The aromatic fringe features including the length and moment angle HRTEM
The molecular structural features of coals have been studied by HRTEM image analysis technique, using the acquired high BV6 fringe images [3], [9], [10], [11], [12], [17], [24], [27] and [30]. The HRTEM images of the coal samples were acquired from a 200 kV Tecnai F20 FEGTEM and captured using a Gatan Inc. ORIUS™ CCD camera (Model 895). Image analyses were performed on the HRTEM micrographs to extract lattice fringes, using Adobe Photoshop CS5 in combination with an image processing tool kit (IPTK 5.0) plug-in (developed by Reindeer Graphics, USA). HRTEM image analysis was achieved following the procedure proposed by Sharma et al. [12].
Mathews and co-workers [24] however noted that, although the assignment of the HRTEM fringe lengths to the number of carbon atoms is not ‘absolute’, inflammatory response is a good approximation of the molecular feature of the assigned aromatic component. On this basis, some cut-offs were made for small molecules. Molecules with Cave: <3 Å were assigned to benzene; <4.4 Å to naphthalene and <5.9 Å to anthracene. Both the individual average molecular weight of the fringes and the overall average molecular weight of the samples’ fringes were evaluated using this technique. Demineralised coal samples were used for this analysis.