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Carbon Nanotubes T2, Reshma Apartments, 3rd Floor, No.324, MKN

Road, Alandur , Chennai – 16Mobile: 95000 48577, 96000 88172,

Mail:[email protected], URL: www.averzs.com

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General FactGraphite vs. DiamondsWhat's the difference between graphite and diamonds? Both materials are made of carbon, but both have vastly different properties. Graphite is soft; diamonds are hard. Graphite conducts electricity, but diamonds are insulators and can't conduct electricity. Graphite is opaque; diamonds are usually transparent. Graphite and diamonds have these properties because of the way the carbon atoms bond together at the nanoscale.

T2, Reshma Apartments, 3rd Floor, No.324, MKN Road, Alandur , Chennai – 16

Mobile: 95000 48577, 96000 88172, Mail:[email protected], URL: www.averzs.com



Ø A carbon nanotube is a Nano-size cylinder of carbon atoms.

Ø Imagine a sheet of carbon atoms, which would look like a sheet of hexagons. If you roll that sheet into a tube, you'd have a carbon nanotube.

Ø Carbon nanotube properties depend on how you roll the sheet.

Ø In other words, even though all carbon nanotubes are made of carbon, they can be very different from one another based on how you align the individual atoms.

Ø With the right arrangement of atoms, you can create a carbon nanotube that's hundreds of times stronger than steel, but six times lighter

Ø Engineers plan to make building material out of carbon nanotubes, particularly for things like cars and airplanes.

Ø Lighter vehicles would mean better fuel efficiency, and the added strength translates to increased passenger safety.

Ø Carbon nanotubes can also be effective semiconductors with the right arrangement of atoms.

Ø Scientists are still working on finding ways to make carbon nanotubes a realistic option for transistors in microprocessors and other electronics.





Carbon NanotubeDiscovered in 1991 by Lijima

It has Unique material properties

They are nearly One-dimensional structures

There are two types Single-walled and Multi-walled





Introduction: nanotube structureRoll a Graphene sheet in a certain direction:

Armchair structure

Zigzag structure

Chiral structure

Single-walled carbon nanotubes exist in a variety of structures corresponding to the many ways a sheet of Graphene can be wrapped into a seamless tube.

Each structure has a Wrapping Angle say (a).





Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level





Rolling a graphene sheet to get SWNTClick to edit Master text stylesSecond level


● Fifth level





Armchair

The “armchair” structures, with a = 30°, have metallic character





ZigzagThe “zigzag” tubes, for which a = 0°, can be either semimetallic or semiconducting, depending on the specific diameter.





ChiralNanotubes with chiral angles intermediate between 0 and 30° include both semimetals and semiconductors. (“Armchair” and “zigzag” refer to the pattern of carbon–carbon bonds along a tube’s circumference.)





Special propertiesDifference in chemical reactivity for end caps and side wall

High axial mechanical strength

Special electrical properties:

Metallic

Semi conducting





Properties of nanotubes

CNTs have High Electrical Conductivity

CNTs have Very High Tensile Strength

CNT are Highly Flexible- can be bent considerably without damage

CNTs are Very Elastic ~18% elongation to failure

CNTs have High Thermal Conductivity

CNTs have a Low Thermal Expansion Coefficient

CNTs are Good Electron Field Emitters

CNTs have a High Aspect Ratio (length = ~1000 x diameter





MWNT



● Fifth level





Synthesis: overviewCommonly applied techniques:Chemical Vapor Deposition (CVD)

Arc-Discharge

Laser ablation

Techniques differ by:

Type of nanotubes (SWNT / MWNT )

Catalyst used

Yield

Purity





Synthesis: CVD

•Gas phase deposition•Large scale possible•Relatively cheap





Arc discharge

• Relatively cheap• Many side-products





Synthesis: laser ablation



● Fifth level

• Use of very strong laser• Expensive (energy costs)• Commonly applied





PurificationContaminants: Catalyst particles

Carbon clusters

Smaller fullerenes: C60 / C70

Demerits in purification of Nanotubes:

Completely retain nanotube structure

Single-step purification

Only possible on very small scale:

● Isolation of either semi-conducting SWNTs





Purification techniques

Removal of catalyst:Acidic treatment (+ sonication)

Thermal oxidation

Magnetic separation (Fe)

Removal of small fullerenes

Micro filtration

Extraction with CS2

Removal of other carbonaceous impurities

Thermal oxidation

Selective functionalisation of nanotubes

Annealing





ApplicationsThermal Conductivity of CNTs

Field Emission of CNTs

Conductive Plastics with CNTs

Energy Storage using CNTs

Conductive Adhesives and Connectors with CNTs

Molecular Electronics based on CNTs

Thermal Materials with CNTs

Structural Composites with CNTs

Fibers and Fabrics with CNTs

Catalyst Supports using CNTs

Biomedical Applications of CNTs

Air and Water Filtration using CNTs

Ceramic Applications with CNTs





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