Aluminum is a cheap, non-magnetic, resistant to corrosion, extremely common, and easy-to-produce metal. It has a density of 2.7 grams per cubic centimetre--if you drop it on a container full of water, it would sink to the bottom. However, if you rearrange them in a certain way at the molecular level, it could actually become lighter than water.
This opens up a whole new range of possible uses for the material. “Spaceflight, medicine, wiring and more lightweight, more fuel-efficient automotive parts are some applications that come to mind,” Boldyrev says.
So, using computational modelling, researchers tried making a new, metastable, ultralight form of crystal aluminium. “My colleagues’ approach to this challenge was very innovative,” says Utah State University chemist Alexander Boldyrev.
“They started with a known crystal lattice, in this case, a diamond, and substituted every carbon atom with an aluminum tetrahedron.” The resulting material is so lightweight--its density is just 0.61 grams per cubic centimetre; so much lighter than the conventional form’s density.
“That means the new crystallized form will float on water, which has a density of one gram per cubic centimeter,” says Boldyrev. But since it was computationally made, its strength and durability is still unknown.
Nonetheless, this breakthrough gives a new way of how to approach material design. “An amazing aspect of this research is the approach: using a known structure to design a new material. This approach paves the way for future discoveries,” Boldyrev says. If they can do this to aluminium, what about other metals? Only time will tell.
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