Atomic-Scale Structure and Morphology of Ferric Oxyhydroxides Formed by Corrosion of an Iron–Silicon Alloy

Abstract

Quantitative X-ray structural analysis using an in-house X-ray diffraction apparatus has been used for characterizing the atomic-scale structure of the -FeOOH (lepidocrocite) particles prepared by dipping a pure iron and an iron-silicon alloy into aqueous solutions containing sodium chloride. The morphology of the -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 -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 FeO 6 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.

Analysis of Iron Oxyhydroxides and Oxides Converted from Green Rust in Aqueous Solution

“…In this schematic diagram, the structures of iron oxyhydroxides and oxides are described using FeO 6 octahedral and partially bonded FeO 4 tetrahedral units, and SO 4 tetrahedral units are included in the GR structure. The atomic-scale structure of iron oxyhydroxides was also shown to be distorted by the incorporation of foreign cations and anions, [5][6][7][8][9] although their reaction processes are not fully understood. Further, as GR is converted to iron oxyhydroxides and oxides through oxidation in an aqueous solution, 1,10) the influence of the oxidation conditions on the conversion is still unclear.…”

Atomic-scale Structure and Morphology of .GAMMA.-FeOOH Particles Formed during Corrosion of Fe-based Alloys in Aqueous Solution

“…The atomicscale structure of the γ-FeOOH particles was described using the partial distribution functions calculated from the interference functions obtained by statistical optimization through the RMC simulation technique [16][17][18]. The RMC routine is essentially identical to that used in our previous study [9,12]. The supercells of γ-FeOOH had dimensions of 3.756×3.870×3.684 nm 3 .…”

“…They are linked to each other by corners, edges, or faces to form different structural arrays that are maintained even in the amorphous state [6]. As the linkages of the octahedral units are strongly related with the morphology and stability of ferric oxyhydroxides, the atomic-scale structure of ferric oxyhydroxides containing foreign ions has been studied [7][8][9][10][11][12]. In these studies, the extended X-ray absorption fine structure (EX-AFS) [13,14] and anomalous X-ray scattering (AXS) [15] are measured for characterizing the atomic-scale structure of different ferric oxyhydroxides.…”

Characterization of Different Solid Particles Transformed from Green Rust in Aqueous Solution — Using XRD, Mössbauer Spectroscopy, and XANES

“…11,12) The atomic-scale structures of these ferric oxyhydroxides have been shown to be distorted by the incorporation of foreign cations and anions. [13][14][15][16][17] In addition, in-situ and ex-situ X-ray diffraction measurements have also shown that GR was formed between an upper layer of corrosion products and metallic iron substrate and then it transformed into different components in the final corrosion products. 18,19) Thus, when the final corrosion products are formed from GR, reaction conditions, such as the chemical state and temperature of aqueous solution, are considered to play important roles in the formation of different ferric oxyhydroxides and iron oxides.…”