Correlation of textural and surface properties with cobalt modification efficiencies of γ-Fe2O3

Cobalt modification of a number of commercial samples of γ-Fe2O3had been carried out by implementing the so-called "Epitaxial Process". The initial powder coercivities and specific surface areas of these samples ranged from 280-400 Oe and 12-30 m²/g, respectively. The cobalt modification efficiencies were found to range from 0-50, Oe/% Co. Textural properties (surface area and porosity) and surface chemistry of these samples were found to be responsible for the observed variation and an interesting correlation between cobalt efficiency and the degree of microporosity of these samples was obtained. For a given external surface area, the cobalt efficiency increased linearly with the degree of microporosity. The correlation obtained is explained in terms of induced conflict of anisotropies and improvement in particle morphology in view of the recent findings of Corradi, et. al.