Carbon nanotube arrays decorated with multi-layer graphene-nanopetals enhance mechanical strength and durability

We report growth of a hierarchical nanostructure consisting of multi-layer graphene-petals decorating individual carbon nanotubes in a vertically aligned CNT array. The structure obtained by post-growth treatment of the CNT array in a microwave plasma chemical vapor deposition process leads to a remarkable increase in array stability, stiffness, elastic recovery and energy absorption capacity and a decrease in stress softening. Further, the change in properties can be tuned by controlling the petal growth time. For a 50 mu m tall array, growth of graphene petals increases the buckling load and energy absorbed in load-unload cycles by a factor of about 60. The petal-coated CNT arrays also retain their morphology during solvent immersion and evaporation cycles, while arrays without petals coalesce into highly dense regions. The results open a new pathway towards tuning mechanical behavior of any arbitrary CNT array and also demonstrate the importance of structural hierarchy in tailoring the behavior of nanostructures. (C) 2014 Elsevier Ltd. All rights reserved.