Estudo das propriedades magnéticas de compósito de ferrita de níquel em matriz polimérica de PVA

Abstract

Ferrites are ferrimagnetic oxides that can be manufactured in different geometric shapes. Their specimen can be formed of polycrystalline ferrites (sintered body) or ferrite composites dispersed in some type of matrix (polymeric, ceramic or metallic). Poly (vinyl alcohol) is a biodegradable poly (vinyl acetate) derivative, useful for film making, which exhibits chemical resistance and good mechanical properties. In this work, composite films formed by a poly (vinyl alcohol) 99% hydrolyzed (PVA) polymer matrix were prepared as dispersed phases of the nickel ferrite ceramic (NiFe2O4) in 10; 20; 30 and 50% (m/m) concentrations, (m/m), respectively, for the purpose of application in the telecommunication area. The method of combustion was used to obtain the nickel ferrite. The nickel ferrite powder produced in the combustion was calcined at 750°C/ 2h with a heating rate of 10°C/ min. The films were obtained by the casting method. All the products obtained were characterized by the techniques of X-ray diffraction (XRD), Thermogravimetry (TG-DTG), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) with EDS, Sample Magnetometer Vibrant (MAV) and Paramagnetic Resonance Spectroscopy (RPE). The results of XRD together with the Rietveld refinement, showed a mean crystallite size of 32.5 nm and formation of secondary phases of Fe2O3 and NiO. The SEM spectra showed spherical and porous particles, while the data collected from the EDS are in line with the XRD result. The MAV magnetic measurements have characteristics of soft magnetic materials useful for application in telecommunication technology. The EPR spectra showed the presence of groups binding to the Fe3+ íons.