Chemical Strengthening of Glass: Lessons Learned and Yet To Be Learned

TLDR

The review summarizes nearly five decades of progress in chemical strengthening of glass by ion exchange, noting that while ion interdiffusion kinetics and technology are well understood, the mechanisms of stress generation, relaxation, and their relation to glass strength, hardness, toughness, and brittleness remain unclear. The study aims to elucidate how the glass network plasticity accommodates larger ions and to investigate damage evolution under extreme loading for expanded applications. Key lessons include the recognition that network topology influences yield strength in both shear and hydrostatic modes, while many aspects yet to be learned remain.

Abstract

This paper reviews the progress that has been made in our understanding of the chemical strengthening of glass by ion exchange over its nearly five decades of history. Lessons learned are briefly discussed; more importantly, those which are yet to be learned are highlighted. It is recognized that, except for detailed compositional effects, the kinetics of ion interdiffusion process and the chemical strengthening technology are reasonably well understood. However, the science of stress generation and its concurrent relaxation is far from being clear despite the elegant analogy to thermal stresses invoked by Cooper. The need to understand plasticity of glass network during accommodation of a larger invading ion is emphasized. In turn, the influence of network topology on its yield strength in shear as well as hydrostatic modes is recognized. For expanded applications under extreme conditions of loading, damage evolution in chemically strengthened glass needs to be studied. Such a study is linked to our understanding of the terms “strength,”“hardness,”“toughness,” and “brittleness” of glass.