Preparation of monodisperse Ni/PS spheres and hollow nickel spheres by ultrasonic electroless plating

Monodisperse Ni/PS spheres with polystyrene (PS) core and nickel shell were fabricated by ultrasonic electroless plating. Hollow nickel spheres were consequently prepared by calcination and reduction of these Ni/PS spheres at high temperature. The samples were characterized by SEM, TEM, XRD, TG, TPR and EDX. The effects of sensitization time and agitation type on the preparation and dispersity of the Ni/PS spheres were examined. The results indicated that long sensitization time was necessary for the uniform deposition of nickel on the surfaces of the PS spheres. Ultrasonic waves could prevent the polystyrene spheres and Ni/PS spheres from agglomeration, and enhanced the rate of reaction in electroless plating. Optimum electroless plating conditions were found to be as that the polystyrene spheres were sensitized for 30 min, followed by electroless plating for 5 min in the presence of ultrasonic wave. The hollow nickel spheres were consequently obtained by calcining these Ni/PS spheres in air at 550 °C for 4 h and reducing in hydrogen at 550 °C for 3 h.