Multi-scale mechanics and electrical transport in a free-standing 3D architecture of graphene and carbon nanotubes fabricated by pressure assisted welding

A free-standing, 3D nanohybrid structure is fabricated by welding 2D graphene (Gr) and 1D carbon nanotubes (CNT) by localized Joule heating under high pressure. Multi-scale mechanical properties and electrical transport behavior of the hierarchical nanostructure are investigated. Nanoindentation revealed anisotropy in mechanical properties with respect to the orientation of the graphene layers. CNTs were found to act as anchors between graphene layers during in situ indentation, enhancing the resistance to failure. Gr-CNT is characterized by excellent damping capability, with loss tangent values as high as 0.8. Anisotropy in loss tangent was observed, indicating the potential to dissipate energy in a desired orientation while allowing unattenuated energy transfer in the other orientation. A two-fold increase in electrical conductivity is observed (similar to 108 S/cm) as compared to pure graphene monolith (similar to 55 S/cm) fabricated by the same technique. In addition, out-of-graphene plane conductivity is also improved by 23% due to nanotube addition. CNTs act as conduction pathways and compensate for resistance at interfaces and linkages in the hybrid. Development of a large-scale 3D architecture with strongly bonded nano-constituents and excellent electrical transport opens up scope for numerous applications, such as nano-microelectromechanical systems, sensors, dampers, precision systems, thermal management, and scaffolds for tissue and neural engineering. (C) 2017 Elsevier Ltd. All rights reserved.