Characterization of phases formed in the iron carbide process by X-ray diffraction, Mossbauer, X-ray photoelectron spectroscopy, and Raman spectroscopy analyses

Iron carbide was prepared by iron ore reduction and iron cementation using Ar-H-2-CH4 gas mixture with and without sulfur. Phases formed in the reduction/cementation process were examined by Xray diffraction (XRD), Mossbauer, and Raman spectroscopy. The sample surface was also analyzed by X-ray photoelectron spectroscopy (XPS). XRD and Mossbauer analyses showed that iron oxide was first reduced to metallic iron, and then, metallic iron was carburized to cementite. Addition of a small amount of H2S to the reaction gas retarded the cementite formation but made the cementite more stable. XPS analysis showed that the surface of samples converted to iron carbide using sulfur-containing gas consisted of mainly Fe3C and a small amount of graphitic carbon. Raman spectra of a sample produced in the iron carbide process showed the G and D bands, which are characteristic for carbon-carbon bonds. The intensity ratio of G/D bands depended on the sulfur content in the reducing/carburizing gas.