In an effort to develop a low-cost high thermal conductivity carbon fiber, ribbon-shaped fibers were meltspun from a liquid crystalline, mesophase pitch precursor. Initial tests indicated that the ribbon-shaped fibers could be processed more easily and exhibited improved thermal conductivities when compared to commercial round fibers. Evidently, it is the more linear, polycrystalline structure within these fibers that accounts for their improved thermal conductivities. Thus, studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to fully analyze the transverse and longitudinal structure of these high thermal conductivity fibers.Ribbon-shaped fibers, melt-spun from a synthetic mesophase pitch and then heat treated, were tested to determine their tensile strengths, tensile moduli and thermal conductivities. A Jeol JSM-I C848 SEM at an accelerating voltage of 20 kV was used to obtain general structural information, such as extent and texture of lamellar organization of the graphitic layers within the fibers, and the microstructure of the fibers was studied by TEM.
Microstructure of high thermal conductivity mesophase pitch-based carbon fibers
