For Aluminum Electrolysis Of Nife <sub> 2 </ Sub> The O <sub> 4 </ Sub>-based Inert Anodes Preparation And Performance Study

The purpose of this study is to develop inert anodes for aluminum electrolysis. NiFe₂O₄ based cermets with Cu additive to improve electrical conductivity were successfully prepared by powder metallurgy method. The influences of different sintering temperatures and time on powder and bulk NiFe₂O₄ were studied. The properties on electricity, oxidation resistance at high temperature and corrosion resistance in electrolyte of different composition electrodes were analyzed. The obtained results are as follows:NiO and Fe₂O₃ powders were used to NiFe₂O₄ under different sintering temperatures and time. The results show that the best process to synthesize NiFe₂O₄ spinel is at 1100℃-1200℃for 6 hours. Cold isostatic pressing and subsequently vacuum sintering method was adopted to synthesize Cu-NiFe₂O₄ inert anodes. The results indicate that the best process to synthesize Cu-NiFe₂O₄ is at 1300℃for 8h.The open porosity of the inert anodes is smaller while the density is higher under the best preparation process (at 1300℃for 8h).The Cu additive can improve the electricity of NiFe₂O₄ cermets effectively. The electrical conductivity increases with increasing environmental temperature. For the cermet with less more 20% Cu, their electrical conductivities are (200³00)×10-2?-1·cm-1 at 1233K, which indicates that adding the Cu can make NiFe₂O₄ be acceptable for inert anodes.The oxidation resistance experiment at high temperature shows the curve of oxidation mass gain as a function of time follows parabolic rate law. The oxidation rate is slow that indicates the inert anode samples exhibit good oxidation resistance properties and that the oxidation mechanism is protective oxidation.NiFe₂O₄ based inert anodes show very small corrosion rate after hot and electrolysis corrosion in electrolyte. The smallest corrosion rate for 5%Cu-NiFe₂O₄ is 0.96×10-3g/cm2·h and the estimated annual corrosion rate is 15.26 mm/y.