The effect of reaction condition on composition and properties of ultrafine amorphous powders in (Fe, Co, Ni)-b systems prepared by chemical reduction

Amorphous ultrafine powders in (Fe, Co, Ni)-B binary systems were prepared in different reduction conditions of metal ions in an aqueous solution by use of KBH₄, with the aim of clarifying the effect of reaction conditions on the composition, thermal stability, and magnetic properties of the resultant amorphous powders. As the mol ratio of KBH₄ to metal ions decreases, the structure of the ultrafine powders changes from amorphous to crystalline phase. The morphology of these powders is in a nearly spherical shape with a particle size of about 20 nm for the amorphous phase and changes to the chain-like or net-like shape for the crystalline phase. The B content in the Fe-B amorphous powder decreases with a decrease of the ratio of KBH₄ to metal ions, and the powder size decreases with an increase of the reduction temperature.