STRUCTURE AND PROPERTIES OF PRECIPITATED NICKEL-IRON HYDROXIDES

Iron-substituted nickel hydroxides have been prepared by precipitation for y iron substitution rates ranging from 0.10 to 0.50. Chemical and physical studies have shown, as in the case of the homologous 'chimie douce materials', the presence of (1-y)Ni2+ and yFe3+ ions within the slab; the compensation of the excess of positive charge mainly results from the intercalation of CO32- ions in the interslab space. The IR study and the chemical analysis provide evidence for the presence of SO42+ ions in T(d) symmetry (originating from the precipitation medium) that are mainly adsorbed on the grain surface. These materials are stable in concentrated KOH solution but their ageing in such a medium induces a modification of the crystallinity as well as a spontaneous exchange of CO32- ions for SO42- ions.