Electronic Densities of States and Pseudo-gaps in Al-based Complex Intermetallics

The results of an investigation of the electronic structure of the valence band of various Al-based complex intermetallic alloys, carried out using the X-ray emission spectroscopy technique, are presented and discussed. It is shown that the electronic structure results from an interplay between covalency and repulsive interactions that contributes to the formation of a pseudo-gap at the Fermi level in the Al electronic distributions.</p

Friction and solid-solid adhesion on complex metallic alloys Friction and solid-solid adhesion on complex metallic alloys

International audienceThe discovery in 1987 of stable quasicrystals in the Al–Cu–Fe system was soon exploited to patent specific coatings that showed reduced friction in ambient air against hard antagonists. Henceforth, it was possible to develop a number of applications, potential or commercially exploited to date, that will be alluded to in this topical review. A deeper understanding of the characteristics of complex metallic alloys (CMAs) may explain why material made of metals like Al, Cu and Fe offers reduced friction; low solid–solid adhesion came later. It is linked to the surface energy being significantly lower on those materials, in which translational symmetry has become a weak property, that is determined by the depth of the pseudo-gap at the Fermi energy. As a result, friction is anisotropic in CMAs that builds up according to the translation symmetry along one direction, but is aperiodic along the other two directions. A review is given in this article of the most salient data found along these lines during the past two decades or so

Spectres X du silicium, de l'aluminium et du magnésium dans divers minéraux

Energy shifts of SiKα, AlKα and MgKα emission lines from seven natural silicates and two oxides have been measured comparatively to the pure element. The results are discussed ; an attempt is made to correlate the measurements to the surrounding of each element in the compound.Les déplacements énergétiques des émissions SiKα, AlKα et MgKα ont été mesurés par rapport à l'élément pur dans 7 silicates naturels et dans 2 oxydes. Les résultats observés sont discutés en liaison avec l'environnement de chaque élément dans les composés.Pitault Bernard, Belin-Ferré Esther, Sénémaud Christiane. Spectres X du silicium, de l'aluminium et du magnésium dans divers minéraux. In: Bulletin de Minéralogie, volume 104, 2-3, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Première partie : croissance cristalline / Physique des minéraux / Microscopie électronique