Tiny tubes of rusty glass are surprisingly springy, which could prove useful in powering nanorobotic devices.
Most metals oxidise when left in the air 鈥� when this happens in iron, it is called rusting 鈥� which can change their properties, such as making them more brittle or less dense.
at City University of Hong Kong and his colleagues found that when they oxidised copper and zirconium nanotubes of metallic glass, which are metals that, like glass, lack a repeating molecular structure, they instead became extremely elastic.
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Yang and his team tested their elasticity by seeing how far they could bend the tubes and still have them return to their original position, called the recoverable strain.
鈥淲hen we deformed these oxidised nanotubes, we found that the recoverable strain can get to 10 to 20 per cent,鈥� says Yang. 鈥淭hat鈥檚 really unusual.鈥�
They looked at the oxidised nanotubes using a technique called atom probe tomography and found that instead of forming a layer of oxide on the surface, like most metals, the nanotubes incorporated the oxygen throughout their molecular structure, holding the other atoms in place and giving them elastic superpowers.
So far, the elastic effect in these nanotubes has only been measured at scales 10,000 times smaller than the width of a human hair, which limits their applications to very small electrical components like springs or sensors. However, Yang is hopeful that the effect can be replicated on larger scales, such as with large sheets made up of many nanotubes, so that the material could be used for things like indestructible spectacle frames that aren鈥檛 at risk of oxidation.
鈥淚t鈥檚 revealed something that we would never have thought would be possible if you oxidised a metal,鈥� says at the University of Sheffield, UK. 鈥淚f they can demonstrate that they can scale it up, in terms of section size, somehow, then I think the world will be really interested in it and a lot of people will pursue it.鈥�
Nature Materials, DOI:
