Synthesis of Hybrid Silica-Carbon Tubular Structures by Chemical Vapor Deposition with Methane or Ethene

Silica microtube and carbon nanotube hybrid structures have been synthesized by catalytic chemical vapor deposition using either methane or ethene as the carbon source, and cobalt-grafted or impregnated silica tubes (200–800 nm) as catalyst. The cobalt-grafted catalyst shows a high resistance to reduction (>1000 °C) and selectivity to single-wall carbon nanotubes (SWCNT). While ethene deposition produces more carbonaceous material, methane experiments show higher selectivity for SWCNT. After removing the silica with an excess of HF, the carbon nanostructure endured, resulting in a coaxial carbon nanostructure. The novel hybrid nanostructures obtained consist of a submicron-sized tube, with walls that are formed by a succession of carbon/silica/carbon layers to which multiwall (20–25 nm) and/or single-wall (0.6–2.0 nm) carbon nanotubes are attached. This synthesis approach combines the mechanical properties of carbon nanotubes and the thermal properties of silica tubes into a synergetic nanostructured material, opening further possibilities for polymer reinforcement and potential applications in catalysis