Enhancing the strength of carbon nanotubes reinforced copper matrix composites by optimizing the interface structure and dispersion uniformity

Interface between carbon nanotubes (CNTs) and copper matrix is generally weak mechanical bonding due to the lack of wetting and interaction between them. In the present study, the homogeneous distribution of CNTs in copper matrix was realized through a novel mixing method and spark plasma sintering (SPS). The interface structures of CNTs/Cu composites were optimized by using decorated CNTs. Transmission electron microscopy (TEM) observation revealed the formation of interfacial products, amorphous transition areas and interfacial stress zones at the decorated-CNT/Cu interfaces. The compressive tests showed that the composite containing 2 vol% of Ni-coated CNTs has a maximum compression yield strength of 554 MPa, which was increased by 55% and 30% compared with that of pure Cu and the composite reinforced with pristine CNTs, respectively. The strong strengthening effects of the decorated CNTs can be attributed to their interaction with Cu matrix. The strengthening mechanisms, load transfer efficiency and interfacial shear strength were also discussed from the point of interface structure. This work underscores the importance of the surface state of CNTs on the interface structure in metal matrix composites, and may provide insights into the composites where reinforcements and matrix are lack of wetting and interactions.