Structural investigations of Eocene coals from foreland basin of central Nepal Himalaya

Abstract

Structural investigations of Eocene coal from foreland basin of central Nepal Himalaya were subjected to attenuated total reflection Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and scanning electron microscopy to study their chemical and structural characteristics. The attenuated total reflection Fourier transform infrared spectroscopy data show that the less matured coal sample (sub-bituminous) has more aliphatic moieties, whereas the relatively more matured (bituminous) coal samples contain higher fractions of poly-aromatic moieties and saturated long-chain hydrocarbons. Fourier transform infrared spectroscopy spectra reveals the presence of stretching vibrations of aliphatic –CH, –CH 2 and –CH 3 absorptions, –OH bonds, C=C and –CH of aromatic structures and C=O stretching vibrations of carbonyl groups. X-ray diffraction indicates the presence of crystalline carbon having turbostratic structure along with some highly disordered amorphous carbon while high-resolution transmission electron microscopy study shows the formation of carbon nanostructures of 1.73–8.03 nm size and nominal areas in the range of 11–14 nm 2 . Single-wall nanotubes of 12.67–36.23 nm diameters were also formed. The nominal size of the single-wall nanotubes is in the range of 16–20 nm. The presence of micro-pores, micro-fissures and micro-cracks were revealed in the scanning electron microscopy study.