Sinterização, microestrutura e propriedades magnéticas de ferrita Ni-Cu-Zn.

Abstract

This dissertation aims the study of the influence of the sintering temperature in the microstructure and magnetic property of ferrite of Ni-Zn samples obtained from the post nanometric with the size of particles in the range from 23 to 29 nm previously prepared by combustion reaction. The post ferrite Ni-Cu-Zn were compacted by uniaxial pressed of 385 MPa. The work was divided in to two parts. The first part consists of evaluating the microstructure and magnetic properties to the sintering temperature at 1000°C/2h with heating rate of 10°C/min. In this stage it was verified that all of the studied systems presented the phase formation though for the composition x = 0.1 and x = 0.4 it was observed the presence of line in the second stage identified as hematite Fe20;,. It was observed the increase in the size of the grains and of the intergranula pores r with the growth in the copper concentration and the sintering at temperature of 1000°C/2h was not sufficient to supply driving power for obtaining the proper microstructure. It was also observed that there was a reduction of the magnetizing saturation, of the coersivity and the losses through hysterisis with the increase of copper concentration. The second part consists of evaluating microstructure and magnetic properties in the sintering temperature at 1200°C/2h with the heating rate 10°C/min for the above system described. In this stage it was verified that there was a complete formation of the cubic crystalline phase of the inverse spinel to all compositions. The increase of the copper concentration caused an increase in the size of pores and of the grains, the formation of a hexagonal microstructure with inter and intramolecular pores and the formation of liquid phase in the outlines grain. As for the magnetic parameters there were no significant changes compared to the corresponding of sintering at temperature of 1000°C.