Preparation And Properties Research On Co-Ni-xNiFe₂O₄ Inert Anode

This dissertation mainly focuses on metal based inert anodes for aluminum electrolysis. A new kind of inert anodes was prepared by cold isostatic press-sintering method based upon the fact that inverse spinel oxide NiFe₂O₄ has good corrosion resistance and Co-Ni alloy has excellent oxidation resistance. The dissertation mainly includes the following parts: preparation of highly pure NiFe₂O₄ powder, preparation of Co-Ni metal based inert anodes, elaborate investigation into the influence of the porosity of the inert anodes which different sintering time and different sintering temperatures can affect and the influence of the porosity of the inert anodes which different NiFe₂O₄ contents can affect, testing electric conductivity of inert anodes with different NiFe₂O₄ contents, study the relationship between NiFe₂O₄ contents and high temperature oxidation resistance and corrosion resistance of inert anodes. The mainly conclusions and findings can be summarized as follows:1.The prepare condition of NiFe₂O₄ adopted in this dissertation is solid phase calcination at 1200℃for 4 hours in the air. The black prepared powder is tested by XRD and is confirmed pure.2.The preparation craft was carried out on sample 47.5%Co+47.5%Ni+ 5.0%NiFe₂O₄. It turns out that the best sintering craft is sintering at 1300℃for 8 hours from the perspective of low porosity and saving energy.3.By using two-port electrodes method the electric conductivities of sample 47.5%Co+47.5%Ni+5.0%NiFe₂O₄ and sample 42.5%Co+15.0%NiFe₂O₄+42.5% Ni were tested and as a result both satisfy the requirements of the inert anode at high temperature. The electric conductivities are 550s·cm-1å’Œ300s·cm-1 respec-tively.4.It is discovered that all oxidized dynamics curves obeyed a parabolic rate law for four different samples at 960℃. Oxidation resistance increases with NiFe₂O₄ content increases.5.The nick of the oxided sample was observed by SEM and crack was found at the interface between the oxidation film and the substrate at nick. The oxidation film is mainly composed of CoNiO2.