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Synthesis of CNTs
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Synthesis of CNTs

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Transcript

  • 1. Carbon Nanotubes
    Introduction
    &
    Synthesis
  • 2. Introduction: Common Facts
    • Discovered in 1991 by Iijima
    • 3. Unique material properties
    • 4. Nearly one-dimensional structures
    • 5. Single - and Multi-walled
  • Introduction: nanotube structure
    Roll a graphene sheet in a certain direction:
    • Armchair structure
    • 6. Zigzag structure
    • 7. Chiral structure
    Defects result in bends and transitions
  • 8. Introduction: special properties
    • Difference in chemical reactivity for end caps and side wall
    • 9. High axial mechanical strength
    • 10. Special electrical properties:
    Metallic
    Semi conducting
  • 11. Synthesis: growth mechanism
    Metal Catalyst
    Tip Growth / Extrusion Growth
  • 12. Synthesis: overview
    Commonly Applied Techniques:
    • Chemical Vapor Deposition (CVD)
    • 13. Arc-Discharge
    • 14. Laser ablation
    Techniques Differ in:
    • Type of nanotubes (SWNT / MWNT / Aligned)
    • 15. Catalyst used
    • 16. Yield
    • 17. Purity
  • Synthesis: CVD
    • Gas phase deposition
    • 18. Large scale possible
    • 19. Relatively cheap
    • 20. SWNTs / MWNTs
    • 21. Aligned nanotubes
    • 22. Patterned substrates
  • Synthesis: laser ablation
    • Catalyst / no catalyst
    • 23. MWNTs / SWNTs
    • 24. Yield <70%
    • 25. Use of very strong laser
    • 26. Expensive (energy costs)
    • 27. Commonly applied
  • Synthesis: arc discharge
    • Relatively cheap
    • 28. Many side-products
    • 29. MWNTs and SWNTs
    • 30. Batch process
  • Purification
    Contaminants:
    • Catalyst particles
    • 31. Carbon clusters
    • 32. Smaller fullerenes: C60 / C70
    Impossibilities:
    • Completely retain nanotube structure
    • 33. Single-step purification
    Only possible on very small scale:
    • Isolation of either semi-conducting SWNTs
  • Purification: techniques
    Removal of catalyst:
    • Acidic treatment (+ sonication)
    • 34. Thermal oxidation
    • 35. Magnetic separation (Fe)
    Removal of small fullerenes
    • Micro filtration
    • 36. Extraction with CS2
    Removal of other carbonaceous impurities
    • Thermal oxidation
    • 37. Selective functionalization of nanotubes
    • 38. Annealing