Scientists have developed a way to make tiny diamonds quickly and easily with surprisingly little heat and no catalyst.
The technique involves extracting special cage-like molecules from petroleum and natural gas and then heating them with a laser under intense pressures.
The applications of the diamonds created may be limited, however, as the technique is not able to make precious stones any larger than the width of a human hair.
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Scientists have developed a way to make tiny diamonds (pictured) quickly and with surprisingly little heat and no catalyst. The technique involves extracting cage-like molecules from petroleum and natural gas and then heating them with a laser under intense pressures
‘What’s exciting about this paper is it shows a way of cheating the thermodynamics of what’s typically required for diamond formation,’ said paper author and geologist Rodney Ewing of Stanford University, in California.
The natural diamonds we have today formed from carbon buried hundreds of miles underground, where temperatures reached some thousands of degrees Fahrenheit.
The precious stones were then carried upwards to the surface by volcanic activity — bringing with them ancient minerals that can shine a light on conditions deep within the Earth’s interior.
‘Diamonds are vessels for bringing back samples from the deepest parts of the Earth,’ added Stanford university mineralogist Wendy Mao, who leads the laboratory where Professor Ewing and colleagues conducted most of their research.
In contrast, the researchers were interested in the processes that can be used to make diamonds in the lab, such that could eventually help apply the unique properties of the the precious stones to other applications.
Diamonds are extremely hard, transparent to light, chemically stable and transfer heat efficiently — properties that could find myriad uses, including in medicine, biological sensing, quantum computing hardware and general industry.
Experts have been making artificial diamonds for more than six decades, but conventional methods for diamond synthesis typically require massive amounts of energy or time — or the addition of a catalyst that diminishes the resulting material.
‘We wanted to see just a clean system, in which a single substance transforms into pure diamond – without a catalyst,’ said lead author and geologist Sulgiye Park.
The applications of the diamonds created may be limited, however, as the technique is not able to make precious stones any larger than the width of a human hair. Pictured, lead author Sulgiye Park poses with a sample of the diamondoid powder and a model of its structure
In their study, the team started with samples of a powder — which superficially resembles rock salt — that they refined from the fossil fuel petroleum.
On an atomic scale, the powders — known as diamondoids — are structured similarly to a diamond, albeit one in which the crystal lattice had been split into small units composed of one, two or three molecular cages.
Unlike real diamonds, which are made of pure carbon, the diamondoids also contain atoms of hydrogen.
‘Starting with these building blocks you can make diamond more quickly and easily,’ Professor Mao explained.
‘You can also learn about the [diamond formation] process in a more complete, thoughtful way than if you just mimic the high pressure and high temperature found in the part of the Earth where diamond forms naturally.’
Only a ‘tiny amount’ of the diamondoid powders was used by the researchers. ‘We use a needle to pick up a little bit to get it under a microscope for our experiments,’ Professor Mao added
The team placed the powder sample into a tiny pressure chamber — a so-called ‘diamond anvil cell’ — which used two polished diamonds to apply the same kind of forces between them as would be found deep within the Earth
Only a ‘tiny amount’ of the diamondoid powders was used by the researchers.
‘We use a needle to pick up a little bit to get it under a microscope for our experiments,’ Professor Mao added.
The team placed the powder sample into a tiny pressure chamber — a so-called ‘diamond anvil cell’ — which used two polished diamonds to apply the same kind of forces between them as would be found deep within the Earth.
The final step involved heating the sample with a laser — transforming the powder into diamonds in a mere fraction of a second.
On an atomic scale, the powders — known as diamondoids — are structured similarly to a diamond, albeit one in which the crystal lattice had been split into small units composed of one, two or three molecular cages. Pictured, paper author Yu Lin with models of diamondoids with one, two and three cages, along with a diamond lattice
‘A fundamental question we tried to answer is whether the structure or number of cages affects how diamondoids transform into diamond,’ said paper author and geologist Yu Lin.
The team found that the three-cage diamondoid — which is known as triamantane — requires surprisingly little energy to rearrange itself into diamond.
Specifically, this transition — which sees the diamond’s hydrogen atoms scatter — occurs at around 1,160°F, about the temperature of red-hot lava, and pressures some hundreds of thousands of times greater than those found in the Earth’s atmosphere.
The researchers note that the limitations of the size of the sample than can be pressurised within a diamond anvil cell means that this approach can only be used to create tiny specks of diamonds.
‘But now we know a little bit more about the keys to making pure diamonds,’ Professor Mao noted.
The full findings of the study were published in the journal Science Advances.
HOW DO SCIENTISTS ‘GROW’ DIAMONDS IN A LABORATORY?
Diamonds fetch their lofty price tags because they form over millions of years under high pressures and temperatures deep within the Earth’s crust.
But a number of companies are now growing the gems in laboratories across the world, threatening to shake up the diamond industry.
A small ‘seed’ diamond acts as a scaffolding for the process.
Scientists first place this seed into a vacuum chamber to remove impurities from the air.
Lab-made gems are threatening to upset the diamond industry, with several companies worldwide now growing the stones for jewellery. In this image Pure Grown Diamonds CEO Lisa Bissell unveils a lab-cultivated diamond in New York in 2015
They then funnel hydrogen and methane gas heat to 3,000°C (5,400°F) into the chamber to create a highly charged gas known as plasma.
The gases rapidly break apart, releasing carbon atoms from the methane that collected on the diamond ‘seed’.
These atoms naturally copy the crystal structure of organic diamond, which is also made up of carbon atoms.
Each artificial stone grows at a rate of around 0.0002 inches (0.006mm) an hour.
