HIGH THERMAL-CONDUCTIVITY RIBBON FIBERS FROM NAPHTHALENE-BASED MESOPHASE

Their extremely high thermal conductivity, combined with their relatively low density, make mesophase pitch-based carbon fibers attractive for many applications where heat transfer is critical. Although many thermal management applications could create large markets for mesophase fibers, the current high cost of these fibers makes their use uneconomical. The objective of the present research is to produce low-cost, mesophase pitch-based carbon fibers with high mechanical and thermal properties. In the current study, circular and ribbon fibers were produced from a naphthalene-based mesophase. After stabilization and carbonization, their mechanical and electrical properties were compared to fibers produced at similar conditions, but using a heat-soaked mesophase precursor. The ribbon fibers produced from the naphthalene-based mesophase exhibited higher moduli and electrical resistivities than round fibers formed from the same precursor. Also, the mechanical and electrical properties of the naphthalene-based ribbon fibers were superior to ribbon fibers previously produced using a heat-soaked mesophase and heat treated at equivalent conditions. At carbonization temperatures of only 2250-degrees-C, the ribbon fibers produced from naphthalene-based mesophase developed electrical resistivities as low as 2.68 muohm . m, a factor of three lower than those previously produced from the heat-soaked mesophase. Thus, ribbon fibers formed from naphthalene-based mesophase should exhibit higher thermal conductivities than either round fibers formed from the same precursor or ribbon fibers formed from a heat-soaked precursor. An additional benefit is that fibers formed from naphthalene-based mesophase develop excellent properties at relatively low carbonization temperatures.