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Researchers from North Carolina State University have discovered a new phase of solid carbon, called Q-carbon, which is distinct from the known phases of graphite and diamond. They have also developed a technique for using Q-carbon to make diamond-related structures at room temperature and at ambient atmospheric pressure in air.
Phases are distinct forms of the same material. Graphite is one of the solid phases of carbon; diamond is another.
“We’ve now created a third solid phase of carbon,” 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 has some unusual characteristics. For one thing, it is ferromagnetic – which other solid forms of carbon are not.
“We didn’t even think that was possible,” Narayan says.
In addition, Q-carbon is harder than diamond, and glows when exposed to even low levels of energy.
“Q-carbon’s strength and low work-function – its willingness to release electrons – make it very promising for developing new electronic display technologies,” Narayan says.
But Q-carbon can also be used to create a variety of single-crystal diamond objects. To understand that, you have to understand the process for creating Q-carbon.
Researchers start with a substrate, such as such as sapphire, glass or a plastic polymer. The substrate is then coated with amorphous carbon – elemental carbon that, unlike graphite or diamond, does not have a regular, well-defined crystalline structure. The carbon is then hit with a single laser pulse lasting approximately 200 nanoseconds. During this pulse, the temperature of the carbon is raised to 4,000 Kelvin (or around 3,727 degrees Celsius) and then rapidly cooled. This operation takes place at one atmosphere – the same pressure as the surrounding air.
The end result is a film of Q-carbon, and researchers can control the process to make films between 20 nanometers and 500 nanometers thick.
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