Effects of Homogeneous Irradiation of Electron Beam with Low Potential on Microscopic Fracture Resistance of Borosilicate Glass Surface

Abstract

An effect of homogeneous irradiation of electron beam with low potential (HIEBL) on the micro-fracture resistance of borosilicate glass was studied by using indentation of hardness test. 0.04 MGy-HIEBL increased the critical resistant energy (E_f) of micro plastic deformation to generate the crack and tremendously decreased their experimental errors. Furthermore, the high values of the midpoints (E_f^mid) of E_f values were obtained from 0.04 to 0.22 MGy of irradiation dose. If HIEBL annihilated the spontaneous crack origins, the minimum E_f value (E_f^min) before irradiation was the critical resistant energy of micro-plastic deformation to propagate the crack (E_f^p). Since HIEBL of less than 0.43 MGy didn’t affect the fracture toughness (K_IC) estimated by fracture toughness to propagate the crack using standard indentation fracture method, the E_f^p value of the borosilicate glass didn’t depend on the irradiation dose. On the other hand, the critical resistant energy of micro-plastic deformation to generate the crack (E_fⁿ; E_fⁿ=E_f−E_f^p) was defined. Thus, HIEBL increased the E_f values because of increasing E_fⁿ values. Based on the increasing the height of electron spin resonance (ESR) spectra, HIEBL formed dangling bonds in silica glassy network structure, as well as reformed the crack tip from sharp to dull. Thus, they probably relaxed the residual strain. If the partial relaxation of the residual strain mainly occurred around these dangling bonds of the silicon-oxygen pairs in the network structure, the increased E_f value was mainly due to the relaxation of the network structure, as well as the annihilation of crack origin. Therefore, HIEBL prevented the crack generation.