Droplet Conductivity Strongly Influences Bump and Crater Formation on Electrodes during Charge Transfer
Droplet Conductivity Strongly Influences Bump and Crater Formation on Electrodes during Charge Transfer
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DOI：
10.1021/acs.langmuir.8b01234
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发表时间：
2018-06-26
期刊：
影响因子：
3.9
通讯作者：
Ristenpart, William D.
中科院分区：
文献类型：
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作者：
Elton, Eric S.;Tibrewala, Yash, V;Ristenpart, William D.
液滴在高压电场中接触电极时获得电荷，但电荷传递的确切机制尚不清楚。埃尔顿等人最近的研究表明，在与水滴的电荷转移过程中，电极会产生物理凹坑。这些凹坑被认为是当电介质击穿电弧发生时产生的，因为液滴接近电极，并且相关的高电流密度瞬间局部熔化电极，在电极表面留下明显的陨石坑状变形。研究表明，液滴电导率对点蚀形貌有很强的调节作用，但对电荷转移量的影响很小。电子和原子力显微镜显示，去离子水滴不产生可观察到的变形，但当水滴中的盐浓度增加到10(-3)M以上时，变形变得越来越大。电介质击穿电弧释放的闪光强度随液滴电导率的增加而增加。令人惊讶的是，尽管点蚀形态和相应的电弧强度有很大差异，但任何导电性的液滴都能获得相似的电荷量。这些结果表明，电介质击穿过程中转移的能量是电极点蚀的主要原因，而不是电荷转移过程中释放的总能量。
Aqueous droplets acquire charge when they contact electrodes in high voltage electric fields, but the exact mechanism of charge transfer is not understood. Recent work by Elton et al. revealed that electrodes are physically pitted during charge transfer with aqueous droplets. The pits are believed to result when a dielectric breakdown arc occurs as a droplet approaches the electrode and the associated high current density transiently locally melts the electrode, leaving distinct crater-like deformations on the electrode surface. Here we show that the droplet conductivity strongly modulates the pitting morphology but has little effect on the amount of charge transferred. Electron and atomic force microscopy shows that deionized water droplets yield no observable deformations, but as the salt concentration in the droplet increases above 10(-3) M, the deformations become increasingly large. The observed intensity of the flash of light released during the dielectric breakdown arc also increases with droplet conductivity. Surprisingly, despite the large difference in pitting morphology and corresponding arc intensity, droplets of any conductivity acquire similar amounts of charge. These results suggest that the energy transferred during dielectric breakdown is primarily responsible for electrode pitting rather than the total amount of energy released during charge transfer.