RELATIONSHIPS BETWEEN THE SURFACE-PROPERTIES OF GAMMA-FE2O3 AND ITS COBALT-MODIFIED PRODUCTS

Products resulting from the Co modification of γ-Fe2O3 samples prepared by different procedures were studied. Large specific surface areas and the occurrence of a complex porous texture increased Co uptake and decreased the BET surface, while samples with small areas increased their external surface by adhesion of fine CoFe2O4 particles. For one ex-γ-FeOOH sample, Co was nearly uniformly distributed in the bulk of the solid. The γ → α-Fe2O3 transformation temperature increased with the Co content. For excolloidal Fe3O4, an Fe Co spinel solid solution was obtained after thermal treatment; it preserved the spinel structure up to 700°C. The presence of surface hydroxylated species was observed in all samples. © 1990.