Preparing γ′-Fe₄N ultrafine powder by twice-nitriding method

Fe/N ultrafine powder is prepared by the method of one-step gas phase synthesis, using FeCl₂ and NH₃ as raw materials, and γ′-Fe₄N ultrafine powder is prepared by twice-nitriding the powder above. The processing and technique of preparing nitrided iron ultrafine powder by the twice-nitriding method was studied. Results show that γ′-Fe₄N can be produced. The physical properties of Fe/N and γ′-Fe₄N powder, such as crystalline state, physical phase, shape, chemical composition and magnetic properties are characterized by means of XRD, TEM, XPS and VSM. The experimental results show that γ′-Fe₄N powder prepared by twice-nitriding is highly pure, ultrafine and single phase. The value of saturation magnetic susceptibility σ_s and coercive force H_c of this powder is preferable to Tanaka's corresponding study results [T. Tanaka, Japan Patent, 60-111403, 1985.].