Abstract
The basis of laser Raman spectroscopy and its recent application to the structural study of coals and related carbonaceous materials are briefly outlined along with experimental technique. In Raman scattering, skeletal vibrations such as condensed aromatic ring vibrations in coals appear strongly, differing from infrared absorption in that stretching vibrations of functional groups such as carbonyl and hydroxyl groups linked to the aromatic rings show strong absorption. All Raman spectra of raw coals of different rank exhibit two broad Raman bands around 1600cm-1 and 1380cm-1, which are very similar to those of PVC cokes and some resin chars heat treated at about 450°C. With increase in coal rank, both Raman bands increase gradually their intensity and become sharp.Similar trends can be also observed for carbonized coals when the carbonization temperature is increased. The half band widths and intensity ratio of the 1600cm-1 and 1360cm-1 bands for cokes from Miike coal show a remarkable change with carbonization temperature and, therefore, can be used as parameters for the structural characterization of cokes derived from various coals. A certain relationship is found among the intensity ratio of Raman bands, optical reflectance and microcrystallite size for some foreign coals.
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