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

Etienne Portuguez,Arnaud Alzina,Agnès Smith,Philippe Michaud

doi:10.4236/ampc.2016.67017

Abstract

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.

Highlights

The creation of ceramic materials is generally divided into a set of common steps [1]
The methods used do not provide any indications concerning the drying behavior at a local scale as they consider the system on a macroscopic scale: whether it is experimental approaches or numerical resolutions
Liquid Bridge Volume and Area Evaluation The present study proposes an evaluation of the volume and the area of the liquid bridge during drying

Summary

Introduction

The creation of ceramic materials is generally divided into a set of common steps [1]. Except in the case of dry shaping processes such as pressing, a drying step is necessary to remove the liquid phase before the firing stage, which gives to the material its final characteristics. We investigate the case of drying materials by evaporation under various temperatures and relative humidities of the drying air, in particular the local capillary phenomena during the departure of the liquid phase. The material passes, at a local scale, from an almost liquid-saturated condition to a state where shrinking liquid bridges are surrounded by a binary mix of air and liquid vapor [5]. The liquid volumes and pore sizes are small enough to consider that gravity effects are negligible compared to the other forces, namely the capillary forces directly related to the hydrostatic pressure and surface tension of the liquid bridges [6] [7]

Methods

Results

Conclusion