Sharafat Ali

Trends in Effective Diffusion Coefficients for Ion-Exchange Strengthening of Soda-Lime-Silicate Glasses

Monovalent cations enable efficient ion exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda lime silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+ and Cs+) by drawing relations to physico-chemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion exchange rate.

Alkali salt vapour deposition and in-line ion exchange on flat glass surfaces

This study suggests a different route for the modification of flat/float glass surfaces; i.e. exchange of ionic species originatingfrom in-line vapour deposition of salt as compared to the conventional route of immersing the glass in a molten saltbath. The aim of this work is to develop a more flexible and, eventually, more rapid process for improving the mechanicalstrength of flat glass by introducing external material into the surface. We discuss how chemical strengthening can beperformed through the application of potassium chloride on the glass surface by vapour deposition, and in-line thermallyactivated ion exchange. The method presented here has the potential to be up-scaled and to be used in in-line productionin the future, which would make it possible to produce large quantities of chemically strengthened flat glass at aconsiderably lower cost.

Hardness, elastic modulus and refractive index of oxynitride glasses prepared from woody biofuel ashes

This paper reports the hardness, elastic modulus and refractive index values of the oxynitride glasses prepared from woody biofuel ashes. The glasses were prepared in nitrogen atmosphere at 1350-15 ...