Double strengthening by ion exchange of sintered nepheline glass-ceramics: a new simplified method

The possibility of achieving very high compressive stresses at the surface of nepheline glass-ceramics, owing to the transformation of main crystal phase into kalsilite, was discovered more than 40 years ago, but the very long processing times associated to conventional glass-ceramic manufacturing prevented extensive applications. The present work aims, on one hand, to explore the feasibility of nepheline-containing glass-ceramics by rapid sintering of fine glass powders and, on the other hand, to renew interest on strengthening by ion exchange induced transformation. For a selected glass-ceramic, developed using glass cullet as main raw material and sintered at very low temperature (840 ⁰C), ion exchange treatments were found to be effective especially in increasing the reliability of samples (e.g. Weibull’s modulus exceeding 18).