Abstract
FeCo nanoparticles coated with (Fe,Co)3O4 (magnetite doped with cobalt) were synthesized by the proteic sol-gel chemical route. The synthesized materials were characterized by Thermogravimetry (TG), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), vibrating-sample magnetometer (VSM) and Mossbauer spectroscopy (MS). The results show that the increase in temperature and the choice of the correct air/N2 flow directly influence on the final physical-chemical properties of the nanocomposite. The SEM and TEM images confirmed that a thin layer of oxide was formed on the alloy, indicating that it was obtained a self-assembled FeCo-(Fe,Co)3O4 nanocomposites. In addition, the VSM results show that a possible exchange-spring coupling in magnetic FeCo-(Fe,Co)3O4 nanoparticles occurred with high saturation magnetization from FeCo alloy and high coercivity from (Fe,Co)3O4. The rotary oven allows the uniform contact of the powder with the atmosphere of synthesis during the different oxidation-reduction steps, generating more homogeneous particles.
Highlights
A great attention has been given to a class of solids named nanocomposites, containing multicomponent hybrid nanostructures with two or more nanosized constituents assembled in a controlled way 1,2
A temperature of 400°C was used for the re-oxidation process of the FeCo alloy to obtain a layer of oxide on the alloy
It is worth to emphasize that a mixture of air and N2 was used, since it is desired to obtain only a thin layer of oxide on the alloy, avoiding complete oxidation of the alloy
Summary
A great attention has been given to a class of solids named nanocomposites, containing multicomponent hybrid nanostructures with two or more nanosized constituents assembled in a controlled way 1,2. Nanocomposite solids have been studied extensively since it is possible to obtain properties which cannot be acquired with the isolated phases. Different types of composites have been prepared due to their mechanical, structural, chemical, morphological and magnetic properties which are usually different compared to each phase taken alone. These advantages make nanocomposites one of the most promising candidates for the exploration of new applications compared to isolated solids containing a single phase 3-7. Several methods are being used for the synthesis of composite materials such as mechanical alloying, reduction of oxides in gels, infiltration techniques, high-energy ball milling, reduction, decomposition of metallic precursors in polymers, among others .
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