铝在NaCl-AlCl_3熔体中的电化学沉积

采用伏安扫描法、计时电流法和恒电流沉积法研究了铝在 NaAlCl_4 熔体中的电化学沉积过程。铝的电化学还原反应涉及一个成核/生长机理,且成核过程是渐进的。沉积铝的形状取决于电流密度。只有当电流密度为 2—10 mA/cm~2 时,沉积铝才是规则平整的。在高电流密度下(>15 mA/cm~2),由于含铝离子的扩散缓慢,沉积铝是枝晶状或蓬松状的。在低电流密度下(<0.7 mA/cm~2),由于电成核过程的控制作用,沉积铝呈棉絮状。

Electrochemical Deposition of Aluminum from NaCl-AlCl_3 Melt

Voltammetry, chronoamperometry and constant-current deposition were used to study the electrochemical deposition of aluminum from NaAlCl4 melt. The deposition of aluminum was found to proceed via a nucleation/growth mechanism,and the nucleation process was found to be progressive.The morphology of aluminum deposits was examined with photomicroscopy.It was shown that depending on the current densities(c.d.)applied,three types of aluminum deposits could be obtained,i.e.spongy deposits formed at lower c.d. (below 0.7mA/ cm2),smooth layer deposited at intermediate c.d. (between 2 and 10 mA/cm2) , and dendritic or porous deposits obtained at high c.d.(above 15 mA/cm2). The smooth aluminum deposits were,however,about 5 times more voluminous than the theoretical value. The spongy deposits were formed due to difficulties in electronucleation,and could be inhibited by application of pulsed currents.