Síntese e caracterização de nanocompósitos constituídos por nanopartículas de ferrita de cobalto e polianilina

Abstract

The study of nanomaterials containing magnetic particles has been the subject of intense research due to its many applications in a va riety of technological areas such as the automotive industry, military and aerospace technology, medical applications, telecommunications, and others. The scientific research of these materials has been directed to the search of methods of production of na nocomposites with optimized properties, good performance and low cost. Nanocomposites based on ferrites are part of this group of materials because of their interesting electrical and magnetic properties, as well as their thermal and chemical stability. This work aimed at the production and characterization of nanoparticulate cobalt ferrite as well as the preparation and characterization of nanocomposites composed of cobalt ferrite (CoFe 2O4) and polyaniline (PANI). The magnetic nanoparticles were obtained by the modified Pechini method, varying the calcination temperature of the samples and the nanocomposites were synthesized using the in situ polymerization methodology. The samples were characterized by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, thermogravimetry and vibration sample magnetometry. The analysis of the nanoparticles of cobalt ferrite indicated that through the route of synthesis developed it is possible to produce a monophasic and nanometric system of CoFe2O4, with a cubic spinel structure. The average particle size of the cobalt ferrit e samples was of the order of 51 nm. The magnetic characterization of the samples indicated saturation magnetization in the order of 80 emu / g (bulk) except for samples heat treated at 900 ° C. For the samples calcined at 750 ° C, they showed a coercivity of 1.407 kOe and this value decreases for the samples with the average increase of the particle. The characterization of PANI by the techniques described above, indicated the formatio n of polyaniline in its conductive form, emeraldine salt. In the case of nanocomposites, from the structural and morphological analysis of the samples, it was verified that the nanoparticles of cobalt ferrite were well dispersed in the polymer chain, resulting in interaction between them. This interaction was reflected in the better thermal stability of nanocomposites when compared to pure polyaniline. On the other hand, the magnetic characterization indicated that the magnetization of saturation and coercivity decreased compared to pure cobalt ferrite. Nanocomposites with better structural and magnetic properties were those formed from cobalt ferrite nanoparticles calcined at a temperature of 750 ° C