International audienceRaman structural imaging can extract original information in order to answer new questions raised in the recent studies on iron and low alloy steel corrosion. Up to now, this technique has allowed the extraction of the qualitative distribution of the compounds constituting the corrosion product layers. We propose here a methodology to extract quantitative parameters from Raman hyperspectral maps, executed by a home-developed software: LADIR-CAT. Specifically developed for iron corrosion quantitative component imaging, the approach and program operation are described. The LADIR-CAT is applied on ancient corroded iron samples originating from the Amiens cathedral (France) to establish the description and the composition of the corrosion system through quantitative compound imaging
Silicon carbide fibers of different generation/processing routes (NLM-Nicalon and Tyranno SA3) were thermally treated to trigger the growth of nanocrystals, which were analyzed using Raman spectroscopy and transmission electron microscopy (TEM). The nanocrystals were also aged in molten sodium nitrate to investigate their reactivity. The spatial correlation model has been used to model the Raman spectra and extract accurate and statistical information on the nanocrystallites' structure and dimension. For the NLM fibers, an average size of 2.5 to 7.0 nm was calculated, which was in good agreement with TEM observations. For the Tyranno SA3 fiber, despite the heavily faulted stacking sequence, the Raman peaks remained sharp, indicating that the crystallite dimension calculated from the Raman spectra is only dependent on the actual size of the nanocrystals and is not affected by the sequence of the stacking faults.
Nanosized and nanophased materials exhibit special properties. First they offer a good compromise between the high density of chemical bonds by unit volume, needed for good mechanical properties and the homogeneity of amorphous materials that prevents crack initiation. Second, interfaces are in very high concentration and they have a strong influence on many electrical and redox properties. The analysis of nanophased, low crystallinity materials is not straigtforward. The recording of Raman spectra with a geometric resolution close to 0.5 µm 3 and the deep understanding of the Raman signature allow to locate the different nanophases and to predict the properties of the material. Case studies are discussed: advanced polymer fibres, ceramic fibres and composites, textured piezoelectric ceramics and corroded (ancient) steel. 3.1 Raman Spectroscopy and (Nano)materials Properties Nanosized and nanophased materials possess a high concentration of interfaces, which results in unique optical and redox properties, as well as a good resistance to crack propagation. Not all conventional materials science research techniques are
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