Chemical strengthening of Na2O---Al2O3---SiO2 system glasses by surface controlled crystallization

Appropriate glass compositions of the Na₂O---Al₂O₃---SiO₂ system and glass melting technology were investigated. The dependence of some factors, such as composition of molten salts, time and temperature of ion exchange treatment on the modulus of rupture was studied. As expected, the coefficient of interdiffusion is a function of concentration and has the mixed-alkali effect. The order of the interdiffusion coefficient is 10⁻⁶ cm²/s. The effect of binary and ternary salt baths on the surface controlled crystallization was reported. The experimental data showed that there is a series of technological advantages from applying molten salts of the ternary system Li₂SO₄---Na₂SO₄---K₂SO₄ in comparison with the binary system Li₂SO₄---Na₂SO₄.