Carbon nano tubes

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Carbon nano tubes

  1. 1. SYNTHESIS OF CARBON NANOTUBES BY USING CVD METHOD By JEETENDRA KUMAR SHRI MATA VAISHNO DEVI UNIVERSITY KATRA (J&K) To Dr. PRATHAP HARIDOSS ASSOCIATE PROFESSOR IIT MADRAS
  2. 2. Carbon Nano Tubes Contents: 1. Introduction 2. Classification of CNTs 3. Properties & Applications 4. Synthesis methods 5. Precursors 6. Catalysts 7. Catalyst supporters 8. Growth mechanism 9. References
  3. 3. Introduction Carbon nano tubes are allotrope of carbon with a cylindrical nanostructure or Carbon nanotubes (CNTs) are rolled up cylinders of graphene sheets.
  4. 4. Classification Carbon nano tubes Single walled carbon nano tube (SWCNT) Multi walled carbon nano tube (MWCNT) Arm chair Zigzag Chiral Herringbone Bamboo
  5. 5. (a) Armchair, (b) Zigzag, (c) Chiral Nano tubes
  6. 6. Textures of MWCNTs (a) herringbone texture and (b) bamboo texture Multi walled carbon nano tube
  7. 7. Properties:- 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. Applications:-  In automobile Aerospace design Bio medical sensors Electronic circuit design Mechanical reinforcement Energy storage (hydrogen storage.)
  8. 8. 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)
  9. 9. Electric arc-discharge method
  10. 10. Laser ablation method
  11. 11. Chemical Vapor Deposition (CVD) Reactor tube is made up of Quartz. CxHx- Carbon precursor Substrates- SiO2, Al2O3, MgO, TiO2
  12. 12. List of different precursors with their phase and decomposition temperature:- S No. Precursors Phase Decomposition Temperature ͦc 1. Methane Gas 500-800 2. Ethane Gas 550-640 3. Acetylene Gas 1500-1800 4. Ethanol Liquid 780-1085 5. Carbon mono oxide(with catalyst) Gas 700 6. Carbon mono oxide(without catalyst) Gas 2900 7. Acetylene(with catalyst- Fe) used for MWCNTs Gas 700
  13. 13. Different catalysts used in synthesis of carbon nano tubes by using chemical vapor deposition (CVD):- Ni, Fe, Co, Mo, Cu, Au etc. Catalysts supporters MgO, Al2O3, SiO2, TiO2. these aare also called substrates where catalysts are placed in the tube furnace and heated upto 500 to 1000ºC.
  14. 14. Some important points regarding to catalyst supporters- • 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- 100nm)-
  15. 15. 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.
  16. 16. We are working on synthesis of carbon nano tubes by using chemical vapor deposition based on Methane. Methane decomposition temperature for different catalysts:- 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 6. Fe–Co-impregnated zeolite support 1200
  17. 17. CNTs growth mechanism:- 1. Tip growth model 2. Base growth model
  18. 18. References 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 Bhupesh Chandra. 4. A Review on Growth Mechanism and Mass Production of CNTs by Mukul Kumar and Yoshinori Ando.

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