Probing molecular structural properties of middle-high rank coal using XRD
This study probes the molecular structural properties of five middle-high rank coal (MHRC) samples using X-ray diffraction (XRD). X-ray diffraction (XRD) has been employed to examine the molecular arrangement of coals across various ranks. Its primary application lies in determining the structural parameters of carbonaceous materials. These parameters, such as carbon stacking layer spacing (d 002 ), average lateral sizes (L a ), and stacking height of crystallite (L c ), serve to describe the three-dimensional carbon-filled structure of coal. The dimensions of the microcrystalline unit in coal are predominantly influenced by coal rank. With increasing coal rank, L a expands, d 002 contracts, and L c initially grows but subsequently diminishes.
X-ray diffraction (XRD) has been employed to examine the molecular arrangement XRD is primarily utilized to ascertain the structural parameters of carbonaceous materials, particularly in the context of coal characterization. These parameters, such as carbon stacking layer spacing (d 002 ), average lateral sizes (L a ), and stacking height of crystallite (L c ), serve to describe the three-dimensional carbon-filled structure within coal. The analysis using XRD also reveals the presence of a significant quantity of disordered substances and amorphous carbon in , with a gradual decrease observed during the coalification process. The XRD spectra of five middle-high-rank coal (MHRC) samples are depicted in Fig. 1 , showing casing consistent graphite characteristics and a notable background intensity. This suggests the inclusion of Highly disordered materials in the form of amorphous carbon within the coal samples. Two distinct peaks, namely the 002 and 100 bands, are evident, with corresponding diffraction angles around 26° and 47°, respectively ( Fig. 1 ). The 002 band is associated with the stacking between aromatic rings, representing microcrystals in polycondensed aromatic rings. On the left side of the 002 peak is the γ band, attributed to aliphatic hydrocarbon branch chains, various functional groups, and alicyclic hydrocarbons connected to the condensed aromatic rings. of coals across various ranks. Its primary application lies in determining the structural parameters of carbonaceous materials. These parameters, such as carbon stacking layer spacing (d 002 ), average lateral sizes (L a ), and stacking height of crystallite (L c ), serve to describe the three-dimensional carbon-filled structure of coal. The dimensions of the microcrystalline unit in coal are predominantly influenced by coal rank. With increasing coal rank, La expands, d002 contracts, and Lc initially grows but subsequently diminishes. Additionally, XRD analysis reveals the presence of a substantial amount of highly disordered substances and amorphous carbon in coal, which gradually decreases during the process of coalification.
Reference:
Jiang J, Yang W, Cheng Y, Liu Z, Zhang Q, Zhao K. Molecular structure characterization of middle-high rank coal via XRD, Raman and FTIR spectroscopy: Implications for coalification. Fuel 2019;239:559–72. https: //doi.org/10.1016/j.fuel.2018.11.057.
