Phase state and magnetic characteristics of finely dispersed iron powders prepared by mechanical activation in organic medium in the presence of surfactant

The effect of a surfactant (oleic acid) on the dispersity, structure, phase composition, and magnetic properties of powders prepared by iron grinding in the medium of liquid hydrocarbon (heptane) in a planetary ball mill was studied by the methods of X-ray diffraction analysis, Mossbauer and Auger s pectroscopy, secondary ion mass spectrometry, and by magnetic measurements. It was shown that the presence of surfactant results in an increase in dis persity, a change in the shape of particles, and in their magnetic properti es. Coercive force increases 20-fold and specific saturation magnetization decreases twofold after a 99-h grinding. The powders prepared possess a nan ocrystalline structure (grain size 4 nm) and represent supersaturated solid solutions of oxygen and carbon in bcc-iron with inclusions of iron carbide Fe3C. The concentration of impurities introduced by heptane (C) and oleic acid (C, O) rises with an increase in the duration of grinding. It was demo nstrated that changes in magnetic characteristics depend on the content of impurities in powders, as well as on the size and shape of particles obtain ed.