New Diamond Nanotube Composite Material Created

October 20th, 2005

Argonne researchers have combined the world's hardest known material – diamond – with the world's strongest structural form – carbon nanotubes. A new process for "growing” diamond and carbon nanotubes together opens the way for its use in a number of energy-related applications.

Image above: Argonne's carbon-nanotube research was featured on the June 2005 cover of Advanced Materials

The resulting material has potential for use in low-friction, wear-resistant coatings, catalyst supports for fuel cells, high-voltage electronics, low-power, high-bandwidth radio frequency microelectromechanical/nanoelectromechanical systems (MEMS/NEMS), thermionic energy generation, low-energy consumption flat panel displays and hydrogen storage.

“Diamond is hard because of its dense atomic structure and the strength of the bonds between atoms,” said John Carlisle, one of the developers of the new material. “The larger the distance between atoms, the weaker the links binding them together. Carbon's bond strength and small size enable it to form a denser, stronger mesh of atomic bonds than any other material.”

Diamond has its drawbacks, however. Diamond is a brittle material and is normally not electrically conducting. Nanotubes, on the other hand, are incredibly strong and are also great electrical conductors, but harnessing these attributes into real materials has proved elusive. By integrating these two novel forms of carbon together at the nanoscale, a new material is produced that combines the material properties of both diamond and nanotubes.

The new hybrid material was created using Ultrananocrystalline™ diamond (UNCD), a novel form of carbon developed at Argonne. The researchers made the two materials – ultrananocrystalline diamond and carbon nanotubes – grow simultaneously into dense thin films.

A surface covered with a mixture of diamond nanoparticles and iron nanoparticle "seeds” was exposed to the argon-rich, hydrogen-poor plasma normally used to make UNCD. The diamond and iron “seeds” catalyzed the UNCD and carbon nanotube growth, respectively, and the plasma temperature and deposition time were regulated to control the speed at which the composite material grows, since carbon nanotubes normally grow much faster than UNCD.

"Experimenting with these variables led us to the right combination,” said Jeffrey Elam. Xingcheng Xiao, another researcher, added, “It is possible that the plasma environment causes local charging effects that cause attractive forces to arise between the ultrananocrystalline diamond supergrains and the carbon nanotubes. If so, such hybrid structures could have interesting electronic and photonic transport properties.”

The next step is to develop patterning techniques to control the relative position and orientation of the ultrananocrystalline diamond and carbon nanotubes within the material.

“In addition, we hope to understand the structure and properties of these materials, particularly the mechanical, tribological and transport properties,” developer Orlando Auciello said.

Source: Argonne National Laboratory