Elastic improvement of carbon nanotube sponges by depositing amorphous carbon coating

Porous materials such as foams, sponges and aerogels typically exhibit large energy dissipation during deformation, resulting in structural weakening and incomplete recovery. Here, we adopted a vapor deposition method to introduce a uniform amorphous carbon (AC) coating with controlled thickness throughout the porous network, on the surface of individual carbon nanotubes (CNTs) as well as their junctions, forming AC-CNT sponges. The AC-CNT sponges show enhanced mechanical properties (compressive strength, modulus), and in particular, significantly narrowed stress-strain loops with small energy loss coefficients compared with previous CNT or graphene-based aerogels typically having large hysteresis. Mechanism study has revealed several important factors that contribute to the observed superelasticity, including the thickening of nanotube struts, welding of nanotube junctions, and inhibition of bundle formation. Our method could systematically tailor the structure and properties of porous CNT (or other nanostructure) sponges, which have applications in microelectromechanical systems and mechanical energy storage.