Mechanical properties and adhesion of hydrated glass surface layers

• Published in: Journal of non-crystalline solids 1990-04, Vol.120 (1), p.126-137
• Main Authors: Michalske, T.A., Bunker, B.C., Keefer, K.D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Chemical industry and chemicals; Exact sciences and technology; Glasses; Structure, analysis, properties
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/0022-3093(90)90198-U

This paper reviews results for interfacial adhesion and fracture of silicate glasses that demonstrate the effect of hydrated glass surface layers on the mechanical properties of glass. First, it is shown how the generation of hydrated surface layers formed on alkali borosilicate glasses can control crack propagation rates. Crack growth data, solution analysis and surface stress measurements are used to support a fracture model that involves the generation of surface stress on the crack walls behind the crack tip. A fracture mechanics based model is used to show that stressed layers can contribute to the crack tip stress intensity in a way that either increases or decreases the rate of crack propagation. In the case of alkali containing silicate glasses, tensile stresses formed on the crack walls increase the crack tip stress and contribute to the formation of a low velocity plateau in the stress intensity vs. crack velocity curve. Second, fracture mechanics test techniques are used to examine the adhesive bond formed between hydrated surface layers and bulk silicate glass. The adhesive bonds formed by sol-gel precursors composed of colloidal silica, hydrolyzed organosilanes and alkali silicate solutions are compared to determine the mechanism of interfacial bonding to dense silica substrates. The formation of siloxane bonds across the interface depends upon the nature of the silicate polyanions in solution. For the case of soluble alkali silicate derived films, heat treatments at temperatures as low as 200°C can result interferfacial adhesion energies as large as the fracture energy of silica glass. These results have important implications to the aging and repair of surface damage in glass as well as the adhesion of sol-gel derived thin films.