In this paper, we are at first demonstrating 3D-SPRITE which has been shown to be successfulfor studying short relaxation time systems and which is free from distortions due to susceptibilityvariations for coals. The results obtained were discussed in relation to the three-dimensionaldistribution of mobile components for two kinds of coal. At the same time, inversion recoverypreparation experiments, for example,
T1 mapping and
T2* mapping based on SPRITE methodsare presented in order to clarify the chemical heterogeneity of coals. Also, we have carried outthe first systematic in-situ variable-temperature NMR microimaging study of coals between 25and 600
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C with our newly developed high-temperature microimaging probe and systems in orderto clarify the behavior of mobile components at high temperatures in heterogeneous coalspecimens. Both the mechanism of softening and melting process for coals and the coal mappingfor the softening and melting properties using in-situ imaging experiments which are based onthe local information are proposed.