Rapid preparation and magnetic properties of Fe₃Si–Al₂O₃ nanocomposite by mechanical alloying and heat treatment

Abstract

nanocomposite has been prepared by mechanical alloying of Fe 3 O 4 , Al and Si powder mixture and heat treatment. Powder XRD patterns, TEM and HRTEM images and XPS spectra revealed the crystalline transformations from raw materials to Fe 3 Si-Al 2 O 3 nanocomposite during mechanical alloying and annealing and from Fe to Fe 3 Si to a mixture of Fe 3 Si, Fe 5 Si 3 and FeSi with the proportion of Si in raw materials increasing. The average particle size of smaller Fe 3 Si nanoparticles was about 20 nm and the aggregation under high temperature leaded to larger Fe 3 Si nanoparticles with average particle size of about 60 nm. 57 Fe M€ ossbauer spectra illustrated the existence of amorphous phases and effectively supplemented other characterisation results. The samples exhibited ferromagnetic behaviour with hysteresis loops and their saturation magnetisations decreased with the proportion of Si in samples increasing.

Effects of Fe/Si Stoichiometry on Formation of Fe3Si/FeSi-Al2O3 Composites by Aluminothermic Combustion Synthesis

“…Figure 5a It is believed that the addition of Si transformed a part of the Si-lean phase Fe 3 Si to monosilicide FeSi, thus resulting in a decrease of Fe 3 Si but an increase of FeSi. As proposed by Guan et al [15], the reaction of Fe 3 Si with additional Si generated an intermediate phase Fe 5 Si 3 which further converted into the stable FeSi via the reaction of Fe 5 Si 3 + 2Si → 5FeSi. The microstructure and elemental compositions of the product from Reaction (1) Figure 6 presents the XRD spectrum of the product synthesized from Reaction (1) with x = 3.0 (i.e., Fe-50% Si).…”

“…Zakeri et al [14] conducted mechanical alloying of SiO 2 and Al powders with stainless steel balls for 45 h to fabricate FeSi-Al 2 O 3 nanocomposite powders from induced reactions. According to Guan et al [15], Fe 3 Si-Al 2 O 3 nanocomposites were produced from Fe 3 O 4 , Al, and Si reactant powders through 4-h mechanical alloying followed by an annealing process at 900 • C for 1 h. Besides, Li et al [16] produced iron silicide nanoparticles of various phases by thermal annealing of Fe-FeSi 2 samples with a core-shell structure and identified the phase transformation from Fe-FeSi 2 to FeSi and Fe 3 Si under an annealing time of 2 h and temperatures of 600 and 700 • C. Recently, an in situ fabrication approach combining the chemical interaction between Fe and Si with aluminothermic reduction of Fe 2 O 3 and SiO 2 has been attempted to produce FeSi-Al 2 O 3 and α-FeSi 2 -Al 2 O 3 composites in the mode of self-propagating high-temperature synthesis (SHS) [17,18]. With the advantages of energy efficiency, rapid reaction, simplicity, and high-purity products [19], the SHS scheme has been recognized as one of the most effective methods for preparing transition metal silicides in monolithic and composite forms [20][21][22][23].…”