Optimization of Process Conditions for Continuous Growth of CNTs on the Surface of Carbon Fibers

Grafting carbon nanotubes (CNTs) is one of the most commonly used methods for modifying carbon fiber surface, during which complex device is usually needed and the growth of CNTs is difficult to control. Herein, we provide an implementable and continuous chemical vapor deposition (CVD) process, by which the novel multiscale reinforcement of carbon nanotube (CNT)-grafted carbon fiber is prepared. After exploring the effects of the moving speed and growth atmosphere on the morphology and mechanical properties of carbon nanotubes/carbon fiber (CNTs/CF) reinforcement, the optimal CVD process conditions are determined. The results show that low moving speeds of carbon fibers passing through the reactor can prolong the growth time of CNTs, increasing the thickness and density of the CNTs layer. When the moving speed is 3 cm/min or 4 cm/min, the surface graphitization degree and tensile strength of CNTs/CF almost simultaneously reach the highest value. It is also found that H-2 in the growth atmosphere can inhibit the cracking of C2H2 and has a certain effect on prolonging the life of the catalyst. Meanwhile, the graphitization degree is promoted gradually with the increase in H-2 flow rate from 0 to 0.9 L/min, which is beneficial to CNTs/CF tensile properties.