In-Situ Doping B 4 C Nanoparticles in Mesophase Pitch for Preparing Carbon Fibers with High Thermal Conductivity by Boron Catalytic Graphitization.

The boron carbide (B ₄ C) 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 B ₄ C on mechanical, electrical and thermal properties of CFs. The results showed that the B ₄ C 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.% B ₄ C increased to 1051 W/m•K, which was much higher than that of B0-MP-CF prepared without B ₄ C (659 W/m•K). While the tensile strength of B ₄ C-doped CFs was lower than that of pristine CFs. In addition, a linear relationship equation between the graphite microcrystallite parameter (I _D /I _G ) 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 B ₄ C 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.