Investigation of tribological behavior of MOFs/g-C3N4 nanocomposite for insight into effect of flake-on-sheet and ball-on-sheet nanostructure

Herein, we designed two catalogs of metal organic frame materials (MOF)/carbon nitride(g-C3N4) composite nanostructures (flake-on-sheet and ball-on-sheet nanostructure appearances) to probe the effect of composite nanostructures on the cooperative friction mechanism. The tribological behaviors of MOF/g-C3N4 composite nanostructures were extensively investigated in base oil on the four-ball friction tester. The results showed that the anti-wear ability of flake-on-sheet shaped MOF/g-C3N4 in oil was superior to the ball-on-sheet shaped MOF/g-C3N4, whereas the anti-friction and load-bearing ability of latter was preferable to the former. The flake-on-sheet shaped MOF/g-C3N4 enabled the friction coefficient (COF) and wear scar diameter (WSD) of oil to reduce 31.90% and 45.46%, while the ball-on-sheet shaped MOF/g-C3N4 enabled the friction coefficient (COF) and wear scar diameter (WSD) of oil to decrease 37.07% and 42.15%, respectively. Due to the morphology difference, the anti-frition and anti-wear mechanism of the flake-on-sheet shaped MOF/g-C3N4 were reliable to the tribo-film consisting of adsorption film and tribochemical film, whereas that of ball-on-sheet shaped MOF/g-C3N4 depended on the synergistic effect of the tribo-film and the ball bearing effect of MOF nanospehere in composite structure. Moreover, the interface interaction in composite structure also had a underlying influence in the friction behavior of nanoadditive.