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Competitive effects of free volume, rigidity, and self‐adaptivity on indentation response of silicoaluminoborate glasses
Author(s) -
Liu Pengfei,
Januchta Kacper,
Jensen Lars R.,
Bauchy Mathieu,
Smedskjaer Morten M.
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16790
Subject(s) - materials science , indentation , glass transition , composite material , rigidity (electromagnetism) , coordination number , tetrahedron , network structure , crystallography , polymer , chemistry , ion , organic chemistry , machine learning , computer science
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 SiO 2 to a 25Li 2 O–20Al 2 O 3 –55B 2 O 3 glass 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 SiO 2 , and thus removal of Al 2 O 3 and/or B 2 O 3 , 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 SiO 2 addition. 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.