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In this work, nanocomposites constituted of FeCo alloy nanoparticles dispersed on a highly porous silica aerogel have been designed as catalysts for low temperature Fischer-Tropsch synthesis. The catalysts were characterized by XRD, TEM, N physisorption and SEM analysis. A high catalytic activity with CO conversions up to 95 % has been obtained, with enhanced selectivity for the C-C hydrocarbons. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The structural properties of CoFe2O4–SiO2 highly porous nanocomposite aerogels have been investigated by X-ray Absorption Spectroscopy and Transmission Electron Microscopy techniques. The aerogels are obtained by supercritical drying of composite gels obtained using a two step procedure where fast gelation is achieved using urea in the second step. The formation of CoFe2O4 nanocrystals in the silica matrix begins after calcination at 750°C of the parent aerogel and is complete after calcination at 900°C, while the high porosity of the sample is mostly retained. [Copyright &y& Elsevier]

Abstract: Mesoporous silica films with controlled porosity were utilized as the host matrices to prepare FeCo–SiO2 nanocomposites through an impregnation process. The mesoporous silica films were first impregnated with a solution containing Co(II) and Fe(III) ions and then submitted to a reduction treatment under H2 flow. FeCo nanocrystals growth took place inside the mesopores, and their monodisperse size was dictated only by the size of the mesopores. We illustrate this process by the use of two different silica film matrices having different pore size and mesophase symmetry as the templates for the growth of FeCo alloy nanocrystals. The films and the nanocomposite samples were investigated by grazing-incidence small-angle X-ray scattering, X-ray diffraction and transmission electron microscopy. Unimpregnated mesoporous silica samples before and after the same thermal reduction treatment were also studied in order to investigate the mesopore structure variation upon the reduction treatment. [Copyright &y& Elsevier]

A comprehensive study of iron oxide nanocrystal growth through non-hydrolitic, surfactant- mediated thermal reaction of iron pentacarbonyl and an oxidizer has been conducted, which includes size control, anisotropic shape evolution, and crystallographic phase transition of monodisperse iron oxide colloidal nanocrystals. The reaction was monitored via in situ UV-vis spectroscopy, taking advantage of the color change accompanying the iron oxide colloid formation, allowing measurement of the induction time for nucleation. Features of the synthesis such as the size control and reproducibility are related to the occurrence of the observed delayed nucleation process. As a separate source of iron and oxygen is adopted, phase control could also be achieved by sequential injections of oxidizer. [ABSTRACT FROM AUTHOR]