Silica in humid air environment (I): Diffusion in the absence of stresses. Open Access at KIT

Diffusion of water into silica results in diffusion zones near the silica surface. Due to the chemical reaction between H2O and SiO2 the material expands, i.e. swelling takes place. Since the unaffected bulk material suppresses free expansion, biaxial compressive swelling stresses will occur near the surface. For constant concentrations of molecular water at the surface, we already outlined the problem in earlier papers.