Preparation and Properties of Uniform Coated Inorganic Colloidal Particles. 11. Nickel and Its Compounds on Manganese Compounds

Abstract

Uniform cubic manganese carbonate, MnCO3, particles of two modal sizes (∼0.8 and 8 μm) were produced by homogeneous precipitation from aqueous solutions of manganese sulfate and urea at elevated temperatures under limited experimental conditions. The larger particles were converted into Mn2O3 and MnO on calcination at 700 °C either in the flow of air and or in nitrogen. The MnCO3 particles were also coated with NiCO3.Ni(OH)2·H2O by aging dispersions of the cores in aqueous solutions of nickel sulfate and urea at 80 °C, yielding a molar ratio [Ni]/[Mn] = 0.45 in the final solid. On calcination at 700 °C in air, the shell and core materials of the coated particles transformed independently into NiO and Mn2O3, which on further heating at 350 °C in hydrogen were reduced to Ni and Mn, respectively. The coating solutions aged at the same temperature in the absence of cores resulted in nearly spherical of NiCO3·Ni(OH)2·H2O particles of narrow size distribution. The latter solids transformed into NiO on calcinati...