Carbon Nanotube Growth On The Surface Of Carbon Fiber And Its Structure And Properties Investigation

The carbon fiber and carbon nanotube (CNT) are both effective reinforcement, the combination of both of them effectively to improve the interface properties of the fibers and the matrix, forming a composite reinforcement. So as to give full play to the performance of carbon fiber, at the same time the use of CNT excellent mechanics, electricity, thermal and other special properties. However, the CNT with high surface energy and large aspect ratio, is easy to tangle and agglomerate, thus has poor dispersion. So far, the methods of preparation of CNT/CF can solve the above referred questions and drawbacks, but CNTs obtained by these methods has weak bonding force with the carbon fiber surface and easy to be detached during practical application. These problems have impeded their application in composite. On the basis of preparation of carbon nanotubes using solid carbon sources, it can be a feasible way that the carbon nanotubes were grown firmly and vertically on the surface of carbon fiber in the presence of a certain amount of co-catalyst thiophene and water vapor.In this dissertation, carbon fibers were acid-treated at high temperature and loaded with nickel nitrate, and the carbon nanotubes were firmly grown on the surface of carbon fiber in the presence of a certain amount of co-catalyst thiophene and water vapor. By SEM, TEM, XRD, Raman, FT-IR and other test means to study the morphology of carbon fibers and carbon nanotubes structure, observing the growth of the fiber surface carbon nanotube diameter of 20-150 nm, the length can be up to a few microns. By means of SEM, TEM, XRD, Raman, FT-IR and other test means to study the morphology and structure of carbon fibers and carbon nanotubes, observing the CNTs growing on the fiber surface with diameter of 20-150 nm and length up to a few micrometers. In the experiment, we systematically studied the effects of the acid treatment, catalyst, reaction temperature, reaction time and the amount of water vapor and thiophene on firmly growth CNTs on the surface of carbon fiber. Finally, we obtained the optimal experimental conditions. Carbon fibers were acid-treated for 1～2h and optimum concentration of Ni(NO3)2 is 1-1.5mol/L, and reacted at 850℃ for 2～3h with the flow of 40～60 ml/min nitrogen through thiophene and the flow of 100～120 ml/L through water.According to experimental results, we infer the mechanism of CNTs f growth on the surface of carbon fiber, the main process is as follows: First, carbon fibers after acid treatment introduce a large number of oxygen-containing functional groups and highly reactive carbon atoms, and load catalyst on the fiber surface. As the reaction temperature, catalyst is reduced and reduces the melting point by absorbing sulfur atom, being a molten state to dissolve higher activity carbon atoms of fiber and other carbon sources while it etches fiber surface. Finally, it becomes a supersaturated metal-carbon particle. Carbon atoms start to precipitate in the form of graphite sheet and forms CNTs.The single fiber tensile strength of CNT/CF we obtained is 2.4～ 2.7GPa and keeps 67%～73% strength of original carbon fiber. The resistivity of CNT/CF is 5.7×10-3～7.3×10-3Ω·cm and 2.75 to 3.5 times the original carbon fiber. And the longer CNTs, resistivity decreases. Resistivity of CNT/CF greatly reduced after graphitization, about 50% of the original carbon fiber. Single fiber tensile strength of CF with CNT continuous growth only reduces by 14.6% and resistivity increases about 11.5%, Compared with original CF. CNT/CF can effectively improve the performances of carbon fiber reinforced plastic composites, their ILSS increased by 10.15%, and its interlaminar resistivity is about 7.96% of original carbon fiber reinforced plastic composites.