How on earth can concentric carbon nanotubes turn into diamond after an intense bomabrdement of radiation? That’s the question that physicists have been struggling with since observing this phenomenon during the last decade or so.

Today, we get a full theoretical description of what’s going on thanks to a model built by Michael Zaiser and Stefan Chartier at the University of Edinburgh in the UK.

They say that the radiation bombardment knocks entire atoms out of the structure of nanotubes, causing the resulting defects to ricochet through the structure. This makes the structure bend and buckle, eventually forming into carbon spheres.

In fact, under intense radiation bombardment, this process turns multiwall nanotubes into carbon onions, ie concentric spheres.

As more atoms are knocked out of the structure, the spheres shrink, placing enormous streeses on the layers beneath. It is this stress that eventually causes diamond to form at the centre of the onion. “The resulting pressures are sufficient to explain the nucleation of diamond in irradiated carbon onions,” say Zaiser and Chartier

And when that happens, the carbon onion has clearly become a carbon oyster (of kinds)!

Ref: http://arxiv.org/abs/1009.4035: Irradiated Carbon Nanostructures as Nanoscopic Pressure Cells