Unique synergistic effects of graphene oxide and carbon nanotube hybrids on the tribological properties of polyimide nanocomposites

The graphene oxide (GO) nanosheets/carboxyl-functionalized multi-walled carbon nanotubes (CNTs) hybrids (GO/CNTs) were synthesized via vacuum filtration solution hybrid dispersion and the corresponding GO/CNTs/polyimide (GO/CNTs/PI) nanocomposite films were facilely prepared by in situ polymerization. Both the thermal stability, mechanical and tribological properties of GO/CNTs/PI nanocomposites were greatly improved compared with those of pure PI due to the homogeneous dispersion of GO/CNTs and the strong interfacial covalent bonds between GO/CNTs and the PI matrix. Furthermore, GO/CNTs/PI nanocomposites exhibited the much lower friction coefficient compared to that of PI composites with the same loading of GO or CNTs only, suggesting the synergistic effects of GO/CNTs hybrids on the tribological properties of polyimide nanocomposites, especially the weight ratio of GO and CNTs was 3:1.