Glass with Hydration-Induced Compressive Stress Profiles

Tim Gross
Corning Incorporated
MRC 136, Rensselaer Polytechnic Institute
Wed, April 05, 2023 at 11:00 AM

A novel potassium phospho-aluminosilicate (KPAS) glass composition is described that can be strengthened by water vapor to achieve deep compressive stress profiles. This material was initially discovered through a series of hydration experiments in which the KPAS specimen achieved a 29 micron compressive depth after being held in a 85oC, 85% relative humidity chamber for 65 days, thus exhibiting diffusivity orders of magnitude greater than comparative glasses. Not only did the KPAS glass have a high Vickers indentation crack resistance of >20 kilograms force (kgf), but it also displayed considerable stored energy at failure. This indication of a residual stress profile was subsequently measured and a compressive stress (CS) of 400 MPa and compressive depth of layer (DOL) of 29 microns was found. It is demonstrated that hydration strengthened glasses are capable of a variety of stress profiles and can provide high retained strength following flaw introduction compared with ion-exchanged soda-lime silicate glass. It is further shown that the process can be optimized by utilizing pressurized steam vessels to achieve stress profiles with surface CS >300 MPa and DOL >30 microns in less than 8 h, making this a practical solution for manufacturing strong glass. The sustainability benefits of steam strengthening include less waste byproduct and lower carbon footprint compared to traditional molten salt ion-exchange strengthening.

Tim Gross

Tim has worked at Corning Incorporated since 2008 as a subject matter expert in fracture mechanics and glass formulation. He is the inventor of numerous commercial products including various iterations of Corning® Gorilla® Glass, Corning® Bendable Glass, and Corning® Guardiant® antimicrobial powder. His research group specializes in various areas of technology including mechanically advantaged materials, antimicrobial materials, automotive glass solutions, and key corporate sustainability initiatives. Tim was the youngest Corning Incorporated scientist ever promoted to Research Fellow. He has published 26 peer-reviewed journal articles and 3 book chapters. He has also been granted 109 United States patents. Tim received his Ph.D. in materials engineering at Rensselaer Polytechnic Institute in 2008.

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