Home – Home – Jornals – Chemistry for Sustainable Development 2005 number 2

Dispersity, structure, phase composition and magnetic properties of the powder obtained by grinding the alloy of iron with silicon (with the atomic concentration of Si equal to 20 %) in liquid hydrocarbons (heptane, heptane with oleic acid as an additive) in a ball planetary mill were investigated by means of X-ray structural analysis, Mössbauer and Auger spectroscopy, secondary ion mass spectrometry, magnetic measurements. It was shown that during grinding the alloys get saturated with the products of destruction of the organic liquid (C, O, H) with the formation of metastable amorphous and carbide phases. With an increase in grinding time, the particle size decreases to 0.1-0.2 mm. Isochronous (500 ^oC, 1 h) annealing leads to the crystallization of the amorphous phase with the formation of ferric silicocarbide Fe₈Si₂C, Fe₃Si and C in the case of grinding in heptane, and Fe₃C with SiO₂ in the case of grinding with oleic acid added. The magnetic characteristics of the powder depend on the time and medium of grinding, and also on annealing temperature. An increase in coercivity from 10 to 180 A/cm correlates with the amount of the formed silicocarbide. The resulting silicocarbide has the composition Fe₈Si₂C; it has a triclinic lattice with the parameters: a=6.401Å, b=6.434Å, c=9.884 Å, α=83.590^o, β=99.343^o, γ=120.924^o; it is a ferromagnetic with Curie temperature T_C equal to 788 K, stable up to 870 K.