Particle Size Dependence of Iron on the Fe₁₆N₂ Formation by Low Temperature Nitridation

Abstract

The dependence of α-Fe particle size on the formation of Fe₁₆N₂ with giant magnetization was studied by nitriding α-Fe fine particles below 200°C with different particle size (60nm, 120nm, 300nm) derived from α-Fe₂O₃. Nitridation of the largest α-Fe particle (300nm) was difficult to obtain Fe₁₆N₂. Mixtures of Fe₁₆N₂ with unreacted α-Fe and Fe₄N were obtained by nitridation of the smaller α-Fe particles (120nm, 60nm). The nitridation process was most controllable for α-Fe particle of 120nm to obtain the most amount of Fe₁₆N₂. Magnetization was not enhanced by the formation of Fe₁₆N₂ probably due to disordering of the nitrogen introduced into Fe lattice. Monodispersed α-Fe particles could be obtained by thermal decomposition of Fe(CO)₅ in octylether. Their size could be controlled with the amount of added stabilizer in the ether. They could be nitrided to Fe₁₆N₂ in low temperature nitridation.