Resolidification temperatures cokes

A Microscopic Study of the Optical Anisotropy of Some Cokes Near Their Resolidification Temperatures... 

A comparative study has been made by optical and electron microscopy of the anisotropic texture of several cokes from caking coals and pitches carbonized near their resolidification temperature. A simple technique made it possible to examine, by both methods, the same area of each sample and to identify the corresponding zones of the two very similar images. The anisotropy observed in polarized light appears in electron microscopy as differences in contrast resulting not from inequalities in electron absorption, but, as revealed by microdiffraction and dark Reid examinations, from diffraction phenomena depending on the general orientation of the carbon layers within each anisotropic area. 

Over the temperature range 623 K to 773 K, caking coals begin to soften, coalesce, swell and then re-solidify into a porous structure which, at temperatures just above the resolidification temperature, is green coke. 

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