Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Materials Research With Antiparticles: Unravelling The Secret Of Nanocrystalline Materials

29.11.2010
Certain structural defects in materials are what make innovative nanocrystalline bulk metals very hard and yet readily malleable. As these defects are found at the atomic level of the metal structure they are difficult to investigate in experiments.

However, Austrian scientists have recently taken a significant step towards understanding such atomic defects. They succeeded in doing so by combining two special methods in a project funded by the Austrian Science Fund FWF. The results have now been published in the renowned scientific journal Physical Review Letters.

Extremely hard but still easily malleable - the properties of the so-called nanocrystalline bulk metals give rise to many questions among physicists. Scientists at Graz University of Technology have finally managed to answer some of those questions through experiments.

The scientists set out to monitor the structural changes in the metals in real time. They were thus able to conclude that atomic defects are a central cause of the interesting physical material properties. Nanocrystalline metals consist of countless crystallites (grains), which are mostly smaller than one hundred nanometres - and the smaller the grain, the more solid is the metal. The structure of nanocrystalline metals is actually very regular: the atoms in the grains lie tightly packed in rank and file. However, when the metals are produced, atomic defects are involuntarily introduced which disturb the atomic order within the grains. For example, certain layers are not located directly on top of each other: some atoms are missing or rows are misaligned. Austrian materials physicists have now produced the first experimental evidence of these effects, which are closely related to the mechanical properties. They have published their results in the journal Physical Review Letters, where they describe how the combination of two special methods can be used to closely examine atomic defects.

SPY ATTACKS ON METALS
As atomic defects on the nanoscale are difficult to spot, the scientists worked with so-called positrons. Dr. Wolfgang Sprengel from Graz University of Technology explains: "A positron is a subatomic particle that is almost identical to the electron, with one difference: it is positively charged. If a positron and an electron meet, they annihilate each other. In the places where atomic defects are present, there are fewer electrons and therefore fewer occurrences of annihilation. The positrons therefore serve as spies that deliver detailed information about the atomic defects. We have used this effect to analyse the fast processes of atomic defects in metals." To carry out the experiments, the scientists availed themselves of the FRM II research reactor at the Technische Universität München (TUM), where they deployed the positron beam with the highest intensity in the world.
TWO METHODS, ONE RESULT
In addition to the positron-electron annihilation, macroscopic length-change measurements were made upon annihilation of the defects - by means of dilatometry. This combination of dilatometry and positron-electron annihilation is a first of its kind and it delivered the evidence that some of the seemingly mysterious physical properties of the nanocrystalline bulk metals can be attributed to these structural defects. The cause of the defects can be found in the production background of the metals. Nanocrystalline bulk metals are produced using very complex methods - such as high-pressure torsion (Erich Schmidt Institute Leoben) - which give rise to the atomic defects.

The FWF project headed by Dr. Roland Würschum is carried out in close cooperation with the University of Vienna and the Erich Schmidt Institute in Leoben, and is also closely linked to the National Research Network (NFN) on nanocrystalline bulk metals. The project has enabled a better understanding of fundamental principles, which is essential for the application of these innovative materials.

Originalpublikation:
In situ probing of fast defect annealing in Cu and Ni with a high-intensity positron beam. B. Oberdorfer, E-M. Steyskal, W. Sprengel, W. Puff, P. Pikart, C. Hugenschmidt, M. Zehetbauer, R. Pippan, R. Wüschum. Published September 28, 2010. Physical Review Letters 105, 146101. DOI: 10.1103/PhysRevLett.105.146101.
Scientific Contact:
Wissenschaftlicher Kontakt:
Univ.-Prof. Dr. Roland Würschum
Technische Universität Graz
Institut für Materialphysik
Petersgasse 16/IV
8010 Graz, Austria
T +43 / 316 / 873 - 8481
E wuerschum@tugraz.at
Austrian Science Fund FWF:
Mag. Stefan Bernhardt
Haus der Forschung
Sensengasse 1
1090 Vienna, Austria
T +43 / 1 / 505 67 40 - 8111
E stefan.bernhardt@fwf.ac.at
Copy Editing & Distribution:
PR&D - Public Relations for Research & Education Mariannengasse 8 1090 Vienna, Austria T +43 / 1 / 505 70 44 E contact@prd.at W http://www.prd.at

Maria Fraczek | PR&D
Further information:
http://www.fwf.ac.at

More articles from Materials Sciences:

nachricht Reliable molecular toggle switch developed
30.03.2017 | Karlsruher Institut für Technologie (KIT)

nachricht Researchers shoot for success with simulations of laser pulse-material interactions
29.03.2017 | DOE/Oak Ridge National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

'On-off switch' brings researchers a step closer to potential HIV vaccine

30.03.2017 | Health and Medicine

Penn studies find promise for innovations in liquid biopsies

30.03.2017 | Health and Medicine

An LED-based device for imaging radiation induced skin damage

30.03.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>