In order to study the influence of different sulfonation routes on its thermal and structural properties sulfonated polyaniline (SPAni) was prepared. FT-IR revealed that the formation of PAni salt or ring sulfonation depends on the route. UV-visible spectra pointed out that the level of the PAni protonation was dependent on the sulfonation route. A new approach was given for TG/DTG and DSC results correlating different energy levels with the distinguished sulfonation routes. The TG/DTG degradation steps and the amount of the released material corroborated the structural differences of the polyanilines. For each DSC first regime of heating, a broad and intense peak (from -30 to 250 ºC) with different level of energy was noticed. That peak could be ascribed to the multiple relaxations and breaking of the PAni intra and inter hydrogen bonds after sulfonation.

Sol-gel synthesis has been investigated in order to produce stoichiometric compositions of Ba3Co2Fe24O41 (Co2Z) at lower calcination temperatures, using citric acid as quelant complex. Using this method, Co2Z ferrite could be synthesized at 950 °C, about 400 °C lower than that of conventional method. Nanocomposites (80:20% weight) of this ferrite with polychloroprene (CR) were obtained for the microwave absorption measurements by mixing, molding and curing mixtures of Ba3Co2Fe24O41 powders with polychloroprene and the additives of vulcanization. The microwave absorption measurements was carried out using the Transmission/Reflection method for the S and X-Ku bands and showed the best performance as Radar Absorber Material (RAM) in 8.0-16.0 GHz range. Thus, the material can be used by reducing the radar signature of the Brazilian Frigates' superstructures.

The magnetic behavior and its relationship with microwave absorbing properties have been investigated for doped Z-type barium hexaferrites (Ba3Co1.3Zn0.3Cu0.4Fe 24O41)/ polychloroprene (CR) nanocomposites. Simultaneous substitutions by Co2+, Cu2+, and Zn2+ ions make possible the use of these materials as RAMs, due to the frequency dependence of µr* (permeability), responsible for the location of the hexaferrite natural resonance. The Cu2+ ions distort the crystalline field due to their electronic configuration, and this behavior results in an increase in the saturation magnetization (Ms), which improve the magnetic permeability. Similarly, the superparamagnetic contribution (associated to the nanometric size) led to the improvement of the microwave absorption.