carbon, they
can be very different from one another based on how you align the
individual atoms.
 With the right arrangement of atoms, you can create a carbon nanotube
that's hundreds of times stronger than steel, but six times lighter
 Carbon nanotubes can also be effective semiconductors with the right
arrangement of atoms.
 Scientists are still working on finding ways to make carbon nanotubes a
realistic option for transistors in microprocessors and other electronics.

3. CNT: ROLLING-UP A GRAPHENE SHEET TO FORM
A TUBE
Schematic
of a CNT
SEMimage
of CNT

4. TYPES OF CARBON NANO TUBES:
 Single walled CNT (SWCNT)
 Multi walled CNT (MWCNT)
 Can be metallic or semi conducting

5. SINGLE WALLED
 -Most single-walled nanotubes (SWNTs) have a diameter of cloes 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 cylender

6. • The way the graphene sheet is wrapped is represented by a pair of
indices (n,m) called the chiral vector.
• The integers n and m denote the number of unit vectors along two
directions in the honeycomb crystal lattice of graphene
• If m = 0, the nanotubes are called "zigzag". If n = m, the nanotubes
are called "armchair". Otherwise, they are called "chiral".

7. MULTI WALLED
• Multi-walled nanotubes (MWNTs) consist of multiple rolled layer( concentric tubes) of
graphene

8. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders
• 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 close to the distance
between graphene layers in graphite, approximately 3.4 Å. The Russian Doll
structure is observed more commonly. Its individual shells can be described
as SWNTs, which can be metallic or semiconducting.
the Russian Doll model, sheets of graphite are arranged in concentric cylinders
In the Russian Doll model, sheets of graphite are arranged in concentric cylinders
In the Russian Doll model, sheets of graphite are arranged in concentric cylinders
In the Russian Doll model, sheets of graphite are arranged in concentric cylindersIn the Russian Doll model, sheets of graphite
are arranged in concentric cylinders
In the Russian Doll model, sheets of graphite
are arranged in concentric cylinders.
In the

9. SYNTHESIS OF CARBON NANO TUBES
• Commonly applied techniques:
• Chemical Vapor Deposition (CVD)
• Arc-Discharge
• Laser ablation
• Techniques differ by:
• Type of nanotubes (SWNT / MWNT )
• Catalyst used
• Yield
• Purity

10. ARC DIS CHARGE
• CNT production requires 3 elements ,
I. Carbon feed
II. Metal catalyst
III. Heat
a) Two Graphite electrodes placed in an inert Helium atmosphere .
b) When DC current is passed anode is consumed and material forms
on cathode.
c) For SWNT mixed metal catalyst is inserted into anode
d) Pure iron catalyst + Hydrogen-inert gas mixture gives 20 to 30cm
long tube.
e) The nanotubes were initially discovered using this technique, it has
been the most widely-used method of nanotube synthesis.

12. ARC DIS CHARGE 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.
• 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.
• Producing CNTs in high yield depends on the uniformity of the plasma arc,
and the temperature of the deposit forming on the carbon electrode.

13. LASER ABLATION PROCESS
 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 the laser ablation process, a pulsed laser vaporizes a graphite target in a
high-temperature reactor while an inert gas is bled into the chamber.
 Nanotubes develop on the cooler surfaces of the reactor as the vaporized
carbon condenses.
 A water-cooled surface may be included in the system to collect the
nanotubes.
 The laser ablation method yields around 70% and produces primarily
single-walled carbon nanotubes with a controllable diameter determined
by the reaction temperature.
 it is more expensive than either arc discharge or chemical vapor
deposition.

15. CHEMICAL VAPOR DEPOSITION (CVD):
 During CVD, a substrate is prepared with a layer of metal catalyst articles, most
commonly nickel, cobalt, iron, or a combination.
 The diameters of the nanotubes that are to be grown are related to the size of the
metal particles.
 The substrate is heated to approximately 700°c.
 To initiate the growth of nanotubes, 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.

17. APPLICATIONS:
 CVD is used to grow a thin layer of advanced materials on the surface
of a substrate.
 Applications may be found in the areas of:
 integrated circuits, optoelectronic devices and sensors
 catalysts
 micromachines, and fine metal and ceramic powders protective
coatings

18. 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.

19. Arc Discharge Method Chemical Vapor Deposition Laser Ablation (Vaporization)
Connect two graphite rods to a
power supply, place them
millimeters apart, and throw
switch. At 100 amps, carbon
vaporizes in a hot plasma.
Place substrate in oven, heat to
600 C, and slowly add a carbon-
bearing gas such as methane. As
gas decomposes it frees up
carbon atoms, which recombine in
the form of NTS
Blast graphite with intense laser
pulses; use the laser pulses rather
than electricity to generate carbon
gas from which the NTS form; try
various conditions until hit on one
that produces prodigious amounts
of SWNTS
Can produce SWNT and MWNTs
with few structural defects
Easiest to scale to industrial
production; long length
Primarily SWNTS, with a large
diameter range that can be
controlled by varying the reaction
temperature
Tubes tend to be short with
random sizes and directions
NTS are usually MWNTS and
often riddled with defects
By far the most costly, because
requires expensive lasers

20. ADVANTAGES:
 Extremely small and lightweight.
 Resources required to produce them are plentiful, and many can be
made with only a small amount of material
 Are resistant to temperature changes, meaning they function
almost just as well in extreme cold as they do in extreme heat
 Improves conductive, mechanical, and flame barrier properties of
plastics and composites.
 Enables clean, bulk micromachining and assembly of components.
 Improves conductive, mechanical, and flame barrier properties of
plastics and composites.

21. DIS ADVANTAGES:
 Despite all the research, scientists still don't understand exactly how
they work.
 Extremely small, so are difficult to work with.
 Currently, the process is relatively expensive to produce the
nanotubes.
 Would be expensive to implement this new technology in and replace
the older technology in all the places that we could.
 At the rate our technology has been becoming obsolete, it may be a
gamble to bet on this technology.

22. APPLICATIONS:
 Micro-electronics / semiconductors
 Conducting Composites
 Controlled Drug Delivery/release
 Artificial muscles
 Super capacitors
 Batteries
 Field emission flat panel displays
 Field Effect transistors and Single electron
transistors

23.  Molecular Quantum wires
 Hydrogen Storage
 Noble radioactive gas storage
 Solar storage
 Waste recycling
 Electromagnetic shielding
 Dialysis Filters
 Thermal protection
 Nanotube reinforced composites
 Reinforcement of armour and other materials
 Reinforcement of polymer
 Avionics
 Collision-protection materials
 Fly wheels

24. CONCLUSION:
 CNTs are nanometer-length shells of carbon.
 Possess a combination of unique physical and chemical properties.
 Programmable .
 Can be applied in a variety of fields.
 Exhibits incredible strength, elasticity, thermal electrical conductivity.
 Pivotal element in Nano technology.
 Exhibits incredible strength, elasticity, thermal and electrical
conductivity.
 Can be applied to a variety of fields.
 Technology is in its infancy and will take several years to develop.

25. REFERENCE:
1. D.A.Bochvar and E.G.Gal'pern, Dokl.Akad.Nauk.USSR, 209, (610,
1973 )
2.http://www.ou.edu/engineering/nanotube, 2003
3. http://nanotube.msu.edu/
4.http://www.pa.msu.edu/cmp/csc/nanotube.html
5.http://en.wikipedia.org/wiki/Carbon_nanotube
6.http://students.chem.tue.nl/carbonnanotubes/applications.html

26. Thanks for your listening…