Monday, November 21, 2005

"MATERIALS: Carbon nanotube 'paper' stronger than steel"

Recent research using carbon nanotubes in place of conventional carbon fibers is revealing large gains in such critical material properties as tensile strength and electrical and thermal conductivity. A striking example is a paper product that is ultrathin, electrically conducting and 10 times lighter than steel while still being 250 times stronger. Called buckypaper by its developer, the Florida Advanced Center for Composite Technologies (FAC2T), the material could enable the development of stronger ultralight aircraft or of lighter-weight yet more-effective body armor. It might also find a role in vehicle armor or the construction of stiff, durable yet paper-thin computer displays, researchers said. Buckypaper is created from carbon nanotubes, which can be magnetically aligned during fabrication using the National High Magnetic Field Laboratory's 25 Tesla supermagnet, located at Florida State University. Carbon nanotubes have a high aspect ratio, measuring nanometers wide but extending tens or hundreds of microns in length. Carbon commonly forms into graphite, a flat sheet of carbon atoms bonded in a hexagonal, closely packed structure. Although the carbon-carbon bond is very strong, the two-dimensional sheets do not have much strength in any direction out of their plane. Carbon atoms can also bond into diamond, a three-dimensional crystal that is identical to crystalline silicon-a form that demonstrates the potential strength of carbon bonding. FSU has four U.S. patents pending for buckypaper. Among the smorgasbord of applications slated for development using the material, FAC2T predicts buckypaper will prove applicable as a large-scale electron-field emitter for flat-panel displays, as a thermal conductor for superefficient heat sinks and as high-current protective film for the exteriors of airplanes. Such film would allow lightning strikes to flow around a plane and dissipate without damaging it.