APPLIED PHYSICS OF QUASICRYSTALS AND APPLICATIONS. Jean Marie Dubois, Laboratoire de Science et Genie des Materiaux Metalliques, CNRS URA 159 et GDR CINQ, Ecole des Mines, Parc de Saurupt, F-54042 Nancy

Despite a small fraction of its atomic positions cannot be fully specified, the structure of quasicrystals is now well understood with the help of high-dimensional crystallography techniques. The interest of (quasi)crystallographers therefore turns at present towards exploring the physical, mechanical and chemical properties.

This task is made easier by the availability of stable quasicrystals and of single "grained samples the quality of which competes with that of the best crystalline specimens. The result of all such measurements is rather outstanding: quasicrystals, basically made of seventy atomic percent of aluminum and of transition metals, are heat insulators, they show a very weak electronic conductivity which furthermore increases with temperature. Their optical properties dramatically depart from those of a free electron metal. They produce surprinsingly low friction as compared to usual metallic alloys, they exhibit catalytic properties and good corrosion resistance. Altogether, their electronic structure proves to be different from that of their elemental constituents. This picture can be understood by reference to the hierarchy of atomic clusters which characterizes this specific structure.

The purpose of the lecture will be to review the most significant applied properties discovered in recent years with stable quasicrystals. The fields of potential technological applications that follow will be evoked such as thermal barriers, low wear coatings, thin quasicrystalline films sandwiched between dielectric layers for solar light absorption, weak adhesion surfaces, hydrogen storage or the reinforcement of metal-matrix composites.