Preparation and characterization of uniformly coated particles by homogeneous precipitation (cobalt compounds on nickel compounds)

Nickel basic carbonate [NiCO3 · Ni(OH)2 · H2O] particles were coated with crystalline cobalt carbonate (CoCO3) by heating their suspension in an aqueous solution of cobalt nitrate and urea at elevated temperatures. In the absence of core particles, the same reactant mixture produced a dispersion of amorphous cobalt basic carbonate [2CoCO3 · Co(OH)2 · H2O] particles. On calcination at 700°C, the shell and core materials of the coated particles transformed, respectively, into Co2O3, and NiO, while producing a third phase (NiCo2O4) at the core/coating interface. No sintering was observed during calcination and the particles retained their morphological features to a significant extent.