Interface-dominated strengthening, deformation and electrical transport behaviors of Cu nanocomposites rendered by nitrogen-doped carbon nanotubes

The intrinsic incompatibility between carbon nanotubes (CNTs) and Cu matrix generally renders the formation of weak interface and thus low strengthening efficiency. To address the above dilemma, a nitrogen-doped CNT (NCNT), fabricated via plasma treatment, was used to reinforce Cu matrix composites. It is found that in addition to promoting the homogeneous dispersion, nitrogen-doped treatment of CNTs facilitates the robust interface in the NCNTs/Cu, associated with disorder area featuring intense localized normal strain. Such interface guarantees the accurate load-transfer from the matrix to NCNTs, thereby contributing to the prominent yield strength of NCNTs/Cu over raw CNTs/Cu. Meanwhile, the N-mediated CNT-Cu interface provides strong dislocation pinning force, which turns to encourage dislocation planar slip at the early plastic deformation and occurrence of “yield point elongation”, coupled with rapid dislocation multiplication and lower dislocation velocity. The sufficient interface dislocation interactions and extra-toughening introduced by crack bridging and deflection were achieved in the NCNTs/Cu during subsequent deformation, thereby delaying necking. Electrical transport analysis demonstrates that the doped N lowers the interface inelastic scattering and accelerates extra electron transfer from Cu matrix to NCNT. Such nitrogen-doping characteristics of CNT were accentuated to address their contribution to the prominent mechanical-electrical property synergy.