A new type of damage-resistant glass, which is made of a microalloy using palladium, has been developed by researchers at the US Department of Energy's Lawrence Berkeley National Laboratory and the California Institute of Technology.

The metallic glass exhibits a high "bulk-to-shear" stiffness ratio which helps to offset the brittleness of glassy materials, and is capable of bending rather than cracking when subjected to force.

"Because of the high bulk-to-shear modulus ratio of palladium-containing material, the energy needed to form shear bands is much lower than the energy required to turn these shear bands into cracks," said Robert Ritchie, lead scientist on the project for Berkeley Lab.

It follows the development of a metallic glass, known as DH3, which blocks the formation of cracks through the introduction of a second, crystalline phase of the metal which creates microstructural barriers.

The newly-developed glass, meanwhile, uses its unique chemical composition to lend plastic qualities to the material instead of cracking.

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

He went on to say that when developing a metallic glass, it is important to use at least five difference elements so that when the material is quenched, it "doesn't know what crystal structure to form", lending it its unique properties.

The development means that strength and toughness, hitherto considered mutually exclusive properties, can now be combined in a single material, opening up new avenues for damage tolerance with a wide range of applications.

ChemistryViews reports that the new material will likely be used for dental and medical implants initially, due to the high cost of palladium.

However, it suggests that a cheaper version that uses copper, iron or aluminium is in development for engineering purposes.

Sources:



New glass tops steel in strength and toughness (10/01/11)



Damage-tolerant glass (10/01/11)

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