Textures of MWCNTs (a) herringbone
texture and (b) bamboo texture
Multi walled carbon
132,000,000:1 Length-To Diameter Ratio
Diameter of 3 to 9 nm
Lengths in the millimeter range
Efficient electrical conductors
High thermal conductivity(6000 W/MK for SWCNT & MWCNT is 3000
W/MK) that is grater then diamond (2000 W/MK).
Its tensile strength is (45GPa)more then diamond, steel, etc.
Bio medical sensors
Electronic circuit design
Energy storage (hydrogen storage.)
Synthesis of CNT:-
There are three methods of synthesis of Carbon Nano Tubes-
•Electric arc-discharge method,
•Laser ablation method and
•Chemical Vapor Deposition (CVD)
Chemical Vapor Deposition
Reactor tube is made up of Quartz.
CxHx- Carbon precursor
Substrates- SiO2, Al2O3, MgO, TiO2
List of different precursors with their phase and
S No. Precursors Phase Decomposition
1. Methane Gas 500-800
2. Ethane Gas 550-640
3. Acetylene Gas 1500-1800
4. Ethanol Liquid 780-1085
5. Carbon mono
6. Carbon mono
catalyst- Fe) used
Different catalysts used in synthesis of carbon
nano tubes by using chemical vapor deposition (CVD):-
Ni, Fe, Co, Mo, Cu, Au etc.
MgO, Al2O3, SiO2, TiO2. these aare also called substrates
where catalysts are placed in the tube furnace and heated
upto 500 to 1000ºC.
Some important points regarding to catalyst
• Metal supported on MgO shows low catalytic activity towards
decomposition of methane and this reason impels the researchers to
search the suitable transition metal supported on MgO for effective
production of SWCNTs.
• Ni/Ti02has an advantage over Ni/Si02 by reason of the catalytic
activity of Ni/Ti02 is kept higher during catalyst regeneration cycles.
Conversely, catalytic activity of Ni/Si02 for methane decomposition is
higher at early cycles and decreases gradually with the regeneration
cycles. This phenomenon is mainly due to the changes of these metallic
particles size after several regeneration cycles, i.e. nickel particles in
Ni/Ti02 approach the optimum size for methane decomposition (60-
Some important points regarding
to catalyst supporters contd.
-with the regeneration cycles while nickel particles
in Ni/Si02 aggregated into size larger than
150nm, which are inactive for methane
decomposition, after several regeneration cycles.
• Ti02 helps to reduce the activation energy in
methane decomposition, and 60 KJ/mol was
achieved over 13wt% Ni/Ti02 in methane
decomposition reaction. This activation energy is
the lowest activation energy reported in
literature for this reaction.
We are working on synthesis of carbon nano
tubes by using chemical vapor deposition based
Methane decomposition temperature for
S.No. Catalysts Temperature in
1. Ni/SiO2 500-600
2. Fe/SiO2 680-1200
3. Co/MgO 900-1000
4. Co/Al2O3 475-500
5. Ni/SiO2 700
CNTs growth mechanism:-
1. Tip growth model
2. Base growth model
1. Fabrication And Characterization Of Carbon
Nano tubes thesis by Zhiyang Rong
2. Production of carbon nano tubes by chemical
vapor deposition thesis by Umut Baris Ayhan.
3. Synthesis and Electronic Transport in Known
Chirality Single Wall Carbon Nanotubes by
4. A Review on Growth Mechanism and Mass
Production of CNTs by Mukul Kumar and