Brainy Quote of the Day

Monday, August 15, 2016

Brittle to Ductile...

Plastic fantastic? Quasicrystal deformations and bending observed
Topics: Materials Science, Nanotechnology, Quasicrystal

Caveat emptor: I did notice one comment on the article at the main site referencing "Laplace Pressure" as a source explaining how quasicrystal structures become pliable at the nanoscale.  The link (I've provided) is to a Wikipedia page. In blogging, one can play kind of "fast and loose" with reference links if trying to make a point as in an essay, but I wouldn't in general use an open source page with the subtitle "A Free Encyclopedia that everyone can edit" referring to a science article. Out of curiosity, I did look it up on Scholarpedia: "the peer-reviewed open-access encyclopedia, where knowledge is curated by communities of experts." The search term Laplace Pressure came up with four links that did not seem to relate to a nanoscale phenomena.

When shrunk to the nanoscale, quasicrystals become plastic. That is the finding of an international team of researchers, which says that its results could potentially widen the material's applications. Quasicrystals – materials in which the atoms show long-range order but have no finite, periodically repeated unit cell – have fascinated materials scientists ever since their Nobel-prize-winning discovery in 1984. Their practical use, however, has been limited by their brittleness.

Conventional crystals plastically deform through dislocations in their lattice that can allow individual unit cells to swap places relatively easily. This makes some crystals, such as pure metals like copper and gold, highly ductile. In quasicrystals, however, there are no unit cells, so it takes more energy to move dislocations. "Normally, the dislocations in quasicrystals are quite mobile at high temperatures," says materials-scientist Yu Zou of Massachusetts Institute of Technology in the US. "However, below 500 °C, the dislocations are not that mobile, so this can make the quasicrystal very brittle."

Physics World: Brittle quasicrystals become ductile at the nanoscale, Tim Wogan

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