Comparison of glass hydration layer thickness measured by transmission electron microscopy and nanoindentation

The thicknesses of the hydration layers on the surfaces of 2 silicate glasses have been assessed using a) a combination of focused ion beam milling and transmission electron microscopy and b) nanoindentation; the two approaches give consistent layer thicknesses. Lighter contrast of the hydrated layers in TEM suggests that the layers have reduced density when compared to the bulk glasses; this is consistent with the reduced near surface modulus and hardness of hydrated glasses observed in nanoindentation.