Recent Patents on ZnO Nanoparticles as Lubricating Grease Additive

Background: An effective method of enlarging grease application fields is to improve its lubricant behavior by adding reinforced particle. This paper reviews various recent patents on nanoparticle as additive phase to improve lubrication performance. Objective: To provide an overview on the effect of various amounts of ZnO nanoparticles on the tribological behavior of lubricant grease. Methods: By means of a friction and wear testing machine, the tribological behavior of lubricant grease containing ZnO nanoparticles on a range from 1 to 1.8wt.% was investigated in detail. Results: Results show that the lubricant properties of nanoadditive based grease containing 1.2wt.% ZnO nanoparticles possessed the smallest friction coefficient and wear scar diameter in all experiments. It was determined that during the course of friction, the additive amount of 1.2wt.% promoted the deposition of ZnO nanoparticles and effectively repaired wear scar morphology, which led to less wear on the ball-disc frictional pair. Conclusion: The list of patents reviewed here is by no means supposed to be completed or extensive but shows evolution trends concerning latent nano-lubrication. Keywords: Friction coefficient, lubricant grease, nano-lubrication, wear, wear scar diameter, ZnO nanoparticles.