Carbon Nanotube POF
Fig 1: Computer model of a single-walled carbon nanotube.
History of Carbon Nanotubes
Sumio Iijima of the NEC Corporation first discovered carbon nanotubes in 1991. Richard Smalley's group described an alternative method of preparing single-walled nanotubes in 1996. Like the original method of preparing carbon nanotubes, this involved the laser-vaporization of graphite, and resulted in a high yield of single-walled tubes with unusually uniform diameters. These highly uniform tubes had a greater tendency to form aligned bundles than those prepared using arc-evaporation, and led Smalley to christen the bundles nanotube "ropes". The ability to manufacture large amounts of carbon fibrils led to a great amount of research into the properties of carbon nanotubes.1
Fig 2: Single-walled nanotubes with a diameter close to 1.4 nm.
Properties of Carbon Nanotubes
Carbon Nanotubes (CNT) have a very basic chemical structure. It easy to think of them as small graphene sheets rolled into a cylinder. In 2002 a study from UC Berkeley incorporated the use of a suspended testing device to measure CNT thermal conductivity. Their experimental results yielded a conductivity of approximately 3100 W/mK at 300K, with a maximum value of 3250 W/mK was obtained at 323K.3
A study by B.G. Demczyk et al. in 2002 gave accurate measurements of the tensile strength and Young's modulus. By using a microfabricated nanotube tensile device, they observed the tensile strength to be .15 TPa and the Young's modulus to be .9 TPa. For comparison, the tensile strength of some common steels is about 0.00068 TPa with a Young's modulus of 0.19 TPa.2
Fig 3: Microfabricated nanotube tensile testing device.
Fig 4: Multiwall carbon nanotube spanning device gap.
Current Research in the Polymer Optics Lab
Current research focuses on creating a carbon nanotube polymer composite fiber. By drawing a large diameter composite rod into a fiber, there will be significant alignment of the nanotube within the polymer matrix. If enough alignment is achieved, the fiber will start to display some of the properties of the nanotubes such as low electrical and thermal resistivity and high tensile strength.
The current technology of nanotube polymer composites provides advantages in conductivity and weight savings over metals. Their flexibility, durability, and low-temperature processability have prompted increasing interest in applying nanotube polymer composites in industrial applications.
Fig 3: Nanotubes in a polymer matrix.
- "A Carbon Nanotube Page", Peter Harris, Chemistry Department of the University of Reading, http://www.personal.rdg.ac.uk/~scsharip/tubes.htm.
- B.G. Demczyk et al., Materials Science and Engineering A334 (2002) 173-178.
- P. Kim et al., Physica B 323 (2002) 67-70.
- The Smalley Group at Rice University, http://www.ruf.rice.edu/~smalleyg/index.htm.