Abstract: In the article, Lithium greases with different particle sizes and mass concentrations of SiO₂ nanoparticles was fabricated via SG65 three-roll grinder. The tribological properties and rheological properties of different particle sizes and mass concentrations SiO₂ nanoparticales as additives in lithium base greases was investigated via MRS-1J four-ball friction tester and Anton Paar MCR301 rheometer. It is shown that the friction coefficient of grease is lowest and anti-wear performance is best when SiO₂ nanoparticles size is 30 nm and the mass concentration is 4%. Under low and moderate shear rate, the rheological experimental data was fitted and a new grease rheological model was proposed, containing nanoparticals mass concentrations parameter. SiO₂ nanoparticles as additives can improve the thixotropic properties of lithium grease, enhance the anti-shear ability and thermostability of greases.

Key words: nano-silica, lithium grease, tribological properties, rheological properties