Síntese de ferrita NiFe2O4 e sua incorporação em matriz de poliamida 6 para o desenvolvimento de compósitos absorvedores magnéticos.

Abstract

In this work, NiFe204 ferrite was synthesized by reaction of combustion, in which the powders produced were added to a polyamide 6 in order to obtain a composite. The ferrite powders of NiFe204 were prepared in accordance with the concept of the chemistry of propellants and explosives using a container of steel/stainless steel with a capacity for 100g of powder. They were characterized by: XRD, adsorption of N2 and SEM. The results of XRD showed the formation of inverse spinel phase of the ferrite of NiFe204 , and traces of secondary hematite (Fe203). The size of crystallites, the surface area and the equivalent spherical diameter/crystallite size calculated by XRD relation (DBET/DDRX) of clusters were 36.88 nm, 2.63 m2 / g, and 11.2 respectively, aiming to evaluate the influence of these structural and morphological characteristics in the powders. During the synthesis was measured the temperature and time of flame combustion. After this step of obtaining the powders, they were incorporated into the polymer matrix of polyamide 6, using an internal mixer of Haake Buchler at a temperature of 240 °C and 60rpm, which were used concentrations of 10, 30, 50 and 60 wt% of ferrite powders of NiFe204. The polyamide 6/ferrite of NiFe204 composites were characterized by: XRD, SEM, TEM and electromagnetic analysis. Apparently, it was observed by XRD that the presence of ferrite altered the crystalline form of the polyamide 6 matrix. It was verified by scanning electron microscopy, which was formed clusters at concentrations of 50 and 60wt%, moreover, giving a larger amount of particles, which was expected by the quantity of ferrite powder to be greater. In the concentration of 10% the particles are more scattered. This can be explained due to the magnetic characteristics of ferrite, with a tendency of the particles are agglomerated or during the combustion reaction to form particles with early pre-sintering. By mean of the electromagnetic analysis, it was seen that the samples with 10 and 30wt% not presented attenuation in all studied frequency range, being these materials considered transparent practically at radiofrequency. This can be explained for large quantity of voids and/or bubbles present in the polymer matrix that to make the radiation not interact with the filler, occurring very loss due to defects presence.