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Carbon nanotubes - applications

Dr. Dmitri Kopeliovich

Carbon nanotubes

Carbone nanotubes (CNT) are graphene sheets rolled into tubular fibers.

Graphene is a single plate of Graphite crystalline structure consisting of hexagonal rings in which each carbon atom is covalently bonded to three other atoms in the plate.

Single wall carbon nanotubes (SWNT) are made of a single graphene sheet.
Multi-wall carbon nanotubes (MWNT) are made of multiple graphene sheets.

Typically nanotubes have a diameter of several nanometers (0.4-2nm of SWNT, 5-80nm of MWNT) and the length of tens of microns (1 nm = 1×10-3 μm = 1×10-9 m).

Carbon nanotubes are fabricated by the method of Chemical Vapor Deposition (CVD).

The most prominent properties of carbon nanotubes:

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Carbon nanotubes in composite materials

Reinforcement of a polymer by dispersed carbon nanotubes enhances the material strength, stiffness (modulus of elsticity) and toughness.

Strength and stiffness are increased as a result of extremely high strength and modulus of elesticity of the incorporated carbon nanotubes.

Higher toughness is provided by an interaction between the polymer matrix and the reinforcing nanotubes. Such effect is a result of cracks deflection at the interface matrix-nanotube. When a crack propagating through the matrix reaches nanotubes, the relatively weak bonding between the matrix and the fiber at their interface allows their relative sliding. The nanotubes bridge the crack and stop its propagation.

The main problem in fabrication of polymer composites reinforced with carbon nanotubes is agglomeration of the nanotubes and poor Homogenization of the material during its mixing.
The nanotubes tend to cluster together due to the great surface.

Examples of application of carbon nanotubes in polymer base composites:

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Carbon nanotubes in coatings

Polymer coatings containig dispersed carbon nanotubes are in fact polymer matrix composites deposited on a substrate in form of a thin layer.

The most promissing application of CNT of this type is conductive coatings.
0.5-1% of carbon nanotubes impart anti-static property to the polymer coating.
2-4% of CNT make the coating really conductive.

CNT containing conductive coatings are also used for anti-corrosion paints. The electrical conductivity of the coatings allows using Cathodic protection for corrosion inhibition.

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Carbon nanotubes in electronics

Exeptional electrical properties of carbon nanotubes (low electron scattering, high current carrying capacity, resistance to electromigration) has have generated a significant efforts in developing electronic devices based on CNT.

Examples of application of carbon nanotubes in electronics:

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Carbon nanotubes in lithium ion batteries

Multi-wall carbon nanotubes (MWNT) are widely used in lithium batteries. Incorporation od nanotubes in graphite anodes and LiCoO2 cathodes results in better electrical connectivity and higher mechanical properties of the batteries.

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Carbon nanotubes in water treatment devices

Carbon nanotubes are used for fabrication fine water filters for drinking water purification.
Membranes made of aligned encapsulated carbon nanotubes possess very high permeability of liuids and gases and therefore. Therefore the water desalination by reverse osmosis utilizing such membranes is more cost effective than that with polycarbonate membranes.

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