Strain sensitivity and microscopic deformation mechanism of graphene foam containing active nanoparticles under magnetic fields

Magnetic aerogels have attracted many practical applications in recent years, which requisites a comprehensive understanding on basic mechanics of this hybrid composite system. In this paper, the microscopic deformation mechanism and strain variation (ε_Δ) of such a hybrid material under external magnetic field (E_f) is systematically studied by the coarse-grained molecular dynamics simulation method. The major factors like layer thickness, magnitude of external magnetic field and crosslinks effects are mainly considered. The recovery behavior is also studied under cyclic E_f. Interestingly, the ε_Δ of such a hybrid material is much affected by the graphene sheet thickness, magnitude of applied E_f and crosslinks, due to their direct influences on the microstructural evolution. The ε_Δ of non-bonded hybrid composite with single layer thick graphene sheet (ε_Δ⁓0.19) is four times higher relative to eight layers thick system (ε_Δ⁓0.045). With the increase of graphene sheet thickness, the microstructural evolution of nanoparticles will change from wrapping of single layer sheets around them to flow and jump from one thick sheet to other. We also found the critical value of E_f, i.e., 200 nN for single layer thick graphene sheet hybrid systems beyond which the ε_Δ tend to decrease, however, ε_Δ for eight layers system continue to increase as a function of E_f magnitude. The addition of crosslinks remarkably enhances the ε_Δ (⁓0.74) and recovery (⁓90%) of hybrid composite system. The bonded nanoparticles initiate the folding and unfolding mechanism of graphene sheets during cyclic E_f. The results clarify the micro mechanism and basic mechanics of magnetic aerogels that will be helpful to the design the future devices and advanced sensors.