Controlled friction behaviors of gradient porous Cu-Zn composites storing ionic liquids under electric field

Porous copper matrix composites (PCMCs) as a novel potential sliding electrical contact material has superior self-lubricating properties, which could store lubricant and during working release it under external stimuli (frictional force, electricity, etc.) to improve the tribological performance. However, the porous structure of the composites may lead to the decrease of its mechanical strength. The method to synthesize PCMCs with enhanced mechanical properties, high electrical conductivity, and novel self-lubricating properties is explored. In this study, gradient porous copper-zinc composites (GPCMCs) are fabricated with novel self-lubricating properties and enhanced strength. The basic physical and mechanical properties of PCMCs and GPCMCs with different porosities are investigated firstly and their frictional behaviors with or without stored ionic liquid (IL) under electric currents have also been studied. Results showed that the GPCMCs exhibit excellent comprehensive mechanical and tribological properties than the PCMCs with homogenous pore structure. The coefficient of friction (COF) values and wear rates of PCMCs under dry friction are higher, and increase with the increase of applied voltages, and those with IL lubricant under various applied voltages are much lower and exhibit excellent electronically controlled effects. This is because that IL stored in PCMCs and GPCMCs can be released under external electrical and frictional stimulations improving the tribological performance greatly. This work provides a strategy to fabricate sliding electrical contact material with novel self-lubricating and enhanced mechanical properties.