Modification of Float Glass Surfaces by Ion Exchange

Glass is a common material in each person’s life, e.g. drinking vessels, windows, displays, insulation and optical fibres. By modifying the glass surface it is possible to change the performance of the entire glass object, generally known as Surface Engineering. Ion exchange is a convenient technique to modify the glass surface composition and its properties, e.g. optical, mechanical, electrical and chemical properties, without ruining the surface finish of the glass. This thesis reports the findings of two different research tasks; characterisation of the single-side ion exchange process and the novel properties induced. The characterisation of the ion exchange process was mainly performed by utilising a novel analytical equipment: the Surface Ablation Cell (SAC), allowing continuous removal of the flat glass surface by controlled isotropic dissolution. SAC-AAS has provided concentration vs. depth profiles of float glass ion exchanged with K+, Cu+, Rb+ and Cs+. In addition, SEM-EDX has provided concentration vs. depth profiles of Ag+ ion exchanged samples and validation of a copper concentration vs. depth profile. From the concentration vs. depth profiles, the effective diffusion coefficients and activation energies of the ion exchange processes have been calculated. Depending on the treatment time and treatment temperature, penetration depths in the range of 5-10 μm (Rb+, Cs+), 20-30 μm (K+, Cu+) and 80-100 μm (Ag+) can be readily obtained. The effective diffusion coefficients followed the order Ag+>K+>Cu+>Rb+>Cs+. This is in accordance with the ionic radii for the alkali ions (K+<Rb+<Cs+) but reverse for the noble metal ions (Cu+<Ag+). The glass properties modified by single-side ion exchange have mainly been characterised by UV-VIS spectroscopy and flexural strength measurements. Cu+ and Ag+ ion exchange give rise to surface colouration, Cu+ copper-ruby and Ag+ yellow/amber. The surface-ruby colouration was found to depend on the residual tin ions in the tin-side of the float glass. The flexural strength was studied using the coaxial double ring-test method which also was suitable for holed specimens. The flexural strength of K+ ion exchanged float glass samples was found to substantially increase compared to untreated