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Extended X-ray absorption fine structure and X-ray absorption near edge structure techniques are used to study in detail the formation of FeCo alloy nanoparticles in a silica matrix during their sol-gel preparation. The final nanocomposites contain bcc FeCo nanoparticles, which are sometimes accompanied by fcc Co depending both on the intermediate products and on the porous structure of the samples.

Extended X-ray absorption fine structure and x-ray absorption near-edge structure techniques are used to study in detail the structural characteristics of FeCo-Al2O3 nanocomposite xerogels and aerogels. The investigation of the xerogels and aerogels calcined at increasing temperature indicates that Fe(III) and ions are present and they are located in the tetrahedral sites of the spinel is more ordered in the aerogel sample than the xerogel sample.

We show a novel chemical vapour deposition (CVD) approach, in which the large-scale fabrication of ferromagnetically-filled cm-scale buckypapers is achieved through the deposition of a mesoporous supported catalyst (SBA-16) on a silicon substrate. We demonstrate that SBA-16 has the crucial role of promoting the growth of carbon nanotubes (CNTs) on a horizontal plane with random orientation rather than in a vertical direction, therefore allowing a facile fabrication of cm-scale CNTs buckypapers free from the onion-crust by-product observed on the buckypaper-surface in previous reports. The morphology and composition of the obtained CNTs-buckypapers are analyzed in detail by scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX), transmission electron microscopy (TEM), high resolution TEM (HRTEM), and thermogravimetric analysis (TGA), while structural analysis is performed by Rietveld Refinement of XRD data. The room temperature magnetic properties of the produced buckypapers are also investigated and reveal the presence of a high coercivity of 650 Oe. Additionally, the electrochemical performances of these buckypapers are demonstrated and reveal a behavior that is compatible with that of a pseudo-capacitor (resistive-capacitor) with better performances than those presented in other previously studied layered-buckypapers of Fe-filled CNTs, obtained by pyrolysis of dichlorobenzene-ferrocene mixtures. These measurements indicate that these materials show promise for applications in energy storage systems as flexible electrodes. [ABSTRACT FROM AUTHOR]

Abstract The ancient Neoplatonic doctrine that the rational soul has one or more vehicles-bodies of a semi-material nature which it acquires during its descent through the spheres-plays a crucial part in Marsilio Ficino's philosophical system, especially in his theory of sense-perception and in his account of the afterlife. Of the soul's three vehicles, the one made of more or less rarefied air is particularly important, according to Ficino, during the soul's embodied existence, for he identifies it with the spiritus, the pneumatic substance based in the brain which was believed to serve as an instrument for perception and imagination. He refers to the vehicles in his arguments against the theory of the transmigration of souls into the bodies of animals, claiming that the imaginative suffering experienced after death by souls in their aerial bodies are much more acute than the physical pain they might feel in bodies made of flesh and blood. Since the power of the imagination, for Ficino, is stronger than that of the four senses, the soul's perceptive activity is more intense after death, when it has lost its earthly body and lives instead in a body made of air. The vehicles, moreover, provided Ficino with evidence for the individual immortality of souls, a doctrine that he was attempting to demonstrate philosophically against the position of Averroes and his followers. In his view, the vehicles ensured the survival after death of two faculties which were intimately connected to personal identity: the imagination and memory. By pointing out the role of the vehicles in transporting the soul's innermost representations and memories through the universe, Ficino was able to show that the distinguishing traits of our personality are not lost with bodily death, but survive along with the vehicle that carries them. [ABSTRACT FROM AUTHOR]

Magnetic nanocomposite materials consisting of 5 and 10 wt% CoFe2O4 nanoparticles in a silica aerogel matrix have been synthesized by the sol-gel method. For the CoFe2O4-10wt% sample, bright-field scanning transmission electron microscopy (BF STEM) and high-resolution transmission electron microscopy (HREM) images showed distinct, rounded CoFe2O4 nanoparticles, with typical diameters of roughly 8 nm. For the CoFe2O4-5wt% sample, BF STEM images and energy dispersive X-ray (EDX) measurements showed CoFe2O4 nanoparticles with diameters of roughly 3 ± 1 nm. EDX measurements indicate that all nanoparticles consist of stoichiometric CoFe2O4, and electron energy-loss spectroscopy measurements from lines crossing nanoparticles in the CoFe2O4-10wt% sample show a uniform composition within nanoparticles, with a precision of at best than ±0.5 nm in analysis position. BF STEM images obtained for the CoFe2O4-10wt% sample showed many "needle-like" nanostructures that typically have a length of ∼10 nm and a width of ∼1 nm, and frequently appear to be attached to nanoparticles. These needle-like nanostructures are observed to contain layers with interlayer spacing 0.33 ± 0.1 nm, which could be consistent with Co silicate hydroxide, a known precursor phase in these nanocomposite materials. [ABSTRACT FROM AUTHOR]

CuFe2O4 is an example of ferrites whose physico-chemical properties can vary greatly at the nanoscale. Here, sol-gel techniques are used to produce CuFe2O4-SiO2 nanocomposites where copper ferrite nanocrystals are grown within a porous dielectric silica matrix. Nanocomposites in the form of both xerogels and aerogels with variable loadings of copper ferrite (5 wt%, 10 wt% and 15 wt%) were synthesized. Transmission electron microscopy and X-ray diffraction investigations showed the occurrence of CuFe2O4 nanoparticles with average crystal size ranging from a few nanometers up to around 9 nm, homogeneously distributed within the porous silica matrix, after thermal treatment of the samples at 900 °C. Evidence of some impurities of CuO and α-Fe2O3 was found in the aerogel samples with 10 wt% and 15 wt% loading. DC magnetometry was used to investigate the magnetic properties of these nanocomposites, as a function of the loading of copper ferrite and of the porosity characteristics. All the nanocomposites show a blocking temperature lower than RT and soft magnetic features at low temperature. The observed magnetic parameters are interpreted taking into account the occurrence of size and interaction effects in an ensemble of superparamagnetic nanoparticles distributed in a matrix. These results highlight how aerogel and xerogel matrices give rise to nanocomposites with different magnetic features and how the spatial distribution of the nanophase in the matrices modifies the final magnetic properties with respect to the case of conventional unsupported nanoparticles. [ABSTRACT FROM AUTHOR]

Extended X-ray absorption fine structure and X-ray absorption near-edge structure techniques were used to study in detail the structural characteristics of FeCo−Al2O3 nanocomposite xerogels and aerogels. The formation of bcc FeCo alloy, which cannot be assessed unambiguously by X-ray diffraction, dispersed within the alumina matrix was evidenced in the final samples obtained by heat treatment at 800 °C in reducing atmosphere. Aerogel samples reduced below 800 °C still present a fraction of oxidized metal together with the bcc alloy. The investigation of the xerogels and aerogels calcined at increasing temperature indicates that Fe(III) and Co(II) ions are present and they are located in the tetrahedral sites of the spinel structure of the matrix (γ-Al2O3); moreover, the precursor of the spinel is more ordered in the aerogel sample than the xerogel sample. [ABSTRACT FROM AUTHOR]

Nanocrystalline γ-Al2O3 and FeCo-Al2O3 nanocomposites containing FeCo alloy nanoparticles well dispersed in the nanocrystalline γ-Al2O3 matrix were successfully obtained by the sol-gel method using aluminum tri-sec-butoxide and iron and cobalt nitrates as precursors. The gels were submitted to high temperature supercritical drying which allowed to obtain aerogels with high surface areas and pore volumes. [ABSTRACT FROM AUTHOR]