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Posted: Oct 17, 2014
Atomic trigger shatters mystery of how glass deforms
(Nanowerk News) Throw a rock through a window
The latest news from academia, regulators
research labs and other things of interest
Posted: Oct 17, 2014
Atomic trigger shatters mystery of how glass deforms
(Nanowerk News) Throw a rock through a window made of silica glass, and the brittle, insulating oxide pane shatters. But whack a golf ball with a club made of metallic glass—a resilient conductor that looks like metal—and the glass not only stays intact but also may drive the ball farther than conventional clubs. In light of this contrast, the nature of glass seems anything but clear.
A new study at the Department of Energy’s Oak Ridge National Laboratory, published Sept. 24 in Nature Communications ("How Thermally Activated Deformation Starts in Metallic Glass"), has cracked one mystery of glass to shed light on the mechanism that triggers its deformation before shattering. The study improves understanding of glassy deformation and may accelerate broader application of metallic glass, a moldable, wear-resistant, magnetically exploitable material that is thrice as strong as the mightiest steel and ten times as springy.
Joint Institute for Neutron Sciences Director Takeshi Egami, left, and Wigner Fellow Yue Fan, holding a metallic glass thumb drive, discovered the mechanism by which metallic glass deforms.
Whereas metals are usually crystalline, metallic glasses are amorphous in atomic structure. Amorphous metals, studied since the 1950s, have a tendency to crystallize when heated, which makes them extremely brittle. Metallic glass alloys that did not crystallize so easily were discovered at Tohoku University and Caltech in 1991 and introduced commercially in golf clubs in 2001.
Glass hangs in a metastable state in which the energy of the system is higher than the lowest-energy state the system could assume, a crystalline state. But its state is stable enough at room temperature to last a human lifetime.
“Exactly speaking, a metastable state cannot last; it evolves,” said project leader Takeshi Egami, a distinguished scientist/professor at ORNL and the University of Tennessee–Knoxville who directs the Joint Institute for Neutron Sciences (JINS), a partnership of ORNL and UT. “For instance, diamond is only metastable. Graphite is a stable state. Hollywood says ‘Diamonds Are Forever.’ Scientifically that is completely incorrect.”
Due to its relative stability, metallic g