ABSTRACT
The structural and compositive evolution of tectonically deformed coals (TDCs) and their influencing factors were investigated and analyzed in detail through Fourier transform infrared spectroscopy (FTIR) and laser Raman spectra analysis. The TDC samples (0.7% < Ro,max <3.1%) were collected from Huaibei coalfield with different deformation mechanisms and intensity. The FTIR of TDCs shows that the metamorphism and the deformation affect the degradation and polycondensation process of macromolecular structure to different degree. The Raman spectra analysis indicates that secondary structure defects can be produced mainly by structural deformation, also the metamorphism influences the secondary structure defects and aromatic structure. Through comprehensive analysis, it was discussed that the ductile deformation could change to strain energy through the increase and accumulation of dislocation in molecular structure units of TDC, and it could make an obvious influence on degradation and polycondensation. While the brittle deformation could change to frictional heat energy and promote the metamorphism and degradation of TDC structure, but has less effect on polycondensation. Furthermore, degradation is the main reason for affecting the structural evolution of coal in lower metamorphic stage, and polycondensation is the most important controlling factor in higher metamorphic stage. Under metamorphism and deformation, the small molecules which break and fall off from the macromolecular tructure of TDC are preferentially replenished and embedded into the secondary structure defects or the residual aromatic rings were formed into aromatic structure by polycondensation. This process improved the stability of coal structure. It is easier for ductile deformation of coal to induce the secondary structure defects than brittle deformation.
ABSTRACT
Fourier transform infrared spectroscopy (FTIR) was applied to the study of the stress effect of compositions of macromolecular structure in tectonically deformed coals. The results showed that in different kinds of tectonically deformed coals, the absorption band of aromatic structure, aliphatic structure and oxygen functional groups nearly consistent in the peak wave number, but the intensity of the peak is different which is justly influenced by different deformation degree and deformation mechanism of tectonically deformed coals under tectonic stress. In the metamorphic and deformed environments of the low, middle and high coal rank, for tectonically deformed coals, with the increasing stress, hydrogen-enriched degree and oxygen-enriched degree decrease, while the degree of ring condensation increases. But there are differences in the change of compositions contents of macromolecular structure. This might indicate that the FTIR could be used in the stress effect of compositions of macromolecular structure in tectonically deformed coals.
