Enhancing mechanical endurance of chemical-tempered thin soda-lime silicate float glass by ion exchange

Abstract

The aim of this study is to determine the mechanical properties differences in between the air and tin surfaces of thin soda-lime silicate float glasses that subjected to ion exchange using KNO3 salt bath. The ion exchange process was carried out at different times and temperatures. Chemically tempered glasses were investigated by means of compressive stress (CS), microhardness measurements, cracking probability, fractographic analysis, and flexural strength. The relationship among these properties was also discussed. The Weibull distributions of the samples were determined for a better understanding of the strength results. The AFM was used to determine the surface roughness. The weight of glass samples was increased gradually with increasing ion exchange time and temperature due to the inter-diffusion of K+–Na+ ions. The fracture load of chemically strengthened glass with ion exchange at 435 °C-8 h showed an increase of ~ 4.4 times that of untreated glass (raw glass), and it was selected as the optimum process conditions. The number of broken pieces was increased by increasing flexural strength, and smaller pieces were obtained with a great deal of branching. The air side always has greater compressive stress than the tin side. The maximum hardness value was reached with ion exchange at 435 °C for 12 h on a tin surface was 8.25 GPa with an increase of ~ 18% with respect to the raw glass. The crack resistance of chemically tempered glasses showed an increase in the range of 410–1290% and 241–1895% for air and tin surfaces, respectively. According to the AFM analysis, surface roughness of the samples after ion exchange did not change dramatically. SEM-EDS analysis revealed that the surface potassium concentration and diffusion depth increase with temperature.