The structural alignment of coal and the analogous case of Argonne Upper Freeport coal

It has long been recognized that coal is somewhat aligned. Multiple techniques imply a structural alignment but its quantification has been challenging. Moreover, discrepancies exist among techniques as to whether low-rank coals are aligned. The extent of structural alignment for the rank range was quantified directly via image analysis of high-resolution transmission electron micrograph lattice fringes. Alignment was quantified, for each coal, by the contribution to the total fringe length within the prominent 45 degrees of orientation over random orientation (1/4 of the possible orientations). It was evident that there is structural alignment across the rank range. Thus it is time for the community to desist from making the erroneous statement that: low-rank coals are randomly oriented. The slight orientation was similar for low-rank Beulah-Zap lignite and Illinois No. 6 bituminous coals (24% and 22%) with Pocahontas (lvb) coal showing slightly greater (39%) alignment with extensive alignment (65%) in the case of an anthracite coal. The degree of ordering is illustrated with the aid of false-color lattice fringe images and Rose diagrams. The fringe contribution 90 degrees opposed to the maximum length contribution had the minimum or near minimum percentage length contribution for all coals except Upper Freeport and to a lesser degree Illinois No. 6. For the Upper Freeport coal the alignment is lower than expected given its mvb rank (14% over random) and is attributed to a variant of T-stacking for the small aromatic moieties sited perpendicular and between horizontal displaced fringes. (C) 2011 Elsevier Ltd. All rights reserved.