Preparation of Fe-50 wt.% Co nanopowders by calcination and hydrogen reduction of nitrate powders

Abstract

An optimum route to synthesize Fe-50 wt.% Co nanoparticles and their magnetic properties were investigated. The powder mixture of Fe-oxide and Co(3)O(4) were prepared by calcination of Fe- and Co-nitrate powders. The hydrogen reduction behavior of calcined powders was analyzed by DTA-TG. Thermal analysis revealed that the Fe-oxides and Co(3)O(4) were hydrogen-reduced to Fe-Co alloy particles with an average size of 30 nm in the temperature range of 260-420 degrees C. The powder hydrogen-reduced at 600 degrees C showed saturation magnetization (M(s)) of 204.4 emu/g and coercive force (H(c)) of 96.3 Oe. However, in case of the reduced powder at 350 degrees C, the M(s) and H(c) values are changed to 120.0 emu/g and 826.8 Oe, respectively. The change of magnetic properties was explained by the formation of ferrimagnetic particles. (C) 2011 Elsevier B.V. All rights reserved.