Characterization of iron nitride powders formed by mechanical alloying and atmospheric heat treatment techniques

Abstract

Iron nitrides were manufactured by mechanical alloying of Fe_2.33N and Fe powder mixtures at starting compositions of Fe₁₂N₂ and Fe₁₆N₂ and annealed in air at 200 and 240°C. It was found that the supersaturated nanocrystalline α‐Fe solid solution phase was produced after MA, and iron nitrides were formed after heat treatment. The saturation magnetization (σ) of the heat‐treated powders is higher than those of the as‐milled powders. The σ values for the specimens heat treated at 200°C are higher than those heat treated at 240°C, and the highest value among all of the samples is 218 e.m.u./g which is obtained by annealing of as‐milled Fe₁₂N₂ powders in air at 200°C for 6 hours. The possible existence of the α”‐Fe₁₆N₂ phase is responsible for the high saturation magnetization in mechanically alloyed Fe₁₆N₂ and Fe₁₂N₂ powders.

Key Words:

• mechanical alloying
• iron nitrides
• heat treatment
• saturation magnetization

Notes

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