Effects of the partially-unzipped carbon nanotubes on the microstructure and properties of CuCr matrix composites

Poor interfacial adhesion and the aggregation of carbon nanotubes (CNTs) are important factors that restrict effective synthesis in CNTs-reinforced copper matrix composites (CMCs). Here, chemical unzipping and matrix-alloying (addition of Cr) methods were integrated to address these two limitations of CMCs. The CuCr matrix composite reinforced with partially-unzipped CNTs (PUCNTs) was manufactured using flake powder metallurgy and spark plasma sintering (SPS) processes. The effects of PUCNTs on microstructure, microhardness , electrical conductivity , and tribological properties of the composites were studied. The results showed that the in-situ interfacial carbides (Cr 7 C 3 or Cr 23 C 6 ) improved interfacial adhesion between PUCNTs and CuCr matrix. Additionally, the microhardness and tribological performances of PUCNTs/CuCr composites were obviously improved with increased concentrations of PUCNTs. When the PUCNTs content reached 8 vol%, the microhardness of the PUCNTs/CuCr composite was about 116% and 63% higher than that of unreinforced CuCr and CNTs/CuCr composite, respectively. The coefficient of friction and wear rate of the PUCNTs/CuCr composite were about 70% and 68% lower, respectively, than those of unreinforced CuCr. A balance was obtained between the electrical conductivity and tribological properties of the PUCNTs/CuCr composite. The results of this study show PUCNTs are better reinforcement fillers than CNTs, and suggest a new strategy for the fabrication of sliding electrical contact composites with high performance.