Gamma‐ray irradiation effect on microstructure and physical performances of porous silica

Abstract

In this paper, the gamma irradiation effect on the microstructure and physical performances of porous silica, including mechanical, thermal, and optical performances, are systematically investigated by using molecular dynamics and density‐functional theory‐based methods. The study of bond angle distribution, pair distribution function, coordination number distribution, and average ring size distribution show that, after gamma‐ray irradiation, the microstructure of porous silica is obviously modified. The tight packing of SiO2 tetrahedrons in the porous silica network is broken by gamma‐ray irradiation. Defects of three‐coordinated Si and non‐bridging oxygen are induced by gamma‐ray irradiation. Moreover, we find that the defects concentrations rapidly grow as gamma‐ray dose increases. The mechanical, thermal, and optical performances of porous silica are all seriously degenerated by gamma‐ray irradiation. Our results show that, for mechanical performance, Young's modulus, Bulk modulus, and Shear modulus first decrease and then keep stable as gamma‐ray dose increases, but the change of Poisson's ratio is slight. For thermal performance, the thermal conductivity decreases exponentially as gamma‐ray dose increases. For optical performance, light absorption coefficients increase exponentially and light transmittance drops as gamma‐ray dose increases in the working range (photon energy range around 3.5 eV) of inertial confinement fusion. Present work is expected to be valuable for studying the degradation mechanism of silicate materials under gamma radiation and developing gamma‐ray irradiation protection technology.