EFFECT OF ION EXCHANGE ON BOROSILICATE GLASS SURFACE COMPOSITION AND PROPERTIES

Strengthening of the borosilicate flat glass using a low-temperature ion exchange method was investigated. Molten KNO3 salt mixed with small amounts of KOH, KF or potassium pyroantimonate acid were separately chosen as the ion exchange sources. The K+–Na+ ion exchange of the borosilicate glass was performed at temperatures below the glass transition temperature. The glass surface composition variation was measured using electron probe microanalysis. The microhardness, bending strength and transmit- tance were tested. The relationships between bending strength and additives were studied. It shows that the mole fraction of K+ on glass surface is increased after the ions exchange and the ion exchange depth even reaches 30 μm. The bending strength of borosili- cate glass is increased after K+–Na+ ion exchange, reaching about 3 times of the strength before ion exchange.