Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Twinning phenomenon found in nanocrystalline aluminum

31.07.2003


Using a powerful electron microscope to view atomic-level details, Johns Hopkins researchers have discovered a "twinning" phenomenon in a nanocrystalline form of aluminum that was plastically deformed during lab experiments. The finding will help scientists better predict the mechanical behavior and reliability of new types of specially fabricated metals. The research results, an important advance in the understanding of metallic nanomaterials, were published in a recent issue of the journal Science.



At the microscopic level, most metals are made up of tiny crystallites, or grains. Through careful lab processing, however, scientists in recent years have begun to produced nanocrystalline forms of metals in which the individual grains are much smaller. These nanocrystalline forms are prized because they are much stronger and harder than their commercial-grade counterparts. Although they are costly to produce in large quantities, these nanomaterials can be used to make critical components for tiny machines called microelectromechanical systems, often referred to as MEMS, or even smaller nanoelectromechanical systems, NEMS.

But before they build devices with nanomaterials, engineers need a better idea of how the metals will behave. For example, under what conditions will they bend or break? To find out what happens to these new metals under stress at the atomic level, Johns Hopkins researchers, led by Mingwei Chen, conducted experiments on a thin film of nanocrystalline aluminum. Grains in this form of aluminum are 1,000th the size of the grains in commercial aluminum.


Chen and his colleagues employed two methods to deform the nanomaterial or cause it to change shape. The researchers used a diamond-tipped indenter to punch a tiny hole in one piece of film and subjected another piece to grinding in a mortar. The ultra-thin edge of the punched hole and tiny fragments from the grinding were then examined under a transmission electron microscope, which allowed the researchers to study what had happened to the material at the atomic level. The researchers saw that some rows of atoms had shifted into a zig-zag pattern, resembling the bellows of an accordion. This type of realignment, called deformation twinning, helps explain how the nanomaterial, which is stronger and harder than conventional materials, deforms when subjected to high loads.

"This was an important finding because deformation twinning does not occur in traditional coarse-grain forms of aluminum," said Chen, an associate research scientist in the Department of Mechanical Engineering in the university’s Whiting School of Engineering. "Using computer simulations, other researchers had predicted that deformation twinning would be seen in nanocrystalline aluminum. We were the first to confirm this through laboratory experiments."

By seeing how the nanomaterial deforms at the atomic level, researchers are gaining a better understanding of why these metals do not bend or break as easily as commercial metals do. "This discovery will help us build new models to predict how reliably new nanoscale materials will perform when subjected to mechanical forces in real-world devices," said Kevin J. Hemker, a professor of mechanical engineering and a co-author of the Science paper. "Before we can construct these models, we need to improve our fundamental understanding of what happens to nanomaterials at the atomic level. This is a key piece of the puzzle."

The nanocrystalline aluminum used in the experiments was fabricated in the laboratory of En Ma, a professor in the Department of Materials Science and Engineering and another co-author of the research paper. "This discovery nails down one deformation process that occurs in nanocrystalline metals," Ma said. "This is the first time a new mechanism, which is unique to nanostructures and improbable in normal aluminum, has been conclusively demonstrated."

Other co-authors of the paper were Hongwei Sheng, an associate research scientist in the Department of Materials Science and Engineering; Yinmin Wang, a graduate student in the Department of Materials Science and Engineering; and Xuemei Cheng, a graduate student in the Department of Physics and Astronomy.

Phil Sneiderman | EurekAlert!
Further information:
http://www.me.jhu.edu

More articles from Physics and Astronomy:

nachricht Enhancing the quantum sensing capabilities of diamond
23.11.2017 | The Hebrew University of Jerusalem

nachricht Quantum optics allows us to abandon expensive lasers in spectroscopy
22.11.2017 | Lomonosov Moscow State University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Underwater acoustic localization of marine mammals and vehicles

23.11.2017 | Information Technology

Enhancing the quantum sensing capabilities of diamond

23.11.2017 | Physics and Astronomy

Meadows beat out shrubs when it comes to storing carbon

23.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>