(西安建筑科技大學(xué) 冶金工程學(xué)院，西安 710055)
摘 要: 采用改進(jìn)型陰極電解膨脹率測試儀，結(jié)合電解后試樣剖面元素線掃描和面掃描(SEM)的結(jié)果，研究電解過程中堿金屬K、Na在TiB2-C復(fù)合陰極中的滲透遷移行為；同時(shí)采用循環(huán)伏安法研究K、Na的電極電化學(xué)行為，結(jié)果表明：電解過程中，堿金屬K、Na均滲透進(jìn)入了陰極內(nèi)部，K在陰極中的擴(kuò)散系數(shù)及所引起的最大陰極電解膨脹率分別為2.86×10-5 cm2/s和1.35%，均高于Na的，說明K的滲透力強(qiáng)于Na的。堿金屬K、Na在TiB2-C復(fù)合陰極中表現(xiàn)出了相似的滲透遷移路徑，堿金屬K、Na首先隨電解質(zhì)一同滲透進(jìn)入陰極的孔隙當(dāng)中，隨后又滲透進(jìn)入粘結(jié)劑結(jié)焦碳中，隨著電解的進(jìn)行，最終滲透進(jìn)入陰極碳質(zhì)骨料中，但K、Na不會(huì)滲透進(jìn)入TiB2顆粒中。滲透進(jìn)入粘結(jié)劑和碳質(zhì)骨料中的K、Na均會(huì)引起陰極的電解膨脹，并隨陰極中堿金屬濃度的飽和而達(dá)到平衡。而對(duì)堿金屬K、Na電極行為的研究表明：電解過程中，K、Na會(huì)在陰極表面共同析出，但在陽極過程中，與Na相比，C-K插層化合物所表現(xiàn)出的氧化電勢更正，C-K插層化合物的穩(wěn)定性更高，插入石墨層間形成插層化合物的K很難脫出，其對(duì)陰極的破壞力較Na的更強(qiáng)。
關(guān)鍵字: 鋁電解；陰極；堿金屬；滲透；遷移；插層
（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
