The Influence Of Ion Exchange On The Structure And Properties Of Borosilicate Flat Glass

Compared with sodium calcium silicate glasses, the borosilicate glasses with many excellent properties, such as mechanical property, are widely used in many field especially new and high tech special glasses. For example the borosilicate flat glasses can be applied to display base plate, solar cell base plate and cover and flame resistant glasses. With the applied fields augment and the new products development, borosilicate flat glasses strengthened by ion exchange are focused on. The borosilicate flat glasses strengthened by ion exchange are expected to play an important role in glass curtain wall, flame resistance glasses and bullet proof glasses fields.In this study, 4mm thickness borosilicate flat glasses were treated below glass transition temperature using ion exchange strengthening method. The relationship between the molten salt component, the ion exchange temperature and time, the ion exchange depth were researched by EPMA, SEM, ATR combined with the test of bending strength, microhardness, thermal property and transmittance. The influence on the structure and properties of borosilicate flat glasses after ion exchange were studied. The molten salt component and the ion exchange temperature and time were determined by experiment, and the high strength borosilicate flat glasses were prepared. The mechanism of additives and ion exchange strengthening effect were discussed.The results show:1.when the addition of additives and ion exchange system were appropriate, the bending strength,microhardness and thermal property of the borosilicate flat glass were improved.; the K⁺ ion concentration decreased from the glass surface to the glass interior; the thickness of the ion exchange achieved 10～20μm; Si-O bond shifted to lower wave number while the B-O bond shifted to higher wave number.2.The properties were even more excellent when 0.4% KOH was added into the KNO₃ molten salt, the maximum bending strength reached 157.43MPa, and the microhardness achieved 569.35Kg·mm^-2, while for the K₂H₂Sb₂O₇·2H₂O and KNO₃ mixed molten salt, the strengthening effect was obvious when 0.6% K₂H₂Sb₂O₇·2H₂O was added. The bending strength increased much, reaching 168.38MPa, and the microhardness was 587.68Kg@mm^-2, about 1.73 times and 1.3 times of the origin glass; the ion exchange depth even reached 22.5μm. Compared with the strengthening effect of KOH and K₂H₂Sb₂O₇·2H₂O, the strengthening effect of K₂H₂Sb₂O₇·2H₂O was considered to be more obvious.3.At the temperature below transition temperature, the bending strength and microhardness of the borosilicate flat glass increased after ion exchange at higher temperature and for longer time. But the bending strength did not increase infinitely with longer time. All of the properties of the borosilicate flat glass performed better after treated the KNO₃ mixed with 0.6% K₂H₂Sb₂O₇·2H₂O molten salt.The project got the financial supports by Whuhan scientific and technological project (200870834412).