Featured Research

from universities, journals, and other organizations

Intermetallic Mystery Solved With Atomic Resolution Microscope

Date:
February 19, 2005
Source:
Brown University
Summary:
Intermetallics could be the key to faster jets and more efficient car engines. But these heat-resistant, lightweight compounds have stumped scientists for decades. Why do so many break so easily? A team from Brown University, Oak Ridge National Laboratory, and UES Inc. used the world’s most powerful electron microscope to see, for the first time, atomic details that may provide the answer for the most common class of intermetallics. Their results – which could open the door for new materials for commercial use – are published in the current issue of Science.

Atomic resolution Z-contrast image from the world’s most powerful microscope of a non-defective region of Cr2Hf. In this view, the hafnium atoms appear yellow and the chromium atoms are red.
Credit: Image : Sharvan Kumar

PROVIDENCE, RI — Intermetallics can withstand searing heat and are often lightweight. These properties intrigue the aerospace, defense, energy and automotive industries, which are experimenting with this class of materials in hopes of building high-performance jet engines, improved rocket motors and missile components, more efficient steam turbines and better car engine valves.

Many intermetallics, however, break easily. These compounds are typically stronger than simple metals at high temperatures. Yet they are almost as fragile as ceramics at room temperature. This fragility limits their commercial use.

But why do most intermetallics shatter? How can that be prevented?

In a new report in Science, researchers from Brown University, Oak Ridge National Laboratory and UES Inc. for the first time describe detailed atomic arrangements in Laves phases – the most common class of intermetallics. Their discovery may be the first step in explaining the origin of this brittleness in some of these compounds.

“It has long been known that a dislocation, or crystal defect, moves when force is applied to a material. The easier it is to move this defect, the less brittle the material will be,” said Sharvan Kumar, professor of engineering at Brown University, who has studied Laves phases for more than a decade. “In materials with complex crystal structures, such as Laves phases, the atomic arrangement around these defects, and how these defects move, are not well understood.”

In the 1950s, a concept called “synchroshear” was proposed to explain how this defect moved in many complex structures. Under that theory, this movement is accomplished by coordinated shifting of atoms in two adjacent atomic layers. This synchronized movement is necessary to prevent atoms in one layer from colliding with atoms in the neighboring layer.

But because atoms are so tightly packed in compounds with complex structures, as they are in Laves phases, the theory could never be proven. There wasn’t a microscope powerful enough to show, in clear detail, how the atoms behaved.

Enter Matthew Chisholm, a staff researcher at Oak Ridge National Laboratory. Chisholm uses a unique Z-contrast scanning transmission electron microscope (STEM) to study defects in materials. The microscope was recently outfitted with an aberration-correction system, which corrects errors produced by imperfections in the electron lens. The system doubled the microscope’s resolving ability, making it the most powerful electron microscope on the planet.

Even though atoms in the test material – the Laves phase Cr2Hf – were spaced less than one ten-billionth of a meter away, the microscope produced crisp images of atoms arranged in tidy columns. Scientists put sheared material in the microscope, saw the defects and analyzed them.

“Aberration-correction combined with direct Z-contrast imaging produces an ideal technique to study unknown defect structures,” Chisholm said. “The resulting images have clearly shown for the first time that the accepted dislocation models built up over years of research on simple metals do not work in this more complex material.”

Kumar, who coordinated the project, said careful examination confirmed that synchroshear did indeed occur. “This is a first in science,” he said.

In the case of Laves phases, it is important to understand defect structures. With this knowledge, materials scientists may be able to identify methods that enhance their motion – and create intermetallic compounds that resist shattering.

The study illustrates the utility of Oak Ridge’s STEM in studying a variety of crystal structures and defects. The findings could be applied to materials with other complex structures, such as other classes of intermetallics as well as ceramics, inorganic salts and others.

The late Peter Hazzledine of UES Inc., a materials science research and development firm based in Dayton, Ohio, helped analyze and interpret the experimental results. Hazzledine was a leading authority on dislocation theory.

The U.S. Department of Energy’s Office of Basic Energy Sciences, the National Science Foundation-sponsored Materials Research Science and Engineering Center at Brown University, and the U.S Air Force Research Laboratory funded the work.


Story Source:

The above story is based on materials provided by Brown University. Note: Materials may be edited for content and length.


Cite This Page:

Brown University. "Intermetallic Mystery Solved With Atomic Resolution Microscope." ScienceDaily. ScienceDaily, 19 February 2005. <www.sciencedaily.com/releases/2005/02/050211082039.htm>.
Brown University. (2005, February 19). Intermetallic Mystery Solved With Atomic Resolution Microscope. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2005/02/050211082039.htm
Brown University. "Intermetallic Mystery Solved With Atomic Resolution Microscope." ScienceDaily. www.sciencedaily.com/releases/2005/02/050211082039.htm (accessed October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Gulfstream G500, G600 Unveiling

Gulfstream G500, G600 Unveiling

Flying (Oct. 20, 2014) Watch Gulfstream's public launch of the G500 and G600 at their headquarters in Savannah, Ga., along with a surprise unveiling of the G500, which taxied up under its own power. Video provided by Flying
Powered by NewsLook.com
Japanese Scientists Unveil Floating 3D Projection

Japanese Scientists Unveil Floating 3D Projection

Reuters - Innovations Video Online (Oct. 20, 2014) Scientists in Tokyo have demonstrated what they say is the world's first 3D projection that floats in mid air. A laser that fires a pulse up to a thousand times a second superheats molecules in the air, creating a spark which can be guided to certain points in the air to shape what the human eye perceives as an image. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
What We Know About Microsoft's Rumored Smartwatch

What We Know About Microsoft's Rumored Smartwatch

Newsy (Oct. 20, 2014) Microsoft will reportedly release a smartwatch that works across different mobile platforms, has a two-day battery life and tracks heart rate. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins