A team of material scientists in the United States has discovered a novel allotrope of carbon, Q-carbon.
Nucleation of microdiamond from nanodiamond filaments which were quenched after the formation at 6,740 degrees Fahrenheit. Image credit: Jagdish Narayan / Anagh Bhaumik.
Q-carbon is distinct from graphite and diamond. The only place it may be found in the natural world would be possibly in the core of some planets, according to team leader Prof. Jagdish Narayan, of North Carolina State University.
The new carbon allotrope has some unusual characteristics: it is ferromagnetic, harder than diamond, and it glows when exposed to 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,” Prof. Narayan explained.
Prof. Narayan and his colleague, North Carolina State University Ph.D. student Anagh Bhaumik, have also developed a technique for using Q-carbon to make diamond-related structures at room temperature and at ambient atmospheric pressure in air.
To produce Q-carbon, the material scientists start with a glass or sapphire substrate. The substrate is then coated with an amorphous metastable phase of carbon, where bonding characteristics are a mixture of graphite and diamond.
The carbon is then hit with a single KrF laser pulse lasting 200 nanoseconds. During this pulse, the temperature of the carbon is raised to 6,740 degrees Fahrenheit (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 scientists can control the process to make films between 20 nanometers and 500 nanometers thick.
By using different substrates and changing the duration of the laser pulse, they can also control how quickly the carbon cools. By changing the rate of cooling, they are able to create diamond structures within the Q-carbon.
“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,” Prof. Narayan explained.
“These objects have a single-crystalline structure, making them stronger than polycrystalline materials,” he added.
“And it is all done at room temperature and at ambient atmosphere. So, not only does this allow us to develop new applications, but the process itself is relatively inexpensive.”
Bhaumik and Prof. Narayan reported their results in a pair of papers in the Journal of Applied Physics and the journal APL Materials.
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Jagdish Narayan & Anagh Bhaumik. Novel Phase of Carbon, Ferromagnetism and Conversion into Diamond. Journal of Applied Physics, published online November 30, 2015; doi: 10.1063/1.4936595
Jagdish Narayan & Anagh Bhaumik. 2015. Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air. APL Mater. 3, 100702; doi: 10.1063/1.4932622
