CuS Nanoparticle Additives for Enhanced Ester Lubricant Performance

Lubrication performance of CuS nanoparticle additive in ester lubricant for the friction pair of ZrO2 ball and copper plate was investigated under different electric potential conditions. When the potential of the copper plate is lower than −14 V, the friction coefficient decreases from 0.18 to 0.05 after an induction period of running-in, the time of which is shorter if the voltage is lower. The significant friction reduction is attributed to the excess of positively charged nanoparticles in the vicinity of the negatively charged surface.