Preparation and magnetic properties of Fe/C composite powders

Fe/C composite magnetic powders were prepared by a sol-gel method from aqueous-mesophase pitch (AMP) and ferric chloride. The AMP was prepared by the oxidation of coal tar pitch with a mixture of concentrated sulfuric acid and nitric acid (7:3v/v), to which ferric chloride and ammonia were added to form aqueous Fe/C based gels. The gels were displaced by ethanol, dried at ambient temperature and pressure, and carbonized at 900℃ to obtain the Fe/C magnetic powders. The powders were characterized by FT-IR, XRD, TG and TEM. Results show that primary particles in the powders have an ellipsoidal shape with a uniform particle size about 5nm, which are aggregated into secondary particles with a size about 20-30nm. The carbon has a turbostratic structure and the Fe exists in the form of α-Fe、Fe₂O₃ and Fe₃C. The powders are soft magnetic materials with a saturation magnetization increasing with Fe content.