Very long carbon nanotubes

Carbon nanotubes1 can now be produced in large quantities by either arc methods2,3 or thermal decomposition of hydrocarbons4,5. Here we report that pyrolysis of acetylene over iron/silica substrates is an effective method with which to produce very long, multiwalled carbon nanotubes that reach about 2 mm in length, which is an order of magnitude longer than that described in most previous reports1,2,3,4,5,.