Chemical Strengthening of Alkali‐Free Glass via Pressure Vessel Ion Exchange

Abstract

Ion exchange is a popular technique for chemically strengthening alkali‐containing glass articles, such as Corning® Gorilla® Glass. The ion exchange process is based on a replacement of small alkali ions in the glass with larger alkali ions from a molten salt bath through inter‐diffusion. As the larger alkali ions from the salt bath supplant the smaller alkali ions in the glass, a compressive stress profile is generated near the surface of the glass, which increases its strength and damage resistance. However, certain applications of high‐tech glasses require alkali‐free environments, such as glasses used as substrates for flat panel display applications. In this paper, we report the first successful chemical strengthening of an alkali‐free glass. This is achieved via an aqueous ion exchange of barium salts under high pressure and temperature. X‐ray photoelectron spectroscopy reveals that Ba2+ replaces both Ca2+ and B3+ in the glass, producing surface compressive stress values near 200 MPa. This technology may enable chemical strengthening for a wide range of applications, including flat panel display substrates.

Towards a Glass New World: The Role of Ion-Exchange in Modern Technology

“…On the other hand, the total absence of alkaline ions (e.g., sodium ions, Na + ) in these products would seem to preclude the use of any chemical treatment aimed at further strengthening them. In this context, the interesting work by Mauro et al would seem to offer an elegant solution to the problem, bypassing this impasse through the use of a particular ion-exchange process in alkali-free boroaluminosilicate glass [193]. The idea behind this original method is to replace ions such as Ca 2+ and B 3+ present inside the pristine glass matrix with Ba 2+ ions coming from an ion source where the sample is immersed.…”

Chemical strengthening of zirconia/swelling mica composites by ion-exchange in molten salts

“…As the strengthening method for glasses, chemical strengthening by ion-exchange is well known [8][9][10][11]. In this method, alkali ions in glasses are exchanged for other cations with a larger size in the molten salts, which induces the compressive stress near surface of the glasses.…”

“…Recently, the chemically strengthened glasses have been used as protective covers of smartphones, etc. [11]. This strengthening method is applied to glass ceramics [-12-23].…”