Monique Tillard

Compositional and Structural Variations in the Ternary System Li-Al-Si.

Abstract The Li–Al–Si ternary system has been investigated and four ternary phases characterized using both powder and single crystal X-ray diffraction data. LiAlSi and Li7Al3Si4 crystallize in the F4̅3m, cubic system, Li18Al2Si6 in tetragonal I41/amd and Li15Al3Si6 in hexagonal P63/m space group. The structure of LiAlSi (a = 5.94 Å), previously reported from powder data, has been confirmed. The new compound Li7Al3Si4 has been identified and, due to a higher lithium content, its cell parameter is slightly larger (a = 6.115 Å). The tetragonal cell (a = 6.179(1) Å, c = 12.199(4) Å) of Li18Al2Si6 may be considered as a (1 × 1 × 2) supercell of the cubic one. Structural variations are strongly correlated to compositional fluctuations and atomic substitutions, in every case the SI–Al network displays some covalent character. In the Li15Al3Si6 hexagonal cell, bonding is more covalent leading to a heterographite-like SI–Al network.

Redetermination of the iron–zinc phase FeZn13

In iron tridecazinc, the FeZn13 unit cell contains two Zn12 icosahedra which are Fe-centred and two Zn2 dumb-bells coordinated by eight icosahedra. Zn12 icosahedra form chains along the c axis by vertex-sharing, and are further interlinked through octahedra-sharing and vertex-to-vertex bonds.

Electroactive Nanorods and Nanorings Designed by Supramolecular Association of π-Conjugated Oligomers

In investigations into the design and isolation of semiconducting nano-objects, the synthesis of a new bisureido pi-conjugated organogelator has been achieved. This oligo(phenylenethienylene) derivative was found to be capable of forming one-dimensional supramolecular assemblies, leading to the gelation of several solvents. Its self-assembling properties have been studied with different techniques (AFM, EFM, etc.). Nano-objects have successfully been fabricated from the pristine organogel under appropriate dilution conditions. In particular, nanorods and nanorings composed of the electroactive organogelator have been isolated and characterized. With additional support from an electrochemical study of the organogelator in solution, it has been demonstrated by the EFM technique that such nano-objects were capable of exhibiting charge transport properties, a requirement in the fabrication of nanoscale optoelectronic devices. It was observed that positive charges can be injected and delocalized all along an individual nano-object (nanorod and nanoring) over micrometers and, remarkably, that no charge was stored in the center of the nanoring. It was also observed that topographic constructions in the nanostructures prevent transport and delocalization. The same experiments were performed with a negative bias (i.e., electron injection), but no charge delocalization was observed. These results could be correlated with the nature of 1, which is a good electron-donor, so it can easily be oxidized, but can be reduced only with difficulty.

First syntheses of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes via intramolecular esterification

Abstract Synthesis of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes via either intramolecular transesterification, using potassium tert -butylate as catalytic agent, or phosphinic acid esterification, is described for the first time.

Atomic structure of the (Al,Si)CuFe cubic approxi­mant phase

The structure of the alpha-(Al,Si)CuFe approximant phase is determined by a single-crystal X-ray diffraction study and compared to the ideal structure obtained by the perpendicular shear method of the parent icosahedral phase. It is shown that the local environments (typical atomic clusters) of the two phases are similar and expand significantly farther than the size of the unit cell of the approximant. The orbit Al(2) issuing from the theoretical icosahedral model corresponding to the inner dodecahedron of the Mackay-type cluster is not found in the approximant and is replaced by a partially occupied inner icosahedron with an unusually large Debye-Waller factor.

β-Keto-enol Tethered Pyridine and Thiophene: Synthesis, Crystal Structure Determination and Its Organic Immobilization on Silica for Efficient Solid-Liquid Extraction of Heavy Metals

Molecules bearing β-keto-enol functionality are potential candidates for coordination chemistry. Reported herein is the first synthesis and use of a novel designed ligand based on β-keto-enol group embedded with pyridine and thiophene moieties. The product was prepared in a one-step procedure by mixed Claisen condensation and was characterized by EA, m/z, FT-IR, (1H, 13C) NMR and single-crystal X-ray diffraction analysis. The new structure was grafted onto silica particles to afford a chelating matrix which was well-characterized by EA, FT-IR, solid-state 13C-NMR, BET, BJH, SEM and TGA. The newly prepared organic-inorganic material was used as an adsorbent for efficient solid-phase extraction (SPE) of Cu(II), Zn(II), Cd(II) and Pb(II) from aqueous solutions and showed a capture capacity of 104.12 mg·g−1, 98.90 mg·g−1, 72.02 mg·g−1, and 65.54 mg·g−1, respectively. The adsorption capacity was investigated, in a batch method, using time of contact, pH, initial concentration, kinetics (Langmuir and Freundlich models), and thermodynamic parameters (ΔG°, ΔH° and ΔS°) of the system effects.

Li15Al3Si6 (Li14.6Al3.4Si6), a compound displaying a heterographite-like anionic framework.

The title compound, lithium aluminium silicide (15/3/6), crystallizes in the hexagonal centrosymmetric space group P6(3)/m. The three-dimensional structure of this ternary compound may be depicted as two interpenetrating lattices, namely a graphite-like Li(3)Al(3)Si(6) layer and a distorted diamond-like lithium lattice. As is commonly found for LiAl alloys, the Li and Al atoms are found to share some crystallographic sites. The diamond-like lattice is built up of Li cations, and the graphite-like anionic layer is composed of Si, Al and Li atoms in which Si and Al are covalently bonded [Si-Al = 2.4672 (4) A].

Mg2Al3, a complex and disordered intermetallic compound as anode material for metal-air batteries

The intermetallic compound Mg2Al3 has been selected for this work to be tested as anode in a metal-air battery. The compound is prepared by a high-temperature synthesis from elements and its cubic structure (Fd 3¯

Structural Versatility of the ε-SmGax Phase : X-Ray, Electron Diffraction, and DFT Studies

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