Pressure-Strengthened Carbon Fibers from Mesophase Pitch Carbonization Processes.

Little attention has been devoted to studying the pressures during the mesophase pitches carbonization processes and their effects on the as-produced carbon fibers' mechanical properties. Herein, we study the pressure-enhanced graphitization of mesophase pitch and the promoted tensile stresses of the produced carbon fibers using full atomistic simulations based on reactive force fields. Results show that pressures increase the tensile stress of as-produced fibers by 3.7-11 times under 1-6 GPa isotropic compressing pressure. The highest tensile stress can reach 4.39 GPa in carbonized coal tar pitch at 4000 K under 6 GPa. In experimental work, the pressurized laser-processed mesophase pitch generates less gas and shows more ordered carbonized structures in Raman spectra. This work provides a fundamental understanding of the reaction mechanism of carbon fiber production under pressure, and also illustrates a promising method to manufacture mesophase pitch-based carbon fibers with exceptional mechanical properties.