[Raman spectroscopic characteristics of different rank coals and the relation with XRD structural parameters]

The Raman spectroscopic analysis for eleven different rank coals (57.58% to 94.01% of Cdaf, %) indicated that two distinct bands, i.e., D band (1340-1380 cm(-1)) and G band (1580-1600 cm(-1)), exist in the first order of Raman spectra, with the former being broader and the latter rather sharp. As the two bands were overlapped each other, each spectrum was fitted with two Lorentz peaks and the Raman information about position, intensity and FWHM of each band was thus obtained. The relation of these Raman parameters with Cdaf% showed that with the increase in C%, the position of D band and G band shifts to lower and higher frequency, respectively; the separation of the two band positions increases with the increase in C%; FWHM-D, FWHM-G and I(D)/I(G) have linear relationship with Cdaf% in the range of Cdaf% 75%-94%. The coal structural parameters, d002 and Lc from XRD are related with the position and FWHM of G band; the comparison of La from XRD and both from the Cancado and the KW equation indicated that the values from Cancado and the KW equation are unreasonable.