Structure evolution of the interface between graphene oxide-reinforced calcium silicate hydrate gel particles exposed to high temperature

Abstract

Structure, reactivity, and dynamics of the interface between graphene oxide (GO)-reinforced calcium silicate hydrate (CSH) gel particles at the temperature from 900 to 1100 K are investigated by means of reactive molecular dynamics. The results show that, high temperature weakens the CSH structure, including the stretching of Si-O bonds, the decomposition of silicate chains, and the hydrolysis weakening caused by water molecules. The high kinetic energy and weakened structure result in the melting and diffusion of CSH gel. However, the incorporation of GO can effectively stabilize the CSH structure by following three factors. (1) GO prevents the diffusion of the gel, and the packing of gel on the GO nanosheet increases the compatibility between them. (2) Reduction reaction of GO creates the defects on the carbon plane, providing the space for silicate chains crossing GO sheet. (3) Frequency exchange of oxygen between GO and CSH promotes the formation of chemical bonding between them. The improvement of the stability of CSH gel can effectively reduce the ablation velocity under high temperature.