Alterable fracture toughness of amorphous silica by injection and removal of electrostatic charge

In this study, we demonstrate that the fracture toughness of amorphous silica, an electrical insulator, can be dramatically increased and restored via injecting and removing the electrical charge content. Micropillar specimens of amorphous silica were fabricated using focused ion beam machining. The specimens were charged by electron-beam irradiation (charged specimens), and the charge was removed from the specimens by exposure to atmospheric conditions and annealing (charge-removed specimens). Fracture toughness testing was conducted on non-charged, charged, and charge-removed micropillar specimens. The fracture toughness of the charged specimen was 2.4 times higher than that of the non-charged specimens. Furthermore, the fracture toughness of the charge-removed specimens was restored to a level similar to that of the non-charged specimens, but not completely restored. These results indicate that the fracture toughness of amorphous silica can be controlled by injecting and removing electrostatic charges.