Form of solid carbide harder than diamond

Researchers at North Carolina State University reported the discovery of a distinct form of solid carbon they estimate is about 10 percent harder than diamond and could play an important role in machining. They also claim to have developed a relatively inexpensive technique for producing the substance, called Q-carbon, at room temperature and ambient atmospheric pressure.

Besides being superhard, Q-carbon is ferromagnetic, unlike other solid forms of carbon, and glows when exposed to even low levels of energy, according to the scientists.

The researchers believe Q-carbon may exist in the cores of some planets. To produce it artificially, they coat a substrate with amorphous carbon, which lacks a well-defined crystalline structure. A laser pulse lasting about 200 nanoseconds hits the carbon, during which time the material’s temperature reaches 4,000° K. The heated spot then rapidly cools via quenching to become a film of Q-carbon. At present, the researchers can make films from 20nm to 500nm thick.

Figure 1. (a) Q-carbon is a third phase of carbon alongside graphite and diamond; (b) The Q-carbon layer breaks into a cellular (filamentary) structure upon quenching. Images courtesy North Carolina State University.