Formation of mesophase microbeads from bulk mesophase pitch induced by fullerene

Abstract

A transformation of naphthalene-based coalescenced mesophase pitch (NMP) to mesophase microbeads was achieved by heating a mixture of NMP and fullerene (C₆₀). This is different from the conventional process of the liquid-phase carbonization of isotropic pitch to the emergence of carbon microbeads in the matrix and finally their growth to form a 100% anisotropic bulk mesophase, but rather a reverse transformation. The effects of C₆₀ loading and reaction temperature on the morphological transformation of mesophase were investigated by polarizing optical and scanning electron microscopies. The physical changes in the NMP induced by C₆₀ were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffractometry and Raman spectroscopy. The results show that the coalesced NMP can be converted to a spherical type at 300–320 °C with the addition of 5% C₆₀, and the size of the mesophase microbeads increases with increasing temperature. Furthermore, a model is established to explain the unique induction effect of C₆₀ in the transformation process. This work makes the morphological transformation of MP controllable, and provides a new idea for the understanding and research of mesophase pitch.