Wetting and interfacial behavior of Sn–Ti alloys on zirconia

The isothermal wetting and spreading behaviors of Sn–Ti/ZrO₂ systems were investigated by the sessile drop method, and the interfacial microstructures were characterized by XRD and TEM. The wettability improved significantly with the increase in Ti content or with the increase in temperature as a result of the interfacial phenomena. For example, for tests at 1000 °C, we found that: (1) X_Ti = 0 to X_Ti = 2.0%, the final contact angle decreased from 144° to 42° along with the increase in the coverage of ZrO₂ by a Ti₂O₃ interfacial layer; (2) X_Ti = 2.0% to X_Ti = 4.0%, the contact angle decreased to 22° because of the replacement of Ti₂O₃ by a more metallic layer; (3) X_Ti = 4.0% to X_Ti = 8.0%, no further decrease in the angle was observed as the interfacial layer remains Ti_11.31Sn₃O₁₀. For X_Ti = 4.0%, the temperature increase from 900 to 1000 °C led to a decrease in contact angle from 47° to 22°, respectively, due to the interfacial layer shifting from Ti₂O₃ to Ti_11.31Sn₃O₁₀. For all the systems, the Ti enhanced the loss of oxygen from zirconia leading to the formation of black ZrO_2–x. Spreading kinetics of Sn–Ti/ZrO₂ systems was controlled by the reaction-limited dynamics. The diffusion of released oxygen changed the spreading rate in the rapid-spreading stage.