Microstructure and texture of pitch-based ribbon fibers for thermal management

The textures and microstructures of three different experimental mesophase pitch-based ribbon fibers were studied using the complementary techniques of scanning and transmission electron microscopy and wide angle X-ray diffraction. The effect of mesophase pitch precursor and capillary entry design on the structure and heat transfer capabilities of these ribbon-shaped fibers was investigated. It was found that ribbon fibers melt-spun from a synthetic, naphthalene-based mesophase had higher degrees of preferred orientation and graphitization, larger crystallite sizes and lower electrical resistivities than those of fibers melt-spun from a petroleum-based, heat-soaked mesophase. However, capillary entry design proved to be critical to the development of a more linear transverse texture and a structure that one might expect to be more conducive to axial heat transfer.