SCHOTT solutions no. 2/2010 > Otto Schott Research Award 2010

Prof. Tanguy Rouxel (2nd from right) was recognized with the Otto Schott Research Award 2010 by SCHOTT Board member and the trustee chair of the Ernst Abbe Fund, Dr. Hans Joachim Konz (left), for his pioneering research work on gaining a better understanding of the mechanical properties of glass. Curator Prof. Reinhard Conradt from the RWTH Aachen (2nd from left) and curator Prof. Carlo Pantano from Penn State University (right) also offered their congratulations. Photo: SCHOTT/B. Haggard

Innovative Glass Research

Prof. Tanguy Rouxel received this year’s Otto Schott Research Award for his work on the mechanical properties of glasses and glassy materials.

Bernhard Gerl

On May 18, 2010, the Otto Schott Research Award worth 25,000 euros was presented to the researcher Prof. Dr. Tanguy Rouxel in Corning, New York, during the Annual Meeting of the Glass and Optical Materials Division (GOMD) organized by the American Ceramic Society. The Otto Schott Research Award is presented every other year on an alternating basis with the Carl Zeiss Research Award to recognize exceptional scientific achievements in fundamental research and technology development in the areas of specialized materials, components and systems for applications in optics, electronics, solar energy, health and lifestyle. Both Research Awards are managed by the Stifterverband for German Science.

Prof. ­Tanguy Rouxel is a mechanical engineer who has worked at the University of Rennes 1 as a full professor since 1997. He served as Director of the Institute of Applied Mechanical Engineering (LARMAUR), at which 19 employees focus on doing research on the mechanical properties of glasses, among other topics, until September 2009. In addition, in 2009, he became an associate professor at the Institute of Ceramics in Shanghai and a guest professor at the Indian Institute of Science in Bangalore. Prof. Rouxel has already received several international awards for his scientific research.
The test melting of glass serves to determine the best composition of the raw materials.
Photo: SCHOTT/D. Fonda
“One of Tanguy Rouxel’s most remarkable strengths is his ability to use insights from what appear to be completely different faculties in glass science and technology,” noted Prof. Carlo Pantano, a member of the Board of Trustees in his laudation on the choice of this year’s award winner. “His work is instrumental to gaining a better understanding of the elastic properties and deformation of glass and how to reduce damages,” he added.

Although people would normally associate optical characteristics with glass to start with, the mechanical properties are also of great interest to researchers in developing new materials. For instance, the hard disks of computers made of aluminum-­magnesium alloys are being replaced more and more often by glasses with a high elastic modulus. This makes higher rotation speeds and thus faster access times possible. Increasing the modulus of elasticity also allows for thinner windows in vehicles that are also easier to manufacture. This, in turn, results in energy savings. Other components made of glass in which high stability is important include load bearing parts of buildings, implants, reinforcing fibers, ceramic additives, cooking plates, refractory gaskets and many others.
Until now, it was assumed that the modulus of elasticity depends mainly on the glass transition temperature. The higher it is, the more stable the glass will be. By examining a large number of different glasses ranging from ice in a glassy state to metallic glasses, Prof. Rouxel was able to show that the interrelationships are more complex. Poisson‘s ratio, in particular, which is of great importance to the mechanical properties of a material, in other words the ratio between the relative variation in thickness and the relative variation in length under the influence of an external force or tension also depends on the short or medium-range structural arrangements inside a glass.
Professor ­Tanguy Rouxel
Here, zero-dimensional clusters, one-dimensional chains, two-dimensional layers or units with three-dimensional networking can be found. During his studies, it became evident that the deformability of the glass materials depends not only on the binding strength of the network-forming components, but also on their packing density. Therefore, it is quite possible that Poisson‘s ratio will decline, although a component that only engages in bonding with two neighboring atoms has been replaced by one that bonds with three neighbors. The reason is that the new molecule is larger, requires more space and thus reduces the packing density. Although they only form clusters, metallic glasses that are still extremely sturdy because their components are packed together quite closely are one prime example of the importance of packing density. This also explains why the modulus of elasticity can usually be increased by up to 20 percent by performing subsequent tempering. This results in higher density microstructures.

Now, Prof. Rouxel’s results can be put to use in describing molecular orbitals in glasses more accurately and developing better computer simulations so that less expensive theoretical tests can replace some of the experimental trials in laboratories, if new types of glass materials with certain properties are to be developed for high-precision tools, hard disks or buildings.
With the help of so-called “indentation” measurements, in other words the scratch patterns on glass, statements can be made on the mechanical properties of glass. The method itself has been known for quite some time; however, Professor Tanguy Rouxel (below) developed the apparatuses much further and thus gained new insights on a number of new materials. Photos: LARMAUR
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