PREPARATION OF NICKEL FERRITE USING LIQUID-METAL CARBOXYLATES

Unusual metal carboxylates that are liquids at room temperature have b een synthesized and applied to the preparation of nickel Ferrite. Thes e salts Ni(MEEA)(2) . 0.5H(2)O and Fe3O(MEEA) (7) . 5.5(H2O) bear the polyether carboxylate anion 2-[2-(2-methoxyethoxy)ethoxy]acetate (MEEA = CH3OCH2CH2OCH2CH2OCH2CO2-). They may be utilized for the low-temper ature preparation of nickel ferrite by using Ni(MEEA)(2) . 0.5H(2)O to coat Fe2O3 powders with a continuous film of NiO. Upon heating this m aterial to 800 degrees C, a remarkable solid-state reaction occurs to puff the precursor particles into broccoli floret-like collections of very small particles. A homogeneous precursor solution for nickel ferr ite may be prepared via dissolution of Ni(NO3)(2) in Fe3O(MEEA)(7) . 5 .5(H2O). This precursor solution yields a metastable amorphous NiFe2O4 phase at 300 degrees C which undergoes an exothermic crystallization at 374 degrees C with an energy change of -126.1 kJ/mol.