Fe-TiB2/Al2O3复合阴极的电解性能及元素迁移行为

Electrolytic properties and element migration behavior in a Fe-TiB2/Al2O3 composite cathode

  • 摘要: 以氧化铝溶胶为黏结剂、金属Fe为烧结助剂, 采用冷压-烧结制备出铝电解用Fe-TiB2/Al2O3复合阴极材料, 利用20A电解试验研究其电解性能; 利用能谱仪(EDS) 对电解试验前后的复合阴极材料进行了成分物相分析, 研究电解过程中各种元素迁移行为.研究结果表明: 金属Fe作为烧结助剂在烧结过程中能有效的填充骨料之间的空隙, 使该复合阴极材料的烧结致密度显著提高; 20 A电解试验过程电压稳定, 电流效率93. 2%, 原铝中铝元素质量分数为99. 47%, 杂质元素质量分数为0. 53%.在电解试验后, 铝液能有效润湿阴极表面, 表明Fe-TiB2/Al2O3复合阴极材料具有较理想的可润湿性; 从复合阴极电解后的能谱分析可知, 在电解过程中, 碱金属主要是通过液态电解质渗透进入阴极材料中, 随后又逐渐渗透进入黏结剂相中, 并在骨料之间氧化铝溶胶和金属烧结助剂均未能充分填充的空隙进行富集. K元素较Na元素对黏结相的渗透力更强; 与此同时, 阴极表面生成的Al通过复合材料的空隙进入阴极内部, 而Fe金属会利用材料内部的空隙反向扩散至铝液层中.在试验中, 阴极表面的铝液层的稳定存在是该阴极高效稳定运行的基础.

     

    Abstract: Wettable cathodes are a very important part of the non-carbon electrolysis process. This study prepared Fe-TiB2/Al2O3 composite cathode materials by cold pressing and sintering using alumina sol as a binder and metal Fe as a sintering agent for aluminum electrolysis. The electrolytic performance of aluminum electrolysis was studied using a 20 A electrolysis test, and the composite cathode materials before and after the test were analyzed via EDS. The migration behavior of various elements in the electrolysis process was studied by composition analysis. The results show that Fe metal can effectively fill the gap between the aggregates during the sintering process. Hence, the sintering density of the composite cathode material can be significantly improved. In the 20 A electrolysis test, the voltage is stable, the current efficiency is 93.2%, the original aluminum quality is 99.47%, and the impurity in the aluminum liquid is 0.53%. After the electrolysis test, the aluminum liquid can moisten the cathode surface effectively. Therefore, the Fe-TiB2/Al2O3 composite is an ideal wettable cathode material. Based on the EDS analysis of the composite cathode electrolysis, the alkali metal in the liquid electrolyte permeates into the cathode material during the electrolysis process. Subsequently, alkali metals gradually penetrate into the binder phase and fill the voids that are not completely filled by alumina sol or metal sintering additives. As the electrolysis proceeds, the penetration depth of the element K is greater than that of Na. The Al generated at the cathode surface also enters the cathode through the gap of the composite material. However, owing to the gap in the cathode, the Fe metal in the cathode will also be reversely dispersed into the liquid aluminum. This study indicates that the stability of the aluminum liquid layer on the cathode surface is the foundation for efficient and stable operation of the cathode.

     

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