2, Bruker Nano Surfaces, Minneapolis, Minnesota, United States
Understanding plastic deformation in silicate glasses is important in the development of glasses with improved resistance to mechanical failure. Plastic deformation under a point contact determines the stress state, which determines whether a surface flaw forms, which in turn determines the strength of the glass. Unfortunately, relatively little is known about the atomic scale mechanisms that control plasticity in silicate glasses. To date, most effort has focused on the continuum concepts of shear and densification. Raman spectroscopy has been used to study structure of glass glasses deformed by indentation ex-situ. To investigate the structure of plastically deformed glass under load, we have developed an instrument in which the deformed material under the indenter can be investigated in-situ, while the load is being applied. Measured changes in spectra can be correlated to changes in ring size, bond angles, and other structural motifs with load. Transient structural changes which disappear after load is removed were identified.