| At present,the technology of aluminum electrolysis is Hall-Heorult process,the carbon anode involves in the electrode reaction and gives out CO2 during the aluminum electrolysis,so that there are many problems in the traditional technology of aluminum electrolysis,such as producing greenhouse gas,consuming high-quality carbon and so on.Developing a new type inert anode to replace traditional carbon anode is an effective way to solve these problems.In view of its properties:excellent chemical stability,good corrosion resistance in Na3AlF6-Al2O3 molten salt,small swell-coefficient at high temperature and so on,NiFe2O4 ceramic is one of the most promising industrial application inert anode materials,which has been researched widely by scholars.However,the application of NiFe2O4 ceramic is impeded in aluminium electrolysis because its low-conductivity and large brittleness.In this paper,the effect of metal network structure in cermet on the performance of inert anode is studied,on the basis of these,the Ni-NiFe2O4 cermet inert anode with hige-conductivity and interpenetrating metallic network structure is made by the process of powder metallurgy,then its performance and structure are analysed and the electrolysis experiments is conducted.The contents and results of research are shown as follow:(1)The process of traditional electroless nickel plating is improved in this paper,add 4wt%Ni to Fe2O3?NiO synthesis Ni-NiFe2O4 ceramic,which the content of Ni is 4wt%.Then prepare Ni-P electroless coating by taking Ni on the surface of ceramic particles as active site after crushing and screening,and make it success that preparing Ni-P electroless coating on ceramic particles without sensitizing and activating.(2)Effects of dosage of NiCl2·6H2O,pH,temperature on deposition rate and quality of coating are invetigated mainly by using single factor experiments.Optimum electroless plating conditions are NiCl2 6H20 32g/L,NaH2PO2·H2O 32g/L,C3H6O3 20ml/L,C6H5Na307 2H2025g/L,CH3COONa 15g/L,pH 9.0,70?.Smooth and uniform coating can be obtained under optimum conditions,and the average coating thickness is 8?m.(3)Slender specimens are prepared with electroless nickel plating particles,Ni powder and NiFe2O4 as raw materials.Influences of Ni-P coating on formation of metal network structure in cermet and the performance of conductivity and bending strength is studied.The researches show that the porosity of the anodes increases is decreased with the content of electroless plating particles increasing,and the bending strength increase first,then decrease,the bending strength reaches the maximum which is 89.1384MPa when addtion of electroless plating particles is 60%.The metal network structure are more perfect and the conductivity of specimens improves greatly with the increase of electroless plating particles the normal temperature conductivity of cermet reaches the maximum which is 20000S cm-1 when addtion of electroless plating particles is 70%.(4)Use electroless nickel plating particles,Ni powder,and NiFe2O4 as raw materials in grain graduation to prepare ?50x40mm cermet inert anode under the process of ball-milling,cold isostatic pressing and sintering in argon cover gas atmosphere.The electrolysis test of inert anode was carried out,the results show that the cell voltage is stable in electrolysis test and the conductivity of inert anode is good.Surface roughness of the inert anode goes worse,but the outward appearance of the inert anode seldom changes after 24 hours electrolysis proceeding,which reflects the favorable thermal shock resistance and molten salt corrosion resistance.The result of plane sweep shows that the corrosion resistance of high-conductivity inert anode does not decrease. |
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