Sheet Nano-graphite And Inorganic Fullerene-like Molybdenum Disulfide As The Tribological Properties Of Lubricating Oil Additives

Upon researching and developing lubricating oil additives with good antiwear, high load-carrying capacity and self-repair of the worn surface, the tribological properties of nanoparticles as oil additives were investigated, and their tribological mechanisms were also evaluated.Graphite nanosheets, which keep the previous laminated structure, were prepared by stirring ball milling, and IF-MoS₂ nanoparticles were synthesized by desulphurizing the precipitated MoS₃ precursor. Their morphology and structure were observed using transimission electron microscope (TEM) and X-ray diffraction (XRD). It is found that graphite nanosheets have a diameter of 100-300 nm, thickness of 10-20 nm, and its structure is laminated. IF-MoS₂ nanoparticles have an average diameter of 100 nm, and its structure is spherical and nested.Their tribological properties as oil additives were evaluated with MMW-1 four-ball tribotester respectively. The results indicated that:(1) The load-carrying capacity and antiwear ability of the base oil were improved, and the friction coefficient was decreased by the addition of graphite nanosheets. The optimal concentration of the additive in paraffin oil is about 1.0 ×10^-2 wt.%. The worn surface were analysed with SEM also. It is found that graphite nanosheets deposited on the rubbing surface. Its mechanism is: The graphite nanosheets form a continuous, compact and firm physical film under the shear force, which not only bears the load of the steel ball but also separates the rubbing faces and prevents them from direct contact, so the wear and friction decrease.(2) The wear resistance of the paraffin oil was improved and the friction coefficient of the oil was decreased by the addition of the IF-MoS₂ nanoparticles. The higher the concentration is, the more effective the antiwear and friction-reducing are. Analysing its worn surface, it is found that spherical nanoparticles were flattened. Its mechanism is: IF-MoS₂ penetrated into the rubbing surface and rolled in the rubbing surface. During the friction test, the spherical nanoparticles were flattened, and formed physical tribofilm, meanwhile, some nanoparticles filled into the valley. IF nanoparticles can be furnished form the valleys to thecontact surface, so the antiwear ability of base oil was improved, and the friction coefficient was decreased significantly.In conclusion, the tribological properties of the base oil could be improved by the addition of nanopartilces, and their possessed different mechanism from traditional anti-wear and friction-reducing additives.