Catalytic Pyrolysis Synthesis Of Carbon Nanotubes And Silica Nanofibers

Carbon nanotubes (CNTs) have the unique one-dimensional structures and properties. The CNT based nanocomposites have important applications in functional devices. The synthesis of CNTs and their nanocomposite structures is significant to their applications.Highly pure single-walled carbon nanotubes (SWNTs) was synthesized from the catalytic high temperature gas flow reactions using ethanol as the carbon source. The studies on the reaction chemistry indicated that the carbon source of ethanol and the catalyst precursor of ferrocene favored the growth of CNTs in high yield and purity comparing to the other hydrocarbons like hexanes, xylene and cobalt acetate. The initial fast heating of the aerosol of the reactants in use of a low thermal conductive nozzle promoted the growth of CNTs. In the case of ethanol as the carbon source, the reaction in an Ar flow did not yield CNTs.Based on the above gas flow reactions for the synthesis of CNTs, we extended this process for the synthesis of silica-CNT coaxial fibers. This new method uses the in-situ generated CNTs in the gas flow as the suspended support and pyrolysis of a polysiloxane in the downstream. Such a process and the reaction design allowed silica being wrapped onto the CNTs to form the well defined coaxial fibers. This new process enables producing the highly pure silica nanofibers in high yield. Further annealing of the coaxial tubes in the air generated the inner hollow silica fibers. We studied the properties of the silica nanofibers and their surface and observed strong photoluminescence and their excellent combination with metal nanocrystallines.