Korean scientists develop superfast method for producing diamonds

In the Budget for 2023-24, Finance Minister Nirmala Sitaraman announced reduction in customs duties for ‘seeds’ for lab grown diamonds, to give a fillip to diamond manufacturing in India. The government also gave a grant of ₹242 crore to IIT Madras for setting up an India Centre for Lab Grown Diamonds (InCent-LGD) for research into LGDs.

Growing diamonds is a time-consuming process — it takes about 12 days for a diamond to grow through the conventional ‘high pressure, high temperature’ method — discovered by GE in 1955 — by which almost all the synthetic diamonds are produced today.

Diamonds are just carbon atoms arranged in a certain way. The HPHT method involves dissolving carbon in liquid metal at a high pressure of about 5 Giga Pascals (50,000 times the atmospheric pressure) at 1,300–1,600^oC. The molten metal behaves like a solvent for the dissolved carbon; the carbon atoms move towards the diamond seed crystal and deposit themselves on it — just growing the lattice structure. Over a few days, it becomes diamond. Diamonds produced by this method cannot be very big.

Is there a way to produce diamonds easier, faster and bigger? Yes, says a group of Korean scientists.

In a recent paper published in Nature, they describe how they grew diamonds in just 15 minutes at a temperature of 1,025^oC, with no seed particles. Importantly, this was at ambient pressure.

How they did it

The group of 15 scientists (including an Indian, Babu Ram) of the Ulsan National Institute of Science and Technology, created a cocktail of gallium, iron, nickel and silicon by putting them in a graphite crucible. Then they pumped in methane at 1,175^oC. Diamonds formed at the bottom, where the liquid metal had solidified, and “had rainbow colours to the eye”. Then they used a different methane — ¹³CH₄ — where the carbon atom is of an isotope of carbon and they found diamonds were purer. The researchers established that the crystals were diamond using methods of Raman spectroscopy, transmission electron microscopy and X-ray diffraction.

They found that diamonds nucleate and grew at the centre, where they believe there was a “temperature gradient” (slight lower temperature). Carbon atoms rushed to the spot, piled on each other and formed a structure that we know to be diamond. They did many runs, spanning different lengths of time. They found that diamonds start forming between 10 minutes and 15 minutes (compared with 12 days through the HPTP method!) The diamonds keep growing with time but stop growing at around 150 minutes.

This method is a path-breaking discovery. That this is done at ambient pressure is significant. It may not be perfect, but it suggests a new way of making diamonds. The Korean scientists suggest that the system could be tweaked, such as with a different cocktail of metals, for better results.

“The possibilities of exploring diamond growth with this type of approach seem promising,” they say in their paper.