These changes in the structural features of chars can be quatified by means of structural ratios calculated from the Raman spectra of the chars. Values of \(\frac{ID}{IG}\) and \(\frac{IV}{ID}\)ratios as well as the Total Raman Area TRA are given in table 1.

One can observe that the ratio ID/IG significantly increases with the pyrolysis temperature indicating the formation of condensed aromatic ring structures having defects, which proportion is higher than the graphitized structures. These D structures would be formed by the condensation of small aromatic amorphous carbon structures (valley region), which contribution to the Raman signal decreases significantly with pyrolysis temperature increase. This feature is also reported in previous study [19]