Influence du traitement chimique par échange ionique sur la microstructure et les propriétés mécaniques et optiques

Abstract

The potassium ion exchange process makes it possible to improve the mechanical strength of the glasses thanks to the substitution of Na + ions by K+ ions of larger ionic radius. It thus makes it possible to block the superficial cracks of the glass and to reduce the breakage of the material. This work is devoted to understanding the principle of diffusion of K+ ions within the silicate structure of glass. The parameters, time, temperature and glass composition, influence the kinetics of the ion exchange. The conditions of thermal and temporal quenching act on the diffusion kinetics of the ions. They reduce the ease of movement of the ions through the silicate structure of the material with a change of behavior beyond 5 hours of immersion in molten salts. Scanning electron microscopy allows to determine the concentrations of the ions exchanged for different immersion times and to highlight the structural modifications of the glasses subjected to this ion exchange process. During the introduction of K+ ions, the glass structure depolymerizes and creates non-bridging oxygen. This makes it possible to show that the ion exchange leads to the improvement of the mechanical reinforcement of the glasses.