Study On The Preparation And Electrolysis Of Cu-Ni-NiFe₂O₄ Inert Anode Under Low Oxygen Partial Pressure

As a hot topic of electrolytic aluminum industry,inert anode materials especially achieve environment protection,reduce emissions and improve the efficiency of important development method.After years of research,greater progress has been made in the preparation and property research of inert anode.However it fails to achieve industrial aluminum electrolytic industry to inert anode under the corrosion resistance and mechanical properties and so on,seriously hindering the use of inert anode of aluminum electrolysis process of industrialization.In the study of NiFe₂O₄ based inert anode,17?85Cu-15Ni?-NiFe₂O₄ based metal inert anode appeared together overflow phenomenon leading to the inert anode performance degradation in the high temperature sintering process.This paper is based on Cu-Ni-NiFe₂O₄ inert anode as the research object and use one-way axial pressure and lower oxygen partial pressure sintering method preparation of Cu-Ni-NiFe₂O₄ inert anode.This paper adopts the method of powder metallurgy of high temperature sintering NiFe₂O₄ substrate preparation with the NiO and Fe2O3 as raw material,in air atmosphere.Under 120?,this experiment gets black sintered sample NiFe₂O₄ substrate materials by sintering 6 hours,and crushes and screens NiFe₂O₄ powder materials less than 74?m.NiFe₂O₄ adds 17%metal powder?85Cu+15Ni?and mix.Inert anode under 1125?,1150?,1175?,1200? and 1175? sinters respectively,by 200MPa pressure molding,under low oxygen partial pressure.The preparation of inert anode under different sintering temperature,respectively,study the shrinkage rate,density,porosity,bending strength and thermal shock resistance and other properties.Anode samples of open porosity decreased from 13.6%to 7.28%,porosity decreased from 15.59%to 5.067%,bending strength from 75 MPa to 117 MPa.Considering all properties and Micro-Structure of sintered samples,Cu-Ni-NiFe₂O₄ inert anode of sintering the optimal sintering temperature is 1200?.Under the condition of the sintering temperature,Cu-Ni-NiFe₂O₄ inert anode still has a small amount of metal reunion overflow.To prevent the reunion and precipitin of metallic phase,by improving the metal nickel content in the metal component improve the wettability of metal copper and ceramics phase.Cu-Ni-Fe₂O₄ inert anode with varied nickel content of 15%,17.5%,20%,22.5%and 25%was prepared.The performance of Cu-Ni-NiFe₂O₄ inert anode was detected.Anode samples of open pore rate fell from 7.28%to 7.28%,the porosity decreased from 5.15%to 4.86%,anodic specimen bending fold strength from 117 MPa to 152 MPa.The strength of the anode sample residual rate increased with the increase of nickel content in slow decline,nickel content increased from 22.5%to 25%,and the strength of the residual rate has fallen sharply from 94.5%to 94.5%.Considering all properties and Micro-Structure of sintered samples,the content of nickel in the metal component of Cu-Ni-NiFe₂O₄ inert anode was 20%.Mainly because the metal nickel can improve the wettability between metal and ceramic,and when the metal nickel content is too high,there will be the non-melting metal,which leads to the inert anode performance degradation.By changing the Cu-Ni-NiFe₂O₄ inert anode metal components in nickel content and sintering temperature so as to solve the agglomerated Cu-Ni-NiFe₂O₄ inert anode metal overflow problem,and improves the performance of inert anode.Inert anode for 8 hours electrolysis experiment was carried out with which the Na₃AlF₆-CaF₂-Al₂O₃ electrolyte system,consists of w?Al₂O₃?=5%,w?CaF₂?=5%,w?Na₃AlF₆?=90%,which molecules of cryolite ratio was 2.2,the electrolysis temperature is 960?,current density is 0.5A·cm-3,the distance between the anode and cathode is 3.0cm.In the process of electrolysis,the groove voltage is maintained between 3.7?3.9V.The testing results show that the cell voltage is stable in the process of electrolysis and the conductivity of inert anode is good.The outward appearance of the inert anode seldom changes.The still flat surface without cracking,swelling and peeling layers reflects the favorable thermal shock resistance and molten salt corrosion resistance,through SEM.ICP analysis after the electrolysis.Results show that Ni less than 0.01%,Fe is 0.013%,Cu is 0.042%.