Multidimensional structure and enhancement performance of modified graphene/carbon nanotube assemblies in tribological properties of polyimide nanocomposites

Modified graphene/carbon nanotube (abbreviated GCNT) assemblies were prepared by chemical compounding from amino-functionalized graphene (abbreviated MG) and carboxyl-functionalized multi-walled carbon nanotube (abbreviated MCNT). Diverse hybrid structures, such as graphene-shelled CNT microspheres, graphene/CNT interlayers and CNT-coated graphene nanosheets, have been obtained by adjusting the reaction ratio of the two precursor particles. The as-prepared GCNTs were incorporated into polyimide (PI) matrix to yield GCNT/PI composites by in situ polymerization. The mechanical, thermo-mechanical and tribological properties of GCNT/PI composites were investigated and synergistic effects in terms of lubrication and wear resistance have been acquired. The friction coefficient and wear rate decreased by 29.3% and 75.8%, respectively, with only 0.5 wt% addition of GCNT14 (W-MG/W-MCNT = 1 : 4), compared to virgin PI. The results indicate that combinational structure of multidimensional assemblies has a great influence on the enhancement performance and tribological mechanism of nanocomposites.