Nanoporosity boosts irradiation-induced dynamics in silica.

Abstract

Hard X-ray irradiation can activate relaxations in glasses even at temperatures well below their glass transition temperature, yet the nature of the involved structural rearrangements remains poorly understood. Here we compare bulk amorphous SiO₂ with nanoporous silica to test how porosity and internal surfaces affect the radiation-induced structural and dynamical changes. In nanoporous silica, the intensity of the characteristic SiO₂ first sharp diffraction peak is reduced by irradiation as in the bulk counterpart, but on a time scale more than an order of magnitude faster. Despite this accelerated structural evolution, the induced atomic-scale dynamics in nanoporous silica remains predominantly ballistic-like and displays reproducible intermittent fluctuations. At the first sharp diffraction peak, both materials show compressed-exponential relaxations, with markedly shorter time scales and stronger fluctuations in presence of nanostructures. These results identify internal interfaces as a key factor controlling hard-X-ray-driven relaxation in nanoporous silica, suggesting a practical route to tune radiation sensitivity in nanostructured glasses.