Micro-properties of Australian Coking Coals

The properties of a suite of experimental cokes made from Australian coals were studied. Image analysis was used to quantify the coke pore and pore wall microstructure, while ultra-micro indentation characterised the strength of the coke wall textures. The micro-properties were compared with compact tension measurements of bulk coke strength. The microstructural features of good cokes included a relatively thick coke wall, and a pore size distribution that has small mean pore size combined with a high pore density. It was found that inert maceral derived coke microtextures displayed the highest hardness values. The hardness of reactive maceral derived coke was lower and decreased with increasing mosaic size. For the set of cokes studied, the hardness and modulus were comparable for the same coke microtexture, irrespective of the coal source. Fracture toughness could not be determined for the coarser mosaic textures using the crack measurement approach. For those textures where measurements were possible, fracture toughness for the components was found to be independent of the parent coal.