Synthesis, Characterization And Application Of Double-Walled Carbon Nanotubes By Arc-Discharge Technique

Double-walled carbon nanotubes (DWCNTs) have many advantages over single-walledcarbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). To study theproperties and application of DWCNTs deeply and thoroughly, controllable synthesis ofDWCNTs must be addressed. In this thesis, the fabrication of DWCNTs by arc-discharge isstudied, and the potential applications in the field of hydrogenation, direct methanol fuel celland nanocomposites have been explored.One Chinese anthracite coal is used as carbon source that was mixed with catalystpowder and coal tar directly to prepare electrode rods. Synthesis of DWCNTs fromcoal-derived anodes with iron, alloy and ferreous salts as catalyst is studied in differentatmosphere. The results indicate that iron catalysts and hydrogen atmosphere are importantfactors for the production of DWCNTs.The coal-derived anode with iron nanoparticles can be prepared by liquid impregnationmethod. The effects of atmosphere on fabrication of DWCNTs are studied. The results showthat high quality DWCNTs can be obtained in large scale when the mixture of argon andhydrogen (300 Torr, V_Ar:V_H2=2:1) is used in the process. The yield of DWCNTs fromcoal-derived anode using iron as catalyst is higher than that using cobalt or nickel as catalyst.Fullerene waste soot (FWS) was used to make anodes with Fe₂(SO₄)₃ and FeCl₂ ascatalyst precursor, and the anodes were used to produce DWCNTs. In the mixture of argonand hydrogen (300 Torr, V_Ar:V_H2=2:1), high quality DWCNTs can be fabricated in large scalefrom these FWS-derived anodes.The as-synthesized DWCNTs from coal were purified with a mixture of concentratedsulfuric and nitric acids (3:1, 98wt.% and 70wt.%, respectively) which removes most ironparticles in high efficiency. After oxidation by air and being washed with HCl solution, thepurity of DWCNTs can reach ca.90wt.%.Most impurity in the as-synthesized DWCNTs from FWS can be removed by two stepspurification of being oxidized by air and washed with HCl acid. After purification process, thepurity of DWCNTs can reach ca.80wt.%.Raw DWCNTs from coal with iron, nickel or cobalt as catalyst show activity ofhydrogenation o-chloronitrobenzene (o-CNB). Meanwhile, the magnetic property of metalnanoparticles encapsulated with carbon shell in the raw DWCNTs is favorable for isolating the catalyst from reaction system. The conversion will increase evidently after the rawDWCNTs supported with Ru nanoparticles. As loading weight or reaction temperatureincrease, the conversion will be improved evidently.The properties of purified DWCNTs and other carbon materials supported with Runanoparticles behaving in hydrogenation o-CNB are researched. As a result, mostmonodisperse Ru particles on the purified DWCNTs is less than 3 nm, but conversion ofo-CNB is not high for the reason that there are still some large assemble particles in thecatalyst.Results of cyclic voltammetry and single cell performance indicate that high purityDWCNTs loading Pt and Ru may be a good anode catalyst for direct methanol fuel cells.The nanocomposites of DWCNTs filled with AgCl nanowires were synthesized bycapillarity in nitrogen atmosphere. Raman spectroscopy is used to characterize the product,and the Raman results indicate that in the filled sample the charge transfer occurs betweenAgCl nanowires and inner tube of DWCNT evidently.Furthermore, SWCNTs, carbon tubes filled with foreign material and Y-junction carbontubes synthesized by arc-discharge in suitable conditions are also studied in the paper.