Surface strengthening of lithium disilicate glass-ceramic by ion-exchange using Rb,Cs nitrates

In order to further improve the flexural strength of lithium disilicate glass-ceramic, surface strengthening by ion exchange using Rb, Cs nitrates has been studied for the first time. The influences of ion exchange using rubidium and cesium salts on the flexural strength and corrosion resistance have been investigated. It was found that the mechanical properties of the lithium disilicate glass-ceramic could be increased greatly by the ion exchange in rubidium nitrate (RbNO₃) salt. After ion exchange for 4?h in RbNO₃ salt, the flexural strength and microhardness increased from 169?MPa and 587?kgf?mm^?2 (5.75?Gpa) of the original lithium disilicate glass-ceramic to 493?MPa and 654?kgf?mm^?2 (6.4?Gpa), respectively. Moreover, the corrosion resistance of the lithium disilicate glass-ceramic was further improved by ion exchange in rubidium and cesium nitrate salts. Furthermore, the maximum thickness of the ion exchange layer using RbNO₃ and CsNO₃ was only 4.3?µm and 0.45?µm respectively. Such a thin exchange layer, which will only require very low Rb⁺, Cs⁺ ions exchange amount, indicates that the molten salts of RbNO₃ and CsNO₃ can be reused for many times. So it is suggested that surface strengthening of lithium disilicate glass-ceramic by ion exchange using Rb, Cs nitrates is cost-efficient and very suitable for the actual production and applications.