Preparation Of Novel Carbon Nanomaterials By DC Arc Discharge Under Nitrogen Atmosphere

Novel carbon nanomaterials include nanoparticles, nanotubes, nanorods, nanoribbons, nanofilms, and three-dimensional (3D) nanostructures. They have excellent electrical, mechanical and optical properties, showing good prospect of applications, and become one of the forefront and hot topics of nanomaterial research.In this thesis, DC arc discharge method was employed and the iron, cobalt and nickel oxides were used as the catalysts. The effect of the high temperature nitrogen gas on the deposits formed on the top of the cathode was investigated. The effects of carbon sources, the temperature of nitrogen gas, substrates and their positions on the morphologies, microstructures and composition of the films formed on the surfaces of substrates were also investigated.The results of TEM and HRTEM characterizations show that the large diameter carbon tubes (LDCTs) with different morphologies were formed in the spinous products around the column-shaped product deposited on the top of the cathode. The results of SAED and EDX characterizations show that the LDCTs were doped with the nitrogen and transition metal elements. The results of HRTEM and Raman characterizations show that the 3-8 layer graphene nanosheets were formed in the inner core of the column-shaped product and their yield was up to 50 wt. %. The results of XRD and EDX characterizations show that the graphene nanosheets were doped with nitrogen, and may be also doped with the transition metal elements.The results of SEM characterization show that when the substrates were put above, at one side of, and under the arc discharge region, the effects of the temperature of nitrogen gas and carbon sources on the morphologies of the films formed on the stainless steel, quartz and Si(100) substrates gradually reduced, and the morphologies of the carbon films changed from the quasi-3D netlike structure to the dense film composed of carbon particles; and the effect of the substrates, which included stainless steel, quartz and Si(100) substrates, on the morphologies of the films formed on their surfaces was not very obvious and without the remarkable regularity. Under the same conditions of the temperature of nitrogen gas and carbon source, the effects of the positions of the stainless steel, quartz and Si(100) substrates, which were put above, at one side of, and under the arc discharge region, on the morphologies of the films formed on their surfaces gradually increased, and the morphologies of the carbon films also changed from the quasi-3D netlike structure to the dense film composed of carbon particles. The results of TEM characterization show that the carbon films formed on stainless steel, quartz and Si(100) substrates, which were put above, at one side of, and under the arc discharge region, mainly consist of carbon nanoparticles or carbon particles. It is deduced from the results of SEM, TEM and HRTEM characterizations that the quasi-3D netlike structure is mainly composed of carbon nanoparticles. The formation mechanisms of the LDCT, graphene nanosheet and quasi-3D netlike structure were discussed, respectively.The results in this thesis not only provide an important experimental basis, but also have some theoretical significance for the preparation of novel carbon films, the molecular design of carbon nanomaterials and the development of arc discharge chemistry.