Structure, chemical durability, and melting properties of aluminosilicate glass

Borosilicate glasses possess excellent melting properties and high stability against chemical attack by aqueous solutions, enabling this glass family to be used in various fields. In this article, we design a novel glass network in order to achieve a chemically robust glass with a low melting temperature. Therefore, the substitution effect of Na₂O by MgO, Al₂O₃, Li₂O, and K₂O on the chemical durability and melting properties of sodium aluminosilicate glass (i.e., 80SiO₂‒5Al₂O₃‒15Na₂O [mol%]) was examined using a standard hydrolytic resistance test and viscosity measurement. Interestingly, we found that the partial replacement of Na₂O by Al₂O₃, Li₂O, and K₂O (i.e., 80SiO₂‒5Al₂O₃‒15Na₂O → 80SiO₂‒6.5Al₂O₃‒9Li₂O‒2.25Na₂O‒2.25K₂O) makes the glass network with chemical durability and melting properties comparable to those of the commercial borosilicate network, resulting in a low HCl consumption of 0.04 mL/g and working temperature of 1238°C (i.e., temperature at viscosity 10⁴ dPa s). The structural characterizations indicate that the high chemical stability of this glass composition originates from the abundance of SiO₄ tetrahedrons with three and four bridging oxygen in the glass network as well as the increase in cationic field strength of mixed alkali ions. These excellent melting properties and superior chemical durability of glass imply the possibility of using the mixed alkali metal oxides aluminosilicate glass together with the commercial borosilicate glass in the markets for numerous practical applications.