Preparation and properties of 4.25Cu-0. 75Ni/NiFe2O4 cermet

4.25Cu-0.75Ni/NiFe2O4 cermets were prepared by doping NiFe2O4 ceramic matrix with the mixed powders of Cu and Ni or Cu-Ni alloy powder as the electrical conducting metallic elements. The effects of technological parameters, such as the adding modes of metallic elements, the ball milling time, the sintering time and the sintering temperature, on the relative density and resistivity of the cermets were studied. The results show that the resistivity of 4.25Cu-0.75Ni/NiFe2O4 cermets decreases with increasing temperature, and has a turning point at 590 degrees C, which is similar to that of NiFe2O4 ceramic. The sintering temperature and adding modes of metallic elements have a great influence on the properties of 4.25Cu-0.75Ni/NiFe2O4 cermets. When the sintering temperature increases from 1 200 degrees C to 1 300 degrees C, the relative density increases from 89.86% to 95.33%, and the resistivity at 960 degrees C decreases from 0.11 Omega center dot cm to 0. 03 Omega center dot cm, respectively. When the metallic elements are added with the mixed powders of Cu and Ni, the cermets of finely and uniformly dispersed metallic phase, high density and electric conductivity are obtained. The relative density and resistivity at 960 degrees C are 90.23% and 0.04 Omega center dot cm respectively for the cermet samples sintered at 1 200 degrees C for 2 h, which are both better than those of the cermets prepared under the same technique conditions but with the metallic elements added as 85Cu-15Ni alloy powders.