(西安建筑科技大学 冶金工程学院，西安 710055)
摘 要: 采用改进型阴极电解膨胀率测试仪，结合电解后试样剖面元素线扫描和面扫描(SEM)的结果，研究电解过程中碱金属K、Na在TiB2-C复合阴极中的渗透迁移行为；同时采用循环伏安法研究K、Na的电极电化学行为，结果表明：电解过程中，碱金属K、Na均渗透进入了阴极内部，K在阴极中的扩散系数及所引起的最大阴极电解膨胀率分别为2.86×10-5 cm2/s和1.35%，均高于Na的，说明K的渗透力强于Na的。碱金属K、Na在TiB2-C复合阴极中表现出了相似的渗透迁移路径，碱金属K、Na首先随电解质一同渗透进入阴极的孔隙当中，随后又渗透进入粘结剂结焦碳中，随着电解的进行，最终渗透进入阴极碳质骨料中，但K、Na不会渗透进入TiB2颗粒中。渗透进入粘结剂和碳质骨料中的K、Na均会引起阴极的电解膨胀，并随阴极中碱金属浓度的饱和而达到平衡。而对碱金属K、Na电极行为的研究表明：电解过程中，K、Na会在阴极表面共同析出，但在阳极过程中，与Na相比，C-K插层化合物所表现出的氧化电势更正，C-K插层化合物的稳定性更高，插入石墨层间形成插层化合物的K很难脱出，其对阴极的破坏力较Na的更强。
关键字: 铝电解；阴极；碱金属；渗透；迁移；插层
（School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China）
Abstract:During aluminum electrolysis, the electrochemical insertions of alkali metals (potassium and sodium) as well as their migratory behavior in TiB2-C composite cathodes was investigated by means of line scanning and map scanning through SEM and self-made modified Rapoport apparatus. The electrochemical behavior of alkali metals on the electrode was also studied by cyclic voltammetry. The results suggest that, in the aluminum electrolysis process, both K and Na penetrate into the cathode, the diffusion coefficient of K in the cathode and the induced maximal electrolysis expansion are 2.86×10-5 cm2/s and 1.35%, respectively, both of which are higher than those of Na, illustrating that the penetration ability of K is stronger than that of Na. Meanwhile, the penetration and migration path of K and Na in TiB2-C composite cathode is similar: firstly, alkali metals (K and Na) penetrate into the pores of the cathode together with the electrolyte, subsequently into the binder coke, with the progress of the electrolysis, finally into the carbonaceous aggregates of the cathode, while K and Na can not penetrate into TiB2. K and Na penetrate into both binder and aggregates, leading to the expansion of TiB2-C composite cathodes, which will become constant when the content of alkali metals (K and Na) in the cathode is saturated. While the results on the electrode behavior of alkali metals K and Na indicate that, in the aluminum electrolysis process, K and Na will co-deposit on cathode, while during the anodic process, the intercalation compound of K represent more positive potential than that of Na, illustrating better stability of intercalation compound of K. K inserted into the interlayer of carbon materials is difficult to break away, the destructive force is stronger than that of Na.
Key words: aluminum electrolysis; cathode; alkali metals; penetration; migration; insertion
