気相-固相反応法による針状Fe₃C微粒子の合成とその磁気特性

抄録

Small particles of Fe₃C (cementite) in an acicular shape (0.2 μm in length, 10/1 in axial ratio) have been synthesized by heating acicular shaped powders of iron (α-Fe) in a flow of carbon monoxide or/and hydrogen gas mixture. X-ray analyses, electron microscopy, magnetic measurements and Mössbauer spectroscopy are employed for the characterizations. The chemical treatment required to obtain single phase Fe₃C particles has been studied in the carburizing temperature range from 623 to 873 K. The saturation magnetization (σ_s) and intrinsic coercive force (_iH_c) attained are around 138×10⁻⁶ Wb·m·kg⁻¹ (110 emu·g⁻¹) and 51.7 kA·m⁻¹ (650 Oe), respectively. Possible applications for magnetic recording powders are found for Fe₃C particles synthesized at 823 K and above through a durability test of magnetic properties, by placing the particles in air of 333 K-90% relative humidity for a prolonged time.