Correlations between free volume and pile-up behavior in nanoindentation reference glasses

Reliable interpretation of nanoindentation data often requires that corrections be made for geometric effects such as material pile-up. These corrections are often made with the assumption that the reference glasses used to calibrate the instrument are not susceptible to such effects. This letter presents the pile-up behavior of four silicate reference glasses, (a proprietary fused silica supplied by Hysitron, Inc., Corning 1737f, Corning 2947 (soda-lime-silica), and Schott BK-7, respectively), and correlates their tendency to pile-up with the free volume of their network structures. Irrespective of the reference glass that is used, shallow penetration depths (i.e., < 150nm) should be corrected for the errors induced by pile-up in the reference glass to avoid anomalous trends in modulus and hardness during nanoindentation studies.