While attempting to develop a new method to produce
synthetic diamond, scientists at North Carolina State University have discovered
an entirely new phase of carbon called “Q-carbon”. This new material was found
to possess fascinating physical and chemical properties some of which resolve
long-standing scientific mysteries. It is harder than diamond, magnetic at room
temperature, stable at ambient conditions and is electrically conductive. Further,
its production doesn’t require extreme temperature and pressure and it can easily
be converted into conventional diamond.
 |
| Phase diagram of carbon. Conventional methods to produce diamond push graphite into diamond by increasing temperature and pressure. The dotted green line shows the interface between supercooled liquid carbon and diamond, which can be crossed at ambient pressure. Source: http://dx.doi.org/10.1063/1.4936595 |
Diamond is an extremely useful material due to its physical characteristics. Its hardness and clarity lend it to use in a wide variety of industrial applications such as in abrasives and optics while its thermal and electrical traits are useful in technological hardware. However, the scarcity of diamond of appropriate quality in nature forces scientists to look for ways to mass produce it. The conventional approach requires extremely high temperatures and pressures along with chemical catalysts. This is extremely energy-intensive, costly and inefficient.
Researchers Jagdish Narayana and Anagh Bhaumik at North
Carolina State were hoping to find a more straightforward synthetic pathway to
diamond by utilizing a strange quirk of physics called ‘supercooling’. Most
people are familiar with supercooling as it applies to water. A common
demonstration involves placing a bottle of very pure water in the freezer and
taking it out after around two and a half hours. It appears liquid, but upon
hitting it against a surface, it suddenly crystallizes and forms fluffy ice.
This is a slightly different process from the one used for
making Q-carbon, though. While the water demonstration starts in the liquid form,
becomes supercooled liquid and then returns to its normal freezing point to
crystallize into ice, the scientists at NCSU melted solid carbon with a laser
tuned to a highly specific energy. The laser excites the atoms electrically
rather than thermally, and so their crystal structure falls apart at a much
lower temperature than it conventionally would. This liquid carbon was then cooled
extremely rapidly, a process known as ‘quenching’ (hence the “Q” in Q-carbon).
This locked the carbon atoms in their unusual physical arrangement. The rapid
cooling doesn’t allow the atoms any time to form an organized crystal, and thus
Q-carbon was born.
 |
| (left) Q-carbon formed by quenching supercooled liquid carbon, (right) a thread of Q-carbon (white) ending at a crystal of conventional diamond. Source: http://dx.doi.org/10.1063/1.4936595 |
Subsequent
characterization experiments revealed its surprising physical properties. Its
magnetic qualities solve an old mystery regarding carbon’s potential as a candidate
for ferromagnetism. Scientists had theoretically predicted it, but it had never
been experimentally verified until now. It is also suggested that because the
physical conditions necessary to produce it exist at the centers of many of our
solar system’s planets, it could potentially be responsible for their magnetic
fields.
The potential applications for this new material are as yet
largely unknown. In any case, its ability to transform into conventional
diamond through a second laser pulse is bound to be useful as it circumvents
the problems of current energy-intensive production methods. Further studies
will certainly need to be done before we can be sure that Q-carbon has
practical use, but if verified, the discovery could prove revolutionary for
technology and industry.
Written by: Aisling M Williams
References
Narayan, J.; Bhaumik, A. Novel Phase of Carbon, Ferromagnetism, and Conversion into Diamond. J. Appl. Phys. Journal of Applied Physics. Dec 2015, 118, 215303.
mrsciguy. "Supercooled Water". Online Video Clip. Youtube. 11 Feb 2016. Web. https://youtu.be/DpiUZI_3o8s
