Hydrocarbons decomposition was investigated on cobalt, nickel and iron catalysts under atmospheric pressure and in the temperature range of 500-700 degrees C. As a carbon source, methane, ethane and ethylene were used. In lower temperatures, the cobalt catalyst revealed the highest activity, whereas in higher temperatures, larger carbon amounts were obtained on the nickel and iron catalysts. According to the observed results the decomposition of hydrocarbons on the cobalt sample led to the formation of a stable form of fcc-Co in room temperature. On the cobalt and iron catalysts, multiwalled carbon nanotubes at 700 degrees C were obtained, but on the nickel catalyst many disordered carbon structures and Ni nanocapsules coated with a graphite layer were found. (C) 2010 Elsevier B.V. All rights reserved.