Carbon Nanotubes

DEFINITION FOR CARBON NANOTUBES  Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties.  They are among the stiffest and strongest fibres known.  For these reasons they have attracted huge academic and industrial interest,

HISTORY

Japanese scientist Sumio Iijima in 1991. The tubes contained at least two layers. In 1993, a new class of carbon nanotube was discovered, with just a single layer.

SYNTHESIS

Catalytically Arc-Evaporation Laser methoda

Ca ta lyt ic ally

The best quality nanotubes, involves passing a current of about 50 amps between two graphite electrodes in an atmosphere of helium.

ARC-EVAPORATION METHOD

That carbon nanotubes can also be made by passing a carboncontaining gas, such as a hydrocarbon, over a catalyst.

LASER METHOD

It involves using a powerful laser to vaporise a metal-graphite target. This can be used to produce single-walled tubes with high yield.

NANOHORNS

They were produced by high temperature heat treatments of fullerene soot.

STRUCTURE

TYPES OF CARBON NANOTUBES  The bonding in carbon is sp², with each atom joined to three neighbours, as in graphite.

 The structure of a nanotube can be specified by a vector, (n,m), which defines how the graphene sheet is rolled up.  Nanotubes naturally align themselves into "ropes" held together by

SINGLE WALLED

To create a logic gate you must have both a p-FET and an n-FET.

MULTI-WALLED

 This is especially important when functionalisation is required to add new properties to the CNT.

PROPERTIES  Strength  Kinetic  Thermal  Electrical

STRENTH

Carbon nanotubes are one of the strongest and stiffest materials known, in terms of tensile strength and elastic modulus respectively.

KINETIC This is one of the first true examples of molecular technology, the precise positioning of atoms to create useful machines.

ELECTRICAL 

Because of the symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties.

THERMAL All nanotubes are expected to be very good thermal conductors along the tube, exhibiting a property known as "ballistic conduction,"



ONE DIMENTIONAL TRANSPORT The nanoscale dimensions, electron transport in carbon nanotubes will take place through quantum effects and will only propagate along the axis of the tube. This behavior is the same as that of a quantum wire.

DEFECTS Material, the existence of defects affects the material properties.. The tube's electrical properties are also affected The tube's thermal properties are heavily affected by defects.

POTENTIAL AND CURRENT APPLICATIONS The joining of two carbon nanotubes with different electrical properties to form a diode . The strength and flexibility of carbon nanotubes makes potential use in controlling other nanoscale structures,

STRUCTURAL APPLICATION A good example of a practical use for the carbon nanotubules is the bicycle Floyd Landis used at the 2006 Tour de France, Recent research has revealed the possibility of cross-linking CNT molecules prior to incorporation in a polymer matrix

IN ELECRIAL CIRCUIT Carbon nanotubes have many properties—from their unique dimensions to an unusual current conduction mechanism. Nanotube based transistors have been made that operate at room temperature and that are capable of digital switching using

OTHER APPLICATION Carbon tubes used for mechanical memory elements (NRAM being developed by Nantero Inc.) and nanoscale electric motors Eikos Inc of Franklin, Massachusetts and Unidym Inc. of Silicon Valley, California are develoeping transparent, electrically conductive

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