Strong, lightweight, and ductile (yes, ductile) silica glass nanofibersPublished on January 11th, 2013 | By: Eileen De Guire
It looks like a team of optoelectronics researchers from the University of Southampton in Britain may be getting into the structural composites business.
According to the press release, the group discovered how to make “the strongest, lightest weight silica nanofibers,” which it claims are 15 times stronger than steel and potentially can be manufactured in lengths that measure in the thousands of kilometers. They say the discovery could transform the aviation, marine, and safety industries and be used in products like aircraft, speedboats, helicopters, and more.
The breakthrough came when they found that, paradoxically, the strength of the silica glass nanofibers increased as the diameter decreased. In a press release, Brambilla says, ”Usually if you increase the strength of a fiber you have to increase its diameter and thus its weight, but our research has shown that as you decrease the size of silica nanofibers their strength increases, yet they still remain very lightweight.”
(Along similar lines, earlier this year a NIST group published a paper documenting that they observed an increase in the fracture strengths in silicon nano wires from 12 to 18 GPa as the radius of nanowires was decreased from 60 to 20 nm.)
The ORC group recognized what that could mean in terms of structural composites. Payne says in the press release, “Weight for weight, silica nanowires are 15 times stronger than high strength steel and 10 times stronger than conventional [glass reinforced plastic]. We can decrease the amount of material used thereby reducing the weight of the object.”
How is it that a team of optoelectronics researchers crossed over into investigating the glass fiber reinforcements? That is not clear, but according to the ORC’s website, Brambilla’s group has a number of active research projects investigating sensors and devices based on optical fibers and nanofibers, so presumably, they would have a natural interest in the mechanical properties of the nanofibers for handling purposes.
Some of Brambilla’s observations may lead to new insights into the relationship between structure and properties of silica glass, too. Not only do the silica nanofibers increase in strength as they decrease in size, he says, “In fact when they become very, very small they behave in a completely different way. They stop being fragile and don’t break like glass but instead become ductile and break like plastic. This means they can be strained a lot.”
The press release says Brambilla shared the work at a seminar he recently organized in the UK. I hope he also publishes a paper on this work so that the ductility secrets of these nanofibers can start to be unlocked.
The topic of glass strength keeps coming up, for example, with the introduction of Gorilla Glass 3 or the recently formed Usable Glass Strength Coalition, but this is the first time I recall seeing glass described as ductile.
I was not able to find out how the fibers are made, and in the press release Brambilla says he handled the nanofibers with his “bare hands,” which conventional wisdom says is a great way to introduce surface flaws. For sure, this is an exciting discovery, but there is a lot more the group could be telling us.
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