Formation of the amorphous multicomponent iron-based alloy during carbothermal reduction of Fe2O3 by waste activated sludge

Abstract

The process related to the formation of a multicomponent amorphous material during the reduction of α-Fe2O3 with the products of thermodestruction of WAS is studied using x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Because WAS contains sand and clay along with its bio-components, the thermal treatment of WAS is accompanied by the formation of amorphous carbon, SiO2, Al2O3, and multicomponent alloys. At T = 1000 °C, under oxygen-deficient conditions, iron oxide was reduced according to the scheme: α-Fe2O3 → (amorphous phase)main part + (Fe + Fe0.94O)(crystalline)little part. The main product of the Fe2O3 reduction is amorphous iron with a lamellar structure. Newly formed amorphous alloys form interlayers between the iron plates and 3D inclusions. Inclusions of C, SiO2, and Al2O3 agglomerates are observed between the lamellar packs. This macrostructure of the material allows slow cooling of the 3D-samples while preserving the amorphous state of iron.