In a paper published online Feb. 26 in the journal Nature Communications, a Yale University team and collaborators propose a way of predicting whether a given glass will be brittle or ductile ? a desirable property typically associated with metals like steel or aluminum ? and assert that any glass could have either quality.
Ductility refers to a material's plasticity, or its ability to change shape without breaking.
"Most of us think of glasses as brittle, but our finding shows that any glass can be made ductile or brittle," said Jan Schroers, a professor of mechanical engineering and materials science at Yale, who led the research with Golden Kumar, a professor at Texas Tech University. "We identified a special temperature that tells you whether you form a ductile or brittle glass."
The key to forming a ductile glass, they said, is cooling it fast. Exactly how fast depends on the nature of the specific glass.
Focusing on a new group of glasses known as bulk metallic glasses (BMGs) ? metal alloys, or blends, that can be extremely pliable yet also as strong as steel ? researchers studied the effect of a so-called critical fictive temperature (CFT) on the glasses' mechanical properties at room temperature.
When forming from liquid, there is a temperature at which glass becomes too viscous for reconfiguration and freezes. This temperature is called the glass transition temperature. Based on experiments with three representative bulk metallic glasses, the researchers said there is also, for each distinct alloy, a critical temperature that determines the brittleness or plasticity of the glass. This is the CFT.
Researchers said it's possible to categorize glasses in two groups ? those that will be brittle because in liquid form their CFT is above the glass transition temperature, and those that will be ductile, because in liquid form their CFT is below the glass transition temperature.
They previously thought a liquid's chemical composition alone would determine whether a glass would be brittle or ductile.
"That's not the case," Schroers said. "We can make any glass theoretically ductile or brittle. And it is the critical fictive temperature which determines how experimentally difficult it is to make a ductile glass. That is the major contribution of this work."
The finding applies theoretically to all glasses, not metallic glasses only, he said.
"A glass can have completely different properties depending on the rate at which you cool it," Schroers said. "If you cool it fast, it is very ductile, and if you cool it slow it?s very brittle. We anticipate that our finding will contribute to the design of ductile glasses, and in general contribute to a deeper understanding of glass formation."
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Yale University: http://www.yale.edu
Thanks to Yale University for this article.
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Source: http://www.labspaces.net/127036/In_probing_mysteries_of_glass__researchers_find_a_key_to_toughness
Google’s Super Sync Sports Chrome Experiment is what happens when you put modern web technology, smartphones and a love of 80s sports games into one rather wacky package where cupcakes race moose heads for virtual gold. The new game, which Google announced this morning, runs in your desktop browser, but you use your smartphone or tablet as the game controller to make your avatars run, cycle and swim. Super Sync Sports uses new browser technologies like the HTML5 audio, CSS3, SVG and Canvas, but the highlight is obviously its use of the Touch API to recognize the gestures you make on your mobile device and WebSockets to make sure your phone(s) and browser stay in sync. Up to four players can join in every race. We’ve seen our fair share of cool browser demos recently, but Super Sync Sports’ ability to turn your mobile browser into what is essentially a very basic Wii U GamePad clearly shows how far our mobile and desktop browsers have come over the last year or so. To get started, you have to fire up Super Sync Sports on your desktop browser and mobile phone or tablet (Android 4.0+ and iOS 4.3+). After choosing whether you want to play a multiplayer or single-player game, you simply type a sync code into the web app and then it’s off to the races. The music will quickly drive you crazy, but the overall experience is quite a bit of fun, especially if you manage to recruit a few other people to play with you. Google says it will publish more information about how it built this experience in the next few weeks. Until then, you can always use your browser’s built-in developer tools to take a look under the hood.
