Transcript Document

Carbon Nanotubes
Joey Sulpizio, Rice University
Introduction
Properties
Carbon nanotubes comprise an extraordinary class of organic macromolecules. These
molecules are basically cylindrical sheets of sp2 hybridized carbon. Carbon nanotubes are very long
in relation to their width and can contain millions of carbon atoms per molecule. The amazing
structure of these molecules allows for a variety of interesting physical properties such as high
tensile strength, thermal conductivity, and electrical conductivity. There is a wide range of possible
applications for carbon nanotubes, including electronics, probing, and structural support.
http://cnst.rice.edu/tube_1010.jpg
Fig 1. A computer drawing of a carbon
nanotube
History
In 1991, Japanese scientist Sujimo Iijima of NEC discovered carbon nanotubes. Iijima, an
electron microscopist, was studying materials deposited on the cathode during the arc-evaporation
synthesis of fullerenes. Arc-evaporators are devices used for evaporating and condensing
substances between electrodes. On examination of the central core of the cathodic deposit, Iijima
found a variety of closed graphene structures which included many never discovered nanoparticles
including carbon nanotubes. Single-walled and multi-walled nanotubes were later produced in bulk
using this arc-evaporation method. The arc-evaporation method was modified in 1993 by adding
metals such as cobalt to the graphite electrodes to produce single-walled-nanotubes, which are the
subject of much research today. In 1996, the Smalley group of Rice University found an alternative
method for producing carbon nanotubes using laser-evaporation of graphite in a way similar to their
preparation for C60. This method gave a relatively high yield and formed tubes aligned in bundlelike ropes.
•Average diameter of single-walled tubes 1.2-1.4 nm
•Distance from opposite carbon atoms (line 1) 2.8 A
•Analogous carbon atom separation (line 2) 2.46 A
•Parallel carbon bond separation (line 3) 2.45 A
http://www.pa.msu.edu/cmp/csc/
•Carbon bond length (line 4) 1.42 A
ntproperties/carbonspacing2.gif
3
•Average density 1.36 g/cm
Fig 5. Nanotube carbon
spacing diagram
•High thermal conductivity ~2000W/m/K
•Delocalized pi electron system (aromatic) due to sp2 hybridization
•Lateral flexibility related to reversible buckling of the atomic layers
•High axial strength and stiffness, with Young’s modulus ~1TPa and maximum tensile
strength ~30 GPa
•Metallic or semi-conducting depending on helicity, with metallic fundamental gap at 0
eV and semi-conducting gap ~0.5 eV Maximum Current Density ~1013 A/m2
•Diamagnetic with axial magnetization susceptibility
•Fairly chemically inert
Applications
•Structural elements in bridges, buildings, towers, and cables
•Material for making lightweight vehicles for all terrains
•Heavy-duty shock absorbers
http://www.cnrs.org/cw/en/pres/compress/n384a6a.jpg
•Open-ended straws for chemical probing and cellular injection
Fig 6. Optical microscope view
•Nanoelectronics including batteries capacitors, and diodes
of a nanotube structural fiber
•Microelectronic heat-sinks and insulation due to high thermal conductivity
-white line is 25 um
•Quantum wires and single-electron transistors due to electrical properties
•Nanoscale gears and mechanical components
•Electron guns for flat-panel displays
http://focus.aps.org/v3/st35f1.jpg
Fig 7. Atoms inside a
•Nanotube-buckyball encapsulation coupling for molecular computing with high
nanotube act as a
RAM capacity
semi-conductor
Fig 2. Diagram of
laser used for laservaporization nanotube
synthesis
junction
xhttp://www.sigmaxi.org/amsci/articles/97articles/fig03nanotube.gif?37,64
Fig 9. A carbon nanotube
transistor
http://www.nas.nasa.gov/Groups/Nanotechnology/pub
lications/MGMS_EC1/simulation/normal.gif
Fig 8. Nanotubes as gears
http://www.aip.org/physnews/graphics/images/tubefet.jpg
Structure
References
•Cylindrical carbon fullerene cages
consisting of only hexagons and pentagons
“Researchers Explore Applications for Carbon Nanotubes.” Online APS News. (1997): n. pag. Online. Internet. 21 Apr. 2001. Available:
http://www.aps.org/apsnews/0697/11962c.html
Fig 3
http://www.phys.psu.edu/~crespi/research/carbon.1d/imag
es/nanotube-70.gif
•Helical structure related to mechanisms of
formation
Fig 3. Nanotube fullerene structure
http://www.sigmaxi.org/amsci/articles/97articles/cap04.html
• Either multi-walled or single-walled
•Single-walled tubes are either armchair,
zig-zag, or chiral in structure Fig 4
• Helical shape described by chiral vector
(n,m) Fig 5
Adams, Thomas A. Physical Properties of Carbon Nanotubes. n. pag. Online. Internet. 21 Apr. 2001. Available:
http://www.pa.msu.edu/cmp/csc/ntproperties/main.html.
Fig 4. Types of single-walled nanotube:
1-armchair 2-zig-zag 3-chiral
Collins, Philip, Hiroshi Bando, and A. Zettl. “Nanoscale Electronic Devices on Carbon Nanotubes.” Fifth Foresight Conference on Molecular
Nanotechnology. (1997): n. pag. Online. Internet. 21 Apr. 2001. Available:
http;//www.foresight.org/Conferences/MNT05/Papers/Collins.
Dresselhaus, Mildred, Peter Eklund, and Riichiro Saito. “Carbon Nanotubes.” Physics World. (1998): n. pag. Online. Internet. 21. Apr. 2001.
Available: http://physicsweb.org/article/world/11/1/9.
Harris, Peter J F. “Carbon Nanotube Science and technology.” A Carbon Nanotube Page. n. pag. Online. Internet. 21 Apr. 2001. Available:
http://www.rdg.ac.uk/~scsharip/tubes.htm.
Fig 5. Diagram of the
Chiral vector, where
R = na1 + ma2
http://www.pa.msu.edu/cmp/csc/ntproperties/hex.gif
Liu, J. “Fullerene Pipes.” Science. (1998): n. pag. Online. Internet. 21 Apr. 2001. Available: http://cnst.rice.edu/pipes.pdf
Tomanek, David. The Nanotube Site. n. pag. Online. Internet. 21 Apr. 2001. Available: http://www.pa.msu.edu/cmp/csc/nanotube.html.
Yakobsin, Boris, and Richard Smalley. “Fullerene Nanotubes: C1,000,000 and Beyond.” American Scientist. (1997): n. pag. Online. Internet. 21
Apr. 2001. Available: http://www.sigmaxi.org/amsci/articles/97articles/intro.html