Surface Modification and Enhanced Performance of Chemically Synthesized Nanosized Amorphous Fe Particles

The fully amorphous Fe nanoparticles with controllable size ranging from 80 to 120 nm have been fabricated by direct reduction reactions of Fe²⁺ ions with NaBH₄ as reducing agent. The morphologies and surface structures of these amorphous samples can be modified by varying the addition rate of NaBH₄ solution during the reaction process. The uniform nanosized amorphous Fe particles with an average size of about 90 nm can be obtained at suitable reaction addition. The B element is observed to accumulate in the surface of the amorphous samples, which promotes their good thermal and air stability. The surface B concentration can be decreased with increasing the NaBH₄ addition rate. Slight surface oxidation varying from FeO to Fe₃O₄ in the amorphous samples may lead to their different saturation magnetization of 126–140 A ⋅ m²/kg. This simple method, good stability, and high saturation magnetization for these nanosized amorphous Fe particles promise their potential applications in high-frequency and high-temperature soft magnetic devices.