Effect of the Silica Sol-Gel Coatings on the Properties of Glass Substrate

Abstract

Strengthening of the glass substrate with silica sol-gel coatings was investigated. Sol-gel silica coating microstructure (is related to the degree of substrate strengthening), as it is known depends on the silica sol structure. In order to produce different microstructures of the silica coating, a variety of silica sols were prepared starting from TEOS and changing the water and solvent content, catalyst type and concentration, at room temperature. Carefully prepared glass surfaces were coated with silica sol using a dipping technique, with constant withdrawing rate (all physical parameters of the deposition were constant, since they can additionally change the coating microstructure). After specific heat treatment of the samples, the modulus of rupture was calculated using the measured flexural strength data. The degree of the substrate strengthening depends on the quantity of water used for the sol preparation, coating sol pH, state of the substrate surface and the degree of the coating bonding to the substrate (all mentioned parameters are discussed as to how they effect the silica sol structure). Results showed that strengthening of the glass substrate is effected by the micro structure of the silica coating. © 1998 Elsevier Science Limited and Techna S.r.l.