Structural characterization of milled mesophase pitch-based carbon fibers

The microstructure of milled mesophase pitch-based carbon fibers (mMPCFs) that have been developed as an anode material for Li ion batteries has been studied as a function of heat treatment temperature (HTT) mainly by Raman spectroscopy, and the results obtained are compared with those by X-ray diffraction (XRD) and scanning electron microscopy (SEM) observations. As a functional material, SEM measurements indicate that these mMPCFs have a characteristic controlled cross-sectional morphology like a bamboo skin structure which is different to that of conventional mesophase pitch-based carbon fibers for composite use. The mMPCFs with HTT>2000°C clearly show the 110 and 112 XRD peaks indicating the development of three-dimensional graphite stacking from a turbostratic structure. The mMPCFs heat-treated at temperatures >2000°C contain larger domain sizes along their longitudinal surface that those along the periphery of the fiber, as demonstrated by microprobe Raman scattering experiments. These mMPCFs could be promising as a functional material for applications, such as to Li ion batteries, but not for composite applications.