Carbon nanotubes


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Carbon nanotubes

  1. 1. Carbon Nanotubes
  2. 2. 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.
  3. 3. <ul><li>A carbon nanotube is a Nano-size cylinder of carbon atoms. </li></ul><ul><li>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. </li></ul><ul><li>Carbon nanotube properties depend on how you roll the sheet. </li></ul><ul><li>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. </li></ul><ul><li>With the right arrangement of atoms, you can create a carbon nanotube that's hundreds of times stronger than steel, but six times lighter </li></ul><ul><li>Engineers plan to make building material out of carbon nanotubes, particularly for things like cars and airplanes. </li></ul><ul><li>Lighter vehicles would mean better fuel efficiency, and the added strength translates to increased passenger safety. </li></ul><ul><li>Carbon nanotubes can also be effective semiconductors with the right arrangement of atoms. </li></ul><ul><li>Scientists are still working on finding ways to make carbon nanotubes a realistic option for transistors in microprocessors and other electronics. </li></ul>
  4. 4. Carbon Nanotube <ul><li>Discovered in 1991 by Lijima </li></ul><ul><li>It has Unique material properties </li></ul><ul><li>They are nearly One-dimensional structures </li></ul><ul><li>There are two types Single-walled and Multi-walled </li></ul>
  5. 5. Introduction: nanotube structure <ul><ul><li>Roll a Graphene sheet in a certain direction: </li></ul></ul><ul><ul><li>Armchair structure </li></ul></ul><ul><ul><li>Zigzag structure </li></ul></ul><ul><ul><li>Chiral structure </li></ul></ul><ul><li>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. </li></ul><ul><li>Each structure has a Wrapping Angle say (a) . </li></ul>
  6. 7. Rolling a graphene sheet to get SWNT
  7. 8. Armchair <ul><li>The “armchair” structures, with a = 30°, have metallic character </li></ul>
  8. 9. Zigzag <ul><li>The “zigzag” tubes, for which a = 0°, can be either semimetallic or semiconducting, depending on the specific diameter. </li></ul>
  9. 10. Chiral <ul><li>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.) </li></ul>
  10. 11. Special properties <ul><li>Difference in chemical reactivity for end caps and side wall </li></ul><ul><li>High axial mechanical strength </li></ul><ul><li>Special electrical properties: </li></ul><ul><ul><li>Metallic </li></ul></ul><ul><ul><li>Semi conducting </li></ul></ul>
  11. 12. Properties of nanotubes <ul><li>                         </li></ul><ul><li>CNTs have High Electrical Conductivity </li></ul><ul><li>CNTs have Very High Tensile Strength </li></ul><ul><li>CNT are Highly Flexible- can be bent considerably without damage </li></ul><ul><li>CNTs are Very Elastic ~18% elongation to failure </li></ul><ul><li>CNTs have High Thermal Conductivity </li></ul><ul><li>CNTs have a Low Thermal Expansion Coefficient </li></ul><ul><li>CNTs are Good Electron Field Emitters </li></ul><ul><li>CNTs have a High Aspect Ratio (length = ~1000 x diameter </li></ul>
  12. 13. MWNT
  13. 14. Synthesis: overview <ul><li>Commonly applied techniques: </li></ul><ul><ul><li>Chemical Vapor Deposition (CVD) </li></ul></ul><ul><ul><li>Arc-Discharge </li></ul></ul><ul><ul><li>Laser ablation </li></ul></ul><ul><li>Techniques differ by: </li></ul><ul><ul><li>Type of nanotubes (SWNT / MWNT ) </li></ul></ul><ul><ul><li>Catalyst used </li></ul></ul><ul><ul><li>Yield </li></ul></ul><ul><ul><li>Purity </li></ul></ul>
  14. 15. Synthesis: CVD <ul><li>Gas phase deposition </li></ul><ul><li>Large scale possible </li></ul><ul><li>Relatively cheap </li></ul>
  15. 16. Arc discharge <ul><li>Relatively cheap </li></ul><ul><li>Many side-products </li></ul>
  16. 17. Synthesis: laser ablation <ul><li>Use of very strong laser </li></ul><ul><li>Expensive (energy costs) </li></ul><ul><li>Commonly applied </li></ul>
  17. 18. Purification <ul><li>Contaminants: </li></ul><ul><ul><li>Catalyst particles </li></ul></ul><ul><ul><li>Carbon clusters </li></ul></ul><ul><ul><li>Smaller fullerenes: C 60 / C 70 </li></ul></ul><ul><li>Demerits in purification of Nanotubes: </li></ul><ul><ul><li>Completely retain nanotube structure </li></ul></ul><ul><ul><li>Single-step purification </li></ul></ul><ul><ul><li>Only possible on very small scale: </li></ul></ul><ul><ul><ul><li>Isolation of either semi-conducting SWNTs </li></ul></ul></ul>
  18. 19. Purification techniques <ul><li>Removal of catalyst: </li></ul><ul><ul><li>Acidic treatment (+ sonication) </li></ul></ul><ul><ul><li>Thermal oxidation </li></ul></ul><ul><ul><li>Magnetic separation (Fe) </li></ul></ul><ul><li>Removal of small fullerenes </li></ul><ul><ul><li>Micro filtration </li></ul></ul><ul><ul><li>Extraction with CS 2 </li></ul></ul><ul><li>Removal of other carbonaceous impurities </li></ul><ul><ul><li>Thermal oxidation </li></ul></ul><ul><ul><li>Selective functionalisation of nanotubes </li></ul></ul><ul><ul><li>Annealing </li></ul></ul>
  19. 20. Applications <ul><li>Thermal Conductivity of CNTs </li></ul><ul><li>Field Emission of CNTs </li></ul><ul><li>Conductive Plastics with CNTs </li></ul><ul><li>Energy Storage using CNTs </li></ul><ul><li>Conductive Adhesives and Connectors with CNTs </li></ul><ul><li>Molecular Electronics based on CNTs </li></ul><ul><li>Thermal Materials with CNTs </li></ul><ul><li>Structural Composites with CNTs </li></ul><ul><li>Fibers and Fabrics with CNTs </li></ul><ul><li>Catalyst Supports using CNTs </li></ul><ul><li>Biomedical Applications of CNTs </li></ul><ul><li>Air and Water Filtration using CNTs </li></ul><ul><li>Ceramic Applications with CNTs </li></ul><ul><li>Other Applications </li></ul>