Sonochemical synthesis of iron nitride nanoparticles

A method for the preparation of nanoparticles of iron nitride powders is reported. Iron nitride particles have been synthesised by two methods. In the first, Fe(CO)₅ was sonicated in a decane solution under a gaseous mixture of NH₃ and H₂ (3.5:1 molar ratio) at ca. 0°C. The second method was based on nitriding the sonochemically prepared amorphous iron at ca. 400°C for 4 h under a mixed stream of NH₃-H₂ (3.5:1 molar ratio). Different products were obtained in the two cases. The product of the sonication of Fe(CO)₅ was amorphous Fe_2-3N and a small quantity of iron oxide. The X-ray diffraction patterns in the second case showed Fe₄N as a main product. The magnetic properties of both products were measured. The coercive force H_c of the Fe₄N is 190 Oe, and the saturation magnetization σ_s is 170 emu g^-1.