Researcher : Céline RAGOEN

Glass is a material with many qualities like transparency, heat resistance, durability, etc. Yet, this material is brittle and its mechanical strength is strongly affected by its surface state. One way to improve the mechanical properties of glass is to chemically strengthen the glass. This technique represents a concrete solution to improve both the impact and scratch resistance of this material. It consists in exchanging smaller hosts alkali ions such as Na+ by bigger ions such as K+. The exchange is performed in a molten salt bath at a temperature below the glass transition temperature. This exchange is at the origin of a high compression layer located near the glass surface. One goal of this thesis is to optimize the chemical tempering process thanks to an adaptation of the initial glass composition. This will result in lowering the production costs and further improvement of the mechanical properties. For this purpose, it will be necessary to develop a good understanding of the physico-chemical phenomena that occur during the process and specifically of the link existing between glass structure and diffusion. The interdiffusion properties are evaluated by measuring potassium profiles that were carried out by Energy Dispersive X-ray on a scanning electron microscope. The following figure highlights the effect of the glass composition on the interdiffusion properties. Actually, it is clear that the potassium profiles of a glass containing CaO and MgO are different.