Effects of silver and potassium ions on ion exchange in float glass

Abstract

The variation of optical and mechanical properties in ion-exchanged glasses was investigated. Ion exchange was carried out in KNO3, NaNO3 melts and their mixed melts with AgNO3. The glasses used were soda-lime-silicate glasses produced by the float process. In order to analyse the effects of ion exchange, colour variation for optical properties, bending strength, surface microhardness and softening point for mechanical properties, and resistivity for electrical properties, were measured. In the optical properties, silver ions play an important role in colouring, ion exchange in the mixed melt of KNO3 and AgNO3, and additional heat treatment in air made it possible to obtain a range of colours from yellow to reddish-brown. Bending strength was increased by five times over the values of the parent glasses, surface microhardness was increased about 50 kg mm−2, and the softening point was increased linearly with the amount of ion exchange resulting from ion exchange in the KNO3 melt, because the potassium ion plays a great role in strengthening in the mechanical properties. On the other hand, in the mixed melt of KNO3 and AgNO3, bending strength and surface microhardness were increased slightly in contrast with the KNO3 melt, and the softening point decreased on increasing the amount of ion exchange.