Carbon nanotubes have great potential as
components of new materials. The rolled-up sheets of carbon atoms are
stronger than steel, have useful electrical and optical properties, and
can be narrower than one nanometer, or the span of 10 atoms.
Adding nanotubes to polymers can greatly increase the strength
and durability of the material, but getting the most out of the mix requires
aligning the tiny tubes. The trouble is, the tubes can be unruly, not
unlike a bowl of spaghetti.
Researchers from the Georgia Institute of Technology and Florida
State University have developed a way to orient the nanotubes in a polymer
mix using a magnetic field.
The researchers mixed single-walled nanotubes with thixotropic
resin. When they exposed to the mix to magnetic fields larger than 15
tesla the nanotubes lined up in the direction of the field. The magnetic
field did not affect the nanotubes directly, but instead oriented the
long, chain-like polymers of the resin, which dragged the carbon nanotubes
along with them as they were moved by the magnetic field.
Fifteen tesla is is about 150 times the strength of the field
of an ordinary kitchen magnet, and about 300,000 times as strong as the
earth's magnetic field.
Such high magnetic fields would make manufacturing processes expensive,
according to the researchers. They are working on ways of reducing the
required field strength.
The method could be used in practical applications within two
years, according to the researchers. The work appeared in the November
17, 2003 issue of Advanced Materials.
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