Characteristics of coal Raman spectrum

There is graphite microcrystallite in coal. The study on microcrystallite structure and its evolution of coal is extremely important for coal petrology,coal chemistry and coal geology. Through the test of coal with different ranks and tectonically deformations,it is found that there is intimate connection between microcrystallite structure and its evolution of coal and Raman spectrum:there are 5 bands in first order,they are respectively D1 -D4 band and G band. The function of aromatization and aromatic ring condensation lead to the rapid increase of the peak position difference (G-D1 ) and the rapid decrease of the half-width ratio (G / D1 ),the spell fold function results in the decrease of peak position difference (G-D1 ) and half-width ratio ( G / D1 ). There are 3 bands in second order,they are respectively 2D1 ,D1 +G and 2G band,it is hard to distinguish them in low rank coal but easy in high rank coal which indicate that the graphite microcrystallite in coal goes through the evolution process from small and disordered to big and ordered. The difference of position difference (G-D1 ) and half-width ratio (G / D1 ) of coal in the same layer reflects the de- gree of coalification of soft coal is higher than hard coal. So Raman spectrum is a kind of effective measure for analy- zing coal structure.