Magnets align nanotubes in resin

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.