Tokyo, 28 April, /AJMEDIA/
Diamonds in nature famously form under immense pressure in Earth’s mantle. But a new laboratory technique allows diamonds to skip the squeeze.
The most common method for producing synthetic diamonds, known as high-pressure and high-temperature growth, or HPHT, requires around 5 gigapascals of pressure, similar to that in the upper mantle where diamonds form naturally. With this technique, carbon dissolved in liquid metal forms diamonds at temperatures around 1400° Celsius.
But diamonds can be grown at atmospheric pressure in a liquid of gallium, iron, nickel and silicon exposed to a gas of carbon-rich methane as well as hydrogen, scientists report April 24 in Nature. The technique also required lower temperatures than HPHT: 1025° C. The addition of silicon in particular seems to kick off the initial stages of growth, allowing a tiny bit of diamond to nucleate, says physical chemist Rodney Ruoff. From there, the rest of the crystal can grow.
