Effect of Nano-coppers with Different Dimensions on Tribological Properties of Lithium Grease

As an excellent anti-wear and friction-reducing additive, nano-copper has attracted extensive researches and attention in tribology ifeld. However, the existing researches are still limited to zero-dimensional nano-copper, that is, the effect of copper nanoparticles on the tribological properties of lubricants. In this paper, the effects of nano-coppers with different dimensions (copper nanoparticles, copper nanowires and copper nanoplates) on the anti-wear ability and friction-reducing performance of lithium grease were systematically investigated. And the mechanism of interaction between dimension and tribological properties was explained in detail. It is concluded that the tribological properties of lithium grease can be improved by the addition of nano-coppers due to the formation of the molten copper film and the CuO tribochemical reaction iflm on the worn surface. And the dimension of nano-copper has a great inlfuence on its tribological property. The copper nanoparticles can play the role of nano-bearing to change the friction form from sliding friction to rolling friction, which would decrease the wear loss of friction pairs. The wear loss can be sharply decreased by addition of copper nanoplates with micron-scale diameter and lamellar structure which signiifcantly prevents the direct contact of micro-protrusions on the surface of friction pairs and reduces the"welding"between micro-protrusions due to local high temperature caused by friction.