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Q-Carbon and The Man Who Makes His Own Diamonds

Posted on March 15th, 2016 by in New Materials & Applications

Galileo is said to have disproved the popular astronomical beliefs in early seventeenth century.  He spoiled the public perception of lunar beauty by reporting craters on the moon’s face!  Alas the smooth face was just an illusion. Poetic analogies of beauty had to be thought over….  Professor Jay Narayan does make diamonds but he is not about to pull a Galileo on diamond lovers. And definitely he is too much a gentleman to try to spoil anyone’s diamond ring shopping.  So, all diamond-heads relax and continue shopping.   Let’s find out what he is really doing!

Naturally, I called Jay Narayan, C. C. Fan Distinguished Chair Professor, at the Materials Science and Engineering Department of the North Carolina State University.  He is a highly decorated professor and has received numerous honors.  He was most kind to call me back just a couple of hours after I left him a message.  He described the basic facts of the diamond making process his research group has developed. Prof. Narayan confirmed he has found a fairly easy way to make diamonds!  But let’s first talk diamonds in general.

A primer on diamonds

The world’s most popular gemstone is diamond. It is shiny, glitters and sparkles and has been marketed brilliantly. In 2010 some $18 billion was spent on diamonds in the United States alone (Source: http://geology.com). Diamonds are not found on the Earth’s surface. Rather they form at high temperatures (4723K) and pressures (120,000 bars) in Earth’s mantle at 160 km depths. Volcanic eruptions of deep origin carry diamonds to the surface of the Earth.  Asteroids and meteorites have been purported to carry diamonds to the Earth or help form them.

A tangible characteristic of diamond is its hardness of 10 on Mohs scale (1-10, 10 being hardest).  That makes diamonds quite useful in different industries. Indeed there is a very large industrial market for diamonds exceeding the available natural supply. Industrial diamonds are synthetic, not to be confused with artificial diamonds like cubic zirconia (ZrO2).  Majority of industrial diamonds are consumed in manufacturing abrasive products. Small particles of diamond are also embedded in saw blades, drill bits or grinding wheels for the purpose of cutting, drilling or grinding.  They can be ground into a powder and formulated into a diamond paste applied in polishing or for very fine grinding.  Diamonds have other applications in protective coatings and biomedical applications to superior diamond electronics, photonics and display devices.  Examples include optical windows, contact surface of micro-bearings, microelectronics heat sink, coatings on wear resistant parts and others.  Nearly 90% of the industrial diamonds consumed is synthetic [Ref G. Davies, Diamond, Adams Hilgor, Bristol, UK, 1984].  China is the world leader with a production of over 4 billion carats per year.

How are synthetic diamonds made?

Flawless synthetic diamonds, up to a few carats, are manufactured by chemical vapor deposition (CVD) technique (at temperatures >1300ºC) and sold into gem market.  Another method utilizes detonation of explosives in a metal chamber. The common processe (HPHT) for producing industrial diamonds employs high-pressures (55000 bars) and high-temperatures (1400-1500ºC).  All these processes are operated at extreme conditions at low production volumes thus resulting in fairly expensive diamonds, though below the cost of natural stones.

Enter Prof. Jay Narayan.  He and Anagh Bhaumik, a PhD candidate in his research group, have developed a method for direct conversion of carbon into diamonds at ambient pressure and temperature.  The have solved a scientifically challenging age-old problem with immense technological significance.

They have discovered a new phase of solid carbon, called Q-carbon, which is distinct from the known phases of graphite and diamond.  Q-carbon has some unusual characteristics. For one thing, it is ferromagnetic in contrast to the other solid forms of carbon. 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.

Narayan and Bhaumik have developed a technique for using Q-carbon to make diamond-related structures at room temperature and at atmospheric pressure in air.  In an interview Prof. Narayan said: “We’ve now created a third solid phase of carbon.  The only place it may be found in the natural world would be possibly in the core of some planets.”

To produce Q-carbon, the material scientists start with a glass or sapphire or polymer 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 ArF laser pulse lasting 20 nanoseconds. During this pulse, the temperature of the carbon is raised to 3,727ºC and then rapidly cooled. This operation takes place under atmospheric pressure. 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 [Ref J. Narayan, A. Bhaumik, Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air, http://dx.doi.org/10.1063/1.4932622, APL Mater. 3, 100702, 2015].

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 [Figure 1], with applications for drug delivery, industrial processes and for creating high-temperature switches and power electronics,” Prof. Narayan explains. “These objects have a single-crystalline structure, making them stronger than polycrystalline materials,” he added.

Figure1

Figure 1 Formation of Q-carbon and nano- and microdiamonds after one laser pulse: (a) SEM micrograph showing Q-carbon after single laser pulse of ArF laser at 0.5 J/cm2 or outer regions of 0.6 J/cm2; (b) formation of microdiamonds from the filaments toward the edge of 0.6 J/cm2 sample; (c) nano- and microdiamonds in the middle of 0.6 J/cm2 sample; and (d) only microdiamonds covering the entire area in certain regions of 0.6 J/cm2 sample. [Ref J. Narayan, A. Bhaumik, Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air, http://dx.doi.org/10.1063/1.4932622, APL Mater. 3, 100702, 2015]

“We know a lot about diamonds, 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,” he says.

I found Prof. Narayan’s work fascinating for many reasons starting with a relatively simple solution dreamed about for centuries.  But if it had been up to me go choose a research area, studying carbon would not have been among them.  After all it is an old settled topic; carbon is either in the form of graphite or diamond – end of discussion.  Fortunately, Professor Narayan and PhD candidate Bhaumik had the genius of avoiding my presumption and researched carbon phases.  Sometimes the greatest innovations come from taking another look at the so-called long settled subjects.


All opinions shared in this post are the author’s own.

 

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