“Transparent Aluminium!?!”

As Scotty demonstrates in this scene from Star Trek IV (the most entertaining one, imo) a material which is strong like a metal but clear like glass would cause quite a stir.

A paper published today in Nature Materials entitled “A Damage-Tolerant Glass” reports on a “bulk glassy palladium alloy” which displays both strength and toughness.

In materials science, strength and toughness mean two different things.

Strength is a term given to materials which are scratch-resistant and difficult to bend out of shape. However, these types of materials tend to be quite brittle, and therefore break or shatter easily. Glass is an example of a strong material.

Toughness is a term given to materials which are difficult to break. However, these materials can be scratched and are also fairly easy to mold them into a particular shape. Metals are good examples of tough materials.

Finding a material which displays both strength and toughness therefore is a quite an achievement.

The alloy described in this study is called an amorphous metal which is made up of atoms which are highly disordered; as opposed to normal metals which have atoms arranged in a crystalline structure.

Examples of "Glassy Metals". From Wikipedia

 

When atoms are arranged in a crystalline pattern, they are able to slip past each other easily, and this is why metals tend to be malleable and ductile.

An amorphous metal (or “glassy metal”) has a disordered structure and therefore does not bend to change shape as easily as normal metals. Amorphous metals are created by rapidly cooling a molten metal, freezing the atoms in place before they can arrange themselves in a neat crystal pattern.

The team in this study hit on a nice recipe for an alloy (chemical formula Pd₇₉Ag_3.5P₆Si_9.5Ge₂₎ that would give both strength and toughness.

From Scientific American:

The successful recipe was mostly palladium, with a small fraction of silver and a smattering of other elements. “We don’t yet know why this particular composition works — it will take a deeper investigation to find out what chemical properties have been altered that affect the material’s toughness,” [study author Marios D. Demetriou] says.

The team tested the glassy metal’s toughness by monitoring how quickly and deeply a crack could move through it. “We found that it is as tough as the toughest steel,” he says.

Since this material would be very expensive to produce, it would most likely be used in medical implants, not buildings.

Not quite transparent aluminium, but materials scientists are working on some pretty cool stuff.