Abstract
Aluminothermic combustion synthesis was conducted with Fe2O3–Al–Fe–Si reaction systems under Fe/Si stoichiometry from Fe-20 to Fe-50 at. % Si to investigate the formation Fe3Si/FeSi–Al2O3 composites. The solid-state combustion was sufficiently exothermic to sustain the overall reaction in the mode of self-propagating high-temperature synthesis (SHS). Dependence of iron silicide phases formed from SHS on Fe/Si stoichiometry was examined. Experimental evidence indicated that combustion exothermicity and flame-front velocity were affected by the Si percentage. According to the X-ray diffraction (XRD) analysis, Fe3Si–Al2O3 composites were synthesized from the reaction systems with Fe-20 and Fe-25 at.% Si. The increase of Si content led to the formation of both Fe3Si and FeSi in the final products of Fe-33.3 and Fe-40 at.% Si reaction systems, and the content of FeSi increased with Si percentage. Further increase of Si to Fe-50 at.% Si produced the FeSi–Al2O3 composite. Scanning electron microscopy (SEM) images revealed that the fracture surface morphology of the products featured micron-sized and nearly spherical Fe3Si and FeSi particles distributing over the dense and connecting substrate formed by Al2O3.
Highlights
Transition metal silicides have been promising for a wide range of applications including microelectronic transistors, high-temperature structural components, thin film coatings, thermoelectrics, spintronic devices, and catalysts [1,2,3,4,5,6]
As an extension of the previous studies [17,18], this work aims to investigate the production of Fe3Si/FeSi–Al2O3 composites by aluminothermite-based combustion synthesis in the SHS mode, with an emphasis on exploring the effect of Fe/Si stoichiometry on the formation of Fe3Si and FeSi
The increase of ∆Hro is caused by the fact that both the aluminothermic reduction of Fe2O3 and formation of iron silicides are heat-releasing reactions
Summary
Transition metal silicides have been promising for a wide range of applications including microelectronic transistors, high-temperature structural components, thin film coatings, thermoelectrics, spintronic devices, and catalysts [1,2,3,4,5,6]. Among various fabrication routes to prepare iron silicides in monolithic and composite forms, the reaction synthesis methods associated with mechanical alloying and combustion process have been of great interest. An in situ fabrication approach combining the chemical interaction between Fe and Si with aluminothermic reduction of Fe2O3 and SiO2 has been attempted to produce FeSi–Al2O3 and α-FeSi2–Al2O3 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]
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