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

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 + Fe_0.94O)(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.