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Inspired by nature

Sun, 7th Dec 2008

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Scientists this week have unveiled a brand new material that was inspired by nature and is thought to be the toughest, strongest ceramic-type material that has ever been made.

Nacre - a calcium carbonate structureThis new invention was announced this week in the journal Science, by Robert Richie and his colleagues from the Lawrence Berkley National Laboratory in California in the United States.

Their inspiration came from mother of pearl or nacre, the iridescent, shiny covering found on the inside of seashells, itís also the same stuff that pearls are made from.

Essentially, mother of pearl is made from calcium carbonate, which in itself doesnít seem to be all that remarkable. But it is the arrangement of strong but brittle layers of calcium carbonate, interspersed with slippery organic layers that act like a lubricant and ultimately makes nacre three times tougher and less likely to shatter than normal calcium carbonate. These layers are also the key to the beautiful lustre of mother of pearl and pearls.

And while scientists have for a while known the secret to these incredibly tough natural materials, until now, no-one has been able to artificially recreate them except in just very thin sheets of material.

This new material isnít actually made form calcium carbonate, but from a mixture of aluminium oxide and plain old water. By mixing the two together then carefully freezing the mixture, the researchers were able to encourage the aluminium oxide to form sheets. Freeze drying the mixture then gets rid of the water leaving a scaffold of aluminium oxide into which a polymer is then added.

This allowed Richie and his team to mimic the same interspersed layers that are found inside mother of pearl which are the secret to creating a material that is extremely strong but even if cracks start to form, they donít get bigger.

The team think they should be able to further refine their super-tough ceramics, but making the structures even finer and closer to the actual structure of natural mother of pearl.



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