Influence of QI on mesophase structure

Abstract

The influence of quinoline insoluble (QI) particles on the transformation of isotropic pitch to mesophase has been studied using light microscopy, scanning electron microscopy, and transmission electron microscopy. The authors conclude that QI does not significantly affect either the nucleation of mesophase spheres or the rate at which mesophase forms. However, QI does profoundly affect the structure of the pitch at all stages of conversion and the structure of carbons derived from mesophase. QI particles appear to “pin” the mesophase structures in their vicinity, making the mesophase behave as a much more viscous material than would otherwise be the case; this is consistent with the many changes of layer plane orientation observed within QI-rich mesophase. The complex structure caused by the QI persists through to the stage of solidification so that some properties of the carbon product may be much modified by controlling the occurrence of QI in the parent pitch. All as-received pitch samples, including nominally “QI-free pitches” contain significant numbers of QI particles.