Lamellar nickel hydroxy-halides: anionic exchange synthesis, structural characterization and magnetic behavior:

Nickel-layered hydroxy-halides LHS-Ni-X (X = Cl, Br, and I) have been prepared by exchange reactions conducted in an aqueous medium under an inert atmosphere starting from the parent nickel-layered hydroxyacetate. The latter was prepared by a hydrolysis reaction conducted in a polyol medium. IR and X-ray diffraction (XRD) studies show total exchange. These compounds exhibit a brucite-like structure with a turbostratic nature. Their interlamellar distance varies linearly with the radius of the halide anion in the range 7.9-8.7 angstrom while the hydroxyacetate interlamellar distance is 10.53 angstrom. In comparison with the acetate ion which replaces hydroxyl groups in the brucite-like layer, EXAFS and XRD investigations show that halide ions are intercalated into the interlayer space along with water molecules without any covalent bonding to the nickel ion. All compounds have similar structural features and can be considered as alpha-type nickel hydroxides, alpha-Ni(OH)(2). These compounds exhibit a ferromagnetic character. The latter is discussed on the basis of the Drillon-Panissod model of ferromagnetic layers interacting via dipole interactions and taking into account the structural features established by XANES and XRD studies along with the intrinsic properties of the halide anions

Synthèse par réduction en milieu polyol de particules métalliques de cobalt et de ruthénium (contrôle morphologique et caractérisations physico-chimiques)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Synthèse par chimie douce et caractérisation de poudres et de films nanocristallins de ferrites mixtes de Ni - Zn (études des propriétés magnétiques statiques)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Nanoparticules métalliques anisotropes synthétisées par vie chimique (fils, plaquettes et particules hybrides de cobalt-nickel, caractérisations physico-chimiques et propriétés magnétiques)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Synthèse et préparation de catalyseurs adaptés au craquage en milieu supercritique

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Encapsulation de micro-algues dans des matrices minérales en vue d'élaboration bio-contrôlée de nanoparticules

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Magnetic properties of zinc ferrite nanoparticles synthesized by hydrolysis in a polyol medium

International audienceHighly crystalline, nanometre sized ZnFe2O4 particles with different diameters, 6.6 and 14.8 nm, were prepared by forced hydrolysis in a polyol medium. The DC magnetic properties exhibit a strong dependence on the particle size as a result of the unusual cation distribution. They clearly establish their superparamagnetic character at room temperature and the occurrence of ferrimagnetic or ferromagnetic ordering at low temperature. The magnetization is found to increase with grain size reduction. The 57Fe M¨ossbauer spectra were recorded at 300 and 4.5 K. There is no evidence for the presence of the Fe2+ charge state, confirming the perfect stoichiometry of the two samples. At 300 K, the M¨ossbauer spectra consist of doublets due to the superparamagnetic behaviour whereas at 4.5 K they reveal a magnetically blocked state. M¨ossbauer spectra at 10 K in an external 6 T magnetic field applied parallel to the direction of the gamma rays clearly show a close to collinear N´eel-like ferrimagnetic ordering for the 6.6 nm particles and a canted Yafet–Kittel-like ferrimagnetic ordering for the 14.8 nm ones