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 (εΔ) of such a hybrid material under external magnetic field (Ef) 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 Ef. Interestingly, the εΔ of such a hybrid material is much affected by the graphene sheet thickness, magnitude of applied Ef and crosslinks, due to their direct influences on the microstructural evolution. The εΔ of non-bonded hybrid composite with single layer thick graphene sheet (εΔ⁓0.19) is four times higher relative to eight layers thick system (εΔ⁓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 Ef, i.e., 200 nN for single layer thick graphene sheet hybrid systems beyond which the εΔ tend to decrease, however, εΔ for eight layers system continue to increase as a function of Ef magnitude. The addition of crosslinks remarkably enhances the εΔ (⁓0.74) and recovery (⁓90%) of hybrid composite system. The bonded nanoparticles initiate the folding and unfolding mechanism of graphene sheets during cyclic Ef. 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.