‘Q-carbon’ may offer quick route to diamonds

A glow-in-the dark, magnetic, stronger-than-diamond material might be a bizarre new form of carbon.

Scientists call it Q-carbon. After diamond and graphite, it’s the third known solid phase, or form, of the element, materials scientists Jagdish Narayan and Anagh Bhaumik report December 2 in the Journal of Applied Physics.

Q-carbon’s unusual properties make it ideal for all sorts of applications, Narayan says, from electronic displays to abrasive coatings on tools to biomedical sensors that are compatible with the body. The new material could also offer scientists an easy way to manufacture diamonds.

“If these claims stand up, the formation of a new phase of carbon would be extraordinary,” says Penn State University chemist John Badding. But, he notes, “extraordinary claims require extraordinary evidence.”

Carbon exists in several structural forms. At room temperature and pressure, the atoms link together in 2-D honeycomb sheets called graphene that stack together to form graphite, the shiny charcoal-colored material used in pencils. Crank up the heat and pressure, and carbon can turn to liquid or vapor. Crush carbon under high pressure and the atomic bonds buckle, popping atoms into the 3-D tetrahedral arrangement of diamonds.

Scientists have made other carbon structures too, including nanotubes (rolled up versions of the flat honeycomb sheets) and soccer ball‒shaped structures called buckyballs that contain 60 carbon atoms.

“When carbon goes into a new structural arrangement, really exciting properties can arise,” Badding says. Diamonds and carbon nanotubes, for example, are superstrong, and graphene can conduct electricity.

One of Q-carbon’s exciting properties is its magnetism, Narayan says. “You could actually see Q-carbon flakes stick to steel tweezers.” That’s a big deal, he says, because no other forms of carbon are magnetic.

Narayan and Bhaumik, both of North Carolina State University in Raleigh, created the new material using a laser heating technique. First, they zapped a carbon pellet with a high-power laser beam, which blasted a thin carbon coating onto a flat sheet of sapphire about the size of a postage stamp. Then they turned the power down and hit the coat with just enough heat to make it melt (about 4,000 kelvins, or roughly two-thirds as hot as the sun’s surface). 

After the quick toasting, the carbon was rapidly cooled, or quenched (that’s where Q-carbon gets its name), transforming it into the new material. Instead of interlocking in the neat lattices of diamonds, carbon tetrahedrals jumbled together in an amorphous heap. It’s as if someone smashed a diamond’s structure, but left most of its individual building blocks intact, Narayan says. 

From these building blocks, the team could grow tiny dots, films and needles of diamonds by providing the seeds for crystal growth. “The fact that they can convert Q-carbon into diamond at ambient temperature and pressure could be of great interest,” says materials scientist Amit Goyal of the State University of New York at Buffalo. Other ways of creating diamonds are slow, expensive and require high pressures and heat.

Narayan and Bhaumik probed Q-carbon’s structure by measuring the atoms’ locations and bonds and by using Raman spectroscopy, a kind of molecular fingerprinting technique that measures atoms’ vibrations. But while the fingerprints of diamond and carbon nanotubes are clear-cut, those of amorphous carbon are notoriously complex, Badding says. So it might be tricky to decipher exactly what material was created.

Goyal believes Q-carbon “may well be a new phase of carbon.” But, just like any other new discovery, he says, the findings will need to be replicated.