Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Technique Creates Metal Memory and Could Lead To Vanishing Dents

30.03.2007
Crumpled kitchen foil that lays flat for reuse. Bent bumpers that straighten overnight. Dents in car doors that disappear when heated with a hairdryer. These and other physical feats may become possible with a technique to make memory metals discovered by researchers at the University of Illinois.

Normally, when a piece of metal - such as a paperclip - is bent, the change in shape becomes permanent. But, when heat is added to bent metal films having the right microstructure, the researchers found, the films return to their original shapes. The higher the temperature, the sooner the metal films revert.

"It's as though the metal has a memory of where it came from," said Taher A. Saif, a professor of mechanical science and engineering at Illinois, and senior author of a paper that describes the findings in the March 30 issue of the journal Science.

In the study, Saif and graduate students Jagannathan Rajagopalan and Jong H. Han explored aluminum films and gold films. The aluminum films were 200 nanometers thick, 50-60 microns wide and 300-360 microns long. The gold films were 200 nanometers thick, 12-20 microns wide and 185 microns long. The average grain size in the aluminum films was 65 nanometers; in the gold films, 50 nanometers.

"We found that the type of metal doesn't matter, said Saif, who also is a Willett Faculty Scholar and a researcher at the university's Micro and Nanotechnology Laboratory. "What matters is the size of the grains in the metal's crystalline microstructure, and a distribution in the size."

Grain sizes are typically one-third to one-half the thickness of a metal film. Raising the temperature by about 50 degrees Celsius causes the grains to grow larger.

If the grains are uniformly too small, the metal will be brittle and break while being bent. If the grains are uniformly too large, the metal will bend, but then stay in that position. To return to the initial shape, what's needed is a balance between brittleness and malleability.

That balance can be achieved through a combination of small and large grains, the researchers report.

Variations in the microstructure lead to plastic deformation in the larger grains and elastic accommodations in the smaller grains, Saif said. The bigger grains bend, but push and pull on the smaller grains, which become elastically deformed like a spring. If the metal is then left alone, the smaller grains will release this energy and force the bigger grains back to their original shapes over time. This local release of energy can be speeded up by applying heat.

Controlling the crystalline microstructure of thin films also could reduce energy loss in oscillators and resonators used in electronic circuits, Saif said. Oscillators and resonators are found in products ranging from air bag sensors and camcorders to digital projectors and global positioning systems.

"If the grains that constitute the metal films in these devices are between 50 and 100 nanometers, they can be very lossy," Saif said. "However, if we decrease the grain size, we can reduce much of the energy loss."

The work was funded by the National Science Foundation.

James E. Kloeppel | University of Illinois
Further information:
http://www.uiuc.edu

More articles from Physics and Astronomy:

nachricht Pulses of electrons manipulate nanomagnets and store information
21.07.2017 | American Institute of Physics

nachricht Vortex photons from electrons in circular motion
21.07.2017 | National Institutes of Natural Sciences

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: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>