Diamonds are a lab's best friend

We know they make the rich look richer, but most diamonds are used in industry, and synthetic diamonds are hot on their heels, writes JOHN HOLDEN

THEY USED TO be a girl’s best friend, but now they’re in demand as much from engineers in labs and factories as from glamorous celebrities: so what makes diamonds so special?

No one could ever accuse the diamond of being humble. Its association with glamour, wealth and extravagance was copper-fastened by the likes of Liberace, Elizabeth Taylor and J-Lo. But while diamonds may be better known as the trinkets of the rich and famous, only 20 per cent of those found or manufactured become jewellery. The other 80 per cent are used in industry.

Engineers in factories and labs surround themselves with the precious stone, and they make better use of them than celebrities. Diamonds have become essential in a variety of high-tech manufacturing processes. Their superlative physical properties mean they are used in industrial applications such as cutting, drilling, grinding and polishing.

“On the Mohs Scale of Mineral Hardness [measurement for scratch resistance of minerals], talc is at number one, as the softest, and diamonds are at number 10,” says Prof Martin Feely of NUI Galway. Feely runs the only course in gemmology in the country.

“Diamonds are made of carbon, and carbon is extraordinary in how it assembles at an atomic level. It gives you one of the softest metals – graphite – as well as diamonds at its hardest level.”

The chemical composition of diamonds and graphite is the same, and yet the two are very different. “This has to do with their atomic scaffolding: how atoms of carbon are bound together, and the architecture of that atomic structure,” says Feely. “If you take graphite, for example, you can rub it and carbon will come off on your thumb. That’s because the carbon atoms are bound together. They are actually in layers. At an atomic level they are held together by the weakest bonds in nature.

“In a diamond, each carbon atom is bonded to four other carbon atoms. These are very robust strong bonds. They have the same strength as graphite but each carbon is bonded to another atom rather than just being in layers.”

Natural diamonds are formed about 160km below the surface of the earth at temperatures of around 1,100 degrees at pressures in excess of 20 kilobars. “Imagine 160km of rock on top of you,” says Feely. “The pressure is immense. A diamond is formed there by the coming together of carbon atoms and there they reside in a diamond stability zone. At some point an eruption will occur with a fracturing of the rock above. The type of rock that brings the diamonds up is known as kimberlite [it was first discovered in Kimberly, South Africa].

“Natural diamonds have been found in younger rock, but some could be as old as three billion years. They tend to reside in very old parts of the Earth’s crust, in Africa, Canada and Russia, for example.”

Making rich people look richer is only a fraction of what the global diamond manufacturing industry accounts for. Mining is a big, controversial business. The increasing demand, expense and rarity of the natural diamonds created so laboriously by nature has made synthetic manufacture of diamonds a huge industry, particularly for industrial use. Scientists have only recently been able to grow diamonds the same way in a lab as is done in nature. But they can be grown quite effectively, so much so that man-made diamonds are now used in some jewellery.

Still, the diamond enthusiast will always know the difference. “Industry can now make perfect diamonds, bespoke for any particular type of industry need, but beauty is in the eye of the beholder,” says Feely. “Artificial diamonds will share many of the same characteristics as the natural kind. Sometimes they are even more perfect. But it’s not the real thing and the big money will always be for the natural grade.”

Not all natural diamonds are suitable for jewellery though. A diamond field with trillions of carats was recently found in Siberia under a giant meteorite crater. The diamonds were created by a large bolide – an unidentified missile from space – that hit the Earth several million years ago. They are are reportedly “twice as hard as normal”, so could only be used for industrial purposes.

But there’s plenty of need for them in industry. A pre-spinout company based in Trinity College, Dublin is tapping into the growing industrial demand for diamonds. Adama Innovations design novel diamond-patterning technology. The unique strengths of the diamond is at the heart of what they do.

“For starters, it is the hardest material on Earth,” says Prof Graham Cross of Trinity’s Crann Institute and Adama Innovations. “It doesn’t wear away against other surfaces, even other diamonds. Plus, it is resistant to any other chemistry, so it doesn’t react. Heat moves through a diamond faster than anything else in nature: it is an excellent heat conductor. Lastly, it is one of the best insulators in existence.”

Diamonds have become essential to high-tech applications. People need shapes to perform all sorts of different functions. This falls into the discipline of metrology, or the science of measurement.

Cross is the cofounder of Adama Innovations, which patterns and shapes diamonds efficiently at every scale, from the nano to the macro. The company has just manufactured its first line of diamond shapes for semiconductor wafers for computer giant Intel.

Diamonds form important parts for microchips in computers and are an essential component in the billions of electronic devices used around the world. “Heat moves faster through them than anything else,” says Cross. “So they are very useful for electronic devices. Computers are limited in terms of their capacity by all the heat they produce. Diamonds are used to conduct that heat away, allowing the computer to run faster.”

'Cut' from a diamond cloth

The diamond may be a precious stone, but it is hard as nails and won’t be pushed around by anyone. But a new hard lad may be about to take over.

A team of scientists from Carnegie Mellon University in Pittsburgh may have discovered a new form of hard carbon clusters capable of indenting diamond. We’ll have to watch this space.

Until more research is done, how do you cut a diamond? With more diamonds, of course, although cutting isn’t the term used. “It’s a bit of a misnomer to talk about ‘cutting’ diamonds,” says minerologist Professor Martin Feely of NUI Galway. “If you’re cutting a rough diamond into a cut stone, you use diamond studded cloths on wheels. You rub the stone with different grades against the wheel as it circulates, and you abrade the diamond to make the shape you want.

“So you don’t cut them in the traditional sense of the word; you abrade them and get the shape by using various angles. But no other materials could be used to cut diamond, only other diamonds. The angles at which you abrade are key,” he says.

That is what gives the “fire”, or glistening effect, to any diamond. This is produced by accurately abrading the face on the brilliant cut, so it captures sunlight to give that glistening effect.

As strong as they are, diamonds have one Achilles’ heel. “Diamonds can have weak cleavage, and they will naturally break along these planes at the atomic scale. A well-experienced cutter will be able to find that Achilles’ heel and use it as the initial start of cutting.”