PREPARATION OF NICKEL SUBMICRON POWDER BY ULTRASONIC SPRAY-PYROLYSIS

Submicron nickel powders were obtained by ultrasonic spray pyrolysis o f an aqueous solution of NiCl2 and Ni(NO3)(2) followed by thermal deco mposition of the resulting aerosol in a H-2/N-2 atmosphere. The soluti on was sprayed by means of an aerosol generator operating at 2.5MHz. T he droplet size was 2.26 mu m. Nitrogen at a flow rate of 3.33dm(3)/mi n(-1) was used as the carrier gas and hydrogen at a flow rate of 0.66d m(3)/min(-1) was used for reduction. Droplet-particle residence time i nside the reactor was 20s, at a velocity of 0.051m/s(-1) and a heating rate of 59K/s(-1). The particle size of the powder can be controlled by changing reaction temperature and the initial solution concentratio n. For pyrolysis temperatures in the range 1173-1273K, non-agglomerate d relatively spherical nickel particles with a mean diameter of 0.55-0 .68 mu m were obtained. At 1273K complete transformation of NiCl2, and Ni(NO3)(2), into nickel occurred.