Cu-ni-of Nife <sub> 2 </ Sub> The O <sub> 4 </ Sub> Preparation And Properties Of Metal Ceramics

The project of cermets, used as the inert anodes for aluminum electrolysis, has been carrying out combined with low corrosion of oxides and perfect conductivity of alloy. NiFe2O4-based cermets were prepared by doping the NiFe2O4 ceramic matrix with the mixed powders of Cu and Ni as the electrical conducting metallic elements. The corrosive behaviors of several ferrites in melts are investigated with isothermal-saturation method. The effects of calcining atmosphere on synthesized condition of NiFe2O4 are studied with DTA-TG and XRD. On the basis, sintering atmosphere are analyzed the oxidization of metal phase and decomposition of ceramic phase during the sintering process. The effects of technics parameters, such as the ball milling time, the adding styles of metallic elements, the sintering time, the sintering temperature and the contents of metallic phase on the relative density and electrical conductivity of the cermets were studied. The electrical conductive mechanism of NiFe2O4-based cermets was investigated.The mainly conclusions and findings can be summarized as follows:1) The NiFe2O4 ceramic is selected to be the based materials of cermets duo to its lowest saturated solution in Na3AlF6-Al2O3 melts among several ferrites;2) The synthetical condition of NiFe2O4 is found to be suitable as Fe2O3 and NiO calcined at 1150℃ for 6 hours;3) The sintering atmosphere has an effect on the molding performance apparently. Sintering atmosphere are efficaciously controlled at various temperature to avoid the oxidization of metal phase and decomposition of ceramic phase during the sintering process;4) Raising sintering temperature can increase the relative density and conductivity of cermets, however, excessively high sintering temperature may make low-melting-point metals melt and flowed out of the sample or deformation;5) Nickel is a favorable sintering aid. It can improve the wettability between Cu and NiFe2O4 due to a good sintering performance between NiFe2O4 andNi.6) NiFe2O4-based cermets obey the semi-conductive mechanism. When the content of metal is less than 30%, the pyroconductivity of cermets are mainly determined by the conductivity of ceramic phase and the dispersion and content of metallic phase.7) The adding styles, compounds and content of metallic elements have notable influence on the properties of the NiFe2O4-based cermets. The high density and electric conductivity are obtained when the metallic elements were added in the form of the Cu and Ni powders owing to metallic phase dispersed finely and uniformly, Ni-NiFe2O4 cermets were easier to obtain the compacted structure than Cu-NiFe2O4 and Cu-Ni-NiFe2O4 sintered at the same temperature and preconditioned without metal effusion from cermets and distribution homogeneousness of metal phase in cermets when the contents of addictive metal was added from 0 to 20%. The conductivity of the above cermets, which the best conductive behavior of cermet is Cu-Ni-NiFe2O4, is at least 2-3 magnitude higher than that of nickel ferrite;...