Evaluation of graphitization and tensile property in microwave plasma treated carbon fiber

Plasma technology can be used as a green and novel method for the graphitization of carbon fiber. The effect of graphitization time on the main element content along with microstructure of carbon fiber in the plasma treatment process was investigated. It took an extremely short time (less than 100 ms) for the temperature of the system to increase until a relatively stable stage was reached. Furthermore, compared with the original carbon fiber, the increase in the carbon content and graphitization degree of carbon fiber was observed after microwave plasma treatment. Moreover, the original imperfect turbostratic graphite-like structure transformed to an ordered graphite structure with the escape of non‑carbon elements from the disordered region of graphite-like crystallites. With the graphitization time of 180 s and microwave power of 800 W, corresponding to the temperature of 2100 °C, a high graphitization degree (R = 0.61) was observed and the crystallite size was as large as 5.10 nm, which are better than that of M40J and T800H. After 5 mins treatment, the average tensile modulus of samples apparently increased by 23% from 189 GPa to 245 GPa. This work demonstrated that the microwave plasma is an alternative approach for the development of carbon fibers with good microstructure and high graphitization degree.