Wood液态合金在NaOH溶液中的电化学反应及表面张力变化行为

通过改变液体金属在NaOH溶液中所处的环境介质，利用石墨电极对其施加电场，研究了液态金属的表面张力、界面电化学反应、氧化膜的产生、溶液中电润湿等动态过程。实验发现Wood合金液滴在阳极发生电化学反应产生的氧化膜会迅速减小表面张力并发生铺展，在阴极发生还原反应会使带氧化膜的金属在3 s内恢复到原状，电毛细作用力使氧化膜破裂，各氧化物与NaOH反应产生Sn（OH）₆^2-、SnO₃^2-、SnO₂^2-、PbO₃^2-、Cd（OH）₄^2-使溶液的颜色发生改变，溶液中生成Bi₂O₃-Bi（OH）₃白色共聚物。薄膜电介质层润湿和溶液中电润湿机理在本质上相同，表面张力随着电压的增大而减小并发生明显的电润湿铺展过程，但由于金属液滴通过电化学反应所能吸附的OH^-数量有限，润湿角存在饱和性。

Electrochemical reaction and surface tension change of Wood liquid alloy in NaOH solution

By variation of liquid Wood metal's environment in NaOH solution and application of electric field with graphite electrode, surface tension of the liquid metal, interfacial electrochemical reaction, generation of oxidation film, and other dynamic processes were studied. The results showed that thin oxidation film on the surface of Wood alloy droplets which was formed by anodic oxidation reaction quickly reduced surface tension of Wood alloy and the oxidation film on surface of liquid alloy droplets would return to neutral state by cathodic reduction reaction within 3 seconds. The electrical capillary force broke the oxide film so that metal oxides reacted with NaOH to generate ions of Sn(OH)₆^2-、SnO₃^2-、SnO₂^2-、PbO₃^2-、Cd(OH)₄^2- which altered solution colors with a white precipitate of Bi₂O₃-Bi(OH)₃ copolymer. The dielectric wetting and solution electrowetting on thin film essentially had the same mechanism. With the increase of voltage, the surface tension was decreased and electrowetting spreading process was occurred obviously, but the wetting angle exhibited saturation as a result of limited number of OH^- ions adsorbed on alloy droplets by electrochemical reactions.