Carbon

C-60 fullerene

  • consist of pentagons(12) and hexagons(20)
  • 7Å in diameter
  • Is isolator and is diamagnetic
  • Doped with K -> can be conductor or even superconductor

Electronic structure

Carbon (diamond) vs Si and Ge

  • Band gap much larger for carbon than the two other. Diamond is insulator, but the others are semiconductors
  • Yellow diamonds are because of Nitrogen doping which adds an energy level in the band gap of diamond.

Graphene

  • Lookalikes: h-BN, BCN\(_2\), BC\(_2\)N

Synthesis:

  • Scotch tape
  • Sonication in liquid medium
  • Bottom-up with sugars as reactants
  • Reduction of ethanol with sodium followed by pyrolysis
  • Catalytic CVD process
  • Reduction of Graphene Oxide (most used industrially)
    • Done in strong acid.
    • T<150C, can explode if above..
  • rGO Pillaring: introducing molecules in between rGO layers, which separates the layers

Carbon nanotubes

  • Extreme strength
  • Strength is lowered by defects usually, but for practical composite use, it does not change much.
  • Defects:
    • Can be pentagons in the hexagonal plane, or heptagons, or penta-heptagon chains or agglomerations and so on.
    • Deformation defects can be plastic, and can be corrected by removing the strain.
  • MWNT vs Scroll.
    • Difference can be hard to distinguish.
    • CNT’s are only in tubes.
    • Scroll example: Vanadium oxide. Can have several layers in the scrolls.
  • Types of CNT’s
    • (n,m) notation, n=m -> armchair, m = 0 -> zigzag
  • Low temp chemical routes:
    • Carbonyls with 3d catalyst metal.
    • Boudourd Reaction: 2CO(g) = C + CO\(_2\)

Carbon cones

  • Specific opening angles: Caused by how you roll the sheets.
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