Irradiation Damage of Nano-C2S Particles Studied by In-Situ Transmission Electron Microscopy

Abstract

Development of a reactive nanocement is a new approach to improve the physical and chemical properties of construction materials. However, due to the decreased size of cement particles, beam damage during transmission electron microscope (TEM) observation becomes more severe than in conventional cement. In this work, irradiation damage to nano-C 2 S (dicalcium silicate) is observed and studied by in-situ evolution of diffraction patterns (DP), high resolution TEM (HRTEM), and electron energy-loss spectroscopy (EELS). The results show that the damage to nano-C 2 S occurs through a decomposition reaction. Nano-C 2 S is first amorphized, and then re-crystallized into CaO nano-crystals with average size of 7 nm surrounded by an amorphous matrix of Si and SiO 2 . During this process, C 2 S particles exhibit volume shrinkage. The damage energy causing the reaction was analyzed and electron-electron inelastic scattering produced radiolysis and heat, leading to the observed phenomena.