BBC Online :
To a chemist, diamonds are a three-dimensional cubic lattice of carbon atoms. To most of us, they are the ultimate status symbol – but how long will they remain so, now that they can be mass-produced?
It was the US giant General Electric that first figured out how to bake a diamond back in the 1950s.
The High Pressure High Temperature (HPHT) technology they pioneered
— which recreates the conditions under which natural diamonds form deep inside the earth – is still used today.
A giant steel vice crushes a canister of graphite the size of your fist with a force equivalent to the weight of an upturned Eiffel Tower.
At the same time, the canister is baked at up to 2,000C. That’s enough to encourage the layered sheets of carbon atoms in graphite to re-jig themselves into a 3D diamond arrangement.
Diamonds are the hardest material in the world, and HPHT is still the best way of knocking out the millions of tiny stones – diamond “grit” costing a few dollars for a small pot – that are used as abrasives in everything from oil drill heads to stone grinders and cutters.
Back in the day, the world’s biggest diamond company, South Africa’s De Beers, was quick to see the threat – and opportunity – that this new technology posed, and rapidly moved into the sector itself.
Steven Coe, research head at De Beers’ synthetic diamonds subsidiary Element 6 – named after carbon’s place in the periodic table – says these super-compressed crystals still comprise 90% of everything they sell.
But the technology has one drawback. Trace amounts of nitrogen from the air infiltrate the diamonds, turning them an unattractive cloudy snot-green colour.
And that’s where an exciting new way of making diamonds comes into play – “chemical vapour deposition”.
Instead of crushing graphite, this technique grows a diamond wafer, using a carbon-containing gas such as methane.
It is much slower – taking weeks instead of minutes – but the crystals are purer and clearer, and can be made to the size and dimensions needed.
This has opened up a whole new world of industrial applications, driving rapid growth in the industry.
