Base elements → Materials → Carbon → Composite materials

CARBON NANOTUBES (CNT)

Table of main properties of carbon nanotubes (CNT’s)

Property Typical Value Remarks
Density ~1.3–1.4 g/cm³ Very low
Young’s modulus (E) ~1000–1500 GPa Extremely high
Tensile strength ~50–150 GPa Exceptional
Hardness (HV) Not applicable Nanostructured material
Thermal conductivity ~2000–6000 W/m·K Extremely high (along axis)
Electrical conductivity Very high Metallic or semiconducting behavior
Thermal expansion ~0–1 ×10⁻⁶ /K Extremely low
Melting point Not applicable Decomposes at very high temperature
Magnetism No Non-magnetic
Corrosion resistance Excellent Chemically stable
Machinability Not machinable Used as reinforcement or in composites

Carbon nanotubes are cylindrical structures made of graphene sheets rolled at the nanometric scale. Derived from nanotechnology, they exhibit exceptional mechanical, thermal, and physical properties, far superior to those of traditional materials.

Due to environmental hazards and potential health risks, carbon nanotubes have been subject to REACH regulations since 2020.

In watchmaking, their use remains very limited and mainly experimental, particularly in the development of composite hairsprings aimed at improving the performance of the regulating organ.

Main Properties

Carbon nanotubes are characterized by:

  • Extremely high Young’s modulus (~1 TPa)
  • Exceptional mechanical strength
  • Very low density (~1.3–1.4 g/cm³)
  • Excellent fatigue resistance
  • Very low thermal expansion coefficient
  • Non-magnetic material
  • Excellent chemical stability

These properties make them a theoretically ideal material for high-precision dynamic components.

Carbon nanotubes can be:

  • Single-walled (SWCNT) → a single graphene layer
  • Multi-walled (MWCNT) → multiple concentric layers

They are generally used:

  • In the form of networks
  • Integrated into a composite matrix

At the macroscopic scale, their properties strongly depend on:

  • Their orientation
  • Their dispersion
  • Their density

In watchmaking, carbon nanotubes have been explored experimentally for:

Their main interest lies in their ability to:

  • Provide highly stable elasticity
  • Reduce sensitivity to thermal variations
  • Eliminate the effects of magnetism

Advantages

  • Exceptional mechanical properties
  • Very low density
  • Outstanding thermal stability
  • Non-magnetic
  • High fatigue resistance

Limitations

  • Complex processing
  • Difficulty in large-scale production
  • Properties dependent on structuring
  • Very high cost
  • Still largely experimental use
  • Limited industrial reproducibility
  • Subject to REACH regulations (health and environmental risks)