Poor thermal conductivity in the through-thickness direction
is
a critical limitation in the performance of carbon fiber-reinforced
polymer (CFRP) composites over a broad range of applications in the
aviation industry, where heat dissipation is required (e.g., battery
packs, electronic housing, and heat spreaders). In this work, it is
demonstrated for the first time that a hierarchical network of vertically
oriented graphene nanoflakes (GNFs), with nanoconfined silicon carbide
(SiC) nanocrystals, self-assembled on carbon fibers (CFs) can provide
significant improvement to the thermal conductivity (TC) of CFRPs
in the through-thickness direction. The vertically aligned SiC/GNF
heterostructures were grown directly on CFs for the first time by
single-step plasma-enhanced chemical vapor deposition (PECVD) employing
tetramethylsilane (TMS) and methane (CH4) gases at temperatures
of 800 and 950 °C. At the deposition temperature of 950 °C,
the controlled introduction of SiC/GNF heterostructures induced a
56% improvement in through-thickness TC over the bare CFRP counterparts
while simultaneously preserving the tensile strength. The increase
in thermal conductivity is accomplished by SiC nanocrystals, which
serve as linkage thermal conducting paths between the vertical graphene
layers, further enhancing the smooth transmission of phonons in the
vertical direction. The work demonstrates for the first time the unique
potential of novel SiC/GNF heterostructures for attaining strong and
thermally conductive multifunctional CFRPs.