Super nanowire composite solves 'valley of death' riddle

March 12, 2013, University of Western Australia

(Phys.org) —In a world first, a team of researchers from Australia, China and the US has created a super strong metallic composite by harnessing the extraordinary mechanical properties of nanowires.

Co-author and Head of the School of Mechanical and Chemical Engineering at The University of Western Australia, Winthrop Professor Yinong Liu, said the work has effectively overcome a challenge that has frustrated the world's top scientists and engineers for more than three decades, nicknamed the "valley of death" in nanocomposite design.

"We know that nanowires exhibit extraordinary , in particular ultrahigh strengths in the order of several gigapascal, approaching the theoretical limits. With the fast development of our capability to produce more in variety, more in quantity and better in shape and size of nanowires, the chance of creating bulk engineering composite materials reinforced by these nanowires has become high," Professor Liu said. However, all the attempts to date have failed to realise the extraordinary properties of the nanowires in bulk materials.

Professor Liu says the problem is with the matrix: "In a normal metal matrix-nanowire composite, when we pull the composite to a very high stress, the nanowires will experience a large elastic deformation of several per cent. That is OK for the nanowires, but the normal metals that form the matrix cannot. They can stretch elastically to no more than 1 per cent. Beyond that, the matrix deforms plastically," he said.

Plastic deformation damages the at the interface between the nanowires and the matrix. In this regard, the properties of the composite are limited by the properties of the ordinary matrix, and not determined by the extraordinary properties of the nanowires.

"The trick is with the NiTi matrix," Professor Liu said. "NiTi is a , a fancy name but not totally new. It is no stronger than other common metals but it has one special property that is its martensitic transformation. The transformation can produce a deformation compatible to the elastic deformation of the nanowires without plastic damage to the structure of the composite. This effectively gives the nanowires a chance to do their job, that is, to bear the high load and to be super strong. With this we have crossed the 'valley of death'!" Professor Liu said.

Using this idea, the researchers have created materials that are twice as strong as high strength steels, that have elastic strain limits up to six per cent - which is 5-10 times greater than the elastic strains of the best spring steels currently available - and a Young's modulus of ~30 GPa, which is unmatched by any engineering materials so far.

The breakthrough opens the door for a range of new and innovative applications. The very low Young's modulus matches that of human bone, making it a much better material for medical applications as implants, for example. The ability to produce and maintain extremely large elastic strains also provides an unprecedented opportunity for "elastic strain engineering", which could lead to improvements in many functional properties of solid materials, such as electronic, optoelectronic, piezoelectric, piezomagnetic, photocatalytic and chemical sensing .

"A Transforming Metal Nanocomposite with Large , Low Modulus and High Strength" has been published in the journal Science.

Explore further: Researchers create highly conductive and elastic conductors using silver nanowires

Related Stories

Researchers solve the mystery of nanowire breakage

September 12, 2012

Most materials will break when a force is applied to an imperfection in their structure—such as a notch or dislocation. The behavior of these imperfections, and the resulting breakage, differ markedly between small structures, ...

3-D view of 1-D nanostructures

January 6, 2012

Semiconductor gallium nitride nanowires show great promise in the next generation of nano- and optoelectronic systems. Recently, researchers at the McCormick School of Engineering have found new piezoelectric properties of ...

Coiled nanowires may hold key to stretchable electronics

January 11, 2011

Researchers at North Carolina State University have created the first coils of silicon nanowire on a substrate that can be stretched to more than double their original length, moving us closer to incorporating stretchable ...

Recommended for you

Meteorite source in asteroid belt not a single debris field

February 17, 2019

A new study published online in Meteoritics and Planetary Science finds that our most common meteorites, those known as L chondrites, come from at least two different debris fields in the asteroid belt. The belt contains ...

Diagnosing 'art acne' in Georgia O'Keeffe's paintings

February 17, 2019

Even Georgia O'Keeffe noticed the pin-sized blisters bubbling on the surface of her paintings. For decades, conservationists and scholars assumed these tiny protrusions were grains of sand, kicked up from the New Mexico desert ...

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

hemitite
not rated yet Mar 12, 2013
Why not pre-stressed nano wires?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.