Tougher than steel

Scientists in the U.S. have created glass that's tougher to break than steel.

The damage-tolerant metallic glass was fabricated by combining up to five elements, including the rare metal palladium.

Whereas the other metals add strength, palladium increases the plasticity of the glass and prevents cracks from spreading.

Dr Robert Ritchie, a material scientist at the U.S. Department of Energy, said:

The result is that glass undergoes extensive plasticity in response to stress, allowing it to bend rather than crack.

The rare combination of toughness and strength, or damage tolerance, extends beyond the benchmark ranges established by the toughest and strongest materials known.

There is one significant drawback - palladium is extremely expensive.

It currently trades at just over £500 an ounce; gold, by comparison, trades at £830.

However, Dr Ritchie believes the unique selling point of 'unbreakable' glass will overcome this hurdle.

Traditionally strength and toughness have been mutually exclusive properties in materials

We’re bucking the trend here and pushing the envelope of the damage tolerance that’s accessible to a structural metal.

Initial samples of the metallic glass were micro-alloys of palladium with phosphorous, silicon and germanium that yielded glass rods approximately 1mm in diameter.

By adding silver the researchers expanded the thickness of the glass rods to 6mm.

Adding silver to the mix enabled the University of California researchers, who also worked on the project, to expand the thickness of the glass rods to six mm.

Dr Ritchie said: 'Our game now is to try and extend this approach of inducing extensive plasticity prior to fracture to other metallic glasses through changes in composition.'

The glass was created by scientists at the U.S. Department of Energy and the California Institute of Technology.

Graham Smith