Abstract:
Ribbon-shaped carbon fibers have been prepared from mesophase pitch by melt-spinning,
oxidative stabilization and further heat treatment. The internal graphitic layers of ribbon-shaped
carbon fibers graphitized at 2800 C show a highly preferred orientation along the
longitudinal direction. Parallel stretched and unidirectional arranged ribbon-shaped carbon
fibers treated at about 450 C were sprayed with a mesophase pitch powder grout,
and then hot-pressed at 500 C and subsequently carbonized and graphitized at various
temperatures to produce one-dimensional carbon/carbon (C/C) composite blocks. The
shape and microstructural orientation of ribbon fibers have been maintained in the process
of hot-pressing and subsequent heat treatments and the main planes of the ribbon fibers
are orderly accumulated along the hot-pressing direction. Microstructural analyses indicate
that the C/C composite blocks have a typical structural anisotropy derived from the
unidirectional arrangement of the highly oriented wide ribbon-shaped fibers in the composite
block. The thermal conductivities of the C/C composites along the longitudinal
direction of ribbon fibers increase with heat-treatment temperatures. The longitudinal
thermal conductivity and thermal diffusivity at room temperature of the C/C composite
blocks graphitized at 3100 C are 896 W/m K and 642 mm2/s, respectively.
