Preparation of Magnetic Particles by the Pyrolysis of Ferrous Oxalate in Various Atmospheres

Abstract

Preparation conditions and formation process of magnetic particles, Fe₃O₄, γ-Fe₂O₃, ε-Fe_xN and γ'-Fe₄N were studied by the pyrolysis of ferrous oxalate derived from FeSO₄ and (NH₄)₂C₂O₄ at temperatures of 300-600°C in various atmospheres such as air, Ar gas, CO₂ gas and NH₃ gas. The resulting product from the pyrolysis of the ferrous oxalate at 350°C in various atmospheres was a reactive Fe₃O₄, and γ-Fe₂O₃ and ε-Fe_xN were prepared at heating the Fe₃O₄ at 350°C in air and at 500°C in NH₃ gas, respectively. The preparation conditions of single phase Fe₃O₄, γ-Fe₂O₃, ε-Fe_xN and γ'-Fe₄N fine powders from the ferrous oxalate were as follows: (1)Fe₃O₄ were prepared by heating both at 350-600°C for lh in CO₂ gas and at 350-450°C for lh in Ar gas. (2) γ-Fe₂O₃ was prepared by heating at 350°C for lh in air. (3)ε-Fe_xN was prepared by heating at 500°C for 2h in NH3 gas. (4)γ'-Fe₄N was prepared by heating at 600°C for 2h in NH₃ gas.