Affiliation: | * Northern Coke Research Laboratory, School of Chemistry, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK † Electron Microscopy Laboratory, School of Chemistry, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK c Department of Materials Science, Pennsylvania State University, University Park, Pennsylvania 16802, USA |
Abstract: | Coal-tar pitches, from coals of different rank and with various quinoline-insoluble contents, were carbonized under pressure (67 to 200 MN m−2) to maximum temperatures of 923 K. The resultant cokes were examined by optical and scanning electron microscopy in terms of size and shape of anisotropic structures within the coke. Natural quinoline-insolubles and carbon blacks both destroyed growth of the mesophase and development of anisotropy. Graphite particles (<10 μm) promoted growth and coalescence of the mesophase. Fourteen coals, of carbon content 77 to 91 wt%, VM 41 to 26%, were similarly carbonized under pressure. In the lower-rank coals no microscopically resolvable anisotropic mesophase was produced, but at a carbon content of 85% anisotropic units 1–2 μm in diameter were detected, increasing in size at a carbon content of 90% to 5 μm diameter. Results are discussed in terms of the origins of anisotropic mosaics observed in cokes, their variation in size with coal rank, and their significance in the carbonization of coal. |