The model of drying presented in earlier parts of this series is reviewed. In those papers, the gel network was assumed to be either purely elastic or purely viscous. The latter solution seems most appropriate for alkoxide-derived gels, which exhibit considerable irreversible shrinkage during drying, but it does not describe the rise in stress as evaporation begins. In this paper, an analysis is presented of the stresses and strains that develop during drying of a plate of gel in which the solid phase is viscoelastic. Initially the pressure in the liquid phase rises as predicted by the elastic analysis (Part V of this series), then evolves into the distribution predicted by the viscous analysis (Parts I and II of this series). The viscous solution is shown to apply at times greater than the viscoelastic relaxation time, which is small compared to the drying time of alkoxide-derived gels. Therefore, the simple equations provided by the viscous solution are suitable for prediction of the stress development and shrinkage during drying of gels.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry