PREPARATION AND PROPERTIES OF UNIFORM COATED INORGANIC COLLOIDAL PARTICLES - 11 - NICKEL AND ITS COMPOUNDS ON MANGANESE COMPOUNDS

Uniform cubic manganese carbonate, MnCO3, particles of two modal sizes (similar to 0.8 and 8 mu m) were produced by homogeneous precipitatio n from aqueous solutions of manganese sulfate and urea at elevated tem peratures under limited experimental conditions. The larger particles were converted into Mn2O3 and MnO on calcination at 700 degrees C eith er in the flow of air and or in nitrogen. The MnCO3 particles were als o coated with NiCO3 . Ni(OH)(2) . H2O by aging dispersions of the core s in aqueous solutions of nickel sulfate and urea at 80 degrees C, yie lding a molar ratio [Ni]/[Mn] = 0.45 in the final solid. On calcinatio n at 700 degrees C in air, the shell and core materials of the coated particles transformed independently into NiO and Mn2O3, which on furth er heating at 350 degrees C in hydrogen were reduced to Ni and Mn, res pectively. The coating solutions aged at the same temperature in the a bsence of cores resulted in nearly spherical of NiCO3 . Ni(OH)(2) . H2 O particles of narrow size distribution. The latter solids transformed into NiO on calcination at 700 degrees C and to Ni on reduction with H-2 at 350 degrees C without a significant change in their morphology.