Investigation the effect of thickness and cutting on chemical tempering of aluminosilicate and soda lime silicate glasses

Nowadays, the thickness of glasses has gradually decreased with developing technology and increasing aesthetic and functional demands. As the glass gets thinner, its weight decreases and it has a better aesthetic appearance. At this point, it is expected to reach similar mechanical strength values in both thicknesses. Increasing the mechanical strength of glasses is possible through different methods secondary treatments. Thermal and chemical tempering processes are the most common techniques used for this purpose. The chemical tempering process, which is initially used in ceramic materials for decoration purposes about 100 years ago, is an applicable mechanical strengthening process in glasses without any thickness restrictions. This makes chemical tempering much preferable over thermal thempering since thermal tempering process can not be applied to glasses having thicknesses of 2 mm and less. Chemical tempering is basically based on an ion exchange process in which the glass material, which is desired to be mechanically strengthened, immersed in a molten salt bath at a temperature below the glass transition temperature of that glass and above the melting temperature of the used salt. During the ion exchange prosess, small sized alkali ions in the glass structure are replaced by large sized alkali ions present in the molten salt bath. Accordingly, the large sized ions penetrate to a certain depth through the glass surface without forming a chemical bond and form residual stresses. These residual stresses which are compensated by the central tension consequently increase the mechanical strength of the glass. There are several factors that might affect the efficiency of chemical tempering process which is based on a simple diffusion mechanism. These factors are chemical tempering process temperature and time, salt purity and composition, glass composition, process stages such as preheating / postcooling and type of furnace. In the literature, chemical tempering studies are generally concentrated on the effect of process temperature and time, salt purity and composition on chemical tempering process efficiency. However, to the best of our knowledge, there is no study on the effect of glass thickness and cutting type on chemical tempering process. The increase in use of chemical tempering process for thin glasses has a significant commercial role for different applications of glass such as electronic display glasses, automobile glasses and glassware.. Therefore, it is important to know the effect of glass thickness on chemical tempering process to ultimately determine the applicability of thin glass for different usage areas. In addition, new contactless glass cutting techniques are developed as with decreasing glass thicknesses. In this sense, it becomes important to know the effect of the edge quality on the efficiency of chemical tempering process originated from different cutting types. The aim of this thesis is to mechanically strengthen alumina silicate and soda lime silicate glasses using chemical tempering process at different process temperatures and times and to investigate the effect of glass thickness and cutting type on chemical tempering process. In the first part of the experimental studies two different glass compositions as soda lime and aluminosilicate with different thicknesses of 1.1 and 0.7 mm were studied at different temperature and times; the effect of thickness on chemical tempering process was investigated by mechanical, optical and structural analyses. In the second group of studies, soda lime silicate glasses with 1.1 mm of thickness were cutted with CO₂ laser, diamond and green laser cutting techniques and were subjected to chemical tempering process at selected temperatureand the effect of cutting type on chemical tempering process was investigated by mechanical analyses. As a result of the experimental studies, it has been determined that the glass thickness has not an effect on chemical tempering efficiency, while the cutting type substantially affectes the efficiency and the samples cutted with CO₂ laser show the better performance due to their supeior edge quality.