Explosive energy-dense material made from air (with plasma)

Chemists have made an extremely energy-dense, environmentally friendly fuel out of nitrogen.

They’ve done it by employing one of chemistry’s favourite hobbies, bullying nitrogen n (N₂₎ into weird structures. An explosion occurred, but it was a small one.

The Chinese team has successfully made the element adopt a diamond-like structure, called cubic gauche nitrogen (cg-N) and importantly made it without extremely high pressures. In fact, they managed it at standard atmospheric pressure.

They’ve published their triumph in Science Advances.

Pure nitrogen-based molecules have drawn interest from chemists because they can release a tremendous amount of energy when they decompose.

Nitrogen atoms are highly stable when bonded together in N₂ molecules, and anything else made of pure nitrogen will release energy quickly to achieve this stability.

This reaction also doesn’t release any toxic materials. In fact, since the air around us is three-quarters N₂ gas, it essentially releases air.

Cubic gauche nitrogen, where nitrogen atoms are arranged in a lattice structure similar to the way carbon atoms are arranged in a diamond, has been a particularly interesting target.Chemists first made cg-N in 2004, but they needed temperatures of nearly 2,000°C and pressure more than a million times stronger than standard atmospheric pressure to do it.

While later research has managed slightly kinder conditions, until now no-one has been able to make the compound and keep it stable at standard air pressures.

This team used theoretical calculations to find ways to stabilise the surface of cg-N.

Based on this, they decided a potassium-based nitrogen substance (potassium azide, or KN₃) would stabilise it.

They placed 200 milligrams (0.2 grams) of potassium azide in a crucible, then put it in a furnace and blasted it with plasma-forming gases at 300°C for 3 hours.

They analysed the sample and found about 0.4% of the mixture had turned into cg-N.

They tested the stability of their cg-N by heating it with a laser.

It stayed stable up to 488°C, at which point it decomposed with a “micro-explosion” and a tiny shock wave.

In their paper, the researchers say that their method “not only demonstrates the feasibility of producing cg-N but also holds promise for inspiring future developments in high-energy density materials”.