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Have you ever wondered why there are gaps in footpaths, and at the ends of bridges? Bridges, footpaths and many other structures get bigger when they heat up, and they need gaps so they don’t break on hot days. But Australian scientists have discovered a material that stays the same size over a wide range of temperatures, both hotter and colder than any footpath.

This stable substance was discovered by accident. Researchers at the University of New South Wales were trying to make a better battery when they realised that they’d found something special. Further tests showed that their material did not change in volume from −269 °C (colder than liquid nitrogen), all the way up to 1126 °C (about the same temperature as lava flowing from a volcano)!

Staying the same size might not sound important, but it could be super useful. For example, the inside of a jet engine needs to be perfectly balanced, with very tight gaps between fast moving parts. Some bits of the engine are heated to hundreds of degrees, while others are cooled by the extremely cold air found 10 kilometres above Earth.

Peering inside

To find out where this stuff’s superpower comes from, scientists ran tests using instruments at ANSTO. Using these tools, they observed what was happening inside the material while heating and cooling it to different temperatures. As the temperature changed, chemical bonds inside the material changed length, angles between atoms grew and shrank, and oxygen was displaced. And yet, on the outside, it stayed the same size.

The team think that all these changes might be working cooperatively, balancing each other out. But there might also be something else going on. They’re doing more experiments with a different instrument to keep uncovering the mystery.

Cool chemistry

This super stable material has the slightly strange formula of Sc_1.5Al_0.5W₃O₁₂. That indicates it’s a combination of scandium (Sc), aluminium (Al), tungsten (W) and oxygen (O). Why the decimals? It shows the ratio that’s likely to appear in a repeating unit of this material.

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