First ever single crystal metallic glass created under 25 gigapascals of pressure

Jun 16, 2011
Scientists recently used a diamond anvil like this one to squeeze tiny samples of metallic glass. Under very high pressure, the samples switched from their amorphous, glassy state to form a single crystal -- the first time this behavior has been seen in a glass. The discovery. published in the June 17 issue of Science, could help scientists design better metallic glasses, which are widely used in power transformers, anti-theft tags and other products, and it may help explain why these materials are so tough. Credit: Image courtesy Brad Plummer/SLAC.

Glass, by definition, is amorphous; its atoms lack order and are arranged every which way. But when scientists squeezed tiny samples of a metallic glass under high pressure, they got a surprise: The atoms lined up in a regular pattern to form a single crystal.

It's the first time researchers have glimpsed this hidden property in a glass. The discovery, reported June 17th in Science, offers a new window into the atomic structure and behavior of metallic glasses, which have been used for decades in products such as anti-theft tags and power transformers but are still poorly understood. The more scientists learn about the structure of these commercially important materials, the more effectively they can design new metallic glasses and tinker with old ones to improve their performance.

"Maybe a lot of glasses have this underlying structure, but we just didn't know how to look for it," said paper co-author Wendy Mao, a mineral physicist at the Department of Energy's (DOE) SLAC National Accelerator Laboratory and Stanford University.

Daniel Miracle, a metallurgist at the Air Force Research Laboratory in Ohio who was not involved in the research, called the discovery "a really, really neat, important finding." Not only will it help researchers design better metallic glasses, he said, but it may help explain why these materials can be so tough: If each piece of glass is a single crystal at heart, it doesn't have any of the weak spots at the boundaries between crystals where and tend to start.

Unlike familiar window glass, metallic glasses are made of metals—in this case cerium and aluminum. They resist wear and corrosion and they have useful magnetic properties. If you took apart the plastic anti-theft tag on a DVD case, you'd find a thin piece of metallic glass that looks like aluminum foil. When you rent or buy a DVD, the checkout clerk rubs it across a pad to demagnetize the metallic glass so it won't trigger an alarm when you leave. By placing the cerium-aluminum glass under 25 gigapascals of pressure -- about 250,000 times normal atmospheric pressure -- the team was able to create a single crystal.

Scientists have been investigating metallic glasses for half a century, and in 1982 turned up the surprising discovery that these glasses do have some , forming patterns over distances spanning just a few atoms. But no long-range patterns were apparent.

"The structure of glass is still mysterious. We know little about it, even though we use glass a lot," said Qiaoshi (Charles) Zeng of Zhejiang University in China, who led a research team of scientists from SLAC, Stanford, the Carnegie Institution of Washington, George Mason University and China's Jilin University. "And it's not easy investigating the structure of glass by traditional methods."

Zeng, Mao and their colleagues were not looking for order when they squeezed samples of the metallic glass between the tips of two diamonds at Argonne National Laboratory's Advanced Photon Source, applying 250,000 bars of pressure (250,000 times the pressure of the Earth's atmosphere at sea level). They were simply doing a series of experiments on how materials behave in extreme conditions.

All the samples were taken from a centimeter-long, extremely thin ribbon of the . Under intense pressure, all of the samples "devitrified," abruptly switching out of their glassy state to form a face-centered cubic crystal—one whose atoms are arranged like ping-pong balls packed into a box.

What's more, all the atoms in the crystallized samples lined up in the same direction—an indication, the researchers wrote, that this underlying structure ran throughout the whole ribbon of glass, and was put there when the glass formed.

Zeng, who will be joining Mao's group at Stanford in July, said the high-pressure technique may offer a new approach for making single-crystal materials from glasses. In addition, he said, it provides a unified understanding of the atomic structures of materials by directly linking the two most extreme examples: highly ordered single and highly disorganized glass.

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User comments : 8

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alysdexia
1.3 / 5 (14) Jun 16, 2011
Metals are not thin; this was narrow, shallow, squat, or slim.
long -> wide
http://google.com...parisons for the illiterate%22
Scottingham
4.2 / 5 (5) Jun 16, 2011
Metals are not thin; this was narrow, shallow, squat, or slim.
long -> wide
http://google.com...parisons for the illiterate%22


Tin foil? Gold leaf?
dirk_bruere
4.5 / 5 (4) Jun 16, 2011
Stable when the pressure was released?
MediocreSmoke
3 / 5 (4) Jun 16, 2011
Metals are not thin; this was narrow, shallow, squat, or slim.
long -> wide
http://google.com...parisons for the illiterate%22


You should look up the words you used and see if any of them are synonyms, or what they actually mean. dictionary.com for the illiterate (you) and the ignorant (you again)
DavidMcC
not rated yet Jun 17, 2011
What was the area of the "single crystal" region, and what was its quality in terms of defect density?
that_guy
not rated yet Jun 17, 2011
What was the area of the "single crystal" region, and what was its quality in terms of defect density?


By the tone of the article, it sounds as if there is no significant structural defect. furthermore, you would have to quantify what type or size of defect you are counting before coming up with a number. But either way, the article does not give us enough info to estimate :(.

I know from offhand knowledge that the maximum size it could have using a diamond anvil capable of those pressures is no more than a few millimeters.
Eoprime
not rated yet Jun 20, 2011
@dirk

"The single crystal was preserved after decompressed to the ambient pressure"
Macksb
1 / 5 (1) Jun 23, 2011
See also "Cerium's Unusual Behavior" dated January 27 this year. That article also describes interesting behavior of cerium under extremely high pressure.