Li+/Na+ Co-Assisted Hydrothermal Exfoliation for Graphite into Few-Layer Graphene Nanosheets and Their Excellent Friction-Reducing Performance

We have successfully developed Li + /Na + co-intercalated exfoliation for graphene nanosheets by a hydrothermal method without the participation of any organic solvents. The effect of the Li + /Na + ratio on the exfoliation of graphite was intensively studied. The chemical structure of the as-prepared graphene nanosheets was confirmed by the characterizations. Moreover, the results verified that the thickness of the as-prepared graphene nanosheets was 2.65–2.78 nm (about 7–8 layers). The potential application of the as-prepared graphene nanosheets in antifriction and antiwear behaviors was investigated in castor oil. The results demonstrated that the antifriction and antiwear performance of the castor oil with 0.04 wt % as-prepared graphene nanosheets was significantly enhanced, up to 36.84% and 48.57%, respectively. The antifriction mechanism was probed by detecting the morphologies and Raman spectra of worn surfaces.