Metallic Glass: A Crystal at Heart

JUNE 17, 2011

Bookmark and Share

Scientists used a diamond anvil cell 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. (Image by 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, 2011, 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’s) 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 fractures and corrosion tend to start.

Unlike familiar window glass, metallic glasses are alloys 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.

Scientists have been investigating metallic glasses for half a century, and in 1982 turned up the surprising discovery that these glasses do have some atomic structure, 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 in a diamond anvil cell (DAC) at x-ray beamline 16-ID-B of the High Pressure Collaborative Access Team 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 metallic glass. 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 crystals and highly disorganized glass.

See: Qiaoshi Zeng1,2, Hongwei Sheng3, Yang Ding2, Lin Wang2,4, Wenge Yang2, Jian-Zhong Jiang1*, Wendy L. Mao1,5,6, and Ho-Kwang Mao1,2**, “Long-Range Topological Order in Metallic Glass,” Science 332, 1404 (17 June 2011). DOI: 10.1126/science.1200324

Author affiliations: 1Zhejiang University, 2Carnegie Institution of Washington, 3George Mason University, 4Jilin University, 5Stanford University, 6SLAC National Accelerator Laboratory

Correspondence: **mao@gl.ciw.edu, *jiangjz@zju.edu.cn

The original SLAC National Accelerator Laboratory press release can be found here.

This material is based on work funded by the U.S. Department of Energy (DOE), Energy Frontier Research Center grant DE-SC0001057 (EFree). The use of HP-CAT is supported by Carnegie Institute of Washington, Carnegie DOE Alliance Center, University of Nevada at Las Vegas, and Lawrence Livermore National Laboratory through funding from DOE–National Nuclear Security Administration, DOE–Basic Energy Sciences, and the National Science Foundation. TEM measurements were conducted at the Electron Microscopy Center at Argonne National Laboratory. The SLAC effort is supported by DOE and DE-AC02-76SF00515. The Zhejiang University participants are supported by the National Natural Science Foundation of China (grants 10979002, 50920105101, and 51050110136), the China Postdoctoral Science Foundation, the Zhejiang University-Helmholtz Cooperation Fund, the Ministry of Education of China, and Zhejiang Provincial Department of Science and Technology.

Use of the Advanced Photon Source at Argonne National Laboratory was supported by the DOE’s Office of Science under Contract No. DE-AC02-06CH11357.

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science, Office of Basic Energy Sciences (DOE-BES). The APS is the source of the Western Hemisphere’s brightest high-energy x-ray beams for research in virtually every scientific discipline. More than 3,500 scientists representing universities, industry, and academic institutions from every U.S. state and several foreign nations visit the APS each year to carry out applied and basic research in support of the BES mission to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels in order to provide the foundations for new energy technologies and to support DOE missions in energy, environment, and national security. To learn more about the Office of Basic Energy Sciences and its x-ray user facilities, visit http://www.sc.doe.gov/bes/BES.html.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.