Carbon Nanotubes

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Carbon Nanotubes

• J. A.

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Introduction

• nano sized in nanometres 10-9 m, or nm
• Nanotube rolled up net of graphine single
  sheet of graphite
• Peter Wiles and myself published first accounts
  of finding nanotubes in 1978, first structure
  analysis 1979 (cf. Ijiima 1991 in Japan)

1978 TEM
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After air operation
After operation in nitrogen
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Carbon Nanotubes

• Properties,
• potential uses,
• methods of manufacture
• General references
• Harris, P. J.F. Carbon nanotubes and related
  structures Cambridge Uni. Press 1999
• Tomanek, D. Enbody, R.J.(eds) Science and
  application of nanotubes. Kluwer Acad. 2000

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Properties of nanotubes

• Geometry, size, direction of roll
• Multwall (MWNT) 5-50 nm dia, 10 mm long
• single-wall (SWNT) 1-10 nm dia, 1 mm long
• Pentagons or heptagons give defects caps at
  ends, and junctions
• Electrical conduction or non-conduction
• Armchair metallic,
• Zigzag, chiral - semiconductor

Armchair, zigzag, chiral
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Single nanotubes

• Pull-out and release of MWNT Van der Waals
  force
• Worlds smallest balance

Weighing a 22 fg particle Science 283,
1513(1999) Applying hf voltage got frequency for
resonance
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Single nanotubes

• Atomic force microscope tip resiliant and large
  aspect ratio can sense deep into surface
  cavities

nanotube on AFM cantilever (1999)
resulting image
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Uses of nanotubes?

• Electron emission
• Hydrogen adsorption
• Easy electrolyte contact
• Polymer strengthening
• Transistor components
• Drug or chemical storage
• Leading to Computer, TV displays hydrogen for
  fuel cells, electrodes for Li ion battery, car
  parts

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Electron emission

• Minature cathode ray tube using battery
  voltages 10s of V
• Displays for computers, lamps

Lamp 2000
Samsung display 1999
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Hydrogen adsorption
H2

• Hydrogen storage for mobile fuel cells need 6.5
  , 62 kg / m3, best near room temp, a few bar
• Many nanotube samples give up to 2 , some up to
  6 and a few 20 or more metal loading.
• Understanding why physisorb vs chemisorb
  around 90 kJ /mole activation energy

tank
P, T ?
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Battery/fuel cell electrodes

• One electrode in a Li ion battery is porous
  carbon, where Li intercalates a nanotube
  electrode is sought for ease of ion approach,
  reducing polarization
• Fuel cell electrode for hydrogen oxidation

Canterbury nanotubes on carbon fibres 2002
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Polymer-nanotube composites

• Stronger than with carbon fibres?
• Theory small defects, so stronger Practice
  stronger, but poor dispersion, smooth surface
• Electrical conductivity with photo- luminescent
  polymer 108 times, also more robust because of
  nano heat fins
• Membrane materials
• Bioimplant materials