Indentation Behavior of Permanently Densified Oxide Glasses

Hot isostatic compression can be used as a post treatment method to tune the properties of glass materials as
well as to obtain improved understanding of the pressure-induced structural changes and densification
mechanisms, e.g., during sharp contact loading. Here, we review the pressure-induced changes in density,
structure, and indentation behavior of a range of oxide glasses, including silicates, borates, and phosphates.
The effect of compression on the structure is analyzed through both Raman and NMR spectroscopy, while
the mechanical properties are investigated using Vickers micro-indentation. The magnitude of the changes in
all macroscopic properties (e.g., density, hardness, and crack resistance) is found to correlate well with the
magnitude and type of structural change induced by hot compression. We show that the structural changes
depend largely on the type of network former, the coordination number distribution of network formers, the
number of non-bridging oxygens, and the packing efficiency in the glasses.