Indentation cracking behaviour and structures of nanophase separation of glasses

Correlative microscopy is used to compare the performance and nanophase structures of soda–lime–silica, fused silica and borosilicate glasses using Vickers indentation crack analysis and the transmission electron microscopy (TEM) Fresnel contrast method. It is found that the observed indentation cracking behaviour is correlated to the nanophase separation structure of these glasses. The so-called "normal" cracking behaviour of soda–lime–silica glass is influenced by its spinodal nanophase separation; while the "anomalous" cracking behaviour of fused silica is due to the uniform single phase structure. Borosilicate glass has a droplet nanophase separation and shows "intermediate" cracking behaviour. These results indicate that in order to produce low brittleness glasses it is important to control nanophase separation structure of a glass.