Electric Response of Fe3O4/Epoxy Composites

LEANDRO RAMAJO; ADRIAN CRISTÓBAL; JOSE PORTO LOPÉZ; MARIA MARTA REBOREDO; MIRIAM CASTRO

Rio de Janeiro.

Congreso; International Conference on Science and Technology of Composite Materials; 2007

Magnetic composites are being taken under consideration for applications in motors and actuator devices or magnetic memories, due to their good performance low cost, and low weight. In this way, magnetite has the potential to provide the desired magnetic, electric and mechanical properties to the final composite because it has high saturation magnetization and low bulk receptivity. Composites of Fe3O4 particles in an epoxy resin were produced in order to study the influence of particle concentration on the dielectric and magnetic behavior of composites. The powder was milled during 180 minutes using a planetary laboratory ball-mill with balls of hardened Cr-steel under Ar atmosphere (Po2 < 1 Pa). This step reduces the particles size and guaranties a good dispersion in the mixing process. Particle distribution was determined, and lattice parameters were obtained by X-Ray Diffraction. Epoxy was diluted using tetrahydrofurane to reduce matrix viscosity and to facilitate the mixing step. Ceramic filler was mixed with the resin during 5 minutes in an ultra sound bath. The composites were prepared pouring them into suitable moulds. Microstructures were examined by scanning electron microscopy. Dielectric measurements were performed from 25Hz to 1 MHz and from 20 to 120 ºC using a Hewlett Packard 4284A Impedance Analyzer. Also, composite inductances on a spiral inductor were measured at room temperature by impedance analysis. It was found that the final materials had low porosity and few defects. Permittivity was strongly dependent on the filler concentration and frequency, while electrical relaxation was generated by resin dominions detected in the composite and it was influenced by temperature. Inductance of spiral inductors increased with filler concentration and was slightly affected by the frequency in the range of 1KHz to 1MHz.