NiFe_2O_4惰性阳极的制备及其电解腐蚀机理

PREPARATION OF NiFe_2O_4 INERT ANODE AND ITS ELECTROLYSIS CORROSION MECHANISM

以Fe_2O_3和NiO为主要原料,添加2%(按质量计)MnO_2,采用固相烧结工艺制备了NiFe_2O_4惰性阳极。用X射线衍射和扫描电子显微镜对材料的组成和微观结构进行了研究,测量了样品在冰晶石熔盐中不同电流密度下的电解腐蚀速率,并对其腐蚀机理作了初步探讨。结果表明:惰性阳极由NiO和NiFe_2O_4尖晶石两相组成,MnO_2作为固溶体在尖晶石晶界处富集。电解腐蚀呈现出物理化学溶解过程,熔盐对试样的电解腐蚀首先要在晶界处发生反应生成更稳定的FeAl_2O_4相,而FeAl_2O_4相结构致密,冰晶石熔盐通过该相向NiFe_2O_4尖晶石晶粒内扩散速度减慢,从而降低了腐蚀速率。

NiFe2 O4 inert anodes were prepared by the solid-state sintering method using Fe2O3 and NiO as the main raw materials with 2 % in mass of MnO2 powder added. The NiFe2O4 inert anodes were characterized by X-ray diffraction and scanning electron microscopy. The electrolysis corrosion rates in the cryolite molten salt under different current densities were measured and the corrosion mechanism was preliminarily discussed. It is found that the inert anode is composed of both NiO and NiFe2O4 phases, and the MnO2 dopant is enriched at the spinal crystal boundary as a solid solution. The electrolysis corrosion demonstrates the physicochemical dissolution process. The electrolysis corrosion reaction of the molten salt to crystal grain occurs firstly at the crystal boundary to produce a stable FeAl2O4 phase with a dense structure, which can prevent the cryolite molten salt from penetrating the inert anode, resulting in the reduction of the corrosion rate.