Evaporation Kinetics and Breaking of a Thin Water Liquid Bridge between Two Plates of Silicon Wafer

In ceramic processing, the study of the different phases of the drying stage considers the material at a macroscopic scale. Very often, the various parameters (among which the temperature and the relative humidity) are chosen in an empirical way, mostly through visual observations. This stage is governed by capillary phenomena which take place within the material, responsible for both the shrinkage and the risk of cracks which can damage the final piece. As part of a better understanding of the local mechanisms during drying, liquids contained in the pores have been reproduced in an ideal case. Drying kinetics and parameter measurements from 303 to 343 K of deionized water liquid bridges between two plates of silicon wafers are presented. Experimental work was carried out using specific device to create liquid bridges, coupled with image analysis and within an adapted instrumented climatic chamber. While the volume and the exchange surface of liquid bridges decrease regularly throughout the drying process, contact angles only diminish at the end. One of the four contact angles may have a different variation, which results in a pinned contact line in its area and reveals a local change of the surface state. From these measurements and observations, the liquid bridge break is proposed as a cracking criterion of porous materials during drying. Indeed, the challenge is to limit the risk of cracking and damaging pieces during this crucial step in material processing.