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Abstract Although the interactions among glass formers and modifiers, for example, connectivity and charge distribution, have been studied extensively in oxide glasses, the impact of a particular modifier species on the mechanical performance of aluminoborosilicate (ABS) glasses is not well understood. This work compares the indentation properties of six ABS glasses, each of which contains a different network modifier (NWM) with varying field strength (FS). Three alkali and three alkaline earth ABS glasses were designed with low NWM content and [NWM] ≈ [Al2O3], to test the modifier FS effect at low concentrations and to maximize three‐coordinated boron. It has been found that both hardness and crack resistance increase with increasing FS in these ABS systems, which is surprising in the context of historical reports. Using11B,27Al, and29Si solid‐state nuclear magnetic resonance, this work provides evidence of how charge distributions differ as a function of NWM species, and how this relates to the observed indentation behaviors.
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Competitive effects of free volume, rigidity, and self‐adaptivity on indentation response of silicoaluminoborate glasses
Abstract Lithium aluminoborate glasses have recently been found to feature high resistance to crack initiation during indentation, but suffer from relatively low hardness and chemical durability. To further understand the mechanical properties of this glass family and their correlation with the network structure, we here study the effect of adding SiO2to a 25Li2O–20Al2O3–55B2O3glass on the structure and mechanical properties. Addition of silica increases the average network rigidity, but meanwhile its open tetrahedral structure decreases the atomic packing density. Consequently, we only observe a minor increase in hardness and glass transition temperature, and a decrease in Poisson's ratio. The addition of SiO2, and thus removal of Al2O3and/or B2O3, also makes the network less structurally adaptive to applied stress, since Al and B easily increase their coordination number under pressure, while this is not the case for Si under modest pressures. As such, although the silica‐containing networks have more free volume, they cannot densify more during indentation, which in turn leads to an overall decrease in crack resistance upon SiO2addition. Our work shows that, although pure silica glass has very high glass transition temperature and relatively high hardness, its addition in oxide glasses does not necessarily lead to significant increase in these properties due to the complex structural interactions in mixed network former glasses and the competitive effects of free volume and network rigidity.
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- Award ID(s):
- 1826420
- PAR ID:
- 10459517
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 103
- Issue:
- 2
- ISSN:
- 0002-7820
- Format(s):
- Medium: X Size: p. 944-954
- Size(s):
- p. 944-954
- Sponsoring Org:
- National Science Foundation
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