Gas phase preparation of spherical core-shell α''-Fe16N2/SiO2 magnetic nanoparticles.

Well-dispersed spherical core-shell α''-Fe16N2/SiO2 ferro-magnetic nanoparticles were successfully synthesized from core-shell α-Fe/SiO2 nanoparticles. Introduction of oxidation prior to the nitridation process gives 90% of α''-Fe16N2 phase contained in the core while no phase change is observed without oxidation. Saturation magnetization and coercivity are 148 emu g(-1) and 1.82 kOe, respectively.