Surface metallization with Ni–Cu bimetal for ZTA by electroless plating

The surface metallization of zirconia-toughened alumina (ZTA) particles with Ni–Cu bimetallic coatings is performed by electroless plating assisted with choline chloride–ethylene glycol (ChCl-EG) ionic liquid. The possible reactions and deposition sequences of the plating process have been analyzed based on the micro-morphologies of the Ni–Cu coated ZTA (ZTA@Ni–Cu) particles obtained at different reaction stages. The roles of ChCl-EG additive, reaction temperature, and ZTA concentration on the surface morphology, coating thickness, and element content of the ZTA@Ni–Cu particles are also investigated. Results show that uniform cauliflower-characteristic Ni–Cu coatings are formed on ZTA surfaces with 35 g·L−1 ChCl-EG at 65°C. The coating thickness is about 26.9 μm, and the element contents of Cu and Ni are 38.1 at% and 61.9 at%, respectively. Besides, a schematic illustration about the fabrication of ZTA@Ni–Cu particles is proposed to elaborate the formation process of Ni–Cu coatings and the function mechanism of ChCl-EG additive.