Understanding the role of post-indentation recovery on the hardness of glasses: Case of silica, borate, and borosilicate glasses

摘要

Hardness is an important property of glasses, which depends strongly on the method of measurement. Herein, we estimate the hardness of three oxide glasses, namely, pure silica (0B), borosilicate (37B), and sodium borate (75B) glass samples at micro and nanoscale. We observe that annealing of these glass samples, after polishing, has little effect on their hardness and modulus. Interestingly, we observe that the nanoindentation is unable to capture the full extent of elastic recovery, thereby underestimating the hardness of these glasses. We show that the post-indentation elastic recovery is highly dependent on the chemical composition of glass. Combining nanoindentation and atomic force microscopy (AFM) imaging, we accurately capture the complete elastic recovery of glass samples, thereby calculating the true hardness values from indentation depth profiles. Overall, we show that post-indentation elastic recovery plays a crucial role in determining the hardness of glasses.