The influence of the drying method on the microstructure and the compression behavior of graphene aerogel

Supercritical CO₂ drying and freeze-drying are two standard drying methods for fabricating aerogels. We conducted a comprehensive experimental study for clarifying the influence of the drying method on the properties of graphene aerogel, and further discussed its deformation mechanism via characterization and simulation results. The results showed that the specific modulus of two drying methods prepared graphene aerogels is similar. The supercritical CO₂ dried sample had a higher compression strength due to the plastic collapse of the mesopore walls. In the freeze-drying process without thermal baffle, the reformed honeycomb geometric microstructure can be divided into three regions according to the growth of ice crystals: vertical, transition, and gradient regions. Therefore, the freeze-dried graphene aerogels exhibited a nonlinear superelastic behavior due to the random out-of-plane buckling of the thicker pore walls. In addition, two cellular structures were developed by mimicing the microstructure of two kinds of graphene aerogels for numerical analysis. Simulation results highlighted the decisive role of geometric nonlinearity in the deformation mechanism.