Polarity effects on the wettability and interfacial chemistry at Cu-YSZ interface by applying a direct current

The application of a direct current, regardless of its polarity, can significantly improve the wettability of ZrO2-8 mol% Y2O3 (YSZ) by molten Cu at 1373 K, and this effect was more pronounced when YSZ was connected to cathode. The mechanisms for the wetting improvement varied with the change in the current polarity. When YSZ was connected to the cathode, the oxygen ions in the YSZ body driven by the external electric power moved to the solid-liquid interface and dissolved into liquid Cu, forming OCu clusters. As a consequence, the solid-liquid interfacial energy and liquid surface tension were greatly reduced and wettability improved. On the other hand, when YSZ was connected to anode, the improvement in the wettability was mainly driven by the formation of nonstoichiometric zirconia and metallic Zr at the interface. Nevertheless, the newly formed ZrO2 at the triple line region inhibited further spreading of liquid front.