Controllable growth of uniform carbon nanotubes/carbon nanofibers on the surface of carbon fibers

Abstract

An efficient method to obtain a good and uniform catalyst coating on the surface of carbon fibers was developed by modifying carbon fibers with electrochemical anodic oxidation (EAO), the homogeneous growth of carbon nanotubes (CNTs)/carbon nanofibers (CNFs) was then achieved on the surface of carbon fibers via chemical vapor deposition (CVD). According to the study on the effect of both the catalyst type and concentration on CNT/CNF growth, it was found that when the concentration of catalyst precursor is higher than a critical value, catalytic efficiency decreases apparently with the increase of catalyst concentration regardless of the catalyst type employed. The influence of CVD temperature on tensile strength of CNT/CNF-grafted carbon fibers was also investigated. At low temperatures, such as 500 °C and 550 °C, growing CNTs/CNFs without any degradation of mechanical properties of carbon fibers was successfully achieved, which demonstrated the feasibility of growing CNTs/CNFs directly on carbon fibers. A mathematical model for CNT growth was established to explain the experimental results successfully, which can be used to accurately control the morphology and yield of CNTs/CNFs grown on the surface of carbon fibers. Hence it provides theoretical guidance for the large-scale synthesis processes.