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.

Laser Direct-Write Sensors on Carbon-Fiber-Reinforced Poly-Ether-Ether-Ketone for Smart Orthopedic Implants.

Mechanically close-to-bone carbon-fiber-reinforced poly-ether-ether-ketone (CFR-PEEK)-based orthopedic implants are rising to compete with metal implants, due to their X-ray transparency, superior biocompatibility, and body-environment stability. While real-time strain assessment of implants is crucial for the postsurgery study of fracture union and failure of prostheses, integrating precise and durable sensors on orthopedic implants remains a great challenge. Herein, a laser direct-write technique is presented to pattern conductive features (minimum sheet resistance <1.7 Ω sq-1 ) on CRF-PEEK-based parts, which can act as strain sensors. The as-fabricated sensors exhibit excellent linearity (R2  = 0.997) over the working range (0-2.5% strain). While rigid silicon- or metal-based sensor chips have to be packaged onto flat surfaces, all-carbon-based sensors can be written on the complex curved surfaces of CFR-PEEK joints using a portable laser mounted on a six-axis robotic manipulator. A wireless transmission prototype is also demonstrated using a Bluetooth module. Such results will allow a wider space to design sensors (and arrays) for detailed loading progressing monitoring and personalized diagnostic applications.