Study on the microstructure, properties and strengthening mechanisms of electrophoretic deposited carbon-nanotubes/Cu composites

Abstract

The laminated carbon-nanotubes/Cu (CNTs/Cu) composites were fabricated by electrophoretic deposition (EPD), spark plasma sintering (SPS), and hot rolling to achieve a good combination of properties. The microstructure, mechanical properties, and electrical conductivity were investigated, and the strengthening mechanism was discussed. Results indicated that functional groups were introduced onto the surface of CNTs after acid treatment, enabling the formation of an optimal CNT deposition morphology on the Cu matrix at an electrophoretic deposition voltage of 75 V. The sintered CNTs/Cu composite exhibits a laminated structure with coarse grains and randomly distributed textures. Compared to sintered pure Cu, the sintered composite demonstrates a 42.07 % increase in tensile strength and a 17.8 % improvement in elongation. And the electrical conductivity reaches 93.05 % of the International Annealed Copper Standard (IACS). Subsequent hot rolling refined the grains and reoriented the texture to deformation textures. The hot-rolled composites achieve a tensile strength of 355 MPa, an elongation of 12.2 %, and a conductivity of 85.53 % IACS. The strengthening mechanisms of CNTs/Cu composites involve grain refinement, load transfer, and thermal mismatch strengthening, with grain refinement as the primary factor. Grain refinement, crack deflection, and bridging-pullout of CNTs are mainly responsible for the good combination of strength, ductility and electrical conductivity.