Abstract
Oxide glasses are one of the most important engineering and functional material families owing to their unique features, such as tailorable physical properties. However, at the same time intrinsic brittleness has been their main drawback, which severely restricts many applications. Despite much progress, a breakthrough in developing ultra‐damage‐resistant and ductile oxide glasses still needs to be made. Here, a critical advancement toward such oxide glasses is presented. In detail, a bulk oxide glass with a record‐high crack resistance is obtained by subjecting a caesium aluminoborate glass to surface aging under humid conditions, enabling it to sustain sharp contact deformations under loads of ≈500 N without forming any strength‐limiting cracks. This ultra‐high crack resistance exceeds that of the annealed oxide glasses by more than one order of magnitude, making this glass micro‐ductile. In addition, a remarkable indentation behavior, i.e., a time‐dependent shrinkage of the indent cavity, is demonstrated. Based on structural analyses, a molecular‐scale deformation model to account for both the ultra‐high crack resistance and the time‐dependent shrinkage in the studied glass is proposed.
Highlights
Oxide glasses are one of the most important engineering and functional of glass has been the major hindrance for material families owing to their unique features, such as tailorable physical properties
We discover that a caesium aluminoborate glass the compositional design of damage-resistant, and potentially exhibits superior crack resistance and micro-ductility when it ductile, oxide glass compositions
We propose a molecular-scale deformation mechanism to account for the macroscopic shrinkage of the indentation impressions along with the structural changes of the surface based on the Raman spectroscopy analysis
Summary
The most striking feature of the present aluminoborate glass is its extremely high resistance to crack initiation. The annealed aluminoborate glass, which is free of any compressive or tensile stresses, is able to withstand much higher loads without radial cracking compared to both soda-lime-silica and the more crack-resistant aluminosilicate glass. Given the observation of a crack-free Vickers indent at 490 N (Figure 2a) and based on our various measurements conditions, we estimate the average crack resistance to be at least around 400 N (Figure 2b) This is a record value for annealed oxide glasses, i.e., glasses that have not undergone any extrinsic strengthening procedure. Independent of the actual crack resistance value, the present observation of crackfree indents at the very high loads shows that rational design of the chemical composition is a powerful strategy to improve the damage resistance, even compared with other methods such as ion exchange, thermal strengthening, or hot compression (Figure 2c).[37,38,39]
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