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Sci Tech
Harder, stronger nanocrystals
RESEARCHERS AT Purdue University have made a surprising discovery that could open up numerous applications for metal `nanocrystals,' or tiny crystals that are often harder, stronger and more wear resistant than the same materials in bulk form.
The research engineers have discovered that the coveted nanocrystals are contained in common scrap, the chips that are normally collected and melted down for reuse.
"Imagine, you have all of these bins full of chips, and they get melted down as scrap," said Srinivasan Chandrasekar, a professor of industrial engineering. "But, in some sense, the scrap could be more valuable pound-for-pound than the material out of which the part is made."
Nanocrystals might be used to make super-strong and long-lasting metal parts. The crystals might be added to plastics and other metals to make new types of composite structures — from cars to electronics.
However, nanocrystals have been far too expensive and difficult to produce to be of any practical industrial or commercial use. The cost of making nanocrystals is at least 100 dollars per pound, while nanocrystals of certain metals critical to industry cannot be made at all with present laboratory techniques, said Chandrasekar. The result of the findings will appear in the Journal of Materials Research.
One process now used to make nanocrystals in research labs involves heating a metal until it vaporises and then collecting nanocrystals as the vaporised metal condenses onto a cold surface.
Metal nanocrystals might be incorporated into car bumpers, making the parts stronger, or into aluminium, making it more wear resistant. Metal nanocrystals might be used to produce bearings that last longer than their conventional counterparts, new types of sensors and components for computers and electronic hardware.
Nanocrystals of various metals have been shown to be 100 per cent, 200 per cent and even as much as 300 per cent harder than the same materials in bulk form. Because wear resistance often is dictated by the hardness of a metal, parts made from nanocrystals might last significantly longer than conventional parts.
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