Formation Behaviour and Magnetic Properties of Acicular Iron Carbides Particles by Reaction of Various Starting Sources and CO Gas

The formation behaviour and magnetic properties of iron carbides (Fe3C, Fe5C2) with acicular particles were investigated. The particles were prepared by the reaction of various starting acicular particles (α-Fe, α-Fe2O3, Fe3O4) with CO gas. The formation behaviour of the iron carbides was affected by the kinds of starting particles. α-Fe particles resulted in the formation of only Fe3C at 450-500°C. On the other hand, α-Fe2O3 starting particles yielded Fe5C2 at 375-400°C or Fe3C at 450-550°C. When the starting particles were Fe3O4 particles, Fe5C2 was formed at 375-400°C. The formed iron carbides particles lose the acicular form during the carburization. The magnetic properties of Fe3C particles prepared from α-Fe at 500°C were as follows: σs: 90 emu/g, Hc: 600 Oe, σr/σs: 0.4.