Preparation and characterization of Ni-Cu dual coated ZTA particles by ionic liquid-assisted electroless plating as reinforcement of metal-based composites

An ionic liquid assisted electroless plating is adopted to prepare continuous and dense Ni-Cu dual coatings on the surface of ZTA particles. The effects of l-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) additive, NiSO4 and CuSO4 concentrations on the surface morphologies, coating thickness, and element content of Ni-Cu dual coated ZrO2-toughened Al2O3 (ZTA@Ni-Cu) particles have been characterized systematically. Results show that with incremental addition of [bmim]BF4, suspended Ni-Cu particles in plating bath can be diminished but the incubation period and plating time of Ni-Cu coatings are prolonged significantly. The addition of 20 g.L-1 [bmim]BF4 is optimum for the preparation of uniform and compact ZTA@Ni-Cu particles. Besides, the thickness of Ni-Cu coating is about 20-30 im and the Cu element content can be controlled in the range of 14.10-60.76 at % through adjusting Cu(II) ions concentration. Furthermore, the possible reactions and deposition sequences for the preparation of Ni-Cu coatings on ZTA surfaces are analyzed and an empirical model of the deposition process assisted with [bmim]BF4 additive is also proposed to expound the function mechanism of [bmim]BF4 additive and the formation process of Ni-Cu coatings on ZTA surfaces.