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Aslibeiki B.,University of Tabriz | Kameli P.,Isfahan University of Technology | Ehsani M.H.,Semnan University | Salamati H.,Isfahan University of Technology | And 5 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2016

Manganese spinel ferrite nanoparticles were synthesized by a solvothermal route based on high temperature decomposition of metal nitrates in the presence of different contents of Triethylene glycol. This simple and low cost method can be applied to prepare large quantities of nanoparticles (tens of grams). Powder X-ray diffraction (PXRD) and Transmission Electron Microscopy (TEM) confirmed that nanoparticles with a good crystalline quality were obtained. A good agreement between the average particle size calculated by PXRD and TEM was observed. Fourier-transform infrared spectra showed that polymer molecules have the tendency to form bonds with the surface of ferrite nanoparticles reducing the surface spin disorder, and then enhancing the saturation magnetization (MS). Therefore, much higher MS value (up to ∼91 emu/g at 5 K) was observed compared with that of bare nanoparticles without surfactant. The blocking temperature showed a remarkable shift to lower values with increasing the polymer starting amount. In addition, by increasing the polymer initial content, a more homogeneous size distribution was obtained and the initial strongly interacting superspin glass behavior changed to a weakly interacting superparamagnetic state. © 2015 Elsevier B.V. All rights reserved. Source


Muscas G.,University of Cagliari | Muscas G.,CNR Institute of Structure of Matter | Yaacoub N.,CNRS Le Mans Institute of Molecules and Materials | Concas G.,University of Cagliari | And 11 more authors.
Nanoscale | Year: 2015

Magnetic properties of iron oxide nanoparticles with spinel structure are strictly related to a complex interplay between cationic distribution and the presence of a non-collinear spin structure (spin canting). With the aim to gain better insight into the effect of the magnetic structure on magnetic properties, in this paper we investigated a family of small crystalline ferrite nanoparticles of the formula CoxNi1-xFe2O4 (0 ≤ x ≤ 1) having equal size (≈4.5 nm) and spherical-like shape. The field dependence of magnetization at low temperatures indicated a clear increase of magnetocrystalline anisotropy and saturation magnetization (higher than the bulk value for CoFe2O4: ∼130 A m2 kg-1) with the increase of cobalt content. The magnetic structure of nanoparticles has been investigated by Mössbauer spectroscopy under an intense magnetic field (8 T) at a low temperature (10 K). The magnetic properties have been explained in terms of an evolution of the magnetic structure with the increase of cobalt content. In addition a direct correlation between cationic distribution and spin canting has been proposed, explaining the presence of a noncollinear spin structure in terms of superexchange interaction energy produced by the average cationic distribution and vacancies in the spinel structure. This journal is © The Royal Society of Chemistry. Source


Casciardi S.,National Institution for Insurance Against Accidents at Work INAIL Research | Sisto R.,National Institution for Insurance Against Accidents at Work INAIL Research | Diociaiuti M.,Italian National Institute of Health ISS
Journal of Nanomaterials | Year: 2013

Chemical and physical characterization of nanomaterials is essential to improve synthesis processes, for new technological and commercial applications, and to assess their toxicity through in vitro and in vivo studies. New nanomaterials and new synthesis processes are continuously tested and updated to exploit their innovative properties. In this paper, low-dimensional carbon nanostructure characterization was performed using analytical transmission electron microscopy. Conventional and advanced microscopy techniques, such as acquisition of high resolution images, nanobeam electron diffraction patterns, X-ray energy dispersion, and electron energy loss spectra, were used to determine the main physical and chemical properties of single wall and multiwall carbon nanotubes, graphene flakes, and amorphous carbon films. Through the resulting micrographs, diffraction patterns, and spectra, the main low-dimensional carbon nanostructures properties were determined in terms of structural defects and/or the presence of metallic or heavy elements, such as those used as catalyst or to decorate nanotubes. The obtained information is of crucial importance to investigate low-dimension nanomaterial biological activity. © 2013 Stefano Casciardi et al. Source

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