Controllable synthesis of different morphologies of CuO nanostructures for tribological evaluation as water-based lubricant additives

In this study, water soluble CuO nanostructures having nanobelt, nanorod, or spindle morphologies were synthesized using aqueous solutions of Cu(NO3)(2)center dot 3H(2)O and NaOH by adjusting the type of surface modifier and reaction temperature. The effect of morphologies of these various CuO nanostructures as water-based lubricant additives on tribological properties was evaluated on a UMT-2 micro-friction tester, and the mechanisms underlying these properties are discussed. The three different morphologies of CuO nanostructures exhibited excellent friction-reducing and anti-wear properties. Tribological mechanisms differed in the initial stage of frictional interactions, but in the stable stage, a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs, leading to improved tribological properties.