The document summarizes the arc-discharge method for synthesizing carbon nanotubes. In the arc-discharge method, a plasma is generated between two graphite electrodes in an inert gas atmosphere by applying a voltage. Parameters like gas pressure, electrode material/purity, distance between electrodes, cooling, and current/voltage determine the structures formed. Single-walled nanotubes are produced when metals like iron and nickel are added to the anode along with sulfur, which acts as a surfactant. The arc-discharge method can produce high-quality multi-walled and single-walled carbon nanotubes for applications in electronics, batteries, solar cells, and more.

1. A SEMINAR ON
SYNTHESIS OF CNT BY ARC-
DISCHARGE METHOD
K. GANAPATHI RAO
(13031D6603)
Presented
By
Presence of
Mr. G. Venkaiah

2. Outline
Introduction
Synthesis Overview
Arc Discharge
Applications
Reference

3. Carbon Nano Tubes

4. These are allotropes of carbon with
a cylindrical nanostructure.
Nanotubes have been constructed with length-to-
diameter ratio of up to 132,000,000:1
Nanotubes are members of the fullerene structural family.
Naturally align themselves into "ropes" held together
by van der Waals forces.
The chemical bonding of nanotubes is composed entirely
of sp2 bonds.
In 1991 Sumio Iijima (Japanese Scientist) observed
Multiwalled carbon Nanotube and in 1993 he discovered
Single wall carbon Nanotube.

5. Types:

6. CNT types can
be described by
the chiral vector
(n, m),
where n and m a
re integers of the
vector equation
R = na1 + ma2.

7. CNT Synthesis Methods Overview
1 Arc discharge synthesis
2 Laser ablation synthesis
3 Thermal synthesis
3.1 Chemical vapor deposition
3.2 High-pressure carbon monoxide
synthesis
3.3 Flame synthesis
4 PECVD synthesis

8. Arc Discharge Method:

9. Arc evaporation technique involves evaporation of
graphite anode rod and condensation of the deposit
on the cathode rod under inert atmosphere.
A plasma is achieved by making a gas to conduct
electricity by providing a potential difference across
two electrodes
Electrodes are made of conducting materials
In arc discharge method, two high purity graphite
electrodes as anode and cathode are held a short
distance apart under a helium atmosphere.

10. Inert atmosphere/Gas
Inert gas is meant for cooling / condensation
of the sample.
The chamber must be connected both to a
vacuum line with a diffusion pump and to
helium supply.

11. Important parameters of gas
Pressure Material
1000 torr Soot/ Carbon onions
500 torr Carbon nanotubes
100 torr Fullerenes
20 torr Amorphous carbon/soot
Therefore pressure & type of inert gas
used determines the structure of carbons to
be obtained.

12. Electrodes:
In arc evaporation method, graphite rods are
used as electrodes.
Graphite rods with 99.99% purity are used.
Major impurities in graphite are sulphur
atoms as Sulphur changes the morphology of
CNTs.
The anode is a long rod of 6mm diameter &
the cathode is a short rod of 9mm diameter

13. Cooling of Electrode
Efficient cooling of the electrodes & the
chamber are essential to produce good quality
nanotubes and also to avoid excessive sintering.
Without proper cooling-sintering occurs-with a
hard deposit of mass
With proper cooling-sintering does not occurs-
forms a uniform deposit i.e., Homogeneous
deposit with aligned bundles of nanotubes.

14. Current & Voltage
 DC power supply is given in the range of 50-100mA
and the discharge voltage is between 20 – 50 V.
DISTANCE BETWEEN ELECTRODES
The position of the anode can be adjustable from outside
the chamber.
Distance between the electrodes must be constant to obtain
a stable current.
The two electrodes are maintained at constant distance for
obtaining CNTs
When two electrodes are in contact / not at a particular
distance - fullerenes can be formed.

15. Arc Discharge Method Parameters of SWNTs:
 In the arc discharge production method sulfur
functions as a SWNTs growth promoter and
surfactant when added together with Ni/Fe/Co,
Ni/Co, Ni/Y/Fe or Ni/Ce/Fe catalysts into the anode.
 The metal-sulfur interactions change surface
tension and melting point of small droplets of
metals. This can support the creation of SWNTs for
metals which in pure form catalyze badly.
 The highest yield of web product containing the
smallest concentration of metals was obtained for
the sample C where the composition of the anode
is Fe:Y:S:C at6.6%:1.1%:1.6%:90.7%.

16. SEM images of the samples which were synthesized
(a) in an air atmosphere at 300 Torr and
(b) in the helium atmosphere at 500 Torr

17. SEM images of MWNT’s produced by arc
discharge (Kunsan National Univ)

18. Applications
Electrical circuits
Electrical cables and wires
Actuators
Paper batteries
Solar cells
Hydrogen storage
Super capacitor
Radar absorption
Medical
Textile
Optical power detectors
Environmental remediation

19. References:
http://en.wikipedia.org/wiki/Carbon_nanotube
http://www.nanocyl.com/en/CNT-Expertise-
Centre/Carbon-Nanotubes
http://www.sciencedaily.com/articles/c/carbon_nanotube.
htm
https://www.youtube.com/watch?v=B4VTfgaKLAM&hd=1
http://www.azonano.com/article.aspx?ArticleID=1561