Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers image atomic structural changes that control properties of sapphires

26.11.2010
Materials scientists from Case Western Reserve University and the Institute of Solid State Research in Jülich, Germany have produced particularly clear changes in the atomic structure of sapphire following deformation at high temperatures.

Peering through an electron microscope down to a level where a human hair would seem as wide as a washer and dryer set, they were able to quantify deviations from the regular columns of aluminum and oxygen atoms - the stuff of perfect sapphire crystals. The work, which will be published in the journal Science Friday, Nov. 26, is embargoed until 2 p.m. Thursday, Nov. 25.

These structural changes are called dislocations and include very small rearrangements of some of the aluminum atoms from their normal surroundings of six oxygen atoms to a layout of four surrounding oxygen atoms.

While the changes in structure are minute, they deliver a punch.

In the orderly world of crystals, dislocations can control electrical, chemical and magnetic properties as well as strength and durability. And, the information and imaging technique used in the study can be applied to all crystalline solids, from microchips to thermal protection systems that shield jet engines from extreme heat.

"We imagined this might have been the possible change in structure a year or so ago and now we're able to see how the atoms are moving with respect to one another," said Arthur Heuer, Distinguished University Professor and Kyocera Professor of Ceramics in the department of materials science and engineering at the Case School of Engineering. "The important thing is we were able to image it with atomic resolution."

Peter Lagerlöf, an associate professor of materials science and engineering at Case Western Reserve, noted that "understanding the structure of the dislocations is important because it allows increased understanding of material properties."

Heuer traveled to Julich, Germany, where he worked with Chunlin Jia at the Institute of Solid State Research and Ernst Ruska-Centre for Electron Microscopy. There, using an ultra high magnification transmission electron microscope, the scientists employed negative spherical aberration imaging to a section of synthetic sapphire to see dislocation cores.

This is the first time the technique was applied at subangstrom resolution to structural defects in ceramics.

The scientists were able to distinguish columns of oxygen from columns of aluminum in synthetic sapphire, used to make substrates for specialty advanced computer chips (because of sapphire's good thermal conductivity and electrical resistivity), and grocery store scanners and expensive watch faces (because of sapphire's superior scratch-resistance compared to glass).

Dislocation cores terminate with aluminum atoms and electrical neutrality is maintained as the cores occupy only half of the aluminum sites. A complex mix of six-fold and four-fold coordinated aluminum polyhedra are found in the dislocation cores.

Jacques Castaing, a materials scientist at Laboratorie Physique des Materiaux, CNRS Bellevue, F 92195 Meudon Cedex, France, was not involved in the experiment but with Heuer and Lagerlöf, last year published a theory that the atomic structure would change this way.

Castaing said that being able to see the dislocations, "for the basic knowledge of materials, is very important. These dislocations are everywhere."

Kevin Mayhood | EurekAlert!
Further information:
http://www.case.edu

More articles from Materials Sciences:

nachricht Serendipity uncovers borophene's potential
23.02.2017 | Northwestern University

nachricht Switched-on DNA
20.02.2017 | Arizona State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>