Nickel-catalyzed in situ formation of carbon nanotubes and turbostratic carbon in polymer-derived ceramics

Nickel acetate-impregnated poly(methyl phenyl silsesquioxane) was pyrolyzed in argon atmosphere between 700 and 1000 °C to investigate the influence of the nickel transition metal on the structure evolution of the carbon phase. The formation of the different carbon microstructures and the resulting nanocomposition were studied in detail. The elemental compositions, carbon nanostructures and electrical conductivities of both filler-loaded and filler-free samples at the different temperatures were compared. The filler-loaded samples showed a significantly higher electrical conductivity and a higher carbon-to-hydrogen molar ratio in the investigated temperature range which is attributed to the formation of a percolating turbostratic carbon network already at 700 °C. Thus, the addition of the dehydrogenation-active transition metal Ni leads to a decrease in the starting temperature of the formation of turbostratic carbon by some hundred degrees. Moreover, the formation of multiwall carbon nanotubes was observed within the pores of the filler-loaded polymer matrices. These pores can be regarded as catalytic microreactors. Controlling of the catalyst particle distribution and of the transient porosity generation can enable the development of novel ceramic/carbon nanotube composite materials.