Valérie Demange

One-pot synthesis and characterizations of bi-functional phosphor–magnetic @SiO2nanoparticles: controlled and structured association of Mo6 cluster units and γ-Fe2O3nanocrystals

Nanostructured silica coated bifunctional nanoparticles based on [Mo(6)Br(14)](2-) units as phosphorescent dye and magnetic gamma-Fe(2)O(3) nanocrystals were synthesized and characterized.

New approximants in the Al-Cr-Fe system and their oxidation resistance

Abstract Two new orthorhombic approximants of the decagonal phase as well as a γ-brass type phase are pointed out in the Al–Cr–Fe system. Analysis of diffraction data shows that they are isotypic with compounds already known in the Al–Cu–Fe–Cr and Al–Cr alloys, respectively. Resistance to oxidation in water as well as at high temperature is significantly enhanced thanks to the addition of Cr.

New approximant phases in Al-Cr-Fe

Recently, new approximant phases were pointed out in the Al-Cr-Fe system, namely orthorhombic O-Al-Cr-Fe, hexagonal H-Al-Cr-Fe and monoclinic M-Al-Cr-Fe. In the corresponding analysed samples, the new approximant phases were always coexisting with metallic aluminium. We have studied the Al-Cr-Fe system within a broad composition range. In one alloy with composition Al81Cr11Fe8, two new crystalline approximants of the decagonal phase were discovered. These phases were analysed by differential thermal analysis (DTA), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and microprobe analysis. The phases were found to be isomorphic with a C-3.1-phase earlier discovered by Van Tendeloo et al. in Al-Mn-Ni and an O-1-phase earlier discovered by Dong et al. in Al-Cr-Cu-Fe. Moreover, we have found in the same sample the O-Al-Cr-Fe phase as well as metallic aluminium

About γ-brass phases in the Al–Cr–Fe system and their relationships to quasicrystals and approximants

We have identified two γ-brass phases in the Al–Cr–Fe system by X-ray diffraction and transmission electron microscopy. These structures (rhombohedral and cubic) are closely related to each other and can co-exist in the same alloy together with approximants of quasicrystals. In particular, a long-period superlattice, typical of γ-brass phases, was characterized in the cubic structure. This superstructure is constituted of inversion domains separated by boundaries lying at ( 10) planes. The displacement vector between like domains was determined from high resolution microscopy data. This study deals also with a description of some structural links between γ-brass phases and approximants of decagonal and icosahedral quasicrystals.

Aperiodic Intermetallics: The Example of Quasicrystals

This article presents an overview about the properties of quasicrystals. The atomic structure of icosahedral and decagonal compounds is described within the framework of high-dimensional crystallography and emphasis is put on phase diagrams. Attention is also paid to the electronic structure of these intermetallics. Several physical properties in connection with possible applications are briefly presented.

Electron microscopy study of approximant phases in the Al-Cr-Fe system

We have characterized by transmission electron microscopy several new phases that we have discovered in bulk alloys of the Al–Cr–Fe system. These structures are an icosahedral compound and several approximants of the decagonal phase. According to the indexation of the electron diffraction patterns (EDPs), some of the approximants are not of Fibonacci type. These EDPs correspond to nanodomains, which are due to disorder introduced by quenching the alloys after melting the pure constituent metals. For these new types of approximant, we propose a crystallographic description related to the usual Fibonacci description. In addition, we suggest a construction of the corresponding tilings. The orientation relationships between these structures are described.