Material scientists are developing composites which are made of dissimilar materials in order to be able to offer new customised application profiles. Researchers at the Vienna University of Technology (TU) have examined promising metal-matrix composites, which are very good conductors of heat and are able to withstand mechanical loads at elevated temperatures of up to 550 degrees and expand only very little with increasing temperature.
These material combinations may be used in the ITER nuclear reactor, which is currently being constructed at Cadarache, France, and where they are intended to be used in cooling the first wall of the experimental reactor. Enhanced heat removal is playing an increasingly important role in the field of power electronics for engines and computers. Unless excess heat can be dissipated, the power of computers can no longer be increased. Last but not least, metal matrix composites can be used as cooling materials in rocket engines.
Four TU institutes are working on material combinations as part of an EU project of the 6th Framework Programme called ExtreMat (http://www.extremat.org/), which stands for "New Materials for Extreme Environments". "We examined some metal matrix composites and their interfacial bonding which are promising for use in nuclear reactor heat sinks, rocket engines or in power electronics. The characterisation of these heterogeneous materials falls within our area of competency", says Professor H. Peter Degischer, Head of the Institute of Materials Science and Material Technology at the TU Vienna. Copper and silver are efficient conductors, but due to their relatively high coefficient of thermal expansion, do not provide enough inherent strength when changes in temperature occur. In addition, their mechanical strength is sharply reduced at elevated temperatures. Copper deforms like butter from 300 degrees onwards". Strengthening with silicon carbide or tungsten fibres with some 0.1 millimetres or carbon fibres with less than 1/100 millimetres diameter increases the strength and the form stability without reducing conductivity. Degischer believes that a combination of silver with diamond particles of approx. 0.1 millimetres of diameter which are connected by means of thin silicon bridges holds the most promise for power electronics.
By using simulation calculations, both the internal stresses and the thermal conductivity were predicted for given internal arrangements of composites. The Austrian company PLANSEE could set up industrial production for these new materials. "During our investigations with a synchrotron, a particularly brilliant X-ray source, in Grenoble we were able to see how the composites? components, which are arranged three-dimensionally, deformed in different ways upon being repeatedly heated up and cooled down. Furthermore, we were able to ascertain the point at which debonds on the interface between metal matrix and diamond particles become visible in micro-tomography. These debonds are a consequence of local tensile stresses during changes in temperature. The conducting bond to the cooling plate was produced using a new coating procedure", says Degischer.
Chemists (Ass. Prof. C. Edtmaier), physicists (Prof. C. Eisenmenger-Sittner), micro-mechanicists (Prof. H. Böhm) and material scientists from the TU collaborated with two Austrian partners and 35 other European research institutes and companies on the research project "ExtreMat". Four doctoral students successfully carried out the scientific work for the project part on behalf of the TU. Almost 1 million euro has been spent on the project over the past 4 years, 50 percent of which was financed by the European Commission.
Photo download: https://www.tuwien.ac.at/index.php?id=8822
Video: http://www.tuwien.ac.at/flash_video/090507metall_mit_diamanten/Please direct queries to:
Werner Sommer | idw
Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)
Successful Mechanical Testing of Nanowires
07.12.2017 | Helmholtz-Zentrum Geesthacht - Zentrum für Material- und Küstenforschung
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
12.12.2017 | Earth Sciences
12.12.2017 | Power and Electrical Engineering
12.12.2017 | Life Sciences