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

Abstract

Uniform cubic manganese carbonate, MnCO 3, 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 Mn 2 O 3 and MnO on calcination at 700 °C either in the flow of air and or in nitrogen. The MnCO 3 particles were also coated with NiCO 3 .Ni(OH) 2 ·H 2 O 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 Mn 2 O 3, 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 NiCO 3 ·Ni(OH) 2 ·H 2 O particles of narrow size distribution. The latter solids transformed into NiO on calcination at 700 °C and to Ni on reduction with H 2 at 350 °C without a significant change in their morphology.