Abstract
Spreading and rapid solidification behavior of millimeter-scale molten drops of 8 wt.% yttria-stabilized zirconia (YSZ) has been experimentally studied utilizing a novel splittable aerodynamic levitator (ADL). The focus was especially on the effect of initial undercooling on the splat formation. An YSZ sphere approximately 2.3 mm in diameter was levitated in a splittable ADL nozzle and melted by a carbon dioxide laser. The molten drop was dropped by splitting the ADL nozzle and impacted on a substrate 15 cm below at a speed of 1.7 m/s. The spreading and solidification behavior of the impacting drop was observed with a high-speed digital video camera. The undercooling of YSZ drops reached to more than 500 K at a containerless state, and the solidification rate was on the order of 1 m/s at this state. When drops were dropped at superheated states, the drop solidified after flattening completed. Meanwhile, when impacted at large undercooling, the drop spreading was suppressed by the solidification. Drastic difference was observed when a drop was impacted on a substrate covered with acetone liquid. The drop was splashing, recoiling, and rebounding despite fact that splashing would not occur at this impact condition.
