Microstructural studies of coal and carbonaceous mixtures using differential interference-contrast microscopy

The need for obtaining increased microstructural information from optical microscopy of coals and carbonaceous mixtures led to the present study in which the use of Differential Interference Contrast (DIC) microscopy was investigated. The three-dimensional quality conveyed to the micrographs through DIC reveals the order of hardness of the individual organic constituents. In addition, the nature of the cellular structure of semi-fusinites are more clearly identified by using DIC. Furthermore, visually observable contrast between carbonized coal fragments and semicoke formed in coal conversion systems was observable under DIC conditions, whereas in bright field conditions, these constituents are nearly indistinguishable. The results of this study suggest that DIC microscopy should be used routinely in studies of complex microstructures.