Chemical imaging of iron oxides and oxyhydroxides using near infrared Raman imaging microscopy

A new method of identifying and mapping the distribution of both iron oxide s and oxyhydroxides using near infrared Raman imaging microscopy (NIRIM) is reported. This technique offers an important alternative to conventional s pectroscopic techniques that provide spatially averaged data. The NIRIM ins trument used for these studies combines fibre bundle image compression hard ware and multivariate signal processing software to identify and map differ ent iron minerals and corrosion products. The NIRIM images clearly distingu ish hematite, magnetite, wustite, goethite, and lepidocrocite microstructur es. The first chemical maps of naturally occurring iron minerals and corrod ed steel surfaces obtained using NIRIM spectral images, classified with the aid of a library of pure compound spectra, are presented.