In-Situ Doping BC Nanoparticles in Mesophase Pitch for Preparing Carbon Fibers with High Thermal Conductivity by Boron Catalytic Graphitization.

The boron carbide (BC) nanoparticles doping mesophase pitch (MP) was synthesized by the in-situ doping method with tetrahydrofuran solvent, and the corresponding MP-based carbon fibers (CFs) were successfully prepared through the melt-spinning, stabilization, carbonization and graphitization processes. The structural evolution and properties of boron-containing pitches and fibers in different processes were investigated for exploring the effect of BC on mechanical, electrical and thermal properties of CFs. The results showed that the BC was evenly dispersed in pitch fibers to provide active sites of oxygen, resulting in a homogeneous stabilization and ameliorating the split-ting microstructures of CFs. Moreover, the thermal conductivity of B1-MP-CF prepared with 1 wt.% BC increased to 1051 W/m•K, which was much higher than that of B0-MP-CF prepared without BC (659 W/m•K). While the tensile strength of BC-doped CFs was lower than that of pristine CFs. In addition, a linear relationship equation between the graphite microcrystallite parameter (I/I) calculated from Raman spectra and the thermal conductivity (λ) calculated according to the electrical resistivity was found, which was beneficial to understand the thermal properties of CFs. Therefore, the doping BC nanoparticles in MP did play a significant role in reducing the graphitization temperatures due to the boron catalytic graphitization but decreasing the mechanical properties due to the introduction of impurities.