Improving graphitization degree of mesophase pitch-derived carbon fiber by solid-phase annealing of spun fiber

摘要

The solid-phase annealing of the mesophase pitch spun fiber was examined between the glass transition (T_g) and softening (T_s) temperatures of tepitch to improve the graphitization degree of the graphitized fiber through recovering or further improving the stacking height of the mesogen molecules in the spun fiber,since the rapidspinning reduced markedly stacking height in the as-spun fiber.A naphthalene mesophase pitch as received carried stacking height of the mesogen molecules in the spun fiber,since the rapidspinning reduced markedly stacking height in the as-spun fiber.A naphthalene mesophase pitch as received carried stacking height of 2.9 nm which was markedly reduced to 1.7nm by spinning at 230 m/min,giving Lc=40 nm for its gaphitized fiber.Annelaing at 206degC improved the stacking height of the spun fiber to 2.4 nm and Lc(002) of the gaphitized fiber to 54 nm.Annealing of the methylnaphthalene mesophase pitch fiber at 200degC was much more effective in improving the stacking height from 3.5 to 5.0 nm and its graphitized fiber to Lc=91 from 40 nm.Such an improved graphitization degree led to improved thermal conductivity and tensile modulus of the graphitized fiber.it must be noted that the annealing of the spun fiber reduced its stabilization rate,indicating densification of molecular stacking in the fiber.The transformation scheme of mesophse pitch into graphite fibers is discussed to clarify the roles of molecular stacking in the clusters and their arrangement in the mesophase pitch fiber during the carbon manufacturing process.