Low Dimensional System & Nanostructures Angel Rubio & Nerea Zabala. Carbon Nanotubes A New Era

Transcription

1 Low Dimensional System & Nanostructures Angel Rubio & Nerea Zabala Carbon Nanotubes A New Era By Afaf El-Sayed 2009

2 Outline World of Carbon - Graphite - Diamond - Fullerene Carbon Nanotubes CNTs - Discovery of CNTs - Basic Structure & Types of Nanotubes - Electronic Structure of CNTs Properties & Applications of CNTs

3 World of Carbon sp sp 2 sp 3

4 Graphite & Diamond In graphite, The sp 2 orbital form the strong σ-bonds between carbon atoms in the graphite planes, while the p z, or π,, orbital provide the weak Van der waals bonds between the planes. In diamond, each carbon atom has four nearest neighbors. The sp 3 orbital form the strong σ-bonds between carbon atoms.

5 Fullerene In the C 60 molecule, the carbon atoms are bonded in a structure made up of 20 hexagons and 12 pentagons.. Each of the carbon atoms in C 60 is joined to three neighbors, so the bonding is the bonding is essentially sp 2, although there may be a small a mount of sp 3 character due to the curvature. The carbon 60 atoms are bonded together in an array of hexagons and pentagons, like a soccer ball. These molecules are called Buckminster fullerenes in honor of Buckminster Fuller who first designed similarly shaped geodesic domes.

6 Carbon Nanotubes

7 Discovery of CNTs Since the early 1960s, Harry Kroto,, of the University of Sussex,, had been fascinated in the processes occurring on the surfaces of stars, and believed that experiments on the vaporization of graphite might provide key insights into these processes. On the other hand, Richard Smalley,, of Rice University,, Houston, had different reasons for being interested in what might happen when one vaporizes carbon. In August 1985,, the two scientists began the now famous series of experiments on the vaporization of graphite.. They were immediately struck by the formation of C 60. The discovery of C 60, published in nature in November 1985, had an impact which extended way beyond the confines nes of academic chemical physics, and marked the beginning of a new era in carbon science. Perhaps, Carbon nanotubes are the most important fruits of this research. Discovered by the electron microscopist Sumio Iijima,, of the NEC laboratories in Japan, in 1991,, these molecular carbon fibers consist of tiny cylinders of graphite, closed at each end with caps which contain c precisely six pentagonal rings.

8 ϕ Basic Structure & Types of CNTs ϕ R = na 1 + ma 2 0 m n & Φ<30 o

9 Neural Tree SWNTs, MWNTs and!!!!!

10 Electronic Structure of Graphene Zero-bandgap Semiconductor Unit cell π* anti-bonding orbitals Brillouin Zone π bonding orbitals

11 Graphene to SWNT = T = t1a1 + t2a2 C h na 1 + ma 2 K K 1 2 = = 1 N 1 N r r ( t b + t b ) 2 r r ( mb nb )

12 Different Properties of CNTs Properties Nanotubes By Comparison Current carrying capacity Field Emission Heat Transmission Temperature Stability Estimated at 1 X 10 9 A/cm 2 for MWCNT: nm Can activate phosphors at 1 3 volts if electrodes are spaced 1 micron apart Predicted to be as high as 6,000 W/m.K at room temperature Stable up to 2,800 o C in vacuum, 750 o C in air Copper wires burn out at about 1X 10 6 A/cm 2 Molybdenum tips require fields of V/m and have very limited lifetimes Nearly pure diamond transmits heat at 3,320 W/m.K Metal wires in microchips melt at 600 1,000 o C Elasticity Elastic modulus ~ 10 3 GPa Yield Strength ~ 65 GPa ~ 200 GPa for steel ~ 0.8 GPa for steel

13 Applications of CNTs Glucose sensors CNT-FETs CNT scanning tip CNT-Solar Cells CNT- Flexible Displays CNT interconnects Neural Tree

14 Future!!!!!! Space Elevator Space Platform Faster, Better and Cheaper Space Aircrafts

15 Conclusion A new era has begun of Carbon Nano-Science!!! We should think of our needs?!!!

16 Bibliographic Search R. Saito, et.al, Physical Propertiest of Carbon Nanotubes, Imperial College Press, Peter Morgan, Carbon Fibers and their composites, CRC press, Michael J.O Connell, Carbon Nanotubes: Properties and Applications, CRC press, Charles Kittle, Introduction to Solid State Physics, John Wiley & Sons, Inc., 8th Edition, Karl M. Kadish and Rodney S.Ruoff, Fullerenes: Chemistry, Physics and Technology, Wiley- IEEE, Peter J.F. Harris, "Carbon Nanotubes and Related Structure: New Materials for the Twenty First Century", Cambridge University Press, The nanotube Sites: A. Appenzeller, E. Joselevich, W. Honlein, Carbon Nanotubes for Data Processing, in R. Waser, Nanoelectronics and Information Technology, Wiley- VCH (2003). A. Adams, "Physical Properties of Carbon Nanotubes", as a part of the honours chemistry research project, Thomas A. Adams, "Physical Properties of Carbon Nanotubes", as a part of the honours chemistry research project, J. Hone, " Carbon Nanotubes: Thermal Properties", Dekker Encyclopedia of Nanoscience and Nanotechnology, D. Yokoyama et al., Appl. Phys. Lett., 91, , Christina Guice, Henry C. Foley, Head and Robb Chair and Bo Yi, "Dynamics of Nanotube Synthesis", McNair Scholar, Pennsylvania State University, NASA web site; NASA web site; SPACE.com -- Russians Plan New Space Platform.

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