To make diamonds, the industry typically resorts to subjecting graphite to immense pressure and temperature, which makes production volumes low and costly. This paradigm is about to change, since researchers at North Carolina State University found a new phase for carbon called Q-carbon, produced at ambient temperatures and pressure. This is surprisingly close to diamond in structure, with the added benefit of exhibiting a couple of unique properties.
"We've now created a third solid phase of carbon (besides graphite and diamond)," says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of three papers describing the work. "The only place it may be found in the natural world would be possibly in the core of some planets."
Q-carbon is actually harder than diamond. Among other things, it glows (a sort of fluorescence) even when exposed to low energy levels and is ferromangnetic. Ferromagnetism manifests itself in the fact that a small externally imposed magnetic field, say from a solenoid, can cause the magnetic domains to line up with each other and the material is said to be magnetized. Thus, a material that isn't actually a magnetic can act like one for a brief period of time. "We didn't even think that was possible," Narayan said, further mystifying the properties of Q-carbon.
To make Q-carbon, you first coast sapphire, glass or a plastic polymer with a layer of non-crystalline amorphous carbon. Then blast the whole material with a very short, but intense laser pulse. The pulse lasts only 200 nanoseconds (200 billionths of a second), but it's enough to raise the temperature of the carbon to 4,000 Kelvin (or around 3,727 degrees Celsius). By altering the duration of the laser pulse, the researchers can alter the quality and quantity of the carbon. For instance, you can make single crystal or other diamond shapes. Further demonstrating its versatility, the researchers made Q-carbon films ranging from 20 nanometers to 500 nanometers in thickness.
More work and research is required to understand this peculiar new carbon phase. We don't know for sure how useful Q-carbon is, but it's readiness to release electrons makes it suitable in the field of electronics. Other uses might follow following closer investigation.
"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 says. "These diamond objects have a single-crystalline structure, making them stronger than polycrystalline materials. And it is all done at room temperature and at ambient atmosphere – we're basically using a laser like the ones used for laser eye surgery. So, not only does this allow us to develop new applications, but the process itself is relatively inexpensive."
"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 says. "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."
Referece: Jagdish Narayan et al. Research Update: Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air, APL Materials (2015). DOI: 10.1063/1.4932622
