Structural and morphological characterization of FeCo2O4 and CoFe2O4 spinels prepared by a coprecipitation method

The crystal chemistry of AM2O4 oxometallates

Fe–Co based metal/spinel to produce light olefins from syngas

Cobalt ferrite exhibits a high coercivity at room temperature and a strong magnetic anisotropy compared to the other spinel ferrites and, consequently appears as an interesting material for permanent magnets and high-density recording. The magnetic properties depend also on the crystallite size. In order to keep the powder properties in a bulk material, dense nanostructured cobalt ferrite has to be sintered. A field activated sintering process like spark plasma sintering (SPS) may be promising for such challenge. The present paper deals with: (i) the preparation of cobalt ferrite by two methods: coprecipitation and hydrothermal synthesis in supercritical water; (ii) the SPS sintering of the cobalt ferrite nanopowder prepared by coprecipitation. The sintering of the as-processed powder and that obtained after a thermal treatment resulting in the spinel phase has been investigated. The influence of the starting powder and the sintering parameters such as the temperature, the duration of the SPS stage on the grain growth and the densification degree of bulk materials will be presented.

Spark plasma sintering of cobalt ferrite nanopowders prepared by coprecipitation and hydrothermal synthesis

Fe–Co-based metal/oxide composite materials (Co0.730Fe0.270)0.82 [Co0.35Fe2.65O4], (Co0.950Fe0.050)0.62 [Co0.31Fe2.69O4] and (Co0.900Fe0.100) [Co0.10Fe2.90O4] were prepared to be used in Fischer–Tropsch (F–T) synthesis in view of producing light alkenes. The metal is an iron–cobalt alloy of bcc structure in the former and of fcc structure in the two latter and the oxide, a cobalt containing magnetite. The metal, obtained directly by preparation method, is embedded in the oxide phase. Then, catalysts were not subjected to a reducing pre-treatment. Although, catalysts were not reduced, the two former materials are efficient as catalysts in F–T reaction to produce C2–C4 (50 wt.%) with high alkene:alkane ratio and a low selectivity of CO2 (25% molar at CO conversion of 5%); the third catalyst presents a typical distribution of hydrocarbons obtained with cobalt catalyst in F–T reaction. The possible modifications of the catalysts during the catalytic reaction are studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). High resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) show the surface composition under test is identical for the first two catalysts, although their initial bulk composition is different. The characterisation results, obtained by combined methods (XRD, electron-microscopy, surface analysis) provide explanations to individual catalytic behaviour of the three catalysts studied.

Effect of Fischer–Tropsch synthesis on the microstructure of Fe–Co-based metal/spinel composite materials

Magnetic properties of a new metal-ferrite composite

Crystallization of iron-magnetite composite by using Fe(II) disproportionation in an aqueous media

Syncrystallization of CoFe2O4 from ferric and cobaltous chlorides: Physical properties of the precipitate

A new metal-spinel composite (Fe0.2Co0.8)0.8[Fe2.38Co0.62 O4]: thermal behaviour under vacuum

Thermal Stability of a Metal Alloy—Spinel Ferrite Composite Prepared by Disproportionation in a Liquid Medium

A. Malats i Riera

Papers

Magnetic properties of a new metal-ferrite composite

Crystallization of iron-magnetite composite by using Fe(II) disproportionation in an aqueous media

Syncrystallization of CoFe2O4 from ferric and cobaltous chlorides: Physical properties of the precipitate

A new metal-spinel composite (Fe0.2Co0.8)0.8[Fe2.38Co0.62 O4]: thermal behaviour under vacuum

Thermal Stability of a Metal Alloy—Spinel Ferrite Composite Prepared by Disproportionation in a Liquid Medium