On Nov. 30, researchers announced that they have discovered a new phase of carbon at standard temperature and pressure.
“We’ve now created a third solid phase of carbon,” Jay Narayan, a materials scientist at North Carolina State University, said in a press release. “The only place it may be found in the natural world would be possibly in the core of some planets.”
Researchers call the new phase Q-carbon. Q-carbon is made by depositing a thin layer (50-500 nanometers thick) of amorphous carbon onto a substrate of sapphire or glass using a krypton flouride laser. Amorphous carbon has bonding characteristics which are a mixture of graphite (sp2 bonded) and diamond (sp3 bonded). The coated substrate is then subjected to pulses from an argon flouride laser. This raises the temperature of the carbon to 4000 K while maintaining standard pressure conditions and keeping the substrate near ambient temperature. The Gibbs free energy of amorphous carbon under these conditions equals that of an undercooled liquid and metastable diamond phase. This is quenched (giving us the Q in Q-carbon) and retained at room temperature, which leads to the nucleation of nano- and micro-crystals. This produces a unique diamond-like material at conditions much different than the 5000 K temperature and 12 GPa pressure needed to produce diamonds.
Q-carbon is harder than diamond, making it perhaps the hardest known substance. It also has other properties that differ from diamond. “Q-carbon’s strength and low work-function − its willingness to release electrons − make it very promising for developing new electronic display technologies,” Narayan said.
The extent of undercooling, ratio of sp2 bonded to sp3 bonded carbon, laser parameters, substrates, and cooling rate can all be modified to alter the end result. Applications for the various Q-carbons produced may include abrasives, biomedical products, catalytics, microelectronics, nanoelectronics, and smart displays. “We can create diamond nanoneedles or microneedles, nanodots, or large-area diamond films, with applications for drug delivery, industrial processes and for creating high-temperature switches and power electronics,” Narayan explained.
The process is less expensive than previous methods of producing synthetic diamonds, but Q-carbon is still in the early stages of development. “We can make Q-carbon films, and we’re learning its properties, but we are still in the early stages of understanding how to manipulate it,” Narayan said. “We know a lot about diamond, so we can make diamond nanodots. We don’t yet know how to make Q-carbon nanodots or microneedles. That’s something we’re working on.”