Preparation And Modification Of Carbon Materials Using Plasma Methods

In recent decades, the plasma methods for preparation and modification of carbon materials have attracted extensive attentions in both scientific research and practical industrial applications. Carbon materials synthesized via plasma methods show abundant applications in various fields due to their high degree of graphitization and electrical properties, and these technological processes have vast application prospect. In this paper, synthesis and surface modification of carbon nanomaterials were realized via plasma methods. Morphology, structure and content of carbon materials were characterized using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, elemental analysis and Specific surface area measuring instrumenton.In the preparation of carbon materials:(1) Carbon nanomaterials with a controlled structure was synthesized through an one-group alternating current(AC) arc plasma method based on the decomposition of propane. Arc discharge plasma method in a fluidized bed had been employed for preparation of carbon nanoparticles. The effects of electrode material, frequency of bipolar power supply, argon flow rate, propane flow rate and cracking temperature were discussed in order to obtain optimal conditions for generating carbon black(CB) with high productivity and well developed structure. Mechanism of CB formation was assumed and CB was successfully prepared by non-thermal plasma arc discharge process which was enhanced by electrical heating pyrolysis.(2) Preparation of carbon nanomaterials on a large scale using two-group arc discharge was realized based on two kinds of plasma methods, in which propane was cracked into CB with controlled structure and hydrogen. Combination of an AC and a direct current(DC) arc discharge plasma had been employed in this study. Parameters like the type of electrodes, frequency of AC arc discharge, current of DC arc discharge and gas flow rate(propane: argon(Ar)) were investigated. A systematic study of size, morphology, microstructure and surface chemical composition of CB was carried out using diverse characterization methods. Then, as-prepared CB were used to adsorb heavy-metal ions in water and to reinforce the engineering plastic. The adsorption rate of the Cr(Ⅵ) ion was increased significantly and that the CB enhanced the electrical and mechanical properties of the engineering plastic.In the modification of carbon materials:(1) One combination of an AC arc reactor and a fluidized bed has been developed to offer one new route for the surface modification of CB. CB were directly injected into arc plasma region by the carrier gas air and nitrigen(N2). The effects of bipolar power supply and time of modification were studied. The hydrophilic behavior and Specific surface area of CB and carbon nanotubes(CNTs) after air modification were improved evidently and the morphology of CNTs after N2 modification was changed.(2) CB were modified by using an atmospheric dielectric barrier discharge(DBD) air plasma in a downer. The DBD plasma voltage was investigated. The plasma treatment voltage greatly enhanced oxygen and nitrogen content on CB surface to change surface nature from hydrophobic to hydrophilic in modification step. CNTs surfaces were treated using N2 and Ar plasma. The parameters like voltages and treatment times of N2 and Ar plasma treatment were investigated. After N2 modification, nitrogenated functionalities could be added to the surface of CNTs and bamboo-like tubes were formed. A cleaning process for surface was achieved by DBD Ar plasma, and the modification did not change the inner structure. Surface roughness and specific surface area of the modified CNTs were increased, enhancing the adsorption rate of heavy metal ion.