A thin film of plastic was, for the first time ever, turned into tiny diamonds in the blink of an eye after being blasted with a laser beam.
Synthetic diamonds are valuable for their hardness and are used to make high-quality cutting and polishing tools, but equally so for their thermal conductivity, and electrical insulation.
How do you transform something that costs pennies into the hardest and one of the rarest minerals on Earth? At their fundamental level, diamonds are simply a solid form of carbon, arranged in a particular crystalline structure alongside hydrogen and oxygen.
In tests, a sheet of PET plastic (polyethylene terephthalate - which is made of petroleum, which is known in the industry as a hydrocarbon) and normally used for food packaging, was heated by a laser beam up to 6,000°C. The shock waves generated by the laser pulse brought the plastic to pressures equal to one-fifth the pressure in Earth’s core. This separated the hydrogen and oxygen from the carbon, leaving behind tiny diamonds a few nanometres across and a form of water called superionic water, which conducts electricity more easily than regular water.
“In the other experiments, where the necessary pressure was much higher, the conditions were so extreme and dynamic that the diamonds ended up falling apart,” says Siegfried Glenzer at SLAC National Accelerator Laboratory in California. “Now that we’ve found a way to make the diamonds at lower pressure, we may have a chance to actually harvest the diamonds.”
The further good news is that opening up synthetic diamond production from plastic should lead to more 'circular' demand for discarded water bottles and other plastic detritus.