Usage of Laser Raman Spectroscopy to Identify the Unstable Compounds in Iron Oxides

Abstract

In this work laser Raman Spectroscopy was used to identify the unstable compounds in five samples of iron oxides (hematite, magnetite, goethite, akaganeite and 2-line ferrihydrite). Firstly iron oxide samples were prepared using Fe (N03)3 9H2O and KOH with different molar ratios through the chemical method in lab. These samples were irradiated using 5mW frequency doubled Nd-YAG laser with 532 nm at room temperature. Spectra database was used for the spectral analysis of the Raman shift of these five samples. The obtained results showed that the bands of unstable compounds are appeared clearly in the spectra of the samples. Characteristic bands of hematite were appeared in the spectra of magnetite, goethite, akaganeite and 2-line ferrihydrite compounds while bands of magnetite compounds were appeared in the spectra of hematite. The laser power causes the bands to broaden and to undergo a small shift to lower wavenumbers. Other materials were appeared in spectra of the five samples, like disulfide, alkyl disulfide, chlorolkanes and aliphatic fluoro. Raman spectroscopy proved to be suitable for the identification of unstable compounds in hematite, magnetite, goethite, akaganeite and ferrihydrite and could be used for other materials