1. AVERZS TECHNOLOGIES
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Carbon Nanotubes
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2. AVERZS TECHNOLOGIES
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General Fact
Graphite vs. Diamonds
What'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.
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3. AVERZS TECHNOLOGIES
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A carbon nanotube is a Nano-size cylinder of carbon atoms.
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.
Carbon nanotube properties depend on how you roll the sheet.
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.
With the right arrangement of atoms, you can create a carbon nanotube
that's hundreds of times stronger than steel, but six times lighter
Engineers plan to make building material out of carbon nanotubes,
particularly for things like cars and airplanes.
Lighter vehicles would mean better fuel efficiency, and the added strength
translates to increased passenger safety.
Carbon nanotubes can also be effective semiconductors with the right
arrangement of atoms.
Scientists are still working on finding ways to make carbon nanotubes a
realistic option for transistors in microprocessors and other electronics.
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4. AVERZS TECHNOLOGIES
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Carbon Nanotube
• Discovered in 1991 by Lijima
• It has Unique material properties
• They are nearly One-dimensional structures
• There are two types Single-walled and Multi-walled
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5. AVERZS TECHNOLOGIES
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Introduction:
nanotube structure
Roll 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).
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6. AVERZS TECHNOLOGIES
A leading Research and Development Division
EMERGING EXCELLENCE
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7. AVERZS TECHNOLOGIES
A leading Research and Development Division
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Rolling a graphene sheet to get SWNT
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8. AVERZS TECHNOLOGIES
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Armchair
• The “armchair” structures, with a = 30°, have metallic
character
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9. AVERZS TECHNOLOGIES
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Zigzag
• The “zigzag” tubes, for which a = 0°, can be either
semimetallic or semiconducting, depending on the specific
diameter.
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10. AVERZS TECHNOLOGIES
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Chiral
• Nanotubes 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.)
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11. AVERZS TECHNOLOGIES
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Special properties
• Difference in chemical reactivity for
end caps and side wall
• High axial mechanical strength
• Special electrical properties:
• Metallic
• Semi conducting
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12. AVERZS TECHNOLOGIES
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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
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13. AVERZS TECHNOLOGIES
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MWNT
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14. AVERZS TECHNOLOGIES
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Synthesis: overview
• Commonly applied techniques:
• Chemical Vapor Deposition (CVD)
• Arc-Discharge
• Laser ablation
• Techniques differ by:
• Type of nanotubes (SWNT / MWNT )
• Catalyst used
• Yield
• Purity
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Synthesis:
CVD
•Gas phase deposition
•Large scale possible
•Relatively cheap
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16. AVERZS TECHNOLOGIES
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Arc discharge
• Relatively cheap
• Many side-products
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17. AVERZS TECHNOLOGIES
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Synthesis: laser ablation
• Use of very strong laser
• Expensive (energy costs)
• Commonly applied
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18. AVERZS TECHNOLOGIES
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Purification
• Contaminants:
• 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
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19. AVERZS TECHNOLOGIES
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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
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20. AVERZS TECHNOLOGIES
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Applications
• Thermal 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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