Cyclic Leaching and Annealing of Soda Lime Silica Glass: Improving Mechanical Durability During Indentation by Removal

ABSTRACT Soda lime silica (SLS) glass is a widely used material, and as such, the impact of surface treatments on the mechanical and chemical properties has been extensively studied. For example, it is well established in the literature that treating SLS in acidic solutions results in the formation of a sodium‐depleted surface layer, as sodium exchanges with hydrous species from the solution. Separately, a great deal of work has examined the impact of sub‐ T _g thermal annealing on the properties of SLS and its ability to repopulate the weathered glass with sodium from the bulk and relieve residual network stress from processing. Within this work, a process is studied where SLS glass is treated with alternating steps of sub‐ T _g thermal annealing and exposure to a pH 1 solution of nitric acid at 90°C. Through x‐ray photoelectron spectroscopy and surface‐sensitive vibrational spectroscopy, it was found that annealing the acid‐leached glass resulted in an approximately 10% increase in the bridging oxygen content at the surface, implying repolymerization of silanol groups formed during acid treatment. While leaching the glass completely halted cracking during Vickers indentation at 0.05 kgf, it also corresponded to a decrease in Vickers hardness by 0.15 GPa. Annealing the leached layer retained the majority of the crack resistance (95% probability of no cracks), while mitigating this decrease in hardness.