Atomic-scale structure and morphology of ferric oxyhydroxides formed by corrosion of an iron-silicon alloy

Quantitative X-ray structural analysis using an in-house X-ray diffraction apparatus has been used for characterizing the atomic-scale structure of the γ-FeOOH (lepidocrocite) particles prepared by dipping a pure iron and an iron-silicon alloy into aqueous solutions containing sodium chloride. The morphology of the γ-FeOOH particles was observed by transmission electron microscopy (TEM), and their bonding structure were analyzed using Fourier transform infrared spectroscopy (FT-IR). The realistic atomic-scale structures in the γ-FeOOH particles were estimated by fitting the interference functions with the help of the reverse Monte Carlo (RMC) simulation technique. The results showed that the linkages of fundamental FeO₆, octahedral units in the particles were deviated from the ideal crystal structure. The structural deviation is considered to be due to the incorporation of foreign ions during the formation of these particles in the aqueous solutions.