Thermal stability and structure of acicular Fe–Co metal particles

Abstract We have found that the thermal stability of Fe–Co metal particles improves with the increase of Co contents. The oxidation reaction mechanism of Fe–Co particles controls the rate of diffusion in the continuous product layer. The cross section of the Fe–Co particles is circular and the surface oxide grows to be coherent with the core α-Fe. The number of defects in the surface oxide layer is reduced, whereas the cross section of Fe metal particles is less clearly circular and the surface oxide layer shows diffuse diffraction spots. These results suggest that the improvement in the thermal stability of Fe–Co metal particles can be attributed to the morphology of the particles and the structure of the surface oxide layer around the core α-Fe.